WorldWideScience

Sample records for plasma membrane transporters

  1. Sulfate transport in Penicillium chrysogenum plasma membranes.

    OpenAIRE

    Hillenga, Dirk J.; Versantvoort, Hanneke J.M.; Driessen, Arnold J. M.; Konings, Wil N.

    1996-01-01

    Transport studies with Penicillium chrysogenum plasma membranes fused with cytochrome c oxidase liposomes demonstrate that sulfate uptake is driven by the transmembrane pH gradient and not by the transmembrane electrical potential. Ca2+ and other divalent cations are not required. It is concluded that the sulfate transport system catalyzes the symport of two protons with one sulfate anion.

  2. Sulfate transport in Penicillium chrysogenum plasma membranes

    NARCIS (Netherlands)

    Hillenga, Dirk J.; Versantvoort, Hanneke J.M.; Driessen, Arnold J.M.; Konings, Wil N.

    1996-01-01

    Transport studies with Penicillium chrysogenum plasma membranes fused with cytochrome c oxidase liposomes demonstrate that sulfate uptake is driven by the transmembrane pH gradient and not by the transmembrane electrical potential. Ca2+ and other divalent cations are not required. It is concluded th

  3. Vesicular and Plasma Membrane Transporters for Neurotransmitters

    OpenAIRE

    2012-01-01

    The regulated exocytosis that mediates chemical signaling at synapses requires mechanisms to coordinate the immediate response to stimulation with the recycling needed to sustain release. Two general classes of transporter contribute to release, one located on synaptic vesicles that loads them with transmitter, and a second at the plasma membrane that both terminates signaling and serves to recycle transmitter for subsequent rounds of release. Originally identified as the target of psychoacti...

  4. Transport proteins of the plant plasma membrane

    Science.gov (United States)

    Assmann, S. M.; Haubrick, L. L.; Evans, M. L. (Principal Investigator)

    1996-01-01

    Recently developed molecular and genetic approaches have enabled the identification and functional characterization of novel genes encoding ion channels, ion carriers, and water channels of the plant plasma membrane.

  5. Facilitative plasma membrane transporters function during ER transit.

    Science.gov (United States)

    Takanaga, Hitomi; Frommer, Wolf B

    2010-08-01

    Although biochemical studies suggested a high permeability of the endoplasmic reticulum (ER) membrane for small molecules, proteomics identified few specialized ER transporters. To test functionality of transporters during ER passage, we tested whether glucose transporters (GLUTs, SGLTs) destined for the plasma membrane are active during ER transit. HepG2 cells were characterized by low-affinity ER transport activity, suggesting that ER uptake is protein mediated. The much-reduced capacity of HEK293T cells to take up glucose across the plasma membrane correlated with low ER transport. Ectopic expression of GLUT1, -2, -4, or -9 induced GLUT isoform-specific ER transport activity in HEK293T cells. In contrast, the Na(+)-glucose cotransporter SGLT1 mediated efficient plasma membrane glucose transport but no detectable ER uptake, probably because of lack of a sufficient sodium gradient across the ER membrane. In conclusion, we demonstrate that GLUTs are sufficient for mediating ER glucose transport en route to the plasma membrane. Because of the low volume of the ER, trace amounts of these uniporters contribute to ER solute import during ER transit, while uniporters and cation-coupled transporters carry out export from the ER, together potentially explaining the low selectivity of ER transport. Expression levels and residence time of transporters in the ER, as well as their coupling mechanisms, could be key determinants of ER permeability.

  6. Plasma membrane electron transport in frog blood vessels

    Indian Academy of Sciences (India)

    Rashmi P Rao; K Nalini; J Prakasa Rao

    2009-12-01

    In an attempt to see if frog blood vessels possess a plasma membrane electron transport system, the postcaval vein and aorta isolated from Rana tigrina were tested for their ability to reduce ferricyanide, methylene blue, and 2,6-dichloroindophenol. While the dyes remained unchanged, ferricyanide was reduced to ferrocyanide. This reduction was resistant to inhibition by cyanide and azide. Heptane extraction or formalin fixation of the tissues markedly reduced the capability to reduce ferricyanide. Denuded aortas retained only 30% of the activity of intact tissue. Our results indicate that the amphibian postcaval vein and aorta exhibit plasma membrane electron transport

  7. Structure and function of thyroid hormone plasma membrane transporters.

    Science.gov (United States)

    Schweizer, Ulrich; Johannes, Jörg; Bayer, Dorothea; Braun, Doreen

    2014-09-01

    Thyroid hormones (TH) cross the plasma membrane with the help of transporter proteins. As charged amino acid derivatives, TH cannot simply diffuse across a lipid bilayer membrane, despite their notorious hydrophobicity. The identification of monocarboxylate transporter 8 (MCT8, SLC16A2) as a specific and very active TH transporter paved the way to the finding that mutations in the MCT8 gene cause a syndrome of psychomotor retardation in humans. The purpose of this review is to introduce the current model of transmembrane transport and highlight the diversity of TH transmembrane transporters. The interactions of TH with plasma transfer proteins, T3 receptors, and deiodinase are summarized. It is shown that proteins may bind TH owing to their hydrophobic character in hydrophobic cavities and/or by specific polar interaction with the phenolic hydroxyl, the aminopropionic acid moiety, and by weak polar interactions with the iodine atoms. These findings are compared with our understanding of how TH transporters interact with substrate. The presumed effects of mutations in MCT8 on protein folding and transport function are explained in light of the available homology model.

  8. Glycine transporter dimers: evidence for occurrence in the plasma membrane

    DEFF Research Database (Denmark)

    Bartholomäus, Ingo; Milan-Lobo, Laura; Nicke, Annette

    2008-01-01

    membrane based on hydrodynamic and native gel electrophoretic studies. Here, we used cysteine substitution and oxidative cross-linking to show that of GlyT1 and GlyT2 also form dimeric complexes within the plasma membrane. GlyT oligomerization at the cell surface was confirmed for both GlyT1 and GlyT2......Different Na(+)/Cl(-)-dependent neurotransmitter transporters of the SLC6a family have been shown to form dimers or oligomers in both intracellular compartments and at the cell surface. In contrast, the glycine transporters (GlyTs) GlyT1 and -2 have been reported to exist as monomers in the plasma...

  9. Plant Phosphoproteomics: Analysis of Plasma Membrane Transporters by Mass Spectrometry

    DEFF Research Database (Denmark)

    Ye, Juanying; Rudashevskaya, Elena; Young, Clifford

    important physiological functions, such as stomata aperture, cell elongation, or cellular pH regulation. It is known that the activity of plant plasma membrane H+-ATPase is regulated by phosphorylation. Therefore, we first investigated the phosphorylation profile of plant H+-ATPase by enriching...... the phosphopeptides with optimized TiO2 and IMAC enrichment methods prior to MS analysis. We further investigated the global phosphorylation profile of the whole plant plasma membrane proteins using the combination of our recently established phosphopeptide enrichment method, Calcium phosphate precipitation......  Phosphorylation is a key regulatory factor in all aspects of eukaryotic biology including the regulation of plant membrane-bound transport proteins. To date, mass spectrometry (MS) has been introduced as powerful technology for study of post translational modifications (PTMs), including protein...

  10. Carboxylic Acids Plasma Membrane Transporters in Saccharomyces cerevisiae.

    Science.gov (United States)

    Casal, Margarida; Queirós, Odília; Talaia, Gabriel; Ribas, David; Paiva, Sandra

    2016-01-01

    This chapter covers the functionally characterized plasma membrane carboxylic acids transporters Jen1, Ady2, Fps1 and Pdr12 in the yeast Saccharomyces cerevisiae, addressing also their homologues in other microorganisms, as filamentous fungi and bacteria. Carboxylic acids can either be transported into the cells, to be used as nutrients, or extruded in response to acid stress conditions. The secondary active transporters Jen1 and Ady2 can mediate the uptake of the anionic form of these substrates by a H(+)-symport mechanism. The undissociated form of carboxylic acids is lipid-soluble, crossing the plasma membrane by simple diffusion. Furthermore, acetic acid can also be transported by facilitated diffusion via Fps1 channel. At the cytoplasmic physiological pH, the anionic form of the acid prevails and it can be exported by the Pdr12 pump. This review will highlight the mechanisms involving carboxylic acids transporters, and the way they operate according to the yeast cell response to environmental changes, as carbon source availability, extracellular pH and acid stress conditions.

  11. Plasma membrane microdomains regulate turnover of transport proteins in yeast

    Science.gov (United States)

    Grossmann, Guido; Malinsky, Jan; Stahlschmidt, Wiebke; Loibl, Martin; Weig-Meckl, Ina; Frommer, Wolf B.; Opekarová, Miroslava; Tanner, Widmar

    2008-01-01

    In this study, we investigate whether the stable segregation of proteins and lipids within the yeast plasma membrane serves a particular biological function. We show that 21 proteins cluster within or associate with the ergosterol-rich membrane compartment of Can1 (MCC). However, proteins of the endocytic machinery are excluded from MCC. In a screen, we identified 28 genes affecting MCC appearance and found that genes involved in lipid biosynthesis and vesicle transport are significantly overrepresented. Deletion of Pil1, a component of eisosomes, or of Nce102, an integral membrane protein of MCC, results in the dissipation of all MCC markers. These deletion mutants also show accelerated endocytosis of MCC-resident permeases Can1 and Fur4. Our data suggest that release from MCC makes these proteins accessible to the endocytic machinery. Addition of arginine to wild-type cells leads to a similar redistribution and increased turnover of Can1. Thus, MCC represents a protective area within the plasma membrane to control turnover of transport proteins. PMID:19064668

  12. Arrestin-mediated endocytosis of yeast plasma membrane transporters.

    Science.gov (United States)

    Nikko, Elina; Pelham, Hugh R B

    2009-12-01

    Many plasma membrane transporters in yeast are endocytosed in response to excess substrate or certain stresses and degraded in the vacuole. Endocytosis invariably requires ubiquitination by the HECT domain ligase Rsp5. In the cases of the manganese transporter Smf1 and the amino acid transporters Can1, Lyp1 and Mup1 it has been shown that ubiquitination is mediated by arrestin-like adaptor proteins that bind to Rsp5 and recognize specific transporters. As yeast contains a large family of arrestins, this has been suggested as a general model for transporter regulation; however, analysis is complicated by redundancy amongst the arrestins. We have tested this model by removing all the arrestins and examining the requirements for endocytosis of four more transporters, Itr1 (inositol), Hxt6 (glucose), Fur4 (uracil) and Tat2 (tryptophan). This reveals functions for the arrestins Art5/Ygr068c and Art4/Rod1, and additional roles for Art1/Ldb19, Art2/Ecm21 and Art8/Csr2. It also reveals functional redundancy between arrestins and the arrestin-like adaptors Bul1 and Bul2. In addition, we show that delivery to the vacuole often requires multiple additional ubiquitin ligases or adaptors, including the RING domain ligase Pib1, and the adaptors Bsd2, Ear1 and Ssh4, some acting redundantly. We discuss the similarities and differences in the requirements for regulation of different transporters.

  13. The plasma membrane transport systems and adaptation to salinity.

    Science.gov (United States)

    Mansour, Mohamed Magdy F

    2014-11-15

    Salt stress represents one of the environmental challenges that drastically affect plant growth and yield. Evidence suggests that glycophytes and halophytes have a salt tolerance mechanisms working at the cellular level, and the plasma membrane (PM) is believed to be one facet of the cellular mechanisms. The responses of the PM transport proteins to salinity in contrasting species/cultivars were discussed. The review provides a comprehensive overview of the recent advances describing the crucial roles that the PM transport systems have in plant adaptation to salt. Several lines of evidence were presented to demonstrate the correlation between the PM transport proteins and adaptation of plants to high salinity. How alterations in these transport systems of the PM allow plants to cope with the salt stress was also addressed. Although inconsistencies exist in some of the information related to the responses of the PM transport proteins to salinity in different species/cultivars, their key roles in adaptation of plants to high salinity is obvious and evident, and cannot be precluded. Despite the promising results, detailed investigations at the cellular/molecular level are needed in some issues of the PM transport systems in response to salinity to further evaluate their implication in salt tolerance.

  14. A plasma membrane association module in yeast amino acid transporters

    NARCIS (Netherlands)

    Popov-Čeleketić, Dušan; Bianchi, Frans; Ruiz, Stephanie J; Meutiawati, Febrina; Poolman, Bert

    2016-01-01

    Amino acid permeases (AAPs) in the plasma membrane (PM) of Saccharomyces cerevisiae are responsible for the uptake of amino acids and involved in regulation of their cellular levels. Here, we report on a strong and complex module for PM association found in the C-terminal tail of AAPs. Using in sili

  15. A plasma membrane association module in yeast amino acid transporters

    NARCIS (Netherlands)

    Popov-Čeleketić, Dušan; Bianchi, Frans; Ruiz, Stephanie J; Meutiawati, Febrina; Poolman, Bert

    2016-01-01

    Amino acid permeases (AAPs) in the plasma membrane (PM) of Saccharomyces cerevisiae are responsible for the uptake of amino acids and involved in regulation of their cellular levels. Here, we report on a strong and complex module for PM association found in the C-terminal tail of AAPs. Using in

  16. Influence of nonequilibrium lipid transport, membrane compartmentalization, and membrane proteins on the lateral organization of the plasma membrane

    Science.gov (United States)

    Fan, Jun; Sammalkorpi, Maria; Haataja, Mikko

    2010-01-01

    Compositional lipid domains (lipid rafts) in plasma membranes are believed to be important components of many cellular processes. The mechanisms by which cells regulate the sizes, lifetimes, and spatial localization of these domains are rather poorly understood at the moment. We propose a robust mechanism for the formation of finite-sized lipid raft domains in plasma membranes, the competition between phase separation in an immiscible lipid system and active cellular lipid transport processes naturally leads to the formation of such domains. Simulations of a continuum model reveal that the raft size distribution is broad and the average raft size is strongly dependent on the rates of cellular and interlayer lipid transport processes. We demonstrate that spatiotemporal variations in the recycling may enable the cell to localize larger raft aggregates at specific parts along the membrane. Moreover, we show that membrane compartmentalization may further facilitate spatial localization of the raft domains. Finally, we demonstrate that local interactions with immobile membrane proteins can spatially localize the rafts and lead to further clustering.

  17. Rapid Preparation of a Plasma Membrane Fraction: Western Blot Detection of Translocated Glucose Transporter 4 from Plasma Membrane of Muscle and Adipose Cells and Tissues.

    Science.gov (United States)

    Yamamoto, Norio; Yamashita, Yoko; Yoshioka, Yasukiyo; Nishiumi, Shin; Ashida, Hitoshi

    2016-08-01

    Membrane proteins account for 70% to 80% of all pharmaceutical targets, indicating their clinical relevance and underscoring the importance of identifying differentially expressed membrane proteins that reflect distinct disease properties. The translocation of proteins from the bulk of the cytosol to the plasma membrane is a critical step in the transfer of information from membrane-embedded receptors or transporters to the cell interior. To understand how membrane proteins work, it is important to separate the membrane fraction of cells. This unit provides a protocol for rapidly obtaining plasma membrane fractions for western blot analysis. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

  18. Ubiquitination regulates the plasma membrane expression of renal UT-A urea transporters.

    Science.gov (United States)

    Stewart, Gavin S; O'Brien, Jennifer H; Smith, Craig P

    2008-07-01

    The renal UT-A urea transporters UT-A1, UT-A2, and UT-A3 are known to play an important role in the urinary concentrating mechanism. The control of the cellular localization of UT-A transporters is therefore vital to overall renal function. In the present study, we have investigated the effect of ubiquitination on UT-A plasma membrane expression in Madin-Darby canine kidney (MDCK) cell lines expressing each of the three renal UT-A transporters. Inhibition of the ubiquitin-proteasome pathway caused an increase in basal transepithelial urea flux across MDCK-rat (r)UT-A1 and MDCK-mouse (m)UT-A2 monolayers (P UT-A transporter expression in the plasma membrane (P UT-A3 expression in the plasma membrane (P UT-A urea transporters, but that this is not the mechanism primarily used by vasopressin to produce its physiological effects.

  19. ATP-binding cassette-like transporters are involved in the transport of lignin precursors across plasma and vacuolar membranes

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Y.C.; Liu, C.

    2010-12-28

    Lignin is a complex biopolymer derived primarily from the condensation of three monomeric precursors, the monolignols. The synthesis of monolignols occurs in the cytoplasm. To reach the cell wall where they are oxidized and polymerized, they must be transported across the cell membrane. However, the molecular mechanisms underlying the transport process are unclear. There are conflicting views about whether the transport of these precursors occurs by passive diffusion or is an energized active process; further, we know little about what chemical forms are required. Using isolated plasma and vacuolar membrane vesicles prepared from Arabidopsis, together with applying different transporter inhibitors in the assays, we examined the uptake of monolignols and their derivatives by these native membrane vesicles. We demonstrate that the transport of lignin precursors across plasmalemma and their sequestration into vacuoles are ATP-dependent primary-transport processes, involving ATP-binding cassette-like transporters. Moreover, we show that both plasma and vacuolar membrane vesicles selectively transport different forms of lignin precursors. In the presence of ATP, the inverted plasma membrane vesicles preferentially take up monolignol aglycones, whereas the vacuolar vesicles are more specific for glucoconjugates, suggesting that the different ATP-binding cassette-like transporters recognize different chemical forms in conveying them to distinct sites, and that glucosylation of monolignols is necessary for their vacuolar storage but not required for direct transport into the cell wall in Arabidopsis.

  20. ADENOSINE-TRIPHOSPHATE DEPENDENT TAUROCHOLATE TRANSPORT IN HUMAN LIVER PLASMA-MEMBRANES

    NARCIS (Netherlands)

    WOLTERS, H; KUIPERS, F; SLOOFF, MJH; VONK, RJ

    1992-01-01

    Transport systems involved in uptake and biliary secretion of bile salts have been extensively studied in rat liver; however, little is known about these systems in the human liver. In this study, we investigated taurocholate (TC) transport in canalicular and basolateral plasma membrane vesicles iso

  1. Organic Anion Transporter 4-Mediated Transport of Olmesartan at Basal Plasma Membrane of Human Placental Barrier.

    Science.gov (United States)

    Noguchi, Saki; Nishimura, Tomohiro; Fujibayashi, Ayasa; Maruyama, Tetsuo; Tomi, Masatoshi; Nakashima, Emi

    2015-09-01

    Mechanisms regulating fetal transfer of olmesartan, an angiotensin-II receptor type 1 antagonist, are important as potential determinants of life-threatening adverse fetal effects. The purpose of this study was to examine the olmesartan transport mechanism through the basal plasma membrane (BM) of human syncytiotrophoblasts forming the placental barrier. Uptake of olmesartan by human placental BM vesicles was potently inhibited by dehydroepiandrosterone sulfate (DHEAS), estrone 3-sulfate, and bromosulfophthalein, which are all typical substrates of organic anion transporter (OAT) 4 localized at the BM of syncytiotrophoblasts, and was increased in the absence of chloride. In tetracycline-inducible OAT4-expressing cells, [(3) H]olmesartan uptake was increased by tetracycline treatment. Olmesartan uptake via OAT4 was concentration dependent with a Km of 20 μM, and was increased in the absence of chloride. [(3) H]Olmesartan efflux via OAT4 was also observed and was trans-stimulated by extracellular chloride and DHEAS. Thus, OAT4 mediates bidirectional transport of olmesartan and appears to regulate fetal transfer of olmesartan at the BM of syncytiotrophoblasts. Efflux transport of olmesartan via OAT4 from syncytiotrophoblasts to the fetal circulation might be facilitated in the presence of an inwardly directed physiological chloride gradient and extracellular DHEAS. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  2. The plasma membrane monoamine transporter (PMAT): Structure, function, and role in organic cation disposition.

    Science.gov (United States)

    Wang, J

    2016-11-01

    Plasma membrane monoamine transporter (PMAT) is a new polyspecific organic cation transporter that transports a variety of biogenic amines and xenobiotic cations. Highly expressed in the brain, PMAT represents a major uptake2 transporter for monoamine neurotransmitters. At the blood-cerebrospinal fluid (CSF) barrier, PMAT is the principal organic cation transporter for removing neurotoxins and drugs from the CSF. Here I summarize our latest understanding of PMAT and its roles in monoamine uptake and xenobiotic disposition. © 2016 American Society for Clinical Pharmacology and Therapeutics.

  3. Forward transport of proteins in the plasma membrane of migrating cerebellar granule cells.

    Science.gov (United States)

    Wang, Dong; She, Liang; Sui, Ya-nan; Yuan, Xiao-bing; Wen, Yunqing; Poo, Mu-ming

    2012-12-18

    Directional flow of membrane components has been detected at the leading front of fibroblasts and the growth cone of neuronal processes, but whether there exists global directional flow of plasma membrane components over the entire migrating neuron remains largely unknown. By analyzing the trajectories of antibody-coated single quantum dots (QDs) bound to two membrane proteins, overexpressed myc-tagged synaptic vesicle-associated membrane protein VAMP2 and endogenous neurotrophin receptor TrkB, we found that these two proteins exhibited net forward transport, which is superimposed upon Brownian motion, in both leading and trailing processes of migrating cerebellar granule cells in culture. Furthermore, no net directional transport of membrane proteins was observed in nonmigrating cells with either growing or stalling leading processes. Analysis of the correlation of motion direction between two QDs on the same process in migrating neurons also showed a higher frequency of correlated forward than rearward movements. Such correlated QD movements were markedly reduced in the presence of myosin II inhibitor blebbistatin,suggesting the involvement of myosin II-dependent active transport processes. Thus, a net forward transport of plasma membrane proteins exists in the leading and trailing processes of migrating neurons, in line with the translocation of the soma.

  4. Ultrastructural and immunohistochemical localization of plasma membrane Ca2+-ATPase 4 in Ca2+-transporting epithelia

    DEFF Research Database (Denmark)

    Alexander, R Todd; Beggs, Megan R; Zamani, Reza

    2015-01-01

    Plasma Membrane Ca(2+)-ATPase's (PMCA) participate in epithelial Ca(2+) transport and intracellular Ca(2+) signaling. The Pmca4 isoform is enriched in distal nephron isolates and decreased in mice lacking the epithelial Ca(2+) channel, Trpv5. We therefore hypothesized that Pmca4 plays a significant...... in distal nephron cells at both the basolateral membrane and intracellular perinuclear compartments, but not submembranous vesicles, suggesting rapid trafficking to the plasma membrane is unlikely to occur in vivo. Pmca4 expression was not altered by perturbations in Ca(2+) balance, pointing...... detected Pmca1 in lateral membranes of enterocytes. In kidney, Pmca4 showed broad localization to the distal nephron. In mouse, expression was most abundant in segments coexpressing the epithelial Ca(2+) channel, Trpv5. Significant, albeit lower expression, was also evident in the region encompassing...

  5. Ssh4, Rcr2 and Rcr1 affect plasma membrane transporter activity in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kota, Jhansi; Melin-Larsson, Monika; Ljungdahl, Per O; Forsberg, Hanna

    2007-04-01

    Nutrient uptake in the yeast Saccharomyces cerevisiae is a highly regulated process. Cells adjust levels of nutrient transporters within the plasma membrane at multiple stages of the secretory and endosomal pathways. In the absence of the ER-membrane-localized chaperone Shr3, amino acid permeases (AAP) inefficiently fold and are largely retained in the ER. Consequently, shr3 null mutants exhibit greatly reduced rates of amino acid uptake due to lower levels of AAPs in their plasma membranes. To further our understanding of mechanisms affecting AAP localization, we identified SSH4 and RCR2 as high-copy suppressors of shr3 null mutations. The overexpression of SSH4, RCR2, or the RCR2 homolog RCR1 increases steady-state AAP levels, whereas the genetic inactivation of these genes reduces steady-state AAP levels. Additionally, the overexpression of any of these suppressor genes exerts a positive effect on phosphate and uracil uptake systems. Ssh4 and Rcr2 primarily localize to structures associated with the vacuole; however, Rcr2 also localizes to endosome-like vesicles. Our findings are consistent with a model in which Ssh4, Rcr2, and presumably Rcr1, function within the endosome-vacuole trafficking pathway, where they affect events that determine whether plasma membrane proteins are degraded or routed to the plasma membrane.

  6. Plasma membrane electron transport in Saccharomyces cerevisiae depends on the presence of mitochondrial respiratory subunits.

    Science.gov (United States)

    Herst, Patries M; Perrone, Gabriel G; Dawes, Ian W; Bircham, Peter W; Berridge, Michael V

    2008-09-01

    Most investigations into plasma membrane electron transport (PMET) in Saccharomyces cerevisiae have focused on the inducible ferric reductase responsible for iron uptake under iron/copper-limiting conditions. In this paper, we describe a PMET system, distinct from ferric reductase, which reduces the cell-impermeable water-soluble tetrazolium dye, 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulphophenyl)-2H-tetrazolium monosodium salt (WST-1), under normal iron/copper conditions. WST-1/1-methoxy-phenazine methosulphate reduction was unaffected by anoxia and relatively insensitive to diphenyleneiodonium. Dye reduction was increased when intracellular NADH levels were high, which, in S. cerevisiae, required deletion of numerous genes associated with NADH recycling. Genome-wide screening of all viable nuclear gene-deletion mutants of S. cerevisiae revealed that, although mitochondrial electron transport per se was not required, the presence of several nuclear and mitochondrially encoded subunits of respiratory complexes III and IV was mandatory for PMET. This suggests some form of interaction between components of mitochondrial and plasma membrane electron transport. In support of this, mitochondrial tubular networks in S. cerevisiae were shown to be located in close proximity to the plasma membrane using confocal microscopy.

  7. Calcium ion transport across plasma membranes isolated from rat kidney cortex.

    Science.gov (United States)

    Gmaj, P; Murer, H; Kinne, R

    1979-03-15

    Basal-lateral-plasma-membrane vesicles and brush-border-membrane vesicles were isolated from rat kidney cortex by differential centrifugation followed by free-flow-electrophoresis. Ca2+ uptake into these vesicles was investigated by a rapid filtration method. Both membranes show a considerable binding of Ca2+ to the vesicle interior, making the analysis of passive fluxes in uptake experiments difficult. Only the basal-lateral-plasma-membrane vesicles exhibit an ATP-dependent pump activity which can be distinguished from the activity in mitochondrial and endoplasmic reticulum by virtue of the different distribution during free-flow electrophoresis and its lack of sensitivity to oligomycin. The basal-lateral plasma membranes contain in addition a Na+/Ca2+-exchange system which mediates a probably rheogenic counter-transport of Ca2+ and Na+ across the basal cell border. The latter system is probably involved in the secondary active Na+-dependent and ouabain-inhibitable Ca2+ reabsorption in the proximal tubule, the ATP-driven system is probably more important for the maintenance of a low concentration of intracellular Ca2+.

  8. Sites of glucose transporter-4 vesicle fusion with the plasma membrane correlate spatially with microtubules.

    Directory of Open Access Journals (Sweden)

    Jennine M Dawicki-McKenna

    Full Text Available In adipocytes, vesicles containing glucose transporter-4 (GLUT4 redistribute from intracellular stores to the cell periphery in response to insulin stimulation. Vesicles then fuse with the plasma membrane, facilitating glucose transport into the cell. To gain insight into the details of microtubule involvement, we examined the spatial organization and dynamics of microtubules in relation to GLUT4 vesicle trafficking in living 3T3-L1 adipocytes using total internal reflection fluorescence (TIRF microscopy. Insulin stimulated an increase in microtubule density and curvature within the TIRF-illuminated region of the cell. The high degree of curvature and abrupt displacements of microtubules indicate that substantial forces act on microtubules. The time course of the microtubule density increase precedes that of the increase in intensity of fluorescently-tagged GLUT4 in this same region of the cell. In addition, portions of the microtubules are highly curved and are pulled closer to the cell cortex, as confirmed by Parallax microscopy. Microtubule disruption delayed and modestly reduced GLUT4 accumulation at the plasma membrane. Quantitative analysis revealed that fusions of GLUT4-containing vesicles with the plasma membrane, detected using insulin-regulated aminopeptidase with a pH-sensitive GFP tag (pHluorin, preferentially occur near microtubules. Interestingly, long-distance vesicle movement along microtubules visible at the cell surface prior to fusion does not appear to account for this proximity. We conclude that microtubules may be important in providing spatial information for GLUT4 vesicle fusion.

  9. Solanaceae XIPs are plasma membrane aquaporins that facilitate the transport of many uncharged substrates.

    Science.gov (United States)

    Bienert, Gerd Patrick; Bienert, Manuela Désirée; Jahn, Thomas Paul; Boutry, Marc; Chaumont, François

    2011-04-01

    Major intrinsic proteins (MIPs) transport water and uncharged solutes across membranes in all kingdoms of life. Recently, an uncharacterized MIP subfamily was identified in the genomes of plants and fungi and named X Intrinsic Proteins (XIPs). Here, we describe the genetic features, localization, expression, and functions of a group of Solanaceae XIPs. XIP cDNA and gDNA were cloned from tobacco, potato, tomato, and morning glory. A conserved sequence motif in the first intron of Solanaceae XIPs initiates an RNA-processing mechanism that results in two splice variants (α and β). When transiently or stably expressed in tobacco plants, yellow fluorescent protein-tagged NtXIP1;1α and NtXIP1;1β were both localized in the plasma membrane. Transgenic tobacco lines expressing NtXIP1;1-promoter-GUS constructs and RT-PCR studies showed that NtXIP1;1 was expressed in all organs. The NtXIP1;1 promoter was mainly active in cell layers facing the environment in all above-ground tissues. Heterologous expression of Solanaceae XIPs in Xenopus laevis oocytes and various Saccharomyces cerevisiae mutants demonstrated that these isoforms facilitate the transport of bulky solutes, such as glycerol, urea, and boric acid. In contrast, permeability for water was undetectable. These data suggest that XIPs function in the transport of uncharged solutes across the cell plasma membrane in specific plant tissues, including at the interface between the environment and external cell layers.

  10. Enquiry into the Topology of Plasma Membrane-Localized PIN Auxin Transport Components.

    Science.gov (United States)

    Nodzyński, Tomasz; Vanneste, Steffen; Zwiewka, Marta; Pernisová, Markéta; Hejátko, Jan; Friml, Jiří

    2016-11-07

    Auxin directs plant ontogenesis via differential accumulation within tissues depending largely on the activity of PIN proteins that mediate auxin efflux from cells and its directional cell-to-cell transport. Regardless of the developmental importance of PINs, the structure of these transporters is poorly characterized. Here, we present experimental data concerning protein topology of plasma membrane-localized PINs. Utilizing approaches based on pH-dependent quenching of fluorescent reporters combined with immunolocalization techniques, we mapped the membrane topology of PINs and further cross-validated our results using available topology modeling software. We delineated the topology of PIN1 with two transmembrane (TM) bundles of five α-helices linked by a large intracellular loop and a C-terminus positioned outside the cytoplasm. Using constraints derived from our experimental data, we also provide an updated position of helical regions generating a verisimilitude model of PIN1. Since the canonical long PINs show a high degree of conservation in TM domains and auxin transport capacity has been demonstrated for Arabidopsis representatives of this group, this empirically enhanced topological model of PIN1 will be an important starting point for further studies on PIN structure-function relationships. In addition, we have established protocols that can be used to probe the topology of other plasma membrane proteins in plants.

  11. OsHT, a Rice Gene Encoding for a Plasma-Membrane Localized Histidine Transporter

    Institute of Scientific and Technical Information of China (English)

    Di LIU; Wei GONG; Yong BAI; Jing-Chu LUO; Yu-Xian ZHU

    2005-01-01

    Using a degenerative probe designed according to the most conservative region of a known Lys- and His-specific amino acid transporter (LHT1) from Arabidopsis, we isolated a full-length cDNA named OsHT (histidine transporter of Oryza sativa L.) by screening the rice cDNA library. The cDNA is 1.3kb in length and the open reading frame encodes for a 441 amino acid protein with a calculated molecular mass of 49 kDa. Multiple sequence alignments showed that OsHT shares a high degree of sequence conservation at the deduced amino acid level with the Arabidopsis LHT1 and six putative lysine and histidine transporters. Computational analysis indicated that OsHT is an integral membrane protein with 11 putative transmembrane helices. This was confirmed by the transient expression assay because the OsHT-GFP fusion protein was, indeed, localized mainly in the plasma membrane of onion epidermal cells. Functional complementation experiments demonstrated that OsHT was able to work as a histidine transporter in Saccharomyces cerevisiae, suggesting that OsHT is a gene that encodes for a histidine transporter from rice.This is the first time that an LHT-type amino acid transporter gene has been cloned from higher plants other than A rabidopsis.

  12. THE RELATIONSHIPS BETWEEN PLASMA CHOLESTEROL、TRIGLYCERIDE、HIGH DENSITY LIPOPROTEIN AND ION TRANSPORT ENZYMES IN ERYTHROCYTE MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    符云峰; 王素敏; 卢振敏; 李红

    2002-01-01

    Objective To investigate the relationships between levels of plasma cholesterol (Ch), triglyceride (TG)、high density lipoprotein(HDL) and ion transport enzyme activities in red cell membranes of essential hypertensive patients.Methods Plasma Ch, TG, HDL-c, activites of Na+ -K+ -ATPase and Ca2+-ATPase, Ca2+-binding capacity of interior membrane surface, and membrane Ch, phospholipid(PL) were measured in 32 normotensive (NT) subjects and 55 essential hypertensive patients(HT).Results ①Mean artery pressure(MAP), plasma Ch、TG and membrane Ch levels, and membrane cholesterol/phospholipid(C/P) molar ratio were significantly increased compared with those in NT group, respectively; ②The plasma HDL-c level, the activities of Na+-K+-ATPase and Ca2+-ATPase, and the Ca2+-binding capacity of the interior membrane surface in HT group were significantly lower than those in NT group, respectively.Conclusion The depressed activities of Na+-K+-ATPase and Ca2+-ATPase, and Ca2+-binding capacity of the interior surface in cell membranes are the major evidence of ion transport abnormalities in essential hypertension. The plasma TG and membrance C/P molar ratio-dependent changes in membrane microviscosity seem to be responsible for the modulation of particular ion transport pathways.

  13. D6 PROTEIN KINASE activates auxin transport-dependent growth and PIN-FORMED phosphorylation at the plasma membrane.

    Science.gov (United States)

    Barbosa, Inês C R; Zourelidou, Melina; Willige, Björn C; Weller, Benjamin; Schwechheimer, Claus

    2014-06-23

    The directed cell-to-cell transport of the phytohormone auxin by efflux and influx transporters is essential for proper plant growth and development. Like auxin efflux facilitators of the PIN-FORMED (PIN) family, D6 PROTEIN KINASE (D6PK) from Arabidopsis thaliana localizes to the basal plasma membrane of many cells, and evidence exists that D6PK may directly phosphorylate PINs. We find that D6PK is a membrane-bound protein that is associated with either the basal domain of the plasma membrane or endomembranes. Inhibition of the trafficking regulator GNOM leads to a rapid internalization of D6PK to endomembranes. Interestingly, the dissociation of D6PK from the plasma membrane is also promoted by auxin. Surprisingly, we find that auxin transport-dependent tropic responses are critically and reversibly controlled by D6PK and D6PK-dependent PIN phosphorylation at the plasma membrane. We conclude that D6PK abundance at the plasma membrane and likely D6PK-dependent PIN phosphorylation are prerequisites for PIN-mediated auxin transport.

  14. Characterization of cadmium plasma membrane transport in gills of a mangrove crab Ucides cordatus

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, P.; Custódio, M.R. [Instituto de Biociências, Departamento de Fisiologia, Universidade de São Paulo, Rua do Matão, Travessa 14, #101, São Paulo 05508-900, SP (Brazil); Zanotto, F.P., E-mail: fzanotto@usp.br [Instituto de Biociências, Departamento de Fisiologia, Universidade de São Paulo, Rua do Matão, Travessa 14, #101, São Paulo 05508-900, SP (Brazil); Departamento de Biofísica, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Três de Maio 100, São Paulo 04044-020 (Brazil)

    2014-12-15

    Highlights: • Cd{sup 2+} gill cell transport, a non-essential toxic metal, was characterized in a hypo-hyper-regulating mangrove crab Ucides cordatus. • Cd{sup 2+} enter gill cells through Ca{sup 2+} channels and is dependent of intracellular Ca{sup 2+} levels. • Route of entry in gill cells also involves a Cd{sup 2+}/Ca{sup 2+} (2Na) exchanger. • Cd transport depends on Na{sup +}/K{sup +}-ATPase and gill cell electrochemical gradient. • Vanadate inhibits gill Cd{sup 2+} transport and ouabain increase gill Cd{sup 2+} transport. - Abstract: Membrane pathway for intracellular cadmium (Cd{sup 2+}) accumulation is not fully elucidated in many organisms and has not been studied in crab gill cells. To characterize membrane Cd{sup 2+} transport of anterior and posterior gill cells of Ucides cordatus, a hypo-hyper-regulating crab, a change in intracellular Cd{sup 2+} concentration under various experimental conditions was examined by using FluoZin, a fluorescent probe. The membrane Cd{sup 2+} transport was estimated by the augmentation of FluoZin fluorescence induced by extracellular application of CdCl{sub 2} and different inhibitors. Addition of extracellular calcium (Ca{sup 2+}) to the cells affected little the fluorescence of FluoZin, confirming that Cd{sup 2+} was the main ion increasing intracellular fluorescence. Ca{sup 2+} channels blockers (nimodipine and verapamil) decreased Cd{sup 2+} influx as well as vanadate, a Ca{sup 2+}-ATPase blocker. Chelating intracellular Ca{sup 2+} (BAPTA) decreased Cd{sup 2+} influx in gill cells, while increasing intracellular Ca{sup 2+} (caffeine) augmented Cd influx. Cd{sup 2+} and ATP added at different temporal conditions were not effective at increasing intracellular Cd{sup 2+} accumulation. Ouabain (Na{sup +}/K{sup +}-ATPase inhibitor) increased Cd{sup 2+} influx probably through a change in intracellular Na and/or a change in cell membrane potential. Routes of Cd{sup 2+} influx, a non-essential metal, through the

  15. CHX14 is a plasma membrane K-efflux transporter that regulates K+ redistribution in "Arabidopsis thaliana"

    Science.gov (United States)

    Potassium (K(+)) is essential for plant growth and development, yet the molecular identity of many K(+) transporters remains elusive. Here we characterized cation/H(+) exchanger (CHX) 14 as a plasma membrane K(+) transporter. "CHX14" expression was induced by elevated K(+) and histochemical analysis...

  16. Plasma Membrane Na+-Coupled Citrate Transporter (SLC13A5 and Neonatal Epileptic Encephalopathy

    Directory of Open Access Journals (Sweden)

    Yangzom D. Bhutia

    2017-02-01

    Full Text Available SLC13A5 is a Na+-coupled transporter for citrate that is expressed in the plasma membrane of specific cell types in the liver, testis, and brain. It is an electrogenic transporter with a Na+:citrate3− stoichiometry of 4:1. In humans, the Michaelis constant for SLC13A5 to transport citrate is ~600 μM, which is physiologically relevant given that the normal concentration of citrate in plasma is in the range of 150–200 μM. Li+ stimulates the transport function of human SLC13A5 at concentrations that are in the therapeutic range in patients on lithium therapy. Human SLC13A5 differs from rodent Slc13a5 in two important aspects: the affinity of the human transporter for citrate is ~30-fold less than that of the rodent transporter, thus making human SLC13A5 a low-affinity/high-capacity transporter and the rodent Slc13a5 a high-affinity/low-capacity transporter. In the liver, SLC13A5 is expressed exclusively in the sinusoidal membrane of the hepatocytes, where it plays a role in the uptake of circulating citrate from the sinusoidal blood for metabolic use. In the testis, the transporter is expressed only in spermatozoa, which is also only in the mid piece where mitochondria are located; the likely function of the transporter in spermatozoa is to mediate the uptake of citrate present at high levels in the seminal fluid for subsequent metabolism in the sperm mitochondria to generate biological energy, thereby supporting sperm motility. In the brain, the transporter is expressed mostly in neurons. As astrocytes secrete citrate into extracellular medium, the potential function of SLC13A5 in neurons is to mediate the uptake of circulating citrate and astrocyte-released citrate for subsequent metabolism. Slc13a5-knockout mice have been generated; these mice do not have any overt phenotype but are resistant to experimentally induced metabolic syndrome. Recently however, loss-of-function mutations in human SLC13A5 have been found to cause severe epilepsy

  17. Basic Amino Acid Transport in Plasma Membrane Vesicles of Penicillium chrysogenum

    NARCIS (Netherlands)

    Hillenga, Dirk J.; Versantvoort, Hanneke J.M.; Driessen, Arnold J.M.; Konings, Wil N.

    1996-01-01

    The characteristics of the basic amino acid permease (system VI) of the filamentous fungus Penicillium chrysogenum were studied in plasma membranes fused with liposomes containing the beef heart mitochondrial cytochrome c oxidase. In the presence of reduced cytochrome c, the hybrid membranes accumul

  18. A model for the biosynthesis and transport of plasma membrane-associated signaling receptors to the cell surface

    Directory of Open Access Journals (Sweden)

    Sorina Claudia Popescu

    2012-04-01

    Full Text Available Intracellular protein transport is emerging as critical in determining the outcome of receptor-activated signal transduction pathways. In plants, relatively little is known about the nature of the molecular components and mechanisms involved in coordinating receptor synthesis and transport to the cell surface. Recent advances in this field indicate that signaling pathways and intracellular transport machinery converge and coordinate to render receptors competent for signaling at their plasma membrane activity sites. The biogenesis and transport to the cell surface of signaling receptors appears to require both general trafficking and receptor-specific factors. Several molecular determinants, residing or associated with compartments of the secretory pathway and known to influence aspects in receptor biogenesis, are discussed and integrated into a predictive cooperative model for the functional expression of signaling receptors at the plasma membrane.

  19. Ca2+-Transport through Plasma Membrane as a Test of Auxin Sensitivity

    Directory of Open Access Journals (Sweden)

    Anastasia A. Kirpichnikova

    2014-03-01

    Full Text Available Auxin is one of the crucial regulators of plant growth and development. The discovered auxin cytosolic receptor (TIR1 is not involved in the perception of the hormone signal at the plasma membrane. Instead, another receptor, related to the ABP1, auxin binding protein1, is supposed to be responsible for the perception at the plasma membrane. One of the fast and sensitive auxin-induced reactions is an increase of Ca2+ cytosolic concentration, which is suggested to be dependent on the activation of Ca2+ influx through the plasma membrane. This investigation was carried out with a plasmalemma enriched vesicle fraction, obtained from etiolated maize coleoptiles. The magnitude of Ca2+ efflux through the membrane vesicles was estimated according to the shift of potential dependent fluorescent dye diS-C3-(5. The obtained results showed that during coleoptiles ageing (3rd, 4th and 5th days of seedling etiolated growth the magnitude of Ca2+ efflux from inside-out vesicles was decreased. Addition of ABP1 led to a recovery of Ca2+ efflux to the level of the youngest and most sensitive cells. Moreover, the efflux was more sensitive, responding from 10−8 to 10−6 M 1-NAA, in vesicles containing ABP1, whereas native vesicles showed the highest efflux at 10−6 M 1-NAA. We suggest that auxin increases plasma membrane permeability to Ca2+ and that ABP1 is involved in modulation of this reaction.

  20. FAM21 directs SNX27-retromer cargoes to the plasma membrane by preventing transport to the Golgi apparatus.

    Science.gov (United States)

    Lee, Seongju; Chang, Jaerak; Blackstone, Craig

    2016-03-09

    The endosomal network maintains cellular homeostasis by sorting, recycling and degrading endocytosed cargoes. Retromer organizes the endosomal sorting pathway in conjunction with various sorting nexin (SNX) proteins. The SNX27-retromer complex has recently been identified as a major endosomal hub that regulates endosome-to-plasma membrane recycling by preventing lysosomal entry of cargoes. Here, we show that SNX27 directly interacts with FAM21, which also binds retromer, within the Wiskott-Aldrich syndrome protein and SCAR homologue (WASH) complex. This interaction is required for the precise localization of SNX27 at an endosomal subdomain as well as for recycling of SNX27-retromer cargoes. Furthermore, FAM21 prevents cargo transport to the Golgi apparatus by controlling levels of phosphatidylinositol 4-phosphate, which facilitates cargo dissociation at the Golgi. Together, our results demonstrate that the SNX27-retromer-WASH complex directs cargoes to the plasma membrane by blocking their transport to lysosomes and the Golgi.

  1. Plasma membrane ATPases

    DEFF Research Database (Denmark)

    Palmgren, Michael Broberg; Bækgaard, Lone; Lopez Marques, Rosa Laura

    2011-01-01

    The plasma membrane separates the cellular contents from the surrounding environment. Nutrients must enter through the plasma membrane in order to reach the cell interior, and toxic metabolites and several ions leave the cell by traveling across the same barrier. Biological pumps in the plasma me...

  2. The ATP-binding cassette transporter-2 (ABCA2) regulates esterification of plasma membrane cholesterol by modulation of sphingolipid metabolism.

    Science.gov (United States)

    Davis, Warren

    2014-01-01

    The ATP-binding cassette transporters are a large family (~48 genes divided into seven families A-G) of proteins that utilize the energy of ATP-hydrolysis to pump substrates across lipid bilayers against a concentration gradient. The ABC "A" subfamily is comprised of 13 members and transport sterols, phospholipids and bile acids. ABCA2 is the most abundant ABC transporter in human and rodent brain with highest expression in oligodendrocytes, although it is also expressed in neurons. Several groups have studied a possible connection between ABCA2 and Alzheimer's disease as well as early atherosclerosis. ABCA2 expression levels have been associated with changes in cholesterol and sphingolipid metabolism. In this paper, we hypothesized that ABCA2 expression level may regulate esterification of plasma membrane-derived cholesterol by modulation of sphingolipid metabolism. ABCA2 overexpression in N2a neuroblastoma cells was associated with an altered bilayer distribution of the sphingolipid ceramide that inhibited acylCoA:cholesterol acyltransferase (ACAT) activity and cholesterol esterification. In contrast, depletion of endogenous ABCA2 in the rat schwannoma cell line D6P2T increased esterification of plasma membrane cholesterol following treatment with exogenous bacterial sphingomyelinase. These findings suggest that control of ABCA2 expression level may be a key locus of regulation for esterification of plasma membrane-derived cholesterol through modulation of sphingolipid metabolism.

  3. Oxygen transport membrane

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof.......The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof....

  4. Intracellular protein transport to the thyrocyte plasma membrane: potential implications for thyroid physiology.

    Science.gov (United States)

    Arvan, P; Kim, P S; Kuliawat, R; Prabakaran, D; Muresan, Z; Yoo, S E; Abu Hossain, S

    1997-02-01

    We present a snapshot of developments in epithelial biology that may prove helpful in understanding cellular aspects of the machinery designed for the synthesis of thyroid hormones on the thyroglobulin precursor. The functional unit of the thyroid gland is the follicle, delimited by a monolayer of thyrocytes. Like the cells of most simple epithelia, thyrocytes exhibit specialization of the cell surface that confronts two different extracellular environments-apical and basolateral, which are separated by tight junctions. Specifically, the basolateral domain faces the interstitium/bloodstream, while the apical domain is in contact with the lumen that is the primary target for newly synthesized thyroglobulin secretion and also serves as a storage depot for previously secreted protein. Thyrocytes use their polarity in several important ways, such as for maintaining basolaterally located iodide uptake and T4 deiodination, as well apically located iodide efflux and iodination machinery. The mechanisms by which this organization is established, fall in large part under the more general cell biological problem of intracellular sorting and trafficking of different proteins en route to the cell surface. Nearly all exportable proteins begin their biological life after synthesis in an intracellular compartment known as the endoplasmic reticulum (ER), upon which different degrees of difficulty may be encountered during nascent polypeptide folding and initial export to the Golgi complex. In these initial stages, ER molecular chaperones can assist in monitoring protein folding and export while themselves remaining as resident proteins of the thyroid ER. After export from the ER, most subsequent sorting for protein delivery to apical or basolateral surfaces of thyrocytes occurs within another specialized intracellular compartment known as the trans-Golgi network. Targeting information encoded in secretory proteins and plasma membrane proteins can be exposed or buried at different

  5. Exercise-induced increase in glucose transport, GLUT-4, and VAMP-2 in plasma membrane from human muscle

    DEFF Research Database (Denmark)

    Kristiansen, S; Hargreaves, Mark; Richter, Erik

    1996-01-01

    contractions may induce trafficking of GLUT-4-containing vesicles via a mechanism similar to neurotransmitter release. Our results demonstrate for the first time exercise-induced translocation of GLUT-4 and VAMP-2 to the plasma membrane of human muscle and increased sarcolemmal glucose transport.......A major effect of muscle contractions is an increase in sarcolemmal glucose transport. We have used a recently developed technique to produce sarcolemmal giant vesicles from human muscle biopsy samples obtained before and after exercise. Six men exercised for 10 min at 50% maximal O2 uptake (Vo2max...

  6. Ist2 in the yeast cortical endoplasmic reticulum promotes trafficking of the amino acid transporter Bap2 to the plasma membrane.

    Directory of Open Access Journals (Sweden)

    Wendelin Wolf

    Full Text Available The equipment of the plasma membrane in Saccharomyces cerevisiae with specific nutrient transporters is highly regulated by transcription, translation and protein trafficking allowing growth in changing environments. The activity of these transporters depends on a H(+ gradient across the plasma membrane generated by the H(+-ATPase Pma1. We found that the polytopic membrane protein Ist2 in the cortical endoplasmic reticulum (ER is required for efficient leucine uptake during the transition from fermentation to respiration. Experiments employing tandem fluorescence timer protein tag showed that Ist2 was necessary for efficient trafficking of newly synthesized leucine transporter Bap2 from the ER to the plasma membrane. This finding explains the growth defect of ist2Δ mutants during nutritional challenges and illustrates the important role of physical coupling between cortical ER and plasma membrane.

  7. Quantitative transporter proteomics by liquid chromatography with tandem mass spectrometry: addressing methodologic issues of plasma membrane isolation and expression-activity relationship.

    Science.gov (United States)

    Kumar, Vineet; Prasad, Bhagwat; Patilea, Gabriela; Gupta, Anshul; Salphati, Laurent; Evers, Raymond; Hop, Cornelis E C A; Unadkat, Jashvant D

    2015-02-01

    To predict transporter-mediated drug disposition using physiologically based pharmacokinetic models, one approach is to measure transport activity and relate it to protein expression levels in cell lines (overexpressing the transporter) and then scale these to via in vitro to in vivo extrapolation (IVIVE). This approach makes two major assumptions. First, that the expression of the transporter is predominantly in the plasma membrane. Second, that there is a linear correlation between expression level and activity of the transporter protein. The present study was conducted to test these two assumptions. We evaluated two commercially available kits that claimed to separate plasma membrane from other cell membranes. The Qiagen Qproteome kit yielded very little protein in the fraction purported to be the plasma membrane. The Abcam Phase Separation kit enriched the plasma membrane but did not separate it from other intracellular membranes. For the Abcam method, the expression level of organic anion-transporting polypeptides (OATP) 1B1/2B1 and breast cancer resistance protein (BCRP) proteins in all subcellular fractions isolated from cells or human liver tissue tracked that of Na⁺-K⁺ ATPase. Assuming that Na⁺-K⁺ ATPase is predominantly located in the plasma membrane, these data suggest that the transporters measured are also primarily located in the plasma membrane. Using short hairpin RNA, we created clones of cell lines with varying degrees of OATP1B1 or BCRP expression level. In these clones, transport activity of OATP1B1 or BCRP was highly correlated with protein expression level (r² > 0.9). These data support the use of transporter expression level data and activity data from transporter overexpressing cell lines for IVIVE of transporter-mediated disposition of drugs.

  8. Expression and function of thyroid hormone transporters in the microvillous plasma membrane of human term placental syncytiotrophoblast.

    Science.gov (United States)

    Loubière, L S; Vasilopoulou, E; Glazier, J D; Taylor, P M; Franklyn, J A; Kilby, M D; Chan, Shiao Y

    2012-12-01

    The transplacental passage of thyroid hormones (THs) from mother to fetus in humans has been deduced from observational clinical studies and is important for normal fetoplacental development. To investigate the transporters that regulate TH uptake by syncytiotrophoblast (the primary barrier to maternal-fetal exchange, which lies in direct contact with maternal blood), we isolated the microvillous plasma membrane (MVM) of human term syncytiotrophoblasts. We have demonstrated that MVM vesicles express plasma membrane TH transporter proteins, including system-L (L-type amino acid transporter 1 and CD98), monocarboxylate transporters (MCTs) 8 and 10, organic anion-transporting polypeptides 1A2 and 4A1. We provide the first definitive evidence that the human syncytiotrophoblast MVM is capable of rapid, saturable T(4) and T(3) uptake at similar rates and in a Na(+)-independent manner. These two major forms of THs could not significantly inhibit each others' uptake, suggesting that each is mediated by largely different transporters. No single transporter was noted to play a dominant role in either T(4) or T(3) uptake. Using combinations of transporter inhibitors that had an additive effect on TH uptake, we provide evidence that 67% of saturable T(4) uptake is facilitated by system-L and MCT10 with a minor role played by organic anion-transporting polypeptides, whereas 87% of saturable T(3) uptake is mediated by MCT8 and MCT10. Our data demonstrate that syncytiotrophoblast may control the quantity and forms of THs taken up by the human placenta. Thus, syncytiotrophoblast could be critical in regulating transplacental TH supply from the mother to the fetus.

  9.   Plant Phosphoproteomics: Analysis of Plasma Membrane Transporters by Mass Spectrometry

    DEFF Research Database (Denmark)

    Ye, Juanying; Rudashevskaya, Elena; Young, Clifford

    phosphorylation. Due to the low abundance of phosphoprotein, the specific enrichment prior to MS analysis is necessary. Plant proton pump (H+-ATPase) is an enzyme controls the major transport processes in the plant, such as root nutrient uptake. Moreover, this pump has been proposed to be involved in other......  Phosphorylation is a key regulatory factor in all aspects of eukaryotic biology including the regulation of plant membrane-bound transport proteins. To date, mass spectrometry (MS) has been introduced as powerful technology for study of post translational modifications (PTMs), including protein...

  10. The Arabidopsis nitrate transporter AtNRT2.1 is targeted to the root plasma membrane.

    Science.gov (United States)

    Chopin, Franck; Wirth, Judith; Dorbe, Marie-France; Lejay, Laurence; Krapp, Anne; Gojon, Alain; Daniel-Vedele, Françoise

    2007-08-01

    Arabidopsis AtNRT2.1 protein is the best characterized high affinity nitrate transporter in higher plants. However, nothing is known about its sub-cellular localization. In this work, we used GFP imaging to follow the targeting of the AtNRT2.1 protein to the different cell membranes. A polyclonal antibody was also raised against a peptide derived from the AtNRT2.1 sequence. Comparison of wild type and mutant plant extracts showed that this antibody recognized specifically the AtNRT2.1 protein. Microsomal membranes were fractionated on sucrose gradients and immunological detections were performed on the different fractions. Altogether, our results demonstrate that the AtNRT2.1 protein is located in the plasma membrane of the root cells.

  11. Brain-derived neurotrophic factor (BDNF) enhances GABA transport by modulating the trafficking of GABA transporter-1 (GAT-1) from the plasma membrane of rat cortical astrocytes.

    Science.gov (United States)

    Vaz, Sandra H; Jørgensen, Trine N; Cristóvão-Ferreira, Sofia; Duflot, Sylvie; Ribeiro, Joaquim A; Gether, Ulrik; Sebastião, Ana M

    2011-11-25

    The γ-aminobutyric acid (GABA) transporters (GATs) are located in the plasma membrane of neurons and astrocytes and are responsible for termination of GABAergic transmission. It has previously been shown that brain derived neurotrophic factor (BDNF) modulates GAT-1-mediated GABA transport in nerve terminals and neuronal cultures. We now report that BDNF enhances GAT-1-mediated GABA transport in cultured astrocytes, an effect mostly due to an increase in the V(max) kinetic constant. This action involves the truncated form of the TrkB receptor (TrkB-t) coupled to a non-classic PLC-γ/PKC-δ and ERK/MAPK pathway and requires active adenosine A(2A) receptors. Transport through GAT-3 is not affected by BDNF. To elucidate if BDNF affects trafficking of GAT-1 in astrocytes, we generated and infected astrocytes with a functional mutant of the rat GAT-1 (rGAT-1) in which the hemagglutinin (HA) epitope was incorporated into the second extracellular loop. An increase in plasma membrane of HA-rGAT-1 as well as of rGAT-1 was observed when both HA-GAT-1-transduced astrocytes and rGAT-1-overexpressing astrocytes were treated with BDNF. The effect of BDNF results from inhibition of dynamin/clathrin-dependent constitutive internalization of GAT-1 rather than from facilitation of the monensin-sensitive recycling of GAT-1 molecules back to the plasma membrane. We therefore conclude that BDNF enhances the time span of GAT-1 molecules at the plasma membrane of astrocytes. BDNF may thus play an active role in the clearance of GABA from synaptic and extrasynaptic sites and in this way influence neuronal excitability.

  12. Carrier subunit of plasma membrane transporter is required for oxidative folding of its helper subunit.

    Science.gov (United States)

    Rius, Mònica; Chillarón, Josep

    2012-05-25

    We study the amino acid transport system b(0,+) as a model for folding, assembly, and early traffic of membrane protein complexes. System b(0,+) is made of two disulfide-linked membrane subunits: the carrier, b(0,+) amino acid transporter (b(0,+)AT), a polytopic protein, and the helper, related to b(0,+) amino acid transporter (rBAT), a type II glycoprotein. rBAT ectodomain mutants display folding/trafficking defects that lead to type I cystinuria. Here we show that, in the presence of b(0,+)AT, three disulfides were formed in the rBAT ectodomain. Disulfides Cys-242-Cys-273 and Cys-571-Cys-666 were essential for biogenesis. Cys-673-Cys-685 was dispensable, but the single mutants C673S, and C685S showed compromised stability and trafficking. Cys-242-Cys-273 likely was the first disulfide to form, and unpaired Cys-242 or Cys-273 disrupted oxidative folding. Strikingly, unassembled rBAT was found as an ensemble of different redox species, mainly monomeric. The ensemble did not change upon inhibition of rBAT degradation. Overall, these results indicated a b(0,+)AT-dependent oxidative folding of the rBAT ectodomain, with the initial and probably cotranslational formation of Cys-242-Cys-273, followed by the oxidation of Cys-571-Cys-666 and Cys-673-Cys-685, that was completed posttranslationally.

  13. Carrier Subunit of Plasma Membrane Transporter Is Required for Oxidative Folding of Its Helper Subunit*

    Science.gov (United States)

    Rius, Mònica; Chillarón, Josep

    2012-01-01

    We study the amino acid transport system b0,+ as a model for folding, assembly, and early traffic of membrane protein complexes. System b0,+ is made of two disulfide-linked membrane subunits: the carrier, b0,+ amino acid transporter (b0,+AT), a polytopic protein, and the helper, related to b0,+ amino acid transporter (rBAT), a type II glycoprotein. rBAT ectodomain mutants display folding/trafficking defects that lead to type I cystinuria. Here we show that, in the presence of b0,+AT, three disulfides were formed in the rBAT ectodomain. Disulfides Cys-242-Cys-273 and Cys-571-Cys-666 were essential for biogenesis. Cys-673-Cys-685 was dispensable, but the single mutants C673S, and C685S showed compromised stability and trafficking. Cys-242-Cys-273 likely was the first disulfide to form, and unpaired Cys-242 or Cys-273 disrupted oxidative folding. Strikingly, unassembled rBAT was found as an ensemble of different redox species, mainly monomeric. The ensemble did not change upon inhibition of rBAT degradation. Overall, these results indicated a b0,+AT-dependent oxidative folding of the rBAT ectodomain, with the initial and probably cotranslational formation of Cys-242-Cys-273, followed by the oxidation of Cys-571-Cys-666 and Cys-673-Cys-685, that was completed posttranslationally. PMID:22493502

  14. The product of the ABC half-transporter gene ABCG2 (BCRP/MXR/ABCP) is expressed in the plasma membrane

    DEFF Research Database (Denmark)

    Rocchi, E; Khodjakov, A; Volk, E L

    2000-01-01

    by Western blot and immunohistochemistry. This protein is highly overexpressed in several drug-resistant cell lines and localizes predominantly to the plasma membrane, instead of to intracellular membranes as seen with all other known half-transporters. Therefore, BCRP/MXR is unique among the ABC half...

  15. The role of the calcium transporter protein plasma membrane calcium ATPase PMCA2 in cerebellar Purkinje neuron function.

    Science.gov (United States)

    Empson, R M; Akemann, W; Knöpfel, Thomas

    2010-01-01

    Genetic deletion of the plasma membrane calcium ATPase type 2 (PMCA2), a calcium transporter protein, is associated with an overtly ataxic phenotype in mice. PMCA2 is expressed at high levels in cerebellar Purkinje neurons (PNs) where functional integrity is essential for normal cerebellar function. Indeed, loss of PN function accompanies cerebellar ataxia in humans and mouse models. In the ataxic PMCA2 knockout (PMCA2-/-) mouse the ability of the PNs to control their cytosolic calcium levels was severely impaired; basal calcium levels were high and calcium recovery kinetics slow. Whole cell patch clamp recordings from PMCA2-/- PNs revealed that they possessed hyperpolarised membrane potentials, reduced frequency and increased irregularity of spontaneous action potential firing, curtailed complex spikes and sustained calcium-dependent outward K+ currents. We propose that these alterations limit pathological excursions in PN cytosolic calcium as an aid to survival but that they are insufficient to prevent loss of functional cerebellar output.

  16. Plasma membrane H+ and K+ transporters are involved in the weak-acid preservative response of disparate food spoilage yeasts.

    Science.gov (United States)

    Macpherson, Neil; Shabala, Lana; Rooney, Henrietta; Jarman, Marcus G; Davies, Julia M

    2005-06-01

    The food spoilage yeasts Zygosaccharomyces bailii and Saccharomyces cerevisiae have been proposed to resist weak-acid preservative stress by different means; Z. bailii by limiting influx of preservative combined with its catabolism, S. cerevisiae by active extrusion of the preservative weak-acid anion and H(+). Measurement of H(+) extrusion by exponential-phase Z. bailii cells suggest that, in common with S. cerevisiae, this yeast uses a plasma membrane H(+)-ATPase to expel H(+) when challenged by weak-acid preservative (benzoic acid). Simultaneous measurement of Z. bailii net H(+) and K(+) fluxes showed that net K(+) influx accompanies net H(+) efflux during acute benzoic acid stress. Such ionic coupling is known for S. cerevisiae in short-term preservative stress. Both yeasts significantly accumulated K(+) on long-term exposure to benzoic acid. Analysis of S. cerevisiae K(+) transporter mutants revealed that loss of the high affinity K(+) uptake system Trk1 confers sensitivity to growth in preservative. The results suggest that cation accumulation is an important factor in adaptation to weak-acid preservatives by spoilage yeasts and that Z. bailii and S. cerevisiae share hitherto unsuspected adaptive responses at the level of plasma membrane ion transport.

  17. Rotavirus NSP4: Cell type-dependent transport kinetics to the exofacial plasma membrane and release from intact infected cells

    Directory of Open Access Journals (Sweden)

    Parr Rebecca D

    2011-06-01

    Full Text Available Abstract Background Rotavirus NSP4 localizes to multiple intracellular sites and is multifunctional, contributing to RV morphogenesis, replication and pathogenesis. One function of NSP4 is the induction of early secretory diarrhea by binding surface receptors to initiate signaling events. The aims of this study were to determine the transport kinetics of NSP4 to the exofacial plasma membrane (PM, the subsequent release from intact infected cells, and rebinding to naïve and/or neighboring cells in two cell types. Methods Transport kinetics was evaluated using surface-specific biotinylation/streptavidin pull-downs and exofacial exposure of NSP4 was confirmed by antibody binding to intact cells, and fluorescent resonant energy transfer. Transfected cells similarly were monitored to discern NSP4 movement in the absence of infection or other viral proteins. Endoglycosidase H digestions, preparation of CY3- or CY5- labeled F(ab2 fragments, confocal imaging, and determination of preferential polarized transport employed standard laboratory techniques. Mock-infected, mock-biotinylated and non-specific antibodies served as controls. Results Only full-length (FL, endoglycosidase-sensitive NSP4 was detected on the exofacial surface of two cell types, whereas the corresponding cell lysates showed multiple glycosylated forms. The C-terminus of FL NSP4 was detected on exofacial-membrane surfaces at different times in different cell types prior to its release into culture media. Transport to the PM was rapid and distinct yet FL NSP4 was secreted from both cell types at a time similar to the release of virus. NSP4-containing, clarified media from both cells bound surface molecules of naïve cells, and imaging showed secreted NSP4 from one or more infected cells bound neighboring cell membranes in culture. Preferential sorting to apical or basolateral membranes also was distinct in different polarized cells. Conclusions The intracellular transport of NSP4 to

  18. Disrupted plasma membrane localization and loss of function reveal regions of human equilibrative nucleoside transporter 1 involved in structural integrity and activity.

