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Sample records for cell rbc membrane

  1. 1. Introduction 2. Red blood cell (RBC)-based

    E-print Network

    Zhang, Liangfang

    1. Introduction 2. Red blood cell (RBC)-based systems as long-circulating drug carriers 3. RBC as red blood cells to evade the immune system Ronnie Hongbo Fang, Che-Ming Jack Hu & Liangfang Zhang-circulating entities, red blood cells (RBCs). Such a system disguises drug nanocarriers as `self' using membrane

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

    PubMed

    Craiem, Damian; Magin, Richard L

    2010-01-01

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

  3. Autoantibodies against mouse bromelain-modified RBC are specifically inhibited by a common membrane phospholipid, phosphatidylcholine.

    PubMed Central

    Cox, K O; Hardy, S J

    1985-01-01

    Sera from mice injected 4 days earlier with lipopolysaccharide lysed mouse RBC treated with bromelain (brom). This lytic activity was totally inhibited by including phosphatidylcholine at final concentrations of about 2 micrograms/ml, or more, in the lytic mixtures. In contrast, the lytic activity of antibodies against rat RBC was not inhibited, even at concentrations of phosphatidylcholine up to 2.5 mg/ml. Various components of the phosphatidylcholine molecule, and other lipids including the closely-related molecule dipalmitoyl phosphatidyl-dimethyl-ethanolamine which is identical to dipalmitoyl phosphatidylcholine, except for the absence of a CH2 group on the polar head group, did not inhibit lysis by the autoantibodies. Autoantibodies against mouse brom RBC, but not antibodies against rat RBC, bound to, and could be eluted from, phosphatidylcholine molecules attached to an insoluble matrix. Liposomes of phosphatidylcholine prepared in the presence of phosphatidic acid or phosphatidylinositol did not inhibit the lysis of mouse brom RBC by autoantibodies to the same extent as liposomes of only phosphatidylcholine. This suggests that phosphatidylcholine is recognized by the autoantibodies only if presented in a certain configuration. We suggest that the function of these autoantibodies may be to facilitate the removal of membrane-damaged cells from the body. Such cells may arise by the process of ageing, or because of the effects of infectious agents such as viruses. PMID:4007927

  4. Spectrin Folding versus Unfolding Reactions and RBC Membrane Stiffness

    PubMed Central

    Zhu, Qiang; Asaro, Robert J.

    2008-01-01

    Spectrin (Sp), a key component of the erythrocyte membrane, is routinely stretched to near its fully folded contour length during cell deformations. Such dynamic loading may induce domain unfolding as suggested by recent experiments. Herein we develop a model to describe the folding/unfolding of spectrin during equilibrium or nonequilibrium extensions. In both cases, our model indicates that there exists a critical extension beyond which unfolding occurs. We further deploy this model, together with a three-dimensional model of the junctional complex in the erythrocyte membrane, to explore the effect of Sp unfolding on the membrane's mechanical properties, and on the thermal fluctuation of membrane-attached beads. At large deformations our results show a distinctive strain-induced unstiffening behavior, manifested in the slow decrease of the shear modulus, and accompanied by an increase in bead fluctuation. Bead fluctuation is also found to be influenced by mode switching, a phenomenon predicted by our three-dimensional model. The amount of stiffness reduction, however, is modest compared with that reported in experiments. A possible explanation for the discrepancy is the occurrence of spectrin head-to-head disassociation which is also included within our modeling framework and used to analyze bead motion as observed via experiment. PMID:18065469

  5. Optical rheology for live cell membranes

    E-print Network

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

    2007-01-01

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

  6. ALTERATIONS OF RBC MEMBRANE PROTEINS IN DIABETIC PATIENTS WITH AND WITHOUT PERIODONTITIS.

    PubMed

    Gabunia, T; Turabelidze-Robaqidze, S; Sujashvili, R; Ioramashvili, I; Gogebashvili, N; Sanikidze, T

    2015-11-01

    The RBC membrane is considered as a key element in their rheology. The rheological properties of RBCs significantly depend on their membranes properties - deformability. The essential contribution of integral membrane proteins in establishing/maintaining membrane stability is due to their ability to anchor the membrane skeleton to the lipid bilayer, their capacity to bind and stabilize membrane lipids, and their ability to influence and regulate local membrane curvature. The goal of the research was investigation the alterations in RBC membrane protein component in diabetic patients with or without periodontitis. We examined peripheral blood samples from type-1 diabetic patients with and without variable severity periodontitis and healthy volunteers. Freshly drawn blood samples from type 1 diabetes with and without periodontitis were obtained from the Railway Hospital (Tbilisi, Georgia). The blood samples from healthy volunteers were obtained from the the Blood Bank of the Institute of Hematology and Transfusiology (Tbilisi, Georgia). Individuals often consume alcohol addicts, pregnant women and patients with other chronic diseases were excluded from the study. The study protocol was approved by Ethical Committee of the Dabid Aghmashenebeli University of Georgia. RBCs membrane proteins have been extracted from human heparinized blood and studied by electrophoresis method. In patients with diabetes type-1 decreased of RBCs membrane low molecular weight proteins (18-22 kDa) content was detected, whereas their electrophoretic mobility (and hence their charge) does not change significantly compared to the control. In patients with diabetes type-1, suffering from periodontitis RBCs membrane low molecular weight (45-29 kDa) and high molecular weight (200, 116, 97, 55 kDa) proteins content reduced as compared with those in diabetic patients not suffering from periodontitis. In this group the electrophoretic mobility of membrane proteins reduces (especially with increasing severity of periodontitis). Reducing the negative charge (apparently caused by a decrease in the carring negative charge glycophorin C and band 3 protein content) and high molecular fraction (weight of 200, 116, 97, 55 kDa) proteins (due to a low content of Band 4.1, band 4.2, band 3 proteins, adducin and ankyrin, actively involved in the regulation of RBCs mechanical stability, deformability and shape) in RBCs membrane in patients with diabetes type-1 suffering from periodontitis, contributes to violation of RBC-RBC interactions as well disorders of their deformability and may induce adhesion of RBCs to the endothelium and disorders of blood circulation. Thus in patients with diabet-1 suffered by periodontitis alterations of the content and the mobility of RBCs membrane proteins were detected (this alterations corelated with severity of periodontitis but was not related with patients sex and age). Changes in the protein composition of the RBCs membranes promote disorder of RBCs membrane deformability and their adherence to the endothelium, pathogenetically related to the disorders of the microcirculation. So that alterations of the content and the mobility of RBCs membrane proteins may be considered as a predictor of microcirculation disturbance during periodontitis. PMID:26656549

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

    NASA Astrophysics Data System (ADS)

    Carpenter, Cody Westcott

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

  8. RBC nuclear scan

    MedlinePLUS

    An RBC nuclear scan uses small amounts of radioactive material to mark (tag) red blood cells (RBCs). Your body is then ... scanner does not give off any radiation. Most nuclear scans (including an RBC scan) are not recommended ...

  9. Diagnostic tool for red blood cell membrane disorders: Assessment of a new generation ektacytometer.

    PubMed

    Da Costa, Lydie; Suner, Ludovic; Galimand, Julie; Bonnel, Amandine; Pascreau, Tiffany; Couque, Nathalie; Fenneteau, Odile; Mohandas, Narla

    2016-01-01

    Inherited red blood cell (RBC) membrane disorders, such as hereditary spherocytosis, elliptocytosis and hereditary ovalocytosis, result from mutations in genes encoding various RBC membrane and skeletal proteins. The RBC membrane, a composite structure composed of a lipid bilayer linked to a spectrin/actin-based membrane skeleton, confers upon the RBC unique features of deformability and mechanical stability. The disease severity is primarily dependent on the extent of membrane surface area loss. RBC membrane disorders can be readily diagnosed by various laboratory approaches that include RBC cytology, flow cytometry, ektacytometry, electrophoresis of RBC membrane proteins and genetics. The reference technique for diagnosis of RBC membrane disorders is the osmotic gradient ektacytometry. However, in spite of its recognition as the reference technique, this technique is rarely used as a routine diagnosis tool for RBC membrane disorders due to its limited availability. This may soon change as a new generation of ektacytometer has been recently engineered. In this review, we describe the workflow of the samples shipped to our Hematology laboratory for RBC membrane disorder analysis and the data obtained for a large cohort of French patients presenting with RBC membrane disorders using a newly available version of the ektacytomer. PMID:26603718

  10. Podocalyxin Is a Glycoprotein Ligand of the Human Pluripotent Stem Cell-Specific Probe rBC2LCN

    PubMed Central

    Tateno, Hiroaki; Matsushima, Asako; Hiemori, Keiko; Onuma, Yasuko; Ito, Yuzuru; Hasehira, Kayo; Nishimura, Ken; Ohtaka, Manami; Takayasu, Satoko; Nakanishi, Mahito; Ikehara, Yuzuru; Nakanishi, Mio; Ohnuma, Kiyoshi; Chan, Techuan; Toyoda, Masashi; Akutsu, Hidenori; Umezawa, Akihiro; Asashima, Makoto

    2013-01-01

    In comprehensive glycome analysis with a high-density lectin microarray, we have previously shown that the recombinant N-terminal domain of the lectin BC2L-C from Burkholderia cenocepacia (rBC2LCN) binds exclusively to undifferentiated human induced pluripotent stem (iPS) cells and embryonic stem (ES) cells but not to differentiated somatic cells. Here we demonstrate that podocalyxin, a heavily glycosylated type 1 transmembrane protein, is a glycoprotein ligand of rBC2LCN on human iPS cells and ES cells. When analyzed by DNA microarray, podocalyxin was found to be highly expressed in both iPS cells and ES cells. Western and lectin blotting revealed that rBC2LCN binds to podocalyxin with a high molecular weight of more than 240 kDa in undifferentiated iPS cells of six different origins and four ES cell lines, but no binding was observed in either differentiated mouse feeder cells or somatic cells. The specific binding of rBC2LCN to podocalyxin prepared from a large set of iPS cells (138 types) and ES cells (15 types) was also confirmed using a high-throughput antibody-overlay lectin microarray. Alkaline digestion greatly reduced the binding of rBC2LCN to podocalyxin, indicating that the major glycan ligands of rBC2LCN are presented on O-glycans. Furthermore, rBC2LCN was found to exhibit significant affinity to a branched O-glycan comprising an H type 3 structure (Ka, 2.5 × 104 M?1) prepared from human 201B7 iPS cells, indicating that H type 3 is a most probable potential pluripotency marker. We conclude that podocalyxin is a glycoprotein ligand of rBC2LCN on human iPS cells and ES cells. PMID:23526252

  11. RBC Antibody Screen

    MedlinePLUS

    ... limited. Home Visit Global Sites Search Help? RBC Antibody Screen Share this page: Was this page helpful? ... Indirect Coombs Test; Indirect Anti-human Globulin Test; Antibody Screen Formal name: Red Blood Cell Antibody Screen ...

  12. Detection and characterization of red blood cell (RBC) aggregation with photoacoustics

    NASA Astrophysics Data System (ADS)

    Hysi, Eno; Saha, Ratan K.; Rui, Min; Kolios, Michael C.

    2012-02-01

    Red blood cells (RBCs) aggregate in the presence of increased plasma fibrinogen and low shear forces during blood flow. RBC aggregation has been observed in deep vein thrombosis, sepsis and diabetes. We propose using photoacoustics (PA) as a non-invasive imaging modality to detect RBC aggregation. The theoretical and experimental feasibility of PA for detecting and characterizing aggregation was assessed. A simulation study was performed to generate PA signals from non-aggregated and aggregated RBCs using a frequency domain approach and to study the PA signals' dependence on hematocrit and aggregate size. The effect of the finite bandwidth nature of transducers on the PA power spectra was also investigated. Experimental confirmation of theoretical results was conducted using porcine RBC samples exposed to 1064 nm optical wavelength using the Imagio Small Animal PA imaging system (Seno Medical Instruments, Inc., San Antonio, TX). Aggregation was induced with Dextran-70 (Sigma-Aldrich, St. Louis, MO) and the effect of hematocrit and aggregation level was investigated. The theoretical and experimental PA signal amplitude increased linearly with increasing hematocrit. The theoretical dominant frequency content of PA signals shifted towards lower frequencies (<30 MHz) and 9 dB enhancements in spectral power were observed as the size of aggregates increased compared to non-aggregating RBCs. Calibration of the PA spectra with the transducer response obtained from a 200 nm gold film was performed to remove system dependencies. Analysis of the spectral parameters from the calibrated spectra suggested that PA can assess the degree of aggregation at multiple hematocrit and aggregation levels.

  13. A classic technique... RBC begin with adult stem cells in the bone marrow that differentiate into erythroblasts.

    E-print Network

    Sniadecki, Nathan J.

    A classic technique... 1 #12;RBC begin with adult stem cells in the bone marrow that differentiate into erythroblasts. While in the bone marrow, these cells expel their nuclei and become erythrocytes (RBCs).While in the bone marrow, these cells expel their nuclei and become erythrocytes (RBCs). Their final form at rest

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

    PubMed

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

    2014-10-01

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

  15. RBC urine test

    MedlinePLUS

    Red blood cells in urine; Hematuria test; Urine - red blood cells ... A normal result is 4 red blood cells per high power field (RBC/HPF) or less when the sample is examined under a microscope. The example above is a common measurement ...

  16. Pf155/RESA protein influences the dynamic microcirculatory behavior of ring-stage Plasmodium falciparum infected red blood cells

    E-print Network

    Diez Silva, Monica

    Proteins exported by Plasmodium falciparum to the red blood cell (RBC) membrane modify the structural properties of the parasitized RBC (Pf-RBC). Although quasi-static single cell assays show reduced ring-stage Pf-RBCs ...

  17. Light scattering of human red blood cells during metabolic remodeling of membrane

    E-print Network

    Park, YongKeun

    We present the light scattering properties of individual human red blood cells (RBCs). We show that both the RBC static and dynamic scattering signals are altered by adenosine 5’-triphosphate (ATP)-driven membrane metabolic ...

  18. Large Deformation Properties of Red Blood Cell Membrane Based on a Higher Order Gradient Quasi-continuum Model.

    PubMed

    Wang, X Y; Wang, J B; Qiu, B B; Hu, L F

    2015-12-01

    Based on the proposed higher order gradient quasi-continuum model, the numerical investigations of the basic mechanical properties and deformation behaviors of human red blood cell (RBC) membrane under large deformation at room temperature (i.e., 300 K) are carried out in the present paper. The results show that RBC membrane is a nonlinear hyperelastic material. The mechanical properties of RBC membrane is dominated by isotropic nature at the stage of initial deformation, however, its anisotropic material properties emerge clearly with the loading increasing. The out-of-plane wrinkling of RBC membrane upon shear loading can be reproduced numerically. With the use of the so-called higher order Cauchy-Born rule as the kinematic description, the bending stiffness of RBC membrane can be considered conveniently. PMID:25972107

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  20. Tissue distribution of blood group membrane proteins beyond red cells: evidence from cDNA libraries.

    PubMed

    Rojewski, Markus T; Schrezenmeier, Hubert; Flegel, Willy A

    2006-08-01

    The proteins of blood group systems are expressed on red blood cells (RBC) by definition. We searched nucleotide databases of human expressed sequence tags (EST) to collate the distribution of 22 distinct membrane proteins in cells and tissues other than RBC. The documented blood group genes are: MNS, Rh, Lutheran, Kell, Duffy, Kidd, Diego, Yt, Xg, Scianna, Dombrock, Colton, Landsteiner-Wiener, Kx, Gerbich, Cromer, Knops, Indian, Ok, Raph, John-Milton-Hagen and Gill. The genes were grouped according to their overall and their relative expression in embryo and adults. We describe the distribution of EST in cells, tissues and cell lines with a focus on non-RBC tissues. PMID:16956794

  1. RBC indices

    MedlinePLUS

    ... hemoglobin concentration (MCHC); Mean corpuscular volume (MCV); Red blood cell indices ... hemoglobin. The MCV reflects the size of red blood cells. The MCH and MCHC reflect the hemoglobin content ...

  2. Transformation of membrane nanosurface of red blood cells under hemin action

    PubMed Central

    Kozlova, Elena; Chernysh, Alexander; Moroz, Victor; Gudkova, Olga; Sergunova, Victoria; Kuzovlev, Artem

    2014-01-01

    Hemin is the product of hemoglobin oxidation. Some diseases may lead to a formation of hemin. The accumulation of hemin causes destruction of red blood cells (RBC) membranes. In this study the process of development of topological defects of RBC membranes within the size range from nanoscale to microscale levels is shown. The formation of the grain-like structures in the membrane (“grains”) with typical sizes of 120–200?nm was experimentally shown. The process of formation of “grains” was dependent on the hemin concentration and incubation time. The possible mechanism of membrane nanostructure alterations is proposed. The kinetic equations of formation and transformation of small and medium topological defects were analyzed. This research can be used to study the cell intoxication and analyze the action of various agents on RBC membranes. PMID:25112597

  3. Transformation of membrane nanosurface of red blood cells under hemin action

    NASA Astrophysics Data System (ADS)

    Kozlova, Elena; Chernysh, Alexander; Moroz, Victor; Gudkova, Olga; Sergunova, Victoria; Kuzovlev, Artem

    2014-08-01

    Hemin is the product of hemoglobin oxidation. Some diseases may lead to a formation of hemin. The accumulation of hemin causes destruction of red blood cells (RBC) membranes. In this study the process of development of topological defects of RBC membranes within the size range from nanoscale to microscale levels is shown. The formation of the grain-like structures in the membrane (``grains'') with typical sizes of 120-200 nm was experimentally shown. The process of formation of ``grains'' was dependent on the hemin concentration and incubation time. The possible mechanism of membrane nanostructure alterations is proposed. The kinetic equations of formation and transformation of small and medium topological defects were analyzed. This research can be used to study the cell intoxication and analyze the action of various agents on RBC membranes.

  4. Composite fuel cell membranes

    DOEpatents

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

    1997-08-05

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

  5. Composite fuel cell membranes

    DOEpatents

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

    1997-01-01

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

  6. Plant cell membranes

    SciTech Connect

    Packer, L.; Douce, R.

    1987-01-01

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

  7. Dynamic actin filaments control the mechanical behavior of the human red blood cell membrane

    PubMed Central

    Gokhin, David S.; Nowak, Roberta B.; Khoory, Joseph A.; de la Piedra, Alfonso; Ghiran, Ionita C.; Fowler, Velia M.

    2015-01-01

    Short, uniform-length actin filaments function as structural nodes in the spectrin-actin membrane skeleton to optimize the biomechanical properties of red blood cells (RBCs). Despite the widespread assumption that RBC actin filaments are not dynamic (i.e., do not exchange subunits with G-actin in the cytosol), this assumption has never been rigorously tested. Here we show that a subpopulation of human RBC actin filaments is indeed dynamic, based on rhodamine-actin incorporation into filaments in resealed ghosts and fluorescence recovery after photobleaching (FRAP) analysis of actin filament mobility in intact RBCs (?25–30% of total filaments). Cytochalasin-D inhibition of barbed-end exchange reduces rhodamine-actin incorporation and partially attenuates FRAP recovery, indicating functional interaction between actin subunit turnover at the single-filament level and mobility at the membrane-skeleton level. Moreover, perturbation of RBC actin filament assembly/disassembly with latrunculin-A or jasplakinolide induces an approximately twofold increase or ?60% decrease, respectively, in soluble actin, resulting in altered membrane deformability, as determined by alterations in RBC transit time in a microfluidic channel assay, as well as by abnormalities in spontaneous membrane oscillations (flickering). These experiments identify a heretofore-unrecognized but functionally important subpopulation of RBC actin filaments, whose properties and architecture directly control the biomechanical properties of the RBC membrane. PMID:25717184

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  9. Membrane in cancer cells

    SciTech Connect

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

    1988-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Morss, Andrew J.

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

  11. Membrane Cells for Brine Electrolysis.

    ERIC Educational Resources Information Center

    Tingle, M.

    1982-01-01

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

  12. IgG red blood cell autoantibodies in autoimmune hemolytic anemia bind to epitopes on red blood cell membrane band 3 glycoprotein

    SciTech Connect

    Victoria, E.J.; Pierce, S.W.; Branks, M.J.; Masouredis, S.P. )

    1990-01-01

    Red blood cell (RBC) autoantibodies from patients with IgG warm-type autoimmune hemolytic anemia were labeled with iodine 125 and their RBC binding behavior characterized. Epitope-bearing RBC membrane polypeptides were identified after autoantibody immunoprecipitation of labeled membranes and immunoblotting. Immunoaffinity isolation of labeled membrane proteins with 12 different IgG hemolytic autoantibodies with protein A-agarose revealed a major polypeptide at Mr 95 to 110 kd, which coelectrophoresed on sodium dodecylsulfate-polyacrylamide gel electrophoresis with a membrane component isolated with sheep IgG anti-band 3. Immunoprecipitation studies with chymotrypsinized RBCs resulted in the recovery of two labeled membrane polypeptides with molecular weights characteristically resulting from the chymotryptic fragmentation of band 3. Immunoblotting with sheep IgG anti-band 3 of the immunoprecipitated polypeptides confirmed that hemolytic autoantibody binding led to recovery of band 3 or its fragments. Two 125I-labeled IgG hemolytic autoantibodies showed binding behavior consistent with epitope localization on band 3. The labeled RBC autoantibodies bound immunospecifically to all types of human RBC tested, including those of rare Rh type (Rh-null, D--) at a site density of approximately 10(6) per RBC. The 125I-IgG in two labeled autoantibodies was 84% and 92% adsorbable by human and higher nonhuman primate RBCs. Antigen-negative animal RBC bound less than 10%, consistent with immunospecific RBC binding. IgG-1 was the major subclass in five autoantibodies tested; one of six fixed complement; and autoantibody IgG appeared polyclonal by isoelectric focusing. We conclude that IgG eluted from RBCs of patients with autoimmune hemolytic anemia consists predominantly of a single totally RBC-adsorbable antibody population that binds to antigenic determinants on band 3.

  13. Rheological properties of RBC in the microcirculation of mammalian skeletal muscle. [red blood cells

    NASA Technical Reports Server (NTRS)

    Ehrenberg, M. H.

    1974-01-01

    In the investigation the established technique of direct microscopic viewing was combined with the use of a closed circuit television system and cinematography. The red cell flow patterns in all capillaries were found to be oscillatory with characteristic cycle frequencies and amplitudes for all concentrations of inspired oxygen greater than 8%. Generally, there was a transient decrease in mean flow rate with increasing severity of hypoxia, with a gradual return toward control values. Red cell flow patterns are discussed along with questions of red cell configuration.

  14. Fuel cell membrane humidification

    DOEpatents

    Wilson, Mahlon S. (Los Alamos, NM)

    1999-01-01

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

  15. RBC deformability and amino acid concentrations after hypo-osmotic challenge may reflect chronic cell hydration status in healthy young men

    PubMed Central

    Stookey, Jodi D; Klein, Alexis; Hamer, Janice; Chi, Christine; Higa, Annie; Ng, Vivian; Arieff, Allen; Kuypers, Frans A; Larkin, Sandra; Perrier, Erica; Lang, Florian

    2013-01-01

    Biomarkers of chronic cell hydration status are needed to determine whether chronic hyperosmotic stress increases chronic disease risk in population-representative samples. In vitro, cells adapt to chronic hyperosmotic stress by upregulating protein breakdown to counter the osmotic gradient with higher intracellular amino acid concentrations. If cells are subsequently exposed to hypo-osmotic conditions, the adaptation results in excess cell swelling and/or efflux of free amino acids. This study explored whether increased red blood cell (RBC) swelling and/or plasma or urine amino acid concentrations after hypo-osmotic challenge might be informative about relative chronic hyperosmotic stress in free-living men. Five healthy men (20–25 years) with baseline total water intake below 2 L/day participated in an 8-week clinical study: four 2-week periods in a U-shaped A-B-C-A design. Intake of drinking water was increased by +0.8 ± 0.3 L/day in period 2, and +1.5 ± 0.3 L/day in period 3, and returned to baseline intake (0.4 ± 0.2 L/day) in period 4. Each week, fasting blood and urine were collected after a 750 mL bolus of drinking water, following overnight water restriction. The periods of higher water intake were associated with significant decreases in RBC deformability (index of cell swelling), plasma histidine, urine arginine, and urine glutamic acid. After 4 weeks of higher water intake, four out of five participants had ½ maximal RBC deformability below 400 mmol/kg; plasma histidine below 100 ?mol/L; and/or undetectable urine arginine and urine glutamic acid concentrations. Work is warranted to pursue RBC deformability and amino acid concentrations after hypo-osmotic challenge as possible biomarkers of chronic cell hydration. PMID:24303184

  16. Red Blood Cell Membrane as a Biomimetic Nanocoating for Prolonged Circulation Time and Reduced Accelerated Blood Clearance.

    PubMed

    Rao, Lang; Bu, Lin-Lin; Xu, Jun-Hua; Cai, Bo; Yu, Guang-Tao; Yu, Xiaolei; He, Zhaobo; Huang, Qinqin; Li, Andrew; Guo, Shi-Shang; Zhang, Wen-Feng; Liu, Wei; Sun, Zhi-Jun; Wang, Hao; Wang, Tza-Huei; Zhao, Xing-Zhong

    2015-12-01

    For decades, poly(ethylene glycol) (PEG) has been widely incorporated into nanoparticles for evading immune clearance and improving the systematic circulation time. However, recent studies have reported a phenomenon known as "accelerated blood clearance (ABC)" where a second dose of PEGylated nanomaterials is rapidly cleared when given several days after the first dose. Herein, we demonstrate that natural red blood cell (RBC) membrane is a superior alternative to PEG. Biomimetic RBC membrane-coated Fe3 O4 nanoparticles (Fe3 O4 @RBC NPs) rely on CD47, which is a "don't eat me" marker on the RBC surface, to escape immune clearance through interactions with the signal regulatory protein-alpha (SIRP-?) receptor. Fe3 O4 @RBC NPs exhibit extended circulation time and show little change between the first and second doses, with no ABC suffered. In addition, the administration of Fe3 O4 @RBC NPs does not elicit immune responses on neither the cellular level (myeloid-derived suppressor cells (MDSCs)) nor the humoral level (immunoglobulin M and G (IgM and IgG)). Finally, the in vivo toxicity of these cell membrane-camouflaged nanoparticles is systematically investigated by blood biochemistry, hematology testing, and histology analysis. These findings are significant advancements toward solving the long-existing clinical challenges of developing biomaterials that are able to resist both immune response and rapid clearance. PMID:26488923

  17. The First Cell Membranes

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  18. The First Cell Membranes

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  19. Two-dimensional strain-hardening membrane model for large deformation behavior of multiple red blood cells in high shear conditions

    PubMed Central

    2014-01-01

    Background Computational modeling of Red Blood Cell (RBC) flow contributes to the fundamental understanding of microhemodynamics and microcirculation. In order to construct theoretical RBC models, experimental studies on single RBC mechanics have presented a material description for RBC membranes based on their membrane shear, bending and area moduli. These properties have been directly employed in 3D continuum models of RBCs but practical flow analysis with 3D models have been limited by their computationally expensive nature. As such, various researchers have employed 2D models to efficiently and qualitatively study microvessel flows. Currently, the representation of RBC dynamics using 2D models is a limited methodology that breaks down at high shear rates due to excessive and unrealistic stretching. Methods We propose a localized scaling of the 2D elastic moduli such that it increases with RBC local membrane strain, thereby accounting for effects such as the Poisson effect and membrane local area incompressibility lost in the 2D simplification. Validation of our 2D Large Deformation (2D-LD) RBC model was achieved by comparing the predicted RBC deformation against the 3D model from literature for the case of a single RBC in simple shear flow under various shear rates (dimensionless shear rate G?=?0.05, 0.1, 0.2, 0.5). The multi-cell flow of RBCs (38% Hematocrit) in a 20 ?m width microchannel under varying shear rates (50, 150, 150 s-1) was then simulated with our proposed model and the popularly-employed 2D neo-Hookean model in order to evaluate the efficacy of our proposed 2D-LD model. Results The validation set indicated similar RBC deformation for both the 2D-LD and the 3D models across the studied shear rates, highlighting the robustness of our model. The multi-cell simulation indicated that the 2D neo-Hookean model predicts noodle-like RBC shapes at high shear rates (G?=?0.5) whereas our 2D-LD model maintains sensible RBC deformations. Conclusion The ability of the 2D-LD model to limit RBC strain even at high shear rates enables this proposed model to be employed in practical simulations of high shear rate microfluidic flows such as blood separation channels. PMID:24885482

  20. Fuel cell with ionization membrane

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T. (Inventor)

    2007-01-01

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

  1. Evaluation of Red Cell Membrane Cytoskeletal Disorders Using a Flow Cytometric Method in South Iran

    PubMed Central

    Golafshan, Habib Alah; Ranjbaran, Reza; Kalantari, Tahereh; Moezzi, Leili; Karimi, Mehran; Behzad- Behbahani, Abbas; Aboualizadeh, Farzaneh; Sharifzadeh, Sedigheh

    2014-01-01

    Objective: The diagnosis of hereditary red blood cell (RBC) membrane disorders, and in particular hereditary spherocytosis (HS) and Southeast Asian ovalocytosis (SAO), is based on clinical history, RBC morphology, and other conventional tests such as osmotic fragility. However, there are some milder cases of these disorders that are difficult to diagnose. The application of eosin-5’-maleimide (EMA) was evaluated for screening of RBC membrane defects along with some other anemias. We used EMA dye, which binds mostly to band 3 protein and to a lesser extent some other membrane proteins, for screening of some membrane defects such as HS. Materials and Methods: Fresh RBCs from hematologically normal controls and patients with HS, SAO, hereditary elliptocytosis, hereditary spherocytosis with pincered cells, severe iron deficiency, thalassemia minor, and autoimmune hemolytic anemia were stained with EMA dye and analyzed for mean fluorescent intensity (MFI) using a flow cytometer. Results: RBCs from patients with HS and iron deficiency showed a significant reduction in MFI compared to those from normal controls (p<0.0001 and p<0.001, respectively), while macrocytic RBCs showed a significant increase in MFI (p<0.01). A significant correlation was shown between mean corpuscular volume and MFI, with the exceptions of HS and thalassemia minor. Conclusion: Our results showed that the flow cytometric method could be a reliable diagnostic method for screening and confirmation, with higher sensitivity and specificity (95% and 93%, respectively) than conventional routine tests for HS patients prior to further specific membrane protein molecular tests. PMID:24764726

  2. The Molecules of the Cell Membrane.

    ERIC Educational Resources Information Center

    Bretscher, Mark S.

    1985-01-01

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

  3. Factors Influencing RBC Alloimmunization: Lessons Learned from Murine Models

    PubMed Central

    Ryder, Alex B.; Zimring, James C.; Hendrickson, Jeanne E.

    2014-01-01

    Summary Red blood cell (RBC) alloimmunization may occur following transfusion or pregnancy/delivery. Although observational human studies have described the immunogenicity of RBC antigens and the clinical significance of RBC alloantibodies, studies of factors influencing RBC alloimmunization in humans are inherently limited by the large number of independent variables involved. This manuscript reviews data generated in murine models that utilize transgenic donor mice, which express RBC-specific model or authentic human blood group antigens. Transfusion of RBCs from such donors into nontransgenic but otherwise genetically identical recipient mice allows for the investigation of individual donor or recipient-specific variables that may impact RBC alloimmunization. Potential donor-related variables include methods of blood product collection, processing and storage, donor-specific characteristics, RBC antigen-specific factors, and others. Potential recipient-related variables include genetic factors (MHC/HLA type and polymorphisms of immunoregulatory genes), immune activation status, phenotype of regulatory immune cell subsets, immune cell functional characteristics, prior antigen exposures, and others. Although murine models are not perfect surrogates for human biology, these models generate phenomenological and mechanistic hypotheses of RBC alloimmunization and lay the groundwork for follow-up human studies. Long-term goals include improving transfusion safety and minimizing the morbidity/mortality associated with RBC alloimmunization. PMID:25670928

  4. Responses of red blood cell-membrane systems: temperature and calcium effects on volume, deformability, and osmotic fragility as studied by resistive pulse spectroscopy

    SciTech Connect

    Richieri, G.V.

    1984-04-01

    The effects exerted by temperature and calcium on red blood cells were studied using resistive pulse spectroscopy (RPS). A new RPS protocol is presented which enables cell volume and shape to be determined more accurately than previously possible. Repair processes of the RBC membrane following osmotic hemolysis were examined. 140 references, 44 figures, 6 tables.

  5. RBC micromotors carrying multiple cargos towards potential theranostic applications

    NASA Astrophysics Data System (ADS)

    Wu, Zhiguang; Esteban-Fernández de Ávila, Berta; Martín, Aída; Christianson, Caleb; Gao, Weiwei; Thamphiwatana, Soracha Kun; Escarpa, Alberto; He, Qiang; Zhang, Liangfang; Wang, Joseph

    2015-08-01

    Red blood cell (RBC)-based micromotors containing both therapeutic and diagnostic modalities are described as a means for potential theranostic applications. In this natural RBC-based multicargo-loaded micromotor system, quantum dots (QDs), anti-cancer drug doxorubicin (DOX), and magnetic nanoparticles (MNPs), were co-encapsulated into RBC micromotors. The fluorescent emission of both QDs and DOX provides direct visualization of their loading inside the RBC motors at two distinct wavelengths. The presence of MNPs within the RBCs allows for efficient magnetic guidance under ultrasound propulsion along with providing the potential for magnetic resonance imaging. The simultaneous encapsulation of the imaging nanoparticles and therapeutic payloads within the same RBC micromotor has a minimal effect upon its propulsion behavior. The ability of the RBC micromotors to transport imaging and therapeutic agents at high speed and spatial precision through a complex microchannel network is also demonstrated. Such ability to load and transport diagnostic imaging agents and therapeutic drugs within a single cell-based motor, in addition to a lower toxicity observed once the drug is encapsulated within the multicargo RBC motor, opens the door to the development of theranostic micromotors that may simultaneously treat and monitor diseases.Red blood cell (RBC)-based micromotors containing both therapeutic and diagnostic modalities are described as a means for potential theranostic applications. In this natural RBC-based multicargo-loaded micromotor system, quantum dots (QDs), anti-cancer drug doxorubicin (DOX), and magnetic nanoparticles (MNPs), were co-encapsulated into RBC micromotors. The fluorescent emission of both QDs and DOX provides direct visualization of their loading inside the RBC motors at two distinct wavelengths. The presence of MNPs within the RBCs allows for efficient magnetic guidance under ultrasound propulsion along with providing the potential for magnetic resonance imaging. The simultaneous encapsulation of the imaging nanoparticles and therapeutic payloads within the same RBC micromotor has a minimal effect upon its propulsion behavior. The ability of the RBC micromotors to transport imaging and therapeutic agents at high speed and spatial precision through a complex microchannel network is also demonstrated. Such ability to load and transport diagnostic imaging agents and therapeutic drugs within a single cell-based motor, in addition to a lower toxicity observed once the drug is encapsulated within the multicargo RBC motor, opens the door to the development of theranostic micromotors that may simultaneously treat and monitor diseases. Electronic supplementary information (ESI) available: Videos of the propulsion of the multicargo-loaded, RBC-based micromotors and more data are available in the ESI. See DOI: 10.1039/c5nr03730a

  6. Dielectric Breakdown of Cell Membranes

    PubMed Central

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

    1974-01-01

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

  7. Metabolic remodeling of the human red blood cell membrane

    E-print Network

    Suresh, Subra

    The remarkable deformability of the human red blood cell (RBC) results from the coupled dynamic response of the phospholipid bilayer and the spectrin molecular network. Here we present quantitative connections between ...

  8. Corrugated Membrane Fuel Cell Structures

    SciTech Connect

    Grot, Stephen President, Ion Power Inc.

