WorldWideScience

Sample records for cell membrane integrity

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

    Science.gov (United States)

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

    2016-08-15

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

  2. Double-Staining Method for Differentiation of Morphological Changes and Membrane Integrity of Campylobacter coli Cells

    OpenAIRE

    Alonso, Jose L.; Mascellaro, Salvatore; Moreno, Yolanda; Ferrús, María A.; Hernández, Javier

    2002-01-01

    We developed a double-staining procedure involving NanoOrange dye (Molecular Probes, Eugene, Oreg.) and membrane integrity stains (LIVE/DEAD BacLight kit; Molecular Probes) to show the morphological and membrane integrity changes of Campylobacter coli cells during growth. The conversion from a spiral to a coccoid morphology via intermediary forms and the membrane integrity changes of the C. coli cells can be detected with the double-staining procedure. Our data indicate that young or actively...

  3. Cell membrane integrity in myotonic dystrophy type 1: implications for therapy.

    Directory of Open Access Journals (Sweden)

    Anchel González-Barriga

    Full Text Available Myotonic Dystrophy type 1 (DM1 is a multisystemic disease caused by toxic RNA from a DMPK gene carrying an expanded (CTG•CAGn repeat. Promising strategies for treatment of DM1 patients are currently being tested. These include antisense oligonucleotides and drugs for elimination of expanded RNA or prevention of aberrant binding to RNP proteins. A significant hurdle for preclinical development along these lines is efficient systemic delivery of compounds across endothelial and target cell membranes. It has been reported that DM1 patients show elevated levels of markers of muscle damage or loss of sarcolemmal integrity in their serum and that splicing of dystrophin, an essential protein for muscle membrane structure, is abnormal. Therefore, we studied cell membrane integrity in DM1 mouse models commonly used for preclinical testing. We found that membranes in skeletal muscle, heart and brain were impermeable to Evans Blue Dye. Creatine kinase levels in serum were similar to those in wild type mice and expression of dystrophin protein was unaffected. Also in patient muscle biopsies cell surface expression of dystrophin was normal and calcium-positive fibers, indicating elevated intracellular calcium levels, were only rarely seen. Combined, our findings indicate that cells in DM1 tissues do not display compromised membrane integrity. Hence, the cell membrane is a barrier that must be overcome in future work towards effective drug delivery in DM1 therapy.

  4. Yeast cell wall integrity sensors form specific plasma membrane microdomains important for signalling.

    Science.gov (United States)

    Kock, Christian; Arlt, Henning; Ungermann, Christian; Heinisch, Jürgen J

    2016-09-01

    The cell wall integrity (CWI) pathway of the yeast Saccharomyces cerevisiae relies on the detection of cell surface stress by five sensors (Wsc1, Wsc2, Wsc3, Mid2, Mtl1). Each sensor contains a single transmembrane domain and a highly mannosylated extracellular region, and probably detects mechanical stress in the cell wall or the plasma membrane. We here studied the distribution of the five sensors at the cell surface by using fluorescently tagged variants in conjunction with marker proteins for established membrane compartments. We find that each of the sensors occupies a specific microdomain at the plasma membrane. The novel punctate 'membrane compartment occupied by Wsc1' (MCW) shows moderate overlap with other Wsc-type sensors, but not with those of the Mid-type sensors or other established plasma membrane domains. We further observed that sensor density and formation of the MCW compartment depends on the cysteine-rich head group near the N-terminus of Wsc1. Yet, signalling capacity depends more on the sensor density in the plasma membrane than on clustering within its microcompartment. We propose that the MCW microcompartment provides a quality control mechanism for retaining functional sensors at the plasma membrane to prevent them from endocytosis. PMID:27337501

  5. Yeast cell wall integrity sensors form specific plasma membrane microdomains important for signalling.

    Science.gov (United States)

    Kock, Christian; Arlt, Henning; Ungermann, Christian; Heinisch, Jürgen J

    2016-09-01

    The cell wall integrity (CWI) pathway of the yeast Saccharomyces cerevisiae relies on the detection of cell surface stress by five sensors (Wsc1, Wsc2, Wsc3, Mid2, Mtl1). Each sensor contains a single transmembrane domain and a highly mannosylated extracellular region, and probably detects mechanical stress in the cell wall or the plasma membrane. We here studied the distribution of the five sensors at the cell surface by using fluorescently tagged variants in conjunction with marker proteins for established membrane compartments. We find that each of the sensors occupies a specific microdomain at the plasma membrane. The novel punctate 'membrane compartment occupied by Wsc1' (MCW) shows moderate overlap with other Wsc-type sensors, but not with those of the Mid-type sensors or other established plasma membrane domains. We further observed that sensor density and formation of the MCW compartment depends on the cysteine-rich head group near the N-terminus of Wsc1. Yet, signalling capacity depends more on the sensor density in the plasma membrane than on clustering within its microcompartment. We propose that the MCW microcompartment provides a quality control mechanism for retaining functional sensors at the plasma membrane to prevent them from endocytosis.

  6. Micro direct methanol fuel cell with perforated silicon-plate integrated ionomer membrane

    DEFF Research Database (Denmark)

    Larsen, Jackie Vincent; Dalslet, Bjarke Thomas; Johansson, Anne-Charlotte Elisabeth Birgitta;

    2014-01-01

    This article describes the fabrication and characterization of a silicon based micro direct methanol fuel cell using a Nafion ionomer membrane integrated into a perforated silicon plate. The focus of this work is to provide a platform for micro- and nanostructuring of a combined current collector...

  7. Further Improvement and System Integration of High Temperature Polymer Electrolyte Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Li, Qingfeng; Jensen, Jens Oluf

    The strategic developments of the FURIM are in three steps: (1) further improvement of the high temperature polymer membranes and related materials; (2) development of technological units including fuel cell stack, hydrocarbon reformer and afterburner, that are compatible with the HT-PEMFC; and (3...... hydrocarbon reformer and a catalytic burner are to be developed and integrated with the stack. The key issue of the project is development and improvement of the temperature-resistant polymer membranes with respect to durability, conductivity, mechanical and other properties. For this purpose, basic polymers...

  8. Up against the wall: is yeast cell wall integrity ensured by mechanosensing in plasma membrane microdomains?

    Science.gov (United States)

    Kock, Christian; Dufrêne, Yves F; Heinisch, Jürgen J

    2015-02-01

    Yeast cell wall integrity (CWI) signaling serves as a model of the regulation of fungal cell wall synthesis and provides the basis for the development of antifungal drugs. A set of five membrane-spanning sensors (Wsc1 to Wsc3, Mid2, and Mtl1) detect cell surface stress and commence the signaling pathway upon perturbations of either the cell wall structure or the plasma membrane. We here summarize the latest advances in the structure/function relationship primarily of the Wsc1 sensor and critically review the evidence that it acts as a mechanosensor. The relevance and physiological significance of the information obtained for the function of the other CWI sensors, as well as expected future developments, are discussed.

  9. Microbial responses to membrane cleaning using sodium hypochlorite in membrane bioreactors: Cell integrity, key enzymes and intracellular reactive oxygen species.

    Science.gov (United States)

    Han, Xiaomeng; Wang, Zhiwei; Wang, Xueye; Zheng, Xiang; Ma, Jinxing; Wu, Zhichao

    2016-01-01

    Sodium hypochlorite (NaClO) is a commonly used reagent for membrane cleaning in membrane bioreactors (MBRs), while it, being a kind of disinfectant (oxidant), may impair viability of microbes or even totally inactivate them upon its diffusion into mixed liquor during membrane cleaning. In this study, we systematically examine the effects of NaClO on microorganisms in terms of microbial cell integrity, metabolism behaviours (key enzymes), and intracellular reactive oxygen species (ROS) under various NaClO concentrations. Different proportions of microbial cells in activated sludge were damaged within several minutes dependent on NaClO dosages (5-50 mg/g-SS), and correspondingly organic matters were released to bulk solution. Inhibition of key enzymes involved in organic matter biodegradation, nitrification and denitrification was observed in the presence of NaClO above 1 mg/g-SS, and thus organic matter and nitrogen removal efficiencies were decreased. It was also demonstrated that intracellular ROS production was increased with the NaClO dosage higher than 1 mg/g-SS, which likely induced further damage to microbial cells.

  10. Eugenol alters the integrity of cell membrane and acts against the nosocomial pathogen Proteus mirabilis.

    Science.gov (United States)

    Devi, K Pandima; Sakthivel, R; Nisha, S Arif; Suganthy, N; Pandian, S Karutha

    2013-03-01

    Eugenol, a member of the phenylpropanoids class of chemical compounds, is a clear to pale yellow oily liquid extracted from certain essential oils especially from clove oil, nutmeg, cinnamon, and bay leaf. The antibacterial activity of eugenol and its mechanism of bactericidal action against Proteus mirabilis were evaluated. Treatment with eugenol at their minimum inhibitory concentration [0.125 % (v/v)] and minimum bactericidal concentration [0.25 % (v/v)] reduced the viability and resulted in complete inhibition of P. mirabilis. A strong bactericidal effect on P. mirabilis was also evident, as eugenol inactivated the bacterial population within 30 min exposure. Chemo-attractant property and the observance of highest antibacterial activity at alkaline pH suggest that eugenol can work more effectively when given in vivo. Eugenol inhibits the virulence factors produced by P. mirabilis as observed by swimming motility, swarming behavior and urease activity. It interacts with cellular membrane of P. mirabilis and makes it highly permeable, forming nonspecific pores on plasma membrane, which in turn directs the release of 260 nm absorbing materials and uptake of more crystal violet from the medium into the cells. SDS-polyacrylamide gel, scanning electron microscopy and Fourier transform infrared analysis further proves the disruptive action of eugenol on the plasma membrane of P. mirabilis. The findings reveal that eugenol shows an excellent bactericidal activity against P. mirabilis by altering the integrity of cell membrane. PMID:23444040

  11. High-fat Diet Accelerates Intestinal Tumorigenesis Through Disrupting Intestinal Cell Membrane Integrity

    Science.gov (United States)

    Park, Mi-Young; Kim, Min Young; Seo, Young Rok; Kim, Jong-Sang; Sung, Mi-Kyung

    2016-01-01

    Background: Excess energy supply induces chronic low-grade inflammation in association with oxidative stress in various tissues including intestinal epithelium. The objective of this study was to investigate the effect of high-fat diet (HFD) on intestinal cell membrane integrity and intestinal tumorigenesis in ApcMin/+ mice. Methods: Mice were fed with either normal diet (ND) or HFD for 12 weeks. The number of intestinal tumors were counted and biomarkers of endotoxemia, oxidative stress, and inflammation were determined. Changes in intestinal integrity was measured by fluorescein isothiocyanate (FITC)-dextran penetration and membrane gap junction protein expression. Results: HFD group had significantly higher number of tumors compared to ND group (P < 0.05). Blood total antioxidant capacity was lower in HFD group, while colonic 8-hydroxy-2′-deoxyguanosine level, a marker of oxidative damage, was higher in HFD group compared to that of ND group (P < 0.05). The penetration of FITC-dextran was substantially increased in HFD group (P < 0.05) while the expressions of membrane gap junction proteins including zonula occludens-1, claudin-1, and occludin were lower in HFD group (P < 0.05) compared to those in ND group. Serum concentration of lipopolysaccharide (LPS) receptor (CD14) and colonic toll-like receptor 4 (a LPS receptor) mRNA expression were significantly higher in HFD group than in ND group (P < 0.05), suggesting that significant endotoxemia may occur in HFD group due to the increased membrane permeability. Serum interleukin-6 concentration and myeloperoxidase activity were also higher in HFD group compared to those of ND group (P < 0.05). Conclusions: HFD increases oxidative stress disrupting intestinal gap junction proteins, thereby accelerating membrane permeability endotoxemia, inflammation, and intestinal tumorigenesis. PMID:27390738

  12. Anti-Candida activity of geraniol involves disruption of cell membrane integrity and function.

    Science.gov (United States)

    Sharma, Y; Khan, L A; Manzoor, N

    2016-09-01

    Candidiasis is a major problem in immunocompromised patients. Candida, an opportunistic fungal pathogen, is a major health concern today as conventional drugs are highly toxic with undesirable side effects. Their fungistatic nature is responsible for drug resistance in continuously evolving strains. Geraniol, an acyclic monoterpene alcohol, is a component of several plant essential oils. In the present study, an attempt has been made to understand the antifungal activity of geraniol at the cell membrane level in three Candida species. With an MIC of 30-130μg/mL, this natural compound was fungicidal at concentrations 2×MIC. There was complete suppression of fungal growth at MIC values (growth curves) and encouragingly geraniol is non-toxic even at the concentrations approaching 5×MIC (hemolysis assay). Exposed cells showed altered morphology, wherein the cells appeared either broken or shrivelled up (SEM studies). Significant reduction was seen in ergosterol levels at sub-MIC and glucose-induced H(+) efflux at concentrations>MIC values. Our results suggest that geraniol disrupts cell membrane integrity by interfering with ergosterol biosynthesis and inhibiting the very crucial PM-ATPase. It may hence be used in the management and treatment of both superficial and invasive candidiasis but further studies are required to elaborate its mode of action. PMID:27554866

  13. Hemorrhagic shock impairs myocardial cell volume regulation and membrane integrity in dogs

    Energy Technology Data Exchange (ETDEWEB)

    Horton, J.W.

    1987-06-01

    An in vitro myocardial slice technique was used to quantitate alterations in cell volume regulation and membrane integrity after 2 h or hemorrhagic shock. After in vitro incubation in Krebs-Ringer-phosphate medium containing trace (/sup 14/C)inulin, values (ml H/sub 2/O/g dry wt) for control nonshocked myocardial slices were 4.03 /plus minus/ 0.11 (SE) for total water, 2.16 /plus minus/ 0.07 for inulin impermeable space, and 1.76 /plus minus/ 0.15 for inulin diffusible space. Shocked myocardial slices showed impaired response to cold incubation. After 2 h of in vivo shock, total tissue water, inulin diffusible space, and inulin impermeable space increased significantly for subendocardium, whereas changes in subepicardium parameters were minimal. Shock-induced cellular swelling was accompanied by an increased total tissue sodium, but no change in tissue potassium. Calcium entry blockade in vivo significantly reduced subendocardial total tissue water as compared with shock-untreated dogs. In addition, calcium entry blockade reduced shock-induced increases in inulin diffusible space. In vitro myocardial slice studies confirm alterations in subendocardial membrane integrity after 2 h of in vivo hemorrhagic shock. Shock-induced abnormalities in myocardial cell volume regulation are reduced by calcium entry blockade in vivo.

  14. Further Improvement and System Integration of High Temperature Polymer Electrolyte Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf; Li, Qingfeng

    Polymer electrolyte membrane fuel cell (PEMFC) technology based on Nafion membranes can operate at temperatures around 80°C. The new development in the field is high temperature PEMFC for operation above 100°C, which has been successfully demonstrated through the previous EC Joule III and the 5th...

  15. Further Improvement and System Integration of High Temperature Polymer Electrolyte Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Li, Qingfeng; Jensen, Jens Oluf

    The new development in the field of polymer electrolyte membrane fuel cell (PEMFC) is high temperature PEMFC for operation above 100°C, which has been successfully demonstrated through the previous EC Joule III and the 5th framework programme. New challenges are encountered, bottlenecks for the new...

  16. Effect of integral proteins in the phase stability of a lipid bilayer: Application to raft formation in cell membranes

    Science.gov (United States)

    Gómez, Jordi; Sagués, Francesc; Reigada, Ramon

    2010-04-01

    The existence of lipid rafts is a controversial issue. The affinity of cholesterol for saturated lipids is manifested in macroscopic phase separation in model membranes, and is believed to be the thermodynamic driving force for raft formation. However, there is no clear reason to explain the small (nanometric) size of raft domains in cell membranes. In a recent paper Yethiraj and Weisshaar [Biophys. J. 93, 3113 (2007)] proposed that the effect of neutral integral membrane proteins may prevent from the formation of large lipid domains. In this paper we extend this approach by studying the effect of the protein size, as well as the lipid-protein interaction. Depending on these factors, two different mechanisms for nanodomain stabilization are shown to be possible for static proteins. The application of these results to a biological context is discussed.

  17. Performance analysis of an integrated biomass gasification and PEMFC (proton exchange membrane fuel cell) system: Hydrogen and power generation

    International Nuclear Information System (INIS)

    The PEMFC (proton exchange membrane fuel cell) is expected to play a significant role in next-generation energy systems. Because most hydrogen that is used as a fuel for PEMFCs is derived from the reforming of natural gas, the use of renewable energy sources such as biomass to produce this hydrogen offers a promising alternative. This study is focused on the performance analysis of an integrated biomass gasification and PEMFC system. The combined heat and power generation output of this integrated system is designed for residential applications, taking into account thermal and electrical demands. A flowsheet model of the integrated PEMFC system is developed and employed to analyze its performance with respect to various key operating parameters. A purification process consisting of a water–gas shift reactor and a preferential oxidation reactor is also necessary in order to reduce the concentration of CO in the synthesis gas to below 10 ppm for subsequent use in the PEMFC. The effect of load level on the performance of the PEMFC system is investigated. Based on an electrical load of 5 kW, it is found that the electrical efficiency of the PEMFC integrated system is 22%, and, when waste heat recovery is considered, the total efficiency of the PEMFC system is 51%. - Highlights: • Performance of a biomass gasification and PEMFC integrated system is analyzed. • A flowsheet model of the PEMFC integrated system is developed. • Effect of biomass sources and key parameters on hydrogen and power generation is presented. • The PEMFC integrated system is designed for small-scale power demand. • Effect of load changes on the performance of PEMFC is investigated

  18. Evaluation of an integrated methane autothermal reforming and high-temperature proton exchange membrane fuel cell system

    International Nuclear Information System (INIS)

    The aim of this study was to investigate the performance and efficiency of an integrated autothermal reforming and HT-PEMFC (high-temperature proton exchange membrane fuel cell) system fueled by methane. Effect of the inclusion of a CO (carbon monoxide) removal process on the integrated HT-PEMFC system was considered. An increase in the S/C (steam-to-carbon) ratio and the reformer temperature can enhance the hydrogen fraction while the CO formation reduces with increasing S/C ratio. The fuel processor efficiency of the methane autothermal reformer with a WGS (water gas shift reactor) reactor, as the CO removal process, is higher than that without a WGS reactor. A higher fuel processor efficiency can be obtained when the feed of the autothermal reformer is preheated to the reformer temperature. Regarding the cell performance, the reformate gas from the methane reformer operated at Tin = TR and with a high S/C ratio is suitable for the HT-PEMFC system without a WGS reactor. When considering the HT-PEMFC system with a WGS reactor, the CO poisoning has less significant impact on the cell performance and the system can be operated over a broader range to minimize the required total active area. A WGS reactor is necessary for the methane autothermal reforming and HT-PEMFC integrated system with regard to the system efficiency. - Highlights: • An integrated autothermal reforming and HT-PEMFC system was studied. • The HT-PEMFC system with and without a CO removal process was considered. • Parametric analysis was performed to obtain a high system efficiency. • The HT-PEMFC system with the WGS reactor can be run over a broader range. • The efficiencies of the HT-PEMFC systems without and with a WGS reactor were reported

  19. Effectiveness of heat-integrated methanol steam reformer and polymer electrolyte membrane fuel cell stack systems for portable applications

    Science.gov (United States)

    Lotrič, A.; Sekavčnik, M.; Hočevar, S.

    2014-12-01

    Efficiently combining proton exchange membrane fuel cell (PEMFC) stack with methanol steam reformer (MSR) into a small portable system is still quite a topical issue. Using methanol as a fuel in PEMFC stack includes a series of chemical processes where each proceeds at a unique temperature. In a combined MSR-PEMFC-stack system with integrated auxiliary fuel processors (vaporizer, catalytic combustor, etc.) the processes are both endothermic and exothermic hence their proper thermal integration can help raising the system efficiency. A concept of such fully integrated and compact system is proposed in this study. Three separate systems are designed based on different PEMFC stacks and MSR. Low-temperature (LT) and conventional high-temperature (cHT) PEMFC stack characteristics are based on available data from suppliers. Also, a novel high-temperature (nHT) PEMFC stack is proposed because its operating temperature coincides with that of MSR. A comparative study of modelled systems is performed using a mass and energy balances zero-dimensional model, which is interdependently coupled to a physical model based on finite element method (FEM). The results indicate that a system with nHT PEMFC stack is feasible and has the potential to reach higher system efficiencies than systems with LT or cHT PEMFC stacks.

  20. High Efficiency Solar Integrated Roof Membrane Product

    Energy Technology Data Exchange (ETDEWEB)

    Partyka, Eric; Shenoy, Anil

    2013-05-15

    This project was designed to address the Solar Energy Technology Program objective, to develop new methods to integrate photovoltaic (PV) cells or modules within a building-integrated photovoltaic (BIPV) application that will result in lower installed cost as well as higher efficiencies of the encapsulated/embedded PV module. The technology assessment and development focused on the evaluation and identification of manufacturing technologies and equipment capable of producing such low-cost, high-efficiency, flexible BIPV solar cells on single-ply roofing membranes.

  1. Analysis of the control structures for an integrated ethanol processor for proton exchange membrane fuel cell systems

    Energy Technology Data Exchange (ETDEWEB)

    Biset, S.; Nieto Deglioumini, L.; Basualdo, M. [GIAIP-CIFASIS (UTN-FRRo-CONICET-UPCAM-UNR), BV. 27 de Febrero 210 Bis, S2000EZP Rosario (Argentina); Garcia, V.M.; Serra, M. [Institut de Robotica i Informatica Industrial, C. Llorens i Artigas 4-6, 08028 Barcelona (Spain)

    2009-07-01

    The aim of this work is to investigate which would be a good preliminary plantwide control structure for the process of Hydrogen production from bioethanol to be used in a proton exchange membrane (PEM) accounting only steady-state information. The objective is to keep the process under optimal operation point, that is doing energy integration to achieve the maximum efficiency. Ethanol, produced from renewable feedstocks, feeds a fuel processor investigated for steam reforming, followed by high- and low-temperature shift reactors and preferential oxidation, which are coupled to a polymeric fuel cell. Applying steady-state simulation techniques and using thermodynamic models the performance of the complete system with two different control structures have been evaluated for the most typical perturbations. A sensitivity analysis for the key process variables together with the rigorous operability requirements for the fuel cell are taking into account for defining acceptable plantwide control structure. This is the first work showing an alternative control structure applied to this kind of process. (author)

  2. Analysis of the control structures for an integrated ethanol processor for proton exchange membrane fuel cell systems

    Science.gov (United States)

    Biset, S.; Nieto Deglioumini, L.; Basualdo, M.; Garcia, V. M.; Serra, M.

    The aim of this work is to investigate which would be a good preliminary plantwide control structure for the process of Hydrogen production from bioethanol to be used in a proton exchange membrane (PEM) accounting only steady-state information. The objective is to keep the process under optimal operation point, that is doing energy integration to achieve the maximum efficiency. Ethanol, produced from renewable feedstocks, feeds a fuel processor investigated for steam reforming, followed by high- and low-temperature shift reactors and preferential oxidation, which are coupled to a polymeric fuel cell. Applying steady-state simulation techniques and using thermodynamic models the performance of the complete system with two different control structures have been evaluated for the most typical perturbations. A sensitivity analysis for the key process variables together with the rigorous operability requirements for the fuel cell are taking into account for defining acceptable plantwide control structure. This is the first work showing an alternative control structure applied to this kind of process.

  3. Ophiobolin A from Bipolaris oryzae Perturbs Motility and Membrane Integrities of Porcine Sperm and Induces Cell Death on Mammalian Somatic Cell Lines

    Directory of Open Access Journals (Sweden)

    Ottó Bencsik

    2014-09-01

    Full Text Available Bipolaris oryzae is a phytopathogenic fungus causing a brown spot disease in rice, and produces substance that strongly perturbs motility and membrane integrities of boar spermatozoa. The substance was isolated from the liquid culture of the fungal strain using extraction and a multi-step semi-preparative HPLC procedures. Based on the results of mass spectrometric and 2D NMR techniques, the bioactive molecule was identified as ophiobolin A, a previously described sesterterpene-type compound. The purified ophiobolin A exhibited strong motility inhibition and viability reduction on boar spermatozoa. Furthermore, it damaged the sperm mitochondria significantly at sublethal concentration by the dissipation of transmembrane potential in the mitochondrial inner membrane, while the plasma membrane permeability barrier remained intact. The study demonstrated that the cytotoxicity of ophiobolin A toward somatic cell lines is higher by 1–2 orders of magnitude compared to other mitochondriotoxic mycotoxins, and towards sperm cells unique by replacing the progressive motility by shivering tail beating at low exposure concentration.

  4. Cell Membrane Integrity in Myotonic Dystrophy Type 1: Implications for Therapy

    OpenAIRE

    Anchel González-Barriga; Julia Kranzen; Croes, Huib J. E.; Suzanne Bijl; van den Broek, Walther J. A. A.; van Kessel, Ingeborg D. G.; Van Engelen, Baziel G M; Judith C T van Deutekom; Bé Wieringa; Susan A M Mulders; Derick G Wansink

    2015-01-01

    Myotonic Dystrophy type 1 (DM1) is a multisystemic disease caused by toxic RNA from a DMPK gene carrying an expanded (CTG*CAG)n repeat. Promising strategies for treatment of DM1 patients are currently being tested. These include antisense oligonucleotides and drugs for elimination of expanded RNA or prevention of aberrant binding to RNP proteins. A significant hurdle for preclinical development along these lines is efficient systemic delivery of compounds across endothelial and target cell me...

  5. Characterisation of micro direct methanol fuel cells with silicon plate supported integrated ionomer membranes

    DEFF Research Database (Denmark)

    Larsen, Jackie Vincent; Dalslet, Bjarke Thomas; Kallesee, C.;

    2013-01-01

    This work deals with the investigation and fabrication of Micro Direct Methanol Fuel Cells (μDMFC). They are investigated as a possible alternative for zinc-air batteries in small size consumer devices such as hearing aids. In such devices the conventional rechargeable batteries such as lithium......-ion batteries have insufficiently low energy density in the range 240 Wh/L to 300 Wh/L Methanol is a promising fuel for such devices due to the high energy density, with pure methanol having an energy density of 4400 Wh/L. Using a liquid fuel also allows refueling, which can be achieved much faster than battery...

  6. 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.

  7. 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

  8. Cell Membrane Softening in Cancer Cells

    Science.gov (United States)

    Schmidt, Sebastian; Händel, Chris; Käs, Josef

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

  9. Linking Cellular Mechanisms to Behavior: Entorhinal Persistent Spiking and Membrane Potential Oscillations May Underlie Path Integration, Grid Cell Firing, and Episodic Memory

    Directory of Open Access Journals (Sweden)

    Michael E. Hasselmo

    2008-01-01

    Full Text Available The entorhinal cortex plays an important role in spatial memory and episodic memory functions. These functions may result from cellular mechanisms for integration of the afferent input to entorhinal cortex. This article reviews physiological data on persistent spiking and membrane potential oscillations in entorhinal cortex then presents models showing how both these cellular mechanisms could contribute to properties observed during unit recording, including grid cell firing, and how they could underlie behavioural functions including path integration. The interaction of oscillations and persistent firing could contribute to encoding and retrieval of trajectories through space and time as a mechanism relevant to episodic memory.

  10. Bilayer-thickness-mediated interactions between integral membrane proteins

    CERN Document Server

    Kahraman, Osman; Klug, William S; Haselwandter, Christoph A

    2016-01-01

    Hydrophobic thickness mismatch between integral membrane proteins and the surrounding lipid bilayer can produce lipid bilayer thickness deformations. Experiment and theory have shown that protein-induced lipid bilayer thickness deformations can yield energetically favorable bilayer-mediated interactions between integral membrane proteins, and large-scale organization of integral membrane proteins into protein clusters in cell membranes. Within the continuum elasticity theory of membranes, the energy cost of protein-induced bilayer thickness deformations can be captured by considering compression and expansion of the bilayer hydrophobic core, membrane tension, and bilayer bending, resulting in biharmonic equilibrium equations describing the shape of lipid bilayers for a given set of bilayer-protein boundary conditions. Here we develop a combined analytic and numerical methodology for the solution of the equilibrium elastic equations associated with protein-induced lipid bilayer deformations. Our methodology al...

  11. EFFECT OF REDUCING THE NUMBER OF SPERM CELLS (PER INSEMINATION, INCREASING ENERGY AND CRYOPROTECTING CONCENTRATIONS ON MOTION CHARACTERISTICS AND MEMBRANE INTEGRITY IN FROZEN THAWED BUFFALO SPERMATOZOA

    Directory of Open Access Journals (Sweden)

    A.Abbas, S. M. H. Andrabiand N. Ahmad

    2001-07-01

    Full Text Available The objective of this study was to find out the minimum number of sperm cells per dose of insemination that will not affect the conception rate, if levels of egg yolk and glycerol are increased. For this purpose, sperm motion characteristics and plasma membrane integrity in three concentrations of sperm cells per dose, each with two levels of egg yolk and glycerol were compared. Semen was collected from buffalo bulls using an artificial vagina. Split pool ejaculates possessing more than 60% visual sperm motility were diluted in Tris-citric acid (TCA extender at 37°C, either in (1 30-6-20 (Number of sperm cells in millions/0.5 ml insemi1:1ation dose-Glycerol%-Egg yolk %,(2 15-6-20, (3 7.5-6-20, (4 30-10- 20, (5 15-10-20, (6 7.5-10-20, (7 30-6-30, (8 15-6-30, (9 7.5-6-30, (10 30-10-30, (11 15-10-30 and (12 7.5-10-30. Semen was cooled to 4°C in 2 hours, equilibrated at 4aC for 4 hours, filled in 0.5 ml straws and frozen in a programmable cell freezer ( + 4 to -15°C @ -3°C/minute and then to -80°C@ -10°C/minute before plunging them into liquid nitrogen (-196°C. Thawing of frozen semen was performed after 24 hours at 37°C for 15 seconds. Sperm motion characteristics, including motilities (computer-assisted, linear and circular, velocities (straight-line, average path and curvilinear, and lateral head displacement (LHD were assessed using computer assisted semen analyzer (CASA. Plasma membrane integrity was determined by using Hypo-Osmotic Swelling assay (HOS. Analysis of variance revealed that visual motility, computer-assisted motility, linear motility, circular motility, and plasma membrane integrity did not vary significantly when cell number was reduced from 30x106/dose to 15x106/dose. However, visual motility, computer-assisted motility and plasma membrane integrity were reduced significantly (P<0.05 when cell number was decreased to 7.5x106/dose. The velocities (straight- line, average path, curvilinear and LHD did not vary

  12. Fuel cell with ionization membrane

    Science.gov (United States)

    Hartley, Frank T. (Inventor)

    2007-01-01

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

  13. 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...

  14. Two Golgi integral membrane proteins (GIMPS) exhibit region- and cell type-specific distribution in the epididymis of the adult rat.

    Science.gov (United States)

    Suarez-Quian, C A; Jelesoff, N

    1994-12-15

    The epididymis participates in the post-testicular maturation and storage of spermatozoa by secreting proteins into the tubule lumen in a region-specific fashion. The underlying molecular mechanisms leading to biogenesis of these region-specific differences, however, are not known, although components of the Golgi complex membrane container must undoubtedly be intimately involved. Two monoclonal antibodies raised against Golgi integral membrane proteins, recognizing either the cis (GIMPc) or trans Golgi (GIMPt) cisternae, were used as molecular probes of these regions to begin the characterization of the Golgi complex of in vivo and in vitro epididymal cells. Immunolocalization of GIMPs was performed on frozen sections and in cultured cells using biotin-streptavidin-peroxidase immunocytochemistry. In tissue sections, immunostaining of GIMPt was extremely robust in the supranuclear cytoplasm throughout the epididymis. In contrast, no GIMPc immunostaining was detected in the initial segment or in clear cells of the distal caput, corpus, and cauda. Immunodetection of GIMPc and GIMPt in epididymal cells in vitro revealed a reticular, perinuclear pattern, and NH4Cl treatment preferentially disrupted the GIMPt immunolocalization. These results characterizing the molecular components of the Golgi complex will form the basis of additional studies to gain further insight into mechanisms leading to generation of regional differences in epididymal function. PMID:7873795

  15. Bilayer-thickness-mediated interactions between integral membrane proteins.

    Science.gov (United States)

    Kahraman, Osman; Koch, Peter D; Klug, William S; Haselwandter, Christoph A

    2016-04-01

    Hydrophobic thickness mismatch between integral membrane proteins and the surrounding lipid bilayer can produce lipid bilayer thickness deformations. Experiment and theory have shown that protein-induced lipid bilayer thickness deformations can yield energetically favorable bilayer-mediated interactions between integral membrane proteins, and large-scale organization of integral membrane proteins into protein clusters in cell membranes. Within the continuum elasticity theory of membranes, the energy cost of protein-induced bilayer thickness deformations can be captured by considering compression and expansion of the bilayer hydrophobic core, membrane tension, and bilayer bending, resulting in biharmonic equilibrium equations describing the shape of lipid bilayers for a given set of bilayer-protein boundary conditions. Here we develop a combined analytic and numerical methodology for the solution of the equilibrium elastic equations associated with protein-induced lipid bilayer deformations. Our methodology allows accurate prediction of thickness-mediated protein interactions for arbitrary protein symmetries at arbitrary protein separations and relative orientations. We provide exact analytic solutions for cylindrical integral membrane proteins with constant and varying hydrophobic thickness, and develop perturbative analytic solutions for noncylindrical protein shapes. We complement these analytic solutions, and assess their accuracy, by developing both finite element and finite difference numerical solution schemes. We provide error estimates of our numerical solution schemes and systematically assess their convergence properties. Taken together, the work presented here puts into place an analytic and numerical framework which allows calculation of bilayer-mediated elastic interactions between integral membrane proteins for the complicated protein shapes suggested by structural biology and at the small protein separations most relevant for the crowded membrane

  16. Bilayer-thickness-mediated interactions between integral membrane proteins

    Science.gov (United States)

    Kahraman, Osman; Koch, Peter D.; Klug, William S.; Haselwandter, Christoph A.

    2016-04-01

    Hydrophobic thickness mismatch between integral membrane proteins and the surrounding lipid bilayer can produce lipid bilayer thickness deformations. Experiment and theory have shown that protein-induced lipid bilayer thickness deformations can yield energetically favorable bilayer-mediated interactions between integral membrane proteins, and large-scale organization of integral membrane proteins into protein clusters in cell membranes. Within the continuum elasticity theory of membranes, the energy cost of protein-induced bilayer thickness deformations can be captured by considering compression and expansion of the bilayer hydrophobic core, membrane tension, and bilayer bending, resulting in biharmonic equilibrium equations describing the shape of lipid bilayers for a given set of bilayer-protein boundary conditions. Here we develop a combined analytic and numerical methodology for the solution of the equilibrium elastic equations associated with protein-induced lipid bilayer deformations. Our methodology allows accurate prediction of thickness-mediated protein interactions for arbitrary protein symmetries at arbitrary protein separations and relative orientations. We provide exact analytic solutions for cylindrical integral membrane proteins with constant and varying hydrophobic thickness, and develop perturbative analytic solutions for noncylindrical protein shapes. We complement these analytic solutions, and assess their accuracy, by developing both finite element and finite difference numerical solution schemes. We provide error estimates of our numerical solution schemes and systematically assess their convergence properties. Taken together, the work presented here puts into place an analytic and numerical framework which allows calculation of bilayer-mediated elastic interactions between integral membrane proteins for the complicated protein shapes suggested by structural biology and at the small protein separations most relevant for the crowded membrane

  17. Integrated Microbial Electrolysis Cell (MEC) with an anaerobic Membrane Bioreactor (MBR) for low strength wastewater treatment, energy harvesting and water reclamation

    KAUST Repository

    Jimenez Sandoval, Rodrigo J.

    2013-11-01

    Shortage of potable water is a problem that affects many nations in the world and it will aggravate in a near future if pertinent actions are not carried out. Decrease in consumption, improvements in water distribution systems to avoid losses and more efficient water treatment processes are some actions that can be implemented to attack this problem. Membrane technology and biological processes are used in wastewater treatment to achieve high water quality standards. Some other technologies, besides water treatment, attempt to obtain energy from organic wastes present in water. In this study, a proof-of-concept was accomplished demonstrating that a Microbial Electrolysis Cell can be fully integrated with a Membrane Bioreactor to achieve wastewater treatment and harvest energy. Conductive hollow fiber membranes made of nickel functioned as both filter material for treated water reclamation and as a cathode to catalyze hydrogen production reaction. The produced hydrogen was subsequently converted into methane by hydrogenotrophic methanogens. Organic removal was 98.9% irrespective of operation mode. Maximum volumetric hydrogen production rate was 0.2 m3/m3d, while maximum current density achieved was 6.1 A/m2 (based on cathode surface area). Biofouling, an unavoidable phenomenon in traditional MBRs, can be minimized in this system through self-cleaning approach of hybrid membranes by hydrogen production. The increased rate of hydrogen evolution at high applied voltage (0.9 V) reduces the membrane fouling. Improvements can be done in the system to make it as a promising net energy positive technology for the low strength wastewater treatment.

  18. Cell-free production of integral membrane aspartic acid proteases reveals zinc-dependent methyltransferase activity of the Pseudomonas aeruginosa prepilin peptidase PilD

    Science.gov (United States)

    Aly, Khaled A; Beebe, Emily T; Chan, Chi H; Goren, Michael A; Sepúlveda, Carolina; Makino, Shin-ichi; Fox, Brian G; Forest, Katrina T

    2013-01-01

    Integral membrane aspartic acid proteases are receiving growing recognition for their fundamental roles in cellular physiology of eukaryotes and prokaryotes, and may be medically important pharmaceutical targets. The Gram-negative Pseudomonas aeruginosa PilD and the archaeal Methanococcus voltae FlaK were synthesized in the presence of unilamellar liposomes in a cell-free translation system. Cosynthesis of PilD with its full-length substrate, PilA, or of FlaK with its full-length substrate, FlaB2, led to complete cleavage of the substrate signal peptides. Scaled-up synthesis of PilD, followed by solubilization in dodecyl-β-d-maltoside and chromatography, led to a pure enzyme that retained both of its known biochemical activities: cleavage of the PilA signal peptide and S-adenosyl methionine-dependent methylation of the mature pilin. X-ray fluorescence scans show for the first time that PilD is a zinc-binding protein. Zinc is required for the N-terminal methylation of the mature pilin, but not for signal peptide cleavage. Taken together, our work identifies the P. aeruginosa prepilin peptidase PilD as a zinc-dependent N-methyltransferase and provides a new platform for large-scale synthesis of PilD and other integral membrane proteases important for basic microbial physiology and virulence. PMID:23255525

  19. Dielectric breakdown of cell membranes.

    Science.gov (United States)

    Zimmermann, U; Pilwat, G; Riemann, F

    1974-11-01

    With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 . 10(6) V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector

  20. Influence of carvacrol and 1,8-cineole on cell viability, membrane integrity, and morphology of Aeromonas hydrophila cultivated in a vegetable-based broth.

    Science.gov (United States)

    de Sousa, Jossana Pereira; de Oliveira, Kataryne Árabe Rimá; de Figueiredo, Regina Celia Bressan Queiroz; de Souza, Evandro Leite

    2015-02-01

    This study investigated the effects of carvacrol (CAR) and 1,8-cineole (CIN) alone (at the MIC) or in combination at subinhibitory amounts (both at 1/8 MIC) on the cell viability, membrane permeability, and morphology of Aeromonas hydrophila INCQS 7966 (A. hydrophila) cultivated in a vegetable-based broth. CAR and CIN alone or in combination severely affected the viability of the bacteria and caused dramatic changes in the cell membrane permeability, leading to cell death, as observed by confocal laser microscopy. Scanning and transmission electron microscopy images of bacterial cells exposed to CAR or CIN or the mixture of both compounds revealed severe changes in cell wall structure, rupture of the plasma membrane, shrinking of cells, condensation of cytoplasmic content, leakage of intracellular material, and cell collapse. These findings suggest that CAR and CIN alone or in combination at subinhibitory amounts could be applied to inhibit the growth of A. hydrophila in foods, particularly as sanitizing agents in vegetables.

  1. Integrated Ceramic Membrane System for Hydrogen Production

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Joseph; Lim, Hankwon; Drnevich, Raymond

    2010-08-05

    Phase I was a technoeconomic feasibility study that defined the process scheme for the integrated ceramic membrane system for hydrogen production and determined the plan for Phase II. The hydrogen production system is comprised of an oxygen transport membrane (OTM) and a hydrogen transport membrane (HTM). Two process options were evaluated: 1) Integrated OTM-HTM reactor – in this configuration, the HTM was a ceramic proton conductor operating at temperatures up to 900°C, and 2) Sequential OTM and HTM reactors – in this configuration, the HTM was assumed to be a Pd alloy operating at less than 600°C. The analysis suggested that there are no technical issues related to either system that cannot be managed. The process with the sequential reactors was found to be more efficient, less expensive, and more likely to be commercialized in a shorter time than the single reactor. Therefore, Phase II focused on the sequential reactor system, specifically, the second stage, or the HTM portion. Work on the OTM portion was conducted in a separate program. Phase IIA began in February 2003. Candidate substrate materials and alloys were identified and porous ceramic tubes were produced and coated with Pd. Much effort was made to develop porous substrates with reasonable pore sizes suitable for Pd alloy coating. The second generation of tubes showed some improvement in pore size control, but this was not enough to get a viable membrane. Further improvements were made to the porous ceramic tube manufacturing process. When a support tube was successfully coated, the membrane was tested to determine the hydrogen flux. The results from all these tests were used to update the technoeconomic analysis from Phase I to confirm that the sequential membrane reactor system can potentially be a low-cost hydrogen supply option when using an existing membrane on a larger scale. Phase IIB began in October 2004 and focused on demonstrating an integrated HTM/water gas shift (WGS) reactor to

  2. Corrugated Membrane Fuel Cell Structures

    Energy Technology Data Exchange (ETDEWEB)

    Grot, Stephen [President, Ion Power Inc.

    2013-09-30

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

  3. Chip integrated fuel cell accumulator

    Science.gov (United States)

    Frank, M.; Erdler, G.; Frerichs, H.-P.; Müller, C.; Reinecke, H.

    A unique new design of a chip integrated fuel cell accumulator is presented. The system combines an electrolyser and a self-breathing polymer electrolyte membrane (PEM) fuel cell with integrated palladium hydrogen storage on a silicon substrate. Outstanding advantages of this assembly are the fuel cell with integrated hydrogen storage, the possibility of refuelling it by electrolysis and the opportunity of simply refilling the electrolyte by adding water. By applying an electrical current, wiring the palladium hydrogen storage as cathode and the counter-electrode as anode, the electrolyser produces hydrogen at the palladium surface and oxygen at the electrolyser cell anode. The generated hydrogen is absorbed by the palladium electrode and the hydrogen storage is refilled consequently enabling the fuel cell to function.

  4. Exocytosis and endocytosis in neurodocrine cells: inseparable membranes !

    Directory of Open Access Journals (Sweden)

    Sébastien eHouy

    2013-10-01

    Full Text Available Although much has been learned concerning the mechanisms of secretory vesicle formation and fusion at donor and acceptor membrane compartments, relatively little attention has been paid towards understanding how cells maintain a homeostatic membrane balance through vesicular trafficking. In neurons and neuroendocrine cells, release of neurotransmitters, neuropeptides and hormones occurs through calcium-regulated exocytosis at the plasma membrane. To allow recycling of secretory vesicle components and to preserve organelles integrity, cells must initiate and regulate compensatory membrane uptake. This review relates the fate of secretory granule membranes after full fusion exocytosis in neuroendocrine cells. In particular, we focus on the potential role of lipids in preserving and sorting secretory granule membranes after exocytosis and we discuss the potential mechanisms of membrane retrieval.

  5. Membrane topology and mutational analysis of the TolQ protein of Escherichia coli required for the uptake of macromolecules and cell envelope integrity.

    OpenAIRE

    Vianney, A; Lewin, T M; Beyer, W F; Lazzaroni, J C; Portalier, R; Webster, R E

    1994-01-01

    TolQ is a 230-amino-acid protein required to maintain the integrity of the bacterial envelope and to facilitate the import of both filamentous bacteriophage and group A colicins. Cellular fractionation experiments showed TolQ to be localized to the cytoplasmic membrane. Bacteria expressing a series of TolQ-beta-galactosidase and TolQ-alkaline phosphatase fusion proteins were analyzed for the appropriate enzyme activity, membrane location, and sensitivity to exogenously added protease. The res...

  6. The multi-facet aspects of cell sentience and their relevance for the integrative brain actions: role of membrane protein energy landscape.

    Science.gov (United States)

    Agnati, Luigi F; Marcoli, Manuela; Maura, Guido; Fuxe, Kjell; Guidolin, Diego

    2016-06-01

    Several ion channels can be randomly and spontaneously in an open state, allowing the exchange of ion fluxes between extracellular and intracellular environments. We propose that the random changes in the state of ion channels could be also due to proteins exploring their energy landscapes. Indeed, proteins can modify their steric conformation under the effects of the physicochemical parameters of the environments with which they are in contact, namely, the extracellular, intramembrane and intracellular environments. In particular, it is proposed that the random walk of proteins in their energy landscape is towards attractors that can favor the open or close condition of the ion channels and/or intrinsic activity of G-protein-coupled receptors. The main aspect of the present proposal is that some relevant physicochemical parameters of the environments (e.g. molecular composition, temperature, electrical fields) with which some signaling-involved plasma membrane proteins are in contact alter their conformations. In turn, these changes can modify their information handling via a modulatory action on their random walk towards suitable attractors of their energy landscape. Thus, spontaneous and/or signal-triggered electrical activities of neurons occur that can have emergent properties capable of influencing the integrative actions of brain networks. Against this background, Cook's hypothesis on 'cell sentience' is developed by proposing that physicochemical parameters of the environments with which the plasma-membrane proteins of complex cellular networks are in contact fulfill a fundamental role in their spontaneous and/or signal-triggered activity. Furthermore, it is proposed that a specialized organelle, the primary cilium, which is present in most cells (also neurons and astrocytes), could be of peculiar importance to pick up chemical signals such as ions and transmitters and to detect physical signals such as pressure waves, thermal gradients, and local field

  7. 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

  8. Thermoelectric integrated membrane evaporation water recovery technology

    Science.gov (United States)

    Roebelen, G. J., Jr.; Winkler, H. E.; Dehner, G. F.

    1982-01-01

    The recently developed Thermoelectric Integrated Membrane Evaporation Subsystem (TIMES) offers a highly competitive approach to water recovery from waste fluids for future on-orbit stations such as the Space Operations Center. Low power, compactness and gravity insensitive operation are featured in this vacuum distillation subsystem that combines a hollow fiber membrane evaporator with a thermoelectric heat pump. The hollow fiber elements provide positive liquid/gas phase control with no moving parts other than pumps and an accumulator, thus solving problems inherent in other reclamation subsystem designs. In an extensive test program, over 850 hours of operation were accumulated during which time high quality product water was recovered from both urine and wash water at an average steady state production rate of 2.2 pounds per hour.

  9. Design of Incremental Conductance Sliding Mode MPPT Control Applied by Integrated Photovoltaic and Proton Exchange Membrane Fuel Cell System under Various Operating Conditions for BLDC Motor

    Directory of Open Access Journals (Sweden)

    Jehun Hahm

    2015-01-01

    Full Text Available This paper proposes an integrated photovoltaic (PV and proton exchange membrane fuel cell (PEMFC system for continuous energy harvesting under various operating conditions for use with a brushless DC motor. The proposed scheme is based on the incremental conductance (IncCond algorithm combined with the sliding mode technique. Under changing atmospheric conditions, the energy conversion efficiency of a PV array is very low, leading to significant power losses. Consequently, increasing efficiency by means of maximum power point tracking (MPPT is particularly important. To manage such a hybrid system, control strategies need to be established to achieve the aim of the distributed system. Firstly, a Matlab/Simulink based model of the PV and PEMFC is developed and validated, as well as the incremental conductance sliding (ICS MPPT technique; then, different MPPT algorithms are employed to control the PV array under nonuniform temperature and insolation conditions, to study these algorithms effectiveness under various operating conditions. Conventional techniques are easy to implement but produce oscillations at MPP. Compared to these techniques, the proposed technique is more efficient; it produces less oscillation at MPP in the steady state and provides more precise tracking.

