WorldWideScience

Sample records for alkaline membrane cell

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

    Energy Technology Data Exchange (ETDEWEB)

    Choe, Yoong-Kee [National Institute of Advanced Industrial Science and Technology, Umezono 1-1-1, Tsukuba (Japan); Henson, Neil J.; Kim, Yu Seung [Los Alamos National Laboratory, Los Alamos, NM (United States)

    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.

  2. Alkaline fuel cell with nitride membrane

    Science.gov (United States)

    Sun, Shen-Huei; Pilaski, Moritz; Wartmann, Jens; Letzkus, Florian; Funke, Benedikt; Dura, Georg; Heinzel, Angelika

    2017-06-01

    The aim of this work is to fabricate patterned nitride membranes with Si-MEMS-technology as a platform to build up new membrane-electrode-assemblies (MEA) for alkaline fuel cell applications. Two 6-inch wafer processes based on chemical vapor deposition (CVD) were developed for the fabrication of separated nitride membranes with a nitride thickness up to 1 μm. The mechanical stability of the perforated nitride membrane has been adjusted in both processes either by embedding of subsequent ion implantation step or by optimizing the deposition process parameters. A nearly 100% yield of separated membranes of each deposition process was achieved with layer thickness from 150 nm to 1 μm and micro-channel pattern width of 1μm at a pitch of 3 μm. The process for membrane coating with electrolyte materials could be verified to build up MEA. Uniform membrane coating with channel filling was achieved after the optimization of speed controlled dip-coating method and the selection of dimethylsulfoxide (DMSO) as electrolyte solvent. Finally, silver as conductive material was defined for printing a conductive layer onto the MEA by Ink-Technology. With the established IR-thermography setup, characterizations of MEAs in terms of catalytic conversion were performed successfully. The results of this work show promise for build up a platform on wafer-level for high throughput experiments.

  3. Block Copolymers for Alkaline Fuel Cell Membrane Materials

    Science.gov (United States)

    2014-07-30

    temperature fuel cells including proton exchange membrane fuel cell ( PEMFC ) and alkaline fuel cell (AFC) with operation temperature usually lower than 120...advantages over proton exchange membrane fuel cells ( PEMFCs ) resulting in the popularity of AFCs in the US space program.[8-11] The primary benefit AFC...offered over PEMFC is better electrochemical kinetics on the anode and cathode under the alkaline environment, which results in the ability to use

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

    International Nuclear Information System (INIS)

    Haryadi,; Sugianto, D.; Ristopan, E.

    2015-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Haryadi,, E-mail: haryadi@polban.ac.id; Sugianto, D.; Ristopan, E. [Department of Chemical Engineering, Politeknik Negeri Bandung Jl. Gegerkalong Hilir, Ds. Ciwaruga, Bandung West Java (Indonesia)

    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.

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

    Science.gov (United States)

    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.

  7. A high selectivity quaternized polysulfone membrane for alkaline direct methanol fuel cells

    CSIR Research Space (South Africa)

    Abuin, GC

    2015-04-01

    Full Text Available polysulfone membrane for alkaline direct methanol fuel cells Graciela C. Abuina, Esteban A. Franceschinib, Patrick Nonjolac, Mkhulu K. Mathec, Mmalewane Modibedic, Horacio R. Cortib,* aCentro de Procesos Superficiales, Instituto Nacional de Tecnología...

  8. Introducing catalyst in alkaline membrane for improved performance direct borohydride fuel cells

    Science.gov (United States)

    Qin, Haiying; Lin, Longxia; Chu, Wen; Jiang, Wei; He, Yan; Shi, Qiao; Deng, Yonghong; Ji, Zhenguo; Liu, Jiabin; Tao, Shanwen

    2018-01-01

    A catalytic material is introduced into the polymer matrix to prepare a novel polymeric alkaline electrolyte membrane (AEM) which simultaneously increases ionic conductivity, reduces the fuel cross-over. In this work, the hydroxide anion exchange membrane is mainly composed of poly(vinylalcohol) and alkaline exchange resin. CoCl2 is added into the poly(vinylalcohol) and alkaline exchange resin gel before casting the membrane to introduce catalytic materials. CoCl2 is converted into CoOOH after the reaction with KOH solution. The crystallinity of the polymer matrix decreases and the ionic conductivity of the composite membrane is notably improved by the introduction of Co-species. A direct borohydride fuel cell using the composite membrane exhibits an open circuit voltage of 1.11 V at 30 °C, which is notably higher than that of cells using other AEMs. The cell using the composite membrane achieves a maximum power density of 283 mW cm-2 at 60 °C while the cell using the membrane without Co-species only reaches 117 mW cm-2 at the same conditions. The outstanding performance of the cell using the composite membrane benefits from impregnation of the catalytic Co-species in the membrane, which not only increases the ionic conductivity but also reduces electrode polarization thus improves the fuel cell performance. This work provides a new approach to develop high-performance fuel cells through adding catalysts in the electrolyte membrane.

  9. Polybenzimidazole membranes for zero gap alkaline electrolysis cells

    DEFF Research Database (Denmark)

    Kraglund, Mikkel Rykær; Aili, David; Christensen, Erik

    Membranes of m-PBI doped in KOH (aq), 15-35 wt%, show high ionic conductivity in the temperature range 20-80 ºC. In electrolysis cells with nickel foam electrodes m-PBI membranesprovide low internal resistance. With a 60 µm membraneat 80ºC in 20 wt% KOH,1000 mA/cm2 is achieved at 2.25....

  10. Multi-layer membrane model for mass transport in a direct ethanol fuel cell using an alkaline anion exchange membrane

    Science.gov (United States)

    Bahrami, Hafez; Faghri, Amir

    2012-11-01

    A one-dimensional, isothermal, single-phase model is presented to investigate the mass transport in a direct ethanol fuel cell incorporating an alkaline anion exchange membrane. The electrochemistry is analytically solved and the closed-form solution is provided for two limiting cases assuming Tafel expressions for both oxygen reduction and ethanol oxidation. A multi-layer membrane model is proposed to properly account for the diffusive and electroosmotic transport of ethanol through the membrane. The fundamental differences in fuel crossover for positive and negative electroosmotic drag coefficients are discussed. It is found that ethanol crossover is significantly reduced upon using an alkaline anion exchange membrane instead of a proton exchange membrane, especially at current densities higher than 500 A m

  11. Development of anionic membranes produced by radiation-grafting for alkaline fuel cell applications

    International Nuclear Information System (INIS)

    Pereira, Clotilde Coppini

    2017-01-01

    Anion Exchange Membranes (AEMs) are a promising alternative to the development of more efficient electrolytes for alkaline fuel cells. In general, the AEMs are ionomeric membranes able to conduct hydroxide ions (OH - ) due to the quaternary ammonium groups, which confer high pH equivalent to the AEM. In order to develop alkaline membranes with high chemical and thermal stability, besides satisfactory ionic conductivity for alkaline fuel cells, membranes based on low density polyethylene (LDPE), ultrahigh weight molecular weight polyethylene (UHWHPE), poly(ethylene-co-tetrafluoroethylene) (PETFE) and poly(hexafluoropropylene-co-tetrafluoroethylene) (PFEP) previously irradiated by using 60 Co gamma and electron beam sources, have been synthesized by styrene-grafting, and functionalized with trimethylamine to introduced quaternary ammonium groups. The resulting membranes were characterized by electron paramagnetic resonance (EPR), Raman spectroscopy, thermogravimetry (TG) and electrochemical impedance spectroscopy (EIS). The determination of the grafting degree and water uptake were conducted by gravimetry and ion exchange capacity, by titration. The membranes synthesized with PELD and PEUHMW polymers pre-irradiated at 70 kGy and stored at low temperature (-70 deg C), up to 10 months, showed ionic conductivity results, in hydroxide form (OH - ), of 29 mS.cm -1 and 14 mS.cm -1 at 65 deg C, respectively. The PFEP polymers irradiated by the simultaneous process showed insufficient grating levels for the membrane synthesis, requiring more studies to improve the irradiation and grafting process. The styrene-grafted PETFE membranes, pre-irradiated at 70 kGy and stored at low temperature (-70 deg C), up to 10 months, showed ionic conductivity results, in hydroxide form (OH - ), of 90 mS.cm -1 to 165 mS.cm -1 , in the temperature range 30 to 60 deg C. Such results have demonstrated that LDPE, UHMWPE and PETFE based AEMs are promising electrolytes for alkaline fuel cell

  12. Imidazolium-Based Polymeric Materials as Alkaline Anion-Exchange Fuel Cell Membranes

    Science.gov (United States)

    Narayan, Sri R.; Yen, Shiao-Ping S.; Reddy, Prakash V.; Nair, Nanditha

    2012-01-01

    Polymer electrolyte membranes that conduct hydroxide ions have potential use in fuel cells. A variety of polystyrene-based quaternary ammonium hydroxides have been reported as anion exchange fuel cell membranes. However, the hydrolytic stability and conductivity of the commercially available membranes are not adequate to meet the requirements of fuel cell applications. When compared with commercially available membranes, polystyrene-imidazolium alkaline membrane electrolytes are more stable and more highly conducting. At the time of this reporting, this has been the first such usage for imidazolium-based polymeric materials for fuel cells. Imidazolium salts are known to be electrochemically stable over wide potential ranges. By controlling the relative ratio of imidazolium groups in polystyrene-imidazolium salts, their physiochemical properties could be modulated. Alkaline anion exchange membranes based on polystyrene-imidazolium hydroxide materials have been developed. The first step was to synthesize the poly(styrene-co-(1-((4-vinyl)methyl)-3- methylimidazolium) chloride through a free-radical polymerization. Casting of this material followed by in situ treatment of the membranes with sodium hydroxide solutions provided the corresponding hydroxide salts. Various ratios of the monomers 4-chloromoethylvinylbenzine (CMVB) and vinylbenzine (VB) provided various compositions of the polymer. The preferred material, due to the relative ease of casting the film, and its relatively low hygroscopic nature, was a 2:1 ratio of CMVB to VB. Testing confirmed that at room temperature, the new membranes outperformed commercially available membranes by a large margin. With fuel cells now in use at NASA and in transportation, and with defense potential, any improvement to fuel cell efficiency is a significant development.

  13. Characterization of an anionic-exchange membranes for direct methanol alkaline fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Abuin, Graciela C. [Centro de Procesos Superficiales, Instituto Nacional de Tecnologia Industrial (INTI), Av. Gral. Paz 5445, B1650KNA, San Martin, Buenos Aires (Argentina); Nonjola, Patrick; Mathe, Mkhulu K. [Council for Scientific and Industrial Research (CSIR), Material Science and Manufacturing, PO Box 395, Brumeria, Pretoria 0001 (South Africa); Franceschini, Esteban A.; Izraelevitch, Federico H.; Corti, Horacio R. [Departamento de Fisica de la Materia Condensada, Comision Nacional de Energia Atomica (CNEA), Av. Gral. Paz 1499, B1650KNA, San Martin, Buenos Aires (Argentina)

    2010-06-15

    Ammonium quaternized polymers such as poly (arylene ether sulfones) are being developed and studied as candidates of ionomeric materials for application in alkaline fuel cells, due to their low cost and promising electrochemical properties. In this work, a quaternary ammonium polymer was synthesized by chloromethylation of a commercial polysulfone followed by amination process. Quaternized polysulfone membrane properties such us water and water-methanol uptake, electrical conductivity and Young's modulus were evaluated and compared to Nafion 117, commonly employed in direct methanol fuel cells. The anionic polysulfone membrane sorbs more water than Nafion all over the whole range of water activities, but it uptakes much less methanol as compared to Nafion. The specific conductivity of the fully hydrated polysulfone membrane equilibrated with KOH solutions at ambient temperature increases with the KOH concentration, reaching a maximum of 0.083 S cm{sup -1} for 2 M KOH, slightly less conductive than Nafion 117. The elastic modulus of the polysulfone membranes inmersed in water is similar to that reported for Nafion membranes under the same conditions. We concluded that quaternized polysulfone membrane are good candidates as electrolytes in alkaline direct methanol fuel cells. (author)

  14. Hot topics in alkaline exchange membrane fuel cells

    Science.gov (United States)

    Serov, Alexey; Zenyuk, Iryna V.; Arges, Christopher G.; Chatenet, Marian

    2018-01-01

    The tremendous progress from the first discovery of fuel cell principles by Sir William Robert Grove in 1839 [1] and independent observation of electricity generated in electrochemical reaction of hydrogen and air by a Swiss scientist Christian F. Shoenbein [2] to the recent breakthroughs in the fuel cell field resulted in the appearance of this clean energy technology around us. Indeed, fuel cell technology undoubtedly has entered into our life with the first introduction of Toyota Mirai Fuel Cell Vehicle (FCV) by Toyota Motor Co. in December of 2014 [3,4]. This FCV is commercially available and can be purchased in several countries. However, its sticker price of 57,500 substantially limits the number of customers that can purchase it. There are numerous factors that contribute to the high cost of fuel cell stack, however the price of platinum and platinum alloys is the main contributor [5].

  15. Experimental and analytical analysis of polarization and water transport behaviors of hydrogen alkaline membrane fuel cell

    Science.gov (United States)

    Huo, Sen; Zhou, Jiaxun; Wang, Tianyou; Chen, Rui; Jiao, Kui

    2018-04-01

    Experimental test and analytical modeling are conducted to investigate the operating behavior of an alkaline electrolyte membrane (AEM) fuel cell fed by H2/air (or O2) and explore the effect of various operating pressures on the water transfer mechanism. According to the experimental test, the cell performance is greatly improved through increasing the operating pressure gradient from anode to cathode which leads to significant liquid water permeation through the membrane. The high frequency resistance of the A901 alkaline membrane is observed to be relatively stable as the operating pressure varies based on the electrochemical impedance spectroscopy (EIS) method. Correspondingly, based on the modeling prediction, the averaged water content in the membrane electrode assembly (MEA) does not change too much which leads to the weak variation of membrane ohmic resistance. This reveals that the performance enhancement should give the credit to better electro-chemical reaction kinetics for both the anode and cathode, also prone by the EIS results. The reversion of water back diffusion direction across the membrane is also observed through analytical solution.

  16. Novel fluoropolymer anion exchange membranes for alkaline direct methanol fuel cells.

    Science.gov (United States)

    Zhang, Yanmei; Fang, Jun; Wu, Yongbin; Xu, Hankun; Chi, Xianjun; Li, Wei; Yang, Yixu; Yan, Ge; Zhuang, Yongze

    2012-09-01

    A series of novel fluoropolymer anion exchange membranes based on the copolymer of vinylbenzyl chloride, butyl methacrylate, and hexafluorobutyl methacrylate has been prepared. Fourier transform infrared (FT-IR) spectroscopy and elemental analysis techniques are used to study the chemical structure and chemical composition of the membranes. The water uptake, ion-exchange capacity (IEC), conductivity, methanol permeability, and chemical stability of the membranes are also determined. The membranes exhibit high anionic conductivity in deionized water at 65 °C ranging from 3.86×10(-2) S cm(-1) to 4.36×10(-2) S cm(-1). The methanol permeability coefficients of the membranes are in the range of 4.21-5.80×10(-8) cm(2) s(-1) at 65 °C. The novel membranes also show good chemical and thermal stability. An open-circuit voltage of 0.7 V and a maximum power density of 53.2 mW cm(-2) of alkaline direct methanol fuel cell (ADMFC) with the membrane C, 1 M methanol, 1 M NaOH, and humidified oxygen are achieved at 65 °C. Therefore, these membranes have great potential for applications in fuel cell systems. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Quaternized poly(vinyl alcohol)/alumina composite polymer membranes for alkaline direct methanol fuel cells

    Science.gov (United States)

    Yang, Chun-Chen; Chiu, Shwu-Jer; Chien, Wen-Chen; Chiu, Sheng-Shin

    The quaternized poly(vinyl alcohol)/alumina (designated as QPVA/Al 2O 3) nanocomposite polymer membrane was prepared by a solution casting method. The characteristic properties of the QPVA/Al 2O 3 nanocomposite polymer membranes were investigated using thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), micro-Raman spectroscopy, and AC impedance method. Alkaline direct methanol fuel cell (ADMFC) comprised of the QPVA/Al 2O 3 nanocomposite polymer membrane were assembled and examined. Experimental results indicate that the DMFC employing a cheap non-perfluorinated (QPVA/Al 2O 3) nanocomposite polymer membrane shows excellent electrochemical performances. The peak power densities of the DMFC with 4 M KOH + 1 M CH 3OH, 2 M CH 3OH, and 4 M CH 3OH solutions are 28.33, 32.40, and 36.15 mW cm -2, respectively, at room temperature and in ambient air. The QPVA/Al 2O 3 nanocomposite polymer membranes constitute a viable candidate for applications on alkaline DMFC.

  18. High-Efficiency Artificial Photosynthesis Using a Novel Alkaline Membrane Cell

    Science.gov (United States)

    Narayan, Sri; Haines, Brennan; Blosiu, Julian; Marzwell, Neville

    2009-01-01

    A new cell designed to mimic the photosynthetic processes of plants to convert carbon dioxide into carbonaceous products and oxygen at high efficiency, has an improved configuration using a polymer membrane electrolyte and an alkaline medium. This increases efficiency of the artificial photosynthetic process, achieves high conversion rates, permits the use of inexpensive catalysts, and widens the range of products generated by this type of process. The alkaline membrane electrolyte allows for the continuous generation of sodium formate without the need for any additional separation system. The electrolyte type, pH, electrocatalyst type, and cell voltage were found to have a strong effect on the efficiency of conversion of carbon dioxide to formate. Indium electrodes were found to have higher conversion efficiency compared to lead. Bicarbonate electrolyte offers higher conversion efficiency and higher rates than water solutions saturated with carbon dioxide. pH values between 8 and 9 lead to the maximum values of efficiency. The operating cell voltage of 2.5 V, or higher, ensures conversion of the carbon dioxide to formate, although the hydrogen evolution reaction begins to compete strongly with the formate production reaction at higher cell voltages. Formate is produced at indium and lead electrodes at a conversion efficiency of 48 mg of CO2/kilojoule of energy input. This efficiency is about eight times that of natural photosynthesis in green plants. The electrochemical method of artificial photosynthesis is a promising approach for the conversion, separation and sequestration of carbon dioxide for confined environments as in space habitats, and also for carbon dioxide management in the terrestrial context. The heart of the reactor is a membrane cell fabricated from an alkaline polymer electrolyte membrane and catalyst- coated electrodes. This cell is assembled and held in compression in gold-plated hardware. The cathode side of the cell is supplied with carbon

  19. DEVELOPMENT AND SELECTION OF IONIC LIQUID ELECTROLYTES FOR HYDROXIDE CONDUCTING POLYBENZIMIDAZOLE MEMBRANES IN ALKALINE FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Fox, E.

    2012-05-01

    Alkaline fuel cell (AFC) operation is currently limited to specialty applications such as low temperatures and pure HO due to the corrosive nature of the electrolyte and formation of carbonates. AFCs are the cheapest and potentially most efficient (approaching 70%) fuel cells. The fact that non-Pt catalysts can be used, makes them an ideal low cost alternative for power production. The anode and cathode are separated by and solid electrolyte or alkaline porous media saturated with KOH. However, CO from the atmosphere or fuel feed severely poisons the electrolyte by forming insoluble carbonates. The corrosivity of KOH (electrolyte) limits operating temperatures to no more than 80°C. This chapter examines the development of ionic liquids electrolytes that are less corrosive, have higher operating temperatures, do not chemically bond to CO and enable alternative fuels. Work is detailed on the IL selection and characterization as well as casting methods within the polybenzimidazole based solid membrane. This approach is novel as it targets the root of the problem (the electrolyte) unlike other current work in alkaline fuel cells which focus on making the fuel cell components more durable.

  20. Highly Zeolite-Loaded Polyvinyl Alcohol Composite Membranes for Alkaline Fuel-Cell Electrolytes

    Directory of Open Access Journals (Sweden)

    Po-Ya Hsu

    2018-01-01

    Full Text Available Having a secure and stable energy supply is a top priority for the global community. Fuel-cell technology is recognized as a promising electrical energy generation system for the twenty-first century. Polyvinyl alcohol/zeolitic imidazolate framework-8 (PVA/ZIF-8 composite membranes were successfully prepared in this work from direct ZIF-8 suspension solution (0–45.4 wt % and PVA mixing to prevent filler aggregation for direct methanol alkaline fuel cells (DMAFCs. The ZIF-8 fillers were chosen for the appropriate cavity size as a screening aid to allow water and suppress methanol transport. Increased ionic conductivities and suppressed methanol permeabilities were achieved for the PVA/40.5% ZIF-8 composites, compared to other samples. A high power density of 173.2 mW cm−2 was achieved using a KOH-doped PVA/40.5% ZIF-8 membrane in a DMAFC at 60 °C with 1–2 mg cm−2 catalyst loads. As the filler content was raised beyond 45.4 wt %, adverse effects resulted and the DMAFC performance (144.9 mW cm−2 was not improved further. Therefore, the optimal ZIF-8 content was approximately 40.5 wt % in the polymeric matrix. The specific power output was higher (58 mW mg−1 than most membranes reported in the literature (3–18 mW mg−1.

  1. Invited: A Stability Study of Alkali Doped PBI Membranes for Alkaline Electrolyzer Cells

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf; Aili, David; Hansen, Martin Kalmar

    2014-01-01

    Alkaline fuel cells and electrolyzers are attracting increasing interest. This is to a large extent due to the broad selection of catalyst materials not based on resource limited and expensive noble metals. The first fuel cells in practical use were Francis Thomas Bacon’s based on an alkaline...

  2. Platinum- and membrane-free swiss-roll mixed-reactant alkaline fuel cell.

    Science.gov (United States)

    Aziznia, Amin; Oloman, Colin W; Gyenge, Előd L

    2013-05-01

    Eliminating the expensive and failure-prone proton exchange membrane (PEM) together with the platinum-based anode and cathode catalysts would significantly reduce the high capital and operating costs of low-temperature (<373 K) fuel cells. We recently introduced the Swiss-roll mixed-reactant fuel cell (SR-MRFC) concept for borohydride-oxygen alkaline fuel cells. We now present advances in anode electrocatalysis for borohydride electrooxidation through the development of osmium nanoparticulate catalysts supported on porous monolithic carbon fiber materials (referred to as an osmium 3D anode). The borohydride-oxygen SR-MRFC operates at 323 K and near atmospheric pressure, generating a peak power density of 1880 W m(-2) in a single-cell configuration by using an osmium-based anode (with an osmium loading of 0.32 mg cm(-2)) and a manganese dioxide gas-diffusion cathode. To the best of our knowledge, 1880 W m(-2) is the highest power density ever reported for a mixed-reactant fuel cell operating under similar conditions. Furthermore, the performance matches the highest reported power densities for conventional dual chamber PEM direct borohydride fuel cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Quaternized poly(methyl methacrylate-co-butyl acrylate-co-vinylbenzyl chloride) membrane for alkaline fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yanting; Guo, Juchen; Wang, Chunsheng [Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742 (United States); Chu, Deryn [Sensors and Electron Device Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783 (United States)

    2010-06-15

    Instead of modification of pre-existing polymers, a new route of preparation of polyelectrolyte OH{sup -} conductive membranes via copolymerization of selected functional monomers was reported in this study. A random copolymer of poly(methyl methacrylate-co-butyl acrylate-co-vinylbenzyl chloride) was synthesized via copolymerization, which was followed by quaternization and membrane casting. The intrinsic OH{sup -} conductivity of the free-standing polyelectrolyte membranes can reach 8.2 x 10{sup -3} S cm{sup -1} at 80 C. The alkaline fuel cells using copolymer polyelectrolytes demonstrated the feasibility of the preparation concept of these membranes. (author)

  4. Plasma Membranes Modified by Plasma Treatment or Deposition as Solid Electrolytes for Potential Application in Solid Alkaline Fuel Cells

    Science.gov (United States)

    Reinholdt, Marc; Ilie, Alina; Roualdès, Stéphanie; Frugier, Jérémy; Schieda, Mauricio; Coutanceau, Christophe; Martemianov, Serguei; Flaud, Valérie; Beche, Eric; Durand, Jean

    2012-01-01

    In the highly competitive market of fuel cells, solid alkaline fuel cells using liquid fuel (such as cheap, non-toxic and non-valorized glycerol) and not requiring noble metal as catalyst seem quite promising. One of the main hurdles for emergence of such a technology is the development of a hydroxide-conducting membrane characterized by both high conductivity and low fuel permeability. Plasma treatments can enable to positively tune the main fuel cell membrane requirements. In this work, commercial ADP-Morgane® fluorinated polymer membranes and a new brand of cross-linked poly(aryl-ether) polymer membranes, named AMELI-32®, both containing quaternary ammonium functionalities, have been modified by argon plasma treatment or triallylamine-based plasma deposit. Under the concomitant etching/cross-linking/oxidation effects inherent to the plasma modification, transport properties (ionic exchange capacity, water uptake, ionic conductivity and fuel retention) of membranes have been improved. Consequently, using plasma modified ADP-Morgane® membrane as electrolyte in a solid alkaline fuel cell operating with glycerol as fuel has allowed increasing the maximum power density by a factor 3 when compared to the untreated membrane. PMID:24958295

  5. Plasma membranes modified by plasma treatment or deposition as solid electrolytes for potential application in solid alkaline fuel cells.

    Science.gov (United States)

    Reinholdt, Marc; Ilie, Alina; Roualdès, Stéphanie; Frugier, Jérémy; Schieda, Mauricio; Coutanceau, Christophe; Martemianov, Serguei; Flaud, Valérie; Beche, Eric; Durand, Jean

    2012-07-30

    In the highly competitive market of fuel cells, solid alkaline fuel cells using liquid fuel (such as cheap, non-toxic and non-valorized glycerol) and not requiring noble metal as catalyst seem quite promising. One of the main hurdles for emergence of such a technology is the development of a hydroxide-conducting membrane characterized by both high conductivity and low fuel permeability. Plasma treatments can enable to positively tune the main fuel cell membrane requirements. In this work, commercial ADP-Morgane® fluorinated polymer membranes and a new brand of cross-linked poly(aryl-ether) polymer membranes, named AMELI-32®, both containing quaternary ammonium functionalities, have been modified by argon plasma treatment or triallylamine-based plasma deposit. Under the concomitant etching/cross-linking/oxidation effects inherent to the plasma modification, transport properties (ionic exchange capacity, water uptake, ionic conductivity and fuel retention) of membranes have been improved. Consequently, using plasma modified ADP-Morgane® membrane as electrolyte in a solid alkaline fuel cell operating with glycerol as fuel has allowed increasing the maximum power density by a factor 3 when compared to the untreated membrane.

  6. Synthesis and characterisation of alkaline anionic-exchange membranes for direct alcohol fuel cells

    CSIR Research Space (South Africa)

    Nonjola, P

    2007-12-01

    Full Text Available , but the most important being proton exchange membrane fuel cell (PEMFC), which uses an acidic membrane like Nafion (sulfonated fluorocarbon polymers) as an electrolyte. The use of polymer electrolytes represents an interesting path to pursue...

  7. Anion exchange membrane based on alkali doped poly(2,5-benzimidazole) for alkaline membrane fuel cell

    CSIR Research Space (South Africa)

    Luo, H

    2010-03-01

    Full Text Available was prepared. The alkali doped poly(2,5-benzimidazole) membrane is a promising candidate as anion exchange membrane for fuel cell application. The alkali doped poly(2,5-benzimidazole) membrane reached an anion conductivity of 2.3×10-2 S cm-1 at room temperature...

  8. Recyclable cross-linked anion exchange membrane for alkaline fuel cell application

    Science.gov (United States)

    Hou, Jianqiu; Liu, Yazhi; Ge, Qianqian; Yang, Zhengjin; Wu, Liang; Xu, Tongwen

    2018-01-01

    Cross-linking can effectively solve the conductivity-swelling dilemma in anion exchange membranes (AEMs) but will generate solid wastes. To address this, we developed an AEM cross-linked via disulfide bonds, bearing quaternary ammonium groups, which can be easily recycled. The membrane (RC-QPPO) with IEC of 1.78 mmol g-1, when cross-linked, showed enhanced mechanical properties and good hydroxide conductivity (24.6 mS cm-1 at 30 °C). Even at higher IEC value (2.13 mmol g-1), it still has low water uptake, low swelling ratio and delivers a peak power density of 150 mW cm-2 at 65 °C. Exploiting the formation of disulfide bonds from -SH groups, the membrane can be readily cross-linked in alkaline condition and recycled by reversibly breaking disulfide bonds with dithiothreitol (DTT). The recycled membrane solution can be directly utilized to cast a brand-new AEM. By washing away the residual DTT with water and exposure to air, it can be cross-linked again and this process is repeatable. During the recycling and cross-linking processes, the membrane showed a slight IEC decrease of 5% due to functional group degradation. The strategy presented here is promising in enhancing AEM properties and reducing the impact of artificial polymers on the environment.

  9. Characterization of anionic-exchange membranes for direct alcohol alkaline fuel cells

    CSIR Research Space (South Africa)

    Abuin, GC

    2009-06-01

    Full Text Available and Young modulus were evaluated and compared to other membrane materials commonly employed in PEM fuel cells. A quartz crystal microbalance (QMC) was used to measure the water uptake of thin membranes of this material casted over the quartz crystals...

  10. Radiolytic preparation of ETFE and PFA based anion exchange membranes for alkaline fuel cell

    International Nuclear Information System (INIS)

    Ko, Beom-Seok; Sohn, Joon-Yong; Nho, Young-Chang; Shin, Junhwa

    2011-01-01

    In this study, a versatile monomer, vinylbenzyl chloride (VBC) was radiolytically grafted onto a partially fluorinated ETFE and perfluorinated polymer PFA films. The VBC grafted films were treated with trimethylamine to prepare the alkaline anion exchange membranes (AAEMs). No significant differences in the ion exchange capacities and water uptakes were observed between the ETFE and PFA based AAEMs with similar degree of grafting (DOG). However, the distribution patterns of the graft chains over the cross-section of the ETFE and PFA based AAEMs were found to be quite different; the even distribution was observed from the ETFE based AAEMs while the uneven distribution was observed from the PFA based AAEMs. It was also found that the PFA based AAEMs have the higher ionic conductivity and chemical stability, compared to the ETFE based AAEMs.

  11. A Stability Study of Alkali Doped PBI Membranes for Alkaline Electrolyzer Cells

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf; Aili, David; Hansen, Martin Kalmar

    2014-01-01

    conductivity was similar to a commercial Zirfon membrane and suitable for a water electrolyzer. Some chemical degradation was seen during the aging period, but the crosslinked and the cured materials were both integral after 176 days of aging. A simplified electrolyzer test cell was operated successfully....

  12. Development of alkaline fuel cells.

    Energy Technology Data Exchange (ETDEWEB)

    Hibbs, Michael R.; Jenkins, Janelle E.; Alam, Todd Michael; Janarthanan, Rajeswari; Horan, James L.; Caire, Benjamin R.; Ziegler, Zachary C.; Herring, Andrew M.; Yang, Yuan; Zuo, Xiaobing; Robson, Michael H.; Artyushkova, Kateryna; Patterson, Wendy; Atanassov, Plamen Borissov

    2013-09-01

    This project focuses on the development and demonstration of anion exchange membrane (AEM) fuel cells for portable power applications. Novel polymeric anion exchange membranes and ionomers with high chemical stabilities were prepared characterized by researchers at Sandia National Laboratories. Durable, non-precious metal catalysts were prepared by Dr. Plamen Atanassovs research group at the University of New Mexico by utilizing an aerosol-based process to prepare templated nano-structures. Dr. Andy Herrings group at the Colorado School of Mines combined all of these materials to fabricate and test membrane electrode assemblies for single cell testing in a methanol-fueled alkaline system. The highest power density achieved in this study was 54 mW/cm2 which was 90% of the project target and the highest reported power density for a direct methanol alkaline fuel cell.

  13. Carbon-supported co-pyridine as non-platinum cathode catalyst for alkaline membrane fuel cells

    International Nuclear Information System (INIS)

    Qiao, Jinli; Xu, Li; Liu, Yuyu; Xu, Pan; Shi, Jingjing; Liu, Shiyao; Tian, Binglun

    2013-01-01

    Development of high-performance cost-effective electrocatalyts that can replace Pt catalyst have been a central theme in polymer electrolyte membrane fuel cells (PEMFCs) including direct methanol fuel cells (DMFCs). Here we show that carbon-supported pyridine–cobalt nanoparticles (CoPy/C) can generate a high catalytic activity toward the oxygen reduction reaction (ORR). The catalysts are synthesized using cobalt sulfate heptahydrate (CoSO 4 ·7H 2 O) and pyridine (Py) as the Co and N precursors via a solid state reaction by heat-treatment in an inert atmosphere at 800 °C. In particular, the ORR kinetics on these catalyst materials are evaluated using rotating disk electrode (RDE) technique in electrolytes of various KOH concentrations, ranging from 0.05 to 12 M. The Koutecky–Levich equation analyses indicate that the transferred electron number, n, per oxygen molecule on CoPy/C electrode depend on the low negative ovevrpotentials in low KOH concentrations, whereas in high KOH concentrations the values of n for oxygen reduction depend on the high negative overpotentials, and varies between 3.5 and 4.0. These catalysts exhibit the superior methanol tolerance to commercial 40%Pt/C catalyst, and the negative effect of high KOH concentration is much less for CoPy/C than for Pt/C, suggesting the promising utilization of CoPy/C as electrocatalysts for alkaline polymer electrolyte membrane fuel cells

  14. Study of poly(vinyl alcohol)/titanium oxide composite polymer membranes and their application on alkaline direct alcohol fuel cell

    Science.gov (United States)

    Yang, Chun-Chen; Chiu, Shwu-Jer; Lee, Kuo-Tong; Chien, Wen-Chen; Lin, Che-Tseng; Huang, Ching-An

    The novel poly(vinyl alcohol)/titanium oxide (PVA/TiO 2) composite polymer membrane was prepared using a solution casting method. The characteristic properties of the PVA/TiO 2 composite polymer membrane were investigated by thermal gravimetric analysis (TGA), a scanning electron microscopy (SEM), a micro-Raman spectroscopy, a methanol permeability measurement and the AC impedance method. An alkaline direct alcohol (methanol, ethanol and isopropanol) fuel cell (DAFC), consisting of an air cathode based on MnO 2/C inks, an anode based on PtRu (1:1) black and a PVA/TiO 2 composite polymer membrane, was assembled and examined for the first time. The results indicate that the alkaline DAFC comprised of a cheap, non-perfluorinated PVA/TiO 2 composite polymer membrane shows an improved electrochemical performances. The maximum power densities of alkaline DAFCs with 4 M KOH + 2 M CH 3OH, 2 M C 2H 5OH and 2 M isopropanol (IPA) solutions at room temperature and ambient air are 9.25, 8.00, and 5.45 mW cm -2, respectively. As a result, methanol shows the highest maximum power density among three alcohols. The PVA/TiO 2 composite polymer membrane with the permeability values in the order of 10 -7 to 10 -8 cm 2 s -1 is a potential candidate for use on alkaline DAFCs.

  15. Development of a mathematical model for a single alkaline membrane fuel cell (AMFC) with fixed volume and general square section

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, Elise Meister; Vargas, Jose Viriato Coelho [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Centro Politecnico. Setor de Tecnologia], Email: jvargas@demec.ufpr.br; Martins, Lauber de Souza; Ordonez, Juan Carlos [Florida State University, Tallahasse, FL (United States). Dept. of Mechanical Engineering and Center for Advanced Power Systems], Emails: martins@caps.fsu.edu, ordonez@eng.fsu.edu

    2010-07-01

    The Alkaline Membrane Fuel Cell (AMFC) is a recently developed fuel cell type, which has shown good experimental results in the laboratory. This paper introduces a mathematical model for the single AMFC with fixed volume and general square section. The main objective is to produce a reliable model (and computationally fast) to predict the response of the single AMFC according to variations of the physical properties of manufacturing materials and operating and design parameters. The model is based on mass, momentum, energy and species conservation, and electrochemical principles, and takes into account pressure drops in the gas channels and temperature gradients with respect to space in the flow direction. The simulation results comprise the AMFC temperature distribution, net power and polarization curves. It is shown that temperature spatial gradients and gas channels pressure drops significantly affect fuel cell performance. Such effects are not usually investigated in the models available in the literature, with most of them assuming uniform pressure and temperature operation. Therefore, the model is expected to be a useful tool for AMFC design and optimization. (author)

  16. Exploring Alkaline Stable Organic Cations for Polymer Hydroxide Exchange Membranes

    Science.gov (United States)

    2015-04-29

    1   1.1.2   Proton exchange membrane fuel cells ( PEMFCs ) ......................... 3   1.1.3   Alkaline fuel cells (AFCs...160   xi LIST OF FIGURES Figure 1.1:   Schematic diagram of a PEMFC ...according to the type of electrolyte they use. Nowadays, there are six major types of fuel cells: proton-exchange membrane fuel cells ( PEMFCs ), hydroxide

  17. Anionic-exchange membrane development for application in alcohol alkaline fuel cells

    CSIR Research Space (South Africa)

    Nonjola, S

    2010-09-01

    Full Text Available . In this work, a quaternary ammonium polymer was synthesized by chloromethylation of a commercial polysulfone followed by amination process. Quaternized polysulfone membrane properties such us water and water-methanol uptake, electrical conductivity and Young...

  18. Development of nano-composite membranes to improve alkaline fuel cell performance

    CSIR Research Space (South Africa)

    Nonjola, P

    2011-09-01

    Full Text Available The work presented here describes modification of commercially available polysulfone (PSU) as well as the formation of nano-composite membrane i.e. TiO2 nano particles incorporated into anion exchange polymer matrix....

  19. Fabrication and Characterization of Chitosan Nanoparticle-Incorporated Quaternized Poly(Vinyl Alcohol) Composite Membranes as Solid Electrolytes for Direct Methanol Alkaline Fuel Cells

    International Nuclear Information System (INIS)

    Li, Pin-Chieh; Liao, Guan–Ming; Kumar, S. Rajesh; Shih, Chao-Ming; Yang, Chun-Chen; Wang, Da-Ming; Lue, Shingjiang Jessie

    2016-01-01

    Highlights: • Preparation of chitosan nanoparticles from bulk to enhance the degree of deacetylation. • The incorporation of chitosan nanoparticles into a QPVA matrix to form a nanocomposite membrane. • The nanocomposite constructed into thin-film membranes using the solution casting method. • To improve permeability, glutaraldehyde was cross-linked with the nanocomposite membranes. • A direct methanol alkaline fuel cell was studied at different temperatures. - Abstract: In this study, we designed a method for the preparation of chitosan nanoparticles incorporated into a quaternized poly(vinyl alcohol) (QPVA) matrix for direct methanol alkaline fuel cells (DMAFCs). The structural and morphological properties of the prepared nanocomposites were studied using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and dynamic laser-light scattering (DLS). The crystallinity of the nanocomposite solid electrolytes containing 0 and 10% chitosan nanoparticles were investigated using differential scanning calorimetry (DSC). The electrochemical measurement of resulting nanocomposite membranes were analyzed according to the following parameters: methanol permeability, liquid uptakes, ionic conductivity and cell performances. The composite membranes with 10% chitosan nanoparticles in a QPVA matrix (CQPVA) show suppressed methanol permeability and higher ionic conductivity than pristine QPVA. In addition, the glutaraldehyde cross-linked nanocomposite film exhibited improvement on the methanol barrier property at 80 °C. The peak power density of the DMAFCs reached 67 mW cm −2 when fed into 1 M of methanol in 6 M of KOH.

  20. Alkaline fuel cells applications

    Science.gov (United States)

    Kordesch, Karl; Hacker, Viktor; Gsellmann, Josef; Cifrain, Martin; Faleschini, Gottfried; Enzinger, Peter; Fankhauser, Robert; Ortner, Markus; Muhr, Michael; Aronson, Robert R.

    On the world-wide automobile market technical developments are increasingly determined by the dramatic restriction on emissions as well as the regimentation of fuel consumption by legislation. Therefore there is an increasing chance of a completely new technology breakthrough if it offers new opportunities, meeting the requirements of resource preservation and emission restrictions. Fuel cell technology offers the possibility to excel in today's motive power techniques in terms of environmental compatibility, consumer's profit, costs of maintenance and efficiency. The key question is economy. This will be decided by the costs of fuel cell systems if they are to be used as power generators for future electric vehicles. The alkaline hydrogen-air fuel cell system with circulating KOH electrolyte and low-cost catalysed carbon electrodes could be a promising alternative. Based on the experiences of Kordesch [K. Kordesch, Brennstoffbatterien, Springer, Wien, 1984, ISBN 3-387-81819-7; K. Kordesch, City car with H 2-air fuel cell and lead-battery, SAE Paper No. 719015, 6th IECEC, 1971], who operated a city car hybrid vehicle on public roads for 3 years in the early 1970s, improved air electrodes plus new variations of the bipolar stack assembly developed in Graz are investigated. Primary fuel choice will be a major issue until such time as cost-effective, on-board hydrogen storage is developed. Ammonia is an interesting option. The whole system, ammonia dissociator plus alkaline fuel cell (AFC), is characterised by a simple design and high efficiency.

  1. based anion exchange membrane for alkaline polymer electrolyte

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Hydroxyl ion (OH–) conducting anion exchange membranes based on modified poly (phenylene oxide) are fabricated for their application in alkaline polymer electrolyte fuel cells (APEFCs). In the present study, chloromethylation of poly(phenylene oxide) (PPO) is performed by aryl substitution rather than benzyl.

  2. The cellular prion protein interacts with the tissue non-specific alkaline phosphatase in membrane microdomains of bioaminergic neuronal cells.

    Directory of Open Access Journals (Sweden)

    Myriam Ermonval

    Full Text Available BACKGROUND: The cellular prion protein, PrP(C, is GPI anchored and abundant in lipid rafts. The absolute requirement of PrP(C in neurodegeneration associated to prion diseases is well established. However, the function of this ubiquitous protein is still puzzling. Our previous work using the 1C11 neuronal model, provided evidence that PrP(C acts as a cell surface receptor. Besides a ubiquitous signaling function of PrP(C, we have described a neuronal specificity pointing to a role of PrP(C in neuronal homeostasis. 1C11 cells, upon appropriate induction, engage into neuronal differentiation programs, giving rise either to serotonergic (1C11(5-HT or noradrenergic (1C11(NE derivatives. METHODOLOGY/PRINCIPAL FINDINGS: The neuronal specificity of PrP(C signaling prompted us to search for PrP(C partners in 1C11-derived bioaminergic neuronal cells. We show here by immunoprecipitation an association of PrP(C with an 80 kDa protein identified by mass spectrometry as the tissue non-specific alkaline phosphatase (TNAP. This interaction occurs in lipid rafts and is restricted to 1C11-derived neuronal progenies. Our data indicate that TNAP is implemented during the differentiation programs of 1C11(5-HT and 1C11(NE cells and is active at their cell surface. Noteworthy, TNAP may contribute to the regulation of serotonin or catecholamine synthesis in 1C11(5-HT and 1C11(NE bioaminergic cells by controlling pyridoxal phosphate levels. Finally, TNAP activity is shown to modulate the phosphorylation status of laminin and thereby its interaction with PrP. CONCLUSION/SIGNIFICANCE: The identification of a novel PrP(C partner in lipid rafts of neuronal cells favors the idea of a role of PrP in multiple functions. Because PrP(C and laminin functionally interact to support neuronal differentiation and memory consolidation, our findings introduce TNAP as a functional protagonist in the PrP(C-laminin interplay. The partnership between TNAP and PrP(C in neuronal cells may

  3. Porous poly(perfluorosulfonic acid) membranes for alkaline water electrolysis

    DEFF Research Database (Denmark)

    Aili, David; Hansen, Martin Kalmar; Andreasen, Jens Wenzel

    2015-01-01

    Poly(perfluorosulfonic acid) (PFSA) is one of a few polymer types that combine excellent alkali resistance with extreme hydrophilicity. It is therefore of interest as a base material in separators for alkaline water electrolyzers. In the pristine form it, however, shows high cation selectivity. T...... for the unmodified membrane. The technological feasibility was demonstrated by testing the membranes in an alkaline water electrolysis cell with encouraging performance.......Poly(perfluorosulfonic acid) (PFSA) is one of a few polymer types that combine excellent alkali resistance with extreme hydrophilicity. It is therefore of interest as a base material in separators for alkaline water electrolyzers. In the pristine form it, however, shows high cation selectivity...... and washed out and the obtained porous materials allowed for swelling to reach water contents up to λ=85 [H2O] [−SO3K]−1. After equilibration in 22 wt% aqueous KOH, ion conductivity of 0.2 S cm−1 was recorded for this membrane type at room temperature, which is significantly higher than 0.01 S cm−1...

  4. Analysis of alkaline exchange membrane fuel cells performance at different operating conditions using DC and AC methods

    Science.gov (United States)

    Reshetenko, Tatyana; Odgaard, Madeleine; Schlueter, Debbie; Serov, Alexey

    2018-01-01

    Membrane electrode assemblies (MEAs) for anion exchange membrane fuel cells (AEMFCs) were manufactured from commercial materials: Pt/C catalyst, A201 AEM and AS4 ionomer by using an industrial mass-production digital printing method. The MEA designs selected are close to those recommended by US Department of Energy, including low loading of platinum on the cathode side (0.2 mg cm-2). Polarization curves and electrochemical impedance spectroscopy (EIS) were applied for MEA evaluation in fuel cell conditions with variation of gas humidification and oxygen partial pressure (air vs oxygen). The typical impedance curves recorded at H2/O2 gas configuration consist of high- and medium-frequency arcs responsible for hydrogen oxidation and oxygen reduction, respectively. Operation with air as a cathode feed gas resulted in a decrease in AEMFC performance due to possible CO2 poisoning and mass transfer losses. At the same time, EIS demonstrated formation of a low frequency loop due to diffusion limitations. Despite the low loading of platinum on the cathode (0.2 mg cm-2), a peak power density of ∼330 mW cm-2 was achieved (at 50/50% of RH on anode and cathode), which is substantially higher performance than for AEMFC MEAs tested at similar conditions.

  5. Fumed Silica Nanoparticles Incorporated in Quaternized Poly(Vinyl Alcohol Nanocomposite Membrane for Enhanced Power Densities in Direct Alcohol Alkaline Fuel Cells

    Directory of Open Access Journals (Sweden)

    Selvaraj Rajesh Kumar

    2015-12-01

    Full Text Available A nanocomposite polymer membrane based on quaternized poly(vinyl alcohol/fumed silica (QPVA/FS was prepared via a quaternization process and solution casting method. The physico-chemical properties of the QPVA/FS membrane were investigated. Its high ionic conductivity was found to depend greatly on the concentration of fumed silica in the QPVA matrix. A maximum conductivity of 3.50 × 10−2 S/cm was obtained for QPVA/5%FS at 60 °C when it was doped with 6 M KOH. The permeabilities of methanol and ethanol were reduced with increasing fumed silica content. Cell voltage and peak power density were analyzed as functions of fumed silica concentration, temperature, methanol and ethanol concentrations. A maximum power density of 96.8 mW/cm2 was achieved with QPVA/5%FS electrolyte using 2 M methanol + 6 M KOH as fuel at 80 °C. A peak power density of 79 mW/cm2 was obtained using the QPVA/5%FS electrolyte with 3 M ethanol + 5 M KOH as fuel. The resulting peak power densities are higher than the majority of published reports. The results confirm that QPVA/FS exhibits promise as a future polymeric electrolyte for use in direct alkaline alcoholic fuel cells.

  6. Development of Preparation Methods for Alkaline Anion Exchange Membranes by Radiation

    International Nuclear Information System (INIS)

    Shin, Jun Hwa; Nho, Young Chang; Sohn, Joon Yong

    2010-01-01

    The objective of this project is to contribute to the environmentally friendly fuel cell system by developing a radiation grafting method for the preparation of anion exchange membranes for alkaline fuel cell and finally to the radiation technology industry. In this project, the preparation methods for the VBC-grafted fluoropolymer films using radiation have been developed and anion exchange membranes have been prepared via the reaction between the VBC-grafted fluoropolymer films and amines. The prepared anion exchange membranes were characterized and the performance of the membranes were evaluated

  7. Cationic Polymers Developed for Alkaline Fuel Cell Applications

    Science.gov (United States)

    2015-01-20

    into five categories: proton exchange membrane fuel cell ( PEMFC ), alkaline fuel cell (AFC), molten carbonate fuel cell (MCFC), solid oxide fuel...SOFC and PAFC belong to high temperature fuel cell, which can be applied in stationary power generation. PEMFC and AFC belong to low temperature fuel...function of the polymer electrolyte is to serve as electrolyte to transport ions between electrodes. PEMFC uses a polymer as electrolyte and works

  8. Substrate Specificity, Membrane Topology, and Activity Regulation of Human Alkaline Ceramidase 2 (ACER2)*

    OpenAIRE

    Sun, Wei; Jin, Junfei; Xu, Ruijuan; Hu, Wei; Szulc, Zdzislaw M.; Bielawski, Jacek; Obeid, Lina M.; Mao, Cungui

    2010-01-01

    Human alkaline ceramidase 2 (ACER2) plays an important role in cellular responses by regulating the hydrolysis of ceramides in cells. Here we report its biochemical characterization, membrane topology, and activity regulation. Recombinant ACER2 was expressed in yeast mutant cells (Δypc1Δydc1) that lack endogenous ceramidase activity, and microsomes from ACER2-expressiong yeast cells were used to biochemically characterize ACER2. ACER2 catalyzed the hydrolysis of various ceramides and followed...

  9. Principles and Materials Aspects of Direct Alkaline Alcohol Fuel Cells

    Directory of Open Access Journals (Sweden)

    Eileen Hao Yu

    2010-08-01

    Full Text Available Direct alkaline alcohol fuel cells (DAAFCs have attracted increasing interest over the past decade because of their favourable reaction kinetics in alkaline media, higher energy densities achievable and the easy handling of the liquid fuels. In this review, principles and mechanisms of DAAFCs in alcohol oxidation and oxygen reduction are discussed. Despite the high energy densities available during the oxidation of polycarbon alcohols they are difficult to oxidise. Apart from methanol, the complete oxidation of other polycarbon alcohols to CO2 has not been achieved with current catalysts. Different types of catalysts, from conventional precious metal catalyst of Pt and Pt alloys to other lower cost Pd, Au and Ag metal catalysts are compared. Non precious metal catalysts, and lanthanum, strontium oxides and perovskite-type oxides are also discussed. Membranes like the ones used as polymer electrolytes and developed for DAAFCs are reviewed. Unlike conventional proton exchange membrane fuel cells, anion exchange membranes are used in present DAAFCs. Fuel cell performance with DAAFCs using different alcohols, catalysts and membranes, as well as operating parameters are summarised. In order to improve the power output of the DAAFCs, further developments in catalysts, membrane materials and fuel cell systems are essential.

  10. Preparation and performance evaluation of novel alkaline stable anion exchange membranes

    Science.gov (United States)

    Irfan, Muhammad; Bakangura, Erigene; Afsar, Noor Ul; Hossain, Md. Masem; Ran, Jin; Xu, Tongwen

    2017-07-01

    Novel alkaline stable anion exchange membranes are prepared from various amounts of N-methyl dipicolylamine (MDPA) and brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). The dipicolylamine and MDPA are synthesized through condensation reaction and confirmed by 1H NMR spectroscopy. The morphologies of prepared membranes are investigated by atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), 1H NMR spectroscopy and scanning electron microscopy (SEM). The electrochemical and physical properties of AEMs are tested comprising water uptake (WU), ion exchange capacity (IEC), alkaline stability, linear expansion ratio (LER), thermal stability and mechanical stability. The obtained hydroxide conductivity of MDPA-4 is 66.5 mS/cm at 80 °C. The MDPA-4 membrane shows good alkaline stability, high hydroxide conductivity, low methanol permeability (3.43 × 10-7 cm2/s), higher selectivity (8.26 × 107 mS s/cm3), less water uptake (41.1%) and lower linear expansion (11.1%) despite of high IEC value (1.62 mmol/g). The results prove that MDPA membranes have great potential application in anion exchange membrane fuel cell.

  11. Alkaline fuel cell technology in the lead

    International Nuclear Information System (INIS)

    Nor, J.K.

    2004-01-01

    The Alkaline Fuel Cell (AFC) was the first fuel cell successfully put into practice, a century after William Grove patented his 'hydrogen battery' in 1839. The space program provided the necessary momentum, and alkaline fuel cells became the power source for both the U.S. and Russian manned space flight. Astris Energi's mission has been to bring this technology down to earth as inexpensive, rugged fuel cells for everyday applications. The early cells, LABCELL 50 and LABCELL 200 were aimed at deployment in research labs, colleges and universities. They served well in technology demonstration projects such as the 1998 Mini Jeep, 2001 Golf Car and a series of portable and stationary fuel cell generators. The present third generation POWERSTACK MC250 poised for commercialization is being offered to AFC system integrators as a building block of fuel cell systems in numerous portable, stationary and transportation applications. It is also used in Astris' own E7 and E8 alkaline fuel cell generators. Astris alkaline technology leads the way toward economical, plentiful fuel cells. The paper highlights the progress achieved at Astris, improvements of performance, durability and simplicity of use, as well as the current and future thrust in technology development and commercialization. (author)

  12. Alkaline Phosphatase in Stem Cells

    Czech Academy of Sciences Publication Activity Database

    Štefková, K.; Procházková, Jiřina; Pachernik, J.

    2015-01-01

    Roč. 2015, č. 2015 (2015) ISSN 1687-966X Institutional support: RVO:68081707 Keywords : PRIMORDIAL GERM-CELLS * P38 MAP KINASE * EMBRYONAL CARCINOMA-CELLS Subject RIV: BO - Biophysics Impact factor: 3.687, year: 2015

  13. Novel inorganic materials for polymer electrolyte and alkaline fuel cells

    Science.gov (United States)

    Tadanaga, Kiyoharu

    2012-06-01

    Inorganic materials with high ionic conductivity must have big advantages for the thermal and long term stability when the materials are used as the electrolyte of fuel cells. In the present paper, novel ionic conductive inorganic materials for polymer electrolyte fuel cells (PEFCs) and all solid state alkaline fuel cells (AFCs) that have been developed by our group have been reviewed. PEFCs which can operate in temperature range from 100 to 200 °C are intensively studied because of some advantages such as reduction of CO poisoning of Pt catalyst and acceleration of electrode reactions. We showed that the fuel cells using the composite membranes prepared from phosphosilicate gel powder and polyimide precursor can operate in the temperature range from 30 to 180 °C. We also found that the inorganic-organic hybrid membranes with acid-base pairs from 3-aminopropyl triethoxy silane and H2SO4 or H3PO4 show high proton conductivity under dry atmosphere, and the membranes are thermally stable at intermediate temperatures. On the other hand, because the use of noble platinum is the serious problem for the commercialization of PEFCs and because oxidation reactions are usually faster than those of acid-type fuel cells, alkaline type fuel cells, in which a nonplatinum catalyst can be used, are attractive. Recently, we have proposed an alkaline-type direct ethanol fuel cell (DEFC) using a natural clay electrolyte with non-platinum catalysts. So-called hydrotalcite clay, Mg-Al layered double hydroxide intercalated with CO32- (Mg-Al CO32- LDH), has been proved to be a hydroxide ion conductor. An alkalinetype DEFC using Mg-Al CO32- LDH as the electrolyte and aqueous solution of ethanol and potassium hydroxide as a source of fuel exhibited excellent electrochemical performance.

  14. A novel IrNi@PdIr/C core-shell electrocatalyst with enhanced activity and durability for the hydrogen oxidation reaction in alkaline anion exchange membrane fuel cells.

    Science.gov (United States)

    Qin, Bowen; Yu, Hongmei; Jia, Jia; Jun, Chi; Gao, Xueqiang; Yao, Dewei; Sun, Xinye; Song, Wei; Yi, Baolian; Shao, Zhigang

    2018-03-08

    Herein, a novel non-platinum core-shell catalyst, namely, IrNi@PdIr/C was prepared via a galvanic replacement reaction; it exhibits enhanced hydrogen oxidation activity and excellent stability under alkaline conditions. Electrochemical experiments demonstrated that the mass and specific activities at 50 mV of IrNi@PdIr/C are 2.1 and 2.2 times that of commercial Pt/C in 0.1 M KOH at 298 K, respectively. Moreover, accelerated degradation tests have shown that the electrochemically active surface area (ECSA) of IrNi@PdIr/C reduces by only 5.1%, which is almost 4 times less than that of commercial Pt/C and the mass activity at 50 mV of IrNi@PdIr/C after 2000 potential cycles is still 1.8 times higher than that of aged Pt/C. XRD and XPS analysis suggest that the enhanced HOR activity is attributed to the weakening of the hydrogen binding to the PdIr overlayers induced by the IrNi core. The better stability to potential cycling can be associated with the PdIr shell, which inhibits oxide formation. These results suggest that IrNi@PdIr/C is a promising non-platinum anode catalyst for alkaline anion exchange membrane fuel cells.

  15. Plasma-polymerized alkaline anion-exchange membrane: Synthesis and structure characterization

    International Nuclear Information System (INIS)

    Hu Jue; Meng Yuedong; Zhang Chengxu; Fang Shidong

    2011-01-01

    After-glow discharge plasma polymerization was developed for alkaline anion-exchange membranes synthesis using vinylbenzyl chloride as monomer. X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy were used to characterize the chemical structure properties of plasma-polymerized membranes. Ion-exchange capacities of quaternized poly(vinylbenzyl chloride) (QPVBC) membranes were measured to evaluate their capability of hydroxyl ion transport. A mechanism of plasma polymerization using VBC as monomer that accounts for the competitive effects of free radicals polymerization and plasma ablation in the plasma polymerization process was proposed. Our results indicate that plasma discharge power influences the contents of functional groups and the structure of the plasma polymer membranes, which attribute to the coactions of polymerization and ablation. The properties of uniform morphology, good adhesion to the substrate, high thermal stability and satisfying anion conduction level suggest the potential application of QPVBC membrane deposited at discharge power of 20 W in alkaline direct methanol fuel cells.

  16. Development of anionic membranes produced by radiation-grafting for alkaline fuel cell applications; Desenvolvimento de membranas aniônicas obtidas por enxertia via irradiação para aplicação em células a combustível alcalinas

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Clotilde Coppini

    2017-07-01

    Anion Exchange Membranes (AEMs) are a promising alternative to the development of more efficient electrolytes for alkaline fuel cells. In general, the AEMs are ionomeric membranes able to conduct hydroxide ions (OH{sup -}) due to the quaternary ammonium groups, which confer high pH equivalent to the AEM. In order to develop alkaline membranes with high chemical and thermal stability, besides satisfactory ionic conductivity for alkaline fuel cells, membranes based on low density polyethylene (LDPE), ultrahigh weight molecular weight polyethylene (UHWHPE), poly(ethylene-co-tetrafluoroethylene) (PETFE) and poly(hexafluoropropylene-co-tetrafluoroethylene) (PFEP) previously irradiated by using {sup 60}Co gamma and electron beam sources, have been synthesized by styrene-grafting, and functionalized with trimethylamine to introduced quaternary ammonium groups. The resulting membranes were characterized by electron paramagnetic resonance (EPR), Raman spectroscopy, thermogravimetry (TG) and electrochemical impedance spectroscopy (EIS). The determination of the grafting degree and water uptake were conducted by gravimetry and ion exchange capacity, by titration. The membranes synthesized with PELD and PEUHMW polymers pre-irradiated at 70 kGy and stored at low temperature (-70 deg C), up to 10 months, showed ionic conductivity results, in hydroxide form (OH{sup -}), of 29 mS.cm{sup -1} and 14 mS.cm{sup -1} at 65 deg C, respectively. The PFEP polymers irradiated by the simultaneous process showed insufficient grating levels for the membrane synthesis, requiring more studies to improve the irradiation and grafting process. The styrene-grafted PETFE membranes, pre-irradiated at 70 kGy and stored at low temperature (-70 deg C), up to 10 months, showed ionic conductivity results, in hydroxide form (OH{sup -}), of 90 mS.cm{sup -1} to 165 mS.cm{sup -1}, in the temperature range 30 to 60 deg C. Such results have demonstrated that LDPE, UHMWPE and PETFE based AEMs are promising

  17. The viability of MCM-41 as separator in secondary alkaline cells

    Science.gov (United States)

    Meskon, S. R.; Othman, R.; Ani, M. H.

