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Sample records for membrane skeleton organization

  1. Organic membranous skeleton of the Precambrian metazoans from Namibia

    NASA Astrophysics Data System (ADS)

    Dzik, Jerzy

    1999-06-01

    Unlike the celebrated Ediacara fossils, those from the roughly coeval localities of the Kuibis Quarzite of Namibia are preserved not as imprints on the sandstone bedding plane, but three-dimensionally, within the rock matrix. The pattern of deformation and the presence of sand in lower parts of the bodies of Ernietta, the most common and typical of those organisms, indicate that their three-dimensional preservation is a result of a density-controlled sinking of sand-filled organic skeletons within hydrated mud layers. Specimens of Ernietta have preserved various stages of migration across the mud beds. Their wall material, as documented by the mode of deformation, was not only flexible, but also elastic, which makes it unlike chitin. The walls thus seem to be proteinaceous, built probably of a collagenous fabric. The Ernietta skeleton was built of series of parallel chambers, which excludes the possibility that these were external body covers. The chambers apparently represent walls of hydraulic skeleton units, resembling the basement membrane of chaetognaths or the notochord sheath of primitive chordates. Such chambers are widespread among the earliest fossil animals represented by fossils preserved in sandstone. The rise and fall of the Ediacaran faunas thus seem to be partially preservational artifacts. The range of its occurrence is a result of two successive evolutionary events: the origin of an internal hydraulic skeleton enclosed by a strong basement membrane, and the appearance of decomposers with abilities to disintegrate such collagenous sheaths.

  2. Contribution of ankyrin-band 3 complexes to the organization and mechanical properties of the membrane skeleton of human erythrocyte

    SciTech Connect

    Shen, B.W.

    1995-02-01

    To understand the role of ankyrin-band 3 complexes in the organization of the spectrin-based membrane skeleton and its contribution to the mechanical properties of human erythrocytes, intact skeletons and single-layered skeleton leaflets were prepared from intact and physically sheared membrane ghosts, expanded in low salt buffer, and examined by transmission electron microscopy. While the structures of intact skeletons and single-layered skeleton leaflets shared many common features, including rigid junctional complexes of spectrin, actin, and band 4.1; short stretches ({approximately}50 {angstrom}) of flexible spectrin filaments; and globular masses of ankyrin-band 3 complexes situated close to the middle of the spectrin filaments, the definition of structural units in the intact skeleton is obscured by the superposition of the two layers. However, the spatial disposition of structural elements can be clearly defined in the images of the single-layered skeleton leaflets. Partially expanded skeletal leaflets contain conglomerates of ankyrin-band 3 complexes arranged in a circular or clove-leaf configuration that straddles multiple strands of thick spectrin cables, presumably reflecting the association of ankyrin-band 3 complexes on neighboring spectrin tetramers as well as the lateral association of the spectrin filaments. Hyperexpansion of the skeleton leaflets led to dissociation of the conglomerates of ankyrin-band 3 complexes, full-extension of the spectrin tetramers, and separation of the individual strands of spectrin tetramers. Clearly defined stands of spectrin tetramers in the hyperexpanded single-layered skeletal leaflets often contained two sets of globular protein masses that divided the spectrin tetramers into three segments of approximately equal length.

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

    PubMed

    Lux, Samuel E

    2016-01-14

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

  4. Proteome analysis of the triton-insoluble erythrocyte membrane skeleton.

    PubMed

    Basu, Avik; Harper, Sandra; Pesciotta, Esther N; Speicher, Kaye D; Chakrabarti, Abhijit; Speicher, David W

    2015-10-14

    Erythrocyte shape and membrane integrity is imparted by the membrane skeleton, which can be isolated as a Triton X-100 insoluble structure that retains the biconcave shape of intact erythrocytes, indicating isolation of essentially intact membrane skeletons. These erythrocyte "Triton Skeletons" have been studied morphologically and biochemically, but unbiased proteome analysis of this substructure of the membrane has not been reported. In this study, different extraction buffers and in-depth proteome analyses were used to more fully define the protein composition of this functionally critical macromolecular complex. As expected, the major, well-characterized membrane skeleton proteins and their associated membrane anchors were recovered in good yield. But surprisingly, a substantial number of additional proteins that are not considered in erythrocyte membrane skeleton models were recovered in high yields, including myosin-9, lipid raft proteins (stomatin, flotillin1 and 2), multiple chaperone proteins (HSPs, protein disulfide isomerase and calnexin), and several other proteins. These results show that the membrane skeleton is substantially more complex than previous biochemical studies indicated, and it apparently has localized regions with unique protein compositions and functions. This comprehensive catalog of the membrane skeleton should lead to new insights into erythrocyte membrane biology and pathogenic mutations that perturb membrane stability. Biological significance Current models of erythrocyte membranes describe fairly simple homogenous structures that are incomplete. Proteome analysis of the erythrocyte membrane skeleton shows that it is quite complex and includes a substantial number of proteins whose roles and locations in the membrane are not well defined. Further elucidation of interactions involving these proteins and definition of microdomains in the membrane that contain these proteins should yield novel insights into how the membrane skeleton

  5. Existence of a Flat Phase in Red Cell Membrane Skeletons

    NASA Astrophysics Data System (ADS)

    Schmidt, Christoph F.; Svoboda, Karel; Lei, Ning; Petsche, Irena B.; Berman, Lonny E.; Safinya, Cyrus R.; Grest, Gary S.

    1993-02-01

    Biomolecular membranes display rich statistical mechanical behavior. They are classified as liquid in the absence of shear elasticity in the plane of the membrane and tethered (solid) when the neighboring molecules or subunits are connected and the membranes exhibit solid-like elastic behavior in the plane of the membrane. The spectrin skeleton of red blood cells was studied as a model tethered membrane. The static structure factor of the skeletons, measured by small-angle x-ray and light scattering, was fitted with a structure factor predicted with a model calculation. The model describes tethered membrane sheets with free edges in a flat phase, which is a locally rough but globally flat membrane configuration. The fit was good for large scattering vectors. The membrane roughness exponent, zeta, defined through h propto L^zeta, where h is the average amplitude of out-of-plane fluctuations and L is the linear membrane dimension, was determined to be 0.65 ± 0.10. Computer simulations of model red blood cell skeletons also showed this flat phase. The value for the roughness exponent, which was determined from the scaling properties of membranes of different sizes, was consistent with that from the experiments.

  6. Atomic force microscopy of the erythrocyte membrane skeleton.

    PubMed

    Swihart, A H; Mikrut, J M; Ketterson, J B; Macdonald, R C

    2001-12-01

    The atomic force microscope was used to examine the cytoplasmic surface of untreated as well as fixed human erythrocyte membranes that had been continuously maintained under aqueous solutions. To assess the effects of drying, some membranes were examined in air. Erythrocytes attached to mica or glass were sheared open with a stream of isotonic buffer, which allowed access to the cytoplasmic membrane face without exposing cells to non-physiological ionic strength solutions. Under these conditions of examination, the unfixed cytoplasmic membrane face revealed an irregular meshwork that appeared to be a mixture largely of triangular and rectilinear openings with mesh sizes that varied from 35 to 100 nm, although few were at the upper limit. Fixed ghosts were similar, but slightly more contracted. These features represent the membrane skeleton, as when the ghosts were treated to extract spectrin and actin, these meshworks were largely removed. Direct measurements of the thickness of the membrane skeleton and of the lateral dimensions of features in the images suggested that, especially when air dried, spectrin can cluster into large, quite regularly distributed aggregates. Aggregation of cytoskeletal components was also favoured when the cells were attached to a polylysine-treated substrate. In contrast, the membrane skeletons of cells attached to substrates rendered positively charged by chemical derivatization with a cationic silane were much more resistant to aggregation. As steps were taken to reduce the possibility of change of the skeleton after opening the cells, the aggregates and voids were eliminated, and the observed structures became shorter and thinner. Ghosts treated with Triton X-100 solutions to remove the bilayer revealed a meshwork having aggregated components resembling those seen in air. These findings support the proposition that the end-to-end distance of spectrin tetramers in the cell in the equilibrium state is much shorter than the contour

  7. The skeleton as an endocrine organ.

    PubMed

    DiGirolamo, Douglas J; Clemens, Thomas L; Kousteni, Stavroula

    2012-11-01

    Surprising new discoveries in the field of skeletal biology show that bone cells produce endocrine hormones that regulate phosphate and glucose homeostasis. In this Review, we examine the features of these new endocrine pathways and discuss their physiological importance in the context of our current understanding of energy metabolism and mineral homeostasis. Consideration of evolutionary and comparative biology provides clues that a key driving force for the emergence of these hormonal pathways was the development of a large, energy-expensive musculoskeletal system. Specialized bone cells also evolved and produced endocrine hormones to integrate the skeleton in global mineral and nutrient homeostasis. The recognition of bone as a true endocrine organ represents a fertile area for further research and should improve the diagnosis and treatment of metabolic diseases such as osteoporosis and diabetes mellitus. PMID:23045255

  8. Multifractal characterization of morphology of human red blood cells membrane skeleton.

    PubMed

    Ţălu, Ş; Stach, S; Kaczmarska, M; Fornal, M; Grodzicki, T; Pohorecki, W; Burda, K

    2016-04-01

    The purpose of this paper is to show applicability of multifractal analysis in investigations of the morphological changes of ultra-structures of red blood cells (RBCs) membrane skeleton measured using atomic force microscopy (AFM). Human RBCs obtained from healthy and hypertensive donors as well as healthy erythrocytes irradiated with neutrons (45 μGy) were studied. The membrane skeleton of the cells was imaged using AFM in a contact mode. Morphological characterization of the three-dimensional RBC surfaces was realized by a multifractal method. The nanometre scale study of human RBCs surface morphology revealed a multifractal geometry. The generalized dimensions Dq and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of their membrane skeleton organization. Surface characterization was made using areal ISO 25178-2: 2012 topography parameters in combination with AFM topography measurement. The surface structure of human RBCs is complex with hierarchical substructures resulting from the organization of the erythrocyte membrane skeleton. The analysed AFM images confirm a multifractal nature of the surface that could be useful in histology to quantify human RBC architectural changes associated with different disease states. In case of very precise measurements when the red cell surface is not wrinkled even very fine differences can be uncovered as was shown for the erythrocytes treated with a very low dose of ionizing radiation. PMID:27002485

  9. WASP localizes to the membrane skeleton of platelets.

    PubMed

    Lutskiy, Maxim I; Shcherbina, Anna; Bachli, Eric T; Cooley, Jessica; Remold-O'Donnell, Eileen

    2007-10-01

    Patients with Wiskott-Aldrich syndrome (WAS), an X-linked blood cell disease, suffer from severe thrombocytopenia due to accelerated loss of defective platelets. The affected gene encodes WASP, an actin regulatory protein thought to reside in the cytoplasm of resting leucocytes. In contrast, this study showed that, for platelets, one-quarter of WASP molecules fractionate in the detergent-insoluble high speed pellet characterized as the membrane skeleton, the scaffold structure that underlies the lipid bilayer and stabilizes the surface membrane. Following treatment of platelets with thrombin and stirring, which induces cytoarchitectural remodelling, WASP and other membrane skeletal components sedimented at lower g force and partitioned in the low-speed pellet. Thrombin and stirring also induced WASP tyrosine phosphorylation, a rapid activating reaction, and proteolytic inactivation by cysteine protease calpain. Both the alteration of the sedimentation profile and the proteolytic inactivation were specific for the membrane skeletal pool of WASP and were abrogated in alphaIIb beta3 integrin-deficient platelets and in normal platelets treated with an integrin antagonist. The findings demonstrate that WASP is a component of the resting platelet membrane skeleton and participates in membrane skeletal rearrangements downstream of integrin outside-in signalling. The possible implications for the platelet defect in WAS are discussed. PMID:17854313

  10. The membrane skeleton of erythrocytes. A percolation model.

    PubMed Central

    Saxton, M J

    1990-01-01

    The spectrin network on the cytoplasmic surface of the erythrocyte membrane is modeled as a triangular lattice of spectrin tetramers. This network obstructs lateral diffusion of proteins and provides mechanical reinforcement to the membrane. These effects are treated in a systematic and unified manner in terms of a percolation model. The diffusion coefficient is obtained as a function of the fraction of normal spectrin tetramers for both static and fluctuating barriers. The elasticity of the network is calculated as a function of the fraction of normal spectrin and the ratio of bending to stretching energies. For static barriers, elasticity and lateral diffusion are incompatible: if a network is connected enough to be elastic, it is connected enough to block long-range lateral diffusion. The elasticity and the force required for mechanical breakdown go to zero at the percolation threshold; experimental evidence suggests the existence of a stability threshold at or near the percolation threshold. The model is qualitatively applicable to other cells with membrane skeletons, such as epithelial cells, in which localization of membrane proteins is essential to differentiation. PMID:2393702

  11. Interactions between Plasmodium falciparum skeleton-binding protein 1 and the membrane skeleton of malaria-infected red blood cells

    PubMed Central

    Buckingham, Donna W.; Blanc, Lionel; Hale, John; Guo, Xinhua; Pei, Xinhong; Herrmann, Susann; Hanssen, Eric G.; Coppel, Ross L.; Mohandas, Narla; An, Xiuli; Cooke, Brian M.

    2015-01-01

    During development inside red blood cells (RBCs), Plasmodium falciparum malaria parasites export proteins that associate with the RBC membrane skeleton. These interactions cause profound changes to the biophysical properties of RBCs that underpin the often severe and fatal clinical manifestations of falciparum malaria. P. falciparum erythrocyte membrane protein 1 (PfEMP1) is one such exported parasite protein that plays a major role in malaria pathogenesis since its exposure on the parasitised RBC surface mediates their adhesion to vascular endothelium and placental syncytioblasts. En route to the RBC membrane skeleton, PfEMP1 transiently associates with Maurer's clefts (MCs), parasite-derived membranous structures in the RBC cytoplasm. We have previously shown that a resident MC protein, skeleton-binding protein 1 (SBP1), is essential for the placement of PfEMP1 onto the RBC surface and hypothesised that the function of SBP1 may be to target MCs to the RBC membrane. Since this would require additional protein interactions, we set out to identify binding partners for SBP1. Using a combination of approaches, we have defined the region of SBP1 that binds specifically to defined subdomains of two major components of the RBC membrane skeleton, protein 4.1R and spectrin. We show that these interactions serve as one mechanism to anchor MCs to the RBC membrane skeleton, however, while they appear to be necessary, they are not sufficient for the translocation of PfEMP1 onto the RBC surface. The N-terminal domain of SBP1 that resides within the lumen of MCs clearly plays an essential, but presently unknown role in this process. PMID:25883090

  12. Learning about Skeletons and Other Organ Systems of Vertebrate Animals.

    ERIC Educational Resources Information Center

    Tunnicliffe, Sue Dale; Reiss, Michael

    1999-01-01

    Describes students' (n=175) understandings of the structure of animal (including human) skeletons and the internal organs found in them. Finds that older students have a better knowledge of animals' internal anatomies, although knowledge of human internal structure is significantly better than knowledge of rat, bird, and fish internal structure.…

  13. Surface shape change during fusion of erythrocyte membranes is sensitive to membrane skeleton agents.

    PubMed Central

    Wu, Y; Rosenberg, J D; Sowers, A E

    1994-01-01

    We previously reported that the induction of membrane fusion between pairs of erythrocyte ghosts is accompanied by the formation of a multipore fusion zone that undergoes an area expansion with condition-dependent characteristics. These characteristics allowed us to hypothesize substantial, if not major, involvement of the spectrin-based membrane skeleton in controlling this expansion. It was also found that the fusion zone, which first appears in phase optics as a flat diaphragm, has a lifetime that is also highly condition-dependent. We report here that 2,3-diphosphoglycerate, wheat germ agglutinin, diamide, and N-ethylmaleimide, all known to have binding sites primarily on skeleton components (including spectrin), have condition-dependent effects on specific components of the fusion zone diameter versus time expansion curve and the flat diaphragm lifetime. We also report a pH/ionic strength condition that causes a dramatic stabilization of flat diaphragms in a manner consistent with the known pH/ionic strength dependence of the spectrin calorimetric transition, thus further supporting the hypothesis of spectrin involvement. Our data suggest that the influence of the membrane skeleton on cell fusion is to restrain the rounding up that takes place after membrane fusion and that it may have variable, rather than fixed, mechanical properties. Data show that WGA, a known ligand for sialic acid, and DPG, a known metabolite, influences the flat diaphragm stability and late period expansion rates, raising the possibility that some of these mechanical properties are biologically regulated. Images FIGURE 2 PMID:7858126

  14. Protein 4.1R–deficient mice are viable but have erythroid membrane skeleton abnormalities

    PubMed Central

    Shi, Zheng-Tao; Afzal, Veena; Coller, Barry; Patel, Dipti; Chasis, Joel A.; Parra, Marilyn; Lee, Gloria; Paszty, Chris; Stevens, Mary; Walensky, Loren; Peters, Luanne L.; Mohandas, Narla; Rubin, Edward; Conboy, John G.

    1999-01-01

    A diverse family of protein 4.1R isoforms is encoded by a complex gene on human chromosome 1. Although the prototypical 80-kDa 4.1R in mature erythrocytes is a key component of the erythroid membrane skeleton that regulates erythrocyte morphology and mechanical stability, little is known about 4.1R function in nucleated cells. Using gene knockout technology, we have generated mice with complete deficiency of all 4.1R protein isoforms. These 4.1R-null mice were viable, with moderate hemolytic anemia but no gross abnormalities. Erythrocytes from these mice exhibited abnormal morphology, lowered membrane stability, and reduced expression of other skeletal proteins including spectrin and ankyrin, suggesting that loss of 4.1R compromises membrane skeleton assembly in erythroid progenitors. Platelet morphology and function were essentially normal, indicating that 4.1R deficiency may have less impact on other hematopoietic lineages. Nonerythroid 4.1R expression patterns, viewed using histochemical staining for lacZ reporter activity incorporated into the targeted gene, revealed focal expression in specific neurons in the brain and in select cells of other major organs, challenging the view that 4.1R expression is widespread among nonerythroid cells. The 4.1R knockout mice represent a valuable animal model for exploring 4.1R function in nonerythroid cells and for determining pathophysiological sequelae to 4.1R deficiency. PMID:9927493

  15. Structure of the erythrocyte membrane skeleton as observed by atomic force microscopy.

    PubMed Central

    Takeuchi, M; Miyamoto, H; Sako, Y; Komizu, H; Kusumi, A

    1998-01-01

    The structure of the membrane skeleton on the cytoplasmic surface of the erythrocyte plasma membrane was observed in dried human erythrocyte ghosts by atomic force microscopy (AFM), taking advantage of its high sensitivity to small height variations in surfaces. The majority of the membrane skeleton can be imaged, even on the extracellular surface of the membrane. Various fixation and drying methods were examined for preparation of ghost membrane samples for AFM observation, and it was found that freeze-drying (freezing by rapid immersion in a cryogen) of unfixed specimens was a fast and simple way to obtain consistently good results for observation without removing the membrane or extending the membrane skeleton. Observation of the membrane skeleton at the external surface of the cell was possible mainly because the bilayer portion of the membrane sank into the cell during the drying process. The average mesh size of the spectrin network observed at the extracellular and cytoplasmic surfaces of the plasma membrane was 4800 and 3000 nm2, respectively, which indicates that spectrin forms a three-dimensionally folded meshwork, and that 80% of spectrin can be observed at the extracellular surface of the plasma membrane. PMID:9591644

  16. Extensive but Coordinated Reorganization of the Membrane Skeleton in Myofibers of Dystrophic (mdx) Mice

    PubMed Central

    Williams, McRae W.; Bloch, Robert J.

    1999-01-01

    We used immunofluorescence techniques and confocal imaging to study the organization of the membrane skeleton of skeletal muscle fibers of mdx mice, which lack dystrophin. β-Spectrin is normally found at the sarcolemma in costameres, a rectilinear array of longitudinal strands and elements overlying Z and M lines. However, in the skeletal muscle of mdx mice, β-spectrin tends to be absent from the sarcolemma over M lines and the longitudinal strands may be disrupted or missing. Other proteins of the membrane and associated cytoskeleton, including syntrophin, β-dystroglycan, vinculin, and Na,K-ATPase are also concentrated in costameres, in control myofibers, and mdx muscle. They also distribute into the same altered sarcolemmal arrays that contain β-spectrin. Utrophin, which is expressed in mdx muscle, also codistributes with β-spectrin at the mutant sarcolemma. By contrast, the distribution of structural and intracellular membrane proteins, including α-actinin, the Ca-ATPase and dihydropyridine receptors, is not affected, even at sites close to the sarcolemma. Our results suggest that in myofibers of the mdx mouse, the membrane- associated cytoskeleton, but not the nearby myoplasm, undergoes widespread coordinated changes in organization. These changes may contribute to the fragility of the sarcolemma of dystrophic muscle. PMID:10087268

  17. XANES mapping of organic sulfate in three scleractinian coral skeletons

    NASA Astrophysics Data System (ADS)

    Cuif, Jean-Pierre; Dauphin, Yannicke; Doucet, Jean; Salome, Murielle; Susini, Jean

    2003-01-01

    The presence and localization of organic sulfate within coral skeletons are studied by using X-ray absorption near edge structure spectroscopy (XANES) fluorescence. XANES spectra are recorded from four reference sulfur-bearing organic molecules: three amino acids (H-S-C bonds in cysteine; C-S-C bonds in methionine; one disulfide bond C-S-S-C bonds in cystine) and a sulfated sugar (C-SO 4 bonds in chondroitin sulfate). Spectral responses of three coral skeletons show that the sulfated form is extremely dominant in coral aragonite, and practically exclusive within both centres of calcification and the surrounding fibrous tissues of coral septa. Mapping of S-sulfate concentrations in centres and fibres gives us direct evidence of high concentration of organic sulfate in centres of calcification. Additionally, a banding pattern of S-sulfate is visible in fibrous part of the coral septa, evidencing a biochemical zonation that corresponds to the step-by-step growth of fibres.

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

    PubMed

    Kozlov, M M; Markin, V S

    1987-12-21

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

  19. Actin Skeletons at the Membrane as Liquid Crystal Elastomers

    NASA Astrophysics Data System (ADS)

    Discher, Dennis; Dalhaimer, Paul; Levine, Alex; Lubensky, Tom

    2002-03-01

    Actin filaments crosslinked by proteins such as spectrin form plasma membrane networks in a number of cell-types, including the red blood cell and the outer hair cell of the inner ear. Actin filaments are stiff compared to spectrin and can be considered hard rods. We statistically simulate network phase behavior at finite temperature by Monte Carlo methods, and explore the effects of spectrin and actin length as well as isotropic and shear stresses. Relative lengths required for a zero pressure nematic phase are determined, for exmaple, and indicate structural requirements for obtaining a 2D anisotropic elastomer. Emerging studies of network elasticity examine the anisotropic state and begin to probe the relevance of hyper-soft modes to hearing.

  20. Energy of dissociation of lipid bilayer from the membrane skeleton of red blood cells.

    PubMed Central

    Hwang, W C; Waugh, R E

    1997-01-01

    The association between the lipid bilayer and the membrane skeleton is important to cell function. In red blood cells, defects in this association can lead to various forms of hemolytic anemia. Although proteins involved in this association have been well characterized biochemically, the physical strength of this association is only beginning to be studied. Formation of a small cylindrical strand of membrane material (tether) from the membrane involves separation of the lipid bilayer from the membrane skeleton. By measuring the force required to form a tether, and knowing the contribution to the force due to the deformation of a lipid bilayer, it is possible to calculate the additional contribution to the work of tether formation due to the separation of membrane skeleton from the lipid bilayer. In the present study, we measured the tethering force during tether formation using a microcantilever (a thin, flexible glass fiber) as a force transducer. Numerical calculations of the red cell contour were performed to examine how the shape of the contour affects the calculation of tether radius, and subsequently separation work per unit area W(sk) and bending stiffness k(c). At high aspiration pressure and small external force, the red cell contour can be accurately modeled as a sphere, but at low aspiration pressure and large external force, the contour deviates from a sphere and may affect the calculation. Based on an energy balance and numerical calculations of the cell contour, values of the membrane bending stiffness k(c) = 2.0 x 10(-19) Nm and the separation work per unit area W(sk) = 0.06 mJ/m2 were obtained. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 8 PMID:9168042

  1. The spectrin-based membrane skeleton stabilizes mouse megakaryocyte membrane systems and is essential for proplatelet and platelet formation.

    PubMed

    Patel-Hett, Sunita; Wang, Hongbei; Begonja, Antonija J; Thon, Jonathan N; Alden, Eva C; Wandersee, Nancy J; An, Xiuli; Mohandas, Narla; Hartwig, John H; Italiano, Joseph E

    2011-08-11

    Megakaryocytes generate platelets by remodeling their cytoplasm first into proplatelets and then into preplatelets, which undergo fission to generate platelets. Although the functions of microtubules and actin during platelet biogenesis have been defined, the role of the spectrin cytoskeleton is unknown. We investigated the function of the spectrin-based membrane skeleton in proplatelet and platelet production in murine megakaryocytes. Electron microscopy revealed that, like circulating platelets, proplatelets have a dense membrane skeleton, the main fibrous component of which is spectrin. Unlike other cells, megakaryocytes and their progeny express both erythroid and nonerythroid spectrins. Assembly of spectrin into tetramers is required for invaginated membrane system maturation and proplatelet extension, because expression of a spectrin tetramer-disrupting construct in megakaryocytes inhibits both processes. Incorporation of this spectrin-disrupting fragment into a novel permeabilized proplatelet system rapidly destabilizes proplatelets, causing blebbing and swelling. Spectrin tetramers also stabilize the "barbell shapes" of the penultimate stage in platelet production, because addition of the tetramer-disrupting construct converts these barbell shapes to spheres, demonstrating that membrane skeletal continuity maintains the elongated, pre-fission shape. The results of this study provide evidence for a role for spectrin in different steps of megakaryocyte development through its participation in the formation of invaginated membranes and in the maintenance of proplatelet structure. PMID:21566095

  2. An elastic network model based on the structure of the red blood cell membrane skeleton.

    PubMed Central

    Hansen, J C; Skalak, R; Chien, S; Hoger, A

    1996-01-01

    A finite element network model has been developed to predict the macroscopic elastic shear modulus and the area expansion modulus of the red blood cell (RBC) membrane skeleton on the basis of its microstructure. The topological organization of connections between spectrin molecules is represented by the edges of a random Delaunay triangulation, and the elasticity of an individual spectrin molecule is represented by the spring constant, K, for a linear spring element. The model network is subjected to deformations by prescribing nodal displacements on the boundary. The positions of internal nodes are computed by the finite element program. The average response of the network is used to compute the shear modulus (mu) and area expansion modulus (kappa) for the corresponding effective continuum. For networks with a moderate degree of randomness, this model predicts mu/K = 0.45 and kappa/K = 0.90 in small deformations. These results are consistent with previous computational models and experimental estimates of the ratio mu/kappa. This model also predicts that the elastic moduli vary by 20% or more in networks with varying degrees of randomness. In large deformations, mu increases as a cubic function of the extension ratio lambda 1, with mu/K = 0.62 when lambda 1 = 1.5. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16 FIGURE 17 FIGURE 18 FIGURE 20 FIGURE A1 FIGURE A2 FIGURE A3 PMID:8770194

  3. Essential control of an endothelial cell ISOC by the spectrin membrane skeleton.

    PubMed

    Wu, S; Sangerman, J; Li, M; Brough, G H; Goodman, S R; Stevens, T

    2001-09-17

    Mechanism(s) underlying activation of store-operated Ca2+ entry currents, ISOC, remain incompletely understood. F-actin configuration is an important determinant of channel function, although the nature of interaction between the cytoskeleton and ISOC channels is unknown. We examined whether the spectrin membrane skeleton couples Ca2+ store depletion to Ca2+ entry. Thapsigargin activated an endothelial cell ISOC (-45 pA at -80 mV) that reversed at +40 mV, was inwardly rectifying when Ca2+ was the charge carrier, and was inhibited by La3+ (50 microM). Disruption of the spectrin-protein 4.1 interaction at residues A207-V445 of betaSpIISigma1 decreased the thapsigargin-induced global cytosolic Ca2+ response by 50% and selectively abolished the endothelial cell ISOC, without altering activation of a nonselective current through cyclic nucleotide-gated channels. In contrast, disruption of the spectrin-actin interaction at residues A47-K186 of betaSpIISigma1 did not decrease the thapsigargin-induced global cytosolic Ca2+ response or inhibit ISOC. Results indicate that the spectrin-protein 4.1 interaction selectively controls ISOC, indicating that physical coupling between calcium release and calcium entry is reliant upon the spectrin membrane skeleton. PMID:11564759

  4. Essential control of an endothelial cell ISOC by the spectrin membrane skeleton

    PubMed Central

    Wu, Songwei; Sangerman, Jose; Li, Ming; Brough, George H.; Goodman, Steven R.; Stevens, Troy

    2001-01-01

    Mechanism(s) underlying activation of store-operated Ca2+ entry currents, ISOC, remain incompletely understood. F-actin configuration is an important determinant of channel function, although the nature of interaction between the cytoskeleton and ISOC channels is unknown. We examined whether the spectrin membrane skeleton couples Ca2+ store depletion to Ca2+ entry. Thapsigargin activated an endothelial cell ISOC (−45 pA at −80 mV) that reversed at +40 mV, was inwardly rectifying when Ca2+ was the charge carrier, and was inhibited by La3+ (50 μM). Disruption of the spectrin–protein 4.1 interaction at residues A207-V445 of βSpIIΣ1 decreased the thapsigargin-induced global cytosolic Ca2+ response by 50% and selectively abolished the endothelial cell ISOC, without altering activation of a nonselective current through cyclic nucleotide–gated channels. In contrast, disruption of the spectrin–actin interaction at residues A47-K186 of βSpIIΣ1 did not decrease the thapsigargin-induced global cytosolic Ca2+ response or inhibit ISOC. Results indicate that the spectrin–protein 4.1 interaction selectively controls ISOC, indicating that physical coupling between calcium release and calcium entry is reliant upon the spectrin membrane skeleton. PMID:11564759

  5. What's Inside Bodies? Learning about Skeletons and Other Organ Systems of Vertebrate Animals.

    ERIC Educational Resources Information Center

    Tunnicliffe, Sue Dale; Reiss, Michael

    This paper describes a study of young children's understanding of what is on the inside of animals--skeletons and other organ systems. The study uses 2-D drawings based on the idea that a drawing is the representational model and is the outward expression of the mental model. The 617 drawings made by participants in the study were awarded one of…

  6. Skeleton-supported stochastic networks of organic memristive devices: Adaptations and learning

    SciTech Connect

    Erokhina, Svetlana; Sorokin, Vladimir; Erokhin, Victor

    2015-02-15

    Stochastic networks of memristive devices were fabricated using a sponge as a skeleton material. Cyclic voltage-current characteristics, measured on the network, revealed properties, similar to the organic memristive device with deterministic architecture. Application of the external training resulted in the adaptation of the network electrical properties. The system revealed an improved stability with respect to the networks, composed from polymer fibers.

  7. Effect of Radiographic Contrast Media on the Spectrin/Band3-Network of the Membrane Skeleton of Erythrocytes

    PubMed Central

    Franke, Ralf-Peter; Scharnweber, Tim; Fuhrmann, Rosemarie; Wenzel, Folker; Krüger, Anne; Mrowietz, Christof; Jung, Friedrich

    2014-01-01

    The membrane of red blood cells consists of a phospholipid bilayer with embedded membrane proteins and is associated on the cytoplasmatic side with a network of proteins, the membrane skeleton. Band3 has an important role as centre of the functional complexes e.g. gas exchange complex and as element of attachment for the membrane skeleton maintaining membrane stability and flexibility. Up to now it is unclear if band3 is involved in the morphology change of red blood cells after contact with radiographic contrast media. The study revealed for the first time that Iopromide induced markedly more severe alterations of the membrane skeleton compared to Iodixanol whose effects were similar to erythrocytes suspended in autologous plasma. A remarkable clustering of band3 was found associated with an accumulation of band3 in spicules and also a sequestration of band3 to the extracellular space. This was evidently accompanied by a gross reduction of functional band3 complexes combined with a dissociation of spectrin from band3 leading to a loss of homogeneity of the spectrin network. It could be demonstrated for the first time that RCM not only induced echinocyte formation but also exocytosis of particles at least coated with band3. PMID:24586837

  8. An aqueous route to organically functionalized silica diatom skeletons

    NASA Astrophysics Data System (ADS)

    Fowler, Christabel E.; Buchber, Catherine; Lebeau, Bénédicte; Patarin, Joël; Delacôte, Cyril; Walcarius, Alain

    2007-04-01

    Diatomaceous earth was functionalized by grafting organotrialkoxysilane precursors onto the surface of the porous silica cell walls of this biomineral. Vinyl- and mercapto-containing structures were prepared in aqueous media without disruption of the diatomic architecture. Successful grafting of the organic moieties was confirmed using solid state 29Si MAS NMR spectroscopy, and the presence of the intact diatom framework by scanning electron microscopy. The sorption properties of mercaptopropyl-functionalized diatoms towards heavy metals was studied by measuring the accessibility and diffusion rates of mercury(II) species to the binding sites (-SH) by the means of electrochemical methods.

  9. Hollow silica-copper-carbon anodes using copper metal-organic frameworks as skeletons

    NASA Astrophysics Data System (ADS)

    Sun, Zixu; Xin, Fengxia; Cao, Can; Zhao, Chongchong; Shen, Cai; Han, Wei-Qiang

    2015-12-01

    Hollow silica-copper-carbon (H-SCC) nanocomposites are first synthesized using copper metal-organic frameworks as skeletons to form Cu-MOF@SiO2 and then subjected to heat treatment. In the composites, the hollow structure and the void space from the collapse of the MOF skeleton can accommodate the huge volume change, buffer the mechanical stress caused by lithium ion insertion/extraction and maintain the structural integrity of the electrode and a long cycling stability. The ultrafine copper with a uniform size of around 5 nm and carbon with homogeneous distribution from the decomposition of the MOF skeleton can not only enhance the electrical conductivity of the composite and preserve the structural and interfacial stabilization, but also suppress the aggregation of silica nanoparticles and cushion the volume change. In consequence, the resulting material as an anode for lithium-ion batteries (LIBs) delivers a reversible capacity of 495 mA h g-1 after 400 cycles at a current density of 500 mA g-1. The synthetic method presented in this paper provides a facile and low-cost strategy for the large-scale production of hollow silica/copper/carbon nanocomposites as an anode in LIBs.Hollow silica-copper-carbon (H-SCC) nanocomposites are first synthesized using copper metal-organic frameworks as skeletons to form Cu-MOF@SiO2 and then subjected to heat treatment. In the composites, the hollow structure and the void space from the collapse of the MOF skeleton can accommodate the huge volume change, buffer the mechanical stress caused by lithium ion insertion/extraction and maintain the structural integrity of the electrode and a long cycling stability. The ultrafine copper with a uniform size of around 5 nm and carbon with homogeneous distribution from the decomposition of the MOF skeleton can not only enhance the electrical conductivity of the composite and preserve the structural and interfacial stabilization, but also suppress the aggregation of silica nanoparticles and

  10. A novel strain energy relationship for red blood cell membrane skeleton based on spectrin stiffness and its application to micropipette deformation.

    PubMed

    Svetina, Saša; Kokot, Gašper; Kebe, Tjaša Švelc; Žekš, Boštjan; Waugh, Richard E

    2016-06-01

    Red blood cell (RBC) membrane skeleton is a closed two-dimensional elastic network of spectrin tetramers with nodes formed by short actin filaments. Its three-dimensional shape conforms to the shape of the bilayer, to which it is connected through vertical linkages to integral membrane proteins. Numerous methods have been devised over the years to predict the response of the RBC membrane to applied forces and determine the corresponding increase in the skeleton elastic energy arising either directly from continuum descriptions of its deformation, or seeking to relate the macroscopic behavior of the membrane to its molecular constituents. In the current work, we present a novel continuum formulation rooted in the molecular structure of the membrane and apply it to analyze model deformations similar to those that occur during aspiration of RBCs into micropipettes. The microscopic elastic properties of the skeleton are derived by treating spectrin tetramers as simple linear springs. For a given local deformation of the skeleton, we determine the average bond energy and define the corresponding strain energy function and stress-strain relationships. The lateral redistribution of the skeleton is determined variationally to correspond to the minimum of its total energy. The predicted dependence of the length of the aspirated tongue on the aspiration pressure is shown to describe the experimentally observed system behavior in a quantitative manner by taking into account in addition to the skeleton energy an energy of attraction between RBC membrane and the micropipette surface. PMID:26376642

  11. Linkage of a membrane skeleton to integral membrane glycoproteins in human platelets. Identification of one of the glycoproteins as glycoprotein Ib.

