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Sample records for macrophage membrane properties

  1. The interaction of laminin and its membrane receptor on mouse macrophage membrane studied by STM and FRAP

    Institute of Scientific and Technical Information of China (English)

    WEIXINHUA; YONGZHAO; XIAOMINGDONG; YAXIANSU; ZILIMA; CHANGXINZHU; SHIJINPANG

    1993-01-01

    The variation of membrane surface and lateral diffusion of membrane protein was studied after the interaction of laminin with its membrane receptor in mouse macrophages. A pattern of membrane surface which showed smaller and bigger peaks was obtained by scanning tunneling microscope(STM), looking like the domains of lipid groups and proteins in the model of fluid mosaic biomembraoe. Some even more higher and wider peaks projected out from the membrane surface in STM im-age after the interacting of laminin with membrane receptor were probably, tile complexes of laminin and membraue receptor. Furthermore. the deeceasad lateral diffusion coofficeent value(D_) was obtained by Huorescence recovery after photobleaching (FRAP) after the laminin was reacted with membrane receptor. This phenomenon provides an evidence that the complexes of laminin and its membrane receptor were located on the membrane of macrophages. So we could consider that the laminin is combined with membrane receptor leading to the variation in the properties of membrane surface.

  2. Membrane elastic properties and cell function.

    Directory of Open Access Journals (Sweden)

    Bruno Pontes

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

  3. Effect of oxidative stress on plasma membrane fluidity of THP-1 induced macrophages.

    Science.gov (United States)

    de la Haba, Carlos; Palacio, José R; Martínez, Paz; Morros, Antoni

    2013-02-01

    Plasma membrane is one of the preferential targets of reactive oxygen species which cause lipid peroxidation. This process modifies membrane properties such as membrane fluidity, a very important physical feature known to modulate membrane protein localization and function. The aim of this study is to evaluate the effect of oxidative stress on plasma membrane fluidity regionalization of single living THP-1 macrophages. These cells were oxidized with H(2)O(2) at different concentrations, and plasma membrane fluidity was analyzed by two-photon microscopy in combination with the environment-sensitive probe Laurdan. Results show a significant H(2)O(2) concentration dependent increase in the frequency of rigid lipid regions, mainly attributable to lipid rafts, at the expense of the intermediate fluidity regions. A novel statistical analysis evaluated changes in size and number of lipid raft domains under oxidative stress conditions, as lipid rafts are platforms aiding cell signaling and are thought to have relevant roles in macrophage functions. It is shown that H(2)O(2) causes an increase in the number, but not the size, of raft domains. As macrophages are highly resistant to H(2)O(2), these new raft domains might be involved in cell survival pathways.

  4. Electrical properties of polar membranes

    CERN Document Server

    Mosgaard, Lars D; Heimburg, Thomas

    2014-01-01

    Biological membranes are capacitors that can be charged by applying a field across the membrane. The charges on the capacitor exert a force on the membrane that leads to electrostriction, i.e. a thinning of the membrane. Since the force is quadratic in voltage, negative and positive voltage have an identical influence on the physics of symmetric membranes. However, this is not the case for a membrane with an asymmetry leading to a permanent electric polarization. Positive and negative voltages of identical magnitude lead to different properties. Such an asymmetry can originate from a lipid composition that is different on the two monolayers of the membrane, or from membrane curvature. The latter effect is called 'flexoelectricity'. As a consequence of permanent polarization, the membrane capacitor is discharged at a voltage different from zero. This leads to interesting electrical phenomena such as outward or inward rectification of membrane permeability. Here, we introduce a generalized theoretical framework...

  5. Macrophage invasion does not contribute to muscle membrane injury during inflammation

    Science.gov (United States)

    Tidball, J. G.; Berchenko, E.; Frenette, J.

    1999-01-01

    Previous observations have shown that neutrophil invasion precedes macrophage invasion during muscle inflammation and that peak muscle injury is observed at the peak of ED1+ macrophage invasion. We tested the hypothesis that neutrophil invasion causes subsequent invasion by ED1+ macrophages and that ED1+ macrophages then contribute significantly to muscle membrane injury during modified muscle use. Rat hindlimbs were unloaded for 10 days followed by reloading by normal ambulation to induce inflammation. Membrane injury was measured by assaying Evans blue-bound serum protein influx through membrane lesions. Muscle neutrophil populations increased significantly during the first 2 h of reloading but ED1+ macrophages did not increase until 24 h. Neutrophil invasion was uncoupled from subsequent macrophage invasion by reloading rat hindlimbs for 2 h to cause neutrophil invasion, followed by resuspension for hours 2-24. This produced similar increases in neutrophil concentration as measured in muscles continuously reloaded for 24 h without causing an increase in macrophages. However, resuspension did not reduce the extent of muscle damage compared with that occurring in muscles that were reloaded continuously for 24 h. Thus, muscle invasion by neutrophils is not sufficient to cause invasion by ED1+ macrophages. In addition, muscle membrane injury that occurs during reloading is independent of invasion by ED1+ macrophages.

  6. Activation of Macrophages by Lipopolysaccharide for Assessing the Immunomodulatory Property of Biomaterials.

    Science.gov (United States)

    Han, Shengwei; Chen, Zetao; Han, Pingping; Hu, Qingang; Xiao, Yin

    2017-03-24

    The design paradigm of biomaterials has been changed to ones with favorable immunomodulatory effects, indicating the importance of accurately evaluating the immunomodulatory properties of biomaterials. Among all the immune cells macrophages receive most attention, due to their plasticity and multiple roles in the materials and host interactions, and thereby become model immune cells for the evaluation of immunomodulatory properties of biomaterials in many studies. Lipopolysaccharides (LPS), a polysaccharide in the outer membrane of Gram-negative bacteria, elicit strong immune responses, which was often applied to activate macrophages, resulting in a proinflammatory M1 phenotype, and the release of proinflammatory cytokines, including tumor necrosis factor alpha (TNFα), interleukin (IL)-1, and IL-6. However, there is no consensus on how to apply macrophages and LPS to detect the immunomodulatory properties of biomaterials. The lack of scientific consideration of this issue has led to some inaccurate and insufficient conclusions on the immunomodulatory properties of biomaterials, and inconsistences between different research groups. In this study, we carried out a systemic study to investigate the stimulatory effects of LPS with different times, doses, and conditions on the activation of macrophages. An experimental pathway was proposed accordingly for the activation of macrophages using LPS for assessing the immunomodulatory property of biomaterials.

  7. HIV-1 buds predominantly at the plasma membrane of primary human macrophages.

    Directory of Open Access Journals (Sweden)

    Sonja Welsch

    2007-03-01

    Full Text Available HIV-1 assembly and release are believed to occur at the plasma membrane in most host cells with the exception of primary macrophages, for which exclusive budding at late endosomes has been reported. Here, we applied a novel ultrastructural approach to assess HIV-1 budding in primary macrophages in an immunomarker-independent manner. Infected macrophages were fed with BSA-gold and stained with the membrane-impermeant dye ruthenium red to identify endosomes and the plasma membrane, respectively. Virus-filled vacuolar structures with a seemingly intracellular localization displayed intense staining with ruthenium red, but lacked endocytosed BSA-gold, defining them as plasma membrane. Moreover, HIV budding profiles were virtually excluded from gold-filled endosomes while frequently being detected on ruthenium red-positive membranes. The composition of cellular marker proteins incorporated into HIV-1 supported a plasma membrane-derived origin of the viral envelope. Thus, contrary to current opinion, the plasma membrane is the primary site of HIV-1 budding also in infected macrophages.

  8. Influence of membrane properties on fouling in submerged membrane bioreactors

    NARCIS (Netherlands)

    Marel, van der P.; Zwijnenburg, A.; Kemperman, A.; Wessling, M.; Temmink, B.G.; Meer, van der W.

    2010-01-01

    Polymeric flat-sheet membranes with different properties were used in filtration experiments with activated sludge from a pilot-scale MBR to investigate the influence of membrane pore size, surface porosity, pore morphology, and hydrophobicity on membrane fouling. An improved flux-step method was us

  9. Macrophage Chemotaxis in Anti-tubular Basement Membrane-Induced Interstitial Nephritis in Guinea Pigs

    NARCIS (Netherlands)

    Kennedy, Thomas L.; Merrow, Martha; Phillips, S. Michael; Norman, Michael; Neilson, Eric G.

    1985-01-01

    Interstitial renal lesions containing T cells and macrophages develop after 14 days in guinea pigs immunized to produce anti-tubular basement membrane-induced interstitial nephritis. We serially examined the renal venous and systemic arterial sera from such animals to determine if chemotactic factor

  10. Free-cholesterol loading does not trigger phase separation of the fluorescent sterol dehydroergosterol in the plasma membrane of macrophages

    DEFF Research Database (Denmark)

    Wüstner, Daniel

    2008-01-01

    membrane distribution of the fluorescent cholesterol-mimicking sterol dehydroergosterol (DHE) was investigated in FC-loaded J774 macrophages. Wide field fluorescence and deconvolution microscopy were combined with quantitative assessment of sterol distribution in straightened plasma membrane image segments...... with increased membrane cholesterol content, sterols do not form a separate phase in the plasma membrane....

  11. Identification of macrophage external membrane proteins and their possible role in cell adhesion.

    Science.gov (United States)

    Pearlstein, E; Dienstman, S R; Defendi, V

    1978-10-01

    Starch-activated mouse peritoneal macrophages (STpMAC) plated on plastic demonstrate the adhesive properties typical for activated pMAC: attaching as round cells and, within 15 min, spreading out with marginal membrane ruffles. These attached STpMAC were labeled by lactoperoxidase-catalysed 125I surface iodination, sodium dodecyl-sulfate-lysed, and the lysates electrophoresed on polyacrylamide gels which were examined by autoradiography. The STpMAC morphological phenotype correlates with the labeling of a particular protein (195,000, estimated mol wt). Normal pMAC (NpMAC), from unstimulated mice, do not spread and do not display the 195,000 band. Both pMAC band patterns, including the 195,000 band, are relatively resistant to trypsin digestion, as is pMAC adhesion itself trypsin-resistant. Neither class of pMAC exhibits fibronectin (Cell Adhesion Factor, LETS protein) which is a component in the adhesive matrix of cells forming trypsin-sensitive monolayers. When pMAC are tested against antifibronectin antibody, these cells do not give immunofluorescent staining. In summary, two functions in pMAC adhesion, enzyme resistance and the ability to spread, appear related to molecular properties distinctive for pMAC surface protein.

  12. Macrophage Cell Membrane Camouflaged Au Nanoshells for in Vivo Prolonged Circulation Life and Enhanced Cancer Photothermal Therapy.

    Science.gov (United States)

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

    2016-04-20

    Macrophage cell membrane (MPCM)-camouflaged gold nanoshells (AuNS) that can serve as a new generation of photothermal conversion agents for in vivo photothermal cancer therapy are presented. They are constructed by the fusion of biocompatible AuNSs and MPCM vesicles. The resulting MPCM-coated AuNSs exhibited good colloidal stability and kept the original near-infrared (NIR) adsorption of AuNSs. Because AuNS carried high-density coverage of MPCMs, the totally functional portions of macrophage cells membrane were grafted onto the surface of AuNSs. This surface functionalization provided active targeting ability by recognizing tumor endothelium and thus improved tumoritropic accumulation compared to the red blood cell membrane-coating approach. These biomimetic nanoparticles significantly enhance in vivo blood circulation time and local accumulation at the tumor when administered systematically. Upon NIR laser irradiation, local heat generated by the MPCM-coated AuNS achieves high efficiency to suppress tumor growth and selectively ablate cancerous cells within the illuminated zone. Therefore, MPCM-coated AuNSs remained the natural properties of their source cells, which may improve the efficacy of photothermal therapy modulated by AuNSs and other noble-metal nanoparticles.

  13. Sialic acid mediates the initial binding of positively charged inorganic particles to alveolar macrophage membranes.

    Science.gov (United States)

    Gallagher, J E; George, G; Brody, A R

    1987-06-01

    Pulmonary macrophages phagocytize inhaled particles and are postulated to play a role in the development of pulmonary interstitial fibrogenesis. The basic biologic mechanisms through which inhaled particles bind to macrophage membranes and subsequently are phagocytized remain unclear. We hypothesize that positively charged particles bind to negatively charged sialic acid (SA) residues on macrophage membranes. Alveolar Macrophages (AM) were collected by saline lavage from normal rat lungs. The cells adhered to plastic coverslips in serum-free phosphate buffered saline at 37 degrees C for 45 min and then were maintained at 4 degrees C for the binding experiments. Even distribution of SA groups on AM surfaces was demonstrated by scanning electron microscopy of wheat germ agglutinin (WGA) conjugated to 50 nm gold spheres. The WGA is a lectin that binds specifically to sialic acid, and pretreatment of AM with this lectin prevented the binding of positively charged carbonyl iron (C-Fe) spheres, aluminum (Al) spheres, and chrysotile asbestos fibers to AM surfaces. Limulus protein, another lectin with binding specificity for SA, similarly blocked the binding of positively charged spheres and chrysotile asbestos fibers but not negatively charged glass spheres or crocidolite asbestos fibers. Con A and ricin, lectins that bind to mannose and galactose residues, respectively, did not block particle binding. When both positively charged iron spheres and negatively charged glass spheres were prebound to AM membranes, subsequent treatment with WGA displaced only the positively charged spheres from macrophage surfaces. Con A and ricin had no effect on prebound positively charged C-Fe and Al spheres.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. Ratiometric fluorescent probe with AIE property for monitoring endogenous hydrogen peroxide in macrophages and cancer cells.

    Science.gov (United States)

    Liu, Yong; Nie, Jing; Niu, Jie; Meng, Fangfang; Lin, Weiying

    2017-08-04

    Hydrogen peroxide (H2O2) plays a key role in the progression of human illnesses, such as autoimmune and auto-inflammatory diseases, infectious diseases, diabetes, and cancer, etc. In this work, we have discribed a novel probe, TPE-TLE, which remarkably displayed AIE property and ratiometric fluorescence emission profiles in the presence of H2O2. This ratiometric fluorescent probe with AIE property exhibits outstanding features such as the well-resolved emission peaks, high sensitivity, high selectivity, low cytotoxicity, and good cell-membrane permeability. These excellent attributes enable us to demonstrate the ratiometric imaging of endogenously produced H2O2 in macrophages and cancer cells based on the novel ratiometric probe with AIE property for the first time. By comparing two kinds of cells, it is firstly found that cancer cells should contain much more endogenous H2O2 than macrophages. We expect that TPE-TLE will be useful fluorescent platform for the development of a variety of ratiometric fluorescent probes with AIE property to achieve unique biological applications.

  15. Outer Membrane Vesicles Prime and Activate Macrophage Inflammasomes and Cytokine Secretion In Vitro and In Vivo

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    Jessica D. Cecil

    2017-08-01

    Full Text Available Outer membrane vesicles (OMVs are proteoliposomes blebbed from the surface of Gram-negative bacteria. Chronic periodontitis is associated with an increase in subgingival plaque of Gram-negative bacteria, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. In this study, we investigated the immune-modulatory effects of P. gingivalis, T. denticola, and T. forsythia OMVs on monocytes and differentiated macrophages. All of the bacterial OMVs were phagocytosed by monocytes, M(naïve and M(IFNγ macrophages in a dose-dependent manner. They also induced NF-κB activation and increased TNFα, IL-8, and IL-1β cytokine secretion. P. gingivalis OMVs were also found to induce anti-inflammatory IL-10 secretion. Although unprimed monocytes and macrophages were resistant to OMV-induced cell death, lipopolysaccharide or OMV priming resulted in a significantly reduced cell viability. P. gingivalis, T. denticola, and T. forsythia OMVs all activated inflammasome complexes, as monitored by IL-1β secretion and ASC speck formation. ASC was critical for OMV-induced inflammasome formation, while AIM2−/− and Caspase-1−/− cells had significantly reduced inflammasome formation and NLRP3−/− cells exhibited a slight reduction. OMVs were also found to provide both priming and activation of the inflammasome complex. High-resolution microscopy and flow cytometry showed that P. gingivalis OMVs primed and activated macrophage inflammasomes in vivo with 80% of macrophages exhibiting inflammasome complex formation. In conclusion, periodontal pathogen OMVs were found to have significant immunomodulatory effects upon monocytes and macrophages and should therefore influence pro-inflammatory host responses associated with disease.

  16. Outer Membrane Vesicles Prime and Activate Macrophage Inflammasomes and Cytokine Secretion In Vitro and In Vivo

    Science.gov (United States)

    Cecil, Jessica D.; O’Brien-Simpson, Neil M.; Lenzo, Jason C.; Holden, James A.; Singleton, William; Perez-Gonzalez, Alexis; Mansell, Ashley; Reynolds, Eric C.

    2017-01-01

    Outer membrane vesicles (OMVs) are proteoliposomes blebbed from the surface of Gram-negative bacteria. Chronic periodontitis is associated with an increase in subgingival plaque of Gram-negative bacteria, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. In this study, we investigated the immune-modulatory effects of P. gingivalis, T. denticola, and T. forsythia OMVs on monocytes and differentiated macrophages. All of the bacterial OMVs were phagocytosed by monocytes, M(naïve) and M(IFNγ) macrophages in a dose-dependent manner. They also induced NF-κB activation and increased TNFα, IL-8, and IL-1β cytokine secretion. P. gingivalis OMVs were also found to induce anti-inflammatory IL-10 secretion. Although unprimed monocytes and macrophages were resistant to OMV-induced cell death, lipopolysaccharide or OMV priming resulted in a significantly reduced cell viability. P. gingivalis, T. denticola, and T. forsythia OMVs all activated inflammasome complexes, as monitored by IL-1β secretion and ASC speck formation. ASC was critical for OMV-induced inflammasome formation, while AIM2−/− and Caspase-1−/− cells had significantly reduced inflammasome formation and NLRP3−/− cells exhibited a slight reduction. OMVs were also found to provide both priming and activation of the inflammasome complex. High-resolution microscopy and flow cytometry showed that P. gingivalis OMVs primed and activated macrophage inflammasomes in vivo with 80% of macrophages exhibiting inflammasome complex formation. In conclusion, periodontal pathogen OMVs were found to have significant immunomodulatory effects upon monocytes and macrophages and should therefore influence pro-inflammatory host responses associated with disease. PMID:28890719

  17. Legionella pneumophila-Derived Outer Membrane Vesicles Promote Bacterial Replication in Macrophages.

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    Anna Lena Jung

    2016-04-01

    Full Text Available The formation and release of outer membrane vesicles (OMVs is a phenomenon of Gram-negative bacteria. This includes Legionella pneumophila (L. pneumophila, a causative agent of severe pneumonia. Upon its transmission into the lung, L. pneumophila primarily infects and replicates within macrophages. Here, we analyzed the influence of L. pneumophila OMVs on macrophages. To this end, differentiated THP-1 cells were incubated with increasing doses of Legionella OMVs, leading to a TLR2-dependent classical activation of macrophages with the release of pro-inflammatory cytokines. Inhibition of TLR2 and NF-κB signaling reduced the induction of pro-inflammatory cytokines. Furthermore, treatment of THP-1 cells with OMVs prior to infection reduced replication of L. pneumophila in THP-1 cells. Blocking of TLR2 activation or heat denaturation of OMVs restored bacterial replication in the first 24 h of infection. With prolonged infection-time, OMV pre-treated macrophages became more permissive for bacterial replication than untreated cells and showed increased numbers of Legionella-containing vacuoles and reduced pro-inflammatory cytokine induction. Additionally, miRNA-146a was found to be transcriptionally induced by OMVs and to facilitate bacterial replication. Accordingly, IRAK-1, one of miRNA-146a's targets, showed prolonged activation-dependent degradation, which rendered THP-1 cells more permissive for Legionella replication. In conclusion, L. pneumophila OMVs are initially potent pro-inflammatory stimulators of macrophages, acting via TLR2, IRAK-1, and NF-κB, while at later time points, OMVs facilitate L. pneumophila replication by miR-146a-dependent IRAK-1 suppression. OMVs might thereby promote spreading of L. pneumophila in the host.

  18. Properties of Polyethylene Naphthalate Track Membranes

    CERN Document Server

    Akimenko, S N; Orelovich, O L; Maekawa, J; Ioshida, M; Apel, P Yu

    2002-01-01

    Basic characteristics of track membranes made of polyethylene naphthalate (which is a polyester synthesized from dimethyl naphthalate and ethylene glycol) are studied and presented. Polyethylene naphthalate possesses some properties (mechanical strength, thermal and chemical stability), which make this polymer a promising material for the production of track membranes. Water flow rate and air flow rate characteristics, burst strength, wettability, and amount of extractables are determined. Surface structure and pore structure are examined using scanning electron microscopy. It is found that the pores in the membranes are cylindrical in shape. The measured water and air flow rates follow known theoretical relations for the transport in narrow capillaries. The burst strength of polyethylene naphthalate membranes is found to be similar to that of polyethylene terephthalate track membranes. Polyethylene naphthalate track membranes can be categorized as moderately hydrophilic. Being treated with boiling water, pol...

  19. Leishmania donovani infection enhances lateral mobility of macrophage membrane protein which is reversed by liposomal cholesterol.

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    Moumita Ghosh

    2014-12-01

    Full Text Available The protozoan parasite Leishmania donovani (LD reduces cellular cholesterol of the host possibly for its own benefit. Cholesterol is mostly present in the specialized compartment of the plasma membrane. The relation between mobility of membrane proteins and cholesterol depletion from membrane continues to be an important issue. The notion that leishmania infection alters the mobility of membrane proteins stems from our previous study where we showed that the distance between subunits of IFNγ receptor (R1 and R2 on the cell surface of LD infected cell is increased, but is restored to normal by liposomal cholesterol treatment.We determined the lateral mobility of a membrane protein in normal, LD infected and liposome treated LD infected cells using GFP-tagged PLCδ1 as a probe. The mobility of PLCδ1 was computationally analyzed from the time lapse experiment using boundary distance plot and radial profile movement. Our results showed that the lateral mobility of the membrane protein, which is increased in infection, is restored to normal upon liposomal cholesterol treatment. The results of FRAP experiment lent further credence to the above notion. The membrane proteins are intimately linked with cellular actin and alteration of cellular actin may influence lateral mobility. We found that F-actin is decreased in infection but is restored to normal upon liposomal cholesterol treatment as evident from phalloidin staining and also from biochemical analysis by immunoblotting.To our knowledge this is the first direct demonstration that LD parasites during their intracellular life cycle increases lateral mobility of membrane proteins and decreases F-actin level in infected macrophages. Such defects may contribute to ineffective intracellular signaling and other cellular functions.

  20. Leishmania donovani activates SREBP2 to modulate macrophage membrane cholesterol and mitochondrial oxidants for establishment of infection.

    Science.gov (United States)

    Mukherjee, Madhuchhanda; Basu Ball, Writoban; Das, Pijush K

    2014-10-01

    Establishment of infection by an intracellular pathogen depends on successful internalization with a concomitant neutralization of host defense machinery. Leishmania donovani, an intramacrophage pathogen, targets host SREBP2, a critical transcription factor, to regulate macrophage plasma membrane cholesterol and mitochondrial reactive oxygen species generation, favoring parasite invasion and persistence. Leishmania infection triggered membrane-raft reorientation-dependent Lyn-PI3K/Akt pathway activation which in turn deactivated GSK3β to stabilize nuclear SREBP2. Moreover, cells perceiving less available intracellular cholesterol due to its sequestration at the plasma membrane resulted in the deregulation of the ER-residing SCAP-SREBP2-Insig circuit thereby assisting increased nuclear translocation of SREBP2. Both increased nuclear transport and stabilization of SREBP2 caused HMGCR-catalyzed cholesterol biosynthesis-mediated plasma membrane cholesterol enrichment leading to decreased membrane-fluidity and plausibly assisting delay in phagosomal acidification. Parasite survival ensuing entry was further ensured by SREBP2-dependent transcriptional up-regulation of UCP2, which suppressed mitochondrial ROS generation, one of the primary microbicidal molecules in macrophages recognized for its efficacy against Leishmania. Functional knock-down of SREBP2 both in vitro and in vivo was associated with reduction in macrophage plasma membrane cholesterol, increased ROS production and lower parasite survival. To our knowledge, this study, for the first time, reveals that Leishmania exploits macrophage cholesterol-dependent SREBP2 circuit to facilitate its entry and survival within the host.

  1. New membrane structures with proton conducting properties

    DEFF Research Database (Denmark)

    Nørgaard, Casper Frydendal

    Perfluorosulfonic acid membranes (e.g. Nafion®) are the most widely applied electrolytes in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) because of their good chemical stability, mechanical properties and high proton conductivity, when well hydrated. The upper limit of operating temperature...... [1, 2, 3]. Improved fuel cell performance from incorporation of hygroscopic oxides or solid proton conductors (e.g. zirconium phosphates) has been reported. The poster exhibits upcoming work in the field of composite electrolyte membranes at the University of Southern Denmark, combining radiation...

  2. Viscoelastic properties of actin-coated membranes

    Science.gov (United States)

    Helfer, E.; Harlepp, S.; Bourdieu, L.; Robert, J.; Mackintosh, F. C.; Chatenay, D.

    2001-02-01

    In living cells, cytoskeletal filaments interact with the plasma membrane to form structures that play a key role in cell shape and mechanical properties. To study the interaction between these basic components, we designed an in vitro self-assembled network of actin filaments attached to the outer surface of giant unilamellar vesicles. Optical tweezers and single-particle tracking experiments are used to study the rich dynamics of these actin-coated membranes (ACM). We show that microrheology studies can be carried out on such an individual microscopic object. The principle of the experiment consists in measuring the thermally excited position fluctuations of a probe bead attached biochemically to the membrane. We propose a model that relates the power spectrum of these thermal fluctuations to the viscoelastic properties of the membrane. The presence of the actin network modifies strongly the membrane dynamics with respect to a fluid, lipid bilayer one. It induces first a finite (ω=0) two-dimensional (2D) shear modulus G02D~0.5 to 5 μN/m in the membrane plane. Moreover, the frequency dependence at high frequency of the shear modulus [G'2D(f )~f0.85+/-0.07] and of the bending modulus (κACM(f)~f0.55+/-0.21) demonstrate the viscoelastic behavior of the composite membrane. These results are consistent with a common exponent of 0.75 for both moduli as expected from our model and from prior measurements on actin solutions.

  3. The interaction of lipopolysaccharide-coated polystyrene particle with membrane receptor proteins on macrophage measured by optical tweezers

    Science.gov (United States)

    Wei, Ming-Tzo; Hua, Kuo-Feng; Hsu, Jowey; Karmenyan, Artashes; Hsu, Hsien-Yeh; Chiou, Arthur

    2006-08-01

    Lipopolysaccharide (LPS) is one of the cell wall components of Gram-positive bacteria recognized by and interacted with receptor proteins such as CD14 on macrophage cells. Such a process plays an important role in our innate immune system. In this paper, we report the application of optical tweezers (λ = 1064nm Gaussian beam focused by a water-immersed objective lens with N.A. = 1.0) to the study of the dynamics of the binding of a LPS-coated polystyrene particle (diameter = 1.5μm) onto the plasma membrane of a macrophage cell. We demonstrated that the binding rate increased significantly when the macrophage cell was pre-treated with the extract of Reishi polysaccharides (EORP) which has been shown to enhance the cell surface expression of CD14 (receptor of LPS) on macrophage cells.

  4. Plutonium behavior after pulmonary administration according to solubility properties, and consequences on alveolar macrophage activation.

    Science.gov (United States)

    Van der Meeren, Anne; Gremy, Olivier; Renault, Daniel; Miroux, Amandine; Bruel, Sylvie; Griffiths, Nina; Tourdes, Françoise

    2012-01-01

    The physico-chemical form in which plutonium enters the body influences the lung distribution and the transfer rate from lungs to blood. In the present study, we evaluated the early lung damage and macrophage activation after pulmonary contamination of plutonium of various preparation modes which produce different solubility and distribution patterns. Whatever the solubility properties of the contaminant, macrophages represent a major retention compartment in lungs, with 42 to 67% of the activity from broncho-alveolar lavages being associated with macrophages 14 days post-contamination. Lung changes were observed 2 and 6 weeks post-contamination, showing inflammatory lesions and accumulation of activated macrophages (CD68 positive) in plutonium-contaminated rats, although no increased proliferation of pneumocytes II (TTF-1 positive cells) was found. In addition, acid phosphatase activity in macrophages from contaminated rats was enhanced 2 weeks post-contamination as compared to sham groups, as well as inflammatory mediator levels (TNF-α, MCP-1, MIP-2 and CINC-1) in macrophage culture supernatants. Correlating with the decrease in activity remaining in macrophages after plutonium contamination, inflammatory mediator production returned to basal levels 6 weeks post-exposure. The production of chemokines by macrophages was evaluated after contamination with Pu of increasing solubility. No correlation was found between the solubility properties of Pu and the activation level of macrophages. In summary, our data indicate that, despite the higher solubility of plutonium citrate or nitrate as compared to preformed colloids or oxides, macrophages remain the main lung target after plutonium contamination and may participate in the early pulmonary damage.

  5. The Impact of Membrane Lipid Composition on Macrophage Activation in the Immune Defense against Rhodococcus equi and Pseudomonas aeruginosa

    Directory of Open Access Journals (Sweden)

    Julia Schumann

    2011-11-01

    Full Text Available Nutritional fatty acids are known to have an impact on membrane lipid composition of body cells, including cells of the immune system, thus providing a link between dietary fatty acid uptake, inflammation and immunity. In this study we reveal the significance of macrophage membrane lipid composition on gene expression and cytokine synthesis thereby highlighting signal transduction processes, macrophage activation as well as macrophage defense mechanisms. Using RAW264.7 macrophages as a model system, we identified polyunsaturated fatty acids (PUFA of both the n-3 and the n-6 family to down-regulate the synthesis of: (i the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α; (ii the co-stimulatory molecule CD86; as well as (iii the antimicrobial polypeptide lysozyme. The action of the fatty acids partially depended on the activation status of the macrophages. It is particularly important to note that the anti-inflammatory action of the PUFA could also be seen in case of infection of RAW264.7 with viable microorganisms of the genera R. equi and P. aeruginosa. In summary, our data provide strong evidence that PUFA from both the n-3 and the n-6 family down-regulate inflammation processes in context of chronic infections caused by persistent pathogens.

  6. Discovery of Salmonella virulence factors translocated via outer membrane vesicles to murine macrophages.

    Science.gov (United States)

    Yoon, Hyunjin; Ansong, Charles; Adkins, Joshua N; Heffron, Fred

    2011-06-01

    Salmonella enterica serovar Typhimurium, an intracellular pathogen and leading cause of food-borne illness, encodes a plethora of virulence effectors. Salmonella virulence factors are translocated into host cells and manipulate host cellular activities, providing a more hospitable environment for bacterial proliferation. In this study, we report a new set of virulence factors that is translocated into the host cytoplasm via bacterial outer membrane vesicles (OMV). PagK (or PagK1), PagJ, and STM2585A (or PagK2) are small proteins composed of ∼70 amino acids and have high sequence homology to each other (>85% identity). Salmonella lacking all three homologues was attenuated for virulence in a mouse infection model, suggesting at least partial functional redundancy among the homologues. While each homologue was translocated into the macrophage cytoplasm, their translocation was independent of all three Salmonella gene-encoded type III secretion systems (T3SSs)-Salmonella pathogenicity island 1 (SPI-1) T3SS, SPI-2 T3SS, and the flagellar system. Selected methods, including direct microscopy, demonstrated that the PagK-homologous proteins were secreted through OMV, which were enriched with lipopolysaccharide (LPS) and outer membrane proteins. Vesicles produced by intracellular bacteria also contained lysosome-associated membrane protein 1 (LAMP1), suggesting the possibility of OMV convergence with host cellular components during intracellular trafficking. This study identified novel Salmonella virulence factors secreted via OMV and demonstrated that OMV can function as a vehicle to transfer virulence determinants to the cytoplasm of the infected host cell.

  7. Discovery of Salmonella Virulence Factors Translocated via Outer Membrane Vesicles to Murine Macrophages.

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Hyunjin; Ansong, Charles; Adkins, Joshua N.; Heffron, Fred

    2011-06-01

    We have previously shown that the regulators SpvR, FruR, IHF, PhoP/PhoQ, SsrA/SsrB, SlyA, Hnr, RpoE, SmpB, CsrA, RpoS, Crp, OmpR/EnvZ, and Hfq are essential for Salmonella Typhimurium virulence in mice. Here we use quantitative LC-MS-based proteomics profiling of in-frame deletion mutants of these 14 regulators to identify proteins that are coordinately regulated by these virulence regulators and are thus presumably novel factors contributing to Salmonella pathogenesis. Putative candidate proteins from proteomics analysis were determined, which exhibited similar abundance profiles to those of Salmonella pathogenicity island (SPI)-2 type III secretion system (TTSS) proteins. A subset of 5 proteins including STM0082, STM1548, PdgL, STM1633, and STM3595 was selected for further analysis. All 5 proteins were expressed inside macrophage cells and STM0082 (SrfN) was secreted into host cytoplasm. Furthermore, deletion of STM0082 attenuated virulence in mice when administered intraperitoneally as determined by competitive index. srfN transcription was positively regulated by SsrAB, however, secretion was independent of SPI-2 TTSS as well as SPI-1 TTSS and flagella. Proteins including PagK and STM2585A, which are positively regulated by PhoP/PhoQ, have sec signal peptides as predicted for SrfN and were secreted into macrophage cytoplasm regardless of SPI-2 TTSS. Isolation of outer membrane vesicles (OMVs) revealed the presence of SrfN, PagK, and STM2585A inside vesicle compartments. This result is the first case showing delivery of virulence effectors via OMVs in S. Typhimurium. Moreover, Hfq regulation of SrfN translation suggests that small non-coding RNAs may be responsible for regulating effector protein expression.

  8. Filopodia and membrane blebs drive efficient matrix invasion of macrophages transformed by the intracellular parasite Theileria annulata.

    Directory of Open Access Journals (Sweden)

    Min Ma

    Full Text Available Recent technical advances have broadened our understanding of processes that govern mammalian cell migration in health and disease but many of the molecular and morphological alterations that precede and accompany movement of cells - in particular in three-dimensional (3D environments - are still incompletely understood. In this manuscript, using high-resolution and time-lapse microscopy imaging approaches, we describe morphodynamic processes during rounded/amoeboid cell invasion and molecules associated with the cellular invasion structures. We used macrophages infected with the intracellular protozoan parasite Theileria annulata, which causes Tropical Theileriosis in susceptible ruminants such as domestic cattle. T. annulata transforms its host cell that, as a result, acquires many characteristics of human cancer cells including a markedly increased potential to migrate, disseminate and expand in the body of the host animal. Hence, virulence of the disease is associated with the capability of infected cells to disseminate inside the host. Using T. annulata-transformed macrophages as a model system, we described a novel mode of rounded/amoeboid macrophage migration. We show that filopodia-like membrane extensions at the leading edge lead the way and further evolve in blebbing membrane protrusions to promote progressive expansion of the matrix. Associated with focal invasion structures we detected ezrin, radixin, moesin-family proteins and their regulatory kinase MAP4K4. Furthermore, we linked Rho-kinase activity to contractile force generation, which is essential for infected cell motility. Thus, the motility mode of these parasite-transformed macrophages contrasts with those described so far in human macrophages such as the tunneling or mesenchymal modes, which require engulfment, compaction and ingestion of matrix or proteolytic matrix degradation, respectively. Together, our data reveal protrusion dynamics at the leading edge of invading

  9. VARIATION IN MEMBRANE PROPERTIES FROM THE ACTION OF LAMININ ON MEMBRANE RECEPTORS

    Institute of Scientific and Technical Information of China (English)

    苏雅娴; 薛燕玲; 肖军军

    1995-01-01

    Biophysical studies were conducted on the action of laminin through membrane receptors of cancer cells. The results showed that variations occurred in the thermodynamic properties of membrane proteins, the mobility of hydrocarbon chains of membrane lipids, and the permeshility and transportation pathways of the membrane.

  10. Increased inflammatory properties of adipose tissue macrophages recruited during diet-induced obesity.

    Science.gov (United States)

    Lumeng, Carey N; Deyoung, Stephanie M; Bodzin, Jennifer L; Saltiel, Alan R

    2007-01-01

    Although recent studies show that adipose tissue macrophages (ATMs) participate in the inflammatory changes in obesity and contribute to insulin resistance, the properties of these cells are not well understood. We hypothesized that ATMs recruited to adipose tissue during a high-fat diet have unique inflammatory properties compared with resident tissue ATMs. Using a dye (PKH26) to pulse label ATMs in vivo, we purified macrophages recruited to white adipose tissue during a high-fat diet. Comparison of gene expression in recruited and resident ATMs using real-time RT-PCR and cDNA microarrays showed that recruited ATMs overexpress genes important in macrophage migration and phagocytosis, including interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS), and C-C chemokine receptor 2 (CCR2). Many of these genes were not induced in ATMs from high-fat diet-fed CCR2 knockout mice, supporting the importance of CCR2 in regulating recruitment of inflammatory ATMs during obesity. Additionally, expression of Apoe was decreased, whereas genes important in lipid metabolism, such as Pparg, Adfp, Srepf1, and Apob48r, were increased in the recruited macrophages. In agreement with this, ATMs from obese mice had increased lipid content compared with those from lean mice. These studies demonstrate that recruited ATMs in obese animals represent a subclass of macrophages with unique properties.

  11. Bioelectric modulation of macrophage polarization

    Science.gov (United States)

    Li, Chunmei; Levin, Michael; Kaplan, David L.

    2016-02-01

    Macrophages play a critical role in regulating wound healing and tissue regeneration by changing their polarization state in response to local microenvironmental stimuli. The native roles of polarized macrophages encompass biomaterials and tissue remodeling needs, yet harnessing or directing the polarization response has been largely absent as a potential strategy to exploit in regenerative medicine to date. Recent data have revealed that specific alteration of cells’ resting potential (Vmem) is a powerful tool to direct proliferation and differentiation in a number of complex tissues, such as limb regeneration, craniofacial patterning and tumorigenesis. In this study, we explored the bioelectric modulation of macrophage polarization by targeting ATP sensitive potassium channels (KATP). Glibenclamide (KATP blocker) and pinacidil (KATP opener) treatment not only affect macrophage polarization, but also influence the phenotype of prepolarized macrophages. Furthermore, modulation of cell membrane electrical properties can fine-tune macrophage plasticity. Glibenclamide decreased the secretion and gene expression of selected M1 markers, while pinacidil augmented M1 markers. More interestingly, glibencalmide promoted macrophage alternative activation by enhancing certain M2 markers during M2 polarization. These findings suggest that control of bioelectric properties of macrophages could offer a promising approach to regulate macrophage phenotype as a useful tool in regenerative medicine.

  12. Gas Permeation Properties of Organic-inorganic Ultrathin Membranes

    Institute of Scientific and Technical Information of China (English)

    H. Kawakami

    2005-01-01

    @@ 1Introduction Recently, a great interest has been noted in the synthesis of inorganic membranes for gas separation. One of the candidates is a carbon molecular sieve (CMS) membrane, which is synthesized by the pyrolysis of a polymer. However, CMS membranes are very brittle and fragile. Additionally, it requires more careful handling and it is very difficult to prepare a thin CMS membrane because of its poor mechanical property. Therefore, the gas permeances of CMS membranes were not very high.

  13. [Membrane fouling by secondary effluent of urban sewage and the membrane properties].

    Science.gov (United States)

    Meng, Xiao-rong; Zhang, Hai-zhen; Wang, Lei; Wang, Xu-dong; Zhao, Liang

    2013-05-01

    The fouling behavior of UF membranes by secondary effluent of municipal wastewater was investigated using both original PVDF membranes and PVA, PVP and PMMA modified PVDF membranes. The results showed that the structure parameters of UF membranes were optimized by blending; PVP and PVA could effectively improve the hydrophilicity and permeate flux of the membranes. The hydrophilicity and structure properties of UF membrane had stronger effect on the anti-fouling properties. Pore plugging resistance was the main reason for the unrecoverable fouling. For UF membranes with stronger hydrophilicity, there was some flux reduction in the initial filtration, which was attributed to the formation of concentration polarization layer. However, this layer can be easily removed and the irreversible fouling index (r(ir)) was 0, thus guaranteeing the membrane a better anti-fouling property. The dense membrane surface could prevent low-molecular-weight pollutants from entering the internal pores of the membrane. For UF membrane with fully developed macropores in the cross-section and loose spongy layer structure, pollutants deposition to membrane internal pores, which would cause membrane pore plugging, could be effectively inhibited. In contrast, for membranes with porous surface and not fully developed macropores in the cross-section, pore plugging was more prone to occur. As a result, flux declined seriously and was difficult to be recovered by physical cleaning, which gave rise to the irreversible fouling.

  14. Egr-1 Mediates SiO2-driven Transcription of Membrane Type Ⅰ Matrix Metalloproteinase in Macrophages

    Institute of Scientific and Technical Information of China (English)

    XIANG Fei; BAI Ming; JIN Yang; MA Wanli; XIN Jianbao

    2007-01-01

    The up-regulation mechanism of membrane type Ⅰ matrix metalloproteinase (MT1-MMP) in macrophages stimulated by silica in vitro and the contribution of early growth response 1 (Egr-1) transcription factor in the gene expression pathway were investigated. Macrophages stimulated by silica were treated with Egr-1 antibody or Egr-1 decoy oligodeoxynucleotides (ODN). The levels of MT1-MMP proteins were determined by Western blot and the expression of MT1-MMP mRNAs was detected by RT-PCR. The results showed as compared with control macrophages, silica-stimulated group showed up-regulated gene expression of MT1-MMP via Egr-1 (P<0.01). Compared with silica-stimulated macrophages untreated with antibody, the cells treated with 5 μg/mL Egr-1 antibody were associated with reduced expression of MTI-MMP protein (P<0.01) and mRNA (P<0.01). Compared with silica-stimulated untransfected group, the Egr-1 "decoy" ODN group was associated with reduction in the expression of MT1-MMP protein and mRNA (P<0.01). It was concluded gene expression of MT1-MMP which may play a critical role in silicosis was up-regulated by silica in macrophages. Egr-1 participated in the expression of MT1-MMP and positively regulated the expression. Both Egr-1 antibody and Egr-1 decoy ODN suppressed the expression of MT1-MMP through the Egr-1 pathway and may become a potential therapeutic tool in the management of silicosis in the future.

  15. Monocyte-macrophage membrane possesses free radicals scavenging activity: stimulation by polyphenols or by paraoxonase 1 (PON1).

    Science.gov (United States)

    Rosenblat, M; Elias, A; Volkova, N; Aviram, M

    2013-04-01

    In the current study, we analysed free radicals scavenging activity of monocytes-macrophages in the absence or presence of antioxidants such as polyphenols or paraoxonase 1 (PON1). THP-1 human monocytic cell line, murine J774A.1 macrophages, as well as human primary monocytes have the capability to scavenge free radicals, as measured by the 1-diphenyl-2-picryl-hydrazyl (DPPH) assay. This effect (which could be attributed to the cell's membrane) was cell number and incubation time dependent. Upon incubation of J774A.1 macrophages with acetylated LDL (Ac-LDL), with VLDL, or with the radical generator, AAPH, the cells' lipid peroxides content, and paraoxonase 2 (PON2) activity were significantly increased. While non-treated cells decreased DPPH absorbance by 65%, the Ac-LDL-, VLDL- or AAPH-treated cells, decreased it by only 33%, 30%, or 45%, respectively. We next analysed the effect of J774A.1 macrophage enrichment with antioxidants, such as polyphenols or PON1 on the cells' free radicals scavenging activity. Non-treated cells decreased DPPH absorbance by 50%, whereas vitamin E-, punicalagin- or PJ-treated cells significantly further decreased it, by 75%. Similarly, in PON1-treated cells DPPH absorbance was further decreased by 63%, in association with 23% increment in PON1 catalytic activity. In cells under oxidative stress [treated with AAPH-, or with oxidized LDL], PON1 activity was decreased by 31% or 40%, as compared to the activity observed in PON1 incubated with non-treated cells. We conclude that monocytes-macrophages possess free radicals scavenging activity, which is decreased under atherogenic conditions, and increased upon cell enrichment with potent antioxidants such as nutritional polyphenols, or PON1.

  16. Mechanical properties of nanoporous graphene membrane

    Science.gov (United States)

    Liu, Yilun; Chen, Xi

    2014-01-01

    Nanoporous graphene holds great promise in the application of filtration such as seawater desalination, gas separation, and ionic channels. In this paper, we study the mechanical properties of nanoporous graphene with different size, shape, and density of nanopore. The strength decreases as the size and porosity of the nanopore increases. However, the rough edges of the nanopore has significant influence to the strength where the blunt tip perpendicular to the loading direction has higher strength. The effective tensile modulus is only determined by porosity of the nanopore as ΔE ˜ -p0.64, while the strength is determined by the size, shape, and porosity of the nanopore, for the same type of nanopore the strength scales with the porosity as Δσs ˜ -p. In contrast, the effective fracture strain increases as porosity increases for small and moderate porosities. The work is a first study of the relation between mechanical properties and porosity of nanoporous graphene and is helpful to the design of high performance nanoporous graphene membrane.

  17. Polyvinylidenefluoride/carbon nanotubes mixed matrix membranes with tailored properties

    Science.gov (United States)

    Fontananova, Enrica; Grosso, Valentina; Aljlil, Saad A.; Bahattab, Mohammed A.; Vuono, Danilo; Di Profio, Gianluca; Drioli, Enrico

    2016-05-01

    Membrane operations are promising tools for efficient and environmentally friendly separations. However, the development of advanced membranes with tailored properties is a key issue to be addressed in order to better exploit the potentialities of membrane-based separations. An important approach toward this aim is the development of mixed matrix membranes in which an organic and an inorganic phase coexist in order to have synergic effects on membrane properties. The peculiar properties of carbon nanotubes (CNTs) such as high electrical and thermal conductivity, high strength and unique transport properties, has motivated a considerable effort to produce CNT-polymer composites in order to engineer membrane properties. In this work the roughness, wettability, morphology, crystalline phase and pore size of polyvinylidenefluoride (PVDF) membranes were tailored working on the membrane preparation conditions, as well as, by blending the polymer with multiwalled carbon nanotubes (MWCNTs). A study on the effect of concentration of the polymer, use of pore forming additives, type and concentration of MWCNTs (pristine and functionalized), was carried out. The results highlighted interesting relationships between membrane microstructure and composition, as well as, MWCNTs distribution, on transport and wettability properties, in the perspectives of a more efficient application of PVDF membranes in liquid phase separations.

  18. Separation performance and interfacial properties of nanocomposite reverse osmosis membranes

    KAUST Repository

    Pendergast, MaryTheresa M.

    2013-01-01

    Four different types of nanocomposite reverse osmosis (RO) membranes were formed by interfacial polymerization of either polyamide (PA) or zeolite A-polyamide nanocomposite (ZA-PA) thin films over either pure polysulfone (PSf) or zeolite A-polysulfone nanocomposite (ZA-PSf) support membranes cast by wet phase inversion. All three nanocomposite membranes exhibited superior separation performance and interfacial properties relative to hand-cast TFC analogs including: (1) smoother, more hydrophilic surfaces (2) higher water permeability and salt rejection, and (3) improved resistance to physical compaction. Less compaction occurred for membranes with nanoparticles embedded in interfacially polymerized coating films, which adds further proof that flux decline associated with physical compaction is influenced by coating film properties in addition to support membrane properties. The new classes of nanocomposite membrane materials continue to offer promise of further improved RO membranes for use in desalination and advanced water purification. © 2011 Elsevier B.V.

  19. Fabrication and Properties of Multilayer Chitosan Membrane Loaded with Tinidazole

    Institute of Scientific and Technical Information of China (English)

    HONG Hua; CHI Ping; LIU Changsheng

    2007-01-01

    With the aim of providing effective periodontal disease therapeutic method, multilayer membranes which were loaded with drug for guided tissue regeneration were prepared using an immerseprecipitation phase inversion technique. Single layer, bi-layer and tri-layer membranes were fabricated with chitosan used as carrier and tinidazole as medicine model which was loaded on the membrane. The influence of layer on structure and properties of membrane were studied by SEM, UV spectrophotometer and mechanical test. Drug release properties of three types of layer membranes were also investigated. The results showed that release rate could be slown down in both bi-layer and tri-layer membranes (to 11 days and 14 days respectively)and tri-layer membrane lasted the longest. After a process of rapid release, the concentration of tinidazole which was released by the membrane was maintained at an efficient dosage level. Compared with single layer and bilayer membranes, we found tri-layer membrane could play a role in controlling low-rate drug release especially at the early stage of release, and keep an efficient dosage at affected part for a long period of time. The loss of drug which loaded on membrane decreased from 84.6% for single layer to 13.04% for tri-layer. The mechanical strength of three types of membrane were detected and showed that it could meet the requiremens of clinical practice. The membranes especially with tri-layer could be more valuable in application.

  20. High flux and antifouling properties of negatively charged membrane for dyeing wastewater treatment by membrane distillation.

    Science.gov (United States)

    An, Alicia Kyoungjin; Guo, Jiaxin; Jeong, Sanghyun; Lee, Eui-Jong; Tabatabai, S Assiyeh Alizadeh; Leiknes, TorOve

    2016-10-15

    This study investigated the applicability of membrane distillation (MD) to treat dyeing wastewater discharged by the textile industry. Four different dyes containing methylene blue (MB), crystal violet (CV), acid red 18 (AR18), and acid yellow 36 (AY36) were tested. Two types of hydrophobic membranes made of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) were used. The membranes were characterized by testing against each dye (foulant-foulant) and the membrane-dye (membrane-foulant) interfacial interactions and their mechanisms were identified. The MD membranes possessed negative charges, which facilitated the treatment of acid and azo dyes of the same charge and showed higher fluxes. In addition, PTFE membrane reduced the wettability with higher hydrophobicity of the membrane surface. The PTFE membrane evidenced especially its resistant to dye absorption, as its strong negative charge and chemical structure caused a flake-like (loose) dye-dye structure to form on the membrane surface rather than in the membrane pores. This also enabled the recovery of flux and membrane properties by water flushing (WF), thereby direct-contact MD with PTFE membrane treating 100 mg/L of dye mixtures showed stable flux and superior color removal during five days operation. Thus, MD shows a potential for stable long-term operation in conjunction with a simple membrane cleaning process, and its suitability in dyeing wastewater treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. 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.

  2. Phagocytosis of IgG‐Coated Polystyrene Beads by Macrophages Induces and Requires High Membrane Order

    National Research Council Canada - National Science Library

    Magenau, Astrid; Benzing, Carola; Proschogo, Nicholas; Don, Anthony S; Hejazi, Leila; Karunakaran, Denuja; Jessup, Wendy; Gaus, Katharina

    2011-01-01

    ...)‐coated polystyrene particles. We found that the plasma membrane undergoes rapid actin‐independent condensation to form highly ordered phagosomal membranes, the biophysical hallmark of lipid rafts...

  3. Imaging and measuring the biophysical properties of Fc gamma receptors on single macrophages using atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Mi [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Lianqing, E-mail: lqliu@sia.cn [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); Xi, Ning [Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong (China); Wang, Yuechao [State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016 (China); Xiao, Xiubin [Department of Lymphoma, Affiliated Hospital of Military Medical Academy of Sciences, Beijing 100071 (China); Zhang, Weijing, E-mail: zhangwj3072@163.com [Department of Lymphoma, Affiliated Hospital of Military Medical Academy of Sciences, Beijing 100071 (China)

    2013-09-06

    Highlights: •Nanoscale cellular ultra-structures of macrophages were observed. •The binding affinities of FcγRs were measured directly on macrophages. •The nanoscale distributions of FcγRs were mapped on macrophages. -- Abstract: Fc gamma receptors (FcγR), widely expressed on effector cells (e.g., NK cells, macrophages), play an important role in clinical cancer immunotherapy. The binding of FcγRs to the Fc portions of antibodies that are attached to the target cells can activate the antibody-dependent cell-mediated cytotoxicity (ADCC) killing mechanism which leads to the lysis of target cells. In this work, we used atomic force microscopy (AFM) to observe the cellular ultra-structures and measure the biophysical properties (affinity and distribution) of FcγRs on single macrophages in aqueous environments. AFM imaging was used to obtain the topographies of macrophages, revealing the nanoscale cellular fine structures. For molecular interaction recognition, antibody molecules were attached onto AFM tips via a heterobifunctional polyethylene glycol (PEG) crosslinker. With AFM single-molecule force spectroscopy, the binding affinities of FcγRs were quantitatively measured on single macrophages. Adhesion force mapping method was used to localize the FcγRs, revealing the nanoscale distribution of FcγRs on local areas of macrophages. The experimental results can improve our understanding of FcγRs on macrophages; the established approach will facilitate further research on physiological activities involved in antibody-based immunotherapy.

  4. High flux and antifouling properties of negatively charged membrane for dyeing wastewater treatment by membrane distillation

    KAUST Repository

    An, Alicia Kyoungjin

    2016-07-25

    This study investigated the applicability of membrane distillation (MD) to treat dyeing wastewater discharged by the textile industry. Four different dyes containing methylene blue (MB), crystal violet (CV), acid red 18 (AR), and acid yellow 36 (AY) were tested. Two types of hydrophobic membranes made of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) were used. The membranes were characterized by testing against each dye (foulant-foulant) and the membrane–dye (membrane-foulant) interfacial interactions and their mechanisms were identified. The MD membranes possessed negative charges, which facilitated the treatment of acid and azo dyes of the same charge and showed higher fluxes. In addition, PTFE membrane reduced the wettability with higher hydrophobicity of the membrane surface. The PTFE membrane evidenced especially its resistant to dye absorption, as its strong negative charge and chemical structure caused a flake-like (loose) dye–dye structure to form on the membrane surface rather than in the membrane pores. This also enabled the recovery of flux and membrane properties by water flushing (WF), thereby direct-contact MD with PTFE membrane treating 100 mg/L of dye mixtures showed stable flux and superior color removal during five days operation. Thus, MD shows a potential for stable long-term operation in conjunction with a simple membrane cleaning process, and its suitability in dyeing wastewater treatment.

  5. Characterization of ion-exchange membrane materials: properties vs structure.

    Science.gov (United States)

    Berezina, N P; Kononenko, N A; Dyomina, O A; Gnusin, N P

    2008-06-22

    This review focuses on the preparation, structure and applications of ion-exchange membranes formed from various materials and exhibiting various functions (electrodialytic, perfluorinated sulphocation-exchange and novel laboratory-tested membranes). A number of experimental techniques for measuring electrotransport properties as well as the general procedure for membrane testing are also described. The review emphasizes the relationships between membrane structures, physical and chemical properties and mechanisms of electrochemical processes that occur in charged membrane materials. The water content in membranes is considered to be a key factor in the ion and water transfer and in polarization processes in electromembrane systems. We suggest the theoretical approach, which makes it possible to model and characterize the electrochemical properties of heterogeneous membranes using several transport-structural parameters. These parameters are extracted from the experimental dependences of specific electroconductivity and diffusion permeability on concentration. The review covers the most significant experimental and theoretical research on ion-exchange membranes that have been carried out in the Membrane Materials Laboratory of the Kuban State University. These results have been discussed at the conferences "Membrane Electrochemistry", Krasnodar, Russia for many years and were published mainly in Russian scientific sources.

  6. Membrane permeability properties of dental adhesive films.

    Science.gov (United States)

    Carrilho, Marcela R; Tay, Franklin R; Donnelly, Adam M; Agee, Kelli A; Carvalho, Ricardo M; Hosaka, Keiichi; Reis, Alessandra; Loguercio, Alessandro D; Pashley, David H

    2009-02-01

    This study evaluated the permeability properties of five experimental resin membranes that ranged from relatively hydrophobic to relatively hydrophilic to seal acid-etched dentin saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents or as solutions solvated with ethanol (70% resin/30% ethanol). The quality of dentin sealing by these experimental resins was expressed in terms of reflection coefficients calculated as the ratio of the effective osmotic pressure to the theoretical osmotic pressure of test solutions. The effective osmotic pressure produced across resin-bonded dentin was induced in hypertonic solutions (CaCl(2) or albumin) at zero hydrostatic pressure. The outward fluid flow induced by these solutions was brought to zero by applying an opposing negative hydrostatic pressure. The least hydrophilic resins blends, R1 and R2, exhibited significantly (p < 0.05) higher reflection coefficients than the most hydrophilic resins (R4 and R5) in both conditions of dentin saturation (water and ethanol). The reflection coefficients of neat resins were, in general, significantly higher when compared with their corresponding solvated versions in both conditions of dentin saturation. In dentin saturated with ethanol, bonding with neat or solvated resins, resulted in reflection coefficients that were significantly higher when compared with the results obtained in dentin saturated with water. Reflection coefficients of CaCl(2) (ca. 1 x 10(-4)) were significantly lower (p < 0.05) than for albumin (ca. 3 x 10(-2)). Application of hydrophobic resins may provide better sealing of acid-etched dentin if the substrate is saturated with ethanol, instead of water.

  7. Disruption of the phagosomal membrane and egress of Legionella pneumophila into the cytoplasm during the last stages of intracellular infection of macrophages and Acanthamoeba polyphaga.

    Science.gov (United States)

    Molmeret, Maëlle; Bitar, Dina M; Han, Lihui; Kwaik, Yousef Abu

    2004-07-01

    Although the early stages of intracellular infection by Legionella pneumophila are well established at the ultrastructural level, a detailed ultrastructural analysis of late stages of intracellular replication has never been done. Here we show that the membrane of the L. pneumophila-containing phagosome (LCP) is intact for up to 8 h postinfection of macrophages and Acanthamoeba polyphaga. At 12 h, 71 and 74% of the LCPs are disrupted within macrophages and A. polyphaga, respectively, while the plasma membrane remains intact. At 18 and 24 h postinfection, cytoplasmic elements such as mitochondria, lysosomes, vesicles, and amorphous material are dispersed among the bacteria and these bacteria are considered cytoplasmic. At 18 h, 77% of infected macrophages and 32% of infected A. polyphaga amoebae harbor cytoplasmic bacteria. At 24 h, 99 and 78% of infected macrophages and amoebae, respectively, contain cytoplasmic bacteria. On the basis of lysosomal acid phosphatase staining of infected macrophages and A. polyphaga, the lysosomal enzyme is present among the bacteria when host vesicles are dispersed among bacteria. Our data indicate that bacterial replication proceeds despite physical disruption of the phagosomal membrane. We also show that an lspG mutant that is defective in the type II secretion system and therefore does not secrete the hydrolytic enzymes metalloprotease, p-nitrophenol phosphorylcholine hydrolase, lipase, phospholipase A, and lysophospholipase A is as efficient as the wild-type strain in disruption of the LCP. Therefore, L. pneumophila disrupts the phagosomal membrane and becomes cytoplasmic at the last stages of infection in both macrophages and A. polyphaga. Lysosomal elements, mitochondria, cytoplasmic vesicles, and amorphous material are all dispersed among the bacteria, after phagosomal disruption, within both human macrophages and A. polyphaga. The disruption of the LCP is independent of the hydrolytic enzymes exported by the type II secretion

  8. Membranes with Surface-Enhanced Antifouling Properties for Water Purification

    Science.gov (United States)

    Shahkaramipour, Nima; Tran, Thien N.; Ramanan, Sankara; Lin, Haiqing

    2017-01-01

    Membrane technology has emerged as an attractive approach for water purification, while mitigation of fouling is key to lower membrane operating costs. This article reviews various materials with antifouling properties that can be coated or grafted onto the membrane surface to improve the antifouling properties of the membranes and thus, retain high water permeance. These materials can be separated into three categories, hydrophilic materials, such as poly(ethylene glycol), polydopamine and zwitterions, hydrophobic materials, such as fluoropolymers, and amphiphilic materials. The states of water in these materials and the mechanisms for the antifouling properties are discussed. The corresponding approaches to coat or graft these materials on the membrane surface are reviewed, and the materials with promising performance are highlighted. PMID:28273869

  9. Membranes with Surface-Enhanced Antifouling Properties for Water Purification

    Directory of Open Access Journals (Sweden)

    Nima Shahkaramipour

    2017-03-01

    Full Text Available Membrane technology has emerged as an attractive approach for water purification, while mitigation of fouling is key to lower membrane operating costs. This article reviews various materials with antifouling properties that can be coated or grafted onto the membrane surface to improve the antifouling properties of the membranes and thus, retain high water permeance. These materials can be separated into three categories, hydrophilic materials, such as poly(ethylene glycol, polydopamine and zwitterions, hydrophobic materials, such as fluoropolymers, and amphiphilic materials. The states of water in these materials and the mechanisms for the antifouling properties are discussed. The corresponding approaches to coat or graft these materials on the membrane surface are reviewed, and the materials with promising performance are highlighted.

  10. Barrier Membrane, a Device for Regeneration: Properties and Applications

    OpenAIRE

    Soheilifar; Bidgoli; Torkzaban

    2014-01-01

    Context This article reviews the available evidence about the barrier membranes utilized in Guided Tissue Regeneration process to prevent the migration of unfavorable cells to the wound area. Evidence Acquisition Available evidence about membranes properties and their different uses were reviewed, and the results of clinical and animal studies and systematic reviews were gathered. Results ...

  11. Interfacial properties and emulsification performance of thylakoid membrane fragments

    NARCIS (Netherlands)

    Tamayo Tenorio, A.; Jong, de E.W.M.; Nikiforidis, K.; Boom, R.M.; Goot, van der A.J.

    2017-01-01

    Thylakoids membranes are sophisticated, dynamic structures found in plant leaves, composed of protein complexes in a dynamic lipid matrix. The interfacial absorption dynamics and viscoelasticity of thylakoid membranes fragments were measured to assess the properties of the interfacial layer and to e

  12. New membrane structures with proton conducting properties

    DEFF Research Database (Denmark)

    Nørgaard, Casper Frydendal

    operating temperatures (>100 °C) are desired as they improve reaction kinetics and reduce the problem of CO poisoning the catalyst, thus allowing reduced noble metal loading in the catalyst layers of the membrane electrode assembly of the fuel cell. Moreover water and heat management can be simplified...... [1, 2, 3]. Improved fuel cell performance from incorporation of hygroscopic oxides or solid proton conductors (e.g. zirconium phosphates) has been reported. The poster exhibits upcoming work in the field of composite electrolyte membranes at the University of Southern Denmark, combining radiation...

  13. Polyunsaturation in lipid membranes: dynamic properties and lateral pressure profiles.

    Science.gov (United States)

    Ollila, Samuli; Hyvönen, Marja T; Vattulainen, Ilpo

    2007-03-29

    We elucidate the influence of unsaturation on single-component membrane properties, focusing on their dynamical aspects and lateral pressure profiles across the membrane. To this end, we employ atomistic molecular dynamics simulations to study five different membrane systems with varying degrees of unsaturation, starting from saturated membranes and systematically increasing the level of unsaturation, ending up with a bilayer of phospholipids containing the docosahexaenoic acid. For an increasing level of unsaturation, we find considerable effects on dynamical properties, such as accelerated dynamics of the phosphocholine head groups and glycerol backbones and speeded up rotational dynamics of the lipid molecules. The lateral pressure profile is found to be altered by the degree of unsaturation. For an increasing number of double bonds, the peak in the middle of the bilayer decreases. This is compensated for by changes in the membrane-water interface region in terms of increasing peak heights of the lateral pressure profile. Implications of the findings are briefly discussed.

  14. Tumor associated macrophage × cancer cell hybrids may acquire cancer stem cell properties in breast cancer.

    Directory of Open Access Journals (Sweden)

    Jingxian Ding

    Full Text Available Breast cancer is one of the most frequently diagnosed cancers among women, and metastasis makes it lethal. Tumor-associated macrophages (TAMs that acquire an alternatively activated macrophage (M2 phenotype may promote metastasis. However, the underlying mechanisms are still elusive. Here, we examined how TAMs interact with breast cancer cells to promote metastasis. Immunohistochemistry was used to examine the expression of the M2-specific antigen CD163 in paraffin-embedded mammary carcinoma blocks to explore fusion events in breast cancer patients. U937 cells were used as a substitute for human monocytes, and these cells differentiated into M2 macrophages following phorbol 12-myristate 13-acetate (PMA and M-CSF stimulation. M2 macrophages and the breast cancer cell lines MCF-7 and MDA-MB-231 fused in the presence of 50% polyethylene glycol. Hybrids were isolated by fluorescence-activated cell sorting, and the relevant cell biological properties were compared with their parental counterparts. Breast cancer stem cell (BCSC-related markers were quantified by immunofluorescence staining, RT-PCR, quantitative RT-PCR and/or western blotting. The tumor-initiating and metastatic capacities of the hybrids and their parental counterparts were assessed in NOD/SCID mice. We found that the CD163 expression rate in breast cancer tissues varied significantly and correlated with estrogen receptor status (p0.05. Characterization of the fusion hybrids revealed a more aggressive phenotype, including increased migration, invasion and tumorigenicity, but reduced proliferative ability, compared with the parental lines. The hybrids also gained a CD44(+CD24(-/low phenotype and over-expressed epithelial-mesenchymal transition-associated genes. These results indicate that TAMs may promote breast cancer metastasis through cell fusion, and the hybrids may gain a BCSC phenotype.

  15. STRUCTURE AND PROPERTIES OF COMPOSITE POLYURETHANE HOLLOW FIBER MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    Xian-feng Li; Chang-fa Xiao

    2005-01-01

    Composite polyurethane (PU)-SiO2 hollow fiber membranes were successfully prepared via optimizing the technique of dry-jet wet spinning, and their pressure-responsibilities were confirmed by the relationships of pure water fluxtransmembrane pressure (PWF-TP) for the first time. The origin for this phenomenon was analyzed on the basis of membrane structure and material characteristics. The effects of SiO2 content on the structure and properties of membrane were investigated. The experimental results indicated that SiO2 in membrane created a great many interfacial micro-voids and played an important role in pressure-responsibility, PWF and rejection of membrane: with the increase of SiO2 content, the ability of membrane recovery weakened, PWF increased, and rejection decreased slightly.

  16. Characterization and Pervaporation Properties of Modified PU Membranes

    Directory of Open Access Journals (Sweden)

    Ye Hong

    2015-01-01

    Full Text Available Pervaporation will have broad application prospects in the treatment of phenolic wastewater. Polyurethane (PU membrane is promising but needs to be further modified. In this study, both β-CD and CNT were used to modify the PU membrane. The structure and property of these membranes were characterized by FTIR, DSC and TGA. The pervaporation performances were investigated, and the effects of β-CD and CNT on membrane separation were discussed. TGA shows that three kinds of modified membranes have enough thermal stability to afford pervaporation test and start weight loss at about 200 °C. In pervaporaiton, the total flux, separation factor and PSI value all increase with increased feed temperature. That is anti-trade-off phenomenon. Among these membranes, HTPB+β-CD-PU shows the best comprehensive performance at 80°C and has great potential for further application.

  17. Barrier Membrane, a Device for Regeneration: Properties and Applications

    Directory of Open Access Journals (Sweden)

    Soheilifar

    2014-10-01

    Full Text Available Context This article reviews the available evidence about the barrier membranes utilized in Guided Tissue Regeneration process to prevent the migration of unfavorable cells to the wound area. Evidence Acquisition Available evidence about membranes properties and their different uses were reviewed, and the results of clinical and animal studies and systematic reviews were gathered. Results A large number of existing membranes with different features and compositions may lead to different study results; none of the available membranes can result in %100 predictable outcomes. Conclusions Effectiveness of membranes in treating intrabony defects is very controversial; however, treating furcation defects using membranes was reported to be successful in a large number of studies.

  18. Nafion–clay nanocomposite membranes: Morphology and properties

    KAUST Repository

    Herrera Alonso, Rafael

    2009-05-01

    A series of Nafion-clay nanocomposite membranes were synthesized and characterized. To minimize any adverse effects on ionic conductivity the clay nanoparticles were H+ exchanged prior to mixing with Nafion. Well-dispersed, mechanically robust, free-standing nanocomposite membranes were prepared by casting from a water suspension at 180 °C under pressure. SAXS profiles reveal a preferential orientation of Nafion aggregates parallel to the membrane surface, or normal plane. This preferred orientation is induced by the platy nature of the clay nanoparticles, which tend to align parallel to the surface of the membrane. The nanocomposite membranes show dramatically reduced methanol permeability, while maintaining high levels of proton conductivity. The hybrid films are much stiffer and can withstand much higher temperatures compared to pure Nafion. The superior thermomechanical, electrochemical and barrier properties of the nanocomposite membranes are of significant interest for direct methanol fuel cell applications. © 2009 Elsevier Ltd. All rights reserved.

  19. Properties of liposomal membranes containing lysolecithin.

    Science.gov (United States)

    Kitagawa, T; Inoue, K; Nojima, S

    1976-06-01

    Liposomes have been prepared with lysolecithin (1-acyl-sn-3-glycerylphosphorylcholine), egg lecithin (3-sn-phosphatidylcholine), dicetyl phosphate, and cholesterol. The ability to function as a barrier to the diffusion of glucose marker and the sensitivities of the liposomes to hypotonic treatment and other reagents which modified the permeability were examined. Generally, lysolecithin incorporation decreased the effectiveness of the membranes as a barrier to glucose and made the membranes more "osmotically fragile." Cholesterol incorporation counteracted the effect of incorporated lysolecithin. The more cholesterol incorporated into liposomes, the more lysolecthin could be incorporated into the membrane without loss of function as a barrier. With more than 50 mole% of colesterol, lysolecithin alone could form membranes which were practically impermeable to glucose. The hemolytic activity of lysolecithin was affected by mixing with various lecithins or cholesterol. Liposomes containing lysolecithin, which have the ability to trap glucose marker, showed poor hemolytic activity, while lipid micelles with lysolecithin (which could trap little glucose) showed almost the same hemolytic activity as lysolecithin itself. There seems to be a close correlation between hemolytic activity and barrier function of lipid micelles.

  20. Packing properties 1-alkanols and alkanes in a phospholipid membrane

    DEFF Research Database (Denmark)

    Westh, Peter

    2006-01-01

    into the membrane, Vm(puremem), was positive for small (C4-C6) 1-alkanols while it was negative for larger alcohols and all alkanes. The magnitude of Vm(puremem) ranged from about +4 cm3/mol for alcohols with an alkyl chain about half the length of the fatty acids of DMPC, to -10 to -15 cm3/mol for the alkanes......We have used vibrating tube densitometry to investigate the packing properties of four alkanes and a homologous series of ten alcohols in fluid-phase membranes of dimyristoyl phosphatidylcholine (DMPC). It was found that the volume change of transferring these compounds from their pure states...... and long chain alcohols. On the basis of these observations, previously published information on the structure of the membrane-solute complexes and the free volume properties of (pure) phospholipid membranes, we suggest that two effects dominate the packing properties of hydrophobic solutes in DMPC. First...