  10. Improved Membrane Materials for PEM Fuel Cell Application

    Energy Technology Data Exchange (ETDEWEB)

    Kenneth A. Mauritz; Robert B. Moore

    2008-06-30

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

  11. STUDYING MEMBRANE ANCHOR ORGANIZATION IN LIVING CELL MEMBRANES

    OpenAIRE

    Huang, Hector Han-Li

    2011-01-01

    The cell membrane is a complex mixture of various lipids, proteins and other biomolecules that are all organized into a fluid 2-dimensional bilayer. A rather unique trait of this organelle is the lateral mobility of the component molecules. Surprisingly, these molecules are not necessarily distributed homogeneously in the membrane. From a physical perspective, these inhomogeneities are interesting because they indicate some level of organization in the membrane. From a biological perspect...

  12. 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.

  13. POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

    DEFF Research Database (Denmark)

    2001-01-01

    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...

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

    International Nuclear Information System (INIS)

    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

  15. 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.

  16. In-membrane micro fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Omosebi, Ayokunle; Besser, Ronald

    2016-09-06

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

  17. Fuel cell and membrane therefore

    Energy Technology Data Exchange (ETDEWEB)

    Aindow, Tai-Tsui

    2016-08-09

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

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

    Science.gov (United States)

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

    2014-09-01

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

  19. Variability in permeability and integrity of cell membrane and depletion of food reserves in neem (Azadirachta indica) seeds from trees of differ-ent age classes

    Institute of Scientific and Technical Information of China (English)

    Devendra Kumar; Dhruv Kumar Mishra

    2014-01-01

    We quantified cell membrane permeability (electrical conduc-tivity-EC, water soluble sugar-WSS, and amino acids-AA) and integrity (phospholipids,α-tocopherol and lipid peroxidation) along with food reserve deterioration (total proteins, total sugar, and total starch) of neem seeds collected from various mother tree age classes and stored for 65 days in airtight plastic containers at ambient room temperature (35±5°C). Results show that the activities were higher in fresh seeds (EC 267.56-2950.01 µS/g, WSS 19.96-19.48 mg/g and AA 5.40-5.35 mg/g) and declined with increasing duration of storage period (EC 153.37-195.17 µS/g, WSS 3.13-4.17 mg/g and AA 4.29-4.49 mg/g after 35 days and EC 144.02-161.56 µS/g, WSS 2.06-2.40 mg/g and AA 3.98-4.27 mg/g after 65 days of storage). Phospholipids andα-tocopherol were higher in fresh seed (0.073-0.093 OD at 710 nm and 0.080-0.105 OD, respectively) and declined as storage duration in-creased (0.033-0.042 OD at 710 nm and 00.0010-0.0020 OD, respec-tively). Dead seeds showed reduced amounts of phospholipids and minimum activity ofα- tocopherol (antioxidants). The level of MDA was lower in fresh seeds (0.0066-0.0087 OD at 600-535 nm) and increased as storage duration increased (0.0248-0.0268 OD after 65 days of stor-age). The higher amount of MDA indicated that seeds died due to rancid-ity of the oil inside the seed. Neem seed cake was assessed for deteriora-tion of food reserves (total proteins, total sugar, and total starch), concen-trations of which were higher in fresh seed and declined as storage dura-tion increased. Germination was higher in fresh seeds and after 65 days, no germination was received perhaps due to deterioration of biochemi-cals in seeds. Patterns of seed deterioration were similar across all seed lots.

  20. Membrane Organization and Dynamics in Cell Polarity

    OpenAIRE

    Orlando, Kelly; Guo, Wei

    2009-01-01

    The establishment and maintenance of cell polarity is important to a wide range of biological processes ranging from chemotaxis to embryogenesis. An essential feature of cell polarity is the asymmetric organization of proteins and lipids in the plasma membrane. In this article, we discuss how polarity regulators such as small GTP-binding proteins and phospholipids spatially and kinetically control vesicular trafficking and membrane organization. Conversely, we discuss how membrane trafficking...

  1. Polyethylenimine-mediated impairment of mitochondrial membrane potential, respiration and membrane integrity

    DEFF Research Database (Denmark)

    Larsen, Anna Karina; Malinska, Dominika; Koszela-Piotrowska, Izabela;

    2012-01-01

    The 25 kDa branched polyethylenimine (PEI) is a highly efficient synthetic polycation used in transfection protocols, but also triggers mitochondrial-mediated apoptotic cell death processes where the mechanistic issues are poorly understood. We now demonstrate that PEI in a concentration- and time......-dependent manner can affect functions (membrane potential, swelling and respiration) and ultrastructural integrity of freshly isolated rat liver mitochondria. The threshold concentration for detection of PEI-mediated impairment of rat liver mitochondrial functions is 3 µg/mL, however, lower PEI levels still exert...... some effects on mitochondrial morphology and respiration, and these may be related to the inherent membrane perturbing properties of this polycation. The PEI-mediated mitochondrial swelling phase is biphasic, with a fast decaying initial period (most prominent from 4 µg/mL PEI) followed by a slower...

  2. 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...

  3. Salmonella enterotoxin (Stn regulates membrane composition and integrity

    Directory of Open Access Journals (Sweden)

    Masayuki Nakano

    2012-07-01

    The mechanism of action of Salmonella enterotoxin (Stn as a virulence factor in disease is controversial. Studies of Stn have indicated both positive and negative effects on Salmonella virulence. In this study, we attempted to evaluate Stn function and its effects on Salmonella virulence. To investigate Stn function, we first performed in vitro and in vivo analysis using mammalian cells and a murine ileal loop model. In these systems, we did not observe differences in virulence phenotypes between wild-type Salmonella and an stn gene-deleted mutant. We next characterized the phenotypes and molecular properties of the mutant strain under various in vitro conditions. The proteomic profiles of the total cell membrane protein fraction differed between wild type and mutant in that there was an absence of a protein in the mutant strain, which was identified as OmpA. By far-western blotting, OmpA was found to interact directly with Stn. To verify this result, the morphology of Salmonella was examined by transmission electron microscopy, with OmpA localization being analyzed by immunogold labeling. Compared with wild-type Salmonella, the mutant strain had a different pole structure and a thin periplasmic space; OmpA was not seen in the mutant. These results indicate that Stn, via regulation of OmpA membrane localization, functions in the maintenance of membrane composition and integrity.

  4. 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.

  5. Does ATP cross the cell plasma membrane.

    OpenAIRE

    Chaudry, I. H.

    1982-01-01

    Although there is an abundance of evidence which indicates that ATP is released as well as taken up by cells, the concept that ATP cannot cross the cell membrane has tended to prevail. This article reviews the evidence for the release as well as uptake of ATP by cells. The evidence presented by various investigators clearly indicates that ATP can cross the cell membrane and suggests that the release and uptake of ATP are physiological processes.

  6. Mechanical tension drives cell membrane fusion

    OpenAIRE

    Kim, Ji Hoon; Ren, Yixin; Ng, Win Pin; Li, Shuo; Son, Sungmin; Kee, Yee-Seir; Zhang, Shiliang; Zhang, Guofeng; Fletcher, Daniel A.; Robinson, Douglas N.; Chen, Elizabeth H.

    2015-01-01

    Membrane fusion is an energy-consuming process that requires tight juxtaposition of two lipid bilayers. Little is known about how cells overcome energy barriers to bring their membranes together for fusion. Previously, we have shown that cell-cell fusion is an asymmetric process in which an “attacking” cell drills finger-like protrusions into the “receiving” cell to promote cell fusion. Here we show that the receiving cell mounts a Myosin II (MyoII)-mediated mechanosensory response to its inv...

  7. Profiling of the toxicity mechanisms of coated and uncoated silver nanoparticles to yeast Saccharomyces cerevisiae BY4741 using a set of its 9 single-gene deletion mutants defective in oxidative stress response, cell wall or membrane integrity and endocytosis.

    Science.gov (United States)

    Käosaar, Sandra; Kahru, Anne; Mantecca, Paride; Kasemets, Kaja

    2016-09-01

    The widespread use of nanosilver in various antibacterial, antifungal, and antiviral products warrants the studies of the toxicity pathways of nanosilver-enabled materials toward microbes and viruses. We profiled the toxicity mechanisms of uncoated, casein-coated, and polyvinylpyrrolidone-coated silver nanoparticles (AgNPs) using Saccharomyces cerevisiae wild-type (wt) and its 9 single-gene deletion mutants defective in oxidative stress (OS) defense, cell wall/membrane integrity, and endocytosis. The 48-h growth inhibition assay in organic-rich growth medium and 24-h cell viability assay in deionized (DI) water were applied whereas AgNO3, H2O2, and SDS served as positive controls. Both coated AgNPs (primary size 8-12nm) were significantly more toxic than the uncoated (~85nm) AgNPs. All studied AgNPs were ~30 times more toxic if exposed to yeast cells in DI water than in the rich growth medium: the IC50 based on nominal concentration of AgNPs in the growth inhibition test ranged from 77 to 576mg Ag/L and in the cell viability test from 2.7 to 18.7mg Ag/L, respectively. Confocal microscopy showed that wt but not endocytosis mutant (end3Δ) internalized AgNPs. Comparison of toxicity patterns of wt and mutant strains defective in OS defense and membrane integrity revealed that the toxicity of the studied AgNPs to S. cerevisiae was not caused by the OS or cell wall/membrane permeabilization. PMID:27260961

  8. Protective effect of black tea on integral membrane proteins in rat liver.

    Science.gov (United States)

    Szachowicz-Petelska, Barbara; Skrzydlewska, Elżbieta; Figaszewski, Zbigniew

    2013-01-01

    Ethanol intoxication is accompanied by oxidative stress formation. Consequently, it leads to disturbances in cellular metabolism that can alter the structure and function of cell membrane components. Black tea displays antioxidant properties, protects membrane phospholipids and may protect integral membrane proteins. In the present study, we examined whether black tea induces changes in the liver integral membrane proteins of 12-months old rats chronically intoxicated with ethanol. To estimate qualitatively and quantitatively the levels of the liver integral membrane proteins, the proteins were selectively hydrolyzed by trypsin, the obtained peptides were resolved by HPLC and the levels of specific amino acids within the individual peptides were determined. All of the obtained peptides contained phenylalanine (Phe), cysteine (Cys) and lysine (Lys). Compared to the control group, rats in the ethanol intoxication group showed decreased liver levels of integral membrane proteins as well as fewer trypsin-hydrolyzed peptides and amino acids in the hydrolyzed peptides. Administration of black tea to ethanol-intoxicated rats partially protected proteins against the structural changes caused by ethanol. Black tea prevented decreases in the levels of cysteine (in about 90% of cases), lysine (in about 60% of cases), phenylalanine (in about 70% of cases) and examined peptides (in about 60% of cases). The liver protein level was higher (by about 18%) in rats who received black tea and ethanol than in those who received ethanol alone. In conclusion, black tea partially protects the composition and level of rat liver cell integral membrane proteins against changes caused by ethanol intoxication.

  9. Nuclear myosin I regulates cell membrane tension

    Science.gov (United States)

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

    2016-01-01

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

  10. Proton conducting membrane for fuel cells

    Science.gov (United States)

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

    2007-03-27

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

  11. 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

  12. 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

  13. 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.

  14. Advanced membrane electrode assemblies for fuel cells

    Science.gov (United States)

    Kim, Yu Seung; Pivovar, Bryan S

    2014-02-25

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

  15. Study of the effect of membrane thickness on microcapsule strength, permeability, and cell proliferation.

    Science.gov (United States)

    Ma, Ying; Zhang, Ying; Wang, Yu; Wang, Qiuyan; Tan, Mingqian; Liu, Yang; Chen, Li; Li, Na; Yu, Weiting; Ma, Xiaojun

    2013-04-01

    Cell microencapsulation is one of the promising strategies for in vitro production of proteins or in vivo delivery of therapeutic products. Membrane thickness controls microcapsule strength and permeability, which may in return affect cell growth and metabolism. In this study, the strength, permeability, and encapsulated Chinese hamster ovary cell proliferation and metabolism of four groups of microcapsules with different membrane thicknesses were investigated. It was found that increasing membrane thickness increases microcapsule strength, whereas decreases membrane permeability. During the first 6 days, cells within microcapsules with 10 μm thickness membrane proliferated fast and could reach a cell density of 1.9 × 10(7) cells/mL microcapsule with 92% cell density. A cell density of 5.5 × 10(7) cells/mL microcapsule with >85% cell density was achieved within microcapsules with 15 μm membrane thickness and these microcapsules kept over 88% integrity ratio after 11 days, which was much higher than that of microcapsules with 10 μm membrane thickness. Membrane with more than 20 μm thickness was not suited for encapsulated cell culture owing to low-protein diffusion rate. These results indicated that cells survived shortly within the thinnest membrane thickness. There was a specific membrane thickness more suitable for cell growth for a long-time culture. These findings will be useful for preparing microcapsules with the desired membrane thickness for microencapsulated cell culture dependent on various purposes.

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

    Science.gov (United States)

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

    2016-06-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    José Manuel Molina-Guijarro

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

  19. 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.

  20. Metric dynamics for membrane transformation through regulated cell proliferation

    OpenAIRE

    Ito, Hiroshi C.

    2016-01-01

    This study develops an equation for describing three-dimensional membrane transformation through proliferation of its component cells regulated by morphogen density distributions on the membrane. The equation is developed in a two-dimensional coordinate system mapped on the membrane, referred to as the membrane coordinates. When the membrane expands, the membrane coordinates expand in the same manner so that the membrane is invariant in the coordinates. In the membrane coordinate system, the ...

  1. High temperature polymer electrolyte membrane fuel cells

    DEFF Research Database (Denmark)

    This book is a comprehensive review of high-temperature polymer electrolyte membrane fuel cells (PEMFCs). PEMFCs are the preferred fuel cells for a variety of applications such as automobiles, cogeneration of heat and power units, emergency power and portable electronics. The first 5 chapters...

  2. Electrically Conductive, Hydrophilic Porous Membrane for Fuel Cell Applications Project

    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...

  3. Resting microglial cells exhibit tubular membrane protrusions

    Directory of Open Access Journals (Sweden)

    Ulrike Gimsa

    2002-11-01

    Full Text Available Nano- and microtubular structures have recently become a subject of increasing interest due to their importance in biology and medicine as well as their technological potential. Such structures have been observed in anorganic (Iijima, 1991 as well as in organic (Schnur 1993; Oda et al. 1991 systems. Micro- and nanotubular protrusions of bilayer membranes have been found in cells (Kralj-Iglic et al. 1998; Kralj-Iglic et al. 2001a and phospholipid vesicles (Kralj-Iglic et al. 2002; Kralj-Iglic et al. 2001b. In this work we describe membrane protrusions in microglial cells.

  4. Expression Screening of Integral Membrane Proteins by Fusion to Fluorescent Reporters.

    Science.gov (United States)

    Bird, Louise E; Nettleship, Joanne E; Järvinen, Valtteri; Rada, Heather; Verma, Anil; Owens, Raymond J

    2016-01-01

    The production of recombinant integral membrane proteins for structural and functional studies remains technically challenging due to their relatively low levels of expression. To address this problem, screening strategies have been developed to identify the optimal membrane sequence and expression host for protein production. A common approach is to genetically fuse the membrane protein to a fluorescent reporter, typically Green Fluorescent Protein (GFP) enabling expression levels, localization and detergent solubilisation to be assessed. Initially developed for screening the heterologous expression of bacterial membrane proteins in Escherichia coli, the method has been extended to eukaryotic hosts, including insect and mammalian cells. Overall, GFP-based expression screening has made a major impact on the number of membrane protein structures that have been determined in the last few years. PMID:27553231

  5. Transfer Printed Nanomembranes for Heterogeneously Integrated Membrane Photonics

    Directory of Open Access Journals (Sweden)

    Hongjun Yang

    2015-11-01

    Full Text Available Heterogeneous crystalline semiconductor nanomembrane (NM integration is investigated for single-layer and double-layer Silicon (Si NM photonics, III-V/Si NM lasers, and graphene/Si NM total absorption devices. Both homogeneous and heterogeneous integration are realized by the versatile transfer printing technique. The performance of these integrated membrane devices shows, not only intact optical and electrical characteristics as their bulk counterparts, but also the unique light and matter interactions, such as Fano resonance, slow light, and critical coupling in photonic crystal cavities. Such a heterogeneous integration approach offers tremendous practical application potentials on unconventional, Si CMOS compatible, and high performance optoelectronic systems.

  6. Multiplex lithography for multilevel multiscale architectures and its application to polymer electrolyte membrane fuel cell.

    Science.gov (United States)

    Cho, Hyesung; Moon Kim, Sang; Sik Kang, Yun; Kim, Junsoo; Jang, Segeun; Kim, Minhyoung; Park, Hyunchul; Won Bang, Jung; Seo, Soonmin; Suh, Kahp-Yang; Sung, Yung-Eun; Choi, Mansoo

    2015-01-01

    The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area. PMID:26412619

  7. Fabrication and Testing of a Bi-Conductive Polymer Membrane Fuel Cell

    International Nuclear Information System (INIS)

    This paper reports the fabrication process and testing of a bi-conductive polymer membrane (BCPM) fuel cell that integrates lateral current collectors on both sides with an ionic conductive path through the membrane. The new membrane shows major advantages over standard Nafion® membranes used in Polymer Electrolyte Fuel Cells (PEMFCs). In addition to being mechanically stable when wet, the flexible BCPM integrates efficient thin film current collectors (ICCs) on an ionic conductive membrane with a high active area ratio. Also, ICCs leave all the surface of the electrode free to eventually integrate a more efficient water and gas management system than traditional gas diffusion layers. Moreover, the fabricated membrane has shown superior volumetric power density than standard PEMFC (0.76 vs 0.47 mW/cm2μm)

  8. Nanocarbon-based membrane filtration integrated with electric field driving for effective membrane fouling mitigation.

    Science.gov (United States)

    Fan, Xinfei; Zhao, Huimin; Quan, Xie; Liu, Yanming; Chen, Shuo

    2016-01-01

    Membrane filtration provides an effective solution for removing pollutants from water but is limited by serious membrane fouling. In this work, an effective approach was used to mitigate membrane fouling by integrating membrane filtration with electropolarization using an electroconductive nanocarbon-based membrane. The electropolarized membrane (EM) by alternating square-wave potentials between +1.0 V and -1.0 V with a pulse width of 60 s exhibited a permeate flux 8.1 times as high as that without electropolarization for filtering feed water containing bacteria, which confirms the ability of the EM to achieve biofouling mitigation. Moreover, the permeate flux of EM was 1.5 times as high as that without electropolarization when filtrating natural organic matter (NOM) from water, and demonstrated good performance in organic fouling mitigation with EM. Furthermore, the EM was also effective for complex fouling mitigation in filtering water containing coexisting bacteria and NOM, and presented an increased flux rate 1.9 times as high as that without electropolarization. The superior fouling mitigation performance of EM was attributed to the synergistic effects of electrostatic repulsion, electrochemical oxidation and electrokinetic behaviors. This work opens an effective avenue for membrane fouling mitigation of water-treatment membrane filtration systems.

  9. 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

  10. Lipid signalling dynamics at the β-cell plasma membrane.

    Science.gov (United States)

    Wuttke, Anne

    2015-04-01

    Pancreatic β-cells are clustered in islets of Langerhans and secrete insulin in response to increased concentrations of circulating glucose. Insulin in turn acts on liver, muscle and fat tissue to store energy and normalize the blood glucose level. Inappropriate insulin release may lead to impaired glucose tolerance and diabetes. In addition to glucose, other nutrients, neural stimuli and hormonal stimuli control insulin secretion. Many of these signals are perceived at the plasma membrane, which is also the site where insulin granules undergo exocytosis. Therefore, it is not surprising that membrane lipids play an important role in the regulation of insulin secretion. β-cells release insulin in a pulsatile fashion. Signalling lipids integrate the nutrient and neurohormonal inputs to fine-tune, shape and co-ordinate the pulsatility. An important group of signalling lipids are phosphoinositides and their downstream messengers. This MiniReview will discuss new insights into lipid signalling dynamics in β-cells obtained from live-cell imaging experiments with fluorescent translocation biosensors. The plasma membrane concentration of several phosphoinositides and of their downstream messengers changes rapidly upon nutrient or neurohormonal stimulation. Glucose induces the most complex spatio-temporal patterns, typically involving oscillations of messenger concentrations, which sometimes are locally restricted. The tightly controlled levels of lipid messengers can mediate specific binding of downstream effectors to the plasma membrane, contributing to the appropriate regulation of insulin secretion.

  11. Integrally skinned polysulfone hollow fiber membranes for pervaporation

    NARCIS (Netherlands)

    Koops, G.H.; Nolten, J.A.M.; Mulder, M.H.V.; Smolders, C.A.

    1994-01-01

    From polysulfone as polymer, integrally skinned hollow fiber membranes with a defect-free top layer have been spun. The spinning process described here differs from the traditional dry-wet spinning process where the fiber enters the coagulation bath after passing a certain air gap. In the present pr

  12. ARAMEMNON, a novel database for Arabidopsis integral membrane proteins

    DEFF Research Database (Denmark)

    Schwacke, Rainer; Schneider, Anja; van der Graaff, Eric;

    2003-01-01

    A specialized database (DB) for Arabidopsis membrane proteins, ARAMEMNON, was designed that facilitates the interpretation of gene and protein sequence data by integrating features that are presently only available from individual sources. Using several publicly available prediction programs, put...... is accessible at the URL http://aramemnon.botanik.uni-koeln.de....

  13. 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.

  14. Block copolymers for alkaline fuel cell membrane materials

    Science.gov (United States)

    Li, Yifan

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

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

    Science.gov (United States)

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

    2016-08-01

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2016-03-01

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

  18. Direct ultrafiltration performance and membrane integrity monitoring by microbiological analysis.

    Science.gov (United States)

    Ferrer, O; Casas, S; Galvañ, C; Lucena, F; Bosch, A; Galofré, B; Mesa, J; Jofre, J; Bernat, X

    2015-10-15

    The feasibility of substituting a conventional pre-treatment, consisting of dioxi-chlorination, coagulation/flocculation, settling and sand filtration, of a drinking water treatment plant (DWTP) by direct ultrafiltration (UF) has been assessed from a microbiological standpoint. Bacterial indicators, viral indicators and human viruses have been monitored in raw river, ultrafiltered and conventionally pre-treated water samples during two years. Direct UF has proven to remove bacterial indicators quite efficiently and to a greater extent than the conventional process does. Nevertheless, the removal of small viruses such as some small bacteriophages and human viruses (e.g. enteroviruses and noroviruses) is lower than the current conventional pre-treatment. Membrane integrity has been assessed during two years by means of tailored tests based on bacteriophages with different properties (MS-2, GA and PDR-1) and bacterial spores (Bacillus spores). Membrane integrity has not been compromised despite the challenging conditions faced by directly treating raw river water. Bacteriophage PDR-1 appears as a suitable microbe to test membrane integrity, as its size is slightly larger than the considered membrane pore size. However, its implementation at full scale plant is still challenging due to difficulties in obtaining enough phages for its seeding.

  19. Integral membrane protein structure determination using pseudocontact shifts

    International Nuclear Information System (INIS)

    Obtaining enough experimental restraints can be a limiting factor in the NMR structure determination of larger proteins. This is particularly the case for large assemblies such as membrane proteins that have been solubilized in a membrane-mimicking environment. Whilst in such cases extensive deuteration strategies are regularly utilised with the aim to improve the spectral quality, these schemes often limit the number of NOEs obtainable, making complementary strategies highly beneficial for successful structure elucidation. Recently, lanthanide-induced pseudocontact shifts (PCSs) have been established as a structural tool for globular proteins. Here, we demonstrate that a PCS-based approach can be successfully applied for the structure determination of integral membrane proteins. Using the 7TM α-helical microbial receptor pSRII, we show that PCS-derived restraints from lanthanide binding tags attached to four different positions of the protein facilitate the backbone structure determination when combined with a limited set of NOEs. In contrast, the same set of NOEs fails to determine the correct 3D fold. The latter situation is frequently encountered in polytopical α-helical membrane proteins and a PCS approach is thus suitable even for this particularly challenging class of membrane proteins. The ease of measuring PCSs makes this an attractive route for structure determination of large membrane proteins in general

  20. Integral membrane protein structure determination using pseudocontact shifts

    Energy Technology Data Exchange (ETDEWEB)

    Crick, Duncan J.; Wang, Jue X. [University of Cambridge, Department of Biochemistry (United Kingdom); Graham, Bim; Swarbrick, James D. [Monash University, Monash Institute of Pharmaceutical Sciences (Australia); Mott, Helen R.; Nietlispach, Daniel, E-mail: dn206@cam.ac.uk [University of Cambridge, Department of Biochemistry (United Kingdom)

    2015-04-15

    Obtaining enough experimental restraints can be a limiting factor in the NMR structure determination of larger proteins. This is particularly the case for large assemblies such as membrane proteins that have been solubilized in a membrane-mimicking environment. Whilst in such cases extensive deuteration strategies are regularly utilised with the aim to improve the spectral quality, these schemes often limit the number of NOEs obtainable, making complementary strategies highly beneficial for successful structure elucidation. Recently, lanthanide-induced pseudocontact shifts (PCSs) have been established as a structural tool for globular proteins. Here, we demonstrate that a PCS-based approach can be successfully applied for the structure determination of integral membrane proteins. Using the 7TM α-helical microbial receptor pSRII, we show that PCS-derived restraints from lanthanide binding tags attached to four different positions of the protein facilitate the backbone structure determination when combined with a limited set of NOEs. In contrast, the same set of NOEs fails to determine the correct 3D fold. The latter situation is frequently encountered in polytopical α-helical membrane proteins and a PCS approach is thus suitable even for this particularly challenging class of membrane proteins. The ease of measuring PCSs makes this an attractive route for structure determination of large membrane proteins in general.

  1. 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

  2. α-Synuclein oligomers induced by docosahexaenoic acid affect membrane integrity.

    Directory of Open Access Journals (Sweden)

    Chiara Fecchio

    Full Text Available A key feature of Parkinson disease is the aggregation of α-synuclein and its intracellular deposition in fibrillar form. Increasing evidence suggests that the pathogenicity of α-synuclein is correlated with the activity of oligomers formed in the early stages of its aggregation process. Oligomers toxicity seems to be associated with both their ability to bind and affect the integrity of lipid membranes. Previously, we demonstrated that α-synuclein forms oligomeric species in the presence of docosahexaenoic acid and that these species are toxic to cells. Here we studied how interaction of these oligomers with membranes results in cell toxicity, using cellular membrane-mimetic and cell model systems. We found that α-synuclein oligomers are able to interact with large and small unilamellar negatively charged vesicles acquiring an increased amount of α-helical structure, which induces small molecules release. We explored the possibility that oligomers effects on membranes could be due to pore formation, to a detergent-like effect or to fibril growth on the membrane. Our biophysical and cellular findings are consistent with a model where α-synuclein oligomers are embedded into the lipid bilayer causing transient alteration of membrane permeability.

  3. Fuel cell membranes and crossover prevention

    Science.gov (United States)

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

    2009-08-04

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

  4. VAMP-1: a synaptic vesicle-associated integral membrane protein.

    Science.gov (United States)

    Trimble, W S; Cowan, D M; Scheller, R H

    1988-01-01

    Several proteins are associated with, or are integral components of, the lipid bilayer that forms the delineating membrane of neuronal synaptic vesicles. To characterize these molecules, we used a polyclonal antiserum raised against purified cholinergic synaptic vesicles from Torpedo to screen a cDNA expression library constructed from mRNA of the electromotor nucleus. One clone encodes VAMP-1 (vesicle-associated membrane protein 1), a nervous-system-specific protein of 120 amino acids whose primary sequence can be divided into three domains: a proline-rich amino terminus, a highly charged internal region, and a hydrophobic carboxyl-terminal domain that is predicted to comprise a membrane anchor. Tryptic digestion of intact and lysed vesicles suggests that the protein faces the cytoplasm, where it may play a role in packaging, transport, or release of neurotransmitters. Images PMID:3380805

  5. A new integrated membrane filtration and chromatographic device.

    Science.gov (United States)

    Xu, Yanke; Sirkar, Kamalesh K; Dai, Xiao-Ping; Luo, Robert G

    2005-01-01

    To improve protein separation, a novel integrated device combining membrane filtration and chromatography has been developed. The device basically consists of a hollow fiber filtration module whose shell side is filled with chromatographic resin beads. However, there is an essentially impermeable coated zone near the hollow fiber module outlet. The integrated device enjoys the advantages of both membrane filtration and chromatography; it also allows one to load the chromatographic media directly from the fermentation broth or lysate and separate the adsorbed proteins through the subsequent elution step in a cyclic process. Interfacial polymerization was carried out to coat the bottom section of the hollow fiber membrane; the rest of the hollow fiber membrane remained unaffected. Myoglobin (Mb) and alpha-lactalbumin (alpha-LA) were primarily used as model proteins in a binary mixture; binary mixtures of Mb and bovine serum albumin (BSA) were also investigated. Separation behaviors of binary protein mixtures were studied in devices having either an ultrafiltration (UF) or a microfiltration (MF) membrane. Experimental results show that the breakthrough time and the protein loading capacities were dramatically improved after introducing the impermeable coating in both UF and MF modules. For a synthetic yeast fermentation broth feed, four loading-washing-elution-reequilibration-based cyclic runs for separation of Mb and alpha-LA were performed in the device using a MF membrane with a coated zone without cleaning in between. The Mb and alpha-LA elution profiles for the four consecutive runs were almost superimposable. Due to lower transmembrane flux in this device plus the periodical washing-elution during the chromatographic separation, fouling was not a problem, unlike in conventional microfiltration. PMID:15801803

  6. Proton-exchange membrane regenerative fuel cells

    Science.gov (United States)

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

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

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

    Science.gov (United States)

    Eisman, G. A.

    1990-02-01

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

  8. Solution NMR Structure of Membrane-Integral Diacylglycerol Kinase

    OpenAIRE

    Van Horn, Wade D.; Kim, Hak-Jun; Ellis, Charles D.; Hadziselimovic, Arina; Sulistijo, Endah S.; Karra, Murthy D.; Tian, Changlin; Sönnichsen, Frank D.; Sanders, Charles R.

    2009-01-01

    Escherichia coli diacylglycerol kinase (DAGK) represents a family of integral membrane enzymes that is unrelated to all other phosphotransferases. We have determined the three-dimensional structure of the DAGK homotrimer using solution NMR. The third transmembrane helix from each subunit is domain-swapped with the first and second transmembrane segments from an adjacent subunit. Each of DAGK’s three active sites resembles a portico. The cornice of the portico appears to be the determinant of ...

  9. 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

  10. Ion transport through biological membranes an integrated theoretical approach

    CERN Document Server

    Mackey, Michael C

    1975-01-01

    This book illustrates some of the ways physics and mathematics have been, and are being, used to elucidate the underlying mechan­ isms of passive ion movement through biological membranes in general, and the membranes of excltable cells in particular. I have made no effort to be comprehensive in my introduction of biological material and the reader interested in a brief account of single cell electro­ physlology from a physically-oriented biologists viewpoint will find the chapters by Woodbury (1965) an excellent introduction. Part I is introductory in nature, exploring the basic electrical properties of inexcitable and excitable cell plasma membranes. Cable theory is utilized to illustrate the function of the non-decrementing action potential as a signaling mechanism for the long range trans­ mission of information in the nervous system, and to gain some in­ sight into the gross behaviour of neurons. The detailed analysis of Hodgkin and Huxley on the squid giant axon membrane ionic conductance properties...

  11. Cell membrane-camouflaged nanoparticles for drug delivery.

    Science.gov (United States)

    Luk, Brian T; Zhang, Liangfang

    2015-12-28

    Nanoparticles can preferentially accumulate at sites of action and hold great promise to improve the therapeutic index of many drugs. While conventional methods of nanocarrier-mediated drug delivery have focused on primarily synthetic approaches, engineering strategies that combine synthetic nanoparticles with natural biomaterials have recently gained much attention. In particular, cell membrane-camouflaged nanoparticles are a new class of biomimetic nanoparticles that combine the unique functionalities of cellular membranes and engineering versatility of synthetic nanomaterials for effective delivery of therapeutic agents. Herein, we report on the recent progress on cell membrane-coated nanoparticles for drug delivery. In particular, we highlight three areas: (i) prolonging systemic circulation via cell membrane coating, (ii) cell-specific targeting via cell membrane coating, and (iii) applications of cell membrane coating for drug delivery. The cell membrane-camouflaged nanoparticle platform has emerged as a novel delivery strategy with the potential to improve the therapeutic efficacy for the treatment of a variety of diseases.

  12. Cell-free methods to produce structurally intact mammalian membrane proteins.

    Science.gov (United States)

    Shinoda, Takehiro; Shinya, Naoko; Ito, Kaori; Ishizuka-Katsura, Yoshiko; Ohsawa, Noboru; Terada, Takaho; Hirata, Kunio; Kawano, Yoshiaki; Yamamoto, Masaki; Tomita, Taisuke; Ishibashi, Yohei; Hirabayashi, Yoshio; Kimura-Someya, Tomomi; Shirouzu, Mikako; Yokoyama, Shigeyuki

    2016-01-01

    The crystal structures of four membrane proteins, from bacteria or a unicellular alga, have been solved with samples produced by cell-free protein synthesis. In this study, for mammalian membrane protein production, we established the precipitating and soluble membrane fragment methods: membrane proteins are synthesized with the Escherichia coli cell-free system in the presence of large and small membrane fragments, respectively, and are simultaneously integrated into the lipid environments. We applied the precipitating membrane fragment method to produce various mammalian membrane proteins, including human claudins, glucosylceramide synthase, and the γ-secretase subunits. These proteins were produced at levels of about 0.1-1.0 mg per ml cell-free reaction under the initial conditions, and were obtained as precipitates by ultracentrifugation. Larger amounts of membrane proteins were produced by the soluble membrane fragment method, collected in the ultracentrifugation supernatants, and purified directly by column chromatography. For several proteins, the conditions of the membrane fragment methods were further optimized, such as by the addition of specific lipids/detergents. The functional and structural integrities of the purified proteins were confirmed by analyses of their ligand binding activities, size-exclusion chromatography profiles, and/or thermal stabilities. We successfully obtained high-quality crystals of the complex of human claudin-4 with an enterotoxin. PMID:27465719

  13. Fluid levity of the cell: Role of membrane lipid architecture in genetic sphingolipidoses.

    Science.gov (United States)

    D'Auria, Ludovic; Bongarzone, Ernesto R

    2016-11-01

    Sphingolipidoses arise from inherited loss of function of key enzymes regulating the sphingolipid (SL) metabolism and the accumulation of large quantities of these lipids in affected cells. Most frequently, toxicity is manifested in the nervous system, where survival and function of neurons and glial cells are most affected. Although detailed information is available on neuroglial alterations during terminal stages of the disease, the initial pathogenic mechanisms triggering neuropathology are largely unclear. Because they are key components of biological membranes, changes in the local concentration of SLs are likely to impact the organization of membrane domains and functions. This Commentary proposes that SL toxicity involves initial defects in the integrity of lipid domains, membrane fluidity, and membrane bending, leading to membrane deformation and deregulation of cell signaling and function. Understanding how SLs alter membrane architecture may provide breakthroughs for more efficient treatment of sphingolipidoses. © 2016 Wiley Periodicals, Inc. PMID:27638586

  14. High temperature polymer electrolyte membrane fuel cell

    Institute of Scientific and Technical Information of China (English)

    K.Scott; M. Mamlouk

    2006-01-01

    One of the major issues limiting the introduction of polymer electrolyte membrane fuel cells (PEMFCs) is the low temperature of operation which makes platinum-based anode catalysts susceptible to poisoning by the trace amount of CO, inevitably present in reformed fuel. In order to alleviate the problem of CO poisoning and improve the power density of the cell, operating at temperature above 100 ℃ is preferred. Nafion(R) -type perfluorosulfonated polymers have been typically used for PEMFC. However, the conductivity of Nafion(R) -type polymers is not high enough to be used for fuel cell operations at higher temperature ( > 90 ℃) and atmospheric pressure because they dehydrate under these condition.An additional problem which faces the introduction of PEMFC technology is that of supplying or storing hydrogen for cell operation,especially for vehicular applications. Consequently the use of alternative fuels such as methanol and ethanol is of interest, especially if this can be used directly in the fuel cell, without reformation to hydrogen. A limitation of the direct use of alcohol is the lower activity of oxidation in comparison to hydrogen, which means that power densities are considerably lower. Hence to improve activity and power output higher temperatures of operation are preferable. To achieve this goal, requires a new polymer electrolyte membrane which exhibits stability and high conductivity in the absence of liquid water.Experimental data on a polybenzimidazole based PEMFC were presented. A simple steady-state isothermal model of the fuel cell is also used to aid in fuel cell performance optimisation. The governing equations involve the coupling of kinetic, ohmic and mass transport. This paper also considers the advances made in the performance of direct methanol and solid polymer electrolyte fuel cells and considers their limitations in relation to the source and type of fuels to be used.

  15. 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.

  16. Origin of subdiffusion of water molecules on cell membrane surfaces

    CERN Document Server

    Yamamoto, Eiji; Yasui, Masato; Yasuoka, Kenji

    2014-01-01

    Water molecules play an important role in providing unique environments for biological reactions on cell membranes. It is widely believed that water molecules form bridges that connect lipid molecules and stabilize cell membranes. Using all-atom molecular dynamics simulations, we show that translational and rotational diffusion of water molecules on lipid membrane surfaces exhibit subdiffusion. Moreover, we provide evidence that both divergent mean trapping time (continuous-time random walk) and long-correlated noise (fractional Brownian motion) contribute to this subdiffusion. These results suggest that subdiffusion on cell membranes causes the water retardation, an enhancement of cell membrane stability, and a higher reaction efficiency.

  17. Cryodamage to plasma membrane integrity in head and tail regions of human sperm

    Institute of Scientific and Technical Information of China (English)

    Wei-JieZHU; Xue-GaoLIU

    2000-01-01

    Aim: To investigate the effect of cryopreservation on the plasma membrane integrity in the head and tail regions of individual sperm, and the relationship between intact cryopreserved sperm and its motility and zona-free hamster oocyte penetration rate. Methods: The eosin Y exclusion and the hypoosmotic swelling tests were combined to form a single test (HOS-EY test) to identify the spermatozoa with four types of membrane integrity. Results: After cryopreservation, there was a marked decline in the percentage of spermatozoa with Type IV membrane integrity (head membrane intact/tail membrane intact), and a significant increase in those with Type Ⅰ (head membrane damaged/tail membrane damaged) and Type Ⅲ (head membrane damaged/tail membrane intact) membrane integrity (n = 50, P0.05). Conclusion: (1) The HOS-EY test has the advantage of showing four patterns of membrane integrity in individual spermatozoon; (2) Cryopreservation causes a significant membrane rupture in the head and tail regions of spermatozoa; Type IT[ is the main transitional state of membrane cryodamage; (3) Cryodamage to head and tail membrane may occur independently; the presence of an intact tail membrane does not necessarily indicate the intactness of head membrane. (4) Intact membranes am closely related to postthaw motility, but do not reflect the fertilizing potential.

  18. Utilization of pyrolytic substrate by microalga Chlamydomonas reinhardtii: cell membrane property change as a response of the substrate toxicity.

    Science.gov (United States)

    Zhao, Xuefei; Jarboe, Laura; Wen, Zhiyou

    2016-05-01

    Acetic acid derived from fast pyrolysis of lignocellulosic biomass is a promising substrate for microalgae fermentation for producing lipid-rich biomass. However, crude pyrolytic acetic acid solution contains various toxic compounds inhibiting algal growth. It was hypothesized that such an inhibition was mainly due to the cell membrane damage. In this work, the cell membrane property of algal cells was evaluated at various conditions to elucidate the mechanisms of inhibition caused by the pyrolytic substrate solution. It was found that acetic acid itself served a carbon source for boosting algal cell growth but also caused cell membrane leakage. The acetic acid concentration for highest cell density was 4 g/L. Over-liming treatment of crude pyrolytic acetic acid increased the algal growth with a concurrent reduction of cell membrane leakage. Directed evolution of algal strain enhanced cell membrane integrity and thus increased its tolerance to the toxicity of the crude substrate. Statistical analysis shows that there was a significant correlation between the cell growth performance and the cell membrane integrity (leakage) but not membrane fluidity. The addition of cyto-protectants such as Pluronic F68 and Pluronic F127 enhanced the cell membrane integrity and thus, resulted in enhanced cell growth. The transmission electron microscopy (TEM) of algal cells visually confirmed the cell membrane damage as the mechanism of the pyrolytic substrate inhibition. Collectively, this work indicates that the cell membrane is one major reason for the toxicity of pyrolytic acetic acid when being used for algal culture. To better use this pyrolytic substrate, cell membrane of the microorganism needs to be strengthened through either strain improvement or addition of membrane protectant reagents. PMID:26995605

  19. Association of lipids with integral membrane surface proteins of Mycoplasma hyorhinis

    International Nuclear Information System (INIS)

    Triton X-114 (TX-114)-phase fractionation was used to identify and characterize integral membrane surface proteins of the wall-less procaryote Mycoplasma hyorhinis GDL. Phase fractionation of mycoplasmas followed by analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed selective partitioning of approximately 30 [35S]methionine-labeled intrinsic membrane proteins into the TX-114 phase. Similar analysis of [3H]palmitate-labeled cells showed that approximately 20 proteins of this organism were associated with lipid, all of which also efficiently partitioned as integral membrane components into the detergent phase. Immunoblotting and immunoprecipitation of TX-114-phase proteins from 125I-surface-labeled cells with four monoclonal antibodies to distinct surface epitopes of M. hyorhinis identified surface proteins p120, p70, p42, and p23 as intrinsic membrane components. Immunoprecipitation of [3H]palmitate-labeled TX-114-phase proteins further established that surface proteins p120, p70, and p23 (a molecule that mediates complement-dependent mycoplasmacidal monoclonal antibody activity) were among the lipid-associated proteins of this organism. Two of these proteins, p120 and p123, were acidic (pI less than or equal to 4.5), as shown by two-dimensional isoelectric focusing. This study established that M. hyorhinis contains an abundance of integral membrane proteins tightly associated with lipids and that many of these proteins are exposed at the external surface of the single limiting plasma membrane. Monoclonal antibodies are reported that will allow detailed analysis of the structure and processing of lipid-associated mycoplasma proteins

  20. Preparation of cell membranes for high resolution imaging by AFM

    International Nuclear Information System (INIS)

    Studies of cell membrane structure by atomic force microscopy (AFM) have been limited because of the softness of cell membranes. Here, we utilize a new technique of sample preparation to lay red blood cell membranes on the top of a mica surface to obtain high resolution images by in-situ AFM on both sides of cell membranes. Our results indicate that the location of oligosaccharides and proteins in red blood cell membranes might be different from the current membrane model. The inner membrane leaflet is covered by dense proteins with fewer free lipids than expected. In contrast, the outer membrane leaflet is quite smooth; oligosaccharides and peptides supposed to protrude out of the outer membrane leaflet surface might be actually hidden in the middle of hydrophilic lipid heads; transmembrane proteins might form domains in the membranes revealed by PNGase F and trypsin digestion. Our result could be significant to interpret some functions about red blood cell membranes and guide to heal the blood diseases related to cell membranes.

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

    OpenAIRE

    Jodie Lopez; Amina Bittame; Céline Massera; Virginie Vasseur; Grégory Effantin; Anne Valat; Célia Buaillon; Sophie Allart; Barbara A. Fox; Leah M. Rommereim; David J. Bzik; Guy Schoehn; Winfried Weissenhorn; Jean-François Dubremetz; Jean Gagnon

    2015-01-01

    Apicomplexa parasites such as Toxoplasma gondii target effectors to and across the boundary of their parasitophorous vacuole (PV), resulting in host cell subversion and potential presentation by MHC class I molecules for CD8 T cell recognition. The host-parasite interface comprises the PV limiting membrane and a highly curved, membranous intravacuolar network (IVN) of uncertain function. Here, using a cell-free minimal system, we dissect how membrane tubules are shaped by the parasite effecto...

  2. Expression and purification of integral membrane fatty acid desaturases.

    Directory of Open Access Journals (Sweden)

    Haiqin Chen

    Full Text Available Fatty acid desaturase enzymes perform dehydrogenation reactions leading to the insertion of double bonds in fatty acids, and are divided into soluble and integral membrane classes. Crystal structures of soluble desaturases are available; however, membrane desaturases have defied decades of efforts due largely to the difficulty of generating recombinant desaturase proteins for crystallographic analysis. Mortierella alpina is an oleaginous fungus which possesses eight membrane desaturases involved in the synthesis of saturated, monounsaturated and polyunsaturated fatty acids. Here, we describe the successful expression, purification and enzymatic assay of three M. alpina desaturases (FADS15, FADS12, and FADS9-I. Estimated yields of desaturases with purity >95% are approximately 3.5% (Ca. 4.6 mg/L of culture for FADS15, 2.3% (Ca. 2.5 mg/L of culture for FADS12 and 10.7% (Ca. 37.5 mg/L of culture for FADS9-I. Successful expression of high amounts of recombinant proteins represents a critical step towards the structural elucidation of membrane fatty acid desaturases.

  3. Durable Catalysts for High Temperature Proton Exchange Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Durability of proton exchange membrane fuel cells (PEMFCs) is recognized as one of the most important issues to be addressed before the commercialization. The failure mechanisms are not well understood, however, degradation of carbon supported noble metal catalysts is identified as a major failure...... significant attention in recent years because of its potential advantages such as high CO tolerance, easy cooling, better heat utilization and possible integration with fuel processing units. However, the high temperature obviously aggravates the carbon corrosion and catalyst degradation. Based on thermally...

  4. 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 membran...

  5. Resting microglial cells exhibit tubular membrane protrusions

    OpenAIRE

    Ulrike Gimsa; Veronika Kralj-Iglic; Jan Gimsa; Ales Iglic

    2002-01-01

    Nano- and microtubular structures have recently become a subject of increasing interest due to their importance in biology and medicine as well as their technological potential. Such structures have been observed in anorganic (Iijima, 1991) as well as in organic (Schnur 1993; Oda et al. 1991) systems. Micro- and nanotubular protrusions of bilayer membranes have been found in cells (Kralj-Iglic et al. 1998; Kralj-Iglic et al. 2001a) and phospholipid vesicles (Kralj-Iglic et al. 2002; Kralj-Igl...

  6. Nanocomposite Membranes based on Perlfuorosulfonic Acid/Ceramic for Proton Exchange Membrane Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    LI Qiong; WANG Guangjin; YE Hong; YAN Shilin

    2015-01-01

    Perlfuorosulfonic acid/ceramic nanocomposite membranes were investigated as electrolytes for polymer electrolyte membrane fuel cell applications under low relative humidity. Different nanosized ceramics (SiO2, ZrO2, TiO2) with diameters in the range of 2-6 nm were synthesized in situ in Nafion solution through a sol-gel process and the formed nanosized ceramics were well-dispersed in the solution. The nanocomposite membranes were formed through a casting process. The nanocomposite membrane showes enhanced water retention ability and improved proton conductivity compared to those of pure Naifon membrane. The mechanical strength of the formed nanocomposite membranes is slightly less than that of pure Naifon membrane. The experimental results demonstrate that the polymer ceramic nanocompsite membranes are potential electrolyte for fuel cells operating at elevated temperature.

  7. Solution NMR Structure of Membrane-Integral Diacylglycerol Kinase

    Science.gov (United States)

    Van Horn, Wade D.; Kim, Hak-Jun; Ellis, Charles D.; Hadziselimovic, Arina; Sulistijo, Endah S.; Karra, Murthy D.; Tian, Changlin; Sönnichsen, Frank D.; Sanders, Charles R.