    2018-01-01

    The viability of MCM-41 membrane as a separator material in secondary alkaline cell is investigated. The inorganic membrane was employed in an alkaline nickel-zinc system. MCM-41 mesoporous material consists of arrays of hexagonal nano-pore channels. The membrane was synthesized using sol-gel route from parent solution comprising of quarternary ammonium surfactant, cethyltrimethylammonium bromide C16H33(CH3)3NBr (CTAB), hydrochloric acid (HCl), deionized water (H2O), ethanol (C2H5OH), and tetraethylortosilicate (TEOS). Both the anodic zinc/zinc oxide and cathodic nickel hydroxide electrodeposited film were coated with MCM-41 membrane. The Ni/MCM-41/Zn alkaline cell was then subjected to 100-cycle durability test and the structural stability of MCM-41 separator throughout the progression of the charge-discharge cycles is studied. X-ray diffraction (XRD) analysis on the dismantled cell shows that MCM-41 began to transform to lamellar MCM-50 on the 5th cycle and transformed almost completely on the 25th cycle. The phase transformation of MCM-41 hexagonal structure into gel-like MCM-50 prevents the mesoporous cell separator from diminished in the caustic alkaline surround. This work has hence demonstrated MCM-41 membrane is viable to be employed in secondary alkaline cells.

  18. Technological development and prospect of alkaline fuel cells

    International Nuclear Information System (INIS)

    Meng Ni; Michael KH Leung; Dennis YC Leung

    2006-01-01

    This paper reviewed the technological development of alkaline fuel cell (AFC). Although the technology was popular in 1970's and 1980's, there has been a decline in AFC research over the past decade, mainly due to the poisoning of CO 2 . Continuous efforts have demonstrated that CO 2 concentration could be reduced to an acceptable level by a number of viable methods such as absorption, adsorption, electrochemical process, electrolyte circulation, use of liquid hydrogen, and use of solid anionic exchange membranes. Literature survey showed that AFC lifetime could achieve up to 5000 hours. In addition, the use of ammonia as a fuel for AFC was identified as a promising technology. Comparison between AFC and proton exchange membrane fuel cell (PEMFC) was presented to evaluate the AFC technology and its economics. The present review and assessment showed the promise of AFC for the coming hydrogen economy and sustainable development. (authors)

  19. Osteocalcin and bone-specific alkaline phosphatase in Sickle cell ...

    African Journals Online (AJOL)

    specific alkaline phosphatase (b-AP) total protein levels were evaluated as indicators of bone turnover in twenty patients with sickle cell haemoglobinopathies and in twenty normal healthy individuals. The serum bonespecific alkaline phosphatase ...

  20. Heterogeneous anion conducting membranes based on linear and crosslinked KOH doped polybenzimidazole for alkaline water electrolysis

    DEFF Research Database (Denmark)

    Aili, David; Hansen, Martin Kalmar; Renzaho, Richard Fulgence

    2013-01-01

    Polybenzimidazole is a highly hygroscopic polymer that can be doped with aqueous KOH to give a material with high ion conductivity in the 10−2Scm−1 range, which in combination with its low gas permeability makes it an interesting electrolyte material for alkaline water electrolysis. In this study...... on their linear counterpart. The technical feasibility of the membranes was evaluated by the preliminary water electrolysis tests showing performance comparable to that of commercially available cell separators with great potential of further improvement....

  1. Alkaline membrane water electrolysis with non-noble catalysts

    DEFF Research Database (Denmark)

    Kraglund, Mikkel Rykær

    at 1.7 V and 2800 mA cm-2 at 2.0 V. Electrochemical impedance spectroscopy data showed a 6-fold reduction in ohmic cell resistance compared to conventional materials. Albeit good performance, ex-situ characterization and durability tests showed that polymer backbone and membrane stability remained......As renewable energy sources reach higher grid penetration, large scale energy storage solutions are becoming increasingly important. Hydrogen produced with renewable energy by water electrolysis is currently the only option to solve this challenge on a global scale, and green hydrogen is essential...

  2. Properties of cathode materials in alkaline cells

    International Nuclear Information System (INIS)

    Salkind, A.J.; McBreen, J.; Freeman, R.; Parkhurst, W.A.

    1985-01-01

    Conventional and new cathode materials in primary and secondary alkaline cells were investigated for stability, structure, electrochemical reversibility and efficiency. Included were various forms of AgO for reserve-type silver-zinc batteries, a new material - AgNiO/sub 2/ - and several nickel electrodes for nickel-cadmium and nickel-hydrogen cells for aerospace applications. A comparative study was made of the stability of electroformed and chemically prepared AgO. Stability was correlated with impurities detected by XPS and SAM. After the first discharge AgNiO/sub 2/ can be recharged to the monovalent level. The discharge product is predominantly silver. Plastic-bonded nickel electrodes display a second plateau on discharge. Additions of Co(OH)/sub 2/ largely eliminate this

  3. Hydroxide Self-Feeding High-Temperature Alkaline Direct Formate Fuel Cells.

    Science.gov (United States)

    Li, Yinshi; Sun, Xianda; Feng, Ying

    2017-05-22

    Conventionally, both the thermal degradation of the anion-exchange membrane and the requirement of additional hydroxide for fuel oxidation reaction hinder the development of the high-temperature alkaline direct liquid fuel cells. The present work addresses these two issues by reporting a polybenzimidazole-membrane-based direct formate fuel cell (DFFC). Theoretically, the cell voltage of the high-temperature alkaline DFFC can be as high as 1.45 V at 90 °C. It has been demonstrated that a proof-of-concept alkaline DFFC without adding additional hydroxide yields a peak power density of 20.9 mW cm -2 , an order of magnitude higher than both alkaline direct ethanol fuel cells and alkaline direct methanol fuel cells, mainly because the hydrolysis of formate provides enough OH - ions for formate oxidation reaction. It was also found that this hydroxide self-feeding high-temperature alkaline DFFC shows a stable 100 min constant-current discharge at 90 °C, proving the conceptual feasibility. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Transport phenomena in alkaline direct ethanol fuel cells for sustainable energy production

    Science.gov (United States)

    An, L.; Zhao, T. S.

    2017-02-01

    Alkaline direct ethanol fuel cells (DEFC), which convert the chemical energy stored in ethanol directly into electricity, are one of the most promising energy-conversion devices for portable, mobile and stationary power applications, primarily because this type of fuel cell runs on a carbon-neutral, sustainable fuel and the electrocatalytic and membrane materials that constitute the cell are relatively inexpensive. As a result, the alkaline DEFC technology has undergone a rapid progress over the last decade. This article provides a comprehensive review of transport phenomena of various species in this fuel cell system. The past investigations into how the design and structural parameters of membrane electrode assemblies and the operating parameters affect the fuel cell performance are discussed. In addition, future perspectives and challenges with regard to transport phenomena in this fuel cell system are also highlighted.

  5. Fuel cell membrane humidification

    Science.gov (United States)

    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.

  6. Membrane treatment of alkaline bleaching effluents from elementary chlorine free kraft softwood cellulose production.

    Science.gov (United States)

    Oñate, Elizabeth; Rodríguez, Edgard; Bórquez, Rodrigo; Zaror, Claudio

    2015-01-01

    This paper reports experimental results on the sequential use of ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) to fractionate alkaline extraction bleaching effluents from kraft cellulose production. The aim was to unveil the way key pollutants are distributed when subjected to sequential UF/NF/RO membrane separation processes. Alkaline bleaching effluents were obtained from a local pinewood-based mill, featuring elementary chlorine free bleaching to produce high-brightness cellulose. The experimental system was based on a laboratory-scale membrane system, DSS LabStak® M20 Alfa Laval, using Alfa Laval UF and NF/RO membranes, operated at a constant transmembrane pressure (6 bar for UF membranes and 32 bar for NF/RO membranes), at 25°C. Results show that 78% chemical oxygen demand (COD) and total phenols, 82% adsorbable organic halogens (AOX) and 98% colour were retained by UF membranes which have molecular weight cut-off (MWCO) above 10 kDa. In all, 16% of original COD, total phenols and AOX, and the remaining 2% colour were retained by UF membranes within the 1 to 10 kDa MWCO range. Chloride ions were significantly present in all UF permeates, and RO was required to obtain a high-quality permeate with a view to water reuse. It is concluded that UF/NF/RO membranes offer a feasible option for water and chemicals recovery from alkaline bleaching effluents in kraft pulp production.

  7. A micro alkaline direct ethanol fuel cell with platinum-free catalysts

    Science.gov (United States)

    Verjulio, R. W.; Alcaide, F.; Álvarez, G.; Sabaté, N.; Torres-Herrero, N.; Esquivel, J. P.; Santander, J.

    2013-11-01

    This paper presents the fabrication and characterization of a micro alkaline direct ethanol fuel cell. The device has been conceived as a feasibility demonstrator, using microtechnologies for the fabrication of the current collectors and traditional techniques for the membrane electrode assembly production. The fuel cell works in passive mode, as expected for the simplicity required for micro power systems. Non-noble catalysts have been used in order to implement the main advantage of alkaline systems, showing the feasibility of such a device as a potential very-low-cost power device at mini- and micro scales.

  8. A micro alkaline direct ethanol fuel cell with platinum-free catalysts

    International Nuclear Information System (INIS)

    Verjulio, R W; Sabaté, N; Torres-Herrero, N; Esquivel, J P; Santander, J; Alcaide, F; Álvarez, G

    2013-01-01

    This paper presents the fabrication and characterization of a micro alkaline direct ethanol fuel cell. The device has been conceived as a feasibility demonstrator, using microtechnologies for the fabrication of the current collectors and traditional techniques for the membrane electrode assembly production. The fuel cell works in passive mode, as expected for the simplicity required for micro power systems. Non-noble catalysts have been used in order to implement the main advantage of alkaline systems, showing the feasibility of such a device as a potential very-low-cost power device at mini- and micro scales. (paper)

  9. Production of alkaline protease by Teredinobacter turnirae cells ...

    African Journals Online (AJOL)

    The conditions for immobilizing the new alkaline protease-producing bacteria strain Teredinobacter turnirae by entrapment in calcium alginate gel were investigated. The influence of alginate concentration (20, 25 and 30 g/l) and initial cell loading (ICL) on enzyme production were studied. The production of alkaline ...

  10. Dietary free fatty acids form alkaline phosphatase-enriched microdomains in the intestinal brush border membrane

    DEFF Research Database (Denmark)

    Hansen, Gert H; Rasmussen, Karina; Niels-Christiansen, Lise-Lotte

    2011-01-01

    this membrane passage in organ cultured intestinal mucosal explants. We found that in addition to a rapid uptake into the cytoplasm, a fraction of the fatty acid analogs were inserted directly into the brush border membrane. Furthermore, a brief exposure of microvillar membrane vesicles to a fat mixture...... mimicking a physiological solution of dietary mixed micelles, rearranged the lipid raft microdomain organization of the membranes. Thus, the fat mixture generated a low-density subpopulation of microvillar detergent resistant membranes (DRMs) highly enriched in alkaline phosphatase (AP). Since this GPI-linked...... enzyme is the membrane protein in the brush border with the highest affinity for lipid rafts, this implies that free fatty acids selectively insert stably into these membrane microdomains. We have previously shown that absorption of dietary lipids transiently induce a selective endocytosis of AP from...

  11. Carbonate and Bicarbonate Ion Transport in Alkaline Anion Exchange Membranes

    Science.gov (United States)

    2013-06-25

    comparable assumptions, a similar equation can be derived starting with the Nernst -Planck equation . σ = ∑ σi = ∑ F2z2i RT (ε− ε0)q D0i 1 + δi Ci [1] Using Eq...an appropriate ion-membrane diffusion coefficient. Finally, an equation derived from the dusty fluid model can be used to calculate the ionic...Finally, an equation derived from the dusty fluid model can be used to calculate the ionic conductivity of the membrane in different counter ion forms

  12. Proton exchange membrane fuel cells

    CERN Document Server

    Qi, Zhigang

    2013-01-01

    Preface Proton Exchange Membrane Fuel CellsFuel CellsTypes of Fuel CellsAdvantages of Fuel CellsProton Exchange Membrane Fuel CellsMembraneCatalystCatalyst LayerGas Diffusion MediumMicroporous LayerMembrane Electrode AssemblyPlateSingle CellStackSystemCell Voltage Monitoring Module (CVM)Fuel Supply Module (FSM)Air Supply Module (ASM)Exhaust Management Module (EMM)Heat Management Module (HMM)Water Management Module (WMM)Internal Power Supply Module (IPM)Power Conditioning Module (PCM)Communications Module (COM)Controls Module (CM)SummaryThermodynamics and KineticsTheoretical EfficiencyVoltagePo

  13. Preparation of anion exchange membrane using polyvinyl chloride (PVC) for alkaline water electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Gab-Jin; Bong, Soo-Yeon; Ryu, Cheol-Hwi [Hoseo University, Asan (Korea, Republic of); Lim, Soo-Gon [Energy and Machinery Korea Co., Ltd., Changwon (Korea, Republic of); Choi, Ho-Sang [Kyungil University, Gyeongsan (Korea, Republic of)

    2015-09-15

    An anion exchange membrane was prepared by the chloromethylation and the amination of polyvinyl chloride (PVC), as the base polymer. The membrane properties of the prepared anion exchange membrane, including ionic conductivity, ion exchange capacity, and water content were measured. The ionic conductivity of the prepared anion exchange membrane was in the range of 0.098x10{sup -2} -7.0x10{sup -2}S cm{sup -1}. The ranges of ion exchange capacity and water content were 1.9-3.7meq./g-dry-membrane and 35.1-63.1%, respectively. The chemical stability of the prepared anion exchange membrane was tested by soaking in 30 wt% KOH solution to determine its availability as a separator in the alkaline water electrolysis. The ionic conductivity during the chemical stability test largely did not change.

  14. Tumor-promoting phorbol esters effect alkalinization of canine renal proximal tubular cells

    International Nuclear Information System (INIS)

    Mellas, J.; Hammerman, M.R.

    1986-01-01

    We have demonstrated the presence of specific receptors for tumor-promoting phorbol esters in the plasma membrane of the canine renal proximal tubular cell. These compounds affect proximal tubular metabolism in vitro. For example, we have shown that they inhibit gluconeogenesis in canine renal proximal tubular segments. Tumor-promoting phorbol esters have been shown to effect alkalinization of non-renal cells, by enhancing Na + -H + exchange across the plasma membrane. To determine whether the actions of tumor-promoting phorbol esters in proximal tubular segments might be mediated by a similar process, we incubated suspensions of segments from dog kidney with these compounds and measured changes in intracellular pH using [ 14 C]-5,5-dimethoxazoladine-2-4-dione (DMO) and flow dialysis. Incubation of segments with phorbol 12,13 dibutyrate, but not inactive phorbol ester, 4 γ phorbol, effected alkalinization of cells within the segments in a concentration-dependent manner. Alkalinization was dependent upon the presence of extracellular [Na + ] > intracellular [Na + ], was prevented by amiloride and was demonstrable in the presence of SITS. Our findings suggest that tumor-promoting esters stimulate the Na + -H + exchanger known to be present in the brush border membrane of the renal proximal tubular cell. It is possible that the stimulation reflects a mechanism by which phorbol esters affect metabolic processes in these cells

  15. Radiation effects on cell membranes

    International Nuclear Information System (INIS)

    Koeteles, G.J.

    1982-01-01

    The recent developments in the field of membrane biology of eukaryotic cells result in revival of relevant radiobiological studies. The spatial relations and chemical nature of membrane components provide rather sensitive targets. Experimental data are presented concerning the effects of relatively low doses of X-irradiation and low concentration of tritiated water (HTO) on various receptor functions - concanavalin A, cationized ferritin, poliovirus - of plasma membranes of animal and human cells which point to early and temporary disturbances of the composite structures and functions of membranes. References are given to the multifold roles of radiationinduced membrane phenomena on the development and regeneration of radiation injuries. (orig.)

  16. Radiation effects on cell membranes

    Energy Technology Data Exchange (ETDEWEB)

    Koeteles, G.J.

    1982-11-01

    The recent developments in the field of membrane biology of eukaryotic cells result in revival of relevant radiobiological studies. The spatial relations and chemical nature of membrane components provide rather sensitive targets. Experimental data are presented concerning the effects of relatively low doses of X-irradiation and low concentration of tritiated water (HTO) on various receptor functions - concanavalin A, cationized ferritin, poliovirus - of plasma membranes of animal and human cells which point to early and temporary disturbances of the composite structures and functions of membranes. References are given to the multifold roles of radiationinduced membrane phenomena on the development and regeneration of radiation injuries.

  17. Alkaline Comet Assay for Assessing DNA Damage in Individual Cells.

    Science.gov (United States)

    Pu, Xinzhu; Wang, Zemin; Klaunig, James E

    2015-08-06

    Single-cell gel electrophoresis, commonly called a comet assay, is a simple and sensitive method for assessing DNA damage at the single-cell level. It is an important technique in genetic toxicological studies. The comet assay performed under alkaline conditions (pH >13) is considered the optimal version for identifying agents with genotoxic activity. The alkaline comet assay is capable of detecting DNA double-strand breaks, single-strand breaks, alkali-labile sites, DNA-DNA/DNA-protein cross-linking, and incomplete excision repair sites. The inclusion of digestion of lesion-specific DNA repair enzymes in the procedure allows the detection of various DNA base alterations, such as oxidative base damage. This unit describes alkaline comet assay procedures for assessing DNA strand breaks and oxidative base alterations. These methods can be applied in a variety of cells from in vitro and in vivo experiments, as well as human studies. Copyright © 2015 John Wiley & Sons, Inc.

  18. hydrogel membrane as electrolyte for direct borohydride fuel cells

    Indian Academy of Sciences (India)

    A direct borohydride fuel cell (DBFC) employing a poly (vinyl alcohol) hydrogel membrane electrolyte (PHME) is reported. The DBFC employs an AB5 Misch metal alloy as anode and a goldplated stainless steel mesh as cathode in conjunction with aqueous alkaline solution of sodium borohydride as fuel and aqueous ...

  19. Zero-Gap Alkaline Water Electrolysis Using Ion-Solvating Polymer Electrolyte Membranes at Reduced KOH Concentrations

    DEFF Research Database (Denmark)

    Kraglund, Mikkel Rykær; Aili, David; Jankova Atanasova, Katja

    2016-01-01

    Membranes based on poly(2,2'-(m-phenylene)-5,5-bibenzimidazole) (m-PBI) can dissolve large amounts of aqueous KOH to give electrolyte systems with ion conductivity in a practically useful range. The conductivity of the membrane strongly depends on the concentration of the aqueous KOH phase......, reaching about 10-1 S cm-1 or higher in 15-25 wt% KOH. Herein, m-PBI membranes are systematically characterized with respect to performance and short-term stability as electrolyte in a zero-gap alkaline water electrolyzer at different KOH concentrations. Using plain uncatalyzed nickel foam electrodes......, the cell based on m-PBI outperforms the cell based on the commercially available state-of-the-art diaphragm and reaches a current density of 1500 mA cm-2 at 2.4 V in 20 wt% KOH at 80°C. The cell performance remained stable during two days of operation, though post analysis of the membrane using size...

  20. Model cell membranes

    DEFF Research Database (Denmark)

    Günther-Pomorski, Thomas; Nylander, Tommy; Cardenas Gomez, Marite

    2014-01-01

    The high complexity of biological membranes has motivated the development and application of a wide range of model membrane systems to study biochemical and biophysical aspects of membranes in situ under well defined conditions. The aim is to provide fundamental understanding of processes control...

  1. Endurance test and evaluation of alkaline water electrolysis cells

    Science.gov (United States)

    Burke, K. A.; Schubert, F. H.

    1981-01-01

    Utilization in the development of multi-kW low orbit power systems is discussed. The following technological developments of alkaline water electrolysis cells for space power application were demonstrated: (1) four 92.9 cm2 single water electrolysis cells, two using LST's advanced anodes and two using LST's super anodes; (2) four single cell endurance test stands for life testing of alkaline water electrolyte cells; (3) the solid performance of the advanced electrode and 355 K; (4) the breakthrough performance of the super electrode; (5) the four single cells for over 5,000 hours each significant cell deterioration or cell failure. It is concluded that the static feed water electrolysis concept is reliable and due to the inherent simplicity of the passive water feed mechanism coupled with the use of alkaline electrolyte has greater potential for regenerative fuel cell system applications than alternative electrolyzers. A rise in cell voltage occur after 2,000-3,000 hours which was attributed to deflection of the polysulfone end plates due to creepage of the thermoplastic. More end plate support was added, and the performance of the cells was restored to the initial performance level.

  2. Modification of the Selectivity Properties of Tubular Ceramic Membranes after Alkaline Treatment

    Directory of Open Access Journals (Sweden)

    Patrick Dutournié

    2017-11-01

    Full Text Available This work focuses on the selectivity modification of ceramic membranes after a mild alkaline treatment. Filtration of pure salt-water solutions was carried out with commercial titania membranes before and after the treatment. After treatment, the rejection of NaF significantly decreased, while the rejection of NaCl and NaBr increased. Additionally, NaI and Na2SO4 remained close to zero. Pore size and electrical charge being almost unchanged, only significant modifications in the dielectric effects can explain this modification of selectivity. Therefore, the surface chemistry and the interaction (nature and magnitude with the solvent and with the species present in the solution appear to be modified by the alkaline treatment. This trend is also illustrated by discussing the electric and the dielectric properties that were numerically identified before and after treatment. The alkaline treatment significantly decreased the apparent dielectric constant of NaCl-water solution in the pore, highlighting the rejection of sodium chloride. Contrariwise, the modification of the surface chemistry increased the apparent dielectric constant of NaF-water solution by promoting fluoride transmission.

  3. Extraction of lithium ion from alkaline aqueous media by a liquid surfactant membrane

    International Nuclear Information System (INIS)

    Kinugasa, Takumi; Ono, Yuri; Kawamura, Yuko; Watanabe, Kunio; Takeuchi, Hiroshi.

    1995-01-01

    Extraction of lithium ion from aqueous alkaline media by a liquid surfactant membrane was performed using a mixture of LIX54 and TOPO as the extractant. Stripping of lithium from the kerosene solution to the acid solution was suppressed with increasing content of polyamine (ECA) surfactant. The extraction rate of lithium by the liquid membrane could be interpreted taking account of an interfacial resistance due to ECA. It was confirmed that swelling of the (W/O) emulsion drops by water permeation through the liquid membrane is evaluated in terms of a change in osmotic pressure gradient between the external and internal aqueous phases during the lithium extraction. In the present operation, the extraction ratio of Li + from the external feed and the uptake into the internal phase reached as high as 95%. (author)

  4. Electrochemical kinetic and mass transfer model for direct ethanol alkaline fuel cell (DEAFC)

    Science.gov (United States)

    Abdullah, S.; Kamarudin, S. K.; Hasran, U. A.; Masdar, M. S.; Daud, W. R. W.

    2016-07-01

    A mathematical model is developed for a liquid-feed DEAFC incorporating an alkaline anion-exchange membrane. The one-dimensional mass transport of chemical species is modelled using isothermal, single-phase and steady-state assumptions. The anode and cathode electrochemical reactions use the Tafel kinetics approach, with two limiting cases, for the reaction order. The model fully accounts for the mixed potential effects of ethanol oxidation at the cathode due to ethanol crossover via an alkaline anion-exchange membrane. In contrast to a polymer electrolyte membrane model, the current model considers the flux of ethanol at the membrane as the difference between diffusive and electroosmotic effects. The model is used to investigate the effects of the ethanol and alkali inlet feed concentrations at the anode. The model predicts that the cell performance is almost identical for different ethanol concentrations at a low current density. Moreover, the model results show that feeding the DEAFC with 5 M NaOH and 3 M ethanol at specific operating conditions yields a better performance at a higher current density. Furthermore, the model indicates that crossover effects on the DEAFC performance are significant. The cell performance decrease from its theoretical value when a parasitic current is enabled in the model.

  5. Radiation effects on cell membranes

    International Nuclear Information System (INIS)

    Koeteles, G.J.

    1982-01-01

    Experimental data are presented concerning the effects of relatively low doses of x radiation and low concentration of tritiated water (HTO) on various receptor functions - concanavalin A, cationized ferritin, poliovirus of plasma membranes of animal and human cells which point to early and temporary disturbances of the composite structures and functions of membranes. References are given to the manifold influence of radiation-induced membrane phenomenon on the development and regeneration of radiation injuries. (author)

  6. Towards Extrusion of Ionomers to Process Fuel Cell Membranes

    Directory of Open Access Journals (Sweden)

    Jean-Yves Sanchez

    2011-07-01

    Full Text Available While Proton Exchange Membrane Fuel Cell (PEMFC membranes are currently prepared by film casting, this paper demonstrates the feasibility of extrusion, a solvent-free alternative process. Thanks to water-soluble process-aid plasticizers, duly selected, it was possible to extrude acidic and alkaline polysulfone ionomers. Additionally, the feasibility to extrude composites was demonstrated. The impact of the plasticizers on the melt viscosity was investigated. Following the extrusion, the plasticizers were fully removed in water. The extrusion was found to impact neither on the ionomer chains, nor on the performances of the membrane. This environmentally friendly process was successfully validated for a variety of high performance ionomers.

  7. Stress-life interrelationships associated with alkaline fuel cells

    Science.gov (United States)

    Thaller, Lawrence H.; Martin, Ronald E.; Stedman, James K.

    1987-01-01

    A review is presented concerning the interrelationships between applied stress and the expected service life of alkaline fuel cells. Only the physical, chemical, and electrochemical phenomena that take place within the fuel cell stack portion of an overall fuel cell system will be discussed. A brief review will be given covering the significant improvements in performance and life over the past two decades as well as summarizing the more recent advances in understanding which can be used to predict the performance and life characteristics of fuel cell systems that have yet to be built.

  8. POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

    DEFF Research Database (Denmark)

    2001-01-01

    A method for preparing polybenzimidazole or polybenzimidazole blend membranes and fabricating gas diffusion electrodes and membrane-electrode assemblies is provided for a high temperature polymer electrolyte membrane fuel cell. Blend polymer electrolyte membranes based on PBI and various...... thermoplastic polymers for high temperature polymer electrolyte fuel cells have also been developed. Miscible blends are used for solution casting of polymer membranes (solid electrolytes). High conductivity and enhanced mechanical strength were obtained for the blend polymer solid electrolytes....... With the thermally resistant polymer, e.g., polybenzimidazole or a mixture of polybenzimidazole and other thermoplastics as binder, the carbon-supported noble metal catalyst is tape-cast onto a hydrophobic supporting substrate. When doped with an acid mixture, electrodes are assembled with an acid doped solid...

  9. Membranes for direct ethanol fuel cells: An overview

    International Nuclear Information System (INIS)

    Zakaria, Z.; Kamarudin, S.K.; Timmiati, S.N.

    2016-01-01

    Highlights: • DEFCs have emerged as alternative energy source. • But many issue need to be addressed. • This paper describes current problem and advancement of membrane in DEFC. - Abstract: Direct ethanol fuel cells (DEFCs) are attractive as a power source options because ethanol is a nontoxic, leading to ease of handling and a high energy density fuel, leading to high system energy density. However, to provide practical DEFCs power source there are several issues that still must be addressed including low power density, effect of ethanol crossover on efficiency of fuel utilization, electrical, mechanical and thermal stability and water uptake of the DEFCs electrolyte membrane. This paper describes the proton exchange membrane and alkaline exchange membrane for DEFCs, focusing on current problems and advancements in DEFC membranes. It also presents the specifications and performances of the membranes used in DEFC.

  10. Model-based analysis of water management in alkaline direct methanol fuel cells

    Science.gov (United States)

    Weinzierl, C.; Krewer, U.

    2014-12-01

    Mathematical modelling is used to analyse water management in Alkaline Direct Methanol Fuel Cells (ADMFCs) with an anion exchange membrane as electrolyte. Cathodic water supply is identified as one of the main challenges and investigated at different operation conditions. Two extreme case scenarios are modelled to study the feasible conditions for sufficient water supply. Scenario 1 reveals that water supply by cathodic inlet is insufficient and, thus, water transport through membrane is essential for ADMFC operation. The second scenario is used to analyse requirements on water transport through the membrane for different operation conditions. These requirements are influenced by current density, evaporation rate, methanol cross-over and electro-osmotic drag of water. Simulations indicate that water supply is mainly challenging for high current densities and demands on high water diffusion are intensified by water drag. Thus, current density might be limited by water transport through membrane. The presented results help to identify important effects and processes in ADMFCs with a polymer electrolyte membrane and to understand these processes. Furthermore, the requirements identified by modelling show the importance of considering water transport through membrane besides conductivity and methanol cross-over especially for designing new membrane materials.

  11. Extracellular Alkalinization as a Defense Response in Potato Cells.

    Science.gov (United States)

    Moroz, Natalia; Fritch, Karen R; Marcec, Matthew J; Tripathi, Diwaker; Smertenko, Andrei; Tanaka, Kiwamu

    2017-01-01

    A quantitative and robust bioassay to assess plant defense response is important for studies of disease resistance and also for the early identification of disease during pre- or non-symptomatic phases. An increase in extracellular pH is known to be an early defense response in plants. In this study, we demonstrate extracellular alkalinization as a defense response in potatoes. Using potato suspension cell cultures, we observed an alkalinization response against various pathogen- and plant-derived elicitors in a dose- and time-dependent manner. We also assessed the defense response against a variety of potato pathogens, such as protists ( Phytophthora infestans and Spongospora subterranea ) and fungi ( Verticillium dahliae and Colletotrichum coccodes ). Our results show that extracellular pH increases within 30 min in proportion to the number of pathogen spores added. Consistently with the alkalinization effect, the higher transcription level of several defense-related genes and production of reactive oxygen species was observed. Our results demonstrate that the alkalinization response is an effective marker to study early stages of defense response in potatoes.

  12. Endurance Test and Evaluation of Alkaline Water Electrolysis Cells

    Science.gov (United States)

    Kovach, Andrew J.; Schubert, Franz H.; Chang, B. J.; Larkins, Jim T.

    1985-01-01

    The overall objective of this program is to assess the state of alkaline water electrolysis cell technology and its potential as part of a Regenerative Fuel Cell System (RFCS) of a multikilowatt orbiting powerplant. The program evaluates the endurance capabilities of alkaline electrolyte water electrolysis cells under various operating conditions, including constant condition testing, cyclic testing and high pressure testing. The RFCS demanded the scale-up of existing cell hardware from 0.1 sq ft active electrode area to 1.0 sq ft active electrode area. A single water electrolysis cell and two six-cell modules of 1.0 sq ft active electrode area were designed and fabricated. The two six-cell 1.0 sq ft modules incorporate 1.0 sq ft utilized cores, which allow for minimization of module assembly complexity and increased tolerance to pressure differential. A water electrolysis subsystem was designed and fabricated to allow testing of the six-cell modules. After completing checkout, shakedown, design verification and parametric testing, a module was incorporated into the Regenerative Fuel Cell System Breadboard (RFCSB) for testing at Life Systems, Inc., and at NASA JSC.

  13. Cell membranes in radiation injury

    International Nuclear Information System (INIS)

    Koeteles, G.J.

    1986-01-01

    Cell membrane-related phenomena caused by low linear energy transfer radiation with doses lower than those producing cell killing are outlined. Micromorphological alterations as well as functional activities appearing with the receptors and in binding sites render it possible to reveal early and temporary changes. The cell injuries are suggested to transfer damaging conditions to surviving cells and to contribute to further development of non-stochastic effects in tissues

  14. Seeking effective dyes for a mediated glucose-air alkaline battery/fuel cell

    Science.gov (United States)

    Eustis, Ross; Tsang, Tsz Ming; Yang, Brigham; Scott, Daniel; Liaw, Bor Yann

    2014-02-01

    A significant level of power generation from an abiotic, air breathing, mediated reducing sugar-air alkaline battery/fuel cell has been achieved in our laboratories at room temperature without complicated catalysis or membrane separation in the reaction chamber. Our prior studies suggested that mass transport limitation by the mediator is a limiting factor in power generation. New and effective mediators were sought here to improve charge transfer and power density. Forty-five redox dyes were studied to identify if any can facilitate mass transport in alkaline electrolyte solution; namely, by increasing the solubility and mobility of the dye, and the valence charge carried per molecule. Indigo dyes were studied more closely to understand the complexity involved in mass transport. The viability of water-miscible co-solvents was also explored to understand their effect on solubility and mass transport of the dyes. Using a 2.0 mL solution, 20% methanol by volume, with 100 mM indigo carmine, 1.0 M glucose and 2.5 M sodium hydroxide, the glucose-air alkaline battery/fuel cell attained 8 mA cm-2 at short-circuit and 800 μW cm-2 at the maximum power point. This work shall aid future optimization of mediated charge transfer mechanism in batteries or fuel cells.

  15. Foam Based Gas Diffusion Electrodes for Reversible Alkaline Electrolysis Cells

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    Alkaline electrolysis cells operated at 250 °C and 40 bar have shown to be able to convert electrical energy into hydrogen at very high efficiencies and power densities. Foam based gas diffusion electrodes and an immobilized electrolyte allow for reversible operation as electrolysis cell or fuel...... cell. In the present work we demonstrate the application of hydrophobic, porous, and electro-catalytically active gas diffusion electrodes. PTFE particles and silver nanowires as electro-catalysts were used in the gas diffusion electrodes. Impedance spectroscopy and cyclic voltammetry were performed...... to determine the cell characteristics. The thickness of the electrolyte matrix was only 200 µm, thereby achieving a serial resistance and area specific resistance of 60 mΩ cm2 and 150 mΩ cm2, respectively, at 200 °C and 20 bar. A new production method was developed to increase the cell size from lab scale (1...

  16. Foam Based Gas Diffusion Electrodes for Reversible Alkaline Electrolysis Cells

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    Alkaline electrolysis cells operated at 250 °C and 40 bar have shown to be able to convert electrical energy into chemical energy in the form of hydrogen at very high efficiencies and power densities. Foam based gas diffusion electrodes and a liquid immobilized electrolyte allow the operation...... of the newly designed electrolysis cell as a fuel cell, but condensation of steam may lead to blocked pores, thereby inhibiting gas diffusion and decreasing the performance of the cell. In the here presented work we present the application of a hydrophobic, porous, and electro-catalytically active layer...... the electrochemical characteristics of the cell. The thickness of the electrolyte matrix was reduced to 200 µm, thereby achieving a serial resistance and area specific resistance as low as 60 mΩ cm2 and 150 mΩ cm2, respectively, at a temperature of 200 °C and 20 bar pressure. A new production method was developed...

  17. Ethanol tolerant precious metal free cathode catalyst for alkaline direct ethanol fuel cells

    International Nuclear Information System (INIS)

    Grimmer, Ilena; Zorn, Paul; Weinberger, Stephan; Grimmer, Christoph; Pichler, Birgit; Cermenek, Bernd; Gebetsroither, Florian; Schenk, Alexander; Mautner, Franz-Andreas

    2017-01-01

    Highlights: • Selective ORR catalysts are presented for alkaline direct ethanol fuel cells. • Perovskite based cathode catalysts show high tolerance toward ethanol. • A membrane-free alkaline direct ethanol fuel cell is presented. - Abstract: La 0.7 Sr 0.3 (Fe 0.2 Co 0.8 )O 3 and La 0.7 Sr 0.3 MnO 3 −based cathode catalysts are synthesized by the sol-gel method. These perovskite cathode catalysts are tested in half cell configuration and compared to MnO 2 as reference material in alkaline direct ethanol fuel cells (ADEFCs). The best performing cathode is tested in single cell setup using a standard carbon supported Pt 0.4 Ru 0.2 based anode. A backside Luggin capillary is used in order to register the anode potential during all measurements. Characteristic processes of the electrodes are investigated using electrochemical impedance spectroscopy. Physical characterizations of the perovskite based cathode catalysts are performed with a scanning electron microscope (SEM) and by X-ray diffraction showing phase pure materials. In half cell setup, La 0.7 Sr 0.3 MnO 3 shows the highest tolerance toward ethanol with a performance of 614 mA cm −2 at 0.65 V vs. RHE in 6 M KOH and 1 M EtOH at RT. This catalyst outperforms the state-of-the-art precious metal-free MnO 2 catalyst in presence of ethanol. In fuel cell setup, the peak power density is 27.6 mW cm −2 at a cell voltage of 0.345 V and a cathode potential of 0.873 V vs. RHE.

  18. Alkaline elution of DNA from mammalian cells on cellulose triacetate filters

    International Nuclear Information System (INIS)

    Moss, A.J. Jr.; Nagle, W.A.; Henle, K.J.; Prior, R.M.

    1984-01-01

    The alkaline elution technique is widely used for the estimation of cellular DNA damage because of its sensitivity in the biologically relevant dose range. The authors have extended the original studies and provide additional characterization of the cellulose triacetate alkaline elution method. This filter material permits the elution of approximately 80 percent of cellular DNA from untreated V79 cells. the total radioactivity in the system was compartmentalized with respect to 1) lysing solution, 2) washing solution, 3) elution fractions, and 4) membrane retained activity. In these studies [/sup 3/H]-thymidine labeled untreated internal control cells were co-eluted with X-irradiated [/sup 14/C]-thymidine labeled cells. For the estimation of DNA damage, elution profiles for treated cells were directly compared with untreated internal control cells. The quantity of DNA eluting in excess of the labeled internal control per fraction is directly proportional to the extent of DNA damage in the treated sample. Using the technique the necessity of an irradiated internal control is eliminated

  19. Molecular machines open cell membranes.

    Science.gov (United States)

    García-López, Víctor; Chen, Fang; Nilewski, Lizanne G; Duret, Guillaume; Aliyan, Amir; Kolomeisky, Anatoly B; Robinson, Jacob T; Wang, Gufeng; Pal, Robert; Tour, James M

    2017-08-30

    Beyond the more common chemical delivery strategies, several physical techniques are used to open the lipid bilayers of cellular membranes. These include using electric and magnetic fields, temperature, ultrasound or light to introduce compounds into cells, to release molecular species from cells or to selectively induce programmed cell death (apoptosis) or uncontrolled cell death (necrosis). More recently, molecular motors and switches that can change their conformation in a controlled manner in response to external stimuli have been used to produce mechanical actions on tissue for biomedical applications. Here we show that molecular machines can drill through cellular bilayers using their molecular-scale actuation, specifically nanomechanical action. Upon physical adsorption of the molecular motors onto lipid bilayers and subsequent activation of the motors using ultraviolet light, holes are drilled in the cell membranes. We designed molecular motors and complementary experimental protocols that use nanomechanical action to induce the diffusion of chemical species out of synthetic vesicles, to enhance the diffusion of traceable molecular machines into and within live cells, to induce necrosis and to introduce chemical species into live cells. We also show that, by using molecular machines that bear short peptide addends, nanomechanical action can selectively target specific cell-surface recognition sites. Beyond the in vitro applications demonstrated here, we expect that molecular machines could also be used in vivo, especially as their design progresses to allow two-photon, near-infrared and radio-frequency activation.

  20. Molecular machines open cell membranes

    Science.gov (United States)

    García-López, Víctor; Chen, Fang; Nilewski, Lizanne G.; Duret, Guillaume; Aliyan, Amir; Kolomeisky, Anatoly B.; Robinson, Jacob T.; Wang, Gufeng; Pal, Robert; Tour, James M.

    2017-08-01

    Beyond the more common chemical delivery strategies, several physical techniques are used to open the lipid bilayers of cellular membranes. These include using electric and magnetic fields, temperature, ultrasound or light to introduce compounds into cells, to release molecular species from cells or to selectively induce programmed cell death (apoptosis) or uncontrolled cell death (necrosis). More recently, molecular motors and switches that can change their conformation in a controlled manner in response to external stimuli have been used to produce mechanical actions on tissue for biomedical applications. Here we show that molecular machines can drill through cellular bilayers using their molecular-scale actuation, specifically nanomechanical action. Upon physical adsorption of the molecular motors onto lipid bilayers and subsequent activation of the motors using ultraviolet light, holes are drilled in the cell membranes. We designed molecular motors and complementary experimental protocols that use nanomechanical action to induce the diffusion of chemical species out of synthetic vesicles, to enhance the diffusion of traceable molecular machines into and within live cells, to induce necrosis and to introduce chemical species into live cells. We also show that, by using molecular machines that bear short peptide addends, nanomechanical action can selectively target specific cell-surface recognition sites. Beyond the in vitro applications demonstrated here, we expect that molecular machines could also be used in vivo, especially as their design progresses to allow two-photon, near-infrared and radio-frequency activation.

  1. Investigation of an alkaline direct ethanol fuel cell with non Pt-catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, M.; Guelzow, E.; Uhm, S. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Stuttgart (Germany). Inst. fuer Technische Thermodynamik

    2010-07-01

    This paper focuses on the characterisation of an alkaline direct ethanol fuel cell (ADEFC). Ethanol and for comparison also methanol was fed to the anode in a caustic potash solution at different concentrations and temperatures. An anion exchange membrane (Tokuyama) sandwiched between two Hypermec electrodes (Acta SpA.) was investigated in a single cell. Current-voltage-measurements (U(I) characteristics), short term operation under load, electrochemical impedance spectroscopy (EIS) and pH recording were carried out to characterize fuel cell performance. The long term objective is to investigate the mechanism of ethanol electro oxidation reaction (EOR). 18 mW/cm{sup 2} was reached at room temperature with a technically oriented 50 cm{sup 2} cell with ethanol. However, poor long term stability under load of the fuel cell is observed. Furthermore in the U(I) characteristics a negative hysteresis is present in the forward and backward scan at room temperature which indicates poisoning intermediates of electrode reactions. A pH decline appears during operation indicating a development of either acetic acid or acetates or acetaldehyde as main products of the ethanol oxidation, which may be responsible for rate decrease of ethanol oxidation with time. EIS measurement shows an increased membrane resistance. (orig.)

  2. Alkaline direct ethanol fuel cell performance using alkali-impregnated polyvinyl alcohol/functionalized carbon nano-tube solid electrolytes

    Science.gov (United States)

    Huang, Chien-Yi; Lin, Jia-Shiun; Pan, Wen-Han; Shih, Chao-Ming; Liu, Ying-Ling; Lue, Shingjiang Jessie

    2016-01-01

    This study investigates the application of a polyvinyl alcohol (PVA)/functionalized carbon nano-tubes (m-CNTs) composite in alkaline direct ethanol fuel cells (ADEFC). The m-CNTs are functionalized with PVA using the ozone mediation method, and the PVA composite containing the modified CNTs is prepared. Adding m-CNT into the PVA matrix enhances the alkaline uptake and the ionic conductivity of the KOH-doped electrolyte. Meanwhile, the m-CNT-containing membrane exhibited a lower swelling ratio and suppressed ethanol permeability compared to the pristine PVA film. The optimal condition for the ADEFC is determined to be under operation at an anode feed of 3 M ethanol in a 5 M KOH solution (at a flow rate of 5 cm3 min-1) with a cathode feed of moisturized oxygen (with a flow rate of 100 cm3 min-1) and the KOH-doped PVA/m-CNT electrolyte. We achieved a peak power density value of 65 mW cm-2 at 60 °C, which is the highest among the ADEFC literature data and several times higher than the proton-exchange direct ethanol fuel cells using sulfonated membrane electrolytes. Therefore, the KOH-doped PVA/m-CNT electrolyte is a suitable solid electrolyte for ADEFCs and has potential for commercialization in alkaline fuel cell applications.

  3. Fuel-Cell Structure Prevents Membrane Drying

    Science.gov (United States)

    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.

  4. Introducing Membrane Charge and Membrane Potential to T Cell Signaling

    Directory of Open Access Journals (Sweden)

    Yuanqing Ma

    2017-11-01

    Full Text Available While membrane models now include the heterogeneous distribution of lipids, the impact of membrane charges on regulating the association of proteins with the plasma membrane is often overlooked. Charged lipids are asymmetrically distributed between the two leaflets of the plasma membrane, resulting in the inner leaflet being negatively charged and a surface potential that attracts and binds positively charged ions, proteins, and peptide motifs. These interactions not only create a transmembrane potential but they can also facilitate the formation of charged membrane domains. Here, we reference fields outside of immunology in which consequences of membrane charge are better characterized to highlight important mechanisms. We then focus on T cell receptor (TCR signaling, reviewing the evidence that membrane charges and membrane-associated calcium regulate phosphorylation of the TCR–CD3 complex and discuss how the immunological synapse exhibits distinct patterns of membrane charge distribution. We propose that charged lipids, ions in solution, and transient protein interactions form a dynamic equilibrium during T cell activation.

  5. A Tenebrio molitor GPI-anchored alkaline phosphatase is involved in binding of Bacillus thuringiensis Cry3Aa to brush border membrane vesicles.

    Science.gov (United States)

    Zúñiga-Navarrete, Fernando; Gómez, Isabel; Peña, Guadalupe; Bravo, Alejandra; Soberón, Mario

    2013-03-01

    Bacillus thuringiensis Cry toxins recognizes their target cells in part by the binding to glycosyl-phosphatidyl-inositol (GPI) anchored proteins such as aminopeptidase-N (APN) or alkaline phosphatases (ALP). Treatment of Tenebrio molitor brush border membrane vesicles (BBMV) with phospholipase C that cleaves out GPI-anchored proteins from the membranes, showed that GPI-anchored proteins are involved in binding of Cry3Aa toxin to BBMV. A 68 kDa GPI-anchored ALP was shown to bind Cry3Aa by toxin overlay assays. The 68 kDa GPI-anchored ALP was preferentially expressed in early instar larvae in comparison to late instar larvae. Our work shows for the first time that GPI-anchored ALP is important for Cry3Aa binding to T. molitor BBMV suggesting that the mode of action of Cry toxins is conserved in different insect orders. Copyright © 2012 Elsevier Inc. All rights reserved.

  6. Pma1 is an alkali/alkaline earth metal cation ATPase that preferentially transports Na(+) and K(+) across the Mycobacterium smegmatis plasma membrane.

    Science.gov (United States)

    Ayala-Torres, Carlos; Novoa-Aponte, Lorena; Soto, Carlos Y

    2015-07-01

    Mycobacterium smegmatis Pma1 is the orthologue of M. tuberculosis P-type ATPase cation transporter CtpF, which is activated under stress conditions, such as hypoxia, starvation and response to antituberculous and toxic substances. The function of Pma1 in the mycobacterial processes across the plasma membrane has not been characterised. In this work, bioinformatic analyses revealed that Pma1 likely contains potential sites for, Na(+), K(+) and Ca(2+) binding and transport. Accordingly, RT-qPCR experiments showed that M. smegmatis pma1 transcription is stimulated by sub-lethal doses of Na(+), K(+) and Ca(2+); in addition, the ATPase activity of plasma membrane vesicles in recombinant Pma1-expressing M. smegmatis cells is stimulated by treatment with these cations. In contrast, M. smegmatis cells homologously expressing Pma1 displayed tolerance to high doses of Na(+) and K(+) but not to Ca(2+) ions. Consistently, the recombinant protein Km embedded in plasma membrane demonstrated that Ca(2+) has more affinity for Pma1 than Na(+) and K(+) ions; furthermore, the estimation of Vmax/Km suggests that Na(+) and K(+) ions are more efficiently translocated than Ca(2+). Thus, these results strongly suggest that Pma1 is a promiscuous alkali/alkaline earth cation ATPase that preferentially transports Na(+) and/or K(+) across the mycobacterial plasma membrane. Copyright © 2015 Elsevier GmbH. All rights reserved.

  7. [Germ cell membrane lipids in spermatogenesis].

    Science.gov (United States)

    Wang, Ting; Shi, Xiao; Quan, Song

    2016-05-01

    Spermatogenesis is a complex developmental process in which a diploid progenitor germ cell transforms into highly specialized spermatozoa. During spermatogenesis, membrane remodeling takes place, and cell membrane permeability and liquidity undergo phase-specific changes, which are all associated with the alteration of membrane lipids. Lipids are important components of the germ cell membrane, whose volume and ratio fluctuate in different phases of spermatogenesis. Abnormal lipid metabolism can cause spermatogenic dysfunction and consequently male infertility. Germ cell membrane lipids are mainly composed of cholesterol, phospholipids and glycolipids, which play critical roles in cell adhesion and signal transduction during spermatogenesis. An insight into the correlation of membrane lipids with spermatogenesis helps us to better understand the mechanisms of spermatogenesis and provide new approaches to the diagnosis and treatment of male infertility.

  8. Lipids as organizers of cell membranes.

    Science.gov (United States)

    Kornmann, Benoît; Roux, Aurélien

    2012-08-01

    The 105th Boehringer Ingelheim Fonds International Titisee Conference 'Lipids as Organizers of Cell Membranes' took place in March 2012, in Germany. Kai Simons and Gisou Van der Goot gathered cell biologists and biophysicists to discuss the interplay between lipids and proteins in biological membranes, with an emphasis on how technological advances could help fill the gap in our understanding of the lipid part of the membrane.

  9. A Comparison of Water Diffusion in Polymer Based Fuel Cell and Reverse Osmosis Membrane Materials

    Science.gov (United States)

    Soles, Christopher; Frieberg, Bradley; Tarver, Jacob; Tyagi, Madhusudan; Jeong, Cheol; Chan, Edwin; Stafford, Christopher

    Hydrated polymer membranes are critical in both fuel cells and water filtration and desalination. In both of these applications the membrane function (selectively transporting or separating ions) is coupled with the transport of water through the membrane. There is a significant need to understand the nature by which the water and ions distribute and move through these membranes. This presentation compares the transport mechanisms in in an ion containing block copolymer alkaline fuel cell membrane with that of a polyamide membrane that is used as the active layer in a reverse osmosis water desalination membrane. Small angle neutron scattering measurements are used to locally probe how water swells the different materials and quantitatively describe the distribution of water within the membrane microstructures. Quasielastic neutron scattering measurements are then used to separate the polymer dynamics of the host membranes from the dynamics of the water inside the membranes. This reveals that water moves at least an order of magnitude slower through the ion containing fuel cell membrane materials, consistent with a solution-diffusion model, while the water in the polyamide membranes moves faster, consistent with a pore-flow diffusion mechanism. These insights will be discussed in terms of a coupling of the water and polymer dynamics and design cues for high performance membrane materials.

  10. Interaction of Defensins with Model Cell Membranes

    Science.gov (United States)

    Sanders, Lori K.; Schmidt, Nathan W.; Yang, Lihua; Mishra, Abhijit; Gordon, Vernita D.; Selsted, Michael E.; Wong, Gerard C. L.

    2009-03-01

    Antimicrobial peptides (AMPs) comprise a key component of innate immunity for a wide range of multicellular organisms. For many AMPs, activity comes from their ability to selectively disrupt and lyse bacterial cell membranes. There are a number of proposed models for this action, but the detailed molecular mechanism of selective membrane permeation remains unclear. Theta defensins are circularized peptides with a high degree of selectivity. We investigate the interaction of model bacterial and eukaryotic cell membranes with theta defensins RTD-1, BTD-7, and compare them to protegrin PG-1, a prototypical AMP, using synchrotron small angle x-ray scattering (SAXS). The relationship between membrane composition and peptide induced changes in membrane curvature and topology is examined. By comparing the membrane phase behavior induced by these different peptides we will discuss the importance of amino acid composition and placement on membrane rearrangement.

  11. Asymmetric membranes for destabilization of oil droplets in produced water from alkaline-surfactant-polymer (ASP) flooding

    Science.gov (United States)

    Ramlee, Azierah; Chiam, Chel-Ken; Sarbatly, Rosalam

    2018-05-01

    This work presents a study of destabilization of oil droplets in the produced water from alkaline-surfactant-polymer (ASP) flooding by using four types of laboratory-fabricated polyvinylidene fluoride (PVDF) membranes. The PVDF membranes were fabricated via immersion precipitation method with ethanol (0 - 30 %, v/v) as the coagulant. The membranes with the effective area of 17.35 cm2 were tested with synthesized ASP solution as the feed in cross-flow microfiltration process. The ASP feed solution initially contained the oil droplets with radius ranged from 40 to 100 nm and the mean radius was 61 nm. Results have shown that the concentration of the ethanol in the coagulation bath affects the formation of the membrane structure and the corresponding porosity, while no significance influence on the membrane thickness. Coalescence of the oil droplets was occurred when the ASP solution permeated through the asymmetric PVDF membranes. Through the coalescence process, the oil droplets were destabilized where the radius of the oil droplets in the permeates increased to 1.5-4 µm with the corresponding mean radius ranged from 2.4 to 2.7 µm.

  12. Functional dynamics of cell surface membrane proteins.

    Science.gov (United States)

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

    2014-04-01

    Cell surface receptors are integral membrane proteins that receive external stimuli, and transmit signals across plasma membranes. In the conventional view of receptor activation, ligand binding to the extracellular side of the receptor induces conformational changes, which convert the structure of the receptor into an active conformation. However, recent NMR studies of cell surface membrane proteins have revealed that their structures are more dynamic than previously envisioned, and they fluctuate between multiple conformations in an equilibrium on various timescales. In addition, NMR analyses, along with biochemical and cell biological experiments indicated that such dynamical properties are critical for the proper functions of the receptors. In this review, we will describe several NMR studies that revealed direct linkage between the structural dynamics and the functions of the cell surface membrane proteins, such as G-protein coupled receptors (GPCRs), ion channels, membrane transporters, and cell adhesion molecules. Copyright © 2013 Elsevier Inc. All rights reserved.

  13. Alkaline anion exchange membrane water electrolysis: Effects of electrolyte feed method and electrode binder content

    Science.gov (United States)

    Cho, Min Kyung; Park, Hee-Young; Lee, Hye Jin; Kim, Hyoung-Juhn; Lim, Ahyoun; Henkensmeier, Dirk; Yoo, Sung Jong; Kim, Jin Young; Lee, So Young; Park, Hyun S.; Jang, Jong Hyun

    2018-04-01

    Herein, we investigate the effects of catholyte feed method and anode binder content on the characteristics of anion exchange membrane water electrolysis (AEMWE) to construct a high-performance electrolyzer, revealing that the initial AEMWE performance is significantly improved by pre-feeding 0.5 M aqueous KOH to the cathode. The highest long-term activity during repeated voltage cycling is observed for AEMWE operation in the dry cathode mode, for which the best long-term performance among membrane electrode assemblies (MEAs) featuring polytetrafluoroethylene (PTFE) binder-impregnated (5-20 wt%) anodes is detected for a PTFE content of 20 wt%. MEAs with low PTFE content (5 and 9 wt%) demonstrate high initial performance, rapid performance decay, and significant catalyst loss from the electrode during long-term operation, whereas the MEA with 20 wt% PTFE allows stable water electrolysis for over 1600 voltage cycles. Optimization of cell operating conditions (i.e., operation in dry cathode mode at an optimum anode binder content following an initial solution feed) achieves an enhanced water splitting current density (1.07 A cm-2 at 1.8 V) and stable long-term AEMWE performance (0.01% current density reduction per voltage cycle).

  14. Corneal regeneration by induced human buccal mucosa cultivated on an amniotic membrane following alkaline injury.

    Science.gov (United States)

    Man, Rohaina Che; Yong, Then Kong; Hwei, Ng Min; Halim, Wan Haslina Wan Abdul; Zahidin, Aida Zairani Mohd; Ramli, Roszalina; Saim, Aminuddin Bin; Idrus, Ruszymah Binti Hj

    2017-01-01

    Various clinical disorders and injuries, such as chemical, thermal, or mechanical injuries, may lead to corneal loss that results in blindness. PURPOSE : The aims of this study were to differentiate human buccal mucosa (BMuc) into corneal epithelial-like cells, to fabricate engineered corneal tissue using buccal mucosal epithelial cells, and to reconstruct a damaged corneal epithelium in a nude rat model. BMuc were subjected to 10 d of induction factors to investigate the potential of cells to differentiate into corneal lineages. Corneal stem cell markers β1-integrin, C/EBPδ, ABCG2, p63, and CK3 were upregulated in the gene expression analysis in induced BMuc, whereas CK3 and p63 showed significant protein expression in induced BMuc compared to the uninduced cells. BMuc were then left to reach 80% confluency after differential trypsinization. The cells were harvested and cultivated on a commercially available untreated air-dried amniotic membrane (AM) in a Transwell system in induction medium. The corneal constructs were fabricated and then implanted into damaged rat corneas for up to 8 weeks. A significant improvement was detected in the treatment group at 8 weeks post-implantation, as revealed by slit lamp biomicroscopy analysis. The structure and thickness of the corneal layer were also analyzed using histological staining and time-domain optical coherence tomography scans and were found to resemble a native corneal layer. The protein expression for CK3 and p63 were continuously detected throughout the corneal epithelial layer in the corneal construct. In conclusion, human BMuc can be induced to express a corneal epithelial-like phenotype. The addition of BMuc improves corneal clarity, prevents vascularization, increases corneal thickness and stromal alignment, and appears to have no adverse effect on the host after implantation.

  15. Cellular reactions of osteoblast-like cells to a novel nanocomposite membrane for guided bone regeneration

    International Nuclear Information System (INIS)

    Meng Yao; Liu Man; Wang Shaoan; Mo Anchun; Huang, Cui; Zuo Yi; Li Jidong

    2008-01-01

    This study investigated the bioactivity and biocompatibility of hydroxyapatite nanoparticles (n-HA)/Polyamide-66 (PA66) nanocomposite membrane and expanded-polytetrafluoroethylene (e-PTFE) membrane (as control) to MG63 osteoblast-like cells. The attachment and proliferation of the cells on the porous surface of nHA/PA66 membrane and the surface of e-PTFE membrane were evaluated by scanning electron microscope (SEM) observation and the MTT assay. The bioactivity of the cells on the surface of the two membranes was evaluated by testing cell viability and alkaline phosphatase (ALP) activities. The results suggested that the bioresponse of MG63 osteoblast-like cells on the porous surface of nHA/PA66 membrane was better than the bioresponse on the opposite surface of e-PTFE membrane. Because of a better cell attachment manner, there is a potential utilization of the guided bone regeneration (GBR) membrane to substitute nHA/PA66 membrane for e-PTFE membrane

  16. Membrane lipidome of an epithelial cell line

    DEFF Research Database (Denmark)

    Sampaio, Julio L; Gerl, Mathias J; Klose, Christian

    2011-01-01

    Tissue differentiation is an important process that involves major cellular membrane remodeling. We used Madin-Darby canine kidney cells as a model for epithelium formation and investigated the remodeling of the total cell membrane lipidome during the transition from a nonpolarized morphology...... to an epithelial morphology and vice versa. To achieve this, we developed a shotgun-based lipidomics workflow that enabled the absolute quantification of mammalian membrane lipidomes with minimal sample processing from low sample amounts. Epithelial morphogenesis was accompanied by a major shift from sphingomyelin...... to generate an apical membrane domain that serves as a protective barrier for the epithelial sheet....

  17. Functional imaging of microdomains in cell membranes.

    Science.gov (United States)

    Duggan, James; Jamal, Ghadir; Tilley, Mark; Davis, Ben; McKenzie, Graeme; Vere, Kelly; Somekh, Michael G; O'Shea, Paul; Harris, Helen

    2008-10-01

    The presence of microdomains or rafts within cell membranes is a topic of intense study and debate. The role of these structures in cell physiology, however, is also not yet fully understood with many outstanding problems. This problem is partly based on the small size of raft structures that presents significant problems to their in vivo study, i.e., within live cell membranes. But the structure and dynamics as well as the factors that control the assembly and disassembly of rafts are also of major interest. In this review we outline some of the problems that the study of rafts in cell membranes present as well as describing some views of what are considered the generalised functions of membrane rafts. We point to the possibility that there may be several different 'types' of membrane raft in cell membranes and consider the factors that affect raft assembly and disassembly, particularly, as some researchers suggest that the lifetimes of rafts in cell membranes may be sub-second. We attempt to review some of the methods that offer the ability to interrogate rafts directly as well as describing factors that appear to affect their functionality. The former include both near-field and far-field optical approaches as well as scanning probe techniques. Some of the advantages and disadvantages of these techniques are outlined. Finally, we describe our own views of raft functionality and properties, particularly, concerning the membrane dipole potential, and describe briefly some of the imaging strategies we have developed for their study.