    Science.gov (United States)

    Nivillac, Nicole M I; Wasal, Karanvir; Villani, Daniela F; Naydenova, Zlatina; Hanna, W J Brad; Coe, Imogen R

    2009-10-01

    Human Equilibrative Nucleoside Transporter 1 (hENT1) is an integral membrane protein that transports nucleosides and analog drugs across cellular membranes. Very little is known about intracellular processing and localization of hENT1. Here we show that disruption of a highly conserved triplet (PWN) near the N-terminus, or the last eight C-terminal residues (two hydrophobic triplets separated by a positive arginine) result in loss of plasma membrane localization and/or transport function. To understand the role of specific residues within these regions, we studied the localization patterns of N- or C-terminal deletion and/or substitution mutants of GFP-hENT1 using confocal microscopy. Quantification of GFP-hENT1 (mutant and wildtype) protein at the plasma membrane was conducted using nitrobenzylthioinosine (NBTI) binding. Functionality of the GFP-hENT1 mutants was determined by heterologous expression in Xenopus laevis oocytes followed by measurement of uridine uptake. Mutation of the proline within the PWN motif disrupts plasma membrane localization. C-terminal mutations (primarily within the hydrophobic triplets) lead to hENT1 retention within the cell (e.g. in the ER). Some mutants still localize to the plasma membrane but show reduced transport activity. These data suggest that these two regions contribute to the structural integrity and thus correct processing and function of hENT1.

  19. The plant plasma membrane H+-ATPase

    DEFF Research Database (Denmark)

    Ekberg, Kira

      The very high mobility of protons in aqueous solutions demands special features of membrane proton transporters to sustain efficient yet regulated proton transport across biological membranes. By the use of the chemical energy of ATP, plasma-membrane-embedded H+-ATPases extrude protons from cells...... of plants and fungi to generate electrochemical proton gradients. A recently published crystal structure of a plasma membrane H(+)-ATPase contributes to our knowledge about the mechanism of these essential enzymes. Together with biochemical and structural data presented in this thesis we are now able...... to describe the basic molecular components that allow the plasma membrane proton H+-ATPase to carry out proton transport against large membrane potentials. Moreover, a completely new paradigm for post-translational activation of these proteins is presented. The talk will focus on the following themes...

  20. The plant plasma membrane H+-ATPase

    DEFF Research Database (Denmark)

    Ekberg, Kira

      The very high mobility of protons in aqueous solutions demands special features of membrane proton transporters to sustain efficient yet regulated proton transport across biological membranes. By the use of the chemical energy of ATP, plasma-membrane-embedded H+-ATPases extrude protons from cells...... of plants and fungi to generate electrochemical proton gradients. A recently published crystal structure of a plasma membrane H(+)-ATPase contributes to our knowledge about the mechanism of these essential enzymes. Together with biochemical and structural data presented in this thesis we are now able...... to describe the basic molecular components that allow the plasma membrane proton H+-ATPase to carry out proton transport against large membrane potentials. Moreover, a completely new paradigm for post-translational activation of these proteins is presented. The talk will focus on the following themes...

  1. Cytotoxic cholesterol is generated by the hydrolysis of cytoplasmic cholesteryl ester and transported to the plasma membrane.

    Science.gov (United States)

    Kellner-Weibel, G; Geng, Y J; Rothblat, G H

    1999-10-01

    The present study examines the fate and effects of free cholesterol (FC) generated by the hydrolysis of cytoplasmic cholesteryl esters (CE) in model macrophage foam cells. J774 or elicited mouse peritoneal macrophages (MPM) were enriched with CE by incubating with acetylated low density lipoprotein (acLDL) and FC/phospholipid dispersions, thus creating model foam cells. Treatment of the foam cells with the acyl coenzyme-A:cholesterol acyltransferase (ACAT) inhibitor, CP-113,818, in the absence of any extracellular cholesterol acceptors, resulted in cellular toxicity. This was accompanied by an increase in the amount of FC available for oxidation by an exogenous cholesterol oxidase. Furthermore, cellular toxicity was proportional to the size of the oxidase susceptible pool of FC over time. Morphological analysis and in situ DNA fragmentation assay demonstrated the occurrence of apoptosis in the ACAT inhibited cells. Co-treatment with the hydrophobic amine U18666A, an intracellular cholesterol transport inhibitor, led to a dose dependent reduction in cytotoxicity and apoptosis, and blocked the movement of FC into the oxidase susceptible pool. In addition, treating model foam cells with CP-113,818 plus chloroquine, a compound that inhibits the function of acidic vesicles, also diminished cellular toxicity. Staining with the cholesterol binding dye filipin revealed that the macrophages treated with CP-113,818 contained a cholesterol oxidase accessible pool of FC in the plasma membrane. These results suggest that FC generated by the hydrolysis of cytoplasmic CE is transported through acidic vesicles to the plasma membrane, and accumulation of FC in this pool triggers cell death by necrosis and apoptosis.

  2. INTRACELLULAR TRANSPORT. PI4P/phosphatidylserine countertransport at ORP5- and ORP8-mediated ER-plasma membrane contacts.

    Science.gov (United States)

    Chung, Jeeyun; Torta, Federico; Masai, Kaori; Lucast, Louise; Czapla, Heather; Tanner, Lukas B; Narayanaswamy, Pradeep; Wenk, Markus R; Nakatsu, Fubito; De Camilli, Pietro

    2015-07-24

    Lipid transfer between cell membrane bilayers at contacts between the endoplasmic reticulum (ER) and other membranes help to maintain membrane lipid homeostasis. We found that two similar ER integral membrane proteins, oxysterol-binding protein (OSBP)-related protein 5 (ORP5) and ORP8, tethered the ER to the plasma membrane (PM) via the interaction of their pleckstrin homology domains with phosphatidylinositol 4-phosphate (PI4P) in this membrane. Their OSBP-related domains (ORDs) harbored either PI4P or phosphatidylserine (PS) and exchanged these lipids between bilayers. Gain- and loss-of-function experiments showed that ORP5 and ORP8 could mediate PI4P/PS countertransport between the ER and the PM, thus delivering PI4P to the ER-localized PI4P phosphatase Sac1 for degradation and PS from the ER to the PM. This exchange helps to control plasma membrane PI4P levels and selectively enrich PS in the PM.

  3. Criticality in Plasma Membranes

    Science.gov (United States)

    Machta, Benjamin; Papanikolaou, Stefanos; Sethna, James; Veatch, Sarah

    2011-03-01

    We are motivated by recent observations of micron-sized critical fluctuations in the 2d Ising Universality class in plasma membrane vesicles that are isolated from cortical cytoskeleton. We construct a minimal model of the plasma membrane's interaction with intact cytoskeleton which explains why large scale phase separation has not been observed in Vivo. In addition, we use analytical techniques from conformal field theory and numerical simulations to investigate the form of effective forces mediated by the membrane's proximity to criticality. We show that the range of this force is maximized near a critical point and we quantify its usefulness in mediating communication using techniques from information theory. Finally we use theoretical techniques from statistical physics in conjunction with Monte-Carlo simulations to understand how criticality can be used to increase the efficiency of membrane bound receptor mediated signaling. We expect that this sort of analysis will be broadly useful in understanding and quantifying the role of lipid ``rafts'' in a wide variety of membrane bound processes. Generally, we demonstrate that critical fluctuations provide a physical mechanism to organize and spatially segregate membrane components by providing channels for interaction over relatively large distances.

  4. Role of the Plasma Membrane Transporter of Organic Cations OCT1 and Its Genetic Variants in Modern Liver Pharmacology

    Directory of Open Access Journals (Sweden)

    Elisa Lozano

    2013-01-01

    Full Text Available Changes in the uptake of many drugs by the target cells may dramatically affect the pharmacological response. Thus, downregulation of SLC22A1, which encodes the organic cation transporter type 1 (OCT1, may affect the response of healthy hepatocytes and liver cancer cells to cationic drugs, such as metformin and sorafenib, respectively. Moreover, the overall picture may be modified to a considerable extent by the preexistence or the appearance during the pathogenic process of genetic variants. Some rare OCT1 variants enhance transport activity, whereas other more frequent variants impair protein maturation, plasma membrane targeting or the function of this carrier, hence reducing intracellular active drug concentrations. Here, we review current knowledge of the role of OCT1 in modern liver pharmacology, which includes the use of cationic drugs to treat several diseases, some of them of great clinical relevance such as diabetes and primary liver cancer (cholangiocarcinoma and hepatocellular carcinoma. We conclude that modern pharmacology must consider the individual evaluation of OCT1 expression/function in the healthy liver and in the target tissue, particularly if this is a tumor, in order to predict the lack of response to cationic drugs and to be able to design individualized pharmacological treatments with the highest chances of success.

  5. ADENOSINE TRIPHOSPHATE-DEPENDENT COPPER TRANSPORT IN ISOLATED RAT-LIVER PLASMA-MEMBRANES

    NARCIS (Netherlands)

    INTVELD, G; VANDENBERG, GJ; MULLER, M; KUIPERS, F; VONK, RJ

    1995-01-01

    The process of hepatobiliary copper (Cu) secretion is still poorly understood: Cu secretion as a complex with glutathione and transport via a lysosomal pathway have been proposed. The recent cloning and sequencing of the gene for Wilson disease indicates that Cu transport in liver cells may be media

  6. Membrane Transport Phenomena (MTP)

    Science.gov (United States)

    Mason, Larry W.

    1997-01-01

    The third semi-annual period of the MTP project has been involved with performing experiments using the Membrane Transport Apparatus (MTA), development of analysis techniques for the experiment results, analytical modeling of the osmotic transport phenomena, and completion of a DC-9 microgravity flight to test candidate fluid cell geometries. Preparations were also made for the MTP Science Concept Review (SCR), held on 13 June 1997 at Lockheed Martin Astronautics in Denver. These activities are detailed in the report.

  7. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  8. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  9. Sec61β, a subunit of the Sec61 protein translocation channel at the Endoplasmic Reticulum, is involved in the transport of Gurken to the plasma membrane.

    Directory of Open Access Journals (Sweden)

    Kelkar Anshuman

    2009-02-01

    Full Text Available Abstract Background Protein translocation across the membrane of the Endoplasmic Reticulum (ER is the first step in the biogenesis of secretory and membrane proteins. Proteins enter the ER by the Sec61 translocon, a proteinaceous channel composed of three subunits, α, β and γ. While it is known that Sec61α forms the actual channel, the function of the other two subunits remains to be characterized. Results In the present study we have investigated the function of Sec61β in Drosophila melanogaster. We describe its role in the plasma membrane traffic of Gurken, the ligand for the Epidermal Growth Factor (EGF receptor in the oocyte. Germline clones of the mutant allele of Sec61β show normal translocation of Gurken into the ER and transport to the Golgi complex, but further traffic to the plasma membrane is impeded. The defect in plasma membrane traffic due to absence of Sec61β is specific for Gurken and is not due to a general trafficking defect. Conclusion Based on our study we conclude that Sec61β, which is part of the ER protein translocation channel affects a post-ER step during Gurken trafficking to the plasma membrane. We propose an additional role of Sec61β beyond protein translocation into the ER.

  10. Hydrogen transport membranes

    Science.gov (United States)

    Mundschau, Michael V.

    2005-05-31

    Composite hydrogen transport membranes, which are used for extraction of hydrogen from gas mixtures are provided. Methods are described for supporting metals and metal alloys which have high hydrogen permeability, but which are either too thin to be self supporting, too weak to resist differential pressures across the membrane, or which become embrittled by hydrogen. Support materials are chosen to be lattice matched to the metals and metal alloys. Preferred metals with high permeability for hydrogen include vanadium, niobium, tantalum, zirconium, palladium, and alloys thereof. Hydrogen-permeable membranes include those in which the pores of a porous support matrix are blocked by hydrogen-permeable metals and metal alloys, those in which the pores of a porous metal matrix are blocked with materials which make the membrane impervious to gases other than hydrogen, and cermets fabricated by sintering powders of metals with powders of lattice-matched ceramic.

  11. Enhanced Boron Tolerance in Plants Mediated by Bidirectional Transport Through Plasma Membrane Intrinsic Proteins.

    Science.gov (United States)

    Mosa, Kareem A; Kumar, Kundan; Chhikara, Sudesh; Musante, Craig; White, Jason C; Dhankher, Om Parkash

    2016-02-23

    High boron (B) concentration is toxic to plants that limit plant productivity. Recent studies have shown the involvement of the members of major intrinsic protein (MIP) family in controlling B transport. Here, we have provided experimental evidences showing the bidirectional transport activity of rice OsPIP1;3 and OsPIP2;6. Boron transport ability of OsPIP1;3 and OsPIP2;6 were displayed in yeast HD9 mutant strain (∆fps1∆acr3∆ycf1) as a result of increased B sensitivity, influx and accumulation by OsPIP1;3, and rapid efflux activity by OsPIP2;6. RT-PCR analysis showed strong upregulation of OsPIP1;3 and OsPIP2;6 transcripts in roots by B toxicity. Transgenic Arabidopsis lines overexpressing OsPIP1;3 and OsPIP2;6 exhibited enhanced tolerance to B toxicity. Furthermore, B concentration was significantly increased after 2 and 3 hours of tracer boron ((10)B) treatment. Interestingly, a rapid efflux of (10)B from the roots of the transgenic plants was observed within 1 h of (10)B treatment. Boron tolerance in OsPIP1;3 and OsPIP2;6 lines was inhibited by aquaporin inhibitors, silver nitrate and sodium azide. Our data proved that OsPIP1;3 and OsPIP2;6 are indeed involved in both influx and efflux of boron transport. Manipulation of these PIPs could be highly useful in improving B tolerance in crops grown in high B containing soils.

  12. [Function of transport H+-ATPases in plant cell plasma and vacuolar membranes of maize under salt stress conditions and effect of adaptogenic preparations].

    Science.gov (United States)

    Rybchenko, Zh I; Palladina, T O

    2011-01-01

    Participations of electrogenic H+-pumps of plasma and vacuolar membranes represented by E1-E2 and V-type H+-ATPases in plant cell adaptation to salt stress conditions has been studied by determination of their transport activities. Experiments were carried out on corn seedlings exposed during 1 or 10 days at 0.1 M NaCl. Preparations Methyure and Ivine were used by seed soaking at 10(-7) M. Plasma and vacuolar membrane fractions were isolated from corn seedling roots. In variants without NaCl a hydrolytical activity of plasma membrane H+-ATPase was increased with seedling age and its transport one was changed insignificantly, wherease the response of the weaker vacuolar H+-ATPase was opposite. NaCl exposition decreased hydrolytical activities of both H+-ATPases and increased their transport ones. These results demonstrated amplification of H+-pumps function especially represented by vacuolar H+-ATPase. Both preparations, Methyure mainly, caused a further increase of transport activity which was more expressed in NaCl variants. Obtained results showed the important role of these H+-pumps in plant adaptation under salt stress conditions realized by energetical maintenance of the secondary active Na+/H+ -antiporters which remove Na+ from cytoplasm.

  13. The BBSome Controls Energy Homeostasis by Mediating the Transport of the Leptin Receptor to the Plasma Membrane.

    Directory of Open Access Journals (Sweden)

    Deng-Fu Guo

    2016-02-01

    Full Text Available Bardet-Biedl syndrome (BBS is a highly pleiotropic autosomal recessive disorder associated with a wide range of phenotypes including obesity. However, the underlying mechanism remains unclear. Here, we show that neuronal BBSome is a critical determinant of energy balance through its role in the regulation of the trafficking of the long signaling form of the leptin receptor (LRb. Targeted disruption of the BBSome by deleting the Bbs1 gene from the nervous system causes obesity in mice, and this phenotype is reproduced by ablation of the Bbs1 gene selectively in the LRb-expressing cells, but not from adipocytes. Obesity developed as a consequence of both increased food intake and decreased energy expenditure in mice lacking the Bbs1 gene in LRb-expressing cells. Strikingly, the well-known role of BBS proteins in the regulation of ciliary formation and function is unlikely to account for the obesogenic effect of BBS1 loss as disruption of the intraflagellar transport (IFT machinery required for ciliogenesis by deleting the Ift88 gene in LRb-expressing cells caused a marginal increase in body weight and adiposity. Instead, we demonstrate that silencing BBS proteins, but not IFT88, impair the trafficking of the LRb to the plasma membrane leading to central leptin resistance in a manner independent of obesity. Our data also demonstrate that postnatal deletion of the Bbs1 gene in the mediobasal hypothalamus can cause obesity in mice, arguing against an early neurodevelopmental origin of obesity in BBS. Our results depict a novel mechanism underlying energy imbalance and obesity in BBS with potential implications in common forms of human obesity.

  14. The BBSome Controls Energy Homeostasis by Mediating the Transport of the Leptin Receptor to the Plasma Membrane.

    Science.gov (United States)

    Guo, Deng-Fu; Cui, Huxing; Zhang, Qihong; Morgan, Donald A; Thedens, Daniel R; Nishimura, Darryl; Grobe, Justin L; Sheffield, Val C; Rahmouni, Kamal

    2016-02-01

    Bardet-Biedl syndrome (BBS) is a highly pleiotropic autosomal recessive disorder associated with a wide range of phenotypes including obesity. However, the underlying mechanism remains unclear. Here, we show that neuronal BBSome is a critical determinant of energy balance through its role in the regulation of the trafficking of the long signaling form of the leptin receptor (LRb). Targeted disruption of the BBSome by deleting the Bbs1 gene from the nervous system causes obesity in mice, and this phenotype is reproduced by ablation of the Bbs1 gene selectively in the LRb-expressing cells, but not from adipocytes. Obesity developed as a consequence of both increased food intake and decreased energy expenditure in mice lacking the Bbs1 gene in LRb-expressing cells. Strikingly, the well-known role of BBS proteins in the regulation of ciliary formation and function is unlikely to account for the obesogenic effect of BBS1 loss as disruption of the intraflagellar transport (IFT) machinery required for ciliogenesis by deleting the Ift88 gene in LRb-expressing cells caused a marginal increase in body weight and adiposity. Instead, we demonstrate that silencing BBS proteins, but not IFT88, impair the trafficking of the LRb to the plasma membrane leading to central leptin resistance in a manner independent of obesity. Our data also demonstrate that postnatal deletion of the Bbs1 gene in the mediobasal hypothalamus can cause obesity in mice, arguing against an early neurodevelopmental origin of obesity in BBS. Our results depict a novel mechanism underlying energy imbalance and obesity in BBS with potential implications in common forms of human obesity.

  15. Transmembrane electron transport in sealed and NAD(P)H-loaded right-side-out plasma membrane vesicles isolated from maize (Zea mays L.) roots.

    Science.gov (United States)

    Menckhoff, Mathias; Lüthje, Sabine

    2004-06-01

    Electron transport across plasma membranes has been observed in vivo in several plant species and tissues after the application of ferricyanide (hexacyanoferrate III, HCF III). In the present work, a transmembrane electron flow was demonstrated in sealed and NAD(P)H-loaded right-side-out (apoplastic-side-out) plasma membrane vesicles isolated from maize (Zea mays L.) roots. HCF III was reduced at a rate of up to 126 nmol min(-1) mg(-1) protein by NADPH-loaded vesicles, while reduction rates with NADH-loaded vesicles were several-fold lower. Coincident with the reduction of HCF III, NAD(P)H oxidation was observed inside the vesicles. The dependence of reduction on K+ indicated an electrogenic transmembrane electron flow. Application of 100 microM calcium decreased HCF III reduction up to 66%, while pre-incubation with 200 microM warfarin or diphenylene iodonium inhibited transmembrane electron transport only weakly. Fe(3+)-EDTA was not reduced significantly by NADPH-loaded plasma membrane vesicles, whereas XTT was reduced at a rate of 765 pmol min(-1) mg(-1) protein. The results suggested a major function for NADPH in transmembrane electron flow and were discussed in conjunction with in vivo experiments.

  16. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-02-01

    under air separation mode (small gradient) were completed on the membrane of LSCrF-2828 at 900 C. Low pO{sub 2} atmospheres based on with CO-CO{sub 2} mixtures have also been admitted to the delivery side of the LSCrF-2828 membrane to produce the gradients which exist under syngas generation conditions. The CO-CO{sub 2} mixtures have normal isotopic {sup 18}O abundances. The evolution of {sup 18}O on the delivery side in these experiments after an {sup 18}O pulse on the air side reveals a wealth of information about the oxygen transport processes.

  17. Urea transporters UT-A1 and UT-A3 accumulate in the plasma membrane in response to increased hypertonicity.

    Science.gov (United States)

    Blessing, Nathan W; Blount, Mitsi A; Sands, Jeff M; Martin, Christopher F; Klein, Janet D

    2008-11-01

    The UT-A1 and UT-A3 urea transporters are expressed in the terminal inner medullary collecting duct (IMCD) and play an important role in the production of concentrated urine. We showed that both hyperosmolarity and vasopressin increase urea permeability in perfused rat terminal IMCDs and that UT-A1 and UT-A3 accumulate in the plasma membrane in response to vasopressin. In this study, we investigated whether hyperosmolarity causes UT-A1 and/or UT-A3 to accumulate in the plasma membrane or represents a complimentary stimulatory pathway. Rat IMCD suspensions were incubated in 450 vs. 900 mosM solutions. We biotinylated the IMCD surface proteins, collected, and analyzed them. Membrane accumulation was assessed by Western blotting of the biotinylated protein pool probed with anti-UT-A1 or anti-UT-A3. We studied the effect of NaCl, urea, and sucrose as osmotic agents. Membrane-associated UT-A1 and UT-A3 increased relative to control levels when either NaCl (UT-A1 increased 37 +/- 6%; UT-A3 increased 46 +/- 13%) or sucrose (UT-A1 increased 81 +/- 13%; UT-A3 increased 60 +/- 8%) was used to increase osmolarity. There was no increase in membrane UT-A1 or UT-A3 when urea was added. Analogously, UT-A1 phosphorylation was increased in NaCl- and sucrose- but not in urea-based hyperosmolar solutions. Hypertonicity also increased UT-A3 phosphorylation. We conclude that the increase in the urea permeability in response to hyperosmolarity reflects both UT-A1 and UT-A3 movement to the plasma membrane and may be a direct response to tonicity. Furthermore, this movement is accompanied by, and may require, increased phosphorylation in response to hypertonicity.

  18. Elevated mRNA-levels of distinct mitochondrial and plasma membrane Ca2+ transporters in individual hypoglossal motor neurons of endstage SOD1 transgenic mice.

    Directory of Open Access Journals (Sweden)

    Tobias eMühling

    2014-11-01

    Full Text Available Disturbances in Ca2+ homeostasis and mitochondrial dysfunction have emerged as major pathogenic features in familial and sporadic forms of Amyotrophic Lateral Sclerosis (ALS, a fatal degenerative motor neuron disease. However, the distinct molecular ALS-pathology remains unclear. Recently, an activity-dependent Ca2+ homeostasis deficit, selectively in highly vulnerable cholinergic motor neurons in the hypoglossal nucleus (hMNs from a common ALS mouse model, endstage superoxide dismutase SOD1G93A transgenic mice, was described. This functional deficit was defined by a reduced hMN mitochondrial Ca2+ uptake capacity and elevated Ca2+ extrusion across the plasma membrane. To address the underlying molecular mechanisms, here we quantified mRNA-levels of respective potential mitochondrial and plasma membrane Ca2+ transporters in individual, choline-acetyltransferase (ChAT positive hMNs from wildtype (WT and endstage SOD1G93A mice, by combining UV laser microdissection with RT-qPCR techniques, and specific data normalization. As ChAT cDNA levels as well as cDNA and genomic DNA levels of the mitochondrially encoded NADH dehydrogenase ND1 were not different between hMNs from WT and endstage SOD1G93A mice, these genes were used to normalize hMN-specific mRNA-levels of plasma membrane and mitochondrial Ca2+ transporters, respectively. We detected about 2-fold higher levels of the mitochondrial Ca2+ transporters MCU/MICU1, Letm1 and UCP2 in remaining hMNs from endstage SOD1G93A mice. These higher expression-levels of mitochondrial Ca2+ transporters in individual hMNs were not associated with a respective increase in number of mitochondrial genomes, as evident from hMN specific ND1 DNA quantification. Normalized mRNA-levels for the plasma membrane Na2+/Ca2+exchanger NCX1 was also about 2-fold higher in hMNs from SOD1G93A mice. Thus, pharmacological stimulation of Ca2+ transporters in highly vulnerable hMNs might offer a novel neuroprotective strategy for ALS.

  19. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana; X.-D Zhou; Q. Cai; J. Yang; W.B. Yelon; W.J. James; H.U. Anderson; Alan Jacobson; C.A. Mims

    2004-05-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In this report, in situ neutron diffraction was used to characterize the chemical and structural properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} (here after as L2SF55T) specimen, which was subject to measurements of neutron diffraction from room temperature to 900 C. It was found that space group of R3c yielded a better refinement than a cubic structure of Pm3m. Oxygen occupancy was nearly 3 in the region from room temperature to 700 C, above which the occupancy decreased due to oxygen loss. Dense OTM bars provided by Praxair were loaded to fracture at varying stress rates. Studies were done at room temperature in air and at 1000 C in a specified environment to evaluate slow crack growth behavior. The X-Ray data and fracture mechanisms points to non-equilibrium decomposition of the LSFCO OTM membrane. The non-equilibrium conditions could probably be due to the nature of the applied stress field (stressing rates) and leads to transition in crystal structures and increased kinetics of decomposition. The formations of a Brownmillerite or Sr2Fe2O5 type structures, which are orthorhombic are attributed to the ordering of oxygen vacancies. The cubic to orthorhombic transitions leads to 2.6% increase in strains and thus residual stresses generated could influence the fracture behavior of the OTM membrane. Continued investigations on the thermodynamic properties (stability and phase-separation behavior) and total conductivity of prototype membrane materials were carried out. The data are needed together with the kinetic information to develop a complete model for the membrane transport. Previously characterization, stoichiometry and conductivity measurements for samples of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} were reported. In this report

  20. Evidence for functional interaction of plasma membrane electron transport, voltage-dependent anion channel and volume-regulated anion channel in frog aorta

    Indian Academy of Sciences (India)

    Rashmi P Rao; J Prakasa Rao

    2010-12-01

    Frog aortic tissue exhibits plasma membrane electron transport (PMET) owing to its ability to reduce ferricyanide even in the presence of mitochondrial poisons, such as cyanide and azide. Exposure to hypotonic solution (108 mOsmol/kg H2O) enhanced the reduction of ferricyanide in excised aortic tissue of frog. Increment in ferricyanide reductase activity was also brought about by the presence of homocysteine (100 M dissolved in isotonic frog Ringer solution), a redox active compound and a potent modulator of PMET. Two plasma-membrane-bound channels, the volume regulated anion channel (VRAC) and the voltage-dependent anion channel (VDAC), are involved in the response to hypotonic stress. The presence of VRAC and VDAC antagonists–tamoxifen, glibenclamide, fluoxetine and verapamil, and 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS), respectively–inhibited this enhanced activity brought about by either hypotonic stress or homocysteine. The blockers do not affect the ferricyanide reductase activity under isotonic conditions. Taken together, these findings indicate a functional interaction of the three plasma membrane proteins, namely, ferricyanide reductase (PMET), VDAC and VRAC.

  1. The role of charged residues in the transmembrane helices of monocarboxylate transporter 1 and its ancillary protein basigin in determining plasma membrane expression and catalytic activity

    OpenAIRE

    Manoharan, Christine; Wilson, Marieangela C.; Sessions, Richard B; Halestrap, Andrew P.

    2006-01-01

    Monocarboxylate transporters MCT1-MCT4 require basigin (CD147) or embigin (gp70), ancillary proteins with a glutamate residue in their single transmembrane (TM) domain, for plasma membrane (PM) expression and activity. Here we use site-directed mutagenesis and expression in COS cells or Xenopus oocytes to investigate whether this glutamate (Glu218 in basigin) may charge-pair with a positively charged TM-residue of MCT1. Such residues were predicted using a new molecular model of MCT1 based up...

  2. The cortical acto-myosin network: from diffusion barrier to functional gateway in the transport of neurosecretory vesicles to the plasma membrane

    Directory of Open Access Journals (Sweden)

    Andreas ePapadopulos

    2013-10-01

    Full Text Available Dysregulation of regulated exocytosis is linked to an array of pathological conditions, including neurodegenerative disorders, asthma and diabetes. Understanding the molecular mechanisms underpinning neuroexocytosis including the processes that allow neurosecretory vesicles to access and fuse with the plasma membrane and to recycle post-fusion, is therefore critical to the design of future therapeutic drugs that will efficiently tackle these diseases. Despite considerable efforts to determine the principles of vesicular fusion, the mechanisms controlling the approach of vesicles to the plasma membrane in order to undergo tethering, docking, priming, and fusion remain poorly understood. All these steps involve the cortical actin network, a dense mesh of actin filaments localized beneath the plasma membrane. Recent work overturned the long-held belief that the cortical actin network only plays a passive constraining role in neuroexocytosis functioning as a physical barrier that partly breaks down upon entry of Ca2+ to allow secretory vesicles to reach the plasma membrane. A multitude of new roles for the cortical actin network in regulated exocytosis have now emerged and point to highly dynamic novel functions of key myosin molecular motors. Myosins are not only believed to help bring about dynamic changes in the actin cytoskeleton, tethering and guiding vesicles to their fusion sites, but they also regulate the size and duration of the fusion pore, thereby directly contributing to the release of neurotransmitters and hormones.Here we discuss the functions of the cortical actin network, myosins and their effectors in controlling the processes that lead to tethering, directed transport, docking, and fusion of exocytotic vesicles in regulated exocytosis.

  3. Conical nanopore membranes. Preparation and transport properties.

    Science.gov (United States)

    Li, Naichao; Yu, Shufang; Harrell, C Chad; Martin, Charles R

    2004-04-01

    We have been investigating applications of nanopore membranes in analytical chemistry-specifically in membrane-based bioseparations, in electroanalytical chemistry, and in the development of new approaches to biosensor design. Membranes that have conically shaped pores (as opposed to the more conventional cylindrical shape) may offer some advantages for these applications. We describe here a simple plasma-etch method that converts cylindrical nanopores in track-etched polymeric membranes into conically shaped pores. This method allows for control of the shape of the resulting conical nanopores. For example, the plasma-etched pores may be cylindrical through most of the membrane thickness blossoming into cones at one face of the membrane (trumpet-shaped), or they may be nearly perfect cones. The key advantage of the conical pore shape is a dramatic enhancement in the rate of transport through the membrane, relative to an analogous cylindrical pore membrane. We demonstrate this here by measuring the ionic resistances of the plasma-etched conical pore membranes.

  4. Oxygen Transport Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay

    2008-08-30

    The focus of this research was to develop new membrane materials by synthesizing different compounds and determining their defect structures, crystallographic structures and electrical properties. In addition to measuring electrical conductivity, oxygen vacancy concentration was also evaluated using thermogravimetry, Neutron diffraction and Moessbauer Spectroscopy. The reducing conditions (CO{sub 2}/CO/H{sub 2} gas mixtures with steam) as encountered in a reactor environment can be expected to have significant influence on the mechanical properties of the oxides membranes. Various La based materials with and without Ti were selected as candidate membrane materials for OTM. The maximum electrical conductivity of LSF in air as a function of temperature was achieved at < 600 C and depends on the concentration of Sr (acceptor dopant). Oxygen occupancy in LSF was estimated using Neutron diffractometry and Moessbauer Spectroscopy by measuring magnetic moment changes depending on the Fe{sup 3+} and Fe{sup 4+} ratio. After extensive studies of candidate materials, lanthanum ferrites (LSF and LSFT) were selected as the favored materials for the oxygen transport membrane (OTM). LSF is a very good material for an OTM because of its high electronic and oxygen ionic conductivity if long term stability and mechanical strength are improved. LSFT not only exhibits p-type behavior in the high oxygen activity regime, but also has n-type conduction in reducing atmospheres. Higher concentrations of oxygen vacancies in the low oxygen activity regime may improve the performance of LSFT as an OTM. The hole concentration is related to the difference in the acceptor and donor concentration by the relation p = [Sr'{sub La}]-[Ti{sm_bullet}{sub Fe}]. The chemical formulation predicts that the hole concentration is, p = 0.8-0.45 or 0.35. Experimental measurements indicated that p is about {approx} 0.35. The activation energy of conduction is 0.2 eV which implies that LSCF conducts via the

  5. Exercise-induced increase in glucose transport, GLUT-4, and VAMP-2 in plasma membrane from human muscle

    DEFF Research Database (Denmark)

    Kristiansen, S; Hargreaves, Mark; Richter, Erik

    1996-01-01

    ) and then to fatigue at 100% Vo2max (5.7 +/- 0.2 min). Vesicle glucose transport at 5 mM increased from 3.3 +/- 0.6 pmol.microgram-1.min-1 at rest to 6.6 +/- 1.0 pmol.microgram-1.min-1 at fatigue (mean +/- SE, n = 6, P increase in glucose transport was associated with a 1.6-fold increase in vesicle GLUT......A major effect of muscle contractions is an increase in sarcolemmal glucose transport. We have used a recently developed technique to produce sarcolemmal giant vesicles from human muscle biopsy samples obtained before and after exercise. Six men exercised for 10 min at 50% maximal O2 uptake (Vo2max......-4 protein content. Glucose transport normalized to GLUT-4 protein content also increased with exercise, suggesting increased intrinsic activity of GLUT-4. Furthermore, exercise resulted in a 1.4-fold increase in sarcolemmal vesicle-associated membrane protein (VAMP-2) content, suggesting that muscle...

  6. Oxygen Transport Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay

    2008-08-30

    The focus of this research was to develop new membrane materials by synthesizing different compounds and determining their defect structures, crystallographic structures and electrical properties. In addition to measuring electrical conductivity, oxygen vacancy concentration was also evaluated using thermogravimetry, Neutron diffraction and Moessbauer Spectroscopy. The reducing conditions (CO{sub 2}/CO/H{sub 2} gas mixtures with steam) as encountered in a reactor environment can be expected to have significant influence on the mechanical properties of the oxides membranes. Various La based materials with and without Ti were selected as candidate membrane materials for OTM. The maximum electrical conductivity of LSF in air as a function of temperature was achieved at < 600 C and depends on the concentration of Sr (acceptor dopant). Oxygen occupancy in LSF was estimated using Neutron diffractometry and Moessbauer Spectroscopy by measuring magnetic moment changes depending on the Fe{sup 3+} and Fe{sup 4+} ratio. After extensive studies of candidate materials, lanthanum ferrites (LSF and LSFT) were selected as the favored materials for the oxygen transport membrane (OTM). LSF is a very good material for an OTM because of its high electronic and oxygen ionic conductivity if long term stability and mechanical strength are improved. LSFT not only exhibits p-type behavior in the high oxygen activity regime, but also has n-type conduction in reducing atmospheres. Higher concentrations of oxygen vacancies in the low oxygen activity regime may improve the performance of LSFT as an OTM. The hole concentration is related to the difference in the acceptor and donor concentration by the relation p = [Sr'{sub La}]-[Ti{sm_bullet}{sub Fe}]. The chemical formulation predicts that the hole concentration is, p = 0.8-0.45 or 0.35. Experimental measurements indicated that p is about {approx} 0.35. The activation energy of conduction is 0.2 eV which implies that LSCF conducts via the

  7. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana; X.-D Zhou; Q. Cai; J. Yang; W.B. Yelon; W.J. James; H.U. Anderson; Alan Jacobson; C.A. Mims

    2004-10-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In this report, Moessbauer spectroscopy was used to study the local environmentals of LSFT with various level of oxygen deficiency. Ionic valence state, magnetic interaction and influence of Ti on superexchange are discussed Stable crack growth studies on Dense OTM bars provided by Praxair were done at elevated temperature, pressure and elevated conditions. Post-fracture X-ray data of the OTM fractured at 1000 C in environment were refined by FullProf code and results indicate a distortion of the parent cubic perovskite to orthorhombic structure with reduced symmetry. TGA-DTA studies on the post-fracture samples also indicated residual effect arising from the thermal and stress history of the samples. An electrochemical cell has been designed and built for measurements of the Seebeck coefficient as a function of temperature and pressure. The initial measurements on La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} are reported. Neutron diffraction measurements of the same composition are in agreement with both the stoichiometry and the kinetic behavior observed in coulometric titration measurements. A series of isotope transients under air separation mode (small gradient) were completed on the membrane of LSCrF-2828 at 900 C. Low pO{sub 2} atmospheres based on with CO-CO{sub 2} mixtures have also been admitted to the delivery side of the LSCrF-2828 membrane to produce the gradients which exist under syngas generation conditions. The COCO{sub 2} mixtures have normal isotopic {sup 18}O abundances. The evolution of {sup 18}O on the delivery side in these experiments after an {sup 18}O pulse on the air side reveals a wealth of information about the oxygen transport processes.

  8. Determination of the mean transit time for the transport of aerosolized 99mTc-DTPA across the pulmonary epithelial membrane. A plasma sample method

    DEFF Research Database (Denmark)

    Groth, Sofie; Lassen, N A; Rossing, Niels Nygaard

    1988-01-01

    During the last decade it has been customary to estimate pulmonary epithelial permeability (P-P) as the pulmonary clearance of inhaled nebulized 99mTc-DTPA from a time-activity (t-a) curve registered externally by monitoring over the chest. The t-a curve, however, is not defined by the degree of P......-P alone but also by factors such as the deposition of the 99mTc-DTPA in the lungs. To avoid these problems a plasma sample method was derived. It describes P-P by the mean transit time (t) for the transport of 99mTc-DTPA across the pulmonary epithelial membrane, t(L). The calculation of t(L) involves two...... steps. Following the inhalation of Tc-DTPA the plasma t-a curve is defined and used to calculate t for the transport for 99mTc-DTPA across the pulmonary epithelial membrane, through the ECV and until elimination by the kidneys, t(L+ECV). Subsequently, 99mTc-DTPA is injected as a bolus i.v. and the new t...

  9. Nanoengineered membranes for controlled transport

    Science.gov (United States)

    Doktycz, Mitchel J [Oak Ridge, TN; Simpson, Michael L [Knoxville, TN; McKnight, Timothy E [Greenback, TN; Melechko, Anatoli V [Oak Ridge, TN; Lowndes, Douglas H [Knoxville, TN; Guillorn, Michael A [Knoxville, TN; Merkulov, Vladimir I [Oak Ridge, TN

    2010-01-05

    A nanoengineered membrane for controlling material transport (e.g., molecular transport) is disclosed. The membrane includes a substrate, a cover definining a material transport channel between the substrate and the cover, and a plurality of fibers positioned in the channel and connected to an extending away from a surface of the substrate. The fibers are aligned perpendicular to the surface of the substrate, and have a width of 100 nanometers or less. The diffusion limits for material transport are controlled by the separation of the fibers. In one embodiment, chemical derivitization of carbon fibers may be undertaken to further affect the diffusion limits or affect selective permeability or facilitated transport. For example, a coating can be applied to at least a portion of the fibers. In another embodiment, individually addressable carbon nanofibers can be integrated with the membrane to provide an electrical driving force for material transport.

  10. The E3 Ubiquitin Ligase SCFTIR1/AFB and Membrane Sterols Play Key Roles in Auxin Regulation of Endocytosis, Recycling, and Plasma Membrane Accumulation of the Auxin Efflux Transporter PIN2 in Arabidopsis thaliana[C][W][OA

    Science.gov (United States)

    Pan, Jianwei; Fujioka, Shozo; Peng, Jianling; Chen, Jianghua; Li, Guangming; Chen, Rujin

    2009-01-01

    The PIN family of auxin efflux transporters exhibit polar plasma membrane (PM) localization and play a key role in auxin gradient-mediated developmental processes. Auxin inhibits PIN2 endocytosis and promotes its PM localization. However, the underlying mechanisms remain elusive. Here, we show that the inhibitory effect of auxin on PIN2 endocytosis was impaired in SCFTIR1/AFB auxin signaling mutants. Similarly, reducing membrane sterols impaired auxin inhibition of PIN2 endocytosis. Gas chromatography–mass spectrometry analyses indicate that membrane sterols were significantly reduced in SCFTIR1/AFB mutants, supporting a link between membrane sterols and auxin signaling in regulating PIN2 endocytosis. We show that auxin promoted PIN2 recycling from endosomes to the PM and increased PIN2 steady state levels in the PM fraction. Furthermore, we show that the positive effect of auxin on PIN2 levels in the PM was impaired by inhibiting membrane sterols or auxin signaling. Consistent with this, the sterol biosynthetic mutant fk-J79 exhibited pronounced defects in primary root elongation and gravitropic response. Our data collectively indicate that, although there are distinct processes involved in endocytic regulation of specific PM-resident proteins, the SCFTIR1/AFB-dependent processes are required for auxin regulation of endocytosis, recycling, and PM accumulation of the auxin efflux transporter PIN2 in Arabidopsis thaliana. PMID:19218398

  11. Regulation of the Plasma Membrane H+-ATPase

    DEFF Research Database (Denmark)

    Falhof, Janus

    The plasma membrane (PM) H+-ATPase is responsible for generating the electrochemical gradientthat drives the secondary transport of nutrients across the cellular membrane. It belongs to a familyof cation and lipid transporters that are vital to many organisms. PM H+-ATPases are Type P3AATPases...

  12. Dual regulation of root hydraulic conductivity and plasma membrane aquaporins by plant nitrate accumulation and high-affinity nitrate transporter NRT2.1.

    Science.gov (United States)

    Li, Guowei; Tillard, Pascal; Gojon, Alain; Maurel, Christophe

    2016-04-01

    The water status and mineral nutrition of plants critically determine their growth and development. Nitrate (NO3(-)), the primary nitrogen source of higher plants, is known to impact the water transport capacity of roots (root hydraulic conductivity, Lpr). To explore the effects and mode of action of NO3(-) on Lpr, we used an extended set of NO3(-) transport (nrt1.1, nrt1.2, nrt1.5 and nrt2.1), signaling (nrt1.1 and nrt2.1) and metabolism (nia) mutants in Arabidopsis, grown under various NO3(-) conditions. First, a strong positive relationship between Lpr and NO3(-) accumulation, in shoots rather than in roots, was revealed. Secondly, a specific 30% reduction of Lpr in nrt2.1 plants unraveled a major role for the high-affinity NO3(-) transporter NRT2.1 in increasing Lpr These results indicate that NO3(-)signaling rather than nitrogen assimilation products governs Lpr in Arabidopsis. Quantitative real-time reverse transcription-PCR and enzyme-linked immunosorbent assays (ELISAs) were used to investigate the effects of NO3(-) availability on plasma membrane aquaporin (plasma membrane intrinsic protein; PIP) expression. Whereas PIP regulation mostly occurs at the post-translational level in wild-type plants, a regulation of PIPs at both the transcriptional and translational levels was uncovered in nrt2.1 plants. In conclusion, this work reveals that control of Arabidopsis Lpr and PIP functions by NO3(-) involves novel shoot to root signaling and NRT2.1-dependent functions.

  13. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-11-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the current research, the electrical conductivity and Seebeck coefficient were measured as a function of temperature in air. Based on these measurements, the charge carrier concentration, net acceptor dopant concentration, activation energy of conduction and mobility were estimated. The studies on the fracture toughness of the LSFT and dual phase membranes at room temperature have been completed and reported previously. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affects the mechanical properties. To study the effect of temperature on the membranes when exposed to an inert environment, the membranes (LAFT and Dual phase) were heat treated at 1000 C in air and N{sub 2} atmosphere and hardness and fracture toughness of the membranes were studied after the treatment. The indentation method was used to find the fracture toughness and the effect of the heat treatment on the mechanical properties of the membranes. Further results on the investigation of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appears to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model will serve to study ''frozen'' profiles in patterned or composite membranes.

  14. CsNIP2;1 is a Plasma Membrane Transporter from Cucumis sativus that Facilitates Urea Uptake When Expressed in Saccharomyces cerevisiae and Arabidopsis thaliana.

    Science.gov (United States)

    Zhang, Lu; Yan, Jiapei; Vatamaniuk, Olena K; Du, Xiangge

    2016-03-01

    Urea is an important source of nitrogen (N) for the growth and development of plants. It occurs naturally in soils, is the major N source in agricultural fertilizers and is an important N metabolite in plants. Therefore, the identification and characterization of urea transporters in higher plants is important for the fundamental understanding of urea-based N nutrition in plants and for designing novel strategies for improving the N-use efficiency of urea based-fertilizers. Progress in this area, however, is hampered due to scarce knowledge of plant urea transporters. From what is known, urea uptake from the soil into plant roots is mediated by two types of transporters: the major intrinsic proteins (MIPs) and the DUR3 orthologs, mediating low- and high-affinity urea transport, respectively. Here we characterized a MIP family member from Cucumis sativus, CsNIP2;1, with regard to its contribution to urea transport. We show that CsNIP2;1 is a plasma membrane transporter that mediates pH-dependent urea uptake when expressed in yeast. We also found that ectopic expression of CsNIP2;1 improves growth of wild-type Arabidopsis thaliana and rescues growth and development of the atdur3-3 mutant on medium with urea as the sole N source. In addition, CsNIP2;1 is transcriptionally up-regulated by N deficiency, urea and NO3 (-). These data and results from the analyses of the pattern of CsNIP2;1 expression in A. thaliana and cucumber suggest that CsNIP2;1 might be involved in multiple steps of urea-based N nutrition, including urea uptake and internal transport during N remobilization throughout seed germination and N delivery to developing tissues.

  15. Composite oxygen transport membrane

    Energy Technology Data Exchange (ETDEWEB)

    Christie, Gervase Maxwell; Lane, Jonathan A.

    2016-11-15

    A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

  16. Composite oxygen transport membrane

    Science.gov (United States)

    Christie, Gervase Maxwell; Lane, Jonathan A.

    2014-08-05

    A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

  17. Phosphatidylinositol and phosphatidic acid transport between the ER and plasma membrane during PLC activation requires the Nir2 protein.

    Science.gov (United States)

    Kim, Yeun Ju; Guzman-Hernandez, Maria Luisa; Wisniewski, Eva; Echeverria, Nicolas; Balla, Tamas

    2016-02-01

    Phospholipase C (PLC)-mediated hydrolysis of the limited pool of plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] requires replenishment from a larger pool of phosphatidylinositol (PtdIns) via sequential phosphorylation by PtdIns 4-kinases and phosphatidylinositol 4-phosphate (PtdIns4P) 5-kinases. Since PtdIns is synthesized in the endoplasmic reticulum (ER) and PtdIns(4,5)P2 is generated in the PM, it has been postulated that PtdIns transfer proteins (PITPs) provide the means for this lipid transfer function. Recent studies identified the large PITP protein, Nir2 as important for PtdIns transfer from the ER to the PM. It was also found that Nir2 was required for the transfer of phosphatidic acid (PtdOH) from the PM to the ER. In Nir2-depleted cells, activation of PLC leads to PtdOH accumulation in the PM and PtdIns synthesis becomes severely impaired. In quiescent cells, Nir2 is localized to the ER via interaction of its FFAT domain with ER-bound VAMP-associated proteins VAP-A and-B. After PLC activation, Nir2 also binds to the PM via interaction of its C-terminal domains with diacylglycerol (DAG) and PtdOH. Through these interactions, Nir2 functions in ER-PM contact zones. Mutations in VAP-B that have been identified in familial forms of amyotrophic lateral sclerosis (ALS or Lou-Gehrig's disease) cause aggregation of the VAP-B protein, which then impairs its binding to several proteins, including Nir2. These findings have shed new lights on the importance of non-vesicular lipid transfer of PtdIns and PtdOH in ER-PM contact zones with a possible link to a devastating human disease.

  18. Extracellular GTP is a potent water-transport regulator via aquaporin 5 plasma-membrane insertion in M1-CCD epithelial cortical collecting duct cells.

    Science.gov (United States)

    Mancinelli, Rosa; La Rovere, Rita Maria Laura; Fulle, Stefania; Miscia, Sebastiano; Marchisio, Marco; Pierdomenico, Laura; Lanuti, Paola; Procino, Giuseppe; Barbieri, Claudia; Svelto, Maria; Fanò-Illic, Giorgio; Pietrangelo, Tiziana

    2014-01-01

    Extracellular GTP is able to modulate some specific functions in neuron, glia and muscle cell models as it has been demonstrated over the last two decades. In fact, extracellular GTP binds its specific plasma membrane binding sites and induces signal transduction via [Ca(2+)]i increase. We demonstrate, for the first time, that extracellular GTP is able to modulate cell swelling in M1-CCD cortical collecting duct epithelial cells via upregulation of aquaporin 5 (AQP5) expression. We used videoimaging, immunocitochemistry, flow cytometry, confocal techniques, Western blotting and RT-PCR for protein and gene expression analysis, respectively. We demonstrate that AQP5 mRNA is up-regulated 7 h after the GTP exposure in the cell culture medium, and its protein level is increased after 12-24 h. We show that AQP5 is targeted to the plasma membrane of M1-CCD cells, where it facilitates cell swelling, and that the GTP-dependent AQP5 up-regulation occurs via [Ca(2+)]i increase. Indeed, GTP induces both oscillating and transient [Ca(2+)]i increase, and specifically the oscillating kinetic appears to be responsible for blocking cell cycle in the S-phase while the [Ca(2+)]i influx, with whatever kinetic, seems to be responsible for inducing AQP5 expression. The role of GTP as a regulator of AQP5-mediated water transport in renal cells is of great importance in the physiology of renal epithelia, due to its possible physiopathological implications. GTP-dependent AQP5 expression could act as osmosensor. In addition, the data presented here suggest that GTP might play the same role in other tissues where rapid water transport is required for cell volume regulation and maintenance of the homeostasis. © 2014 S. Karger AG, Basel.

  19. Extracellular GTP is a Potent Water-Transport Regulator via Aquaporin 5 Plasma-Membrane Insertion in M1-CCD Epithelial Cortical Collecting Duct Cells

    Directory of Open Access Journals (Sweden)

    Rosa Mancinelli

    2014-03-01

    Full Text Available Background/Aims: Extracellular GTP is able to modulate some specific functions in neuron, glia and muscle cell models as it has been demonstrated over the last two decades. In fact, extracellular GTP binds its specific plasma membrane binding sites and induces signal transduction via [Ca2+]i increase. We demonstrate, for the first time, that extracellular GTP is able to modulate cell swelling in M1-CCD cortical collecting duct epithelial cells via upregulation of aquaporin 5 (AQP5 expression. Methods: We used videoimaging, immunocitochemistry, flow cytometry, confocal techniques, Western blotting and RT-PCR for protein and gene expression analysis, respectively. Results: We demonstrate that AQP5 mRNA is up-regulated 7 h after the GTP exposure in the cell culture medium, and its protein level is increased after 12-24 h. We show that AQP5 is targeted to the plasma membrane of M1-CCD cells, where it facilitates cell swelling, and that the GTP-dependent AQP5 up-regulation occurs via [Ca2+]i increase. Indeed, GTP induces both oscillating and transient [Ca2+]i increase, and specifically the oscillating kinetic appears to be responsible for blocking cell cycle in the S-phase while the [Ca2+]i influx, with whatever kinetic, seems to be responsible for inducing AQP5 expression. Conclusion: The role of GTP as a regulator of AQP5-mediated water transport in renal cells is of great importance in the physiology of renal epithelia, due to its possible physiopathological implications. GTP-dependent AQP5 expression could act as osmosensor. In addition, the data presented here suggest that GTP might play the same role in other tissues where rapid water transport is required for cell volume regulation and maintenance of the homeostasis.

  20. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-07-01

    This is the fourth quarterly report on a new study to develop a ceramic membrane/metal joint. The first experiments using the La-Sr-Fe-O ceramic are reported. Some of the analysis performed on the samples obtained are commented upon. A set of experiments to characterize the mechanical strength and thermal fatigue properties of the joints has been designed and begun. Finite element models of joints used to model residual stresses are described.

  1. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-08-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the previous research, the reference point of oxygen occupancy was determined and verified. In the current research, the oxygen occupancy was investigated at 1200 C as a function of oxygen activity and compared with that at 1000 C. The cause of bumps at about 200 C was also investigated by using different heating and cooling rates during TGA. The fracture toughness of LSFT and dual phase membranes at room temperature is an important mechanical property. Vicker's indentation method was used to evaluate this toughness. Through this technique, a K{sub Ic} (Mode-I Fracture Toughness) value is attained by means of semi-empirical correlations between the indentation load and the length of the cracks emanating from the corresponding Vickers indentation impression. In the present investigation, crack propagation behavior was extensively analyzed in order to understand the strengthening mechanisms involved in the non-transforming La based ceramic composites. Cracks were generated using Vicker's indenter and used to identify and evaluate the toughening mechanisms involved. Preliminary results of an electron microscopy study of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Modeling of the isotopic transients on operating membranes (LSCrF-2828 at 900 C) and a ''frozen'' isotope profile have been analyzed in conjunction with a 1-D model to reveal the gradient in oxygen diffusivity through the membrane under conditions of high chemical gradients.

  2. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-02-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. The in situ electrical conductivity and Seebeck coefficient measurements were made on LSFT at 1000 and 1200 C over the oxygen activity range from air to 10{sup -15} atm. The electrical conductivity measurements exhibited a p to n type transition at an oxygen activity of 1 x 10{sup -10} at 1000 C and 1 x 10{sup -6} at 1200 C. Thermogravimetric studies were also carried out over the same oxygen activities and temperatures. Based on the results of these measurements, the chemical and mechanical stability range of LSFT were determined and defect structure was established. The studies on the fracture toughness of the LSFT and dual phase membranes exposed to air and N{sub 2} at 1000 C was done and the XRD and SEM analysis of the specimens were carried out to understand the structural and microstructural changes. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affect the mechanical properties. A complete transformation of fracture behavior was observed in the N{sub 2} treated LSFT samples. Further results to investigate the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Recent results on transient kinetic data are presented. The 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model is used to study ''frozen'' profiles in patterned or composite membranes.

  3. Functional characterization of mouse urea transporters UT-A2 and UT-A3 expressed in purified Xenopus laevis oocyte plasma membranes.

    Science.gov (United States)

    Maciver, Bryce; Smith, Craig P; Hill, Warren G; Zeidel, Mark L

    2008-04-01

    Urea is a small solute synthesized by many terrestrial organisms as part of the catabolism of protein. In mammals it is transported across cellular membranes by specific urea transporter (UT) proteins that are the products of two separate, but closely related genes, referred to as UT-A and UT-B. Three major UT-A isoforms are found in the kidney, namely UT-A1, UT-A2, and UT-A3. UT-A2 is found in the thin, descending limb of the loop of Henle, whereas UT-A1 and UT-A3 are concentrated in the inner medullary collecting duct. UT-A2 and UT-A3 effectively represent two halves of the whole UT-A gene and, when joined together by 73 hydrophilic amino acids, constitute UT-A1. A biophysical characterization of mouse UT-A2 and UT-A3 was undertaken by expression in Xenopus laevis oocytes and subsequent preparation of highly enriched plasma membrane vesicles for use in stopped-flow fluorometry. Both isoforms were found to be highly specific for urea, and did not permeate water, ammonia, or other molecules closely related to urea (formamide, acetamide, methylurea, and dimethylurea). Single transporter flux rates of 46,000 +/- 10,000 and 59,000 +/- 15,000 (means +/- SE) urea molecules/s/channel for UT-A2 and UT-A3, respectively, were obtained. Overall, the UT-A2 and UT-A3 isoforms appear to have identical functional kinetics.

  4. Composite oxygen transport membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zigui; Plonczak, Pawel J.; Lane, Jonathan A.

    2016-11-08

    A method is described of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. Preferred materials are (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.7Fe.sub.0.3O.sub.3-.delta. for the porous fuel oxidation layer, (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer, and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.3Fe.sub.0.7O.sub.3-.delta. for the porous surface exchange layer. Firing the said fuel activation and separation layers in nitrogen atmosphere unexpectedly allows the separation layer to sinter into a fully densified mass.

  5. Molecular characterization of carnitine-dependent transport of acetyl-CoA from peroxisomes to mitochondria in Saccharomyces cerevisiae and identification of a plasma membrane carnitine transporter, Agp2p.

    Science.gov (United States)

    van Roermund, C W; Hettema, E H; van den Berg, M; Tabak, H F; Wanders, R J

    1999-11-01

    In Saccharomyces cerevisiae, beta-oxidation of fatty acids is confined to peroxisomes. The acetyl-CoA produced has to be transported from the peroxisomes via the cytoplasm to the mitochondrial matrix in order to be degraded to CO(2) and H(2)O. Two pathways for the transport of acetyl-CoA to the mitochondria have been proposed. The first involves peroxisomal conversion of acetyl-CoA into glyoxylate cycle intermediates followed by transport of these intermediates to the mitochondria. The second pathway involves peroxisomal conversion of acetyl-CoA into acetylcarnitine, which is subsequently transported to the mitochondria. Using a selective screen, we have isolated several mutants that are specifically affected in the second pathway, the carnitine-dependent acetyl-CoA transport from the peroxisomes to the mitochondria, and assigned these CDAT mutants to three different complementation groups. The corresponding genes were identified using functional complementation of the mutants with a genomic DNA library. In addition to the previously reported carnitine acetyl-CoA transferase (CAT2), we identified the genes for the yeast orthologue of the human mitochondrial carnitine acylcarnitine translocase (YOR100C or CAC) and for a transport protein (AGP2) required for carnitine transport across the plasma membrane.

  6. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham

    2006-12-31

    Ti doping on La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} (LSF) tends to increase the oxygen equilibration kinetics of LSF in lower oxygen activity environment because of the high valence state of Ti. However, the addition of Ti decreases the total conductivity because the acceptor ([Sr{prime}{sub La}]) is compensated by the donor ([Ti{sub Fe}{sup {sm_bullet}}]) which decreases the carrier concentration. The properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 1-x}Ti{sub x}O{sub 3-{delta}} (LSFT, x = 0.45) have been experimentally and theoretically investigated to elucidate (1) the dependence of oxygen occupancy and electrochemical properties on temperature and oxygen activity by thermogravimetric analysis (TGA) and (2) the electrical conductivity and carrier concentration by Seebeck coefficient and electrical measurements. In the present study, dual phase (La{sub 0.2}Sr{sub 0.8}Fe{sub 0.6}Ti{sub 0.4}O{sub 3-{delta}}/Ce{sub 0.9}Gd{sub 0.1}O{sub 2-{delta}}) membranes have been evaluated for structural properties such as hardness, fracture toughness and flexural strength. The effect of high temperature and slightly reducing atmosphere on the structural properties of the membranes was studied. The flexural strength of the membrane decreases upon exposure to slightly reducing conditions at 1000 C. The as-received and post-fractured membranes were characterized using XRD, SEM and TG-DTA to understand the fracture mechanisms. Changes in structural properties of the composite were sought to be correlated with the physiochemical features of the two-phases. We have reviewed the electrical conductivity data and stoichiometry data for La{sub 0.2}Sr{sub 0.8}Cr{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} some of which was reported previously. Electrical conductivity data for La{sub 0.2}Sr{sub 0.8}Cr{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCrF) were obtained in the temperature range, 752 {approx} 1055 C and in the pO{sub 2} range, 10{sup -18} {approx} 0.5 atm. The slope of the plot of log {sigma} vs

  7. Flow in a rotating membrane plasma separator.

    Science.gov (United States)

    Lueptow, R M; Hajiloo, A

    1995-01-01

    Rotating filter separators are very effective in the separation of plasma from whole blood, but details of the flow field in the device have not been investigated. The flow in a commercial device has been modeled computationally using the finite element code FIDAP. Taylor vortices appear in the upstream end of the annulus but disappear in the downstream end because of increasing blood viscosity as plasma is removed. Fluid transport at the upstream end of the annulus results from both translation of Taylor vortices and fluid winding around the vortices. If the inertial effects of the axial flow are reduced, less fluid winds around the vortices and more fluid is transported by the translation of the vortices. The pressure at the membrane is nonuniform in the region where vortices appear, although the relative magnitude of the fluctuations is small.

  8. Lipid organization of the plasma membrane

    NARCIS (Netherlands)

    Ingólfsson, Helgi I; Melo, Manuel N; van Eerden, Floris J; Arnarez, Clément; Lopez, Cesar A; Wassenaar, Tsjerk A; Periole, Xavier; de Vries, Alex H; Tieleman, D Peter; Marrink, Siewert J

    2014-01-01

    The detailed organization of cellular membranes remains rather elusive. Based on large-scale molecular dynamics simulations, we provide a high-resolution view of the lipid organization of a plasma membrane at an unprecedented level of complexity. Our plasma membrane model consists of 63 different

  9. Recycling from endosomes to the plasma membrane

    NARCIS (Netherlands)

    Dam, E.M. van

    2001-01-01

    Summary V Chapter?Summary Many membrane proteins are, after endocytic uptake, efficiently recycled back to the plasma membrane. The aim of the studies presented in this thesis was to determine pathways and molecular mechanisms that are involved in recycling. Plasma membrane-derived clathrin-coated v

  10. Recycling from endosomes to the plasma membrane

    NARCIS (Netherlands)

    Dam, E.M. van

    2001-01-01

    Summary V Chapter?Summary Many membrane proteins are, after endocytic uptake, efficiently recycled back to the plasma membrane. The aim of the studies presented in this thesis was to determine pathways and molecular mechanisms that are involved in recycling. Plasma membrane-derived clathrin-coated

  11. Lipid organization of the plasma membrane

    NARCIS (Netherlands)

    Ingólfsson, Helgi I; Melo, Manuel N; van Eerden, Floris J; Arnarez, Clément; Lopez, Cesar A; Wassenaar, Tsjerk A; Periole, Xavier; de Vries, Alex H; Tieleman, D Peter; Marrink, Siewert J

    2014-01-01

    The detailed organization of cellular membranes remains rather elusive. Based on large-scale molecular dynamics simulations, we provide a high-resolution view of the lipid organization of a plasma membrane at an unprecedented level of complexity. Our plasma membrane model consists of 63 different li

  12. Nod factor effects on root hair-specific transcriptome of Medicago truncatula: focus on plasma membrane transport systems and reactive oxygen species networks

    Directory of Open Access Journals (Sweden)

    Isabelle eDAMIANI

    2016-06-01

    Full Text Available Root hairs are involved in water and nutrient uptake, and thereby in plant autotrophy. In legumes, they also play a crucial role in establishment of rhizobial symbiosis. To obtain a holistic view of Medicago truncatula genes expressed in root hairs and of their regulation during the first hours of the engagement in rhizobial symbiotic interaction, a high throughput RNA sequencing on isolated root hairs from roots challenged or not with lipochitooligosaccharides Nod factors (NF for 4 h or 20 h was carried out. This provided a repertoire of genes displaying expression in root hairs, responding or not to NF and specific or not to legumes. In analyzing the transcriptome dataset, special attention was paid to pumps, transporters or channels active at the plasma membrane, to other proteins likely to play a role in nutrient ion uptake, NF electrical and calcium signaling, control of the redox status or the dynamic reprogramming of root hair transcriptome induced by NF treatment, and to the identification of papilionoid legume-specific genes expressed in root hairs. About 10 percent of the root hair expressed genes were significantly up- or down-regulated by NF treatment, suggesting their involvement in remodeling plant functions to allow establishment of the symbiotic relationship. For instance, NF-induced changes in expression of genes encoding plasma membrane transport systems or disease response proteins indicate that root hairs reduce their involvement in nutrient ion absorption and adapt their immune system in order to engage in the symbiotic interaction. It also appears that the redox status of root hair cells is tuned in response to NF perception. In addition, 1,176 genes that could be considered as papilionoid legume-specific were identified in the M. truncatula root hair transcriptome, from which 141 were found to possess an orthologue in every of the 6 legume genomes that we considered, suggesting their involvement in essential functions

  13. Nod Factor Effects on Root Hair-Specific Transcriptome of Medicago truncatula: Focus on Plasma Membrane Transport Systems and Reactive Oxygen Species Networks.