    2009-01-01

    Escherichia coli diacylglycerol kinase (DAGK) represents a family of integral membrane enzymes that is unrelated to all other phosphotransferases. We have determined the three-dimensional structure of the DAGK homotrimer using solution NMR. The third transmembrane helix from each subunit is domain-swapped with the first and second transmembrane segments from an adjacent subunit. Each of DAGK’s three active sites resembles a portico. The cornice of the portico appears to be the determinant of DAGK’s lipid substrate specificity and overhangs the site of phosphoryl transfer near the water-membrane interface. Mutations to cysteine that caused severe misfolding were located in or near the active site, indicating a high degree of overlap between sites responsible for folding and for catalysis. PMID:19556511

  8. Roles of membrane trafficking in plant cell wall dynamics

    OpenAIRE

    Ebine, Kazuo; Ueda, Takashi

    2015-01-01

    The cell wall is one of the characteristic components of plant cells. The cell wall composition differs among cell types and is modified in response to various environmental conditions. To properly generate and modify the cell wall, many proteins are transported to the plasma membrane or extracellular space through membrane trafficking, which is one of the key protein transport mechanisms in eukaryotic cells. Given the diverse composition and functions of the cell wall in plants, the transpor...

  9. Plasma membranes from insect midgut cells

    Directory of Open Access Journals (Sweden)

    Walter R. Terra

    2006-06-01

    Full Text Available Plasma membranes from insect midgut cells are separated into apical and basolateral domains. The apical domain is usually modified into microvilli with a molecular structure similar to other animals. Nevertheless, the microvillar structure should differ in some insects to permit the traffic inside them of secretory vesicles that may budd laterally or pinch-off from the tips of microvilli. Other microvillar modifications are associated with proton-pumping or with the interplay with an ensheathing lipid membrane (the perimicrovilllar membrane observed in the midgut cells of hemipterans (aphids and bugs. The perimicrovillar membranes are thought to be involved in amino acid absorption from diluted diets. The microvillar and perimicrovillar membranes have densities (and protein content that depend on the insect taxon. The role played by the microvillar and perimicrovillar proteins in insect midgut physiology is reviewed here trying to provide a coherent picture of data and highlighting further research areas.As membranas plasmáticas das células intestinais dos insetos apresentam um domínio apical e outro basal. O domínio apical é geralmente modificado em microvilosidades com organização molecular similar a de outros animais, embora possam diferir naqueles insetos que apresentam vesículas secretoras em trânsito que brotam lateralmente ou destacam-se das extremidades das microvilosidades. Outras modificações microvilares estão associadas a bombeamento de prótons ou a interrelações com uma membrana lipídica (a membrana perimicrovilar que reveste as microvilosidades de células intestinais de hemípteros (pulgões e percevejos. Admite-se que as membranas perimicrovilares estejam envolvidas na absorção de aminoácidos a partir de dietas diluídas. As membranas microvilares e perimicrovilares tem densidades distintas (e conteúdo protéico que dependem do táxon do inseto. O papel desempenhado pelas proteínas microvilares e

  10. Integrity of the plasma membrane, the acrosomal membrane, and the mitochondrial membrane potential of sperm in Nelore bulls from puberty to sexual maturity

    Directory of Open Access Journals (Sweden)

    L.S.L.S. Reis

    2016-06-01

    Full Text Available ABSTRACT This study evaluated the plasma membrane integrity, acrosomal membrane integrity, and mitochondrial membrane potential of Nelore bull sperm from early puberty to early sexual maturity and their associations with sperm motility and vigor, the mass motility of the spermatozoa (wave motion, scrotal circumference, and testosterone. Sixty Nelore bulls aged 18 to 19 months were divided into four lots (n=15 bulls/lot and evaluated over 280 days. Semen samples, collected every 56 days by electroejaculation, were evaluated soon after collection for motility, vigor and wave motion under an optical microscope. Sperm membrane integrity, acrosomal integrity, and mitochondrial activity were evaluated under a fluorescent microscope using probe association (FITC-PSA, PI, JC-1, H342. The sperm were classified into eight integrity categories depending on whether they exhibited intact or damaged membranes, an intact or damaged acrosomal membrane, and high or low mitochondrial potential. The results show that bulls have a low amount of sperm with intact membranes at puberty, and the sperm show low motility, vigor, and wave motion; however, in bulls at early sexual maturity, the integrity of the sperm membrane increased significantly. The rate of sperm membrane damage was negatively correlated with motility, vigor, wave motion, and testosterone in the bulls, and a positive correlation existed between sperm plasma membrane integrity and scrotal circumference. The integrity of the acrosomal membrane was not influenced by puberty. During puberty and into early sexual maturity, bulls show low sperm mitochondrial potential, but when bulls reached sexual maturity, high membrane integrity with high mitochondrial potential was evident.

  11. 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

    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...... 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...

  12. Changes of Saccharomyces cerevisiae cell membrane components and promotion to ethanol tolerance during the bioethanol fermentation.

    Science.gov (United States)

    Dong, Shi-Jun; Yi, Chen-Feng; Li, Hao

    2015-12-01

    During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane might provide main protection to tolerate accumulated ethanol, and S. cerevisiae cells might also remodel their membrane compositions or structure to try to adapt to or tolerate the ethanol stress. However, the exact changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation still remains poorly understood. This study was performed to clarify changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation. Both cell diameter and membrane integrity decreased as fermentation time lasting. Moreover, compared with cells at lag phase, cells at exponential and stationary phases had higher contents of ergosterol and oleic acid (C18:1) but lower levels of hexadecanoic (C16:0) and palmitelaidic (C16:1) acids. Contents of most detected phospholipids presented an increase tendency during fermentation process. Increased contents of oleic acid and phospholipids containing unsaturated fatty acids might indicate enhanced cell membrane fluidity. Compared with cells at lag phase, cells at exponential and stationary phases had higher expressions of ACC1 and HFA1. However, OLE1 expression underwent an evident increase at exponential phase but a decrease at following stationary phase. These results indicated that during bioethanol fermentation process, yeast cells remodeled membrane and more changeable cell membrane contributed to acquiring higher ethanol tolerance of S. cerevisiae cells. These results highlighted our knowledge about relationship between the variation of cell membrane structure and compositions and ethanol tolerance, and would contribute to a better understanding of bioethanol fermentation process and construction of industrial ethanologenic strains with higher ethanol tolerance.

  13. Simulation and in situ measurement of stress distribution in a polymer electrolyte membrane fuel cell stack

    Science.gov (United States)

    de la Cruz, Javier; Cano, Ulises; Romero, Tatiana

    2016-10-01

    A critical parameter for PEM fuel cell's electric contact is the nominal clamping pressure. Predicting the mechanical behavior of all components in a fuel cell stack is a very complex task due to the diversity of materials properties. Prior to the integration of a 3 kW PEMFC power plant, a numerical simulation was performed in order to obtain the mechanical stress distribution for two of the most pressure sensitive components of the stack: the membrane, and the graphite plates. The stress distribution of the above mentioned components was numerically simulated by finite element analysis and the stress magnitude for the membrane was confirmed using pressure films. Stress values were found within the elastic zone which guarantees mechanical integrity of fuel cell components. These low stress levels particularly for the membrane will allow prolonging the life and integrity of the fuel cell stack according to its design specifications.

  14. Integrity of the plasma membrane, the acrosomal membrane, and the mitochondrial membrane potential of sperm in Nelore bulls from puberty to sexual maturity

    OpenAIRE

    L. S. L. S. Reis; A.A. Ramos; A.S. Camargos; E. Oba

    2016-01-01

    ABSTRACT This study evaluated the plasma membrane integrity, acrosomal membrane integrity, and mitochondrial membrane potential of Nelore bull sperm from early puberty to early sexual maturity and their associations with sperm motility and vigor, the mass motility of the spermatozoa (wave motion), scrotal circumference, and testosterone. Sixty Nelore bulls aged 18 to 19 months were divided into four lots (n=15 bulls/lot) and evaluated over 280 days. Semen samples, collected every 56 days by e...

  15. Integration of oxygen membranes for oxygen production in cement plants

    DEFF Research Database (Denmark)

    Puig Arnavat, Maria; Søgaard, Martin; Hjuler, Klaus;

    2015-01-01

    a concentrated CO2 source that can be used for enhanced oil recovery, in combination with biomass gasification and electrolysis for synthesis gas production, or possibly sequestered. The cases with oxygen enriched air provide very promising economic figures of merit with discounted payback periods slightly......The present paper describes the integration of oxygen membranes in cement plants both from an energy, exergy and economic point of view. Different configurations for oxygen enrichment of the tertiary air for combustion in the pre-calciner and full oxy-fuel combustion in both pre-calciner and kiln...

  16. Cytocompatibility of Three Corneal Cell Types with Amniotic Membrane

    Institute of Scientific and Technical Information of China (English)

    CHENJian-su; CHENRui; XUJin-tang; DINGYong; ZHAOSong-bin; LISui-lian

    2004-01-01

    Rabbit limbal corneal epithelial cells, corneal endothelial cells and keratocytes were cultured on amniotic membrane. Phase contrast microscope examination was performed daily. Histological and scan electron microscopic examinations were carried out to observe the growth, arrangement and adhesion of cultivated cells. Results showed that three corneal cell types seeded on amniotic membrane grew well and had normal cell morphology. Cultured cells attached firmly on the surface of amniotic membrane. Corneal epithelial cells showed singular layer or stratification. Cell boundaries were formed and tightly opposed. Corneal endothelial cells showed cobblestone or polygonal morphologic characteristics that appeared uniform in size. The cellular arrangement was compact. Keratocytes elongated and showed triangle or dendritic morphology with many intercellular joints which could form networks. In conclusion, amniotic membrane has good scaffold property, diffusion effect and compatibility with corneal cells. The basement membrane side of amniotic membrane facilitated the growth of corneal epithelial cells and endothelial cells and cell junctions were tightly developed. The spongy layer of amniotic membrane facilitated the growth of keratocytes and intercellular joints were rich. Amniotic membrane is an ideal biomaterial for layering tissue engineered cornea.

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

    Science.gov (United States)

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

    2016-02-01

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

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

    Science.gov (United States)

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

    2015-12-15

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

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

    International Nuclear Information System (INIS)

    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

  20. 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.

  1. 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.

  2. A fluctuating elastic plate and a cell model for lipid membranes

    Science.gov (United States)

    Liang, Xiaojun; Purohit, Prashant K.

    2016-05-01

    The thermal fluctuations of lipid bi-layer membranes are key to their interaction with cellular components as well as the measurement of their mechanical properties. Typically, membrane fluctuations are analyzed by decomposing into normal modes or by molecular simulations. Here we propose two new approaches to calculate the partition function of a membrane. In the first approach we view the membrane as a fluctuating von Karman plate and discretize it into triangular elements. We express its energy as a function of nodal displacements, and then compute the partition function and co-variance matrix using Gaussian integrals. We recover well-known results for the dependence of the projected area of the membrane on the applied tension and recent simulation results on the dependence of membrane free energy on geometry, spontaneous curvature and tension. As new applications we compute the fluctuations of the membrane of a malaria infected cell and analyze the effects of boundary conditions on fluctuations. Our second approach is based on the cell model of Lennard-Jones and Devonshire. This model, which was developed for liquids, assumes that each molecule fluctuates within a cell on which a potential is imposed by all the surrounding molecules. We adapt the cell model to a lipid membrane by recognizing that it is a 2D liquid with the ability to deform out of plane whose energetic penalty must be factored into the partition function of a cell. We show, once again, that some results on membrane fluctuations can be recovered using this new cell model. However, unlike some well established results, our cell model gives an entropy that scales with the number of molecules in a membrane. Our model makes predictions about the heat capacity of the membrane that can be tested in experiments.

  3. Selective effect of cell membrane on synaptic neurotransmission

    Science.gov (United States)

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

    2016-01-01

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

  4. Finite element analysis of microelectrotension of cell membranes

    OpenAIRE

    Bae, Chilman; Butler, Peter J.

    2007-01-01

    Electric fields can be focused by micropipette-based electrodes to induce stresses on cell membranes leading to tension and poration. To date, however, these membrane stress distributions have not been quantified. In this study, we determine membrane tension, stress, and strain distributions in the vicinity of a microelectrode using finite element analysis of a multiscale electro-mechanical model of pipette, media, membrane, actin cortex, and cytoplasm. Electric field forces are coupled to me...

  5. Membrane Fouling in Microfiltration used for Cell Harvesting

    Institute of Scientific and Technical Information of China (English)

    Tahereh Kaghazchi; Farzin Zokaee; Abbas Zare

    2001-01-01

    In the present study the membrane fouling in microfiltration used for cell harvesting in a deadend system has been investigated. Experimental results were analysed in terms of existing membrane filtration models and membrane resistances. The cake filtration model (CFM) and standard blocking model (SBM) have been considered in this study.Various membrane resistances were determined at different processing time, feed concentration and stirring speed. Resistances to permeation in this system include filter medium, pore blocking, adsorption, cake layer and concentration polarization.

  6. Efficient ethanol recovery from yeast fermentation broth with integrated distillation-membrane process

    Science.gov (United States)

    A hybrid process integrating vapor stripping with vapor compression and vapor permeation membrane separation, termed Membrane Assisted Vapor Stripping (MAVS), was evaluated for recovery and dehydration of ethanol from aqueous solution as an alternative to conventional distillatio...

  7. 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. methyl (MePSU), ethyl (EtPSU) and butyl (BuPSU) imidazoliums, as revealed by 1H NMR spectra. The imidazolium polysulfone membranes are then doped with phosphoric acid and used as a proton exchange membrane electrolyte in fuel cells. An acid doping level of about 10–11mol H3PO4 per mole of the imidazolium...

  8. Deformation of Two-Dimensional Nonuniform-Membrane Red Blood Cells Simulated by a Lattice Boltzmann Model

    Institute of Scientific and Technical Information of China (English)

    LI Hua-Bing; JIN Li; QIU Bing

    2008-01-01

    To study two-dimensional red blood cells deforming in a shear flow with the membrane nonuniform on the rigidity and mass, the membrane is discretized into equilength segments. The fluid inside and outside the red blood cell is simulated by the D2Q9 lattice Boltzmann model and the hydrodynamic forces exerted on the membrane from the inner and outer of the red blood cell are calculated by a stress-integration method. Through the global deviation from the curvature of uniform-membrane, we find that when the membrane is nonuniform on the rigidity, the deviation first decreases with the time increases and implies that the terminal profile of the red blood cell is static. To a red blood cell with the mass nonuniform on the membrane, the deviation becomes more large, and the mass distribution affects the profile of the two sides of the flattened red blood cell in a shear flow.

  9. Engineered nanoparticles mimicking cell membranes for toxin neutralization.

    Science.gov (United States)

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

    2015-08-01

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

  10. Membrane tension and cytoskeleton organization in cell motility

    International Nuclear Information System (INIS)

    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)

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

    Science.gov (United States)

    Lux, Samuel E

    2016-01-14

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

  12. Electrochemical proton gradient in Micrococcus lysodeikticus cells and membrane vesicles.

    OpenAIRE

    Friedberg, I.; Kaback, H R

    1980-01-01

    Using the distribution of weak acids to measure the pH gradient (delta pH; interior alkaline) and the distribution of the lipophilic cation [3H]tetraphenylphosphonium+ to monitor the membrane potential (delta psi; interior negative), we studied the electrochemical gradient or protons (delta mu- H+) across the membrane of Micrococcus lysodeikticus cells and plasma membrane vesicles. With reduced phenazine methosulfate as electron donor, intact cells exhibited a relatively constant delta mu- H+...

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

    OpenAIRE

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

    2016-01-01

    Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membran...

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

    International Nuclear Information System (INIS)

    Composite membranes based on poly(2,2′(m-phenylene)-5,5′bibenzimidazole) (PBI) and sulfonated polyhedral oligosilsesquioxane (S-POSS) with S-POSS contents of 5 and 10 wt.% were prepared by solution casting as base materials for high temperature polymer electrolyte membrane fuel cells. With membranes based on pure PBI as a reference point, the composite membranes were characterized with respect to spectroscopic and physicochemical properties. After doping with phosphoric acid, the composite membranes showed considerably improved ex situ proton conductivity under anhydrous as well as under fully humidified conditions in the 120-180 °C temperature range. The conductivity improvements were also confirmed by in situ fuel cell tests at 160 °C and further supported by the electrochemical impedance spectroscopy data based on the operating membrane electrode assemblies, demonstrating the technical feasibility of the novel electrolyte materials

  15. The Stirred Tank Reactor Polymer Electrolyte Membrane Fuel Cell

    CERN Document Server

    Benziger, J; Karnas, E; Moxley, J; Teuscher, C; Kevrekidis, Yu G; Benziger, Jay

    2003-01-01

    The design and operation of a differential Polymer Electrolyte Membrane (PEM) fuel cell is described. The fuel cell design is based on coupled Stirred Tank Reactors (STR); the gas phase in each reactor compartment was well mixed. The characteristic times for reactant flow, gas phase diffusion and reaction were chosen so that the gas compositions at both the anode and cathode are uniform. The STR PEM fuel cell is one-dimensional; the only spatial gradients are transverse to the membrane. The STR PEM fuel cell was employed to examine fuel cell start- up, and its dynamic responses to changes in load, temperature and reactant flow rates. Multiple time scales in systems response are found to correspond to water absorption by the membrane, water transport through the membrane and stress-related mechanical changes of the membrane.

  16. 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....... 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...... 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...

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2016-08-01

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

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

    Science.gov (United States)

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

    2015-10-14

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

  20. Nano thermo-hydrodynamics method for investigating cell membrane fluidity

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    As a barrier to compartmentalize cells,mem-branes form the interface between a cell and its surround-ings.The essential function of a membrane is to maintain a relatively stable environment in the cell,exchange sub-stances selectively and transfer energy and information continually from the outside.It is intriguing that above the phase transition temperature,the membrane lipid molecule will have three modes-lateral diffusion,rotational movement and flip-flop activity.These thermodynamic processes are vital to cell existence,growth,division,differentiation and are also responsible for hundreds of thousands of phenomena in life.Previously,species transport across the membrane was interpreted mainly from a phenomenological view using a lumped system model.Therefore,detailed flow processes occurred in the membrane domain and clues related to life mechanism were not sufficiently tackled.Such important issues can be clarifled by modeling nano scale thermal hydrodynamics over the gap space of a cell membrane.Previously observed complex membrane behaviors will be shown in this paper and explained by the thermally induced fluidic convections inside the membrane.A correlation between nano scale hydrodynamics,non-equilibrium thermodynamics and eell membrane activities is set up.The disclosed mechanisms are expected to provide a new viewpoint on the interaction between intracellular and extracellular processes through the membrane.

  1. Oncostatin M regulates membrane traffic and stimulates bile canalicular membrane biogenesis in HepG2 cells

    NARCIS (Netherlands)

    Van der Wouden, Johanna M.; Van IJzendoorn, Sven C.D.; Hoekstra, Dick

    2002-01-01

    Hepatocytes are the major epithelial cells of the liver and they display membrane polarity: the sinusoidal membrane representing the basolateral surface, while the bile canalicular membrane is typical of the apical membrane. In polarized HepG2 cells an endosomal organelle, SAC, fulfills a prominent

  2. 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

    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...

  3. Electron Spin Resonance Study of Fuel Cell Polymer Membrane Degradation

    Institute of Scientific and Technical Information of China (English)

    Alexander Panchenko; Elena Aleksandrova; Emil Roduner

    2005-01-01

    @@ 1Introduction The long term stability of the membrane is an important factor limiting the fuel cell lifetime. During extended use the membrane degrades, probably via reaction with hydroxyl and superoxide radicals which are regular intermediates of the oxygen reduction at the cathode. Only extremely stable membranes can withstand the aggressive chemical and physical environment in an operating fuel cell. Within a given set of operating conditions, intrinsic chemical and mechanical properties of the membrane as well as its water content impact its durability dramatically.

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

    Science.gov (United States)

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

    2016-01-01

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

  5. The Use of Fibrous, Supramolecular Membranes and Human Tubular Cells for Renal Epithelial Tissue Engineering : Towards a Suitable Membrane for a Bioartificial Kidney

    NARCIS (Netherlands)

    Dankers, Patricia Y. W.; Boomker, Jasper M.; Huizinga-van der Vlag, Ali; Smedts, Frank M. M.; Harmsen, Martin C.; van Luyn, Marja J. A.

    2010-01-01

    A bioartificial kidney, which is composed of a membrane cartridge with renal epithelial cells, can substitute important kidney functions in patients with renal failure. A particular challenge is the maintenance of monolayer integrity and specialized renal epithelial cell functions ex vivo. We hypoth

  6. Detecting Nanodomains in Living Cell Membrane by Fluorescence Correlation Spectroscopy

    Science.gov (United States)

    He, Hai-Tao; Marguet, Didier

    2011-05-01

    Cell membranes actively participate in numerous cellular functions. Inasmuch as bioactivities of cell membranes are known to depend crucially on their lateral organization, much effort has been focused on deciphering this organization on different length scales. Within this context, the concept of lipid rafts has been intensively discussed over recent years. In line with its ability to measure diffusion parameters with great precision, fluorescence correlation spectroscopy (FCS) measurements have been made in association with innovative experimental strategies to monitor modes of molecular lateral diffusion within the plasma membrane of living cells. These investigations have allowed significant progress in the characterization of the cell membrane lateral organization at the suboptical level and have provided compelling evidence for the in vivo existence of raft nanodomains. We review these FCS-based studies and the characteristic structural features of raft nanodomains. We also discuss the findings in regards to the current view of lipid rafts as a general membrane-organizing principle.

  7. Biodegradable, Tethered Lipid Bilayer-Microsphere Systems with Membrane-Integrated α-Helical Peptide Anchors.

    Science.gov (United States)

    Fried, Eric S; Luchan, Joshua; Gilchrist, M Lane

    2016-04-12

    Supported lipid bilayers (SLBs) are ideally suited for the study of biomembrane-biomembrane interactions and for the biomimicry of cell-to-cell communication, allowing for surface ligand displays that contain laterally mobile elements. However, the SLB paradigm does not include three-dimensionality and biocompatibility. As a way to bypass these limitations, we have developed a biodegradable form of microsphere SLBs, also known as proteolipobeads (PLBs), using PLGA microspheres. Microspheres were synthesized using solvent evaporation and size selected with fluorescence activated cell sorting (FACS). Biomembranes were covalently tethered upon fusion to microsphere supports via short-chain PEG spacers connecting membrane-integrated α-helical peptides and the microsphere surface, affecting membrane diffusivity and mobility as indicated by confocal FRAP analysis. Membrane heterogeneities, which are attributed to PLGA hydrophobicity and rough surface topography, are curtailed by the addition of PEG tethers. This method allows for the presentation of tethered, laterally mobile biomembranes in three dimensions with functionally embedded attachment peptides for mobile ligand displays. PMID:26972467

  8. Integrating Microbial Electrochemical Technology with Forward Osmosis and Membrane Bioreactors: Low-Energy Wastewater Treatment, Energy Recovery and Water Reuse

    KAUST Repository

    Werner, Craig M.

    2014-06-01

    Wastewater treatment is energy intensive, with modern wastewater treatment processes consuming 0.6 kWh/m3 of water treated, half of which is required for aeration. Considering that wastewater contains approximately 2 kWh/m3 of energy and represents a reliable alternative water resource, capturing part of this energy and reclaiming the water would offset or even eliminate energy requirements for wastewater treatment and provide a means to augment traditional water supplies. Microbial electrochemical technology is a novel technology platform that uses bacteria capable of producing an electric current outside of the cell to recover energy from wastewater. These bacteria do not require oxygen to respire but instead use an insoluble electrode as their terminal electron acceptor. Two types of microbial electrochemical technologies were investigated in this dissertation: 1) a microbial fuel cell that produces electricity; and 2) a microbial electrolysis cell that produces hydrogen with the addition of external power. On their own, microbial electrochemical technologies do not achieve sufficiently high treatment levels. Innovative approaches that integrate microbial electrochemical technologies with emerging and established membrane-based treatment processes may improve the overall extent of wastewater treatment and reclaim treated water. Forward osmosis is an emerging low-energy membrane-based technology for seawater desalination. In forward osmosis water is transported across a semipermeable membrane driven by an osmotic gradient. The microbial osmotic fuel cell described in this dissertation integrates a microbial fuel cell with forward osmosis to achieve wastewater treatment, energy recovery and partial desalination. This system required no aeration and generated more power than conventional microbial fuel cells using ion exchange membranes by minimizing electrochemical losses. Membrane bioreactors incorporate semipermeable membranes within a biological wastewater

  9. Effects of Bloom-Forming Algae on Fouling of Integrated Membrane Systems in Seawater Desalination

    Science.gov (United States)

    Ladner, David Allen

    2009-01-01

    Combining low- and high-pressure membranes into an integrated membrane system is an effective treatment strategy for seawater desalination. Low-pressure microfiltration (MF) and ultrafiltration (UF) membranes remove particulate material, colloids, and high-molecular-weight organics leaving a relatively foulant-free salt solution for treatment by…

  10. 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].

  11. Loss of elongation factor P disrupts bacterial outer membrane integrity

    DEFF Research Database (Denmark)

    Zou, S Betty; Hersch, Steven J; Roy, Hervé;

    2012-01-01

    Elongation factor P (EF-P) is posttranslationally modified at a conserved lysyl residue by the coordinated action of two enzymes, PoxA and YjeK. We have previously established the importance of this modification in Salmonella stress resistance. Here we report that, like poxA and yjeK mutants......, Salmonella strains lacking EF-P display increased susceptibility to hypoosmotic conditions, antibiotics, and detergents and enhanced resistance to the compound S-nitrosoglutathione. The susceptibility phenotypes are largely explained by the enhanced membrane permeability of the efp mutant, which exhibits...... background ameliorates the detergent, antibiotic, and osmosensitivity phenotypes and restores wild-type permeability to NPN. Our data support a role for EF-P in the translational regulation of a limited number of proteins that, when perturbed, renders the cell susceptible to stress by the adventitious...

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

    Science.gov (United States)

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

    2011-05-01

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

  13. 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

    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...... 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...

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

    Science.gov (United States)

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

    2015-04-21

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

  15. Nafion-layered silicate nanocomposite membrane for fuel cell application

    OpenAIRE

    Thomassin, Jean-Michel; Pagnoulle, Christophe; Bizzari, Didier; Caldarella, Giuseppe; Germain, Albert; Jérôme, Robert

    2004-01-01

    Direct methanol fuel cells (DMFCs) using a proton exchange membrane as electrolyte is an attractive option for electricity generation. The most widely used membrane in the DMFC system is based on a perfluorinated polymer bearing sulfonic acid functions like Nafion®. The latter combines chemical, mechanical and thermal stability and high protonic conductivity but shows elevated methanol permeability. We propose the preparation of a novel type of hybrid membranes to tentatively solve this probl...

  16. 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. T

  17. Cell-free synthesis of cytochrome bo(3) ubiquinol oxidase in artificial membranes.

    Science.gov (United States)

    Yildiz, Ahu Arslan; Knoll, Wolfgang; Gennis, Robert B; Sinner, Eva-Kathrin

    2012-04-01

    The analysis of membrane proteins is notoriously difficult because isolation and detergent-mediated reconstitution often results in compromising the protein structure and function. We introduce a novel strategy of combining a cell-free expression method for synthesis of a protein species coping with one of the most important obstacles in membrane protein research-preserving the structural-functional integrity of a membrane protein species and providing a stable matrix for application of analytical tools to characterize the membrane protein of interest. We address integration and subsequent characterization of the cytochrome bo(3) ubiquinol oxidase (Cyt-bo(3)) from de novo synthesis without the effort of conventional cell culture, isolation, and purification procedures. The experimental output supports our idea of a suitable platform for in vitro protein synthesis and functional integration into a membrane-mimicking structure. We show the compatibility of different concepts of in vitro synthesis toward biosensor applicability by the example of Cyt-bo(3) protein expression. Our results obtained from in vitro synthesized proteins displayed similar behavior to proteins isolated from the cellular context. Overall, our approach is suitable for the in vitro expression of "complex" protein species such as Cyt-bo(3), which can be reproducible and stably synthesized and preserved in robust, synthetic planar membrane architecture. PMID:22306473

  18. Microbial fuel cells and osmotic membrane bioreactors have mutual benefits for wastewater treatment and energy production.

    Science.gov (United States)

    Hou, Dianxun; Lu, Lu; Ren, Zhiyong Jason

    2016-07-01

    This study demonstrates that microbial fuel cells (MFCs) and osmotic membrane bioreactors (OMBRs) can be mutually beneficial when integrated together for wastewater treatment. When connecting MFCs with OMBRs, the solute buildup increased conductivity and buffer capacity, which greatly increased MFC power density from 3 W/m(3) up to 11.5 W/m(3). In turn, the MFCs conditioned and reduced sludge production and therefore reduced forward osmosis (FO) membrane fouling. The MFC-OMBR equipped with new thin-film composite (TFC) membrane showed excellent organic (>95%) and phosphorus removal (>99%) and therefore maintained effluent sCOD below 20 mg/L. However, the nitrogen removal was limited due to the negative surface charge of the thin-film composite membrane and solution chemistry, which led to higher flux of ammonium toward the OMBR draw solution. Further studies are needed to improve nitrogen removal, reduce fouling, and optimize system integration. PMID:27105032

  19. Membrane integrity of Campylobacter jejuni subjected to high pressure is pH-dependent

    Science.gov (United States)

    Lerasle, M.; Guillou, S.; Simonin, H.; Laroche, M.; de Lamballerie, M.; Federighi, M.

    2012-03-01

    Our study focuses on a foodborne pathogen, Campylobacter, which is responsible for the most frequent bacterial enteritis worldwide. Membrane integrity of Campylobacter jejuni NCTC 11168 cells treated at high pressure (300 MPa, 20°C, 10 min) at pH 7.0 and pH 5.6 was measured by fluorescence spectroscopy of propidium iodide (PI) uptake. The percentage of membrane-damaged cells by high pressure, in which PI is allowed to penetrate, was determined using two calibration methods based on the PI fluorescence signal obtained with cells killed either by a heat treatment (80°C for 15 min) or by a pressure treatment (400 MPa, 20°C, 10 min). Both calibrations were shown to be statistically different (P<0.05), particularly at acidic pH, suggesting that a difference in the penetration of PI into bacterial cells might depend on the mode of cell inactivation. These results corroborate the fact that the mechanism of microbial inactivation by high pressure is pH-dependent.

  20. 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....

  1. The new approaches to preservation of graft cell integrity in preservation for transplantation.

    Science.gov (United States)

    Gewartowska, Magdalena; Olszewski, Waldemar L

    2005-01-01

    Restoration of cell plasma membrane integrity after injury is essential for the survival of animal cells. In case of graft preservation or during chemotherapy in cancer, cell membrane integrity and the process of its repair are disrupted. Cytoprotective substances are important in such cases, as well as in other diseases, for example in myocardial infarction, acute insults and in chronic neurodegenerative diseases. Hyperosmolarity is a condition in which cell membrane stability may be damaged in vivo but preserved in the in vitro conditions. Hypertonicity causes water leaving from cells by osmosis, decreasing cell volume and increasing of intracellular ionic strength. High intracellular ionic strength perturbs cellular function by decreasing the rates of biochemical reaction. We review the new experimentally studied cytoprotective substances and their application in cell membrane protection. Moreover, we present our data on the effects of hyperosmolarity and its protective effect on cell internal structure. PMID:17037081

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

    Science.gov (United States)

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

    2015-03-01

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

  3. 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.

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

    Science.gov (United States)

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

    2016-06-01

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

  5. BLEND MEMBRANES FOR DIRECT METHANOL AND PROTON EXCHANGE MEMBRANE FUEL CELLS

    Institute of Scientific and Technical Information of China (English)

    Perurnal Bhavani; Dharmalingam Sangeetha

    2012-01-01

    Sulphonated polystyrene ethylene butylene polystyrene (SPSEBS) prepared with 35% sulphonation was found to be highly elastic and enlarged up to 300%-400% of its initial length.It absorbed over 110% of water by weight.A major drawback of this membrane is its poor mechanical properties which are not adequate for use as polymer electrolytes in fuel cells.To overcome this,SPSEBS was blended with poly(vinylidene fluoride) (PVDF),a hydrophobic polymer.The blend membranes showed better mechanical properties than the base polymer.The effect of PVDF content on water uptake,ion exchange capacity and proton conductivity of the blend membranes was investigated.This paper presents the results of recent studies applied to develop an optimized in-house membrane electrode assembly (MEA) preparation technique combining catalyst ink spraying and assembly hot pressing.Easy steps were chosen in this preparation technique in order to simplify the method,aiming at cost reduction.The open circuit voltage for the cell with SPSEBS is 0.980 V which is higher compared to that of the cell with Nafion 117 (0.790 V).From this study,it is concluded that a polymer electrolyte membrane suitable for proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) application can be obtained by blending SPSEBS and PVDF in appropriate proportions.The methanol permeability and selectivity showed a strong influence on DMFC performance.

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

    Science.gov (United States)

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

    2015-09-01

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

  7. Gangliosides in cell recognition and membrane protein regulation

    OpenAIRE

    Lopez, Pablo H. H.; Schnaar, Ronald L.

    2009-01-01

    Gangliosides, sialic acid-bearing glycosphingolipids, are expressed on all vertebrate cells, and are the major glycans on nerve cells. They are anchored to the plasma membrane through their ceramide lipids with their varied glycans extending into the extracellular space. Through sugar-specific interactions with glycan binding proteins on apposing cells, gangliosides function as receptors in cell-cell recognition, regulating natural killer cell cytotoxicity via Siglec-7 binding, myelin-axon in...

  8. Chip-based optical microscopy for imaging membrane sieve plates of liver scavenger cells

    Science.gov (United States)

    Helle, Øystein I.; Øie, Cristina I.; McCourt, Peter; Ahluwalia, Balpreet S.

    2015-08-01

    The evanescent field on top of optical waveguides is used to image membrane network and sieve-plates of liver endothelial cells. In waveguide excitation, the evanescent field is dominant only near the surface (~100-150 nm) providing a default optical sectioning by illuminating fluorophores in close proximity to the surface and thus benefiting higher signal-to-noise ratio. The sieve plates of liver sinusoidal endothelial cells are present on the cell membrane, thus near-field waveguide chip-based microscopy configuration is preferred over epi-fluorescence. The waveguide chip is compatible with optical fiber components allowing easy multiplexing to different wavelengths. In this paper, we will discuss the challenges and opportunities provided by integrated optical microscopy for imaging cell membranes.

  9. 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.

  10. Novel Membrane for Highly Efficient Fuel Cells Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Proton Exchange Membrane (PEM) fuel cells and electrolyzers are key technologies for NASA space systems utilizing hydrogen, oxygen, or water as reactants. In order...

  11. Novel High Temperature Membrane for PEM Fuel Cells Project

    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...

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

    International Nuclear Information System (INIS)

    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 H2/O2 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

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

    Directory of Open Access Journals (Sweden)

    Jodie Lopez

    2015-12-01

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

  14. Electrospun nanofibre composite polymer electrolyte fuel cell and electrolysis membranes

    OpenAIRE

    Sood, Rakhi; Cavaliere, Sara; Rozière, Jacques; Jones, Deborah

    2016-01-01

    International audience Large-scale commercialisation of Proton Exchange Membrane Fuel Cell (PEMFC) technology for automotive and stationary applications demands the development of a robust, durable and cost-effective materials. In this regard, ionomer membranes being present at the core of PEMFCs are required to maintain elevated proton conductivity, high mechanical strength and low gas permeability during the lifespan of the fuel cell. These challenges are addressed by investigating novel...

  15. The Acinar Cage: Basement Membranes Determine Molecule Exchange and Mechanical Stability of Human Breast Cell Acini.

    Directory of Open Access Journals (Sweden)

    Aljona Gaiko-Shcherbak

    Full Text Available The biophysical properties of the basement membrane that surrounds human breast glands are poorly understood, but are thought to be decisive for normal organ function and malignancy. Here, we characterize the breast gland basement membrane with a focus on molecule permeation and mechanical stability, both crucial for organ function. We used well-established and nature-mimicking MCF10A acini as 3D cell model for human breast glands, with ether low- or highly-developed basement membrane scaffolds. Semi-quantitative dextran tracer (3 to 40 kDa experiments allowed us to investigate the basement membrane scaffold as a molecule diffusion barrier in human breast acini in vitro. We demonstrated that molecule permeation correlated positively with macromolecule size and intriguingly also with basement membrane development state, revealing a pore size of at least 9 nm. Notably, an intact collagen IV mesh proved to be essential for this permeation function. Furthermore, we performed ultra-sensitive atomic force microscopy to quantify the response of native breast acini and of decellularized basement membrane shells against mechanical indentation. We found a clear correlation between increasing acinar force resistance and basement membrane formation stage. Most important native acini with highly-developed basement membranes as well as cell-free basement membrane shells could both withstand physiologically relevant loads (≤ 20 nN without loss of structural integrity. In contrast, low-developed basement membranes were significantly softer and more fragile. In conclusion, our study emphasizes the key role of the basement membrane as conductor of acinar molecule influx and mechanical stability of human breast glands, which are fundamental for normal organ function.

  16. Surface-enhanced Raman spectroscopy of the endothelial cell membrane.

    Directory of Open Access Journals (Sweden)

    Simon W Fogarty

    Full Text Available We applied surface-enhanced Raman spectroscopy (SERS to cationic gold-labeled endothelial cells to derive SERS-enhanced spectra of the bimolecular makeup of the plasma membrane. A two-step protocol with cationic charged gold nanoparticles followed by silver-intensification to generate silver nanoparticles on the cell surface was employed. This protocol of post-labelling silver-intensification facilitates the collection of SERS-enhanced spectra from the cell membrane without contribution from conjugated antibodies or other molecules. This approach generated a 100-fold SERS-enhancement of the spectral signal. The SERS spectra exhibited many vibrational peaks that can be assigned to components of the cell membrane. We were able to carry out spectral mapping using some of the enhanced wavenumbers. Significantly, the spectral maps suggest the distribution of some membrane components are was not evenly distributed over the cells plasma membrane. These results provide some possible evidence for the existence of lipid rafts in the plasma membrane and show that SERS has great potential for the study and characterization of cell surfaces.

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

    Science.gov (United States)

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

    2016-09-01

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

  18. An Integrated Framework Advancing Membrane Protein Modeling and Design.

    Directory of Open Access Journals (Sweden)

    Rebecca F Alford

    2015-09-01

    Full Text Available Membrane proteins are critical functional molecules in the human body, constituting more than 30% of open reading frames in the human genome. Unfortunately, a myriad of difficulties in overexpression and reconstitution into membrane mimetics severely limit our ability to determine their structures. Computational tools are therefore instrumental to membrane protein structure prediction, consequently increasing our understanding of membrane protein function and their role in disease. Here, we describe a general framework facilitating membrane protein modeling and design that combines the scientific principles for membrane protein modeling with the flexible software architecture of Rosetta3. This new framework, called RosettaMP, provides a general membrane representation that interfaces with scoring, conformational sampling, and mutation routines that can be easily combined to create new protocols. To demonstrate the capabilities of this implementation, we developed four proof-of-concept applications for (1 prediction of free energy changes upon mutation; (2 high-resolution structural refinement; (3 protein-protein docking; and (4 assembly of symmetric protein complexes, all in the membrane environment. Preliminary data show that these algorithms can produce meaningful scores and structures. The data also suggest needed improvements to both sampling routines and score functions. Importantly, the applications collectively demonstrate the potential of combining the flexible nature of RosettaMP with the power of Rosetta algorithms to facilitate membrane protein modeling and design.

  19. MUNI Ways and Structures Building Integrated Solar Membrane Project

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Randall

    2014-07-03

    The initial goal of the MUNI Ways and Structures Building Integrated Solar Membrane Installation Project was for the City and County of San Francisco (CCSF) to gain experience using the integrated higher efficiency solar photovoltaic (PV) single-ply membrane product, as it differs from the conventional, low efficiency, thin-film PV products, to determine the feasibility of success of larger deployment. As several of CCSF’s municipal rooftops are constrained with respect to weight restrictions, staff of the Energy Generation Group of the San Francisco Public Utilities Commission (SFPUC) proposed to install a solar PV system using single-ply membrane The installation of the 100 kW (DC-STC) lightweight photo voltaic (PV) system at the MUNI Ways and Structures Center (700 Pennsylvania Ave., San Francisco) is a continuation of the commitment of the City and County of San Francisco (CCSF) to increase the pace of municipal solar development, and serve its municipal facilities with clean renewable energy. The fourteen (14) solar photovoltaic systems that have already been installed at CCSF municipal facilities are assisting in the reduction of fossil-fuel use, and reduction of greenhouse gases from fossil combustion. The MUNI Ways & Structures Center roof has a relatively low weight-bearing capacity (3.25 pounds per square foot) and use of traditional crystalline panels was therefore rejected. Consequently it was decided to use the best available highest efficiency Building-Integrated PV (BIPV) technology, with consideration for reliability and experience of the manufacturer which can meet the low weight-bearing capacity criteria. The original goal of the project was to provide an opportunity to monitor the results of the BIPV technology and compare these results to other City and County of San Francisco installed PV systems. The MUNI Ways and Structures Center was acquired from the Cookson Doors Company, which had run the Center for many decades. The building was

  20. Type IV Collagens and Basement Membrane Diseases: Cell Biology and Pathogenic Mechanisms.

    Science.gov (United States)

    Mao, Mao; Alavi, Marcel V; Labelle-Dumais, Cassandre; Gould, Douglas B

    2015-01-01

    Basement membranes are highly specialized extracellular matrices. Once considered inert scaffolds, basement membranes are now viewed as dynamic and versatile environments that modulate cellular behaviors to regulate tissue development, function, and repair. Increasing evidence suggests that, in addition to providing structural support to neighboring cells, basement membranes serve as reservoirs of growth factors that direct and fine-tune cellular functions. Type IV collagens are a major component of all basement membranes. They evolved along with the earliest multicellular organisms and have been integrated into diverse fundamental biological processes as time and evolution shaped the animal kingdom. The roles of basement membranes in humans are as complex and diverse as their distributions and molecular composition. As a result, basement membrane defects result in multisystem disorders with ambiguous and overlapping boundaries that likely reflect the simultaneous interplay and integration of multiple cellular pathways and processes. Consequently, there will be no single treatment for basement membrane disorders, and therapies are likely to be as varied as the phenotypes. Understanding tissue-specific pathology and the underlying molecular mechanism is the present challenge; personalized medicine will rely upon understanding how a given mutation impacts diverse cellular functions.

  1. Acetaminophen Changes Intestinal Epithelial Cell Membrane Properties, Subsequently Affecting Absorption Processes

    Directory of Open Access Journals (Sweden)

    Christine Schäfer

    2013-08-01

    Full Text Available Background/Aims: Acetaminophen (APAP effects on intestinal barrier properties are less investigated. APAP may lead to a changed bioavailability of a subsequently administered drug or diet in the body. We investigated the influence of APAP on enterocytic cell membrane properties that are able to modify the net intestinal absorption of administered substances across the Caco-2 barrier model. Methods: The effect of APAP on cytotoxicity was measured by LDH assay, TER value and cell capacitance label-free using impedance monitoring, membrane permeability by FITC-dextrans, and efflux transporter MDR1 activity by Rh123. APAP levels were determined by HPLC analysis. Cell membrane topography and microvilli were investigated using SEM and intestinal alkaline phosphatase (Alpi and tight junction protein 1 (TJP1 expression by western blot analysis. Results: APAP changed the apical cell surface, reduced the number of microvilli and protein expression of Alpi as a brush border marker and TJP1, increased the membrane integrity and concurrently decreased cell capacitance over time. In addition, APAP decreased the permeability to small molecules and increased the efflux transporter activity, MDR1. Conclusion: APAP alters the Caco-2 cell membrane properties by different mechanisms and reduces the permeability to administered substances. These findings may help to optimize therapeutic implications.

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

    DEFF Research Database (Denmark)

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

    2005-01-01

    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...... very rapidly, within seconds. At a molar ratio of anandamide to BSA of...

  3. Microfabrication of a Polymer Based Bi-Conductive Membrane for a Polymer Electrolyte Membrane Fuel Cell

    International Nuclear Information System (INIS)

    This paper reports a novel fabrication process of a high active area ratio bi-conductive membrane for PEMFCs. The fabricated device is a 50μm thick flexible polyimide based membrane that integrates for the first time lateral electrical conductive layers on both sides with a through ionic conductive path. With the use of thermo-conductive rubber as a bonding agent allowing a quick-flip process, five configurations of double-sided multilayer metal sputtering on polyimide were tested. An approach for filling through pores in the membrane with the ionic conductor (Nafion) with a temporary reservoir was also developed. The development of these new processes allowed to fabricate a membrane with 50μm wide holes filled with ionic conductor with double-sided electrical conductive layers

  4. A new integrated approach for dye removal from wastewater by polyoxometalates functionalized membranes.

    Science.gov (United States)

    Yao, Lei; Zhang, Lizhi; Wang, Rong; Chou, Shuren; Dong, ZhiLi

    2016-01-15

    Membrane technique is a promising way for the removal of dyes from wastewater. A unique approach combining both the adsorptive and the catalytic membrane processes was proposed on the basis of a new functionalized membrane. The membrane integrating both the adsorptive and catalytic activities was developed by introducing polyoxometalates (POMs) as an ideal candidate for the membrane functionalization via a novel sol-gel method. A two-step protocol, adsorptive separation and catalytic degradation, was designed for dye removal, realizing an excellent dye rejection with easy and economic membrane regeneration through simply soaking the membrane in a limited volume of dilute oxidant solution. This approach is feasible and versatile owing to the flexible selection of distinct POMs and design of catalytic degradation routes as required. As a result, the current research provides insight into a new methodology of the membrane technique in dye removal applications. PMID:26410275

  5. Classification of Cells with Membrane Staining and/or Fixation Based on Cellular Specific Membrane Capacitance and Cytoplasm Conductivity

    Directory of Open Access Journals (Sweden)

    Song-Bin Huang

    2015-01-01

    Full Text Available Single-cell electrical properties (e.g., specific membrane capacitance (Cspecific membrane and cytoplasm conductivity (σcytoplasm have been regarded as potential label-free biophysical markers for the evaluation of cellular status. However, whether there exist correlations between these biophysical markers and cellular status (e.g., membrane-associate protein expression is still unknown. To further validate the utility of single-cell electrical properties in cell type classification, Cspecific membrane and σcytoplasm of single PC-3 cells with membrane staining and/or fixation were analyzed and compared in this study. Four subtypes of PC-3 cells were prepared: untreated PC-3 cells, PC-3 cells with anti-EpCAM staining, PC-3 cells with fixation, and fixed PC-3 cells with anti-EpCAM staining. In experiments, suspended single cells were aspirated through microfluidic constriction channels with raw impedance data quantified and translated to Cspecific membrane and σcytoplasm. As to experimental results, significant differences in Cspecific membrane were observed for both live and fixed PC-3 cells with and without membrane staining, indicating that membrane staining proteins can contribute to electrical properties of cellular membranes. In addition, a significant decrease in σcytoplasm was located for PC-3 cells with and without fixation, suggesting that cytoplasm protein crosslinking during the fixation process can alter the cytoplasm conductivity. Overall, we have demonstrated how to classify single cells based on cellular electrical properties.

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

    Science.gov (United States)

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

    2012-01-01

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

  7. Pendant dual sulfonated poly(arylene ether ketone) proton exchange membranes for fuel cell application

    Science.gov (United States)

    Nguyen, Minh Dat Thinh; Yang, Sungwoo; Kim, Dukjoon

    2016-10-01

    Poly(arylene ether ketone) (PAEK) possessing carboxylic groups at the pendant position is synthesized, and the substitution degree of pendant carboxylic groups is controlled by adjusting the ratio of 4,4-bis(4-hydroxyphenyl)valeric acid and 2,2-bis(4-hydroxyphenyl)propane. Dual sulfonated 3,3-diphenylpropylamine (SDPA) is grafted onto PAEK as a proton-conducting moiety via the amidation reaction with carboxylic groups. The transparent and flexible membranes with different degrees of sulfonation are fabricated so that we can test and compare their structure and properties with a commercial Nafion® 115 membrane for PEMFC applications. All prepared PAEK-SDPA membranes exhibit good oxidative and hydrolytic stability from Fenton's and high temperature water immersion test. SAXS analysis illustrates an excellent phase separation between the hydrophobic backbone and hydrophilic pendant groups, resulting in big ionic clusters. The proton conductivity was measured at different relative humidity, and its behavior was analyzed by hydration number of the membrane. Among a series of membranes, some samples (including B20V80-SDPA) show not only higher proton conductivity, but also higher integrated cell performance than those of Nafion® 115 at 100% relative humidity, and thus we expect these to be good candidate membranes for proton exchange membrane fuel cells (PEMFCs).