    PubMed Central

    Fox, J E

    1985-01-01

    Experiments were performed to determine whether platelets contain a membrane skeleton. Platelets were labeled by a sodium periodate/sodium [3H]borohydride method and lysed with Triton X-100. Much of the filamentous actin could be sedimented at low g forces (15,600 g, 4 min), but some of the actin filaments required high-speed centrifugation for their sedimentation (100,000 g, 3 h). The latter filaments differed from those in the low-speed pellet in that they could not be depolymerized by Ca2+ and could not be sedimented at low g forces even from Triton X-100 lysates of platelets that had been activated with thrombin. Actin-binding protein sedimented with both types of filaments, but 3H-labeled membrane glycoproteins were recovered mainly with the high-speed filaments. The primary 3H-labeled glycoprotein recovered with this "membrane skeleton" was glycoprotein (GP) Ib. Approximately 70% of the platelet GP Ib was present in this skeleton. Several other minor glycoproteins, including greater than 50% of the GP Ia and small amounts of three unidentified glycoproteins of Mr greater than 200,000, were also recovered with the membrane skeleton. The Triton X-100 insolubility of GP Ib, GP Ia, a minor membrane glycoprotein of 250,000 Mr, and actin-binding protein resulted from their association with actin filaments as they were rendered Triton X-100-soluble when actin filaments were depolymerized with deoxyribonuclease I and co-isolated with actin filaments on sucrose gradients. When isolated platelet plasma membranes were extracted with Triton X-100, actin, actin-binding protein, and GP Ib were recovered as the Triton X-100 residue. These studies show that unstimulated platelets contain a membrane skeleton composed of actin filaments and actin-binding protein that is distinct from the rest of the cytoskeleton and is attached to GP Ib, GP Ia, and a minor glycoprotein of 250,000 Mr on the plasma membrane. Images PMID:2932470

  12. Regulation of the glycophorin C-protein 4.1 membrane-to-skeleton bridge and evaluation of its contribution to erythrocyte membrane stability.

    PubMed

    Chang, S H; Low, P S

    2001-06-22

    The band 3-ankyrin-spectrin bridge and the glycophorin C-protein 4.1-spectrin/actin bridge constitute the two major tethers between the erythrocyte membrane and its spectrin skeleton. Although a structural requirement for the band 3-ankyrin bridge is well established, the contribution of the glycophorin C-protein 4.1 bridge to red cell function remains to be defined. In order to explore this latter bridge further, we have identified and/or characterized five stimuli that sever the linkage in intact erythrocytes and have examined the impact of this rupture on membrane mechanical properties. We report here that elevation of cytosolic 2,3-bisphosphoglycerate, an increase in intracellular Ca(2+), removal of cell O(2), a decrease in intracellular pH, and activation of erythrocyte protein kinase C all promote dissociation of protein 4.1 from glycophorin C, leading to reduced retention of glycophorin C in detergent-extracted spectrin/actin skeletons. Significantly, where mechanical studies could be performed, we also observe that rupture of the membrane-to-skeleton bridge has little or no impact on the mechanical properties of the cell, as assayed by ektacytometry and nickel mesh filtration. We, therefore, suggest that, although regulation of the glycophorin C-protein 4.1-spectrin/actin bridge likely occurs physiologically, the role of the tether and the associated regulatory changes remain to be established. PMID:11294862

  13. Axial Skeleton

    MedlinePlus

    ... Site-specific Modules Resources Archived Modules Updates Axial Skeleton (80 bones) Skull (28) Cranial Bones Parietal (2) ... Sternum (1) Ribs (24) « Previous (Divisions of the Skeleton) Next (Appendicular Skeleton (126 bones)) » Contact Us | Privacy ...

  14. A 39-kD plasma membrane protein (IP39) is an anchor for the unusual membrane skeleton of Euglena gracilis

    SciTech Connect

    Rosiere, T.K.; Marrs, J.A.; Bouck, G.B. )

    1990-04-01

    The major integral plasma membrane protein (IP39) of Euglena gracilis was radiolabeled, peptide mapped, and dissected with proteases to identify cytoplasmic domains that bind and anchor proteins of the cell surface. When plasma membranes were radioiodinated and extracted with octyl glucoside, 98% of the extracted label was found in IP39 or the 68- and 110-kD oligomers of IP39. The octyl glucoside extracts were incubated with unlabeled cell surface proteins immobilized on nitrocellulose (overlays). Radiolabel from the membrane extract bound one (80 kD) of the two (80 and 86 kD) major membrane skeletal protein bands. Resolubilization of the bound label yielded a radiolabeled polypeptide identical in Mr to IP39. Intact plasma membranes were also digested with papain before or after radioiodination, thereby producing a cytoplasmically truncated IP39. The octyl glucoside extract of truncated IP39 no longer bound to the 80-kD membrane skeletal protein in the nitrocellulose overlays. EM of intact or trypsin digested plasma membranes incubated with membrane skeletal proteins under stringent conditions similar to those used in the nitrocellulose overlays revealed a partially reformed membrane skeletal layer. Little evidence of a membrane skeletal layer was found, however, when plasma membranes were predigested with papain before reassociation. A candidate 80-kD binding domain of IP39 has been tentatively identified as a peptide fragment that was present after trypsin digestion of plasma membranes, but was absent after papain digestion in two-dimensional peptide maps of IP39. Together, these data suggest that the unique peripheral membrane skeleton of Euglena binds to the plasma membrane through noncovalent interactions between the major 80-kD membrane skeletal protein and a small, papain sensitive cytoplasmic domain of IP39.

  15. Effect of actuating cell source on locomotion of organic living machines with electrocompacted collagen skeleton.

    PubMed

    Webster, Victoria A; Hawley, Emma L; Akkus, Ozan; Chiel, Hillel J; Quinn, Roger D

    2016-01-01

    In robotics, there is a need for small scale, compliant actuators for use in medical applications or minimally invasive environmental monitoring. Biohybrid devices offer one solution to this need by using muscle cells to actuate compliant scaffolds. Such devices typically use biocompatible synthetic polymers as compliant scaffolds, which require additional processing steps to promote cellular alignment and attachment. Instead, electrocompacted and aligned collagen (ELAC) can be used as a completely organic scaffold, requiring no additional processing steps, with alignment being innately promoted by the topography. Locomotive living machines have been fabricated in this study using ELAC scaffolds. Devices have been produced using either primary cardiomyocytes or primary skeletal muscle cells isolated from chick embryos as actuators. When tested under the same conditions, skeletal muscle cell powered devices were approximately an order of magnitude faster, having a mean velocity of 77.6 ± 86.4 μm min(-1), compared to 9.34 ± 6.69 μm min(-1) for cardiomyocyte powered devices. In conclusion, completely organic living machines have been fabricated using electrocompacted collagen skeletons, and it was found that skeletal muscle powered devices were significantly faster than cardiomyocyte powered devices. PMID:27159923

  16. Appendicular Skeleton

    MedlinePlus

    ... Site-specific Modules Resources Archived Modules Updates Appendicular Skeleton (126 bones) Pectoral girdles Clavicle (2) Scapula (2) ... Tarsals (14) Metatarsals (10) Phalanges (28) « Previous (Axial Skeleton (80 bones)) Next (Articulations) » Contact Us | Privacy Policy | ...

  17. The membrane skeleton in Paramecium: Molecular characterization of a novel epiplasmin family and preliminary GFP expression results.

    PubMed

    Pomel, Sébastien; Diogon, Marie; Bouchard, Philippe; Pradel, Lydie; Ravet, Viviane; Coffe, Gérard; Viguès, Bernard

    2006-02-01

    Previous attempts to identify the membrane skeleton of Paramecium cells have revealed a protein pattern that is both complex and specific. The most prominent structural elements, epiplasmic scales, are centered around ciliary units and are closely apposed to the cytoplasmic side of the inner alveolar membrane. We sought to characterize epiplasmic scale proteins (epiplasmins) at the molecular level. PCR approaches enabled the cloning and sequencing of two closely related genes by amplifications of sequences from a macronuclear genomic library. Using these two genes (EPI-1 and EPI-2), we have contributed to the annotation of the Paramecium tetraurelia macronuclear genome and identified 39 additional (paralogous) sequences. Two orthologous sequences were found in the Tetrahymena thermophila genome. Structural analysis of the 43 sequences indicates that the hallmark of this new multigenic family is a 79 aa domain flanked by two Q-, P- and V-rich stretches of sequence that are much more variable in amino-acid composition. Such features clearly distinguish members of the multigenic family from epiplasmic proteins previously sequenced in other ciliates. The expression of Green Fluorescent Protein (GFP)-tagged epiplasmin showed significant labeling of epiplasmic scales as well as oral structures. We expect that the GFP construct described herein will prove to be a useful tool for comparative subcellular localization of different putative epiplasmins in Paramecium. PMID:16427359

  18. A cell surface integral membrane glycoprotein of 85,000 mol wt (gp85) associated with triton X-100-insoluble cell skeleton.

    PubMed

    Tarone, G; Ferracini, R; Galetto, G; Comoglio, P

    1984-08-01

    The Triton X-100-insoluble skeleton of baby hamster kidney BHK cells consists of the nucleus, intermediate-size filaments, and actin fibers. By transmission electron microscopy, membrane fragments were found to be associated with these insoluble structures. When radioiodinated or [3H]glucosamine-labeled cells were extracted with 0.5% Triton, most plasma membrane glycoproteins were solubilized except for a glycoprotein with a molecular weight of 85,000 (gp85) that remained associated with the insoluble skeletons. Immunoprecipitation with a specific antiserum indicated that the gp85 is not a proteolytic degradation product of fibronectin, an extracellular matrix glycoprotein insoluble in detergent. A monoclonal antibody of BHK cells specific for gp85 was produced. Immunofluorescence analysis with this monoclonal antibody indicated that gp85 is not associated with the extracellular matrix, but is confined to the cell membrane. Both in fixed and unfixed intact cells, fluorescence was concentrated in dots preferentially aligned in streaks on the cell surface. Gp85 was found to behave as an integral membrane protein interacting with the hydrophobic core of the lipid bilayer since it was extracted from membrane preparations by ionic detergents such as SDS, but not by 0.1 N NaOH (pH 12) in the absence of detergents, a condition known to release peripheral molecules. Association of gp85 with the cell skeleton was unaffected by increasing the Triton concentration up to 5%, but it was affected when actin filaments were dissociated or when a protein-denaturing agent (6 M urea) was used in the presence of Triton, suggesting that protein-protein interactions are involved in the association of gp85 with the cell skeleton. We conclude that gp85 is an integral plasma membrane glycoprotein that might have a role in cell surface-cytoskeleton interaction. PMID:6378925

  19. Porous membrane with high curvature, three-dimensional heat-resistance skeleton: a new and practical separator candidate for high safety lithium ion battery.

    PubMed

    Shi, Junli; Xia, Yonggao; Yuan, Zhizhang; Hu, Huasheng; Li, Xianfeng; Zhang, Huamin; Liu, Zhaoping

    2015-01-01

    Separators with high reliability and security are in urgent demand for the advancement of high performance lithium ion batteries. Here, we present a new and practical porous membrane with three-dimension (3D) heat-resistant skeleton and high curvature pore structure as a promising separator candidate to facilitate advances in battery safety and performances beyond those obtained from the conventional separators. The unique material properties combining with the well-developed structural characteristics enable the 3D porous skeleton to own several favorable properties, including superior thermal stability, good wettability with liquid electrolyte, high ion conductivity and internal short-circuit protection function, etc. which give rise to acceptable battery performances. Considering the simply and cost-effective preparation process, the porous membrane is deemed to be an interesting direction for the future lithium ion battery separator. PMID:25653104

  20. Porous membrane with high curvature, three-dimensional heat-resistance skeleton: a new and practical separator candidate for high safety lithium ion battery

    PubMed Central

    Shi, Junli; Xia, Yonggao; Yuan, Zhizhang; Hu, Huasheng; Li, Xianfeng; Zhang, Huamin; Liu, Zhaoping

    2015-01-01

    Separators with high reliability and security are in urgent demand for the advancement of high performance lithium ion batteries. Here, we present a new and practical porous membrane with three-dimension (3D) heat-resistant skeleton and high curvature pore structure as a promising separator candidate to facilitate advances in battery safety and performances beyond those obtained from the conventional separators. The unique material properties combining with the well-developed structural characteristics enable the 3D porous skeleton to own several favorable properties, including superior thermal stability, good wettability with liquid electrolyte, high ion conductivity and internal short-circuit protection function, etc. which give rise to acceptable battery performances. Considering the simply and cost-effective preparation process, the porous membrane is deemed to be an interesting direction for the future lithium ion battery separator. PMID:25653104

  1. The combined application of organic sulphur and isotope geochemistry to assess multiple sources of palaeobiochemicals with identical carbon skeletons

    NASA Technical Reports Server (NTRS)

    Kohnen, M. E.; Schouten, S.; Sinninghe Damste, J. S.; de Leeuw, J. W.; Merrit, D.; Hayes, J. M.

    1992-01-01

    Five immature sediments from a Messinian evaporitic basin, representing one evaporitic cycle, were studied using molecular organic sulphur and isotope geochemistry. It is shown that a specific carbon skeleton which is present in different "modes of occurrence" ("free" hydrocarbon, alkylthiophene, alkylthiolane, alkyldithiane, alkylthiane, and sulphur-bound in macromolecules) may have different biosynthetic precursors which are possibly derived from different biota. It is demonstrated that the mode of occurrence and the carbon isotopic composition of a sedimentary lipid can be used to "reconstruct" its biochemical precursor. This novel approach of recognition of the suite of palaeobiochemicals present during the time of deposition allows for identification of the biological sources with an unprecedented specificity.

  2. Prevalent presence of periodic actin–spectrin-based membrane skeleton in a broad range of neuronal cell types and animal species

    PubMed Central

    He, Jiang; Zhou, Ruobo; Wu, Zhuhao; Carrasco, Monica A.; Kurshan, Peri T.; Farley, Jonathan E.; Simon, David J.; Wang, Guiping; Han, Boran; Hao, Junjie; Heller, Evan; Freeman, Marc R.; Shen, Kang; Maniatis, Tom; Tessier-Lavigne, Marc

    2016-01-01

    Actin, spectrin, and associated molecules form a periodic, submembrane cytoskeleton in the axons of neurons. For a better understanding of this membrane-associated periodic skeleton (MPS), it is important to address how prevalent this structure is in different neuronal types, different subcellular compartments, and across different animal species. Here, we investigated the organization of spectrin in a variety of neuronal- and glial-cell types. We observed the presence of MPS in all of the tested neuronal types cultured from mouse central and peripheral nervous systems, including excitatory and inhibitory neurons from several brain regions, as well as sensory and motor neurons. Quantitative analyses show that MPS is preferentially formed in axons in all neuronal types tested here: Spectrin shows a long-range, periodic distribution throughout all axons but appears periodic only in a small fraction of dendrites, typically in the form of isolated patches in subregions of these dendrites. As in dendrites, we also observed patches of periodic spectrin structures in a small fraction of glial-cell processes in four types of glial cells cultured from rodent tissues. Interestingly, despite its strong presence in the axonal shaft, MPS is disrupted in most presynaptic boutons but is present in an appreciable fraction of dendritic spine necks, including some projecting from dendrites where such a periodic structure is not observed in the shaft. Finally, we found that spectrin is capable of adopting a similar periodic organization in neurons of a variety of animal species, including Caenorhabditis elegans, Drosophila, Gallus gallus, Mus musculus, and Homo sapiens. PMID:27162329

  3. Prevalent presence of periodic actin-spectrin-based membrane skeleton in a broad range of neuronal cell types and animal species.

    PubMed

    He, Jiang; Zhou, Ruobo; Wu, Zhuhao; Carrasco, Monica A; Kurshan, Peri T; Farley, Jonathan E; Simon, David J; Wang, Guiping; Han, Boran; Hao, Junjie; Heller, Evan; Freeman, Marc R; Shen, Kang; Maniatis, Tom; Tessier-Lavigne, Marc; Zhuang, Xiaowei

    2016-05-24

    Actin, spectrin, and associated molecules form a periodic, submembrane cytoskeleton in the axons of neurons. For a better understanding of this membrane-associated periodic skeleton (MPS), it is important to address how prevalent this structure is in different neuronal types, different subcellular compartments, and across different animal species. Here, we investigated the organization of spectrin in a variety of neuronal- and glial-cell types. We observed the presence of MPS in all of the tested neuronal types cultured from mouse central and peripheral nervous systems, including excitatory and inhibitory neurons from several brain regions, as well as sensory and motor neurons. Quantitative analyses show that MPS is preferentially formed in axons in all neuronal types tested here: Spectrin shows a long-range, periodic distribution throughout all axons but appears periodic only in a small fraction of dendrites, typically in the form of isolated patches in subregions of these dendrites. As in dendrites, we also observed patches of periodic spectrin structures in a small fraction of glial-cell processes in four types of glial cells cultured from rodent tissues. Interestingly, despite its strong presence in the axonal shaft, MPS is disrupted in most presynaptic boutons but is present in an appreciable fraction of dendritic spine necks, including some projecting from dendrites where such a periodic structure is not observed in the shaft. Finally, we found that spectrin is capable of adopting a similar periodic organization in neurons of a variety of animal species, including Caenorhabditis elegans, Drosophila, Gallus gallus, Mus musculus, and Homo sapiens. PMID:27162329

  4. Protein 4.1, a component of the erythrocyte membrane skeleton and its related homologue proteins forming the protein 4.1/FERM superfamily.

    PubMed

    Diakowski, Witold; Grzybek, Michał; Sikorski, Aleksander F

    2006-01-01

    The review is focused on the domain structure and function of protein 4.1, one of the proteins belonging to the membrane skeleton. The protein 4.1 of the red blood cells (4.1R) is a multifunctional protein that localizes to the membrane skeleton and stabilizes erythrocyte shape and membrane mechanical properties, such as deformability and stability, via lateral interactions with spectrin, actin, glycophorin C and protein p55. Protein 4.1 binding is modulated through the action of kinases and/or calmodulin-Ca2+. Non-erythroid cells express the 4.1R homologues: 4.1G (general type), 4.1B (brain type), and 4.1N (neuron type), and the whole group belongs to the protein 4.1 superfamily, which is characterized by the presence of a highly conserved FERM domain at the N-terminus of the molecule. Proteins 4.1R, 4.1G, 4.1N and 4.1B are encoded by different genes. Most of the 4.1 superfamily proteins also contain an actin-binding domain. To date, more than 40 members have been identified. They can be divided into five groups: protein 4.1 molecules, ERM proteins, talin-related molecules, protein tyrosine phosphatase (PTPH) proteins and NBL4 proteins. We have focused our attention on the main, well known representatives of 4.1 superfamily and tried to choose the proteins which are close to 4.1R or which have distinct functions. 4.1 family proteins are not just linkers between the plasma membrane and membrane skeleton; they also play an important role in various processes. Some, such as focal adhesion kinase (FAK), non-receptor tyrosine kinase that localizes to focal adhesions in adherent cells, play the role in cell adhesion. The other members control or take part in tumor suppression, regulation of cell cycle progression, inhibition of cell proliferation, downstream signaling of the glutamate receptors, and establishment of cell polarity; some are also involved in cell proliferation, cell motility, and/or cell-to-cell communication. PMID:17219717

  5. Orbiter's Skeleton

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The structure of NASA's Mars Reconnaissance Orbiter spacecraft is constructed from composite panels of carbon layers over aluminum honeycomb, lightweight yet strong. This forms a basic structure or skeleton on which the instruments, electronics, propulsion and power systems can be mounted. The propellant tank is contained in the center of the orbiter's structure. This photo was taken at Lockheed Martin Space Systems, Denver, during construction of the spacecraft.

  6. Constructing Free Standing Metal Organic Framework MIL-53 Membrane Based on Anodized Aluminum Oxide Precursor

    PubMed Central

    Zhang, Yunlu; Gao, Qiuming; Lin, Zhi; Zhang, Tao; Xu, Jiandong; Tan, Yanli; Tian, Weiqian; Jiang, Lei

    2014-01-01

    Metal organic framework (MOF) materials have attracted great attention due to their well-ordered and controllable pores possessing of prominent potentials for gas molecule sorption and separation performances. Organizing the MOF crystals to a continuous membrane with a certain scale will better exhibit their prominent potentials. Reports in recent years concentrate on well grown MOF membranes on specific substrates. Free standing MOF membranes could have more important applications since they are independent from the substrates. However, the method to prepare such a membrane has been a great challenge because good mechanical properties and stabilities are highly required. Here, we demonstrate a novel and facile technique for preparing the free standing membrane with a size as large as centimeter scale. The substrate we use proved itself not only a good skeleton but also an excellent precursor to fulfill the reaction. This kind of membrane owns a strong mechanical strength, based on the fact that it is much thinner than the composite membranes grown on substrates and it could exhibit good property of gas separation. PMID:24821299

  7. Gas Separation Using Organic-Vapor-Resistent Membranes In Conjunctin With Organic-Vapor-Selective Membranes

    DOEpatents

    Baker, Richard W.; Pinnau, Ingo; He, Zhenjie; Da Costa, Andre R.; Daniels, Ramin; Amo, Karl D.; Wijmans, Johannes G.

    2003-06-03

    A process for treating a gas mixture containing at least an organic compound gas or vapor and a second gas, such as natural gas, refinery off-gas or air. The process uses two sequential membrane separation steps, one using membrane selective for the organic compound over the second gas, the other selective for the second gas over the organic vapor. The second-gas-selective membranes use a selective layer made from a polymer having repeating units of a fluorinated polymer, and demonstrate good resistance to plasticization by the organic components in the gas mixture under treatment, and good recovery after exposure to liquid aromatic hydrocarbons. The membrane steps can be combined in either order.

  8. Protein 4.1, a multifunctional protein of the erythrocyte membrane skeleton: structure and functions in erythrocytes and nonerythroid cells.

    PubMed

    Takakuwa, Y

    2000-10-01

    Protein 4.1 of red blood cells (4.1R) is a multifunctional protein essential for maintaining erythrocyte shape and membrane mechanical properties, such as deformability and stability, through lateral interactions with spectrin and actin in the skeletal network and vertical interactions with cytoplasmic domains of transmembrane proteins, glycophorin C, and band 3. The primary stucture of the major 80-kd isoform of 4.1R has been elucidated, and on the basis of this identification, the functional domains and sites for binding partners have been clarified. Posttranslational modification of 4.1 R, such as phosphorylation and proteolysis, as well as binding of regulatory proteins including calmodulin-Ca2+ to 4.1R, modulates its interactions with other membrane proteins and, consequently, the membrane functions of red blood cells. Alternative splicing occurs in the 4.1R gene, and various isoforms are expressed not only in erythroid but also in nonerythroid cells. This review introduces current knowledge on biochemical, biophysical, genetic, and functional aspects of 4.1R and its family proteins, 4.1G (general type), 4.1B (brain type), and 4.1N (neuron type), recently identified in nonerythroid cells. PMID:11185985

  9. Characterization of TtALV2, an Essential Charged Repeat Motif Protein of the Tetrahymena thermophila Membrane Skeleton

    PubMed Central

    El-Haddad, Houda; Przyborski, Jude M.; Kraft, Lesleigh G. K.; McFadden, Geoffrey I.; Waller, Ross F.

    2013-01-01

    Alveolins are a recently described class of proteins common to all members of the superphylum Alveolata that are characterized by conserved charged repeat motifs (CRMs) but whose exact function remains unknown. We have analyzed the smaller of the two alveolins of Tetrahymena thermophila, TtALV2. The protein localizes to dispersed, broken patches arranged between the rows of the longitudinal microtubules. Macronuclear knockdown of Ttalv2 leads to multinuclear cells with no apparent cell polarity and randomly occurring cell protrusions, either by interrupting pellicle integrity or by disturbing cytokinesis. Correct association of TtALV2 with the alveoli or the pellicle is complex and depends on both the termini as well as the charged repeat motifs of the protein. Proteins containing similar CRMs are a dominant part of the ciliate membrane cytoskeleton, suggesting that these motifs may play a more general role in mediating membrane attachment and/or cytoskeletal association. To better understand their integration into the cytoskeleton, we localized a range of CRM-based fusion proteins, which suggested there is an inherent tendency for proteins with CRMs to be located in the peripheral cytoskeleton, some nucleating as filaments at the basal bodies. Even a synthetic protein, mimicking the charge and repeat pattern of these proteins, directed a reporter protein to a variety of peripheral cytoskeletal structures in Tetrahymena. These motifs might provide a blueprint for membrane and cytoskeleton affiliation in the complex pellicles of Alveolata. PMID:23606287

  10. Characterization of TtALV2, an essential charged repeat motif protein of the Tetrahymena thermophila membrane skeleton.

    PubMed

    El-Haddad, Houda; Przyborski, Jude M; Kraft, Lesleigh G K; McFadden, Geoffrey I; Waller, Ross F; Gould, Sven B

    2013-06-01

    Alveolins are a recently described class of proteins common to all members of the superphylum Alveolata that are characterized by conserved charged repeat motifs (CRMs) but whose exact function remains unknown. We have analyzed the smaller of the two alveolins of Tetrahymena thermophila, TtALV2. The protein localizes to dispersed, broken patches arranged between the rows of the longitudinal microtubules. Macronuclear knockdown of Ttalv2 leads to multinuclear cells with no apparent cell polarity and randomly occurring cell protrusions, either by interrupting pellicle integrity or by disturbing cytokinesis. Correct association of TtALV2 with the alveoli or the pellicle is complex and depends on both the termini as well as the charged repeat motifs of the protein. Proteins containing similar CRMs are a dominant part of the ciliate membrane cytoskeleton, suggesting that these motifs may play a more general role in mediating membrane attachment and/or cytoskeletal association. To better understand their integration into the cytoskeleton, we localized a range of CRM-based fusion proteins, which suggested there is an inherent tendency for proteins with CRMs to be located in the peripheral cytoskeleton, some nucleating as filaments at the basal bodies. Even a synthetic protein, mimicking the charge and repeat pattern of these proteins, directed a reporter protein to a variety of peripheral cytoskeletal structures in Tetrahymena. These motifs might provide a blueprint for membrane and cytoskeleton affiliation in the complex pellicles of Alveolata. PMID:23606287

  11. NOVEL POLYMERIC MEMBRANE FOR DEHYDRATION OF ORGANIC SOLVENTS

    EPA Science Inventory

    Pervaporation has emerged as an economically viable alternative technology for dehydration of organic solvents, removal of organic compounds and organic/organic separations. Development of a membrane system with suitable flux and selectivity characteristics plays a critical role...

  12. Characterization of organic membrane foulants in a forward osmosis membrane bioreactor treating anaerobic membrane bioreactor effluent.

    PubMed

    Ding, Yi; Tian, Yu; Li, Zhipeng; Liu, Feng; You, Hong

    2014-09-01

    In this study, two aerobic forward osmosis (FO) membrane bioreactors (MBR) were utilized to treat the effluent of mesophilic (35°C) and atmospheric (25°C) anaerobic MBRs, respectively. The results showed that the FO membrane process could significantly improve the removal efficiencies of N and P. Meanwhile, the flux decline of the FOMBR treating effluent of mesophilic AnMBR (M-FOMBR) was higher than that treating effluent of atmospheric AnMBR (P-FOMBR). The organic membrane foulants in the two FOMBRs were analyzed to understand the membrane fouling behavior in FO processes. It was found that the slightly increased accumulation of protein-like substances into external foulants did not cause faster flux decline in P-FOMBR than that in M-FOMBR. However, the quantity of organic matter tended to deposit or adsorb into FO membrane pores in P-FOMBR was less than that in M-FOMBR, which was accordance with the tendency of membrane fouling indicated by flux decline. PMID:24976492

  13. Purification, in vitro reassembly, and preliminary sequence analysis of epiplasmins, the major constituent of the membrane skeleton of Paramecium.

    PubMed

    Coffe, G; Le Caer, J P; Lima, O; Adoutte, A

    1996-01-01

    The epiplasmic layer, a continuous rigid granulo-fibrillar sheet directly subtending the surface membranes of Paramecium, is one of the outermost of the various cytoskeletal networks that compose it cortex. We have previously shown that the epiplasm consists of a set of 30 to 50 protein bands on SDS-PAGE in the range 50 to 33 kDa, the epiplasmins. We report a purification procedure for the set of epiplasmic proteins, a description of their physicochemical and reassembly properties, and a preliminary characterization of their sequence. The conditions for solubilization of the epiplasm and for in vitro reassembly of its purified constituents ar described. Reassembly of the entire set of proteins and of some (but not all) subsets are shown to yield filamentous aggregates. Microsequences of two purified bands of epiplasmins reveal a striking amino acid sequence consisting of heptad repeats of only three main amino acids, P, V, and Q. These repeats were confirmed by DNA sequencing of polymerase chain reaction products. The motif is QPVQ-h, in which h is a hydrophobic residue. This may constitute the core of the epiplasmin sequence and, in view of the tendency of such a sequence to form a coiled-coil, may account for the remarkable self-aggregation properties of epiplasmins. PMID:8769725

  14. The origin of the vertebrate skeleton

    NASA Astrophysics Data System (ADS)

    Pivar, Stuart

    2011-01-01

    The anatomy of the human and other vertebrates has been well described since the days of Leonardo da Vinci and Vesalius. The causative origin of the configuration of the bones and of their shapes and forms has been addressed over the ensuing centuries by such outstanding investigators as Goethe, Von Baer, Gegenbauer, Wilhelm His and D'Arcy Thompson, who sought to apply mechanical principles to morphogenesis. However, no coherent causative model of morphogenesis has ever been presented. This paper presents a causative model for the origin of the vertebrate skeleton, based on the premise that the body is a mosaic enlargement of self-organized patterns engrained in the membrane of the egg cell. Drawings illustrate the proposed hypothetical origin of membrane patterning and the changes in the hydrostatic equilibrium of the cytoplasm that cause topographical deformations resulting in the vertebrate body form.

  15. Chlorine-resistant composite membranes with high organic rejection

    DOEpatents

    McCray, Scott B.; Friesen, Dwayne T.; Barss, Robert P.; Nelson, Leslie D.

    1996-01-01

    A method for making a chlorine-resistant composite polyamide membrane having high organic rejection, the essential step of which comprises treating a conventional composite membrane with an acyl halide. The novel membrane is especially suitable for the treatment of water containing chlorine or lower molecular weight organic compounds.

  16. Organic fluid permeation through fluoropolymer membranes

    SciTech Connect

    Nemser, Stuart M.; Kosaraju, Praveen; Bowser, John

    2015-07-14

    Separation of the components of liquid mixtures is achieved by contacting a liquid mixture with a nonporous membrane having a fluoropolymer selectively permeable layer and imposing a pressure gradient across the membrane from feed side to permeate side. Unusually high transmembrane flux is obtained when the membrane is subjected to one or more process conditions prior to separation. These include (a) leaving some residual amount of membrane casting solvent in the membrane, and (b) contacting the membrane with a component of the mixture to be separated for a duration effective to saturate the membrane with the component.

  17. Lateral organization of membranes and cell shapes.

    PubMed Central

    Markin, V S

    1981-01-01

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

  18. A requirement for epsin in mitotic membrane and spindle organization

    PubMed Central

    2009-01-01

    Eukaryotic cells possess a sophisticated membrane system to facilitate diverse functions. Whereas much is known about the nature of membrane systems in interphase, the organization and function of the mitotic membrane system are less well understood. In this study, we show that epsin, an endocytic adapter protein, regulates mitotic membrane morphology and spindle integrity in HeLa cells. Using epsin that harbors point mutations in the epsin NH2-terminal homology domain and spindle assembly assays in Xenopus laevis egg extracts, we show that epsin-induced membrane curvature is required for proper spindle morphogenesis, independent of its function in endocytosis during interphase. Although several other membrane-interacting proteins, including clathrin, AP2, autosomal recessive hypercholesterolemia, and GRASP65, are implicated in the regulation of mitosis, whether they participate through regulation of membrane organization is unclear. Our study of epsin provides evidence that mitotic membrane organization influences spindle integrity. PMID:19704019

  19. [Skeleton extractions and applications].

    SciTech Connect

    Quadros, William Roshan

    2010-05-01

    This paper focuses on the extraction of skeletons of CAD models and its applications in finite element (FE) mesh generation. The term 'skeleton of a CAD model' can be visualized as analogous to the 'skeleton of a human body'. The skeletal representations covered in this paper include medial axis transform (MAT), Voronoi diagram (VD), chordal axis transform (CAT), mid surface, digital skeletons, and disconnected skeletons. In the literature, the properties of a skeleton have been utilized in developing various algorithms for extracting skeletons. Three main approaches include: (1) the bisection method where the skeleton exists at equidistant from at least two points on boundary, (2) the grassfire propagation method in which the skeleton exists where the opposing fronts meet, and (3) the duality method where the skeleton is a dual of the object. In the last decade, the author has applied different skeletal representations in all-quad meshing, hex meshing, mid-surface meshing, mesh size function generation, defeaturing, and decomposition. A brief discussion on the related work from other researchers in the area of tri meshing, tet meshing, and anisotropic meshing is also included. This paper concludes by summarizing the strengths and weaknesses of the skeleton-based approaches in solving various geometry-centered problems in FE mesh generation. The skeletons have proved to be a great shape abstraction tool in analyzing the geometric complexity of CAD models as they are symmetric, simpler (reduced dimension), and provide local thickness information. However, skeletons generally require some cleanup, and stability and sensitivity of the skeletons should be controlled during extraction. Also, selecting a suitable application-specific skeleton and a computationally efficient method of extraction is critical.

  20. The membrane: transertion as an organizing principle in membrane heterogeneity

    PubMed Central

    Matsumoto, Kouji; Hara, Hiroshi; Fishov, Itzhak; Mileykovskaya, Eugenia; Norris, Vic

    2015-01-01

    The bacterial membrane exhibits a significantly heterogeneous distribution of lipids and proteins. This heterogeneity results mainly from lipid–lipid, protein–protein, and lipid–protein associations which are orchestrated by the coupled transcription, translation and insertion of nascent proteins into and through membrane (transertion). Transertion is central not only to the individual assembly and disassembly of large physically linked groups of macromolecules (alias hyperstructures) but also to the interactions between these hyperstructures. We review here these interactions in the context of the processes in Bacillus subtilis and Escherichia coli of nutrient sensing, membrane synthesis, cytoskeletal dynamics, DNA replication, chromosome segregation, and cell division. PMID:26124753

  1. Membrane Driven Spatial Organization of GPCRs

    NASA Astrophysics Data System (ADS)

    Mondal, Sayan; Johnston, Jennifer M.; Wang, Hao; Khelashvili, George; Filizola, Marta; Weinstein, Harel

    2013-10-01

    Spatial organization of G-protein coupled receptors (GPCRs) into dimers and higher order oligomers has been demonstrated in vitro and in vivo. The pharmacological readout was shown to depend on the specific interfaces, but why particular regions of the GPCR structure are involved, and how ligand-determined states change them remains unknown. Here we show why protein-membrane hydrophobic matching is attained upon oligomerization at specific interfaces from an analysis of coarse-grained molecular dynamics simulations of the spontaneous diffusion-interaction of the prototypical beta2-adrenergic (β2AR) receptors in a POPC lipid bilayer. The energy penalty from mismatch is significantly reduced in the spontaneously emerging oligomeric arrays, making the spatial organization of the GPCRs dependent on the pattern of mismatch in the monomer. This mismatch pattern is very different for β2AR compared to the highly homologous and structurally similar β1AR, consonant with experimentally observed oligomerization patterns of β2AR and β1AR. The results provide a mechanistic understanding of the structural context of oligomerization.