    Science.gov (United States)

    Damiani, Isabelle; Drain, Alice; Guichard, Marjorie; Balzergue, Sandrine; Boscari, Alexandre; Boyer, Jean-Christophe; Brunaud, Véronique; Cottaz, Sylvain; Rancurel, Corinne; Da Rocha, Martine; Fizames, Cécile; Fort, Sébastien; Gaillard, Isabelle; Maillol, Vincent; Danchin, Etienne G J; Rouached, Hatem; Samain, Eric; Su, Yan-Hua; Thouin, Julien; Touraine, Bruno; Puppo, Alain; Frachisse, Jean-Marie; Pauly, Nicolas; Sentenac, Hervé

    2016-01-01

    Root hairs are involved in water and nutrient uptake, and thereby in plant autotrophy. In legumes, they also play a crucial role in establishment of rhizobial symbiosis. To obtain a holistic view of Medicago truncatula genes expressed in root hairs and of their regulation during the first hours of the engagement in rhizobial symbiotic interaction, a high throughput RNA sequencing on isolated root hairs from roots challenged or not with lipochitooligosaccharides Nod factors (NF) for 4 or 20 h was carried out. This provided a repertoire of genes displaying expression in root hairs, responding or not to NF, and specific or not to legumes. In analyzing the transcriptome dataset, special attention was paid to pumps, transporters, or channels active at the plasma membrane, to other proteins likely to play a role in nutrient ion uptake, NF electrical and calcium signaling, control of the redox status or the dynamic reprogramming of root hair transcriptome induced by NF treatment, and to the identification of papilionoid legume-specific genes expressed in root hairs. About 10% of the root hair expressed genes were significantly up- or down-regulated by NF treatment, suggesting their involvement in remodeling plant functions to allow establishment of the symbiotic relationship. For instance, NF-induced changes in expression of genes encoding plasma membrane transport systems or disease response proteins indicate that root hairs reduce their involvement in nutrient ion absorption and adapt their immune system in order to engage in the symbiotic interaction. It also appears that the redox status of root hair cells is tuned in response to NF perception. In addition, 1176 genes that could be considered as "papilionoid legume-specific" were identified in the M. truncatula root hair transcriptome, from which 141 were found to possess an ortholog in every of the six legume genomes that we considered, suggesting their involvement in essential functions specific to legumes. This

  14. TRANSPORT OF BIOSYNTHETIC SPHINGOLIPIDS FROM GOLGI TO PLASMA-MEMBRANE IN HT29 CELLS - INVOLVEMENT OF DIFFERENT CARRIER VESICLE POPULATIONS

    NARCIS (Netherlands)

    BABIA, T; KOK, JW; VANDERHAAR, M; Kalicharan, Ruby; HOEKSTRA, D

    Intracellular transport of the sphingolipids glucosylceramide (GlcCer) and sphingomyelin (SM), was examined in HT29 human colon adenocarcinoma cells. After synthesis from a fluorescent precursor, 6-[N-(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]hexanoylceramide (C-6-NBD-Cer), transfer of SM from the

  15. Effect of vanadate on glucose transporter (GLUT4) intrinsic activity in skeletal muscle plasma membrane giant vesicles

    DEFF Research Database (Denmark)

    Kristiansen, S; Youn, J; Richter, Erik

    1996-01-01

    for 1.5 h with concentrations of vanadate ranging from 3 to 40 mmol l-1 at 34 degrees C before being used for determination of glucose transport. The dose-response curve showed that vanadate decreased the specific D-glucose uptake by a maximum of 70% compared with a control preparation. The vanadate...

  16. Nitrate transport in cucumber leaves is an inducible process involving an increase in plasma membrane H+-ATPase activity and abundance

    Directory of Open Access Journals (Sweden)

    Nikolic Miroslav

    2012-05-01

    Full Text Available Abstract Background The mechanisms by which nitrate is transported into the roots have been characterized both at physiological and molecular levels. It has been demonstrated that nitrate is taken up in an energy-dependent way by a four-component uptake machinery involving high- and low- affinity transport systems. In contrast very little is known about the physiology of nitrate transport towards different plant tissues and in particular at the leaf level. Results The mechanism of nitrate uptake in leaves of cucumber (Cucumis sativus L. cv. Chinese long plants was studied and compared with that of the root. Net nitrate uptake by roots of nitrate-depleted cucumber plants proved to be substrate-inducible and biphasic showing a saturable kinetics with a clear linear non saturable component at an anion concentration higher than 2 mM. Nitrate uptake by leaf discs of cucumber plants showed some similarities with that operating in the roots (e.g. electrogenic H+ dependence via involvement of proton pump, a certain degree of induction. However, it did not exhibit typical biphasic kinetics and was characterized by a higher Km with values out of the range usually recorded in roots of several different plant species. The quantity and activity of plasma membrane (PM H+-ATPase of the vesicles isolated from leaf tissues of nitrate-treated plants for 12 h (peak of nitrate foliar uptake rate increased with respect to that observed in the vesicles isolated from N-deprived control plants, thus suggesting an involvement of this enzyme in the leaf nitrate uptake process similar to that described in roots. Molecular analyses suggest the involvement of a specific isoform of PM H+-ATPase (CsHA1 and NRT2 transporter (CsNRT2 in root nitrate uptake. At the leaf level, nitrate treatment modulated the expression of CsHA2, highlighting a main putative role of this isogene in the process. Conclusions Obtained results provide for the first time evidence that a saturable

  17. Analysis of transcriptional regulation and tissue-specific expression of Avicennia marina Plasma Membrane Protein 3 suggests it contributes to Na(+) transport and homoeostasis in A. marina.

    Science.gov (United States)

    Chidambaram, Rajalakshmi; Venkataraman, Gayatri; Parida, Ajay

    2015-07-01

    Plasma membrane proteins (PMP3) play a role in cation homoeostasis. The 5' flanking sequence of stress inducible, Avicennia marina PMP3 (AmPMP3prom) was transcriptionally fused to (a) GUS or (b) GFP-AmPMP3 and analyzed in transgenic tobacco. Tissue-histochemical GUS and GFP:AmPMP3 localization are co-incident under basal and stress conditions. AmPMP3prom directed GUS activity is highest in roots. Basal transcription is conferred by a 388bp segment upstream of the translation start site. A 463bp distal enhancer in the AmPMP3prom confers enhanced expression under salinity in all tissues and also responds to increases in salinity. The effect of a central, stem-specific negative regulatory region is suppressed by the distal enhancer. The A. marina rhizosphere encounters dynamic changes in salinity at the inter-tidal interface. The complex, tissue-specific transcriptional responsiveness of AmPMP3 to salinity appears to have evolved in response to these changes. Under salinity, guard cell and phloem-specific expression of GFP:AmPMP3 is highly enhanced. Mesophyll, trichomes, bundle sheath, parenchymatous cortex and xylem parenchyma also show GFP:AmPMP3 expression. Cis-elements conferring stress, root and vascular-specific expression are enriched in the AmPMP3 promoter. Pronounced vascular-specific AmPMP3 expression suggests a role in salinity induced Na(+) transport, storage, and secretion in A. marina.

  18. Crystal structure of the plasma membrane proton pump

    DEFF Research Database (Denmark)

    Pedersen, Bjørn Panyella; Buch-Pedersen, Morten J; Morth, Jens Preben

    2007-01-01

    define the functional unit of ATP-coupled proton transport across the plasma membrane, and the structure is locked in a functional state not previously observed in P-type ATPases. The transmembrane domain reveals a large cavity, which is likely to be filled with water, located near the middle......A prerequisite for life is the ability to maintain electrochemical imbalances across biomembranes. In all eukaryotes the plasma membrane potential and secondary transport systems are energized by the activity of P-type ATPase membrane proteins: H+-ATPase (the proton pump) in plants and fungi 1, 2......, 3 , and Na+,K+-ATPase (the sodium–potassium pump) in animals 4 . The name P-type derives from the fact that these proteins exploit a phosphorylated reaction cycle intermediate of ATP hydrolysis 5 . The plasma membrane proton pumps belong to the type III P-type ATPase subfamily, whereas Na...

  19. Crystal structure of the plasma membrane proton pump

    DEFF Research Database (Denmark)

    Pedersen, Bjørn Panyella; Buch-Pedersen, Morten J; Morth, Jens Preben;

    2007-01-01

    A prerequisite for life is the ability to maintain electrochemical imbalances across biomembranes. In all eukaryotes the plasma membrane potential and secondary transport systems are energized by the activity of P-type ATPase membrane proteins: H+-ATPase (the proton pump) in plants and fungi 1, 2......, 3 , and Na+,K+-ATPase (the sodium–potassium pump) in animals 4 . The name P-type derives from the fact that these proteins exploit a phosphorylated reaction cycle intermediate of ATP hydrolysis 5 . The plasma membrane proton pumps belong to the type III P-type ATPase subfamily, whereas Na...... define the functional unit of ATP-coupled proton transport across the plasma membrane, and the structure is locked in a functional state not previously observed in P-type ATPases. The transmembrane domain reveals a large cavity, which is likely to be filled with water, located near the middle...

  20. Turbulent transport in magnetized plasmas

    CERN Document Server

    Horton, Wendell

    2012-01-01

    This book explains how magnetized plasmas self-organize in states of electromagnetic turbulence that transports particles and energy out of the core plasma faster than anticipated by the fusion scientists designing magnetic confinement systems in the 20th century. It describes theory, experiments and simulations in a unified and up-to-date presentation of the issues of achieving nuclear fusion power.

  1. Intermittent transport in edge plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, O.E.; Naulin, V.; Nielsen, A.H.; Juul Rasmussen, J. [Association EURATOM-Riso National Laboratory, Optics and Plasma Research, Roskilde (Denmark)

    2004-07-01

    The properties of low-frequency convective fluctuations and transport are investigated for the boundary region of magnetized plasmas. We employ a two-dimensional fluid model for the evolution of the global plasma quantities in a geometry and with parameters relevant to the scrape-off layer of confined toroidal plasmas. Strongly intermittent plasma transport is regulated by self-consistently generated sheared poloidal flows and is mediated by burst ejection of particles and heat from the bulk plasma in the form of blobs. Coarse grained probe signals reveal a highly skewed and flat distribution on short time scales, but tends towards a normal distribution at large time scales. Conditionally averaged signals are in perfect agreement with experimental measurements. (authors)

  2. The Role of Oxygen Partial Pressure in Controlling the Phase Composition of La1- x Sr x Co y Fe1- y O3- δ Oxygen Transport Membranes Manufactured by Means of Plasma Spray-Physical Vapor Deposition

    Science.gov (United States)

    Marcano, D.; Mauer, G.; Sohn, Y. J.; Vaßen, R.; Garcia-Fayos, J.; Serra, J. M.

    2016-04-01

    La0.58Sr0.4Co0.2Fe0.8O3 - δ (LSCF) deposited on a metallic porous support by plasma spray-physical vapor deposition is a promising candidate for oxygen-permeation membranes. Ionic transport properties are regarded to depend on the fraction of perovskite phase present in the membrane. However, during processing, the LSCF powder decomposes into perovskite and secondary phases. In order to improve the ionic transport properties of the membranes, spraying was carried out at different oxygen partial pressures p(O2). It was found that coatings deposited at lower and higher oxygen partial pressures consist of 70% cubic/26% rhombohedral and 61% cubic/35% rhombohedral perovskite phases, respectively. During annealing, the formation of non-perovskite phases is driven by oxygen non-stoichiometry. The amount of oxygen added during spraying can be used to increase the perovskite phase fraction and suppress the formation of non-perovskite phases.

  3. Very long-chain fatty acid-containing lipids rather than sphingolipids per se are required for raft association and stable surface transport of newly synthesized plasma membrane ATPase in yeast.

    Science.gov (United States)

    Gaigg, Barbara; Toulmay, Alexandre; Schneiter, Roger

    2006-11-10

    The proton-pumping H+-ATPase, Pma1p, is an abundant and very long lived polytopic protein of the yeast plasma membrane. Pma1p constitutes a major cargo of the secretory pathway and thus serves as a model to study plasma membrane biogenesis. Pma1p associates with detergent-resistant membrane domains (lipid "rafts") already in the ER, and a lack of raft association correlates with mistargeting of the protein to the vacuole, where it is degraded. We are analyzing the role of specific lipids in membrane domain formation and have previously shown that surface transport of Pma1p is independent of newly synthesized sterols but that sphingolipids with C26 very long chain fatty acid are crucial for raft association and surface transport of Pma1p (Gaigg, B., Timischl, B., Corbino, L., and Schneiter, R. (2005) J. Biol. Chem. 280, 22515-22522). We now describe a more detailed analysis of the function that sphingolipids play in this process. Using a yeast strain in which the essential function of sphingolipids is substituted by glycerophospholipids containing C26 very long chain fatty acids, we find that sphingolipids per se are dispensable for raft association and surface delivery of Pma1p but that the C26 fatty acid is crucial. We thus conclude that the essential function of sphingolipids for membrane domain formation and stable surface delivery of Pma1p is provided by the C26 fatty acid that forms part of the yeast ceramide.

  4. Membrane transport of hydrogen peroxide.

    Science.gov (United States)

    Bienert, Gerd P; Schjoerring, Jan K; Jahn, Thomas P

    2006-08-01

    Hydrogen peroxide (H2O2) belongs to the reactive oxygen species (ROS), known as oxidants that can react with various cellular targets thereby causing cell damage or even cell death. On the other hand, recent work has demonstrated that H2O2 also functions as a signalling molecule controlling different essential processes in plants and mammals. Because of these opposing functions the cellular level of H2O2 is likely to be subjected to tight regulation via processes involved in production, distribution and removal. Substantial progress has been made exploring the formation and scavenging of H2O2, whereas little is known about how this signal molecule is transported from its site of origin to the place of action or detoxification. From work in yeast and bacteria it is clear that the diffusion of H2O2 across membranes is limited. We have now obtained direct evidence that selected aquaporin homologues from plants and mammals have the capacity to channel H2O2 across membranes. The main focus of this review is (i) to summarize the most recent evidence for a signalling role of H2O2 in various pathways in plants and mammals and (ii) to discuss the relevance of specific transport of H2O2.

  5. Induction of nitrate uptake in maize roots: expression of a putative high-affinity nitrate transporter and plasma membrane H+-ATPase isoforms.

    Science.gov (United States)

    Santi, Simonetta; Locci, Geraldine; Monte, Rossella; Pinton, Roberto; Varanini, Zeno

    2003-08-01

    An investigation was carried out to assess the effect of nitrate supply on the root plasma membrane (PM) H+-ATPase of etiolated maize (Zea mays L.) seedlings grown in hydroponics. The treatment induced higher uptake rates of the anion and the expression of a putative high-affinity nitrate transporter gene (ZmNRT2.1), the first to be identified in maize. Root PM H+-ATPase activity displayed a similar time-course pattern as that of net nitrate uptake and investigations were carried out to determine which of the two isoforms reported to date in maize, MHA1 and 2, responded to the treatment. MHA1 was not expressed under the conditions analysed. Genome analysis revealed that MHA2, described as the most abundant form in all maize tissues, was not present in the maize hybrid investigated, but a similar form was found instead and named MHA3. A second gene (named MHA4) was also identified and partially sequenced. Both genes, classified as members of the PM H+-ATPase subfamily II, responded to nitrate supply, although to different degrees: MHA4, in particular, proved more sensitive than MHA3, with a greater up- and down-regulation in response to the treatment. Increased expression of subfamily II genes resulted in higher steady-state levels of the enzyme in the root tissues and enhanced ATP-hydrolysing activity. The results support the idea that greater proton-pumping activity is required when nitrate inflow increases and suggest that nitrate may be the signal triggering the expression of the two members of PM H+-ATPase subfamily II.

  6. Composite plasma polymerized sulfonated polystyrene membrane for PEMFC

    Energy Technology Data Exchange (ETDEWEB)

    Nath, Bhabesh Kumar; Khan, Aziz; Chutia, Joyanti, E-mail: jchutiaiasst@gmail.com

    2015-10-15

    Highlights: • Methyl methane sulfonate (MMS) is used as the sulfonating agent. • The proton conductivity of the membrane is found to be 0.141 S cm{sup −1}. • Power density of fuel cell with styrene/MMS membrane is 0.5 W cm{sup −2}. • The membrane exhibits thermal stability up to 140 °C. - Abstract: This work presents the introduction of an organic compound methyl methane sulfonate (MMS) for the first time in fabrication of polystyrene based proton exchange membrane (PEM) by plasma polymerization process. The membrane is fabricated by co-polymerizing styrene and MMS in capacitively coupled continuous RF plasma. The chemical composition of the plasma polymerized polymer membrane is investigated using Fourier Transform Infrared Spectroscopy which reveals the formation of composite structure of styrene and MMS. The surface morphology studied using AFM and SEM depicts the effect of higher partial pressure of MMS on surface topography of the membrane. The proton transport property of the membrane studied using electrochemical impedance spectroscopy shows the achievement of maximum proton conductivity of 0.141 S cm{sup −1} which is comparable to Nafion 117 membrane. Fuel cell performance test of the synthesized membrane shows a maximum power density of 500 mW cm{sup −2} and current density of 0.62 A cm{sup −2} at 0.6 V.

  7. Iontophoretic Transport Across a Multiple Membrane System

    OpenAIRE

    Molokhia, Sarah A.; Zhang, Yanhui; Higuchi, William I.; Li, S. Kevin

    2008-01-01

    The objective of the present study was to investigate the iontophoretic transport behavior across multiple membranes of different barrier properties. Spectra/Por® (SP) and Ionac membranes were the synthetic membranes and sclera was the biomembrane in this model study. The barrier properties of SP membranes were determined individually in passive and iontophoresis transport experiments with tetraethylammonium ion (TEA), chloride ion (Cl), and mannitol as the model permeants. Passive and iontop...

  8. Brain-derived neurotrophic factor (BDNF) enhances GABA transport by modulating the trafficking of GABA transporter-1 (GAT-1) from the plasma membrane of rat cortical astrocytes

    DEFF Research Database (Denmark)

    Vaz, Sandra H; Jørgensen, Trine Nygaard; Cristóvão-Ferreira, Sofia

    2011-01-01

    /MAPK pathway and requires active adenosine A(2A) receptors. Transport through GAT-3 is not affected by BDNF. To elucidate if BDNF affects trafficking of GAT-1 in astrocytes, we generated and infected astrocytes with a functional mutant of the rat GAT-1 (rGAT-1) in which the hemagglutinin (HA) epitope...

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

    Science.gov (United States)

    Mason, Kevin; Evans, Brian

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

  10. The dynamics of plant plasma membrane proteins: PINs and beyond.

    Science.gov (United States)

    Luschnig, Christian; Vert, Grégory

    2014-08-01

    Plants are permanently situated in a fixed location and thus are well adapted to sense and respond to environmental stimuli and developmental cues. At the cellular level, several of these responses require delicate adjustments that affect the activity and steady-state levels of plasma membrane proteins. These adjustments involve both vesicular transport to the plasma membrane and protein internalization via endocytic sorting. A substantial part of our current knowledge of plant plasma membrane protein sorting is based on studies of PIN-FORMED (PIN) auxin transport proteins, which are found at distinct plasma membrane domains and have been implicated in directional efflux of the plant hormone auxin. Here, we discuss the mechanisms involved in establishing such polar protein distributions, focusing on PINs and other key plant plasma membrane proteins, and we highlight the pathways that allow for dynamic adjustments in protein distribution and turnover, which together constitute a versatile framework that underlies the remarkable capabilities of plants to adjust growth and development in their ever-changing environment.

  11. Catalyst containing oxygen transport membrane

    Science.gov (United States)

    Christie, Gervase Maxwell; Wilson, Jamie Robyn; van Hassel, Bart Antonie

    2012-12-04

    A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a high average pore diameter and the intermediate porous layer has a lower permeability and lower pore diameter than the porous support layer. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

  12. Catalyst containing oxygen transport membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lane, Jonathan A.; Wilson, Jamie R.; Christie, Gervase Maxwell; Petigny, Nathalie; Sarantopoulos, Christos

    2017-02-07

    A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a microstructure exhibiting substantially uniform pore size distribution as a result of using PMMA pore forming materials or a bi-modal particle size distribution of the porous support layer materials. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

  13. Giant plasma membrane vesicles: models for understanding membrane organization.

    Science.gov (United States)

    Levental, Kandice R; Levental, Ilya

    2015-01-01

    The organization of eukaryotic membranes into functional domains continues to fascinate and puzzle cell biologists and biophysicists. The lipid raft hypothesis proposes that collective lipid interactions compartmentalize the membrane into coexisting liquid domains that are central to membrane physiology. This hypothesis has proven controversial because such structures cannot be directly visualized in live cells by light microscopy. The recent observations of liquid-liquid phase separation in biological membranes are an important validation of the raft hypothesis and enable application of the experimental toolbox of membrane physics to a biologically complex phase-separated membrane. This review addresses the role of giant plasma membrane vesicles (GPMVs) in refining the raft hypothesis and expands on the application of GPMVs as an experimental model to answer some of key outstanding problems in membrane biology. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Membrane Transporters as Mediators of Cisplatin Effects and Side Effects

    Directory of Open Access Journals (Sweden)

    Giuliano Ciarimboli

    2012-01-01

    Full Text Available Transporters are important mediators of specific cellular uptake and thus, not only for effects, but also for side effects, metabolism, and excretion of many drugs such as cisplatin. Cisplatin is a potent cytostatic drug, whose use is limited by its severe acute and chronic nephro-, oto-, and peripheral neurotoxicity. For this reason, other platinum derivatives, such as carboplatin and oxaliplatin, with less toxicity but still with antitumoral action have been developed. Several transporters, which are expressed on the cell membranes, have been associated with cisplatin transport across the plasma membrane and across the cell: the copper transporter 1 (Ctr1, the copper transporter 2 (Ctr2, the P-type copper-transporting ATPases ATP7A and ATP7B, the organic cation transporter 2 (OCT2, and the multidrug extrusion transporter 1 (MATE1. Some of these transporters are also able to accept other platinum derivatives as substrate. Since membrane transporters display a specific tissue distribution, they can be important molecules that mediate the entry of platinum derivatives in target and also nontarget cells possibly mediating specific effects and side effects of the chemotherapeutic drug. This paper summarizes the literature on toxicities of cisplatin compared to that of carboplatin and oxaliplatin and the interaction of these platinum derivatives with membrane transporters.

  15. Endomembrane Cation Transporters and Membrane Trafficking

    Energy Technology Data Exchange (ETDEWEB)

    Sze, Heven [Univ. of Maryland, College Park, MD (United States). Dept. of Cell Biology & Molecular Genetics

    2017-04-01

    Multicellular, as well as unicellular, organisms have evolved mechanisms to regulate ion and pH homeostasis in response to developmental cues and to a changing environment. The working hypothesis is that the balance of fluxes mediated by diverse transporters at the plasma membrane and in subcellular organelles determines ionic cellular distribution, which is critical for maintenance of membrane potential, pH control, osmolality, transport of nutrients, and protein activity. An emerging theme in plant cell biology is that cells respond and adapt to diverse cues through changes of the dynamic endomembrane system. Yet we know very little about the transporters that might influence the operation of the secretory system in plants. Here we focus on transporters that influence alkali cation and pH homeostasis, mainly in the endomembrane/ secretory system. The endomembrane system of eukaryote cells serves several major functions: i) sort cargo (e.g. enzymes, transporters or receptors) to specific destinations, ii) modulate the protein and lipid composition of membrane domains through remodeling, and iii) determine and alter the properties of the cell wall through synthesis and remodeling. We had uncovered a novel family of predicted cation/H+ exchangers (CHX) and K+ efflux antiporters (KEA) that are prevalent in higher plants, but rare in metazoans. We combined phylogenetic and transcriptomic analyses with molecular genetic, cell biological and biochemical studies, and have published the first reports on functions of plant CHXs and KEAs. CHX studied to date act at the endomembrane system where their actions are distinct from the better-studied NHX (Na/K-H+ exchangers). Arabidopsis thaliana CHX20 in guard cells modulate stomatal opening, and thus is significant for vegetative survival. Other CHXs ensure reproductive success on dry land, as they participate in organizing pollen walls, targeting of pollen tubes to the ovule or promoting

  16. Activity assay of membrane transport proteins

    Institute of Scientific and Technical Information of China (English)

    Hao Xie

    2008-01-01

    Membrane transport proteins are integral membrane proteins and considered as potential drug targets. Activity assay of transport proteins is essential for developing drugs to target these proteins. Major issues related to activity assessment of transport proteins include availability of transporters,transport activity of transporters, and interactions between ligands and transporters. Researchers need to consider the physiological status of proteins (bound in lipid membranes or purified), availability and specificity of substrates, and the purpose of the activity assay (screening, identifying, or comparing substrates and inhibitors) before choosing appropriate assay strategies and techniques. Transport proteins bound in vesicular membranes can be assayed for transporting substrate across membranes by means of uptake assay or entrance counterflow assay. Alternatively, transport proteins can be assayed for interactions with ligands by using techniques such as isothermal titration calorimetry, nuclear magnetic resonance spectroscopy, or surface plasmon resonance. Other methods and techniques such as fluorometry, scintillation proximity assay, electrophysiological assay, or stopped-flow assay could also be used for activity assay of transport proteins. In this paper the major strategies and techniques for activity assessment of membrane transport proteins are reviewed.

  17. The N-terminal region of organic anion transporting polypeptide 1B3 (OATP1B3) plays an essential role in regulating its plasma membrane trafficking.

    Science.gov (United States)

    Chun, Se-Eun; Thakkar, Nilay; Oh, Yunseok; Park, Ji Eun; Han, Songhee; Ryoo, Gongmi; Hahn, Hyunggu; Maeng, Sang Hyun; Lim, Young-Ran; Han, Byung Woo; Lee, Wooin

    2017-05-01

    Organic anion transporting polypeptide 1B3 (OATP1B3) is a major influx transporter mediating the hepatic uptake of various endogenous substrates as well as clinically important drugs such as statins and anticancer drugs. However, molecular mechanisms controlling the membrane trafficking of OATP1B3 have been largely unknown. Several reports recently indicated the presence of a distinct, cancer-type OATP1B3 variant lacking the N-terminal 28 amino acids compared to OATP1B3 expressed in non-malignant hepatocytes. Interestingly, the cancer-type OATP1B3 variant is located predominantly in the cytoplasm, implicating the involvement of the N-terminal region of OATP1B3 in its membrane trafficking. In the current study, we set out to experimentally validate the importance of the N-terminal region of OATP1B3 and to identify responsible sequence motif(s) in that region. A number of truncation or point mutants of OATP1B3 were transiently expressed in HEK293T, HCT-8 or MDCK II cells and their expression in cytoplasmic and surface membrane fractions were analyzed by immunoblotting. Our results indicated that the N-terminal sequence of OATP1B3, in particular, at the amino acid positions between 12 and 28, may be indispensable in its membrane trafficking. Moreover, our results using a fusion construct indicated that the first 50 amino acids of OATP1B3 are sufficient for its membrane localization. The importance of the N-terminal region in membranous localization was shared among the other OATP1B subfamily members, OATP1B1 and rat Oatp1b2. Our efforts to identify the responsible amino acid(s) or structure motif(s) in the N-terminal region did not pinpoint individual amino acids or motifs with putative secondary structures. Our current findings however demonstrate that the N-terminal region is important for the membrane localization of the OATP1B subfamily members and should facilitate future investigations of the mechanisms involved in the regulation and membrane trafficking of

  18. Reverse-osmosis membranes by plasma polymerization

    Science.gov (United States)

    Hollahan, J. R.; Wydeven, T.

    1972-01-01

    Thin allyl amine polymer films were developed using plasma polymerization. Resulting dry composite membranes effectively reject sodium chloride during reverse osmosis. Films are 98% sodium chloride rejective, and 46% urea rejective.

  19. Paracrine signaling through plasma membrane hemichannels

    National Research Council Canada - National Science Library

    Wang, Nan; De Bock, Marijke; Decrock, Elke; Bol, Mélissa; Gadicherla, Ashish; Vinken, Mathieu; Rogiers, Vera; Bukauskas, Feliksas F; Bultynck, Geert; Leybaert, Luc

    2013-01-01

    Plasma membrane hemichannels composed of connexin (Cx) proteins are essential components of gap junction channels but accumulating evidence suggests functions of hemichannels beyond the communication provided by junctional channels...

  20. Proteomics and the dynamic plasma membrane

    DEFF Research Database (Denmark)

    Sprenger, Richard R; Jensen, Ole Nørregaard

    2010-01-01

    plasma membrane is of particular interest, by not only serving as a barrier between the "cell interior" and the external environment, but moreover by organizing and clustering essential components to enable dynamic responses to internal and external stimuli. Defining and characterizing the dynamic plasma...... membrane proteome is crucial for understanding fundamental biological processes, disease mechanisms and for finding drug targets. Protein identification, characterization of dynamic PTMs and protein-ligand interactions, and determination of transient changes in protein expression and composition are among...... the challenges in functional proteomic studies of the plasma membrane. We review the recent progress in MS-based plasma membrane proteomics by presenting key examples from eukaryotic systems, including mammals, yeast and plants. We highlight the importance of enrichment and quantification technologies required...

  1. Role of zinc in plasma membrane function

    National Research Council Canada - National Science Library

    O'Dell, B L

    2000-01-01

    ... with a posttranslational change in plasma membrane proteins. Among the signs of zinc deficiency in rats is a bleeding tendency associated with failure of platelet aggregation, a phenomenon that correlates with impaired uptake of Ca(2+) when stimulated...

  2. Localization of the ATP-binding cassette (ABC transport proteins PfMRP1, PfMRP2, and PfMDR5 at the Plasmodium falciparum plasma membrane

    Directory of Open Access Journals (Sweden)

    Luty Adrian JF

    2009-08-01

    Full Text Available Abstract Background The spread of drug resistance has been a major obstacle to the control of malaria. The mechanisms underlying drug resistance in malaria seem to be complex and multigenic. The current literature on multiple drug resistance against anti-malarials has documented PfMDR1, an ATP-binding cassette (ABC protein, as an important determinant of resistance. In the Plasmodium falciparum genome, there are several ABC transporters some of which could be putative drug transporting proteins. In order to understand the molecular mechanisms underlying drug resistance, characterization of these transporters is essential. The aim of this study was to characterize and localize putative ABC transporters. Methods In the plasmoDB database, 16 members of the P. falciparum ABC family can be identified, 11 of which are putative transport proteins. A phylogenetic analysis of the aligned NBDs of the PfABC genes was performed. Antibodies against PfMRP1 (PfABCC1, PfMRP2 (PfABCC2, and PfMDR5 (PfABCB5 were generated, affinity purified and used in immunocytochemistry to localize the proteins in the asexual stages of the parasite. Results The ABC family members of P. falciparum were categorized into subfamilies. The ABC B subfamily was the largest and contained seven members. Other family members that could be involved in drug transport are PfABCC1, PfABCC2, PfABCG1, and PfABCI3. The expression and localization of three ABC transport proteins was determined. PfMRP1, PfMRP2, and PfMDR5 are localized to the plasma membrane in all asexual stages of the parasite. Conclusion In conclusion, 11 of the 16 ABC proteins in the P. falciparum genome are putative transport proteins, some of which might be involved in drug resistance. Moreover, it was demonstrated that three of these proteins are expressed on the parasite's plasma membrane.

  3. Stability properties of elementary dynamic models of membrane transport.

    Science.gov (United States)

    Hernández, Julio A

    2003-01-01

    Living cells are characterized by their capacity to maintain a stable steady state. For instance, cells are able to conserve their volume, internal ionic composition and electrical potential difference across the plasma membrane within values compatible with the overall cell functions. The dynamics of these cellular variables is described by complex integrated models of membrane transport. Some clues for the understanding of the processes involved in global cellular homeostasis may be obtained by the study of the local stability properties of some partial cellular processes. As an example of this approach, I perform, in this study, the neighborhood stability analysis of some elementary integrated models of membrane transport. In essence, the models describe the rate of change of the intracellular concentration of a ligand subject to active and passive transport across the plasma membrane of an ideal cell. The ligand can be ionic or nonionic, and it can affect the cell volume or the plasma membrane potential. The fundamental finding of this study is that, within the physiological range, the steady states are asymptotically stable. This basic property is a necessary consequence of the general forms of the expressions employed to describe the active and passive fluxes of the transported ligand.

  4. Ion transport membrane module and vessel system

    Science.gov (United States)

    Stein, VanEric Edward; Carolan, Michael Francis; Chen, Christopher M.; Armstrong, Phillip Andrew; Wahle, Harold W.; Ohrn, Theodore R.; Kneidel, Kurt E.; Rackers, Keith Gerard; Blake, James Erik; Nataraj, Shankar; van Doorn, Rene Hendrik Elias; Wilson, Merrill Anderson

    2008-02-26

    An ion transport membrane system comprising (a) a pressure vessel having an interior, an exterior, an inlet, and an outlet; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region, wherein any inlet and any outlet of the pressure vessel are in flow communication with exterior regions of the membrane modules; and (c) one or more gas manifolds in flow communication with interior regions of the membrane modules and with the exterior of the pressure vessel.The ion transport membrane system may be utilized in a gas separation device to recover oxygen from an oxygen-containing gas or as an oxidation reactor to oxidize compounds in a feed gas stream by oxygen permeated through the mixed metal oxide ceramic material of the membrane modules.

  5. Analysis of pedestal plasma transport

    Energy Technology Data Exchange (ETDEWEB)

    Callen, J. D. [University of Wisconsin, Madison; Groebner, R. [General Atomics, San Diego; Osborne, T.H. [General Atomics, San Diego; Canik, John [ORNL; Owen, Larry W [ORNL; Pankin, A. Y. [Lehigh University, Bethlehem, PA; Rafiq, T. [Lehigh University, Bethlehem, PA; Rognlien, T. D. [Lawrence Livermore National Laboratory (LLNL); Stacey, W. M. [Georgia Institute of Technology

    2010-01-01

    An H-mode edge pedestal plasma transport benchmarking exercise was undertaken for a single DIII-D pedestal. Transport modelling codes used include 1.5D interpretive (ONETWO, GTEDGE), 1.5D predictive (ASTRA) and 2D ones (SOLPS, UEDGE). The particular DIII-D discharge considered is 98889, which has a typical low density pedestal. Profiles for the edge plasma are obtained from Thomson and charge-exchange recombination data averaged over the last 20% of the average 33.53 ms repetition time between type I edge localized modes. The modelled density of recycled neutrals is largest in the divertor X-point region and causes the edge plasma source rate to vary by a factor similar to 10(2) on the separatrix. Modelled poloidal variations in the densities and temperatures on flux surfaces are small on all flux surfaces up to within about 2.6 mm (rho(N) > 0.99) of the mid-plane separatrix. For the assumed Fick's-diffusion-type laws, the radial heat and density fluxes vary poloidally by factors of 2-3 in the pedestal region; they are largest on the outboard mid-plane where flux surfaces are compressed and local radial gradients are largest. Convective heat flows are found to be small fractions of the electron (less than or similar to 10%) and ion (less than or similar to 25%) heat flows in this pedestal. Appropriately averaging the transport fluxes yields interpretive 1.5D effective diffusivities that are smallest near the mid-point of the pedestal. Their 'transport barrier' minima are about 0.3 (electron heat), 0.15 (ion heat) and 0.035 (density) m(2) s(-1). Electron heat transport is found to be best characterized by electron-temperature-gradient-induced transport at the pedestal top and paleoclassical transport throughout the pedestal. The effective ion heat diffusivity in the pedestal has a different profile from the neoclassical prediction and may be smaller than it. The very small effective density diffusivity may be the result of an inward pinch flow nearly

  6. The transporter SynPAM71 is located in the plasma membrane and thylakoids, and mediates manganese tolerance in Synechocystis PCC6803

    DEFF Research Database (Denmark)

    Gandini, Chiara; Schmidt, Sidsel Birkelund; Husted, Søren

    2017-01-01

    symptoms were observed in WT cells exposed to excess Mn. Moreover, CyanoP, which is involved in the early steps of PSII assembly, is massively upregulated in ΔSynPAM71. SynPAM71 was detected in both the plasma membrane and, to a lesser extent, the thylakoid membranes. Our results suggest that SynPAM71...... to chloroplast Mn homeostasis in Arabidopsis thaliana. Here, we characterize the function of its homolog in Synechocystis (SynPAM71). We used a loss-of-function line (ΔSynPAM71), wild-type (WT) cells exposed to Mn stress and strains expressing a tagged variant of SynPAM71 to characterize the role of SynPAM71...... in cyanobacterial Mn homeostasis. The ΔSynPAM71 strain displays an Mn-sensitive phenotype with reduced levels of chlorophyll and PSI accumulation, defects in PSII photochemistry and intracellular Mn enrichment, particularly in the thylakoid membranes. These effects are attributable to Mn toxicity, as very similar...

  7. Ceramic oxygen transport membrane array reactor and reforming method

    Science.gov (United States)

    Kelly, Sean M.; Christie, Gervase Maxwell; Robinson, Charles; Wilson, Jamie R.; Gonzalez, Javier E.; Doraswami, Uttam R.

    2016-11-08

    The invention relates to a commercially viable modular ceramic oxygen transport membrane reforming reactor configured using repeating assemblies of oxygen transport membrane tubes and catalytic reforming reactors.

  8. Ceramic oxygen transport membrane array reactor and reforming method

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Sean M.; Christie, Gervase Maxwell; Robinson, Charles; Wilson, Jamie R.; Gonzalez, Javier E.; Doraswami, Uttam R.

    2016-11-08

    The invention relates to a commercially viable modular ceramic oxygen transport membrane reforming reactor configured using repeating assemblies of oxygen transport membrane tubes and catalytic reforming reactors.

  9. Liners for ion transport membrane systems

    Science.gov (United States)

    Carolan, Michael Francis; Miller, Christopher Francis

    2010-08-10

    Ion transport membrane system comprising (a) a pressure vessel comprising an interior, an exterior, an inlet, an inlet conduit, an outlet, and an outlet conduit; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region, wherein the inlet and the outlet of the pressure vessel are in flow communication with exterior regions of the membrane modules; (c) a gas manifold having an interior surface wherein the gas manifold is in flow communication with the interior region of each of the planar ion transport membrane modules and with the exterior of the pressure vessel; and (d) a liner disposed within any of the inlet conduit, the outlet conduit, and the interior surface of the gas manifold.

  10. Transport and sorting of membrane lipids

    NARCIS (Netherlands)

    van Meer, G.|info:eu-repo/dai/nl/068570368

    1993-01-01

    The lipid composition of cellular membranes may seem unnecessarily complex. However, the lipid composition of each membrane is carefully regulated by local metabolism and specificity in transport, marking the functional significance for the cell. Recent research has revealed unexpected discoveries c

  11. Membrane transporters and new drug development

    Institute of Scientific and Technical Information of China (English)

    EndoH

    2002-01-01

    Molecular biology has made it possible to identify membrane transporter molecules that transport hydrophilic endogenous and exogenous compounds across cellular membranes.Ther are two possibilities on transporters relevant to new drug development,drug targets and pharmacokinetics.Human genome database predicts that more than 10% of common diseases may be tightly related with membrane transporter dysfunction.Thus,membrane transporters would be possible molecular targets for new drug development.As an example,I will talk on our discovery of L-type amino acid transporter 1(LAT1) being oncofetal and upregulated in cancers for their rapid growth and metastasis.We provide evidence that inhibition of LAT1 functions may become novel types of anticancer tools.As another example in human pharmacokinetics,application of stable expressing cell lines of human drug transporters will be proposed including organic anion and cation transporters which are distributed in various organs including the liver and kidney.These transporters are multispecific in their substrate recognition,and better molecules to anticipate drug-drug interactions in human bodies before new drug candidates are given in clinical trials.This in vitro technique may contribute to decide suitable compounds in particular by high throughout screening strategy.

  12. Differential Activity of Plasma and Vacuolar Membrane Transporters Contributes to Genotypic Differences in Salinity Tolerance in a Halophyte Species, Chenopodium quinoa

    Directory of Open Access Journals (Sweden)

    Edgar Bonales-Alatorre

    2013-04-01

    Full Text Available Halophytes species can be used as a highly convenient model system to reveal key ionic and molecular mechanisms that confer salinity tolerance in plants. Earlier, we reported that quinoa (Chenopodium quinoa Willd., a facultative C3 halophyte species, can efficiently control the activity of slow (SV and fast (FV tonoplast channels to match specific growth conditions by ensuring that most of accumulated Na+ is safely locked in the vacuole (Bonales-Alatorre et al. (2013 Plant Physiology. This work extends these finding by comparing the properties of tonoplast FV and SV channels in two quinoa genotypes contrasting in their salinity tolerance. The work is complemented by studies of the kinetics of net ion fluxes across the plasma membrane of quinoa leaf mesophyll tissue. Our results suggest that multiple mechanisms contribute towards genotypic differences in salinity tolerance in quinoa. These include: (i a higher rate of Na+ exclusion from leaf mesophyll; (ii maintenance of low cytosolic Na+ levels; (iii better K+ retention in the leaf mesophyll; (iv a high rate of H+ pumping, which increases the ability of mesophyll cells to restore their membrane potential; and (v the ability to reduce the activity of SV and FV channels under saline conditions. These mechanisms appear to be highly orchestrated, thus enabling the remarkable overall salinity tolerance of quinoa species.

  13. Differential activity of plasma and vacuolar membrane transporters contributes to genotypic differences in salinity tolerance in a Halophyte Species, Chenopodium quinoa.

    Science.gov (United States)

    Bonales-Alatorre, Edgar; Pottosin, Igor; Shabala, Lana; Chen, Zhong-Hua; Zeng, Fanrong; Jacobsen, Sven-Erik; Shabala, Sergey

    2013-04-29

    Halophytes species can be used as a highly convenient model system to reveal key ionic and molecular mechanisms that confer salinity tolerance in plants. Earlier, we reported that quinoa (Chenopodium quinoa Willd.), a facultative C3 halophyte species, can efficiently control the activity of slow (SV) and fast (FV) tonoplast channels to match specific growth conditions by ensuring that most of accumulated Na+ is safely locked in the vacuole (Bonales-Alatorre et al. (2013) Plant Physiology). This work extends these finding by comparing the properties of tonoplast FV and SV channels in two quinoa genotypes contrasting in their salinity tolerance. The work is complemented by studies of the kinetics of net ion fluxes across the plasma membrane of quinoa leaf mesophyll tissue. Our results suggest that multiple mechanisms contribute towards genotypic differences in salinity tolerance in quinoa. These include: (i) a higher rate of Na+ exclusion from leaf mesophyll; (ii) maintenance of low cytosolic Na+ levels; (iii) better K+ retention in the leaf mesophyll; (iv) a high rate of H+ pumping, which increases the ability of mesophyll cells to restore their membrane potential; and (v) the ability to reduce the activity of SV and FV channels under saline conditions. These mechanisms appear to be highly orchestrated, thus enabling the remarkable overall salinity tolerance of quinoa species.

  14. Fundamental aspects of plasma chemical physics transport

    CERN Document Server

    Capitelli, Mario; Laricchiuta, Annarita

    2013-01-01

    Fundamental Aspects of Plasma Chemical Physics: Tranpsort develops basic and advanced concepts of plasma transport to the modern treatment of the Chapman-Enskog method for the solution of the Boltzmann transport equation. The book invites the reader to consider actual problems of the transport of thermal plasmas with particular attention to the derivation of diffusion- and viscosity-type transport cross sections, stressing the role of resonant charge-exchange processes in affecting the diffusion-type collision calculation of viscosity-type collision integrals. A wide range of topics is then discussed including (1) the effect of non-equilibrium vibrational distributions on the transport of vibrational energy, (2) the role of electronically excited states in the transport properties of thermal plasmas, (3) the dependence of transport properties on the multitude of Saha equations for multi-temperature plasmas, and (4) the effect of the magnetic field on transport properties. Throughout the book, worked examples ...

  15. Plasma membrane regulates Ras signaling networks.

    Science.gov (United States)

    Chavan, Tanmay Sanjeev; Muratcioglu, Serena; Marszalek, Richard; Jang, Hyunbum; Keskin, Ozlem; Gursoy, Attila; Nussinov, Ruth; Gaponenko, Vadim

    2015-01-01

    Ras GTPases activate more than 20 signaling pathways, regulating such essential cellular functions as proliferation, survival, and migration. How Ras proteins control their signaling diversity is still a mystery. Several pieces of evidence suggest that the plasma membrane plays a critical role. Among these are: (1) selective recruitment of Ras and its effectors to particular localities allowing access to Ras regulators and effectors; (2) specific membrane-induced conformational changes promoting Ras functional diversity; and (3) oligomerization of membrane-anchored Ras to recruit and activate Raf. Taken together, the membrane does not only attract and retain Ras but also is a key regulator of Ras signaling. This can already be gleaned from the large variability in the sequences of Ras membrane targeting domains, suggesting that localization, environment and orientation are important factors in optimizing the function of Ras isoforms.

  16. Arabidopsis TWISTED DWARF1 functionally interacts with Auxin Exporter ABCB1 on the root plasma membrane

    DEFF Research Database (Denmark)

    Wang, Bangjun; Bailly, Aurélien; Zwiewka, Marta

    2013-01-01

    Plant architecture is influenced by the polar, cell-to-cell transport of auxin that is primarily provided and regulated by plasma membrane efflux catalysts of the PIN-FORMED and B family of ABC transporter (ABCB) classes. The latter were shown to require the functionality of the FK506 binding...... assays, we demonstrate a predominant lateral, mainly outward-facing, plasma membrane location for TWD1 in the root epidermis characterized by the lateral marker ABC transporter G36/PLEIOTROPIC DRUG-RESISTANCE8/PENETRATION3. At these epidermal plasma membrane domains, TWD1 colocalizes with nonpolar ABCB1....... In planta bioluminescence resonance energy transfer analysis was used to verify specific ABC transporter B1 (ABCB1)-TWD1 interaction. Our data support a model in which TWD1 promotes lateral ABCB-mediated auxin efflux via protein-protein interaction at the plasma membrane, minimizing reflux from the root...

  17. Lithium transport across biological membranes

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H

    1990-01-01

    Li+ is actively transported out of cells, and across different epithelia of both mammalian and amphibian origin. Due to the low affinity of the Na+/K(+)-ATPase for Li+, the transport is most likely energized by exchange and/or cotransport processes. The detailed mechanism by which Li+ is reabsorb...

  18. Microcompartments within the yeast plasma membrane.

    Science.gov (United States)

    Merzendorfer, Hans; Heinisch, Jürgen J

    2013-02-01

    Recent research in cell biology makes it increasingly clear that the classical concept of compartmentation of eukaryotic cells into different organelles performing distinct functions has to be extended by microcompartmentation, i.e., the dynamic interaction of proteins, sugars, and lipids at a suborganellar level, which contributes significantly to a proper physiology. As different membrane compartments (MCs) have been described in the yeast plasma membrane, such as those defined by Can1 and Pma1 (MCCs and MCPs), Saccharomyces cerevisiae can serve as a model organism, which is amenable to genetic, biochemical, and microscopic studies. In this review, we compare the specialized microcompartment of the yeast bud neck with other plasma membrane substructures, focusing on eisosomes, cell wall integrity-sensing units, and chitin-synthesizing complexes. Together, they ensure a proper cell division at the end of mitosis, an intricately regulated process, which is essential for the survival and proliferation not only of fungal, but of all eukaryotic cells.

  19. RNAi-mediated downregulation of poplar plasma membrane intrinsic proteins (PIPs) changes plasma membrane proteome composition and affects leaf physiology.

    Science.gov (United States)

    Bi, Zhen; Merl-Pham, Juliane; Uehlein, Norbert; Zimmer, Ina; Mühlhans, Stefanie; Aichler, Michaela; Walch, Axel Karl; Kaldenhoff, Ralf; Palme, Klaus; Schnitzler, Jörg-Peter; Block, Katja

    2015-10-14

    Plasma membrane intrinsic proteins (PIPs) are one subfamily of aquaporins that mediate the transmembrane transport of water. To reveal their function in poplar, we generated transgenic poplar plants in which the translation of PIP genes was downregulated by RNA interference investigated these plants with a comprehensive leaf plasma membrane proteome and physiome analysis. First, inhibition of PIP synthesis strongly altered the leaf plasma membrane protein composition. Strikingly, several signaling components and transporters involved in the regulation of stomatal movement were differentially regulated in transgenic poplars. Furthermore, hormonal crosstalk related to abscisic acid, auxin and brassinosteroids was altered, in addition to cell wall biosynthesis/cutinization, the organization of cellular structures and membrane trafficking. A physiological analysis confirmed the proteomic results. The leaves had wider opened stomata and higher net CO2 assimilation and transpiration rates as well as greater mesophyll conductance for CO2 (gm) and leaf hydraulic conductance (Kleaf). Based on these results, we conclude that PIP proteins not only play essential roles in whole leaf water and CO2 flux but have important roles in the regulation of stomatal movement.

  20. Plasma deposited fluorinated films on porous membranes

    Energy Technology Data Exchange (ETDEWEB)

    Gancarz, Irena [Department of Polymer and Carbon Materials, Wrocław University of Technology, 50-370 Wrocław (Poland); Bryjak, Marek, E-mail: marek.bryjak@pwr.edu.pl [Department of Polymer and Carbon Materials, Wrocław University of Technology, 50-370 Wrocław (Poland); Kujawski, Jan; Wolska, Joanna [Department of Polymer and Carbon Materials, Wrocław University of Technology, 50-370 Wrocław (Poland); Kujawa, Joanna; Kujawski, Wojciech [Nicolaus Copernicus University, Faculty of Chemistry, 7 Gagarina St., 87-100 Torun (Poland)

    2015-02-01

    75 KHz plasma was used to modify track etched poly(ethylene terephthalate) membranes and deposit on them flouropolymers. Two fluorine bearing monomers were used: perflourohexane and hexafluorobenzene. The modified surfaces were analyzed by means of attenuated total reflection infra-red spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and wettability. It was detected that hexaflourobenxene deposited to the larger extent than perflourohaxane did. The roughness of surfaces decreased when more fluoropolymer was deposited. The hydrophobic character of surface slightly disappeared during 20-days storage of hexaflourobenzene modified membrane. Perfluorohexane modified membrane did not change its character within 120 days after modification. It was expected that this phenomenon resulted from post-reactions of oxygen with radicals in polymer deposits. The obtained membranes could be used for membrane distillation of juices. - Highlights: • Plasma deposited hydrophobic layer of flouropolymers. • Deposition degree affects the surface properties. • Hydrohilization of surface due to reaction of oxygen with entrapped radicals. • Possibility to use modified porous membrane for water distillation and apple juice concentration.

  1. Understanding transport in model water desalination membranes

    Science.gov (United States)

    Chan, Edwin

    Polyamide based thin film composites represent the the state-of-the-art nanofiltration and reverse osmosis membranes used in water desalination. The performance of these membranes is enabled by the ultrathin (~100 nm) crosslinked polyamide film in facilitating the selective transport of water over salt ions. While these materials have been refined over the last several decades, understanding the relationships between polyamide structure and membrane performance remains a challenge because of the complex and heterogeneous nature of the polyamide film. In this contribution, we present our approach to addressing this challenge by studying the transport properties of model polyamide membranes synthesized via molecular layer-by-layer (mLbL) assembly. First, we demonstrate that mLbL can successfully construct polyamide membranes with well-defined nanoscale thickness and roughness using a variety of monomer formulations. Next, we present measurement tools for characterizing the network structure and transport of these model polyamide membranes. Specifically, we used X-ray and neutron scattering techniques to characterize their structure as well as a recently-developed indentation based poromechanics approach to extrapolate their water diffusion coefficient. Finally, we illustrate how these measurements can provide insight into the original problem by linking the key polyamide network properties, i.e. water-polyamide interaction parameter and characteristic network mesh size, to the membrane performance.

  2. [Kinetics of inhibitory effect of calix[4]arene C-90 on activity of transporting plasma membrane Ca2+, Mg2+-ATPase of smooth muscle cells].

    Science.gov (United States)

    Veklich, T O; Shkrabak, O A; Mazur, Iu Iu; Rodik, R V; Kal'chenko, V I; Kosterin, S O

    2014-01-01

    In experiments on the suspension of myometrium cell plasma membrane, processed by 0.1% digitonin, the inhibitory action of calix[4]arene C-90 (5,11,17,23-tetra(threeftor)methyl(phenilsulphonilimino)-methylamino-25,26,27,28-tetrapropoxy-calix[4]arene) on the activity of Ca2+,Mg2+-ATPase was investigated. The authors also examined the influence of calix[4]arene in different concentration on affinity of enzyme (Ca2,Mg2+-ATPase) for the ATP and ions of Mg and Ca, and its influence on cooperative effect and maximum velocity of ATP hydrolysis. It is shown that calix[4]arene does not influence the affinity of Ca2+,Mg2+-ATPase for the ATP, which means that these two compounds have different binding centers. Also calix[4]arene has no influence on affinity and cooperative effect of Ca ions, if it is used in concentration lower than 50 μM. Calix[4]arene slightly increases coefficient of Ca2+,Mg2+-ATPase activation by magnesium chloride. In all three cases, where ATP, Mg and Ca ions are used to test the impact of calix[4]arene, maximum velocity of ATP hydrolysis significantly decreases. All these results clarify that calix[4]arene implements its inhibitory action through mechanism of uncompetitive inhibition of Ca2+,Mg2+-ATPase activity.

  3. Polyene antibiotic that inhibits membrane transport proteins

    NARCIS (Netherlands)

    Te Welscher, Y.M.; van Leeuwen, M.R.; de Kruijff, B.; Dijksterhuis, J.; Breukink, E.

    2012-01-01

    The limited therapeutic arsenal and the increase in reports of fungal resistance to multiple antifungal agents have made fungal infections a major therapeutic challenge. The polyene antibiotics are the only group of antifungal antibiotics that directly target the plasma membrane via a specific inter

  4. Monitoring Transport Across Modified Nanoporous Alumina Membranes

    Directory of Open Access Journals (Sweden)

    Erich D. Steinle

    2007-11-01

    Full Text Available This paper describes the use of several characterization methods to examinealumina nanotubule membranes that have been modified with specific silanes. The functionof these silanes is to alter the transport properties through the membrane by changing thelocal environment inside the alumina nanotube. The presence of alkyl groups, either long(C18 or short and branched (isopropyl hydrocarbon chains, on these silanes significantlydecreases the rate of transport of permeant molecules through membranes containingalumina nanotubes as monitored via absorbance spectroscopy. The presence of an ionicsurfactant can alter the polarity of these modified nanotubes, which correlates to anincreased transport of ions. Fluorescent spectroscopy is also utilized to enhance thesensitivity of detecting these permeant molecules. Confirmation of the alkylsilaneattachment to the alumina membrane is achieved with traditional infrared spectroscopy,which can also examine the lifetime of the modified membrane. The physical parameters ofthese silane-modified porous alumina membranes are studied via scanning electronmicroscopy. The alumina nanotubes are not physically closed off or capped by the silanesthat are attached to the alumina surfaces.

  5. An overview of membrane transport proteins in Saccharomyces cerevisiae.

    Science.gov (United States)

    Andre, B

    1995-12-01

    All eukaryotic cells contain a wide variety of proteins embedded in the plasma and internal membranes, which ensure transmembrane solute transport. It is now established that a large proportion of these transport proteins can be grouped into families apparently conserved throughout organisms. This article presents the data of an in silicio analysis aimed at establishing a preliminary classification of membrane transport proteins in Saccharomyces cerevisiae. This analysis was conducted at a time when about 65% of all yeast genes were available in public databases. In addition to approximately 60 transport proteins whose function was at least partially known, approximately 100 deduced protein sequences of unknown function display significant sequence similarity to membrane transport proteins characterized in yeast and/or other organisms. While some protein families have been well characterized by classical genetic experimental approaches, others have largely if not totally escaped characterization. The proteins revealed by this in silicio analysis also include a putative K+ channel, proteins similar to aquaporins of plant and animal origin, proteins similar to Na+-solute symporters, a protein very similar to electroneural cation-chloride cotransporters, and a putative Na+-H+ antiporter. A new research area is anticipated: the functional analysis of many transport proteins whose existence was revealed by genome sequencing.

  6. Uterine receptivity and the plasma membrane transformation

    Institute of Scientific and Technical Information of China (English)

    Christopher R MURPHY

    2004-01-01

    This review begins with a brief commentary on the diversity of placentation mechanisms, and then goes on to examine the extensive alterations which occur in the plasma membrane of uterine epithelial cells during early pregnancy across species. Ultrastructural, biochemical and more general morphological data reveal that strikingly common phenomena occur in this plasma membrane during early pregnancy despite the diversity of placental types-from epitheliochorial to hemochorial, which ultimately form in different species. To encapsulate the concept that common morphological and molecular alterations occur across species, that they are found basolaterally as well as apically, and that moreover they are an ongoing process during much of early pregnancy, not just an event at the time attachment,brane during early pregnancy are key to uterine receptivity.

  7. Inside job: ligand-receptor pharmacology beneath the plasma membrane.

    Science.gov (United States)

    Babcock, Joseph J; Li, Min

    2013-07-01

    Most drugs acting on the cell surface receptors are membrane permeable and thus able to engage their target proteins in different subcellular compartments. However, these drugs' effects on cell surface receptors have historically been studied on the plasma membrane alone. Increasing evidence suggests that small molecules may also modulate their targeted receptors through membrane trafficking or organelle-localized signaling inside the cell. These additional modes of interaction have been reported for functionally diverse ligands of GPCRs, ion channels, and transporters. Such intracellular drug-target engagements affect cell surface expression. Concurrent intracellular and cell surface signaling may also increase the complexity and therapeutic opportunities of small molecule modulation. Here we discuss examples of ligand-receptor interactions that are present in both intra- and extracellular sites, and the potential therapeutic opportunities presented by this phenomenon.

  8. Inside job: ligand-receptor pharmacology beneath the plasma membrane

    Institute of Scientific and Technical Information of China (English)

    Joseph J BABCOCK; Min LI

    2013-01-01

    Most drugs acting on the cell surface receptors are membrane permeable and thus able to engage their target proteins in different subcellular compartments.However,these drugs' effects on cell surface receptors have historically been studied on the plasma membrane alone.Increasing evidence suggests that small molecules may also modulate their targeted receptors through membrane trafficking or organelle-localized signaling inside the cell.These additional modes of interaction have been reported for functionally diverse ligands of GPCRs,ion channels,and transporters.Such intracellular drug-target engagements affect cell surface expression.Concurrent intracellular and cell surface signaling may also increase the complexity and therapeutic opportunities of small molecule modulation.Here we discuss examples of ligand-receptor interactions that are present in both intra- and extracellular sites,and the potential therapeutic opportunities presented by this phenomenon.

  9. Nondiffusive plasma transport at tokamak edge

    Science.gov (United States)

    Krasheninnikov, S. I.

    2000-10-01

    Recent findings show that cross field edge plasma transport at tokamak edge does not necessarily obey a simple diffusive law [1], the only type of a transport model applied so far in the macroscopic modeling of edge plasma transport. Cross field edge transport is more likely due to plasma filamentation with a ballistic motion of the filaments towards the first wall. Moreover, it so fast that plasma recycles on the main chamber first wall rather than to flow into divertor as conventional picture of edge plasma fluxes suggests. Crudely speaking particle recycling wise diverted tokamak operates in a limiter regime due to fast anomalous non-diffusive cross field plasma transport. Obviously that this newly found feature of edge plasma anomalous transport can significantly alter a design of any future reactor relevant tokamaks. Here we present a simple model describing the motion of the filaments in the scrape off layer and discuss it implications for experimental observations. [1] M. Umansky, S. I. Krasheninnikov, B. LaBombard, B. Lipschultz, and J. L. Terry, Phys. Plasmas 6 (1999) 2791; M. Umansky, S. I. Krasheninnikov, B. LaBombard and J. L. Terry, Phys. Plasmas 5 (1998) 3373.

  10. Transport processes of the legume symbiosome membrane

    Directory of Open Access Journals (Sweden)

    Victoria C Clarke

    2014-12-01

    Full Text Available The symbiosome membrane (SM is a physical barrier between the host plant and nitrogen-fixing bacteria in the legume-rhizobium symbiosis, and represents a regulated interface for the movement of solutes between the symbionts that is under plant control. The primary nutrient exchange across the SM is the transport of a carbon energy source from plant to bacteroid in exchange for fixed nitrogen. At a biochemical level two channels have been implicated in movement of fixed nitrogen across the SM and a uniporter that transports monovalent dicarboxylate ions has been characterized that would transport fixed carbon. The aquaporin NOD26 may provide a channel for ammonia, but the genes encoding the other transporters have not been identified. Transport of several other solutes, including calcium and potassium, have been demonstrated in isolated symbiosomes, and genes encoding transport systems for the movement of iron, nitrate, sulfate and zinc in nodules have been identified. However, definitively matching transport activities with these genes has proved difficult and many further transport processes are expected on the SM to facilitate the movement of nutrients between the symbionts. Recently, work detailing the SM proteome in soybean has been completed, contributing significantly to the database of known SM proteins. This represents a valuable resource for the identification of transporter protein candidates, some of which may correspond to transport processes previously described, or to novel transport systems in the symbiosis. Putative transporters identified from the proteome include homologues of transporters of sulfate, calcium, peptides and various metal ions. Here we review current knowledge of transport processes of the SM and discuss the requirements for additional transport routes of other nutrients exchanged in the symbiosis, with a focus on transport systems identified through the soybean SM proteome.

  11. Existence and characteristics of nitrate reductase in plasma membrane of maize roots

    Institute of Scientific and Technical Information of China (English)

    陈珈; 王学臣

    1995-01-01

    The existence and characteristics of nitrate reductase (NR) have been investigated with microsomes and purified plasma membrane vesicles (RV and IV) from the primary root tips of maize (Zea mays L.). An integral membrane protein capable of reducing nitrate is presented in the plasma membrane which is obviously different from the soluble cytoplasmic NR in respect of NO3- induction and Triton X-100 activation Plasma membrane-bound NR did not have direct coupling relationship with the transmembrane H-transport, however, it could inhibit the electron transmission from NADH to K3[Fe(CN)6]. The possible action mode of plasma membrane redox system that the membrane-bound NR is involved in is discussed.

  12. Modulation of Erythrocyte Plasma Membrane Redox System Activity by Curcumin

    Directory of Open Access Journals (Sweden)

    Prabhakar Singh

    2016-01-01

    Full Text Available Plasma membrane redox system (PMRS is an electron transport chain system ubiquitously present throughout all cell types. It transfers electron from intracellular substrates to extracellular acceptors for regulation of redox status. Curcumin, isolated from Curcuma longa, has modulatory effects on cellular physiology due to its membrane interaction ability and antioxidant potential. The present study investigates the effect of curcumin on PMRS activity of erythrocytes isolated from Wistar rats in vitro and in vivo and validated through an in silico docking simulation study using Molegro Virtual Docker (MVD. Effects of curcumin were also evaluated on level of glutathione (GSH and the oxidant potential of plasma measured in terms of plasma ferric equivalent oxidative potentials (PFEOP. Results show that curcumin significantly (p<0.01 downregulated the PMRS activity in a dose-dependent manner. Molecular docking results suggest that curcumin interacts with amino acids at the active site cavity of cytochrome b5 reductase, a key constituent of PMRS. Curcumin also increased the GSH level in erythrocytes and plasma while simultaneously decreasing the oxidant potential (PFEOP of plasma. Altered PMRS activity and redox status are associated with the pathophysiology of several health complications including aging and diabetes; hence, the above finding may explain part of the role of curcumin in health beneficial effects.

  13. Development of stable oxygen transport membranes

    NARCIS (Netherlands)

    Donkelaar, ten S.F.P.

    2015-01-01

    Chapter 1 provides an introduction of relevant developments in the field of oxygen transport membranes, and presents the aims of the work described in this thesis. In Chapter 2, the development of a versatile one-pot auto-combustion method for the synthesis of powders of the perovskite oxide titani

  14. Labeling the plasma membrane with TMA-DPH.

    Science.gov (United States)

    Chazotte, Brad

    2011-05-01

    INTRODUCTION TMA-DPH (trimethylamine-diphenylhexatriene) is a fluorescent membrane probe that has classically been used to label the outer leaflet of a membrane bilayer, to label the outer leaflet of the plasma membrane in cells, and to report on membrane dynamics using the techniques of fluorescence polarization and/or fluorescence lifetime. This probe has also been used to follow exocytosis and endocytosis of labeled plasma membranes. The interaction of the aqueous environment with mitochondrial inner membrane dynamics has also been studied following the fluorescence polarization and the lifetime of TMA-DPH. This protocol describes the use of TMA-DPH to label the plasma membrane.

  15. Cholesterol transport in model membranes

    Science.gov (United States)

    Garg, Sumit; Porcar, Lionel; Butler, Paul; Perez-Salas, Ursula

    2010-03-01

    Physiological processes distribute cholesterol unevenly within the cell. The levels of cholesterol are maintained by intracellular transport and a disruption in the cell's ability to keep these normal levels will lead to disease. Exchange rates of cholesterol are generally studied in model systems using labeled lipid vesicles. Initially donor vesicles have all the cholesterol and acceptor vesicles are devoid of it. They are mixed and after some time the vesicles are separated and cholesterol is traced in each vesicle. The studies performed up to date have significant scatter indicating that the methodologies are not consistent. The present work shows in-situ Time-Resolved SANS studies of cholesterol exchange rates in unsaturated PC lipid vesicles. Molecular dynamics simulations were done to investigate the energetic and kinetic behavior of cholesterol in this system. This synergistic approach will provide insight into our efforts to understand cholesterol traffic.

  16. Perturbative Transport Studies in Fusion Plasmas

    NARCIS (Netherlands)

    Cardozo, N. J. L.

    1995-01-01

    Studies of transport in fusion plasmas using perturbations of an equilibrium state reviewed. Essential differences between steady-state and perturbative transport studies are pointed out. Important transport issues that can be addressed with perturbative experiments are identified as: (i) Are the tr

  17. Advanced Hydrogen Transport Membrane for Coal Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Joseph [Praxair, Inc., Tonawanda, NY (United States); Porter, Jason [Colorado School of Mines, Golden, CO (United States); Patki, Neil [Colorado School of Mines, Golden, CO (United States); Kelley, Madison [Colorado School of Mines, Golden, CO (United States); Stanislowski, Josh [Univ. of North Dakota, Grand Forks, ND (United States); Tolbert, Scott [Univ. of North Dakota, Grand Forks, ND (United States); Way, J. Douglas [Colorado School of Mines, Golden, CO (United States); Makuch, David [Praxair, Inc., Tonawanda, NY (United States)

    2015-12-23

    A pilot-scale hydrogen transport membrane (HTM) separator was built that incorporated 98 membranes that were each 24 inches long. This separator used an advanced design to minimize the impact of concentration polarization and separated over 1000 scfh of hydrogen from a hydrogen-nitrogen feed of 5000 scfh that contained 30% hydrogen. This mixture was chosen because it was representative of the hydrogen concentration expected in coal gasification. When tested with an operating gasifier, the hydrogen concentration was lower and contaminants in the syngas adversely impacted membrane performance. All 98 membranes survived the test, but flux was lower than expected. Improved ceramic substrates were produced that have small surface pores to enable membrane production and large pores in the bulk of the substrate to allow high flux. Pd-Au was chosen as the membrane alloy because of its resistance to sulfur contamination and good flux. Processes were developed to produce a large quantity of long membranes for use in the demonstration test.

