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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. Structural organization of the actin-spectrin–based membrane skeleton in dendrites and soma of neurons

    PubMed Central

    Han, Boran; Zhou, Ruobo; Xia, Chenglong

    2017-01-01

    Actin, spectrin, and associated molecules form a membrane-associated periodic skeleton (MPS) in neurons. In the MPS, short actin filaments, capped by actin-capping proteins, form ring-like structures that wrap around the circumference of neurites, and these rings are periodically spaced along the neurite by spectrin tetramers, forming a quasi-1D lattice structure. This 1D MPS structure was initially observed in axons and exists extensively in axons, spanning nearly the entire axonal shaft of mature neurons. Such 1D MPS was also observed in dendrites, but the extent to which it exists and how it develops in dendrites remain unclear. It is also unclear whether other structural forms of the membrane skeleton are present in neurons. Here, we investigated the spatial organizations of spectrin, actin, and adducin, an actin-capping protein, in the dendrites and soma of cultured hippocampal neurons at different developmental stages, and compared results with those obtained in axons, using superresolution imaging. We observed that the 1D MPS exists in a substantial fraction of dendritic regions in relatively mature neurons, but this structure develops slower and forms with a lower propensity in dendrites than in axons. In addition, we observed that spectrin, actin, and adducin also form a 2D polygonal lattice structure, resembling the expanded erythrocyte membrane skeleton structure, in the somatodendritic compartment. This 2D lattice structure also develops substantially more slowly in the soma and dendrites than the development of the 1D MPS in axons. These results suggest membrane skeleton structures are differentially regulated across different subcompartments of neurons. PMID:28739933

  3. Structural organization of the actin-spectrin-based membrane skeleton in dendrites and soma of neurons.

    PubMed

    Han, Boran; Zhou, Ruobo; Xia, Chenglong; Zhuang, Xiaowei

    2017-08-08

    Actin, spectrin, and associated molecules form a membrane-associated periodic skeleton (MPS) in neurons. In the MPS, short actin filaments, capped by actin-capping proteins, form ring-like structures that wrap around the circumference of neurites, and these rings are periodically spaced along the neurite by spectrin tetramers, forming a quasi-1D lattice structure. This 1D MPS structure was initially observed in axons and exists extensively in axons, spanning nearly the entire axonal shaft of mature neurons. Such 1D MPS was also observed in dendrites, but the extent to which it exists and how it develops in dendrites remain unclear. It is also unclear whether other structural forms of the membrane skeleton are present in neurons. Here, we investigated the spatial organizations of spectrin, actin, and adducin, an actin-capping protein, in the dendrites and soma of cultured hippocampal neurons at different developmental stages, and compared results with those obtained in axons, using superresolution imaging. We observed that the 1D MPS exists in a substantial fraction of dendritic regions in relatively mature neurons, but this structure develops slower and forms with a lower propensity in dendrites than in axons. In addition, we observed that spectrin, actin, and adducin also form a 2D polygonal lattice structure, resembling the expanded erythrocyte membrane skeleton structure, in the somatodendritic compartment. This 2D lattice structure also develops substantially more slowly in the soma and dendrites than the development of the 1D MPS in axons. These results suggest membrane skeleton structures are differentially regulated across different subcompartments of neurons.

  4. 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.

  5. Identification of a membrane skeleton in platelets

    PubMed Central

    1988-01-01

    Platelets have previously been shown to contain actin filaments that are linked, through actin-binding protein, to the glycoprotein (GP) Ib- IX complex, GP Ia, GP IIa, and an unidentified GP of Mr 250,000 on the plasma membrane. The objective of the present study was to use a morphological approach to examine the distribution of these membrane- bound filaments within platelets. Preliminary experiments showed that the Triton X-100 lysis buffers used previously to solubilize platelets completely disrupt the three-dimensional organization of the cytoskeletons. Conditions were established that minimized these postlysis changes. The cytoskeletons remained as platelet-shaped structures. These structures consisted of a network of long actin filaments and a more amorphous layer that outlined the periphery. When Ca2+ was present, the long actin filaments were lost but the amorphous layer at the periphery remained; conditions were established in which this amorphous layer retained the outline of the platelet from which it originated. Immunocytochemical experiments showed that the GP Ib-IX complex and actin-binding protein were associated with the amorphous layer. Analysis of the amorphous material on SDS-polyacrylamide gels showed that it contained actin, actin-binding protein, and all actin- bound GP Ib-IX. Although actin filaments could not be visualized in thin section, the actin presumably was in a filamentous form because it was solubilized by DNase I and bound phalloidin. These studies show that platelets contain a membrane skeleton and suggest that it is distinct from the network of cytoplasmic actin filaments. This membrane skeleton exists as a submembranous lining that, by analogy to the erythrocyte membrane skeleton, may stabilize the plasma membrane and contribute to determining its shape. PMID:3372587

  6. Erythrocyte membrane skeleton inhibits nanoparticle endocytosis

    NASA Astrophysics Data System (ADS)

    Gao, Xinli; Yue, Tongtao; Tian, Falin; Liu, Zhiping; Zhang, Xianren

    2017-06-01

    Red blood cells (RBCs), also called erythrocytes, have been experimentally proposed in recent decades as the biological drug delivery systems through entrapping certain drugs by endocytosis. However, the internalization pathway of endocytosis seems to conflict with the robust mechanical properties of RBCs that is induced by the spectrin-actin network of erythrocyte membrane skeleton. In this work, we employed a minimum realistic model and the dissipative particle dynamics method to investigate the influence of the spectrin-actin membrane skeleton on the internalization of nanoparticles (NPs). Our simulations show that the existence of skeleton meshwork indeed induces an inhibiting effect that effectively prevents NPs from internalization. The inhibiting effect is found to depend on the membrane-NP attraction, skeleton tension and relative size of the NP to the membrane skeleton mesh. However, our simulations also demonstrate that there are two possibilities for successful internalization of NPs in the presence of the membrane skeleton. The first case is for NPs that has a much smaller size than the dimension of skeleton meshes, and the other is that the skeleton tension is rather weak so that the formed vesicle can still move inward for NP internalization.

  7. Tropomodulin1 is required for membrane skeleton organization and hexagonal geometry of fiber cells in the mouse lens

    PubMed Central

    Nowak, Roberta B.; Fischer, Robert S.; Zoltoski, Rebecca K.; Kuszak, Jerome R.

    2009-01-01

    Hexagonal packing geometry is a hallmark of close-packed epithelial cells in metazoans. Here, we used fiber cells of the vertebrate eye lens as a model system to determine how the membrane skeleton controls hexagonal packing of post-mitotic cells. The membrane skeleton consists of spectrin tetramers linked to actin filaments (F-actin), which are capped by tropomodulin1 (Tmod1) and stabilized by tropomyosin (TM). In mouse lenses lacking Tmod1, initial fiber cell morphogenesis is normal, but fiber cell hexagonal shapes and packing geometry are not maintained as fiber cells mature. Absence of Tmod1 leads to decreased γTM levels, loss of F-actin from membranes, and disrupted distribution of β2-spectrin along fiber cell membranes. Regular interlocking membrane protrusions on fiber cells are replaced by irregularly spaced and misshapen protrusions. We conclude that Tmod1 and γTM regulation of F-actin stability on fiber cell membranes is critical for the long-range connectivity of the spectrin–actin network, which functions to maintain regular fiber cell hexagonal morphology and packing geometry. PMID:19752024

  8. Ultrastructure of the intact skeleton of the human erythrocyte membrane.

    PubMed

    Shen, B W; Josephs, R; Steck, T L

    1986-03-01

    Filamentous skeletons were liberated from isolated human erythrocyte membranes in Triton X-100, spread on fenestrated carbon films, negatively stained, and viewed intact and unfixed in the transmission electron microscope. Two forms of the skeleton were examined: (a) basic skeletons, stripped of accessory proteins with 1.5 M NaCl so that they contain predominantly polypeptide bands 1, 2, 4.1, and 5; and (b) unstripped skeletons, which also bore accessory proteins such as ankyrin and band 3 and small plaques of residual lipid. Freshly prepared skeletons were highly condensed. Incubation at low ionic strength and in the presence of dithiothreitol for an hour or more caused an expansion of the skeletons, which greatly increased the visibility of their elements. The expansion may reflect the opening of spectrin from a compact to an elongated disposition. Expanded skeletons appeared to be organized as networks of short actin filaments joined by multiple (5-8) spectrin tetramers. In unstripped preparations, globular masses were observed near the centers of the spectrin filaments, probably corresponding to complexes of ankyrin with band 3 oligomers. Some of these globules linked pairs of spectrin filaments. Skeletons prepared with a minimum of perturbation had thickened actin protofilaments, presumably reflecting the presence of accessory proteins. The length of these actin filaments was highly uniform, averaging 33 +/- 5 nm. This is the length of nonmuscle tropomyosin. Since there is almost enough tropomyosin present to saturate the F-actin, our data support the hypothesis that tropomyosin may determine the length of actin protofilaments in the red cell membrane.

  9. 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.

  10. 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

  11. 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.

  12. Visualization of the hexagonal lattice in the erythrocyte membrane skeleton.

    PubMed

    Liu, S C; Derick, L H; Palek, J

    1987-03-01

    The isolated membrane skeleton of human erythrocytes was studied by high resolution negative staining electron microscopy. When the skeletal meshwork is spread onto a thin carbon film, clear images of a primarily hexagonal lattice of junctional F-actin complexes crosslinked by spectrin filaments are obtained. The regularly ordered network extends over the entire membrane skeleton. Some of the junctional complexes are arranged in the form of pentagons and septagons, approximately 3 and 8%, respectively. At least five forms of spectrin crosslinks are detected in the spread skeleton including a single spectrin tetramer linking two junctional complexes, three-armed Y-shaped spectrin molecules linking three junctional complexes, three-armed spectrin molecules connecting two junctional complexes with two arms bound to one complex and the third arm bound to the adjacent complex, double spectrin filaments linking two junctional complexes, and four-armed spectrin molecules linking two junctional complexes. Of these, the crosslinks of single spectrin tetramers and three-armed molecules are the most abundant and represent 84 and 11% of the total crosslinks, respectively. These observations are compatible with the presence of spectrin tetramers and oligomers in the erythrocyte membrane skeleton. Globular structures (9-12 nm in diameter) are attached to the majority of the spectrin tetramers or higher order oligomer-like molecules, approximately 80 nm from the distal ends of the spectrin tetramers. These globular structures are ankyrinor ankyrin/band 3-containing complexes, since they are absent when ankyrin and residual band 3 are extracted from the skeleton under hypertonic conditions.

  13. 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.

  14. Biogenesis of erythrocyte membrane skeleton in health and disease.

    PubMed

    Hanspal, M; Prchal, J T; Palek, J

    1993-05-01

    To study the biogenesis of red cell membrane skeleton at various stages of erythroid differentiation, we have chosen the following model systems: a) Rauscher erythroleukemia cell line representing the early stages of differentiation, b) Friend erythroleukemia cells, and c) in vitro cultured human erythroblasts. The latter two systems represent terminally differentiated erythroblasts. Using these model systems, we have shown asynchronous synthesis of membrane proteins during erythroid differentiation. At the early stages of erythroid development, the synthesis of spectrin, ankyrin and band 4.1 proteins is initiated before that of the band 3 protein. Following erythroid induction with erythropoietin and dimethylsulfoxide (DMSO), there is a dramatic increase in the synthesis of the band 3 protein without noticeable changes in the synthesis of other membrane proteins. This increase in band 3 synthesis is accompanied by increased stability and recruitment of the skeletal proteins into the membrane skeleton, leading to increased steady state levels. The progressive increase in band 3 synthesis continues during terminal maturation of erythroblasts. This is accompanied by increased stability and assembly of spectrin and ankyrin on the membrane, despite their reduced synthesis. These results point to a key role for the band 3 protein in anchoring and stabilizing these proteins into the permanent skeletal network. Finally, to detect defects of skeletal biosynthesis, we have extended these studies to a patient with severe hereditary spherocytosis characterized by a combined deficiency of spectrin and ankyrin. We have shown that this combined deficiency is a consequence of reduced ankyrin synthesis and mRNA content representing a thalassemia-like membrane protein mutation.

  15. Soluble organic matrices of aragonitic skeletons of Merulinidae (Cnidaria, Anthozoa).

    PubMed

    Dauphin, Yannicke; Cuif, Jean-Pierre; Williams, C Terry

    2008-05-01

    Our interpretation of the overall taxonomy and evolution of the Scleractinia, the most important reef builders in tropical areas, has long depended exclusively on morphology of the calcareous skeletons. The reported series of physical and biochemical characterizations of skeletons and the mineralizing matrices extracted from the skeletons allow, for the first time, the level of biochemical diversity among corallites of the same family to be estimated. Similarities and differences observed in the micro- and nanostructures of the skeletons reflect those of the soluble organic matrices. Sulphur is mainly associated with sulphated acidic sugars. The role of sulphated sugars on the biomineralization processes is still underestimated. The resulting data suggest that environmental conditions may act on the mineralization process through the detailed compositions of the mineralizing matrices.

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

    PubMed

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

    2012-12-01

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

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

    PubMed

    Kats, Lev M; Proellocks, Nicholas I; 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

    2015-07-01

    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 sub-domains 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.

  18. 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

  19. Visualization of the Protein Associations in the Erythrocyte Membrane Skeleton

    NASA Astrophysics Data System (ADS)

    Byers, Timothy J.; Branton, Daniel

    1985-09-01

    We have obtained clear images of the erythrocyte membrane skeleton from negatively stained preparations that originate directly from the intact cell but in which the spectrin meshwork is artificially spread to allow close inspection. Our procedure requires less than 2 min at 5 degrees C in phosphate buffers. We find 200-nm-long spectrin tetramers crosslinked by junctional complexes. Each junction contains a regular 37-nm rod, probably an actin oligomer of approximately 13 monomers. Densities appear at variable places in the meshwork but distinct globules occur with great frequency 78 nm from the spectrin tetramer's junctional insertion end, very close to the known binding site for ankyrin. Most frequently, five or six spectrin tetramers insert into each junction, producing a meshwork that displays remarkably regular long range order.

  20. Developmental mechanism of the periodic membrane skeleton in axons

    PubMed Central

    Zhong, Guisheng; He, Jiang; Zhou, Ruobo; Lorenzo, Damaris; Babcock, Hazen P; Bennett, Vann; Zhuang, Xiaowei

    2014-01-01

    Actin, spectrin, and associated molecules form a periodic sub-membrane lattice structure in axons. How this membrane skeleton is developed and why it preferentially forms in axons are unknown. Here, we studied the developmental mechanism of this lattice structure. We found that this structure emerged early during axon development and propagated from proximal regions to distal ends of axons. Components of the axon initial segment were recruited to the lattice late during development. Formation of the lattice was regulated by the local concentration of βII spectrin, which is higher in axons than in dendrites. Increasing the dendritic concentration of βII spectrin by overexpression or by knocking out ankyrin B induced the formation of the periodic structure in dendrites, demonstrating that the spectrin concentration is a key determinant in the preferential development of this structure in axons and that ankyrin B is critical for the polarized distribution of βII spectrin in neurites. DOI: http://dx.doi.org/10.7554/eLife.04581.001 PMID:25535840

  1. 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.…

  2. 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.…

  3. Regulation Mechanism of the Lateral Diffusion of Band 3 in Erythrocyte Membranes by the Membrane Skeleton

    PubMed Central

    Tomishige, Michio; Sako, Yasushi; Kusumi, Akihiro

    1998-01-01

    Mechanisms that regulate the movement of a membrane spanning protein band 3 in erythrocyte ghosts were investigated at the level of a single or small groups of molecules using single particle tracking with an enhanced time resolution (0.22 ms). Two-thirds of band 3 undergo macroscopic diffusion: a band 3 molecule is temporarily corralled in a mesh of 110 nm in diameter, and hops to an adjacent mesh an average of every 350 ms. The rest (one-third) of band 3 exhibited oscillatory motion similar to that of spectrin, suggesting that these band 3 molecules are bound to spectrin. When the membrane skeletal network was dragged and deformed/translated using optical tweezers, band 3 molecules that were undergoing hop diffusion were displaced toward the same direction as the skeleton. Mild trypsin treatment of ghosts, which cleaves off the cytoplasmic portion of band 3 without affecting spectrin, actin, and protein 4.1, increased the intercompartmental hop rate of band 3 by a factor of 6, whereas it did not change the corral size and the microscopic diffusion rate within a corral. These results indicate that the cytoplasmic portion of band 3 collides with the membrane skeleton, which causes temporal confinement of band 3 inside a mesh of the membrane skeleton. PMID:9722611

  4. Organic Electrolyte Permselective Membranes.

    DTIC Science & Technology

    ORGANIC SOLVENTS), (*STORAGE BATTERIES, (*BATTERY SEPARATORS, MEMBRANES ), (* MEMBRANES , TRANSPORT PROPERTIES), LITHIUM, COPPER COMPOUNDS, DIFFUSION, CHLORIDES, IONS, ELECTRODIALYSIS , ION EXCHANGE RESINS.

  5. Membrane skeleton orchestrates the platelet glycoprotein (GP) Ib-IX complex clustering and signaling.

    PubMed

    Shang, Dan; Zhang, Zuping; Wang, Qian; Ran, Yali; Shaw, Tanner S; Van, John N; Peng, Yuandong

    2016-10-01

    Platelet glycoprotein Ib-IX complex is affixed to the membrane skeleton through interaction with actin binding protein 280 (ABP-280). We find that removal of the ABP-280 binding sites in GP Ibα cytoplasmic tail has little impact on the complex clustering induced by antibody crosslinking. However, large truncation of the GP Ibα cytoplasmic tail allows the formation of larger patches of the complex, suggesting that an ABP-280 independent force may exist. Besides, we observe that the signaling upon GP Ib-IX clustering is elicited in both membrane lipid domain dependent and independent manner, a choice that relies on how the membrane skeleton interacts with the complex. Our findings suggest a more complex mechanism for how the membrane skeleton regulates the GP Ib-IX function. © 2016 IUBMB Life, 68(10):823-829, 2016.

  6. 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.

  7. Detergent-resistant membranes in human erythrocytes and their connection to the membrane-skeleton.

    PubMed

    Ciana, Annarita; Balduini, Cesare; Minetti, Giampaolo

    2005-06-01

    In cell membranes, local inhomogeneity in the lateral distribution of lipids and proteins is thought to exist in vivo in the form of lipid 'rafts', microdomains enriched in cholesterol and sphingolipids, and in specific classes of proteins, that appear to play specialized roles for signal transduction, cell-cell recognition, parasite or virus infection, and vesicular trafficking. These structures are operationally defined as membranes resistant to solubilization by nonionic detergents at 4 degree C (detergent-resistant membranes, DRMs). This definition appears to be necessary and sufficient, although additional manoeuvres, not always described with sufficient detail, may be needed to ensure isolation of DRMs, like mechanical homogenization, and changes in the pH and/or ionic strength of the solubilization medium. We show here for the human erythrocyte that the different conditions adopted may lead to the isolation of qualitatively and quantitatively different DRM fractions, thus contributing to the complexity of the notion itself of lipid raft. A significant portion of erythrocyte DRMs enriched in reported lipid raft markers, such as flotillin-1, flotillin-2 and GM1, is anchored to the spectrin membrane-skeleton via electrostatic interactions that can be disrupted by the simultaneous increase in pH and ionic strength of the solubilization medium.

  8. The skeleton as an intracrine organ for vitamin D metabolism.

    PubMed

    Anderson, Paul H; Atkins, Gerald J

    2008-12-01

    The endocrine hormone, 1alpha,25-dihydroxyvitamin D(3) (1,25D) is an important regulator of calcium and phosphorus homeostasis. In this context, 1,25D is generally recognized as necessary for the maintenance of a healthy skeleton through its actions on the small intestine. In this review, we highlight the direct effects of 1,25D on the constituent cells of the bone, actions that are independent of effects on the intestine and kidney. We also consider the evidence that 25D levels, not 1,25D levels, correlate best with parameters of bone health, and that the bone itself is a site of metabolic conversion of 25D into 1,25D, by virtue of its expression of the 25-hydroxyvitamin D 1alpha-hydroxylase, CYP27B1. We review the evidence that at least osteoblasts and chondrocytes, and possibly also bone resorbing osteoclasts, are capable of such metabolic conversion, and therefore that these cells likely participate in autocrine and paracrine loops of vitamin D metabolism. We conclude that the skeleton is an intracrine organ for vitamin D metabolism, challenging the long-held notion that 1,25D is solely an endocrine hormone.