  1. Ascorbic acid pre-treated quartz stimulates TNF-α release in RAW 264.7 murine macrophages through ROS production and membrane lipid peroxidation

    Directory of Open Access Journals (Sweden)

    Benvenuto Federica

    2009-03-01

    Full Text Available Abstract Background Inhalation of crystalline silica induces a pulmonary fibrotic degeneration called silicosis caused by the inability of alveolar macrophages to dissolve the crystalline structure of phagocytosed quartz particles. Ascorbic acid is capable of partially dissolving quartz crystals, leading to an increase of soluble silica concentration and to the generation of new radical sites on the quartz surface. The reaction is specific for the crystalline forms of silica. It has been already demonstrated an increased cytotoxicity and stronger induction of pro-inflammatory cyclooxygenase-2 (COX-2 by ascorbic acid pre-treated quartz (QA compared to untreated quartz (Q in the murine macrophage cell line RAW 264.7. Methods Taking advantage of the enhanced macrophage response to QA as compared to Q particles, we investigated the first steps of cell activation and the contribution of early signals generated directly from the plasma membrane to the production of TNF-α, a cytokine that activates both inflammatory and fibrogenic pathways. Results Here we demonstrate that TNF-α mRNA synthesis and protein secretion are significantly increased in RAW 264.7 macrophages challenged with QA as compared to Q particles, and that the enhanced response is due to an increase of intracellular ROS. Plasma membrane-particle contact, in the absence of phagocytosis, is sufficient to trigger TNF-α production through a mechanism involving membrane lipid peroxidation and this appears to be even more detrimental to macrophage survival than particle phagocytosis itself. Conclusion Taken together these data suggest that an impairment of pulmonary macrophage phagocytosis, i.e. in the case of alcoholic subjects, could potentiate lung disease in silica-exposed individuals.

  2. Reverse osmosis membrane of high urea rejection properties. [water purification

    Science.gov (United States)

    Johnson, C. C.; Wydeven, T. J. (Inventor)

    1980-01-01

    Polymeric membranes suitable for use in reverse osmosis water purification because of their high urea and salt rejection properties are prepared by generating a plasma of an unsaturated hydrocarbon monomer and nitrogen gas from an electrical source. A polymeric membrane is formed by depositing a polymer of the unsaturated monomer from the plasma onto a substrate, so that nitrogen from the nitrogen gas is incorporated within the polymer in a chemically combined form.

  3. Proteomic Analysis of Detergent Resistant Membrane Domains during Early Interaction of Macrophages with Rough and Smooth Brucella melitensis

    Science.gov (United States)

    Lauer, Sabine A.; Iyer, Srinivas; Sanchez, Timothy; Forst, Christian V.; Bowden, Brent; Carlson, Kay; Sriranganathan, Nammalwar; Boyle, Stephen M.

    2014-01-01

    The plasma membrane contains discrete nanometer-sized domains that are resistant to non-ionic detergents, and which are called detergent resistant membrane domains (DRMDs) or lipid rafts. Exposure of host cells to pathogenic bacteria has been shown to induce the re-distribution of specific host proteins between DRMDs and detergent soluble membranes, which leads to the initiation of cell signaling that enable pathogens to access host cells. DRMDs have been shown to play a role in the invasion of Brucella into host macrophages and the formation of replicative phagosomes called Brucella-containing vacuoles (BCVs). In this study we sought to characterize changes to the protein expression profiles in DRMDs and to respective cellular pathways and networks of Mono Mac 6 cells in response to the adherence of rough VTRM1 and smooth 16 M B. melitensis strains. DRMDs were extracted from Mono Mac 6 cells exposed for 2 minutes at 4°C to Brucella (no infection occurs) and from unexposed control cells. Protein expression was determined using the non-gel based quantitative iTRAQ (Isobaric Tags for Relative and Absolute Quantitation) mass spectrometry technique. Using the identified iTRAQ proteins we performed enrichment analyses and probed constructed human biochemical networks for interactions and metabolic reactions. We identified 149 proteins, which either became enriched, depleted or whose amounts did not change in DRMDs upon Brucella exposure. Several of these proteins were distinctly enriched or depleted in DRMDs upon exposure to rough and smooth B. melitensis strains which results in the differential engagement of cellular pathways and networks immediately upon Brucella encounter. For some of the proteins such as myosin 9, small G protein signaling modulator 3, lysine-specific demethylase 5D, erlin-2, and voltage-dependent anion-selective channel protein 2, we observed extreme differential depletion or enrichment in DRMDs. The identified proteins and pathways could provide

  4. Effect of activated sludge properties and membrane operation conditions on fouling characteristics in membrane bioreactors.

    Science.gov (United States)

    Choi, Hyeok; Zhang, Kai; Dionysiou, Dionysios D; Oerther, Daniel B; Sorial, George A

    2006-06-01

    Biofouling control is considered to be a major challenge in operating membrane bioreactors (MBRs) for the treatment of wastewater. This study examined the impact of biological, chemical, and physical properties of activated sludge on membrane filtration performance in laboratory-scale MBRs. Sludges with different microbial communities were produced using pseudo-continuous stirred-tank reactors and pseudo-plug flow reactors treating a synthetic paper mill wastewater. Various filtration resistances were used to investigate membrane fouling characteristics, and molecular biology tools targeting 16S ribosomal DNA gene sequences were used to identify predominant bacterial populations in the sludges or attached to the fouled membranes. Filtration experiments using axenic cultures of Escherichia coli, Acinetobacter calcoaceticus, and Gordonia amarae were also performed to better understand the initiation and development of biofouling. The results showed that the tendency of membranes to biofoul depended upon membrane operating conditions as well as the properties of the activated sludge in the MBR systems. Specific bacterial populations, which were not dominant in the activated sludges, were selectively accumulated on the membrane surface leading to the development of irreversible biofouling.

  5. Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

    Science.gov (United States)

    Li, Jian-Hua; Li, Mi-Zi; Miao, Jing; Wang, Jia-Bin; Shao, Xi-Sheng; Zhang, Qi-Qing

    2012-06-01

    An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

  6. Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

    Energy Technology Data Exchange (ETDEWEB)

    Li Jianhua, E-mail: jhli_2005@163.com [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Li Mizi; Miao Jing; Wang Jiabin; Shao Xisheng [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Zhang Qiqing, E-mail: zhangqiq@126.com [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China) and Institute of Biomedical Engineering, Chinese Academy of Medical Science, Peking Union Medical College, Tianjin 300192 (China)

    2012-06-15

    An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

  7. Modeling the Elastic Properties of Lipid Bilayer Membranes

    Science.gov (United States)

    Barry, Edward; Gibaud, Thomas; Zakhary, Mark; Dogic, Zvonimir

    2011-03-01

    Model membranes such as lipid bilayers have been indispensable tools for our understanding of the elastic properties of biological membranes. In this talk, I will introduce a colloidal model for membranes and demonstrate that the physical properties of these colloidal membranes are identical to lipid bilayers. The model system is unique in that the constituent molecules are homogenous and non-amphiphilic, yet their self-assembly into membranes and other hierarchical assemblages, such as a lamellar type phases and chiral ribbons, proceeds spontaneously in solution. Owing to the large size of the constituent molecules, individual molecules can be directly visualized and simultaneous observations at the continuum and molecular lengthscales are used to characterize the behavior of model membranes with unprecedented detail. Moreover, once assembled in solution, molecular interactions can be controlled in situ. In particular, the strength of chiral interactions can be varied, leading to fascinating transitions in behavior that resembles the formation of starfish vesicles. These observations point towards the important role of line tension, and have potential implications for phase separated lipid mixtures or lipid rafts.

  8. Application of MD Simulations to Predict Membrane Properties of MOFs

    Directory of Open Access Journals (Sweden)

    Elda Adatoz

    2015-01-01

    Full Text Available Metal organic frameworks (MOFs are a new group of nanomaterials that have been widely examined for various chemical applications. Gas separation using MOF membranes has become an increasingly important research field in the last years. Several experimental studies have shown that thin-film MOF membranes can outperform well known polymer and zeolite membranes due to their higher gas permeances and selectivities. Given the very large number of available MOF materials, it is impractical to fabricate and test the performance of every single MOF membrane using purely experimental techniques. In this study, we used molecular simulations, Monte Carlo and Molecular Dynamics, to estimate both single-gas and mixture permeances of MOF membranes. Predictions of molecular simulations were compared with the experimental gas permeance data of MOF membranes in order to validate the accuracy of our computational approach. Results show that computational methodology that we described in this work can be used to accurately estimate membrane properties of MOFs prior to extensive experimental efforts.

  9. Membrane Protein Properties Revealed through Data-Rich Electrostatics Calculations.

    Science.gov (United States)

    Marcoline, Frank V; Bethel, Neville; Guerriero, Christopher J; Brodsky, Jeffrey L; Grabe, Michael

    2015-08-04

    The electrostatic properties of membrane proteins often reveal many of their key biophysical characteristics, such as ion channel selectivity and the stability of charged membrane-spanning segments. The Poisson-Boltzmann (PB) equation is the gold standard for calculating protein electrostatics, and the software APBSmem enables the solution of the PB equation in the presence of a membrane. Here, we describe significant advances to APBSmem, including full automation of system setup, per-residue energy decomposition, incorporation of PDB2PQR, calculation of membrane-induced pKa shifts, calculation of non-polar energies, and command-line scripting for large-scale calculations. We highlight these new features with calculations carried out on a number of membrane proteins, including the recently solved structure of the ion channel TRPV1 and a large survey of 1,614 membrane proteins of known structure. This survey provides a comprehensive list of residues with large electrostatic penalties for being embedded in the membrane, potentially revealing interesting functional information.

  10. Membrane properties in small cutaneous nerve fibers in humans

    DEFF Research Database (Denmark)

    Hennings, Kristian; Frahm, Ken Steffen; Petrini, Laura;

    2016-01-01

    than large fibers (rmANOVA, Bonferroni, P=0.006). CONCLUSION: This study is a reliable method to investigate the membrane properties of small cutaneous nerve fibers in humans and may be used in clinical settings as a diagnostic or profiling tool. This article is protected by copyright. All rights...

  11. 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.

  12. Phase behaviors and membrane properties of model liposomes: Temperature effect

    Science.gov (United States)

    Wu, Hsing-Lun; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2014-09-01

    The phase behaviors and membrane properties of small unilamellar vesicles have been explored at different temperatures by dissipative particle dynamics simulations. The vesicles spontaneously formed by model lipids exhibit pre-transition from gel to ripple phase and main transition from ripple to liquid phase. The vesicle shape exhibits the faceted feature at low temperature, becomes more sphere-like with increasing temperature, but loses its sphericity at high temperature. As the temperature rises, the vesicle size grows but the membrane thickness declines. The main transition (Tm) can be identified by the inflection point. The membrane structural characteristics are analyzed. The inner and outer leaflets are asymmetric. The length of the lipid tail and area density of the lipid head in both leaflets decrease with increasing temperature. However, the mean lipid volume grows at low temperature but declines at high temperature. The membrane mechanical properties are also investigated. The water permeability grows exponentially with increasing T but the membrane tension peaks at Tm. Both the bending and stretching moduli have their minima near Tm. Those results are consistent with the experimental observations, indicating that the main signatures associated with phase transition are clearly observed in small unilamellar vesicles.

  13. How cellular membrane properties are affected by the actin cytoskeleton.

    Science.gov (United States)

    Lemière, J; Valentino, F; Campillo, C; Sykes, C

    2016-11-01

    Lipid membranes define the boundaries of living cells and intracellular compartments. The dynamic remodelling of these membranes by the cytoskeleton, a very dynamic structure made of active biopolymers, is crucial in many biological processes such as motility or division. In this review, we present some aspects of cellular membranes and how they are affected by the presence of the actin cytoskeleton. We show that, in parallel with the direct study of membranes and cytoskeleton in vivo, biomimetic in vitro systems allow reconstitution of biological processes in a controlled environment. In particular, we show that liposomes, or giant unilamellar vesicles, encapsulating a reconstituted actin network polymerizing at their membrane are suitable models of living cells and can be used to decipher the relative contributions of membrane and actin on the mechanical properties of the cellular interface. Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  14. The nucleotide receptor P2X7 mediates actin reorganization and membrane blebbing in RAW 264.7 macrophages via p38 MAP kinase and Rho.

    Science.gov (United States)

    Pfeiffer, Zachary A; Aga, Mini; Prabhu, Usha; Watters, Jyoti J; Hall, David J; Bertics, Paul J

    2004-06-01

    Extracellular nucleotides regulate macrophage function via P2X nucleotide receptors that form ligand-gated ion channels. In particular, P2X7 activation is characterized by pore formation, membrane blebbing, and cytokine release. P2X7 is also linked to mitogen-activated protein kinases (MAPK) and Rho-dependent pathways, which are known to affect cytoskeletal structure in other systems. As cytoskeletal function is critical for macrophage behavior, we have tested the importance of these pathways in actin filament reorganization during P2X7 stimulation in RAW 264.7 macrophages. We observed that the P2X7 agonists adenosine 5'-triphosphate (ATP) and 3'-O-(4-benzoylbenzoyl) ATP (BzATP) stimulated actin reorganization and concomitant membrane blebbing within 5 min. Disruption of actin filaments with cytochalasin D attenuated membrane blebbing but not P2X7-dependent pore formation or extracellular-regulated kinase (ERK)1/ERK2 and p38 activation, suggesting that these latter processes do not require intact actin filaments. However, we provide evidence that p38 MAPK and Rho activation but not ERK1/ERK2 activation is important for P2X7-mediated actin reorganization and membrane blebbing. First, activation of p38 and Rho was detected within 5 min of BzATP treatment, which is coincident with membrane blebbing. Second, the p38 inhibitors SB202190 and SB203580 reduced nucleotide-induced blebbing and actin reorganization, whereas the MAPK kinase-1/2 inhibitor U0126, which blocks ERK1/ERK2 activation, had no discernable effect. Third, the Rho-selective inhibitor C3 exoenzyme and the Rho effector kinase, Rho-associated coiled-coil kinase, inhibitor Y-27632, markedly attenuated BzATP-stimulated actin reorganization and membrane blebbing. These data support a model wherein p38- and Rho-dependent pathways are critical for P2X7-dependent actin reorganization and membrane blebbing, thereby facilitating P2X7 involvement in macrophage inflammatory responses.

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

    Science.gov (United States)

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

    2012-10-01

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

  16. The membrane-bound ectopeptidase CPM as a marker of macrophage maturation in vitro and in vivo.

    Science.gov (United States)

    Rehli, M; Krause, S W; Andreesen, R

    2000-01-01

    During terminal maturation of human blood monocytes into macrophages, a multitude of phenotypic and functional changes occurs: cells increase in size, they enhance their capacity for phagocytosis and tumor cytotoxicity but decrease their ability for T-lymphocyte stimulation. The pattern of secreted cytokines is shifted as is the profile of surface antigens. We recently identified carboxypeptidase M (CPM) as a macrophage maturation-associated antigen detected by mAb MAX. 1/MAX. 11. CPM, a phosphoinositol-linked ectopeptidase, is able to process a multitude of different substrates, among them immunologically important peptides like bradykinin, anaphylatoxins and enkephalins. It was previously shown to be expressed in placenta, lung, and kidney. CPM as detected by MAX. 1/11 shows a strong expression on monocyte-derived macrophages in vitro and on macrophages in vivo accompanying T-lymphocyte activation like during allogeneic transplant rejection or allergic alveolitis. In contrast, its expression is suppressed on macrophages by some types of tumor cells. CPM expression seems to correlate with macrophage cytotoxic functions. However, the biological importance of CPM expression in human macrophages in vivo is difficult to predict. A wide range of biologically active peptides are cleaved by CPM, and the relevance of CPM peptide processing during an immune reaction is only poorly understood. The generation and analysis of CPM-deficient animals might improve our understanding of CPM function. Therefore we cloned a cDNA for the murine homologue of CPM. However, expression of mCPM was undetectable in murine primary macrophages and macrophage cell-lines, suggesting that CPM expression and function is not conserved between human and mouse macrophages.

  17. Influences of acid-base property of membrane on interfacial interactions related with membrane fouling in a membrane bioreactor based on thermodynamic assessment.

    Science.gov (United States)

    Zhao, Leihong; Qu, Xiaolu; Zhang, Meijia; Lin, Hongjun; Zhou, Xiaoling; Liao, Bao-Qiang; Mei, Rongwu; Hong, Huachang

    2016-08-01

    Failure of membrane hydrophobicity in predicting membrane fouling requires a more reliable indicator. In this study, influences of membrane acid base (AB) property on interfacial interactions in two different interaction scenarios in a submerged membrane bioreactor (MBR) were studied according to thermodynamic approaches. It was found that both the polyvinylidene fluoride (PVDF) membrane and foulant samples in the MBR had relatively high electron donor (γ(-)) component and low electron acceptor (γ(+)) component. For both of interaction scenarios, AB interaction was the major component of the total interaction. The results showed that, the total interaction monotonically decreased with membrane γ(-), while was marginally affected by membrane γ(+), suggesting that γ(-) could act as a reliable indicator for membrane fouling prediction. This study suggested that membrane modification for fouling mitigation should orient to improving membrane surface γ(-) component rather than hydrophilicity.

  18. 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.

  19. Effect of surface properties of silica nanoparticles on their cytotoxicity and cellular distribution in murine macrophages

    Directory of Open Access Journals (Sweden)

    Nagano Kazuya

    2011-01-01

    Full Text Available Abstract Surface properties are often hypothesized to be important factors in the development of safer forms of nanomaterials (NMs. However, the results obtained from studying the cellular responses to NMs are often contradictory. Hence, the aim of this study was to investigate the relationship between the surface properties of silica nanoparticles and their cytotoxicity against a murine macrophage cell line (RAW264.7. The surface of the silica nanoparticles was either unmodified (nSP70 or modified with amine (nSP70-N or carboxyl groups (nSP70-C. First, the properties of the silica nanoparticles were characterized. RAW264.7 cells were then exposed to nSP70, nSP70-N, or nSP70-C, and any cytotoxic effects were monitored by analyzing DNA synthesis. The results of this study show that nSP70-N and nSP70-C have a smaller effect on DNA synthesis activity by comparison to unmodified nSP70. Analysis of the intracellular localization of the silica nanoparticles revealed that nSP70 had penetrated into the nucleus, whereas nSP70-N and nSP70-C showed no nuclear localization. These results suggest that intracellular localization is a critical factor underlying the cytotoxicity of these silica nanoparticles. Thus, the surface properties of silica nanoparticles play an important role in determining their safety. Our results suggest that optimization of the surface characteristics of silica nanoparticles will contribute to the development of safer forms of NMs.

  20. Nature of the charged headgroup determines the fusogenic potential and membrane properties of lithocholic acid phospholipids.

    Science.gov (United States)

    Bhargava, Priyanshu; Singh, Manish; Sreekanth, Vedagopuram; Bajaj, Avinash

    2014-08-07

    Phospholipids play a crucial role in many cellular processes ranging from selective membrane permeability, to membrane fission and fusion, to cellular signaling. Headgroups of phospholipids determine the membrane properties and fusogenicity of these lipids with target cell membranes. We studied the fusogenic and membrane properties of phospholipids possessing unnatural charged headgroups with model membranes using laurdan based membrane hydration studies, DPH based membrane fluidity, and differential scanning calorimetry. We unravel that fusogenicity, membrane hydration, and fluidity of membranes are strongly contingent on the nature of the phospholipid charged headgroup. Our studies unraveled that introduction of bulky headgroups like dimethylamino pyridine induces maximum membrane hydration and perturbations with high fusogenicity as compared to small headgroup based phospholipids. These phospholipids also have the capability of high retention in DPPC membranes. Hydration and fluidity of these phospholipid-doped DPPC membranes are contingent on the nature of the charged headgroup. This study would help in future design of phospholipid based nanomaterials for effective drug delivery.

  1. Application of MD simulations to predict membrane properties of MOFs

    OpenAIRE

    Elda Adatoz; Seda Keskin

    2015-01-01

    Research Article Application of MD Simulations to Predict Membrane Properties of MOFs Elda Adatoz and Seda Keskin Chemical and Biological Engineering, Koc University, Rumelifeneri Yolu, Sariyer, 34450 Istanbul, Turkey Correspondence should be addressed to Seda Keskin; Received 22 May 2015; Accepted 13 July 2015 Academic Editor: Yanlin Song Copyright © 2015 E. Adatoz and S. Keskin. This is an open access article distributed under the Creative Commons A...

  2. Effect of glucosylceramide on the biophysical properties of fluid membranes.

    Science.gov (United States)

    Varela, Ana R P; Gonçalves da Silva, Amélia M P S; Fedorov, Alexander; Futerman, Anthony H; Prieto, Manuel; Silva, Liana C

    2013-03-01

    Glucosylceramide (GlcCer), a relevant intermediate in the pathways of glycosphingolipid metabolism, plays key roles in the regulation of cell physiology. The molecular mechanisms by which GlcCer regulates cellular processes are unknown, but might involve changes in membrane biophysical properties and formation of lipid domains. In the present study, fluorescence spectroscopy, confocal microscopy and surface pressure-area (π-A) measurements were used to characterize the effect of GlcCer on the biophysical properties of model membranes. We show that C16:0-GlcCer has a high tendency to segregate into highly ordered gel domains and to increase the order of the fluid phase. Monolayer studies support the aggregation propensity of C16:0-GlcCer. π-A isotherms of single C16:0-GlcCer indicate that bilayer domains, or crystal-like structures, coexist within monolayer domains at the air-water interface. Mixtures with POPC exhibit partial miscibility with expansion of the mean molecular areas relative to the additive behavior of the components. Moreover, C16:0-GlcCer promotes morphological alterations in lipid vesicles leading to formation of flexible tubule-like structures that protrude from the fluid region of the bilayer. These results support the hypothesis that alterations in membrane biophysical properties induced by GlcCer might be involved in its mechanism of action.

  3. Modulation of human alveolar macrophage properties by ozone exposure in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Becker, S.; Madden, M.C.; Newman, S.L.; Devlin, R.B.; Koren, H.S. (ABB Environmental Services, Inc., Chapel Hill, NC (United States))

    1991-09-15

    The authors have investigated changes in human alveolar macrophage (HAM) function after exposure in vitro to ozone (O3). The functions studied reflect concern that O3 is detrimental to host defense mechanisms in the bronchoalveolar spaces. Exposure of HAM to O3 caused a concentration-dependent increase in release of prostaglandin E2 (PGE2), an important modulator of inflammation, phagocytosis, and oxidative burst. Although phagocytosis of particulate immune complexes was decreased by O3, we found no change in the quantity of Fc receptors and complement receptors on the HAM surface. Superoxide (O2-) production in response to phorbol ester was reduced after exposure of HAM to O3 while the basal O2- release in response to plastic adherence was not affected. Growth inhibition of the opportunistic yeast Cryptococcus neoformans by HAM was not affected by O3 exposure. The production of inflammatory mediators and immune modulators such as tumor necrosis factor-alpha, interleukin 1, and interleukin 6 were not induced by exposure to O3. However, compared to controls, O3- exposed HAM produced significantly lower levels of these cytokines when stimulated with bacterial lipopolysaccharide (LPS). Two-dimensional gel electrophoretic analysis of proteins made by HAM following in vitro exposure to O3 identified 11 proteins whose rate of synthesis was significantly altered. Thus, these studies show that exposure to O3 alters the functional competence of HAM. While there is a minimal effect on protein expression or synthesis, the responses of HAM to particulate immune complexes, to bacterial LPS, and to PMA are impaired. The release of arachidonic acid and PGE2 suggest that the effect of O3 is primarily targeted to the HAM cell membrane. These changes may ultimately result in increased susceptibility to inhaled infectious agents in the O3-exposed individual.

  4. Correlation between thermotolerance and membrane properties in Paramecium aurelia.

    Science.gov (United States)

    Sasaki, Toshiaki; Konoha, Yoshimi; Toyoda, Taichi; Yasaka, Yuta; Przybos, Eva; Nakaoka, Yasuo

    2006-09-01

    The relationship between thermotolerance and membrane properties was studied by using a ciliated protozoan, Paramecium aurelia. P. aurelia is a complex of sibling species termed ;syngens' whose cell morphology appear similar on microscopic examination. From the comparison of tolerance to increasing temperature among 14 syngens of P. aurelia, we selected syngens 2 and 3 as low thermotolerant examples, and syngens 8 and 10 as high thermotolerant examples. The membrane resistance of high thermotolerant syngens measured by injection of a constant inward current was greater than that of low thermotolerant syngens. Membrane fluidity measurements of living cells using the fluorescent dye, 6-lauroyl-2-dimethylaminonaphtalene (laurdan) showed that the fluidity at the cultured temperature was decreased in high thermotolerant syngens compared to that of low thermotolerant syngens. However, when the temperature was increased to the killing temperature of each syngens, the fluidity was increased to almost the same level irrespective of syngen. Furthermore, analysis of fatty acids extracted from whole cells showed that the ratios of unsaturated to saturated fatty acids was smaller in high thermotolerant syngens than in low thermotolerant syngens. These results suggest that the thermotolerance of P. aurelia syngens is determined by the membrane fluidity which is related to the fatty acids composition.

  5. Heterotrimeric Galphaq11 co-immunoprecipitates with surface-anchored GRP78 from plasma membranes of alpha2M*-stimulated macrophages.

    Science.gov (United States)

    Misra, Uma Kant; Pizzo, Salvatore Vincent

    2008-05-01

    We have previously shown that a fraction of newly expressed GRP78 is translocated to the cell surface in association with the co-chaperone MTJ-1. Proteinase and methylamine-activated alpha(2)M (alpha(2)M*) bind to cell surface-associated GRP78 activating phosphoinositide-specific phospholipase C coupled to a pertussis toxin-insensitive heterotrimeric G protein, generating IP(3)/calcium signaling. We have now studied the association of pertussis toxin-insensitive Galphaq11, with GRP78/MTJ-1 complexes in the plasma membranes of alpha(2)M*-stimulated macrophages. When GRP78 was immunoprecipitated from plasma membranes of macrophages stimulated with alpha(2)M*, Galphaq11, and MTJ-1 were co-precipitated. Likewise Galphaq11 and GRP78 co-immunoprecipitated with MTJ-1 while GRP78 and MTJ-1 co-immunoprecipitated with Galphaq11. Silencing GRP78 expression with GRP78 dsRNA or MTJ-1 with MTJ-1 dsRNA greatly reduced the levels of Galphaq11 co-precipitated with GRP78 or MTJ-1. In conclusion, we show here that plasma membrane-associated GRP78 is coupled to pertussis toxin-insensitive Galphaq11 and forms a ternary signaling complex with MTJ-1.

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

    Science.gov (United States)

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

    2012-01-01

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

  7. PDMS/PVDF hybrid electrospun membrane with superhydrophobic property and drop impact dynamics for dyeing wastewater treatment using membrane distillation

    KAUST Repository

    An, Alicia Kyoungjin

    2016-10-21

    Fouling in membrane distillation (MD) results in an increase in operation costs and deterioration in a water quality. In this work, a poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) electrospun (E-PH) membrane was fabricated by hybridizing polydimethylsiloxane (PDMS) polymeric microspheres with superhydrophobicity onto the E-PH membrane via electrospinning. The resulting hybrid PDMS with E-PH (E-PDMS) membrane showed a significant enhancement in surface hydrophobicity (contact angle, CA = 155.4°) and roughness (Ra = 1,285mm). The zeta potential of E-PDMS membrane surface showed a higher negative value than that of a commercial PVDF (C-PVDF) membrane. These properties of E-PDMS membrane provided an antifouling in treating of differently-charged dyes and generated a flake-like dye–dye (loosely bound foulant) structure on the membrane surface rather than in the membrane pores. This also led to a high productivity of E-PDMS membrane (34 Lm-2h-1, 50% higher than that of C-PVDF membrane) without fouling or wetting. In addition, complete color removal and pure water production were achieved during a long-term operation. An application of intermittent water flushing (WF) in direct contact MD (DCMD) operation led to a 99% CA recovery of E-PDMS membrane indicating its sustainability. Therefore, the E-PDMS membrane is a promising candidate for MD application in dyeing wastewater treatment.

  8. PREPARATION AND PERVAPORATION PROPERTIES OF PROPENE/1-DECENE COPOLYMER MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    Xiu-zhi Tian; Bao-ku Zhu; Xue Jiang; You-yi Xu

    2005-01-01

    Propene/1-decene copolymers (P-co-D) were synthesized by means of slurry polymerization process under atmospheric pressure using Ziegler-Natta catalyst (MgCl2/TiCl4/AlEt3). The random P-co-Ds were elastic, low-crystalline,thermally stable and therefore suitable to be used as membrane materials in organophilic pervaporation with chloroform/water mixture. Its mechanical strength is better than polydimethylsiloxane (PDMS). The correlation between structural parameters (glass transition temperature and crystallinity) and properties of organophilic pervaporation were investigated.

  9. Properties of Polymer Electrolyte Membranes Prepared by Blending of Sulfonated Polystyrene-Lignosulfonate

    Directory of Open Access Journals (Sweden)

    Siang Tandi Gonggo

    2012-11-01

    Full Text Available Electrolyte polymer membrane widely used in PEMFC and DMFC is a perfluorosulfonated membrane such as Nafion. This membrane material exhibits good chemical stability and proton conductivity, but it is very expensive and difficult to recycle. It has high cross-over methanol in DMFC that causes the decrease efficiency and performance of fuel cell, so that the electrolyte polymer membrane with low cross-over methanol has been needed to substitute Nafion membrane. One of the materials used as a polymer electrolyte membrane is polyblends of a sulfonated polystyrene-lignosulfonate (SPS-LS. These polyblends have been prepared by casting polymer solution and characterized as a polyelectrolyte membrane for DMFC. SPS was prepared by sulfonation of polystyrene with acetyl sulfate used as a sulfonating agent. The membranes of SPS-LS were characterized by analysis of functional groups, mechanical properties, and methanol permeability. The maximum mechanical properties of the SPS-LS membrane were observed in LS ratio of 7.5%. However, the methanol permeability of membrane increases as the increase of LS ratio in SPS-LS membranes. The properties of membranes, especially the mechanical property and methanol permeability close to that of Nafion® 117 membrane, so the SPS-LS membrane is highly potential used as the electrolyte membrane for direct methanol fuel cell.

  10. Isolation, Characterization and Biological Properties of Membrane Vesicles Produced by the Swine Pathogen Streptococcus suis.

    Directory of Open Access Journals (Sweden)

    Bruno Haas

    Full Text Available Streptococcus suis, more particularly serotype 2, is a major swine pathogen and an emerging zoonotic agent worldwide that mainly causes meningitis, septicemia, endocarditis, and pneumonia. Although several potential virulence factors produced by S. suis have been identified in the last decade, the pathogenesis of S. suis infections is still not fully understood. In the present study, we showed that S. suis produces membrane vesicles (MVs that range in diameter from 13 to 130 nm and that appear to be coated by capsular material. A proteomic analysis of the MVs revealed that they contain 46 proteins, 9 of which are considered as proven or suspected virulence factors. Biological assays confirmed that S. suis MVs possess active subtilisin-like protease (SspA and DNase (SsnA. S. suis MVs degraded neutrophil extracellular traps, a property that may contribute to the ability of the bacterium to escape the host defense response. MVs also activated the nuclear factor-kappa B (NF-κB signaling pathway in both monocytes and macrophages, inducing the secretion of pro-inflammatory cytokines, which may in turn contribute to increase the permeability of the blood brain barrier. The present study brought evidence that S. suis MVs may play a role as a virulence factor in the pathogenesis of S. suis infections, and given their composition be an excellent candidate for vaccine development.

  11. Mechano-capacitive properties of polarized membranes and the application to conductance measurements of lipid membrane patches

    Science.gov (United States)

    Zecchi, Karis A.; Mosgaard, Lars D.; Heimburg, Thomas

    2017-01-01

    Biological membranes are capacitors that can be charged by applying an electric field across the membrane. The charges on the capacitor exert a force on the membrane that leads to electrostriction, i.e., a thinning of the membrane. This effect is especially strong close to chain melting transitions. A consequence is voltage induced pore formation in the lipid membrane. Since the force is quadratic in voltage, negative and positive voltages have an identical influence on the physics of symmetric membranes. This is not the case for a membrane with an asymmetry leading to a permanent electric polarization. Positive and negative voltages of identical magnitude lead to different physical properties. Such an asymmetry can originate from a lipid composition that is different on the two monolayers of the membrane, or from membrane curvature. The latter effect is called flexoelectricity. It was investigated in detail by A.G. Petrov in the recent decades. As a consequence of permanent polarization, the membrane capacitor is discharged at a voltage different from zero. This leads to interesting electrical phenomena such as outward or inward rectification of membrane permeability. The changes in current-voltage relationships are consistent with the known magnitude of the flexoelectric effect.

  12. Effect of nanoclay on properties of porous PVdF membranes

    Institute of Scientific and Technical Information of China (English)

    Hae-Young HWANG; Deuk-Ju KIM; Hyung-Jun KIM; Young-Taik HONG; Sang-Yong NAM

    2011-01-01

    The main requirements for battery separators are high porosity which can serve pathways of lithium ion and space for gel electrolytes to impregnate in a membrane and mechanical strength to allow easy handling for battery assembly. Generally, it appears the trade-off relationship between the porosity and mechanical strength of the membrane. PVdF composite membranes containing nano-size clays were used to improve the mechanical strength of the membrane without affecting the membrane porosity. The composite membranes were prepared by phase inversion method controlling the membrane preparation conditions such as retention time. The resultant membranes show increased mechanical properties with similar membrane porosity around 80 % compared to the pristine PVdF membrane. Incorporation of nonoclay can be considered as an effective method to improve the mechanical strength in porous membrane supports, especially in a separator.

  13. Subtoxic Doses of Cadmium Modulate Inflammatory Properties of Murine RAW 264.7 Macrophages

    Directory of Open Access Journals (Sweden)

    Sina Riemschneider

    2015-01-01

    Full Text Available Cadmium (Cd is a toxic heavy metal that exhibits various adverse effects in the human and animal organism. Its resemblance to essential metals such as calcium, iron, and zinc leads to an unintended uptake in cells after intake through inhalation and ingestion. In this study we investigated the toxicity and the immunomodulatory potential of Cd in nonactivated and activated murine macrophages (i.e., cell line RAW 264.7. Cadmium alone caused a dose-dependent decreased viability of exposed cells. Subtoxic Cd concentrations delayed cell death in macrophages, resulting from cytotoxic storm, producing reactive oxygen species (ROS and nitric oxide (NO, in response to their stimulation by bacterial antigens via pattern-recognition receptors (PRRs. In addition, production of selected pro- and anti-inflammatory cytokines, the chemokine CXCL1 (KC, and NO was determined. We observed that proinflammatory IL-1β and also CXCL1 were highly upregulated whereas anti-inflammatory or regulatory cytokines IL-6 and IL-10 were suppressed by 10 µM Cd. Also production of antibacterial NO was significantly reduced through exposure to 10 µM Cd, maybe explaining better survival of macrophages. Additionally, we could show by analysis via ICP-MS that different effects of Cd in nonactivated and activated macrophages definitely did not result from different Cd uptake rates.

  14. Distinct immunoregulatory properties of macrophage migration inhibitory factors encoded by Eimeria parasites and their chicken host

    Science.gov (United States)

    Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that plays an important role in host defense against a variety of microorganisms including protozoan parasites. Interestingly, some microbial pathogens also express a MIF-like protein, although its role in disease pathogenesi...

  15. Surface interactions and fouling properties of Micrococcus luteus with microfiltration membranes.

    Science.gov (United States)

    Feng, Lei; Li, Xiufen; Song, Ping; Du, Guocheng; Chen, Jian

    2011-11-01

    This study was conducted to investigate microbial adhesion of Micrococcus luteus to polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes in relation to the variation of the interfacial energies in the membrane-bacteria systems, for revealing effects of short-range surface interactions on filtration behavior. Both the membranes and M. luteus showed typical strong electron donors and hydrophilic properties. The AB component was dominant in the interfacial energies of the two membrane-bacteria systems. M. luteus presented larger negative U(mlb)(XDLVO) to the PP membrane than to the PVDF membrane. The adhesion experiments also proved that M. luteus had higher adhesion percentage to the PP membrane. This study demonstrated that the adhesion potentials of M. luteus to the PP and PVDF membranes might be explained in terms of bacterium, membrane, and intervening medium surface properties, which are mainly determined by the interfacial energies in the systems according to the XDLVO theory.

  16. Properties of glycolipid-enriched membrane rafts in antigen presentation.

    Science.gov (United States)

    Rodgers, William; Smith, Kenneth

    2005-01-01

    Presentation of antigen to T cells represents one of the central events in the engagement of the immune system toward the defense of the host against pathogens. Accordingly, understanding the mechanisms by which antigen presentation occurs is critical toward our understanding the properties of host defense against foreign antigen, as well as insight into other features of the immune system, such as autoimmune disease. The entire antigen-presentation event is complex, and many features of it remain poorly understood. However, recent studies have provided evidence showing that glycolipid-enriched membrane rafts are important for efficient antigen presentation; the studies suggest that one such function of rafts is trafficking of antigen-MHC II complexes to the presentation site on the surface of the antigen-presenting cell. Here, we present a critical discussion of rafts and their proposed functions in antigen presentation. Emerging topics of rafts and antigen presentation that warrant further investigation are also highlighted.

  17. A membrane-type acoustic metamaterial with adjustable acoustic properties

    Science.gov (United States)

    Langfeldt, F.; Riecken, J.; Gleine, W.; von Estorff, O.

    2016-07-01

    A new realization of a membrane-type acoustic metamaterial (MAM) with adjustable sound transmission properties is presented. The proposed design distinguishes itself from other realizations by a stacked arrangement of two MAMs which is inflated using pressurized air. The static pressurization leads to large nonlinear deformations and, consequently, geometrical stiffening of the MAMs which is exploited to adjust the eigenmodes and sound transmission loss of the structure. A theoretical analysis of the proposed inflatable MAM design using numerical and analytical models is performed in order to identify two important mechanisms, namely the shifting of the eigenfrequencies and modal residuals due to the pressurization, responsible for the transmission loss adjustment. Analytical formulas are provided for predicting the eigenmode shifting and normal incidence sound transmission loss of inflated single and double MAMs using the concept of effective mass. The investigations are concluded with results from a test sample measurement inside an impedance tube, which confirm the theoretical predictions.

  18. Effect of amorphisation on the thermal properties of nanostructured membranes

    Energy Technology Data Exchange (ETDEWEB)

    Termentzidis, Konstantinos; Verdier, Maxime; Lacroix, David [CNRS, LEMTA, UMR 7563, Vandoeuvre les Nancy (France); Lorraine Univ., Vandoeuvre les Nancy (France). LEMTA UMR 7563

    2017-05-01

    The majority of the silicon devices contain amorphous phase and amorphous/crystalline interfaces which both considerably affect the transport of energy carriers as phonons and electrons. In this article, we investigate the impact of amorphous phases (both amorphous silicon and amorphous SiO{sub 2}) of silicon nanoporous membranes on their thermal properties via molecular dynamics simulations. We show that a small fraction of amorphous phase reduces dramatically the thermal transport. One can even create nanostructured materials with subamorphous thermal conductivity, while keeping an important crystalline fraction. In general, the a-SiO{sub 2} shell around the pores reduces the thermal conductivity by a factor of five to ten compared to a-Si shell. The phonon density of states for several systems is also given to give the impact of the amorphisation on the phonon modes.

  19. Effect of Amorphisation on the Thermal Properties of Nanostructured Membranes

    Science.gov (United States)

    Termentzidis, Konstantinos; Verdier, Maxime; Lacroix, David

    2017-02-01

    The majority of the silicon devices contain amorphous phase and amorphous/crystalline interfaces which both considerably affect the transport of energy carriers as phonons and electrons. In this article, we investigate the impact of amorphous phases (both amorphous silicon and amorphous SiO2) of silicon nanoporous membranes on their thermal properties via molecular dynamics simulations. We show that a small fraction of amorphous phase reduces dramatically the thermal transport. One can even create nanostructured materials with subamorphous thermal conductivity, while keeping an important crystalline fraction. In general, the a-SiO2 shell around the pores reduces the thermal conductivity by a factor of five to ten compared to a-Si shell. The phonon density of states for several systems is also given to give the impact of the amorphisation on the phonon modes.

  20. Mechanosensitive channel properties and membrane mechanics in mouse dystrophic myotubes.

    Science.gov (United States)

    Suchyna, Thomas M; Sachs, Frederick

    2007-05-15

    Muscular dystrophy is associated with increased activity of mechanosensitive channels (MSCs) and increased cell calcium levels. MSCs in patches from mdx mouse myotubes have higher levels of resting activity, compared to patches from wild-type mice, and a pronounced latency of activation and deactivation. Measurements of patch capacitance and geometry reveal that the differences are linked to cortical membrane mechanics rather than to differences in channel gating. We found unexpectedly that patches from mdx mice are strongly curved towards the pipette tip by actin pulling normal to the membrane. This force produces a substantial tension (approximately 5 mN m(-1)) that can activate MSCs in the absence of overt stimulation. The inward curvature of patches from mdx mice is eliminated by actin inhibitors. Applying moderate suction to the pipette flattens the membrane, reducing tension, and making the response appear to be stretch inactivated. The pronounced latency to activation in patches from mdx mice is caused by the mechanical relaxation time required to reorganize the cortex from inward to outward curvature. The increased latency is equivalent to a three-fold increase in cortical viscosity. Disruption of the cytoskeleton by chemical or mechanical means eliminates the differences in kinetics and curvature between patches from wild-type and mdx mice. The stretch-induced increase in specific capacitance of the patch, approximately 80 fF microm(-2), far exceeds the specific capacitance of bilayers, suggesting the presence of stress-sensitive access to large pools of membrane, possibly caveoli, T-tubules or portions of the gigaseal. In mdx mouse cells the intrinsic gating property of fast voltage-sensitive inactivation is lost. It is robust in wild-type mouse cells (observed in 50% of outside-out patches), but never observed in mdx cells. This link between dystrophin and inactivation may lead to increased background cation currents and Ca2+ influx. Spontaneous Ca2

  1. Mimicking the cell membrane: bio-inspired simultaneous functions with monovalent anion selectivity and antifouling properties of anion exchange membrane

    Science.gov (United States)

    Zhao, Yan; Liu, Huimin; Tang, Kaini; Jin, Yali; Pan, Jiefeng; der Bruggen, Bart Van; Shen, Jiangnan; Gao, Congjie

    2016-11-01

    A new bio-inspired method was applied in this study to simultaneously improve the monovalent anion selectivity and antifouling properties of anion exchange membranes (AEMs). Three-layer architecture was developed by deposition of polydopamine (PDA) and electro-deposition of N-O-sulfonic acid benzyl chitosan (NSBC). The innermost and outermost layers were PDA with different deposition time. The middle layer was prepared by NSBC. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that PDA and NSBC were successfully modified on the surfaces of AEMs. The contact angle of the membranes indicated an improved hydrophilicity of the modified membranes. A series of electrodialysis experiments in which Cl‑/SO42‑ separation was studied, demonstrating the monovalent anion selectivity of the samples. The Cl‑/SO42‑ permselectivity of the modified membranes can reach up to 2.20, higher than that of the commercial membrane (only 0.78) during 90 minutes in electrodialysis (ED). The increase value of the resistance of the membranes was also measured to evaluate the antifouling properties. Sodium dodecyl benzene sulfonate (SDBS) was used as the fouling material in the ED process and the membrane area resistance of modified membrane increase value of was only 0.08 Ωcm2 30 minutes later.

  2. Analysis of the membrane proteome of ciprofloxacin-resistant macrophages by stable isotope labeling with amino acids in cell culture (SILAC.

    Directory of Open Access Journals (Sweden)

    Nancy E Caceres

    Full Text Available Overexpression of multidrug transporters is a well-established mechanism of resistance to chemotherapy, but other changes may be co-selected upon exposure to drugs that contribute to resistance. Using a model of J774 macrophages made resistant to the fluoroquinolone antibiotic ciprofloxacin and comparing it with the wild-type parent cell line, we performed a quantitative proteomic analysis using the stable isotope labeling with amino acids in cell culture technology coupled with liquid chromatography electrospray ionization Fourier transform tandem mass spectrometry (LC-ESI-FT-MS/MS on 2 samples enriched in membrane proteins (fractions F1 and F2 collected from discontinuous sucrose gradient. Nine hundred proteins were identified with at least 3 unique peptides in these 2 pooled fractions among which 61 (F1 and 69 (F2 showed a significantly modified abundance among the 2 cell lines. The multidrug resistance associated protein Abcc4, known as the ciprofloxacin efflux transporter in these cells, was the most upregulated, together with Dnajc3, a protein encoded by a gene located downstream of Abcc4. The other modulated proteins are involved in transport functions, cell adhesion and cytoskeleton organization, immune response, signal transduction, and metabolism. This indicates that the antibiotic ciprofloxacin is able to trigger a pleiotropic adaptative response in macrophages that includes the overexpression of its efflux transporter.

  3. Macrophage inducible nitric oxide synthase gene expression is blocked by a benzothiophene derivative with anti-HIV properties.

    Science.gov (United States)

    Carballo, M; Conde, M; Tejedo, J; Gualberto, A; Jimenez, J; Monteseirín, J; Santa María, C; Bedoya, F J; Hunt, S W; Pintado, E; Baldwin, A S; Sobrino, F

    2002-04-01

    Nitric oxide (NO) has been shown to mediate multiple physiological and toxicological functions. The inducible nitric oxide synthase (iNOS) is responsible for the high output generation of NO by macrophages following their stimulation by cytokines or bacterial antigens. The inhibition of TNF alpha-stimulated HIV expression and the anti-inflammatory property of PD144795, a new benzothiophene derivative, have been recently described. We have now analyzed whether some of these properties could be mediated by an effect of PD144795 on NO-dependent inflammatory events. We show that PD144795 suppresses the lipopolysaccharide-elicited production of nitrite (NO(-)(2)) by primary peritoneal mouse macrophages and by a macrophage-derived cell line, RAW 264.7. This effect was dependent on the dose and timing of addition of PD144795 to the cells. Suppression of NO(-)(2) production was associated with a decrease in the amount of iNOS protein, iNOS enzyme activity and mRNA expression. The effect of PD144795 was partially abolished by coincubation of the cells with LPS and IFN gamma. However, the inhibitory effect of PD144795 was not abrogated by the simultaneous addition of LPS and TNF alpha, which indirectly suggests that the effect of PD144795 was not due to the inhibition of TNF alpha synthesis. Additionally, PD144795 did not block NF-kappa B nuclear translocation induced by LPS. Inhibition of iNOS gene expression represents a novel mechanism of PD144795 action that underlines the anti-inflammatory effects of this immunosuppressive drug.

  4. Properties of soluble and particulate angiotensin-converting enzymes of rabbit lung, induced macrophage and serum.

    Science.gov (United States)

    Friedland, J; Silverstein, E

    1983-01-01

    Rabbit serum, lung and corticosteroid-induced macrophage angiotensin-converting enzymes were compared with respect to migration on polyacrylamide-gel electrophoresis, sucrose gradient centrifugation and Km. Cellular particulate enzymes solubilized by nonidet P40 had approximately half the electrophoretic mobility of soluble enzymes and a similar Km (1.2 mM). Trypsin treatment of nonidet P40 solubilized particulate enzyme converted its electrophoretic mobility to that of soluble enzyme, and rendered it non-aggregating in sucrose gradients lacking detergent, similar to soluble enzyme. Approximate molecular weights by sucrose gradient centrifugation were similar for all enzymes (135,000-158,000). The data suggest that lung and macrophage enzymes are similar and that cellular particulate enzyme may be convertible to soluble enzyme.

  5. Macrophages driven to a novel state of activation have anti-inflammatory properties in mice.

    Science.gov (United States)

    Brem-Exner, Beate G; Sattler, Christine; Hutchinson, James A; Koehl, Gudrun E; Kronenberg, Katharina; Farkas, Stefan; Inoue, Seiichiro; Blank, Christian; Knechtle, Stuart J; Schlitt, Hans J; Fändrich, Fred; Geissler, Edward K

    2008-01-01

    Recurrent episodes of inflammation underlie numerous pathologies, notably those of inflammatory bowel diseases. In this study, we describe a population of macrophages in a novel state of activation that mitigates colitis in mice. The cells responsible for this effect, called IFN-gamma-stimulated monocyte-derived cells (IFNgamma-MdC), derive from mouse spleen, blood, and bone marrow monocytes and are distinguished from known macrophage populations by mode of generation, cell surface phenotype, and function. IFNgamma-MdC only arise when macrophages are cultivated in the presence of CD40L-expressing CD4+ T cells, M-CSF, and IFN-gamma. IFNgamma-MdC express markers including F4/80, CD11b/c, CD86, and CD274; they are negative for CD4, CD8, Gr1, CD19, CD80, and CD207. Functionally, IFNgamma-MdC are defined by their capacity to enrich cocultured T cell populations for CD4+CD25+Foxp3+ regulatory cells; this enrichment, constituting up to 60% or more of residual lymphocytes, is attributed to an expansion, but also to a cell contact and caspase-dependent depletion of activated T cells. In mice, IFNgamma-MdC delivered i.v. traffic to gut-associated peripheral lymphoid tissues, including the mesenteric lymph nodes, Peyer's patches, and colonic mucosa, and promote the clinical and histological resolution of chronic colitis. We conclude that IFNgamma-MdC represent macrophages in a novel state of activation, possessing multiple T cell-suppressive effects with therapeutic potential for the treatment of autoimmune inflammation.

  6. Mycobacterium tuberculosis Chaperonin 10 Is Secreted in the Macrophage Phagosome: Is Secretion Due to Dissociation and Adoption of a Partially Helical Structure at the Membrane?

    Science.gov (United States)

    Fossati, Gianluca; Izzo, Gaetano; Rizzi, Emanuele; Gancia, Emanuela; Modena, Daniela; Moras, Maria Luisa; Niccolai, Neri; Giannozzi, Elena; Spiga, Ottavia; Bono, Letizia; Marone, Piero; Leone, Eugenio; Mangili, Francesca; Harding, Stephen; Errington, Neil; Walters, Christopher; Henderson, Brian; Roberts, Michael M.; Coates, Anthony R. M.; Casetta, Bruno; Mascagni, Paolo

    2003-01-01

    To confirm that Mycobacterium tuberculosis chaperonin 10 (Cpn10) is secreted outside the live bacillus, infected macrophages were examined by electron microscopy. This revealed that the mycobacterial protein accumulates both in the wall of the bacterium and in the matrix of the phagosomes in which ingested mycobacteria survive within infected macrophages. To understand the structural implications underlying this secretion, a structural study of M. tuberculosis Cpn10 was performed under conditions that are generally believed to mimic the membrane environment. It was found that in buffer-organic solvent mixtures, the mycobacterial protein forms two main species, namely, a partially helical monomer that prevails in dilute solutions at room temperature and a dimer that folds into a β-sheet-dominated structure and prevails in either concentrated protein solutions at room temperature or in dilute solutions at low temperature. A partially helical monomer was also found and was completely associated with negatively charged detergents in a micelle-bound state. Remarkably, zwitterionic lipids had no effect on the protein structure. By using N- and C-truncated forms of the protein, the C- and N-terminal sequences were identified as possessing an amphiphilic helical character and as selectively associating with acidic detergent micelles. When the study was extended to other chaperonins, it was found that human Cpn10 is also monomeric and partially helical in dilute organic solvent-buffer mixtures. In contrast, Escherichia coli Cpn10 is mostly dimeric and predominately β-sheet in both dilute and concentrated solutions. Interestingly, human Cpn10 also crosses biological membranes, whereas the E. coli homologue is strictly cytosolic. These results suggest that dissociation to partially helical monomers and interaction with acidic lipids may be two important steps in the mechanism of secretion of M. tuberculosis Cpn10 to the external environment. PMID:12837802

  7. Sludge Bulking Property of Membrane Bio-reactor in Albumen Wqastewater Treatment

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    Albumen wastewater was treated by Membrane Bio-reactor. Sludge bulking property of Membrane Bio-Reactor was investigated in this study through contrast research. When the sludge bulking appeared, the removal efficiency of COD in Membrane Bio-reactor increased slightly under the function of filamentous bacteria. However, the negative effects of the higher net water-head differential pressures,the higher block rate of membrane pore and the great quantity of filamentous bacteria at the externalsurface pres...

  8. Properties of chicken liver membrane-associated thiamine triphosphatase

    Directory of Open Access Journals (Sweden)

    I. K. Kolas

    2015-06-01

    Full Text Available The enzymes involved in thiamine triphosphate (ThTP metabolism in birds are not characteri­zed so far. The aim of the present work was to study some properties of ThTPase in chicken liver. In liver homogenate, ThTPase activity has been found to display a bell-like pH-profile with a maximum of 5.5-6.0. Low activity was observed without divalent metal ions, while the addition of Mg2+ or Ca2+, each at 5 mM concentration, enhanced the rate of ThTP hydrolysis by a factor of 17-20. In the presence of 5 mM Mg2+ an apparent Km of the enzyme for ThTP was estimated by the method of non-linear regression as well as from the Hanes plot to be 1.7-2.2 mM. Monovalent anions such as I–, SCN–, NO3–, Br–, Cl– (at 150 mM concentration showed inhibitory effect decreasing the rate of ThTPase reaction by 20-60%. After the homogenate was centrifuged, more than 85% of ThTPase activity was revealed in the fraction of insoluble particles indicating a membrane localization of the enzyme. The precipitate treatment with 1% sodium deoxycholate caused about 53% solubilization of the activity. During Toyopeal HW-55 chromatography, ThTPase activity was eluted simultaneously with ATPase and ITPase peaks in the void volume of the column. Thus, a non-specific high molecular mass protein complex seems to be involved in ThTP hydrolysis in the chicken liver. The chicken liver phosphatase is clearly distinguishable from all membrane-bound ThTPases reported previously.

  9. [PROPERTIES OF CHICKEN LIVER MEMBRANE-ASSOCIATED THIAMINE TRIPHOSPHATASE].

    Science.gov (United States)

    Kolas, I K; Makarchikov, A F

    2015-01-01

    The enzymes involved in thiamine triphosphate (ThTP) metabolism in birds are not characterized so far. The aim of the present work was to study some properties of ThTPase in chicken liver. In liver homogenate, ThTPase activity has been found to display a bell-like pH-profile with a maximum of 5.5-6.0. Low activity was observed without divalent metal ions, while the addition of Mg2+ or Ca2+, each at 5 mM concentration, enhanced the rate of ThTP hydrolysis by a factor of 17-20. In the presence of 5 mM Mg2+ an apparent K(m) of the enzyme for ThTP was estimated by the method of non-linear regression as well as from the Hanes plot to be 1.7-2.2 mM. Monovalent anions such as I-, SCN-, NO3-, Br-, Cl- (at 150 mM concentration) showed inhibitory effect decreasing the rate of ThTPase reaction by 20-60%. After the homogenate was centrifuged, more than 85% of ThTPase activity was revealed in the fraction of insoluble particles indicating a membrane localization of the enzyme. The precipitate treatment with 1% sodium deoxycholate caused about 53% solubilization of the activity. During Toyopeal HW-55 chromatography, ThTPase activity was eluted simultaneously with ATPase and ITPase peaks in the void volume of the column. Thus, a non-specific high molecular mass protein complex seems to be involved in ThTP hydrolysis in the chicken liver. The chicken liver phosphatase is clearly distinguishable from all membrane-bound ThTPases reported previously.

  10. Comparative acoustic performance and mechanical properties of silk membranes for the repair of chronic tympanic membrane perforations.

    Science.gov (United States)

    Allardyce, Benjamin J; Rajkhowa, Rangam; Dilley, Rodney J; Xie, Zhigang; Campbell, Luke; Keating, Adrian; Atlas, Marcus D; von Unge, Magnus; Wang, Xungai

    2016-12-01

    The acoustic and mechanical properties of silk membranes of different thicknesses were tested to determine their suitability as a repair material for tympanic membrane perforations. Membranes of different thickness (10-100μm) were tested to determine their frequency response and their resistance to pressure loads in a simulated ear canal model. Their mechanical rigidity to pressure loads was confirmed by tensile testing. These membranes were tested alongside animal cartilage, currently the strongest available myringoplasty graft as well as paper, which is commonly used for simpler procedures. Silk membranes showed resonant frequencies within the human hearing range and a higher vibrational amplitude than cartilage, suggesting that silk may offer good acoustic energy transfer characteristics. Silk membranes were also highly resistant to simulated pressure changes in the middle ear, suggesting they can resist retraction, a common cause of graft failure resulting from chronic negative pressures in the middle ear. Part of this strength can be explained by the substantially higher modulus of silk films compared with cartilage. This allows for the production of films that are much thinner than cartilage, with superior acoustic properties, but that still provide the same level of mechanical support as thicker cartilage. Together, these in vitro results suggest that silk membranes may provide good hearing outcomes while offering similar levels of mechanical support to the reconstructed middle ear.

  11. Structure and Properties of Polytetrafluorethylene and Polyurethane Layered Membrane for Protective Clothing

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper presents a new idea for intensifying protective and stretch recovery properties of micro porous polytetrafluorethylene and hydrophilic polyurethane (PTFE/PU) layered membrane through a co-stretching process. The structure and properties of co-stretching PTFE/PU layered membrane and coated PTFE/PU layered membrane by means of directly coating the PU on the PTFE membrane were investigated using Electron Microscope, Universal Materials Testing Machine, and the water vapor permeability (WVP) was measured according to absorption method of water vapor of GB/T 12704 - 91. Contrasted to PU coating process, the PU membrane on the co-stretching PTFE/PU membrane is nonporous because of heat treatment process, which can prevent the SARS virus from permeating the Co-stretching PTFE/PU membrane. The stretch and recovery properties of the Co-stretching PTFE/PU membrane is at least 66% after being stretched to 50% of its original length in transverse directions and that of the coated PTFE/PU membrane is 52%. The WVP of the Coresults suggest that when Co-stretching PTFE/PU membrane is laminated to a stretchable fabric, the fabric would have excellent stretch and recovery properties while waterproof and being permeable to water vapor. So, the Costretching PTFE/PU membrane laminated fabric will be a comfortable protective clothing material.

  12. Membrane binding properties of EBV gp110 C-terminal domain; evidences for structural transition in the membrane environment.

    Science.gov (United States)

    Park, Sung Jean; Seo, Min-Duk; Lee, Suk Kyeong; Lee, Bong Jin

    2008-09-30

    Gp110 of Epstein-Barr virus (EBV) mainly localizes on nuclear/ER membranes and plays a role in the assembly of EBV nucleocapsid. The C-terminal tail domain (gp110 CTD) is essential for the function of gp110 and the nuclear/ER membranes localization of gp110 is ruled by its C-terminal unique nuclear localization signal (NLS), consecutive four arginines. In the present study, the structural properties of gp110 CTD in membrane mimics were investigated using CD, size-exclusion chromatography, and NMR, to elucidate the effect of membrane environment on the structural transition and to compare the structural feature of the protein in the solution state with that of the membrane-bound form. CD and NMR analysis showed that gp110 CTD in a buffer solution appears to adopt a stable folding intermediate which lacks compactness, and a highly helical structure is formed only in membrane environments. The helical content of gp110 CTD was significantly affected by the negative charge as well as the size of membrane mimics. Based on the elution profiles of the size-exclusion chromatography, we found that gp110 CTD intrinsically forms a trimer, revealing that a trimerization region may exist in the C-terminal domain of gp110 like the ectodomain of gp110. The mutation of NLS (RRRR) to RTTR does not affect the overall structure of gp110 CTD in membrane mimics, while the helical propensity in a buffer solution was slightly different between the wild-type and the mutant proteins. This result suggests that not only the helicity induced in membrane environment but also the local structure around NLS may be related to trafficking to the nuclear membrane. More detailed structural difference between the wild-type and the mutant in membrane environment was examined using synthetic two peptides including the wild-type NLS and the mutant NLS.

  13. Evaluation of transport properties of nanofiltration membranes exposed to radioactive liquid waste

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Elizabeth E.M.; Barbosa, Celina C.R.; Bastos, Edna T.R., E-mail: eemo@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeira, RJ (Brazil); Afonso, Julio C., E-mail: Julio@iq.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Quimica. Dept. de Quimica Analitica

    2011-07-01

    The application of membrane separation processes (PSM) for treatment of radioactive waste requires the selection of a suitable membrane for the treatment of waste, as the membrane will be directly exposed to the radioactive liquid waste, and also exposed to ionizing radiation. The nanofiltration membrane is most suitable for treatment of radioactive waste, since it has high rejection of multivalent ions. Usually the membranes are made of polymers and depending on the composition of the waste, type and dose of radiation absorbed may be changes in the structure of the membrane, resulting in loss of its transport properties. We tested two commercial nanofiltration membranes: NF and SW Dow/Filmtec. The waste liquid used was obtained in the process of conversion of uranium hexafluoride gas to solid uranium dioxide, known as 'carbonated water'. The membranes were characterized as their transport properties (hydraulic permeability, permeate flux and salt rejection) before and after their immersion in the waste for 24 hours. The surface of the membranes was also evaluated by SEM and FTIR. It was observed that in both the porosity of the membrane selective layer was altered, but not the membrane surface charge, which is responsible for the selectivity of the membrane. The NF membranes and SW showed uranium ion rejection of 64% and 55% respectively. (author)

  14. Surface Properties and Permeability of Poly(Vinylidene Fluoride)-Clays (PVDF/Clays) Composite Membranes

    Science.gov (United States)

    Pramono, E.; Ahdiat, M.; Simamora, A.; Pratiwi, W.; Radiman, C. L.; Wahyuningrum, D.

    2017-07-01

    Surface properties are important factors that determine the performance of ultrafiltration membranes. This study aimed to investigate the effects of clay addition on the surface properties and membrane permeability of PVDF (poly-vinylidene fluoride) membranes. Three types of clay with different particle size were used in this study, namely montmorillonite-MMT, bentonite-BNT and cloisite 15A-CLS. The PVDF-clay composite membranes were prepared by phase inversion method using PEG as additive. The hydrophobicity of membrane surface was characterized by contact angle. The membrane permeability was determined by dead- end ultrafiltration with a trans-membrane pressure of 2 bars. In contact angle measurement, water contact angle of composite membranes is higher than PVDF membrane. The addition of clays decreased water flux but increased of Dextran rejection. The PVDF-BNT composite membranes reach highest Dextran rejection value of about 93%. The type and particle size of clay affected the hydrophobicity of membrane surface and determined the resulting membrane structure as well as the membrane performance.

  15. How To Functionalize Ceramics by Perfluoroalkylsilanes for Membrane Separation Process? Properties and Application of Hydrophobized Ceramic Membranes.

    Science.gov (United States)

    Kujawa, Joanna; Cerneaux, Sophie; Kujawski, Wojciech; Bryjak, Marek; Kujawski, Jan

    2016-03-23

    The combination of microscopic (atomic force microscopy and scanning electron microscopy) and goniometric (static and dynamic measurements) techniques, and surface characterization (surface free energy determination, critical surface tension, liquid entry pressure, hydraulic permeability) was implemented to discuss the influence of perfluoroalkylsilanes structure and grafting time on the physicochemistry of the created hydrophobic surfaces on the titania ceramic membranes of 5 kD and 300 kD. The impact of molecular structure of perfluoroalkylsilanes modifiers (possessing from 6 to 12 carbon atoms in the fluorinated part of the alkyl chain) and the time of the functionalization process in the range of 5 to 35 h was studied. Based on the scanning electron microscopy with energy-dispersive X-ray spectroscopy, it was found that the localization of grafting molecules depends on the membrane pore size (5 kD or 300 kD). In the case of 5 kD titania membranes, modifiers are attached mainly on the surface and only partially inside the membrane pores, whereas, for 300 kD membranes, the perfluoroalkylsilanes molecules are present within the whole porous structure of the membranes. The application of 4 various types of PFAS molecules enabled for interesting observations and remarks. It was explained how to obtain ceramic membrane surfaces with controlled material (contact angle, roughness, contact angle hysteresis) and separation properties. Highly hydrophobic surfaces with low values of contact angle hysteresis and low roughness were obtained. These surfaces possessed also low values of critical surface tension, which means that surfaces are highly resistant to wetting. This finding is crucial in membrane applicability in separation processes. The obtained and characterized hydrophobic membranes were subsequently applied in air-gap membrane distillation processes. All membranes were very efficient in MD processes, showing good transport and selective properties (∼99% of Na

  16. Properties of casting solutions and ultrafiltration membranes based on fullerene-polyamide nanocomposites

    Directory of Open Access Journals (Sweden)

    N. N. Sudareva

    2012-03-01

    Full Text Available Poly(phenylene isophtalamide (PA was modified by fullerene C60 using solid-phase method. Novel ultrafiltration membranes based on nanocomposites containing up to 10 wt% of fullerene and carbon black were prepared. Properties of PA/C60 composites in solutions were studied by light scattering and rheological methods. The relationship between characteristics of casting solutions and properties of nanocomposite membranes was studied. Scanning electron microscopy was used for structural characterization of the membranes. It was found that increase in fullerene content in nanocomposite enhances the membrane rigidity. All nanocomposite membranes were tested in dynamic (ultrafiltration and static sorption experiments using a solution of protein mixture, with the purpose of studying protein sorption. The membranes modified by fullerene demonstrate the best values of flux reduced recovery after contact with protein solution. It was found that addition of fullerene C60 to the polymer improves technological parameters of the obtained composite membranes.

  17. Preparation and characterization of polystyrene based Nickel molybdate composite membrane electrical–electrochemical properties

    Directory of Open Access Journals (Sweden)

    Urfi Ishrat

    2016-09-01

    Full Text Available The functional properties of the polystyrene based Nickel Molybdate composite membrane prepared by applying 70 MPa pressure are described. The fabricated membrane was characterized by using Fourier Transform Infrared, X-ray diffraction, particle size analyzer and Scanning electron microscopy technique and has been investigated for its functional, diffusive, electrochemical and electrical properties. The impedance data of membrane having capacitive and resistive components are plotted, which show the sequence of semicircles representing an electrical phenomenon due to grain material, grain boundary and interfacial phenomenon. The diffusion of electrolytes was determined by the TMS method revealing dependence of membrane potential on the charge on the membrane matrix, charge and size of permeating ions. The membrane determined the activity of cations with good accuracy in the higher concentration range and shows a great selectivity for K+. Other electrochemical properties like transport number have been discussed its selectivity.

  18. Rheological properties of poly(vinyl alcohol) (PVA) derived composite membranes for fuel cells

    Science.gov (United States)

    Remiš, T.

    2017-01-01

    Rheological properties of new anhydrous proton conducting membrane based on PVA, tetraethyl orthosilicate (TEOS),sulfosuccinic acid (SSA), titanium dioxide (TiO2)was examined at various stoichiometric ratios. SSA was used as sulfonating agents to form a crosslinked structure and as proton source, whereas TEO Sand TiO2were utilized to improve the thermal and mechanical properties of the membrane. In order to verify that all the substances were immobilized into the matrix, the membranes were analysed by means of FT-IR. The rheological, mechanical and thermal properties of the membranes were investigated using rheometer ARES G2 and thermogravimetic analyser (TGA).The analysis of mixed PVA solutions exhibited a unique behaviour of viscosity with increased crosslink density. The dynamic storage modulus G´ of dried composite membranes shows better mechanical resistance and increased tolerance to pressure applied during membrane electrode assembly (MEA).

  19. Hydrophilicity and antifouling property of membrane materials from cellulose acetate/polyethersulfone in DMAc.

    Science.gov (United States)

    Sun, Zhonghua; Chen, Fushan

    2016-10-01

    In this study, cellulose acetate (CA) was blended with polyethersulfone (PES) to endow the ultrafiltration membrane with the improved hydrophilicity and antifouling property by using N,N-dimethylacetamide (DMAc) as the solvent. The effects of blend composition and evaporation time on the mechanical strength and pure water flux were investigated. It was found that the optimal composition of the casting solution was: 18wt% (PES), 4wt% (Polyvinylpyrrolidone K30), 3wt% (CA) and 20s (Evaporation time). The characteristics of CA-PES blend membranes were investigated through the methods of contact angle goniometer, antifouling property, compatibility, thermo gravimetric analysis and SEM. The results showed that the hydrophilicity and antifouling property of CA-PES ultrafiltration membranes were enhanced in comparison with the pure PES membranes. The CA-PES membranes exhibited semi-compatibility and good thermal stability below 270°C. This study provided a potential industrial application prospect of CA-PES membranes prepared in DMAc.

  20. Reciprocal bystander effect between α-irradiated macrophage and hepatocyte is mediated by cAMP through a membrane signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    He, Mingyuan [Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai 200032 (China); Department of Radiation Oncology, China–Japan Union Hospital of Jilin University, Changchun 130033 (China); Dong, Chen; Xie, Yuexia; Li, Jitao; Yuan, Dexiao; Bai, Yang [Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai 200032 (China); Shao, Chunlin, E-mail: clshao@shmu.edu.cn [Institute of Radiation Medicine, Fudan University, No. 2094 Xie-Tu Road, Shanghai 200032 (China)

    2014-05-15

    Highlights: • α-Irradiation induced reciprocal effects between macrophage and hepatocyte cells. • cAMP played a protective role in regulating the reverse bystander effect. • cAMP communication contributed to the reciprocal effects via membrane signaling. • p53 was required for cAMP-regulated bystander effect in the recipient cells. - Abstract: Irradiated cells can induce biological effects on vicinal non-irradiated bystander cells, meanwhile the bystander cells may rescue the irradiated cells through a feedback signal stress. To elucidate the nature of this reciprocal effect, we examined the interaction between α-irradiated human macrophage cells U937 and its bystander HL-7702 hepatocyte cells using a cell co-culture system. Results showed that after 6 h of cell co-culture, mitochondria depolarization corresponding to apoptosis was significantly induced in the HL-7702 cells, but the formation of micronuclei in the irradiated U937 cells was markedly decreased compared to that without cell co-culture treatment. This reciprocal effect was not observed when the cell membrane signaling pathway was blocked by filipin that inhibited cAMP transmission from bystander cells to irradiated cells. After treatment of cells with exogenous cAMP, forskolin (an activator of cAMP) or KH-7 (an inhibitor of cAMP), respectively, it was confirmed that cAMP communication from bystander cells to targeted cells could mitigate radiation damage in U739 cells, and this cAMP insufficiency in the bystander cells contributed to the enhancement of bystander apoptosis. Moreover, the bystander apoptosis in HL-7702 cells was aggravated by cAMP inhibition but it could not be evoked when p53 of HL-7702 cells was knocked down no matter of forskolin and KH-7 treatment. In conclusion, this study disclosed that cAMP could be released from bystander HL-7702 cells and compensated to α-irradiated U937 cells through a membrane signaling pathway and this cAMP communication played a profound role in

  1. Berteroin Present in Cruciferous Vegetables Exerts Potent Anti-Inflammatory Properties in Murine Macrophages and Mouse Skin

    Directory of Open Access Journals (Sweden)

    Yoo Jin Jung

    2014-11-01

    Full Text Available Berteroin (5-methylthiopentyl isothiocyanate is a sulforaphane analog present in cruciferous vegetables, including Chinese cabbage, rucola salad leaves, and mustard oil. We examined whether berteroin exerts anti-inflammatory activities using lipopolysaccharide (LPS-stimulated Raw 264.7 macrophages and 12-O-tetradecanoylphorbol-13-acetate (TPA-induced mouse skin inflammation models. Berteroin decreased LPS-induced release of inflammatory mediators and pro-inflammatory cytokines in Raw 264.7 macrophages. Berteroin inhibited LPS-induced degradation of inhibitor of κBα (IκBα and nuclear factor-κB p65 translocation to the nucleus and DNA binding activity. Furthermore, berteroin suppressed degradation of IL-1 receptor-associated kinase and phosphorylation of transforming growth factor β activated kinase-1. Berteroin also inhibited LPS-induced phosphorylation of p38 MAPK, ERK1/2, and AKT. In the mouse ear, berteroin effectively suppressed TPA-induced edema formation and down-regulated iNOS and COX-2 expression as well as phosphorylation of AKT and ERK1/2. These results demonstrate that berteroin exhibits potent anti-inflammatory properties and suggest that berteroin can be developed as a skin anti-inflammatory agent.