  2. Current approaches to studying membrane organization

    PubMed Central

    van Zanten, Thomas S.; Mayor, Satyajit

    2015-01-01

    The local structure and composition of the outer membrane of an animal cell are important factors in the control of many membrane processes and mechanisms. These include signaling, sorting, and exo- and endocytic processes that are occurring all the time in a living cell. Paradoxically, not only are the local structure and composition of the membrane matters of much debate and discussion, the mechanisms that govern its genesis remain highly controversial. Here, we discuss a swathe of new technological advances that may be applied to understand the local structure and composition of the membrane of a living cell from the molecular scale to the scale of the whole membrane. PMID:26918150

  3. Graphene oxide membranes with tunable semipermeability in organic solvents.

    PubMed

    Huang, Liang; Li, Yingru; Zhou, Qinqin; Yuan, Wenjing; Shi, Gaoquan

    2015-07-01

    Graphene oxide membranes (GOMs) are mechanically stable in various organic solvents, and their nanochannels can be narrowed by thermal annealing or widened by solvation. Therefore, the semipermeability of GOMs can be easily modulated, and they can be used as "multipurpose membranes" for molecular sieving in organic media. PMID:25994919

  4. Coral Skeletons Defend against Ultraviolet Radiation

    PubMed Central

    Reef, Ruth; Kaniewska, Paulina; Hoegh-Guldberg, Ove

    2009-01-01

    Background Many coral reef organisms are photosynthetic or have evolved in tight symbiosis with photosynthetic symbionts. As such, the tissues of reef organisms are often exposed to intense solar radiation in clear tropical waters and have adapted to trap and harness photosynthetically active radiation (PAR). High levels of ultraviolet radiation (UVR) associated with sunlight, however, represent a potential problem in terms of tissue damage. Methodology/Principal Findings By measuring UVR and PAR reflectance from intact and ground bare coral skeletons we show that the property of calcium carbonate skeletons to absorb downwelling UVR to a significant extent, while reflecting PAR back to the overlying tissue, has biological advantages. We placed cnidarians on top of bare skeletons and a UVR reflective substrate and showed that under ambient UVR levels, UVR transmitted through the tissues of cnidarians placed on top of bare skeletons were four times lower compared to their counterparts placed on a UVR reflective white substrate. In accordance with the lower levels of UVR measured in cnidarians on top of coral skeletons, a similar drop in UVR damage to their DNA was detected. The skeletons emitted absorbed UVR as yellow fluorescence, which allows for safe dissipation of the otherwise harmful radiation. Conclusions/Significance Our study presents a novel defensive role for coral skeletons and reveals that the strong UVR absorbance by the skeleton can contribute to the ability of corals, and potentially other calcifiers, to thrive under UVR levels that are detrimental to most marine life. PMID:19946361

  5. Membrane-Organized Chemical Photoredox Systems

    SciTech Connect

    Hurst, James K.

    2014-09-18

    This project has three interrelated goals relevant to solar water photolysis, which are to develop: (1) vesicle-organized assemblies for H2 photoproduction that utilize pyrylium and structurally related compounds as combined photosensitizers and cyclic electroneutral transmembrane electron carriers; (2) transmembrane redox systems whose reaction rates can be modulated by light; and (3) homogeneous catalysts for water oxidation. . In area (1), initial efforts to photogenerate H2 from vectorially-organized vesicles containing occluded colloidal Pt and commonly available pyrylium ions as transmembrane redox mediators were unsuccessful. New pyrylium compounds with significantly lower reduction potentials have been synthesized to address this problem, their apparent redox potentials in functioning systems have been now evaluated by using a series of occluded viologens, and H2 photoproduction has been demonstrated in continuous illumination experiments. In area (2), spirooxazine-quinone dyads have been synthesized and their capacity to function as redox mediators across bilayer membranes has been evaluated through continuous photolysis and transient spectrophotometric measurements. Photoisomerization of the spiro moiety to the ring-open mero form caused net quantum yields to decrease significantly, providing a basis for photoregulation of transmembrane redox. Research on water oxidation (area 3) has been directed at understanding mechanisms of catalysis by cis,cis-[(bpy)2Ru(OH2)]2O4+ and related polyimine complexes. Using a variety of physical techniques, we have: (i) identified the redox state of the complex ion that is catalytically active; (ii) shown using 18O isotopic labeling that there are two reaction pathways, both of which involve participation of solvent H2O; and (iii) detected and characterized by EPR and resonance Raman spectroscopies new species which may be key intermediates in the catalytic cycle.

  6. Spatiotemporal Organization of Spin-Coated Supported Model Membranes

    NASA Astrophysics Data System (ADS)

    Simonsen, Adam Cohen

    All cells of living organisms are separated from their surroundings and organized internally by means of flexible lipid membranes. In fact, there is consensus that the minimal requirements for self-replicating life processes include the following three features: (1) information carriers (DNA, RNA), (2) a metabolic system, and (3) encapsulation in a container structure [1]. Therefore, encapsulation can be regarded as an essential part of life itself. In nature, membranes are highly diverse interfacial structures that compartmentalize cells [2]. While prokaryotic cells only have an outer plasma membrane and a less-well-developed internal membrane structure, eukaryotic cells have a number of internal membranes associated with the organelles and the nucleus. Many of these membrane structures, including the plasma membrane, are complex layered systems, but with the basic structure of a lipid bilayer. Biomembranes contain hundreds of different lipid species in addition to embedded or peripherally associated membrane proteins and connections to scaffolds such as the cytoskeleton. In vitro, lipid bilayers are spontaneously self-organized structures formed by a large group of amphiphilic lipid molecules in aqueous suspensions. Bilayer formation is driven by the entropic properties of the hydrogen bond network in water in combination with the amphiphilic nature of the lipids. The molecular shapes of the lipid constituents play a crucial role in bilayer formation, and only lipids with approximately cylindrical shapes are able to form extended bilayers. The bilayer structure of biomembranes was discovered by Gorter and Grendel in 1925 [3] using monolayer studies of lipid extracts from red blood cells. Later, a number of conceptual models were developed to rationalize the organization of lipids and proteins in biological membranes. One of the most celebrated is the fluid-mosaic model by Singer and Nicolson (1972) [4]. According to this model, the lipid bilayer component of

  7. Nitrogen isotopic composition of organic matter from a 168 year-old coral skeleton: Implications for coastal nutrient cycling in the Great Barrier Reef Lagoon

    NASA Astrophysics Data System (ADS)

    Erler, Dirk V.; Wang, Xingchen T.; Sigman, Daniel M.; Scheffers, Sander R.; Martínez-García, Alfredo; Haug, Gerald H.

    2016-01-01

    Ongoing human activities are known to affect nitrogen cycling on coral reefs, but the full history of anthropogenic impact is unclear due to a lack of continuous records. We have used the nitrogen isotopic composition of skeleton-bound organic matter (CS-δ15N) in a coastal Porites coral from Magnetic Island in the Great Barrier Reef as a proxy for N cycle changes over a 168 yr period (1820-1987 AD). The Magnetic Island inshore reef environment is considered to be relatively degraded by terrestrial runoff; given prior CS-δ15N studies from other regions, there was an expectation of both secular change and oscillations in CS-δ15N since European settlement of the mainland in the mid 1800s. Surprisingly, CS-δ15N varied by less than 1.5‰ despite significant land use change on the adjacent mainland over the 168-yr measurement period. After 1930, CS-δ15N may have responded to changes in local river runoff, but the effect was weak. We propose that natural buffering against riverine nitrogen load in this region between 1820 and 1987 is responsible for the observed stability in CS-δ15N. In addition to coral derived skeletal δ15N, we also report, for the first time, δ15N measurements of non-coral derived organic N occluded within the coral skeleton, which appear to record significant changes in the nature of terrestrial N inputs. In the context of previous CS-δ15N records, most of which yield CS-δ15N changes of at least 5‰, the Magnetic Island coral suggests that the inherent down-core variability of the CS-δ15N proxy is less than 2‰ for Porites.

  8. Isotopic composition of skeleton-bound organic nitrogen in reef-building symbiotic corals: A new method and proxy evaluation at Bermuda

    NASA Astrophysics Data System (ADS)

    Wang, X. T.; Sigman, D. M.; Cohen, A. L.; Sinclair, D. J.; Sherrell, R. M.; Weigand, M. A.; Erler, D. V.; Ren, H.

    2015-01-01

    The skeleton-bound organic nitrogen in reef-building symbiotic corals may be a high-resolution archive of ocean nitrogen cycle dynamics and a tool for understanding coral biogeochemistry and physiological processes. However, the existing methods for measuring the isotopic composition of coral skeleton-bound organic nitrogen (hereafter, CS-δ15N) either require too much skeleton material or have low precision, limiting the applications of this relatively new proxy. In addition, the controlling factors on CS-δ15N remain poorly understood: the δ15N of source nitrogen and the internal nitrogen cycle of the coral/zooxanthellae symbiosis may both be important. Here, we describe a new ("persulfate/denitrifier"-based) method for measuring CS-δ15N, requiring only 5 mg of skeleton material and yielding a long-term precision better than 0.2‰ (1σ). Using this new method, we investigate CS-δ15N at Bermuda. Ten modern Diploria labyrinthiformis coral cores/colonies from 4 sampling sites were measured for CS-δ15N. Nitrogen concentrations (nitrate + nitrite, ammonium, and dissolved organic nitrogen) and δ15N of plankton were also measured at these coral sites. Among the 4 sampling sites, CS-δ15N shows an increase with proximity to the island, from ∼3.8‰ to ∼6.8‰ vs. atmospheric N2, with the northern offshore site having a CS-δ15N 1-2‰ higher than the δ15N of thermocline nitrate in the surrounding Sargasso Sea. Two annually resolved CS-δ15N time series suggest that the offshore-inshore CS-δ15N gradient has persisted since at least the 1970s. Plankton δ15N among these 4 sites also has an inshore increase, but of only ∼1‰. Coral physiological change must explain the remaining (∼2‰) inshore increase in CS-δ15N, and previous work points to the coral/zooxanthellae N cycle as a control on host tissue (and thus carbonate skeletal) δ15N. The CS-δ15N gradient is hypothesized to result mainly from varying efficiency in the internal nitrogen recycling of the

  9. The Skeletons' Halloween

    ERIC Educational Resources Information Center

    Bourque, Simone

    2010-01-01

    Mexican printer Jose Guadalupe Posada's (1851-1913) numerous prints of "calaveras" gave vast popularity to skeleton figures through his satirical and politically critical renditions of skeletons engaged in daily activities. They are oftentimes represented in festive and playful posturing. Calaveras have now become the most original trait of…

  10. Theoretical analysis of protein organization in lipid membranes.

    PubMed

    Gil, T; Ipsen, J H; Mouritsen, O G; Sabra, M C; Sperotto, M M; Zuckermann, M J

    1998-11-10

    The fundamental physical principles of the lateral organization of trans-membrane proteins and peptides as well as peripheral membrane proteins and enzymes are considered from the point of view of the lipid-bilayer membrane, its structure, dynamics, and cooperative phenomena. Based on a variety of theoretical considerations and model calculations, the nature of lipid-protein interactions is considered both for a single protein and an assembly of proteins that can lead to aggregation and protein crystallization in the plane of the membrane. Phenomena discussed include lipid sorting and selectivity at protein surfaces, protein-lipid phase equilibria, lipid-mediated protein-protein interactions, wetting and capillary condensation as means of protein organization, mechanisms of two-dimensional protein crystallization, as well as non-equilibrium organization of active proteins in membranes. The theoretical findings are compared with a variety of experimental data. PMID:9804966

  11. Amphiphobic Polytetrafluoroethylene Membranes for Efficient Organic Aerosol Removal.

    PubMed

    Feng, Shasha; Zhong, Zhaoxiang; Zhang, Feng; Wang, Yong; Xing, Weihong

    2016-04-01

    Polytetrafluoroethylene (PTFE) membrane is an extensively used air filter, but its oleophilicity leads to severe fouling of the membrane surface due to organic aerosol deposition. Herein, we report the fabrication of a new amphiphobic 1H,1H,2H,2H-perfluorodecyl acrylate (PFDAE)-grafted ZnO@PTFE membrane with enhanced antifouling functionality and high removal efficiency. We use atomic-layer deposition (ALD) to uniformly coat a layer of nanosized ZnO particles onto porous PTFE matrix to increase surface area and then subsequently graft PFDAE with plasma. Consequently, the membrane surface showed both superhydrophobicity and oleophobicity with a water contact angle (WCA) and an oil contact angle (OCA) of 150° and 125°, respectively. The membrane air permeation rate of 513 (m(3) m(-2) h(-1) kPa(-1)) was lower than the pristine membrane rate of 550 (m(3) m(-2) h(-1) kPa(-1)), which indicates the surface modification slightly decreased the membrane air permeation. Significantly, the filtration resistance of this amphiphobic membrane to the oil aerosol system was much lower than the initial one. Moreover, the filter exhibited exceptional organic aerosol removal efficiencies that were greater than 99.5%. These results make the amphiphobic PTFE membranes very promising for organic aerosol-laden air-filtration applications. PMID:27002786

  12. Differential Effect of Plant Lipids on Membrane Organization

    PubMed Central

    Grosjean, Kevin; Mongrand, Sébastien; Beney, Laurent; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

    2015-01-01

    The high diversity of the plant lipid mixture raises the question of their respective involvement in the definition of membrane organization. This is particularly the case for plant plasma membrane, which is enriched in specific lipids, such as free and conjugated forms of phytosterols and typical phytosphingolipids, such as glycosylinositolphosphoceramides. This question was here addressed extensively by characterizing the order level of membrane from vesicles prepared using various plant lipid mixtures and labeled with an environment-sensitive probe. Fluorescence spectroscopy experiments showed that among major phytosterols, campesterol exhibits a stronger ability than β-sitosterol and stigmasterol to order model membranes. Multispectral confocal microscopy, allowing spatial analysis of membrane organization, demonstrated accordingly the strong ability of campesterol to promote ordered domain formation and to organize their spatial distribution at the membrane surface. Conjugated sterol forms, alone and in synergy with free sterols, exhibit a striking ability to order membrane. Plant sphingolipids, particularly glycosylinositolphosphoceramides, enhanced the sterol-induced ordering effect, emphasizing the formation and increasing the size of sterol-dependent ordered domains. Altogether, our results support a differential involvement of free and conjugated phytosterols in the formation of ordered domains and suggest that the diversity of plant lipids, allowing various local combinations of lipid species, could be a major contributor to membrane organization in particular through the formation of sphingolipid-sterol interacting domains. PMID:25575593

  13. Membrane permeation process for dehydration of organic liquid mixtures using sulfonated ion-exchange polyalkene membranes

    DOEpatents

    Cabasso, Israel; Korngold, Emmanuel

    1988-01-01

    A membrane permeation process for dehydrating a mixture of organic liquids, such as alcohols or close boiling, heat sensitive mixtures. The process comprises causing a component of the mixture to selectively sorb into one side of sulfonated ion-exchange polyalkene (e.g., polyethylene) membranes and selectively diffuse or flow therethrough, and then desorbing the component into a gas or liquid phase on the other side of the membranes.

  14. Organization and dynamics of SNARE proteins in the presynaptic membrane

    PubMed Central

    Milovanovic, Dragomir; Jahn, Reinhard

    2015-01-01

    Our view of the lateral organization of lipids and proteins in the plasma membrane has evolved substantially in the last few decades. It is widely accepted that many, if not all, plasma membrane proteins and lipids are organized in specific domains. These domains vary widely in size, composition, and stability, and they represent platforms governing diverse cell functions. The presynaptic plasma membrane is a well-studied example of a membrane which undergoes rearrangements, especially during exo- and endocytosis. Many proteins and lipids involved in presynaptic function are known, and major efforts have been made to understand their spatial organization and dynamics. Here, we focus on the mechanisms underlying the organization of SNAREs, the key proteins of the fusion machinery, in distinct domains, and we discuss the functional significance of these clusters. PMID:25852575

  15. Remove volatile organic compounds (VOCs) with membrane separation techniques.

    PubMed

    Zhang, Lin; Weng, Huan-xin; Chen, Huan-lin; Gao, Cong-jie

    2002-04-01

    Membrane separation, a new technology for removing VOCs including pervaporation, vapor permeation, membrane contactor, and membrane bioreactor was presented. Comparing with traditional techniques, these special techniques are an efficient and energy-saving technology. Vapor permeation can be applied to recovery of organic solvents from exhaust streams. Membrane contactor could be used for removing or recovering VOCs from air or wastewater. Pervaporation and vapor permeation are viable methods for removing VOCs from wastewater to yield a VOC concentrate which could either be destroyed by conventional means, or be recycled for reuse. PMID:12046285

  16. Asymmetric hydrogel membranes for biohybrid artificial organs and bioseparations

    NASA Astrophysics Data System (ADS)

    Dai, Weihua Sonya

    1999-11-01

    Homogeneous hydrogel membranes were prepared by crosslinking poly(vinyl alcohol) (PVA) with glutaraldehyde. These membranes were then modified to create asymmetry by establishing a glutaraldehyde concentration gradient across the hydrogel thickness. Creatinine (MW: 113), goat Fab (MW: 50 kD) and human IgG (MW: 150 kD) were used to simulate the molecular size of nutrients, therapeutic proteins, and immunological molecules, respectively, involved in cell encapsulation. Permeation experiments were performed in a stirred diffusion cell through homogeneous and asymmetric PVA hydrogels. At a given value of IgG rejection, the asymmetric membranes had higher creatinine and Fab permeabilities than the corresponding homogeneous membranes, indicating that creating mesh size asymmetry in a hydrogel can result in a high-flux, high-selectivity membrane for bioartificial organs and bioseparations. The hydrogel membranes with mesh size asymmetry were characterized with laser scanning confocal fluorescence microscopy. A fluorescent label, DTAF (5-{[4,6-dichlorotriazin-2-yl] amino}-fluorescein) was attached to poly(vinyl alcohol), which then was used to prepare homogeneous and asymmetric hydrogel membranes. Structural asymmetry was clearly present in the gradient-modified membranes from the intensity as a function of membrane depth. From the relationships between fluorescence intensity and water content and between solute permeability and water content for homogeneous membranes, the permeabilities of creatinine, Fab and IgG for the asymmetric membranes were predicted from a sum-of-resistances model. The predicted solute permeabilities compared well to experimental values. The hydrogel membranes were mechanically supported with flat-sheet microfiltration membranes by impregnating the pores with a PVA solution, which was crosslinked with glutaraldehyde and then modified under a glutaraldehyde gradient to produce mesh size asymmetry. The supported, PVA hydrogel membranes with mesh size

  17. Nanoscale membrane organization: where biochemistry meets advanced microscopy

    PubMed Central

    Cambi, Alessandra; Lidke, Diane S.

    2011-01-01

    Understanding the molecular mechanisms that shape an effective cellular response is a fundamental question in biology. Biochemical measurements have revealed critical information about the order of protein-protein interactions along signaling cascades, but lack the resolution to determine kinetics and localization of interactions on the plasma membrane. Furthermore, the local membrane environment influences membrane receptor distributions and dynamics, which in turn influences signal transduction. To measure dynamic protein interactions and elucidate the consequences of membrane architecture interplay, direct measurements at high spatiotemporal resolution are needed. In this review, we discuss the biochemical principles regulating membrane nanodomain formation and protein function, ranging from the lipid nanoenvironment to the cortical cytoskeleton. We also discuss recent advances in fluorescence microscopy that are making it possible to quantify protein organization and biochemical events at the nanoscale in the living cell membrane. PMID:22004174

  18. Investigation of membrane fouling in ultrafiltration using model organic compounds.

    PubMed

    Kweon, J H; Lawler, D F

    2005-01-01

    Natural organic matter (NOM) is known to be the worst foulant in the membrane processes, but the complexities of NOM make it difficult to determine its effects on membrane fouling. Therefore, simple organic compounds (surrogates for NOM) were used in this research to investigate the fouling mechanisms in ultrafiltration. Previous research on NOM components in membrane processes indicated that polysaccharides formed an important part of the fouling cake. Three polysaccharides (dextran, alginic acid, and polygalacturonic acid) and a smaller carbohydrate (tannic acid) were evaluated for their removal in softening (the treatment process in the City of Austin). Two polysaccharides (dextran and alginic acid) were selected and further investigated for their effects on membrane fouling. The two raw organic waters (4 mg/L C) showed quite different patterns of flux decline indicating different fouling mechanisms. Softening pretreatment was effective to reduce flux decline of both waters. The SEM images of the fouled membrane clearly showed the shapes of deposited foulants. The high resolution results of the XPS spectra showed substantially different spectra of carbon, C(1s), in the membrane fouled by two raw organic waters. The XPS was beneficial in determining the relative composition of each fouling material on the membrane surface. PMID:16003967

  19. Hyperthin Organic Membranes for Gas Separations

    NASA Astrophysics Data System (ADS)

    Wang, Minghui

    Gas separation is practically important in many aspects, e.g., clean energy production and global warming prevention. Compared to other separation technologies like cryogenic distillation and pressure swing adsorption, membrane separation is considered to be more energy efficient. For practical purposes, the ultimate goal is to construct membranes producing high flux and high gas permeation selectivity at the same time. Based on the inverse relationship between flux and membrane thickness, it is clear that fabricating highly selective membranes as thin as possible could increase the flux through the membrane without sacrificing selectivity. But it has proven to be challenging to manufacture selective membranes in the hyperthin (< 100nm) region. [Note: 100 nm is the typical dense layer thickness of commercial membranes to separation gases.] In this dissertation, the focus is on the development of hyperthin selective membranes that were supported by poly(1-trimethylsilyl-1-propyne) (PTMSP), using Langmuir-Blodgett (LB) and Layer-by-Layer (LbL) deposition methods. A "gluing" strategy has been successfully introduced into LB films by our laboratory recently, in which LB monolayers are ionically crosslinked with polyelectrolytes. This success stimulated the pursuance of LB films with improved gas separation properties by: (i) examining calix[n]arene-based surfactants with different sizes (ii) using polymeric surfactants as LB forming materials, and (iii) optimizing the condition of the subphase containing polyelectrolytes. Both a strong polyelectrolyte poly(4-styrene sulfonate) (PSS) and a weak polyelectrolyte poly(acrylic acid) (PAA) were used to create glued LB bilayers. The gas permeation through PSS or PAA-glued LB bilayers made of calix[n]arenes was found to be dominated by solution-diffusion rather than molecular-sieving mechanism. The porous nature of calix[n]arene-based surfactants also turned out to be unnecessary for constructing LB films with high gas

  20. MreB-Dependent Organization of the E. coli Cytoplasmic Membrane Controls Membrane Protein Diffusion.

    PubMed

    Oswald, Felix; Varadarajan, Aravindan; Lill, Holger; Peterman, Erwin J G; Bollen, Yves J M

    2016-03-01

    The functional organization of prokaryotic cell membranes, which is essential for many cellular processes, has been challenging to analyze due to the small size and nonflat geometry of bacterial cells. Here, we use single-molecule fluorescence microscopy and three-dimensional quantitative analyses in live Escherichia coli to demonstrate that its cytoplasmic membrane contains microdomains with distinct physical properties. We show that the stability of these microdomains depends on the integrity of the MreB cytoskeletal network underneath the membrane. We explore how the interplay between cytoskeleton and membrane affects trans-membrane protein (TMP) diffusion and reveal that the mobility of the TMPs tested is subdiffusive, most likely caused by confinement of TMP mobility by the submembranous MreB network. Our findings demonstrate that the dynamic architecture of prokaryotic cell membranes is controlled by the MreB cytoskeleton and regulates the mobility of TMPs. PMID:26958890

  1. Organic Fouling of Graphene Oxide Membranes and Its Implications for Membrane Fouling Control in Engineered Osmosis.

    PubMed

    Hu, Meng; Zheng, Sunxiang; Mi, Baoxia

    2016-01-19

    This study provides experimental evidence to mechanistically understand some contradicting effects of the characteristic properties of graphene oxide (GO), such as the high hydrophilicity, negative charge, strong adsorption capability, and large surface area, on the antifouling properties of GO membranes. Furthermore, this study demonstrates the effectiveness of forming a dense GO barrier layer on the back (i.e., porous) side of an asymmetric membrane for fouling control in pressure-retarded osmosis (PRO), an emerging engineered osmosis process whose advancement has been much hindered due to the severe irreversible fouling that occurs as foulants accumulate inside the porous membrane support. In the membrane fouling experiments, protein and alginate were used as model organic foulants. When operated in forward osmosis mode, the GO membrane exhibited fouling performance comparable with that of a polyamide (PA) membrane. Analysis of the membrane adsorption capacity showed that, likely due to the presence of hydrophobic regions in the GO basal plane, the GO membrane has an affinity toward organic foulants 4 to 5 times higher than the PA membrane. Such a high adsorption capacity along with a large surface area, however, did not noticeably aggravate the fouling problem. Our explanation for this phenomenon is that organic foulants are adsorbed mainly on the basal plane of GO nanosheets, and water enters the GO membrane primarily around the oxidized edges of GO, making foulant adsorption not create much hindrance to water flux. When operated in PRO mode, the GO membrane exhibited much better antifouling performance than the PA membrane. This is because unlike the PA membrane for which foulants can be easily trapped inside the porous support and hence cause severe irreversible fouling, the GO membrane allows the foulants to accumulate primarily on its surface due to the sealing effect of the GO layer assembled on the porous side of the asymmetric membrane support. Results

  2. Role of mitochondrial inner membrane organizing system in protein biogenesis of the mitochondrial outer membrane

    PubMed Central

    Bohnert, Maria; Wenz, Lena-Sophie; Zerbes, Ralf M.; Horvath, Susanne E.; Stroud, David A.; von der Malsburg, Karina; Müller, Judith M.; Oeljeklaus, Silke; Perschil, Inge; Warscheid, Bettina; Chacinska, Agnieszka; Veenhuis, Marten; van der Klei, Ida J.; Daum, Günther; Wiedemann, Nils; Becker, Thomas; Pfanner, Nikolaus; van der Laan, Martin

    2012-01-01

    Mitochondria contain two membranes, the outer membrane and the inner membrane with folded cristae. The mitochondrial inner membrane organizing system (MINOS) is a large protein complex required for maintaining inner membrane architecture. MINOS interacts with both preprotein transport machineries of the outer membrane, the translocase of the outer membrane (TOM) and the sorting and assembly machinery (SAM). It is unknown, however, whether MINOS plays a role in the biogenesis of outer membrane proteins. We have dissected the interaction of MINOS with TOM and SAM and report that MINOS binds to both translocases independently. MINOS binds to the SAM complex via the conserved polypeptide transport–associated domain of Sam50. Mitochondria lacking mitofilin, the large core subunit of MINOS, are impaired in the biogenesis of β-barrel proteins of the outer membrane, whereas mutant mitochondria lacking any of the other five MINOS subunits import β-barrel proteins in a manner similar to wild-type mitochondria. We show that mitofilin is required at an early stage of β-barrel biogenesis that includes the initial translocation through the TOM complex. We conclude that MINOS interacts with TOM and SAM independently and that the core subunit mitofilin is involved in biogenesis of outer membrane β-barrel proteins. PMID:22918945

  3. Hierarchical organization and structural flexibility of thylakoid membranes.

    PubMed

    Garab, Győző

    2014-04-01

    Chloroplast thylakoid membranes accommodate densely packed protein complexes in ordered, often semi-crystalline arrays and are assembled into highly organized multilamellar systems, an organization warranting a substantial degree of stability. At the same time, they exhibit remarkable structural flexibility, which appears to play important - yet not fully understood - roles in different short-term adaptation mechanisms in response to rapidly changing environmental conditions. In this review I will focus on dynamic features of the hierarchically organized photosynthetic machineries at different levels of structural complexity: (i) isolated light harvesting complexes, (ii) molecular macroassemblies and supercomplexes, (iii) thylakoid membranes and (iv) their multilamellar membrane systems. Special attention will be paid to the most abundant systems, the major light harvesting antenna complex, LHCII, and to grana. Two physical mechanisms, which are less frequently treated in the literature, will receive special attention: (i) thermo-optic mechanism -elementary structural changes elicited by ultrafast local heat transients due to the dissipation of photon energy, which operates both in isolated antenna assemblies and the native thylakoid membranes, regulates important enzymatic functions and appears to play role in light adaptation and photoprotection mechanisms; and (ii) the mechanism by which non-bilayer lipids and lipid phases play key role in the functioning of xanthophyll cycle de-epoxidases and are proposed to regulate the protein-to-lipid ratio in thylakoid membranes and contribute to membrane dynamics. This article is part of a Special Issue entitled: Dynamic and ultrastructure of bioenergetic membranes and their components. PMID:24333385

  4. Natural organic matter fouling behaviors on superwetting nanofiltration membranes.

    PubMed

    Shan, Linglong; Fan, Hongwei; Guo, Hongxia; Ji, Shulan; Zhang, Guojun

    2016-04-15

    Nanofiltration has been widely recognized as a promising technology for the removal of micro-molecular organic components from natural water. Natural organic matter (NOM), a very important precursor of disinfection by-products, is currently considered as the major cause of membrane fouling. It is necessary to develop a membrane with both high NOM rejection and anti-NOM fouling properties. In this study, both superhydrophilic and superhydrophobic nanofiltration membranes for NOM removal have been fabricated. The fouling behavior of NOM on superwetting nanofiltration membranes has been extensively investigated by using humic acid (HA) as the model foulant. The extended Derjaguin-Landau-Verwey-Overbeek approach and nanoindentor scratch tests suggested that the superhydrophilic membrane had the strongest repulsion force to HA due to the highest positive total interaction energy (ΔG(TOT)) value and the lowest critical load. Excitation emission matrix analyses of natural water also indicated that the superhydrophilic membrane showed resistance to fouling by hydrophobic substances and therefore high removal thereof. Conversely, the superhydrophobic membrane showed resistance to fouling by hydrophilic substances and therefore high removal capacity. Long-term operation suggested that the superhydrophilic membrane had high stability due to its anti-NOM fouling capacity. Based on the different anti-fouling properties of the studied superwetting membranes, a combination of superhydrophilic and superhydrophobic membranes was examined to further improve the removal of both hydrophobic and hydrophilic pollutants. With a combination of superhydrophilic and superhydrophobic membranes, the NOM rejection (RUV254) and DOC removal rates (RDOC) could be increased to 83.6% and 73.3%, respectively. PMID:26900973

  5. Removal of organic contaminants by RO and NF membranes

    NASA Technical Reports Server (NTRS)

    Yoon, Yeomin; Lueptow, Richard M.

    2005-01-01

    Rejection characteristics of organic and inorganic compounds were examined for six reverse osmosis (RO) membranes and two nanofiltration (NF) membranes that are commercially available. A batch stirred-cell was employed to determine the membrane flux and the solute rejection for solutions at various concentrations and different pH conditions. The results show that for ionic solutes the degree of separation is influenced mainly by electrostatic exclusion, while for organic solutes the removal depends mainly upon the solute radius and molecular structure. In order to provide a better understanding of rejection mechanisms for the RO and NF membranes, the ratio of solute radius (r(i,s)) to effective membrane pore radius (r(p)) was employed to compare rejections. An empirical relation for the dependence of the rejection of organic compounds on the ratio r(i,s)/r(p) is presented. The rejection for organic compounds is over 75% when r(i,s)/r(p) is greater than 0.8. In addition, the rejection of organic compounds is examined using the extended Nernst-Planck equation coupled with a steric hindrance model. The transport of organic solutes is controlled mainly by diffusion for the compounds that have a high r(i,s)/r(p) ratio, while convection is dominant for compounds that have a small r(i,s)/r(p) ratio. c2005 Elsevier B.V. All rights reserved.

  6. Transformation of metal-organic frameworks for molecular sieving membranes

    PubMed Central

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-01-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively. PMID:27090597

  7. Transformation of metal-organic frameworks for molecular sieving membranes

    NASA Astrophysics Data System (ADS)

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-04-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively.

  8. Transformation of metal-organic frameworks for molecular sieving membranes.

    PubMed

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-01-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively. PMID:27090597

  9. Removal of trace organics by anaerobic membrane bioreactors.

    PubMed

    Monsalvo, Victor M; McDonald, James A; Khan, Stuart J; Le-Clech, Pierre

    2014-02-01

    The biological removal of 38 trace organics (pharmaceuticals, endocrine disruptors, personal care products and pesticides) was studied in an anaerobic membrane bioreactor (AnMBR). This work presents complete information on the different removal mechanisms involved in the removal of trace organics in this process. In particular, it is focused on advanced characterization of the relative amount of TO accumulated within the fouling layers formed on the membranes. The results show that only 9 out of 38 compounds were removed by more than 90% while 23 compounds were removed by less than 50%. These compounds are therefore removed in an AnMBR biologically and partially adsorbed and retained by flocs and the deposition developed on the membranes, respectively. A total amount of 288 mg of trace organics was retained per m(2) of membrane, which were distributed along the different fouling layers. Among the trace organics analyzed, 17α-ethynylestradiol, estrone, octylphenol and bisphenol A were the most retained by the fouling layers. Among the fouling layers deposited on the membranes, the non-readily detachable layer has been identified as the main barrier for trace organics. PMID:24321247

  10. Porous Organic Cage Thin Films and Molecular-Sieving Membranes.

    PubMed

    Song, Qilei; Jiang, Shan; Hasell, Tom; Liu, Ming; Sun, Shijing; Cheetham, Anthony K; Sivaniah, Easan; Cooper, Andrew I

    2016-04-01

    Porous organic cage molecules are fabricated into thin films and molecular-sieving membranes. Cage molecules are solution cast on various substrates to form amorphous thin films, with the structures tuned by tailoring the cage chemistry and processing conditions. For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation. PMID:26800019

  11. Domain Organization of Membrane-Bound Factor VIII

    PubMed Central

    Stoilova-McPhie, Svetla; Lynch, Gillian C.; Ludtke, Steven; Pettitt, B. Montgomery

    2014-01-01

    Factor VIII (FVIII) is the blood coagulation protein which when defective or deficient causes for hemophilia A, a severe hereditary bleeding disorder. Activated FVIII (FVIIIa) is the cofactor to the serine protease factor IXa (FIXa) within the membrane-bound Tenase complex, responsible for amplifying its proteolytic activity more than 100,000 times, necessary for normal clot formation. FVIII is composed of two noncovalently linked peptide chains: a light chain (LC) holding the membrane interaction sites and a heavy chain (HC) holding the main FIXa interaction sites. The interplay between the light and heavy chains (HCs) in the membrane-bound state is critical for the biological efficiency of FVIII. Here, we present our cryo-electron microscopy (EM) and structure analysis studies of human FVIII-LC, when helically assembled onto negatively charged single lipid bilayer nanotubes. The resolved FVIII-LC membrane-bound structure supports aspects of our previously proposed FVIII structure from membrane-bound two-dimensional (2D) crystals, such as only the C2 domain interacts directly with the membrane. The LC is oriented differently in the FVIII membrane-bound helical and 2D crystal structures based on EM data, and the existing X-ray structures. This flexibility of the FVIII-LC domain organization in different states is discussed in the light of the FVIIIa-FIXa complex assembly and function. PMID:23616213

  12. EMERGING TECHNOLOGY BULLETIN: VOLATILE ORGANIC COMPOUND REMOVAL FROM AIR STREAMS BY MEMBRANES SEPARATION MEMBRANE TECHNOLOGY AND RESEARCH, INC.

    EPA Science Inventory

    This membrane separation technology developed by Membrane Technology and Research (MTR), Incorporated, is designed to remove volatile organic compounds (VOCs) from contaminated air streams. In the process, organic vapor-laden air contacts one side of a membrane that is permeable ...

  13. Investigating the Human Skeleton.

    ERIC Educational Resources Information Center

    Slesnick, Irwin L.

    1982-01-01

    Instructions are provided for assembly of a pull-out, two-sided picture puzzle of the skeleton of a seven-year-old girl. Suggestions for activities using the assembled puzzle and comments on bones and bone morphology are also provided. (Author/JN)

  14. PREDICTIVE TEST METHODS: PERMEATION OF POLYMERIC MEMBRANES BY ORGANIC SOLVENTS

    EPA Science Inventory

    As the result of screening elastomeric materials that may be suitable for formulating chemical-protective clothing, a simple test method has been developed that allows the prediction of the permeation of an organic solvent through a polymeric membrane. The test method, based on l...

  15. Functionalized Silicon Membranes for Selective Bio-Organisms Capture

    SciTech Connect

    Letant, S E; Hart, B R; van Buuren, A W; Terminello, L J

    2003-01-09

    Membranes with various pore size, length, morphology and density have been synthesized out of diverse materials for size exclusion-based separation. An example of application is the sterilization of intravenous lines by exclusion of bacteria and viruses using Polyvinylidene Fluoride membranes with 0.1 {micro}m diameter pores. The need for chemically specific filtration has recently been addressed, but for small molecules only. An important problem remaining to be solved is the selective capture of large bio-organisms for decontamination or analysis of air and liquids such as drinking water and body fluids. To achieve this goal, materials with controlled pore diameter, length and surface chemistry are required. In this letter, we present the first functionalized silicon membranes and demonstrate their ability to selectively capture simulated bio-organisms. These extremely versatile and rigid devices open the door on a new class of materials able to recognize the external fingerprints of bio-organisms such as size and outer membrane proteins for specific capture and detection applications.