  9. Membrane skeleton-bilayer interaction is not the major determinant of membrane phospholipid asymmetry in human erythrocytes.

    PubMed

    Gudi, S R; Kumar, A; Bhakuni, V; Gokhale, S M; Gupta, C M

    1990-03-30

    Transbilayer phospholipid distribution, membrane skeleton dissociation/association, and spectrin structure have been analysed in human erythrocytes after subjecting them to heating at 50 degrees C for 15 min. The membrane skeleton dissociation/association was determined by measuring the Tris-induced dissociation of Triton-insoluble membrane skeletons (Triton shells), the spectrin-actin extractability under low ionic conditions, and the binding of spectrin-actin with normal erythrocyte membrane inside-out vesicles (IOVs). The spectrin structure was ascertained by measuring the spectrin dimer-to-tetramer ratio as well as the spectrin tryptophan fluorescence. Both the Tris-induced Triton shell dissociation and the spectrin-actin extractability under low ionic conditions were considerably reduced by the heat treatment. Also, the binding of heated erythrocyte spectrin-actin to IOVs was significantly smaller than that observed with the normal cell spectrin-actin. Further, the quantity of spectrin dimers was appreciably increased in heat-treated erythrocytes as compared to the normal cells. This change in the spectrin dimer-to-tetramer ratio was accompanied by marked changes in the spectrin tryptophan fluorescence. In spite of these heat-induced alterations in structure and bilayer interactions of the membrane skeleton, the inside-outside glycerophospholipid distribution remained virtually unaffected in the heat-treated cells, as judged by employing bee venom and pancreatic phospholipase A2, fluorescamine and Merocyanine 540 as the external membrane probes. These results strongly indicate that membrane bilayer-skeleton interaction is not the major factor in determining the transbilayer phospholipid asymmetry in human erythrocyte membrane.

  10. 2,3-Diphosphoglycerate and ATP dissociate erythrocyte membrane skeletons.

    PubMed

    Sheetz, M P; Casaly, J

    1980-10-25

    Since ATP and 2,3-diphosphoglycerate cause an increase in the lateral mobility of integral membrane proteins in the erythrocyte (Schindler, M., Koppel, D., and Sheetz, M. P. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 1457-1461), we have studied their effects on the membrane skeletal complex or shell (composed of spectrin, actin, and bands 4.1 (78,000 daltons) and 4.9 (50,000 daltons)) and its interaction with the erythrocyte membrane. Both phosphate compounds dissociated the delipidated shell complex, with half-maximal dissociation at 2.5 mM 2,3-diphosphoglycerate and 8 mM ATP, whereas equivalent concentrations of EDTA did not. Concomitant with complex dissociation, spectrin was solubilized but band 4.1 and actin remained in a complexed or polymeric form. When proteins which were involved in linking spectrin to the membrane were present on the shell, higher concentrations of the phosphate compounds still dissociated the complex but less spectrin was solubilized. Treatment of erythrocyte membranes with the same phosphate compounds caused membrane vesiculation but no proteins were solubilized. We suggest that ATP and 2,3-diphosphoglycerate, at concentrations which are normally present in erythrocytes, can weaken associations in the shell but will not dissociate the complex from membrane attachment sites.

  11. Stress-free state of the red blood cell membrane and the deformation of its skeleton.

    PubMed

    Svelc, Tjaša; Svetina, Saša

    2012-06-01

    The response of a red blood cell (RBC) to deformation depends on its membrane, a composite of a lipid bilayer and a skeleton, which is a closed, two-dimensional network of spectrin tetramers as its bonds. The deformation of the skeleton and its lateral redistribution are studied in terms of the RBC resting state for a fixed geometry of the RBC, partially aspirated into a micropipette. The geometry of the RBC skeleton in its initial state is taken to be either two concentric circles, a references biconcave shape or a sphere. It is assumed that in its initial state the skeleton is distributed laterally in a homogeneous manner with its bonds either unstressed, presenting its stress-free state, or prestressed. The lateral distribution was calculated using a variational calculation. It was assumed that the spectrin tetramer bonds exhibit a linear elasticity. The results showed a significant effect of the initial skeleton geometry on its lateral distribution in the deformed state. The proposed model is used to analyze the measurements of skeleton extension ratios by the method of applying two modes of RBC micropipette aspiration.

  12. Modeling of the axon membrane skeleton structure and implications for its mechanical properties

    PubMed Central

    Tzingounis, Anastasios V.

    2017-01-01

    Super-resolution microscopy recently revealed that, unlike the soma and dendrites, the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under tension. Currently, the structure-function relationship of the axonal structure is unclear. Here, we used atomic force microscopy (AFM) to show that the stiffness of the axon plasma membrane is significantly higher than the stiffnesses of dendrites and somata. To examine whether the structure of the axon plasma membrane determines its overall stiffness, we introduced a coarse-grain molecular dynamics model of the axon membrane skeleton that reproduces the structure identified by super-resolution microscopy. Our proposed computational model accurately simulates the median value of the Young’s modulus of the axon plasma membrane determined by atomic force microscopy. It also predicts that because the spectrin filaments are under entropic tension, the thermal random motion of the voltage-gated sodium channels (Nav), which are bound to ankyrin particles, a critical axonal protein, is reduced compared to the thermal motion when spectrin filaments are held at equilibrium. Lastly, our model predicts that because spectrin filaments are under tension, any axonal injuries that lacerate spectrin filaments will likely lead to a permanent disruption of the membrane skeleton due to the inability of spectrin filaments to spontaneously form their initial under-tension configuration. PMID:28241082

  13. Feisty filaments: actin dynamics in the red blood cell membrane skeleton

    PubMed Central

    Gokhin, David S.; Fowler, Velia M.

    2016-01-01

    STRUCTURED ABSTRACT Purpose of review The purpose of this review is to discuss recent advances and unsolved questions in our understanding of actin filament organization and dynamics in the red blood cell (RBC) membrane skeleton, a two-dimensional quasi-hexagonal network consisting of (α1β1)2-spectrin tetramers interconnecting short actin filament-based junctional complexes. Recent findings In contrast to the long-held view that RBC actin filaments are static structures that do not exchange subunits with the cytosol, RBC actin filaments are dynamic structures that undergo subunit exchange and turnover, as evidenced by monomer incorporation experiments with rhodamine-actin and filament disruption experiments with actin-targeting drugs. The malaria-causing parasite, Plasmodium falciparum, co-opts RBC actin dynamics to construct aberrantly branched actin filament networks. Even though RBC actin filaments are dynamic, RBC actin filament lengths are highly uniform (~37 nm). RBC actin filament lengths are thought to be stabilized by the capping proteins, tropomodulin-1 and αβ-adducin, as well as the side-binding protein tropomyosin, present in an equimolar combination of two isoforms, TM5b (Tpm1.9) and TM5NM1 (Tpm3.1). Summary New evidence indicates that RBC actin filaments are not simply passive cytolinkers, but rather dynamic structures whose assembly and disassembly play important roles in RBC membrane function. PMID:27055045

  14. Actin protofilament orientation in deformation of the erythrocyte membrane skeleton.

    PubMed Central

    Picart, C; Dalhaimer, P; Discher, D E

    2000-01-01

    The red cell's spectrin-actin network is known to sustain local states of shear, dilation, and condensation, and yet the short actin filaments are found to maintain membrane-tangent and near-random azimuthal orientations. When calibrated with polarization results for single actin filaments, imaging of micropipette-deformed red cell ghosts has allowed an assessment of actin orientations and possible reorientations in the network. At the hemispherical cap of the aspirated projection, where the network can be dilated severalfold, filaments have the same membrane-tangent orientation as on a relatively unstrained portion of membrane. Likewise, over the length of the network projection pulled into the micropipette, where the network is strongly sheared in axial extension and circumferential contraction, actin maintains its tangent orientation and is only very weakly aligned with network extension. Similar results are found for the integral membrane protein Band 3. Allowing for thermal fluctuations, we deduce a bound for the effective coupling constant, alpha, between network shear and azimuthal orientation of the protofilament. The finding that alpha must be about an order of magnitude or more below its tight-coupling value illustrates how nanostructural kinematics can decouple from more macroscopic responses. Monte Carlo simulations of spectrin-actin networks at approximately 10-nm resolution further support this conclusion and substantiate an image of protofilaments as elements of a high-temperature spin glass. PMID:11106606

  15. Hematopoietic protein-1 regulates the actin membrane skeleton and membrane stability in murine erythrocytes.

    PubMed

    Chan, Maia M; Wooden, Jason M; Tsang, Mark; Gilligan, Diana M; Hirenallur-S, Dinesh K; Finney, Greg L; Rynes, Eric; Maccoss, Michael; Ramirez, Julita A; Park, Heon; Iritani, Brian M

    2013-01-01

    Hematopoietic protein-1 (Hem-1) is a hematopoietic cell specific member of the WAVE (Wiskott-Aldrich syndrome verprolin-homologous protein) complex, which regulates filamentous actin (F-actin) polymerization in many cell types including immune cells. However, the roles of Hem-1 and the WAVE complex in erythrocyte biology are not known. In this study, we utilized mice lacking Hem-1 expression due to a non-coding point mutation in the Hem1 gene to show that absence of Hem-1 results in microcytic, hypochromic anemia characterized by abnormally shaped erythrocytes with aberrant F-actin foci and decreased lifespan. We find that Hem-1 and members of the associated WAVE complex are normally expressed in wildtype erythrocyte progenitors and mature erythrocytes. Using mass spectrometry and global proteomics, Coomassie staining, and immunoblotting, we find that the absence of Hem-1 results in decreased representation of essential erythrocyte membrane skeletal proteins including α- and β- spectrin, dematin, p55, adducin, ankyrin, tropomodulin 1, band 3, and band 4.1. Hem1⁻/⁻ erythrocytes exhibit increased protein kinase C-dependent phosphorylation of adducin at Ser724, which targets adducin family members for dissociation from spectrin and actin, and subsequent proteolysis. Increased adducin Ser724 phosphorylation in Hem1⁻/⁻ erythrocytes correlates with decreased protein expression of the regulatory subunit of protein phosphatase 2A (PP2A), which is required for PP2A-dependent dephosphorylation of PKC targets. These results reveal a novel, critical role for Hem-1 in the homeostasis of structural proteins required for formation and stability of the actin membrane skeleton in erythrocytes.

  16. Hematopoietic Protein-1 Regulates the Actin Membrane Skeleton and Membrane Stability in Murine Erythrocytes

    PubMed Central

    Chan, Maia M.; Wooden, Jason M.; Tsang, Mark; Gilligan, Diana M.; Hirenallur-S, Dinesh K.; Finney, Greg L.; Rynes, Eric; MacCoss, Michael; Ramirez, Julita A.; Park, Heon; Iritani, Brian M.

    2013-01-01

    Hematopoietic protein-1 (Hem-1) is a hematopoietic cell specific member of the WAVE (Wiskott-Aldrich syndrome verprolin-homologous protein) complex, which regulates filamentous actin (F-actin) polymerization in many cell types including immune cells. However, the roles of Hem-1 and the WAVE complex in erythrocyte biology are not known. In this study, we utilized mice lacking Hem-1 expression due to a non-coding point mutation in the Hem1 gene to show that absence of Hem-1 results in microcytic, hypochromic anemia characterized by abnormally shaped erythrocytes with aberrant F-actin foci and decreased lifespan. We find that Hem-1 and members of the associated WAVE complex are normally expressed in wildtype erythrocyte progenitors and mature erythrocytes. Using mass spectrometry and global proteomics, Coomassie staining, and immunoblotting, we find that the absence of Hem-1 results in decreased representation of essential erythrocyte membrane skeletal proteins including α- and β- spectrin, dematin, p55, adducin, ankyrin, tropomodulin 1, band 3, and band 4.1. Hem1−/− erythrocytes exhibit increased protein kinase C-dependent phosphorylation of adducin at Ser724, which targets adducin family members for dissociation from spectrin and actin, and subsequent proteolysis. Increased adducin Ser724 phosphorylation in Hem1−/− erythrocytes correlates with decreased protein expression of the regulatory subunit of protein phosphatase 2A (PP2A), which is required for PP2A-dependent dephosphorylation of PKC targets. These results reveal a novel, critical role for Hem-1 in the homeostasis of structural proteins required for formation and stability of the actin membrane skeleton in erythrocytes. PMID:23424621

  17. 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.

  18. Elliptical erythrocyte membrane skeletons and heat-sensitive spectrin in hereditary elliptocytosis.

    PubMed

    Tomaselli, M B; John, K M; Lux, S E

    1981-03-01

    Erythrocyte membranes (ghosts) and membrane skeletons (submembranous reticula of spectrin, actin, and protein 4.1 prepared by extracting ghosts with Triton X-100) from 15 patients with hereditary elliptocytosis (HE) were elliptical, which indicates that the primary defect responsible for the abnormal shape of these cells resides in the skeleton. The protein composition of HE skeletons was normal, but in three kindreds purified spectrin heterodimer from 7/7 HE patients was heat sensitive and denatured at 48.0 +/- 0.1 degrees C instead of 49.0 +/- 0.3 degrees C (P less than 0.0005). Heat sensitivity was detected by precipitation and, in the spectrin from one patient, by changes in circular dichroism. In one other kindred spectrin dimer from 3/3 patients denatured at the normal temperature. In two of the three kindreds with heat-sensitive spectrin, intact erythrocytes exhibited budding and fragmentation at the temperature at which spectrin denatured. In the third kindred spectrin was heat sensitive, but erythrocytes were not. The symptoms in the latter kindred were clinically more severe (hemolytic HE with spherocytosis) than in the other three (mild HE). We conclude that defects in the erythrocyte membrane skeleton may be a common feature of HE. As judged by heat denaturation of erythrocytes and purified spectrin dimer, three phenotypically distinct forms of HE exist, two of which are characterized by defective, heat-sensitive spectrin. It remains to be determined whether the molecular defect in spectrin responsible for heat sensitivity is the primary genetic defect responsible for HE.

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

    PubMed Central

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

    2011-01-01

    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

  20. [The interactions of actin cell and membrane skeleton proteins with lipids].

    PubMed

    Bok, Ewa; Hryniewicz-Jankowska, Anita; Sikorski, Aleksander F

    2009-01-01

    The results of many studies indicate that many cytoskeletal proteins interact with lipids, or are regulated by phosphoinositides. Proteins may associate with membranes through specific domains, amphipathic helices and undefined motifs that interact through electrostatic or hydrophobic interactions. The interaction between specific proteins and certain lipids affect stabilization of lipid microdomains, which may provide an anchor for cytoskeletal proteins. In vitro, proteins that sever or depolymerize actin filaments, such as gelsolin, villin, cofilin and profilin, are inactivated by PI(4,5)P2. Conversely, proteins like e.g. vinculin, talin, alpha-actinin, ezrin, N-WASP, WAVE that promote actin polymerization and link actin filaments to each other, are activated by this lipid. The major components of red blood cell membrane skeleton: spectrin and protein 4.1, also their nonerythroid counterparts interact with lipids, and those interactions may be regulated by phosphoinositides.

  1. Antibodies to betaISigma2 spectrin identify in-homogeneities in the erythrocyte membrane skeleton.

    PubMed

    Pradhan, Deepti; Tseng, Kenneth; Cianci, Carol D; Morrow, Jon S

    2004-01-01

    The cortical cytoskeleton of the mammalian red cell, composed of spectrin, actin, protein 4.1, adducin, and protein 4.9, is generally regarded as a homogeneous structure that maintains the integrity of the membrane and the lateral disposition of integral membrane proteins. The major component of this structure is a hetero-oligomer of alphaI and betaISigma1 spectrin. In other tissues, most notably muscle and brain, a transcript of the betaI spectrin gene is generated by alternative exon utilization, yielding a protein that has the COOH-terminal 19 residues of betaISigma1 spectrin replaced by 210 novel residues to generate betaISigma2 spectrin. This new transcript contains a pleckstrin homology (PH) domain and may even exist under some conditions in a homopolymeric form. Using antibodies specific for the COOH-terminal domains of either betaISigma1 or betaISigma2 spectrin, we find that contrary to previous understandings, mature human erythrocytes contain a subpopulation of spectrin that is immunoreactive with antibodies to the betaISigma2 isoform, and that this spectrin is distributed into distinct plasma membrane patches. These results suggest that the native mammalian erythrocyte membrane skeleton, rather than being homogeneous, contains discrete submicron-scale microdomains that differ in both their composition and dispersion across the cell surface. The precise nature and role of these putative microdomains is under active investigation.

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

    PubMed

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

    2008-08-01

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

  3. 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…

  4. Segmentation of Skeleton and Organs in Whole-Body CT Images via Iterative Trilateration.

    PubMed

    Bieth, Marie; Peter, Loic; Nekolla, Stephan G; Eiber, Matthias; Langs, Georg; Schwaiger, Markus; Menze, Bjoern

    2017-06-27

    Whole body oncological screening using CT images requires a good anatomical localisation of organs and of the skeleton. While a number of algorithms for multi-organ localisation have been presented, developing algorithms for a dense anatomical annotation of the whole skeleton, however, has not been addressed until now. Only methods for specialised applications, e.g., in spine imaging, have been previously described. In this work, we propose an approach for localising and annotating different parts of the human skeleton in CT images. We introduce novel anatomical trilateration features and employ them within iterative scale-adaptive random forests in a hierarchical fashion to annotate the whole skeleton. The anatomical trilateration features provide high-level long-range context information that complements the classical local contextbased features used in most image segmentation approaches. They rely on anatomical landmarks derived from the previous element of the cascade to express positions relative to reference points. Following a hierarchical approach, large anatomical structures are segmented first, before identifying substructures. We develop this method for bone annotation but also illustrate its performance, although not specifically optimised for it, for multi-organ annotation. Our method achieves average Dice Scores of 77.4 to 85.6 for bone annotation on three different datasets. It can also segment different organs with sufficient performance for oncological applications, e.g. for PET/CT analysis, and its computation time allows for its use in clinical practice.

  5. 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.

  6. Organic matrices in metazoan calcium carbonate skeletons: Composition, functions, evolution.

    PubMed

    Marin, Frédéric; Bundeleva, Irina; Takeuchi, Takeshi; Immel, Françoise; Medakovic, Davorin

    2016-11-01

    Calcium carbonate skeletal tissues in metazoans comprise a small quantity of occluded organic macromolecules, mostly proteins and polysaccharides that constitute the skeletal matrix. Because its functions in modulating the biomineralization process are well known, the skeletal matrix has been extensively studied, successively via classical biochemical approaches, via molecular biology and, in recent years, via transcriptomics and proteomics. The optimistic view that the deposition of calcium carbonate minerals requires a limited number of macromolecules has been challenged, in the last decade, by high-throughput approaches. Such approaches have made possible the rapid identification of large sets of mineral-associated proteins, i.e., 'skeletal repertoires' or 'skeletomes', in several calcifying animal models, ranging from sponges to echinoderms. One of the consequences of this expanding set of data is that a simple definition of the skeletal matrix is no longer possible. This increase in available data, however, makes it easier to compare skeletal repertoires, shedding light on the fundamental evolutionary mechanisms affecting matrix components. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. 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

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

    PubMed Central

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

    2015-01-01

    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

  9. 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.

  10. 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

  11. Membrane Organization and Lipid Rafts

    PubMed Central

    Simons, Kai; Sampaio, Julio L.