  2. Preparation of hydrophilic vinyl chloride copolymer hollow fiber membranes with antifouling properties

    Science.gov (United States)

    Rajabzadeh, Saeid; Sano, Rie; Ishigami, Toru; Kakihana, Yuriko; Ohmukai, Yoshikage; Matsuyama, Hideto

    2015-01-01

    Hydrophilic vinyl chloride copolymer hollow fiber membranes with antifouling properties were prepared from brominated vinyl chloride-hydroxyethyl methacrylate copolymer (poly(VC-co-HEMA-Br)). The base membrane was grafted with two different zwitterionic monomers, (2-methacryloyloxyethylphosphorylcholine) (MPC) and [2-(methacryloyloxy) ethyl] dimethyl (3-sulfopropyl) ammonium hydroxide) (MEDSAH), and poly(ethylene glycol) methyl ether methacrylate (PEGMA). The effect of the grafting on the base membrane hydrophilicity and antifouling properties was investigated. For comparison of the results, the pure water permeabilities and pore sizes at the outer surfaces of the grafted hollow fiber membranes were controlled to be similar. A poly(VC-co-HEMA-Br) hollow fiber membrane with similar pure water permeability and pore size was also prepared as a control membrane. A BSA solution was used as a model fouling solution for evaluation of the antifouling properties. Grafting with zwitterionic monomers and PEGMA improved the antifouling properties compared with the control membrane. The PEGMA grafted membrane showed the best antifouling properties among the grafted membranes

  3. Active principles of Grindelia robusta exert antiinflammatory properties in a macrophage model.

    Science.gov (United States)

    La, Vu Dang; Lazzarin, Francesco; Ricci, Donata; Fraternale, Daniele; Genovese, Salvatore; Epifano, Francesco; Grenier, Daniel

    2010-11-01

    Plant extracts and/or secondary metabolites are receiving considerable attention as therapeutic agents for treating inflammatory diseases such as periodontitis, which affects the tooth supporting tissues. The aim of this study was to investigate the effect of a Grindelia robusta extract enriched in saponins and polyphenols on Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS)-induced inflammatory mediator (IL-6, TNF-a, RANTES, MCP-1, PGE(2) ) and matrix metalloproteinase (MMP-1, -3, -7, -8, -9, -13) secretion by macrophages. LPS induced a marked increase in the secretion of all inflammatory mediators and MMPs tested by macrophages, as determined by enzyme-linked immunosorbent assays. At non-cytotoxic concentrations, the G. robusta extract inhibited dose-dependently the secretion of IL-6, RANTES, MCP-1 and, to a lesser extent, PGE(2) and TNF-a. Such inhibition was also observed for MMP-1, -3, -7, -8, -9 and -13 secretion. This ability of G. robusta extract to reduce the LPS-induced secretion of inflammatory mediators and MMPs was associated with a reduction of nuclear factor-kappa B (NF-kB) p65 activation. The results suggest that G. robusta extract possesses an antiinflammatory therapeutic potential through its capacity to reduce the accumulation of inflammatory mediators and MMPs.

  4. Preparation Methods and Properties of PdCu Alloy Membrane for Hydrogen Transition

    Institute of Scientific and Technical Information of China (English)

    SUN Xiaoliang; MA Guang; LI Jin; ZHANG Ke

    2012-01-01

    Pd and Pd alloy membranes are of increasing interest for hydrogen separation and purification due to their good thermal stability,high permeability and perfect selectivity.PdCu alloy (60wt% Pd) membranes have similar hydrogen permeability compared with PdAg alloy; meanwhile,it is cheaper than PdAg alloy.Furthermore,it has been reported that PdCu membrane has better resistance to poisoning and deactivation by H2S impurity.This paper reviews the properties and manufacturing methods of PdCu alloy membrane,finally,introduced some achievement made by us on PdCu alloy membrane.

  5. Preparation and Properties of Hydrothermally Stable γ-Alumina Membranes

    NARCIS (Netherlands)

    Nijmeijer, Arian; Kruidhof, Henk; Bredesen, Rune; Verweij, Henk

    2001-01-01

    Supported mesoporous γ-Al2O3 membranes deteriorate and blister in steam-containing environments at high temperatures. This deterioration led us to the development of a new type of supported γ-Al2O3 membrane with significantly improved stability under hostile conditions. Two measures were taken to ac

  6. A new concept in polymeric thin-film composite nanofiltration membranes with antibacterial properties.

    Science.gov (United States)

    Mollahosseini, Arash; Rahimpour, Ahmad

    2013-01-01

    A new, thin film, biofouling resistant, nanofiltration (NF) membrane was fabricated with two key characteristics, viz. a low rate of silver (Ag) release and long-lasting antibacterial properties. In the new approach, nanoparticles were embedded completely in a polymeric thin-film layer. A comparison was made between the new thin-film composite (TFC), NF membrane and thin-film nanocomposite (TFN), and antibacterial NF membranes. Both types of NF membrane were fabricated by interfacial polymerization on a polysulphone sublayer using m-phenylenediamine and trimesoyl chloride as an amine monomer and an acid chloride monomer, respectively. Energy dispersive X-ray (EDX) microanalysis demonstrated the presence of Ag nanoparticles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the cross-sectional and surface morphological properties of the NF membranes. Permeability and salt rejection were tested using a dead-end filtration cell. Ag leaching from the membranes was measured using inductively coupled mass spectrometry (ICP-MS). Morphological studies showed that the TFC NF membranes had better thin-film formation (a more compact structure and a smoother surface) than TFN NF membranes. Performance experiments on TFC NF membranes revealed that permeability was good, without sacrificing salt rejection. The antibacterial properties of the fabricated membranes were tested using the disk diffusion method and viable plate counts. The antibiofouling properties of the membranes were examined by measuring the quantity of bacterial cells released from the biofilm formed (as a function of the amount of biofilm present). A more sensitive surface was observed compared to that of a typical antibacterial NF membrane. The Ag leaching rates were low, which will likely result in long-lasting antibacterial and biofouling resistant properties.

  7. Magnetic properties of the magnetic hybrid membranes based on various polymer matrices and inorganic fillers

    Energy Technology Data Exchange (ETDEWEB)

    Rybak, Aleksandra, E-mail: Aleksandra.Rybak@polsl.pl [Department of Physical Chemistry and Technology of Polymers, Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Kaszuwara, Waldemar [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warszawa (Poland)

    2015-11-05

    Magnetic hybrid membranes based on ethylcellulose (EC), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and various magnetic praseodymium and neodymium powder microparticles as fillers were obtained. Permeability, diffusion and sorption coefficients of O{sub 2}, N{sub 2} and synthetic air components were estimated for homogeneous and heterogeneous membranes using the Time Lag method based on constant pressure permeation technique. The microstructure studies and the phase analysis of magnetic membranes were also performed using SEM and XRD. The influence of magnetic parameters, like coercivity, remanence and saturation magnetization of created membranes on the gas transport properties was studied. The results showed that their coercivity depended on composition and microstructure of the magnetic powder. On the other hand, remanence and saturation magnetization increased with the increase of the powder addition in the membrane. It was found that the magnetic membrane's gas transport properties were improved with the increase of membrane's remanence, saturation magnetization and magnetic particle filling. The decrease in powder particle size and associated increase of the membrane's coercivity also positively influenced the gas transport and separation properties of investigated membranes. It was observed that the magnetic ethylcellulose and poly(2,6-dimethyl-1,4-phenylene oxide) membranes had higher gas permeability, while their permselectivity and solubility coefficient values were rather maintained or slightly increased. The results also showed that the magnetic powder content enhanced significantly gas diffusivity in EC and PPO membranes. It was also analyzed the dependence of the drift coefficient w on the magnetic parameters of investigated membranes. The correlation between the membrane selectivity, permeability and magnetic properties with their XRD characteristics was stated. - Highlights: • Membrane's production consisting of EC or PPO

  8. Mechanical, thermal and swelling properties of phosphorylated nanocellulose fibrils/PVA nanocomposite membranes.

    Science.gov (United States)

    Niazi, Muhammad Bilal Khan; Jahan, Zaib; Berg, Sigrun Sofie; Gregersen, Øyvind Weiby

    2017-12-01

    Cellulose nanofibrils (CNF) have strong reinforcing properties when incorporated in a compatible polymer matrix. This work reports the effect of the addition of phosphorylated nanocellulose (PCNF) on the mechanical, thermal and swelling properties of poly(vinyl alcohol) (PVA) nanocomposite membranes. The incorporation of nanocellulose in PVA reduced the crystallinity at 0%RH. However, when the films were exposed to higher humidities the crystallinity increased. No apparent trend is observed for mechanical properties for dry membranes (0% RH). However, at 93% RH the elastic modulus increased strongly from 0.12MPa to 0.82MPa when adding 6% PCNF. At higher humidities, the moisture uptake has large influence on storage modulus, tan δ and tensile properties. Membranes containing 1% PCNF absorbed most moisture. Swelling, thermal and mechanical properties indicate a good potential for applying of PVA/phosphorylated nanocellulose composite membranes for CO2 separation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Water adsorption properties controlled by coating/filling ordered mesoporous silica inside cellulose membranes.

    Science.gov (United States)

    Kimura, Tatsuo

    2013-09-28

    Porous organic membranes have been utilized as hard templates not only for replication of porous macrostructures but also for fabrication of hierarchical porous solids through infiltration of precursor solutions in ordered mesoporous materials. However, such organic membranes are usually burned out as sacrificial skeletons by calcination. In addition, replicated macropores are too big to enhance properties due to inorganic oxide frameworks. In this study, when cellulose membranes were used as organic membranes, a coating/filling technology of ordered mesoporous silicas was proposed and the water adsorption-desorption properties were directly investigated by using the composite membranes after extraction of nonionic surfactants used. The composite membranes possessed enough adsorption capacity for water, which will be potentially useful for improving total energy efficiency in heat-pump and desiccant air conditioning systems.

  10. Restoration of IFNγR subunit assembly, IFNγ signaling and parasite clearance in Leishmania donovani infected macrophages: role of membrane cholesterol.

    Directory of Open Access Journals (Sweden)

    Subha Sen

    2011-09-01

    Full Text Available Despite the presence of significant levels of systemic Interferon gamma (IFNγ, the host protective cytokine, Kala-azar patients display high parasite load with downregulated IFNγ signaling in Leishmania donovani (LD infected macrophages (LD-MØs; the cause of such aberrant phenomenon is unknown. Here we reveal for the first time the mechanistic basis of impaired IFNγ signaling in parasitized murine macrophages. Our study clearly shows that in LD-MØs IFNγ receptor (IFNγR expression and their ligand-affinity remained unaltered. The intracellular parasites did not pose any generalized defect in LD-MØs as IL-10 mediated signal transducer and activator of transcription 3 (STAT3 phosphorylation remained unaltered with respect to normal. Previously, we showed that LD-MØs are more fluid than normal MØs due to quenching of membrane cholesterol. The decreased rigidity in LD-MØs was not due to parasite derived lipophosphoglycan (LPG because purified LPG failed to alter fluidity in normal MØs. IFNγR subunit 1 (IFNγR1 and subunit 2 (IFNγR2 colocalize in raft upon IFNγ stimulation of normal MØs, but this was absent in LD-MØs. Oddly enough, such association of IFNγR1 and IFNγR2 could be restored upon liposomal delivery of cholesterol as evident from the fluorescence resonance energy transfer (FRET experiment and co-immunoprecipitation studies. Furthermore, liposomal cholesterol treatment together with IFNγ allowed reassociation of signaling assembly (phospho-JAK1, JAK2 and STAT1 in LD-MØs, appropriate signaling, and subsequent parasite killing. This effect was cholesterol specific because cholesterol analogue 4-cholestene-3-one failed to restore the response. The presence of cholesterol binding motifs [(L/V-X(1-5-Y-X(1-5-(R/K] in the transmembrane domain of IFNγR1 was also noted. The interaction of peptides representing this motif of IFNγR1 was studied with cholesterol-liposome and analogue-liposome with difference of two orders of

  11. Molecular dynamics simulations of lipid membranes with lateral force: rupture and dynamic properties.

    Science.gov (United States)

    Xie, Jun Yu; Ding, Guang Hong; Karttunen, Mikko

    2014-03-01

    Membranes' response to lateral tension, and eventual rupture, remains poorly understood. In this study, pure dipalmitoylphosphatidylcholine (DPPC) lipid bilayers, under tension/pressure, were studied using molecular dynamics (MD) simulations. The irreversible membrane breakdown is demonstrated to depend on the amplitude of lateral tension, loading rate, and the size of the bilayer. In all of our simulations, -200bar lateral pressure was found to be enough to rupture lipid membrane regardless of the loading rate or the membrane size. Loading rate and membrane size had a significant impact on rupture. A variety of dynamic properties of lipid molecules, probability distribution of area per lipid particularly, have been determined, and found to be fundamental for describing membrane behavior in detail, thus providing the quantitative description for the requirement of membrane rupture.

  12. The Potential of α-Spinasterol to Mimic the Membrane Properties of Natural Cholesterol.

    Science.gov (United States)

    Haralampiev, Ivan; Scheidt, Holger A; Huster, Daniel; Müller, Peter

    2017-08-22

    Sterols play a unique role for the structural and dynamical organization of membranes. The current study reports data on the membrane properties of the phytosterol (3β,5α,22E)-stigmasta-7,22-dien-3-β-ol (α-spinasterol), which represents an important component of argan oil and have not been investigated so far in molecular detail. In particular, the impact of α-spinasterol on the structure and organization of lipid membranes was investigated and compared with those of cholesterol. Various membrane parameters such as the molecular packing of the phospholipid fatty acyl chains, the membrane permeability toward polar molecules, and the formation of lateral membrane domains were studied. The experiments were performed on lipid vesicles using methods of NMR spectroscopy and fluorescence spectroscopy and microscopy. The results show that α-spinasterol resembles the membrane behavior of cholesterol to some degree.

  13. Mechanics and dynamics of triglyceride-phospholipid model membranes: Implications for cellular properties and function.

    Science.gov (United States)

    Pakkanen, Kirsi I; Duelund, Lars; Qvortrup, Klaus; Pedersen, Jan S; Ipsen, John H

    2011-08-01

    We demonstrate here that triolein alters the mechanical properties of phospholipid membranes and induces extraordinary conformational dynamics. Triolein containing membranes exhibit fluctuations up to size range of 100μm and with the help of these are e.g. able to squeeze through narrow passages between neighbouring structures. Triolein-phosphatidylcholine membranes were found to have bending rigidity significantly lower than that of corresponding pure phosphatidylcholine membrane. Moreover, the triolein containing membranes were found to be reluctant to fuse, which is in good accordance with larger lamellar distances observed in the TOPOPC membranes. These findings suggest repulsion between adjacent membranes. We provide a comprehensive discussion on the possible explanations for the observed mechanics and dynamics in the TOPOPC system and on their potential cellular implications. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Application of Nano PAC on Mitigating Membrane Fouling by Surface Properties Optimization

    Directory of Open Access Journals (Sweden)

    Mi Hairong

    2016-01-01

    Full Text Available Membrane material has been widely accepted owing to the ability in water treatment, but the membrane fouling problem in using process is seriously restricted the promotion of membrane technology. So in this research nano PAC flocculant is added into the raw water to reach the goals of strengthening treatment efficiency and mitigating membrane fouling. According to the TMP change, it results that the PAC dosage of 45mg/L can realize the purpose to mitigate membrane fouling best. Compared with MBR, the MCBR is 16 days tardiness at the change of TMP, 1/3 gel layer filtration resistance less and 3.5% C element content fewer. The sum of C, O and N elements content, in addition, in the gel layer pollutants is more than 95%. That means membrane pollution is mainly caused by organic matter and nano PAC has the effect on surface properties optimization and membrane fouling mitigating.

  15. Carbon Nanotube Membranes: Synthesis, Properties, and Future Filtration Applications

    Science.gov (United States)

    Rashid, Md. Harun-Or; Ralph, Stephen F.

    2017-01-01

    Over the course of the past decade, there has been growing interest in the development of different types of membranes composed of carbon nanotubes (CNTs), including buckypapers and composite materials, for an ever-widening range of filtration applications. This article provides an overview of how different types of CNT membranes are prepared and the results obtained from investigations into their suitability for different applications. The latter involve the removal of small particles from air samples, the filtration of aqueous solutions containing organic compounds and/or bacteria, and the separation of individual liquids present in mixtures. A growing number of reports have demonstrated that the incorporation of CNTs into composite membranes confers an improved resistance to fouling caused by biomacromolecules and bacteria. These results are discussed, along with evidence that demonstrates it is possible to further reduce fouling by taking advantage of the inherent conductivity of composite membranes containing CNTs, as well as by using different types of electrochemical stimuli. PMID:28468314

  16. The membrane expression of Neisseria meningitidis adhesin A (NadA) increases the proimmune effects of MenB OMVs on human macrophages, compared with NadA- OMVs, without further stimulating their proinflammatory activity on circulating monocytes.

    Science.gov (United States)

    Tavano, Regina; Franzoso, Susanna; Cecchini, Paola; Cartocci, Elena; Oriente, Francesca; Aricò, Beatrice; Papini, Emanuele

    2009-07-01

    Hypervirulent MenB causing fatal human infections frequently display the oligomeric-coiled coil adhesin NadA, a 45-kDa intrinsic outer membrane protein implicated in binding to and invasion of respiratory epithelial cells. A recombinant soluble mutant lacking the 10-kDa COOH terminal membrane domain (NadA(Delta351-405)) also activates human monocytes/macrophages/DCs. As NadA is physiologically released during sepsis as part of OMVs, in this study, we tested the hypothesis that NadA(+) OMVs have an enhanced or modified proinflammatory/proimmune action compared with NadA(-) OMVs. To do this we investigated the activity of purified free NadA(Delta351-405) and of OMVs from MenB and Escherichia coli strains, expressing or not full-length NadA. NadA(Delta351-405) stimulated monocytes and macrophages to secrete cytokines (IL-1beta, TNF-alpha, IL-6, IL-12p40, IL-12p70, IL-10) and chemokines (IL-8, MIP-1alpha, MCP-1, RANTES), and full-length NadA improved MenB OMV activity, preferentially on macrophages, and only increased cytokine release. NadA(Delta351-405) induced the lymphocyte costimulant CD80 in monocytes and macrophages, and NadA(+) OMVs induced a wider set of molecules supporting antigen presentation (CD80, CD86, HLA-DR, and ICAM-1) more efficiently than NadA(-) OMVs only in macrophages. Moreover, membrane NadA effects, unlike NadA(Delta351-405) ones, were much less IFN-gamma-sensitive. The activity of NadA-positive E. coli OMVs was similar to that of control OMVs. NadA in MenB OMVs acted at adhesin concentrations approximately 10(6) times lower than those required to stimulate cells with free NadA(Delta351-405).

  17. Mass transfer properties of chlorinated aromatic polyamide reverse osmosis membranes

    OpenAIRE

    Ettori, Axel; Gaudichet-Maurin, Emmanuelle; Aimar, Pierre; Causserand, Christel

    2012-01-01

    International audience; Water (A) and solute (B) permeability of aromatic polyamide (PA) reverse osmosis membranes (RO) were monitored under varying applied pressure, solute nature and concentration to assess their evolution after exposure of the membrane to free chlorine. Above a threshold value of 400 ppm h HOCl water permeability was influenced by permeation conditions during both filtration of ultrapure water (UP water) and reverse osmosis of salts performed sequentially. Water permeabili...

  18. Effects of chitosan solution concentration and incorporation of chitin and glycerol on dense chitosan membrane properties.

    Science.gov (United States)

    Dallan, Paula Rulf Marreco; Moreira, Patrícia da Luz; Petinari, Leandro; Malmonge, Sônia Maria; Beppu, Marisa Masumi; Genari, Selma Candelária; Moraes, Angela Maria

    2007-02-01

    The aim of this work was to perform a systematic study about the effects induced by chitosan solution concentration and by chitin or glycerol incorporation on dense chitosan membranes with potential use as burn dressings. The membrane properties analyzed were total raw material cost, thickness, morphology, swelling ratio, tensile strength, percentage of strain at break, crystallinity, in vitro enzymatic degradation with lysozyme, and in vitro Vero cells adhesion. While the use of the most concentrated chitosan solution (2.5% w/w) increased membrane cost, it also improved the biomaterial mechanical resistance and ductility, as well as reduced membrane degradation when exposed for 2 months to lysozyme. The remaining evaluated properties were not affected by initial chitosan solution concentration. Chitin incorporation, on the other hand, reduced the membranes cost, swelling ratio, mechanical properties, and crystallinity, resulting in thicker biomaterials with irregular surface more easily degradable when exposed to lysozyme. Glycerol incorporation also reduced the membranes cost and crystallinity and increased membranes degradability after exposure to lysozyme. Strong Vero cells adhesion was not observed in any of the tested membrane formulations. The overall results indicate that the majority of the prepared membranes meet the performance requirements of temporary nonbiodegradable burn dressings (e.g. adequate values of mechanical resistance and ductility, low values of in vitro cellular adhesion on their surfaces, low extent of degradation when exposed to lysozyme solution, and high stability in aqueous solutions).

  19. Ultrafiltration of biologically treated domestic wastewater: How membrane properties influence performance

    KAUST Repository

    Filloux, Emmanuelle

    2014-09-01

    In this study, the impact of membrane properties on membrane fouling and permeate water quality was investigated. Short- and long-term laboratory scale experiments using four commercially available hollow fiber UF membranes were performed to study the impact of membrane properties on reversible and irreversible fouling. No significant differences in terms of permeate quality (i.e. biopolymer rejection) were observed over the four tested membranes. It was found that membrane characteristics including pore size, pore distribution and especially materials had a strong impact on the filtration performances in terms of both reversible and irreversible fouling. The short-term filtration tests showed that due to its specific hydrodynamic condition only the inside-out mode UF membrane was subjected to irreversible fouling. These data demonstrate the importance of membrane selection with appropriate operating conditions for optimum performances. The added value of membrane characterization to lab-scale filtration tests for membrane performance was discussed. © 2014 Elsevier B.V. All rights reserved.

  20. Relating rejection of trace organic contaminants to membrane properties in forward osmosis: measurements, modelling and implications.

    Science.gov (United States)

    Xie, Ming; Nghiem, Long D; Price, William E; Elimelech, Menachem

    2014-02-01

    This study elucidates the relationship between membrane properties and the rejection of trace organic contaminants (TrOCs) in forward osmosis (FO). An asymmetric cellulose triacetate (CTA) and a thin-film composite (TFC) polyamide FO membrane were used for this investigation. The effective average pore radius (rp), selective barrier thickness over porosity parameter (l/ε), surface charge, support layer structural parameter (S), pure water permeability coefficient (A) and salt (NaCl) permeability coefficient (B) of the two membranes were systematically characterised. Results show that measured rejection of TrOCs as a function of permeate water flux can be well described by the pore hindrance transport model. This observation represents the first successful application of this model, which was developed for pressure-driven nanofiltration, to an osmotically-driven membrane process. The rejection of charged TrOCs by the CTA and TFC membranes was high and was governed by both electrostatic repulsion and steric hindrance. The TFC membrane exhibited higher rejection of neutral TrOCs with low molecular weight than the CTA membrane, although the estimated pore size of the TFC membrane (0.42 nm) was slightly larger than that of the CTA membrane (0.37 nm). This higher rejection of neutral TrOCs by the TFC membrane is likely attributed to its active layer properties, namely a more effective active layer structure, as indicated by a larger l/ε parameter, and pore hydration induced by the negative surface charge.

  1. Investigation of Electrochemical and Morphological Properties of Mixed Matrix Polysulfone-Silica Anion Exchange Membrane

    Directory of Open Access Journals (Sweden)

    Khoiruddin

    2016-02-01

    Full Text Available Mixed matrix anion exchange membranes (AEMs were synthesized using dry-wet phase inversion. The casting solutions were prepared by dispersing finely ground anion-exchange resin particles in N,N-dimethylacetamide (DMAc solutions of polysulfone (PSf. Subsequently, nanosilica particles were introduced into the membranes. The results show that evaporation time (tev and solution composition contributed to membrane properties formation. A longer tev produces membranes with reduced void fraction inside the membranes, thus the amount of water adsorbed and membrane conductivity are reduced. Meanwhile, the permselectivity was improved by increasing tev, since a longer tev produces membranes with a narrower channel for ion migration and more effective Donnan exclusion. The incorporation of 0.5 %-wt nanosilica particles into the polymer matrix led to conductivity improvement (from 2.27 to 3.41 mS.cm-1. This may be associated with additional pathway formation by hydroxyl groups on the silica surface that entraps water and assists ion migration. However, at further silica loading (1.0 and 1.5 %-wt, these properties decreased (to 1.9 and 1.4 mS.cm-1 respectively, which attributed to inaccessibility of ion-exchange functional groups due to membrane compactness. It was found from the results that nanosilica contributes to membrane formation (increases casting solution viscosity then reduces void fraction and membrane functional group addition (provides hydroxyl groups.

  2. Effect of membrane property and operating conditions on phytochemical properties and permeate flux during clarification of pineapple juice

    KAUST Repository

    Laorko, Aporn

    2010-10-01

    The effects of membrane property on the permeate flux, membrane fouling and quality of clarified pineapple juice were studied. Both microfiltration (membrane pore size of 0.1 and 0.2 μm) and ultrafiltration (membrane molecular weight cut-off (MWCO) of 30 and 100 kDa) membranes were employed. Membrane filtration did not have significant effects on the pH, reducing sugar and acidity of clarified juice whereas the suspended solids and microorganism were completely removed. The 0.2 μm membrane gave the highest permeate flux, total vitamin C content, total phenolic content and antioxidant capacity as well as the highest value of irreversible fouling. Based on these results, the membrane with pore size of 0.2 μm was considered to be the most suitable membrane for the clarification of pineapple juice. The optimum operating conditions for the clarification pineapple juice by membrane filtration was a cross-flow velocity of 3.4 ms-1 and transmembrane pressure (TMP) of 0.7 bar. An average flux of about 37 lm-2 h-1 was obtained during the microfiltration of pineapple juice under the optimum conditions using batch concentration mode. © 2010 Elsevier Ltd. All rights reserved.

  3. Mechanics and dynamics of triglyceride-phospholipid model membranes: Implications for cellular properties and function

    DEFF Research Database (Denmark)

    Pakkanen, Kirsi I.; Duelund, Lars; Qvortrup, Klaus

    2011-01-01

    We demonstrate here that triolein alters the mechanical properties of phospholipid membranes and induces extraordinary conformational dynamics. Triolein containing membranes exhibit fluctuations up to size range of 100µm and with the help of these are e.g. able to squeeze through narrow passages ...

  4. Mechanics and dynamics of triglyceride-phospholipid model membranes: Implications for cellular properties and function

    DEFF Research Database (Denmark)

    Pakkanen, Kirsi I.; Duelund, Lars; Qvortrup, Klaus

    2011-01-01

    We demonstrate here that triolein alters the mechanical properties of phospholipid membranes and induces extraordinary conformational dynamics. Triolein containing membranes exhibit fluctuations up to size range of 100µm and with the help of these are e.g. able to squeeze through narrow passages ...

  5. Membraner

    DEFF Research Database (Denmark)

    Bach, Finn

    2009-01-01

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

  6. [Properties of the chorioamnios zone inducing premature membranes rupture].

    Science.gov (United States)

    Meraz Cruz, M C Noemí; Beltrán Montoya, Jorge; Bustos López, Hugo; Flores Pliego, Arturo; Espejel, Aurora; Buendía Díaz, Gerardo; Vadillo-Ortega, Felipe

    2003-11-01

    Premature membrane rupture (PMR) is one of the most serious public health problems in the world, ocurring in 10% of all pregnancies. PMR has important adverse effects on maternofetal morbidity-mortality, as it has been estimated that it accounts on the whole for 70% and 40% of neonatal morbidity and mortality, respectively. PMR treatment is empirical, as its aetiology is unknown and its physiopathogenic description has just been initiated. This work analyzes the possibility of documenting functional differences in human chorio-amnios, comparing the zone where rupture most frequently occurs in PMR with some other distant chorio-amnionic zones and with equivalent zones of fetal membranes obtained from nine month pregnancies which have not undergone labor. The membrane zone which was nearest to the cervical os was identified and marked to be analyzed later for extracellular matrix metalloprotease (MMP) activity, histology and topographical MMP distribution. The MMP expression was quantitatively determined in explant culture media from membrane fragments using specific immuno-enzymatic essays (ELISA) and zymography. In addition, immuno-histochemistry methods were used to reveal MMP expression in the different tissues. This methods allowed us to show the existence of a decreasing MMP activity gradient, with the greatest value corresponding to the zone nearest to the cervical os in the membranes obtained from PMR cases. In membranes obtained from cesarean operations no characteristic pattern was documented and values were always lower than those obtained for PMR tissues. We conclude that there is a chorio-amnionic zone in which connective tissue degradation is specifically induced and which coincides with the membrane zone in contact with the cervical os.

  7. Modulation of human alveolar macrophage properties by ozone exposure in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Becker, S.; Madden, M.C.; Newman, S.L.; Devlin, R.B.; Koren, H.S.

    1991-01-01

    The study investigated changes in human alveolar macrophage (HAM) function after exposure in vitro to ozone (O3)(0.1-1.0 ppm for 2-4 hr). The functions studied reflect concern that O3 is detrimental to host defense mechanisms in the bronchoalveolar spaces. Exposure of HAM to O3 caused a concentration-dependent increase in release of prostaglandin E2(PGE2), an important modulator of inflammation, phagocytosis, and oxidative burst. Although phagocytosis of particulate immune complexes was decreased by O3, the authors found no change in the quantity of Fc receptors and complement receptors on the HAM surface. Superoxide (O2) production in response to phorbol ester was reduced after exposure of HAM to O3 while the basal O2 release in response to plastic adherence was not affected. Growth inhibition of the opportunistic yeast Cryptococcus neoformans by HAM was not affected by O3 exposure. The production of inflammatory mediators and immune modulators such as tumor necrosis factor-alpha, interleukin 1, and interleukin 6 were not induced by exposure to O3. However, compared to controls, O3-exposed HAM produced significantly lower levels of these cytokines when simulated with bacterial lipopolysaccharide (LPS).

  8. Endothelin-1 and macrophage colony-stimulating factor are co-localized in human amnion membrane cells and secreted into amniotic fluid.

    Science.gov (United States)

    Fried, Gabriel; Sand, Anna; Ostlund, Eva; Andersson, Eva; Byström, Birgitta; Ståbi, Berit

    2003-11-01

    We have examined the cellular localization and human amniotic fluid content of endothelin-1 (ET-1) and macrophage colony-stimulating factor (M-CSF). The study material consisted of amniotic fluid from 20 patients referred for amniocentesis, and placental samples from normal deliveries. ET-1 and M-CSF were analysed by radioimmunoassay and enzyme-linked immunosorbent assay respectively. The cellular localization of ET-1 and M-CSF in the amnion membranes was analysed by double-labelling immunocytochemistry using fluorescein isothiocyanate- and Cy3-labelled secondary antibodies. Release of ET-1 and M-CSF was studied in cultured amniocytes. We found that the mean +/- SD concentrations of ET-1 and M-CSF in fetal amniotic fluid were 45.6 +/- 17.3 pmol/l (range 16.8-85.5) and 7323 +/- 3415 ng/l (range 2640-12 110) respectively. Double-labelling immunocytochemistry showed that both M-CSF and ET-1 were co-localized in the same cells to a high extent. Further analysis revealed that levels of M-CSF, but not ET-1, were significantly correlated with pregnancy length. Both M-CSF and ET-1 were released from cultured amniocytes in response to interleukin-1. These findings show that ET-1 and M-CSF are partly co-localized to specific cells in the human amniotic membrane. As both M-CSF and ET-1 were released from cultured amniocytes in vitro, this suggests that they both may be secreted into fetal amniotic fluid in vivo as well.

  9. Reciprocal bystander effect between α-irradiated macrophage and hepatocyte is mediated by cAMP through a membrane signaling pathway.

    Science.gov (United States)

    He, Mingyuan; Dong, Chen; Xie, Yuexia; Li, Jitao; Yuan, Dexiao; Bai, Yang; Shao, Chunlin

    2014-01-01

    Irradiated cells can induce biological effects on vicinal non-irradiated bystander cells, meanwhile the bystander cells may rescue the irradiated cells through a feedback signal stress. To elucidate the nature of this reciprocal effect, we examined the interaction between α-irradiated human macrophage cells U937 and its bystander HL-7702 hepatocyte cells using a cell co-culture system. Results showed that after 6h of cell co-culture, mitochondria depolarization corresponding to apoptosis was significantly induced in the HL-7702 cells, but the formation of micronuclei in the irradiated U937 cells was markedly decreased compared to that without cell co-culture treatment. This reciprocal effect was not observed when the cell membrane signaling pathway was blocked by filipin that inhibited cAMP transmission from bystander cells to irradiated cells. After treatment of cells with exogenous cAMP, forskolin (an activator of cAMP) or KH-7 (an inhibitor of cAMP), respectively, it was confirmed that cAMP communication from bystander cells to targeted cells could mitigate radiation damage in U739 cells, and this cAMP insufficiency in the bystander cells contributed to the enhancement of bystander apoptosis. Moreover, the bystander apoptosis in HL-7702 cells was aggravated by cAMP inhibition but it could not be evoked when p53 of HL-7702 cells was knocked down no matter of forskolin and KH-7 treatment. In conclusion, this study disclosed that cAMP could be released from bystander HL-7702 cells and compensated to α-irradiated U937 cells through a membrane signaling pathway and this cAMP communication played a profound role in regulating the reciprocal bystander effects.

  10. Preparation and properties of metal-PVA composite hydrophilic ultrafiltration membranes

    Institute of Scientific and Technical Information of China (English)

    邱运仁; 张启修

    2003-01-01

    Metal-polyvinyl alcohol(PVA) composite ultrafiltration membranes were prepared by coating a certain concentration of PVA solution on metallic fiber sintered membranes. The effects of preparation conditions, such as the coating solution concentration, sequence and times of coating, and heat-treatment on the properties of the composite membranes were studied. The results show that the hole diameter of the composite membrane decreases with the increase of the concentration of PVA, the hole diameter of composite membrane is different when the sequence of coating is different. When the higher concentration of PVA solution is used to coat the metallic membrane for the first time and the other smaller one for the second time, the hole diameter of the composite membrane is relatively small, compared with that of the composite membrane made by the smaller concentration of PVA solution for the first time and the other higher one for the second time. The holes of the composite membrane contract and the stability of the membrane is improved by heat treatment. When metal-PVA composite hydrophilic membranes are used to treat the oil/water emulsion with the concentration of 1 000 mg@ L -1, the retention is from 80% to 90%, and the permeate flux is from 15 L @ m-2 @ h-1 to 40 L @ m-2 @ h-1 at pressure of 0.2 to 0.3 MPa.

  11. [Study on spectroscopic characterization and property of PES/ micro-nano cellulose composite membrane material].

    Science.gov (United States)

    Tang, Huan-Wei; Zhang, Li-Ping; Li, Shuai; Zhao, Guang-Jie; Qin, Zhu; Sun, Su-Qin

    2010-03-01

    In the present paper, the functional groups of PES/micro-nano cellulose composite membrane materials were characterized by Fourier transform infrared spectroscopy (FTIR). Also, changes in crystallinity in composite membrane materials were analyzed using X-ray diffraction (XRD). The effects of micro-nano cellulose content on hydrophilic property of composite membrane material were studied by measuring hydrophilic angle. The images of support layer structure of pure PES membrane material and composite membrane material were showed with scanning electron microscope (SEM). These results indicated that in the infrared spectrogram, the composite membrane material had characteristic peaks of both PES and micro-nano cellulose without appearance of other new characteristics peaks. It revealed that there were no new functional groups in the composite membrane material, and the level of molecular compatibility was achieved, which was based on the existence of inter-molecular hydrogen bond association between PES and micro-nano cellulose. Due to the existence of micro-nano cellulose, the crystallinity of composite membrane material was increased from 37.7% to 47.9%. The more the increase in micro-nano cellulose mass fraction, the better the van de Waal force and hydrogen bond force between composite membrane material and water were enhanced. The hydrophilic angle of composite membrane material was decreased from 55.8 degrees to 45.8 degrees and the surface energy was raised from 113.7 to 123.5 mN x m(-2). Consequently, the hydrophilic property of composite membrane material was improved. The number of pores in the support layer of composite membrane material was lager than that of pure PES membrane. Apparently, pores were more uniformly distributed.

  12. Dynamical and structural properties of lipid membranes in relation to liposomal drug delivery systems

    DEFF Research Database (Denmark)

    Jørgensen, Kent; Høyrup, Lise Pernille Kristine; Pedersen, Tina B.

    2001-01-01

    The structural and dynamical properties of DPPC liposomes containing lipopolymers (PEG-lipids) and charged DPPS lipids have been,studied in relation to the lipid membrane interaction of enzymes and peptides. The results suggest that both the lipid membrane structure and dynamics and in particular...... the appearance of small-scale lipid structures might be of importance for the activity of membrane associated and liposome degrading enzymes as well as for the membrane interaction of acylated peptides. The combined experimental and simulation results are of relevance for a rational development of peptide loaded...

  13. Quantum description of nanoantenna properties of a graphene membrane

    Science.gov (United States)

    Firsova, N. E.; Firsov, Yu. A.

    2016-06-01

    We considered a graphene membrane irradiated by a weak activating periodic electric field in the terahertz range. We used the quantum approach based on the time-dependent density matrix method to analyze the graphene electromagnetic response. For this goal the exact solution was found for the graphene membrane density matrix equation in linear approximation on the external field. On this basis the induced current was studied and then we obtained the formula for quantum conductivity as a function of external field frequency and temperature. The found formula for the conductivity corrected the one obtained in 2007 by Gusynin, Sharapov and Carbotte (Phys. Rev. B, 75 (2007) 165407). The corrected formula allowed to see that the graphene membrane was an oscillating contour, its fundamental eigenfrequency coinciding with a singularity point of the conductivity. The obtained formula allowed us also to calculate the graphene membrane quantum inductivity and capacitance. So in effect we demonstrated that the graphene membrane could be used as an antenna or a transistor. It was shown also that its eigenfrequency could be tuned by doping as its value was found to depend on electrons concentration. It was obtained that the eigenfrequency could be tuned in a rather large terahertz-infrared frequency range as electrons concentration in graphene may differ considerably. The found dependence on concentration is consistent with experiments. The presented formula for conductivity can be used to correct the SPPs Dispersion Relation and for the description of radiation process. It would be useful to take the obtained results into account when constructing devices containing a graphene membrane nanoantenna. Such project could make it possible to create wireless communications among nanosystems. This would be a promising research area of energy harvesting applications.

  14. Mechanically enhanced PES electrospun nanofiber membranes (ENMs) for microfiltration: The effects of ENM properties on membrane performance.

    Science.gov (United States)

    Bae, Jiyeol; Baek, Inchan; Choi, Heechul

    2016-11-15

    The application of electrospun nanofiber membranes (ENMs) as microfilters for the process of water purification requires the substrate to possess suitable strength, permeability, and a smooth surface. Therefore, the fiber homogeneity, inter-fiber adhesion, and surface roughness of the ENMs must be carefully controlled. Concurrently, an understanding of the ENMs' rejection mechanism for contaminants is necessary for the effective application of ENMs. In this study, we demonstrate the fabrication of polyethersulfone (PES) ENMs, which are useful for water purification as water treatment membranes. An optimum fabrication condition that can significantly improve the mechanical property and surface roughness of the PES membrane is also illustrated. This technique induces the solvent remaining on the fiber's surface after the electrospinning process, and the mechanical properties and surface roughness of the membrane are improved by the solvent-induced fusion of the fiber. The fabricated PES ENMs also show higher clean water productivity. Additionally, we show that a particulate contaminant in water is mainly rejected on the ENM surface by using a water filtration test. Based on our conclusions, we suggest the appropriate ENM regeneration method and confirm that the fabricated ENMs show excellent regeneration ability.

  15. Phosphocreatine interacts with phospholipids, affects membrane properties and exerts membrane-protective effects.

    Directory of Open Access Journals (Sweden)

    Malgorzata Tokarska-Schlattner

    Full Text Available A broad spectrum of beneficial effects has been ascribed to creatine (Cr, phosphocreatine (PCr and their cyclic analogues cyclo-(cCr and phospho-cyclocreatine (PcCr. Cr is widely used as nutritional supplement in sports and increasingly also as adjuvant treatment for pathologies such as myopathies and a plethora of neurodegenerative diseases. Additionally, Cr and its cyclic analogues have been proposed for anti-cancer treatment. The mechanisms involved in these pleiotropic effects are still controversial and far from being understood. The reversible conversion of Cr and ATP into PCr and ADP by creatine kinase, generating highly diffusible PCr energy reserves, is certainly an important element. However, some protective effects of Cr and analogues cannot be satisfactorily explained solely by effects on the cellular energy state. Here we used mainly liposome model systems to provide evidence for interaction of PCr and PcCr with different zwitterionic phospholipids by applying four independent, complementary biochemical and biophysical assays: (i chemical binding assay, (ii surface plasmon resonance spectroscopy (SPR, (iii solid-state (31P-NMR, and (iv differential scanning calorimetry (DSC. SPR revealed low affinity PCr/phospholipid interaction that additionally induced changes in liposome shape as indicated by NMR and SPR. Additionally, DSC revealed evidence for membrane packing effects by PCr, as seen by altered lipid phase transition. Finally, PCr efficiently protected against membrane permeabilization in two different model systems: liposome-permeabilization by the membrane-active peptide melittin, and erythrocyte hemolysis by the oxidative drug doxorubicin, hypoosmotic stress or the mild detergent saponin. These findings suggest a new molecular basis for non-energy related functions of PCr and its cyclic analogue. PCr/phospholipid interaction and alteration of membrane structure may not only protect cellular membranes against various insults

  16. Laurdan and Di-4-ANEPPDHQ probe different properties of the membrane

    Science.gov (United States)

    Amaro, Mariana; Reina, Francesco; Hof, Martin; Eggeling, Christian; Sezgin, Erdinc

    2017-04-01

    Lipid packing is a crucial feature of cellular membranes. Quantitative analysis of membrane lipid packing can be achieved using polarity sensitive probes whose emission spectrum depends on the lipid packing. However, detailed insights into the exact mechanisms that cause the changes in the spectra are necessary to interpret experimental fluorescence emission data correctly. Here, we analysed frequently used polarity sensitive probes, Laurdan and di-4-ANEPPDHQ, to test whether the underlying physical mechanisms of their spectral changes are the same and, thus, whether they report on the same physico-chemical properties of the cell membrane. Steady-state spectra as well as time-resolved emission spectra of the probes in solvents and model membranes revealed that they probe different properties of the lipid membrane. Our findings are important for the application of these dyes in cell biology.

  17. Zwitterionic glycosyl modified polyethersulfone membranes with enhanced anti-fouling property and blood compatibility.

    Science.gov (United States)

    Xie, Yi; Li, Shuang-Si; Jiang, Xin; Xiang, Tao; Wang, Rui; Zhao, Chang-Sheng

    2015-04-01

    In this study, novel zwitterionic glycosyl modified polyethersulfone (PES) ultrafiltration membranes were prepared via in-situ cross-linking polymerization coupled with phase inversion technique, and the following reactions. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), (1)HNMR spectrum, and static water contact angles (WCAs) measurements. The modified membranes showed excellent anti-fouling property, and the flux recovery ratio could reach almost 100%. Meanwhile, the blood compatibility of the membranes was measured by protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT), and thrombin time (TT). The results implied that the zwitterionic glycosyl modified PES membranes had good anti-fouling property and blood compatibility.

  18. Effect of Heat Treatment on Structures and Properties of Polyurethane Blend Ultrafiltration Membranes

    Institute of Scientific and Technical Information of China (English)

    封严; 肖长发

    2004-01-01

    The polyurethane/polyacrylonitrile ( PU/PAN ) and polyurethane/cellulose acetate (PU/CA) blend ultra filtration membranes were prepared based on LoebSourirajan phase transition method. The change of the structures and properties of the PU/PAN and PU/CA membranes with the heat treatment process was studied.The results showed: the water flux decreased and retention increased with the increase of heat treatment temperature of PU/PAN blend membrane, but the water flux of PU/CA blend membrane got the maximum with heat treatment temperature of 60℃ and decreased rapidly with the heat treatment temperature of 100 ℃. The interfacial microvoid structure and its influence on the properties of PU/PAN and PU/CA blend membranes were studied.

  19. Studies on synthesis and property of novel acid-base proton exchange membranes

    Institute of Scientific and Technical Information of China (English)

    Yong Fang Liang; Hai Yan Pan; Xiu Ling Zhu; Yao Xia Zhang; Xi Gao Jian

    2007-01-01

    Sulfonated poly(phthalazinone)s (SPPENK, SPPESK and SPPBEK) were prepared by direct polymerization reaction from sulfonated monomers. The novel acid-base membranes were composed of sulfonated polymers as the acidic compounds, and polyetherimide (PEI) as the basic compounds, casting from their N-methylpyrrolidone (NMP) solution directly onto clean glass plates at 60 ℃ aiming at enhancing membrane toughness and other relative properties. The resulted acid-base composite membranes had excellent resistance to swelling, thermo-stability, hydrolysis resistance and oxidative resistance properties with highly ion-exchange capacity (IEC).

  20. Pathological levels of glucosylceramide change the biophysical properties of artificial and cell membranes.

    Science.gov (United States)

    Varela, Ana R P; Ventura, Ana E; Carreira, Ana C; Fedorov, Aleksander; Futerman, Anthony H; Prieto, Manuel; Silva, Liana C

    2016-12-21

    Glucosylceramide (GlcCer) plays an active role in the regulation of various cellular events. Moreover, GlcCer is also a key modulator of membrane biophysical properties, which might be linked to the mechanism of its biological action. In order to understand the biophysical implications of GlcCer on membranes of living cells, we first studied the effect of GlcCer on artificial membranes containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), sphingomyelin (SM) and cholesterol (Chol). Using an array of biophysical methods, we demonstrate that at lower GlcCer/Chol ratios, GlcCer stabilizes SM/Chol-enriched liquid-ordered domains. However, upon decreasing the Chol content, GlcCer significantly increased membrane order through the formation of gel domains. Changes in pH disturbed the packing properties of GlcCer-containing membranes, leading to an increase in membrane fluidity and reduced membrane electronegativity. To address the biophysical impact of GlcCer in biological membranes, studies were performed in wild type and in fibroblasts treated with conduritol-B-epoxide (CBE), which causes intracellular GlcCer accumulation, and in fibroblasts from patients with type I Gaucher disease (GD). Decreased membrane fluidity was observed in cells containing higher levels of GlcCer, such as in CBE-treated and GD cells. Together, we demonstrate that elevated GlcCer levels change the biophysical properties of cellular membranes, which might compromise membrane-associated cellular events and be of relevance for understanding the pathology of diseases, such as GD, in which GlcCer accumulates at high levels.

  1. Structure and Dynamic Properties of Membrane Proteins using NMR

    DEFF Research Database (Denmark)

    Rösner, Heike; Kragelund, Birthe

    2012-01-01

    , a large variety of developments of well-established techniques are available providing insight into membrane protein flexibility, dynamics, and interactions. Inspired by the speed of development in the application of new strategies, by invention of methods to measure solvent accessibility and describe low...

  2. Carbon Nanotube Membranes: Synthesis, Properties, and Future Filtration Applications

    Directory of Open Access Journals (Sweden)

    Md. Harun-Or Rashid

    2017-05-01

    Full Text Available Over the course of the past decade, there has been growing interest in the development of different types of membranes composed of carbon nanotubes (CNTs, including buckypapers and composite materials, for an ever-widening range of filtration applications. This article provides an overview of how different types of CNT membranes are prepared and the results obtained from investigations into their suitability for different applications. The latter involve the removal of small particles from air samples, the filtration of aqueous solutions containing organic compounds and/or bacteria, and the separation of individual liquids present in mixtures. A growing number of reports have demonstrated that the incorporation of CNTs into composite membranes confers an improved resistance to fouling caused by biomacromolecules and bacteria. These results are discussed, along with evidence that demonstrates it is possible to further reduce fouling by taking advantage of the inherent conductivity of composite membranes containing CNTs, as well as by using different types of electrochemical stimuli.

  3. Theoretical modeling and experimental validation of transport and separation properties of carbon nanotube electrospun membrane distillation

    KAUST Repository

    Lee, Jung-Gil

    2016-12-27

    Developing a high flux and selective membrane is required to make membrane distillation (MD) a more attractive desalination process. Amongst other characteristics membrane hydrophobicity is significantly important to get high vapor transport and low wettability. In this study, a laboratory fabricated carbon nanotubes (CNTs) composite electrospun (E-CNT) membrane was tested and has showed a higher permeate flux compared to poly(vinylidene fluoride-co-hexafluoropropylene) (PH) electrospun membrane (E-PH membrane) in a direct contact MD (DCMD) configuration. Only 1% and 2% of CNTs incorporation resulted in an enhanced permeate flux with lower sensitivity to feed salinity while treating a 35 and 70 g/L NaCl solutions. Experimental results and the mechanisms of E-CNT membrane were validated by a proposed new step-modeling approach. The increased vapor transport in E-CNT membranes could not be elucidated by an enhancement of mass transfer only at a given physico-chemical properties. However, the theoretical modeling approach considering the heat and mass transfers simultaneously enabled to explain successfully the enhanced flux in the DCMD process using E-CNT membranes. This indicates that both mass and heat transfers improved by CNTs are attributed to the enhanced vapor transport in the E-CNT membrane.

  4. Physical–chemical properties, separation performance, and fouling resistance of mixed-matrix ultrafiltration membranes

    KAUST Repository

    Hoek, Eric M.V.

    2011-12-01

    Herein we report on the formation and characterization of mixed-matrix ultrafiltration (UF) membranes hand-cast by nonsolvent induced phase inversion. We evaluated nanometer-to-micrometer sized inorganic fillers (silver, copper, silica, zeolite, and silver-zeolite) materials with polysulfone (PSf) as the polymeric dispersing matrix. In general, mixed-matrix membranes were rougher, more hydrophilic, and more mechanically robust. Only sub-micron zeolite-PSf mixed-matrix membranes exhibited simultaneous improvements in water permeability and solute selectivity; all other mixed-matrix membranes were more permeable, but less selective due to defects associated with poor polymer-filler binding. Protein and bacterial fouling resistance of mixed-matrix membranes containing silver, zeolite, and silver-zeolite nanoparticles were compared to a low-fouling, poly(acrylonitrile) (PAN) UF membrane. Zeolite and silver containing membranes exhibited better protein fouling resistance (due to higher hydrophilicity), whereas silver and silver-zeolite based membranes produce better bacterial fouling resistance due to antimicrobial properties. Overall, zeolite-PSf and silver exchanged zeolite-PSf membranes offered the best combination of improved permeability, selectivity, and fouling resistance - superior to the commercial PAN membrane. © 2011 Elsevier B.V.

  5. Mechanical properties of electrospun bilayer fibrous membranes as potential scaffolds for tissue engineering.

    Science.gov (United States)

    Pu, Juan; Komvopoulos, Kyriakos

    2014-06-01

    Bilayer fibrous membranes of poly(l-lactic acid) (PLLA) were fabricated by electrospinning, using a parallel-disk mandrel configuration that resulted in the sequential deposition of a layer with fibers aligned across the two parallel disks and a layer with randomly oriented fibers, both layers deposited in a single process step. Membrane structure and fiber alignment were characterized by scanning electron microscopy and two-dimensional fast Fourier transform. Because of the intricacies of the generated electric field, bilayer membranes exhibited higher porosity than single-layer membranes consisting of randomly oriented fibers fabricated with a solid-drum collector. However, despite their higher porosity, bilayer membranes demonstrated generally higher elastic modulus, yield strength and toughness than single-layer membranes with random fibers. Bilayer membrane deformation at relatively high strain rates comprised multiple abrupt microfracture events characterized by discontinuous fiber breakage. Bilayer membrane elongation yielded excessive necking of the layer with random fibers and remarkable fiber stretching (on the order of 400%) in the layer with fibers aligned in the stress direction. In addition, fibers in both layers exhibited multiple localized necking, attributed to the nonuniform distribution of crystalline phases in the fibrillar structure. The high membrane porosity, good mechanical properties, and good biocompatibility and biodegradability of PLLA (demonstrated in previous studies) make the present bilayer membranes good scaffold candidates for a wide range of tissue engineering applications.

  6. A hyperspectral and toxicological analysis of protein corona impact on silver nanoparticle properties, intracellular modifications, and macrophage activation.

    Science.gov (United States)

    Shannahan, Jonathan H; Podila, Ramakrishna; Brown, Jared M

    2015-01-01

    The inevitable adsorption of biomolecules on nanomaterials results in the formation of a protein corona (PC), which modifies the nanoparticle (NP)-cell interface resulting in modified uptake, activity, clearance, and toxicity. While the physicochemical properties of the NP govern the composition of PC, the formation of PC in turn alters the characteristics of the NP by imparting a new unique "biological" identity. To assess how the PC influences AgNP properties, intracellular modifications, and cellular responses, we utilized a combination of hyperspectral and toxicological analyses. AgNPs were coated with a complex PC (multiple proteins, eg, 10% fetal bovine serum) or a simple PC (single protein, eg, bovine serum albumin [BSA]) and evaluated by hyperspectral and dynamic light scattering for modifications in AgNP properties. Mouse macrophages were exposed to AgNPs with PCs and examined for differences in uptake, cytotoxicity, and cell activation. Hyperspectral imaging revealed intracellular modifications to AgNPs that were found to spectrally match alterations in AgNPs following incubation in lysosomal fluid. Addition of the PC influenced AgNP uptake and cytotoxicity; however, hydrodynamic size and surface charge did not contribute to these responses. Assessments of all endpoints demonstrated differences between complex and BSA PC, suggesting that these responses are not purely driven by the primary protein component of the complex PC (ie, BSA). Alterations in cellular-NP uptake/interactions may be driven through cell surface receptor recognition of protein constituents that make up the PC rather than the physicochemical differences in AgNPs.

  7. A hyperspectral and toxicological analysis of protein corona impact on silver nanoparticle properties, intracellular modifications, and macrophage activation

    Directory of Open Access Journals (Sweden)

    Shannahan JH

    2015-10-01

    Full Text Available Jonathan H Shannahan,1 Ramakrishna Podila,2,3 Jared M Brown1 1Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, The University of Colorado Anschutz Medical Campus, Aurora, CO, 2Department of Physics and Astronomy, Clemson University, Clemson, 3Clemson Nanomaterials Center and COMSET, Clemson University, Anderson, SC, USA Abstract: The inevitable adsorption of biomolecules on nanomaterials results in the formation of a protein corona (PC, which modifies the nanoparticle (NP–cell interface resulting in modified uptake, activity, clearance, and toxicity. While the physicochemical properties of the NP govern the composition of PC, the formation of PC in turn alters the characteristics of the NP by imparting a new unique “biological” identity. To assess how the PC influences AgNP properties, intracellular modifications, and cellular responses, we utilized a combination of hyperspectral and toxicological analyses. AgNPs were coated with a complex PC (multiple proteins, eg, 10% fetal bovine serum or a simple PC (single protein, eg, bovine serum albumin [BSA] and evaluated by hyperspectral and dynamic light scattering for modifications in AgNP properties. Mouse macrophages were exposed to AgNPs with PCs and examined for differences in uptake, cytotoxicity, and cell activation. Hyperspectral imaging revealed intracellular modifications to AgNPs that were found to spectrally match alterations in AgNPs following incubation in lysosomal fluid. Addition of the PC influenced AgNP uptake and cytotoxicity; however, hydrodynamic size and surface charge did not contribute to these responses. Assessments of all endpoints demonstrated differences between complex and BSA PC, suggesting that these responses are not purely driven by the primary protein component of the complex PC (ie, BSA. Alterations in cellular–NP uptake/interactions may be driven through cell surface receptor recognition of protein constituents

  8. A Study of Retentive Properties of Track Membranes

    CERN Document Server

    Oganesyan, V R; Yanina, I V; Apel, P Yu

    2000-01-01

    The influence of the size and shape of pores in track membranes (TMs) on the retention of polystyrene particles with the sizes from 40 to 100 nm has been studied. The relationship between the structural parameters of TMs and the efficiency of filtration of calibrated particles has been analyzed. Determination of the efficiency is based on measurements of absorption in ultraviolet spectral region. Potentialities and limitations of the method applied to nanometer-sized latex beads have been considered.

  9. Preparation and Properties of Nano-Hydroxyapatite/Gelatin/Poly(vinyl alcohol) Composite Membrane.

    Science.gov (United States)

    Liao, Haotian; Shi, Kun; Peng, Jinrong; Qu, Ying; Liao, Jinfeng; Qian, Zhiyong

    2015-06-01

    In this study, the bone-like composite membrane based on blends of gelatin (Gel), nano-hydroxyapatite (n-HA) and poly(vinyl alcohol) (PVA) was fabricated by solvent casting and evaporation methods. The effect of n-HA content and the ratio of Gel/PVA on the properties of the composite was investigated. The Gel/PVA and n-HA/Gel/PVA composite membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), water contact angle measurement and scanning electron microscopy (SEM). The mechanical properties of the composites were determined by tensile tests. The as prepared composite membranes exhibited hydrophobility, the water contact angle of composite membrane was 126.6 when its mass ratio of n-HA/Gel/PVA was 10/50/40. The tensile strength of composite membranes was greatly increased due to the introduction of n-HA, and the tensile strength was increased to 74.92 MPa when the mass ratio of n-HA/Gel/PVA was 10/50/40. SEM observation indicated that n-HA was dispersed in the membranes and a sea-island structure was formed in the n-HA/Gel/PVA composite membranes, resulting in a significant increase in tensile strength. The as-prepared n-HA/Gel/PVA composite membranes may be applied in the field of bone tissue engineering.

  10. Enhancing the Compatibility, Hydrophilicity and Mechanical Properties of Polysulfone Ultrafiltration Membranes with Lignocellulose Nanofibrils

    Directory of Open Access Journals (Sweden)

    Zhaodong Ding

    2016-10-01

    Full Text Available Lignocellulose nanofibrils (LCN and cellulose nanofibrils (CNF are popular nanometer additives to improve mechanical properties and hydrophilic abilities; moreover, lignocellulose has potential as a natural adhesion promoter in fiber-reinforced composites. LCN and CNF were blended into polysulfone (PSF to prepare ultrafiltration membranes via the phase inversion method. These additives were characterized by Fourier transform infrared spectroscopy and transmission electron microscopy, and the rheological properties such as shear viscosity and non-Newtonian fluid index of the casting solutions were analyzed using a rotational rheometer. The performance of ultrafiltration membranes was characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The pure water flux, bovine serum albumin retention ratio, water contact angle, surface energy, molecular weight cut-off, pore size and mechanical properties were measured. The equilibrium contact angle of water decreased from 63.5° on the PSF membrane to 42.1° on the CNF/PSF membrane and then decreased to 33.9° on the LCN/PSF membrane when the nanometer additives content was 0.8 wt %. The results reveal that LCN and CNF were successfully combined with PSF. Moreover, the combination of LCN/PSF ultrafiltration membranes was more promising than that of CNF/PSF ultrafiltration membranes.

  11. Ceramic membranes for catalytic membrane reactors with high ionic conductivities and low expansion properties

    Science.gov (United States)

    Mackay, Richard; Sammells, Anthony F.

    2000-01-01

    Ceramics of the composition: Ln.sub.x Sr.sub.2-x-y Ca.sub.y B.sub.z M.sub.2-z O.sub.5+.delta. where Ln is an element selected from the fblock lanthanide elements and yttrium or mixtures thereof; B is an element selected from Al, Ga, In or mixtures thereof; M is a d-block transition element of mixtures thereof; 0.01.ltoreq.x.ltoreq.1.0; 0.01.ltoreq.y.ltoreq.0.7; 0.01.ltoreq.z.ltoreq.1.0 and .delta. is a number that varies to maintain charge neutrality are provided. These ceramics are useful in ceramic membranes and exhibit high ionic conductivity, high chemical stability under catalytic membrane reactor conditions and low coefficients of expansion. The materials of the invention are particularly useful in producing synthesis gas.

  12. The depth of porphyrin in a membrane and the membrane's physical properties affect the photosensitizing efficiency.

    Science.gov (United States)

    Lavi, Adina; Weitman, Hana; Holmes, Robert T; Smith, Kevin M; Ehrenberg, Benjamin

    2002-01-01

    Photosensitized biological processes, as applied in photodynamic therapy, are based on light-triggered generation of molecular singlet oxygen by a membrane-residing sensitizer. Most of the sensitizers currently used are hydrophobic or amphiphilic porphyrins and their analogs. The possible activity of the short-lived singlet oxygen is limited to the time it is diffusing in the membrane, before it emerges into the aqueous environment. In this paper we demonstrate the enhancement of the photosensitization process that is obtained by newly synthesized protoporphyrin derivatives, which insert their tetrapyrrole chromophore deeper into the lipid bilayer of liposomes. The insertion was measured by fluorescence quenching by iodide and the photosensitization efficiency was measured with 9,10-dimethylanthracene, a fluorescent chemical target for singlet oxygen. We also show that when the bilayer undergoes a melting phase transition, or when it is fluidized by benzyl alcohol, the sensitization efficiency decreases because of the enhanced diffusion of singlet oxygen. The addition of cholesterol or of dimyristoyl phosphatydilcholine to the bilayer moves the porphyrin deeper into the bilayer; however, the ensuing effect on the sensitization efficiency is different in these two cases. These results could possibly define an additional criterion for the choice and design of hydrophobic, membrane-bound photosensitizers. PMID:11916866

  13. Soybean-derived Bowman-Birk inhibitor inhibits neurotoxicity of LPS-activated macrophages

    Directory of Open Access Journals (Sweden)

    Persidsky Yuri

    2011-02-01

    Full Text Available Abstract Background Lipopolysaccharide (LPS, the major component of the outer membrane of gram-negative bacteria, can activate immune cells including macrophages. Activation of macrophages in the central nervous system (CNS contributes to neuronal injury. Bowman-Birk inhibitor (BBI, a soybean-derived protease inhibitor, has anti-inflammatory properties. In this study, we examined whether BBI has the ability to inhibit LPS-mediated macrophage activation, reducing the release of pro-inflammatory cytokines and subsequent neurotoxicity in primary cortical neural cultures. Methods Mixed cortical neural cultures from rat were used as target cells for testing neurotoxicity induced by LPS-treated macrophage supernatant. Neuronal survival was measured using a cell-based ELISA method for expression of the neuronal marker MAP-2. Intracellular reactive oxygen species (ROS production in macrophages was measured via 2', 7'-dichlorofluorescin diacetate (DCFH2DA oxidation. Cytokine expression was determined by quantitative real-time PCR. Results LPS treatment of macrophages induced expression of proinflammatory cytokines (IL-1β, IL-6 and TNF-α and of ROS. In contrast, BBI pretreatment (1-100 μg/ml of macrophages significantly inhibited LPS-mediated induction of these cytokines and ROS. Further, supernatant from BBI-pretreated and LPS-activated macrophage cultures was found to be less cytotoxic to neurons than that from non-BBI-pretreated and LPS-activated macrophage cultures. BBI, when directly added to the neuronal cultures (1-100 μg/ml, had no protective effect on neurons with or without LPS-activated macrophage supernatant treatment. In addition, BBI (100 μg/ml had no effect on N-methyl-D-aspartic acid (NMDA-mediated neurotoxicity. Conclusions These findings demonstrate that BBI, through its anti-inflammatory properties, protects neurons from neurotoxicity mediated by activated macrophages.

  14. Membrane properties and synaptic connectivity of fast-spiking interneurons in rat ventral striatum

    NARCIS (Netherlands)

    Taverna, S.; Canciani, B.; Pennartz, C.M.A.

    2007-01-01

    In vitro patch-clamp recordings were made to study the membrane properties and synaptic connectivity of fast-spiking interneurons in rat ventral striatum. Using a whole-cell configuration in acutely prepared slices, fast-spiking interneurons were recognized based on their firing properties and their

  15. Divorcing folding from function: how acylation affects the membrane-perturbing properties of an antimicrobial peptide

    DEFF Research Database (Denmark)

    Vad, Brian Stougaard; Thomsen, Line Aagot Hede; Bertelsen, Kresten

    2010-01-01

    Many small cationic peptides, which are unstructured in aqueous solution, have antimicrobial properties. These properties are assumed to be linked to their ability to permeabilize bacterial membranes, accompanied by the transition to an alpha-helical folding state. Here we show that there is no d...... to an anti-permeabilizing "plugging" effect....

  16. Improving the Performance and Antifouling Properties of Thin-Film Composite Membranes for Water Separation Technologies

    Science.gov (United States)

    Tiraferri, Alberto

    Membrane-based water separation processes utilize semi-permeable membranes to retain dissolved solids and contaminants. Deployment of these technologies for desalination and wastewater reuse has the potential to sustainably increase the supply of potable, agricultural, and industrial water. Despite considerable development of semi-permeable membranes in the last decades, several design obstacles hampering their progress have yet to be overcome. Specifically, major membrane improvements are currently sought with respect to their performance and productivity, as well as their resistance to fouling. This dissertation research aims at the advancement of semi-permeable membranes by rational optimization of their design to: (i) understand and improve their transport properties and (ii) reduce fouling by organic molecules and delay biofouling by microorganisms. In particular, thin-film composite polyamide membranes for both reverse osmosis and forward osmosis processes are the main target of the investigation. The structural and physicochemical properties of thin-film composite membranes are both characterized and tailored through implementation of original techniques and novel functionalization protocols. The membrane structure and morphology are rationally modified to enhance the mass transport within the support layer. The influence of fabrication conditions on support layer formation and on its final structure is elucidated. The intricate interrelationship among the performance of the different layers of the composite membrane is highlighted and a new protocol is developed to characterize the transport properties of membranes deployed in forward osmosis processes. Novel approaches to impart targeted properties to the active surface of thin-film composite membranes are also proposed. The functionalization is achieved by exploiting the inherent moieties of the polyamide layer to irreversibly bind nanomaterials with desired properties. An experimental method to determine

  17. Partially Fluorinated Sulfonated Poly(ether amide Fuel Cell Membranes: Influence of Chemical Structure on Membrane Properties

    Directory of Open Access Journals (Sweden)

    Chulsung Bae

    2011-01-01

    Full Text Available A series of fluorinated sulfonated poly (ether amides (SPAs were synthesized for proton exchange membrane fuel cell applications. A polycondensation reaction of 4,4’-oxydianiline, 2-sulfoterephthalic acid monosodium salt, and tetrafluorophenylene dicarboxylic acids (terephthalic and isophthalic or fluoroaliphatic dicarboxylic acids produced SPAs with sulfonation degrees of 80–90%. Controlling the feed ratio of the sulfonated and unsulfonated dicarboxylic acid monomers afforded random SPAs with ion exchange capacities between 1.7 and 2.2 meq/g and good solubility in polar aprotic solvents. Their structures were characterized using NMR and FT IR spectroscopies. Tough, flexible, and transparent films were obtained with dimethylsulfoxide using a solution casting method. Most SPA membranes with 90% sulfonation degree showed high proton conductivity (>100 mS/cm at 80 °C and 100% relative humidity. Among them, two outstanding ionomers (ODA-STA-TPA-90 and ODA-STA-IPA-90 showed proton conductivity comparable to that of Nafion 117 between 40 and 80 °C. The influence of chemical structure on the membrane properties was systematically investigated by comparing the fluorinated polymers to their hydrogenated counterparts. The results suggest that the incorporation of fluorinated moieties in the polymer backbone of the membrane reduces water absorption. High molecular weight and the resulting physical entanglement of the polymers chains played a more important role in improving stability in water, however.

  18. Water uptake, ionic conductivity and swelling properties of anion-exchange membrane

    Energy Technology Data Exchange (ETDEWEB)

    Duan, QJ; Ge, SH; Wang, CY

    2013-12-01

    Water uptake, ionic conductivity and dimensional change of the anion-exchange membrane made by Tokuyama Corporation (A201 membrane) are investigated at different temperatures and water activities. Specifically, the amount of water taken up by membranes exposed to water vapor and membranes soaked in liquid water is determined. The water uptake of the A201 membrane increases with water content as well as temperature. In addition, water sorption data shows Schroeder's paradox for the AEMs investigated. The swelling properties of the A201 membrane exhibit improved dimensional stability compared with Nafion membrane. Water sorption of the A201 membrane occurs with a substantial negative excess volume of mixing. The threshold value of hydrophilic fraction in the A201 membrane for ionic conductivity is around 0.34, above which, the conductivity begins to rise quickly. This indicates that a change in the connectivity of the hydrophilic domains occurs when hydrophilic fraction approaches 0.34. (C) 2013 Elsevier B.V. All rights reserved.