  18. Alkaline and non-aqueous proton-conducting pouch-cell batteries

    Science.gov (United States)

    Young, Kwo-hsiung; Nei, Jean; Meng, Tiejun

    2018-01-02

    Provided are sealed pouch-cell batteries that are alkaline batteries or non-aqueous proton-conducing batteries. A pouch cell includes a flexible housing such as is used for pouch cell construction where the housing is in the form of a pouch, a cathode comprising a cathode active material suitable for use in an alkaline battery, an anode comprising an anode active material suitable for use in an alkaline battery, an electrolyte that is optionally an alkaline or proton-conducting electrolyte, and wherein the pouch does not include or require a safety vent or other gas absorbing or releasing system as the anode active material and the cathode active material do not increase the internal atmospheric pressure any more than 2 psig during cycling. The batteries provided function contrary to the art recognized belief that such battery systems were impossible due to unacceptable gas production during cycling.

  19. Polyarylenethioethersulfone Membranes for Fuel Cells (Postprint)

    Science.gov (United States)

    2010-01-01

    The Electrochemical SocietyProton exchange membrane fuel cells PEMFCs are an attrac- tive power source due to their energy efficiency and...standard in PEMFC technology.3,4 Nafion membranes have a polytetrafluoro- ethylene PTFE backbone, which provides thermal and chemical stability, and...diffusion layers to fabricate MEAs. Single-cell test (H- PEMFC ).— MEAs were positioned in a single-cell fixture with graphite blocks as current

  20. Diffuse Charge Effects in Fuel Cell Membranes

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Franco, A.A.; Bazant, M.Z.

    2009-01-01

    It is commonly assumed that electrolyte membranes in fuel cells are electrically neutral, except in unsteady situations, when the double-layer capacitance is heuristically included in equivalent circuit calculations. Indeed, the standard model for electron transfer kinetics at the membrane/electrode

  1. Cellular reactions of osteoblast-like cells to a novel nanocomposite membrane for guided bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Meng Yao [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Department of Orthodontics, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Liu Man [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Stomatology Health Care Center, Shenzhen Maternity and Child Healthcare Hospital, Shenzhen 518048 (China); Wang Shaoan [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Mo Anchun [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China)], E-mail: moanchun@163.com; Huang, Cui [State Key Laboratory of Oral Diseases, West China Stomatology Hospital, Sichuan University, Chengdu 610041 (China); Zuo Yi; Li Jidong [Research Center for Nano-biomaterials, Sichuan University, Chengdu 610041 (China)

    2008-11-15

    This study investigated the bioactivity and biocompatibility of hydroxyapatite nanoparticles (n-HA)/Polyamide-66 (PA66) nanocomposite membrane and expanded-polytetrafluoroethylene (e-PTFE) membrane (as control) to MG63 osteoblast-like cells. The attachment and proliferation of the cells on the porous surface of nHA/PA66 membrane and the surface of e-PTFE membrane were evaluated by scanning electron microscope (SEM) observation and the MTT assay. The bioactivity of the cells on the surface of the two membranes was evaluated by testing cell viability and alkaline phosphatase (ALP) activities. The results suggested that the bioresponse of MG63 osteoblast-like cells on the porous surface of nHA/PA66 membrane was better than the bioresponse on the opposite surface of e-PTFE membrane. Because of a better cell attachment manner, there is a potential utilization of the guided bone regeneration (GBR) membrane to substitute nHA/PA66 membrane for e-PTFE membra0008.

  2. USING CERAMIC MEMBRANES TO RECYCLE TWO NONIONIC ALKALINE METAL-CLEANING SOLUTIONS

    Science.gov (United States)

    One ZrO2 ultrafilter (0.05 um pore size) and two a-Al2O3 microfilters (0.2 and 0.8 um) were used to remove one synthetic ester oil and two polyalphaolefin-based and two petroleum hydrocarbon-based oils and greases from two nonionic alkaline cleaning solutions (e.g., Turco 4215-NC...

  3. Alkaline polymer electrolyte fuel cells stably working at 80 °C

    Science.gov (United States)

    Peng, Hanqing; Li, Qihao; Hu, Meixue; Xiao, Li; Lu, Juntao; Zhuang, Lin

    2018-06-01

    Alkaline polymer electrolyte fuel cells are a new class of polymer electrolyte fuel cells that fundamentally enables the use of nonprecious metal catalysts. The cell performance mostly relies on the quality of alkaline polymer electrolytes, including the ionic conductivity and the chemical/mechanical stability. For a long time, alkaline polymer electrolytes are thought to be too weak in stability to allow the fuel cell to be operated at elevated temperatures, e.g., above 60 °C. In the present work, we report a progress in the state-of-the-art alkaline polymer electrolyte fuel cell technology. By using a newly developed alkaline polymer electrolyte, quaternary ammonia poly (N-methyl-piperidine-co-p-terphenyl), which simultaneously possesses high ionic conductivity and excellent chemical/mechanical stability, the fuel cell can now be stably operated at 80 °C with high power density. The peak power density reaches ca. 1.5 W/cm2 at 80 °C with Pt/C catalysts used in both the anode and the cathode. The cell works stably in a period of study over 100 h.

  4. Membrane elastic properties and cell function.

    Directory of Open Access Journals (Sweden)

    Bruno Pontes

    Full Text Available 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.

  5. Durability of PEM Fuel Cell Membranes

    Science.gov (United States)

    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.

  6. Correlation between membrane fluidity cellular development and stem cell differentiation

    KAUST Repository

    Noutsi, Bakiza Kamal

    2016-01-01

    Cell membranes are made up of a complex structure of lipids and proteins that diffuse laterally giving rise to what we call membrane fluidity. During cellular development, such as neuronal differentiation, cell membranes undergo dramatic structural

  7. Nitrogen-Doped Nanoporous Carbon Membranes with Co/CoP Janus-Type Nanocrystals as Hydrogen Evolution Electrode in Both Acidic and Alkaline Environments

    KAUST Repository

    Wang, Hong

    2017-03-31

    Self-supported electrocatalysts being generated and employed directly as electrodes for energy conversion has been intensively pursued in the fields of materials chemistry and energy. Herein, we report a synthetic strategy to prepare freestanding hierarchically structured, nitrogen-doped nanoporous graphitic carbon membranes functionalized with Janus-type Co/CoP nanocrystals (termed as HNDCM-Co/CoP), which were successfully applied as a highly efficient, binder-free electrode in the hydrogen evolution reaction (HER). Benefited from multiple structural merits, such as a high degree of graphitization, three-dimensionally interconnected micro/meso/macropores, uniform nitrogen doping, well-dispersed Co/CoP nanocrystals, as well as the confinement effect of the thin carbon layer on the nanocrystals, HNDCM-Co/CoP exhibited superior electrocatalytic activity and long-term operation stability for HER under both acidic and alkaline conditions. As a proof-of-concept of practical usage, a 5.6 cm × 4 cm × 60 μm macroscopic piece of HNDCM-Co/CoP was prepared in our laboratory. Driven by a solar cell, electroreduction of water in alkaline conditions (pH 14) was performed, and H was produced at a rate of 16 mL/min, demonstrating its potential as real-life energy conversion systems.

  8. Cooperative tumour cell membrane targeted phototherapy

    Science.gov (United States)

    Kim, Heegon; Lee, Junsung; Oh, Chanhee; Park, Ji-Ho

    2017-06-01

    The targeted delivery of therapeutics using antibodies or nanomaterials has improved the precision and safety of cancer therapy. However, the paucity and heterogeneity of identified molecular targets within tumours have resulted in poor and uneven distribution of targeted agents, thus compromising treatment outcomes. Here, we construct a cooperative targeting system in which synthetic and biological nanocomponents participate together in the tumour cell membrane-selective localization of synthetic receptor-lipid conjugates (SR-lipids) to amplify the subsequent targeting of therapeutics. The SR-lipids are first delivered selectively to tumour cell membranes in the perivascular region using fusogenic liposomes. By hitchhiking with extracellular vesicles secreted by the cells, the SR-lipids are transferred to neighbouring cells and further spread throughout the tumour tissues where the molecular targets are limited. We show that this tumour cell membrane-targeted delivery of SR-lipids leads to uniform distribution and enhanced phototherapeutic efficacy of the targeted photosensitizer.

  9. MONITORING REACTIONS IN ALKALINE DIRECT ETHANOL FUEL CELLS ASSEMBLED WITH NON-PT-CATALYST

    OpenAIRE

    Gülzow, Erich; Beyer, Monique; Friedrich, K. Andreas; Pengel, Stefanie; Fischer, Peter; Bettermann, Hans

    2011-01-01

    This contribution shows how Raman spectroscopy can be used to pursue chemical reactions within fuel cells. For this, the oxidation of ethanol occurring in an alkaline direct ethanolic fuel cell was investigated. The analysis of a sequence of Raman spectra recorded during the reaction shows that ethanol was solely oxidized to acetate in a unique reaction.

  10. Fuel cell subassemblies incorporating subgasketed thrifted membranes

    Science.gov (United States)

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

    2016-03-01

    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.

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

    Science.gov (United States)

    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.

  12. Reduced levels of membrane-bound alkaline phosphatase are common to lepidopteran strains resistant to Cry toxins from Bacillus thuringiensis.

    Directory of Open Access Journals (Sweden)

    Juan Luis Jurat-Fuentes

    Full Text Available Development of insect resistance is one of the main concerns with the use of transgenic crops expressing Cry toxins from the bacterium Bacillus thuringiensis. Identification of biomarkers would assist in the development of sensitive DNA-based methods to monitor evolution of resistance to Bt toxins in natural populations. We report on the proteomic and genomic detection of reduced levels of midgut membrane-bound alkaline phosphatase (mALP as a common feature in strains of Cry-resistant Heliothis virescens, Helicoverpa armigera and Spodoptera frugiperda when compared to susceptible larvae. Reduced levels of H. virescens mALP protein (HvmALP were detected by two dimensional differential in-gel electrophoresis (2D-DIGE analysis in Cry-resistant compared to susceptible larvae, further supported by alkaline phosphatase activity assays and Western blotting. Through quantitative real-time polymerase chain reaction (qRT-PCR we demonstrate that the reduction in HvmALP protein levels in resistant larvae are the result of reduced transcript amounts. Similar reductions in ALP activity and mALP transcript levels were also detected for a Cry1Ac-resistant strain of H. armigera and field-derived strains of S. frugiperda resistant to Cry1Fa. Considering the unique resistance and cross-resistance phenotypes of the insect strains used in this work, our data suggest that reduced mALP expression should be targeted for development of effective biomarkers for resistance to Cry toxins in lepidopteran pests.

  13. Effect of ozone on leaf cell membranes

    Energy Technology Data Exchange (ETDEWEB)

    Swanson, E S; Thomson, W W; Mudd, J B

    1973-01-01

    The objective of this study was to determine the effects of ozone on membrane lipids and on the electron-density patterns of cell membranes in electron micrographs. Analysis of fatty acids from tobacco leaves fumigated with ozone indicated that there was no significant difference between the ozone-treated and the control plants in the relative amounts of the fatty acids. This suggests that if the primary site of ozone action is unsaturated lipids in membranes then the amounts of affected unsaturated fatty acids are too small to be detected by gas chromatography. In support of this, characteristic electron-microscopic images of membranes are observed in cells of fumigated leaves. However, measurements of the length and width of the chloroplasts and the determination of axial ratios indicated that the ozone treatment resulted in a shrinkage of the chloroplasts. In contrast, mitochondrial changes are apparently explained in terms of ozone-induced swelling. 33 references, 3 figures, 1 table.

  14. Cystic fibrosis transmembrane conductance regulator contributes to reacidification of alkalinized lysosomes in RPE cells.

    Science.gov (United States)

    Liu, Ji; Lu, Wennan; Guha, Sonia; Baltazar, Gabriel C; Coffey, Erin E; Laties, Alan M; Rubenstein, Ronald C; Reenstra, William W; Mitchell, Claire H

    2012-07-15

    The role of the cystic fibrosis transmembrane conductance regulator (CFTR) in lysosomal acidification has been difficult to determine. We demonstrate here that CFTR contributes more to the reacidification of lysosomes from an elevated pH than to baseline pH maintenance. Lysosomal alkalinization is increasingly recognized as a factor in diseases of accumulation, and we previously showed that cAMP reacidified alkalinized lysosomes in retinal pigmented epithelial (RPE) cells. As the influx of anions to electrically balance proton accumulation may enhance lysosomal acidification, the contribution of the cAMP-activated anion channel CFTR to lysosomal reacidification was probed. The antagonist CFTR(inh)-172 had little effect on baseline levels of lysosomal pH in cultured human RPE cells but substantially reduced the reacidification of compromised lysosomes by cAMP. Likewise, CFTR activators had a bigger impact on cells whose lysosomes had been alkalinized. Knockdown of CFTR with small interfering RNA had a larger effect on alkalinized lysosomes than on baseline levels. Inhibition of CFTR in isolated lysosomes altered pH. While CFTR and Lamp1 were colocalized, treatment with cAMP did not increase targeting of CFTR to the lysosome. The inhibition of CFTR slowed lysosomal degradation of photoreceptor outer segments while activation of CFTR enhanced their clearance from compromised lysosomes. Activation of CFTR acidified RPE lysosomes from the ABCA4(-/-) mouse model of recessive Stargardt's disease, whose lysosomes are considerably alkalinized. In summary, CFTR contributes more to reducing lysosomal pH from alkalinized levels than to maintaining baseline pH. Treatment to activate CFTR may thus be of benefit in disorders of accumulation associated with lysosomal alkalinization.

  15. Structure and properties of cell membranes. Volume 3: Methodology and properties of membranes

    International Nuclear Information System (INIS)

    Benga, G.

    1985-01-01

    This book covers the topics: Quantum chemical approach to study the mechanisms of proton translocation across membranes through protein molecules; monomolecular films as biomembrane models; planar lipid bilayers in relation to biomembranes; relation of liposomes to cell membranes; reconstitution of membrane transport systems; structure-function relationships in cell membranes as revealed by X-ray techniques; structure-function relationships in cell membranes as revealed by spin labeling ESR; structure and dynamics of cell membranes as revealed by NMR techniques; the effect of dietary lipids on the composition and properties of biological membranes and index

  16. Focus on Membrane Differentiation and Membrane Domains in the Prokaryotic Cell

    NARCIS (Netherlands)

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

    2013-01-01

    A summary is presented of membrane differentiation in the prokaryotic cell, with an emphasis on the organization of proteins in the plasma/cell membrane. Many species belonging to the Eubacteria and Archaea have special membrane domains and/or membrane proliferation, which are vital for different

  17. Alternate Fuel Cell Membranes for Energy Independence

    Energy Technology Data Exchange (ETDEWEB)

    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

  18. Membrane phosphorylation and nerve cell function

    International Nuclear Information System (INIS)

    Baer, P.R.

    1982-01-01

    This thesis deals with the phosphorylation of membrane components. In part I a series of experiments is described using the hippocampal slice as a model system. In part II a different model system - cultured hybrid cells - is used to study protein and lipid phosphorylation, influenced by incubation with neuropeptides. In part III in vivo and in vitro studies are combined to study protein phosphorylation after neuroanatomical lesions. In a section of part II (Page 81-90) labelling experiments of the membrane inositol-phospholipids are described. 32 P-ATP was used to label phospholipids in intact hybrid cells, and short incubations were found to be the most favourable. (C.F.)

  19. NASA fuel cell applications for space: Endurance test results on alkaline fuel cell electrolyzer components

    International Nuclear Information System (INIS)

    Sheibley, D.W.

    1984-01-01

    Fuel cells continue to play a major role in manned spacecraft power generation. The Gemini and Apollo programs used fuel cell power plants as the primary source of mission electrical power, with batteries as the backup. The current NASA use for fuel cells is in the Orbiter program. Here, low temperature alkaline fuel cells provide all of the on-board power with no backup power source. Three power plants per shipset are utilized; the original power plant contained 32-cell substacks connected in parallel. For extended life and better power performance, each power plant now contains three 32-cell substacks connected in parallel. One of the possible future applications for fuel cells will be for the proposed manned Space Station in low earth orbit (LEO)(1, 2, 3). By integrating a water electrolysis capability with a fuel cell (a regenerative fuel cell system), a multikilowatt energy storage capability ranging from 35 kW to 250 kW can be achieved. Previous development work on fuel cell and electrolysis systems would tend to minimize the development cost of this energy storage system. Trade studies supporting initial Space Station concept development clearly show regenerative fuel cell (RFC) storage to be superior to nickel-cadmium and nickel-hydrogen batteries with regard to subsystem weight, flexibility in design, and integration with other spacecraft systems when compared for an initial station power level ranging from 60 kW to 75 kW. The possibility of scavenging residual O 2 and H 2 from the Shuttle external tank for use in fuel cells for producing power also exists

  20. High Temperature Alkaline Electrolysis Cells with Metal Foam Based Gas Diffusion Electrodes

    DEFF Research Database (Denmark)

    Chatzichristodoulou, Christodoulos; Allebrod, Frank; Mogensen, Mogens Bjerg

    2016-01-01

    Alkaline electrolysis cells operating at 250°C and 40 bar are able to convert electrical energy into hydrogen at very high efficiencies and power densities. In the present work we demonstrate the application of a PTFE hydrophobic network and Ag nanowires as oxygen evolution electrocatalyst...

  1. Cell Membrane Transport Mechanisms: Ion Channels and Electrical Properties of Cell Membranes.

    Science.gov (United States)

    Kulbacka, Julita; Choromańska, Anna; Rossowska, Joanna; Weżgowiec, Joanna; Saczko, Jolanta; Rols, Marie-Pierre

    2017-01-01

    Cellular life strongly depends on the membrane ability to precisely control exchange of solutes between the internal and external (environmental) compartments. This barrier regulates which types of solutes can enter and leave the cell. Transmembrane transport involves complex mechanisms responsible for passive and active carriage of ions and small- and medium-size molecules. Transport mechanisms existing in the biological membranes highly determine proper cellular functions and contribute to drug transport. The present chapter deals with features and electrical properties of the cell membrane and addresses the questions how the cell membrane accomplishes transport functions and how transmembrane transport can be affected. Since dysfunctions of plasma membrane transporters very often are the cause of human diseases, we also report how specific transport mechanisms can be modulated or inhibited in order to enhance the therapeutic effect.

  2. Redistribution of wastewater alkalinity with a microbial fuel cell to support nitrification of reject water.

    Science.gov (United States)

    Modin, Oskar; Fukushi, Kensuke; Rabaey, Korneel; Rozendal, René A; Yamamoto, Kazuo

    2011-04-01

    In wastewater treatment plants, the reject water from the sludge treatment processes typically contains high ammonium concentrations, which constitute a significant internal nitrogen load in the plant. Often, a separate nitrification reactor is used to treat the reject water before it is fed back into the plant. The nitrification reaction consumes alkalinity, which has to be replenished by dosing e.g. NaOH or Ca(OH)(2). In this study, we investigated the use of a two-compartment microbial fuel cell (MFC) to redistribute alkalinity from influent wastewater to support nitrification of reject water. In an MFC, alkalinity is consumed in the anode compartment and produced in the cathode compartment. We use this phenomenon and the fact that the influent wastewater flow is many times larger than the reject water flow to transfer alkalinity from the influent wastewater to the reject water. In a laboratory-scale system, ammonium oxidation of synthetic reject water passed through the cathode chamber of an MFC, increased from 73.8 ± 8.9 mgN/L under open-circuit conditions to 160.1 ± 4.8 mgN/L when a current of 1.96 ± 0.37 mA (15.1 mA/L total MFC liquid volume) was flowing through the MFC. These results demonstrated the positive effect of an MFC on ammonium oxidation of alkalinity-limited reject water. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Lithium. Effects on excitable cell membranes

    NARCIS (Netherlands)

    Ploeger, Egbert Johan

    1974-01-01

    LITHIUM: Effects on excitable cell membranes. Lithium salts have been used in the treatment of manic-depressive psychosis for many years but their mechanism of action is not well understood. Many workers assume that the action of lithium on catecholamine metabolism and/or on electrolyte distribution

  4. Evaluation of an alkaline fuel cell system as a micro-CHP

    International Nuclear Information System (INIS)

    Verhaert, Ivan; Mulder, Grietus; De Paepe, Michel

    2016-01-01

    Highlights: • Sensitivity analysis on system configuration of the AFC as a micro-CHP. • Flow rate in the secondary heating circuit can be used to control water management. • Part load behavior of fuel cells is compared to other micro-CHP technologies. • For future energy demand in buildings fuel cells have the best performance. - Abstract: Micro-cogeneration is an emerging technology to reduce the non-renewable energy demand in buildings and reduce peak load in the grid. Fuel cell based cogeneration (CHP) has interesting prospects for building applications, even at relatively low heat demand. This is due to their partial load behavior which is completely different, compared to other micro-CHP technologies. Within the fuel cell technologies suitable for small scale CHP or micro-CHP, the existing configuration of an alkaline fuel cell system is analyzed. This analysis is based on validated models and offers a control strategy to optimize both water management and energy performance of the alkaline fuel cell system. Finally, the model of the alkaline fuel cell system with optimized control strategy is used to compare its part load behavior to other micro-CHP technologies.

  5. Embryo Cell Membranes Reconstruction by Tensor Voting

    OpenAIRE

    Michelin , Gaël; Guignard , Léo; Fiuza , Ulla-Maj; Malandain , Grégoire

    2014-01-01

    International audience; Image-based studies of developing organs or embryos produce a huge quantity of data. To handle such high-throughput experimental protocols, automated computer-assisted methods are highly desirable. This article aims at designing an efficient cell segmentation method from microscopic images. The proposed approach is twofold: first, cell membranes are enhanced or extracted by the means of structure-based filters, and then perceptual grouping (i.e. tensor voting) allows t...

  6. Optimization of synthesis of the nickel-cobalt oxide based anode electrocatalyst and of the related membrane-electrode assembly for alkaline water electrolysis

    Science.gov (United States)

    Chanda, Debabrata; Hnát, Jaromir; Bystron, Tomas; Paidar, Martin; Bouzek, Karel

    2017-04-01

    In this work, the Ni-Co spinel oxides are synthesized via different methods and using different calcination temperatures. Properties of the prepared materials are compared. The best route is selected and used to prepare a Ni1+xCo2-xO4 (-1 ≤ x ≤ 1) series of materials in order to investigate their catalytic activity towards the oxygen evolution reaction (OER). The results show that hydroxide preparation yields NiCo2O4 oxide with the highest activity. 325 °C is identified as the optimum calcination temperature. Subsequently, the catalysts are tested in an electrolysis cell. To prepare an anode catalyst layer based on NiCo2O4 catalyst on top of a nickel foam substrate for membrane electrode assembly (MEA) construction, following polymer binders are used: anion-selective quaternized polyphenylene oxide (qPPO), inert polytetrafluoroethylene (PTFE®), and cation-selective Nafion®. qPPO ionomer containing MEA exhibited highest OER activity. The current density obtained using a MEA containing qPPO binder attains a value of 135 mA cm-2 at a cell voltage of 1.85 V. After 7 h chronopotentiometric experiment at a constant current density of 225 mA cm-2, the MEA employing PTFE® binder shows higher stability than the other binders in alkaline water electrolysis at 50 °C. Under similar conditions, stability of the PTFE®-binding MEA is examined for 135 h.

  7. Selectivity of Direct Methanol Fuel Cell Membranes

    Directory of Open Access Journals (Sweden)

    Antonino S. Aricò

    2015-11-01

    Full Text Available 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.

  8. Selectivity of Direct Methanol Fuel Cell Membranes.

    Science.gov (United States)

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

    2015-11-24

    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).

  9. Ultrafine polybenzimidazole (PBI) fibers. [separators for alkaline batteries and dfuel cells

    Science.gov (United States)

    Chenevey, E. C.

    1979-01-01

    Mats were made from ultrafine polybenzimidazole (PBI) fibers to provide an alternate to the use of asbestos as separators in fuel cells and alkaline batteries. To minimize distortion during mat drying, a process to provide a dry fibrid was developed. Two fibrid types were developed: one coarse, making mats for battery separators; the other fine, making low permeability matrices for fuel cells. Eventually, it was demonstrated that suitable mat fabrication techniques yielded fuel cell separators from the coarser alkaline battery fibrids. The stability of PBI mats to 45% KOH at 123 C can be increased by heat treatment at high temperatures. Weight loss data to 1000 hours exposure show the alkali resistance of the mats to be superior to that of asbestos.

  10. Porous matrix structures for alkaline electrolyte fuel cells

    Science.gov (United States)

    Vine, R. W.; Narsavage, S. T.

    1975-01-01

    A number of advancements have been realized by a continuing research program to develop higher chemically stable porous matrix structures with high bubble pressure (crossover resistance) for use as separators in potassium hydroxide electrolyte fuel cells. More uniform, higher-bubble-pressure asbestos matrices were produced by reconstituting Johns-Manville asbestos paper; Fybex potassium titanate which was found compatible with 42% KOH at 250 F for up to 3000 hr; good agreement was found between bubble pressures predicted by an analytical study and those measured with filtered structures; Teflon-bonded Fybex matrices with bubble pressures greater than 30 psi were obtained by filtering a water slurry of the mixture directly onto fuel cell electrodes; and PBI fibers have satisfactory compatibility with 42% KOH at 250 F.

  11. Proton exchange membrane fuel cells modeling

    CERN Document Server

    Gao, Fengge; Miraoui, Abdellatif

    2013-01-01

    The fuel cell is a potential candidate for energy storage and conversion in our future energy mix. It is able to directly convert the chemical energy stored in fuel (e.g. hydrogen) into electricity, without undergoing different intermediary conversion steps. In the field of mobile and stationary applications, it is considered to be one of the future energy solutions.Among the different fuel cell types, the proton exchange membrane (PEM) fuel cell has shown great potential in mobile applications, due to its low operating temperature, solid-state electrolyte and compactness.This book pre

  12. Interactions of Model Cell Membranes with Nanoparticles

    Science.gov (United States)

    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

  13. A study for the research trends of membranes for proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Sener, T.

    2004-01-01

    'Full text:' A single PEM fuel cell is comprised of a membrane electrode assembly, two bipolar plates and two fields. Membrane electrode assembly is the basic component of PEM fuel cell due to its cost and function, and it consists a membrane sandwiched between two electrocatalyst layers/electrodes and two gas diffusion layers. Increasing the PEM fuel cell operation temperature from 80 o C to 150-200 o C will prevent electrocatalysts CO poisoning and increase the fuel cell performance. Therefore, membranes must have chemical and mechanical resistance and must keep enough water at high temperatures. The aim of membrane studies through fuel cell commercialization is to produce a less expensive thin membrane with high operation temperature, chemical and mechanical resistance and water adsorption capacity. Within this frame, alternative membrane materials, membrane electrode assembly manufacture and evaluation methods are being studied. In this paper, recent studies are reviewed to give a conclusion for research trends. (author)

  14. Cell membrane disruption stimulates cAMP and Ca2+ signaling to potentiate cell membrane resealing in neighboring cells

    Directory of Open Access Journals (Sweden)

    Tatsuru Togo

    2017-12-01

    Full Text Available Disruption of cellular plasma membranes is a common event in many animal tissues, and the membranes are usually rapidly resealed. Moreover, repeated membrane disruptions within a single cell reseal faster than the initial wound in a protein kinase A (PKA- and protein kinase C (PKC-dependent manner. In addition to wounded cells, recent studies have demonstrated that wounding of Madin-Darby canine kidney (MDCK cells potentiates membrane resealing in neighboring cells in the short-term by purinergic signaling, and in the long-term by nitric oxide/protein kinase G signaling. In the present study, real-time imaging showed that cell membrane disruption stimulated cAMP synthesis and Ca2+ mobilization from intracellular stores by purinergic signaling in neighboring MDCK cells. Furthermore, inhibition of PKA and PKC suppressed the ATP-mediated short-term potentiation of membrane resealing in neighboring cells. These results suggest that cell membrane disruption stimulates PKA and PKC via purinergic signaling to potentiate cell membrane resealing in neighboring MDCK cells.

  15. Somatic cell count and alkaline phosphatase activity in milk for evaluation of mastitis in buffalo

    Science.gov (United States)

    Patil, M. P.; Nagvekar, A. S.; Ingole, S. D.; Bharucha, S. V.; Palve, V. T.

    2015-01-01

    Background and Aim: Mastitis is a serious disease of dairy animals causing great economic losses due to a reduction in milk yield as well as lowering its nutritive value. The application of somatic cell count (SCC) and alkaline phosphatase activity in the milk for diagnosis of mastitis in buffalo is not well documented. Therefore, the present study was conducted to observe the SCC and alkaline phosphatase activity for evaluation of mastitis in buffalo. Materials and Methods: Milk samples of forty apparently healthy lactating buffaloes were selected and categorized into five different groups viz. normal buffaloes, buffaloes with subclinical mastitis with CMT positive milk samples (+1 Grade), (+2 Grade), (+3 Grade), and buffaloes with clinical mastitis with 8 animals in each group. The milk samples were analyzed for SCC and alkaline phosphatase activity. Results: The levels of SCC (×105 cells/ml) and alkaline phosphatase (U/L) in different groups were viz. normal (3.21±0.179, 16.48±1.432), subclinical mastitis with CMT positive milk samples with +1 Grade (4.21±0.138, 28.11±1.013), with +2 Grade (6.34±0.183, 34.50±1.034), with +3 Grade (7.96±0.213, 37.73±0.737) and buffaloes with clinical mastitis (10.21±0.220, 42.37±0.907) respectively, indicating an increasing trend in the values and the difference observed among various group was statistically significant. Conclusion: In conclusion, the results of the present study indicate that the concentration of milk SCC and alkaline phosphatase activity was higher in the milk of buffaloes with mastitis than in the milk of normal buffaloes. PMID:27047098

  16. Somatic cell count and alkaline phosphatase activity in milk for evaluation of mastitis in buffalo

    Directory of Open Access Journals (Sweden)

    M. P. Patil

    2015-03-01

    Full Text Available Background and Aim: Mastitis is a serious disease of dairy animals causing great economic losses due to a reduction in milk yield as well as lowering its nutritive value. The application of somatic cell count (SCC and alkaline phosphatase activity in the milk for diagnosis of mastitis in buffalo is not well documented. Therefore, the present study was conducted to observe the SCC and alkaline phosphatase activity for evaluation of mastitis in buffalo. Materials and Methods: Milk samples of forty apparently healthy lactating buffaloes were selected and categorized into five different groups viz. normal buffaloes, buffaloes with subclinical mastitis with CMT positive milk samples (+1 Grade, (+2 Grade, (+3 Grade, and buffaloes with clinical mastitis with 8 animals in each group. The milk samples were analyzed for SCC and alkaline phosphatase activity. Results: The levels of SCC (×105 cells/ml and alkaline phosphatase (U/L in different groups were viz. normal (3.21±0.179, 16.48±1.432, subclinical mastitis with CMT positive milk samples with +1 Grade (4.21±0.138, 28.11±1.013, with +2 Grade (6.34±0.183, 34.50±1.034, with +3 Grade (7.96±0.213, 37.73±0.737 and buffaloes with clinical mastitis (10.21±0.220, 42.37±0.907 respectively, indicating an increasing trend in the values and the difference observed among various group was statistically significant. Conclusion: In conclusion, the results of the present study indicate that the concentration of milk SCC and alkaline phosphatase activity was higher in the milk of buffaloes with mastitis than in the milk of normal buffaloes.

  17. Epithelial cell-cell junctions and plasma membrane domains

    NARCIS (Netherlands)

    Giepmans, Ben N. G.; van Ijzendoorn, Sven C. D.

    Epithelial cells form a barrier against the environment, but are also required for the regulated exchange of molecules between an organism and its surroundings. Epithelial cells are characterised by a remarkable polarization of their plasma membrane, evidenced by the appearance of structurally,

  18. Signaling alkaline pH stress in the yeast Saccharomyces cerevisiae through the Wsc1 cell surface sensor and the Slt2 MAPK pathway.

    Science.gov (United States)

    Serrano, Raquel; Martín, Humberto; Casamayor, Antonio; Ariño, Joaquín

    2006-12-29

    Alkalinization of the external environment represents a stress situation for Saccharomyces cerevisiae. Adaptation to this circumstance involves the activation of diverse response mechanisms, the components of which are still largely unknown. We show here that mutation of members of the cell integrity Pkc1/Slt2 MAPK module, as well as upstream and downstream elements of the system, confers sensitivity to alkali. Alkalinization resulted in fast and transient activation of the Slt2 MAPK, which depended on the integrity of the kinase module and was largely abolished by sorbitol. Lack of Wsc1, removal of specific extracellular and intracellular domains, or substitution of Tyr(303) in this putative membrane stress sensor rendered cells sensitive to alkali and considerably decreased alkali-induced Slt2 activation. In contrast, constitutive activation of Slt2 by the bck1-20 allele increased pH tolerance in the wsc1 mutant. DNA microarray analysis revealed that several genes encoding cell wall proteins, such as GSC2/FKS2, DFG5, SKT5, and CRH1, were induced, at least in part, by high pH in an Slt2-dependent manner. We observed that dfg5, skt5, and particularly dfg5 skt5 cells were alkali-sensitive. Therefore, our results show that an alkaline environment imposes a stress condition on the yeast cell wall. We propose that the Slt2-mediated MAPK pathway plays an important role in the adaptive response to this insult and that Wsc1 participates as an essential cell-surface pH sensor. Moreover, these results provide a new example of the complexity of the response of budding yeast to the alkalinization of the environment.

  19. Annexin A4 and A6 induce membrane curvature and constriction during cell membrane repair

    DEFF Research Database (Denmark)

    Boye, Theresa Louise; Maeda, Kenji; Pezeshkian, Weria

    2017-01-01

    Efficient cell membrane repair mechanisms are essential for maintaining membrane integrity and thus for cell life. Here we show that the Ca2+- and phospholipid-binding proteins annexin A4 and A6 are involved in plasma membrane repair and needed for rapid closure of micron-size holes. We demonstrate...... that annexin A4 binds to artificial membranes and generates curvature force initiated from free edges, whereas annexin A6 induces constriction force. In cells, plasma membrane injury and Ca2+ influx recruit annexin A4 to the vicinity of membrane wound edges where its homo-trimerization leads to membrane...... that induction of curvature force around wound edges is an early key event in cell membrane repair....

  20. Response of MG63 osteoblast-like cells onto polycarbonate membrane surfaces with different micropore sizes.

    Science.gov (United States)

    Lee, Sang Jin; Choi, Jin San; Park, Ki Suk; Khang, Gilson; Lee, Young Moo; Lee, Hai Bang

    2004-08-01

    Response of different types of cells on materials is important for the applications of tissue engineering and regenerative medicine. It is recognized that the behavior of the cell adhesion, proliferation, and differentiation on materials depends largely on surface characteristics such as wettability, chemistry, charge, rigidity, and roughness. In this study, we examined the behavior of MG63 osteoblast-like cells cultured on a polycarbonate (PC) membrane surfaces with different micropore sizes (0.2-8.0 microm in diameter). Cell adhesion and proliferation to the PC membrane surfaces were determined by cell counting and MTT assay. The effect of surface micropore on the MG63 cells was evaluated by cell morphology, protein content, and alkaline phosphatase (ALP) specific activity. It seems that the cell adhesion and proliferation were progressively inhibited as the PC membranes had micropores with increasing size, probably due to surface discontinuities produced by track-etched pores. Increasing micropore size of the PC membrane results in improved protein synthesis and ALP specific activity in isolated cells. There was a statistically significant difference (Pmicropore sizes. The MG63 cells also maintained their phenotype under conditions that support a round cell shape. RT-PCR analysis further confirmed the osteogenic phenotype of the MG63 cells onto the PC membranes with different micropore sizes. In results, as micropore size is getting larger, cell number is reduced and cell differentiation and matrix production is increased. This study demonstrated that the surface topography plays an important role for phenotypic expression of the MG63 osteoblast-like cells.

  1. High-performance alkaline direct methanol fuel cell using a nitrogen-postdoped anode.

    Science.gov (United States)

    Joghee, Prabhuram; Pylypenko, Svitlana; Wood, Kevin; Bender, Guido; O'Hayre, Ryan

    2014-07-01

    A commercial PtRu/C catalyst postdoped with nitrogen demonstrates a significantly higher performance (~10-20% improvement) in the anode of an alkaline direct methanol fuel cell than an unmodified commercial PtRu/C catalyst control. The enhanced performance shown herein is attributed at least partially to the increased electrochemical surface area of the PtRu/C after postdoping with nitrogen. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Alkaline water electrolysis technology for Space Station regenerative fuel cell energy storage

    Science.gov (United States)

    Schubert, F. H.; Hoberecht, M. A.; Le, M.

    1986-01-01

    The regenerative fuel cell system (RFCS), designed for application to the Space Station energy storage system, is based on state-of-the-art alkaline electrolyte technology and incorporates a dedicated fuel cell system (FCS) and water electrolysis subsystem (WES). In the present study, emphasis is placed on the WES portion of the RFCS. To ensure RFCS availability for the Space Station, the RFCS Space Station Prototype design was undertaken which included a 46-cell 0.93 cu m static feed water electrolysis module and three integrated mechanical components.

  3. A One-compartment direct glucose alkaline fuel cell with methyl viologen as electron mediator

    International Nuclear Information System (INIS)

    Liu, Xianhua; Hao, Miaoqing; Feng, Mengnan; Zhang, Lin; Zhao, Yong; Du, Xiwen; Wang, Guangyi

    2013-01-01

    Highlights: ► A glucose–air alkaline fuel cell without using noble metal catalysts has been developed. ► The rudimentary fuel cell generates a maximum power density of 0.62 mW m −2 . ► The high performance is attributed to the use of MV and nickel foam. ► Main oxidation products are small organic acids indicating deep oxidation of glucose. - Abstract: Glucose is abundant, renewable, non-toxic and convenient as a fuel for fuel cells, but current technologies are unavailable for us to directly oxidize it to obtain energy. Fuel cells using enzymes and micro-organisms as catalysts are limited by their extremely low power output and rather short durability. Fuel cells using precious metal catalyst are expensive for large-scale use. In this work, a one-compartment direct glucose alkaline fuel cell has been developed that use methyl viologen (MV) as electron mediator and nickel foam as the anode. The rudimentary fuel cell generates a maximum power density of 0.62 mW cm −2 , while the maximum current density is 5.03 mA cm −2 . Electro-catalytic activities of MV and the nickel foam in alkaline conditions were studied by cyclic voltammetry. It is indicated that the high performance of the fuel cell is attributed to the combined use of MV and nickel foam. 13 C-NMR and HPLC were used to analyze oxidation products of glucose. The result shows that the principal oxidation products are short-chain organic acids indicating deep oxidation of glucose is achieved

  4. Sodium selectivity of Reissner's membrane epithelial cells

    Directory of Open Access Journals (Sweden)

    Kim Kyunghee X

    2011-02-01

    Full Text Available Abstract 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

  5. An empirical study into the effect of long term storage (−36±2 °C) of electron-beamed ETFE on the properties of radiation-grafted alkaline anion-exchange membranes

    International Nuclear Information System (INIS)

    Kizewski, Jamie Peter; Mudri, Nurul H.; Varcoe, John R.

    2013-01-01

    The application of alkaline anion-exchange membranes (AAEM) in solid alkaline fuel cells is growing in prominence mainly due to enhanced tolerance to carbon dioxide, compared to alkaline fuel cells containing aqueous electrolytes, and the potential for using non precious metal catalysts. Radiation grafting is a common methodology for the production of functional polymers and membranes. This statistical study examines the synthesis of radiation grafted AAEMs that are formed from electron beam irradiated poly(ethylene-co-tetrafluoroethylene), EB-ETFE. It is shown that EB-ETFE can be cold stored for at least 16 months and still be used to produce ionically conductive AAEMs. The limitations of routine measurements of properties, such as dimensional increases, ion-exchange capacity, water uptakes and ionic conductivities, are also highlighted. - Highlights: • EB-ETFE films can be used to synthesise viable AAEMs even after storage at −36±2 °C for 16 months. • The AAEMs exhibited ion-exchange capacities in the range 1.0–1.8 mmol g −1 and ionic conductivities (through plane, fully hydrated) in the range 20–40 mS cm −1 at room temperature. • The ionic conductivities of the AAEMs are insensitive to the EB-ETFE storage time (up to the 16 months of this study). • The previously reported bubble formation phenomenon (within the AAEMs) is a major interference in the determination of swelling and water uptake properties. This interference appears more prominent at longer EB-ETFE cold storage times. • Water uptakes are too high for optimal utilisation in fuel cells and AAEMs with both improved ionic conductivities and lower swelling are required

  6. Fuel cell membrane hydration and fluid metering

    Science.gov (United States)

    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).

  7. Membrane Purification Cell for Aluminum Recycling

    Energy Technology Data Exchange (ETDEWEB)

    David DeYoung; James Wiswall; Cong Wang

    2011-11-29

    Recycling mixed aluminum scrap usually requires adding primary aluminum to the scrap stream as a diluent to reduce the concentration of non-aluminum constituents used in aluminum alloys. Since primary aluminum production requires approximately 10 times more energy than melting scrap, the bulk of the energy and carbon dioxide emissions for recycling are associated with using primary aluminum as a diluent. Eliminating the need for using primary aluminum as a diluent would dramatically reduce energy requirements, decrease carbon dioxide emissions, and increase scrap utilization in recycling. Electrorefining can be used to extract pure aluminum from mixed scrap. Some example applications include producing primary grade aluminum from specific scrap streams such as consumer packaging and mixed alloy saw chips, and recycling multi-alloy products such as brazing sheet. Electrorefining can also be used to extract valuable alloying elements such as Li from Al-Li mixed scrap. This project was aimed at developing an electrorefining process for purifying aluminum to reduce energy consumption and emissions by 75% compared to conventional technology. An electrolytic molten aluminum purification process, utilizing a horizontal membrane cell anode, was designed, constructed, operated and validated. The electrorefining technology could also be used to produce ultra-high purity aluminum for advanced materials applications. The technical objectives for this project were to: - Validate the membrane cell concept with a lab-scale electrorefining cell; - Determine if previously identified voltage increase issue for chloride electrolytes holds for a fluoride-based electrolyte system; - Assess the probability that voltage change issues can be solved; and - Conduct a market and economic analysis to assess commercial feasibility. The process was tested using three different binary alloy compositions (Al-2.0 wt.% Cu, Al-4.7 wt.% Si, Al-0.6 wt.% Fe) and a brazing sheet scrap composition (Al-2

  8. Membrane Proteins : The Key Players of a Cancer Cell

    NARCIS (Netherlands)

    Kampen, Kim R.

    Membrane proteins are involved in the prognosis of the most common forms of cancer. Membrane proteins are the hallmark of a cancer cell. The overexpressed membrane receptors are becoming increasingly important in cancer cell therapy. Current renewing therapy approaches based on receptor

  9. Membrane fluidity adjustments in ethanol-stressed Oenococcus oeni cells

    NARCIS (Netherlands)

    Silveira, da M.G.; Golovina, E.A.; Hoekstra, F.A.; Rombouts, F.M.; Abee, T.

    2003-01-01

    The effect of ethanol on the cytoplasmic membrane of Oenococcus oeni cells and the role of membrane changes in the acquired tolerance to ethanol were investigated. Membrane tolerance to ethanol was defined as the resistance to ethanol-induced leakage of preloaded carboxyfluorescein (cF) from cells.

  10. Human Lipoproteins at Model Cell Membranes

    DEFF Research Database (Denmark)

    Browning, K L; Lind, T K; Maric, S

    2017-01-01

    High and low density lipoproteins (HDL and LDL) are thought to play vital roles in the onset and development of atherosclerosis; the biggest killer in the western world. Key issues of initial lipoprotein (LP) interactions at cellular membranes need to be addressed including LP deposition and lipid...... exchange. Here we present a protocol for monitoring the in situ kinetics of lipoprotein deposition and lipid exchange/removal at model cellular membranes using the non-invasive, surface sensitive methods of neutron reflection and quartz crystal microbalance with dissipation. For neutron reflection, lipid...... support the notion of HDL acting as the 'good' cholesterol, removing lipid material from lipid-loaded cells, whereas LDL acts as the 'bad' cholesterol, depositing lipid material into the vascular wall....

  11. Dendronized Polymer Architectures for Fuel Cell Membranes

    DEFF Research Database (Denmark)

    Nielsen, Mads Møller; Dimitrov, Ivaylo; Takamuku, S.

    2013-01-01

    Multi‐step synthetic pathways to low‐ion exchange capacity (IEC) polysulfone (PSU) with sulfonic acid functionalized aliphatic dendrons and sulfonated comb‐type PSU structures are developed and investigated in a comparative study as non‐fluorinated proton exchange membrane (PEM) candidates. In each...... case the side chains are synthesized and introduced in their sulfonated form onto an azide‐functionalized PSU via click chemistry. Three degrees of substitution of each architecture were prepared in order to evaluate the dependence on number of sulfonated side chains. Solution cast membranes were...... evaluated as PEMs for use in fuel cells by proton conductivity measurements, and in the case of dendronized architectures: thermal stability. The proposed synthetic strategy facilitates exploration of a non‐fluorous system with various flexible side chains where IEC is tunable by the degree of substitution....

  12. Hydroponics gel as a new electrolyte gelling agent for alkaline zinc-air cells

    Science.gov (United States)

    Othman, R.; Basirun, W. J.; Yahaya, A. H.; Arof, A. K.

    The viability of hydroponics gel as a new alkaline electrolyte gelling agent is investigated. Zinc-air cells are fabricated employing 12 wt.% KOH electrolyte immobilised with hydroponics gel. The cells are discharged at constant currents of 5, 50 and 100 mA. XRD and SEM analysis of the anode plates after discharge show that the failure mode is due to the formation of zinc oxide insulating layers and not due to any side reactions between the gel and the plate or the electrolyte.

  13. Alkaline electrolysis cell at high temperature and pressure of 250 °C and 42 bar

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2013-01-01

    A new type of alkaline electrolysis cells with nickel foam based gas diffusion electrodes and KOH (aq) immobilized in mesoporous SrTiO3 has been developed and tested at temperatures and pressures up to 250 °C and 42 bar, respectively. Current densities of 1.0 A cm−2 have been measured at a cell v...... voltage of 1.5 V without the use of expensive noble metal catalysts. High electrical efficiency and current density combined with relatively small production costs may lead to both reduced investment and operating costs for hydrogen and oxygen production....

  14. Nonlinear electro-mechanobiological behavior of cell membrane during electroporation

    KAUST Repository

    Deng, Peigang; Lee, Yi-Kuen; Lin, Ran; Zhang, Tong-Yi

    2012-01-01

    A nonlinear electroporation (EP) model is proposed to study the electro-mechanobiological behavior of cell membrane during EP, by taking the nonlinear large deformation of the membrane into account. The proposed model predicts the critical

  15. Polybenzimidazole and sulfonated polyhedral oligosilsesquioxane composite membranes for high temperature polymer electrolyte membrane fuel cells

    DEFF Research Database (Denmark)

    Aili, David; Allward, Todd; Alfaro, Silvia Martinez

    2014-01-01

    Composite membranes based on poly(2,2′(m-phenylene)-5,5́bibenzimidazole) (PBI) and sulfonated polyhedral oligosilsesquioxane (S-POSS) with S-POSS contents of 5 and 10wt.% were prepared by solution casting as base materials for high temperature polymer electrolyte membrane fuel cells. With membranes...

  16. Production, secretion, and stability of human secreted alkaline phosphatase in tobacco NT1 cell suspension cultures.

    Science.gov (United States)

    Becerra-Arteaga, Alejandro; Mason, Hugh S; Shuler, Michael L

    2006-01-01

    Tobacco NT1 cell suspension cultures secreting active human secreted alkaline phosphatase (SEAP) were generated for the first time as a model system to study recombinant protein production, secretion, and stability in plant cell cultures. The SEAP gene encodes a secreted form of the human placental alkaline phosphatase (PLAP). During batch culture, the highest level of active SEAP in the culture medium (0.4 U/mL, corresponding to approximately 27 mg/L) was observed at the end of the exponential growth phase. Although the level of active SEAP decreased during the stationary phase, the activity loss did not appear to be due to SEAP degradation (based on Western blots) but due to SEAP denaturation. The protein-stabilizing agents polyvinylpirrolidone (PVP) and bacitracin were added extracellularly to test for their ability to reduce the loss of SEAP activity during the stationary phase. Bacitracin (100 mg/L) was the most effective treatment at sustaining activity levels for up to 17 days post-subculture. Commercially available human placental alkaline phosphatase (PLAP) was used to probe the mechanism of SEAP deactivation. Experiments with PLAP in sterile and conditioned medium corroborated the denaturation of SEAP by factors generated by cell growth and not due to simple proteolysis. We also show for the first time that the factors promoting activity loss are heat labile at 95 degrees C but not at 70 degrees C, and they are not inactivated after a 5 day incubation period under normal culture conditions (27 degrees C). In addition, there were no significant changes in pH or redox potential when comparing sterile and cell-free conditioned medium during PLAP incubation, indicating that these factors were unimportant.

  17. Fabrication of hydrogels with elasticity changed by alkaline phosphatase for stem cell culture.

    Science.gov (United States)

    Toda, Hiroyuki; Yamamoto, Masaya; Uyama, Hiroshi; Tabata, Yasuhiko

    2016-01-01

    The objective of this study is to design hydrogels whose elasticity can be changed by alkaline phosphatase (ALP) in cell culture and evaluate the effect of hydrogel elasticity on an osteogenic gene expression of cells. Hydrogels were prepared by the radical polymerization of acrylamide (AAm), N,N'-methylenebisacrylamide (BIS), and Phosmer™M containing phosphate groups (PE-PAAm hydrogels). The storage modulus of PE-PAAm hydrogels prepared was changed by the preparation conditions. When human mesenchymal stem cells (hMSC) were cultured on the ALP-responsive PE-PAAm hydrogels in the presence or absence of ALP, the morphology of hMSC was observed and one of the osteogenic differentiation markers, Runx2, was evaluated. By ALP addition into the culture medium, the morphology of hMSC was changed into an elongated shape without cell damage. ALP addition modified the level of Runx2 gene expression, which was influenced by the modulus of PE-PAAm hydrogels. It is concluded that the elasticity change of hydrogel substrates in cell culture had an influence on the Runx2 gene expression of hMSC. Stem cells sense the surface elasticity of culture substrates, and their differentiation fate is biologically modified by substrate properties. Most of experiments have been performed in static conditions during cell culture, while the in vivo microenvironment is dynamically changed. In this study, we established to design an enzyme-responsive hydrogel whose elasticity can be changed by alkaline phosphatase (ALP) in cell culture to mimic in vivo conditions. As a result, the cells were deformed and the gene expression level of an osteogenic maker, Runx2, was modified by ALP treatment. This is the novel report describing to demonstrate that the dynamic alteration of hydrogel substrate elasticity could modulate the osteoblastic gene expression of human MSC in vitro. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. Modeling Bubble Flow and Current Density Distribution in an Alkaline Electrolysis Cell

    Directory of Open Access Journals (Sweden)

    Ravichandra S. Jupudi

    2009-12-01

    Full Text Available The effect of bubbles on the current density distribution over the electrodes of an alkaline electrolyzer cell is studied using a two-dimensional computational fluid dynamics model. Model includes Eulerian-Eulerian two-phase flow methodology to model the multiphase flow of Hydrogen and Oxygen with water and the behavior of each phase is accounted for using first principle. Hydrogen/Oxygen evolution, flow field and current density distribution are incorporated in the model to account for the complicated physics involved in the process. Fluent 6.2 is used to solve two-phase flow and electrochemistry is incorporated using UDF (User Defined Function feature of Fluent. Model is validated with mesh refinement study and by comparison with experimental measurements. Model is found to replicate the effect of cell voltage and inter-electrode gap (distance between the electrodes on current density accurately. Further, model is found to capture the existence of optimum cell height. The validated model is expected to be a very useful tool in the design and optimization of alkaline electrolyzer cells.

  19. Channels in cell membranes and synchrotron radiation

    International Nuclear Information System (INIS)

    Yan Xiaohui; Tian Liang; Zhang Xinyi

    2004-01-01

    For long time a lot of scientists have devoted to study how matter, such as water molecules and K + , Na + , Ca 2+ , Cl - ions, move through cell membranes and complete the matter exchange between the inside and outside of cells. Peter Agre discovered and characterized the first water channel protein in 1988 and Roderick MacKinnon elucidated the structural and mechanistic basis for ion channel function in 1998. These achievements have made it possible for us to 'see' these exquisitely designed molecular machines in action at the atomic level. The Nobel Prize in Chemistry for 2003 is shared between these two scientists. In determining the high resolution 3D structure of these channels, the synchrotron X-ray diffraction plays an important role

  20. A fuel-cell reactor for the direct synthesis of hydrogen peroxide alkaline solutions from H(2) and O(2).

    Science.gov (United States)

    Yamanaka, Ichiro; Onisawa, Takeshi; Hashimoto, Toshikazu; Murayama, Toru

    2011-04-18

    The effects of the type of fuel-cell reactors (undivided or divided by cation- and anion-exchange membranes), alkaline electrolytes (LiOH, NaOH, KOH), vapor-grown carbon fiber (VGCF) cathode components (additives: none, activated carbon, Valcan XC72, Black Pearls 2000, Seast-6, and Ketjen Black), and the flow rates of anolyte (0, 1.5, 12 mL h(-1)) and catholyte (0, 12 mL h(-1)) on the formation of hydrogen peroxide were studied. A divided fuel-cell system, O(2) (g)|VGCF-XC72 cathode|2 M NaOH catholyte|cation-exchange membrane (Nafion-117)|Pt/XC72-VGCF anode|2 M NaOH anolyte at 12 mL h(-1) flow|H(2) (g), was effective for the selective formation of hydrogen peroxide, with 130 mA cm(-2) , a 2 M aqueous solution of H(2)O(2)/NaOH, and a current efficiency of 95 % at atmospheric pressure and 298 K. The current and formation rate gradually decreased over a long period of time. The cause of the slow decrease in electrocatalytic performance was revealed and the decrease was stopped by a flow of catholyte. Cyclic voltammetry studies at the VGCF-XC72 electrode indicated that fast diffusion of O(2) from the gas phase to the electrode, and quick desorption of hydrogen peroxide from the electrode to the electrolyte were essential for the efficient formation of solutions of H(2)O(2)/NaOH. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Alkaline pH activates the transport activity of GLUT1 in L929 fibroblast cells.

    Science.gov (United States)

    Gunnink, Stephen M; Kerk, Samuel A; Kuiper, Benjamin D; Alabi, Ola D; Kuipers, David P; Praamsma, Riemer C; Wrobel, Kathryn E; Louters, Larry L

    2014-04-01

    The widely expressed mammalian glucose transporter, GLUT1, can be acutely activated in L929 fibroblast cells by a variety of conditions, including glucose deprivation, or treatment with various respiration inhibitors. Known thiol reactive compounds including phenylarsine oxide and nitroxyl are the fastest acting stimulators of glucose uptake, implicating cysteine biochemistry as critical to the acute activation of GLUT1. In this study, we report that in L929 cells glucose uptake increases 6-fold as the pH of the uptake solution is increased from 6 to 9 with the half-maximal activation at pH 7.5; consistent with the pKa of cysteine residues. This pH effect is essentially blocked by the pretreatment of the cells with either iodoacetamide or cinnamaldehyde, compounds that form covalent adducts with reduced cysteine residues. In addition, the activation by alkaline pH is not additive at pH 8 with known thiol reactive activators such as phenylarsine oxide or hydroxylamine. Kinetic analysis in L929 cells at pH 7 and 8 indicate that alkaline conditions both increases the Vmax and decreases the Km of transport. This is consistent with the observation that pH activation is additive to methylene blue, which activates uptake by increasing the Vmax, as well as to berberine, which activates uptake by decreasing the Km. This suggests that cysteine biochemistry is utilized in both methylene blue and berberine activation of glucose uptake. In contrast a pH increase from 7 to 8 in HCLE cells does not further activate glucose uptake. HCLE cells have a 25-fold higher basal glucose uptake rate than L929 cells and the lack of a pH effect suggests that the cysteine biochemistry has already occurred in HCLE cells. The data are consistent with pH having a complex mechanism of action, but one likely mediated by cysteine biochemistry. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  2. The influence of saponins on cell membrane cholesterol.

    Science.gov (United States)

    Böttger, Stefan; Melzig, Matthias F

    2013-11-15

    We studied the influence of structurally different saponins on the cholesterol content of cellular membranes. Therefore a cell culture model using ECV-304 urinary bladder carcinoma cells was developed. To measure the cholesterol content we used radiolabeled (3)H-cholesterol which is chemically and physiologically identical to natural cholesterol. The cells were pre-incubated with (3)H-cholesterol and after a medium change, they were treated with saponins to assess a saponin-induced cholesterol liberation from the cell membrane. In another experiment the cells were pre-incubated with saponins and after a medium change, they were treated with (3)H-cholesterol to assess a saponin-induced inhibition of cholesterol uptake into the cell membrane. Furthermore, the membrane toxicity of all applied saponins was analyzed using extracellular LDH quantification and the general cytotoxicity was analyzed using a colorimetric MTT-assay and DNA quantification. Our results revealed a correlation between membrane toxicity and general cytotoxicity. We also compared the results from the experiments on the saponin-induced cholesterol liberation as well as the saponin-induced inhibition of cholesterol uptake with the membrane toxicity. A significant reduction in the cell membrane cholesterol content was noted for those saponins who showed membrane toxicity (IC50 saponins either liberated (3)H-cholesterol from intact cell membranes or blocked the integration of supplemented (3)H-cholesterol into the cell membrane. Saponins with little influence on the cell membrane (IC50 >100 μM) insignificantly altered the cell membrane cholesterol content. The results suggested that the general cytotoxicity of saponins is mainly dependent on their membrane toxicity and that the membrane toxicity might be caused by the loss of cholesterol from the cell membrane. We also analyzed the influence of a significantly membrane toxic saponin on the cholesterol content of intracellular membranes such as those

  3. Synthesis of Nanogels via Cell Membrane-Templated Polymerization.

    Science.gov (United States)

    Zhang, Jianhua; Gao, Weiwei; Fang, Ronnie H; Dong, Anjie; Zhang, Liangfang

    2015-09-09

    The synthesis of biomimetic hydrogel nanoparticles coated with a natural cell membrane is described. Compared to the existing strategy of wrapping cell membranes onto pre-formed nanoparticle substrates, this new approach forms the cell membrane-derived vesicles first, followed by growing nanoparticle cores in situ. It adds significant controllability over the nanoparticle properties and opens unique opportunities for a broad range of biomedical applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Perforate on CHO cell membranes induced by electromagnetic ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-06-17

    Jun 17, 2009 ... Key words: Electromagnetic pulse (EMP), atomic force microscope, CHO cell, cell membrane. INTRODUCTION .... of perforation ranges from 390 to 660 nm and the depth is. 392.95 nm. ... cell membrane perforations increased when both the field intensity and ..... Melatonin and a spin-trap compound block.

  5. Cell membrane temperature rate sensitivity predicted from the Nernst equation.

    Science.gov (United States)

    Barnes, F S

    1984-01-01

    A hyperpolarized current is predicted from the Nernst equation for conditions of positive temperature derivatives with respect to time. This ion current, coupled with changes in membrane channel conductivities, is expected to contribute to a transient potential shift across the cell membrane for silent cells and to a change in firing rate for pacemaker cells.

  6. Effects of tunicamycin, mannosamine, and other inhibitors of glycoprotein processing on skeletal alkaline phosphatase in human osteoblast-like cells.