    2011-01-01

    Cell membranes are composed of a lipid bilayer, containing proteins that span the bilayer and/or interact with the lipids on either side of the two leaflets. Although recent advances in lipid analytics show that membranes in eukaryotic cells contain hundreds of different lipid species, the function of this lipid diversity remains enigmatic. The basic structure of cell membranes is the lipid bilayer, composed of two apposing leaflets, forming a two-dimensional liquid with fascinating properties designed to perform the functions cells require. To coordinate these functions, the bilayer has evolved the propensity to segregate its constituents laterally. This capability is based on dynamic liquid–liquid immiscibility and underlies the raft concept of membrane subcompartmentalization. This principle combines the potential for sphingolipid-cholesterol self-assembly with protein specificity to focus and regulate membrane bioactivity. Here we will review the emerging principles of membrane architecture with special emphasis on lipid organization and domain formation. PMID:21628426

  12. Spectrin-ankyrin interaction mechanics: A key force balance factor in the red blood cell membrane skeleton.

    PubMed

    Saito, Masakazu; Watanabe-Nakayama, Takahiro; Machida, Shinichi; Osada, Toshiya; Afrin, Rehana; Ikai, Atsushi

    2015-01-01

    As major components of red blood cell (RBC) cytoskeleton, spectrin and F-actin form a network that covers the entire cytoplasmic surface of the plasma membrane. The cross-linked two layered structure, called the membrane skeleton, keeps the structural integrity of RBC under drastically changing mechanical environment during circulation. We performed force spectroscopy experiments on the atomic force microscope (AFM) as a means to clarify the mechanical characteristics of spectrin-ankyrin interaction, a key factor in the force balance of the RBC cytoskeletal structure. An AFM tip was functionalized with ANK1-62k and used to probe spectrin crosslinked to mica surface. A force spectroscopy study gave a mean unbinding force of ~30 pN under our experimental conditions. Two energy barriers were identified in the unbinding process. The result was related to the well-known flexibility of spectrin tetramer and participation of ankyrin 1-spectrin interaction in the overall balance of membrane skeleton dynamics. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. 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.

  14. Evidence that the red cell skeleton protein 4.2 interacts with the Rh membrane complex member CD47.

    PubMed

    Mouro-Chanteloup, Isabelle; Delaunay, Jean; Gane, Pierre; Nicolas, Virginie; Johansen, Mette; Brown, Eric J; Peters, Luanne L; Van Kim, Caroline Le; Cartron, Jean Pierre; Colin, Yves

    2003-01-01

    Rh(null) red cells are characteristically stomato-spherocytic. This and other evidence suggest that the Rh complex represents a major attachment site between the membrane lipid bilayer and the erythroid skeleton. As an attempt to identify the linking protein(s) between the red cell skeleton and the Rh complex, we analyzed the expression of Rh, RhAG, CD47, LW, and glycophorin B proteins in red cells from patients with hereditary spherocytosis associated with complete protein 4.2 deficiency but normal band 3 (4.2(-)HS). Flow cytometric and immunoblotting analysis revealed a severe reduction of CD47 (up to 80%) and a slower mobility of RhAG on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, possibly reflecting an overglycosylation state. Unexpectedly, 4.2(-/-) mice, which are anemic, displayed a normal red cell expression of CD47 and RhAG. These results suggest that human protein 4.2, through interaction with CD47, is involved in the skeleton linkage and/or membrane translocation of the Rh complex. However, these potential role(s) of protein 4.2 might be not conserved across species. Finally, the absence or low expression of red cell CD47 in CD47(-/-) mice and in some humans carrying RHCE gene variants (D--, D., and R(N)), respectively, had no detectable effect on protein 4.2 and RhAG expression. Since these cells are morphologically normal with no sign of hemolysis, it is assumed that CD47 deficiency per se is not responsible for the cell shape abnormalities and for the compensated hemolytic anemia typical of 4.2(-) and Rh(null) red cells.

  15. Biogenesis of the avian erythroid membrane skeleton: receptor-mediated assembly and stabilization of ankyrin (goblin) and spectrin.

    PubMed

    Moon, R T; Lazarides, E

    1984-05-01

    Ankyrin is an extrinsic membrane protein in human erythrocytes that links the alpha beta-spectrin-based extrinsic membrane skeleton to the membrane by binding simultaneously to the beta-spectrin subunit and to the transmembrane anion transporter. To analyse the temporal and spatial regulation of assembly of this membrane skeleton, we investigated the kinetics of synthesis and assembly of ankyrin ( goblin ) with respect to those of spectrin in chicken embryo erythroid cells. Electrophoretic analysis of Triton X-100 soluble and cytoskeletal fractions show that at steady state both ankyrin and spectrin are detected exclusively in the cytoskeleton. In contrast, continuous labeling of erythroid cells with [35S]methionine, and immunoprecipitation of ankyrin and alpha- and beta-spectrin, reveals that newly synthesized ankyrin and spectrin are partitioned into both the cytoskeletal and Triton X-100 soluble fractions. The soluble pools of ankyrin and beta-spectrin reach a plateau of labeling within 1 h, whereas the soluble pool of alpha-spectrin is substantially larger and reaches a plateau more slowly, reflecting an approximately 3:1 ratio of synthesis of alpha- to beta-spectrin. Ankyrin and beta-spectrin enter the cytoskeletal fraction within 10 min of labeling, and the amount assembled into the cytoskeletal fraction exceeds the amount present in their respective soluble pools within 1 h of labeling. Although alpha-spectrin enters the cytoskeletal fraction with similar kinetics to beta-spectrin and ankyrin, and in amounts equimolar to beta-spectrin, the amount of cytoskeletal alpha-spectrin does not exceed the amount of soluble alpha-spectrin even after 3 h of labeling. Pulse-chase labeling experiments reveal that ankyrin and alpha- and beta-spectrin assembled into the cytoskeleton exhibit no detectable turnover, whereas the Triton X-100 soluble polypeptides are rapidly catabolized, suggesting that stable assembly of the three polypeptides is dependent upon their

  16. Lipids and Membrane Lateral Organization

    PubMed Central

    Sonnino, Sandro; Prinetti, Alessandro

    2010-01-01

    Shortly after the elucidation of the very basic structure and properties of cellular membranes, it became evident that cellular membranes are highly organized structures with multiple and multi-dimensional levels of order. Very early observations suggested that the lipid components of biological membranes might be active players in the creation of these levels of order. In the late 1980s, several different and diverse experimental pieces of evidence coalesced together giving rise to the lipid raft hypothesis. Lipid rafts became enormously (and, in the opinion of these authors, sometimes acritically) popular, surprisingly not just within the lipidologist community (who is supposed to be naturally sensitive to the fascination of lipid rafts). Today, a PubMed search using the key word “lipid rafts” returned a list of 3767 papers, including 690 reviews (as a term of comparison, searching over the same time span for a very hot lipid-related key word, “ceramide” returned 6187 hits with 799 reviews), and a tremendous number of different cellular functions have been described as “lipid raft-dependent.” However, a clear consensus definition of lipid raft has been proposed only in recent times, and the basic properties, the ruling forces, and even the existence of lipid rafts in living cells has been recently matter of intense debate. The scenario that is gradually emerging from the controversies elicited by the lipid raft hypothesis emphasizes multiple roles for membrane lipids in determining membrane order, that encompass their tendency to phase separation but are clearly not limited to this. In this review, we would like to re-focus the attention of the readers on the importance of lipids in organizing the fine structure of cellular membranes. PMID:21423393

  17. 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

    2016-05-09

    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.

  18. Comparative analysis of the soluble organic matrix of axial skeleton and sclerites of Corallium rubrum: insights for biomineralization.

    PubMed

    Debreuil, J; Tambutté, S; Zoccola, D; Segonds, N; Techer, N; Allemand, D; Tambutté, E

    2011-05-01

    We analysed the soluble organic matrix (SOM) of two biominerals formed by the same organism but differing by their morphological characteristics: the axial skeleton and the sclerites of Corallium rubrum. The results of 1D SDS-PAGE electrophoresis show for the two biominerals that SOM proteins bands have similar apparent molecular weight but differ in quantity. Further analysis by 2D electrophoresis reveals each protein band as a line of spots with different isoelectric points. Our results suggest that each SOM protein band consists of a mix of proteins and/or one unique protein with post-translational modifications. By immunohistochemistry, we show that antibodies raised against the SOM of axial skeleton and sclerites label the SOM of the two biominerals but also label the insoluble organic matrix suggesting the presence of common epitopes between the two biominerals and the two organic fractions.

  19. Mechanical compression insults induce nanoscale changes of membrane-skeleton arrangement which could cause apoptosis and necrosis in dorsal root ganglion neurons.

    PubMed

    Quan, Xin; Guo, Kai; Wang, Yuqing; Huang, Liangliang; Chen, Beiyu; Ye, Zhengxu; Luo, Zhuojing

    2014-01-01

    In a primary spinal cord injury, the amount of mechanical compression insult that the neurons experience is one of the most critical factors in determining the extent of the injury. The ultrastructural changes that neurons undergo when subjected to mechanical compression are largely unknown. In the present study, using a compression-driven instrument that can simulate mechanical compression insult, we applied mechanical compression stimulation at 0.3, 0.5, and 0.7 MPa to dorsal root ganglion (DRG) neurons for 10 min. Combined with atomic force microscopy, we investigated nanoscale changes in the membrane-skeleton, cytoskeleton alterations, and apoptosis induced by mechanical compression injury. The results indicated that mechanical compression injury leads to rearrangement of the membrane-skeleton compared with the control group. In addition, mechanical compression stimulation induced apoptosis and necrosis and also changed the distribution of the cytoskeleton in DRG neurons. Thus, the membrane-skeleton may play an important role in the response to mechanical insults in DRG neurons. Moreover, sudden insults caused by high mechanical compression, which is most likely conducted by the membrane-skeleton, may induce necrosis, apoptosis, and cytoskeletal alterations.

  20. 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.

  1. Heat-induced alterations in monkey erythrocyte membrane phospholipid organization and skeletal protein structure and interactions.

    PubMed

    Kumar, A; Gudi, S R; Gokhale, S M; Bhakuni, V; Gupta, C M

    1990-12-14

    Rhesus monkey erythrocytes were subjected to heating at 50 degrees C for 5-15 min, and the heat-induced effects on the membrane structure were ascertained by analysing the membrane phospholipid organization and membrane skeleton dynamics and interactions in the heated cells. Membrane skeleton dynamics and interactions were determined by measuring the Tris-induced dissociation of the Triton-insoluble membrane skeleton (Triton shells), the spectrin-actin extractability at low ionic strength, spectrin self-association and spectrin binding to normal monkey erythrocyte membrane inside-out vesicles (IOVs). The Tris-induced Triton shell dissociation and spectrin-actin extractability were markedly decreased by the erythrocyte heating. Also, the binding of the heated erythrocyte membrane spectrin-actin with the IOVs was much smaller than that observed with the normal erythrocyte spectrin-actin. Further, the spectrin structure was extensively modified in the heated cells, as compared to the normal erythrocytes. Transbilayer phospholipid organization was ascertained by employing bee venom and pancreatic phospholipases A2, fluorescamine, and Merocyanine 540 as the external membrane probes. The amounts of aminophospholipids hydrolysed by phospholipases A2 or labeled by fluorescamine in intact erythrocytes considerably increased after subjecting them to heating at 50 degrees C for 15 min. Also, the fluorescent dye Merocyanine 540 readily stained the 15-min-heated cells but not the fresh erythrocytes. Unlike these findings, the extent of aminophospholipid hydrolysis in 5-min-heated cells by phospholipases A2 depended on the incubation time. While no change in the membrane phospholipid organization could be detected in 10 min, prolonged incubations led to the increased aminophospholipid hydrolysis. Similarly, fluorescamine failed to detect any change in the transbilayer phospholipid distribution soon after the 5 min heating, but it labeled greater amounts of aminophospholipids in

  2. CaMKII inhibition mitigates ischemia/reperfusion-elicited calpain activation and the damage to membrane skeleton proteins in isolated rat hearts.

    PubMed

    Kong, Ling-Heng; Gu, Xiao-Ming; Wu, Feng; Jin, Zhen-Xiao; Zhou, Jing-Jun

    2017-09-23

    Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been implicated in myocardial ischemia/reperfusion (IR) injury. The aim of this study was to determine the effect of CaMKII on the damage to membrane skeleton proteins, which is an important cause of IR injury. Isolated rat hearts were subjected to 45-min global ischemia/2-h reperfusion. Both KN-62 and KN-93 were used to inhibit CaMKII. Compared with controls, the hearts in the IR group exhibited remarkable myocardial injury area, LDH release, cell apoptosis and contractile dysfunction, along with an increase in the phosphorylation of CaMKII and its substrate phospholamban. Treatment with either KN-62 or KN-93 mitigated both the heart injury and the phosphorylation of CaMKII and phospholamban. The analysis of cell skeleton proteins revealed that IR injury resulted in an increase in the 150-kDa fragments resulting from the degradation of α-fodrin and dystrophin translocating from the sarcolemmal membrane to the cytosol and a decrease in the 220-kDa isoform of ankyrin-B. As expected, Evans blue dye staining showed an increase in membrane permeability or membrane rupture in the IR group. All of these alterations were alleviated by treatment with either KN-62 or KN-93. In addition, both KN-62 and KN-93 blocked the activity and membrane recruitment of calpain, a key protease responsible for destroying cell skeleton proteins during IR injury. In conclusion, our data provide evidence that damage to membrane skeleton proteins via calpain is a destructive downstream event of CaMKII activation in the setting of myocardial IR injury. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    PubMed

    Levental, Kandice R; Levental, Ilya

    2015-01-01

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

  4. 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

  5. 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

    2015-02-05

    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.

  6. Alterations of erythrocyte membrane organization in alcoholics.

    PubMed

    Beaugé, F; Stibler, H; Borg, S

    1987-01-01

    Studies of fluorescence polarization of DPH have shown that erythrocyte membrane "fluidity" and fluidization by ethanol are significantly reduced in alcoholics. By using probes of the polar part of the membrane, ANS and TMA-DPH, in addition to DPH, it was shown in the present study that disturbances also exist in the polar region of the membrane which probably are related to changes in surface glycoconjugates. Furthermore, the acute fluidizing effect of ethanol was correlated with the capacity of the membrane to bind ethanol, which in turn appeared to be linked to the glycans. Chronic ethanol abuse thus causes complex disturbances of membrane organization at different levels of the membrane.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Evidence that red blood cell protein p55 may participate in the skeleton-membrane linkage that involves protein 4.1 and glycophorin C.

    PubMed

    Alloisio, N; Dalla Venezia, N; Rana, A; Andrabi, K; Texier, P; Gilsanz, F; Cartron, J P; Delaunay, J; Chishti, A H

    1993-08-15

    Human erythrocyte p55 is a peripheral membrane protein that contains three distinct domains in its primary structure: an N-terminal domain, an SH3 motif, and a C-terminal guanylate kinase domain. We used naturally mutated red blood cells (RBCs) with primary genetic defects resulting in the absence of protein 4.1 (4.1[-] hereditary elliptocytosis) or glycophorin C (Leach elliptocytosis). The absence of either protein was associated with the absence of p55. On a stoichiometric basis, the reduction in glycophorin C (about 80%) was concomitant to the lack of p55 in RBCs devoid of protein 4.1. Similarly, the reduction of protein 4.1 (about 20%) was equivalent to the absence of p55 in RBCs devoid of glycophorin C. These correlations suggest that p55 is associated, in precise proportions, with the protein 4.1-glycophorin-C complex, linking the skeleton and the membrane. The protein 4.1-glycophorin-C cross-bridge is known to be critically important for the stability and mechanical properties of human RBC plasma membrane. Because isoforms of protein 4.1, glycophorin C, and p55 exist in many tissues, these results provide evidence of a linkage between the skeleton and the membrane that may have implications in many nonerythroid cells.

  12. Biochemical analysis of potential sites for protein 4.1-mediated anchoring of the spectrin-actin skeleton to the erythrocyte membrane.

    PubMed

    Workman, R F; Low, P S

    1998-03-13

    Erythrocyte protein 4.1 has been hypothesized to link the spectrin-actin junctional complex directly to the cytoplasmic domain of glycophorin C, but this bridging function has never been directly demonstrated. Because an alternative protein-mediated bridge between the junctional complex and the cytoplasmic domain of band 3 is also plausible, we have undertaken to characterize the membrane sites to which protein 4.1 can anchor the spectrin and actin skeleton. We demonstrate that proteolytic removal of the cytoplasmic domain of band 3 has minimal effect on the ability of protein 4.1 to promote 125I-labeled spectrin and actin binding to KI-stripped erythrocyte membrane vesicles. We also show that quantitative blockade of all band 3 sites with either monoclonal or polyclonal antibodies to band 3 is equally ineffective in preventing protein 4.1-mediated association of spectrin and actin with the membrane. In contrast, obstruction of protein 4.1 binding to its docking site on the cytoplasmic pole of glycophorin C is demonstrated to reduce the same protein 4.1 bridging function by approximately 85%. We conclude from these data that (i) glycophorin C contributes the primary anchoring site of the protein 4.1-mediated bridge to the spectrin-actin skeleton; (ii) band 3 is incapable of serving the same function; and (iii) additional minor protein 4.1 bridging sites may exist on the human erythrocyte membrane.

  13. Palmitoylation of MPP1 (Membrane-palmitoylated Protein 1)/p55 Is Crucial for Lateral Membrane Organization in Erythroid Cells*

    PubMed Central

    Łach, Agnieszka; Grzybek, Michał; Heger, Elżbieta; Korycka, Justyna; Wolny, Marcin; Kubiak, Jakub; Kolondra, Adam; Bogusławska, Dżamila M.; Augoff, Katarzyna; Majkowski, Michał; Podkalicka, Joanna; Kaczor, Jakub; Stefanko, Adam; Kuliczkowski, Kazimierz; Sikorski, Aleksander F.

    2012-01-01

    S-Acylation of proteins is a ubiquitous post-translational modification and a common signal for membrane association. The major palmitoylated protein in erythrocytes is MPP1, a member of the MAGUK family and an important component of the ternary complex that attaches the spectrin-based skeleton to the plasma membrane. Here we show that DHHC17 is the only acyltransferase present in red blood cells (RBC). Moreover, we give evidence that protein palmitoylation is essential for membrane organization and is crucial for proper RBC morphology, and that the effect is specific for MPP1. Our observations are based on the clinical cases of two related patients whose RBC had no palmitoylation activity, caused by a lack of DHHC17 in the membrane, which resulted in a strong decrease of the amount of detergent-resistant membrane (DRM) material. We confirmed that this loss of detergent-resistant membrane was due to the lack of palmitoylation by treatment of healthy RBC with 2-bromopalmitic acid (2-BrP, common palmitoylation inhibitor). Concomitantly, fluorescence lifetime imaging microscopy (FLIM) analyses of an order-sensing dye revealed a reduction of membrane order after chemical inhibition of palmitoylation in erythrocytes. These data point to a pathophysiological relationship between the loss of MPP1-directed palmitoylation activity and perturbed lateral membrane organization. PMID:22496366

  14. Palmitoylation of MPP1 (membrane-palmitoylated protein 1)/p55 is crucial for lateral membrane organization in erythroid cells.

    PubMed

    Łach, Agnieszka; Grzybek, Michał; Heger, Elzbieta; Korycka, Justyna; Wolny, Marcin; Kubiak, Jakub; Kolondra, Adam; Bogusławska, Dzamila M; Augoff, Katarzyna; Majkowski, Michał; Podkalicka, Joanna; Kaczor, Jakub; Stefanko, Adam; Kuliczkowski, Kazimierz; Sikorski, Aleksander F

    2012-06-01

    S-Acylation of proteins is a ubiquitous post-translational modification and a common signal for membrane association. The major palmitoylated protein in erythrocytes is MPP1, a member of the MAGUK family and an important component of the ternary complex that attaches the spectrin-based skeleton to the plasma membrane. Here we show that DHHC17 is the only acyltransferase present in red blood cells (RBC). Moreover, we give evidence that protein palmitoylation is essential for membrane organization and is crucial for proper RBC morphology, and that the effect is specific for MPP1. Our observations are based on the clinical cases of two related patients whose RBC had no palmitoylation activity, caused by a lack of DHHC17 in the membrane, which resulted in a strong decrease of the amount of detergent-resistant membrane (DRM) material. We confirmed that this loss of detergent-resistant membrane was due to the lack of palmitoylation by treatment of healthy RBC with 2-bromopalmitic acid (2-BrP, common palmitoylation inhibitor). Concomitantly, fluorescence lifetime imaging microscopy (FLIM) analyses of an order-sensing dye revealed a reduction of membrane order after chemical inhibition of palmitoylation in erythrocytes. These data point to a pathophysiological relationship between the loss of MPP1-directed palmitoylation activity and perturbed lateral membrane organization.