  8. Proton Exchange Membrane Fuel Cell Characterization for Electric Vehicle Applications

    OpenAIRE

    Swan, D.H.; Dickinson, B.E.; Arikara, M.P.

    1994-01-01

    This paper presents experimental data and an analysis of a proton exchange membrane fuel cell system for electric vehicle applications. The dependence of the fuel cell system's performance on air stoichiometry, operating temperature, and reactant gas pressure was assessed in terms of the fuel cell's polarity and power density-efficiency graphs. All the experiments were performed by loading the fuel cell with resistive heater coils which could be controlled to provide a constant current or con...

  9. 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...... 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...

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

    Science.gov (United States)

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

    2016-05-01

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

  11. Cell Membrane-Cloaked Nanoparticles for Targeted Therapeutics

    Science.gov (United States)

    Luk, Brian Tsengchi

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

  12. Communication Between the Cell Membrane and the Nucleus: Role of Protein Compartmentalization

    Energy Technology Data Exchange (ETDEWEB)

    Lelievre, Sophie A; Bissell, Mina J

    1998-10-21

    Understanding how the information is conveyed from outside to inside the cell is a critical challenge for all biologists involved in signal transduction. The flow of information initiated by cell-cell and cell-extracellular matrix contacts is mediated by the formation of adhesion complexes involving multiple proteins. Inside adhesion complexes, connective membrane skeleton (CMS) proteins are signal transducers that bind to adhesion molecules, organize the cytoskeleton, and initiate biochemical cascades. Adhesion complex-mediated signal transduction ultimately directs the formation of supramolecular structures in the cell nucleus, as illustrated by the establishment of multi complexes of DNA-bound transcription factors, and the redistribution of nuclear structural proteins to form nuclear subdomains. Recently, several CMS proteins have been observed to travel to the cell nucleus, suggesting a distinctive role for these proteins in signal transduction. This review focuses on the nuclear translocation of structural signal transducers of the membrane skeleton and also extends our analysis to possible translocation of resident nuclear proteins to the membrane skeleton. This leads us to envision the communication between spatially distant cellular compartments (i.e., membrane skeleton and cell nucleus) as a bidirectional flow of information (a dynamic reciprocity) based on subtle multilevel structural and biochemical equilibria. At one level, it is mediated by the interaction between structural signal transducers and their binding partners, at another level it may be mediated by the balance and integration of signal transducers in different cellular compartments.

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

    DEFF Research Database (Denmark)

    Hosseinzadeh, Elham; Rokni, Masoud

    2011-01-01

    in order to account for water back diffusion. Further Membrane water content is assumed to be a linear function of thickness. PEM fuel cell is working at rather low operating conditions which makes it suitable for the automotive systems. In this paper motive power part of a lift truck has been investigated......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. 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.

  15. Attachment of killed Mycoplasma gallisepticum cells and membranes to erythrocytes

    International Nuclear Information System (INIS)

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

  16. 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

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

    Science.gov (United States)

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

    2014-10-01

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

  18. Membrane Mechanics of Endocytosis in Cells with Turgor

    CERN Document Server

    Dmitrieff, Serge

    2015-01-01

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

  19. Altered Membrane Potential and Electrolyte in Sickle Cell Anemia

    Directory of Open Access Journals (Sweden)

    JK Nnodim

    2014-01-01

    Full Text Available Aim: This study has been to evaluate the level of membrane potential and electrolyte in sickle cell disease patients. Material and methods: 100 sickle cell patients in steady state ages 5 to 30 years attending General Hospital Owerri were used in the study while 100 normal subjects (HbAA were used as control. Also 30 HbSS in crisis have been involved. Results: The results obtained showed that the level of membrane potential was significantly lower in sickle cell anemia as compared to the controls. Also, the level of the electrolyte was found significantly decreased in HbSS when compared with HbAA at P<0.05. Conclusion: The membrane potential translates to energy which means that there is less energy in sickle cell disease which is linked to electrolyte imbalance. Hence people with sickle disease should be monitored closely for their electrolytes to avoid crisis.

  20. Plasma membrane and cytoskeleton dynamics during single-cell wound healing.

    Science.gov (United States)

    Boucher, Eric; Mandato, Craig A

    2015-10-01

    Wounding leads not only to plasma membrane disruption, but also to compromised cytoskeleton structures. This results not only in unwarranted exchanges between the cytosol and extracellular milieu, but also in loss of tensegrity, which may further endanger the cell. Tensegrity can be described as the interplay between the tensile forces generated by the apparent membrane tension, actomyosin contraction, and the cytoskeletal structures resisting those changes (e.g., microtubules). It is responsible for the structural integrity of the cell and for its ability to sense mechanical signals. Recent reviews dealing with single-cell healing mostly focused on the molecular machineries controlling the traffic and fusion of specific vesicles, or their role in different pathologies. In this review, we aim to take a broader view of the different modes of single cell repair, while focussing on the different ways the changes in plasmalemma surface area and composition, plasmalemma tension, and cytoskeletal dynamics may influence and affect single-cell repair. PMID:26209916

  1. Integrated membrane systems incorporating coagulation, activated carbon and ultrafiltration for the removal of toxic cyanobacterial metabolites from Anabaena circinalis.

    Science.gov (United States)

    Dixon, M B; Richard, Y; Ho, L; Chow, C W K; O'Neill, B K; Newcombe, G

    2011-01-01

    The use of integrated membrane systems (a train of treatment processes incorporating one or more membranes) is increasing globally as the technology is very effective for the production of high quality drinking water. In this investigation a laboratory scale integrated membrane system (IMS) featuring coagulation, powdered activated carbon (PAC) and ultrafiltration (UF) was investigated for the removal of an Australian strain of the cyanobacteria Anabaena circinalis and the cyanotoxin it produced. Three coagulants were compared, aluminium chlorohydrate (ACH), aluminium sulphate (alum) and an engineered aluminium coagulant referred to as high performance aluminium chlorohydrate (HPAC). PAC (Acticarb PS1000) was tested to determine adsorption of extracellular saxitoxin. Removal of A. circinalis cells was 100% by UF alone and the removal of cells prior to the membrane by coagulation reduced fouling attributed to algogenic organic material. Alum was the least efficient coagulant for removal of cells while ACH and HPAC were similar. Saxitoxin removal reached a maximum of 80% using ACH and PAC. The UF-IMS was challenged using a natural bloom of A. circinalis that occurred in the Myponga Reservoir in South Australia. PMID:21508543

  2. 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...

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

    NARCIS (Netherlands)

    Yildirim, Mustafa Hakan

    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

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

    Science.gov (United States)

    Mamlouk, M.; Scott, K.

    2015-07-01

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

  5. Characterization of the major integral protein of vacuolar membrane.

    Science.gov (United States)

    Maeshima, M

    1992-04-01

    The vacuolar membrane of radish (Raphanus sativus) taproot contained a large quantity of a protein of 23 kilodaltons that accounted for more than 25% of the total membrane proteins. The protein, tentatively named VM 23, was purified and characterized. VM 23 tends to aggregate at high temperature even in the presence of 1% sodium dodecyl sulfate. The apparent molecular size of VM 23 was estimated to be about 400 kilodaltons by polyacrylamide gel electrophoresis in the presence of 0.1% Triton X-100. VM 23 was partially extracted from the vacuolar membranes with chloroform:methanol, indicating its high hydrophobicity. The hydrophobic carboxyl modifier N,N'-dicyclohexylcarbodiimide bound covalently to VM 23. The results suggest that VM 23 may act as a secondary transport system coupled with the proton transport. The antibody against radish VM 23 reacted with the major proteins in the vacuolar membranes of mung bean (Vigna radiata) and castor bean (Ricinus communis) hypocotyls and pumpkin (Cucurbita moschata) epicotyl, but not with that of sugar beet (Beta vulgaris) taproot. VM 23 comigrated with vacuolar H(+)-pyrophosphatase on sucrose density gradient centrifugation after sonication of membranes, indicating that it is associated with the vacuolar membrane.

  6. Nanodomain stabilization dynamics in plasma membranes of biological cells

    Science.gov (United States)

    Das, Tamal; Maiti, Tapas K.; Chakraborty, Suman

    2011-02-01

    We discover that a synergistically amplifying role of stabilizing membrane proteins and continuous lipid recycling can explain the physics governing the stability, polydispersity, and dynamics of lipid raft domains in plasma membranes of biological cells. We establish the conjecture using a generalized order parameter based on theoretical formalism, endorsed by detailed scaling arguments and domain mapping. Quantitative agreements with morphological distributions of raft complexes, as obtained from Förster resonance energy transfer based visualization, support the present theoretical conjecture.

  7. Efficient ethanol recovery from fermentation broths with integrated distillation-membrane process

    Science.gov (United States)

    The energy demand of distillation-molecular sieve systems for ethanol recovery/dehydration can be significant, particularly for dilute solutions. An alternative process integrating vapor stripping (like a beer still) with vapor compression and a vapor permeation membrane separati...

  8. Integrating membrane filtration into bioelectrochemical systems as next generation energy-efficient wastewater treatment technologies for water reclamation: A review.

    Science.gov (United States)

    Yuan, Heyang; He, Zhen

    2015-11-01

    Bioelectrochemical systems (BES) represent an energy-efficient approach for wastewater treatment, but the effluent still requires further treatment for direct discharge or reuse. Integrating membrane filtration in BES can achieve high-quality effluents with additional benefits. Three types of filtration membranes, dynamic membrane, ultrafiltration membrane and forward osmosis membrane that are grouped based on pore size, have been studied for integration in BES. The integration can be accomplished either in an internal or an external configuration. In an internal configuration, membranes can act as a separator between the electrodes, or be immersed in the anode/cathode chamber as a filtration component. The external configuration allows BES and membrane module to be operated independently. Given much progress and interest in the integration of membrane filtration into BES, this paper has reviewed the past studies, described various integration methods, discussed the advantages and limitations of each integration, and presented challenges for future development.

  9. Integrating membrane filtration into bioelectrochemical systems as next generation energy-efficient wastewater treatment technologies for water reclamation: A review.

    Science.gov (United States)

    Yuan, Heyang; He, Zhen

    2015-11-01

    Bioelectrochemical systems (BES) represent an energy-efficient approach for wastewater treatment, but the effluent still requires further treatment for direct discharge or reuse. Integrating membrane filtration in BES can achieve high-quality effluents with additional benefits. Three types of filtration membranes, dynamic membrane, ultrafiltration membrane and forward osmosis membrane that are grouped based on pore size, have been studied for integration in BES. The integration can be accomplished either in an internal or an external configuration. In an internal configuration, membranes can act as a separator between the electrodes, or be immersed in the anode/cathode chamber as a filtration component. The external configuration allows BES and membrane module to be operated independently. Given much progress and interest in the integration of membrane filtration into BES, this paper has reviewed the past studies, described various integration methods, discussed the advantages and limitations of each integration, and presented challenges for future development. PMID:26026232

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

    Science.gov (United States)

    Cheah, May Jean

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

  11. Mass spectrometric analysis of integral membrane proteins: application to complete mapping of bacteriorhodopsins and rhodopsin.

    OpenAIRE

    Ball, L. E.; Oatis, J. E.; Dharmasiri, K.; Busman, M.; Wang, J.; Cowden, L. B.; Galijatovic, A.; N. Chen; Crouch, R K; Knapp, D R

    1998-01-01

    Integral membrane proteins have not been readily amenable to the general methods developed for mass spectrometric (or internal Edman degradation) analysis of soluble proteins. We present here a sample preparation method and high performance liquid chromatography (HPLC) separation system which permits online HPLC-electrospray ionization mass spectrometry (ESI-MS) and -tandem mass spectrometry (MS/MS) analysis of cyanogen bromide cleavage fragments of integral membrane proteins. This method has...

  12. Integrally heated electrochemical cell method and apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Brothers, J.A.; Kane, W.T.; Brouneus, H.A.; Layton, M.M.; Walsh, P.L.

    1987-04-21

    An electrochemical cell is described comprising: an electrolyte; integral cell electrode/heater means contacting the electrolyte and adapted for heating at least a portion of the electrolyte to an elevated temperature for ionic conduction operation; a pair of lead means each extending from a different location on the integral cell electrode/heater means for coupling the integral cell electrode/heater means in a circuit across an electric current source; a second cell electrode means separately contacting the electrolyte and adapted for developing an ionic conduction across the heated electrolyte and a related emf with the integral cell electrode/heater. A method is described of operating an apparatus for sensing a particular gaseous substance, the apparatus comprising an electrochemical cell heated to an elevated temperature for ionic conduction operation and circuit means for responding to ionic emf developed by the electrochemical cell.

  13. Corona discharge in electroporation of cell membranes

    Energy Technology Data Exchange (ETDEWEB)

    Cramariuc, R; Nisiparu, L [Competence Centre in Electrostatics and Electrotehchnologies (Romania); Tudorache, A; Branduse, E; Fotescu, L [Research Institute of Wine Processing, Valea Mantei Street, No.l, Valea Calugareasca (Romania); Popa, M E; Mitelut, A [Biotechnology Faculty, University of Agronomical Sciences and Veterinary Medicine (Romania); Turtoi, M O

    2008-12-01

    The objective of the present work is to demonstrate that electrical corona discharge is very efficient in cellular membrane electroporation due to current pulses with sharp front (2-5 ns) and to the fact that corona discharge is associated with UV radiation and micro particles emission. A comparison between DC and AC at 800 Hz and a special waveform to corona application is presented. The comparison is analyzed by means of applying all these in the maceration process (electroplasmolysis) of red wine production and in the processes of different types of the microbes.

  14. Applicability of in vitro methods to study patulin bioaccessibility and its effects on intestinal membrane integrity.

    Science.gov (United States)

    Assunção, Ricardo; Ferreira, Mariana; Martins, Carla; Diaz, Irene; Padilla, Beatriz; Dupont, Didier; Bragança, Mauro; Alvito, Paula

    2014-01-01

    In human health risk assessment, ingestion of food is considered a major route of exposure to many contaminants, although the total amount of an ingested contaminant (external dose) does not always reflect the quantity available for the body (internal dose). In this study, two in vitro methods were applied to study bioaccessibility and intestinal membrane integrity of cells exposed to patulin, a mycotoxin with significant public health risk. Seven artificially contaminated fruit juices were assayed in the presence or absence of a standard meal, showing a significant difference for bioaccessibility values between contaminated samples alone (mean 27.65 ± 13.50%) and combinations with a standard meal (mean 7.89 ± 4.03%). Different concentrations of patulin (PAT) and cysteine (CYS) (protector agent) were assayed in Caco-2 cells monolayers. At 95 μM, PAT produced a marked decrease in transepithelial electrical resistance (TEER). This effect was significantly reduced when 400 μM and 4000 μM CYS was added to the cells. Combined use of in vitro digestion models with other techniques using intestinal cell lines, such as in vitro intestinal absorption models that use Caco-2 cells, may offer a more comprehensive model of what is occurring during digestion and absorption processes. The study of beneficial effects of protective agents would also be enhanced. PMID:25072729

  15. 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 not in...

  16. Suppression of fluid membrane fluctuations by a periodic pinning potential: Applications to red blood cells.

    Science.gov (United States)

    Henle, Mark L.; Levine, Alex J.

    2009-03-01

    The membrane of the red blood cell (RBC) is tethered to a two- dimensional triangular network of semi-flexible elastic spectrin filaments. This network allows the cell to maintain its structural integrity during the large shape deformations that occur as it circulates through the microvasculature. The lipid membrane is anchored to the spectrin filaments at the nodes of the network. Consequently, these attachments impose a two-dimensional periodic pinning potential upon the membrane. In this talk, we investigate the effect of this pinning potential on the thermal bending fluctuations of the membrane. We show that there is an exact mapping of this system onto the classic problem of non-interacting electrons subject to a periodic potential; we exploit this mapping to obtain an exact analytic solution for a defect-free triangular array of harmonic pinning sites. The pinning potential affects both the local and global structure of the bending fluctuations. To investigate the local structure we consider the bending correlations between two nearby points in the membrane, while for the global structure we consider the total area stored in the fluctuations. We also investigate the effective area modulus of the membrane/spectrin composite structure.

  17. Mapping of unfolding states of integral helical membrane proteins by GPS-NMR and scattering techniques

    DEFF Research Database (Denmark)

    Calcutta, Antonello; Jessen, Christian Moestrup; Behrens, Manja Annette;

    2012-01-01

    Membrane proteins are vital for biological function, and their action is governed by structural properties critically depending on their interactions with the membranes. This has motivated considerable interest in studies of membrane protein folding and unfolding. Here the structural changes...... induced by unfolding of an integral membrane protein, namely TFE-induced unfolding of KcsA solubilized by the n-dodecyl ß-d-maltoside (DDM) surfactant is investigated by the recently introduced GPS-NMR (Global Protein folding State mapping by multivariate NMR) (Malmendal et al., PlosONE 5, e10262 (2010...

  18. Correlation study of microalgae carbonation in membrane integrated photobioreactor

    Science.gov (United States)

    Suali, E.; Sarbatly, R.; Shaleh, S. R. M.; Lahin, F. A.; Anisuzzaman, S. M.

    2016-06-01

    Microalgae ability to utilise CO2 higher compared to terrestrial plant making it suitable for biomass production and as CO2 utiliser. This could be one of many ways to preserve a safer and healthier environment with less air pollutant. For study purposes, CO2 usually transported to microalgae culture broth with the aid of membrane technology to prevent formation of large bubble and to accelerate the carbonation of microalgal media. However, membrane susceptible to accumulation of CO2, which can cause extreme acidic to microalgal media. This prevents microalgae to assimilate CO2. Thus, this study proposes correlations to prevent the extreme acidic: which represents the relationship of: (1) CO2 inlet and accumulation, (2) CO2 inlet and CO2 at the membrane-liquid interphase and (3) CO2 inlet and CO2 solubility in the media. The correlations were successfully validated with a deviation of less than 20% compared to the theoretical value.

  19. 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.

  20. Classification of Cells with Membrane Staining and/or Fixation Based on Cellular Specific Membrane Capacitance and Cytoplasm Conductivity

    OpenAIRE

    Song-Bin Huang; Yang Zhao; Deyong Chen; Shing-Lun Liu; Yana Luo; Tzu-Keng Chiu; Junbo Wang; Jian Chen; Min-Hsien Wu

    2015-01-01

    Single-cell electrical properties (e.g., specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm)) have been regarded as potential label-free biophysical markers for the evaluation of cellular status. However, whether there exist correlations between these biophysical markers and cellular status (e.g., membrane-associate protein expression) is still unknown. To further validate the utility of single-cell electrical properties in cell type classification, Cspe...

  1. Effects of n-3 PUFAs on breast cancer cells through their incorporation in plasma membrane

    Directory of Open Access Journals (Sweden)

    Berra Bruno

    2011-05-01

    Full Text Available Abstract Background PUFAs are important molecules for membrane order and function; they can modify inflammation-inducible cytokines production, eicosanoid production, plasma triacylglycerol synthesis and gene expression. Recent studies suggest that n-3 PUFAs can be cancer chemopreventive, chemosuppressive and auxiliary agents for cancer therapy. N-3 PUFAs could alter cancer growth influencing cell replication, cell cycle, and cell death. The question that remains to be answered is how n-3 PUFAs can affect so many physiological processes. We hypothesize that n-3 PUFAs alter membrane stability, modifying cellular signalling in breast cancer cells. Methods Two lines of human breast cancer cells characterized by different expression of ER and EGFR receptors were treated with AA, EPA or DHA. We have used the MTT viability test and expression of apoptotic markers to evaluate the effect of PUFAs on cancer growth. Phospholipids were analysed by HPLC/GC, to assess n-3 incorporation into the cell membrane. Results We have observed that EPA and DHA induce cell apoptosis, a reduction of cell viability and the expression of Bcl2 and procaspase-8. Moreover, DHA slightly reduces the concentration of EGFR but EPA has no effect. Both EPA and DHA reduce the activation of EGFR. N-3 fatty acids are partially metabolized in both cell lines; AA is integrated without being further metabolized. We have analysed the fatty acid pattern in membrane phospholipids where they are incorporated with different degrees of specificity. N-3 PUFAs influence the n-6 content and vice versa. Conclusions Our results indicate that n-3 PUFA feeding might induce modifications of breast cancer membrane structure that increases the degree of fatty acid unsaturation. This paper underlines the importance of nutritional factors on health maintenance and on disease prevention.

  2. Evaluation on the Morphology and Membrane Integrity of Immotile Human Sperm

    Institute of Scientific and Technical Information of China (English)

    Wei-Jie ZHU; Jing LI

    2006-01-01

    Objective To determine the membrane integrity in the head and tail regions of individual spermatozoon, and observe sperm morphology for samples with totally immotile sperm.Methods Ten infertile men with immotile sperm were enrolled into this study (group A).The membrane integrity in the head and tail regions of individual spermatozoon of immotile sperm was examined by using the combined hypo-osmotic swelling-eosin Y exclusion test (HOS-EY test). Sperm morphology was observed by light, scanning and transmission electron microscopy. Ten semen samples from normospermic donors were used as the control (group B).Results The percentage of sperm with intact both head and tail membranes in group A was significantly lower than that in group B (P<0.01), whereas the value of sperm with defective head membrane but intact tail membrane in group A was significantly higher than that in group B (P<0.01) Abnormal sperm morphology in group A had a high incidence, and immotile sperm with viability and normal morphology could be observed in some cases. Most sperm had multiple ultrastructural defects.Conclussion Some immotile sperm had intact tail membrane but defective head membrane. Immotile sperm with viability and normal morphology could exist in some cases though abnormal sperm were in a great proportion. Carefully evaluating immotile sperm membrane integrity and morphology should benefit the treatment of patients with immotile sperm.

  3. High quality single crystal Ge nano-membranes for opto-electronic integrated circuitry

    Energy Technology Data Exchange (ETDEWEB)

    Shah, V. A., E-mail: vishal.shah@warwick.ac.uk; Gammon, P. M. [Department of Engineering, The University of Warwick, Coventry CV4 7AL (United Kingdom); Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Rhead, S. D.; Halpin, J. E.; Trushkevych, O.; Wilson, N. R.; Myronov, M.; Edwards, R. S.; Patchett, D. H.; Allred, P. S.; Prest, M. J.; Whall, T. E.; Parker, E. H. C.; Leadley, D. R. [Department of Physics, The University of Warwick, Coventry CV4 7AL (United Kingdom); Chávez-Ángel, E. [ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); Department of Physics, UAB, 08193 Bellaterra (Barcelona) (Spain); Shchepetov, A.; Prunnila, M. [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Espoo (Finland); Kachkanov, V.; Dolbnya, I. P. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE (United Kingdom); Reparaz, J. S. [ICN2-Institut Catala de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); and others

    2014-04-14

    A thin, flat, and single crystal germanium membrane would be an ideal platform on which to mount sensors or integrate photonic and electronic devices, using standard silicon processing technology. We present a fabrication technique compatible with integrated-circuit wafer scale processing to produce membranes of thickness between 60 nm and 800 nm, with large areas of up to 3.5 mm{sup 2}. We show how the optical properties change with thickness, including appearance of Fabry-Pérot type interference in thin membranes. The membranes have low Q-factors, which allow the platforms to counteract distortion during agitation and movement. Finally, we report on the physical characteristics showing sub-nm roughness and a homogenous strain profile throughout the freestanding layer, making the single crystal Ge membrane an excellent platform for further epitaxial growth or deposition of materials.

  4. Intracellular distribution of an integral nuclear pore membrane protein fused to green fluorescent protein--localization of a targeting domain.

    Science.gov (United States)

    Söderqvist, H; Imreh, G; Kihlmark, M; Linnman, C; Ringertz, N; Hallberg, E

    1997-12-15

    The 121-kDa pore membrane protein (POM121) is a bitopic integral membrane protein specifically located in the pore membrane domain of the nuclear envelope with its short N-terminal tail exposed on the luminal side and its major C-terminal portion adjoining the nuclear pore complex. In order to locate a signal for targeting of POM121 to the nuclear pores, we overexpressed selected regions of POM121 alone or fused to the green fluorescent protein (GFP) in transiently transfected COS-1 cells or in a stably transfected neuroblastoma cell line. Microscopic analysis of the GFP fluorescence or immunostaining was used to determine the intracellular distribution of the overexpressed proteins. The endofluorescent GFP tag had no effect on the distribution of POM121, since the chimerical POM121-GFP fusion protein was correctly targeted to the nuclear pores of both COS-1 cells and neuroblastoma cells. Based on the differentiated intracellular sorting of the POM121 variants, we conclude that the first 128 amino acids of POM121 contains signals for targeting to the continuous endoplasmic reticulum/nuclear envelope membrane system but not specifically to the nuclear pores and that a specific nuclear pore targeting signal is located between amino acids 129 and 618 in the endoplasmically exposed portion of POM121. PMID:9461306

  5. The Synthetic Amphipathic Peptidomimetic LTX109 Is a Potent Fungicide That Disturbs Plasma Membrane Integrity in a Sphingolipid Dependent Manner

    DEFF Research Database (Denmark)

    Bojsen, Rasmus; Torbensen, Rasmus; Larsen, Camilla Eggert;

    2013-01-01

    The peptidomimetic LTX109 (arginine-tertbutyl tryptophan-arginine-phenylethan) was previously shown to have antibacterial properties. Here, we investigated the activity of this novel antimicrobial peptidomimetic on the yeast Saccharomyces cerevisiae. We found that LTX109 was an efficient fungicid...... observations are consistent with a model in which LTX109 kills S. cerevisiae by nonspecific destabilization of the plasma membrane through direct or indirect interaction with the sphingolipids....... that killed all viable cells in an exponentially growing population as well as a large proportion of cells in biofilm formed on an abiotic surface. LTX109 had similar killing kinetics to the membrane-permeabilizing fungicide amphotericin B, which led us to investigate the ability of LTX109 to disrupt plasma...... membrane integrity. S. cerevisiae cells exposed to a high concentration of LTX109 showed rapid release of potassium and amino acids, suggesting that LTX109 acted by destabilizing the plasma membrane. This was supported by the finding that cells were permeable to the fluorescent nucleic acid stain SYTOX...

  6. Integrated Electrowetting Nanoinjector for Single Cell Transfection

    OpenAIRE

    Elaheh Shekaramiz; Ganeshkumar Varadarajalu; Day, Philip J.; Kumar Wickramasinghe, H.

    2016-01-01

    Single cell transfection techniques are essential to understand the heterogeneity between cells. We have developed an integrated electrowetting nanoinjector (INENI) to transfect single cells. The high transfection efficiency, controlled dosage delivery and ease of INENI fabrication promote the widespread application of the INENI in cell transfection assays.

  7. FABRICATION AND BIOCOMPATIBILITY OF CELL OUTER MEMBRANE MIMETIC SURFACES

    Institute of Scientific and Technical Information of China (English)

    Ming-ming Zong; Yong-kuan Gong

    2011-01-01

    The surface design used for improving biocompatibility is one of the most important issues for the fabrication of medical devices. For mimicking the ideal surface structure of cell outer membrane, a large number of polymers bearing phosphorylcholine (PC) groups have been employed to modify the surfaces of biomaterials and medical devices. It has been demonstrated that the biocompatibility of the modified materials whose surface is required to interact with a living organism has been obviously improved by introducing PC groups. In this review, the fabrication strategies of cell outer membrane mimetic surfaces and their resulted biocompatibilities were summarized.

  8. 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

  9. Flow cytometry immunodetection and membrane integrity assessment of Escherichia coli O157:H7 in ready-to-eat pasta salad during refrigerated storage.

    Science.gov (United States)

    Subires, Alicia; Yuste, Josep; Capellas, Marta

    2014-01-01

    Over the past years, products of non-animal origin have been increasingly linked to foodborne diseases caused by the enterohemorrhagic pathogen Escherichia coli O157:H7. Contaminated fresh produce and derived ready-to-eat meals are of major concern, since no further or only minimal processing is applied. In this study, flow cytometry was evaluated as a rapid technique to detect E. coli O157:H7 by immunofluorescence, using polyclonal antibodies conjugated to R-phycoerythrin, in refrigerated ready-to-eat pasta salad containing acetic acid and benzoic acid. Signal filtering strategies were applied during sample analysis to reduce the limit of detection of the technique to 5 log CFU/g. Simultaneously with pathogen detection, physiological state was assessed by staining with the membrane integrity indicators propidium iodide and SYBR Green I. Fine tuning of dye concentrations and ratios allowed discrimination of not only cells with intact or damaged membranes, but also of cells with partially damaged membranes, which were considered injured cells. Then, changes in membrane integrity of inoculated E. coli O157:H7 cells were monitored throughout 14-day refrigerated storage. Most cells were injured at the beginning of refrigeration, but showed an intact membrane at the end. This suggests that injured E. coli O157:H7 cells underwent a membrane repair during exposure to refrigeration and acid stresses, and survived in ready-to-eat pasta salad. This highlights the importance of the implementation of control measures to limit the presence of this pathogen in non-animal origin food products. Additionally, the proposed immunodetection and membrane integrity three-color assay in food is a good tool to monitor the effect of a number of food-related treatments on E. coli O157:H7 cell membrane.

  10. 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 advance

  11. Proton Exchange Membranes for Fuel Cells Challenges and Recent Developments

    Institute of Scientific and Technical Information of China (English)

    Qingfeng Li; Jens Oluf Jensen; Pernille P. Noyé; Chao Pan; Niels J. Bjerrum

    2005-01-01

    @@ 1Introduction The current technology of proton exchange membrane fuel cells (PEMFC) is based on perfluorosulfonic acid (PFSA) membranes (e. g. Nafion(R)) as electrolyte. It operates on pure hydrogen and oxygen/air at typically 80℃ with high power density and long-term durability. For the membranes to be conductive, a minimum threshold of absorbed water molecules is about 6 to 7 mole per sulfonic site. The highest conductivity is only obtained under fully hydrated conductions, i.e. 21 - 22 mole water per sulfonic acid site. In other words, the proton conductivity is achieved by the locally liquid-like hydrophilic domain of the nanostructure.This strong dependence of conductivity on the water content in membranes limits the operational temperatureof PEMFC below 100℃.

  12. Smoking and red blood cell phospholipid membrane fatty acids.

    Science.gov (United States)

    Murff, H J; Tindle, H A; Shrubsole, M J; Cai, Q; Smalley, W; Milne, G L; Swift, L L; Ness, R M; Zheng, W

    2016-09-01

    Smoking is associated with lower n-3 long chain polyunsaturated fatty acids (LCPUFA) concentrations; however, limited studies have accounted for dietary PUFA intake or whether tobacco dose or smoking duration influences this association. We measured red blood cell phospholipid (RBC) membrane concentrations of fatty acids in 126 current smokers, 311 former smokers, and 461 never smokers using gas liquid chromatography and tandem mass spectrometry. Smokers had lower RBC membrane percentages of total n-3 LCPUFAs compared to former smokers or never smokers (median percent: 5.46, [interquartile range (IQR) 4.52, 6.28] versus 6.39; [IQR: 5.18, 7.85] versus 6.59; [IQR 5.34, 8.01]) (psmoking and cigarettes per day were not associated with RBC membrane n-3 LCPUFA differences. Smoking is associated with lower n-3 LCPUFA RBC membrane percentages and this association was not influenced by diet or smoking dose or duration. PMID:27637337

  13. Cell Wall Integrity Signaling in Saccharomyces cerevisiae

    OpenAIRE

    Levin, David E.

    2005-01-01

    The yeast cell wall is a highly dynamic structure that is responsible for protecting the cell from rapid changes in external osmotic potential. The wall is also critical for cell expansion during growth and morphogenesis. This review discusses recent advances in understanding the various signal transduction pathways that allow cells to monitor the state of the cell wall and respond to environmental challenges to this structure. The cell wall integrity signaling pathway controlled by the small...

  14. Durability Issues of High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

    DEFF Research Database (Denmark)

    To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, phosphoric acid doped polybenzimidazole (PBI) membrane represents an effective approach, which in recent years has motivated extensive research activities with great progress...... 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...

  15. Integration of Bioreactor and Membrane Separation Processes: A Model Based Approach

    DEFF Research Database (Denmark)

    Prado Rubio, Oscar Andres

    This work is motivated by the need for tighter integration of industrial processes in an attempt to improve process sustainability. To this end, this work considers a interesting case study around which different systematic approaches are used or developed to achieve the above goal. The thesis...... is concerned with the understanding of an integrated bioreactor and electrically driven membrane separation processes for lactic acid fermentation. This is achieved through a model based investigation of the individual units and the integrated system. Development of system understanding is the key to reveal...... how the system should be designed and operated in accordance with different production goals. The selected case includes a fermenter and a two stage membrane separation. In the first membrane stage the lactate is exchanged by hydroxide by means of anion exchange membranes, in a process referred...

  16. Nonbilayer lipids affect peripheral and integral membrane proteins via changes in the lateral pressure profile.

    Science.gov (United States)

    van den Brink-van der Laan, Els; Killian, J Antoinette; de Kruijff, Ben

    2004-11-01

    Nonbilayer lipids can be defined as cone-shaped lipids with a preference for nonbilayer structures with a negative curvature, such as the hexagonal phase. All membranes contain these lipids in large amounts. Yet, the lipids in biological membranes are organized in a bilayer. This leads to the question: what is the physiological role of nonbilayer lipids? Different models are discussed in this review, with a focus on the lateral pressure profile within the membrane. Based on this lateral pressure model, predictions can be made for the effect of nonbilayer lipids on peripheral and integral membrane proteins. Recent data on the catalytic domain of Leader Peptidase and the potassium channel KcsA are discussed in relation to these predictions and in relation to the different models on the function of nonbilayer lipids. The data suggest a general mechanism for the interaction between nonbilayer lipids and membrane proteins via the membrane lateral pressure. PMID:15519321

  17. Model of red blood cell membrane skeleton: electrical and mechanical properties.

    Science.gov (United States)

    Kozlov, M M; Markin, V S

    1987-12-21

    A theoretical membrane skeleton model of erythrocyte has been developed and successfully applied to interpret electrical and mechanical properties of the red blood cell spectrin-actin network. The model is based on the structure of the membrane skeleton that is comprised of unit cells each containing an actin protofilament and shooting forth a few spectrin heterodimers. The loose ends of the heterodimers of adjacent cells can form bonds with each other giving rise to an integrated network. The number of bonds depends on the temperature. The bond length being excessive (2.6 times the distance between the centers of adjacent cells), the bonds are flexible, and can thus be regarded as entropy springs. The advanced model has been employed to calculate the shear modulus of the membrane skeleton as well as to establish its temperature dependence. In a wide range of temperatures mu(T) is a decreasing function well fitting the experimental data. The relationship between the membrane bilayer-free size of the skeleton and the ionic strength of the solution has been derived to appear in good agreement with the results obtained previously. Experimental data combined with the advanced theory yield the average number of heterodimers per unit cell, m0, as equal to ca. 5; the spectrin heterodimer charge has been estimated. PMID:3455470

  18. Integral and peripheral association of proteins and protein complexes with Yersinia pestis inner and outer membranes

    Directory of Open Access Journals (Sweden)

    Bunai Christine L

    2009-02-01

    Full Text Available Abstract Yersinia pestis proteins were sequentially extracted from crude membranes with a high salt buffer (2.5 M NaBr, an alkaline solution (180 mM Na2CO3, pH 11.3 and membrane denaturants (8 M urea, 2 M thiourea and 1% amidosulfobetaine-14. Separation of proteins by 2D gel electrophoresis was followed by identification of more than 600 gene products by MS. Data from differential 2D gel display experiments, comparing protein abundances in cytoplasmic, periplasmic and all three membrane fractions, were used to assign proteins found in the membrane fractions to three protein categories: (i integral membrane proteins and peripheral membrane proteins with low solubility in aqueous solutions (220 entries; (ii peripheral membrane proteins with moderate to high solubility in aqueous solutions (127 entries; (iii cytoplasmic or ribosomal membrane-contaminating proteins (80 entries. Thirty-one proteins were experimentally associated with the outer membrane (OM. Circa 50 proteins thought to be part of membrane-localized, multi-subunit complexes were identified in high Mr fractions of membrane extracts via size exclusion chromatography. This data supported biologically meaningful assignments of many proteins to the membrane periphery. Since only 32 inner membrane (IM proteins with two or more predicted transmembrane domains (TMDs were profiled in 2D gels, we resorted to a proteomic analysis by 2D-LC-MS/MS. Ninety-four additional IM proteins with two or more TMDs were identified. The total number of proteins associated with Y. pestis membranes increased to 456 and included representatives of all six β-barrel OM protein families and 25 distinct IM transporter families.

  19. Electrospun fiber membranes enable proliferation of genetically modified cells

    Directory of Open Access Journals (Sweden)

    Borjigin M

    2013-02-01

    Full Text Available Mandula Borjigin*, Chris Eskridge*, Rohina Niamat, Bryan Strouse, Pawel Bialk, Eric B KmiecDepartment of Chemistry, Delaware State University, Dover, DE, USA *These authors contributed equally to this work Abstract: Polycaprolactone (PCL and its blended composites (chitosan, gelatin, and lecithin are well-established biomaterials that can enrich cell growth and enable tissue engineering. However, their application in the recovery and proliferation of genetically modified cells has not been studied. In the study reported here, we fabricated PCL-biomaterial blended fiber membranes, characterized them using physicochemical techniques, and used them as templates for the growth of genetically modified HCT116-19 colon cancer cells. Our data show that the blended polymers are highly miscible and form homogenous electrospun fiber membranes of uniform texture. The aligned PCL nanofibers support robust cell growth, yielding a 2.5-fold higher proliferation rate than cells plated on standard plastic plate surfaces. PCL-lecithin fiber membranes yielded a 2.7-fold higher rate of proliferation, while PCL-chitosan supported a more modest growth rate (1.5-fold higher. Surprisingly, PCL-gelatin did not enhance cell proliferation when compared to the rate of cell growth on plastic surfaces. Keywords: nanofibers, PCL-biomaterial blends, miscibility, gene editing, cell proliferation

  20. Antigenicity and immunogenicity of an extract from the cell wall and cell membrane of Histoplasma capsulatum yeast cells.

    OpenAIRE

    Gómez, A M; Rhodes, J C; Deepe, G S

    1991-01-01

    In order to identify T-cell antigens from Histoplasma capsulatum yeast cells, we prepared a detergent extract of the cell wall and cell membrane of yeast-phase H. capsulatum G217B and analyzed its antigenicity and immunogenicity. Mice injected with viable H. capsulatum yeast cells or with 500 or 1,000 micrograms of the extract mounted a delayed-type hypersensitivity response to solubilized cell wall and cell membrane. Vaccination with this antigenic preparation conferred a protective immune r...

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

    Science.gov (United States)

    Morss, Andrew J.

    Optical tweezers allow for manipulating micron-sized objects using pN level optical forces. In this work, we use an optical trapping setup to aid in three separate experiments, all related to the physics of the cellular membrane. In the first experiment, in conjunction with Brian Henslee, we use optical tweezers to allow for precise positioning and control of cells in suspension to evaluate the cell size dependence of electroporation. Theory predicts that all cells porate at a transmembrane potential VTMof roughly 1 V. The Schwann equation predicts that the transmembrane potential depends linearly on the cell radius r, thus predicting that cells should porate at threshold electric fields that go as 1/r. The threshold field required to induce poration is determined by applying a low voltage pulse to the cell and then applying additional pulses of greater and greater magnitude, checking for poration at each step using propidium iodide dye. We find that, contrary to expectations, cells do not porate at a constant value of the transmembrane potential but at a constant value of the electric field which we find to be 692 V/cm for K562 cells. Delivering precise dosages of nanoparticles into cells is of importance for assessing toxicity of nanoparticles or for genetic research. In the second experiment, we conduct nano-electroporation—a novel method of applying precise doses of transfection agents to cells—by using optical tweezers in conjunction with a confocal microscope to manipulate cells into contact with 100 nm wide nanochannels. This work was done in collaboration with Pouyan Boukany of Dr. Lee's group. The small cross sectional area of these nano channels means that the electric field within them is extremely large, 60 MV/m, which allows them to electrophoretically drive transfection agents into the cell. We find that nano electroporation results in excellent dose control (to within 10% in our experiments) compared to bulk electroporation. We also find that

  2. Effect of stress on the membrane capacitance of the auditory outer hair cell.

    OpenAIRE

    Iwasa, K H

    1993-01-01

    The membrane capacitance of the outer hair cell, which has unique membrane potential-dependent motility, was monitored during application of membrane tension. It was found that the membrane capacitance of the cell decreased when stress was applied to the membrane. This result is the opposite of stretching the lipid bilayer in the plasma membrane. It thus indicates the importance of some other capacitance component that decreases on stretching. It has been known that charge movement across the...

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

    Science.gov (United States)

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

    2016-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Chris Roger; David Mountz; Wensheng He; Tao Zhang

    2011-03-17

    The development of low cost, durable membranes and membranes electrode assemblies (MEAs) that operate under reduced relative humidity (RH) conditions remain a critical challenge for the successful introduction of fuel cells into mass markets. It was the goal of the team lead by Arkema, Inc. to address these shortages. Thus, this project addresses the following technical barriers from the fuel cells section of the Hydrogen Fuel Cells and Infrastructure Technologies Program Multi-Year Research, Development and Demonstration Plan: (A) Durability (B) Cost Arkema’s approach consisted of using blends of polyvinylidenefluoride (PVDF) and proprietary sulfonated polyelectrolytes. In the traditional approach to polyelectrolytes for proton exchange membranes (PEM), all the required properties are “packaged” in one macromolecule. The properties of interest include proton conductivity, mechanical properties, durability, and water/gas transport. This is the case, for example, for perfluorosulfonic acid-containing (PFSA) membranes. However, the cost of these materials is high, largely due to the complexity and the number of steps involved in their synthesis. In addition, they suffer other shortcomings such as mediocre mechanical properties and insufficient durability for some applications. The strength and originality of Arkema’s approach lies in the decoupling of ion conductivity from the other requirements. Kynar® PVDF provides an exceptional combination of properties that make it ideally suited for a membrane matrix (Kynar® is a registered trademark of Arkema Inc.). It exhibits outstanding chemical resistance in highly oxidative and acidic environments. In work with a prior grant, a membrane known as M41 was developed by Arkema. M41 had many of the properties needed for a high performance PEM, but had a significant deficiency in conductivity at low RH. In the first phase of this work, the processing parameters of M41 were explored as a means to increase its proton

  5. Formation of functional cell membrane domains: the interplay of lipid- and protein-mediated interactions.

    OpenAIRE

    Harder, Thomas

    2003-01-01

    Numerous cell membrane associated processes, including signal transduction, membrane sorting, protein processing and virus trafficking take place in membrane subdomains. Protein-protein interactions provide the frameworks necessary to generate biologically functional membrane domains. For example, coat proteins define membrane areas destined for sorting processes, viral proteins self-assemble to generate a budding virus, and adapter molecules organize multimolecular signalling assemblies, whi...

  6. On controllability of an integrated bioreactor and periodically operated membrane separation process

    DEFF Research Database (Denmark)

    Prado Rubio, Oscar Andres; Jørgensen, Sten Bay; Jonsson, Gunnar Eigil

    to understand the controlled operation of the integrated process, it is convenient to use a model based approach supported by experimental evidence. Recently, an integrated bioreactor and electrically driven membrane separation process (Reverse Electro- Enhanced Dialysis - REED) has been proposed as a method...

  7. Spontaneous Packaging and Hypothermic Storage of Mammalian Cells with a Cell-Membrane-Mimetic Polymer Hydrogel in a Microchip.

    Science.gov (United States)

    Xu, Yan; Mawatari, Kazuma; Konno, Tomohiro; Kitamori, Takehiko; Ishihara, Kazuhiko

    2015-10-21

    Currently, continuous culture/passage and cryopreservation are two major, well-established methods to provide cultivated mammalian cells for experiments in laboratories. Due to the lack of flexibility, however, both laboratory-oriented methods are unable to meet the need for rapidly growing cell-based applications, which require cell supply in a variety of occasions outside of laboratories. Herein, we report spontaneous packaging and hypothermic storage of mammalian cells under refrigerated (4 °C) and ambient conditions (25 °C) using a cell-membrane-mimetic methacryloyloxyethyl phosphorylcholine (MPC) polymer hydrogel incorporated within a glass microchip. Its capability for hypothermic storage of cells was comparatively evaluated over 16 days. The results reveal that the cytocompatible MPC polymer hydrogel, in combination with the microchip structure, enabled hypothermic storage of cells with quite high viability, high intracellular esterase activity, maintained cell membrane integrity, and small morphological change for more than 1 week at 4 °C and at least 4 days at 25 °C. Furthermore, the stored cells could be released from the hydrogel and exhibited the ability to adhere to a surface and achieve confluence under standard cell culture conditions. Both hypothermic storage conditions are ordinary flexible conditions which can be easily established in places outside of laboratories. Therefore, cell packaging and storage using the hydrogel incorporated within the microchip would be a promising miniature and portable solution for flexible supply and delivery of small amounts of cells from bench to bedside.

  8. The Autohumidification Polymer Electrolyte Membrane Fuel Cell

    CERN Document Server

    Benziger, J B; Tulyani, S; Turner, A; Bocarsly, A B; Kevrekidis, Yu G

    2003-01-01

    A PEM fuel cell was specially constructed to determine kinetics under conditions of well-defined gas phase composition and cell temperature. Steady state multiplicity was discovered in the autohumidification PEM fuel cell, resulting from a balance between water production and water removal. Ignition was observed in the PEM fuel cell for a critical water activity of about 0.1. Ignition is a consequence of the exponential increase of proton conductivity with water activity, which creates an autocatalytic feedback between the water production and the proton conduction. The steady state current in the ignited state decreases with increasing temperature between 50 to 105 deg C. At temperatures greater than 70 deg C five steady states were observed in the PEM fuel cell. The steady state performance has been followed with variable load resistance and hysteresis loops have been mapped. The dynamics of transitions between steady states are slow about 10^3 to 10^4 s. These slow dynamics are suggested to result from a c...

  9. Identification of FtsW as a transporter of lipid-linked cell wall precursors across the membrane.

    Science.gov (United States)

    Mohammadi, Tamimount; van Dam, Vincent; Sijbrandi, Robert; Vernet, Thierry; Zapun, André; Bouhss, Ahmed; Diepeveen-de Bruin, Marlies; Nguyen-Distèche, Martine; de Kruijff, Ben; Breukink, Eefjan

    2011-04-20

    Bacterial cell growth necessitates synthesis of peptidoglycan. Assembly of this major constituent of the bacterial cell wall is a multistep process starting in the cytoplasm and ending in the exterior cell surface. The intracellular part of the pathway results in the production of the membrane-anchored cell wall precursor, Lipid II. After synthesis this lipid intermediate is translocated across the cell membrane. The translocation (flipping) step of Lipid II was demonstrated to require a specific protein (flippase). Here, we show that the integral membrane protein FtsW, an essential protein of the bacterial division machinery, is a transporter of the lipid-linked peptidoglycan precursors across the cytoplasmic membrane. Using Escherichia coli membrane vesicles we found that transport of Lipid II requires the presence of FtsW, and purified FtsW induced the transbilayer movement of Lipid II in model membranes. This study provides the first biochemical evidence for the involvement of an essential protein in the transport of lipid-linked cell wall precursors across biogenic membranes. PMID:21386816

  10. Consequences of lipidic nanoemulsions on membrane integrity and ultrastructural morphology of Staphylococcus aureus

    International Nuclear Information System (INIS)

    The present study divulges the consequences of lipidic nanoemulsions (cationized and non-cationized) on morphology and membrane integrity of Staphylococcus aureus using transmission electron microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Transmission electron microscopic (TEM) images reveal that the cationized lipidic emulsions (CLEs) remained adhered even after the hostile treatment to remove nanoemulsions by centrifugation owing to electrostatic attraction between CLE and negatively charged bacterial surface. TEM images portray the extensive cell lyses owing to the release of cytoplasmic content when treated with both CLE and Non-CLE (NCLE). The AFM analysis of the NCLE and CLE treated S. aureus cells showed the root mean square roughness of 11.3 ± 2.8 nm and 17.7 ± 3.2 nm, respectively. The complete losses of bacterial colonies after 45 min of contact with NCLE were observed. No viable bacterial colonies were noticeable after 10 min of contact when treated with CLE, indicating better rate of killing with respect to NCLE. Similar results were obtained in the zone of inhibition studies. Significant (p < 0.05) increase of cytoplasmic material was observed both in NCLE (0.192 ± 0.003) and CLE (0.308 ± 0.012) as compared to control (0.019 ± 0.002). The present finding illustrates that the NCLE and CLE had caused significant membrane disorganization leading to release of cytoplasmic content causing irreversible cell damage, which is in accordance with the TEM, SEM and AFM studies. (papers)

  11. Successful Integration of Membrane Technologies in a Conventional Purification Process of Tannery Wastewater Streams

    Directory of Open Access Journals (Sweden)

    Angelo Chianese

    2013-07-01

    Full Text Available The aim of this work is to design and integrate an optimized batch membrane process in a conventional purification process used for the treatment of tannery wastewater. The integration was performed by using two spiral wound membrane modules in series, that is, nanofiltration and reverse osmosis, as substitutes to the biological reactor. The membrane process was designed in terms of sensible fouling issues reduction, which may be observed on the nanofiltration membrane if no optimization is performed. The entity of the fouling phenomena was estimated by pressure cycling measurements, determining both the critical and the threshold flux on the nanofiltration membrane. The obtained results were used to estimate the need of the overdesign of the membrane plant, as well as to define optimized operating conditions in order to handle fouling issues correctly for a long period of time. Finally, the developed membrane process was compared, from a technical and economic point of view, with the conventional biological process, widely offered as an external service near tannery production sites, and, here, proposed to be substituted by membrane technologies.