  19. Improving Anti-Protein-Fouling Property of Polyacrylonitrile Ultrafiltration Membrane by Grafting Sulfobetaine Zwitterions

    Directory of Open Access Journals (Sweden)

    Hong Meng

    2014-01-01

    Full Text Available Zwitterions show great superiority in the field of polymer membrane surface functionalization, as the synthesis process is simple, the adaptability of functional groups is strong, and zwitterions with strong hydration capacity in aqueous solutions can inhibit protein adsorption. In this study, a polyacrylonitrile ultrafiltration membrane was modified to improve anti-protein-fouling capacity by grafting short-chain sulfonic type zwitterions. 3-Dimethylaminopropylamine was first grafted onto hydrolyzed polyacrylonitrile (PAN membrane by the activation of 1-(3-dimethylaminopropyl-3-ethylcarbodiimide hydrochloride (EDC. Subsequently, sulfobetaine zwitterions emerged on the membrane surface by quaternization of 1,3-propane sultone. The sulfobetaine zwitterionic membranes were analyzed for surface chemical composition, hydrophilic properties, and surface and cross-sectional structure of the membrane, by a combination of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, contact angle measurement, and scanning electron microscopy. Static protein adsorption and dynamic filtration experiments were undertaken to show that the modified membrane had excellent resistance to protein adsorption. It was found that the molecular weight cutoff of the substrate membrane had great influence on the flux recovery rate of the modified membrane.

  20. Anti-biofouling property of vanillin on Aeromonas hydrophila initial biofilm on various membrane surfaces.

    Science.gov (United States)

    Ponnusamy, K; Kappachery, S; Thekeettle, M; Song, J H; Kweon, J H

    2013-09-01

    Biofouling is a serious problem on filter membranes of water purification systems due to formation of bacterial biofilms, which can be detrimental to the membrane performance. Biofouling occurs on membrane surface and therefore greatly influences the physical and chemical aspects of the surface. Several membranes including microfiltration, ultrafiltration, and reverse osmosis (RO) membranes were used to learn about the anti-biofouling properties of vanillin affecting the membrane performances. Vanillin has been recognized as a potential quorum quenching compound for Aeromonas hydrophila biofilms. The initial attachment and dynamics of biofilm growth were monitored using scanning electron microscopy and confocal laser scanning microscopy. Biofilm quantities were measured using a plate count method and total protein determinations. Vanillin addition was effective in the prevention of biofilm formation on the tested membrane surfaces. Among the membranes, RO membranes made with cellulose acetate showed the most substantial reduction of biofilm formation by addition of vanillin. The biofilm reduction was confirmed by the results of surface coverage, biomass and protein accumulation. The HPLC spectrum of the spent culture with vanillin addition showed that vanillin may interfere with quorum sensing molecules and thus prevent the formation of the biofilms.

  1. 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.

  2. Effect of membranes with various hydrophobic/hydrophilic properties on lipase immobilized activity and stability.

    Science.gov (United States)

    Chen, Guan-Jie; Kuo, Chia-Hung; Chen, Chih-I; Yu, Chung-Cheng; Shieh, Chwen-Jen; Liu, Yung-Chuan

    2012-02-01

    In this study, three membranes: regenerated cellulose (RC), glass fiber (GF) and polyvinylidene fluoride (PVDF), were grafted with 1,4-diaminobutane (DA) and activated with glutaraldehyde (GA) for lipase covalent immobilization. The efficiencies of lipases immobilized on these membranes with different hydrophobic/hydrophilic properties were compared. The lipase immobilized on hydrophobic PVDF-DA-GA membrane exhibited more than an 11-fold increase in activity compared to its immobilization on a hydrophilic RC-DA-GA membrane. The relationship between surface hydrophobicity and immobilized efficiencies was investigated using hydrophobic/hydrophilic GF membranes which were prepared by grafting a different ratio of n-butylamine/1,4-diaminobutane (BA/DA). The immobilized lipase activity on the GF membrane increased with the increased BA/DA ratio. This means that lipase activity was exhibited more on the hydrophobic surface. Moreover, the modified PVDF-DA membrane was grafted with GA, epichlorohydrin (EPI) and cyanuric chloride (CC), respectively. The lipase immobilized on the PVDF-DA-EPI membrane displayed the highest specific activity compared to other membranes. This immobilized lipase exhibited more significant stability on pH, thermal, reuse, and storage than did the free enzyme. The results exhibited that the EPI modified PVDF is a promising support for lipase immobilization.

  3. PREPARATION AND PROPERTIES OF SPAES-TiO_2 HYBRID MEMBRANES FOR DIRECT METHANOL FUEL CELL

    Institute of Scientific and Technical Information of China (English)

    Ni Zhang; Hui-ling Liu; Jun-jing Li; Zhi Xia

    2009-01-01

    Sulfonated poly(arylene ether sulfone) (SPAES) copolymer with degree of sulfonation of 1.0 was synthesized and characterized. A series of SPAES-TiO_2 hybrid membranes with various contents of nano-sized TiO_2 particles were prepared and characterized through sol-gel reactions. Scanning electron microscopy (SEM) images indicated the TiO_2 particles were well dispersed within polymer matrix. These composite membranes were evaluated for proton exchange membranes (PEMs) in direct methanol fuel cell (DMFC). These membranes showed good thermal stability and mechanical properties. It was found that the water uptake of these membranes increased with the increase of the TiO_2 contents in the hybrid membranes. Meanwhile, the introduction of inorganic particles increased the proton conductivity and reduced the methanol permeability. The proton conductivities (0.118-0.162 S/cm) of SPAES-TiO_2 hybrid membranes with 8% TiO_2 particles are much higher than those of Nation 117 membrane (0.095-0.117 S/cm) and pure SPAES membrane (0.100-0.124 S/cm) with degree of sulfonation of 1.0 at all temperatures (25-100℃). Especially, the methanol diffusion coefficient (8.4×10~(-7) cm~2/s) of SPAES-TiO_2 hybrid membranes with 8% TiO_2 is much lower than that of Nation 117 membrane (2.1 ×10~(-6) cm~2/s). SPAES-TiO_2 hybrid membranes were therefore proposed as candidates of material for PEM in DMFC.

  4. Use of ionophores in epithelia: characterizing membrane properties.

    Science.gov (United States)

    Lewis, S A; Wills, N K

    1989-01-01

    In this chapter we have described the use of antibiotics for studying epithelial membrane resistances and permeabilities, as well as active and passive transport processes. We placed particular emphasis on sources of artifacts that could result in erroneous determination of any of the above parameters, as well as methods for assessing such artifacts (where possible). Although the number of possible artifacts seems large, it is not our intention to dissuade researchers from using this probe of epithelial function, but rather to point out how data might be incorrectly interpreted.

  5. Effects of non-thermal plasma on the electrical properties of an erythrocyte membrane

    Science.gov (United States)

    Lee, Jin Young; Baik, Ku Youn; Kim, Tae Soo; Lim, Jaekwan; Uhm, Han S.; Choi, Eun Ha

    2015-09-01

    Non-thermal plasma is used here for membrane oxidation and permeabilization in which the electrical properties of an erythrocyte membrane are investigated after treatments. The zeta potential as measured by electrophoresis shows the increased negativity of the membrane surface potential (Ψs). The secondary electron emission coefficient ( γ) measured by a focused ion beam shows a decrease in the dipole potential (Ψd) of lipid molecules. The voltage-sensitive fluorescent intensity as measured by flow cytometry shows a decrease in the trans-membrane potential (ΔΨ) through the lipid bilayer membrane. These results allow us to take a step forward to unveil the complex events occurring in plasma-treated cells.

  6. Liquid but Durable: Molecular Dynamics Simulations Explain the Unique Properties of Archaeal-Like Membranes

    Science.gov (United States)

    Chugunov, Anton O.; Volynsky, Pavel E.; Krylov, Nikolay A.; Boldyrev, Ivan A.; Efremov, Roman G.

    2014-12-01

    Archaeal plasma membranes appear to be extremely durable and almost impermeable to water and ions, in contrast to the membranes of Bacteria and Eucaryota. Additionally, they remain liquid within a temperature range of 0-100°C. These are the properties that have most likely determined the evolutionary fate of Archaea, and it may be possible for bionanotechnology to adopt these from nature. In this work, we use molecular dynamics simulations to assess at the atomistic level the structure and dynamics of a series of model archaeal membranes with lipids that have tetraether chemical nature and ``branched'' hydrophobic tails. We conclude that the branched structure defines dense packing and low water permeability of archaeal-like membranes, while at the same time ensuring a liquid-crystalline state, which is vital for living cells. This makes tetraether lipid systems promising in bionanotechnology and material science, namely for design of new and unique membrane nanosystems.

  7. Exploring the Local Elastic Properties of Bilayer Membranes Using Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Pieffet, Gilles; Botero, Alonso; Peters, Günther H.J.;

    2014-01-01

    of mean force (PMF) allowed us to dissect the elastic contribution. With this information, we calculated an effective linear spring constant of 44 +/- 4 kJ.nm-2.mol-1 for the DOPC membrane, in agreement with experimental estimates. The membrane deformation profile was determined independently during...... the stretching process in molecular detail, allowing us to fit this profile to a previously proposed continuum elastic model. Through this approach, we calculated an effective membrane spring constant of 42 kJ-2.mol-1, which is in good agreement with the PMF calculation. Furthermore, the solvation energy we...... derived from the data is shown to match the solvation energy estimated from critical micelle formation constants. This methodology can be used to determine how changes in lipid composition or the presence of membrane modifiers can affect the elastic properties of a membrane at a local level....

  8. Experimental study on the microstructure and nanomechanical properties of the wing membrane of dragonfly

    Institute of Scientific and Technical Information of China (English)

    Kewei Xiao; Ke Bai; Wensheng Wang; Fan Song

    2007-01-01

    Detailed investigations on the microstructure and the mechanical properties of the wing membrane of the dragonfly are carded out. It is found that in the direction of the thickness the membrane was divided into three layers rather than a single entity as traditionally considered,and on the surfaces the membrane displays a random distribution rough microstructure that is composed of numerous nanometer scale columns coated by the cuticle wax secreted.The characteristics of the surface structure are measured and described. The mechanical properties of the membranes taken separately from the wings of live and dead dragonflies are investigated by the nanoindentation technique. The Young's moduli obtained here are approximately two times greater than the previous result, and the reasons that yield the difference are discussed.

  9. Correlation Between Pyrolysis Atmosphere and Carbon Molecular Sieve Membrane Performance Properties

    KAUST Repository

    Kiyono, Mayumi

    2011-01-01

    Carbon molecular sieve (CMS) membranes have attractive separation performance properties, greatly exceeding an "upper bound" trade-off curve of polymeric membrane performance. CMS membranes are prepared by pyrolyzing polymers, well above their glass transition temperatures. Multiple factors, such as polymer precursor and pyrolysis protocol, are known to affect the separation performance. In this study, a correlation observed between pyrolysis atmosphere and CMS separation performance properties is discussed. Specifically, oxygen exposure during the pyrolysis process is the focus. The theory and details of the oxygen exposure and development of a new CMS preparation method using oxygen as a "dopant" will be described with a strong correlation observed with separation performance for CMS membranes prepared with various polymer precursors. In addition, study of possible mass transfer limitations on the oxygen "doping" process will be described to clarify the basis for the equilibrium-based interpretation of doping data. The method is also explored by changing the pyrolysis temperature. © 2011 Elsevier B.V.

  10. Transport Properties of Aqueous Glycerol and Aqueous Mannitol through the Zirconium Oxide Membrane

    Science.gov (United States)

    Blokhra; Sharma; Blokhra

    1997-08-15

    The transport properties of aqueous glycerol and aqueous mannitol across a zirconium oxide membrane are, investigated from the point of view of irreversible thermodynamics. The data on hydrodynamic permeability are analyzed in terms of frictional coefficients and entropy of activation. The phenomenological coefficient characterizing the electroosmotic flow and the membrane characteristics are also estimated for the various solutions with the object of determining the efficiencies of electrokinetic energy conversion and zeta potential. Copyright 1997Academic Press

  11. Amphotericin B nephrotoxicity: the adverse consequences of altered membrane properties.

    Science.gov (United States)

    Sawaya, B P; Briggs, J P; Schnermann, J

    1995-08-01

    Amphotericin B (AmB) has been in clinical use for more than 30 yr but has remained the most effective drug for treatment of serious fungal infections. Its use has increased in recent years, as the result of increases in aggressive intensive care support and increased numbers of immunocompromised patients. Nephrotoxic manifestations are common, and this is the major factor limiting the clinical use of the drug. A number of recent studies have contributed to a better understanding of the mechanism by which AmB exerts its nephrotoxic effect. AmB alters cell membrane permeability and probably as a consequence alters tubular and vascular smooth muscle cell function, leading to various tubular transport defects and vasoconstriction. Decreased RBF appears to play a major role in AmB-induced reduction GFR, and recurrent ischemia may be the basis of permanent structural nephrotoxic effects. Salt loading is the only measure proven by controlled prospective study to ameliorate AmB nephrotoxicity in humans. Liposomal AmB and the formulation of an emulsion of AmB in lipid may provide a protective effect based on altering the affinity of AmB for mammalian cell membranes, while preserving high efficacy against fungal cells. However, further studies are needed to evaluate the efficacy and safety of these new AmB formulations.

  12. Biophysical study of resin acid effects on phospholipid membrane structure and properties

    DEFF Research Database (Denmark)

    Jagalski, Vivien; Barker, Robert; Topgaard, Daniel

    2016-01-01

    Hydrophobic resin acids (RAs) are synthesized by conifer trees as part of their defense mechanisms. One of the functions of RAs in plant defense is suggested to be the perturbation of the cellular membrane. However, there is a vast diversity of chemical structures within this class of molecules...... membranes and the polar lipid extract of soybeans. The complementarity of the biophysical techniques used (NMR, DLS, NR, DSC, Cryo-TEM) allowed correlating changes at the vesicle level with changes at the molecular level and the co-localization of RAs within DPPC monolayer. Effects on DPPC membranes...... are correlated with the physical chemical properties of the RA and their toxicity....

  13. Microwave tunable dielectric properties of multilayer CNT membranes for smart applications

    Science.gov (United States)

    Liu, L.; Yang, Z. H.; Kong, L. B.; Yin, W. Y.; Wang, S.

    2012-09-01

    Multilayer multiwall carbon nanotube (MWCNT) silicone composite membranes with thickness greater than 10 μm were prepared with a spin-coating method. Dielectric permittivity and tunability of the circular membranes were measured from 0.1 to 7 GHz by using a single-port coaxial line method. The frequency and bias voltage dependent dielectric properties were interpreted based on percolation theory. The MWCNT membranes could be potentially used to develop smart components and structures working at radio wave or microwave frequencies.

  14. Improved antifouling properties of PVDF membranes modified with oppositely charged copolymer.

    Science.gov (United States)

    Shen, Xiang; Zhao, Yiping; Feng, Xia; Bi, Sixin; Ding, Wenbin; Chen, Li

    2013-01-01

    Biofouling resulting from the attachment of microorganisms communities to the membrane surface is the major obstacle for the widespread application of membrane technology. This work develops a feasible approach to prepare an anti-biofouling poly(vinylidene fluoride) (PVDF) membrane. A copolymer that possessed oppositely charged groups was first synthesized via radical copolymerization with methyl methacrylate, 2-methacryloxy ethyltrimethyl ammonium chloride and 2-acrylamide-2-methyl propane sulphonic acid as monomers. The copolymer was blended with the PVDF powder to prepare the antifouling membrane via the immersed phase inversion method. The antifouling properties of the modified PVDF membrane were studied by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, water contact angle measurement, zeta-potential measurement, protein adsorption, microbial adhesion and filtration experiments. The modified PVDF membrane showed limited adsorption and adhesion of protein bovine serum albumin and microbes (Escherichia coli and Saccharomyces cerevisiae) with increasing copolymer concentration in the casting solution. The modified PVDF membrane exhibited excellent antibiofouling properties.

  15. Structure and transport properties of ethylcellulose membranes with different types and granulation of magnetic powder

    Science.gov (United States)

    Krasowska, Monika; Strzelewicz, Anna; Rybak, Aleksandra; Dudek, Gabriela; Cieśla, Michał

    2016-06-01

    Structure and transport properties of ethylcellulose membranes with dispersed magnetic powder were investigated. The study mainly focused on diffusion, which is one of the transport mechanisms. The transport properties depend on many parameters like: polymeric matrix used, type of powder, its amount and granulation. The structure of the pattern formed by magnetic particles in the membrane matrix was studied. Description of the system was based on the phenomenological and molecular (random walk on a fractal lattice) approaches. Two parameters were calculated: the fractal dimension of random walk dw, and the fractal dimension of membrane structure df. The knowledge of both parameters made it possible to use the generalized equation of diffusion on the fractal structure obtained by Metzler et al. The research was carried out to determine the influence of magnetic powder granulation on the transport properties. The results showed that the random walk within the membranes of the smallest magnetic powder granulation was of the most subdiffusive character. Detailed investigation and quantitative description of gas transport through the membranes enables designing the membranes to be used in air oxygen enrichment.

  16. Improving the mechanical properties of collagen-based membranes using silk fibroin for corneal tissue engineering.

    Science.gov (United States)

    Long, Kai; Liu, Yang; Li, Weichang; Wang, Lin; Liu, Sa; Wang, Yingjun; Wang, Zhichong; Ren, Li

    2015-03-01

    Although collagen with outstanding biocompatibility has promising application in corneal tissue engineering, the mechanical properties of collagen-based scaffolds, especially suture retention strength, must be further improved to satisfy the requirements of clinical applications. This article describes a toughness reinforced collagen-based membrane using silk fibroin. The collagen-silk fibroin membranes based on collagen [silk fibroin (w/w) ratios of 100:5, 100:10, and 100:20] were prepared by using silk fibroin and cross-linking by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. These membranes were analyzed by scanning electron microscopy and their optical property, and NaCl and tryptophan diffusivity had been tested. The water content was found to be dependent on the content of silk fibroin, and CS10 membrane (loading 10 wt % of silk fibroin) performed the optimal mechanical properties. Also the suture experiments have proved CS10 has high suture retention strength, which can be sutured in rabbit eyes integrally. Moreover, the composite membrane proved good biocompatibility for the proliferation of human corneal epithelial cells in vitro. Lamellar keratoplasty shows that CS10 membrane promoted complete epithelialization in 35 ± 5 days, and their transparency is restored quickly in the first month. Corneal rejection reaction, neovascularization, and keratoconus are not observed. The composite films show potential for use in the field of corneal tissue engineering.

  17. Red Blood Cell Susceptibility to Pneumolysin: CORRELATION WITH MEMBRANE BIOCHEMICAL AND PHYSICAL PROPERTIES.

    Science.gov (United States)

    Bokori-Brown, Monika; Petrov, Peter G; Khafaji, Mawya A; Mughal, Muhammad K; Naylor, Claire E; Shore, Angela C; Gooding, Kim M; Casanova, Francesco; Mitchell, Tim J; Titball, Richard W; Winlove, C Peter

    2016-05-06

    This study investigated the effect of the biochemical and biophysical properties of the plasma membrane as well as membrane morphology on the susceptibility of human red blood cells to the cholesterol-dependent cytolysin pneumolysin, a key virulence factor of Streptococcus pneumoniae, using single cell studies. We show a correlation between the physical properties of the membrane (bending rigidity and surface and dipole electrostatic potentials) and the susceptibility of red blood cells to pneumolysin-induced hemolysis. We demonstrate that biochemical modifications of the membrane induced by oxidative stress, lipid scrambling, and artificial cell aging modulate the cell response to the toxin. We provide evidence that the diversity of response to pneumolysin in diabetic red blood cells correlates with levels of glycated hemoglobin and that the mechanical properties of the red blood cell plasma membrane are altered in diabetes. Finally, we show that diabetic red blood cells are more resistant to pneumolysin and the related toxin perfringolysin O relative to healthy red blood cells. Taken together, these studies indicate that the diversity of cell response to pneumolysin within a population of human red blood cells is influenced by the biophysical and biochemical status of the plasma membrane and the chemical and/or oxidative stress pre-history of the cell.

  18. Salt transport properties of model reverse osmosis membranes using electrochemical impedance spectroscopy

    Science.gov (United States)

    Feldman, Kathleen; Chan, Edwin; Stafford, Gery; Stafford, Christopher

    With the increasing shortage of clean water, efficient purification technologies including membrane separations are becoming critical. The main requirement of reverse osmosis in particular is to maximize water permeability while minimizing salt permeability. Such performance optimization has typically taken place through trial and error approaches. In this work, key salt transport metrics are instead measured in model reverse osmosis membranes using electrochemical impedance spectroscopy (EIS). As shown previously, EIS can provide both the membrane resistance Rm and membrane capacitance Cm, with Rm directly related to salt permeability. The membranes are fabricated in a molecular layer by layer approach, which allows for control over such parameters as thickness, surface and bulk chemistry, and network geometry/connectivity. Rm, and therefore salt permeability, follows the expected trends with thickness and membrane area but shows unusual behavior when the network geometry is systematically varied. By connecting intrinsic material properties such as the salt permeability with macroscopic performance measures we can begin to establish design rules for improving membrane efficiency and facilitate the creation of next-generation separation membranes.

  19. Relationship between erythrocyte membrane phase properties and susceptibility to secretory phospholipase A2.

    Science.gov (United States)

    Best, Katrina B; Ohran, Allison J; Hawes, Andrea C; Hazlett, Theodore L; Gratton, Enrico; Judd, Allan M; Bell, John D

    2002-11-26

    Normally, cell membranes resist hydrolysis by secretory phospholipase A(2). However, upon elevation of intracellular calcium, the cells become susceptible. Previous investigations demonstrated a possible relationship between changes in lipid order caused by increased calcium and susceptibility to phospholipase A(2). To further explore this relationship, we used temperature as an experimental means of manipulating membrane physical properties. We then compared the response of human erythrocytes to calcium ionophore at various temperatures in the range of 20-50 degrees C using fluorescence spectroscopy and two-photon fluorescence microscopy. The steady state fluorescence emission of the environment-sensitive probe, laurdan, revealed that erythrocyte membrane order decreases systematically with temperature throughout this range, especially between 28 and 45 degrees C. Furthermore, the ability of calcium ionophore to induce increased membrane order and susceptibility to phospholipase A(2) depended similarly on temperature. Both responses to calcium influx were enhanced as membrane fluidity increased. Analysis of the spatial distribution of laurdan fluorescence at several temperatures indicated that the ordering effect of intracellular calcium on fluid membranes generates an increase in the number of fluid-solid boundaries. Hydrolysis of the membrane appeared to progress outward from these boundaries. We conclude that phospholipase A(2) prefers to hydrolyze lipids in fluid regions of human erythrocyte membranes, but primarily when those regions coexist with domains of ordered lipids.

  20. Preparation and characterization of electrospun poly(phthalazinone ether nitrile ketone) membrane with novel thermally stable properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Gang; Zhang, Hao; Qian, Bingqing [Carbon Research Laboratory, Liaoning Key Lab for Energy Materials and Chemical Engineering, State Key Lab of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Wang, Jinyan, E-mail: wangjinyan@dlut.edu.cn [Department of Polymer Science and Materials, Dalian University of Technology, Dalian 116024 (China); Jian, Xigao [Department of Polymer Science and Materials, Dalian University of Technology, Dalian 116024 (China); Qiu, Jieshan, E-mail: jqiu@dlut.edu.cn [Carbon Research Laboratory, Liaoning Key Lab for Energy Materials and Chemical Engineering, State Key Lab of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China)

    2015-10-01

    Highlights: • Poly (phthalazinone ether nitrile ketone) (PPENK) was used to successfully prepare nanofiber membranes by electrospinning. • Electrospun membrane exhibits a good thermostability. • Electrospun membrane. - Abstract: Electrospun nanofibrous membranes have several applications because of their excellent properties, such as high porosity, small fiber diameter, and large surface area. However, high-temperature resistant electrospun membranes remain a challenge because of the absence of precursors that offer spinnability, scalability, and superior thermal stability. In this study, poly(phthalazinone ether nitrile ketone) (PPENK) was used to successfully prepare nanofiber membranes by electrospinning. Electrospun PPENK membranes were characterized by scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, and tensile stress–strain tests. Results indicated that the prepared electrospun membranes had a very high glass transition temperature, superior chemical resistance, and excellent mechanical strength. These desirable properties broaden their potential application in membranes and treatment of various hot fluid streams without strict temperature control.

  1. Viscoelastic Properties of Extracellular Polymeric Substances Can Strongly Affect Their Washing Efficiency from Reverse Osmosis Membranes.

    Science.gov (United States)

    Ferrando Chavez, Diana Lila; Nejidat, Ali; Herzberg, Moshe

    2016-09-01

    The role of the viscoelastic properties of biofouling layers in their removal from the membrane was studied. Model fouling layers of extracellular polymeric substances (EPS) originated from microbial biofilms of Pseudomonas aeruginosa PAO1 differentially expressing the Psl polysaccharide were used for controlled washing experiments of fouled RO membranes. In parallel, adsorption experiments and viscoelastic modeling of the EPS layers were conducted in a quartz crystal microbalance with dissipation (QCM-D). During the washing stage, as shear rate was elevated, significant differences in permeate flux recovery between the three different EPS layers were observed. According to the amount of organic carbon remained on the membrane after washing, the magnitude of Psl production provides elevated resistance of the EPS layer to shear stress. The highest flux recovery during the washing stage was observed for the EPS with no Psl. Psl was shown to elevate the layer's shear modulus and shear viscosity but had no effect on the EPS adhesion to the polyamide surface. We conclude that EPS retain on the membrane as a result of the layer viscoelastic properties. These results highlight an important relation between washing efficiency of fouling layers from membranes and their viscoelastic properties, in addition to their adhesion properties.

  2. Humidity Sensing Properties of Pre-irradiation Grafted HDPE Membranes

    Institute of Scientific and Technical Information of China (English)

    Zheng Jiao; Qun Fu; Xiang Geng; Zhen Li; Haijian Zhong

    2006-01-01

    Grafted high density polyethylene (HDPE) films have been prepared by grafting sodium styrene sulfonate (SSS) and acrylic acid (AA) onto HDPE using preirradiation method. The structure and surface morphology of both grafted and ungrafted HDPE films were observed by FTIR spectroscopy and scanning electron microscope (SEM), respectively. The humidity sensing properties of grafted HDPE films were investigated. The results show that the impedance of the film decreases with increasing of relative humidity (RH). The films display high sensitivity with nearly three orders of magnitude change in the resistance during the relative humidity variation from 5% to 98%. Grafted HDPE films exhibit excellent properties as humidity sensors.

  3. Membrane Properties Involved in Calcium-Stimulated Microparticle Release from the Plasma Membranes of S49 Lymphoma Cells

    Directory of Open Access Journals (Sweden)

    Lauryl E. Campbell

    2014-01-01

    Full Text Available This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32–42°C. A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.

  4. Membrane properties involved in calcium-stimulated microparticle release from the plasma membranes of S49 lymphoma cells.

    Science.gov (United States)

    Campbell, Lauryl E; Nelson, Jennifer; Gibbons, Elizabeth; Judd, Allan M; Bell, John D

    2014-01-01

    This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32-42°C). A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.

  5. Edelfosine and miltefosine effects on lipid raft properties: membrane biophysics in cell death by antitumor lipids.

    Science.gov (United States)

    Castro, Bruno M; Fedorov, Aleksander; Hornillos, Valentin; Delgado, Javier; Acuña, A Ulises; Mollinedo, Faustino; Prieto, Manuel

    2013-07-03

    Edelfosine (1-O-octadecyl-2-O-methyl-sn-glycero-phosphocholine) and miltefosine (hexadecylphosphocholine) are synthetic alkylphospholipids (ALPs) that are reported to selectively accumulate in tumor cell membranes, inducing Fas clustering and activation on lipid rafts, triggering apoptosis. However, the exact mechanism by which these lipids elicit these events is still not fully understood. Recent studies propose that their mode of action might be related with alterations of lipid rafts biophysical properties caused by these lipid drugs. To achieve a clear understanding of this mechanism, we studied the effects of pharmacologically relevant amounts of edelfosine and miltefosine in the properties of model and cellular membranes. The influence of these molecules on membrane order, lateral organization, and lipid rafts molar fraction and size were studied by steady-state and time-resolved fluorescence methods, Förster resonance energy transfer (FRET), confocal and fluorescence lifetime imaging microscopy (FLIM). We found that the global membrane and lipid rafts biophysical properties of both model and cellular membranes were not significantly affected by both the ALPs. Nonetheless, in model membranes, a mild increase in membrane fluidity induced by both alkyl lipids was detected, although this effect was more noticeable for edelfosine than miltefosine. This absence of drastic alterations shows for the first time that ALPs mode of action is unlikely to be directly linked to alterations of lipid rafts biophysical properties caused by these drugs. The biological implications of this result are discussed in the context of ALPs effects on lipid metabolism, mitochondria homeostasis modulation, and their relationship with tumor cell death.

  6. Physical chemistry and membrane properties of two phosphatidylinositol bisphosphate isomers.

    Science.gov (United States)

    Slochower, David R; Wang, Yu-Hsiu; Radhakrishnan, Ravi; Janmey, Paul A

    2015-05-21

    The most highly charged phospholipids, polyphosphoinositides, are often involved in signaling pathways that originate at cell-cell and cell-matrix contacts, and different isomers of polyphosphoinositides have distinct biological functions that cannot be explained by separate highly specific protein ligand binding sites [Lemmon, Nat. Rev. Mol. Cell Biol., 2008, 9, 99-111]. PtdIns(3,5)P2 is a low abundance phosphoinositide localized to cytoplasmic-facing membrane surfaces, with relatively few known ligands, yet PtdIns(3,5)P2 plays a key role in controlling membrane trafficking events and cellular stress responses that cannot be duplicated by other phosphoinositides [Dove et al., Nature, 1997, 390, 187-192; Michell, FEBS J., 2013, 280, 6281-6294]. Here we show that PtdIns(3,5)P2 is structurally distinct from PtdIns(4,5)P2 and other more common phospholipids, with unique physical chemistry. Using multiscale molecular dynamics techniques on the quantum level, single molecule, and in bilayer settings, we found that the negative charge of PtdIns(3,5)P2 is spread over a larger area, compared to PtdIns(4,5)P2, leading to a decreased ability to bind divalent ions. Additionally, our results match well with experimental data characterizing the cluster forming potential of these isomers in the presence of Ca(2+) [Wang et al., J. Am. Chem. Soc., 2012, 134, 3387-3395; van den Bogaart et al., Nature, 2011, 479, 552-555]. Our results demonstrate that the different cellular roles of PtdIns(4,5)P2 and PtdIns(3,5)P2in vivo are not simply determined by their localization by enzymes that produce or degrade them, but also by their molecular size, ability to chelate ions, and the partial dehydration of those ions, which might affect the ability of PtdIns(3,5)P2 and PtdIns(4,5)P2 to form phosphoinositide-rich clusters in vitro and in vivo.

  7. Dissimilar and similar functional properties of complement receptor-3 in microglia and macrophages in combating yeast pathogens by phagocytosis.

    Science.gov (United States)

    Hadas, Smadar; Reichert, Fanny; Rotshenker, Shlomo

    2010-05-01

    Central nervous system (CNS) microglia (MG) and peripheral tissue macrophages (MO) remove pathogens by phagocytosis. Zymosan, a model yeast pathogen, is a beta-glucan rich particle that readily activates the complement system and then becomes C3bi-opsonized (op). Complement receptor-3 (CR3) has initially been implicated in mediating the phagocytosis of both C3bi-op and non-opsonized (nop) zymosan by MO through C3bi and beta-glucan binding sites, respectively. Later, the role of CR3 as a phagocytic beta-glucan receptor has been questioned and the supremacy of beta-glucan receptor Dectin-1 advocated. We compare here between primary mouse CNS MG and peripheral tissue MO with respect to CR3 and Dectin-1 mediated phagocytosis of C3bi-op and nop zymosan. We report that MG and MO display similar as well as dissimilar functional properties in this respect. Although CR3 and Dectin-1 function both as beta-glucan/non-opsonic receptors in MG during nop zymosan phagocytosis, Dectin-1, but not CR3, does so in MO. CR3 functions also as a C3bi/opsonic receptor in MG and MO during C3bi-op zymosan phagocytosis, leading to phagocytosis which is more efficient than that of nop zymosan. Dectin-1 contributes, albeit less than CR3, to phagocytosis of C3bi-op zymosan in MG and further less in MO, suggesting that C3bi-opsonization does not block all beta-glucan sites on zymosan from binding Dectin-1 on phagocytes. Thus, altogether CR3 and Dectin-1 contribute both to phagocytosis of nop and C3bi-op zymosan in MG, whereas MO switch from CR3-independent/Dectin-1-dependent phagocytosis of nop zymosan to phagocytosis of C3bi-op zymosan where CR3 dominates over Dectin-1.

  8. Immobilization and Properties of Lipase from Candida rugosa on Electrospun Nanofibrous Membranes with Biomimetic Phospholipid Moities

    Institute of Scientific and Technical Information of China (English)

    HUANG Xiao-jun; YU An-guo; GE Dan; XU Zhi-kang

    2008-01-01

    Reported here is a protocol to fabricate a biocatalyst with high enzyme loading and activity retention,from the conjugation of electrospun nanofibrous membrane having biomimetic phospholipid moiety and lipase.To improve the catalytic efficiency and activity of the immobilized enzyme,poly(acrylonitrile-co-2-methacryloyloxyethyl phosphorylcholine)s(PANCMPCs)were,respectively,electrospun into nanofibrous membranes with a mean diameter of 90 nm,as a support for enzyme immobilization.Lipase from Candida rugosa Was immobilized on these nanofibrous membranes by adsorption.Properties of immobilized lipase on PANCMPC nanofibrous membranes were compared with those of the lipase immobilized on the polyacrylonitrile(PAN)nanofibrous and sheet membranes,respectively.Efiective enzyme loading on the nanofibrous membranes was achieved up to22mg/g,which was over 10times that on the sheet membrane.The activity retention of immobilized lipase increased from 56.4%to 76.8%with an increase in phospholipid moiety from 0 to 9.6%(molar fraction)in the nanofibrous membrane.Kinetic parameter Km was also determined for free and immobilized lipase.The Km valae of the immobilized lipase on the nanofibrous membrane was obviously lower than that on the sheet membrane.The optimum pH was 7.7 for free lipase.but shifted to 8.3-8.5 for immobilized lipases.The optimum temperature was determined to be 35℃ for the free enzyme.but 42-44℃ for the immobilized ones,respectively.In addition,the thermal stability,reusability,and storage stability of the immobilized lipase were obviously improved compared to the free one.

  9. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  10. Molecular properties of steroids involved in their effects on the biophysical state of membranes.

    Science.gov (United States)

    Wenz, Jorge J

    2015-10-01

    The activity of steroids on membranes was studied in relation to their ordering, rigidifying, condensing and/or raft promoting ability. The structures of 82 steroids were modeled by a semi-empirical procedure (AM1) and 245 molecular descriptors were next computed on the optimized energy conformations. Principal component analysis, mean contrasting and logistic regression were used to correlate the molecular properties with 212 cases of documented activities. It was possible to group steroids based on their properties and activities, indicating that steroids having similar molecular properties have similar activities on membranes. Steroids having high values of area, partition coefficient, volume, number of rotatable bonds, molar refractivity, polarizability or mass displayed ordering, rigidifying, condensing and/or raft promoting activity on membranes higher than those steroids having low values in such molecular properties. After a variable selection procedure circumventing correlation problems among descriptors, area and log P were found as the most relevant properties in governing and predicting the activity of steroids on membranes. A logistic regression model as a function of the area and log P of the steroids is proposed, which is able to predict correctly 92.5% of the cases. A rationale of the findings is discussed.

  11. Development and modulation of intrinsic membrane properties control the temporal precision of auditory brain stem neurons.

    Science.gov (United States)

    Franzen, Delwen L; Gleiss, Sarah A; Berger, Christina; Kümpfbeck, Franziska S; Ammer, Julian J; Felmy, Felix

    2015-01-15

    Passive and active membrane properties determine the voltage responses of neurons. Within the auditory brain stem, refinements in these intrinsic properties during late postnatal development usually generate short integration times and precise action-potential generation. This developmentally acquired temporal precision is crucial for auditory signal processing. How the interactions of these intrinsic properties develop in concert to enable auditory neurons to transfer information with high temporal precision has not yet been elucidated in detail. Here, we show how the developmental interaction of intrinsic membrane parameters generates high firing precision. We performed in vitro recordings from neurons of postnatal days 9-28 in the ventral nucleus of the lateral lemniscus of Mongolian gerbils, an auditory brain stem structure that converts excitatory to inhibitory information with high temporal precision. During this developmental period, the input resistance and capacitance decrease, and action potentials acquire faster kinetics and enhanced precision. Depending on the stimulation time course, the input resistance and capacitance contribute differentially to action-potential thresholds. The decrease in input resistance, however, is sufficient to explain the enhanced action-potential precision. Alterations in passive membrane properties also interact with a developmental change in potassium currents to generate the emergence of the mature firing pattern, characteristic of coincidence-detector neurons. Cholinergic receptor-mediated depolarizations further modulate this intrinsic excitability profile by eliciting changes in the threshold and firing pattern, irrespective of the developmental stage. Thus our findings reveal how intrinsic membrane properties interact developmentally to promote temporally precise information processing.

  12. Membrane fouling in a submerged membrane bioreactor with focus on surface properties and interactions of cake sludge and bulk sludge.

    Science.gov (United States)

    Yu, Haiying; Lin, Hongjun; Zhang, Meijia; Hong, Huachang; He, Yiming; Wang, Fangyuan; Zhao, Leihong

    2014-10-01

    In this study, the fouling behaviors and surface properties of cake sludge and bulk sludge in a submerged membrane bioreactor (MBR) were investigated and compared. It was found that the specific filtration resistance (SFR) of cake sludge was about 5 times higher than that of bulk sludge. Two types of sludge possessed similar extracellular polymeric substances (EPS) content, particle size distribution (PSD) and zeta potential. However, their surface properties in terms of surface tensions were significantly different. Further analysis showed that cake sludge was more hydrophilic and had worse aggregation ability. Moreover, cake sludge surface possessed more hydrocarbon, less oxygen and nitrogen moieties than bulk sludge surface. It was suggested that, rather than EPS and PSD differences, the differences in the surface composition were the main cause of the great differences in SFR and adhesion ability between cake sludge and bulk sludge.

  13. New Studies of the Physical Properties of Metallic Amorphous Membranes for Hydrogen Purification

    Directory of Open Access Journals (Sweden)

    Oriele Palumbo

    2017-02-01

    Full Text Available Amorphous metallic membranes display promising properties for hydrogen purification up to an ultrapure grade (purity > 99.999%. The hydrogen permeability through amorphous membranes has been widely studied in the literature. In this work we focus on two additional properties, which should be considered before possible application of such materials: the propensity to crystallize at high temperatures should be avoided, as the crystallized membranes can become brittle; the hydrogen solubility should be high, as solubility and permeability are proportional. We investigate the crystallization process and the hydrogen solubility of some membranes based on Ni, Nb, and Zr metals, as a function of Zr content, and with the addition of Ta or B. The boron doping does not significantly affect the crystallization temperature and the thermal stability of the membrane. However, the hydrogen solubility for p ~7 bar is as high as H/M ~0.31 at T = 440 °C and H/M ~0.27 at T = 485 °C. Moreover, the membrane does not pulverize even after repeated thermal cycles and hydrogenation processes up to 485 °C and 7 bar, and it retains its initial shape.

  14. Membranolytic Activity of Bile Salts: Influence of Biological Membrane Properties and Composition

    Directory of Open Access Journals (Sweden)

    Alfred Blume

    2007-10-01

    Full Text Available The two main steps of the membranolytic activity of detergents: 1 the partitioning of detergent molecules in the membrane and 2 the solubilisation of the membrane are systematically investigated. The interactions of two bile salt molecules, sodium cholate (NaC and sodium deoxycholate (NaDC with biological phospholipid model membranes are considered. The membranolytic activity is analysed as a function of the hydrophobicity of the bile salt, ionic strength, temperature, membrane phase properties, membrane surface charge and composition of the acyl chains of the lipids. The results are derived from calorimetric measurements (ITC, isothermal titration calorimetry. A thermodynamic model is described, taking into consideration electrostatic interactions, which is used for the calculation of the partition coefficient as well as to derive the complete thermodynamic parameters describing the interaction of detergents with biological membranes (change in enthalpy, change in free energy, change in entropy etc. The solubilisation properties are described in a so-called vesicle-to-micelle phase transition diagram. The obtained results are supplemented and confirmed by data obtained from other biophysical techniques (DSC differential scanning calorimetry, DLS dynamic light scattering, SANS small angle neutron scattering.

  15. SAXS and NMR analysis for the cast solvent effect on sPEEK membrane properties.

    Science.gov (United States)

    Luu, Dinh Xuan; Cho, Eun-Bum; Han, Oc Hee; Kim, Dukjoon

    2009-07-30

    The cast solvent effect on the structure and properties of sulfonated poly(ether ether ketone) (sPEEK) was studied. PEEK was sulfonated to have different sulfonation degrees of 65, 70, and 75%, and its membrane was prepared using the two types of solvents, N,N-dimethylacetamide (DMA) and 1-methyl-2-pyrrolidinone (NMP). Ionic cluster size was analyzed using small-angle X-ray scattering (SAXS), and it was correlated with a few essential membrane properties such as water uptake, methanol permeability, proton conductivity, and cell performance in direct methanol fuel cells (DMFCs). Synchrotron SAXS and solid state NMR data revealed the structural difference between the sPEEK membranes prepared using NMP and DMA, regarding the cluster dimensions of 3.22 and 2.70 nm, respectively. Although the water uptake, methanol permeability, and proton conductivity of the membranes prepared with NMP were higher than those with DMA, the overall cell performance was vice versa. The dimensional instability associated with high water swelling as well as high methanol permeability were the main causes for this inferior cell efficiency of NMP cast membranes. This report demonstrates the importance of selection of cast solvent in preparation of SPEEK electrolyte membranes for DMFC application.

  16. Phase coexistence in a triolein-phosphatidylcholine system. Implications for lysosomal membrane properties.

    Science.gov (United States)

    Pakkanen, Kirsi I; Duelund, Lars; Vuento, Matti; Ipsen, John Hjort

    2010-02-01

    The effects of tri- and monoglycerides on phospholipid (POPC) membranes were studied using spectroscopical methods. Triolein was found to form two types of POPC-rich membranes, both with POPC or as a three-component system with monopalmitin. These two membrane types were determined as co-existing phases based on their spontaneous and stable separation and named heavy and light phase according to their sedimentation behaviour. Marked differences were seen in the physical properties of these phases, even though only minor compositional variation was detected. The light, less polar phase was found to be less ordered and more fluid and seemed to allow significantly lower amount of water penetration into the membrane-water interface than pure POPC membrane. The heavy phase, apart from their slightly altered water penetration, resembled more a pure POPC membrane. As triglycerides are present in lysosomal membranes, the present results can be seen as an implication for polarity-based water permeability barrier possibly contributing to the integrity of lysosomes.

  17. Predictive model of transport properties of fuel cell membrane : from microscopic to macroscopic level

    Energy Technology Data Exchange (ETDEWEB)

    Colinart, T.; Lottin, O.; Maranzana, G.; Didierjean, S.; Moyne, C. [Nancy-Univ., Vandoeuvre-les-Nancy (France). Laboratoire d' Energetique et de Mecanique Theorique et Appliquee

    2007-07-01

    Because of their attractiveness as efficient and clean energy producers, proton exchange membrane fuel cells (PEMFC) can be used in automotive and small stationary applications. The electrochemical reaction takes place on two electrodes separated by a ionomer membrane. An important component of fuel cell water management and a problem for fuel cell performances involves the transport of protons from the anode to the cathode as its' transport properties are highly water dependent. Nafion membranes are widely used as an electrolyte for PEMFC. This paper presented a model to predict transport properties of polymer membranes such as Nafion used as electrolytes in a low temperature fuel cell. The paper discussed the electrical double layer that was used to determine surface charge density. The paper then discussed the analytical solution to the physical problem in the diffuse part of a cylindrical pore which involved solving the Poisson-Boltzmann, the Navier-Stokes and the Nernst-Planck equations. The properties of the electrolytic solution were equal to those of water and they were considered to be constant within the pore. A literature comparison with other models was also presented. It was concluded that in order to supplement the model, it is necessary to investigate the mechanics of the membrane, particularly the swelling behaviour, and the adsorption phenomena of the ions in the stern layer. 15 refs., 1 tab., 3 figs.

  18. The influence of increased membrane conductance on response properties of spinal motoneurons

    DEFF Research Database (Denmark)

    Grigonis, Ramunas; Guzulaitis, Robertas; Buisas, Rokas

    2016-01-01

    During functional spinal neural network activity motoneurons receive massive synaptic excitation and inhibition, and their membrane conductance increases considerably – they are switched to a high-conductance state. High-conductance states can substantially alter response properties of motoneurons....... In the present study we investigated how an increase in membrane conductance affects spike frequency adaptation, the gain (i.e., the slope of the frequency-current relationship) and the threshold for action potential generation. We used intracellular recordings from adult turtle motoneurons in spinal cord slices....... Membrane conductance was increased pharmacologically by extracellular application of the GABAA receptor agonist muscimol. Our findings suggest that an increase in membrane conductance of about 40–50% increases the magnitude of spike frequency adaptation, but does not change the threshold for action...

  19. Large-scale identification of membrane proteins with properties favorable for crystallization.

    Science.gov (United States)

    Kim, Jared; Kagawa, Allison; Kurasaki, Kellie; Ataie, Niloufar; Cho, Il Kyu; Li, Qing X; Ng, Ho Leung

    2015-11-01

    Membrane protein crystallography is notoriously difficult due to challenges in protein expression and issues of degradation and structural stability. We have developed a novel method for large-scale screening of native sources for integral membrane proteins that have intrinsic biochemical properties favorable for crystallization. Highly expressed membrane proteins that are thermally stable and nonaggregating in detergent solutions were identified by mass spectrometry from Escherichia coli, Saccharomyces cerevisiae, and Sus scrofa cerebrum. Many of the membrane proteins identified had been crystallized previously, supporting the promise of the approach. Most identified proteins have known functions and include high-value targets such as transporters and ATPases. To validate the method, we recombinantly expressed and purified the yeast protein, Yop1, which is responsible for endoplasmic reticulum curvature. We demonstrate that Yop1 can be purified with the detergent dodecylmaltoside without aggregating.

  20. Structure-property relationships in flavour-barrier membranes with reduced high-temperature diffusivity

    Energy Technology Data Exchange (ETDEWEB)

    Heitfeld, Kevin A.; Schaefer, Dale W.

    2010-10-12

    Encapsulation is used to decrease the premature release of volatile flavour ingredients while offering protection against environmental damage such as oxidation, light-induced reactions, etc. Hydroxypropyl cellulose (HPC) is investigated here as a 'smart,' temperature responsive membrane for flavour encapsulation and delivery. Gel films were synthesized and characterized by diffusion and small-angle neutron and X-ray scattering techniques. Increasing temperature typically increases the diffusion rate across a membrane; HPC, however, can be tailored to give substantially improved elevated temperature properties. Scattering results indicate processing conditions have a significant impact on membrane morphology (micro phase separation). Under certain synthetic conditions, micro phase separation is mitigated and the membranes show temperature-independent diffusivity between 25 C and 60 C.

  1. Elastic Properties and Line Tension of Self-Assembled Bilayer Membranes

    CERN Document Server

    Li, Jianfeng; Shi, An-Chang; Schmid, Friederike; Zhou, Jiajia

    2013-01-01

    The elastic properties of a self-assembled bilayer membrane are studied using the self-consistent field theory, applied to a model system composed of flexible amphiphilic chains dissolved in hydrophilic polymeric solvents. Examining the free energy of bilayer membranes with different geometries allows us to calculate their bending modulus, Gaussian modulus, two fourth-order membrane moduli, and the line tension. The dependence of these parameters on the microscopic characteristics of the amphiphilic chain, characterized by the volume fraction of the hydrophilic component, is systematically studied. The theoretical predictions are compared with the results from a simple monolayer model, which approximates a bilayer membrane by two monolayers. Finally the region of validity of the linear elasticity theory is analyzed by examining the higher-order contributions.

  2. Unaltered membrane properties of arterial muscle in Dahl strain genetic hypertension.

    Science.gov (United States)

    Abel, P W; Trapani, A; Matsuki, N; Ingram, M J; Ingram, F D; Hermsmeyer, K

    1981-08-01

    To characterize membrane properties of arterial muscle from Dahl strain hypertensive rats, we measured caudal artery contractile sensitivity to norepinephrine and serotonin, membrane potential at 16 and 37 degrees C, and intracellular potassium, sodium, and chloride content. Dahl salt-resistant (R) strain fed low- or high-salt diets and Dahl salt-sensitive (S) strain fed a low-salt diet remained normotensive. The Dahl S strain on high-salt diets became hypertensive after 4 wk of high salt feeding. There was no significant difference in the norepinephrine or serotonin effective concentration (EC) EC50, EC10, or maximum response between the hypertensive and any of the three normotensive groups. Membrane potential measured at 37 and 16 degrees C and electron-probe analysis of intracellular potassium, sodium, and chloride concentration showed no significant differences between the four groups of animals. These results that arterial muscle membrane mechanisms are not altered in genetically hypertensive Dahl salt-sensitive rats.

  3. DETERMINATION OF PERMEATION PROPERTIES OF GAS THROUGH POLYMER MEMBRANE BY GAS CHROMATOGRAPHY

    Institute of Scientific and Technical Information of China (English)

    JIN Xigao; FU Xiucheng; ZHAN Yongjian; QIAN Renyuan

    1987-01-01

    An apparatus constructed for measuring permeation properties of polymer membranes using a mixture of gases is described. A gas chromatographic system was applied to determine the individual transport characteristics of component gases without a vacuum line. This paper also discusses some experimental factors effecting the precision of measurement. The results show that there is a linear relationship between the permeation time and the volume of the gas permeated through the membrane within certain permeation period, which depends on the permeation rate (from 10-4 to 10-7 cm3 (STP)/cm2.sec. cmHg) of the membrane. The reproducibility has been found to be good with a relative standard deviation of 3.5%. This method is more sensitive, considerably faster and more convenient for determining both the permeability coefficient and the separation factor of a polymer membrane from a chromat ogram using mixed penetrant gases.

  4. Spectral Properties and Orientation of Voltage-Sensitive Dyes in Lipid Membranes

    KAUST Repository

    Matson, Maria

    2012-07-24

    Voltage-sensitive dyes are frequently used for probing variations in the electric potential across cell membranes. The dyes respond by changing their spectral properties: measured as shifts of wavelength of absorption or emission maxima or as changes of absorption or fluorescence intensity. Although such probes have been studied and used for decades, the mechanism behind their voltage sensitivity is still obscure. We ask whether the voltage response is due to electrochromism as a result of direct field interaction on the chromophore or to solvatochromism, which is the focus of this study, as result of changed environment or molecular alignment in the membrane. The spectral properties of three styryl dyes, di-4-ANEPPS, di-8-ANEPPS, and RH421, were investigated in solvents of varying polarity and in model membranes using spectroscopy. Using quantum mechanical calculations, the spectral dependence of monomer and dimer ANEPPS on solvent properties was modeled. Also, the kinetics of binding to lipid membranes and the binding geometry of the probe molecules were found relevant to address. The spectral properties of all three probes were found to be highly sensitive to the local environment, and the probes are oriented nearly parallel with the membrane normal. Slow binding kinetics and scattering in absorption spectra indicate, especially for di-8-ANEPPS, involvement of aggregation. On the basis of the experimental spectra and time-dependent density functional theory calculations, we find that aggregate formation may contribute to the blue-shifts seen for the dyes in decanol and when bound to membrane models. In conclusion, solvatochromic and other intermolecular interactions effects also need to be included when considering electrochromic response voltage-sensitive dyes. © 2012 American Chemical Society.

  5. LAURDAN fluorescence properties in membranes: a journey from the fluorometer to the microscope

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2012-01-01

    After 32 years since its introduction, the particular fluorescence properties of 6-lauroyl-2-(dimethylamino)-naphtalene (LAURDAN) in model and biological membranes are revisited. This review includes a historical perspective about the design, synthesis and initial description of the probe’s fluor...

  6. Modeling Yeast Organelle Membranes and How Lipid Diversity Influences Bilayer Properties.

    Science.gov (United States)

    Monje-Galvan, Viviana; Klauda, Jeffery B

    2015-11-17

    Membrane lipids are important for the health and proper function of cell membranes. We have improved computational membrane models for specific organelles in yeast Saccharomyces cerevisiae to study the effect of lipid diversity on membrane structure and dynamics. Previous molecular dynamics simulations were performed by Jo et al. [(2009) Biophys J. 97, 50-58] on yeast membrane models having six lipid types with compositions averaged between the endoplasmic reticulum (ER) and the plasma membrane (PM). We incorporated ergosterol, phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol lipids in our models to better describe the unique composition of the PM, ER, and trans-Golgi network (TGN) bilayers of yeast. Our results describe membrane structure based on order parameters (SCD), electron density profiles (EDPs), and lipid packing. The average surface area per lipid decreased from 63.8 ± 0.4 Å(2) in the ER to 47.1 ± 0.3 Å(2) in the PM, while the compressibility modulus (KA) varied in the opposite direction. The high SCD values for the PM lipids indicated a more ordered bilayer core, while the corresponding lipids in the ER and TGN models had lower parameters by a factor of at least 0.7. The hydrophobic core thickness (2DC) as estimated from EDPs is the thickest for PM, which is in agreement with estimates of hydrophobic regions of transmembrane proteins from the Orientation of Proteins in Membranes database. Our results show the importance of lipid diversity and composition on a bilayer's structural and mechanical properties, which in turn influences interactions with the proteins and membrane-bound molecules.

  7. Macrophage Activation by Ursolic and Oleanolic Acids during Mycobacterial Infection

    Directory of Open Access Journals (Sweden)

    Sonia López-García

    2015-08-01

    Full Text Available Oleanolic (OA and ursolic acids (UA are triterpenes that are abundant in vegetables, fruits and medicinal plants. They have been described as active moieties in medicinal plants used for the treatment of tuberculosis. In this study, we analyzed the effects of these triterpenes on macrophages infected in vitro with Mycobacterium tuberculosis (MTB. We evaluated production of nitric oxide (NO, reactive oxygen species (ROS, and cytokines (TNF-α and TGF-β as well as expression of cell membrane receptors (TGR5 and CD36 in MTB-infected macrophages following treatment with OA and UA. Triterpenes caused reduced MTB growth in macrophages, stimulated production of NO and ROS in the early phase, stimulated TNF-α, suppressed TGF-β and caused over-expression of CD36and TGR5 receptors. Thus, our data suggest immunomodulatory properties of OA and UA on MTB infected macrophages. In conclusion, antimycobacterial effects induced by these triterpenes may be attributable to the conversion of macrophages from stage M2 (alternatively activated to M1 (classically activated.

  8. Structure and properties of PVDF membrane with PES-C addition via thermally induced phase separation process

    Science.gov (United States)

    Wu, Lishun; Sun, Junfen

    2014-12-01

    Polyvinylidene fluoride (PVDF) membrane and PVDF membrane with phenolphthalein polyethersulfone (PES-C) addition were prepared via thermally induced phase separation (TIPS) method by using diphenyl carbonate (DPC) and dimethyl acetamide (DMAc) as mixed diluents. The effects of coagulation temperature and pre-evaporation time on structure and properties of membranes were studied. The changes of sewage flux in MBR and the attenuation coefficient of sewage flux were investigated. The resistance distributions of PVDF and PVDF/PES-C membranes were compared by resistance analysis. Membrane composition and structure were characterized by ATR-FTIR, TGA, SEM and AFM. The foulant on membranes was analyzed by FTIR. The contact angle of PVDF/PES-C membrane was lower than that of PVDF membrane. A thinner skin layer and a porous cellular support layer formed in PVDF/PES-C membrane and resulted in a higher porosity and pure water flux. The pure water flux and porosity of PVDF/PES-C membrane increased with rising coagulation temperature and decreased with extending pre-evaporation time. The flux attenuation coefficient, the cake layer resistance and internal fouling resistance of PVDF/PES-C membrane in MBR were smaller than those of PVDF membrane in MBR. The FTIR spectrum of foulant on membrane indicated that the foulant on PVDF/PES-C membrane was mostly composed of protein and polysaccharide, while the foulant on pure PVDF membrane included biopolymer clusters besides protein and polysaccharide.

  9. Influence of collagen source on fibrillar architecture and properties of vitrified collagen membranes.

    Science.gov (United States)

    Majumdar, Shoumyo; Guo, Qiongyu; Garza-Madrid, Marcos; Calderon-Colon, Xiomara; Duan, Derek; Carbajal, Priscilla; Schein, Oliver; Trexler, Morgana; Elisseeff, Jennifer

    2016-02-01

    Collagen vitrigel membranes are transparent biomaterials characterized by a densely organized, fibrillar nanostructure that show promise in the treatment of corneal injury and disease. In this study, the influence of different type I collagen sources and processing techniques, including acid-solubilized collagen from bovine dermis (Bov), pepsin-solubilized collagen from human fibroblast cell culture (HuCC), and ficin-solubilized collagen from recombinant human collagen expressed in tobacco leaves (rH), on the properties of the vitrigel membranes was evaluated. Postvitrification carbodiimide crosslinking (CX) was also carried out on the vitrigels from each collagen source, forming crosslinked counterparts BovXL, HuCCXL, and rHXL, respectively. Collagen membrane ultrastructure and biomaterial properties were found to rely heavily on both collagen source and crosslinking. Bov and HuCC samples showed a random fibrillar organization of collagen, whereas rH vitrigels showed remarkable regional fibril alignment. After CX, light transmission was enhanced in all groups. Denaturation temperatures after CX increased in all membranes, of which the highest increase was seen in rH (14.71°C), suggesting improved thermal stability of the collagen fibrils in the membranes. Noncrosslinked rH vitrigels may be reinforced through CX to reach levels of mechanical strength and thermal stability comparable to Bov.

  10. Macrophages and Iron Metabolism.

    Science.gov (United States)

    Soares, Miguel P; Hamza, Iqbal

    2016-03-15

    Iron is a transition metal that due to its inherent ability to exchange electrons with a variety of molecules is essential to support life. In mammals, iron exists mostly in the form of heme, enclosed within an organic protoporphyrin ring and functioning primarily as a prosthetic group in proteins. Paradoxically, free iron also has the potential to become cytotoxic when electron exchange with oxygen is unrestricted and catalyzes the production of reactive oxygen species. These biological properties demand that iron metabolism is tightly regulated such that iron is available for core biological functions while preventing its cytotoxic effects. Macrophages play a central role in establishing this delicate balance. Here, we review the impact of macrophages on heme-iron metabolism and, reciprocally, how heme-iron modulates macrophage function.

  11. Quantitative GPCR and ion channel transcriptomics in primary alveolar macrophages and macrophage surrogates

    Directory of Open Access Journals (Sweden)

    Groot-Kormelink Paul J

    2012-10-01

    Full Text Available Abstract Background Alveolar macrophages are one of the first lines of defence against invading pathogens and play a central role in modulating both the innate and acquired immune systems. By responding to endogenous stimuli within the lung, alveolar macrophages contribute towards the regulation of the local inflammatory microenvironment, the initiation of wound healing and the pathogenesis of viral and bacterial infections. Despite the availability of protocols for isolating primary alveolar macrophages from the lung these cells remain recalcitrant to expansion in-vitro and therefore surrogate cell types, such as monocyte derived macrophages and phorbol ester-differentiated cell lines (e.g. U937, THP-1, HL60 are frequently used to model macrophage function. Methods The availability of high throughput gene expression technologies for accurate quantification of transcript levels enables the re-evaluation of these surrogate cell types for use as cellular models of the alveolar macrophage. Utilising high-throughput TaqMan arrays and focussing on dynamically regulated families of integral membrane proteins, we explore the similarities and differences in G-protein coupled receptor (GPCR and ion channel expression in alveolar macrophages and their widely used surrogates. Results The complete non-sensory GPCR and ion channel transcriptome is described for primary alveolar macrophages and macrophage surrogates. The expression of numerous GPCRs and ion channels whose expression were hitherto not described in human alveolar macrophages are compared across primary macrophages and commonly used macrophage cell models. Several membrane proteins known to have critical roles in regulating macrophage function, including CXCR6, CCR8 and TRPV4, were found to be highly expressed in macrophages but not expressed in PMA-differentiated surrogates. Conclusions The data described in this report provides insight into the appropriate choice of cell models for

  12. Changes in physicochemical and transport properties of a reverse osmosis membrane exposed to chloraminated seawater

    KAUST Repository

    Valentino, Lauren

    2015-02-17

    This study contributed to improving our understanding of how disinfectants, applied to control biofouling of reverse osmosis (RO) membranes, result in membrane performance degradation. We investigated changes in physicochemical properties and permeation performance of a RO membrane with fully aromatic polyamide (PA) active layer. Membrane samples were exposed to varying concentrations of monochloramine, bromide, and iodide in both synthetic and natural seawater. Elemental analysis of the membrane active layer by Rutherford backscattering spectrometry (RBS) revealed the incorporation of bromine and iodine into the polyamide. The kinetics of polyamide bromination were first order with respect to the concentration of the secondary oxidizing agent Br2 for the conditions investigated. Halogenated membranes were characterized after treatment with a reducing agent and heavy ion probes to reveal the occurrence of irreversible ring halogenation and an increase in carboxylic groups, the latter produced as a result of amide bond cleavage. Finally, permeation experiments revealed increases in both water permeability and salt passage as a result of oxidative damage.

  13. Improved antifouling properties of polymer membranes using a ‘layer-by-layer’ mediated method

    KAUST Repository

    Chen, Lin

    2013-01-01

    Polymeric reverse osmosis membranes were modified with antifouling polymer brushes through a \\'layer by layer\\' (LBL) mediated method. Based on pure physical electrostatic interaction, the attachment of LBL films did not alter separation performance of the membranes. In addition, the incorporation of an LBL film also helped to amplify the number of potential reaction sites on the membrane surfaces for attachment of antifouling polymer brushes, which were then attached to the surface. Attachment of the brushes included two different approaches, grafting to and grafting from. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements showed successful growth of the LBL films and subsequently the polymer brushes. Using this method to modify reverse osmosis membranes, preliminary performance testing showed the antifouling properties of the as-modified membranes were much better than the virgin membrane with no significant loss in water flux and salt rejection. © 2013 The Royal Society of Chemistry.

  14. Changes in physicochemical and transport properties of a reverse osmosis membrane exposed to chloraminated seawater.

    Science.gov (United States)

    Valentino, Lauren; Renkens, Tennie; Maugin, Thomas; Croué, Jean-Philippe; Mariñas, Benito J

    2015-02-17

    This study contributed to improving our understanding of how disinfectants, applied to control biofouling of reverse osmosis (RO) membranes, result in membrane performance degradation. We investigated changes in physicochemical properties and permeation performance of a RO membrane with fully aromatic polyamide (PA) active layer. Membrane samples were exposed to varying concentrations of monochloramine, bromide, and iodide in both synthetic and natural seawater. Elemental analysis of the membrane active layer by Rutherford backscattering spectrometry (RBS) revealed the incorporation of bromine and iodine into the polyamide. The kinetics of polyamide bromination were first order with respect to the concentration of the secondary oxidizing agent Br2 for the conditions investigated. Halogenated membranes were characterized after treatment with a reducing agent and heavy ion probes to reveal the occurrence of irreversible ring halogenation and an increase in carboxylic groups, the latter produced as a result of amide bond cleavage. Finally, permeation experiments revealed increases in both water permeability and salt passage as a result of oxidative damage.

  15. Synthesis and Transport Properties of Novel MOF/PIM-1/MOF Sandwich Membranes for Gas Separation

    Directory of Open Access Journals (Sweden)

    Alessio Fuoco

    2017-02-01

    Full Text Available Metal-organic frameworks (MOFs were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1. Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8 and Copper benzene tricarboxylate ((HKUST-1, were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes. The pure gas permeabilities of He, H2, O2, N2, CH4, CO2 were studied to understand the effect of the surface modification on the basic transport properties and evaluate the potential use of these membranes for industrially relevant gas separations. The pure gas transport was discussed in terms of permeability and selectivity, highlighting the effect of the MOF growth on the diffusion coefficients of the gas in the new composite polymer membranes. The results confirm that the growth of MOFs on polymer membranes can enhance the selectivity of the appropriately functionalized PIM-1, without a dramatic decrease of the permeability.

  16. Synthesis and Transport Properties of Novel MOF/PIM-1/MOF Sandwich Membranes for Gas Separation.

    Science.gov (United States)

    Fuoco, Alessio; Khdhayyer, Muhanned R; Attfield, Martin P; Esposito, Elisa; Jansen, Johannes C; Budd, Peter M

    2017-02-11

    Metal-organic frameworks (MOFs) were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1). Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8) and Copper benzene tricarboxylate ((HKUST-1), were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA) -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes. The pure gas permeabilities of He, H₂, O₂, N₂, CH₄, CO₂ were studied to understand the effect of the surface modification on the basic transport properties and evaluate the potential use of these membranes for industrially relevant gas separations. The pure gas transport was discussed in terms of permeability and selectivity, highlighting the effect of the MOF growth on the diffusion coefficients of the gas in the new composite polymer membranes. The results confirm that the growth of MOFs on polymer membranes can enhance the selectivity of the appropriately functionalized PIM-1, without a dramatic decrease of the permeability.

  17. Structural and functional properties of hydration and confined water in membrane interfaces.

    Science.gov (United States)

    Disalvo, E A; Lairion, F; Martini, F; Tymczyszyn, E; Frías, M; Almaleck, H; Gordillo, G J

    2008-12-01

    The scope of the present review focuses on the interfacial properties of cell membranes that may establish a link between the membrane and the cytosolic components. We present evidences that the current view of the membrane as a barrier of permeability that contains an aqueous solution of macromolecules may be replaced by one in which the membrane plays a structural and functional role. Although this idea has been previously suggested, the present is the first systematic work that puts into relevance the relation water-membrane in terms of thermodynamic and structural properties of the interphases that cannot be ignored in the understanding of cell function. To pursue this aim, we introduce a new definition of interphase, in which the water is organized in different levels on the surface with different binding energies. Altogether determines the surface free energy necessary for the structural response to changes in the surrounding media. The physical chemical properties of this region are interpreted in terms of hydration water and confined water, which explain the interaction with proteins and could affect the modulation of enzyme activity. Information provided by several methodologies indicates that the organization of the hydration states is not restricted to the membrane plane albeit to a region extending into the cytoplasm, in which polar head groups play a relevant role. In addition, dynamic properties studied by cyclic voltammetry allow one to deduce the energetics of the conformational changes of the lipid head group in relation to the head-head interactions due to the presence of carbonyls and phosphates at the interphase. These groups are, apparently, surrounded by more than one layer of water molecules: a tightly bound shell, that mostly contributes to the dipole potential, and a second one that may be displaced by proteins and osmotic stress. Hydration water around carbonyl and phosphate groups may change by the presence of polyhydroxylated compounds

  18. Structure/property relationships in polymer membranes for water purification and energy applications

    Science.gov (United States)

    Geise, Geoffrey

    Providing sustainable supplies of purified water and energy is a critical global challenge for the future, and polymer membranes will play a key role in addressing these clear and pressing global needs for water and energy. Polymer membrane-based processes dominate the desalination market, and polymer membranes are crucial components in several rapidly developing power generation and storage applications that rely on membranes to control rates of water and/or ion transport. Much remains unknown about the influence of polymer structure on intrinsic water and ion transport properties, and these relationships must be developed to design next generation polymer membrane materials. For desalination applications, polymers with simultaneously high water permeability and low salt permeability are desirable in order to prepare selective membranes that can efficiently desalinate water, and a tradeoff relationship between water/salt selectivity and water permeability suggests that attempts to prepare such materials should rely on approaches that do more than simply vary polymer free volume. One strategy is to functionalize hydrocarbon polymers with fixed charge groups that can ionize upon exposure to water, and the presence of charged groups in the polymer influences transport properties. Additionally, in many emerging energy applications, charged polymers are exposed to ions that are very different from sodium and chloride. Specific ion effects have been observed in charged polymers, and these effects must be understood to prepare charged polymers that will enable emerging energy technologies. This presentation discusses research aimed at further understanding fundamental structure/property relationships that govern water and ion transport in charged polymer films considered for desalination and electric potential field-driven applications that can help address global needs for clean water and energy.

  19. Dendritic attenuation of synaptic potentials and currents: the role of passive membrane properties.

    Science.gov (United States)

    Spruston, N; Jaffe, D B; Johnston, D

    1994-04-01

    The dendritic trees of neurons are structurally and functionally complex integrative units receiving thousands of synaptic inputs that have excitatory and inhibitory, fast and slow, and electrical and biochemical effects. The pattern of activation of these synaptic inputs determines if the neuron will fire an action potential at any given point in time and how it will respond to similar inputs in the future. Two critical factors affect the integrative function of dendrites: the distribution of voltage-gated ion channels in the dendritic tree and the passive electrical properties, or 'electrotonic structure', upon which these active channels are superimposed. The authors review recent data from patch-clamp recordings that provide new estimates of the passive membrane properties of hippocampal neurons, and show, with examples, how these properties affect the shaping and attenuation of synaptic potentials as they propagate in the dendrites, as well as how they affect the measurement of current from synapses located in the dendrites. Voltage-gated channels might influence the measurement of 'passive' membrane properties and, reciprocally, passive membrane properties might affect the activation of voltage-gated channels in dendrites.

  20. Thermal properties of phosphoric acid-doped polybenzimidazole membranes in water and methanol-water mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Nores-Pondal, Federico J.; Corti, Horacio R. [Grupo de Pilas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Av. General Paz 1499, B1650KNA San Martin, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Buera, M. Pilar [Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Cantilo s/n, Ciudad Universitaria (1428) Buenos Aires (Argentina)

    2010-10-01

    The thermal properties of phosphoric acid-doped poly[2-2'-(m-phenylene)-5-5' bi-benzimidazole] (PBI) and poly[2,5-benzimidazole] (ABPBI) membranes, ionomeric materials with promising properties to be used as electrolytes in direct methanol and in high temperature polymer electrolyte membrane (PEM) fuel cells, were studied by means of differential scanning calorimetry (DSC) technique in the temperature range from -145 C to 200 C. The DSC scans of samples equilibrated in water at different relative humidities (RH) and in liquid water-methanol mixtures were analyzed in relation to glass transition, water crystallization/melting and solvent desorption in different temperature regions. The thermal relaxation observed in the very low temperature region could be ascribed to the glass transition of the H{sub 3}PO{sub 4}-H{sub 2}O mixture confined in the polymeric matrix. After cooling the samples up to -145 C, frozen water was detected in PBI and ABPBI at different RH, although at 100% RH less amount of water had crystallized than that observed in Nafion membranes under the same conditions. Even more important is the fact that the freezing degree of water is much lower in ABPBI membranes equilibrated in liquid water-methanol mixtures than that observed for PBI and, in a previous study, for Nafion. Thus, apart from other well known properties, acid-doped ABPBI emerges as an excellent ionomer for applications in direct methanol fuel cells working in cold environments. (author)

  1. The effects of cationic contamination on the physio-chemical properties of perfluoroionomer membranes

    Science.gov (United States)

    Molter, Trent M.