    Science.gov (United States)

    Farley, J R; Magnusson, P

    2005-01-01

    Skeletal alkaline phosphatase (sALP) is a glycoprotein- approximately 20% carbohydrate by weight, with five presumptive sites for N-linked glycosylation, as well as a carboxy-terminal site for attachment of the glycolipid structure (glycosylphosphatidylinositol, GPI), which anchors sALP to the outer surface of osteoblasts. The current studies were intended to characterize the effects of inhibiting glycosylation and glycosyl-processing on the synthesis, plasma membrane attachment, cellular-extracellular distribution, and reaction kinetics of sALP in human osteosarcoma (SaOS-2) cells. sALP synthesis, glycosylation, and GPI-anchor attachment were assessed as total protein synthesis/immunospecific sALP synthesis, sialic acid content (i.e., wheat germ agglutinin precipitation), and insolubility (i.e., temperature-dependent phase-separation), respectively. sALP reaction kinetics were characterized by analysis of dose-dependent initial velocity data, with a phosphoryl substrate. The results of these studies revealed that the inhibition of either N-linked glycosylation or oligosaccharide synthesis for GPI-anchor addition could affect the synthesis and the distribution of sALP, but not the kinetics of the phosphatase reaction. Tunicamycin-which blocks N-linked glycosylation by inhibiting core oligosaccharide synthesis-decreased cell layer protein and the total amount of sALP in the cells, while increasing the relative level of sALP in the cell-conditioned culture medium (CM, i.e., the amount of sALP released). These effects were attributed to dose- and time-dependent decreases in sALP synthesis and N-linked glycosylation, and an increase in apoptotic cell death (P sALP specific activity, in the cells and in the CM; and (3) increases in the percentages of both anchorless and wheat germ agglutinin (WGA)-soluble sALP in the medium, but not in the cells (P sALP to the outside of the plasma membrane surface. Neither mannosammine nor tunicamycin had any effect on the reaction

  7. Low-cost non-fluorinated membranes for fuel cells

    CSIR Research Space (South Africa)

    Luo, H

    2010-08-31

    Full Text Available the driver of the next growth wave of the world’s economy. A proton conductive membrane is the core of the polymer electrolyte membrane fuel cell (PEMFC). Presently, Nafion® membranes are widely used in PEMFC. However, the high cost, low operation temperature...

  8. Impedance study of membrane dehydration and compression in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Le Canut, Jean-Marc; Latham, Ruth; Merida, Walter; Harrington, David A. [Institute for Integrated Energy Systems, University of Victoria, Victoria, British Columbia (Canada)

    2009-07-15

    Electrochemical impedance spectroscopy (EIS) is used to measure drying and rehydration in proton exchange membrane fuel cells running under load. The hysteresis between forward and backward acquisition of polarization curves is shown to be largely due to changes in the membrane resistance. Drying tests are carried out with hydrogen and simulated reformate (hydrogen and carbon dioxide), and quasi-periodic drying and rehydration conditions are studied. The membrane hydration state is clearly linked to the high-frequency arc in the impedance spectrum, which increases in size for dry conditions indicating an increase in membrane resistance. Changes in impedance spectra as external compression is applied to the cell assembly show that EIS can separate membrane and interfacial effects, and that changes in membrane resistance dominate. Reasons for the presence of a capacitance in parallel with the membrane resistance are discussed. (author)

  9. Application of the nanocomposite membrane as electrolyte of proton exchange membrane fuel cell

    International Nuclear Information System (INIS)

    Mahreni

    2010-01-01

    Hydrogen fuel cells proton exchange membrane fuel cell (PEMFC) is currently still in development and commercialization. Several barriers to the commercialization of these Nafion membrane as electrolyte is its very sensitive to humidity fluctuation. Nafion must be modified by making a composite Nafion-SiO 2 -HPA to increase electrolyte resistance against humidity fluctuations during the cell used. Research carried out by mixing Nafion solution with Tetra Ethoxy Ortho Silicate (TEOS) and conductive materials is phosphotungstic acid (PWA) by varying the ratio of Nafion, TEOS and PWA. The membrane is produced by heating a mixture of Nafion, TEOS and PWA by varying the evaporation temperature, time and annealing temperature to obtain the transparent membrane. The resulting membrane was analyzed its physical, chemical and electrochemical properties by applying the membrane as electrolyte of PEMFC at various humidity and temperature of operation. The results showed that at low temperatures (30-90 °C) and high humidity at 100 % RH, pure Nafion membrane is better than composite membrane (Nafion-SiO 2 -PWA), but at low humidity condition composite membrane is better than the pure Nafion membrane. It can be concluded that the composite membranes of (Nafion-SiO 2 -PWA) can be used as electrolyte of PEMFC operated at low humidity (40 % RH) and temperature between (30-90 °C). (author)

  10. Selective effect of cell membrane on synaptic neurotransmission

    DEFF Research Database (Denmark)

    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 membr...... the importance of cell membrane and specific lipids for neurotransmission, should to be of interest to neuroscientists, drug industry and the general public alike.......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...

  11. MnO2/MCMB electrocatalyst for all solid-state alkaline zinc-air cells

    International Nuclear Information System (INIS)

    Zhang, G.Q.; Zhang, X.G.

    2004-01-01

    Nanostructured MnO 2 /mesocarbon microbeads (MCMB) composite has been prepared successfully for use in zinc-air cell as electrocatalyst for oxygen reaction. The scanning electron microscope (SEM) images showed that the MnO 2 nanorods were formed and covered on the surface of MCMB in bird's nest morphology. X-ray diffraction (XRD) pattern indicated that the MnO 2 has the hollandite structure with a composition approximating KMn 8 O 16 . By the cathodic polarization curve tests, the nanostructured material demonstrated excellent electrocatalytic activity as a kind of oxygen electrode electrocatalyst compared with electrolytic MnO 2 . An all solid-state zinc-air cell has been fabricated with this material as electrocatalyst for oxygen electrode and potassium salt of cross-linked poly(acrylic acid) as an alkaline polymer gel electrolyte. The cell has good discharge characteristics at room temperature

  12. Theoretical design strategies of bipolar membrane fuel cell with enhanced self-humidification behavior

    Science.gov (United States)

    Li, Qiushi; Gong, Jian; Peng, Sikan; Lu, Shanfu; Sui, Pang-Chieh; Djilali, Ned; Xiang, Yan

    2016-03-01

    The bipolar membrane fuel cells (BPMFCs), which have a unique acid-alkaline jointed membrane electrode assembly (MEA) structure, have demonstrated their great potential for self-humidification during operation. Although the self-humidification ability of such bipolar membranes (BPMs) has recently been validated by a one-dimensional BPM model, the transport mechanism and the formation of self-humidification in the MEAs are not well understood. In the present study, a two-dimensional cross-channel MEA model is developed to elucidate the mechanisms and enhancement of water transport on self-humidification with comprehensive consideration of the three electrochemical reaction zones. The water-formation interface model has been successfully investigated by theoretical and experimental interface reaction kinetics, streamlines of water flux present the formation process and mechanism of self-humidification. A critical current (voltage) value, beyond which self-humidification is initiated, is identified. It is also found that such critical current (voltage) can be adjusted by changing the membrane thickness and the water uptake property of the ionomer. It is concluded that fabricating BPMs with proper membrane thickness and water uptake property are effective strategies to enhance the water management and cell performance in BPMFCs.

  13. Membrane glycoproteins of differentiating skeletal muscle cells

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  14. Joint influence of temperature and ions of metals on level of activity alkaline phosphatase the mucous membrane of intestines beluga, the starlet and their hybrid

    Directory of Open Access Journals (Sweden)

    D. A. Bednyakov

    2010-01-01

    Full Text Available In work joint influence of ions of bivalent metals (Mn, Fe, Co, Ni, Cu and Zn and temperatures on level of activity alkaline phosphatase mucous membrane beluga, starlet and their hybrid is shown. Dependence of response of enzyme on action of ions of metals according to their position in a periodic table of chemical elements is shown. The given dependence remains and at temperature change incubation, only at low temperatures the activating effect of metals being in the period beginning is maximum, and at high, is maximum inhibiting effect of metals being in the period end.

  15. At the border: the plasma membrane-cell wall continuum.

    Science.gov (United States)

    Liu, Zengyu; Persson, Staffan; Sánchez-Rodríguez, Clara

    2015-03-01

    Plant cells rely on their cell walls for directed growth and environmental adaptation. Synthesis and remodelling of the cell walls are membrane-related processes. During cell growth and exposure to external stimuli, there is a constant exchange of lipids, proteins, and other cell wall components between the cytosol and the plasma membrane/apoplast. This exchange of material and the localization of cell wall proteins at certain spots in the plasma membrane seem to rely on a particular membrane composition. In addition, sensors at the plasma membrane detect changes in the cell wall architecture, and activate cytoplasmic signalling schemes and ultimately cell wall remodelling. The apoplastic polysaccharide matrix is, on the other hand, crucial for preventing proteins diffusing uncontrollably in the membrane. Therefore, the cell wall-plasma membrane link is essential for plant development and responses to external stimuli. This review focuses on the relationship between the cell wall and plasma membrane, and its importance for plant tissue organization. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  16. Nanoscale spin sensing in artificial cell membranes

    International Nuclear Information System (INIS)

    Simpson David

    2014-01-01

    The use of the nitrogen-vacancy (NV) centre in diamond as a single spin sensor or magnetometer has attracted considerable interest in recent years because of its unique combination of sensitivity, nanoscale resolution, and optical initialisation and readout at room temperature. Nanodiamonds in particular hold great promise as an optical magnetometer probe for bio applications. In this work we employ nanodiamonds containing single NV spins to detect freely diffusing Mn2+ ions by detecting changes in the transverse relaxation time (T2) of the single spin probe. We also report the detection of gadolinium spin labels present in an artificial cell membrane by measuring changes in the longitudinal relaxation time (T1) of the probe. (author)

  17. Roles of membrane trafficking in plant cell wall dynamics

    Directory of Open Access Journals (Sweden)

    Kazuo eEbine

    2015-10-01

    Full Text Available 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.

  18. Epigallocatechin gallate incorporation into lignin enhances the alkaline delignification and enzymatic saccharification of cell walls

    Directory of Open Access Journals (Sweden)

    Elumalai Sasikumar

    2012-08-01

    Full Text Available Abstract Background Lignin is an integral component of the plant cell wall matrix but impedes the conversion of biomass into biofuels. The plasticity of lignin biosynthesis should permit the inclusion of new compatible phenolic monomers such as flavonoids into cell wall lignins that are consequently less recalcitrant to biomass processing. In the present study, epigallocatechin gallate (EGCG was evaluated as a potential lignin bioengineering target for rendering biomass more amenable to processing for biofuel production. Results In vitro peroxidase-catalyzed polymerization experiments revealed that both gallate and pyrogallyl (B-ring moieties in EGCG underwent radical cross-coupling with monolignols mainly by β–O–4-type cross-coupling, producing benzodioxane units following rearomatization reactions. Biomimetic lignification of maize cell walls with a 3:1 molar ratio of monolignols and EGCG permitted extensive alkaline delignification of cell walls (72 to 92% that far exceeded that for lignified controls (44 to 62%. Alkali-insoluble residues from EGCG-lignified walls yielded up to 34% more glucose and total sugars following enzymatic saccharification than lignified controls. Conclusions It was found that EGCG readily copolymerized with monolignols to become integrally cross-coupled into cell wall lignins, where it greatly enhanced alkaline delignification and subsequent enzymatic saccharification. Improved delignification may be attributed to internal trapping of quinone-methide intermediates to prevent benzyl ether cross-linking of lignin to structural polysaccharides during lignification, and to the cleavage of ester intra-unit linkages within EGCG during pretreatment. Overall, our results suggest that apoplastic deposition of EGCG for incorporation into lignin would be a promising plant genetic engineering target for improving the delignification and saccharification of biomass crops.

  19. Membrane phospholipids and radiation-induced death of mammalian cells

    International Nuclear Information System (INIS)

    Wolters, H.

    1987-01-01

    Radiation-induced cell killing is generally believed to be a consequence of residual DNA damage or damage that is mis-repaired. However, besides this DNA damage, damage to other molecules or structures of the cell may be involved in the killing. Especially membranes have been suggested as a determinant in cellular radiosensitivity. In this thesis experiments are described, dealing with the possible involvement of membranes in radiation-induced killing of mammalian cells. A general treatise of membrane structure is followed by information concerning deleterious effects of radiation on membranes. Consequences of damage to structure and function of membranes are reviewed. Thereafter evidence relating to the possible involvement of membranes in radiation-induced cell killing is presented. (Auth.)

  20. Membrane tension and cytoskeleton organization in cell motility

    International Nuclear Information System (INIS)

    Sens, Pierre; Plastino, Julie

    2015-01-01

    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. (topical review)

  1. Membrane tension and cytoskeleton organization in cell motility.

    Science.gov (United States)

    Sens, Pierre; Plastino, Julie

    2015-07-15

    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.

  2. Mathematical model of water transport in Bacon and alkaline matrix-type hydrogen-oxygen fuel cells

    Science.gov (United States)

    Prokopius, P. R.; Easter, R. W.

    1972-01-01

    Based on general mass continuity and diffusive transport equations, a mathematical model was developed that simulates the transport of water in Bacon and alkaline-matrix fuel cells. The derived model was validated by using it to analytically reproduce various Bacon and matrix-cell experimental water transport transients.

  3. Wnt5a attenuates Wnt3a-induced alkaline phosphatase expression in dental follicle cells

    International Nuclear Information System (INIS)

    Sakisaka, Yukihiko; Tsuchiya, Masahiro; Nakamura, Takashi; Tamura, Masato; Shimauchi, Hidetoshi; Nemoto, Eiji

    2015-01-01

    Wnt signaling regulates multiple cellular events such as cell proliferation, differentiation, and apoptosis through β-catenin-dependent canonical and β-catenin-independent noncanonical pathways. Canonical Wnt/β-catenin signaling can promote the differentiation of dental follicle cells, putative progenitor cells for cementoblasts, osteoblasts, and periodontal ligament cells, toward a cementoblast/osteoblast phenotype during root formation, but little is known about the biological significance of noncanonical Wnt signaling in this process. We identified the expression of Wnt5a, a representative noncanonical Wnt ligand, in tooth root lining cells (i.e. precementoblasts/cementoblasts) and dental follicle cells during mouse tooth root development, as assessed by immunohistochemistry. Silencing expression of the Wnt5a gene in a dental follicle cell line resulted in enhancement of the Wnt3a (a representative canonical Wnt ligand)-mediated increase in alkaline phosphatase (ALP) expression. Conversely, treatment with recombinant Wnt5a inhibited the increase in ALP expression, suggesting that Wnt5a signaling functions as a negative regulator of canonical Wnt-mediated ALP expression of dental follicle cells. Wnt5a did not affect the nuclear translocation of β-catenin as well as β-catenin-mediated transcriptional activation of T-cell factor (Tcf) triggered by Wnt3a, suggesting that Wnt5a inhibits the downstream part of the β-catenin-Tcf pathway. These findings suggest the existence of a feedback mechanism between canonical and noncanonical Wnt signaling during the differentiation of dental follicle cells. - Highlights: • Dental follicle cells express Wnt5a during tooth root development. • Silencing of Wnt5a enhances Wnt3a-mediated ALP expression of dental follicle cells. • Conversely, treatment with rWnt5a inhibited the increase in ALP expression. • Wnt5a functions as a negative regulator of Wnt3a-mediated ALP expression

  4. Wnt5a attenuates Wnt3a-induced alkaline phosphatase expression in dental follicle cells

    Energy Technology Data Exchange (ETDEWEB)

    Sakisaka, Yukihiko [Department of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, Sendai 980-8575 (Japan); Tsuchiya, Masahiro [Department of Oral Diagnosis, Tohoku University Graduate School of Dentistry, Sendai 980-8575 (Japan); Tohoku Fukushi University, Sendai 989-3201 (Japan); Nakamura, Takashi [Department of Pediatric Dentistry, Tohoku University Graduate School of Dentistry, Sendai 980-8575 (Japan); Liason Center for Innovative Dentistry, Tohoku University Graduate School of Dentistry, Sendai 980-8575 (Japan); Tamura, Masato [Department of Biochemistry and Molecular Biology, Hokkaido University Graduate School of Dentistry, Sapporo 060-8586 (Japan); Shimauchi, Hidetoshi [Department of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, Sendai 980-8575 (Japan); Nemoto, Eiji, E-mail: e-nemoto@dent.tohoku.ac.jp [Department of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, Sendai 980-8575 (Japan)

    2015-08-01

    Wnt signaling regulates multiple cellular events such as cell proliferation, differentiation, and apoptosis through β-catenin-dependent canonical and β-catenin-independent noncanonical pathways. Canonical Wnt/β-catenin signaling can promote the differentiation of dental follicle cells, putative progenitor cells for cementoblasts, osteoblasts, and periodontal ligament cells, toward a cementoblast/osteoblast phenotype during root formation, but little is known about the biological significance of noncanonical Wnt signaling in this process. We identified the expression of Wnt5a, a representative noncanonical Wnt ligand, in tooth root lining cells (i.e. precementoblasts/cementoblasts) and dental follicle cells during mouse tooth root development, as assessed by immunohistochemistry. Silencing expression of the Wnt5a gene in a dental follicle cell line resulted in enhancement of the Wnt3a (a representative canonical Wnt ligand)-mediated increase in alkaline phosphatase (ALP) expression. Conversely, treatment with recombinant Wnt5a inhibited the increase in ALP expression, suggesting that Wnt5a signaling functions as a negative regulator of canonical Wnt-mediated ALP expression of dental follicle cells. Wnt5a did not affect the nuclear translocation of β-catenin as well as β-catenin-mediated transcriptional activation of T-cell factor (Tcf) triggered by Wnt3a, suggesting that Wnt5a inhibits the downstream part of the β-catenin-Tcf pathway. These findings suggest the existence of a feedback mechanism between canonical and noncanonical Wnt signaling during the differentiation of dental follicle cells. - Highlights: • Dental follicle cells express Wnt5a during tooth root development. • Silencing of Wnt5a enhances Wnt3a-mediated ALP expression of dental follicle cells. • Conversely, treatment with rWnt5a inhibited the increase in ALP expression. • Wnt5a functions as a negative regulator of Wnt3a-mediated ALP expression.

  5. Detergent insolubility of alkaline phosphatase during biosynthetic transport and endocytosis. Role of cholesterol

    NARCIS (Netherlands)

    Cerneus, D. P.; Ueffing, E.; Posthuma, G.; Strous, G. J.; van der Ende, A.

    1993-01-01

    Alkaline phosphatase is anchored to the outer leaflet of the plasma membrane by a covalently attached glycosyl-phosphatidylinositol anchor. We have studied the biosynthetic transport and endocytosis of alkaline phosphatase in the choriocarcinoma cell line BeWo, which endogenously expresses this

  6. New ETFE-based membrane for direct methanol fuel cell

    International Nuclear Information System (INIS)

    Saarinen, V.; Kallio, T.; Paronen, M.; Tikkanen, P.; Rauhala, E.; Kontturi, K.

    2005-01-01

    The investigated membranes are based on 35-bar μ m thick commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) films. The films were made proton conductive by means of irradiation treatment followed by sulfonation. These membranes have exceptionally low water uptake and excellent dimensional stability. The new membranes are investigated widely in a laboratory-scale direct methanol fuel cell (DMFC). The temperature range used in the fuel cell tests was 30-85-bar o C and the measurement results were compared to those of the Nafion ( R)115 membrane. Also methanol permeability through the ETFE-based membrane was measured as a function of temperature, resulting in values less than 10% of the corresponding values for Nafion ( R)115, which was considerably thicker than the experimental membrane. Methanol crossover was reported to decrease when the thickness of the membrane increases, so the ETFE-based membrane compares favourably to Nafion ( R) membranes. The maximum power densities achieved with the experimental ETFE-based membrane were about 40-65% lower than the corresponding values of the Nafion ( R)115 membrane, because of the lower conductivity and noticeably higher IR-losses. Chemical and mechanical stability of the ETFE-based membrane appeared to be promising since it was tested over 2000-bar h in the DMFC without any performance loss

  7. Role of Membrane Biophysics in Alzheimer's - related cell pathways

    Directory of Open Access Journals (Sweden)

    Donghui eZhu

    2015-05-01

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

  8. Review of cell performance in anion exchange membrane fuel cells

    Science.gov (United States)

    Dekel, Dario R.

    2018-01-01

    Anion exchange membrane fuel cells (AEMFCs) have recently received increasing attention since in principle they allow for the use of non-precious metal catalysts, which dramatically reduces the cost per kilowatt of power in fuel cell devices. Until not long ago, the main barrier in the development of AEMFCs was the availability of highly conductive anion exchange membranes (AEMs); however, improvements on this front in the past decade show that newly developed AEMs have already reached high levels of conductivity, leading to satisfactory cell performance. In recent years, a growing number of research studies have reported AEMFC performance results. In the last three years, new records in performance were achieved. Most of the literature reporting cell performance is based on hydrogen-AEMFCs, although an increasing number of studies have also reported the use of fuels others than hydrogen - such as alcohols, non-alcohol C-based fuels, as well as N-based fuels. This article reviews the cell performance and performance stability achieved in AEMFCs through the years since the first reports in the early 2000s.

  9. Cell volume and membrane stretch independently control K+ channel activity

    DEFF Research Database (Denmark)

    Bomholtz, Sofia Hammami; Willumsen, Niels J; Olsen, Hervør L

    2009-01-01

    A number of potassium channels including members of the KCNQ family and the Ca(2+) activated IK and SK, but not BK, are strongly and reversibly regulated by small changes in cell volume. It has been argued that this general regulation is mediated through sensitivity to changes in membrane stretch...... was not affected by membrane stretch. The results indicate that (1) activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and (2) activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. We conclude....... To test this hypothesis we have studied the regulation of KCNQ1 and BK channels after expression in Xenopus oocytes. Results from cell-attached patch clamp studies (approximately 50 microm(2) macropatches) in oocytes expressing BK channels demonstrate that the macroscopic volume-insensitive BK current...

  10. Performance enhancement of membrane electrode assemblies with plasma etched polymer electrolyte membrane in PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Yong-Hun; Yoon, Won-Sub [School of Advanced Materials Engineering, Kookmin University, 861-1 Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea); Bae, Jin Woo; Cho, Yoon-Hwan; Lim, Ju Wan; Ahn, Minjeh; Jho, Jae Young; Sung, Yung-Eun [World Class University (WCU) program of Chemical Convergence for Energy and Environment (C2E2), School of Chemical and Biological Engineering, College of Engineering, Seoul National University (SNU), 599 Gwanak-Ro, Gwanak-gu, Seoul 151-744 (Korea); Kwon, Nak-Hyun [Fuel Cell Vehicle Team 3, Advanced Technology Center, Corporate Research and Development Division, Hyundai-Kia Motors, 104 Mabuk-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-912 (Korea)

    2010-10-15

    In this work, a surface modified Nafion 212 membrane was fabricated by plasma etching in order to enhance the performance of a membrane electrode assembly (MEA) in a polymer electrolyte membrane fuel cell. Single-cell performance of MEA at 0.7 V was increased by about 19% with membrane that was etched for 10 min compared to that with untreated Nafion 212 membrane. The MEA with membrane etched for 20 min exhibited a current density of 1700 mA cm{sup -2} at 0.35 V, which was 8% higher than that of MEA with untreated membrane (1580 mA cm{sup -2}). The performances of MEAs containing etched membranes were affected by complex factors such as the thickness and surface morphology of the membrane related to etching time. The structural changes and electrochemical properties of the MEAs with etched membranes were characterized by field emission scanning electron microscopy, Fourier transform-infrared spectrometry, electrochemical impedance spectroscopy, and cyclic voltammetry. (author)

  11. Production of membrane proteins without cells or detergents.

    Science.gov (United States)

    Rajesh, Sundaresan; Knowles, Timothy; Overduin, Michael

    2011-04-30

    The production of membrane proteins in cellular systems is besieged by several problems due to their hydrophobic nature which often causes misfolding, protein aggregation and cytotoxicity, resulting in poor yields of stable proteins. Cell-free expression has emerged as one of the most versatile alternatives for circumventing these obstacles by producing membrane proteins directly into designed hydrophobic environments. Efficient optimisation of expression and solubilisation conditions using a variety of detergents, membrane mimetics and lipids has yielded structurally and functionally intact membrane proteins, with yields several fold above the levels possible from cell-based systems. Here we review recently developed techniques available to produce functional membrane proteins, and discuss amphipols, nanodisc and styrene maleic acid lipid particle (SMALP) technologies that can be exploited alongside cell-free expression of membrane proteins. Copyright © 2010 Elsevier B.V. All rights reserved.

  12. Correlation between membrane fluidity cellular development and stem cell differentiation

    KAUST Repository

    Noutsi, Pakiza

    2016-12-01

    Cell membranes are made up of a complex structure of lipids and proteins that diffuse laterally giving rise to what we call membrane fluidity. During cellular development, such as neuronal differentiation, cell membranes undergo dramatic structural changes induced by proteins such as ARC and Cofilin among others in the case of synaptic modification. In this study we used the generalized polarization (GP) property of fluorescent probe Laurdan using two-photon microscopy to determine membrane fluidity as a function of time and for various cell lines. A low GP value corresponds to a higher fluidity and a higher GP value is associated with a more rigid membrane. Four different cell lines were monitored such as hN2, NIH3T3, HEK293 and L6 cells. As expected, NIH3T3 cells have more rigid membrane at earlier stages of their development. On the other hand neurons tend to have the highest membrane fluidity early in their development emphasizing its correlation with plasticity and the need for this malleability during differentiation. This study sheds light on the involvement of membrane fluidity during neuronal differentiation and development of other cell lines.

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

    Science.gov (United States)

    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.

  14. Membrane transport of anandamide through resealed human red blood cell membranes

    DEFF Research Database (Denmark)

    Bojesen, I.N.; Hansen, Harald S.

    2005-01-01

    The use of resealed red blood cell membranes (ghosts) allows the study of the transport of a compound in a nonmetabolizing system with a biological membrane. Transmembrane movements of anandamide (N-arachidonoylethanolamine, arachidonoylethanolamide) have been studied by exchange efflux experiments...... at 0°C and pH 7.3 with albumin-free and albumin-filled human red blood cell ghosts. The efflux kinetics is biexponential and is analyzed in terms of compartment models. The distribution of anandamide on the membrane inner to outer leaflet pools is determined to be 0.275 ± 0.023, and the rate constant...... of unidirectional flux from inside to outside is 0.361 ± 0.023 s. The rate constant of unidirectional flux from the membrane to BSA in the medium ([BSA]) increases with the square root of [BSA] in accordance with the theory of an unstirred layer around ghosts. Anandamide passed through the red blood cell membrane...

  15. Analysis of proton exchange membrane fuel cell performance with alternate membranes

    Energy Technology Data Exchange (ETDEWEB)

    Wakizoe, Masanobu; Velev, O A; Srinivasan, S [Texas A and M Univ., College Station, TX (United States). Texas Engineering Experiment Station

    1995-02-01

    Renewed interest in proton exchange membrane fuel cell technology for space and terrestrial (particularly electric vehicles) was stimulated by the demonstration, in the mid 1980s, of high energy efficiencies and high power densities. One of the most vital components of the PEMFC is the proton conducting membrane. In this paper, an analysis is made of the performances of PEMFCs with Dupont`s Nafion, Dow`s experimental, and Asahi Chemical`s Aciplex-S membranes. Attempts were also made to draw correlations between the PEMFC performances with the three types of membranes and their physico-chemical characteristics. Practically identical levels of performances (energy efficiency, power density, and lifetime) were achieved in PEMFCs with the Dow and the Aciplex-S membranes and these performances were better than in the PEMFCs with the Nafion-115 membrane. The electrode kinetic parameters for oxygen reduction are better for the PEMFCs with the Aciplex-S and Nafion membranes than with the Dow membranes. The PEMFCs with the Aciplex-S and Dow membranes have nearly the same internal resistances which are considerably lower than for the PEMFC with the Nafion membrane. The desired membrane characteristics to obtain high levels of performance are low equivalent weight and high water content. (Author)

  16. Empirical membrane lifetime model for heavy duty fuel cell systems

    Science.gov (United States)

    Macauley, Natalia; Watson, Mark; Lauritzen, Michael; Knights, Shanna; Wang, G. Gary; Kjeang, Erik

    2016-12-01

    Heavy duty fuel cells used in transportation system applications such as transit buses expose the fuel cell membranes to conditions that can lead to lifetime-limiting membrane failure via combined chemical and mechanical degradation. Highly durable membranes and reliable predictive models are therefore needed in order to achieve the ultimate heavy duty fuel cell lifetime target of 25,000 h. In the present work, an empirical membrane lifetime model was developed based on laboratory data from a suite of accelerated membrane durability tests. The model considers the effects of cell voltage, temperature, oxygen concentration, humidity cycling, humidity level, and platinum in the membrane using inverse power law and exponential relationships within the framework of a general log-linear Weibull life-stress statistical distribution. The obtained model is capable of extrapolating the membrane lifetime from accelerated test conditions to use level conditions during field operation. Based on typical conditions for the Whistler, British Columbia fuel cell transit bus fleet, the model predicts a stack lifetime of 17,500 h and a membrane leak initiation time of 9200 h. Validation performed with the aid of a field operated stack confirmed the initial goal of the model to predict membrane lifetime within 20% of the actual operating time.

  17. In-situ membrane hydration measurement of proton exchange membrane fuel cells

    Science.gov (United States)

    Lai, Yeh-Hung; Fly, Gerald W.; Clapham, Shawn

    2015-01-01

    Achieving proper membrane hydration control is one of the most critical aspects of PEM fuel cell development. This article describes the development and application of a novel 50 cm2 fuel cell device to study the in-situ membrane hydration by measuring the through-thickness membrane swelling via an array of linear variable differential transducers. Using this setup either as an air/air (dummy) cell or as a hydrogen/air (operating) cell, we performed a series of hydration and dehydration experiments by cycling the RH of the inlet gas streams at 80 °C. From the linear relationship between the under-the-land swelling and the over-the-channel water content, the mechanical constraint within the fuel cell assembly can suppress the membrane water uptake by 11%-18%. The results from the air/air humidity cycling test show that the membrane can equilibrate within 120 s for all RH conditions and that membrane can reach full hydration at a RH higher than 140% in spite of the use of a liquid water impermeable Carbel MP30Z microporous layer. This result confirms that the U.S. DOE's humidity cycling mechanical durability protocol induces sufficient humidity swings to maximize hygrothermal mechanical stresses. This study shows that the novel experimental technique can provide a robust and accurate means to study the in-situ hydration of thin membranes subject to a wide range of fuel cell conditions.

  18. Apoptosis may determine the release of skeletal alkaline phosphatase activity from human osteoblast-line cells.

    Science.gov (United States)

    Farley, J R; Stilt-Coffing, B

    2001-01-01

    Although quantitative measurement of skeletal alkaline phosphatase (sALP) activity in serum can provide an index of the rate of bone formation, the metabolic process that determines the release of sALP - from the surface of osteoblasts, into circulation-is unknown. The current studies were intended to examine the hypothesis that the release of sALP from human osteoblasts is a consequence of apoptotic cell death. We measured the release of sALP activity from human osteosarcoma (SaOS-2) cells and normal human bone cells, under basal conditions and in response to agents that increased apoptosis (TNF-a, okadiac acid) and agents that inhibit apoptosis (IGF-I, calpain, and caspase inhibitors). Apoptosis was determined by the presence of nucleosomes (histone-associated DNA) in the cytoplasm of the cells by using a commercial kit. The results of these studies showed that TNF-a and okadiac acid caused dose- and time-dependent increases in apoptosis in the SaOS-2 cells (r = 0.78 for doses of TNF-a and r = 0.93 for doses of okadiac acid, P sALP activity (e.g., r = 0.89 for TNF-a and r = 0.75 for okadiac acid, P sALP activity (P sALP activity (P sALP release. The associations between apoptosis and sALP release were not unique to osteosarcoma (i.e., SaOS-2) cells, but also seen with osteoblast-line cells derived from normal human bone. Together, these data demonstrate that the release of sALP activity from human osteoblast-line cells in vitro is associated with, and may be a consequence of, apoptotic cell death. These findings are consistent with the general hypothesis that the appearance of sALP activity in serum may reflect the turnover of osteoblast-line cells.

  19. Bimetallic Ag–Ni/C particles as cathode catalyst in AFCs (alkaline fuel cells)

    International Nuclear Information System (INIS)

    Song, Xingjuan; Zhang, Dongming

    2014-01-01

    AFCs (alkaline fuel cells) is one of the promising fuel cells, due to their low working temperature and less corrosive environment. However, decreasing the catalyst cost and improving its performance are still the challenges in its application. Transition metal as the catalyst for AFCs not only can reduce its cost, but also has great electro-catalytic efficiency. In this paper, Carbon supported Ag–Ni bimetallic catalysts with differential Ag/Ni atomic ratios were prepared by chemically reducing silver and nickel salts. Ag 3 Ni/C shows the relatively higher ORR (oxygen reduction reaction) activity among the differential Ag/Ni bimetallic particles. In order to improve the activity and stability, the catalysts were heat-treated at the temperature of 500 °C. The results indicate that the limiting current density has been improved greatly for Ag 3 Ni/C-500 °C, which is as high as 2.5× that of Ag/C. The microstructure investigation show that the non-equilibrium state of Ag–Ni alloy by heat treatment is confirmed by HRTEM (high-resolution transmission electron microscopy) images, and Ag(111) surfaces are decreased in XRD pattern, which results in the ORR activity improved and overpotential decreased. Heat treatment also has contributed to Ag–Ni/C electrochemistry stability in some degree. - Highlights: • Ag–Ni/C is applied as cathode catalyst for AFCs (alkaline fuel cells). • Ag 3 Ni/C-500 °C shows the best performance. • Non-equilibrium state of Ag–Ni alloy by heat treatment is observed. • The decreased Ag(111) surfaces are favor to improve the catalyst activity

  20. A mathematical model of the maximum power density attainable in an alkaline hydrogen/oxygen fuel cell

    Science.gov (United States)

    Kimble, Michael C.; White, Ralph E.

    1991-01-01

    A mathematical model of a hydrogen/oxygen alkaline fuel cell is presented that can be used to predict the polarization behavior under various power loads. The major limitations to achieving high power densities are indicated and methods to increase the maximum attainable power density are suggested. The alkaline fuel cell model describes the phenomena occurring in the solid, liquid, and gaseous phases of the anode, separator, and cathode regions based on porous electrode theory applied to three phases. Fundamental equations of chemical engineering that describe conservation of mass and charge, species transport, and kinetic phenomena are used to develop the model by treating all phases as a homogeneous continuum.

  1. Phosphoric acid doped imidazolium polysulfone membranes for high temperature proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Li, Qingfeng; Jensen, Jens Oluf

    2012-01-01

    A novel acid–base polymer membrane is prepared by doping of imidazolium polysulfone with phosphoric acid for high temperature proton exchange membrane fuel cells. Polysulfone is first chloromethylated, followed by functionalization of the chloromethylated polysulfone with alkyl imidazoles i.e. me...

  2. Functional implications of plasma membrane condensation for T cell activation.

    Directory of Open Access Journals (Sweden)

    Carles Rentero

    2008-05-01

    Full Text Available 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.

  3. Molecular organization in bacterial cell membranes

    International Nuclear Information System (INIS)

    Larraga, V.; Munoz, E.

    1975-01-01

    The paper reports about an investigation into the question of the specific labelling and topological distribution of glycoproteins and proteins in Streptomyces albus membranes. The method of sample preparation is described: Tritium labelling of glycoproteins in protoplasts and membranes, iodination of proteins, trypsin treatment and polyacrylamide gel electrophoresis. The findings suggest an asymmetrical distribution of the glycoproteins in membranes and a weak accessibility to iodine label. A structural model of the plasma membranes of Streptomyces albus is proposed similar to the general 'fluid mosaic' model of Singer and Nicholson. (BSC) [de

  4. Pyroelectricity as a possible mechanism for cell membrane permeabilization.

    Science.gov (United States)

    García-Sánchez, Tomás; Muscat, Adeline; Leray, Isabelle; Mir, Lluis M

    2018-02-01

    The effects of pyroelectricity on cell membrane permeability had never been explored. Pyroelectricity consists in the generation of an electric field in the surface of some materials when a change in temperature is produced. In the present study, tourmaline microparticles, which are known to display pyroelectrical properties, were subjected to different changes in temperature upon exposure to cells in order to induce an electric field at their surface. Then, the changes in the permeability of the cell membrane to a cytotoxic agent (bleomycin) were assessed by a cloning efficacy test. An increase in the permeability of the cell membrane was only detected when tourmaline was subjected to a change in temperature. This suggests that the apparition of an induced pyroelectrical electric field on the material could actually be involved in the observed enhancement of the cell membrane permeability as a result of cell electropermeabilization. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. A cell culture technique for human epiretinal membranes to describe cell behavior and membrane contraction in vitro.

    Science.gov (United States)

    Wertheimer, Christian; Eibl-Lindner, Kirsten H; Compera, Denise; Kueres, Alexander; Wolf, Armin; Docheva, Denitsa; Priglinger, Siegfried G; Priglinger, Claudia; Schumann, Ricarda G

    2017-11-01

    To introduce a human cell culture technique for investigating in-vitro behavior of primary epiretinal cells and membrane contraction of fibrocellular tissue surgically removed from eyes with idiopathic macular pucker. Human epiretinal membranes were harvested from ten eyes with idiopathic macular pucker during standard vitrectomy. Specimens were fixed on cell culture plastic using small entomological pins to apply horizontal stress to the tissue, and then transferred to standard cell culture conditions. Cell behavior of 400 epiretinal cells from 10 epiretinal membranes was observed in time-lapse microscopy and analyzed in terms of cell migration, cell velocity, and membrane contraction. Immunocytochemistry was performed for cell type-specific antigens. Cell specific differences in migration behavior were observed comprising two phenotypes: (PT1) epiretinal cells moving fast, less directly, with small round phenotype and (PT2) epiretinal cells moving slowly, directly, with elongated large phenotype. No mitosis, no outgrowth and no migration onto the plastic were seen. Horizontal contraction measurements showed variation between specimens. Masses of epiretinal cells with a myofibroblast-like phenotype expressed cytoplasmatic α-SMA stress fibers and correlated with cell behavior characteristics (PT2). Fast moving epiretinal cells (PT1) were identified as microglia by immunostaining. This in-vitro technique using traction application allows for culturing surgically removed epiretinal membranes from eyes with idiopathic macular pucker, demonstrating cell behavior and membrane contraction of primary human epiretinal cells. Our findings emphasize the abundance of myofibroblasts, the presence of microglia and specific differences of cell behavior in these membranes. This technique has the potential to improve the understanding of pathologies at the vitreomacular interface and might be helpful in establishing anti-fibrotic treatment strategies.

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

    Science.gov (United States)

    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].

  7. Models of dynamic extraction of lipid tethers from cell membranes

    International Nuclear Information System (INIS)

    Nowak, Sarah A; Chou, Tom

    2010-01-01

    When a ligand that is bound to an integral membrane receptor is pulled, the membrane and the underlying cytoskeleton can deform before either the membrane delaminates from the cytoskeleton or the ligand detaches from the receptor. If the membrane delaminates from the cytoskeleton, it may be further extruded and form a membrane tether. We develop a phenomenological model for this process by assuming that deformations obey Hooke's law up to a critical force at which the cell membrane locally detaches from the cytoskeleton and a membrane tether forms. We compute the probability of tether formation and show that tethers can be extruded only within an intermediate range of force loading rates and pulling velocities. The mean tether length that arises at the moment of ligand detachment is computed as are the force loading rates and pulling velocities that yield the longest tethers

  8. Palladium-based electrocatalysts for ethanol oxidation reaction in alkaline direct ethanol fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Moraes, Leticia Poras Reis de; Amico, Sandro Campos; Malfatti, Celia de Fraga, E-mail: leticiamoraes@usp.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre (Brazil); Matos, Bruno R.; Santiago, Elisabete Inacio; Fonseca, Fabio Coral [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2016-07-01

    Full text: Direct ethanol fuel cells require adequate electrocatalysts to promote the carbon carbon cleavage of ethanol molecule. Typical electrocatalysts are based on platinum, which have shown improved activity in acidic media. However, Pt-based catalysts have high cost and are easily deactivated by CO poisoning. Therefore, novel catalysts have been developed, and among then, palladium-based materials have shown promising results for the oxidation of ethanol in alkaline media. The present study reports on the performance of alkaline direct ethanol fuel cell (ADEFC) by using carbon-supported Pd, PdSn, PdNi, and PdNiSn produced by impregnation-reduction of the metallic precursors. The effect of chemical functionalization by acid treatment of the carbon support (Vulcan) was investigated. The electrocatalysts were studied by thermogravimetric analysis (TGA), X-rays diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), and ADEFC tests. TGA measurements of functionalized Vulcan evidenced the characteristic weight losses attributed to the presence of surface functional groups due to the acid treatment. A high degree of alloying between Pd and Sn was inferred from XRD data, whereas in both PdNi and PdNiSn, Ni occurs mostly segregated in the oxide form. TEM analyses indicated agglomeration of Pd and PdSn particles, whereas a more uniform particle distribution was observed for PdNi and PdNiSn samples. CV curves showed that the peak potential for the oxidation of ethanol shifts towards negative values for all samples supported on functionalized Vulcan indicating that ethanol oxidation is facilitated. Microstructural and electrochemical features were confirmed by ADEFC tests, which revealed that the highest open circuit voltage and maximum power density were achieved for PdNiSn electrocatalysts supported on functionalized Vulcan with uniform particle distribution and improved triple phase boundaries. (author)

  9. Palladium-based electrocatalysts for ethanol oxidation reaction in alkaline direct ethanol fuel cell

    International Nuclear Information System (INIS)

    Moraes, Leticia Poras Reis de; Amico, Sandro Campos; Malfatti, Celia de Fraga; Matos, Bruno R.; Santiago, Elisabete Inacio; Fonseca, Fabio Coral

    2016-01-01

    Full text: Direct ethanol fuel cells require adequate electrocatalysts to promote the carbon carbon cleavage of ethanol molecule. Typical electrocatalysts are based on platinum, which have shown improved activity in acidic media. However, Pt-based catalysts have high cost and are easily deactivated by CO poisoning. Therefore, novel catalysts have been developed, and among then, palladium-based materials have shown promising results for the oxidation of ethanol in alkaline media. The present study reports on the performance of alkaline direct ethanol fuel cell (ADEFC) by using carbon-supported Pd, PdSn, PdNi, and PdNiSn produced by impregnation-reduction of the metallic precursors. The effect of chemical functionalization by acid treatment of the carbon support (Vulcan) was investigated. The electrocatalysts were studied by thermogravimetric analysis (TGA), X-rays diffraction (XRD), transmission electron microscopy (TEM), cyclic voltammetry (CV), and ADEFC tests. TGA measurements of functionalized Vulcan evidenced the characteristic weight losses attributed to the presence of surface functional groups due to the acid treatment. A high degree of alloying between Pd and Sn was inferred from XRD data, whereas in both PdNi and PdNiSn, Ni occurs mostly segregated in the oxide form. TEM analyses indicated agglomeration of Pd and PdSn particles, whereas a more uniform particle distribution was observed for PdNi and PdNiSn samples. CV curves showed that the peak potential for the oxidation of ethanol shifts towards negative values for all samples supported on functionalized Vulcan indicating that ethanol oxidation is facilitated. Microstructural and electrochemical features were confirmed by ADEFC tests, which revealed that the highest open circuit voltage and maximum power density were achieved for PdNiSn electrocatalysts supported on functionalized Vulcan with uniform particle distribution and improved triple phase boundaries. (author)

  10. A Quaternary Polybenzimidazole Membrane for Intermediate Temperature Polymer Electrolyte Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Xu, C.; Scott, K.; Li, Qingfeng

    2013-01-01

    at 150 °C with the PA acid loading level of 3.5 PRU (amount of H3PO4 per repeat unit of polymer QPBI). The QPBI membrane was characterized in terms of composition, structure and morphology by NMR, FTIR, SEM, and EDX. The fuel cell performance with the membrane gave peak power densities of 440 and 240 m......A quaternary ammonium polybenzimidazole (QPBI) membrane was synthesized for applications in intermediate temperature (100–200 °C) hydrogen fuel cells. The QPBI membrane was imbibed with phosphoric acid to provide suitable proton conductivity. The proton conductivity of the membrane was 0.051 S cm–1......W cm–2 using oxygen and air, respectively, at 175 °C....

  11. Nanoscale cell membrane organization : a near-field optical view

    NARCIS (Netherlands)

    Koopman, Marjolein

    2006-01-01

    The cell plasma membrane of eukaryotic cells is a lipid bi-layer that separates the cell cytosol from the extracellular environment. The composition and organization of proteins and lipids within this bi-layer have a direct impact on many cellular processes, since they form the senses of the cell.

  12. Single cell wound generates electric current circuit and cell membrane potential variations that requires calcium influx.

    Science.gov (United States)

    Luxardi, Guillaume; Reid, Brian; Maillard, Pauline; Zhao, Min

    2014-07-24

    Breaching of the cell membrane is one of the earliest and most common causes of cell injury, tissue damage, and disease. If the compromise in cell membrane is not repaired quickly, irreversible cell damage, cell death and defective organ functions will result. It is therefore fundamentally important to efficiently repair damage to the cell membrane. While the molecular aspects of single cell wound healing are starting to be deciphered, its bio-physical counterpart has been poorly investigated. Using Xenopus laevis oocytes as a model for single cell wound healing, we describe the temporal and spatial dynamics of the wound electric current circuitry and the temporal dynamics of cell membrane potential variation. In addition, we show the role of calcium influx in controlling electric current circuitry and cell membrane potential variations. (i) Upon wounding a single cell: an inward electric current appears at the wound center while an outward electric current is observed at its sides, illustrating the wound electric current circuitry; the cell membrane is depolarized; calcium flows into the cell. (ii) During cell membrane re-sealing: the wound center current density is maintained for a few minutes before decreasing; the cell membrane gradually re-polarizes; calcium flow into the cell drops. (iii) In conclusion, calcium influx is required for the formation and maintenance of the wound electric current circuitry, for cell membrane re-polarization and for wound healing.

  13. Layer-by-layer cell membrane assembly

    Science.gov (United States)

    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.

  14. Radiation Interaction with Therapeutic Drugs and Cell Membranes

    International Nuclear Information System (INIS)

    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.

    2007-01-01

    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

  15. Tissue non-specific alkaline phosphatase production by human dental pulp stromal cells is enhanced by high density cell culture.

    Science.gov (United States)

    Tomlinson, Matthew J; Dennis, Caitriona; Yang, Xuebin B; Kirkham, Jennifer

    2015-08-01

    The cell surface hydrolase tissue non-specific alkaline phosphatase (TNAP) (also known as MSCA-1) is used to identify a sub-population of bone marrow stromal cells (BMSCs) with high mineralising potential and is found on subsets of cells within the dental pulp. We aim to determine whether TNAP is co-expressed by human dental pulp stromal cells (hDPSCs) alongside a range of BMSC markers, whether this is an active form of the enzyme and the effects of culture duration and cell density on its expression. Cells from primary dental pulp and culture expanded hDPSCs expressed TNAP. Subsequent analyses revealed persistent TNAP expression and co-expression with BMSC markers such as CD73 and CD90. Flow cytometry and biochemical assays showed that increased culture durations and cell densities enhanced TNAP expression by hDPSCs. Arresting the hDPSC cell cycle also increased TNAP expression. These data confirm that TNAP is co-expressed by hDPSCs together with other BMSC markers and show that cell density affects TNAP expression levels. We conclude that TNAP is a potentially useful marker for hDPSC selection especially for uses in mineralised tissue regenerative therapies.

  16. Radiation Grafted Polymer Membranes for Fuel Cell Applications

    International Nuclear Information System (INIS)

    Scherer, G.G.; Wallasch, F.; Ben Youcef, H.; Gubler, L.

    2012-01-01

    Partially fluorinated proton exchange membranes prepared via radiation induced graft copolymerization ('radiation grafting') offer the prospect of cost-effective and tailor made membrane electrolytes for the polymer electrolyte fuel cell (PEFC). The composition and structure of radiation grafted membranes can be adjusted in a broad range to balance the different requirements of proton transport and mechanical robustness. Based on the earlier work on Styrene grafting, the novel monomer combination α-methyl-styrene/methacrylonitrile (AMS/MAN) is introduced for improved stability in the prevailing fuel cell environment. Successful fuel cell experiments proved the concept. (author)

  17. Radiation Grafted Polymer Membranes for Fuel Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Scherer, G G; Wallasch, F; Ben Youcef, H; Gubler, L [Electrochemistry Laboratory, Paul Scherrer Institut, CH-5232 Villigen (Switzerland)

    2012-09-15

    Partially fluorinated proton exchange membranes prepared via radiation induced graft copolymerization ('radiation grafting') offer the prospect of cost-effective and tailor made membrane electrolytes for the polymer electrolyte fuel cell (PEFC). The composition and structure of radiation grafted membranes can be adjusted in a broad range to balance the different requirements of proton transport and mechanical robustness. Based on the earlier work on Styrene grafting, the novel monomer combination {alpha}-methyl-styrene/methacrylonitrile (AMS/MAN) is introduced for improved stability in the prevailing fuel cell environment. Successful fuel cell experiments proved the concept. (author)

  18. Differentiation-dependent activation of the human intestinal alkaline phosphatase promoter by HNF-4 in intestinal cells

    DEFF Research Database (Denmark)

    Olsen, Line; Bressendorff, Simon; Troelsen, Jesper T

    2005-01-01

    The intestinal alkaline phosphatase gene (ALPI) encodes a digestive brush-border enzyme, which is highly upregulated during small intestinal epithelial cell differentiation. To identify new putative promoter motifs responsible for the regulation of ALPI expression during differentiation of the en...

  19. Perforate on CHO cell membranes induced by electromagnetic ...

    African Journals Online (AJOL)

    Atomic force microscopy (AFM) has been used to visualize the morphological change on the surface of Chinese hamster ovary (CHO) cell membranes before and after electromagnetic pulses (EMP) irradiation. The results show that there were different sizes and shapes of membrane perforate (width ranging from 0.39 - 0.66 ...

  20. Catalytic membranes for CO oxidation in fuel cells

    Science.gov (United States)

    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.

  1. Toughness of membranes applied in polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kiefer, J; Brack, H P; Scherer, G G [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Since several years we apply the radiation-grafting technique to prepare polymeric membranes for application in polymer electrolyte fuel cells (PEFCs). Our investigations presented here focus on changes in toughness of these materials after the various synthesis steps and the importance of membrane toughness for their application in PEFCs. (author) 2 figs., 4 refs.

  2. Innovative membrane development for fuel cells

    CSIR Research Space (South Africa)

    Vaivars, G

    2011-10-01

    Full Text Available The innovative membranes for alternative energy devices will be presented. An electrical car is long waited solution to environmental and fuel supply problems in transport. Most probably, the shift from a combustion engine to an electrical car...

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

    Science.gov (United States)

    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.

  4. Novel High Temperature Membrane for PEM Fuel Cells, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The innovation proposed in this STTR program is a high temperature membrane to increase the efficiency and power density of PEM fuel cells. The NASA application is...

  5. Stimulated-healing of proton exchange membrane fuel cell catalyst

    NARCIS (Netherlands)

    Latsuzbaia, R.; Negro, E.; Koper, G.J.M.

    2013-01-01

    Platinum nanoparticles, which are used as catalysts in Proton Exchange Membrane Fuel Cells (PEMFC), tend to degrade after long-term operation. We discriminate the following mechanisms of the degradation: poisoning, migration and coalescence, dissolution, and electrochemical Ostwald ripening. There

  6. Stimulation by parathyroid hormone of sup 45 Ca sup 2+ uptake in osteoblast-like cells: Possible involvement of alkaline phosphatase

    Energy Technology Data Exchange (ETDEWEB)

    Fukayama, S.; Tashjian, A.H. Jr. (Harvard School of Public Health, Boston, MA (USA))

    1990-04-01

    We have investigated the actions of human PTH (hPTH-(1-34)) on the association of 45Ca2+ with two human (SaOS-2 and MG-63) and two rat (ROS 17/2.8 and UMR-106) osteoblast-like cell types. In SaOS-2 cells, hPTH-(1-34) binds to specific membrane receptors to activate adenylate cyclase. Treatment of SaOS-2 cells with hPTH-(1-34) resulted in an increase in 45Ca2+ uptake, in a dose-dependent fashion, up to 2- to 4-fold above control values. The increase was first evident at 10 min and persisted for at least 30 min. Treatment with nimodipine, a calcium channel antagonist, was without effect on the stimulatory action of PTH. A similar enhancement of cell-associated 45Ca2+ was observed when the cells were incubated with vasoactive intestinal peptide, which acts via different receptors to activate adenylate cyclase in SaOS-2 cells. Treatment with (Bu)2cAMP also induced an increase in cell-associated 45Ca2+. Pretreatment of SaOS-2 cells with hPTH-(1-34) for 4 h, which induced homologous desensitization to a second challenge with the same peptide for stimulation of cAMP production, did not attenuate the further enhancement of cell-associated 45Ca2+ by a second treatment with hPTH-(1-34). We then examined a possible relationship between alkaline phosphatase (ALPase) and 45Ca2+ uptake. SaOS-2 cells contained high levels of alkaline phosphatase activity and continuously released the enzyme into the medium. Release was enhanced by treatment with hPTH-(1-34) for 10 min. Incubation of cells with levamisole (an inhibitor of the liver/bone/kidney type of ALPase) resulted in a rapid decrease in basal and PTH-stimulated 45Ca2+ uptake, while treatment with L-Phe-Gly-Gly was without effect. Treatment of the cells with ALPase (bovine kidney) enhanced 45Ca2+ uptake. In MG-63 cells, a stimulatory effect of hPTH-(1-34) on cell-associated 45Ca2+ was also observed; however, hPTH-(1-34) did not stimulate cAMP production in MG-63 cells.

  7. Poly (ether ether ketone) membranes for fuel cells

    International Nuclear Information System (INIS)

    Marrero, Jacqueline C.; Gomes, Ailton de S.; Filho, Jose C.D.; Hui, Wang S.; Oliveira, Vivianna S. de

    2015-01-01

    Polymeric membranes were developed using a SPEEK polymer matrix (sulphonated poly (ether ether ketone)), containing hygroscopic particles of zirconia (Zr) (incorporated by sol-gel method), for use as electrolyte membranes in fuel cells. SPEEK with different sulfonation degrees were used: 63 and 86%. The thermal analysis (TGA and DSC) was carried out to characterize the membranes and electrochemical impedance spectroscopy (EIS) was carried out to evaluating the proton conductivity of the membranes. Additional analysis were underway in order to characterize these membranes, which include: X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in order to evaluate the influence of zirconia and sulfonation degree on the properties of the membranes. (author)

  8. Mesenchymal stem cells with osteogenic potential in human maxillary sinus membrane: an in vitro study.

    Science.gov (United States)

    Berbéri, Antoine; Al-Nemer, Fatima; Hamade, Eva; Noujeim, Ziad; Badran, Bassam; Zibara, Kazem

    2017-06-01

    The aim of our study is to prove and validate the existence of an osteogenic progenitor cell population within the human maxillary Schneiderian sinus membrane (hMSSM) and to demonstrate their potential for bone formation. Ten hMSSM samples of approximately 2 × 2 cm were obtained during a surgical nasal approach for treatment of chronic rhinosinusitis and were retained for this study. The derived cells were isolated, cultured, and assayed at passage 3 for their osteogenic potential using the expression of Alkaline phosphatase, alizarin red and Von Kossa staining, flow cytometry, and quantitative real-time polymerase chain reaction. hMSSM-derived cells were isolated, showed homogenous spindle-shaped fibroblast-like morphology, characteristic of mesenchymal progenitor cells (MPCs), and demonstrated very high expression of MPC markers such as STRO-1, CD44, CD90, CD105, and CD73 in all tested passages. In addition, von Kossa and Alizarin red staining showed significant mineralization, a typical feature of osteoblasts. Moreover, alkaline phosphatase (ALP) activity was significantly increased at days 7, 14, 21, and 28 of culture in hMSSM-derived cells grown in osteogenic medium, in comparison to controls. Furthermore, osteogenic differentiation significantly upregulated the transcriptional expression of osteogenic markers such as ALP, Runt-related transcription factor 2 (Runx-2), bone morphogenetic protein (BMP)-2, osteocalcin (OCN), osteonectin (ON), and osteopontin (OPN), confirming that hMSSM-derived cells are of osteoprogenitor origin. Finally, hMSSM-derived cells were also capable of producing OPN proteins upon culturing in an osteogenic medium. Our data showed that hMSSM holds mesenchymal osteoprogenitor cells capable of differentiating to the osteogenic lineage. hMSSM contains potentially multipotent postnatal stem cells providing a promising clinical application in preimplant and implant therapy.

  9. Bipolar membranes in forward bias region for fuel cell reactors

    International Nuclear Information System (INIS)

    Lobyntseva, Elena; Kallio, Tanja; Kontturi, Kyoesti

    2006-01-01

    Three bipolar membranes, two home-made composed of commercial cation (DuPont) and anion (FuMA-Tech) exchange membranes (called Nafion/FT-FAA and Nafion/FT-FAS) and a commercial one, BP-1 from FuMA-Tech, were investigated in order to characterize their suitability to use in a H 2 /O 2 fuel cell intended to produce hydrogen peroxide on the cathode instead of water. The Nafion/FT-FAA and Nafion/FT-FAS membranes were prepared using a hot-pressing method. The optimal hot-pressing conditions were determined by measuring the ionic conductivity of the membranes. The latter was observed to depend on the relative humidity of the bipolar membrane. Of the studied bipolar membranes, Nafion/FT-FAA showed the best performance. The transport number of protons measured in a concentration cell was observed to depend on the direction of the proton diffusion flux through these membranes so that transport numbers of ca. unity were obtained when the cation exchange side faced the solution with higher proton concentration. In the opposite case, when the higher concentration faced anion exchange side, the transport number of proton was clearly lower, indicating the usefulness of the bipolar membranes for hydrogen peroxide production in the fuel cell

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

    Science.gov (United States)

    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

  11. Modeling of interactions between nanoparticles and cell membranes

    Science.gov (United States)

    Ban, Young-Min

    containing the nanoparticles exhibit localized perturbation around the nanoparticle. The nanoparticles are not likely to affect membrane protein function by the weak perturbation of the internal stress in the membrane. Due to the short-ranged interactions between the nanoparticles, the nanoparticles would not form aggregates inside membranes. The effect of lipid peroxidation on cell membrane deformation is assessed. The peroxidized lipids introduce a perturbation to the internal structure of the membrane leading to higher amplitude of the membrane fluctuations. Higher concentration of the peroxidized lipids induces more significant perturbation. Cumulative effects of lipid peroxidation caused by nanoparticles are examined for the first time. The considered amphiphilic particle appears to reduce the perturbation of the membrane structure at its equilibrium position inside the peroxidized membrane. This suggests a possibility of antioxidant effect of the nanoparticle.

  12. Chapter 6: cubic membranes the missing dimension of cell membrane organization.

    Science.gov (United States)

    Almsherqi, Zakaria A; Landh, Tomas; Kohlwein, Sepp D; Deng, Yuru

    2009-01-01

    Biological membranes are among the most fascinating assemblies of biomolecules: a bilayer less than 10 nm thick, composed of rather small lipid molecules that are held together simply by noncovalent forces, defines the cell and discriminates between "inside" and "outside", survival, and death. Intracellular compartmentalization-governed by biomembranes as well-is a characteristic feature of eukaryotic cells, which allows them to fulfill multiple and highly specialized anabolic and catabolic functions in strictly controlled environments. Although cellular membranes are generally visualized as flat sheets or closely folded isolated objects, multiple observations also demonstrate that membranes may fold into "unusual", highly organized structures with 2D or 3D periodicity. The obvious correlation of highly convoluted membrane organizations with pathological cellular states, for example, as a consequence of viral infection, deserves close consideration. However, knowledge about formation and function of these highly organized 3D periodic membrane structures is scarce, primarily due to the lack of appropriate techniques for their analysis in vivo. Currently, the only direct way to characterize cellular membrane architecture is by transmission electron microscopy (TEM). However, deciphering the spatial architecture solely based on two-dimensionally projected TEM images is a challenging task and prone to artifacts. In this review, we will provide an update on the current progress in identifying and analyzing 3D membrane architectures in biological systems, with a special focus on membranes with cubic symmetry, and their potential role in physiological and pathophysiological conditions. Proteomics and lipidomics approaches in defined experimental cell systems may prove instrumental to understand formation and function of 3D membrane morphologies.