  12. 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...

  13. 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

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

    DEFF Research Database (Denmark)

    Foged, Camilla; Nielsen, Hanne Moerck

    2008-01-01

    , 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...

  15. Dendronized Polymer Architectures for Fuel Cell Membranes

    DEFF Research Database (Denmark)

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

    2013-01-01

    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....

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

    Science.gov (United States)

    Bier, M.

    2006-05-01

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

  17. Integrated nanoscale tools for interrogating living cells

    Science.gov (United States)

    Jorgolli, Marsela

    and fabricated a new hybrid chip that combines a front-side nanowire-based interface for neuronal recording with backside complementary metal oxide semiconductor (CMOS) circuits for on-chip multiplexing, voltage control for stimulation, signal amplification, and signal processing. Individual chips contain 1024 stimulation/recording sites enabling large-scale interfacing of neuronal networks with single cell resolution. Through electrical and electrochemical characterization of the devices, we demonstrated their enhanced functionality at a massively parallel scale. In our initial cell experiments, we achieved intracellular stimulations and recordings of changes in the membrane potential in a variety of cells including: HEK293T, cardiomyocytes, and rat cortical neurons. This demonstrated the device capability for single-cell-resolution recording/stimulation which when extended to a large number of neurons in a massively parallel fashion will enable the functional mapping of a complex neuronal network.

  18. Integrated Water Gas Shift Membrane Reactors Utilizing Novel, Non Precious Metal Mixed Matrix Membrane

    Energy Technology Data Exchange (ETDEWEB)

    Ferraris, John

    2013-09-30

    Nanoparticles of zeolitic imidazolate frameworks and other related hybrid materials were prepared by modifying published synthesis procedures by introducing bases, changing stoichiometric ratios, or adjusting reaction conditions. These materials were stable at temperatures >300 °C and were compatible with the polymer matrices used to prepare mixed- matrix membranes (MMMs). MMMs tested at 300 °C exhibited a >30 fold increase in permeability, compared to those measured at 35 °C, while maintaining H{sub 2}/CO{sub 2} selectivity. Measurements at high pressure (up to 30 atm) and high temperature (up to 300 °C) resulted in an increase in gas flux across the membrane with retention of selectivity. No variations in permeability were observed at high pressures at either 35 or 300 °C. CO{sub 2}-induced plasticization was not observed for Matrimid®, VTEC, and PBI polymers or their MMMs at 30 atm and 300 °C. Membrane surface modification by cross-linking with ethanol diamine resulted in an increase in H{sub 2}/CO{sub 2} selectivity at 35 °C. Spectrometric analysis showed that the cross-linking was effective to temperatures <150 °C. At higher temperatures, the cross-linked membranes exhibit a H{sub 2}/CO{sub 2} selectivity similar to the uncross-linked polymer. Performance of the polybenzimidazole (PBI) hollow fibers prepared at Santa Fe Science and Technology (SFST, Inc.) showed increased flux o to a flat PBI membrane. A water-gas shift reactor has been built and currently being optimized for testing under DOE conditions.

  19. Effects of Perfluorocarbons on surfactant exocytosis and membrane properties in isolated alveolar type II cells

    Directory of Open Access Journals (Sweden)

    Ravasio Andrea

    2010-05-01

    Full Text Available Abstract Background Perfluorocarbons (PFC are used to improve gas exchange in diseased lungs. PFC have been shown to affect various cell types. Thus, effects on alveolar type II (ATII cells and surfactant metabolism can be expected, data, however, are controversial. Objective The study was performed to test two hypotheses: (I the effects of PFC on surfactant exocytosis depend on their respective vapor pressures; (II different pathways of surfactant exocytosis are affected differently by PFC. Methods Isolated ATII cells were exposed to two PFC with different vapor pressures and spontaneous surfactant exocytosis was measured. Furthermore, surfactant exocytosis was stimulated by either ATP, PMA or Ionomycin. The effects of PFC on cell morphology, cellular viability, endocytosis, membrane permeability and fluidity were determined. Results The spontaneous exocytosis was reduced by PFC, however, the ATP and PMA stimulated exocytosis was slightly increased by PFC with high vapor pressure. In contrast, Ionomycin-induced exocytosis was decreased by PFC with low vapor pressure. Cellular uptake of FM 1-43 - a marker of membrane integrity - was increased. However, membrane fluidity, endocytosis and viability were not affected by PFC incubation. Conclusions We conclude that PFC effects can be explained by modest, unspecific interactions with the plasma membrane rather than by specific interactions with intracellular targets.

  20. Experimental Investigation and Discussion on the Mechanical Endurance Limit of Nafion Membrane Used in Proton Exchange Membrane Fuel Cell

    OpenAIRE

    Yang Xiao; Chongdu Cho

    2014-01-01

    As a solution of high efficiency and clean energy, fuel cell technologies, especially proton exchange membrane fuel cell (PEMFC), have caught extensive attention. However, after decades of development, the performances of PEMFCs are far from achieving the target from the Department of Energy (DOE). Thus, further understanding of the degradation mechanism is needed to overcome this obstacle. Due to the importance of proton exchange membrane in a PEMFC, the degradation of the membrane, such as ...

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

    Science.gov (United States)

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

    2010-01-01

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

  2. Combining in Vitro Folding with Cell Free Protein Synthesis for Membrane Protein Expression.

    Science.gov (United States)

    Focke, Paul J; Hein, Christopher; Hoffmann, Beate; Matulef, Kimberly; Bernhard, Frank; Dötsch, Volker; Valiyaveetil, Francis I

    2016-08-01

    Cell free protein synthesis (CFPS) has emerged as a promising methodology for protein expression. While polypeptide production is very reliable and efficient using CFPS, the correct cotranslational folding of membrane proteins during CFPS is still a challenge. In this contribution, we describe a two-step protocol in which the integral membrane protein is initially expressed by CFPS as a precipitate followed by an in vitro folding procedure using lipid vesicles for converting the protein precipitate to the correctly folded protein. We demonstrate the feasibility of using this approach for the K(+) channels KcsA and MVP and the amino acid transporter LeuT. We determine the crystal structure of the KcsA channel obtained by CFPS and in vitro folding to show the structural similarity to the cellular expressed KcsA channel and to establish the feasibility of using this two-step approach for membrane protein production for structural studies. Our studies show that the correct folding of these membrane proteins with complex topologies can take place in vitro without the involvement of the cellular machinery for membrane protein biogenesis. This indicates that the folding instructions for these complex membrane proteins are contained entirely within the protein sequence. PMID:27384110

  3. Polycation-mediated integrated cell death processes

    DEFF Research Database (Denmark)

    Parhamifar, Ladan; Andersen, Helene; Wu, Linping;

    2014-01-01

    standard. PEIs are highly efficient transfectants, but depending on their architecture and size they induce cytotoxicity through different modes of cell death pathways. Here, we briefly review dynamic and integrated cell death processes and pathways, and discuss considerations in cell death assay design...

  4. Performance of Membrane-Assisted Solid Oxide Fuel Cell System Fuelled by Bioethanol

    Directory of Open Access Journals (Sweden)

    Amornchai Arpornwichanop

    2011-04-01

    Full Text Available The membrane separation units for bioethanol purification including pervaporation and vapor permeation are integrated with the bioethanol-fuelled solid oxide fuel cell (SOFC system. The preliminary calculations indicate that Hydrophilic type is a suitable membrane for vapor permeation to be installed after a hydrophobic pervaporation. Based on energy self-sufficient condition and data of available pervaporation membranes, the simulation results show that the use of vapor permeation unit after the pervaporation can significantly improve the overall electrical efficiency from 10.96% for the system with pervaporation alone to 26.56%. Regarding the effect of ethanol recovery, the ethanol recovery at 75% can offer the optimal overall efficiency from the proposed purification system compared to the ethanol recovery at 31.16% for the case with the single pervaporation.

  5. Chemical Imaging of the Cell Membrane by NanoSIMS

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-02-23

    The existence of lipid microdomains and their role in cell membrane organization are currently topics of great interest and controversy. The cell membrane is composed of a lipid bilayer with embedded proteins that can flow along the two-dimensional surface defined by the membrane. Microdomains, known as lipid rafts, are believed to play a central role in organizing this fluid system, enabling the cell membrane to carry out essential cellular processes, including protein recruitment and signal transduction. Lipid rafts are also implicated in cell invasion by pathogens, as in the case of the HIV. Therefore, understanding the role of lipid rafts in cell membrane organization not only has broad scientific implications, but also has practical implications for medical therapies. One of the major limitations on lipid organization research has been the inability to directly analyze lipid composition without introducing artifacts and at the relevant length-scales of tens to hundreds of nanometers. Fluorescence microscopy is widely used due to its sensitivity and specificity to the labeled species, but only the labeled components can be observed, fluorophores can alter the behavior of the lipids they label, and the length scales relevant to imaging cell membrane domains are between that probed by fluorescence resonance energy transfer (FRET) imaging (<10 nm) and the diffraction limit of light. Topographical features can be imaged on this length scale by atomic force microscopy (AFM), but the chemical composition of the observed structures cannot be determined. Immuno-labeling can be used to study the distribution of membrane proteins at high resolution, but not lipid composition. We are using imaging mass spectrometry by secondary ion mass spectrometry (SIMS) in concert with other high resolution imaging methods to overcome these limitations. The experimental approach of this project is to combine molecule-specific stable isotope labeling with high-resolution SIMS using a

  6. Durability aspects of polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Sethuraman, Vijay Anand

    In order for the successful adoption of proton exchange membrane (PEM) fuel cell technology, it is imperative that durability is understood, quantified and improved. A number of mechanisms are known to contribute to PEMFC membrane electrode assembly (MEA) performance degradation. In this dissertation, we show, via experiments, some of the various processes that degrade the proton exchange membrane in a PEM fuel cell; and catalyst poisoning due to hydrogen sulfide (H2S) and siloxane. The effect of humidity on the chemical stability of two types of membranes, [i.e., perfluorosulfonic acid type (PFSA, NafionRTM 112) and biphenyl sulfone hydrocarbon type, (BPSH-35)] was studied by subjecting the MEAs to open-circuit voltage (OCV) decay and potential cycling tests at elevated temperatures and low inlet gas relative humidities. The BPSH-35 membranes showed poor chemical stability in ex situ Fenton tests compared to that of NafionRTM membranes. However, under fuel cell conditions, BPSH-35 MEAs outperformed NafionRTM 112 MEAs in both the OCV decay and potential cycling tests. For both membranes, (i) at a given temperature, membrane degradation was more pronounced at lower humidities and (ii) at a given relative humidity operation, increasing the cell temperature accelerated membrane degradation. Mechanical stability of these two types of membranes was also studied using relative humidity (RH) cycling. Hydrogen peroxide (H2O2) formation rates in a proton exchange membrane (PEM) fuel cell were estimated by studying the oxygen reduction reaction (ORR) on a rotating ring disc electrode (RRDE). Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the disk and by varying the temperature, dissolved O2 concentration and the acidity levels in HClO4. The HClO4 acidity was correlated to ionomer water activity and hence fuel cell humidity. H 2O2 formation rates showed a linear dependence on oxygen concentration and square dependence on water

  7. Biophysical Studies of Nanosecond Pulsed Electric Field Induced Cell Membrane Permeabilization

    Science.gov (United States)

    Wu, Yu-Hsuan

    rate) on electropermeabilization. The effects of chemical agents that either promote (H2O2) or inhibit (lanthanide ions and Hg2+) electropermeabilization are also studied. To characterize the population of pores created by nsPEFs, we isoosmotically substitute different size of neutral molecules in the pulsing medium, and estimate pore size by analyzing cell volume changes that result from the permeation of these substituted molecules through the plasma membrane of Jurkat T lymphoblasts. The basis of this method is regulation of osmotic balance across the plasma membrane as well. We find that most pores opened by 5-100 5 ns pulses in plasma memebrane of Jurkat T lymphoblasts have diameter between 0.7-0.9 nm. In Chapter 5, we report the design and construction of a delivery system for nsPEF. We integrate a pair of delicately fabricated tungsten wire electrodes spaced 100 mum, a solid-state high-voltage nanosecond pulse generator and a fluorescent microscope coupling with a fast and sensitive digital recording camera. This system enables real-time biophotonic investigations of the nsPEF-induced biological responses of living mammalian cells in-vitro.

  8. A Novel and Facile Method to Prepare Integrated Electrospun Nanofibrous Membrane with Soldered Junctions.

    Science.gov (United States)

    Shen, Lingdi; Chen, Jiajia; Hong, Guishan; Wang, Xuefen

    2016-01-01

    Integrated electrospun nanofibrous membrane was prepared by creating soldered junctions between nanofibers via a facile strategy. Polyacrylonitrile (PAN) mixed with poly(vinylidene fluoride) (PVDF) at different ratios of PVDF were prepared in N,N'-dimethyl formamide (DMF), then electrospun to fabricate PAN/PVDF membranes. PVDF can form microgels in DMF which slows down volatile speed of DMF and affects the solidification of PAN/PVDF nanofibers. The resulting membranes were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, dynamic water contact angle and tensile testing to confirm the morphology and mechanical properties. Soldered junctions were observed between nanofibers with the increase of PVDF content. These junctions made the membrane integrated and greatly enhanced tensile strength from 5.1 to 8.1 MPa (increased by ~60%) and tensile modulus from 49.4 to 117.9 MPa (increased by ~139%) without compromising porosity when the content of PVDF increased from 0 to 60 wt%. PMID:27398532

  9. Enzymatic synthesis of hydrophobic compounds integrated with membrane separation

    Directory of Open Access Journals (Sweden)

    Noworyta Andrzej

    2016-03-01

    Full Text Available The enzymatic synthesis of a highly hydrophobic product (dipeptide precursor in which the reaction is accompanied by the mass transfer of the reaction product to the organic phase and the substrates to the water phase is considered. Equations describing both continuous and batch processes are formulated. The range of variability in the operating parameters of such a bioreactor is specified, and the correlations reported in the literature to describe mass transfer in the membrane contactor are validated. The proposed process was verified experimentally, and good agreement between the determined and calculated concentrations was obtained in both phases.

  10. The Unfolded Protein Response Is Induced by the Cell Wall Integrity Mitogen-activated Protein Kinase Signaling Cascade and Is Required for Cell Wall Integrity in Saccharomyces cerevisiae

    OpenAIRE

    Scrimale, Thomas; DiDone, Louis; de Mesy Bentley, Karen L.; Krysan, Damian J.

    2009-01-01

    The yeast cell wall is an extracellular structure that is dependent on secretory and membrane proteins for its construction. We investigated the role of protein quality control mechanisms in cell wall integrity and found that the unfolded protein response (UPR) and, to a lesser extent, endoplasmic reticulum (ER)-associated degradation (ERAD) pathways are required for proper cell wall construction. Null mutation of IRE1, double mutation of ERAD components (hrd1Δ and ubc7Δ) and ire1Δ, or expres...

  11. Genistein and Daidzein Effects on Proliferation, Cell Membranes,Cell Cycles and Cell Apoptosis of Different Cell Lines

    Institute of Scientific and Technical Information of China (English)

    李重华; 王洪钟; 肖锐; 张勇; 于江涛; 谢莉萍; 张荣庆

    2001-01-01

    Genistein and daidzein are two principle isoflavonoids in soybeans. They have received increasing attention in the past few years because of their possible roles in cancer prevention. Here are provided experimental evidences that genistein could inhibit the growth of human bladder carcinoma cells (ECV-304), human colon cancer cells (HT29), human uterus cervix cancer cells (Hela), and murine transformed muscle cells (3T3). Different from genistein, daidzein could only inhibit the growth of ECV-304, HT29, and 3T3 cells. To elucidate the mechanisms of the anti-tumor effect of genistein and daidzein, fluorescent polarization, circular dichroism, and flow cytometric analysis were employed to study the influence of genistein and daidzein on membrane fluidity and membrane protein conformation of these cell lines. The results showed that genistein increased the order of membrane protein conformation and reduced the membrane fluidity of ECV-304, HT29, and Hela cells. Daidzein also increased the order of membrane protein conformation of ECV-304 and HT29, but had no effect on the membrane fluidity of all these four cell lines. Also demonstrated was that both compounds affected the apoptosis and cell cycle progression of some cell lines. However, the effects of genistein and daidzein were not the same. These evidences suggested that the effects of genistein and daidzein on malignant cells were multisites and multiapproaches, and there were differences between their functional mechanisms. The amelioration effect on cell conditions may represent one of the mechanisms of the effect of genistein and daidzein on the growth, differentiation, and transference of malignant cells.

  12. A parametric study of assembly pressure, thermal expansion, and membrane swelling in PEM fuel cells

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2016-01-01

    Full Text Available Proton Exchange membrane (PEM fuel cells are still undergoing intense development, and the combination of new and optimized materials, improved product development, novel architectures, more efficient transport processes, and design optimization and integration are expected to lead to major gains in performance, efficiency, durability, reliability, manufacturability and cost-effectiveness. PEM fuel cell assembly pressure is known to cause large strains in the cell components. All components compression occurs during the assembly process of the cell, but also during fuel cell operation due to membrane swelling when absorbs water and cell materials expansion due to heat generating in catalyst layers. Additionally, the repetitive channel-rib pattern of the bipolar plates results in a highly inhomogeneous compressive load, so that while large strains are produced under the rib, the region under the channels remains approximately at its initial uncompressed state. This leads to significant spatial variations in GDL thickness and porosity distributions, as well as in electrical and thermal bulk conductivities and contact resistances (both at the ribe-GDL and membrane-GDL interfaces. These changes affect the rates of mass, charge, and heat transport through the GDL, thus impacting fuel cell performance and lifetime. In this paper, computational fluid dynamics (CFD model of a PEM fuel cell has been developed to simulate the pressure distribution inside the cell, which are occurring during fuel cell assembly (bolt assembling, and membrane swelling and cell materials expansion during fuel cell running due to the changes of temperature and relative humidity. The PEM fuel cell model simulated includes the following components; two bi-polar plates, two GDLs, and, an MEA (membrane plus two CLs. This model is used to study and analyses the effect of assembling and operating parameters on the mechanical behaviour of PEM. The analysis helped identifying critical

  13. 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.

  14. A Theory for the Membrane Potential of Living Cells

    CERN Document Server

    Endresen, L P; Høye, J S; Myrheim, Jan

    1998-01-01

    We give an explicit formula for the membrane potential of cells in terms of the intracellular and extracellular ionic concentrations, and derive equations for the ionic currents that flow through channels, exchangers and electrogenic pumps. We demonstrate that the work done by the pumps equals the change in potential energy of the cell, plus the energy lost in downhill ionic fluxes through the channels and exchangers. The theory is illustrated in a simple model of spontaneously active cells in the cardiac pacemaker. The model predicts the experimentally observed intracellular ionic concentration of potassium, calcium, and sodium. Likewise the shapes of the simulated action potential and five membrane currents are in good agreement with experiments. We do not see any drift in the values of the concentrations in a long time simulation, and we obtain the same asymptotic values when starting from the full equilibrium situation with equal intracellular and extracellular ionic concentrations.

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

    Science.gov (United States)

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

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

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

    Science.gov (United States)

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

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

  17. Low-temperature bonded glass-membrane microfluidic device for in vitro organ-on-a-chip cell culture models

    Science.gov (United States)

    Pocock, Kyall J.; Gao, Xiaofang; Wang, Chenxi; Priest, Craig; Prestidge, Clive A.; Mawatari, Kazuma; Kitamori, Takehiko; Thierry, Benjamin

    2015-12-01

    The integration of microfluidics with living biological systems has paved the way to the exciting concept of "organson- a-chip", which aims at the development of advanced in vitro models that replicate the key features of human organs. Glass based devices have long been utilised in the field of microfluidics but the integration of alternative functional elements within multi-layered glass microdevices, such as polymeric membranes, remains a challenge. To this end, we have extended a previously reported approach for the low-temperature bonding of glass devices that enables the integration of a functional polycarbonate porous membrane. The process was initially developed and optimised on specialty low-temperature bonding equipment (μTAS2001, Bondtech, Japan) and subsequently adapted to more widely accessible hot embosser units (EVG520HE Hot Embosser, EVG, Austria). The key aspect of this method is the use of low temperatures compatible with polymeric membranes. Compared to borosilicate glass bonding (650 °C) and quartz/fused silica bonding (1050 °C) processes, this method maintains the integrity and functionality of the membrane (Tg 150 °C for polycarbonate). Leak tests performed showed no damage or loss of integrity of the membrane for up to 150 hours, indicating sufficient bond strength for long term cell culture. A feasibility study confirmed the growth of dense and functional monolayers of Caco-2 cells within 5 days.

  18. Inferring maps of forces inside cell membrane microdomains

    CERN Document Server

    Masson, J -B; Tuerkcan, S; Voisinne, G; Popoff, M R; Vergassola, M; Alexandrou, A

    2015-01-01

    Mapping of the forces on biomolecules in cell membranes has spurred the development of effective labels, e.g. organic fluorophores and nanoparticles, to track trajectories of single biomolecules. Standard methods use particular statistics, namely the mean square displacement, to analyze the underlying dynamics. Here, we introduce general inference methods to fully exploit information in the experimental trajectories, providing sharp estimates of the forces and the diffusion coefficients in membrane microdomains. Rapid and reliable convergence of the inference scheme is demonstrated on trajectories generated numerically. The method is then applied to infer forces and potentials acting on the receptor of the $\\epsilon$-toxin labeled by lanthanide-ion nanoparticles. Our scheme is applicable to any labeled biomolecule and results show show its general relevance for membrane compartmentation.

  19. Nanoporous silicon membrane for fuel cells realized by electrochemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Jaouadi, M., E-mail: mohja05.08@hotmail.com [Laboratoire de Photovoltaieque, Centre de Recherches et des Technologies de l' Energie, Technopole de Borj-Cedria, BP 95 Hammam-Lif 2050 (Tunisia); Dimassi, W.; Gaidi, M.; Chtourou, R.; Ezzaouia, H. [Laboratoire de Photovoltaieque, Centre de Recherches et des Technologies de l' Energie, Technopole de Borj-Cedria, BP 95 Hammam-Lif 2050 (Tunisia)

    2012-05-15

    In this work we propose a simple method to realize nanoporous silicon proton exchange membranes for fuel cells. The electrochemical etching allows in a single step, the grooving of the membrane and the realization of double porous silicon (PS) layer. We have studied the impact of the different electrochemical conditions: current density, the electrolyte concentration (ethanoic HF) and the anodization time leading to optimal thickness (of 50-90 {mu}m) and nanoporosity for silicon microstructures. The experimental techniques employed for surface studies and depths of groove in silicon are mainly scanning electronic microscopy (SEM) and atomic force microscopy (AFM) which give information of the silicon microstructures. Photoluminescence (PL) measurements of porous silicon membrane were carried out in order to investigate the optical properties of the PS.

  20. Benzimidazole grafted polybenzimidazoles for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Aili, David; Li, Qingfeng;

    2013-01-01

    High molecular weight polybenzimidazole (PBI) was synthesized and grafted with benzimidazole pendant groups. The high molecular weight of PBI resulted in good film-forming properties and superior tensile strength. With a phosphoric acid doping level (ADL) of 13.1, a tensile strength of 16 MPa...... was achieved at room temperature. Grafting of benzimidazole moieties onto the PBI macromolecular chain introduced additional basic sites which allowed the membrane to achieve higher phosphoric acid uptakes. A molar acid conductivity, defined as the specific conductivity of each mole of doping acid......, was proposed to evaluate the effective conductivity contributed from the doping acids. With a grafting degree of 5.3% and an ADL of 13.1, the PBI membranes exhibited a total conductivity of 0.15 S cm-1. A H2-air fuel cell based on this membrane showed a peak power density of 378 mW cm-2 at 180 °C without...

  1. 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...

  2. Inorganic-organic Composite Membranes with Novel Microstructure for High Temperature Proton Exchange Membrane Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    Zhigang Ma; Jiandong Gao; Jing Guo; Zhenghua Deng; Jishuan Suo

    2007-01-01

    Nowadays,more and more fossil fuels are consumed and air pollurion has become a threat to the survival of people.Therefore,we need some other power sources to provide energy without damaging the environment.Proton exchange membrane fuel cells(PEMFCs)have received wide attention due to their advantages Such as high energy density and zero emission[1].Particularly, direct methanol fuel cells (DMFCs)were considered as the most suitable energy sources for electric vehicles(EVs)and portable electronics.

  3. Effect of powdered activated carbon on integrated submerged membrane bioreactor-nanofiltration process for wastewater reclamation.

    Science.gov (United States)

    Woo, Yun Chul; Lee, Jeong Jun; Shim, Wang-Geun; Shon, Ho Kyong; Tijing, Leonard D; Yao, Minwei; Kim, Han-Seung

    2016-06-01

    The aim of this study was to determine the effect of powdered activated carbon (PAC) on the overall performance of a submerged membrane bioreactor (SMBR) system integrated with nanofiltration (NF) for wastewater reclamation. It was found that the trans-membrane pressure of SMBR increased continuously while that of the SMBR with PAC was more stable, mainly because water could still pass through the PACs and membrane even though foulants adhered on the PAC surface. The presence of PAC was able to mitigate fouling in SMBR as well as in NF. SMBR-NF with PAC obtained a higher flux of 8.1 LMH compared to that without PAC (6.6 LMH). In addition, better permeate quality was obtained with SMBR-NF integrated process added with PAC. The present results suggest that the addition of PAC in integrated SMBR-NF process could possibly lead to satisfying water quality and can be operated for a long-term duration.

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

    Science.gov (United States)

    Gasa, Jeffrey

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

  5. BLM Experimentation and opto-electrical characterization in microchips, towards an integrated platform for drug screening on membrane proteins

    NARCIS (Netherlands)

    Stimberg, V.C.; Uitert, van I.; Le Gac, S.; Berg, van den A.; Verpoorte, S; Andersson-Svahn, S.M.H.; Emneus, J.; Pamme, N

    2010-01-01

    Experimentation on cell membranes and on membrane proteins commonly makes use of planar and simplified membrane models, or bilayer lipid membranes (BLMs). Although these models are extensively employed, the experimentation is tedious and time-consuming, and mostly limited to electrical measurements.

  6. 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

  7. 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.

  8. 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.

  9. Reconstitution of Membrane Proteins into Model Membranes: Seeking Better Ways to Retain Protein Activities

    OpenAIRE

    Trevor Lithgow; Lisa Martin; Hsin-Hui Shen

    2013-01-01

    The function of any given biological membrane is determined largely by the specific set of integral membrane proteins embedded in it, and the peripheral membrane proteins attached to the membrane surface. The activity of these proteins, in turn, can be modulated by the phospholipid composition of the membrane. The reconstitution of membrane proteins into a model membrane allows investigation of individual features and activities of a given cell membrane component. However, the activity of mem...

  10. SH4-domain-induced plasma membrane dynamization promotes bleb-associated cell motility.

    Science.gov (United States)

    Tournaviti, Stella; Hannemann, Sebastian; Terjung, Stefan; Kitzing, Thomas M; Stegmayer, Carolin; Ritzerfeld, Julia; Walther, Paul; Grosse, Robert; Nickel, Walter; Fackler, Oliver T

    2007-11-01

    SH4 domains provide bipartite membrane-targeting signals for oncogenic Src family kinases. Here we report the induction of non-apoptotic plasma membrane (PM) blebbing as a novel and conserved activity of SH4 domains derived from the prototypic Src kinases Src, Fyn, Yes and Lck as well as the HASPB protein of Leishmania parasites. SH4-domain-induced blebbing is highly dynamic, with bleb formation and collapse displaying distinct kinetics. These reorganizations of the PM are controlled by Rho but not Rac or Cdc42 GTPase signalling pathways. SH4-induced membrane blebbing requires the membrane association of the SH4 domain, is regulated by the activities of Rock kinase and myosin II ATPase, and depends on the integrity of F-actin as well as microtubules. Endogenous Src kinase activity is crucial for PM blebbing in SH4-domain-expressing cells, active Src and Rock kinases are enriched in SH4-domain-induced PM blebs, and PM blebbing correlates with enhanced cell invasion in 3D matrices. These results establish a novel link between SH4 domains, Src activity and Rho signalling, and implicate SH4-domain-mediated PM dynamization as a mechanism that influences invasiveness of cells transformed by SH4-domain-containing oncoproteins. PMID:17959630

  11. 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...

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

    Science.gov (United States)

    Ratajczak, M Z; Adamiak, M

    2015-07-01

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

  13. Near-critical fluctuations and cytoskeleton-assisted phase separation lead to subdiffusion in cell membranes

    CERN Document Server

    Ehrig, Jens; Schwille, Petra

    2010-01-01

    We address the relationship between membrane microheterogeneity and anomalous subdiffusion in cell membranes by carrying out Monte Carlo simulations of two-component lipid membranes. We find that near-critical fluctuations in the membrane lead to transient subdiffusion, while membrane-cytoskeleton interaction strongly affects phase separation, enhances subdiffusion, and eventually leads to hop diffusion of lipids. Thus, we present a minimum realistic model for membrane rafts showing the features of both microscopic phase separation and subdiffusion.

  14. Near-Critical Fluctuations and Cytoskeleton-Assisted Phase Separation Lead to Subdiffusion in Cell Membranes

    OpenAIRE

    Ehrig, Jens; Petrov, Eugene P.; Schwille, Petra

    2011-01-01

    We address the relationship between membrane microheterogeneity and anomalous subdiffusion in cell membranes by carrying out Monte Carlo simulations of two-component lipid membranes. We find that near-critical fluctuations in the membrane lead to transient subdiffusion, while membrane-cytoskeleton interaction strongly affects phase separation, enhances subdiffusion, and eventually leads to hop diffusion of lipids. Thus, we present a minimum realistic model for membrane rafts showing the featu...

  15. 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 30...

  16. Multi-layer graphene membrane based memory cell

    Science.gov (United States)

    Siahlo, Andrei I.; Popov, Andrey M.; Poklonski, Nikolai A.; Lozovik, Yurii E.; Vyrko, Sergey A.; Ratkevich, Sergey V.

    2016-10-01

    The scheme and operational principles of the nanoelectromechanical memory cell based on the bending of a multi-layer graphene membrane by the electrostatic force are proposed. An analysis of the memory cell total energy as a function of the memory cell sizes is used to determine the sizes corresponding to a bistable memory cell with the conducting ON and non-conducting OFF states and to calculate the switching voltage between the OFF and ON states. It is shown that a potential barrier between the OFF and ON states is huge for practically all sizes of a bistable memory cell which excludes spontaneous switching and allows the proposed memory cell to be used for long-term archival storage.

  17. Stimulating Effect of Terfenadine on Erythrocyte Cell Membrane Scrambling

    Directory of Open Access Journals (Sweden)

    Elena Signoretto

    2016-04-01

    Full Text Available Background/Aims: The antihistaminic drug Terfenadine may trigger apoptosis of tumor cells, an effect unrelated to its effect on histamine receptors. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal death of erythrocytes characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Signaling triggering eryptosis include increase of cytosolic Ca2+ activity ([Ca2+]i, oxidative stress, and ceramide. The present study explored, whether Terfenadine is capable to trigger eryptosis. Methods: Flow cytometry was employed to estimate phosphatidylserine abundance at the erythrocyte surface from annexin-V-binding, cell volume from forward scatter, [Ca2+]i from Fluo3-fluorescence, abundance of reactive oxygen species (ROS from 2′,7′-dichlorodihydrofluorescein (DCF diacetate dependent fluorescence, and ceramide abundance at the human erythrocyte surface utilizing specific antibodies. Hemolysis was quantified from haemoglobin concentration in the supernatant. Results: A 48 hours exposure of human erythrocytes to Terfenadine (≥ 5 µM significantly increased the percentage of annexin-V-binding cells and triggered hemolysis without significantly modifying the average forward scatter. Terfenadine (7.5 µM significantly increased Fluo3-fluorescence, but did not significantly modify DCF fluorescence or ceramide abundance. The effect of Terfenadine on annexin-V-binding was significantly blunted but not abolished by removal of extracellular Ca2+. Exposure of human erythrocytes to Ca2+ ionophore ionomycin (1 µM, 15 min triggered annexin-V-binding, an effect augmented by Terfenadine pretreatment (10 µM, 48 hours. Conclusions: Terfenadine triggers phospholipid scrambling of the human erythrocyte cell membrane, an effect in part due to entry of extracellular Ca2+ and in part due to sensitizing human erythrocyte cell membrane scrambling to Ca2+.

  18. Effects of NaCl and Ca2+on Membrane Potential of Epidermal Cells of Maize Roots

    Institute of Scientific and Technical Information of China (English)

    HUA Jia-min; WANG Xiao-li; ZHAI Fu-qin; YAN Feng; FENG Ke

    2008-01-01

    The effects of salt-stress on plants involve not only the water stress caused by low osmotic pressure,but also the toxicity of excess Na+.A large amount of Na+ entering cells would reduce K+ uptake,which leads to an imbalance of K:Na ratio in cells.One of the reasons for the reduced K+-uptake iS the closure of K+-channel which is controlled by membrane potential.Calcium is usually applied to improve the growth of plants on saline soils and shows positive influence in the integrality of cell membrane.This study applied glass microelectrode technique to monitoring the NaCl-induced changes of membrane potential of root epidermal cells of maize(Zea mays L.,Denghai 11)seedlings at NaCl concentrations of 0,8,20,50,100,200 mmol L-1,respectively.The effect of Ca2+ on the changes of membrane potential caused by NaCl Was also studied.The results showed that:NaCl caused cell membrane depolarization.The depolarization became greater and faster with increasing of NaCl concentration.Moreover,the extent of depolarization was positively correlated with NaCl concentration.The addition of calcium postponed the depolarization,and decreased the degree of depolarization caused by NaCl.High NaCl concentration leads to depolarization of maize root cell membrane,which can partly be counteracted by calcium.

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

    International Nuclear Information System (INIS)

    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)

  20. 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.

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

    Science.gov (United States)

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

    2016-05-19

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

  2. Exegoeconomic Analysis On A Proton Electrolyte Membrane Fuel Cell

    International Nuclear Information System (INIS)

    The objective of this study is to perform an exergy and economic analysis on proton electrolyte membrane fuel cell power system (PEMFC) known as exegoeconomic. A 5 kW PEMFC was taken as case study. The fuel cell includes the hydrogen processing system and a fuel cell stack. The hydrogen processing system consisted of an auto-thermal reactor (ATR), a water gas shift reactor (WGS), tubular ceramic membrane module (TCR) and a pressure swing adsorber (PSA). The fuel cell stack was the main power generator. It was obseved that TCM and PSA have low energy efficiency of 0.29 % and 0.09 % respectively. Energy efficiency for the auto-thermal reactor and fuel cell stack were higher at 22.44 % and 31.97 % respectively and both values are comparable with other studies. The exergoeconomics for the 5kW fuel cell system was determined as RM4756.62 per GJ. From the analysis, it is also found that the fuel cell cost can more competitive, if the cost of operation, maintenance and fuel can be reduced. (author)

  3. A laser microsurgical method of cell wall removal allows detection of large-conductance ion channels in the guard cell plasma membrane

    Science.gov (United States)

    Miedema, H.; Henriksen, G. H.; Assmann, S. M.; Evans, M. L. (Principal Investigator)

    1999-01-01

    Application of patch clamp techniques to higher-plant cells has been subject to the limitation that the requisite contact of the patch electrode with the cell membrane necessitates prior enzymatic removal of the plant cell wall. Because the wall is an integral component of plant cells, and because cell-wall-degrading enzymes can disrupt membrane properties, such enzymatic treatments may alter ion channel behavior. We compared ion channel activity in enzymatically isolated protoplasts of Vicia faba guard cells with that found in membranes exposed by a laser microsurgical technique in which only a tiny portion of the cell wall is removed while the rest of the cell remains intact within its tissue environment. "Laser-assisted" patch clamping reveals a new category of high-conductance (130 to 361 pS) ion channels not previously reported in patch clamp studies on plant plasma membranes. These data indicate that ion channels are present in plant membranes that are not detected by conventional patch clamp techniques involving the production of individual plant protoplasts isolated from their tissue environment by enzymatic digestion of the cell wall. Given the large conductances of the channels revealed by laser-assisted patch clamping, we hypothesize that these channels play a significant role in the regulation of ion content and electrical signalling in guard cells.

  4. Membraner

    DEFF Research Database (Denmark)

    Bach, Finn

    2009-01-01

    Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner......Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner...

  5. Structure of the major membrane protein complex from urinary bladder epithelial cells by cryo-electron crystallography

    NARCIS (Netherlands)

    Oostergetel, GT; Keegstra, W; Brisson, A

    2001-01-01

    Numerous protein plaques cover the apical surface of mammalian urinary bladder epithelial cells. These plaques contain four integral membrane proteins, called uroplakins, which form a well-ordered array of hexameric complexes. The 3D structure of these naturally occurring 2D crystals was studied by

  6. Development and application of a procedure for evaluating the long-term integrity of membranes for the anaerobic fluidized membrane bioreactor (AFMBR).

    Science.gov (United States)

    Shin, Chungheon; Kim, Kihyun; McCarty, Perry L; Kim, Jeonghwan; Bae, Jaeho

    2016-01-01

    A bench-scale short-term test, developed to predict the long-term integrity of membranes with potential for use in anaerobic fluidized-bed membrane bioreactors, was used to evaluate several commercial hollow-fiber membranes. It was found that membrane performance varied widely, some membranes failing much more rapidly than others. Also found was that larger sizes of the fluidized media, in this case granular activated carbon (GAC), severely affected membrane structural integrity more than did smaller sizes, as did the method used for membrane attachment. Within the limits studied, the GAC packing ratio had only a minor impact. A decrease in membrane permeability that sometimes resulted during the testing and was caused by the deposition of fine GAC particles could be eliminated without membrane damage through simultaneous chemical cleaning and sonication. This new testing procedure should be useful for selecting membranes and reactor operating conditions to better ensure long-term operating performance of anaerobic fluidized-bed membrane bioreactors. PMID:27438251

  7. Melittin interaction with sulfated sugars and cell membranes

    OpenAIRE

    Klocek, Gabriela

    2008-01-01

    The presented work focused on an alternative mechanism of action of melittin on the cell membranes. The study using ITC reveals that melittin has a high affinity for several glycosaminoglycans (GAGs), i.e. heparan sulfate (HS), dermatan sulfate and heparin. The interaction between peptide and GAGs comprised both electrostatic and non-ionic components. Circular dichroism (CD) spectroscopy demonstrates that the binding of melittin to HS and other GAGs induces a conformational cha...

  8. Collaboration between primitive cell membranes and soluble catalysts

    OpenAIRE

    Adamala, Katarzyna P.; Engelhart, Aaron E.; SZOSTAK, JACK W.

    2016-01-01

    One widely held model of early life suggests primitive cells consisted of simple RNA-based catalysts within lipid compartments. One possible selective advantage conferred by an encapsulated catalyst is stabilization of the compartment, resulting from catalyst-promoted synthesis of key membrane components. Here we show model protocell vesicles containing an encapsulated enzyme that promotes the synthesis of simple fatty acid derivatives become stabilized to Mg2+, which is required for ribozyme...

  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. Understanding Peptide Dendrimer Interactions with Model Cell Membrane Mimics

    DEFF Research Database (Denmark)

    Lind, Tania Kjellerup

    membranes or highly conserved motifs, effectively making resistance due to mutations less likely to develop and spread. For this we studied the conditions to form supported lipid bilayers with basic systems and further established a protocol for producing biomimetic bacterial model membranes via the vesicle......Since mass production of antimicrobial agents was established 70 years ago these miracle-drugs have been integral tools in modern medicine, saving an uncountable number of lives. However, bacteria are now consistently and with alarming rates developing resistance towards common antibiotics. Very...... few new drugs have been marketed over the last decades, making it impossible to keep pace with the disturbing levels of multi-drug resistant bacteria. Research in the area of novel drugs, which are less prone to induce resistance, and in-depth knowledge on their uptake mechanisms is thus of paramount...

  11. Interface-designed Membranes with Shape-controlled Patterns for High-performance Polymer Electrolyte Membrane Fuel Cells

    OpenAIRE

    Yukwon Jeon; Dong Jun Kim; Jong Kwan Koh; Yunseong Ji; Jong Hak Kim; Yong-Gun Shul

    2015-01-01

    Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method...

  12. Stimulation of Erythrocyte Cell Membrane Scrambling by Mushroom Tyrosinase

    Directory of Open Access Journals (Sweden)

    Leonie Frauenfeld

    2014-03-01

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

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

    Science.gov (United States)

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

    2015-06-01

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

  14. 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.

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

    Science.gov (United States)

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

    2010-01-01

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

  16. Microfluidic application-specific integrated device for monitoring direct cell-cell communication via gap junctions between individual cell pairs

    Science.gov (United States)

    Lee, Philip J.; Hung, Paul J.; Shaw, Robin; Jan, Lily; Lee, Luke P.

    2005-05-01

    Direct cell-cell communication between adjacent cells is vital for the development and regulation of functional tissues. However, current biological techniques are difficult to scale up for high-throughput screening of cell-cell communication in an array format. In order to provide an effective biophysical tool for the analysis of molecular mechanisms of gap junctions that underlie intercellular communication, we have developed a microfluidic device for selective trapping of cell-pairs and simultaneous optical characterizations. Two different cell populations can be brought into membrane contact using an array of trapping channels with a 2μm by 2μm cross section. Device operation was verified by observation of dye transfer between mouse fibroblasts (NIH3T3) placed in membrane contact. Integration with lab-on-a-chip technologies offers promising applications for cell-based analytical tools such as drug screening, clinical diagnostics, and soft-state biophysical devices for the study of gap junction protein channels in cellular communications. Understanding electrical transport mechanisms via gap junctions in soft membranes will impact quantitative biomedical sciences as well as clinical applications.

  17. Graphene-doped electrospun nanofiber membrane electrodes and proton exchange membrane fuel cell performance

    Science.gov (United States)

    Wei, Meng; Jiang, Min; Liu, Xiaobo; Wang, Min; Mu, Shichun

    2016-09-01

    A rational electrode structure can allow proton exchange membrane (PEM) fuel cells own high performance with a low noble metal loading and an optimal transport pathway for reaction species. In this study, we develop a graphene doped polyacrylonitile (PAN)/polyvinylident fluoride (PVDF) (GPP) electrospun nanofiber electrode with improved electrical conductivity and high porosity, which could enhance the triple reaction boundary and promote gas and water transport throughout the porous electrode. Thus the increased electrochemical active surface area (ECSA) of Pt catalysts and fuel cell performance can be expected. As results, the ECSA of hot-pressed electrospun electrodes with 2 wt% graphene oxide (GO) is up to 84.3 m2/g, which is greatly larger than that of the conventional electrode (59.5 m2/g). Significantly, the GPP nanofiber electrospun electrode with Pt loading of 0.2 mg/cm2 exhibits higher fuel cell voltage output and stability than the conventional electrode.

  18. Integrative Signaling Networks of Membrane Guanylate Cyclases: Biochemistry and Physiology

    Science.gov (United States)

    Sharma, Rameshwar K.; Duda, Teresa; Makino, Clint L.

    2016-01-01

    This monograph presents a historical perspective of cornerstone developments on the biochemistry and physiology of mammalian membrane guanylate cyclases (MGCs), highlighting contributions made by the authors and their collaborators. Upon resolution of early contentious studies, cyclic GMP emerged alongside cyclic AMP, as an important intracellular second messenger for hormonal signaling. However, the two signaling pathways differ in significant ways. In the cyclic AMP pathway, hormone binding to a G protein coupled receptor leads to stimulation or inhibition of an adenylate cyclase, whereas the cyclic GMP pathway dispenses with intermediaries; hormone binds to an MGC to affect its activity. Although the cyclic GMP pathway is direct, it is by no means simple. The modular design of the molecule incorporates regulation by ATP binding and phosphorylation. MGCs can form complexes with Ca2+-sensing subunits that either increase or decrease cyclic GMP synthesis, depending on subunit identity. In some systems, co-expression of two Ca2+ sensors, GCAP1 and S100B with ROS-GC1 confers bimodal signaling marked by increases in cyclic GMP synthesis when intracellular Ca2+ concentration rises or falls. Some MGCs monitor or are modulated by carbon dioxide via its conversion to bicarbonate. One MGC even functions as a thermosensor as well as a chemosensor; activity reaches a maximum with a mild drop in temperature. The complexity afforded by these multiple limbs of operation enables MGC networks to perform transductions traditionally reserved for G protein coupled receptors and Transient Receptor Potential (TRP) ion channels and to serve a diverse array of functions, including control over cardiac vasculature, smooth muscle relaxation, blood pressure regulation, cellular growth, sensory transductions, neural plasticity and memory.

  19. Impact of the antimicrobial peptide Novicidin on membrane structure and integrity

    DEFF Research Database (Denmark)

    Nielsen, Søren B; Otzen, Daniel Erik

    2010-01-01

    We have studied the impact of an 18-residue cationic antimicrobial peptide Novicidin (Nc) on the structure and integrity of partially anionic lipid membranes using oriented circular dichroism (OCD), quartz crystal microbalance with dissipation (QCM-D), dual polarization interferometry (DPI...... fluorescence spectroscopy and by loss of lipid alignment in DPI analysis. Laurdan generalized polarity shows a decrease in water accessibility or mobility in the hydrophobic/hydrophilic interface of the lipid membrane, consistent with rearrangement of lipid packing. QCM-D studies on the interaction of Nc...... with lipid membranes emphasize the importance of including the dissipation factor in data analysis, revealing formation of a highly hydrated film after exposure to 3muMNc. Our findings suggest a carpet mechanism of membrane disruption in which peptide binding first induces leakage at a critical surface...

  20. Integral PVA-PES Composite Membranes by Surface Segregation Method for Pervaporation Dehydration of Ethanol

    Institute of Scientific and Technical Information of China (English)

    吴洪; 李宪实; 聂明成; 李犇; 姜忠义

    2011-01-01

    A facile surface segregation method was utilized to fabricate poly(vinyl alcohol)-polyethersulfone (PVA-PES) composite membranes. PVA and PES were first dissolved in dimethyl sulfoxide (DMSO), then casted on a glass plate and immersed in a coagulation bath. During the phase inversion process in coagulation bath, PVA spontaneously segregated to the polymer solution/coagulation bath interface. The enriched PVA on the surface was further crosslinked by glutaraldehyde. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS) confirmed the integral and asymmetric membrane structure with a dense PVA-enriched surface and a porous PES-enriched support, as well as the surface enrichment of PVA. The coverage fraction of the membrane surtace by PVA reacned up to 86.8% when me PVA content m me membrane recipe was 16.7% (by mass). The water contact angle decreased with the increase of PVA content. The effect of coagulation bath type on membrane structure was analyzed. The membrane pervaporation performance was evaluated by varying the PVA content, the annealing temperature, feed concentration and operation temperature. The membrane exhibited a fairly good ethanol dehydration capacity and long-term operational stability.