  16. ISTP CDF Skeleton Editor

    NASA Technical Reports Server (NTRS)

    Chimiak, Reine; Harris, Bernard; Williams, Phillip

    2013-01-01

    Basic Common Data Format (CDF) tools (e.g., cdfedit) provide no specific support for creating International Solar-Terrestrial Physics/Space Physics Data Facility (ISTP/SPDF) standard files. While it is possible for someone who is familiar with the ISTP/SPDF metadata guidelines to create compliant files using just the basic tools, the process is error-prone and unreasonable for someone without ISTP/SPDF expertise. The key problem is the lack of a tool with specific support for creating files that comply with the ISTP/SPDF guidelines. There are basic CDF tools such as cdfedit and skeletoncdf for creating CDF files, but these have no specific support for creating ISTP/ SPDF compliant files. The SPDF ISTP CDF skeleton editor is a cross-platform, Java-based GUI editor program that allows someone with only a basic understanding of the ISTP/SPDF guidelines to easily create compliant files. The editor is a simple graphical user interface (GUI) application for creating and editing ISTP/SPDF guideline-compliant skeleton CDF files. The SPDF ISTP CDF skeleton editor consists of the following components: A swing-based Java GUI program, JavaHelp-based manual/ tutorial, Image/Icon files, and HTML Web page for distribution. The editor is available as a traditional Java desktop application as well as a Java Network Launching Protocol (JNLP) application. Once started, it functions like a typical Java GUI file editor application for creating/editing application-unique files.

  17. Membrane contactor/separator for an advanced ozone membrane reactor for treatment of recalcitrant organic pollutants in water

    SciTech Connect

    Chan, Wai Kit; Joueet, Justine; Heng, Samuel; Yeung, King Lun; Schrotter, Jean-Christophe

    2012-05-15

    An advanced ozone membrane reactor that synergistically combines membrane distributor for ozone gas, membrane contactor for pollutant adsorption and reaction, and membrane separator for clean water production is described. The membrane reactor represents an order of magnitude improvement over traditional semibatch reactor design and is capable of complete conversion of recalcitrant endocrine disrupting compounds (EDCs) in water at less than three minutes residence time. Coating the membrane contactor with alumina and hydrotalcite (Mg/Al=3) adsorbs and traps the organics in the reaction zone resulting in 30% increase of total organic carbon (TOC) removal. Large surface area coating that diffuses surface charges from adsorbed polar organic molecules is preferred as it reduces membrane polarization that is detrimental to separation. - Graphical abstract: Advanced ozone membrane reactor synergistically combines membrane distributor for ozone, membrane contactor for sorption and reaction and membrane separator for clean water production to achieve an order of magnitude enhancement in treatment performance compared to traditional ozone reactor. Highlights: Black-Right-Pointing-Pointer Novel reactor using membranes for ozone distributor, reaction contactor and water separator. Black-Right-Pointing-Pointer Designed to achieve an order of magnitude enhancement over traditional reactor. Black-Right-Pointing-Pointer Al{sub 2}O{sub 3} and hydrotalcite coatings capture and trap pollutants giving additional 30% TOC removal. Black-Right-Pointing-Pointer High surface area coating prevents polarization and improves membrane separation and life.

  18. Membrane organization and cell fusion during mating in fission yeast requires multipass membrane protein Prm1.

    PubMed

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

    2014-04-01

    The involvement of Schizosaccharomyces pombe prm1(+) in cell fusion during mating and its relationship with other genes required for this process have been addressed. S. pombe prm1Δ mutant exhibits an almost complete blockade in cell fusion and an abnormal distribution of the plasma membrane and cell wall in the area of cell-cell interaction. The distribution of cellular envelopes is similar to that described for mutants devoid of the Fig1-related claudin-like Dni proteins; however, prm1(+) and the dni(+) genes act in different subpathways. Time-lapse analyses show that in the wild-type S. pombe strain, the distribution of phosphatidylserine in the cytoplasmic leaflet of the plasma membrane undergoes some modification before an opening is observed in the cross wall at the cell-cell contact region. In the prm1Δ mutant, this membrane modification does not take place, and the cross wall between the mating partners is not extensively degraded; plasma membrane forms invaginations and fingers that sometimes collapse/retract and that are sometimes strengthened by the synthesis of cell-wall material. Neither prm1Δ nor prm1Δ dniΔ zygotes lyse after cell-cell contact in medium containing and lacking calcium. Response to drugs that inhibit lipid synthesis or interfere with lipids is different in wild-type, prm1Δ, and dni1Δ strains, suggesting that membrane structure/organization/dynamics is different in all these strains and that Prm1p and the Dni proteins exert some functions required to guarantee correct membrane organization that are critical for cell fusion. PMID:24514900

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

    PubMed Central

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

    2014-01-01

    The involvement of Schizosaccharomyces pombe prm1+ in cell fusion during mating and its relationship with other genes required for this process have been addressed. S. pombe prm1Δ mutant exhibits an almost complete blockade in cell fusion and an abnormal distribution of the plasma membrane and cell wall in the area of cell–cell interaction. The distribution of cellular envelopes is similar to that described for mutants devoid of the Fig1-related claudin-like Dni proteins; however, prm1+ and the dni+ genes act in different subpathways. Time-lapse analyses show that in the wild-type S. pombe strain, the distribution of phosphatidylserine in the cytoplasmic leaflet of the plasma membrane undergoes some modification before an opening is observed in the cross wall at the cell–cell contact region. In the prm1Δ mutant, this membrane modification does not take place, and the cross wall between the mating partners is not extensively degraded; plasma membrane forms invaginations and fingers that sometimes collapse/retract and that are sometimes strengthened by the synthesis of cell-wall material. Neither prm1Δ nor prm1Δ dniΔ zygotes lyse after cell–cell contact in medium containing and lacking calcium. Response to drugs that inhibit lipid synthesis or interfere with lipids is different in wild-type, prm1Δ, and dni1Δ strains, suggesting that membrane structure/organization/dynamics is different in all these strains and that Prm1p and the Dni proteins exert some functions required to guarantee correct membrane organization that are critical for cell fusion. PMID:24514900

  20. Analysis of Membrane Lipids of Airborne Micro-Organisms

    NASA Technical Reports Server (NTRS)

    MacNaughton, Sarah

    2006-01-01

    A method of characterization of airborne micro-organisms in a given location involves (1) large-volume filtration of air onto glass-fiber filters; (2) accelerated extraction of membrane lipids of the collected micro-organisms by use of pressurized hot liquid; and (3) identification and quantitation of the lipids by use of gas chromatography and mass spectrometry. This method is suitable for use in both outdoor and indoor environments; for example, it can be used to measure airborne microbial contamination in buildings ("sick-building syndrome"). The classical approach to analysis of airborne micro-organisms is based on the growth of cultureable micro-organisms and does not provide an account of viable but noncultureable micro-organisms, which typically amount to more than 90 percent of the micro-organisms present. In contrast, the present method provides an account of all micro-organisms, including cultureable, noncultureable, aerobic, and anaerobic ones. The analysis of lipids according to this method makes it possible to estimate the number of viable airborne micro-organisms present in the sampled air and to obtain a quantitative profile of the general types of micro-organisms present along with some information about their physiological statuses.

  1. Membrane organization and regulation of cellular Cholesterol homeostasis

    PubMed Central

    Jaureguiberry, María S.; Tricerri, M. Alejandra; Sanchez, Susana A; Garda, Horacio A; Finarelli, Gabriela S.; Gonzalez, Marina C.; Rimoldi, Omar J.

    2010-01-01

    An excess of intracellular free Cholesterol (Chol) is cytotoxic, and its homeostasis is crucial for cell viability. Apolipoprotein A–I (apoA-I) is a highly efficient Chol acceptor as it activates complex cellular pathways that tend to mobilize and export Chol from cellular depots. Here we hypothesize that membrane composition and/or organization is strongly involved in Chol homeostasis. To test this hypothesis, we constructed a cell line over expressing Stearoyl CoA desaturase (SCD-cells), which modifies plasma membrane (PM) composition by the enrichment of monounsaturated fatty,acids and determined this effect on membrane properties, cell viability and cholesterol homeostasis. PM in SCD-cells has a higher phospholipids/sphingomyelin ratio and is slightly enriched in Chol. These cells showed an increase in the cholesteryl esters/free Chol ratio, they were more resistant to Chol toxicity and in addition, they exported more caveolin than Control cells. The data suggest that cell functionality is preserved by regulating membrane fluidity and Chol exportation and storage. PMID:20336284

  2. The skeleton in space

    NASA Technical Reports Server (NTRS)

    Goode, A. W.; Rambaut, P. C.

    1985-01-01

    Calcium loss experience by astronauts under weightless conditions is discussed. I-125 photon absorption measurements on astronauts on the Apollo 14, 15, and 16 flights showed bone density decreases of 6.6 percent in one astronaut and 7.3 percent in another. The estimated total body calcium loss on Apollo 17 was 0.2 percent. The test results indicate that calcium losses occur mainly from the weight-bearing parts of the skeleton. Measures to counteract the losses include 'penguin' suits, maintenance of nutrient intakes at high levels, and extensive exercise on ergometer and treadmill.

  3. [WHAT SKELETONS TELL US].

    PubMed

    Catalano, Paola

    2015-01-01

    The recent excavations carried out by the Superintendence for the Colosseum, the Roman National Museum and the Archaeological Area of Rome allowed to uncover a large number of burial grounds of Imperial Age. In this work we present the data for 11 cemeteries scattered throughout the Suburbiumn, dating between 1st and 3rd centuries AD. A whole sample of 6061 tombs has been investigated and 5280 skeletons were anthropologically analyzed. All the field data have been scored in appropriate standardized charts in order to make easy their storage and processing in a dedicated database. PMID:27348986

  4. Expression of human membrane skeleton protein genes for protein 4.1 and betaIISigma2-spectrin assayed by real-time RT-PCR.

    PubMed

    Taylor-Harris, Pamela M; Felkin, Leanne E; Birks, Emma J; Franklin, Rodney C G; Yacoub, Magdi H; Baines, Anthony J; Barton, Paul J R; Pinder, Jennifer C

    2005-01-01

    The proteins, spectrin and 4.1 confer support and resilience to animal cell membranes, and promote assembly of multimeric, membrane-bound signalling complexes. Protein 4.1 also plays important roles in tumour suppression and the regulation of cell proliferation. To assess relative tissue expression of the four genes encoding human protein 4.1, we measured mRNA levels using quantitative real-time polymerase chain reaction. We compared 4.1 expression with that of a major splice variant of spectrin, betaIISigma2 that has a shortened C-terminus lacking a pleckstrin homology domain. mRNA for 4.1R is four-fold higher in bone marrow than in tissues with the next highest prevalence: cerebellum, lung, testis and thymus. 4.1G mRNA is highly expressed in brain, spinal cord and testis; 4.1N in brain, spinal cord and adrenal gland; 4.1B in testis, brain, spinal cord, and kidney. Thus, 4.1N, 4.1B and 4.1G all show high accumulation in nervous tissues. mRNA for betaIISigma2-spectrin is ubiquitous, but most abundant in cardiac and nervous tissues. Comparative transcript abundance was analysed in heart and brain. betaIISigma2-spectrin was the most abundant transcript in heart with levels 5 fold greater than 4.1G or 4.1N and at least 9 fold greater than 4.1B. In brain, 4.1N was the most abundant transcript, with levels 2.4 fold greater than 4.1B and at least 4 fold greater than 4.1G or betaIISigma2-spectrin. 4.1R abundance was very low in both tissues. Whilst we expected that 4.1 mRNAs would feature highly in muscle and nerve, we note their high abundance in testis, indicating previously unsuspected functions in reproduction. PMID:15809685

  5. Electrospun Superhydrophobic Organic/Inorganic Composite Nanofibrous Membranes for Membrane Distillation.

    PubMed

    Li, Xiong; Yu, Xufeng; Cheng, Cheng; Deng, Li; Wang, Min; Wang, Xuefen

    2015-10-01

    Electrospun superhydrophobic organic/inorganic composite nanofibrous membranes exhibiting excellent direct contact membrane distillation (DCMD) performance were fabricated by a facile route combining the hydrophobization of silica nanoparticles (SiO2 NPs) and colloid electrospinning of the hydrophobic silica/poly(vinylidene fluoride) (PVDF) matrix. Benefiting from the utilization of SiO2 NPs with three different particle sizes, the electrospun nanofibrous membranes (ENMs) were endowed with three different delicate nanofiber morphologies and fiber diameter distribution, high porosity, and superhydrophobic property, which resulted in excellent waterproofing and breathability. Significantly, structural attributes analyses have indicated the major contributing role of fiber diameter distribution on determining the augment of permeate vapor flux through regulating mean flow pore size (MFP). Meanwhile, the extremely high liquid entry pressure of water (LEPw, 2.40 ± 0.10 bar), robust nanofiber morphology of PVDF immobilized SiO2 NPs, remarkable mechanical properties, thermal stability, and corrosion resistance endowed the as-prepared membranes with prominent desalination capability and stability for long-term MD process. The resultant choreographed PVDF/silica ENMs with optimized MFP presented an outstanding permeate vapor flux of 41.1 kg/(m(2)·h) and stable low permeate conductivity (∼2.45 μs/cm) (3.5 wt % NaCl salt feed; ΔT = 40 °C) over a DCMD test period of 24 h without membrane pores wetting detected. This result was better than those of typical commercial PVDF membranes and PVDF and modified PVDF ENMs reported so far, suggesting them as promising alternatives for MD applications. PMID:26371965

  6. Graphene oxide membrane for liquid phase organic molecular separation

    NASA Astrophysics Data System (ADS)

    Liu, Renlong; Arabale, Girish; Kim, Jinseon; Sun, Ke; Lee, Yongwoon; Ryu, Changkook; Lee, Changgu

    2015-03-01

    The selective permeation of organic solvents and water through graphene oxide (GO) membranes has been demonstrated. Water was found to permeate through GO membranes faster than various alcohols. The permeation rates of propanol are about 80 times lower than that of water. Taking advantage of the differences in the permeation rates, we separated water from the alcohols and obtained alcohols with high purity. For ethanol and 1-propanol, binary solutions of the alcohol and water were filtered efficiently to produce alcohols with concentration of about 97%. However, the selectivity of the filtration of methanol is significantly lower than those of the other alcohols. To understand the mechanism we followed the structural changes in the GO membranes by X-Ray diffraction analysis. From the X-ray diffraction results we speculate that the selectivity of the permeation of water and alcohols is closely related to the molecular sizes of the solvents and their polarity. In order to demonstrate the potential applications of this process for the selective removal of water from aqueous organic mixtures, we performed the separation of water from a bio-oil containing 73% of water. The majority of the water was filtered out resulting in a higher purity bio-oil.

  7. Connexins in the skeleton.

    PubMed

    Stains, Joseph P; Civitelli, Roberto

    2016-02-01

    Shaping of the skeleton (modeling) and its maintenance throughout life (remodeling) require coordinated activity among bone forming (osteoblasts) and resorbing cells (osteoclasts) and osteocytes (bone embedded cells). The gap junction protein connexin43 (Cx43) has emerged as a key modulator of skeletal growth and homeostasis. The skeletal developmental abnormalities present in oculodentodigital and craniometaphyseal dysplasias, both linked to Cx43 gene (GJA1) mutations, demonstrate that the skeleton is a major site of Cx43 action. Via direct action on osteolineage cells, including altering production of pro-osteoclastogenic factors, Cx43 contributes to peak bone mass acquisition, cortical modeling of long bones, and maintenance of bone quality. Cx43 also contributes in diverse ways to bone responsiveness to hormonal and mechanical signals. Skeletal biology research has revealed the complexity of Cx43 function; in addition to forming gap junctions and "hemichannels", Cx43 provides a scaffold for signaling molecules. Hence, Cx43 actively participates in generation and modulation of cellular signals driving skeletal development and homeostasis. Pharmacological interference with Cx43 may in the future help remedy deterioration of bone quality occurring with aging, disuse and hormonal imbalances. PMID:26740471

  8. Isolation of differentiated membrane domains from Escherichia coli and Salmonella typhimurium, including a fraction containing sites between the inner and outer membranes and Murein skeleton of the cell envelope

    SciTech Connect

    Not Available

    1986-01-05

    Cell envelopes of Salmonella typhimurium and Escherichia coli were disrupted in a French pressure cell and fractionated by successive cycles of sedimentation and floatation density gradient centrifugation. This permitted the identification and isolation of several membrane fractions in addition to the major inner membrane and murein-outer membrane fractions. One of these fractions (fraction OM/sub L/) accounted for about 10% of the total cell envelope protein, and is likely to include the murein-membrane adhesion zones that are seen in electron micrographs of plasmolyzed cells. Fraction OM/sub L/ contained inner membrane, murein, and outer membrane in an apparently normal configuration, was capable of synthesizing murein from UDP-(/sup 3/H)N-acetylglucosamine and UDP-N-acetylmuramyl-pentapeptide and covalently linking it to the endogenous murein of the preparation. It showed a labeling pattern in (/sup 3/H)galactose pulse-chase experiments that was consistent with its acting as an intermediate in the movement of newly synthesized lipopolysaccharide from inner membrane to outer membrane.

  9. Solution and laser ablation inductively coupled plasma-mass spectrometry measurements of Br, I, Pb, Mn, Cd, Zn, and B in the organic skeleton of soft corals and black corals

    NASA Astrophysics Data System (ADS)

    Williams, B.; Grottoli, A. G.

    2011-03-01

    Proxy records can be derived from soft corals and black corals using minor and trace element measurements of the organic skeleton of these corals. Here, concentrations of Br, I, Pb, Mn, Cd, Zn, and B in the organic skeleton were determined using solution inductively coupled plasma-mass spectrometry (ICP-MS) in one black coral from 5 m depth and two soft corals from 85 and 105 m depth collected from a reef offshore of Palau in the western tropical Pacific. Solution ICP-MS results indicate that concentrations of some elements vary as expected with depth (Cd and Mn) while others are taxa specific (I) or colony specific (Br, Pb, Zn, and B). The intensities of the same elements normalized to 13C were also measured at high resolution using laser ablation (LA) ICP-MS along radial transects covering the lifespan of the colonies. The results here indicate that high-resolution LA ICP-MS elemental records in black corals could be more fully developed for paleoceanographic reconstructions. In contrast, results of the laser transects from the two soft corals were not reproducible for any of the elements, and no discernible patterns were detected that could be developed into reliable proxy records using the current LA ICP-MS method.

  10. Molecular organization of cholesterol in polyunsaturated membranes: microdomain formation.

    PubMed Central

    Brzustowicz, Michael R; Cherezov, Vadim; Caffrey, Martin; Stillwell, William; Wassall, Stephen R

    2002-01-01

    The molecular organization of cholesterol in phospholipid bilayers composed of 1,2-diarachidonylphosphatidylcholine (20:4-20:4PC), 1-stearoyl-2-arachidonylphosphatidylcholine (18:0-20:4PC), and 20:4-20:4PC/18:0-20:4PC (1/1 mol) was investigated by solid-state (2)H NMR and by low- and wide-angle x-ray diffraction (XRD). On the basis of distinct quadrupolar powder patterns arising from [3 alpha-(2)H(1)]cholesterol intercalated into the membrane and phase separated as solid, solubility chi(NMR)(chol) = 17 +/- 2 mol% and tilt angle alpha(0) = 25 +/- 1 degrees in 20:4-20:4PC were determined. The corresponding values in 18:0-20:4PC were chi (NMR)(chol) > or = 50 mol% and alpha(0) = 16 +/- 1 degrees. Cholesterol solubility determined by XRD was chi(NMR)(chol) = 15 +/- 2 mol% and chi(NMR)(chol) = 49 +/- 1 mol% for 20:4-20:4PC and 18:0-20:4PC, respectively. XRD experiments show that the solid sterol is monohydrate crystals presumably residing outside the bilayer. The (2)H NMR spectrum for equimolar [3 alpha-(2)H(1)]cholesterol added to mixed 20:4-20:4PC/18:0-20:4PC (1/1 mol) membranes is consistent with segregation of cholesterol into 20:4-20:4PC and 18:0-20:4PC microdomains of <160 A in size that preserve the molecular organization of sterol in the individual phospholipid constituents. Our results demonstrate unambiguously that cholesterol has low affinity to polyunsaturated fatty acids and support hypotheses of lateral phase separation of membrane constituents into sterol-poor/polyunsaturated fatty acid-rich and sterol-rich/saturated fatty acid-rich microdomains. PMID:11751316

  11. A NOVEL HYDROPHILIC POLYMER MEMBRANE FOR THE DEHYDRATION OF ORGANIC SOLVENTS

    EPA Science Inventory

    Novel hydrophilic polymer membranes based on polyallylamine ydrochloride- polyvinylalcohol are developed. The high selectivity and flux characteristics of these membranes for the dehydration of organic solvents are evaluated using pervaporation technology and are found to be ver...

  12. Organic membranes determine the pattern of the columnar prismatic layer of mollusc shells.

    PubMed

    Checa, Antonio G; Macías-Sánchez, Elena; Harper, Elizabeth M; Cartwright, Julyan H E

    2016-05-11

    The degree to which biological control is exercised compared to physical control of the organization of biogenic materials is a central theme in biomineralization. We show that the outlines of biogenic calcite domains with organic membranes are always of simple geometries, while without they are much more complex. Moreover, the mineral prisms enclosed within the organic membranes are frequently polycrystalline. In the prismatic layer of the mollusc shell, organic membranes display a dynamics in accordance with the von Neumann-Mullins and Lewis Laws for two-dimensional foam, emulsion and grain growth. Taken together with the facts that we found instances in which the crystals do not obey such laws, and that the same organic membrane pattern can be found even without the mineral infilling, our work indicates that it is the membranes, not the mineral prisms, that control the pattern, and the mineral enclosed within the organic membranes passively adjusts to the dynamics dictated by the latter. PMID:27147096

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

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    2000-01-01

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

  14. Composite proton exchange membrane based on sulfonated organic nanoparticles

    NASA Astrophysics Data System (ADS)

    Pitia, Emmanuel Sokiri

    As the world sets its sight into the future, energy remains a great challenge. Proton exchange membrane (PEM) fuel cell is part of the solution to the energy challenge because of its high efficiency and diverse application. The purpose of the PEM is to provide a path for proton transport and to prevent direct mixing of hydrogen and oxygen at the anode and the cathode, respectively. Hence, PEMs must have good proton conductivity, excellent chemical stability, and mechanical durability. The current state-of-the-art PEM is a perfluorosulfonate ionomer, Nafion®. Although Nafion® has many desirable properties, it has high methanol crossover and it is expensive. The objective of this research was to develop a cost effective two-phase, composite PEM wherein a dispersed conductive organic phase preferentially aligned in the transport direction controls proton transport, and a continuous hydrophobic phase provides mechanical durability to the PEM. The hypothesis that was driving this research was that one might expect better dispersion, higher surface to volume ratio and improved proton conductivity of a composite membrane if the dispersed particles were nanometer in size and had high ion exchange capacity (IEC, = [mmol sulfonic acid]/gram of polymer). In view of this, considerable efforts were employed in the synthesis of high IEC organic nanoparticles and fabrication of a composite membrane with controlled microstructure. High IEC, ~ 4.5 meq/g (in acid form, theoretical limit is 5.4 meq/g) nanoparticles were achieved by emulsion copolymerization of a quaternary alkyl ammonium (QAA) neutralized-sulfonated styrene (QAA-SS), styrene, and divinylbenzene (DVB). The effects of varying the counterion of the sulfonated styrene (SS) monomer (alkali metal and QAA cations), SS concentration, and the addition of a crosslinking agent (DVB) on the ability to stabilize the nanoparticles to higher IECs were assessed. The nanoparticles were ion exchanged to acid form. The extent of ion

  15. The Milky Way Skeleton

    NASA Astrophysics Data System (ADS)

    Zucker, Catherine; Battersby, Cara; Goodman, Alyssa A.

    2015-01-01

    Recently, Goodman et al. (2014) argued that a very long, very thin infrared dark cloud 'Nessie' lies directly in the Galactic mid-plane and runs along the Scutum-Centaurus arm in position-position-velocity space as traced by low density CO and high density NH3 gas. Nessie was presented as the first 'bone' of the Milky Way, an extraordinarily long, thin, high contrast filament that can be used to map our galaxy's 'skeleton.' We present the first evidence of additional 'bones' in the Milky Way Galaxy, arguing that Nessie is not a curiosity but one of many filaments that could potentially trace galactic structure. Our ten bone candidates are all long, filamentary, mid-infrared extinction features which lie parallel to, and no more than twenty parsecs from, the physical Galactic mid-plane. We use CO, N2H+, and NH3 radial velocity data to establish the location of the candidates in position-velocity space. Of the ten filaments, three candidates have a projected aspect ratio of >50:1 and run along, or extremely close to, the Scutum-Centaurus arm in position-velocity space. Evidence suggests that these three candidates are Nessie-like features which mark the location of the spiral arms in both physical space and position-velocity space. Other candidates could be spurs, feathers, or interarm clouds associated with the Milky Way's galactic structure. As molecular spectral-line and extinction maps cover more of the sky at increasing resolution and sensitivity, we hope to find more bones in future studies, to ultimately create a global-fit to the Galaxy's spiral arms by piecing together individual skeletal features. This work is supported in part by the NSF REU and DOD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  16. High flux thin film nanocomposite membranes based on metal-organic frameworks for organic solvent nanofiltration.

    PubMed

    Sorribas, Sara; Gorgojo, Patricia; Téllez, Carlos; Coronas, Joaquín; Livingston, Andrew G

    2013-10-01

    Thin-film nanocomposite membranes containing a range of 50-150 nm metal-organic framework (MOF) nanoparticles [ZIF-8, MIL-53(Al), NH2-MIL-53(Al) and MIL-101(Cr)] in a polyamide (PA) thin film layer were synthesized via in situ interfacial polymerization on top of cross-linked polyimide porous supports. MOF nanoparticles were homogeneously dispersed in the organic phase containing trimesoyl chloride prior to the interfacial reaction, and their subsequent presence in the PA layer formed was inferred by a combination of contact angle measurements, FT-IR spectroscopy, SEM, EDX, XPS, and TEM. Membrane performance in organic solvent nanofiltration was evaluated on the basis of methanol (MeOH) and tetrahydrofuran (THF) permeances and rejection of styrene oligomers (PS). The effect of different post-treatments and MOF loadings on the membrane performance was also investigated. MeOH and THF permeance increased when MOFs were embedded into the PA layer, whereas the rejection remained higher than 90% (molecular weight cutoff of less than 232 and 295 g·mol(-1) for MeOH and THF, respectively) in all membranes. Moreover, permeance enhancement increased with increasing pore size and porosity of the MOF used as filler. The incorporation of nanosized MIL-101(Cr), with the largest pore size of 3.4 nm, led to an exceptional increase in permeance, from 1.5 to 3.9 and from 1.7 to 11.1 L·m(-2)·h(-1)·bar(-1) for MeOH/PS and THF/PS, respectively. PMID:24044635

  17. Pervaporative removal of organics from water using hydrophobic membranes. Binary mixtures

    SciTech Connect

    Kujawski, W.

    2000-01-01

    Results of pervaporation experiments are presented for the separation of several polar and nonpolar organic solvents from their aqueous solutions. Three membranes were evaluated: a polydimethylsiloxane (PERVAP-1060) membrane, a PDMS ZSM-5 zeolite filled (PERVAP-1070) membrane, and a poly(ether-block-amide) (PEBAX-4033) membrane. The effect of feed composition on flux and selectivity was also investigated. Performance parameters of a given membrane depended both on the kind of the organic solvent and the feed composition. The PERVAP-1070 membrane exhibited the highest selectivity with a separation factor over 900 in contact with a water-butyl acetate mixture. Polar solvents like methanol were also preferentially separated from aqueous solutions, but the separation factors were close to those obtained from liquid-vapor equilibria data. Permeate fluxes of organics increased with increasing feed concentration. Synergetic effects between water and organics fluxes were also observed.

  18. Study of polytopic membrane protein topological organization as a function of membrane lipid composition.

    PubMed

    Bogdanov, Mikhail; Heacock, Philip N; Dowhan, William

    2010-01-01

    A protocol is described using lipid mutants and thiol-specific chemical reagents to study lipid-dependent and host-specific membrane protein topogenesis by the substituted-cysteine accessibility method as applied to transmembrane domains (SCAM). SCAM is adapted to follow changes in membrane protein topology as a function of changes in membrane lipid composition. The strategy described can be adapted to any membrane system. PMID:20419405

  19. Composite Membranes for CO2 Capture: High Performance Metal Organic Frameworks/Polymer Composite Membranes for Carbon Dioxide Capture

    SciTech Connect

    2010-07-01

    IMPACCT Project: A team of six faculty members at Georgia Tech are developing an enhanced membrane by fitting metal organic frameworks, compounds that show great promise for improved carbon capture, into hollow fiber membranes. This new material would be highly efficient at removing CO2 from the flue gas produced at coal-fired power plants. The team is analyzing thousands of metal organic frameworks to identify those that are most suitable for carbon capture based both on their ability to allow coal exhaust to pass easily through them and their ability to select CO2 from that exhaust for capture and storage. The most suitable frameworks would be inserted into the walls of the hollow fiber membranes, making the technology readily scalable due to their high surface area. This composite membrane would be highly stable, withstanding the harsh gas environment found in coal exhaust.

  20. Effects of dissolved organic matters (DOMs) on membrane fouling in anaerobic ceramic membrane bioreactors (AnCMBRs) treating domestic wastewater.

    PubMed

    Yue, Xiaodi; Koh, Yoong Keat Kelvin; Ng, How Yong

    2015-12-01

    Anaerobic membrane bioreactors (AnMBRs) have been regarded as a potential solution to achieve energy neutrality in the future wastewater treatment plants. Coupling ceramic membranes into AnMBRs offers great potential as ceramic membranes are resistant to corrosive chemicals such as cleaning reagents and harsh environmental conditions such as high temperature. In this study, ceramic membranes with pore sizes of 80, 200 and 300 nm were individually mounted in three anaerobic ceramic membrane bioreactors (AnCMBRs) treating real domestic wastewater to examine the treatment efficiencies and to elucidate the effects of dissolved organic matters (DOMs) on fouling behaviours. The average overall chemical oxygen demands (COD) removal efficiencies could reach around 86-88%. Although CH4 productions were around 0.3 L/g CODutilised, about 67% of CH4 generated was dissolved in the liquid phase and lost in the permeate. When filtering mixed liquor of similar properties, smaller pore-sized membranes fouled slower in long-term operations due to lower occurrence of pore blockages. However, total organic removal efficiencies could not explain the fouling behaviours. Liquid chromatography-organic carbon detection, fluorescence spectrophotometer and high performance liquid chromatography coupled with fluorescence and ultra-violet detectors were used to analyse the DOMs in detail. The major foulants were identified to be biopolymers that were produced in microbial activities. One of the main components of biopolymers--proteins--led to different fouling behaviours. It is postulated that the proteins could pass through porous cake layers to create pore blockages in membranes. Hence, concentrations of the DOMs in the soluble fraction of mixed liquor (SML) could not predict membrane fouling because different components in the DOMs might have different interactions with membranes. PMID:26255104

  1. A Stochastic Skeleton Model for the MJO

    NASA Astrophysics Data System (ADS)

    Stechmann, S. N.; Thual, S.; Majda, A.

    2014-12-01

    The Madden-Julian oscillation (MJO) is the dominant mode of variability in the tropical atmosphere on intraseasonal time scales and planetary spatial scales. Despite the primary importance of the MJO and the decades of research progress since its original discovery, a generally accepted theory for its essential mechanisms has remained elusive. In recent work by two of the authors, a minimal dynamical model has been proposed that recovers robustly the most fundamental MJO features of (i) a slow eastward speed of roughly 5 m/s, (ii) a peculiar dispersion relation with dω/dk≈0, and (iii) a horizontal quadrupole vortex structure. This model, the skeleton model, depicts the MJO as a neutrally stable atmospheric wave that involves a simple multiscale interaction between planetary dry dynamics, planetary lower-tropospheric moisture, and the planetary envelope of synoptic-scale activity. In this article, it is shown that the skeleton model can further account for (iv) the intermittent generation of MJO events and (v) the organization of MJO events into wave trains with growth and demise, as seen in nature. The goal is achieved by developing a simple stochastic parameterization for the unresolved details of synoptic-scale activity, which is coupled to otherwise deterministic processes in the skeleton model. In particular, the intermittent initiation, propagation, and shut down of MJO wave trains in the skeleton model occur through these stochastic effects. This includes examples with a background warm pool where some initial MJO-like disturbances propagate through the western region but stall at the peak of background convection/heating corresponding to the Maritime Continent in nature. Also shown are examples with an idealized seasonal cycle, namely a background warm pool state of heating/moistening displacing meridionally during the year. This seasonally varying case considers both equatorial and off-equatorial components of the envelope of synoptic scale convective

  2. Selective aqueous extraction of organics coupled with trapping by membrane separation

    DOEpatents

    van Eikeren, Paul; Brose, Daniel J.; Ray, Roderick J.

    1991-01-01

    An improvement to processes for the selective extractation of organic solutes from organic solvents by water-based extractants is disclosed, the improvement comprising coupling various membrane separation processes with the organic extraction process, the membrane separation process being utilized to continuously recycle the water-based extractant and at the same time selectively remove or concentrate organic solute from the water-based extractant.

  3. [Research of performances for the organic membrane modified by inorganic material].

    PubMed

    Lu, Yan; Yu, Shui-Li; Sun, Xian-Da; Cai, Bao-Xiang

    2007-02-01

    Nano-sized alumina particles as inorganic additive were dispersed in the poly (vinylidene fluoride) uniformly to prepare organic-inorganic composite membranes. Contact angle between water and the membrane surface were measured by contact angle measurement in order to characterize the hydrophilicity changing of the membrane surface. The membrane surface structures, porous distribution on the membrane surface, the cross-sectional structures and nanometer particles distribution were examined by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Membrane properties were characterized by ultrafiltration (UF) experiments in terms of water flux and antifouling properties. Membranes mechanical performances were measured by omnipotence electronic intensity measuring instrument (W-56). Experiments indicate that Al2 O3 -PVDF composite membranes exhibit significant differences in surface hydrophilicity properties, flux, and intensity and antifouling performances due to nano-sized particles addition. PMID:17489200

  4. Membrane tension and cytoskeleton organization in cell motility

    NASA Astrophysics Data System (ADS)

    Sens, Pierre; Plastino, Julie

    2015-07-01

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

  5. Enhanced gypsum scaling by organic fouling layer on nanofiltration membrane: Characteristics and mechanisms.

    PubMed

    Wang, Jiaxuan; Wang, Lei; Miao, Rui; Lv, Yongtao; Wang, Xudong; Meng, Xiaorong; Yang, Ruosong; Zhang, Xiaoting

    2016-03-15

    To investigate how the characteristics of pregenerated organic fouling layers on nanofiltration (NF) membranes influence the subsequent gypsum scaling behavior, filtration experiments with gypsum were carried out with organic-fouled poly(piperazineamide) NF membranes. Organic fouling layer on membrane was induced by bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), respectively. The morphology and components of the scalants, the role of Ca(2+) adsorption on the organic fouling layer during gypsum crystallization, and the interaction forces of gypsum on the membrane surface were investigated. The results indicated that SA- and HA-fouled membranes had higher surface crystallization tendency along with more severe flux decline during gypsum scaling than BSA-fouled and virgin membranes because HA and SA macromolecules acted as nuclei for crystallization. Based on the analyses of Ca(2+) adsorption onto organic adlayers and adhesion forces, it was found that the flux decline rate and extent in the gypsum scaling experiment was positively related to the Ca(2+)-binding capacity of the organic matter. Although the dominant gypsum scaling mechanism was affected by coupling physicochemical effects, the controlling factors varied among foulants. Nevertheless, the carboxyl density of organic matter played an important role in determining surface crystallization on organic-fouled membrane. PMID:26799710

  6. Influence of membrane phospholipid composition and structural organization on spontaneous lipid transfer between membranes.