  13. Catalyst Degradation in High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    DEFF Research Database (Denmark)

    Cleemann, Lars Nilausen; Buazar, F.; Li, Qingfeng

    2013-01-01

    and multi‐walled carbon nanotubes were used as supports for electrode catalysts and evaluated in accelerated durability tests under potential cycling at 150 °C. Measurements of open circuit voltage, area specific resistance and hydrogen permeation through the membrane were carried out, indicating little...... contribution of the membrane degradation to the performance losses during the potential cycling tests. As the major mechanism of the fuel cell performance degradation, the electrochemical active area of the cathodic catalysts showed a steady decrease in the cyclic voltammetric measurements, which was also......Degradation of carbon supported platinum catalysts is a major failure mode for the long term durability of high temperature proton exchange membrane fuel cells based on phosphoric acid doped polybenzimidazole membranes. With Vulcan carbon black as a reference, thermally treated carbon black...

  14. Protein diffusion in plant cell plasma membranes: The cell-wall corral

    Directory of Open Access Journals (Sweden)

    Alexandre eMartinière

    2013-12-01

    Full Text Available 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.

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

    Science.gov (United States)

    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.

  16. Membrane potential and cation channels in rat juxtaglomerular cells

    DEFF Research Database (Denmark)

    Friis, U G; Jørgensen, F; Andreasen, D

    2004-01-01

    The relationship between membrane potential and cation channels in juxtaglomerular (JG) cells is not well understood. Here we review electrophysiological and molecular studies of JG cells demonstrating the presence of large voltage-sensitive, calcium-activated potassium channels (BK(Ca)) of the Z......The relationship between membrane potential and cation channels in juxtaglomerular (JG) cells is not well understood. Here we review electrophysiological and molecular studies of JG cells demonstrating the presence of large voltage-sensitive, calcium-activated potassium channels (BK...

  17. X-radiation effects on muscle cell membrane electrical parameters

    International Nuclear Information System (INIS)

    Portela, A.; Vaccari, J.G.; Llobera, O.; Campi, M.; Delbue, M.A.; Perez, J.C.; Stewart, P.A.; Gosztonyi, A.E.; Brown Univ., Providence, R.I.

    1975-01-01

    Early effects of 100 Kilorads of X-rays on muscle cell membrane properties have been measured in sartorius muscles from Leptodactylus ocellatus. Threshold strength for rectangular current pulses increased 10% after irradiation, and action potential propagation velocity decreased 10%. Passive membrane parameters were calculated from potential responses to sub-threshold current pulses, assuming conventional cable theory. Specific membrane conductance increased to 18% after irradiation, membrane capacitance increased 14%, and length constant decreased 10% but membrane time constant was unchanged. Cell diameter decreased 5%, and resting membrane potential decreased 8%. Membrane parameters during an action potential were also evaluated by the phase-plane and current-voltage plot techniques. Irradiation significantly decreased the action potential amplitude, the excitation potential, and the maximum rates of rise and fall of membrane potential. Increases were observed in dynamic sodium and potassium conductances, peak sodium current, and net charge accumulation per action potential. This X-ray dose also produced signficant changes in the timing of peak events during the action potential; in general the whole action potential process is slower after irradiation

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

    International Nuclear Information System (INIS)

    Harper, Jeffrey F.

    2004-01-01

    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. Anion exchange membrane

    Science.gov (United States)

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  20. Fuel cell electrolyte membrane with basic polymer

    Science.gov (United States)

    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.

  1. The lipid organisation of the cell membrane

    Directory of Open Access Journals (Sweden)

    Ladha, S.

    2000-04-01

    Full Text Available Lipids and proteins in biological membranes are arranged in a mosaic of domains in the membrane. These domains represent small-scale heterogeneities in composition, shape and fluidity within the plane of the membrane, over the range of hundreds of nanometers to a few micrometers. They arise from the complex interactions of the heterogeneous mixtures of phospholipids, sterols, and proteins that make up all biological membranes.Los lípidos y las proteínas en las membranas biológicas están dispuestos en un mosaico de campos en la membrana. Estos campos representan heterogeneidades a pequeña escala en la composición, forma y fluidez dentro del plano de la membrana, en un rango que va de los cientos de nanómetros a los pocos micrómetros. Estos campos se originan de las complejas interacciones de las mezclas heterogéneas de fosfolípidos, esteroles y proteínas de las que están hechas todas y cada una de las membranas biológicas.

  2. Polybenzimidazole Membranes Containing Benzimidazole Side Groups for High Temprature Polymer Electrolyte Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Li, Xueyuan; Xu, Yizin

    2013-01-01

    Polybenzimidazole (PBI) with a high molecular weight of 69,000 was first synthesized. It was afterwards grafted with benzimidazole pendant groups on the backbones. The acid doped benzimidaozle grafted PBI membranes were investigated and characterized including fuel cell tests at elevated temperat......Polybenzimidazole (PBI) with a high molecular weight of 69,000 was first synthesized. It was afterwards grafted with benzimidazole pendant groups on the backbones. The acid doped benzimidaozle grafted PBI membranes were investigated and characterized including fuel cell tests at elevated...... temperatures without humidification. At an acid doping level of 13.1 mol H3PO4 per average molar repeat unit, the PBI membranes with a benzimidazole grafting degree of 10.6% demonstrated a conductivity of 0.15 S cm-1 and a H2-air fuel cell peak power density of 378 mW cm-2 at 180 oC at ambient pressure without...

  3. Direct visualization of membrane architecture of myelinating cells in transgenic mice expressing membrane-anchored EGFP.

    Science.gov (United States)

    Deng, Yaqi; Kim, BongWoo; He, Xuelian; Kim, Sunja; Lu, Changqing; Wang, Haibo; Cho, Ssang-Goo; Hou, Yiping; Li, Jianrong; Zhao, Xianghui; Lu, Q Richard

    2014-04-01

    Myelinogenesis is a complex process that involves substantial and dynamic changes in plasma membrane architecture and myelin interaction with axons. Highly ramified processes of oligodendrocytes in the central nervous system (CNS) make axonal contact and then extrapolate to wrap around axons and form multilayer compact myelin sheathes. Currently, the mechanisms governing myelin sheath assembly and axon selection by myelinating cells are not fully understood. Here, we generated a transgenic mouse line expressing the membrane-anchored green fluorescent protein (mEGFP) in myelinating cells, which allow live imaging of details of myelinogenesis and cellular behaviors in the nervous systems. mEGFP expression is driven by the promoter of 2'-3'-cyclic nucleotide 3'-phosphodiesterase (CNP) that is expressed in the myelinating cell lineage. Robust mEGFP signals appear in the membrane processes of oligodendrocytes in the CNS and Schwann cells in the peripheral nervous system (PNS), wherein mEGFP expression defines the inner layers of myelin sheaths and Schmidt-Lanterman incisures in adult sciatic nerves. In addition, mEGFP expression can be used to track the extent of remyelination after demyelinating injury in a toxin-induced demyelination animal model. Taken together, the membrane-anchored mEGFP expression in the new transgenic line would facilitate direct visualization of dynamic myelin membrane formation and assembly during development and process remodeling during remyelination after various demyelinating injuries.

  4. Preliminary study on biological dosimetry using alkaline single cell gel electrophoresis of human peripheral lymphocytes

    International Nuclear Information System (INIS)

    Liu Qingjie; Lu Xue; Feng Jiangbing; Chen Deqing; Chen Xiaosui

    2006-01-01

    Objective: To explore the feasibility of alkaline single cell gel electrophoresis (SCGE) in biological dosimetry of ionizing radiation. Methods: Normal peripheral blood samples from two healthy males were exposed to different doses coblat-60 gamma-rays, ranged from 0 to 5 Gy, and the tail length (TL) and Oliver tail moment (TM) of the lymphocytes were analyzed with SCGE. The dose-effect curves of TL and TM were fitted respectively. The TL and TM of lymphocytes for eight radiation workers were analyzed with SCGE, cumulative doses were estimated using the fitted TL and TM equations, and then compared with the recorded monitoring doses. Results: The TLs or TMs of normal human lymphocytes were increased with the irradiation doses, and its relationship can be fitted with a linear-quadratic equations: Y=13.59 + 20.87X - 2.27 X 2 for TL, and Y = 8.50 + 15.04X - 1.43X 2 for TM, respectively (Y denotes TL or TM value, X is radiation dose). The doses estimated with TM equation were closer to the recorded monitoring doses than that with TL equation. Conclusions: The TM in lymphocytes analyzed with SCGE is a promising radiation biological dosimeter. (authors)

  5. With or without rafts? Alternative views on cell membranes.

    Science.gov (United States)

    Sevcsik, Eva; Schütz, Gerhard J

    2016-02-01

    The fundamental mechanisms of protein and lipid organization at the plasma membrane have continued to engage researchers for decades. Among proposed models, one idea has been particularly successful which assumes that sterol-dependent nanoscopic phases of different lipid chain order compartmentalize proteins, thereby modulating protein functionality. This model of membrane rafts has sustainably sparked the fields of membrane biophysics and biology, and shifted membrane lipids into the spotlight of research; by now, rafts have become an integral part of our terminology to describe a variety of cell biological processes. But is the evidence clear enough to continue supporting a theoretical concept which has resisted direct proof by observation for nearly twenty years? In this essay, we revisit findings that gave rise to and substantiated the raft hypothesis, discuss its impact on recent studies, and present alternative mechanisms to account for plasma membrane heterogeneity. © 2015 WILEY Periodicals, Inc.

  6. Polybenzimidazole/Mxene composite membranes for intermediate temperature polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Fei, Mingming; Lin, Ruizhi; Deng, Yuming; Xian, Hongxi; Bian, Renji; Zhang, Xiaole; Cheng, Jigui; Xu, Chenxi; Cai, Dongyu

    2018-01-01

    This report demonstrated the first study on the use of a new 2D nanomaterial (Mxene) for enhancing membrane performance of intermediate temperature (>100 °C) polymer electrolyte membrane fuel cells (ITPEMFCs). In this study, a typical Ti3C2T x -MXene was synthesized and incorporated into polybenzimidazole (PBI)-based membranes by using a solution blending method. The composite membrane with 3 wt% Ti3C2T x -MXene showed the proton conductivity more than 2 times higher than that of pristine PBI membrane at the temperature range of 100 °C-170 °C, and led to substantial increase in maximum power density of fuel cells by ˜30% tested at 150 °C. The addition of Ti3C2T x -MXene also improved the mechanical properties and thermal stability of PBI membranes. At 3 wt% Ti3C2T x -MXene, the elongation at break of phosphoric acid doped PBI remained unaffected at 150 °C, and the tensile strength and Young’s modulus was increased by ˜150% and ˜160%, respectively. This study pointed out promising application of MXene in ITPEMFCs.

  7. Nonlinear electro-mechanobiological behavior of cell membrane during electroporation

    KAUST Repository

    Deng, Peigang

    2012-01-01

    A nonlinear electroporation (EP) model is proposed to study the electro-mechanobiological behavior of cell membrane during EP, by taking the nonlinear large deformation of the membrane into account. The proposed model predicts the critical transmembrane potential and the activation energy for EP, the equilibrium pore size, and the resealing process of the pore. Single-cell EP experiments using a micro EP chip were conducted on chicken red blood cells at different temperatures to determine the activation energy and the critical transmembrane potential for EP. The experimental results are in good agreement with the theoretical predictions. © 2012 American Institute of Physics.

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

    Science.gov (United States)

    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

  9. Cell-penetrating peptides for drug delivery across membrane barriers

    DEFF Research Database (Denmark)

    Foged, Camilla; Nielsen, Hanne Moerck

    2008-01-01

    During the last decade, cell-penetrating peptides have been investigated for their ability to overcome the plasma membrane barrier of mammalian cells for the intracellular or transcellular delivery of cargoes as diverse as low molecular weight drugs, imaging agents, oligonucleotides, peptides......, proteins and colloidal carriers such as liposomes and polymeric nanoparticles. Their ability to cross biological membranes in a non-disruptive way without apparent toxicity is highly desired for increasing drug bioavailability. This review provides an overview of the application of cell......-penetrating peptides as transmembrane drug delivery agents, according to the recent literature, and discusses critical issues and future challenges in relation to fully understanding the fundamental principles of the cell-penetrating peptide-mediated membrane translocation of cargoes and the exploitation...

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

    Science.gov (United States)

    Zhang, Tao

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

  11. Characterization of soluble and membrane-bound alkaline phosphatase in Nilaparvata lugens and their potential relation to development and insecticide resistance.

    Science.gov (United States)

    Wang, Zengxia; Liu, Shuhua; Yang, Baojun; Liu, Zewen

    2011-09-01

    Two forms (soluble and membrane-bound) of alkaline phosphatases (ALPs) were found in the brown planthopper, Nilaparvata lugens. In order to further study ALPs in N. lugens, two putative ALP genes (Nl-ALP1 and Nl-ALP2) were identified in this pest. Both Nl-ALP1 and Nl-ALP2 show approximately the same degree of sequence identity (40-50%) to other insect soluble and membrane-bound forms of ALP. Correlation of ALP activity and mRNA levels at different developmental stages, or following application of 20-hydroxyecdysone (20E) and insecticide fenvalerate, suggests that Nl-ALP1 and Nl-ALP2 might encode a soluble (sALP) and a membrane-bound ALP (mALP), respectively. Nl-ALP1-specific antibody Nl1-I detected only a specific band in soluble protein preparations and Nl-ALP2 specific antibody Nl2-I only detected a specific band in insoluble protein preparations, which provided conclusive linkages between Nl-ALP1 and a sALP and between Nl-ALP2 and a m ALP. Then, Nl-ALP1 was denoted as Nl-sALP for a sALP and Nl-ALP2 was denoted as Nl-mALP for a mALP. Only sALP activity and Nl-sALP mRNA level were induced by 20E and fenvalerate, which was confirmed by the density of specific band detected by Nl1-I in Sus strain with or without fenvalerate treatment. Additionally, the sALP activity, as well as Nl-sALP mRNA level, was significantly higher in a fenvalerate resistant population, compared with Sus strain. These results indicate that the sALP is more responsive to chemical stimulus, such as hormone and insecticide, and might play dual roles in development and insecticide tolerance. © 2011 Wiley Periodicals, Inc.

  12. A small-scale flow alkaline fuel cell for on-site production of hydrogen peroxide

    International Nuclear Information System (INIS)

    Brillas, Enric; Alcaide, Francisco; Cabot, Pere-Lluis

    2002-01-01

    The behavior of a small-scale flow alkaline fuel cell (AFC) built-up for on-site production of HO 2 - using commercial gas-diffusion electrodes has been studied. It produces a spontaneous current due to the oxidation of H 2 to H 2 O at the H 2 -diffusion anode and the reduction of O 2 to HO 2 - at the O 2 -diffusion cathode, while a fresh 1.0-6.0 mol dm -3 KOH electrolyte at 15.0-45.0 deg. C is injected through it. Under circulation of HO 2 - +KOH solutions in open circuit, the flow AFC behaves as a two-electron reversible system. When it is shorted with an external load (R ext ), steady cell voltage-current density curves are found. The use of O 2 /N 2 mixtures to fed the cathode causes a loss of its performance, being required to supply pure O 2 to yield a maximum HO 2 - electrogeneration. The current density and HO 2 - productivity increase with raising OH - concentration, temperature and pressure of O 2 fed. At R ext =0.10 Ω, a current efficiency close to 100% is obtained, and current densities >100 mA cm -2 are achieved for 1.0 mol dm -3 KOH at 45.0 deg. C and for higher KOH concentrations at 25.0 deg. C. The flow AFC can work under optimum conditions up to 6.0 mol dm -3 KOH and 45.0 deg. C for possible industrial applications

  13. Application of Proton Exchange Membrane Fuel Cell for Lift Trucks

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham; Rokni, Masoud

    2011-01-01

    In this study a general PEMFC (Proton Exchange Membrane Fuel Cell) model has been developed to take into account the effect of pressure losses, water crossovers, humidity aspects and voltage over potentials in the cells. The model is zero dimensional and it is assumed to be steady state. The effect...

  14. Development of new membrane materials for direct methanol fuel cells

    NARCIS (Netherlands)

    Yildirim, M.H.

    2009-01-01

    Development of new membrane materials for direct methanol fuel cells Direct methanol fuel cells (DMFCs) can convert the chemical energy of a fuel directly into electrical energy with high efficiency and low emission of pollutants. DMFCs can be used as the power sources to portable electronic devices

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

    Science.gov (United States)

    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.

  16. Cell membrane damage by iron nanoparticles: an invitro study

    Directory of Open Access Journals (Sweden)

    Gelare Hajsalimi

    2016-12-01

    Full Text Available Application of nanotechnology in medicinal and biological fields has attracted a great interest in the recent yeras. In this paper the cell membrane leakage induced by iron nanoparticles (Fe-NP against PC12 cell line which is known as a model of nervous system cell line was investigated by the lactate dehydrogenase (LDH test. Therefore, PC12 cells were incubated with different concentration of Fe-NP and test was performed after 48h of incubation of the cells with Fe-NP. The resulting data showed that the Fe-NP induced the damage of PC12 cell membrane in a concentration dependent manner. Hence, it may be concluded that the different cytotoxicty effect of NPs may be referred to the concentration of NPs, type of the NPs and the cells. Indeed, the kind of cytotoxic impacts of NPs on the cells can be reduced by the considering of above-mentioned parameters. The resulting data showed that the Fe-NP induced the damage of PC12 cell membrane in a concentration dependent manner. Hence, it may be concluded that the different cytotoxicty effect of NPs may be referred to the concentration of NPs, type of the NPs and the cells. Indeed, the kind of cytotoxic impacts of NPs on the cells can be reduced by the considering of above-mentioned parameters.

  17. Oxidative degradation of polybenzimidazole membranes as electrolytes for high temperature proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Liao, J.H.; Li, Qingfeng; Rudbeck, H.C.

    2011-01-01

    the oxidative degradation of the polymer membrane was studied under the Fenton test conditions by the weight loss, intrinsic viscosity, size exclusion chromatography, scanning electron microscopy and Fourier transform infrared spectroscopy. During the Fenton test, significant weight losses depending...... on the initial molecular weight of the polymer were observed. At the same time, viscosity and SEC measurements revealed a steady decrease in molecular weight. The degradation of acid doped PBI membranes under Fenton test conditions is proposed to start by the attack of hydroxyl radicals at the carbon atom......Polybenzimidazole membranes imbibed with acid are emerging as a suitable electrolyte material for high-temperature polymer electrolyte fuel cells. The oxidative stability of polybenzimidazole has been identified as an important issue for the long-term durability of such cells. In this paper...

  18. Electrically Conductive, Hydrophilic Porous Membrane for Fuel Cell Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I effort seeks to produce a conductive polyethersulfone (PES) microporous membrane for fuel cell water management applications. This membrane will...

  19. Comparative Detection of Alkaline Protease Production in Exiguobacterium acetylicum

    International Nuclear Information System (INIS)

    Gomaa, O.M.; EI Shafey, H.M.

    2009-01-01

    Alkaline protease is one of the most important enzymes in industry, medicine, and research. In the present work, a comparative detection for alkaline protease activity was established for instant detection of enzyme activity. Eight different alkalophilic bacterial isolates were compared based on the clear zone they produced on skim milk agar. One strain gave an absolute clear zone in 16 hours and was used for alkaline protease detection. The result of Phenotypic identification using Biology Microlog 3 identified the isolate as Exiguobacterium acetylicum. The isolate under study showed slightly different characteristics from a known Exiguobacterium acetylicum strain. The isolate tolerated alkaline conditions up to ph 11, while good growth was evident at ph 7, the maximum alkaline protease activity was observed at ph 9 which reached up to 109.01 U/ml. The alkaline activity assay using alkaline protease enzyme assay were coordinating with those obtained by conductivity; there was a relevant decrease in conductivity at the maximum increase in enzyme activity, which proved the cell membrane conductivity has a close relation to alkaline protease production. This isolate has tolerated gamma radiation, the increase in dose (up to 4 Gy) gave wider clear zones in terms of diameter and this was relevant to the conductivity measurements

  20. Difference in membrane repair capacity between cancer cell lines and a normal cell line

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; McNeil, Anna K.; Novak, Ivana

    2016-01-01

    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...... cancer cell lines (p immortalized cell line (p

  1. In Plant and Animal Cells, Detergent-Resistant Membranes Do Not Define Functional Membrane Rafts

    Czech Academy of Sciences Publication Activity Database

    Tanner, W.; Malínský, Jan; Opekarová, Miroslava

    2011-01-01

    Roč. 23, č. 4 (2011), s. 1191-1193 ISSN 1040-4651 Institutional research plan: CEZ:AV0Z50390512; CEZ:AV0Z50200510 Keywords : plasma-membrane * lipod rafts * proteins Subject RIV: EA - Cell Biology Impact factor: 8.987, year: 2011

  2. Estimation of membrane hydration status for standby proton exchange membrane fuel cell systems by impedance measurement

    DEFF Research Database (Denmark)

    Bidoggia, Benoit; Rugholt, Mark; Nielsen, Morten Busk

    2014-01-01

    Fuel cells are getting growing interest in both backup systems and electric vehicles. Although these systems are characterized by long periods of inactivity, they must be able to start at any instant in the shortest time. However, the membrane of which PEMFCs are made tends to dry out when...

  3. Importance of balancing membrane and electrode water in anion exchange membrane fuel cells

    Science.gov (United States)

    Omasta, T. J.; Wang, L.; Peng, X.; Lewis, C. A.; Varcoe, J. R.; Mustain, W. E.

    2018-01-01

    Anion exchange membrane fuel cells (AEMFCs) offer several potential advantages over proton exchange membrane fuel cells (PEMFCs), most notably to overcome the cost barrier that has slowed the growth and large scale implementation of fuel cells for transportation. However, limitations in performance have held back AEMFCs, specifically in the areas of stability, carbonation, and maximum achievable current and power densities. In order for AEMFCs to contend with PEMFCs for market viability, it is necessary to realize a competitive cell performance. This work demonstrates a new benchmark for a H2/O2 AEMFC with a peak power density of 1.4 W cm-2 at 60 °C. This was accomplished by taking a more precise look at balancing necessary membrane hydration while preventing electrode flooding, which somewhat surprisingly can occur both at the anode and the cathode. Specifically, radiation-grafted ETFE-based anion exchange membranes and anion exchange ionomer powder, functionalized with benchmark benzyltrimethylammonium groups, were utilized to examine the effects of the following parameters on AEMFC performance: feed gas flow rate, the use of hydrophobic vs. hydrophilic gas diffusion layers, and gas feed dew points.

  4. Nafion®/ODF-silica composite membranes for medium temperature proton exchange membrane fuel cells

    KAUST Repository

    Treekamol, Yaowapa

    2014-01-01

    A series of composite membranes were prepared by dispersing fluorinated polyoxadiazole oligomer (ODF)-functionalized silica nanoparticles in a Nafion matrix. Both melt-extrusion and solvent casting processes were explored. Ion exchange capacity, conductivity, water uptake and dimensional stability, thermal stability and morphology were characterized. The inclusion of functionalized nanoparticles proved advantageous, mainly due to a physical crosslinking effect and better water retention, with functionalized nanoparticles performing better than the pristine silica particles. For the same filler loading, better nanoparticle dispersion was achieved for solvent-cast membranes, resulting in higher proton conductivity. Filler agglomeration, however,was more severe for solvent-castmembranes at loadings beyond 5wt.%. The composite membranes showed excellent thermal stability, allowing for operation in medium temperature PEM fuel cells. Fuel cell performance of the compositemembranesdecreaseswithdecreasing relativehumidity, but goodperformance values are still obtained at 34% RHand 90 °C,with the best results obtained for solvent castmembranes loaded with 10 wt.% ODF-functionalized silica. Hydrogen crossover of the composite membranes is higher than that forpureNafion membranes,possiblydue toporosityresulting fromsuboptimalparticle- matrixcompatibility. © 2013 Crown Copyright and Elsevier BV. All rights reserved.

  5. Mouse endometrial stromal cells produce basement-membrane components

    DEFF Research Database (Denmark)

    Wewer, U M; Damjanov, A; Weiss, J

    1986-01-01

    During mouse pregnancy, uterine stromal cells transform into morphologically distinct decidual cells under the influence of the implanting embryo and a proper hormonal environment. Mechanical stimulation of hormonally primed uterine stromal cells leads to the same morphologic alterations. The dec......During mouse pregnancy, uterine stromal cells transform into morphologically distinct decidual cells under the influence of the implanting embryo and a proper hormonal environment. Mechanical stimulation of hormonally primed uterine stromal cells leads to the same morphologic alterations....... Mouse decidual cells isolated from 6- to 7-day pregnant uteri explanted in vitro continue to synthesize basement-membrane-like extracellular matrix. Using immunohistochemistry and metabolic labeling followed by immunoprecipitation, SDS-PAGE, and fluorography, it was shown that the decidual cells...... to undergo pseudodecidualization. We thus showed that stromal cells from pregnant and nonpregnant mouse uteri synthesize significant amounts of basement-membrane components in vitro, and hence could serve as a good model for the study of normal basement-membrane components....

  6. Plasma membrane associated membranes (PAM) from Jurkat cells contain STIM1 protein is PAM involved in the capacitative calcium entry?

    Science.gov (United States)

    Kozieł, Katarzyna; Lebiedzinska, Magdalena; Szabadkai, Gyorgy; Onopiuk, Marta; Brutkowski, Wojciech; Wierzbicka, Katarzyna; Wilczyński, Grzegorz; Pinton, Paolo; Duszyński, Jerzy; Zabłocki, Krzysztof; Wieckowski, Mariusz R

    2009-12-01

    A proper cooperation between the plasma membrane, the endoplasmic reticulum and the mitochondria seems to be essential for numerous cellular processes involved in Ca(2+) signalling and maintenance of Ca(2+) homeostasis. A presence of microsomal and mitochondrial proteins together with those characteristic for the plasma membrane in the fraction of the plasma membrane associated membranes (PAM) indicates a formation of stabile interactions between these three structures. We isolated the plasma membrane associated membranes from Jurkat cells and found its significant enrichment in the plasma membrane markers including plasma membrane Ca(2+)-ATPase, Na(+), K(+)-ATPase and CD3 as well as sarco/endoplasmic reticulum Ca(2+) ATPase as a marker of the endoplasmic reticulum membranes. In addition, two proteins involved in the store-operated Ca(2+) entry, Orai1 located in the plasma membrane and an endoplasmic reticulum protein STIM1 were found in this fraction. Furthermore, we observed a rearrangement of STIM1-containing protein complexes isolated from Jurkat cells undergoing stimulation by thapsigargin. We suggest that the inter-membrane compartment composed of the plasma membrane and the endoplasmic reticulum, and isolated as a stabile plasma membrane associated membranes fraction, might be involved in the store-operated Ca(2+) entry, and their formation and rebuilding have an important regulatory role in cellular Ca(2+) homeostasis.

  7. Reconstruction of limbal stem cell deficient corneal surface with induced human bone marrow mesenchymal stem cells on amniotic membrane.

    Science.gov (United States)

    Rohaina, Che Man; Then, Kong Yong; Ng, Angela Min Hwei; Wan Abdul Halim, Wan Haslina; Zahidin, Aida Zairani Mohd; Saim, Aminuddin; Idrus, Ruszymah B H

    2014-03-01

    The cornea can be damaged by a variety of clinical disorders or chemical, mechanical, and thermal injuries. The objectives of this study were to induce bone marrow mesenchymal stem cells (BMSCs) to corneal lineage, to form a tissue engineered corneal substitute (TEC) using BMSCs, and to treat corneal surface defects in a limbal stem cell deficiency model. BMSCs were induced to corneal lineage using limbal medium for 10 days. Induced BMSCs demonstrated upregulation of corneal stem cell markers; β1-integrin, C/EBPδ, ABCG2, and p63, increased protein expression of CK3 and p63 significantly compared with the uninduced ones. For TEC formation, passage 1 BMSCs were trypsinized and seeded on amniotic membrane in a transwell co-culture system and were grown in limbal medium. Limbal stem cell deficiency models were induced by alkaline injury, and the TEC was implanted for 8 weeks. Serial slit lamp evaluation revealed remarkable improvement in corneal regeneration in terms of corneal clarity and reduced vascularization. Histologic and optical coherence tomography analyses demonstrated comparable corneal thickness and achieved stratified epithelium with a compact stromal layer resembling that of normal cornea. CK3 and p63 were expressed in the newly regenerated cornea. In conclusion, BMSCs can be induced into corneal epithelial lineage, and these cells are viable for the formation of TEC, to be used for the reconstruction of the corneal surface in the limbal stem cell deficient model. Copyright © 2014 Mosby, Inc. All rights reserved.

  8. Proton-conductive nanochannel membrane for fuel-cell applications.

    Science.gov (United States)

    Oleksandrov, Sergiy; Lee, Jeong-Woo; Jang, Joo-Hee; Haam, Seungjoo; Chung, Chan-Hwa

    2009-02-01

    Novel design of proton conductive membrane for direct methanol fuel cells is based on proton conductivity of nanochannels, which is acquired due to the electric double layer overlap. Proton conductivity and methanol permeability of an array of nanochannels were studied. Anodic aluminum oxide with pore diameter of 20 nm was used as nanochannel matrix. Channel surfaces of an AAO template were functionalized with sulfonic groups to increase proton conductivity of nanochannels. This was done in two steps; at first -SH groups were attached to walls of nanochannels using (3-Mercaptopropyl)-trimethyloxysilane and then they were converted to -SO3H groups using hydrogen peroxide. Treatment steps were analyzed by Fourier Transform Infrared spectroscopy and X-ray Photoelectron Spectroscopy. Proton conductivity and methanol permeability were measured. The data show methanol permeability of membrane to be an order of magnitude lower, than that measured of Nafion. Ion conductivity of functionalized AAO membrane was measured by an impedance analyzer at frequencies ranging from 1 Hz to 100 kHz and voltage 50 mV to be 0.15 Scm(-1). Measured ion conductivity of Nafion membrane was 0.05 Scm(-1). Obtained data show better results in comparison with commonly used commercial available proton conductive membrane Nafion, thus making nanochannel membrane very promising for use in fuel cell applications.

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

    Science.gov (United States)

    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.

  10. Microstructured Electrolyte Membranes to Improve Fuel Cell Performance

    Science.gov (United States)

    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

  11. Cell cycle dependent changes in the plasma membrane organization of mammalian cells.

    Science.gov (United States)

    Denz, Manuela; Chiantia, Salvatore; Herrmann, Andreas; Mueller, Peter; Korte, Thomas; Schwarzer, Roland

    2017-03-01

    Lipid membranes are major structural elements of all eukaryotic and prokaryotic organisms. Although many aspects of their biology have been studied extensively, their dynamics and lateral heterogeneity are still not fully understood. Recently, we observed a cell-to-cell variability in the plasma membrane organization of CHO-K1 cells (Schwarzer et al., 2014). We surmised that cell cycle dependent changes of the individual cells from our unsynchronized cell population account for this phenomenon. In the present study, this hypothesis was tested. To this aim, CHO-K1 cells were arrested in different cell cycle phases by chemical treatments, and the order of their plasma membranes was determined by various fluorescent lipid analogues using fluorescence lifetime imaging microscopy. Our experiments exhibit significant differences in the membrane order of cells arrested in the G2/M or S phase compared to control cells. Our single-cell analysis also enabled the specific selection of mitotic cells, which displayed a significant increase of the membrane order compared to the control. In addition, the lipid raft marker GPImYFP was used to study the lateral organization of cell cycle arrested cells as well as mitotic cells and freely cycling samples. Again, significant differences were found between control and arrested cells and even more pronounced between control and mitotic cells. Our data demonstrate a direct correlation between cell cycle progression and plasma membrane organization, underlining that cell-to-cell heterogeneities of membrane properties have to be taken into account in cellular studies especially at the single-cell level. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Effect of alkaline and acidic fractions of industrial effluents on some lymphoid cells of the fish Rasbora daniconius

    Energy Technology Data Exchange (ETDEWEB)

    Elizabeth, T K; Balasubramanian, N K; John, P A

    1981-01-01

    The percentage frequency of the different types of lymphoid cell found in the head-kidney of Rasbora daniconius exposed for 24 h to lc/sub 50/ levels of the ammonia (alkali), phosphoric and sulphuric acid fractions of the effluent from a fertiliser factory was determined by the imprint method. 'T' tests showed that both the alkaline and the acidic fractions could significantly affect the composition of the lymphoid cell population. Different types of lymphoid cell reacted differently to the different fractions; some cell types increased in number while others decreased. Some cell types were not affected. This indicated some sort of specificity in the action of the fractions on the lymphoid cells.

  13. Role of membranes and membrane reactors in the hydrogen supply of fuel cells for transports

    Energy Technology Data Exchange (ETDEWEB)

    Julbe, A.; Guizard, Ch. [Institut Europeen des Membranes, UMII, Lab. des Materiaux et des Procedes Membranaires, CNRS UMR 5635, 34 - Montpellier (France)

    2000-07-01

    Production, storage and supply of high-purity hydrogen as a clean and efficient fuel is central to fuel cells technology, in particular in vehicle traction. Actually, technologies for handling liquefied or gaseous hydrogen in transports are not available so that a number of alternative fuels are considered with the aim of in-situ generation of hydrogen through catalytic processes. The integrated concept of membrane reactors (MRs) can greatly benefit to these technologies. Particular emphasis is put on inorganic membranes and their role in MRs performance for H{sub 2} production.

  14. Flavivirus cell entry and membrane fusion

    NARCIS (Netherlands)

    Smit, Jolanda M.; Moesker, Bastiaan; Rodenhuis-Zybert, Izabela; Wilschut, Jan

    2011-01-01

    Flaviviruses, such as dengue virus and West Nile virus, are enveloped viruses that infect cells through receptor-mediated endocytosis and fusion from within acidic endosomes. The cell entry process of flaviviruses is mediated by the viral E glycoprotein. This short review will address recent

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

    Science.gov (United States)

    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. Graphene-cobaltite-Pd hybrid materials for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cells.

    Science.gov (United States)

    Sharma, Chandra Shekhar; Awasthi, Rahul; Singh, Ravindra Nath; Sinha, Akhoury Sudhir Kumar

    2013-12-14

    Hybrid materials comprising of Pd, MCo2O4 (where M = Mn, Co or Ni) and graphene have been prepared for use as efficient bifunctional electrocatalysts in alkaline direct methanol fuel cells. Structural and electrochemical characterizations were carried out using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, chronoamperometry and cyclic, CO stripping, and linear sweep voltammetries. The study revealed that all the three hybrid materials are active for both methanol oxidation (MOR) and oxygen reduction (ORR) reactions in 1 M KOH. However, the Pd-MnCo2O4/GNS hybrid electrode exhibited the greatest MOR and ORR activities. This active hybrid electrode has also outstanding stability under both MOR and ORR conditions, while Pt- and other Pd-based catalysts undergo degradation under similar experimental conditions. The Pd-MnCo2O4/GNS hybrid catalyst exhibited superior ORR activity and stability compared to even Pt in alkaline solutions.

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

    International Nuclear Information System (INIS)

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

    1988-01-01

    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- 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

  18. Proton Exchange Membrane Fuel Cells Applied for Transport Sector

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham; Rokni, Masoud

    2010-01-01

    A thermodynamic analysis of a PEMFC (proton exchange membrane fuel cell) is investigated. PEMFC may be the most promising technology for fuel cell automotive systems, which is operating at quite low temperatures, (between 60 to 80℃). In this study the fuel cell motive power part of a lift truck has...... been investigated. The fuel cell stack used in this model is developed using a Ballard PEMFC [1], so that the equations used in the stack modeling are derived from the experimental data. The stack can produce 3 to 15 kilowatt electricity depending on the number of cells used in the stack. Some...

  19. Separation of alkali, alkaline earth and rare earth cations by liquid membranes containing macrocyclic carriers. Third progress report, September 1, 1980-April 1, 1981

    International Nuclear Information System (INIS)

    Christensen, J.J.

    1981-01-01

    The overall objective of this project is to study the use of liquid membrane systems employing macrocyclic ligand carriers in making separations among metal cations. During the third year of the project, work continued in the development of a mathematical model to describe cation transport. The model was originally developed to describe the relationship between cation transport rate (J/sub M/) and the cation-macrocycle stability constant (K). The model was tested by determining the rates of transport of alkali and alkaline earth cations through chloroform membranes containing carrier ligands where the stability constants for their reaction with cations in methanol were known. From the results, it is clear that the model correctly describes the dependence of J/sub M/ on log K. The model also correctly describes the effect of cation concentration and carrier concentration on cation transport rates, as detailed in the previous progress report. During the third year of the project, the transport model was expanded so as to apply to competitive transport of cations from mixtures of two cations in the source aqueous phase. Data were collected under these conditions and the ability of the model to predict the flux of each cation was tested. Representative data of this type are presented along with corresponding data which were obtained when each cation was transported by the same carrier from a source phase containing only that cation. Comparison of transport rates determined under the two experimental conditions indicates that the relationship between the two sets of data is complex. To date, a few of these data involving transport from binary cation mixtures have been tested against the transport model. It was found that the model correctly predicts the cation fluxes from cation mixtures. These preliminary results indicate that the transport model can successfully predict separation factors when cation mixtures are used

  20. Multi-membrane chitosan hydrogels as chondrocytic cell bioreactors.

    Science.gov (United States)

    Ladet, S G; Tahiri, K; Montembault, A S; Domard, A J; Corvol, M-T M

    2011-08-01

    We investigated the bioactivity of new chitosan-based multi-membrane hydrogel (MMH) architectures towards chondrocyte-like cells. The microstructure of the hydrogels constituting the membranes precludes any living cell penetration, whereas their lower scale architecture allows the protein diffusion. The biological behavior of chondrocytes implanted within the MMH inter-membrane spaces was studied for 45 days in culture. Chondrocytes formed cell aggregates and proliferated without loosing their chondrogenic phenotype as illustrated by collagen II and aggrecan expressions at the mRNA and protein levels. Cells produced neo-formed alcyan blue matrix proteins filling MMH interspaces. The HiF-2α/SOX9 pattern of expression suggested that the elevated chondrocytic phenotype in MMH could be related to a better hypoxic local environment than in classical culture conditions. Pro-inflammatory markers were not expressed during the period of culture. The low level of nitric oxide accumulation within the inter-membrane spaces and in the incubation medium implied that chitosan consumed nitrites produced by entrapped chondrocytes, in relation with the decrease of its molecular weight of 50%. Our data suggest that MMH structures may be considered as complex chondrocytic cell bioreactors; "active decoys of biological media", potentially promising for various biomedical applications like the inter-vertebral disk replacement. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Chemically and compositionally modified solid solution disordered multiphase nickel hydroxide positive electrode for alkaline rechargeable electrochemical cells

    Science.gov (United States)

    Ovshinsky, Stanford R.; Corrigan, Dennis; Venkatesan, Srini; Young, Rosa; Fierro, Christian; Fetcenko, Michael A.

    1994-01-01

    A high capacity, long cycle life positive electrode for use in an alkaline rechargeable electrochemical cell comprising: a solid solution nickel hydroxide material having a multiphase structure that comprises at least one polycrystalline .gamma.-phase including a polycrystalline .gamma.-phase unit cell comprising spacedly disposed plates with at least one chemical modifier incorporated around the plates, the plates having a range of stable intersheet distances corresponding to a 2.sup.+ oxidation state and a 3.5.sup.+, or greater, oxidation state; and at least one compositional modifier incorporated into the solid solution nickel hydroxide material to promote the multiphase structure.

  2. High alkaline tolerant electrolyte membrane with improved conductivity and mechanical strength via lithium chloride/dimethylacetamide dissolved microcrystalline cellulose for Zn-Air batteries

    International Nuclear Information System (INIS)

    Zhang, Yuansong; Li, Cong; Cai, Xiaoxia; Yao, Jinshui; Li, Mei; Zhang, Xian; Liu, Qinze

    2016-01-01

    LiCl/DMAc (dimethylacetamide) solution dissolved microcrystalline cellulose (LD-MCC) showed potential benefits to the alkaline solid polymer electrolyte (ASPE). High alkali tolerance (up to 70 wt% KOH loading), remarkable improvements in ionic conductivity (from 0.018 S cm −1 to 0.153 S cm −1 ) and mechanical properties (3-fold increase in tensile strength from 0.28 MPa to 0.76 MPa) were achieved just via an incorporation of 5 wt% of LD-MCC into the ASPE matrix. Wide-angle X-ray diffraction indicated that LD-MCC entrapped KOH and hindered its aggregation. X-ray Energy Dispersive Spectrometer revealed that K + was preferentially located on the LD-MCC surfaces rather than the polymeric matrix. Scanning Electron Microscopy of freeze-dry sample demonstrated a submicro-porous morphology with reduced average pore size (175 nm) after the incorporation of LD-MCC in ASPE matrix. The incorporated LD-MCC acted as KOH stabilizer, hydrophilicity agent and OH − transport media. Distinct micro-structures before and after the incorporation of LD-MCC were investigated to reveal the special role of LD-MCC in the performance improvement of ASPE membrane.

  3. Canine osteosarcoma cell lines from patients with differing serum alkaline phosphatase concentrations display no behavioural differences in vitro.

    Science.gov (United States)

    Holmes, K E; Thompson, V; Piskun, C M; Kohnken, R A; Huelsmeyer, M K; Fan, T M; Stein, T J

    2015-09-01

    Osteosarcoma is an aggressive malignancy and represents the most frequent primary bone malignancy of dogs and humans. Prognostic factors reported for osteosarcoma include tumour size, presence of metastatic disease and serum alkaline phosphatase (ALP) concentration at the time of diagnosis. To date, there have been no studies to determine whether the behaviour of osteosarcoma cells differ based on serum ALP concentration. Here, we report on the generation of six canine osteosarcoma cell lines from osteosarcoma-bearing dogs with differences in serum ALP concentration. To determine whether in vitro behaviour differs between primary osteosarcoma cell lines generated from patients with normal or increased serum ALP, assays were performed to evaluate proliferation, migration, invasion and chemosensitivity. There were no significant differences in cell proliferation, migration, invasion or chemosensitivity between cell lines associated with normal or increased serum ALP concentration. © 2013 Blackwell Publishing Ltd.

  4. Canine osteosarcoma cell lines from patients with differing serum alkaline phosphatase concentrations display no behavioral differences in vitro

    Science.gov (United States)

    Holmes, Katie E.; Thompson, Victoria; Piskun, Caroline M.; Kohnken, Rebecca A.; Huelsmeyer, Michael K.; Fan, Timothy M.; Stein, Timothy J.

    2013-01-01

    Osteosarcoma is an aggressive malignancy and represents the most frequent primary bone malignancy of dogs and humans. Prognostic factors reported for osteosarcoma include tumor size, presence of metastatic disease, and serum alkaline phosphatase (ALP) concentration at the time of diagnosis. To date, there have been no studies to determine whether the behavior of osteosarcoma cells differ based on serum ALP concentration. Here we report on the generation of six canine osteosarcoma cell lines from osteosarcoma-bearing dogs with differences in serum ALP concentration. To determine whether in vitro behavior differs between primary osteosarcoma cell lines generated from patients with normal or increased serum ALP assays were performed to evaluate proliferation, migration, invasion, and chemosensitivity. There were no significant differences in cell proliferation, migration, invasion, or chemosensitivity between cell lines associated normal or increased serum ALP concentration. PMID:23489774

  5. Membrane dynamics and the regulation of epithelial cell polarity

    NARCIS (Netherlands)

    van der Wouden, JM; Maier, O; van IJzendoorn, SCD; Hoekstra, D

    2003-01-01

    Plasma membranes of epithelial cells consist of two domains, an apical and a basolateral domain, the surfaces of which differ in composition. The separation of these domains by a tight junction and the fact that specific transport pathways exist for intracellular communication between these domains

  6. Cell biology symposium: Membrane trafficking and signal transduction

    Science.gov (United States)

    In general, membrane trafficking is a broad group of processes where proteins and other large molecules are distributed throughout the cell as well as adjacent extracellular spaces. Whereas signal transduction is a process where signals are transmitted through a series of chemical or molecular event...

  7. Denaturation of membrane proteins and hyperthermic cell killing

    NARCIS (Netherlands)

    Burgman, Paulus Wilhelmus Johannes Jozef

    1993-01-01

    Summarizing: heat induced denaturation of membrane proteins is probably related to hyperthermic cell killing. Induced resistance of heat sensitive proteins seems to be involved in the development of thermotolerance. Although many questions remain still to be answered, it appears that HSP72, when

  8. Polymers application in proton exchange membranes for fuel cells (PEMFCs)

    Science.gov (United States)

    Walkowiak-Kulikowska, Justyna; Wolska, Joanna; Koroniak, Henryk

    2017-07-01

    This review presents the most important research on alternative polymer membranes with ionic groups attached, provides examples of materials with a well-defined chemical structure that are described in the literature. Furthermore, it elaborates on the synthetic methods used for preparing PEMs, the current status of fuel cell technology and its application. It also briefly discusses the development of the PEMFC market.

  9. Interaction of Dendritic Polymers with Synthetic Lipid and Cell Membranes

    Science.gov (United States)

    Mecke, Almut; Hong, Seungpyo; Bielinska, Anna U.; Banaszak Holl, Mark M.; Orr, Bradford G.; Baker, James R., Jr.

    2004-03-01

    Polyamidoamine (PAMAM) dendrimers are promising candidates for the development of nanoscale therapeutic transport agents. Here we present studies on dendrimer-membrane interactions leading to a better understanding of possible uptake mechanisms into cells. Using synthetic lipid and natural cell membranes as model systems it is shown that the effect of PAMAM dendrimers on a membrane strongly depends on the dendrimer generation, architecture and chemical properties of the branch end groups. Atomic force microscopy data indicates that generation 7 dendrimers have the ability to form small ( 10-100 nm) holes in a lipid bilayer. When dendrimers with otherwise identical chemical properties are arranged in a covalently linked cluster, no hole formation occurs. Dendrimer-lipid micelle formation is proposed and investigated as a possible mechanism for this behavior. Smaller dendrimers (generation 5) have a greatly reduced ability to remove lipid molecules from a bilayer. In addition to the size of the dendrimer, the charge of the branch end groups plays a significant role for dendrimer-membrane interactions. These results agree well with biological studies using cultured cells and point to a new mechanism of specific targeting and uptake into cells.

  10. The roles of membrane microdomains (rafts) in T cell activation

    Czech Academy of Sciences Publication Activity Database

    Hořejší, Václav

    2003-01-01

    Roč. 191, - (2003), s. 148-164 ISSN 0105-2896 R&D Projects: GA MŠk LN00A026 Grant - others:Wellcome Trust(GB) J1116W24Z Institutional research plan: CEZ:AV0Z5052915 Keywords : membrane microdomain * raft * T cell Subject RIV: EC - Immunology Impact factor: 7.052, year: 2003

  11. Salinity induced changes in cell membrane stability, protein and ...

    African Journals Online (AJOL)

    control), 4.7, 9.4 and 14.1 dS m-1 to determine the effect of salt on vegetative growth, relative water content, cell membrane stability, protein and RNA contents in sand culture experiment. Fresh and dry weights of plants, shoots and roots decreased ...

  12. Characterisation of cell-wall polysaccharides from mandarin segment membranes

    NARCIS (Netherlands)

    Coll-Almela, L.; Saura-Lopez, D.; Laencina-Sanchez, J.; Schols, H.A.; Voragen, A.G.J.; Ros-García, J.M.

    2015-01-01

    In an attempt to develop a process of enzymatic peeling of mandarin segments suitable for use on an industrial scale, the cell wall fraction of the segment membrane of Satsuma mandarin fruits was extracted to obtain a chelating agent-soluble pectin fraction (ChSS), a dilute sodium hydroxide-soluble

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

    Science.gov (United States)

    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...

  14. An adhesion-based method for plasma membrane isolation: evaluating cholesterol extraction from cells and their membranes.

    Science.gov (United States)

    Bezrukov, Ludmila; Blank, Paul S; Polozov, Ivan V; Zimmerberg, Joshua

    2009-11-15

    A method to isolate large quantities of directly accessible plasma membrane from attached cells is presented. The method is based on the adhesion of cells to an adsorbed layer of polylysine on glass plates, followed by hypotonic lysis with ice-cold distilled water and subsequent washing steps. Optimal conditions for coating glass plates and time for cell attachment were established. No additional chemical or mechanical treatments were used. Contamination of the isolated plasma membrane by cell organelles was less than 5%. The method uses inexpensive, commercially available polylysine and reusable glass plates. Plasma membrane preparations can be made in 15 min. Using this method, we determined that methyl-beta-cyclodextrin differentially extracts cholesterol from fibroblast cells and their plasma membranes and that these differences are temperature dependent. Determination of the cholesterol/phospholipid ratio from intact cells does not reflect methyl-beta-cyclodextrin plasma membrane extraction properties.

  15. Modeling Of Proton Exchange Membrane Fuel Cell Systems

    DEFF Research Database (Denmark)

    Nielsen, Mads Pagh

    The objective of this doctoral thesis was to develop reliable steady-state and transient component models suitable to asses-, develop- and optimize proton exchange membrane (PEM) fuel cell systems. Several components in PEM fuel cell systems were characterized and modeled. The developed component...... cell systems. Consequences of indirectly fueling PEM stacks with hydrocarbons using reforming technology were investigated using a PEM stack model including CO poisoning kinetics and a transient Simulink steam reforming system model. Aspects regarding the optimization of PEM fuel cell systems...

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

    Science.gov (United States)

    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.

  17. Artificial Red Cells with Polyhemoglobin Membranes.

    Science.gov (United States)

    1981-09-01

    Y. Reciprocal binding of oxygen and diphosphoglycerate by human hemoglobin. Proc. Natl. Acad. Sci. USA 59:526-532, 1968. 12. Bunn, H. F., Seal, U. S...and Scott, A. F. The role of 2,3- diphosphoglycerate in mediating hemoglobin function of mammalian red cells. Ann. N.Y. Acad. Sciences 241:498-519

  18. Rotavirus RRV associates with lipid membrane microdomains during cell entry

    International Nuclear Information System (INIS)

    Isa, Pavel; Realpe, Mauricio; Romero, Pedro; Lopez, Susana; Arias, Carlos F.

    2004-01-01

    Rotavirus cell entry is a multistep process, not completely understood, which requires at least four interactions between the virus and cell surface molecules. In this work, we investigated the role of the sphingolipid- and cholesterol-enriched lipid microdomains (rafts) in the entry of rotavirus strain RRV to MA104 cells. We found that ganglioside GM1, integrin subunits α2 and β3, and the heat shock cognate protein 70 (hsc70), all of which have been implicated as rotavirus receptors, are associated with TX-100 and Lubrol WX detergent-resistant membranes (DRMs). Integrin subunits α2 and β3 were found to be particularly enriched in DRMs resistant to lysis by Lubrol WX. When purified RRV particles were incubated with cells at 4 deg. C, about 10% of the total infectious virus was found associated with DRMs, and the DRM-associated virus increased to 37% in Lubrol-resistant membrane domains after 60-min incubation at 37 deg. C. The virus was excluded from DRMs if the cells were treated with methyl-β-cyclodextrin (MβCD). Immunoblot analysis of the viral proteins showed that the virus surface proteins became enriched in DRMs upon incubation at 37 deg. C, being almost exclusively localized in Lubrol-resistant DRMs after 60 min. These data suggest that detergent-resistant membrane domains play an important role in the cell entry of rotaviruses, which could provide a platform to facilitate the efficient interaction of the rotavirus receptors with the virus particle

  19. Imidazolium-based Block Copolymers as Solid-State Separators for Alkaline Fuel Cells and Lithium Ion Batteries

    Science.gov (United States)

    Nykaza, Jacob Richard

    In this study, polymerized ionic liquid (PIL) diblock copolymers were explored as solid-state polymer separators as an anion exchange membrane (AEM) for alkaline fuel cells AFCs and as a solid polymer electrolyte (SPE) for lithium-ion batteries. Polymerized ionic liquid (PIL) block copolymers are a distinct set of block copolymers that combine the properties of both ionic liquids (e.g., high conductivity, high electrochemical stability) and block copolymers (e.g., self-assembly into various nanostructures), which provides the opportunity to design highly conductive robust solid-state electrolytes that can be tuned for various applications including AFCs and lithium-ion batteries via simple anion exchange. A series of bromide conducting PIL diblock copolymers with an undecyl alkyl side chain between the polymer backbone and the imidazolium moiety were first synthesized at various compositions comprising of a PIL component and a non-ionic component. Synthesis was achieved by post-functionalization from its non-ionic precursor PIL diblock copolymer, which was synthesized via the reverse addition fragmentation chain transfer (RAFT) technique. This PIL diblock copolymer with long alkyl side chains resulted in flexible, transparent films with high mechanical strength and high bromide ion conductivity. The conductivity of the PIL diblock copolymer was three times higher than its analogous PIL homopolymer and an order of magnitude higher than a similar PIL diblock copolymer with shorter alkyl side chain length, which was due to the microphase separated morphology, more specifically, water/ion clusters within the PIL microdomains in the hydrated state. Due to the high conductivity and mechanical robustness of this novel PIL block copolymer, its application as both the ionomer and AEM in an AFC was investigated via anion exchange to hydroxide (OH-), where a maximum power density of 29.3 mW cm-1 (60 °C with H2/O2 at 25 psig (172 kPa) backpressure) was achieved. Rotating disk

  20. Identification of glycan structure alterations on cell membrane proteins in desoxyepothilone B resistant leukemia cells.

    Science.gov (United States)

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

    2011-11-01

    Resistance to tubulin-binding agents used in cancer is often multifactorial and can include changes in drug accumulation and modified expression of tubulin isotypes. Glycans on cell membrane proteins play important roles in many cellular processes such as recognition and apoptosis, and this study investigated whether changes to the glycan structures on cell membrane proteins occur when cells become resistant to drugs. Specifically, we investigated the alteration of glycan structures on the cell membrane proteins of human T-cell acute lymphoblastic leukemia (CEM) cells that were selected for resistance to desoxyepothilone B (CEM/dEpoB). The glycan profile of the cell membrane glycoproteins was obtained by sequential release of N- and O-glycans from cell membrane fraction dotted onto polyvinylidene difluoride membrane with PNGase F and β-elimination respectively. The released glycan alditols were analyzed by liquid chromatography (graphitized carbon)-electrospray ionization tandem MS. The major N-glycan on CEM cell was the core fucosylated α2-6 monosialo-biantennary structure. Resistant CEM/dEpoB cells had a significant decrease of α2-6 linked sialic acid on N-glycans. The lower α2-6 sialylation was caused by a decrease in activity of β-galactoside α2-6 sialyltransferase (ST6Gal), and decreased expression of the mRNA. It is clear that the membrane glycosylation of leukemia cells changes during acquired resistance to dEpoB drugs and that this change occurs globally on all cell membrane glycoproteins. This is the first identification of a specific glycan modification on the surface of drug resistant cells and the mechanism of this downstream effect on microtubule targeting drugs may offer a route to new interventions to overcome drug resistance.

  1. Chemical Imaging of the Cell Membrane by NanoSIMS

    International Nuclear Information System (INIS)

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

    2010-01-01

    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

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

    Science.gov (United States)

    Kim, Tae Young; Cho, Sung Yong

    2011-08-01

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

  3. Characterization of an anionic-exchange membranes for direct methanol alkaline fuel cells

    CSIR Research Space (South Africa)

    Abuin, GC

    2010-06-01

    Full Text Available doi:10.1016/j.ijhydene.2009.12.128 D PROO l de Tecnologı´a Industrial (INTI), Av. Gral. Paz 5445, B1650KNA, San Martı´n, , Material Science & Manufacturing, PO Box 395, Brumeria, Pretoria 0001, South Africa nsada, Comisio´n Nacional de Energı...

  4. Advanced alkaline water electrolysis

    International Nuclear Information System (INIS)

    Marini, Stefania; Salvi, Paolo; Nelli, Paolo; Pesenti, Rachele; Villa, Marco; Berrettoni, Mario; Zangari, Giovanni; Kiros, Yohannes

    2012-01-01

    A short review on the fundamental and technological issues relevant to water electrolysis in alkaline and proton exchange membrane (PEM) devices is given. Due to price and limited availability of the platinum group metal (PGM) catalysts they currently employ, PEM electrolyzers have scant possibilities of being employed in large-scale hydrogen production. The importance and recent advancements in the development of catalysts without PGMs are poised to benefit more the field of alkaline electrolysis rather than that of PEM devices. This paper presents our original data which demonstrate that an advanced alkaline electrolyzer with performances rivaling those of PEM electrolyzers can be made without PGM and with catalysts of high stability and durability. Studies on the advantages/limitations of electrolyzers with different architectures do show how a judicious application of pressure differentials in a recirculating electrolyte scheme helps reduce mass transport limitations, increasing efficiency and power density.

  5. Enhancement of growth and osteogenic differentiation of MC3T3-E1 cells via facile surface functionalization of polylactide membrane with chitooligosaccharide based on polydopamine adhesive coating

    International Nuclear Information System (INIS)

    Li, Huihua; Luo, Chuang; Luo, Binghong; Wen, Wei; Wang, Xiaoying; Ding, Shan; Zhou, Changren

    2016-01-01

    Graphical abstract: - Highlights: • COS was conveniently immobilized on PDLLA membrane based on PDOPA adhesive layer. • The hydrophilicity of PDLLA membrane was improved by modified with PDOPA and COS. • COS-functionalized PDLLA membrane is favorable to cell adhesion and proliferation. • COS-coated PDLLA membrane notably promote osteogenic differentiation of MC3T3-E1. - Abstract: To develop a chitooligosaccharide(COS)-functionalized poly(D,L-lactide) (PDLLA) membrane to enhance growth and osteogenic differentiation of MC3T3-E1 cells, firstly a thin polydopamine (PDOPA) layer was adhered to the PDLLA membrane via the self-polymerization and strong adhesion behavior of dopamine. Subsequently, COS was immobilized covalently on the resultant PDLLA/PDOPA composite membrane by coupling with PDOPA active coating. The successful immobilization of the PDOPA and COS was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) results indicated that the surface topography and roughness of the membranes were changed, and the root mean square increased from 0.613 nm to 6.96 and 7.12 nm, respectively after coating PDOPA and COS. Water contact angle and surface energy measurements revealed that the membrane hydrophilicity was remarkably improved by surface modification. In vitro cells culture results revealed that the PDOPA- and COS-functionalized surfaces showed a significant increase in MC3T3-E1 cells adhesion, proliferation, osteogenic differentiation and alkaline phosphate activity compared to the pristine PDLLA substrate. Furthermore the COS-functionalized PDLLA membrane was more effectively at enhancing osteoblast activity than the PDOPA-functionalized PDLLA membrane.

  6. Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability.

    Science.gov (United States)

    Smith, Alyson S; Nowak, Roberta B; Zhou, Sitong; Giannetto, Michael; Gokhin, David S; Papoin, Julien; Ghiran, Ionita C; Blanc, Lionel; Wan, Jiandi; Fowler, Velia M

    2018-05-08

    The biconcave disk shape and deformability of mammalian RBCs rely on the membrane skeleton, a viscoelastic network of short, membrane-associated actin filaments (F-actin) cross-linked by long, flexible spectrin tetramers. Nonmuscle myosin II (NMII) motors exert force on diverse F-actin networks to control cell shapes, but a function for NMII contractility in the 2D spectrin-F-actin network of RBCs has not been tested. Here, we show that RBCs contain membrane skeleton-associated NMIIA puncta, identified as bipolar filaments by superresolution fluorescence microscopy. MgATP disrupts NMIIA association with the membrane skeleton, consistent with NMIIA motor domains binding to membrane skeleton F-actin and contributing to membrane mechanical properties. In addition, the phosphorylation of the RBC NMIIA heavy and light chains in vivo indicates active regulation of NMIIA motor activity and filament assembly, while reduced heavy chain phosphorylation of membrane skeleton-associated NMIIA indicates assembly of stable filaments at the membrane. Treatment of RBCs with blebbistatin, an inhibitor of NMII motor activity, decreases the number of NMIIA filaments associated with the membrane and enhances local, nanoscale membrane oscillations, suggesting decreased membrane tension. Blebbistatin-treated RBCs also exhibit elongated shapes, loss of membrane curvature, and enhanced deformability, indicating a role for NMIIA contractility in promoting membrane stiffness and maintaining RBC biconcave disk cell shape. As structures similar to the RBC membrane skeleton exist in many metazoan cell types, these data demonstrate a general function for NMII in controlling specialized membrane morphology and mechanical properties through contractile interactions with short F-actin in spectrin-F-actin networks.