    2013-09-30

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

  9. Influence of a hyperlipidic diet on the composition of the non-membrane lipid pool of red blood cells of male and female rats

    PubMed Central

    Remesar, Xavier; Antelo, Arantxa; Llivina, Clàudia; Albà, Emma; Berdié, Lourdes; Agnelli, Silvia; Arriarán, Sofía; Fernández-López, José Antonio

    2015-01-01

    Background and objectives. Red blood cells (RBC) are continuously exposed to oxidative agents, affecting their membrane lipid function. However, the amount of lipid in RBCs is higher than the lipids of the cell membrane, and includes triacylglycerols, which are no membrane components. We assumed that the extra lipids originated from lipoproteins attached to the cell surface, and we intended to analyse whether the size and composition of this lipid pool were affected by sex or diet. Experimental design. Adult male and female Wistar rats were fed control or cafeteria diets. Packed blood cells and plasma lipids were extracted and analysed for fatty acids by methylation and GC-MS, taking care of not extracting membrane lipids. Results. The absence of ?3-PUFA in RBC extracts (but not in plasma) suggest that the lipids extracted were essentially those in the postulated lipid surface pool and not those in cell membrane. In cells’ extracts, there was a marked depletion of PUFA (and, in general, of insaturation). Fatty acid patterns were similar for all groups studied, with limited effects of sex and no effects of diet in RBC (but not in plasma) fatty acids. Presence of trans fatty acids was small but higher in RBC lipids, and could not be justified by dietary sources. Conclusions. The presence of a small layer of lipid on the RBC surface may limit oxidative damage to the cell outer structures, and help explain its role in the transport of lipophilic compounds. However, there may be other, so far uncovered, additional functions for this lipid pool. PMID:26213652

  10. Cell handling using microstructured membranes

    PubMed Central

    Irimia, Daniel

    2013-01-01

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

  11. Marathon Running Fails to Influence RBC Survival Rates in Iron-Replete Women.

    ERIC Educational Resources Information Center

    Steenkamp, Irene; And Others

    1986-01-01

    This study used radiolabeling to measure red blood cell (RBC) survival rates in six iron-replete female marathon runners, and urinary tests were conducted to search for secondary evidence of RBC damage. The hypothesized RBC fragmentation was not disclosed. (Author/MT)

  12. Marked increase in rat red blood cell membrane protein glycosylation by one-month treatment with a cafeteria diet

    PubMed Central

    Oliva, Laia; Baron, Cristian; Fernández-López, José-Antonio; Remesar, Xavier

    2015-01-01

    Background and Objectives. Glucose, an aldose, spontaneously reacts with protein amino acids yielding glycosylated proteins. The compounds may reorganize to produce advanced glycosylation products, which regulatory importance is increasingly being recognized. Protein glycosylation is produced without the direct intervention of enzymes and results in the loss of function. Glycosylated plasma albumin, and glycosylated haemoglobin are currently used as index of mean plasma glucose levels, since higher glucose availability results in higher glycosylation rates. In this study we intended to detect the early changes in blood protein glycosylation elicited by an obesogenic diet. Experimental Design. Since albumin is in constant direct contact with plasma glucose, as are the red blood cell (RBC) membranes, we analyzed their degree or glycosylation in female and male rats, either fed a standard diet or subjected to a hyper-energetic self-selected cafeteria diet for 30 days. This model produces a small increase in basal glycaemia and a significant increase in body fat, leaving the animals in the initial stages of development of metabolic syndrome. We also measured the degree of glycosylation of hemoglobin, and the concentration of glucose in contact with this protein, that within the RBC. Glycosylation was measured by colorimetric estimation of the hydroxymethylfurfural liberated from glycosyl residues by incubation with oxalate. Results. Plasma glucose was higher in cafeteria diet and in male rats, both independent effects. However, there were no significant differences induced by sex or diet in either hemoglobin or plasma proteins. Purified RBC membranes showed a marked effect of diet: higher glycosylation in cafeteria rats, which was more marked in females (not in controls). In any case, the number of glycosyl residues per molecule were higher in hemoglobin than in plasma proteins (after correction for molecular weight). The detected levels of glucose in RBC were lower than those of plasma, even when expressed in molal units, and were practically nil in cafeteria-diet fed rats compared with controls; there was no effect of sex. Conclusions. RBC membrane glycosylation is a sensitive indicator of developing metabolic syndrome-related hyperglycemia, more sensitive than the general measurement of plasma or RBC protein glycosylation. The extensive glycosylation of blood proteins does not seem to be markedly affected by sex; and could be hardly justified from an assumedly sustained plasma hyperglycemia. The low levels of glucose found within RBC, especially in rats under the cafeteria diet, could hardly justify the extensive glycosylation of hemoglobin and the lack of differences with controls, which contained sizeable levels of intracellular glucose. Additional studies are needed to study the dynamics of glucose in vivo in the RBC to understand how such extensive protein glycosylation could take place. PMID:26213657

  13. Defected red blood cell membranes and direct correlation with the uraemic milieu: the connection with the decreased red blood cell lifespan observed in haemodialysis patients

    NASA Astrophysics Data System (ADS)

    Stamopoulos, D.; Grapsa, E.; Manios, E.; Gogola, V.; Bakirtzi, N.

    2012-12-01

    Together with impaired production of erythropoietin and iron deficiency, the decreased lifespan of red blood cells (RBCs) is a main factor contributing to the chronic anaemia observed in haemodialysis (HD) patients. Atomic force microscopy is employed in this work to thoroughly survey the membrane of intact RBCs (iRBCs) of HD patients in comparison to those of healthy donors, aiming to obtain direct information on the structural status of RBCs that can be related to their decreased lifespan. We observed that the iRBC membrane of the HD patients is overpopulated with extended circular defects, termed ‘orifices’, that have typical dimension ranging between 0.2 and 1.0 ?m. The ‘orifice’ index—that is, the mean population of ‘orifices’ per top membrane surface—exhibits a pronounced relative increase of order 54 ± 12% for the HD patients as compared to healthy donors. Interestingly, for the HD patients, the ‘orifice’ index, which relates to the structural status of the RBC membrane, correlates strongly with urea concentration, which is a basic index of the uraemic milieu. Thus, these results indicate that the uraemic milieu downgrades the structural status of the RBC membrane, possibly triggering biochemical processes that result in their premature elimination from the circulation. This process could decrease the lifespan of RBCs, as observed in HD patients.

  14. Lateral organization of membranes and cell shapes.

    PubMed Central

    Markin, V S

    1981-01-01

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

  15. Following-up changes in red blood cell deformability and membrane stability in the presence of PTFE graft implanted into the femoral artery in a canine model

    NASA Astrophysics Data System (ADS)

    Toth, Csaba; Kiss, Ferenc; Klarik, Zoltan; Gergely, Eszter; Toth, Eniko; Peto, Katalin; Vanyolos, Erzsebet; Miko, Iren; Nemeth, Norbert

    2014-05-01

    It is known that a moderate mechanical stress can even improve the red blood cells' (RBC) micro-rheological characteristics, however, a more significant stress causes deterioration in the deformability. In this study, we aimed to investigate the effect of the presence of artificial graft on the RBC deformability and membrane stability in beagles. In the Control group only anesthesia was induced and in the postoperative (p.o.) period blood samplings were carried out. In the Grafted group under general anesthesia, the left femoral artery was isolated, from which a 3.5 cm segment was resected and a PTFE graft (O.D.: 3 mm) of equal in length was implanted into the gap. On the 1st, 3rd, 5th, 7th and 14th p.o. days blood was collected the cephalic veins and RBC deformability was determined ektacytometry (LoRRca MaxSis Osmoscan). Membrane stability test consisted of two deformability measurements before and after the cells were being exposed to mechanical stress (60 or 100 Pa for 300 seconds). Compared to the Control group and the baseline values the red blood cell deformability showed significant deterioration on the 3rd, 5th and mainly on the 7th postoperative day after the graft implantation. The membrane stability of erythrocyte revealed marked inter-group difference on the 3rd, 5th and 7th day: in the Grafted group the deformability decreased and during the membrane stability test smaller difference was observed between the states before and after shearing. We concluded that the presence of a PTFE graft in the femoral artery may cause changes in RBC deformability in the first p.o. week. RBC membrane stability investigation shows a lower elongation index profile for the grafted group and a narrowed alteration in the deformability curves due to mechanical stress.

  16. Prolongation of RBC survival in the hypophysectomized rat.

    NASA Technical Reports Server (NTRS)

    Landaw, S. A.; Bristol, S. K.

    1971-01-01

    Red blood cell (RBC) survival was prolonged in hypophysectomized rats. While the rate of random hemolysis was decreased in some hypophysectomized hosts, in all directly injected and cross-transfused hypophysectomized rat hosts, there was a significant prolongation of the phase of senescent death. In contrast, RBCs from hypophysectomized donors survived normally in normal hosts. These experiments are further evidence of a relationship between RBC aging and metabolic rate, and suggest an intimate involvement with the calorigenic hormones.

  17. General coarse-grained red blood cell models: I. Mechanics

    E-print Network

    Dmitry A. Fedosov; Bruce Caswell; George E. Karniadakis

    2009-05-01

    We present a rigorous procedure to derive coarse-grained red blood cell (RBC) models, which lead to accurate mechanical properties of realistic RBCs. Based on a semi-analytic theory linear and non-linear elastic properties of the RBC membrane can be matched with those obtained in optical tweezers stretching experiments. In addition, we develop a nearly stress-free model which avoids a number of pitfalls of existing RBC models, such as non-biconcave equilibrium shape and dependence of RBC mechanical properties on the triangulation quality. The proposed RBC model is suitable for use in many existing numerical methods, such as Lattice Boltzmann, Multiparticle Collision Dynamics, Immersed Boundary, etc.

  18. Actinide transport across cell membranes.

    PubMed

    Bulman, R A; Griffin, R J

    1980-01-01

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

  19. A membrane reservoir at the cell surface

    PubMed Central

    Figard, Lauren; Sokac, Anna Marie

    2014-01-01

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

  20. Kinetics of Influenza Hemagglutinin-Mediated Membrane Fusion as a Function of Technique

    E-print Network

    Mittal, Aditya

    - quenching in a cuvette with a suspension of RBC/HA- cell complexes; (2) video fluorescence microscopy (VFM in the cuvette was much slower, i.e., it monitors a much later stage of dye redistribution. Membrane fusion

  1. Polymer electrolyte membrane assembly for fuel cells

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  2. Polymer electrolyte membrane assembly for fuel cells

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  3. Elastic behavior of a red blood cell with the membrane's nonuniform natural state: equilibrium shape, motion transition under shear flow, and elongation during tank-treading motion.

    PubMed

    Tsubota, Ken-Ichi; Wada, Shigeo; Liu, Hao

    2014-08-01

    Direct numerical simulations of the mechanics of a single red blood cell (RBC) were performed by considering the nonuniform natural state of the elastic membrane. A RBC was modeled as an incompressible viscous fluid encapsulated by an elastic membrane. The in-plane shear and area dilatation deformations of the membrane were modeled by Skalak constitutive equation, while out-of-plane bending deformation was formulated by the spring model. The natural state of the membrane with respect to in-plane shear deformation was modeled as a sphere ([Formula: see text]), biconcave disk shape ([Formula: see text]) and their intermediate shapes ([Formula: see text]) with the nonuniformity parameter [Formula: see text], while the natural state with respect to out-of-plane bending deformation was modeled as a flat plane. According to the numerical simulations, at an experimentally measured in-plane shear modulus of [Formula: see text] and an out-of-plane bending rigidity of [Formula: see text] of the cell membrane, the following results were obtained. (i) The RBC shape at equilibrium was biconcave discoid for [Formula: see text] and cupped otherwise; (ii) the experimentally measured fluid shear stress at the transition between tumbling and tank-treading motions under shear flow was reproduced for [Formula: see text]; (iii) the elongation deformation of the RBC during tank-treading motion from the simulation was consistent with that from in vitro experiments, irrespective of the [Formula: see text] value. Based on our RBC modeling, the three phenomena (i), (ii), and (iii) were mechanically consistent for [Formula: see text]. The condition [Formula: see text] precludes a biconcave discoid shape at equilibrium (i); however, it gives appropriate fluid shear stress at the motion transition under shear flow (ii), suggesting that a combined effect of [Formula: see text] and the natural state with respect to out-of-plane bending deformation is necessary for understanding details of the RBC mechanics at equilibrium. Our numerical results demonstrate that moderate nonuniformity in a membrane's natural state with respect to in-plane shear deformation plays a key role in RBC mechanics. PMID:24104211

  4. Advanced composite polymer electrolyte fuel cell membranes

    SciTech Connect

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

    1995-09-01

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

  5. Fuel cell ion-exchange membrane investigation

    NASA Technical Reports Server (NTRS)

    Toy, M. S.

    1972-01-01

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

  6. Plasmodium falciparum STEVOR Proteins Are Highly Expressed in Patient Isolates and Located in the Surface Membranes of Infected Red Blood Cells and the Apical Tips of Merozoites? †

    PubMed Central

    Blythe, Jane E.; Yam, Xue Yan; Kuss, Claudia; Bozdech, Zbynek; Holder, Anthony A.; Marsh, Kevin; Langhorne, Jean; Preiser, Peter R.

    2008-01-01

    The human parasite Plasmodium falciparum has the potential to express a vast repertoire of variant proteins on the surface of the infected red blood cell (iRBC). Variation in the expression pattern of these proteins is linked to antigenic variation and thereby evasion of host antibody-mediated immunity. The genes in the stevor multigene family code for small variant antigens that are expressed in blood-stage parasites where they can be detected in membranous structures called Maurer's clefts (MC). Some studies have indicated that STEVOR protein may also be trafficked to the iRBC membrane. To address the location of STEVOR protein in more detail, we have analyzed expression in several cultured parasite lines and in parasites obtained directly from patients. We detected STEVOR expression in a higher proportion of parasites recently isolated from patients than in cultured parasite lines and show that STEVOR is trafficked in schizont-stage parasites from the MC to the RBC cytosol and the iRBC membrane. Furthermore, STEVOR protein is also detected at the apical end of merozoites. Importantly, we show that culture-adapted parasites do not require STEVOR for survival. These findings provide new insights into the role of the stevor multigene family during both the schizont and merozoite stages of the parasite and highlight the importance of studying freshly isolated parasites, rather than parasite lines maintained in culture, when investigating potential mediators of host-parasite interactions. PMID:18474651

  7. Association of n3 and n6 polyunsaturated fatty acids in red blood cell membrane and plasma with severity of normal tension glaucoma

    PubMed Central

    Yu, Man; Chen, Bo; Gong, Bo; Shuai, Ping; Wu, Zheng-Zheng; Lin, Wei

    2015-01-01

    AIM To determine whether red blood cell (RBC) membrane and plasma lipids, particularly long-chain polyunsaturated fatty acids such as eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), arachidonic acid (AA) are significantly correlated with severity of normal tension glaucoma (NTG). METHODS This study included 35 patients with NTG and 12 healthy normal control subjects, matched for age and sex with the study group. The stage of glaucoma was determined according to the Hodapp-Parrish-Anderson classification. Lipids were extracted from RBC membranes and plasma, and fatty acid methyl esters prepared and analyzed by gas chromatography-mass spectrometry (GC-MS). RESULTS When RBC lipids were analyzed, the levels of EPA, the levels of DHA and the ratio of n3 to n6 were positively associated with the Humphrey Perimetry mean deviation (MD) score (r=0.617, P<0.001; r=0.727, P<0.001 and r=0.720, P<0.001, respectively), while the level of AA was negatively associated with the MD score (r=-0.427, P=0.001). When plasma lipids were analyzed, there was a significant positive relationship between the levels of EPA and the MD score (r=0.648, P<0.001), and the levels of AA were inversely correlated with the MD score (r=-0.638, P<0.001). CONCLUSION The levels of n3 and n6 polyunsaturated fatty acids in RBC membrane and plasma lipids were associated with severity of NTG. PMID:26085994

  8. Proton Exchange Membranes for Fuel Cells

    SciTech Connect

    Devanathan, Ramaswami

    2010-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  10. Functional dynamics of cell surface membrane proteins

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  11. Membrane proteomic analysis of pancreatic cancer cells

    PubMed Central

    2010-01-01

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

  12. Interactions between anion exchange and other membrane proteins in rabbit kidney medullary collecting duct cells.

    PubMed

    Janoshazi, A; Seifter, J L; Solomon, A K

    1989-11-01

    In separated outer medullary collecting duct (MCD) cells, the time course of binding of the fluorescent stilbene anion exchange inhibitor, DBDS (4,4'-dibenzamido-2,2'-stilbene disulfonate), to the MCD cell analog of band 3, the red blood cell (rbc) anion exchange protein, can be measured by the stopped-flow method and the reaction time constant, tau TDBDS, can be used to report on the conformational state of the band 3 analog. In order to validate the method we have now shown that the ID50D,DBDS,MCD (0.5 +/- 0.1 microM) for the H2-DIDS (4,4'-diisothiocyano-2,2'-dihydrostilbene disulfonate) inhibition of tau DBDS is in agreement with the ID50,Cl-MCD (0.94 +/- 0.07 microM) for H2-DIDS inhibition of MCD cell Cl- flux, thus relating tau DBDS directly to anion exchange. The specific cardiac glycoside cation transport inhibitor, ouabain, not only modulates DBDS binding kinetics, but also increases the time constant for Cl- exchange by a factor of two, from tau Cl- = 0.30 +/- 0.02 sec to 0.56 +/- 0.06 sec (30 mM NaHCO3). The ID50,DBDS,MCD for the ouabain effect on DBDS binding kinetics is 0.003 +/- 0.001 microM, so that binding is about an order of magnitude tighter than that for inhibition of rbc K+ flux (KI,K+,rbc = 0.017 microM). These experiments indicate that the Na+,K+-ATPase, required to maintain cation gradients across the MCD cell membrane, is close enough to the band 3 analog that conformational information can be exchanged. Cytochalasin E (CE), which binds to the spectrin/actin complex in rbc and other cells. modulates DBDS binding kinetics with a physiological ID50,DBDS,MCD (0.076 +/- 0.005 microM); 2 microM CE also more than doubles the Cl- exchange time constant from 0.20 +/- 0.04 sec to 0.50 +/- 0.08 sec (30 mM NaHCO3). These experiments indicate that conformational information can also be exchanged between the MCD cell band 3 analog and the MCD cell cytoskeleton. PMID:2593138

  13. Red blood cell in simple shear flow

    NASA Astrophysics Data System (ADS)

    Chien, Wei; Hew, Yayu; Chen, Yeng-Long

    2013-03-01

    The dynamics of red blood cells (RBC) in blood flow is critical for oxygen transport, and it also influences inflammation (white blood cells), thrombosis (platelets), and circulatory tumor migration. The physical properties of a RBC can be captured by modeling RBC as lipid membrane linked to a cytoskeletal spectrin network that encapsulates cytoplasm rich in hemoglobin, with bi-concave equilibrium shape. Depending on the shear force, RBC elasticity, membrane viscosity, and cytoplasm viscosity, RBC can undergo tumbling, tank-treading, or oscillatory motion. We investigate the dynamic state diagram of RBC in shear and pressure-driven flow using a combined immersed boundary-lattice Boltzmann method with a multi-scale RBC model that accurately captures the experimentally established RBC force-deformation relation. It is found that the tumbling (TU) to tank-treading (TT) transition occurs as shear rate increases for cytoplasm/outer fluid viscosity ratio smaller than 0.67. The TU frequency is found to be half of the TT frequency, in agreement with experiment observations. Larger viscosity ratios lead to the disappearance of stable TT phase and unstable complex dynamics, including the oscillation of the symmetry axis of the bi-concave shape perpendicular to the flow direction. The dependence on RBC bending rigidity, shear modulus, the order of membrane spectrin network and fluid field in the unstable region will also be discussed.

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

    PubMed Central

    Gallagher, Patrick G.

    2008-01-01

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

  15. Metabolomics of AS-5 RBC supernatants following routine storage

    PubMed Central

    D’Alessandro, A.; Hansen, K. C.; Silliman, C. C.; Moore, E. E.; Kelher, M.; Banerjee, A.

    2015-01-01

    Background and Objectives The safety and efficacy of stored red blood cells (RBCs) transfusion has been long debated due to retrospective clinical evidence and laboratory results, indicating a potential correlation between increased morbidity and mortality following transfusion of RBC units stored longer than 14 days. We hypothesize that storage in Optisol additive solution-5 leads to a unique metabolomics profile in the supernatant of stored RBCs. Materials and Methods Whole blood was drawn from five healthy donors, RBC units were manufactured, and prestorage leucoreduced by filtration. Samples were taken on days 1 and 42, the cells removed, and mass spectrometry-based metabolomics was performed. Results The results confirmed the progressive impairment of RBC energy metabolism by day 42 with indirect markers of a parallel alteration of glutathione and NADPH homeostasis. Moreover, oxidized pro-inflammatory lipids accumulated by the end of storage. Conclusion The supernatants from stored RBCs may represent a burden to the transfused recipients from a metabolomics standpoint. PMID:25200932

  16. Proton conducting membrane for fuel cells

    DOEpatents

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

    2005-12-20

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

  17. Proton conducting membrane for fuel cells

    DOEpatents

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

    2007-03-27

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

  18. Toxic effects of Litsea elliptica Blume essential oil on red blood cells of Sprague-Dawley rats.

    PubMed

    Taib, Izatus Shima; Budin, Siti Balkis; Siti Nor Ain, Seri Maseran; Mohamed, Jamaludin; Louis, Santhana Raj; Das, Srijit; Sallehudin, Sulaiman; Rajab, Nor Fadilah; Hidayatulfathi, Othman

    2009-11-01

    Litsea elliptica Blume leaves have been traditionally used as medicinal herbs because of its antimutagenicity, chemopreventative and insecticidal properties. In this study, the toxic effects of L. elliptica essential oil against Sprague-Dawley rat's red blood cells (RBCs) were evaluated. L. elliptica essential oil was given by oral gavage 5 times per week for 3 treated groups in the doses of 125, 250, and 500 mg/(kg body weight), respectively, and the control group received distilled water. Full blood count, RBC osmotic fragility, RBC morphological changes, and RBC membrane lipid were analyzed 28 d after the treatment. Although L. elliptica essential oil administration had significantly different effects on hemoglobin (Hb), mean cell hemoglobin concentration (MCHC), mean cell volume (MCV), and mean cell hemoglobin (MCH) in the experimental groups as compared to the control group (P<0.05), the values were still within the normal range. L. elliptica induced morphological changes of RBC into the form of echinocyte. The percentage of echinocyte increased significantly among the treated groups in a dose-response manner (P<0.001). The concentrations of RBC membrane phospholipids and cholesterol of all treated groups were significantly lower than those of control group (P<0.001). However, the RBC membrane osmotic fragility and total proteins of RBC membrane findings did not differ significantly between control and treated groups (P>0.05). It is concluded that structural changes in the RBC membrane due to L. elliptica essential oil administration did not cause severe membrane damage. PMID:19882755

  19. A novel bioactive membrane by cell electrospinning.

    PubMed

    Chen, Haiping; Liu, Yuanyuan; Hu, Qingxi

    2015-11-01

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

  20. Alternate Fuel Cell Membranes for Energy Independence

    SciTech Connect

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

    2012-12-18

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

  1. Advanced membrane electrode assemblies for fuel cells

    DOEpatents

    Kim, Yu Seung; Pivovar, Bryan S

    2014-02-25

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

  2. Advanced membrane electrode assemblies for fuel cells

    DOEpatents

    Kim, Yu Seung; Pivovar, Bryan S.

    2012-07-24

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

  3. Durability of PEM Fuel Cell Membranes

    NASA Astrophysics Data System (ADS)

    Huang, Xinyu; Reifsnider, Ken

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

  4. Red blood cell membrane fluidity in the etiology of multiple sclerosis.

    PubMed

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

    2009-12-01

    Organisms adjust the order, or fluidity, of their cellular membranes in response to changes in their physiochemical environment by adjusting the lipid composition of their membranes. We investigated membrane fluidity using the phospholipid, fatty acid and cholesterol content of red blood cells (RBCs) from multiple sclerosis (MS) patients and correlated this with C-reactive protein (CRP) as well as with the severity of neurological outcome as measured by the Kurtzke Expanded Disability Status Scale (EDSS) and its Functional System Scores. The study group consisted of 31 patients with MS and 30 healthy control subjects. Phospholipids were determined using a colorimetric assay, fatty acids by gas chromatography, cholesterol by an enzymatic assay and CRP by a Beckman nephelometer. Cell membrane fluidity was calculated according to previously established formulae. RBC membrane fluidity as measured by the saturated to polyunsaturated fatty acid ratio was higher in patients than in controls (P = 0.04). The phosphatidylethanolamine saturated to polyunsaturated fatty acid ratio showed highly significant positive correlations with the EDSS and CRP < 5 microg/ml. CRP showed significant inverse correlations with the saturated nature but positive correlations with the ordered-crystalline-phase to liquid-crystalline-phase lipid ratio. In this study we show that membrane fluidity as measured by the relationship between membrane fatty acids, phospholipids and cholesterol is closely interrelated with inflammation and disease outcome in patients with MS. In conclusion, our findings suggest that the membrane lipid composition of patients with MS and, consequently, membrane fluidity are altered, which seems to be influenced by the inflammatory status. PMID:19915887

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  6. Fuel cell subassemblies incorporating subgasketed thrifted membranes

    SciTech Connect

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

    2014-01-28

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

  7. Selectivity of Direct Methanol Fuel Cell Membranes.

    PubMed

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

    2015-01-01

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

  8. Cell or Cell Membrane-Based Drug Delivery Systems

    PubMed Central

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

    2015-01-01

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

  9. Erythrocyte membrane is an alternative coating to polyethylene glycol for prolonging the circulation lifetime of gold nanocages for photothermal therapy.

    PubMed

    Piao, Ji-Gang; Wang, Limin; Gao, Feng; You, Ye-Zi; Xiong, Yujie; Yang, Lihua

    2014-10-28

    Gold nanocages (AuNCs), which have tunable near-infrared (NIR) absorption and intrinsically high photothermal conversion efficiency, have been actively investigated as photothermal conversion agents for photothermal therapy (PTT). The short blood circulation lifetime of AuNCs, however, limits their tumor uptake and thus in vivo applications. Here we show that such a limitation can be overcome by cloaking AuNCs with red blood cell (RBC) membranes, a natural stealth coating. The fusion of RBC membranes over AuNC surface does not alter the unique porous and hollow structures of AuNCs, and the resulting RBC-membrane-coated AuNCs (RBC-AuNCs) exhibit good colloidal stability. Upon NIR laser irradiation, the RBC-AuNCs demonstrate in vitro photothermal effects and selectively ablate cancerous cells within the irradiation zone as do the pristine biopolymer-stealth-coated AuNCs. Moreover, the RBC-AuNCs exhibit significantly enhanced in vivo blood retention and circulation lifetime compared to the biopolymer-stealth-coated counterparts, as demonstrated using a mouse model. With integrated advantages of photothermal effects from AuNCs and long blood circulation lifetime from RBCs, the RBC-AuNCs demonstrate drastically enhanced tumor uptake when administered systematically, and mice that received PPT cancer treatment modulated by RBC-AuNCs achieve 100% survival over a span of 45 days. Taken together, our results indicate that the long circulating RBC-AuNCs may facilitate the in vivo applications of AuNCs, and the RBC-membrane stealth coating technique may pave the way to improved efficacy of PPT modulated by noble metal nanoparticles. PMID:25286086

  10. Pattern formation in cell membrane adhesion

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

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

  11. IMPEDANCE SPECTROSCOPY FLOW CYTOMETRY: PARAMETERS FOR LABEL-FREE CELL DIFFERENTIATION

    E-print Network

    Cheung, Karen C.

    -buffered saline (PBS). RBC ghost preparation: RBCs were suspended in a hypotonic solution which lyses the cells. The resulting ghosts are clear membranes filled with saline solution. RBCs fixed in glutaraldehyde: RBCs were

  12. Hypercompliant Apical Membranes of Bladder Umbrella Cells

    PubMed Central

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

    2014-01-01

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

  13. Membrane electrode assembly for a fuel cell

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  14. Sputter-deposited fuel cell membranes and electrodes

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  15. Membrane protein expression: no cells required.

    PubMed

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

    2009-08-01

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

  16. Membrane processes relevant for the polymer electrolyte fuel cell

    E-print Network

    Kjelstrup, Signe

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

  17. Change dynamics of RBC morphology after injection glucose for diabetes by diffraction phase microscope

    NASA Astrophysics Data System (ADS)

    Talaykova, N. A.; Kalyanov, A. L.; Lychagov, V. V.; Ryabukho, V. P.; Malinova, L. I.

    2013-11-01

    Experimental setup of diffraction phase microscope (DPM) with double low-coherence lighting system is presented in the paper. Algorithm of interference picture processing and optical thickness, height, volume and mean cells volume (MCV) of RBC calculating is shown. We demonstrate results of experiments with blood smears and ability of the method to calculate 3D model of the biological cells shape. Investigation change dynamics of RBC morphology after injection glucose for diabetes by DPM is shown in the paper.

  18. Interactions of Model Cell Membranes with Nanoparticles

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  19. Catalytic membranes for fuel cells

    DOEpatents

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

    2011-04-19

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

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

    PubMed

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

    2008-04-10

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

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

    PubMed Central

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

    2015-01-01

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

  2. Fuel cell membranes and crossover prevention

    DOEpatents

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

    2009-08-04

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

  3. Use of mouse models to study the mechanisms and consequences of RBC clearance

    PubMed Central

    Hod, E. A.; Arinsburg, S. A.; Francis, R. O.; Hendrickson, J. E.; Zimring, J. C.; Spitalnik, S. L.

    2013-01-01

    Mice provide tractable animal models for studying the pathophysiology of various human disorders. This review discusses the use of mouse models for understanding red-blood-cell (RBC) clearance. These models provide important insights into the pathophysiology of various clinically relevant entities, such as autoimmune haemolytic anaemia, haemolytic transfusion reactions, other complications of RBC transfusions and immunomodulation by Rh immune globulin therapy. Mouse models of both antibody- and non-antibody-mediated RBC clearance are reviewed. Approaches for exploring unanswered questions in transfusion medicine using these models are also discussed. PMID:20345515

  4. Different activities of the reovirus FAST proteins and influenza hemagglutinin in cell-cell fusion assays and in response to membrane curvature agents

    SciTech Connect

    Clancy, Eileen K.; Barry, Chris; Ciechonska, Marta; Duncan, Roy

    2010-02-05

    The reovirus fusion-associated small transmembrane (FAST) proteins evolved to induce cell-cell, rather than virus-cell, membrane fusion. It is unclear whether the FAST protein fusion reaction proceeds in the same manner as the enveloped virus fusion proteins. We now show that fluorescence-based cell-cell and cell-RBC hemifusion assays are unsuited for detecting lipid mixing in the absence of content mixing during FAST protein-mediated membrane fusion. Furthermore, membrane curvature agents that inhibit hemifusion or promote pore formation mediated by influenza hemagglutinin had no effect on p14-induced cell-cell fusion, even under conditions of limiting p14 concentrations. Standard assays used to detect fusion intermediates induced by enveloped virus fusion proteins are therefore not applicable to the FAST proteins. These results suggest the possibility that the nature of the fusion intermediates or the mechanisms used to transit through the various stages of the fusion reaction may differ between these distinct classes of viral fusogens.

  5. Membrane catalyst layer for fuel cells

    DOEpatents

    Wilson, Mahlon S. (Los Alamos, NM)

    1993-01-01

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

  6. Fuel cell membrane hydration and fluid metering

    DOEpatents

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

    1999-01-01

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

  7. Fuel cell membrane hydration and fluid metering

    DOEpatents

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

    2003-01-01

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

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

    E-print Network

    Benjamin Winkler; Igor S. Aranson; Falko Ziebert

    2015-09-02

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2007-01-01

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

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

    E-print Network

    Park, YongKeun

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

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

    PubMed

    Fournier, S; Trifaró, J M

    1988-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  15. Effects of 5-hydroxymethyl-2-furfural on the volume and membrane permeability of red blood cells from patients with sickle cell disease

    E-print Network

    Hannemann, Anke; Cytlak, Urszula M.; Rees, David C.; Tewari, Sanjay; Gibson, John S.

    2014-08-13

    The heterocyclic aldehyde 5-hydroxymethyl-2-furfural (5HMF) interacts allosterically with HbS in red blood cells (RBCs) from patients with sickle cell disease (SCD), thereby increasing oxygen affinity and decreasing HbS polymerisation and RBC...

  16. Ion transport through cell membrane channels

    E-print Network

    Jan Gomulkiewicz; Jacek Miekisz; Stanislaw Miekisz

    2007-06-05

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

  17. Membrane Cells in Chlor Alkali Application 

    E-print Network

    Lesker, K.

    1992-01-01

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

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

    PubMed

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

    2013-01-01

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

  19. Membrane Purification Cell for Aluminum Recycling

    SciTech Connect

    David DeYoung; James Wiswall; Cong Wang

    2011-11-29

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

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

    E-print Network

    Cahill, Kevin

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

  1. Physical principles of membrane remodelling during cell mechanoadaptation.

    PubMed

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

    2015-01-01

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

  2. Physical principles of membrane remodelling during cell mechanoadaptation

    PubMed Central

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

    2015-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Kinder, James D.

    2005-01-01

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

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

    E-print Network

    Boxer, Steven G.

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

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

    E-print Network

    Bae-Yeun Ha

    2000-06-02

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

  6. Roles of membrane trafficking in plant cell wall dynamics

    PubMed Central

    Ebine, Kazuo; Ueda, Takashi

    2015-01-01

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

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

    DOEpatents

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

    2014-12-09

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

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

    NASA Technical Reports Server (NTRS)

    Eisman, G. A.

    1989-01-01

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

  9. Membrane tension and cytoskeleton organization in cell motility

    NASA Astrophysics Data System (ADS)

    Sens, Pierre; Plastino, Julie

    2015-07-01

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

  10. Exo70 Generates Membrane Curvature for Morphogenesis and Cell Migration

    PubMed Central

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

    2013-01-01

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

  11. Membrane glycoproteins of differentiating skeletal muscle cells

    SciTech Connect

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

    1987-05-01

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

  12. Isoprenoid pathway-related membrane dysfunction in neuropsychiatric disorders.

    PubMed

    Kurup, Ravi Kumar; Kurup, Parameswara Achutha

    2003-11-01

    The membrane composition and the isoprenoid pathway metabolites important in maintaining cell membrane integrity was studied in neurological and psychiatric disorders. The results indicate alteration in cholesterol:phospholipid ratio of the RBC membrane which is increased in glioma, schizophrenia, and bipolar mood disorder (MDP); decreased in multiple sclerosis and Parkinson's disease; and not significantly altered in epilepsy. The concentration of total glycosaminoglycans (GAG), hexose, and fucose decreased in the RBC membrane and increased in the serum. The RBC membrane Na+-K+ ATPase activity was reduced and serum HMG CoA reductase activity was increased. There were increased serum levels of digoxin, cholesterol, and dolichol and decreased levels of ubiquinone. The serum magnesium and tyrosine levels were reduced and tryptophan increased. The results indicate a defect in membrane formation and a decreased membrane Na+-K+ ATPase activity in all the disorders studied. The results are discussed, and a hypothesis regarding the relationship between these disorders and defective membrane architecture and membrane Na+-K+ ATPase inhibition is presented. PMID:14585755

  13. Electron-beam direct processing on living cell membrane

    SciTech Connect

    Hoshino, Takayuki; Morishima, Keisuke

    2011-10-24

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

  14. Hemoglobin s polymerization and red cell membrane changes.

    PubMed

    Kuypers, Frans A

    2014-04-01

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

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

    SciTech Connect

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

    2006-01-01

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

  16. Effect of EMP fields on cell membrane potentials

    SciTech Connect

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

    1993-06-01

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

  17. Potential electron mediators to extract electron energies of RBC glycolysis for prolonged in vivo functional lifetime of hemoglobin vesicles.

    PubMed

    Kettisen, Karin; Bülow, Leif; Sakai, Hiromi

    2015-04-15

    Developing a functional blood substitute as an alternative to donated blood for clinical use is believed to relieve present and future blood shortages, and to reduce the risks of infection and blood type mismatching. Hemoglobin vesicle (HbV) encapsulates a purified and concentrated human-derived Hb solution in a phospholipid vesicle (liposome). The in vivo safety and efficacy of HbV as a transfusion alternative have been clarified. Auto-oxidation of ferrous Hb in HbV gradually increases the level of ferric methemoglobin (metHb) and impairs the oxygen transport capabilities. The extension of the functional half-life of HbV has recently been proposed using an electron mediator, methylene blue (MB), which acts as a shuttle between red blood cells (RBC) and HbV. MB transfers electron energies of NAD(P)H, produced by RBC glycolysis, to metHb in HbV. Work presented here focuses on screening of 15 potential electron mediators, with appropriate redox potential and water solubility, for electron transfer from RBC to HbV. The results are assessed with regard to the chemical properties of the candidates. The compounds examined in this study were dimethyl methylene blue (DMB), methylene green, azure A, azure B, azure C, toluidine blue (TDB), thionin acetate, phenazine methosulfate, brilliant cresyl blue, cresyl violet, gallocyanine, toluylene blue, indigo carmine, indigotetrasulfonate, and MB. Six candidates were found to be unsuitable because of their insufficient diffusion across membranes, or overly high or nonexistent reactivity with relevant biomolecules. However, 9 displayed favorable metHb reduction. Among the suitable candidates, phenothiazines DMB and TDB exhibited effectiveness like MB did. In comparison to MB, they showed faster reduction by electron-donating NAD(P)H, coupled with showing a lower rate of reoxidation in the presence of molecular oxygen. Ascertaining the best electron mediator can provide a pathway for extending the lifetime and efficiency of potential blood substitutes. PMID:25734688

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

    E-print Network

    Petta, Jason

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

  19. Finite element analysis of microelectrotension of cell membranes

    PubMed Central

    Bae, Chilman

    2011-01-01

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

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

    PubMed Central

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

    2014-01-01

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

  1. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Deformation and Motion of a Red Blood Cell in a Shear Flow Simulated by a Lattice Boltzmann Model

    NASA Astrophysics Data System (ADS)

    Shi, Juan; Qiu, Bing; Tan, Hui-Li

    2009-06-01

    A lattice Boltzmann model is presented to simulate the deformation and motions of a red blood cell (RBC) in a shear flow. The curvatures of the membrane of a static RBC with different chemical potential drops calculated by our model agree with those computed by a shooting method very well. Our simulation results show that in a shear flow, a biconcave RBC becomes highly flattened and undergoes tank-treading motion. With intrinsically parallel dynamics, this lattice Boltzmann method is expected to find wide applications to both single and multi-vesicles suspension as well as complex open membranes in various fluid flows for a wide range of Reynolds numbers.

  2. Activation of protein kinase C by phorbol ester increases red blood cell scramblase activity and external phosphatidylserine.