  18. Interaction between La(III) and proteins on the plasma membrane of horseradish

    Science.gov (United States)

    Yang, Guang-Mei; Chu, Yun-Xia; Lv, Xiao-Fen; Zhou, Qing; Huang, Xiao-Hua

    2012-06-01

    Lanthanum (La) is an important rare earth element in the ecological environment of plant. The proteins on the plasma membrane control the transport of molecules into and out of cell. It is very important to investigate the effect of La(III) on the proteins on the plasma membrane in the plant cell. In the present work, the interaction between La(III) and proteins on the plasma membrane of horseradish was investigated using optimization of the fluorescence microscopy and fluorescence spectroscopy. It is found that the fluorescence of the complex system of protoplasts and 1-aniline Kenai-8-sulfonic acid in horseradish treated with the low concentration of La(III) is increased compared with that of the control horseradish. The opposite effect is observed in horseradish treated with the high concentration of La(III). These results indicated that the low concentration of La(III) can interact with the proteins on the plasma membrane of horseradish, causing the improvement in the structure of proteins on the plasma membrane. The high concentration of La(III) can also interact with the proteins on the plasma membrane of horseradish, leading to the destruction of the structure of proteins on the plasma membrane. We demonstrate that the proteins on the plasma membrane are the targets of La(III) action on plant cell.

  19. Response of plasma membrane H+-ATPase in rice (Oryza sativa) seedlings to simulated acid rain.

    Science.gov (United States)

    Liang, Chanjuan; Ge, Yuqing; Su, Lei; Bu, Jinjin

    2015-01-01

    Understanding the adaptation of plants to acid rain is important to find feasible approaches to alleviate such damage to plants. We studied effects of acid rain on plasma membrane H(+)-ATPase activity and transcription, intracellular H(+), membrane permeability, photosynthetic efficiency, and relative growth rate during stress and recovery periods. Simulated acid rain at pH 5.5 did not affect plasma membrane H(+)-ATPase activity, intracellular H(+), membrane permeability, photosynthetic efficiency, and relative growth rate. Plasma membrane H(+)-ATPase activity and transcription in leaves treated with acid rain at pH 3.5 was increased to maintain ion homeostasis by transporting excessive H(+) out of cells. Then intracellular H(+) was close to the control after a 5-day recovery, alleviating damage on membrane and sustaining photosynthetic efficiency and growth. Simulated acid rain at pH 2.5 inhibited plasma membrane H(+)-ATPase activity by decreasing the expression of H(+)-ATPase at transcription level, resulting in membrane damage and abnormal intracellular H(+), and reduction in photosynthetic efficiency and relative growth rate. After a 5-day recovery, all parameters in leaves treated with pH 2.5 acid rain show alleviated damage, implying that the increased plasma membrane H(+)-ATPase activity and its high expression were involved in repairing process in acid rain-stressed plants. Our study suggests that plasma membrane H(+)-ATPase can play a role in adaptation to acid rain for rice seedlings.

  20. Transport properties of inertial confinement fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Issanova, M.K.; Kodanova, S.K.; Ramazanov, T.S. [IETP, Al-Farabi Kazakh National University, Almaty (Kazakhstan); Hoffmann, D.H.H. [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany)

    2016-06-15

    In this paper the transport properties of non-isothermal dense deuterium-tritium plasmas were studied. Based on the effective interaction potentials between particles, the Coulomb logarithm for a two-temperature nonisothermal dense plasma was obtained. These potentials take into consideration long-range multi-particle screening effects and short-range quantum-mechanical effects in two-temperature plasmas. Transport processes in such plasmas were studied using the Coulomb logarithm. The obtained results were compared with the theoretical works of other authors and with the results of molecular dynamics simulations. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Topography and functional information of plasma membrane

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12―40 nm for their diameter and 0.7―2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their

  2. Topography and functional information of plasma membrane

    Institute of Scientific and Technical Information of China (English)

    SUN DeLan; CHEN JianMin; SONG YanMei; ZHU ChuanFeng; PAN GeBo; WAN LiJun

    2008-01-01

    By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasta from winter wheat mesophyll cells were observed, and compared with dead protoplssts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasta was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasta were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased.The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 200 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12 to 40 nm. The diameter of mid-sized protein particles was between 40-60 nm,and a range of 1.8-5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12-40 nm for their diameter and 0.7-2.2 nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplsst. Distributlon density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we

  3. Cellular membrane collapse by atmospheric-pressure plasma jet

    Science.gov (United States)

    Kim, Kangil; Jun Ahn, Hak; Lee, Jae-Hyeok; Kim, Jae-Ho; Sik Yang, Sang; Lee, Jong-Soo

    2014-01-01

    Cellular membrane dysfunction caused by air plasma in cancer cells has been studied to exploit atmospheric-pressure plasma jets for cancer therapy. Here, we report that plasma jet treatment of cervical cancer HeLa cells increased electrical conductivity across the cellular lipid membrane and caused simultaneous lipid oxidation and cellular membrane collapse. We made this finding by employing a self-manufactured microelectrode chip. Furthermore, increased roughness of the cellular lipid membrane and sequential collapse of the membrane were observed by atomic force microscopy following plasma jet treatment. These results suggest that the cellular membrane catastrophe occurs via coincident altered electrical conductivity, lipid oxidation, and membrane roughening caused by an atmospheric-pressure plasma jet, possibly resulting in cellular vulnerability to reactive species generated from the plasma as well as cytotoxicity to cancer cells.

  4. Cellular membrane collapse by atmospheric-pressure plasma jet

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kangil; Sik Yang, Sang, E-mail: jsjlee@ajou.ac.kr, E-mail: ssyang@ajou.ac.kr [Department of Electrical and Computer Engineering, Ajou University, Suwon 443-749 (Korea, Republic of); Jun Ahn, Hak; Lee, Jong-Soo, E-mail: jsjlee@ajou.ac.kr, E-mail: ssyang@ajou.ac.kr [Department of Biological Sciences, Ajou University, Suwon 443-749 (Korea, Republic of); Lee, Jae-Hyeok; Kim, Jae-Ho [Department of Molecular Science and Technology, Ajou University, Suwon 443-749 (Korea, Republic of)

    2014-01-06

    Cellular membrane dysfunction caused by air plasma in cancer cells has been studied to exploit atmospheric-pressure plasma jets for cancer therapy. Here, we report that plasma jet treatment of cervical cancer HeLa cells increased electrical conductivity across the cellular lipid membrane and caused simultaneous lipid oxidation and cellular membrane collapse. We made this finding by employing a self-manufactured microelectrode chip. Furthermore, increased roughness of the cellular lipid membrane and sequential collapse of the membrane were observed by atomic force microscopy following plasma jet treatment. These results suggest that the cellular membrane catastrophe occurs via coincident altered electrical conductivity, lipid oxidation, and membrane roughening caused by an atmospheric-pressure plasma jet, possibly resulting in cellular vulnerability to reactive species generated from the plasma as well as cytotoxicity to cancer cells.

  5. The plasma membrane redox system: a candidate source of aging-related oxidative stress

    OpenAIRE

    de Grey, Aubrey D. N. J

    2005-01-01

    The plasma membrane redox system (PMRS) is an electron transport chain in the plasma membrane that transfers electrons from either intra- or extracellular donors to extracellular acceptors. Unlike the superoxide-generating NADPH oxidase of phagocytes and the homologous (but much less active) enzymes found in some other cells, the PMRS is still incompletely characterised at the molecular level. Much is known, however, concerning its function and affinity for both physiological and non-physiolo...

  6. TonB-dependent outer membrane transport: going for Baroque?

    Science.gov (United States)

    Wiener, Michael C

    2005-08-01

    The import of essential organometallic micronutrients (such as iron-siderophores and vitamin B(12)) across the outer membrane of Gram-negative bacteria proceeds via TonB-dependent outer membrane transporters (TBDTs). The TBDT couples to the TonB protein, which is part of a multiprotein complex in the plasma (inner) membrane. Five crystal structures of TBDTs illustrate clearly the architecture of the protein in energy-independent substrate-free and substrate-bound states. In each of the TBDT structures, an N-terminal hatch (or plug or cork) domain occludes the lumen of a 22-stranded beta barrel. The manner by which substrate passes through the transporter (the "hatch-barrel problem") is currently unknown. Solution NMR and X-ray crystallographic structures of various TonB domains indicate a striking structural plasticity of this protein. Thermodynamic, biochemical and bacteriological studies of TonB and TBDTs indicate further that existing structures do not yet capture critical energy-dependent and in vivo conformations of the transport cycle. The reconciliation of structural and non-structural experimental data, and the unambiguous experimental elucidation of a detailed molecular mechanism of transport are current challenges for this field.

  7. Microdomains of SNARE proteins in the plasma membrane

    NARCIS (Netherlands)

    Bogaart, G. van den; Lang, T.; Jahn, R.

    2013-01-01

    Exocytosis is catalyzed by the engagement of SNARE proteins embedded in the plasma membrane with complementary SNAREs in the membrane of trafficking vesicles undergoing exocytosis. In most cells studied so far, SNAREs are not randomly distributed across the plasma membrane but are clustered and

  8. Nanoclustering as a dominant feature of plasma membrane organization

    NARCIS (Netherlands)

    Garcia-Parajo, M.F.; Cambi, A.; Torreno-Pina, J.A.; Thompson, N.; Jacobson, K.

    2014-01-01

    Early studies have revealed that some mammalian plasma membrane proteins exist in small nanoclusters. The advent of super-resolution microscopy has corroborated and extended this picture, and led to the suggestion that many, if not most, membrane proteins are clustered at the plasma membrane at

  9. Neobiosynthesis of glycosphingolipids by plasma membrane-associated glycosyltransferases.

    Science.gov (United States)

    Crespo, Pilar M; Demichelis, Vanina Torres; Daniotti, José L

    2010-09-17

    Gangliosides, complex glycosphingolipids containing sialic acids, are synthesized in the endoplasmic reticulum and in the Golgi complex. These neobiosynthesized gangliosides move via vesicular transport to the plasma membrane, becoming components of the external leaflet. Gangliosides can undergo endocytosis followed by recycling to the cell surface or sorting to the Golgi complex or lysosomes for remodeling and catabolism. Recently, glycosphingolipid catabolic enzymes (glycohydrolases) have been found to be associated with the plasma membrane, where they display activity on the membrane components. In this work, we demonstrated that ecto-ganglioside glycosyltransferases may catalyze ganglioside synthesis outside the Golgi compartment, particularly at the cell surface. Specifically, we report the first direct evidence of expression and activity of CMP-NeuAc:GM3 sialyltransferase (Sial-T2) at the cell surface of epithelial and melanoma cells, with membrane-integrated ecto-Sial-T2 being able to sialylate endogenously synthesized GM3 ganglioside as well as exogenously incorporated substrate. Interestingly, we also showed that ecto-Sial-T2 was able to synthesize GD3 ganglioside at the cell surface using the endogenously synthesized cytidine monophospho-N-acetylneuraminic acid (CMP-NeuAc) available at the extracellular milieu. In addition, the expression of UDP-GalNAc:LacCer/GM3/GD3 N-acetylgalactosaminyltransferase (GalNAc-T) was also detected at the cell surface of epithelial cells, whose catalytic activity was only observed after feeding the cells with exogenous GM3 substrate. Thus, the relative interplay between the plasma membrane-associated glycosyltransferase and glycohydrolase activities, even when acting on a common substrate, emerges as a potential level of regulation of the local glycosphingolipid composition in response to different external and internal stimuli.

  10. Ceramic oxygen transport membrane array reactor and reforming method

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Sean M.; Christie, Gervase Maxwell; Rosen, Lee J.; Robinson, Charles; Wilson, Jamie R.; Gonzalez, Javier E.; Doraswami, Uttam R.

    2016-09-27

    A commercially viable modular ceramic oxygen transport membrane reforming reactor for producing a synthesis gas that improves the thermal coupling of reactively-driven oxygen transport membrane tubes and catalyst reforming tubes required to efficiently and effectively produce synthesis gas.

  11. Transport through track etched polymeric blend membrane

    Indian Academy of Sciences (India)

    Kamlendra Awasthi; Vaibhav Kulshreshtha; B Tripathi; N K Acharya; M Singh; Y K Vijay

    2006-06-01

    Polymer blends of polycarbonate (PC) and polysulphone (PSF) having thickness, 27 m, are prepared by solution cast method. The transport properties of pores in a blend membrane are examined. The pores were produced in this membrane by a track etching technique. For this purpose, a thin polymer membrane was penetrated by a single heavy ion of Ni7+ of 100 MeV, followed by preferential chemical etching of the ion track. Ion permeation measurements show that pores in polymeric membrane are charged or neutralized, which depends upon the variation in concentration of the solvent. The – curve at concentration, N/10, shows that the pores are negatively charged, whereas at concentration, N/20, the linear nature of – curve indicates that the pores approach towards neutralized state and on further concentration, N/40, the pores become fully neutralized, consequently the rectifier behaviour of pores has been omitted. The gas permeability of hydrogen and carbon dioxide of this membrane was measured with increasing etching time. The permeability was measured from both the sides. Permeability at the front was larger than the permeability at the back which shows asymmetric behaviour of membranes.

  12. Regulation of Plasma Membrane Recycling by CFTR

    Science.gov (United States)

    Bradbury, Neil A.; Jilling, Tamas; Berta, Gabor; Sorscher, Eric J.; Bridges, Robert J.; Kirk, Kevin L.

    1992-04-01

    The gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) is defective in patients with cystic fibrosis. Although the protein product of the CFTR gene has been proposed to function as a chloride ion channel, certain aspects of its function remain unclear. The role of CFTR in the adenosine 3',5'-monophosphate (cAMP)-dependent regulation of plasma membrane recycling was examined. Adenosine 3',5'-monophosphate is known to regulate endocytosis and exocytosis in chloride-secreting epithelial cells that express CFTR. However, mutant epithelial cells derived from a patient with cystic fibrosis exhibited no cAMP-dependent regulation of endocytosis and exocytosis until they were transfected with complementary DNA encoding wild-type CFTR. Thus, CFTR is critical for cAMP-dependent regulation of membrane recycling in epithelial tissues, and this function of CFTR could explain in part the pleiotropic nature of cystic fibrosis.

  13. The mitochondria-plasma membrane contact site.

    Science.gov (United States)

    Westermann, Benedikt

    2015-08-01

    Mitochondria are dynamic organelles that are highly motile and frequently fuse and divide. It has recently become clear that their complex behavior is governed to a large extent by interactions with other cellular structures. This review will focus on a mitochondria-plasma membrane tethering complex that was recently discovered and molecularly analyzed in budding yeast, the Num1/Mdm36 complex. This complex attaches mitochondria to the cell cortex and ensures that a portion of the organelles is retained in mother cells during cell division. At the same time, it supports mitochondrial division and integrates mitochondrial dynamics into cellular architecture. Recent evidence suggests that similar mechanisms might exist also in mammalian cells.

  14. Membrane potential modulates plasma membrane phospholipid dynamics and K-Ras signaling

    Science.gov (United States)

    Zhou, Yong; Wong, Ching-On; Cho, Kwang-jin; van der Hoeven, Dharini; Liang, Hong; Thakur, Dhananiay P.; Luo, Jialie; Babic, Milos; Zinsmaier, Konrad E.; Zhu, Michael X.; Hu, Hongzhen; Venkatachalam, Kartik; Hancock, John F.

    2015-01-01

    Plasma membrane depolarization can trigger cell proliferation, but how membrane potential influences mitogenic signaling is uncertain. Here, we show that plasma membrane depolarization induces nanoscale reorganization of phosphatidylserine and phosphatidylinositol 4,5-bisphosphate but not other anionic phospholipids. K-Ras, which is targeted to the plasma membrane by electrostatic interactions with phosphatidylserine, in turn undergoes enhanced nanoclustering. Depolarization-induced changes in phosphatidylserine and K-Ras plasma membrane organization occur in fibroblasts, excitable neuroblastoma cells, and Drosophila neurons in vivo and robustly amplify K-Ras–dependent mitogen-activated protein kinase (MAPK) signaling. Conversely, plasma membrane repolarization disrupts K-Ras nanoclustering and inhibits MAPK signaling. By responding to voltage-induced changes in phosphatidylserine spatiotemporal dynamics, K-Ras nanoclusters set up the plasma membrane as a biological field-effect transistor, allowing membrane potential to control the gain in mitogenic signaling circuits. PMID:26293964

  15. Cellular transport and membrane dynamics of the glycine receptor

    Directory of Open Access Journals (Sweden)

    Andrea Dumoulin

    2010-02-01

    Full Text Available Regulation of synaptic transmission is essential to tune individual-to-network neuronal activity. One way to modulate synaptic strength is to regulate neurotransmitter receptor numbers at postsynaptic sites. This can be achieved either through plasma membrane insertion of receptors derived from intracellular vesicle pools, a process depending on active cytoskeleton transport, or through surface membrane removal via endocytosis. In parallel, lateral diffusion events along the plasma membrane allow the exchange of receptor molecules between synaptic and extrasynaptic compartments, contributing to synaptic strength regulation. In recent years, results obtained from several groups studying glycine receptor (GlyR trafficking and dynamics shed light on the regulation of synaptic GlyR density. Here, we review i proteins and mechanisms involved in GlyR cytoskeletal transport, ii the diffusion dynamics of GlyR and of its scaffolding protein gephyrin that control receptor numbers, and its relationship with synaptic plasticity, and iii adaptative changes in GlyR diffusion in response to global activity modifications, as a homeostatic mechanism.

  16. Hydrogen Production from Ammonia Using a Plasma Membrane Reactor

    Directory of Open Access Journals (Sweden)

    Shinji Kambara

    2016-06-01

    Full Text Available In this study, an efficient method for using pulsed plasma to produce hydrogen from ammonia was developed. An original pulsed plasma reactor with a hydrogen separation membrane was developed for efficient hydrogen production, and its hydrogen production performance was investigated. Hydrogen production in the plasma was affected by the applied voltage and flow rate of ammonia gas. The maximum hydrogen production flow rate of a typical plasma reactor was 8.7 L/h, whereas that of the plasma membrane reactor was 21.0 L/h. We found that ammonia recombination reactions in the plasma controlled hydrogen production in the plasma reactor. In the plasma membrane reactor, a significant increase in hydrogen production was obtained because ammonia recombination reactions were inhibited by the permeation of hydrogen radicals generated in the plasma through a palladium alloy membrane. The energy efficiency was 4.42 mol-H2/kWh depending on the discharge power.

  17. Radial plasma transport in Saturn's magnetosphere (Invited)

    Science.gov (United States)

    Hill, T. W.

    2010-12-01

    Radial plasma transport in the magnetosphere of Saturn, like that of Jupiter, is driven by the centrifugal force of (partial) corotation acting on internally generated plasma. A significant difference is that the internal plasma source is evidently broadly distributed throughout the inner magnetosphere of Saturn (4 CAPS and MAG), and reproduced in numerical simulations (RCM) that contain a distributed plasma source, although it has not, to my knowledge, been explained by an analytical theory containing an active plasma source. Both planets exhibit strong magnetospheric modulations near the planetary spin period, probably indicating a persistent longitudinal asymmetry of the radial plasma transport process. At Jupiter such an asymmetry is readily understood as a consequence of the dramatic asymmetry of the intrinsic planetary magnetic field. This is not so at Saturn, where any such field asymmetry is known to be very modest at best. In neither case has the precise nature of the asymmetry been identified either observationally or theoretically.

  18. Report membrane transport of lactic acid in the filamentous fungus Rhizopus

    Science.gov (United States)

    The fungus Rhizopus is frequently used for fermentative production of lactic acid, but little is known about the mechanisms or proteins for transporting this carboxylic acid. Since transport of the lactate anion across the plasma membrane is critical to prevent acidification of the cytoplasm, we ev...

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

    Science.gov (United States)

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

    2012-07-30

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

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

    Directory of Open Access Journals (Sweden)

    Christophe Coutanceau

    2012-07-01

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

  1. Transport of ions across peritoneal membrane.

    Science.gov (United States)

    Islam, Nurul; Bulla, Nisar A; Islam, Shahina

    2004-12-15

    The electrical conductance of ions across the peritoneal membrane of young buffalo (approximately 18-24 months old) has been recorded. Aqueous solutions of NaF, NaNO3, NaCl, Na2SO4, KF, KNO3, KCl, K2SO4, MgCl2, CaCl2, CrCl3, MnCl2, FeCl3, CoCl2, and CuCl2 were used. The conductance values have been found to increase with increase in concentration as well as with temperature (15 to 35 degrees C) in these cases. The slope of plots of specific conductance, kappa, versus concentration exhibits a decrease in its values at relatively higher concentrations compared to those in extremely dilute solutions. Also, such slopes keep on increasing with increase in temperature. In addition, the conductance also attains a maximum limiting value at higher concentrations in the said cases. This may be attributed to a progressive accumulation of ionic species within the membrane. The kappa values of electrolytes follow the sequence for the anions: SO4(2-)>Cl->NO3->F- while that for the cations: K+>Na+>Ca2+>Mn2+>Co2+>Cu2+>Mg2+>Cr3+>Fe3+. In addition, the diffusion of ions depends upon the charge on the membrane and its porosity. The membrane porosity in relation to the size of the hydrated species diffusing through the membrane appears to determine the above sequence. As the diffusional paths in the membrane become more difficult in aqueous solutions, the mobility of large hydrated ions gets impeded by the membrane framework and the interaction with the fixed charge groups on the membrane matrix. Consequently, the membrane pores reduce the conductance of small ions, which are much hydrated. An increase in conductance with increase in temperature may be due to the state of hydration, which implies that the energy of activation for the ionic transport across the membrane follows the sequence of crystallographic radii of ions accordingly. The Eyring's equation, kappa=(RT/Nh)exp[-DeltaH*/RT]exp[DeltaS*/R], has been found suitable for explaining the temperature dependence of conductance in

  2. Teaching the Modes of Ca[superscript 2+] Transport between the Plasma Membrane and Endoplasmic Reticulum Using a Classic Paper by Kwan et al.

    Science.gov (United States)

    Liang, Willmann

    2009-01-01

    This teaching article uses the report by Kwan et al., "Effects of methacholine, thapsigargin, and La[superscript 3+] on plasmalemmal and intracellular Ca[superscript 2+] transport in lacrimal acinar cells," where the effects of Ca[superscript 2+]-mobilizing agents in regulating Ca[superscript 2+] fluxes were examined under various conditions.…

  3. Inhibition of protein kinase CbetaII increases glucose uptake in 3T3-L1 adipocytes through elevated expression of glucose transporter 1 at the plasma membrane.

    NARCIS (Netherlands)

    Bosch, R.R.; Bazuine, M.; Wake, M.M.; Span, P.N.; Olthaar, A.J.; Schurmann, A.; Maassen, J.A.; Hermus, A.R.M.M.; Willems, P.H.G.M.; Sweep, C.G.J.

    2003-01-01

    The mechanism via which diacylglycerol-sensitive protein kinase Cs (PKCs) stimulate glucose transport in insulin-sensitive tissues is poorly defined. Phorbol esters, such as phorbol-12-myristate-13-acetate (PMA), are potent activators of conventional and novel PKCs. Addition of PMA increases the rat

  4. The Plasma Membrane Ca2+ ATPase and the Plasma Membrane Sodium Calcium Exchanger Cooperate in the Regulation of Cell Calcium

    Science.gov (United States)

    Brini, Marisa; Carafoli, Ernesto

    2011-01-01

    Calcium is an ambivalent signal: it is essential for the correct functioning of cell life, but may also become dangerous to it. The plasma membrane Ca2+ ATPase (PMCA) and the plasma membrane Na+/Ca2+ exchanger (NCX) are the two mechanisms responsible for Ca2+ extrusion. The NCX has low Ca2+ affinity but high capacity for Ca2+ transport, whereas the PMCA has a high Ca2+ affinity but low transport capacity for it. Thus, traditionally, the PMCA pump has been attributed a housekeeping role in maintaining cytosolic Ca2+, and the NCX the dynamic role of counteracting large cytosolic Ca2+ variations (especially in excitable cells). This view of the roles of the two Ca2+ extrusion systems has been recently revised, as the specific functional properties of the numerous PMCA isoforms and splicing variants suggests that they may have evolved to cover both the basal Ca2+ regulation (in the 100 nM range) and the Ca2+ transients generated by cell stimulation (in the μM range). PMID:21421919

  5. Plasma membrane proteomics and its application in clinical cancer biomarker discovery

    DEFF Research Database (Denmark)

    Leth-Larsen, Rikke; Lund, Rikke; Ditzel, Henrik J

    2010-01-01

    Plasma membrane proteins that are exposed on the cell surface have important biological functions, such as signaling into and out of the cells, ion transport, and cell-cell and cell-matrix interactions. The expression level of many of the plasma membrane proteins involved in these key functions...... targeted by protein drugs, such as human antibodies, that have enhanced survival of several groups of cancer patients. The combination of novel analytical approaches and subcellular fractionation procedures has made it possible to study the plasma membrane proteome in more detail, which will elucidate...... cancer biology, particularly metastasis, and guide future development of novel drug targets. The technical advances in plasma membrane proteomics and the consequent biological revelations will be discussed herein. Many of the advances have been made using cancer cell lines, but because the main goal...

  6. Transport coefficients of a relativistic plasma

    Science.gov (United States)

    Pike, O. J.; Rose, S. J.

    2016-05-01

    In this work, a self-consistent transport theory for a relativistic plasma is developed. Using the notation of Braginskii [S. I. Braginskii, in Reviews of Plasma Physics, edited by M. A. Leontovich (Consultants Bureau, New York, 1965), Vol. 1, p. 174], we provide semianalytical forms of the electrical resistivity, thermoelectric, and thermal conductivity tensors for a Lorentzian plasma in a magnetic field. This treatment is then generalized to plasmas with arbitrary atomic number by numerically solving the linearized Boltzmann equation. The corresponding transport coefficients are fitted by rational functions in order to make them suitable for use in radiation-hydrodynamic simulations and transport calculations. Within the confines of linear transport theory and on the assumption that the plasma is optically thin, our results are valid for temperatures up to a few MeV. By contrast, classical transport theory begins to incur significant errors above kBT ˜10 keV, e.g., the parallel thermal conductivity is suppressed by 15% at kBT =20 keV due to relativistic effects.

  7. The major myelin-resident protein PLP is transported to myelin membranes via a transcytotic mechanism : involvement of sulfatide

    NARCIS (Netherlands)

    Baron, Wia; Ozgen, Hande; Klunder, Bert; de Jonge, Jenny C; Nomden, Anita; Plat, Annechien; Trifilieff, Elisabeth; de Vries, Hans; Hoekstra, Dick

    2015-01-01

    Myelin membranes are sheet-like extensions of oligodendrocytes that can be considered as membrane domains distinct from the cell's plasma membrane. Consistent with the polarized nature of oligodendrocytes we demonstrate that transcytotic transport of the major myelin-resident protein, PLP, is a key

  8. Plasma membranes from insect midgut cells

    Directory of Open Access Journals (Sweden)

    Walter R. Terra

    2006-06-01

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

  9. Human NKCC2 cation–Cl– co-transporter complements lack of Vhc1 transporter in yeast vacuolar membranes.

    Science.gov (United States)

    Petrezselyova, Silvia; Dominguez, Angel; Herynkova, Pavla; Macias, Juan F; Sychrova, Hana

    2013-10-01

    Cation–chloride co-transporters serve to transport Cl– and alkali metal cations. Whereas a large family of these exists in higher eukaryotes, yeasts only possess one cation–chloride co-transporter, Vhc1, localized to the vacuolar membrane. In this study, the human cation–chloride co-transporter NKCC2 complemented the phenotype of VHC1 deletion in Saccharomyces cerevisiae and its activity controlled the growth of salt-sensitive yeast cells in the presence of high KCl, NaCl and LiCl. A S. cerevisiae mutant lacking plasma-membrane alkali–metal cation exporters Nha1 and Ena1-5 and the vacuolar cation–chloride co-transporter Vhc1 is highly sensitive to increased concentrations of alkali–metal cations, and it proved to be a suitable model for characterizing the substrate specificity and transport activity of human wild-type and mutated cation–chloride co-transporters.

  10. Saturn Plasma Sources and Associated Transport Processes

    Science.gov (United States)

    Blanc, M.; Andrews, D. J.; Coates, A. J.; Hamilton, D. C.; Jackman, C. M.; Jia, X.; Kotova, A.; Morooka, M.; Smith, H. T.; Westlake, J. H.

    2015-10-01

    This article reviews the different sources of plasma for Saturn's magnetosphere, as they are known essentially from the scientific results of the Cassini-Huygens mission to Saturn and Titan. At low and medium energies, the main plasma source is the H2O cloud produced by the "geyser" activity of the small satellite Enceladus. Impact ionization of this cloud occurs to produce on the order of 100 kg/s of fresh plasma, a source which dominates all the other ones: Titan (which produces much less plasma than anticipated before the Cassini mission), the rings, the solar wind (a poorly known source due to the lack of quantitative knowledge of the degree of coupling between the solar wind and Saturn's magnetosphere), and the ionosphere. At higher energies, energetic particles are produced by energy diffusion and acceleration of lower energy plasma produced by the interchange instabilities induced by the rapid rotation of Saturn, and possibly, for the highest energy range, by contributions from the CRAND process acting inside Saturn's magnetosphere. Discussion of the transport and acceleration processes acting on these plasma sources shows the importance of rotation-induced radial transport and energization of the plasma, and also shows how much the unexpected planetary modulation of essentially all plasma parameters of Saturn's magnetosphere remains an unexplained mystery.

  11. Channelopathies linked to plasma membrane phosphoinositides.

    Science.gov (United States)

    Logothetis, Diomedes E; Petrou, Vasileios I; Adney, Scott K; Mahajan, Rahul

    2010-07-01

    The plasma membrane phosphoinositide phosphatidylinositol 4,5-bisphosphate (PIP2) controls the activity of most ion channels tested thus far through direct electrostatic interactions. Mutations in channel proteins that change their apparent affinity to PIP2 can lead to channelopathies. Given the fundamental role that membrane phosphoinositides play in regulating channel activity, it is surprising that only a small number of channelopathies have been linked to phosphoinositides. This review proposes that for channels whose activity is PIP2-dependent and for which mutations can lead to channelopathies, the possibility that the mutations alter channel-PIP2 interactions ought to be tested. Similarly, diseases that are linked to disorders of the phosphoinositide pathway result in altered PIP2 levels. In such cases, it is proposed that the possibility for a concomitant dysregulation of channel activity also ought to be tested. The ever-growing list of ion channels whose activity depends on interactions with PIP2 promises to provide a mechanism by which defects on either the channel protein or the phosphoinositide levels can lead to disease.

  12. Differential activity of Plasma and Vacuolar Membrane Transporters contributes to Genotypic Differences in Salinity Tolerance in a Halophyte Species, Chenopodium quinoa

    DEFF Research Database (Denmark)

    Bonales-Alatorre, Edgar; Pottosin, Igor; Shabala, Lana

    2013-01-01

    Halophytes species can be used as a highly convenient model system to reveal key ionic and molecular mechanisms that confer salinity tolerance in plants. Earlier, we reported that quinoa (Chenopodium quinoa Willd.), a facultative C3 halophyte species, can efficiently control the activity of slow...... (SV) and fast (FV) tonoplast channels to match specific growth conditions by ensuring that most of accumulated Na+ is safely locked in the vacuole (Bonales-Alatorre et al. (2013) Plant Physiology). This work extends these finding by comparing the properties of tonoplast FV and SV channels in two....... These include: (i) a higher rate of Na+ exclusion from leaf mesophyll; (ii) maintenance of low cytosolic Na+ levels; (iii) better K+ retention in the leaf mesophyll; (iv) a high rate of H+ pumping, which increases the ability of mesophyll cells to restore their membrane potential; and (v) the ability to reduce...

  13. Enhancement of proton conductivity of sulfonated polystyrene membrane prepared by plasma polymerization process

    Indian Academy of Sciences (India)

    Bhabesh Kumar Nath; Aziz Khan; Joyanti Chutia; Arup Ratan Pal; Heremba Bailung; Neelotpal Sen Sarma; Devasish Chowdhury; Nirab Chandra Adhikary

    2014-12-01

    This work reports the achievement of higher proton conductivity of polystyrene based proton exchange membrane synthesized in a continuous RF plasma polymerization process using two precursors, styrene (C8H8) and trifluoromethane sulfonic acid (CF3SO3H). The chemical composition of the developed membranes is investigated using Fourier transform infrared spectroscopy and energy dispersive spectroscopy. Scanning electron microscopy has been used for the study of surface morphology and thickness measurement of the membrane. The membranes deposited in the power range from 0.114 to 0.318 Wcm-2 exhibit a lot of variation in the properties like proton transport, water uptake, sulfonation rate, ion exchange capacity and thermal behaviour. The proton conductivity of the membranes is achieved up to 0.6 Scm-1, measured with the help of potentiostat/galvanostat. The thermogravimetric study of the plasma polymerized membrane shows the thermal stability up to 140 °C temperature.

  14. [Updated detection of the function of sperm plasma membrane].

    Science.gov (United States)

    Zhou, Xin; Xia, Xin-Yi; Huang, Yu-Feng

    2010-08-01

    The sperm plasma membrane is rich in polyunsaturated fatty acids and a variety of proteins, and its function is associated with sperm capacitation, acrosome reaction and sperm-egg fusion. Sperm fertilizability can be predicted by detecting the function of the sperm plasma membrane, which is performed mainly with the following five techniques: sperm hypoosmotic swelling test, Eosin gamma water test, sperm membrane lipid peroxidation determination, seminal plasma superoxide dismutase determination, and flow cytometry. The evaluation of the function of sperm plasma membrane can be applied in detecting semen quality, selecting semen centrifugation, assessing the quality and fertilizability of sex-sorted sperm, improving cryopreservation, and guiding the optimization of intracytoplasmic sperm injection. This review presents an update on the principles, methods and steps of the detection of sperm plasma membrane function, as well as an overview of its status quo and application.

  15. Plasma deposition of silver nanoparticles on ultrafiltration membranes: antibacterial and anti-biofouling properties.

    Science.gov (United States)

    Cruz, Mercedes Cecilia; Ruano, Gustavo; Wolf, Marcus; Hecker, Dominic; Vidaurre, Elza Castro; Schmittgens, Ralph; Rajal, Verónica Beatriz

    2015-02-01

    A novel and versatile plasma reactor was used to modify Polyethersulphone commercial membranes. The equipment was applied to: i) functionalize the membranes with low-temperature plasmas, ii) deposit a film of poly(methyl methacrylate) (PMMA) by Plasma Enhanced Chemical Vapor Deposition (PECVD) and, iii) deposit silver nanoparticles (SNP) by Gas Flow Sputtering. Each modification process was performed in the same reactor consecutively, without exposure of the membranes to atmospheric air. Scanning electron microscopy and transmission electron microscopy were used to characterize the particles and modified membranes. SNP are evenly distributed on the membrane surface. Particle fixation and transport inside membranes were assessed before- and after-washing assays by X-ray photoelectron spectroscopy depth profiling analysis. PMMA addition improved SNP fixation. Plasma-treated membranes showed higher hydrophilicity. Anti-biofouling activity was successfully achieved against Gram-positive (Enterococcus faecalis) and -negative (Salmonella Typhimurium) bacteria. Therefore, disinfection by ultrafiltration showed substantial resistance to biofouling. The post-synthesis functionalization process developed provides a more efficient fabrication route for anti-biofouling and anti-bacterial membranes used in the water treatment field. To the best of our knowledge, this is the first report of a gas phase condensation process combined with a PECVD procedure in order to deposit SNP on commercial membranes to inhibit biofouling formation.

  16. Plasma deposition of silver nanoparticles on ultrafiltration membranes: antibacterial and anti-biofouling properties

    Science.gov (United States)

    Cruz, Mercedes Cecilia; Ruano, Gustavo; Wolf, Marcus; Hecker, Dominic; Vidaurre, Elza Castro; Schmittgens, Ralph; Rajal, Verónica Beatriz

    2015-01-01

    A novel and versatile plasma reactor was used to modify Polyethersulphone commercial membranes. The equipment was applied to: i) functionalize the membranes with low-temperature plasmas, ii) deposit a film of poly(methyl methacrylate) (PMMA) by Plasma Enhanced Chemical Vapor Deposition (PECVD) and, iii) deposit silver nanoparticles (SNP) by Gas Flow Sputtering. Each modification process was performed in the same reactor consecutively, without exposure of the membranes to atmospheric air. Scanning electron microscopy and transmission electron microscopy were used to characterize the particles and modified membranes. SNP are evenly distributed on the membrane surface. Particle fixation and transport inside membranes were assessed before- and after-washing assays by X-ray photoelectron spectroscopy depth profiling analysis. PMMA addition improved SNP fixation. Plasma-treated membranes showed higher hydrophilicity. Anti-biofouling activity was successfully achieved against Gram-positive (Enterococcus faecalis) and -negative (Salmonella Typhimurium) bacteria. Therefore, disinfection by ultrafiltration showed substantial resistance to biofouling. The post-synthesis functionalization process developed provides a more efficient fabrication route for anti-biofouling and anti-bacterial membranes used in the water treatment field. To the best of our knowledge, this is the first report of a gas phase condensation process combined with a PECVD procedure in order to deposit SNP on commercial membranes to inhibit biofouling formation. PMID:26166926

  17. 生长素调控极性运输载体PIN2质膜丰度与降解%Auxin regulation of its efflux transporter PIN2 plasma membrane abundance and degradation

    Institute of Scientific and Technical Information of China (English)

    付伟; 严旭; 王超; 潘建伟

    2013-01-01

    The effects of long-term (8 h) treatments with exogenous auxins on auxin efflux transporter PIN2-GFP plasma membrane (PM) abundance,and low temperature,KCN and auxin receptors TIR1/AFBs mutation on auxin regulation of PIN2-GFP PM abundance,and ConA,a vacuolar H +-ATPase inhibitor,on vacuolar accumulation of PIN2-GFP in wild-type and auxin receptor quadruple mutants tir1afb1,2,3 cells in Arabidopsis were systematically studied.The results revealed that exogenous auxins down-regulated PIN2-GFP PM abundance through TIR1/AFB-mediated signaling and promoted PIN2-GFP internalization,intracellular membrane trafficking,and vacuolar degradation,indicating that auxin feedback regulates PIN2-GFP PM levels through TIR1/AFB-mediated signaling and inhibits excessive transport of intracellular auxin out of the cell.%主要观察了外源生长素长时间(8 h)处理对拟南芥生长素极性输出载体PIN2-GFP质膜丰度的影响,低温、KCN处理和生长素受体突变对生长素调控质膜PIN2-GFP丰度的影响,以及液泡H+-ATPase抑制剂ConA对野生型和生长素受体四突变体tir1aafb1,2,3液泡中PIN2-GFP积累的影响.结果表明:外源生长素通过其受体TIR1/AFB介导的信号途径下调质膜PIN2-GFP的丰度,促进PIN2-GFP的内吞、胞内运输和液泡降解.暗示生长素通过TIR1/AFB介导的信号途径反馈调控质膜PIN2-GFP的水平,从而阻止了胞内生长素的过多输出.

  18. The Lunar dusty plasmas -levitation and transport.

    Science.gov (United States)

    Atamaniuk, Barbara; Rothkaehl, Hanna

    Lunar dust can exhibit unusual behavior -due to electron photoemission via solar-UV radiation the lunar surface represents a complex plasma -"dusty plasma". The dust grains and lunar surface are electrostatically charged by the Moon's interaction with the local plasma environ-ment and the photoemission of electrons due to solar UV and X-rays. This effect causes the like-charged surface and dust particles to repel each other, and creates a near-surface electric field. Lunar dust must be treated as a dusty plasma. Using analytic (kinetic (Vlasov) and magnetohydrodynamic theory ) and numerical modeling we show physical processes related to levitation and transport dusty plasma on the Moon. These dust grains could affect the lunar environment for radio wave and plasma diagnostics and interfere with exploration activities. References: 1. Wilson T.L. (1992), in Analysis of Interplanetary Dust, M. Zolensky et al. AIP Conf.Proc. 310, 33-44 (AIP, NY), 2.Wilson T.L."LUNAR DUST AND DUSTY PLASMA PHYSICS".40th Lunar and Planetary Science Conference (2009), 3. Grün E., et al.(1993),Nature 363, 144. 4. Morfill G. and Grün E.(1979), Planet. Space Sci.. 27, 1269, 1283, 5. Manka R. and Michel F. (1971), Proc. 2nd Lun. Sci. Conf. 2, 1717 (MIT Press, Cambridge). 6. Manka R. et al.(1973), Lun. Sci.-III, 504. 7. Barbara Atamaniuk "Kinetic Description of Localized Plasma Structure in Dusty Plasmas". Czechoslovak Journal of Physics Vol.54 C 2004

  19. Plasma transport in an Eulerian AMR code

    Science.gov (United States)

    Vold, E. L.; Rauenzahn, R. M.; Aldrich, C. H.; Molvig, K.; Simakov, A. N.; Haines, B. M.

    2017-04-01

    A plasma transport model has been implemented in an Eulerian AMR radiation-hydrodynamics code, xRage, which includes plasma viscosity in the momentum tensor, viscous dissipation in the energy equations, and binary species mixing with consistent species mass and energy fluxes driven by concentration gradients, ion and electron baro-diffusion terms and temperature gradient forces. The physics basis, computational issues, numeric options, and results from several test problems are discussed. The transport coefficients are found to be relatively insensitive to the kinetic correction factors when the concentrations are expressed with the molar fractions and the ion mass differences are large. The contributions to flow dynamics from plasma viscosity and mass diffusion were found to increase significantly as scale lengths decrease in an inertial confinement fusion relevant Kelvin-Helmholtz instability mix layer. The mixing scale lengths in the test case are on the order of 100 μm and smaller for viscous effects to appear and 10 μm or less for significant ion species diffusion, evident over durations on the order of nanoseconds. The temperature gradient driven mass flux is seen to deplete a high Z tracer ion at the ion shock front. The plasma transport model provides the generation of the atomic mix per unit of interfacial area between two species with no free parameters. The evolution of the total atomic mix then depends also on an accurate resolution or estimate of the interfacial area between the species mixing by plasma transport. High resolution simulations or a more Lagrangian-like treatment of species interfaces may be required to distinguish plasma transport and numerical diffusion in an Eulerian computation of complex and dynamically evolving mix regions.

  20. Membrane Compartment Occupied by Can1 (MCC and Eisosome Subdomains of the Fungal Plasma Membrane

    Directory of Open Access Journals (Sweden)

    James B. Konopka

    2011-12-01

    Full Text Available Studies on the budding yeast Saccharomyces cerevisiae have revealed that fungal plasma membranes are organized into different subdomains. One new domain termed MCC/eisosomes consists of stable punctate patches that are distinct from lipid rafts. The MCC/eisosome domains correspond to furrows in the plasma membrane that are about 300 nm long and 50 nm deep. The MCC portion includes integral membrane proteins, such as the tetraspanners Sur7 and Nce102. The adjacent eisosome includes proteins that are peripherally associated with the membrane, including the BAR domains proteins Pil1 and Lsp1 that are thought to promote membrane curvature. Genetic analysis of the MCC/eisosome components indicates these domains broadly affect overall plasma membrane organization. The mechanisms regulating the formation of MCC/eisosomes in model organisms will be reviewed as well as the role of these plasma membrane domains in fungal pathogenesis and response to antifungal drugs.

  1. Towards structural and functional analysis of the plant plasma membrane proton pump

    DEFF Research Database (Denmark)

    Justesen, Bo Højen

    The plasma membrane H+-ATPase is a proton pump essential for several physiological important processes in plants. Through the extrusion of protons from the cell, the PM H+-ATPase establishes and maintains a proton gradient used by proton coupled transporters and secondary active transport......, and regulation of H+-ATPases, key questions, in particular concerning the detailed interaction of regulator proteins with the H+-ATPases, remains answering that may require the use of new approaches. In this work the proton pump Arabidopsis thaliana plasma membrane H+-ATPase isoform 2 has been reconstituted...... into soluble nanoscale lipid bilayers, also termed nanodiscs. Extensive analysis confirms the correct assembly and reconstitution of active proton pump into nanodiscs. The pump inserts as a monomer, which through activity analysis confirms this as the minimal functional unit of the plasma membrane H...

  2. Co-overexpressing a plasma membrane and a vacuolar membrane sodium/proton antiporter significantly improves salt tolerance in transgenic Arabidopsis plants.

    Science.gov (United States)

    The Arabidopsis gene AtNHX1 encodes a vacuolar membrane bound sodium/proton (Sodium/Hydrogen) antiporter that transports sodium into the vacuole and exports hydrogen into the cytoplasm. The Arabidopsis gene SOS1 encodes a plasma membrane bound sodium/hydrogen antiporter that exports sodium to the ex...

  3. Electron thermal transport in tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Konings, J.A.

    1994-11-30

    The process of fusion of small nuclei thereby releasing energy, as it occurs continuously in the sun, is essential for the existence of mankind. The same process applied in a controlled way on earth would provide a clean and an abundant energy source, and be the long term solution of the energy problem. Nuclear fusion requires an extremely hot (10{sup 8} K) ionized gas, a plasma, that can only be maintained if it is kept insulated from any material wall. In the so called `tokamak` this is achieved by using magnetic fields. The termal insulation, which is essential if one wants to keep the plasma at the high `fusion` temperature, can be predicted using basic plasma therory. A comparison with experiments in tokamaks, however, showed that the electron enery losses are ten to hundred times larger than this theory predicts. This `anomalous transport` of thermal energy implies that, to reach the condition for nuclear fusion, a fusion reactor must have very large dimensions. This may put the economic feasibility of fusion power in jeopardy. Therefore, in a worldwide collaboration, physicists study tokamak plasmas in an attempt to understand and control the energy losses. From a scientific point of view, the mechanisms driving anomalous transport are one of the challenges in fudamental plasma physics. In Nieuwegein, a tokamak experiment (the Rijnhuizen Tokamak Project, RTP) is dedicated to the study of anomalous transport, in an international collaboration with other laboratories. (orig./WL).

  4. Transport Studies in Fusion Plasmas - Perturbative Experiments

    NARCIS (Netherlands)

    Cardozo, N. J. L.

    1994-01-01

    By subjecting a plasma in steady state to small perturbations and measuring the response, it is possible to determine elements of the matrix of transport coefficients. Experimentally this is difficult, and results are mainly limited to tranpsport driven by the pressure and temperature gradients. Imp

  5. Transport studies in fusion plasmas: Perturbative experiments

    NARCIS (Netherlands)

    Cardozo, N. J. L.

    1996-01-01

    By subjecting a plasma in steady state to small perturbations and measuring the response, it is possible to determine elements of the matrix of transport coefficients. Experimentally this is difficult, and results are mainly limited to tranpsport driven by the pressure and temperature gradients. Imp

  6. Electronic transport in partially ionized water plasmas

    Science.gov (United States)

    French, Martin; Redmer, Ronald

    2017-09-01

    We use ab initio simulations based on density functional theory to calculate the electrical and thermal conductivities of electrons in partially ionized water plasmas at densities above 0.1 g/cm3. The resulting conductivity data are then fitted to analytic expressions for convenient application. For low densities, we develop a simple and fully analytic model for electronic transport in low-density plasmas in the chemical picture using the relaxation-time approximation. In doing so, we derive a useful analytic expression for electronic transport cross sections with neutral particles, based on a model potential. In the regime of thermal ionization, electrical conductivities from the analytic model agree with the ab initio data within a factor of 2. Larger deviations are observed for the thermal conductivity, and their origin is discussed. Our results are relevant for modeling the interior and evolution of water-rich planets as well as for technical plasma applications.

  7. Membrane-Transport Systems for Sucrose in Relation to Whole-Plant Carbon Partitioning

    Institute of Scientific and Technical Information of China (English)

    Brian G. Ayre

    2011-01-01

    T Sucrose is the principal product of photosynthesis used for the distribution of assimilated carbon in plants. Transport mechanisms and efficiency influence photosynthetic productivity by relieving product inhibition and contribute to plant vigor by controlling source/sink relationships and biomass partitioning. Sucrose is synthesized in the cytoplasm and may move cell to cell through plasmodesmata or may cross membranes to be compartmentalized or exported to the apoplasm for uptake into adjacent cells. As a relatively large polar compound, sucrose requires proteins to facilitate efficient membrane transport. Transport across the tonoplast by facilitated diffusion, antiport with protons, and symport with protons have been proposed; for transport across plasma membranes, symport with protons and a mechanism resembling facilitated diffusion are evident. Despite decades of research, only symport with protons is well established at the molecular level. This review aims to integrate recent and older studies on sucrose flux across membranes with principles of whole-plant carbon partitioning.

  8. The plasma membrane proteome of germinating barley embryos

    DEFF Research Database (Denmark)

    Hynek, Radovan; Svensson, Birte; Jensen, O.N.

    2009-01-01

    was used to reduce soluble protein contamination and enrich for hydrophobic proteins. Sixty-one proteins in 14 SDS-PAGE bands were identified by LC-MS/MS and database searches. The identifications provide new insight into the plasma membrane functions in seed germination.......Cereal seed germination involves a complex coordination between different seed tissues. Plasma membranes must play crucial roles in coordination and execution of germination; however, very little is known about seed plasma membrane proteomes due to limited tissue amounts combined...... with amphiphilicity and low abundance of membrane proteins. A fraction enriched in plasma membranes was prepared from embryos dissected from 18 h germinated barley seeds using aqueous two-phase partitioning. Reversed-phase chromatography on C-4 resin performed in micro-spin columns with stepwise elution by 2-propanol...

  9. DCCD inhibits protein translocation into plasma membrane vesicles from Escherichia coli at two different steps.

    OpenAIRE

    1987-01-01

    In vitro translocation of periplasmic and outer membrane proteins into inverted plasma membrane vesicles from Escherichia coli was completely prevented by the H+-ATPase inhibitor N,N'-dicyclohexylcarbodiimide (DCCD). DCCD was inhibitory to both co- and post-translational translocations, suggesting an involvement of the H+-translocating F1F0-ATPase in either mode of transport. This was verified by (i) the dependence of efficient co-translational translocation upon a low salt, i.e. F1-containin...

  10. Membrane potential governs lateral segregation of plasma membrane proteins and lipids in yeast.

    Science.gov (United States)

    Grossmann, Guido; Opekarová, Miroslava; Malinsky, Jan; Weig-Meckl, Ina; Tanner, Widmar

    2007-01-10

    The plasma membrane potential is mainly considered as the driving force for ion and nutrient translocation. Using the yeast Saccharomyces cerevisiae as a model organism, we have discovered a novel role of the membrane potential in the organization of the plasma membrane. Within the yeast plasma membrane, two non-overlapping sub-compartments can be visualized. The first one, represented by a network-like structure, is occupied by the proton ATPase, Pma1, and the second one, forming 300-nm patches, houses a number of proton symporters (Can1, Fur4, Tat2 and HUP1) and Sur7, a component of the recently described eisosomes. Evidence is presented that sterols, the main lipid constituent of the plasma membrane, also accumulate within the patchy compartment. It is documented that this compartmentation is highly dependent on the energization of the membrane. Plasma membrane depolarization causes reversible dispersion of the H(+)-symporters, not however of the Sur7 protein. Mitochondrial mutants, affected in plasma membrane energization, show a significantly lower degree of membrane protein segregation. In accordance with these observations, depolarized membranes also considerably change their physical properties (detergent sensitivity).

  11. Shuttling of G protein subunits between the plasma membrane and intracellular membranes.

    Science.gov (United States)

    Chisari, Mariangela; Saini, Deepak Kumar; Kalyanaraman, Vani; Gautam, Narasimhan

    2007-08-17

    Heterotrimeric G proteins (alphabetagamma) mediate the majority of signaling pathways in mammalian cells. It is long held that G protein function is localized to the plasma membrane. Here we examined the spatiotemporal dynamics of G protein localization using fluorescence recovery after photobleaching, fluorescence loss in photobleaching, and a photoswitchable fluorescent protein, Dronpa. Unexpectedly, G protein subunits shuttle rapidly (t1/2 bromopalmitate. Thus, contrary to present thought, G proteins do not reside permanently on the plasma membrane but are constantly testing the cytoplasmic surfaces of the plasma membrane and endomembranes to maintain G protein pools in intracellular membranes to establish direct communication between receptors and endomembranes.

  12. Collective motor dynamics in membrane transport in vitro

    NARCIS (Netherlands)

    Shaklee, Paige Marie

    2009-01-01

    Key cellular processes such as cell division, internal cellular organization, membrane compartmentalization and intracellular transport rely on motor proteins. Motor proteins, ATP-based mechanoenzymes, actively transport cargo throughout the cell by walking on cytoskeletal filaments. Motors have bee

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

    DEFF Research Database (Denmark)

    Bojesen, Inge Norby; Bojesen, Eigil

    1998-01-01

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

  14. Potassium as an intrinsic uncoupler of the plasma membrane H+-ATPase

    DEFF Research Database (Denmark)

    Palmgren, Michael Gjedde; Buch-Pedersen, Morten Jeppe

    The plant plasma membrane proton pump (H(+)-ATPase) is stimulated by potassium, but it has remained unclear whether potassium is actually transported by the pump or whether it serves other roles. We now show that K(+) is bound to the proton pump at a site involving Asp(617) in the cytoplasmic...

  15. Fatty acid profiles from the plasma membrane and detergent resistant membranes of two plant species.

    Science.gov (United States)

    Carmona-Salazar, Laura; El Hafidi, Mohammed; Gutiérrez-Nájera, Nora; Noyola-Martínez, Liliana; González-Solís, Ariadna; Gavilanes-Ruíz, Marina

    2015-01-01

    It is essential to establish the composition of the plant plasma membrane in order to understand its organization and behavior under continually changing environments. Knowledge of the lipid phase, in particular the fatty acid (FA) complex repertoire, is important since FAs determine many of the physical-chemical membrane properties. FAs are constituents of the membrane glycerolipid and sphingolipid backbones and can also be linked to some sterols. In addition, FAs are components of complex lipids that can constitute membrane micro-domains, and the use of detergent-resistant membranes is a common approach to study their composition. The diversity and cellular allocation of the membrane lipids containing FAs are very diverse and the approaches to analyze them provide only general information. In this work, a detailed FA analysis was performed using highly purified plasma membranes from bean leaves and germinating maize embryos and their respective detergent-resistant membrane preparations. The analyses showed the presence of a significant amount of very long chain FAs (containing 28C, 30C and 32C), in both plasma membrane preparations from bean and maize, that have not been previously reported. Herein is demonstrated that a significant enrichment of very long chain saturated FAs and saturated FAs can occur in detergent-resistant membrane preparations, as compared to the plasma membranes from both plant species. Considering that a thorough analysis of FAs is rarely performed in purified plasma membranes and detergent-resistant membranes, this work provides qualitative and quantitative evidence on the contributions of the length and saturation of FAs to the organization of the plant plasma membrane and detergent-resistant membranes.

  16. Sphingolipid transport to the apical plasma membrane domain in human hepatoma cells is controlled by PKC and PKA activity : A correlation with cell polarity in HepG2 cells

    NARCIS (Netherlands)

    Zegers, MMP; Hoekstra, D

    1997-01-01

    The regulation of sphingolipid transport to the bile canalicular apical membrane in the well differentiated HepG2 hepatoma cells was studied. By employing fluorescent lipid analogs, trafficking in a transcytosis-dependent pathway and a transcytosis-independent ('direct') route between the trans-Golg

  17. Proteoliposomes as Tool for Assaying Membrane Transporter Functions and Interactions with Xenobiotics

    Directory of Open Access Journals (Sweden)

    Annamaria Tonazzi

    2013-09-01

    Full Text Available Proteoliposomes represent a suitable and up to date tool for studying membrane transporters which physiologically mediate absorption, excretion, trafficking and reabsorption of nutrients and metabolites. Using recently developed reconstitution strategies, transporters can be inserted in artificial bilayers with the same orientation as in the cell membranes and in the absence of other interfering molecular systems. These methodologies are very suitable for studying kinetic parameters and molecular mechanisms. After the first applications on mitochondrial transporters, in the last decade, proteoliposomes obtained with optimized methodologies have been used for studying plasma membrane transporters and defining their functional and kinetic properties and structure/function relationships. A lot of information has been obtained which has clarified and completed the knowledge on several transporters among which the OCTN sub-family members, transporters for neutral amino acid, B0AT1 and ASCT2, and others. Transporters can mediate absorption of substrate-like derivatives or drugs, improving their bioavailability or can interact with these compounds or other xenobiotics, leading to side/toxic effects. Therefore, proteoliposomes have recently been used for studying the interaction of some plasma membrane and mitochondrial transporters with toxic compounds, such as mercurials, H2O2 and some drugs. Several mechanisms have been defined and in some cases the amino acid residues responsible for the interaction have been identified. The data obtained indicate proteoliposomes as a novel and potentially important tool in drug discovery.

  18. Receptors and ionic transporters in nuclear membranes: new targets for therapeutical pharmacological interventions.

    Science.gov (United States)

    Bkaily, Ghassan; Avedanian, Levon; Al-Khoury, Johny; Ahmarani, Lena; Perreault, Claudine; Jacques, Danielle

    2012-08-01

    Work from our group and other laboratories showed that the nucleus could be considered as a cell within a cell. This is based on growing evidence of the presence and role of nuclear membrane G-protein coupled receptors and ionic transporters in the nuclear membranes of many cell types, including vascular endothelial cells, endocardial endothelial cells, vascular smooth muscle cells, cardiomyocytes, and hepatocytes. The nuclear membrane receptors were found to modulate the functioning of ionic transporters at the nuclear level, and thus contribute to regulation of nuclear ionic homeostasis. Nuclear membranes of the mentioned types of cells possess the same ionic transporters; however, the type of receptors is cell-type dependent. Regulation of cytosolic and nuclear ionic homeostasis was found to be dependent upon a tight crosstalk between receptors and ionic transporters of the plasma membranes and those of the nuclear membrane. This crosstalk seems to be the basis for excitation-contraction coupling, excitation-secretion coupling, and excitation - gene expression coupling. Further advancement in this field will certainly shed light on the role of nuclear membrane receptors and transporters in health and disease. This will in turn enable the successful design of a new class of drugs that specifically target such highly vital nuclear receptors and ionic transporters.

  19. Lagrangian coherent structures and plasma transport processes

    CERN Document Server

    Falessi, M V; Schep, T J

    2015-01-01

    A dynamical system framework is used to describe transport processes in plasmas embedded in a magnetic field. For periodic systems with one degree of freedom the Poincar\\'e map provides a splitting of the phase space into regions where particles have different kinds of motion: periodic, quasi-periodic or chaotic. The boundaries of these regions are transport barriers; i.e., a trajectory cannot cross such boundaries during the whole evolution of the system. Lagrangian Coherent Structure (LCS) generalize this method to systems with the most general time dependence, splitting the phase space into regions with different qualitative behaviours. This leads to the definition of finite-time transport barriers, i.e. trajectories cannot cross the barrier for a finite amount of time. This methodology can be used to identify fast recirculating regions in the dynamical system and to characterize the transport between them.

  20. Membrane transport mechanism 3D structure and beyond

    CERN Document Server

    Ziegler, Christine

    2014-01-01

    This book provides a molecular view of membrane transport by means of numerous biochemical and biophysical techniques. The rapidly growing number of atomic structures of transporters in different conformations and the constant progress in bioinformatics have recently added deeper insights.   The unifying mechanism of energized solute transport across membranes is assumed to consist of the conformational cycling of a carrier protein to provide access to substrate binding sites from either side of a cellular membrane. Due to the central role of active membrane transport there is considerable interest in deciphering the principles of one of the most fundamental processes in nature: the alternating access mechanism.   This book brings together particularly significant structure-function studies on a variety of carrier systems from different transporter families: Glutamate symporters, LeuT-like fold transporters, MFS transporters and SMR (RND) exporters, as well as ABC-type importers.   The selected examples im...

  1. Identification and role of plasma membrane aquaporin in maize root

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Using antiserum against expressed aquaporin fusion protein, GST-RD28, the distribution of aquaporin in the plasma membrane of maize root protoplasts has been examined under confocal laser scanning microscopy by indirect fluorescence staining. Results indicate that there are abundant aquaporins in maize roots, which are distributed in plasma membrane unevenly. Western blotting analysis of total protein solubilized from maize root plasma membrane shows that antiserum against GST-RD28 can cross-react with one protein around 55 ku. Another 28 ku protein can also be detected when the concentration of SDS and DTT in SDS-PAGE sample buffer is increased. The 55 and 28 ku proteins may be dimeric and monomeric of aquaporin respectively. Functional experiments show that aquaporin blocker HgCl2 and aquaporin antiserum can suppress the swelling of maize root protoplasts in hypotonic solution, indicating that aquaporin in plasma membrane of protoplast facilitates rapid transmembrane water flow.

  2. Transport through liquid membranes containing omeprazole and lansoprazole.

    Science.gov (United States)

    Nagappa, A N; Pandi, P V; Mishra, P K; Girish, Rahul K; Shanmukh, I

    2002-12-01

    Omeprazole and lansoprazole, the therapeutically important drugs belonging to proton pump inhibitor category are extensively used in the treatment of gastric ulcers. Transport through liquid membranes generated by these drugs in lecithin-cholesterol mixture in series with a supporting membrane has been studied. The data obtained show the formation of liquid membrane in series with the supporting membrane. Transport of cations, chloride and bicarbonate ions in the presence liquid membranes generated by omeprazole and lanzoprazole indicate the modification in the permeability of various permeants.

  3. Lateral mobility of plasma membrane lipids in dividing Xenopus eggs

    OpenAIRE

    de Laat, S W; Tetteroo, P.A.T.; Bluemink, J.G.; Dictus, W.J.A.G.; Zoelen, E.J.J. van

    1984-01-01

    The lateral mobility of plasma membrane lipids was analyzed during first cleavage of Xaopus Levis eggs by fluorescence photobleaching recovery (FPR) measurements, using the lipid analogs 5-(N-hexadecanoyl)aminofluorescein (“HEDAF”) and 5-(N-tetradecanoyl)aminofluorescein (“TEDAF”) as probes. The preexisting plasma membrane of the animal side showed an inhomogeneous, dotted fluorescence pattern after labeling and the lateral mobility of both probes used was below the detection limits of the FP...

  4. Analytical Applications of Transport Through Bulk Liquid Membranes.

    Science.gov (United States)

    Diaconu, Ioana; Ruse, Elena; Aboul-Enein, Hassan Y; Bunaciu, Andrei A

    2016-07-03

    This review discusses the results of research in the use of bulk liquid membranes in separation processes and preconcentration for analytical purposes. It includes some theoretical aspects, definitions, types of liquid membranes, and transport mechanism, as well as advantages of using liquid membranes in laboratory studies. These concepts are necessary to understand fundamental principles of liquid membrane transport. Due to the multiple advantages of liquid membranes several studies present analytical applications of the transport through liquid membranes in separation or preconcentration processes of metallic cations and some organic compounds, such as phenol and phenolic derivatives, organic acids, amino acids, carbohydrates, and drugs. This review presents coupled techniques such as separation through the liquid membrane coupled with flow injection analysis.

  5. Organization and Dynamics of Receptor Proteins in a Plasma Membrane.

    Science.gov (United States)

    Koldsø, Heidi; Sansom, Mark S P

    2015-11-25

    The interactions of membrane proteins are influenced by their lipid environment, with key lipid species able to regulate membrane protein function. Advances in high-resolution microscopy can reveal the organization and dynamics of proteins and lipids within living cells at resolutions membranes of in vivo-like complexity. We explore the dynamics of proteins and lipids in crowded and complex plasma membrane models, thereby closing the gap in length and complexity between computations and experiments. Our simulations provide insights into the mutual interplay between lipids and proteins in determining mesoscale (20-100 nm) fluctuations of the bilayer, and in enabling oligomerization and clustering of membrane proteins.

  6. New Advances in Urea Transporter UT-A1 Membrane Trafficking

    Directory of Open Access Journals (Sweden)

    Guangping Chen

    2013-05-01

    Full Text Available The vasopressin-regulated urea transporter UT-A1, expressed in kidney inner medullary collecting duct (IMCD epithelial cells, plays a critical role in the urinary concentrating mechanisms. As a membrane protein, the function of UT-A1 transport activity relies on its presence in the plasma membrane. Therefore, UT-A1 successfully trafficking to the apical membrane of the polarized epithelial cells is crucial for the regulation of urea transport. This review summarizes the research progress of UT-A1 regulation over the past few years, specifically on the regulation of UT-A1 membrane trafficking by lipid rafts, N-linked glycosylation and a group of accessory proteins.