  15. MicroCT-based phenomics in the zebrafish skeleton reveals virtues of deep phenotyping in a distributed organ system

    PubMed Central

    Hur, Matthew; Gistelinck, Charlotte A; Huber, Philippe; Lee, Jane; Thompson, Marjorie H; Monstad-Rios, Adrian T; Watson, Claire J; McMenamin, Sarah K; Willaert, Andy; Parichy, David M; Coucke, Paul

    2017-01-01

    Phenomics, which ideally involves in-depth phenotyping at the whole-organism scale, may enhance our functional understanding of genetic variation. Here, we demonstrate methods to profile hundreds of phenotypic measures comprised of morphological and densitometric traits at a large number of sites within the axial skeleton of adult zebrafish. We show the potential for vertebral patterns to confer heightened sensitivity, with similar specificity, in discriminating mutant populations compared to analyzing individual vertebrae in isolation. We identify phenotypes associated with human brittle bone disease and thyroid stimulating hormone receptor hyperactivity. Finally, we develop allometric models and show their potential to aid in the discrimination of mutant phenotypes masked by alterations in growth. Our studies demonstrate virtues of deep phenotyping in a spatially distributed organ system. Analyzing phenotypic patterns may increase productivity in genetic screens, and facilitate the study of genetic variants associated with smaller effect sizes, such as those that underlie complex diseases. PMID:28884682

  16. Dematin, a Component of the Erythrocyte Membrane Skeleton, Is Internalized by the Malaria Parasite and Associates with Plasmodium 14-3-3*

    PubMed Central

    Lalle, Marco; Currà, Chiara; Ciccarone, Fabio; Pace, Tomasino; Cecchetti, Serena; Fantozzi, Luca; Ay, Bernhard; Breton, Catherine Braun; Ponzi, Marta

    2011-01-01

    The malaria parasite invades the terminally differentiated erythrocytes, where it grows and multiplies surrounded by a parasitophorous vacuole. Plasmodium blood stages translocate newly synthesized proteins outside the parasitophorous vacuole and direct them to various erythrocyte compartments, including the cytoskeleton and the plasma membrane. Here, we show that the remodeling of the host cell directed by the parasite also includes the recruitment of dematin, an actin-binding protein of the erythrocyte membrane skeleton and its repositioning to the parasite. Internalized dematin was found associated with Plasmodium 14-3-3, which belongs to a family of conserved multitask molecules. We also show that, in vitro, the dematin-14-3-3 interaction is strictly dependent on phosphorylation of dematin at Ser124 and Ser333, belonging to two 14-3-3 putative binding motifs. This study is the first report showing that a component of the erythrocyte spectrin-based membrane skeleton is recruited by the malaria parasite following erythrocyte infection. PMID:21084299

  17. Image of the Month: Multifocal 68Ga Prostate-Specific Membrane Antigen Ligand Uptake in the Skeleton in a Man With Both Prostate Cancer and Multiple Myeloma.

    PubMed

    Rauscher, Isabel; Maurer, Tobias; Steiger, Katja; Schwaiger, Markus; Eiber, Matthias

    2017-03-31

    Ga prostate-specific membrane antigen (PSMA) HBED-CC PET/CT in a 65-year-old man with first diagnosis of prostate cancer (PC) and a history of multiple myeloma showing multifocal PSMA ligand uptake in the skeleton with corresponding osteolytic lesions in CT. Although osteolytic bone metastases are very rare in PC, PSMA expression in PET raised the suspicion of PC bone metastases. Bone marrow biopsy excluded PC metastases with immunohistochemistry showing endothelial expression of PSMA in small vessels within the myeloma.

  18. Histological investigation of organisms with hard skeletons: a case study of siliceous sponges.

    PubMed

    Hoffmann, F; Janussen, D; Dröse, W; Arp, G; Reitner, J

    2003-01-01

    Siliceous and calcareous sponges commonly are treated with acid to remove the spicules prior to embedding and cutting for histological investigations. Histology of spiculated sponge tissue represents a challenging problem in sponge histotechnology. Furthermore, fluorescence in situ hybridization (FISH), a key method for studying sponge-associated microbes, is not possible after acid treatment. For a broad range of siliceous sponge species, we developed and evaluated methods for embedding in paraffin, methylmethacrylate resins, LR White resin and cryomatrix. Different methods for cutting tissue blocks as well as mounting and staining sections also were tested. Our aim was to enable histological investigations and FISH without prior removal of the spicules. To obtain an overview of tissue and skeleton arrangement, we recommend embedding tissue blocks with LR White resin combined with en bloc staining techniques for large specimens with thick and numerous spicules, but paraffin embedding and subsequent staining for whole small specimens. For FISH on siliceous sponges, we recommend Histocryl embedding if the spicule content is high, but paraffin embedding if it is low. Classical histological techniques are used for detailed tissue examinations.

  19. Organization and function of membrane contact sites.

    PubMed

    Helle, Sebastian C J; Kanfer, Gil; Kolar, Katja; Lang, Alexander; Michel, Agnès H; Kornmann, Benoît

    2013-11-01

    Membrane-bound organelles are a wonderful evolutionary acquisition of the eukaryotic cell, allowing the segregation of sometimes incompatible biochemical reactions into specific compartments with tailored microenvironments. On the flip side, these isolating membranes that crowd the interior of the cell, constitute a hindrance to the diffusion of metabolites and information to all corners of the cell. To ensure coordination of cellular activities, cells use a network of contact sites between the membranes of different organelles. These membrane contact sites (MCSs) are domains where two membranes come to close proximity, typically less than 30nm. Such contacts create microdomains that favor exchange between two organelles. MCSs are established and maintained in durable or transient states by tethering structures, which keep the two membranes in proximity, but fusion between the membranes does not take place. Since the endoplasmic reticulum (ER) is the most extensive cellular membrane network, it is thus not surprising to find the ER involved in most MCSs within the cell. The ER contacts diverse compartments such as mitochondria, lysosomes, lipid droplets, the Golgi apparatus, endosomes and the plasma membrane. In this review, we will focus on the common organizing principles underlying the many MCSs found between the ER and virtually all compartments of the cell, and on how the ER establishes a network of MCSs for the trafficking of vital metabolites and information. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Freely turning over palmitate in erythrocyte membrane proteins is not responsible for the anchoring of lipid rafts to the spectrin skeleton: a study with bio-orthogonal chemical probes.

    PubMed

    Ciana, Annarita; Achilli, Cesare; Hannoush, Rami N; Risso, Angela; Balduini, Cesare; Minetti, Giampaolo

    2013-03-01

    Erythrocyte lipid rafts are anchored to the underlying spectrin membrane skeleton [A. Ciana, C. Achilli, C. Balduini, G. Minetti, On the association of lipid rafts to the spectrin skeleton in human erythrocytes, Biochim. Biophys. Acta 1808 (2011) 183-190]. The nature of this linkage and the molecules involved are poorly understood. The interaction is sensitive to the increase in pH and ionic strength induced by carbonate. Given the role of palmitoylation in modulating the partitioning of certain proteins between various sub-cellular compartments and the plasma membrane, we asked whether palmitoylation of p55, a peripheral protein located at the junctional complex between spectrin-actin-protein 4.1 that anchors the membrane skeleton to the lipid bilayer via the transmembrane protein glycophorin C, could contribute to the anchoring of lipid rafts to the membrane skeleton. We adopted a new, non-radioactive method for studying protein palmitoylation, based on bio-orthogonal chemical analogues of fatty acids, containing an omega-alkynyl group, to metabolically label cell proteins, which are then revealed by a "click chemistry" reaction of the alkynyl moiety with an azide-containing reporter tag. We show that the membrane localization and palmitoylation levels of p55 did not change after carbonate treatment. 2-bromopalmitate and cerulenin, two known palmitoylation inhibitors, completely inhibited p55 palmitoylation, and protein palmitoyl thioesterase-1 (PPT1) reduced it, without affecting the association between lipid rafts and membrane-skeleton, indicating, on the one hand, that p55 palmitoylation is enzymatic, and, on the other, that it is not involved in the modulation of the linkage of lipid rafts to the membrane-skeleton.

  1. 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.

  2. Tryptophan-rich domains of Plasmodium falciparum SURFIN4.2 and Plasmodium vivax PvSTP2 interact with membrane skeleton of red blood cell.

    PubMed

    Zhu, Xiaotong; He, Yang; Liang, Yifan; Kaneko, Osamu; Cui, Liwang; Cao, Yaming

    2017-03-20

    Plasmodium falciparum dramatically alters the morphology and properties of the infected red blood cells (iRBCs). A large group of exported proteins participate in these parasite-host interactions occurring at the iRBC membrane skeleton. SURFIN4.2 is one of iRBC surface protein that belongs to surface-associated interspersed protein (SURFIN) family. Although the intracellular tryptophan-rich domain (WRD) was proposed to be important for the translocation of SURFINs from Maurer's clefts to iRBC surface, the molecular basis of this observation has yet to be defined. The WRDs of P. falciparum SURFIN proteins and their orthologous Plasmodium vivax subtelomeric transmembrane proteins (PvSTPs) show homology to the intracellular regions of PfEMP1 and Pf332, both of which are involved in RBC membrane skeleton interactions, and contribute to malaria pathology. Two transfected lines expressing recombinant SURFINs (NTC-GFP and NTC-4.2WRD2-GFP) of the 3D7 sequence were generated by transfection in P. falciparum. In vitro binding assays were performed by using recombinant WRDs of SURFIN4.2/PvSTP2 and inside-out vesicles (IOVs). The interactions between the recombinant WRDs of SURFIN4.2/PvSTP2 with actin and spectrin were evaluated by the actin spin down assay and an enzyme-linked immunosorbent assay based binding assays, respectively. The recombinant SURFINs (NTC-4.2WRD2-GFP), in which the second WRD from SURFIN4.2 was added back to NTC-GFP, show diffused pattern of fluorescence in the iRBC cytosol. Furthermore, WRDs of SURFIN4.2/PvSTP2 were found to directly interact with the IOVs of RBC, with binding affinities ranging from 0.26 to 0.68 μM, values that are comparable to other reported parasite proteins that bind to the RBC membrane skeleton. Further experiments revealed that the second WRD of SURFIN4.2 bound to F-actin (K d = 5.16 μM) and spectrin (K d = 0.51 μM). Because PfEMP1 and Pf332 also bind to actin and/or spectrin, the authors propose that the interaction

  3. Skeleton-binding protein 1 functions at the parasitophorous vacuole membrane to traffic PfEMP1 to the Plasmodium falciparum–infected erythrocyte surface

    PubMed Central

    Maier, Alexander G.; Rug, Melanie; O'Neill, Matthew T.; Beeson, James G.; Marti, Matthias; Reeder, John; Cowman, Alan F.

    2007-01-01

    A key feature of Plasmodium falciparum, the parasite causing the most severe form of malaria in humans, is its ability to export parasite molecules onto the surface of the erythrocyte. The major virulence factor and variant surface protein PfEMP1 (P falciparum erythrocyte membrane protein 1) acts as a ligand to adhere to endothelial receptors avoiding splenic clearance. Because the erythrocyte is devoid of protein transport machinery, the parasite provides infrastructure for trafficking across membranes it traverses. In this study, we show that the P falciparum skeleton-binding protein 1 (PfSBP1) is required for transport of PfEMP1 to the P falciparum–infected erythrocyte surface. We present evidence that PfSBP1 functions at the parasitophorous vacuole membrane to load PfEMP1 into Maurer clefts during formation of these structures. Furthermore, the major reactivity of antibodies from malaria-exposed multigravid women is directed toward PfEMP1 because this is abolished in the absence of PfSBP1. PMID:17023587

  4. Skeleton-binding protein 1 functions at the parasitophorous vacuole membrane to traffic PfEMP1 to the Plasmodium falciparum-infected erythrocyte surface.

    PubMed

    Maier, Alexander G; Rug, Melanie; O'Neill, Matthew T; Beeson, James G; Marti, Matthias; Reeder, John; Cowman, Alan F

    2007-02-01

    A key feature of Plasmodium falciparum, the parasite causing the most severe form of malaria in humans, is its ability to export parasite molecules onto the surface of the erythrocyte. The major virulence factor and variant surface protein PfEMP1 (P falciparum erythrocyte membrane protein 1) acts as a ligand to adhere to endothelial receptors avoiding splenic clearance. Because the erythrocyte is devoid of protein transport machinery, the parasite provides infrastructure for trafficking across membranes it traverses. In this study, we show that the P falciparum skeleton-binding protein 1 (PfSBP1) is required for transport of PfEMP1 to the P falciparum-infected erythrocyte surface. We present evidence that PfSBP1 functions at the parasitophorous vacuole membrane to load PfEMP1 into Maurer clefts during formation of these structures. Furthermore, the major reactivity of antibodies from malaria-exposed multigravid women is directed toward PfEMP1 because this is abolished in the absence of PfSBP1.

  5. Para-Conjugated Dicarboxylates with Extended Aromatic Skeletons as the Highly Advanced Organic Anodes for K-Ion Battery.

    PubMed

    Li, Chao; Deng, Qijiu; Tan, Haochen; Wang, Chuan; Fan, Cong; Pei, Jingfang; Cao, Bei; Wang, Zhihong; Li, Jingze

    2017-08-23

    A new family of the para-conjugated dicarboxylates embedding in biphenyl skeletons was exploited as the highly advanced organic anodes for K-ion battery. Two members of this family, namely potassium 1,1'-biphenyl-4,4'-dicarboxylate (K2BPDC) and potassium 4,4'-E-stilbenedicarboxylate (K2SBDC), were selectively studied and their detailed redox behaviors in K-ion battery were also clearly unveiled. Both K2BPDC and K2SBDC could exhibit very clear and highly reversible two-electron redox mechanism in K-ion battery, as well as higher potassiation potentials (above 0.3 V vs K(+)/K) when compared to the inorganic anodes of carbon materials recently reported. Meanwhile, the satisfactory specific and rate capacities could be realized for K2BPDC and K2SBDC. For example, the K2BPDC anode could realize the stable rate capacities of 165/143/135/99 mAh g(-1) under the high current densities of 100/200/500/1000 mA g(-1), respectively, after its electronic conductivity was improved by mixing a very small amount of graphene. More impressively, the average specific capacities of ∼75 mAh g(-1) could be maintained for the K2BPDC anode for 3000 cycles under the high current density of 1 A g(-1).

  6. 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.

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  9. Single-component organic conductors based on neutral radicals containing the pyrazino-TCNQ skeleton

    SciTech Connect

    Tsubata, Yoshiaki; Susuki, Takanori; Miyashi, Tsutomu ); Yoshiro Yamashita )

    1992-12-04

    Pyrazino-TCNQ (1a) prepared from 5, 8-diiodoquinoxaline (4a) is, like TCNQ itself, a strong electron acceptor and gives a stable anion radical salt as well as highly conductive charge-transfer crystals with donors. Substituted derivatives 1b-i were similarly prepared from 3,6-diiodo- 1,2-phenylenediamine (5) as a common intermediate, and bulky substituents such as the phenyl or pyridyl groups have very little effect on either the redox properties or planar geometry of 1a. Neutral radicals 3d-g derived from pyridyl-substituted derivatives 1d-g, respectively, are open-shell donor-[pi]-acceptor systems with high electrical amphotericity designed as a new motif for single-component organic conductors. The powder conductivity of 3f was as high as 3.2 [times] 10[sup [minus]5] S cm[sup [minus]1]. 29 refs., 4 figs., 2 tabs.

  10. The nuclear membrane organization of leukotriene synthesis

    PubMed Central

    Mandal, Asim K.; Jones, Phillip B.; Bair, Angela M.; Christmas, Peter; Miller, Douglas; Yamin, Ting-ting D.; Wisniewski, Douglas; Menke, John; Evans, Jilly F.; Hyman, Bradley T.; Bacskai, Brian; Chen, Mei; Lee, David M.; Nikolic, Boris; Soberman, Roy J.

    2008-01-01

    Leukotrienes (LTs) are signaling molecules derived from arachidonic acid that initiate and amplify innate and adaptive immunity. In turn, how their synthesis is organized on the nuclear envelope of myeloid cells in response to extracellular signals is not understood. We define the supramolecular architecture of LT synthesis by identifying the activation-dependent assembly of novel multiprotein complexes on the outer and inner nuclear membranes of mast cells. These complexes are centered on the integral membrane protein 5-Lipoxygenase-Activating Protein, which we identify as a scaffold protein for 5-Lipoxygenase, the initial enzyme of LT synthesis. We also identify these complexes in mouse neutrophils isolated from inflamed joints. Our studies reveal the macromolecular organization of LT synthesis. PMID:19075240

  11. [Morphology and development of the cranium of Felis silvestris f. catus Linné 1758--IV: Visceral skeleton, membrane bones: summary, conclusions and bibliography].

    PubMed

    Timm, S

    1987-01-01

    The present last part of the study on morphology and development of the cranium of Felis silvestris f. catus provides a detailed description and discussion of the development of the visceral skeleton and the membrane bones. Finally, there is given a summary with conclusions of the whole investigation. In Felis 2, the Cartilago Meckeli is still in homocontinuous connection with the Malleus. Probably, only the rostral part of the Cartilago will ossify enchondrally, while the caudal part shows some beginning resorption. In this 95 mm Embryo, the Cartilago Reicherti still remains cartilaginous. A small cartilaginous Spence's cartilage lies in dorsolateral position towards the Chorda tympani. All membrane bones of the adult cranium are present in Felis 1. The following development of the osseous skull towards the stage of Felis 2 is characterized by covering the wide fissures of the side wall and by resorption of certain primordial supporting constructions. The interparietal develops from a paired anlage. In Felis 1 and 2, the cartilago within the pterygoid probably serves as a gliding surface for the M. tensor veli palatini. The dental bone contains some largely extended particles of secondary cartilage.

  12. Analysis of the kinetics of band 3 diffusion in human erythroblasts during assembly of the erythrocyte membrane skeleton

    PubMed Central

    Kodippili, Gayani C.; Spector, Jeff; Kang, Grace E.; Liu, Hui; Wickrema, Amittha; Ritchie, Ken; Low, Philip S.

    2012-01-01

    Summary During definitive erythropoiesis, erythroid precursors undergo differentiation through multiple nucleated states to an enucleated reticulocyte, which loses its residual RNA/organelles to become a mature erythrocyte. Over the course of these transformations, continuous changes in membrane proteins occur, including shifts in protein abundance, rates of expression, isoform prominence, states of phosphorylation, and stability. In an effort to understand when assembly of membrane proteins into an architecture characteristic of the mature erythrocyte occurs, we quantitated the lateral diffusion of the most abundant membrane protein, band 3 (AE1), during each stage of erythropoiesis using single particle tracking. Analysis of the lateral trajectories of individual band 3 molecules revealed a gradual reduction in mobility of the anion transporter as erythroblasts differentiated. Evidence for this progressive immobilization included a gradual decline in diffusion coefficients as determined at a video acquisition rate of 120 frames/s and a decrease in the percentage of compartment sizes >100 nm. Because complete acquisition of the properties of band 3 seen in mature erythrocytes is not observed until circulating erythrocytes are formed, we suggest that membrane maturation involves a gradual and cooperative assembly process that is not triggered by the synthesis of any single protein. PMID:20553270

  13. Analysis of the kinetics of band 3 diffusion in human erythroblasts during assembly of the erythrocyte membrane skeleton.