    PubMed

    Barber, Latorya A; Palascak, Mary B; Qi, Xiaoyang; Joiner, Clinton H; Franco, Robert S

    2015-11-01

    Externalization of phosphatidylserine (PS) is thought to contribute to sickle cell disease (SCD) pathophysiology. The red blood cell (RBC) aminophospholipid translocase (APLT) mediates the transport of PS from the outer to the inner RBC membrane leaflet to maintain an asymmetric distribution of PL, while phospholipid scramblase (PLSCR) equilibrates PL across the RBC membrane, promoting PS externalization. We previously identified an association between PS externalization level and PLSCR activity in sickle RBC under basal conditions. Other studies showed that activation of protein kinase C (PKC) by PMA (phorbol-12-myristate-13-acetate) causes increased external PS on RBC. Therefore, we hypothesized that PMA-activated PKC stimulates PLSCR activity in RBC and thereby contributes to increased PS externalization. In the current studies, we show that PMA treatment causes immediate and variable PLSCR activation and subsequent PS externalization in control and sickle RBC. While TfR+ sickle reticulocytes display some endogenous PLSCR activity, we observed a robust activation of PLSCR in sickle reticulocytes treated with PMA. The PKC inhibitor, chelerythrine (Chel), significantly inhibited PMA-dependent PLSCR activation and PS externalization. Chel also inhibited endogenous PLSCR activity in sickle reticulocytes. These data provide evidence that PKC mediates PS externalization in RBC through activation of PLSCR. PMID:25600460

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

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

    PubMed

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

    2015-10-14

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

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

    E-print Network

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

  8. Phosphorylation and Activation of the Plasma Membrane Na+/H+ Exchanger (NHE1) during Osmotic Cell Shrinkage

    PubMed Central

    Rigor, Robert R.; Damoc, Catalina; Phinney, Brett S.; Cala, Peter M.

    2011-01-01

    The Na+/H+ Exchanger isoform 1 (NHE1) is a highly versatile, broadly distributed and precisely controlled transport protein that mediates volume and pH regulation in most cell types. NHE1 phosphorylation contributes to Na+/H+ exchange activity in response to phorbol esters, growth factors or protein phosphatase inhibitors, but has not been observed during activation by osmotic cell shrinkage (OCS). We examined the role of NHE1 phosphorylation during activation by OCS, using an ideal model system, the Amphiuma tridactylum red blood cell (atRBC). Na+/H+ exchange in atRBCs is mediated by an NHE1 homolog (atNHE1) that is 79% identical to human NHE1 at the amino acid level. NHE1 activity in atRBCs is exceptionally robust in that transport activity can increase more than 2 orders of magnitude from rest to full activation. Michaelis-Menten transport kinetics indicates that either OCS or treatment with the phosphatase inhibitor calyculin-A (CLA) increase Na+ transport capacity without affecting transport affinity (Km?=?44 mM) in atRBCs. CLA and OCS act non-additively to activate atNHE1, indicating convergent, phosphorylation-dependent signaling in atNHE1 activation. In situ 32P labeling and immunoprecipitation demonstrates that the net phosphorylation of atNHE1 is increased 4-fold during OCS coinciding with a more than 2-order increase in Na+ transport activity. This is the first reported evidence of increased NHE1 phosphorylation during OCS in any vertebrate cell type. Finally, liquid chromatography and mass spectrometry (LC-MS/MS) analysis of atNHE1 immunoprecipitated from atRBC membranes reveals 9 phosphorylated serine/threonine residues, suggesting that activation of atNHE1 involves multiple phosphorylation and/or dephosphorylation events. PMID:22216214

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

    PubMed

    Besingi, Richard N; Clark, Patricia L

    2015-12-01

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

  10. JournalofCellScience Membrane and actin reorganization in electropulse-

    E-print Network

    Schwarz, Ulrich

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

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

    PubMed

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

    2011-12-01

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

  12. Radiation Interaction with Therapeutic Drugs and Cell Membranes

    SciTech Connect

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

    2007-04-23

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

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

    PubMed

    Konings, A W; Ruifrok, A C

    1985-04-01

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

  14. Improved Membrane Materials for PEM Fuel Cell Application

    SciTech Connect

    Kenneth A. Mauritz; Robert B. Moore

    2008-06-30

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  16. Predicting dynamics and rheology of blood flow: A comparative study of multiscale and low-dimensional models of red blood cells

    SciTech Connect

    Pan, Wenxiao; Fedosov, Dmitry A.; Caswell, Bruce; Karniadakis, George E.

    2011-05-27

    In this work we compare the predictive capability of two mathematical models for red blood cells (RBCs) focusing on blood flow in capillaries and arterioles. Both RBC models as well as their corresponding blood flows are based on the dissipative particle dynamics (DPD) method, a coarse-grained molecular dynamics approach. The first model employs a multiscale description of the RBC (MS-RBC), with its membrane represented by hundreds or even thousands of DPD-particles connected by springs into a triangular network in combination with out-of-plane elastic bending resistance. Extra dissipation within the network accounts for membrane viscosity, while the characteristic biconcave RBC shape is achieved by imposition of constraints for constant membrane area and constant cell volume. The second model is based on a low-dimensional description (LD-RBC) constructed as a closed torus-like ring of only 10 large DPD colloidal particles. They are connected into a ring by worm-like chain (WLC) springs combined with bending resistance. The LD-RBC model can be fitted to represent the entire range of nonlinear elastic deformations as measured by optical-tweezers for healthy and for infected RBCs in malaria. MS-RBCs suspensions model the dynamics and rheology of blood flow accurately for any size vessel but this approach is computationally expensive above 100 microns. Surprisingly, the much more economical suspensions of LD-RBCs also capture the blood flow dynamics and rheology accurately except for vessels with sizes comparable to RBC diameter. In particular, the LD-RBC suspensions are shown to properly capture the experimental data for the apparent viscosity of blood and its cell-free layer (CFL) in tube flow. Taken together, these findings suggest a hierarchical approach in modeling blood flow in the arterial tree, whereby the MS-RBC model should be employed for capillaries and arterioles below 100 microns, the LD-RBC model for arterioles, and the continuum description for arteries.

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

    PubMed

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

    2015-04-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Technical Reports Server (NTRS)

    Eisman, G. A.

    1989-01-01

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

  20. Protein sorting in Plasmodium falciparum-infected red blood cells permeabilized with the pore-forming protein streptolysin O.

    PubMed

    Ansorge, I; Benting, J; Bhakdi, S; Lingelbach, K

    1996-04-01

    Plasmodium falciparum is an intracellular parasite of human red blood cells (RBCs). Like many other intracellular parasites, P. falciparum resides and develops within a parasitophorous vacuole which is bound by a membrane that separates the host cell cytoplasm from the parasite surface. Some parasite proteins are secreted into the vacuolar space and others are secreted, by an as yet poorly defined pathway, into the RBC cytosol. The transport of proteins from the parasite has been followed mainly using morphological methods. In search of an experimental system that would allow (i) dissection of the individual steps involved in transport from the parasite surface into the RBC cytosol, and (ii) an assessment of the molecular requirements for the process at the erythrocytic side of the vacuolar membrane, we permeabilized infected RBCs with the pore-forming protein streptolysin O using conditions which left the vacuole intact. The distribution of two parasite proteins which served as markers for the vacuolar space and the RBC cytosol respectively was analysed morphologically and biochemically. In permeabilized RBCs the two marker proteins were sorted to the same compartments as in intact RBCs. The protein which was destined for the RBC cytosol traversed the vacuolar space before it was translocated across the vacuolar membrane. Protein transport could be arrested in the vacuole by removing the RBC cytosol. Translocation across the vacuolar membrane required ATP and a protein source at the erythrocytic face of the membrane, but it was independent of the intracellular ionic milieu of the RBC. PMID:8670123

  1. Membrane Transport Chloride Transport Across Vesicle and Cell

    E-print Network

    Smith, Bradley D.

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

  2. Catalytic membranes for CO oxidation in fuel cells

    DOEpatents

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

    2010-06-08

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

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

    E-print Network

    Dokmeci, Mehmet

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

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

    PubMed Central

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

    2010-01-01

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

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

    PubMed

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

    2005-04-15

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

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

    PubMed Central

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

    1999-01-01

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

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

    PubMed Central

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

    2014-01-01

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

  8. Layer-by-layer cell membrane assembly

    NASA Astrophysics Data System (ADS)

    Matosevic, Sandro; Paegel, Brian M.

    2013-11-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  10. Decreasing Outer Hair Cell Membrane Cholesterol Increases Cochlear Electromechanics

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  11. Fibronectin coating of oxygenator membranes enhances endothelial cell attachment

    PubMed Central

    2013-01-01

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

  12. Ion Exchange Membrane Cathodes for Scalable Microbial Fuel Cells

    E-print Network

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

  13. Photobleaching Regions of Living Cells to Monitor Membrane Traffic

    E-print Network

    Snapp, Erik Lee

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

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

    PubMed Central

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

    2014-01-01

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

  15. The surface charge of a cell lipid membrane

    E-print Network

    M. Pekker; M. N. Shneider

    2014-10-26

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

  16. Membrane-electrode assemblies for electrochemical cells

    DOEpatents

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

    1993-01-01

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

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

    PubMed Central

    1980-01-01

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

  18. Adaptation of yeast cell membranes to ethanol

    SciTech Connect

    Jimenez, J.; Benitez, T.

    1987-05-01

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

  19. Modeling of interactions between nanoparticles and cell membranes

    NASA Astrophysics Data System (ADS)

    Ban, Young-Min

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

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

    PubMed

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

    2015-12-15

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

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

    DOEpatents

    Laible, Philip D; Hanson, Deborah K

    2013-06-04

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

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

    E-print Network

    Ljubljana, University of

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

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

    E-print Network

    Sens, Pierre

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

  4. Bacteria May Cope Differently from Similar Membrane Damage Caused by the Australian Tree Frog Antimicrobial Peptide Maculatin 1.1.

    PubMed

    Sani, Marc-Antoine; Henriques, Sónia Troeira; Weber, Daniel; Separovic, Frances

    2015-08-01

    Maculatin 1.1 (Mac1) is an antimicrobial peptide from the skin of Australian tree frogs and is known to possess selectivity toward Gram-positive bacteria. Although Mac1 has membrane disrupting activity, it is not known how Mac1 selectively targets Gram-positive over Gram-negative bacteria. The interaction of Mac1 with Escherichia coli, Staphylococcus aureus, and human red blood cells (hRBC) and with their mimetic model membranes is here reported. The peptide showed a 16-fold greater growth inhibition activity against S. aureus (4 ?M) than against E. coli (64 ?M) and an intermediate cytotoxicity against hRBC (30 ?M). Surprisingly, Sytox Green uptake monitored by flow cytometry showed that Mac1 compromised both bacterial membranes with similar efficiency at ?20-fold lower concentration than the reported minimum inhibition concentration against S. aureus. Mac1 also reduced the negative potential of S. aureus and E. coli membrane with similar efficacy. Furthermore, liposomes mimicking the cell membrane of S. aureus (POPG/TOCL) and E. coli (POPE/POPG) were lysed at similar concentrations, whereas hRBC-like vesicles (POPC/SM/Chol) remained mostly intact in the presence of Mac1. Remarkably, when POPG/TOCL and POPE/POPG liposomes were co-incubated, Mac1 did not induce leakage from POPE/POPG liposomes, suggesting a preference toward POPG/TOCL membranes that was supported by surface plasma resonance assays. Interestingly, circular dichroism spectroscopy showed a similar helical conformation in the presence of the anionic liposomes but not the hRBC mimics. Overall, the study showed that Mac1 disrupts bacterial membranes in a similar fashion before cell death events and would preferentially target S. aureus over E. coli or hRBC membranes. PMID:26100634

  5. Anhydrous Proton-Conducting Membranes for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Yen, Shiao-Pin S.

    2005-01-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  8. Deformation of a single red blood cell in bounded Poiseuille flows

    NASA Astrophysics Data System (ADS)

    Shi, Lingling; Pan, Tsorng-Whay; Glowinski, Roland

    2012-11-01

    An immersed boundary method (IBM) combined with the elastic spring model is applied to investigate the deformation of a single red blood cell (RBC) in two-dimensional bounded Poiseuille flows. The equilibrium shape of the cell under flow depends on the swelling ratio ((s*)), the initial angle of the long axis of the cell at the centerline (?), the maximum velocity of the flow (umax), the membrane bending stiffness of the RBC (kb), and the height of the microchannel(H). Two motions of oscillation and vacillating breathing of the RBC are observed in narrow channel considered here. The strength of the vacillating-breathing motion depends on degree of confinement and umax. For the different kb, the RBC obtains the same equilibrium shape for the same capillary number. Parachute shape and bullet-like shape, depending on the angle ?, coexist for the elliptic shape cell with lower umax in a narrower channel. NSF Grant No. DMS-0914788.

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

    PubMed

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

    2004-04-01

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

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

    PubMed

    Gasparski, Alexander N; Beningo, Karen A

    2015-11-15

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

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

    SciTech Connect

    Jeffrey F. Harper, Ph.D.

    2004-06-30

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

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

    PubMed Central

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

    2008-01-01

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

  13. Gradiently crosslinked polymer electrolyte membranes in fuel cells

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  15. Isolated primary squamous cell carcinoma of the tympanic membrane

    PubMed Central

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

    2012-01-01

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

  16. In vitro and in vivo study of hazardous effects of Ag nanoparticles and Arginine-treated multi walled carbon nanotubes on blood cells: application in hemodialysis membranes.

    PubMed

    Zare-Zardini, Hadi; Amiri, Ahmad; Shanbedi, Mehdi; Taheri-Kafrani, Asghar; Kazi, S N; Chew, B T; Razmjou, Amir

    2015-09-01

    One of the novel applications of the nanostructures is the modification and development of membranes for hemocompatibility of hemodialysis. The toxicity and hemocompatibility of Ag nanoparticles and arginine-treated multiwalled carbon nanotubes (MWNT-Arg) and possibility of their application in membrane technology are investigated here. MWNT-Arg is prepared by amidation reactions, followed by characterization by FTIR spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The results showed a good hemocompatibility and the hemolytic rates in the presence of both MWNT-Arg and Ag nanoparticles. The hemolytic rate of Ag nanoparticles was lower than that of MWNT-Arg. In vivo study revealed that Ag nanoparticle and MWNT-Arg decreased Hematocrit and mean number of red blood cells (RBC) statistically at concentration of 100 µg mL(-1) . The mean decrease of RBC and Hematocrit for Ag nanoparticles (18% for Hematocrit and 5.8 × 1,000,000/µL) was more than MWNT-Arg (20% for Hematocrit and 6 × 1000000/µL). In addition, MWNT-Arg and Ag nanoparticles had a direct influence on the White Blood Cell (WBC) drop. Regarding both nanostructures, although the number of WBC increased in initial concentration, it decreased significantly at the concentration of 100 µg mL(-1) . It is worth mentioning that the toxicity of Ag nanoparticle on WBC was higher than that of MWNT-Arg. Because of potent antimicrobial activity and relative hemocompatibility, MWNT-Arg could be considered as a new candidate for biomedical applications in the future especially for hemodialysis membranes. PMID:25690431

  17. An Adaptive Finite Element Method For The Modeling Of The Equilibrium Of Red Blood Cells

    E-print Network

    Saramito, Pierre

    An Adaptive Finite Element Method For The Modeling Of The Equilibrium Of Red Blood Cells Aymen with a the numerical modeling of an isolated red blood cell (RBC), and more generally of phospholipid membranes. We, Lagrange multipliers, Numerical methods, Vesicle, Red Blood Cell, Elastic bending energy, Canham

  18. Rotating Biological Contractors (RBC's). Instructor's Guide. Biological Treatment Process Control.

    ERIC Educational Resources Information Center

    Zickefoose, Charles S.

    This two-lesson unit on rotating biological contactors (RBC's) is designed to be used with students who have had some experience in wastewater treatment and a basic understanding of biological treatment. The first lesson provides information on the concepts and components of RBC treatment systems. The second lesson focuses on design operation and…

  19. Rotating Biological Contactors (RBC's). Student Manual. Biological Treatment Process Control.

    ERIC Educational Resources Information Center

    Zickefoose, Charles S.

    This student manual provides the textual material for a unit on rotating biological contactors (RBC's). Topic areas considered include: (1) flow patterns of water through RBC installations; (2) basic concepts (shaft and stage); (3) characteristics of biomass; (4) mechanical features (bearings, mechanical drive systems, and air drive systems); (5)…

  20. Spring-network-based model of a red blood cell for simulating mesoscopic blood flow.

    PubMed

    Nakamura, Masanori; Bessho, Sadao; Wada, Shigeo

    2013-01-01

    We developed a mechanical model of a red blood cell (RBC) that is capable of expressing its characteristic behaviors in shear flows. The RBC was modeled as a closed shell membrane consisting of spring networks in the framework of the energy minimum concept. The fluid forces acting on RBCs were modeled from Newton's viscosity law and the conservation of momentum. In a steady shear flow, the RBC model exhibited various behaviors, depending on the shear rate; it tumbled, tank-treaded, or both. The transition from tumbling to tank-treading occurred at a shear rate of 20 s(?-?1). The simulation of an RBC in steady and unsteady parallel shear flows (Couette flows) showed that the deformation parameters of the RBC were consistent with experimental results. The RBC in Poiseuille flow migrated radially towards the central axis of the flow channel. Axial migration became faster with an increase in the viscosity of the media, qualitatively consistent with experimental results. These results demonstrate that the proposed model satisfies the essential conditions for simulating RBC behavior in blood flow. Finally, a large-scale RBC flow simulation was implemented to show the capability of the proposed model for analyzing the mesoscopic nature of blood flow. PMID:23293072

  1. Aluminum chloride and membrane potentials of barley root cells

    SciTech Connect

    Etherton, B.; Shane, M.

    1986-04-01

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

  2. Membrane Mechanics of Endocytosis in Cells with Turgor

    E-print Network

    Dmitrieff, Serge

    2015-01-01

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

  3. Alloimmunization against RBC or PLT antigens is independent of TRIM21 expression in a murine model.

    PubMed

    Patel, Seema R; Hendrickson, Jeanne E; Smith, Nicole H; Cadwell, Chantel M; Ozato, Keiko; Morse, Herbert C; Yoshimi, Ryusuke; Zimring, James C

    2011-03-01

    Generation of alloantibodies to transfused RBCs can be a serious medical problem for patients who require chronic RBC transfusion therapy. Patients with sickle cell disease have a substantially increased rate of alloimmunization compared to other chronically transfused populations. A recent study has forwarded the hypothesis that a polymorphism in an immunoregulatory gene in close proximity to beta-globin (TRIM21 rs660) plays a role in the increased rates of RBC alloimmunization in sickle cell patients. In particular, it was hypothesized that rs660C/T decreases expression of TRIM21, resulting in loss of a negative feedback pathway in immune responses and increased RBC alloimmunization. To test the effects of TRIM21 expression on alloimmunization, we analyzed antibody responses to alloantigens on RBCs and platelets transfused into wild-type and TRIM21 KO mice. No significant increases were seen in the frequency or magnitude of humoral immunization to alloantigens on transfused RBCs or platelets in adult or juvenile TRIM21 KO recipients compared to wild-type controls. Moreover, recipient inflammation with poly (I:C) enhanced RBC alloimmunization to similar degrees in both TRIM21 KO and wild-type control recipients. Together, these data rule out the hypothesis that decreased TRIM21 expression enhances transfusion induced humoral alloimmunization, in the context of a reductionist murine model. PMID:21269695

  4. Fuel cell electrolyte membrane with basic polymer

    DOEpatents

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

    2010-11-23

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

  5. Fuel cell electrolyte membrane with basic polymer

    DOEpatents

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

    2012-12-04

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

  6. Theory on Plasmon Modes of the Cell Membranes

    E-print Network

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

    2007-06-12

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

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

    E-print Network

    Cruz-Gonzalez, Tizoc, 1982-

    2004-01-01

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

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

    SciTech Connect

    Chance, S.C.

    1987-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhang, Tao

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

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

    NASA Astrophysics Data System (ADS)

    Cheah, May Jean

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

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

    NASA Astrophysics Data System (ADS)

    Mamlouk, M.; Scott, K.

    2015-07-01

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

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

    PubMed

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

    2012-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Hendrix, D. L.

    1978-01-01

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

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

    PubMed Central

    Bradley, Ryan; Radhakrishnan, Ravi

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

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

  17. Microstructured Electrolyte Membranes to Improve Fuel Cell Performance

    NASA Astrophysics Data System (ADS)

    Wei, Xue

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  19. Membrane Mechanics of Endocytosis in Cells with Turgor

    PubMed Central

    Dmitrieff, Serge; Nédélec, François

    2015-01-01

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

  20. Membrane Mechanics of Endocytosis in Cells with Turgor

    E-print Network

    Serge Dmitrieff; François Nédélec

    2015-09-02

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

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  2. Interaction of Sickle Cell Hemoglobin with Erythrocyte Membranes

    NASA Astrophysics Data System (ADS)

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

    1981-01-01

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

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

    SciTech Connect

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

    1982-05-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-07-01

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

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

    E-print Network

    Wonjune Choi; Juyeon Yi; Yong Woon Kim

    2015-08-28

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2015-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Kinder, James D.

    2004-01-01

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

  11. Membrane and MEA Development in Polymer Electrolyte Fuel Cells

    NASA Astrophysics Data System (ADS)

    Trogadas, Panagiotis; Ramani, Vijay

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

  12. Dipole relaxation in erythrocyte membrane: involvement of spectrin skeleton.

    PubMed

    Ivanov, I T; Paarvanova, B; Slavov, T

    2012-12-01

    Polarization of spectrin-actin undermembrane skeleton of red blood cell (RBC) plasma membranes was studied by impedance spectroscopy. Relatedly, dielectric spectra of suspensions that contained RBCs of humans, mammals (bovine, horse, dog, cat) and birds (turkey, pigeon, duck), and human RBC ghost membranes were continuously obtained during heating from 20 to 70°C. Data for the complex admittance and capacitance were used to derive the suspension resistance, R, and capacitance, C, as well as the energy loss as a function of temperature. As in previous studies, two irreversible temperature-induced transitions in the human RBC plasma membrane were detected at 49.5°C and at 60.7°C (at low heating rate). The transition at 49.5°C was evident from the abrupt changes in R, and C and the fall in the energy loss, due to dipole relaxation. For the erythrocytes of indicated species the changes in R and C displayed remarkable and similar frequency profiles within the 0.05-13MHz domain. These changes were subdued after cross-linking of membranes by diamide (0.3-1.3mM) and glutaraldehyde (0.1-0.4%) and at the presence of glycerol (10%). Based on the above results and previous reports, the dielectric changes at 49.5°C were related to dipole relaxation and segmental mobility of spectrin cytoskeleton. The results open the possibility for selective dielectric thermolysis of cell cytoskeleton. PMID:22513264

  13. Structural Analysis of the Rubisco-Assembly Chaperone RbcX-II from Chlamydomonas reinhardtii

    PubMed Central

    Liu, Cuimin; Hartl, F. Ulrich; Hayer-Hartl, Manajit

    2015-01-01

    The most prevalent form of the Rubisco enzyme is a complex of eight catalytic large subunits (RbcL) and eight regulatory small subunits (RbcS). Rubisco biogenesis depends on the assistance by specific molecular chaperones. The assembly chaperone RbcX stabilizes the RbcL subunits after folding by chaperonin and mediates their assembly to the RbcL8 core complex, from which RbcX is displaced by RbcS to form active holoenzyme. Two isoforms of RbcX are found in eukaryotes, RbcX-I, which is more closely related to cyanobacterial RbcX, and the more distant RbcX-II. The green algae Chlamydomonas reinhardtii contains only RbcX-II isoforms, CrRbcX-IIa and CrRbcX-IIb. Here we solved the crystal structure of CrRbcX-IIa and show that it forms an arc-shaped dimer with a central hydrophobic cleft for binding the C-terminal sequence of RbcL. Like other RbcX proteins, CrRbcX-IIa supports the assembly of cyanobacterial Rubisco in vitro, albeit with reduced activity relative to cyanobacterial RbcX-I. Structural analysis of a fusion protein of CrRbcX-IIa and the C-terminal peptide of RbcL suggests that the peptide binding mode of RbcX-II may differ from that of cyanobacterial RbcX. RbcX homologs appear to have adapted to their cognate Rubisco clients as a result of co-evolution. PMID:26305355

  14. Electrospun fiber membranes enable proliferation of genetically modified cells

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

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

    2011-01-01

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

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

    SciTech Connect

    Chris Roger; David Mountz; Wensheng He; Tao Zhang

    2011-03-17

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

  17. THE ENZYMATIC IODINATION OF THE RED CELL MEMBRANE

    PubMed Central

    Hubbard, Ann L.; Cohn, Zanvil A.

    1972-01-01

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

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

    EPA Science Inventory

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

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

    E-print Network

    Ljubljana, University of

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

  20. Nonminimum-Phase Phenomenon of PEM Fuel Cell Membrane

    E-print Network

    Peng, Huei

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

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

    NASA Astrophysics Data System (ADS)

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

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

  2. Mechanisms shaping cell membranes Michael M Kozlov1

    E-print Network

    McMahon, Harvey

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

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

    NASA Astrophysics Data System (ADS)

    Bier, M.

    2006-05-01

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

  4. Mastoparan selectively activates phospholipase D2 in cell membranes.

    PubMed

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

    2003-04-01

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

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

    E-print Network

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

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

    E-print Network

    Sniadecki, Nathan J.

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

  7. Numerical study on the dynamics and oxygen transport of a healthy red blood cell and a malaria-infected red blood cell

    NASA Astrophysics Data System (ADS)

    Jayathilake, Pahala; Gang, Liu; Boo Cheong, Khoo

    2011-11-01

    In the present work, a red blood cell (RBC) and a malaria-infected red blood cell (IRBC) moving along a capillary are simulated with including their permeable properties of the membranes by using a numerical technique based on the two-dimensional immersed interface method. The adhesiveness of the IRBC membrane is modeled by means of a potential function. Then, the model is employed to simulate the motion of a biconcave RBC in the absence of membrane stickiness and a more rigid and circular IRBC in the presence of membrane stickiness. The results show that the RBC gradually moves away from the capillary wall while the IRBC rolls on the capillary wall due to its stickiness. This rolling behavior of the IRBC agrees well with experimental findings. It is found that the resistance on the plasma flow given by the IRBC is larger than the corresponding resistance given by the RBC revealing that macrovascular blockage could happen due to malaria infection. Furthermore, oxygen transport in capillaries and oxygen absorption by nearby muscles are investigated in the presence of a RBC and an IRBC.

  8. Multiscale Modeling of Red Blood Cell Mechanics and Blood Flow in Malaria

    E-print Network

    Suresh, Subra

    Multiscale Modeling of Red Blood Cell Mechanics and Blood Flow in Malaria Dmitry A. Fedosov1 Abstract Red blood cells (RBCs) infected by a Plasmodium parasite in malaria may lose their membrane. In the present work, we simulate infected RBCs in malaria using a multiscale RBC model based on the dissipative

  9. Probing cell membrane dynamics using plasmon coupling microscopy

    NASA Astrophysics Data System (ADS)

    Rong, Guoxin

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

  10. VIEW OF RBC (REFINED BICARBONATE) BUILDING LOOKING NORTHEAST. DEMOLITION IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW OF RBC (REFINED BICARBONATE) BUILDING LOOKING NORTHEAST. DEMOLITION IN PROGRESS. "ARM & HAMMER BAKING SODA WAS MADE HERE FOR OVER 50 YEARS AND THEN SHIPPED ACROSS THE STREET TO THE CHURCH & DWIGHT PLANT ON WILLIS AVE. (ON THE RIGHT IN THIS PHOTO). LAYING ON THE GROUND IN FRONT OF C&D BUILDING IS PART OF AN RBC DRYING TOWER. - Solvay Process Company, Refined Bicarbonate Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

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

    PubMed

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

    2015-10-01

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

  12. Chemical Imaging of the Cell Membrane by NanoSIMS

    SciTech Connect

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

    2010-02-23

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

  13. A Novel Unitized Regenerative Proton Exchange Membrane Fuel Cell

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  15. Structural and mechanical heterogeneity of the erythrocyte membrane reveals hallmarks of membrane stability.

    PubMed

    Picas, Laura; Rico, Félix; Deforet, Maxime; Scheuring, Simon

    2013-02-26

    The erythrocyte membrane, a metabolically regulated active structure that comprises lipid molecules, junctional complexes, and the spectrin network, enables the cell to undergo large passive deformations when passing through the microvascular system. Here we use atomic force microscopy (AFM) imaging and quantitative mechanical mapping at nanometer resolution to correlate structure and mechanics of key components of the erythrocyte membrane, crucial for cell integrity and function. Our data reveal structural and mechanical heterogeneity modulated by the metabolic state at unprecedented nanometer resolution. ATP-depletion, reducing skeletal junction phosphorylation in RBC cells, leads to membrane stiffening. Analysis of ghosts and shear-force opened erythrocytes show that, in the absence of cytosolic kinases, spectrin phosphorylation results in membrane stiffening at the extracellular face and a reduced junction remodeling in response to loading forces. Topography and mechanical mapping of single components at the cytoplasmic face reveal that, surprisingly, spectrin phosphorylation by ATP softens individual filaments. Our findings suggest that, besides the mechanical signature of each component, the RBC membrane mechanics is regulated by the metabolic state and the assembly of its structural elements. PMID:23347043

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

    PubMed

    Kim, Tae Young; Cho, Sung Yong

    2011-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  18. Block copolymers for alkaline fuel cell membrane materials

    NASA Astrophysics Data System (ADS)

    Li, Yifan

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

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

    PubMed

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

    2015-10-01

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

  20. Integration of Cell Membranes and Nanotube Transistors

    E-print Network

    Gruner, George

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

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

    NASA Astrophysics Data System (ADS)

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

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

  2. Vesiculation of healthy and defective red blood cells

    NASA Astrophysics Data System (ADS)

    Li, He; Lykotrafitis, George

    2015-07-01

    Vesiculation of mature red blood cells (RBCs) contributes to removal of defective patches of the erythrocyte membrane. In blood disorders, which are related to defects in proteins of the RBC membrane, vesiculation of the plasma membrane is intensified. Several hypotheses have been proposed to explain RBC vesiculation but the exact underlying mechanisms and what determines the sizes of the vesicles are still not completely understood. In this work, we apply a two-component coarse-grained molecular dynamics RBC membrane model to study how RBC vesiculation is controlled by the membrane spontaneous curvature and by lateral compression of the membrane. Our simulation results show that the formation of small homogeneous vesicles with a diameter less than 40 nm can be attributed to a large spontaneous curvature of membrane domains. On the other hand, compression on the membrane can cause the formation of vesicles with heterogeneous composition and with sizes comparable with the size of the cytoskeleton corral. When spontaneous curvature and lateral compression are simultaneously considered, the compression on the membrane tends to facilitate formation of vesicles originating from curved membrane domains. We also simulate vesiculation of RBCs with membrane defects connected to hereditary elliptocytosis (HE) and to hereditary spherocytosis (HS). When the vertical connectivity between the lipid bilayer and the membrane skeleton is elevated, as in normal RBCs, multiple vesicles are shed from the compressed membrane with diameters similar to the cytoskeleton corral size. In HS RBCs, where the connectivity between the lipid bilayer and the cytoskeleton is reduced, larger-size vesicles are released under the same compression ratio as in normal RBCs. Lastly, we find that vesicles released from HE RBCs can contain cytoskeletal filaments due to fragmentation of the membrane skeleton while vesicles released from the HS RBCs are depleted of cytoskeletal filaments.

  3. Probing red blood cell mechanics, rheology and dynamics with a two-component multi-scale model

    PubMed Central

    Li, Xuejin; Peng, Zhangli; Lei, Huan; Dao, Ming; Karniadakis, George Em

    2014-01-01

    This study is partially motivated by the validation of a new two-component multi-scale cell model we developed recently that treats the lipid bilayer and the cytoskeleton as two distinct components. Here, the whole cell model is validated and compared against several available experiments that examine red blood cell (RBC) mechanics, rheology and dynamics. First, we investigated RBC deformability in a microfluidic channel with a very small cross-sectional area and quantified the mechanical properties of the RBC membrane. Second, we simulated twisting torque cytometry and compared predicted rheological properties of the RBC membrane with experimental measurements. Finally, we modelled the tank-treading (TT) motion of a RBC in a shear flow and explored the effect of channel width variation on the TT frequency. We also investigated the effects of bilayer–cytoskeletal interactions on these experiments and our simulations clearly indicated that they play key roles in the determination of cell membrane mechanical, rheological and dynamical properties. These simulations serve as validation tests and moreover reveal the capabilities and limitations of the new whole cell model. PMID:24982252

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

    E-print Network

    Brinker, C. Jeffrey

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

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

    E-print Network

    MacGregor II, R.D.

    2010-01-01

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

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

    E-print Network

    Bazant, Martin Z.

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

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

    SciTech Connect

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

    1988-04-01

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

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

    SciTech Connect

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

    1989-04-01

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

  9. Mechanical properties of stored red blood cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, Adriana; Alexandre de Thomaz, Andre; de Ysasa Pozzo, Liliana; de Lourdes Barjas-Castro, Maria; Brandao, Marcelo M.; Saad, Sara T. O.; Barbosa, Luiz Carlos; Cesar, Carlos Lenz

    2005-08-01

    We have developed a method for measuring the red blood cell (RBC) membrane overall elasticity ? by measuring the deformation of the cells when dragged at a constant velocity through a plasma fluid by an optical tweezers. The deformability of erythrocytes is a critical determinant of blood flow in the microcirculation. We tested our method and hydrodynamic models, which included the presence of two walls, by measuring the RBC deformation as a function of drag velocity and of the distance to the walls. The capability and sensitivity of this method can be evaluated by its application to a variety of studies, such as, the measurement of RBC elasticity of sickle cell anemia patients comparing homozygous (HbSS), including patients taking hydroxyrea (HU) and heterozygous (HbAS) with normal donors and the RBC elasticity measurement of gamma irradiated stored blood for transfusion to immunosupressed patients as a function of time and dose. These studies show that the technique has the sensitivity to discriminate heterozygous and homozygous sickle cell anemia patients from normal donors and even follow the course of HU treatment of Homozygous patients. The gamma irradiation studies show that there is no significant change in RBC elasticity over time for up to 14 days of storage, regardless of whether the unit was irradiated or not, but there was a huge change in the measured elasticity for the RBC units stored for more than 21 days after irradiation. These finds are important for the assessment of stored irradiated RBC viability for transfusion purposes because the present protocol consider 28 storage days after irradiation as the limit for the RBC usage.

  10. Proton exchange membrane fuel cell technology for transportation applications

    SciTech Connect

    Swathirajan, S.

    1996-04-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2016-01-01

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

  14. Novel Lipophilic Probe for Detecting Near-Membrane Reactive Oxygen Species Responses and Its Application for Studies of Pancreatic Acinar Cells: Effects of Pyocyanin and L-Ornithine

    PubMed Central

    Chvanov, Michael; Huang, Wei; Jin, Tao; Wen, Li; Armstrong, Jane; Elliot, Vicky; Alston, Ben; Burdyga, Alex; Criddle, David N.; Sutton, Robert

    2015-01-01

    Abstract Aims: The aim of this study was to develop a fluorescent reactive oxygen species (ROS) probe, which is preferentially localized in cellular membranes and displays a strong change in fluorescence upon oxidation. We also aimed to test the performance of this probe for detecting pathophysiologically relevant ROS responses in isolated cells. Results: We introduced a novel lipophilic ROS probe dihydrorhodamine B octadecyl ester (H2RB-C18). We then applied the new probe to characterize the ROS changes triggered by inducers of acute pancreatitis in pancreatic acinar cells. We resolved ROS changes produced by L-ornithine, L-arginine, cholecystokinin-8, acetylcholine, taurolithocholic acid 3-sulfate, palmitoleic acid ethyl ester, and the bacterial toxin pyocyanin. Particularly prominent ROS responses were induced by pyocyanin and L-ornithine. These ROS responses were accompanied by changes in cytosolic Ca2+concentration ([Ca2+]i), mitochondrial membrane potential (??), and NAD(P)H concentration. Innovation: The study describes a novel sensitive lipophilic ROS probe. The probe is particularly suitable for detecting ROS in near-membrane regions and therefore for reporting the ROS environment of plasma membrane channels and pumps. Conclusions: In our experimental conditions, the novel probe was more sensitive than 5-(and-6)-chloromethyl-2?,7?-dichlorodihydrofluorescein (CM-H2DCF) and dihydrorhodamine123 (H2R123) and allowed us to resolve ROS responses to secretagogues, pyocyanin, and L-ornithine. Changes in the fluorescence of the new probe were particularly prominent in the peripheral plasma membrane-associated regions. Our findings suggest that the new probe will be a useful tool in studies of the contribution of ROS to the pathophysiology of exocrine pancreas and other organs/tissues. Antioxid. Redox Signal. 22, 451–464. PMID:24635199

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

    PubMed Central

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

    2014-01-01

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

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

    SciTech Connect

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

    1998-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Gasa, Jeffrey

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

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

    PubMed

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

    1988-08-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  1. 2?-Hydroxy ceramide in membrane homeostasis and cell signaling

    PubMed Central

    Kota, Venkatesh; Hama, Hiroko

    2013-01-01

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

  2. Do heavy ions cause microlesions in cell membranes?

    NASA Technical Reports Server (NTRS)

    Koniarek, Jan P.; Worgul, Basil V.