    PubMed

    Pankov, R; Markovska, T; Antonov, P; Ivanova, L; Momchilova, A

    2006-09-01

    Investigations were carried out on the influence of phospholipid composition of model membranes on the processes of spontaneous lipid transfer between membranes. Acceptor vesicles were prepared from phospholipids extracted from plasma membranes of control and ras-transformed fibroblasts. Acceptor model membranes with manipulated levels of phosphatidylethanolamine (PE), sphingomyelin and phosphatidic acid were also used in the studies. Donor vesicles were prepared of phosphatidylcholine (PC) and contained two fluorescent lipid analogues, NBD-PC and N-Rh-PE, at a self-quenching concentration. Lipid transfer rate was assessed by measuring the increase of fluorescence in acceptor membranes due to transfer of fluorescent lipid analogues from quenched donor to unquenched acceptor vesicles. The results showed that spontaneous NBD-PC transfer increased upon fluidization of acceptor vesicles. In addition, elevation of PE concentration in model membranes was also accompanied by an increase of lipid transfer to all series of acceptor vesicles. The results are discussed with respect to the role of lipid composition and structural order of cellular plasma membranes in the processes of spontaneous lipid exchange between membrane bilayers. PMID:17197729

  7. THE SKELETON IN THE CLOSET

    PubMed Central

    Kaplan, Frederick S.

    2015-01-01

    The origins of fibrodysplasia ossificans progressiva (FOP) in human history are unknown but the condition has been well described since Freke’s account in 1740. Important contributions by physicians and scientists in the past two and a half centuries have converged on the remarkable skeleton of Harry Eastlack at The Mutter Museum of The College of Physicians in Philadelphia. PMID:23810943

  8. The skeleton in the closet.

    PubMed

    Kaplan, Frederick S

    2013-10-01

    The origins of fibrodysplasia ossificans progressiva (FOP) in human history are unknown but the condition has been well described since Freke's account in 1740. Important contributions by physicians and scientists in the past two and a half centuries have converged on the remarkable skeleton of Harry Eastlack at The Mutter Museum of The College of Physicians in Philadelphia. PMID:23810943

  9. Actomyosin dynamics drive local membrane component organization in an in vitro active composite layer.

    PubMed

    Köster, Darius Vasco; Husain, Kabir; Iljazi, Elda; Bhat, Abrar; Bieling, Peter; Mullins, R Dyche; Rao, Madan; Mayor, Satyajit

    2016-03-22

    The surface of a living cell provides a platform for receptor signaling, protein sorting, transport, and endocytosis, whose regulation requires the local control of membrane organization. Previous work has revealed a role for dynamic actomyosin in membrane protein and lipid organization, suggesting that the cell surface behaves as an active composite composed of a fluid bilayer and a thin film of active actomyosin. We reconstitute an analogous system in vitro that consists of a fluid lipid bilayer coupled via membrane-associated actin-binding proteins to dynamic actin filaments and myosin motors. Upon complete consumption of ATP, this system settles into distinct phases of actin organization, namely bundled filaments, linked apolar asters, and a lattice of polar asters. These depend on actin concentration, filament length, and actin/myosin ratio. During formation of the polar aster phase, advection of the self-organizing actomyosin network drives transient clustering of actin-associated membrane components. Regeneration of ATP supports a constitutively remodeling actomyosin state, which in turn drives active fluctuations of coupled membrane components, resembling those observed at the cell surface. In a multicomponent membrane bilayer, this remodeling actomyosin layer contributes to changes in the extent and dynamics of phase-segregating domains. These results show how local membrane composition can be driven by active processes arising from actomyosin, highlighting the fundamental basis of the active composite model of the cell surface, and indicate its relevance to the study of membrane organization. PMID:26929326

  10. Synthesis of PVDF ultrafiltration membranes supported on polyester fabrics for separation of organic matter from water

    NASA Astrophysics Data System (ADS)

    Mhlanga, Sabelo D.; Tshabalala, Tumelo G.; Nxumalo, Edward N.; Mamba, Bhekie B.

    2014-08-01

    Polyvinylidene flouride (PVDF) membranes supported on non-woven fabrics (NWF) of polyester are reported. The PVDF membranes were fabricated using the phase inversion method followed by modification of the active top layer of the PVDF thin film by adding polyvinylpyrolidone (PVP) into the cast solution. A PVDF resin was used with N- methyl-2-pyrrolidone (NMP) as a solvent. Sessile drop contact angle measurements and scanning electron microscopy (SEM) were used to study the physical properties of the membranes. Membrane rejection of humic acid was studied using a cross-flow membrane testing unit. The contact angle results revealed that the hydrophilicity of PVDF membranes increased as the PVP concentration was increased from 3 to 10 wt%. SEM analysis of the membranes revealed that the membrane pore sizes increased when PVP was added. AFM analysis also showed that membrane roughness changed when PVP was added. Total organic carbon (TOC) analysis of water samples spiked with humic acid was performed to test the rejection capacity of the membranes. Rejections of up to 97% were achieved for PVDF membranes supported on polyester NWF1, which had smaller thickness and higher permeability compared to polyester NWF2. The NWFs provided the high strength required for the membranes despite the modifications done on the PDVF surface and microstructure.

  11. Remodeling the shape of the skeleton in the intact red cell.

    PubMed Central

    Khodadad, J K; Waugh, R E; Podolski, J L; Josephs, R; Steck, T L

    1996-01-01

    The role of the membrane skeleton in determining the shape of the human red cell was probed by weakening it in situ with urea, a membrane-permeable perturbant of spectrin. Urea by itself did not alter the biconcave disk shape of the red cell; however, above threshold conditions (1.5 M, 37 degrees C, 10 min), it caused an 18% reduction in the membrane elastic shear modulus. It also potentiated the spiculation of cells by lysophosphatidylcholine. These findings suggest that the contour of the resting cell is not normally dependent on the elasticity of or tension in the membrane skeleton. Rather, the elasticity of the skeleton stabilizes membranes against deformation. Urea treatment also caused the projections induced both by micropipette aspiration and by lysophosphatidylcholine to become irreversible. Furthermore, urea converted the axisymmetric conical spicules induced by lysophosphatidylcholine into irregular, curved and knobby spicules; i.e., echinocytosis became acanthocytosis. Unlike controls, the ghosts and membrane skeletons obtained from urea-generated acanthocytes were imprinted with spicules. These data suggest that perturbing interprotein associations with urea in situ allowed the skeleton to evolve plastically to accommodate the contours imposed upon it by the overlying membrane. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:8789122

  12. A vanished history of skeletonization in Cambrian comb jellies

    PubMed Central

    Ou, Qiang; Xiao, Shuhai; Han, Jian; Sun, Ge; Zhang, Fang; Zhang, Zhifei; Shu, Degan

    2015-01-01

    Ctenophores are traditionally regarded as “lower” metazoans, sharing with cnidarians a diploblastic grade of organization. Unlike cnidarians, where skeletonization (biomineralization and sclerotization) evolved repeatedly among ecologically important taxa (for example, scleractinians and octocorals), living ctenophores are characteristically soft-bodied animals. We report six sclerotized and armored ctenophores from the early Cambrian period. They have diagnostic ctenophore features (for example, an octamerous symmetry, oral-aboral axis, aboral sense organ, and octaradially arranged ctene rows). Unlike most modern counterparts, however, they lack tentacles, have a sclerotized framework, and have eight pairs of ctene rows. They are resolved as a monophyletic group (Scleroctenophora new class) within the ctenophores. This clade reveals a cryptic history and sheds new light on the early evolution of this basal animal phylum. Skeletonization also occurs in some other Cambrian animal groups whose extant members are exclusively soft-bodied, suggesting the ecological importance of skeletonization in the Cambrian explosion. PMID:26601209

  13. A vanished history of skeletonization in Cambrian comb jellies.

    PubMed

    Ou, Qiang; Xiao, Shuhai; Han, Jian; Sun, Ge; Zhang, Fang; Zhang, Zhifei; Shu, Degan

    2015-07-01

    Ctenophores are traditionally regarded as "lower" metazoans, sharing with cnidarians a diploblastic grade of organization. Unlike cnidarians, where skeletonization (biomineralization and sclerotization) evolved repeatedly among ecologically important taxa (for example, scleractinians and octocorals), living ctenophores are characteristically soft-bodied animals. We report six sclerotized and armored ctenophores from the early Cambrian period. They have diagnostic ctenophore features (for example, an octamerous symmetry, oral-aboral axis, aboral sense organ, and octaradially arranged ctene rows). Unlike most modern counterparts, however, they lack tentacles, have a sclerotized framework, and have eight pairs of ctene rows. They are resolved as a monophyletic group (Scleroctenophora new class) within the ctenophores. This clade reveals a cryptic history and sheds new light on the early evolution of this basal animal phylum. Skeletonization also occurs in some other Cambrian animal groups whose extant members are exclusively soft-bodied, suggesting the ecological importance of skeletonization in the Cambrian explosion. PMID:26601209

  14. Making an Inexpensive Skeleton for the Classroom.

    ERIC Educational Resources Information Center

    Shaw, Edward L., Jr.; Pruitt, Nancy E.

    1990-01-01

    Presented is an activity in which a skeleton is built using papier mache' and various household items. The materials; procedures for building each part of the skeleton; and directions for painting, assembling, and varnishing are included. (KR)

  15. Membrane fouling controlled by coagulation/adsorption during direct sewage membrane filtration (DSMF) for organic matter concentration.

    PubMed

    Gong, Hui; Jin, Zhengyu; Wang, Xian; Wang, Kaijun

    2015-06-01

    Unlike the role of the membrane in a membrane bioreactor, which is designed to replace a sediment tank, direct sewage membrane filtration (DSMF), with the goal of concentrating organic matters, is proposed as a pretreatment process in a novel sewage treatment concept. The concept of membrane-based pretreatment is proposed to divide raw sewage into a concentrated part retaining most organics and a filtered part with less pollutant remaining, so that energy recovery and water reuse, respectively, could be realized by post-treatment. A pilot-scale experiment was carried out to verify the feasibility of coagulant/adsorbent addition for membrane fouling control, which has been the main issue during this DSMF process. The results showed that continuous coagulant addition successfully slowed down the increase in filtration resistance, with the resistance maintained below 1.0×10(13) m(-1) in the first 70 hr before a jump occurred. Furthermore, the adsorbent addition contributed to retarding the occurrence of the filtration resistance jump, achieving simultaneous fouling control and chemical oxygen demand (COD) concentration improvement. The final concentrated COD amounted to 7500 mg/L after 6 days of operation. PMID:26040725

  16. Analysis of UF membrane fouling mechanisms caused by organic interactions in seawater.

    PubMed

    Resosudarmo, Adhikara; Ye, Yun; Le-Clech, Pierre; Chen, Vicki

    2013-02-01

    Organic fouling remains a significant challenge in the application of ultrafiltration (UF) pretreatment systems in the desalination industry. In this study, the fouling potential of organic materials in seawater was investigated using model seawater solution containing humic acid and alginate. The buildup of organic fouling on UF membranes was studied after consecutive filtration cycles with periodical backwash. The effects of varying backwash conditions (duration, frequency, permeate/deionized water) on membrane performance were analysed. It was observed that the variation in filtration condition resulted in minor differences in membrane performance provided the total backwash volume applied remained constant. However, the substitution of permeate water backwash with deionized water improved fouling reversibility significantly. Furthermore, advanced characterisation of the membrane fouling layer after filtration revealed significant differences in foulant distribution due to the nature of the backwash solution. Deionized water backwash was found to be particularly effective in removing alginate from the membrane fouling layer, although the humic acid adsorbed onto the membrane surface were not significantly affected. However, permeability testing of the membranes after chemical cleaning revealed higher levels of irrecoverable fouling after deionized water backwash. From the data obtained in this study, a fouling mechanism is therefore proposed, in which the alginate fouling layer performs as a dynamic membrane, prefiltering smaller humic acid molecules and reducing adsorption on the membrane surface. PMID:23219388

  17. Differential effect of plant lipids on membrane organization: specificities of phytosphingolipids and phytosterols.

    PubMed

    Grosjean, Kevin; Mongrand, Sébastien; Beney, Laurent; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

    2015-02-27

    The high diversity of the plant lipid mixture raises the question of their respective involvement in the definition of membrane organization. This is particularly the case for plant plasma membrane, which is enriched in specific lipids, such as free and conjugated forms of phytosterols and typical phytosphingolipids, such as glycosylinositolphosphoceramides. This question was here addressed extensively by characterizing the order level of membrane from vesicles prepared using various plant lipid mixtures and labeled with an environment-sensitive probe. Fluorescence spectroscopy experiments showed that among major phytosterols, campesterol exhibits a stronger ability than β-sitosterol and stigmasterol to order model membranes. Multispectral confocal microscopy, allowing spatial analysis of membrane organization, demonstrated accordingly the strong ability of campesterol to promote ordered domain formation and to organize their spatial distribution at the membrane surface. Conjugated sterol forms, alone and in synergy with free sterols, exhibit a striking ability to order membrane. Plant sphingolipids, particularly glycosylinositolphosphoceramides, enhanced the sterol-induced ordering effect, emphasizing the formation and increasing the size of sterol-dependent ordered domains. Altogether, our results support a differential involvement of free and conjugated phytosterols in the formation of ordered domains and suggest that the diversity of plant lipids, allowing various local combinations of lipid species, could be a major contributor to membrane organization in particular through the formation of sphingolipid-sterol interacting domains. PMID:25575593

  18. Combined organic-inorganic fouling of forward osmosis hollow fiber membranes.

    PubMed

    Arkhangelsky, Elizabeth; Wicaksana, Filicia; Tang, Chuyang; Al-Rabiah, Abdulrahman A; Al-Zahrani, Saeed M; Wang, Rong

    2012-12-01

    This research focused on combined organic-inorganic fouling and cleaning studies of forward osmosis (FO) membranes. Various organic/inorganic model foulants such as sodium alginate, bovine serum albumin (BSA) and silica nanoparticles were applied to polyamide-polyethersulfone FO hollow fiber membranes fabricated in our laboratory. In order to understand all possible interactions, experiments were performed with a single foulant as well as combinations of foulants. Experimental results suggested that the degree of FO membrane fouling could be promoted by synergistic effect of organic foulants, the presence of divalent cations, low cross-flow velocity and high permeation drag force. The water flux of fouled FO hollow fibers could be fully restored by simple physical cleaning. It was also found that hydrodynamic regime played an important role in combined organic-inorganic fouling of FO membranes. PMID:23026125

  19. NOVEL CERAMIC-ORGANIC VAPOR PERMEATION MEMBRANES FOR VOC REMOVAL - PHASE II

    EPA Science Inventory

    Vapor permeation with highly permeable and organic-selective membranes is becoming an increasingly popular technique for preventing VOC emissions that are generated by a variety of stationary sources, including solvent and surface coating operations, gasoline storage operat...

  20. Natural organic matter removal and fouling in a low pressure hybrid membrane systems.

    PubMed

    Uyak, Vedat; Akdagli, Muge; Cakmakci, Mehmet; Koyuncu, Ismail

    2014-01-01

    The objective of this study was to investigate powdered activated carbon (PAC) contribution to natural organic matter (NOM) removal by a submerged MF and UF hybrid systems. It was found that filtration of surface waters by a bare MF and UF membranes removed negligible TOC; by contrast, significant amounts of TOC were removed when daily added PAC particles were predeposited on the membrane surfaces. These results support the assumption that the membranes surface properties and PAC layer structure might have considerably influential factor on NOM removal. Moreover, it was concluded that the dominant removal mechanism of hybrid membrane system is adsorption of NOM within PAC layer rather than size exclusion of NOM by both of membrane pores. Transmembrane pressure (TMP) increases with PAC membrane systems support the view that PAC adsorption pretreatment will not prevent the development of membrane pressure; on the contrary, PAC particles themselves caused membrane fouling by blocking the entrance of pores of MF and UF membranes. Although all three source waters have similar HPI content, it appears that the PAC interaction with the entrance of membrane pores was responsible for offsetting the NOM fractional effects on membrane fouling for these source waters. PMID:24523651

  1. Wavelet-based approach to character skeleton.

    PubMed

    You, Xinge; Tang, Yuan Yan

    2007-05-01

    Character skeleton plays a significant role in character recognition. The strokes of a character may consist of two regions, i.e., singular and regular regions. The intersections and junctions of the strokes belong to singular region, while the straight and smooth parts of the strokes are categorized to regular region. Therefore, a skeletonization method requires two different processes to treat the skeletons in theses two different regions. All traditional skeletonization algorithms are based on the symmetry analysis technique. The major problems of these methods are as follows. 1) The computation of the primary skeleton in the regular region is indirect, so that its implementation is sophisticated and costly. 2) The extracted skeleton cannot be exactly located on the central line of the stroke. 3) The captured skeleton in the singular region may be distorted by artifacts and branches. To overcome these problems, a novel scheme of extracting the skeleton of character based on wavelet transform is presented in this paper. This scheme consists of two main steps, namely: a) extraction of primary skeleton in the regular region and b) amendment processing of the primary skeletons and connection of them in the singular region. A direct technique is used in the first step, where a new wavelet-based symmetry analysis is developed for finding the central line of the stroke directly. A novel method called smooth interpolation is designed in the second step, where a smooth operation is applied to the primary skeleton, and, thereafter, the interpolation compensation technique is proposed to link the primary skeleton, so that the skeleton in the singular region can be produced. Experiments are conducted and positive results are achieved, which show that the proposed skeletonization scheme is applicable to not only binary image but also gray-level image, and the skeleton is robust against noise and affine transform. PMID:17491454

  2. Spatiotemporal mapping of diffusion dynamics and organization in plasma membranes

    NASA Astrophysics Data System (ADS)

    Bag, Nirmalya; Ng, Xue Wen; Sankaran, Jagadish; Wohland, Thorsten

    2016-09-01

    Imaging fluorescence correlation spectroscopy (FCS) and the related FCS diffusion law have been applied in recent years to investigate the diffusion modes of lipids and proteins in membranes. These efforts have provided new insights into the membrane structure below the optical diffraction limit, new information on the existence of lipid domains, and on the influence of the cytoskeleton on membrane dynamics. However, there has been no systematic study to evaluate how domain size, domain density, and the probe partition coefficient affect the resulting imaging FCS diffusion law parameters. Here, we characterize the effects of these factors on the FCS diffusion law through simulations and experiments on lipid bilayers and live cells. By segmenting images into smaller 7  ×  7 pixel areas, we can evaluate the FCS diffusion law on areas smaller than 2 µm and thus provide detailed maps of information on the membrane structure and heterogeneity at this length scale. We support and extend this analysis by deriving a mathematical expression to calculate the mean squared displacement (MSDACF) from the autocorrelation function of imaging FCS, and demonstrate that the MSDACF plots depend on the existence of nanoscopic domains. Based on the results, we derive limits for the detection of domains depending on their size, density, and relative viscosity in comparison to the surroundings. Finally, we apply these measurements to bilayers and live cells using imaging total internal reflection FCS and single plane illumination microscopy FCS.

  3. Spatio-temporal Remodeling of Functional Membrane Microdomains Organizes the Signaling Networks of a Bacterium

    PubMed Central

    Schneider, Johannes; Klein, Teresa; Mielich-Süss, Benjamin; Koch, Gudrun; Franke, Christian; Kuipers, Oscar P.; Kovács, Ákos T.; Sauer, Markus; Lopez, Daniel

    2015-01-01

    Lipid rafts are membrane microdomains specialized in the regulation of numerous cellular processes related to membrane organization, as diverse as signal transduction, protein sorting, membrane trafficking or pathogen invasion. It has been proposed that this functional diversity would require a heterogeneous population of raft domains with varying compositions. However, a mechanism for such diversification is not known. We recently discovered that bacterial membranes organize their signal transduction pathways in functional membrane microdomains (FMMs) that are structurally and functionally similar to the eukaryotic lipid rafts. In this report, we took advantage of the tractability of the prokaryotic model Bacillus subtilis to provide evidence for the coexistence of two distinct families of FMMs in bacterial membranes, displaying a distinctive distribution of proteins specialized in different biological processes. One family of microdomains harbors the scaffolding flotillin protein FloA that selectively tethers proteins specialized in regulating cell envelope turnover and primary metabolism. A second population of microdomains containing the two scaffolding flotillins, FloA and FloT, arises exclusively at later stages of cell growth and specializes in adaptation of cells to stationary phase. Importantly, the diversification of membrane microdomains does not occur arbitrarily. We discovered that bacterial cells control the spatio-temporal remodeling of microdomains by restricting the activation of FloT expression to stationary phase. This regulation ensures a sequential assembly of functionally specialized membrane microdomains to strategically organize signaling networks at the right time during the lifespan of a bacterium. PMID:25909364

  4. Enhanced ethylene separation and plasticization resistance in polymer membranes incorporating metal-organic framework nanocrystals

    NASA Astrophysics Data System (ADS)

    Bachman, Jonathan E.; Smith, Zachary P.; Li, Tao; Xu, Ting; Long, Jeffrey R.

    2016-08-01

    The implementation of membrane-based separations in the petrochemical industry has the potential to reduce energy consumption significantly relative to conventional separation processes. Achieving this goal, however, requires the development of new membrane materials with greater selectivity, permeability and stability than available at present. Here, we report composite materials consisting of nanocrystals of metal-organic frameworks dispersed within a high-performance polyimide, which can exhibit enhanced selectivity for ethylene over ethane, greater ethylene permeability and improved membrane stability. Our results suggest that framework-polymer interactions reduce chain mobility of the polymer while simultaneously boosting membrane separation performance. The increased stability, or plasticization resistance, is expected to improve membrane utility under real process conditions for petrochemical separations and natural gas purification. Furthermore, this approach can be broadly applied to numerous polymers that encounter aggressive environments, potentially making gas separations possible that were previously inaccessible to membranes.

  5. Enhanced ethylene separation and plasticization resistance in polymer membranes incorporating metal-organic framework nanocrystals.

    PubMed

    Bachman, Jonathan E; Smith, Zachary P; Li, Tao; Xu, Ting; Long, Jeffrey R

    2016-08-01

    The implementation of membrane-based separations in the petrochemical industry has the potential to reduce energy consumption significantly relative to conventional separation processes. Achieving this goal, however, requires the development of new membrane materials with greater selectivity, permeability and stability than available at present. Here, we report composite materials consisting of nanocrystals of metal-organic frameworks dispersed within a high-performance polyimide, which can exhibit enhanced selectivity for ethylene over ethane, greater ethylene permeability and improved membrane stability. Our results suggest that framework-polymer interactions reduce chain mobility of the polymer while simultaneously boosting membrane separation performance. The increased stability, or plasticization resistance, is expected to improve membrane utility under real process conditions for petrochemical separations and natural gas purification. Furthermore, this approach can be broadly applied to numerous polymers that encounter aggressive environments, potentially making gas separations possible that were previously inaccessible to membranes. PMID:27064528

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

    PubMed

    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. PMID:24345822

  7. Landform skeleton reconstruction from unorganized points

    NASA Astrophysics Data System (ADS)

    Luo, Mingliang; Tang, Guoan; Liu, Xuejun; Bian, Lu

    2007-11-01

    Landform skeleton are lines that indicate significant topographic features of the terrain. It is widely used in mapping and surveying, hydrology simulation, topography representation and engineering designing. In order to derive the landform skeleton, many kinds of data source have been used, including digitized contour lines, Grid-DEMs and TIN. As time goes by, more and more unorganized points have been acquired, created, maintained and disseminated in many fields. Those unorganized points are the most original and important information which is vital for mapping and surveying. How to extract the feature lines from unorganized points has been the hot-pot in computer design and reverse-engineering. Methods used to extract landform features in existence have shown dependence on data types and thresholds more or less. In the paper, the view sheds principle used to extract the feature points has been put forward and then those points have been organized into feature lines according to related rules. The result has shown that the view sheds principle can extract the features and give the levels of feature points.

  8. Quantifying the deformation of the red blood cell skeleton in shear flow

    NASA Astrophysics Data System (ADS)

    Peng, Zhangli; Zhu, Qiang

    2012-02-01

    To quantitatively predict the response of red blood cell (RBC) membrane in shear flow, we carried out multiphysics simulations by coupling a three-level multiscale approach of RBC membranes with a Boundary Element Method (BEM) for surrounding flows. Our multiscale approach includes a model of spectrins with the domain unfolding feature, a molecular-based model of the junctional complex with detailed protein connectivity and a whole cell Finite Element Method (FEM) model with the bilayer-skeleton friction derived from measured transmembrane protein diffusivity based on the Einstein-Stokes relation. Applying this approach, we investigated the bilayer-skeleton slip and skeleton deformation of healthy RBCs and RBCs with hereditary spherocytosis anemia during tank-treading motion. Compared with healthy cells, cells with hereditary spherocytosis anemia sustain much larger skeleton-bilayer slip and area deformation of the skeleton due to deficiency of transmembrane proteins. This leads to extremely low skeleton density and large bilayer-skeleton interaction force, both of which may cause bilayer loss. This finding suggests a possible mechanism of the development of hereditary spherocytosis anemia.

  9. The effects of organic fouling on the removal of radionuclides by reverse osmosis membranes.

    PubMed

    Ding, Shiyuan; Yang, Yu; Li, Chen; Huang, Haiou; Hou, Li-An

    2016-05-15

    The removals of cesium (Cs) and strontium (Sr), two hazardous and abundant radionuclides in aquatic environment, were assessed with their isotopes in a synthetic water containing Suwannee River natural organic matter (SRNOM), a natural surface water (SW) and a wastewater effluent (WW) by two different types of ultra-low pressure RO membranes (M1 and M2). The rejections of Sr by the membranes M1 and M2 were higher than 97.5% and 96.0%, respectively, and the rejections of Cs exceeded 90.0% and 85.0%, respectively, in the filtration of real water. The membrane M1 exhibited a more significant flux decline in the filtration of the SRNOM solution, while more severe flux declines were observed with the membrane M2 in the filtration of SW and WW. Protein-like materials with relatively high molecular weight were the main contributors to the flux decline, and humic-acid-like compounds had little effect on the flux decline. Donnan exclusion and size exclusion by humic-acid-like compounds improved the rejections by the membrane M2 with weaker hydrophilicity, while the cake-enhanced concentration polarization reduced the rejections of Cs and Sr by the membrane M1 with stronger hydrophilicity. The ionic strength in the real water resulted in the mitigation of membrane fouling. This study provided important insights into foulant characterization and the mechanisms of organic-fouling-enhanced rejections of Cr and Sr by ultra-low pressure RO membranes. PMID:26994696

  10. DEVELOPMENTAL PALEOBIOLOGY OF THE VERTEBRATE SKELETON

    PubMed Central

    RÜCKLIN, MARTIN; DONOGHUE, PHILIP C. J.; CUNNINGHAM, JOHN A.; MARONE, FEDERICA; STAMPANONI, MARCO

    2015-01-01

    Studies of the development of organisms can reveal crucial information on homology of structures. Developmental data are not peculiar to living organisms, and they are routinely preserved in the mineralized tissues that comprise the vertebrate skeleton, allowing us to obtain direct insight into the developmental evolution of this most formative of vertebrate innovations. The pattern of developmental processes is recorded in fossils as successive stages inferred from the gross morphology of multiple specimens and, more reliably and routinely, through the ontogenetic stages of development seen in the skeletal histology of individuals. Traditional techniques are destructive and restricted to a 2-D plane with the third dimension inferred. Effective non-invasive methods of visualizing paleohistology to reconstruct developmental stages of the skeleton are necessary. In a brief survey of paleohistological techniques we discuss the pros and cons of these methods. The use of tomographic methods to reconstruct development of organs is exemplified by the study of the placoderm dentition. Testing evidence for the presence of teeth in placoderms, the first jawed vertebrates, we compare the methods that have been used. These include inferring the development from morphology, and using serial sectioning, microCT or synchrotron X-ray tomographic microscopy (SRXTM) to reconstruct growth stages and directions of growth. The ensuing developmental interpretations are biased by the methods and degree of inference. The most direct and reliable method is using SRXTM data to trace sclerochronology. The resulting developmental data can be used to resolve homology and test hypotheses on the origin of evolutionary novelties. PMID:26306050

  11. Development of polymer membranes with improved haemocompatibility for biohybrid organ technology.

    PubMed

    Groth, T; Seifert, B; Albrecht, W; Malsch, G; Gross, U; Fey-Lamprecht, F; Michanetzis, G; Missirlis, Y; Engbers, G

    2005-01-01

    Biomedical technology has opened up possibilities of treating the failure of internal organs like kidney and liver by artificial organ therapy. Most of these techniques are based on polymer membranes, which allow the removal of excess of water, salts and toxins from the circulation. However, haemodialysis for the replacement of kidney function results in an increased morbidity and mortality of patients after long-term application. Conventional therapy, such as haemofiltration for the treatment of acute liver failure does not improve significantly the survival rate of patients. Biohybrid organ support as a combination of the artificial organ therapy with the functional activity of immobilised cells seems to be a solution of the problem. Membranes applied in these devices have to face both tissue cells and blood. Organ cells in biohybrid organs have to make intimate contact with the surface of membrane but must also develop close cell-cell-connections as a prerequisite for their survival and high functional activity. Blood to be detoxified will contact the other side of membrane and may not become activated by the synthetic material. New polymer membranes based on acrylonitrile were developed to address these requirements by tailoring the composition of copolymers and to be applied in a specific hollow fibre bioreactor with an outer fibre for blood contact, and an inner fibre for tissue contact or vice versa. PMID:15764821

  12. Organization of cGMP sensing structures on the rod photoreceptor outer segment plasma membrane

    PubMed Central

    Nemet, Ina; Tian, Guilian; Imanishi, Yoshikazu

    2014-01-01

    A diffusion barrier segregates the plasma membrane of the rod photoreceptor outer segment into 2 domains; one which is optimized for the conductance of ions in the phototransduction cascade and another for disk membrane synthesis. We propose the former to be named “phototransductive plasma membrane domain," and the latter to be named “disk morphogenic plasma membrane domain." Within the phototransductive plasma membrane, cGMP-gated channels are concentrated in striated membrane features, which are proximally located to the sites of active cGMP production within the disk membranes. For proper localization of cGMP-gated channel to the phototransductive plasma membrane, the glutamic acid-rich protein domain encoded in the β subunit plays a critical role. Quantitative study suggests that the disk morphogenic domain likely plays an important role in enriching rhodopsin prior to its sequestration into closed disk membranes. Thus, this and our previous studies provide new insight into the mechanism that spatially organizes the vertebrate phototransduction cascade. PMID:25616687

  13. Fouling of microfiltration membranes by organic polymer coagulants and flocculants: controlling factors and mechanisms.

    PubMed

    Wang, Sen; Liu, Charles; Li, Qilin

    2011-01-01

    Organic polymers are commonly used as coagulants or flocculants in pretreatment for microfiltration (MF). These high molecular weight compounds are potential membrane foulants when carried over to the MF filters. This study examined fouling of three MF membranes of different materials by three commonly used water treatment polymers: poly(diallyldimethylammonium) chloride (pDADMAC), polyacrylamide (PAM), and poly(acrylic acid-co-acrylamide (PACA) with a wide range of molecular weights. The effects of polymer molecular characteristics, membrane surface properties, solution condition and polymer concentration on membrane fouling were investigated. Results showed severe fouling of microfiltration membranes at very low polymer concentrations, suggesting that residual polymers carried over from the coagulation/flocculation basin can contribute significantly to membrane fouling. The interactions between polymers and membranes depended strongly on the molecular size and charge of the polymer. High molecular weight, positively charged polymers caused the greatest fouling. Blockage of membrane pore openings was identified as the main fouling mechanism with no detectable internal fouling in spite of the small molecular size of the polymers relative to the membrane pore size. Solution conditions (e.g., pH and calcium concentration) that led to larger polymer molecular or aggregate sizes resulted in greater fouling. PMID:20828779

  14. Emerging Insights into the Roles of Membrane Tethers from Analysis of Whole Organisms: The Tip of an Iceberg?

    PubMed Central

    Toh, Wei Hong; Gleeson, Paul A.

    2016-01-01

    Membrane tethers have been identified throughout different compartments of the endomembrane system. It is now well established that a number of membrane tethers mediate docking of membrane carriers in anterograde and retrograde transport and in regulating the organization of membrane compartments. Much of our information on membrane tethers have been obtained from the analysis of individual membrane tethers in cultured cells. In the future it will be important to better appreciate the network of interactions mediated by tethers and the potential co-ordination of their collective functions in vivo. There are now a number of studies which have analyzed membrane tethers in tissues and organisms which are providing new insights into the role of this class of membrane protein at the physiological level. Here we review recent advances in the understanding of the function of membrane tethers from knock outs (or knock downs) in whole organisms and from mutations in tethers associated with disease. PMID:26973835

  15. Lipid Interactions and Organization in Complex Bilayer Membranes.

    PubMed

    Engberg, Oskar; Yasuda, Tomokazu; Hautala, Victor; Matsumori, Nobuaki; Nyholm, Thomas K M; Murata, Michio; Slotte, J Peter

    2016-04-12

    Bilayer lipids influence the lateral structure of the membranes, but the relationship between lipid properties and the lateral structure formed is not always understood. Model membrane studies on bilayers containing cholesterol and various phospholipids (PLs) suggest that high and low temperature melting PLs may segregate, especially in the presence of cholesterol. The effect of different PL headgroups on lateral structure of bilayers is also not clear. Here, we have examined the formation of lateral heterogeneity in increasingly complex (up to five-component) multilamellar bilayers. We have used time-resolved fluorescence spectroscopy with domain-selective fluorescent probes (PL-conjugated trans-parinaric acid), and (2)H NMR spectroscopy with site or perdeuterated PLs. We have measured changes in bilayer order using such domain-selective probes both as a function of temperature and composition. Our results from time-resolved fluorescence and (2)H NMR showed that in ternary bilayers, acyl chain order and thermostability in sphingomyelin-rich domains were not affected to any greater extent by the headgroup structure of the monounsaturated PLs (phosphatidylcholine, phosphatidylethanolamine, or phosphatidylserine) in the bilayer. In the complex five-component bilayers, we could not detect major differences between the different monounsaturated PLs regarding cholesterol-induced ordering. However, cholesterol clearly influenced deuterated N-palmitoyl sphingomyelin differently than the other deuterated PLs, suggesting that cholesterol favored N-palmitoyl sphingomyelin over the other PLs. Taken together, both the fluorescence spectroscopy and (2)H NMR data suggest that the complex five-component membranes displayed lateral heterogeneity, at least in the lower temperature regimen examined. PMID:27074681

  16. Membrane-localized estrogen receptor α is required for normal organ development and function.

    PubMed

    Pedram, Ali; Razandi, Mahnaz; Lewis, Michael; Hammes, Stephen; Levin, Ellis R

    2014-05-27

    Steroid receptors are found in discrete cellular locations, but it is unknown whether extranuclear pools are necessary for normal organ development. To assess this, we developed a point mutant estrogen receptor α (ERα) knockin mouse (C451A) that precludes palmitoylation and membrane trafficking of the steroid receptor in all organs. Homozygous knockin female mice (nuclear-only ERα [NOER]) show loss of rapid signaling that occurs from membrane ERα in wild-type mice. Multiple developmental abnormalities were found, including infertility, relatively hypoplastic uteri, abnormal ovaries, stunted mammary gland ductal development, and abnormal pituitary hormone regulation in NOER mice. These abnormalities were rescued in heterozygous NOER mice that were comparable to wild-type mice. mRNAs implicated in organ development were often poorly stimulated by estrogen only in homozygous NOER mice. We conclude that many organs require membrane ERα and resulting signal transduction to collaborate with nuclear ERα for normal development and function. PMID:24871949

  17. Intracellular lipid flux and membrane microdomains as organizing principles in inflammatory cell signaling1

    PubMed Central

    Fessler, Michael B.; Parks, John S.