    PubMed

    Kodippili, Gayani C; Spector, Jeff; Kang, Grace E; Liu, Hui; Wickrema, Amittha; Ritchie, Ken; Low, Philip S

    2010-09-01

    During definitive erythropoiesis, erythroid precursors undergo differentiation through multiple nucleated states to an enucleated reticulocyte, which loses its residual RNA/organelles to become a mature erythrocyte. Over the course of these transformations, continuous changes in membrane proteins occur, including shifts in protein abundance, rates of expression, isoform prominence, states of phosphorylation, and stability. In an effort to understand when assembly of membrane proteins into an architecture characteristic of the mature erythrocyte occurs, we quantitated the lateral diffusion of the most abundant membrane protein, band 3 (AE1), during each stage of erythropoiesis using single particle tracking. Analysis of the lateral trajectories of individual band 3 molecules revealed a gradual reduction in mobility of the anion transporter as erythroblasts differentiated. Evidence for this progressive immobilization included a gradual decline in diffusion coefficients as determined at a video acquisition rate of 120 frames/s and a decrease in the percentage of compartment sizes >100 nm. Because complete acquisition of the properties of band 3 seen in mature erythrocytes is not observed until circulating erythrocytes are formed, we suggest that membrane maturation involves a gradual and cooperative assembly process that is not triggered by the synthesis of any single protein.

  14. The spectrin-ankyrin-4.1-adducin membrane skeleton: adapting eukaryotic cells to the demands of animal life.

    PubMed

    Baines, Anthony J

    2010-08-01

    The cells in animals face unique demands beyond those encountered by their unicellular eukaryotic ancestors. For example, the forces engendered by the movement of animals places stresses on membranes of a different nature than those confronting free-living cells. The integration of cells into tissues, as well as the integration of tissue function into whole animal physiology, requires specialisation of membrane domains and the formation of signalling complexes. With the evolution of mammals, the specialisation of cell types has been taken to an extreme with the advent of the non-nucleated mammalian red blood cell. These and other adaptations to animal life seem to require four proteins--spectrin, ankyrin, 4.1 and adducin--which emerged during eumetazoan evolution. Spectrin, an actin cross-linking protein, was probably the earliest of these, with ankyrin, adducin and 4.1 only appearing as tissues evolved. The interaction of spectrin with ankyrin is probably a prerequisite for the formation of tissues; only with the advent of vertebrates did 4.1 acquires the ability to bind spectrin and actin. The latter activity seems to allow the spectrin complex to regulate the cell surface accumulation of a wide variety of proteins. Functionally, the spectrin-ankyrin-4.1-adducin complex is implicated in the formation of apical and basolateral domains, in aspects of membrane trafficking, in assembly of certain signalling and cell adhesion complexes and in providing stability to otherwise mechanically fragile cell membranes. Defects in this complex are manifest in a variety of hereditary diseases, including deafness, cardiac arrhythmia, spinocerebellar ataxia, as well as hereditary haemolytic anaemias. Some of these proteins also function as tumor suppressors. The spectrin-ankyrin-4.1-adducin complex represents a remarkable system that underpins animal life; it has been adapted to many different functions at different times during animal evolution.

  15. 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...

  16. 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...

  17. Intracellular Localization of Phosphatidylinositide 3-kinase and Insulin Receptor Substrate-1 in Adipocytes: Potential Involvement of a Membrane Skeleton

    PubMed Central

    Clark, Sharon F.; Martin, Sally; Carozzi, Amanda J.; Hill, Michelle M.; James, David E.

    1998-01-01

    Phosphatidylinositide (PI) 3-kinase binds to tyrosyl-phosphorylated insulin receptor substrate-1 (IRS-1) in insulin-treated adipocytes, and this step plays a central role in the regulated movement of the glucose transporter, GLUT4, from intracellular vesicles to the cell surface. PDGF, which also activates PI 3-kinase in adipocytes, has no significant effect on GLUT4 trafficking in these cells. We propose that this specificity may be mediated by differential localization of PI 3-kinase in response to insulin versus PDGF activation. Using subcellular fractionation in 3T3-L1 adipocytes, we show that insulin- and PDGF-stimulated PI 3-kinase activities are located in an intracellular high speed pellet (HSP) and in the plasma membrane (PM), respectively. The HSP is also enriched in IRS-1, insulin-stimulated tyrosyl-phosphorylated IRS-1 and intracellular GLUT4-containing vesicles. Using sucrose density gradient sedimentation, we have been able to segregate the HSP into two separate subfractions: one enriched in IRS-1, tyrosyl-phosphorylated IRS-1, PI 3-kinase as well as cytoskeletal elements, and another enriched in membranes, including intracellular GLUT4 vesicles. Treatment of the HSP with nonionic detergent, liberates all membrane constituents, whereas IRS-1 and PI 3-kinase remain insoluble. Conversely, at high ionic strength, membranes remain intact, whereas IRS-1 and PI 3-kinase become freely soluble. We further show that this IRS-1–PI 3-kinase complex exists in CHO cells overexpressing IRS-1 and, in these cells, the cytosolic pool of IRS-1 and PI 3-kinase is released subsequent to permeabilization with Streptolysin-O, whereas the particulate fraction of these proteins is retained. These data suggest that IRS-1, PI 3-kinase, as well as other signaling intermediates, may form preassembled complexes that may be associated with the actin cytoskeleton. This complex must be in close apposition to the cell surface, enabling access to the insulin receptor and presumably

  18. 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.

  19. Intertwined αβ spectrin meeting helical actin protofilament in the erythrocyte membrane skeleton: wrap-around vs. point-attachment.

    PubMed

    Sche, Paul; Vera, Carlos; Sung, L Amy

    2011-07-01

    Our 3-D model for a junctional complex (JC) in the erythrocyte membrane skeleton proposed that the helical actin protofilament functions as a mechanical axis for three pairs of αβ spectrin (Sp), and each pair wraps around the protofilament in a back-to-back fashion. The distal end of each Sp is further associated with the lipid bilayer by a suspension complex (SC). Here, we detail how splitting and rejoining of αβ Sp around a protofilament may form a loop that sustains and equilibrates tension. Sequential association of β and α Sp solves the challenge of constructing multiple loops along the protofilament, and topological connection facilitates their re-association. The wrap-around model minimizes the strain of the actin binding site on β Sp due to tension, redirection, or sliding of intertwined Sp. Pairing Sp balances the opposing forces and provides a mechanism for elastic recovery. The wrap-around junction thus provides mechanical advantages over a point-attachment junction in maintaining the integrity and functionality of the network. Severing α or β Sp may convert a wrapping-around junction to a point-attachment junction. In that case, a "bow up" motion of JC during deformation may disturb or flip the overlaid lipid bilayer, and mark stressed erythrocytes for phagocytosis.

  20. 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.

  1. 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.

  2. 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.

  3. Review of hydrophilic PP membrane for organic waste removal

    NASA Astrophysics Data System (ADS)

    Ariono, Danu; Wardani, Anita Kusuma

    2017-05-01

    The acceleration of industrialization in developing countries has given an impact of environmental pollution rapidly, such as contamination of groundwater with organic waste. To solve this problem, some membrane techniques have been performed to remove organic waste from water, such as membrane contactors, membrane bioreactors, and supported liquid membranes. Polypropylene (PP) membrane is one of the promising candidates for these membrane processes due to its chemical stability, low cost, good mechanical resistance, and being easily available. However, different processes require membranes with different surface properties. Hydrophobic PP membranes with excellent chemical stability can be directly used in membrane contactors, in which the organic phase wets the porous membrane and slightly excessive pressure applied to the other phase. On the other hand, hydrophilization of PP membrane is necessary for some other processes, such as for fouling reduction on membrane bioreactors due to organic matters deposition. The aim of this paper is to give a brief overview of removal of organic waste by PP membrane. Moreover, the effects of PP surface hydrophilization on antifouling properties are also discussed.

  4. Organic fluid permeation through fluoropolymer membranes

    DOEpatents

    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.

  5. 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

  6. The membrane organization of leukotriene synthesis

    PubMed Central

    Mandal, Asim K.; Skoch, Jesse; Bacskai, Brian J.; Hyman, Bradley T.; Christmas, Peter; Miller, Douglas; Yamin, Ting-ting D.; Xu, Shihua; Wisniewski, Douglas; Evans, Jilly F.; Soberman, Roy J.

    2004-01-01

    Cell signaling leading to the formation of leukotriene (LT)C4 requires the localization of the four key biosynthetic enzymes on the outer nuclear membrane and endoplasmic reticulum. Whether any macromolecular organization of these proteins exists is unknown. By using fluorescence lifetime imaging microscopy and biochemical analysis, we demonstrate the presence of two distinct multimeric complexes that regulate the formation of LTs in RBL-2H3 cells. One complex consists of multimers of LTC4 synthase and the 5-lipoxygenase activating protein (FLAP). The second complex consists of multimers of FLAP. Surprisingly, all LTC4 synthase was found to be in association with FLAP. The results indicate that the formation of LTC4 and LTB4 may be determined by the compartmentalization of biosynthetic enzymes in discrete molecular complexes. PMID:15084748

  7. 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

  8. X-ray - skeleton

    MedlinePlus

    ... medlineplus.gov/ency/article/003381.htm X-ray - skeleton To use the sharing features on this page, ... ray views may be uncomfortable. If the whole skeleton is being imaged, the test usually takes 1 ...

  9. 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

  10. [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.

  11. 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.

  12. 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

  13. 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

  14. Rejection of trace organic compounds by high-pressure membranes.

    PubMed

    Kim, T U; Amy, G; Drewes, J E

    2005-01-01

    High-pressure membranes, encompassing reverse osmosis (RO), nanofiltration (NF), and low-pressure RO, may provide an effective treatment barrier for trace organic compounds including disinfection by-products (DBPs), pesticides, solvents, endocrine disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs). The objective is to develop a mechanistic understanding of the rejection of trace organic compounds by high-pressure membranes, based on an integrated framework of compound properties, membrane properties, and operational conditions. Eight trace organic compounds, four DBPs and four chlorinated (halogenated) solvents, are being emphasized during an initial study, based on considerations of compound properties, occurrence, and health effects (regulations). Four polyamide FilmTec membranes; three reverse osmosis/RO (BW-400, LE-440, XLE-440) and one nanofiltration/NF (NF-90); are being characterized according to pure water permeability (PWP), molecular weight cutoff (MWCO), hydrophobicity (contact angle), and surface charge (zeta potential). It is noteworthy that rejections of compounds of intermediate hydrophobicity by the candidate membranes were observed to be less than salt rejections reported for these membranes, suggesting that transport of these solutes through these membranes is facilitated by solute-membrane interactions. We are continuing with diffusion cell measurements to describe solute-membrane interactions by estimation of diffusion coefficients through membranes pores, either hindered or facilitated.

  15. Importance of the hexagonal lipid phase in biological membrane organization

    PubMed Central

    Jouhet, Juliette

    2013-01-01

    Domains are present in every natural membrane. They are characterized by a distinctive protein and/or lipid composition. Their size is highly variable from the nano- to the micrometer scale. The domains confer specific properties to the membrane leading to original structure and function. The determinants leading to domain organization are therefore important but remain obscure. This review presents how the ability of lipids to organize into hexagonal II or lamellar phases can promote particular local structures within membranes. Since biological membranes are composed of a mixture of lipids, each with distinctive biophysical properties, lateral and transversal sorting of lipids can promote creation of domains inside the membrane through local modulation of the lipid phase. Lipid biophysical properties have been characterized for long based on in vitro analyses using non-natural lipid molecules; their re-examinations using natural lipids might open interesting perspectives on membrane architecture occurring in vivo in various cellular and physiological contexts. PMID:24348497

  16. Coal gasification process wastewater reusability: separation of organics by membranes

    SciTech Connect

    Bhattacharyya, D.; Kermode, R.I.; Dickinson, R.L.

    1983-02-01

    The developing coal-gasification technologies generate gaseous process streams laden with water-soluble species such as H/sub 2/S, NH/sub 3/, HCN, phenols, cresols etc. The primary raw gas clean-up (gas quenching) results in large volumes of highly contaminated wastewaters. The development of a membrane separation process for the removal of selected organics, salts, and scale-forming compounds from stripped coal-conversion process wastewaters, will minimise surface-water pollution and decrease water consumption by permeate recycling. The recent industrial development of non-cellulosic thin-film composite membranes has provided membranes with high salt and low molecular weight organic separation characteristics and insignificant compaction problems. The low pressure membranes (used for brackish water) have definite advantages in terms of energy saving and lower capital cost. The composite membranes perform better than cellulose-acetate membranes. 24 references.

  17. 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.

  18. 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

  19. Amphiphobic Polytetrafluoroethylene Membranes for Efficient Organic Aerosol Removal.

    PubMed

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

    2016-04-06

    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.

  20. 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

  1. 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.

  2. Separation membranes. Interfacial microfluidic processing of metal-organic framework hollow fiber membranes.

    PubMed

    Brown, Andrew J; Brunelli, Nicholas A; Eum, Kiwon; Rashidi, Fereshteh; Johnson, J R; Koros, William J; Jones, Christopher W; Nair, Sankar

    2014-07-04

    Molecular sieving metal-organic framework (MOF) membranes have great potential for energy-efficient chemical separations, but a major hurdle is the lack of a scalable and inexpensive membrane fabrication mechanism. We describe a route for processing MOF membranes in polymeric hollow fibers, combining a two-solvent interfacial approach for positional control over membrane formation (at inner and outer surfaces, or in the bulk, of the fibers), a microfluidic approach to replenishment or recycling of reactants, and an in situ module for membrane fabrication and permeation. We fabricated continuous molecular sieving ZIF-8 membranes in single and multiple poly(amide-imide) hollow fibers, with H2/C3H8 and C3H6/C3H8 separation factors as high as 370 and 12, respectively. We also demonstrate positional control of the ZIF-8 films and characterize the contributions of membrane defects and lumen bypass.

  3. Mechanisms of Ras membrane organization and signaling

    PubMed Central

    Abankwa, Daniel; Gorfe, Alemayehu A.; Hancock, John F.

    2009-01-01

    Understanding the signalling function of Ras GTPases has been the focus of much research for over 20 years. Both the catalytic domain and the membrane anchoring C terminal hypervariable region (HVR) of Ras are necessary for its cellular function. However, while the highly conserved catalytic domain has been characterized in atomic detail, the structure of the full-length membrane-bound Ras has remained elusive. Lack of structural knowledge on the full-length protein limited our understanding of Ras signalling. For example, structures of the Ras catalytic domain solved in complex with effectors do not provide a basis for the functional specificity of different Ras isoforms. Recent molecular dynamics simulations in combination with biophysical and cell biological experiments have shown that the HVR and parts of the G domain cofunction with the lipid tails to anchor H-ras to the plasma membrane. In the GTP-bound state, H-ras adopts an orientation that allows read out by Ras effectors and translation into corresponding MAPK signalling. Here we discuss details of an analysis that suggests a novel balance model for Ras functioning. The balance model rationalizes Ras membrane orientation and may help explain isoform specific interactions of Ras with its effectors and modulators. PMID:18758236

  4. 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.

  5. 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…

  6. 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…

  7. Cholesterol-dependent thermotropic behavior and organization of neuronal membranes.

    PubMed

    Reddy, S Thirupathi; Shrivastava, Sandeep; Mallesham, K; Chattopadhyay, Amitabha

    2016-11-01

    The composition of neuronal membranes is unique with diverse lipid composition due to evolutionary requirement. The organization and dynamics of neuronal membranes are crucial for efficient functioning of neuronal receptors. We have previously established hippocampal membranes as a convenient natural source for exploring lipid-protein interactions, and organization of neuronal receptors. Keeping in mind the pathophysiological role of neuronal cholesterol, in this work, we used differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) to explore thermotropic phase behavior and organization (thickness) of hippocampal membranes under conditions of varying cholesterol content. Our results show that the apparent phase transition temperature of hippocampal membranes displays characteristic linear dependence on membrane cholesterol content. These results are in contrast to earlier results with binary lipid mixtures containing cholesterol where phase transition temperature was found to be not significantly dependent on cholesterol concentration. Interestingly, SAXS data showed that hippocampal membrane thickness remained more or less invariant, irrespective of cholesterol content. We believe that these results constitute one of the early reports on the thermotropic phase behavior and organizational characterization of hippocampal membranes under varying cholesterol content. These results could have implications in the functioning of neuronal receptors in healthy and diseased states. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. 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

  9. Morphological comparison of five species of poison dart frogs of the genus Ranitomeya (Anura: Dendrobatidae) including the skeleton, the muscle system and inner organs.

    PubMed

    Krings, Markus; Klein, Benjamin; Heneka, Markus J; Rödder, Dennis

    2017-01-01

    The morphology of larvae stages of most amphibians are often completely different than in adults. Tadpole descriptions have historically been based on external characters like morphometrics, color pattern and oral disc structure. Other papers described anatomical details by the use of dissections. The increase in micro-CT scanning technology provides an opportunity to quantify and describe in detail internal characters like skeleton, musculature and organs. To date, no such tadpole descriptions exist for the well-studied Neotropical poison dart frog genus Ranitomeya (Anura: Dendrobatidae). Here we provide descriptions of the internal skeletal, musculature and organ structures of five Ranitomeya species and then provide morphological comparisons. Contrary to previous observations, closely related species display several morphological differences. For example, we observed considerable variation in chondrocranial characters, the extent of cranial ossifications, the appearance of some cranial muscles and the arrangement of inner organs. Further studies on the tadpole morphology of more species of Ranitomeya and other dendrobatid genera are needed to enable us to understand the complete morphological variation in this group.

  10. Morphological comparison of five species of poison dart frogs of the genus Ranitomeya (Anura: Dendrobatidae) including the skeleton, the muscle system and inner organs

    PubMed Central

    Krings, Markus; Klein, Benjamin; Heneka, Markus J.

    2017-01-01

    The morphology of larvae stages of most amphibians are often completely different than in adults. Tadpole descriptions have historically been based on external characters like morphometrics, color pattern and oral disc structure. Other papers described anatomical details by the use of dissections. The increase in micro-CT scanning technology provides an opportunity to quantify and describe in detail internal characters like skeleton, musculature and organs. To date, no such tadpole descriptions exist for the well-studied Neotropical poison dart frog genus Ranitomeya (Anura: Dendrobatidae). Here we provide descriptions of the internal skeletal, musculature and organ structures of five Ranitomeya species and then provide morphological comparisons. Contrary to previous observations, closely related species display several morphological differences. For example, we observed considerable variation in chondrocranial characters, the extent of cranial ossifications, the appearance of some cranial muscles and the arrangement of inner organs. Further studies on the tadpole morphology of more species of Ranitomeya and other dendrobatid genera are needed to enable us to understand the complete morphological variation in this group. PMID:28235032

  11. 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.

  12. 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

  13. Plasma membrane-associated platforms: dynamic scaffolds that organize membrane-associated events.

    PubMed

    Astro, Veronica; de Curtis, Ivan

    2015-03-10

    Specialized regions of the plasma membrane dedicated to diverse cellular processes, such as vesicle exocytosis, extracellular matrix remodeling, and cell migration, share a few cytosolic scaffold proteins that associate to form large plasma membrane-associated platforms (PMAPs). PMAPs organize signaling events and trafficking of membranes and molecules at specific membrane domains. On the basis of the intrinsic disorder of the proteins constituting the core of these PMAPs and of the dynamics of these structures at the periphery of motile cells, we propose a working model for the assembly and turnover of these platforms. Copyright © 2015, American Association for the Advancement of Science.

  14. 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

    2016-03-08

    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. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Reduced Graphene Oxide Membranes for Ultrafast Organic Solvent Nanofiltration.

    PubMed

    Huang, Liang; Chen, Ji; Gao, Tiantian; Zhang, Miao; Li, Yingru; Dai, Liming; Qu, Liangti; Shi, Gaoquan

    2016-10-01

    Solvated reduced graphene oxide (S-rGO) membranes are stable in organic solvents, and strong acidic, alkaline, or oxidative media. They show high rejections to small molecules with charges the same as that of S-rGO coatings or neutral molecules larger than 3.4 nm, while retaining their high permeances to organic solvents.