  1. Differential expression profiling of membrane proteins by quantitative proteomics in a human mesenchymal stem cell line undergoing osteoblast differentiation

    DEFF Research Database (Denmark)

    Foster, Leonard J; Zeemann, Patricia A; Li, Chen;

    2005-01-01

    One of the major limitations for understanding the biology of human mesenchymal stem cells (hMSCs) is the absence of prospective markers needed for distinguishing them from other cells and for monitoring lineage-specific differentiation. Mass spectrometry (MS)-based proteomics has proven extremely...... in a cell model of hMSCs established by overexpression of human telomerase reverse-transcriptase gene. We identified 463 unique proteins with extremely high confidence, including all known markers of hMSCs (e.g., SH3 [CD71], SH2 [CD105], CD166, CD44, Thy1, CD29, and HOP26 [CD63]) among 148 integral membrane...... or membrane-anchored proteins and 159 membrane-associated proteins. Twenty-nine integrins and cell adhesion molecules, 20 receptors, and 18 Ras-related small GTPases were also identified. Upon OB differentiation, the expression levels of 83 proteins increased by at least twofold whereas the levels of another...

  2. Bacterial porin disrupts mitochondrial membrane potential and sensitizes host cells to apoptosis.

    Directory of Open Access Journals (Sweden)

    Vera Kozjak-Pavlovic

    2009-10-01

    Full Text Available The bacterial PorB porin, an ATP-binding beta-barrel protein of pathogenic Neisseria gonorrhoeae, triggers host cell apoptosis by an unknown mechanism. PorB is targeted to and imported by host cell mitochondria, causing the breakdown of the mitochondrial membrane potential (DeltaPsi(m. Here, we show that PorB induces the condensation of the mitochondrial matrix and the loss of cristae structures, sensitizing cells to the induction of apoptosis via signaling pathways activated by BH3-only proteins. PorB is imported into mitochondria through the general translocase TOM but, unexpectedly, is not recognized by the SAM sorting machinery, usually required for the assembly of beta-barrel proteins in the mitochondrial outer membrane. PorB integrates into the mitochondrial inner membrane, leading to the breakdown of DeltaPsi(m. The PorB channel is regulated by nucleotides and an isogenic PorB mutant defective in ATP-binding failed to induce DeltaPsi(m loss and apoptosis, demonstrating that dissipation of DeltaPsi(m is a requirement for cell death caused by neisserial infection.

  3. Membrane-attached Cytokines Expressed by mRNA Electroporation Act as Potent T-Cell Adjuvants.

    Science.gov (United States)

    Weinstein-Marom, Hadas; Pato, Aviad; Levin, Noam; Susid, Keren; Itzhaki, Orit; Besser, Michal J; Peretz, Tamar; Margalit, Alon; Lotem, Michal; Gross, Gideon

    2016-01-01

    Proinflammatory cytokines are widely explored in different adoptive cell therapy protocols for enhancing survival and function of the transferred T cells, but their systemic administration is often associated with severe toxicity which limits their clinical use. To confine cytokine availability to the therapeutic T cells, we expressed 3 key cytokines, IL-2, IL-12, and IL-15, as integral T-cell membrane proteins. To prevent permanent activation of growth signaling pathways, we delivered these genes to T cells through mRNA electroporation. The engineered cytokines could be detected on the surface of mRNA-transfected cells and binding to their cell-surface receptors mainly occurred in cis. The 3 human cytokines supported the ex vivo growth of activated human CD8 and CD4 T cells for at least 6 days posttransfection, comparably to high-dose soluble IL-2. Similarly, membrane IL-2, membrane IL-12, and, to a lesser extent, membrane IL-15, were comparable with their soluble counterparts in supporting proliferation of splenic mouse CD8 T cells. Following electroporation of human CD8 T cells and antimelanoma tumor-infiltrating lymphocytes, membrane cytokines synergized with constitutively active toll-like receptor 4 in inducing interferon-γ secretion. Efficient cooperation with TLR4 was also evident in the upregulation of the activation molecules CD25, CD69, CD137 (4-1BB), and CD134 (OX40). Taken together, membrane cytokines expressed through mRNA transfection emerge as effective tools for enhancing T-cell proliferation and function and may have potential use in adoptive T-cell therapy. PMID:26849075

  4. 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.

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

    Science.gov (United States)

    Wu, Xiaojuan; Zhou, Boyang

    2016-08-01

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

  6. Polymer Materials for Fuel Cell Membranes :Sulfonated Poly(ether sulfone) for Universal Fuel Cell Operations

    Institute of Scientific and Technical Information of China (English)

    Hyoung-Juhn Kim

    2005-01-01

    @@ 1Introduction Polymer electrolyte fuel cells (PEFCs) have been spotlighted because they are clean and highly efficient power generation system. Proton exchange membrane fuel cells (PEMFCs), which use reformate gases or pure H2 for a fuel, have been employed for automotives and residential usages. Also, liquid-feed fuel cells such as direct methanol fuel cell (DMFC) and direct formic acid fuel cell (DFAFC) were studied for portable power generation.

  7. Membrane-integrated oxy-fuel combustion of coal: Process design and simulation

    NARCIS (Netherlands)

    Chen, Wei; Ham, van der A.G.J.; Nijmeijer, A.; Winnubst, A.J.A.

    2015-01-01

    A membrane-integrated oxy-fuel combustion process is designed and simulated in UniSim Design®. The results of the simulation indicate that a net efficiency of 31.8% is obtained for a coal-fired power plant of 182 MWth (assuming only carbon in the coal), including the compression of CO2 to 100 bar. T

  8. INTEGRATION OF FILTRATION AND ADVANCED OXIDATION: DEVELOPMENT OF A MEMBRANE LIQUID-PHASE PLASMA REACTOR

    Science.gov (United States)

    A tiered approach will be undertaken to achieve the overall project goal of demonstrating the integrated membrane/plasma process as an innovative, affordable, sustainable and effective treatment technology for small treatment systems. The team will first use a regimented ap...

  9. 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.

  10. 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.

  11. The synthetic amphipathic peptidomimetic LTX109 is a potent fungicide that disturbs plasma membrane integrity in a sphingolipid dependent manner.

    Science.gov (United States)

    Bojsen, Rasmus; Torbensen, Rasmus; Larsen, Camilla Eggert; Folkesson, Anders; Regenberg, Birgitte

    2013-01-01

    The peptidomimetic LTX109 (arginine-tertbutyl tryptophan-arginine-phenylethan) was previously shown to have antibacterial properties. Here, we investigated the activity of this novel antimicrobial peptidomimetic on the yeast Saccharomyces cerevisiae. We found that LTX109 was an efficient fungicide that killed all viable cells in an exponentially growing population as well as a large proportion of cells in biofilm formed on an abiotic surface. LTX109 had similar killing kinetics to the membrane-permeabilizing fungicide amphotericin B, which led us to investigate the ability of LTX109 to disrupt plasma membrane integrity. S. cerevisiae cells exposed to a high concentration of LTX109 showed rapid release of potassium and amino acids, suggesting that LTX109 acted by destabilizing the plasma membrane. This was supported by the finding that cells were permeable to the fluorescent nucleic acid stain SYTOX Green after a few minutes of LTX109 treatment. We screened a haploid S. cerevisiae gene deletion library for mutants resistant to LTX109 to uncover potential molecular targets. Eight genes conferred LTX109 resistance when deleted and six were involved in the sphingolipid biosynthetic pathway (SUR1, SUR2, SKN1, IPT1, FEN1 and ORM2). The involvement of all of these genes in the biosynthetic pathway for the fungal-specific lipids mannosylinositol phosphorylceramide (MIPC) and mannosyl di-(inositol phosphoryl) ceramide (M(IP)2C) suggested that these lipids were essential for LTX109 sensitivity. Our observations are consistent with a model in which LTX109 kills S. cerevisiae by nonspecific destabilization of the plasma membrane through direct or indirect interaction with the sphingolipids.

  12. The synthetic amphipathic peptidomimetic LTX109 is a potent fungicide that disturbs plasma membrane integrity in a sphingolipid dependent manner.

    Directory of Open Access Journals (Sweden)

    Rasmus Bojsen

    Full Text Available The peptidomimetic LTX109 (arginine-tertbutyl tryptophan-arginine-phenylethan was previously shown to have antibacterial properties. Here, we investigated the activity of this novel antimicrobial peptidomimetic on the yeast Saccharomyces cerevisiae. We found that LTX109 was an efficient fungicide that killed all viable cells in an exponentially growing population as well as a large proportion of cells in biofilm formed on an abiotic surface. LTX109 had similar killing kinetics to the membrane-permeabilizing fungicide amphotericin B, which led us to investigate the ability of LTX109 to disrupt plasma membrane integrity. S. cerevisiae cells exposed to a high concentration of LTX109 showed rapid release of potassium and amino acids, suggesting that LTX109 acted by destabilizing the plasma membrane. This was supported by the finding that cells were permeable to the fluorescent nucleic acid stain SYTOX Green after a few minutes of LTX109 treatment. We screened a haploid S. cerevisiae gene deletion library for mutants resistant to LTX109 to uncover potential molecular targets. Eight genes conferred LTX109 resistance when deleted and six were involved in the sphingolipid biosynthetic pathway (SUR1, SUR2, SKN1, IPT1, FEN1 and ORM2. The involvement of all of these genes in the biosynthetic pathway for the fungal-specific lipids mannosylinositol phosphorylceramide (MIPC and mannosyl di-(inositol phosphoryl ceramide (M(IP2C suggested that these lipids were essential for LTX109 sensitivity. Our observations are consistent with a model in which LTX109 kills S. cerevisiae by nonspecific destabilization of the plasma membrane through direct or indirect interaction with the sphingolipids.

  13. 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

  14. Silymarin protects plasma membrane and acrosome integrity in sperm treated with sodium arsenite

    Directory of Open Access Journals (Sweden)

    Farzaneh Eskandari

    2016-01-01

    Full Text Available Background: Exposure to arsenic is associated with impairment of male reproductive function by inducing oxidative stress. Silymarin with an antioxidant property scavenges free radicals. Objective: The aim of this study was to investigate if silymarin can prevent the adverse effects of sodium arsenite on ram sperm plasma membrane and acrosome integrity. Materials and Methods: Ram epidydimal spermatozoa were divided into five groups: spermatozoa at 0 hr, spermatozoa at 180 min (control, spermatozoa treated with silymarin (20 μM + sodium arsenite (10 μM for 180 min, spermatozoa treated with sodium arsenite (10 μM for 180 min and spermatozoa treated with silymarin (20 μM for 180 min. Double staining of Hoechst and propidium iodide was performed to evaluate sperm plasma membrane integrity, whereas comassie brilliant blue staining was used to assess acrosome integrity. Results: Plasma membrane (p< 0.001 and acrosome integrity (p< 0.05 of the spermatozoa were significantly reduced in sodium arsenite group compared to the control. In silymarin + sodium arsenite group, silymarin was able to significantly (p< 0.001 ameliorate the adverse effects of sodium arsenite on these sperm parameters compared to sodium arsenite group. The incubation of sperm for 180 min (control group showed a significant (p< 0.001 decrease in acrosome integrity compared to the spermatozoa at 0 hour. The application of silymarin alone for 180 min could also significantly (p< 0.05 increase sperm acrosome integrity compared to the control. Conclusion: Silymarin as a potent antioxidant could compensate the adverse effects of sodium arsenite on the ram sperm plasma membrane and acrosome integrity.

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

    Energy Technology Data Exchange (ETDEWEB)

    Matsuoka, Koji; Iriyama, Yasutoshi; Abe, Takeshi; Ogumi, Zempachi [Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan); Matsuoka, Masao [Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577 (Japan)

    2005-10-04

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

  16. Porous polybenzimidazole membranes doped with phosphoric acid: Preparation and application in high-temperature proton-exchange-membrane fuel cells

    International Nuclear Information System (INIS)

    Highlights: • Porous polybenzimidazole membrane was prepared with glucose as porogen. • Phosphoric acid content was as high as 15.7 mol H3PO4 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 H3PO4 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

  17. Mechanistic Insight into CM18-Tat11 Peptide Membrane-Perturbing Action by Whole-Cell Patch-Clamp Recording

    Directory of Open Access Journals (Sweden)

    Anna Fasoli

    2014-07-01

    Full Text Available The membrane-destabilization properties of the recently-introduced endosomolytic CM18-Tat11 hybrid peptide (KWKLFKKIGAVLKVLTTG-YGRKKRRQRRR, residues 1–7 of cecropin-A, 2–12 of melittin, and 47–57 of HIV-1 Tat protein are investigated in CHO-K1 cells by using the whole-cell configuration of the patch-clamp technique. CM18-Tat11, CM18, and Tat11 peptides are administered to the cell membrane with a computer-controlled micro-perfusion system. CM18-Tat11 induces irreversible cell-membrane permeabilization at concentrations (≥4 µM at which CM18 triggers transient pore formation, and Tat11 does not affect membrane integrity. We argue that the addition of the Tat11 module to CM18 is able to trigger a shift in the mechanism of membrane destabilization from “toroidal” to “carpet”, promoting a detergent-like membrane disruption. Collectively, these results rationalize previous observations on CM18-Tat11 delivery properties that we believe can guide the engineering of new modular peptides tailored to specific cargo-delivery applications.

  18. Mechanistic insight into CM18-Tat11 peptide membrane-perturbing action by whole-cell patch-clamp recording.

    Science.gov (United States)

    Fasoli, Anna; Salomone, Fabrizio; Benedusi, Mascia; Boccardi, Claudia; Rispoli, Giorgio; Beltram, Fabio; Cardarelli, Francesco

    2014-01-01

    The membrane-destabilization properties of the recently-introduced endosomolytic CM18-Tat11 hybrid peptide (KWKLFKKIGAVLKVLTTG-YGRKKRRQRRR, residues 1-7 of cecropin-A, 2-12 of melittin, and 47-57 of HIV-1 Tat protein) are investigated in CHO-K1 cells by using the whole-cell configuration of the patch-clamp technique. CM18-Tat11, CM18, and Tat11 peptides are administered to the cell membrane with a computer-controlled micro-perfusion system. CM18-Tat11 induces irreversible cell-membrane permeabilization at concentrations (≥4 µM) at which CM18 triggers transient pore formation, and Tat11 does not affect membrane integrity. We argue that the addition of the Tat11 module to CM18 is able to trigger a shift in the mechanism of membrane destabilization from "toroidal" to "carpet", promoting a detergent-like membrane disruption. Collectively, these results rationalize previous observations on CM18-Tat11 delivery properties that we believe can guide the engineering of new modular peptides tailored to specific cargo-delivery applications. PMID:24991756

  19. Investigating the role of viral integral membrane proteins in promoting the assembly of nepovirus and comovirus replication factories

    Directory of Open Access Journals (Sweden)

    Helene eSanfacon

    2013-01-01

    Full Text Available Formation of plant virus membrane-associated replication factories requires the association of viral replication proteins and viral RNA with intracellular membranes, the recruitment of host factors and the modification of membranes to form novel structures that house the replication complex. Many viruses encode integral membrane proteins that act as anchors for the replication complex. These hydrophobic proteins contain trans-membrane domains and/or amphipathic helices that associate with the membrane and modify its structure. The comovirus Co-Pro and NTP-binding (NTB, putative helicase proteins and the cognate nepovirus X2 and NTB proteins are among the best characterized plant virus integral membrane replication proteins and are functionally related to the picornavirus 2B, 2C and 3A membrane proteins. The identification of membrane-association domains and analysis of the membrane topology of these proteins is discussed. The evidence suggesting that these proteins have the ability to induce membrane proliferation, alter the structure and integrity of intracellular membranes and modulate the induction of symptoms in infected plants is also reviewed. Finally, areas of research that need further investigation are highlighted.

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

    Science.gov (United States)

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

    2015-04-24

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

  1. 160 C PROTON EXCHANGE MEMBRANE (PEM) FUEL CELL SYSTEM DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    L.G. Marianowski

    2001-12-21

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

  2. ACME: automated cell morphology extractor for comprehensive reconstruction of cell membranes.

    Directory of Open Access Journals (Sweden)

    Kishore R Mosaliganti

    Full Text Available The quantification of cell shape, cell migration, and cell rearrangements is important for addressing classical questions in developmental biology such as patterning and tissue morphogenesis. Time-lapse microscopic imaging of transgenic embryos expressing fluorescent reporters is the method of choice for tracking morphogenetic changes and establishing cell lineages and fate maps in vivo. However, the manual steps involved in curating thousands of putative cell segmentations have been a major bottleneck in the application of these technologies especially for cell membranes. Segmentation of cell membranes while more difficult than nuclear segmentation is necessary for quantifying the relations between changes in cell morphology and morphogenesis. We present a novel and fully automated method to first reconstruct membrane signals and then segment out cells from 3D membrane images even in dense tissues. The approach has three stages: 1 detection of local membrane planes, 2 voting to fill structural gaps, and 3 region segmentation. We demonstrate the superior performance of the algorithms quantitatively on time-lapse confocal and two-photon images of zebrafish neuroectoderm and paraxial mesoderm by comparing its results with those derived from human inspection. We also compared with synthetic microscopic images generated by simulating the process of imaging with fluorescent reporters under varying conditions of noise. Both the over-segmentation and under-segmentation percentages of our method are around 5%. The volume overlap of individual cells, compared to expert manual segmentation, is consistently over 84%. By using our software (ACME to study somite formation, we were able to segment touching cells with high accuracy and reliably quantify changes in morphogenetic parameters such as cell shape and size, and the arrangement of epithelial and mesenchymal cells. Our software has been developed and tested on Windows, Mac, and Linux platforms and is

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

    Science.gov (United States)

    Sens, Pierre; Gov, Nir

    2007-01-01

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

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

    Science.gov (United States)

    Shore, Lawrence

    2012-02-28

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

  5. Recovery of Flavonoids from Orange Press Liquor by an Integrated Membrane Process

    Directory of Open Access Journals (Sweden)

    Alfredo Cassano

    2014-08-01

    Full Text Available Orange press liquor is a by-product generated by the citrus processing industry containing huge amounts of natural phenolic compounds with recognized antioxidant activity. In this work, an integrated membrane process for the recovery of flavonoids from orange press liquors was investigated on a laboratory scale. The liquor was previously clarified by ultrafiltration (UF in selected operating conditions by using hollow fiber polysulfone membranes. Then, the clarified liquor with a total soluble solids (TSS content of 10 g·100 g−1 was pre-concentrated by nanofiltration (NF up to 32 g TSS 100 g−1 by using a polyethersulfone spiral-wound membrane. A final concentration step, up to 47 g TSS 100 g−1, was performed by using an osmotic distillation (OD apparatus equipped with polypropylene hollow fiber membranes. Suspended solids were completely removed in the UF step producing a clarified liquor containing most part of the flavonoids of the original press liquor due to the low rejection of the UF membrane towards these compounds. Flavanones and anthocyanins were highly rejected by the NF membrane, producing a permeate stream with a TSS content of 4.5 g·100 g−1. An increasing of both the flavanones and anthocyanins concentration was observed in the NF retentate by increasing the volume reduction factor (VRF. The final concentration of flavonoids by OD produced a concentrated solution of interest for nutraceutical and pharmaceutical applications.

  6. Investigation of interaction between the drug and cell membrane by capillary electrophoresis

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    By introducing cell membrane into electrophoretic buffer as pseudo-stationary phase,a novel capillary electrophoresis method was established to explore the interaction between drugs and cell membrane,where the interaction between citalopram and rabbit red blood cell membrane was used as an example. A series of concentrations of cell membrane were suspended into the running buffer by peak-shift method. The binding constant of citalopram to rabbit red blood cell membrane of 0.977 g-1·L was obtained after treatment of Scatchard plot. This method could provide not only a new way for the investigation on the interactions between drugs and cell membrane,but also a new approach for high throughput screening of the drug membrane permeability,biological activity,and evaluating drugs in vivo.

  7. Nanowire-integrated microporous silicon membrane for continuous fluid transport in micro cooling device

    International Nuclear Information System (INIS)

    We report an efficient passive micro pump system combining the physical properties of nanowires and micropores. This nanowire-integrated microporous silicon membrane was created to feed coolant continuously onto the surface of the wick in a micro cooling device to ensure it remains hydrated and in case of dryout, allow for regeneration of the system. The membrane was fabricated by photoelectrochemical etching to form micropores followed by hydrothermal growth of nanowires. This study shows a promising approach to address thermal management challenges for next generation electronic devices with absence of external power

  8. A theory for the membrane potential of cells

    CERN Document Server

    Endresen, L P; Endresen, Lars Petter; Hall, Kevin

    1997-01-01

    We give an explicit formula for the membrane potential of cells in terms of the intracellular and extracellular ionic concentrations, and derive equations for the ionic currents that flow through channels, exchangers and electrogenic pumps based on simple energy considerations and conservation laws. We demonstrate that the work done by the pump is equal to the potential energy of the cell plus the energy loss due to the downhill ionic fluxes through the channels and the exchanger. Our equations predict osmotic pressure variations. The theory is illustrated in a simple model of spontaneously active cells in the cardiac pacemaker. The simulated action potential and the five currents in the model are in excellent agreement with experiments. The model predicts the experimental observed intracellular ionic concentration of potassium, calcium and sodium. We do not see any drift of the values for the concentrations in a long time simulation, instead we can obtain the same asymptotic values starting with equal intrac...

  9. Cryptosporidia: epicellular parasites embraced by the host cell membrane.

    Science.gov (United States)

    Valigurová, Andrea; Jirků, Miloslav; Koudela, Bretislav; Gelnar, Milan; Modrý, David; Slapeta, Jan

    2008-07-01

    The ultrastructure of two gastric cryptosporidia, Cryptosporidium muris from experimentally infected rodents (Mastomys natalensis) and Cryptosporidium sp. 'toad' from naturally infected toads (Duttaphrynus melanostictus), was studied using electron microscopy. Observations presented herein allowed us to map ultrastructural aspects of the cryptosporidian invasion process and the origin of a parasitophorous sac. Invading parasites attach to the host cell, followed by gradual envelopment, with the host's cell membrane folds, eventually forming the parasitophorous sac. Cryptosporidian developmental stages remain epicellular during the entire life cycle. The parasite development is illustrated in detail using high resolution field emission scanning electron microscopy. This provides a new insight into the ultrastructural detail of host-parasite interactions and species-specific differences manifested in frequency of detachment of the parasitophorous sac, radial folds of the parasitophorous sac and stem-formation of the parasitised host cell. PMID:18158154

  10. Alterations of red cell membrane properties in neuroacanthocytosis.

    Directory of Open Access Journals (Sweden)

    Claudia Siegl

    Full Text Available Neuroacanthocytosis (NA refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc, McLeod syndrome (MLS, Huntington's disease-like 2 (HDL2 and pantothenate kinase associated neurodegeneration (PKAN, that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation, associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10% and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN red cells but not in patient cells without shape abnormalities. These data suggest an "acanthocytic state" of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration.

  11. Nafion and modified-Nafion membranes for polymer electrolyte fuel cells: An overview

    Indian Academy of Sciences (India)

    A K Sahu; S Pitchumani; P Sridhar; A K Shukla

    2009-06-01

    Polymer electrolyte fuel cells (PEFCs) employ membrane electrolytes for proton transport during the cell reaction. The membrane forms a key component of the PEFC and its performance is controlled by several physical parameters, viz. water up-take, ion-exchange capacity, proton conductivity and humidity. The article presents an overview on Nafion membranes highlighting their merits and demerits with efforts on modified-Nafion membranes.

  12. Geometry of the Contact Zone between Fused Membrane-Coated Beads Mimicking Cell-Cell Fusion.

    Science.gov (United States)

    Savić, Filip; Kliesch, Torben-Tobias; Verbeek, Sarah; Bao, Chunxiao; Thiart, Jan; Kros, Alexander; Geil, Burkhard; Janshoff, Andreas

    2016-05-24

    The fusion of lipid membranes is a key process in biology. It enables cells and organelles to exchange molecules with their surroundings, which otherwise could not cross the membrane barrier. To study such complex processes we use simplified artificial model systems, i.e., an optical fusion assay based on membrane-coated glass spheres. We present a technique to analyze membrane-membrane interactions in a large ensemble of particles. Detailed information on the geometry of the fusion stalk of fully fused membranes is obtained by studying the diffusional lipid dynamics with fluorescence recovery after photobleaching experiments. A small contact zone is a strong obstruction for the particle exchange across the fusion spot. With the aid of computer simulations, fluorescence-recovery-after-photobleaching recovery times of both fused and single-membrane-coated beads allow us to estimate the size of the contact zones between two membrane-coated beads. Minimizing delamination and bending energy leads to minimal angles close to those geometrically allowed. PMID:27224487

  13. Analysis of plasma membrane phosphoinositides from fusogenic carrot cells

    International Nuclear Information System (INIS)

    Phosphatidylinositol monophosphate (PIP) and phosphatidylinositol bisphosphate (PIP2) were found to be associated with the plasma membrane-rich fractions isolated by aqueous polymer two-phase partitioning from fusogenic cells. They represented at least 5% and 0.7% of the total inositol-labeled lipids in the plasma membrane-rich fractions, respectively, and were present in a ratio of about 7:1 (PIP:PIP2). In addition, two unidentified inositol-labeled compounds, which together were approximately 3% of the inositol-labeled lipids, were found predominantly in the plasma membrane-rich fractions and migrated between PIP2 and PIP. The R/sub f/s of these compounds were approximately 0.31 and 0.34 in the solvent system CHCl3:MeOH:15N NH4OH:H2O (90:90:7:22) using LK5 plates presoaked in 1% potassium oxalate. These compounds incorporated 32P/sub i/, (3H)inositol and were hydrolyzed in mild base. These data suggested that they were glycero-phospholipids. Although the compounds did not comigrate with lysoPIP obtained from bovine brain (R/sub f/ ∼ 0.35), when endogenous PIP was hydrolyzed to lysoPIP, the breakdown product migrated in the region of the unidentified inositol lipids

  14. Study of the effect of membrane thickness on microcapsule strength, permeability, and cell proliferation

    DEFF Research Database (Denmark)

    Ma, Ying; Zhang, Ying; Wang, Yu;

    2013-01-01

    Cell microencapsulation is one of the promising strategies for in vitro production of proteins or in vivo delivery of therapeutic products. Membrane thickness controls microcapsule strength and permeability, which may in return affect cell growth and metabolism. In this study, the strength......, permeability, and encapsulated Chinese hamster ovary cell proliferation and metabolism of four groups of microcapsules with different membrane thicknesses were investigated. It was found that increasing membrane thickness increases microcapsule strength, whereas decreases membrane permeability. During...... the first 6 days, cells within microcapsules with 10 μm thickness membrane proliferated fast and could reach a cell density of 1.9 × 10(7) cells/mL microcapsule with 92% cell density. A cell density of 5.5 × 10(7) cells/mL microcapsule with >85% cell density was achieved within microcapsules with 15 μm...

  15. Membrane Nanotubes between peritoneal mesothelial cells: functional connectivity and crucial participation during inflammatory reactions

    Directory of Open Access Journals (Sweden)

    Julia eRanzinger

    2014-10-01

    Full Text Available Peritoneal dialysis (PD has attained increased relevance as continuous renal replacement therapy over the past years. During this treatment, the peritoneum functions as dialysis membrane to eliminate diffusible waste products from the blood-stream. Success and efficacy of this treatment is dependent on the integrity of the peritoneal membrane. Chronic inflammatory conditions within the peritoneal cavity coincide with elevated levels of proinflammatory cytokines leading to the impairment of tissue integrity. High glucose concentrations and glucose metabolites in PD solutions contribute to structural and functional reorganization processes of the peritoneal membrane during long-term PD. The subsequent loss of ultrafiltration is causal for the treatment failure over time. It was shown that peritoneal mesothelial cells are functionally connected via Nanotubes (NTs and that a correlation of NT-occurrence and defined pathophysiological conditions exists. Additionally, an important participation of NTs during inflammatory reactions was shown. Here, we will summarize recent developments of NT-related research and provide new insights into NT-mediated cellular interactions under physiological as well as pathophysiological conditions.

  16. 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......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...... to the corrosion of carbon support in the catalyst layer and degradation of the PBI membrane. During the continuous test with methanol containing H2 as the fuel the reaction kinetic resistance and mass transfer resistance of both single cells increased, which may be caused by the adsorption of methanol...

  17. Grafting of Vinyl Pyrrolidone/Styrene onto Ethylene/Chlorotrifluoroethylene Membrane for Proton ExchangeMembrane Fuel Cell

    International Nuclear Information System (INIS)

    Highlights: • Gamma irradiation was used as a tool for membranes grafting. • Sty and VP were grafted ECTFE. • The membranes were characterized using; FT-IR, TGA and SEM. • The membranes were investigated for their ability into the PEMFCusing different techniques. • The highest fuel cell performance was at 75 °C and more durableup to 450 hours. - Abstract: Simultaneous gamma irradiation was proved to be an effective tool for ethylene/ chlorotrifluoroethylene grafting by styrene and vinyl pyrrolidone with different ratios. It was found that; the optimum grafting yield was 81% by using 40 kGy gamma irradiation dose when the binary monomers ratio was 1:1 (styrene: vinyl pyrrolidone). The grafted membranes were investigated for chemical structure by FT-IR and thermal properties by thermal gravimetric analysis. The mechanical properties were studied by measuring tensile strength while morphological structure was characterized by scanning electron microscope. The membranes’ free volume sizes were determined using positron annihilation lifetime spectroscopy (PALS). Ion exchange capacity, water uptake and membranes thickness were investigated and proton conductivity was evaluated. The optimum temperature for attaining the maximum fuel cell performance was at 75 °C while it reduced by decreasing the temperature to 50 °C or increasing it to 85 °C. The fuel cell performance based highest yield of the grafted membrane was more durable than compressed Nr.118 (commercial membranes) up to 450 hours

  18. Steam reforming of methane in equilibrium membrane reactors for integration in power cycles

    Energy Technology Data Exchange (ETDEWEB)

    Bottino, A.; Comite, A.; Capannelli, G. [Department of Chemistry and Industrial Chemistry, Via Dodecaneso 31, 16146 Genoa (Italy); Di Felice, R. [Department of Process and Chemical Engineering ' G. Bonino, Via Opera Pia 15, Genoa (Italy); Pinacci, P. [CESI, Via Rubattino 54, 20134 Milano (Italy)

    2006-10-30

    Methane steam reforming is the most important industrial route to produce H{sub 2}. The process is governed by equilibrium reactions, the overall process is endothermic and high temperatures are required to reach satisfactory methane conversions. The possibility of using a membrane reactor, which separates H{sub 2} from the reaction zone with a subsequent improvement of the conversions, is a challenge of many academic and industrial researchers. A great effort of membrane reactor analysis applied to steam reforming is necessary in the light of the novel and potential process applications (fuel cells, CO{sub 2} capture). This paper presents the model of a non-adiabatic methane steam reformer membrane reactor (MSRMR) working in equilibrium conditions. The model was used to investigate the effects of some variables (e.g. temperature profile, separation efficiency, plant size) on the membrane area and the energy required by the process, which in turn affect fixed and operating costs. The simulations showed that the membrane area required sharp increases in the reactor size and that for large plants the development of thin and permeable membranes is a key issue. (author)

  19. Technology advancement for integrative stem cell analyses.

    Science.gov (United States)

    Jeong, Yoon; Choi, Jonghoon; Lee, Kwan Hyi

    2014-12-01

    Scientists have endeavored to use stem cells for a variety of applications ranging from basic science research to translational medicine. Population-based characterization of such stem cells, while providing an important foundation to further development, often disregard the heterogeneity inherent among individual constituents within a given population. The population-based analysis and characterization of stem cells and the problems associated with such a blanket approach only underscore the need for the development of new analytical technology. In this article, we review current stem cell analytical technologies, along with the advantages and disadvantages of each, followed by applications of these technologies in the field of stem cells. Furthermore, while recent advances in micro/nano technology have led to a growth in the stem cell analytical field, underlying architectural concepts allow only for a vertical analytical approach, in which different desirable parameters are obtained from multiple individual experiments and there are many technical challenges that limit vertically integrated analytical tools. Therefore, we propose--by introducing a concept of vertical and horizontal approach--that there is the need of adequate methods to the integration of information, such that multiple descriptive parameters from a stem cell can be obtained from a single experiment.

  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. Stability of transmembrane amyloid β-peptide and membrane integrity tested by molecular modeling of site-specific Aβ42 mutations.

    Directory of Open Access Journals (Sweden)

    Chetan Poojari

    Full Text Available Interactions of the amyloid β-protein (Aβ with neuronal cell membranes, leading to the disruption of membrane integrity, are considered to play a key role in the development of Alzheimer's disease. Natural mutations in Aβ42, such as the Arctic mutation (E22G have been shown to increase Aβ42 aggregation and neurotoxicity, leading to the early-onset of Alzheimer's disease. A correlation between the propensity of Aβ42 to form protofibrils and its effect on neuronal dysfunction and degeneration has been established. Using rational mutagenesis of the Aβ42 peptide it was further revealed that the aggregation of different Aβ42 mutants in lipid membranes results in a variety of polymorphic aggregates in a mutation dependent manner. The mutant peptides also have a variable ability to disrupt bilayer integrity. To further test the connection between Aβ42 mutation and peptide-membrane interactions, we perform molecular dynamics simulations of membrane-inserted Aβ42 variants (wild-type and E22G, D23G, E22G/D23G, K16M/K28M and K16M/E22G/D23G/K28M mutants as β-sheet monomers and tetramers. The effects of charged residues on transmembrane Aβ42 stability and membrane integrity are analyzed at atomistic level. We observe an increased stability for the E22G Aβ42 peptide and a decreased stability for D23G compared to wild-type Aβ42, while D23G has the largest membrane-disruptive effect. These results support the experimental observation that the altered toxicity arising from mutations in Aβ is not only a result of the altered aggregation propensity, but also originates from modified Aβ interactions with neuronal membranes.

  2. Preservation of Supported Lipid Membrane Integrity from Thermal Disruption: Osmotic Effect.

    Science.gov (United States)

    Zhu, Tao; Jiang, Zhongying; Ma, Yuqiang; Hu, Yong

    2016-03-01

    Preservation of structural integrity under various environmental conditions is one major concern in the development of the supported lipid membrane (SLM)-based devices. It is common for SLMs to experience temperature shifts from manufacture, processing, storage, and transport to operation. In this work, we studied the thermal adaption of the supported membranes on silica substrates. Homogenous SLMs with little defects were formed through the vesicle fusion method. The mass and fluidity of the bilayers were found to deteriorate from a heating process but not a cooling process. Fluorescence characterizations showed that the membranes initially budded as a result of heating-induced lipid lateral area expansion, followed by the possible fates including maintenance, retraction, and fission, among which the last contributes to the irreversible compromise of the SLM integrity and spontaneous release of the interlipid stress accumulated. Based on the mechanism, we developed a strategy to protect SLMs from thermal disruption by increasing the solute concentration in medium. An improved preservation of the membrane mass and fluidity against the heating process was observed, accompanied by a decrease in the retraction and fission of the buds. Theoretical analysis revealed a high osmotic energy penalty for the fission, which accounts for the depressed disruption. This osmotic-based protection strategy is facile, solute nonspecific, and long-term efficient and has little impact on the original SLM properties. The results may help broaden SLM applications and sustain the robustness of SLM-based devices under multiple thermal conditions. PMID:26886864

  3. On the Efficiency of NHS Ester Cross-Linkers for Stabilizing Integral Membrane Protein Complexes

    Science.gov (United States)

    Chen, Fan; Gerber, Sabina; Korkhov, Volodymyr M.; Mireku, Samantha; Bucher, Monika; Locher, Kaspar P.; Zenobi, Renato

    2015-03-01

    We have previously presented a straightforward approach based on high-mass matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) to study membrane proteins. In addition, the stoichiometry of integral membrane protein complexes could be determined by MALDI-MS, following chemical cross-linking via glutaraldehyde. However, glutaraldehyde polymerizes in solution and reacts nonspecifically with various functional groups of proteins, limiting its usefulness for structural studies of protein complexes. Here, we investigated the capability of N-hydroxysuccinimide (NHS) esters, which react much more specifically, to cross-link membrane protein complexes such as PglK and BtuC2D2. We present clear evidence that NHS esters are capable of stabilizing membrane protein complexes in situ, in the presence of detergents such as DDM, C12E8, and LDAO. The stabilization efficiency strongly depends on the membrane protein structure (i.e, the number of primary amine groups and the distances between primary amines). A minimum number of primary amine groups is required, and the distances between primary amines govern whether a cross-linker with a specific spacer arm length is able to bridge two amine groups.

  4. Integration of micro-filtration into osmotic membrane bioreactors to prevent salinity build-up.

    Science.gov (United States)

    Wang, Xinhua; Yuan, Bo; Chen, Yao; Li, Xiufen; Ren, Yueping

    2014-09-01

    The high salinity remains as one of major obstacles of the osmotic membrane bioreactor (OMBR). In this study, a new pathway was explored to prevent the salinity build-up by integrating the micro-filtration (MF) membrane to the OMBR (MF-OMBR). The results indicated that the salinity characterized by conductivity in the MF-OMBR was effectively alleviated and controlled at a lower value of about 5 mS/cm, and the stable flux of forward osmosis (FO) membrane correspondingly increased to approximately 5.5L/(m(2)h). Besides, the addition of MF membrane in the OMBR could increase the total organic carbon (TOC) and ammonium nitrogen (NH3-N) removals due to the activated sludge by improving the microbial activity. The membrane fouling especially the reversible fouling in the MF-OMBR was severer compared to that in the conventional OMBR, which resulted in a lower water flux than the expectation due to the increase of filtration resistance and external concentration polarization.

  5. Optimal microporous layer for proton exchange membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wei-Mon; Wu, Dong-Kai [Department of Greenergy, National University of Tainan, Tainan 700 (China); Wang, Xiao-Dong [Department of Thermal Engineering, School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Ong, Ai-Lien [Department of Chemistry and Industrial Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genoa (Italy); Lee, Duu-Jong [Department of Chemical Engineering, National Taiwan University, Taipei 106 (China); Su, Ay [Department of Mechanical Engineering, Fuel Cell Center, Yuan Ze University, Taoyuan 300 (China)

    2010-09-01

    This study elucidates how fabrication processes (screen-printing and spraying) and constituent materials (carbon paper as backing, Acetylene Black (AB) carbon (42 nm), XC-72R carbon (30 nm) or BP2000 (15 nm) as carbon powders, and 10-50% fluorinated ethylene propylene (FEP) as hydrophobic substances) for microporous layers (MPLs) affect the performance of proton exchange membrane fuel cells. The screen-printing process produces MPLs with smaller surface fractures than does the spraying process. The effect of optimal FEP content on cell performance is noted. The presence of an optimal FEP content is due to the counterbalance between enhanced performance produced with increased gas permeability and decreased performance yielded with small contact area and electrical conductivity with excess FEP. The MPL with large carbon powders is preferred when oxygen supply is limited; otherwise, small carbon powders should be utilized. Optimal MPL design should address negative effects possibly associated with contact resistance, gas permeation resistance, and excess water resistance. (author)

  6. New hybrid model of proton exchange membrane fuel cell

    Institute of Scientific and Technical Information of China (English)

    WANG Rui-min; CAO Guang-yi; ZHU Xin-jian

    2007-01-01

    Model and simulation are good tools for design optimization of fuel cell systems. This paper proposes a new hybrid model of proton exchange membrane fuel cell (PEMFC). The hybrid model includes physical component and black-box component. The physical component represents the well-known part of PEMFC, while artificial neural network (ANN) component estimates the poorly known part of PEMFC. The ANN model can compensate the performance of the physical model. This hybrid model is implemented on Matlab/Simulink software. The hybrid model shows better accuracy than that of the physical model and ANN model. Simulation results suggest that the hybrid model can be used as a suitable and accurate model for PEMFC.

  7. 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.

  8. Pyro-electrification of polymer membranes for cell patterning

    Science.gov (United States)

    Rega, R.; Gennari, O.; Mecozzia, L.; Grilli, S.; Pagliarulo, V.; Ferraro, P.

    2016-05-01

    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].

  9. Immunoprecipitation of membrane proteins of cultured human sarcoma cells.

    Science.gov (United States)

    Grófová, M; Forchhammer, J; Lizonová, A; Popovic, M

    1981-01-01

    Human sarcoma associated antigens (HSAA) have previously been identified by indirect immune fluorescence in human sarcoma cells in culture using sera from patients bearing different types of sarcoma. To further characterize these HSAA, surface proteins of cultured cells were labeled with 125Iodine, [3H]-glucosamine and [35S]-methionine and solubilized. After immunoprecipitation labeled proteins were detected in immune complexes by SDS polyacrylamide gel electrophoresis and autoradiography, which allowed comparison with antigens described by other groups. A surface protein (Mr 96 000) was precipitated with sera from sarcoma bearing patients, and two glycoproteins (Mr 115 000 and 85 000) were preferentially precipitated with antisera from rabbits immunized with membranes from two human sarcoma cell lines. At least two of these proteins were found in each of five human sarcoma cell lines studied (U-4SS, U-3930S, U-20S, B-5GT and B-6FS). None of the proteins were precipitated with three human control sera, and only occasionally a faint band was observed in immunoprecipitates from control cells (B-25F, B-41B, B-42FC, U-2S, and U-393S with the immune sera. These proteins are probably some of the antigens responsible for the immune fluorescence observed in determination of HSAA. However, purification of the proteins and competition experiments are needed before this can be finally established.

  10. DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Shamsuddin Ilias

    2002-06-11

    The Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for stand-alone utility and electric vehicle applications. Platinum (Pt) Catalyst is used for both fuel and air electrodes in PEMFCs. However, carbon monoxide (CO) contamination of H{sub 2} greatly affects electro catalysts used at the anode of PEMFCs and decreases cell performance. The irreversible poisoning of the anode can occur even in CO concentrations as low as few parts per million (ppm). In this work, we have synthesized several novel elctrocatalysts (Pt/C, Pt/Ru/C, Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell, using CO concentrations in the H{sub 2} fuel that varies from 10 to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effects of catalyst composition and electrode film preparation method on the performance of PEM fuel cell were also studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalyst (10 wt% Pt/Ru/C, 20 wt% Pt/Mo/C) were more CO tolerant than the 20 wt% Pt/C catalyst alone. It was also observed that spraying method was better than the brushing technique for the preparation of electrode film.

  11. Effect of powdered activated carbon on integrated submerged membrane bioreactor-nanofiltration process for wastewater reclamation.

    Science.gov (United States)

    Woo, Yun Chul; Lee, Jeong Jun; Shim, Wang-Geun; Shon, Ho Kyong; Tijing, Leonard D; Yao, Minwei; Kim, Han-Seung

    2016-06-01

    The aim of this study was to determine the effect of powdered activated carbon (PAC) on the overall performance of a submerged membrane bioreactor (SMBR) system integrated with nanofiltration (NF) for wastewater reclamation. It was found that the trans-membrane pressure of SMBR increased continuously while that of the SMBR with PAC was more stable, mainly because water could still pass through the PACs and membrane even though foulants adhered on the PAC surface. The presence of PAC was able to mitigate fouling in SMBR as well as in NF. SMBR-NF with PAC obtained a higher flux of 8.1 LMH compared to that without PAC (6.6 LMH). In addition, better permeate quality was obtained with SMBR-NF integrated process added with PAC. The present results suggest that the addition of PAC in integrated SMBR-NF process could possibly lead to satisfying water quality and can be operated for a long-term duration. PMID:26879205

  12. Development of a living membrane comprising a functional human renal proximal tubule cell monolayer on polyethersulfone polymeric membrane

    NARCIS (Netherlands)

    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, R.; Stamatialis, Dimitrios

    2015-01-01

    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

  13. Peripheral Blood Mononuclear Cell Membrane Fluidity and Disease Outcome in Patients with Multiple Sclerosis

    OpenAIRE

    Gloudina M Hon; Hassan, Mogamat S.; van Rensburg, Susan J.; Abel, Stefan; Erasmus, Rajiv T; Matsha, Tandi

    2011-01-01

    Immune cell membrane lipids are important determinants of membrane fluidity, eicosanoid production and phagocytosis and fatty acid metabolic abnormalities have been reported in immune cells from patients with multiple sclerosis. The aim of this study was to investigate the relationship between peripheral blood mononuclear cell membrane fluidity, permeability status, and disease outcome as measured by the Kurtzke expanded disability status scale. Phospholipids, fatty acids and cholesterol comp...

  14. Cell membrane stability in two barley genotypes under water stress conditions

    OpenAIRE

    Hanna Bandurska; Halina Gniazdowska-Skoczek

    2014-01-01

    The effect of water stress induced in vitro by polyethylene glycol 6000 (PEG) and under drought stress on cell membrane stability was examined in two barley genotypes, the cultivar Aramir and line R567. The injury of cell membranes was markely influenced by leaf age, leaf position on the stem, and the degree of drought stress. The differences in percentage of injury to cell membrane between these genotypes were also found. The cv. Aramir exhibited a lower percentage injury value as compared t...

  15. 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 ℃.

  16. Single cell membrane poration by bubble-induced microjets in a microfluidic chip.

    Science.gov (United States)

    Li, Z G; Liu, A Q; Klaseboer, E; Zhang, J B; Ohl, C D

    2013-03-21

    This paper demonstrates membrane poration of a single suspension cell due to a fast liquid microjet. The jet is formed during the collapse of a laser induced bubble created at a variable stand-off distance from the target cell. The cell is trapped by a converging structure within a microfluidic chip. The asymmetrical growth and collapse of the cavitation bubble next to the cell lead to the microjetting, which deforms and porates the cell membrane. In the experiments, the membrane porations of myeloma cells are probed with the uptake of trypan blue. Time-resolved studies of the diffusion of trypan blue show a marked dependency on the bubble dynamics, i.e. the stand-off distance. The penetration length of the dye increases with shorter distances. Numerical simulations of the diffusion process agree with larger pores formed on the cell membrane. This method allows for a fast, repeatable, and localized rupture of membranes of individual cells in suspension. PMID:23364762

  17. 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].

  18. Rapid fabrication of microfluidic polymer electrolyte membrane fuel cell in PDMS by surface patterning of perfluorinated ion-exchange resin

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yong-Ak; Han, Jongyoon [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Batista, Candy [Roxbury Community College, 1234 Columbus Ave., Roxbury Crossing, MA 02120 (United States); Sarpeshkar, Rahul [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States)

    2008-09-01

    In this paper we demonstrate a simple and rapid fabrication method for a microfluidic polymer electrolyte membrane (PEM) fuel cell using polydimethylsiloxane (PDMS), which has become the de facto standard material in BioMEMS. Instead of integrating a Nafion sheet film between two layers of a PDMS device in a traditional ''sandwich format,'' we pattern a perfluorinated ion-exchange resin such as a Nafion resin on a glass substrate using a reversibly bonded PDMS microchannel to generate an ion-selective membrane between the fuel-cell electrodes. After this patterning step, the assembly of the microfluidic fuel cell is accomplished by simple oxygen plasma bonding between the PDMS chip and the glass substrate. In an example implementation, the planar PEM microfluidic fuel cell generates an open circuit voltage of 600-800 mV and delivers a maximum current output of nearly 4 {mu}A. To enhance the power output of the fuel cell we utilize self-assembled colloidal arrays as a support matrix for the Nafion resin. Such arrays allow us to increase the thickness of the ion-selective membrane to 20 {mu}m and increase the current output by 166%. Our novel fabrication method enables rapid prototyping of microfluidic fuel cells to study various ion-exchange resins for the polymer electrolyte membrane. Our work will facilitate the development of miniature, implantable, on-chip power sources for biomedical applications. (author)

  19. Development of more efficient and cheaper MEA's for PEM fuel cells; Membrane-electrode-assembly

    Energy Technology Data Exchange (ETDEWEB)

    Yde Andersen, S. (IRD Fuel Cell A/S, Svendborg (Denmark)); Nilsson, M.S. (Danish Power System Aps, Charlottenlund (Denmark)); Siu, A.; Plackett, D. (Technical Univ. of Denmark. Risoe National Lab. for Sustainable Energy, Dansk Polymer Center, Roskilde (Denmark)); Li, Q. (Technical Univ. of Denmark, Dept. of Chemistry, Kgs. Lyngby (Denmark))

    2008-06-15

    The project covered 5 main areas: 1) polymer and membranes; 2) electrocatalysts; 3) gas diffusion electrodes; 4) MEAs; and 5) evaluation techniques. For the polymers, by purification of monomers and optimizing parameters, high molecular weight polybenzimidazoles have been synthesized in batches of 50 g with good reproducibility. Based on the polymer, two types of new membranes have been prepared. One is the cross-linked (covalently and acid-base) PBI blend membranes. The blend membranes were systematically characterized and show excellent properties such as very high acid doping levels, conductivity, mechanical strength and durability. The other type is composite membranes based on PBI and nanoclay. Using the modified nanoclay, good dispersion and transparent composite membranes have been achieved. For catalyst preparation, the carbon supports have been modified with thermal treatment. Improved corrosion resistance was achieved with little sacrificing of the catalytic activity. High Pt loading catalysts were prepared, based on which high performance gas diffusion electrodes were fabricated. The performance target of both cathode and anode was achieved, as evaluated by the PTFE half cell tests. New gas diffusion layer (GDL) materials have been developed and tested in different MEA configurations. Significant performance improvement has been achieved with also potential to reduce the cost. Techniques for applying micro porous layers and catalyst layers have been optimized, including tape casting, spraying, and catalyst-coated membrane (CCM). Using the developed membranes and gas diffusion electrodes, membrane-electrode assemblies (MEAs) were fabricated for both single cell and stack tests. Selection of sealing materials and design of integrated gaskets have been made for both low and high temperature MEAs. Parameters for hot-pressing such as temperature, pressure and duration were systematically studied. 44 MEAs with an active area of 256 cm{sup 2} have been prepared

  20. 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.