  7. New advances in urea transporter UT-A1 membrane trafficking.

    Science.gov (United States)

    Chen, Guangping

    2013-05-21

    The vasopressin-regulated urea transporter UT-A1, expressed in kidney inner medullary collecting duct (IMCD) epithelial cells, plays a critical role in the urinary concentrating mechanisms. As a membrane protein, the function of UT-A1 transport activity relies on its presence in the plasma membrane. Therefore, UT-A1 successfully trafficking to the apical membrane of the polarized epithelial cells is crucial for the regulation of urea transport. This review summarizes the research progress of UT-A1 regulation over the past few years, specifically on the regulation of UT-A1 membrane trafficking by lipid rafts, N-linked glycosylation and a group of accessory proteins.

  8. Autoinhibitory Regulation of Plasma Membrane H+-ATPases

    DEFF Research Database (Denmark)

    Pedersen, Jesper Torbøl

    Electrochemical gradients across cell membranes are essential for nutrient uptake. In plant and fungal cells the electrochemical gradient across the plasma membrane (PM) can build much higher than in mammalian cells. The protein responsible for this gradient is the essential PM H+-ATPase that uses...

  9. Intrarenal localization of the plasma membrane ATP channel pannexin1.

    Science.gov (United States)

    Hanner, Fiona; Lam, Lisa; Nguyen, Mien T X; Yu, Alan; Peti-Peterdi, János

    2012-11-15

    In the renal tubules, ATP released from epithelial cells stimulates purinergic receptors, regulating salt and water reabsorption. However, the mechanisms by which ATP is released into the tubular lumen are multifaceted. Pannexin1 (Panx1) is a newly identified. ubiquitously expressed protein that forms connexin-like channels in the plasma membrane, which have been demonstrated to function as a mechanosensitive ATP conduit. Here, we report on the localization of Panx1 in the mouse kidney. Using immunofluorescence, strong Panx1 expression was observed in renal tubules, including proximal tubules, thin descending limbs, and collecting ducts, along their apical cell membranes. In the renal vasculature, Panx1 expression was localized to vascular smooth muscle cells in renal arteries, including the afferent and efferent arterioles. Additionally, we tested whether Panx1 channels expressed in renal epithelial cells facilitate luminal ATP release by measuring the ATP content of urine samples freshly collected from wild-type and Panx1(-/-) mice. Urinary ATP levels were reduced by 30% in Panx1(-/-) compared with wild-type mice. These results suggest that Panx1 channels in the kidney may regulate ATP release and via purinergic signaling may participate in the control of renal epithelial fluid and electrolyte transport and vascular functions.

  10. A structural overview of the plasma membrane Na+,K+-ATPase and H+-ATPase ion pumps

    DEFF Research Database (Denmark)

    Morth, Jens Preben; Pedersen, Bjørn Panella; Buch-Pedersen, Morten Jeppe

    2011-01-01

    Plasma membrane ATPases are primary active transporters of cations that maintain steep concentration gradients. The ion gradients and membrane potentials derived from them form the basis for a range of essential cellular processes, in particular Na(+)-dependent and proton-dependent secondary...... transport systems that are responsible for uptake and extrusion of metabolites and other ions. The ion gradients are also both directly and indirectly used to control pH homeostasis and to regulate cell volume. The plasma membrane H(+)-ATPase maintains a proton gradient in plants and fungi and the Na...

  11. Molecular characterization of carnitine-dependent transport of acetyl-CoA from peroxisomes to mitochondria in Saccharomyces cerevisiae and identification of a plasma membrane carnitine transporter, Agp2p.

    OpenAIRE

    van Roermund, C W; Hettema, E H; van den Berg, M.; Tabak, H F; Wanders, R.J.

    1999-01-01

    In Saccharomyces cerevisiae, beta-oxidation of fatty acids is confined to peroxisomes. The acetyl-CoA produced has to be transported from the peroxisomes via the cytoplasm to the mitochondrial matrix in order to be degraded to CO(2) and H(2)O. Two pathways for the transport of acetyl-CoA to the mitochondria have been proposed. The first involves peroxisomal conversion of acetyl-CoA into glyoxylate cycle intermediates followed by transport of these intermediates to the mitochondria. The second...

  12. Validation metrics for turbulent plasma transport

    Science.gov (United States)

    Holland, C.

    2016-06-01

    Developing accurate models of plasma dynamics is essential for confident predictive modeling of current and future fusion devices. In modern computer science and engineering, formal verification and validation processes are used to assess model accuracy and establish confidence in the predictive capabilities of a given model. This paper provides an overview of the key guiding principles and best practices for the development of validation metrics, illustrated using examples from investigations of turbulent transport in magnetically confined plasmas. Particular emphasis is given to the importance of uncertainty quantification and its inclusion within the metrics, and the need for utilizing synthetic diagnostics to enable quantitatively meaningful comparisons between simulation and experiment. As a starting point, the structure of commonly used global transport model metrics and their limitations is reviewed. An alternate approach is then presented, which focuses upon comparisons of predicted local fluxes, fluctuations, and equilibrium gradients against observation. The utility of metrics based upon these comparisons is demonstrated by applying them to gyrokinetic predictions of turbulent transport in a variety of discharges performed on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)], as part of a multi-year transport model validation activity.

  13. Cosmic ray transport in astrophysical plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- & Astrophysik, Ruhr-Universität, Bochum (Germany)

    2015-09-15

    Since the development of satellite space technology about 50 years ago the solar heliosphere is explored almost routinely by several spacecrafts carrying detectors for measuring the properties of the interplanetary medium including energetic charged particles (cosmic rays), solar wind particle densities, and electromagnetic fields. In 2012, the Voyager 1 spacecraft has even left what could be described as the heliospheric modulation region, as indicated by the sudden disappearance of low energy heliospheric cosmic ray particles. With the available in-situ measurements of interplanetary turbulent electromagnetic fields and of the momentum spectra of different cosmic ray species in different interplanetary environments, the heliosphere is the best cosmic laboratory to test our understanding of the transport and acceleration of cosmic rays in space plasmas. I review both the historical development and the current state of various cosmic ray transport equations. Similarities and differences to transport theories for terrestrial fusion plasmas are highlighted. Any progress in cosmic ray transport requires a detailed understanding of the electromagnetic turbulence that is responsible for the scattering and acceleration of these particles.

  14. Validation metrics for turbulent plasma transport

    Energy Technology Data Exchange (ETDEWEB)

    Holland, C., E-mail: chholland@ucsd.edu [Center for Energy Research, University of California, San Diego, La Jolla, California 92093-0417 (United States)

    2016-06-15

    Developing accurate models of plasma dynamics is essential for confident predictive modeling of current and future fusion devices. In modern computer science and engineering, formal verification and validation processes are used to assess model accuracy and establish confidence in the predictive capabilities of a given model. This paper provides an overview of the key guiding principles and best practices for the development of validation metrics, illustrated using examples from investigations of turbulent transport in magnetically confined plasmas. Particular emphasis is given to the importance of uncertainty quantification and its inclusion within the metrics, and the need for utilizing synthetic diagnostics to enable quantitatively meaningful comparisons between simulation and experiment. As a starting point, the structure of commonly used global transport model metrics and their limitations is reviewed. An alternate approach is then presented, which focuses upon comparisons of predicted local fluxes, fluctuations, and equilibrium gradients against observation. The utility of metrics based upon these comparisons is demonstrated by applying them to gyrokinetic predictions of turbulent transport in a variety of discharges performed on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)], as part of a multi-year transport model validation activity.

  15. A cell-free assay to determine the stoichiometry of plasma membrane proteins.

    Science.gov (United States)

    Trigo, Cesar; Vivar, Juan P; Gonzalez, Carlos B; Brauchi, Sebastian

    2013-04-01

    Plasma membrane receptors, transporters, and ion channel molecules are often found as oligomeric structures that participate in signaling cascades essential for cell survival. Different states of protein oligomerization may play a role in functional control and allosteric regulation. Stochastic GFP-photobleaching (SGP) has emerged as an affordable and simple method to determine the stoichiometry of proteins at the plasma membrane. This non-invasive optical approach can be useful for total internal reflection of fluorescence microscopy (TIRFM), where signal-to-noise ratio is very high at the plasma membrane. Here, we report an alternative methodology implemented on a standard laser scanning confocal microscope (LSCM). The simplicity of our method will allow for its implementation in any epifluorescence microscope of choice.

  16. The connection of cytoskeletal network with plasma membrane and the cell wall

    Institute of Scientific and Technical Information of China (English)

    Zengyu Liu; Staffan Persson; Yi Zhang

    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 biosyn-thesis and modifications, and aim to provide a platform for further studies in this field.

  17. Preparation of artificial plasma membrane mimicking vesicles with lipid asymmetry.

    Directory of Open Access Journals (Sweden)

    Qingqing Lin

    Full Text Available Lipid asymmetry, the difference in lipid distribution across the lipid bilayer, is one of the most important features of eukaryotic cellular membranes. However, commonly used model membrane vesicles cannot provide control of lipid distribution between inner and outer leaflets. We recently developed methods to prepare asymmetric model membrane vesicles, but facile incorporation of a highly controlled level of cholesterol was not possible. In this study, using hydroxypropyl-α-cyclodextrin based lipid exchange, a simple method was devised to prepare large unilamellar model membrane vesicles that closely resemble mammalian plasma membranes in terms of their lipid composition and asymmetry (sphingomyelin (SM and/or phosphatidylcholine (PC outside/phosphatidylethanolamine (PE and phosphatidylserine (PS inside, and in which cholesterol content can be readily varied between 0 and 50 mol%. We call these model membranes "artificial plasma membrane mimicking" ("PMm" vesicles. Asymmetry was confirmed by both chemical labeling and measurement of the amount of externally-exposed anionic lipid. These vesicles should be superior and more realistic model membranes for studies of lipid-lipid and lipid-protein interaction in a lipid environment that resembles that of mammalian plasma membranes.

  18. Preparation of artificial plasma membrane mimicking vesicles with lipid asymmetry.

    Science.gov (United States)

    Lin, Qingqing; London, Erwin

    2014-01-01

    Lipid asymmetry, the difference in lipid distribution across the lipid bilayer, is one of the most important features of eukaryotic cellular membranes. However, commonly used model membrane vesicles cannot provide control of lipid distribution between inner and outer leaflets. We recently developed methods to prepare asymmetric model membrane vesicles, but facile incorporation of a highly controlled level of cholesterol was not possible. In this study, using hydroxypropyl-α-cyclodextrin based lipid exchange, a simple method was devised to prepare large unilamellar model membrane vesicles that closely resemble mammalian plasma membranes in terms of their lipid composition and asymmetry (sphingomyelin (SM) and/or phosphatidylcholine (PC) outside/phosphatidylethanolamine (PE) and phosphatidylserine (PS) inside), and in which cholesterol content can be readily varied between 0 and 50 mol%. We call these model membranes "artificial plasma membrane mimicking" ("PMm") vesicles. Asymmetry was confirmed by both chemical labeling and measurement of the amount of externally-exposed anionic lipid. These vesicles should be superior and more realistic model membranes for studies of lipid-lipid and lipid-protein interaction in a lipid environment that resembles that of mammalian plasma membranes.

  19. Development of Human Membrane Transporters: Drug Disposition and Pharmacogenetics.

    Science.gov (United States)

    Mooij, Miriam G; Nies, Anne T; Knibbe, Catherijne A J; Schaeffeler, Elke; Tibboel, Dick; Schwab, Matthias; de Wildt, Saskia N

    2016-05-01

    Membrane transporters play an essential role in the transport of endogenous and exogenous compounds, and consequently they mediate the uptake, distribution, and excretion of many drugs. The clinical relevance of transporters in drug disposition and their effect in adults have been shown in drug-drug interaction and pharmacogenomic studies. Little is known, however, about the ontogeny of human membrane transporters and their roles in pediatric pharmacotherapy. As they are involved in the transport of endogenous substrates, growth and development may be important determinants of their expression and activity. This review presents an overview of our current knowledge on human membrane transporters in pediatric drug disposition and effect. Existing pharmacokinetic and pharmacogenetic data on membrane substrate drugs frequently used in children are presented and related, where possible, to existing ex vivo data, providing a basis for developmental patterns for individual human membrane transporters. As data for individual transporters are currently still scarce, there is a striking information gap regarding the role of human membrane transporters in drug therapy in children.

  20. Membranes for nanometer-scale mass fast transport

    Science.gov (United States)

    Bakajin, Olgica; Holt, Jason; Noy, Aleksandr; Park, Hyung Gyu

    2011-10-18

    Nanoporous membranes comprising single walled, double walled, and multiwalled carbon nanotubes embedded in a matrix material were fabricated for fluid mechanics and mass transfer studies on the nanometer scale and commercial applications. Average pore size can be 2 nm to 20 nm, or seven nm or less, or two nanometers or less. The membrane can be free of large voids spanning the membrane such that transport of material such as gas or liquid occurs exclusively through the tubes. Fast fluid, vapor, and liquid transport are observed. Versatile micromachining methods can be used for membrane fabrication. A single chip can comprise multiple membranes. These membranes are a robust platform for the study of confined molecular transport, with applications in liquid and gas separations and chemical sensing including desalination, dialysis, and fabric formation.

  1. Ion Transport through Diffusion Layer Controlled by Charge Mosaic Membrane

    Directory of Open Access Journals (Sweden)

    Akira Yamauchi

    2012-01-01

    Full Text Available The kinetic transport behaviors in near interface of the membranes were studied using commercial anion and cation exchange membrane and charge mosaic membrane. Current-voltage curve gave the limiting current density that indicates the ceiling of conventional flux. From chronopotentiometry above the limiting current density, the transition time was estimated. The thickness of boundary layer was derived with conjunction with the conventional limiting current density and the transition time from steady state flux. On the other hand, the charge mosaic membrane was introduced in order to examine the ion transport on the membrane surface in detail. The concentration profile was discussed by the kinetic transport number with regard to the water dissociation (splitting on the membrane surface.

  2. Recent achievements in facilitated transport membranes for separation processes

    Directory of Open Access Journals (Sweden)

    H. C. Ferraz

    2007-03-01

    Full Text Available Membrane separation processes have been extensively used for some important industrial separations, substituting traditional methods. However, some applications require the development of new membranes. In this work, we discuss recent progress achieved in this field, focusing on gas and liquid separation using facilitated transport membranes. The advantages of using a carrier species either in a liquid membrane or fixed in a polymer matrix to enhance both the flux and the selectivity of the transport are summarized. The most probable transport mechanisms in these membranes are presented and the improvements needed to spread this technology are also discussed. As examples, we discuss our very successful experiences in air fractioning, olefin/paraffin separation and sugar recovery using liquid and fixed carrier membranes.

  3. Transport of Carbon Dioxide through a Biomimetic Membrane

    Directory of Open Access Journals (Sweden)

    Efstathios Matsaridis

    2011-01-01

    Full Text Available Biomimetic membranes (BMM based on polymer filters impregnated with lipids or their analogues are widely applied in numerous areas of physics, biology, and medicine. In this paper we report the design and testing of an electrochemical system, which allows the investigation of CO2 transport through natural membranes such as alveoli barrier membrane system and also can be applied for solid-state measurements. The experimental setup comprises a specially designed two-compartment cell with BMM connected with an electrochemical workstation placed in a Faraday cage, two PH meters, and a nondispersive infrared gas analyzer. We prove, experimentally, that the CO2 transport through the natural membranes under different conditions depends on pH and displays a similar behavior as natural membranes. The influence of different drugs on the CO2 transport process through such membranes is discussed.

  4. There Is No Simple Model of the Plasma Membrane Organization

    Science.gov (United States)

    Bernardino de la Serna, Jorge; Schütz, Gerhard J.; Eggeling, Christian; Cebecauer, Marek

    2016-01-01

    Ever since technologies enabled the characterization of eukaryotic plasma membranes, heterogeneities in the distributions of its constituents were observed. Over the years this led to the proposal of various models describing the plasma membrane organization such as lipid shells, picket-and-fences, lipid rafts, or protein islands, as addressed in numerous publications and reviews. Instead of emphasizing on one model we in this review give a brief overview over current models and highlight how current experimental work in one or the other way do not support the existence of a single overarching model. Instead, we highlight the vast variety of membrane properties and components, their influences and impacts. We believe that highlighting such controversial discoveries will stimulate unbiased research on plasma membrane organization and functionality, leading to a better understanding of this essential cellular structure. PMID:27747212

  5. There is no simple model of the plasma membrane organisation

    Directory of Open Access Journals (Sweden)

    Jorge Bernardino De La Serna

    2016-09-01

    Full Text Available Ever since technologies enabled the characterisation of eukaryotic plasma membranes, heterogeneities in the distributions of its constituents were observed. Over the years this led to the proposal of various models describing the plasma membrane organisation such as lipid shells, picket-and-fences, lipid rafts, or protein islands, as addressed in numerous publications and reviews. Instead of emphasising on one model we in this review give a brief overview over current models and highlight how current experimental work in one or the other way do not support the existence of a single overarching model. Instead, we highlight the vast variety of membrane properties and components, their influences and impacts. We believe that highlighting such controversial discoveries will stimulate unbiased research on plasma membrane organisation and functionality, leading to a better understanding of this essential cellular structure.

  6. Effects of electrolytes on ion transport in Chitosan membranes

    Science.gov (United States)

    Rupiasih, N. N.

    2016-11-01

    Recently, charged polymer membranes are widely used for water purification applications involving control of water and ion transport, such as reverse osmosis and electrodialysis. In this study, we have explored the effects of electrolyte solutions on ion transport properties of chitosan synthetic membranes via concentration gradient driven transport. Also, the water uptake of those membranes, before (control) as well used membranes have studied. The membrane used was chitosan membrane 2%. The electrolyte solutions used were HCl, KCl, CaCl2, MgCl2 and AlCl3, with various concentrations of 0.1 mM, 1 mM, 10 mM, 100 mM and 1000 mM. Ion transport experiments were carried out in a cell membrane model which composed of two compartments and the potential difference of membrane was measured using Ag/AgCl calomel electrodes. Those measurements were conducted at ambient temperature 28.8 °C. The results showed that the current density (J) increased with increased in concentration gradient of solution. The current density was higher in electrolyte solution which has higher molar conductivity than those of a solution with a small molar conductivity. Meanwhile the current density was smaller in electrolyte solution which has larger Stokes radii than those of a solution with small Stokes radii. Except membrane which has been used in HCl solution, the water uptakes of the used membranes were greater than the control membrane. These results can develop and validate a common framework to interpret data of concentration gradient driven transport in chitosan synthetic membranes and to use it to design of membranes with improved performance.

  7. Significance of the plasma membrane for the nerve cell function, development and plasticity.

    Science.gov (United States)

    Mourek, Jindrich; Langmeier, Milos; Pokorny, Jaroslav

    2009-01-01

    Lipoid character of plasma membrane namely the presence of polyenic fatty acids enables to interact with membrane proteins and in certain extent also to modulate their function. During the development, molecules of membrane fatty acids become more and more complex, and the ratio of polyenic fatty acids/saturated fatty acids in the brain rises, while the concentration of monoenic fatty acids remained relatively stable. This phenomenon is apparent also in the ratio of unsaturated fatty acids OMEGA-3 in plasma of newborns which correlates with the birth weight. Plasma membrane reflects local specializations of nerve cells. Its composition varies in functionally specialized regions called domains. Specialized domains of nerve cells determine the function of dendrites, soma, axon, axon hillock ect. Premature weaning of laboratory rats results in structural changes and in the increase of excitability of neuronal circuits in hypothalamus, septum and hippocampus which indicate the possibility of membrane composition changes. In synapses, transport proteins of synaptic vesicles, act together with the specific proteins of the presynaptic membrane. Membrane proteins determine the release of neurotransmitter at different conditions of synaptic activity, and they can contribute to the recovery of neurotransmitter content after the repeated hyperactivity. In the model of experimental kindling, repeated seizures bring about decreases and distribution changes of synaptic vesicles.

  8. Feed gas contaminant removal in ion transport membrane systems

    Science.gov (United States)

    Underwood, Richard Paul [Allentown, PA; Makitka, III, Alexander; Carolan, Michael Francis [Allentown, PA

    2012-04-03

    An oxygen ion transport membrane process wherein a heated oxygen-containing gas having one or more contaminants is contacted with a reactive solid material to remove the one or more contaminants. The reactive solid material is provided as a deposit on a support. The one or more contaminant compounds in the heated oxygen-containing gas react with the reactive solid material. The contaminant-depleted oxygen-containing gas is contacted with a membrane, and oxygen is transported through the membrane to provide transported oxygen.

  9. Instabilities, turbulence and transport in a magnetized plasma; Instabilites, turbulence et transport dans un plasma magnetise

    Energy Technology Data Exchange (ETDEWEB)

    Garbet, X

    2001-06-01

    The purpose of this work is to introduce the main processes that occur in a magnetized plasma. During the last 2 decades, the understanding of turbulence has made great progress but analytical formulas and simulations are far to produce reliable predictions. The values of transport coefficients in a tokamak plasma exceed by far those predicted by the theory of collisional transport. This phenomenon is called abnormal transport and might be due to plasma fluctuations. An estimation of turbulent fluxes derived from the levels of fluctuations, is proposed. A flow description of plasma allows the understanding of most micro-instabilities. The ballooning representation deals with instabilities in a toric geometry. 3 factors play an important role to stabilize plasmas: density pinch, magnetic shear and speed shear. The flow model of plasma gives an erroneous value for the stability threshold, this is due to a bad description of the resonant interaction between wave and particle. As for dynamics, flow models can be improved by adding dissipative terms so that the linear response nears the kinetic response. The kinetic approach is more accurate but is complex because of the great number of dimensions involved. (A.C.)

  10. Geometry changes transient transport in plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Kimitaka [National Inst. for Fusion Science, Toki, Gifu (Japan); Itoh, Sanae-I. [Research Institute for Applied Mechanics, Kyushu Univ., Kasuga, Fukuoka (Japan)

    2001-06-01

    Role of ballooning effect in toroidal plasmas on the transient transport problems is investigated. Due to the mode localization along the magnetic field line, a meso scale appears in a radial correlation length of fluctuating fields. This scale length introduces the interference of the gradient and flux in different radial locations. For the fluctuation which gives the gyro-Bohm-like diffusion in a stationary state, this long radial correlation of the fluctuating field causes a fast propagation of response against a rapid transient perturbation. Upper bound of transient thermal diffusivity is derived. (author)

  11. Surface modification of nanoporous alumina membranes by plasma polymerization.

    Science.gov (United States)

    Losic, Dusan; Cole, Martin A; Dollmann, Björn; Vasilev, Krasimir; Griesser, Hans J

    2008-06-18

    The deposition of plasma polymer coatings onto porous alumina (PA) membranes was investigated with the aim of adjusting the surface chemistry and the pore size of the membranes. PA membranes from commercial sources with a range of pore diameters (20, 100 and 200 nm) were used and modified by plasma polymerization using n-heptylamine (HA) monomer, which resulted in a chemically reactive polymer surface with amino groups. Heptylamine plasma polymer (HAPP) layers with a thickness less than the pore diameter do not span the pores but reduce their diameter. Accordingly, by adjusting the deposition time and thus the thickness of the plasma polymer coating, it is feasible to produce any desired pore diameter. The structural and chemical properties of modified membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and x-ray electron spectroscopy (XPS). The resultant PA membranes with specific surface chemistry and controlled pore size are applicable for molecular separation, cell culture, bioreactors, biosensing, drug delivery, and engineering complex composite membranes.

  12. Free-flow electrophoresis of plasma membrane vesicles enriched by two-phase partitioning enhances the quality of the proteome from Arabidopsis seedlings

    DEFF Research Database (Denmark)

    de Michele, Roberto; McFarlane, Heather E; Parsons, Harriet Tempé

    2016-01-01

    The plant plasma membrane is the interface between the cell and its environment undertaking a range of important functions related to transport, signaling, cell wall biosynthesis, and secretion. Multiple proteomic studies have attempted to capture the diversity of proteins in the plasma membrane ...

  13. Detergent-resistant membrane subfractions containing proteins of plasma membrane, mitochondrial, and internal membrane origins.

    Science.gov (United States)

    Mellgren, Ronald L

    2008-04-24

    HEK293 cell detergent-resistant membranes (DRMs) isolated by the standard homogenization protocol employing a Teflon pestle homogenizer yielded a prominent opaque band at approximately 16% sucrose upon density gradient ultracentrifugation. In contrast, cell disruption using a ground glass tissue homogenizer generated three distinct DRM populations migrating at approximately 10%, 14%, and 20% sucrose, named DRM subfractions A, B, and C, respectively. Separation of the DRM subfractions by mechanical disruption suggested that they are physically associated within the cellular environment, but can be dissociated by shear forces generated during vigorous homogenization. All three DRM subfractions possessed cholesterol and ganglioside GM1, but differed in protein composition. Subfraction A was enriched in flotillin-1 and contained little caveolin-1. In contrast, subfractions B and C were enriched in caveolin-1. Subfraction C contained several mitochondrial membrane proteins, including mitofilin and porins. Only subfraction B appeared to contain significant amounts of plasma membrane-associated proteins, as revealed by cell surface labeling studies. A similar distribution of DRM subfractions, as assessed by separation of flotillin-1 and caveolin-1 immunoreactivities, was observed in CHO cells, in 3T3-L1 adipocytes, and in HEK293 cells lysed in detergent-free carbonate. Teflon pestle homogenization of HEK293 cells in the presence of the actin-disrupting agent latrunculin B generated DRM subfractions A-C. The microtubule-disrupting agent vinblastine did not facilitate DRM subfraction separation, and DRMs prepared from fibroblasts of vimentin-null mice were present as a single major band on sucrose gradients, unless pre-treated with latrunculin B. These results suggest that the DRM subfractions are interconnected by the actin cytoskeleton, and not by microtubes or vimentin intermediate filaments. The subfractions described may prove useful in studying discrete protein

  14. Ras diffusion is sensitive to plasma membrane viscosity.

    Science.gov (United States)

    Goodwin, J Shawn; Drake, Kimberly R; Remmert, Catha L; Kenworthy, Anne K

    2005-08-01

    The cell surface contains a variety of barriers and obstacles that slow the lateral diffusion of glycosylphosphatidylinositol (GPI)-anchored and transmembrane proteins below the theoretical limit imposed by membrane viscosity. How the diffusion of proteins residing exclusively on the inner leaflet of the plasma membrane is regulated has been largely unexplored. We show here that the diffusion of the small GTPase Ras is sensitive to the viscosity of the plasma membrane. Using confocal fluorescence recovery after photobleaching, we examined the diffusion of green fluorescent protein (GFP)-tagged HRas, NRas, and KRas in COS-7 cells loaded with or depleted of cholesterol, a well-known modulator of membrane bilayer viscosity. In cells loaded with excess cholesterol, the diffusional mobilities of GFP-HRas, GFP-NRas, and GFP-KRas were significantly reduced, paralleling the behavior of the viscosity-sensitive lipid probes DiIC(16) and DiIC(18). However, the effects of cholesterol depletion on protein and lipid diffusion in cell membranes were highly dependent on the depletion method used. Cholesterol depletion with methyl-beta-cyclodextrin slowed Ras diffusion by a viscosity-independent mechanism, whereas overnight cholesterol depletion slightly increased both protein and lipid diffusion. The ability of Ras to sense membrane viscosity may represent a general feature of proteins residing on the cytoplasmic face of the plasma membrane.

  15. Transport of Ions Across the Inner Envelope Membrane of Chloroplasts

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, R. E.

    2004-06-02

    The technical report outlines the results of nine years of research on how ions cross the inner envelope membrane of chloroplasts. The ions include protons, nitrite, calcium and ferrous iron. Bicarbonate transport was also studied.

  16. Characterization of auxin-binding proteins from zucchini plasma membrane

    Science.gov (United States)

    Hicks, G. R.; Rice, M. S.; Lomax, T. L.

    1993-01-01

    We have previously identified two auxin-binding polypeptides in plasma membrane (PM) preparations from zucchini (Cucurbita pepo L.) (Hicks et al. 1989, Proc. Natl. Acad. Sci. USA 86, 4948-4952). These polypeptides have molecular weights of 40 kDa and 42 kDa and label specifically with the photoaffinity auxin analog 5-N3-7-3H-IAA (azido-IAA). Azido-IAA permits both the covalent and radioactive tagging of auxin-binding proteins and has allowed us to characterize further the 40-kDa and 42-kDa polypeptides, including the nature of their attachment to the PM, their relationship to each other, and their potential function. The azido-IAA-labeled polypeptides remain in the pelleted membrane fraction following high-salt and detergent washes, which indicates a tight and possibly integral association with the PM. Two-dimensional electrophoresis of partially purified azido-IAA-labeled protein demonstrates that, in addition to the major isoforms of the 40-kDa and 42-kDa polypeptides, which possess isoelectric points (pIs) of 8.2 and 7.2, respectively, several less abundant isoforms that display unique pIs are apparent at both molecular masses. Tryptic and chymotryptic digestion of the auxin-binding proteins indicates that the 40-kDa and 42-kDa polypeptides are closely related or are modifications of the same polypeptide. Phase extraction with the nonionic detergent Triton X-114 results in partitioning of the azido-IAA-labeled polypeptides into the aqueous (hydrophilic) phase. This apparently paradoxical behavior is also exhibited by certain integral membrane proteins that aggregate to form channels. The results of gel filtration indicate that the auxin-binding proteins do indeed aggregate strongly and that the polypeptides associate to form a dimer or multimeric complex in vivo. These characteristics are consistent with the hypothesis that the 40-kDa and 42-kDa polypeptides are subunits of a multimeric integral membrane protein which has an auxin-binding site, and which may

  17. Detection of glycoproteins in the Acanthamoeba plasma membrane

    Energy Technology Data Exchange (ETDEWEB)

    Paatero, G.I.L. (Abo Akademi (Finland)); Gahmberg, C.G. (Univ. of Helsinki (Finland))

    1988-11-01

    In the present study the authors have shown that glycoproteins are present in the plasma membrane of Acanthamoeba castellanii by utilizing different radioactive labeling techniques. Plasma membrane proteins in the amoeba were iodinated by {sup 125}I-lactoperoxidase labeling and the solubilized radiolabeled glycoproteins were separated by lectin-Sepharose affinity chromatography followed by polyacrylamide gel electrophoresis. The periodate/NaB{sup 3}H{sub 4} and galactose oxidase/NaB{sup 3}H{sub 4} labeling techniques were used for labeling of surface carbohydrates in the amoeba. Several surface-labeled glycoproteins were observed in addition to a diffusely labeled region with M{sub r} of 55,000-75,000 seen on electrophoresis, which could represent glycolipids. The presence of glycoproteins in the plasma membrane of Acanthamoeba castellanii was confirmed by metabolic labeling with ({sup 35}S)methionine followed by lectin-Sepharose affinity chromatography and polyacrylamide gel electrophoresis.

  18. Plasma membrane organization and function: moving past lipid rafts.

    Science.gov (United States)

    Kraft, Mary L

    2013-09-01

    "Lipid raft" is the name given to the tiny, dynamic, and ordered domains of cholesterol and sphingolipids that are hypothesized to exist in the plasma membranes of eukaryotic cells. According to the lipid raft hypothesis, these cholesterol- and sphingolipid-enriched domains modulate the protein-protein interactions that are essential for cellular function. Indeed, many studies have shown that cellular levels of cholesterol and sphingolipids influence plasma membrane organization, cell signaling, and other important biological processes. Despite 15 years of research and the application of highly advanced imaging techniques, data that unambiguously demonstrate the existence of lipid rafts in mammalian cells are still lacking. This Perspective summarizes the results that challenge the lipid raft hypothesis and discusses alternative hypothetical models of plasma membrane organization and lipid-mediated cellular function.

  19. Molecular Modeling of Interfacial Proton Transport in Polymer Electrolyte Membranes

    OpenAIRE

    2014-01-01

    The proton conductivity of polymer electrolyte membranes (PEMs) plays a crucial role for the performance of polymer electrolyte fuel cells (PEFCs). High hydration of Nafion-like membranes is crucial to high proton conduction across the PEM, which limits the operation temperature of PEFCs to <100o C. At elevated temperatures (>100o C) and minimal hydration, interfacial proton transport becomes vital for membrane operation. Along with fuel cell systems, interfacial proton conduction is of...

  20. ULTRATHIN SILICON MEMBRANES TO STUDY SUPERCURRENT TRANSPORT IN CRYSTALLINE SEMICONDUCTORS

    NARCIS (Netherlands)

    VANHUFFELEN, WM; DEBOER, MJ; KLAPWIJK, TM

    1991-01-01

    We have developed a two-step anisotropic etching process to fabricate thin silicon membranes, used to study supercurrent transport in semiconductor coupled weak links. The process uses a shallow BF2+ implantation, and permits easy control of membrane thickness less-than-or-equal-to 100 nm. Prelimina

  1. Facilitated oxygen transport in liquid membranes: review and new concepts

    NARCIS (Netherlands)

    Figoli, A.; Sager, W.F.C.; Mulder, M.H.V.

    2001-01-01

    In this paper, an overview is given on membranes with oxygen facilitated transport properties to enrich the oxygen content in air. Special emphasis is paid to recent developments of oxygen carrier systems and carrier containing membranes. Concepts leading to a structural evolution of supported liqui

  2. Endosomal recycling controls plasma membrane area during mitosis.

    Science.gov (United States)

    Boucrot, Emmanuel; Kirchhausen, Tomas

    2007-05-08

    The shape and total surface of a cell and its daughters change during mitosis. Many cells round up during prophase and metaphase and reacquire their extended and flattened shape during cytokinesis. How does the total area of plasma membrane change to accommodate these morphological changes and by what mechanism is control of total membrane area achieved? Using single-cell imaging methods, we have found that the amount of plasma membrane in attached cells in culture decreases at the beginning of mitosis and recovers rapidly by the end. Clathrin-based endocytosis is normal throughout all phases of cell division, whereas recycling of internalized membranes back to the cell surface slows considerably during the rounding up period and resumes at the time at which recovery of cell membrane begins. Interference with either one of these processes by genetic or chemical means impairs cell division. The total cell-membrane area recovers even in the absence of a functional Golgi apparatus, which would be needed for export of newly synthesized membrane lipids and proteins. We propose a mechanism by which modulation of endosomal recycling controls cell area and surface expression of membrane-bound proteins during cell division.

  3. Nanodomain stabilization dynamics in plasma membranes of biological cells

    Science.gov (United States)

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

    2011-02-01

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

  4. Development of active-transport membrane devices

    Energy Technology Data Exchange (ETDEWEB)

    Laciak, D.V.

    1994-07-01

    This report introduces the concept of Air Products` AT membranes for the separation of NH{sub 3} and CO{sub 2} from process gas streams and presents results from the first year fabrication concept development studies.

  5. A plant plasma membrane Ca2+ pump is required for normal pollen tube growth and fertilization

    DEFF Research Database (Denmark)

    Schiøtt, Morten; Romanowsky, Shawn M; Bækgaard, Lone

    2004-01-01

    Ca(2+) signals are thought to play important roles in plant growth and development, including key aspects of pollen tube growth and fertilization. The dynamics of a Ca(2+) signal are largely controlled by influx (through channels) and efflux (through pumps and antiporters). The Arabidopsis genome...... and a high frequency of aborted fertilization, resulting in a >80% reduction in seed set. These findings identify a plasma membrane Ca(2+) transporter as a key regulator of pollen development and fertilization in flowering plants....

  6. Therapeutic plasmapheresis using membrane plasma separation.

    Science.gov (United States)

    Sinha, Aditi; Tiwari, Anand Narain; Chanchlani, Rahul; Seetharamanjaneyulu, V; Hari, Pankaj; Bagga, Arvind

    2012-08-01

    The authors present their experience with therapeutic plasmapheresis (TPE) using membrane filters at the pediatric dialysis unit of a referral center. Between January 2006 and December 2010, 486 sessions of TPE were performed in 39 patients (range 6-17 y), chiefly for atypical hemolytic uremic syndrome (HUS, n = 22), crescentic glomerulonephritis (n = 8) and focal segmental glomerulosclerosis (n = 5). Satisfactory response was noted in 32 patients, particularly with HUS (n = 22) or crescentic glomerulonephritis (n = 6). Adverse effects included chills or urticaria (n = 8 sessions), hypocalcemia (n = 6) and hypotension (n = 5). The present findings highlight the safety, efficacy and feasibility of TPE using membrane filtration.

  7. Magnetic apatite for structural insights on the plasma membrane.

    Science.gov (United States)

    Stanca, Sarmiza E; Müller, Robert; Dellith, Jan; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang

    2015-01-21

    The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.

  8. Magnetic apatite for structural insights on the plasma membrane

    Science.gov (United States)

    Stanca, Sarmiza E.; Müller, Robert; Dellith, Jan; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang

    2015-01-01

    The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.

  9. Water and Molecular Transport across Nanopores in Monolayer Graphene Membranes

    Science.gov (United States)

    Jang, Doojoon; O'Hern, Sean; Kidambi, Piran; Boutilier, Michael; Song, Yi; Idrobo, Juan-Carlos; Kong, Jing; Laoui, Tahar; Karnik, Rohit

    2015-11-01

    Graphene's atomic thickness and high tensile strength allow it to outstand as backbone material for next-generation high flux separation membrane. Molecular dynamics simulations predicted that a single-layer graphene membrane could exhibit high permeability and selectivity for water over ions/molecules, qualifying as novel water desalination membranes. However, experimental investigation of water and molecular transport across graphene nanopores had remained barely explored due to the presence of intrinsic defects and tears in graphene. We introduce two-step methods to seal leakage across centimeter scale single-layer graphene membranes create sub-nanometer pores using ion irradiation and oxidative etching. Pore creation parameters were varied to explore the effects of created pore structures on water and molecular transport driven by forward osmosis. The results demonstrate the potential of nanoporous graphene as a reliable platform for high flux nanofiltration membranes.

  10. Calculation of transport coefficients in an axisymmetric plasma

    Energy Technology Data Exchange (ETDEWEB)

    Shumaker, D.E.

    1977-01-01

    A method of calculating the transport coefficient in an axisymmetric toroidal plasma is presented. This method is useful in calculating the transport coefficients in a Tokamak plasma confinement device. The particle density and temperature are shown to be a constant on a magnetic flux surface. Transport equations are given for the total particle flux and total energy flux crossing a closed toroidal surface. Also transport equations are given for the toroidal magnetic flux. A computer code was written to calculate the transport coefficients for a three species plasma, electrons and two species of ions. This is useful for calculating the transport coefficients of a plasma which contains impurities. It was found that the particle and energy transport coefficients are increased by a large amount, and the transport coefficients for the toroidal magnetic field are reduced by a small amount.

  11. Hijacking membrane transporters for arsenic phytoextraction.

    Science.gov (United States)

    LeBlanc, Melissa S; McKinney, Elizabeth C; Meagher, Richard B; Smith, Aaron P

    2013-01-10

    Arsenic is a toxic metalloid and recognized carcinogen. Arsenate and arsenite are the most common arsenic species available for uptake by plants. As an inorganic phosphate (Pi) analog, arsenate is acquired by plant roots through endogenous Pi transport systems. Inside the cell, arsenate is reduced to the thiol-reactive form arsenite. Glutathione (GSH)-conjugates of arsenite may be extruded from the cell or sequestered in vacuoles by members of the ATP-binding cassette (ABC) family of transporters. In the present study we sought to enhance both plant arsenic uptake through Pi transporter overexpression, and plant arsenic tolerance through ABC transporter overexpression. We demonstrate that Arabidopsis thaliana plants overexpressing the high-affinity Pi transporter family members, AtPht1;1 or AtPht1;7, are hypersensitive to arsenate due to increased arsenate uptake. These plants do not exhibit increased sensitivity to arsenite. Co-overexpression of the yeast ABC transporter YCF1 in combination with AtPht1;1 or AtPht1;7 suppresses the arsenate-sensitive phenotype while further enhancing arsenic uptake. Taken together, our results support an arsenic transport mechanism in which arsenate uptake is increased through Pi transporter overexpression, and arsenic tolerance is enhanced through YCF1-mediated vacuolar sequestration. This work substantiates the viability of coupling enhanced uptake and vacuolar sequestration as a means for developing a prototypical engineered arsenic hyperaccumulator.

  12. Identification of calcium-binding proteins associated with the human sperm plasma membrane

    National Research Council Canada - National Science Library

    Naaby-Hansen, Soren; Diekman, Alan; Shetty, Jagathpala; Flickinger, Charles J; Westbrook, Anne; Herr, John C

    2010-01-01

    The precise composition of the human sperm plasma membrane, the molecular interactions that define domain specific functions, and the regulation of membrane associated proteins during the capacitation...

  13. Kinetics of plasma membrane and mitochondrial alterations in cells undergoing apoptosis

    National Research Council Canada - National Science Library

    Lizard, G; Fournel, S; Genestier, L; Dhedin, N; Chaput, C; Flacher, M; Mutin, M; Panaye, G; Revillard, J P

    1995-01-01

    ... of the nucleus, whereas integrity of the plasma membrane and organelles is preserved. Conversely cells undergoing necrosis display an early desintegration of cytoplasmic membrane and swelling of mitochondria...

  14. A 22-year experience in global transport extracorporeal membrane oxygenation.

    Science.gov (United States)

    Coppola, Christopher P; Tyree, Melissa; Larry, Karen; DiGeronimo, Robert

    2008-01-01

    Transport extracorporeal membrane oxygenation (ECMO) is currently available at 12 centers. We report a 22-year experience from the only facility providing global transport ECMO. Indications for transport ECMO include lack of ECMO services, inability to transport conventionally, inability to wean from cardiopulmonary bypass, extracorporeal cardiopulmonary resuscitation, and need to move a patient on ECMO for specialized services such as organ transplantation. Retrospective database review of children undergoing inhouse and transport ECMO from 1985 to 2007. Sixty-eight children underwent transport ECMO. Fifty-six were transported on ECMO into our facility. The remaining 12 were moved between 2 outside locations. Ground vehicles and fixed-wing aircraft were used. Distance transported was 8 to 7500 miles (13-12070 km), mean 1380 miles (2220 km). There were 116 inhouse ECMO runs. No child died during transport. Survival to discharge after transport ECMO was 65% (44/68) and, for inhouse ECMO, was 70% (81/116). Transport ECMO is feasible and effective, with survival rates comparable to inhouse ECMO. We have used transport ECMO to help children at non-ECMO centers with pulmonary failure who have not improved with inhaled nitric oxide and high-frequency ventilation. We have also transported a child after extracorporeal cardiopulmonary resuscitation, which may represent an emerging indication for transport ECMO. Transport ECMO often is the only option for children too unstable for conventional transport or those already on ECMO and requiring a specialized service at another facility, such as organ transplantation.

  15. Transport Bifurcation in a Rotating Tokamak Plasma

    CERN Document Server

    Highcock, E G; Schekochihin, A A; Parra, F I; Roach, C M; Cowley, S C

    2010-01-01

    The effect of flow shear on turbulent transport in tokamaks is studied numerically in the experimentally relevant limit of zero magnetic shear. It is found that the plasma is linearly stable for all non-zero flow shear values, but that subcritical turbulence can be sustained nonlinearly at a wide range of temperature gradients. Flow shear increases the nonlinear temperature gradient threshold for turbulence but also increases the sensitivity of the heat flux to changes in the temperature gradient, except over a small range near the threshold where the sensitivity is decreased. A bifurcation in the equilibrium gradients is found: for a given input of heat, it is possible, by varying the applied torque, to trigger a transition to significantly higher temperature and flow gradients.

  16. Transport Bifurcation in Plasma Interchange Turbulence

    Science.gov (United States)

    Li, Bo

    2016-10-01

    Transport bifurcation and mean shear flow generation in plasma interchange turbulence are explored with self-consistent two-fluid simulations in a flux-driven system with both closed and open field line regions. The nonlinear evolution of interchange modes shows the presence of two confinement regimes characterized by the low and high mean flow shear. By increasing the input heat flux above a certain threshold, large-amplitude oscillations in the turbulent and mean flow energy are induced. Both clockwise and counter-clockwise types of oscillations are found before the transition to the second regime. The fluctuation energy is decisively transferred to the mean flows by large-amplitude Reynolds power as turbulent intensity increases. Consequently, a transition to the second regime occurs, in which strong mean shear flows are generated in the plasma edge. The peak of the spectrum shifts to higher wavenumbers as the large-scale turbulent eddies are suppressed by the mean shear flow. The transition back to the first regime is then triggered by decreasing the input heat flux to a level much lower than the threshold for the forward transition, showing strong hysteresis. During the back transition, the mean flow decreases as the energy transfer process is reversed. This transport bifurcation, based on a field-line-averaged 2D model, has also been reproduced in our recent 3D simulations of resistive interchange turbulence, in which the ion and electron temperatures are separated and the parallel current is involved. Supported by the MOST of China Grant No. 2013GB112006, US DOE Contract No. DE-FC02-08ER54966, US DOE by LLNL under Contract DE-AC52-07NA2734.

  17. Lateral mobility of plasma membrane lipids in dividing Xenopus eggs

    NARCIS (Netherlands)

    Laat, S.W. de; Tetteroo, P.A.T.; Bluemink, J.G.; Dictus, W.J.A.G.; Zoelen, E.J.J. van

    1984-01-01

    The lateral mobility of plasma membrane lipids was analyzed during first cleavage of Xaopus Levis eggs by fluorescence photobleaching recovery (FPR) measurements, using the lipid analogs 5-(N-hexadecanoyl)aminofluorescein (“HEDAF”) and 5-(N-tetradecanoyl)aminofluorescein (“TEDAF”) as probes. The pre

  18. Lateral mobility of plasma membrane lipids in dividing Xenopus eggs

    NARCIS (Netherlands)

    Laat, S.W. de; Tetteroo, P.A.T.; Bluemink, J.G.; Dictus, W.J.A.G.; Zoelen, E.J.J. van

    1984-01-01

    The lateral mobility of plasma membrane lipids was analyzed during first cleavage of Xaopus Levis eggs by fluorescence photobleaching recovery (FPR) measurements, using the lipid analogs 5-(N-hexadecanoyl)aminofluorescein (“HEDAF”) and 5-(N-tetradecanoyl)aminofluorescein (“TEDAF”) as probes. The

  19. The Plasma Membrane of Saccharomyces cerevisiae : Structure, Function, and Biogenesis

    NARCIS (Netherlands)

    VANDERREST, ME; KAMMINGA, AH; NAKANO, A; ANRAKU, Y; POOLMAN, B; KONINGS, WN

    1995-01-01

    The composition of phospholipids, sphingolipids, and sterols in the plasma membrane has a strong influence on the activity of the proteins associated or embedded in the lipid bilayer. Since most lipid-synthesizing enzymes in Saccharomyces cerevisiae are located in intracellular organelles, an extens

  20. Mammalian gamete plasma membranes re-assessments and reproductive implications

    Science.gov (United States)

    Establishment of the diploid status occurs with the fusion of female and male gametes. Both the mammalian oocyte and spermatozoa are haploid cells surrounded with plasma membranes that are rich in various proteins playing a crucial role during fertilization. Fertilization is a complex and ordered st...

  1. The Plasma Membrane of Saccharomyces cerevisiae : Structure, Function, and Biogenesis

    NARCIS (Netherlands)

    VANDERREST, ME; KAMMINGA, AH; NAKANO, A; ANRAKU, Y; POOLMAN, B; KONINGS, WN

    The composition of phospholipids, sphingolipids, and sterols in the plasma membrane has a strong influence on the activity of the proteins associated or embedded in the lipid bilayer. Since most lipid-synthesizing enzymes in Saccharomyces cerevisiae are located in intracellular organelles, an

  2. Epithelial cell-cell junctions and plasma membrane domains

    NARCIS (Netherlands)

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

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

  3. Epithelial cell-cell junctions and plasma membrane domains

    NARCIS (Netherlands)

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

    2009-01-01

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

  4. Perforin rapidly induces plasma membrane phospholipid flip-flop.

    Directory of Open Access Journals (Sweden)

    Sunil S Metkar

    Full Text Available The cytotoxic cell granule secretory pathway is essential for host defense. This pathway is fundamentally a form of intracellular protein delivery where granule proteases (granzymes from cytotoxic lymphocytes are thought to diffuse through barrel stave pores generated in the plasma membrane of the target cell by the pore forming protein perforin (PFN and mediate apoptotic as well as additional biological effects. While recent electron microscopy and structural analyses indicate that recombinant PFN oligomerizes to form pores containing 20 monomers (20 nm when applied to liposomal membranes, these pores are not observed by propidium iodide uptake in target cells. Instead, concentrations of human PFN that encourage granzyme-mediated apoptosis are associated with pore structures that unexpectedly favor phosphatidylserine flip-flop measured by Annexin-V and Lactadherin. Efforts that reduce PFN mediated Ca influx in targets did not reduce Annexin-V reactivity. Antigen specific mouse CD8 cells initiate a similar rapid flip-flop in target cells. A lipid that augments plasma membrane curvature as well as cholesterol depletion in target cells enhance flip-flop. Annexin-V staining highly correlated with apoptosis after Granzyme B (GzmB treatment. We propose the structures that PFN oligomers form in the membrane bilayer may include arcs previously observed by electron microscopy and that these unusual structures represent an incomplete mixture of plasma membrane lipid and PFN oligomers that may act as a flexible gateway for GzmB to translocate across the bilayer to the cytosolic leaflet of target cells.

  5. Exclusive photorelease of signalling lipids at the plasma membrane.

    Science.gov (United States)

    Nadler, André; Yushchenko, Dmytro A; Müller, Rainer; Stein, Frank; Feng, Suihan; Mulle, Christophe; Carta, Mario; Schultz, Carsten

    2015-12-21

    Photoactivation of caged biomolecules has become a powerful approach to study cellular signalling events. Here we report a method for anchoring and uncaging biomolecules exclusively at the outer leaflet of the plasma membrane by employing a photocleavable, sulfonated coumarin derivative. The novel caging group allows quantifying the reaction progress and efficiency of uncaging reactions in a live-cell microscopy setup, thereby greatly improving the control of uncaging experiments. We synthesized arachidonic acid derivatives bearing the new negatively charged or a neutral, membrane-permeant coumarin caging group to locally induce signalling either at the plasma membrane or on internal membranes in β-cells and brain slices derived from C57B1/6 mice. Uncaging at the plasma membrane triggers a strong enhancement of calcium oscillations in β-cells and a pronounced potentiation of synaptic transmission while uncaging inside cells blocks calcium oscillations in β-cells and causes a more transient effect on neuronal transmission, respectively. The precise subcellular site of arachidonic acid release is therefore crucial for signalling outcome in two independent systems.

  6. Plasma membrane ubiquinone controls ceramide production and prevents cell death induced by serum withdrawal.

    Science.gov (United States)

    Barroso, M P; Gómez-Díaz, C; Villalba, J M; Burón, M I; López-Lluch, G; Navas, P

    1997-06-01

    Serum provides cultured cells with survival factors required to maintain growth. Its withdrawal induces the development of programmed cell death. HL-60 cells were sensitive to serum removal, and an increase of lipid peroxidation and apoptosis was observed. Long-term treatment with ethidium bromide induced the mitochondria-deficient rho(o)HL-60 cell line. These cells were surprisingly more resistant to serum removal, displaying fewer apoptotic cells and lower lipid peroxidation. HL-60 cells contained less ubiquinone at the plasma membrane than rho(o)HL-60 cells. Both cell types increased plasma membrane ubiquinone in response to serum removal, although this increase was much higher in rho(o) cells. Addition of ubiquinone to both cell cultures in the absence of serum improved cell survival with decreasing lipid peroxidation and apoptosis. Ceramide was accumulated after serum removal in HL-60 but not in rho(o)HL-60 cells, and exogenous ubiquinone reduced this accumulation. These results demonstrate a relationship between ubiquinone levels in the plasma membrane and the induction of serum withdrawal-induced apoptosis, and ceramide accumulation. Thus, ubiquinone, which is a central component of the plasma membrane electron transport system, can represent a first level of protection against oxidative damage caused by serum withdrawal.

  7. Current topics in membranes and transport

    Energy Technology Data Exchange (ETDEWEB)

    Kleinzeller, A.

    1987-01-01

    This book contains 10 chapters. Some of the chapter titles are: Expression of the Oxytocin and Vasopressin Genes; Steroid Effects on Excitable Membranes: The Secretory Vesicle in Processing and Secretion of Neuropeptides: and Steroid Hormone Influences on Cyclic AMP-Generating Systems.

  8. ATP-binding cassette transporters and sterol O-acyltransferases interact at membrane microdomains to modulate sterol uptake and esterification.

    Science.gov (United States)

    Gulati, Sonia; Balderes, Dina; Kim, Christine; Guo, Zhongmin A; Wilcox, Lisa; Area-Gomez, Estela; Snider, Jamie; Wolinski, Heimo; Stagljar, Igor; Granato, Juliana T; Ruggles, Kelly V; DeGiorgis, Joseph A; Kohlwein, Sepp D; Schon, Eric A; Sturley, Stephen L

    2015-11-01

    A key component of eukaryotic lipid homeostasis is the esterification of sterols with fatty acids by sterol O-acyltransferases (SOATs). The esterification reactions are allosterically activated by their sterol substrates, the majority of which accumulate at the plasma membrane. We demonstrate that in yeast, sterol transport from the plasma membrane to the site of esterification is associated with the physical interaction of the major SOAT, acyl-coenzyme A:cholesterol acyltransferase (ACAT)-related enzyme (Are)2p, with 2 plasma membrane ATP-binding cassette (ABC) transporters: Aus1p and Pdr11p. Are2p, Aus1p, and Pdr11p, unlike the minor acyltransferase, Are1p, colocalize to sterol and sphingolipid-enriched, detergent-resistant microdomains (DRMs). Deletion of either ABC transporter results in Are2p relocalization to detergent-soluble membrane domains and a significant decrease (53-36%) in esterification of exogenous sterol. Similarly, in murine tissues, the SOAT1/Acat1 enzyme and activity localize to DRMs. This subcellular localization is diminished upon deletion of murine ABC transporters, such as Abcg1, which itself is DRM associated. We propose that the close proximity of sterol esterification and transport proteins to each other combined with their residence in lipid-enriched membrane microdomains facilitates rapid, high-capacity sterol transport and esterification, obviating any requirement for soluble intermediary proteins.

  9. Electron Pathways through Erythrocyte Plasma Membrane in Human Physiology and Pathology: Potential Redox Biomarker?

    Directory of Open Access Journals (Sweden)

    Elena Matteucci

    2007-01-01

    Full Text Available Erythrocytes are involved in the transport of oxygen and carbon dioxide in the body. Since pH is the influential factor in the Bohr-Haldane effect, pHi is actively maintained via secondary active transports Na+/H+ exchange and HC3 -/Cl- anion exchanger. Because of the redox properties of the iron, hemoglobin generates reactive oxygen species and thus, the human erythrocyte is constantly exposed to oxidative damage. Although the adult erythrocyte lacks protein synthesis and cannot restore damaged proteins, it is equipped with high activity of protective enzymes. Redox changes in the cell initiate various signalling pathways. Plasma membrane oxido-reductases (PMORs are transmembrane electron transport systems that have been found in the membranes of all cells and have been extensively characterized in the human erythrocyte. Erythrocyte PMORs transfer reducing equivalents from intracellular reductants to extracellular oxidants, thus their most important role seems to be to enable the cell respond to changes in intra- and extra-cellular redox environments.So far the activity of erythrocyte PMORs in disease states has not been systematically investigated. This review summarizes present knowledge on erythrocyte electron transfer activity in humans (health, type 1 diabetes, diabetic nephropathy, and chronic uremia and hypothesizes an integrated model of the functional organization of erythrocyte plasma membrane where electron pathways work in parallel with transport metabolons to maintain redox homeostasis.

  10. Electron Pathways through Erythrocyte Plasma Membrane in Human Physiology and Pathology: Potential Redox Biomarker?

    Science.gov (United States)

    Matteucci, Elena; Giampietro, Ottavio

    2007-09-17

    Erythrocytes are involved in the transport of oxygen and carbon dioxide in the body. Since pH is the influential factor in the Bohr-Haldane effect, pHi is actively maintained via secondary active transports Na(+)/H(+) exchange and HC(3) (-)/Cl(-) anion exchanger. Because of the redox properties of the iron, hemoglobin generates reactive oxygen species and thus, the human erythrocyte is constantly exposed to oxidative damage. Although the adult erythrocyte lacks protein synthesis and cannot restore damaged proteins, it is equipped with high activity of protective enzymes. Redox changes in the cell initiate various signalling pathways. Plasma membrane oxido-reductases (PMORs) are transmembrane electron transport systems that have been found in the membranes of all cells and have been extensively characterized in the human erythrocyte. Erythrocyte PMORs transfer reducing equivalents from intracellular reductants to extracellular oxidants, thus their most important role seems to be to enable the cell respond to changes in intra- and extra-cellular redox environments.So far the activity of erythrocyte PMORs in disease states has not been systematically investigated. This review summarizes present knowledge on erythrocyte electron transfer activity in humans (health, type 1 diabetes, diabetic nephropathy, and chronic uremia) and hypothesizes an integrated model of the functional organization of erythrocyte plasma membrane where electron pathways work in parallel with transport metabolons to maintain redox homeostasis.

  11. Chloroplast membrane transport: interplay of prokaryotic and eukaryotic traits.

    Science.gov (United States)

    Vothknecht, Ute C; Soll, Jürgen

    2005-07-18

    Chloroplasts are specific plant organelles of prokaryotic origin. They are separated from the surrounding cell by a double membrane, which represents an effective barrier for the transport of metabolites and proteins. Specific transporters in the inner envelope membrane have been described, which facilitate the exchange of metabolites. In contrast, the outer envelope has been viewed for a long time as a molecular sieve that offers a mere size constriction to the passage of molecules. This view has been challenged lately, and a number of specific and regulated pore proteins of the outer envelope (OEPs) have been identified. These pores seem to have originated by adaptation of outer membrane proteins of the cyanobacterial ancestor of the chloroplast. In a similar fashion, the transport of proteins across the two envelope membranes is achieved by two hetero-oligomeric protein complexes called Toc (translocon in the outer envelope of chloroplasts) and Tic (translocon in the inner envelope of chloroplasts). The phylogenetic provenance of the translocon components is less clear, but at least the channel protein of the Toc translocon is of cyanobacterial origin. Characteristic of cyanobacteria and chloroplasts is furthermore a specialized internal membrane system, the thylakoids, on which the components of the photosynthetic machinery are located. Despite the importance of this membrane, very little is known about its phylogenetic origin or the manner of its synthesis. Vipp1 appears to be a ubiquitous component of thylakoid formation, while in chloroplasts of land plants, additionally a vesicle transport system of eukaryotic origin might be involved in this process.

  12. Biomechanics and thermodynamics of nanoparticle interactions with plasma and endosomal membrane lipids in cellular uptake and endosomal escape.

    Science.gov (United States)

    Peetla, Chiranjeevi; Jin, Shihua; Weimer, Jonathan; Elegbede, Adekunle; Labhasetwar, Vinod

    2014-07-01

    To be effective for cytoplasmic delivery of therapeutics, nanoparticles (NPs) taken up via endocytic pathways must efficiently transport across the cell membrane and subsequently escape from the secondary endosomes. We hypothesized that the biomechanical and thermodynamic interactions of NPs with plasma and endosomal membrane lipids are involved in these processes. Using model plasma and endosomal lipid membranes, we compared the interactions of cationic NPs composed of poly(D,L-lactide-co-glycolide) modified with the dichain surfactant didodecyldimethylammonium bromide (DMAB) or the single-chain surfactant cetyltrimethylammonium bromide (CTAB) vs anionic unmodified NPs of similar size. We validated our hypothesis in doxorubicin-sensitive (MCF-7, with relatively fluid membranes) and resistant breast cancer cells (MCF-7/ADR, with rigid membranes). Despite their cationic surface charges, DMAB- and CTAB-modified NPs showed different patterns of biophysical interaction: DMAB-modified NPs induced bending of the model plasma membrane, whereas CTAB-modified NPs condensed the membrane, thereby resisted bending. Unmodified NPs showed no effects on bending. DMAB-modified NPs also induced thermodynamic instability of the model endosomal membrane, whereas CTAB-modified and unmodified NPs had no effect. Since bending of the plasma membrane and destabilization of the endosomal membrane are critical biophysical processes in NP cellular uptake and endosomal escape, respectively, we tested these NPs for cellular uptake and drug efficacy. Confocal imaging showed that in both sensitive and resistant cells DMAB-modified NPs exhibited greater cellular uptake and escape from endosomes than CTAB-modified or unmodified NPs. Further, paclitaxel-loaded DMAB-modified NPs induced greater cytotoxicity even in resistant cells than CTAB-modified or unmodified NPs or drug in solution, demonstrating the potential of DMAB-modified NPs to overcome the transport barrier in resistant cells. In

  13. A Plasmodium falciparum copper-binding membrane protein with copper transport motifs

    Directory of Open Access Journals (Sweden)

    Choveaux David L

    2012-11-01

    Full Text Available Abstract Background Copper is an essential catalytic co-factor for metabolically important cellular enzymes, such as cytochrome-c oxidase. Eukaryotic cells acquire copper through a copper transport protein and distribute intracellular copper using molecular chaperones. The copper chelator, neocuproine, inhibits Plasmodium falciparum ring-to-trophozoite transition in vitro, indicating a copper requirement for malaria parasite development. How the malaria parasite acquires or secretes copper still remains to be fully elucidated. Methods PlasmoDB was searched for sequences corresponding to candidate P. falciparum copper-requiring proteins. The amino terminal domain of a putative P. falciparum copper transport protein was cloned and expressed as a maltose binding fusion protein. The copper binding ability of this protein was examined. Copper transport protein-specific anti-peptide antibodies were generated in chickens and used to establish native protein localization in P. falciparum parasites by immunofluorescence microscopy. Results Six P. falciparum copper-requiring protein orthologs and a candidate P. falciparum copper transport protein (PF14_0369, containing characteristic copper transport protein features, were identified in PlasmoDB. The recombinant amino terminal domain of the transport protein bound reduced copper in vitro and within Escherichia coli cells during recombinant expression. Immunolocalization studies tracked the copper binding protein translocating from the erythrocyte plasma membrane in early ring stage to a parasite membrane as the parasites developed to schizonts. The protein appears to be a PEXEL-negative membrane protein. Conclusion Plasmodium falciparum parasites express a native protein with copper transporter characteristics that binds copper in vitro. Localization of the protein to the erythrocyte and parasite plasma membranes could provide a mechanism for the delivery of novel anti-malarial compounds.

  14. Transport Physics in Reversed Shear Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Levinton, F.M.; Batha, S.H. [Fusion Physics and Technology, Inc., Torrance, CA (United States); Beer, M.A.; Bell, M.G.; Budny, R.V.; Efthimion, P.C.; Mazzucato, E.; Nazikian, R.; Park, H.K.; Ramsey, A.T.; Schmidt, G.L.; Scott, S.D.; Synakowski, E.J.; Taylor, G.; Von Goeler, S.; Zarnstorff, M.C. [Princeton University, NJ (United States). Plasma Physics Laboratory; Bush, C.E. [Oak Ridge National Lab., TN (United States)

    1997-12-31

    Reversed magnetic shear is considered a good candidate for improving the tokamak concept because it has the potential to stabilize MHD instabilities and reduce particle and energy transport. With reduced transport the high pressure gradient would generate a strong off-axis bootstrap current and could sustain a hollow current density profile. Such a combination of favorable conditions could lead to an attractive steady-state tokamak configuration. Indeed, a new tokamak confinement regime with reversed magnetic shear has been observed on the Tokamak Fusion Test Reactor (TFTR) where the particle, momentum, and ion thermal diffusivities drop precipitously, by over an order of magnitude. The particle diffusivity drops to the neoclassical level and the ion thermal diffusivity drops to much less than the neoclassical value in the region with reversed shear. This enhanced reversed shear (ERS) confinement mode is characterized by an abrupt transition with a large rate of rise of the density in the reversed shear region during neutral beam injection, resulting in nearly a factor of three increase in the central density to 1.2 X 10(exp 20) cube m. At the same time the density fluctuation level in the reversed shear region dramatically decreases. The ion and electron temperatures, which are about 20 keV and 7 keV respectively, change little during the ERS mode. The transport and transition into and out of the ERS mode have been studied on TFTR with plasma currents in the range 0.9-2.2 MA, with a toroidal magnetic field of 2.7-4.6 T, and the radius of the q(r) minimum, q{sub min}, has been varied from r/a = 0.35 to 0.55. Toroidal field and co/counter neutral beam injection toroidal rotation variations have been used to elucidate the underlying physics of the transition mechanism and power threshold of the ERS mode.