    1992-01-01

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

  3. Amniotic membrane transplantation for partial limbal stem cell deficiency

    PubMed Central

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

    2001-01-01

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

  4. Importance of Heparin Provocation and SPECT/CT in Detecting Obscure Gastrointestinal Bleeding on 99mTc-RBC Scintigraphy

    PubMed Central

    Haghighatafshar, Mahdi; Gheisari, Farshid; Ghaedian, Tahereh

    2015-01-01

    Abstract We presented a pediatric case with a history of intermittent melena for 3 years because of angiodyplasia of small intestine. The results of frequent upper gastrointestinal endoscopies and colonoscopies as well as both 99mTc-red blood cell (RBC) and Meckel's scintigraphies for several times were negative in detection of bleeding site. However, 99mTc-RBC scintigraphy with single-photon emission computed tomography (SPECT)/computed tomography (CT) after heparin augmentation detected a site of bleeding in the distal ileum which later was confirmed during surgery with final diagnosis of angiodysplasia. It could be stated that heparin provocation of bleeding before 99mTc-RBC scintigraphy accompanied by fused SPECT/CT images should be kept in mind for management of intestinal bleeding especially in difficult cases. PMID:26313771

  5. Correlation of cell membrane dynamics and cell motility

    E-print Network

    Veronika, Merlin

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

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

    E-print Network

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

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Ulusoy, Sehribani

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

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

    NASA Technical Reports Server (NTRS)

    Narayan, Sri; Reddy, Prakash

    2012-01-01

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

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

    SciTech Connect

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

    2013-04-30

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

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

    E-print Network

    Snapp, Erik Lee

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

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

    E-print Network

    Van Zee, John W.

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

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

    DOEpatents

    Shore, Lawrence (Edison, NJ)

    2012-02-28

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

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

    PubMed Central

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

    2015-01-01

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

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

    E-print Network

    Fayer, Michael D.

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

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

    ERIC Educational Resources Information Center

    Downie, Roger

    1987-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    PubMed

    Yue, Tongtao; Zhang, Xianren; Huang, Fang

    2015-01-21

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

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

    PubMed

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

    2015-04-24

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

  1. Elastic thickness compressibilty of the red cell membrane.

    PubMed

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

    2001-09-01

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

  2. High temperature polymers for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Einsla, Brian Russel

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

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

    NASA Astrophysics Data System (ADS)

    Mishler, Jeffrey Harris

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

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

    NASA Technical Reports Server (NTRS)

    Belieres, Jean-Philippe

    2004-01-01

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

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

    SciTech Connect

    Stacy, Stephen; Allen, Jeffrey

    2012-07-01

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

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

    PubMed Central

    2015-01-01

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

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

    PubMed

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

    2014-04-01

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

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

    PubMed Central

    Spoerl, Edward; Doyle, R. J.

    1968-01-01

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

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

    PubMed

    Spoerl, E; Doyle, R J

    1968-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2008-08-01

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

  14. Effective Temperature of Red Blood Cell Membrane Fluctuations

    E-print Network

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

    2011-05-04

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

  15. Effective Temperature of Red Blood Cell Membrane Fluctuations

    E-print Network

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

    2011-01-01

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

  16. 2011 Alkaline Membrane Fuel Cell Workshop Final Report

    SciTech Connect

    Pivovar, B.

    2012-02-01

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

  17. Grafted polyelectrolyte membranes for lithium batteries and fuel cells

    SciTech Connect

    Kerr, John B.

    2003-06-24

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

  18. Deformation of a single red blood cell in bounded Poiseuille flows

    NASA Astrophysics Data System (ADS)

    Shi, Lingling; Pan, Tsorng-Whay; Glowinski, Roland

    2012-01-01

    Deformation of a red blood cell (RBC) in bounded two-dimensional Poiseuille flows is studied by using an immersed boundary method (IBM). An elastic spring model is applied to simulate the skeleton structure of a RBC membrane. As a benchmarking test, the dynamical behavior of a single RBC under a simple shear flow has been validated. Then we focus on investigating the motion and the deformation of a single RBC in Poiseuille flows by varying the swelling ratio (s*), the initial angle of the long axis of the cell at the centerline (?), the maximum velocity at the centerline of fluid flow (umax), the membrane bending stiffness of a RBC (kb), and the height of the microchannel (H). Two motions of oscillation and vacillating breathing (swing) of a RBC are observed in both narrow and wide channels. The strength of the vacillating-breathing motion depends on the degree of confinement and the value of umax. A RBC exhibits a strong vacillating-breathing motion as the degree of confinement is larger or the value of umax is higher. For the same degree of confinement, the vacillating-breathing motion appears to be relatively weaker but persists longer as the value of umax is lower. The continuation of shape change from the slippery to the parachute by varying the value of umax is obtained for the biconcave shape cell in a narrower channel. In particular, parachute shape and bulletlike shape, depending on the angle ?, coexist for the elliptic shape cell given initially with lower umax in a narrower channel.

  19. Analysis of plasma membrane phosphoinositides from fusogenic carrot cells

    SciTech Connect

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

    1987-04-01

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

  20. Engineered cell instructive matrices for fetal membrane healing.

    PubMed

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Hase, M.; Yoshikawa, K.

    2006-03-01

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

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

    PubMed

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

    2015-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Songprakorp, Roongrojana

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

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

    NASA Astrophysics Data System (ADS)

    Secanell Gallart, Marc

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

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

    E-print Network

    Kandlikar, Satish

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

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

    E-print Network

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

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

    E-print Network

    Theodorakis, Emmanuel

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

  8. Platelet and red blood cell interactions and their role in rheumatoid arthritis.

    PubMed

    Olumuyiwa-Akeredolu, Oore-Ofe O; Pretorius, Etheresia

    2015-12-01

    Cytokines, lymphocytes, platelets and several biomolecules have long been implicated in the pathology of rheumatoid arthritis (RA), and the influences of antibody production and tagging, and cytokine, chemokine and enzyme production at specific rheumatoid joints were thought to be exclusive to the advancement of disease parameters. Another role player in RA is red blood cells (RBCs) which, of late, have been found to be involved in RA pathobiology, as there is a positive correlation between RBC counts and joint pathology, as well as with inflammatory biomarkers in the disease. There is also an association between RBC distribution width and the incidence of myocardial infarction amongst RA patients, and there is a change in the lipid distribution within RBC membranes. Of late, certain RBC-associated factors with previously obscure roles and cell-derived particles thought to be inconsequential to the other constituents of plasma were found to be active biomolecular players. Several of these have been discovered to be present in or originating from RBCs. Their influences have been shown to involve in membrane dynamics that cause structural and functional changes in both platelets and RBCs. RBC-derived microparticles are emerging entities found to play direct roles in immunomodulation via interactions with other plasma cells. These correlations highlight the direct influences of RBCs on exacerbating RA pathology. This review will attempt to shed more light on how RBCs, in the true inflammatory milieu of RA, are playing an even greater role than previously assumed. PMID:26059943

  9. Aggregation and deformation of red blood cells as probed by a laser light scattering technique in a concentrated suspension: comparison between normal and pathological red blood cells

    NASA Astrophysics Data System (ADS)

    Gandjbakhche, Amir H.; Othmane, Ali; Mills, Pierre; Snabre, Patrick; Dufaux, Jacques

    1994-07-01

    Changes in aggregability and/or deformability of red blood cells (RBC) can cause severe complications in blood circulation. We use a laser light scattering technique, which can distinguish between normal and pathological RBCs by studying the angular distributions of backscattered and transmitted light of concentrated suspensions of RBCs submitted to a simple shear flow. In order to study the deformation, we induced partial rigidity in the RBC membrane, and showed that the gradients of deformation and the relaxation times of normal and partially rigidified RBC membranes can be quantified using a non-Newtonian rheological model. We observe that blood aggregation of patients with `microcirculatory' diseases, such as diabetes, differs from that of healthy individuals.

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

    PubMed

    Choi, Mi Young; Park, Kyoung Ho

    2014-09-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  13. Cell-Culture Reactor Having a Porous Organic Polymer Membrane

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    2000-01-01

    A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The substrate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphory1choline groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge, wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic regions, and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

  14. Infectious rotavirus enters cells by direct cell membrane penetration, not by endocytosis

    SciTech Connect

    Kaljot, K.T.; Shaw, R.D.; Greenberg, H.B. Palo Alto Veterans Administration Medical Center, CA ); Rubin, D.H. )

    1988-04-01

    Rotaviruses are icosahedral viruses with a segmented, double-stranded RNA genome. They are the major cause of severe infantile infectious diarrhea. Rotavirus growth in tissue culture is markedly enhanced by pretreatment of virus with trypsin. Trypsin activation is associated with cleavage of the viral hemagglutinin (viral protein 3 (VP3); 88 kilodaltons) into two fragments (60 and 28 kilodaltons). The mechanism by which proteolytic cleavage leads to enhanced growth is unknown. To determine whether trypsin treatment affected rotavirus internalization, the authors studied the kinetics of entry of infectious rhesus rotavirus (RRV) into MA104 cells. Trypsin-activated RRV was internalized with a half-time of 3 to 5 min, while nonactivated virus disappeared from the cell surface with a half-time of 30 to 50 min. In contrast to trypsin-activated RRV, loss of nonactivated RRV from the cell surface did not result in the appearance of infection, as measured by plaque formation. Purified trypsin-activated RRV added to cell monolayers at pH 7.4 mediated {sup 51}Cr, ({sup 14}C)choline, and ({sup 3}H)inositol released from prelabeled MA104 cells. This release could be specifically blocked by neutralizing antibodies to VP3. These results suggest that MA104 cell infection follows the rapid entry of trypsin-activated RRV by direct cell membrane penetration. Cell membrane penetration of infectious RRV is initiated by trypsin cleavage of VP3. Neutralizing antibodies can inhibit this direct membrane penetration.

  15. Association rates of membrane-coupled cell adhesion molecules.

    PubMed

    Bihr, Timo; Fenz, Susanne; Sackmann, Erich; Merkel, Rudolf; Seifert, Udo; Sengupta, Kheya; Smith, Ana-Sun?ana

    2014-12-01

    Thus far, understanding how the confined cellular environment affects the lifetime of bonds, as well as the extraction of complexation rates, has been a major challenge in studies of cell adhesion. Based on a theoretical description of the growth curves of adhesion domains, we present a new (to our knowledge) method to measure the association rate k(on) of ligand-receptor pairs incorporated into lipid membranes. As a proof of principle, we apply this method to several systems. We find that the k(on) for the interaction of biotin with neutravidin is larger than that for integrin binding to RGD or sialyl Lewis(x) to E-selectin. Furthermore, we find k(on) to be enhanced by membrane fluctuations that increase the probability for encounters between the binders. The opposite effect on k(on) could be attributed to the presence of repulsive polymers that mimic the glycocalyx, which points to two potential mechanisms for controlling the speed of protein complexation during the cell recognition process. PMID:25468354

  16. Direct deposit of catalyst on the membrane of direct feed fuel cells

    NASA Technical Reports Server (NTRS)

    Chun, William (Inventor); Narayanan, Sekharipuram R. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Valdez, Thomas I. (Inventor); Linke, Juergen (Inventor)

    2001-01-01

    An improved direct liquid-feed fuel cell having a solid membrane electrolyte for electrochemical reactions of an organic fuel. Catalyst utilization and catalyst/membrane interface improvements are disclosed. Specifically, the catalyst layer is applied directly onto the membrane electrolyte.

  17. Microfluidic characterization of specific membrane capacitance and cytoplasm conductivity of single cells

    E-print Network

    Sun, Yu

    Microfluidic characterization of specific membrane capacitance and cytoplasm conductivity of single membrane capacitance and cytoplasm conductivity) characterization at a speed of 5­10 cells/s (vs. minutes the impedance data and to determine the specific membrane capacitance and cytoplasm conductivity of individual

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

    SciTech Connect

    Shamsuddin Ilias

    2002-06-11

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

  19. Alloantibodies to a paternally derived RBC KEL antigen lead to hemolytic disease of the fetus/newborn in a murine model

    PubMed Central

    Stowell, Sean R.; Henry, Kate L.; Smith, Nicole H.; Hudson, Krystalyn E.; Halverson, Greg R.; Park, Jaekeun C.; Bennett, Ashley M.; Girard-Pierce, Kathryn R.; Arthur, C. Maridith; Bunting, Silvia T.; Zimring, James C.

    2013-01-01

    Exposure to nonself red blood cell (RBC) antigens, either from transfusion or pregnancy, may result in alloimmunization and incompatible RBC clearance. First described as a pregnancy complication 80 years ago, hemolytic disease of the fetus and newborn (HDFN) is caused by alloimmunization to paternally derived RBC antigens. Despite the morbidity/mortality of HDFN, women at risk for RBC alloimmunization have few therapeutic options. Given that alloantibodies to antigens in the KEL family are among the most clinically significant, we developed a murine model with RBC-specific expression of the human KEL antigen to evaluate the impact of maternal/fetal KEL incompatibility. After exposure to fetal KEL RBCs during successive pregnancies with KEL-positive males, 21 of 21 wild-type female mice developed anti-KEL alloantibodies; intrauterine fetal anemia and/or demise occurred in a subset of KEL-positive pups born to wild type, but not agammaglobulinemic mothers. Similar to previous observations in humans, pregnancy-associated alloantibodies were detrimental in a transfusion setting, and transfusion-associated alloantibodies were detrimental in a pregnancy setting. This is the first pregnancy-associated HDFN model described to date, which will serve as a platform to develop targeted therapies to prevent and/or mitigate the dangers of RBC alloantibodies to fetuses and newborns. PMID:23801629

  20. Porous polybenzimidazole membranes with excellent chemical stability and ion conductivity for direct borohydride fuel cells

    NASA Astrophysics Data System (ADS)

    Chen, Dongju; Yu, Shanshan; Liu, Xue; Li, Xianfeng

    2015-05-01

    Porous membranes based on polybenzimidazole (PBI) are firstly introduced in direct borohydride fuel cell application (DBFC). Membranes with different thicknesses and porosity are successfully fabricated via water vapor phase inversion process. The prepared membranes show excellent ion conductivity and chemical stability under DBFC operating condition. Compare with Nafion 115, the prepared membranes show higher ion conductivity, as a result, much higher peak power density. No weight loss is observed after immersing the prepared membranes in a 3 M NaOH solution for 30 days, indicating the excellent chemical stability of porous PBI membranes. And the DBFC cells assembled with prepared membranes could discharge at 200 mA cm-2 for more than 250 h without voltage decay, which is the longest time reported by far. This work provides a totally new idea for fabricating versatile DBFC membranes.

  1. Red blood cell transfusion and increased length of storage are not associated with deep vein thrombosis in medical and surgical critically ill patients: a prospective observational cohort study

    PubMed Central

    2011-01-01

    Introduction With prolonged storage times, cell membranes of red blood cells (RBCs) undergo morphologic and biochemical changes, termed 'RBC storage lesions'. Storage lesions may promote inflammation and thrombophilia when transfused. In trauma patients, RBC transfusion was an independent risk factor for deep vein thrombosis (DVT), specifically when RBC units were stored > 21 days or when 5 or more units were transfused. The objective of this study was to determine if RBC transfusions or RBC storage age predicts incident DVT in medical or surgical intensive care unit (ICU) patients. Methods Using a database which prospectively enrolled 261 patients over the course of 1 year with an ICU stay of at least 3 days, we analyzed DVT and RBC transfusions using Cox proportional hazards regression. Transfusions were analyzed with 4 thresholds, and storage age using 3 thresholds. DVTs were identified by twice-weekly proximal leg ultrasounds. Multivariable analyses were adjusted for 4 significant DVT predictors in this population (venous thrombosis history, chronic dialysis, platelet transfusion and inotropes). Results Of 261 patients, 126 (48.3%) had at least 1 RBC transfusion; 46.8% of those transfused had ? 5 units in ICU. Patients receiving RBCs were older (68.8 vs 64.1 years), more likely to be female (47.0 vs 30.7), sicker (APACHEII 26.8 vs 24.4), and more likely to be surgical (21.4 vs 8.9) (P < 0.05). The total number of RBCs per patient was 1-64, mean was 6.3 (SD 7.5), median was 4 (IQR 2,8). In univariate analyses, there was no association between DVT and RBC exposure (1 day earlier, 3 days earlier, 7 days earlier, or ever) or RBC storage (? 7 or > 7 days, ? 14 or > 14 days, ? 21 or > 21 days). Among patients transfused, no multivariable analyses showed that RBC transfusion or storage age predicted DVT. Trends were counter to the hypothesis (e.g., RBC storage for ? 7 days suggested a higher DVT risk compared to > 7 days (HR 5.3; 95% CI 1.3-22.1). Conclusions We were unable to detect any association between RBC transfusions or prolonged red cell storage and increased risk of DVT in medical or surgical ICU patients. Alternate explanations include a lack of sufficient events or patients' interaction, between patient groups, a mixing of red cell storage times creating differential effects on DVT risk, and unmeasured confounders. PMID:22044745

  2. Disentangling Membrane Dynamics and Cell Migration; Differential Influences of F-actin and Cell-Matrix Adhesions

    PubMed Central

    Kowalewski, Jacob M.; Shafqat-Abbasi, Hamdah; Jafari-Mamaghani, Mehrdad; Endrias Ganebo, Bereket; Gong, Xiaowei

    2015-01-01

    Cell migration is heavily interconnected with plasma membrane protrusion and retraction (collectively termed “membrane dynamics”). This makes it difficult to distinguish regulatory mechanisms that differentially influence migration and membrane dynamics. Yet such distinctions may be valuable given evidence that cancer cell invasion in 3D may be better predicted by 2D membrane dynamics than by 2D cell migration, implying a degree of functional independence between these processes. Here, we applied multi-scale single cell imaging and a systematic statistical approach to disentangle regulatory associations underlying either migration or membrane dynamics. This revealed preferential correlations between membrane dynamics and F-actin features, contrasting with an enrichment of links between cell migration and adhesion complex properties. These correlative linkages were often non-linear and therefore context-dependent, strengthening or weakening with spontaneous heterogeneity in cell behavior. More broadly, we observed that slow moving cells tend to increase in area, while fast moving cells tend to shrink, and that the size of dynamic membrane domains is independent of cell area. Overall, we define macromolecular features preferentially associated with either cell migration or membrane dynamics, enabling more specific interrogation and targeting of these processes in future. PMID:26248038

  3. In situ single molecule imaging of cell membranes: linking basic nanotechniques to cell biology, immunology and medicine

    NASA Astrophysics Data System (ADS)

    Pi, Jiang; Jin, Hua; Yang, Fen; Chen, Zheng W.; Cai, Jiye

    2014-10-01

    The cell membrane, which consists of a viscous phospholipid bilayer, different kinds of proteins and various nano/micrometer-sized domains, plays a very important role in ensuring the stability of the intracellular environment and the order of cellular signal transductions. Exploring the precise cell membrane structure and detailed functions of the biomolecules in a cell membrane would be helpful to understand the underlying mechanisms involved in cell membrane signal transductions, which could further benefit research into cell biology, immunology and medicine. The detection of membrane biomolecules at the single molecule level can provide some subtle information about the molecular structure and the functions of the cell membrane. In particular, information obtained about the molecular mechanisms and other information at the single molecule level are significantly different from that detected from a large amount of biomolecules at the large-scale through traditional techniques, and can thus provide a novel perspective for the study of cell membrane structures and functions. However, the precise investigations of membrane biomolecules prompts researchers to explore cell membranes at the single molecule level by the use of in situ imaging methods, as the exact conformation and functions of biomolecules are highly controlled by the native cellular environment. Recently, the in situ single molecule imaging of cell membranes has attracted increasing attention from cell biologists and immunologists. The size of biomolecules and their clusters on the cell surface are set at the nanoscale, which makes it mandatory to use high- and super-resolution imaging techniques to realize the in situ single molecule imaging of cell membranes. In the past few decades, some amazing imaging techniques and instruments with super resolution have been widely developed for molecule imaging, which can also be further employed for the in situ single molecule imaging of cell membranes. In this review, we attempt to summarize the characteristics of these advanced techniques for use in the in situ single molecule imaging of cell membranes. We believe that this work will help to promote the technological and methodological developments of super-resolution techniques for the single molecule imaging of cell membranes and help researchers better understand which technique is most suitable for their future exploring of membrane biomolecules; ultimately promoting further developments in cell biology, immunology and medicine.

  4. Water-Free Proton-Conducting Membranes for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Yen, Shiao-Pin

    2007-01-01

    Poly-4-vinylpyridinebisulfate (P4VPBS) is a polymeric salt that has shown promise as a water-free proton-conducting material (solid electrolyte) suitable for use in membrane/electrode assemblies in fuel cells. Heretofore, proton-conducting membranes in fuel cells have been made from perfluorinated ionomers that cannot conduct protons in the absence of water and, consequently, cannot function at temperatures >100 C. In addition, the stability of perfluorinated ionomers at temperatures >100 C is questionable. However, the performances of fuel cells of the power systems of which they are parts could be improved if operating temperatures could be raised above 140 C. What is needed to make this possible is a solid-electrolyte material, such as P4VPBS, that can be cast into membranes and that both retains proton conductivity and remains stable in the desired higher operating temperature range. A family of solid-electrolyte materials different from P4VPBS was described in Anhydrous Proton-Conducting Membranes for Fuel Cells (NPO-30493), NASA Tech Briefs, Vol. 29, No. 8 (August 2005), page 48. Those materials notably include polymeric quaternized amine salts. If molecules of such a polymeric salt could be endowed with flexible chain structures, it would be possible to overcome the deficiencies of simple organic amine salts that must melt before being able to conduct protons. However, no polymeric quaternized amine salts have yet shown to be useful in this respect. The present solid electrolyte is made by quaternizing the linear polymer poly- 4-vinylpyridine (P4VP) to obtain P4VPBS. It is important to start with P4VP having a molecular weight of 160,000 daltons because P4VPBS made from lower-molecular-weight P4VP yields brittle membranes. In an experimental synthesis, P4VP was dissolved in methanol and then reacted with an excess of sulfuric acid to precipitate P4VPBS. The precipitate was recovered, washed several times with methanol to remove traces of acid, and dried to a white granular solid. In another synthesis, nanoparticles of silica rich with surface hydroxyl groups were added to P4VP in methanol solution, which was then reacted with excess sulfuric acid to precipitate granules of a composite that most probably had the composition (P4VPBS)-SiO2-SiO(HSO4)2. The granular P4VPBS produced in the first-mentioned synthesis was dissolved in water to make a glue-like, turbid solution; the granular P4VPBS/silica composite produced in the second-mentioned synthesis was mixed with water to make a turbid, glue-like suspension. The proportions of polymer salt to water in such preparations can be varied; it was found that approximately equal parts of water and polymer salt yield a solution or suspension amenable to further processing.

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

    SciTech Connect

    Shamsuddin Ilias

    2003-04-24

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

  6. Acetylcholine Receptor Organization in Membrane Domains in Muscle Cells

    PubMed Central

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

    2011-01-01

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

  7. Molecular phylogeny of cycads inferred from rbcL sequences

    NASA Astrophysics Data System (ADS)

    Treutlein, Jens; Wink, Michael

    2002-03-01

    The chloroplast gene rbcL was sequenced to elucidate the evolution of the gymnosperm plant order Cycadales. In accordance with traditional systematics, the order Cycadales and the corresponding genera cluster as monophyletic clades. Among them, the genus Cycas forms a basal group. The genetic distances within the genus Encephalartos and between the sister groups Encephalartos, Lepidozamia and Macrozamia, are unexpectedly small, suggesting that the extant species are the result of Miocene and Pliocene speciation. Their distribution in Africa or Australia, respectively, may therefore rather be due to long-distance dispersal than to Cretaceous continental drift, as had previously been assumed. The rbcL sequences also indicate that the colonisation of Madagascar by Cycas thouarsii occurred only recently as the sequences of C. thouarsii and Cycas rumphii from Indonesia are identical. In contrast, the divergence of the Cycadaceae and Zamiaceae apparently occurred in the Mesozoic.

  8. Smoking and fluidity of erythrocyte membranes: a high resolution scanning electron and atomic force microscopy investigation.

    PubMed

    Pretorius, Etheresia; du Plooy, Jeanette N; Soma, Prashilla; Keyser, Ina; Buys, Antoinette V

    2013-11-30

    Smoking affects the general health of an individual, however, the red blood cells (RBCs) and their architecture are particularly vulnerable to inhaled toxins related to smoking. Smoking is one of the lifestyle diseases that are responsible for the most deaths worldwide and an individual who smokes is exposed to excessive amounts of oxidants and toxins which generate up to 10(18) free radicals in the human body. Recently, it was reported that smoking decreases RBC membrane fluidity. Here we confirm this and we show changes visible in the topography of RBC membranes, using scanning electron microscopy (SEM). RBC membranes show bubble formation of the phospholipid layer, as well as balloon-like smooth areas; while their general discoid shapes are changed to form pointed extensions. We also investigate membrane roughness using atomic force microscopy (AFM) and these results confirm SEM results. Due to the vast capability of RBCs to be adaptable, their state of well-being is a major indication for the general health status of an individual. We conclude that these changes, using an old technique in a novel application, may provide new insights and new avenues for future improvements in clinical medicine pertaining to conditions like COPD. PMID:23973530

  9. A novel Bruch's membrane-mimetic electrospun substrate scaffold for human retinal pigment epithelium cells.

    PubMed

    Xiang, Ping; Wu, Kun-Chao; Zhu, Ying; Xiang, Lue; Li, Chong; Chen, Deng-Long; Chen, Feng; Xu, Guotong; Wang, Aijun; Li, Min; Jin, Zi-Bing

    2014-12-01

    Various artificial membranes have been used as scaffolds for retinal pigment epithelium cells (RPE) for monolayer reconstruction, however, long-term cell viability and functionality are still largely unknown. This study aimed to construct an ultrathin porous nanofibrous film to mimic Bruch's membrane, and in particular to investigate human RPE cell responses to the resultant substrates. An ultrathin porous nanofibrous membrane was fabricated by using regenerated wild Antheraea pernyi silk fibroin (RWSF), polycaprolactone (PCL) and gelatin (Gt) and displayed a thickness of 3-5 ?m, with a high porosity and an average fiber diameter of 166 ± 85 nm. Human RPE cells seeded on the RWSF/PCL/Gt membranes showed a higher cell growth rate (p < 0.05), and a typical expression pattern of RPE signature genes, with reduced expression of inflammatory mediators. With long-term cultivation on the substrates, RPE cells exhibited characteristic polygonal morphology and development of apical microvilli. Immunocytochemisty demonstrated RPE-specific expression profiles in cells after 12-weeks of co-culture on RWSF/PCL/Gt membranes. Interestingly, the cells on the RWSF/PCL/Gt membranes functionally secreted polarized PEDF and phagocytosed labeled porcine POS. Furthermore, RWSF/PCL/Gt membranes transplanted subsclerally exhibited excellent biocompatibility without any evidence of inflammation or rejection. In conclusion, we established a novel RWSF-based substrate for growth of RPE cells with excellent cytocompatibility in vitro and biocompatibility in vivo for potential use as a prosthetic Bruch's membrane for RPE transplantation. PMID:25220295

  10. Thylakoid Membrane Maturation and PSII Activation Are Linked in Greening Synechocystis sp. PCC 6803 Cells1

    PubMed Central

    Barthel, Sandra; Bernát, Gábor; Seidel, Tobias; Rupprecht, Eva; Kahmann, Uwe; Schneider, Dirk

    2013-01-01

    Thylakoid membranes are typical and essential features of both chloroplasts and cyanobacteria. While they are crucial for phototrophic growth of cyanobacterial cells, biogenesis of thylakoid membranes is not well understood yet. Dark-grown Synechocystis sp. PCC 6803 cells contain only rudimentary thylakoid membranes but still a relatively high amount of phycobilisomes, inactive photosystem II and active photosystem I centers. After shifting dark-grown Synechocystis sp. PCC 6803 cells into the light, “greening” of Synechocystis sp. PCC 6803 cells, i.e. thylakoid membrane formation and recovery of photosynthetic electron transport reactions, was monitored. Complete restoration of a typical thylakoid membrane system was observed within 24 hours after an initial lag phase of 6 to 8 hours. Furthermore, activation of photosystem II complexes and restoration of a functional photosynthetic electron transport chain appears to be linked to the biogenesis of organized thylakoid membrane pairs. PMID:23922268

  11. Identification of Rubisco rbcL and rbcS in Camellia oleifera and their potential as molecular markers for selection of high tea oil cultivars

    PubMed Central

    Chen, Yongzhong; Wang, Baoming; Chen, Jianjun; Wang, Xiangnan; Wang, Rui; Peng, Shaofeng; Chen, Longsheng; Ma, Li; Luo, Jian

    2015-01-01

    Tea oil derived from seeds of Camellia oleifera Abel. is high-quality edible oil in China. This study isolated full-length cDNAs of Rubisco subunits rbcL and rbcS from C. oleifera. The rbcL has 1,522 bp with a 1,425 bp coding region, encoding 475 amino acids; and the rbcS has 615 bp containing a 528 bp coding region, encoding 176 amino acids. The expression level of the two genes, designated as Co-rbcL and Co-rbcS, was determined in three C. oleifera cultivars: Hengchong 89, Xianglin 1, and Xianglin 14 whose annual oil yields were 546.9, 591.4, and 657.7 kg ha-1, respectively. The Co-rbcL expression in ‘Xianglin 14’ was significantly higher than ‘Xianglin 1’, and ‘Xianglin 1’ was greater than ‘Hengchong 89’. The expression levels of Co-rbcS in ‘Xianglin 1’ and ‘Xianglin 14’ were similar but were significantly greater than in ‘Hengchong 89’. The net photosynthetic rate of ‘Xianglin 14’ was significantly higher than ‘Xianglin 1’, and ‘Xianglin 1’ was higher than ‘Hengchong 89’. Pearson’s correlation analysis showed that seed yields and oil yields were highly correlated with the expression level of Co-rbcL at P < 0.001 level; and the expression of Co-rbcS was correlated with oil yield at P < 0.01 level. Net photosynthetic rate was also correlated with oil yields and seed yields at P < 0.001 and P < 0.01 levels, respectively. Our results suggest that Co-rbcS and Co-rbcL in particular could potentially be molecular markers for early selection of high oil yield cultivars. In combination with the measurement of net photosynthetic rates, the early identification of potential high oil production cultivars would significantly shorten plant breeding time and increase breeding efficiency. PMID:25873921

  12. Quantitative Analysis of Surface Plasma Membrane Proteins of Primary and Metastatic Melanoma Cells

    PubMed Central

    Qiu, Haibo; Wang, Yinsheng

    2016-01-01

    Plasma membrane proteins play critical roles in cell-to-cell recognition, signal transduction and material transport. Because of their accessibility, membrane proteins constitute the major targets for protein-based drugs. Here, we described an approach, which included stable isotope labeling by amino acids in cell culture (SILAC), cell surface biotinylation, affinity peptide purification and LC-MS/MS for the identification and quantification of cell surface membrane proteins. We applied the strategy for the quantitative analysis of membrane proteins expressed by a pair of human melanoma cell lines, WM-115 and WM-266-4, which were derived initially from the primary and metastatic tumor sites of the same individual. We were able to identify more than 100 membrane and membrane-associated proteins from these two cell lines, including cell surface histones. We further confirmed the surface localization of histone H2B and three other proteins by immunocytochemical analysis with confocal microscopy. The contamination from cytoplasmic and other nonmembrane-related sources is greatly reduced by using cell surface biotinylation and affinity purification of biotinylated peptides. We also quantified the relative expression of 62 identified proteins in the two types of melanoma cells. The application to quantitative analysis of membrane proteins of primary and metastatic melanoma cells revealed great potential of the method in the comprehensive identification of tumor progression markers as well as in the discovery of new protein-based therapeutic targets. PMID:18410138

  13. Characterization of the Small Exported Plasmodium falciparum Membrane Protein SEMP1

    PubMed Central

    Dietz, Olivier; Rusch, Sebastian; Brand, Françoise; Mundwiler-Pachlatko, Esther; Gaida, Annette; Voss, Till; Beck, Hans-Peter

    2014-01-01

    Survival and virulence of the human malaria parasite Plasmodium falciparum during the blood stage of infection critically depend on extensive host cell refurbishments mediated through export of numerous parasite proteins into the host cell. The parasite-derived membranous structures called Maurer's clefts (MC) play an important role in protein trafficking from the parasite to the red blood cell membrane. However, their specific function has yet to be determined. We identified and characterized a new MC membrane protein, termed small exported membrane protein 1 (SEMP1). Upon invasion it is exported into the RBC cytosol where it inserts into the MCs before it is partly translocated to the RBC membrane. Using conventional and conditional loss-of-function approaches we showed that SEMP1 is not essential for parasite survival, gametocytogenesis, or PfEMP1 export under culture conditions. Co-IP experiments identified several potential interaction partners, including REX1 and other membrane-associated proteins that were confirmed to co-localize with SEMP1 at MCs. Transcriptome analysis further showed that expression of a number of exported parasite proteins was up-regulated in SEMP1-depleted parasites. By using Co-IP and transcriptome analysis for functional characterization of an exported parasite protein we provide a new starting point for further detailed dissection and characterisation of MC-associated protein complexes. PMID:25062022

  14. Novel Polyoxometalate Containing Membranes for PEM Fuel Cells

    SciTech Connect

    Mason K. Harrup; Frederick F. Stewart; Thomas A Luther; Tammy Trowbridge

    2009-03-01

    Current proton exchange membrane (PEM) technologies are inadequate to address the projected needs for fuel cell performance above 80 ºC. Continuing research into traditional ion carriers in novel membrane materials offers the promise of marginal improvement, representing only an evolutionary increase in performance. This conclusion is supported by the role of water in conduction. Thus, the key to better PEMs is not to eliminate water, but to change the role of water by developing ion carriers that will bind water more tightly than traditional sulfur or phosphorus based carriers resulting in materials that will conduct at higher temperatures. This change entails having a carrier structure that interacts more intimately with water and by increasing the ion carrier anionic charge to result in more tightly held inner shell protonated waters of hydration. Both of these factors synergistically act to maintain a critical water concentration at the carrier necessary for conduction. In this work, polyoxometalate (POM) clusters were selected to serve as these different proton carriers.

  15. Thermodynamics, Structure and Transport in Model Fuel Cell Membranes

    NASA Astrophysics Data System (ADS)

    Balsara, Nitash

    2008-03-01

    Polymer electrolyte membranes (PEM), used to conduct protons from the anode to the cathode of hydrogen fuel cells, are open systems that exchange water with the surrounding air. Proton conductivity is closely coupled to the presence of contiguous hydrated channels within the membrane. In an attempt to understand the underpinnings of the morphology of these systems, the phase behavior of model PEMs comprising block copolymers in equilibrium with humidified air was studied as a function of the relative humidity of the surrounding air, ion content of the copolymer, and temperature. At low humidity, the copolymers exhibit an order-to-disorder transition as a function of increasing temperature. At high humidity, however, increasing temperature results in a disorder-to-order transition. In-situ small angle neutron scattering experiments on the open block copolymer system, when combined with water uptake measurement indicate that the disorder-to-order transition is driven by an increase in the partial molar entropy of the water molecules in the ordered phase relative to that in the disordered phase. This is in contrast to most systems wherein increasing entropy results in stabilization of the disordered phase. The coupling between entropy and proton conductivity will be discussed.

  16. Tuning nano electric field to affect restrictive membrane area on localized single cell nano-electroporation

    NASA Astrophysics Data System (ADS)

    Santra, Tuhin Subhra; Wang, Pen-Cheng; Chang, Hwan-You; Tseng, Fan-Gang

    2013-12-01

    Interaction of electric field with biological cells is an important phenomenon for field induced drug delivery system. We demonstrate a selective and localized single cell nano-electroporation (LSCNEP) by applying an intense electric field on a submicron region of the single cell membrane, which can effectively allow high efficient molecular delivery but low cell damage. The delivery rate is controlled by adjusting transmembrane potential and manipulating membrane status. Thermal and ionic influences are deteriorated from the cell membrane by dielectric passivation. Either reversible or irreversible by LSCNEP can fully controlled with potential applications in medical diagnostics and biological studies.

  17. Use of red blood cell membranes to evaluate the antioxidant potential of plant extracts.

    PubMed

    Cavallini, Gabriella; Dachà, Marina; Potenza, Lucia; Ranieri, Annamaria; Scattino, Claudia; Castagna, Antonella; Bergamini, Ettore

    2014-06-01

    Antioxidant phytochemicals in fruits and vegetables of a vegetarian diet may account for the reduced risk of aging and stress oxidative associated diseases. In this study, a simple, rapid and accurate new bioassay for the determination of the antioxidant activity of purified or crude plant extracts and thier interactions is described, based on the fluorimetric determination of thiobarbituric acid reactive substances (TBARS) released by UV-B radiated red blood cell (RBC) ghosts. Pure resveratrol, white and red wine and pomegranate juice (PJ) were used as antioxidant source to test the biological method. TBARS production is a function of radiation time, the number of RBC ghosts in the radiated sample and the loaded antioxidant. The antioxidant activity of resveratrol was detected at a submicromolar concentration range [0.02 ?g/mL-0.1 ?mol/L]. The activity of red wine was almost 10 times higher than that of white wine, and PJ juice had the highest activity. Submaximal protective effects of PJ and red wine were additive. PMID:24682659

  18. Red fluorescent luminogen from pyrrole derivatives with aggregation-enhanced emission for cell membrane imaging.

    PubMed

    Liu, Guogang; Chen, Didi; Kong, Lingwei; Shi, Jianbing; Tong, Bin; Zhi, Junge; Feng, Xiao; Dong, Yuping

    2015-05-18

    A dye emitted red fluorescence with aggregation-enhanced emission properties was reported here. It can be utilized to specifically recognize the cell membrane of MCF-7 and 293T cell lines during bio-imaging. PMID:25896404

  19. Investigation of the performance and water transport of a polymer electrolyte membrane (pem) fuel cell 

    E-print Network

    Park, Yong Hun

    2009-05-15

    Fuel cell performance was obtained as functions of the humidity at the anode and cathode sites, back pressure, flow rate, temperature, and channel depth. The fuel cell used in this work included a membrane and electrode assembly (MEA) which...