    2011-01-01

    Lipid rafts and caveolae play a pivotal role in organization of signaling by Toll-like Receptor (TLR)4 and several other immune receptors. Beyond the simple cataloguing of signaling events compartmentalized by these membrane microdomains, recent studies have revealed the surprisingly central importance of dynamic remodeling of membrane lipid domains to immune signaling. Simple interventions upon membrane lipid, such as changes in cholesterol loading or crosslinking of raft lipids, are sufficient to induce micron-scale reordering of membranes and their protein cargo with consequent signal transduction. In this review, using TLR signaling in the macrophage as a central focus, we discuss emerging evidence that environmental and genetic perturbations of membrane lipid regulate protein signaling, illustrate how homeostatic flow of cholesterol and other lipids through rafts regulates the innate immune response, and highlight recent attempts to harness these insights towards therapeutic development. PMID:21810617

  18. Metal-Organic Framework/PVDF Composite Membranes with High H2 Permselectivity Synthesized by Ammoniation.

    PubMed

    Li, Wanbin; Meng, Qin; Zhang, Congyang; Zhang, Guoliang

    2015-05-01

    Herein we report a new ammoniation-based chemical modification strategy for synthesis of continuous and uniform metal-organic framework (MOF)/polyvinylidene fluoride (PVDF) membranes with attractive performance. Ammoniation can promote the support PVDF membrane to produce amino groups, form a nanoparticle structure, and be well cross-linked; therefore, the high-density heterogeneous nucleation sites for MOFs growth were provided and the thermal stability and chemical resistance of composite membranes can be greatly improved. The high-quality layers of representative Cu-BTC and ZIF-8 were synthesized on the chemically modified PVDF membranes. By ammoniation, ZIF-7 can even be grown under harsh synthetic conditions such as in DMF precursor solutions at 403 K. The fabricated MOF/PVDF composite membranes with excellent hollow fiber structures and enhanced structural stability exhibited high H2 permselectivities for H2 /CO2 and H2 /N2 . PMID:25810142

  19. 2-Hydroxy Fatty Acid Enantiomers of Gb3 Impact Shiga Toxin Binding and Membrane Organization.

    PubMed

    Schütte, Ole M; Patalag, Lukas J; Weber, Lucas M C; Ries, Annika; Römer, Winfried; Werz, Daniel B; Steinem, Claudia

    2015-06-16

    Shiga toxin subunit B (STxB) binding to its cellular receptor Gb3 leads to the formation of protein-lipid clusters and bending of the membrane. A newly developed synthetic route allowed synthesizing the biologically most relevant Gb3-C24:1 2OH species with both, the natural (Gb3-R) as well as the unnatural (Gb3-S) configuration of the 2OH group. The derivatives bind STxB with identical nanomolar affinity, while the propensity to induce membrane tubules in giant unilamellar vesicles is more pronounced for Gb3-S. Fluorescence and atomic force microscopy images of phase-separated supported membranes revealed differences in the lateral organization of the protein on the membrane. Gb3-R favorably induces large and tightly packed protein clusters, while a lower protein density is found on Gb3-S doped membranes. PMID:26083916

  20. Plasma membrane organization promotes virulence of the human fungal pathogen Candida albicans.

    PubMed

    Douglas, Lois M; Konopka, James B

    2016-03-01

    Candida albicans is a human fungal pathogen capable of causing lethal systemic infections. The plasma membrane plays key roles in virulence because it not only functions as a protective barrier, it also mediates dynamic functions including secretion of virulence factors, cell wall synthesis, invasive hyphal morphogenesis, endocytosis, and nutrient uptake. Consistent with this functional complexity, the plasma membrane is composed of a wide array of lipids and proteins. These components are organized into distinct domains that will be the topic of this review. Some of the plasma membrane domains that will be described are known to act as scaffolds or barriers to diffusion, such as MCC/eisosomes, septins, and sites of contact with the endoplasmic reticulum. Other zones mediate dynamic processes, including secretion, endocytosis, and a special region at hyphal tips that facilitates rapid growth. The highly organized architecture of the plasma membrane facilitates the coordination of diverse functions and promotes the pathogenesis of C. albicans. PMID:26920878

  1. Optimum Membrane Structures for Growth of Coliform and Fecal Coliform Organisms

    PubMed Central

    Sladek, K. J.; Suslavich, R. V.; Sohn, B. I.; Dawson, F. W.

    1975-01-01

    The purpose of this study was to determine the optimum membrane filter structure and characteristics for recovery of coliform organisms. Additionally, other factors such as sterilization method and membrane composition were examined. Fecal coliform growth tests with varied samples indicated that the most critical factor in recovery was surface pore morphology and not other factors previously suspected. Fecal coliform counts showed a dramatic increase, with increasing surface opening sizes. Membrane structures with surface openings large enough to surround the entrapped bacteria are required for optimum growth of fecal coliform organisms. Maximum fecal coliform recoveries are obtained using membranes composed of mixed esters of cellulose exhibiting a surface opening diameter of 2.4 μm and a retention pore size of 0.7 μm. Images PMID:1103734

  2. Hamilton-Jacobi skeleton on cortical surfaces.

    PubMed

    Shi, Y; Thompson, P M; Dinov, I; Toga, A W

    2008-05-01

    In this paper, we propose a new method to construct graphical representations of cortical folding patterns by computing skeletons on triangulated cortical surfaces. In our approach, a cortical surface is first partitioned into sulcal and gyral regions via the solution of a variational problem using graph cuts, which can guarantee global optimality. After that, we extend the method of Hamilton-Jacobi skeleton [1] to subsets of triangulated surfaces, together with a geometrically intuitive pruning process that can trade off between skeleton complexity and the completeness of representing folding patterns. Compared with previous work that uses skeletons of 3-D volumes to represent sulcal patterns, the skeletons on cortical surfaces can be easily decomposed into branches and provide a simpler way to construct graphical representations of cortical morphometry. In our experiments, we demonstrate our method on two different cortical surface models, its ability of capturing major sulcal patterns and its application to compute skeletons of gyral regions. PMID:18450539

  3. Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membranes.

    PubMed

    Koh, Dong-Yeun; McCool, Benjamin A; Deckman, Harry W; Lively, Ryan P

    2016-08-19

    Liquid-phase separations of similarly sized organic molecules using membranes is a major challenge for energy-intensive industrial separation processes. We created free-standing carbon molecular sieve membranes that translate the advantages of reverse osmosis for aqueous separations to the separation of organic liquids. Polymer precursors were cross-linked with a one-pot technique that protected the porous morphology of the membranes from thermally induced structural rearrangement during carbonization. Permeation studies using benzene derivatives whose kinetic diameters differ by less than an angstrom show kinetically selective organic liquid reverse osmosis. Ratios of single-component fluxes for para- and ortho-xylene exceeding 25 were observed and para- and ortho- liquid mixtures were efficiently separated, with an equimolar feed enriched to 81 mole % para-xylene, without phase change and at ambient temperature. PMID:27540170

  4. Morphological plasticity of the coral skeleton under CO2-driven seawater acidification.

    PubMed

    Tambutté, E; Venn, A A; Holcomb, M; Segonds, N; Techer, N; Zoccola, D; Allemand, D; Tambutté, S

    2015-01-01

    Ocean acidification causes corals to calcify at reduced rates, but current understanding of the underlying processes is limited. Here, we conduct a mechanistic study into how seawater acidification alters skeletal growth of the coral Stylophora pistillata. Reductions in colony calcification rates are manifested as increases in skeletal porosity at lower pH, while linear extension of skeletons remains unchanged. Inspection of the microstructure of skeletons and measurements of pH at the site of calcification indicate that dissolution is not responsible for changes in skeletal porosity. Instead, changes occur by enlargement of corallite-calyxes and thinning of associated skeletal elements, constituting a modification in skeleton architecture. We also detect increases in the organic matrix protein content of skeletons formed under lower pH. Overall, our study reveals that seawater acidification not only causes decreases in calcification, but can also cause morphological change of the coral skeleton to a more porous and potentially fragile phenotype. PMID:26067341

  5. Morphological plasticity of the coral skeleton under CO2-driven seawater acidification

    PubMed Central

    Tambutté, E.; Venn, A. A.; Holcomb, M.; Segonds, N.; Techer, N.; Zoccola, D.; Allemand, D.; Tambutté, S.

    2015-01-01

    Ocean acidification causes corals to calcify at reduced rates, but current understanding of the underlying processes is limited. Here, we conduct a mechanistic study into how seawater acidification alters skeletal growth of the coral Stylophora pistillata. Reductions in colony calcification rates are manifested as increases in skeletal porosity at lower pH, while linear extension of skeletons remains unchanged. Inspection of the microstructure of skeletons and measurements of pH at the site of calcification indicate that dissolution is not responsible for changes in skeletal porosity. Instead, changes occur by enlargement of corallite-calyxes and thinning of associated skeletal elements, constituting a modification in skeleton architecture. We also detect increases in the organic matrix protein content of skeletons formed under lower pH. Overall, our study reveals that seawater acidification not only causes decreases in calcification, but can also cause morphological change of the coral skeleton to a more porous and potentially fragile phenotype. PMID:26067341

  6. The nanoscale organization of signaling domains at the plasma membrane.

    PubMed

    Griffié, Juliette; Burn, Garth; Owen, Dylan M

    2015-01-01

    In this chapter, we present an overview of the role of the nanoscale organization of signaling domains in regulating key cellular processes. In particular, we illustrate the importance of protein and lipid nanodomains as triggers and mediators of cell signaling. As particular examples, we summarize the state of the art of understanding the role of nanodomains in the mounting of an immune response, cellular adhesion, intercellular communication, and cell proliferation. Thus, this chapter underlines the essential role the nanoscale organization of key signaling proteins and lipid domains. We will also see how nanodomains play an important role in the lifecycle of many pathogens relevant to human disease and therefore illustrate how these structures may become future therapeutic targets. PMID:26015282

  7. Surface modification of PTMSP membranes by plasma treatment: Asymmetry of transport in organic solvent nanofiltration.

    PubMed

    Volkov, A V; Tsarkov, S E; Gilman, A B; Khotimsky, V S; Roldughin, V I; Volkov, V V

    2015-08-01

    For the first time, the effect of asymmetry of the membrane transport was studied for organic solvents and solutes upon their nanofiltration through the plasma-modified membranes based on poly(1-trimethylsilyl-1-propyne) (PTMSP). Plasma treatment is shown to provide a marked hydrophilization of the hydrophobic PTMSP surface (the contact angle of water decreases from 88 down to 20°) and leads to the development of a negative charge of -5.2 nC/cm(2). The XPS measurements prove the formation of the oxygen-containing groups (Si-O and C-O) due to the surface modification. The AFM images show that the small-scale surface roughness of the plasma-treated PTMSP sample is reduced but the large-scale surface heterogeneities become more pronounced. The modified membranes retain their hydrophilic surface properties even after the nanofiltration tests and 30-day storage under ambient conditions. The results of the filtration tests show that when the membrane is oriented so that its modified layer contacts the feed solution, the membrane permeability for linear alcohols (methanol-propanol) and acetone decreases nearly two times. When the modified membrane surface faces the permeate, the membrane is seen to regain its transport characteristics: the flux becomes equal to that of the unmodified PTMSP. The well-pronounced effect of the transport asymmetry is observed for the solution of the neutral dye Solvent Blue 35 in methanol, ethanol, and acetone. For example, the initial membrane shows the negative retention for the Solvent Blue 35 dye (-16%) upon its filtration from the ethanol solution whereas, for the modified PTMSP membrane, the retention increases up to 17%. Various effects contributing to the asymmetry of the membrane transport characteristics are discussed. PMID:25482845

  8. The effect of compatible solute ectoines on the structural organization of lipid monolayer and bilayer membranes.

    PubMed

    Harishchandra, Rakesh Kumar; Wulff, Stephanie; Lentzen, Georg; Neuhaus, Thorsten; Galla, Hans-Joachim

    2010-08-01

    Compatible solutes are small organic osmolytes responsible for osmotic balance and at the same time compatible with the cellular metabolism. Here, we have investigated the effect of the compatible solutes, ectoine and hydroxyectoine, on the fluid-rigid domain structure of lipid monolayer and bilayer membranes. Mainly saturated dipalmitoyl-phosphatidylcholine membranes exhibiting a clear le/lc phase transition were used. Fluorescence microscopy showed that ectoines added to the aqueous subphase expand and fluidize the lipid monolayers especially at surface pressures below 30mN/m. The domain structure at the le/lc phase transition is sensitively modified leading to smaller but more numerous domains in the presence of ectoines. Hydroxyectoine was more efficient than ectoine. These results are explained by the replacement theory assuming that the ectoines are likely to be expelled from the membrane surface thus favoring the hydration of the lipid membrane. This effect reduces the line tension, which is the interfacial energy at the domain edges leading to reduced domain sizes and increased number of rigid domains. Isotherms of negatively charged phosphatidylglycerol membranes show a similar expansion, while unsaturated lipids are less affected. Mixed phosphatidylcholine/phosphatidylglycerol membranes exhibit the same effect on the line tension increasing the tendency for a phase separation. This could be shown also in bilayer vesicles, where the compatible solutes have only a minor effect on the lipid main phase transition in pure DPPC membranes but reduce the extent of the pretransition. In mixed DPPC/DPPG bilayer membranes ectoines cause a phase separation leading to the enrichment of expanded DPPC domains. In conclusion, our study gives for the first time evidence that ectoines have an effect on lipid membranes increasing the hydration of the surface and thus increasing the mobility of the lipid head groups and fluidizing the lipid layer accordingly. This increased

  9. Novel Organic Membrane-based Thin-film Microsensors for the Determination of Heavy Metal Cations

    PubMed Central

    Arida, Hassan A.; Kloock, Joachim P.; Schöning, Michael J.

    2006-01-01

    A first step towards the fabrication and electrochemical evaluation of thin-film microsensors based on organic PVC membranes for the determination of Hg(II), Cd(II), Pb(II) and Cu(II) ions in solutions has been realised. The membrane-coating mixture used in the preparation of this new type of microsensors is incorporating PVC as supporting matrix, o-nitrophenyloctylether (o-NPOE) as solvent mediator and a recently synthesized Hg[dimethylglyoxime(phene)]2+ and Bis-(4-hydroxyacetophenone)-ethylenediamine as electroactive materials for Hg(II) and Cd(II), respectively. A set of three commercialised ionophores for Cd(II), Pb(II) and Cu(II) has been also used for comparison. Thin-film microsensors based on these membranes showed a Nernstian response of slope (26-30 mV/dec.) for the respective tested cations. The potentiometric response characteristics (linear range, pH range, detection limit and response time) are comparable with those obtained by conventional membranes as well as coated wire electrodes prepared from the same membrane. The realisation of the new organic membrane-based thin-film microsensors overcomes the problem of an insufficient selectivity of solid-state-based thin-film sensors.

  10. Lateral organization, bilayer asymmetry, and inter-leaflet coupling of biological membranes

    SciTech Connect

    Smith, Jeremy C.; Cheng, Xiaolin; Nickels, Jonathan D.

    2015-07-29

    Understanding of cell membrane organization has evolved significantly from the classic fluid mosaic model. It is now recognized that biological membranes are highly organized structures, with differences in lipid compositions between inner and outer leaflets and in lateral structures within the bilayer plane, known as lipid rafts. These organizing principles are important for protein localization and function as well as cellular signaling. However, the mechanisms and biophysical basis of lipid raft formation, structure, dynamics and function are not clearly understood. One key question, which we focus on in this review, is how lateral organization and leaflet compositional asymmetry are coupled. Detailed information elucidating this question has been sparse because of the small size and transient nature of rafts and the experimental challenges in constructing asymmetric bilayers. Resolving this mystery will require advances in both experimentation and modeling. We discuss here the preparation of model systems along with experimental and computational approaches that have been applied in efforts to address this key question in membrane biology. Furthermore, we seek to place recent and future advances in experimental and computational techniques in context, providing insight into in-plane and transverse organization of biological membranes.

  11. Lateral organization, bilayer asymmetry, and inter-leaflet coupling of biological membranes

    DOE PAGESBeta

    Smith, Jeremy C.; Cheng, Xiaolin; Nickels, Jonathan D.

    2015-07-29

    Understanding of cell membrane organization has evolved significantly from the classic fluid mosaic model. It is now recognized that biological membranes are highly organized structures, with differences in lipid compositions between inner and outer leaflets and in lateral structures within the bilayer plane, known as lipid rafts. These organizing principles are important for protein localization and function as well as cellular signaling. However, the mechanisms and biophysical basis of lipid raft formation, structure, dynamics and function are not clearly understood. One key question, which we focus on in this review, is how lateral organization and leaflet compositional asymmetry are coupled.more » Detailed information elucidating this question has been sparse because of the small size and transient nature of rafts and the experimental challenges in constructing asymmetric bilayers. Resolving this mystery will require advances in both experimentation and modeling. We discuss here the preparation of model systems along with experimental and computational approaches that have been applied in efforts to address this key question in membrane biology. Furthermore, we seek to place recent and future advances in experimental and computational techniques in context, providing insight into in-plane and transverse organization of biological membranes.« less

  12. Lipids in the Assembly of Membrane Proteins and Organization of Protein Supercomplexes

    PubMed Central

    Bogdanov, Mikhail; Mileykovskaya, Eugenia; Dowhan, William

    2008-01-01

    Lipids play important roles in cellular dysfunction leading to disease. Although a major role for phospholipids is in defining the membrane permeability barrier, phospholipids play a central role in a diverse range of cellular processes and therefore are important factors in cellular dysfunction and disease. This review is focused on the role of phospholipids in normal assembly and organization of the membrane proteins, multimeric protein complexes, and higher order supercomplexes. Since lipids have no catalytic activity, it is difficult to determine their function at the molecular level. Lipid function has generally been defined by affects on protein function or cellular processes. Molecular details derived from genetic, biochemical, and structural approaches are presented for involvement of phosphatidylethanolamine and cardiolipin in protein organization. Experimental evidence is presented that changes in phosphatidylethanolamine levels results in misfolding and topological misorientation of membrane proteins leading to dysfunctional proteins. Examples are presented for diseases in which proper protein folding or topological organization is not attained due to either demonstrated or proposed involvement of a lipid. Similar changes in cardiolipin levels affects the structure and function of individual components of the mitochondrial electron transport chain and their organization into supercomplexes resulting in reduced mitochondrial oxidative phosphorylation efficiency and apoptosis. Diseases in which mitochondrial dysfunction has been linked to reduced cardiolipin levels are described. Therefore, understanding the principles governing lipid-dependent assembly and organization of membrane proteins and protein complexes will be useful in developing novel therapeutic approaches for disorders in which lipids play an important role. PMID:18751913

  13. Specific oriented metal-organic framework membranes and their facet-tuned separation performance.

    PubMed

    Mao, Yiyin; Su, Binbin; Cao, Wei; Li, Junwei; Ying, Yulong; Ying, Wen; Hou, Yajun; Sun, Luwei; Peng, Xinsheng

    2014-09-24

    Modulating the crystal morphology, or the exposed crystal facets, of metal-organic frameworks (MOFs) expands their potential applications in catalysis, adsorption, and separation. In this article, by immobilizing the citrate modulators on Au nanoparticles and subsequently being fixed on solid copper hydroxide nanostrands, a well-intergrown and oriented HKUST-1 cube crystal membrane was formed at room temperature. In contrast, in the absence of Au nanoparticles, well-intergrown and oriented cuboctahedron and octahedron membranes were formed in water/ethanol and ethanol, respectively. The gas separation performances of these HKUST-1 membranes were tuned via their exposed facets with defined pore sizes. The HKUST-1 cube membrane with exposed {001} facets demonstrated the highest permeance but lowest gas binary separation factors, while the octahedron membrane with exposed {111} facets presented the highest separation factors but lowest permeance, since the window size of {111} facets is 0.46 nm which is smaller than 0.9 nm of {001} facets. Separation of 0.38 nm CO2 from 0.55 nm SF6 was realized by the HKUST-1 octahedron membrane. As a proof of concept, this will open a new way to design MOF-related separation membranes by facet controlling. PMID:25184955

  14. Ultrathin films of organic networks as nanofiltration membranes via solution-based molecular layer deposition.

    PubMed

    Qian, Huidong; Li, Shenghai; Zheng, Jifu; Zhang, Suobo

    2012-12-21

    Ultrathin films of organic networks on various substrates were fabricated through the solution-based molecular layer deposition (MLD) technique. The rigid tetrahedral geometries of polyfunctional amine and acyl chloride involved in the reaction ensure the continuity of the polymerization process. A linear increase in film thickness with respect to cycle number was observed by UV-vis adsorption, ellipsometry, and quartz crystal microbalance. The growth rate per MLD cycle is 1.6 nm, which can be controlled at the single molecular level. For the first time, we develop the MLD method on the top of hydrolyzed PAN substrate, resulting in nanofiltration (NF) membranes. The stepwise growth was monitored via attenuated total reflectance infrared studies. The separation performance of the obtained membrane for various solutes was sensitive to the terminated layers and number of cycles. The rejection of NH(2)-terminated membranes follows the order of CaCl(2) > Na(2)SO(4) > NaCl, while the order for COOH-capped surface is Na(2)SO(4) > CaCl(2) > NaCl. The absolute value of zeta potential for the MLD membranes decreases with the addition of deposition layers. The moderate water flux for the resulting membrane is due to the reduced porosity of the support as well as the low roughness and hydrophilicity of the membrane surface. This bottom-up process provides a promising approach for construction of long-term steady NF membranes with nanoscale dimensions. PMID:23198774

  15. Modification of plasma membrane organization in tobacco cells elicited by cryptogein.

    PubMed

    Gerbeau-Pissot, Patricia; Der, Christophe; Thomas, Dominique; Anca, Iulia-Andra; Grosjean, Kevin; Roche, Yann; Perrier-Cornet, Jean-Marie; Mongrand, Sébastien; Simon-Plas, Françoise

    2014-01-01

    Lipid mixtures within artificial membranes undergo a separation into liquid-disordered and liquid-ordered phases. However, the existence of this segregation into microscopic liquid-ordered phases has been difficult to prove in living cells, and the precise organization of the plasma membrane into such phases has not been elucidated in plant cells. We developed a multispectral confocal microscopy approach to generate ratiometric images of the plasma membrane surface of Bright Yellow 2 tobacco (Nicotiana tabacum) suspension cells labeled with an environment sensitive fluorescent probe. This allowed the in vivo characterization of the global level of order of this membrane, by which we could demonstrate that an increase in its proportion of ordered phases transiently occurred in the early steps of the signaling triggered by cryptogein and flagellin, two elicitors of plant defense reactions. The use of fluorescence recovery after photobleaching revealed an increase in plasma membrane fluidity induced by cryptogein, but not by flagellin. Moreover, we characterized the spatial distribution of liquid-ordered phases on the membrane of living plant cells and monitored their variations induced by cryptogein elicitation. We analyze these results in the context of plant defense signaling, discuss their meaning within the framework of the "membrane raft" hypothesis, and propose a new mechanism of signaling platform formation in response to elicitor treatment. PMID:24235133

  16. Modification of Plasma Membrane Organization in Tobacco Cells Elicited by Cryptogein1[W

    PubMed Central

    Gerbeau-Pissot, Patricia; Der, Christophe; Thomas, Dominique; Anca, Iulia-Andra; Grosjean, Kevin; Roche, Yann; Perrier-Cornet, Jean-Marie; Mongrand, Sébastien; Simon-Plas, Françoise

    2014-01-01

    Lipid mixtures within artificial membranes undergo a separation into liquid-disordered and liquid-ordered phases. However, the existence of this segregation into microscopic liquid-ordered phases has been difficult to prove in living cells, and the precise organization of the plasma membrane into such phases has not been elucidated in plant cells. We developed a multispectral confocal microscopy approach to generate ratiometric images of the plasma membrane surface of Bright Yellow 2 tobacco (Nicotiana tabacum) suspension cells labeled with an environment sensitive fluorescent probe. This allowed the in vivo characterization of the global level of order of this membrane, by which we could demonstrate that an increase in its proportion of ordered phases transiently occurred in the early steps of the signaling triggered by cryptogein and flagellin, two elicitors of plant defense reactions. The use of fluorescence recovery after photobleaching revealed an increase in plasma membrane fluidity induced by cryptogein, but not by flagellin. Moreover, we characterized the spatial distribution of liquid-ordered phases on the membrane of living plant cells and monitored their variations induced by cryptogein elicitation. We analyze these results in the context of plant defense signaling, discuss their meaning within the framework of the “membrane raft” hypothesis, and propose a new mechanism of signaling platform formation in response to elicitor treatment. PMID:24235133

  17. Membrane pretreatment: A method for reducing fouling by natural organic matter

    SciTech Connect

    Maartens, A.; Swart, P.; Jacobs, E.P.

    2000-01-15

    The prevention of fouling of polysulfone ultrafiltration membranes, used for the purification of natural brown water, was investigated by pretreating the membranes prior to filtration. Polysulfone membranes were pretreated by commercial nonionic surfactants Triton X-100 and Pluronic F108. Specific characterization techniques, developed by Maartens et al. (1998) and Jucker and Clarke, (1994), were used to determine and compare the effects induced by the adsorption of natural organic matter on the permeability of untreated as well as surfactant treated capillary ultrafiltration membranes. The extent of foulant adsorption and the quality of the resultant permeate solutions were determined by ultraviolet visible-light spectroscopy. The findings of this investigation provides information of importance for the operation of future natural brown water ultrafiltration plants.

  18. Polyelectrolyte and silver nanoparticle modification of microfiltration membranes to mitigate organic and bacterial fouling.

    PubMed

    Diagne, Fatou; Malaisamy, Ramamoorthy; Boddie, Vic; Holbrook, R David; Eribo, Broderick; Jones, Kimberly L

    2012-04-01

    Membrane fouling remains one of the most problematic issues surrounding membrane use in water and wastewater treatment applications. Organic and biological fouling contribute to irreversible fouling and flux decline in these processes. The aim of this study was to reduce both organic and biological fouling by modifying the surface of commercially available poly(ether sulfone) (PES) membranes using the polyelectrolyte multilayer modification method with poly(styrenesulfonate) (PSS), poly(diallyldimethylammonium chloride) (PDADMAC), and silver nanoparticles (nanoAg) integrated onto the surface as stable, thin (15 nm) films. PSS increases the hydrophilicity of the membrane and increases the negative surface charge, while integration of nanoAg into the top PSS layer imparts biocidal characteristics to the modified surface. Fouling was simulated by filtering aqueous solutions of humic acid (5 and 20 mg L(-1)), a suspension of Escherichia coli (10(6) colony-forming units (CFU) mL(-1)), and a mixture of both foulants through unmodified and modified PES membranes under batch conditions. Filtration and cleaning studies confirmed that the modification significantly reduced organic and biological fouling. PMID:22329664

  19. Ultrathin Polymer Membranes with Patterned, Micrometric Pores for Organs-on-Chips.

    PubMed

    Pensabene, Virginia; Costa, Lino; Terekhov, Alexander Y; Gnecco, Juan S; Wikswo, John P; Hofmeister, William H

    2016-08-31

    The basal lamina or basement membrane (BM) is a key physiological system that participates in physicochemical signaling between tissue types. Its formation and function are essential in tissue maintenance, growth, angiogenesis, disease progression, and immunology. In vitro models of the BM (e.g., Boyden and transwell chambers) are common in cell biology and lab-on-a-chip devices where cells require apical and basolateral polarization. Extravasation, intravasation, membrane transport of chemokines, cytokines, chemotaxis of cells, and other key functions are routinely studied in these models. The goal of the present study was to integrate a semipermeable ultrathin polymer membrane with precisely positioned pores of 2 μm diameter in a microfluidic device with apical and basolateral chambers. We selected poly(l-lactic acid) (PLLA), a transparent biocompatible polymer, to prepare the semipermeable ultrathin membranes. The pores were generated by pattern transfer using a three-step method coupling femtosecond laser machining, polymer replication, and spin coating. Each step of the fabrication process was characterized by scanning electron microscopy to investigate reliability of the process and fidelity of pattern transfer. In order to evaluate the compatibility of the fabrication method with organs-on-a-chip technology, porous PLLA membranes were embedded in polydimethylsiloxane (PDMS) microfluidic devices and used to grow human umbilical vein endothelial cells (HUVECS) on top of the membrane with perfusion through the basolateral chamber. Viability of cells, optical transparency of membranes and strong adhesion of PLLA to PDMS were observed, thus confirming the suitability of the prepared membranes for use in organs-on-a-chip devices. PMID:27513606

  20. Basic technology for 6Li enrichment using an ionic-liquid impregnated organic membrane

    NASA Astrophysics Data System (ADS)

    Hoshino, Tsuyoshi; Terai, Takayuki

    2011-10-01

    The tritium needed as a fuel for fusion reactors is produced by the neutron capture reaction of lithium-6 ( 6Li) in tritium breeding materials. However, natural Li contains only about 7.6 at.% 6Li. In this paper, a new lithium isotope separation technique using an ionic-liquid impregnated organic membrane is proposed. In order to separate and concentrate lithium isotopes, only lithium ions are able to move through the membrane by electrodialysis between the cathode and the anode in lithium solutions. Preliminary experiments of lithium isotope separation were conducted using this phenomenon. Organic membranes impregnated with TMPA-TFSI and PP13-TFSI as ionic liquids were prepared, and the relationship between the 6Li separation coefficient and the applied electrodialytic conditions was evaluated using them. The results showed that the 6Li isotope separation coefficient in this method (about 1.1-1.4) was larger than that in the mercury amalgam method (about 1.06).

  1. SEPARATION OF HAZARDOUS ORGANICS BY LOW PRESSURE REVERSE OSMOSIS MEMBRANES - PHASE II FINAL REPORT

    EPA Science Inventory

    Extensive experimental studies shoved that thin-film, composite membranes can be used effectively for the separation of selected hazardous organic compounds. his waste treatment technique offers definite advantages in terms of high solute separations at low pressures (<2MPa) and ...

  2. DETERMINATION OF POLAR VOLATILE ORGANIC COMPOUNDS IN WATER BY MEMBRANE PERMEATE AND TRAP GC-MS

    EPA Science Inventory

    A novel approach is presented combining semipermeable membranes with the accepted purge and trap gas chromatography-mass spectrometry (GC-MS) technology to produce a method of selectively extracting polar, volatile organic compounds from water, particularly those compounds not am...

  3. SEPARATION OF HAZARDOUS ORGANICS BY LOW PRESSURE REVERSE OSMOSIS MEMBRANES - PHASE II FINAL REPORT

    EPA Science Inventory

    Extensive experimental studies showed that thin-film, composite membranes can be used effectively for the separation of selected hazardous organic compounds. This waste treatment technique offers definite advantages in terms of high solute separations at low pressures (<2MPa) and...

  4. REMOVAL OF ORGANIC CCL CONTAMINANTS FROM DRINKING WATERS BY MEMBRANE AND GAC PROCESSES

    EPA Science Inventory

    Bench-scale treatment data for membrane and granular activated carbon technologies are presented for the organic contaminants on the U.S. Environmental Protection Agency's Contaminant Candidate List (CCL). For granular activated carbon (GAC), isotherm results are presented and q...

  5. A POLYMER-CERAMIC COMPOSITE MEMBRANE FOR RECOVERING VOLATILE ORGANIC COMPOUNDS FROM WASTEWATERS BY PERVAPORATION

    EPA Science Inventory

    A composite membrane was constructed on a porous ceramic support from a block copolymer of styrene and butadiene (SBS). It was tested in a laboratory pervaporation apparatus for recovering volatile organic compounds (VOCs) such a 1,1,1-trichloroethane (TCA) and trichloroethylene ...

  6. Novel polymer and inorganic/organic hybrid composite materials for proton exchange membrane applications

    NASA Astrophysics Data System (ADS)

    Yang, Zhiwei

    In this study, various novel proton exchange membranes (PEM) have been synthesized and investigated for high temperature PEM applications. Sulfonic acid functionalized polysilsesquioxane hybrid membranes with the empirical formula of R-Si-(O)1.5 consist of a highly cross-linked Si-O backbone and pendant organic side chain R, which is terminated in a proton conducting functional group (i.e., sulfonic acid). The membranes exhibited excellent proton conductivities (sigma) of >10-2 S/cm under low humidity conditions and a wide range of temperatures. The fuel cell (FC) performance of the membranes under low humidity conditions has been evaluated. Acid-doped linear meta-polyaniline membranes have been prepared through solution casting of m-PANI. The obtained membrane shows good proton conductivities at temperatures above 100°C, achieving 10-2.7 S/cm under 120°C and practically no humidity conditions. The effects of doping acids, doping levels and humidity on the conductivity are discussed. Polyethylenimine (PEI)/SiO2 nanocomposites membranes have been synthesized through sol-gel processes. The introduction of SiO2 clusters into high molecule weight, linear PEI greatly improved its thermal stability at high temperatures and O2 atmosphere. During the sol-gel processes, trifluoromethanesulfonimide (HTFSI) was added to dope the amine groups of PEI and form immobilized proton-conducting ionic liquids, which provide the hybrid membranes with proton-conducting behavior. The resultant membranes show good proton conductivities at high temperatures and low to zero humidity conditions. The effects of temperature, humidity and mobility of active groups on the conductivity are discussed. Various organic amine/HTFSI ionic group functionalized polysilsesquioxane hybrid membranes have been prepared. The Si-O backbone provides excellent thermal/chemical/mechanical properties and the HTFSI-doped amine end groups provide the proton conducting properties. The membranes exhibited proton

  7. Imaging lipid lateral organization in membranes with C-laurdan in a confocal microscope[S

    PubMed Central

    Dodes Traian, Martín M.; Flecha, F. Luis González; Levi, Valeria

    2012-01-01

    Lateral organization of biological membranes is frequently studied using fluorescence microscopy. One of the most widely used probes for these studies is 2-dimethylamino-6-lauroylnaphthalene (laurdan). The fluorescence of this probe is sensitive to the environment polarity, and thus laurdan reports the local penetration of water when inserted in membranes. Unfortunately, this probe can only be used under two-photon excitation due to its low photostability. This is a very important limitation, because there are not too many laboratories with capability for two-photon microscopy. In this work, we explored the performance of 6-dodecanoyl-2-[N-methyl-N-(carboxymethyl)amino]naphthalene (C-laurdan), a carboxyl-modified version of laurdan, for imaging biological membranes using a conventional confocal microscopy setup. We acquired generalized polarization (GP) images of C-laurdan inserted in giant unillamelar vesicles composed of binary mixtures of lipids and verified that the probe allows observing the coexistence of different phases. We also tested the performance of the probe for measurement with living cells and registered GP images of melanophore cells labeled with C-laurdan in which we could observe highly ordered regions such as filopodia. These findings show that C-laurdan can be successfully employed for studies of membrane lateral organization using a conventional confocal microscope and can open the possibility of studying a wide variety of membrane-related processes. PMID:22184757

  8. Diffusion, transport, and cell membrane organization investigated by imaging fluorescence cross-correlation spectroscopy.

    PubMed

    Sankaran, Jagadish; Manna, Manoj; Guo, Lin; Kraut, Rachel; Wohland, Thorsten

    2009-11-01

    Cell membrane organization is dynamic and is assumed to have different characteristic length scales. These length scales, which are influenced by lipid and protein composition as well as by the cytoskeleton, can range from below the optical resolution limit (as with rafts or microdomains) to far above the resolution limit (as with capping phenomena or the formation of lipid "platforms"). The measurement of these membrane features poses a significant problem because membrane dynamics are on the millisecond timescale and are thus beyond the time resolution of conventional imaging approaches. Fluorescence correlation spectroscopy (FCS), a widely used spectroscopic technique to measure membrane dynamics, has the required time resolution but lacks imaging capabilities. A promising solution is the recently introduced method known as imaging total internal reflection (ITIR)-FCS, which can probe diffusion phenomena in lipid membranes with good temporal and spatial resolution. In this work, we extend ITIR-FCS to perform ITIR fluorescence cross-correlation spectroscopy (ITIR-FCCS) between pixel areas of arbitrary shape and derive a generalized expression that is applicable to active transport and diffusion. ITIR-FCCS is applied to model systems exhibiting diffusion, active transport, or a combination of the two. To demonstrate its applicability to live cells, we observe the diffusion of a marker, the sphingolipid-binding domain (SBD) derived from the amyloid peptide Abeta, on live neuroblastoma cells. We investigate the organization and dynamics of SBD-bound lipid microdomains under the conditions of cholesterol removal and cytoskeleton disruption. PMID:19883607

  9. Interaction of the organic tin chloride with the liquid model membranes

    NASA Astrophysics Data System (ADS)

    Podolak, M.; Engel, G.; Man, D.

    2007-08-01

    The objective of the work was to investigate the effect of organic tin chloride (C3H7)3SnCl on the electric parameters of membranes in the form of filters of the company Synpor (Czech Republic) impregnated with various fatty acids, dissolved with carbon tetrachloride (CCl4). Three carboxylic acids were used in the study: palmitic, arachidic and oleic, and dissolvent of the acids (CCl4) as well as butylene ester of lauric acid. In all cases, introduction of tin chloride of constant concentration amounting to 0.15 mM to the measurement chamber resulted in induction of membrane voltage. In case of pure lauric acid and CCl4, the voltage reached the maximum value and then decreased to a certain constant value. In the case of all acids dissolved in CCl4, the voltage increased only up to a certain constant value. Voltage drop (below the value) was observed after application of appropriately high concentration of tin chloride, in case of membranes impregnated with the mixture of lauric acid ester with CCl4 and palmitic acid with CCl4. The study also demonstrated that electrical resistance of membranes impregnated with carboxylic acid increased in the presence of tin chloride and decreased in case of membranes impregnated with lauric acid ester. However, electric capacities of membranes did not significant change.