  15. FCCP depolarizes plasma membrane potential by activating proton and Na+ currents in bovine aortic endothelial cells.

    Science.gov (United States)

    Park, Kyu-Sang; Jo, Inho; Pak, Kim; Bae, Sung-Won; Rhim, Hyewhon; Suh, Suk-Hyo; Park, Jin; Zhu, Hong; So, Insuk; Kim, Ki Whan

    2002-01-01

    We investigated the effects of carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore and uncoupler of mitochondrial oxidative phosphorylation in mitochondria, on plasma membrane potential and ionic currents in bovine aortic endothelial cells (BAECs). The membrane potential and ionic currents of BAECs were recorded using the patch-clamp technique in current-clamp and voltage-clamp modes, respectively. FCCP activated ionic currents and depolarized the plasma membrane potential in a dose-dependent manner. Neither the removal of extracellular Ca2+ nor pretreatment with BAPTA/AM affected the FCCP-induced currents, implying that the currents are not associated with the FCCP-induced intracellular [Ca2+]i increase. FCCP-induced currents were significantly influenced by the changes in extracellular or intracellular pH; the increased proton gradient produced by lowering the extracellular pH or intracellular alkalinization augmented the changes in membrane potential and ionic currents caused by FCCP. FCCP-induced currents were significantly reduced under extracellular Na+-free conditions. The reversal potentials of FCCP-induced currents under Na+-free conditions were well fitted to the calculated equilibrium potential for protons. Interestingly, FCCP-induced Na+ transport (subtracted currents, I(control)- I(Na+-free) was closely dependent on extracellular pH, whereas FCCP-induced H+transport was not significantly affected by the absence of Na+. These results suggest that the FCCP-induced ionic currents and depolarization, which are strongly dependent on the plasmalemmal proton gradient, are likely to be mediated by both H+ and Na+ currents across the plasma membrane. The relationship between H+ and Na+ transport still needs to be determined.

  16. Proton transport in proton exchange membranes

    OpenAIRE

    Schmeisser, Jennifer Mary

    2007-01-01

    This work investigated several proton exchange membranes (PEMs): perfluorosulfonic acid-based polymers (Nafion®), sulfonated poly(ether ether ketone) (S-PEEK), radiation-grafted ethylenetetrafluoroethylene-grafted-poly(styrene sulfonic) acid (ETFE-g-PSSA), sulfonated trifluorostyrene-co-substituted trifluorostyrene (BAM®), sulfonated polystyrene-b-poly(ethylene-r-butylene)-b-polystyrene triblock copolymer (S-SEBS), and a series of novel photocurable polyelectrolytes. These polymer systems dif...

  17. Structure and Water Transport in Nafion Nanocomposite Membranes

    Science.gov (United States)

    Davis, Eric; Page, Kirt

    2014-03-01

    Perfluorinated ionomers, specifically Nafion, are the most widely used ion exchange membranes for vanadium redox flow battery applications, where an understanding of the relationship between membrane structure and transport of water/ions is critical to battery performance. In this study, the structure of Nafion/SiO2 nanocomposite membranes, synthesized using sol-gel chemistry, as well as cast directly from Nafion/SiO2 nanoparticle dispersions, was measured using both small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). Through contrast match studies of the SiO2 nanoparticles, direct information on the change in the structure of the Nafion membranes and the ion-transport channels within was obtained, where differences in membrane structure was observed between the solution-cast membranes and the membranes synthesized using sol-gel chemistry. Additionally, water sorption and diffusion in these Nafion/SiO2 nanocomposite membranes were measured using in situ time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and dynamic vapor sorption (DVS).

  18. Natural polyphenols: Influence on membrane transporters

    Directory of Open Access Journals (Sweden)

    Saad Abdulrahman Hussain

    2016-03-01

    Full Text Available Accumulated evidences have focused on the use of natural polyphenolic compounds as nutraceuticals, since they showed a wide range of bioactivities and exhibited protection against variety of age related disorders. Polyphenols have variable potencies to interact, and hence alter the activities of various transporter proteins, many of them classified as ATP-Binding Cassette transporters, like multidrug resistance protein (MDRP, and p-glycoprotein (P-gp. Some of the efflux transporters are generally linked with anticancer and antiviral drug resistance; in this context, polyphenols may be beneficial in modulating drug resistance by increasing the efficacy of anticancer and antiviral drugs. Additionally, these effects were implicated to explain the influence of dietary polyphenols on drug efficacy as result of food-drug interactions. However, limited data are available about the influence of these components on uptake transporters. Therefore, the objective of this article is to review the potential efficacies of polyphenols in modulating the functional integrity of uptake transporter proteins, including those terminated the effect of neurotransmitters, and their possible influence in neuropharmacology. [J Intercult Ethnopharmacol 2016; 5(1.000: 97-104

  19. Lack of effect of flurothyl, a non-anesthetic fluorinated ether, on rat brain synaptic plasma membrane calcium-ATPase.

    Science.gov (United States)

    Horn, J L; Janicki, P K; Franks, J J

    1999-01-01

    Plasma membrane Ca2+-ATPase (PMCA), a regulator of intracellular calcium, is inhibited by volatile anesthetics and by xenon and nitrous oxide. Response of a cellular system to anesthetics, particularly to volatile agents, raises the question of non-specific, even toxic, side effects unrelated to anesthetic action. Compounds with chemical and physical properties similar to halogenated anesthetics, but which lack anesthetic effect, have been used to address this question. We have compared the effects of halothane and flurothyl, a non-anesthetic fluorinated ether, on PMCA Ca2+ transport across isolated brain synaptic plasma membranes (SPM). Flurothyl, at concentrations predicted by the Meyer-Overton curve to range from 0.4 to 2.6 MAC (minimum alveolar concentration), had no significant on PMCA activity. In contrast halothane, 1.3 MAC, reduced Ca2+ transport 30 to 40%. These findings provide further evidence for a specific effect of inhalation anesthetics on neuronal plasma membrane Ca2+-ATPase.

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

    Science.gov (United States)

    Wuttke, Anne

    2015-04-01

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

  1. THE GAS TRANSPORT BEHAVIOR IN AROMATIC POLYESTER MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian; SUN Qiushi; HOU Xiaohuai

    1996-01-01

    Six aromatic polyesters were prepared for gas separation membranes, and their permeation properties for hydrogen, oxygen, nitrogen, carbon dioxide, and methane were measured at 30℃ and 1 atmosphere by low pressure manometric method. The correlation between the gas transport behavior and molecular structure of aromatic polyester membrane is discussed. These data are interpreted qualitatively in terms of the calculated packing density, gas-polymer interaction, concentration of aryl bromine on backbone, and effect of silane group on main chain of polymer.

  2. Membranes with functionalized carbon nanotube pores for selective transport

    Science.gov (United States)

    Bakajin, Olgica; Noy, Aleksandr; Fornasiero, Francesco; Park, Hyung Gyu; Holt, Jason K; Kim, Sangil

    2015-01-27

    Provided herein composition and methods for nanoporous membranes comprising single walled, double walled, or multi-walled carbon nanotubes embedded in a matrix material. Average pore size of the carbon nanotube can be 6 nm or less. These membranes are a robust platform for the study of confined molecular transport, with applications in liquid and gas separations and chemical sensing including desalination, dialysis, and fabric formation.

  3. 13th EU-US Transport Task Force Workshop on transport in fusion plasmas

    DEFF Research Database (Denmark)

    Connor, J.W.; Fasoli, A.; Hidalgo, C.

    2009-01-01

    This report summarizes the contributions presented at the 13th EU-US Transport Task Force Workshop on transport in fusion plasmas, held in Copenhagen, Denmark, 1-4 September 2008. There were sessions on core heat and particle transport; core and edge momentum transport; edge and scrape-off-layer ......This report summarizes the contributions presented at the 13th EU-US Transport Task Force Workshop on transport in fusion plasmas, held in Copenhagen, Denmark, 1-4 September 2008. There were sessions on core heat and particle transport; core and edge momentum transport; edge and scrape...

  4. PLASMA POLYMERIZATION OF HYDROPHILIC AND HYDROPHOBIC MONOMERS FOR SURFACE MODIFICATION OF NUCLE-MICROPOROUS MEMBRANE

    Institute of Scientific and Technical Information of China (English)

    LI Xuefen; LI Zhifen; CHEN Chuanfu; WU Wenhui

    1990-01-01

    Surface modification of nucle-microporous membrane by plasma polymerization of HEMA, NVP and D4 has been studied. The hydrophilicity of membranes was increased with increasing of plasma polymerization time of hydrophilic monomers HEMA and NVP. The flow rate of water through the membrane was increased remarkably after plasma polymerization of HEMA on it.

  5. Does hindered transport theory apply to desalination membranes?

    Science.gov (United States)

    Dražević, Emil; Košutić, Krešimir; Kolev, Vesselin; Freger, Viatcheslav

    2014-10-07

    As reverse osmosis (RO) and nanofiltration polyamide membranes become increasingly used for water purification, prediction of pollutant transport is required for membrane development and process engineering. Many popular models use hindered transport theory (HTT), which considers a spherical solute moving through an array of fluid-filled rigid cylindrical pores. Experiments and molecular dynamic simulations, however, reveal that polyamide membranes have a distinctly different structure of a "molecular sponge", a network of randomly connected voids widely distributed in size. In view of this disagreement, this study critically examined the validity of HTT by directly measuring diffusivities of several alcohols within a polyamide film of commercial RO membrane using attenuated total reflection-FTIR. It is found that measured diffusivities deviate from HTT predictions by as much as 2-3 orders of magnitude. This result indicates that HTT does not adequately describe solute transport in desalination membranes. As a more adequate alternative, the concept of random resistor networks is suggested, with resistances described by models of activated transport in "soft" polymers without a sharp size cutoff and with a proper address of solute partitioning.

  6. Plasma transport simulation modeling for helical confinement systems

    Energy Technology Data Exchange (ETDEWEB)

    Yamazaki, K.; Amano, T.

    1991-08-01

    New empirical and theoretical transport models for helical confinement systems are developed based on the neoclassical transport theory including the effect of radial electric field and multi-helicity magnetic components, and the drift wave turbulence transport for electrostatic and electromagnetic modes, or the anomalous semi-empirical transport. These electron thermal diffusivities are compared with CHS (Compact Helical System) experimental data, which indicates that the central transport coefficient of the ECH plasma agrees with the neoclassical axi-symmetric value and the transport outside the half radius is anomalous. On the other hand, the transport of NBI-heated plasmas is anomalous in the whole plasma region. This anomaly is not explained by the electrostatic drift wave turbulence models in these flat-density-profile discharges. For the detailed prediction of plasma parameters in LHD (Large Helical Device), 3-D(dimensional) equilibrium/1-D transport simulations including empirical or drift wave turbulence models are carried out, which suggests that the global confinement time of LHD is determined mainly by the electron anomalous transport near the plasma edge region rather than the helical ripple transport in the core region. Even if the ripple loss can be eliminated, the increase of the global confinement is 10%. However, the rise in the central ion temperature is more than 20%. If the anomalous loss can be reduced to the half level of the present scaling, like so-called `H-mode` of the tokamak discharge, the neoclassical ripple loss through the ion channel becomes important even in the plasma core. The 5% radial inward shift of the plasma column with respect to the major radius is effective for improving plasma confinement and raising more than 50% of the fusion product by reducing this neoclassical asymmetric ion transport loss and increasing 10% in the plasma radius. (author).

  7. Analysis of lipid-composition changes in plasma membrane microdomains.

    Science.gov (United States)

    Ogiso, Hideo; Taniguchi, Makoto; Okazaki, Toshiro

    2015-08-01

    Sphingolipids accumulate in plasma membrane microdomain sites, such as caveolae or lipid rafts. Such microdomains are considered to be important nexuses for signal transduction, although changes in the microdomain lipid components brought about by signaling are poorly understood. Here, we applied a cationic colloidal silica bead method to analyze plasma membrane lipids from monolayer cells cultured in a 10 cm dish. The detergent-resistant fraction from the silica bead-coated membrane was analyzed by LC-MS/MS to evaluate the microdomain lipids. This method revealed that glycosphingolipids composed the microdomains as a substitute for sphingomyelin (SM) in mouse embryonic fibroblasts (tMEFs) from an SM synthase 1/2 double KO (DKO) mouse. The rate of formation of the detergent-resistant region was unchanged compared with that of WT-tMEFs. C2-ceramide (Cer) stimulation caused greater elevations in diacylglycerol and phosphatidic acid levels than in Cer levels within the microdomains of WT-tMEFs. We also found that lipid changes in the microdomains of SM-deficient DKO-tMEFs caused by serum stimulation occurred in the same manner as that of WT-tMEFs. This practical method for analyzing membrane lipids will facilitate future comprehensive analyses of membrane microdomain-associated responses.

  8. Continuous Modeling of Calcium Transport Through Biological Membranes

    Science.gov (United States)

    Jasielec, J. J.; Filipek, R.; Szyszkiewicz, K.; Sokalski, T.; Lewenstam, A.

    2016-08-01

    In this work an approach to the modeling of the biological membranes where a membrane is treated as a continuous medium is presented. The Nernst-Planck-Poisson model including Poisson equation for electric potential is used to describe transport of ions in the mitochondrial membrane—the interface which joins mitochondrial matrix with cellular cytosis. The transport of calcium ions is considered. Concentration of calcium inside the mitochondrion is not known accurately because different analytical methods give dramatically different results. We explain mathematically these differences assuming the complexing reaction inside mitochondrion and the existence of the calcium set-point (concentration of calcium in cytosis below which calcium stops entering the mitochondrion).

  9. Barriers to Superfast Water Transport in Carbon Nanotube Membranes

    DEFF Research Database (Denmark)

    Walther, Jens Honore; Ritos, Konstantinos; Cruz-Chu, Eduardo R.

    2013-01-01

    Carbon nanotube (CNT) membranes hold the promise of extraordinary fast water transport for applications such as energy efficient filtration and molecular level drug delivery. However, experiments and computations have reported flow rate enhancements over continuum hydrodynamics that contradict each...... other by orders of magnitude. We perform large scale molecular dynamics simulations emulating for the first time the micrometer thick CNTs membranes used in experiments. We find transport enhancement rates that are length dependent due to entrance and exit losses but asymptote to 2 orders of magnitude...

  10. Mechanical reliability of geometrically imperfect tubular oxygen transport membranes

    DEFF Research Database (Denmark)

    Kwok, Kawai; Frandsen, Henrik Lund; Søgaard, Martin

    2014-01-01

    operation. This paper investigates numerically the failure risk of tubular oxygen transport membranes under industrial operating conditions using finite element modeling and Weibull strength analysis. The effects of component manufacturing defects on fracture probability are elucidated by explicit modeling...... of imperfections in the tubular membrane geometry. A supported membrane made of dense and porous Zr-doped-BSCF is studied as an illustrative example. It is shown that stresses induced by oxygen stoichiometry gradients relax over time due to creep and external pressure is the dominating source of stress in the long...... term. Therefore, creep has no adverse effect for geometrically perfect membranes. For geometrically imperfect membranes, curl and eccentricity are found to have insignificant influence on fracture risk while ovality is identified as the most critical geometric imperfection. Under the influence...

  11. Method of making a hydrogen transport membrane, and article

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Joseph M.; Corpus, Joseph M.; Lim, Hankwon

    2015-07-21

    The present invention relates to a method of manufacturing a hydrogen transport membrane and the composite article itself. More specifically, the invention relates to producing a membrane substrate, wherein the ceramic substrate is coated with a metal oxide slurry, thereby eliminating the need for an activation step prior to plating the ceramic membrane through an electroless plating process. The invention also relates to modifying the pore size and porosity of the substrate by oxidation or reduction of the particles deposited by the metal oxide slurry.

  12. A structural overview of the plasma membrane Na+,K+-ATPase and H+-ATPase ion pumps

    DEFF Research Database (Denmark)

    Morth, Jens Preben; Pedersen, Bjørn Panella; Buch-Pedersen, Morten Jeppe

    2011-01-01

    Plasma membrane ATPases are primary active transporters of cations that maintain steep concentration gradients. The ion gradients and membrane potentials derived from them form the basis for a range of essential cellular processes, in particular Na(+)-dependent and proton-dependent secondary tran......(+),K(+)-ATPase maintains a Na(+) and K(+) gradient in animal cells. Structural information provides insight into the function of these two distinct but related P-type pumps....

  13. A mechanism of raft formation on both plasma membrane layers

    Science.gov (United States)

    Sornbundit, Kan; Modchang, Charin; Triampo, Wannapong; Triampo, Darapond; Nuttavut, Narin

    2013-10-01

    A double-layered membrane model is proposed to explain raft formation and induction on extracellular (outer) and cytoplasmic (inner) leaflets of plasma membranes in a situation where only the outer layer has a tendency to phase-separate. In the model, lipid exchange with the surrounding medium is allowed on both layers, but lipid exchange between layers is not allowed. Simulations display domain stabilization on both layers. The effect of the lipid recycling frequencies on stationary domain sizes is also investigated. It is found that stationary domain sizes decrease when lipid recycling frequencies are stronger. Linear stability analysis is used to verify the results.

  14. Autoinhibitory Regulation of Plasma Membrane H+-ATPases

    DEFF Research Database (Denmark)

    Pedersen, Jesper Torbøl

    Electrochemical gradients across cell membranes are essential for nutrient uptake. In plant and fungal cells the electrochemical gradient across the plasma membrane (PM) can build much higher than in mammalian cells. The protein responsible for this gradient is the essential PM H+-ATPase that uses...... in mammalian cells and it has been speculated if they have a similar function in plants. In this thesis we show, that plant PM H+-ATPases are receptors for lysophospholipids and the autoinhibitory terminal inhibition is released upon lysophospholipid binding. Finally, we have used a group of stabilizing...

  15. Remodeling of the postsynaptic plasma membrane during neural development.

    Science.gov (United States)

    Tulodziecka, Karolina; Diaz-Rohrer, Barbara B; Farley, Madeline M; Chan, Robin B; Di Paolo, Gilbert; Levental, Kandice R; Waxham, M Neal; Levental, Ilya

    2016-11-07

    Neuronal synapses are the fundamental units of neural signal transduction and must maintain exquisite signal fidelity while also accommodating the plasticity that underlies learning and development. To achieve these goals, the molecular composition and spatial organization of synaptic terminals must be tightly regulated; however, little is known about the regulation of lipid composition and organization in synaptic membranes. Here we quantify the comprehensive lipidome of rat synaptic membranes during postnatal development and observe dramatic developmental lipidomic remodeling during the first 60 postnatal days, including progressive accumulation of cholesterol, plasmalogens, and sphingolipids. Further analysis of membranes associated with isolated postsynaptic densities (PSDs) suggests the PSD-associated postsynaptic plasma membrane (PSD-PM) as one specific location of synaptic remodeling. We analyze the biophysical consequences of developmental remodeling in reconstituted synaptic membranes and observe remarkably stable microdomains, with the stability of domains increasing with developmental age. We rationalize the developmental accumulation of microdomain-forming lipids in synapses by proposing a mechanism by which palmitoylation of the immobilized scaffold protein PSD-95 nucleates domains at the postsynaptic plasma membrane. These results reveal developmental changes in lipid composition and palmitoylation that facilitate the formation of postsynaptic membrane microdomains, which may serve key roles in the function of the neuronal synapse. © 2016 Tulodziecka et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  16. Transportation of Critically Ill Patients on Extracorporeal Membrane Oxygenation

    OpenAIRE

    Broman, L. Mikael; Frenckner, Björn

    2016-01-01

    Extracorporeal membrane oxygenation (ECMO) may be a life-saving procedure for patients with severe reversible pulmonary or cardiac failure or for patients in need for a bridge to transplantation. ECMO is provided by specialized centers, but patients in need of ECMO are frequently taken care of at other centers. Conventional transports to an ECMO center can be hazardous and deaths have been described. For this reason, many ECMO centers have developed transport programs with mobile ECMO. After ...

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

    Science.gov (United States)

    2013-06-25

    Bicarbonate Ion Transport in Alk Block 13: Supplementary Note © 2013 . Published in Journal of the Electrochemical Society , Vol. Ed. 0 160, (9) (2013...for public release; distribution is unlimited. ... 60325.7-CH-II F994 Journal of The Electrochemical Society , 160 (9) F994-F999 (2013) 0013-4651/2013...160(9)/F994/6/$31.00 © The Electrochemical Society Carbonate and Bicarbonate Ion Transport in Alkaline Anion Exchange Membranes Andrew M. Kiss,a

  18. The insertion and transport of anandamide in synthetic lipid membranes are both cholesterol-dependent.

    Directory of Open Access Journals (Sweden)

    Eric Di Pasquale

    Full Text Available BACKGROUND: Anandamide is a lipid neurotransmitter which belongs to a class of molecules termed the endocannabinoids involved in multiple physiological functions. Anandamide is readily taken up into cells, but there is considerable controversy as to the nature of this transport process (passive diffusion through the lipid bilayer vs. involvement of putative proteic transporters. This issue is of major importance since anandamide transport through the plasma membrane is crucial for its biological activity and intracellular degradation. The aim of the present study was to evaluate the involvement of cholesterol in membrane uptake and transport of anandamide. METHODOLOGY/PRINCIPAL FINDINGS: Molecular modeling simulations suggested that anandamide can adopt a shape that is remarkably complementary to cholesterol. Physicochemical studies showed that in the nanomolar concentration range, anandamide strongly interacted with cholesterol monolayers at the air-water interface. The specificity of this interaction was assessed by: i the lack of activity of structurally related unsaturated fatty acids (oleic acid and arachidonic acid at 50 nM on cholesterol monolayers, and ii the weak insertion of anandamide into phosphatidylcholine or sphingomyelin monolayers. In agreement with these data, the presence of cholesterol in reconstituted planar lipid bilayers triggered the stable insertion of anandamide detected as an increase in bilayer capacitance. Kinetics transport studies showed that pure phosphatidylcholine bilayers were weakly permeable to anandamide. The incorporation of cholesterol in phosphatidylcholine bilayers dose-dependently stimulated the translocation of anandamide. CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that cholesterol stimulates both the insertion of anandamide into synthetic lipid monolayers and bilayers, and its transport across bilayer membranes. In this respect, we suggest that besides putative anandamide protein-transporters

  19. An Adaptable Spectrin/Ankyrin-Based Mechanism for Long-Range Organization of Plasma Membranes in Vertebrate Tissues.

    Science.gov (United States)

    Bennett, Vann; Lorenzo, Damaris N

    2016-01-01

    Ankyrins are membrane-associated proteins that together with their spectrin partners are responsible for micron-scale organization of vertebrate plasma membranes, including those of erythrocytes, excitable membranes of neurons and heart, lateral membrane domains of columnar epithelial cells, and striated muscle. Ankyrins coordinate functionally related membrane transporters and cell adhesion proteins (15 protein families identified so far) within plasma membrane compartments through independently evolved interactions of intrinsically disordered sequences with a highly conserved peptide-binding groove formed by the ANK repeat solenoid. Ankyrins are coupled to spectrins, which are elongated organelle-sized proteins that form mechanically resilient arrays through cross-linking by specialized actin filaments. In addition to protein interactions, cellular targeting and assembly of spectrin/ankyrin domains also critically depend on palmitoylation of ankyrin-G by aspartate-histidine-histidine-cysteine 5/8 palmitoyltransferases, as well as interaction of beta-2 spectrin with phosphoinositide lipids. These lipid-dependent spectrin/ankyrin domains are not static but are locally dynamic and determine membrane identity through opposing endocytosis of bulk lipids as well as specific proteins. A partnership between spectrin, ankyrin, and cell adhesion molecules first emerged in bilaterians over 500 million years ago. Ankyrin and spectrin may have been recruited to plasma membranes from more ancient roles in organelle transport. The basic bilaterian spectrin-ankyrin toolkit markedly expanded in vertebrates through gene duplications combined with variation in unstructured intramolecular regulatory sequences as well as independent evolution of ankyrin-binding activity by ion transporters involved in action potentials and calcium homeostasis. In addition, giant vertebrate ankyrins with specialized roles in axons acquired new coding sequences by exon shuffling. We speculate that

  20. Membrane transporter engineering in industrial biotechnology and whole cell biocatalysis.

    Science.gov (United States)

    Kell, Douglas B; Swainston, Neil; Pir, Pınar; Oliver, Stephen G

    2015-04-01

    Because they mainly do not involve chemical changes, membrane transporters have been a Cinderella subject in the biotechnology of small molecule production, but this is a serious oversight. Influx transporters contribute significantly to the flux towards product, and efflux transporters ensure the accumulation of product in the much greater extracellular space of fermentors. Programmes for improving biotechnological processes might therefore give greater consideration to transporters than may have been commonplace. Strategies for identifying important transporters include expression profiling, genome-wide knockout studies, stress-based selection, and the use of inhibitors. In addition, modern methods of directed evolution and synthetic biology, especially those effecting changes in energy coupling, offer huge opportunities for increasing the flux towards extracellular product formation by transporter engineering.

  1. Triggered Ca2+ influx is required for extended synaptotagmin 1-induced ER-plasma membrane tethering.

    Science.gov (United States)

    Idevall-Hagren, Olof; Lü, Alice; Xie, Beichen; De Camilli, Pietro

    2015-09-01

    The extended synaptotagmins (E-Syts) are ER proteins that act as Ca(2+)-regulated tethers between the ER and the plasma membrane (PM) and have a putative role in lipid transport between the two membranes. Ca(2+) regulation of their tethering function, as well as the interplay of their different domains in such function, remains poorly understood. By exposing semi-intact cells to buffers of variable Ca(2+) concentrations, we found that binding of E-Syt1 to the PI(4,5)P2-rich PM critically requires its C2C and C2E domains and that the EC50 of such binding is in the low micromolar Ca(2+) range. Accordingly, E-Syt1 accumulation at ER-PM contact sites occurred only upon experimental manipulations known to achieve these levels of Ca(2+) via its influx from the extracellular medium, such as store-operated Ca(2+) entry in fibroblasts and membrane depolarization in β-cells. We also show that in spite of their very different physiological functions, membrane tethering by E-Syt1 (ER to PM) and by synaptotagmin (secretory vesicles to PM) undergo a similar regulation by plasma membrane lipids and cytosolic Ca(2+).

  2. Molecular level water and solute transport in reverse osmosis membranes

    Science.gov (United States)

    Lueptow, Richard M.; Shen, Meng; Keten, Sinan

    2015-11-01

    The water permeability and rejection characteristics of six solutes, methanol, ethanol, 2-propanol, urea, Na+, and Cl-, were studied for a polymeric reverse osmosis (RO) membrane using non-equilibrium molecular dynamics simulations. Results indicate that water flux increases with an increasing fraction of percolated free volume in the membrane polymer structure. Solute molecules display Brownian motion and hop from pore to pore as they pass through the membrane. The solute rejection depends on both the size of the solute molecule and the chemical interaction of the solute with water and the membrane. When the open spaces in the polymeric structure are such that solutes have to shed at least one water molecule from their solvation shell to pass through the membrane molecular structure, the water-solute pair interaction energy governs solute rejection. Organic solutes more easily shed water molecules than ions to more readily pass through the membrane. Hydrogen-bonding sites for molecules like urea also lead to a higher rejection. These findings underline the importance of the solute's solvation shell and solute-water-membrane chemistry in solute transport and rejection in RO membranes. Funded by the Institute for Sustainability and Energy at Northwestern with computing resources from XSEDE (NSF grant ACI-1053575).

  3. Plasma membrane protein trafficking in plant-microbe interactions: a plant cell point of view

    Directory of Open Access Journals (Sweden)

    Nathalie eLeborgne-Castel

    2014-12-01

    Full Text Available In order to ensure their physiological and cellular functions, plasma membrane (PM proteins must be properly conveyed from their site of synthesis, i.e. the endoplasmic reticulum, to their final destination, the PM, through the secretory pathway. PM protein homeostasis also relies on recycling and/or degradation, two processes that are initiated by endocytosis. Vesicular membrane trafficking events to and from the PM have been shown to be altered when plant cells are exposed to mutualistic or pathogenic microbes. In this review, we will describe the fine-tune regulation of such alterations, and their consequence in PM protein activity. We will consider the formation of intracellular perimicrobial compartments, the PM protein trafficking machinery of the host, and the delivery or retrieval of signaling and transport proteins such as pattern-recognition receptors, producers of reactive oxygen species, and sugar transporters.

  4. Plasma membrane lipids and their role in fungal virulence.

    Science.gov (United States)

    Rella, Antonella; Farnoud, Amir M; Del Poeta, Maurizio

    2016-01-01

    There has been considerable evidence in recent years suggesting that plasma membrane lipids are important regulators of fungal pathogenicity. Various glycolipids have been shown to impart virulent properties in several fungal species, while others have been shown to play a role in host defense. In addition to their role as virulence factors, lipids also contribute to other virulence mechanisms such as drug resistance, biofilm formation, and release of extracellular vesicles. In addition, lipids also affect the mechanical properties of the plasma membrane through the formation of packed microdomains composed mainly of sphingolipids and sterols. Changes in the composition of lipid microdomains have been shown to disrupt the localization of virulence factors and affect fungal pathogenicity. This review gathers evidence on the various roles of plasma membrane lipids in fungal virulence and how lipids might contribute to the different processes that occur during infection and treatment. Insight into the role of lipids in fungal virulence can lead to an improved understanding of the process of fungal pathogenesis and the development of new lipid-mediated therapeutic strategies.

  5. The apical plasma membrane of chitin-synthesizing epithelia

    Institute of Scientific and Technical Information of China (English)

    Bernard Moussian

    2013-01-01

    Chitin is the second most abundant polysaccharide on earth.It is produced at the apical side of epidermal,tracheal,fore-,and hindgut epithelial cells in insects as a central component of the protective and supporting extracellular cuticle.Chitin is also an important constituent of the midgut peritrophic matrix that encases the food supporting its digestion and protects the epithelium against invasion by possibly ingested pathogens.The enzyme producing chitin is a glycosyltransferase that resides in the apical plasma membrane forming a pore to extrude the chains of chitin into the extracellular space.The apical plasma membrane is not only a platform for chitin synthases but,probably through its shape and equipment with distinct factors,also plays an important role in orienting and organizing chitin fibers.Here,I review findings on the cellular and molecular constitution of the apical plasma membrane of chitin-producing epithelia mainly focusing on work done in the fruit fly Drosophila melanogaster.

  6. Super-resolution optical microscopy of lipid plasma membrane dynamics.

    Science.gov (United States)

    Eggeling, Christian

    2015-01-01

    Plasma membrane dynamics are an important ruler of cellular activity, particularly through the interaction and diffusion dynamics of membrane-embedded proteins and lipids. FCS (fluorescence correlation spectroscopy) on an optical (confocal) microscope is a popular tool for investigating such dynamics. Unfortunately, its full applicability is constrained by the limited spatial resolution of a conventional optical microscope. The present chapter depicts the combination of optical super-resolution STED (stimulated emission depletion) microscopy with FCS, and why it is an important tool for investigating molecular membrane dynamics in living cells. Compared with conventional FCS, the STED-FCS approach demonstrates an improved possibility to distinguish free from anomalous molecular diffusion, and thus to give new insights into lipid-protein interactions and the traditional lipid 'raft' theory.

  7. Oxygen transport membranes for biomass gasification and cement industry

    DEFF Research Database (Denmark)

    Cheng, Shiyang

    Oxygen transport membranes (OTMs) are of particular interest for their potential applications in high purity oxygen separation, biomass gasification and carbon capture and storage in cement production. Gd0.1Ce0.9O1.95-δ (GCO) is one of the interesting materials of OTMs because of its high ionic...

  8. Water vapor and gas transport through polymeric membranes

    NARCIS (Netherlands)

    Metz, S.J.

    2003-01-01

    Water vapor transport through polymeric materials plays an important role in a large number of applications such as: food packaging, breathable clothing, roofing membranes, diapers, and the removal of water vapor from gas streams (e.g. dehydration of natural gas or the drying of compressed air). Dep

  9. Water vapor and Gas Transport through Polymeric Membranes

    NARCIS (Netherlands)

    Metz, S.J.

    2003-01-01

    Water vapor transport through polymeric materials plays an important role in a large number of applications such as: food packaging, breathable clothing, roofing membranes, diapers, and the removal of water vapor from gas streams (e.g. dehydration of natural gas or the drying of compressed air).

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

    Science.gov (United States)

    Cheah, May Jean

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

  11. Multicomponent Transport through Realistic Zeolite Membranes: Characterization & Transport in Nanoporous Networks

    Energy Technology Data Exchange (ETDEWEB)

    William C. Conner

    2007-08-02

    These research studies focused on the characterization and transport for porous solids which comprise both microporosity and mesoporosity. Such materials represent membranes made from zeolites as well as for many new nanoporous solids. Several analytical sorption techniques were developed and evaluated by which these multi-dimensional porous solids could be quantitatively characterized. Notably an approach by which intact membranes could be studied was developed and applied to plate-like and tubular supported zeolitic membranes. Transport processes were studied experimentally and theoretically based on the characterization studies.

  12. Plasma membrane domains enriched in cortical endoplasmic reticulum function as membrane protein trafficking hubs.

    Science.gov (United States)

    Fox, Philip D; Haberkorn, Christopher J; Weigel, Aubrey V; Higgins, Jenny L; Akin, Elizabeth J; Kennedy, Matthew J; Krapf, Diego; Tamkun, Michael M

    2013-09-01

    In mammalian cells, the cortical endoplasmic reticulum (cER) is a network of tubules and cisterns that lie in close apposition to the plasma membrane (PM). We provide evidence that PM domains enriched in underlying cER function as trafficking hubs for insertion and removal of PM proteins in HEK 293 cells. By simultaneously visualizing cER and various transmembrane protein cargoes with total internal reflectance fluorescence microscopy, we demonstrate that the majority of exocytotic delivery events for a recycled membrane protein or for a membrane protein being delivered to the PM for the first time occur at regions enriched in cER. Likewise, we observed recurring clathrin clusters and functional endocytosis of PM proteins preferentially at the cER-enriched regions. Thus the cER network serves to organize the molecular machinery for both insertion and removal of cell surface proteins, highlighting a novel role for these unique cellular microdomains in membrane trafficking.

  13. Human membrane transporter database: a Web-accessible relational database for drug transport studies and pharmacogenomics.

    Science.gov (United States)

    Yan, Q; Sadée, W

    2000-01-01

    The human genome contains numerous genes that encode membrane transporters and related proteins. For drug discovery, development, and targeting, one needs to know which transporters play a role in drug disposition and effects. Moreover, genetic polymorphisms in human membrane transporters may contribute to interindividual differences in the response to drugs. Pharmacogenetics, and, on a genome-wide basis, pharmacogenomics, address the effect of genetic variants on an individual's response to drugs and xenobiotics. However, our knowledge of the relevant transporters is limited at present. To facilitate the study of drug transporters on a broad scale, including the use of microarray technology, we have constructed a human membrane transporter database (HMTD). Even though it is still largely incomplete, the database contains information on more than 250 human membrane transporters, such as sequence, gene family, structure, function, substrate, tissue distribution, and genetic disorders associated with transporter polymorphisms. Readers are invited to submit additional data. Implemented as a relational database, HMTD supports complex biological queries. Accessible through a Web browser user interface via Common Gateway Interface (CGI) and Java Database Connection (JDBC), HMTD also provides useful links and references, allowing interactive searching and downloading of data. Taking advantage of the features of an electronic journal, this paper serves as an interactive tutorial for using the database, which we expect to develop into a research tool.

  14. SNX12 role in endosome membrane transport.

    Directory of Open Access Journals (Sweden)

    Véronique Pons

    Full Text Available In this paper, we investigated the role of sorting nexin 12 (SNX12 in the endocytic pathway. SNX12 is a member of the PX domain-containing sorting nexin family and shares high homology with SNX3, which plays a central role in the formation of intralumenal vesicles within multivesicular endosomes. We found that SNX12 is expressed at very low levels compared to SNX3. SNX12 is primarily associated with early endosomes and this endosomal localization depends on the binding to 3-phosphoinositides. We find that overexpression of SNX12 prevents the detachment (or maturation of multivesicular endosomes from early endosomes. This in turn inhibits the degradative pathway from early to late endosomes/lysosomes, much like SNX3 overexpression, without affecting endocytosis, recycling and retrograde transport. In addition, while previous studies showed that Hrs knockdown prevents EGF receptor sorting into multivesicular endosomes, we find that overexpression of SNX12 restores the sorting process in an Hrs knockdown background. Altogether, our data show that despite lower expression level, SNX12 shares redundant functions with SNX3 in the biogenesis of multivesicular endosomes.

  15. Carrier-mediated ion transport in lipid bilayer membranes.

    Science.gov (United States)

    Laprade, R; Grenier, F; Pagé-Dansereau, M; Dansereau, J

    1984-08-01

    The electrical properties predicted by a widely accepted model for carrier-mediated ion transport in lipid bilayers are described. The different steps leading to ion transport and their associated rate constants are reaction at the interface between an ion in the aqueous phase and a carrier in the membrane (kRi), followed by translocation of the ion-carrier complex across the membrane interior (kis) and its dissociation at the other interface (kDi) after which the free carrier crosses back the membrane interior (ks). Results on glyceryl monooleate (GMO) membranes for a family of homologue carriers, the macrotetralide actin antibiotics (nonactin, monactin, dinactin, trinactin, and tetranactin) and a variety of ions (Na+, Cs+, Rb+, K+, NH4+, and Tl+) are presented. Internally consistent data obtained from steady-state electrical measurements (zero-current potential and conductance, current-voltage relationship) allow us to obtain the equilibrium permeability ratios for the different ions and show that for a given carrier kRi is relatively invariant from one ion to the other, except for Tl+ (larger), which implies that the ionic selectivity is controlled by the dissociation of the complex. The values of the individual rate constants obtained from current relaxation experiments are also presented and confirm the findings from steady-state measurements, as well as the isostericity concept for complexes of different ions with the same carrier (kis invariant). These also allow us to determine the aqueous phase membrane and torus membrane partition coefficients. Finally, the observed increase in kis from nonactin to tetranactin and, for all homologues, from GMO-decane to solvent-free GMO membranes, together with the concomitant decrease in kDi, can be explained in terms of modifications of electrostatic energy profiles induced by variations in carrier size and membrane thickness.

  16. A role for eisosomes in maintenance of plasma membrane phosphoinositide levels

    OpenAIRE

    Fröhlich, Florian; Christiano, Romain; Olson, Daniel K.; Alcazar-Roman, Abel; DeCamilli, Pietro; Walther, Tobias C

    2014-01-01

    The plasma membrane delineates the cell and mediates its communication and material exchange with the environment. Many processes of the plasma membrane occur through interactions of proteins with phosphatidylinositol(4,5)-bisphosphate (PI(4,5)P2), which is highly enriched in this membrane and is a key determinant of its identity. Eisosomes function in lateral organization of the plasma membrane, but the molecular function of their major protein subunits, the BAR domain–containing proteins Pi...

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

    DEFF Research Database (Denmark)

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

    2005-01-01

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

  18. Lipid domain structure of the plasma membrane revealed by patching of membrane components.

    Science.gov (United States)

    Harder, T; Scheiffele, P; Verkade, P; Simons, K

    1998-05-18

    Lateral assemblies of glycolipids and cholesterol, "rafts," have been implicated to play a role in cellular processes like membrane sorting, signal transduction, and cell adhesion. We studied the structure of raft domains in the plasma membrane of non-polarized cells. Overexpressed plasma membrane markers were evenly distributed in the plasma membrane. We compared the patching behavior of pairs of raft markers (defined by insolubility in Triton X-100) with pairs of raft/non-raft markers. For this purpose we cross-linked glycosyl-phosphatidylinositol (GPI)-anchored proteins placental alkaline phosphatase (PLAP), Thy-1, influenza virus hemagglutinin (HA), and the raft lipid ganglioside GM1 using antibodies and/or cholera toxin. The patches of these raft markers overlapped extensively in BHK cells as well as in Jurkat T-lymphoma cells. Importantly, patches of GPI-anchored PLAP accumulated src-like protein tyrosine kinase fyn, which is thought to be anchored in the cytoplasmic leaflet of raft domains. In contrast patched raft components and patches of transferrin receptor as a non-raft marker were sharply separated. Taken together, our data strongly suggest that coalescence of cross-linked raft elements is mediated by their common lipid environments, whereas separation of raft and non-raft patches is caused by the immiscibility of different lipid phases. This view is supported by the finding that cholesterol depletion abrogated segregation. Our results are consistent with the view that raft domains in the plasma membrane of non-polarized cells are normally small and highly dispersed but that raft size can be modulated by oligomerization of raft components.

  19. Collisionality dependent transport in TCV SOL plasmas

    DEFF Research Database (Denmark)

    Garcia, Odd Erik; Pitts, R.A.; Horacek, J.

    2007-01-01

    Results are presented from probe measurements in the low field side scrape-off layer (SOL) region of TCV during plasma current scan experiments. It is shown that with decreasing plasma current the radial particle density profile becomes broader and the fluctuation levels and turbulence driven...... radial particle flux increase. In the far SOL the fluctuations exhibit a high degree of statistical similarity and the particle density and flux at the wall radius scale inversely with the plasma current. Together with previous TCV density scan experiments, this indicates that plasma fluctuations...

  20. The role of membrane fatty-acid transporters in regulating skeletal muscle substrate use during exercise.

    Science.gov (United States)

    Pelsers, Maurice M A L; Stellingwerff, Trent; van Loon, Luc J C

    2008-01-01

    While endogenous carbohydrates form the main substrate source during high-intensity exercise, long-chain fatty acids (LCFA) represent the main substrate source during more prolonged low- to moderate-intensity exercise. Adipose tissue lipolysis is responsible for the supply of LCFA to the contracting muscle. Once taken up by skeletal muscle tissue, LCFA can either serve as a substrate for oxidative phosphorylation or can be directed towards esterification into triacylglycerol. Myocellular uptake of LCFA comprises a complex and incompletely understood process. Although LCFA can enter the cell via passive diffusion, more recent reports indicate that LCFA uptake is tightly regulated by plasma membrane-located transport proteins (fatty acid translocase [FAT/CD36], plasmalemmal-located fatty acid binding protein [FABPpm] and fatty acid transport protein [FATP]). Depending on cardiac and skeletal muscle energy demands, some of these LCFA transporters can translocate rapidly from intracellular pools to the plasma membrane to allow greater LCFA uptake. This translocation process can be induced by insulin and/or muscle contraction. However, the precise signalling pathways responsible for activating the translocation machinery remain to be elucidated. This article will provide an overview on the effects of diet, acute exercise and exercise training on the expression and/or translocation of the various LCFA transporters in skeletal muscle tissue (FAT/CD36, FABPpm, FATP).

  1. Plasma Membrane Protein Ubiquitylation and Degradation as Determinants of Positional Growth in Plants

    Institute of Scientific and Technical Information of China (English)

    Barbara Korbei; Christian Luschnig

    2013-01-01

    Being sessile organisms, plants evolved an unparalleled plasticity in their post-embryonic development, allowing them to adapt and fine-tune their vital parameters to an ever-changing environment. Cross-talk between plants and their environment requires tight regulation of information exchange at the plasma membrane (PM). Plasma membrane proteins mediate such communication, by sensing variations in nutrient availability, external cues as well as by controlled solute transport across the membrane border. Localiza-tion and steady-state levels are essential for PM protein function and ongoing research identified cis- and trans-acting determinants, involved in control of plant PM protein localization and turnover. In this overview, we summarize recent progress in our understanding of plant PM protein sorting and degradation via ubiquitylation, a post-translational and reversible modification of proteins. We highlight characterized components of the machinery involved in sorting of ubiquitylated PM proteins and discuss consequences of protein ubiquitylation on fate of selected PM proteins. Specifically, we focus on the role of ubiquitylation and PM protein degradation in the regulation of polar auxin transport (PAT). We combine this regulatory circuit with further aspects of PM protein sorting control, to address the interplay of events that might control PAT and polarized growth in higher plants.

  2. Contribution of plasma membrane Ca2+ ATPase to cerebellar synapse function

    Institute of Scientific and Technical Information of China (English)

    Helena; Huang; Raghavendra; Y; Nagaraja; Molly; L; Garside; Walther; Akemann; Thomas; Knpfel; Ruth; M; Empson

    2010-01-01

    The cerebellum expresses one of the highest levels of the plasma membrane Ca2+ATPase,isoform 2 in the mammalian brain.This highly efficient plasma membrane calcium transporter protein is enriched within the main output neurons of the cerebellar cortex;i.e. the Purkinje neurons(PNs) .Here we review recent evidence,including electrophysiological and calcium imaging approaches using the plasma membrane calcium ATPase 2(PMCA2) knockout mouse,to show that PMCA2 is critical for the physiological control of calcium at cerebellar synapses and cerebellar dependent behaviour.These studies have also revealed that deletionof PMCA2 throughout cerebellar development in the PMCA2 knockout mouse leads to permanent signalling and morphological alterations in the PN dendrites. Whilst these findings highlight the importance of PMCA2 during cerebellar synapse function and development,they also reveal some limitations in the use of the PMCA2 knockout mouse and the need for additional experimental approaches including cell-specific and reversible manipulation of PMCAs.

  3. Drosophila Lipophorin Receptors Recruit the Lipoprotein LTP to the Plasma Membrane to Mediate Lipid Uptake.

    Directory of Open Access Journals (Sweden)

    Míriam Rodríguez-Vázquez

    2015-06-01

    Full Text Available Lipophorin, the main Drosophila lipoprotein, circulates in the hemolymph transporting lipids between organs following routes that must adapt to changing physiological requirements. Lipophorin receptors expressed in developmentally dynamic patterns in tissues such as imaginal discs, oenocytes and ovaries control the timing and tissular distribution of lipid uptake. Using an affinity purification strategy, we identified a novel ligand for the lipophorin receptors, the circulating lipoprotein Lipid Transfer Particle (LTP. We show that specific isoforms of the lipophorin receptors mediate the extracellular accumulation of LTP in imaginal discs and ovaries. The interaction requires the LA-1 module in the lipophorin receptors and is strengthened by a contiguous region of 16 conserved amino acids. Lipophorin receptor variants that do not interact with LTP cannot mediate lipid uptake, revealing an essential role of LTP in the process. In addition, we show that lipophorin associates with the lipophorin receptors and with the extracellular matrix through weak interactions. However, during lipophorin receptor-mediated lipid uptake, LTP is required for a transient stabilization of lipophorin in the basolateral plasma membrane of imaginal disc cells. Together, our data suggests a molecular mechanism by which the lipophorin receptors tether LTP to the plasma membrane in lipid acceptor tissues. LTP would interact with lipophorin particles adsorbed to the extracellular matrix and with the plasma membrane, catalyzing the exchange of lipids between them.

  4. Function and evolution of channels and transporters in photosynthetic membranes.

    Science.gov (United States)

    Pfeil, Bernard E; Schoefs, Benoît; Spetea, Cornelia

    2014-03-01

    Chloroplasts from land plants and algae originated from an endosymbiotic event, most likely involving an ancestral photoautotrophic prokaryote related to cyanobacteria. Both chloroplasts and cyanobacteria have thylakoid membranes, harboring pigment-protein complexes that perform the light-dependent reactions of oxygenic photosynthesis. The composition, function and regulation of these complexes have thus far been the major topics in thylakoid membrane research. For many decades, we have also accumulated biochemical and electrophysiological evidence for the existence of solute transthylakoid transport activities that affect photosynthesis. However, research dedicated to molecular identification of the responsible proteins has only recently emerged with the explosion of genomic information. Here we review the current knowledge about channels and transporters from the thylakoid membrane of Arabidopsis thaliana and of the cyanobacterium Synechocystis sp. PCC 6803. No homologues of these proteins have been characterized in algae, although similar sequences could be recognized in many of the available sequenced genomes. Based on phylogenetic analyses, we hypothesize a host origin for most of the so far identified Arabidopsis thylakoid channels and transporters. Additionally, the shift from a non-thylakoid to a thylakoid location appears to have occurred at different times for different transport proteins. We propose that closer control of and provision for the thylakoid by products of the host genome has been an ongoing process, rather than a one-step event. Some of the proteins recruited to serve in the thylakoid may have been the result of the increased specialization of its pigment-protein composition and organization in green plants.

  5. Transport studies in fusion plasmas: Perturbative experiments

    NARCIS (Netherlands)

    Cardozo, N. L.

    1998-01-01

    By inducing in a small temperature perturbation in a plasma in a steady state one can determine the conductive and convective components of the heat flux, and the associated thermal diffusivity and convection velocity. The same can be done for the density, and in principle also other plasma paramete

  6. Turbulent transport and structural transition in confined plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Kimitaka; Itoh, Sanae; Fukuyama, Atsushi; Yagi, Masatoshi

    1996-10-01

    Theory of the far-nonequilibrium transport of plasmas is described. Analytic as well as simulation studies are developed. The subcritical nature of turbulence and the mechanism for self-sustaining are discussed. The transport coefficient is obtained. The pressure gradient is introduced as an order parameter, and the bifurcation from the collisional transport to the turbulent one is shown. The generation of the electric field and its influence on the turbulent transport are analyzed. The bifurcation of the radial electric field structure is addressed. The hysteresis appears in the flux-gradient relation. This bifurcation causes the multifold states in the plasma structure, driving the transition in transport coefficient or the self-generating oscillations in the flux. Structural formation and dynamics of plasma profiles are explained. (author)

  7. Plasma membrane mechanical stress activates TRPC5 channels.

    Directory of Open Access Journals (Sweden)

    Bing Shen

    Full Text Available Mechanical forces exerted on cells impose stress on the plasma membrane. Cells sense this stress and elicit a mechanoelectric transduction cascade that initiates compensatory mechanisms. Mechanosensitive ion channels in the plasma membrane are responsible for transducing the mechanical signals to electrical signals. However, the mechanisms underlying channel activation in response to mechanical stress remain incompletely understood. Transient Receptor Potential (TRP channels serve essential functions in several sensory modalities. These channels can also participate in mechanotransduction by either being autonomously sensitive to mechanical perturbation or by coupling to other mechanosensory components of the cell. Here, we investigated the response of a TRP family member, TRPC5, to mechanical stress. Hypoosmolarity triggers Ca2+ influx and cationic conductance through TRPC5. Importantly, for the first time we were able to record the stretch-activated TRPC5 current at single-channel level. The activation threshold for TRPC5 was found to be 240 mOsm for hypoosmotic stress and between -20 and -40 mmHg for pressure applied to membrane patch. In addition, we found that disruption of actin filaments suppresses TRPC5 response to hypoosmotic stress and patch pipette pressure, but does not prevent the activation of TRPC5 by stretch-independent mechanisms, indicating that actin cytoskeleton is an essential transduction component that confers mechanosensitivity to TRPC5. In summary, our findings establish that TRPC5 can be activated at the single-channel level when mechanical stress on the cell reaches a certain threshold.

  8. Ubiquitin initiates sorting of Golgi and plasma membrane proteins into the vacuolar degradation pathway

    Directory of Open Access Journals (Sweden)

    Scheuring David

    2012-09-01

    Full Text Available Abstract Background In yeast and mammals, many plasma membrane (PM proteins destined for degradation are tagged with ubiquitin. These ubiquitinated proteins are internalized into clathrin-coated vesicles and are transported to early endosomal compartments. There, ubiquitinated proteins are sorted by the endosomal sorting complex required for transport (ESCRT machinery into the intraluminal vesicles of multivesicular endosomes. Degradation of these proteins occurs after endosomes fuse with lysosomes/lytic vacuoles to release their content into the lumen. In plants, some PM proteins, which cycle between the PM and endosomal compartments, have been found to be ubiquitinated, but it is unclear whether ubiquitin is sufficient to mediate internalization and thus acts as a primary sorting signal for the endocytic pathway. To test whether plants use ubiquitin as a signal for the degradation of membrane proteins, we have translationally fused ubiquitin to different fluorescent reporters for the plasma membrane and analyzed their transport. Results Ubiquitin-tagged PM reporters localized to endosomes and to the lumen of the lytic vacuole in tobacco mesophyll protoplasts and in tobacco epidermal cells. The internalization of these reporters was significantly reduced if clathrin-mediated endocytosis was inhibited by the coexpression of a mutant of the clathrin heavy chain, the clathrin hub. Surprisingly, a ubiquitin-tagged reporter for the Golgi was also transported into the lumen of the vacuole. Vacuolar delivery of the reporters was abolished upon inhibition of the ESCRT machinery, indicating that the vacuolar delivery of these reporters occurs via the endocytic transport route. Conclusions Ubiquitin acts as a sorting signal at different compartments in the endomembrane system to target membrane proteins into the vacuolar degradation pathway: If displayed at the PM, ubiquitin triggers internalization of PM reporters into the endocytic transport route

  9. Cortisol-sensitive urea transport across the gill basolateral membrane of the gulf toadfish (Opsanus beta).

    Science.gov (United States)

    Rodela, Tamara M; Gilmour, Kathleen M; Walsh, Patrick J; McDonald, M Danielle

    2009-08-01

    Gulf toadfish (Opsanus beta) use a unique pulsatile urea excretion mechanism that allows urea to be voided in large pulses via the periodic insertion or activation of a branchial urea transporter. The precise cellular and subcellular location of the facilitated diffusion mechanism(s) remains unclear. An in vitro basolateral membrane vesicle (BLMV) preparation was used to test the hypothesis that urea movement across the gill basolateral membrane occurs through a cortisol-sensitive carrier-mediated mechanism. Toadfish BLMVs demonstrated two components of urea uptake: a linear element at high external urea concentrations, and a phloretin-sensitive saturable constituent (K(m) = 0.24 mmol/l; V(max) = 6.95 micromol x mg protein(-1) x h(-1)) at low urea concentrations ( 2, further suggestive of carrier-mediated processes. Our data provide evidence that a basolateral urea facilitated transporter accelerates the movement of urea between the plasma and gills to enable the pulsatile excretion of urea. Furthermore, in vivo infusion of cortisol caused a significant 4.3-fold reduction in BLMV urea transport capacity in lab-crowded fish, suggesting that cortisol inhibits the recruitment of urea transporters to the basolateral membrane, which may ultimately affect the size of the urea pulse event in gulf toadfish.

  10. Plasma Transport at the Magnetospheric Flank Boundary. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Otto, Antonius

    2012-04-23

    Progress is highlighted in these areas: 1. Model of magnetic reconnection induced by three-dimensional Kelvin Helmholtz (KH) modes at the magnetospheric flank boundary; 2. Quantitative evaluation of mass transport from the magnetosheath onto closed geomagnetic field for northward IMF; 3. Comparison of mass transfer by cusp reconnection and Flank Kelvin Helmholtz modes; 4. Entropy constraint and plasma transport in the magnetotail - a new mechanism for current sheet thinning; 5. Test particle model for mass transport onto closed geomagnetic field for northward IMF; 6. Influence of density asymmetry and magnetic shear on (a) the linear and nonlinear growth of 3D Kelvin Helmholtz (KH) modes, and (b) three-dimensional KH mediated mass transport; 7. Examination of entropy and plasma transport in the magnetotail; 8. Entropy change and plasma transport by KH mediated reconnection - mixing and heating of plasma; 9. Entropy and plasma transport in the magnetotail - tail reconnection; and, 10. Wave coupling at the magnetospheric boundary and generation of kinetic Alfven waves.

  11. Plant lipid environment and membrane enzymes: the case of the plasma membrane H+-ATPase.

    Science.gov (United States)

    Morales-Cedillo, Francisco; González-Solís, Ariadna; Gutiérrez-Angoa, Lizbeth; Cano-Ramírez, Dora Luz; Gavilanes-Ruiz, Marina

    2015-04-01

    Several lipid classes constitute the universal matrix of the biological membranes. With their amphipathic nature, lipids not only build the continuous barrier that confers identity to every cell and organelle, but they are also active actors that modulate the activity of the proteins immersed in the lipid bilayer. The plasma membrane H(+)-ATPase, an enzyme from plant cells, is an excellent example of a transmembrane protein whose activity is influenced by the hydrophilic compartments at both sides of the membrane and by the hydrophobic domains of the lipid bilayer. As a result, an extensive documentation of the effect of numerous amphiphiles in the enzyme activity can be found. Detergents, membrane glycerolipids, and sterols can produce activation or inhibition of the enzyme activity. In some cases, these effects are associated with the lipids of the membrane bulk, but in others, a direct interaction of the lipid with the protein is involved. This review gives an account of reports related to the action of the membrane lipids on the H(+)-ATPase activity.

  12. Mechanism of unassisted ion transport across membrane bilayers

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.

    1996-01-01

    To establish how charged species move from water to the nonpolar membrane interior and to determine the energetic and structural effects accompanying this process, we performed molecular dynamics simulations of the transport of Na+ and Cl- across a lipid bilayer located between two water lamellae. The total length of molecular dynamics trajectories generated for each ion was 10 ns. Our simulations demonstrate that permeation of ions into the membrane is accompanied by the formation of deep, asymmetric thinning defects in the bilayer, whereby polar lipid head groups and water penetrate the nonpolar membrane interior. Once the ion crosses the midplane of the bilayer the deformation "switches sides"; the initial defect slowly relaxes, and a defect forms in the outgoing side of the bilayer. As a result, the ion remains well solvated during the process; the total number of oxygen atoms from water and lipid head groups in the first solvation shell remains constant. A similar membrane deformation is formed when the ion is instantaneously inserted into the interior of the bilayer. The formation of defects considerably lowers the free energy barrier to transfer of the ion across the bilayer and, consequently, increases the permeabilities of the membrane to ions, compared to the rigid, planar structure, by approximately 14 orders of magnitude. Our results have implications for drug delivery using liposomes and peptide insertion into membranes.

  13. Effects of freezing and cold acclimation on the plasma membrane of isolated protoplasts, progress report

    Energy Technology Data Exchange (ETDEWEB)

    Steponkus, P L

    1993-01-01

    Our goal is to provide a mechanistic understanding of the cellular and molecular aspects of freezing injury and cold acclimation from a perspective of the structural and functional integrity of the plasma membrane -- the primary site of freezing injury in winter cereals. We have utilized protoplasts isolated from leaves of winter rye (Secale cereale L. cv Puma) to study the cryobehavior of the plasma membrane during a freeze/thaw cycle. The focus of our current studies is on lesions in the plasma membrane that result from severe freeze-induced dehydration and result in the alteration of the semipermeable characteristics of the plasma membrane so that the protoplasts are osmotically unresponsive. In protoplasts isolated from non-acclimated rye leaves (NA protoplasts), injury is associated with the formation of aparticulate domains in the plasma membrane, aparticulate lamellae subtending the plasma membrane, and lamellar-to-hexagonal II phase transitions in the plasma membrane and the subtending lamellae. However, lamellar-to-hexagonal II phase transitions are not observed following severe dehydration of protoplasts isolated from cold-acclimated rye leaves (ACC protoplasts). Rather, injury is associated with the fracture-jump lesion,'' which, in freeze-fracture electron microscopy studies, is manifested as localized deviations in the fracture face of the plasma membrane. The fracture plane jumps'' from the plasma membrane to either subtending aparticulate lamellae or aparticulate regions of various endomembranes (predominantly chloroplast envelopes) that are in close apposition with the plasma membrane.

  14. Stable inhibition of brain synaptic plasma membrane calcium ATPase in rats anesthetized with halothane.

    Science.gov (United States)

    Franks, J J; Horn, J L; Janicki, P K; Singh, G

    1995-01-01

    The authors recently showed that plasma membrane Ca(2+)-ATPase (PMCA) activity in cerebral synaptic plasma membrane (SPM) is diminished in a dose-related fashion during exposure in vitro to halothane, isoflurane, xenon, and nitrous oxide at clinically relevant partial pressures. They have now extended their work to in vivo studies, examining PMCA pumping in SPM obtained from control rats decapitated without anesthetic exposure, from rats decapitated during halothane anesthesia, and from rats decapitated after recovery from halothane anesthesia. Three treatment groups were studied: 1) C, control rats that were decapitated without anesthetic exposure, 2) A, anesthetized rats exposed to 1 minimum effective dose (MED) for 20 min and then decapitated, and 3) R, rats exposed to 1 MED for 20 min and then decapitated after recovery from anesthesia, defined as beginning to groom. Plasma membrane Ca(2+)-ATPase pumping and Ca(2+)-dependent ATPase hydrolytic activity, as well as sodium-calcium exchanger activity and Na+-K+-ATPase hydrolytic activity, were assessed in cerebral SPM. In addition, halothane effect on smooth endoplasmic reticulum Ca(2+)-ATPase (SERCA) was examined. Plasma membrane Ca(2+)-ATPase transport of Ca2+ into SPM vesicles from anesthetized rats was reduced to 71% of control (P SPM from rats killed while anesthetized with halothane, compared with rats killed without anesthesia or after recovery from anesthesia. The studies described in this report, in conjunction with previously reported inhibition of PMCA activity in vitro by a wide range of anesthetic agents, indicate a relationship between inhibition of PMCA and action of inhalational anesthetics.

  15. Effects of C-terminal truncations on trafficking of the yeast plasma membrane H+-ATPase.

    Science.gov (United States)

    Mason, A Brett; Allen, Kenneth E; Slayman, Carolyn W

    2006-08-18

    Within the large family of P-type cation-transporting ATPases, members differ in the number of C-terminal transmembrane helices, ranging from two in Cu2+-ATPases to six in H+-, Na+,K+-, Mg2+-, and Ca2+-ATPases. In this study, yeast Pma1 H+-ATPase has served as a model to examine the role of the C-terminal membrane domain in ATPase stability and targeting to the plasma membrane. Successive truncations were constructed from the middle of the major cytoplasmic loop to the middle of the extended cytoplasmic tail, adding back the C-terminal membrane-spanning helices one at a time. When the resulting constructs were expressed transiently in yeast, there was a steady increase in half-life from 70 min in Pma1 delta452 to 348 min in Pma1 delta901, but even the longest construct was considerably less stable than wild-type ATPase (t(1/2) = 11 h). Confocal immunofluorescence microscopy showed that 11 of 12 constructs were arrested in the endoplasmic reticulum and degraded in the proteasome. The only truncated ATPase that escaped the ER, Pma1 delta901, traveled slowly to the plasma membrane, where it hydrolyzed ATP and supported growth. Limited trypsinolysis showed Pma1 delta901 to be misfolded, however, resulting in premature delivery to the vacuole for degradation. As model substrates, this series of truncations affirms the importance of the entire C-terminal domain to yeast H+-ATPase biogenesis and defines a sequence element of 20 amino acids in the carboxyl tail that is critical to ER escape and trafficking to the plasma membrane.

  16. Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

    Science.gov (United States)

    Huang, Xin; Wang, Weiping; Zheng, Zhi; Fan, Wenling; Mao, Chun; Shi, Jialiang; Li, Lei

    2016-01-01

    The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.

  17. Solid polymer electrolyte composite membrane comprising plasma etched porous support

    Science.gov (United States)

    Liu, Han; LaConti, Anthony B.

    2010-10-05

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a rigid, non-electrically-conducting support, the support preferably being a sheet of polyimide having a thickness of about 7.5 to 15 microns. The support has a plurality of cylindrical pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores, which preferably have a diameter of about 0.1 to 5 microns, are made by plasma etching and preferably are arranged in a defined pattern, for example, with fewer pores located in areas of high membrane stress and more pores located in areas of low membrane stress. The pores are filled with a first solid polymer electrolyte, such as a perfluorosulfonic acid (PFSA) polymer. A second solid polymer electrolyte, which may be the same as or different than the first solid polymer electrolyte, may be deposited over the top and/or bottom of the first solid polymer electrolyte.

  18. Plasma membrane repair: the adaptable cell life-insurance.

    Science.gov (United States)

    Jimenez, Ana Joaquina; Perez, Franck

    2017-08-01

    The plasma membrane is the most basic element necessary for the cell to exist and be distinguishable from its environment. Regulated mechanisms allow tightly controlled communication between intacellular and extracellular medium allowing the maintenance of a specific biochemical environment, optimized for cellular functions. The anarchic and uncontrolled opening of a hole in the PM induces a change in the concentration of ions and oxidizing agents perturbing homeostasis. Fortunately, the cell possesses mechanisms that are capable of reacting to sudden extracellular medium entry and to block the leakage locally. Here we summarize the known mechanisms of membrane repair and how the size of the wound and the resulting calcium entry activates preferentially one or another mechanism adapted to the magnitude of the injury. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Membrane transporters and drought resistance – a complex issue

    Directory of Open Access Journals (Sweden)

    Karolina Maria Jarzyniak

    2014-12-01

    Full Text Available Land plants have evolved complex adaptation strategies to survive changes in water status in the environment. Understanding the molecular nature of such adaptive changes allows the development of rapid innovations to improve crop performance. Plant membrane transport systems play a significant role when adjusting to water scarcity. Here we put proteins participating in transmembrane allocations of various molecules in the context of stomatal, cuticular and root responses, representing a part of the drought resistance strategy. Their role in the transport of signaling molecules, ions or osmolytes is summarized and the challenge of the forthcoming research, resulting from the recent discoveries, is highlighted.

  20. Kinetic modelling of coupled transport across biological membranes.

    Science.gov (United States)

    Korla, Kalyani; Mitra, Chanchal K

    2014-04-01

    In this report, we have modelled a secondary active co-transporter (symport and antiport), based on the classical kinetics model. Michaelis-Menten model of enzyme kinetics for a single substrate, single intermediate enzyme catalyzed reaction was proposed more than a hundred years ago. However, no single model for the kinetics of co-transport of molecules across a membrane is available in the literature We have made several simplifying assumptions and have followed the basic Michaelis-Menten approach. The results have been simulated using GNU Octave. The results will be useful in general kinetic simulations and modelling.