  20. Macrophage Cell Membrane Camouflaged Mesoporous Silica Nanocapsules for In Vivo Cancer Therapy.

    PubMed

    Xuan, Minjun; Shao, Jingxin; Dai, Luru; He, Qiang; Li, Junbai

    2015-08-01

    Engineering natural macrophage cell membrane-camouflaged mesoporous silica nanocapsules can reduce the arrested percentage of immune cells and tissues, effectively prolong the survival time of nanoparticles in blood circulation system, and improve the accumulation in tumor. PMID:25960053

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

    PubMed

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

    2015-12-01

    During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane might provide main protection to tolerate accumulated ethanol, and S. cerevisiae cells might also remodel their membrane compositions or structure to try to adapt to or tolerate the ethanol stress. However, the exact changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation still remains poorly understood. This study was performed to clarify changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation. Both cell diameter and membrane integrity decreased as fermentation time lasting. Moreover, compared with cells at lag phase, cells at exponential and stationary phases had higher contents of ergosterol and oleic acid (C18:1) but lower levels of hexadecanoic (C16:0) and palmitelaidic (C16:1) acids. Contents of most detected phospholipids presented an increase tendency during fermentation process. Increased contents of oleic acid and phospholipids containing unsaturated fatty acids might indicate enhanced cell membrane fluidity. Compared with cells at lag phase, cells at exponential and stationary phases had higher expressions of ACC1 and HFA1. However, OLE1 expression underwent an evident increase at exponential phase but a decrease at following stationary phase. These results indicated that during bioethanol fermentation process, yeast cells remodeled membrane and more changeable cell membrane contributed to acquiring higher ethanol tolerance of S. cerevisiae cells. These results highlighted our knowledge about relationship between the variation of cell membrane structure and compositions and ethanol tolerance, and would contribute to a better understanding of bioethanol fermentation process and construction of industrial ethanologenic strains with higher ethanol tolerance. PMID:26515124

  2. Journal of Neuroscience Methods 155 (2006) 180186 Measuring cell viability with membrane impermeable

    E-print Network

    Li, Yang V.

    2006-01-01

    Journal of Neuroscience Methods 155 (2006) 180­186 Measuring cell viability with membrane+ dye to penetrate their plasma membranes, subsequently exhibiting cytosolic and nuclear fluorescence. Two other cell impermeable fluorescent Zn2+ dyes, Fluozin-3 and Zinpyr-4, also stained cytosolic Zn2

  3. Pharmacological targeting of membrane rigidity: implications on cancer cell migration and invasion

    NASA Astrophysics Data System (ADS)

    Braig, Simone; Schmidt, B. U. Sebastian; Stoiber, Katharina; Händel, Chris; Möhn, Till; Werz, Oliver; Müller, Rolf; Zahler, Stefan; Koeberle, Andreas; Käs, Josef A.; Vollmar, Angelika M.

    2015-08-01

    The invasive potential of cancer cells strongly depends on cellular stiffness, a physical quantity that is not only regulated by the mechanical impact of the cytoskeleton but also influenced by the membrane rigidity. To analyze the specific role of membrane rigidity in cancer progression, we treated cancer cells with the Acetyl-CoA carboxylase inhibitor Soraphen A and revealed an alteration of the phospholipidome via mass spectrometry. Migration, invasion, and cell death assays were employed to relate this alteration to functional consequences, and a decrease of migration and invasion without significant impact on cell death has been recorded. Fourier fluctuation analysis of giant plasma membrane vesicles showed that Soraphen A increases membrane rigidity of carcinoma cell membranes. Mechanical measurements of the creep deformation response of whole intact cells were performed using the optical stretcher. The increase in membrane rigidity was observed in one cell line without changing the creep deformation response indicating no restructuring of the cytoskeleton. These data indicate that the increase of membrane rigidity alone is sufficient to inhibit invasiveness of cancer cells, thus disclosing the eminent role of membrane rigidity in migratory processes.

  4. Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode

    E-print Network

    Stefanopoulou, Anna

    Nitrogen Front Evolution in Purged Polymer Electrolyte Membrane Fuel Cell with Dead-Ended Anode in a proton exchange membrane fuel cell operating with a dead-ended anode that is fed by dry hydrogen under dead- ended anode DEA conditions are modeled and measured in this paper. Although a flow

  5. Mathematical modeling of fluorescence diffuse optical imaging of cell membrane potential

    E-print Network

    Ammari, Habib

    Mathematical modeling of fluorescence diffuse optical imaging of cell membrane potential changes optical to- mography. We derive the resolving power of the imaging method in the presence of measurement noise. The proposed mathematical model can be used for cell membrane tracking with the resolution

  6. Three steps in the anode reaction of the polymer electrolyte membrane fuel cell. Effect of CO

    E-print Network

    Kjelstrup, Signe

    Three steps in the anode reaction of the polymer electrolyte membrane fuel cell. Effect of CO Anne in the polymer electrolyte membrane fuel cell (PEMFC) using electrochemical impedance spectroscopy (EIS in the reaction mechanism, the slow adsorption/diffusion step, the charge transfer step and the proton hydration

  7. Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition

    E-print Network

    Increasing Proton Exchange Membrane Fuel Cell Catalyst Effectiveness Through Sputter Deposition, New York 12203, USA Sputter deposition has been investigated as a tool for manufacturing proton January 29, 2002. Proton exchange membrane fuel cells PEMFCs are gaining popularity due to their high

  8. Increased phorbol 12,13-dibutyrate (PDBu) receptor function associated with sickle red cell membrane ghosts

    SciTech Connect

    Ramachandran, M.; Nair, C.N.; Abraham, E.C.

    1987-05-01

    The biological receptor for tumor-promoting phorbol esters has been identified as the CaS /phospholipid dependent enzyme, protein kinase C. In the red cell, this enzyme is mainly cytosolic but becomes translocated to the membrane if the cellular CaS is allowed to rise. Since cellular CaS in sickle red cells is high, it was reasoned that this enzyme may become more membrane-bound. In fact, the authors noticed a four-fold increase in the binding of TH-PDBu by membrane ghosts isolated from sickle red cells compared to normal red cells (pmoles PDBu bound/mg protein; normal = 0.3 vs sickle cell = 1.4). Attempts to assay the enzyme directly as phospholipid-activated TSP incorporation into the acid-precipitable membrane proteins also indicated a two-fold increase in the radiolabelling of sickle cell membrane ghosts. Autophosphorylation of membrane proteins and analysis of the phosphorylation profile by SDS-PAGE and autoradiography revealed phosphorylation predominantly of bands 3, 4.1 and 4.9 which are known protein kinase C substrates for the red cell enzyme. The increased membrane-associated protein kinase C in sickle red cells may have a bearing on the altered membrane properties reported in this condition.

  9. Dynamic maintenance of stochastic molecular clusters on cell membranes

    NASA Astrophysics Data System (ADS)

    Mugler, Andrew; Wehrens, Martijn; Ten Wolde, Pieter Rein

    2015-03-01

    Clustering of molecules on cell membranes is a widely observed phenomenon. A key example is the oncoprotein Ras. Maintenance of Ras clusters has been linked to proper Ras signaling. Yet, the mechanism by which Ras clusters are maintained remains unclear. Recently it was discovered that activated Ras promotes further Ras activation. We show using particle-based simulation that this positive feedback link is sufficient to produce persistent clusters of active Ras molecules via a dynamic nucleation mechanism. The cluster statistics are consistent with experimental observations. Interestingly, our model does not support a Turing regime of macroscopic reaction-diffusion patterning. This means that the clustering we observe is a purely stochastic effect, arising from the coupling of the positive feedback network with the discrete nature of individual molecules. These findings underscore the importance of stochastic and dynamic properties of reaction diffusion systems for biological behavior.

  10. Ezrin is a Major Regulator of Membrane Tension in Epithelial Cells.

    PubMed

    Rouven Brückner, Bastian; Pietuch, Anna; Nehls, Stefan; Rother, Jan; Janshoff, Andreas

    2015-01-01

    Plasma membrane tension is responsible for a variety of cellular functions such as motility, cell division, and endocytosis. Since membrane tension is dominated by the attachment of the actin cortex to the inner leaflet of the plasma membrane, we investigated the importance of ezrin, a major cross-linker of the membrane-cytoskeleton interface, for cellular mechanics of confluent MDCK II cells. For this purpose, we carried out ezrin depletion experiments and also enhanced the number of active ezrin molecules at the interface. Mechanical properties were assessed by force indentation experiments followed by membrane tether extraction. PIP2 micelles were injected into individual living cells to reinforce the linkage between plasma membrane and actin-cortex, while weakening of this connection was reached by ezrin siRNA and administration of the inhibitors neomycin and NSC 668394, respectively. We observed substantial stiffening of cells and an increase in membrane tension after addition of PIP2 micelles. In contrast, reduction of active ezrin led to a decrease of membrane tension accompanied by loss of excess surface area, increase in cortical tension, remodelling of actin cytoskeleton, and reduction of cell height. The data confirm the importance of the ezrin-mediated connection between plasma membrane and cortex for cellular mechanics and cell morphology. PMID:26435322

  11. Ezrin is a Major Regulator of Membrane Tension in Epithelial Cells

    PubMed Central

    Rouven Brückner, Bastian; Pietuch, Anna; Nehls, Stefan; Rother, Jan; Janshoff, Andreas

    2015-01-01

    Plasma membrane tension is responsible for a variety of cellular functions such as motility, cell division, and endocytosis. Since membrane tension is dominated by the attachment of the actin cortex to the inner leaflet of the plasma membrane, we investigated the importance of ezrin, a major cross-linker of the membrane-cytoskeleton interface, for cellular mechanics of confluent MDCK II cells. For this purpose, we carried out ezrin depletion experiments and also enhanced the number of active ezrin molecules at the interface. Mechanical properties were assessed by force indentation experiments followed by membrane tether extraction. PIP2 micelles were injected into individual living cells to reinforce the linkage between plasma membrane and actin-cortex, while weakening of this connection was reached by ezrin siRNA and administration of the inhibitors neomycin and NSC 668394, respectively. We observed substantial stiffening of cells and an increase in membrane tension after addition of PIP2 micelles. In contrast, reduction of active ezrin led to a decrease of membrane tension accompanied by loss of excess surface area, increase in cortical tension, remodelling of actin cytoskeleton, and reduction of cell height. The data confirm the importance of the ezrin-mediated connection between plasma membrane and cortex for cellular mechanics and cell morphology. PMID:26435322

  12. Multiphase transport in polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Gauthier, Eric D.

    Polymer electrolyte membrane fuel cells (PEMFCs) enable efficient conversion of fuels to electricity. They have enormous potential due to the high energy density of the fuels they utilize (hydrogen or alcohols). Power density is a major limitation to wide-scale introduction of PEMFCs. Power density in hydrogen fuel cells is limited by accumulation of water in what is termed fuel cell `flooding.' Flooding may occur in either the gas diffusion layer (GDL) or within the flow channels of the bipolar plate. These components comprise the electrodes of the fuel cell and balance transport of reactants/products with electrical conductivity. This thesis explores the role of electrode materials in the fuel cell and examines the fundamental connection between material properties and multiphase transport processes. Water is generated at the cathode catalyst layer. As liquid water accumulates it will utilize the largest pores in the GDL to go from the catalyst layer to the flow channels. Water collects to large pores via lateral transport at the interface between the GDL and catalyst layer. We have shown that water may be collected in these large pores from several centimeters away, suggesting that we could engineer the GDL to control flooding with careful placement and distribution of large flow-directing pores. Once liquid water is in the flow channels it forms slugs that block gas flow. The slugs are pushed along the channel by a pressure gradient that is dependent on the material wettability. The permeable nature of the GDL also plays a major role in slug growth and allowing bypass of gas between adjacent channels. Direct methanol fuel cells (DMFCs) have analogous multiphase flow issues where carbon dioxide bubbles accumulate, `blinding' regions of the fuel cell. This problem is fundamentally similar to water management in hydrogen fuel cells but with a gas/liquid phase inversion. Gas bubbles move laterally through the porous GDL and emerge to form large bubbles within the flow channel. We have compared the role of GDL materials in liquid drop and gas bubble formation and movement within fuel cells.

  13. C8-glycosphingolipids preferentially insert into tumor cell membranes and promote chemotherapeutic drug uptake.

    PubMed

    Cordeiro Pedrosa, Lília R; van Cappellen, Wiggert A; Steurer, Barbara; Ciceri, Dalila; ten Hagen, Timo L M; Eggermont, Alexander M M; Verheij, Marcel; Goñi, Felix María; Koning, Gerben A; Contreras, F-Xabier

    2015-08-01

    Insufficient drug delivery into tumor cells limits the therapeutic efficacy of chemotherapy. Co-delivery of liposome-encapsulated drug and synthetic short-chain glycosphingolipids (SC-GSLs) significantly improved drug bioavailability by enhancing intracellular drug uptake. Investigating the mechanisms underlying this SC-GSL-mediated drug uptake enhancement is the aim of this study. Fluorescence microscopy was used to visualize the cell membrane lipid transfer intracellular fate of fluorescently labeled C6-NBD-GalCer incorporated in liposomes in tumor and non-tumor cells. Additionally click chemistry was applied to image and quantify native SC-GSLs in tumor and non-tumor cell membranes. SC-GSL-mediated flip-flop was investigated in model membranes to confirm membrane-incorporation of SC-GSL and its effect on membrane remodeling. SC-GSL enriched liposomes containing doxorubicin (Dox) were incubated at 4°C and 37°C and intracellular drug uptake was studied in comparison to standard liposomes and free Dox. SC-GSL transfer to the cell membrane was independent of liposomal uptake and the majority of the transferred lipid remained in the plasma membrane. The transfer of SC-GSL was tumor cell-specific and induced membrane rearrangement as evidenced by a transbilayer flip-flop of pyrene-SM. However, pore formation was measured, as leakage of hydrophilic fluorescent probes was not observed. Moreover, drug uptake appeared to be mediated by SC-GSLs. SC-GSLs enhanced the interaction of doxorubicin (Dox) with the outer leaflet of the plasma membrane of tumor cells at 4°C. Our results demonstrate that SC-GSLs preferentially insert into tumor cell plasma membranes enhancing cell intrinsic capacity to translocate amphiphilic drugs such as Dox across the membrane via a biophysical process. PMID:25917957

  14. Functional up-converting SrTiO3:Er(3+)/Yb(3+) nanoparticles: structural features, particle size, colour tuning and in vitro RBC cytotoxicity.

    PubMed

    Pazik, R; Maczka, M; Malecka, M; Marciniak, L; Ekner-Grzyb, A; Mrowczynska, L; Wiglusz, R J

    2015-06-14

    SrTiO3 nanoparticles co-doped with a broad concentration range of Er(3+) and Yb(3+) ions were fabricated using the citric route as a function of annealing temperatures of 500-1000 °C. The effect of a broad co-dopant concentration range and sintering temperature on structural and up-conversion properties was investigated in detail by X-ray diffraction techniques and optical spectroscopy. The TEM technique was used to estimate the mean particle size, which was around 30 nm for the inorganic product annealed at 600 °C. Up-conversion emission color tuning was achieved by particle size control. Power dependence of the green and red emissions was found to be a result of temperature determination in the operating range of SrTiO3 nanoparticles and a candidate for the fast and local microscopic heating and heat release induced by IR irradiation. The color changed from white-red-yellow-green upon an increase of sintering temperature, inducing changes in the surface-to-volume ratio and the number of optically active ions in particle surface regions. The cytotoxic activity of nanoparticles on human red blood cells was investigated, showing no harmful effects up to a particle concentration of 0.1 mg ml(-1). The cytotoxic response of a colloidal suspension of nanoparticles to RBC cells was connected with the strong affinity of SrTiO3 particles to the cell membranes, blocking the transport of important biological solutes. PMID:25962584

  15. Fabrication of a membrane filter with controlled pore shape and its application to cell separation and strong single cell trapping

    NASA Astrophysics Data System (ADS)

    Choi, Dong-Hoon; Yoon, Gun-Wook; Park, Jeong Won; Ihm, Chunhwa; Lee, Dae-Sik; Yoon, Jun-Bo

    2015-10-01

    A porous membrane filter is one of the key components for sample preparation in lab-on-a-chip applications. However, most of the membranes reported to date have only been used for size-based separation since it is difficult to provide functionality to the membrane or improve the performance of the membrane. In this work, as a method to functionalize the membrane filter, controlling the shape of the membrane pores is suggested, and a convenient and mass-producible fabrication method is provided. With the proposed method, membrane filters with round, conical and funnel shape pores were successfully fabricated, and we demonstrated that the sidewall slope of the conical shape pores could be precisely controlled. To verify that the membrane filter can be functionalized by controlled pore shape, we investigated filtration and trapping performance of the membrane filter with conical shape pores. In a filtration test of 1000 cancer cells (MCF-7, a breast cancer cell line) spiked in phosphate buffered saline (PBS) solution, 77% of the total cancer cells were retained on the membrane, and each cell from among 99.3% of the retained cells was automatically isolated in a single conical pore during the filtration process. Thanks to its engineered pore shape, trapping ability of the membrane with conical pores is dramatically improved. Microparticles trapped in the conical pores maintain their locations without any losses even at a more than 30 times faster external flow rate com-pared with those mounted on conventional cylindrical pores. Also, 78% of the cells trapped in the conical pores withstand an external flow of over 300 ?l min-1 whereas only 18% of the cells trapped in the cylindrical pores remain on the membrane after 120 ?l min-1 of an external flow is applied.

  16. The Structure of Catalyst Layers and Cell Performance in Proton Exchange Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Inoue, Hiroyuki; Daiguji, Hirofumi; Hihara, Eiji

    A catalyst layer is one of the key elements in polymer electrolyte membrane fuel cells (PEMFC). Improvements in the performance of a membrane electrode assembly (MEA) for PEMFC are much influenced by an electrochemically active surface area in a catalyst layer. But the relation between the structure of a catalyst layer and the cell performance has not been clarified yet. In the present study, catalyst layers with different structure and composition were fabricated, and the structural properties of catalyst layers, such as thickness and roughness, and the polarization curves were measured. The experimental results suggested that there is an optimum mass ratio of electrolyte in a catalyst layer for the cell performance, and the thickness and roughness of a catalyst layer change significantly at the optimum mass ratio.

  17. Measurement of Post-Transfusion Red Cell Survival with the Biotin Label

    PubMed Central

    Mock, Donald M; Widness, John A; Veng-Pedersen, Peter; Strauss, Ronald G; Cancelas, Jose A; Cohen, Robert M; Lindsell, Christopher J; Franco, Robert S

    2014-01-01

    The goal of this review is to summarize and critically assess information concerning the biotin method to label red blood cells (RBC) for use in studies of RBC and transfusion biology — information that will prove useful to a broad audience of clinicians and scientists. A review of RBC biology, with emphasis on RBC senescence and in vivo survival is included, followed by an analysis of the advantages and disadvantages of biotin labeled RBC (BioRBC) for measuring circulating RBC volume, post-transfusion RBC recovery, RBC lifespan, and RBC age-dependent properties. The advantages of BioRBC over 51Cr RBC labeling, the current reference method, are discussed. Because the biotin method is straightforward and robust, including the ability to follow the entire lifespans of multiple RBC populations concurrently in the same subject, BioRBC offers distinct advantages for studying RBC biology and physiology, particularly RBC survival. The method for biotin labeling, validation of the method, and application of BioRBCs to studies of sickle cell disease, diabetes, and anemia of prematurity are reviewed. Studies documenting the safe use of BioRBC are reviewed; unanswered questions requiring future studies, remaining concerns, and regulatory barriers to broader application of BioRBC including adoption as a new reference method are also presented. PMID:24969019

  18. Kinetics of small molecule interactions with membrane proteins in single cells measured with mechanical amplification

    PubMed Central

    Guan, Yan; Shan, Xiaonan; Zhang, Fenni; Wang, Shaopeng; Chen, Hong-Yuan; Tao, Nongjian

    2015-01-01

    Measuring small molecule interactions with membrane proteins in single cells is critical for understanding many cellular processes and for screening drugs. However, developing such a capability has been a difficult challenge. We show that molecular interactions with membrane proteins induce a mechanical deformation in the cellular membrane, and real-time monitoring of the deformation with subnanometer resolution allows quantitative analysis of small molecule–membrane protein interaction kinetics in single cells. This new strategy provides mechanical amplification of small binding signals, making it possible to detect small molecule interactions with membrane proteins. This capability, together with spatial resolution, also allows the study of the heterogeneous nature of cells by analyzing the interaction kinetics variability between different cells and between different regions of a single cell. PMID:26601298

  19. Nanoporous gold membranes: From morphological control to fuel cell catalysis

    NASA Astrophysics Data System (ADS)

    Ding, Yi

    Porous noble metals are particularly attractive for scientific research and industrial applications such as catalysis, sensing, and filtration. In this thesis, I will discuss the fabrication, characterization, and application of a new class of porous metals, called nanoporous metals (NPM). NPM is made during selective dissolution (also called dealloying) of reactive components (e.g., silver) from multi-component alloys (e.g., Ag/Au alloy). Commercially available white gold leaf (Ag65Au35) can, for example, be etched into nanoporous gold (NPG) membrane by simply floating the leaf on concentrated nitric acid for periods of a few minutes. NPG leaf adopts a single crystal porous structure within individual grains. The microstructure of NPG, such as the pore size, is tunable between a few nanometers to sub-micron length scale by either thermal annealing or post-treatment in nitric acid for extended period of time. A new gas-liquid-solid interface electroless plating technique is developed to uniformly cover the NPG surface with other metals, such as silver and platinum. This technique allows new opportunities of making functionalized nanostructures. We show that a combination of silver plating and dealloying can be used to make multimodal porous metals, which are expected to have application in sensing field. Electroless platinum plating onto NPG shows very usual growth mode. TEM observation indicates that the platinum layer on NPG surface takes a novel form of layer-islanding growth (Stranski-Krastanov growth). Annealing the Pt/NPG composite smoothens the Pt islands and forms a 1 nm coherent Pt layer on the NPG backbone, possibly with dislocation formation at the Pt/Au interface. Furthermore, it was found that we could dissolve the gold away in aqueous gold etchant, leaving behind the 1 nm-thick Pt shell, a structure we call nanotubular mesoporous platinum (NMP). Pt plated NPG has a series of unique structural properties, such as high active surface area, thermally stable, low Pt usage, and better tolerance to CO poisoning. We incorporated it as a membrane electrode into a working proton exchange membrane fuel cells (PEMFC). Preliminary results show that Pt/NPG has very good fuel cell performance at a very low platinum loading.

  20. Novel pore-filled polyelectrolyte composite membranes for cathodic microbial fuel cell application

    NASA Astrophysics Data System (ADS)

    Gohil, J. M.; Karamanev, D. G.

    2013-12-01

    Novel pore-filled polyelectrolyte membrane (PEM) was produced using track etched polycarbonate (PC) as porous substrate and poly(vinyl alcohol) (PVA) as pore filling material. PVA in PC pores was stabilized through cross-linking of PVA matrix with glutaraldehyde (GA). Cross-link time was varied from 24 h to 96 h while keeping the membranes in GA solution. Pore sizes of substrate PC membrane tested were 0.01, 0.1 and 0.2 ?m. The membranes were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Ionic conductivity, water uptake, contact angle and gel content have been measured to determine membranes performance. The ionic crossover (iron ions and protons) through membranes was studied in a complete fuel cell. The single-cell performance of membrane was tested in a cathodic microbial fuel cell (MFC, Biogenerator). The physiochemical properties and membranes fuel cell performance were highly depended on the cross-link density of PVA matrices. Membranes cross-liked with GA for 72 h showed maximum gel content and their peak power density has reached 110 mW cm-2 at current density of 378 mA cm-2. Among all, membrane cross-linked for 72 h was studied for continuous long-term stability, which showed consistency for application in MFC.

  1. Induction of immune tolerance to RBC, platelet, and neutrophil antigens and IgA.

    PubMed

    Badami, K G

    2015-06-01

    Antibodies to red blood cell (RBC), platelet, and neutrophil antigens, and IgA may cause serious clinical problems. With a few exceptions, preventing these conditions is a matter of limiting exposure to the foreign antigen while treatment consists of managing the consequences. Might immune tolerance induction (ITI) be possible and beneficial in these situations? Neonatal exposure to antigens is known to induce central tolerance. However central tolerance may not be absolute. Factors that determine whether an antibody will be produced in response to an antigen are not well understood but include the appropriate expression of major histocompatibility complex-class II and/or co-stimulatory molecules on dendritic cells, the presence or absence of adjuvants and whether or not the antigen is presented together with agonists for the toll-like receptor. Modifying these may prevent alloimmunization. Peripheral tolerance, in sensitized individuals, as routinely used in patients with allergic/anaphylactic reactions, those with haemophilia A or B with inhibitors and acquired haemophilia, may also be possible. Briefly, monitored, graded, increasing exposure to the antigen of interest with or without additional immunosuppression is used. Neither central nor peripheral ITI has been tried or suggested for individuals sensitizable or sensitised to RBC, platelet, and neutrophil antigens, or IgA. Theoretically, this is possible and may be of benefit. PMID:25795096

  2. Mechanisms regulating cell membrane localization of the chemokine receptor CXCR4 in human hepatocarcinoma cells.

    PubMed

    Cepeda, Edgar B; Dediulia, Tatjana; Fernando, Joan; Bertran, Esther; Egea, Gustavo; Navarro, Estanislao; Fabregat, Isabel

    2015-05-01

    Hepatocellular carcinoma (HCC) cells with a mesenchymal phenotype show an asymmetric subcellular distribution of the chemokine receptor CXCR4, which is required for cell migration and invasion. In this work we examine the mechanisms that regulate the intracellular trafficking of CXCR4 in HCC cells. Results indicate that HCC cells present CXCR4 at the cell surface, but most of this protein is in endomembranes colocalizing with markers of the Golgi apparatus and recycling endosomes. The presence of high protein levels of CXCR4 present at the cell surface correlates with a mesenchymal-like phenotype and a high autocrine activation of the Transforming Growth Factor-beta (TGF-?) pathway. CXCR4 traffics along the Golgi/exocyst/plasma membrane pathway and requires EXOC4 (Sec8) component of the exocyst complex. HCC cells use distinct mechanisms for the CXCR4 internalization such as dynamin-dependent endocytosis and macropinocytosis. Regardless of the endocytic mechanisms, colocalization of CXCR4 and Rab11 is observed, which could be involved not only in receptor recycling but also in its post-Golgi transport. In summary, this work highlights membrane trafficking pathways whose pharmacological targeting could subsequently result in the inactivation of one of the main guiding mechanisms used by metastatic cells to colonize secondary organs and tissues. PMID:25704914

  3. High heterogeneity of plasma membrane microfluidity in multidrug-resistant cancer cells

    NASA Astrophysics Data System (ADS)

    Boutin, Céline; Roche, Yann; Millot, Christine; Deturche, Régis; Royer, Pascal; Manfait, Michel; Plain, Jérôme; Jeannesson, Pierre; Millot, Jean-Marc; Jaffiol, Rodolphe

    2009-05-01

    Diffusion-time distribution analysis (DDA) has been used to explore the plasma membrane fluidity of multidrug-resistant cancer cells (LR73 carcinoma cells) and also to characterize the influence of various membrane agents present in the extracellular medium. DDA is a recent single-molecule technique, based on fluorescence correlation spectroscopy (FCS), well suited to retrieve local organization of cell membrane. The method was conducted on a large number of living cells, which enabled us to get a detailed overview of plasma membrane microviscosity, and plasma membrane micro-organization, between the cells of the same line. Thus, we clearly reveal the higher heterogeneity of plasma membrane in multidrug-resistant cancer cells in comparison with the nonresistant ones (denoted sensitive cells). We also display distinct modifications related to a membrane fluidity modulator, benzyl alcohol, and two revertants of multidrug resistance, verapamil and cyclosporin-A. A relation between the distribution of the diffusion-time values and the modification of membrane lateral heterogeneities is proposed.

  4. Imaging of the membrane surface of MDCK cells by atomic force microscopy.

    PubMed Central

    Le Grimellec, C; Lesniewska, E; Cachia, C; Schreiber, J P; de Fornel, F; Goudonnet, J P

    1994-01-01

    The membrane surface of polarized renal epithelial cells (MDCK cells) grown as a monolayer was imaged with the atomic force microscope. The surface topography of dried cells determined by this approach was consistent with electron microscopy images previously reported. Fixed and living cells in aqueous medium gave more fuzzy images, likely because of the presence of the cell glycocalix. Treatment of living cells with neuraminidase, an enzyme that partly degrades the glycocalix, allowed sub-micrometer imaging. Protruding particles, 10 to 60 nm xy size, occupy most of the membrane surface. Protease treatment markedly reduced the size of these particles, indicating that they corresponded to proteins. Tip structure effects were probably involved in the exaggerated size of imaged membrane proteins. Although further improvements in the imaging conditions, including tip sharpness, are required, atomic force microscope already offers the unique possibility to image proteins at the membrane surface of living cells. Images FIGURE 1 FIGURE 2 PMID:7919007

  5. Liposome-based engineering of cells to package hydrophobic compounds in membrane vesicles for tumor penetration.

    PubMed

    Lee, Junsung; Kim, Jiyoung; Jeong, Moonkyoung; Lee, Hyoungjin; Goh, Unbyeol; Kim, Hyaeyeong; Kim, Byungji; Park, Ji-Ho

    2015-05-13

    Natural membrane vesicles (MVs) derived from various types of cells play an essential role in transporting biological materials between cells. Here, we show that exogenous compounds are packaged in the MVs by engineering the parental cells via liposomes, and the MVs mediate autonomous intercellular migration of the compounds through multiple cancer cell layers. Hydrophobic compounds delivered selectively to the plasma membrane of cancer cells using synthetic membrane fusogenic liposomes were efficiently incorporated into the membrane of MVs secreted from the cells and then transferred to neighboring cells via the MVs. This liposome-mediated MV engineering strategy allowed hydrophobic photosensitizers to significantly penetrate both spheroids and in vivo tumors, thereby enhancing the therapeutic efficacy. These results suggest that innate biological transport systems can be in situ engineered via synthetic liposomes to guide the penetration of chemotherapeutics across challenging tissue barriers in solid tumors. PMID:25806671

  6. Detergent Induction of HEK 293A Cell Membrane Permeability Measured under Quiescent and Superfusion Conditions Using Whole Cell Patch Clamp

    PubMed Central

    2015-01-01

    Detergents have several biological applications but present cytotoxicity concerns, since they can solubilize cell membranes. Using the IonFlux 16, an ensemble whole cell planar patch clamp, we observed that anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB), and cationic, fluorescent octadecyl rhodamine B (ORB) increased the membrane permeability of cells substantially within a second of exposure, under superfusion conditions. Increased permeability was irreversible for 15 min. At subsolubilizing detergent concentrations, patched cells showed increased membrane currents that reached a steady state and were intact when imaged using fluorescence microscopy. SDS solubilized cells at concentrations of 2 mM (2× CMC), while CTAB did not solubilize cells even at concentrations of 10 mM (1000× CMC). The relative activity for plasma membrane current induction was 1:20:14 for SDS, CTAB, and ORB, respectively. Under quiescent conditions, the relative ratio of lipid to detergent in cell membranes at the onset of membrane permeability was 1:7:5 for SDS, CTAB, and ORB, respectively. The partition constants (K) for SDS, CTAB, and ORB were 23000, 55000, and 39000 M–1, respectively. Combining the whole cell patch clamp data and XTT viability data, SDS ? 0.2 mM and CTAB and ORB ? 1 mM induced cell membrane permeability without causing acute toxicity. PMID:24548291

  7. A self-humidifying acidic-alkaline bipolar membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Peng, Sikan; Xu, Xin; Lu, Shanfu; Sui, Pang-Chieh; Djilali, Ned; Xiang, Yan

    2015-12-01

    To maintain membrane hydration and operate effectively, polymer electrolyte membrane fuel cells (PEMFCs) require elaborate water management, which significantly increases the complexity and cost of the fuel cell system. Here we propose a novel and entirely different approach to membrane hydration by exploiting the concept of bipolar membranes. Bipolar membrane (BPM) fuel cells utilize a composite membrane consisting of an acidic polymer electrolyte membrane on the anode side and an alkaline electrolyte membrane on the cathode side. We present a novel membrane electrode assembly (MEA) fabrication method and demonstrate experimentally and theoretically that BPM fuel cells can (a) self-humidify to ensure high ionic conductivity; and (b) allow use of non-platinum catalysts due to inherently faster oxygen reduction kinetics on an alkaline cathode. Our Pt-based BPM fuel cell achieves a two orders of magnitude gain in power density of 327 mW cm-2 at 323 K under dry gas feed, the highest power output achieved under anhydrous operation conditions. A theoretical analysis and in situ measurements are presented to characterize the unique interfacial water generation and transport behavior that make self-humidification possible during operation. Further optimization of these features and advances in fabricating bipolar MEAs would open the way for a new generation of self-humidifying and water-management-free PEMFCs.

  8. Chitosan and alginate types of bio-membrane in fuel cell application: An overview

    NASA Astrophysics Data System (ADS)

    Shaari, N.; Kamarudin, S. K.

    2015-09-01

    The major problems of polymer electrolyte membrane fuel cell technology that need to be highlighted are fuel crossovers (e.g., methanol or hydrogen leaking across fuel cell membranes), CO poisoning, low durability, and high cost. Chitosan and alginate-based biopolymer membranes have recently been used to solve these problems with promising results. Current research in biopolymer membrane materials and systems has focused on the following: 1) the development of novel and efficient biopolymer materials; and 2) increasing the processing capacity of membrane operations. Consequently, chitosan and alginate-based biopolymers seek to enhance fuel cell performance by improving proton conductivity, membrane durability, and reducing fuel crossover and electro-osmotic drag. There are four groups of chitosan-based membranes (categorized according to their reaction and preparation): self-cross-linked and salt-complexed chitosans, chitosan-based polymer blends, chitosan/inorganic filler composites, and chitosan/polymer composites. There are only three alginate-based membranes that have been synthesized for fuel cell application. This work aims to review the state-of-the-art in the growth of chitosan and alginate-based biopolymer membranes for fuel cell applications.

  9. The Anti-inflammatory Drug Indomethacin Alters Nanoclustering in Synthetic and Cell Plasma Membranes*

    PubMed Central

    Zhou, Yong; Plowman, Sarah J.; Lichtenberger, Lenard M.; Hancock, John F.