  1. 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...

  2. Effects of Natural Flavonoids on Photosynthetic Activity and Cell Integrity in Microcystis aeruginosa

    Directory of Open Access Journals (Sweden)

    Haomin Huang

    2015-01-01

    Full Text Available Flavonoids are natural polyphenolic compounds produced by many aquatic plants and released in their environments. In this study, the effects of several aquatic flavonoids on cyanobacterial Microcystis aeruginosa, especially in relation to the cell growth, photosynthetic activity, cell morphology, and cell membrane integrity, were investigated. Significant growth inhibition was observed when the cyanobacteria were exposed to three flavonoids, namely, 5,4'-dihydroxyflavone (DHF, apigenin, and luteolin. Luteolin reduced the effective quantum yield, photosynthetic efficiency, and maximal electron transport rate by 70%, 59% and 44%, respectively, whereas 5,4'-DHF and apigenin slightly affected these parameters, which implies that luteolin disrupts the photosynthetic system. Moreover, 5,4'-DHF and apigenin compromised the membrane integrity, and induced membrane depolarization in 52% and 38%, and permeabilization in 30% and 44% of the cells, respectively. The 5,4'-DHF and apigenin showed more pronounced effects on M. aeruginosa morphology and membrane integrity, compared to the luteolin. These results suggest that flavonoids could have significant effects on growth and physiological functions in cyanobacterial species.

  3. Binding and Fusion of Extracellular Vesicles to the Plasma Membrane of Their Cell Targets.

    Science.gov (United States)

    Prada, Ilaria; Meldolesi, Jacopo

    2016-01-01

    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. PMID:27517914

  4. A rapid method for the evaluation of the ionic permeabilities across epithelial cell membranes.

    Science.gov (United States)

    Movileanu, L

    1999-02-01

    This short note presents a recipe for the calculation of the ionic permeabilities across epithelial cell membranes. The method requires the Goldman-Hodgkin-Katz formalism as well as the consideration of the equivalent electrical circuit for an epithelial cell. The equivalent electrical circuit is solved in terms of the equivalent electromotive forces coupled in series with the ionic resistances of both cell membranes (apical and basolateral). The present procedure is feasible for any leaky epithelial cell membrane with the condition that this membrane (apical or basolateral) does not contain primary or secondary mechanisms for active transport. PMID:10100952

  5. 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.

  6. Coal Integrated Gasification Fuel Cell System Study

    Energy Technology Data Exchange (ETDEWEB)

    Chellappa Balan; Debashis Dey; Sukru-Alper Eker; Max Peter; Pavel Sokolov; Greg Wotzak

    2004-01-31

    This study analyzes the performance and economics of power generation systems based on Solid Oxide Fuel Cell (SOFC) technology and fueled by gasified coal. System concepts that integrate a coal gasifier with a SOFC, a gas turbine, and a steam turbine were developed and analyzed for plant sizes in excess of 200 MW. Two alternative integration configurations were selected with projected system efficiency of over 53% on a HHV basis, or about 10 percentage points higher than that of the state-of-the-art Integrated Gasification Combined Cycle (IGCC) systems. The initial cost of both selected configurations was found to be comparable with the IGCC system costs at approximately $1700/kW. An absorption-based CO2 isolation scheme was developed, and its penalty on the system performance and cost was estimated to be less approximately 2.7% and $370/kW. Technology gaps and required engineering development efforts were identified and evaluated.

  7. On the integrity of a commercial cassette ultrafiltration membrane:implications for marine colloidal biogeochemistry

    Institute of Scientific and Technical Information of China (English)

    LIN Liangshi; CAI Yihua; SUN Xiuwu; CHEN Min

    2014-01-01

    The performance and integrity of a cassette cross-flow ultrafilter (Pellicon 2, Millipore) are examined with a suite of macromolecules of different molecular masses. The retention coefficient during the cross-flow ultrafiltration experiments increases with increasing molecular mass and reaches 90%with 10 kDa dextran in both milli-Q water and ultrafiltered seawater media. Based on a 90%retention coefficient, the molecular mass cut-off for the ultrafiltration membrane is defined at 10 kDa, which is ten times (1 kDa) that rated by the manufacturer. To further validate the accuracy of the laboratory calibration, the samples from the lower Zhujiang River and the Jiulong River Estuary are ultrafiltered with the cassette ultrafiltration membrane and the colloidal organic carbon abundances in these samples are quantified with the ultrafiltration per-meation model based on time series permeation subsamples. The colloidal organic carbon abundances are 5.8%-21.1%in the Jiulong River Estuary and 5.6%-11.0%in the lower Zhujiang River. These are consistent with the reported values for both estuaries as well as with the colloidal organic carbon abundances in ma-rine environments over the coastal and open oceans with 10 kDa cut-off membranes. Therefore, these field data support the laboratory calibration result and indicate the validity of the experimental and quantifica-tion procedure adopted. The discrepancy between the nominal molecular mass cut-off and the actual pore size of the ultrafiltration membrane should be of great concern for research in colloidal and nanoparticle biogeochemistry. Careful examination of the membrane integrity should be taken during ultrafiltration ex-periments in order to avoid misleading molecular mass cut-off information.

  8. DEVELOPMENT OF NOVEL ELECTROCATALYSTS FOR PROTON EXCHANGE MEMBRANE FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Shamsuddin Ilias

    2003-04-24

    Fuel cells are electrochemical devices that convert the available chemical free energy directly into electrical energy, without going through heat exchange process. Of all different types of fuel cells, the Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising power sources for stand-alone utility and electric vehicle applications. Platinum (Pt) Catalyst is used for both fuel and air electrodes in PEMFCs. However, carbon monoxide (CO) contamination of H{sub 2} greatly affects electro catalysts used at the anode of PEMFCs and decreases cell performance. The irreversible poisoning of the anode can occur even in CO concentrations as low as few parts per million (ppm). In this work, we have synthesized several novel elctrocatalysts (Pt/C, Pt/Ru/C, Pt/Mo/C, Pt/Ir and Pt/Ru/Mo) for PEMFCs. These catalysts have been tested for CO tolerance in the H{sub 2}/air fuel cell, using CO concentrations in the H{sub 2} fuel that varies from 10 to 100 ppm. The performance of the electrodes was evaluated by determining the cell potential against current density. The effects of catalyst composition and electrode film preparation method on the performance of PEM fuel cell were also studied. It was found that at 70 C and 3.5 atm pressure at the cathode, Pt-alloy catalyst (10 wt% Pt/Ru/C, 20 wt% Pt/Mo/C) were more CO tolerant than the 20 wt% Pt/C catalyst alone. It was also observed that spraying method was better than the brushing technique for the preparation of electrode film.

  9. 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

  10. Label-free measuring and mapping of binding kinetics of membrane proteins in single living cells

    Science.gov (United States)

    Wang, Wei; Yang, Yunze; Wang, Shaopeng; Nagaraj, Vinay J.; Liu, Qiang; Wu, Jie; Tao, Nongjian

    2012-10-01

    Membrane proteins mediate a variety of cellular responses to extracellular signals. Although membrane proteins are studied intensively for their values as disease biomarkers and therapeutic targets, in situ investigation of the binding kinetics of membrane proteins with their ligands has been a challenge. Traditional approaches isolate membrane proteins and then study them ex situ, which does not reflect accurately their native structures and functions. We present a label-free plasmonic microscopy method to map the local binding kinetics of membrane proteins in their native environment. This analytical method can perform simultaneous plasmonic and fluorescence imaging, and thus make it possible to combine the strengths of both label-based and label-free techniques in one system. Using this method, we determined the distribution of membrane proteins on the surface of single cells and the local binding kinetic constants of different membrane proteins. Furthermore, we studied the polarization of the membrane proteins on the cell surface during chemotaxis.

  11. APACHE: Integrated Hybrid Fuel Cell System for 2-Seat All Electric Aircraft Propulsion

    OpenAIRE

    Hordé, Théophile; Achard, Patrick; Metkemeijer, Rudolf

    2012-01-01

    International audience The French APACHE project aims at demonstrating the feasibility of using a Hybrid Fuel Cell System (HFCS) as the power generator for all electric 2-seat aircrafts. This study focuses on three main topics: airworthiness of Proton Exchange Membrane Fuel Cells (PEMFC), their hybridization with Lithium Ion (Li-Ion) batteries and systems' integration into light aircrafts. Altitude and inclination tests have been led and allow to conclude on the ability of PEMFC to operate...

  12. Sensitive dependence of the coefficient of variation of interspike intervals on the lower boundary of membrane potential for the leaky integrate-and-fire neuron model.

    Science.gov (United States)

    Inoue, Junko; Doi, Shinji

    2007-01-01

    After the report of Softky and Koch [Softky, W.R., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13, 334-350], leaky integrate-and-fire models have been investigated to explain high coefficient of variation (CV) of interspike intervals (ISIs) at high firing rates observed in the cortex. The purpose of this paper is to study the effect of the position of a lower boundary of membrane potential on the possible value of CV of ISIs based on the diffusional leaky integrate-and-fire models with and without reversal potentials. Our result shows that the irregularity of ISIs for the diffusional leaky integrate-and-fire neuron significantly changes by imposing a lower boundary of membrane potential, which suggests the importance of the position of the lower boundary as well as that of the firing threshold when we study the statistical properties of leaky integrate-and-fire neuron models. It is worth pointing out that the mean-CV plot of ISIs for the diffusional leaky integrate-and-fire neuron with reversal potentials shows a close similarity to the experimental result obtained in Softky and Koch [Softky, W.R., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13, 334-350].

  13. Microfabricated polymer electrolyte membrane fuel cells with low catalyst loadings

    Energy Technology Data Exchange (ETDEWEB)

    Gruber, D.; Ponath, N.; Mueller, J. [Hamburg University of Technology, Hamburg (Germany). Department of Micro Systems Technology

    2005-11-01

    Miniaturized fuel cells as compact power sources fabricated in Pyrex glass using standard polymer electrolyte membrane (PEM) and electrode materials are presented. Photolithographic patterned and wet chemically etched serpentine flow channels of 1 mm in width and 250 {mu} m in depth transport the fuels to the cell of 1.44 cm{sup 2} active electrode area. Feeding H{sub 2}/O{sub 2} a maximum power density of 149 mW cm{sup -2} is attained at a very low Pt loading of 0.054 mg cm{sup -2}, ambient pressure, and room temperature. Operated with methanol and oxygen about 9 mW cm{sup -2} are achieved at ambient pressure, 60 C, and 1 mg cm{sup -2} PtRu/Pt (anode/cathode) loading. A planar two-cell stack to demonstrate and investigate the assembly of a fuel cell system on Pyrex wafers has successfully been fabricated. (author)

  14. CFD simulation of fuel cell proton exchange membrane multichannel

    International Nuclear Information System (INIS)

    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)

  15. Effect of storage in short--and long-term commercial semen extenders on the motility, plasma membrane and chromatin integrity of boar spermatozoa.

    Science.gov (United States)

    De Ambrogi, Marco; Ballester, Juan; Saravia, Fernando; Caballero, Ignacio; Johannisson, Anders; Wallgren, Margareta; Andersson, Magnus; Rodriguez-Martinez, Heriberto

    2006-10-01

    For artificial insemination (AI) in pigs, preservation of liquid boar semen at 16-20 degrees C is still common practice as sperm cryopreservation remains suboptimal in this species. To meet the different needs of the swine industry, several extenders have been developed to preserve semen in liquid form for short--and long-term storage. In the present study, three different commercial extenders devised for short-term (BTS+) or long-term preservation (MR-A and X-Cell), were used to test whether storage of semen from four mature, fertile boars at 17 degrees C for 96 h would affect sperm characteristics relevant for fertility, such as motility, membrane integrity and chromatin stability. Computer-assisted sperm analysis, and stainings with the acylated membrane dye SYBR-14/propidium iodide, and acridine orange in connection with flow cytometry were used to evaluate these variables. Percentages of total motile spermatozoa decreased slightly, but significantly, after 72-96 h. While membrane integrity values varied during the period of study, no significant changes in either membrane integrity or chromatin stability were, however, registered. This suggests a customary 96-day storage at 17 degrees C in these extenders was too short an interval to cause losses of integrity in nuclear DNA in the boar population studied. PMID:16573706

  16. Measurement of the cell membrane capacitance and conductance of colonic crypt cells of the rat using the patch clamp technique

    OpenAIRE

    Schill, C.

    2005-01-01

    Using the patch clamp technique the membrane capacitance and membrane conductance of colonic crypt cells of the rat was measured. The influence of the intracellular agonists Ca++, cAMP and of osmotic changes on the membrane capacitance and conductance was studied.

  17. Homeostatic restitution of cell membranes. Nuclear membrane lipid biogenesis and transport of protein from cytosol to intranuclear spaces.

    Directory of Open Access Journals (Sweden)

    Amalia Slomiany, Maria Grabska, Bronislaw L. Slomiany

    2006-01-01

    Full Text Available Our studies on homeostatic restitution of cellular and subcellular membranes showed that vesicular intracellular transport is engaged in systematic and coordinated replacement of lipids and proteins in the membranes of the secretory, non-dividing epithelial cells (Slomiany et al., J. Physiol. Pharmacol. 2004; 55: 837-860. In this report, we present evidence on the homeostatic restitution of lipids in the biomembranes that constitute nuclear envelopes. We investigated nuclear membranes lipid synthesis by employing purified intact nuclei (IN, the outer nuclear membrane (ONM, the inner nuclear membrane (INM and the cell cytosol (CC. In contrast to Endoplasmic Reticulum (ER which in the presence of CC generates new biomembrane that forms ER vesicles transporting ER products to Golgi, the IN, ONM and INM are not producing transport vesicles. Instead, the newly synthesized lipids remain in the nuclear membranes. The membranes (INM, ONM of IN incubated with CC become enriched with newly synthesized phosphatidylcholine (PC, phosphatidylinositol (PI, phosphatidylinositol phosphates (PIPs and phosphatidic acid (PA. The incubation of separated ONM and INM with CC also enriched the membranes with IN specific lipids identified above. Moreover, the incubation of IN or its membranes with CC afforded retention of numerous CC proteins on the nuclear membrane. Here, we concentrated on 30kDa CC protein that displayed affinity to nuclear membrane PIP2. The 30kDa CC protein bound to PIP2 of IN, INM, and ONM. With IN, initially the PIP2-30kDa CC protein complex was detected on ONM, after 30-120 min of incubation, was found on INM and in nuclear contents. At the same time when the 30 kDa protein was released from INM and found in nuclear contents, the PIP2 of INM and ONM became undetectable, while the lipid extract from the membrane displaced from IN contained labeled PI only. Since ONM is an uninterrupted continuum of ER and INM, we speculate that the synthesis of

  18. Mitochondrial Swelling and Incipient Outer Membrane Rupture in Preapoptotic and Apoptotic Cells

    OpenAIRE

    Sesso, A.; Belizário, JE; Marques, MM; Higuchi, ML; Schumacher, RI; Colquhoun, A; Ito, E.; Kawakami, J.

    2012-01-01

    Outer mitochondrial membrane (OMM) rupture was first noted in isolated mitochondria in which the inner mitochondrial membrane (IMM) had lost its selective permeability. This phenomenon referred to as mitochondrial permeability transition (MPT) refers to a permeabilized inner membrane that originates a large swelling in the mitochondrial matrix, which distends the outer membrane until it ruptures. Here, we have expanded previous electron microscopic observations that in apoptotic cells, OMM ru...

  19. Endogenously generated amyloid β increases membrane fluidity in neural 2a cells

    Institute of Scientific and Technical Information of China (English)

    NIU Ying; SHENG BaiYang; SONG Bo; LIU LingLing; ZHANG XiuFang; ZHAO NanMing; GONG YanDao

    2009-01-01

    The effect of endogenously generated amyloid β on membrane fluidity was investigated in Neural 2a cells stably expressing Swedish mutant amyloid precursor protein (APPswe). Membrane fluidity was studied by fluorescence polarizability using 1,6-Diphenyl-1,3,5-Hexatriene (DPH) as the fluorescence probe. It was found that the membrane fluidity in APPswe cells was significantly higher than that in its wild type counterparts. Alleviating the effect of amyloid β either by y secretase activity inhibition or by amyloid antibody treatment decreased membrane fluidity, which indicated an important role of amyloid β in increasing membrane fluidity. Treatment using amyloid β channel blocker, tromethamine and NA4 suggested that channel formed by amyloid β on the cell membrane is a way through which amyloid β takes its membrane fluidizing effect.

  20. Integrated membrane distillation-crystallization: process design and cost estimations for seawater treatment and fluxes of single salt solutions

    NARCIS (Netherlands)

    Creusen, R.J.M.; Medevoort, J. van; Roelands, C.P.M.; Renesse van Duivenbode, J.A.D. van; Hanemaaijer, J.H.; Leerdam, R.C. van

    2013-01-01

    The goal of this research is to design an integrated membrane distillation-crystallization (MDC) process for desalination of seawater with pure water and dry salts as the only products. The process is based on a combination of membrane distillation (MD) and osmotic distillation (OD) steps with integ

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

    Science.gov (United States)

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

    2016-01-15

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

  2. Short-term effects of ultrahigh concentration cationic silica nanoparticles on cell internalization, cytotoxicity, and cell integrity with human breast cancer cell line (MCF-7)

    International Nuclear Information System (INIS)

    High concentrations of cationic colloidal silica nanoparticles (CCS-NPs) have been widely used for the enrichment of plasma membrane proteins. However, the interaction between the CCS-NPs and cells under the required concentration for the isolation of plasma membrane are rarely investigated. We evaluated the internalization and toxicity of the 15 nm CCS-NPs which were exposed at high concentrations with short time in human breast cancer cells (MCF-7) with transmission electron microscopy, energy dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, and colorimetric assays. The NPs were observed throughout the cells, particularly in the cytoplasm and the nucleus, after short incubation periods. Additionally, the NPs significantly influenced the membrane integrity of the MCF-7 cells

  3. Short-term effects of ultrahigh concentration cationic silica nanoparticles on cell internalization, cytotoxicity, and cell integrity with human breast cancer cell line (MCF-7)

    Energy Technology Data Exchange (ETDEWEB)

    Seog, Ji Hyun [Korea Advanced Institute of Science and Technology, Graduate School of Nanoscience and Technology (Korea, Republic of); Kong, Bokyung [Corning Precision Materials (Korea, Republic of); Kim, Dongheun [Korea Advanced Institute of Science and Technology, Graduate School of Nanoscience and Technology (Korea, Republic of); Graham, Lauren M. [University of Maryland, Department of Chemistry and Biochemistry (United States); Choi, Joon Sig [Chungnam National University, Department of Biochemistry (Korea, Republic of); Lee, Sang Bok, E-mail: slee@umd.edu [Korea Advanced Institute of Science and Technology, Graduate School of Nanoscience and Technology (Korea, Republic of)

    2015-01-15

    High concentrations of cationic colloidal silica nanoparticles (CCS-NPs) have been widely used for the enrichment of plasma membrane proteins. However, the interaction between the CCS-NPs and cells under the required concentration for the isolation of plasma membrane are rarely investigated. We evaluated the internalization and toxicity of the 15 nm CCS-NPs which were exposed at high concentrations with short time in human breast cancer cells (MCF-7) with transmission electron microscopy, energy dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, and colorimetric assays. The NPs were observed throughout the cells, particularly in the cytoplasm and the nucleus, after short incubation periods. Additionally, the NPs significantly influenced the membrane integrity of the MCF-7 cells.

  4. The role of forward osmosis and microfiltration in an integrated osmotic-microfiltration membrane bioreactor system.

    Science.gov (United States)

    Luo, Wenhai; Hai, Faisal I; Kang, Jinguo; Price, William E; Nghiem, Long D; Elimelech, Menachem

    2015-10-01

    This study investigates the performance of an integrated osmotic and microfiltration membrane bioreactor (O/MF-MBR) system for wastewater treatment and reclamation. The O/MF-MBR system simultaneously used microfiltration (MF) and forward osmosis (FO) membranes to extract water from the mixed liquor of an aerobic bioreactor. The MF membrane facilitated the bleeding of dissolved inorganic salts and thus prevented the build-up of salinity in the bioreactor. As a result, sludge production and microbial activity were relatively stable over 60 days of operation. Compared to MF, the FO process produced a better permeate quality in terms of nutrients, total organic carbon, as well as hydrophilic and biologically persistent trace organic chemicals (TrOCs). The high rejection by the FO membrane also led to accumulation of hydrophilic and biologically persistent TrOCs in the bioreactor, consequently increasing their concentration in the MF permeate. On the other hand, hydrophobic and readily biodegradable TrOCs were minimally detected in both MF and FO permeates, with no clear difference in the removal efficiencies between two processes.

  5. prpC-related signal transduction is influenced by copper, membrane integrity and the alpha cleavage site

    Institute of Scientific and Technical Information of China (English)

    Cathryn L Haigh; Victoria A Lewis; Laura J Vella; Colin L Masters; Andrew F Hill; Victoria A Lawson; Steven J Collins

    2009-01-01

    The copper-binding, membrane-anchored, cellular prion protein (PrPC) has two constitutive cleavage sites pro-ducing distinct N- and C-terminal fragments (N1/C1 and N2/C2). Using RKI3 cells expressing either human PrPC, mouse PrPC or mouse PrPC carrying the 3F4 epitope, this study explored the influence of the PrPC primary sequence on endoproteolytic cleavage and one putative PrPC function, MAP kinase signal transduction, in response to exoge-nous copper with or without a perturbed membrane environment. PrPC primary sequence, especially that around the N1/C1 cleavage site, appeared to influence basal levels of proteolysis at this location and extracellular signal-regulat-ed kinase 1/2 (ERK1/2) phosphorylation, with increased processing demonstrating an inverse relationship with basal ERK1/2 activation. Human PrPC showed increased N1/C1 cleavage in response to copper alone, accompanied by spe-cific p38 and JNK/SAPK phosphorylation. Combined exposure to copper plus the cholesterol-sequestering antibiotic filipin resulted in a mouse PrPC-specific substantial increase in signal protein phosphorylation, accompanied by an increase in N1/C1 cleavage. Mouse PrPC harboring the human N1/C1 cleavage site assumed more human-like profiles basally and in response to copper and altered membrane environments. Our results demonstrate that the PrPC pri-mary sequence around the N1/C1 cleavage site influences endoproteolytic processing at this location, which appears linked to MAP kinase signal transduction both basally and in response to copper. Further, the primary sequence ap-pears to confer a mutual dependence of N1/C1 cleavage and membrane integrity on the fidelity of prpC-related signal transduction in response to exogenous stimuli.

  6. Shotgun proteomics and network analysis between plasma membrane and extracellular matrix proteins from rat olfactory ensheathing cells.

    Science.gov (United States)

    Liu, Yisong; Teng, Xiaohua; Yang, Xiaoxu; Song, Qing; Lu, Rong; Xiong, Jixian; Liu, Bo; Zeng, Nianju; Zeng, Yu; Long, Jia; Cao, Rui; Lin, Yong; He, Quanze; Chen, Ping; Lu, Ming; Liang, Songping

    2010-01-01

    Olfactory ensheathing cells (OECs) are a special type of glial cells that have characteristics of both astrocytes and Schwann cells. Evidence suggests that the regenerative capacity of OECs is induced by soluble, secreted factors that influence their microenvironment. These factors may regulate OECs self-renewal and/or induce their capacity to augment spinal cord regeneration. Profiling of plasma membrane and extracellular matrix through a high-throughput expression proteomics approach was undertaken to identify plasma membrane and extracellular matrix proteins of OECs under serum-free conditions. 1D-shotgun proteomics followed with gene ontology (GO) analysis was used to screen proteins from primary culture rat OECs. Four hundred and seventy nonredundant plasma membrane proteins and 168 extracellular matrix proteins were identified, the majority of which were never before reported to be produced by OECs. Furthermore, plasma membrane and extracellular proteins were classified based on their protein-protein interaction predicted by STRING quantitatively integrates interaction data. The proteomic profiling of the OECs plasma membrane proteins and their connection with the secretome in serum-free culture conditions provides new insights into the nature of their in vivo microenvironmental niche. Proteomic analysis for the discovery of clinical biomarkers of OECs mechanism warrants further study.

  7. THE ADDITION OF CAFFEINE IN EARLE’S BALANCED SALT SOLUTION MEDIA WITH WASHING UP METHOD INCREASE MEMBRANE INTEGRITY AND ACROSOMAL SPERM

    OpenAIRE

    B. K. Satriyasa; and A. N. Mahendra

    2014-01-01

    Background: caffeine, a methylxanthine derivate, appears to inhibit phosphodiesterase, thereby inhibiting the break down of cAMP and increasing its concentration inside cell. This study aims to assess the effect of caffeine addition in Earles’s Balanced Salt Solution (EBSS) on the increase in membrane integrity and acrosome reaction of spermatozoa using swim up method. Methods: This study was carried out at the Clinic of Sexology and Andrology, Sanglah Public Hospital at Denpasar Bali-Indones...

  8. Dynamic maintenance of stochastic molecular clusters on cell membranes

    Science.gov (United States)

    Mugler, Andrew; Wehrens, Martijn; Ten Wolde, Pieter Rein

    2015-03-01

    Clustering of molecules on cell membranes is a widely observed phenomenon. A key example is the oncoprotein Ras. Maintenance of Ras clusters has been linked to proper Ras signaling. Yet, the mechanism by which Ras clusters are maintained remains unclear. Recently it was discovered that activated Ras promotes further Ras activation. We show using particle-based simulation that this positive feedback link is sufficient to produce persistent clusters of active Ras molecules via a dynamic nucleation mechanism. The cluster statistics are consistent with experimental observations. Interestingly, our model does not support a Turing regime of macroscopic reaction-diffusion patterning. This means that the clustering we observe is a purely stochastic effect, arising from the coupling of the positive feedback network with the discrete nature of individual molecules. These findings underscore the importance of stochastic and dynamic properties of reaction diffusion systems for biological behavior.

  9. Integrated Wireless Monitoring and Control System in Reverse Osmosis Membrane Desalination Plants

    Directory of Open Access Journals (Sweden)

    Al Haji Ahmad

    2015-01-01

    Full Text Available The operational processes of the Reverse Osmosis (RO membrane desalination plants require continuous monitoring through the constant attendance of operators to ensure proper productivity and minimize downtime and prevent membrane failure. Therefore, the plant must be equipped with a control system that monitors and controls the operational variables. Monitoring and controlling the affecting parameters are critical to the evaluation of the performance of the desalination plant, which will help the operator find and resolve problems immediately. Therefore, this paper was aimed at developing an RO unit by utilizing a wireless sensor network (WSN system. Hence, an RO pilot plant with a feed capacity of 1.2 m3/h was utilized, commissioned, and tested in Kuwait to assess and verify the performance of the integrated WSN in RO membrane desalination system. The investigated system allowed the operators to remotely monitor the operational process of the RO system. The operational data were smoothly recorded and monitored. Furthermore, the technical problems were immediately determined, which reduced the time and effort in rectifying the technical problems relevant to the RO performance. The manpower requirements of such treatment system were dramatically reduced by about 50%. Based on a comparison between manual and wireless monitoring operational processes, the availability of the integrated RO unit with a wireless monitoring was increased by 10%

  10. Structure determination of an integral membrane protein at room temperature from crystals in situ

    Energy Technology Data Exchange (ETDEWEB)

    Axford, Danny [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Foadi, James [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Hu, Nien-Jen; Choudhury, Hassanul Ghani [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Iwata, So [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Kyoto University, Kyoto 606-8501 (Japan); Beis, Konstantinos [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom); Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Alguel, Yilmaz, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE (United Kingdom); Imperial College London, London SW7 2AZ (United Kingdom); Rutherford Appleton Laboratory, Oxfordshire OX11 0FA (United Kingdom)

    2015-05-14

    The X-ray structure determination of an integral membrane protein using synchrotron diffraction data measured in situ at room temperature is demonstrated. The structure determination of an integral membrane protein using synchrotron X-ray diffraction data collected at room temperature directly in vapour-diffusion crystallization plates (in situ) is demonstrated. Exposing the crystals in situ eliminates manual sample handling and, since it is performed at room temperature, removes the complication of cryoprotection and potential structural anomalies induced by sample cryocooling. Essential to the method is the ability to limit radiation damage by recording a small amount of data per sample from many samples and subsequently assembling the resulting data sets using specialized software. The validity of this procedure is established by the structure determination of Haemophilus influenza TehA at 2.3 Å resolution. The method presented offers an effective protocol for the fast and efficient determination of membrane-protein structures at room temperature using third-generation synchrotron beamlines.

  11. Preparation of electrolyte membranes for micro tubular solid oxide fuel cells

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Yttria-stabilized zirconia (YSZ) micro tubular electrolyte membranes for solid oxide fuel cells (SOFCs) were prepared via the combined wet phase inversion and sintering technique. The as-derived YSZ mi- cro tubes consist of a thin dense skin layer and a thick porous layer that can serve as the electrode of fuel cells. The dense and the porous electrolyte layers have the thickness of 3-5 μm and 70-90 μm, respectively, while the inner surface porosity of the porous layer is higher than 28.1%. The two layers are perfectly integrated together to preclude the crack or flake of electrolyte film from the electrode. The presented method possesses distinct advantages such as technological simplicity, low cost and high reliability, and thus provides a new route for the preparation of micro tubular SOFCs.

  12. Preparation of electrolyte membranes for micro tubular solid oxide fuel cells

    Institute of Scientific and Technical Information of China (English)

    TAN XiaoYao; YIN WeiNing; MENG Bo; MENG XiuXia; YANG NaiTao; MA ZiFeng

    2008-01-01

    Yttria-stabilized zirconia (YSZ) micro tubular electrolyte membranes for solid oxide fuel cells (SOFCs) were prepared via the combined wet phase inversion and sintering technique. The as-derived YSZ mi-cro tubes consist of a thin dense skin layer and a thick porous layer that can serve as the electrode of fuel cells. The dense and the porous electrolyte layers have the thickness of 3-5 μm and 70-90 μm, respectively, while the inner surface porosity of the porous layer is higher than 28.1%. The two layers are perfectly integrated together to preclude the crack or flake of electrolyte film from the electrode. The presented method possesses distinct advantages such as technological simplicity, low cost and high reliability, and thus provides a new route for the preparation of micro tubular SOFCs.

  13. 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

  14. 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

    2014-11-01

    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

  15. Assessment of Membrane Fluidity Fluctuations during Cellular Development Reveals Time and Cell Type Specificity

    KAUST Repository

    Noutsi, Pakiza

    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.

  16. Assessment of Membrane Fluidity Fluctuations during Cellular Development Reveals Time and Cell Type Specificity.

    Science.gov (United States)

    Noutsi, Pakiza; Gratton, Enrico; Chaieb, Sahraoui

    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. PMID:27362860

  17. Experimental Investigation and Discussion on the Mechanical Endurance Limit of Nafion Membrane Used in Proton Exchange Membrane Fuel Cell

    Directory of Open Access Journals (Sweden)

    Yang Xiao

    2014-10-01

    Full Text Available As a solution of high efficiency and clean energy, fuel cell technologies, especially proton exchange membrane fuel cell (PEMFC, have caught extensive attention. However, after decades of development, the performances of PEMFCs are far from achieving the target from the Department of Energy (DOE. Thus, further understanding of the degradation mechanism is needed to overcome this obstacle. Due to the importance of proton exchange membrane in a PEMFC, the degradation of the membrane, such as hygrothermal aging effect on its properties, are particularly necessary. In this work, a thick membrane (Nafion N117, which is always used as an ionic polymer for the PEMFCs, has been analyzed. Experimental investigation is performed for understanding the mechanical endurance of the bare membranes under different loading conditions. Tensile tests are conducted to compare the mechanical property evolution of two kinds of bare-membrane specimens including the dog-bone and the deeply double edge notched (DDEN types. Both dog-bone and DDEN specimens were subjected to a series of degradation tests with different cycling times and wide humidity ranges. The tensile tests are repeated for both kinds of specimens to assess the strain-stress relations. Furthermore, Fourier transform infrared spectroscopy (FT-IR, X-ray diffraction (XRD and Scanning electron microscope (SEM observation and water absorption measurement were conducted to speculate the cause of this variation. The initial cracks along with the increasing of bound water content were speculated as the primary cause.

  18. Feline immunodeficiency virus decreases cell-cell communication and mitochondrial membrane potential.

    OpenAIRE

    Danave, I R; Tiffany-Castiglioni, E; Zenger, E; Barhoumi, R.; Burghardt, R C; Collisson, E W

    1994-01-01

    The in vitro effects of viral replication on mitochondrial membrane potential (MMP) and gap junctional intercellular communication (GJIC) were evaluated as two parameters of potential cellular injury. Two distinct cell types were infected with the Petaluma strain of feline immunodeficiency virus (FIV). Primary astroglia supported acute FIV infection, resulting in syncytia within 3 days of infection, whereas immortalized Crandell feline kidney (CRFK) cells of epithelial origin supported persis...

  19. Semicontinuous Production of Lactic Acid From Cheese Whey Using Integrated Membrane Reactor

    Science.gov (United States)

    Li, Yebo; Shahbazi, Abolghasem; Coulibaly, Sekou; Mims, Michele M.

    Semicontinuous production of lactic acid from cheese whey using free cells of Bifidobacterium longum with and without nanofiltration was studied. For the semicontinuous fermentation without membrane separation, the lactic acid productivity of the second and third runs is much lower than the first run. The semicontinuous fermentation with nanoseparation was run semicontinuously for 72 h with lactic acid to be harvested every 24 h using a nanofiltration membrane unit. The cells and unutilized lactose were kept in the reactor and mixed with newly added cheese whey in the subsequent runs. Slight increase in the lactic acid productivity was observed in the second and third runs during the semicontinuous fermentation with nanofiltration. It can be concluded that nanoseparation could improve the lactic acid productivity of the semicontinuous fermentation process.

  20. [Transfer of T-DNA from agrobacteria into plant cells through cell walls and membranes].

    Science.gov (United States)

    Chumakov, M I

    2001-01-01

    Discusses probable routes of agrobacterial penetration through the plant integumental tissues, cell wall, and plant cell plasmodesma. Analyzes the contribution of extracellular structures of agrobacteria in penetration through barriers of a plant cell, primary contact (adhesion), and during DNA transfer from bacterial (E. coli, A. tumefaciens) to recipient (bacterial or plant) cells. Discusses the relationship between donor cell adhesion to recipient cell surface and the infectious and conjugation processes. Considers the probable role of piles in conjugative transfer of agrobacterial DNA through membranes of donor and recipient (bacterial and plant) cells. Analyzes the contribution of the plant cell cytoskeleton to T-DNA transfer. Suggests a model of transport of T-DNA-VirD2 complex and VirE2 proteins through independent channels consisting of vir-coded proteins. PMID:11236737

  1. Effects of nitrogen ion implantation on Ca2+ concentration and membrane potential of pollen cell

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effects of low energy nitrogen ion implantation on Ca2+ concentration and membrane potential of lily (lilium davidii Duch) pollen cell have been studied. The results showed that the Ca2+ concentration was increased when pollen grain was implanted by nitrogen ion with energy 100keV and dose 1013 ions/cra2. However, the increase of Ca2+ concentration was partly inhibited by the addition of Ca2+channel inhibitor depending on dose. And nitrogen ion implantation caused depolarization of pollen cell membrane potential. In other words, membrane potential was increased,but the effect decreased by adding Ca2+ channel inhibitor.However, it was still significantly higher than the membrane potential of control cells. It was indicated that the depolarization of cell membrane potential opened the calcium channel on the membrane that caused the increasing of intraceilular calcium concentration. This might be an earlier step of the effect of low energy nitrogen ion implantation on pollen germination.

  2. A microfluidic platform for probing single cell plasma membranes using optically trapped Smart Droplet Microtools (SDMs).

    Science.gov (United States)

    Lanigan, Peter M P; Ninkovic, Tanja; Chan, Karen; de Mello, Andrew J; Willison, Keith R; Klug, David R; Templer, Richard H; Neil, Mark A A; Ces, Oscar

    2009-04-21

    We recently introduced a novel platform based upon optically trapped lipid coated oil droplets (Smart Droplet Microtools-SDMs) that were able to form membrane tethers upon fusion with the plasma membrane of single cells. Material transfer from the plasma membrane to the droplet via the tether was seen to occur. Here we present a customised version of the SDM approach based upon detergent coated droplets deployed within a microfluidic format. These droplets are able to differentially solubilise the plasma membrane of single cells with spatial selectivity and without forming membrane tethers. The microfluidic format facilitates separation of the target cells from the bulk SDM population and from downstream analysis modules. Material transfer from the cell to the SDM was monitored by tracking membrane localized EGFP.

  3. The Investigation and Development of Low Cost Hardware Components for Proton-Exchange Membrane Fuel Cells - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    George A. Marchetti

    1999-12-15

    Proton exchange membrane (PEM) fuel cell components, which would have a low-cost structure in mass production, were fabricated and tested. A fuel cell electrode structure, comprising a thin layer of graphite (50 microns) and a front-loaded platinum catalyst layer (600 angstroms), was shown to produce significant power densities. In addition, a PEM bipolar plate, comprising flexible graphite, carbon cloth flow-fields and an integrated polymer gasket, was fabricated. Power densities of a two-cell unit using this inexpensive bipolar plate architecture were shown to be comparable to state-of-the-art bipolar plates.

  4. Plasma Membrane Lesions In Anthracycline-Resistant Tumor Cells Probed Using A Fluorescent Dye

    Science.gov (United States)

    Burke, Thomas G.; Doroshow, James H.

    1989-06-01

    Human cancer cells selected for resistance to several structurally unrelated cytotoxic drugs are known to display plasma membrane alterations such as amplified levels of a variety of glycoproteins, modifications in lipid composition, alterations in membrane fluidity and increased cellular fragility to osmotic shock. We have studied the plasma membrane fluidity of HL60 human leukemia cells and MCF-7 human breast cancer cells that have been selected for acquired resistance against the cytocidal effects of the anthracycline anticancer drug Adriamycin. Fluidity measurements were accomplished by evaluating the fluorescence anisotropy of the plasma membrane specific probe trimethylamino-1,6-dipihenylhexatriene (TMA.DPH) bound to whole, living cells. TMA.DPH anisotropy values for MCF-7 sensitive and 12-fold resistant cells were 0.306 and 0.285, respectively, while anisotropy values for HL-60 sensitive and 80-fold resistant cells lines were 0.310 and 0.295, respectively. In all cases, cell viability exceeded 97% and anisotropy values were subject to a day-to-day uncertainty of +/-2%. Our results demonstrate that increased plasma membrane fluidity apparently accompanies the development of resistance in both cell lines. Because it is known that increased membrane fluidity results in significantly decreased Adriamycin binding in artificial membrane systems, we propose here that decreased drug associations with fluidized, plasma membrane lipid bilayer regions may be a mechanism which contributes, in part, to the reduced rates of drug accumulation observed in HL60 and MCF-7 cells resistant to Adriamycin.

  5. Water Management Membrane for Fuel Cells and Electrolyzers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Development of an improved water management membrane for a static vapor feed electrolyzer that produces sub-saturated H2 and O2 is proposed. This improved membrane...

  6. Protecting genomic integrity in somatic cells and embryonic stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Y. [Department of Cell biology, Neurobiology and Anatomy, University of Cincinnati Medica Center, 3125 Eden Avenue, Cincinnati, OH 45267-0521 (United States); Cervantes, R.B. [Department of Cell biology, Neurobiology and Anatomy, University of Cincinnati Medica Center, 3125 Eden Avenue, Cincinnati, OH 45267-0521 (United States); Tichy, E. [Department of Cell biology, Neurobiology and Anatomy, University of Cincinnati Medica Center, 3125 Eden Avenue, Cincinnati, OH 45267-0521 (United States); Tischfield, J.A. [Department of Genetics, Rutgers University, Piscataway, NJ 088542 (United States); Stambrook, P.J. [Department of Cell biology, Neurobiology and Anatomy, University of Cincinnati Medica Center, 3125 Eden Avenue, Cincinnati, OH 45267-0521 (United States)]. E-mail: peter.stambrook@uc.edu

    2007-01-03

    Mutation frequencies at some loci in mammalian somatic cells in vivo approach 10{sup -4}. The majority of these events occur as a consequence of loss of heterozygosity (LOH) due to mitotic recombination. Such high levels of DNA damage in somatic cells, which can accumulate with age, will cause injury and, after a latency period, may lead to somatic disease and ultimately death. This high level of DNA damage is untenable for germ cells, and by extrapolation for embryonic stem (ES) cells, that must recreate the organism. ES cells cannot tolerate such a high frequency of damage since mutations will immediately impact the altered cell, and subsequently the entire organism. Most importantly, the mutations may be passed on to future generations. ES cells, therefore, must have robust mechanisms to protect the integrity of their genomes. We have examined two such mechanisms. Firstly, we have shown that mutation frequencies and frequencies of mitotic recombination in ES cells are about 100-fold lower than in adult somatic cells or in isogenic mouse embryonic fibroblasts (MEFs). A second complementary protective mechanism eliminates those ES cells that have acquired a mutational burden, thereby maintaining a pristine population. Consistent with this hypothesis, ES cells lack a G1 checkpoint, and the two known signaling pathways that mediate the checkpoint are compromised. The checkpoint kinase, Chk2, which participates in both pathways is sequestered at centrosomes in ES cells and does not phosphorylate its substrates (i.e. p53 and Cdc25A) that must be modified to produce a G1 arrest. Ectopic expression of Chk2 does not rescue the p53-mediated pathway, but does restore the pathway mediated by Cdc25A. Wild type ES cells exposed to ionizing radiation do not accumulate in G1 but do so in S-phase and in G2. ES cells that ectopically express Chk2 undergo cell cycle arrest in G1 as well as G2, and appear to be protected from apoptosis.

  7. Efficient Nanoporous Silicon Membranes for Integrated Microfluidic Separation and Sensing Systems

    Energy Technology Data Exchange (ETDEWEB)

    Ileri, N; L?tant, S E; Britten, J; Nguyen, H; Larson, C; Zaidi, S; Palazoglu, A; Faller, R; Tringe, J W; Stroeve, P

    2009-04-06

    Nanoporous devices constitute emerging platforms for selective molecule separation and sensing, with great potential for high throughput and economy in manufacturing and operation. Acting as mass transfer diodes similar to a solid-state device based on electron conduction, conical pores are shown to have superior performance characteristics compared to traditional cylindrical pores. Such phenomena, however, remain to be exploited for molecular separation. Here we present performance results from silicon membranes created by a new synthesis technique based on interferometric lithography. This method creates millimeter sized planar arrays of uniformly tapered nanopores in silicon with pore diameter 100 nm or smaller, ideally-suited for integration into a multi-scale microfluidic processing system. Molecular transport properties of these devices are compared against state-of-the-art polycarbonate track etched (PCTE) membranes. Mass transfer rates of up to fifteen-fold greater than commercial sieve technology are obtained. Complementary results from molecular dynamics simulations on molecular transport are reported.

  8. Solution nuclear magnetic resonance structure of membrane-integral diacylglycerol kinase.

    Science.gov (United States)

    Van Horn, Wade D; Kim, Hak-Jun; Ellis, Charles D; Hadziselimovic, Arina; Sulistijo, Endah S; Karra, Murthy D; Tian, Changlin; Sönnichsen, Frank D; Sanders, Charles R

    2009-06-26

    Escherichia coli diacylglycerol kinase (DAGK) represents a family of integral membrane enzymes that is unrelated to all other phosphotransferases. We have determined the three-dimensional structure of the DAGK homotrimer with the use of solution nuclear magnetic resonance. The third transmembrane helix from each subunit is domain-swapped with the first and second transmembrane segments from an adjacent subunit. Each of DAGK's three active sites resembles a portico. The cornice of the portico appears to be the determinant of DAGK's lipid substrate specificity and overhangs the site of phosphoryl transfer near the water-membrane interface. Mutations to cysteine that caused severe misfolding were located in or near the active site, indicating a high degree of overlap between sites responsible for folding and for catalysis. PMID:19556511

  9. Is the surface area of the red cell membrane skeleton locally conserved?

    OpenAIRE

    Fischer, T M

    1992-01-01

    The incompressibility of the lipid bilayer keeps the total surface area of the red cell membrane constant. Local conservation of membrane surface area requires that each surface element of the membrane skeleton keeps its area when its aspect ratio is changed. A change in area would require a flow of lipids past the intrinsic proteins to which the skeleton is anchored. in fast red cell deformations, there is no time for such a flow. Consequently, the bilayer provides for local area conservatio...

  10. Thermal Fluctuations of Red Blood Cell Membrane via a Constant-Area Particle-Dynamics Model

    OpenAIRE

    Marcelli, Gianluca; Parker, Kim H.; Winlove, C. Peter

    2005-01-01

    We describe a model of the mechanical properties of the cell plasma membrane using a finite-temperature particle-dynamics simulation of the whole cell, in which a two-dimensional network of virtual particles embedded in a three-dimensional closed surface represents the membrane. The particles interact via harmonic potential and dihedral angle potential and are subject to a constant area constraint. The evolution of the positions of the particles yields the equilibrium state of the membrane an...

  11. Translocation of annexin Ⅰ from cellular membrane to the nuclear membrane in human esophageal squamous cell carcinoma

    Institute of Scientific and Technical Information of China (English)

    Yu Liu; Xiao-Hang Zhao; Hui-Xin Wang; Ning Lu; You-Sheng Mao; Fang Liu; Ying Wang; Hai-Rong Zhang; Kun Wang; Min Wu

    2003-01-01

    AIM: To investigate the alteration of the annexin I subcellular localization in esophageal squamous cell carcinoma (ESCC)and the correlation between the translocation and the tumorigenesis of ESCC.METHODS: The protein localization of annexin I was detected in both human ESCC tissues and cell line via the indirect immunofiuorescence strategy.RESULTS: In the normal esophageal epithelia the annexin I was mainly located on the plasma membrane and formed a consecutive typical trammels net. Annexin I protein also expressed dispersively in cytoplasm and the nuclei without specific localization on the nuclear membrane. In esophageal cancer annexin I decreased very sharply with scattered disappearance on the cellular membrane, however it translocated and highly expressed on the nuclear membrane,which was never found in normal esophageal epithelia. In cultured esophageal cancer cell line annexin I protein was also focused on the nuclear membrane, which was consistent with the result from esophageal cancer tissues.CONCLUSION: This observation suggests that the translocation of annexin I protein in ESCC may correlate with the tumorigenesis of the esophageal cancer.

  12. Verification of a topology model of PorT as an integral outer membrane protein in Porphyromonas gingivalis

    OpenAIRE

    Nguyen, Ky-Anh; Żylicz, Jasiek; Szczesny, Pawel; Sroka, Aneta; Hunter, Neil; Potempa, Jan

    2009-01-01

    PorT is a membrane-associated protein shown to be essential for the maturation and secretion of a class of cysteine proteinases, the gingipains, from the periodontal pathogen Porphyromonas gingivalis. It was previously reported that PorT is located on the periplasmic surface of the inner membrane to function as a chaperone for the maturing proteinases. Our modeling suggested it to be an integral outer membrane protein with eight anti-parallel, membrane-traversing β-strands. In this report, th...