    Proton Exchange Membrane (PEM) technology cannot meet fuel cell and electrolyzer durability standards for stationary and transportation applications. Cell designs are not of sufficient maturity to demonstrate more than several thousand hours of invariant performance. One of the limiting factors is the operational lifetime of membrane electrode assemblies (MEA's) because of pin-holing, dry-out, mechanical breeches, chemical attack and contamination. This program investigated the role of contamination on the degradation of perfluorinated membranes in fuel cell and electrolysis environments. Tests were conducted to develop an understanding of the effects of cationic contaminants on fundamental design parameters for these membranes including water content, ion exchange capacity, gas diffusion, ionic conductivity, and mechanical properties. Tests showed that cations rapidly transport into the membrane and disperse throughout its structure achieving high equilibrium concentrations. Ion charge density appears to govern membrane water content with small ions demonstrating the highest water content. Permeability studies showed transport in accordance with Fick's law in the following order: H2>O2>N 2>H2O. Cations negatively affect gas and water transport, with charge density affecting transport rates. Unique diffusion coefficients were calculated for each contaminating species suggesting that the contaminant is an integral participant in the transport process. AC resistance measurements showed that size of the ion charge carrier is an important factor in the conduction mechanism and that membrane area specific resistance correlates well with water content. Increases in membrane yield strength and the modulus of elasticity were demonstrated with increased contamination. Tensile tests showed that cation size plays an important role in determining the magnitude of this increase, indicating that larger ions interfere more with strain than smaller ones. Contaminants reduced

  2. Perforated patch-clamp analysis of the passive membrane properties of three classes of hippocampal neurons.

    Science.gov (United States)

    Spruston, N; Johnston, D

    1992-03-01

    1. Perforated patch-clamp recordings were made from the three major classes of hippocampal neurons in conventional in vitro slices prepared from adult guinea pigs. This technique provided experimental estimates of passive membrane properties (input resistance, RN, and membrane time constant, tau m) determined in the absence of the leak conductance associated with microelectrode impalement or the washout of cytoplasmic constituents associated with conventional whole-cell recordings. 2. To facilitate comparison of our data with previous results and to determine the passive membrane properties under conditions as physiological as possible, recordings were made at the resting potential, in physiological saline, and without any added blockers of voltage-dependent conductances. 3. Membrane-potential responses to current steps were analyzed, and four criteria were used to identify voltage responses that were the least affected by activation of voltage-dependent conductances. tau m was estimated from the slowest component (tau 0) of multiexponential fits of responses deemed passive by these criteria. RN was estimated from the slope of the linear region in the hyperpolarizing direction of the voltage-current relation. 4. It was not possible to measure purely passive membrane properties that were completely independent of membrane potential in any of the three classes of hippocampal neurons. Changing the membrane potential by constant current injection resulted in changes in RN and tau 0; subthreshold depolarization produced an increase, and hyperpolarization a decrease, in both RN and tau 0 for all three classes of hippocampal neurons. 5. Each of the three classes of hippocampal neurons also displayed a depolarizing "sag" during larger hyperpolarizing voltage transients. To evaluate the effect of the conductances underlying this sag on passive membrane properties, 2-5 mM Cs+ was added to the physiological saline. Extracellular Cs+ effectively blocked the sag in all three

  3. NONLINEAR PROPERTY MEMBRANE RECTIFIER POTASSIUM CHANNEL AND INHIBITORY EFFECTS OF OXYGEN FREE RADICAL

    Institute of Scientific and Technical Information of China (English)

    鲍光宏; 于德洁; 刘宇; 刘东梅

    1996-01-01

    There are at least eight kinds of different potassium chennels on cardiac cell membrane. This paperpresents a nonlinear property membrane outward; current going rectifying potassium channel and the in-hibitory efeets of oxygen free radical on this channel. The current-vohage relation of this nonlimmr-mem-brahe can be defined by an equation I=8a3/(0.01v2+4a2)2 and the maximum conductance of this channel is-75.3pS.

  4. Zwitterionic polymer functionalization of polysulfone membrane with improved antifouling property and blood compatibility by combination of ATRP and click chemistry.

    Science.gov (United States)

    Xiang, Tao; Lu, Ting; Xie, Yi; Zhao, Wei-Feng; Sun, Shu-Dong; Zhao, Chang-Sheng

    2016-08-01

    The chemical compositions are very important for designing blood-contacting membranes with good antifouling property and blood compatibility. In this study, we propose a method combining ATRP and click chemistry to introduce zwitterionic polymer of poly(sulfobetaine methacrylate) (PSBMA), negatively charged polymers of poly(sodium methacrylate) (PNaMAA) and/or poly(sodium p-styrene sulfonate) (PNaSS), to improve the antifouling property and blood compatibility of polysulfone (PSf) membranes. Attenuated total reflectance-Fourier transform infrared spectra, X-ray photoelectron spectroscopy and water contact angle results confirmed the successful grafting of the functional polymers. The antifouling property and blood compatibility of the modified membranes were systematically investigated. The zwitterionic polymer (PSBMA) grafted membranes showed good resistance to protein adsorption and bacterial adhesion; the negatively charged polymer (PNaSS or PNaMAA) grafted membranes showed improved blood compatibility, especially the anticoagulant property. Moreover, the PSBMA/PNaMAA modified membrane showed both antifouling property and anticoagulant property, and exhibited a synergistic effect in inhibiting blood coagulation. The functionalization of membrane surfaces by a combination of ATRP and click chemistry is demonstrated as an effective route to improve the antifouling property and blood compatibility of membranes in blood-contact.

  5. Influence of membrane microdomin on infection process of mouse macrophages by Francisella tularensis LVS%质膜微区对土拉弗朗西斯菌LVS感染鼠巨噬细胞的影响

    Institute of Scientific and Technical Information of China (English)

    潘欣; 祁建城; 李广渡; 贾文凯; 瞿曼; 赵子夜

    2009-01-01

    目的 评估士拉弗朗西斯菌LNS入侵鼠巨噬细胞过程巾质膜微区的作用.方法 用电穿孔法将穿梭质粒pFNLTP6gro-gfp导人土拉弗朗西斯菌LVS.细胞膜用FM4-64染色,结合单抗的微囊蛋白-1用键合了Alexa 594荧光素的羊抗鼠二抗显色.用Z轴电动聚焦的荧光显微镜分析土拉弗朗西斯菌LNS感染.用甲基-β-环式糊精干扰富含脂质的胞膜损耗胆固醇,以评估质膜微区的损伤埘弗朗西斯菌入侵的影响.菲律平Ⅲ用以榆测胆固醇损耗的效果.结果 土拉弗朗西斯菌疫苗株可以诱导膜结构域伸出伪足将细菌吸收进入巨噬细胞.质膜微区相关成分微囊蛋白-1与含有弗朗西斯菌的囊泡一同进入宿主.弗朗西斯菌入侵巨噬细胞需要胆崮醇丰富的膜结构域.结论 胆固醇丰富的质膜微区和微囊蛋白-1在弗朗西斯菌早期进入巨噬细胞期间发挥重要作用.%Objective To evaluate the role of membrane microdomain on the entry process of Francisella tularensis LVS infecting mouse macrophages.Methods A shuttle plasmid pFNLTP6 gro-gfp was introduced to E tularensis LVS by dectroporation method.Membrane was stained with FM4-64,and cavcolin-1 was detected with mono-antihody and visualized with Alexa Fluor 594 conjugated goat-antkmouse antibodies.F.tularensis INS infection was analyzed by a fluorescence microscope equipped with a motorized Z-focus.In order to evaluate the depletion of membrane microdomain induced by Francisella entering macrophages,interference with lipid-rich plasma membrane through the depletion of cholesterol was pedormed by treatment with methyl beta cyclodextrin.The cholesterol-binding agent Filipin Ⅲ was used to detect the effect of cholesterol deplction.Results It was shown that the live vaccine strain of E tularensis induced membrane domains ruffling for sucoessful entry into maerophages.Menlbrane microdomain-assodated components such as caveolin1 were incorporated into Francisella containing

  6. DMPD: CR3 (CD11b, CD18): a phagocyte and NK cell membrane receptor with multipleligand specificities and functions. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 8485905 CR3 (CD11b, CD18): a phagocyte and NK cell membrane receptor with multipleligand specificities...) (.html) (.csml) Show CR3 (CD11b, CD18): a phagocyte and NK cell membrane receptor with multipleligand specificities...d NK cell membrane receptor with multipleligand specificities and functions. Authors Ross GD, Vetvicka V. Pu

  7. 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.

  8. Piezoresistive Properties of Suspended Graphene Membranes under Uniaxial and Biaxial Strain in Nanoelectromechanical Pressure Sensors

    Science.gov (United States)

    2016-01-01

    Graphene membranes act as highly sensitive transducers in nanoelectromechanical devices due to their ultimate thinness. Previously, the piezoresistive effect has been experimentally verified in graphene using uniaxial strain in graphene. Here, we report experimental and theoretical data on the uni- and biaxial piezoresistive properties of suspended graphene membranes applied to piezoresistive pressure sensors. A detailed model that utilizes a linearized Boltzman transport equation describes accurately the charge-carrier density and mobility in strained graphene and, hence, the gauge factor. The gauge factor is found to be practically independent of the doping concentration and crystallographic orientation of the graphene films. These investigations provide deeper insight into the piezoresistive behavior of graphene membranes. PMID:27797484

  9. Synthesis and characterization of polymer electrolyte membranes with controlled ion transport properties

    Science.gov (United States)

    Xu, Kui

    2011-12-01

    Ion-containing block copolymers hold promise as next-generation polymer electrolyte membrane (PEM) materials due to their capability to self-assemble into ordered nanostructures facilitating proton transport over a wide range of conditions. Ion-containing block copolymers, sulfonated poly(styrene- b-vinylidene fluoride-b-styrene), with varied degrees of sulfonation were synthesized. The synthetic strategy involved a new approach to chain-end functionalized poly(vinylidene fluoride) as a macro-initiator followed by atom transfer polymerization of styrene and sulfonation. Characterization of the polymers were extensively carried out by 1H and 19F nuclear magnetic resonance and Fouriertransform infrared spectroscopy, differential scanning calorimetry, and thermogravimetry analysis. Tapping mode atomic force microscopy and transmission electron microscopy were applied to study the phase separation and self-assembled morphology. Strong dependence of ion exchange capacity, water absorption, morphology and proton conductivity on the degree of sulfonation has been found. It has been observed that the conductivities of the block copolymers are considerably higher than the random copolymers of polystyrene and sulfonated polystyrene possessing similar ion exchange capacities. Copolymers of vinylidene fluoride and perfluoro(4-methyl-3,6-dioxane-7-ene) sulfonyl fluoride containing amino end-groups were synthesized for the first time. The prepared aminoterminated polymers underwent cross-linking reactions with 1,3,5-benzene triisocyanate to form proton conductive networks. The chain-end crosslinked fluoropolymer membranes exhibited excellent thermal, hydrolytic and oxidative stabilities. The ion exchange capacity, water uptake, the state of absorbed water, and transport properties of the membranes were found to be highly dependent upon the chemical composition of the copolymers. The cross-linked membranes showed extremely low methanol permeability, while maintaining high proton

  10. A Theoretical Characterization of Curvature Controlled Adhesive Properties of Bio-Inspired Membranes

    DEFF Research Database (Denmark)

    Afferante, Luciano; Heepe, Lars; Casdorff, Kirstin;

    2016-01-01

    Some biological systems, such as the tree frog, Litoria caerulea, and the bush-cricket, Tettigonia viridissima, have developed the ability to control adhesion by changing the curvature of their pads. Active control systems of adhesion inspired by these biological models can be very attractive...... for the development of devices with controllable adhesive properties. In this paper, we present a theory describing the adhesive behavior of an artificial system consisting of an inflatable membrane clamped to a metallic cylinder and filled with air. In such a system, by controlling the internal pressure acting...... on the membrane, it is possible to modulate the adhesive strength. In particular, an increase of the internal pressure and, hence, the curvature of the membrane, results in a decrease of the pull-off force. Results predicted by the theoretical model are in good agreement with experimental data. The model explains...

  11. Macrophage Polarization Modulates FcγR- and CD13-Mediated Phagocytosis and Reactive Oxygen Species Production, Independently of Receptor Membrane Expression

    Science.gov (United States)

    Mendoza-Coronel, Elizabeth; Ortega, Enrique

    2017-01-01

    In response to microenvironmental cues, macrophages undergo a profound phenotypic transformation acquiring distinct activation phenotypes ranging from pro-inflammatory (M1) to anti-inflammatory (M2). To study how activation phenotype influences phagocytosis and production of reactive oxygen species (ROS) mediated by receptors for IgG antibodies (Fcγ receptors) and by CD13, human monocyte-derived macrophages were polarized to distinct phenotypes using IFN-γ (Mϕ-IFN-γ), IL-4 (Mϕ-IL-4), or IL-10 (Mϕ-IL-10). Phenotypically, Mϕ-IFN-γ were characterized as CD14+CD80+CD86+ cells, Mϕ-IL-4 as CD209highCD206+CD11b+CD14low, and Mϕ-IL-10 as CD16+CD163+ cells. Compared to non-polarized macrophages, FcγRI expression increased in Mϕ-IFN-γ and Mϕ-IL-10 and FcγRIII expression increased in Mϕ-IL-10. None of the polarizing cytokines modified FcγRII or CD13 expression. Functionally, we found that cytokine-mediated activation significantly and distinctively affected FcγR- and CD13-mediated phagocytosis and ROS generation. Compared to non-polarized macrophages, FcγRI-, FcγRII-, and CD13-mediated phagocytosis was significantly increased in Mϕ-IL-10 and decreased in Mϕ-IFN-γ, although both cytokines significantly upregulated FcγRI expression. IL-10 also increased phagocytosis of Escherichia coli, showing that the effect of IL-10 on macrophage phagocytosis is not specific for a particular receptor. Interestingly, Mϕ-IL-4, which showed poor FcγR- and CD13-mediated phagocytosis, showed very high phagocytosis of E. coli and zymosan. Coupled with phagocytosis, macrophages produce ROS that contribute to microbial killing. As expected, Mϕ-IFN-γ showed significant production of ROS after FcγRI-, FcγRII-, or CD13-mediated phagocytosis. Unexpectedly, we found that Mϕ-IL-10 can also produce ROS after simultaneous stimulation through several phagocytic receptors, as coaggregation of FcγRI/FcγRII/CD13 induced a belated but significant ROS production. Together, these

  12. The aqueous layers within the myelin sheath modulate the membrane properties of simulated hereditary demyelinating neuropathies.

    Science.gov (United States)

    Stephanova, D I; Krustev, S M; Daskalova, M

    2011-03-01

    To expand our studies on the mechanisms underlying the clinical decline of the nerve excitability properties in patients with hereditary demyelinating neuropathies, the contribution of myelin sheath aqueous layers on multiple membrane properties of simulated fiber demyelinations is investigated. Three progressively greater degrees of internodal systematic demyelinations (two mild and one severe termed as ISD1, ISD2 and ISD3, respectively) without/with aqueous layers are simulated using our previous multi-layered model of human motor nerve fiber. The calculated multiple membrane excitability properties are as follows: potentials (intracellular action, electrotonic), strength-duration time constants, rheobasic currents and recovery cycles. They reflect the propagating, accommodative and adaptive processes in the fibers. The results show that all membrane properties, except for the strength-duration time constants and refractoriness, worsen when the myelin lamellae and their corresponding aqueous layers are uniformly reduced along the fiber length. The effect of the aqueous layers is significantly higher on the accommodative and adaptive processes than on the propagating processes in the fibers. Our multi-layered model better approximated some of the functional deficits documented for axons of patients with Charcot-Marie-Tooth disease type 1A. The study provides new and important information on the mechanisms underlying the pathophysiology of hereditary demyelinating neuropathies.

  13. ALTERATIONS OF PROPERTIES OF RED BLOOD CELLS MEMBRANES PROTEINS OF DIFFERENT AGE AND SEX VOLUNTEERS.

    Science.gov (United States)

    Pruidze, N; Khetsuriani, R; Sujashvili, R; Ioramashvili, I; Arabuli, M; Sanikidze, T

    2015-01-01

    Considering the age and sex-dependent trend in the manifestation of various diseases, as well as an important pathogenic role of circulatory disorders, we decided to study the age-dependent changes in the physical properties of RBCs membrane proteins (their electric charge and molecular weight) in healthy people of different sex (males and females) and age. Blood of 56 healthy volunteers (Tbilisi, Georgia) of different sex and gender was studied (the patients were divided in 8 groups (7 patients in each groups): 1 - 18-25 years old male, 2 - 18-25 years old female, 3 - 25-44 years old male, 4 - 25-44 years old female, 5 - 44-60 years old male, 6 - 44-60 years old female; 7 - 60-80 years old male, 8 - 70-80 years old female). In groups 6 and 8 were women in menopause was determined according 12 months of amenorrhea. Individuals often consume alcohol addicts, pregnant women and patients with chronic diseases were excluded from the study. The study protocol was approved by Ethical Committee of the Tbilisi State Medical University. RBCs membrane proteins have been extracted from human heparinized blood and their mobility was studied by electrophoretic method. The electrophoretic mobility of RBCs membrane proteins decreases with age of healthy volunteers, that indicates decrease of total charge of proteins, depending on the electrically charged amino acids content. In female patients the electrophoretic mobility of the RBCs membrane proteins especially intensively decreases in period of menopause. Increase of molecular weight of proteins (100-200 kDa) from RBCs' membranes of alder age group was manifested. Intensively decrease electrophoretic mobility of erythrocytes membrane proteins from female patients in period of menopause indicates on estrogen related mechanism of the regulation of membrane protein conformation and composition in females. Increased content of high molecular weight proteins in the RBCs membranes from patients of older age groups may be caused to

  14. Intrinsic membrane properties determine hippocampal differential firing pattern in vivo in anesthetized rats.

    Science.gov (United States)

    Kowalski, Janina; Gan, Jian; Jonas, Peter; Pernía-Andrade, Alejandro J

    2016-05-01

    The hippocampus plays a key role in learning and memory. Previous studies suggested that the main types of principal neurons, dentate gyrus granule cells (GCs), CA3 pyramidal neurons, and CA1 pyramidal neurons, differ in their activity pattern, with sparse firing in GCs and more frequent firing in CA3 and CA1 pyramidal neurons. It has been assumed but never shown that such different activity may be caused by differential synaptic excitation. To test this hypothesis, we performed high-resolution whole-cell patch-clamp recordings in anesthetized rats in vivo. In contrast to previous in vitro data, both CA3 and CA1 pyramidal neurons fired action potentials spontaneously, with a frequency of ∼3-6 Hz, whereas GCs were silent. Furthermore, both CA3 and CA1 cells primarily fired in bursts. To determine the underlying mechanisms, we quantitatively assessed the frequency of spontaneous excitatory synaptic input, the passive membrane properties, and the active membrane characteristics. Surprisingly, GCs showed comparable synaptic excitation to CA3 and CA1 cells and the highest ratio of excitation versus hyperpolarizing inhibition. Thus, differential synaptic excitation is not responsible for differences in firing. Moreover, the three types of hippocampal neurons markedly differed in their passive properties. While GCs showed the most negative membrane potential, CA3 pyramidal neurons had the highest input resistance and the slowest membrane time constant. The three types of neurons also differed in the active membrane characteristics. GCs showed the highest action potential threshold, but displayed the largest gain of the input-output curves. In conclusion, our results reveal that differential firing of the three main types of hippocampal principal neurons in vivo is not primarily caused by differences in the characteristics of the synaptic input, but by the distinct properties of synaptic integration and input-output transformation.

  15. Effects of vegetable oils on biochemical and biophysical properties of membrane retinal pigment epithelium cells.

    Science.gov (United States)

    Said, Toihiri; Tremblay-Mercier, Jennifer; Berrougui, Hicham; Rat, Patrice; Khalil, Abdelouahed

    2013-10-01

    The aim of this study was to investigate the effect of vegetable oil enrichment of retinal pigment epithelial (RPE) cells on their biochemical and biophysical properties. For this, RPE cells were incubated with 4 different vegetables oils (olive oil, corn oil, argan oil, and camelina oil). The cytotoxicity of these vegetable oils was assessed in vivo on 8-week-old mice and in vitro by using the neutral red and YO-PRO-1 tests. Membrane fluidity was evaluated by fluorescence anisotropy using the fluorescent probe diphenylhexatriene, and membrane fatty acid composition was assessed by gas chromatography. None of the oils tested displayed cytotoxic effects. In vitro, omega-3 rich oils improved membrane fluidity by 47% compared with the control cells. The omega-3 PUFA content within membranes decreased by 38% to 55% when cells were incubated separately with olive oil, corn oil, or argan oil, and increased when cells were incubated with a mixture of those oils, or with camelina oil alone (50% and 103% increase, respectively). Our results show that the fatty acids in vegetable oil incorporate into retinal cells and increase the plasma membrane fluidity.

  16. Syntheses and Surface Properties of Polyacrylonitrile-based Copolymer Membranes Containing Sugar Moieties

    Institute of Scientific and Technical Information of China (English)

    HUANG Xiao-jun; WAN Ling-shu; DAI Zheng-wei; KOU Rui-qiang; XU Zhi-kang

    2005-01-01

    To improve the hydrophilicity of polyacrylonitrile-based membranes, sugar moieties were incorporated into acrylonitrile-based copolymers via the radical copolymerization of α-allyl glucoside(AG) with acrylonitrile(AN) with 2,2'-azobis-iso-butyronitrile(AIBN) as the initiator in dimethyl sulphoxide(DMSO). It was found that the yield increased with the increase of the initiator concentration and reaction time, while it decreased with the increase of the monomer molar ratio of AG to AN. Raising the AG proportion in the monomer mixture resulted in the increase of the AG content in the copolymer. Mv of the copolymers decreased with increasing the AG monomer fraction in feed. The copolymers were fabricated into dense membranes and their surface properties were studied by means of the water contact angle measurement and platelet adhesion tests. It was found that the static water contact angle on the membrane decreased significantly from 70° to 33° with the increase of the AG content. The adhesive number of platelets on the membrane surface also decreased significantly with increasing AG content in the copolymers. These results demonstrate that the hydrophilicity and biocompatibility of the acrylonitrile-based copolymer membranes could be improved efficiently by the copolymerization of acrylonitrile with vinyl carbohydrates.

  17. Functional Properties of Punica granatum L. Juice Clarified by Hollow Fiber Membranes

    Directory of Open Access Journals (Sweden)

    Francesco Galiano

    2016-07-01

    Full Text Available There is currently much interest in pomegranate juice because of the high content of phenolic compounds. Moreover, the interest in the separation of bioactive compounds from natural sources has remarkably grown. In this work, for the first time, the Punica granatum L. (pomegranate juice—clarified by using polyvinylidene fluoride (PVDF and polysulfone (PSU hollow fiber (HF membranes prepared in the laboratory—was screened for its antioxidant properties by using different in vitro assays, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid (ABTS, Ferric Reducing Antioxidant Power (FRAP, and β-carotene bleaching tests, and for its potential inhibitory activity of the carbohydrate-hydrolysing enzymes, α-amylase and α-glucosidase. The effects of clarification on quality characteristics of the juice were also investigated in terms of total phenols, flavonoids, anthocyanins, and ascorbic acid. Experimental results indicated that PVDF membranes presented a lower retention towards healthy phytochemicals in comparison to PSU membranes. Accordingly, the juice clarified with PVDF membranes showed the best antioxidant activity. Moreover, the treatment with PVDF membranes produced a clarified juice with 2.9-times fold higher α-amylase inhibitory activity in comparison to PSU (IC50 value of 75.86 vs. 221.31 μg/mL, respectively. The same trend was observed using an α-glucosidase inhibition test. These results highlight the great potential of the clarified juice as a source of functional constituents.

  18. Electrochemical properties of proton exchange membranes: the role of composition and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Holdcroft, S.; Beattie, P.D.; Basura, V.I.; Schmeisser, J.; Chuy, C.; Orfino, F.; Ding, J. [Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Chemistry

    2001-06-01

    To measure electrochemical and proton conduction properties of a large variety of different polyelectrolyte membranes that possess a wide array of equivalent weights and water contents, a number of analytical techniques were employed and the results presented in this paper. At the electrocatalyst/polymer electrolyte interface, kinetic and mass transport parameters play an important role in fuel cell operation, the authors used microelectrodes to study the effects of temperature and pressure on the electrochemical reduction of oxygen at platinum/solid polymer electrolyte interfaces in solid polymer electrolytes under controlled humidity. Under conditions of controlled humidity and temperature, proton conductivity was measured transverse and normal to the membrane surface using an alternate current (a.c.) impedance spectroscopy. A wide array of membranes were investigated, including those based on sulfonated polystyrene-block-hydrogenated butadiene, polystyrenesulfonic acid grafted onto ethylenetetrafluoroethylene, sulfonated trifluorostyrene-copolymers, and a novel series of membranes where the internal biphasic morphology is controlled to yield materials with low water and high conductivity and prepared in house. Transmission electron microscopy and small angle X-ray scattering was used for the analysis of the microstructure of selected membranes. Modelling the scattered intensities was used to quantify aspects of the microstructure.

  19. Influence of the sterol aliphatic side chain on membrane properties: a molecular dynamics study.

    Science.gov (United States)

    Robalo, João R; Ramalho, J P Prates; Huster, Daniel; Loura, Luís M S

    2015-09-21

    Following a recent experimental investigation of the effect of the length of the alkyl side chain in a series of cholesterol analogues (Angew. Chem., Int. Ed., 2013, 52, 12848-12851), we report here an atomistic molecular dynamics characterization of the behaviour of methyl-branched side chain sterols (iso series) in POPC bilayers. The studied sterols included androstenol (i-C0-sterol) and cholesterol (i-C8-sterol), as well as four other derivatives (i-C5, i-C10, i-C12 and i-C14-sterol). For each sterol, both subtle local effects and more substantial differential alterations of membrane properties along the iso series were investigated. The location and orientation of the tetracyclic ring system is almost identical in all compounds. Among all the studied sterols, cholesterol is the sterol that presents the best matching with the hydrophobic length of POPC acyl chains, whereas longer-chained sterols interdigitate into the opposing membrane leaflet. In accordance with the experimental observations, a maximal ordering effect is observed for intermediate sterol chain length (i-C5, cholesterol, i-C10). Only for these sterols a preferential interaction with the saturated sn-1 chain of POPC (compared to the unsaturated sn-2 chain) was observed, but not for either shorter or longer-chained derivatives. This work highlights the importance of the sterol alkyl chain in the modulation of membrane properties and lateral organization in biological membranes.

  20. Transport properties of zeolite Na-X-Nafion membranes: effect of zeolite loadings and particle size

    Energy Technology Data Exchange (ETDEWEB)

    Lavorgna, M. [Institute of Composite and Biomedical Materials, National Research Council, Portici (Italy); Sansone, L.; Scherillo, G. [Department of Materials and Production, University of Napoli Federico II, Napoli (Italy); Gu, R.; Baker, A.P. [Department of Materials Science and Engineering, HIT Graduate School, Xili, Shenzhen (China)

    2011-12-15

    Na-X zeolites particles, synthesized in two size ranges, namely 200-300 nm and 30-100 nm, were used to prepare Nafion/Na-X zeolite composite membranes by recast method. The physical, chemical, and morphological properties of the zeolite powders and composite membranes were examined by XRD, N{sub 2} adsorption isotherms, FTIR, SEM, and SAXS analysis. Furthermore, the effect of zeolite particles size and loadings (i.e., 5 and 10% w/w) on the water, methanol, and proton transport properties was investigated. It has been found that the size of the Na-X zeolite particles plays a key role in the proton and methanol transport behavior since it rules the zeolite hydrophilic behavior, the morphology of polymer-filler interphase, and also the nature of water established in the composite membrane. The results show that the membranes loaded with a 5% w/w of submicron-sized Na-X zeolite exhibit a proton conductivity and selectivity significantly higher than Nafion. In particular the proton conductivity at 120 C is around eight times and the selectivity at 25 C is around 40% higher than those exhibited by recast Nafion. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Electrochemical properties of honeycomb-like structured HFBI self-organized membranes on HOPG electrodes.

    Science.gov (United States)

    Yamasaki, Ryota; Takatsuji, Yoshiyuki; Lienemann, Michael; Asakawa, Hitoshi; Fukuma, Takeshi; Linder, Markus; Haruyama, Tetsuya

    2014-11-01

    HFBI (derived from Trichoderma sp.) is a unique structural protein, which forms a self-organized monolayer at both air/water interface and water/solid interfaces in accurate two-dimensional ordered structures. We have taken advantage of the unique functionality of HFBI as a molecular carrier for preparation of ordered molecular phase on solid substrate surfaces. The HFBI molecular carrier can easily form ordered structures; however, the dense molecular layers form an electrochemical barrier between the electrode and solution phase. In this study, the electrochemical properties of HFBI self-organized membrane-covered electrodes were investigated. Wild-type HFBI has balanced positive and negative charges on its surface. Highly oriented pyrolytic graphite (HOPG) electrodes coated with HFBI molecules were investigated electrochemically. To improve the electrochemical properties of this HFBI-coated electrode, the two types of HFBI variants, with oppositely charged surfaces, were prepared genetically. All three types of HFBI-coated HOPG electrode perform electron transfer between the electrode and solution phase through the dense HFBI molecular layer. This is because the HFBI self-organized membrane has a honeycomb-like structure, with penetrating holes. In the cases of HFBI variants, the oppositely charged HFBI membrane phases shown opposite electrochemical behaviors in electrochemical impedance spectroscopy. HFBI is a molecule with a unique structure, and can easily form honeycomb-like structures on solid material surfaces such as electrodes. The molecular membrane phase can be used for electrochemical molecular interfaces.

  2. RELATION BETWEEN MECHANICAL PROPERTIES AND PYROLYSIS TEMPERATURE OF PHENOL FORMALDEHYDE RESIN FOR GAS SEPARATION MEMBRANES

    Directory of Open Access Journals (Sweden)

    MONIKA ŠUPOVÁ

    2012-03-01

    Full Text Available The aim of this paper has been to characterize the relation between the pyrolysis temperature of phenol-formaldehyde resin, the development of a porous structure, and the mechanical properties for the application of semipermeable membranes for gas separation. No previous study has dealt with this problem in its entirety. Phenol-formaldehyde resin showed an increasing trend toward micropore porosity in the temperature range from 500 till 1000°C, together with closure of mesopores and macropores. Samples cured and pyrolyzed at 1000°C pronounced hysteresis of desorption branch. The ultimate bending strength was measured using a four-point arrangement that is more suitable for measuring of brittle materials. The chevron notch technique was used for determination the fracture toughness. The results for mechanical properties indicated that phenol-formaldehyde resin pyrolyzates behaved similarly to ceramic materials. The data obtained for the material can be used for calculating the technical design of gas separation membranes.

  3. Estimation of cell membrane properties and erythrocyte red-ox balance in patients with metabolic syndrome

    OpenAIRE

    Kowalczyk, Edward; Kowalski, Jan; Błaszczyk, Jan; Gwoździński, Łukasz; Ciećwierz, Julita; Sienkiewicz, Monika

    2012-01-01

    Metabolic syndrome (MS) is associated with occurrence of the many cardiovascular risk factors such as atherogenic dyslipidemia, visceral fat distribution, arterial hypertension and pro-thrombotic and pro-inflammatory status. In our study the effect of disorders that appear in MS on red-ox balance and erythrocyte cell membrane properties were estimated. The study comprised 50 patients with diagnosed MS and in 25 healthy subjects. Content of thiobarbituric acid reactive substances (TBARS) and c...

  4. Physico-mechanical and structural properties of eggshell membrane gelatin- chitosan blend edible films

    DEFF Research Database (Denmark)

    Mohammadi, Reza; Mohammadifar, Mohammad Amin; Rouhi, Milad

    2017-01-01

    This study investigated the physico-mechanical and structural properties of composite edible films based on eggshell membrane gelatin (G) and chitosan (Ch) (75G:25Ch, 50G:50Ch, 25G:75Ch). The results demonstrated that the addition of Ch increased elongation at break significantly (p< 0.05), but r......This study investigated the physico-mechanical and structural properties of composite edible films based on eggshell membrane gelatin (G) and chitosan (Ch) (75G:25Ch, 50G:50Ch, 25G:75Ch). The results demonstrated that the addition of Ch increased elongation at break significantly (p....05), but resulted in no significant change in tensile strength (TS) using 75G:25Ch, 50G:50Ch mixtures in comparison with gelatin-based film. The water solubility and water vapor permeability of the 50G:50Ch film decreased significantly compared to plain films (100G:0Ch and 0G:100Ch) and other composite films (p... interactions introduced by the addition of chitosan to eggshell membrane gelatin as new resources could improve the films’ functional properties....

  5. Sedative, membrane stability, cytotoxic and antioxidant properties of methanol extract of leaves of Protium serratum Wall.

    Directory of Open Access Journals (Sweden)

    Md. Rafikul Islam

    2014-09-01

    Full Text Available Objective: To study the sedative, membrane stability, cytotoxic and antioxidant properties of the leaves of Protium serratum extracted using methanol. Methods: Sedative test was performed using hole cross and open field methods at 200 and 400 mg/kg. Membrane stability of red blood cell was used for anti-inflammatory test at different concentrations. Cytotoxic study was performed using brine shrimp lethality test. Total flavonoid contents, total phenol contents and reducing power were used to assess antioxidant properties of the extract. Results: Extract showed better sedative action at lower doses in both experiments. Maximum 73.33% locomotion reduction was found at 200 mg/kg at 1 20 min and that was 89.29% for diazepam in hole cross test. In membrane stability test, extract and standard drug diclofenac have 35.66% and 91.20% stability, respectively. LC50 value of the extract was 22.91 µg/mL. Total phenol and flavonoid contents were (55.53依14.63 mg gallic acid equivalent per gram of extract and (1 06.33依7.35 mg of quercetin equivalent per gram of extract, respectively per gram of extract. Significant reducing power was observed as compared to ascorbic acid. Conclusions: Extract possesses good pharmacological properties. Hence, further extensive study is essential to find out possible active constituents for the treatment of anxiety, inflammation or sickle cell disease, cancer and free radical mediated abnormalities.

  6. In vitro antioxidant properties of chicken skin enzymatic protein hydrolysates and membrane fractions.

    Science.gov (United States)

    Onuh, John O; Girgih, Abraham T; Aluko, Rotimi E; Aliani, Michel

    2014-05-01

    Chicken thigh and breast skin proteins were hydrolysed using alcalase or a combination of pepsin and pancreatin (PP), each at concentrations of 1-4%. The chicken skin protein hydrolysates (CSPHs) were then fractionated by membrane ultrafiltration into different molecular weight peptides (antioxidant properties. Results showed that the CSPHs had a significantly (pskin hydrolysates had significantly higher DPPH scavenging activity than the chicken thigh skin hydrolysates. DPPH scavenging and metal ion chelation increased significantly (pantioxidant properties decreased as peptide size increased. We conclude that CSPHs and their peptide fractions may be used as ingredients in the formulation of functional foods and nutraceuticals for the control and management of oxidative stress-related diseases.

  7. Studies on Preparation and Properties of Proton Exchange Membranes Based on Phosphotungstic Acid/Silica and Polysulfonamide

    Institute of Scientific and Technical Information of China (English)

    LI Wei-dong; XU Hong; ZHAO Jiong-xin

    2009-01-01

    Membranes formed by polysulfonamide (PSA) and phosphotungstic acid (PWA) supported on nano-silica have been prepared. Fourier transform infrared spectra (FTTR) and thermogravimctric analysis (TGA) were used to characterize the structure and thermal properties of obtained membranes. The analyses of water uptake, proton conductivity and mechanical properties of the membranes revealed that PWA and silica produced a beneficial effect on proton conduction of the membranes. The membranes with 50 wt% of PWA-SiQ2/PSA were mechanically stable and gave proton conductivity of 2. 57 × 10-2 S ?cm-1 at 90℃and 100% relative humidity. According to the obtained results, PWA and SiO2 doped PSA is a promising material for proton exchange membrane.

  8. Hydrodynamic and Membrane Binding Properties of Purified Rous Sarcoma Virus Gag Protein

    Energy Technology Data Exchange (ETDEWEB)

    Dick, Robert A.; Datta, Siddhartha A.K.; Nanda, Hirsh; Fang, Xianyang; Wen, Yi; Barros, Marilia; Wang, Yun-Xing; Rein, Alan; Vogt, Volker M. (NCI); (Cornell); (CM); (NIST)

    2016-05-06

    Previously, no retroviral Gag protein has been highly purified in milligram quantities and in a biologically relevant and active form. We have purified Rous sarcoma virus (RSV) Gag protein and in parallel several truncation mutants of Gag and have studied their biophysical properties and membrane interactionsin vitro. RSV Gag is unusual in that it is not naturally myristoylated. From its ability to assemble into virus-like particlesin vitro, we infer that RSV Gag is biologically active. By size exclusion chromatography and small-angle X-ray scattering, Gag in solution appears extended and flexible, in contrast to previous reports on unmyristoylated HIV-1 Gag, which is compact. However, by neutron reflectometry measurements of RSV Gag bound to a supported bilayer, the protein appears to adopt a more compact, folded-over conformation. At physiological ionic strength, purified Gag binds strongly to liposomes containing acidic lipids. This interaction is stimulated by physiological levels of phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2] and by cholesterol. However, unlike HIV-1 Gag, RSV Gag shows no sensitivity to acyl chain saturation. In contrast with full-length RSV Gag, the purified MA domain of Gag binds to liposomes only weakly. Similarly, both an N-terminally truncated version of Gag that is missing the MA domain and a C-terminally truncated version that is missing the NC domain bind only weakly. These results imply that NC contributes to membrane interactionin vitro, either by directly contacting acidic lipids or by promoting Gag multimerization.

    Retroviruses like HIV assemble at and bud from the plasma membrane of cells. Assembly requires the interaction between thousands of Gag molecules to form a lattice. Previous work indicated that lattice formation at the plasma membrane is influenced by the conformation of monomeric HIV. We have extended this work to the more tractable RSV Gag. Our

  9. The role of ceramide chain length distribution on the barrier properties of the skin lipid membranes.

    Science.gov (United States)

    Mojumdar, E H; Kariman, Z; van Kerckhove, L; Gooris, G S; Bouwstra, J A

    2014-10-01

    The skin barrier function is provided by the stratum corneum (SC). The lipids in the SC are composed of three lipid classes: ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs) which form two crystalline lamellar structures. In the present study, we investigate the effect of CER chain length distribution on the barrier properties of model lipid membranes mimicking the lipid composition and organization of SC. The membranes were prepared with either isolated pig CERs (PCERs) or synthetic CERs. While PCERs have a wide chain length distribution, the synthetic CERs are quite uniform in chain length. The barrier properties were examined by means of permeation studies using hydrocortisone as a model drug. Our studies revealed a reduced barrier in lipid membranes prepared with PCERs compared to synthetic CERs. Additional studies revealed that a wider chain length distribution of PCERs results in an enhanced hexagonal packing and increased conformational disordering of the lipid tails compared to synthetic CERs, while the lamellar phases did not change. This demonstrates that the chain length distribution affects the lipid barrier by reducing the lipid ordering and density within the lipid lamellae. In subsequent studies, the effect of increased levels of FFAs or CERs with a long acyl chain in the PCERs membranes was also studied. These changes in lipid composition enhanced the level of orthorhombic packing, reduced the conformational disordering and increased the barrier of the lipid membranes. In conclusion, the CER chain length distribution is an important key factor for maintaining a proper barrier. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Improved protein-adsorption-resistant property of PES/SPC blend membrane by adjustment of coagulation bath composition.

    Science.gov (United States)

    Wang, Ting; Wang, Yan-qiang; Su, Yan-lei; Jiang, Zhong-yi

    2005-12-30

    To improve surface protein-adsorption-resistant property of polyethersulfone (PES) membranes, soybean phosphatidylcholine (SPC) was added to PES casting solution. The blend membranes were prepared by a phase inversion method in a wet process. The surface of PES/SPC blend membranes was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS data revealed that the phosphorylcholine (PC) groups were concentrated at the surface by changing the composition of coagulation bath. Addition of N,N-dimethylformamide (DMF) in coagulation bath could prolong coagulation time and facilitate the migration of SPC from polymer bulk to membrane surface. The PES/SPC blend membranes dramatically reduced BSA and fibrinogen adsorption compared to PES control membrane due to effective immobilization of PC groups at the surface of PES/SPC blend membranes.

  11. Interfacial interactions in aprotic ionic liquid based protonic membrane and its correlation with high temperature conductivity and thermal properties.

    Science.gov (United States)

    Mistry, Mayur K; Subianto, Surya; Choudhury, Namita Roy; Dutta, Naba K

    2009-08-18

    Novel supported liquid membranes (SLMs) have been developed by impregnating Nafion and Hyflon membranes with ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-BTSI). These supported liquid membranes were characterized in terms of their ionic liquid uptake behavior, leaching of ionic liquid by water, thermal stability, mechanical properties, glass transition temperature, ion exchange capacity, and proton conductivity. In general, modified membranes are more flexible than unmodified samples due to the plasticization effects of the ionic liquid. However, these supported liquid membranes exhibit a significant increase in their operational stability and proton conductivity over unmodified membranes. We also demonstrate that proton conductivity of these supported liquid membranes allows conduction of protons in anhydrous conditions with conductivity increasing with temperature. Conductivity of up to 3.58 mS cm(-1) has been achieved at 160 degrees C in dry conditions, making these materials promising for various electrochemical applications.

  12. Deuterated detergents for structural and functional studies of membrane proteins: Properties, chemical synthesis and applications.

    Science.gov (United States)

    Hiruma-Shimizu, Kazumi; Shimizu, Hiroki; Thompson, Gary S; Kalverda, Arnout P; Patching, Simon G

    2015-01-01

    Detergents are amphiphilic compounds that have crucial roles in the extraction, purification and stabilization of integral membrane proteins and in experimental studies of their structure and function. One technique that is highly dependent on detergents for solubilization of membrane proteins is solution-state NMR spectroscopy, where detergent micelles often serve as the best membrane mimetic for achieving particle sizes that tumble fast enough to produce high-resolution and high-sensitivity spectra, although not necessarily the best mimetic for a biomembrane. For achieving the best quality NMR spectra, detergents with partial or complete deuteration can be used, which eliminate interfering proton signals coming from the detergent itself and also eliminate potential proton relaxation pathways and strong dipole-dipole interactions that contribute line broadening effects. Deuterated detergents have also been used to solubilize membrane proteins for other experimental techniques including small angle neutron scattering and single-crystal neutron diffraction and for studying membrane proteins immobilized on gold electrodes. This is a review of the properties, chemical synthesis and applications of detergents that are currently commercially available and/or that have been synthesized with partial or complete deuteration. Specifically, the detergents are sodium dodecyl sulphate (SDS), lauryldimethylamine-oxide (LDAO), n-octyl-β-D-glucoside (β-OG), n-dodecyl-β-D-maltoside (DDM) and fos-cholines including dodecylphosphocholine (DPC). The review also considers effects of deuteration, detergent screening and guidelines for detergent selection. Although deuterated detergents are relatively expensive and not always commercially available due to challenges associated with their chemical synthesis, they will continue to play important roles in structural and functional studies of membrane proteins, especially using solution-state NMR.

  13. Influence of coagulation concentration on properties of regenerated kenaf core membranes produced in NaOH/urea aqueous solution

    Science.gov (United States)

    Azahari, Nor Aziawati; Jaafar, Sharifah Nabihah Syed; Zakaria, Sarani

    2016-11-01

    Cellulose was extracted from kenaf core pulp by a series of bleaching processes and subsequently dissolved using an alkaline NaOH/urea solvent at low temperature. The produced cellulose solution was coagulated with H2SO4 at concentration from 5 to 12 wt% to produce a series of regenerated cellulose (RC) membranes. The surface morphology, structure and physical properties of the membranes were measured with variable pressure scanning electron microscope (VPSEM), X-ray diffraction (XRD), UV-vis spectrophotometer and tensile testing. The results from VPSEM revealed that the pore size of the membranes changed as a function of the concentration of H2SO4 coagulant. RC membranes coagulated with relatively dilute H2SO4 solution exhibited better mechanical properties. Thus, this work provided a promising way to prepare cellulose membranes with different pore sizes and good physical properties.

  14. Membrane physical properties do not explain increased cyclic AMP production in hepatocytes from rats fed menhaden oil.

    Science.gov (United States)

    Bizeau, M E; Hazel, J R

    2000-06-01

    To study the effect of altering plasma membrane fatty acid composition on the glucagon signal transduction pathway, cAMP accumulation was measured in hepatocytes from rats fed diets containing either menhaden oil (MO) or coconut oil (CO). Hepatocytes from MO-fed animals produced significantly more cAMP in response to glucagon and forskolin compared to CO-fed animals. Glucagon receptor number and affinity were similar in MO- and CO-fed rats. Liver plasma membranes from MO-fed animals were enriched in long-chain n-3 fatty acids and contained significantly lower amounts of saturated C10-C16 and 18:1n-9 than CO-fed animals. Membrane physical properties were examined using both Fourier transform infrared spectroscopy (FTIR) and the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH). FTIR analysis revealed that below 34 degrees C, CO membranes were more ordered than MO membranes. However, as assay temperature approached 37 degrees C, MO and CO membranes became similarly ordered. DPH polarization values indicated no differences in membrane order at 37 degrees C, whereas membrane order was decreased in CO-fed animals at 25 degrees C. These data indicate the importance of assay temperature in assessing the influence of membrane physical properties on the activity of signal transduction pathways. Whereas increased signal transduction activity has been correlated to reduced membrane order in MO-fed animals, these data indicate that at physiological temperatures membrane order did not vary between groups. Enhanced cAMP accumulation in response to forskolin indicates that adenylate cyclase activity or content may be elevated in MO- vs. CO-fed rats. Enhanced adenylate cyclase activity may result, in part, from changes in specific fatty acids in hepatocyte plasma membranes without demonstrable changes in membrane physical properties.

  15. Bacterial reaction centers purified with styrene maleic acid copolymer retain native membrane functional properties and display enhanced stability

    NARCIS (Netherlands)

    Swainsbury, David J K; Scheidelaar, Stefan; Van Grondelle, Rienk; Killian, J. Antoinette; Jones, Michael R.

    2014-01-01

    Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein. Bacterial reaction centers offer a rare opp

  16. Photocatalytic Nanofiltration Membranes with Self-Cleaning Property for Wastewater Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Yan; Zhang, Chao; He, Ai; Yang, Shang-Jin; Wu, Guang-Peng; Darling, Seth B.; Xu, Zhi-Kang

    2017-07-19

    Membrane fouling is one of the most severe problems restricting membrane separation technology for wastewater treatment. This work reports a photocatalytic nanofiltration membrane (NFM) with self-cleaning property fabricated using a facile biomimetic mineralization process. In this strategy, a polydopamine (PDA)/polyethyleneimine (PEI) intermediate layer is fabricated on an ultrafiltration membrane via a co-deposition method followed by mineralization of a photocatalytic layer consisting of beta-FeOOH nanorods. The PDA-PEI layer acts both as a nanofiltration selective layer and an intermediate layer for anchoring the beta-FeOOH nanorods via strong coordination complexes between Fe3+ and catechol groups. In visible light, the beta-(F)eOOH layer exhibits efficient photocatalytic activity for degrading dyes through the photo-Fenton reaction in the presence of hydrogen peroxide, endowing the NFM concurrently with effective nanofiltration performance and self-cleaning capability. Moreover, the mineralized NFMs exhibit satisfactory stability under simultaneous filtration and photocatalysis processing, showing great potential in advanced wastewater treatment.

  17. Simian virus 40 late proteins possess lytic properties that render them capable of permeabilizing cellular membranes.

    Science.gov (United States)

    Daniels, Robert; Rusan, Nasser M; Wilbuer, Anne-Kathrin; Norkin, Leonard C; Wadsworth, Patricia; Hebert, Daniel N

    2006-07-01

    Many nonenveloped viruses have evolved an infectious cycle that culminates in the lysis or permeabilization of the host to enable viral release. How these viruses initiate the lytic event is largely unknown. Here, we demonstrated that the simian virus 40 progeny accumulated at the nuclear envelope prior to the permeabilization of the nuclear, endoplasmic reticulum, and plasma membranes at a time which corresponded with the release of the progeny. The permeabilization of these cellular membranes temporally correlated with late protein expression and was not observed upon the inhibition of their synthesis. To address whether one or more of the late proteins possessed an inherent capacity to induce membrane permeabilization, we examined the permeability of Escherichia coli that separately expressed the late proteins. VP2 and VP3, but not VP1, caused the permeabilization of bacterial membranes. Additionally, VP3 expression resulted in bacterial cell lysis. These findings demonstrate that VP3 possesses an inherent lytic property that is independent of eukaryotic signaling or cell death pathways.

  18. Effect of Organic Tin Compounds on Electric Properties of Model Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Podolak, M.; Engel, G.; Man, D. [Inst. of Physics, Opole Univ., Opole (Poland)

    2006-05-15

    The objective of the present work was to investigate the effect of selected organic tin compounds and potassium chloride (used as a reference substance) on the trans-membrane electric voltage and electric resistance of model membranes, the latter being nitrocellulose filters impregnated with butylene ester of lauric acid. The increasing KCl concentration (in the measurement chambers) caused a rapid rise of the negative trans-membrane voltage, whose value stabilized afterwards. In the case of (C{sub 3}H{sub 7}){sub 3}SnCl an abrupt maximum of the negative voltage was observed followed by a monotonic drop to zero. In the case of highest concentrations of this compound the voltages, after having reached zero, changed their polarization to the opposite. Within the range of small concentrations two slight voltage maxima were observed. Non-ionic tin compounds like (CH{sub 3}){sub 4}Sn and (C{sub 2}H{sub 5}){sub 4}Sn had an insignificant influence on the electric properties of the studied membranes. (orig.)

  19. Preparation and oxygen permeation properties of SrFe(Cu)O3-δ dense ceramic membranes

    Institute of Scientific and Technical Information of China (English)

    Heng Zhang; Tingting Wang; Xinfa Dong; Weiming Lin

    2009-01-01

    Mixed oxygen-ionic and electronic conducting membranes of SrFe(Cu)O3-δ were prepared by solid-state reaction method.The crystal structure,oxygen nonstoichiometry,and phase stability of the materials were studied by TGA and XRD.Oxygen permeation fluxes through these membranes were studied at operating temperature ranging from 750 to 950 ℃.Results showed that doping Cu in SrFeO3-δ compound had a significant effect on the formation of single-phased perovskite structure.For SrFe1-xCuxO3-δ series materials,the oxygen nonstoichiometry and the oxygen permeation flux increased considerably with the increase of Cu-doping content (x = 0.1-0.3).The sintering property of the membrane decreased significantly when the Cu substitution amount reached 40%.SrFe0.7CU0.3O3-δ showed high oxygen permeation flux,but SrCuO2 and Sr2Fe2O5 phases formed in the compound after oxygen permeation test induced cracks in the membrane.

  20. Photoinduced charge transfer properties of bolaamphiphile membrane-gramicidrin diad composites

    Science.gov (United States)

    Thompson, David H.; Kim, Jong-Mok; Di Meglio, Ciro

    1993-04-01

    Ether-linked bolaform amphiphiles (Langmuir 1992 8, 637; J. Am. Chem. Soc. 1992, 9035) and novel gramicidin-porphyrin `diads' (MRS Symposium Series, Vol. 277, 1992, 93) have been synthesized. Protocols for vectorial insertion of the derivatized gramicidins into bolaform lipid vesicles have been developed and the photochemical behavior of these proteinaceous composite membranes probed in the presence of electron donors and acceptors. Photoinduced electron transfer properties of the gramicidin-porphyrin conjugates were compared in TRIS- buffered dihexadecyl-phosphate bilayer (DHP) and bolaform monolayer membrane vesicles containing dithiothreitol as sacrificial donor and methyl viologen as electron acceptor on both the inner and outer vesicle surfaces. Although the rates of methyl viologen photoreduction varied depending on the mode of diad orientation within DHP bilayer membranes, photoreduction rates were not orientation- dependent in bolaform membrane vesicles containing the gramicidin-porphyrin diad. The relevance of these results on vectorial electron transfer processes in lamellar systems and the design of integrated charge transfer components is discussed.

  1. Estimation of cell membrane properties and erythrocyte red-ox balance in patients with metabolic syndrome.

    Science.gov (United States)

    Kowalczyk, Edward; Kowalski, Jan; Błaszczyk, Jan; Gwoździński, Łukasz; Ciećwierz, Julita; Sienkiewicz, Monika

    2012-12-01

    Metabolic syndrome (MS) is associated with occurrence of the many cardiovascular risk factors such as atherogenic dyslipidemia, visceral fat distribution, arterial hypertension and pro-thrombotic and pro-inflammatory status. In our study the effect of disorders that appear in MS on red-ox balance and erythrocyte cell membrane properties were estimated. The study comprised 50 patients with diagnosed MS and in 25 healthy subjects. Content of thiobarbituric acid reactive substances (TBARS) and catalase, superoxide dismutase and glutathione peroxidase activity were estimated in red blood cells. Moreover, conformation status of membrane proteins, membrane fluidity and osmotic fragility were evaluated. MS was found to manifest: (1) the increase of the concentration of TBARS in erythrocytes with no statistically significant differences in antioxidant enzymes activity, (2) disorders in the structure of erythrocyte cytoskeleton proteins, (3) the increase in membrane lipids fluidity at the depth of 5th and 12th carbon atom of fatty acid hydrocarbon chain and significantly decreased fluidity at the depth of 16th carbon atom, (4) increased erythrocyte osmotic fragility.

  2. HIV-1 assembly in macrophages

    Directory of Open Access Journals (Sweden)

    Benaroch Philippe

    2010-04-01

    Full Text Available Abstract The molecular mechanisms involved in the assembly of newly synthesized Human Immunodeficiency Virus (HIV particles are poorly understood. Most of the work on HIV-1 assembly has been performed in T cells in which viral particle budding and assembly take place at the plasma membrane. In contrast, few studies have been performed on macrophages, the other major target of HIV-1. Infected macrophages represent a viral reservoir and probably play a key role in HIV-1 physiopathology. Indeed macrophages retain infectious particles for long periods of time, keeping them protected from anti-viral immune response or drug treatments. Here, we present an overview of what is known about HIV-1 assembly in macrophages as compared to T lymphocytes or cell lines. Early electron microscopy studies suggested that viral assembly takes place at the limiting membrane of an intracellular compartment in macrophages and not at the plasma membrane as in T cells. This was first considered as a late endosomal compartment in which viral budding seems to be similar to the process of vesicle release into multi-vesicular bodies. This view was notably supported by a large body of evidence involving the ESCRT (Endosomal Sorting Complex Required for Transport machinery in HIV-1 budding, the observation of viral budding profiles in such compartments by immuno-electron microscopy, and the presence of late endosomal markers associated with macrophage-derived virions. However, this model needs to be revisited as recent data indicate that the viral compartment has a neutral pH and can be connected to the plasma membrane via very thin micro-channels. To date, the exact nature and biogenesis of the HIV assembly compartment in macrophages remains elusive. Many cellular proteins potentially involved in the late phases of HIV-1 cycle have been identified; and, recently, the list has grown rapidly with the publication of four independent genome-wide screens. However, their respective

  3. Correlation between Electrical Properties and Potentiometric Response of CS-Clay Nanocomposite Membranes

    Directory of Open Access Journals (Sweden)

    M. Oviedo Mendoza

    2015-01-01

    Full Text Available The aim of this work is to study the relationship between electrical, structure, and potentiometric response to nitrate anions using Ion Selective Electrodes (ISE. These ISE are based on chitosan-montmorillonite nanocomposite membranes with different content of montmorillonite. Membrane properties have been studied using SEM, FTIR, and impedance spectroscopy measurements. With the advent of impedance spectroscopy one is allowed to obtain the DC conductivity dependence on montmorillonite concentration and the percolation threshold. Additionally, the potentiometric response to nitrate anions of ISE based on chitosan-clay nanocomposite has been investigated. It is shown that the properties and performance of these membrane electrodes depend upon the clay wt% and that the best sensitivity to nitrate ions (with detection limit 7 × 10−5 M is obtained near the percolation concentration ca. 8 ± 2.5 wt% of clay. This observation is traceable to higher clay content (higher agglomeration that tends to decrease the intercalation and absorption of the number of chitosan chains in the interlayer space of montmorillonite.

  4. Composition, structure and mechanical properties define performance of pulmonary surfactant membranes and films

    DEFF Research Database (Denmark)

    Ortiz, Elisa Parra; Perez-Gil, Jesús

    2015-01-01

    The respiratory surface in the mammalian lung is stabilized by pulmonary surfactant, a membrane-based system composed of multiple lipids and specific proteins, the primary function of which is to minimize the surface tension at the alveolar air-liquid interface, optimizing the mechanics of breath......The respiratory surface in the mammalian lung is stabilized by pulmonary surfactant, a membrane-based system composed of multiple lipids and specific proteins, the primary function of which is to minimize the surface tension at the alveolar air-liquid interface, optimizing the mechanics...... of breathing and avoiding alveolar collapse, especially at the end of expiration. The goal of the present review is to summarize current knowledge regarding the structure, lipid-protein interactions and mechanical features of surfactant membranes and films and how these properties correlate with surfactant...... biological function inside the lungs. Surfactant mechanical properties can be severely compromised by different agents, which lead to surfactant inhibition and ultimately contributes to the development of pulmonary disorders and pathologies in newborns, children and adults. A detailed comprehension...

  5. Unique membrane properties and enhanced signal processing in human neocortical neurons

    Science.gov (United States)

    Eyal, Guy; Verhoog, Matthijs B; Testa-Silva, Guilherme; Deitcher, Yair; Lodder, Johannes C; Benavides-Piccione, Ruth; Morales, Juan; DeFelipe, Javier; de Kock, Christiaan PJ; Mansvelder, Huibert D; Segev, Idan

    2016-01-01

    The advanced cognitive capabilities of the human brain are often attributed to our recently evolved neocortex. However, it is not known whether the basic building blocks of the human neocortex, the pyramidal neurons, possess unique biophysical properties that might impact on cortical computations. Here we show that layer 2/3 pyramidal neurons from human temporal cortex (HL2/3 PCs) have a specific membrane capacitance (Cm) of ~0.5 µF/cm2, half of the commonly accepted 'universal' value (~1 µF/cm2) for biological membranes. This finding was predicted by fitting in vitro voltage transients to theoretical transients then validated by direct measurement of Cm in nucleated patch experiments. Models of 3D reconstructed HL2/3 PCs demonstrated that such low Cm value significantly enhances both synaptic charge-transfer from dendrites to soma and spike propagation along the axon. This is the first demonstration that human cortical neurons have distinctive membrane properties, suggesting important implications for signal processing in human neocortex. DOI: http://dx.doi.org/10.7554/eLife.16553.001 PMID:27710767

  6. Effects of overexpression of SCD-1 on macrophage membrane induced by amyloid beta protein 1-40 grease%过表达SCD-1对β淀粉样蛋白1-40诱导的巨噬细胞膜脂的影响

    Institute of Scientific and Technical Information of China (English)

    单晶丽(通讯作者); 隋丹; 姚秀彬

    2013-01-01

    Objective To observe the effects of Stearoyl-CoA desaturease-1 (SCD-1) overexpression on Changes of membrane phospholipids in macrophages induced by β-amyloid protein (Aβ). Methods the expression vector pcDNA3 with SCD-1 adenovirus, by adenovirus transfection, and its over expression in macrophages. Flow detection untreated group and overexpression of macrophage membrane lipid composition and group cellmembrane changes. Results the expression of macrophage membrane phospholipid degradation in macrophages in the main group (P < 0.05); cellmembrane fluorescence polarization (P), micro viscosity (η) and the molecular ordering coefficient (γ) increased (P < 0.05). Conclusion SCD-1 can increase the expression of macrophage membrane stability of A β1-40.%目的:探讨SCD-1过表达对Aβ1-40诱导的巨噬细胞膜脂的影响。方法用带有SCD-1的腺病毒表达载体pcDNA3,通过腺病毒转染,使其在巨噬细胞中过表达。检测未干预组及过表达组巨噬细胞膜脂成分及细胞膜流动性的改变。结果过表达组巨噬细胞中巨噬细胞膜主要的磷脂成分降解(P<0.05);细胞膜荧光偏振度(ρ)、微粘度(η)和分子排列有序性系数(γ)增加(P<0.05)。结论过表达SCD-1可增加Aβ1-40诱导的巨噬细胞膜的稳定性。

  7. Effects of scandium doping concentration on the properties of strontium cobalt oxide membranes

    Directory of Open Access Journals (Sweden)

    Pingying Zeng

    2009-09-01

    Full Text Available Perovskite-type mixed conducting oxides of SrCo1-ySc yO3-δ (y=0.02-0.7 were synthesized by a combined EDTA-citrate complexing method. Different scandium doping concentrations in SrCo1-ySc yO3-δ have significant effects on the phase structure, electrical conductivity, surface properties and oxygen permeation behaviour of the resultant membranes. SrCoO3-δ without scandium incorporation displayed a 2H BaNiO3-type structure with almost zero oxygen flux at high temperatures. Small amounts of Sc2O3 doping (y0.1 were found to lower the membrane oxygen fluxes, with y³≥0.4 doped SrCo1-ySc yO3-δ ceramics no longer showing any oxygen permeation.

  8. The effects of 7-dehydrocholesterol on the structural properties of membranes

    Science.gov (United States)

    Liu, Yingzhe; Chipot, Christophe; Shao, Xueguang; Cai, Wensheng

    2011-10-01

    Smith-Lemli-Opitz syndrome, a congenital and developmental malformation disease, is typified by abnormal accumulation of 7-dehydrocholesterol (7DHC), the immediate precursor of cholesterol (CHOL), and depletion thereof. Knowledge of the effect of 7DHC on the biological membrane is, however, still fragmentary. In this study, large-scale atomistic molecular dynamics simulations, employing two distinct force fields, have been conducted to elucidate differences in the structural properties of a hydrated dimyristoylphosphatidylcholine bilayer due to CHOL and 7DHC. The present series of results indicate that CHOL and 7DHC possess virtually the same ability to condense and order membranes. Furthermore, the condensing and ordering effects are shown to be strengthened at increasing sterol concentrations.

  9. A thermal and electrochemical properties research on gel polymer electrolyte membrane of lithium ion battery

    Science.gov (United States)

    Li, Libo; Ma, Yue; Wang, Wentao; Xu, Yanping; You, Jun; Zhang, Yonghong

    2016-12-01

    N-methyl-N-propyl-piperidin-bis(trifluoromethylsulfonyl)imide/bis(trifluoromethylsulfonyl) imide lithium base/polymethyl methacrylate(PP13TFSI/LiTFSI/PMMA) gel polymer electrolyte (GPE) membrane was prepared by in situ polymerization. The physical and chemical properties were comprehensively discussed. The decomposition characteristics were emphasized by thermogravimetric (TG-DTG) method in the nitrogen atmosphere at the different heating rates of 5, 10, 15 and 20 °C min-1, respectively. The activation energy was calculated with the iso-conversional methods of Ozawa and Kissinger, Friedman, respectively, and the Coats-Redfern methods were adopted to employ the detailed mechanism of the electrolyte membrane. The equation f(α)=3/2[(1-α)1/3-1] was quite an appropriate kinetic mechanisms to describe the thermal decomposition process with an activation energy (Eα) of 184 kJ/mol and a pre-exponential factor (A) of 1.894×1011 were obtained.

  10. Characterisation of Conformational and Ligand Binding Properties of Membrane Proteins Using Synchrotron Radiation Circular Dichroism (SRCD).

    Science.gov (United States)

    Hussain, Rohanah; Siligardi, Giuliano

    Membrane proteins are notoriously difficult to crystallise for use in X-ray crystallographic structural determination, or too complex for NMR structural studies. Circular dichroism (CD) is a fast and relatively easy spectroscopic technique to study protein conformational behaviour in solution. The advantage of synchrotron radiation circular dichroism (SRCD) measured with synchrotron beamlines compared to the CD from benchtop instruments is the extended spectral far-UV region that increases the accuracy of secondary structure estimations, in particular under high ionic strength conditions. Membrane proteins are often available in small quantities, and for this SRCD measured at the Diamond B23 beamline has successfully facilitated molecular recognition studies. This was done by probing the local tertiary structure of aromatic amino acid residues upon addition of chiral or non-chiral ligands using long pathlength cells (1-5 cm) of small volume capacity (70 μl-350 μl). In this chapter we describe the use of SRCD to qualitatively and quantitatively screen ligand binding interactions (exemplified by Sbma, Ace1 and FsrC proteins); to distinguish between functionally similar drugs that exhibit different mechanisms of action towards membrane proteins (exemplified by FsrC); and to identify suitable detergent conditions to observe membrane protein-ligand interactions using stabilised proteins (exemplified by inositol transporters) as well as the stability of membrane proteins (exemplified by GalP, Ace1). The importance of the in solution characterisation of the conformational behaviour and ligand binding properties of proteins in both far- andnear-UV regions and the use of high-throughput CD (HT-CD) using 96- and 384-well multiplates to study the folding effects in various protein crystallisation buffers are also discussed.

  11. Effects of the Membrane Action of Tetralin on the Functional and Structural Properties of Artificial and Bacterial Membranes

    NARCIS (Netherlands)

    SIKKEMA, J; POOLMAN, B; KONINGS, WN; DEBONT, JAM

    1992-01-01

    Tetralin is toxic to bacterial cells at concentrations below 100-mu-mol/liter. To assess the inhibitory action of tetralin on bacterial membranes, a membrane model system, consisting of proteoliposomes in which beef heart cytochrome c oxidase was reconstituted as the proton motive force-generating m

  12. Preparation of Chitosan/Collagen Blend Membranes for Wound Dressing: A Study on FTIR Spectroscopy and Mechanical Properties

    Science.gov (United States)

    Indrani, D. J.; Lukitowati, F.; Yulizar, Y.

    2017-05-01

    The effect of different gamma-ray irradiations on the functional groups and the mechanical properties of chitosan, collagen, and chitosan/collagen blend have been studied. Commercially available chitosan and extract of collagen from bovine tendon by acid dissolution method were employed. Chitosan, collagen and chitosan/collagen blend membranes were prepared using the solvent evaporation method. The dried membranes were subjected to gamma-ray irradiation using 0, 15, and 25 kGy. The membranes then characterized by Infrared spectroscopy and measured in tensile and elongation at break. The irradiated chitosan membranes displayed reduced intensity of -OH, -CH, -NH and -C-O-C groups, whereas, the collagen membranes revealed amide I, II and III groups. The irradiated chitosan/collagen (50/50%) blend membranes demonstrated the decreased intensities in the -OH and amide groups. The application of gamma-ray irradiation had produced chitosan/collagen blend membranes with a tensile strength and elongation at break between the chitosan and collagen membranes. It was further determined that the decrease in the mechanical properties of the membranes was likely to be due to some changes of the functional groups.

  13. Adsorbent filled membranes for gas separation. Part 1. Improvement of the gas separation properties of polymeric membranes by incorporation of microporous adsorbents

    NARCIS (Netherlands)

    Duval, J.-M.; Folkers, B.; Mulder, M.H.V.; Desgrandchamps, G.; Smolders, C.A.

    1993-01-01

    The effect of the introduction of specific adsorbents on the gas separation properties of polymeric membranes has been studied. For this purpose both carbon molecular sieves and zeolites are considered. The results show that zeolites such as silicate-1, 13X and KY improve to a large extent the separ

  14. Novel ion-exchange nanocomposite membrane containing in-situ formed FeOOH nanoparticles: Synthesis, characterization and transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Heidary, Farhad; Kharat, Ali Nemati [University of Tehran, Tehran (Iran, Islamic Republic of); Khodabakhshi, Ali Reza [Faculty of Science, Arak University, Arak (Iran, Islamic Republic of)

    2016-04-15

    A new type of cation-exchange nanocomposite membrane was prepared via in-situ formation of FeOOH nanoparticles in a blend containing sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) and sulfonated polyvinylchloride by a simple one-step chemical method. Prepared nanocomposite membranes were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. The SEM images showed uniform dispersion of FeOOH nanoparticles throughout the polymeric matrices. The effect of additive loading on physicochemical and electrochemical properties of prepared cation-exchange nanocomposite membranes was studied. Various characterizations showed that the incorporation of different amounts of FeOOH nanoparticles into the basic membrane structure had a significant influence on the membrane performance and could improve the electrochemical properties.

  15. The properties of the outer membrane localized Lipid A transporter LptD

    Energy Technology Data Exchange (ETDEWEB)

    Haarmann, Raimund; Ibrahim, Mohamed; Stevanovic, Mara; Bredemeier, Rolf; Schleiff, Enrico, E-mail: schleiff@bio.uni-frankfurt.d [JWGU Frankfurt/Main, Cluster of Excellence Macromolecular Complexes, Center of Membrane Proteomics, Department of Biosciences, Molecular Cell Biology, Max-von-Laue Strasse 9, D-60439 Frankfurt (Germany)

    2010-11-17

    Gram-negative bacteria are surrounded by a cell wall including the outer membrane. The outer membrane is composed of two distinct monolayers where the outer layer contains lipopolysaccharides (LPS) with the non-phospholipid Lipid A as the core. The synthesis of Lipid A is initiated in the cytosol and thereby the molecule has to be transported across the inner and outer membranes. The {beta}-barrel lipopolysaccharide-assembly protein D (LptD) was discovered to be involved in the transfer of Lipid A into the outer membrane of Gram-negative bacteria. At present the molecular procedure of lipid transfer across the outer membrane remains unknown. Here we approached the functionality of the transfer system by an electrophysiological analysis of the outer membrane protein from Escherichia coli named ecLptD. In vitro the protein shows cation selectivity and has an estimated pore diameter of about 1.8 nm. Addition of Lipid A induces a transition of the open state to a sub-conductance state with two independent off-rates, which might suggest that LptD is able to bind and transport the molecule in vitro. To generalize our findings with respect to the Lipid A transport system of other Gram-negative bacteria we have explored the existence of the proteins involved in this pathway by bioinformatic means. We were able to identify the membrane-inserted components of the Lipid A transport system in all Gram-negative bacteria, whereas the periplasmic components appear to be species-specific. The LptD proteins of different bacteria are characterized by their periplasmic N-terminal domain and a C-terminal barrel region. The latter shows distinct sequence properties, particularly in LptD proteins of cyanobacteria, and this specific domain can be found in plant proteins as well. By electrophysiological experiments on LptD from Anabaena sp. PCC 7120 we are able to confirm the functional relation of anaLptD to Lipid A transport.