    2010-01-01

    The nonsteroidal anti-inflammatory drug indomethacin exhibits diverse biological effects, many of which have no clear molecular mechanism. Membrane-bound receptors and enzymes are sensitive to their phospholipid microenvironment. Amphipathic indomethacin could therefore potentially modulate cell signaling by changing membrane properties. Here we examined the effect of indomethacin on membrane lateral heterogeneity. Fluorescence lifetime imaging of cells expressing lipid-anchored probes revealed that treatment of BHK cells with therapeutic levels of indomethacin enhances cholesterol-dependent nanoclustering, but not cholesterol-independent nanoclustering. Immuno-electron microscopy and quantitative spatial mapping of intact plasma membrane sheets similarly showed a selective effect of indomethacin on promoting cholesterol-dependent, but not cholesterol-independent, nanoclustering. To further evaluate the biophysical effects of indomethacin, we measured fluorescence polarization of the phase-sensitive probe Laurdan and FRET between phase-partitioning probes in model bilayers. Therapeutic levels of indomethacin enhanced phase seperation in DPPC/DOPC/Chol (1:1:1) and DPPC/Chol membranes in a temperature-dependent manner, but had minimal effect on the phase behavior of pure DOPC at any temperature. Taken together, the imaging results on intact epithelial cells and the biophysical assays of model membranes suggest that indomethacin can enhance phase separation and stabilize cholesterol-dependent nanoclusters in biological membranes. These effects on membrane lateral heterogeneity may have significant consequences for cell signaling cascades that are assembled on the plasma membrane. PMID:20826816

  10. Biomechanical properties of red blood cells in health and disease towards microfluidics

    PubMed Central

    Tomaiuolo, Giovanna

    2014-01-01

    Red blood cells (RBCs) possess a unique capacity for undergoing cellular deformation to navigate across various human microcirculation vessels, enabling them to pass through capillaries that are smaller than their diameter and to carry out their role as gas carriers between blood and tissues. Since there is growing evidence that red blood cell deformability is impaired in some pathological conditions, measurement of RBC deformability has been the focus of numerous studies over the past decades. Nevertheless, reports on healthy and pathological RBCs are currently limited and, in many cases, are not expressed in terms of well-defined cell membrane parameters such as elasticity and viscosity. Hence, it is often difficult to integrate these results into the basic understanding of RBC behaviour, as well as into clinical applications. The aim of this review is to summarize currently available reports on RBC deformability and to highlight its association with various human diseases such as hereditary disorders (e.g., spherocytosis, elliptocytosis, ovalocytosis, and stomatocytosis), metabolic disorders (e.g., diabetes, hypercholesterolemia, obesity), adenosine triphosphate-induced membrane changes, oxidative stress, and paroxysmal nocturnal hemoglobinuria. Microfluidic techniques have been identified as the key to develop state-of-the-art dynamic experimental models for elucidating the significance of RBC membrane alterations in pathological conditions and the role that such alterations play in the microvasculature flow dynamics. PMID:25332724

  11. Resonance energy transfer microscopy: observations of membrane-bound fluorescent probes in model membranes and in living cells

    PubMed Central

    1986-01-01

    A conventional fluorescence microscope was modified to observe the sites of resonance energy transfer (RET) between fluorescent probes in model membranes and in living cells. These modifications, and the parameters necessary to observe RET between membrane-bound fluorochromes, are detailed for a system that uses N-4-nitrobenzo-2-oxa- 1,3-diazole (NBD) or fluorescein as the energy donor and sulforhodamine as the energy acceptor. The necessary parameters for RET in this system were first optimized using liposomes. Both quenching of the energy donor and sensitized fluorescence of the energy acceptor could be directly observed in the microscope. RET microscopy was then used in cultured fibroblasts to identify those intracellular organelles labeled by the lipid probe, N-SRh-decylamine (N-SRh-C10). This was done by observing the sites of RET in cells doubly labeled with N-SRh-C10 and an NBD-labeled lipid previously shown to label the endoplasmic reticulum, mitochondria, and nuclear envelope. RET microscopy was also used in cells treated with fluorescein-labeled Lens culinaris agglutinin and a sulforhodamine derivative of phosphatidylcholine to examine the internalization of plasma membrane lipid and protein probes. After internalization, the fluorescent lectin resided in most, but not all of the intracellular compartments labeled by the fluorescent lipid, suggesting sorting of the membrane-bound lectin into a subset of internal compartments. We conclude that RET microscopy can co-localize different membrane-bound components at high resolution, and may be particularly useful in examining temporal and spatial changes in the distribution of fluorescent molecules in membranes of the living cell. PMID:3771633

  12. Static Magnetic Field Attenuates Lipopolysaccharide-Induced Inflammation in Pulp Cells by Affecting Cell Membrane Stability

    PubMed Central

    Tsao, Jeng-Ting; Lee, Lin-Wen; Lin, Che-Tong

    2015-01-01

    One of the causes of dental pulpitis is lipopolysaccharide- (LPS-) induced inflammatory response. Following pulp tissue inflammation, odontoblasts, dental pulp cells (DPCs), and dental pulp stem cells (DPSCs) will activate and repair damaged tissue to maintain homeostasis. However, when LPS infection is too serious, dental repair is impossible and disease may progress to irreversible pulpitis. Therefore, the aim of this study was to examine whether static magnetic field (SMF) can attenuate inflammatory response of dental pulp cells challenged with LPS. In methodology, dental pulp cells were isolated from extracted teeth. The population of DPSCs in the cultured DPCs was identified by phenotypes and multilineage differentiation. The effects of 0.4?T SMF on DPCs were observed through MTT assay and fluorescent anisotropy assay. Our results showed that the SMF exposure had no effect on surface markers or multilineage differentiation capability. However, SMF exposure increases cell viability by 15%. In addition, SMF increased cell membrane rigidity which is directly related to higher fluorescent anisotropy. In the LPS-challenged condition, DPCs treated with SMF demonstrated a higher tolerance to LPS-induced inflammatory response when compared to untreated controls. According to these results, we suggest that 0.4?T SMF attenuates LPS-induced inflammatory response to DPCs by changing cell membrane stability. PMID:25884030

  13. Cell-based capacitance sensor for analysis of EGFR expression on cell membrane

    NASA Astrophysics Data System (ADS)

    Shin, Dong-Myeong; Shin, Yong-Cheol; Ha, Ji Hye; Lee, Jong-Ho; Han, Dong-Wook; Kim, Jong-Man; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2013-02-01

    Cancer cells have many kinds of cancer biomarkers. Among them, the epidermal growth factor (EGF) receptors can show a possibility for a cancer marker because the over-expression of EGF receptor is related with fibrous, colorectal, cervical and gastric tumorigenesis. We fabricated the capacitance sensor with a gap area of 50 ?m × 200 ?m by using photolithography and lift-off method. Using the capacitance sensor, we investigated the time dependent capacitance changes of different kinds of fibrous cells, such as HT1080 fibrosarcoma, L-929 fibroblast cell line and nHDF dermal fibroblast primary cell. We found that when we put the EGF, the capacitance decreased due to the immobilization of EGF to EGF receptor on the cell membrane. The quantitative determination of EGF receptor level for various fibrous cells was carried out and the results showed good correlation with conventional method. Based on our results, we suggest that the capacitance sensor can measure the expression level of the EGF receptor on cell membrane and be a good candidate as a cancer diagnosis.

  14. Performance enhancement of polymer electrolyte membrane fuel cells by dual-layered membrane electrode assembly structures with carbon nanotubes.

    PubMed

    Jung, Dong-Won; Kim, Jun-Ho; Kim, Se-Hoon; Kim, Jun-Bom; Oh, Eun-Suok

    2013-05-01

    The effect of dual-layered membrane electrode assemblies (d-MEAs) on the performance of a polymer electrolyte membrane fuel cell (PEMFC) was investigated using the following characterization techniques: single cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It has been shown that the PEMFC with d-MEAs has better cell performance than that with typical mono-layered MEAs (m-MEAs). In particular, the d-MEA whose inner layer is composed of multi-walled carbon nanotubes (MWCNTs) showed the best fuel cell performance. This is due to the fact that the d-MEAs with MWCNTs have the highest electrochemical surface area and the lowest activation polarization, as observed from the CV and EIS test. PMID:23858921

  15. Modeling of durability of polyelectrolyte membrane of O2/H2 fuel cell

    E-print Network

    Atrazhev, Vadim V

    2014-01-01

    In this paper, we discuss critical aspects of the mechanisms and features of polymer proton exchange membrane (PEM) degradation in low-temperature H2/O2 fuel cell. In this paper, we focused on chemical mechanism of OH radical generation and their distribution in operational fuel cell. According to the current concept, free radicals are generated from hydrogen and oxygen crossover gases at the surface of Pt particles that precipitated in the membrane. We explicitly calculate Pt precipitation rate and electrochemical potential distribution in the membrane that controls it. Based on radical generation rate and Pt distribution we calculate degradation rate of the membrane taking advantage of simple kinetics equations.

  16. Effects of microwaves on cell membrane permeability. Report No. 3 (final) July 1981-June 1984

    SciTech Connect

    Liburdy, R.P.

    1984-07-02

    The objective of this research project was to identify and characterize cell membrane responses to microwave radiation and, importantly, to determine specific conditions or modulators required for these responses. This study has revealed that membrane permeability changes in the erythrocyte and in liposome vesicles, as well as protein shedding in the erythrocyte, are induced by microwaves at the membrane phase transition, and that these responses are strongly dependent on plasma, oxygen tension, and antioxidant free radical scavengers. These findings provide new insight into both the physical and chemical nature of microwave radiation interaction with the cell membrane.

  17. High power density proton exchange membrane fuel cells

    NASA Technical Reports Server (NTRS)

    Murphy, Oliver J.; Hitchens, G. Duncan; Manko, David J.

    1993-01-01

    Proton exchange membrane (PEM) fuel cells use a perfluorosulfonic acid solid polymer film as an electrolyte which simplifies water and electrolyte management. Their thin electrolyte layers give efficient systems of low weight, and their materials of construction show extremely long laboratory lifetimes. Their high reliability and their suitability for use in a microgravity environment makes them particularly attractive as a substitute for batteries in satellites utilizing high-power, high energy-density electrochemical energy storage systems. In this investigation, the Dow experimental PEM (XUS-13204.10) and unsupported high platinum loading electrodes yielded very high power densities, of the order of 2.5 W cm(exp -2). A platinum black loading of 5 mg per cm(exp 2) was found to be optimum. On extending the three-dimensional reaction zone of fuel cell electrodes by impregnating solid polymer electrolyte into the electrode structures, Nafion was found to give better performance than the Dow experimental PEM. The depth of penetration of the solid polymer electrolyte into electrode structures was 50-70 percent of the thickness of the platinum-catalyzed active layer. However, the degree of platinum utilization was only 16.6 percent and the roughness factor of a typical electrode was 274.

  18. Facilitated Anion Transport Induces Hyperpolarization of the Cell Membrane That Triggers Differentiation and Cell Death in Cancer Stem Cells.

    PubMed

    Soto-Cerrato, Vanessa; Manuel-Manresa, Pilar; Hernando, Elsa; Calabuig-Fariñas, Silvia; Martínez-Romero, Alicia; Fernández-Dueñas, Víctor; Sahlholm, Kristoffer; Knöpfel, Thomas; García-Valverde, María; Rodilla, Ananda M; Jantus-Lewintre, Eloisa; Farràs, Rosa; Ciruela, Francisco; Pérez-Tomás, Ricardo; Quesada, Roberto

    2015-12-23

    Facilitated anion transport potentially represents a powerful tool to modulate various cellular functions. However, research into the biological effects of small molecule anionophores is still at an early stage. Here we have used two potent anionophore molecules inspired in the structure of marine metabolites tambjamines to gain insight into the effect induced by these compounds at the cellular level. We show how active anionophores, capable of facilitating the transmembrane transport of chloride and bicarbonate in model phospholipid liposomes, induce acidification of the cytosol and hyperpolarization of plasma cell membranes. We demonstrate how this combined effect can be used against cancer stem cells (CSCs). Hyperpolarization of cell membrane induces cell differentiation and loss of stemness of CSCs leading to effective elimination of this cancer cell subpopulation. PMID:26632983

  19. Induction of gel-phase lipid in plasma membrane of chick intestinal cells after coccidial infection.

    PubMed

    Thompson, J E; Fernando, M A; Pasternak, J

    1979-08-23

    When chickens are infected with the coccidial parasite Eimeria necatrix, the plasma membrane of intestinal cells harbouring second-generation schizonts becomes refractory to mechanical shearing, hypotonic shock and ultrasonication. Plasma membrane from these infected cells was isolated to high purity as judged by enriched levels of ouabain-sensitive (Na+ + K+)-stimulated Mg2-dependent ATPase activity and sialic acid content, the lack of detectable cytochrome oxidase and glucose-6-phosphatase activities and electron microscopic analysis of the final preparation. Wide-angle X-ray diffraction patterns recorded from the isolated membranes revealed that during the later stages of parasite maturation the host cell plasma membrane acquires increasing proportions of gel-phase lipid. By contrast, purified membrane from isolated parasites is in a liquid-crystalline state. The transition temperature of host cell plasmalemma at 100 h postinfection is 61 degrees C, about 20 degrees C above physiological temperature. By contrast, liposomes of plasma membranes from infected cells undergo a thermal transition at about 28 degrees C. The accumulation of gel-phase lipid in the host cell plasma membrane is not attributable either to an increase in the constituent ratio of saturated to unsaturated fatty acids or to a significant change in the cholesterol to phospholipid ratio. During the late stages of infection, the cells become stainable with trypan blue which suggests that the acquisition of crystalline phase lipid disrupts the permeability of the host cell plasmalemma. PMID:486463

  20. In vivo circulation, clearance, and biodistribution of polyglycerol grafted functional red blood cells.

    PubMed

    Chapanian, Rafi; Constantinescu, Iren; Brooks, Donald E; Scott, Mark D; Kizhakkedathu, Jayachandran N

    2012-04-01

    The in vivo circulation of hyperbranched polyglycerol (HPG) grafted red blood cells (RBCs) was investigated in mice. The number of HPG molecules grafted per RBC was measured using tritium labeled HPGs ((3)H-HPG) of different molecular weights; the values ranged from 1 × 10(5) to 2 × 10(6) molecules per RBC. HPG-grafted RBCs were characterized in vitro by measuring the electrophoretic mobility, complement mediated lysis, and osmotic fragility. Our results show that RBCs grafted with 1.5 × 10(5) HPG molecules per RBC having molecular weights 20 and 60 kDa have similar characteristics as that of control RBCs. The in vivo circulation of HPG-grafted RBCs was measured by a tail vain injection of (3)H-HPG60K-RBC in mice. The radioactivity of isolated RBCs, whole blood, plasma, different organs, urine and feces was evaluated at different time intervals. The portion of (3)H-HPG60K-RBC that survived the first day in mice (52%) remained in circulation for 50 days. Minimal accumulation radioactivity in organs other than liver and spleen was observed suggesting the normal clearance mechanism of modified RBCs. Animals gained normal weights and no abnormalities observed in necropsy analysis. The stability of the ester-amide linker between the RBC and HPG was evaluated by comparing the clearance rate of (3)H-HPG60K-RBC and PKH-26 lipid fluorescent membrane marker labeled HPG60K-RBCs. HPG modified RBCs combine the many advantages of a dendritic polymer and RBCs, and hold great promise in systemic drug delivery and other applications of functional RBC. PMID:22261097

  1. Assessing the utility of bipolar membranes for use in photoelectrochemical water-splitting cells.

    PubMed

    Vargas-Barbosa, Nella M; Geise, Geoffrey M; Hickner, Michael A; Mallouk, Thomas E

    2014-11-01

    Membranes are important in water-splitting solar cells because they prevent crossover of hydrogen and oxygen. Here, bipolar membranes (BPMs) were tested as separators in water electrolysis cells. Steady-state membrane and solution resistances, electrode overpotentials, and pH gradients were measured at current densities relevant to solar photoelectrolysis. Under forward bias conditions, electrodialysis of phosphate buffer ions creates a pH gradient across a BPM. Under reverse bias, the BPM can maintain a constant buffer pH on both sides of the cell, but a large membrane potential develops. Thus, the BPM does not present a viable solution for electrolysis in buffered electrolytes. However, the membrane potential is minimized when the anode and cathode compartments of the cell contain strongly basic and acidic electrolytes, respectively. PMID:25256955

  2. Efficient Targeting of Fatty-Acid Modified Oligonucleotides to Live Cell Membranes through Stepwise Assembly

    PubMed Central

    2014-01-01

    Lipid modifications provide efficient targeting of oligonucleotides to live cell membranes in a range of applications. Targeting efficiency is a function of the rate of lipid DNA insertion into the cell surface and its persistence over time. Here we show that increasing lipid hydrophobicity increases membrane persistence, but decreases the rate of membrane insertion due to the formation of nonproductive aggregates in solution. To ameliorate this effect, we split the net hydrophobicity of the membrane anchor between two complementary oligonucleotides. When prehybridized in solution, doubly anchored molecules also aggregate due to their elevated hydrophobicity. However, when added sequentially to cells, aggregation does not occur so membrane insertion is efficient. Hybridization between the two strands locks the complexes at the cell surface by increasing net hydrophobicity, increasing their total concentration and lifetime, and dramatically improving their utility in a variety of biomedical applications. PMID:25325667

  3. Protein disulfide isomerase may facilitate the efflux of nitrite derived S-nitrosothiols from red blood cells?

    PubMed Central

    Kallakunta, Vasantha Madhuri; Slama-Schwok, Anny; Mutus, Bulent

    2013-01-01

    Protein disulfide isomerase (PDI) is an abundant protein primarily found in the endoplasmic reticulum and also secreted into the blood by a variety of vascular cells. The evidence obtained here, suggests that PDI could directly participate in the efflux of NO+ from red blood cells (RBC). PDI was detected both in RBC membranes and in the cytosol. PDI was S-nitrosylated when RBCs were exposed to nitrite under ?50% oxygen saturation but not under ?100% oxygen saturation. Furthermore, it was observed that hemoglobin (Hb) could promote PDI S-nitrosylation in the presence of ?600 nM nitrite. In addition, three lines of evidence were obtained for PDI–Hb interactions: (1) Hb co-immunoprecipitated with PDI; (2) Hb quenched the intrinsic PDI fluorescence in a saturable manner; and (3) Hb–Fe(II)–NO absorption spectrum decreased in a [PDI]-dependent manner. Finally, PDI was detected on the surface RBC under ?100% oxygen saturation and released as soluble under ?50% oxygen saturation. The soluble PDI detected under ?50% oxygen saturation was S-nitrosylated. Based on these data it is proposed that PDI is taken up by RBC and forms a complex with Hb. Hb–Fe(II)–NO that is formed from nitrite reduction under ?50% O2, then transfers NO+ to either Hb–Cys ?93 or directly to PDI resulting in S-nitroso-PDI which transverses the RBC membrane and attaches to the RBC surface. When RBCs enter tissues the S-nitroso-PDI is released from the RBC-surface into the blood where its NO+ is transferred into the endothelium thereby inducing vasodilation, suggesting local oxygen-dependent dynamic interplays between nitrite, NO and S-nitrosylation. PMID:24024174

  4. Temperature-Dependent Simulations of Dry Gas Transport in the Electrodes of Proton Exchange Membrane Fuel Cells

    E-print Network

    Stockie, John

    Membrane Fuel Cells M. J. Kermani1 J. M. Stockie2 mkermani@unb.ca stockie@unb.ca 1 Post Doctoral Fellow the cathode of a proton exchange membrane (PEM) fuel cell is studied numerically. The di usion membrane (PEM) fuel cell. ature onmodelingoftransport processes inPEM fuelcells. The vast majority of work

  5. An alkaline direct ethanol fuel cell with a cation exchange membrane Liang An and T. S. Zhao*

    E-print Network

    Zhao, Tianshou

    An alkaline direct ethanol fuel cell with a cation exchange membrane Liang An and T. S. Zhao the performance of anion exchange membrane (AEM) direct ethanol fuel cells (DEFCs) is that state-of-the-art AEMs exchange membrane direct ethanol fuel cells (AEM- DEFCs) have received ever-increasing attention, mainly

  6. Relationships between Membrane Binding, Affinity and Cell Internalization Efficacy of a Cell-Penetrating Peptide: Penetratin as a Case Study

    PubMed Central

    Alves, Isabel D.; Bechara, Cherine; Walrant, Astrid; Zaltsman, Yefim; Jiao, Chen-Yu; Sagan, Sandrine

    2011-01-01

    Background Penetratin is a positively charged cell-penetrating peptide (CPP) that has the ability to bind negatively charged membrane components, such as glycosaminoglycans and anionic lipids. Whether this primary interaction of penetratin with these cell surface components implies that the peptide will be further internalized is not clear. Methodology Using mass spectrometry, the amount of internalized and membrane bound penetratin remaining after washings, were quantified in three different cell lines: wild type (WT), glycosaminoglycans- (GAGneg) and sialic acid-deficient (SAneg) cells. Additionally, the affinity and kinetics of the interaction of penetratin to membrane models composed of pure lipids and membrane fragments from the referred cell lines was investigated, as well as the thermodynamics of such interactions using plasmon resonance and calorimetry. Principal Findings Penetratin internalized with the same efficacy in the three cell lines at 1 µM, but was better internalized at 10 µM in SAneg>WT>GAGneg. The heat released by the interaction of penetratin with these cells followed the ranking order of internalization efficiency. Penetratin had an affinity of 10 nM for WT cells and µM for SAneg and GAGneg cells and model membrane of phospholipids. The remaining membrane-bound penetratin after cells washings was similar in WT and GAGneg cells, which suggested that these binding sites relied on membrane phospholipids. The interaction of penetratin with carbohydrates was more superficial and reversible while it was stronger with phospholipids, likely because the peptide can intercalate between the fatty acid chains. Conclusion/Significance These results show that accumulation and high-affinity binding of penetratin at the cell-surface do not reflect the internalization efficacy of the peptide. Altogether, these data further support translocation (membrane phospholipids interaction) as being the internalization pathway used by penetratin at low micromolecular concentration, while endocytosis is activated at higher concentration and requires accumulation of the peptide on GAG and GAG clustering. PMID:21915283

  7. Multiphoton Process and Anomalous Potential of Cell Membrane by Laser Radiation

    NASA Technical Reports Server (NTRS)

    Zhang, Kaixi; Zhao, Qingxun; Cui, Zhiyun; Zhar, Ping; Dong, Lifang

    1996-01-01

    In this paper, by the use of quantum biology and quantum optics, the laser induced potential variation of cell membrane has been studied. Theoretically, we have found a method of calculating the monophoton and multiphoton processes in the formation of the anomalous potential of cell membrane. In contrast with the experimental results, our numerical result is in the same order. Therefore, we have found the possibility of cancer caused by the laser induced anomalous cell potential.

  8. Electrochemistry of Fuel Cells and Batteries (ME/MS 545) Course Description: Electrochemistry of fuel cells, batteries, sensors, membrane

    E-print Network

    Lin, Xi

    Electrochemistry of Fuel Cells and Batteries (ME/MS 545) Course Description: Electrochemistry of fuel cells, batteries, sensors, membrane separation and electrolytic methods are discussed such as those represented by fuel cells, batteries, and various sensors and electrolytic cells. Exam schedule

  9. Identifying the Membrane Proteome of HIV-1 Latently Infected Cells*S

    E-print Network

    Vertes, Akos

    Identifying the Membrane Proteome of HIV-1 Latently Infected Cells*S Received for publication, **Department of Biochemistry/ Center for Sickle Cell Disease, Howard University, Washington, D. C. 20059 of established human immunodeficiency virus-1 (HIV-1) latent cell models and parental cell lines. To this end we

  10. Distinct Regulation of Cytoplasmic Calcium Signals and Cell Death Pathways by Different Plasma Membrane Calcium

    E-print Network

    Kenny, Paraic

    Membrane Calcium ATPase Isoforms in MDA-MB-231 Breast Cancer Cells* Received for publication,March 20, 2012-dependent and -independent cell death in MDA-MB-231 cells. Conclusion: PMCA isoforms have distinct roles in the control viability in MDA-MB-231 breast cancer cells. The PMCA1 isoform was the predominant regulator of global Ca2

  11. Growth of Carbon Support for Proton-Exchange-Membrane Fuel Cell by

    E-print Network

    Growth of Carbon Support for Proton-Exchange-Membrane Fuel Cell by Pulsed-Laser Deposition (PLDGDL)(catalyst) (pulsed laser deposition PLD) (plasma plume) () #12;III Abstract key word: Fuel CellPulsed Laser. People begin to develop fuel cells for seeking alternative energy sources. Fuel cell use the chemical

  12. Detection of anti-liver cell membrane antibody using a human hepatocellular carcinoma cell line

    SciTech Connect

    Lobo-Yeo, A.; McSorley, C.; McFarlane, B.M.; Mieli-Vergani, G.; Mowat, A.P.; Vergani, D.

    1989-02-01

    A radioimmunometric technique for the detection of autoantibodies to liver membrane antigens has been developed using Alexander cells, a human hepatocellular carcinoma cell line. After incubation of Alexander cells with serum, antimembrane antibodies were detected by addition of /sup 125/I-labeled Protein A. Binding ratios in 15 children with uncontrolled autoimmune chronic active hepatitis and in seven children with primary sclerosing cholangitis were significantly higher than in 18 age-matched normal controls. Nine patients with inactive autoimmune chronic active hepatitis, 13 with alpha 1-antitrypsin deficiency and five with fulminant hepatic failure had ratios similar to controls. In nine patients with Wilson's disease, there was a modest but significant increase in binding ratio. In four children with autoimmune chronic active hepatitis, binding ratios fell during effective immunosuppressive therapy. Sera from patients with systemic lupus erythematosus or rheumatoid arthritis gave normal results, excluding that binding derives from Fc-mediated immune complex capture. A positive correlation was found between Alexander cell binding values and anti-liver-specific protein antibody titers, suggesting that the two assays detect antibodies against shared antigenic determinants. The Alexander cell assay is a simple, rapid and sensitive technique to detect antibody to liver cell membrane antigens.

  13. Prolongation of lifetime of high temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Oono, Yuka; Sounai, Atsuo; Hori, Michio

    2013-11-01

    In a previous study on the long-term operation of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) with polybenzimidazole (PBI) membranes, it was found that the main cause of the observed decrease in cell voltage with time was phosphoric acid depletion due to evaporation. Based on this result, in the present study, the effects of using a different kind of cell membrane were investigated. Instead of PBI membranes, phosphoric-acid-doped, chemically cross-linked poly(2,5-benzimidazole) (ABPBI) membranes were employed in HT-PEMFCs and long-term power generation tests were carried out. Two separate cells were operated for 1000 and 17,500 h at a temperature of 150 °C and a current density of 0.2 A cm-2. Their membrane electrode assemblies were then subjected to electron probe microanalysis. The results for the cell operated for 17,500 h were directly compared with those for a cell with a PBI membrane operated for 17,800 h in a previous study, allowing the mechanism of cell performance reduction in HT-PEMFCs to be further elucidated.

  14. Reversible Membrane Pearling in Live Cells upon Destruction of the Actin Cortex

    PubMed Central

    Heinrich, Doris; Ecke, Mary; Jasnin, Marion; Engel, Ulrike; Gerisch, Günther

    2014-01-01

    Membrane pearling in live cells is observed when the plasma membrane is depleted of its support, the cortical actin network. Upon efficient depolymerization of actin, pearls of variable size are formed, which are connected by nanotubes of ?40 nm diameter. We show that formation of the membrane tubes and their transition into chains of pearls do not require external tension, and that they neither depend on microtubule-based molecular motors nor pressure generated by myosin-II. Pearling thus differs from blebbing. The pearling state is stable as long as actin is prevented from polymerizing. When polymerization is restored, the pearls are retracted into the cell, indicating continuity of the membrane. Our data suggest that the alternation of pearls and strings is an energetically favored state of the unsupported plasma membrane, and that one of the functions of the actin cortex is to prevent the membrane from spontaneously assuming this configuration. PMID:24606932

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-01-01

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

  18. Membrane interactions of two arginine-rich peptides with different cell internalization capacities.

    PubMed

    Walrant, Astrid; Vogel, Alexander; Correia, Isabelle; Lequin, Olivier; Olausson, Bjoern E S; Desbat, Bernard; Sagan, Sandrine; Alves, Isabel D

    2012-07-01

    Cell penetrating peptides (CPPs) can cross cell membranes in a receptor independent manner and transport cargo molecules inside cells. These peptides can internalize through two independent routes: energy dependent endocytosis and energy independent translocation across the membrane, but the exact mechanisms are still unknown. The interaction of the CPP with different membrane components is certainly a preliminary key point that triggers internalization, such as the interaction with lipids to lead to the translocation process. In this study, we used two arginine-rich peptides, RW9 (RRWWRRWRR-NH2), which is a potent CPP, and RL9 (RRLLRRLRR-NH2) that, although binding tightly and accumulating on membranes, does not enter into cells. Using a set of experimental and theoretical techniques, we studied the binding, insertion and orientation of the peptides into different model membranes as well as the subsequent membrane reorganization. Herein we show that although the two peptides had rather similar behavior regarding lipid membrane interaction, subtle differences were found concerning the depth of peptide insertion, effect on the lipid chain ordering and kinetics of peptide insertion in the membrane, which altogether might explain their different cell internalization capacities. Molecular dynamics simulation studies show that some peptide molecules flipped their orientation over the course of the simulation such that the hydrophobic residues penetrated deeper in the lipid core region while Arg-residues maintained H-bonds with the lipid headgroups, serving as a molecular hinge in a conformation that appeared to correspond to the equilibrium one. PMID:22402267

  19. How does carbon dioxide permeate cell membranes? A discussion of concepts, results and methods

    PubMed Central

    Endeward, Volker; Al-Samir, Samer; Itel, Fabian; Gros, Gerolf

    2013-01-01

    We review briefly how the thinking about the permeation of gases, especially CO2, across cell and artificial lipid membranes has evolved during the last 100 years. We then describe how the recent finding of a drastic effect of cholesterol on CO2 permeability of both biological and artificial membranes fundamentally alters the long-standing idea that CO2—as well as other gases—permeates all membranes with great ease. This requires revision of the widely accepted paradigm that membranes never offer a serious diffusion resistance to CO2 or other gases. Earlier observations of “CO2-impermeable membranes” can now be explained by the high cholesterol content of some membranes. Thus, cholesterol is a membrane component that nature can use to adapt membrane CO2 permeability to the functional needs of the cell. Since cholesterol serves many other cellular functions, it cannot be reduced indefinitely. We show, however, that cells that possess a high metabolic rate and/or a high rate of O2 and CO2 exchange, do require very high CO2 permeabilities that may not be achievable merely by reduction of membrane cholesterol. The article then discusses the alternative possibility of raising the CO2 permeability of a membrane by incorporating protein CO2 channels. The highly controversial issue of gas and CO2 channels is systematically and critically reviewed. It is concluded that a majority of the results considered to be reliable, is in favor of the concept of existence and functional relevance of protein gas channels. The effect of intracellular carbonic anhydrase, which has recently been proposed as an alternative mechanism to a membrane CO2 channel, is analysed quantitatively and the idea considered untenable. After a brief review of the knowledge on permeation of O2 and NO through membranes, we present a summary of the 18O method used to measure the CO2 permeability of membranes and discuss quantitatively critical questions that may be addressed to this method. PMID:24409149

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

    PubMed

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

    2009-02-01

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

  1. Affordable Hydrogen Fuel Cell Vehicles: Quaternary Phosphonium Based Hydroxide Exchange Membranes

    SciTech Connect

    2010-01-01

    Broad Funding Opportunity Announcement Project: The University of Delaware is developing a new fuel cell membrane for vehicles that relies on cheaper and more abundant materials than those used in current fuel cells. Conventional fuel cells are very acidic, so they require acid-resistant metals like platinum to generate electricity. The University of Delaware is developing an alkaline fuel cell membrane that can operate in a non-acidic environment where cheaper materials like nickel and silver, instead of platinum, can be used. In addition to enabling the use of cheaper metals, the University of Delaware’s membrane is 500 times less expensive than other polymer membranes used in conventional fuel cells.

  2. Basement Membrane and Cell Integrity of Self-Tissues in Maintaining Drosophila Immunological Tolerance

    PubMed Central

    Kim, Moon Jong; Choe, Kwang-Min

    2014-01-01

    The mechanism underlying immune system recognition of different types of pathogens has been extensively studied over the past few decades; however, the mechanism by which healthy self-tissue evades an attack by its own immune system is less well-understood. Here, we established an autoimmune model of melanotic mass formation in Drosophila by genetically disrupting the basement membrane. We found that the basement membrane endows otherwise susceptible target tissues with self-tolerance that prevents autoimmunity, and further demonstrated that laminin is a key component for both structural maintenance and the self-tolerance checkpoint function of the basement membrane. Moreover, we found that cell integrity, as determined by cell-cell interaction and apicobasal polarity, functions as a second discrete checkpoint. Target tissues became vulnerable to blood cell encapsulation and subsequent melanization only after loss of both the basement membrane and cell integrity. PMID:25329560

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

    E-print Network

    Shil, Pratip; Vidyasagar, Pandit B

    2007-01-01

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

  4. High-level cell-free production of membrane proteins with nanodiscs.

    PubMed

    Roos, Christian; Kai, Lei; Haberstock, Stefan; Proverbio, Davide; Ghoshdastider, Umesh; Ma, Yi; Filipek, Slawomir; Wang, Xiaoning; Dötsch, Volker; Bernhard, Frank

    2014-01-01

    This chapter addresses two major bottlenecks in cell-free membrane protein production. Firstly, we describe the optimization of expression templates for obtaining membrane proteins in preparative scales. We present details for a newly established tag variation screen providing high success rates in improving expression efficiencies while having only minimal impacts on the target protein structure. Secondly, we present protocols for the efficient co-translational insertion of membrane proteins into defined lipid bilayers. We describe the production of nanodiscs and their implementation into cell-free expression reactions for the co-translational reconstitution of membrane proteins. In addition we give guidelines for the loading of nanodiscs with different lipids in order to systematically analyze effects of lipids on the translocation, functional folding, and stability of cell-free expressed membrane proteins. PMID:24395412

  5. Role of membrane components in thermal injury of cells and development of thermotolerance.

    PubMed

    Jó?wiak, Z; Leyko, W

    1992-12-01

    Exposure of cells to hyperthermia induces a transient resistance to subsequent heat treatment. The specific mechanisms responsible for hyperthermic cell killing and thermotolerance development are not well understood. It seems that heat may induce at least two different states of thermotolerance, of which one is dependent on protein synthesis. The expression of thermotolerance may include multiple cytoplasmic and membrane components. A number of studies have indicated that membranes play an important role in governing the thermal injury of cells. It seems, therefore, that heat denatured plasma membrane proteins may be a potential target for thermal stress and a trigger for the induction of thermotolerance. The localization of heat shock proteins in the plasma membrane and the suggestion of thermal resistance in enucleate erythrocytes support this suggestion. However, a direct relationship between the plasma membrane and hyperthermic killing or development of thermotolerance has not been found. PMID:1362768

  6. Cell-free Expression and In Meso Crystallisation of an Integral Membrane Kinase for Structure Determination

    PubMed Central

    Shah, Syed Tasadaque Ali; Haberstock, Stefan; Dötsch, Volker; Bernhard, Frank; Caffrey, Martin

    2014-01-01

    Membrane proteins are key elements in cell physiology and drug targeting, but getting a high-resolution structure by crystallographic means is still enormously challenging. Novel strategies are in big demand to facilitate the structure determination process that will ultimately hasten the day when sequence information alone can provide a 3-dimensional model. Cell-free or in vitro expression enables rapid access to large quantities of high quality membrane proteins suitable for an array of applications. Despite its impressive efficiency, to date only two membrane proteins produced by the in vitro approach have yielded crystal structures. Here, we have analysed synergies of cell-free expression and crystallisation in lipidic mesophases for generating an X-ray structure of the integral membrane enzyme diacylglycerol kinase to 2.28 Å resolution. The quality of cellular and cell-free expressed kinase samples have been evaluated systematically by comparing i) spectroscopic properties, ii) purity and oligomer formation, iii) lipid content and iv) functionality. DgkA is the first membrane enzyme crystallised based on cell-free expression. The study provides a basic standard for the crystallisation of cell-free expressed membrane proteins and the methods detailed here should prove generally useful and contribute to accelerating the pace at which membrane protein structures are solved. PMID:25012698

  7. Cell-free expression and in meso crystallisation of an integral membrane kinase for structure determination.

    PubMed

    Boland, Coilín; Li, Dianfan; Shah, Syed Tasadaque Ali; Haberstock, Stefan; Dötsch, Volker; Bernhard, Frank; Caffrey, Martin

    2014-12-01

    Membrane proteins are key elements in cell physiology and drug targeting, but getting a high-resolution structure by crystallographic means is still enormously challenging. Novel strategies are in big demand to facilitate the structure determination process that will ultimately hasten the day when sequence information alone can provide a three-dimensional model. Cell-free or in vitro expression enables rapid access to large quantities of high-quality membrane proteins suitable for an array of applications. Despite its impressive efficiency, to date only two membrane proteins produced by the in vitro approach have yielded crystal structures. Here, we have analysed synergies of cell-free expression and crystallisation in lipid mesophases for generating an X-ray structure of the integral membrane enzyme diacylglycerol kinase to 2.28-Å resolution. The quality of cellular and cell-free-expressed kinase samples has been evaluated systematically by comparing (1) spectroscopic properties, (2) purity and oligomer formation, (3) lipid content and (4) functionality. DgkA is the first membrane enzyme crystallised based on cell-free expression. The study provides a basic standard for the crystallisation of cell-free-expressed membrane proteins and the methods detailed here should prove generally useful and contribute to accelerating the pace at which membrane protein structures are solved. PMID:25012698

  8. Comparison of the phosphorylation events in membranes prepared from proliferating versus quiescent endothelial cells

    SciTech Connect

    Kazlauskas, A.; DiColeto, P.E.

    1986-05-01

    Little is known of the intracellular events which regulate the proliferation of endothelial cells (EC). Triton-solubilized membranes from proliferating (sparse) and quiescent (confluent) EC were incubated at pH 6.5 in the presence of divalent cations and (/sup 32/P)ATP. Membrane proteins were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. The overall kinase activity per mg protein was slightly greater in membranes prepared from proliferating versus quiescent cells. They found four proteins labeled in sparse cells to a dramatically greater extent having the following approximate molecular masses: 180, 100, 97 and 55 kilodalton (kd). The first two phosphoproteins were phosphorylated on serine residues exclusively; the 97 kd phosphoprotein contained 39% phosphoserine (p-ser) and 61% phosphothreonine (p-thr); and the 55 kd phosphoprotein contained 62% p-ser, 16% p-thr, and 22% phosphotyrosine (p-tyr). The kinases acting on all four phosphoproteins were independent of Ca/sup 2 +/, cAMP, cGMP, or phorbol 12-myristate 13-acetate. The observed differences in phosphorylation events between sparse and confluent membranes occurred in membranes from two EC lines - pig aortic and bovine aortic - but were not apparent in membranes prepared from human foreskin fibroblasts or 3T3 cells. Sparse endothelial cells made quiescent by serum deprivation were found to resemble confluent cells in the kinase activity; therefore, the enhanced kinase activity in sparse membranes may be growth dependent.