  1. On turbulent transport in burning plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, K. [National Inst. for Fusion Science, Toki, Gifu (Japan); Yagi, M.; Itoh, S.-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Fukuyama, A. [Kyoto Univ. (Japan). Dept. of Nuclear Engineering

    2000-03-01

    The change of the transport coefficient due to the fusion energy source is studied. The scale invariance property of the reduced set of equations is investigated in the presence of the self-heating term due to the fusion reaction. The pressure gradient as well as the fusion power are the free energy sources that dictate the turbulent transport. It is shown that the burning transport coefficient can have a form with much wider variety, and that the transport property could be different owing to the self-heating by the fusion reactions. (author)

  2. Isothermal titration calorimetry of ion-coupled membrane transporters.

    Science.gov (United States)

    Boudker, Olga; Oh, SeCheol

    2015-04-01

    Binding of ligands, ranging from proteins to ions, to membrane proteins is associated with absorption or release of heat that can be detected by isothermal titration calorimetry (ITC). Such measurements not only provide binding affinities but also afford direct access to thermodynamic parameters of binding--enthalpy, entropy and heat capacity. These parameters can be interpreted in a structural context, allow discrimination between different binding mechanisms and guide drug design. In this review, we introduce advantages and limitations of ITC as a methodology to study molecular interactions of membrane proteins. We further describe case studies where ITC was used to analyze thermodynamic linkage between ions and substrates in ion-coupled transporters. Similar type of linkage analysis will likely be applicable to a wide range of transporters, channels, and receptors. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Revisiting transbilayer distribution of lipids in the plasma membrane.

    Science.gov (United States)

    Murate, Motohide; Kobayashi, Toshihide

    2016-01-01

    Whereas asymmetric transbilayer lipid distribution in the plasma membrane is well recognized, methods to examine the precise localization of lipids are limited. In this review, we critically evaluate the methods that are applied to study transbilayer asymmetry of lipids, summarizing the factors that influence the measurement. Although none of the present methods is perfect, the current application of immunoelectron microscopy-based technique provides a new picture of lipid asymmetry. Next, we summarize the transbilayer distribution of individual lipid in both erythrocytes and nucleated cells. Finally we discuss the concept of the interbilayer communication of lipids.

  4. Opposing effects of cAMP and T259 phosphorylation on plasma membrane diffusion of the water channel aquaporin-5 in Madin-Darby canine kidney cells

    DEFF Research Database (Denmark)

    Koffman, Jennifer Skaarup; Christensen, Eva Arnspang; Marlar, Saw

    2015-01-01

    Aquaporin-5 (AQP5) facilitates passive water transport in glandular epithelia in response to secretory stimuli via intracellular pathways involving calcium release, cAMP and protein kinase A (PKA). In epithelial plasma membranes, AQP5 may be acutely regulated to facilitate water transport in resp...

  5. Two-dimensional transport study of scrape off layer plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Nobuyuki [Interdisciplinary Graduate School of Advanced Energy Engineering Sciences, Kyushu University, Fukuoka (Japan); Yagi, Masatoshi; Itoh, Sanae-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    1999-09-01

    Two-dimensional transport code is developed to analyzed the heat pulse propagation in the scrape-off layer plasma. The classical and anomalous transport models are considered as a thermal diffusivity perpendicular to the magnetic field. On the other hand, the classical transport model is chosen as a thermal diffusivity parallel to the magnetic field. The heat deposition profiles are evaluated for various kinds of transport models. It is found that the heat pulse which arrives at the divertor plate due to the classical transport is largest compared with other models. The steady state temperate profiles of the electron and ion are also discussed. (author)

  6. C11ORF24 is a novel type I membrane protein that cycles between the Golgi apparatus and the plasma membrane in Rab6-positive vesicles.

    Science.gov (United States)

    Fraisier, Vincent; Kasri, Amal; Miserey-Lenkei, Stéphanie; Sibarita, Jean-Baptiste; Nair, Deepak; Mayeux, Adeline; Bardin, Sabine; Toyoda, Yusuke; Poser, Ina; Poznyakovskiy, Andrei; Goud, Bruno; Hyman, Anthony A; Dimitrov, Ariane

    2013-01-01

    The Golgi apparatus is an intracellular compartment necessary for post-translational modification, sorting and transport of proteins. It plays a key role in mitotic entry through the Golgi mitotic checkpoint. In order to identify new proteins involved in the Golgi mitotic checkpoint, we combine the results of a knockdown screen for mitotic phenotypes and a localization screen. Using this approach, we identify a new Golgi protein C11ORF24 (NP_071733.1). We show that C11ORF24 has a signal peptide at the N-terminus and a transmembrane domain in the C-terminal region. C11ORF24 is localized on the Golgi apparatus and on the trans-Golgi network. A large part of the protein is present in the lumen of the Golgi apparatus whereas only a short tail extends into the cytosol. This cytosolic tail is well conserved in evolution. By FRAP experiments we show that the dynamics of C11ORF24 in the Golgi membrane are coherent with the presence of a transmembrane domain in the protein. C11ORF24 is not only present on the Golgi apparatus but also cycles to the plasma membrane via endosomes in a pH sensitive manner. Moreover, via video-microscopy studies we show that C11ORF24 is found on transport intermediates and is colocalized with the small GTPase RAB6, a GTPase involved in anterograde transport from the Golgi to the plasma membrane. Knocking down C11ORF24 does not lead to a mitotic phenotype or an intracellular transport defect in our hands. All together, these data suggest that C11ORF24 is present on the Golgi apparatus, transported to the plasma membrane and cycles back through the endosomes by way of RAB6 positive carriers.

  7. Electrostatic fluctuations and turbulent plasma transport in low-β plasmas

    DEFF Research Database (Denmark)

    Nielsen, A.H.; Pécseli, H.L.; Juul Rasmussen, J.

    1995-01-01

    Low frequency electrostatic fluctuations are studied experimentally in a low-beta plasma, with particular attention to their importance for the anomalous plasma transport across magnetic field lines. The presence of large coherent structures in a turbulent background is demonstrated by a conditio......Low frequency electrostatic fluctuations are studied experimentally in a low-beta plasma, with particular attention to their importance for the anomalous plasma transport across magnetic field lines. The presence of large coherent structures in a turbulent background is demonstrated...

  8. Development of thin film oxygen transport membranes on metallic supports

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Ye

    2012-04-25

    interlayer, though it comprised some cracks. The second interlayer had a crack-free and porous structure. The top membrane layer was deposited by physical vapor deposition (magnetron sputtering) with a thickness of 3.8 {mu}m improving the gastightness considerably but showing still reasonable air-leakage. Summarizing, the successful development of a metal-perovskite-composite could be shown, which acts as a basis for a further development of a gas-tight metal supported oxygen transport asymmetric membrane structure. (orig.)

  9. Interchange instability and transport in matter-antimatter plasmas

    CERN Document Server

    Kendl, Alexander; Wiesenberger, Matthias; Held, Markus

    2016-01-01

    Symmetric electron-positron plasmas in inhomogeneous magnetic fields are intrinsically subject to interchange instability and transport. Scaling relations for the propagation velocity of density blob perturbations relevant to transport in isothermal magnetically confined electron-positron plasmas are deduced, including damping effects when Debye lengths are large compared to Larmor radii. The relations are verified by nonlinear full-F gyrofluid computations. Results are in favour of sufficient magnetic confinement for planned electron-positron plasma experiments. The model is generalised to other matter-antimatter plasmas. Magnetised electron-positron-proton-antiproton plasmas are susceptible to interchange driven local matter-antimatter separation, which can be expected to impede (so far unrealised) sustained laboratory magnetic confinement.

  10. Plasma Viscosity with Mass Transport in Spherical ICF Implosion Simulations

    CERN Document Server

    Vold, Erik L; Ortega, Mario I; Moll, Ryan; Fenn, Daniel; Molvig, Kim

    2015-01-01

    The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion (ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. We have implemented a Lagrange hydrodynamic code in one-dimensional spherical geometry with plasma viscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasma viscosity and to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasma viscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Plasma viscosity reduc...

  11. Plasma Interactions with Mixed Materials and Impurity Transport

    Energy Technology Data Exchange (ETDEWEB)

    Rognlien, T. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Beiersdorfer, Peter [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chernov, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Frolov, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Magee, E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rudd, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Umansky, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-10-28

    The project brings together three discipline areas at LLNL to develop advanced capability to predict the impact of plasma/material interactions (PMI) on metallic surfaces in magnetic fusion energy (MFE) devices. These areas are (1) modeling transport of wall impurity ions through the edge plasma to the core plasma, (2) construction of a laser blow-off (LBO) system for injecting precise amounts of metallic atoms into a tokamak plasma, and (3) material science analysis of fundamental processes that modify metallic surfaces during plasma bombardment. The focus is on tungsten (W), which is being used for the ITER divertor and in designs of future MFE devices. In area (1), we have worked with the University of California, San Diego (UCSD) on applications of the UEDGE/DUSTT coupled codes to predict the influx of impurity ions from W dust through the edge plasma, including periodic edge-plasma oscillations, and revived a parallel version of UEDGE to speed up these simulations. In addition, the impurity transport model in the 2D UEDGE code has been implemented into the 3D BOUT++ turbulence/transport code to allow fundamental analysis of the impact of strong plasma turbulence on the impurity transport. In area (2), construction and testing of the LBO injection system has been completed. The original plan to install the LBO on the National Spherical Torus Experiment Upgrade (NSTX-U) at Princeton and its use to validate the impurity transport simulations is delayed owing to NSTX-U being offline for substantial magnetic coil repair period. In area (3), an analytic model has been developed to explain the growth of W tendrils (or fuzz) observed for helium-containing plasmas. Molecular dynamics calculations of W sputtering by W and deuterium (D) ions shows that a spatial blending of interatomic potentials is needed to describe the near-surface and deeper regions of the material.

  12. Turbulent transport and structural transition in confined plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Kimitaka [National Inst. for Fusion Science, Nagoya (Japan); Itoh, Sanae-I; Yagi, Masatoshi [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Fukuyama, Atsushi [Okayama Univ. (Japan). School of Engineering

    1997-05-01

    The theory of far-nonequilibrium transport of plasmas is described. Analytic as well as simulation studies are developed. The subcritical nature coefficient is obtained. The pressure gradient is introduced as an order parameter, and the bifurcation from collisional to turbulent transport is shown. The generation of the electric field and its influence on the turbulent transport are analysed. The bifurcation of the radial electric field structure is addressed. Hysteresis appears in the flux-gradient relation. This bifurcation causes the multifold states in the plasma structure, driving the transition in the transport coefficient or the self-generating oscillations in the flux. The structural formation and dynamics of plasma profiles are explained. (Author).

  13. Numerical simulation of ion transport membrane reactors: Oxygen permeation and transport and fuel conversion

    KAUST Repository

    Hong, Jongsup

    2012-07-01

    Ion transport membrane (ITM) based reactors have been suggested as a novel technology for several applications including fuel reforming and oxy-fuel combustion, which integrates air separation and fuel conversion while reducing complexity and the associated energy penalty. To utilize this technology more effectively, it is necessary to develop a better understanding of the fundamental processes of oxygen transport and fuel conversion in the immediate vicinity of the membrane. In this paper, a numerical model that spatially resolves the gas flow, transport and reactions is presented. The model incorporates detailed gas phase chemistry and transport. The model is used to express the oxygen permeation flux in terms of the oxygen concentrations at the membrane surface given data on the bulk concentration, which is necessary for cases when mass transfer limitations on the permeate side are important and for reactive flow modeling. The simulation results show the dependence of oxygen transport and fuel conversion on the geometry and flow parameters including the membrane temperature, feed and sweep gas flow, oxygen concentration in the feed and fuel concentration in the sweep gas. © 2012 Elsevier B.V.

  14. Effects of freezing and cold acclimation on the plasma membrane of isolated protoplasts

    Energy Technology Data Exchange (ETDEWEB)

    Steponkus, P.L.

    1991-01-01

    This project focuses on lesions in the plasma membrane of protoplasts that occur during freezing to temperatures below {minus}5{degrees} which result in changes in the semipermeablity of the plasma membrane. This injury, referred to as loss of osmotic responsiveness, is associated with the formation of large, aparticulate domains in the plasma membrane, aparticulate lamellae subtending the plasma membrane, and lamellar-to-hexagonal{sub II} phase transitions in the plasma membrane and subtending lamellar. The goals of this project are to provide a mechanistic understanding of the mechanism by which freeze-induced dehydration effects the formation of aparticulate domains and lamellar-to-hexagonal{sub II} phase transitions and to determine the mechanisms by which cold acclimation and cryoprotectants preclude or diminish these ultrastructural changes. Our working hypothesis is the formation of aparticulate domains and lamellar-to-hexagon{sub II} phase transitions in the plasma membrane and subtending lamellae are manifestations of hydration-dependent bilayer-bilayer interactions.

  15. Specific interaction of postsynaptic densities with membrane rafts isolated from synaptic plasma membranes.

    Science.gov (United States)

    Liu, Qian; Yao, Wei-Dong; Suzuki, Tatsuo

    2013-06-01

    Postsynaptic membrane rafts are believed to play important roles in synaptic signaling, plasticity, and maintenance. We recently demonstrated the presence, at the electron microscopic level, of complexes consisting of membrane rafts and postsynaptic densities (PSDs) in detergent-resistant membranes (DRMs) prepared from synaptic plasma membranes (SPMs) ( Suzuki et al., 2011 , J Neurochem, 119, 64-77). To further explore these complexes, here we investigated the nature of the binding between purified SPM-DRMs and PSDs in vitro. In binding experiments, we used SPM-DRMs prepared after treating SPMs with n-octyl-β-d-glucoside, because at concentrations of 1.0% or higher it completely separates SPM-DRMs and PSDs, providing substantially PSD-free unique SPM-DRMs as well as DRM-free PSDs. PSD binding to PSD-free DRMs was identified by mass spectrometry, Western blotting, and electron microscopy. PSD proteins were not incorporated into SPMs, and significantly less PSD proteins were incorporated into DRMs prepared from liver membranes, providing in vitro evidence that binding of PSDs to DRMs is specific and suggestion of the presence of specific interacting molecules. These specific interactions may have important roles in synaptic development, function, and plasticity in vivo. In addition, the binding system we developed may be a good tool to search for binding molecules and binding mechanisms between PSDs and rafts.

  16. Quantum dot single molecule tracking reveals a wide range of diffusive motions of membrane transport proteins

    Science.gov (United States)

    Crane, Jonathan M.; Haggie, Peter M.; Verkman, A. S.

    2009-02-01

    Single particle tracking (SPT) provides information about the microscopic motions of individual particles in live cells. We applied SPT to study the diffusion of membrane transport proteins in cell plasma membranes in which individual proteins are labeled with quantum dots at engineered extracellular epitopes. Software was created to deduce particle diffusive modes from quantum dot trajectories. SPT of aquaporin (AQP) water channels and cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels revealed several types of diffusion. AQP1 was freely mobile in cell membranes, showing rapid, Brownian-type diffusion. The full-length (M1) isoform of AQP4 also diffused rapidly, though the diffusion of a shorter (M23) isoform of AQP4 was highly restricted due to its supermolecular assembly in raft-like orthogonal arrays. CFTR mobility was also highly restricted, in a spring-like potential, due to its tethering to the actin cytoskeleton through PDZ-domain C-terminus interactions. The biological significance of regulated diffusion of membrane transport proteins is a subject of active investigation.

  17. Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It.

    Science.gov (United States)

    Kraft, Mary L

    2016-01-01

    Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with

  18. Regulation of Ras signaling and function by plasma membrane microdomains.

    Science.gov (United States)

    Goldfinger, Lawrence E; Michael, James V

    2017-02-07

    Together H-, N- and KRAS mutations are major contributors to ~30% of all human cancers. Thus, Ras inhibition remains an important anti-cancer strategy. The molecular mechanisms of isotypic Ras oncogenesis are still not completely understood. Monopharmacological therapeutics have not been successful in the clinic. These disappointing outcomes have led to attempts to target elements downstream of Ras, mainly targeting either the Phosphatidylinositol 3-Kinase (PI3K) or Mitogen-Activated Protein Kinase (MAPK) pathways. While several such approaches are moderately effective, recent efforts have focused on preclinical evaluation of combination therapies to improve efficacies. This review will detail current understanding of the contributions of plasma membrane microdomain targeting of Ras to mitogenic and tumorigenic signaling and tumor progression. Moreover, this review will outline novel approaches to target Ras in cancers, including targeting schemes for new drug development, as well as putative re-purposing of drugs in current use to take advantage of blunting Ras signaling by interfering with Ras plasma membrane microdomain targeting and retention.

  19. MLKL Compromises Plasma Membrane Integrity by Binding to Phosphatidylinositol Phosphates

    Directory of Open Access Journals (Sweden)

    Yves Dondelinger

    2014-05-01

    Full Text Available Although mixed lineage kinase domain-like (MLKL protein has emerged as a specific and crucial protein for necroptosis induction, how MLKL transduces the death signal remains poorly understood. Here, we demonstrate that the full four-helical bundle domain (4HBD in the N-terminal region of MLKL is required and sufficient to induce its oligomerization and trigger cell death. Moreover, we found that a patch of positively charged amino acids on the surface of the 4HBD binds to phosphatidylinositol phosphates (PIPs and allows recruitment of MLKL to the plasma membrane. Importantly, we found that recombinant MLKL, but not a mutant lacking these positive charges, induces leakage of PIP-containing liposomes as potently as BAX, supporting a model in which MLKL induces necroptosis by directly permeabilizing the plasma membrane. Accordingly, we found that inhibiting the formation of PI(5P and PI(4,5P2 specifically inhibits tumor necrosis factor (TNF-mediated necroptosis but not apoptosis.

  20. Surface transport in plasma-balls

    CERN Document Server

    Armas, Jay; Kundu, Nilay

    2015-01-01

    We study the surface transport properties of stationary localized configurations of relativistic fluids to the first two non-trivial orders in a derivative expansion. By demanding that these finite lumps of relativistic fluid are described by a thermal partition function with arbitrary stationary background metric and gauge fields, we are able to find several constraints among surface transport coefficients. At leading order, besides recovering the surface thermodynamics, we obtain a generalization of the Young-Laplace equation for relativistic fluid surfaces, by considering a temperature dependence in the surface tension, which is further generalized in the context of superfluids. At the next order, for uncharged fluids in 3+1 dimensions, we show that besides the 3 independent bulk transport coefficients previously known, a generic localized configuration is characterized by 3 additional surface transport coefficients, one of which may be identified with the surface modulus of rigidity. Finally, as an applic...

  1. Multicomponent transport in membranes for redox flow batteries

    Science.gov (United States)

    Monroe, Charles

    2015-03-01

    Redox flow batteries (RFBs) incorporate separator membranes, which ideally prevent mixing of electrochemically active species while permitting crossover of inactive supporting ions. Understanding crossover and membrane selectivity may require multicomponent transport models that account for solute/solute interactions within the membrane, as well as solute/membrane interactions. Application of the Onsager-Stefan-Maxwell formalism allows one to account for all the dissipative phenomena that may accompany component fluxes through RFB membranes. The magnitudes of dissipative interactions (diffusional drag forces) are quantified by matching experimentally established concentration transients with theory. Such transients can be measured non-invasively using DC conductometry, but the accuracy of this method requires precise characterization of the bulk RFB electrolytes. Aqueous solutions containing both vanadyl sulfate (VOSO4) and sulfuric acid (H2SO4) are relevant to RFB technology. One of the first precise characterizations of aqueous vanadyl sulfate has been implemented and will be reported. To assess the viability of a separator for vanadium RFB applications with cell-level simulations, it is critical to understand the tendencies of various classes of membranes to absorb (uptake) active species, and to know the relative rates of active-species and supporting-electrolyte diffusion. It is also of practical interest to investigate the simultaneous diffusion of active species and supports, because interactions between solutes may ultimately affect the charge efficiency and power efficiency of the RFB system as a whole. A novel implementation of Barnes's classical model of dialysis-cell diffusion [Physics 5:1 (1934) 4-8] is developed to measure the binary diffusion coefficients and sorption equilibria for single solutes (VOSO4 or H2SO4) in porous membranes and cation-exchange membranes. With the binary diffusion and uptake measurement in hand, a computer simulation that

  2. HIV-1 Vpu promotes release and prevents endocytosis of nascent retrovirus particles from the plasma membrane.

    Directory of Open Access Journals (Sweden)

    2006-05-01

    Full Text Available The human immunodeficiency virus (HIV type-1 viral protein U (Vpu protein enhances the release of diverse retroviruses from human, but not monkey, cells and is thought to do so by ablating a dominant restriction to particle release. Here, we determined how Vpu expression affects the subcellular distribution of HIV-1 and murine leukemia virus (MLV Gag proteins in human cells where Vpu is, or is not, required for efficient particle release. In HeLa cells, where Vpu enhances HIV-1 and MLV release approximately 10-fold, concentrations of HIV-1 Gag and MLV Gag fused to cyan fluorescent protein (CFP were initially detected at the plasma membrane, but then accumulated over time in early and late endosomes. Endosomal accumulation of Gag-CFP was prevented by Vpu expression and, importantly, inhibition of plasma membrane to early endosome transport by dominant negative mutants of Rab5a, dynamin, and EPS-15. Additionally, accumulation of both HIV and MLV Gag in endosomes required a functional late-budding domain. In human HOS cells, where HIV-1 and MLV release was efficient even in the absence of Vpu, Gag proteins were localized predominantly at the plasma membrane, irrespective of Vpu expression or manipulation of endocytic transport. While these data indicated that Vpu inhibits nascent virion endocytosis, Vpu did not affect transferrin endocytosis. Moreover, inhibition of endocytosis did not restore Vpu-defective HIV-1 release in HeLa cells, but instead resulted in accumulation of mature virions that could be released from the cell surface by protease treatment. Thus, these findings suggest that a specific activity that is present in HeLa cells, but not in HOS cells, and is counteracted by Vpu, traps assembled retrovirus particles at the cell surface. This entrapment leads to subsequent endocytosis by a Rab5a- and clathrin-dependent mechanism and intracellular sequestration of virions in endosomes.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-07-01

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

  4. Cross talk between tetanus neurotoxin-insensitive vesicle-associated membrane protein-mediated transport and L1-mediated adhesion.

    Science.gov (United States)

    Alberts, Philipp; Rudge, Rachel; Hinners, Ina; Muzerelle, Aude; Martinez-Arca, Sonia; Irinopoulou, Theano; Marthiens, Veronique; Tooze, Sharon; Rathjen, Fritz; Gaspar, Patricia; Galli, Thierry

    2003-10-01

    The membrane-trafficking pathway mediated by tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP) in neurons is still unknown. We show herein that TI-VAMP expression is necessary for neurite outgrowth in PC12 cells and hippocampal neurons in culture. TI-VAMP interacts with plasma membrane and endosomal target soluble N-ethylmaleimide-sensitive factor attachment protein receptors, suggesting that TI-VAMP mediates a recycling pathway. L1, a cell-cell adhesion molecule involved in axonal outgrowth, colocalized with TI-VAMP in the developing brain, neurons in culture, and PC12 cells. Plasma membrane L1 was internalized into the TI-VAMP-containing compartment. Silencing of TI-VAMP resulted in reduced expression of L1 at the plasma membrane. Finally, using the extracellular domain of L1 and N-cadherin immobilized on beads, we found that the silencing of TI-VAMP led to impaired L1- but not N-cadherin-mediated adhesion. Furthermore, TI-VAMP- but not synaptobrevin 2-containing vesicles accumulated at the site of the L1 bead-cell junction. We conclude that TI-VAMP mediates the intracellular transport of L1 and that L1-mediated adhesion controls this membrane trafficking, thereby suggesting an important cross talk between membrane trafficking and cell-cell adhesion.

  5. Flexible oligocholate foldamers as membrane transporters and their guest-dependent transport mechanism.

    Science.gov (United States)

    Zhang, Shiyong; Zhao, Yan

    2012-01-14

    Dimeric, trimeric, and tetrameric oligocholates with flexible 4-aminobutyroyl spacers caused the efflux of hydrophilic molecules such as carboxyfluorescein (CF) and glucose from POPC/POPG liposomes. Transport was greatly suppressed across higher-melting DPPC membranes. Lipid-mixing assays and dynamic light scattering (DLS) indicated that the liposomes were intact during the transport. Kinetic analysis supported the involvement of monomeric species in the rate-limiting step of CF transport, consistent with a carrier-based mechanism. Glucose transport, on the other hand, displayed a highly unusual zero-order dependence on the oligocholate concentration at low loading of the transporter. Different selectivity was observed in the oligocholate transporters depending on the guest involved.

  6. Ion transport through biological membranes an integrated theoretical approach

    CERN Document Server

    Mackey, Michael C

    1975-01-01

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

  7. Organized living: formation mechanisms and functions of plasma membrane domains in yeast.

    Science.gov (United States)

    Ziółkowska, Natasza E; Christiano, Romain; Walther, Tobias C

    2012-03-01

    Plasma membrane proteins and lipids organize into lateral domains of specific composition. Domain formation is achieved by a combination of lipid-lipid and lipid-protein interactions, membrane-binding protein scaffolds and protein fences. The resulting domains function in membrane protein turnover and homeostasis, as well as in cell signaling. We review the mechanisms generating plasma membrane domains and the functional consequences of this organization, focusing on recent findings from research on the yeast model system.

  8. Statistical properties of transport in plasma turbulence

    DEFF Research Database (Denmark)

    Naulin, V.; Garcia, O.E.; Nielsen, A.H.;

    2004-01-01

    The statistical properties of the particle flux in different types of plasma turbulence models are numerically investigated using probability distribution functions (PDFs). The physics included in the models range from two-dimensional drift wave turbulence to three-dimensional MHD dynamics...

  9. Properties of fiber cell plasma membranes isolated from the cortex and nucleus of the porcine eye lens.

    Science.gov (United States)

    Mainali, Laxman; Raguz, Marija; O'Brien, William J; Subczynski, Witold K

    2012-04-01

    The organization and physical properties of the lipid bilayer portion of intact cortical and nuclear fiber cell plasma membranes isolated from the eye lenses of two-year-old pigs were studied using electron paramagnetic resonance (EPR) spin-labeling. Membrane fluidity, hydrophobicity, and the oxygen transport parameter (OTP) were assessed from the EPR spectra of precisely positioned spin labels. Intact cortical and nuclear membranes, which include membrane proteins, were found to contain three distinct lipid environments. These lipid environments were termed the bulk lipid domain, boundary lipid domain, and trapped lipid domain (lipids in protein aggregates). The amount of boundary and trapped lipids was greater in intact nuclear membranes than in cortical membranes. The properties of intact membranes were compared with the organization and properties of lens lipid membranes made of the total lipid extracts from the lens cortex or nucleus. In cortical lens lipid membranes, only one homogenous environment was detected, which was designated as a bulk lipid domain (phospholipid bilayer saturated with cholesterol). Lens lipid membranes prepared from the lens nucleus possessed two domains, assigned as a bulk lipid domain and a cholesterol bilayer domain (CBD). In intact nuclear membranes, it was difficult to discriminate the CBD, which was clearly detected in nuclear lens lipid membranes, because the OTP measured in the CBD is the same as in the domain formed by trapped lipids. The two domains unique to intact membranes-namely, the domain formed by boundary lipids and the domain formed by trapped lipids-were most likely formed due to the presence of membrane proteins. It is concluded that formation of rigid and practically impermeable domains is enhanced in the lens nucleus, indicating changes in membrane composition that may help to maintain low oxygen concentration in this lens region.

  10. Plasma membrane calcium pump regulation by metabolic stress

    Institute of Scientific and Technical Information of China (English)

    Jason; IE; Bruce

    2010-01-01

    The plasma membrane Ca2+-ATPase(PMCA)is an ATPdriven pump that is critical for the maintenance of low resting[Ca2+]i in all eukaryotic cells.Metabolic stress, either due to inhibition of mitochondrial or glycolytic metabolism,has the capacity to cause ATP depletion and thus inhibit PMCA activity.This has potentially fatal consequences,particularly for non-excitable cells in which the PMCA is the major Ca2+efflux pathway.This is because inhibition of the PMCA inevitably leads to cytosolic Ca2+ overload and the consequent cell death.However,the relationship between metabolic stress,ATP depletion and inhibition of the PMCA is not as simple as one would have originally predicted.There is increasing evidence that metabolic stress can lead to the inhibition of PMCA activity independent of ATP or prior to substantial ATP depletion.In particular,there is evidence that the PMCA has its own glycolytic ATP supply that can fuel the PMCA in the face of impaired mitochondrial function.Moreover, membrane phospholipids,mitochondrial membrane potential,caspase/calpain cleavage and oxidative stress have all been implicated in metabolic stress-induced inhibition of the PMCA.The major focus of this review is to challenge the conventional view of ATP-dependent regulation of the PMCA and bring together some of the alternative or additional mechanisms by which metabolic stress impairs PMCA activity resulting in cytosolic Ca2+ overload and cytotoxicity.

  11. The plasma membrane: Penultimate regulator of ADAM sheddase function.

    Science.gov (United States)

    Reiss, Karina; Bhakdi, Sucharit

    2017-11-01

    ADAM10 and ADAM17 are the best characterized members of the ADAM (A Disintegrin and Metalloproteinase) - family of transmembrane proteases. Both are involved diverse physiological and pathophysiological processes. ADAMs are known to be regulated by posttranslational mechanisms. However, emerging evidence indicates that the plasma membrane with its unique dynamic properties may additionally play an important role in controlling sheddase function. Membrane events that could contribute to regulation of ADAM-function are summarized. Surface expression of peptidolytic activity should be differentiated from ADAM-sheddase function since the latter additionally requires that the protease finds its substrate in the lipid bilayer. We propose that this is achieved through horizontal and vertical reorganization of membrane nanoarchitecture coordinately occurring at the sites of sheddase activation. Reshuffling of nanodomains thereby guides traffic of enzyme and substrate to each other. For ADAM17 phosphatidylserine exposure is required to then induce its shedding function. The novel concept that physicochemical properties of the lipid bilayer govern the action of ADAM-proteases may be extendable to other functional proteins that act at the cell surface. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John. Copyright © 2017. Published by Elsevier B.V.

  12. High-Throughput Microplate-Based Assay to Monitor Plasma Membrane Wounding and Repair

    Directory of Open Access Journals (Sweden)

    Sarika Pathak-Sharma

    2017-07-01

    Full Text Available The plasma membrane of mammalian cells is susceptible to disruption by mechanical and biochemical damages that frequently occur within tissues. Therefore, efficient and rapid repair of the plasma membrane is essential for maintaining cellular homeostasis and survival. Excessive damage of the plasma membrane and defects in its repair are associated with pathological conditions such as infections, muscular dystrophy, heart failure, diabetes, and lung and neurodegenerative diseases. The molecular events that remodel the plasma membrane during its repair remain poorly understood. In the present work, we report the development of a quantitative high-throughput assay that monitors the efficiency of the plasma membrane repair in real time using a sensitive microplate reader. In this assay, the plasma membrane of living cells is perforated by the bacterial pore-forming toxin listeriolysin O and the integrity and recovery of the membrane are monitored at 37°C by measuring the fluorescence intensity of the membrane impermeant dye propidium iodide. We demonstrate that listeriolysin O causes dose-dependent plasma membrane wounding and activation of the cell repair machinery. This assay was successfully applied to cell types from different origins including epithelial and muscle cells. In conclusion, this high-throughput assay provides a novel opportunity for the discovery of membrane repair effectors and the development of new therapeutic compounds that could target membrane repair in various pathological processes, from degenerative to infectious diseases.

  13. Bile acids modulate signaling by functional perturbation of plasma membrane domains.

    Science.gov (United States)

    Zhou, Yong; Maxwell, Kelsey N; Sezgin, Erdinc; Lu, Maryia; Liang, Hong; Hancock, John F; Dial, Elizabeth J; Lichtenberger, Lenard M; Levental, Ilya

    2013-12-13

    Eukaryotic cell membranes are organized into functional lipid and protein domains, the most widely studied being membrane rafts. Although rafts have been associated with numerous plasma membrane functions, the mechanisms by which these domains themselves are regulated remain undefined. Bile acids (BAs), whose primary function is the solubilization of dietary lipids for digestion and absorption, can affect cells by interacting directly with membranes. To investigate whether these interactions affected domain organization in biological membranes, we assayed the effects of BAs on biomimetic synthetic liposomes, isolated plasma membranes, and live cells. At cytotoxic concentrations, BAs dissolved synthetic and cell-derived membranes and disrupted live cell plasma membranes, implicating plasma membrane damage as the mechanism for BA cellular toxicity. At subtoxic concentrations, BAs dramatically stabilized domain separation in Giant Plasma Membrane Vesicles without affecting protein partitioning between coexisting domains. Domain stabilization was the result of BA binding to and disordering the nonraft domain, thus promoting separation by enhancing domain immiscibility. Consistent with the physical changes observed in synthetic and isolated biological membranes, BAs reorganized intact cell membranes, as evaluated by the spatial distribution of membrane-anchored Ras isoforms. Nanoclustering of K-Ras, related to nonraft membrane domains, was enhanced in intact plasma membranes, whereas the organization of H-Ras was unaffected. BA-induced changes in Ras lateral segregation potentiated EGF-induced signaling through MAPK, confirming the ability of BAs to influence cell signal transduction by altering the physical properties of the plasma membrane. These observations suggest general, membrane-mediated mechanisms by which biological amphiphiles can produce their cellular effects.

  14. Key Role for Intracellular K+ and Protein Kinases Sat4/Hal4 and Hal5 in the Plasma Membrane Stabilization of Yeast Nutrient Transporters▿

    Science.gov (United States)

    Pérez-Valle, Jorge; Jenkins, Huw; Merchan, Stephanie; Montiel, Vera; Ramos, José; Sharma, Sukesh; Serrano, Ramón; Yenush, Lynne

    2007-01-01

    K+ transport in living cells must be tightly controlled because it affects basic physiological parameters such as turgor, membrane potential, ionic strength, and pH. In yeast, the major high-affinity K+ transporter, Trk1, is inhibited by high intracellular K+ levels and positively regulated by two redundant “halotolerance” protein kinases, Sat4/Hal4 and Hal5. Here we show that these kinases are not required for Trk1 activity; rather, they stabilize the transporter at the plasma membrane under low K+ conditions, preventing its endocytosis and vacuolar degradation. High concentrations (0.2 M) of K+, but not Na+ or sorbitol, transported by undefined low-affinity systems, maintain Trk1 at the plasma membrane in the hal4 hal5 mutant. Other nutrient transporters, such as Can1 (arginine permease), Fur4 (uracil permease), and Hxt1 (low-affinity glucose permease), are also destabilized in the hal4 hal5 mutant under low K+ conditions and, in the case of Can1, are stabilized by high K+ concentrations. Other plasma membrane proteins such as Pma1 (H+-pumping ATPase) and Sur7 (an eisosomal protein) are not regulated by halotolerance kinases or by high K+ levels. This novel regulatory mechanism of nutrient transporters may participate in the quiescence/growth transition and could result from effects of intracellular K+ and halotolerance kinases on membrane trafficking and/or on the transporters themselves. PMID:17548466

  15. A conserved cysteine residue is involved in disulfide bond formation between plant plasma membrane aquaporin monomers.

    Science.gov (United States)

    Bienert, Gerd P; Cavez, Damien; Besserer, Arnaud; Berny, Marie C; Gilis, Dimitri; Rooman, Marianne; Chaumont, François

    2012-07-01

    AQPs (aquaporins) are conserved in all kingdoms of life and facilitate the rapid diffusion of water and/or other small solutes across cell membranes. Among the different plant AQPs, PIPs (plasma membrane intrinsic proteins), which fall into two phylogenetic groups, PIP1 and PIP2, play key roles in plant water transport processes. PIPs form tetramers in which each monomer acts as a functional channel. The intermolecular interactions that stabilize PIP oligomer complexes and are responsible for the resistance of PIP dimers to denaturating conditions are not well characterized. In the present study, we identified a highly conserved cysteine residue in loop A of PIP1 and PIP2 proteins and demonstrated by mutagenesis that it is involved in the formation of a disulfide bond between two monomers. Although this cysteine seems not to be involved in regulation of trafficking to the plasma membrane, activity, substrate selectivity or oxidative gating of ZmPIP1s (Zm is Zea mays), ZmPIP2s and hetero-oligomers, it increases oligomer stability under denaturating conditions. In addition, when PIP1 and PIP2 are co-expressed, the loop A cysteine of ZmPIP1;2, but not that of ZmPIP2;5, is involved in the mercury sensitivity of the channels.

  16. Modeling of far SOL plasma transport in NSTX

    Energy Technology Data Exchange (ETDEWEB)

    Sergei Krasheninnikov; Alexander Pigarov

    2005-11-02

    For better understanding and characterization of non-diffusive transport occurring in the NSTX tokamak edge plasma, we performed extensive simulations of NSTX edge plasmas with the multi-fluid two-dimensional UEDGE code by using realistic model for impurity sputtering sources and hybrid model for anomalous cross-field transport. Our cross-field transport model incorporates the effects of non-diffusive intermittent transport by introducing anomalous convective velocities whose spatial profile is adjusted for each ion charge state to match available experimental data. The research in 2002-2005 financial years was focused on the following areas: (i) development of capabilities for UEDGE simulation of NSTX spectroscopy data (i.e., the 3D real-geometry postprocessor UEDGE tools for comparison between UEDGE and experimental data), (ii) simulation of multi-diagnostic data from NSTX with UEDGE, (iii) study of anomalous cross-field convective transport of impurity ions, (iv) analysis of divertor plasma opacity to resonance radiation, and (v) study the effects of ballooning-like anomalous cross-field transport and spherical-torus magnetic configuration on parallel plasma flows in the SOL.

  17. Coarse-grain molecular dynamics study of fullerene transport across a cell membrane

    Science.gov (United States)

    Sridhar, Akshay; Srikanth, Bharath; Kumar, Amit; Dasmahapatra, Ashok Kumar

    2015-07-01

    The study of the ability of drug molecules to enter cells through the membrane is of vital importance in the field of drug delivery. In cases where the transport of the drug molecules through the membrane is not easily accomplishable, other carrier molecules are used. Spherical fullerene molecules have been postulated as potential carriers of highly hydrophilic drugs across the plasma membrane. Here, we report the coarse-grain molecular dynamics study of the translocation of C60 fullerene and its derivatives across a cell membrane modeled as a 1,2-distearoyl-sn-glycero-3-phosphocholine bilayer. Simulation results indicate that pristine fullerene molecules enter the bilayer quickly and reside within it. The addition of polar functionalized groups makes the fullerenes less likely to reside within the bilayer but increases their residence time in bulk water. Addition of polar functional groups to one half of the fullerene surface, in effect creating a Janus particle, offers the most promise in developing fullerene models that can achieve complete translocation through the membrane bilayer.

  18. Monensin and FCCP inhibit the intracellular transport of alphavirus membrane glycoproteins.

    Science.gov (United States)

    Kääriäinen, L; Hashimoto, K; Saraste, J; Virtanen, I; Penttinen, K

    1980-12-01

    Temperature-sensitive mutants of semliki forest virus (SFV) and sindbis virus (SIN) were used to study the intracellular transport of virus membrane glycoproteins in infected chicken embryo fibroblasts. When antisera against purified glycoproteins and (125)I- labeled protein A from staphylococcus aureus were used only small amounts of virus glycoproteins were detected at the surface of SFV ts-1 and SIN Ts-10 infected cells incubated at the restrictive temperature (39 degrees C). When the mutant-infected cells were shifted to the permissive temperature (28 degrees C), in the presence of cycloheximide, increasing amounts of virus glycoproteins appeared at the cell surface from 20 to 80 min after the shift. Both monensin (10muM) and carbonylcyanide-p- trifluoromethoxyphenylhydrazone (FCCP; 10-20 muM) inhibited the appearance of virus membrane glycoproteins at the cell surface. Vinblastine sulfate (10 mug/ml) inhibited the transport by approximately 50 percent, whereas cytochalasin B (1 mug/ml) had only a marginal effect. Intracellular distribution of virus glycoproteins in the mutant-infected cells was visualized in double-fluorescence studies using lectins as markers for endoplasmic reticulum and Golgi apparatus. At 39 degrees C, the virus membrane glycoproteins were located at the endoplasmic reticulum, whereas after shift to 28 degrees C, a bright juxtanuclear reticular fluorescence was seen in the location of the Golgi apparatus. In the presence of monensin, the virus glycoproteins could migrate to the Golgi apparatus, although transport to the cell surface did not take place. When the shift was carried out in the presence of FCCP, negligible fluorescence was seen in the Golgi apparatus and the glycoproteins apparently remained in the rough endoplasmic reticulum. A rapid inhibition in the accumulation of virus glycoproteins at the cell surface was obtained when FCCP was added during the active transport period, whereas with monensin there was a delay of

  19. Isolation of plasma and nuclear membranes of thymocytes. II. Biochemical composition.

    Science.gov (United States)

    Monneron, A; d'Alayer, J

    1978-04-01

    Thymocyte plasma and nuclear membranes obtained by the procedure described in the accompanying paper were analyzed for their biochemical composition. Plasma membranes were very rich in phospholipid, cholesterol, sialic aicd; they did not contain nucleic acids. In comparison, nuclear membranes had a lower phospholipid to protein ratio and contained much less sialic acid and cholesterol. 50% of the cellular cholesterol and of the membrane-bound sialic acid were found in the plasma membranes, 14% in the nuclear membranes. Live cells were labeled with 131I, and the acid-insoluble radioactivity was followed in the subfractions. A good correlation with the distribution and enrichment of plasma membrane market-enzymes was obtained. Label enrichment was about 50-fold in the two lightest of the three plasma membrane fractions. 60% of the label was contained in the plasma membranes, only 4% in the nuclear membranes. Cross-contamination of these two types of membranes was thus negligible. Sodium dodecyl sulfate-gel electrophoresis revealed three different patterns specific for, respectively, plasma membranes, the microsomal-mitochondrial fraction, and nuclear membranes. Each pattern was characterized by a set of proteins and glycoproteins, among which high molecular weight glycoproteins could be considered as marker-proteins of, respectively, 280,000, 260,000, and 230,000 daltons. 131I-labeling of live cells tagged with a very high specific activity three glycoproteins of mol wt 280,000, 200,000, and 135,000 daltons. Nuclear membranes prepared from labeled isolated nuclei had a set of labeled proteins completely different from plasma membranes.

  20. Plasma transport in a simulated magnetic-divertor configuration

    Energy Technology Data Exchange (ETDEWEB)

    Strawitch, C. M.

    1981-03-01

    The transport properties of plasma on magnetic field lines that intersect a conducting plate are studied experimentally in the Wisconsin internal ring D.C. machine. The magnetic geometry is intended to simulate certain aspects of plasma phenomena that may take place in a tokamak divertor. It is found by a variety of measurements that the cross field transport is non-ambipolar; this may have important implications in heat loading considerations in tokamak divertors. The undesirable effects of nonambipolar flow make it preferable to be able to eliminate it. However, we find that though the non-ambipolarity may be reduced, it is difficult to eliminate entirely. The plasma flow velocity parallel to the magnetic field is found to be near the ion acoustic velocity in all cases. The experimental density and electron temperature profiles are compared to the solutions to a one dimensional transport model that is commonly used in divertor theory.

  1. A quasi-linear gyrokinetic transport model for tokamak plasmas

    CERN Document Server

    Casati, Alessandro

    2012-01-01

    The development of a quasi-linear gyrokinetic transport model for tokamak plasmas, ultimately designed to provide physically comprehensive predictions of the time evolution of the thermodynamic relevant quantities, is a task that requires tight links among theoretical, experimental and numerical studies. The framework of the model here proposed, which operates a reduction of complexity on the nonlinear self-organizing plasma dynamics, allows in fact multiple validations of the current understanding of the tokamak micro-turbulence. The main outcomes of this work stem from the fundamental steps involved by the formulation of such a reduced transport model, namely: (1) the verification of the quasi-linear plasma response against the nonlinearly computed solution, (2) the improvement of the turbulent saturation model through an accurate validation of the nonlinear codes against the turbulence measurements, (3) the integration of the quasi-linear model within an integrated transport solver.

  2. Plasma transport driven by the Rayleigh-Taylor instability

    Science.gov (United States)

    Ma, X.; Delamere, P. A.; Otto, A.

    2016-06-01

    Two important differences between the giant magnetospheres (i.e., Jupiter's and Saturn's magnetospheres) and the terrestrial magnetosphere are the internal plasma sources and the fast planetary rotation. Thus, there must be a radially outward flow to transport the plasma to avoid infinite accumulation of plasma. This radial outflow also carries the magnetic flux away from the inner magnetosphere due to the frozen-in condition. As such, there also must be a radial inward flow to refill the magnetic flux in the inner magnetosphere. Due to the similarity between Rayleigh-Taylor (RT) instability and the centrifugal instability, we use a three-dimensional RT instability to demonstrate that an interchange instability can form a convection flow pattern, locally twisting the magnetic flux, consequently forming a pair of high-latitude reconnection sites. This process exchanges a part of the flux tube, thereby transporting the plasma radially outward without requiring significant latitudinal convection of magnetic flux in the ionosphere.

  3. Ion sampling and transport in Inductively Coupled Plasma Mass Spectrometry

    Science.gov (United States)

    Farnsworth, Paul B.; Spencer, Ross L.

    2017-08-01

    Quantitative accuracy and high sensitivity in inductively coupled plasma mass spectrometry (ICP-MS) depend on consistent and efficient extraction and transport of analyte ions from an inductively coupled plasma to a mass analyzer, where they are sorted and detected. In this review we examine the fundamental physical processes that control ion sampling and transport in ICP-MS and compare the results of theory and computerized models with experimental efforts to characterize the flow of ions through plasma mass spectrometers' vacuum interfaces. We trace the flow of ions from their generation in the plasma, into the sampling cone, through the supersonic expansion in the first vacuum stage, through the skimmer, and into the ion optics that deliver the ions to the mass analyzer. At each stage we consider idealized behavior and departures from ideal behavior that affect the performance of ICP-MS as an analytical tool.

  4. The Anisotropic Transport Effects On The Dilute Plasmas

    CERN Document Server

    Devlen, Ebru

    2012-01-01

    We examine the linear stability analysis of a hot, dilute and differentially rotating plasma by considering anisotropic transport effects. In the dilute plasmas, the ion Larmor radius is small compared with its collisional mean free path. In this case, the transport of heat and momentum along the magnetic field lines become important. This paper presents a novel linear instability that may more powerful and greater than ideal magnetothermal instability (MTI) and ideal magnetorotational instability (MRI) in the dilute astrophysical plasmas. This type of plasma is believed to be found in the intracluster medium of galaxy clusters and radiatively ineffective accretion flows around black holes. We derive the dispersion relation of this instability and obtain the instability condition. There is at least one unstable mode that is independent of the temperature gradient direction for a helical magnetic field geometry. This novel instability is driven by the gyroviscosity coupled with differential rotation. Therefore...

  5. Transport properties of partially ionized hydrogen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ramazanov, T S [IETP, Al Farabi Kazakh National University, Tole bi, 96a, 480012, Almaty (Kazakhstan); Galiyev, K Zh [IETP, Al Farabi Kazakh National University, Tole bi, 96a, 480012, Almaty (Kazakhstan); Dzhumagulova, K N [IETP, Al Farabi Kazakh National University, Tole bi, 96a, 480012, Almaty (Kazakhstan); Roepke, G [Fachbereich Physik, Universitaet Rostock, D-18051 Rostock (Germany); Redmer, R [Fachbereich Physik, Universitaet Rostock, D-18051 Rostock (Germany)

    2003-06-06

    We have considered partially ionized hydrogen plasma for the density region n{sub e} = (10{sup 18}-10{sup 22}) cm{sup -3}. Charged particles in the system (electrons, protons) interact via an effective potential taking into account three-particle correlations. We use the Buckingham polarization potential to describe electron-atom and proton-atom interactions. The electrical and thermal conductivity is determined using the Chapman-Enskog method. We compare the obtained results with other available data.

  6. Comparative study of the active cadmium efflux systems operating at the plasma membrane and tonoplast of cucumber root cells.

    Science.gov (United States)

    Migocka, Magdalena; Papierniak, Anna; Kosatka, Ewelina; Klobus, Grazyna

    2011-10-01

    The strategies developed by plants to avoid the toxicity of cadmium (Cd) and other heavy metals involve active sequestration of metals into the apoplast and vacuoles. The protein systems excluding heavy metals from the cell cytosol localize to the plasma membrane and tonoplast and are energized either by ATP or by the electrochemical gradient generated by H(+)-ATPase or by V-ATPase and pyrophosphatase (PPase), respectively. In this work, a comparative study on the contribution of both the plasma membrane and tonoplast in the active detoxification of plant cells after treatment with Cd was performed. The studies using plants treated and untreated with Cd reveal that both, H(+)-coupled and MgATP-driven efflux of Cd across plasma membranes and tonoplast is markedly stimulated in the presence of Cd in the environment. Previous studies on plasma-membrane localized H(+)-coupled Cd efflux together with the present data demonstrating tonoplast H(+)/Cd(2+) antiport activity suggest that H(+)-coupled secondary transport of Cd displays a lower affinity for Cd when compared with Cd primary pumps driven by MgATP. In addition, it is shown that MgATP-energized Cd efflux across both membranes is significantly enhanced by cysteine, dithiothreitol, and glutathione. These results suggest that Cd is excluded from the cytosol through an energy-dependent system as a free ion as well as a complexed form. Although both membranes contribute in the active exclusion of ionized and complexed Cd from the cytosol, the overall calculation of Cd accumulation in the everted plasma membranes and vacuolar vesicles suggests that the tonoplast and vacuole have a major function in Cd efflux from the cytosol in the roots of cucumber subjected to Cd stress.

  7. Large-scale analysis of membrane transport in yeast using invertase reporters.

    Science.gov (United States)

    Dalton, Lauren; Davey, Michael; Conibear, Elizabeth

    2015-01-01

    Transport of membrane proteins between cellular organelles requires the concerted action of many regulatory factors, which aid in cargo recognition and vesicle formation, targeting, and fusion. The yeast Saccharomyces cerevisiae is a useful model system for studying such regulators, due to the availability of genome-wide mutant collections and reporter proteins that provide sensitive biochemical readouts of individual transport pathways. Here, we describe an enzymatic invertase assay for evaluating endocytic recycling using a chimeric GFP-Snc1-Suc2 reporter. Cell surface levels of this reporter can be measured by a colorimetric assay that monitors sucrose hydrolysis at the plasma membrane, using two different methods. The first is a semiquantitative agar overlay assay followed by image densitometry that is suitable for high-throughput screening of arrayed yeast colonies. In the second, more quantitative assay, an enzymatic solution is added to yeast cultures in a multi-well plate and the absorbance is assessed by a plate reader. Furthermore, the modular nature of the chimeric reporter allows alternate transport signals to be introduced, thereby expanding the range of transport pathways that can be evaluated by this method. Together these techniques can be used to explore the function of genes involved in a variety of cellular trafficking pathways.

  8. Artificial membranes with selective nanochannels for protein transport

    KAUST Repository

    Sutisna, B.

    2016-09-05

    A poly(styrene-b-tert-butoxystyrene-b-styrene) copolymer was synthesized by anionic polymerization and hydrolyzed to poly(styrene-b-4-hydroxystyrene-b-styrene). Lamellar morphology was confirmed in the bulk after annealing. Membranes were fabricated by self-assembly of the hydrolyzed copolymer in solution, followed by water induced phase separation. A high density of pores of 4 to 5 nm diameter led to a water permeance of 40 L m−2 h−1 bar−1 and molecular weight cut-off around 8 kg mol−1. The morphology was controlled by tuning the polymer concentration, evaporation time, and the addition of imidazole and pyridine to stabilize the terpolymer micelles in the casting solution via hydrogen bond complexes. Transmission electron microscopy of the membrane cross-sections confirmed the formation of channels with hydroxyl groups beneficial for hydrogen-bond forming sites. The morphology evolution was investigated by time-resolved grazing incidence small angle X-ray scattering experiments. The membrane channels reject polyethylene glycol with a molecular size of 10 kg mol−1, but are permeable to proteins, such as lysozyme (14.3 kg mol−1) and cytochrome c (12.4 kg mol−1), due to the right balance of hydrogen bond interactions along the channels, electrostatic attraction, as well as the right pore sizes. Our results demonstrate that artificial channels can be designed for protein transport via block copolymer self-assembly using classical methods of membrane preparation.

  9. Phosphatidic acid phosphatase and phospholipdase A activities in plasma membranes from fusing muscle cells.

    Science.gov (United States)

    Kent, C; Vagelos, P R

    1976-06-17

    Plasma membrane from fusing embryonic muscle cells were assayed for phospholipase A activity to determine if this enzyme plays a role in cell fusion. The membranes were assayed under a variety of conditions with phosphatidylcholine as the substrate and no phospholipase A activity was found. The plasma membranes did contain a phosphatidic acid phosphatase which was optimally active in the presence of Triton X-100 and glycerol. The enzyme activity was constant from pH 5.2 to 7.0, and did not require divalent cations. Over 97% of the phosphatidic acid phosphatase activity was in the particulate fraction. The subcellular distribution of the phosphatidic acid phosphatase was the same as the distributions of the plasma membrane markers, (Na+ + k+)-ATPase and the acetylcholine receptor, which indicates that this phosphatase is located exclusively in the plasma membranes. There was no detectable difference in the phosphatidic acid phosphatase activities of plasma membranes from fusing and non-fusing cells.

  10. Plasma transport induced by the stochastic magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kubota, Tetsuyuki [Interdisciplinary Graduate School of Engineering Sciences, Kyushu Univ., Kasuga, Fukuoka (Japan); Itoh, Sanae-I.; Yagi, Masatoshi

    1998-10-01

    The anomalous plasma transport induced by the stochastic magnetic field is studied to understand the disruption phenomena in the tokamak plasma. At first, the transport matrix which indicate the plasma transport in the stochastic magnetic field is formulated. For the formulation, the quasi-linear approximation for the diffusivity of the stochastic magnetic field is used and the shifted Maxwellian is assumed to the particle distribution. Using this transport matrix the radial electric field formation, which is generated by the ambipolar condition, and the associated temperature profile is obtained. The temperature profile in the stochastic magnetic field becomes flat because of the rapid temperature diffusion. Next the temperature crash, i.e., the sawtooth oscillation and the giant ELM, is analyzed using the turbulence-turbulence transition model, which describes the transition between the state of the electrostatic turbulence and that of the electromagnetic turbulence. This transition has a hysteresis characteristics. When the state changes to the electromagnetic mode, the stochastic magnetic field appears and the temperature transport is enhanced. This transition model is included in the 1-D transport equation. To calculate this transport equation numerically the crash of the temperature profile and the propagation of the crash front (avalanche) are realized by this model. The collapse without a precursor oscillation is revealed. (author)

  11. Plasma confinement theory and transport simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ross, D.W.

    1992-04-01

    The objectives are: (1) to advance the transport studies of tokamaks, including development and maintenance of the Magnetic Fusion Energy Database, and (2) to provide theoretical interpretation, modeling and equilibrium and stability studies for TEXT-Upgrade. Recent reports, publications, and conference presentations of the Fusion Research Center are listed.

  12. Surface transport in plasma-balls

    Energy Technology Data Exchange (ETDEWEB)

    Armas, Jay [Physique Théorique et Mathématique, Université Libre de Bruxelles andInternational Solvay Institutes,ULB-Campus Plaine CP231, B-1050 Brussels (Belgium); Bhattacharya, Jyotirmoy [Centre for Particle Theory & Department of Mathematical Sciences, Durham University,South Road, Durham DH1 3LE (United Kingdom); Kundu, Nilay [Harish-Chandra Research Institute,Chhatnag Road, Jhunsi, Allahabad 211019 (India)

    2016-06-06

    We study the surface transport properties of stationary localized configurations of relativistic fluids to the first two non-trivial orders in a derivative expansion. By demanding that these finite lumps of relativistic fluid are described by a thermal partition function with arbitrary stationary background metric and gauge fields, we are able to find several constraints among surface transport coefficients. At leading order, besides recovering the surface thermodynamics, we obtain a generalization of the Young-Laplace equation for relativistic fluid surfaces, by considering a temperature dependence in the surface tension, which is further generalized in the context of superfluids. At the next order, for uncharged fluids in 3+1 dimensions, we show that besides the 3 independent bulk transport coefficients previously known, a generic localized configuration is characterized by 3 additional surface transport coefficients, one of which may be identified with the surface modulus of rigidity. Finally, as an application, we study the effect of temperature dependence of surface tension on some explicit examples of localized fluid configurations, which are dual to certain non-trivial black hole solutions via the AdS/CFT correspondence.

  13. Surface transport in plasma-balls

    Science.gov (United States)

    Armas, Jay; Bhattacharya, Jyotirmoy; Kundu, Nilay

    2016-06-01

    We study the surface transport properties of stationary localized configurations of relativistic fluids to the first two non-trivial orders in a derivative expansion. By demanding that these finite lumps of relativistic fluid are described by a thermal partition function with arbitrary stationary background metric and gauge fields, we are able to find several constraints among surface transport coefficients. At leading order, besides recovering the surface thermodynamics, we obtain a generalization of the Young-Laplace equation for relativistic fluid surfaces, by considering a temperature dependence in the surface tension, which is further generalized in the context of superfluids. At the next order, for uncharged fluids in 3+1 dimensions, we show that besides the 3 independent bulk transport coefficients previously known, a generic localized configuration is characterized by 3 additional surface transport coefficients, one of which may be identified with the surface modulus of rigidity. Finally, as an application, we study the effect of temperature dependence of surface tension on some explicit examples of localized fluid configurations, which are dual to certain non-trivial black hole solutions via the AdS/CFT correspondence.

  14. A kinetic study of mercury(II transport through a membrane assisted by new transport reagent

    Directory of Open Access Journals (Sweden)

    Görgülü Ahmet

    2011-07-01

    Full Text Available Abstract Background A new organodithiophosphorus derivative, namely O-(1,3-Bispiperidino-2-propyl-4-methoxy phenyldithiophosphonate, was synthesized and then the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated. Results The compound 1 was characterized by elemental analysis, IR, 1H and 31P NMR spectroscopies. The transport of mercury(II ion by a zwitterionic dithiophosphonate 1 in the liquid membrane was studied and the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated. The compound 1 is expected to serve as a model liquid membrane transport with mercury(II ions. Conclusion A kinetic study of mercury(II transport through a membrane assisted by O-(1,3-Bispiperidino-2-propyl-4-methoxy phenyldithiophosphonate was performed. It can be concluded that the compound 1 can be provided a general and straightforward route to remove toxic metals ions such as mercury(II ion from water or other solution.

  15. A Comparative Study of Hydrophilic Modification of Polypropylene Membranes by Remote and Direct Ar Plasma

    Institute of Scientific and Technical Information of China (English)

    ZHANG Suzhen; CHENG Cheng; LAN Yan; MENG Yuedong

    2009-01-01

    Surface modification of polypropylene membrane by argon (Ar) plasma-induced graft polymerization with hydrophilic monomer [acrylic acid (AA) in this work]was investigated.It was found that both the distance of the membrane from the Ar plasma center and the plasma power had a strong influence on the surface modification,hydrophilicity and graft yield (GY) of the treated membrane.Results suggest that remote plasma treatment with a proper sample position,plasma power and graft polymerization leads to a membrane surface with not only less damage,but also more permanent hydrophilicity,than direct plasma treatment does.By analyzing the morphology and the chemical composition of the membrane surface by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS),as well as Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) respectively,a possible mechanism was tentatively revealed.

  16. Antifouling enhancement of polysulfone/TiO2 nanocomposite separation membrane by plasma etching

    Science.gov (United States)

    Chen, Z.; Yin, C.; Wang, S.; Ito, K.; Fu, Q. M.; Deng, Q. R.; Fu, P.; Lin, Z. D.; Zhang, Y.

    2017-01-01

    A polysulfone/TiO2 nanocomposite membrane was prepared via casting method, followed by the plasma etching of the membrane surface. Doppler broadened energy spectra vs. positron incident energy were employed to elucidate depth profiles of the nanostructure for the as-prepared and treated membranes. The results confirmed that the near-surface of the membrane was modified by the plasma treatment. The antifouling characteristics for the membranes, evaluated using the degradation of Rhodamin B, indicated that the plasma treatment enhances the photo catalytic ability of the membrane, suggesting that more TiO2 nanoparticles are exposed at the membrane surface after the plasma treatment as supported by the positron result.

  17. Regulation of transport processes across the tonoplast membrane

    Directory of Open Access Journals (Sweden)

    Oliver eTrentmann

    2014-09-01

    Full Text Available In plants, the vacuole builds up the cellular turgor and represents an important component in cellular responses to diverse stress stimuli. Rapid volume changes of cells, particularly of motor cells, like guard cells, are caused by variation of osmolytes and consequently of the water contents in the vacuole. Moreover, directed solute uptake into or release out of the large central vacuole allows adaptation of cytosolic metabolite levels according to the current physiological requirements and specific cellular demands. Therefore, solute passage across the vacuolar membrane, the tonoplast, has to be tightly regulated. Important principles in vacuolar transport regulation are changes of tonoplast transport protein abundances by differential expression of genes or changes of their activities, e.g. due to post-translational modification or by interacting proteins. Because vacuolar transport is in most cases driven by an electro-chemical gradient altered activities of tonoplast proton pumps significantly influence vacuolar transport capacities. Intense studies on individual tonoplast proteins but also unbiased system biological approaches have provided important insights into the regulation of vacuolar transport. This short review refers to selected examples of tonoplast proteins and their regulation, with special focus on protein phosphorylation.

  18. Membrane Assembly and Ion Transport Ability of a Fluorinated Nanopore

    Science.gov (United States)

    Godbout, Raphaël; Légaré, Sébastien; Auger, Maud; Carpentier, Claudia; Otis, François; Auger, Michèle; Lagüe, Patrick; Voyer, Normand

    2016-01-01

    A novel 21-residue peptide incorporating six fluorinated amino acids was prepared. It was designed to fold into an amphiphilic alpha helical structure of nanoscale length with one hydrophobic face and one fluorinated face. The formation of a fluorous interface serves as the main vector for the formation of a superstructure in a bilayer membrane. Fluorescence assays showed this ion channel's ability to facilitate the translocation of alkali metal ions through a phospholipid membrane, with selectivity for sodium ions. Computational studies showed that a tetramer structure is the most probable and stable supramolecular assembly for the active ion channel structure. The results illustrate the possibility of exploiting multiple Fδ-:M+ interactions for ion transport and using fluorous interfaces to create functional nanostructures. PMID:27835700

  19. Isolation and characterization of the plasma membrane from the yeast Pichia pastoris.

    Science.gov (United States)

    Grillitsch, Karlheinz; Tarazona, Pablo; Klug, Lisa; Wriessnegger, Tamara; Zellnig, Günther; Leitner, Erich; Feussner, Ivo; Daum, Günther

    2014-07-01

    Despite similarities of cellular membranes in all eukaryotes, every compartment displays characteristic and often unique features which are important for the functions of the specific organelles. In the present study, we biochemically characterized the plasma membrane of the methylotrophic yeast Pichia pastoris with emphasis on the lipids which form the matrix of this compartment. Prerequisite for this effort was the design of a standardized and reliable isolation protocol of the plasma membrane at high purity. Analysis of isolated plasma membrane samples from P. pastoris revealed an increase of phosphatidylserine and a decrease of phosphatidylcholine compared to bulk membranes. The amount of saturated fatty acids in the plasma membrane was higher than in total cell extracts. Ergosterol, the final product of the yeast sterol biosynthetic pathway, was found to be enriched in plasma membrane fractions, although markedly lower than in Saccharomyces cerevisiae. A further characteristic feature of the plasma membrane from P. pastoris was the enrichment of inositol phosphorylceramides over neutral sphingolipids, which accumulated in internal membranes. The detailed analysis of the P. pastoris plasma membrane is discussed in the light of cell biological features of this microorganism especially as a microbial cell factory for heterologous protein production.

  20. Transport studies in high-performance field reversed configuration plasmas

    Science.gov (United States)

    Gupta, S.; Barnes, D. C.; Dettrick, S. A.; Trask, E.; Tuszewski, M.; Deng, B. H.; Gota, H.; Gupta, D.; Hubbard, K.; Korepanov, S.; Thompson, M. C.; Zhai, K.; Tajima, T.

    2016-05-01

    A significant improvement of field reversed configuration (FRC) lifetime and plasma confinement times in the C-2 plasma, called High Performance FRC regime, has been observed with neutral beam injection (NBI), improved edge stability, and better wall conditioning [Binderbauer et al., Phys. Plasmas 22, 056110 (2015)]. A Quasi-1D (Q1D) fluid transport code has been developed and employed to carry out transport analysis of such C-2 plasma conditions. The Q1D code is coupled to a Monte-Carlo code to incorporate the effect of fast ions, due to NBI, on the background FRC plasma. Numerically, the Q1D transport behavior with enhanced transport coefficients (but with otherwise classical parametric dependencies) such as 5 times classical resistive diffusion, classical thermal ion conductivity, 20 times classical electron thermal conductivity, and classical fast ion behavior fit with the experimentally measured time evolution of the excluded flux radius, line-integrated density, and electron/ion temperature. The numerical study shows near sustainment of poloidal flux for nearly 1 ms in the presence of NBI.