  16. Cellulose acetate electrospun nanofibrous membrane: fabrication, characterization, drug loading and antibacterial properties

    Indian Academy of Sciences (India)

    NAZNIN SULTANA; ANISAH ZAINAL

    2016-04-01

    Cellulose-based materials are one of the most commonly used materials for biomedical applications, which normally applied as carriers for pharmaceuticals and drug-releasing scaffolds. In this study, cellulose acetate (CA) was used to fabricate the nanofibrous membrane using the electrospinning technique. CA solutions at different concentrations were prepared by dissolving the polymer in a mixture of acetic acid/acetone solvents with the ratio of 3:1. The field emission scanning electron microscope results showed that electrospinning of 10% (w/v) CA produced nanofibres with many beads. When the CA concentration was increased to 14% (w/v), bead-free nanofibres were produced. The contact angle measurement results confirmed the hydrophilic properties of nanofibres. In order to prevent common bacterial infections, a model drug, Tetracycline · HCL was incorporated into the CA nanofibres. The drug-loaded CA nanofibres showed antibacterial activity against Gram-positive and Gram-negative bacteria.CA nanofibres had high water uptake properties. The CA nanofibrous membrane was non-toxic to human skin fibroblast cells. Thus the CA nanofibres with 14% (w/v) concentration exerted suitable properties for wound healingapplication.

  17. Composition, structure and mechanical properties define performance of pulmonary surfactant membranes and films.

    Science.gov (United States)

    Parra, Elisa; Pérez-Gil, Jesús

    2015-01-01

    The respiratory surface in the mammalian lung is stabilized by pulmonary surfactant, a membrane-based system composed of multiple lipids and specific proteins, the primary function of which is to minimize the surface tension at the alveolar air-liquid interface, optimizing the mechanics of breathing and avoiding alveolar collapse, especially at the end of expiration. The goal of the present review is to summarize current knowledge regarding the structure, lipid-protein interactions and mechanical features of surfactant membranes and films and how these properties correlate with surfactant biological function inside the lungs. Surfactant mechanical properties can be severely compromised by different agents, which lead to surfactant inhibition and ultimately contributes to the development of pulmonary disorders and pathologies in newborns, children and adults. A detailed comprehension of the unique mechanical and rheological properties of surfactant layers is crucial for the diagnostics and treatment of lung diseases, either by analyzing the contribution of surfactant impairment to the pathophysiology or by improving the formulations in surfactant replacement therapies. Finally, a short review is also included on the most relevant experimental techniques currently employed to evaluate lung surfactant mechanics, rheology, and inhibition and reactivation processes.

  18. Correlation of microstructure and thermo-mechanical properties of a novel hydrogen transport membrane

    Science.gov (United States)

    Zhang, Yongjun

    A key part of the FutureGen concept is to support the production of hydrogen to fuel a "hydrogen economy," with the use of clean burning hydrogen in power-producing fuel cells, as well as for use as a transportation fuel. One of the key technical barriers to FutureGen deployment is reliable and efficient hydrogen separation technology. Most Hydrogen Transport Membrane (HTM) research currently focuses on separation technology and hydrogen flux characterization. No significant work has been performed on thermo-mechanical properties of HTMs. The objective of the thesis is to understand the structure-property correlation of HTM and to characterize (1) thermo mechanical properties under different reducing environments and thermal cycles (thermal shock), and (2) evaluate the stability of the novel HTM material. A novel HTM cermet bulk sample was characterized for its physical and mechanical properties at both room temperature and at elevated temperature up to 1000°C. Micro-structural properties and residual stresses were evaluated in order to understand the changing mechanism of the microstructure and its effects on the mechanical properties of materials. A correlation of the microstructural and thermo mechanical properties of the HTM system was established for both HTM and the substrate material. Mechanical properties of both selected structural ceramics and the novel HTM cermet bulk sample are affected mainly by porosity and microstructural features, such as grain size and pore size-distribution. The Young's Modulus (E-value) is positively correlated to the flexural strength for materials with similar crystallographic structure. However, for different crystallographic materials, physical properties are independent of mechanical properties. Microstructural properties, particularly, grain size and crystallographic structure, and thermodynamic properties are the main factors affecting the mechanical properties at both room and high temperatures. The HTM cermet behaves

  19. Changes in membrane properties of CA1 pyramidal neurons after transient forebrain ischemia in vivo.

    Science.gov (United States)

    Gao, T M; Pulsinelli, W A; Xu, Z C

    1999-03-01

    We have previously identified three distinct populations of CA1 pyramidal neurons after reperfusion based on differences in synaptic response, and named these late depolarizing postsynaptic potential neurons (enhanced synaptic transmission), non-late depolarizing postsynaptic potential and small excitatory postsynaptic neurons (depressed synaptic transmission). In the present study, spontaneous activity and membrane properties of CA1 neurons were examined up to 48 h following approximately 14 min ischemic depolarization using intracellular recording and staining techniques in vivo. In comparison with preischemic properties, the spontaneous firing rate and the spontaneous synaptic activity of CA1 neurons decreased significantly during reperfusion; spontaneous synaptic activity ceased completely 36-48 h after reperfusion, except for a low level of activity which persisted in non-late depolarizing postsynaptic potential neurons. Neuronal hyperactivity as indicated by increasing firing rate was never observed in the present study. The membrane input resistance and time constant decreased significantly in late depolarizing postsynaptic potential neurons at 24-48 h reperfusion. In contrast, similar changes were not observed in non-late depolarizing postsynaptic potential neurons. The rheobase, spike threshold and spike frequency adaptation in late depolarizing postsynaptic potential neurons increased progressively following reperfusion. Only a transient increase in rheobase and spike threshold was detected in non-late depolarizing postsynaptic potential neurons and spike frequency adaptation remained unchanged in these neurons. The amplitude of fast afterhyperpolarization increased in all neurons after reperfusion, with the smallest increment in non-late depolarizing postsynaptic potential neurons. Small excitatory postsynaptic potential neurons shared similar changes to those of late depolarizing postsynaptic potential neurons. These results suggest that the enhancement

  20. Semecarpus anacardium L, nuts inhibit lipopolysaccharide induced NO production in rat macrophages along with its hypolipidemic property.

    Science.gov (United States)

    Tripathi, Y B; Pandey, R S

    2004-04-01

    Traditionally S. anacardium is used for rejuvenation, rheumatoid arthritis, fever and neurological disorders. In the present study it was observed that a fraction of S. anacacrdium at dose of 1 mg/100 g body wt, significantly reduced serum cholesterol from 378.87 mg/dl in the rats fed with atherogenic diet (AD) to 197.99 mg/dl (45-52%) in the rats fed with AD diet and increased serum HDL-cholesterol (33-37%). The same fraction also inhibited LPS induced NO production in the culture activated rat peritoneal macrophages in the dose dependent manner with IC50 value at 50 ng/ml of the culture medium. The drug in the above doses was completely safe and non-toxic, (no change in the enzymes), to liver and kidney functions.

  1. Diode-like properties of single- and multi-pore asymmetric track membranes

    Energy Technology Data Exchange (ETDEWEB)

    Zielinska, K., E-mail: kziel@jinr.ru [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Joliot-Curie str. 6, 141980 Dubna (Russian Federation); Faculty of Chemistry, Nicolaus Copernicus University, Gagarina str. 7, 87-100 Torun (Poland); Gapeeva, A.R.; Orelovich, O.L. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Joliot-Curie str. 6, 141980 Dubna (Russian Federation); Apel, P.Yu. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Joliot-Curie str. 6, 141980 Dubna (Russian Federation); The International University “Dubna”, Universitetskaya str. 19, 141980 Dubna (Russian Federation)

    2014-05-01

    In this work, we investigated the ionic transport properties of asymmetric polyethylene terephthalate (PET) track membranes with the thickness of 5 μm. The samples containing single pores and arrays of many pores were fabricated by irradiation with accelerated ions and subsequent physicochemical treatment. The method of etching in the presence of a surface-active agent was used to prepare the pores with highly-tapered tip. The transport of monovalent inorganic ions through the nano-scale holes was studied in a conductivity cell. The effective pore radii, electrical conductance and rectification ratios of pores were measured. The geometric characteristics of nanopores were investigated using FESEM.

  2. Studies on preparation and property of high-substitutional starch acetate hydrophode for the membrane material

    Institute of Scientific and Technical Information of China (English)

    ZUO Xiu-jin; DAI Xiao-min; MA Xiao-jun

    2005-01-01

    @@ Control-release technique is probably the most widely used,films control-release technique is the key of control-release technique,and film materials are the elements.The high-substitutional starch acetate was prepared by acetylation of starch with an acetic anhydride mixture.The best parameter of the technics (time of activation and reaction, reactant ratio) was obtained by orthogonal experiments.It was the hydrophode membrane material that property of the high-substitutional starch acetate was proofed.

  3. The adrenal specific toxicant mitotane directly interacts with lipid membranes and alters membrane properties depending on lipid composition.

    Science.gov (United States)

    Scheidt, Holger A; Haralampiev, Ivan; Theisgen, Stephan; Schirbel, Andreas; Sbiera, Silviu; Huster, Daniel; Kroiss, Matthias; Müller, Peter

    2016-06-15

    Mitotane (o,p'.-DDD) is an orphan drug approved for the treatment of adrenocortical carcinoma. The mechanisms, which are responsible for this activity of the drug, are not completely understood. It can be hypothesized that an impact of mitotane is mediated by the interaction with cellular membranes. However, an interaction of mitotane with (lipid) membranes has not yet been investigated in detail. Here, we characterized the interaction of mitotane and its main metabolite o,p'-dichlorodiphenyldichloroacetic acid (o,p'-DDA) with lipid membranes by applying a variety of biophysical approaches of nuclear magnetic resonance, electron spin resonance, and fluorescence spectroscopy. We found that mitotane and o,p'-DDA bind to lipid membranes by inserting into the lipid-water interface of the bilayer. Mitotane but not o,p'-DDA directly causes a disturbance of bilayer structure leading to an increased permeability of the membrane for polar molecules. Mitotane induced alterations of the membrane integrity required the presence of phosphatidylethanolamine and/or cholesterol. Collectively, our data for the first time characterize the impact of mitotane on the lipid membrane structure and dynamics, which may contribute to a better understanding of specific mitotane effects and side effects.

  4. The influence of hydrodynamic factors, membrane surface properties and channel geometries on membrane performance and fouling mechanisms

    Directory of Open Access Journals (Sweden)

    Pervov Alexey

    2016-01-01

    Full Text Available Modern theoretical understanding of colloidal and suspended matter membrane fouling mechanisms are presented and discussed. State-of-the-art simulation models of concentration polarization calculations for different channel conditions are described and influence of the fouling layers on the flux and rejection decrease are evaluated. Results of experimental investigations are presented that suggest a quantitative evaluation of fouling rates and membrane flux prognosis due to colloidal fouling with time. The influence of channel geometry on fouling is demonstrated and discussed. The main disadvantage of spiral wounded membrane modules which is attributed to the presence of a separation spacer mesh in the feed channel is discussed.

  5. Bioactive Hybrid Composite Membrane with Enhanced Antimicrobial Properties for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Abin Davis

    2016-06-01

    Full Text Available   Azadirachta indica extract has been explored as an antibiotic in hygienic chitosan matrix system to enhance antimicrobial and medicinal property in a cost effective manner. The hygienic composite system has been successfully fabricated via solvent casting. The antibacterial activities of the hybrid system were examined by agar diffusion method against gram positive S.aureus and gram negative K. pneumoniae. From conventional antibacterial test for 24 h, the system exhibited an excellent antimicrobial activity against both bacterial strains in ranges of 1.2 cm - 1.5 cm for S. aureus and 1.8 cm - 2.3 cm for K. pneumoniae Fourier transform infrared spectroscopy revealed successfully embedded A. indica on the chitosan substrate via weak electrostatic interaction, resulting in the easy release of the additive. Moreover, atomic force microscopy showed a membrane roughness of 0.084 nm which confirms the uniform distribution of the additive throughout the membrane. These hybrid membranes have potential applications in skin tissue engineering, wound healing and as coatings for implantable scaffold material.

  6. Two-component membrane material properties and domain formation from dissipative particle dynamics.

    Science.gov (United States)

    Illya, G; Lipowsky, R; Shillcock, J C

    2006-09-21

    The material parameters (area stretch modulus and bending rigidity) of two-component amphiphilic membranes are determined from dissipative particle dynamics simulations. The preferred area per molecule for each species is varied so as to produce homogeneous mixtures or nonhomogeneous mixtures that form domains. If the latter mixtures are composed of amphiphiles with the same tail length, but different preferred areas per molecule, their material parameters increase monotonically as a function of composition. By contrast, mixtures of amphiphiles that differ in both tail length and preferred area per molecule form both homogeneous and nonhomogeneous mixtures that both exhibit smaller values of their material properties compared to the corresponding pure systems. When the same nonhomogeneous mixtures of amphiphiles are assembled into planar membrane patches and vesicles, the resulting domain shapes are different when the bending rigidities of the domains are sufficiently different. Additionally, both bilayer and monolayer domains are observed in vesicles. We conclude that the evolution of the domain shapes is influenced by the high curvature of the vesicles in the simulation, a result that may be relevant for biological vesicle membranes.

  7. Predatory activity of Myxococcus xanthus outer-membrane vesicles and properties of their hydrolase cargo.

    Science.gov (United States)

    Evans, Alun G L; Davey, Hazel M; Cookson, Alan; Currinn, Heather; Cooke-Fox, Gillian; Stanczyk, Paulina J; Whitworth, David E

    2012-11-01

    The deltaproteobacterium Myxococcus xanthus predates upon members of the soil microbial community by secreting digestive factors and lysing prey cells. Like other Gram-negative bacteria, M. xanthus produces outer membrane vesicles (OMVs), and we show here that M. xanthus OMVs are able to kill Escherichia coli cells. The OMVs of M. xanthus were found to contain active proteases, phosphatases, other hydrolases and secondary metabolites. Alkaline phosphatase activity was found to be almost exclusively associated with OMVs, implying that there is active targeting of phosphatases into OMVs, while other OMV components appear to be packaged passively. The kinetic properties of OMV alkaline phosphatase suggest that there may have been evolutionary adaptation of OMV enzymes to a relatively indiscriminate mode of action, consistent with a role in predation. In addition, the observed regulation of production, and fragility of OMV activity, may protect OMV-producing cells from exploitation by M. xanthus cheating genotypes and/or other competitors. Killing of E. coli by M. xanthus OMVs was enhanced by the addition of a fusogenic enzyme (glyceraldehyde-3-phosphate dehydrogenase; GAPDH), which triggers fusion of vesicles with target membranes within eukaryotic cells. This suggests that the mechanism of prey killing involves OMV fusion with the E. coli outer membrane. M. xanthus secretes GAPDH, which could potentially modulate the fusion of co-secreted OMVs with prey organisms in nature, enhancing their predatory activity.

  8. Biochemical Properties and Inhibition Kinetics of Phosphatase from Wheat Thylakoid Membranes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A phosphatase that hydrolyses phosphate monoesters has been isolated from wheat thylakoid membranes.Biochemical properties and inhibition kinetics of the phosphatase were investigated using several ions, organic solvents, and inhibitors. Wheat (Triticum aestivum L. cv. PH82-2-2) thylakoid membrane phosphatase activity was activated by Mg2+, Ca2+, and Fe2+ and was inhibited by Mn2+ and Cu2+. For example, enzyme activity was activated 34.81% by 2 mmol/L Mg2+, but was inhibited 22.3% and 8.5% by 2 and 1 mmol/L Cu2+, respectively.Methanol, ethanol and glycol were all able to activate enzyme activity. Enzyme activity was activated 58.5%, 48.2%,and 8.7% by 40% ethanol, methanol and glycol, respectively. From these results, it can be seen that the degree of activation of the phosphatase was greatest for ethanol and the type of activation was uncompetitive. Moreover,the activity of the thylakoid membrane phosphatase was inhibited by molybdate, vanadate, phosphate, and fluoride and the type of inhibition produced by these elements was uncompetitive, non-competitive, competitive and mixed, respectively.

  9. Effects of APTEOS content and electron beam irradiation on physical and separation properties of hybrid nylon-66 membranes

    Energy Technology Data Exchange (ETDEWEB)

    Linggawati, A. [Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Mohammad, A.W., E-mail: wahabm@eng.ukm.my [Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Leo, C.P. [School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, S.P.S., Penang (Malaysia)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Hybrid nylon-66 membranes were prepared using APTEOS and modified by EB irradiation. Black-Right-Pointing-Pointer APTEOS increase the formation of cellular pores. Black-Right-Pointing-Pointer EB irradiation causes the growth of dense layer. Black-Right-Pointing-Pointer 10 wt% of APTEOS and irradiation at 70 kGy shows satisfactory separation of salt. - Abstract: Nylon-66 contains functional groups which form hydrogen bonds with inorganic silica networks and allow the creation of hybrid membranes. As a typical semicrystalline polymer, nylon-66 can be crosslinked through electron beam (EB) irradiation to form nanofiltration membranes. The effects of {gamma}-aminopropyltriethoxylsilane (APTEOS) and EB irradiation on the physical and separation properties of nylon-66 membranes were studied in this work. Hybrid nylon-66 membranes were prepared by adding an APTEOS solution (5 wt%, 10 wt% and 20 wt%) into nylon-66 which was dissolved in formic acid. Before air drying, membranes were irradiated at 60 kGy, 70 kGy and 80 kGy. More cellular pores were formed in nylon-66 membranes with the addition of APTEOS. However, increased irradiation dose caused the formation of a dense layer in nylon-66 membranes. Crosslinked silica in nylon-66 membranes was confirmed by FT-IR and DMA, while XRD results showed that there was a high degree of crystallinity in some membranes after irradiation. With improvements in membrane pore size and the ratio of membrane thickness to porosity, nylon-66 membrane with 10 wt% of APTEOS irradiated at 70 kGy exhibited satisfactory permeability, excellent removal of neutral solutes and improved rejection of divalent ions.

  10. Hygrothermal characterization of the viscoelastic properties of Gore-Select® 57 proton exchange membrane

    Science.gov (United States)

    Patankar, Kshitish A.; Dillard, David A.; Case, Scott W.; Ellis, Michael W.; Lai, Yeh-Hung; Budinski, Michael K.; Gittleman, Craig S.

    2008-09-01

    When a proton exchange membrane (PEM) based fuel cell is placed in service, hygrothermal stresses develop within the membrane and vary widely with internal operating environment. These hygrothermal stresses associated with hygral contraction and expansion at the operating conditions are believed to be critical in membrane mechanical integrity and durability. Understanding and accurately modeling the viscoelastic constitutive properties of a PEM is important for making hygrothermal stress predictions in the cyclic temperature and humidity environment of operating fuel cells. The tensile stress relaxation moduli of a commercially available PEM, Gore-Select® 57, were obtained over a range of humidities and temperatures. These tests were performed using TA Instruments 2980 and Q800 dynamic mechanical analyzers (DMA), which are capable of applying specified tensile loading conditions on small membrane samples at a given temperature. A special humidity chamber was built in the form of a cup that encloses tension clamps of the DMA. The chamber was inserted in the heating furnace of the DMA and connected to a gas humidification unit by means of plastic tubing through a slot in the chamber. Stress relaxation data over a temperature range of 40 90°C and relative humidity range of 30 90% were obtained. Thermal and hygral master curves were constructed using thermal and hygral shift factors and were used to form a hygrothermal master curve using the time temperature moisture superposition principle. The master curve was also constructed independently using just one shift factor. The hygrothermal master curve was fitted with a 10-term Prony series for use in finite element software. The hygrothermal master curve was then validated using longer term tests. The relaxation modulus from longer term data matches well with the hygrothermal master curve. The long term test showed a plateau at longer times, suggesting an equilibrium modulus.

  11. Aqueous Polymer Dispersion Coating Used for Osmotic Pump Tablets: Membrane Property Investigation and IVIVC Evaluation.

    Science.gov (United States)

    Cheng, Lizhen; Gai, Xiumei; Wen, Haoyang; Liu, Dandan; Tang, Xin; Wang, Yanyan; Wang, Tuanjie; Pan, Weisan; Yang, Xinggang

    2017-07-10

    The objective of this study was to investigate the fundamental properties of propranolol hydrochloride osmotic pump tablets coated by aqueous polymer dispersion, simultaneously exploring the in vitro and in vivo correlation of the tablet. The physicochemical properties and parameters of aqueous polymer dispersion membranes (SEM, water uptake, and water vapor transmission coefficient) were investigated. In addition, the release behavior and the in vitro release and in vivo absorption profiles of the tablets coated by aqueous polymer dispersion were investigated by comparing with propranolol hydrochloride osmotic pump tablets coated by an organic solvent. Results showed that the similarity factor (f 2) between cellulose acetate-coated tablet and Eudragit-coated tablet was 78.1, and f 2 between cellulose acetate-coated tablet and Kollicoat-coated tablet was 77.6. The linear IVIVC of Eudragit-coated and Kollicoat-coated osmotic pump tablets was determined, which confirmed excellent correlation between the absorption in vivo and the drug release in vitro. Consequently, the membrane coated by aqueous polymer dispersion or organic solvent has similar in vitro release rates of controlled release. Also, compared with organic solvent coating, aqueous polymer dispersion has numerous advantages, such as reduced toxicity and no environmental damage. Therefore, the aqueous polymer dispersion technology has enormous potential as a replacement of organic solvent coating.

  12. Changing pattern of the subcellular distribution of erythroblast macrophage protein (Emp) during macrophage differentiation.

    Science.gov (United States)

    Soni, Shivani; Bala, Shashi; Kumar, Ajay; Hanspal, Manjit

    2007-01-01

    Erythroblast macrophage protein (Emp) mediates the attachment of erythroid cells to macrophages and is required for normal differentiation of both cell lineages. In erythroid cells, Emp is believed to be involved in nuclear extrusion, however, its role in macrophage differentiation is unknown. Information on the changes in the expression level and subcellular distribution of Emp in differentiating macrophages is essential for understanding the function of Emp. Macrophages of varying maturity were examined by immunofluorescence microscopy and biochemical methods. Our data show that Emp is expressed in all stages of maturation, but its localization pattern changes dramatically during maturation: in immature macrophages, a substantial fraction of Emp is associated with the nuclear matrix, whereas in more mature cells, Emp is expressed largely at cell surface. Pulse-chase experiments show that nascent Emp migrates intracellularly from the cytoplasm to the plasma membrane more efficiently in mature macrophages than in immature cells. Incubation of erythroid cells with macrophages in culture shows that erythroid cells attach to mature macrophages but not to immature macrophage precursors. Together, our data show that the temporal and spatial expression of Emp correlates with its role in erythroblastic island formation and suggest that Emp may be involved in multiple cellular functions.

  13. Hydration effects and antifouling properties of poly(vinyl chloride-co-PEGMA) membranes studied using molecular dynamics simulations

    Science.gov (United States)

    Shaikh, Abdul Rajjak; Rajabzadeh, Saeid; Matsuo, Ryuichi; Takaba, Hiromitsu; Matsuyama, Hideto

    2016-04-01

    Polyvinyl chloride (PVC) membranes are widely used in water treatment because of their low cost and chemical stability. However, PVC membranes can become fouled, and this restricts their applications in membrane technology. In order to enhance the antifouling property of PVC membranes, copolymers such as poly(vinyl chloride-co-poly(ethylene glycol)methyl ether methacrylate) (poly(VC-co-PEGMA)) with different PEGMA segment percentages were synthesized in our previous work. Experimentally, it was observed that the poly(VC-co-PEGMA) copolymer has better antifouling properties than those of PVC membranes. Here, we explore effect of the PEGMA segment percentage on the surface hydration properties of poly(VC-co-PEGMA) copolymers. Density functional theory calculations and molecular dynamics simulations were carried out to understand the interactions between PVC and PEGMA. Model structures of these systems were validated by comparing the simulated values of their volumetric properties with the experimental values. MD studies showed that increasing PEGMA percentage in the copolymer increases the interaction with water molecules, leading to improved resistance to fouling. The antifouling mechanism is also discussed with respect to surface hydration and water dynamicity. This study could form a basis for the systematic studies of polymeric membranes as well as their stability from the extent of solvent-polymer, solvent-solvent, and polymer-polymer interactions.

  14. Elastic properties of thin poly(vinyl alcohol)-cellulose nanocrystal membranes

    Science.gov (United States)

    Pakzad, A.; Simonsen, J.; Yassar, R. S.

    2012-03-01

    In spite of extensive studies on the preparation and characterization of nanocomposite materials, the correlation of their properties at the nanoscale with those in bulk is a relatively unexplored area. This is of great importance, especially for materials with potential biomedical applications, where surface properties are as important in determining their applicability as bulk characteristics. In this study, the nanomechanical characteristics of thin poly(vinyl alcohol) (PVOH)-poly(acrylic acid) (PAA)-cellulose nanocrystal (CNC) membranes were studied using the nanoindentation module in an atomic force microscope (AFM) and the properties were compared with the macro-scale properties obtained by tensile tests. In general, the elastic properties measured by nanoindentation followed the same trend as macro-scale tensile tests except for the PVOH 85-PAA 0-CNC 15 sample. In comparison to the macro-scale elastic properties, the measured elastic moduli with AFM were higher. Macro-scale tensile test results indicated that, in the presence of PAA, incorporation of CNCs up to 20 wt% improved the elastic modulus of PVOH, but when no PAA was added, increasing the CNC content above 10 wt% resulted in their agglomeration and degradation in mechanical properties of PVOH. The discrepancy between macro-scale tensile tests and nanoindentation in the PVOH 85-PAA 0-CNC 15 sample was correlated to the high degree of inhomogeneity of CNC dispersion in the matrix. It was found that the composites reinforced with cellulose nanocrystals had smaller indentation imprints and the pile-up effect increased with the increase of cellulose nanocrystal content.

  15. Fundamental Studies of Assembly and Mechanical Properties of Lipid Bilayer Membranes and Unilamellar Vesicles

    Science.gov (United States)

    Wang, Xi

    This dissertation work focuses on: (i) obtaining a phospholipid bilayer membrane (LBM)/conducting electrode system with low defect density and optimized rigidity; (ii) investigating vesicle stability and mechanical properties. LBM is a simplified yet representative cell membrane model. LBMs assembled on conductive surfaces can probe protein-LBM interactions activities electrochemically. Sterically stabilized vesicles could be used as cell models or for drug delivery. The main challenges for LBM assembly on gold are vesicles do not spontaneously rupture to form LBMs on gold and the roughness of the gold substrate has considerable influence on molecular film defect density. In this study, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) vesicles were functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine- N-poly(ethylene glycol)-2000-N-[3-(2-pyridyldithio)propionate] (DSPE-PEG-PDP) to yield stable LBMs on gold without surface modification. A template-stripping method was used to obtain atomically flat and pristine gold surfaces. The critical force to initiate vesicle rupture decreases with increasing DSPE-PEG-PDP concentration, indicating that gold-thiolate bonding between DSPE-PEG-PDP and gold substrates promotes LBM formation. Mechanical properties of LBMs and vesicles were investigated as a function of DSPE-PEG-PDP concentration via Atomic Force Microscopy. The elastic moduli of LBMs were determined with DSPE-PEG-PDP concentration ranging from 0mol% to 24mol% and were found to depend on PEG chain conformation. Incorporating DSPE-PEG-PDP molecules with PEG in mushroom conformation results in a decrease of LBM rigidity, while incorporating PEG in brush conformation leads to LBM stiffening. Contrarily, mechanical properties of functionalized vesicles did not vary significantly by varying DSPE-PEG-PDP concentration. LBM with tunable rigidity by adjusting DSPE-PEG-PDP concentration provides a versatile cell membrane model for studying protein or

  16. Liver macrophages in healthy and diseased liver.

    Science.gov (United States)

    Abdullah, Zeinab; Knolle, Percy A

    2017-04-01

    Kupffer cells, the largest tissue resident macrophage population, are key for the maintenance of liver integrity and its restoration after injury and infections, as well as the local initiation and resolution of innate and adaptive immunity. These important roles of Kupffer cells were recently identified in healthy and diseased liver revealing diverse functions and phenotypes of hepatic macrophages. High-level phenotypic and genomic analysis revealed that Kupffer cells are not a homogenous population and that the hepatic microenvironment actively shapes both phenotype and function of liver macrophages. Compared to macrophages from other organs, hepatic macrophages bear unique properties that are instrumental for their diverse roles in local immunity as well as liver regeneration. The diverse and, in part, contradictory roles of hepatic macrophages in anti-tumor and inflammatory immune responses as well as regulatory and regenerative processes have been obscured by the lack of appropriate technologies to specifically target or ablate Kupffer cells or monocyte-derived hepatic macrophages. Future studies will need to dissect the exact role of the hepatic macrophages with distinct functional properties linked to their differentiation status and thereby provide insight into the functional plasticity of hepatic macrophages.

  17. ANTIFOULING PROPERTIES OF POLY(VINYL CHLORIDE) MEMBRANES MODIFIED BY AMPHIPHILIC COPOLYMERS P(MMA-b-MAA)

    Institute of Scientific and Technical Information of China (English)

    Wei-dong Liu; Yong-hua Zhang; Li-feng Fang; Bao-ku Zhu; Li-ping Zhu

    2012-01-01

    Three well-defined diblock copolymers ofpoly(methyl methacrylate-b-methaerylic acid) (P(MMA-b-MAA)) were synthesized using atom transfer radical polymerization method and varying poly(methacrylic acid) (PMAA) chain lengths.These copolymers were blended with PVC to fabricate porous membranes via phase inversion process.Membrane morphologies were observed by scanning electron microscopy (SEM),and chemical composition changes of the membrane surfaces were measured by X-ray photoelectron spectroscopy (XPS).Static and dynamic protein adsorption experiments were used to evaluate antifouling properties of the blend membranes.It was found that,the blend membranes containing longer PMAA arm length showed lower static protein adsorption,higher water permeation flux and better protein solution flux recovery.

  18. THE EFFECT OF THE TYPE OF ADMIXTURE ON THE PROPERTIES OF POLYACRYLONITRILE MEMBRANES MODIFIED WITH NANOTUBES, GRAPHENE OXIDE AND GRAPHENE

    Directory of Open Access Journals (Sweden)

    Beata Fryczkowska

    2017-09-01

    Full Text Available This paper presents the results of research on the production of composite polyacrylonitrile (PAN membranes with nanotubes (MWCNT, graphene (RG and graphene oxide (GO addition. All of the specified additions differ diametrically in terms of properties, starting from the spatial structure of the particles, up to the chemical properties. Membranes were obtained using phase inversion method from a solution of N,N-dimethylformamide (DMF. Subsequently, the impact of the nano-addition on the transport and separation properties of the membranes were investigated using Millipore AMICON ultrafiltration kit. Membranes with graphene addition (PAN/RG are characterized by the best transport properties and the highest specific permeate flux values in the range of ~913÷1006 [dm3/m2×h] for working pressure of 2.0 MPa. To test the separation properties, electroplating waste water generated in one of the Silesian galvanizing plants was used. The qualitative and quantitative composition of the waste water was tested by UV-Vis spectrophotometer (HACH and absorption atomic spectrometry (AAS. The ultrafiltration process carried out on composite membranes allows for the complete removal of phosphate ions and ~88÷94% of iron from the waste water. The rejection coefficient of the remaining metals is high: ~ 35 ÷ 85% for copper and ~ 17 ÷ 100% for cadmium.

  19. Physically Gelled Room-Temperature Ionic Liquid-Based Composite Membranes for CO2/N-2 Separation: Effect of Composition and Thickness on Membrane Properties and Performance

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, PT; Voss, BA; Wiesenauer, EF; Gin, DL; Nobe, RD

    2013-07-03

    An aspartame-based, low molecular-weight organic gelator (LMOG) was used to form melt-infused and composite membranes with two different imidazolium-based room-temperature ionic liquids (RTILs) for CO2 separation from N-2. Previous work demonstrated that LMOGs can gel RTILs at low, loading levels, and this aspartame-based LMOG was selected because it has been reported to gel a large number of RTILs. The imidazolium-based RTILs were used because of their inherent good properties for CO2/light gas separations. Analysis of the resulting bulk RTIL/LMOG physical gels showed that these materials have high sol-gel transition temperatures (ca. 135 degrees C) suitable for flue gas applications. Gas permeabilities and burst pressure measurements of thick, melt infused membranes revealed a trade-off between high CO2 permeabilities and good mechanical stability as a function of the LMOG loading. Defect-free, composite membranes of the gelled RTILs were successfully fabricated by choosing an appropriate porous membrane support (hydrophobic PTFE) using a suitable coating technique (roller coating). The thicknesses of the applied composite gel layers ranged from 10.3 to 20.7 mu m, which represents an order of magnitude decrease in active layer thickness, compared to the original melt-infused gel RTIL membranes.

  20. COMPOSITE OF CHITOSAN VANILIN / SULFONATED POLYSTYRENE AS POLYMER ELECTROLYTE MEMBRANES : CATIONIC EXCHANGE CAPACITY, SWELLING DEGREE AND THERMAL PROPERTIES

    OpenAIRE

    Edi Pramono; Candra Purnawan; Yuniawan Hidayat; Jati Wulansari; Sayekti Wahyuningsih

    2016-01-01

    Research on the preparation and characterization of sulfonated polystyrene (PST) /chitosan vanillin (KV) composite as electrolyte membranes has been conducted in order to investigate the effect of PST and KV composition to its chemical and physical properties. Polystyrene was modified by sulfonation reaction to produces PST, meanwhile chitosan was modified by schift base reaction to produces KV. The composite membranes were prepared by casting method and were characterized in order to identi...

  1. Preparation of graphene oxide modified poly(m-phenylene isophthalamide) nanofiltration membrane with improved water flux and antifouling property

    Science.gov (United States)

    Yang, Mei; Zhao, Changwei; Zhang, Shaofeng; Li, Pei; Hou, Deyin

    2017-02-01

    Poly (m-phenylene isophthalamide)/graphene oxide (PMIA/GO) composite nanofiltartion (NF) membranes were prepared via a facile phase inversion method. Structures, surface properties and hydrophilicities of the membrane were analyzed using FT-IR, XPS, AFM, SEM, water contact angle and Zeta-potential measurements. FTIR spectra indicated the existence of hydrophilic carboxylic acid and hydroxyl groups in the GO molecules. SEM pictures revealed the large and finger-like micro-voids formed in the sublayer of the NF membranes after adding GO. The zeta-potential and water contact angle results proved that PMIA/GO composite membranes had more negatively charged and greater hydrophilic surfaces. The pure water flux of the PMIA/GO (0.3 wt% GO) composite membrane (125.2 (L/m2/h)) was 2.6 times as high as that of the pristine PMIA NF membrane (48.3 (L/m2/h)) at 0.8 MPa with slightly higher rejections to all tested dyes and better fouling resistance to bovine serum albumin (BSA). This study gave an effective method for preparing composite PMIA NF membranes with high water flux and excellent antifouling property, which showed potential application in water treatment.

  2. COMPOSITE OF CHITOSAN VANILIN / SULFONATED POLYSTYRENE AS POLYMER ELECTROLYTE MEMBRANES : CATIONIC EXCHANGE CAPACITY, SWELLING DEGREE AND THERMAL PROPERTIES

    Directory of Open Access Journals (Sweden)

    Edi Pramono

    2016-08-01

    Full Text Available Research on the preparation and characterization of sulfonated polystyrene (PST /chitosan vanillin (KV composite as electrolyte membranes has been conducted in order to investigate the effect of PST and KV composition to its chemical and physical properties. Polystyrene was modified by sulfonation reaction to produces PST, meanwhile chitosan was modified by schift base reaction to produces KV. The composite membranes were prepared by casting method and were characterized in order to identify the functional groups contained in the composite, the cation exchange capacity (CEC, the Swelling Degree (SD, the thermal properties and the morphology. The peak of imine vibration in the FTIR spectrum indicates that the chitosan vanilin was succesfully synthesized. Meanwhile, the peak of sulfonate vibration indicates the product of sulfonation on polystyrene. The result of CEC analysis shows that the addition of sulfonate groups on polystyrene and the addition of phenolic groups on chitosan increase the CEC value. The increasing of PST and KV concentration in membrane enhance the CEC value. However, the increasing of PST concentration in membrane composition even decrease the Swelling Degree of membranes. Meanwhile, the increasing of KV concentration increase the swelling degree of membranes. Thermal analysis shows that the thermal decomposition of membranes occurs in three stages i.e. the dehydration of water molecules, the degradation of the subtituen groups and the plasticizer and the degradation of the back bone of chitosan and polystyrene.

  3. Effect of Amphipathic HIV Fusion Inhibitor Peptides on POPC and POPC/Cholesterol Membrane Properties: A Molecular Simulation Study

    Directory of Open Access Journals (Sweden)

    Luís M. S. Loura

    2013-07-01

    Full Text Available T-20 and T-1249 fusion inhibitor peptides were shown to interact with 1-palmitoyl-2-oleyl-phosphatidylcholine (POPC (liquid disordered, ld and POPC/cholesterol (1:1 (POPC/Chol (liquid ordered, lo bilayers, and they do so to different extents. Although they both possess a tryptophan-rich domain (TRD, T-20 lacks a pocket binding domain (PBD, which is present in T-1249. It has been postulated that the PBD domain enhances FI interaction with HIV gp41 protein and with model membranes. Interaction of these fusion inhibitor peptides with both the cell membrane and the viral envelope membrane is important for function, i.e., inhibition of the fusion process. We address this problem with a molecular dynamics approach focusing on lipid properties, trying to ascertain the consequences and the differences in the interaction of T-20 and T-1249 with ld and lo model membranes. T-20 and T-1249 interactions with model membranes are shown to have measurable and different effects on bilayer structural and dynamical parameters. T-1249’s adsorption to the membrane surface has generally a stronger influence in the measured parameters. The presence of both binding domains in T-1249 appears to be paramount to its stronger interaction, and is shown to have a definite importance in membrane properties upon peptide adsorption.

  4. Mycobacterium tuberculosis replicates within necrotic human macrophages

    Science.gov (United States)

    Lerner, Thomas R.; Repnik, Urska; Herbst, Susanne; Collinson, Lucy M.; Griffiths, Gareth

    2017-01-01

    Mycobacterium tuberculosis modulation of macrophage cell death is a well-documented phenomenon, but its role during bacterial replication is less characterized. In this study, we investigate the impact of plasma membrane (PM) integrity on bacterial replication in different functional populations of human primary macrophages. We discovered that IFN-γ enhanced bacterial replication in macrophage colony-stimulating factor–differentiated macrophages more than in granulocyte–macrophage colony-stimulating factor–differentiated macrophages. We show that permissiveness in the different populations of macrophages to bacterial growth is the result of a differential ability to preserve PM integrity. By combining live-cell imaging, correlative light electron microscopy, and single-cell analysis, we found that after infection, a population of macrophages became necrotic, providing a niche for M. tuberculosis replication before escaping into the extracellular milieu. Thus, in addition to bacterial dissemination, necrotic cells provide first a niche for bacterial replication. Our results are relevant to understanding the environment of M. tuberculosis replication in the host. PMID:28242744

  5. Porous CS based membranes with improved antimicrobial properties for the treatment of infected wound in veterinary applications

    Energy Technology Data Exchange (ETDEWEB)

    Tonda-Turo, C., E-mail: chiara.tondaturo@polito.it [Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Turin (Italy); Ruini, F. [Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Turin (Italy); Argentati, M. [Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Turin (Italy); Clinic for Exotic Animals, CVS, Via Sandro Giovannini 53, 00137 Rome (Italy); Di Girolamo, N. [Clinic for Exotic Animals, CVS, Via Sandro Giovannini 53, 00137 Rome (Italy); Robino, P.; Nebbia, P. [Department of Veterinary Sciences, University of Turin, Largo Braccini 2, 10095 Grugliasco, Turin (Italy); Ciardelli, G. [Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Turin (Italy)

    2016-03-01

    Recently, much attention has been given to the use of innovative solution for the treatment of infected wounds in animals. Current applied treatments are often un-effective leading to infection propagation and animal death. Novel engineered membranes based on chitosan (CS) can be prepared to combine local antimicrobial effect, high flexibility and easy manipulation. In this work, CS crosslinked porous membranes with improved antimicrobial properties were prepared via freeze-drying technique to promote wound healing and to reduce the bacterial proliferation in infected injuries. Silver nanoparticles (AgNPs) and gentamicin sulfate (GS) were incorporated into the CS matrices to impart antibacterial properties on a wild range of strains. CS based porous membranes were tested for their physicochemical, thermal, mechanical as well as swelling and degradation behavior at physiological condition. Additionally, GS release profile was investigated, showing a moderate burst effect in the first days followed by a decreasing release rate which it was maintained for at least 56 days. Moreover, porous membranes loaded with GS or AgNPs showed good bactericidal activity against both of Gram-positive and Gram-negative bacteria. The bacterial strains used in this work were collected in chelonians after carapace injuries to better mimic the environment after trauma. - Highlights: • Innovative scaffolds for wound healing in veterinary applications • Novel engineered membranes based on chitosan with improved antibacterial properties • Highly flexible and versatile membranes for infected wounds.

  6. Carbon Nanotube/Alumina/Polyethersulfone Hybrid Hollow Fiber Membranes with Enhanced Mechanical and Anti-Fouling Properties

    Directory of Open Access Journals (Sweden)

    Yi Feng

    2015-08-01

    Full Text Available Carbon nanotubes (CNTs were incorporated into alumina/polyethersulfone hollow fibre membranes to enhance the mechanical property and the efficiency of water treatment. Results show that the incorporation of CNTs can greatly limit the formation of large surface pores, decrease the void size in support layers and improve the porosity and pore connectivity of alumina/polyethersulfone membranes. As a result of such morphology change and pore size change, both improved flux and rejection were achieved in such CNTs/alumina/polyethersulfone membranes. Moreover, the CNTs/alumina/PES membranes show higher antifouling ability and the flux recoveries after being fouled by bovine serum albumin (BSA and humic acid were improved by 84.1% and 53.2% compared to the samples without CNT incorporation. Besides the improvement in water treatment performance, the incorporation of CNTs enhanced the tensile properties of inorganic/polymer membranes. Therefore, such CNTs/alumina/PES hollow fiber membranes are very promising candidates for good filter media in industry, considering their high efficiency and high mechanical properties.

  7. Carbon Nanotube/Alumina/Polyethersulfone Hybrid Hollow Fiber Membranes with Enhanced Mechanical and Anti-Fouling Properties.

    Science.gov (United States)

    Feng, Yi; Wang, Kun; Davies, Chris H J; Wang, Huanting

    2015-08-20

    Carbon nanotubes (CNTs) were incorporated into alumina/polyethersulfone hollow fibre membranes to enhance the mechanical property and the efficiency of water treatment. Results show that the incorporation of CNTs can greatly limit the formation of large surface pores, decrease the void size in support layers and improve the porosity and pore connectivity of alumina/polyethersulfone membranes. As a result of such morphology change and pore size change, both improved flux and rejection were achieved in such CNTs/alumina/polyethersulfone membranes. Moreover, the CNTs/alumina/PES membranes show higher antifouling ability and the flux recoveries after being fouled by bovine serum albumin (BSA) and humic acid were improved by 84.1% and 53.2% compared to the samples without CNT incorporation. Besides the improvement in water treatment performance, the incorporation of CNTs enhanced the tensile properties of inorganic/polymer membranes. Therefore, such CNTs/alumina/PES hollow fiber membranes are very promising candidates for good filter media in industry, considering their high efficiency and high mechanical properties.

  8. In-Vitro Adhesion and Invasion Properties of Salmonella Typhimurium Competing with Bacteriophage in Epithelial Cells and Chicken Macrophages

    Directory of Open Access Journals (Sweden)

    HY Lee

    2015-12-01

    Full Text Available ABSTRACT This study was designed to assess the role of bacteriophage P22 in the adhesion, invasion, intracellular survival of, and cellular immune response to Salmonella Typhimurium in intestinal epithelial INT-407 and chicken macrophage-like HD11 cells. The ability of S. Typhimurium to adhere, invade, and survive to INT-407 and HD11cells was evaluated under Salmonella infection alone (control, phage treatment followed by Salmonella infection (PS, Salmonella infection followed by phage treatment (SP, and a combination treatment with Salmonella and phage (S+P. The number of S. Typhimurium associated on INT-407 cells was reduced from 4.2 to 2.7 log cfu/cm2 by phage treatment (SP. The number of intracellular S. Typhimurium within INT-407 cells was significantly reduced to below the detection limit (0.7 log cfu/cm2 compared with the control (3.4 log cfu/cm2. S. Typhimurium remained inside HD11 cells at 49% and 17% levels in the absence and presence of phages, respectively, at 24 h post-infection (hpi. The expression levels of IFN-g, IL-10, IL-1b, IL-6, IL-8, iNOS, and IL-12 increased in HD11 cells regardless the absence and presence of phages, while those of IL-16, TLR2-1, TLR3, and TLR7 were decreased at 0 and 24 hpi. This study sheds new light on our understanding of the role of phages in Salmonella adhesion, invasion, survival, and cellular immune responses.

  9. Is nitric oxide decrease observed with naphthoquinones in LPS stimulated RAW 264.7 macrophages a beneficial property?

    Directory of Open Access Journals (Sweden)

    Brígida R Pinho

    Full Text Available The search of new anti-inflammatory drugs has been a current preoccupation, due to the need of effective drugs, with less adverse reactions than those used nowadays. Several naphthoquinones (plumbagin, naphthazarin, juglone, menadione, diosquinone and 1,4-naphthoquinone, plus p-hydroquinone and p-benzoquinone were evaluated for their ability to cause a reduction of nitric oxide (NO production, when RAW 264.7 macrophages were stimulated with lipopolysaccharide (LPS. Dexamethasone was used as positive control. Among the tested compounds, diosquinone was the only one that caused a NO reduction with statistical importance and without cytotoxicity: an IC(25 of 1.09±0.24 µM was found, with 38.25±6.50% (p<0.001 NO reduction at 1.5 µM. In order to elucidate if this NO decrease resulted from the interference of diosquinone with cellular defence mechanisms against LPS or to its conversion into peroxynitrite, by reaction with superoxide radical formed by naphthoquinones redox cycling, 3-nitrotyrosine and superoxide determination was also performed. None of these parameters showed significant changes relative to control. Furthermore, diosquinone caused a decrease in the pro-inflammatory cytokines: tumour necrosis factor-alpha (TNF-α and interleukin 6 (IL-6. Therefore, according to the results obtained, diosquinone, studied for its anti-inflammatory potential for the first time herein, has beneficial effects in inflammation control. This study enlightens the mechanisms of action of naphthoquinones in inflammatory models, by checking for the first time the contribution of oxidative stress generated by naphthoquinones to NO reduction.

  10. Polydopamine-mediated surface functionalization of electrospun nanofibrous membranes: Preparation, characterization and their adsorption properties towards heavy metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chunlin [School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003 (China); Wang, Heyun [School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003 (China); Key Laboratory for Green Processing of Chemical Engineering of Xinjiang bingtuan, Shihezi University, Shihezi 832003 (China); Wei, Zhong, E-mail: steven_weiz@sina.com [School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003 (China); Key Laboratory for Green Processing of Chemical Engineering of Xinjiang bingtuan, Shihezi University, Shihezi 832003 (China); Li, Chuan; Luo, Zhidong [School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003 (China)

    2015-08-15

    Graphical abstract: - Highlights: • A simple and versatile approach to produce PEI-functionalized nanofibers. • Novel PEI-functionalized PVC nanofibrous membrane was prepared. • Adsorption of PVC@PDA and PVC@PDA-PEI nanofibrous membranes for Cu{sup 2+} was tested. • Isotherms, kinetic model and thermodynamic parameters were investigated. • Adsorption mechanism of Cu{sup 2+} on modified membranes was inferred. - Abstract: In this paper, a simple and versatile approach for the fabrication of a polyethyleneimine (PEI)-functionalized nanofibrous membrane utilizing polydopamine (PDA) as a mediator is proposed. The morphology and structure of the PDA-coated and PEI-grafted nanofibrous membranes were confirmed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Due to a large specific surface area and long fibrous morphology, the synthesized membranes were used as novel adsorbents for copper ion (Cu{sup 2+}) removal from aqueous solutions. The adsorption of Cu{sup 2+} was investigated on the synthesized membranes regarding the membrane dosages, initial solution pH values, initial solution concentrations, contact times and temperatures. In addition, the adsorption equilibrium data of PEI-grafted membranes were well fitted with the Langmuir adsorption isotherm, and a maximum adsorption capacity value of 33.59 mg g{sup −1} was determined (while it was 21.94 mg g{sup −1} for the PDA-coated membranes). The thermodynamic parameters indicated that Cu{sup 2+} absorption was a spontaneous and exothermic adsorption process. In addition, XPS peak differentiation imitating analysis permitted the proposal of a copper-amine coordination adsorption mechanism that can be used to explain changes in the adsorption properties compared to PDA coating nanofibrous membranes.

  11. Effects of surface coating process conditions on the water permeation and salt rejection properties of composite polyamide reverse osmosis membranes

    KAUST Repository

    Louie, Jennifer Sarah

    2011-02-01

    The application of polymer surface coatings to improve the fouling resistance of reverse osmosis membranes tends to increase flow resistance across the membrane. This paper presents a systematic analysis on how membrane properties and performance are impacted by the coating process steps, and investigates how such effects could contribute to lower water flux. On one hand, simply pre-soaking dry aromatic polyamide composite membranes in aliphatic alcohols results in a significant increase in water flux, which is attributed to wetting of pores in the selective polyamide layer and to changes in the polymer structure. This flux increase was not readily reversible, based on a 300-h water permeation test. Conversely, drying a wetted membrane led to a decrease in water flux, which we hypothesize is caused by increased interchain hydrogen-bonding in the selective layer. This drop in water flux was not permanent; higher flux was observed if the same wetted/dried membrane was then re-soaked in ethanol prior to the water permeation experiment. An ethanol pre-soaking step also increased water flux of a PEBAX-coated membrane by nearly 70%. In contrast to the reduction in water flux caused by the specific treatment sequence of ethanol-swelling followed by drying, this same sequence actually increased gas transport. The eight- to ten-fold increase in Knudsen diffusion-based gas permeance after this pre-treatment was attributed to an increase in the number or size of membrane defects. © 2010 Elsevier B.V.

  12. Polydopamine-mediated surface functionalization of electrospun nanofibrous membranes: Preparation, characterization and their adsorption properties towards heavy metal ions

    Science.gov (United States)

    Wu, Chunlin; Wang, Heyun; Wei, Zhong; Li, Chuan; Luo, Zhidong

    2015-08-01

    In this paper, a simple and versatile approach for the fabrication of a polyethyleneimine (PEI)-functionalized nanofibrous membrane utilizing polydopamine (PDA) as a mediator is proposed. The morphology and structure of the PDA-coated and PEI-grafted nanofibrous membranes were confirmed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Due to a large specific surface area and long fibrous morphology, the synthesized membranes were used as novel adsorbents for copper ion (Cu2+) removal from aqueous solutions. The adsorption of Cu2+ was investigated on the synthesized membranes regarding the membrane dosages, initial solution pH values, initial solution concentrations, contact times and temperatures. In addition, the adsorption equilibrium data of PEI-grafted membranes were well fitted with the Langmuir adsorption isotherm, and a maximum adsorption capacity value of 33.59 mg g-1 was determined (while it was 21.94 mg g-1 for the PDA-coated membranes). The thermodynamic parameters indicated that Cu2+ absorption was a spontaneous and exothermic adsorption process. In addition, XPS peak differentiation imitating analysis permitted the proposal of a copper-amine coordination adsorption mechanism that can be used to explain changes in the adsorption properties compared to PDA coating nanofibrous membranes.

  13. On Stabilization of PVPA/PVA Electrospun Nanofiber Membrane and Its Effect on Material Properties and Biocompatibility

    Directory of Open Access Journals (Sweden)

    Rose Ann Franco

    2012-01-01

    Full Text Available A novel nanofiber membrane was fabricated by electrospinning composed of polyvinyl phosphonic acid (PVPA and polyvinyl alcohol (PVA. Stabilization was done due to the high dissolvability of the membrane when in contact with water. Physical treatment was done by exposure to heat at 150°C in a vacuum environment at different periods of time. Chemical crosslinking was done by immersion in methanol and methanol/ glutaraldehyde. A heat-exposed membrane was also further crosslinked chemically. All conditions were compared with regards to its effect on the material properties of the membranes and its biological response in vitro with MG-63 osteoblast-like cell line. Visual examination and dimensional analyses showed that heat treatment produced discoloration on the membrane surface and chemical crosslinking reduced membrane dimensions. Tensile strength and strain improved in crosslinked membranes compared to noncrosslinked counterpart. Swelling and degradation was also investigated and was seen to vary depending on the crosslinking condition. Biocompatibility was observed to be more favorable in heat-treated membranes.

  14. Immobilization of tris(2 pyridyl methylamine in a PVC-Membrane Sensor and Characterization of the Membrane Properties

    Directory of Open Access Journals (Sweden)

    Rezayi Majid

    2012-05-01

    Full Text Available Abstract Background Due to the increasing industrial use of titanium compounds, its determination is the subject of considerable efforts. The ionophore or membrane active recognition is the most important component of any polymeric membrane sensor. The sensor’s response depends on the ionophore and bonding between the ionophore and the target ion. Ionophores with molecule-sized dimensions containing cavities or semi-cavities can surround the target ion. The bond between the ionophore and target ion gives different selectivity and sensitivity toward the other ions. Therefore, ionophores with different binding strengths can be used in the sensor. Results In the present work, poly (vinyl chloride (PVC based membrane incorporating tris (2 pyridyl methylamine (tpm as an ionophore has been prepared and explored as a titanium(III selective sensor. Conclusions The strengths of the ion–ionophore (Ti(OH2+-tpm interactions and the role of ionophore on membrane were tested by various techniques such as elemental analysis, UV–vis, Fourier transform infrared (FTIR spectroscopy, scanning electron microscopy (SEM, and powder X-ray diffraction (XRD. All data approved the successful incorporation of organic group via covalent bond.

  15. The relationship between LDL oxidation and macrophage myeloperoxidase activity

    Institute of Scientific and Technical Information of China (English)

    武军驻; 刘艳红; 李小明; 陈丽达; 夏腊菊; 洪嘉玲

    2003-01-01

    Objective To explore low density lipoprotein (LDL) oxidation by macrophage myeloperoxidase (MPO) at molecular level.Methods Using a mouse macrophage model, we examined the relationship between LDL oxidation and macrophage MPO by measuring macrophage MPO activity, LDL oxidation products, MPO gene expression and cellular orientation of LDL oxidation. Results MPO gene expression increased to its maximum gradually when the concentration of LDL was increased, and then maintained at that level. NaN3 inhibied the elevation of MPO activity and LDL oxidation, which was LDL concentration-dependent. After the composition of macrophage membrane was roughly analyzed, it was determined that the contents of MPO and LDL in 5% sucrose were 7.667 and 21 times higher than those in 10% sucrose, respectively. Conclusion LDL is attached to the "microdomain" of the macrophage membrane in which LDL is oxidized by MPO.

  16. Dramatic nano-fluidic properties of carbon nanotube membranes as a platform for protein channel mimetics

    Science.gov (United States)

    Hinds, Bruce

    2013-03-01

    Carbon nanotubes have three key attributes that make them of great interest for novel membrane applications: 1) atomically flat graphite surface allows for ideal fluid slip boundary conditions and extremely fast flow rates 2) the cutting process to open CNTs inherently places functional chemistry at CNT core entrance for chemical selectivity and 3) CNT are electrically conductive allowing for electrochemical reactions and application of electric fields gradients at CNT tips. Pressure driven flux of a variety of solvents (H2O, hexane, decane ethanol, methanol) are 4-5 orders of magnitude higher than conventional Newtonian flow [Nature 2005, 438, 44] due to atomically flat graphite planes inducing nearly ideal slip conditions. However this is eliminated with selective chemical functionalization [ACS Nano 2011 5(5) 3867-3877] needed to give chemical selectivity. These unique properties allow us to explore the hypothesis of producing ``Gatekeeper'' membranes that mimic natural protein channels to actively pump through rapid nm-scale channels. With anionic tip functionality strong electroosmotic flow is induced by unimpeded cation flow with similar 10,000 fold enhancements [Nature Nano 2012 7(2) 133-39]. With enhanced power efficiency, carbon nanotube membranes were employed as the active element of a switchable transdermal drug delivery device that can facilitate more effective treatments of drug abuse and addiction. Recently methods to deposit Pt monolayers on CNT surface have been developed making for highly efficient catalytic platforms. Discussed are other applications of CNT protein channel mimetics, for large area robust engineering platforms, including water purification, flow battery energy storage, and biochemical/biomass separations. DOE EPSCoR (DE-FG02-07ER46375) and DARPA, W911NF-09-1-0267

  17. Intrinsic membrane properties underlying spontaneous tonic firing in neostriatal cholinergic interneurons.

    Science.gov (United States)

    Bennett, B D; Callaway, J C; Wilson, C J

    2000-11-15

    Neostriatal cholinergic interneurons produce spontaneous tonic firing in the absence of synaptic input. Perforated patch recording and whole-cell recording combined with calcium imaging were used in vitro to identify the intrinsic membrane properties underlying endogenous excitability. Spontaneous firing was driven by the combined action of a sodium current and the hyperpolarization-activated cation current (I(h)), which together ensured that there was no zero current point in the subthreshold voltage range. Blockade of sodium channels or I(h) established a stable subthreshold resting membrane potential. A tetrodotoxin-sensitive region of negative slope conductance was observed between approximately -60 mV and threshold (approximately -50 mV) and the h-current was activated at all subthreshold voltages. Calcium imaging experiments revealed that there was minimal calcium influx at subthreshold membrane potentials but that action potentials produced elevations of calcium in both the soma and dendrites. Spike-triggered calcium entry shaped the falling phase of the action potential waveform and activated calcium-dependent potassium channels. Blockade of big-conductance channels caused spike broadening. Application of apamin, which blocks small-conductance channels, abolished the slow spike afterhyperpolarization (AHP) and caused a transition to burst firing. In the absence of synaptic input, a range of tonic firing patterns are observed, suggesting that the characteristic spike sequences described for tonically active cholinergic neurons (TANs) recorded in vivo are intrinsic in origin. The pivotal role of the AHP in regulating spike patterning indicates that burst firing of TANs in vivo could arise from direct or indirect modulation of the AHP without requiring phasic synaptic input.

  18. [Molecular mechanisms regulating the activity of macrophages].

    Science.gov (United States)

    Onoprienko, L V

    2011-01-01

    This article reviews modern concepts of the most common types of macrophage activation: classical, alternative, and type II. Molecular mechanisms of induction and regulation of these three types of activation are discussed. Any population of macrophages was shown to change its properties depending on its microenvironment and concrete biological situation (the "functional plasticity of macrophages"). Many intermediate states of macrophages were described along with the most pronounced and well-known activation types (classical activation, alternative activation, and type II activation). These intermediate states are characterized by a variety of combinations of their biological properties, including elements of the three afore mentioned types of activation. Macrophage activity is regulated by a complex network of interrelated cascade mechanisms.

  19. Saturated fatty acids alter the late secretory pathway by modulating membrane properties.

    Science.gov (United States)

    Payet, Laurie-Anne; Pineau, Ludovic; Snyder, Ellen C R; Colas, Jenny; Moussa, Ahmed; Vannier, Brigitte; Bigay, Joelle; Clarhaut, Jonathan; Becq, Frédéric; Berjeaud, Jean-Marc; Vandebrouck, Clarisse; Ferreira, Thierry

    2013-12-01

    Saturated fatty acids (SFA) have been reported to alter organelle integrity and function in many cell types, including muscle and pancreatic β-cells, adipocytes, hepatocytes and cardiomyocytes. SFA accumulation results in increased amounts of ceramides/sphingolipids and saturated phospholipids (PL). In this study, using a yeast-based model that recapitulates most of the trademarks of SFA-induced lipotoxicity in mammalian cells, we demonstrate that these lipid species act at different levels of the secretory pathway. Ceramides mostly appear to modulate the induction of the unfolded protein response and the transcription of nutrient transporters destined to the cell surface. On the other hand, saturated PL, by altering membrane properties, directly impact vesicular budding at later steps in the secretory pathway, i.e. at the trans-Golgi Network level. They appear to do so by increasing lipid order within intracellular membranes which, in turn, alters the recruitment of loose lipid packing-sensing proteins, required for optimal budding, to nascent vesicles. We propose that this latter general mechanism could account for the well-documented deleterious impacts of fatty acids on the last steps of the secretory pathway in several cell types.

  20. Open-source FCPEM-Performance & Durability Model Consideration of Membrane Properties on Cathode Degradation

    Energy Technology Data Exchange (ETDEWEB)

    Knights, Shanna [Ballard Fuel Cell Systems, Bend, OR (United States); Harvey, David [Ballard Fuel Cell Systems, Bend, OR (United States)

    2017-01-20

    The durability of PEM fuel cells is a primary requirement for large scale commercialization of these power systems in transportation and stationary market applications which target operational lifetimes of 5,000 hours and 60,000 hours by 2020, respectively. Key degradation modes contributing to fuel cell lifetime limitations have been largely associated with the platinum-based cathode catalyst layer. Furthermore, as fuel cells are driven to low cost materials and lower catalyst loadings in order to meet the cost targets for commercialization, the catalyst durability has become even more important. While over the past few years significant progress has been made in identifying the underlying causes of fuel cell degradation and key parameters that greatly influence the degradation rates, many gaps with respect to knowledge of the driving mechanisms still exist; in particular, the acceleration of the mechanisms due to different membrane compositions remains an area not well understood. The focus of this project extension was to enhance the predictive capability of the PEM Fuel Cell Performance & Durability Model called FC-APOLLO (Application Package for Open-source Long Life Operation) by including interaction effects of membrane transport properties such as water transport, changes in proton conductivity, and overall water uptake/adsorption and the state of the catalyst layer local conditions to further understand the driving forces for platinum dissolution.

  1. Properties of Polymer Electrolyte Membranes Prepared by Blending of Sulfonated Polystyrene-Lignosulfonate

    OpenAIRE

    Siang Tandi Gonggo; Cynthia L. Radiman; Bunbun Bundjali; I Made Arcana

    2012-01-01

    Electrolyte polymer membrane widely used in PEMFC and DMFC is a perfluorosulfonated membrane such as Nafion. This membrane material exhibits good chemical stability and proton conductivity, but it is very expensive and difficult to recycle. It has high cross-over methanol in DMFC that causes the decrease efficiency and performance of fuel cell, so that the electrolyte polymer membrane with low cross-over methanol has been needed to substitute Nafion membrane. One of the materials used as a po...

  2. The effect of native silk fibroin powder on the physical properties and biocompatibility of biomedical polyurethane membrane.

    Science.gov (United States)

    Zhuang, Yan; Zhang, Qian; Feng, Jinqi; Wang, Na; Xu, Weilin; Yang, Hongjun

    2017-04-01

    Naturally derived fibers such as silk fibroin can potentially enhance the biocompatibility of currently used biomaterials. This study investigated the physical properties of native silk fibroin powder and its effect on the biocompatibility of biomedical polyurethane. Native silk fibroin powder with an average diameter of 3 µm was prepared on a purpose-built machine. A simple method of phase inversion was used to produce biomedical polyurethane/native silk fibroin powder hybrid membranes at different blend ratios by immersing a biomedical polyurethane/native silk fibroin powder solution in deionized water at room temperature. The physical properties of the membranes including morphology, hydrophilicity, roughness, porosity, and compressive modulus were characterized, and in vitro biocompatibility was evaluated by seeding the human umbilical vein endothelial cells on the top surface. Native silk fibroin powder had a concentration-dependent effect on the number and morphology of human umbilical vein endothelial cells growing on the membranes; cell number increased as native silk fibroin powder content in the biomedical polyurethane/native silk fibroin powder hybrid membrane was increased from 0% to 50%, and cell morphology changed from spindle-shaped to cobblestone-like as the native silk fibroin powder content was increased from 0% to 70%. The latter change was related to the physical characteristics of the membrane, including hydrophilicity, roughness, and mechanical properties. The in vivo biocompatibility of the native silk fibroin powder-modified biomedical polyurethane membrane was evaluated in a rat model; the histological analysis revealed no systemic toxicity. These results indicate that the biomedical polyurethane/native silk fibroin powder hybrid membrane has superior in vitro and in vivo biocompatibility relative to 100% biomedical polyurethane membranes and thus has potential applications in the fabrication of small-diameter vascular grafts and in

  3. Strong pore-size dependence of the optical properties in porous alumina membranes

    Science.gov (United States)

    Jeon, C. H.; Kim, D. H.; Lee, Y. S.; Han, J. K.; Choi, Y. C.; Bu, S. D.; Shin, H. Y.; Yoon, S.

    2013-11-01

    We report on the strong pore-size-dependent optical properties of porous alumina membranes (PAMs) by using the photoluminescence and the optical spectroscopic techniques. The pore diameters of our PAMs varied from 60 to 420 nm. All samples showed a sizable violet/blue emission with a strong temperature dependence. We found that the peak position of the emission shifted to higher energies with increasing pore diameter, which was in accord with the smaller binding energy extracted from the temperature dependence of the emission intensity. From the transmission spectra, we found that the effective bandgap of the PAMs shifted significantly to lower energies with increasing pore diameter, which indicated that the impurity states within the bandgap was affected strongly by the geometry of the PAM.

  4. Electrical properties and flux performance of composite ceramic hydrogen separation membranes

    DEFF Research Database (Denmark)

    Fish, J.S.; Ricote, Sandrine; O'Hayre, R.

    2015-01-01

    The electrical properties and hydrogen permeation flux behavior of the all-ceramic protonic/electronic conductor composite BaCe0.2Zr0.7Y0.1O3-δ/Sr0.95Ti0.9Nb0.1O3-δ (BCZY27/STN95: BS27) are evaluated. Conductivity and hydrogen permeability are examined as a function of phase volume ratios. Total...... with an effective medium approach incorporating a term for the heterojunctions between the two phases. Hydrogen fluxes of 0.004-0.008 μmol cm-2 s-1 are obtained for a 50 volume% STN95 membrane sample (1 mm thickness) at 600-800 °C using dry argon as a sweep gas. Upon adding palladium layers as catalysts more than...

  5. A Theoretical Characterization of Curvature Controlled Adhesive Properties of Bio-Inspired Membranes

    DEFF Research Database (Denmark)

    Afferante, Luciano; Heepe, Lars; Casdorff, Kirstin

    2016-01-01

    Some biological systems, such as the tree frog, Litoria caerulea, and the bush-cricket, Tettigonia viridissima, have developed the ability to control adhesion by changing the curvature of their pads. Active control systems of adhesion inspired by these biological models can be very attractive...... for the development of devices with controllable adhesive properties. In this paper, we present a theory describing the adhesive behavior of an artificial system consisting of an inflatable membrane clamped to a metallic cylinder and filled with air. In such a system, by controlling the internal pressure acting...... the experiments. The present model might help to achieve a better understanding of the adhesion behavior of biological systems and of the fingertips that, in a broad sense, may be regarded as shell-like structures....

  6. Investigation of properties of human epidermal membrane under constant conductance alternating current iontophoresis.

    Science.gov (United States)

    Zhu, Honggang; Peck, Kendall D; Miller, David J; Liddell, Mark R; Yan, Guang; Higuchi, William I; Li, S Kevin

    2003-04-14

    Previous studies in our laboratory have shown that enhanced, constant permeant fluxes across human skin can be achieved by applying an alternating current (AC) to maintain skin electrical conductance at a constant level. Relative to conventional direct current (DC) iontophoresis, for which current is maintained at a constant level, this newly developed constant conductance alternating current (CCAC) method achieves constant fluxes with less inter- and intra-sample variability. The present study focused upon further investigating the permeability properties of human skin during CCAC iontophoresis at a variety of target resistance/conductance values. A three-stage experimental protocol was used with flux measurements determined on 3 consecutive days. Stage I was an AC only protocol (symmetrical AC square-wave signal), stage II was an AC plus DC protocol (AC square-wave with DC offset voltage), and stage III was a repeat of stage I. During this three-stage protocol, the skin electrical resistance was maintained at a constant target value by manually adjusting the applied AC voltage. Radiolabeled mannitol and urea were model permeants in all experiments. Their fluxes were determined and used to characterize the permeability properties of human skin. The results from the present study established that: (i) the CCAC protocol made it possible to reduce HEM electrical resistance to different target levels as low as 0.8 kOmega cm(2) and maintain the specific resistance level throughout the flux experiment, (ii) permeant fluxes are proportional to skin electrical conductance, (iii) under the studied CCAC passive conditions, membrane pore size tends to increase as skin resistance decreases, and (iv) as the membrane breaks down, its pore sizes become larger.

  7. Fresh and cultured human lens epithelial cells: an electrophysiological study of cell coupling and membrane properties.

    Science.gov (United States)

    Jacob, T J

    1988-09-01

    Microelectrode studies of fresh human and rabbit lens epithelia revealed stable membrane potentials [VR (human) = -36 mV; VR (rabbit) = -45 mV] and low input resistances [Ri (human) = 10 M omega; Ri (rabbit) = 20 M omega]. Coupling studies, using two voltage microelectrodes, demonstrated that the low input resistance of the fresh epithelial tissue was due to electrotonic coupling, which was found to be extremely labile and sensitive to perfusion of the apical (fibrefacing) surface of the epithelium. The intercellular coupling could be stabilized by raising the calcium concentration of the perfusate. Studies performed on confluent monolayers of cultured human lens epithelial (HLE) cells demonstrated a membrane potential (VR = -33 mV) and input resistance (Ri = 29 M omega) similar to their fresh counterparts. The intercellular coupling of these cells was found to be much more robust. Ultrastructural studies revealed that the apical junction of cultured HLE cells was less complex than that found in fresh tissue, the latter exhibiting multiple interdigitations and folds. The cultured monolayer was dissociated into single cells by a variety of methods and the membrane properties of individual cells were studied. Single cells were found to have a lower membrane potential (-20 to -25 mV) and an input resistance in the range 110-170 M omega, depending on the method of dissociation. Channel blocking and ion replacement studies revealed significant conductance pathways for potassium, sodium and chloride and a cell-attached patch clamp investigation revealed three distinct channel types. Of the two channels with inward currents at the resting potential, one, with a conductance of 25 pS, is identified as a non-selective cation channel, and the other, with a conductance of 14 pS and reversal potential of - 14 mV, is a possible candidate for a chloride channel but has yet to be characterized. A third channel with an outward current at the resting potential is identified as a

  8. Fabrication of drug-loaded anti-infective guided tissue regeneration membrane with adjustable biodegradation property.