  9. The role of CD4 on mechanical properties of live cell membrane.

    PubMed

    Bui, Van-Chien; Nguyen, Thi-Huong

    2016-01-01

    Although much progress has been made in the characterization and identification of CD4 functions, its role in mechanical properties of cell membrane remains largely unknown. Here an atomic force microscopy (AFM) was used to investigate the roles of CD4 in the elasticity of the leukemic human Jurkat (clone E6-1) cell membranes. Analysis of the approach force curves with Hertz model for a completely elastic soft sample measured on the selected CD4+ and CD4- cells showed that CD4+ cell membrane was softer than CD4- one. To confirm that CD4 plays a role in altering cell elasticity, human embryonic kidney 293T cells were transiently transfected with wild type (wt) CD4 plasmid before being used in AFM nanoindentation experiments. The results also demonstrated CD4- membrane was stiffer than CD4+ one suggesting that CD4 integrated into plasma membrane and altered its mechanical properties. The study gives insights into the role of CD4 on cell membrane mechanical characteristics and might be helpful for development of cell biology and medicine. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 239-244, 2016. PMID:26362701

  10. Composite Nafion/zirconium phosphate fuel cell membranes: Operation at elevated temperature and reduced relative humidity

    NASA Astrophysics Data System (ADS)

    Yang, Christopher

    High temperature polymer electrolyte fuel cells are being developed because of expected improvements in the operating tolerance for carbon morioxide (CO) in the hydrogen fuel stream. However, increases in fuel cell operating temperature typically lead to reductions in membrane water content due to evaporation, and the associated increase in membrane resistance decreases power output and thermal efficiency. Modifications to traditional perfluorinated sulfonic acid membranes (such as Dupont NafionRTM) can improve the performance of these membranes at higher temperature and reduced relative humidity. The addition of inorganic additives like zirconium hydrogen phosphate (Zr(HPO4)2) modifies specific membrane properties relevant for operation under these conditions. Fuel cell testing of the composite Nafion/zirconium phosphate membranes in both hydrogen and methanol fuel cells demonstrates significantly improved performance over unmodified membranes at high temperature (130--150°C) and dehydrating conditions. To understand the reasons for these membrane improvements in more detail, specific physical and chemical membrane characteristics were studied. The ionic cluster structure of modified membranes and changes upon swelling in water was investigated using small angle x-ray scattering (SAXS). A barometric sorption technique and AC impedance spectroscopy were used to measure equilibrium water uptake and conductivity over a range of relative humidities and temperatures. Finally, water transport measurements and a water flux model were used to investigate the effects of changes to diffusion and evaporative resistances on membrane water content. When compared to unmodified membranes, Nafion/zirconium phosphate membranes exhibit an increase in water uptake but a decrease in extent of membrane reorganization with water uptake. This change relates to the reduction in membrane chemical potential due to the hydrophilic zirconium phosphate and greater stability of the composite membrane to thermal treatments. Despite these improvements, the proton conductivity and diffusive transport are reduced, due to lower water and proton mobility in the ionic clusters. To explain the discrepancy between the reduced proton conductivity and the improvement in fuel cell performance, a simple water flux model is proposed, which indicates that reducing evaporative flux with respect to the diffusive flux can increase steady state water content and proton conductivity.

  11. Biological effects of the electrostatic field: red blood cell-related alterations of oxidative processes in blood

    NASA Astrophysics Data System (ADS)

    Harutyunyan, Hayk A.; Sahakyan, Gohar V.

    2015-05-01

    The aim of this study was to determine activities of pro-/antioxidant enzymes, reactive oxygen species (ROS) content, and oxidative modification of proteins and lipids in red blood cells (RBCs) and blood plasma of rats exposed to electrostatic field (200 kV/m) during the short (1 h) and the long periods (6 day, 6 h daily). Short-term exposure was characterized by the increase of oxidatively damaged proteins in blood of rats. This was strongly expressed in RBC membranes. After long-term action, RBC content in peripheral blood was higher than in control (P < 0.01) and the attenuation of prooxidant processes was shown.

  12. Patterned ion exchange membranes for improved power production in microbial reverse-electrodialysis cells

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Geise, Geoffrey M.; Luo, Xi; Hou, Huijie; Zhang, Fang; Feng, Yujie; Hickner, Michael A.; Logan, Bruce E.

    2014-12-01

    Power production in microbial reverse-electrodialysis cells (MRCs) can be limited by the internal resistance of the reverse electrodialysis stack. Typical MRC stacks use non-conductive spacers that block ion transport by the so-called spacer shadow effect. These spacers can be relatively thick compared to the membrane, and thus they increase internal stack resistance due to high solution (ohmic) resistance associated with a thick spacer. New types of patterned anion and cation exchange membranes were developed by casting membranes to create hemispherical protrusions on the membranes, enabling fluid flow between the membranes without the need for a non-conductive spacer. The use of the patterned membrane decreased the MRC stack resistance by ˜22 ?, resulting in a 38% increase in power density from 2.50 ± 0.04 W m-2 (non-patterned membrane with a non-conductive spacer) to 3.44 ± 0.02 W m-2 (patterned membrane). The COD removal rate, coulombic efficiency, and energy efficiency of the MRC also increased using the patterned membranes compared to the non-patterned membranes. These results demonstrate that these patterned ion exchange membranes can be used to improve performance of an MRC.

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

    PubMed

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

    1981-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Abuin, Graciela C.; Franceschini, Esteban A.; Nonjola, Patrick; Mathe, Mkhulu K.; Modibedi, Mmalewane; Corti, Horacio R.

    2015-04-01

    Alkaline membranes based on quaternized poly(arylene ether sulfone) (QPAES) were characterized in relation to their water and methanol uptake, methanol permeability, electrical conductivity, and mechanical properties. The performance of QPAES as electrolyte in alkaline direct methanol fuel cells was studied using a free-breathing single fuel cell at room temperature. Methanol uptake by QPAES membranes is lower than water, while their methanol permeability, determined in the temperature range from 30 °C to 75 °C, was much lower than for Nafion membranes. Young modulus of QPAES membranes decrease with the degree of alkalization of the membrane, although mechanical properties are still satisfactory for fuel cell applications for membrane alkalized with 2 M KOH, which additionally exhibit optimal hydroxide conductivity. Although the specific conductivity of QPAES membranes was lower than that reported for Nafion, its methanol selectivity (conductivity/methanol permeability ratio), is much higher than that reported for Nafion 117, and a commercial amminated polysulfone. In view of these results, QPAES membranes are expected to exhibit promising performance as an electrolyte in alkaline direct methanol fuel cells.

  15. Simplified process for leaching precious metals from fuel cell membrane electrode assemblies

    DOEpatents

    Shore, Lawrence (Edison, NJ); Matlin, Ramail (Berkeley Heights, NJ)

    2009-12-22

    The membrane electrode assemblies of fuel cells are recycled to recover the catalyst precious metals from the assemblies. The assemblies are cryogenically embrittled and pulverized to form a powder. The pulverized assemblies are then mixed with a surfactant to form a paste which is contacted with an acid solution to leach precious metals from the pulverized membranes.

  16. INTERACTION OF INORGANIC MERCURY SALTS WITH MODEL AND RED CELL MEMBRANES: IMPORTANCE OF LIPID BINDING SALTS

    EPA Science Inventory

    The effect induced by two mercury salts, HgCl2 and Hg(NO3)2, on the thermotropic properties of PS model membranes (multilamellar vesicles) and rat red cell membranes was investigated employing 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization. ercury(II) interacts wit...

  17. Unsynchronized Translational and Rotational Diffusion of Nanocargo on a Living Cell Membrane

    SciTech Connect

    Xiao, Lehui; Wei, Lin; Liu, Chang; He, Yan; Yeung, Edward

    2012-03-16

    A robust high-speed and high-precision single nanoparticle translational and rotational tracking method has been developed to directly monitor the interactions between transferrin-modified nanocargos (gold nanorods) and the membrane proteins prior to endocytosis. This approach shows that the translational and rotational diffusions of nanocargos on living cell membranes are unsynchronized in space and in time.

  18. Extensional flow of erythrocyte membrane from cell body to elastic tether. I. Analysis.

    PubMed Central

    Hochmuth, R M; Evans, E A

    1982-01-01

    This is the first of two papers on an analytical and experimental study of the flow of the erythrocyte membrane. In the experiment to be discussed in detail in the second paper, preswollen human erythrocytes are sphered by aspirating a portion of the cell membrane into a small micropipette; and long, thin, membrane filaments or "tethers" are steadily withdrawn from the cell at a point diametrically opposite to the point of aspiration. The aspirated portion of the membrane furnished a "reservoir" of material that replaces the membrane as it flows as a liquid from the nearly spherical cell body to the cylindrical tether. In this paper we show that an application of the principle of conservation of mass permits the tether radius (approximately 200 A or less) to be measured with the light microscope as the tether is formed and extended at a constant rate. A static analysis of the axisymmetric cell deformation and tether formation process reveals that the tether radius is uniquely determined by the isotropic tension in the membrane and the elastic constitutive (material) behavior of the tether itself. A dynamic analysis of the extensional flow process reveals that the tether radius must decrease as the velocity of the tether is increased and that the decrease depends on both the viscosity of the membrane and the elasticity of the tether. The analysis also shows that these two factors (membrane viscosity and tether elasticity) are readily decomposed and determined separately when flow experiments are performed at different isotropic tensions. Images FIGURE 5 PMID:7104453

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

    PubMed Central

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

    2015-01-01

    Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method. The best MEA performance is achieved using patterned Nafion membrane with a circle 2??m in size, which exhibited a very high power density of 1906?mW/cm2 at 75?°C and Pt loading of 0.4?mg/cm2 with 73% improvement compared to the commercial membrane. The improved performance are attributed to the decreased MEA resistances and increased surface area for higher Pt utilization of over 80%. From these enhanced properties, it is possible to operate at lower Pt loading of 0.2?mg/cm2 with an outstanding performance of 1555?mW/cm2 and even at air/low humidity operations. PMID:26552839

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

    PubMed

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

    2015-01-01

    Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method. The best MEA performance is achieved using patterned Nafion membrane with a circle 2??m in size, which exhibited a very high power density of 1906?mW/cm(2) at 75?°C and Pt loading of 0.4?mg/cm(2) with 73% improvement compared to the commercial membrane. The improved performance are attributed to the decreased MEA resistances and increased surface area for higher Pt utilization of over 80%. From these enhanced properties, it is possible to operate at lower Pt loading of 0.2?mg/cm(2) with an outstanding performance of 1555?mW/cm(2) and even at air/low humidity operations. PMID:26552839

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Polymer electrolyte membrane fuel cell is a promising zero-emission power generator for stationary/automotive applications. However, key issues, such as performance and costs, are still remained for an economical commercialization. Here, we fabricated a high-performance membrane electrode assembly (MEA) using an interfacial design based on well-arrayed micro-patterned membranes including circles, squares and hexagons with different sizes, which are produced by a facile elastomeric mold method. The best MEA performance is achieved using patterned Nafion membrane with a circle 2??m in size, which exhibited a very high power density of 1906?mW/cm2 at 75?°C and Pt loading of 0.4?mg/cm2 with 73% improvement compared to the commercial membrane. The improved performance are attributed to the decreased MEA resistances and increased surface area for higher Pt utilization of over 80%. From these enhanced properties, it is possible to operate at lower Pt loading of 0.2?mg/cm2 with an outstanding performance of 1555?mW/cm2 and even at air/low humidity operations.

  2. Isolation of Chinese hamster ovary cell lines temperature conditional for the cell-surface expression of integral membrane glycoproteins

    PubMed Central

    1989-01-01

    A procedure is described to select mutants of Chinese hamster ovary cells that are conditionally defective for the cell-surface expression of integral membrane glycoproteins, including the hemagglutinin (HA) of influenza virus. Using a combination of cell sorting and biochemical screening, seven cell lines were obtained that express more cell- surface HA at 32 degrees C than at 39 degrees C. The production of infectious vesicular stomatitis virus, whose growth requires insertion of an integral membrane protein into the plasma membrane, was also temperature conditional in the majority of these mutant cell lines. Five of the lines synthesized apparently normally core-glycosylated HA at the elevated temperature but the protein was neither displayed on the cell surface nor accumulated intracellularly. In these cell lines, little or no terminally glycosylated HA molecules were observed after synthesis at 39 degrees C. By contrast, the core glycosylation of HA and several other integral membrane proteins was abnormal in the remaining two cell lines at both permissive and restrictive temperatures, due to a lesion in a cellular gene(s) that affects the formation of and/or the addition of mannose-rich oligosaccharide chains to newly synthesized polypeptides. Although HA was transported to the plasma membrane at both 32 and 39 degrees C, it did not accumulate on the cell surface at the higher temperature, apparently because of an increased rate of degradation. PMID:2537314

  3. The connection of cytoskeletal network with plasma membrane and the cell wall

    PubMed Central

    Liu, Zengyu; Persson, Staffan; Zhang, Yi

    2015-01-01

    The cell wall provides external support of the plant cells, while the cytoskeletons including the microtubules and the actin filaments constitute an internal framework. The cytoskeletons contribute to the cell wall biosynthesis by spatially and temporarily regulating the transportation and deposition of cell wall components. This tight control is achieved by the dynamic behavior of the cytoskeletons, but also through the tethering of these structures to the plasma membrane. This tethering may also extend beyond the plasma membrane and impact on the cell wall, possibly in the form of a feedback loop. In this review, we discuss the linking components between the cytoskeletons and the plasma membrane, and/or the cell wall. We also discuss the prospective roles of these components in cell wall biosynthesis and modifications, and aim to provide a platform for further studies in this field. PMID:25693826

  4. Controlled lecithin release from a hierarchical architecture on blood-contacting surface to reduce hemolysis of stored red blood cells.

    PubMed

    Shi, Qiang; Fan, Qunfu; Ye, Wei; Hou, Jianwen; Wong, Shing-Chung; Xu, Xiaodong; Yin, Jinghua

    2014-06-25

    Hemolysis of red blood cells (RBCs) caused by implant devices in vivo and nonpolyvinyl chloride containers for RBC preservation in vitro has recently gained much attention. To develop blood-contacting biomaterials with long-term antihemolysis capability, we present a facile method to construct a hydrophilic, 3D hierarchical architecture on the surface of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS) with poly(ethylene oxide) (PEO)/lecithin nano/microfibers. The strategy is based on electrospinning of PEO/lecithin fibers onto the surface of poly [poly(ethylene glycol) methyl ether methacrylate] [P(PEGMEMA)]-modified SEBS, which renders SEBS suitable for RBC storage in vitro. We demonstrate that the constructed 3D architecture is composed of hydrophilic micro- and nanofibers, which transforms to hydrogel networks immediately in blood; the controlled release of lecithin is achieved by gradual dissolution of PEO/lecithin hydrogels, and the interaction of lecithin with RBCs maintains the membrane flexibility and normal RBC shape. Thus, the blood-contacting surface reduces both mechanical and oxidative damage to RBC membranes, resulting in low hemolysis of preserved RBCs. This work not only paves new way to fabricate high hemocompatible biomaterials for RBC storage in vitro, but provides basic principles to design and develop antihemolysis biomaterials for implantation in vivo. PMID:24830706

  5. Importance of Heparin Provocation and SPECT/CT in Detecting Obscure Gastrointestinal Bleeding on 99mTc-RBC Scintigraphy: A Case Report.

    PubMed

    Haghighatafshar, Mahdi; Gheisari, Farshid; Ghaedian, Tahereh

    2015-08-01

    We presented a pediatric case with a history of intermittent melena for 3 years because of angiodyplasia of small intestine. The results of frequent upper gastrointestinal endoscopies and colonoscopies as well as both Tc-red blood cell (RBC) and Meckel's scintigraphies for several times were negative in detection of bleeding site. However, Tc-RBC scintigraphy with single-photon emission computed tomography (SPECT)/computed tomography (CT) after heparin augmentation detected a site of bleeding in the distal ileum which later was confirmed during surgery with final diagnosis of angiodysplasia.It could be stated that heparin provocation of bleeding before Tc-RBC scintigraphy accompanied by fused SPECT/CT images should be kept in mind for management of intestinal bleeding especially in difficult cases. PMID:26313771

  6. Proton exchange membrane fuel cell conductivity and system analysis

    NASA Astrophysics Data System (ADS)

    Han, Qian

    A fuel cell converts chemical energy to electrical energy. It is a device that uses the electrochemical reaction of hydrogen and an oxidant, to produce electrical energy silently, without combustion. The role of the electrolyte in a PEM fuel cell is played by a proton exchange membrane. NafionRTM and its derivatives are the most widely used and studied polymers. Percolation theory holds a key to understanding the behavior of these polymers. In this dissertation, the percolation phenomenon was first simulated for the thermal conductivity of a representative polymer material. The simulation program was based on the finite element method, using Ansys software, which not only simplifies the method of calculation, but also increases the accuracy of the result. Ansys programs were developed to study the effects of matrix thickness, filler particle volume percentage, and various conductivities of the base material and filler particles. Comparison with existing experimental results and other models showed that the results from the finite element method were more accurate than the other models, especially the three-dimensional model. A similar Ansys program was utilized to predict the percolation threshold for the polymer electric conductivity, and its relationship with extra water content over the studied temperature range. The result showed that the percolation threshold varied with temperature and is in the range of 22% to 26% at room temperature, and matches the experimental data within 10% error margin. A natural gas fuel cell (NGFC) is a direct-energy conversion system which uses natural gas as the hydrogen carrier. A parametric model was developed to predict the overall system performance of a natural-gas-fueled PEM fuel cell system sized for a residential or small commercial building. The model accounts for interactions between various operating parameters: fuel consumption, air and water requirements, power produced, and heat and waste water discharge. For example, for 10 kW electrical output and usage factors of 90% and 80% for the hydrogen and methane respectively, the methane consumption rate is 1.77 kg/h, the heat rejection rate is 16.26 kW, the water discharge rate is 5.13 kg/hr, the overall system efficiency eta is 41.2%. The theoretical maximum system efficiency of a natural-gas-fueled PEM fuel cell was also predicted, providing a standard to value the performance of any commercial system. Finally, a transient model of a PEM fuel cell stack for a short circuit event was developed. The effects of different cooling methods---natural convection, forced air convection, and forced water convection---were discussed. The fuel cell stack reaches 100°C during a short circuit event within 28 seconds under the forced air condition, which should be enough time for a protective device to operate.

  7. Process engineering and economic evaluations of diaphragm and membrane chlorine cell technologies. Final report

    SciTech Connect

    Not Available

    1980-12-01

    The chlor-alkali manufacturing technologies of (1), diaphragm cells (2), current technology membrane cells (3), catalytic cathode membrane cells (4), oxygen-cathode membrane cells and to a lesser extent several other related emerging processes are studied. Comparisons have been made on the two bases of (1) conventional industrial economics, and (2) energy consumption. The current diaphragm cell may have a small economic advantage over the other technologies at the plant size of 544 metric T/D (600 T/D). The three membrane cells all consume less energy, with the oxygen-cathode cell being the lowest. The oxygen-cathode cell appears promising as a low energy chlor-alkali cell where there is no chemical market for hydrogen. Federal funding of the oxygen-cathode cell has been beneficial to the development of the technology, to electrochemical cell research, and may help maintain the US's position in the international chlor-alkali technology marketplace. Tax law changes inducing the installation of additional cells in existing plants would produce the quickest reduction in power consumption by the chlor-alkali industry. Alternative technologies such as the solid polymer electrolyte cell, the coupling of diaphragm cells with fuel cells and the dynamic gel diaphragm have a strong potential for reducing chloralkali industry power consumption. Adding up all the recent and expected improvements that have become cost-effective, the electrical energy required to produce a unit of chlorine by 1990 should be only 50% to 60% of that used in 1970. In the United States the majority of the market does not demand salt-free caustic. About 75% of the electrolytic caustic is produced in diaphragm cells and only a small part of that is purified. This study indicates that unless membrane cell costs are greatly reduced or a stronger demand develops for salt-free caustic, the diaphragm cells will remain competitive. (WHK)

  8. High Performance Fuel Cell and Electrolyzer Membrane Electrode Assemblies (MEAs) for Space Energy Storage Systems

    NASA Technical Reports Server (NTRS)

    Valdez, Thomas I.; Billings, Keith J.; Kisor, Adam; Bennett, William R.; Jakupca, Ian J.; Burke, Kenneth; Hoberecht, Mark A.

    2012-01-01

    Regenerative fuel cells provide a pathway to energy storage system development that are game changers for NASA missions. The fuel cell/ electrolysis MEA performance requirements 0.92 V/ 1.44 V at 200 mA/cm2 can be met. Fuel Cell MEAs have been incorporated into advanced NFT stacks. Electrolyzer stack development in progress. Fuel Cell MEA performance is a strong function of membrane selection, membrane selection will be driven by durability requirements. Electrolyzer MEA performance is catalysts driven, catalyst selection will be driven by durability requirements. Round Trip Efficiency, based on a cell performance, is approximately 65%.

  9. Anti-tumor antibody BR96 blocks cell migration and binds to a lysosomal membrane glycoprotein on cell surface microspikes and ruffled membranes

    PubMed Central

    1994-01-01

    BR 96 is an internalizing antibody that binds to Lewis Y (Le(y)), a carbohydrate determinant expressed at high levels on many human carcinomas (Hellstrom, I., H. J. Garrigues, U. Garrigues, and K. E. Hellstrom. 1990. Cancer Res. 50:2183-2190). Breast carcinoma cell lines grown to confluence bind less BR96 than subconfluent cultures (Garrigues, J., U. Garrigues, I. Hellstrom, and K. E. Hellstrom. 1993. Am. J. Path. 142:607-622). However, when the confluent cells are induced to migrate by scratch wounding, they again bind BR96 suggesting that antigens bearing the Le(y) determinant may promote cell migration. In the present study, BR96 was found to be highly enriched on microspikes and ruffled membranes, cell surface structures involved in cell migration. In addition, BR96 was a potent inhibitor of cell migration in vitro. When stationary BR96 treated cells were exposed to fresh culture media, membrane ruffles and microspikes developed at the cell margin and migration resumed. Immunogold microscopy showed that BR96 antigens were enriched on these membrane protrusions. BR96 cell surface immunoprecipitation analysis of 3H-glucosamine labeled breast carcinoma cells identified antigens with approximate molecular weights of 135 kd (upper antigen) and 85 kd (lower antigen). A short amino terminal sequence (8 residues) of the upper antigen matched that of human lysosomal membrane glycoprotein 1 (LAMP-1). In addition, the upper antigen was detected on immunoblots probed with anti-LAMP-1, and within the intracellular compartment BR96 was found predominantly in endosomes and lysosomes. A soluble LAMP-1/immunoglobulin fusion protein (LAMP-1/Ig) was transiently expressed in both BR96 binding and nonbinding cell lines. Immunoblot analysis of LAMP-1/Ig's from the various cell lines showed that (a) acquisition of the BR96 epitope is probably controlled at the level of polylactosamine modification (e.g., fucosylation) rather than LAMP-1 gene expression; (b) alternate forms of LAMP-1/Ig comigrate with the lower BR96 antigen raising the possibility that it may be a degradation product of the upper antigen; and (c) LAMP-1/Ig expressed in 3396 breast carcinoma cells has approximately 30-fold more BR96 epitopes than LAMP-1/Ig from non- tumorigenic mammary epithelial cells. Together these data indicate that a major BR96 antigen, LAMP-1, is present on unique cell surface domains involved in cell locomotion as well as membranes of the endocytic compartment. Altered glycosylation of LAMP-1 expressed in transformed cells may contribute to their ability to disseminate. PMID:7511141

  10. Probing the Cell Membrane by Magnetic Particle Actuation and Euler Angle Tracking

    PubMed Central

    Irmscher, Matthias; de Jong, Arthur M.; Kress, Holger; Prins, Menno W.J.

    2012-01-01

    The mechanical properties of the cell membrane and the subjacent actin cortex are determinants of a variety of processes in immunity and cell division. The lipid bilayer itself and its connection to the actin cortex are anisotropic. An accurate description of the mechanical structure of the cell membrane and the involved dynamics therefore necessitates a measurement technique that can capture the inherent anisotropy of the system. Here, we combine magnetic particle actuation with rotational and translational particle tracking to simultaneously measure the mechanical stiffness of monocytic cells in three rotational and two translational directions. When using particles that bind via integrins to the cell membrane and the subjacent cortex, we measured an isotropic stiffness and a characteristic power-law dependence of the shear modulus on the applied frequency. When using particles functionalized with immunoglobulin G, we measured an anisotropic stiffness with a 10-fold-reduced value in one dimension. We suggest that the observed reduced stiffness in the plane of the cell membrane is caused by a local detachment of the lipid bilayer from the subjacent cytoskeletal cortex. We expect that our technique will enable new insights into the mechanical properties of the cell membrane that will help us to better understand membrane processes such as phagocytosis and blebbing. PMID:22325294

  11. Modulation of cell membrane area in renal collecting tubules by corticosteroid hormones

    PubMed Central

    1979-01-01

    Isolated renal cortical collecting tubules obtained from rabbits treated chronically with desoxycorticosterone acetate (DOCA) have been found to possess elevated transepithelial potential differences and a greatly increased capacity for ion transport. Structural exmination of tubules from rabbits exposed to either DOCA or dexamethasone for 11--18 d reveals a marked increase in basolateral cell membrane area in these tubules. Morphometric analysis shows that this effect is specifically on the basolateral membrane area of only one of the two cell types found in this nephron segment. Increases of greater than 140% and 90% are found for the basolateral membrane area of the principal cells for DOCA and dexamethasone, respectively, but no change could be detected in the basolateral membrane area of the intercalated cells found in this nephron segment. No siginificant changes were found in luminal membrane area, cell number, or cell volume for either cell type. These observations demonstrate that significant changes in membrane area can occur in differentiated epithelia and suggest that this may be an important mechanism for modulating epithelial transport capacity. PMID:468913

  12. Electrochemical performance and transport properties of a Nafion membrane in a hydrogen-bromine cell environment

    NASA Technical Reports Server (NTRS)

    Baldwin, Richard S.

    1987-01-01

    The overall energy conversion efficiency of a hydrogen-bromine energy storage system is highly dependent upon the characteristics and performance of the ion-exchange membrane utilized as a half-cell separator. The electrochemical performance and transport properties of a duPont Nafion membrane in an aqueous HBr-Br2 environment were investigated. Membrane conductivity data are presented as a function of HBr concentration and temperature for the determination of ohmic voltage losses across the membrane in an operational cell. Diffusion-controlled bromine permeation rates and permeabilities are presented as functions of solution composition and temperature. Relationships between the degree of membrane hydration and the membrane transport characteristics are discussed. The solution chemistry of an operational hydrogen-bromine cell undergoing charge from 45% HBr to 5% HBr is discussed, and, based upon the experimentally observed bromine permeation behavior, predicted cell coulombic losses due to bromine diffusion through the membrane are presented as a function of the cell state-of-charge.

  13. Elastic deformation and failure of lipid bilayer membranes containing cholesterol.

    PubMed Central

    Needham, D; Nunn, R S

    1990-01-01

    Giant bilayer vesicles were reconstituted from several lipids and lipid/cholesterol (CHOL) mixtures: stearolyloleoylphosphatidylcholine (SOPC), bovine sphingomyelin (BSM), diarachidonylphosphatidylcholine (DAPC), SOPC/CHOL, BSM/CHOL, DAPC/CHOL, and extracted red blood cell (RBC) lipids with native cholesterol. Single-walled vesicles were manipulated by micropipette suction and several membrane material properties were determined. The properties measured were the elastic area compressibility modulus K, the critical areal strain alpha c, and the tensile strength tau lys, from which the failure energy or membrane toughness Tf was calculated. The elastic area expansion moduli for these lipid and lipid/cholesterol bilayers ranged from 57 dyn/cm for DAPC to 1,734 dyn/cm for BSM/CHOL. The SOPC/CHOL series and RBC lipids had intermediate values. The results indicated that the presence of cholesterol is the single most influential factor in increasing bilayer cohesion, but only for lipids where both chains are saturated, or mono- or diunsaturated. Multiple unsaturation in both lipid chains inhibits the condensing effect of cholesterol in bilayers. The SOPC/CHOL system was studied in more detail. The area expansion modulus showed a nonlinear increase with increasing cholesterol concentration up to a constant plateau, indicating a saturation limit for cholesterol in the bilayer phase of approximately 55 mol% CHOL. The membrane compressibility was modeled by a property-averaging composite theory involving two bilayer components, namely, uncomplexed lipid and a lipid/cholesterol complex of stoichiometry 1/1.22. The area expansion modulus of this molecular composite membrane was evaluated by a combination of the expansion moduli of each component scaled by their area fractions in the bilayer. Bilayer toughness, which is the energy stored in the bilayer at failure, showed a maximum value at approximately 40 mol% CHOL. This breakdown energy was found to be only a fraction of the available thermal energy, implying that many molecules (approximately 50-100) may be involved in forming the defect structure that leads to failure. The area expansion modulus of extracted RBC lipids with native cholesterol was compared with recent measurements of intact RBC membrane compressibility. The natural membrane was also modeled as a simple composite made up to a compressible lipid/cholesterol matrix containing relatively incompressible transmembrane proteins. It appears that the interaction of incompressible proteins with surrounding lipid confers enhanced compressibility on the composite structure. Images FIGURE 1 PMID:2249000

  14. Advances in cell-free protein synthesis for the functional and structural analysis of membrane proteins.

    PubMed

    Junge, Friederike; Haberstock, Stefan; Roos, Christian; Stefer, Susanne; Proverbio, Davide; Dötsch, Volker; Bernhard, Frank

    2011-04-30

    Cell-free expression has emerged as a powerful technique to overcome major restrictions of classical in vivo membrane protein production, with sample yields of mgms of protein per ml reaction volume possible in less than a day. The open nature and high versatility of cell-free expression allows a variety of completely new ways to rationally design and optimise expression environments as well as to modulate folding kinetics for membrane proteins independent of their origin, size, topology and function. This article summarises the array of currently available options to modify and develop cell-free expression protocols adapted to the specific requirements of individual membrane proteins. We give further an overview of the recent advances of cell-free production of membrane proteins for structural and functional analysis. PMID:20637904

  15. Influence of electrode stress on proton exchange membrane fuel cell performance : experimental characterization and power optimization

    E-print Network

    Gallant, Betar M. (Betar Maurkah)

    2008-01-01

    Compressive stress applied to the electrode area of a Proton Exchange Membrane (PEM) fuel cell is known to significantly affect power output. In practice, electrode stress arises during operation due to the clamping force ...

  16. Diffusion-driven proton exchange membrane fuel cell for converting fermenting biomass to electricity.

    PubMed

    Malati, P; Mehrotra, P; Minoofar, P; Mackie, D M; Sumner, J J; Ganguli, R

    2015-10-01

    A membrane-integrated proton exchange membrane fuel cell that enables in situ fermentation of sugar to ethanol, diffusion-driven separation of ethanol, and its catalytic oxidation in a single continuous process is reported. The fuel cell consists of a fermentation chamber coupled to a direct ethanol fuel cell. The anode and fermentation chambers are separated by a reverse osmosis (RO) membrane. Ethanol generated from fermented biomass in the fermentation chamber diffuses through the RO membrane into a glucose solution contained in the DEFC anode chamber. The glucose solution is osmotically neutral to the biomass solution in the fermentation chamber preventing the anode chamber from drying out. The fuel cell sustains >1.3 mW cm(-2) at 47°C with high discharge capacity. No separate purification or dilution is necessary, resulting in an efficient and portable system for direct conversion of fermenting biomass to electricity. PMID:26208756

  17. Record activity and stability of dealloyed bimetallic catalysts for proton exchange membrane fuel cells

    E-print Network

    Han, Binghong

    We demonstrate the unprecedented proton exchange membrane fuel cell (PEMFC) performance durability of a family of dealloyed Pt–Ni nanoparticle catalysts for the oxygen reduction reaction (ORR), exceeding scientific and ...

  18. ?-Synuclein mediates alterations in membrane conductance: a potential role for ?-synuclein oligomers in cell vulnerability

    PubMed Central

    Feng, Li Rebekah; Federoff, Howard J.; Vicini, Stefano; Maguire-Zeiss, Kathleen A.

    2010-01-01

    ?-Synuclein has been linked to the pathogenesis of Parkinson's disease and other synucleinopathies through its propensity to form toxic oligomers. The exact mechanism for oligomeric synuclein-directed cell vulnerability has not been fully elucidated but one hypothesis portends the formation of synuclein-containing pores within cell membranes leading to leak channel-mediated calcium influx and subsequent cell death. Here we demonstrate synuclein-induced formation of SDS-stable oligomers, intracellular synuclein-positive aggregates, alterations in membrane conductance reminiscent of leak channels and subsequent cytotoxicity in a dopaminergic-like cell line. Furthermore we demonstrate that the synuclein-induced membrane conductance changes are blocked by direct extracellular application of an anti-synuclein antibody. The work presented here confirms that synuclein overexpression leads to membrane conductance changes and demonstrates for the first time through antibody blocking studies that synuclein plays a direct role in the formation of leak channels. PMID:20550572

  19. An Investigation of Different Methods of Fabricating Membrane Electrode Assemblies for Methanol Fuel Cells

    E-print Network

    Hall, Kwame (Kwame J.)

    2009-01-01

    Methanol fuel cells are electrochemical conversion devices that produce electricity from methanol fuel. The current process of fabricating membrane electrode assemblies (MEAs) is tedious and if it is not sufficiently ...

  20. Low platinum loading electrospun electrodes for proton exchange membrane fuel cells

    E-print Network

    Singer, Simcha Lev

    2006-01-01

    An experimental study was performed to evaluate the utility of electrospun carbon nanofiber supports for sputtered platinum catalyst in proton exchange membrane fuel cells. The performance of the sputtered nanofiber supports ...

  1. Strain-Specific RBC Storage, Metabolism, and Eicosanoid Generation in a Mouse Model

    PubMed Central

    Zimring, James C.; Smith, Nicole; Stowell, Sean R.; Johnsen, Jill M.; Bell, Lauren N.; Francis, Richard; Hod, Eldad A.; Hendrickson, Jeanne E.; Roback, John D.; Spitalnik, Steven L.