  7. Plasma membrane of a marine T cell lymphoma: surface labelling, membrane isolation, separation of membrane proteins and distribution of surface label amongst these proteins

    International Nuclear Information System (INIS)

    Crumpton, M.J.; Marchalonis, J.J.; Haustein, D.; Atwell, J.L.; Harris, A.W.

    1976-01-01

    Two established techniques for analysis of plasma membranes, namely, lactoperoxidase catalyzed surface radioiodination of intact cells and bulk membrane isolation following disruption of cells by shear forces, were applied in studies of membrane proteins of continuously cultured cells of the monoclonal T lymphoma line WEHI-22. It was found that macromolecular 125 I-iodide incorporated into plasma membrane proteins of intact cells was at least as good a marker for the plasma as was the commonly used enzyme 5'-nucleotidase, T lymphoma plasma membrane proteins were complex when analysed by polyacrylamide gel electrophoresis in sodium dodecylsulphate-containing buffers and more than thirty distinct components were resolved. More than fifteen of the components observed on a mass basis were also labelled with 125 I-iodide. Certain bands, however, exhibited a degree of label disproportionate to their staining properties with Coomassie Blue. This was interpreted in terms of their accessibility to the solvent in the intact cells. (author)

  8. Nicotine inhibits collagen synthesis and alkaline phosphatase activity, but stimulates DNA synthesis in osteoblast-like cells

    International Nuclear Information System (INIS)

    Ramp, W.K.; Lenz, L.G.; Galvin, R.J.

    1991-01-01

    Use of smokeless tobacco is associated with various oral lesions including periodontal damage and alveolar bone loss. This study was performed to test the effects of nicotine on bone-forming cells at concentrations that occur in the saliva of smokeless tobacco users. Confluent cultures of osteoblast-like cells isolated from chick embryo calvariae were incubated for 2 days with nicotine added to the culture medium (25-600 micrograms/ml). Nicotine inhibited alkaline phosphatase in the cell layer and released to the medium, whereas glycolysis (as indexed by lactate production) was unaffected or slightly elevated. The effects on medium and cell layer alkaline phosphatase were concentration dependent with maximal inhibition occurring at 600 micrograms nicotine/ml. Nicotine essentially did not affect the noncollagenous protein content of the cell layer, but did inhibit collagen synthesis (hydroxylation of [ 3 H]proline and collagenase-digestible protein) at 100, 300, and 600 micrograms/ml. Release of [ 3 H]hydroxyproline to the medium was also decreased in a dose-dependent manner, as was the collagenase-digestible protein for both the medium and cell layer. In contrast, DNA synthesis (incorporation of [ 3 H]thymidine) was more than doubled by the alkaloid, whereas total DNA content was slightly inhibited at 600 micrograms/ml, suggesting stimulated cell turnover. Morphologic changes occurred in nicotine-treated cells including rounding up, detachment, and the occurrence of numerous large vacuoles. These results suggest that steps to reduce the salivary concentration of nicotine in smokeless tobacco users might diminish damaging effects of this product on alveolar bone

  9. Mass Spectrometry of Polymer Electrolyte Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Viktor Johánek

    2016-01-01

    Full Text Available The chemical analysis of processes inside fuel cells under operating conditions in either direct or inverted (electrolysis mode and their correlation with potentiostatic measurements is a crucial part of understanding fuel cell electrochemistry. We present a relatively simple yet powerful experimental setup for online monitoring of the fuel cell exhaust (of either cathode or anode side downstream by mass spectrometry. The influence of a variety of parameters (composition of the catalyst, fuel type or its concentration, cell temperature, level of humidification, mass flow rate, power load, cell potential, etc. on the fuel cell operation can be easily investigated separately or in a combined fashion. We demonstrate the application of this technique on a few examples of low-temperature (70°C herein polymer electrolyte membrane fuel cells (both alcohol- and hydrogen-fed subjected to a wide range of conditions.

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

    Science.gov (United States)

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

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

  11. Nuclear myosin I regulates cell membrane tension

    Czech Academy of Sciences Publication Activity Database

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

    2016-01-01

    Roč. 6, AUG 2 (2016), č. článku 30864. ISSN 2045-2322 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0109; GA ČR GAP305/11/2232; GA MŠk(CZ) LO1304 Institutional support: RVO:68378050 Keywords : neuronal growth cone * rna-polymerase-ii * cancer cells * phosphatidylinositol 4,5-bisphosphate * myo1c * actin * transcription * complex * motor * afm Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.259, year: 2016

  12. MEMBRANE LEc EXPRESSION IN BREAST CANCER CELLS

    Directory of Open Access Journals (Sweden)

    Ya. A. Udalova

    2009-01-01

    Full Text Available Affine chromatography was used to isolate Lec antibodies from the sera of a healthy female donor with the high titers of these anti- bodies, which were labeled with biotin. The study enrolled 51 patients with primary breast cancer (BC. Antigen expression was found by immunohistochemistry and flow cytometry. With these two techniques being used, the detection rate of Lec expression in BC cells was 65% (33/51; the antigen was most frequently found by flow cytometry as compared with immunohistochemistry: 72 and 58% of cases, respectively.

  13. Nature of the elements transporting long-chain fatty acids through the red cell membrane

    DEFF Research Database (Denmark)

    Bojesen, Inge Norby; Bojesen, Eigil

    1998-01-01

    Docosahexaenoic acid, linoleic acid, red cell membrane, transporting elements, transport kinetics, fatty acid transport......Docosahexaenoic acid, linoleic acid, red cell membrane, transporting elements, transport kinetics, fatty acid transport...

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

    Science.gov (United States)

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

    2012-03-16

    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

  15. Effects of X-irradiation on membranes of tumor cells

    International Nuclear Information System (INIS)

    Fonck, K.

    1982-01-01

    The aim of the investigation was to gain more insight into the effect of ionizing radiation on biomembranes, especially the membrane phospholipids. A general outline of the experimental approach is given in the first chapter. The influence of membrane-active agents and hyperthermia on cell survival after irradiation was studied. Phospholipid turnover was followed by measuring the incorporation of radioactive precursors. The second chapter is an introduction to general radiobiology and to phospholipid metabolism. After the presentation of some physico-chemical properties of ionizing radiation, the effects on cells and cellular components are described. In chapters 3 to 6 the experimental part is described. Chapter 3 starts with the determination of the cellular survival of L5178Y lymphoma cells after X-irradiation. In chapter 4 the lipid composition of lymphosarcoma cell nuclei is presented and in chapter 5 studies on the effect of X-irradiation on the incorporation of palmitate and arachidonate into the phospholipids of lymphosarcoma cells are described. Chapter 6 describes experiments in which lymphosarcoma cells isolated from the spleens of tumor-bearing mice were used to study the effect of a low dose of X-rays (5 Gy) on the incorporation of [ 3 H]palmitate and [ 14 C]arachidonate into the lipids of the tumor cells. These fatty acids were rapidly incorporated especially into the phospholipids of the cells. Chapter 7 contains a general discussion on the experimental results. (Auth.)

  16. Phosphoric acid distribution in the membrane electrode assembly of high temperature proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Kwon, Kyungjung; Park, Jung Ock; Yoo, Duck Young; Yi, Jung S.

    2009-01-01

    The ionomer content in electrode is one of the most important parameters for the high performance of fuel cells. The high temperature PEMFC based on phosphoric acid (PA)-doped polymer membrane with unhumidified reactant gases has a difficulty in controlling the liquid state PA ionomer content in electrode. To evaluate the PA content in electrode, the three techniques of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and acid-base titration (ABT) are carried out in situ or ex situ. The properties of membrane electrode assembly (MEA) such as electrochemical surface area (ESA), ohmic resistance, charge transfer resistance, double layer capacitance and the amount of PA in MEA components (anode, cathode and membrane) are extracted by each technique. Ex situ CV with the usage of dry gases has a limitation in assessing the reliable ESA of unhumidified PEMFC. While in situ EIS presents some informative values of resistance and capacitance for understanding the PA distribution in MEA, its sensitivity to the PA content in MEA components needs to be higher for detecting a subtle change in PA distribution. Ex situ ABT supplies a clear PA distribution in MEA at room temperature but does not seem to reflect the operating state well at high temperatures. However, it can be used as a detection tool for the loss of the initial acid content in membrane during a long-term MEA durability study.

  17. Nafion/silane nanocomposite membranes for high temperature polymer electrolyte membrane fuel cell.

    Science.gov (United States)

    Ghi, Lee Jin; Park, Na Ri; Kim, Moon Sung; Rhee, Hee Woo

    2011-07-01

    The polymer electrolyte membrane fuel cell (PEMFC) has been studied actively for both potable and stationary applications because it can offer high power density and be used only hydrogen and oxygen as environment-friendly fuels. Nafion which is widely used has mechanical and chemical stabilities as well as high conductivity. However, there is a drawback that it can be useless at high temperatures (> or = 90 degrees C) because proton conducting mechanism cannot work above 100 degrees C due to dehydration of membrane. Therefore, PEMFC should be operated for long-term at high temperatures continuously. In this study, we developed nanocomposite membrane using stable properties of Nafion and phosphonic acid groups which made proton conducting mechanism without water. 3-Aminopropyl triethoxysilane (APTES) was used to replace sulfonic acid groups of Nafion and then its aminopropyl group was chemically modified to phosphonic acid groups. The nanocomposite membrane showed very high conductivity (approximately 0.02 S/cm at 110 degrees C, <30% RH).

  18. Phosphoric acid distribution in the membrane electrode assembly of high temperature proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Kyungjung [Fuel Cell Group, Energy Lab, SAIT, Samsung Electronics Co., Ltd., San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do, 446-712 (Korea, Republic of)], E-mail: kfromberk@gmail.com; Park, Jung Ock; Yoo, Duck Young; Yi, Jung S. [Fuel Cell Group, Energy Lab, SAIT, Samsung Electronics Co., Ltd., San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do, 446-712 (Korea, Republic of)

    2009-11-01

    The ionomer content in electrode is one of the most important parameters for the high performance of fuel cells. The high temperature PEMFC based on phosphoric acid (PA)-doped polymer membrane with unhumidified reactant gases has a difficulty in controlling the liquid state PA ionomer content in electrode. To evaluate the PA content in electrode, the three techniques of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and acid-base titration (ABT) are carried out in situ or ex situ. The properties of membrane electrode assembly (MEA) such as electrochemical surface area (ESA), ohmic resistance, charge transfer resistance, double layer capacitance and the amount of PA in MEA components (anode, cathode and membrane) are extracted by each technique. Ex situ CV with the usage of dry gases has a limitation in assessing the reliable ESA of unhumidified PEMFC. While in situ EIS presents some informative values of resistance and capacitance for understanding the PA distribution in MEA, its sensitivity to the PA content in MEA components needs to be higher for detecting a subtle change in PA distribution. Ex situ ABT supplies a clear PA distribution in MEA at room temperature but does not seem to reflect the operating state well at high temperatures. However, it can be used as a detection tool for the loss of the initial acid content in membrane during a long-term MEA durability study.

  19. Modified SPEEK membranes for direct ethanol fuel cell

    KAUST Repository

    Maab, Husnul

    2010-07-01

    Membranes with low ethanol crossover were prepared aiming their application for direct ethanol fuel cell (DEFC). They were based on (1) sulfonated poly(ether ether ketone) (SPEEK) coated with carbon molecular sieves (CMS) and (2) on SPEEK/PI homogeneous blends. The membranes were characterized concerning their water and ethanol solution uptake, water and ethanol permeability in pervaporation experiments and their performance in DEFC tests. The ethanol permeabilities for the CMS-coated (180 nm and 400 nm thick layers) SPEEK were 8.5 and 3.1 x 10(-10) kg m s(-1) m(-2) and for the homogeneous SPEEK/PI blends membranes with 10, 20 and 30 wt.% of PI were 4.4, 1.0 and 0.4 x 10(-10) kg m s(-1) m(-2) respectively, which is 2- to 50-fold lower than that for plain SPEEK (19 x 10(-10) kg m s(-1) m(-2)). Particularly the SPEEK/PI membranes had substantially better performance than Nafion 117 membranes in DEFC tests at 60 degrees C and 90 degrees C. (C) 2010 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  1. Modeling and Simulation for Fuel Cell Polymer Electrolyte Membrane

    Directory of Open Access Journals (Sweden)

    Takahiro Hayashi

    2013-01-01

    Full Text Available We have established methods to evaluate key properties that are needed to commercialize polyelectrolyte membranes for fuel cell electric vehicles such as water diffusion, gas permeability, and mechanical strength. These methods are based on coarse-graining models. For calculating water diffusion and gas permeability through the membranes, the dissipative particle dynamics–Monte Carlo approach was applied, while mechanical strength of the hydrated membrane was simulated by coarse-grained molecular dynamics. As a result of our systematic search and analysis, we can now grasp the direction necessary to improve water diffusion, gas permeability, and mechanical strength. For water diffusion, a map that reveals the relationship between many kinds of molecular structures and diffusion constants was obtained, in which the direction to enhance the diffusivity by improving membrane structure can be clearly seen. In order to achieve high mechanical strength, the molecular structure should be such that the hydrated membrane contains narrow water channels, but these might decrease the proton conductivity. Therefore, an optimal design of the polymer structure is needed, and the developed models reviewed here make it possible to optimize these molecular structures.

  2. Lowering the platinum loading of high temperature polymer electrolyte membrane fuel cells with acid doped polybenzimidazole membranes

    DEFF Research Database (Denmark)

    Fernandez, Santiago Martin; Li, Qingfeng; Jensen, Jens Oluf

    2015-01-01

    Membrane electrode assemblies (MEAs) with ultra-low Pt loading electrodes were prepared for high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) based on acid doped polybenzimidazole. With no electrode binders or ionomers, the triple phase boundary of the catalyst layer was establ......Membrane electrode assemblies (MEAs) with ultra-low Pt loading electrodes were prepared for high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) based on acid doped polybenzimidazole. With no electrode binders or ionomers, the triple phase boundary of the catalyst layer...

  3. ZirfonR-composite membranes: properties and applications

    International Nuclear Information System (INIS)

    Leysen, R.; Doyen, W.; Adriansen, W.; Vermeiren, Ph.

    1993-01-01

    In this report, the fabrication and the applications of a new type of composite membrane, the zirconium-oxide-polysulphone membrane (registered trade mark name: Zirfon), are described. The investigated Zirfon membranes are fabricated by the film casting technique and are composed of zirconium oxide powder and a polymeric binder, polysulphone. Zirfon membranes have been developed first for use as separators in electrochemical applications (e.g. alkaline water electrolysis and alkaline fuel cells). Besides their applications in electrochemical systems, Zirfon membranes have been tested as separating membranes for several ultrafiltration purposes. The most recent application of Zirfon membranes is their use for the removal of heavy metals in waste streams by means of incorporated bacteria. In this application, micro-organisms are immobilized on the porous structure of the membrane. Potential future applications are in the field of energy production (fuel cells) and the treatment of non-nuclear or nuclear waste water. (A.S.)

  4. Stability of a Cu0.7Co2.3O4 electrode during the oxygen evolution reaction for alkaline anion-exchange membrane water electrolysis

    Science.gov (United States)

    Kang, Kyoung Eun; Kim, Chi Ho; Lee, Myung Sup; Jung, Chang Wook; Kim, Yang Do; Lee, Jae Ho

    2018-01-01

    The electrode materials for oxygen evolution, especially non-platinum group metal oxides, have attracted increasing attention. Among the spinel-type transition metal oxides, Cu0.7Co2.3O4 powders were evaluated as a potential replacement for expensive dimensionally stabilized anode materials. Cu0.7Co2.3O4 powder for use as an electrode material for oxygen evolution in an alkaline anion-exchange membrane water electrolyzer was prepared using a thermal decomposition method. The Cu0.7Co2.3O4 powders heat-treated at 250 °C exhibited the same X-ray diffraction patterns without any secondary phases as the Co3O4 spinel structure did. The Cu0.7Co2.3O4 powders heat-treated at 250 °C for 30 minutes showed the smallest mean particle size of approximately 376 nm with the powders having a homogeneous shape and size distribution. The fine powders with a relatively homogeneous size distribution showed a higher current density during the oxygen evolution reaction. The lifetime of the Cu0.7Co2.3O4 electrode was relatively long at a low current density, but was quickly shortened due to physical detachment of the Cu0.7Co2.3O4 powders as the current density was increased. This study showed that the efficiency and the stability of Cu0.7Co2.3O4 powders during the oxygen evolution reaction were related directly to the active electrode area.

  5. Development of a proton exchange membrane fuel cell cogeneration system

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Jenn Jiang; Zou, Meng Lin [Department of Greenergy, National University of Tainan, Tainan 700 (China)

    2010-05-01

    A proton exchange membrane fuel cell (PEMFC) cogeneration system that provides high-quality electricity and hot water has been developed. A specially designed thermal management system together with a microcontroller embedded with appropriate control algorithm is integrated into a PEM fuel cell system. The thermal management system does not only control the fuel cell operation temperature but also recover the heat dissipated by FC stack. The dynamic behaviors of thermal and electrical characteristics are presented to verify the stability of the fuel cell cogeneration system. In addition, the reliability of the fuel cell cogeneration system is proved by one-day demonstration that deals with the daily power demand in a typical family. Finally, the effects of external loads on the efficiencies of the fuel cell cogeneration system are examined. Results reveal that the maximum system efficiency was as high as 81% when combining heat and power. (author)

  6. Proton Exchange Membrane Fuel Cell Engineering Model Powerplant. Test Report: Benchmark Tests in Three Spatial Orientations

    Science.gov (United States)

    Loyselle, Patricia; Prokopius, Kevin

    2011-01-01

    Proton exchange membrane (PEM) fuel cell technology is the leading candidate to replace the aging alkaline fuel cell technology, currently used on the Shuttle, for future space missions. This test effort marks the final phase of a 5-yr development program that began under the Second Generation Reusable Launch Vehicle (RLV) Program, transitioned into the Next Generation Launch Technologies (NGLT) Program, and continued under Constellation Systems in the Exploration Technology Development Program. Initially, the engineering model (EM) powerplant was evaluated with respect to its performance as compared to acceptance tests carried out at the manufacturer. This was to determine the sensitivity of the powerplant performance to changes in test environment. In addition, a series of tests were performed with the powerplant in the original standard orientation. This report details the continuing EM benchmark test results in three spatial orientations as well as extended duration testing in the mission profile test. The results from these tests verify the applicability of PEM fuel cells for future NASA missions. The specifics of these different tests are described in the following sections.

  7. Halloysite-derived nitrogen doped carbon electrocatalysts for anion exchange membrane fuel cells

    Science.gov (United States)

    Lu, Yaxiang; Wang, Lianqin; Preuß, Kathrin; Qiao, Mo; Titirici, Maria-Magdalena; Varcoe, John; Cai, Qiong

    2017-12-01

    Developing the low-cost, highly active carbonaceous materials for oxygen reduction reaction (ORR) catalysts has been a high-priority research direction for durable fuel cells. In this paper, two novel N-doped carbonaceous materials with flaky and rod-like morphology using the natural halloysite as template are obtained from urea nitrogen source as well as glucose (denoted as GU) and furfural (denoted as FU) carbon precursors, respectively, which can be directly applied as metal-free electrocatalysts for ORR in alkaline electrolyte. Importantly, compared with a benchmark Pt/C (20wt%) catalyst, the as-prepared carbon catalysts demonstrate higher retention in diffusion limiting current density (after 3000 cycles) and enhanced methanol tolerances with only 50-60mV negative shift in half-wave potentials. In addition, electrocatalytic activity, durability and methanol tolerant capability of the two N-doped carbon catalysts are systematically evaluated, and the underneath reasons of the outperformance of rod-like catalysts over the flaky are revealed. At last, the produced carbonaceous catalysts are also used as cathodes in the single cell H2/O2 anion exchange membrane fuel cell (AEMFC), in which the rod-like FU delivers a peak power density as high as 703 mW cm-2 (vs. 1106 mW cm-2 with a Pt/C benchmark cathode catalyst).

  8. Modeling a Membrane: Using Engineering Design to Simulate Cell Transport Processes

    Science.gov (United States)

    Mason, Kevin; Evans, Brian

    2017-01-01

    The "plasma membrane," which controls what comes in and goes out of a cell, is integral to maintaining homeostasis. Cell transport of small molecules across the cell membrane happens in several different ways. Some small, nonpolar molecules cross the plasma membrane along the concentration gradient directly through the "phospholipid…

  9. Development of a membrane electrode assembly process for proton exchange membrane fuel cell (PEMFC)

    International Nuclear Information System (INIS)

    Baldo, Wilians Roberto

    2003-01-01

    In this work, a Membrane Electrode Assembly (MEA) producing process was developed, involving simple steps, aiming cost reduction and good reproducibility for Proton Exchange Membrane Fuel Cell (PEMFC) commercial applications. The electrodes were produced by spraying ink into both sides of the polymeric membrane, building the catalytic layers, followed by hot pressing of Gas Diffusion Layers (GDL), forming the MEA. This new producing method was called 'Spray and hot pressing hybrid method'. Concerning that all the parameters of spray and hot pressing methods are interdependent, a statistical procedure were used in order to study the mutual variables influences and to optimize the method. This study was earned out in two distinct steps: the first one, where seven variables were considered for the analysis and the second one, where only the variables that interfered in the process performance in the first step were considered for analysis. The results showed that the developed process was adequate, including only simple steps, reaching MEA's performance of 651 m A cm -2 at a potential of 600 mV for catalysts loading of 0,4 mg cm -2 Pt at the anode and 0,6 mg cm -2 Pt at the cathode. This result is compared to available commercial MEA's, with the same fuel cell operations conditions. (author)

  10. Solid Polymer Fuel Cells. Electrode and membrane performance studies

    Energy Technology Data Exchange (ETDEWEB)

    Moeller-Holst, S.

    1996-12-31

    This doctoral thesis studies aspects of fuel cell preparation and performance. The emphasis is placed on preparation and analysis of low platinum-loading solid polymer fuel cell (SPEC) electrodes. A test station was built and used to test cells within a wide range of real operating conditions, 40-150{sup o}C and 1-10 bar. Preparation and assembling equipment for single SPFCs was designed and built, and a new technique of spraying the catalyst layer directly onto the membrane was successfully demonstrated. Low Pt-loading electrodes (0.1 mg Pt/cm{sup 2}) prepared by the new technique exhibited high degree of catalyst utilization. The performance of single cells holding these electrodes is comparable to state-of-the-art SPFCs. Potential losses in single cell performance are ascribed to irreversibilities by analysing the efficiency of the Solid Oxide Fuel Cell by means of the second law of thermodynamics. The water management in membranes is discussed for a model system and the results are relevant to fuel cell preparation and performance. The new spray deposition technique should be commercially interesting as it involves few steps as well as techniques that are adequate for larger scale production. 115 refs., 43 figs., 18 tabs.

  11. Solid Polymer Fuel Cells. Electrode and membrane performance studies

    Energy Technology Data Exchange (ETDEWEB)

    Moeller-Holst, S

    1997-12-31

    This doctoral thesis studies aspects of fuel cell preparation and performance. The emphasis is placed on preparation and analysis of low platinum-loading solid polymer fuel cell (SPEC) electrodes. A test station was built and used to test cells within a wide range of real operating conditions, 40-150{sup o}C and 1-10 bar. Preparation and assembling equipment for single SPFCs was designed and built, and a new technique of spraying the catalyst layer directly onto the membrane was successfully demonstrated. Low Pt-loading electrodes (0.1 mg Pt/cm{sup 2}) prepared by the new technique exhibited high degree of catalyst utilization. The performance of single cells holding these electrodes is comparable to state-of-the-art SPFCs. Potential losses in single cell performance are ascribed to irreversibilities by analysing the efficiency of the Solid Oxide Fuel Cell by means of the second law of thermodynamics. The water management in membranes is discussed for a model system and the results are relevant to fuel cell preparation and performance. The new spray deposition technique should be commercially interesting as it involves few steps as well as techniques that are adequate for larger scale production. 115 refs., 43 figs., 18 tabs.

  12. Proton exchange membrane fuel cell technology for transportation applications

    Energy Technology Data Exchange (ETDEWEB)

    Swathirajan, S. [General Motors R& D Center, Warren, MI (United States)

    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.

  13. Factors Determining the Oxygen Permeability of Biological Membranes: Oxygen Transport Across Eye Lens Fiber-Cell Plasma Membranes.

    Science.gov (United States)

    Subczynski, Witold Karol; Widomska, Justyna; Mainali, Laxman

    2017-01-01

    Electron paramagnetic resonance (EPR) spin-label oximetry allows the oxygen permeability coefficient to be evaluated across homogeneous lipid bilayer membranes and, in some cases, across coexisting membrane domains without their physical separation. The most pronounced effect on oxygen permeability is observed for cholesterol, which additionally induces the formation of membrane domains. In intact biological membranes, integral proteins induce the formation of boundary and trapped lipid domains with a low oxygen permeability. The effective oxygen permeability coefficient across the intact biological membrane is affected not only by the oxygen permeability coefficients evaluated for each lipid domain but also by the surface area occupied by these domains in the membrane. All these factors observed in fiber cell plasma membranes of clear human eye lenses are reviewed here.

  14. Cell-geometry-dependent changes in plasma membrane order direct stem cell signalling and fate

    Science.gov (United States)

    von Erlach, Thomas C.; Bertazzo, Sergio; Wozniak, Michele A.; Horejs, Christine-Maria; Maynard, Stephanie A.; Attwood, Simon; Robinson, Benjamin K.; Autefage, Hélène; Kallepitis, Charalambos; del Río Hernández, Armando; Chen, Christopher S.; Goldoni, Silvia; Stevens, Molly M.

    2018-03-01

    Cell size and shape affect cellular processes such as cell survival, growth and differentiation1-4, thus establishing cell geometry as a fundamental regulator of cell physiology. The contributions of the cytoskeleton, specifically actomyosin tension, to these effects have been described, but the exact biophysical mechanisms that translate changes in cell geometry to changes in cell behaviour remain mostly unresolved. Using a variety of innovative materials techniques, we demonstrate that the nanostructure and lipid assembly within the cell plasma membrane are regulated by cell geometry in a ligand-independent manner. These biophysical changes trigger signalling events involving the serine/threonine kinase Akt/protein kinase B (PKB) that direct cell-geometry-dependent mesenchymal stem cell differentiation. Our study defines a central regulatory role by plasma membrane ordered lipid raft microdomains in modulating stem cell differentiation with potential translational applications.

  15. Internal humidifying of PEM [Proton Exchange Membrane] fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Staschewski, D [Karlsruhe Research Center (FZK), Karlsruhe (Germany). Inst. for Neutron Physics and Reactor Technics

    1996-12-01

    Hydrogen fuel cells (FC) for vehicular traction should stand out for a car-specific lightweight design. As regards PEMFC systems containing proton exchange membranes, this quality can be considerably improved by introducing porous bipolar plates which are conditioned by a water loop and deliver hot humidifying water to the adjacent membrane-electrode assembly (MEA). According to the principle of internal humidification here indicated special fuel cells based on sintered fiber and powder graphite were manufactured at FZK on a semi-technical scale. Self-made Pt/C electrodes hotpressed onto Nafion resulted in currents up to 200 A with pure oxygen as oxidant, providing the precondition for detailed studies of turnover and drainage rates within a monocell test arrangement. (author)

  16. Binding of 18F by cell membranes and cell walls of Streptococcus mutans

    International Nuclear Information System (INIS)

    Yotis, W.W.; Zeb, M.; McNulty, J.; Kirchner, F.; Reilly, C.; Glendenin, L.

    1983-01-01

    The binding of 18 F to isolated cell membranes and cell walls of Streptococcus mutans GS-5 or other bacteria was assayed. The attachment of 18 F to these cell envelopes proceeded slowly and reached equilibrium within 60 min. 18 F binding was stimulated by Ca 2+ (1 mM). The binding of 18 F to cellular components was dependent upon the pH, as well as the amount of 18 F and dose of the binder employed. The binding of 18 F by cell walls prepared from fluoride-sensitive and fluoride-resistant cells of S. salivarius and S. mutans did not differ significantly. The pretreatment of cell walls or cell membranes for 60 min at 30 degrees C with 1 mg of RNase, DNase, or trypsin per ml did not influence the binding of 18 F by the walls and membranes of S. mutans GS-5. However, prior exposure of cell membranes to sodium dodecyl sulfate caused a significant reduction in the number of 18 F atoms bound by the membranes. In saturated assay systems, cell membranes of S. mutans GS-5 bound 10(15) to 10(16) atoms of 18 F per mg (dry weight), whereas cell walls from S. mutans GS-5, FA-1, and HS-6 or Actinomyces viscosus T14V and T14AV bound 10(12) to 10(13) atoms of 18 F per mg (dry weight). 18 F in this quantity (10(12) to 10(13) atoms) cannot be detected with the fluoride electrode. The data provide, for the first time, a demonstration of 18 F binding by cell membranes and walls of oral flora

  17. Palladium and palladium-tin supported on multi wall carbon nanotubes or carbon for alkaline direct ethanol fuel cell

    Science.gov (United States)

    Geraldes, Adriana Napoleão; Furtunato da Silva, Dionisio; Martins da Silva, Júlio César; Antonio de Sá, Osvaldo; Spinacé, Estevam Vitório; Neto, Almir Oliveira; Coelho dos Santos, Mauro

    2015-02-01

    Pd and PdSn (Pd:Sn atomic ratios of 90:10), supported on Multi Wall Carbon Nanotubes (MWCNT) or Carbon (C), are prepared by an electron beam irradiation reduction method. The obtained materials are characterized by X-Ray diffraction (XRD), Energy dispersive X-ray analysis (EDX), Transmission electron Microscopy (TEM) and Cyclic Voltammetry (CV). The activity for ethanol electro-oxidation is tested in alkaline medium, at room temperature, using Cyclic Voltammetry and Chronoamperometry (CA) and in a single alkaline direct ethanol fuel cell (ADEFC), in the temperature range of 60-90 °C. CV analysis finds that Pd/MWCNT and PdSn/MWCNT presents onset potentials changing to negative values and high current values, compared to Pd/C and PdSn/C electrocatalysts. ATR-FTIR analysis, performed during the CV, identifies acetate and acetaldehyde as principal products formed during the ethanol electro-oxidation, with low conversion to CO2. In single fuel cell tests, at 85 °C, using 2.0 mol L-1 ethanol in 2.0 mol L-1 KOH solutions, the electrocatalysts supported on MWCNT, also, show higher power densities, compared to the materials supported on carbon: PdSn/MWCNT, presents the best result (36 mW cm-2). The results show that the use of MWCNT, instead of carbon, as support, plus the addition of small amounts of Sn to Pd, improves the electrocatalytic activity for Ethanol Oxidation Reaction (EOR).

  18. The hydroxyflavone, fisetin, suppresses mast cell activation induced by interaction with activated T cell membranes

    Science.gov (United States)

    Nagai, K; Takahashi, Y; Mikami, I; Fukusima, T; Oike, H; Kobori, M

    2009-01-01

    Background and purpose: Cell-to-cell interactions between mast cells and activated T cells are increasingly recognized as a possible mechanism in the aetiology of allergic or non-allergic inflammatory disorders. To determine the anti-allergic effect of fisetin, we examined the ability of fisetin to suppress activation of the human mast cell line, HMC-1, induced by activated Jurkat T cell membranes. Experimental approach: HMC-1 cells were incubated with or without fisetin for 15 min and then co-cultured with Jurkat T cell membranes activated by phorbol-12-myristate 13-acetate for 16 h. We determined gene expression in activated HMC-1 cells by DNA microarray and quantitative reverse transcription (RT)-PCR analysis. We also examined activation of the transcription factor NF-κB and MAP kinases (MAPKs) in activated HMC-1 cells. Key results: Fisetin suppresses cell spreading and gene expression in HMC-1 cells stimulated by activated T cell membranes. Additionally, we show that these stimulated HMC-1 cells expressed granzyme B. The stimulatory interaction also induced activation of NF-κB and MAPKs; these activations were suppressed by fisetin. Fisetin also reduced the amount of cell surface antigen CD40 and intercellular adhesion molecule-1 (ICAM-1) on activated HMC-1 cells. Conclusions and implications: Fisetin suppressed activation of HMC-1 cells by activated T cell membranes by interfering with cell-to-cell interaction and inhibiting the activity of NF-κB and MAPKs and thereby suppressing gene expression. Fisetin may protect against the progression of inflammatory diseases by limiting interactions between mast cells and activated T cells. PMID:19702784

  19. A practical guide for the identification of membrane and plasma membrane proteins in human embryonic stem cells and human embryonal carcinoma cells.

    Science.gov (United States)

    Dormeyer, Wilma; van Hoof, Dennis; Mummery, Christine L; Krijgsveld, Jeroen; Heck, Albert J R

    2008-10-01

    The identification of (plasma) membrane proteins in cells can provide valuable insights into the regulation of their biological processes. Pluripotent cells such as human embryonic stem cells and embryonal carcinoma cells are capable of unlimited self-renewal and share many of the biological mechanisms that regulate proliferation and differentiation. The comparison of their membrane proteomes will help unravel the biological principles of pluripotency, and the identification of biomarker proteins in their plasma membranes is considered a crucial step to fully exploit pluripotent cells for therapeutic purposes. For these tasks, membrane proteomics is the method of choice, but as indicated by the scarce identification of membrane and plasma membrane proteins in global proteomic surveys it is not an easy task. In this minireview, we first describe the general challenges of membrane proteomics. We then review current sample preparation steps and discuss protocols that we found particularly beneficial for the identification of large numbers of (plasma) membrane proteins in human tumour- and embryo-derived stem cells. Our optimized assembled protocol led to the identification of a large number of membrane proteins. However, as the composition of cells and membranes is highly variable we still recommend adapting the sample preparation protocol for each individual system.

  20. Water Soluble Polymers as Proton Exchange Membranes for Fuel Cells

    Directory of Open Access Journals (Sweden)

    Bing-Joe Hwang

    2012-03-01

    Full Text Available The relentless increase in the demand for useable power from energy-hungry economies continues to drive energy-material related research. Fuel cells, as a future potential power source that provide clean-at-the-point-of-use power offer many advantages such as high efficiency, high energy density, quiet operation, and environmental friendliness. Critical to the operation of the fuel cell is the proton exchange membrane (polymer electrolyte membrane responsible for internal proton transport from the anode to the cathode. PEMs have the following requirements: high protonic conductivity, low electronic conductivity, impermeability to fuel gas or liquid, good mechanical toughness in both the dry and hydrated states, and high oxidative and hydrolytic stability in the actual fuel cell environment. Water soluble polymers represent an immensely diverse class of polymers. In this comprehensive review the initial focus is on those members of this group that have attracted publication interest, principally: chitosan, poly (ethylene glycol, poly (vinyl alcohol, poly (vinylpyrrolidone, poly (2-acrylamido-2-methyl-1-propanesulfonic acid and poly (styrene sulfonic acid. The paper then considers in detail the relationship of structure to functionality in the context of polymer blends and polymer based networks together with the effects of membrane crosslinking on IPN and semi IPN architectures. This is followed by a review of pore-filling and other impregnation approaches. Throughout the paper detailed numerical results are given for comparison to today’s state-of-the-art Nafion® based materials.

  1. Ceramic membrane fuel cells based on solid proton electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Guangyao; Ma, Qianli; Peng, Ranran; Liu, Xingqin [USTC Lab. for Solid State Chemistry and Inorganic Membranes, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China); Ma, Guilin [School of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215123 (China)

    2007-04-15

    The development of solid oxide fuel cells (SOFCs) has reached its new stage characterized with thin electrolytes on porous electrode support, and the most important fabrication techniques developed in which almost all are concerned with inorganic membranes, and so can be named as ceramic membrane fuel cells (CMFCs). CMFCs based on proton electrolytes (CMFC-H) may exhibit more advantages than CMFCs based on oxygen-ion electrolytes (CMFC-O) in many respects, such as energy efficiency and avoiding carbon deposit. Ammonia fuelled CMFC with proton-conducting BaCe{sub 0.8}Gd{sub 0.2}O{sub 2.9} (BCGO) electrolyte (50 {mu}m in thickness) is reported in this works, which showed the open current voltage (OCV) values close to theoretical ones and rather high power density. And also, we have found that the well known super oxide ion conductor, La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3-{alpha}} (LSGM), is a pure proton conductor in H{sub 2} and mixed proton and oxide ion conductor in wet air, while it is a pure oxide ion conductor in oxygen or dry air. To demonstrate the CMFC-H concept to get high performance fuel cells the techniques for thin membranes, chemical vapor deposition (CVD), particularly novel CVD techniques, should be given more attention because of their many advantages. (author)

  2. Collective cell behavior on basement membranes floating in space

    Science.gov (United States)

    Ellison, Sarah; Bhattacharjee, Tapomoy; Morley, Cameron; Sawyer, W.; Angelini, Thomas

    The basement membrane is an essential part of the polarity of endothelial and epithelial tissues. In tissue culture and organ-on-chip devices, monolayer polarity can be established by coating flat surfaces with extracellular matrix proteins and tuning the trans-substrate permeability. In epithelial 3D culture, spheroids spontaneously establish inside-out polarity, morphing into hollow shell-like structures called acini, generating their own basement membrane on the inner radius of the shell. However, 3D culture approaches generally lack the high degree of control provided by the 2D culture plate or organ-on-chip devices, making it difficult to create more faithful in vitro tissue models with complex surface curvature and morphology. Here we present a method for 3D printing complex basement membranes covered in cells. We 3D print collagen-I and Matrigel into a 3D growth medium made from jammed microgels. This soft, yielding material allows extracellular matrix to be formed as complex surfaces and shapes, floating in space. We then distribute MCF10A epithelial cells across the polymerized surface. We envision employing this strategy to study 3D collective cell behavior in numerous model tissue layers, beyond this simple epithelial model.

  3. Rupturing Giant Plasma Membrane Vesicles to Form Micron-sized Supported Cell Plasma Membranes with Native Transmembrane Proteins.

    Science.gov (United States)

    Chiang, Po-Chieh; Tanady, Kevin; Huang, Ling-Ting; Chao, Ling

    2017-11-09

    Being able to directly obtain micron-sized cell blebs, giant plasma membrane vesicles (GPMVs), with native membrane proteins and deposit them on a planar support to form supported plasma membranes could allow the membrane proteins to be studied by various surface analytical tools in native-like bilayer environments. However, GPMVs do not easily rupture on conventional supports because of their high protein and cholesterol contents. Here, we demonstrate the possibility of using compression generated by the air-water interface to efficiently rupture GPMVs to form micron-sized supported membranes with native plasma membrane proteins. We demonstrated that not only lipid but also a native transmembrane protein in HeLa cells, Aquaporin 3 (AQP3), is mobile in the supported membrane platform. This convenient method for generating micron-sized supported membrane patches with mobile native transmembrane proteins could not only facilitate the study of membrane proteins by surface analytical tools, but could also enable us to use native membrane proteins for bio-sensing applications.

  4. Effect of short-term alkaline intervention on the performance of buffer-free single-chamber microbial fuel cell.

    Science.gov (United States)

    Yang, Na; Ren, Yueping; Li, Xiufen; Wang, Xinhua

    2017-06-01

    Anolyte acidification is a drawback restricting the electricity generation performance of the buffer-free microbial fuel cells (MFC). In this paper, a small amount of alkali-treated anion exchange resin (AER) was placed in front of the anode in the KCl mediated single-chamber MFC to slowly release hydroxyl ions (OH - ) and neutralize the H + ions that are generated by the anodic reaction in two running cycles. This short-term alkaline intervention to the KCl anolyte has promoted the proliferation of electroactive Geobacter sp. and enhanced the self-buffering capacity of the KCl-AER-MFC. The pH of the KCl anolyte in the KCl-AER-MFC increased and became more stable in each running cycle compared with that of the KCl-MFC after the short-term alkaline intervention. The maximum power density (P max ) of the KCl-AER-MFC increased from 307.5mW·m -2 to 542.8mW·m -2 , slightly lower than that of the PBS-MFC (640.7mW·m -2 ). The coulombic efficiency (CE) of the KCl-AER-MFC increased from 54.1% to 61.2% which is already very close to that of the PBS-MFC (61.9%). The results in this paper indicate that short-term alkaline intervention to the anolyte is an effective strategy to further promote the performance of buffer-free MFCs. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Dynamic analysis of magnetic nanoparticles crossing cell membrane

    Energy Technology Data Exchange (ETDEWEB)

    Pedram, Maysam Z. [Department of Mechanical Engineering, Sharif University of Tech., Azadi Ave., Tehran (Iran, Islamic Republic of); Shamloo, Amir, E-mail: shamloo@sharif.edu [Department of Mechanical Engineering, Sharif University of Tech., Azadi Ave., Tehran (Iran, Islamic Republic of); Ghafar-Zadeh, Ebrahim [Biologically-Inspired Sensors and Actuators Laboratory, Department of Electrical Engineering and Computer science, York University, Keel Street, Toronto (Canada); Alasty, Aria, E-mail: aalasti@sharif.edu [Department of Mechanical Engineering, Sharif University of Tech., Azadi Ave., Tehran (Iran, Islamic Republic of)

    2017-05-01

    Nowadays, nanoparticles (NPs) are used in a variety of biomedical applications including brain disease diagnostics and subsequent treatments. Among the various types of NPs, magnetic nanoparticles (MNPs) have been implemented by many research groups for an array of life science applications. In this paper, we studied MNPs controlled delivery into the endothelial cells using a magnetic field. Dynamics equations of MNPs were defined in the continuous domain using control theory methods and were applied to crossing the cell membrane. This study, dedicated to clinical and biomedical research applications, offers a guideline for the generation of a magnetic field required for the delivery of MNPs.

  6. Construction of dose-effect curves by irradiating peripheral blood mononuclear cells analyzed with the alkaline comet assay

    International Nuclear Information System (INIS)

    Rueda, Lenin; Rosales Jaime; Leon, Kety; Espinoza, Marco

    2015-01-01

    The suitability of the alkaline comet assay to detect levels of DNA damage in human monocytes and lymphocytes under radiation was tested. For this purpose, four dose-effect curves by irradiation of cells isolated from blood samples of 4 young, health and non-smoker donors. A gamma ray source of "6"0Co was used and doses of 0, 2.5, 5 and 7 Gy were delivered to blood cells. The results show good correlation (R2 = 0.973, SD = 0.009) between the radiation dose and DNA damage as measured by the parameter Tail Intensity (percentage of DNA in the tail of the 'comet'). Furthermore, we observe the variability in predicting DNA damage by Gy (7.59, SD = 1.5). Potential use of this technique in the biological dosimetry of ionizing radiations is being evaluated. (author)

  7. Alkaline-Acid Zn-H2 O Fuel Cell for the Simultaneous Generation of Hydrogen and Electricity.

    Science.gov (United States)

    Cai, Pingwei; Li, Yan; Wang, Genxiang; Wen, Zhenhai

    2018-04-03

    An alkaline-acid Zn-H 2 O fuel cell is proposed for the simultaneous generation of electricity with an open circuit voltage of about 1.25 V and production of H 2 with almost 100 % Faradic efficiency. We demonstrate that, as a result of harvesting energy from both electrochemical neutralization and electrochemical Zn oxidation, the as-developed hybrid cell can deliver a power density of up to 80 mW cm -2 and an energy density of 934 Wh kg -1 and maintain long-term stability for H 2 production with an output voltage of 1.16 V at a current density of 10 mA cm -2 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Localization of Alkaline Phosphatase and Cathepsin D during Cell Restoration after Colchicine Treatment in Primary Cultures of Fetal Rat Hepatocytes

    International Nuclear Information System (INIS)

    Chida, Kohsuke; Taguchi, Meiko

    2011-01-01

    Localization of alkaline phosphatase (ALP) and cathepsin D (CAPD) in primary cultures of fetal rat hepatocytes was examined using double immunofluorescent staining in order to investigate the relationship between lysosome movement and the fate of ALP during cell restoration after microtubule disruption by colchicine. At 3 hr and 24 hr after colchicine treatment, numerous coarse dots containing ALP were observed throughout the cytoplasm, and some of these showed colocalization with CAPD. At 48 hr and 72 hr after colchicine treatment, although most of the dots containing ALP in the cytoplasm disappeared, dots containing CAPD remained. The present results suggest that the denatured ALP proteins remaining in the cytoplasm of hepatocytes during cell restoration after colchicine treatment are digested by lysosomes

  9. Experimental study on the membrane electrode assembly of a proton exchange membrane fuel cell: effects of microporous layer, membrane thickness and gas diffusion layer hydrophobic treatment

    International Nuclear Information System (INIS)

    Ferreira, Rui B.; Falcão, D.S.; Oliveira, V.B.; Pinto, A.M.F.R.

    2017-01-01

    Highlights: • EIS is employed to investigate the MEA design of a PEM fuel cell. • Effects of MPL, membrane thickness and GDL hydrophobic treatment are studied. • MPL increases cell output at low to medium currents but reduces it at high currents. • Better results are obtained when employing a thinner Nafion membrane. • GDL hydrophobic treatment improves the cell performance. - Abstract: In this study, electrochemical impedance spectroscopy (EIS) is employed to analyze the influence of microporous layer (MPL), membrane thickness and gas diffusion layer (GDL) hydrophobic treatment in the performance of a proton exchange membrane (PEM) fuel cell. Results show that adding a MPL increases cell performance at low to medium current densities. Because lower ohmic losses are observed when applying a MPL, such improvement is attributed to a better hydration state of the membrane. The MPL creates a pressure barrier for water produced at the cathode, forcing it to travel to the anode side, therefore increasing the water content in the membrane. However, at high currents, this same phenomenon seems to have intensified liquid water flooding in the anode gas channels, increasing mass transfer losses and reducing the cell performance. Decreasing membrane thickness results into considerably higher performances, due to a decrease in ohmic resistance. Moreover, at low air humidity operation, a rapid recovery from dehydration is observed when a thinner membrane is employed. The GDL hydrophobic treatment significantly improves the cell performance. Untreated GDLs appear to act as water-traps that not only hamper reactants transport to the reactive sites but also impede the proper humidification of the cell. From the different designs tested, the highest maximum power density is obtained from that containing a MPL, a thinner membrane and treated GDLs.

  10. Cobalt and molybdenum activated electrodes in foam based alkaline electrolysis cells at 150-250 °C and 40 bar

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    A new type of alkaline electrolysis cells with nickel foam based gas diffusion electrodes and KOH (aq) immobilized in mesoporous SrTiO3 has been developed and tested at temperatures of 150 C, 200 C and 250 C at a pressure of 40 bar. Two cells have been characterized during the 270 h long test...

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

    Directory of Open Access Journals (Sweden)

    Christopher T. Saeui

    2015-06-01

    Full Text Available 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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

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

    KAUST Repository

    Malaeb, Lilian; Katuri, Krishna; Logan, Bruce E.; Maab, Husnul; Nunes, Suzana Pereira; Saikaly, Pascal

    2013-01-01

    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/m2 (6.8 W/m3) with the biocathode, compared to 0.82 W/m2 (14.5 W/m3) 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. © 2013 American Chemical Society.

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

    KAUST Repository

    Malaeb, Lilian

    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/m2 (6.8 W/m3) with the biocathode, compared to 0.82 W/m2 (14.5 W/m3) 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. © 2013 American Chemical Society.

  16. Durability Issues of High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    DEFF Research Database (Denmark)

    . As a critical concern, issues of long term durability of PBI based fuel cells are addressed in this talk, including oxidative degradation of the polymer, mechanical failures of the membrane, acid leaching out, corrosion of carbon support and sintering of catalysts particles. Excellent polymer durability has...... or ionically cross-linking and structure modification With load, thermal or startup-shutdown cycling, the performance loss was found to be much bigger, about 300 µV per cycle or 40 µV per operating hour, due to the increased acid loss and catalyst support corrosion, particularly under open circuit voltage...... operation. Further efforts are outlined to the future work....

  17. New proton conducting membranes for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Sukumar, P R

    2006-07-01

    In order to synthesize proton-conducting materials which retain acids in the membrane during fuel cell operating conditions, the synthesis of poly(vinylphosphonic acid) grafted polybenzimidazole (PVPA grafted PBI) and the fabrication of multilayer membranes are mainly focussed in this dissertation. Synthesis of PVPA grafted PBI membrane can be done according to ''grafting through'' method. In ''grafting through'' method (or macromonomer method), monomer (e.g., vinylphosphonic acid) is radically copolymerized with olefin group attached macromonomer (e.g., allyl grafted PBI and vinylbenzyl grafted PBI). This approach is inherently limited to synthesize graft-copolymer with well-defined architectural and structural parameters. The incorporation of poly(vinylphosphonic acid) into PBI lead to improvements in proton conductivity up to 10-2 S/cm. Regarding multilayer membranes, the proton conducting layer-by-layer (LBL) assembly of polymers by various strong acids such as poly(vinylphosphonic acid), poly(vinylsulfonic acid) and poly(styrenesulfonic acid) paired with basic polymers such as poly(4-vinylimidazole) and poly(benzimidazole), which are appropriate for Proton Exchange Membrane Fuel Cell applications have been described. Proton conductivity increases with increasing smoothness of the film and the maximum measured conductivity was 10-4 S/cm at 25A C. Recently, anhydrous proton-conducting membranes with flexible structural backbones, which show proton-conducting properties comparable to Nafion have been focus of current research. The flexible backbone of polymer chains allow for a high segmental mobility and thus, a sufficiently low glass transition temperature (Tg), which is an essential factor to reach highly conductive systems. Among the polymers with a flexible chain backbone, poly(vinylphosphonic acid), poly(vinylbenzylphosphonic acid), poly(2-vinylbenzimidazole), poly(4-styrenesulfonic acid), poly(4-vinylimidazole), poly(4-vinylimidazole

  18. New proton conducting membranes for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Sukumar, P.R.

    2006-07-01

    In order to synthesize proton-conducting materials which retain acids in the membrane during fuel cell operating conditions, the synthesis of poly(vinylphosphonic acid) grafted polybenzimidazole (PVPA grafted PBI) and the fabrication of multilayer membranes are mainly focussed in this dissertation. Synthesis of PVPA grafted PBI membrane can be done according to ''grafting through'' method. In ''grafting through'' method (or macromonomer method), monomer (e.g., vinylphosphonic acid) is radically copolymerized with olefin group attached macromonomer (e.g., allyl grafted PBI and vinylbenzyl grafted PBI). This approach is inherently limited to synthesize graft-copolymer with well-defined architectural and structural parameters. The incorporation of poly(vinylphosphonic acid) into PBI lead to improvements in proton conductivity up to 10-2 S/cm. Regarding multilayer membranes, the proton conducting layer-by-layer (LBL) assembly of polymers by various strong acids such as poly(vinylphosphonic acid), poly(vinylsulfonic acid) and poly(styrenesulfonic acid) paired with basic polymers such as poly(4-vinylimidazole) and poly(benzimidazole), which are appropriate for Proton Exchange Membrane Fuel Cell applications have been described. Proton conductivity increases with increasing smoothness of the film and the maximum measured conductivity was 10-4 S/cm at 25A C. Recently, anhydrous proton-conducting membranes with flexible structural backbones, which show proton-conducting properties comparable to Nafion have been focus of current research. The flexible backbone of polymer chains allow for a high segmental mobility and thus, a sufficiently low glass transition temperature (Tg), which is an essential factor to reach highly conductive systems. Among the polymers with a flexible chain backbone, poly(vinylphosphonic acid), poly(vinylbenzylphosphonic acid), poly(2-vinylbenzimidazole), poly(4-styrenesulfonic acid), poly(4-vinylimidazole), poly

  19. Carbon supported Pd-Ni and Pd-Ru-Ni nanocatalysts for the alkaline direct ethanol fuel cell (DEFC)

    CSIR Research Space (South Africa)

    Modibedi, M

    2011-09-01

    Full Text Available be improved by operating DAFCs in alkaline medium. Moreover, catalyst materials that are much cheaper and more abundant than Pt can be used for ethanol electro-oxidation and oxygen reduction reactions in alkaline DAFCs. Furthermore, the alkaline DAFCs use...

  20. Living target of Ce(III) action on horseradish cells: proteins on/in cell membrane.

    Science.gov (United States)

    Yang, Guangmei; Sun, Zhaoguo; Lv, Xiaofen; Deng, Yunyun; Zhou, Qing; Huang, Xiaohua

    2012-12-01

    Positive and negative effects of rare earth elements (REEs) in life have been reported in many papers, but the cellular mechanisms have not been answered, especially the action sites of REEs on plasma membrane are unknown. Proteins on/in the plasma membrane perform main functions of the plasma membrane. Cerium (Ce) is the richest REEs in crust. Thus, the interaction between Ce(III) and the proteins on/in the plasma membrane, the morphology of protoplast, and the contents of nutrient elements in protoplast of horseradish were investigated using the optimized combination of the fluorescence microscopy, fluorescence spectroscopy, circular dichroism, scanning electron microscopy, and X-ray energy dispersive spectroscopy. It was found that Ce(III) at the low concentrations (10, 30 μM) could interact with proteins on/in the plasma membrane of horseradish, leading to the improvement in the structure of membrane proteins and the plasma membrane, which accelerated the intra-/extra-cellular substance exchange and further promoted the development of cells. When horseradish was treated with Ce(III) at the high concentrations (60, 80 μM), Ce(III) also could interact with the proteins on/in the plasma membrane of horseradish, leading to the destruction in the structure of membrane proteins and the plasma membrane. These effects decelerated the intra-/extra-cellular substance exchange and further inhibited the development of cells. Thus, the interaction between Ce(III) and proteins on/in the plasma membrane in plants was an important reason of the positive and negative effects of Ce(III) on plants. The results would provide some references for understanding the cellular effect mechanisms of REEs on plants.

  1. Protonic conductors for proton exchange membrane fuel cells: An overview

    Directory of Open Access Journals (Sweden)

    Jurado Ramon Jose

    2002-01-01

    Full Text Available At present, Nation, which is a perfluorinated polymer, is one of the few materials that deliver the set of chemical and mechanical properties required to perform as a good electrolyte in proton exchange membrane fuel cells (PEMFCs. However, Nation presents some disadvantages, such as limiting the operational temperature of the fuel system (So°C, because of its inability to retain water at higher temperatures and also suffers chemical crossover. In addition to these restrictions, Nation membranes are very expensive. Reducing costs and using environmentally friendly materials are good reasons to make a research effort in this field in order to achieve similar or even better fuel-cell performances. Glass materials of the ternary system SiO2-ZrO2-P2O5, hybrid materials based on Nation, and nanopore ceramic membranes based on SiO2 TiO2, Al2O3, etc. are considered at present, as promising candidates to replace Nation as the electrolyte in PEMFCs. These types of materials are generally prepared by sol-gel processes in order to tailor their channel-porous structure and pore size. In this communication, the possible candidates in the near future as electrolytes (including other polymers different than Nation in PEMFCs are briefly reviewed. Their preparation methods, their electrical transport properties and conduction mechanisms are considered. The advantages and disadvantages of these materials with respect to Nation are also discussed.

  2. Enhanced production of alkaline thermostable keratinolytic protease from calcium alginate immobilized cells of thermoalkalophilic Bacillus halodurans JB 99 exhibiting dehairing activity.

    Science.gov (United States)

    Shrinivas, Dengeti; Kumar, Raghwendra; Naik, G R

    2012-01-01

    The thermoalkalophilic Bacillus halodurans JB 99 cells known for production of novel thermostable alkaline keratinolytic protease were immobilized in calcium alginate matrix. Batch and repeated batch cultivation using calcium alginate immobilized cells were studied for alkaline protease production in submerged fermentation. Immobilized cells with 2.5% alginate and 350 beads/flask of initial cell loading showed enhanced production of alkaline protease by 23.2% (5,275 ± 39.4 U/ml) as compared to free cells (4,280 ± 35.4 U/ml) after 24 h. In the semicontinuous mode of cultivation, immobilized cells under optimized conditions produced an appreciable level of alkaline protease in up to nine cycles and reached a maximal value of 5,975 U/ml after the seventh cycle. The enzyme produced from immobilized cells efficiently degraded chicken feathers in the presence of a reducing agent which can help the poultry industry in the management of keratin-rich waste and obtaining value-added products.

  3. High performance nano-Ni/Graphite electrode for electro-oxidation in direct alkaline ethanol fuel cells

    Science.gov (United States)

    Soliman, Ahmed B.; Abdel-Samad, Hesham S.; Abdel Rehim, Sayed S.; Ahmed, Mohamed A.; Hassan, Hamdy H.

    2016-09-01

    Ni/Graphite electrocatalysts (Ni/G) are successfully prepared through electrodeposition of Ni from acidic (pH = 0.8) and feebly acidic (pH = 5.5) aqueous Ni (II) baths. The efficiencies of such electrodes are investigated as anodes for direct alkaline ethanol fuel cells through their ethanol electrooxidation cyclic voltammetric (CV) response in alkaline medium. A direct proportionality between the amount of the electrodeposited Ni and its CV response is found. The amounts of the deposited Ni from the two baths are recorded using the Electrochemical Quartz Crystal Microbalance (eQCM). The Ni/G electrodes prepared from the feebly acidic bath show a higher electrocatalytic response than those prepared from the acidic bath. Surface morphology of the Ni particles electrodeposited from feebly acidic bath appears in a nano-scale dimension. Various electrochemical experiments are conducted to confirm that the Ni/G ethanol electrooxidation CV response greatly depends on the pH rather than nickel ion concentration of the deposition bath. The eQCM technique is used to detect the crystalline phases of nickel as α-Ni(OH)2/γ-NiOOH and β-Ni(OH)2/β-NiOOH and their in-situ inter-transformations during the potentiodynamic polarization.

  4. Performance of proton exchange membrane fuel cells at elevated temperature

    International Nuclear Information System (INIS)

    Shyu, Jin-Cherng; Hsueh, Kan-Lin; Tsau, Fanghei

    2011-01-01

    Highlights: → At 1 atm, cell has best performance (∼1300 mA/cm at 0.6 V) at 100 deg. C and RH = 100%. → The A value in Eq. increased with increases in the back pressure and RH. →R i dramatically decreased at back pressure of 1 atm. → At each RH, R i decreased and then increased as cell temperature increased at 1 atm. - Abstract: The polarization curves of a single PEMFC having a Nafion membrane fed with H 2 /O 2 with relative humidity (RH) of 35%, 70% and 100% were measured at cell temperatures ranging from 65 deg. C to 120 deg. C at back pressures of 0 atm and 1 atm, respectively. Measured results showed that the best cell performance at 0.6 V operated within 65-120 deg. C at zero back pressure was 1000 mA cm -2 at 65 deg. C and RH = 100%, while the best cell performance at 1 atm back pressure was 1300 mA cm -2 at 100 deg. C and RH = 100%. Based on the analysis of impedance data measured at anode and cathode humidification temperatures of 90 deg. C and cell temperature of 100 deg. C at back pressures of 0 and 1 atm (90-100p0 and 90-100p1), it could be found that the membrane resistance was reduced and the catalyst became more active as the back pressure increases. The present results showed that increasing back pressure was able to dramatically improve cell performance and the effect of the back pressure surpassed that of humidification in the internal resistance of cell.