    Science.gov (United States)

    Xue, Jiajia; Shi, Rui; Niu, Yuzhao; Gong, Min; Coates, Phil; Crawford, Aileen; Chen, Dafu; Tian, Wei; Zhang, Liqun

    2015-11-01

    For guided tissue regeneration (GTR) membrane, synchronization of the membrane biodegradation rate and tissue regeneration rate is important. Besides, the major reason for GTR membrane failure in clinical application is infection which can be prevented by loading anti-bacterial drug. To realize the consistency in membrane degradation rate and tissue regeneration rate of the anti-infective membrane, we developed metronidazole-loaded electrospun poly(ɛ-caprolactone)-gelatin nanofiber membranes with different poly(ɛ-caprolactone)/gelatin ratios (95:5, 90:10, 80:20, 70:30, 60:40, and 50:50). Homogeneous nanofibers were successfully fabricated. The mechanical strength of the membranes increased with the poly(ɛ-caprolactone) content, while the hydrophilicity decreased. The controlled and sustained release of metronidazole from all the membranes prevented the colonization of anaerobic bacteria. At all poly(ɛ-caprolactone)/gelatin ratios, all the membranes presented good biocompatibility while the increase of gelatin content resulted in enhanced cell adhesion and proliferation. Subcutaneous implantation in rabbits for 8 months demonstrated that all the membranes showed good biocompatibility without infection. Both in vitro and in vivo results showed that the biodegradation rate of the membranes was accelerated with the increase of gelatin content. The biodegradation rate and biocompatibility of the membranes can be adjusted by changing the PCL/gelatin ratio. The optimal membrane can be chosen based on the patient and tissue type to realize the synchronization of membrane degradation with tissue regeneration for the best treatment effect.

  9. How does γ-irradiation affect the properties of a microfiltration membrane constituted of two polymers with different radiolytic behavior?

    Science.gov (United States)

    Fortin, Nicolas; Albela, Belén; Bonneviot, Laurent; Rouif, Sophie; Sanchez, Jean-Yves; Portinha, Daniel; Fleury, Etienne

    2012-03-01

    The objective of this work is to present the behavior of a fluorinated microporous membrane composed of poly(vinylidene fluoride) (PVDF) mechanically reinforced by a polyamide-66 (PA-66) fabric under γ-irradiation with dose ranging between 0 and 100 kGy, in inert atmosphere and at room temperature. Particular attention was paid to the evolution of mechanical properties, the surface morphology and pores size distribution of this membrane, in order to study the filtration capacity and selectivity with increasing radiation dose. Moreover, the repartition of the generated radicals onto the two components of the membrane was achieved by electron spin resonance (ESR) spectroscopy. Two different regimes are observed depending on the dose range, and a correlation between the mechanical behavior of the membrane and the evolution of the concentration of the radicals in the PA fabric is observed. Globally, the porosity of the surface membrane does not vary whatever the dose may be, but the mechanical properties of the membrane as well as the permeability are strongly affected, even for low radiation dose such as 10 kGy. These results are related to chain scissions on the PA fabric, which occurred preferentially, compared to cross-linking, in the investigated dose range.

  10. Surface Functionalization of Polyethersulfone Membrane with Quaternary Ammonium Salts for Contact-Active Antibacterial and Anti-Biofouling Properties

    Directory of Open Access Journals (Sweden)

    Xiao Hu

    2016-05-01

    Full Text Available Biofilm is a significant cause for membrane fouling. Antibacterial-coated surfaces can inhibit biofilm formation by killing bacteria. In this study, polyethersulfone (PES microfiltration membrane was photografted by four antibiotic quaternary ammonium compounds (QACs separately, which were synthesized from dimethylaminoethyl methacrylate (DMAEMA by quaternization with butyl bromide (BB, octyl bromide (OB, dodecyl bromide (DB, or hexadecyl bromide (HB. XPS, ATR-FTIR, and SEM were used to confirm the surfaces’ composition and morphology. After modification, the pores on PES-g-DMAEMA-BB and PES-g-DMAEMA-OB were blocked, while PES-g-DMAEMA-DB and PES-g-DMAEMA-HB were retained. We supposed that DMAEMA-BB and DMAEMA-OB aggregated on the membrane surface due to the activities of intermolecular or intramolecular hydrogen bonds. Bacteria testing found the antibacterial activities of the membranes increased with the length of the substituted alkyl chain. Correspondingly, little bacteria were observed on PES-g-DMAEMA-DB and PES-g-DMAEMA-HB by SEM. The antifouling properties were investigated by filtration of a solution of Escherichia coli. Compared with the initial membrane, PES-g-DMAEMA-DB and PES-g-DMAEMA-HB showed excellent anti-biofouling performance with higher relative flux recovery (RFR of 88.3% and 92.7%, respectively. Thus, surface functionalization of the PES membrane with QACs can prevent bacteria adhesion and improve the anti-biofouling activity by the contact-active antibacterial property.

  11. Gc protein-derived macrophage-activating factor (GcMAF) stimulates cAMP formation in human mononuclear cells and inhibits angiogenesis in chick embryo chorionallantoic membrane assay.

    Science.gov (United States)

    Pacini, Stefania; Morucci, Gabriele; Punzi, Tiziana; Gulisano, Massimo; Ruggiero, Marco

    2011-04-01

    The effects of Gc protein-derived macrophage-activating factor (GcMAF) have been studied in cancer and other conditions where angiogenesis is deregulated. In this study, we demonstrate for the first time that the mitogenic response of human peripheral blood mononuclear cells (PBMCs) to GcMAF was associated with 3'-5'-cyclic adenosine monophosphate (cAMP) formation. The effect was dose dependent, and maximal stimulation was achieved using 0.1 ng/ml. Heparin inhibited the stimulatory effect of GcMAF on PBMCs. In addition, we demonstrate that GcMAF (1 ng/ml) inhibited prostaglandin E(1)- and human breast cancer cell-stimulated angiogenesis in chick embryo chorionallantoic membrane (CAM) assay. Finally, we tested different GcMAF preparations on CAM, and the assay proved to be a reliable, reproducible and inexpensive method to determine the relative potencies of different preparations and their stability; we observed that storage at room temperature for 15 days decreased GcMAF potency by about 50%. These data could prove useful for upcoming clinical trials on GcMAF.

  12. Influence of aminosilane precursor concentration on physicochemical properties of composite Nafion membranes for vanadium redox flow battery applications

    Science.gov (United States)

    Kondratenko, Mikhail S.; Karpushkin, Evgeny A.; Gvozdik, Nataliya A.; Gallyamov, Marat O.; Stevenson, Keith J.; Sergeyev, Vladimir G.

    2017-02-01

    A series of composite proton-exchange membranes have been prepared via sol-gel modification of commercial Nafion membranes with [N-(2-aminoethyl)-3-aminopropyl]trimethoxysilane. The structure and physico-chemical properties (water uptake, ion-exchange capacity, vanadyl ion permeability, and proton conductivity) of the prepared composite membranes have been studied as a function of the precursor loading (degree of the membrane modification). If the amount of the precursor is below 0.4/1 M ratio of the amino groups of the precursor to the sulfonic groups of Nafion, the composite membranes exhibit decreased vanadium ion permeability while having relatively high proton conductivity. With respect to the use of a non-modified Nafion membrane, the performance of the composite membrane with an optimum precursor loading in a single-cell vanadium redox flow battery demonstrates enhanced energy efficiency in 20-80 mA cm-2 current density range. The maximum efficiency increase of 8% is observed at low current densities.

  13. PERVAPORATION PROPERTIES OF PDMS MEMBRANES CURED WITH DIFFERENT CROSS-LINKING REAGENTS FOR ETHANOL CONCENTRATION FROM AQUEOUS SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    Xia Zhan; Ji-ding Li; Jun-qi Huang; Cui-xian Chen

    2009-01-01

    Ethanol perm-selective PDMS/PVDF composite membranes were prepared by curing polydimethylsiloxane (PDMS) with various cross-linking reagents, such as tetraethoxylsilane (TEOS), γ-aminopropyltriethoxylsilane (APTEOS), phenyltrimethoxylsilane (PTMOS) and octyltrimethoxylsilane (OTMOS) as well. The cross-linking density and surface properties of the PDMS active layer were adjusted by varying cross-linking reagents. The pervaporation performance of PDMS membranes cured with different cross-linking reagents was investigated in detail. As temperature increased, the total flux of the four kinds of membranes all increased exponentially, and the separation factor followed a reversed order. The increase of thickness of PDMS layers depressed the total flux of composite membranes and had no obvious effect on selectivity of ethanol. It was found that the composite membrane cured by PTMOS showed much better separation performance compared with other membranes. A resistance-in-series model was used to investigate and estimate the overall mass transfer coefficients and boundary layer mass transfer coefficients of ethanol and water according to experimental results. The measured diffusivities of ethanol and water in PDMS membranes had a magnitude of 10-10 m2·s-1 and 10-11 m2·s-1 at 313.15 K, respectively.

  14. Perfluorinated carbon-chain copolymers with functional groups and cation exchange membranes based on them: synthesis, structure and properties

    Science.gov (United States)

    Kirsh, Yu E.; Smirnov, S. A.; Popkov, Yu M.; Timashev, Sergei F.

    1990-06-01

    The review is devoted to perfluorinated polymers with sulphonic and carboxylic acid groups and to cation exchange membranes based on them. The synthesis is described of copolymers of tetrafluoroethylene with perfluorovinyl ethers containing functional groups by radical copolymerisation in an organic medium and in aqueous emulsions. Special features of the copolymerisation and approaches to obtaining copolymers with set characteristics are discussed. Data are presented on the structure and physicochemical properties of the polymeric films. Attempts to form membranes from the polymers obtained, the means of strengthening them and methods for chemical modification are described. Data are correlated on the influence of structure and polymer composition and the nature of the functional groups on the electrochemical characteristics of membranes. Special features of the functioning of perfluorinated membranes in the process for making chlorine and alkali by the electrolysis of sodium chloride solution are considered. The bibliography has 104 references.

  15. Erucin Exerts Anti-Inflammatory Properties in Murine Macrophages and Mouse Skin: Possible Mediation through the Inhibition of NFκB Signaling

    Directory of Open Access Journals (Sweden)

    Ki Won Lee

    2013-10-01

    Full Text Available Erucin, an isothiocyanate, is a hydrolysis product of glucoerucin found in arugula and has recently been reported to have anti-cancer properties in various cancer cells. In this study, we assessed the anti-inflammatory effects of erucin and the underlying mechanisms, using lipopolysaccharide (LPS-stimulated RAW 264.7 murine macrophages and 12-O-tetradecanoylphorbol-13-acetate-treated mouse skin. In RAW 264.7 cells, erucin (2.5, 5 μmol/L inhibited LPS-induced production of nitric oxide and prostaglandin E2. Erucin inhibited LPS-induced degradation of the inhibitor of κBα and translocation of p65 to the nucleus and, subsequently, reduced LPS-induced nuclear factor κB (NFκB DNA binding activities, as well as the transcriptional activity of NFκB, leading to the decreased expression of NFκB-target genes, including tumor necrosis factor-α, interleukin (IL-6, IL-1β, inducible nitric oxide synthase (iNOS and cyclooxygenase (COX-2, as well as transcriptional activity of iNOS and COX-2. In mice, erucin (100, 300 nmoles treatment significantly inhibited phorbol ester-induced formation of ear edema and expression of iNOS and COX-2 proteins. These results indicate that erucin exerts a potent anti-inflammatory activity by inhibiting the pro-inflammatory enzymes and cytokines, which may be mediated, at least in part, via the inhibition of NFκB signaling.

  16. Erucin exerts anti-inflammatory properties in murine macrophages and mouse skin: possible mediation through the inhibition of NFκB signaling.

    Science.gov (United States)

    Cho, Han Jin; Lee, Ki Won; Park, Jung Han Yoon

    2013-10-15

    Erucin, an isothiocyanate, is a hydrolysis product of glucoerucin found in arugula and has recently been reported to have anti-cancer properties in various cancer cells. In this study, we assessed the anti-inflammatory effects of erucin and the underlying mechanisms, using lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophages and 12-O-tetradecanoylphorbol-13-acetate-treated mouse skin. In RAW 264.7 cells, erucin (2.5, 5 μmol/L) inhibited LPS-induced production of nitric oxide and prostaglandin E2. Erucin inhibited LPS-induced degradation of the inhibitor of κBα and translocation of p65 to the nucleus and, subsequently, reduced LPS-induced nuclear factor κB (NFκB) DNA binding activities, as well as the transcriptional activity of NFκB, leading to the decreased expression of NFκB-target genes, including tumor necrosis factor-α, interleukin (IL)-6, IL-1β, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, as well as transcriptional activity of iNOS and COX-2. In mice, erucin (100, 300 nmoles) treatment significantly inhibited phorbol ester-induced formation of ear edema and expression of iNOS and COX-2 proteins. These results indicate that erucin exerts a potent anti-inflammatory activity by inhibiting the pro-inflammatory enzymes and cytokines, which may be mediated, at least in part, via the inhibition of NFκB signaling.

  17. Dietary n-6:n-3 ratio and Vitamin E improve motility characteristics in association with membrane properties of boar spermatozoa.

    Science.gov (United States)

    Liu, Qing; Zhou, Yuan-Fei; Duan, Run-Jia; Wei, Hong-Kui; Peng, Jian; Jiang, Si-Wen

    2017-01-01

    This study was aimed to evaluate the effects of dietary n-6:n-3 ratio and Vitamin E on the membrane properties and motility characteristics of spermatozoa in boars. Forty Duroc boars were randomly distributed in a 2 × 2 factorial design with two n-6:n-3 ratios (14.4 and 6.6) and two Vitamin E levels (200 and 400 mg kg-1 ). During 16 weeks of treatment, fresh semen was collected at weeks 0, 8, 12, and 16 for measurements of motility characteristics, contents of fatty acids, membrane properties (membrane fluidity and membrane integrity), and lipid peroxidation of the spermatozoa. The semen was diluted in Beltsville Thawing Solution (BTS) extender and stored at 17°C, and the sperm motility was assessed at 12, 36, 72, and 120 h of storage. The 6.6 n-6:n-3 dietary ratio increased the contents of n-3 polyunsaturated fatty acids (PUFAs) and docosahexaenoic acid (DHA) and improved the membrane integrity and membrane fluidity of the spermatozoa, resulting in notably increased total motility, sperm progressive motility, and velocity parameters of fresh semen. Feeding diet with Vitamin E (400 mg kg-1 ) prevented sperm lipid peroxidation, and resulted in higher total motility and sperm progressive motility in fresh and liquid stored semen. In conclusion, the adjustment of n-6:n-3 ratio (6.6) and supply of Vitamin E (400 mg kg-1 ) successfully improved sperm motility characteristics and thus may be beneficial to the fertility of boars, which might be due to the modification of the physical and functional properties of spermatozoa membrane in response to dietary supplementation.

  18. Dietary n-6:n-3 ratio and Vitamin E improve motility characteristics in association with membrane properties of boar spermatozoa

    Directory of Open Access Journals (Sweden)

    Qing Liu

    2017-01-01

    Full Text Available This study was aimed to evaluate the effects of dietary n-6:n-3 ratio and Vitamin E on the membrane properties and motility characteristics of spermatozoa in boars. Forty Duroc boars were randomly distributed in a 2 × 2 factorial design with two n-6:n-3 ratios (14.4 and 6.6 and two Vitamin E levels (200 and 400 mg kg−1 . During 16 weeks of treatment, fresh semen was collected at weeks 0, 8, 12, and 16 for measurements of motility characteristics, contents of fatty acids, membrane properties (membrane fluidity and membrane integrity, and lipid peroxidation of the spermatozoa. The semen was diluted in Beltsville Thawing Solution (BTS extender and stored at 17°C, and the sperm motility was assessed at 12, 36, 72, and 120 h of storage. The 6.6 n-6:n-3 dietary ratio increased the contents of n-3 polyunsaturated fatty acids (PUFAs and docosahexaenoic acid (DHA and improved the membrane integrity and membrane fluidity of the spermatozoa, resulting in notably increased total motility, sperm progressive motility, and velocity parameters of fresh semen. Feeding diet with Vitamin E (400 mg kg−1 prevented sperm lipid peroxidation, and resulted in higher total motility and sperm progressive motility in fresh and liquid stored semen. In conclusion, the adjustment of n-6:n-3 ratio (6.6 and supply of Vitamin E (400 mg kg−1 successfully improved sperm motility characteristics and thus may be beneficial to the fertility of boars, which might be due to the modification of the physical and functional properties of spermatozoa membrane in response to dietary supplementation.

  19. Role of the basement membrane in regulation of cardiac electrical properties.

    Science.gov (United States)

    Yang, Huaxiao; Borg, Thomas K; Wang, Zhonghai; Ma, Zhen; Gao, Bruce Z

    2014-06-01

    In the heart muscle, each adult cardiomyocyte is enclosed by a basement membrane (BM). This innermost extracellular matrix is a layered assembly of laminin, collagen IV, glycoproteins, and proteoglycans. In this study, the role of the BM network in regulation of the electrical properties of neonatal cardiomyocytes (NCMs) cultured on an aligned collagen I gel was investigated using a multielectrode array (MEA). A laminin antibody was added to the culture medium for 48-120 h to conjugate newly secreted laminin. Then, morphology of the NCMs on an MEA was monitored using a phase contrast microscope, and the BM network that was immunocytostained for laminin was imaged using a fluorescence microscope. When the BM laminin was absent in this culture model, dramatic changes in NCM morphology were observed. Simultaneously, the MEA-recorded cardiac field potential showed changes compared to that from the control groups: The period of contraction shortened to 1/2 of that from the control groups, and the waveform of the calcium influx shifted from a flat plateau to a peak-like waveform, indicating that the electrical properties of the NCMs were closely related to the components and distribution of the BM network.

  20. Influence of graphene oxide on mechanical, morphological, barrier, and electrical properties of polymer membranes

    Directory of Open Access Journals (Sweden)

    Ali Ammar

    2016-03-01

    Full Text Available This paper expresses a short review of research on the effects of graphene oxide (GO as a nanocomposite element on polymer morphology and resulting property modifications including mechanical, barrier, and electrical conductivity. The effects on mechanical enhancement related to stress measurements in particular are a focus of this review. To first order, varying levels of aggregation of GO in different polymer matrices as a result of their weak inter-particle attractive interactions mainly affect the nanocomposite mechanical properties. The near surface dispersion of GO in polymer/GO nanocomposites can be investigated by studying the surface morphology of these nanocomposites using scanning probe microscopy such as atomic force microscope (AFM and scanning electron microscope (SEM. In the bulk, GO dispersion can be studied by wide-angle X-ray scattering (WAXD by analyzing the diffraction peaks corresponding to the undispersed GO fraction in the polymer matrix. In terms of an application, we review how the hydrophilicity of graphene oxide and its hydrogen bonding potential can enhance water flux of these nanocomposite materials in membrane applications. Likewise, the electrical conductivity of polymer films and bulk polymers can be advantageously enhanced via the percolative dispersion of GO nanoparticles, but this typically requires some additional chemical treatment of the GO nanoparticles to transform it to reduced GO.

  1. Electrical properties of the red blood cell membrane and immunohematological investigation

    Directory of Open Access Journals (Sweden)

    Heloise Pöckel Fernandes

    2011-01-01

    Full Text Available Hemagglutination is widely used in transfusion medicine and depends on several factors including antigens, antibodies, electrical properties of red blood cells and the environment of the reaction. Intermolecular forces are involved in agglutination with cell clumping occurring when the aggregation force is greater than the force of repulsion. Repulsive force is generated by negative charges on the red blood cell surface that occur due to the presence of the carboxyl group of sialic acids in the cell membrane; these charges create a repulsive electric zeta potential between cells. In transfusion services, specific solutions are used to improve hemagglutination, including enzymes that reduce the negative charge of red blood cells, LISS which improves the binding of antibodies to antigens and macromolecules that decrease the distance between erythrocytes. The specificity and sensitivity of immunohematological reactions depend directly on the appropriate use of these solutions. Knowledge of the electrical properties of red blood cells and of the action of enhancement solutions can contribute to the immunohematology practice in transfusion services.

  2. Synthesis and Gas Transport Properties of Hyperbranched Polyimide–Silica Hybrid/Composite Membranes

    Directory of Open Access Journals (Sweden)

    Masako Miki

    2013-12-01

    Full Text Available Hyperbranched polyimide–silica hybrids (HBPI–silica HBDs and hyperbranched polyimide–silica composites (HBPI–silica CPTs were prepared, and their general and gas transport properties were investigated to clarify the effect of silica sources and preparation methods. HBPI–silica HBDs and HBPI–silica CPTs were synthesized by two-step polymerization of A2 + B3 monomer system via polyamic acid as precursor, followed by hybridizing or blending silica sources. Silica components were incorporated by the sol-gel reaction with tetramethoxysilane (TMOS or the addition of colloidal silica. In HBPI-silica HBDs, the aggregation of silica components is controlled because of the high affinity of HBPI and silica caused by the formation of covalent bonds between HBPI and silica. Consequently, HBPI-silica HBDs had good film formability, transparency, and mechanical properties compared with HBPI-silica CPTs. HBPI-silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS showed specific gas permeabilities and permselectivities for CO2/CH4 separation, that is, both CO2 permeability and CO2/CH4 selectivity increased with increasing silica content. This result suggests that gas transport can occur through a molecular sieving effect of the porous silica network derived from the sol-gel reaction and/or through the narrow interfacial region between the silica networks and the organic matrix.

  3. Bicelles and Other Membrane Mimics: Comparison of Structure, Properties, and Dynamics from MD Simulations

    DEFF Research Database (Denmark)

    Vestergaard, Mikkel; Kraft, Johan Frederik; Vosegaard, Thomas

    2015-01-01

    The increased interest in studying membrane proteins has led to the development of new membrane mimics such as bicelles and nanodiscs. However, only limited knowledge is available of how these membrane mimics are affected by embedded proteins and how well they mimic a lipid bilayer. Herein, we pr...

  4. New polymeric electrolyte membranes based on proton donor proton acceptor properties for direct methanol fuel cells

    NARCIS (Netherlands)

    Manea, G.C.; Mulder, M.H.V.

    2002-01-01

    In order to reduce the high methanol permeability of membranes in a direct methanol fuel cell application new and better materials are still required. In this paper membranes made from polybenzimidazole/sulfonated polysulfone are given and compared with homopolymer membranes made from sulfonated pol

  5. Exploring the structure-properties relationships of novel polyamide thin film composite membranes

    DEFF Research Database (Denmark)

    Briceño, Kelly; Javakhishvili, Irakli; Guo, Haofei

    Polysulfone (PSU) is a material widely used in the fabrication of membranes for ultrafiltration and as a support for nanofiltration and reverse osmosis membranes. Interfacial polymerization usually combines amine and acid chloride monomers for the fabrication of thin film composite membranes[1...

  6. Electricity producing property and bacterial community structure in microbial fuel cell equipped with membrane electrode assembly.

    Science.gov (United States)

    Rubaba, Owen; Araki, Yoko; Yamamoto, Shuji; Suzuki, Kei; Sakamoto, Hisatoshi; Matsuda, Atsunori; Futamata, Hiroyuki

    2013-07-01

    It is important for practical use of microbial fuel cells (MFCs) to not only develop electrodes and proton exchange membranes but also to understand the bacterial community structure related to electricity generation. Four lactate fed MFCs equipped with different membrane electrode assemblies (MEAs) were constructed with paddy field soil as inoculum. The MEAs significantly affected the electricity-generating properties of the MFCs. MEA-I was made with Nafion 117 solution and the other MEAs were made with different configurations of three kinds of polymers. MFC-I equipped with MEA-I exhibited the highest performance with a stable current density of 55 ± 3 mA m⁻². MFC-III equipped with MEA-III with the highest platinum concentration, exhibited the lowest performance with a stable current density of 1.7 ± 0.1 mA m⁻². SEM observation revealed that there were cracks on MEA-III. These results demonstrated that it is significantly important to prevent oxygen-intrusion for improved MFC performance. By comparing the data of DGGE and phylogenetic analyzes, it was suggested that the dominant bacterial communities of MFC-I were constructed with lactate-fermenters and Fe(III)-reducers, which consisted of bacteria affiliated with the genera of Enterobacter, Dechlorosoma, Pelobacter, Desulfovibrio, Propioniferax, Pelosinus, and Firmicutes. A bacterium sharing 100% similarity to one of the DGGE bands was isolated from MFC-I. The 16S rRNA gene sequence of the isolate shared 98% similarity to gram-positive Propioniferax sp. P7 and it was confirmed that the isolate produced electricity in an MFC. These results suggested that these bacteria are valuable for constructing the electron transfer network in MFC. Copyright © 2013 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  7. Modification of Thin Film Composite (TFC) Membrane by Incorporation with Copper Nanoparticles (Cu-NPs) for Antibacterial Properties

    Science.gov (United States)

    Zhong, Chen

    Membrane biofouling has been a challenging problem restricting the application of reverse osmosis (RO) desalination process. Copper is known for its antimicrobial properties and is easily available with low cost. In this paper, copper nanoparticles (Cu-NPs) with a mean diameter of 15nm were synthesized by the reduction of copper (II) chloride with sodium borohydride (NaBH4), using cetyl trimethylammonium bromide ((C16H33)N(CH3) 3Br, CTAB) as a capping agent. After purification of Cu-NPs by dialysis, the particles were successfully immobilized onto the surface of thin film composite (TFC) membranes via either electrostatic interactions or by covalent bonding with cysteamine as a linker. The electrostatic method was simply to immerse the newly made TFC membranes to the Cu-NPs suspension. Since the CTAB had formed cationic bilayer outside the Cu-NPs, the Cu-NPs was not only adsorbed on the membranes but also attached to the surface because of the electrostatic effect with the negatively charged membrane surface. The covalent bonding method utilized cysteamine (C4H12N2S 2) to activate the thin film layer with thiol functional groups first and then incorporated the metallic copper nanoparticles to form the stable covalent chemical bonding in between. The resulting membranes by these two methods were labeled as TFC-CuNPs and TFC-S-CuNPs, respectively, in this study. Scanning electron microscopy (SEM) imaging and associated energy-dispersive X-ray spectroscopy (EDS) showed that large amounts of Cu-NPs existed on both types of membranes. Surface hydrophilicity of the membranes was enhanced by the presence of Cu-NPs, as indicated by the measured contact angle of 63.25 +/- 0.75 for TFC, 38.63 +/- 2.16 for TFC-CuNPs, and 58.00 +/- 3.39 for TFC-S-CuNPs. Consistently, the water flux obtained from the RO desalination system was increased from 47.07 +/- 0.84 for TFC, 49.10 +/- 0.22 for TFC-CuNPs, and 69.13 +/- 1.43 for TFC-S-CuNPs, with this increase in hydrophilicity. The salt

  8. Polydopamine/Cysteine surface modified isoporous membranes with self-cleaning properties

    KAUST Repository

    Shevate, Rahul

    2017-02-03

    The major challenge in membrane filtration is fouling which reduces the membrane performance. Fouling is mainly due to the adhesion of foulants on the membrane surfaces. In this work, we studied the fouling behaviour of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) isoporous membrane and the mussel inspired polydopamine/L-cysteine isoporous zwitterionic membrane. Polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) isoporous membranes were fabricated via self-assembly and non-solvent induced phase separation method. Subsequently, the isoporous membrane was modified by a mild mussel-inspired polydopamine (PDA) coating; the isoporous surface structure and the water flux was retained. Zwitterionic L-cysteine was further anchored on the PDA coated membranes via Michael addition reaction at pH 7 and 50 °C to alleviate their antifouling ability with foulants solution. The membranes were thoroughly characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and zeta potential measurements. Contact angle and dynamic scanning calorimetry (DSC) measurements were carried out to examine the hydrophilicity. The pH-responsive behaviour of the modified membrane remains unchanged and antifouling ability after PDA/L-cysteine functionalization was improved. The modified and unmodified isoporous membranes were tested using humic acid and natural organic matter model solutions at 0.5 bar feed pressure.

  9. Separation Properties of Wastewater Containing O/W Emulsion Using Ceramic Microfiltration/Ultrafiltration (MF/UF Membranes

    Directory of Open Access Journals (Sweden)

    Kanji Matsumoto

    2013-06-01

    Full Text Available Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from these systems. Membrane filtration has large potential for the efficient separation of O/W emulsion for reuses of treated water and detergent. The separation properties of O/W emulsions by cross-flow microfiltration and ultrafiltration were studied with ceramic MF and UF membranes. The effects of pore size; applied pressure; cross-flow velocity; and detergent concentration on rejection of O/W emulsion and flux were systematically studied. At the condition achieving complete separation of O/W emulsion the pressure-independent flux was observed and this flux behavior was explained by gel-polarization model. The O/W emulsion tended to permeate through the membrane at the conditions of larger pore size; higher emulsion concentration; and higher pressure. The O/W emulsion could permeate the membrane pore structure by destruction or deformation. These results imply the stability of O/W emulsion in the gel-layer formed on membrane surface play an important role in the separation properties. The O/W emulsion was concentrated by batch cross-flow concentration filtration and the flux decline during the concentration filtration was explained by the gel- polarization model.

  10. Separation Properties of Wastewater Containing O/W Emulsion Using Ceramic Microfiltration/Ultrafiltration (MF/UF) Membranes.

    Science.gov (United States)

    Nakamura, Kazuho; Matsumoto, Kanji

    2013-06-21

    Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from these systems. Membrane filtration has large potential for the efficient separation of O/W emulsion for reuses of treated water and detergent. The separation properties of O/W emulsions by cross-flow microfiltration and ultrafiltration were studied with ceramic MF and UF membranes. The effects of pore size; applied pressure; cross-flow velocity; and detergent concentration on rejection of O/W emulsion and flux were systematically studied. At the condition achieving complete separation of O/W emulsion the pressure-independent flux was observed and this flux behavior was explained by gel-polarization model. The O/W emulsion tended to permeate through the membrane at the conditions of larger pore size; higher emulsion concentration; and higher pressure. The O/W emulsion could permeate the membrane pore structure by destruction or deformation. These results imply the stability of O/W emulsion in the gel-layer formed on membrane surface play an important role in the separation properties. The O/W emulsion was concentrated by batch cross-flow concentration filtration and the flux decline during the concentration filtration was explained by the gel- polarization model.

  11. CORRELATION BETWEEN POLYMER PACKING AND GAS TRANSPORT PROPERTIES FOR CO2/N2 SEPARATION IN GLASSY FLUORINATED POLYIMIDE MEMBRANE

    Directory of Open Access Journals (Sweden)

    P. C. TAN

    2016-07-01

    Full Text Available Gas separation performance of a membrane highly hinges on its physical properties. In this study, the interplay between polymer packing of a membrane and its gas transport behaviours (permeability and selectivity was investigated through a series of 6FDA-DAM:DABA (3:2 polyimide membranes with different polymer compactness. The chemical structure and the polymer packing of the resulting membrane were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR and packing density measurement, respectively. CO2/N2 separation efficiency of the membrane was evaluated at 25oC with feed pressure up to 6 bar. N2 permeability was found to rely on the membrane’s packing density, which signified its greater dependence on molecular sieving. In contrast, sorption showed a more vital role in determining the CO2 permeability. In this work, the membrane with a final thickness of 97±2 µm had successfully surpassed the Robeson’s 2008 upper bound plot with a CO2 permeability of 83 Barrer and CO2/N2 selectivity of 97 at 3 bar permeation.

  12. Gestational Undernourishment Modifies the Composition of Skeletal Muscle Transverse Tubule Membranes and the Mechanical Properties of Muscles in Newborn Rats

    Directory of Open Access Journals (Sweden)

    Ricardo Tonathiu Ramírez-Oseguera

    2013-10-01

    Full Text Available Backgroud/Aims: Skeletal muscle (SM constitutes more than 40% of the body weight in adulthood. Transports dietary glucose mainly through the insulin-dependent glucose transporter (Glut-4 located in the Transverse tubule membrane system (TT. The TT development ends shortly after birth. The TT membrane hosts the proteins involved in excitation-contraction coupling and glucose uptake. Glycaemic regulation through movement is a key function of fully developed skeletal muscle. In this study, we aimed to characterize the effect of gestational undernourishment (GUN in rats GLUT-4 expression and on the protein/lipid content of the TT membranes. We also examined the effect of GUN on the mechanical properties of muscles as an indication of the metabolic condition of the SM at birth. Methods: Isolated TT membrane from SM of GUN rats were used to study lipid/protein content and protein stability by differential scanning calorimetry. The effect of GUN on the SM mechanical properties was determined in isolated Extensor Digitorum Longus (EDL muscle. Results: We demonstrate that compared to control, GUN in the new-born produces; i decreases body weight; ii diminution in SM mass; iii decreases the formation of TT membranes; iv expresses TT membrane proteins with higher thermal stability. The TT membrane expression of GLUT-4 in GUN offspring was twice that of controls. The isolated EDL of GUN offspring was 20% stronger as measured by contractile force and more resistant to fatigue relative to controls. Conclusion; These results provide the first evidence of adaptive changes of the SM in new-borns exposed to severe gestational food restriction. The effects of GUN on muscle at birth are the first step toward detrimental SM metabolic function, contributing to the physiopathology of metabolic diseases in adulthood.

  13. Preparation of PVDF/SiO2 composite membrane for salty oil emulsion separation: Physicochemical properties changes and its impact on fouling propensity

    Science.gov (United States)

    Ngang, H. P.; Ahmad, A. L.; Low, S. C.; Ooi, B. S.

    2017-06-01

    In this study, polyvinylidene fluoride (PVDF)/silica (SiO2) composite membranes were prepared by diffusion induced phase separation through direct blending method. The roles of SiO2 particles concentration on membrane physicochemical properties were evaluated through oil emulsion separation under high ionic strength environment whereby hydrophobic interaction is prevalent. Membranes were characterized using field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), contact angle measurement, membrane porosity and pore size distribution. It was expected that by adding the monodispersed SiO2, it will render the membrane with hydrophilic characteristic. However, it is concomitantly changing the physical properties of the membrane. Addition of SiO2 caused the changes to the physicochemical properties of the composite membrane and its effects on the fouling propensity were evaluated. It was found that the mean pore size of the membranes increased with the increase of SiO2 concentration. The addition of hydrophilic SiO2 had accelerated the precipitation of the membrane dope solution resulting in changes of membrane cross section morphology. FESEM images showed the membrane cross-section morphology of PVDF/SiO2 composite membrane had gradually changed from finger-like to macrovoid-like structure with the increased of SiO2 concentration. The hydrophilicity of the PVDF/SiO2 composite membrane was enhanced which is a desired property for water purification. However, the changes in physical properties (pore size, porosity, and surface roughness) had played more dominant role in the oil emulsion fouling behaviour rather than hydrophilicity enhancement. Due to the salting out effect under high ionic strength environment, hydrophobic interaction played an important role in the oil adsorption. The increment in membrane pore size, porosity, and surface roughness after incorporation of SiO2 particles had encountered more serious relative flux reduction and

  14. RNS60, a charge-stabilized nanostructure saline alters Xenopus Laevis oocyte biophysical membrane properties by enhancing mitochondrial ATP production.

    Science.gov (United States)

    Choi, Soonwook; Yu, Eunah; Kim, Duk-Soo; Sugimori, Mutsuyuki; Llinás, Rodolfo R

    2015-03-01

    We have examined the effects of RNS60, a 0.9% saline containing charge-stabilized oxygen nanobubble-based structures. RNS60 is generated by subjecting normal saline to Taylor-Couette-Poiseuille (TCP) flow under elevated oxygen pressure. This study, implemented in Xenopus laevis oocytes, addresses both the electrophysiological membrane properties and parallel biological processes in the cytoplasm. Intracellular recordings from defolliculated X. laevis oocytes were implemented in: (1) air oxygenated standard Ringer's solution, (2) RNS60-based Ringer's solution, (3) RNS10.3 (TCP-modified saline without excess oxygen)-based Ringer's, and (4) ONS60 (saline containing high pressure oxygen without TCP modification)-based Ringer's. RNS60-based Ringer's solution induced membrane hyperpolarization from the resting membrane potential. This effect was prevented by: (1) ouabain (a blocker of the sodium/potassium ATPase), (2) rotenone (a mitochondrial electron transfer chain inhibitor preventing usable ATP synthesis), and (3) oligomycin A (an inhibitor of ATP synthase) indicating that RNS60 effects intracellular ATP levels. Increased intracellular ATP levels following RNS60 treatment were directly demonstrated using luciferin/luciferase photon emission. These results indicate that RNS60 alters intrinsic the electrophysiological properties of the X. laevis oocyte membrane by increasing mitochondrial-based ATP synthesis. Ultrastructural analysis of the oocyte cytoplasm demonstrated increased mitochondrial length in the presence of RNS60-based Ringer's solution. It is concluded that the biological properties of RNS60 relate to its ability to optimize ATP synthesis.

  15. Non-linear Membrane Properties in Entorhinal Cortical Stellate Cells Reduce Modulation of Input-Output Responses by Voltage Fluctuations.

    Science.gov (United States)

    Fernandez, Fernando R; Malerba, Paola; White, John A

    2015-04-01

    The presence of voltage fluctuations arising from synaptic activity is a critical component in models of gain control, neuronal output gating, and spike rate coding. The degree to which individual neuronal input-output functions are modulated by voltage fluctuations, however, is not well established across different cortical areas. Additionally, the extent and mechanisms of input-output modulation through fluctuations have been explored largely in simplified models of spike generation, and with limited consideration for the role of non-linear and voltage-dependent membrane properties. To address these issues, we studied fluctuation-based modulation of input-output responses in medial entorhinal cortical (MEC) stellate cells of rats, which express strong sub-threshold non-linear membrane properties. Using in vitro recordings, dynamic clamp and modeling, we show that the modulation of input-output responses by random voltage fluctuations in stellate cells is significantly limited. In stellate cells, a voltage-dependent increase in membrane resistance at sub-threshold voltages mediated by Na+ conductance activation limits the ability of fluctuations to elicit spikes. Similarly, in exponential leaky integrate-and-fire models using a shallow voltage-dependence for the exponential term that matches stellate cell membrane properties, a low degree of fluctuation-based modulation of input-output responses can be attained. These results demonstrate that fluctuation-based modulation of input-output responses is not a universal feature of neurons and can be significantly limited by subthreshold voltage-gated conductances.

  16. Brucella ovis PA mutants for outer membrane proteins Omp10, Omp19, SP41, and BepC are not altered in their virulence and outer membrane properties.

    Science.gov (United States)

    Sidhu-Muñoz, Rebeca S; Sancho, Pilar; Vizcaíno, Nieves

    2016-04-15

    Mutants in several genes have been obtained on the genetic background of virulent rough (lacking O-polysaccharide) Brucella ovis PA. The target genes encode outer membrane proteins previously associated with the virulence of smooth (bearing O-polysaccharide chains in the lipopolysaccharide) Brucella strains. Multiple attempts to delete omp16, coding for a homologue to peptidoglycan-associated lipoproteins, were unsuccessful, which suggests that Omp16 is probably essential for in vitro survival of B. ovis PA. Single deletion of omp10 or omp19-that encode two other outer membrane lipoproteins--was achieved, but the simultaneous removal of both genes failed, suggesting an essential complementary function between both proteins. Two other deletion mutants, defective in the Tol-C-homologue BepC or in the SP41 adhesin, were also obtained. Surprisingly when compared to previous results obtained with smooth Brucella, none of the B. ovis mutants showed attenuation in the virulence, either in the mouse model or in cellular models of professional and non-professional phagocytes. Additionally, and in contrast to the observations reported with smooth Brucella strains, several properties related to the outer membrane remained almost unaltered. These results evidence new distinctive traits between naturally rough B. ovis and smooth brucellae.

  17. Effect of Sodium Alginate Concentration on Membrane Strength and Permeating Property of Poly-l-arginine Group Microcapsule

    Institute of Scientific and Technical Information of China (English)

    Shi Bin WANG; Yuan Gang LIU; Lian Jin WENG; Xiao Jun MA

    2004-01-01

    A novel poly-l-arginine microcapsule was prepared due to its nutritional function and pharmacological efficacy. A high-voltage electrostatic droplet generator was used to make uniform microcapsules. The results show that the membrane strength and permeating property are both remarkably affected with the changes of sodium alginate concentration. With the sodium alginate concentration increasing, gel beads sizes increase from 233μm to 350μm, release ratio is also higher at the same time, but the membrane strength decreases.

  18. Non-invasive in Situ Simultaneous Measurement of Multi-parameter Mechanical Properties of Red Blood Cell Membrane

    Institute of Scientific and Technical Information of China (English)

    Jing LI; Yao-Xiong HUANG; Tao JI; Mei TU; Xuan MAO; Wen-Xin CHEN; Guang-Wei CHEN

    2005-01-01

    The purpose of this study was to develop a new dynamic image analyzing technique that will give us the ability to measure the viscoelastic parameters of individual living red blood cells non-invasively, in situ and in real time. With this technique, the bending modulus Kc, the shear elasticityμ and their ratio ε were measured under different temperatures, oxygen partial pressures and osmotic pressures. The results not only show the effects of external conditions on mechanical properties of cell membranes including deformability,flexibility, adhesive ability and plasticity, but also demonstrate that the technique can be used to measure cell membrane parameters continuously under several physiological and pathological conditions.

  19. [Role of calcium ions and cyclic nucleotides in neurotrophic control of the membrane properties of muscle fibers in the frog].

    Science.gov (United States)

    Volkov, E M; Kudriavtseva, N V; Nasledov, G A; Poletaev, G I

    1985-06-01

    Subcutaneous injections of caffeine, calcium ionophore X537A or cAMP did not affect the changes of input resistance (R0) and time constant (T) of membrane caused by denervation of the frog m. sartorius but prevented the MP decrease and ACh sensitivity spread. Injections of cGMP did not affect the denervation changes of R0 and MP but increased the ACh sensitivity. The neurotrophic control of frog muscle membrane properties seems to depend on calcium and involve the cyclic nucleotides system.

  20. The Effects of Sulfonated Poly(ether ether ketone Ion Exchange Preparation Conditions on Membrane Properties

    Directory of Open Access Journals (Sweden)

    Rebecca S. L. Yee

    2013-08-01

    Full Text Available A low cost cation exchange membrane to be used in a specific bioelectrochemical system has been developed using poly(ether ether ketone (PEEK. This material is presented as an alternative to current commercial ion exchange membranes that have been primarily designed for fuel cell applications. To increase the hydrophilicity and ion transport of the PEEK material, charged groups are introduced through sulfonation. The effect of sulfonation and casting conditions on membrane performance has been systematically determined by producing a series of membranes synthesized over an array of reaction and casting conditions. Optimal reaction and casting conditions for producing SPEEK ion exchange membranes with appropriate performance characteristics have been established by this uniquely systematic experimental series. Membrane materials were characterized by ion exchange capacity, water uptake, swelling, potential difference and NMR analysis. Testing this extensive membranes series established that the most appropriate sulfonation conditions were 60 °C for 6 h. For mechanical stability and ease of handling, SPEEK membranes cast from solvent casting concentrations of 15%–25% with a resulting thickness of 30–50 µm were also found to be most suitable from the series of tested casting conditions. Drying conditions did not have any apparent impact on the measured parameters in this study. The conductivity of SPEEK membranes was found to be in the range of 10−3 S cm−1, which is suitable for use as a low cost membrane in the intended bioelectrochemical systems.

  1. Salmonella typhimurium Invasion Induces Apoptosis in Infected Macrophages

    Science.gov (United States)

    Monack, Denise M.; Raupach, Barbel; Hromockyj, Alexander E.; Falkow, Stanley

    1996-09-01

    Invasive Salmonella typhimurium induces dramatic cytoskeletal changes on the membrane surface of mammalian epithelial cells and RAW264.7 macrophages as part of its entry mechanism. Noninvasive S. typhimurium strains are unable to induce this membrane ruffling. Invasive S. typhimurium strains invade RAW264.7 macrophages in 2 h with 7- to 10-fold higher levels than noninvasive strains. Invasive S. typhimurium and Salmonella typhi, independent of their ability to replicate intracellularly, are cytotoxic to RAW264.7 macrophages and, to a greater degree, to murine bone marrow-derived macrophages. Here, we show that the macrophage cytotoxicity mediated by invasive Salmonella is apoptosis, as shown by nuclear morphology, cytoplasmic vacuolization, and host cell DNA fragmentation. S. typhimurium that enter cells causing ruffles but are mutant for subsequent intracellular replication also initiate host cell apoptosis. Mutant S. typhimurium that are incapable of inducing host cell membrane ruffling fail to induce apoptosis. The activation state of the macrophage plays a significant role in the response of macrophages to Salmonella invasion, perhaps indicating that the signal or receptor for initiating programmed cell death is upregulated in activated macrophages. The ability of Salmonella to promote apoptosis may be important for the initiation of infection, bacterial survival, and escape of the host immune response.

  2. Structure–Property Relationships of Inorganically Surface-Modified Zeolite Molecular Sieves for Nanocomposite Membrane Fabrication

    KAUST Repository

    Lydon, Megan E.

    2012-05-03

    A multiscale experimental study of the structural, compositional, and morphological characteristics of aluminosilicate (LTA) and pure-silica (MFI) zeolite materials surface-modified with MgO xH y nanostructures is presented. These characteristics are correlated with the suitability of such materials in the fabrication of LTA/Matrimid mixed-matrix membranes (MMMs) for CO 2/CH 4 separations. The four functionalization methods studied in this work produce surface nanostructures that may appear superficially similar under SEM observation but in fact differ considerably in shape, size, surface coverage, surface area/roughness, degree of attachment to the zeolite surface, and degree of zeolite pore blocking. The evaluation of these characteristics by a combination of TEM, HRTEM, N 2 physisorption, multiscale compositional analysis (XPS, EDX, and ICP-AES elemental analysis), and diffraction (ED and XRD) allows improved understanding of the origin of disparate gas permeation properties observed in MMMs made with four types of surface-modified zeolite LTA materials, as well as a rational selection of the method expected to result in the best enhancement of the desired properties (in the present case, CO 2/CH 4 selectivity increase without sacrificing permeability). A method based on ion exchange of the LTA with Mg 2+, followed by base-induced precipitation and growth of MgO xH y nanostructures, deemed "ion exchange functionalization" here, offers modified particles with the best overall characteristics resulting in the most effective MMMs. LTA/Matrimid MMMs containing ion exchange functionalized particles had a considerably higher CO 2/CH 4 selectivity (∼40) than could be obtained with the other functionalization techniques (∼30), while maintaining a CO 2 permeability of ∼10 barrers. A parallel study on pure silica MFI surface nanostructures is also presented to compare and contrast with the zeolite LTA case. © 2012 American Chemical Society.

  3. Effect of storage duration on the rheological properties of goose liquid egg products and eggshell membranes.

    Science.gov (United States)

    Kumbar, V; Nedomova, S; Trnka, J; Buchar, J; Pytel, R

    2016-07-01

    In practice, goose eggs are increasingly used and, therefore, the rheological properties have to be known for processing. The eggs of geese (Landes Goose, Anser anser f. domestica) were stored for one, 2, 3, 4, 6, and 8 wk at a constant temperature 4°C. First of all, the egg quality parameters were described in terms of egg weight, egg weight loss, egg shape index, yolk height, albumen height, yolk index, albumen index, and Haugh units. In the next step the rheological behavior of liquid egg products (egg yolk, albumen, and whole liquid egg) was studied using a concentric cylinder viscometer. Flow curves of all liquid egg products exhibited non-Newtonian shear thinning behavior. This behavior can be described using the Herschel-Bulkley model and for technical application using the Ostwald-de Waele model. The effect of the storage duration on the rheological behavior is different for the different liquid egg products. With the exception of very low shear rates, the viscosity of the egg yolk as well as of the whole liquid egg decreases with storage time. At lower shear rates there is a tendency toward increased albumen viscosity with storage duration. The storage duration also affects the mechanical properties of the eggshell membrane. This effect has been evaluated in terms of the ultimate tensile strength, fracture strain, and fracture toughness. All these parameters increased with the loading rate, but decreased during the egg storage. These mechanical phenomena should be respected, namely in the design of the egg model for the numerical simulation of the egg behavior under different kinds of the mechanical loading.

  4. Protein composition and biomechanical properties of in vivo-derived basement membranes.

    Science.gov (United States)

    Halfter, Willi; Candiello, Joseph; Hu, Haiyu; Zhang, Peng; Schreiber, Emanuel; Balasubramani, Manimalha

    2013-01-01

    Basement membranes (BMs) evolved together with the first metazoan species approximately 500 million years ago. Main functions of BMs are stabilizing epithelial cell layers and connecting different types of tissues to functional, multicellular organisms. Mutations of BM proteins from worms to humans are either embryonic lethal or result in severe diseases, including muscular dystrophy, blindness, deafness, kidney defects, cardio-vascular abnormalities or retinal and cortical malformations. In vivo-derived BMs are difficult to come by; they are very thin and sticky and, therefore, difficult to handle and probe. In addition, BMs are difficult to solubilize complicating their biochemical analysis. For these reasons, most of our knowledge of BM biology is based on studies of the BM-like extracellular matrix (ECM) of mouse yolk sac tumors or from studies of the lens capsule, an unusually thick BM. Recently, isolation procedures for a variety of BMs have been described, and new techniques have been developed to directly analyze the protein compositions, the biomechanical properties and the biological functions of BMs. New findings show that native BMs consist of approximately 20 proteins. BMs are four times thicker than previously recorded, and proteoglycans are mainly responsible to determine the thickness of BMs by binding large quantities of water to the matrix. The mechanical stiffness of BMs is similar to that of articular cartilage. In mice with mutation of BM proteins, the stiffness of BMs is often reduced. As a consequence, these BMs rupture due to mechanical instability explaining many of the pathological phenotypes. Finally, the morphology and protein composition of human BMs changes with age, thus BMs are dynamic in their structure, composition and biomechanical properties.

  5. Enhanced sludge properties and distribution study of sludge components in electrically-enhanced membrane bioreactor.

    Science.gov (United States)

    Giwa, Adewale; Ahmed, Iftikhar; Hasan, Shadi Wajih

    2015-08-15

    This study investigated the impact of electric field on the physicochemical and biological characteristics of sludge wasted from an electrically-enhanced membrane bioreactor treating medium-strength raw wastewater. This method offers a chemical-free electrokinetic technique to enhance sludge properties and remove heavy metals. For example, sludge volume index (SVI), time-to-filter (TTF), mean sludge particle diameter (PSD), viscosity, and oxidation-reduction potential (ORP) of 21.7 mL/g, 7 min, 40.2 μm, 3.22 mPa s, and -4.9 mV were reported, respectively. Also, X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses provided mechanisms for heavy metal removal so as to establish relevant pathways for nutrient recovery. Furthermore, variations in dissolved oxygen (DO), conductivity, viscosity, ORP, total suspended solids (MLSS), and volatile suspended solids (MLVSS) were interrelated to evaluate the quality of wasted sludge. A pathway study on the transport and chemical distribution of nutrients and metals in sludge showed great potential for metal removal and nutrient recovery.

  6. Sensing inhomogeneous mechanical properties of human corneal Descemet's membrane with AFM nano-indentation.

    Science.gov (United States)

    Di Mundo, Rosa; Recchia, Giuseppina; Parekh, Mohit; Ruzza, Alessandro; Ferrari, Stefano; Carbone, Giuseppe

    2017-10-01

    The paper describes a highly space-resolved characterization of the surface mechanical properties of the posterior human corneal layer (Descemet's membrane). This has been accomplished with Atomic Force Microscopy (AFM) nano-indentation by using a probe with a sharp tip geometry. Results indicate that the contact with this biological tissue in liquid occurs with no (or very low) adhesion. More importantly, under the same operating conditions, a broad distribution of penetration depth can be measured on different x-y positions of the tissue surface, indicating a high inhomogeneity of surface stiffness, not yet clearly reported in the literature. An important contribution to such inhomogeneity should be ascribed to the discontinuous nature of the collagen/proteoglycans fibers matrix tissue, as can be imaged by AFM when the tissue is semi-dry. Using classical contact mechanics calculations adapted to the specific geometry of the tetrahedral tip it has been found that the elastic modulus E of the material in the very proximity of the surface ranges from 0.23 to 2.6 kPa. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Focus on Extracellular Vesicles: Physiological Role and Signalling Properties of Extracellular Membrane Vesicles

    Directory of Open Access Journals (Sweden)

    Nunzio Iraci

    2016-02-01

    Full Text Available Extracellular vesicles (EVs are a heterogeneous population of secreted membrane vesicles, with distinct biogenesis routes, biophysical properties and different functions both in physiological conditions and in disease. The release of EVs is a widespread biological process, which is conserved across species. In recent years, numerous studies have demonstrated that several bioactive molecules are trafficked with(in EVs, such as microRNAs, mRNAs, proteins and lipids. The understanding of their final impact on the biology of specific target cells remains matter of intense debate in the field. Also, EVs have attracted great interest as potential novel cell-free therapeutics. Here we describe the proposed physiological and pathological functions of EVs, with a particular focus on their molecular content. Also, we discuss the advances in the knowledge of the mechanisms regulating the secretion of EV-associated molecules and the specific pathways activated upon interaction with the target cell, highlighting the role of EVs in the context of the immune system and as mediators of the intercellular signalling in the brain.

  8. Electrode-analytical properties of polyvinylchloride membranes based on triple metal-polymeric complexes

    OpenAIRE

    Matorina, Katerina V.; Chmilenko, Tetyana S.; Chmilenko, Fedor O.

    2015-01-01

    The influence of the nature of the electrode-active substances (EAS), the composition of the external and internal solutions on the formation of the analytical signal of polyvinylchloride (PVC) membranes based on associates and triple metal-polymeric complexes (TMPC) was established. Dehumidification of synthesized membranes increases with the content of polyvinylpyrrolidone (PVP). The value of the swelling degree is more than two times greater for membranes, which contain as EAS TMPC, relati...

  9. Design of poly(vinylidene fluoride)-g-p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) membrane via surface modification for enhanced fouling resistance and release property

    Science.gov (United States)

    Zhao, Guili; Chen, Wei Ning

    2017-03-01

    Thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAAm), hydrophilic polymer poly(hydroxyethyl methacrylate) (PHEMA) and copolymer p(hydroxyethyl methacrylate-co-N-isopropylacrylamide) [P(HEMA-co-NIPAAm)] were synthesized onto poly(vinylidene fluoride) (PVDF) membrane via atom transfer radical polymerization (ATRP) in order to improve not only fouling resistance but also fouling release property. The physicochemical properties of membranes including hydrophilicity, morphology and roughness were examined by contact angle analyzer, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The antifouling property of membranes was improved remarkably after surface modification according to protein and bacterial adhesion testing, and filtration experiment. Minimum protein adsorption and bacterial adhesion were both obtained on PVDF-g-P(HEMA-co-NIPAAm) membrane, with reduction by 44% and 71% respectively compared to the pristine membrane. The minimum bacterial cells after detachment at 25 °C were observed on the PVDF-g-P(HEMA-co-NIPAAm) membrane with the detachment rate of 77%, indicating high fouling release property. The filtration testing indicated that the copolymer modified membrane exhibited high resistance to protein fouling and the foulant on the surface was released and removed easily by washing, suggesting high fouling release and easy-cleaning capacity. This study provides useful insight in the combined "fouling resistance" and "fouling release" property of P(HEMA-co-NIPAAm) for PVDF membrane modification, even for other types of the membrane in wide application.

  10. 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.

  11. 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

  12. Segregated phases in pulmonary surfactant membranes do not show coexistence of lipid populations with differentiated dynamic properties

    DEFF Research Database (Denmark)

    Bernardino de la Serna, Jorge; Orädd, Greger; Bagatolli, Luis

    2009-01-01

    The composition of pulmonary surfactant membranes and films has evolved to support a complex lateral structure, including segregation of ordered/disordered phases maintained up to physiological temperatures. In this study, we have analyzed the temperature-dependent dynamic properties of native...... surfactant membranes and membranes reconstituted from two surfactant hydrophobic fractions (i.e., all the lipids plus the hydrophobic proteins SP-B and SP-C, or only the total lipid fraction). These preparations show micrometer-sized fluid ordered/disordered phase coexistence, associated with a broad...... from the two types of surfactant hydrophobic extract. These latter results suggest that lipid dynamics are similar in the coexisting fluid phases observed by fluorescence microscopy. Additionally, it is found that surfactant proteins significantly reduce the average intramolecular lipid mobility...

  13. Aluminum ions alter the function of non-specific phospholipase C through the changes in plasma membrane physical properties.

    Science.gov (United States)

    Pejchar, Přemysl; Martinec, Jan

    2015-01-01

    The first indication of the aluminum (Al) toxicity in plants growing in acidic soils is the cessation of root growth, but the detailed mechanism of Al effect is unknown. Here we examined the impact of Al stress on the activity of non-specific phospholipase C (NPC) in the connection with the processes related to the plasma membrane using fluorescently labeled phosphatidylcholine. We observed a rapid and significant decrease of labeled diacylglycerol (DAG), product of NPC activity, in Arabidopsis seedlings treated with AlCl₃. Interestingly, an application of the membrane fluidizer, benzyl alcohol, restored the level of DAG during Al treatment. Our observations suggest that the activity of NPC is affected by Al-induced changes in plasma membrane physical properties.

  14. Thermo-mechanical properties of mixed ion-electron conducting membrane materials

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Bingxin

    2011-07-01

    The thesis presents thermo-mechanical properties of La{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF) and Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (BSCF) perovskite materials, which are considered as oxygen transport membranes (OTM) for gas separation units. Ring-on-ring bending test with disk-shaped samples and depth-sensitive micro-indentation have been used as macroscopic and microscopic tests, respectively. In addition, the thermo-mechanical properties of a third OTM candidate material La{sub 2}NiO{sub 4+{delta}} (LNO) were investigated. The results of the thermo-mechanical measurements with the BSCF revealed an anomaly between 200 C and 400 C. In particular, the temperature dependence of Young's modulus shows a minimum at {proportional_to} 200 C. Fracture stress and toughness exhibit a qualitatively similar behavior with a minimum between 200 C and 400 C, before recovering between 500 C and 800 C. X-ray diffraction analyses verified that BSCF remains cubic in the relevant temperature range. Hence the anomalies were assumed to be related to the transition of Co{sup 3+} spin states reported for other Co-containing perovskites. This assumption could be experimentally confirmed by magnetic susceptibility measurements. The fracture surfaces of the specimens are not affected by the mechanical anomalies at intermediate temperatures, since only a transgranular fracture mode has been observed. Complementary to the mechanical characterization of BSCF, also the temperature dependency of fracture stress and elastic behavior of LSCF have been determined. Phase compositions of LSCF have been studied by in-situ high temperature XRD. Changes in phase composition with temperature are observed. At ambient temperature the LSCF perovskite material comprises two phases: rhombohedral and cubic symmetry. The ratio of the two phases depends on both cooling rate and atmosphere. The transition of rhombohedral to cubic occurs between 700 C and

  15. Macrophage phenotype modulation by CXCL4 in vascular disease

    Directory of Open Access Journals (Sweden)

    Christian Albert Gleissner

    2012-01-01

    Full Text Available During atherogenesis, blood monocytes transmigrate into the subendothelial space and differentiate towards macrophages and foam cells. The major driver of this differentiation process is macrophage colony-stimulation factor (M-CSF. M-CSF-induced macrophages are important promoters of atherogenesis as demonstrated in M-CSF and M-CSF receptor knock out mice. However, M-CSF is not the only relevant promoter of macrophage differentiation. The platelet chemokine CXCL4 prevents monocyte apoptosis and promotes macrophage differentiation in vitro. It is secreted from activated platelets and has effects on various cell types relevant in atherogenesis. Knocking out the Pf4 gene coding for CXCL4 in Apoe-/- mice leads to reduced atherogenesis. Thus, it seems likely that CXC4-induced macrophages may have specific pro-atherogenic capacities. We have studied CXC4-induced differentiation of human macrophages using gene chips, systems biology and functional in vitro and ex vivo experiments. Our data indicate that CXCL4-induced macrophages are distinct from both their M-CSF-induced counterparts and other known macrophage polarizations like M1 macrophages (induced by LPS and interferon-gamma or M2 macrophages (induced by interleukin-4. CXCL4-induced macrophages have distinct phenotypic and functional characteristics, e.g. the complete loss of the hemoglobin-haptoglobin (Hb-Hp scavenger receptor CD163 which is necessary for effective hemoglobin clearance after plaque hemorrhage. Lack of CD163 is accompanied by the inability to upregulate the atheroprotective enzyme heme oxygenase-1 in response to Hb-Hp complexes.This review covers the current knowledge about CXCL4-induced macrophages, which based on their unique properties we have suggested to call these macrophages M4. CXCL4 may represent an important driver of macrophage heterogeneity within atherosclerotic lesions. Further dissecting its effects on macrophage differentiation may help to identify novel

  16. Macrophage receptors of polysaccharide isolated from a marine filamentous fungus Phoma herbarum YS4108

    Institute of Scientific and Technical Information of China (English)

    Song CHEN; Deng-ke YIN; Wen-bing YAO; Yi-dan WANG; Yi-ran ZHANG; Xiang-dong GAO

    2009-01-01

    Aim:YCP,a novel (1,4)-α-D-glucan,was isolated from the mycelium of the marine filamentous fungus Phoma herbarum YS4108.In this work,we investigated a YCP-binding cellular receptor expressed by macrophages and the intracellular signal transduction pathways involved in YCP-induced macrophage activation.Methods:Fluorescence-labeled YCP (fl-YCP) was prepared using the CDAP-activation method.Fluorescence confocal laser microscopy and fluorescence-activated cell sorting (FACS) were used to analyze the effect of fl-YCP on macrophages.To characterize the properties of the YCP receptor,carbohydrates and antibodies were used to inhibit the binding of fl-YCP to macrophages.Moreover,we investigated the role of membrane receptors Toll-like receptor 2 (TLR2),Toll-like receptor 4 (TLR4),Toll-like receptor 6 (TLR6) and complement receptor 3 (CR3).We also examined the role of the p38 kinase pathway in mediating nitric oxide (NO) production.Results:YCP had an in vitro stimulatory effect on the release of NO in macrophage,and fl-YCP can bind directly to receptors on the surface of macrophages in a time- and dose-dependent manner.Competition studies show that LPS,laminarin,anti-TLR4 antibody and anti-CD11b (CR3) antibody could inhibit fl-YCP binding to macrophages.Conversely,mannose,anti-TLR2 and anti-TLR6 antibody could not.Treatment of RAW264.7 cells with YCP resulted in significant activation of p38 in a time-dependent manner.The specific p38 inhibitor SB203580 abrogated YCP-induced NO generation.Treatment of RAW264.7 cells with anti-TLR4 antibody and anti-CR3 antibody significantly reduced YCP-induced NO production and p38 activation.Conclusion:We have demonstrated that YCP-induced NO production occurs through the TLR4 and CR3 membrane receptors in a p38 kinase-dependent manner in macrophages.

  17. Depletion of resident macrophages does not alter sensory regeneration in the avian cochlea.

    Directory of Open Access Journals (Sweden)

    Mark E Warchol

    Full Text Available Macrophages are the primary effector cells of the innate immune system and are also activated in response to tissue injury. The avian cochlea contains a population of resident macrophages, but the precise function of those cells is not known. The present study characterized the behavior of cochlear macrophages after aminoglycoside ototoxicity and also examined the possible role of macrophages in sensory regeneration. We found that the undamaged chick cochlea contains a large resting population of macrophages that reside in the hyaline cell region, immediately outside the abneural (inferior border of the sensory epithelium. Following ototoxic injury, macrophages appear to migrate out of the hyaline cell region and towards the basilar membrane, congregating immediately below the lesioned sensory epithelium. In order to determine whether recruited macrophages contribute to the regeneration of sensory receptors, we quantified supporting cell proliferation and hair cell recovery after the elimination of most resident macrophages via application of liposomally-encapsulated clodronate. Examination of macrophage-depleted specimens at two days following ototoxic injury revealed no deficits in hair cell clearance, when compared to normal controls. In addition, we found that elimination of macrophages did not affect either regenerative proliferation of supporting cells or the production of replacement hair cells. However, we did find that macrophage-depleted cochleae contained reduced numbers of proliferative mesothelial cells below the basilar membrane. Our data suggest that macrophages are not required for normal debris clearance and regeneration, but that they may play a role in the maintenance of the basilar membrane.

  18. Alteration of membrane lipid biophysical properties and resistance of human lung adenocarcinoma A549 cells to cisplatin

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Alterations of membrane lipid biophysical properties of sensitiveA549 and resistant A549/DDP cells to the Cis-dichlorodiammine platinum (Cisplatin) were performed by measurements of fluorescence and flow cytometry approaches using fluorescence dyes of DPH, N-AS and Merocyanine 540 (MC 540) respectively. Fatty acids of membrane lipid of the two cell lines were analyzed by gas chromatography. The results indicated clearly that fluorescence polarization (P) of the DPH probe is 0.169 for the sensitive A549 cell and 0.194 for the resistant A549/DDP cells. Statistical analysis showed significant difference between the two cell lines. The polarizations of 2-AS and 7-AS which reflect the fluidity of surface and middle of lipid bilayer are 0.134 and 0.144 for the sensitive A549 cells as well as 0.171 and 0.178 for the resistant A549/DDP cells respectively, but there is no significant difference of the polarization of 12-AS between the two cell lines. This shows that altera-tions of the membrane fluidity of both cells were mainly located on the surface and middle of the lipid bilayer. In addition, the packing density of phospholipid molecules in the membrane of the two cell lines detected by MC540 probe indicated that lipid packing of A549 cell membranes was looser than that of the A549/DDP cells. And unsaturation degree of plasma membrane fatty acids of the A549/DDP cells was also lower than that of A549 cells. Taken together, it was proposed that the al-teration of membrane lipid biophysical state may be involved in the resistance of A549/DDP cells to cisplatin.

  19. Physicochemical characterization of camptothecin membrane binding properties and polymeric microsphere formulations

    Science.gov (United States)

    Selvi, Bilge

    In an effort to design novel formulation strategies to optimize the antitumor activity of camptothecin (CPT), the physicochemical and membrane binding properties of the drug, were investigated by various techniques in acidic and physiological pH. The intrinsic solubility of the CPT-lactone free base was determined to be 3.44 muM and 5.11 muM at 22°C and 37°C, respectively. The equilibrium solubility of the drug was found to increase with increasing temperature and decreasing pH. The enhanced solubility of the drug at very low pH is attributed to the protonation of the nitrogen atom in the ring B and the increased solvency of the highly acidic media. The logarithmic value of the intrinsic partition coefficient P of the free base CPT-lactone form was estimated to be 1.65, characteristic of a molecule suitable for oral absorption. The association constants Kf of the drug for bilayers composed of the zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and the negatively-charged 1,2-dioleoyl-sn-glycero-3-phospho- rac-(1-glycerol) (DOPG) were studied at acidic pH by fluorescence anisotropy and determined to be 35.4 +/- 4.5 M-1 and 93.1 +/- 11.0 M-1 for DOPC and DOPG, respectively, indicating a tendency of CPT to preferentially bind to negatively charged membranes. The energy of activation for the hydrolysis of CPT at physiological pH was found to be 114.3 +/- 33.4 kj/mole. The calculated t½ of the reaction at pH 7.2 at temperatures 25°C and 10°C was found to be 0.07 days and 5.12 days, respectively, whereas the time required for 1% of CPT-lactone to hydrolyze to CPT-carboxylate (t99%) was determined to be 1.8 hours, thus offering enough time to safely handle CPT-lactone at low temperatures. The preformulation results indicated that at highly acidic media CPT is positively charged and exists at its stable lactone form of increased solubility and has a capacity to bind to negatively charged membranes. Taking advantage of the increased stability of CPT in

  20. Surface Functionalization of Thin-Film Composite Membranes with Copper Nanoparticles for Antimicrobial Surface Properties

    KAUST Repository

    Ben-Sasson, Moshe

    2014-01-07

    Biofouling is a major operational challenge in reverse osmosis (RO) desalination, motivating a search for improved biofouling control strategies. Copper, long known for its antibacterial activity and relatively low cost, is an attractive potential biocidal agent. In this paper, we present a method for loading copper nanoparticles (Cu-NPs) on the surface of a thin-film composite (TFC) polyamide RO membrane. Cu-NPs were synthesized using polyethyleneimine (PEI) as a capping agent, resulting in particles with an average radius of 34 nm and a copper content between 39 and 49 wt.%. The positive charge of the Cu-NPs imparted by the PEI allowed a simple electrostatic functionalization of the negatively charged RO membrane. We confirmed functionalization and irreversible binding of the Cu-NPs to the membrane surface with SEM and XPS after exposing the membrane to bath sonication. We also demonstrated that Cu-NP functionalization can be repeated after the Cu-NPs dissolve from the membrane surface. The Cu-NP functionalization had minimal impact on the intrinsic membrane transport parameters. Surface hydrophilicity and surface roughness were also maintained, and the membrane surface charge became positive after functionalization. The functionalized membrane exhibited significant antibacterial activity, leading to an 80-95% reduction in the number of attached live bacteria for three different model bacterial strains. Challenges associated with this functionalization method and its implementation in RO desalination are discussed. © 2013 American Chemical Society.

  1. Enzymatic Oxidation of Cholesterol: Properties and Functional Effects of Cholestenone in Cell Membranes

    DEFF Research Database (Denmark)

    Neuvonen, M.; Manna, M.; Mokkila, S.

    2014-01-01

    of cholestenone using simulations and cell biological experiments and assessed the functional effects of cholestenone in human cells. Atomistic simulations predicted that cholestenone reduces membrane order, undergoes faster flip-flop and desorbs more readily from membranes than cholesterol. In primary human...

  2. Structure–property tuning in hydrothermally stable sol–gel-processed hybrid organosilica molecular sieving membranes

    NARCIS (Netherlands)

    Elshof, ten J.E.; Dral, A.P.