  20. Organic ionic salt draw solutions for osmotic membrane bioreactors.

    PubMed

    Bowden, Katie S; Achilli, Andrea; Childress, Amy E

    2012-10-01

    This investigation evaluates the use of organic ionic salt solutions as draw solutions for specific use in osmotic membrane bioreactors. Also, this investigation presents a simple method for determining the diffusion coefficient of ionic salt solutions using only a characterized membrane. A selection of organic ionic draw solutions underwent a desktop screening process before being tested in the laboratory and evaluated for performance using specific salt flux (reverse salt flux per unit water flux), biodegradation potential, and replenishment cost. Two of the salts were found to have specific salt fluxes three to six times lower than two commonly used inorganic draw solutions, NaCl and MgCl(2). All of the salts tested have organic anions with the potential to degrade in the bioreactor as a carbon source and aid in nutrient removal. Results demonstrate the potential benefits of organic ionic salt draw solutions over currently implemented inorganics in osmotic membrane bioreactor systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Aquaporins and membrane diffusion of CO2 in living organisms.

    PubMed

    Kaldenhoff, Ralf; Kai, Lei; Uehlein, Norbert

    2014-05-01

    Determination of CO2 diffusion rates in living cells revealed inconsistencies with existing models about the mechanisms of membrane gas transport. Mainly, these discrepancies exist in the determined CO2 diffusion rates of bio-membranes, which were orders of magnitudes below those for pure lipid bilayers or theoretical considerations as well as in the observation that membrane insertion of specific aquaporins was rescuing high CO2 transport rates. This effect was confirmed by functional aquaporin protein analysis in heterologous expression systems as well as in bacteria, plants and partly in mammals. This review summarizes the arguments in favor of and against aquaporin facilitated membrane diffusion of CO2 and reports about its importance for the physiology of living organisms. Most likely, the aquaporin tetramer forming an additional fifth pore is required for CO2 diffusion facilitation. Aquaporin tetramer formation, membrane integration and disintegration could provide a mechanism for regulation of cellular CO2 exchange. The physiological importance of aquaporin mediated CO2 membrane diffusion could be shown for plants and cyanobacteria and partly for mammals. Taking the mentioned results into account, consequences for our current picture of cell membrane transport emerge. It appears that in some or many instances, membranes might not be as permeable as it was suggested by current bio-membrane models, opening an additional way of controlling the cellular influx or efflux of volatile substances like CO2. This article is part of a Special Issue entitled Aquaporins. © 2013.

  2. 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

  3. New insights into erythrocyte membrane organization and microelasticity.

    PubMed

    Discher, D E

    2000-03-01

    The erythrocyte membrane's ability to withstand the stresses of circulation has its origins in various levels of structural organization. Central to this membrane's structure-function relationships is a quasi-two-dimensional meshwork of spectrin-actin-protein 4.1 that imparts a resilence to the overlying plasma membrane. New insights into the nonlinear microelasticity of this substructure are being provided by experiments that range from elegant atomic force microscopy tests of single spectrin chains to patterned photobleaching of the micropipette-deformed network. Breakthroughs in atomic level structure determinations are further complemented by emerging biophysical studies of transgenically engineered mice lacking specific erythrocyte membrane proteins. Recent theoretical efforts (computational approaches most notably) also have begun to correlate molecular scale aspects of structure with mechanical measures. All of this recent activity in the biophysics of erythrocyte structure-function is certain to challenge and refine some of the most basic tenets in cell membrane structure-function.

  4. 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.

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

    PubMed Central

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

    2016-01-01

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

  6. 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

    2016-04-06

    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.

  7. [Effect of charged ultrafiltration membrane on natural organic matter removal and membrane fouling].

    PubMed

    Hou, Juan; Shao, Jia-Hui; He, Yi-Liang

    2010-06-01

    With the deterioration of water pollution and stringency of water standards, ultrafiltration (UF) has become one of the best alternatives replacing conventional drinking water treatment technologies. However, UF is not very effectively to remove natural organic matter (NOM) due to the comparatively large pore size compared to the size of NOM. Fouling issue is another factor that restricts its widespread application. The rejection coefficient and flux decline during ultrafiltration of humic acid (HA) and raw water through neutral unmodified and negatively charge-modified regenerated cellulose (RC) membranes were investigated, and the analysis for membrane resistance was provided. The initial removal rate for HA is 59% and the flux decline is 32% on neutral unmodified RC membrane with MWCO of 100 x 10(3), while the initial removal rate for HA increases to 92% and the flux decline decreases to 25% on negatively charge-modified RC membrane. Compared to neutral unmodified RC membrane, the removal rate for NOM on negatively charge-modified RC membrane increases 20% and the flux decline decreases 12%. Results indicated that charged UF membrane could be an effective way for better removal of NOM and reduction of the membrane fouling due to the electrostatic interaction with the combination effect of membrane pore size.

  8. Chapter 6: cubic membranes the missing dimension of cell membrane organization.

    PubMed

    Almsherqi, Zakaria A; Landh, Tomas; Kohlwein, Sepp D; Deng, Yuru

    2009-01-01

    Biological membranes are among the most fascinating assemblies of biomolecules: a bilayer less than 10 nm thick, composed of rather small lipid molecules that are held together simply by noncovalent forces, defines the cell and discriminates between "inside" and "outside", survival, and death. Intracellular compartmentalization-governed by biomembranes as well-is a characteristic feature of eukaryotic cells, which allows them to fulfill multiple and highly specialized anabolic and catabolic functions in strictly controlled environments. Although cellular membranes are generally visualized as flat sheets or closely folded isolated objects, multiple observations also demonstrate that membranes may fold into "unusual", highly organized structures with 2D or 3D periodicity. The obvious correlation of highly convoluted membrane organizations with pathological cellular states, for example, as a consequence of viral infection, deserves close consideration. However, knowledge about formation and function of these highly organized 3D periodic membrane structures is scarce, primarily due to the lack of appropriate techniques for their analysis in vivo. Currently, the only direct way to characterize cellular membrane architecture is by transmission electron microscopy (TEM). However, deciphering the spatial architecture solely based on two-dimensionally projected TEM images is a challenging task and prone to artifacts. In this review, we will provide an update on the current progress in identifying and analyzing 3D membrane architectures in biological systems, with a special focus on membranes with cubic symmetry, and their potential role in physiological and pathophysiological conditions. Proteomics and lipidomics approaches in defined experimental cell systems may prove instrumental to understand formation and function of 3D membrane morphologies.

  9. Capacities of membrane lipids to accumulate neutral organic chemicals.

    PubMed

    Endo, Satoshi; Escher, Beate I; Goss, Kai-Uwe

    2011-07-15

    Lipids have been considered as the predominant components for bioaccumulation of organic chemicals. However, differences in accumulation properties between different types of lipid (e.g., storage and membrane lipids) have rarely been considered. Moreover, in view of toxic effects on organisms, chemical accumulation specifically in biological membranes is of particular importance. In this review article, partition coefficients of 240 neutral organic compounds between liposomes (phospholipid membrane vesicles) and water (K(lipw)), reported in the literature or measured additionally for this work, were evaluated. Values of log K(lipw) and log K(ow) (octanol-water partition coefficients) differ by 0.4 on average. Polyparameter linear free energy relationships (PP-LFERs) can describe the log K(lipw) data even better (standard deviations = 0.28-0.31) than the log K(ow) model. Recent experimental data for highly hydrophobic compounds fit well to the PP-LFERs and do not indicate the existence of a previously postulated "hydrophobicity cutoff". Predictive approaches based only on the molecular structure (KOWWIN, SPARC, COSMOthermX, COSMOmic) were also evaluated for K(lipw) prediction. The PP-LFERs revealed that partition coefficients into membrane lipids can be two log units higher than those into storage lipids for H-bond donor compounds, suggesting that distinguishing between the two lipids is necessary to account for the bioaccumulation of these compounds, and that tissues rich in membrane lipids (e.g., kidneys, liver) instead of fat tissue can be the primary phase for accumulation.

  10. Production of organic nanoparticles by using nanoporous membranes

    NASA Astrophysics Data System (ADS)

    Tuz, A. A.; Şimşek, A. K.; Kazanci, M.

    2017-02-01

    In this research, organic nanoparticles are produced by using different nanoporous membranes with different diameters in different solutions. In production; two liquids, a feed solution and a receiver solution, are seperated by a nanoporous polycarbonate tracketched (PCTE) membrane. The feed solution is pumped through the membrane into the receiver solution. The feed solution contained biopolymers dissolved in HCl and the receiver solution contained NaOH. pH change is used as precipitation method. Chitosan, collagen and alginic acid sodium salt from brown algae are used as biomaterials in order to obtain nanoparticles. Different sized nanoporous membranes are used to find the ideal pore and particle sizes. Nanoparticles are illustrated by SEM and sphere-shaped nanoparticles with different diameters and needle shaped structures are observed.

  11. Metal-organic frameworks for membrane-based separations

    NASA Astrophysics Data System (ADS)

    Denny, Michael S.; Moreton, Jessica C.; Benz, Lauren; Cohen, Seth M.

    2016-12-01

    As research into metal-organic frameworks (MOFs) enters its third decade, efforts are naturally shifting from fundamental studies to applications, utilizing the unique features of these materials. Engineered forms of MOFs, such as membranes and films, are being investigated to transform laboratory-synthesized MOF powders to industrially viable products for separations, chemical sensors and catalysts. Following encouraging demonstrations of gas separations using MOF-based membranes, liquid-phase separations are now being explored in an effort to build effective membranes for these settings. In this Review, we highlight MOF applications that are in their nascent stages, specifically liquid-phase separations using MOF-based mixed-matrix membranes. We also highlight the analytical techniques that provide important insights into these materials, particularly at surfaces and interfaces, to better understand MOFs and their interactions with other materials, which will ultimately lead to their use in advanced technologies.

  12. Coalification process waste water reusability: separation of organics by membranes

    SciTech Connect

    Bhattacharyya, D.; Kermode, R.I.; Dickinson, R.L.

    1983-02-01

    The overall objective of this investigation is to provide a critical evaluation of the current information concerning coal-gasification wastewaters and to establish experimentally the extent of separation of phenolics and polynuclear aromatic hydrocarbons (from single and multi-solute synthetic systems) by low-and high-pressure composite membranes. The compounds selected for experimental investigation were: phenol, O-cresol, 2,3-dimethylphenol, catechol, resorcinol, 2-naphthol, naphthalene, and indole. The development of membrane separation processes is gaining considerable importance because of the feasibility of simultaneous removal of organics and inorganic dissolved solids. Cellulose-acetate membranes developed for desalination processes show no rejection of phenolics; however, recently developed thin-film, noncellulosic composite membranes (even at low-pressure operation) may be useful in gasification wastewater reuse schemes. 24 references, 11 figures, 5 tables.

  13. [Effect of different organic fraction on membrane flux declines].

    PubMed

    Zhou, Xian-Jiao; Dong, Bing-Zhi

    2009-02-15

    Organic matter in the tap water was isolated into strongly hydrophobic acids, weakly hydrophobic acids, charged hydrophilic and neutral hydrophilic by DAX-8, XAD-4 and IRA-958 synthetic resins. Filtration tests using polyvinylidene fluoride (PVDF), polyethersulphone (PES) and cellulose acetate (CA) membranes were conducted to investigate the contribution of different organic fractions to membrane fouling. The results show that in filtration of raw water, flux declines with PES, PVDF and CA membrane are 67%, 59% and 19% of the initial flux, indicating that the more hydrophobic membrane resulted in more severe fouling. For the effect of different fractions on flux, flux decline with neutral hydrophilic is 41%-75% of the initial flux, whereas weakly hydrophobic acids is 6%-33%, suggesting that neutral hydrophilic has a great impact on filtration flux. Among three membranes tested, CA membrane shows the lowest flux decline compared with other membranes in spite of rejection of as high as 14.69% of neutral hydrophilic, suggesting that the extent of flux decline may not be associated with the total amount of NOM removed. The mechanism of fouling was discussed and found that the neutral hydrophilic fraction with greater than 3 x 10(4) of molecular weight caused a significant flux decline, through blocking the pore for the MF or UF having greater relative molecular mass cut-off (MWCO), but resulted in a little impact on flux with the UF having lower MWCO, through forming cake layer on the surface of membrane due to not entering the inside of pore.

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

    PubMed

    Kraft, Mary L

    2013-09-01

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

  15. 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 ...

  16. 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 ...

  17. Permeability of low molecular weight organics through nanofiltration membranes.

    PubMed

    Meylan, Sébastien; Hammes, Frederik; Traber, Jacqueline; Salhi, Elisabeth; von Gunten, Urs; Pronk, Wouter

    2007-09-01

    The removal of natural organic matter (NOM) using nanofiltration (NF) is increasingly becoming an option for drinking water treatment. Low molecular weight (LMW) organic compounds are nevertheless only partially retained by such membranes. Bacterial regrowth and biofilm formation in the drinking water distribution system is favoured by the presence of such compounds, which in this context are considered as the assimilable organic carbon (AOC). In this study, the question of whether NF produces microbiologically stable water was addressed. Two NF membranes (cut-off of about 300Da) were tested with different natural and synthetic water samples in a cross-flow filtration unit. NOM was characterised by liquid chromatography with organic carbon detection (LC-OCD) using a size-exclusion column in addition to specific organic acid measurements, while AOC was measured in a batch growth bioassay. Similarly to high molecular weight organic compounds like polysaccharides or humic substances that have a permeability lower than 1%, charged LMW organic compounds were efficiently retained by the NF membranes tested and showed a permeability lower than 3%. However, LMW neutrals and hydrophobic organic compounds permeate to a higher extent through the membranes and have a permeability of up to 6% and 12%, respectively. Furthermore, AOC was poorly retained by NF and the apparent AOC concentration measured in the permeated water was above the proposed limit for microbiologically stable water. This indicates that the drinking water produced by NF might be biologically unstable in the distribution system. Nevertheless, in comparison with the raw water, NF significantly reduced the AOC concentration.

  18. Permeability of uncharged organic molecules in reverse osmosis desalination membranes.

    PubMed

    Dražević, Emil; Košutić, Krešimir; Svalina, Marin; Catalano, Jacopo

    2017-06-01

    Reverse osmosis (RO) membranes are primarily designed for removal of salts i.e. for desalination of brackish and seawater, but they have also found applications in removal of organic molecules. While it is clear that steric exclusion is the dominant removal mechanism, the fundamental explanation for how and why the separation occurs remains elusive. Until recently there was no strong microscopic evidences elucidating the structure of the active polyamide layers of RO membranes, and thus they have been conceived as "black boxes"; or as an array of straight capillaries with a distribution of radii; or as polymers with a small amount of polymer free domains. The knowledge of diffusion and sorption coefficients is a prerequisite for understanding the intrinsic permeability of any organic solute in any polymer. At the same time, it is technically challenging to accurately measure these two fundamental parameters in very thin (20-300 nm) water-swollen active layers. In this work we have measured partition and diffusion coefficients and RO permeabilities of ten organic solutes in water-swollen active layers of two types of RO membranes, low (SWC4+) and high flux (XLE). We deduced from our results and recent microscopic studies that the solute flux of organic molecules in polyamide layer of RO membranes occurs in two domains, dense polymer (the key barrier layer) and the water filled domains. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Cubic membranes: a legend beyond the Flatland* of cell membrane organization

    PubMed Central

    Almsherqi, Zakaria A.; Kohlwein, Sepp D.; Deng, Yuru

    2006-01-01

    Cubic membranes represent highly curved, three-dimensional nanoperiodic structures that correspond to mathematically well defined triply periodic minimal surfaces. Although they have been observed in numerous cell types and under different conditions, particularly in stressed, diseased, or virally infected cells, knowledge about the formation and function of nonlamellar, cubic structures in biological systems is scarce, and research so far is restricted to the descriptive level. We show that the “organized smooth endoplasmic reticulum” (OSER; Snapp, E.L., R.S. Hegde, M. Francolini, F. Lombardo, S. Colombo, E. Pedrazzini, N. Borgese, and J. Lippincott-Schwartz. 2003. J. Cell Biol. 163:257–269), which is formed in response to elevated levels of specific membrane-resident proteins, is actually the two-dimensional representation of two subtypes of cubic membrane morphology. Controlled OSER induction may thus provide, for the first time, a valuable tool to study cubic membrane formation and function at the molecular level. PMID:16785319

  20. Comparative molecular biological analysis of membrane transport genes in organisms

    PubMed Central

    Nagata, Toshifumi; Iizumi, Shigemi; Satoh, Kouji

    2008-01-01

    Comparative analyses of membrane transport genes revealed many differences in the features of transport homeostasis in eight diverse organisms, ranging from bacteria to animals and plants. In bacteria, membrane-transport systems depend mainly on single genes encoding proteins involved in an ATP-dependent pump and secondary transport proteins that use H+ as a co-transport molecule. Animals are especially divergent in their channel genes, and plants have larger numbers of P-type ATPase and secondary active transporters than do other organisms. The secondary transporter genes have diverged evolutionarily in both animals and plants for different co-transporter molecules. Animals use Na+ ions for the formation of concentration gradients across plasma membranes, dependent on secondary active transporters and on membrane voltages that in turn are dependent on ion transport regulation systems. Plants use H+ ions pooled in vacuoles and the apoplast to transport various substances; these proton gradients are also dependent on secondary active transporters. We also compared the numbers of membrane transporter genes in Arabidopsis and rice. Although many transporter genes are similar in these plants, Arabidopsis has a more diverse array of genes for multi-efflux transport and for response to stress signals, and rice has more secondary transporter genes for carbohydrate and nutrient transport. Electronic supplementary material The online version of this article (doi:10.1007/s11103-007-9287-z) contains supplementary material, which is available to authorized users. PMID:18293089

  1. Influence of organic solvent mixtures on biological membranes.

    PubMed Central

    Gustafson, C; Tagesson, C

    1985-01-01

    A simple experimental model was used to study the influence of organic solvents and solvent mixtures on the integrity of biological membranes. Radiolabelled membranes were prepared biosynthetically by growing Escherichia coli in the presence of 14C-oleic acid; the bulk of the radioactivity was incorporated into 14C-phosphatidylethanolamine, the predominant phospholipid species in E coli membranes. The radiolabelled bacteria were incubated at 37 degrees C in the presence of solvent, and the mixture filtrated through a Millipore 0.45 micron filter. This filtration retained radiolabel associated with the bacteria, and only radiolabel released as a result of solvent action was allowed through the filter. The radioactivity in the filtrate was then counted and expressed as a percentage of the total radioactivity. Results showed that aliphatic alcohols released membrane constituents in relation to their hydrocarbon chain length (1-propanol greater than 2-propanol greater than ethanol greater than methanol); the effects of aliphatic alcohols were potentiated by acetone, ethyl methyl ketone, ethylene glycol, and N,N'-dimethylformamide, and the effects of ethanol were potentiated by 1-butanol, benzyl alcohol, and ethylacetate. These findings point to the possibility that certain mixtures of organic solvents are more damaging to membranes than the components of the mixture would indicate, and suggest that the experimental model used might help in showing mixtures that are particularly harmful. PMID:3899160

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

    SciTech Connect

    van Eikeren, P.; Brose, D.J.; Ray, R.J.

    1991-08-20

    This patent describes improvement in an organic/aqueous extraction process for the extraction of an organic solute from an organic solvent or solvent mixture with an aqueous-based extractant. The improvement comprises continuously recycling the aqueous-based extractant through a membrane separation process that selectively removes the organic solute from the aqueous-based extractant, the membrane separation process being selected from at least one of reverse osmosis, nanofiltration, ultrafiltration, membrane distillation, pervaporation, membrane contactor and supported-liquid membrane.

  3. Porous organic cage membranes for water desalination: a simulation exploration.

    PubMed

    Kong, Xian; Jiang, Jianwen

    2017-07-19

    Porous organic cages (POCs) have emerged as a new class of porous materials and received considerable interest for their potential applications. Herein we report the first proof-of-concept simulation study on POC membranes for water desalination. Five [4+6] POCs (CC1, CC2, CC3, CC16, and CC17) are considered with similar crystal structures, but different periphery groups and pore morphologies. CC1 is found to be impermeable to water due to disconnected pores. With an interconnected tetrahedral pore network, CC3 and CC16 have an intermediate water permeability of 1-5 × 10(-7) kg m (m(2) h bar)(-1). CC2 and CC17 contain straight pores and a widely open pore network, respectively, thus exhibit a high water permeability of 2-3 × 10(-6) kg m (m(2) h bar)(-1); nevertheless, salt rejection in CC17 is only 89%. Among the five POC membranes, CC2 is the best for water desalination with performance superior to other membranes reported in the literature. The membrane flexibility is revealed to have a weak effect on water permeation. To provide further microscopic understanding, the permeation duration, diffusion and hydrogen bonding of water in the POC membranes are quantitatively analyzed. From this simulation study, the key factors governing water permeation in the POC membranes are unraveled and CC2 is identified to be an interesting candidate for water desalination.