  10. Eisosomes promote the ability of Sur7 to regulate plasma membrane organization in Candida albicans

    PubMed Central

    Wang, Hong X.; Douglas, Lois M.; Veselá, Petra; Rachel, Reinhard; Malinsky, Jan; Konopka, James B.

    2016-01-01

    The plasma membrane of the fungal pathogen Candida albicans forms a protective barrier that also mediates many processes needed for virulence, including cell wall synthesis, invasive hyphal morphogenesis, and nutrient uptake. Because compartmentalization of the plasma membrane is believed to coordinate these diverse activities, we examined plasma membrane microdomains termed eisosomes or membrane compartment of Can1 (MCC), which correspond to ∼200-nm-long furrows in the plasma membrane. A pil1∆ lsp1∆ mutant failed to form eisosomes and displayed strong defects in plasma membrane organization and morphogenesis, including extensive cell wall invaginations. Mutation of eisosome proteins Slm2, Pkh2, and Pkh3 did not cause similar cell wall defects, although pkh2∆ cells formed chains of furrows and pkh3∆ cells formed wider furrows, identifying novel roles for the Pkh protein kinases in regulating furrows. In contrast, the sur7∆ mutant formed cell wall invaginations similar to those for the pil1∆ lsp1∆ mutant even though it could form eisosomes and furrows. A PH-domain probe revealed that the regulatory lipid phosphatidylinositol 4,5-bisphosphate was enriched at sites of cell wall invaginations in both the sur7∆ and pil1∆ lsp1∆ cells, indicating that this contributes to the defects. The sur7∆ and pil1∆ lsp1∆ mutants displayed differential susceptibility to various types of stress, indicating that they affect overlapping but distinct functions. In support of this, many mutant phenotypes of the pil1∆ lsp1∆ cells were rescued by overexpressing SUR7. These results demonstrate that C. albicans eisosomes promote the ability of Sur7 to regulate plasma membrane organization. PMID:27009204

  11. Graphene oxide based ultrafiltration membranes for photocatalytic degradation of organic pollutants in salty water.

    PubMed

    Pastrana-Martínez, Luisa M; Morales-Torres, Sergio; Figueiredo, José L; Faria, Joaquim L; Silva, Adrián M T

    2015-06-15

    Flat sheet ultrafiltration (UF) membranes with photocatalytic properties were prepared with lab-made TiO2 and graphene oxide-TiO2 (GOT), and also with a reference TiO2 photocatalyst from Evonik (P25). These membranes were tested in continuous operation mode for the degradation and mineralization of a pharmaceutical compound, diphenhydramine (DP), and an organic dye, methyl orange (MO), under both near-UV/Vis and visible light irradiation. The effect of NaCl was investigated considering simulated brackish water (NaCl 0.5 g L(-1)) and simulated seawater (NaCl 35 g L(-1)). The results indicated that the membranes prepared with the GOT composite (M-GOT) exhibited the highest photocatalytic activity, outperforming those prepared with bare TiO2 (M-TiO2) and P25 (M-P25), both inactive under visible light illumination. The best performance of M-GOT may be due to the lower band-gap energy (2.9 eV) of GOT. In general, the permeate flux was also higher for M-GOT probably due to a combined effect of its highest photocatalytic activity, highest hydrophilicity (contact angles of 11°, 17° and 18° for M-GOT, M-TiO2 and M-P25, respectively) and higher porosity (71%). The presence of NaCl had a detrimental effect on the efficiency of the membranes, since chloride anions can act as hole and hydroxyl radical scavengers, but it did not affect the catalytic stability of these membranes. A hierarchically ordered membrane was also prepared by intercalating a freestanding GO membrane in the structure of the M-GOT membrane (M-GO/GOT). The results showed considerably higher pollutant removal in darkness and good photocatalytic activity under near-UV/Vis and visible light irradiation in continuous mode experiments. PMID:25875927

  12. Nanofibrous asymmetric membranes self-organized from chemically heterogeneous electrospun mats for skin tissue engineering.

    PubMed

    Wu, Chaoxi; Chen, Tian; Xin, Yanjiao; Zhang, Zhen; Ren, Zhe; Lei, Jing; Chu, Bin; Wang, Yifei; Tang, Shunqing

    2016-01-01

    Asymmetric membranes, which mimic the structure and functions of human skin, have been extensively pursued as ideal skin tissue engineering constructs. In this study, we demonstrated that nanostructured asymmetric membranes can be prepared by the self-organization of chemically heterogeneous bilayer electrospun membranes in aqueous solutions. Structurally, the skin layer consists of hydrophobic β-glucan butyrate nanofibers and its inner layer consists of hydrophilic β-glucan acetate nanofibers. After the electrospinning process, both of the layers are in a dense state. When placed in water, the skin layer absorbs little water and still remains dense, but the fibers in the inner layer become extensively hydrated and spontaneously reorganize into a fully stretched structure, resulting in a significant volume increase and a density decrease of the inner layer. SEM imaging showed that β-glucan ester nanofibers exhibited a bead-free and uniform structure. Contact angle measurement and swelling tests showed that the inner layer was highly hydrophilic with extensive swelling, but the skin layer was highly hydrophobic with little swelling. Mechanical tests indicated that the nanofibrous asymmetric membranes had good mechanical properties in both the dry and wet states. In vitro cytocompatibility tests showed that nanofibrous asymmetric membranes could promote the adhesion and proliferation of fibroblasts and keratinocytes. A preliminary in vivo study performed on a full thickness mouse skin wound model demonstrated that the nanofibrous asymmetric membranes significantly accelerated the wound healing process by promoting re-epithelialization, tissue remodeling and collagen deposition. Taken together, our study provides a novel model for the design and fabrication of nanostructured asymmetric membranes, and our β-glucan based nanofibrous asymmetric membranes could be used as an advanced platform for skin tissue engineering. PMID:27327625

  13. Contribution of assimilable organic carbon to biological fouling in seawater reverse osmosis membrane treatment.

    PubMed

    Weinrich, Lauren; LeChevallier, Mark; Haas, Charles N

    2016-09-15

    Biological fouling occurs on RO membranes when bacteria and nutrients are present in conditions that are conducive to growth and proliferation of the bacteria. Controlling microbial growth on the membranes is typically limited to biocide application (i.e., disinfectants) in seawater RO plants. However, biological growth and subsequent fouling has not been well-managed. Pretreatment has not been focused on nutrient limitation. This project used a biological assay, the assimilable organic carbon (AOC) test to evaluate pretreatment effects on the nutrient supply. The AOC test provided a useful surrogate measurement for the biodegradability or biofouling potential of RO feed water. Biofouling observed in controlled conditions at the bench- and pilot-scale resulted in statistically significant correlations between AOC and the operational effects caused by biofouling. Membrane fouling rates are observed through operational changes over time such as increased differential pressure between the membrane feed and concentrate locations and decreased permeate flux through the membrane. In full scale plants there were strong correlations when AOC was used as a predictor variable for increased differential pressure (0.28-0.55 bar from September-December 2012) and decreased specific flux (1.40 L per hour/(m(2) · bar)). Increased differential pressure was associated with RO membrane biological fouling when the median AOC was 50 μg/L during pilot testing. Conditions were also evaluated at the bench-scale using a flat sheet RO membrane. In a comparison test using 30 and 1000 μg/L AOC, fouling was detected on more portions of the membrane when AOC was higher. Biofilm and bacterial deposits were apparent from scanning electron microscope imaging and biomass measurements using ATP. PMID:27262548

  14. Spatially variant morphological restoration and skeleton representation.

    PubMed

    Bouaynaya, Nidhal; Charif-Chefchaouni, Mohammed; Schonfeld, Dan

    2006-11-01

    The theory of spatially variant (SV) mathematical morphology is used to extend and analyze two important image processing applications: morphological image restoration and skeleton representation of binary images. For morphological image restoration, we propose the SV alternating sequential filters and SV median filters. We establish the relation of SV median filters to the basic SV morphological operators (i.e., SV erosions and SV dilations). For skeleton representation, we present a general framework for the SV morphological skeleton representation of binary images. We study the properties of the SV morphological skeleton representation and derive conditions for its invertibility. We also develop an algorithm for the implementation of the SV morphological skeleton representation of binary images. The latter algorithm is based on the optimal construction of the SV structuring element mapping designed to minimize the cardinality of the SV morphological skeleton representation. Experimental results show the dramatic improvement in the performance of the SV morphological restoration and SV morphological skeleton representation algorithms in comparison to their translation-invariant counterparts. PMID:17076415

  15. Chemically Stable Covalent Organic Framework (COF)-Polybenzimidazole Hybrid Membranes: Enhanced Gas Separation through Pore Modulation.

    PubMed

    Biswal, Bishnu P; Chaudhari, Harshal D; Banerjee, Rahul; Kharul, Ulhas K

    2016-03-24

    Highly flexible, TpPa-1@PBI-BuI and TpBD@PBI-BuI hybrid membranes based on chemically stable covalent organic frameworks (COFs) could be obtained with the polymer. The loading obtained was substantially higher (50 %) than generally observed with MOFs. These hybrid membranes show an exciting enhancement in permeability (about sevenfold) with appreciable separation factors for CO2/N2 and CO2/CH4. Further, we found that with COF pore modulation, the gas permeability can be systematically enhanced. PMID:26865381

  16. Notch Signaling and the Skeleton.

    PubMed

    Zanotti, Stefano; Canalis, Ernesto

    2016-06-01

    Notch 1 to 4 receptors are important determinants of cell fate and function, and Notch signaling plays an important role in skeletal development and bone remodeling. After direct interactions with ligands of the Jagged and Delta-like families, a series of cleavages release the Notch intracellular domain (NICD), which translocates to the nucleus where it induces transcription of Notch target genes. Classic gene targets of Notch are hairy and enhancer of split (Hes) and Hes-related with YRPW motif (Hey). In cells of the osteoblastic lineage, Notch activation inhibits cell differentiation and causes cancellous bone osteopenia because of impaired bone formation. In osteocytes, Notch1 has distinct effects that result in an inhibition of bone resorption secondary to an induction of osteoprotegerin and suppression of sclerostin with a consequent enhancement of Wnt signaling. Notch1 inhibits, whereas Notch2 enhances, osteoclastogenesis and bone resorption. Congenital disorders of loss- and gain-of-Notch function present with severe clinical manifestations, often affecting the skeleton. Enhanced Notch signaling is associated with osteosarcoma, and Notch can influence the invasive potential of carcinoma of the breast and prostate. Notch signaling can be controlled by the use of inhibitors of Notch activation, small peptides that interfere with the formation of a transcriptional complex, or antibodies to the extracellular domain of specific Notch receptors or to Notch ligands. In conclusion, Notch plays a critical role in skeletal development and homeostasis, and serious skeletal disorders can be attributed to alterations in Notch signaling. PMID:27074349

  17. Interactive Thermal Effects on Metal-Organic Framework Polymer Composite Membranes.

    PubMed

    Cacho-Bailo, Fernando; Téllez, Carlos; Coronas, Joaquín

    2016-07-01

    Polymeric membranes are important tools for intensifying separation processes in chemical industries, concerning strategic tasks such as CO2 sequestration, H2 production, and water supply and disposal. Mixed-matrix and supported membranes have been widely developed; recently many of them have been based on metal-organic frameworks (MOFs). However, most of the impacts MOFs have within the polymer matrix have yet to be determined. The effects related to thermal behavior arising from the combination of MOF ZIF-8 and polysulfone have now been quantified. The catalyzed oxidation of the polymer is strongly affected by the MOF crystal size and distribution inside the membrane. A 16 wt % 140 nm-sized ZIF-8 loading causes a 40 % decrease in the observed activation energy of the polysulfone oxidation that takes place at a temperature (545 °C) 80 °C lower than in the raw polymer (625 °C). PMID:27156113

  18. Golgi sorting regulates organization and activity of GPI-proteins at apical membranes

    PubMed Central

    Tivodar, Simona; Formiggini, Fabio; Ossato, Giulia; Gratton, Enrico; Tramier, Marc; Coppey-Moisan, Maïté; Zurzolo, Chiara

    2014-01-01

    Here, we combined classical biochemistry with novel biophysical approaches to study with high spatial and temporal resolution the organization of GPI-anchored proteins (GPI-APs) at the plasma membrane of polarized epithelial cells. We show that in polarized MDCK cells, following sorting in the Golgi, each GPI-AP reaches the apical surface in homo-clusters. Golgi-derived homo-clusters are required for their subsequent plasma membrane organization into cholesterol-dependent hetero-clusters. By contrast, in non-polarized MDCK cells GPI-APs are delivered to the surface as monomers in an unpolarized manner and are not able to form hetero-clusters. We further demonstrate that this GPI-AP organization is regulated by the content of cholesterol in the Golgi apparatus and is required to maintain the functional state of the protein at the apical membrane. Thus, different from fibroblasts, in polarized epithelial cells a selective cholesterol-dependent sorting mechanism in the Golgi regulates both the organization and the function of GPI-APs at the apical surface. PMID:24681536

  19. Middle holocene age of the sunnyvale human skeleton.

    PubMed

    Taylor, R E; Payen, L A; Gerow, B; Donahue, D J; Zabel, T H; Jull, A J; Damon, P E

    1983-06-17

    A morphologically modern human skeleton from Sunnyvale, California, previously dated by aspartic acid racemization to be approximately 70,000 years old and by uranium series isotopic ratios to be 8300 and 9000 years old, appears to be younger when dated by the carbon-14 method. Four carbon-14 determinations made by both decay and direct counting on three organic fractions of postcranial bone support a middle Holocene age assignment for the skeleton, probably in the range of 3500 to 5000 carbon-14 years before the present. This dating evidence is consistent with the geologic, archeological, and anthropometric relationships of the burial as well as previously determined carbon-14 determinations on associated materials. PMID:17769367

  20. Peripheral protein organization and its influence on lipid diffusion in biomimetic membranes

    PubMed Central

    Vats, Kanika; Knutson, Kristofer; Hinderliter, Anne; Sheets, Erin D.

    2010-01-01

    Protein organization on biomembranes and their dynamics are essential for cellular function. It is not clear, however, how protein binding may influence the assembly of underlying lipids or how the membrane structure leads to functional protein organization. Toward this goal, we investigated the effects of annexin a5 binding to biomimetic membranes using fluorescence imaging and correlation spectroscopy. Annexin a5 (anx a5), a peripheral intracellular protein that plays a membrane remodeling role in addition to other functions, binds specifically and tightly to anionic (e.g., phosphatidylserine)-containing membranes in the presence of calcium ion. Our fluorescence microscopy reveals that annexin likely forms assemblies, along with a more dispersed population, upon binding to anionic biomembranes in the presence of calcium ion, which is reflected in its two-component Brownian motion. To investigate the effects of annexin binding on the underlying lipids, we used specific acyl chain-labeled phospholipid analogs, NBD-phosphatidylcholine (NBD-PC) and NBD-phosphatidylserine (NBD-PS). We find that both NBD-labeled lipids cluster under anx a5 assemblies, as compared with when they are found under the dispersed annexin population, and NBD-PS exhibits two-component lateral diffusion under the annexin assemblies. In contrast, NBD-PC diffusion is slower by an order of magnitude under the annexin assemblies in contrast to its diffusion when not localized under anx a5 assemblies. Our results indicate that upon binding to membranes, the peripheral protein annexin organizes the underlying lipids into domains, which may have functional implications in vivo. PMID:20175560

  1. Inflammation-associated changes in lipid composition and the organization of the erythrocyte membrane

    PubMed Central

    Dinkla, Sip; van Eijk, Lucas T.; Fuchs, Beate; Schiller, Jürgen; Joosten, Irma; Brock, Roland; Pickkers, Peter; Bosman, Giel J.C.G.M.

    2016-01-01

    Background Reduced erythrocyte survival and deformability may contribute to the so-called anemia of inflammation observed in septic patients. Erythrocyte structure and function are affected by both the membrane lipid composition and the organization. We therefore aimed to determine whether these parameters are affected during systemic inflammation. Methods A sensitive matrix-assisted laser desorption and ionization time-of-flight mass spectrometric method was used to investigate the effect of plasma components of 10 patients with septic shock and of 10 healthy volunteers subjected to experimental endotoxemia on erythrocyte membrane lipid composition. Results Incubation of erythrocytes from healthy control donors with plasma from patients with septic shock resulted in membrane phosphatidylcholine hydrolysis into lysophosphatidylcholine (LPC). Plasma from volunteers undergoing experimental human endotoxemia did not induce LPC formation. The secretory phospholipase A2 IIA concentration was enhanced up to 200-fold in plasma of septic patients and plasma from endotoxin-treated subjects, but did not correlate with the ability of these plasmas to generate LPC. Erythrocyte phosphatidylserine exposure increased up to two-fold during experimental endotoxemia. Conclusions Erythrocyte membrane lipid remodeling as reflected by LPC formation and/or PS exposure occurs during systemic inflammation in a secretory phospholipase A2 IIA-independent manner. General significance Sepsis-associated inflammation induces a lipid remodeling of the erythrocyte membrane that is likely to affect erythrocyte function and survival, and that is not fully mimicked by experimental endotoxemia. PMID:27200268

  2. MICOS and phospholipid transfer by Ups2-Mdm35 organize membrane lipid synthesis in mitochondria.

    PubMed

    Aaltonen, Mari J; Friedman, Jonathan R; Osman, Christof; Salin, Bénédicte; di Rago, Jean-Paul; Nunnari, Jodi; Langer, Thomas; Tatsuta, Takashi

    2016-06-01

    Mitochondria exert critical functions in cellular lipid metabolism and promote the synthesis of major constituents of cellular membranes, such as phosphatidylethanolamine (PE) and phosphatidylcholine. Here, we demonstrate that the phosphatidylserine decarboxylase Psd1, located in the inner mitochondrial membrane, promotes mitochondrial PE synthesis via two pathways. First, Ups2-Mdm35 complexes (SLMO2-TRIAP1 in humans) serve as phosphatidylserine (PS)-specific lipid transfer proteins in the mitochondrial intermembrane space, allowing formation of PE by Psd1 in the inner membrane. Second, Psd1 decarboxylates PS in the outer membrane in trans, independently of PS transfer by Ups2-Mdm35. This latter pathway requires close apposition between both mitochondrial membranes and the mitochondrial contact site and cristae organizing system (MICOS). In MICOS-deficient cells, limiting PS transfer by Ups2-Mdm35 and reducing mitochondrial PE accumulation preserves mitochondrial respiration and cristae formation. These results link mitochondrial PE metabolism to MICOS, combining functions in protein and lipid homeostasis to preserve mitochondrial structure and function. PMID:27241913

  3. Effects of ozonation and coagulation on effluent organic matter characteristics and ultrafiltration membrane fouling.

    PubMed

    Jeong, Kwon; Lee, Dae-Sung; Kim, Do-Gun; Ko, Seok-Oh

    2014-06-01

    Effluent organic matter (EfOM) is the major cause of fouling in the low pressure membranes process for wastewater reuse. Coagulation and oxidation of biological wastewater treatment effluent have been applied for the fouling control of microfiltration membranes. However, the change in EfOM structure by pre-treatments has not been clearly identified. The changes of EfOM characteristics induced by coagulation and ozonation were investigated through size exclusion chromatography, UV/Vis spectrophotometry, fluorescence spectrophotometry and titrimetric analysis to identify the mechanisms in the reduction of ultrafiltration (UF) membrane fouling. The results indicated that reduction of flux decline by coagulation was due to modified characteristics of dissolved organic carbon (DOC) content. Total concentration of DOC was not reduced by ozonation. However, the mass fraction of the molecules with molecular weight larger than 5 kDa, fluorescence intensity, aromaticity, highly condensed chromophores, average molecular weight and soluble microbial byproducts decreased greatly after ozonation. These results indicated that EfOM was partially oxidized by ozonation to low molecular weight, highly charged compounds with abundant electron-withdrawing functional groups, which are favourable for alleviating UF membrane flux decline. PMID:25079844

  4. Distribution and deposition of organic fouling on the microfiltration membrane evaluated by high-frequency ultrasound

    PubMed Central

    Lin, Yi-Hsun; Tung, Kuo-Lun; Wang, Shyh-Hau; Zhou, Qifa; Shung, K. Kirk

    2014-01-01

    A 50 MHz high-frequency ultrasound and analysis method were developed to further improve the in situ assessment of deposition and distribution of organic fouling on the polyvinylidene fluoride (PVDF) membranes. Measurements of fouling depositions were performed from PVDF membranes filtrated with aqueous humic acid solutions (HAS) of 2 and 4 ppm concentrations in a flat-sheet module. Ultrasound signals reflected from the PVDF membranes, following filtrations at various durations including 0, 5, 15, 30, 60, and 100 min, were acquired. The thickness and distribution of fouling estimated and assessed by peak-to-peak echo voltage (Vpp) and C-mode images were found to be non-homogeneously deposited on the membranes. Following the filtrations with 2 and 4 ppm HAS for 100 min, the corresponding thickness of fouling deposition increased from 1.81±9 to 2.4571.57 mm, respectively; those average Vpp decreased from 2.05±07 to 1.13±16 V and from 2.11±08 to 0.94±15 V. These results demonstrated that the deposition and distribution of organic fouling could be sensitively and rapidly evaluated by high-frequency ultrasound image incorporated with the analysis method. PMID:25309028

  5. Dynamics measured by neutron scattering correlates with the organization of bioenergetics complexes in natural membranes from hyperthermophile and mesophile bacteria.

    PubMed

    Peters, J; Giudici-Orticoni, M T; Zaccai, G; Guiral, M

    2013-07-01

    Various models on membrane structure and organization of proteins and complexes in natural membranes emerged during the last years. However, the lack of systematic dynamical studies to complement structural investigations hindered the establishment of a more complete picture of these systems. Elastic incoherent neutron scattering gives access to the dynamics on a molecular level and was applied to natural membranes extracted from the hyperthermophile Aquifex aeolicus and the mesophile Wolinella succinogenes bacteria. The results permitted to extract a hierarchy of dynamic flexibility and atomic resilience within the samples, which correlated with the organization of proteins in bioenergetics complexes and the functionality of the membranes. PMID:23880731

  6. Percutaneous needle biopsy of the irradiated skeleton

    SciTech Connect

    Edeiken, B.; deSantos, L.A.

    1983-03-01

    Percutaneous needle biopsy was performed in 20 patients who had radiologic abnormalities after irradiation of the skeleton. The biopsies were performed to determine the nature of the bone changes and to differentiate radiation necrosis from metastases or local tumor extension. Eleven patients had tumors, two of which were radiation-induced sarcomas; nine patients did not show evidence of tumor. One patient had osteomyelitis rather than the suspected tumor. The value of percutaneous needle biopsy in the postirradiated skeleton is discussed.

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

    SciTech Connect

    Lelievre, Sophie A; Bissell, Mina J

    1998-10-21

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

  8. Characterization of organic fouling in reverse osmosis membranes by headspace solid phase microextraction and gas chromatography-mass spectrometry.

    PubMed

    Martínez, C; Gómez, V; Pocurull, E; Borrull, F

    2015-01-01

    Adsorption of organic substances on reverse osmosis (RO) membrane surfaces may form an organic film on the membrane, known as organic fouling, and cause flow-rate loss. This problem is mostly unavoidable as no pretreatment method exists for perfect removal of possible foulants, including organic compounds resulting from undesirable bioactivity. Understanding the characteristics of fouling layers is an essential step towards overall improvement of RO membrane operations. In this study, the organic fouling in RO membranes treating the effluent of a secondary treatment from an urban wastewater treatment plant was characterized. Headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry has been used for the first time, to provide valuable information of organic fouling. Different polarity SPME fibers were tested for this purpose. In addition, the characterization of the organic fouling obtained by HS-SPME was compared with the results obtained by extraction using several organic solvents. The results indicated that more compound families can be identified by HS-SPME than by organic solvent extraction. Moreover, complementary organic analyses were done for better understanding of the organic fouling in RO membranes, such as total organic carbon and loss on ignition. PMID:25607678

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

    PubMed

    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. PMID:23925426

  10. Stitching Organelles: Organization and Function of Specialized Membrane Contact Sites in Plants.

    PubMed

    Pérez-Sancho, Jessica; Tilsner, Jens; Samuels, A Lacey; Botella, Miguel A; Bayer, Emmanuelle M; Rosado, Abel

    2016-09-01

    The coordination of multiple metabolic activities in plants relies on an interorganelle communication network established through membrane contact sites (MCS). The MCS are maintained in transient or durable configurations by tethering structures which keep the two membranes in close proximity, and create chemical microdomains that allow localized and targeted exchange of small molecules and possibly proteins. The past few years have witnessed a dramatic increase in our understanding of the structural and molecular organization of plant interorganelle MCS, and their crucial roles in plant specialized functions including stress responses, cell to cell communication, and lipid transport. In this review we summarize recent advances in understanding the molecular components, structural organization, and functions of different plant-specific MCS architectures. PMID:27318776

  11. Reduction of absorbed doses in radiography of the facial skeleton

    SciTech Connect

    Julin, P.; Kraepelien, T.

    1984-11-01

    Radiation absorbed doses from radiography of the paranasal sinuses and the facial skeleton were measured with thermoluminescent dosimeters (TLD) on a phantom head using high-sensitivity screens in an Orbix stand. The entrance doses to the skin of the head ranged from 0.31 to 2.9 mGy per exposure. The absorbed dose from a full series of sinus exposures averaged 0.33 mGy for the oral mucous membrane, 0.33 mGy for the maxillary sinus mucous membrane, 0.11 mGy for the parotid gland, 0.15 mGy for the submandibular gland, 0.61 mGy for the eye lens, and 0.75 mGy for the thyroid gland region. A leaded soft collar adapted to the thyroid region reduced the thyroid doses by more than one order of magnitude, but also reduced the image field. The mean energy imparted from a full series of paranasal sinus projections was 4.8 mJ and from a total series of the facial skeleton, 7.9 mJ.

  12. A novel inorganic/organic composite membrane tailored by various organic silane coupling agents for use in direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Tao; Yang, Yong

    A series of organic silica/Nafion composite membranes has been prepared by using organic silane coupling agents (SCA) bearing different hydrophilic functional groups. The physico-chemical properties of the composite membranes have been characterized by electrochemical techniques, scanning electron microscopy (SEM), diffuse-reflection Fourier-transform infrared spectroscopy (DRFTIR), wide-angle X-ray diffraction (WAXRD), thermogravimetric analysis (TGA), and thermogravimetric mass spectrometry (TG-MS). It has been found that some organic silica/Nafion composite membranes modified by organic silane agents bearing amino groups exhibit extremely low methanol crossover and proton conductivity values, e.g., a composite membrane shows a proton conductivity that is about five orders of magnitude lower and a methanol permeability that is about three orders of magnitude lower than those of a Nafion117 membrane. However, under optimized conditions for controlling the basicity of the amino groups, we also obtained a composite membrane with 89% lower methanol permeability and 49% lower proton conductivity compared with Nafion117 membrane. The results clearly demonstrate that the diffusion of methanol and protons through the membrane can be controlled by adjusting the functional groups on the organic silica.

  13. Organic-inorganic hybrid proton exchange membrane based on polyhedral oligomeric silsesquioxanes and sulfonated polyimides containing benzimidazole

    NASA Astrophysics Data System (ADS)

    Pan, Haiyan; Zhang, Yuanyuan; Pu, Hongting; Chang, Zhihong

    2014-10-01

    A new series of organic-inorganic hybrid proton exchange membranes (PEMs) were prepared using sulfonated polyimides containing benzimidazole (SPIBIs) and glycidyl ether of polyhedral oligomeric silsesquioxanes (G-POSS). SPIBIs were synthesized using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 5-amino-2-(4-aminophenyl) benzimidazole (APBIA) and 4,4‧-diaminodiphenyl ether-2,2‧-disulfonic acid (ODADS). The organic-inorganic cross-linked membranes can be prepared by SPIBIs with G-POSS by a thermal treatment process. The cross-linking density of the membranes was evaluated by gel fractions. The water uptake, swelling ratio, mechanical property, thermal behavior, proton conductivity, oxidative and hydrolytic stability of the cross-linked organic-inorganic membranes were intensively investigated. All the cross-linked membranes exhibit high cross-linking density for the gel fraction higher than 70%. Compared to pristine membranes (SPIBIs) and membranes without benzimidazole groups (SPI), the anti-free-radical oxidative and hydrolytic stabilities of cross-linked membranes are significantly higher. The anti-free-oxidative stability of SPIBI-100-P (cross-linked SPIBI membrane with 100% degree of sulfonation) is nearly four-fold higher than that of SPIBI-100. The proton conductivity of the cross-linked membranes ranges from 10-3 S cm-1 to 10-2 S cm-1 depending both on the degree of sulfonation (DS) of the SPIBI and temperature.

  14. Reduction of absorbed doses in radiography of the facial skeleton

    SciTech Connect

    Julin, P.; Kraepelien, T.

    1984-11-01

    Radiation absorbed doses from radiography of the paranasal sinuses and the facial skeleton were measured with thermoluminescent dosimeters (TLD) on a phantom head using high-sensitivity screens in an Orbix stand. The entrance doses to the skin of the head ranged from 0.31 to 2.9 mGy per exposure. The absorbed dose from a full series of sinus exposures averaged 0.33 mGy for the oral mucous membrane, 0.33 mGy for the maxillary sinus mucous membrane, 0.11 MgY for the parotid gland, 0.15 MgY for the submandibular gland, 0.61 mGy for the eye lens, and 0.75 mGy for the thyroid gland region. A leaded soft collar adapted to the thyroid region reduced the thyroid doses by more than one order of magnitude, but also reduced the image field.

  15. Detection of persistent organic pollutants in the Mississippi Delta using semipermeable membrane devices

    USGS Publications Warehouse

    Zimmerman, L.R.; Thurman, E.M.; Bastian, K.C.

    2000-01-01

    From semipermeable membrane devices (SPMDs) placed in five Mississippi Delta streams in 1996 and 1997, the persistent organic pollutants (POPs) aldrin, chlordane, DCPA, DDT, dieldrin, endrin, heptachlor, mirex, nonachlor, and toxaphene were detected. In addition, the insecticides chlorpyriphos, endosulfan, and hexachlorocyclohexanes were detected. Two low-solubility herbicides not detected commonly in surface water, pendimethalin and trifluralin, were also detected. Copyright (C) 2000 Elsevier Science B.V.

  16. Organic Solvent Tolerance of Escherichia coli Is Independent of OmpF Levels in the Membrane

    PubMed Central

    Asako, Hiroyuki; Kobayashi, Kei; Aono, Rikizo

    1999-01-01

    The organic solvent tolerance of Escherichia coli was measured under conditions in which OmpF levels were controlled by various means as follows: alteration of NaCl concentration in the medium, transformation with a stress-responsive gene (marA, robA, or soxS), or disruption of the ompF gene. It was shown that solvent tolerance of E. coli did not depend upon OmpF levels in the membrane. PMID:9872794

  17. Solvent-filled dialysis membranes simulate uptake of pollutants by aquatic organisms

    SciTech Connect

    Soedergren, A.

    1987-09-01

    Dialysis membranes filled with hexane accumulate persistent lipophilic pollutants in a way similar to that of aquatic organisms. The uptake of low molecular weight (< 1000), lipophilic compounds seems to be a passive process governed by partitioning mechanisms. The technique may be used to confirm bioaccumulation mechanisms, to predict environmental hazards of bioavailable compounds, and to monitor lipophilic pollutants, especially in environments too severe for biological indicators to survive.

  18. MEMBRANE SYSTEM FOR RECOVERY OF VOLATILE ORGANIC COMPOUNDS FROM REMEDIATION OFF-GASES

    SciTech Connect

    J.G. Wijmans

    2003-11-17

    In situ vacuum extraction, air or steam sparging, and vitrification are widely used to remediate soil contaminated with volatile organic compounds (VOCs). All of these processes produce a VOC-laden air stream from which the VOC must be removed before the air can be discharged or recycled to the generating process. Treatment of these off-gases is often a major portion of the cost of the remediation project. Currently, carbon adsorption and catalytic incineration are the most common methods of treating these gas streams. Membrane Technology and Research, Inc. (MTR) proposed an alternative treatment technology based on selective membranes that separate the organic components from the gas stream, producing a VOC-free air stream. This technology can be applied to off-gases produced by various remediation activities and the systems can be skid-mounted and automated for easy transportation and unattended operation. The target performance for the membrane systems is to produce clean air (less than 10 ppmv VOC) for discharge or recycle, dischargeable water (less than 1 ppmw VOC), and a concentrated liquid VOC phase. This report contains the results obtained during Phase II of a two-phase project. In Phase I, laboratory experiments were carried out to demonstrate the feasibility of the proposed approach. In the subsequent Phase II project, a demonstration system was built and operated at the McClellan Air Force Base near Sacramento, California. The membrane system was fed with off-gas from a Soil Vacuum Extraction (SVE) system. The work performed in Phase II demonstrated that the membrane system can reduce the VOC concentration in remediation off-gas to 10 ppmv, while producing a concentrated VOC phase and dischargeable water containing less than 1 ppmw VOC. However, the tests showed that the presence of 1 to 3% carbon dioxide in the SVE off-gas reduced the treatment capacity of the system by a factor of three to four. In an economic analysis, treatment costs of the membrane

  19. In situ surface chemical modification of thin-film composite forward osmosis membranes for enhanced organic fouling resistance.