  5. Cell-substrate interaction with cell-membrane-stress dependent adhesion.

    Science.gov (United States)

    Jiang, H; Yang, B

    2012-01-10

    Cell-substrate interaction is examined in a two-dimensional mechanics model. The cell and substrate are treated as a shell and an elastic solid, respectively. Their interaction through adhesion is treated using nonlinear springs. Compared to previous cell mechanics models, the present model introduces a cohesive force law that is dependent not only on cell-substrate distance but also on internal cell-membrane stress. It is postulated that a living cell would establish focal adhesion sites with density dependent on the cell-membrane stress. The formulated mechanics problem is numerically solved using coupled finite elements and boundary elements for the cell and the substrate, respectively. The nodes in the adhesion zone from either side are linked by the cohesive springs. The specific cases of a cell adhering to a homogeneous substrate and a heterogeneous bimaterial substrate are examined. The analyses show that the substrate stiffness affects the adhesion behavior significantly and regulates the direction of cell adhesion, in good agreement with the experimental results in the literature. By introducing a reactive parameter (i.e., cell-membrane stress) linking biological responses of a living cell to a mechanical environment, the present model offers a unified mechanistic vehicle for characterization and prediction of living cell responses to various kinds of mechanical stimuli including local extracellular matrix and neighboring cells. Copyright © 2011 Elsevier Ltd. All rights reserved.

  6. Porous polybenzimidazole membranes doped with phosphoric acid: Preparation and application in high-temperature proton-exchange-membrane fuel cells

    International Nuclear Information System (INIS)

    Li, Jin; Li, Xiaojin; Yu, Shuchun; Hao, Jinkai; Lu, Wangting; Shao, Zhigang; Yi, Baolian

    2014-01-01

    Highlights: • Porous polybenzimidazole membrane was prepared with glucose as porogen. • Phosphoric acid content was as high as 15.7 mol H 3 PO 4 per PBI repeat unit. • 200 h Constant current density test was carried out at 150 °C. • Degradation was due to the gap between membrane and catalyst layer. - Abstract: In this paper, the preparation and characterization of porous polybenzimidazole membranes doped with phosphoric acid were reported. For the preparation of porous polybenzimidazole membranes, glucose and saccharose were selected as porogen and added into PBI resin solution before solvent casting. The prepared porous PBI membranes had high proton conductivity and high content of acid doping at room temperature with 15.7 mol H 3 PO 4 per PBI repeat unit, much higher than pure PBI membrane at the same condition. Further, the performance and stability of the porous PBI membrane in high-temperature proton-exchange-membrane fuel cells was tested. It was found that the cell performance remained stable during 200 h stability test under a constant current discharge of 0.5 A cm −2 except for the last fifty hours. The decay in the last fifty hours was ascribed to the delamination between the catalyst layer and membrane increasing the charge-transfer resistance

  7. Determine equilibrium dissociation constant of drug-membrane receptor affinity using the cell membrane chromatography relative standard method.

    Science.gov (United States)

    Ma, Weina; Yang, Liu; Lv, Yanni; Fu, Jia; Zhang, Yanmin; He, Langchong

    2017-06-23

    The equilibrium dissociation constant (K D ) of drug-membrane receptor affinity is the basic parameter that reflects the strength of interaction. The cell membrane chromatography (CMC) method is an effective technique to study the characteristics of drug-membrane receptor affinity. In this study, the K D value of CMC relative standard method for the determination of drug-membrane receptor affinity was established to analyze the relative K D values of drugs binding to the membrane receptors (Epidermal growth factor receptor and angiotensin II receptor). The K D values obtained by the CMC relative standard method had a strong correlation with those obtained by the frontal analysis method. Additionally, the K D values obtained by CMC relative standard method correlated with pharmacological activity of the drug being evaluated. The CMC relative standard method is a convenient and effective method to evaluate drug-membrane receptor affinity. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    Ingermann, R.L.

    1989-01-01

    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

  9. Real-time fluorescence assay of alkaline phosphatase in living cells using boron-doped graphene quantum dots as fluorophores.

    Science.gov (United States)

    Chen, Li; Yang, Guancao; Wu, Ping; Cai, Chenxin

    2017-10-15

    This work reports a convenient and real-time assay of alkaline phosphatase (ALP) in living cells based on a fluorescence quench-recovery process at a physiological pH using the boron-doped graphene quantum dots (BGQDs) as fluorophore. The fluorescence of BGQDs is found to be effectively quenched by Ce 3+ ions because of the coordination of Ce 3+ ions with the carboxyl group of BGQDs. Upon addition of adenosine triphosphate (ATP) into the system, the quenched fluorescence can be recovered by the ALP-positive expressed cells (such as MCF-7 cells) due to the removal of Ce 3+ ions from BGQDs surface by phosphate ions, which are generated from ATP under catalytic hydrolysis of ALP that expressed in cells. The extent of fluorescence signal recovery depends on the level of ALP in cells, which establishes the basis of ALP assay in living cells. This approach can also be used for specific discrimination of the ALP expression levels in different type of cells and thus sensitive detection of those ALP-positive expressed cells (for example MCF-7 cells) at a very low abundance (10±5 cells mL -1 ). The advantages of this approach are that it has high sensitivity because of the significant suppression of the background due to the Ce 3+ ion quenching the fluorescence of BGQDs, and has the ability of avoiding false signals arising from the nonspecific adsorption of non-target proteins because it operates via a fluorescence quench-recovery process. In addition, it can be extended to other enzyme systems, such as ATP-related kinases. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Bleb Expansion in Migrating Cells Depends on Supply of Membrane from Cell Surface Invaginations.

    Science.gov (United States)

    Goudarzi, Mohammad; Tarbashevich, Katsiaryna; Mildner, Karina; Begemann, Isabell; Garcia, Jamie; Paksa, Azadeh; Reichman-Fried, Michal; Mahabaleshwar, Harsha; Blaser, Heiko; Hartwig, Johannes; Zeuschner, Dagmar; Galic, Milos; Bagnat, Michel; Betz, Timo; Raz, Erez

    2017-12-04

    Cell migration is essential for morphogenesis, organ formation, and homeostasis, with relevance for clinical conditions. The migration of primordial germ cells (PGCs) is a useful model for studying this process in the context of the developing embryo. Zebrafish PGC migration depends on the formation of cellular protrusions in form of blebs, a type of protrusion found in various cell types. Here we report on the mechanisms allowing the inflation of the membrane during bleb formation. We show that the rapid expansion of the protrusion depends on membrane invaginations that are localized preferentially at the cell front. The formation of these invaginations requires the function of Cdc42, and their unfolding allows bleb inflation and dynamic cell-shape changes performed by migrating cells. Inhibiting the formation and release of the invaginations strongly interfered with bleb formation, cell motility, and the ability of the cells to reach their target. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

    Shore, Lawrence [Edison, NJ

    2012-02-28

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

  12. Membrane fluidity increases during apoptosis of sheep ileal Peyer's patch B cells

    International Nuclear Information System (INIS)

    Jourd'heuil, D.; Aspinall, A.; Reynolds, J.D.; Meddings, J.B.

    1996-01-01

    To investigate specific plasma membrane structural changes associated with apoptosis, whole cells and purified plasma membranes of apoptotic B cells from the ileal Peyer's patch of sheep were analyzed for their 'membrane fluidity'. The ileal Peyer's patch of sheep provided a large number of B cells required for plasma membrane isolation (>5 x 10 9 ). As the incidence of apoptosis increased with time of culture, the fluidity of purified plasma membranes, as measured with the fluorophore DPH (diphenylhexatriene), increased. To evaluate this phenomenon with intact cells, B cells at different apoptotic stages were fractionated on discontinuous Percoll gradients. Similar results were obtained using the fluorophore TMA-DPH (trimethylammoniumdiphenylhexatriene), which has been shown to localize specifically to the plasma membrane. Functionally, the increase in plasma membrane fluidity associated with apoptosis may represent either a mechanism to cycle phosphatidylserine to the outer leaflet, mediating phagocytic recognition of apoptotic cells, or a consequence of this event. (author). 20 refs., 1 tab., 4 figs

  13. Comparison of gas membrane separation cascades using conventional separation cell and two-unit separation cells

    International Nuclear Information System (INIS)

    Ohno, Masayoshi; Morisue, Tetsuo; Ozaki, Osamu; Miyauchi, Terukatsu.

    1978-01-01

    The adoption of two-unit separation cells in radioactive rare gas membrane separation equipment enhances the separation factor, but increases the required membrane area and compressive power. An analytical economic evaluation was undertaken to compare the conventional separation cell with the two-unit separation cells, adopting as parameters the number of cascade stages, the membrane area and the operating power requirements. This paper describes the models used for evaluating the separation performance and the economics of cascade embodying these different concepts of separation cell taken up for study, and the results obtained for the individual concepts are mutually compared. It proved that, in respect of the number required of cascade stages, of operating power requirements and of the annual expenditure, better performance could always be expected of the two-unit separation cells as compared with the conventional separation cell, at least in the range of parameters adopted in this study. As regards the minimum membrane area, the conventional separation cell and the series-type separation cell yielded almost the same values, with the parallel-type separation cell falling somewhat behind. (auth.)

  14. Triggering of Erythrocyte Cell Membrane Scrambling by Emodin

    Directory of Open Access Journals (Sweden)

    Morena Mischitelli

    2016-11-01

    Full Text Available Background/Aims: The natural anthraquinone derivative emodin (1,3,8-trihydroxy-6-methylanthraquinone is a component of several Chinese medicinal herbal preparations utilized for more than 2000 years. The substance has been used against diverse disorders including malignancy, inflammation and microbial infection. The substance is effective in part by triggering suicidal death or apoptosis. Similar to apoptosis of nucleated cells erythrocytes may enter suicidal erythrocyte death or eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Signaling involved in the triggering of eryptosis include increase of cytosolic Ca2+ activity ([Ca2+]i, oxidative stress and ceramide. The present study aimed to test, whether emodin induces eryptosis and, if so, to elucidate underlying cellular mechanisms. Methods: Phosphatidylserine abundance at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter, [Ca2+]i from Fluo3-fluorescence, ROS formation from DCFDA dependent fluorescence, and ceramide abundance utilizing specific antibodies. Results: Exposure of human erythrocytes for 48 hours to emodin (≥ 10 µM significantly increased the percentage of annexin-V-binding cells, and at higher concentrations (≥ 50 µM significantly increased forward scatter. Emodin significantly increased Fluo3-fluorescence (≥ 10 µM, DCFDA fluorescence (75 µM and ceramide abundance (75 µM. The effect of emodin on annexin-V-binding was significantly blunted but not abolished by removal of extracellular Ca2+. Conclusions: Emodin triggers phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part due to stimulation of Ca2+ entry and paralleled by oxidative stress and ceramide appearance at the erythroctye surface.

  15. Cell dualism: presence of cells with alternative membrane potentials in growing populations of bacteria and yeasts.

    Science.gov (United States)

    Ivanov, Volodymyr; Rezaeinejad, Saeid; Chu, Jian

    2013-10-01

    It is considered that all growing cells, for exception of acidophilic bacteria, have negatively charged inside cytoplasmic membrane (Δψ⁻-cells). Here we show that growing populations of microbial cells contain a small portion of cells with positively charged inside cytoplasmic membrane (Δψ⁺-cells). These cells were detected after simultaneous application of the fluorescent probes for positive membrane potential (anionic dye DIBAC⁻) and membrane integrity (propidium iodide, PI). We found in exponentially growing cell populations of Escherichia coli and Saccharomyces cerevisiae that the content of live Δψ⁻-cells was 93.6 ± 1.8 % for bacteria and 90.4 ± 4.0 % for yeasts and the content of live Δψ⁺-cells was 0.9 ± 0.3 % for bacteria and 2.4 ± 0.7 % for yeasts. Hypothetically, existence of Δψ⁺-cells could be due to short-term, about 1 min for bacteria and 5 min for yeasts, change of membrane potential from negative to positive value during the cell cycle. This change has been shown by the reversions of K⁺, Na⁺, and Ca²⁺ ions fluxes across the cell membrane during synchronous yeast culture. The transformation of Δψ(⁻-cells to Δψ⁺-cells can be explained by slow influx of K⁺ ions into Δψ⁻-cell to the trigger level of K⁺ concentration ("compression of potassium spring"), which is forming "alternative" Δψ⁺-cell for a short period, following with fast efflux of K⁺ ions out of Δψ⁺-cell ("release of potassium spring") returning cell to normal Δψ⁻ state. We anticipate our results to be a starting point to reveal the biological role of cell dualism in form of Δψ⁻- and Δψ⁺- cells.

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

    Science.gov (United States)

    Mishler, Jeffrey Harris

    Polymer Electrolyte Membrane (PEM) Fuel Cells are capable of high efficiency operation, and are free of NOx, SOx, and CO2 emissions when using hydrogen fuel, and ideally suited for use in transportation applications due to their high power density and low operating temperatures. However, under subfreezing conditions which may be encountered during winter seasons in some areas, product water will freeze within the membrane, cathode side catalyst layer and gas diffusion media, leading to voltage loss and operation failure. Experiments were undertaken in order to characterize the amount and location of water during fuel cell operation. First, in-situ neutron radiography was undertaken on the fuel cells at a normal operating temperature for various operating current densities, inlet relative humidities, and diffusion media hydrophobicities. It was found that more hydrophobic cathode microporous layer (MPL) or hydrophilic anode MPL may result in a larger amount of water transporting back to the anode. The water profiles along the channels were measured and the point of liquid water emergence, where two phase flow begins, was compared to previous models. Secondly, under subfreezing temperatures, neutron imaging showed that water ice product accumulates because of lack of a water removal mechanism. Water was observed under both the lands and channels, and increased almost linearly with time. It is found that most ice exists in the cathode side. With evidence from experimental observation, a cold start model was developed and explained, following existing approaches in the literature. Three stages of cold start are explained: membrane saturation, ice storage in catalyst layer pores, and then ice melting. The voltage losses due to temperature change, increased transport resistance, and reduced electrochemical surface area. The ionic conductivity of the membrane at subfreezing temperatures was modeled. Voltage evolution over time for isothermal cold starts was predicted and

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

    DEFF Research Database (Denmark)

    Neuvonen, M.; Manna, M.; Mokkila, S.

    2014-01-01

    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...... 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....

  18. Dynamic water management of polymer electrolyte membrane fuel cells using intermittent RH control

    KAUST Repository

    Hussaini, I.S.; Wang, C.Y.

    2010-01-01

    A novel method of water management of polymer electrolyte membrane (PEM) fuel cells using intermittent humidification is presented in this study. The goal is to maintain the membrane close to full humidification, while eliminating channel flooding

  19. The structure and function of cell membranes studied by atomic force microscopy.

    Science.gov (United States)

    Shi, Yan; Cai, Mingjun; Zhou, Lulu; Wang, Hongda

    2018-01-01

    The cell membrane, involved in almost all communications of cells and surrounding matrix, is one of the most complicated components of cells. Lack of suitable methods for the detection of cell membranes in vivo has sparked debates on the biochemical composition and structure of cell membranes over half a century. The development of single molecule techniques, such as AFM, SMFS, and TREC, provides a versatile platform for imaging and manipulating cell membranes in biological relevant environments. Here, we discuss the latest developments in AFM and the progress made in cell membrane research. In particular, we highlight novel structure models and dynamic processes, including the mechanical properties of the cell membranes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Cytotopographical specialization of enzymatically isolated rabbit retinal Müller (glial) cells: K+ conductivity of the cell membrane.

    Science.gov (United States)

    Reichenbach, A; Eberhardt, W

    1988-01-01

    Müller (radial glial) cells were isolated from rabbit retinae by means of papaine and mechanical dissociation. Regional membrane properties of these cells were studied by intracellular microelectrode recordings of potential responses to local application of high K+ solutions. When different parts of the cell membrane were exposed to high K+, the amplitude of the depolarizing responses varied greatly, indicating a strong regional specialization of the membrane properties. Using morphometrical data of isolated rabbit Müller cells, and a simple circuit model, we calculated the endfoot membrane to constitute more than 80% of the total K+ conductance of the cell; the specific resistivity of the endfoot membrane was about 400 omega cm2, i.e., more than 40 times less than that of the membrane of the vitread process, which is immediately adjacent. This kind of regional membrane specialization seems to be optimized in respect to the Müller cells' ability to carry spatial buffering K+ currents.

  1. Radiation injuries of plasmatic membrane and lethal action of radiation on cells

    Energy Technology Data Exchange (ETDEWEB)

    Fomenko, B S; Akoev, I G [AN SSSR, Pushchino-na-Oke. Inst. Biologicheskoj Fiziki

    1984-01-01

    Data on modification of procaryotes and eukaryotes cell injuries using preparations not penetrating into cells and also membrane-specific drugs localized in cells in a lipid phase are generalized. A conclusion is drawn that radiation injuries of plasmatic membrane of prokaryotes and eukaryotes contribute considerably to lethal action of radiation on cells.

  2. Radiation injuries of plasmatic membrane and lethal action of radiation on cells

    International Nuclear Information System (INIS)

    Fomenko, B.S.; Akoev, I.G.

    1984-01-01

    Data on modification of procaryotes and eukaryotes cell injuries using preparations not penetrating into cells and also membrane-specific drugs localized in cells in a lipid phase are generalized. A conclusion is drawn that radiation injuries of plasmatic membrane of prokaryotes and eukaryotes contribute considerably to lethal action of radiation on cells

  3. Calcium pumps of plasma membrane and cell interior

    DEFF Research Database (Denmark)

    Strehler, Emanuel E; Treiman, Marek

    2004-01-01

    Calcium entering the cell from the outside or from intracellular organelles eventually must be returned to the extracellular milieu or to intracellular storage organelles. The two major systems capable of pumping Ca2+ against its large concentration gradient out of the cell or into the sarco....../endoplasmatic reticulum are the plasma membrane Ca2+ ATPases (PMCAs) and the sarco/endoplasmic reticulum Ca2+ ATPases (SERCAs), respectively. In mammals, multigene families code for these Ca2+ pumps and additional isoform subtypes are generated via alternative splicing. PMCA and SERCA isoforms show developmental-, tissue......- and cell type-specific patterns of expression. Different PMCA and SERCA isoforms are characterized by different regulatory and kinetic properties that likely are optimized for the distinct functional tasks fulfilled by each pump in setting resting cytosolic or intra-organellar Ca2+ levels, and in shaping...

  4. High performance direct methanol fuel cell with thin electrolyte membrane

    Science.gov (United States)

    Wan, Nianfang

    2017-06-01

    A high performance direct methanol fuel cell is achieved with thin electrolyte membrane. 320 mW cm-2 of peak power density and over 260 mW cm-2 at 0.4 V are obtained when working at 90 °C with normal pressure air supply. It is revealed that the increased anode half-cell performance with temperature contributes primarily to the enhanced performance at elevated temperature. From the comparison of iR-compensated cathode potential of methanol/air with that of H2/air fuel cell, the impact of methanol crossover on cathode performance decreases with current density and becomes negligible at high current density. Current density is found to influence fuel efficiency and methanol crossover significantly from the measurement of fuel efficiency at different current density. At high current density, high fuel efficiency can be achieved even at high temperature, indicating decreased methanol crossover.

  5. Phosphoric acid doped polybenzimidazole membranes: Physiochemical characterization and fuel cell applications [PEM fuel cells

    DEFF Research Database (Denmark)

    Qingfeng, Li; Hjuler, Hans Aage; Bjerrum, Niels

    2001-01-01

    A polymer electrolyte membrane fuel cell operational at temperatures around 150-200 degrees C is desirable for fast electrode kinetics and high tolerance to fuel impurities. For this purpose polybenzimidazole (PBI) membranes have been prepared and H/sub 3/PO/sub 4/-doped in a doping range from 300...... doping level. At 160 degrees C a conductivity as high as 0.13 S cm/sup -1/ is obtained for membranes of high doping levels. Mechanical strength measurements show, however, that a high acid doping level results in poor mechanical properties. At operational temperatures up to 190 degrees C, fuel cells...... based on this polymer membrane have been tested with both hydrogen and hydrogen containing carbon monoxide....

  6. Highly efficient transition metal and nitrogen co-doped carbide-derived carbon electrocatalysts for anion exchange membrane fuel cells

    Science.gov (United States)

    Ratso, Sander; Kruusenberg, Ivar; Käärik, Maike; Kook, Mati; Puust, Laurits; Saar, Rando; Leis, Jaan; Tammeveski, Kaido

    2018-01-01

    The search for an efficient electrocatalyst for oxygen reduction reaction (ORR) to replace platinum in fuel cell cathode materials is one of the hottest topics in electrocatalysis. Among the many non-noble metal catalysts, metal/nitrogen/carbon composites made by pyrolysis of cheap materials are the most promising with control over the porosity and final structure of the catalyst a crucial point. In this work we show a method of producing a highly active ORR catalyst in alkaline media with a controllable porous structure using titanium carbide derived carbon as a base structure and dicyandiamide along with FeCl3 or CoCl2 as the dopants. The resulting transition metal-nitrogen co-doped carbide derived carbon (M/N/CDC) catalyst is highly efficient for ORR electrocatalysis with the activity in 0.1 M KOH approaching that of commercial 46.1 wt.% Pt/C. The catalyst materials are also investigated by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy to characterise the changes in morphology and composition causing the raise in electrochemical activity. MEA performance of M/N/CDC cathode materials in H2/O2 alkaline membrane fuel cell is tested with the highest power density reached being 80 mW cm-2 compared to 90 mW cm-2 for Pt/C.

  7. Alkaline phosphatase role in bone marrow and spleen hemopoietic cells recovery after mouse whole-body irradiation

    International Nuclear Information System (INIS)

    Al Mouhamad, K.; Al Sheikh, F.

    2013-04-01

    Hematopoietic tissue is consisted of two distinctly different tissues, the first part is the hematopoietic stem cells and the second tissue is a mixture of many supportive cells which the most important one of them is alkaline phosphatase (ALP)-secreted-fibroblastic cells (FBCs). It was thought that FBCs play an important role in the hematopoiesis through ALP secretion. Our previous studies indicated that the ALP secretion in bone marrow (BM) increased after a whole mouse body irradiation when the BM cellular component is completely destroyed and, then it was decreased when the BM regain its cellular component. We performed some experiences to verify if there is any role to the ALP in the hematopoiesis. We irradiated three groups of mice to non-lethal dose, the first one was injected by Tetramizole (anti-ALP) 24 hours before irradiation, and the second was injected by Lisinopril (anti-hematopoiesis) 24 hours before irradiation and the third left without any injection. The fourth left as control. Many histological sections were taken from BM and spleen on 1, 3, 7 and 30 days after irradiation to perform ALP-histological detection. These experiences were repeated to count BM cells. ALP secretion level in the BM was reached the maximum 3 days after irradiation without any injection when the cell number was in minimum then, the level of ALP start to decrease and the cell number start to increase. ALP secretion delayed when the mice were injected by Tetramizole and BM cell population also delayed to return to its normal position. But, the ALP secretion increased directly after irradiation when the mice were injected by Lisinopril which, the ALP secretion, normally reached the maximum by the third day. These results may indicate a role to the ALP in BM and spleen hematopoietic cell recovery (author).

  8. Nutrient Sensing at the Plasma Membrane of Fungal Cells.

    Science.gov (United States)

    Van Dijck, Patrick; Brown, Neil Andrew; Goldman, Gustavo H; Rutherford, Julian; Xue, Chaoyang; Van Zeebroeck, Griet

    2017-03-01

    To respond to the changing environment, cells must be able to sense external conditions. This is important for many processes including growth, mating, the expression of virulence factors, and several other regulatory effects. Nutrient sensing at the plasma membrane is mediated by different classes of membrane proteins that activate downstream signaling pathways: nontransporting receptors, transceptors, classical and nonclassical G-protein-coupled receptors, and the newly defined extracellular mucin receptors. Nontransporting receptors have the same structure as transport proteins, but have lost the capacity to transport while gaining a receptor function. Transceptors are transporters that also function as a receptor, because they can rapidly activate downstream signaling pathways. In this review, we focus on these four types of fungal membrane proteins. We mainly discuss the sensing mechanisms relating to sugars, ammonium, and amino acids. Mechanisms for other nutrients, such as phosphate and sulfate, are discussed briefly. Because the model yeast Saccharomyces cerevisiae has been the most studied, especially regarding these nutrient-sensing systems, each subsection will commence with what is known in this species.

  9. The effect of MLS laser radiation on cell lipid membrane.

    Science.gov (United States)

    Pasternak, Kamila; Wróbel, Dominika; Nowacka, Olga; Pieszyński, Ireneusz; Bryszewska, Maria; Kujawa, Jolanta

    2018-03-14

    Authors of numerous publications have proved the therapeutic effect of laser irradiation on biological material, but the mechanisms at cellular and subcellular level are not yet well understood. The aim of this study was to assess the effect of laser radiation emitted by the MLS M1 system (Multiwave Locked System) at two wavelengths (808 nm continuous and 905 nm pulsed) on the stability and fluidity of liposomes with a lipid composition similar to that of human erythrocyte membrane or made of phosphatidylocholine. Liposomes were exposed to low-energy laser radiation at surface densities 195 mW/cm2 (frequency 1,000 Hz) and 230 mW/cm2 (frequency 2,000 Hz). Different doses of radiation energy in the range 0-15 J were applied. The surface energy density was within the range 0.46 - 4.9 J/cm 2. The fluidity and stability of liposomes subjected to such irradiation changed depending on the parameters of radiation used. Since MLS M1 laser radiation, depending on the parameters used, affects fluidity and stability of liposomes with the lipid content similar to erythrocyte membrane, it may also cause structural and functional changes in cell membranes.

  10. Aprediction study for the behaviour of fuel cell membrane subjected to hygro and thermal stresses in running PEM fuel cell

    OpenAIRE

    Maher A.R. Sadiq Al-Baghdadi

    2016-01-01

    A three-dimensional, multi–phase, non-isothermal computational fluid dynamics model of a proton exchange membrane fuel cell has been used and developed to investigate the hygro and thermal stresses in polymer membrane, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the membrane during operation of a unit cell has been studied and investigated under real cell operating conditions. The results show that the non-uniform distrib...

  11. Tandem cathode for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Siahrostami, Samira; Björketun, Mårten E.; Strasser, Peter

    2013-01-01

    The efficiency of proton exchange membrane fuel cells is limited mainly by the oxygen reduction reaction at the cathode. The large cathodic overpotential is caused by correlations between binding energies of reaction intermediates in the reduction of oxygen to water. This work introduces a novel...... to identify potentially active and selective materials for both catalysts. Co-porphyrin is recommended for the first step, formation of hydrogen peroxide, and three different metal oxides – SrTiO3(100), CaTiO3(100) and WO3(100) – are suggested for the subsequent reduction step....

  12. Nafion-based nanocomposite membranes for fuel cells

    CSIR Research Space (South Africa)

    Cele, NP

    2008-11-01

    Full Text Available . Zhang, J. Wang and F. Sheu, Journal of Electroanalytical Chemistry, 577 (2005) 295 J. James, T.Z. McMaster, J.M. Newton, M.J. Miles, Polymer 41 (2000) 4223 M. Ludvigsson, J. Lindgren, J. Tegenfeldt, Electrochim. Acta (2000) 2267 Shoibal Banerjee..., Dennis E. Curtin Journal of Fluorine Chemistry 125 (2004) 1211–1216 1. 2. 3. 4. 5. CPO-0023 By incorporating multi walled carbon nanotubes onto proton exchange membranes (PEM), its thermal stability is increased, making PEM fuel cells ideal...

  13. Kinetic comparison of tissue non-specific and placental human alkaline phosphatases expressed in baculovirus infected cells: application to screening for Down's syndrome.

    Science.gov (United States)

    Denier, Colette C; Brisson-Lougarre, Andrée A; Biasini, Ghislaine G; Grozdea, Jean J; Fournier, Didier D

    2002-01-01

    In humans, there are four alkaline phosphatases, and each form exhibits a characteristic pattern of tissue distribution. The availability of an easy method to reveal their activity has resulted in large amount of data reporting correlations between variations in activity and illnesses. For example, alkaline phosphatase from neutrophils of mothers pregnant with a trisomy 21 fetus (Down's syndrome) displays significant differences both in its biochemical and immunological properties, and in its affinity for some specific inhibitors. To analyse these differences, the biochemical characteristics of two isozymes (non specific and placental alkaline phosphatases) were expressed in baculovirus infected cells. Comparative analysis of the two proteins allowed us to estimate the kinetic constants of denaturation and sensitivity to two inhibitors (L-p-bromotetramisole and thiophosphate), allowing better discrimination between the two enzymes. These parameters were then used to estimate the ratio of the two isoenzymes in neutrophils of pregnant mothers with or without a trisomy 21 fetus. It appeared that the placental isozyme represented 13% of the total activity of neutrophils of non pregnant women. This proportion did not significantly increase with normal pregnancy. By contrast, in pregnancies with trisomy 21 fetus, the proportion reached 60-80% of activity. Over-expression of the placental isozyme compared with the tissue-nonspecific form in neutrophils of mother with a trisomy 21 fetus may explain why the characteristics of the alkaline phosphatase in these cells is different from normal. Application of this knowledge could improve the potential of using alkaline phosphatase measurements to screen for Down's syndrome.

  14. The effects of membrane cholesterol and simvastatin on red blood cell deformability and ATP release.

    Science.gov (United States)

    Forsyth, Alison M; Braunmüller, Susanne; Wan, Jiandi; Franke, Thomas; Stone, Howard A

    2012-05-01

    It is known that deformation of red blood cells (RBCs) is linked to ATP release from the cells. Further, membrane cholesterol has been shown to alter properties of the cell membrane such as fluidity and bending stiffness. Membrane cholesterol content is increased in some cardiovascular diseases, for example, in individuals with acute coronary syndromes and chronic stable angina, and therefore, because of the potential clinical relevance, we investigated the influence of altered RBC membrane cholesterol levels on ATP release. Because of the correlation between statins and reduced membrane cholesterol in vivo, we also investigated the effects of simvastatin on RBC deformation and ATP release. We found that reducing membrane cholesterol increases cell deformability and ATP release. We also found that simvastatin increases deformability by acting directly on the membrane in the absence of the liver, and that ATP release was increased for cells with enriched cholesterol after treatment with simvastatin. Copyright © 2012 Elsevier Inc. All rights reserved.

  15. In vitro induction of alkaline phosphatase levels predicts in vivo bone forming capacity of human bone marrow stromal cells

    Directory of Open Access Journals (Sweden)

    Henk-Jan Prins

    2014-03-01

    Full Text Available One of the applications of bone marrow stromal cells (BMSCs that are produced by ex vivo expansion is for use in in vivo bone tissue engineering. Cultured stromal cells are a mixture of cells at different stages of commitment and expansion capability, leading to a heterogeneous cell population that each time can differ in the potential to form in vivo bone. A parameter that predicts for in vivo bone forming capacity is thus far lacking. We employed single colony-derived BMSC cultures to identify such predictive parameters. Using limiting dilution, we have produced sixteen single CFU-F derived BMSC cultures from human bone marrow and found that only five of these formed bone in vivo. The single colony-derived BMSC strains were tested for proliferation, osteogenic-, adipogenic- and chondrogenic differentiation capacity and the expression of a variety of associated markers. The only robust predictors of in vivo bone forming capacity were the induction of alkaline phosphatase, (ALP mRNA levels and ALP activity during in vitro osteogenic differentiation. The predictive value of in vitro ALP induction was confirmed by analyzing “bulk-cultured” BMSCs from various bone marrow biopsies. Our findings show that in BMSCs, the additional increase in ALP levels over basal levels during in vitro osteogenic differentiation is predictive of in vivo performance.

  16. Emerging methanol-tolerant AlN nanowire oxygen reduction electrocatalyst for alkaline direct methanol fuel cell.

    Science.gov (United States)

    Lei, M; Wang, J; Li, J R; Wang, Y G; Tang, H L; Wang, W J

    2014-08-11

    Replacing precious and nondurable Pt catalysts with cheap materials is a key issue for commercialization of fuel cells. In the case of oxygen reduction reaction (ORR) catalysts for direct methanol fuel cell (DMFC), the methanol tolerance is also an important concern. Here, we develop AlN nanowires with diameters of about 100-150 nm and the length up to 1 mm through crystal growth method. We find it is electrochemically stable in methanol-contained alkaline electrolyte. This novel material exhibits pronounced electrocatalytic activity with exchange current density of about 6.52 × 10(-8) A/cm(2). The single cell assembled with AlN nanowire cathodic electrode achieves a power density of 18.9 mW cm(-2). After being maintained at 100 mA cm(-2) for 48 h, the AlN nanowire-based single cell keeps 92.1% of the initial performance, which is in comparison with 54.5% for that assembled with Pt/C cathode. This discovery reveals a new type of metal nitride ORR catalyst that can be cheaply produced from crystal growth method.

  17. Evidence for Transfer of Membranes from Mesenchymal Stem Cells to HL-1 Cardiac Cells.

    Science.gov (United States)

    Boomsma, Robert A; Geenen, David L

    2014-01-01

    This study examined the interaction of mouse bone marrow mesenchymal stem cells (MSC) with cardiac HL-1 cells during coculture by fluorescent dye labeling and then flow cytometry. MSC were layered onto confluent HL-1 cell cultures in a 1 : 4 ratio. MSC gained gap junction permeant calcein from HL-1 cells after 4 hours which was partially reduced by oleamide. After 20 hours, 99% MSC gained calcein, unaffected by oleamide. Double-labeling HL-1 cells with calcein and the membrane dye DiO resulted in transfer of both calcein and DiO to MSC. When HL-1 cells were labeled with calcein and MSC with DiO, MSC gained calcein while HL-1 cells gained DiO. Very little fusion was observed since more than 90% Sca-1 positive MSC gained DiO from HL-1 cells while less than 9% gained gap junction impermeant CMFDA after 20 hours with no Sca-1 transfer to HL-1 cells. Time dependent transfer of membrane DiD was observed from HL-1 cells to MSC (100%) and vice versa (50%) after 20 hours with more limited transfer of CMFDA. These results demonstrate that MSC and HL-1 cells exchange membrane components which may account for some of the beneficial effect of MSC in the heart after myocardial infarction.

  18. The actin homologue MreB organizes the bacterial cell membrane.

    Science.gov (United States)

    Strahl, Henrik; Bürmann, Frank; Hamoen, Leendert W

    2014-03-07

    The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate bacterial cell wall synthesis. We noticed that the MreB cytoskeleton influences fluorescent staining of the cytoplasmic membrane. Detailed analyses combining an array of mutants, using specific lipid staining techniques and spectroscopic methods, revealed that MreB filaments create specific membrane regions with increased fluidity (RIFs). Interference with these fluid lipid domains (RIFs) perturbs overall lipid homeostasis and affects membrane protein localization. The influence of MreB on membrane organization and fluidity may explain why the active movement of MreB stimulates membrane protein diffusion. These novel MreB activities add additional complexity to bacterial cell membrane organization and have implications for many membrane-associated processes.

  19. A novel membrane-less direct alcohol fuel cell

    Science.gov (United States)

    Yi, Qingfeng; Chen, Qinghua; Yang, Zheng

    2015-12-01

    Membrane-less fuel cell possesses such advantages as simplified design and lower cost. In this paper, a membrane-less direct alcohol fuel cell is constructed by using multi-walled carbon nanotubes (MWCNT) supported Pd and ternary PdSnNi composites as the anode catalysts and Fe/C-PANI composite, produced by direct pyrolysis of Fe-doped polyaniline precursor, as the oxygen reduction reaction (ORR) catalyst. The alcohols investigated in the present study are methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol and sec-butanol. The cathode catalyst Fe/C-PANI is electrochemically inactive to oxidation of the alcohols. The performance of the cell with various alcohols in 1 mol L-1 NaOH solution on either Pd/MWCNT or PdSnNi/MWCNT catalyst has been evaluated. In any case, the performance of the cell using the anode catalyst PdSnNi/MWCNT is considerably better than Pd/MWCNT. For the PdSnNi/MWCNT, the maximum power densities of the cell using methanol (0.5 mol L-1), ethanol (0.5 mol L-1), n-propanol (0.5 mol L-1), iso-propanol (0.5 mol L-1), n-butanol (0.2 mol L-1), iso-butanol (0.2 mol L-1) and sec-butanol (0.2 mol L-1) are 0.34, 1.03, 1.07, 0.44, 0.50, 0.31 and 0.15 mW cm-2, respectively.

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

    Science.gov (United States)

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

    2015-12-08

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

  1. Rapid Preparation of a Plasma Membrane Fraction: Western Blot Detection of Translocated Glucose Transporter 4 from Plasma Membrane of Muscle and Adipose Cells and Tissues.

    Science.gov (United States)

    Yamamoto, Norio; Yamashita, Yoko; Yoshioka, Yasukiyo; Nishiumi, Shin; Ashida, Hitoshi

    2016-08-01

    Membrane proteins account for 70% to 80% of all pharmaceutical targets, indicating their clinical relevance and underscoring the importance of identifying differentially expressed membrane proteins that reflect distinct disease properties. The translocation of proteins from the bulk of the cytosol to the plasma membrane is a critical step in the transfer of information from membrane-embedded receptors or transporters to the cell interior. To understand how membrane proteins work, it is important to separate the membrane fraction of cells. This unit provides a protocol for rapidly obtaining plasma membrane fractions for western blot analysis. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

  2. Annexins are instrumental for efficient plasma membrane repair in cancer cells.

    Science.gov (United States)

    Lauritzen, Stine Prehn; Boye, Theresa Louise; Nylandsted, Jesper

    2015-09-01

    Plasma membrane stress can cause damage to the plasma membrane, both when imposed by the extracellular environment and by enhanced oxidative stress. Cells cope with these injuries by rapidly activating their plasma membrane repair system, which is triggered by Ca(2+) influx at the wound site. The repair system is highly dynamic, depends on both lipid and protein components, and include cytoskeletal reorganization, membrane replacements, and membrane fusion events. Cancer cells experience enhanced membrane stress when navigating through dense extracellular matrix, which increases the frequency of membrane injuries. In addition, increased motility and oxidative stress further increase the risk of plasma membrane lesions. Cancer cells compensate by overexpressing Annexin proteins including Annexin A2 (ANXA2). Annexin family members can facilitate membrane fusion events and wound healing by binding to negatively charged phospholipids in the plasma membrane. Plasma membrane repair in cancer cells depends on ANXA2 protein, which is recruited to the wound site and forms a complex with the Ca(2+)-binding EF-hand protein S100A11. Here they regulate actin accumulation around the wound perimeter, which is required for wound closure. In this review, we will discuss the requirement for Annexins, S100 proteins and actin cytoskeleton in the plasma membrane repair response of cancer cells, which reveals a novel avenue for targeting metastatic cancers. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Electricity generation from banana peels in an alkaline fuel cell with a Cu2O-Cu modified activated carbon cathode.

    Science.gov (United States)

    Liu, Peng; Liu, Xianhua; Dong, Feng; Lin, Qingxia; Tong, Yindong; Li, Yang; Zhang, Pingping

    2018-08-01

    Low-cost and highly active catalyst for oxygen reduction reaction is of great importance in the design of alkaline fuel cells. In this work, Cu 2 O-Cu composite catalyst has been fabricated by a facile laser-irradiation method. The addition of Cu 2 O-Cu composite in activated carbon air-cathode greatly improves the performance of the cathode. Our results indicate the enhanced performance is likely attributed to the synergistic effect of high conductivity of Cu and the catalytic activity of Cu 2 O towards the oxygen reduction reaction. Furthermore, an alkaline fuel cell equipped with the composite air-cathode has been built to turn banana peels into electricity. Peak power density of 16.12Wm -2 is obtained under the condition of 3M KOH and 22.04gL -1 reducing sugar, which is higher than other reported low-temperature direct biomass alkaline fuel cells. HPLC results indicate the main oxidation products in the alkaline fuel cell were small organic acids. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Purification and differentiation of human adipose-derived stem cells by membrane filtration and membrane migration methods

    Science.gov (United States)

    Lin, Hong Reng; Heish, Chao-Wen; Liu, Cheng-Hui; Muduli, Saradaprasan; Li, Hsing-Fen; Higuchi, Akon; Kumar, S. Suresh; Alarfaj, Abdullah A.; Munusamy, Murugan A.; Hsu, Shih-Tien; Chen, Da-Chung; Benelli, Giovanni; Murugan, Kadarkarai; Cheng, Nai-Chen; Wang, Han-Chow; Wu, Gwo-Jang

    2017-01-01

    Human adipose-derived stem cells (hADSCs) are easily isolated from fat tissue without ethical concerns, but differ in purity, pluripotency, differentiation ability, and stem cell marker expression, depending on the isolation method. We isolated hADSCs from a primary fat tissue solution using: (1) conventional culture, (2) a membrane filtration method, (3) a membrane migration method where the primary cell solution was permeated through membranes, adhered hADSCs were cultured, and hADSCs migrated out from the membranes. Expression of mesenchymal stem cell markers and pluripotency genes, and osteogenic differentiation were compared for hADSCs isolated by different methods using nylon mesh filter membranes with pore sizes ranging from 11 to 80 μm. hADSCs isolated by the membrane migration method had the highest MSC surface marker expression and efficient differentiation into osteoblasts. Osteogenic differentiation ability of hADSCs and MSC surface marker expression were correlated, but osteogenic differentiation ability and pluripotent gene expression were not. PMID:28071738

  5. Morphological alteration, lysosomal membrane fragility and apoptosis of the cells of Indian freshwater sponge exposed to washing soda (sodium carbonate).

    Science.gov (United States)

    Mukherjee, Soumalya; Ray, Mitali; Dutta, Manab Kumar; Acharya, Avanti; Mukhopadhyay, Sandip Kumar; Ray, Sajal

    2015-12-01

    Washing soda is chemically known as sodium carbonate and is a component of laundry detergent. Domestic effluent, drain water and various anthropogenic activities have been identified as major routes of sodium carbonate contamination of the freshwater ecosystem. The freshwater sponge, Eunapius carteri, bears ecological and evolutionary significance and is considered as a bioresource in aquatic ecosystems. The present study involves estimation of morphological damage, lysosomal membrane integrity, activity of phosphatases and apoptosis in the cells of E. carteri under the environmentally realistic concentrations of washing soda. Exposure to washing soda resulted in severe morphological alterations and damages in cells of E. carteri. Fragility and destabilization of lysosomal membranes of E. carteri under the sublethal exposure was indicative to toxin induced physiological stress in sponge. Prolonged exposure to sodium carbonate resulted a reduction in the activity of acid and alkaline phosphatases in the cells of E. carteri. Experimental concentration of 8 mg/l of washing soda for 192 h yielded an increase in the physiological level of cellular apoptosis among the semigranulocytes and granulocytes of E. carteri, which was suggestive to possible shift in apoptosis mediated immunoprotection. The results were indicative of an undesirable shift in the immune status of sponge. Contamination of the freshwater aquifers by washing soda thus poses an alarming ecotoxicological threat to sponges. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Cell-Culture Reactor Having a Porous Organic Polymer Membrane

    Science.gov (United States)

    Koontz, Steven L. (Inventor)

    2000-01-01

    A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The substrate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphory1choline groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge, wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic regions, and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

  7. Environmental and economic assessment of a cracked ammonia fuelled alkaline fuel cell for off-grid power applications

    Science.gov (United States)

    Cox, Brian; Treyer, Karin

    2015-02-01

    Global mobile telecommunication is possible due to millions of Base Transceiver Stations (BTS). Nearly 1 million of these are operating off-grid, typically powered by diesel generators and therefore leading to significant CO2 emissions and other environmental burdens. A novel type of Alkaline Fuel Cell (AFC) powered by cracked ammonia is being developed for replacement of these generators. This study compares the environmental and economic performance of the two systems by means of Life Cycle Assessment (LCA) and Levelised Cost of Electricity (LCOE), respectively. Results show that the production of ammonia dominates the LCA results, and that renewable ammonia production pathways greatly improve environmental performance. Sensitivity analyses reveal that the fuel cell parameters that most affect system cost and environmental burdens are cell power density and lifetime and system efficiency. Recycling of anode catalyst and electrode substrate materials is found to have large impacts on environmental performance, though without large cost incentives. For a set of target parameter values and fossil sourced ammonia, the AFC is calculated to produce electricity with life cycle CO2 eq emissions of 1.08 kg kWh-1, which is 23% lower than a diesel generator with electricity costs that are 14% higher in the same application.

  8. Nanocarbon/oxide composite catalysts for bifunctional oxygen reduction and evolution in reversible alkaline fuel cells: A mini review

    Science.gov (United States)

    Chen, Mengjie; Wang, Lei; Yang, Haipeng; Zhao, Shuai; Xu, Hui; Wu, Gang

    2018-01-01

    A reversible fuel cell (RFC), which integrates a fuel cell with an electrolyzer, is similar to a rechargeable battery. This technology lies on high-performance bifunctional catalysts for the oxygen reduction reaction (ORR) in the fuel cell mode and the oxygen evolution reaction (OER) in the electrolyzer mode. Current catalysts are platinum group metals (PGM) such as Pt and Ir, which are expensive and scarce. Therefore, it is highly desirable to develop PGM-free catalysts for large-scale application of RFCs. In this mini review, we discussed the most promising nanocarbon/oxide composite catalysts for ORR/OER bifunctional catalysis in alkaline media, which is mainly based on our recent progress. Starting with the effectiveness of selected oxides and nanocarbons in terms of their activity and stability, we outlined synthetic methods and the resulting structures and morphologies of catalysts to provide a correlation between synthesis, structure, and property. A special emphasis is put on understanding of the possible synergistic effect between oxide and nanocarbon for enhanced performance. Finally, a few nanocomposite catalysts are discussed as typical examples to elucidate the rules of designing highly active and durable bifunctional catalysts for RFC applications.

  9. Vesicles mimicking normal and cancer cell membranes exhibit differential responses to the cell-penetrating peptide Pep-1.

    Science.gov (United States)

    Almarwani, Bashiyar; Phambu, Esther Nzuzi; Alexander, Christopher; Nguyen, Ha Aimee T; Phambu, Nsoki; Sunda-Meya, Anderson

    2018-06-01

    The cell-penetrating peptide (CPP) Pep-1 presents a great potential in drug delivery due to its intrinsic property to cross plasma membrane. However, its mechanism of entry into the cell remains unresolved. In this study, we compare the selectivity of Pep-1 towards vesicles mimicking normal and cancer cell membranes. The interaction was performed in a wide range of peptide-to-lipid molar ratios using infrared (IR), fluorescence, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. At low peptide concentration, fluorescence experiments show that lipid-phosphatidylserine (PS) seems to enable Pep-1 translocation into cancer cell membrane as evidenced by the blue shift of its maximal emission wavelength. DSC data show that Pep-1 induces segregation of lipids. At high peptide concentration, IR data indicate that the interaction of Pep-1 is relatively stronger with normal cell membrane than with cancer cell membrane through the phosphate groups, while the interaction is weaker with normal cell membrane than with cancer cell membrane through the carbonyl groups. TGA and DSC data reveal that vesicles of normal cell membrane are thermally more stable than vesicles of cancer cell membrane. This suggests that the additional lipid PS included in cancer cell membrane has a destabilizing effect on the membrane structure. SEM images reveal that Pep-1 form superstructures including spherical particles and fibrils in the presence of both model membranes. PS seems to enhance peptide transport across cellular membranes. The biophysical techniques in this study provide valuable insights into the properties of CPPs in drug delivery systems. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Modelling and validation of Proton exchange membrane fuel cell (PEMFC)

    Science.gov (United States)

    Mohiuddin, A. K. M.; Basran, N.; Khan, A. A.

    2018-01-01

    This paper is the outcome of a small scale fuel cell project. Fuel cell is an electrochemical device that converts energy from chemical reaction to electrical work. Proton Exchange Membrane Fuel Cell (PEMFC) is one of the different types of fuel cell, which is more efficient, having low operational temperature and fast start up capability results in high energy density. In this study, a mathematical model of 1.2 W PEMFC is developed and simulated using MATLAB software. This model describes the PEMFC behaviour under steady-state condition. This mathematical modeling of PEMFC determines the polarization curve, power generated, and the efficiency of the fuel cell. Simulation results were validated by comparing with experimental results obtained from the test of a single PEMFC with a 3 V motor. The performance of experimental PEMFC is little lower compared to simulated PEMFC, however both results were found in good agreement. Experiments on hydrogen flow rate also been conducted to obtain the amount of hydrogen consumed to produce electrical work on PEMFC.

  11. Pyro-electrification of polymer membranes for cell patterning

    Energy Technology Data Exchange (ETDEWEB)

    Rega, R.; Gennari, O.; Mecozzia, L.; Grilli, S.; Pagliarulo, V.; Ferraro, P. [National Council of Research, Institute of Applied Science & Intelligent Systems (ISASI) ‘E. Caianiello’, Via Campi Flegrei 34, 80078 Pozzuoli (Italy)

    2016-05-18

    In the recent years, much attention has been devoted to the possibility of charging polymer-based materials, due to their potential in developing large-scale and inexpensive flexible thin-film technology. The availability of localized electrostatic fields is in of great interest for a huge amount of applications such as distribution of biomolecules and cells from the liquid phase. Here we report a voltage-free pyro-electrification (PE) process able to induce permanent dipoles into polymer layers; the lithium niobate (LN) crystal is the key component that plays the multi-purpose role of sustaining, heating and poling the polymer layer that is then peeled-off easily in order to have a free-standing charged membrane. The results show the fascinating application for the living cell patterning. It well known that cell behaviour is affected by chemical and topographical cues of substrate. In fact, polymers, such as polystyrene (PS) and poly(methyl methacrylate) (PMMA), are naturally cytophobic and require specific functionalization treatments in order to promote cell adhesion. Through our proposal technique, it’s possible to obtain spontaneous organization and a driven growth of SH-SY5Y cells that is solely dictated by the nature of the charge polymer surface, opening, in this way, the innovative chance to manipulate and transfer biological samples on a free-standing polymer layer [1].

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

    International Nuclear Information System (INIS)

    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 3 H-thymidine uptake. The axolemmal mitogen was sensitive to heat (80 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 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

  13. Performance Degradation Tests of Phosphoric Acid Doped Polybenzimidazole Membrane Based High Temperature Polymer Electrolyte Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Zhou, Fan; Araya, Samuel Simon; Grigoras, Ionela

    2015-01-01

    Degradation tests of two phosphoric acid (PA) doped PBI membrane based HT-PEM fuel cells were reported in this paper to investigate the effects of start/stop and the presence of methanol in the fuel to the performance degradation of the HT-PEM fuel cell. Continuous tests with pure dry H2 and meth...

  14. A practical guide for the identification of membrane and plasma membrane proteins in human embryonic stem cells and human embryonal carcinoma cells.

    NARCIS (Netherlands)

    Dormeyer, W.; van Hoof, D.; Mummery, C.L.; Krijgsveld, J.; Heck, A.

    2008-01-01

    The identification of (plasma) membrane proteins in cells can provide valuable insights into the regulation of their biological processes. Pluripotent cells such as human embryonic stem cells and embryonal carcinoma cells are capable of unlimited self-renewal and share many of the biological

  15. Two 3D structured Co-Ni bimetallic oxides as cathode catalysts for high-performance alkaline direct methanol fuel cells

    Science.gov (United States)

    Liu, Yan; Shu, Chengyong; Fang, Yuan; Chen, Yuanzhen; Liu, Yongning

    2017-09-01

    Two NiCo2O4 bimetallic oxides were synthesized via a facile hydrothermal method. SEM and TEM observations show that these materials have three-dimensional (3D) dandelion-like (DL) and flower-like (FL) morphologies. Their large specific surface areas (90.68 and 19.8 m2·g-1) and porous structures provide many active sites and effective transport pathways for the oxygen reduction reaction (ORR). Electrochemical measurements with a rotating ring-disc electrode (RRDE) indicate that the electron transfer numbers of the NiCo2O4-DL and NiCo2O4-FL catalysts for ORR in an alkaline solution are 3.97 and 3.91, respectively. Fuel cells were assembled with the bimetallic oxides, PtRu/C and a polymer fiber membrane (PFM) as cathode catalysts, anode catalyst and electrolyte film, respectively. For NiCo2O4-DL, the peak power density reaches up to 73.5 mW·cm-2 at 26 °C, which is the highest room-temperature value reported to date. The high catalytic activity of NiCo2O4 is mainly attributed to the presence of many Co3+ cations that directly donate electrons to O2 to reduce it via a more efficient and effective route. Furthermore, the catalytic performance of NiCo2O4-DL is superior to that of NiCo2O4-FL because it has a higher specific surface area and is less crystalline.

  16. Influence of Silica/Sulfonated Polyether-Ether Ketone as Polymer Electrolyte Membrane for Hydrogen Fueled Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Sri Handayani

    2011-12-01

    Full Text Available The operation of non-humidified condition of proton exchange membrane fuel cell (PEMFC using composite sPEEK-silica membrane is reported. Sulfonated membrane of PEEK is known as hydrocarbon polyelectrolyte membrane for PEMFC and direct methanol fuel cell (DMFC. The state of the art of fuel cells is based on the perluorosulfonic acid membrane (Nafion. Nafion has been the most used in both PEMFC and DMFC due to good performance although in low humidified condition showed poor current density. Here we reported the effect of silica in hydrocarbon sPEEK membrane that contributes for a better water management system inside the cell, and showed 0.16 W/cm2 of power density which is 78% higher than that of non-silica modified [Keywords: composite membrane, polyether-ether ketone, silica, proton exchange membrane fuel cell].

  17. Development of a living membrane comprising a functional human renal proximal tubule cell monolayer on polyethersulfone polymeric membrane.

    Science.gov (United States)

    Schophuizen, Carolien M S; De Napoli, Ilaria E; Jansen, Jitske; Teixeira, Sandra; Wilmer, Martijn J; Hoenderop, Joost G J; Van den Heuvel, Lambert P W; Masereeuw, Rosalinde; Stamatialis, Dimitrios

    2015-03-01

    The need for improved renal replacement therapies has stimulated innovative research for the development of a cell-based renal assist device. A key requirement for such a device is the formation of a "living membrane", consisting of a tight kidney cell monolayer with preserved functional organic ion transporters on a suitable artificial membrane surface. In this work, we applied a unique conditionally immortalized proximal tubule epithelial cell (ciPTEC) line with an optimized coating strategy on polyethersulfone (PES) membranes to develop a living membrane with a functional proximal tubule epithelial cell layer. PES membranes were coated with combinations of 3,4-dihydroxy-l-phenylalanine and human collagen IV (Coll IV). The optimal coating time and concentrations were determined to achieve retention of vital blood components while preserving high water transport and optimal ciPTEC adhesion. The ciPTEC monolayers obtained were examined through immunocytochemistry to detect zona occludens 1 tight junction proteins. Reproducible monolayers were formed when using a combination of 2 mg ml(-1) 3,4-dihydroxy-l-phenylalanine (4 min coating, 1h dissolution) and 25 μg ml(-1) Coll IV (4 min coating). The successful transport of (14)C-creatinine through the developed living membrane system was used as an indication for organic cation transporter functionality. The addition of metformin or cimetidine significantly reduced the creatinine transepithelial flux, indicating active creatinine uptake in ciPTECs, most likely mediated by the organic cation transporter, OCT2 (SLC22A2). In conclusion, this study shows the successful development of a living membrane consisting of a reproducible ciPTEC monolayer on PES membranes, an important step towards the development of a bioartificial kidney. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. Nafion/Silicon Oxide Composite Membrane for High Temperature Proton Exchange Membrane Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nafion/Silicon oxide composite membranes were produced via in situ sol-gel reaction of tetraethylorthosilicate (TEOS) in Nafion membranes. The physicochemical properties of the membranes were studied by FT-IR, TG-DSC and tensile strength. The results show that the silicon oxide is compatible with the Nafion membrane and the thermo stability of Nafion/Silicon oxide composite membrane is higher than that of Nafion membrane. Furthermore, the tensile strength of Nafion/Silicon oxide composite membrane is similar to that of the Nafion membrane. The proton conductivity of Nafion/Silicon oxide composite membrane is higher than that of Nafion membrane. When the Nafion/Silicon oxide composite membrane was employed as an electrolyte in H2/O2 PEMFC, a higher current density value (1 000 mA/cm2 at 0.38 V) than that of the Nafion 1135 membrane (100 mA/cm2 at 0.04 V) was obtained at 110 ℃.

  19. Lipid-protein interactions in plasma membranes of fiber cells isolated from the human eye lens.

    Science.gov (United States)

    Raguz, Marija; Mainali, Laxman; O'Brien, William J; Subczynski, Witold K

    2014-03-01

    The protein content in human lens membranes is extremely high, increases with age, and is higher in the nucleus as compared with the cortex, which should strongly affect the organization and properties of the lipid bilayer portion of intact membranes. To assess these effects, the intact cortical and nuclear fiber cell plasma membranes isolated from human lenses from 41- to 60-year-old donors were studied using electron paramagnetic resonance spin-labeling methods. Results were compared with those obtained for lens lipid membranes prepared from total lipid extracts from human eyes of the same age group [Mainali, L., Raguz, M., O'Brien, W. J., and Subczynski, W. K. (2013) Biochim. Biophys. Acta]. Differences were considered to be mainly due to the effect of membrane proteins. The lipid-bilayer portions of intact membranes were significantly less fluid than lipid bilayers of lens lipid membranes, prepared without proteins. The intact membranes were found to contain three distinct lipid environments termed the bulk lipid domain, boundary lipid domain, and trapped lipid domain. However, the cholesterol bilayer domain, which was detected in cortical and nuclear lens lipid membranes, was not detected in intact membranes. The relative amounts of bulk and trapped lipids were evaluated. The amount of lipids in domains uniquely formed due to the presence of membrane proteins was greater in nuclear membranes than in cortical membranes. Thus, it is evident that the rigidity of nuclear membranes is greater than that of cortical membranes. Also the permeability coefficients for oxygen measured in domains of nuclear membranes were significantly lower than appropriate coefficients measured in cortical membranes. Relationships between the organization of lipids into lipid domains in fiber cells plasma membranes and the organization of membrane proteins are discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Modelling membrane hydration and water balance of a pem fuel cell

    DEFF Research Database (Denmark)

    Liso, Vincenzo; Nielsen, Mads Pagh

    2015-01-01

    Polymer electrolyte membrane (PEM) fuel cells requires an appropriate hydration in order to ensure high efficiency and long durability. As water is essential for promoting proton conductivity in the membrane, it is important to control membrane water hydration to avoid flooding. In this study we...

  1. New polymeric electrolyte membranes based on proton donor proton acceptor properties for direct methanol fuel cells

    NARCIS (Netherlands)

    Manea, G.C.; Mulder, M.H.V.