  4. Hierarchical organization of chiral rafts in colloidal membranes

    NASA Astrophysics Data System (ADS)

    Sharma, Prerna; Ward, Andrew; Gibaud, T.; Hagan, Michael F.; Dogic, Zvonimir

    2014-09-01

    Liquid-liquid phase separation is ubiquitous in suspensions of nanoparticles, proteins and colloids. It has an important role in gel formation, protein crystallization and perhaps even as an organizing principle in cellular biology. With a few notable exceptions, liquid-liquid phase separation in bulk proceeds through the continuous coalescence of droplets until the system undergoes complete phase separation. But when colloids, nanoparticles or proteins are confined to interfaces, surfaces or membranes, their interactions differ fundamentally from those mediated by isotropic solvents, and this results in significantly more complex phase behaviour. Here we show that liquid-liquid phase separation in monolayer membranes composed of two dissimilar chiral colloidal rods gives rise to thermodynamically stable rafts that constantly exchange monomeric rods with the background reservoir to maintain a self-limited size. We visualize and manipulate rafts to quantify their assembly kinetics and to show that membrane distortions arising from the rods' chirality lead to long-range repulsive raft-raft interactions. Rafts assemble into cluster crystals at high densities, but they can also form bonds to yield higher-order structures. Taken together, our observations demonstrate a robust membrane-based pathway for the assembly of monodisperse membrane clusters that is complementary to existing methods for colloid assembly in bulk suspensions. They also reveal that chiral inclusions in membranes can acquire long-range repulsive interactions, which might more generally have a role in stabilizing assemblages of finite size.

  5. Quantitative understanding of cell signaling: The importance of membrane organization

    PubMed Central

    Radhakrishnan, Krishnan; Halász, Ádám; Vlachos, Dion; Edwards, Jeremy S.

    2010-01-01

    Systems biology modeling of signal transduction pathways traditionally employs ordinary differential equations, deterministic models based on assumptions of spatial homogeneity. However, this can be a poor approximation for certain aspects of signal transduction, especially its initial steps: the cell membrane exhibits significant spatial organization, with diffusion rates approximately two orders of magnitude slower than those in the cytosol. Thus, to unravel the complexities of signaling pathways, quantitative models must consider spatial organization as an important feature of cell signaling. Furthermore, spatial separation limits the number of molecules that can physically interact, requiring stochastic simulation methods that account for individual molecules. Herein, we discuss the need for mathematical models and experiments that appreciate the importance of spatial organization in the membrane. PMID:20829029

  6. 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.

  7. Surface functionalization of metal organic frameworks for mixed matrix membranes

    DOEpatents

    Albenze, Erik; Lartey, Michael; Li, Tao; Luebke, David R.; Nulwala, Hunaid B.; Rosi, Nathaniel L.; Venna, Surendar R.

    2017-03-21

    Mixed Matrix Membrane (MMM) are composite membranes for gas separation and comprising a quantity of inorganic filler particles, in particular metal organic framework (MOF), dispersed throughout a polymer matrix comprising one or more polymers. This disclosure is directed to MOF functionalized through addition of a pendant functional group to the MOF, in order to improve interaction with a surrounding polymer matrix in a MMM. The improved interaction aids in avoiding defects in the MMM due to incompatible interfaces between the polymer matrix and the MOF particle, in turn increasing the mechanical and gas separation properties of the MMM. The disclosure is also directed to a MMM incorporating the surface functionalized MOF.

  8. Pervaporation membranes--a novel separation technique for trace organics

    SciTech Connect

    Zhu, C.L.; Yuang, C.W.; Fried, J.R.; Greenberg, D.B.

    1983-05-01

    A viable separation of chlorinated hydrocarbons from dilute aqueous solutions can be achieved by a process known as pervaporation. It is applicable to the removal of chlorinated organics, pesticides, herbicides, etc., from industrial and municipal water supplies. The process separates trace amounts of hydrocarbons through polymer membranes by means of a liquid-vapor mass-transfer. The method involves the selective sorption of a liquid mixture, followed by diffusion, and then desorption into a vapor phase on the downstream side of the membrane. (JMT)

  9. 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)

  10. 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)

  11. Comparison of the filtration characteristics of organic and inorganic membranes in a membrane-coupled anaerobic bioreactor.

    PubMed

    Kang, In-Joong; Yoon, Seong-Hoon; Lee, Chung-Hak

    2002-04-01

    Comparison of filtration characteristics of organic and inorganic membranes was made in terms of physicochemical properties of the membrane materials, cake layer formation, backflushing and backfeeding effects in a membrane-coupled anaerobic bioreactor. For the inorganic membrane, struvite (MgNH4PO4 x 6H2O) was found to have accumulated inside the membrane pore and plays a key role in flux decline. For the organic, however, a thick cake layer composed of biomass and struvite formed on the membrane surface, thus causing a major hydraulic resistance. In order to mitigate flux decline for both membranes, backflushing and backfeeding modes were examined. With acidic (pH 2.0) backflushing, the flux was approximately doubled for the organic membrane. However, unexpectedly a negative effect was observed for the inorganic membrane. An alkaline backflushing instead of acidic backflushing gave rise to a flux improvement by a factor of two without any negative effect, even for the inorganic membrane. The backfeeding mode gave rise to a much higher flux compared with the normal mode in both types of membrane, although the flux returned to the same level as that with the normal mode after 6 days for the inorganic membrane. The differences between the two types of membranes were explained by membrane morphology, a ligand exchange reaction as well as a surface charge effect.

  12. Membrane bioreactor for control of volatile organic compound emissions

    SciTech Connect

    Ergas, S.J.; McGrath, M.S.

    1997-06-01

    A membrane bioreactor system that overcomes many of the limitations of conventional compost biofilters is described. The system utilizes microporous hydrophobic hollow fiber membranes for mass transfer of volatile organic compounds (VOCs) from the gas phase to a microbially active liquid phase. The reactor design provides a high biomass concentration, a method for wasting biomass, and a method for addition of pH buffers, nutrients, cometabolites, and/or other amendments. A theoretical model is developed, describing mass transfer and biodegradation in the membrane bioreactor. Reactor performance was determined in a laboratory scale membrane bioreactor over a range of gas loading rates using toluene as a model VOC. Toluene removal efficiency was greater than 98% at an inlet concentration of 100 ppm, and a gas residence time of less than 2 s. Factors controlling bioreactor performance were determined through both experiments and theoretical modeling to include: compound Henry`s law constant, membrane specific surface area, gas and VOC loading rates, liquid phase turbulence, and biomass substrate utilization rate.

  13. Roles of Viscous Membrane in an MHD Self-Organization

    NASA Astrophysics Data System (ADS)

    Yabuki, Kentaro; Watanabe, Kunihiko; Sato, Tetsuya

    1997-07-01

    In order to examine the role of the energy input in the formation of an ordered structure in a semi-open system, we have developed a nonlinear simulation model in which the energy input time and the dynamic response time of the system are changeable. For this purpose, a viscous membrane (boundary layer) is placed between a steady convection source and a nonlinear feedback system in which a dissipation-free magnetohydrodynamic plasma and a resistive weakly-ionized plasma are coupled.It is found that the thin viscous membrane acts to be a high-pass filter that can play a role of a fixed boundary for the dc component but a free boundary for the ac component. Because of this character of the membrane, when the ratio of the ac energy input time to the dynamic response time of the system becomes relatively large, the membrane acts to release the fluctuation (ac) energy from the system. Consequently, the positive feedback effect for the fluctuation is weakened and the structure formation is prevented as the ratio exceeds a certain critical value.It is also found that the viscous membrane plays another important role in self-organization, namely, that as the structure formation is highly progressed, the dc energy input rate is autonomously adjusted so as to keep the developed structure in a steady form.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  17. 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.

  18. 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

  19. Membrane organization and regulation of cellular cholesterol homeostasis.

    PubMed

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

    2010-04-01

    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 because it activates complex cellular pathways that tend to mobilize and export Chol from cellular depots. We hypothesize that membrane composition and/or organization is strongly involved in Chol homeostasis. To test this hypothesis, we constructed a cell line overexpressing stearoyl coenzyme A (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 Chol homeostasis. PM in SCD cells has a higher ratio of phospholipids to sphingomyelin and is slightly enriched in Chol. These cells showed an increase in the ratio of cholesteryl esters to free Chol; they were more resistant to Chol toxicity, and they exported more caveolin than control cells. The data suggest that cell functionality is preserved by regulating membrane fluidity and Chol exportation and storage.

  20. Membrane remodeling and organization: Elements common to prokaryotes and eukaryotes.

    PubMed

    Vega-Cabrera, Luz A; Pardo-López, Liliana

    2017-02-01

    Membrane remodeling processes in eukaryotes, such as those involved in endocytosis and intracellular trafficking, are mediated by a large number of structural, accessory and regulatory proteins. These processes occur in all cell types, enabling the exchange of signals and/or nutrients with the external medium and with neighboring cells; likewise, they are required for the intracellular trafficking of various cargo molecules between organelles, as well as the recycling of these structures. Recent studies have demonstrated that some elements of the molecular machinery involved in regulating and mediating endocytosis in eukaryotic cells are also present in some bacteria, where they participate in processes such as cell division, sporulation and signal transduction. However, the mechanism whereby this prokaryotic machinery carries out such functions has barely begun to be elucidated. This review summarizes recent information about the cytoskeletal and membrane-organizing proteins for which bacterial homologs have been identified; given their known functions, they may be considered to be part of an ancestral membrane organization system that first emerged in prokaryotes and which further evolved into the more complex regulatory networks operating in eukaryotes. © 2017 IUBMB Life, 69(2):55-62, 2017.

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

    PubMed

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

    2015-10-07

    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.

  2. Efficient synthesis of a multi-substituted diphenylmethane skeleton as a steroid mimetic.

    PubMed

    Misawa, Takashi; Tanaka, Katsuya; Demizu, Yosuke; Kurihara, Masaaki

    2017-03-24

    Steroids are important components of cell membranes and are involved in several physiological functions. A diphenylmethane (DPM) skeleton has recently been suggested to act as a mimetic of the steroid skeleton. However, difficulties are associated with efficiently introducing different substituents between two phenyl rings of the DPM skeleton, and, thus, further structural development based on the DPM skeleton has been limited. We herein developed an efficient synthetic method for introducing different substituents into two phenyl rings of the DPM skeleton. We also synthesized DPM-based estrogen receptor (ER) modulators using our synthetic method and evaluated their ER transcriptional activities.

  3. Depth-Dependent Organization and Dynamics of Archaeal and Eukaryotic Membranes: Development of Membrane Anisotropy Gradient with Natural Evolution.

    PubMed

    Chakraborty, Hirak; Haldar, Sourav; Chong, Parkson Lee-Gau; Kombrabail, Mamata; Krishnamoorthy, G; Chattopadhyay, Amitabha

    2015-10-27

    The lipid composition of archaea is unique and has been correlated with increased stability under extreme environmental conditions. In this article, we have focused on the evolution of membrane organization and dynamics with natural evolution. Dynamic anisotropy along the membrane normal (i.e., gradients of mobility, polarity, and heterogeneity) is a hallmark of fluid phase diester or diether phospholipid membranes. We monitored gradients of mobility, polarity, and heterogeneity along the membrane normal in membranes made of a representative archaeal lipid using a series of membrane depth-dependent fluorescent probes, and compared them to membranes prepared from a typical diether lipid from higher organisms (eukaryotes). Our results show that the representative dynamic anisotropy gradient along the membrane normal is absent in membranes made from archaeal lipids. We hypothesize that the dynamic gradient observed in membranes of diester and diether phospholipids is a consequence of natural evolution of membrane lipids in response to the requirement of carrying out complex cellular functions by membrane proteins.

  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.

  5. [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.

  6. 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.

  7. Progress on Zeolite-membrane-aided Organic Acid Esterification

    NASA Astrophysics Data System (ADS)

    Makertiharta, I. G. B. N.; Dharmawijaya, P. T.

    2017-07-01

    Esterification is a common route to produce carboxylic acid esters as important intermediates in chemical and pharmaceutical industries. However, the reaction is equilibrium limited and needs to be driven forward by selective removal one of the products. There have been some efforts to selectively remove water from reaction mixture via several separation processes (such as pervaporation and reactive distillation). Integrated pervaporation and esterification has gained increasing attention towards. Inorganic zeolite is the most popular material for pervaporation due to its high chemical resistant and separation performance towards water. Zeolite also has proven to be an effective material in removing water from organic compound. Zeolite can act not only as selective layer but also simultaneously act as a catalyst on promoting the reaction. Hence, there are many configurations in integrating zeolite membrane for esterification reaction. As a selective layer to remove water from reaction mixture, high Si/Al zeolite is preferred to enhance its hydrophilicity. However, low Si/Al zeolite is unstable in acid condition due to dealumination thus eliminate its advantages. As a catalyst, acid zeolites (e.g. H-ZSM-5) provide protons for autoprotolysis of the carboxylic acid similar to other catalyst for esterification (e.g. inorganic acid, and ion exchange resins). There are many studies related to zeolite membrane aided esterification. This paper will give brief information related to zeolite membrane role in esterification and also research trend towards it.

  8. Path similarity skeleton graph matching.

    PubMed

    Bai, Xiang; Latecki, Longin Jan

    2008-07-01

    This paper presents a novel framework to for shape recognition based on object silhouettes. The main idea is to match skeleton graphs by comparing the shortest paths between skeleton endpoints. In contrast to typical tree or graph matching methods, we completely ignore the topological graph structure. Our approach is motivated by the fact that visually similar skeleton graphs may have completely different topological structures. The proposed comparison of shortest paths between endpoints of skeleton graphs yields correct matching results in such cases. The skeletons are pruned by contour partitioning with Discrete Curve Evolution, which implies that the endpoints of skeleton branches correspond to visual parts of the objects. The experimental results demonstrate that our method is able to produce correct results in the presence of articulations, stretching, and occlusion.

  9. The Bi-Functional Organization of Human Basement Membranes

    PubMed Central

    Halfter, Willi; Monnier, Christophe; Müller, David; Oertle, Philipp; Uechi, Guy; Balasubramani, Manimalha; Safi, Farhad; Lim, Roderick; Loparic, Marko; Henrich, Paul Bernhard

    2013-01-01

    The current basement membrane (BM) model proposes a single-layered extracellular matrix (ECM) sheet that is predominantly composed of laminins, collagen IVs and proteoglycans. The present data show that BM proteins and their domains are asymmetrically organized providing human BMs with side-specific properties: A) isolated human BMs roll up in a side-specific pattern, with the epithelial side facing outward and the stromal side inward. The rolling is independent of the curvature of the tissue from which the BMs were isolated. B) The epithelial side of BMs is twice as stiff as the stromal side, and C) epithelial cells adhere to the epithelial side of BMs only. Side-selective cell adhesion was also confirmed for BMs from mice and from chick embryos. We propose that the bi-functional organization of BMs is an inherent property of BMs and helps build the basic tissue architecture of metazoans with alternating epithelial and connective tissue layers. PMID:23844050

  10. Connexins in The Skeleton

    PubMed Central

    Stains, Joseph P.; Civitelli, Roberto

    2016-01-01

    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

  11. Sulphur-bound steroid and phytane carbon skeletons in geomacromolecules: Implications for the mechanism of incorporation of sulphur into organic matter

    NASA Astrophysics Data System (ADS)

    Kohnen, Math E. L.; Sinninghe Damsté, Jaap S.; Baas, Marianne; Dalen, A. C. Kock-van; de Leeuw, Jan W.

    1993-06-01

    Sulphur-bound steroid and phytane moieties in macromolecules present in the polar fractions of six immature samples (both crude oils and sediment extracts) have been analyzed using S-selective chemolysis methods and analytical pyrolysis. The identifications of the methylthioethers released from the macromolecule-containing fractions after MeLi/MeI treatment are based on comparison of mass spectral data and chromatographic data with those for synthesized methylthioethers. Evidence is presented that di- or polysulphide linkages are present in geomacromolecules in both sediments and oils and that the location of di- or polysulphide linkages in macromolecularly S-bound moieties is the same as that of monosulphide linkages. Macromolecularly S-bound phytanyl moieties are chiefly bound with S linkages located at the tertiary positions of their carbon skeletons, which indicates that the S incorporation mechanism(s) involve(s) intermediate carbocations. The macromolecularly S-bound steroids are bound with S linkages located mainly at C-2, C-3, C-4, or C-5 of their carbon skeletons, which indicates that the S incorporation took place into sterenes or steradienes - the dehydration products of stanols and stenols, respectively. However, it remains possible that the macromolecularly S-bound steroids with an axial S linkage at C-3 are, in part, resulting from a S N2 reaction of inorganic S species with steryl esters or stanols.

  12. 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.

  13. 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...

  14. Organized living: formation mechanisms and functions of plasma membrane domains in yeast.

    PubMed

    Ziółkowska, Natasza E; Christiano, Romain; Walther, Tobias C

    2012-03-01

    Plasma membrane proteins and lipids organize into lateral domains of specific composition. Domain formation is achieved by a combination of lipid-lipid and lipid-protein interactions, membrane-binding protein scaffolds and protein fences. The resulting domains function in membrane protein turnover and homeostasis, as well as in cell signaling. We review the mechanisms generating plasma membrane domains and the functional consequences of this organization, focusing on recent findings from research on the yeast model system.

  15. A Stochastic Skeleton Model for the MJO

    NASA Astrophysics Data System (ADS)

    thual, S.; Majda, A.; Stechmann, S.

    2013-12-01

    The Madden-Julian oscillation (MJO) is the dominant mode of variability in the tropical atmosphere on intraseasonal timescales and planetary spatial scales. 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 ms-1, (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. Here, we show 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. We achieve this goal by developing a simple stochastic parametrization for the unresolved details of synoptic-scale activity, that 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.

  16. MemO: a consensus approach to the annotation of a protein's membrane organization.

    PubMed

    Davis, Melissa J; Zhang, Fasheng; Yuan, Zheng; Teasdale, Rohan D

    2006-01-01

    Membrane organization describes the relationship of proteins to the membrane, that is, whether the protein crosses the membrane or is integral to the membrane and its orientation with respect to the membrane. Membrane organization is determined primarily by the presence of two features which target proteins to the secretory pathway: the endoplasmic reticulum signal peptide and the ?-helical transmembrane domain. In order to generate membrane organization annotation of high quality, confidence and throughput, the Membrane Organization (MemO) pipeline was developed, incorporating consensus feature prediction modules with integration and annotation rules derived from biological observations. The pipeline classifies proteins into six categories based on the presence or absence of predicted features: Soluble, intracellular proteins; Soluble, secreted proteins; Type I membrane proteins; Type II membrane proteins; Multi-span membrane proteins and Glycosylphosphatidylinositol anchored membrane proteins. The MemO pipeline represents an integrated strategy for the application of state-of-the-art bioinformatics tools to the annotation of protein membrane organization, a property which adds biological context to the large quantities of protein sequence information available.

  17. 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.

  18. 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

  19. Discovery of a Cretaceous Scleractinian Coral with a Calcitic Skeleton

    NASA Astrophysics Data System (ADS)

    Stolarski, J.; Meibom, A.; Przenioslo, R.; Mazur, M.

    2007-12-01

    It has been generally thought that scleractinian corals form purely aragonitic skeletons. We show that a well- preserved fossil coral, Coelosmilia sp. from the Upper Cretaceous (ca. 70 Ma), has preserved skeletal structural features identical to those observed in present day scleractinians. However, the skeleton of Coelosmilia sp. is entirely calcitic. Its fine-scale structure and chemistry indicate that the calcite is primary and did not from via diagenetic alteration of aragonite. This result implies that corals, like other groups of marine, calcium carbonate- producing organisms, can form skeletons of different carbonate polymorphs. Implications for coral biomineralization and evolution will be discussed.