  13. Maitotoxin-induced membrane blebbing and cell death in bovine aortic endothelial cells

    Directory of Open Access Journals (Sweden)

    Schilling William P

    2001-02-01

    Full Text Available Abstract Background Maitotoxin, a potent cytolytic agent, causes an increase in cytosolic free Ca2+ concentration ([Ca2+]i via activation of Ca2+-permeable, non-selective cation channels (CaNSC. Channel activation is followed by formation of large endogenous pores that allow ethidium and propidium-based vital dyes to enter the cell. Although activation of these cytolytic/oncotic pores, or COP, precedes release of lactate dehydrogenase, an indication of oncotic cell death, the relationship between CaNSC, COP, membrane lysis, and the associated changes in cell morphology has not been clearly defined. In the present study, the effect maitotoxin on [Ca2+]i, vital dye uptake, lactate dehydrogenase release, and membrane blebbing was examined in bovine aortic endothelial cells. Results Maitotoxin produced a concentration-dependent increase in [Ca2+]i followed by a biphasic uptake of ethidium. Comparison of ethidium (Mw 314 Da, YO-PRO-1 (Mw 375 Da, and POPO-3 (Mw 715 Da showed that the rate of dye uptake during the first phase was inversely proportional to molecular weight, whereas the second phase appeared to be all-or-nothing. The second phase of dye uptake correlated in time with the release of lactate dehydrogenase. Uptake of vital dyes at the single cell level, determined by time-lapse videomicroscopy, was also biphasic. The first phase was associated with formation of small membrane blebs, whereas the second phase was associated with dramatic bleb dilation. Conclusions These results suggest that maitotoxin-induced Ca2+ influx in bovine aortic endothelial cells is followed by activation of COP. COP formation is associated with controlled membrane blebbing which ultimately gives rise to uncontrolled bleb dilation, lactate dehydrogenase release, and oncotic cell death.

  14. Lipid bilayer-bound conformation of an integral membrane beta barrel protein by multidimensional MAS NMR

    Energy Technology Data Exchange (ETDEWEB)

    Eddy, Matthew T. [The Scripps Research Institute, Department of Integrative Structural and Computational Biology (United States); Su, Yongchao; Silvers, Robert; Andreas, Loren; Clark, Lindsay [Massachusetts Institute of Technology, Department of Chemistry (United States); Wagner, Gerhard [Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology (United States); Pintacuda, Guido; Emsley, Lyndon [Université de Lyon, Centre de RMN à Très Hauts Champs, Institut des Sciences Analytiques (CNRS, ENS Lyon, UCB Lyon 1) (France); Griffin, Robert G., E-mail: rgg@mit.edu [Massachusetts Institute of Technology, Department of Chemistry (United States)

    2015-04-15

    The human voltage dependent anion channel 1 (VDAC) is a 32 kDa β-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms two-dimensional lipid crystals, showing remarkable spectral resolution (0.5–0.3 ppm for {sup 13}C line widths and <0.5 ppm {sup 15}N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane β-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the

  15. Lipid bilayer-bound conformation of an integral membrane beta barrel protein by multidimensional MAS NMR

    International Nuclear Information System (INIS)

    The human voltage dependent anion channel 1 (VDAC) is a 32 kDa β-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms two-dimensional lipid crystals, showing remarkable spectral resolution (0.5–0.3 ppm for 13C line widths and <0.5 ppm 15N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane β-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported

  16. (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 lip

  17. Changes in membrane lipid composition of Mycoplasma capricolum affect the cell volume.

    OpenAIRE

    N. Romano; Shirvan, M H; Rottem, S.

    1986-01-01

    The cellular water volume of Mycoplasma capricolum was markedly increased by a decrease in the cholesterol-to-phospholipid molar ratio in the membrane. An increase in cell volume was also observed with the increase in the phospholipid cell membrane content obtained by the incorporation of exogenous phosphatidylcholine from the growth medium.

  18. 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 co

  19. Optimisation of the Factor VIII yield in mammalian cell cultures by reducing the membrane bound fraction

    DEFF Research Database (Denmark)

    Kolind, Mille Petersen; Nørby, Peder Lisby; Berchtold, Martin Werner;

    2011-01-01

    of active membrane bound rFVIII to the culture medium. Moreover, the attachment of rFVIII to cell membranes of un-transfected HEK293 cells was studied in the presence of compounds that competes for interactions between rFVIII and PS. Competitive assays between iodinated rFVIII (¹²5I-rFVIII) and annexin V...

  20. Membrane potential and ion transport in lung epithelial type II cells

    International Nuclear Information System (INIS)

    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: [3H]triphenylmethylphosphonium ([3H]TPMP+), rubidium 86, and the fluorescent dye DiOC5. 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. 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...

  2. Plasma membrane microorganization of LR73 multidrug-resistant cells revealed by FCS

    Science.gov (United States)

    Winckler, Pascale; Jaffiol, Rodolphe; Cailler, Aurélie; Morjani, Hamid; Jeannesson, Pierre; Deturche, Régis

    2011-03-01

    Tumoral cells could present a multidrug resistance (MDR) to chemotherapeutic treatments. This drug resistance would be associated to biomechanisms occurring at the plasma membrane level, involving modification of membrane fluidity, drug permeability, presence of microdomains (rafts, caveolae...), and membrane proteins overexpression such as Pglycoprotein. Fluorescence correlation spectroscopy (FCS) is the relevant method to investigate locally the fluidity of biological membranes through the lateral diffusion of a fluorescent membrane probe. Thus, we use FCS to monitor the plasma membrane local organization of LR73 carcinoma cells and three derived multidrug-resistant cancer cells lines. Measurements were conducted at the single cell level, which enabled us to get a detailed overview of the plasma membrane microviscosity distribution of each cell line studied. Moreover, we propose 2D diffusion simulation based on a Monte Carlo model to investigate the membrane organisation in terms of microdomains. This simulation allows us to relate the differences in the fluidity distributions with microorganization changes in plasma membrane of MDR cells.

  3. 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.

  4. A monolayer graphene - Nafion sandwich membrane for direct methanol fuel cells

    Science.gov (United States)

    Yan, X. H.; Wu, Ruizhe; Xu, J. B.; Luo, Zhengtang; Zhao, T. S.

    2016-04-01

    Methanol crossover due to the low selectivity of proton exchange membranes is a long-standing issue in direct methanol fuel cell technology. Here we attempt to address this issue by designing a composite membrane fabricated by sandwiching a monolayer graphene between two thin Nafion membranes to take advantage of monolayer graphene's selective permeability to only protons. The methanol permeability of the present membrane is demonstrated to have a 68.6% decrease in comparison to that of the pristine Nafion membrane. The test in a passive direct methanol fuel cell (DMFC) shows that the designed membrane retains high proton conductivity while substantially suppressing methanol crossover. As a result, the present membrane enables the passive DMFC to exhibit a decent performance even at a methanol concentration as high as 10.0 M.

  5. Covalently Cross-Linked Sulfone Polybenzimidazole Membranes with Poly(Vinylbenzyl Chloride) for Fuel Cell Applications

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Aili, David; Li, Qingfeng;

    2013-01-01

    Covalently cross-linked polymer membranes were fabricated from poly(aryl sulfone benzimidazole) (SO(2) PBI) and poly(vinylbenzyl chloride) (PVBCl) as electrolytes for high-temperature proton-exchange-membrane fuel cells. The cross-linking imparted organo insolubility and chemical stability against...... radical attack to the otherwise flexible SO(2) PBI membranes. Steady phosphoric acid doping of the cross-linked membranes was achieved at elevated temperatures with little swelling. The acid-doped membranes exhibited increased mechanical strength compared to both pristine SO(2) PBI and poly[2,2'-(m......-phenylene)-5,5'-bibenzimidazole] (mPBI). The superior characteristics of the cross-linked SO(2) PBI membranes allowed higher acid doping levels and, therefore, higher proton conductivity. Fuel-cell tests with the cross-linked membranes demonstrated a high open circuit voltage and improved power performance...

  6. Fluctuations of coupled fluid and solid membranes with application to red blood cells

    Science.gov (United States)

    Auth, Thorsten; Safran, S. A.; Gov, Nir S.

    2007-11-01

    The fluctuation spectra and the intermembrane interaction of two membranes at a fixed average distance are investigated. Each membrane can either be a fluid or a solid membrane, and in isolation, its fluctuations are described by a bare or a wave-vector-dependent bending modulus, respectively. The membranes interact via their excluded-volume interaction; the average distance is maintained by an external, homogeneous pressure. For strong coupling, the fluctuations can be described by a single, effective membrane that combines the elastic properties. For weak coupling, the fluctuations of the individual, noninteracting membranes are recovered. The case of a composite membrane consisting of one fluid and one solid membrane can serve as a microscopic model for the plasma membrane and cytoskeleton of the red blood cell. We find that, despite the complex microstructure of bilayers and cytoskeletons in a real cell, the fluctuations with wavelengths λ≳400nm are well described by the fluctuations of a single, polymerized membrane (provided that there are no inhomogeneities of the microstructure). The model is applied to the fluctuation data of discocytes (“normal” red blood cells), a stomatocyte, and an echinocyte. The elastic parameters of the membrane and an effective temperature that quantifies active, metabolically driven fluctuations are extracted from the experiments.

  7. Membrane regulation of the stress response from prokaryotic models to mammalian cells.

    Science.gov (United States)

    Vigh, Laszlo; Nakamoto, Hitoshi; Landry, Jacques; Gomez-Munoz, Antonio; Harwood, John L; Horvath, Ibolya

    2007-10-01

    "Membrane regulation" of stress responses in various systems is widely studied. In poikilotherms, membrane rigidification could be the first reaction to cold perception: reducing membrane fluidity of membranes at physiological temperatures is coupled with enhanced cold inducibility of a number of genes, including desaturases (see J.L. Harwood's article in this Proceedings volume). A similar role of changes in membrane physical state in heat (oxidative stress, etc.) sensing- and signaling gained support recently from prokaryotes to mammalian cells. Stress-induced remodeling of membrane lipids could influence generation, transduction, and deactivation of stress signals, either through global effects on the fluidity of the membrane matrix, or by specific interactions of boundary (or raft) lipids with receptor proteins, lipases, ion channels, etc. Our data point to membranes not only as targets of stress, but also as sensors in activating a stress response. PMID:17656573

  8. C8-glycosphingolipids preferentially insert into tumor cell membranes and promote chemotherapeutic drug uptake.

    Science.gov (United States)

    Cordeiro Pedrosa, Lília R; van Cappellen, Wiggert A; Steurer, Barbara; Ciceri, Dalila; ten Hagen, Timo L M; Eggermont, Alexander M M; Verheij, Marcel; Goñi, Felix María; Koning, Gerben A; Contreras, F-Xabier

    2015-08-01

    Insufficient drug delivery into tumor cells limits the therapeutic efficacy of chemotherapy. Co-delivery of liposome-encapsulated drug and synthetic short-chain glycosphingolipids (SC-GSLs) significantly improved drug bioavailability by enhancing intracellular drug uptake. Investigating the mechanisms underlying this SC-GSL-mediated drug uptake enhancement is the aim of this study. Fluorescence microscopy was used to visualize the cell membrane lipid transfer intracellular fate of fluorescently labeled C6-NBD-GalCer incorporated in liposomes in tumor and non-tumor cells. Additionally click chemistry was applied to image and quantify native SC-GSLs in tumor and non-tumor cell membranes. SC-GSL-mediated flip-flop was investigated in model membranes to confirm membrane-incorporation of SC-GSL and its effect on membrane remodeling. SC-GSL enriched liposomes containing doxorubicin (Dox) were incubated at 4°C and 37°C and intracellular drug uptake was studied in comparison to standard liposomes and free Dox. SC-GSL transfer to the cell membrane was independent of liposomal uptake and the majority of the transferred lipid remained in the plasma membrane. The transfer of SC-GSL was tumor cell-specific and induced membrane rearrangement as evidenced by a transbilayer flip-flop of pyrene-SM. However, pore formation was measured, as leakage of hydrophilic fluorescent probes was not observed. Moreover, drug uptake appeared to be mediated by SC-GSLs. SC-GSLs enhanced the interaction of doxorubicin (Dox) with the outer leaflet of the plasma membrane of tumor cells at 4°C. Our results demonstrate that SC-GSLs preferentially insert into tumor cell plasma membranes enhancing cell intrinsic capacity to translocate amphiphilic drugs such as Dox across the membrane via a biophysical process.

  9. C8-glycosphingolipids preferentially insert into tumor cell membranes and promote chemotherapeutic drug uptake.

    Science.gov (United States)

    Cordeiro Pedrosa, Lília R; van Cappellen, Wiggert A; Steurer, Barbara; Ciceri, Dalila; ten Hagen, Timo L M; Eggermont, Alexander M M; Verheij, Marcel; Goñi, Felix María; Koning, Gerben A; Contreras, F-Xabier

    2015-08-01

    Insufficient drug delivery into tumor cells limits the therapeutic efficacy of chemotherapy. Co-delivery of liposome-encapsulated drug and synthetic short-chain glycosphingolipids (SC-GSLs) significantly improved drug bioavailability by enhancing intracellular drug uptake. Investigating the mechanisms underlying this SC-GSL-mediated drug uptake enhancement is the aim of this study. Fluorescence microscopy was used to visualize the cell membrane lipid transfer intracellular fate of fluorescently labeled C6-NBD-GalCer incorporated in liposomes in tumor and non-tumor cells. Additionally click chemistry was applied to image and quantify native SC-GSLs in tumor and non-tumor cell membranes. SC-GSL-mediated flip-flop was investigated in model membranes to confirm membrane-incorporation of SC-GSL and its effect on membrane remodeling. SC-GSL enriched liposomes containing doxorubicin (Dox) were incubated at 4°C and 37°C and intracellular drug uptake was studied in comparison to standard liposomes and free Dox. SC-GSL transfer to the cell membrane was independent of liposomal uptake and the majority of the transferred lipid remained in the plasma membrane. The transfer of SC-GSL was tumor cell-specific and induced membrane rearrangement as evidenced by a transbilayer flip-flop of pyrene-SM. However, pore formation was measured, as leakage of hydrophilic fluorescent probes was not observed. Moreover, drug uptake appeared to be mediated by SC-GSLs. SC-GSLs enhanced the interaction of doxorubicin (Dox) with the outer leaflet of the plasma membrane of tumor cells at 4°C. Our results demonstrate that SC-GSLs preferentially insert into tumor cell plasma membranes enhancing cell intrinsic capacity to translocate amphiphilic drugs such as Dox across the membrane via a biophysical process. PMID:25917957

  10. U.S. DOE Progress Towards Developing Low-Cost, High Performance, Durable Polymer Electrolyte Membranes for Fuel Cell Applications

    OpenAIRE

    Dimitrios C. Papageorgopoulos; Reginald Tyler; Jason Marcinkoski; Kathi Epping Martin; Donna Lee Ho; Garland, Nancy L.; David Peterson; John Kopasz; Spendelow, Jacob S.; Greg J. Kleen; Cassidy Houchins

    2012-01-01

    Low cost, durable, and selective membranes with high ionic conductivity are a priority need for wide-spread adoption of polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). Electrolyte membranes are a major cost component of PEMFC stacks at low production volumes. PEMFC membranes also impose limitations on fuel cell system operating conditions that add system complexity and cost. Reactant gas and fuel permeation through the membrane leads to decreased fuel ...

  11. Non-linear Membrane Properties in Entorhinal Cortical Stellate Cells Reduce Modulation of Input-Output Responses by Voltage Fluctuations.

    Science.gov (United States)

    Fernandez, Fernando R; Malerba, Paola; White, John A

    2015-04-01

    The presence of voltage fluctuations arising from synaptic activity is a critical component in models of gain control, neuronal output gating, and spike rate coding. The degree to which individual neuronal input-output functions are modulated by voltage fluctuations, however, is not well established across different cortical areas. Additionally, the extent and mechanisms of input-output modulation through fluctuations have been explored largely in simplified models of spike generation, and with limited consideration for the role of non-linear and voltage-dependent membrane properties. To address these issues, we studied fluctuation-based modulation of input-output responses in medial entorhinal cortical (MEC) stellate cells of rats, which express strong sub-threshold non-linear membrane properties. Using in vitro recordings, dynamic clamp and modeling, we show that the modulation of input-output responses by random voltage fluctuations in stellate cells is significantly limited. In stellate cells, a voltage-dependent increase in membrane resistance at sub-threshold voltages mediated by Na+ conductance activation limits the ability of fluctuations to elicit spikes. Similarly, in exponential leaky integrate-and-fire models using a shallow voltage-dependence for the exponential term that matches stellate cell membrane properties, a low degree of fluctuation-based modulation of input-output responses can be attained. These results demonstrate that fluctuation-based modulation of input-output responses is not a universal feature of neurons and can be significantly limited by subthreshold voltage-gated conductances.

  12. The surface charge of a cell lipid membrane

    CERN Document Server

    Pekker, M

    2014-01-01

    In this paper the problem of surface charge of the lipid membrane is considered. It is shown that the membrane surface is negatively charged. Negative ions are in potential wells formed by the dipole heads of membrane phospholipids. The binding energy of the ion with the membrane surface is much greater than its thermal energy. A self-consistent model of the potential in solution is developed, and a stationary charge density on the membrane surface is found. The estimates given in the paper show that the potential difference across the membrane of the unexcited axon (resting potential) can be explained by the difference in surface densities of the bound charges on the inner and outer surfaces of the membrane.

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

    Science.gov (United States)

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

    2004-06-01

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

  14. First integrals of Generalized Darboux-Halphen systems and Membrane Paradigm

    CERN Document Server

    Chanda, Sumanto; Roychowdhury, Raju

    2016-01-01

    The Darboux-Halphen system of equations have common or individual additive terms depending on the matrices defining Yang-Mills gauge potential fields. Tod (Phys. Lett. A 190 (1994) 221-224), described a conserved quantity for the classical systems with no additive terms. We show that the conserved quantity apply even for the generalized cases with common additive terms. A theory has been presented, with an example, of how to formulate conserved quantities for equation with individual additive terms. We also briefly shed some light on the issues of surface motions of fluids in conncetion to Nahm`s equation and the self-duality and integrability of membrane dynamics.

  15. Ion exchange membrane cathodes for scalable microbial fuel cells.

    Science.gov (United States)

    Zuo, Yi; Cheng, Shaoan; Logan, Bruce E

    2008-09-15

    One of the main challenges for using microbial fuel cells (MFCs) is developing materials and architectures that are economical and generate high power densities. The performance of two cathodes constructed from two low-cost anion (AEM) and cation (CEM) exchange membranes was compared to that achieved using an ultrafiltration (UF) cathode, when the membranes were made electrically conductive using graphite paint and a nonprecious metal catalyst (CoTMPP). The best performance in single-chamber MFCs using graphite fiber brush anodes was achieved using an AEM cathode with the conductive coating facing the solution, at a catalyst loading of 0.5 mg/cm2 CoTMPP. The maximum power densitywas 449 mW/ m2 (normalized to the projected cathode surface area) or 13.1 W/m3 (total reactor volume), with a Coulombic efficiency up to 70% in a 50 mM phosphate buffer solution (PBS) using acetate. Decreasing the CoTMPP loading by 40-80% reduced power by 28-56%, with only 16% of the power (72 mW/m2) generated using an AEM cathode lacking a catalyst. Using a current collector (a stainless steel mesh) pressed against the inside surface of the AEM cathode and 200 mM PBS, the maximum power produced was further increased to 728 mW/m2 (21.2 W/m3). The use of AEM cathodes and brush anodes provides comparable performance to similar systems that use materials costing nearly an order of magnitude more (carbon paper electrodes) and thus represent more useful materials for reducing the costs of MFCs for wastewater treatment applications. PMID:18853817

  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. Phosphatidic acid phosphatase and phospholipdase A activities in plasma membranes from fusing muscle cells.

    Science.gov (United States)

    Kent, C; Vagelos, P R

    1976-06-17

    Plasma membrane from fusing embryonic muscle cells were assayed for phospholipase A activity to determine if this enzyme plays a role in cell fusion. The membranes were assayed under a variety of conditions with phosphatidylcholine as the substrate and no phospholipase A activity was found. The plasma membranes did contain a phosphatidic acid phosphatase which was optimally active in the presence of Triton X-100 and glycerol. The enzyme activity was constant from pH 5.2 to 7.0, and did not require divalent cations. Over 97% of the phosphatidic acid phosphatase activity was in the particulate fraction. The subcellular distribution of the phosphatidic acid phosphatase was the same as the distributions of the plasma membrane markers, (Na+ + k+)-ATPase and the acetylcholine receptor, which indicates that this phosphatase is located exclusively in the plasma membranes. There was no detectable difference in the phosphatidic acid phosphatase activities of plasma membranes from fusing and non-fusing cells.

  18. Fabrication of a membrane filter with controlled pore shape and its application to cell separation and strong single cell trapping

    International Nuclear Information System (INIS)

    A porous membrane filter is one of the key components for sample preparation in lab-on-a-chip applications. However, most of the membranes reported to date have only been used for size-based separation since it is difficult to provide functionality to the membrane or improve the performance of the membrane. In this work, as a method to functionalize the membrane filter, controlling the shape of the membrane pores is suggested, and a convenient and mass-producible fabrication method is provided. With the proposed method, membrane filters with round, conical and funnel shape pores were successfully fabricated, and we demonstrated that the sidewall slope of the conical shape pores could be precisely controlled. To verify that the membrane filter can be functionalized by controlled pore shape, we investigated filtration and trapping performance of the membrane filter with conical shape pores. In a filtration test of 1000 cancer cells (MCF-7, a breast cancer cell line) spiked in phosphate buffered saline (PBS) solution, 77% of the total cancer cells were retained on the membrane, and each cell from among 99.3% of the retained cells was automatically isolated in a single conical pore during the filtration process. Thanks to its engineered pore shape, trapping ability of the membrane with conical pores is dramatically improved. Microparticles trapped in the conical pores maintain their locations without any losses even at a more than 30 times faster external flow rate com-pared with those mounted on conventional cylindrical pores. Also, 78% of the cells trapped in the conical pores withstand an external flow of over 300 μl min−1 whereas only 18% of the cells trapped in the cylindrical pores remain on the membrane after 120 μl min−1 of an external flow is applied. (paper)

  19. [Radiation-induced changes in structural state of membranes of human blood cells].

    Science.gov (United States)

    Burlakova, E B; Atkarskaia, M V; Fatkullina, L D; Andreev, S G

    2014-01-01

    To evaluate radiation-induced changes in the structural state of the membranes, blood samples of healthy donors were subjected to gamma radiation in the range of small (1-10 cGy) and medium doses (50 cGy-2 Gy). After irradiation, the microviscosity of lipid membranes of red and white blood cells was measured by ESR spin probe method. At doses exceeding 1 cGy, statistically significant changes of the degree of spontaneous erythrocyte hemolysis and of the lymphocyte plasma membrane microviscosity were observed. Under identical irradiation conditions, the stability of lymphocyte membranes was less as compared to erythrocyte membranes.

  20. Wrapping of a deformable nanoparticle by the cell membrane: Insights into the flexibility-regulated nanoparticle-membrane interaction

    Science.gov (United States)

    Tang, Huayuan; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-09-01

    Although many researches have been conducted on the interaction of the cell membrane with the rigid nanoparticle (NP), relatively little is known about the interaction of the membrane with the deformable NP, which is a promising kind of drug delivery carrier. In this paper, we investigate the wrapping of a deformable NP by the membrane, with particular attention paid to the location of the NP. Phase diagrams with respect to the normalized NP-membrane adhesion strength and the bending stiffness ratio between the NP and membrane are presented. The results show that the NP is easier to be fully wrapped but harder to be shallowly wrapped when the NP locates outside than inside the vesicle. For the system with an outside NP, there are three distinct stages separated by two critical bending stiffness ratios as the NP becomes softer. Moreover, the critical normalized adhesion strength required for a deformable NP to be fully wrapped is the same as that for a rigid NP when the bending stiffness ratio is higher than a critical value, which is different from the wrapping behavior by an initially flat membrane. In addition, a larger vesicle size facilitates the full wrapping configuration when the NP is inside, whereas it prohibits it when the NP is outside. These results are consistent with the previous research and can provide guidelines for the design of drug delivery systems based on the flexibility-tunable NPs.

  1. High heterogeneity of plasma membrane microfluidity in multidrug-resistant cancer cells

    Science.gov (United States)

    Boutin, Céline; Roche, Yann; Millot, Christine; Deturche, Régis; Royer, Pascal; Manfait, Michel; Plain, Jérôme; Jeannesson, Pierre; Millot, Jean-Marc; Jaffiol, Rodolphe

    2009-05-01

    Diffusion-time distribution analysis (DDA) has been used to explore the plasma membrane fluidity of multidrug-resistant cancer cells (LR73 carcinoma cells) and also to characterize the influence of various membrane agents present in the extracellular medium. DDA is a recent single-molecule technique, based on fluorescence correlation spectroscopy (FCS), well suited to retrieve local organization of cell membrane. The method was conducted on a large number of living cells, which enabled us to get a detailed overview of plasma membrane microviscosity, and plasma membrane micro-organization, between the cells of the same line. Thus, we clearly reveal the higher heterogeneity of plasma membrane in multidrug-resistant cancer cells in comparison with the nonresistant ones (denoted sensitive cells). We also display distinct modifications related to a membrane fluidity modulator, benzyl alcohol, and two revertants of multidrug resistance, verapamil and cyclosporin-A. A relation between the distribution of the diffusion-time values and the modification of membrane lateral heterogeneities is proposed.

  2. A self-humidifying acidic-alkaline bipolar membrane fuel cell

    Science.gov (United States)

    Peng, Sikan; Xu, Xin; Lu, Shanfu; Sui, Pang-Chieh; Djilali, Ned; Xiang, Yan

    2015-12-01

    To maintain membrane hydration and operate effectively, polymer electrolyte membrane fuel cells (PEMFCs) require elaborate water management, which significantly increases the complexity and cost of the fuel cell system. Here we propose a novel and entirely different approach to membrane hydration by exploiting the concept of bipolar membranes. Bipolar membrane (BPM) fuel cells utilize a composite membrane consisting of an acidic polymer electrolyte membrane on the anode side and an alkaline electrolyte membrane on the cathode side. We present a novel membrane electrode assembly (MEA) fabrication method and demonstrate experimentally and theoretically that BPM fuel cells can (a) self-humidify to ensure high ionic conductivity; and (b) allow use of non-platinum catalysts due to inherently faster oxygen reduction kinetics on an alkaline cathode. Our Pt-based BPM fuel cell achieves a two orders of magnitude gain in power density of 327 mW cm-2 at 323 K under dry gas feed, the highest power output achieved under anhydrous operation conditions. A theoretical analysis and in situ measurements are presented to characterize the unique interfacial water generation and transport behavior that make self-humidification possible during operation. Further optimization of these features and advances in fabricating bipolar MEAs would open the way for a new generation of self-humidifying and water-management-free PEMFCs.

  3. Chitosan and alginate types of bio-membrane in fuel cell application: An overview

    Science.gov (United States)

    Shaari, N.; Kamarudin, S. K.

    2015-09-01

    The major problems of polymer electrolyte membrane fuel cell technology that need to be highlighted are fuel crossovers (e.g., methanol or hydrogen leaking across fuel cell membranes), CO poisoning, low durability, and high cost. Chitosan and alginate-based biopolymer membranes have recently been used to solve these problems with promising results. Current research in biopolymer membrane materials and systems has focused on the following: 1) the development of novel and efficient biopolymer materials; and 2) increasing the processing capacity of membrane operations. Consequently, chitosan and alginate-based biopolymers seek to enhance fuel cell performance by improving proton conductivity, membrane durability, and reducing fuel crossover and electro-osmotic drag. There are four groups of chitosan-based membranes (categorized according to their reaction and preparation): self-cross-linked and salt-complexed chitosans, chitosan-based polymer blends, chitosan/inorganic filler composites, and chitosan/polymer composites. There are only three alginate-based membranes that have been synthesized for fuel cell application. This work aims to review the state-of-the-art in the growth of chitosan and alginate-based biopolymer membranes for fuel cell applications.

  4. Liposome-based engineering of cells to package hydrophobic compounds in membrane vesicles for tumor penetration.

    Science.gov (United States)

    Lee, Junsung; Kim, Jiyoung; Jeong, Moonkyoung; Lee, Hyoungjin; Goh, Unbyeol; Kim, Hyaeyeong; Kim, Byungji; Park, Ji-Ho

    2015-05-13

    Natural membrane vesicles (MVs) derived from various types of cells play an essential role in transporting biological materials between cells. Here, we show that exogenous compounds are packaged in the MVs by engineering the parental cells via liposomes, and the MVs mediate autonomous intercellular migration of the compounds through multiple cancer cell layers. Hydrophobic compounds delivered selectively to the plasma membrane of cancer cells using synthetic membrane fusogenic liposomes were efficiently incorporated into the membrane of MVs secreted from the cells and then transferred to neighboring cells via the MVs. This liposome-mediated MV engineering strategy allowed hydrophobic photosensitizers to significantly penetrate both spheroids and in vivo tumors, thereby enhancing the therapeutic efficacy. These results suggest that innate biological transport systems can be in situ engineered via synthetic liposomes to guide the penetration of chemotherapeutics across challenging tissue barriers in solid tumors.

  5. Microfluidic device for continuous single cells analysis via Raman spectroscopy enhanced by integrated plasmonic nanodimers

    KAUST Repository

    Perozziello, Gerardo

    2015-12-11

    In this work a Raman flow cytometer is presented. It consists of a microfluidic device that takes advantages of the basic principles of Raman spectroscopy and flow cytometry. The microfluidic device integrates calibrated microfluidic channels- where the cells can flow one-by-one -, allowing single cell Raman analysis. The microfluidic channel integrates plasmonic nanodimers in a fluidic trapping region. In this way it is possible to perform Enhanced Raman Spectroscopy on single cell. These allow a label-free analysis, providing information about the biochemical content of membrane and cytoplasm of the each cell. Experiments are performed on red blood cells (RBCs), peripheral blood lymphocytes (PBLs) and myelogenous leukemia tumor cells (K562). © 2015 Optical Society of America.

  6. Control and Experimental Characterization of a Methanol Reformer for a 350 W High Temperature Polymer Electrolyte Membrane Fuel Cell system

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Jensen, Hans-Christian Becker;

    the high temperature waste gas from a cathode air cooled 45 cell HTPEM fuel cell stack. The MEAs used are BASF P2100 which use phosphoric acid doped polybenzimidazole type membranes; an MEA with high CO tolerance and no complex humidity requirements. The methanol reformer used is integrated into a compact...... and burner and the behaviour of the CO concentration of the reformate gas....... unit that allows the use of waste heat from the fuel cell stack in the reformer system, and a burner unit is also integrated to supplement provide heat using the stack anode hydrogen. The reformer is initially placed in an experimental system capable of emulating the interfaces to the fuel cell system...

  7. Life cycle assessment (LCA) methodology: importance in the integration of the fuel cell technology type PEMFC (proton exchange membrane fuel cells); Metodologia da analise de ciclo de vida: importancia na insercao da tecnologia de celula a combustivel do tipo PEMFC (membrana polimerica trocadora de protons)

    Energy Technology Data Exchange (ETDEWEB)

    Fukurozaki, Sandra Harumi; Seo, Emilia Satoshi Miyamaru [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP (Brazil)). Centro de Ciencia e Tecnologia de Materiais], e-mail: shfukuro@ipen.br

    2004-07-01

    To improve the standard of society's quality of life, it is necessary to improve the quality of distributed energy and its inherent services within a sustainability process. Among different technological routes that produce more sustainable energy are the fuel cells - also known as combustible batteries. The Global Environment Facility (GEF) has identified the fuel cells as a potential technology to reduce, in the future, the effect of greenhouse gases in both developed and developing countries. Although there are various types of fuel cells, the most used technology for research studies on fuel cells is the Polymer Electrolyte Fuel Cells (FEMFC). However, economic issues - related to the high cost of the membrane's materials and of the catalysts of groups of platinum metals - are still some of the obstacles that need to be overcome for this technology to be more accessible. There are also socio-environmental aspects related to the impacts caused by the extraction, the use and the destination of these metals. Taking in consideration the challenges of complying with the demands of the market and the society as well as with the growing tendency of more rigid patterns of environmental control, the objective of the present work is to show the tool of environmental management - Life Cycle Assessment (LCA) - and its importance on the pursuit for socio-economic and environmental alternatives feasible to the recycling of the catalysts of platinum of the PEMFC. This way, it intends to collaborate to the progress of the knowledge about environmental and socio-economic subjects related to the productive process of the PEMFC. (author)

  8. High Gain Superstrate Loaded Membrane Antenna Based on Substrate Integrated Waveguide Technology

    Directory of Open Access Journals (Sweden)

    Hamsakutty Vettikalladi

    2015-01-01

    Full Text Available The design and the results of a single slot coupled substrate integrated waveguide (SIW fed membrane antenna loaded with a superstrate layer are presented for 94 GHz communication system. The membrane antenna is designed using ANSYS HFSS and consists of 6 layers. The microstrip patch antenna (MPA placed on the top pyralux substrate layer is excited by means of a longitudinal rectangular slot placed over the SIW structure in the bottom pyralux substrate. The simulated antenna impedance bandwidth is found to be 5 GHz (91.5–96.5 GHz with a gain of 7 dBi. In order to improve the gain a superstrate layer is added above the membrane antenna. The maximum gain achieved is 14.4 dBi with an efficiency of 77.6% at 94 GHz. The results are verified using CST Microwave Studio and are found to be in good agreement.

  9. Process simulation of integrated biohydrogen production: hydrogen recovery by membrane separation

    Directory of Open Access Journals (Sweden)

    László Koók

    2014-10-01

    Full Text Available In this project, the production of biohydrogen, as a renewable and sustainable energy source was studied. Biohydrogen was manufactured by using E. coli strain in a batch dark fermentative process integrated with membrane gas separation. Two different methods were applied: Firstly, the amount of the produced gas and component concentrations were measured, but CO2 and H2 gases were not separated. In the second experiment CO2 was removed from the gas mixture via chemical sorption (reacting with NaOH. Both methods use continuous product removal in order to enhance the biohydrogen formation. In addition, process modeling was carried out with a simulation software (SuperPro Designer, Intelligen Inc. so that experimental and computational results could be compared. CO2 and H2 flow rates and fluxes were calculated on the basis of the membrane permeation data obtained by using pure gases and silicone (PDMS hollow-fiber membrane module (PermSelect – MedArray Inc..

  10. An enzymatic immunoassay microfluidics integrated with membrane valves for microsphere retention and reagent mixing.

    Science.gov (United States)

    Ren, Li; Wang, Jian-Chun; Liu, Wenming; Tu, Qin; Liu, Rui; Wang, Xueqin; Xu, Juan; Wang, Yaolei; Zhang, Yanrong; Li, Li; Wang, Jinyi

    2012-05-15

    The present study presents a new microfluidic device integrated with pneumatic microvalves and a membrane mixer for enzyme-based immunoassay of acute myocardial infarction (AMI) biomarkers, namely, myoglobin, and heart-type fatty acid binding protein (H-FABP). Superparamagnetic microspheres with carboxyl groups on their surfaces were used as antibody solid carriers. A membrane mixer consisting of four ψ-type membrane valves was assembled under the reaction chamber for on-chip performing microsphere trapping and reagent mixing. The entire immunoassay process, including microsphere capture, reagent input, mixing, and subsequent reaction, was accomplished on the device either automatically or manually. The post-reaction substrate resultant was analyzed using a microplate reader. The results show that the average absorbance value is correlated with the concentration of cardiac markers, in agreement with the results obtained using a conventional microsphere-based immunoassay; this indicated that the proposed on-chip immunoassay protocol could be used to detect both myoglobin and H-FABP. The minimum detectable concentration is 5 ng/mL for myoglobin and 1 ng/mL for H-FABP.

  11. Effects of an antibacterial membrane on osteoblast-like cells in vitro

    Directory of Open Access Journals (Sweden)

    Ye J

    2011-09-01

    Full Text Available Jun Ye1, Qianqian Yao1, Anchun Mo2, Jing Nie2, Wenwen Liu1, Cui Ye1, Xianji Chen11State Key Laboratory of Oral Diseases, 2Department of Oral Implant, West China College of Stomatology, Sichuan University, Chengdu, People's Republic of ChinaAbstract: Infection around membranes is often found in guided bone regeneration (GBR. The excellent antibacterial properties of Ag-nHA-nTiO2/polyamide-66 (PA66 nanocomposite membranes have been demonstrated previously. The aim of this study was to observe the microstructure of an Ag-nHA-nTiO2/PA66 membrane and its effects on osteoblast-like cells in vitro. An Ag-nHA-nTiO2/PA66 membrane was used in the experimental group, and both nHA/PA66 and expanded poly tetrafluroethylene (e-PTFE membranes were set as control. MG63 osteoblast-like cells were cultured on the three kinds of membrane and tissue culture polystyrene (TCP. The microstructure of the above membranes and the cells adhered on them were detected by scanning electronic microscope (SEM. Cell proliferation was determined by 3-(4,5-Dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT assay, cell viability with a cell viability analyzer, and alkaline phosphatase (ALP activity and Ca2+ concentration of osteoblast-like cell matrix by enzyme-linked immunosorbent assay. SEM showed that both Ag-nHA-nTiO2/PA66 membranes and nHA/PA66 membranes were composed of porous obverse face and smooth opposite face. The e-PTFE membranes showed elliptic surface structure with many tiny lined cracks. The MG63 cells adhered and proliferated well on all three kinds of membranes. Though cell viability on Ag-nHA-nTiO2/PA66 membranes was significantly lower than that of the control groups (P < 0.05, MTT values, ALP activity, and Ca2+ concentration did not differ significantly among the three kinds of membranes (P > 0.05. From these findings, it can be concluded that Ag-nHA-nTiO2/PA66 membranes are as biocompatible as nHA/PA66 membranes and TCP, thus may be applied safely in

  12. Modeling of durability of polyelectrolyte membrane of O2/H2 fuel cell

    CERN Document Server

    Atrazhev, Vadim V

    2014-01-01

    In this paper, we discuss critical aspects of the mechanisms and features of polymer proton exchange membrane (PEM) degradation in low-temperature H2/O2 fuel cell. In this paper, we focused on chemical mechanism of OH radical generation and their distribution in operational fuel cell. According to the current concept, free radicals are generated from hydrogen and oxygen crossover gases at the surface of Pt particles that precipitated in the membrane. We explicitly calculate Pt precipitation rate and electrochemical potential distribution in the membrane that controls it. Based on radical generation rate and Pt distribution we calculate degradation rate of the membrane taking advantage of simple kinetics equations.

  13. Static Magnetic Field Attenuates Lipopolysaccharide-Induced Inflammation in Pulp Cells by Affecting Cell Membrane Stability

    Directory of Open Access Journals (Sweden)

    Sung-Chih Hsieh

    2015-01-01

    Full Text Available One of the causes of dental pulpitis is lipopolysaccharide- (LPS- induced inflammatory response. Following pulp tissue inflammation, odontoblasts, dental pulp cells (DPCs, and dental pulp stem cells (DPSCs will activate and repair damaged tissue to maintain homeostasis. However, when LPS infection is too serious, dental repair is impossible and disease may progress to irreversible pulpitis. Therefore, the aim of this study was to examine whether static magnetic field (SMF can attenuate inflammatory response of dental pulp cells challenged with LPS. In methodology, dental pulp cells were isolated from extracted teeth. The population of DPSCs in the cultured DPCs was identified by phenotypes and multilineage differentiation. The effects of 0.4 T SMF on DPCs were observed through MTT assay and fluorescent anisotropy assay. Our results showed that the SMF exposure had no effect on surface markers or multilineage differentiation capability. However, SMF exposure increases cell viability by 15%. In addition, SMF increased cell membrane rigidity which is directly related to higher fluorescent anisotropy. In the LPS-challenged condition, DPCs treated with SMF demonstrated a higher tolerance to LPS-induced inflammatory response when compared to untreated controls. According to these results, we suggest that 0.4 T SMF attenuates LPS-induced inflammatory response to DPCs by changing cell membrane stability.

  14. p53's mitochondrial translocation and MOMP action is independent of Puma and Bax and severely disrupts mitochondrial membrane integrity

    Institute of Scientific and Technical Information of China (English)

    Sonja Wolff; Susan Erster; Gustavo Palacios; Ute M Moll

    2008-01-01

    p53's apoptotic program consists of transcription-dependent and transcription-independent pathways. In the latter, physical interactions between mitochondrial p53 and anti-and pro-apoptotic members of the Bcl2 family of mitochondrial permeability regulators are central. Using isogenic cell systems with defined deficiencies, we characterize in detail how mitochondrial p53 contributes to mitochondrial permeabilization, to what extent its action depends on other key Bcl2 family members and define its release activity. We show that mitochondrial p53 is highly efficient in inducing the release of soluble and insoluble apoptogenic factors by severely disrupting outer and inner mitochondrial membrane integrity. This action is associated with wild-type p53-induced oligomerization of Bax, Bak and VDAC and the formation of a stress-induced endogenous complex between p53 and cyclophilin D, normally located at the inner membrane. Tumor-derived p53 mutants are deficient in activating the Bax/Bak lipid pore. These actions are independent of Puma and Bax. Importantly, the latter distinguishes the mitochondrial from the cytosolic p53 death pathway.

  15. Photosensitized damage inflicted on plasma membranes of live cells by an extracellular generator of singlet oxygen--a linear dependence of a lethal dose on light intensity.

    Science.gov (United States)

    Zarębski, Mirosław; Kordon, Magdalena; Dobrucki, Jurek W

    2014-01-01

    We describe a study of the influence of a dose rate, i.e. light intensity or photon flux, on the efficiency of induction of a loss of integrity of plasma membranes of live cells in culture. The influence of a photon flux on the size of the light dose, which was capable of causing lethal effects, was measured in an experimental system where singlet oxygen was generated exclusively outside of live cells by ruthenium(II) phenantroline complex. Instantaneous, sensitive detection of a loss of integrity of a plasma membrane was achieved by fluorescence confocal imaging of the entry of this complex into a cell interior. We demonstrate that the size of the lethal dose of light is directly proportional to the intensity of the exciting light. Thus, the probability of a photon of the exciting light inflicting photosensitized damage on plasma membranes diminishes with increasing density of the incident photons. PMID:24279807

  16. Imaging lipid domains in cell membranes: the advent of super-resolution fluorescence microscopy

    Directory of Open Access Journals (Sweden)

    Dylan Myers Owen

    2013-12-01

    Full Text Available The lipid bilayer of model membranes, liposomes reconstituted from cell lipids, and plasma membrane vesicles and spheres can separate into two distinct liquid phases to yield lipid domains with liquid-ordered and liquid-disordered properties. These observations are the basis of the lipid raft hypothesis that postulates the existence of cholesterol-enriched ordered-phase lipid domains in cell membranes that could regulate protein mobility, localization and interaction. Here we review the evidence that nano-scaled lipid complexes and meso-scaled lipid domains exist in cell membranes and how new fluorescence microscopy techniques that overcome the diffraction limit provide new insights into lipid organization in cell membranes.

  17. Adhesion and receptor clustering stabilizes lateral heterogeneity in cell plasma membranes

    Science.gov (United States)

    Veatch, Sarah

    2013-03-01

    The thermodynamic properties of plasma membrane lipids play a vital role in many functions that initiate at the mammalian cell surface. Some functions are thought to occur, at least in part, because plasma membrane lipids have a tendency to separate into two distinct liquid phases, called liquid-ordered and liquid-disordered. We find that isolated cell plasma membranes are poised near a miscibility critical point separating these two liquid phases, and postulate that critical composition fluctuations provide the physical basis of functional membrane heterogeneity in intact cells. In this talk I will describe several possible mechanisms through which dynamic fluctuations can be stabilized in super-critical membranes, and will present some preliminary evidence suggesting that these structures can be visualized in intact cells using quantitative super-resolution fluorescence localization imaging.

  18. Evaluation of drug-muscarinic receptor affinities using cell membrane chromatography and radioligand binding assay in guinea pig jejunum membrane

    Institute of Scientific and Technical Information of China (English)

    Bing-xiang YUAN; Jin HOU; Lang-chong HE; Guang-de YANG

    2005-01-01

    Aim: To study if cell membrane chromatography (CMC) could reflect drug-receptor interaction and evaluate the affinity and competitive binding to muscarinic acetylcholine receptor (mAChR). Methods: The cell membrane stationary phase(CMSP) was prepared by immobilizing guinea pig jejunum cell membrane on the surface of a silica carrier, and was used for the rapid on-line chromatographic evaluation of ligand binding affinities to mAChR. The affinity to mAChR was also evaluated from radioligand binding assays (RBA) using the same jejunum membrane preparation. Results: The capacity factor (k') profiles in guinea pig jejunum CMSP were: (-)QNB (15.4)>(+)QNB (11.5)>atropine (5.35)>pirenzepine(5.26)>4-DAMP (4.45)>AF-DX 116 (4.18)>pilocarpine (3.93)>acetylcholine(1.31). These results compared with the affinity rank orders obtained from radioligand binding assays indicated that there wasa positive correlation (r2=0.8525, P<0.0001) between both data sets. Conclusion: The CMC method can be used to evaluate drug-receptor affinities for drug candidates.

  19. Vascular endothelial cell membranes differentiate between stretch and shear stress through transitions in their lipid phases.

    Science.gov (United States)

    Yamamoto, Kimiko; Ando, Joji

    2015-10-01

    Vascular endothelial cells (ECs) respond to the hemodynamic forces stretch and shear stress by altering their morphology, functions, and gene expression. However, how they sense and differentiate between these two forces has remained unknown. Here we report that the plasma membrane itself differentiates between stretch and shear stress by undergoing transitions in its lipid phases. Uniaxial stretching and hypotonic swelling increased the lipid order of human pulmonary artery EC plasma membranes, thereby causing a transition from the liquid-disordered phase to the liquid-ordered phase in some areas, along with a decrease in membrane fluidity. In contrast, shear stress decreased the membrane lipid order and increased membrane fluidity. A similar increase in lipid order occurred when the artificial lipid bilayer membranes of giant unilamellar vesicles were stretched by hypotonic swelling, indicating that this is a physical phenomenon. The cholesterol content of EC plasma membranes significantly increased in response to stretch but clearly decreased in response to shear stress. Blocking these changes in the membrane lipid order by depleting membrane cholesterol with methyl-β-cyclodextrin or by adding cholesterol resulted in a marked inhibition of the EC response specific to stretch and shear stress, i.e., phosphorylation of PDGF receptors and phosphorylation of VEGF receptors, respectively. These findings indicate that EC plasma membranes differently respond to stretch and shear stress by changing their lipid order, fluidity, and cholesterol content in opposite directions and that these changes in membrane physical properties are involved in the mechanotransduction that activates membrane receptors specific to each force.

  20. Biocompatibility Assessment of PLCL-Sericin Copolymer Membranes Using Wharton’s Jelly Mesenchymal Stem Cells

    Directory of Open Access Journals (Sweden)

    Kewalin Inthanon

    2016-01-01

    Full Text Available Stem cells based tissue engineering requires biocompatible materials, which allow the cells to adhere, expand, and differentiate in a large scale. An ideal biomaterial for clinical application should be free from mammalian products which cause immune reactivities and pathogen infections. We invented a novel biodegradable poly(L-lactic-co-ε-caprolactone-sericin (PLCL-SC copolymer membrane which was fabricated by electrospinning. Membranes with concentrations of 2.5 or 5% (w/v SC exhibited qualified texture characteristics with a noncytotoxic release profile. The hydrophilic properties of the membranes were 35–40% higher than those of a standard PLCL and commercial polystyrene (PS. The improved characteristics of the membranes were due to an addition of new functional amide groups, C=O, N–H, and C–N, onto their surfaces. Degradation of the membranes was controllable, depending on the content proportion of SC. Results of thermogram indicated the superior stability and crystallinity of the membranes. These membranes enhanced human Wharton’s jelly mesenchymal stem cells (hWJMSC proliferation by increasing cyclin A and also promoted cell adhesion by upregulating focal adhesion kinase (FAK. On the membranes, hWJMSC differentiated into a neuronal lineage with the occurrence of nestin. These data suggest that PLCL-SC electrospun membrane represents some properties which will be useful for tissue engineering and medical applications.