    2016-01-01

    Supported microporous organosilica membranes made from bridged silsesquioxane precursors by an acid-catalyzed sol–gel process have demonstrated a remarkable hydrothermal stability in pervaporation and gas separation processes, making them the first generation of ceramic molecular sieving membranes w

  3. Biophysical implications of sphingosine accumulation in membrane properties at neutral and acidic pH.

    Science.gov (United States)

    Zupancic, Eva; Carreira, Ana C; de Almeida, Rodrigo F M; Silva, Liana C

    2014-05-08

    Sphingosine (Sph) is a simple lipid involved in the regulation of several biological processes. When accumulated in the late endosomal/lysosomal compartments, Sph causes changes in ion signaling and membrane trafficking, leading to the development of Niemann-Pick disease type C. Little is known about Sph interaction with other lipids in biological membranes; however, understanding the effect of Sph in the physical state of membranes might provide insights into its mode of action. Using complementary established fluorescence approaches, we show that Sph accumulation leads to the formation of Sph-enriched gel domains in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and POPC/sphingomyelin (SM)/cholesterol (Chol) model membranes. These domains are more easily formed in membrane models mimicking the neutral pH plasma membrane environment (PM) as compared to the acidic lysosomal membrane environment (LM), where higher Sph concentrations (or lower temperatures) are required. Electrophoretic light scattering measurements further revealed that in PM-raft models (POPC/SM/Chol), Sph is mainly neutral, whereas in LM models, the positive charge of Sph leads to electrostatic repulsion, reducing the Sph ability to form gel domains. Thus, formation of Sph-enriched domains in cellular membranes might be strongly regulated by Sph charge.

  4. Synthesis and textural properties of unsupported and supported rutile (TiO2) membranes

    NARCIS (Netherlands)

    Kumar, Krishnankutty-Nair P.; Keizer, Klaas; Burggraaf, Anthonie J.; Okubo, Tatsuya; Nagamoto, Hidetoshi

    1993-01-01

    Two approaches were postulated for improving the stability of porous texture of titania membranes: (1) retarding the phase transformation and grain growth; (2) avoiding the phase transformation. Based on the second approach, rutile membranes were made directly from a rutile sol, prepared by the prec

  5. Physicochemical properties of phosphoric acid doped polybenzimidazole membranes for fuel cells

    DEFF Research Database (Denmark)

    He, Ronghuan; Li, Qingfeng; Bach, Anders;

    2006-01-01

    Polybenzimidazole (PBI) membranes have been prepared with different molecular weights. The water and acid swelling, mechanical strength,gas permeability and proton conductivity were studied for the pristine and acid doped PBI membranes. When doped with 5 mol of phosphoric acid per mole repeat uni...

  6. Porous ceramic membranes: suspension processing, mechanical and transport properties, and application in the osmotic tensiometer

    NARCIS (Netherlands)

    Biesheuvel, Pieter Maarten

    2000-01-01

    Synthetic membranes are increasingly used for energy-efficient separation of liquid and gaseous mixtures in household applications, environmental technology and the chemical and energy industry. Besides, membranes are used in component-specific sensors in gas and liquid streams, preferably combined

  7. Dense inorganic membranes - studies on transport properties, defect chemistry and catalytic behaviour

    NARCIS (Netherlands)

    Elshof, ten Johan Evert

    1997-01-01

    Oxygen separation with dense oxide membranes may be an attractive method for the production of oxygen from air. Another possible application is the direct supply of oxygen in membrane reactors for the (partial) oxidation of hydrocarbons. The driving force for oxygen permeation through dense mixed io

  8. X-ray structure, thermodynamics, elastic properties and MD simulations of cardiolipin/dimyristoylphosphatidylcholine mixed membranes

    DEFF Research Database (Denmark)

    Boscia, Alexander L.; Treece, Bradley W.; Mohammadyani, Dariush

    2014-01-01

    to cholesterol in that it thickens and stiffens DMPC membranes, orders chains, and is positioned under the umbrella of the PC headgroup. CL may be necessary for hydrophobic matching to inner mitochondrial membrane proteins. Differential scanning calorimetry, S Xray and CGMD simulations all suggest that TMCL does...

  9. Preparation, proton conductivity and mechanical properties of Nafion 117-zirconium phosphate sulphophenylphosphonate composite membranes

    Energy Technology Data Exchange (ETDEWEB)

    Capitani, D. [Istituto di Metodologie Chimiche, CNR, Monterotondo Scalo (Italy); Donnadio, A.; Frittella, V.; Pica, M.; Sganappa, M. [CEMIN - Dipartimento di Chimica, Perugia (Italy); Casciola, M.

    2009-08-15

    Nafion-zirconium phosphate (ZrP) composite membranes, containing 20 to 40 wt.-% ZrP were treated with aqueous solutions of meta-sulphophenylphosphonic acid (H{sub 2}SPP) in order to functionalise the filler particles with strongly acidic sulphonic groups. The functionalised samples (Nafion/ZrSPP) were characterised by {sup 31}P MAS NMR, water uptake determinations, stress-strain mechanical tests and conductivity measurements. The Nafion/ZrSPP membranes are more hydrophilic than Nafion 117 and stiffer than the parent Nafion/ZrP membranes: at room temperature, the elastic modulus of the membranes with 20 and 40 wt.-% ZrP increases from 191 and 329 N mm{sup -2} to 342 and 470 N mm{sup -2}, respectively, after functionalisation. At 100 C and in the RH range of 30-90% the conductivity of the Nafion/ZrSPP membranes decreases with the increase in the filler loading, being however always higher than that of the parent Nafion/ZrP membranes and nearly coincident with that of Nafion 117. Conductivity measurements as a function of temperature in the range of 80-150 C showed that, at 90% RH, the conductivity of the Nafion/ZrSPP membranes is stable up to 140 C thus indicating a better dimensional stability of the composite membrane in comparison with neat Nafion 117. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  10. Transport Properties of Multivalent Cations in Nafion-117 Membrane with Mixed Ionic Composition.

    Science.gov (United States)

    Chaudhury, Sanhita; Agarwal, Chhavi; Goswami, A

    2015-08-20

    The transport characteristics of multivalent cations like Ba(2+) and Eu(3+) have been studied in bi-ionic form of the Nafion-117 membrane. The membranes have been prepared by loading different proportions of H(+)-Ba(2+)/Mg(2+)-Ba(2+)/Ba(2+)-Eu(3+)/H(+)-Eu(3+)/Na(+)-Eu(3+). The cationic compositions of the membranes have been determined from the measured ion exchange isotherms. Results show that the self-diffusion coefficient of Ba(2+) (D(Ba)) in H-Ba/Mg-Ba systems as well as the self-diffusion coefficient of Eu(3+) (D(Eu)) in H-Eu/Na-Eu systems are strongly dependent on the membrane ionic compositions and decreased continuously with increasing concentration of the highly hydrated ions (H(+)/Na(+)/Mg(2+)) in the membrane. Increase in the proportion of H(+)/Na(+)/Mg(2+) ions in the membrane increases the effective charge on the membrane matrix. This causes stronger electrostatic interaction of the less hydrated multivalent ions (Ba(2+)/Eu(3+)) with the membrane matrix charges, which ultimately results in their slower self-diffusion coefficients. The higher the valence, the stronger the electrostatic interaction is with the fixed ionic charges; hence, in general, D(Eu) is affected more as compared to D(Ba). On the basis of the free-volume theory for polymers, the effective interaction potential (Φ) of the Ba(2+) with the fixed ionic sites in the membrane has been calculated and found to be on the order of approximately millivolts. The higher the proportion of hydrated ion in the membrane, the higher the Φ is and the stronger the ion pair formation is with the fixed ionic sites in the membrane. However, in the Ba-Eu system, as the electrostatic interactions of the two ions with the membrane matrix are close, D(Ba) and D(Eu) are independent of the membrane ionic composition. The ionic composition dependence of D(Ba) in the H-Ba system is reflected in the transport rate of Ba(2+), showing the importance of such measurements in understanding the transport

  11. Relationship between performance deterioration of a polyamide reverse osmosis membrane used in a seawater desalination plant and changes in its physicochemical properties.

    Science.gov (United States)

    Suzuki, Tasuma; Tanaka, Ryohei; Tahara, Marina; Isamu, Yuya; Niinae, Masakazu; Lin, Lin; Wang, Jingbo; Luh, Jeanne; Coronell, Orlando

    2016-09-01

    While it is known that the performance of reverse osmosis membranes is dependent on their physicochemical properties, the existing literature studying membranes used in treatment facilities generally focuses on foulant layers or performance changes due to fouling, not on the performance and physicochemical changes that occur to the membranes themselves. In this study, the performance and physicochemical properties of a polyamide reverse osmosis membrane used for three years in a seawater desalination plant were compared to those of a corresponding unused membrane. The relationship between performance changes during long-term use and changes in physicochemical properties was evaluated. The results showed that membrane performance deterioration (i.e., reduced water flux, reduced contaminant rejection, and increased fouling propensity) occurred as a result of membrane use in the desalination facility, and that the main physicochemical changes responsible for performance deterioration were reduction in PVA coating coverage and bromine uptake by polyamide. The latter was likely promoted by oxidant residual in the membrane feed water. Our findings indicate that the optimization of membrane materials and processes towards maximizing the stability of the PVA coating and ensuring complete removal of oxidants in feed waters would minimize membrane performance deterioration in water purification facilities. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Effect of CO{sub 2}-laser irradiation on properties and performance of thin-film composite polyamide reverse osmosis membrane

    Energy Technology Data Exchange (ETDEWEB)

    Jahangiri, Foad; Mousavi, Seyyed Abbas; Farhadi, Fathollah; Sabzi, Behnam; Chenari, Zeinab [Sharif University of Technology, Tehran (Iran, Islamic Republic of); Vatanpour, Vahid [Kharazmi (Tarbiat Moallem) University, Tehran (Iran, Islamic Republic of)

    2016-03-15

    CO{sub 2}-laser irradiation was used to modify the surface properties of thin-film composite (TFC) polyamide reverse osmosis (RO) membranes. These membranes were first synthesized via interfacial polymerization of m-phenylenediamine (MPD) monomers and trimesoyl chloride (TMC) over porous polysulfone ultrafiltration support, followed by a CO{sub 2}-irradiation. AFM, ATR-FTIR, SEM and contact angle measurements were used to characterize the surface properties of these membranes. The ATR-FTIR results indicated that CO{sub 2}-laser irradiation did not induce any functional groups on the membrane surface. However, it was found that the laser irradiation enhanced the NaCl salt rejection and slightly reduced the permeate flux. Moreover, the maintenance of the flux in modified membranes was much higher than untreated ones. Specially, after 180 min of filtration, the reduction in initial flux for the unmodified membranes was 22%. However, the reduction in initial flux for the modified membranes was less than 5%. Bovine serum albumin (BSA) filtration revealed an improvement in the antifouling properties of the modified membranes. The changes in the membrane surface morphology showed that the roughness of membrane surface is reduced significantly.

  13. Physico-chemical properties of alginate/shellac aqueous-core capsules: Influence of membrane architecture on riboflavin release.

    Science.gov (United States)

    Ben Messaoud, Ghazi; Sánchez-González, Laura; Probst, Laurent; Jeandel, Carole; Arab-Tehrany, Elmira; Desobry, Stéphane

    2016-06-25

    To enhance physico-chemical properties of alginate liquid-core capsules, shellac was incorporated into the membrane (composite capsules) or as an additional external layer (coated capsules). The influence of pH, coating time, shellac concentration and preparation mechanism (acid or calcium precipitation) were investigated. Results showed that shellac significantly influenced the capsules properties. The feasibility of shellac incorporation was closely related to the preparation conditions as confirmed by Infrared spectroscopy. Optical, fluorescence and scanning electron microscopy, highlighted different capsules and membranes architectures. In contrast to simple and composite capsules, coated capsules showed a pH-dependent release of the entrapped vitamin especially after shellac crosslinking with calcium. Heating of coated capsules above the glass transition temperature investigated by Differential Scanning Calorimetry, led to irreversible structural change due to thermoplastic behavior of shellac and enhanced riboflavin retention under acidic conditions. This global approach is useful to control release mechanism of low molecular weight molecules from macro and micro-capsules.

  14. Neuronal activity causes rapid changes of lateral amygdala neuronal membrane properties and reduction of synaptic integration and synaptic plasticity in vivo.

    Science.gov (United States)

    Rosenkranz, J Amiel

    2011-04-20

    Neuronal membrane properties dictate neuronal responsiveness. Plasticity of membrane properties alters neuronal function and can arise in response to robust neuronal activity. Despite the potential for great impact, there is little evidence for a rapid effect of activity-dependent changes of membrane properties on many neuronal functions in vivo in mammalian brain. In this study it was tested whether periods of neuronal firing lead to a rapid change of membrane properties in neurons of a rat brain region important for some forms of learning, the lateral nucleus of the amygdala, using in vivo intracellular recordings. Our results demonstrate that rapid plasticity of membrane properties occurs in vivo, in response to action potential firing. This plasticity of membrane properties leads to changes of synaptic integration and subsequent synaptic plasticity. These changes require Ca(2+) and hyperpolarization-activated ion channels, but are NMDA independent. Furthermore, the parameters and time course of these changes would not have been predicted from most in vitro studies. The plasticity of membrane properties demonstrated here may represent a basic form of in vivo short-term plasticity that modifies neuronal function.

  15. Impact of Anti-tacking Agents on Properties of Gas-Entrapped Membrane and Effervescent Floating Tablets

    OpenAIRE

    2014-01-01

    Tackiness caused by the gas-entrapped membrane (Eudragit®RL 30D) was usually observed during storage of the effervescent floating tablets, leading to failure in floatation and sustained release. In this work, common anti-tacking agents (glyceryl monostearate (GMS) and talc) were used to solve this tackiness problem. The impact of anti-tacking agent on the properties of free films and corresponding floating tablets was investigated. GMS was more effective than talc in reducing tackiness of the...

  16. Electrical conductivity, ionic conductivity, optical absorption, and gas separation properties of ionically conductive polymer membranes embedded with Si microwire arrays

    OpenAIRE

    Spurgeon, Joshua M.; Walter, Michael G.; Zhou, Junfeng; Kohl, Paul A.; Lewis, Nathan S.

    2011-01-01

    The optical absorption, ionic conductivity, electronic conductivity, and gas separation properties have been evaluated for flexible composite films of ionically conductive polymers that contain partially embedded arrays of ordered, crystalline, p-type Si microwires. The cation exchange ionomer Nafion, and a recently developed anion exchange ionomer, poly(arylene ether sulfone) that contains quaternary ammonium groups (QAPSF), produced composite microwire array/ionomer membrane films that were...

  17. Evaluation of clinical, antiinflammatory and antiinfective properties of amniotic membrane used for guided tissue regeneration: A randomized controlled trial

    OpenAIRE

    Aravind Kumar; Rampalli Viswa Chandra; Aileni Amarender Reddy; Bavigadda Harish Reddy; Chakravarthy Reddy; Anumala Naveen

    2015-01-01

    Background: The objective of this study was to evaluate the antiinflammatory, antiinfective and clinical properties of amniotic membrane (AM) when used for guided tissue regeneration (GTR) in contained interdental defects. Materials and Methods: A total of 30 subjects participated in this study. Two sites in each subject were randomly assigned into each of the following experimental groups; test group: AM with bone graft and control group: Bone graft only. Clinical parameters included rec...

  18. Sphingosine-1-Phosphate as an Amphipathic Metabolite: Its Properties in Aqueous and Membrane Environments

    Science.gov (United States)

    García-Pacios, Marcos; Collado, M. Isabel; Busto, Jon V.; Sot, Jesús; Alonso, Alicia; Arrondo, José-Luis R.; Goñi, Félix M.

    2009-01-01

    Abstract Sphingosine-1-phosphate (S1P) is currently considered to be an important signaling molecule in cell metabolism. We studied a number of relevant biophysical properties of S1P, using mainly Langmuir balance, differential scanning calorimetry, 31P-NMR, and infrared (IR) spectroscopy. We found that, at variance with other, structurally related sphingolipids that are very hydrophobic, S1P may occur in either an aqueous dispersion or a bilayer environment. S1P behaves in aqueous media as a soluble amphiphile, with a critical micelle concentration of ≈12 μM. Micelles give rise to larger aggregates (in the micrometer size range) at and above a 1 mM concentration. The aggregates display a thermotropic transition at ∼60°C, presumably due to the formation of smaller structures at the higher temperatures. S1P can also be studied in mixtures with phospholipids. Studies with dielaidoylphosphatidylethanolamine (DEPE) or deuterated dipalmitoylphosphatidylcholine (DPPC) show that S1P modifies the gel-fluid transition of the glycerophospholipids, shifting it to lower temperatures and decreasing the transition enthalpy. Low (<10 mol %) concentrations of S1P also have a clear effect on the lamellar-to-inverted hexagonal transition of DEPE, i.e., they increase the transition temperature and stabilize the lamellar versus the inverted hexagonal phase. IR spectroscopy of natural S1P mixed with deuterated DPPC allows the independent observation of transitions in each molecule, and demonstrates the existence of molecular interactions between S1P and the phospholipid at the polar headgroup level that lead to increased hydration of the carbonyl group. The combination of calorimetric, IR, and NMR data allowed the construction of a temperature-composition diagram (“partial phase diagram”) to facilitate a comparative study of the properties of S1P and other related lipids (ceramide and sphingosine) in membranes. In conclusion, two important differences between S1P and ceramide

  19. Effect of solution concentration and composition on the electrochemical properties of ion exchange membranes for energy conversion

    Science.gov (United States)

    Fontananova, E.; Messana, D.; Tufa, R. A.; Nicotera, I.; Kosma, V.; Curcio, E.; van Baak, W.; Drioli, E.; Di Profio, G.

    2017-02-01

    The electrochemical properties of ion exchange membranes (IEMs) applied for salinity-gradient power (SGP) harvesting, are usually measured using diluited NaCl aqueous solutions because of the prevalence of its constituents ions in natural solutions (e.g. seawater). However, in real applications, the IEMs come in contact with other ionic species than Na+ and Cl- that can have a relevant effect on their properties. As a consequence, the obtained results in many cases are not really representative. The aim of the present study was to investigate the effect of solution concentration and compositions on permselectivity, membrane and interface resistance, for both anion and cation exchange membranes (AEMs and CEMs). Special attention was paid to the influence of the most common multivalent ions in seawater (Mg2+, Ca2+ and SO42-) on the electrochemical properties of the AEM and the CEM. It was possible to discriminate the impact on the AEM from that on the CEM. The results highlighted a strong negative effect of Mg2+ on the CEM (relevant increase of ionic resistance and permselectivity) and, at minor extent, on the AEM (moderate reduction of permselectivity).

  20. Effect of Sintering Temperature on Microstructure and Hydrogen Permeation Properties of Perovskite Membrane

    Institute of Scientific and Technical Information of China (English)

    Marzieh Heidari; Akbar Zamaniyan; Aliakbar SafeKordi; Ensieh Ganji Babakhani; Mahdi Amanipour

    2013-01-01

    The BaCe0.9Y0.1O3-δ (BCY) perovskite membrane was successfully synthesized by liquid citrate method.The phase structure of the powder was characterized by X-ray diffraction (XRD).Scanning electron microscopy (SEM) was used to characterize microstructures of the membrane sintered under various conditions.Sintering temperatures and dwell time during sintering influence the final microstructure of the ceramic.Results showed that increasing sintering temperature resulted in a dense membrane with clear grains.An increase of dwell time was favorable to produce membranes with larger grains in the sintered ceramics.A density of 5.87 g/cm3 was reached for the membrane after sintering at 1200 C with dwell time of 10 h.This resulted in the formation of dense membranes with clear structure and average grain size of 0.27 μm.The influence of microstructure on the hydrogen permeation flux through BCY was observed by measuring the hydrogen permeation flux,and the results showed that hydrogen permeation flux increases with increasing the average grain size of the membrane.From H2 permeation rates,it was found that bulk diffusion rather than surface reaction played the dominant role in H2 transport.

  1. Fabrication and Properties of Poly(vinylalcohol)-glycosaminoglycantype I Collagen Composite Membrane as Tissue Regeneration Scaffolds

    Institute of Scientific and Technical Information of China (English)

    LI Qin-hua; LIN Dong-qing

    2015-01-01

    The objective of this paper is to design a porous polyvinyl alcohol (PVA) based on composite membrane with certain mechanical strength and biocompatibilities serving as tissue regenerative scaffolds. PVA-glycosaminoglycan (GAG)-type I collagen (COL) composite membrane was fabricated by PVA with different molecular weight (Mw) and alcoholysis degree (AD) being blended with certain amounts of GAG and COL and dried at 38℃for 24 h. The water content of the composite membranes were from 61.9%to 95.1%and swelling ratio ranged from 123.6%to 621.7%. Scanning electron micro-scope (SEM) analysis proved that PVA-GAG-COL composite membrane has porous and homogenous structure. Biocompatibility test results showed that the composite membrane was nontoxic, which could promote adhesion and proliferation of fibroblasts on the com-posite membrane. In conclusion, PVA-GAG-COL composite membrane with high water content and swelling ratio, suitable mechanical strength and good biocompatibility, has potential in tissue engineering and regenerative medicine.

  2. Effect of coagulant bath on the gas permeation properties of cellulose acetate asymmetric membrane

    Science.gov (United States)

    Mohamed, F.; Hasbullah, H.; Jami'an, W. N. R.; Salleh, W. N. H. W.; Ibrahim, N.; Ali, R. R.

    2016-06-01

    Membrane based gas separation process technology has been recognized as one of the most efficient and advanced unit operation for gas separation. One of the problems in membrane gas separation is membrane performance. This paper explores the application of cellulose acetate (CA) membrane for natural gas purification and separation by improving its permeability and selectivity. The main interest in this research is to study the effect of quench medium on the gas separation performance towards its physical characteristics and gas separation performance of CA membrane. Cellulose acetate polymer was dissolved in n- methyl-2-pyrrolidone solvent and casted onto a glass plate using a pneumatically controlled casting system with fixed shear rate and solvent evaporation times. The parameter varied was the non-solvent used as quench medium during membrane post treatment that were methanol and n-hexane. The different quench media as post treatment affected the O2 and N2 gas permeation and O2/N2 selectivity as well as the tensile strength of the flat sheet asymmetric membrane. Combination of methanol and n-hexane as quench media gave the best result than the other steps. This solvent exchange step influenced the morphology by producing thin skin layer and thus gives better gas separation performance than other steps

  3. [Experimental study of adhesion properties between membrane surface and humic acid during microfiltration].

    Science.gov (United States)

    Wang, Lei; Wang, Lei; Huang, Dan-Xi; Wang, Xu-Dong

    2014-08-01

    To further unravel the humic acid (HA) fouling mechanism during microfiltration under different conditions, such as pH, ionic strength, the concentration of calcium ions, atomic force microscopy (AFM) combined with self-made PVDF colloidal probe was applied to determine the relationship between the adhesion forces of membrane-HA or HA-HA and the flux decline of membrane. The results indicate adhesion forces were the main reason of membrane fouling. With the decrease of pH or increase of the ionic strength, due to the electrical neutralization caused by pH and electrical shielding effect of ionic strength, the adhesion forces of membrane-HA and HA-HA increased. Because of the comprehensive effect of "salt bridge" and electrical neutralization, there was a transition from increase to decrease for the adhesion forces of membrane-HA and HA-HA as the doses of calcium ions increased. In all cases, both of membrane-HA and HA-HA adhesion forces had the same variation tendency, which displayed a good correlation with the flux decline trends during fouling experiments, respectively, and provided certain theoretical support to further understand the formation mechanism of membrane fouling.

  4. Sustainable Antibiofouling Properties of Thin Film Composite Forward Osmosis Membrane with Rechargeable Silver Nanoparticles Loading.

    Science.gov (United States)

    Liu, Zhongyun; Hu, Yunxia

    2016-08-24

    Microbial attachment and biofilm formation on filtration membrane can greatly compromise its flux and separation efficiency. Here, a simple and facile approach has been developed to in situ generate silver nanoparticles (Ag NPs) on the thin film composite forward osmosis (TFC FO) membrane for sustainable antibiofouling performances. Mussel-inspired dopamine chemistry was applied to grow polydopamine coating on both surfaces of FO membranes, followed by the generation of Ag NPs upon a simple dip coating in silver nitrate aqueous solution. Furthermore, the Ag NPs deposited membranes had a long-term silver release profile with rechargability for multiple times upon their depletion, and exhibited strong sustainable bactericidal efficacy against Gram-negative bacteria and Gram-positive bacteria. The Ag NPs had a controllable effect on the membrane performances including the water flux and reverse salt flux in the FO test mode. Our practicable antibacterial strategy may apply to other types of filtration membranes with diverse material surfaces and may pave a new way to achieve the sustainable membrane antibiofouling performance on a large scale.

  5. Preparation and water desalination properties of POSS-polyamide nanocomposite reverse osmosis membranes

    KAUST Repository

    Duan, Jintang

    2015-01-01

    The application of nanotechnology to thin-film nanocomposites (TFN) is a new route to enhance membrane performance in water desalination. Here, the potential of polyhedral oligomeric silsesquioxane (POSS) as the nanofiller in polyamide (PA) reverse osmosis membranes was systematically investigated. Four POSS materials (P-8Phenyl, P-8NH3Cl, P-8NH2 and P-1NH2) were introduced into the selective layer by physical blending or chemical fixation during standard interfacial polymerization. Water flux and NaCl rejection were measured with 2000ppm NaCl solution under 15.5bar pressure, and SEM and TEM images of membrane selective layers were obtained. Membranes prepared without POSS showed water flux of 20.0±0.5L/m2·h and salt rejection of 98.0±0.2%. TFN membranes prepared with 0.4% (w/v) P-8Phenyl in the organic phase showed a 65% increase in water flux compared to the pristine PA membrane while maintaining high salt rejection. The selective layer of this membrane maintained the typical ridge-and-valley structure of aromatic PA. Results with P-8NH3Cl and P-8NH2 added to the organic phase were similar. TFN membranes prepared with monoamine P-1NH2 in the organic phase had poor water flux of 3.2L/m2·h, a smooth and more hydrophobic surface, and a much thicker (~400nm) selective layer. One of the four POSS compounds studied, P-8NH3Cl, is sufficiently soluble in water for incorporation into the selective layer via the aqueous phase. Membranes were prepared with P-8NH3Cl in the aqueous phase at varying reaction time, loading, and additive (triethylamine) concentration. With these parameters optimized, water flux increased to 35.4L/m2·h.

  6. Tetracycline Inhibits Propagation of Deoxyribonucleic Acid Replication and Alters Membrane Properties

    Science.gov (United States)

    Pato, Martin L.

    1977-01-01

    Tetracycline, at concentrations greater than required for inhibition of protein synthesis, rapidly and completely inhibits replication of deoxyribonucleic acid (DNA) in Escherichia coli and Bacillus subtilis. At these concentrations of tetracycline, synthesis of ribonucleic acid is not appreciably altered. In addition to inhibiting DNA replication, tetracycline causes alterations of the cytoplasmic membrane resulting in leakage of intracellular pools of nucleotides, amino acids, and the non-metabolizable sugar analogue, thiomethylgalactoside. As DNA is synthesized at a site on the membrane, alterations of membrane structure by tetracycline may be responsible for the observed inhibition of DNA replication. PMID:403855

  7. PREPARATION AND PROPERTIES OF SPAES-TiO_2 HYBRID MEMBRANES FOR DIRECT METHANOL FUEL CELL

    Institute of Scientific and Technical Information of China (English)

    刘惠玲

    2009-01-01

    Sulfonated poly(arylene ether sulfone)(SPAES) copolymer with degree of sulfonation of 1.0 was synthesized and characterized.A series of SPAES-TiO_2 hybrid membranes with various contents of nano-sized TiO_2 particles were prepared and characterized through sol-gel reactions.Scanning electron microscopy(SEM) images indicated the TiO_2 particles were well dispersed within polymer matrix.These composite membranes were evaluated for proton exchange membranes(PEMs) in direct methanol fuel cell(DMFC).These mem...

  8. Study of polyvinyl alcohol nanofibrous membrane by electrospinning as a magnetic nanoparticle delivery approach

    Science.gov (United States)

    Ger, Tzong-Rong; Huang, Hao-Ting; Huang, Chen-Yu; Hu, Keng-Shiang; Lai, Jun-Yang; Chen, Jiann-Yeu; Lai, Mei-Feng

    2014-05-01

    Electrospinning technique was used to fabricate polyvinyl alcohol (PVA)-based magnetic biodegradable nanofibers. PVA solution was mixed with ferrofluid or magnetic nanoparticles (MNPs) powder and formed two individual nanofibrous membranes (PVA/ferrofluid and PVA/MNPs powder) by electrospinning. The surface morphology of the nanofibrous membrane was characterized by scanning electron microscopy and the magnetic properties were measured by vibrating sample magnetometer. Macrophages (RAW 264.7) were co-cultured with the nanofibrous membranes for 12, 24, and 48 h and exhibited good cell viability (>95%). Results showed that the PVA fibers would be degraded and the embedded Fe3O4 nanoparticles would be released and delivered to cells.

  9. Unique proteomic signatures distinguish macrophages and dendritic cells.

    Directory of Open Access Journals (Sweden)

    Lev Becker

    Full Text Available Monocytes differentiate into heterogeneous populations of tissue macrophages and dendritic cells (DCs that regulate inflammation and immunity. Identifying specific populations of myeloid cells in vivo is problematic, however, because only a limited number of proteins have been used to assign cellular phenotype. Using mass spectrometry and bone marrow-derived cells, we provided a global view of the proteomes of M-CSF-derived macrophages, classically and alternatively activated macrophages, and GM-CSF-derived DCs. Remarkably, the expression levels of half the plasma membrane proteins differed significantly in the various populations of cells derived in vitro. Moreover, the membrane proteomes of macrophages and DCs were more distinct than those of classically and alternatively activated macrophages. Hierarchical cluster and dual statistical analyses demonstrated that each cell type exhibited a robust proteomic signature that was unique. To interrogate the phenotype of myeloid cells in vivo, we subjected elicited peritoneal macrophages harvested from wild-type and GM-CSF-deficient mice to mass spectrometric and functional analysis. Unexpectedly, we found that peritoneal macrophages exhibited many features of the DCs generated in vitro. These findings demonstrate that global analysis of the membrane proteome can help define immune cell phenotypes in vivo.

  10. Preparation and Bioactivity Properties of a Novel Composite Membrane of Fructose Mediated β-Tricalcium Pyrophosphate/(Polyethylene Glycol/Chitosan) for Guided Tissue Regeneration

    OpenAIRE

    Jian-Wen Wang; Min-Hsiung Hon; Yi-Ming Kuo; Mei-Hui Chung

    2015-01-01

    A novel composite membrane of β-tricalcium pyrophosphate (β-TCP) and fructose- (F-) mediated chitosan/poly(ethylene glycol) (CS/PEG) was prepared by thermally induced phase separation technique. The prepared composite membranes were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical property, swelling, degradation, and cytotoxicity of the composite membranes were evaluated in vitro with respect to its potential for use as biodegradable guided ti...

  11. Membrane cholesterol removal changes mechanical properties of cells and induces secretion of a specific pool of lysosomes.

    Directory of Open Access Journals (Sweden)

    Barbara Hissa

    Full Text Available In a previous study we had shown that membrane cholesterol removal induced unregulated lysosomal exocytosis events leading to the depletion of lysosomes located at cell periphery. However, the mechanism by which cholesterol triggered these exocytic events had not been uncovered. In this study we investigated the importance of cholesterol in controlling mechanical properties of cells and its connection with lysosomal exocytosis. Tether extraction with optical tweezers and defocusing microscopy were used to assess cell dynamics in mouse fibroblasts. These assays showed that bending modulus and surface tension increased when cholesterol was extracted from fibroblasts plasma membrane upon incubation with MβCD, and that the membrane-cytoskeleton relaxation time increased at the beginning of MβCD treatment and decreased at the end. We also showed for the first time that the amplitude of membrane-cytoskeleton fluctuation decreased during cholesterol sequestration, showing that these cells become stiffer. These changes in membrane dynamics involved not only rearrangement of the actin cytoskeleton, but also de novo actin polymerization and stress fiber formation through Rho activation. We found that these mechanical changes observed after cholesterol sequestration were involved in triggering lysosomal exocytosis. Exocytosis occurred even in the absence of the lysosomal calcium sensor synaptotagmin VII, and was associated with actin polymerization induced by MβCD. Notably, exocytosis triggered by cholesterol removal led to the secretion of a unique population of lysosomes, different from the pool mobilized by actin depolymerizing drugs such as Latrunculin-A. These data support the existence of at least two different pools of lysosomes with different exocytosis dynamics, one of which is directly mobilized for plasma membrane fusion after cholesterol removal.

  12. Reverse osmosis filtration for space mission wastewater: membrane properties and operating conditions

    Science.gov (United States)

    Lee, S.; Lueptow, R. M.

    2001-01-01

    Reverse osmosis (RO) is a compact process that has potential for the removal of ionic and organic pollutants for recycling space mission wastewater. Seven candidate RO membranes were compared using a batch stirred cell to determine the membrane flux and the solute rejection for synthetic space mission wastewaters. Even though the urea molecule is larger than ions such as Na+, Cl-, and NH4+, the rejection of urea is lower. This indicates that the chemical interaction between solutes and the membrane is more important than the size exclusion effect. Low pressure reverse osmosis (LPRO) membranes appear to be most desirable because of their high permeate flux and rejection. Solute rejection is dependent on the shear rate, indicating the importance of concentration polarization. A simple transport model based on the solution-diffusion model incorporating concentration polarization is used to interpret the experimental results and predict rejection over a range of operating conditions. Grant numbers: NAG 9-1053.

  13. Preparation of Polysulfone-supported Phosphoramidic Acid Type Chelate Membrane and Its Sorption Properties for Ag+

    Institute of Scientific and Technical Information of China (English)

    WANG Bing; CUI Yong-fang; DU Qi-yun; PEI Guang-ling

    2002-01-01

    A blending chelate filter membrane with high chelate capacity for Ag+ has been prepared by blending of phosphoramidic acid resin and polysulfone. The major parameters influencing structure of the chelate filter membranes such as the blending ratio, phosphoramidic acid resin grain size and temperature of casting solution have been studied. The relationship among the chelate amount of Ag+, pH value, Ag+ concentration and phosphoramidic acid resin grain diameter were examined. The chelate filter membrane had a capacity of1438μg/cm2 for Ag+ under appropriate conditions.Sorption isotherm of Ag + could be expressed with the Freundlich sorption model. The dynamic chelate experiments proved that the sorption and desorption of membranes could be realized simultaneously for Ag+.

  14. Effect of radiation on properties of ENR/PVC/SiO2 membrane

    Science.gov (United States)

    Ismail, Nur Farahein Hadina; Abdullah, Ibrahim; Daik, Rusli; Ahmad, Ishak; Jamil, Suzereen; Lazim, Mohammad Azwan Mat; Othaman, Rizafizah

    2015-09-01

    In this study epoxidised natural rubber (ENR)/polyvinyl chloride (PVC) matrix was prepared by melt blending. The matrix was swelled in THF and silica as a filler was introduced to the solution to generate pore formation. The ENR/PVC/10 % SiO2 membrane was prepared using a casting knife technique. The membrane was irradiated using 2 MeV electron beam accelerator at a dose range of 10-100 kGy. The effect of electron beam irradiation of the membrane was studied by undergo characterization of Scanning electron microscope (SEM) and Fourier transform infra red (FTIR). Morphological studies showed that pores generated in ENR/PVC/10 % SiO2 membrane increased with the dosage of radiation. While FTIR analysis showed the presence of peak of Si-O-Si asymmetric stretching at 834 cm-1. There are no significant changes in the functional group before and after radiation.

  15. Reverse osmosis filtration for space mission wastewater: membrane properties and operating conditions

    Science.gov (United States)

    Lee, S.; Lueptow, R. M.

    2001-01-01

    Reverse osmosis (RO) is a compact process that has potential for the removal of ionic and organic pollutants for recycling space mission wastewater. Seven candidate RO membranes were compared using a batch stirred cell to determine the membrane flux and the solute rejection for synthetic space mission wastewaters. Even though the urea molecule is larger than ions such as Na+, Cl-, and NH4+, the rejection of urea is lower. This indicates that the chemical interaction between solutes and the membrane is more important than the size exclusion effect. Low pressure reverse osmosis (LPRO) membranes appear to be most desirable because of their high permeate flux and rejection. Solute rejection is dependent on the shear rate, indicating the importance of concentration polarization. A simple transport model based on the solution-diffusion model incorporating concentration polarization is used to interpret the experimental results and predict rejection over a range of operating conditions. Grant numbers: NAG 9-1053.

  16. X-ray structure, thermodynamics, elastic properties and MD simulations of cardiolipin/dimyristoylphosphatidylcholine mixed membranes

    DEFF Research Database (Denmark)

    Boscia, Alexander L.; Treece, Bradley W.; Mohammadyani, Dariush

    2014-01-01

    Cardiolipins (CLs) are important biologically for their unique role in biomembranes that couple phosphorylation and electron transport like bacterial plasma membranes, chromatophores, chloroplasts and mitochondria. CLs are often tightly coupled to proteins involved in oxidative phosphorylation. T...

  17. Effect of radiation on properties of ENR/PVC/SiO{sub 2} membrane

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Nur Farahein Hadina; Abdullah, Ibrahim; Daik, Rusli; Ahmad, Ishak; Jamil, Suzereen; Lazim, Mohammad Azwan Mat; Othaman, Rizafizah [School of Chemical Sciences and Food Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan. Malaysia (Malaysia)

    2015-09-25

    In this study epoxidised natural rubber (ENR)/polyvinyl chloride (PVC) matrix was prepared by melt blending. The matrix was swelled in THF and silica as a filler was introduced to the solution to generate pore formation. The ENR/PVC/10 % SiO{sub 2} membrane was prepared using a casting knife technique. The membrane was irradiated using 2 MeV electron beam accelerator at a dose range of 10-100 kGy. The effect of electron beam irradiation of the membrane was studied by undergo characterization of Scanning electron microscope (SEM) and Fourier transform infra red (FTIR). Morphological studies showed that pores generated in ENR/PVC/10 % SiO{sub 2} membrane increased with the dosage of radiation. While FTIR analysis showed the presence of peak of Si-O-Si asymmetric stretching at 834 cm{sup −1}. There are no significant changes in the functional group before and after radiation.

  18. Antigenic Properties of HpaA and Omp18, Two Outer Membrane Proteins of Helicobacter pylori

    OpenAIRE

    Voland, Petra; Hafsi, Nadia; Zeitner, Marco; Laforsch, Stephanie; Wagner, Hermann; Prinz, Christian

    2003-01-01

    Outer membrane proteins (OMPs) are incorporated into the outer plasma membrane of Helicobacter pylori and are important for, e.g., ion transport, adherence, structural and osmotic stability, and bacterial virulence but may also be antigenic due to their surface exposure. Previous proteome-based approaches with H. pylori lysates determined a strong serological reaction towards two H. pylori OMPs, HpaA (TIGR HP0797) and Omp18 (TIGR HP1125). PCR was used to detect DNA encoding the two proteins, ...

  19. Interactions between inflammatory mediators in expression of antitumor cytostatic activity of macrophages

    NARCIS (Netherlands)

    I.L. Bonta; S. Ben-Efraim

    1990-01-01

    markdownabstractAbstract Antitumor properties and participation in inflammatory events are important characteristics of activated macrophages. We show here that both antitumor cytostatic function of macrophages and participation of these cells at inflammatory sites are controlled by two main group

  20. The macrophage in HIV-1 infection: From activation to deactivation?

    Directory of Open Access Journals (Sweden)

    Varin Audrey

    2010-04-01

    Full Text Available Abstract Macrophages play a crucial role in innate and adaptative immunity in response to microorganisms and are an important cellular target during HIV-1 infection. Recently, the heterogeneity of the macrophage population has been highlighted. Classically activated or type 1 macrophages (M1 induced in particular by IFN-γ display a pro-inflammatory profile. The alternatively activated or type 2 macrophages (M2 induced by Th-2 cytokines, such as IL-4 and IL-13 express anti-inflammatory and tissue repair properties. Finally IL-10 has been described as the prototypic cytokine involved in the deactivation of macrophages (dM. Since the capacity of macrophages to support productive HIV-1 infection is known to be modulated by cytokines, this review shows how modulation of macrophage activation by cytokines impacts the capacity to support productive HIV-1 infection. Based on the activation status of macrophages we propose a model starting with M1 classically activated macrophages with accelerated formation of viral reservoirs in a context of Th1 and proinflammatory cytokines. Then IL-4/IL-13 alternatively activated M2 macrophages will enter into the game that will stop the expansion of the HIV-1 reservoir. Finally IL-10 deactivation of macrophages will lead to immune failure observed at the very late stages of the HIV-1 disease.

  1. The macrophage in HIV-1 infection: from activation to deactivation?

    Science.gov (United States)

    Herbein, Georges; Varin, Audrey

    2010-04-09

    Macrophages play a crucial role in innate and adaptative immunity in response to microorganisms and are an important cellular target during HIV-1 infection. Recently, the heterogeneity of the macrophage population has been highlighted. Classically activated or type 1 macrophages (M1) induced in particular by IFN-gamma display a pro-inflammatory profile. The alternatively activated or type 2 macrophages (M2) induced by Th-2 cytokines, such as IL-4 and IL-13 express anti-inflammatory and tissue repair properties. Finally IL-10 has been described as the prototypic cytokine involved in the deactivation of macrophages (dM). Since the capacity of macrophages to support productive HIV-1 infection is known to be modulated by cytokines, this review shows how modulation of macrophage activation by cytokines impacts the capacity to support productive HIV-1 infection. Based on the activation status of macrophages we propose a model starting with M1 classically activated macrophages with accelerated formation of viral reservoirs in a context of Th1 and proinflammatory cytokines. Then IL-4/IL-13 alternatively activated M2 macrophages will enter into the game that will stop the expansion of the HIV-1 reservoir. Finally IL-10 deactivation of macrophages will lead to immune failure observed at the very late stages of the HIV-1 disease.

  2. Recovery Properties of Polysulfone Hollow Fiber Chelating Membrane Modified with Thiourea for Mercury ( Ⅱ )

    Institute of Scientific and Technical Information of China (English)

    WANG Bing; XIAO Feng; HUANG Lei

    2007-01-01

    The adsorption isotherms of the polysulfone hollow fiber chelating membrane modified with thiourea as chelating groups for Hg2+ were determined. The effects of mobile phase conditions and the operating parameters on removal performance of the chelating membrane for Hg2+ were also investigated. The recovery of Hg2+ decreased at low pH and the optimum range of pH was from 6 to 7. The feed concentration effected on recovery of Hg2+ at the specified loading amount of Hg2+. The Hg2+ could be removed from different concentration feed solution by chelating membrane. The increase of feed flow rate led to slight decrease of recovery of Hg2+ at the specified loading amount of Hg2+. The chelating membrane could be operated at height feed flow rate and a large-scale removal of Hg2+ could be realized. With the increase of load amount, Hg2+ recovery decreased, but the saturation degree of chelating membrane increased. According to required recovery of Hg2+ and the saturation degree of chelating membrane, the optimum loading amount of Hg2+ should be selected in the actual removal of Hg2+.

  3. Synaptotoxicity of Alzheimer beta amyloid can be explained by its membrane perforating property.

    Directory of Open Access Journals (Sweden)

    Fernando J Sepulveda

    Full Text Available The mechanisms that induce Alzheimer's disease (AD are largely unknown thereby deterring the development of disease-modifying therapies. One working hypothesis of AD is that Abeta excess disrupts membranes causing pore formation leading to alterations in ionic homeostasis. However, it is largely unknown if this also occurs in native brain neuronal membranes. Here we show that similar to other pore forming toxins, Abeta induces perforation of neuronal membranes causing an increase in membrane conductance, intracellular calcium and ethidium bromide influx. These data reveal that the target of Abeta is not another membrane protein, but that Abeta itself is the cellular target thereby explaining the failure of current therapies to interfere with the course of AD. We propose that this novel effect of Abeta could be useful for the discovery of anti AD drugs capable of blocking these "Abeta perforates". In addition, we demonstrate that peptides that block Abeta neurotoxicity also slow or prevent the membrane-perforating action of Abeta.

  4. Influence of preparation procedure and ferric oxide nanoparticles addition on transport properties of homogeneous cation-exchange SPPO/SPVC membrane

    Indian Academy of Sciences (India)

    FARHAD HEIDARY; ALI NEMATI KHARAT; ALIREZA KHODABAKHSHI; SAYED SIAVASH MADAENI

    2017-08-01

    Homogeneous cation-exchange membranes were prepared through evaporation and phase inversion methodsusing sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) and sulfonated polyvinylchloride as binders. The effectof polymers blend’s ratio and preparation method on structure and electrochemical properties of the prepared membraneswere evaluated. The microstructures of the membranes were investigated by scanning electron microscopy (SEM) andthe sulfonation of polyvinylchloride was confirmed by elemental analyses. Moreover, the membranes performance wasevaluated by ion-exchange capacity (IEC), fixed ion concentration, membrane potential, transport number, permselectivity,areal resistance, ionic permeability, flux of ions, current efficiency, membrane oxidative stability, mechanical properties andwater content tests. The results indicated that IEC and water content were affected by the SPPO content and microstructuresof the membranes. The results showed increased efficiency and suitable electrochemical properties for membranes preparedby the evaporation method in comparison with others. Also, Fe$_2$O$_3$ nanoparticles were synthesized at room temperature by a simple sonochemical reaction between ferric chloride and NaOH. The results revealed that the addition of different amounts of Fe$_2$O$_3$ nanoparticles to the polymeric matrix could affect the hydrophilicity and transport properties of ion-exchange membranes.

  5. The dependence of the electrochemical properties of perfluorosulfonic acid membrane/water systems on repeat unit structure

    Science.gov (United States)

    Kim, Young Gyun; Bae, Young Chan

    2009-07-01

    We developed a molecular thermodynamic framework to describe the dependence of the electrochemical properties of a perfluorosulfonic acid (PFSA) membrane/water system on the polymer structure. To better understand the behavior of the polymer membrane/water system, we developed a lattice model based on lattice cluster theory. We performed hypothetical calculations for a variety of repeat unit structures. We also investigated the correlation between the interaction energy and extending or reducing the chain length of the polymer repeat unit using COMPASS force fields. Our results indicate that the ionic conductivity of the nonpolar CF2CF2 group in the main chain varies with the length of the chain. In addition, the ionic conductivity of different CF2CF2 group chain lengths fluctuates according to hydration level. When OCF2CF3CF groups are substituted at 0 and 1, the predictions of the PFSA membrane agreed well with the experimental data from a Dow membrane. To obtain good ionic conductivity at a high vapor equilibrated hydration level, the nonpolar group in the polymer repeat unit and the substituted group chain connecting the nonpolar group length should both be short, and the substituted group chain connected with the sulfonic group should be long.

  6. Self-assembling properties of porphyrinic photosensitizers and their effect on membrane interactions probed by NMR spectroscopy.

    Science.gov (United States)

    Vermathen, Martina; Marzorati, Mattia; Bigler, Peter

    2013-06-13

    Aggregation and membrane penetration of porphyrinic photosensitizers play crucial roles for their efficacy in photodynamic therapy. The current study was aimed at comparing the aggregation behavior of selected photosensitizers and correlating it with membrane affinity. Self-assembling properties of 15 amphiphilic free-base chlorin and porphyrin derivatives bearing carboxylate substituents were studied in phosphate buffered saline (PBS) by (1)H NMR spectroscopy, making use of ring current induced aggregation shifts. All compounds exhibited aggregation in PBS to a different degree with dimers or oligomers showing slow aggregate growth over time. Aggregate structures were proposed on the basis of temperature dependent chemical shift changes. All chlorin compounds revealed similar aggregation maps with their hydrophobic sides overlapping and their carboxylate groups protruding toward the exterior. In contrast, for the porphyrin compounds, the carboxylate groups were located in overlapping regions. Membrane interactions were probed using 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer vesicles and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) micelles as models. The chlorin derivatives had higher membrane affinity and were all monomerized by DHPC micelles as opposed to the porphyrin compounds. The observed differences were attributed to the different aggregate structures proposed for the chlorin and porphyrin derivatives. Free accessibility of the carboxylate groups seemed to promote initial surface interaction with phospholipid bilayers and micelles.

  7. Particulate Systems for Targeting of Macrophages: Basic and Therapeutic Concepts

    DEFF Research Database (Denmark)

    Moghimi, Seyed Moien; Parhamifar, Ladan; Ahmadvand, Davoud;

    2012-01-01

    and intracellular drug release processes can be optimized through modifications of the drug carrier physicochemical properties, which include hydrodynamic size, shape, composition and surface characteristics. Through such modifications together with understanding of macrophage cell biology, targeting may be aimed...... at a particular subset of macrophages. Advances in basic and therapeutic concepts of particulate targeting of macrophages and related nanotechnology approaches for immune cell modifications are discussed.Copyright © 2012 S. Karger AG, Basel...

  8. Preparation and investigation of the gas separation properties of polyurethane-TiO{sub 2} nanocomposite membranes

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi, Morteza; Afarani, Hajar Taheri; Tarashi, Zohreh [Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)

    2015-01-15

    The effect of TiO{sub 2} nanoparticles on the gas separation properties of polyurethane has been investigated. Polyurethane was synthesized using hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) as hard segment and poly(tetramethylene glycol) (PTMG, 2,000 g/mol) as soft segment. The synthesized polymer was in a 1 : 2 : 1 molar ratio of polyol : diisocyanate : chain extender through bulk two-step polymerization. PU membranes were prepared by thermal phase inversion method. Scanning electron microscopy (SEM), X-ray diffraction and Fourier Transform Infrared (FTIR) analyses characterized the prepared membranes. FTIR and SEM results indicate the good interaction between particles and polymer matrix and also the nanoscale dispersion of TiO{sub 2} particles in polymer matrix. Gas permeation properties of PU-TiO{sub 2} nanocomposite membranes with TiO{sub 2} contents up to 30 wt% were studied for N{sub 2}, O{sub 2}, CH{sub 4} and CO{sub 2} gases at 10 bar and 25 .deg. C. Results suggest a decrease in permeability of studied gases and increase in gas selectivities as TiO{sub 2} content increases.

  9. Architecture and regulation of the HIV-1 assembly and holding compartment in macrophages.

    Science.gov (United States)

    Welsch, Sonja; Groot, Fedde; Kräusslich, Hans-Georg; Keppler, Oliver T; Sattentau, Quentin J

    2011-08-01

    Productive infection of macrophages is central to HIV-1 pathogenesis. Newly formed virions bud into a tubular membranous compartment that is contiguous with the plasma membrane. However, little is known about the structure of this compartment and its potential regulation by infection. Here we characterized this compartment in macrophages using electron tomography and electron microscopy with stereology. We found an intricate, interconnected membrane network that constitutes a preexisting physiologic structure in macrophages but which expands in size upon HIV-1 infection. Membranes required for this expansion were apparently derived from preexisting pools of plasma membrane. Physical connections between this compartment and the extracellular milieu were frequently made by tube-like structures of insufficient diameter for virion passage. We conclude that HIV-1 induces the expansion of a complex membranous labyrinth in macrophages in which the virus buds and can be retained, with potential consequences for transmission and immune evasion.

  10. Architecture and Regulation of the HIV-1 Assembly and Holding Compartment in Macrophages

    Science.gov (United States)

    Welsch, Sonja; Groot, Fedde; Kräusslich, Hans-Georg; Keppler, Oliver T.; Sattentau, Quentin J.

    2011-01-01

    Productive infection of macrophages is central to HIV-1 pathogenesis. Newly formed virions bud into a tubular membranous compartment that is contiguous with the plasma membrane. However, little is known about the structure of this compartment and its potential regulation by infection. Here we characterized this compartment in macrophages using electron tomography and electron microscopy with stereology. We found an intricate, interconnected membrane network that constitutes a preexisting physiologic structure in macrophages but which expands in size upon HIV-1 infection. Membranes required for this expansion were apparently derived from preexisting pools of plasma membrane. Physical connections between this compartment and the extracellular milieu were frequently made by tube-like structures of insufficient diameter for virion passage. We conclude that HIV-1 induces the expansion of a complex membranous labyrinth in macrophages in which the virus buds and can be retained, with potential consequences for transmission and immune evasion. PMID:21613397

  11. Electrode-analytical properties of polyvinylchloride membranes based on triple metal-polymeric complexes

    Directory of Open Access Journals (Sweden)

    Katerina V. Matorina

    2015-10-01

    Full Text Available The influence of the nature of the electrode-active substances (EAS, the composition of the external and internal solutions on the formation of the analytical signal of polyvinylchloride (PVC membranes based on associates and triple metal-polymeric complexes (TMPC was established. Dehumidification of synthesized membranes increases with the content of polyvinylpyrrolidone (PVP. The value of the swelling degree is more than two times greater for membranes, which contain as EAS TMPC, relative to membranes based on associates. The value of water absorption of membranes is determined by the nature of EAS. They formed a series of increasing of the swelling degree such as associate < background membrane < TMPC. Swelling of the background membrane is explained by the physical sorption of water molecules on the surface of plasticized membrane. Hydration of PVP macromolecules varies with the introduction of metal ions, macromolecules unit undergoes a conformational transition. PVP macromolecules form tunnels or cavities where complex particles distributed and additional water accumulated through the second coordination layer. Constructed sensors based on TMPC have slope of electrode function equal to 25 mV/pC. Linear dependence of potential on the polymer concentration is observed in the range of 5–7 pC units. Sensors based on associates have slope of the electrode function of 20–25 mV/pC that can be varied depending on the nature of the EAS. Working range is 4–8 pC. Response time of sensor is less than 1 min. The optimal time for conditioning of the synthesized PVC membrane is 24 hours. Potentiometric sensors have been developed for the determination of residual amounts of low molecular PVP which is a food additive E 1201 commonly used for thickening, stabilizing and clarifying of food products. The content of PVP was determined in real objects (apple juice, beer, red wine and cognac with using the polyvinylpyrrolidone sensors (Sr < 0.08. The

  12. Membrane viewpoint on black holes: Properties and evolution of the stretched horizon

    Science.gov (United States)

    Price, Richard H.; Thorne, Kip S.

    1986-02-01

    This paper derives the ``membrane formalism'' for black holes. The membrane formalism rewrites the standard mathematical theory of black holes in a language and notation which (we hope) will facilitate research in black-hole astrophysics: The horizon of a black hole is replaced by a surrogate ``stretched horizon,'' which is viewed as a 2-dimensional membrane that resides in 3-dimensional space and evolves in response to driving forces from the external universe. This membrane, following ideas of Damour and Znajek, is regarded as made from a 2-dimensional viscous fluid that is electrically charged and electrically conducting and has finite entropy and temperature, but cannot conduct heat. The interaction of the stretched horizon with the external universe is described in terms of familiar laws for the horizon's fluid, e.g., the Navier-Stokes equation, Ohm's law, a tidal-force equation, and the first and second laws of thermodynamics. Because these laws have familiar forms, they are likely to help astrophysicists understand intuitively and compute quantitatively the behaviors of black holes in complex external environments. Previous papers have developed and elucidated electromagnetic aspects of the membrane formalism for time-independent rotating holes. This paper derives the full formalism for dynamical, evolving holes, with one exception: In its present form the formalism is not equipped to handle horizon caustics, where new generators attach themselves to the horizon.

  13. Radiation-induced graft polymerization of acrylamide: Reverse osmosis properties of polyethylene-g-poly(acrylamide) membrane

    Science.gov (United States)

    Dessouki, Ahmed M.; Hegazy, El-Sayed A.; El-Assy, Nasef B.; El-Boohy, Hussein A.

    A study has been made of some properties of the graft copolymer obtained by direct radiation grafting of acrylamide (AAm) onto low density polyethylene (LDPE) films. The swelling behaviour was investigated for the grafted and alkali-treated graft copolymer and it was found that this depends mainly on the amount of hydrophilic groups and also on the type of electrolytes (K- or Nasalts). salts). Some other properties of the graft copolymer films such as dimensional change wet and dry, electrical conductivity, and mechanical properties were studied. A trial has been made of such membrane for reverse osmosis desalination of saline water. The effect of operating time, degree of grafting, applied pressure and feed concentration on the water flux and salt rejection was determined.

  14. Properties and degradation of the gasket component of a proton exchange membrane fuel cell--a review.

    Science.gov (United States)

    Basuli, Utpal; Jose, Jobin; Lee, Ran Hee; Yoo, Yong Hwan; Jeong, Kwang-Un; Ahn, Jou-Hyeon; Nah, Changwoon

    2012-10-01

    Proton exchange membrane (PEM) fuel cell stack requires gaskets and seals in each cell to keep the reactant gases within their respective regions. Gasket performance is integral to the successful long-term operation of a fuel cell stack. This review focuses on properties, performance and degradation mechanisms of the different polymer gasket materials used in PEM fuel cell under normal operating conditions. The different degradation mechanisms and their corresponding representative mitigation strategies are also presented here. Summary of various properties of elastomers and their advantages and disadvantages in fuel cell'environment are presented. By considering the level of chemical degradation, mechanical properties and cost effectiveness, it can be proposed that EPDM is one of the best choices for gasket material in PEM fuel cell. Finally, the challenges that remain in using rubber component as in PEM fuel cell, as well as the prospects for exploiting them in the future are discussed.

  15. Membrane fluidity and the surface properties of the lipid bilayer: ESR experiment and computer simulation.

    Science.gov (United States)

    Man, Dariusz; Olchawa, Ryszard; Kubica, Krystian

    2010-09-01

    Penetration of the liposome membranes formed in the gel phase from DPPC (DPPC liposomes) and in the liquid-crystalline phase from egg yolk lecithin (EYL liposomes) by the TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and 16 DOXYL (2-ethyl-2-(15-methoxy-oxopentadecyl)-4,4-dimethyl-3-oxazolidinyloxy) spin probes has been investigated. The penetration process was followed by 120 hours at 24(0)C, using the electron spin resonance (ESR) method. The investigation of the kinetics of the TEMPO probe building into the membranes of both types of liposomes revealed differences appearing 30 minutes after the start of the experiment. The number of TEMPO particles built into the EYL liposome membranes began to clearly rise, aiming asymptotically to a constant value after about 100 minutes, whereas the number of the TEMPO particles built into the DPPC liposome membranes was almost constant in time. The interpretation of the obtained experimental results was enriched with those of computer simulation, following the behavior of the polar heads (dipoles) of the lipid particles forming a lipid layer due to the change in the value of the model parameter, k, determining the mobility of the dipoles. The possibility of the formation of an irregular ordering of the polar part of lipid membranes was proved, which leads to the appearance of spaces filled with of water for k > 0.4. The appearance of these defects enables the penetration of the bilayer by the TEMPO particles. The limited mobility of lipid polar heads (k < 0.2) prevents the appearance of such areas facilitating the penetration of the lipid membrane by alien particles in the gel phase.

  16. Synapse-associated protein 97 regulates the membrane properties of fast-spiking parvalbumin interneurons in the visual cortex.

    Science.gov (United States)

    Akgul, Gulcan; Wollmuth, Lonnie P

    2013-07-31

    Fast-spiking parvalbumin (PV)-positive interneurons in layers 2/3 of the visual cortex regulate gain control and tuning of visual processing. Synapse-associated protein 97 (SAP97) belongs to a family of proteins that have been implicated in regulating glutamatergic synaptic transmission at pyramidal-to-pyramidal connections in the nervous system. For PV interneurons in mouse visual cortex, the expression of SAP97 is developmentally regulated, being expressed in almost all juvenile but only a fraction, ~40%, of adult PV interneurons. Using whole-cell patch-clamping, single-cell RT-PCR to assay endogenous expression of SAP97 and exogenous expression of SAP97, we investigated the functional significance of SAP97 in PV interneurons in layers 2/3 of the visual cortex. PV interneurons expressing SAP97, either endogenously or via exogenous expression, showed distinct membrane properties from those not expressing SAP97. This included an overall decrease in membrane excitability, as indexed by a decrease in membrane resistance and an increase in the stimulus threshold for the first action potential firing. Additionally, SAP97-expressing PV interneurons fired action potentials more frequently and, at moderate stimulus intensities, showed irregular or stuttering firing patterns. Furthermore, SAP97-expressing PV interneurons showed increased glutamatergic input and more extensive dendritic branching when compared with non-expressing PV interneurons. These differences in membrane and synaptic properties would significantly alter how PV interneurons expressing SAP97 compared with those not expressing SAP97 would function in local networks. Thus, our results indicate that the scaffolding protein SAP97 is a critical molecular factor regulating the input-output relationships of cortical PV interneurons.

  17. Pair collisions of fluid-filled elastic capsules in shear flow: Effects of membrane properties and polymer additives

    Science.gov (United States)

    Pranay, Pratik; Anekal, Samartha G.; Hernandez-Ortiz, Juan P.; Graham, Michael D.

    2010-12-01

    The dynamics and pair collisions of fluid-filled elastic capsules during Couette flow in Newtonian fluids and dilute solutions of high-molecular weight (drag-reducing) polymers are investigated via direct simulation. Capsule membranes are modeled using either a neo-Hookean constitutive model or a model introduced by Skalak et al. ["Strain energy function of red blood-cell membranes," Biophys. J. 13, 245 (1973)], which includes an energy penalty for area changes. This model was developed to capture the elastic properties of red blood cells. Polymer molecules are modeled as bead-spring trimers with finitely extensible nonlinearly elastic springs; parameters were chosen to loosely approximate 4000 kDa poly(ethylene oxide). Simulations are performed with a novel Stokes flow formulation of the immersed boundary method for the capsules, combined with Brownian dynamics for the polymer molecules. The results for isolated capsules in shear indicate that at the very low concentrations considered here, polymers have a little effect on the capsule shape. In the case of pair collisions, the effect of polymer is strongly dependent on the elastic properties of the capsules' membranes. For neo-Hookean capsules or for Skalak capsules with only a small penalty for area change, the net displacement in the gradient direction after collision is virtually unaffected by the polymer. For Skalak capsules with a large penalty for area change, polymers substantially decrease the net displacement when compared to the Newtonian case and the effect is enhanced upon increasing the polymer concentration. The differences between the polymer effects in the various cases are associated with the extensional flow generated in the region between the capsules as they leave the collision. The extension rate is highest when there is a strong resistance to a change in the membrane area and is substantially decreased in the presence of polymer.

  18. Mediterranean-style diet effect on the structural properties of the erythrocyte cell membrane of hypertensive patients: the Prevencion con Dieta Mediterranea Study.

    Science.gov (United States)

    Barceló, Francisca; Perona, Javier S; Prades, Jesús; Funari, Sérgio S; Gomez-Gracia, Enrique; Conde, Manuel; Estruch, Ramon; Ruiz-Gutiérrez, Valentina

    2009-11-01

    A currently ongoing randomized trial has revealed that the Mediterranean diet, rich in virgin olive oil or nuts, reduces systolic blood pressure in high-risk cardiovascular patients. Here, we present a structural substudy to assess the effect of a Mediterranean-style diet supplemented with nuts or virgin olive oil on erythrocyte membrane properties in 36 hypertensive participants after 1 year of intervention. Erythrocyte membrane lipid composition, structural properties of reconstituted erythrocyte membranes, and serum concentrations of inflammatory markers are reported. After the intervention, the membrane cholesterol content decreased, whereas that of phospholipids increased in all of the dietary groups; the diminishing cholesterol:phospholipid ratio could be associated with an increase in the membrane fluidity. Moreover, reconstituted membranes from the nuts and virgin olive oil groups showed a higher propensity to form a nonlamellar inverted hexagonal phase structure that was related to an increase in phosphatidylethanolamine lipid class. These data suggest that the Mediterranean-style diet affects the lipid metabolism that is altered in hypertensive patients, influencing the structural membrane properties. The erythrocyte membrane modulation described provides insight in the structural bases underlying the beneficial effect of a Mediterranean-style diet in hypertensive subjects.

  19. Impact of anti-tacking agents on properties of gas-entrapped membrane and effervescent floating tablets.

    Science.gov (United States)

    Kriangkrai, Worawut; Puttipipatkhachorn, Satit; Sriamornsak, Pornsak; Pongjanyakul, Thaned; Sungthongjeen, Srisagul

    2014-12-01

    Tackiness caused by the gas-entrapped membrane (Eudragit(®)RL 30D) was usually observed during storage of the effervescent floating tablets, leading to failure in floatation and sustained release. In this work, common anti-tacking agents (glyceryl monostearate (GMS) and talc) were used to solve this tackiness problem. The impact of anti-tacking agent on the properties of free films and corresponding floating tablets was investigated. GMS was more effective than talc in reducing tackiness of the film. Addition and increasing amount of anti-tacking agents lowered the film mechanical strength, but the coating films were still strong and flexible enough to resist the generated gas pressure inside the floating tablet. Wettability and water vapor permeability of the film decreased with increasing level of anti-tacking agents as a result of their hydrophobicity. No interaction between anti-tacking agents and polymer was observed as confirmed by Fourier transform infrared spectroscopy, powder X-ray diffractometry, and differential scanning calorimetry studies. Increasing amount of anti-tacking agents decreased time to float and tended to retard drug release of the floating tablets. Floating properties and drug release were also influenced by type of anti-tacking agents. The obtained floating tablets still possessed good floating properties and controlled drug release even though anti-tacking agent had some effects. The results demonstrated that the tackiness problem of the floating tablets could be solved by incorporating anti-tacking agent into the gas-entrapped membrane.

  20. N- and O-methylation of sphingomyelin markedly affects its membrane properties and interactions with cholesterol

    DEFF Research Database (Denmark)

    Bjorkbom, A.; Rog, T.; Kankaanpaa, P.

    2011-01-01

    We have prepared palmitoyl sphingomyelin (PSM) analogs in which either the 2-NH was methylated to NMe, the 3-OH was methylated to OMe, or both were methylated simultaneously. The aim of the study was to determine how such modifications in the membrane interfacial region of the molecules affected ...

  1. Simulations of a Membrane-Anchored Peptide: Structure, Dynamics, and Influence on Bilayer Properties

    DEFF Research Database (Denmark)

    Jensen, Morten Østergaard; Mouritsen, O.G.; Peters, Günther H.J.

    2004-01-01

    A three-dimensional structure of a model decapeptide is obtained by performing molecular dynamics simulations of the peptide in explicit water. Interactions between an N-myristoylated form of the folded peptide anchored to dipalmitoylphosphatidylcholine fluid phase lipid membranes are studied at ...

  2. The role of the salt electrolyte on the electrical conductive properties of a polymeric bipolar membrane

    NARCIS (Netherlands)

    Alcaraz, Antonio; Wilhelm, Friedrich G.; Wessling, Matthias; Ramirez, Patricio

    2001-01-01

    We have studied the contribution of the salt electrolyte to the electrical conductive characteristics of a bipolar membrane. We present first a critical analysis of previous theoretical approaches, and discuss the limits of validity. Experimental current-voltage curves of several commercial bipolar

  3. Tailoring the properties of asymmetric cellulose acetate membranes by gas plasma etching

    NARCIS (Netherlands)

    Olde riekerink, M.B.; Engbers, G.H.M.; Wessling, Matthias; Feijen, Jan

    2002-01-01

    Cellulose triacetate (CTA) ultrafilters and cellulose acetate blend (CAB) desalination membranes were treated with a radiofrequency gas plasma (tetrafluoromethane (CF4) or carbon dioxide (CO2), 47¿49 W, 0.04¿0.08 mbar). Treatment times were varied between 15 s and 120 min. The plasma-treated top

  4. Improving gas separation properties of polymeric membranes based on glassy polymers by gas phase fluorination

    NARCIS (Netherlands)

    Syrtsova, D.A.; Kharitonov, A.P.; Teplyakov, V.V.; Koops, G.-H.

    2004-01-01

    The application area of existing gas separation membranes is limited by commercially available polymers for their preparation. In many cases the separation selectivity of these polymers is not sufficient for effective separation processes. One of the ways to improve the separation effectivity of exi

  5. The SC3 hydrophobin self-assembles into a membrane with distinct mass transfer properties

    NARCIS (Netherlands)

    Wang, [No Value; Shi, FX; Wosten, HAB; Hektor, H; Poolman, B; Robillard, GT; Wang, X.; Shi, Fuxin; Wösten, H.A.B.

    Hydrophobins are a class of small proteins that fulfill a wide spectrum of functions in fungal growth and development. They do so by self-assembling into an amphipathic membrane at hydrophilic-hydrophobic interfaces. The SC3 hydrophobin of Schizophyllum commune is the best-studied hydrophobin. It

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

    Directory of Open Access Journals (Sweden)

    Ravasio Andrea

    2010-05-01

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

  7. Modeling the effect of nano-sized polymer particles on the properties of lipid membranes

    Science.gov (United States)

    Rossi, Giulia; Monticelli, Luca

    2014-12-01

    The interaction between polymers and biological membranes has recently gained significant interest in several research areas. On the biomedical side, dendrimers, linear polyelectrolytes, and neutral copolymers find application as drug and gene delivery agents, as biocidal agents, and as platforms for biological sensors. On the environmental side, plastic debris is often disposed of in the oceans and gets degraded into small particles; therefore concern is raising about the interaction of small plastic particles with living organisms. From both perspectives, it is crucial to understand the processes driving the interaction between polymers and cell membranes. In recent times progress in computer technology and simulation methods has allowed computational predictions on the molecular mechanism of interaction between polymeric materials and lipid membranes. Here we review the computational studies on the interaction between lipid membranes and different classes of polymers: dendrimers, linear charged polymers, polyethylene glycol (PEG) and its derivatives, polystyrene, and some generic models of polymer chains. We conclude by discussing some of the technical challenges in this area and future developments.

  8. Synthesis of sulfated Y-doped zirconia particles and effect on properties of polysulfone membranes for treatment of wastewater containing oil

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yuqing, E-mail: zhangyuqing@tju.edu.cn [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); ARC Centre for Functional Nanomaterials, AIBN and School of Engineering, University of Queensland, Brisbane 4072 (Australia); Shan Xing; Jin Zhenhua; Wang Yueling [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2011-08-30

    Highlights: {yields} Novel hybrid membrane material - sulfated Y-doped zirconia particle is prepared. {yields} SZY/PSF membrane is formed by doping SZY particles into PSF membrane. {yields} Hydrophilicity, antifouling and anti-compaction property of PSF membrane is improved. {yields} Treatment efficiency of wastewater containing oil is enhanced. - Abstract: Polysulfone (PSF) membranes are broadly applied in many fields owing to good physicochemical stability, resistance to oxidation and chlorine. But when treated with wastewater containing oil, PSF membranes are easily contaminated due to their hydrophilicity, causing declining flux and lifespan of the membranes thereby limiting their large scale applications. In order to enhance the hydrophilic and anti-fouling capability of PSF membranes for treating wastewater containing oil, sulfated Y-doped zirconia particles (SO{sub 4}{sup 2-}/ZrO{sub 2}-Y{sub 2}O{sub 3} or SZY particles) were firstly synthesized and then doped into polysulfone to fabricate a novel hybrid membrane (SZY/PSF). The optimum preparation conditions of SZY particles were studied and determined. SZY particles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), specific surface area and transmission electron microscopy (TEM). Wastewater containing oil (80 mg/L) was used to investigate the separation properties of SZY/PSF membranes. The results show that the oil concentration in the permeation is 0.67 mg/L, whi