    PubMed

    Lu, Xinglin; Romero-Vargas Castrillón, Santiago; Shaffer, Devin L; Ma, Jun; Elimelech, Menachem

    2013-01-01

    Forward osmosis (FO) is an emerging membrane-based water separation process with potential applications in a host of environmental and industrial processes. Nevertheless, membrane fouling remains a technical obstacle affecting this technology, increasing operating costs and decreasing membrane life. This work presents the first fabrication of an antifouling thin-film composite (TFC) FO membrane by an in situ technique without postfabrication treatment. The membrane was fabricated and modified in situ, grafting Jeffamine, an amine-terminated poly(ethylene glycol) derivative, to dangling acyl chloride surface groups on the nascent polyamide active layer. Surface characterization by contact angle, Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), zeta potential, atomic force microscopy (AFM), and fluorescence microscopy, confirms the presence of Jeffamine on the membrane surface. We demonstrate the improved fouling resistance of the in situ modified membranes through accelerated dynamic fouling FO experiments using a synthetic wastewater feed solution at high concentration (250 mg/L) of alginate, a model macromolecule for the hydrophilic fraction of wastewater effluent organic matter. Our results show a significantly lower flux decline for the in situ modified membranes compared to pristine polyamide (14.3 ± 2.7% vs 2.8 ± 1.4%, respectively). AFM adhesion force measurements between the membrane and a carboxylate-modified latex particle, a surrogate for the organic (alginate) foulant, show weaker foulant-membrane interactions, further confirming the enhanced fouling resistance of the in situ modified membranes. PMID:24066902

  20. Experimental Approach Reveals the Role of alx1 in the Evolution of the Echinoderm Larval Skeleton.

    PubMed

    Koga, Hiroyuki; Fujitani, Haruka; Morino, Yoshiaki; Miyamoto, Norio; Tsuchimoto, Jun; Shibata, Tomoko F; Nozawa, Masafumi; Shigenobu, Shuji; Ogura, Atsushi; Tachibana, Kazunori; Kiyomoto, Masato; Amemiya, Shonan; Wada, Hiroshi

    2016-01-01

    Over the course of evolution, the acquisition of novel structures has ultimately led to wide variation in morphology among extant multicellular organisms. Thus, the origins of genetic systems for new morphological structures are a subject of great interest in evolutionary biology. The larval skeleton is a novel structure acquired in some echinoderm lineages via the activation of the adult skeletogenic machinery. Previously, VEGF signaling was suggested to have played an important role in the acquisition of the larval skeleton. In the present study, we compared expression patterns of Alx genes among echinoderm classes to further explore the factors involved in the acquisition of a larval skeleton. We found that the alx1 gene, originally described as crucial for sea urchin skeletogenesis, may have also played an essential role in the evolution of the larval skeleton. Unlike those echinoderms that have a larval skeleton, we found that alx1 of starfish was barely expressed in early larvae that have no skeleton. When alx1 overexpression was induced via injection of alx1 mRNA into starfish eggs, the expression patterns of certain genes, including those possibly involved in skeletogenesis, were altered. This suggested that a portion of the skeletogenic program was induced solely by alx1. However, we observed no obvious external phenotype or skeleton. We concluded that alx1 was necessary but not sufficient for the acquisition of the larval skeleton, which, in fact, requires several genetic events. Based on these results, we discuss how the larval expression of alx1 contributed to the acquisition of the larval skeleton in the putative ancestral lineage of echinoderms. PMID:26866800

  1. Experimental Approach Reveals the Role of alx1 in the Evolution of the Echinoderm Larval Skeleton

    PubMed Central

    Koga, Hiroyuki; Fujitani, Haruka; Morino, Yoshiaki; Miyamoto, Norio; Tsuchimoto, Jun; Shibata, Tomoko F.; Nozawa, Masafumi; Shigenobu, Shuji; Ogura, Atsushi; Tachibana, Kazunori; Kiyomoto, Masato; Amemiya, Shonan; Wada, Hiroshi

    2016-01-01

    Over the course of evolution, the acquisition of novel structures has ultimately led to wide variation in morphology among extant multicellular organisms. Thus, the origins of genetic systems for new morphological structures are a subject of great interest in evolutionary biology. The larval skeleton is a novel structure acquired in some echinoderm lineages via the activation of the adult skeletogenic machinery. Previously, VEGF signaling was suggested to have played an important role in the acquisition of the larval skeleton. In the present study, we compared expression patterns of Alx genes among echinoderm classes to further explore the factors involved in the acquisition of a larval skeleton. We found that the alx1 gene, originally described as crucial for sea urchin skeletogenesis, may have also played an essential role in the evolution of the larval skeleton. Unlike those echinoderms that have a larval skeleton, we found that alx1 of starfish was barely expressed in early larvae that have no skeleton. When alx1 overexpression was induced via injection of alx1 mRNA into starfish eggs, the expression patterns of certain genes, including those possibly involved in skeletogenesis, were altered. This suggested that a portion of the skeletogenic program was induced solely by alx1. However, we observed no obvious external phenotype or skeleton. We concluded that alx1 was necessary but not sufficient for the acquisition of the larval skeleton, which, in fact, requires several genetic events. Based on these results, we discuss how the larval expression of alx1 contributed to the acquisition of the larval skeleton in the putative ancestral lineage of echinoderms. PMID:26866800

  2. Membrane filtration of agro-industrial wastewaters and isolation of organic compounds with high added values.

    PubMed

    Zagklis, Dimitris P; Paraskeva, Christakis A

    2014-01-01

    The aim of the current study was the exploitation of agro-industrial wastes or by-products such as olive mill wastewater (OMW) and defective wines. A cost-effective system for their maximum exploitation is suggested, using a combined process of membrane filtration and other physicochemical processes. Wastewaters are first treated in a membrane system (prefiltration, ultrafiltration, nanofiltration, and reverse osmosis) where pure water and other organic fractions (by-products) are obtained. Organic fractions, called hereafter byproducts and not wastes, are further treated for the separation of organic compounds and isolation of high added value products. Experiments were performed with OMW and defective wines as characteristic agro-industrial wastewaters. Profit from the exploitation of agro-industrial wastewaters can readily help the depreciation of the indeed high cost process of membrane filtration. The simple phenolic fraction of the OMW was successfully isolated from the rest of the waste, and problems occurring during winemaking, such as high volatile acidity and odours, were tackled. PMID:24434988

  3. Aqueous liquid feed organic fuel cell using solid polymer electrolyte membrane

    NASA Technical Reports Server (NTRS)

    Surampudi, Subbarao (Inventor); Narayanan, Sekharipuram R. (Inventor); Vamos, Eugene (Inventor); Frank, Harvey A. (Inventor); Halpert, Gerald (Inventor); Olah, George A. (Inventor); Prakash, G. K. Surya (Inventor)

    1997-01-01

    A liquid organic fuel cell is provided which employs a solid electrolyte membrane. An organic fuel, such as a methanol/water mixture, is circulated past an anode of a cell while oxygen or air is circulated past a cathode of the cell. The cell solid electrolyte membrane is preferably fabricated from Nafion.TM.. Additionally, a method for improving the performance of carbon electrode structures for use in organic fuel cells is provided wherein a high surface-area carbon particle/Teflon.TM.-binder structure is immersed within a Nafion.TM./methanol bath to impregnate the electrode with Nafion.TM.. A method for fabricating an anode for use in a organic fuel cell is described wherein metal alloys are deposited onto the electrode in an electro-deposition solution containing perfluorooctanesulfonic acid. A fuel additive containing perfluorooctanesulfonic acid for use with fuel cells employing a sulfuric acid electrolyte is also disclosed. New organic fuels, namely, trimethoxymethane, dimethoxymethane, and trioxane are also described for use with either conventional or improved fuel cells.

  4. TiO2 membranes for concurrent photocatalytic organic degradation and corrosion protection

    NASA Astrophysics Data System (ADS)

    Liang, Robert; Hatat-Fraile, Melisa; He, Horatio; Arlos, Maricor; Servos, Mark R.; Zhou, Y. Norman

    2015-10-01

    Organic contaminants and corrosion in water treatment effluents are a current global problem and the development of effective methods to facilitate the removal of organic contaminants and corrosion control strategies are required to mitigate this problem. TiO2 nanomaterials that are exposed to UV light can generate electron-hole pairs, which undergo redox reactions to produce hydroxyl radicals from adsorbed molecular oxygen. They hydroxyl radicals are able to oxidize organic contaminants in water. This same process can be used in conjunction to protect metals from corrosion via cathodic polarization. In this work, TiO2 nanomaterials were synthesized and electrophoretically deposited on conductive substrates to serve as films or membranes. An illuminated TiO2 film on a conductive surface served as the photoanode and assisted in the cathodic protection of stainless steel (SS304) and the degradation of organic pollutants, in this case glucose. This proof-of-concept relied on photoelectrochemical experiments conducted using a potentiostat and a xenon lamp illumination source. The open-circuit potential changes that determine whether a metal is protected from corrosion under illumination was observed; and the electrical characteristics of the TiO2 film or membrane under dark and arc lamp illumination conditions were also analyzed. Furthermore, the effect of organic contaminants on the photocathodic protection mechanism and the oxidation of glucose during this process were explored.

  5. Removal of trace organic chemicals and performance of a novel hybrid ultrafiltration-osmotic membrane bioreactor.

    PubMed

    Holloway, Ryan W; Regnery, Julia; Nghiem, Long D; Cath, Tzahi Y

    2014-09-16

    A hybrid ultrafiltration-osmotic membrane bioreactor (UFO-MBR) was investigated for over 35 days for nutrient and trace organic chemical (TOrC) removal from municipal wastewater. The UFO-MBR system uses both ultrafiltration (UF) and forward osmosis (FO) membranes in parallel to simultaneously extract clean water from an activated sludge reactor for nonpotable (or environmental discharge) and potable reuse, respectively. In the FO stream, water is drawn by osmosis from activated sludge through an FO membrane into a draw solution (DS), which becomes diluted during the process. A reverse osmosis (RO) system is then used to reconcentrate the diluted DS and produce clean water suitable for direct potable reuse. The UF membrane extracts water, dissolved salts, and some nutrients from the system to prevent their accumulation in the activated sludge of the osmotic MBR. The UF permeate can be used for nonpotable reuse purposes (e.g., irrigation and toilet flushing). Results from UFO-MBR investigation illustrated that the chemical oxygen demand, total nitrogen, and total phosphorus removals were greater than 99%, 82%, and 99%, respectively. Twenty TOrCs were detected in the municipal wastewater that was used as feed to the UFO-MBR system. Among these 20 TOrCs, 15 were removed by the hybrid UFO-MBR system to below the detection limit. High FO membrane rejection was observed for all ionic and nonionic hydrophilic TOrCs and lower rejection was observed for nonionic hydrophobic TOrCs. With the exceptions of bisphenol A and DEET, all TOrCs that were detected in the DS were well rejected by the RO membrane. Overall, the UFO-MBR can operate sustainably and has the potential to be utilized for direct potable reuse applications. PMID:25113310

  6. Characterizing algogenic organic matter (AOM) and evaluating associated NF membrane fouling.

    PubMed

    Her, Namguk; Amy, Gary; Park, Hyoung-Ryun; Song, Myoungsuk

    2004-03-01

    Occasional algal blooms, comprised of blue-green algae and/or green algae, cause significant challenges in drinking water treatment due to the release of algogenic organic matter (AOM) into water extracellularly and, upon cell lysis, intracellularly. AOM has been extracted from blue-green algae (cyanobacteria) by various means and analyzed by UV absorbance scanning, HPSEC-UV-fluorescence-DOC, UV absorbance ratio index (URI), FTIR, and fluorescence excitation emission matrix (EEM). AOM extracted in water as a solvent exhibited a high hydrophilic fraction (57.3%) with a low SUVA (1.0 L/m-mg). The molecular weight (MW) distribution showed a significant heterogeneity (high value of polydispersivity) and high protein content (as indicated by specific fluorescence). Significant amounts of proteinaceous components such as mycosporine-like amino acids (MAAs, UV-screening components) and phycobilins (light-harvesting pigment) were detected by UV/visible absorption. The presence of proteins was confirmed by FTIR (at 1661 and 1552 cm(-1)), EEM spectra (EX:278-282 nm and EM:304-353 nm), and high URI values (3.1-6.0). A bench-scale cross-flow unit, employing a flat-sheet membrane specimen, was used to examine nanofiltration (NF) membrane fouling and removal of natural organic matter (NOM) derived from different blends of Suwannee River humic acid (SRHA) and AOM: SRHA 10 mgC/L, AOM 3mg C/L + SRHA 7 mgC/L, AOM 7 mgC/L + SRHA 3 mgC/L, and AOM 10 mgC/L. The study focused mainly on the effects of two different sources of organic matter on NF (NF 200) membrane fouling under otherwise similar conditions. Flux decline and organic matter rejection as a function of delivered DOC (cumulative mass of feed DOC per unit area) showed significantly different results depending on the organic matter composition of samples even though the test conditions were the same (organic matter concentration, pH, temperature, inorganic salt composition and concentration, and recovery). A higher flux decline

  7. Histology of the heterostracan dermal skeleton: Insight into the origin of the vertebrate mineralised skeleton

    PubMed Central

    Marquart, Chloe L.

    2015-01-01

    ABSTRACT Living vertebrates are divided into those that possess a fully formed and fully mineralised skeleton (gnathostomes) versus those that possess only unmineralised cartilaginous rudiments (cyclostomes). As such, extinct phylogenetic intermediates of these living lineages afford unique insights into the evolutionary assembly of the vertebrate mineralised skeleton and its canonical tissue types. Extinct jawless and jawed fishes assigned to the gnathostome stem evidence the piecemeal assembly of skeletal systems, revealing that the dermal skeleton is the earliest manifestation of a homologous mineralised skeleton. Yet the nature of the primitive dermal skeleton, itself, is poorly understood. This is principally because previous histological studies of early vertebrates lacked a phylogenetic framework required to derive evolutionary hypotheses. Nowhere is this more apparent than within Heterostraci, a diverse clade of primitive jawless vertebrates. To this end, we surveyed the dermal skeletal histology of heterostracans, inferred the plesiomorphic heterostracan skeleton and, through histological comparison to other skeletonising vertebrate clades, deduced the ancestral nature of the vertebrate dermal skeleton. Heterostracans primitively possess a four‐layered skeleton, comprising a superficial layer of odontodes composed of dentine and enameloid; a compact layer of acellular parallel‐fibred bone containing a network of vascular canals that supply the pulp canals (L1); a trabecular layer consisting of intersecting radial walls composed of acellular parallel‐fibred bone, showing osteon‐like development (L2); and a basal layer of isopedin (L3). A three layered skeleton, equivalent to the superficial layer L2 and L3 and composed of enameloid, dentine and acellular bone, is possessed by the ancestor of heterostracans + jawed vertebrates. We conclude that an osteogenic component is plesiomorphic with respect to the vertebrate dermal skeleton. Consequently, we

  8. Oriented Nano-Microstructure-Assisted Controllable Fabrication of Metal-Organic Framework Membranes on Nickel Foam.

    PubMed

    Sun, Yuxiu; Yang, Fan; Wei, Qi; Wang, Naixin; Qin, Xi; Zhang, Shaokang; Wang, Bin; Nie, Zuoren; Ji, Shulan; Yan, Hui; Li, Jian-Rong

    2016-03-01

    Oriented nano-microstructure-assisted controllable fabrication, a facile and versatile preparation strategy, is developed to fabricate metal-organic framework (MOF) membranes. With this method, several MOF membranes with tailored structures are prepared, including HKUST-1 (with 3D pores) and M3 (HCOO)6 (with 1D pores; M = Co, Mn, and Mg) membranes, which demonstrate good performances in gas separations. PMID:26808691

  9. Real-time skeleton tracking for embedded systems

    NASA Astrophysics Data System (ADS)

    Coleca, Foti; Klement, Sascha; Martinetz, Thomas; Barth, Erhardt

    2013-03-01

    Touch-free gesture technology is beginning to become more popular with consumers and may have a significant future impact on interfaces for digital photography. However, almost every commercial software framework for gesture and pose detection is aimed at either desktop PCs or high-powered GPUs, making mobile implementations for gesture recognition an attractive area for research and development. In this paper we present an algorithm for hand skeleton tracking and gesture recognition that runs on an ARM-based platform (Pandaboard ES, OMAP 4460 architecture). The algorithm uses self-organizing maps to fit a given topology (skeleton) into a 3D point cloud. This is a novel way of approaching the problem of pose recognition as it does not employ complex optimization techniques or data-based learning. After an initial background segmentation step, the algorithm is ran in parallel with heuristics, which detect and correct artifacts arising from insufficient or erroneous input data. We then optimize the algorithm for the ARM platform using fixed-point computation and the NEON SIMD architecture the OMAP4460 provides. We tested the algorithm with two different depth-sensing devices (Microsoft Kinect, PMD Camboard). For both input devices we were able to accurately track the skeleton at the native framerate of the cameras.

  10. The Effect of Loops on the Structural Organization of α-Helical Membrane Proteins

    PubMed Central

    Tastan, Oznur; Klein-Seetharaman, Judith; Meirovitch, Hagai

    2009-01-01

    Loops connecting the transmembrane (TM) α-helices in membrane proteins are expected to affect the structural organization of the thereby connected helices and the helical bundles as a whole. This effect, which has been largely ignored previously, is studied here by analyzing the x-ray structures of 41 α-helical membrane proteins. First we define the loop flexibility ratio, R, and find that 53% of the loops are stretched, where a stretched loop constrains the distance between the two connected helices. The significance of this constraining effect is supported by experiments carried out with bacteriorhodopsin and rhodopsin, in which cutting or eliminating their (predominately stretched) loops has led to a decrease in protein stability, and for rhodopsin, in most cases, also to the destruction of the structure. We show that for nonstretched loops in the extramembranous regions, the fraction of hydrophobic residues is comparable to that for soluble proteins; furthermore (as is also the case for soluble proteins), the hydrophobic residues in these regions are preferentially buried. This is expected to lead to the compact structural organization of the loops, which is transferred to the TM helices, causing them to assemble. We argue that a soluble protein complexed with a membrane protein similarly promotes compactness; other properties of such complexes are also studied. We calculate complementary attractive interactions between helices, including hydrogen bonds and van der Waals interactions of sequential motifs, such as GXXXG. The relative and combined effects of all these factors on the association of the TM helices are discussed and protein structures with only a few of these factors are analyzed. Our study emphasizes the need for classifying membrane proteins into groups according to structural organization. This classification should be considered when procedures for structural analysis or prediction are developed and applied. Detailed analysis of each structure

  11. The Protein 4.1 family: hub proteins in animals for organizing membrane proteins.

    PubMed

    Baines, Anthony J; Lu, Hui-Chun; Bennett, Pauline M

    2014-02-01

    Proteins of the 4.1 family are characteristic of eumetazoan organisms. Invertebrates contain single 4.1 genes and the Drosophila model suggests that 4.1 is essential for animal life. Vertebrates have four paralogues, known as 4.1R, 4.1N, 4.1G and 4.1B, which are additionally duplicated in the ray-finned fish. Protein 4.1R was the first to be discovered: it is a major mammalian erythrocyte cytoskeletal protein, essential to the mechanochemical properties of red cell membranes because it promotes the interaction between spectrin and actin in the membrane cytoskeleton. 4.1R also binds certain phospholipids and is required for the stable cell surface accumulation of a number of erythrocyte transmembrane proteins that span multiple functional classes; these include cell adhesion molecules, transporters and a chemokine receptor. The vertebrate 4.1 proteins are expressed in most tissues, and they are required for the correct cell surface accumulation of a very wide variety of membrane proteins including G-Protein coupled receptors, voltage-gated and ligand-gated channels, as well as the classes identified in erythrocytes. Indeed, such large numbers of protein interactions have been mapped for mammalian 4.1 proteins, most especially 4.1R, that it appears that they can act as hubs for membrane protein organization. The range of critical interactions of 4.1 proteins is reflected in disease relationships that include hereditary anaemias, tumour suppression, control of heartbeat and nervous system function. The 4.1 proteins are defined by their domain structure: apart from the spectrin/actin-binding domain they have FERM and FERM-adjacent domains and a unique C-terminal domain. Both the FERM and C-terminal domains can bind transmembrane proteins, thus they have the potential to be cross-linkers for membrane proteins. The activity of the FERM domain is subject to multiple modes of regulation via binding of regulatory ligands, phosphorylation of the FERM associated domain and

  12. Wetting and capillary condensation as means of protein organization in membranes.

    PubMed Central

    Gil, T; Sabra, M C; Ipsen, J H; Mouritsen, O G

    1997-01-01

    Wetting and capillary condensation are thermodynamic phenomena in which the special affinity of interfaces to a thermodynamic phase, relative to the stable bulk phase, leads to the stabilization of a wetting phase at the interfaces. Wetting and capillary condensation are here proposed as mechanisms that in membranes may serve to induce special lipid phases in between integral membrane proteins leading to long-range lipid-mediated joining forces acting between the proteins and hence providing a means of protein organization. The consequences of wetting in terms of protein aggregation and protein clustering are derived both within a simple phenomenological theory as well as within a concrete calculation on a microscopic model of lipid-protein interactions that accounts for the lipid bilayer phase equilibria and direct lipid-protein interactions governed by hydrophobic matching between the lipid bilayer hydrophobic thickness and the length of the hydrophobic membrane domain. The theoretical results are expected to be relevant for optimizing the experimental conditions required for forming protein aggregates and regular protein arrays in membranes. Images FIGURE 2 FIGURE 4 FIGURE 6 PMID:9336169

  13. Superhydrophilic thin-film composite forward osmosis membranes for organic fouling control: fouling behavior and antifouling mechanisms.

    PubMed

    Tiraferri, Alberto; Kang, Yan; Giannelis, Emmanuel P; Elimelech, Menachem

    2012-10-16

    This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes. PMID:23002900

  14. Role of LHCII organization in the interaction of substituted 1,4-anthraquinones with thylakoid membranes.

    PubMed

    Apostolova, Emilia; Krumova, Sashka; Markova, Tzvetelina; Filipova, Tzvetanka; Molina, Maria T; Petkanchin, Ivana; Taneva, Stefka G

    2005-02-01

    The chlorophyll fluorescence, photochemical activity and surface electric properties of thylakoid membranes with different stoichiometry of pigment-protein complexes and organization of the light-harvesting chlorophyll a/b protein complex of photosystem II (LHCII) were studied in the presence of substituted 1,4-anthraquinones. Data show strong dependence of the quenching of the chlorophyll fluorescence on the structural organization of LHCII. The increase of the LHCII oligomerization, which is associated with significant reduction of the transmembrane electric charge asymmetry and electric polarizability of the membrane, correlates with enhanced quenching effect of substituted 1,4-athraquinones. Crucial for the large quinone-induced changes in the membrane electric dipole moments is the structure of the quinone molecule. The strongest reduction in the values of the dipole moments is observed after interaction of thylakoids with 3-chloro-9-hydroxy-1,4-anthraquinone (TF33) which has the highest quenching efficiency. The quinone induced changes in the photochemical activity of photosystem II (PSII) correlate with the total amount of the supramolecular LHCII-PSII complex and depend on the number of substituents in the 1,4-anthraquinone molecule. PMID:15664498

  15. Human proximal tubule epithelial cells cultured on hollow fibers: living membranes that actively transport organic cations.

    PubMed

    Jansen, J; De Napoli, I E; Fedecostante, M; Schophuizen, C M S; Chevtchik, N V; Wilmer, M J; van Asbeck, A H; Croes, H J; Pertijs, J C; Wetzels, J F M; Hilbrands, L B; van den Heuvel, L P; Hoenderop, J G; Stamatialis, D; Masereeuw, R

    2015-01-01

    The bioartificial kidney (BAK) aims at improving dialysis by developing 'living membranes' for cells-aided removal of uremic metabolites. Here, unique human conditionally immortalized proximal tubule epithelial cell (ciPTEC) monolayers were cultured on biofunctionalized MicroPES (polyethersulfone) hollow fiber membranes (HFM) and functionally tested using microfluidics. Tight monolayer formation was demonstrated by abundant zonula occludens-1 (ZO-1) protein expression along the tight junctions of matured ciPTEC on HFM. A clear barrier function of the monolayer was confirmed by limited diffusion of FITC-inulin. The activity of the organic cation transporter 2 (OCT2) in ciPTEC was evaluated in real-time using a perfusion system by confocal microscopy using 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (ASP(+)) as a fluorescent substrate. Initial ASP(+) uptake was inhibited by a cationic uremic metabolites mixture and by the histamine H2-receptor antagonist, cimetidine. In conclusion, a 'living membrane' of renal epithelial cells on MicroPES HFM with demonstrated active organic cation transport was successfully established as a first step in BAK engineering. PMID:26567716

  16. Segmentation and Reconstruction of Cultured Neuron Skeleton

    NASA Astrophysics Data System (ADS)

    Yu, Donggang; Pham, Tuan D.; Yan, Hong; Lai, Wei; Crane, Denis I.

    2007-11-01

    One approach to investigating neural death is through systematic studies of the changing morphology of cultured brain neurons in response to cellular challenges. Image segmentation and reconstruction methods developed to date to analyze such changes have been limited by the low contrast of cells. In this paper we present new algorithms that successfully circumvent these problems. The binary method is based on logical analysis of grey and distance difference of images. The spurious regions are detected and removed through use of a hierarchical window filter. The skeletons of binary cell images are extracted. The extension direction and connection points of broken cell skeletons are automatically determined, and broke neural skeletons are reconstructed. The spurious strokes are deleted based on cell prior knowledge. The efficacy of the developed algorithms is demonstrated here through a test of cultured brain neurons from newborn mice.

  17. A General Strategy for the Separation of Immiscible Organic Liquids by Manipulating the Surface Tensions of Nanofibrous Membranes.

    PubMed

    Wang, Li; Zhao, Yong; Tian, Ye; Jiang, Lei

    2015-12-01

    Oil/water separation membranes with different wettability towards water are attractive for their economic efficiency and convenience. The key factor for the separation process is the roughness-enhanced wettability of membranes based on the intrinsic wetting threshold (IWT) of water, that is, the limitation of the wettability caused by hydrophobicity and hydrophilicity. However, the separation of organic liquids (OLs) remains a challenge. Herein, we manipulate the surface tensions of nanofibrous membranes to lie between the IWTs of the two OLs to be separated so that the nanofibrous membranes can be endowed with superlyophobicity and superlyophilicity for the two liquids, and thus lead to successful separation. Our investigations provide a general strategy to separate any immiscible liquids efficiently, and may lead to the development of membranes with a large capacity, high flux, and high selectivity for organic reactions or liquid extraction in chemical engineering. PMID:26492856

  18. Non-rigid registration of small animal skeletons from micro-CT using 3D shape context

    NASA Astrophysics Data System (ADS)

    Xiao, Di; Bourgeat, Pierrick; Fripp, Jurgen; Acosta Tamayo, Oscar; Gregoire, Marie Claude; Salvado, Olivier

    2009-02-01

    Small animal registration is an important step for molecular image analysis. Skeleton registration from whole-body or only partial micro Computerized Tomography (CT) image is often performed to match individual rats to atlases and templates, for example to identify organs in positron emission tomography (PET). In this paper, we extend the shape context matching technique for 3D surface registration and apply it for rat hind limb skeleton registration from CT images. Using the proposed method, after standard affine iterative closest point (ICP) registration, correspondences between the 3D points from sour and target objects were robustly found and used to deform the limb skeleton surface with thin-plate-spline (TPS). Experiments are described using phantoms and actual rat hind limb skeletons. On animals, mean square errors were decreased by the proposed registration compared to that of its initial alignment. Visually, skeletons were successfully registered even in cases of very different animal poses.

  19. Refining image segmentation by polygon skeletonization

    NASA Technical Reports Server (NTRS)

    Clarke, Keith C.

    1987-01-01

    A skeletonization algorithm was encoded and applied to a test data set of land-use polygons taken from a USGS digital land use dataset at 1:250,000. The distance transform produced by this method was instrumental in the description of the shape, size, and level of generalization of the outlines of the polygons. A comparison of the topology of skeletons for forested wetlands and lakes indicated that some distinction based solely upon the shape properties of the areas is possible, and may be of use in an intelligent automated land cover classification system.

  20. [Mechanisms of growth, development and disease of the craniofacial skeleton].

    PubMed

    Yamashiro, Takashi

    2016-01-01

    Craniofacial skeleton is derived from several pieces of bone, which hold the brain and house the sensory organ of vision, hearing, taste and smell. It also serves as an entrance of the digestive and respiratory tracts. Hence, craniofacial complex develops under sophisticated balance between the shape and the function. Disruption of such balance leads to various types of malformation and/or deformation of the face. This review focuses on the molecular aspects of growth and developments of the craniofacial structures and also on the genetic basis of congenital craniofacial malformations. PMID:26728542

  1. The genetics of the protein 4.1 family: organizers of the membrane and cytoskeleton.

    PubMed

    Hoover, K B; Bryant, P J

    2000-04-01

    Protein 4.1 (also called band 4.1 or simply 4.1) was originally identified as an abundant protein of the human erythrocyte, in which it stabilizes the spectrin/actin cytoskeleton. The protein and its relatives have since been found in many cell types of metazoan organisms and they are often concentrated in the nucleus, as well as in cell-cell junctions. They form multimolecular complexes with transmembrane and membrane-associated proteins, and these complexes may be important for both structural stability and signal transduction at sites of cell contact. PMID:10712924

  2. Bridged polysilsesquioxanes: Hybrid organic-inorganic materials as fuel cell polyelectrolyte membranes and functional nanoparticles

    NASA Astrophysics Data System (ADS)

    Khiterer, Mariya

    2007-05-01

    This dissertation describes the design, fabrication, and characterization of organic-inorganic hybrid materials. Several classes of bridged polysilsesquioxanes are presented. The first class is a membrane material suitable for fuel cell technology as a proton conducting polyelectrolyte. The second class includes hybrid nanoparticles for display device applications and chromatographic media. Chapter 1 is an introduction to hybrid organic-inorganic materials. Sol-gel chemistry is discussed, followed by a survey of prominent examples of silica hybrids. Examples of physical organic-silica blends and covalent organo-silicas, including ORMOCERSRTM, polyhedral oligomeric silsesquioxanes, and bridged polysilsesquioxanes are discussed. Bridged polysilsesquioxanes are described in great detail. Monomer synthesis, sol-gel chemistry, processing, characterization, and physical properties are included. Chapter 2 describes the design of polyelectrolyte bridged polysilsesquioxane membranes. The materials contain covalently bound sulfonic acid groups originating from the corresponding disulfides. These organic-inorganic hybrid materials integrate a network supporting component which is systematically changed to fine-tune their physical properties. The membranes are characterized as PEM fuel cell electrolytes, where proton conductivities of 4-6 mS cm-1 were measured. In Chapter 3 techniques for the preparation of bridged polysilsesquioxane nanoparticles are described. An inverse water-in-oil microemulsion polymerization method is developed to prepare cationic nanoparticles, including viologen-bridged materials with applications in electrochromic display devices. An aqueous ammonia system is used to prepare neutral nanoparticles containing hydrocarbon bridging groups, which have potential applications as chromatographic media. Chapter 4 describes electrochromic devices developed in collaboration with the Heflin group of Virginia Tech, which incorporate viologen bridged nanoparticles

  3. Poly(imide)/Organically-Modified Montmorillonite Nanocomposite as a Potential Membrane for Alkaline Fuel Cells

    PubMed Central

    Battirola, Liliane C.; Gasparotto, Luiz H. S.; Rodrigues-Filho, Ubirajara P.; Tremiliosi-Filho, Germano

    2012-01-01

    In this work we evaluated the potentiality of a poly(imide) (PI)/organically-modified montmorillonite (O-MMT) nanocomposite membrane for the use in alkaline fuel cells. Both X-ray diffraction and scanning electron microscopy revealed a good dispersion of O-MMT into the PI matrix and preservation of the O-MMT layered structure. When compared to the pure PI, the addition of O-MMT improved thermal stability and markedly increased the capability of absorbing electrolyte and ionic conductivity of the composite. The results show that the PI/O-MMT nanocomposite is a promising candidate for alkaline fuel cell applications. PMID:24958290

  4. Impact of effluent organic matter on low-pressure membrane fouling in tertiary treatment.

    PubMed

    Ayache, C; Pidou, M; Croué, J P; Labanowski, J; Poussade, Y; Tazi-Pain, A; Keller, J; Gernjak, W

    2013-05-15

    This study aims at comparing low-pressure membrane fouling obtained with two different secondary effluents at bench and pilot-scale based on the determination of two fouling indices: the total fouling index (TFI) and the hydraulically irreversible fouling index (HIFI). The main objective was to investigate if simpler and less costly bench-scale experimentation can substitute for pilot-scale trials when assessing the fouling potential of secondary effluent in large scale membrane filtration plants producing recycled water. Absolute values for specific flux and total fouling index for the bench-scale system were higher than those determined from pilot-scale, nevertheless a statistically significant correlation (r(2) = 0.63, α = 0.1) was obtained for the total fouling index at both scales. On the contrary no such correlation was found for the hydraulically irreversible fouling index. Advanced water characterization tools such as excitation-emission matrix fluorescence spectroscopy (EEM) and liquid chromatography with organic carbon detection (LC-OCD) were used for the characterization of foulants. On the basis of statistical analysis, biopolymers and humic substances were found to be the major contribution to total fouling (r(2) = 0.95 and r(2) = 0.88, respectively). Adsorption of the low molecular weight neutral compounds to the membrane was attributed to hydraulically irreversible fouling (r(2) = 0.67). PMID:23541121

  5. The Effect of Fructan on Membrane Lipid Organization and Dynamics in the Dry State

    PubMed Central

    Vereyken, Ingrid J.; Chupin, Vladimir; Hoekstra, Folkert A.; Smeekens, Sjef C. M.; de Kruijff, Ben

    2003-01-01

    Fructans are a group of fructose-based oligo- and polysaccharides, which appear to be involved in membrane preservation during dehydration by interacting with the membrane lipids. To get further understanding of the protective mechanism, the consequences of the fructan-membrane lipid interaction for the molecular organization and dynamics in the dry state were studied. POPC and DMPC were investigated in the dry state by 2H, 31P NMR, and Fourier transform infrared spectroscopy using two types of fructan and dextran. The order-disorder transition temperature of dry POPC was reduced by 70°C in the presence of fructan. Fructan increased the mobility of the acyl chains, but immobilized the lipid headgroup region. Most likely, fructans insert between the headgroups of lipids, thereby spacing the acyl chains. This results in a much lower phase transition temperature. The headgroup is immobilized by the interaction with fructan. The location of the interaction with the lipid headgroup is different for the inulin-type fructan compared to the levan-type fructan, since inulin shows interaction with the lipid phosphate group, whereas levan does not. Dextran did not influence the phase transition temperature of dry POPC showing that reduction of this temperature is not a general property of polysaccharides. PMID:12770882

  6. Iron deficiency and bioavailability in anaerobic batch and submerged membrane bioreactors (SAMBR) during organic shock loads.

    PubMed

    Ketheesan, Balachandran; Thanh, Pham Minh; Stuckey, David C

    2016-07-01

    This study examined the effects of Fe(2+) and its bioavailability for controlling VFAs during organic shock loads in batch reactors and a submerged anaerobic membrane bioreactor (SAMBR). When seed grown under Fe-sufficient conditions (7.95±0.05mgFe/g-TSS), an organic shock resulted in leaching of Fe from the residual to organically bound and soluble forms. Under Fe-deficient seed conditions (0.1±0.002mgFe/gTSS), Fe(2+) supplementation (3.34mgFe(2+)/g-TSS) with acetate resulted in a 2.1-3.9 fold increase in the rate of methane production, while with propionate it increased by 1.2-1.5 fold compared to non-Fe(2+) supplemented reactors. Precipitation of Fe(2+) as sulphides and organically bound Fe were bioavailable to methanogens for acetate assimilation. The results confirmed that the transitory/long term limitations of Fe play a significant role in controlling the degradation of VFAs during organic shock loads due to their varying physical/chemical states, and bioavailability. PMID:27015020

  7. A novel membrane distillation-thermophilic bioreactor system: biological stability and trace organic compound removal.

    PubMed

    Wijekoon, Kaushalya C; Hai, Faisal I; Kang, Jinguo; Price, William E; Guo, Wenshan; Ngo, Hao H; Cath, Tzahi Y; Nghiem, Long D

    2014-05-01

    The removal of trace organic compounds (TrOCs) by a novel membrane distillation-thermophilic bioreactor (MDBR) system was examined. Salinity build-up and the thermophilic conditions to some extent adversely impacted the performance of the bioreactor, particularly the removal of total nitrogen and recalcitrant TrOCs. While most TrOCs were well removed by the thermophilic bioreactor, compounds containing electron withdrawing functional groups in their molecular structure were recalcitrant to biological treatment and their removal efficiency by the thermophilic bioreactor was low (0-53%). However, the overall performance of the novel MDBR system with respect to the removal of total organic carbon, total nitrogen, and TrOCs was high and was not significantly affected by the conditions of the bioreactor. All TrOCs investigated here were highly removed (>95%) by the MDBR system. Biodegradation, sludge adsorption, and rejection by MD contribute to the removal of TrOCs by MDBR treatment. PMID:24658107

  8. Organization of the ER–Golgi interface for membrane traffic control

    PubMed Central

    Brandizzi, Federica; Barlowe, Charles

    2014-01-01

    Coat protein complex I (COPI) and COPII are required for bidirectional membrane trafficking between the endoplasmic reticulum (ER) and the Golgi. While these core coat machineries and other transport factors are highly conserved across species, high-resolution imaging studies indicate that the organization of the ER–Golgi interface is varied in eukaryotic cells. Regulation of COPII assembly, in some cases to manage distinct cellular cargo, is emerging as one important component in determining this structure. Comparison of the ER–Golgi interface across different systems, particularly mammalian and plant cells, reveals fundamental elements and distinct organization of this interface. A better understanding of how these interfaces are regulated to meet varying cellular secretory demands should provide key insights into the mechanisms that control efficient trafficking of proteins and lipids through the secretory pathway. PMID:23698585

  9. Concise Synthesis of Astellatol Core Skeleton.

    PubMed

    Zhao, Nan; Xie, Shengling; Chen, Gui; Xu, Jing

    2016-08-26

    A ten-step, enantiospecific synthesis of the highly challenging core skeleton of sesterterpenoid astellatol has been achieved. Key transformations of this strategy include a facile, convergent construction of the tricyclic motif and a SmI2 -induced reductive radical cyclization that forms the pivotal cyclobutane ring. PMID:27398681

  10. Advances in evaluating the fetal skeleton

    PubMed Central

    Noel, Ann-Edwidge; Brown, Richard N

    2014-01-01

    In this review, we discuss aspects of the prenatal diagnosis of fetal skeletal malformations, concentrating on the advantages offered by different imaging techniques and the approaches that are of value in evaluating a suspected skeletal dysplasia. We also briefly address the findings in some of the commoner malformations of the fetal skeleton that may be encountered. PMID:24868173