  1. Collisional transport in a plasma with steep gradients

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.; Okamoto, M.; Nakajima, N.; Murakami, S. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    1999-06-01

    The validity is given to the newly proposed two {delta}f method for neoclassical transport calculation, which can be solve the drift kinetic equation considering effects of steep plasma gradients, large radial electric field, finite banana width, and an orbit topology near the axis. The new method is applied to the study of ion transport with steep plasma gradients. It is found that the ion thermal diffusivity decreases as the scale length of density gradient decreases, while the ion particle flux due to ion-ion self collisions increases with increasing gradient. (author)

  2. Exploiting nanotechnologies and TRPV1 channels to investigate the putative anandamide membrane transporter.

    Directory of Open Access Journals (Sweden)

    Alessia Ligresti

    Full Text Available BACKGROUND: Considerable efforts have been made to characterize the pathways regulating the extracellular levels of the endocannabinoid anandamide. However, none of such pathways has been so argued as the existence of a carrier-mediated transport of anandamide across the membrane. Apart from the lack of molecular evidence for such a carrier, the main reasons of this controversy lie in the methodologies currently used to study anandamide cellular uptake. Furthermore, the main evidence in favor of the existence of an "anandamide transporter" relies on synthetic inhibitors of this process, the selectivity of which has been questioned. METHODOLOGY/PRINCIPAL FINDINGS: We used the cytosolic binding site for anandamide on TRPV1 channels as a biosensor to detect anandamide entry into cells, and exploited nanotechnologies to study anandamide membrane transport into intact TRPV1-overexpressing HEK-293 cells. Both fluorescence and digital holographic (DH quantitative phase microscopy were used to study TRPV1 activation. Poly-epsilon-caprolactone nanoparticles (PCL-NPs were used to incorporate anandamide, which could thus enter the cell and activate TRPV1 channels bypassing any possible specific protein(s involved in the uptake process. We reasoned that in the absence of such protein(s, pharmacological tools previously shown to inhibit the "anandamide transporter" would affect in the same way the uptake of anandamide and PCL-NP-anandamide, and hence the activation of TRPV1. However, when masked into PCL-NPs, anandamide cellular uptake became much less sensitive to these agents, although it maintained the same pharmacokinetics and pharmacodynamics as that of "free" anandamide. CONCLUSIONS: We found here that several agents previously reported to inhibit anandamide cellular uptake lose their efficacy when anandamide is prevented from interacting directly with plasma membrane proteins, thus arguing in favor of the specificity of such agents for the putative

  3. One-step isolation of plasma membrane proteins using magnetic beads with immobilized concanavalin A1

    Science.gov (United States)

    Lee, Yu-Chen; Block, Gregory; Chen, Huiwen; Folch-Puy, Emma; Foronjy, Robert; Jalili, Roxana; Jendresen, Christian Bille; Kimura, Masashi; Kraft, Edward; Lindemose, Søren; Lu, Jin; McLain, Teri; Nutt, Leta; Ramon-Garcia, Santiago; Smith, Joseph; Spivak, Aaron; Wang, Michael L.; Zanic, Marija; Lin, Sue-Hwa

    2008-01-01

    We have developed a simple method for isolating and purifying plasma membrane proteins from various cell types. This one-step affinity-chromatography method uses the property of the lectin concanavalin A (ConA) and the technique of magnetic-bead separation to obtain highly purified plasma membrane proteins from crude membrane preparations or cell lines. ConA is immobilized onto magnetic beads by binding biotinylated ConA to streptavidin magnetic beads. When these ConA magnetic beads were used to enrich plasma membranes from a crude membrane preparation, this procedure resulted in 3.7-fold enrichment of plasma membrane marker 5′-nucleotidase activity with 70% recovery of the activity in the crude membrane fraction of rat liver. In agreement with the results of 5′-nucleotidase activity, immunoblotting with antibodies specific for a rat liver plasma membrane protein, CEACAM1, indicated that CEACAM1 was enriched about threefold relative to that of the original membranes. In similar experiments, this method produced 13-fold enrichment of 5′-nucleotidase activity with 45% recovery of the activity from a total cell lysate of PC-3 cells and 7.1-fold enrichment of 5′-nucleotidase activity with 33% recovery of the activity from a total cell lysate of HeLa cells. These results suggest that this one-step purification method can be used to isolate total plasma membrane proteins from tissue or cells for the identification of membrane biomarkers. PMID:18765283

  4. Identification of frog photoreceptor plasma and disk membrane proteins by radioiodination

    Energy Technology Data Exchange (ETDEWEB)

    Witt, P.L.; Bownds, M.D.

    1987-03-24

    Several functions have been identified for the plasma membrane of the rod outer segment, including control of light-dependent changes in sodium conductance and a sodium-calcium exchange mechanism. However, little is known about its constituent proteins. Intact rod outer segments substantially free of contaminants were prepared in the dark and purified on a density gradient of Percoll. Surface proteins were then labeled by lactoperoxidase-catalyzed radioiodination, and intact rod outer segments were reisolated. Membrane proteins were identified by polyacrylamide gel electrophoresis and autoradiography. The surface proteins labeled included rhodopsin, the major membrane protein, and 12 other proteins. To compare the protein composition of plasma membrane with that of the internal disk membrane, purified rod outer segments were lysed by hypotonic disruption or freeze-thawing, and plasma plus disk membranes were radioiodinated. In these membrane preparations, rhodopsin was the major iodinated constituent, with 12 other proteins also labeled. Autoradiographic evidence indicated some differences in protein composition between disk and plasma membranes. A quantitative comparison of the two samples showed that labeling of two proteins, 24 kilodaltons (kDa) and 13 kDa, was enriched in the plasma membrane, while labeling of a 220-kDa protein was enriched in the disk membrane. These plasma membrane proteins may be associated with important functions such as the light-sensitive conductance and the sodium-calcium exchanger.

  5. Stress regulated members of the plant organic cation transporter family are localized to the vacuolar membrane

    Directory of Open Access Journals (Sweden)

    Koch Wolfgang

    2008-07-01

    Full Text Available Abstract Background In Arabidopsis six genes group into the gene family of the organic cation transporters (OCTs. In animals the members of the OCT-family are mostly characterized as polyspecific transporters involved in the homeostasis of solutes, the transport of monoamine neurotransmitters and the transport of choline and carnitine. In plants little is known about function, localisation and regulation of this gene family. Only one protein has been characterized as a carnitine transporter at the plasma membrane so far. Findings We localized the five uncharacterized members of the Arabidopsis OCT family, designated OCT2-OCT6, via GFP fusions and protoplast transformation to the tonoplast. Expression analysis with RNA Gel Blots showed a distinct, organ-specific expression pattern of the individual genes. With reporter gene fusion of four members we analyzed the tissue specific distribution of OCT2, 3, 4, and 6. In experiments with salt, drought and cold stress, we could show that AtOCT4, 5 and 6 are up-regulated during drought stress, AtOCT3 and 5 during cold stress and AtOCT 5 and 6 during salt stress treatments. Conclusion Localisation of the proteins at the tonoplast and regulation of the gene expression under stress conditions suggests a specific role for the transporters in plant adaptation to environmental stress.

  6. The contribution of the sodium-calcium exchanger (NCX) and plasma membrane Ca(2+) ATPase (PMCA) to cerebellar synapse function.

    Science.gov (United States)

    Roome, Chris J; Empson, Ruth M

    2013-01-01

    The cerebellum, a part of the brain critically involved in motor learning and sensory adaptation, expresses high levels of the sodium-calcium exchanger (NCX) and the plasma membrane calcium ATPase (PMCA). Both these transporters control calcium dynamics at a variety of synapses, and here, we draw upon the available literature to discuss how NCX and PMCA work together to shape pre-synaptic calcium dynamics at cerebellar synapses.

  7. Antidiabetogenic Effects of Chromium Mitigate Hyperinsulinemia-Induced Cellular Insulin Resistance via Correction of Plasma Membrane Cholesterol Imbalance

    OpenAIRE

    Horvath, Emily M.; Tackett, Lixuan; McCarthy, Alicia M.; Raman, Priya; Brozinick, Joseph T.; Elmendorf, Jeffrey S.

    2007-01-01

    Previously, we found that a loss of plasma membrane (PM) phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated filamentous actin (F-actin) structure contributes to insulin-induced insulin resistance. Interestingly, we also demonstrated that chromium picolinate (CrPic), a dietary supplement thought to improve glycemic status in insulin-resistant individuals, augments insulin-regulated glucose transport in insulin-sensitive 3T3-L1 adipocytes by lowering PM cholesterol. Here, to gain mechanisti...

  8. Computations of intermittent transport in scrape-off layer plasmas

    DEFF Research Database (Denmark)

    Garcia, O.E.; Naulin, V.; Nielsen, A.H.

    2004-01-01

    Two-dimensional fluid simulations of interchange turbulence for geometry and parameters relevant for the scrape-off layer of magnetized plasmas are presented. The computations, which have distinct plasma production and loss regions, reveal bursty ejection of particles and heat from the bulk plasma...... in the form of blobs. These structures propagate far into the scrape-off layer where they are dissipated due to transport along open magnetic field lines. From single-point recordings it is shown that the blobs have asymmetric conditional wave forms and lead to positively skewed and flattened probability...

  9. Towards a membrane proteome in Drosophila: a method for the isolation of plasma membrane

    Directory of Open Access Journals (Sweden)

    Thomas Graham H

    2010-05-01

    Full Text Available Abstract Background The plasma membrane (PM is a compartment of significant interest because cell surface proteins influence the way in which a cell interacts with its neighbours and its extracellular environment. However, PM is hard to isolate because of its low abundance. Aqueous two-phase affinity purification (2PAP, based on PEG/Dextran two-phase fractionation and lectin affinity for PM-derived microsomes, is an emerging method for the isolation of high purity plasma membranes from several vertebrate sources. In contrast, PM isolation techniques in important invertebrate genetic model systems, such as Drosophila melanogaster, have relied upon enrichment by density gradient centrifugation. To facilitate genetic investigation of activities contributing to the content of the PM sub-proteome, we sought to adapt 2PAP to this invertebrate model to provide a robust PM isolation technique for Drosophila. Results We show that 2PAP alone does not completely remove contaminating endoplasmic reticulum and mitochondrial membrane. However, a novel combination of density gradient centrifugation plus 2PAP results in a robust PM preparation. To demonstrate the utility of this technique we isolated PM from fly heads and successfully identified 432 proteins using MudPIT, of which 37% are integral membrane proteins from all compartments. Of the 432 proteins, 22% have been previously assigned to the PM compartment, and a further 34% are currently unassigned to any compartment and represent candidates for assignment to the PM. The remainder have previous assignments to other compartments. Conclusion A combination of density gradient centrifugation and 2PAP results in a robust, high purity PM preparation from Drosophila, something neither technique can achieve on its own. This novel preparation should lay the groundwork for the proteomic investigation of the PM in different genetic backgrounds in Drosophila. Our results also identify two key steps in this

  10. Slow DNA transport through nanopores in hafnium oxide membranes.

    Science.gov (United States)

    Larkin, Joseph; Henley, Robert; Bell, David C; Cohen-Karni, Tzahi; Rosenstein, Jacob K; Wanunu, Meni

    2013-11-26

    We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2-7 nm thick) freestanding hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with 50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore.

  11. Vacuolar Sorting Receptor (VSR) Proteins Reach the Plasma Membrane in Germinating Pollen Tubes

    Institute of Scientific and Technical Information of China (English)

    Hao Wang; Xiao-Hong Zhuang; Stefan Hillmer; David G. Robinson; Li-Wen Jiang

    2011-01-01

    Vacuolar sorting receptors (VSRs) are type I integral membrane proteins that mediate the vacuolar transport of soluble cargo proteins via prevacuolar compartments (PVCs) in plants.Confocal immunofluorescent and immunogold Electron Microscope (EM) studies have localized VSRs to PVCs or multivesicular bodies (MVBs) and trans-Golgi network (TGN) in various plant cell types,including suspension culture cells,root cells,developing and germinating seeds.Here,we provide evidence that VSRs reach plasma membrane (PM) in growing pollen tubes.Both immunofluorescent and immunogold EM studies with specific VSR antibodies show that,in addition to the previously demonstrated PVC/MVB localization,VSRs also localize to PM in lily and tobacco pollen tubes prepared from chemical fixation or high-pressure freezing/frozen substitution.Such a PM localization suggests an additional role of VSR proteins in mediating protein transport to PM and endocytosis in growing pollen tubes.Using a high-speed Spinning Disc Confocal Microscope,the possible fusion between VSR-positive PVC organelles and the PM was also observed in living tobacco pollen tubes transiently expressing the PVC reporter GFP-VSR.In contrast,the lack of a prominent PM localization of GFP-VSR in living pollen tubes may be due to the highly dynamic situation of vesicular transport in this fast-growing cell type.

  12. Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma

    Institute of Scientific and Technical Information of China (English)

    Hu Liqun; Xu Yi; Wan Baonian; Shi Yuejiang; Zhen Xiangjun; Chen Zhongyong; Lin Shiyao; HT-7 Team

    2005-01-01

    It is found that in HT-7 ohmic plasma, main energy loss comes from electron heat conduction, hence quantitative data of electron heat diffusivity is a very important issue for investigation of electron heat transportation behavior in different target plasmas so as to get high performance plasma. A time-to-peak method of the heat pulse propagation originating from the sawtooth activity on the soft x-ray intensity signal has been adopted to experimentally determine electron heat diffusivity XHPe on the HT-7 tokamak. Aiming to improve the signal-to-noise (S/N)ratio of the original signal to get a stable and reasonable electron heat diffusivity XHDe value, some data processing methods, including average of tens of sawteeth, is discussed. The electron heat diffusivity XHPe is larger than XPBe which is determined from the balance of background plasma power. Based on variation of the measured electron heat diffusivity XHPe, performances of different high confinement plasmas are analyzed.

  13. Fractional Transport in Strongly Turbulent Plasmas

    Science.gov (United States)

    Isliker, Heinz; Vlahos, Loukas; Constantinescu, Dana

    2017-07-01

    We analyze statistically the energization of particles in a large scale environment of strong turbulence that is fragmented into a large number of distributed current filaments. The turbulent environment is generated through strongly perturbed, 3D, resistive magnetohydrodynamics simulations, and it emerges naturally from the nonlinear evolution, without a specific reconnection geometry being set up. Based on test-particle simulations, we estimate the transport coefficients in energy space for use in the classical Fokker-Planck (FP) equation, and we show that the latter fails to reproduce the simulation results. The reason is that transport in energy space is highly anomalous (strange), the particles perform Levy flights, and the energy distributions show extended power-law tails. Newly then, we motivate the use and derive the specific form of a fractional transport equation (FTE), we determine its parameters and the order of the fractional derivatives from the simulation data, and we show that the FTE is able to reproduce the high energy part of the simulation data very well. The procedure for determining the FTE parameters also makes clear that it is the analysis of the simulation data that allows us to make the decision whether a classical FP equation or a FTE is appropriate.

  14. Final technical report on studies of plasma transport

    Energy Technology Data Exchange (ETDEWEB)

    O`Neil, T.M.; Driscoll, C.F.; Malmberg, J.H.

    1997-04-01

    This document gives an overview of the scientific results obtained under the DOE grant, and references the journal articles which give more complete descriptions of the various topics. Recently, the research has been focused on 2-dimensional vortices and turbulence: experiments using a new camera-diagnosed electron plasma apparatus have given surprising results which both clarify and challenge theories. Here, the crossfield E x B flow of the electron plasma is directly analogous to the 2-d flow of an ideal fluid such as water, and may also give insight into more complicated poloidal flows exhibited in toroidal plasmas. The shear-flow instabilities, turbulence, and vortices can be accurately observed, and the free relaxation of this turbulence has been characterized. The physical processes underlying the complicated turbulent evolution can also be studied in more controlled near-linear regimes. The original experimental focus of this program was on radial particle transport from applied external field asymmetries. Here, this research program clearly identified the importance of the collective response of the plasma, giving smaller fields from shielding, or enhanced fields from resonant modes. Experiments and theory work have also elucidated the flow of a plasma along the magnetic field. Finally, some theory was pursued for direct application to fusion plasmas, and to gravitating gas clouds in astrophysics. This program was highly successful in clarifying basic plasma transport processes.

  15. Role of Plasma Elongation on Turbulent Transport in Magnetically Confined Plasmas

    Science.gov (United States)

    Angelino, P.; Garbet, X.; Villard, L.; Bottino, A.; Jolliet, S.; Ghendrih, Ph.; Grandgirard, V.; McMillan, B. F.; Sarazin, Y.; Dif-Pradalier, G.; Tran, T. M.

    2009-05-01

    The theoretical study of plasma turbulence is of central importance to fusion research. Experimental evidence indicates that the confinement time results mainly from the turbulent transport of energy, the magnitude of which depends on the turbulent state resulting from nonlinear saturation mechanisms, in particular, the self-generation of coherent macroscopic structures and large scale flows. Plasma geometry has a strong impact on the structure and magnitude of these flows and also modifies the mode linear growth rates. Nonlinear global gyrokinetic simulations in realistic tokamak magnetohydrodynamic equilibria show how plasma shape can control the turbulent transport. Results are best described in terms of an effective temperature gradient. With increasing plasma elongation, the nonlinear critical effective gradient is not modified while the stiffness of transport is decreasing.

  16. Activation of muscarinic receptors in rat parotid acinar cells induces AQP5 trafficking to nuclei and apical plasma membrane.

    Science.gov (United States)

    Cho, Gota; Bragiel, Aneta M; Wang, Di; Pieczonka, Tomasz D; Skowronski, Mariusz T; Shono, Masayuki; Nielsen, Søren; Ishikawa, Yasuko

    2015-04-01

    The subcellular distribution of aquaporin-5 (AQP5) in rat parotid acinar cells in response to muscarinic acetylcholine receptor (mAChR) activation remains unclear. Immunoconfocal and immunoelectron microscopy were used to visualize the distribution of AQP5 in parotid acinar cells. Western blotting was used to analyze AQP5 levels in membranes. To clarify the characteristics of membrane domains associated with AQP5, detergent solubility and sucrose-density flotation experiments were performed. Under control conditions, AQP5 was diffusely distributed on the apical plasma membrane (APM) and apical plasmalemmal region and throughout the cytoplasm. Upon mAChR activation, AQP5 was predominantly located in the nucleus, APM and lateral plasma membrane (LPM). Subsequently, localization of AQP5 in the nucleus, APM and LPM was decreased. Prolonged atropine treatment inhibited mAChR agonist-induced translocation of AQP5 to the nucleus, APM and LPM. AQP5 levels were enhanced in isolated nuclei and nuclear membranes prepared from parotid tissues incubated with mAChR agonist. mAChR agonist induced AQP5 levels in both soluble and insoluble nuclear fractions solubilized with Triton X-100 or Lubrol WX. Small amounts of AQP5 in nuclei were detected using low-density sucrose gradient. When AQP5 was present in the nuclear membrane, nuclear size decreased. The activation of mAChR induced AQP5 translocation to the nucleus, APM and LPM, and AQP5 may trigger water transport across the nuclear membrane and plasma membrane in rat parotid acinar cells. AQP5 translocates to the nuclear membrane and may trigger the movement of water, inducing shrinkage of the nucleus and the start of nuclear functions. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Glycosidases in the plasma membrane of Ceratitis capitata spermatozoa.

    Science.gov (United States)

    Intra, Jari; De Caro, Daniela; Perotti, Maria-Elisa; Pasini, Maria Enrica

    2011-02-01

    Fruit flies in the family Tephritidae are rated among the world's most destructive agricultural pests. The Mediterranean fruit fly Ceratitis capitata is emerging as a model organism to study the fertilization in Insects. Three integral proteins with glycosidase activity are present in the plasma membrane of spermatozoa. The glycosidases have been purified and characterized. We have demonstrated the presence of three enzymes, a β-N-acetylhexosaminidase, an α-mannosidase and an α-l-fucosidase. The molecular mass of the native enzymes estimated by gel filtration was 160 kDa for β-N-acetylhexosaminidase, 310 kDa for α-mannosidase and 140 kDa for α-l-fucosidase. SDS-PAGE showed that β-N-acetylhexosaminidase is a dimer of a single protein of 73 kDa, α-mannosidase consists of six subunits with different molecular weights and α-l-fucosidase is a dimer made up by two different monomers. Characterization of the purified enzymes included glycosylation pattern, pI, optimal pH, substrate preference, kinetic properties and thermal stability. Soluble forms similar to the sperm associated glycosidases are present. Polyclonal antibodies raised against synthetic peptides designed from the predicted products of the Drosophila melanogaster genes encoding β-N-acetylhexosaminidase and α-l-fucosidase were used. Immunofluorescence labelling of spermatozoa showed that the enzymes are present in the sperm plasma membrane overlying the acrosome and the tail. This work represents the first report on the characterization in C. capitata of sperm proteins that are potentially involved in primary gamete recognition. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Analysis of electron transport in the plasma of thermionic converters

    Energy Technology Data Exchange (ETDEWEB)

    Stoenescu, M.L.; Heinicke, P.H.

    1980-03-01

    Electron transport coefficients of a gaseous ensemble are expressed analytically as function of density, and are expressed analytically as function of temperature up to an unknown function which has to be evaluated for each specific electron-neutral atom cross section. In order to complete the analytical temperature dependence one may introduce a polynomial expansion of the function or one may derive the temperature dependence of a set of coefficients, numbering thirteen for a third approximation transport evaluation, which completely determine the transport coefficients. The latter approach is used for determining the electron transport coefficients of a cesium plasma for any ion neutral composition and any temperature between 500/sup 0/K and 3500/sup 0/K. The relation between the transport coefficients of a fully and partly ionized gas is readily available and shows that, in the classical formalism, electron-ion and electron-neutral resistivities are not additive. The present form of the transport coefficients makes possible an accurate numerical integration of transport equations eliminating lengthy computations which are frequently inaccessible. It thus provides a detailed knowledge of spatial distribution of particle and energy transport and makes possible the determination of one of the three internal voltage drops, surface barrier, sheath and plasma, which are linked together experimentally by current density versus voltage characteristics of thermionic converters.

  19. Production of selective membranes using plasma deposited nanochanneled thin films

    Directory of Open Access Journals (Sweden)

    Rodrigo Amorim Motta Carvalho

    2006-12-01

    Full Text Available The hydrolization of thin films obtained by tetraethoxysilane plasma polymerization results in the formation of a nanochanneled silicone like structure that could be useful for the production of selective membranes. Therefore, the aim of this work is to test the permeation properties of hydrolyzed thin films. The films were tested for: 1 permeation of polar organic compounds and/or water in gaseous phase and 2 permeation of salt in liquid phase. The efficiency of permeation was tested using a quartz crystal microbalance (QCM technique in gas phase and conductimetric analysis (CA in liquid phase. The substrates used were: silicon for characterization of the deposited films, piezoelectric quartz crystals for tests of selective membranes and cellophane paper for tests of permeation. QCM analysis showed that the nanochannels allow the adsorption and/or permeation of polar organic compounds, such as acetone and 2-propanol, and water. CA showed that the films allow salt permeation after an inhibition time needed for hydrolysis of the organic radicals within the film. Due to their characteristics, the films can be used for grains protection against microorganism proliferation during storage without preventing germination.

  20. Detection of boar sperm plasma membrane protein using Rhodamine 640; implications for cryobiology and physiology

    Science.gov (United States)

    Rhodamine 640 (R640) was used to detect changes in boar sperm plasma membrane protein (PMP) during cryopreservation; a poorly understood phenomenon. The protocol was adapted for boar sperm so that semen samples (n = 17) could be analyzed for PMP (R640 positive) and plasma membrane integrity (PMI; Y...

  1. pH-induced proton permeability changes of plasma membrane vesicles

    NARCIS (Netherlands)

    Miedema, H; Prins, HBA; Staal, H.

    In vivo studies with leaf cells of aquatic plant species such as Elodea nuttallii revealed the proton permeability and conductance of the plasma membrane to be strongly pH dependent. The question was posed if similar pH dependent permeability changes also occur in isolated plasma membrane vesicles.

  2. (poly)Phosphoinositide phosphorylation is a marker for plasma membrane in Friend erythroleukaemic cells

    NARCIS (Netherlands)

    Rawyler, A.J.; Roelofsen, B.; Wirtz, K.W.A.; Kamp, J.A.F. op den

    1982-01-01

    Upon subcellular fractionation of (murine) Friend erythroleukaemic cells (FELCs), purified plasma membranes were identified by their high enrichment in specific marker enzymes and typical plasma membrane lipids. When FELCs were incubated for short periods with 32Pi before cell fractionation, the

  3. (poly)Phosphoinositide phosphorylation is a marker for plasma membrane in Friend erythroleukaemic cells

    NARCIS (Netherlands)

    Rawyler, A.J.; Roelofsen, B.; Wirtz, K.W.A.; Kamp, J.A.F. op den

    1982-01-01

    Upon subcellular fractionation of (murine) Friend erythroleukaemic cells (FELCs), purified plasma membranes were identified by their high enrichment in specific marker enzymes and typical plasma membrane lipids. When FELCs were incubated for short periods with 32Pi before cell fractionation, the lip

  4. Monitoring the native phosphorylation state of plasma membrane proteins from a single mouse cerebellum

    DEFF Research Database (Denmark)

    Schindler, J.; Ye, J. Y.; Jensen, Ole Nørregaard

    2013-01-01

    Neuronal processing in the cerebellum involves the phosphorylation and dephosphorylation of various plasma membrane proteins such as AMPA or NMDA receptors. Despite the importance of changes in phosphorylation pattern, no global phospho-proteome analysis has yet been performed. As plasma membrane...

  5. Enzymes of phosphoinositide synthesis in secretory vesicles destined for the plasma membrane in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kinney, A J; Carman, G M

    1990-07-01

    CDP-diacylglycerol synthase, phosphatidylinositol synthase, and phosphatidylinositol kinase activities were associated with post-Golgi apparatus secretory vesicles destined for the plasma membrane of Saccharomyces cerevisiae. These results suggest that the plasma membrane is capable of synthesizing both CDP-diacylglycerol and phosphatidylinositol as well as phosphorylating phosphatidylinositol.

  6. PLASMA-MEMBRANE LIPID ALTERATIONS INDUCED BY NACL IN WINTER-WHEAT ROOTS

    NARCIS (Netherlands)

    MANSOUR, MMF; VANHASSELT, PR; KUIPER, PJC

    1994-01-01

    A highly enriched plasma membrane fraction was isolated by two phase partitioning from wheat roots (Triticum aestivum L. cv. Vivant) grown with and without 100 mM NaCl. The lipids of the plasma membrane fraction were extracted and characterized. Phosphatidylcholine and phosphatidylethanolamine were

  7. One-step isolation of plasma membrane proteins using magnetic beads with immobilized concanavalin A

    DEFF Research Database (Denmark)

    Lee, Yu-Chen; Block, Gregory; Chen, Huiwen;

    2008-01-01

    We have developed a simple method for isolating and purifying plasma membrane proteins from various cell types. This one-step affinity-chromatography method uses the property of the lectin concanavalin A (ConA) and the technique of magnetic bead separation to obtain highly purified plasma membran...

  8. Tetracyclines increase lipid phosphate phosphatase expression on plasma membranes and turnover of plasma lysophosphatidate.

    Science.gov (United States)

    Tang, Xiaoyun; Zhao, Yuan Y; Dewald, Jay; Curtis, Jonathan M; Brindley, David N

    2016-04-01

    Extracellular lysophosphatidate and sphingosine 1-phosphate (S1P) are important bioactive lipids, which signal through G-protein-coupled receptors to stimulate cell growth and survival. The lysophosphatidate and S1P signals are terminated partly by degradation through three broad-specificity lipid phosphate phosphatases (LPPs) on the cell surface. Significantly, the expression of LPP1 and LPP3 is decreased in many cancers, and this increases the impact of lysophosphatidate and S1P signaling. However, relatively little is known about the physiological or pharmacological regulation of the expression of the different LPPs. We now show that treating several malignant and nonmalignant cell lines with 1 μg/ml tetracycline, doxycycline, or minocycline significantly increased the extracellular degradation of lysophosphatidate. S1P degradation was also increased in cells that expressed high LPP3 activity. These results depended on an increase in the stabilities of the three LPPs and increased expression on the plasma membrane. We tested the physiological significance of these results and showed that treating rats with doxycycline accelerated the clearance of lysophosphatidate, but not S1P, from the circulation. However, administering 100 mg/kg/day doxycycline to mice decreased plasma concentrations of lysophosphatidate and S1P. This study demonstrates a completely new property of tetracyclines in increasing the plasma membrane expression of the LPPs.

  9. Kinetic theory of transport processes in partially ionized reactive plasma, II: Electron transport properties

    Science.gov (United States)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-11-01

    The previously obtained in (Zhdanov and Stepanenko, 2016) general transport equations for partially ionized reactive plasma are employed for analysis of electron transport properties in molecular and atomic plasmas. We account for both elastic and inelastic interaction channels of electrons with atoms and molecules of plasma and also the processes of electron impact ionization of neutral particles and three-body ion-electron recombination. The system of scalar transport equations for electrons is discussed and the expressions for non-equilibrium corrections to electron ionization and recombination rates and the diagonal part of the electron pressure tensor are derived. Special attention is paid to analysis of electron energy relaxation during collisions with plasma particles having internal degrees of freedom and the expression for the electron coefficient of inelastic energy losses is deduced. We also derive the expressions for electron vector and tensorial transport fluxes and the corresponding transport coefficients for partially ionized reactive plasma, which represent a generalization of the well-known results obtained by Devoto (1967). The results of numerical evaluation of contribution from electron inelastic collisions with neutral particles to electron transport properties are presented for a series of molecular and atomic gases.

  10. A dileucine motif is involved in plasma membrane expression and endocytosis of rat sodium taurocholate cotransporting polypeptide (Ntcp).

    Science.gov (United States)

    Stross, Claudia; Kluge, Stefanie; Weissenberger, Katrin; Winands, Elisabeth; Häussinger, Dieter; Kubitz, Ralf

    2013-11-15

    The sodium taurocholate cotransporting polypeptide (Ntcp) is the major uptake transporter for bile salts into liver parenchymal cells, and PKC-mediated endocytosis was shown to regulate the number of Ntcp molecules at the plasma membrane. In this study, mechanisms of Ntcp internalization were analyzed by flow cytometry, immunofluorescence, and Western blot analyses in HepG2 cells. PKC activation induced endocytosis of Ntcp from the plasma membrane by ~30%. Endocytosis of Ntcp was clathrin dependent and was followed by lysosomal degradation. A dileucine motif located in the third intracellular loop of Ntcp was essential for endocytosis but also for processing and plasma membrane targeting, suggesting a dual function of this motif for intracellular trafficking of Ntcp. Mutation of two of five potential phosphorylation sites surrounding the dileucine motif (Thr225 and Ser226) inhibited PKC-mediated endocytosis. In conclusion, we could identify a motif, which is critical for Ntcp plasma membrane localization. Endocytic retrieval protects hepatocytes from elevated bile salt concentrations and is of special interest, because NTCP has been identified as a receptor for the hepatitis B and D virus.

  11. Plasma membrane proteomics in the maize primary root growth zone: novel insights into root growth adaptation to water stress.

    Science.gov (United States)

    Voothuluru, Priyamvada; Anderson, Jeffrey C; Sharp, Robert E; Peck, Scott C

    2016-09-01

    Previous work on maize (Zea mays L.) primary root growth under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. These responses involve spatially differential and coordinated regulation of osmotic adjustment, modification of cell wall extensibility, and other cellular growth processes that are required for root growth under water-stressed conditions. As the interface between the cytoplasm and the apoplast (including the cell wall), the plasma membrane likely plays critical roles in these responses. Using a simplified method for enrichment of plasma membrane proteins, the developmental distribution of plasma membrane proteins was analysed in the growth zone of well-watered and water-stressed maize primary roots. The results identified 432 proteins with differential abundances in well-watered and water-stressed roots. The majority of changes involved region-specific patterns of response, and the identities of the water stress-responsive proteins suggest involvement in diverse biological processes including modification of sugar and nutrient transport, ion homeostasis, lipid metabolism, and cell wall composition. Integration of the distinct, region-specific plasma membrane protein abundance patterns with results from previous physiological, transcriptomic and cell wall proteomic studies reveals novel insights into root growth adaptation to water stress.

  12. Ion transport barriers triggered by plasma polarization in gyrokinetic simulations

    Science.gov (United States)

    Strugarek, A.; Sarazin, Y.; Zarzoso, D.; Abiteboul, J.; Brun, A. S.; Cartier-Michaud, T.; Dif-Pradalier, G.; Garbet, X.; Ghendrih, Ph; Grandgirard, V.; Latu, G.; Passeron, C.; Thomine, O.

    2013-07-01

    The creation of ion transport barriers by externally induced sheared E × B flows is investigated with the global, full-f and flux-driven gyrokinetic code GYSELA. A gyrokinetic source of vorticity is designed and proves to be efficient in polarizing the plasma. Induced sheared electric fields develop in the turbulent core and are accompanied by the creation of a transport barrier. The barrier and the sheared flow relax quasi-periodically because of zonal flow activity and a destabilizing temperature anisotropy induced by the vorticity source. A new cyclic mechanism leading to the relaxation of transport barriers in tokamaks is discovered.

  13. Red wine activates plasma membrane redox system in human erythrocytes.

    Science.gov (United States)

    Tedesco, Idolo; Moccia, Stefania; Volpe, Silvestro; Alfieri, Giovanna; Strollo, Daniela; Bilotto, Stefania; Spagnuolo, Carmela; Di Renzo, Massimo; Aquino, Rita P; Russo, Gian Luigi

    2016-01-01

    In the present study, we report that polyphenols present in red wine obtained by a controlled microvinification process are able to protect human erythrocytes from oxidative stress and to activate Plasma Membrane Redox System (PMRS). Human plasma obtained from healthy subjects was incubated in the presence of whole red wine at a concentration corresponding to 9.13-73 μg/ml gallic acid equivalents to verify the capacity to protect against hypochlorous acid (HOCl)-induced plasma oxidation and to minimize chloramine formation. Red wine reduced hemolysis and chloramine formation induced by HOCl of 40 and 35%, respectively. PMRS present on human erythrocytes transfers electrons from intracellular molecules to extracellular electron acceptors. We demonstrated that whole red wine activated PMRS activity in human erythrocytes isolated from donors in a dose-dependent manner with a maximum at about 70-100 μg/ml gallic acid equivalents. We also showed that red wine increased glutathione (GSH) levels and erythrocytic antioxidant capacity, measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) quenching assay. Furthermore, we reported that GSH played a crucial role in regulating PMRS activity in erythrocytes. In fact, the effect of iodoacetamide, an alkylating agent that induces depletion of intracellular GSH, was completely counteracted by red wine. Bioactive compounds present in red wine, such as gallic acid, resveratrol, catechin, and quercetin were unable to activate PMRS when tested at the concentrations normally present in aged red wines. On the contrary, the increase of PMRS activity was associated with the anthocyanin fraction, suggesting the capacity of this class of compounds to positively modulate PMRS enzymatic activity.

  14. The isolation of plasma membrane from protoplasts of soybean suspension cultures.

    Science.gov (United States)

    Galbraith, D W; Northcote, D H

    1977-04-01

    A procedure for the isolation of plasma membranes from protoplasts of suspension-cultured soybean is described. Protoplasts were prepared by enzymic digestion of the cell wall and the plasma membrane was labelled with radioactive diazotized sulphanilic acid. The membrane systems from broken protoplasts were separated by continuous isopycnic sucrose gradient centrifugation. Radioactivity was localized in a band possessing a buoyant density of 1-14 g ml-1. The activities of NADPH- and NADH-cytochrome c reductase, fumarase, Mg2+-ATPase, IDPase and acid phosphodiesterase in the various regions of the density gradient were determined. A plasma membrane fraction was selected which was relatively uncontaminated with membranes derived from endoplasmic reticulum, tonoplasts and mitochondria. The results indicated that Mg2+-ATPase and possibly acid phosphodiesterase were associated with the plasma membrane.

  15. STARD4 knockdown in HepG2 cells disrupts cholesterol trafficking associated with the plasma membrane, ER, and ERC

    DEFF Research Database (Denmark)

    Garbarino, J.; Pan, M. H.; Chin, H. F.

    2012-01-01

    STARD4, a member of the evolutionarily conserved START gene family, has been implicated in the non-vesicular intracellular transport of cholesterol. However, the direction of transport and the membranes with which this protein interacts are not clear. We present studies of STARD4 function using...... small hairpin RNA knockdown technology to reduce STARD4 expression in HepG2 cells. In a cholesterol-poor environment, we found that a reduction in STARD4 expression leads to retention of cholesterol at the plasma membrane, reduction of endoplasmic reticulum-associated cholesterol, and decreased ACAT...... synthesized cholesteryl esters. Furthermore, D4 KD cells exhibited a reduced rate of sterol transport to the endocytic recycling compartment after cholesterol repletion. Although these cells displayed normal endocytic trafficking in cholesterol-poor and replete conditions, cell surface low density lipoprotein...

  16. Coherent structures and transport in drift wave plasma turbulence

    DEFF Research Database (Denmark)

    Korsholm, Søren Bang

    for optimization. The present work is a part of the puzzle to understand the basic physics of transport induced by drift wave turbulence in the edge region of a plasma. The basis for the study is the Hasegawa- Wakatani model. Simulation results for 3D periodic and nonperiodic geometries are presented. The Hasegawa......-Wakatani model is further expanded to include ion temperature effects. Another expansion of the model is derived from the Braginskii electron temperature equation. The result is a self-consistent set of equations describing the dynamical evolution of the drift wave fluctuations of the electron density, electron......Fusion energy research aims at developing fusion power plants providing safe and clean energy with abundant fuels. Plasma turbulence induced transport of energy and particles is a performance limiting factor for fusion devices. Hence the understanding of plasma turbulence is important...

  17. Towards Co-evolution of Membrane Transport and Metabolism

    Science.gov (United States)

    Wei, Chenyu; Pohorille, Andrzej

    2014-01-01

    Protocellular boundaries were inextricably connected to the metabolism they encapsulated: to be inheritable, early metabolism must have led to an increased rate of growth and division of vesicles and, similarly, transport through vesicle boundaries must have supported the evolution of metabolism. Even though explaining how this coupling emerged and evolved in the absence of the complex machinery of modern cells is one of the key issues in studies on the origin of life, little is known about the biochemical and biophysical processes that might have been involved. This gap in our knowledge is a major impediment in efforts to construct scenarios for the origin of life and laboratory models of protocells. A combination of experimental and computational studies carried out by us and our collaborators is aimed at helping to close this gap. Properties of membranes might have contributed to the selection of RNA as an early biopolymer. A kinetic mechanism was proposed (Sacerdote & Szostak, 2005) in which ribose was supplied more quickly than other aldopentoses to primordial cells for preferential incorporation of ribonucleotides into nucleic acids. This proposal is based on a finding that ribose permeates membranes an order of magnitude faster than its diastereomers, arabinose and xylose. Our computer simulations, which yield permeation rates in excellent agreement with experiment, and kinetic modeling explain this phenomenon in terms of inter- and intramolecular interactions involving exocyclic hydroxyl groups attached to carbon atoms of the pyranose ring (Wei and Pohorille, 2009). They also constrain scenarios for the formation of the earliest nucleic acids (Wei and Pohorille, 2013). In one scenario, sugars permeate protocellular walls and subsequently are used to synthesize nucleic acids inside protocells. As long as this process proceeds at the rate faster than 6x10(exp -3)/s, ribose derivatives will be available for synthesis easier than their diastereomers. If

  18. [Participation of proteinkinase CK2 in regulation of human erythrocytes plasma membrane redox system activity: relative contribution of ca(2+)-dependent and ca(2+)-independent mechanisms of its activation].

    Science.gov (United States)

    Iakovenko, I N; Zhirnov, V V; Kozachenko, O P; Shablykin, O V; Brovarets', V S

    2012-01-01

    Involvement of protein kinase CK2 (2.7.11.1) in modulation of live cells trans-plasma membrane electron transport was first discovered. Using human erythrocytes a decrease of plasma membrane redox system (PMRS) activity is shown under the action of specific protein kinase CK2 inhibitors. Using inhibitory analysis the activity regulation of human erythrocytes PMRS by Ca(2+)-dependent and Ca(2+)-independent mechanisms were investigated. It was shown that functional Ca(2+)-antagonists (nitrendipine and calmidazolium) significantly increased, and functional Ca(2+)-agonists to some extent reduced or did not affect the trans-plasma membrane electron transport in these cells.

  19. Accumulation of raft lipids in T-cell plasma membrane domains engaged in TCR signalling

    DEFF Research Database (Denmark)

    Zech, Tobias; Ejsing, Christer S.; Gaus, Katharina;

    2009-01-01

    domains were also enriched in plasmenyl phosphatidylethanolamine and phosphatidylserine. Modulating the T-cell lipidome with polyunsaturated fatty acids impaired the plasma membrane condensation at TCR signalling foci and resulted in a perturbed molecular lipid composition. These results correlate...... and saturated phosphatidylcholine species as compared with control plasma membrane fragments. This provides, for the first time, direct evidence that TCR activation domains comprise a distinct molecular lipid composition reminiscent of liquid-ordered raft phases in model membranes. Interestingly, TCR activation...

  20. Graft polymerization and plasma treatment of polymer membranes for fouling reduction: a review.

    Science.gov (United States)

    Kochkodan, Victor M; Sharma, Virender K

    2012-01-01

    This article presents a review of recent developments in surface modification of polymer membranes via graft polymerization and plasma treatment for reduction of fouling with organic compounds and microorganisms in pressure driven membrane processes. The factors affecting membrane fouling, such as membrane hydrophilicity, charge and surface roughness are discussed. The recent studies in which the reduction of organic fouling and biofouling by the modification of the membrane surface via ultraviolet/redox initiated surface grafting of hydrophilic polymers and low temperature plasma treatment are reviewed.

  1. Fast ions and momentum transport in JET tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Salmi, A.

    2012-07-01

    Fast ions are an inseparable part of fusion plasmas. They can be generated using electromagnetic waves or injected into plasmas as neutrals to heat the bulk plasma and to drive toroidal rotation and current. In future power plants fusion born fast ions deliver the main heating into the plasma. Understanding and controlling the fast ions is of crucial importance for the operation of a power plant. Furthermore, fast ions provide ways to probe the properties of the thermal plasma and get insight of its confinement properties. In this thesis, numerical code packages are used and developed to simulate JET experiments for a range of physics issues related to fast ions. Namely, the clamping fast ion distribution at high energies with RF heating, fast ion ripple torque generation and the toroidal momentum transport properties using NBI modulation technique are investigated. Through a comparison of numerical simulations and the JET experimental data it is shown that the finite Larmor radius effects in ion cyclotron resonance heating are important and that they can prevent fast ion tail formation beyond certain energy. The identified mechanism could be used for tailoring the fast ion distribution in future experiments. Secondly, ASCOT simulations of NBI ions in a ripple field showed that most of the reduction of the toroidal rotation that has been observed in the JET enhanced ripple experiments could be attributed to fast ion ripple torque. Finally, fast ion torque calculations together with momentum transport analysis have led to the conclusion that momentum transport in not purely diffusive but that a convective component, which increases monotonically in radius, exists in a wide range of JET plasmas. Using parameter scans, the convective transport has been shown to be insensitive to collisionality and q-profile but to increase strongly against density gradient. (orig.)

  2. Polymer electrolyte membranes from fluorinated polyisoprene-block-sulfonated polystyrene: Membrane structure and transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Sodeye, Akinbode [Department of Polymer Science and Engineering, University of Massachusetts; Huang, Tianzi [University of Tennessee, Knoxville (UTK); Gido, Samuel [University of Massachusetts, Amherst; Mays, Jimmy [ORNL

    2011-01-01

    With a view to optimizing morphology and ultimately properties, membranes have been cast from relatively inexpensive block copolymer ionomers of fluorinated polyisoprene-block-sulfonated polystyrene (FISS) with various sulfonation levels, in both the acid form and the cesium neutralized form. The morphology of these membranes was characterized by transmission electron microscopy and ultra-small angle X-ray scattering, as well as water uptake, proton conductivity and methanol permeability within the temperature range from 20 to 60 C. Random phase separated morphologies were obtained for all samples except the cesium sample with 50 mol% sulfonation. The transport properties increased with increasing degree of sulfonation and temperature for all samples. The acid form samples absorbed more water than the cesium samples with a maximum swelling of 595% recorded at 60 C for the acid sample having 50 mol% sulfonation. Methanol permeability for the latter sample was more than an order of magnitude less than for Nafion 112 but so was the proton conductivity within the plane of the membrane at 20 C. Across the plane of the membrane this sample had half the conductivity of Nafion 112 at 60 C.

  3. Small Molecule Membrane Transporters in the Mammalian Podocyte: A Pathogenic and Therapeutic Target

    Directory of Open Access Journals (Sweden)

    Cristina Zennaro

    2014-11-01

    Full Text Available The intriguingly complex glomerular podocyte has been a recent object of intense study. Researchers have sought to understand its role in the pathogenesis of common proteinuric diseases such as minimal change disease and focal segmental glomerular sclerosis. In particular, considerable effort has been directed towards the anatomic and functional barrier to macromolecular filtration provided by the secondary foot processes, but little attention has been paid to the potential of podocytes to handle plasma proteins beyond the specialization of the slit diaphragm. Renal membrane transporters in the proximal tubule have been extensively studied for decades, particularly in relation to drug metabolism and elimination. Recently, uptake and efflux transporters for small organic molecules have also been found in the glomerular podocyte, and we and others have found that these transporters can engage not only common pharmaceuticals but also injurious endogenous and exogenous agents. We have also found that the activity of podocyte transporters can be manipulated to inhibit pathogen uptake and efflux. It is conceivable that podocyte transporters may play a role in disease pathogenesis and may be a target for future drug development.

  4. Oscillations and multiple steady states in active membrane transport models.

    Science.gov (United States)

    Vieira, F M; Bisch, P M

    1994-01-01

    The dynamic behavior of some non-linear extensions of the six-state alternating access model for active membrane transport is investigated. We use stoichio-metric network analysis to study the stability of steady states. The bifurcation analysis has been done through standard numerical methods. For the usual six-state model we have proved that there is only one steady state, which is globally asymptotically stable. When we added an autocatalytic step we found self-oscillations. For the competition between a monomer cycle and a dimer cycle, with steps of dimer formation, we have also found self-oscillations. We have also studied models involving the formation of a complex with other molecules. The addition of two steps for formation of a complex of the monomer with another molecule does not alter either the number or the stability of steady states of the basic six-state model. The model which combines the formation of a complex with an autocatalytic step shows both self-oscillations and multiple steady states. The results lead us to conclude that oscillations could be produced by active membrane transport systems if the transport cycle contains a sufficiently large number of steps (six in the present case) and is coupled to at least one autocatalytic reaction,. Oscillations are also predicted when the monomer cycle is coupled to a dimer cycle. In fact, the autocatalytic reaction can be seen as a simplification of the model involving competition between monomer and dimer cycles, which seems to be a more realistic description of biological systems. A self-regulation mechanism of the pumps, related to the multiple stationary states, is expected only for a combined effect of autocatalysis and formation of complexes with other molecules. Within the six-state model this model also leads to oscillation.

  5. Transport of the glutathione-methylmercury complex across liver canalicular membranes on reduced glutathione carriers.

    Science.gov (United States)

    Dutczak, W J; Ballatori, N

    1994-04-01

    Methylmercury transport across liver canalicular membranes into bile, a major route of excretion of this toxic compound, is dependent upon intracellular GSH, and a glutathione-methylmercury complex (CH3Hg.SG) has been detected in liver tissue and bile. To examine whether the CH3Hg.SG complex is itself transported across the canalicular membrane and to identify the transport system involved, studies were performed in isolated rat liver canalicular plasma membrane vesicles. Uptake of CH3(203)Hg.SG (10 microM) into an osmotically active space was temperature-sensitive and unaffected by either ATP (5 mM) or an inwardly directed Na+ gradient (100 mM); however, CH3Hg.SG uptake was enhanced by a valinomycin-induced K+ diffusion potential (inside-positive) indicating that its transport was electrogenic. Transport of CH3Hg.SG exhibited saturation kinetics with both high affinity (Km = 12 +/- 2 microM, Vmax = 0.23 +/- 0.02 nmol.mg-1.20 s-1) and low affinity (Km = 1.47 +/- 0.22 mM, Vmax = 1.23 +/- 0.14 nmol.mg-1.20 s-1) components. Uptake of this complex was inhibited by GSH, the GSH analog ophthalmic acid, S-methyl, S-ethyl, S-butyl, S-hexyl, S-octyl, and S-dinitrophenyl glutathione, but not by GSSG, bile acids, amino acids, and P-glycoprotein inhibitors. Furthermore, GSH competitively inhibited (Ki = 83 microM) and trans-stimulated CH3Hg.SG uptake into the canalicular vesicles. These studies provide the first kinetic characterization of a transport system for glutathione-mercaptides and indicate that CH3Hg.SG is not a substrate for the ATP-dependent, canalicular GSSG or glutathione S-conjugate carriers, but appears to be a substrate for canalicular carriers that also transport GSH. Because efflux systems for GSH are found in all mammalian cells, transport of glutathione-metal complexes by such carriers may be a common mechanism for the removal of methylmercury and possibly other metals from cells.

  6. Preliminary study on plasma membrane fluidity of Psychrophilic Yeast Rhodotorula sp. NJ298 in low temperature

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The ability of cell to modulate the fluidity of plasma membrane was crucial to the survival of microorganism at low temperature. Plasma membrane proteins, fatty acids and carotenoids profiles of Antarctic psychrophilc yeast Rhodotorula sp. NJ298 were investigated at -3 ℃, 0 ℃ and 8 ℃. The results showed that plasma membrane protein content was greater at -3 ℃ than that at 8 ℃, and a unique membrane polypeptide composition with an apparent molecular mass of 94.7 kDa was newly synthesized with SDS-PAGE analysis; GC analysis showed that the main changes of fatty acids were the percentage of unsaturated fatty acids (C18∶ 1 and C18∶ 2) and shorter chain saturated fatty acid (C10∶ 0) increased along with the decrease of the culture temperature from 8 ℃ to -3 ℃; HPLC analysis indicated that astaxanthin was the major functional carotenoids of the plasma membrane, percentage of which increased from 54.6±1.5% at 8 ℃ to 81.9±2.1% at -3 ℃. However the fluidity of plasma membrane which was determined by measuring fluorescence anisotropy was similar at -3 ℃, 0 ℃ and 8 ℃. Hence these changes in plasma membrane's characteristics were involved in the cellular cold-adaptation by which NJ298 could maintain normal plasma membrane fluidity at near-freezing temperature.

  7. Fluorescence interference contrast based approach to study real time interaction of melittin with plasma membranes

    Science.gov (United States)

    Gupta, Sharad; Gui, Dong; Zandi, Roya; Gill, Sarjeet; Mohideen, Umar

    2014-03-01

    Melittin is an anti-bacterial and hemolytic toxic peptide found in bee venom. Cell lysis behavior of peptides has been widely investigated, but the exact interaction mechanism of lytic peptides with lipid membranes and its constituents has not been understood completely. In this paper we study the melittin interaction with lipid plasma membranes in real time using non-invasive and non-contact fluorescence interference contrast microscopy (FLIC). Particularly the interaction of melittin with plasma membranes was studied in a controlled molecular environment, where these plasma membrane were composed of saturated lipid, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and unsaturated lipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine(DOPC) with and without cholesterol. We found out that melittin starts to form nanometer size pores in the plasma membranes shortly after interacting with membranes. But the addition of cholesterol in plasma membrane slows down the pore formation process. Our results show that inclusion of cholesterol to the plasma membranes make them more resilient towards pore formation and lysis of membrane.

  8. Properties of Plasma Membrane from Pea Root Seedlings under Altered Gravity

    Science.gov (United States)

    Klymchuk, D.; Baranenko, V.; Vorobyova, T. V.; Kurylenko, I.; Chyzhykova, O.; Dubovoy, V.

    In this study, the properties of pea (Pisum sativum L.) plasma membrane were examined to determine how the membrane structure and functions are regulated in response to clinorotation (2 rev/min) conditions. Membrane preparations enriched by plasma membrane vesicles were obtained by aqueous two-phase partitioning from 6-day seedling roots. The specific characteristics of H^+-ATPase, lípid composition and peroxidation intensity as well as fluidity of lipid bilayer were analysed. ATP hydrolytic activity was inhibited by ortovanadate and was insensitive to aside and nitrate in sealed plasma membrane vesicles isolated from both clinorotated and control seedlings. Plasma membrane vesicles from clinorotated seedlings in comparison to controls were characterised by increase in the total lipid/protein ratio, ATP hydrolytic activity and intensifying of lipid peroxidation. Sitosterol and campesterol were the predominant free sterol species. Clinorotated seedlings contained a slightly higher level of unsaturated fatty acid than controls. Plasma membrane vesicles were labelled with pyrene and fluorescence originating from monomeric (I_M) molecules and excimeric (I_E) aggregates were measured. The calculated I_E/I_M values were higher in clinorotated seedlings compared with controls reflecting the reduction in membrane microviscosity. The involvement of the changes in plasma membrane lipid content and composition, fluidity and H^+-ATPase activity in response of pea seedlings to altered gravity is discussed.

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

    Science.gov (United States)

    Prada, Ilaria; Meldolesi, Jacopo

    2016-08-09

    Exosomes and ectosomes, extracellular vesicles of two types generated by all cells at multivesicular bodies and the plasma membrane, respectively, play critical roles in physiology and pathology. A key mechanism of their function, analogous for both types of vesicles, is the fusion of their membrane to the plasma membrane of specific target cells, followed by discharge to the cytoplasm of their luminal cargo containing proteins, RNAs, and DNA. Here we summarize the present knowledge about the interactions, binding and fusions of vesicles with the cell plasma membrane. The sequence initiates with dynamic interactions, during which vesicles roll over the plasma membrane, followed by the binding of specific membrane proteins to their cell receptors. Membrane binding is then converted rapidly into fusion by mechanisms analogous to those of retroviruses. Specifically, proteins of the extracellular vesicle membranes are structurally rearranged, and their hydrophobic sequences insert into the target cell plasma membrane which undergoes lipid reorganization, protein restructuring and membrane dimpling. Single fusions are not the only process of vesicle/cell interactions. Upon intracellular reassembly of their luminal cargoes, vesicles can be regenerated, released and fused horizontally to other target cells. Fusions of extracellular vesicles are relevant also for specific therapy processes, now intensely investigated.

  10. Plasma transport in the Scrape-off-Layer of magnetically confined plasma and the plasma exhaust

    DEFF Research Database (Denmark)

    Rasmussen, Jens Juul; Naulin, Volker; Nielsen, Anders Henry

    An overview of the plasma dynamics in the Scrape-off-Layer (SOL) of magnetically confined plasma is presented. The SOL is the exhaust channel of the warm plasma from the core, and the understanding of the SOL plasma dynamics is one of the key issues in contemporary fusion research. It is essential...

  11. Lateral diffusion of phospholipids in the plasma membrane of soybean protoplasts: Evidence for membrane lipid domains.

    Science.gov (United States)

    Metcalf, T N; Wang, J L; Schindler, M

    1986-01-01

    Fluorescent lipid and phospholipid probes were incorporated at 4 degrees C into soybean protoplasts prepared from cultured soybean (SB-1) cells. Fluorescence microscopy showed that the plasma membrane as well as the nucleus were labeled. Fluorescence redistribution after photobleaching (FRAP) analysis was performed on these cells at 18 degrees C to monitor the lateral mobility of the incorporated probes. After labeling at low concentrations (40 mug/ml) of phosphatidyl-N-(4-nitrobenzo-2-oxa-1,3-diazolyl)ethanolamine (NBD-PtdEtn), a single mobile component was observed with a diffusion coefficient (D) of approximately 3 x 10(-9) cm(2)/sec. After labeling at higher probe concentrations (>/=100 mug/ml), two diffusing species were observed, with diffusion coefficients of approximately 3 x 10(-9) cm(2)/sec ("fast") and approximately 5 x 10(-10) cm(2)/sec ("slow"). Similar results were observed with fluorescent derivatives of phosphatidylcholine and fatty acids. In contrast to these results, parallel analysis of 3T3 fibroblasts, using the same probes and conditions, yielded only a single diffusion component. These results suggest that the soybean plasma membrane may contain two distinct lipid domains in terms of lipid mobility. Consistent with this idea, experiments with soybean protoplasts yielded a single diffusion component under the following conditions: (i) labeling with NBD-PtdEtn (100 mug/ml), FRAP analysis at 37 degrees C (D = 1.1 x 10(-8) cm(2)/sec); (ii) labeling with NBD-PtdEtn (100 mug/ml), FRAP analysis at 18 degrees C in the presence of 2 mM EGTA (D = 4.2 x 10(-9) cm(2)/sec); (iii) labeling with 5-(N-dodecanoyl)aminofluorescein (a short-chain lipid probe), FRAP analysis at 18 degrees C or 37 degrees C (D = 2.5 x 10(-8) cm(2)/sec). These results suggest that the plasma membrane of soybean cells may contain stable immiscible domains of fluid and gel-like lipids.

  12. System and method for temperature control in an oxygen transport membrane based reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, Sean M.

    2017-02-21

    A system and method for temperature control in an oxygen transport membrane based reactor is provided. The system and method involves introducing a specific quantity of cooling air or trim air in between stages in a multistage oxygen transport membrane based reactor or furnace to maintain generally consistent surface temperatures of the oxygen transport membrane elements and associated reactors. The associated reactors may include reforming reactors, boilers or process gas heaters.

  13. System and method for air temperature control in an oxygen transport membrane based reactor

    Science.gov (United States)

    Kelly, Sean M

    2016-09-27

    A system and method for air temperature control in an oxygen transport membrane based reactor is provided. The system and method involves introducing a specific quantity of cooling air or trim air in between stages in a multistage oxygen transport membrane based reactor or furnace to maintain generally consistent surface temperatures of the oxygen transport membrane elements and associated reactors. The associated reactors may include reforming reactors, boilers or process gas heaters.

  14. Noninvasive microelectrode ion flux estimation technique (MIFE) for the study of the regulation of root membrane transport by cyclic nucleotides

    KAUST Repository

    Ordoñez, Natalia Maria

    2013-09-03

    Changes in ion permeability and subsequently intracellular ion concentrations play a crucial role in intracellular and intercellular communication and, as such, confer a broad array of developmental and adaptive responses in plants. These changes are mediated by the activity of plasma-membrane based transport proteins many of which are controlled by cyclic nucleotides and/or other signaling molecules. The MIFE technique for noninvasive microelectrode ion flux measuring allows concurrent quantification of net fluxes of several ions with high spatial (μm range) and temporal (ca. 5 s) resolution, making it a powerful tool to study various aspects of downstream signaling events in plant cells. This chapter details basic protocols enabling the application of the MIFE technique to study regulation of root membrane transport in general and cyclic nucleotide mediated transport in particular. © Springer Science+Business Media New York 2013.

  15. Preparation of Citric Acid Crosslinked Chitosan/Poly(Vinyl Alcohol Blend Membranes for Creatinine Transport

    Directory of Open Access Journals (Sweden)

    Retno Ariadi Lusiana

    2016-08-01

    Full Text Available Preparation of membrane using crosslinking reaction between chitosan and citric acid showed that functional group modification increased the number of active carrier groups which lead to better transport capacity of the membrane. In addition, the substitution of the carboxyl group increased creatinine permeation of chitosan membrane. The transport capacity of citric acid crosslinked chitosan membrane for creatinine was found to be 6.3 mg/L. The presence of cyanocobalamin slightly hindered the transport of creatinine although compounds did not able to pass through citric acid crosslinked chitosan/poly(vinyl alcohol blend membrane, as compounds no found in the acceptor phase.

  16. Role of tetanus neurotoxin insensitive vesicle-associated membrane protein (TI-VAMP) in vesicular transport mediating neurite outgrowth.

    Science.gov (United States)

    Martinez-Arca, S; Alberts, P; Zahraoui, A; Louvard, D; Galli, T

    2000-05-15

    How vesicular transport participates in neurite outgrowth is still poorly understood. Neurite outgrowth is not sensitive to tetanus neurotoxin thus does not involve synaptobrevin-mediated vesicular transport to the plasma membrane of neurons. Tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP) is a vesicle-SNARE (soluble N-ethylmaleimide-sensitive fusion protein [NSF] attachment protein [SNAP] receptor), involved in transport to the apical plasma membrane in epithelial cells, a tetanus neurotoxin-resistant pathway. Here we show that TI-VAMP is essential for vesicular transport-mediating neurite outgrowth in staurosporine-differentiated PC12 cells. The NH(2)-terminal domain, which precedes the SNARE motif of TI-VAMP, inhibits the association of TI-VAMP with synaptosome-associated protein of 25 kD (SNAP25). Expression of this domain inhibits neurite outgrowth as potently as Botulinum neurotoxin E, which cleaves SNAP25. In contrast, expression of the NH(2)-terminal deletion mutant of TI-VAMP increases SNARE complex formation and strongly stimulates neurite outgrowth. These results provide the first functional evidence for the role of TI-VAMP in neurite outgrowth and point to its NH(2)-terminal domain as a key regulator in this process.

  17. Cross-scale energy transport in space plasmas

    Science.gov (United States)

    Moore, T. W.; Nykyri, K.; Dimmock, A. P.

    2016-12-01

    The solar wind is a supersonic magnetized plasma streaming far into the heliosphere. Although cooling as it flows, it is rapidly heated upon encountering planetary obstacles. At Earth, this interaction forms the magnetosphere and its sub-regions. The present paper focuses on particle heating across the boundary separating the shocked solar wind and magnetospheric plasma, which is driven by mechanisms operating on fluid, ion and electron scales. The cross-scale energy transport between these scales is a compelling and fundamental problem of plasma physics. Here, we present evidence of the energy transport between fluid and ion scales: free energy is provided in terms of a velocity shear generating fluid-scale Kelvin-Helmholtz instability. We show the unambiguous observation of an ion-scale magnetosonic wave packet, inside a Kelvin-Helmholtz vortex, with sufficient energy to account for observed ion heating. The present finding has universal consequences in understanding cross-scale energy transport, applicable to environments experiencing velocity shears during comparable plasma regimes.

  18. Heat Transport Effects in Rotating Gases and Plasmas

    Science.gov (United States)

    Kolmes, Elijah; Geyko, Vasily; Fisch, Nathaniel

    2016-10-01

    In some contexts, rotating gases and plasmas exhibit heat transport effects that are substantially different from what would be found in the absence of rotation. For instance, a Ranque-Hilsch vortex tube is a device which separates an input stream of (neutral) gas into hot and cold streams by setting up a rotating flow in a specially designed cylindrical chamber. One class of vortex tube models involves radial motion that carries gas up and down the pressure gradients set up by the centrifugal potential inside the tube and which results in adiabatic heating and cooling of the radially moving material. The approach of producing heat transport in a rotating flow using pressure gradients and motion along those gradients may have applications in plasma systems. We discuss possible applications for rotational heat transport effects in plasma systems, including Z-pinch configurations. Princeton Plasma Physics Laboratory; U.S. Defense Reduction Agency Grant No. HDTRA1-11-1-0037; and the NNSA SSAA Program through DOE Research Grant No. DE-NA0002948.

  19. Surface modification of polyacrylonitrile co-polymer membranes using pulsed direct current nitrogen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Dipankar; Neogi, Sudarsan; De, Sirshendu, E-mail: sde@che.iitkgp.ernet.in

    2015-12-31

    Low temperature plasma treatment using pulsed direct current discharge of nitrogen gas was employed to enhance hydrophilicity of the polyacrylonitrile co-polymer membranes. The membranes were characterized in terms of morphology, structure, hydrophilicity, and membrane performance. Properties and functional groups on the surface of polyacrylonitrile co-polymer membranes were investigated by contact angle, scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy. Effects of plasma conditions, namely, pulsed voltage, duty cycle and treatment time on increase in membrane hydrophilicity were studied. Permeability of treated membrane was increased by 47% and it was retained up to 70 days. Surface etching due to plasma treatment was confirmed by weight loss of the treated membranes. Due to surface etching, average pore size increased and rejection of 200 kDa polyethylene glycol decreased to about 70% for the treated membrane. Oxygen and nitrogen functional groups were responsible for surface hydrophilicity. - Highlights: • Surface modification of polyacrylonitrile co-polymer membranes by pulsed direct current nitrogen plasma • Hydrophilic functional groups incorporated on the membrane surface • Significant enhancement of the permeability and wettability of the membranes • Water contact angle increased with storage time and finally stabilized.

  20. Spatial control of plasma membrane domains: ROP GTPase-based symmetry breaking

    Science.gov (United States)

    Yang, Zhenbiao; Lavagi, Irene

    2013-01-01

    Breaking of the cell membrane symmetry to form polarized or localized domains/regions of the plasma membrane (PM) is a fundamental cellular process that occurs in essentially all cellular organisms, and is required for a wide variety of cellular functions/behaviors including cell morphogenesis, cell division and cell differentiation. In plants, the development of localized or polarized PM domains has been linked to a vast array of cellular and developmental processes such as polar cell expansion, asymmetric cell division, cell morphogenesis, the polarization of auxin transporters (and thus auxin polar transport), secondary cell wall patterning, cell type specification, and tissue pattern formation. Rho GTPases from plants (ROPs) are known to be involved in many of these processes. Here, we review the current knowledge on ROP involvement in breaking symmetry and propose that ROP-based self-organizing signaling may provide a common mechanism for the spatial control of PM domains required in various cellular and developmental processes in plants. PMID:23177207