    2002-01-01

    In order to reduce the high methanol permeability of membranes in a direct methanol fuel cell application new and better materials are still required. In this paper membranes made from polybenzimidazole/sulfonated polysulfone are given and compared with homopolymer membranes made from sulfonated

  2. New Insight Into the Roles of Membrane Microdomains in Physiological Activities of Fungal Cells.

    Czech Academy of Sciences Publication Activity Database

    Malínský, Jan; Opekarová, Miroslava

    2016-01-01

    Roč. 325, mar. (2016), s. 119-180 ISSN 1937-6448 R&D Projects: GA ČR(CZ) GA15-10641S Institutional support: RVO:68378041 Keywords : membrane microdomain * membrane structure * fungi * membrane contact sites Subject RIV: EA - Cell Biology Impact factor: 3.752, year: 2015

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

    Science.gov (United States)

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

    2013-01-01

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

  4. DRAM triggers lysosomal membrane permeabilization and cell death in CD4(+ T cells infected with HIV.

    Directory of Open Access Journals (Sweden)

    Mireille Laforge

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

  5. Water-Free Proton-Conducting Membranes for Fuel Cells

    Science.gov (United States)

    Narayanan, Sekharipuram; Yen, Shiao-Pin

    2007-01-01

    Poly-4-vinylpyridinebisulfate (P4VPBS) is a polymeric salt that has shown promise as a water-free proton-conducting material (solid electrolyte) suitable for use in membrane/electrode assemblies in fuel cells. Heretofore, proton-conducting membranes in fuel cells have been made from perfluorinated ionomers that cannot conduct protons in the absence of water and, consequently, cannot function at temperatures >100 C. In addition, the stability of perfluorinated ionomers at temperatures >100 C is questionable. However, the performances of fuel cells of the power systems of which they are parts could be improved if operating temperatures could be raised above 140 C. What is needed to make this possible is a solid-electrolyte material, such as P4VPBS, that can be cast into membranes and that both retains proton conductivity and remains stable in the desired higher operating temperature range. A family of solid-electrolyte materials different from P4VPBS was described in Anhydrous Proton-Conducting Membranes for Fuel Cells (NPO-30493), NASA Tech Briefs, Vol. 29, No. 8 (August 2005), page 48. Those materials notably include polymeric quaternized amine salts. If molecules of such a polymeric salt could be endowed with flexible chain structures, it would be possible to overcome the deficiencies of simple organic amine salts that must melt before being able to conduct protons. However, no polymeric quaternized amine salts have yet shown to be useful in this respect. The present solid electrolyte is made by quaternizing the linear polymer poly- 4-vinylpyridine (P4VP) to obtain P4VPBS. It is important to start with P4VP having a molecular weight of 160,000 daltons because P4VPBS made from lower-molecular-weight P4VP yields brittle membranes. In an experimental synthesis, P4VP was dissolved in methanol and then reacted with an excess of sulfuric acid to precipitate P4VPBS. The precipitate was recovered, washed several times with methanol to remove traces of acid, and dried to a

  6. Binding and Fusion of Extracellular Vesicles to the Plasma Membrane of Their Cell Targets.

    Science.gov (United States)

    Prada, Ilaria; Meldolesi, Jacopo

    2016-08-09

    Exosomes and ectosomes, extracellular vesicles of two types generated by all cells at multivesicular bodies and the plasma membrane, respectively, play critical roles in physiology and pathology. A key mechanism of their function, analogous for both types of vesicles, is the fusion of their membrane to the plasma membrane of specific target cells, followed by discharge to the cytoplasm of their luminal cargo containing proteins, RNAs, and DNA. Here we summarize the present knowledge about the interactions, binding and fusions of vesicles with the cell plasma membrane. The sequence initiates with dynamic interactions, during which vesicles roll over the plasma membrane, followed by the binding of specific membrane proteins to their cell receptors. Membrane binding is then converted rapidly into fusion by mechanisms analogous to those of retroviruses. Specifically, proteins of the extracellular vesicle membranes are structurally rearranged, and their hydrophobic sequences insert into the target cell plasma membrane which undergoes lipid reorganization, protein restructuring and membrane dimpling. Single fusions are not the only process of vesicle/cell interactions. Upon intracellular reassembly of their luminal cargoes, vesicles can be regenerated, released and fused horizontally to other target cells. Fusions of extracellular vesicles are relevant also for specific therapy processes, now intensely investigated.

  7. The study of preparation for immobilized cells membranes of E. Coli. by radiation technique

    International Nuclear Information System (INIS)

    Cao Jin; Chen Pin; Yu Yi

    1991-01-01

    The paper described the preparation of immobilized cells membranes with E. Coli by radiation technique. The nylon 6 was grafted with HEMA, which as a matrix to prepare immobilized cells membranes with E. Coli. by radiation entrapment at low temperature. The results showed that the retentive activity possessed a maximum value for membranes with E. Coli. when the irradiation dose was at 10-12 kGy, the entrapped cells has 2.3 g/ml at 50% HEMA concentration, the optimum pH and optimum temperature for membranes with E. Coli. are as same the original cells

  8. The effects of heavy metal ions on the chlorophyll content and cell membrane permeability of charophytes

    International Nuclear Information System (INIS)

    Fu Hualong; Chen Hao; Dong Bin; Qing Renwei

    2001-01-01

    The authors studied the effects of several heavy metal ions in different concentrations (Cd 2+ , Hg 2+ , Pb 2+ , Cr 6+ ) on the chlorophyll content and cell membrane permeability of Chara vulgaris L. It was discovered that the effects of heavy metal ions on the chlorophyll content and cell membrane permeability of Chara vulgaris L. changed with their different concentration. The trend was that the chlorophyll content and cell membrane permeability were decreased with the increase of the heavy metal ions. The degree of chlorophyll content affected was Cr 6+ , Cd 2+ , Hg 2+ , Pb 2+ , and that of cell membrane permeability affected was Cd 2+ , Cr 6+ , Hg 2+ , Pb 2+

  9. Detection of endogenous alkaline phosphatase activity in intact cells by flow cytometry using the fluorogenic ELF-97 phosphatase substrate

    Science.gov (United States)

    Telford, W. G.; Cox, W. G.; Stiner, D.; Singer, V. L.; Doty, S. B.

    1999-01-01

    BACKGROUND: The alkaline phosphatase (AP) substrate 2-(5'-chloro-2'-phosphoryloxyphenyl)-6-chloro-4-(3H)-quinazolinone (ELF((R))-97 for enzyme-labeled fluorescence) has been found useful for the histochemical detection of endogenous AP activity and AP-tagged proteins and oligonucleotide probes. In this study, we evaluated its effectiveness at detecting endogenous AP activity by flow cytometry. METHODS: The ELF-97 phosphatase substrate was used to detect endogenous AP activity in UMR-106 rat osteosarcoma cells and primary cultures of chick chondrocytes. Cells were labeled with the ELF-97 reagent and analyzed by flow cytometry using an argon ultraviolet (UV) laser. For comparison purposes, cells were also assayed for AP using a Fast Red Violet LB azo dye assay previously described for use in detecting AP activity by flow cytometry. RESULTS: The ELF-97 phosphatase substrate effectively detected endogenous AP activity in UMR-106 cells, with over 95% of the resulting fluorescent signal resulting from AP-specific activity (as determined by levamisole inhibition of AP activity). In contrast, less than 70% of the fluorescent signal from the Fast Red Violet LB (FRV) assay was AP-dependent, reflecting the high intrinsic fluorescence of the unreacted components. The ELF-97 phosphatase assay was also able to detect very low AP activity in chick chondrocytes that was undetectable by the azo dye method. CONCLUSIONS: The ELF-97 phosphatase assay was able to detect endogenous AP activity in fixed mammalian and avian cells by flow cytometry with superior sensitivity to previously described assays. This work also shows the applicability of ELF-97 to flow cytometry, supplementing its previously demonstrated histochemical applications. Copyright 1999 Wiley-Liss, Inc.

  10. Novel composite membranes based on PBI and dicationic ionic liquids for high temperature polymer electrolyte membrane fuel cells

    International Nuclear Information System (INIS)

    Hooshyari, Khadijeh; Javanbakht, Mehran; Adibi, Mina

    2016-01-01

    Two types of innovative composite membranes based on polybenzimidazole (PBI) containing dicationic ionic liquid 1,3-di(3-methylimidazolium) propane bis (trifluoromethylsulfonyl) imide (PDC 3 ) and monocationic ionic liquid 1-hexyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (PMC 6 ) are prepared as electrolyte for high temperature fuel cells applications under anhydrous conditions. The analyses of results display promising characteristics such as high proton conductivity and thermal stability. Moreover the fuel cell performance of PA doped PDC 3 composite membranes is enhanced in comparison with PA doped PMC 6 and PA doped PBI membranes at high temperatures. Dicationic ionic liquid with high number of charge carriers provides well-developed ionic channels which form facile pathways and considerably develop the anhydrous proton conductivity. The highest proton conductivity of 81 mS/cm is achieved for PA doped PDC 3 composite membranes with PBI/IL mole ratio: 4 at 180 °C. A power density of 0.44 W/cm 2 is obtained at 0.5 V and 180 °C for PA doped PDC 3 composite membranes, which proves that these developed composite membranes can be considered as most promising candidates for high temperature fuel cell applications with enhanced proton conductivity.

  11. Infectious rotavirus enters cells by direct cell membrane penetration, not by endocytosis

    International Nuclear Information System (INIS)

    Kaljot, K.T.; Shaw, R.D.; Greenberg, H.B.; Rubin, D.H.

    1988-01-01

    Rotaviruses are icosahedral viruses with a segmented, double-stranded RNA genome. They are the major cause of severe infantile infectious diarrhea. Rotavirus growth in tissue culture is markedly enhanced by pretreatment of virus with trypsin. Trypsin activation is associated with cleavage of the viral hemagglutinin (viral protein 3 [VP3]; 88 kilodaltons) into two fragments (60 and 28 kilodaltons). The mechanism by which proteolytic cleavage leads to enhanced growth is unknown. To determine whether trypsin treatment affected rotavirus internalization, the authors studied the kinetics of entry of infectious rhesus rotavirus (RRV) into MA104 cells. Trypsin-activated RRV was internalized with a half-time of 3 to 5 min, while nonactivated virus disappeared from the cell surface with a half-time of 30 to 50 min. In contrast to trypsin-activated RRV, loss of nonactivated RRV from the cell surface did not result in the appearance of infection, as measured by plaque formation. Purified trypsin-activated RRV added to cell monolayers at pH 7.4 mediated 51 Cr, [ 14 C]choline, and [ 3 H]inositol released from prelabeled MA104 cells. This release could be specifically blocked by neutralizing antibodies to VP3. These results suggest that MA104 cell infection follows the rapid entry of trypsin-activated RRV by direct cell membrane penetration. Cell membrane penetration of infectious RRV is initiated by trypsin cleavage of VP3. Neutralizing antibodies can inhibit this direct membrane penetration

  12. Infectious rotavirus enters cells by direct cell membrane penetration, not by endocytosis

    Energy Technology Data Exchange (ETDEWEB)

    Kaljot, K.T.; Shaw, R.D.; Greenberg, H.B. (Stanford Univ. School of Medicine, CA (USA) Palo Alto Veterans Administration Medical Center, CA (USA)); Rubin, D.H. (Univ. of Pennsylvania, Philadelphia (USA))

    1988-04-01

    Rotaviruses are icosahedral viruses with a segmented, double-stranded RNA genome. They are the major cause of severe infantile infectious diarrhea. Rotavirus growth in tissue culture is markedly enhanced by pretreatment of virus with trypsin. Trypsin activation is associated with cleavage of the viral hemagglutinin (viral protein 3 (VP3); 88 kilodaltons) into two fragments (60 and 28 kilodaltons). The mechanism by which proteolytic cleavage leads to enhanced growth is unknown. To determine whether trypsin treatment affected rotavirus internalization, the authors studied the kinetics of entry of infectious rhesus rotavirus (RRV) into MA104 cells. Trypsin-activated RRV was internalized with a half-time of 3 to 5 min, while nonactivated virus disappeared from the cell surface with a half-time of 30 to 50 min. In contrast to trypsin-activated RRV, loss of nonactivated RRV from the cell surface did not result in the appearance of infection, as measured by plaque formation. Purified trypsin-activated RRV added to cell monolayers at pH 7.4 mediated {sup 51}Cr, ({sup 14}C)choline, and ({sup 3}H)inositol released from prelabeled MA104 cells. This release could be specifically blocked by neutralizing antibodies to VP3. These results suggest that MA104 cell infection follows the rapid entry of trypsin-activated RRV by direct cell membrane penetration. Cell membrane penetration of infectious RRV is initiated by trypsin cleavage of VP3. Neutralizing antibodies can inhibit this direct membrane penetration.

  13. Membrane cholesterol regulates lysosome-plasma membrane fusion events and modulates Trypanosoma cruzi invasion of host cells.

    Directory of Open Access Journals (Sweden)

    Bárbara Hissa

    Full Text Available BACKGROUND: Trypomastigotes of Trypanosoma cruzi are able to invade several types of non-phagocytic cells through a lysosomal dependent mechanism. It has been shown that, during invasion, parasites trigger host cell lysosome exocytosis, which initially occurs at the parasite-host contact site. Acid sphingomyelinase released from lysosomes then induces endocytosis and parasite internalization. Lysosomes continue to fuse with the newly formed parasitophorous vacuole until the parasite is completely enclosed by lysosomal membrane, a process indispensable for a stable infection. Previous work has shown that host membrane cholesterol is also important for the T. cruzi invasion process in both professional (macrophages and non-professional (epithelial phagocytic cells. However, the mechanism by which cholesterol-enriched microdomains participate in this process has remained unclear. METHODOLOGY/PRINCIPAL FINDING: In the present work we show that cardiomyocytes treated with MβCD, a drug able to sequester cholesterol from cell membranes, leads to a 50% reduction in invasion by T. cruzi trypomastigotes, as well as a decrease in the number of recently internalized parasites co-localizing with lysosomal markers. Cholesterol depletion from host membranes was accompanied by a decrease in the labeling of host membrane lipid rafts, as well as excessive lysosome exocytic events during the earlier stages of treatment. Precocious lysosomal exocytosis in MβCD treated cells led to a change in lysosomal distribution, with a reduction in the number of these organelles at the cell periphery, and probably compromises the intracellular pool of lysosomes necessary for T. cruzi invasion. CONCLUSION/SIGNIFICANCE: Based on these results, we propose that cholesterol depletion leads to unregulated exocytic events, reducing lysosome availability at the cell cortex and consequently compromise T. cruzi entry into host cells. The results also suggest that two different pools of

  14. Vaginal epithelial cells regulate membrane adhesiveness to co-ordinate bacterial adhesion.

    Science.gov (United States)

    Younes, Jessica A; Klappe, Karin; Kok, Jan Willem; Busscher, Henk J; Reid, Gregor; van der Mei, Henny C

    2016-04-01

    Vaginal epithelium is colonized by different bacterial strains and species. The bacterial composition of vaginal biofilms controls the balance between health and disease. Little is known about the relative contribution of the epithelial and bacterial cell surfaces to bacterial adhesion and whether and how adhesion is regulated over cell membrane regions. Here, we show that bacterial adhesion forces with cell membrane regions not located above the nucleus are stronger than with regions above the nucleus both for vaginal pathogens and different commensal and probiotic lactobacillus strains involved in health. Importantly, adhesion force ratios over membrane regions away from and above the nucleus coincided with the ratios between numbers of adhering bacteria over both regions. Bacterial adhesion forces were dramatically decreased by depleting the epithelial cell membrane of cholesterol or sub-membrane cortical actin. Thus, epithelial cells can regulate membrane regions to which bacterial adhesion is discouraged, possibly to protect the nucleus. © 2015 John Wiley & Sons Ltd.

  15. Fluorescent Lipids: Functional Parts of Fusogenic Liposomes and Tools for Cell Membrane Labeling and Visualization

    Directory of Open Access Journals (Sweden)

    Christian Kleusch

    2012-01-01

    Full Text Available In this paper a rapid and highly efficient method for controlled incorporation of fluorescent lipids into living mammalian cells is introduced. Here, the fluorescent molecules have two consecutive functions: First, they trigger rapid membrane fusion between cellular plasma membranes and the lipid bilayers of their carrier particles, so called fusogenic liposomes, and second, after insertion into cellular membranes these molecules enable fluorescence imaging of cell membranes and membrane traffic processes. We tested the fluorescent derivatives of the following essential membrane lipids for membrane fusion: Ceramide, sphingomyelin, phosphocholine, phosphatidylinositol-bisphosphate, ganglioside, cholesterol, and cholesteryl ester. Our results show that all probed lipids could more efficiently be incorporated into the plasma membrane of living cells than by using other methods. Moreover, labeling occurred in a gentle manner under classical cell culture conditions reducing cellular stress responses. Staining procedures were monitored by fluorescence microscopy and it was observed that sphingolipids and cholesterol containing free hydroxyl groups exhibit a decreased distribution velocity as well as a longer persistence in the plasma membrane compared to lipids without hydroxyl groups like phospholipids or other artificial lipid analogs. After membrane staining, the fluorescent molecules were sorted into membranes of cell organelles according to their chemical properties and biological functions without any influence of the delivery system.

  16. Label-free evanescent microscopy for membrane nano-tomography in living cells.

    Science.gov (United States)

    Bon, Pierre; Barroca, Thomas; Lévèque-Fort, Sandrine; Fort, Emmanuel

    2014-11-01

    We show that through-the-objective evanescent microscopy (epi-EM) is a powerful technique to image membranes in living cells. Readily implementable on a standard inverted microscope, this technique enables full-field and real-time tracking of membrane processes without labeling and thus signal fading. In addition, we demonstrate that the membrane/interface distance can be retrieved with 10 nm precision using a multilayer Fresnel model. We apply this nano-axial tomography of living cell membranes to retrieve quantitative information on membrane invagination dynamics. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  17. Cross-linked PEEK-WC proton exchange membrane for fuel cell

    CSIR Research Space (South Africa)

    Lou, H

    2009-10-01

    Full Text Available was added to the 15 wt% of SsPEEK-WC solution in NMP with magnetic stir. The solution was cast on a glass Petri dish. The solvent was then removed in a vacuum oven at 130 °C. The membrane was peeled off from the Petri dish. Thereafter, the membrane... and polyetherketone for fuel cell applications. Journal of Membrane Science, 2001. 185(1): p. 41-58. [6] Kerres, J.A., Development of ionomer membranes for fuel cells. Journal of Membrane Science, 2001. 185(1): p. 3-27. [7] Basile, A.; Paturzo, L.; Iulianelli, A...

  18. CFD simulation of fuel cell proton exchange membrane multichannel

    International Nuclear Information System (INIS)

    Argota, Raúl; García, Lázaro; Torre, Raciel de la; González, Daniel

    2015-01-01

    Hydrogen has several applications that make the strongest candidate for implementation as an energy carrier in the future sustainable scenario. Current hydrogen production is based on fossil fuels that have a high contribution to air pollution. The imminent depletion of fossil fuels and high emissions of greenhouse gases that cause consumption has brought the world to consider energy scenarios that are more environmentally friendly and yet profitable. The use of hydrogen as an energy carrier generally occurs with good application prospects. Fuel cells have attracted great interest for its application mainly in the transport sector. The fuel cell PEM proton exchange membrane which convert chemical energy stored in hydrogen into electrical energy directly and efficiently, with water as a byproduct, have the ability to reduce emissions and dependence on fossil fuels. A model for multiple cell PEM five channels using the ANSYS software CFD occurs. Performance analysis and optimization of the thermodynamic and geometric parameters of the fuel cell is performed. It was analyzed the overall electrical performance and assessed performance by local current density, flow and temperatures. (full text)

  19. Cell-autonomous defense, re-organization and trafficking of membranes in plant-microbe interactions.

    Science.gov (United States)

    Dörmann, Peter; Kim, Hyeran; Ott, Thomas; Schulze-Lefert, Paul; Trujillo, Marco; Wewer, Vera; Hückelhoven, Ralph

    2014-12-01

    Plant cells dynamically change their architecture and molecular composition following encounters with beneficial or parasitic microbes, a process referred to as host cell reprogramming. Cell-autonomous defense reactions are typically polarized to the plant cell periphery underneath microbial contact sites, including de novo cell wall biosynthesis. Alternatively, host cell reprogramming converges in the biogenesis of membrane-enveloped compartments for accommodation of beneficial bacteria or invasive infection structures of filamentous microbes. Recent advances have revealed that, in response to microbial encounters, plasma membrane symmetry is broken, membrane tethering and SNARE complexes are recruited, lipid composition changes and plasma membrane-to-cytoskeleton signaling is activated, either for pre-invasive defense or for microbial entry. We provide a critical appraisal on recent studies with a focus on how plant cells re-structure membranes and the associated cytoskeleton in interactions with microbial pathogens, nitrogen-fixing rhizobia and mycorrhiza fungi. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  20. Manipulation of cell membrane using carbon nanotube scaffold as a photoresponsive stimuli generator.

    Science.gov (United States)

    Sada, Takao; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2014-08-01

    We describe, for the first time, the perforation of the cell membrane in the targeted single cell based on the nanosecond pulsed near-infrared (NIR) laser irradiation of a thin film of carbon nanotubes that act as an effective photon absorber as well as stimuli generator. When the power of NIR laser is over 17.5 μ J/pulse, the cell membrane after irradiation is irreversibly disrupted and results in cell death. In sharp contrast, the perforation of the cell membrane occurs at suitable laser power (∼15 μ J/pulse) without involving cell termination.

  1. Effects of Propofol on Several Membrane Characteristics of Cervical Cancer Cell Lines

    Directory of Open Access Journals (Sweden)

    Fan Zhang

    2016-11-01

    Full Text Available Background: Although significant advances have been made toward understanding the molecular mechanisms underlying the effect of propofol on tumor cell metastasis, less is known regarding how cell membrane and cytoskeletal ultrastructure are affected in this process. Here, we investigated the relationship between cell morphology and cell size, which are features mainly defined by the cytoskeleton. Methods: To confirm the effects of propofol on the migratory ability of human cervical carcinoma cells, cell migration and invasion were examined through scratch wound healing and transwell membrane assays. Furthermore, HeLa cells cultivated with different concentrations of propofol were examined by confocal microscopy and atomic force microscopy (AFM, and the mean optical density and migration ability of these cells were also assessed. In addition, cell membrane morphology was inspected using AFM. Results: The results of the wound healing and transwell membrane assays indicated that propofol decreases the migratory ability of cervical carcinoma cells compared to control cells. A comparative analysis of the test results revealed that short-term (3 h exposure to propofol induced marked changes in cell membrane microstructure and in the cytoskeleton in a dose-dependent manner. These morphological changes in the cell membrane were accompanied by cytoskeleton (F-actin derangement. The present findings demonstrate a close relationship between changes in cell membrane ultrastructure and cytoskeletal alterations (F-actin in propofol-treated HeLa cells. AFM scanning analysis showed that cell membrane ultrastructure was significantly changed, including a clear reduction in membrane roughness. Conclusion: The influence of propofol on the HeLa cell cytoskeleton can be directly reflected by changes in cellular morphology, as assessed by AFM. Moreover, the use of AFM is a good method for investigating propofol-mediated changes within cytoskeletal ultrastructure.

  2. The B-domain of factor VIII reduces cell membrane attachement to host cells in serum free conditions

    DEFF Research Database (Denmark)

    Kolind, Mille Petersen; Nørby, Peder Lisby; Flintegaard, Thomas Veje

    2010-01-01

    engineered extensively throughout the years to increase the low production yields that initially were obtained from mammalian cell cultures. The scope of this work was to investigate the interaction of rFVIII with the cell membrane surface of the producing cells in serum free medium. We wondered whether...... binding of rFVIII to the cell membrane could be a factor diminishing the production yield. We studied the contribution of the rFVIII B-domain to membrane attachment by transfecting several constructs containing increasing lengths of the B-domain into cells under serum free conditions. We found that 90......% of rFVIII is attached to the cell membrane of the producing cell when the rFVIII variant contains a short B-domain (21 aa). By increasing the length of the B-domain the membrane attached fraction can be reduced to 50% of the total expressed rFVIII. Further, our studies show that the N...

  3. S-layer and cytoplasmic membrane – exceptions from the typical archaeal cell wall with a focus on double membranes

    Directory of Open Access Journals (Sweden)

    Andreas eKlingl

    2014-11-01

    Full Text Available The common idea of typical cell wall architecture in archaea consists of a pseudo-crystalline proteinaceous surface layer (S-layer, situated upon the cytoplasmic membrane. This is true for the majority of described archaea, hitherto. Within the crenarchaea, the S-layer often represents the only cell wall component, but there are various exceptions from this wall architecture. Beside (glycosylated S-layers in (hyperthermophilic cren- and euryarchaea as well as halophilic archaea, one can find a great variety of other cell wall structures like proteoglycan-like S-layers (Halobacteria, glutaminylglycan (Natronococci, methanochondroitin (Methanosarcina or double layered cell walls with pseudomurein (Methanothermus and Methanopyrus. The presence of an outermost cellular membrane in the crenarchaeal species Ignicoccus hospitalis already gave indications for an outer membrane similar to Gram-negative bacteria. Although there is just limited data concerning their biochemistry and ultrastructure, recent studies on the euryarchaeal methanogen Methanomassiliicoccus luminyensis, cells of the ARMAN group, and the SM1 euryarchaeon delivered further examples for this exceptional cell envelope type consisting of two membranes.

  4. In situ single molecule imaging of cell membranes: linking basic nanotechniques to cell biology, immunology and medicine

    Science.gov (United States)

    Pi, Jiang; Jin, Hua; Yang, Fen; Chen, Zheng W.; Cai, Jiye

    2014-10-01

    The cell membrane, which consists of a viscous phospholipid bilayer, different kinds of proteins and various nano/micrometer-sized domains, plays a very important role in ensuring the stability of the intracellular environment and the order of cellular signal transductions. Exploring the precise cell membrane structure and detailed functions of the biomolecules in a cell membrane would be helpful to understand the underlying mechanisms involved in cell membrane signal transductions, which could further benefit research into cell biology, immunology and medicine. The detection of membrane biomolecules at the single molecule level can provide some subtle information about the molecular structure and the functions of the cell membrane. In particular, information obtained about the molecular mechanisms and other information at the single molecule level are significantly different from that detected from a large amount of biomolecules at the large-scale through traditional techniques, and can thus provide a novel perspective for the study of cell membrane structures and functions. However, the precise investigations of membrane biomolecules prompts researchers to explore cell membranes at the single molecule level by the use of in situ imaging methods, as the exact conformation and functions of biomolecules are highly controlled by the native cellular environment. Recently, the in situ single molecule imaging of cell membranes has attracted increasing attention from cell biologists and immunologists. The size of biomolecules and their clusters on the cell surface are set at the nanoscale, which makes it mandatory to use high- and super-resolution imaging techniques to realize the in situ single molecule imaging of cell membranes. In the past few decades, some amazing imaging techniques and instruments with super resolution have been widely developed for molecule imaging, which can also be further employed for the in situ single molecule imaging of cell membranes. In

  5. Chemically durable polymer electrolytes for solid-state alkaline water electrolysis

    Science.gov (United States)

    Park, Eun Joo; Capuano, Christopher B.; Ayers, Katherine E.; Bae, Chulsung

    2018-01-01

    Generation of high purity hydrogen using electrochemical splitting of water is one of the most promising methods for sustainable fuel production. The materials to be used as solid-state electrolytes for alkaline water electrolyzer require high thermochemical stability against hydroxide ion attack in alkaline environment during the operation of electrolysis. In this study, two quaternary ammonium-tethered aromatic polymers were synthesized and investigated for anion exchange membrane (AEM)-based alkaline water electrolyzer. The membranes properties including ion exchange capacity (IEC), water uptake, swelling degree, and anion conductivity were studied. The membranes composed of all C-C bond polymer backbones and flexible side chain terminated by cation head groups exhibited remarkably good chemical stability by maintaining structural integrity in 1 M NaOH solution at 95 °C for 60 days. Initial electrochemical performance and steady-state operation performance were evaluated, and both membranes showed a good stabilization of the cell voltage during the steady-state operation at the constant current density at 200 mA/cm2. Although both membranes in current form require improvement in mechanical stability to afford better durability in electrolysis operation, the next generation AEMs based on this report could lead to potentially viable AEM candidates which can provide high electrolysis performance under alkaline operating condition.

  6. Assessment of Membrane Fluidity Fluctuations during Cellular Development Reveals Time and Cell Type Specificity

    KAUST Repository

    Noutsi, Bakiza Kamal; Gratton, Enrico; Chaieb, Saharoui

    2016-01-01

    Cell membrane is made up of a complex structure of lipids and proteins that diffuse laterally giving rise to what we call membrane fluidity. During cellular development, such as differentiation cell membranes undergo dramatic fluidity changes induced by proteins such as ARC and Cofilin among others. In this study we used the generalized polarization (GP) property of fluorescent probe Laurdan using two-photon microscopy to determine membrane fluidity as a function of time and for various cell lines. A low GP value corresponds to a higher fluidity and a higher GP value is associated with a more rigid membrane. Four different cell lines were monitored such as hN2, NIH3T3, HEK293 and L6 cells. Membrane fluidity was measured at 12h, 72h and 92 h. Our results show significant changes in membrane fluidity among all cell types at different time points. GP values tend to increase significantly within 92 h in hN2 cells and 72 h in NIH3T3 cells and only at 92 h in HEK293 cells. L6 showed a marked decrease in membrane fluidity at 72 h and starts to increase at 92 h. As expected, NIH3T3 cells have more rigid membrane at earlier time points. On the other hand, neurons tend to have the highest membrane fluidity at early time points emphasizing its correlation with plasticity and the need for this malleability during differentiation. This study sheds light on the involvement of membrane fluidity during neuronal differentiation and development of other cell lines.

  7. Assessment of Membrane Fluidity Fluctuations during Cellular Development Reveals Time and Cell Type Specificity

    KAUST Repository

    Noutsi, Bakiza Kamal

    2016-06-30

    Cell membrane is made up of a complex structure of lipids and proteins that diffuse laterally giving rise to what we call membrane fluidity. During cellular development, such as differentiation cell membranes undergo dramatic fluidity changes induced by proteins such as ARC and Cofilin among others. In this study we used the generalized polarization (GP) property of fluorescent probe Laurdan using two-photon microscopy to determine membrane fluidity as a function of time and for various cell lines. A low GP value corresponds to a higher fluidity and a higher GP value is associated with a more rigid membrane. Four different cell lines were monitored such as hN2, NIH3T3, HEK293 and L6 cells. Membrane fluidity was measured at 12h, 72h and 92 h. Our results show significant changes in membrane fluidity among all cell types at different time points. GP values tend to increase significantly within 92 h in hN2 cells and 72 h in NIH3T3 cells and only at 92 h in HEK293 cells. L6 showed a marked decrease in membrane fluidity at 72 h and starts to increase at 92 h. As expected, NIH3T3 cells have more rigid membrane at earlier time points. On the other hand, neurons tend to have the highest membrane fluidity at early time points emphasizing its correlation with plasticity and the need for this malleability during differentiation. This study sheds light on the involvement of membrane fluidity during neuronal differentiation and development of other cell lines.

  8. Analysis performance of proton exchange membrane fuel cell (PEMFC)

    Science.gov (United States)

    Mubin, A. N. A.; Bahrom, M. H.; Azri, M.; Ibrahim, Z.; Rahim, N. A.; Raihan, S. R. S.

    2017-06-01

    Recently, the proton exchange membrane fuel cell (PEMFC) has gained much attention to the technology of renewable energy due to its mechanically ideal and zero emission power source. PEMFC performance reflects from the surroundings such as temperature and pressure. This paper presents an analysis of the performance of the PEMFC by developing the mathematical thermodynamic modelling using Matlab/Simulink. Apart from that, the differential equation of the thermodynamic model of the PEMFC is used to explain the contribution of heat to the performance of the output voltage of the PEMFC. On the other hand, the partial pressure equation of the hydrogen is included in the PEMFC mathematical modeling to study the PEMFC voltage behaviour related to the input variable input hydrogen pressure. The efficiency of the model is 33.8% which calculated by applying the energy conversion device equations on the thermal efficiency. PEMFC’s voltage output performance is increased by increasing the hydrogen input pressure and temperature.

  9. Meninges: from protective membrane to stem cell niche.

    Science.gov (United States)

    Decimo, Ilaria; Fumagalli, Guido; Berton, Valeria; Krampera, Mauro; Bifari, Francesco

    2012-01-01

    Meninges are a three tissue membrane primarily known as coverings of the brain. More in depth studies on meningeal function and ultrastructure have recently changed the view of meninges as a merely protective membrane. Accurate evaluation of the anatomical distribution in the CNS reveals that meninges largely penetrate inside the neural tissue. Meninges enter the CNS by projecting between structures, in the stroma of choroid plexus and form the perivascular space (Virchow-Robin) of every parenchymal vessel. Thus, meninges may modulate most of the physiological and pathological events of the CNS throughout the life. Meninges are present since the very early embryonic stages of cortical development and appear to be necessary for normal corticogenesis and brain structures formation. In adulthood meninges contribute to neural tissue homeostasis by secreting several trophic factors including FGF2 and SDF-1. Recently, for the first time, we have identified the presence of a stem cell population with neural differentiation potential in meninges. In addition, we and other groups have further described the presence in meninges of injury responsive neural precursors. In this review we will give a comprehensive view of meninges and their multiple roles in the context of a functional network with the neural tissue. We will highlight the current literature on the developmental feature of meninges and their role in cortical development. Moreover, we will elucidate the anatomical distribution of the meninges and their trophic properties in adult CNS. Finally, we will emphasize recent evidences suggesting the potential role of meninges as stem cell niche harbouring endogenous precursors that can be activated by injury and are able to contribute to CNS parenchymal reaction.

  10. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  11. Polymer anion-selective membranes for electrolytic splitting of water. Part II: enhancement of ionic conductivity and performance under conditions of alkaline water electrolysis

    Czech Academy of Sciences Publication Activity Database

    Hnát, J.; Paidar, M.; Schauer, Jan; Žitka, Jan; Bouzek, K.

    2012-01-01

    Roč. 42, č. 8 (2012), s. 545-554 ISSN 0021-891X R&D Projects: GA MŠk(CZ) 7E08005 EU Projects: European Commission(XE) 212903 - WELTEMP Institutional research plan: CEZ:AV0Z40500505 Keywords : water electrolysis * alkaline environment * polymer electrolyte Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.836, year: 2012

  12. Crosslinked wholly aromatic polyether membranes based on quinoline derivatives and their application in high temperature polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Kallitsis, K. J.; Nannou, R.; Andreopoulou, A. K.; Daletou, M. K.; Papaioannou, D.; Neophytides, S. G.; Kallitsis, J. K.

    2018-03-01

    An AB type difunctional quinoline based monomer bearing a pentafluorophenyl unit combined with a phenol functionality is being synthesized and homopolymerized to create linear aromatic polyethers as polymer electrolytes for HT-PEM FCs applications. Several conditions are tested for the optimized synthesis of the monomer and homopolymer. Additionally, covalent crosslinking through aromatic polyether bond formation enables the creation of wholly aromatic crosslinked polymeric electrolyte membranes. More specifically, the perfluorophenyl units are crosslinked with other hydroxyl end functionalized moieties, providing membranes with enhanced chemical and mechanical properties that are moreover easily doped with phosphoric acid even at ambient temperatures. All membranes are evaluated for their structural and thermal characteristics and their doping ability with phosphoric acid. Selected crosslinked membranes are further tested in terms of their single cell performance at the temperature range 160 °C-200 °C showing promising performance and high conductivity values even up to 0.2 S cm-1 in some cases.

  13. Nanoporous gold membranes: From morphological control to fuel cell catalysis

    Science.gov (United States)

    Ding, Yi

    stable, low Pt usage, and better tolerance to CO poisoning. We incorporated it as a membrane electrode into a working proton exchange membrane fuel cells (PEMFC). Preliminary results show that Pt/NPG has very good fuel cell performance at a very low platinum loading.

  14. The next generation fuel cells: anion exchange membrane fuel cells (AEMFC)

    International Nuclear Information System (INIS)

    Tauqir, A.; Zahoor, S.

    2013-01-01

    Many environmentally friendly alternatives (solar, wind, hydroelectric, and geothermal power) can only be used in particular environments. In contrast, fuel cells can have near-zero emissions, are quiet and efficient, and can work in any environment where the temperature is lower than the cell's operating temperature. Among various types of fuel cells, the AEMFC is the most recent one and has advantages such as excellent performance compared to other candidate fuel cells due to its active O/sub 2/ electrode kinetics and flexibility to use a wide range of electro-catalysts such as silver and nickels contrary to expensive one (Platinum) required for proton exchange membrane fuel cell (PEMFC). Anion exchange membrane (AEM) is a crucial part in AEMFC, determining durability and electrochemical performances of membrane electrode assembly (MEA). The role of an AEM is to conduct hydroxyl ions from cathode to anode. If this conduction is not sufficiently high and selective, the corresponding fuel cell will not find any practical application. One of the major problems associated with AEMFC is much lower conductivities of anion compare to proton conductivity in PEMFCs, even upon similar working condition. Thus AEMs is only practical, if it is chemically and mechanically stable against severe basic operation conditions and highly hydroxyl ions conductive. The conventional AEMs based on animated aliphatic and aromatic hydrocarbon or even fluorinated polymers tend to be attacked by hydroxyl ions, causing the degradation during operation is strongly basic conditions. (author)

  15. Sulfonated carbon black-based composite membranes for fuel cell ...

    Indian Academy of Sciences (India)

    the properties of the composite membranes with the addition of S–C particles at high concentrations due to the .... metry and nuclear magnetic resonance that assured no sol- ... BT-512 BekkTech membrane test system at varying relative.

  16. Lipid-linked cell wall precursors regulate membrane association of bacterial actin MreB

    OpenAIRE

    Schirner, Kathrin; Eun, Ye-Jin; Dion, Mike; Luo, Yun; Helmann, John D.; Garner, Ethan C.; Walker, Suzanne

    2014-01-01

    Summary The bacterial actin homolog MreB, which is critical for rod shape determination, forms filaments that rotate around the cell width on the inner surface of the cytoplasmic membrane. What determines filament association with the membranes or with other cell wall elongation proteins is not known. Using specific chemical and genetic perturbations while following MreB filament motion, we find that MreB membrane association is an actively regulated process that depends on the presence of li...

  17. Membrane fusion-competent virus-like proteoliposomes and proteinaceous supported bilayers made directly from cell plasma membranes.

    Science.gov (United States)

    Costello, Deirdre A; Hsia, Chih-Yun; Millet, Jean K; Porri, Teresa; Daniel, Susan

    2013-05-28

    Virus-like particles are useful materials for studying virus-host interactions in a safe manner. However, the standard production of pseudovirus based on the vesicular stomatitis virus (VSV) backbone is an intricate procedure that requires trained laboratory personnel. In this work, a new strategy for creating virus-like proteoliposomes (VLPLs) and virus-like supported bilayers (VLSBs) is presented. This strategy uses a cell blebbing technique to induce the formation of nanoscale vesicles from the plasma membrane of BHK cells expressing the hemagglutinin (HA) fusion protein of influenza X-31. These vesicles and supported bilayers contain HA and are used to carry out single particle membrane fusion events, monitored using total internal reflection fluorescence microscopy. The results of these studies show that the VLPLs and VLSBs contain HA proteins that are fully competent to carry out membrane fusion, including the formation of a fusion pore and the release of fluorophores loaded into vesicles. This new strategy for creating spherical and planar geometry virus-like membranes has many potential applications. VLPLs could be used to study fusion proteins of virulent viruses in a safe manner, or they could be used as therapeutic delivery particles to transport beneficial proteins coexpressed in the cells to a target cell. VLSBs could facilitate high throughput screening of antiviral drugs or pathogen-host cell interactions.

  18. Valproic acid induces hair regeneration in murine model and activates alkaline phosphatase activity in human dermal papilla cells.

    Directory of Open Access Journals (Sweden)

    Soung-Hoon Lee

    Full Text Available Alopecia is the common hair loss problem that can affect many people. However, current therapies for treatment of alopecia are limited by low efficacy and potentially undesirable side effects. We have identified a new function for valproic acid (VPA, a GSK3β inhibitor that activates the Wnt/β-catenin pathway, to promote hair re-growth in vitro and in vivo.Topical application of VPA to male C3H mice critically stimulated hair re-growth and induced terminally differentiated epidermal markers such as filaggrin and loricrin, and the dermal papilla marker alkaline phosphatase (ALP. VPA induced ALP in human dermal papilla cells by up-regulating the Wnt/β-catenin pathway, whereas minoxidil (MNX, a drug commonly used to treat alopecia, did not significantly affect the Wnt/β-catenin pathway. VPA analogs and other GSK3β inhibitors that activate the Wnt/β-catenin pathway such as 4-phenyl butyric acid, LiCl, and BeCl(2 also exhibited hair growth-promoting activities in vivo. Importantly, VPA, but not MNX, successfully stimulate hair growth in the wounds of C3H mice.Our findings indicate that small molecules that activate the Wnt/β-catenin pathway, such as VPA, can potentially be developed as drugs to stimulate hair re-growth.

  19. Increased phorbol 12,13-dibutyrate (PDBu) receptor function associated with sickle red cell membrane ghosts

    International Nuclear Information System (INIS)

    Ramachandran, M.; Nair, C.N.; Abraham, E.C.

    1987-01-01

    The biological receptor for tumor-promoting phorbol esters has been identified as the Ca 2+ /phospholipid dependent enzyme, protein kinase C. In the red cell, this enzyme is mainly cytosolic but becomes translocated to the membrane if the cellular Ca 2+ is allowed to rise. Since cellular Ca 2+ in sickle red cells is high, it was reasoned that this enzyme may become more membrane-bound. In fact, the authors noticed a four-fold increase in the binding of 3 H-PDBu by membrane ghosts isolated from sickle red cells compared to normal red cells (pmoles PDBu bound/mg protein; normal = 0.3 vs sickle cell = 1.4). Attempts to assay the enzyme directly as phospholipid-activated 32 P incorporation into the acid-precipitable membrane proteins also indicated a two-fold increase in the radiolabelling of sickle cell membrane ghosts. Autophosphorylation of membrane proteins and analysis of the phosphorylation profile by SDS-PAGE and autoradiography revealed phosphorylation predominantly of bands 3, 4.1 and 4.9 which are known protein kinase C substrates for the red cell enzyme. The increased membrane-associated protein kinase C in sickle red cells may have a bearing on the altered membrane properties reported in this condition

  20. Membrane potential and ion transport in lung epithelial type II cells

    International Nuclear Information System (INIS)

    Gallo, R.L.

    1986-01-01

    The alveolar type II pneumocyte is critically important to the function and maintenance of pulmonary epithelium. To investigate the nature of the response of type II cells to membrane injury, and describe a possible mechanism by which these cells regulate surfactant secretion, the membrane potential of isolated rabbit type II cells was characterized. This evaluation was accomplished by measurements of the accumulation of the membrane potential probes: [ 3 H]triphenylmethylphosphonium ([ 3 H]TPMP + ), rubidium 86, and the fluorescent dye DiOC 5 . A compartmental analysis of probe uptake into mitochondrial, cytoplasmic, and non-membrane potential dependent stores was made through the use of selective membrane depolarizations with carbonycyanide M-chlorophenylhydrazone (CCCP), and lysophosphatidylcholine (LPC). These techniques and population analysis with flow cytometry, permitted the accurate evaluation of type II cell membrane potential under control conditions and under conditions which stimulated cell activity. Further analysis of ion transport by cells exposed to radiation or adrenergic stimulation revealed a common increase in Na + /K + ATPase activity, and an increase in sodium influx across the plasma membrane. This sodium influx was found to be a critical step in the initiation of surfactant secretion. It is concluded that radiation exposure as well as other pulmonary toxicants can directly affect the membrane potential and ionic regulation of type II cells. Ion transport, particularly of sodium, plays an important role in the regulation of type II cell function

  1. Technological aspects in synthesis and characterization of proton conducting polyetheretherketone (PEEK) membranes for fuel cell applications.

    CSIR Research Space (South Africa)

    Vaivars, G

    2009-08-01

    Full Text Available The research on ion-exchange membranes has grown considerably in recent years with the growing interest in fuel cell technology for the automotive and portable applications. The requirements for a fuel cell membrane are the following: high chemical...

  2. Nafion®/H-ZSM-5 composite membranes with superior performance for direct methanol fuel cells

    NARCIS (Netherlands)

    Yildirim, M.H.; Curos, Anna Roca; Motuzas, Julius; Motuzas, J.; Julbe, Anne; Stamatialis, Dimitrios; Wessling, Matthias

    2009-01-01

    Solution cast composite direct methanol fuel cell membranes (DEZ) based on DE2020 Nafion® dispersion and in-house prepared H-ZSM-5 zeolites with different Si/Al ratios were prepared and thoroughly characterized for direct methanol fuel cell (DMFC) applications. All composite membranes have indeed

  3. Microdomains in the membrane landscape shape antigen-presenting cell function

    NARCIS (Netherlands)

    Zuidscherwoude, M.; Winde, C.M. de; Cambi, A.; Spriel, A.B. van

    2014-01-01

    The plasma membrane of immune cells is a highly organized cell structure that is key to the initiation and regulation of innate and adaptive immune responses. It is well-established that immunoreceptors embedded in the plasma membrane have a nonrandom spatial distribution that is important for

  4. Pharmacological targeting of membrane rigidity: implications on cancer cell migration and invasion

    International Nuclear Information System (INIS)

    Braig, Simone; Stoiber, Katharina; Zahler, Stefan; Vollmar, Angelika M

    2015-01-01

    The invasive potential of cancer cells strongly depends on cellular stiffness, a physical quantity that is not only regulated by the mechanical impact of the cytoskeleton but also influenced by the membrane rigidity. To analyze the specific role of membrane rigidity in cancer progression, we treated cancer cells with the Acetyl-CoA carboxylase inhibitor Soraphen A and revealed an alteration of the phospholipidome via mass spectrometry. Migration, invasion, and cell death assays were employed to relate this alteration to functional consequences, and a decrease of migration and invasion without significant impact on cell death has been recorded. Fourier fluctuation analysis of giant plasma membrane vesicles showed that Soraphen A increases membrane rigidity of carcinoma cell membranes. Mechanical measurements of the creep deformation response of whole intact cells were performed using the optical stretcher. The increase in membrane rigidity was observed in one cell line without changing the creep deformation response indicating no restructuring of the cytoskeleton. These data indicate that the increase of membrane rigidity alone is sufficient to inhibit invasiveness of cancer cells, thus disclosing the eminent role of membrane rigidity in migratory processes. (paper)

  5. (poly)Phosphoinositide phosphorylation is a marker for plasma membrane in Friend erythroleukaemic cells

    NARCIS (Netherlands)

    Rawyler, A.J.; Roelofsen, B.; Wirtz, K.W.A.; Kamp, J.A.F. op den

    1982-01-01

    Upon subcellular fractionation of (murine) Friend erythroleukaemic cells (FELCs), purified plasma membranes were identified by their high enrichment in specific marker enzymes and typical plasma membrane lipids. When FELCs were incubated for short periods with 32Pi before cell fractionation, the

  6. Normal chemotaxis in Dictyostelium discoideum cells with a depolarized plasma membrane potential

    NARCIS (Netherlands)

    Duijn, Bert van; Vogelzang, Sake A.; Ypey, Dirk L.; Molen, Loek G. van der; Haastert, Peter J.M. van

    1990-01-01

    We examined a possible role for the plasma membrane potential in signal transduction during cyclic AMP-induced chemotaxis in the cellular slime mold Dictyostelium discoideum. Chemotaxis, cyclic GMP and cyclic AMP responses in cells with a depolarized membrane potential were measured. Cells can be

  7. Barodiffusion phenomena at active transport of na+ and K+ ions through the cell membrane

    International Nuclear Information System (INIS)

    Khrapijchuk, G.V.; Chalyi, A.V.; Nurishchenko, N.Je.

    2010-01-01

    The influence of ultrasound as the significant motive force of barodiffusion phenomena at the processes of active transport of Na + and K + ions through the cell membrane is considered. The dependence of membrane potential is theoretically estimated at active transport of natrium and potassium ions on the ultrasound intensity and pressure overfall between external and internal medium of the cell.

  8. Low stoichiometry operation of a proton exchange membrane fuel cell employing the interdigitated flow field

    DEFF Research Database (Denmark)

    Berning, Torsten; Kær, Søren Knudsen

    2012-01-01

    A multiphase fuel cell model based on computational fluid dynamics is used to investigate the possibility of operating a proton exchange membrane fuel cell at low stoichiometric flow ratios (ξ gases. A case study...

  9. Investigation of dominant loss mechanisms in low-temperature polymer electrolyte membrane fuel cells

    OpenAIRE

    Gerteisen, D.

    2010-01-01

    This thesis deals with the analysis of dominant loss mechanisms in direct methanol fuel cells (DMFC) and hydrogen fed polymer electrolyte membrane fuel cells (PEFC) by means of experimental characterization and modeling work.

  10. Enhanced biogas production from penicillin bacterial residue by thermal-alkaline pretreatment

    International Nuclear Information System (INIS)

    Zhong, Weizhang; Li, Guixia; Gao, Yan; Li, Zaixing; Geng, Xiaoling; Li, Yubing; Yang, Jingliang; Zhou, Chonghui

    2015-01-01

    In this study, the orthogonal experimental design was used to determine the optimum conditions for the effect of thermal alkaline; pretreatment on the anaerobic digestion of penicillin bacterial residue. The biodegradability of the penicillin; bacterial residue was evaluated by biochemical methane potential tests in laboratory. The optimum values of temperature,; alkali concentration, pretreatment time and moisture content for the thermal-alkaline pretreatment were determined as; 70 °C, 6% (w/v), 30 min, and 85%, respectively. Thermal-alkaline pretreatment could significantly enhance the soluble; chemical oxygen demand solubilization, the suspended solid solubilization and the biodegradability. Biogas production; was enhanced by the thermal-alkaline pretreatment, probably as a result of the breakdown of cell walls and membranes of; micro-organisms, which may facilitate the contact between organic molecules and anaerobic microorganisms.; Keywords: penicillin bacterial residue; anaerobic digestion; biochemical methane potential tests; pretreatment

  11. Kinetic comparison of tissue non-specific and placental human alkaline phosphatases expressed in baculovirus infected cells: application to screening for Down's syndrome

    Science.gov (United States)

    Denier, Colette C; Brisson-Lougarre, Andrée A; Biasini, Ghislaine G; Grozdea, Jean J; Fournier, Didier D

    2002-01-01

    Background In humans, there are four alkaline phosphatases, and each form exibits a characteristic pattern of tissue distribution. The availability of an easy method to reveal their activity has resulted in large amount of data reporting correlations between variations in activity and illnesses. For example, alkaline phosphatase from neutrophils of mothers pregnent with a trisomy 21 fetus (Down's syndrome) displays significant differences both in its biochemical and immunological properties, and in its affinity for some specific inhibitors. Results To analyse these differences, the biochemical characteristics of two isozymes (non specific and placental alkaline phosphatases) were expressed in baculovirus infected cells. Comparative analysis of the two proteins allowed us to estimate the kinetic constants of denaturation and sensitivity to two inhibitors (L-p-bromotetramisole and thiophosphate), allowing better discrimination between the two enzymes. These parameters were then used to estimate the ratio of the two isoenzymes in neutrophils of pregnant mothers with or without a trisomy 21 fetus. It appeared that the placental isozyme represented 13% of the total activity of neutrophils of non pregnant women. This proportion did not significantly increase with normal pregnancy. By contrast, in pregnancies with trisomy 21 fetus, the proportion reached 60–80% of activity. Conclusion Over-expression of the placental isozyme compared with the tissue-nonspecific form in neutrophils of mother with a trisomy 21 fetus may explain why the characteristics of the alkaline phosphatase in these cells is different from normal. Application of this knowledge could improve the potential of using alkaline phosphatase measurements to screen for Down's syndrome. PMID:11818032

  12. Kinetic comparison of tissue non-specific and placental human alkaline phosphatases expressed in baculovirus infected cells: application to screening for Down's syndrome

    Directory of Open Access Journals (Sweden)

    Grozdea Jean J

    2002-01-01

    Full Text Available Abstract Background In humans, there are four alkaline phosphatases, and each form exibits a characteristic pattern of tissue distribution. The availability of an easy method to reveal their activity has resulted in large amount of data reporting correlations between variations in activity and illnesses. For example, alkaline phosphatase from neutrophils of mothers pregnent with a trisomy 21 fetus (Down's syndrome displays significant differences both in its biochemical and immunological properties, and in its affinity for some specific inhibitors. Results To analyse these differences, the biochemical characteristics of two isozymes (non specific and placental alkaline phosphatases were expressed in baculovirus infected cells. Comparative analysis of the two proteins allowed us to estimate the kinetic constants of denaturation and sensitivity to two inhibitors (L-p-bromotetramisole and thiophosphate, allowing better discrimination between the two enzymes. These parameters were then used to estimate the ratio of the two isoenzymes in neutrophils of pregnant mothers with or without a trisomy 21 fetus. It appeared that the placental isozyme represented 13% of the total activity of neutrophils of non pregnant women. This proportion did not significantly increase with normal pregnancy. By contrast, in pregnancies with trisomy 21 fetus, the proportion reached 60–80% of activity. Conclusion Over-expression of the placental isozyme compared with the tissue-nonspecific form in neutrophils of mother with a trisomy 21 fetus may explain why the characteristics of the alkaline phosphatase in these cells is different from normal. Application of this knowledge could improve the potential of using alkaline phosphatase measurements to screen for Down's syndrome.

  13. Electrodeposited gold nanoparticles on carbon nanotube-textile: Anode material for glucose alkaline fuel cells

    KAUST Repository

    Pasta, Mauro; Hu, Liangbing; La Mantia, Fabio; Cui, Yi

    2012-01-01

    In the present paper we propose a new anode material for glucose-gluconate direct oxidation fuel cells prepared by electrodepositing gold nanoparticles onto a conductive textile made by conformally coating single walled carbon nanotubes (SWNT) on a polyester textile substrate. The electrodeposition conditions were optimized in order to achieve a uniform distribution of gold nanoparticles in the 3D porous structure of the textile. On the basis of previously reported studies, the reaction conditions (pH, electrolyte composition and glucose concentration) were tuned in order to achieve the highest oxidation rate, selectively oxidizing glucose to gluconate. The electrochemical characterization was carried out by means of cyclic voltammetry. © 2012 Elsevier B.V. All rights reserved.

  14. Electrodeposited gold nanoparticles on carbon nanotube-textile: Anode material for glucose alkaline fuel cells

    KAUST Repository

    Pasta, Mauro

    2012-06-01

    In the present paper we propose a new anode material for glucose-gluconate direct oxidation fuel cells prepared by electrodepositing gold nanoparticles onto a conductive textile made by conformally coating single walled carbon nanotubes (SWNT) on a polyester textile substrate. The electrodeposition conditions were optimized in order to achieve a uniform distribution of gold nanoparticles in the 3D porous structure of the textile. On the basis of previously reported studies, the reaction conditions (pH, electrolyte composition and glucose concentration) were tuned in order to achieve the highest oxidation rate, selectively oxidizing glucose to gluconate. The electrochemical characterization was carried out by means of cyclic voltammetry. © 2012 Elsevier B.V. All rights reserved.

  15. Hydrostatic pressure decreases membrane fluidity and lipid desaturase expression in chondrocyte progenitor cells.

    Science.gov (United States)

    Montagne, Kevin; Uchiyama, Hiroki; Furukawa, Katsuko S; Ushida, Takashi

    2014-01-22

    Membrane biomechanical properties are critical in modulating nutrient and metabolite exchange as well as signal transduction. Biological membranes are predominantly composed of lipids, cholesterol and proteins, and their fluidity is tightly regulated by cholesterol and lipid desaturases. To determine whether such membrane fluidity regulation occurred in mammalian cells under pressure, we investigated the effects of pressure on membrane lipid order of mouse chondrogenic ATDC5 cells and desaturase gene expression. Hydrostatic pressure linearly increased membrane lipid packing and simultaneously repressed lipid desaturase gene expression. We also showed that cholesterol mimicked and cholesterol depletion reversed those effects, suggesting that desaturase gene expression was controlled by the membrane physical state itself. This study demonstrates a new effect of hydrostatic pressure on mammalian cells and may help to identify the molecular mechanisms involved in hydrostatic pressure sensing in chondrocytes. © 2013 Elsevier Ltd. All rights reserved.

  16. Cat amniotic membrane multipotent cells are nontumorigenic and are safe for use in cell transplantation

    Directory of Open Access Journals (Sweden)

    Vidane AS

    2014-08-01

    Full Text Available Atanasio S Vidane,1 Aline F Souza,1 Rafael V Sampaio,1 Fabiana F Bressan,2 Naira C Pieri,1 Daniele S Martins,2 Flavio V Meirelles,2 Maria A Miglino,1 Carlos E Ambrósio2 1Department of Surgery, Faculty of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil; 2Department of Veterinary Medicine, Faculty of Animal Sciences and Food Engineering, University of São Paulo, São Paulo, Brazil Abstract: Amnion-derived mesenchymal stem cells (AMSCs are multipotent cells with an enhanced ability to differentiate into multiple lineages. AMSCs can be acquired through noninvasive methods, and therefore are exempt from the typical ethical issues surrounding stem cell use. The objective of this study was to isolate and characterize AMSCs from a cat amniotic membrane for future application in regenerative medicine. The cat AMSCs were harvested after mechanical and enzymatic digestion of amnion. In culture medium, the cat AMSCs adhered to a plastic culture dish and displayed a fibroblast-like morphology. Immunophenotyping assays were positive for the mesenchymal stem cell-specific markers CD73 and CD90 but not the hematopoietic markers CD34, CD45, and CD79. Under appropriate conditions, the cat AMSCs differentiated into osteogenic, chondrogenic, and adipogenic cell lineages. One advantage of cat AMSCs was nonteratogenicity, assessed 4 weeks post injection of undifferentiated AMSCs into immunodeficient mice. These findings suggest that cat amniotic membranes may be an important and useful source of mesenchymal stem cells for clinical applications, especially for cell or tissue replacement in chronic and degenerative diseases. Keywords: amnion, cats, cell differentiation, fetal membranes, mesenchymal cells

  17. Increased membrane cholesterol in lymphocytes diverts T-cells toward an inflammatory response.

    Directory of Open Access Journals (Sweden)

    Jacqueline Surls

    Full Text Available Cell signaling for T-cell growth, differentiation, and apoptosis is initiated in the cholesterol-rich microdomains of the plasma membrane known as lipid rafts. Herein, we investigated whether enrichment of membrane cholesterol in lipid rafts affects antigen-specific CD4 T-helper cell functions. Enrichment of membrane cholesterol by 40-50% following squalene administration in mice was paralleled by an increased number of resting CD4 T helper cells in periphery. We also observed sensitization of the Th1 differentiation machinery through co-localization of IL-2Rα, IL-4Rα, and IL-12Rβ2 subunits with GM1 positive lipid rafts, and increased STAT-4 and STAT-5 phosphorylation following membrane cholesterol enrichment. Antigen stimulation or CD3/CD28 polyclonal stimulation of membrane cholesterol-enriched, resting CD4 T-cells followed a path of Th1 differentiation, which was more vigorous in the presence of increased IL-12 secretion by APCs enriched in membrane cholesterol. Enrichment of membrane cholesterol in antigen-specific, autoimmune Th1 cells fostered their organ-specific reactivity, as confirmed in an autoimmune mouse model for diabetes. However, membrane cholesterol enrichment in CD4(+Foxp3(+ T-reg cells did not alter their suppressogenic function. These findings revealed a differential regulatory effect of membrane cholesterol on the function of CD4 T-cell subsets. This first suggests that membrane cholesterol could be a new therapeutic target to modulate the immune functions, and second that increased membrane cholesterol in various physiopathological conditions may bias the immune system toward an inflammatory Th1 type response.

  18. Performance enhancement of polymer electrolyte membrane fuel cells by dual-layered membrane electrode assembly structures with carbon nanotubes.

    Science.gov (United States)

    Jung, Dong-Won; Kim, Jun-Ho; Kim, Se-Hoon; Kim, Jun-Bom; Oh, Eun-Suok

    2013-05-01

    The effect of dual-layered membrane electrode assemblies (d-MEAs) on the performance of a polymer electrolyte membrane fuel cell (PEMFC) was investigated using the following characterization techniques: single cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It has been shown that the PEMFC with d-MEAs has better cell performance than that with typical mono-layered MEAs (m-MEAs). In particular, the d-MEA whose inner layer is composed of multi-walled carbon nanotubes (MWCNTs) showed the best fuel cell performance. This is due to the fact that the d-MEAs with MWCNTs have the highest electrochemical surface area and the lowest activation polarization, as observed from the CV and EIS test.

  19. BENZO[A]PYRENE AND ITS K-REGION DIOL INDUCE DNA DAMAGE IN C3H10T1/2C18 CELLS AS MEASURED BY THE ALKALINE SINGLE CELL GEL (COMET) ASSAY

    Science.gov (United States)

    160. Benzo[a]pyrene and its K-region diol induce DNA damage in C3HlOTl/2Cl8 cells as measured by the alkaline single cell gel (Comet) assay In a continuing series of studies on the genotoxicity ofK-region dihydrodiols of polycyclic aromatic hydrocarbons, we have repo...

  20. Cell membrane and cell junctions in differentiation of preimplanted mouse embryos.

    Science.gov (United States)

    Izquierdo, L; Fernández, S; López, T

    1976-12-01

    Cell membrane and cell junctions in differentiation of preimplanted mouse embryos, (membrana celular y uniones celulares en la diferenciación del embrión de ratón antes de la implantación). Arch. Biol. Med. Exper. 10: 130-134, 1976. The development of cell junctions that seal the peripheral blastomeres could be a decisive step in the differentiation of morulae into blastocysts. The appearance of these junctions is studied by electron microscopy of late morulae and initial blastocysts. Zonulae occludentes as well as impermeability to lanthanum emulsion precedes the appearance of the blastocel and hence might be considered as one of its necessary causes.