    2014-01-01

    Background RBC transfusion is a life-saving therapy, the logistical implementation of which requires RBC storage. However, stored RBCs exhibit substantial donor variability in multiple characteristics, including hemolysis in vitro and RBC recovery in vivo. The basis of donor variability is poorly understood. Study Design and Methods We applied a murine model of RBC storage and transfusion to test the hypothesis that genetically distinct inbred strains of mice would demonstrate strain-specific differences in RBC storage. In vivo recoveries were determined by monitoring transfused RBCs over 24 hours. Timed aliquots of stored RBCs were subjected to tandem chromatography/mass spectrometry analysis to elucidate metabolic changes in the RBCs during storage. Results Using independent inbred mouse strains as donors, we found substantial strain-specific differences in post-transfusion RBC recovery in vivo following standardized refrigerated storage in vitro. Poor post-transfusion RBC recovery correlated with reproducible metabolic variations in the stored RBC units, including increased lipid peroxidation, decreased levels of multiple natural antioxidants, and accumulation of cytidine. Strain-dependent differences were also observed in eicosanoid generation (i.e. prostaglandins and leukotrienes). Conclusion These findings provide the first evidence of strain-specific metabolomic differences following refrigerated storage of murine RBCs. They also provide the first definitive biochemical evidence for strain specific variation of eicosanoid generation during RBC storage. The molecules described that correlate with RBC storage quality, and their associated biochemical pathways, suggest multiple causal hypotheses that can be tested regarding predicting the quality of RBC units prior to transfusion and developing methods of improved RBC storage. PMID:23721209

  2. Molecular Interactions between Cell Penetrating Peptide Pep-1 and Model Cell Membranes

    PubMed Central

    Ding, Bei; Chen, Zhan

    2012-01-01

    We investigated the molecular interactions of a cell penetrating peptide (CPP) Pep-1 with model cell membranes using sum frequency generation (SFG) vibrational spectroscopy, supplemented by attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR). Hydrogenated and deuterated 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG and dDPPG) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1?-rac-glycerol) (POPG), were used in the experiments to represent gel-phase and fluid-phase lipid bilayers, respectively. Our SFG results indicated that Pep-1 molecules adopted a ?-sheet conformation when adsorbed to the surface of gel-phase DPPG lipid bilayers. When interacting with fluid-phase POPG lipid bilayers, Pep-1 adopted a mix of ?-helical and ?-sheet structures over a broad range of peptide concentrations. The orientation distribution of the ?-helical Pep-1 segment associated with the fluid-phase bilayers was found to depend on the peptide concentration. SFG orientation analysis showed that Pep-1 molecules adopted an orientation nearly perpendicular to the plane of the bilayer for peptide concentrations of 0.28 ?M and 1.4 ?M. When the Pep-1 concentration was increased to 7.0 ?M, combined SFG and ATR-FTIR measurements showed that Pep-1 molecules were associated with the bilayer with a broad orientation distribution. Our results demonstrated that lipid bilayer phase and peptide concentration affect the conformation and orientation of Pep-1 molecules associated with model cell membranes, which is crucial to the translocation process of CPPs. A combination of SFG and ATR-FTIR studies can be used to determine the conformation and orientation of CPPs interacting with model cell membranes in situ. PMID:22292835

  3. Development of cesium phosphotungstate salt and chitosan composite membrane for direct methanol fuel cells.

    PubMed

    Xiao, Yanxin; Xiang, Yan; Xiu, Ruijie; Lu, Shanfu

    2013-10-15

    A novel composite membrane has been developed by doping cesium phosphotungstate salt (CsxH3-xPW12O40 (0?x?3), Csx-PTA) into chitosan (CTS/Csx-PTA) for application in direct methanol fuel cells (DMFCs). Uniform distribution of Csx-PTA nanoparticles has been achieved in the chitosan matrix. The proton conductivity of the composite membrane is significantly affected by the Csx-PTA content in the composite membrane as well as the Cs substitution in PTA. The highest proton conductivity for the CTS/Csx-PTA membranes was obtained with x=2 and Cs2-PTA content of 5 wt%. The value is 6×10(-3) S cm(-1) and 1.75×10(-2) S cm(-1) at 298 K and 353 K, respectively. The methanol permeability of CTS/Cs2-PTA membrane is about 5.6×10(-7), 90% lower than that of Nafion-212 membrane. The highest selectivity factor (?) was obtained on CTS/Cs2-PTA-5 wt% composite membrane, 1.1×10(4)/Scm(-3)s. The present study indicates the promising potential of CTS/Csx-PTA composite membrane as alternative proton exchange membranes in direct methanol fuel cells. PMID:23987340

  4. Screening of bioactive compounds in Radix Salviae Miltiorrhizae with liposomes and cell membranes using HPLC.

    PubMed

    Chen, Xiaoping; Deng, Yachen; Xue, Ying; Liang, Jianying

    2012-11-01

    A new method employing HPLC, LC-MS, liposomes and cell membranes for the screening of bioactive compounds in traditional Chinese medicines (TCMs) has been proposed. We hypothesized that exposure of the TCM extracts to liposome membranes or cell membranes should decrease the concentration of membrane-permeable compounds in the solution. Using this approach, the permeability of the compounds in Radix Salviae Miltiorrhizae was investigated. By comparing chromatograms of samples prepared both before and after interaction with liposome membranes, erythrocyte membranes and cardiac myocyte membranes, 12 permeable compounds of Radix Salviae Miltiorrhizae were identified, and they were proven to be biologically active, with the exception of vanillic acid. There was a good correlation between the liposome model and the erythrocyte membranes, which was determined by comparing the binding degree of the permeable compounds (n=0.9059). Additionally, it was found that dihydrotanshinone I, cryptotanshinone, tanshinone I, tanshinone IIA combined specifically with cardiac myocyte membranes, which might indicate a useful approach for revealing the cardiovascular effects of Radix Salviae Miltiorrhizae. Based on these results, this method could be a novel approach for identifying potentially bioactive components in other TCMs. PMID:22789901

  5. Transient Analysis of Proton Electrolyte Membrane Fuel Cells (PEMFC) at Start-Up

    E-print Network

    Yanikoglu, Berrin

    Transient Analysis of Proton Electrolyte Membrane Fuel Cells (PEMFC) at Start-Up and Failure M. F with experiments to study the effect of temperature, humidity, and pressure on fuel cell performance. They concluded that as long as the cell is well humidified, increasing the temperature and pressure always

  6. Cell-Free Synthesis for Analyzing the Membrane Integration, Oligomerization, and Assembly

    E-print Network

    Mullen, Sean P.

    of gap junction subunit proteins, we have used cell-free protein synthesis in translation-competent cellCell-Free Synthesis for Analyzing the Membrane Integration, Oligomerization, and Assembly Institute, La Jolla, California 92037 For gap junction channels to function, their subunit proteins

  7. TERMINAL COMPLEXES IN ,VITELLA 237 on the plasma membrane of Boodlea coacta. Plant Cell Phyiol.

    E-print Network

    Morel, François M. M.

    , D. C. & Crawford, R. M. 1976. A new model for cellulose architecture in some plant cell walls. ProTERMINAL COMPLEXES IN ,VITELLA 237 on the plasma membrane of Boodlea coacta. Plant Cell Phyiol. 26 with a cellulose microfibril- synthesizing complex in higher plants. J. Cell Bzol. 84:315- 26. Neville, A. C., Gubb

  8. Multi-paradigm multi-scale simulations for fuel cell catalysts and membranes

    E-print Network

    van Duin, Adri

    Multi-paradigm multi-scale simulations for fuel cell catalysts and membranes W. GODDARD III*, B improving the performance of fuel cell systems with their complex heterogeneous structures involving in the design and which can be used to monitor performance of working fuel cells. Our strategy is to start

  9. Plasma Membrane Integrity and Survival of Melanoma Cells After Nanosecond Laser Pulses

    E-print Network

    Aguilar, Guillermo

    Plasma Membrane Integrity and Survival of Melanoma Cells After Nanosecond Laser Pulses FRANCISCO G decision-making in the treatment of cancer. Interaction of melanin within melanoma cells with nanosecond) determining melanoma cell survival after laser pulses of 6 ns at k = 355 and 532 nm; (2) comparing

  10. Refractive index maps and membrane dynamics of human red blood cells parasitized

    E-print Network

    Suresh, Subra

    Refractive index maps and membrane dynamics of human red blood cells parasitized by Plasmodium to the host red blood cells (RBCs). To study these modifications, we investigate two intrinsic indicators to host red blood cells (RBCs). Major struc- tural changes include the formation of parasitophorus

  11. Temperature distribution on anodic surface of membrane electrode assembly in proton exchange membrane fuel cell with interdigitated flow bed

    NASA Astrophysics Data System (ADS)

    Guo, Hang; Wang, Mao Hai; Liu, Jia Xing; Nie, Zhi Hua; Ye, Fang; Ma, Chong Fang

    2015-01-01

    Temperature distribution on the surface of a membrane electrode assembly (MEA) significantly influences the performance, lifetime, and reliability of proton exchange membrane fuel cells (PEMFCs). Entire temperature fields on the surface of an MEA anode side under an interdigitated flow field are experimentally measured at non-humidification conditions with a self-designed PEMFC and infrared imaging technology. The highest temperature on the surface of the MEA anode side appears in the bottom bordered two side channels, and the lowest temperature exists in the area closed to the inlet of the middle channel. The hot region on the surface of the MEA anode side is easy to locate in the infrared temperature image. The reason for the temperature distribution under the interdigitated flow field is analyzed. The temperature of the MEA, the non-uniformity of temperature distribution on the surface of the MEA anode side, and the fuel cell temperature increase with the loaded current density.

  12. UNDERSTANDING THE EFFECTS OF COMPRESSION AND CONSTRAINTS ON WATER UPTAKE OF FUEL-CELL MEMBRANES

    SciTech Connect

    Kusoglu, Ahmet; Kienitz, Briian; Weber, Adam

    2011-08-24

    Accurate characterization of polymer-electrolyte fuel cells (PEFCs) requires understanding the impact of mechanical and electrochemical loads on cell components. An essential aspect of this relationship is the effect of compression on the polymer membrane?s water-uptake behavior and transport properties. However, there is limited information on the impact of physical constraints on membrane properties. In this paper, we investigate both theoretically and experimentally how the water uptake of Nafion membrane changes under external compression loads. The swelling of a compressed membrane is modeled by modifying the swelling pressure in the polymer backbone which relies on the changes in the microscopic volume of the polymer. The model successfully predicts the water content of the compressed membrane measured through in-situ swelling-compression tests and neutron imaging. The results show that external mechanical loads could reduce the water content and conductivity of the membrane, especially at lower temperatures, higher humidities, and in liquid water. The modeling framework and experimental data provide valuable insight for the swelling and conductivity of constrained and compressed membranes, which are of interest in electrochemical devices such as batteries and fuel cells.

  13. Computational analysis of the tether-pulling experiment to probe plasma membrane-cytoskeleton interaction in cells

    NASA Astrophysics Data System (ADS)

    Schumacher, Kristopher R.; Popel, Aleksander S.; Anvari, Bahman; Brownell, William E.; Spector, Alexander A.

    2009-10-01

    Tethers are thin membrane tubes that can be formed when relatively small and localized forces are applied to cellular membranes and lipid bilayers. Tether pulling experiments have been used to better understand the fine membrane properties. These include the interaction between the plasma membrane and the underlying cytoskeleton, which is an important factor affecting membrane mechanics. We use a computational method aimed at the interpretation and design of tether pulling experiments in cells with a strong membrane-cytoskeleton attachment. In our model, we take into account the detailed information in the topology of bonds connecting the plasma membrane and the cytoskeleton. We compute the force-dependent piecewise membrane deflection and bending as well as modes of stored energy in three major regions of the system: body of the tether, membrane-cytoskeleton attachment zone, and the transition zone between the two. We apply our method to three cells: cochlear outer hair cells (OHCs), human embryonic kidney (HEK) cells, and Chinese hamster ovary (CHO) cells. OHCs have a special system of pillars connecting the membrane and the cytoskeleton, and HEK and CHO cells have the membrane-cytoskeleton adhesion arrangement via bonds (e.g., PIP2), which is common to many other cells. We also present a validation of our model by using experimental data on CHO and HEK cells. The proposed method can be an effective tool in the analyses of experiments to probe the properties of cellular membranes.

  14. Study on the preparation of chitosan alginate complex membrane and the effects on adhesion and activation of endothelial cells

    NASA Astrophysics Data System (ADS)

    Shi, Guoqi; Chen, Yuanwei; Wan, Changxiu; Yu, Xixun; Feng, Ting; Ding, Yulong

    2008-11-01

    Biomaterials that support vascularization without activating immune competent endothelial cells are desirous in immunoisolation. The aim of the present study was to evaluate effect of chitosan-alginate membrane on adhesion and activation of endothelial cells. The AFM photographs showed that the CS/ALG membrane surface roughness values were less than CS membrane and ALG membrane. The contact angle of CS/ALG membrane was between ALG membrane and CS membrane. The surface roughness and hydrophilicity of CS/ALG membrane affect the adhesion and activation on endothelial cells. The CS/ALG membrane did not allow the majority of cells to adhere well but maintained their viability. The membrane leach-outs were nontoxic to the cells, as confirmed by tetrazolium reduction (MTT) and trypan blue assays. The growth curves of the endothelial cells desquamated from the CS/ALG membrane suggested that the endothelial cells maintain their activation. Taken together these results point out that CS/ALG membrane is compatible with endothelial cells and maintains their nonactivated status.

  15. Carbon corrosion of proton exchange membrane fuel cell catalyst layers studied by scanning transmission X-ray microscopy

    E-print Network

    Hitchcock, Adam P.

    Carbon corrosion of proton exchange membrane fuel cell catalyst layers studied by scanning a l a b s t r a c t STXM is used to analyze polymer membrane fuel cell cathodes. Carbon corrosion and Pt-in- membrane degradation is tracked. Low surface area and medium sur- face area carbon supports

  16. Force Balance and Membrane Shedding at the Red-Blood-Cell Surface Pierre Sens1,* and Nir Gov2,

    E-print Network

    Sens, Pierre

    Force Balance and Membrane Shedding at the Red-Blood-Cell Surface Pierre Sens1,* and Nir Gov2, 1 echinocytosis, membrane is shed from the cell plasma membrane in the form of nanovesicles. We propose days in humans and 10% over 50 days in rabbits [4,5]) by the shedding of small vesicles containing

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  18. Capture and printing of fixed stromal cell membranes for bioactive display on PDMS surfaces

    PubMed Central

    Lee, Jungwoo; Wang, Jennifer B.; Bersani, Francesca; Parekkadan, Biju

    2013-01-01

    Polydimethylsiloxane (PDMS) has emerged as an extremely useful polymer for various biological applications. The conjugation of PDMS with bioactive molecules to create functional surfaces is feasible, yet limited to single molecule display with imprecise localization of the molecules on PDMS. Here we report a robust technique that can transfer and print the membrane surface of glutaraldehyde-fixed stromal cells intact to a PDMS substrate using an intermediate polyvinylalcohol (PVA) film as a transporter system. The cell-PVA film capturing the entirety of surface molecules can be peeled off and subsequently printed onto PDMS while maintaining the spatial display of the original cell surface molecules. Proof-of-concept studies are described using human bone marrow stromal cell membranes, including the demonstration of bioactivity of transferred membranes to capture and adhere hematopoietic cells. The presented process is applicable to virtually any adherent cell and can broaden the functional display of biomolecules on PDMS for biotechnology applications. PMID:23927769

  19. Freeze-fracture identification of sterol-digitonin complexes in cell and liposome membranes

    PubMed Central

    1978-01-01

    To advance our understanding of the organization of cholesterol within cell membranes, we used digitonin in freeze-fracture investigations of model lipid vesicles and tissues. Cholesterol suspensions or multilamellar liposomes composed of phosphatidylcholine with and without cholesterol were exposed to digitonin. Freeze-fracture replicas of those multilamellar liposomes containing cholesterol displayed either 50--60-nm wide intramembrane corrugations or extramembrane tubular complexes. Comparable intramembrane hemitubular scallops and extra-cellular free tubular complexes were observed in thin sections. Exposure of sperm, erythrocytes (whole and ghosts), and intact tissues (skin, liver, adrenal gland, epididymis) to digitonin produced the same types of intra- and extramembrane complexes or furrows as were formed in liposomes. The plasma membrane of guinea pig serum tail had two unfurrowed regions: the annulus and the zipper. Incubating erythrocyte membranes with digitonin resulted in rapid displacement of cholesterol, accompanied by intramembrane particle clustering and membrane faceting, a feature which we did not see in the intact epithelia studied. In freeze-fractured epithelia, we found that plasma membranes, lysosomes, and some vesicular organelles commonly furrowed, but that mitochondrial membranes and nuclear envelopes were generally spared, correlating well with their known cholesterol content. Finally, plasma membrane corrugations approached but did not impinge on either gap or tight junctions, or on coated vesicles. We conclude that freeze-fracture of membranes exposed to digitonin: (a) reveals distinctive cholesterol- digitonin structural complexes; (b) distinguishes cholesterol-rich and - poor organelle membranes; and (c) demonstrates membrane domains rich or poor in cholesterol. PMID:690180

  20. Lipopolysaccharide transport to the cell surface: biosynthesis and extraction from the inner membrane.

    PubMed

    Simpson, Brent W; May, Janine M; Sherman, David J; Kahne, Daniel; Ruiz, Natividad

    2015-10-01

    The cell surface of most Gram-negative bacteria is covered with lipopolysaccharide (LPS). The network of charges and sugars provided by the dense packing of LPS molecules in the outer leaflet of the outer membrane interferes with the entry of hydrophobic compounds into the cell, including many antibiotics. In addition, LPS can be recognized by the immune system and plays a crucial role in many interactions between bacteria and their animal hosts. LPS is synthesized in the inner membrane of Gram-negative bacteria, so it must be transported across their cell envelope to assemble at the cell surface. Over the past two decades, much of the research on LPS biogenesis has focused on the discovery and understanding of Lpt, a multi-protein complex that spans the cell envelope and functions to transport LPS from the inner membrane to the outer membrane. This paper focuses on the early steps of the transport of LPS by the Lpt machinery: the extraction of LPS from the inner membrane. The accompanying paper (May JM, Sherman DJ, Simpson BW, Ruiz N, Kahne D. 2015 Phil. Trans. R. Soc. B 370, 20150027. (doi:10.1098/rstb.2015.0027)) describes the subsequent steps as LPS travels through the periplasm and the outer membrane to its final destination at the cell surface. PMID:26370941

  1. Membrane-integrated microfluidic device for high-resolution live cell imaging

    PubMed Central

    Epshteyn, Alla A.; Maher, Steven; Taylor, Amy J.; Holton, Angela B.; Borenstein, Jeffrey T.; Cuiffi, Joseph D.

    2011-01-01

    The design and fabrication of a membrane-integrated microfluidic cell culture device (five layers,?500??m total thickness) developed for high resolution microscopy is reported here. The multi-layer device was constructed to enable membrane separated cell culture for tissue mimetic in vitro model applications and pharmacodynamic evaluation studies. The microdevice was developed via a unique combination of low profile fluidic interconnect design, substrate transfer methodology, and wet silane bonding. To demonstrate the unique high resolution imaging capability of this device, we used oil immersion microscopy to image stained nuclei and mitochondria in primary hepatocytes adhered to the incorporated membrane PMID:22662065

  2. Radiation grafted and sulfonated (FEP-g-polysterene) - An alternative to perfluorinated membranes for PEM fuel cells?

    NASA Astrophysics Data System (ADS)

    Buechi, F. N.; Gupta, B.; Rouilly, M.; Hauser, P. C.; Chapiro, A.; Scherer, G. G.

    Partially fluorinated proton exchange membranes (PEMs) were synthesized for fuel cell applications by simultaneous radiation grafting of styrene on FEP films followed by sulfonation. Properties of the synthesized membranes can be tailored by varying the degree of grafting and crosslinking. The performance of these membranes was tested in H2/O2 fuel cells. Long time testing showed steady performance for high grafted membranes over periods of more than 300 h at a cell temperature of 60 C. Low grafted membranes and the Morgane CDS membrane showed considerable decay of cell power on the same time scale. A fast degradation of all membranes occurred at a cell temperature of 80 C. It is noted that grafting in film form makes this process a potentially cheap and easy technique for the preparation of solid polymer fuel cell electrolytes.

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

    PubMed

    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. PMID:26512807

  4. Highly conductive anion exchange membrane for high power density fuel-cell performance.

    PubMed

    Ren, Xiaoming; Price, Samuel C; Jackson, Aaron C; Pomerantz, Natalie; Beyer, Frederick L

    2014-08-27

    Anion exchange membrane fuel cells (AEMFCs) are regarded as a new generation of fuel cell technology that has the potential to overcome many obstacles of the mainstream proton exchange membrane fuel cells (PEMFCs) in cost, catalyst stability, efficiency, and system size. However, the low ionic conductivity and poor thermal stability of current anion exchange membranes (AEMs) have been the key factors limiting the performance of AEMFCs. In this study, an AEM made of styrenic diblock copolymer with a quaternary ammonium-functionalized hydrophilic block and a cross-linkable hydrophobic block and possessing bicontinuous phases of a hydrophobic network and hydrophilic conduction paths was found to have high ionic conductivity at 98 mS cm(-1) and controlled membrane swelling with water uptake at 117 wt % at 22 °C. Membrane characterizations and fuel cell tests of the new AEM were carried out together with a commercial AEM, Tokuyama A201, for comparison. The high ionic conductivity and water permeability of the new membrane reported in this study is attributed to the reduced torturosity of the ionic conduction paths, while the hydrophobic network maintains the membrane mechanical integrity, preventing excessive water uptake. PMID:25101785

  5. Tryptophan phosphorescence as a monitor of flexibility of membrane proteins in cells

    NASA Astrophysics Data System (ADS)

    Mazhul, Vladimir M.; Scherbin, Dmitry G.

    1997-05-01

    Method of room temperature tryptophan phosphorescence (RTTP) has been used to study slow intramolecular equilibrium motions in membrane proteins. The conventional home-made instruments were employed for measurement of RTTP kinetic and spectral parameters. Objects of the investigation were suspensions of human erythrocyte membranes, different animal and plant cells. On rat gepathocytes it has been shown that membrane proteins in composition of subcellular structures and native cells are able to the RTTP with tens and hundreds milliseconds lifetimes. An overwhelming part of soluble proteins of cytoplasm, karyoplasm and mitochondrial matrix has not capability to RTTP with lifetimes above 1 ms. It is concluded that unlike membrane proteins soluble proteins as a rule are characterized by motions of protein structure with intensive low frequency and large amplitude, that leads to pronounced quenching of their RTTP. In the case of membrane proteins, which are capable of phosphorescence in a millisecond range, the flexibility of the chromophores environment decreases. These results indicate that RTTP method gives the unique possibility to investigate dynamical structure of membrane proteins without their preliminary isolation from cells. The data on membrane proteins intramolecular dynamics in composition of cells at the action of biological active substances in physiological concentrations--Concavalin A, nerve growth factor, epidermal growth factor, 24-epibrassinosteroid received by the phosphorescent method are presented.

  6. Laurdan fluorescence lifetime discriminates cholesterol content from changes in fluidity in living cell membranes.

    PubMed

    Golfetto, Ottavia; Hinde, Elizabeth; Gratton, Enrico

    2013-03-19

    Detection of the fluorescent properties of Laurdan has been proven to be an efficient tool to investigate membrane packing and ordered lipid phases in model membranes and living cells. Traditionally the spectral shift of Laurdan's emission from blue in the ordered lipid phase of the membrane (more rigid) toward green in the disordered lipid phase (more fluid) is quantified by the generalized polarization function. Here, we investigate the fluorescence lifetime of Laurdan at two different emission wavelengths and find that when the dipolar relaxation of Laurdan's emission is spectrally isolated, analysis of the fluorescence decay can distinguish changes in membrane fluidity from changes in cholesterol content. Using the phasor representation to analyze changes in Laurdan's fluorescence lifetime we obtain two different phasor trajectories for changes in polarity versus changes in cholesterol content. This gives us the ability to resolve in vivo membranes with different properties such as water content and cholesterol content and thus perform a more comprehensive analysis of cell membrane heterogeneity. We demonstrate this analysis in NIH3T3 cells using Laurdan as a biosensor to monitor changes in the membrane water content during cell migration. PMID:23528083

  7. Modification of plasma membrane organization in tobacco cells elicited by cryptogein.

    PubMed

    Gerbeau-Pissot, Patricia; Der, Christophe; Thomas, Dominique; Anca, Iulia-Andra; Grosjean, Kevin; Roche, Yann; Perrier-Cornet, Jean-Marie; Mongrand, Sébastien; Simon-Plas, Françoise

    2014-01-01

    Lipid mixtures within artificial membranes undergo a separation into liquid-disordered and liquid-ordered phases. However, the existence of this segregation into microscopic liquid-ordered phases has been difficult to prove in living cells, and the precise organization of the plasma membrane into such phases has not been elucidated in plant cells. We developed a multispectral confocal microscopy approach to generate ratiometric images of the plasma membrane surface of Bright Yellow 2 tobacco (Nicotiana tabacum) suspension cells labeled with an environment sensitive fluorescent probe. This allowed the in vivo characterization of the global level of order of this membrane, by which we could demonstrate that an increase in its proportion of ordered phases transiently occurred in the early steps of the signaling triggered by cryptogein and flagellin, two elicitors of plant defense reactions. The use of fluorescence recovery after photobleaching revealed an increase in plasma membrane fluidity induced by cryptogein, but not by flagellin. Moreover, we characterized the spatial distribution of liquid-ordered phases on the membrane of living plant cells and monitored their variations induced by cryptogein elicitation. We analyze these results in the context of plant defense signaling, discuss their meaning within the framework of the "membrane raft" hypothesis, and propose a new mechanism of signaling platform formation in response to elicitor treatment. PMID:24235133

  8. Clostridium perfringens?-toxin interaction with red cells and model membranes.

    PubMed

    Jewell, S A; Titball, R W; Huyet, J; Naylor, C E; Basak, A K; Gologan, P; Winlove, C P; Petrov, P G

    2015-10-21

    The effects of Clostridium perfringens?-toxin on host cells have previously been studied extensively but the biophysical processes associated with toxicity are poorly understood. The work reported here shows that the initial interaction between the toxin and lipid membrane leads to measurable changes in the physical properties and morphology of the membrane. A Langmuir monolayer technique was used to assess the response of different lipid species to toxin. Sphingomyelin and unsaturated phosphatidylcholine showed the highest susceptibility to toxin lypolitic action, with a two stage response to the toxin (an initial, rapid hydrolysis stage followed by the insertion and/or reorganisation of material in the monolayer). Fluorescence confocal microscopy on unsaturated phosphatidylcholine vesicles shows that the toxin initially aggregates at discrete sites followed by the formation of localised "droplets" accumulating the hydrolysis products. This process is accompanied by local increases in the membrane dipole potential by about 50 (±42) mV. In contrast, red blood cells incubated with the toxin suffered a decrease of the membrane dipole potential by 50 (±40) mV in areas of high toxin activity (equivalent to a change in electric field strength of 10(7) V m(-1)) which is sufficient to affect the functioning of the cell membrane. Changes in erythrocyte morphology caused by the toxin are presented, and the early stages of interaction between toxin and membrane are characterised using thermal shape fluctuation analysis of red cells which revealed two distinct regimes of membrane-toxin interaction. PMID:26303814

  9. FORMATION OF INTRACYTOPLASMIC MEMBRANE SYSTEM OF MYCOBACTERIA RELATED TO CELL DIVISION

    PubMed Central

    Imaeda, Tamotsu; Ogura, Mituo

    1963-01-01

    Imaeda, Tamotsu (Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela) and Mitua Ogura. Formation of intracytoplasmic membrane system of mycobacteria related to cell division. J. Bacteriol. 85:150–163. 1963.—Mycobacterium leprae, M. lepraemurium, and a Mycobacterium sp. were observed with an electron microscope. In these bacilli, the three-dimensional structure of the intracytoplasmic membrane system consists of tubular infoldings of the invaginated plasma membrane. The moderately dense substance, presumably representing the cell-wall precursor, is found in the membranous system, especially in the rapid growth phase of mycobacteria. This system always shows an intimate relationship with cell division. A low-density zone, probably corresponding to the low-density substance which coats the cell wall, appears in the connecting regions of the system and in the longitudinal portion of the cell wall. These zones extend centripetally, and the separation of the cell wall occurs after the two zones meet. Based on these results, we hypothesize that the intracytoplasmic membrane system may produce cell-wall material during cell division of mycobacteria. Images PMID:13956365

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

    SciTech Connect

    Liepins, A.; Younghusband, H.B.

    1985-12-01

    Temperature shift conditions of 0 degree to 22 degrees C or 0 degree to 37 degrees C induce the formation and shedding of membrane vesicles (MV) from P815 tumor cell surfaces. When the MV shedding process takes place at 22 degrees C it occurs without changes in cell surface membrane permeability, whereas at 37 degrees C, changes in permeability to /sup 51/Cr and trypan blue do occur, thus mimicking the lymphocyte-mediated lytic process of tumor cells. The present studies demonstrate that nuclear DNA fragmentation also occurs in both 0 degree to 22 degrees C and 0 degree to 37 degrees C temperature shifts. However, cell surface membrane permeability to DNA fragments occurs only in the latter condition, i.e., 0 degree to 37 degrees C. The microtubule-stabilizing agent deuterium oxide (D/sub 2/O) inhibited the MV shedding process, the changes in membrane permeability, and DNA fragmentation. When P815 cells which had been induced to shed MV by the 0 degree to 22 degrees C temperature shift were labeled with /sup 51/Cr and used as targets for alloimmune lymphocytes, they were found to be as susceptible to T-cell lysis as control P815 cells. This result indicates that the lytic effect of alloimmune T lymphocytes can be exerted at the target cell surface membrane level independently of nuclear DNA fragmentation.

  11. Measuring Local Viscosities near Plasma Membranes of Living Cells with Photonic Force Microscopy.

    PubMed

    Jünger, Felix; Kohler, Felix; Meinel, Andreas; Meyer, Tim; Nitschke, Roland; Erhard, Birgit; Rohrbach, Alexander

    2015-09-01

    The molecular processes of particle binding and endocytosis are influenced by the locally changing mobility of the particle nearby the plasma membrane of a living cell. However, it is unclear how the particle's hydrodynamic drag and momentum vary locally and how they are mechanically transferred to the cell. We have measured the thermal fluctuations of a 1 ?m-sized polystyrene sphere, which was placed in defined distances to plasma membranes of various cell types by using an optical trap and fast three-dimensional (3D) interferometric particle tracking. From the particle position fluctuations on a 30 ?s timescale, we determined the distance-dependent change of the viscous drag in directions perpendicular and parallel to the cell membrane. Measurements on macrophages, adenocarcinoma cells, and epithelial cells revealed a significantly longer hydrodynamic coupling length of the particle to the membrane than those measured at giant unilamellar vesicles (GUVs) or a plane glass interface. In contrast to GUVs, there is also a strong increase in friction and in mean first passage time normal to the cell membrane. This hydrodynamic coupling transfers a different amount of momentum to the interior of living cells and might serve as an ultra-soft stimulus triggering further reactions. PMID:26331245

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

    PubMed Central

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

    2014-01-01

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

  13. Carbon dioxide (hydrogen sulfide) membrane separations and WGS membrane reactor modeling for fuel cells

    NASA Astrophysics Data System (ADS)

    Huang, Jin

    Acid-gas removal is of great importance in many environmental or energy-related processes. Compared to current commercial technologies, membrane-based CO2 and H2S capture has the advantages of low energy consumption, low weight and space requirement, simplicity of installation/operation, and high process flexibility. However, the large-scale application of the membrane separation technology is limited by the relatively low transport properties. In this study, CO2 (H2S)-selective polymeric membranes with high permeability and high selectivity have been studied based on the facilitated transport mechanism. The membrane showed facilitated effect for both CO2 and H2S. A CO2 permeability of above 2000 Barrers, a CO2/H2 selectivity of greater than 40, and a CO2/N2 selectivity of greater than 200 at 100--150°C were observed. As a result of higher reaction rate and smaller diffusing compound, the H2S permeability and H2S/H2 selectivity were about three times higher than those properties for CO2. The novel CO2-selective membrane has been applied to capture CO 2 from flue gas and natural gas. In the CO2 capture experiments from a gas mixture with N2 and H2, a permeate CO 2 dry concentration of greater than 98% was obtained by using steam as the sweep gas. In CO2/CH4 separation, decent CO 2 transport properties were obtained with a feed pressure up to 500 psia. With the thin-film composite membrane structure, significant increase on the CO2 flux was achieved with the decrease of the selective layer thickness. With the continuous removal of CO2, CO2-selective water-gas-shift (WGS) membrane reactor is a promising approach to enhance CO conversion and increase the purity of H2 at process pressure under relatively low temperature. The simultaneous reaction and transport process in the countercurrent WGS membrane reactor was simulated by using a one-dimensional non-isothermal model. The modeling results show that a CO concentration of less than 10 ppm and a H2 recovery of greater than 97% are achievable from reforming syngases. In an experimental study, the reversible WGS was shifted forward by removing CO2 so that the CO concentration was significantly decreased to less than 10 ppm. The modeling results agreed well with the experimental data.

  14. Water transport in fuel cell membranes measured by laser interferometry

    E-print Network

    Kim, Jungik, 1973-

    2009-01-01

    (cont.) The coefficients of electro-osmotic drag were found to increase with the increasing water content, which indicates that the Grotthuss mechanism of proton transfer is not active in the membranes with low water ...

  15. Biophysics of cell membrane lipids in cancer drug resistance: Implications for drug transport and drug delivery with nanoparticles.

    PubMed

    Peetla, Chiranjeevi; Vijayaraghavalu, Sivakumar; Labhasetwar, Vinod

    2013-11-01

    In this review, we focus on the biophysics of cell membrane lipids, particularly when cancers develop acquired drug resistance, and how biophysical changes in resistant cell membrane influence drug transport and nanoparticle-mediated drug delivery. Recent advances in membrane lipid research show the varied roles of lipids in regulating membrane P-glycoprotein function, membrane trafficking, apoptotic pathways, drug transport, and endocytic functions, particularly endocytosis, the primary mechanism of cellular uptake of nanoparticle-based drug delivery systems. Since acquired drug resistance alters lipid biosynthesis, understanding the role of lipids in cell membrane biophysics and its effect on drug transport is critical for developing effective therapeutic and drug delivery approaches to overcome drug resistance. Here we discuss novel strategies for (a) modulating the biophysical properties of membrane lipids of resistant cells to facilitate drug transport and regain endocytic function and (b) developing effective nanoparticles based on their biophysical interactions with membrane lipids to enhance drug delivery and overcome drug resistance. PMID:24055719

  16. Effect of direct liquid water injection and interdigitated flow field on the performance of proton exchange membrane fuel cells

    E-print Network

    Wood, D. L.; Yi, Y. S.; Van Nguyen, Trung

    1998-01-01

    . INTRODUCTION Proton Exchange Membrane (PEM) fuel cells are becoming more popular as direct electrical energy conversion devices because of their high efficiency and simplicity in design and operation made possible by the use of a proton conducting membrane...

  17. Biophysics of Cell Membrane Lipids in Cancer Drug Resistance: Implications for Drug Transport and Drug Delivery with Nanoparticles

    PubMed Central

    Peetla, Chiranjeevi; Vijayaraghavalu, Sivakumar; Labhasetwar, Vinod

    2013-01-01

    In this review, we focus on the biophysics of cell membrane lipids, particularly when cancers develop acquired drug resistance, and how biophysical changes in resistant cell membrane influence drug transport and nanoparticle-mediated drug delivery. Recent advances in membrane lipid research show the varied roles of lipids in regulating membrane P-glycoprotein function, membrane trafficking, apoptotic pathways, drug transport, and endocytic functions, particularly endocytosis, the primary mechanism of cellular uptake of nanoparticle-based drug delivery systems. Since acquired drug resistance alters lipid biosynthesis, understanding the role of lipids in cell membrane biophysics and its effect on drug transport is critical for developing effective therapeutic and drug delivery approaches to overcoming drug resistance. Here we discuss novel strategies for (a) modulating the biophysical properties of membrane lipids of resistant cells to facilitate drug transport and regain endocytic function and (b) developing effective nanoparticles based on their biophysical interactions with membrane lipids to enhance drug delivery and overcome drug resistance. PMID:24055719

  18. Cell Surface Area and Membrane Folding in Glioblastoma Cell Lines Differing in PTEN and p53 Status

    PubMed Central

    Höring, Marcus; Westerling, Katherine; Fiedler, Vanessa; Katzer, Astrid; Krohne, Georg; Flentje, Michael; Djuzenova, Cholpon S.

    2014-01-01

    Glioblastoma multiforme (GBM) is characterized by rapid growth, invasion and resistance to chemo?/radiotherapy. The complex cell surface morphology with abundant membrane folds, microvilli, filopodia and other membrane extensions is believed to contribute to the highly invasive behavior and therapy resistance of GBM cells. The present study addresses the mechanisms leading to the excessive cell membrane area in five GBM lines differing in mutational status for PTEN and p53. In addition to scanning electron microscopy (SEM), the membrane area and folding were quantified by dielectric measurements of membrane capacitance using the single-cell electrorotation (ROT) technique. The osmotic stability and volume regulation of GBM cells were analyzed by video microscopy. The expression of PTEN, p53, mTOR and several other marker proteins involved in cell growth and membrane synthesis were examined by Western blotting. The combined SEM, ROT and osmotic data provided independent lines of evidence for a large variability in membrane area and folding among tested GBM lines. Thus, DK-MG cells (wild type p53 and wild type PTEN) exhibited the lowest degree of membrane folding, probed by the area-specific capacitance Cm?=?1.9 µF/cm2. In contrast, cell lines carrying mutations in both p53 and PTEN (U373-MG and SNB19) showed the highest Cm values of 3.7–4.0 µF/cm2, which corroborate well with their heavily villated cell surface revealed by SEM. Since PTEN and p53 are well-known inhibitors of mTOR, the increased membrane area/folding in mutant GBM lines may be related to the enhanced protein and lipid synthesis due to a deregulation of the mTOR-dependent downstream signaling pathway. Given that membrane folds and extensions are implicated in tumor cell motility and metastasis, the dielectric approach presented here provides a rapid and simple tool for screening the biophysical cell properties in studies on targeting chemo- or radiotherapeutically the migration and invasion of GBM and other tumor types. PMID:24498019

  19. Cell surface area and membrane folding in glioblastoma cell lines differing in PTEN and p53 status.

    PubMed

    Memmel, Simon; Sukhorukov, Vladimir L; Höring, Marcus; Westerling, Katherine; Fiedler, Vanessa; Katzer, Astrid; Krohne, Georg; Flentje, Michael; Djuzenova, Cholpon S

    2014-01-01

    Glioblastoma multiforme (GBM) is characterized by rapid growth, invasion and resistance to chemo-/radiotherapy. The complex cell surface morphology with abundant membrane folds, microvilli, filopodia and other membrane extensions is believed to contribute to the highly invasive behavior and therapy resistance of GBM cells. The present study addresses the mechanisms leading to the excessive cell membrane area in five GBM lines differing in mutational status for PTEN and p53. In addition to scanning electron microscopy (SEM), the membrane area and folding were quantified by dielectric measurements of membrane capacitance using the single-cell electrorotation (ROT) technique. The osmotic stability and volume regulation of GBM cells were analyzed by video microscopy. The expression of PTEN, p53, mTOR and several other marker proteins involved in cell growth and membrane synthesis were examined by Western blotting. The combined SEM, ROT and osmotic data provided independent lines of evidence for a large variability in membrane area and folding among tested GBM lines. Thus, DK-MG cells (wild type p53 and wild type PTEN) exhibited the lowest degree of membrane folding, probed by the area-specific capacitance C m?=?1.9 µF/cm(2). In contrast, cell lines carrying mutations in both p53 and PTEN (U373-MG and SNB19) showed the highest C m values of 3.7-4.0 µF/cm(2), which corroborate well with their heavily villated cell surface revealed by SEM. Since PTEN and p53 are well-known inhibitors of mTOR, the increased membrane area/folding in mutant GBM lines may be related to the enhanced protein and lipid synthesis due to a deregulation of the mTOR-dependent downstream signaling pathway. Given that membrane folds and extensions are implicated in tumor cell motility and metastasis, the dielectric approach presented here provides a rapid and simple tool for screening the biophysical cell properties in studies on targeting chemo- or radiotherapeutically the migration and invasion of GBM and other tumor types. PMID:24498019

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

    NASA Astrophysics Data System (ADS)

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

    1983-09-01

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