  20. Understanding the fouling of algogenic organic matter in microfiltration using membrane-foulant interaction energy analysis: effects of organic hydrophobicity.

    PubMed

    Huang, Weiwei; Chu, Huaqiang; Dong, Bingzhi

    2014-10-01

    Fouling caused by algogenic organic matter (AOM) in membrane filtration is a critical problem in algae-rich waters, and understanding fouling mechanisms, particularly by identifying the predominant membrane foulants, could have significant effects on algal fouling prediction and pretreatment. In this work, the fouling behavior of Aphanizomenon flos-aquae (APF)- and Anabaena flos-aquae (ANF)-AOM fractions was analyzed using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. The results show that the interfacial energy of membranes and foulants could be used for AOM membrane fouling analysis. The attractive energy was highest between the membrane and the neutral hydrophilic fractions (N-HPI) on clean membrane surfaces, followed by the energy associated with the hydrophobic fractions (HPO) and the transphilic fractions (TPI) in both of the AOMs; on the other hand, the negatively charged hydrophilic organics (C-HPI) in the APF-AOM suffered from repulsive interactions when nearing the membrane surface, which was consistent with their initial filtration flux. After the formation of an initial fouling layer on the membrane surface, membrane fouling was controlled mainly by the cohesion free energy between the approaching foulants and the foulants on the fouled membranes. In addition, it was observed that the interfacial energy between foulants was the dominant factor controlling membrane fouling in AOM filtration. Finally, the interfacial energies between the N-HPI fractions had the greatest effect on both APF-AOM and ANF-AOM membrane fouling. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Intramembrane particles and the organization of lymphocyte membrane proteins

    PubMed Central

    Kuby, JM; Wofsy, L

    1981-01-01

    An experimental system was developed in which the majority of all lymphocyte cell-surface proteins, regardless of antigenic specificity, could be cross-linked and redistributed in the membrane to determine whether this would induce a corresponding redistribution of intramembrane particles (IMP). Mouse spleen cells were treated with P-diazoniumphenyl- β-D-lactoside (lac) to modify all exposed cell-surface proteins. Extensive azo- coupling was achieved without significantly reducing cell viability or compromising cellular function in mitogen- or antigen-stimulated cultures. When the lac-modified cell- surface proteins were capped with a sandwich of rabbit antilactoside antibody and fluorescein-goat anti-rabbit Ig, freeze-fracture preparations obtained from these cells revealed no obvious redistribution of IMP on the majority of fracture faces. However, detailed analysis showed a statistically significant 35 percent decrease (P less than 0.01) in average IMP density in the E face of the lac-capped spleen cells compared with control cells, whereas a few E-face micrographs showed intense IMP aggregation. In contrast, there was no significant alteration of P-face IMP densities or distribution. Apparently, the majority of E-face IMP and virtually all P-face IMP densities or distribution. Apparently, the majority of E-face IMP and virtually all P-face IMP do not present accessible antigenic sites on the lymphocyte surface and do not associate in a stable manner with surface protein antigens. This finding suggests that IMP, as observed in freeze-fracture analysis, may not comprise a representative reflection of lymphocyte transmembrane protein molecules and complexes because other evidence establishes: (a) that at least some common lymphocyte surface antigens are indeed exposed portions of transmembrane proteins and (b) that the aggregation of molecules of any surface antigen results in altered organization of contractile proteins at the cytoplasmic face of the membrane

  2. Intramembrane particles and the organization of lymphocyte membrane proteins.

    PubMed

    Kuby, J M; Wofsy, L

    1981-03-01

    An experimental system was developed in which the majority of all lymphocyte cell-surface proteins, regardless of antigenic specificity, could be cross-linked and redistributed in the membrane to determine whether this would induce a corresponding redistribution of intramembrane particles (IMP). Mouse spleen cells were treated with P-diazoniumphenyl- beta-D-lactoside (lac) to modify all exposed cell-surface proteins. Extensive azo- coupling was achieved without significantly reducing cell viability or compromising cellular function in mitogen- or antigen-stimulated cultures. When the lac-modified cell- surface proteins were capped with a sandwich of rabbit antilactoside antibody and fluorescein-goat anti-rabbit Ig, freeze-fracture preparations obtained from these cells revealed no obvious redistribution of IMP on the majority of fracture faces. However, detailed analysis showed a statistically significant 35 percent decrease (P less than 0.01) in average IMP density in the E face of the lac-capped spleen cells compared with control cells, whereas a few E-face micrographs showed intense IMP aggregation. In contrast, there was no significant alteration of P-face IMP densities or distribution. Apparently, the majority of E-face IMP and virtually all P-face IMP densities or distribution. Apparently, the majority of E-face IMP and virtually all P-face IMP do not present accessible antigenic sites on the lymphocyte surface and do not associate in a stable manner with surface protein antigens. This finding suggests that IMP, as observed in freeze-fracture analysis, may not comprise a representative reflection of lymphocyte transmembrane protein molecules and complexes because other evidence establishes: (a) that at least some common lymphocyte surface antigens are indeed exposed portions of transmembrane proteins and (b) that the aggregation of molecules of any surface antigen results in altered organization of contractile proteins at the cytoplasmic face of the membrane.

  3. Separation of volatile organic compounds from dry and humidified nitrogen using polyurethane membranes

    SciTech Connect

    Ponangi, R.P.; Pintauro, P.N.

    1996-08-01

    Homogeneous polyurethane membranes, containing ether or ester soft segments, were examined for the vapor-phase separation of tetrachloroethylene, carbon tetrachloride, benzene, toluene, p-xylene, hexane, and benzene/toluene/xylene mixtures from nitrogen. Both equilibrium sorption/desorption and organic/N{sub 2} separation experiments were carried out. The membranes performed best with aromatic and chlorine-containing organic compounds, with organic/dry N{sub 2} selectivities ranging from 30 to 210 and pressure-normalized permeabilities as high as 1.25 {times} 10{sup {minus}3} cm{sup 3} (STP)/(cm{sup 2} s cmHg) for saturated organic feeds at 23 C and a downstream pressure of 0.005--0.01 atm. Organic/N{sub 2} selectivities and organic permeabilities were generally higher than those reported in the literature for poly(dimethylsiloxane) and aromatic polyimide membranes. Organic permeabilities in the ether soft segment polyurethane membranes were greater than those measured in the polyester films, due to higher organic solubility coefficients (more polymer swelling). The greater swelling of the polyether membranes increased the nitrogen permeabilities and lowered the organic/N{sub 2} selectivities relative to those for polyester membranes. Water permeabilities in both types of polyurethane membranes were low and independent of the organic feed component. The presence of water vapor in the feed (up to 1.2 vol %) had no effect on transmembrane organic fluxes.

  4. Self-organized liquid-crystalline nanostructured membranes for water treatment: selective permeation of ions.

    PubMed

    Henmi, Masahiro; Nakatsuji, Koji; Ichikawa, Takahiro; Tomioka, Hiroki; Sakamoto, Takeshi; Yoshio, Masafumi; Kato, Takashi

    2012-05-02

    A membrane with ordered 3D ionic nanochannels constructed by in situ photopolymerization of a thermotropic liquid-crystalline monomer shows high filtration performance and ion selectivity. The nanostructured membrane exhibits water-treatment performance superior to that of an amorphous membrane prepared from the isotropic melt of the monomer. Self-organized nanostructured membranes have great potential for supplying high-quality water. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. 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.

  6. Role of the mitochondrial contact site and cristae organizing system in membrane architecture and dynamics.

    PubMed

    Rampelt, Heike; Zerbes, Ralf M; van der Laan, Martin; Pfanner, Nikolaus

    2017-04-01

    The elaborate membrane architecture of mitochondria is a prerequisite for efficient respiration and ATP generation. The cristae membranes, invaginations of the inner mitochondrial membrane, represent a specialized compartment that harbors the complexes of the respiratory chain and the F1Fo-ATP synthase. Crista junctions form narrow openings that connect the cristae membranes to the inner boundary membrane. The mitochondrial contact site and cristae organizing system (MICOS) is located at crista junctions where it stabilizes membrane curvature and forms contact sites between the mitochondrial inner and outer membranes. MICOS is a large machinery, consisting of two dynamic subcomplexes that are anchored in the inner membrane and expose domains to the intermembrane space. The functions of MICOS in mitochondrial membrane architecture and biogenesis are influenced by numerous interaction partners and the phospholipid environment.

  7. 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.

  8. 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.

  9. Red cell membrane disorders.

    PubMed

    Narla, J; Mohandas, N

    2017-05-01

    Significant advances have been made in our understanding of the structural basis for altered cell function in various inherited red cell membrane disorders with reduced red cell survival and resulting hemolytic anemia. The current review summarizes these advances as they relate to defining the molecular and structural basis for disorders involving altered membrane structural organization (hereditary spherocytosis [HS] and hereditary elliptocytosis [HE]) and altered membrane transport function (hereditary overhydrated stomatocytosis and hereditary xerocytosis). Mutations in genes encoding membrane proteins that account for these distinct red cell phenotypes have been identified. These molecular insights have led to improved understanding of the structural basis for altered membrane function in these disorders. Weakening of vertical linkage between the lipid bilayer and spectrin-based membrane skeleton leads to membrane loss in HS. In contrast, weakening of lateral linkages among different skeletal proteins leads to membrane fragmentation and decreased surface area in HE. The degrees of membrane loss and resultant increases in cell sphericity determine the severity of anemia in these two disorders. Splenectomy leads to amelioration of anemia by increasing the circulatory red cell life span of spherocytic red cells that are normally sequestered by the spleen. Disordered membrane cation permeability and resultant increase or decrease in red cell volume account for altered cellular deformability of hereditary overhydrated stomatocytosis and hereditary xerocytosis, respectively. Importantly, splenectomy is not beneficial in these two membrane transport disorders and in fact contraindicated due to severe postsplenectomy thrombotic complications. © 2017 John Wiley & Sons Ltd.

  10. 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.

  11. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. The superlattice model of lateral organization of membranes and its implications on membrane lipid homeostasis.

    PubMed

    Somerharju, Pentti; Virtanen, Jorma A; Cheng, Kwan H; Hermansson, Martin

    2009-01-01

    Most biological membranes are extremely complex structures consisting of hundreds of different lipid and protein molecules. According to the famous fluid-mosaic model lipids and many proteins are free to diffuse very rapidly in the plane of the membrane. While such fast diffusion implies that different membrane lipids would be laterally randomly distributed, accumulating evidence indicates that in model and natural membranes the lipid components tend to adopt regular (superlattice-like) distributions. The superlattice model, put forward based on such evidence, is intriguing because it predicts that 1) there is a limited number of allowed compositions representing local minima in membrane free energy and 2) those energy minima could provide set-points for enzymes regulating membrane lipid compositions. Furthermore, the existence of a discrete number of allowed compositions could help to maintain organelle identity in the face of rapid inter-organelle membrane traffic.

  13. Precambrian Skeletonized Microbial Eukaryotes

    NASA Astrophysics Data System (ADS)

    Lipps, Jere H.

    2017-04-01

    Skeletal heterotrophic eukaryotes are mostly absent from the Precambrian, although algal eukaryotes appear about 2.2 billion years ago. Tintinnids, radiolaria and foraminifera have molecular origins well back into the Precambrian yet no representatives of these groups are known with certainty in that time. These data infer times of the last common ancestors, not the appearance of true representatives of these groups which may well have diversified or not been preserved since those splits. Previous reports of these groups in the Precambrian are misinterpretations of other objects in the fossil record. Reported tintinnids at 1600 mya from China are metamorphic shards or mineral artifacts, the many specimens from 635-715 mya in Mongolia may be eukaryotes but they are not tintinnids, and the putative tintinnids at 580 mya in the Doushantou formation of China are diagenetic alterations of well-known acritarchs. The oldest supposed foraminiferan is Titanotheca from 550 to 565 mya rocks in South America and Africa is based on the occurrence of rutile in the tests and in a few modern agglutinated foraminifera, as well as the agglutinated tests. Neither of these nor the morphology are characteristic of foraminifera; hence these fossils remain as indeterminate microfossils. Platysolenites, an agglutinated tube identical to the modern foraminiferan Bathysiphon, occurs in the latest Neoproterozoic in Russia, Canada, and the USA (California). Some of the larger fossils occurring in typical Ediacaran (late Neoproterozoic) assemblages may be xenophyophorids (very large foraminifera), but the comparison is disputed and flawed. Radiolaria, on occasion, have been reported in the Precambrian, but the earliest known clearly identifiable ones are in the Cambrian. The only certain Precambrian heterotrophic skeletal eukaryotes (thecamoebians) occur in fresh-water rocks at about 750 mya. Skeletonized radiolaria and foraminifera appear sparsely in the Cambrian and radiate in the Ordovician

  14. 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.

  15. Membrane tension and cytoskeleton organization in cell motility.

    PubMed

    Sens, Pierre; Plastino, Julie

    2015-07-15

    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.

  16. Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It.

    PubMed

    Kraft, Mary L

    2016-01-01

    Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with

  17. Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It

    PubMed Central

    Kraft, Mary L.

    2017-01-01

    Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with

  18. 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.

  19. Membrane electro-oxidizer: A new hybrid membrane system with electrochemical oxidation for enhanced organics and fouling control.

    PubMed

    Mameda, Naresh; Park, Hyung-June; Choo, Kwang-Ho

    2017-09-05

    The synergistic combination of membrane filtration with advanced oxidation is of particular interest for next-generation wastewater treatment technologies. A membrane electro-oxidizer (MEO) hybridizing a submerged microfilter and an electrochemical cell was developed and investigated for tertiary treatment of secondary industrial (textile) wastewater effluent. Laboratory- and pilot-scale MEO systems were designed and evaluated for treatment efficiency and membrane fouling control. The MEO achieved substantial removal of color (50-90%), turbidity (>90%), and bacteria (>4 log) as well as chemical oxygen demand (13-31%) and 1,4-dioxane (∼25-53%). Fluorescence-based parallel factor analysis disclosed the degradation of humic-like organics with fluorophores. Size exclusion chromatograms with organic carbon detection confirmed the removal of specific organic molecules with ∼100 Da. While investigating the effects of oxidant quenching agents, reactive chlorine species and hydrogen peroxide were found to be most responsible for the anodic oxidation of secondary effluent organics. The efficacy of membrane fouling mitigation by the MEO was greater when higher electric current densities were applied, but was not dependent on the number of electrochemical cells installed. The MEO is a promising technology for enhanced organics removal with simultaneous fouling control due to its multifunctional active oxidants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Membrane mass spectrometry for the direct trace analysis of volatile organic compounds in air and water

    SciTech Connect

    LaPack, M.A. Michigan State Univ., East Lansing ); Tou, J.C. ); Enke, C.G. )

    1990-07-01

    Very simple membrane inlets can be constructed that are selectively permeable to organic molecules while discriminating against the air or water sample matrix. The membrane thickness directly affects the flow through the membrane such that thinner membranes provide higher throughputs and shorter response times. Higher temperatures result in shortened response times and reduced selectivity of the permeation process. Comparisons of two hollow fiber membrane inlet geometries show that permeation rates are improved in the configuration where the sample flows through the inside of the hollow fiber and the permeating gases are analyzed on the outside, as opposed to the reversed configuration.

  1. The effect of organic loading on bacterial community composition of membrane biofilms in a submerged polyvinyl chloride membrane bioreactor.

    PubMed

    Xia, Siqing; Li, Jixiang; He, Shuying; Xie, Kang; Wang, Xiaojia; Zhang, Yanhao; Duan, Liang; Zhang, Zhiqiang

    2010-09-01

    The effect of organic loading on bacterial community composition of membrane biofilms was investigated using a submerged polyvinyl chloride membrane bioreactor. The low and high loadings were set at 0.33 and 0.52 gCOD/(gVSSd), respectively. The results showed that membrane fouling occurred earlier and faster under the high loading conditions. Denaturing gradient gel electrophoresis (DGGE) analysis revealed that the similarity of bacterial community in the membrane biofilms between the two loadings was 0.67, higher than that in the mixed liquors (0.52-0.55), which indicated that some specific bacteria were selected preferentially on the membranes. Clone library analysis of the membrane biofilms indicated that Betaproteobacteria and Bacteroidetes under the high loading were 54.72% and 19.81%, respectively. Microarray results further confirmed that the two bacteria were the dominant microorganisms in the high loading biofilm. The severe membrane fouling may be aroused mainly by the enrichment of the two bacteria under the high loading. (c) 2010 Elsevier Ltd. All rights reserved.

  2. Nanodomain organization of rhodopsin in native human and murine rod outer segment disc membranes

    PubMed Central

    Whited, Allison M.; Park, Paul S.-H.

    2014-01-01

    Biological membranes display distinct domains that organize membrane proteins and signaling molecules to facilitate efficient and reliable signaling. The organization of rhodopsin, a G protein-coupled receptor, in native rod outer segment disc membranes was investigated by atomic force microscopy. Atomic force microscopy revealed that rhodopsin is arranged into domains of variable size, which we refer to herein as nanodomains, in native membranes. Quantitative analysis of 150 disc membranes revealed that the physical properties of nanodomains are conserved in humans and mice and that the properties of individual disc membranes can be variable. Examining the variable properties of disc membranes revealed some of the factors contributing to the size of rod outer segment discs and the formation of nanodomains in the membrane. The diameter of rod outer segment discs was dependent on the number of rhodopsin molecules incorporated into the membrane but independent of the spatial density of rhodopsin. The number of nanodomains present in a single disc was also dependent on the number of rhodopsin molecules incorporated into the membrane. The size of the nanodomains was largely independent of the number or spatial density of rhodopsin in the membrane. PMID:25305340

  3. Polyamino acid functionalized membranes for metal capture and nanofiltration of organics: Modeling and experimental verification

    NASA Astrophysics Data System (ADS)

    Hestekin, Jamie Allen

    2000-10-01

    addition to functionalized membranes, negatively-charged nanofiltration membranes were studied to establish the role of non-aqueous solvents (alcohols) on flux and rejection behavior of ionized organic molecules.

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

    PubMed Central

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

    2016-01-01

    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

  5. 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.

  6. 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.

  7. Plasma membrane organization and dynamics is probe and cell line dependent.

    PubMed

    Huang, Shuangru; Lim, Shi Ying; Gupta, Anjali; Bag, Nirmalya; Wohland, Thorsten

    2017-09-01

    The action and interaction of membrane receptor proteins take place within the plasma membrane. The plasma membrane, however, is not a passive matrix. It rather takes an active role and regulates receptor distribution and function by its composition and the interaction of its lipid components with embedded and surrounding proteins. Furthermore, it is not a homogenous fluid but contains lipid and protein domains of various sizes and characteristic lifetimes which are important in regulating receptor function and signaling. The precise lateral organization of the plasma membrane, the differences between the inner and outer leaflet, and the influence of the cytoskeleton are still debated. Furthermore, there is a lack of comparisons of the organization and dynamics of the plasma membrane of different cell types. Therefore, we used four different specific membrane markers to test the lateral organization, the differences between the inner and outer membrane leaflet, and the influence of the cytoskeleton of up to five different cell lines, including Chinese hamster ovary (CHO-K1), Human cervical carcinoma (HeLa), neuroblastoma (SH-SY5Y), fibroblast (WI-38) and rat basophilic leukemia (RBL-2H3) cells by Imaging Total Internal Reflection (ITIR)-Fluorescence Correlation Spectroscopy (FCS). We measure diffusion in the temperature range of 298-310K to measure the Arrhenius activation energy (EArr) of diffusion and apply the FCS diffusion law to obtain information on the spatial organization of the probe molecules on the various cell membranes. Our results show clear differences of the FCS diffusion law and EArr for the different probes in dependence of their localization. These differences are similar in the outer and inner leaflet of the membrane. However, these values can differ significantly between different cell lines raising the question how molecular plasma membrane events measured in different cell lines can be compared. This article is part of a Special Issue

  8. 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.

  9. 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. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Mitochondrial contact site and cristae organizing system: A central player in membrane shaping and crosstalk.

    PubMed

    Wollweber, Florian; von der Malsburg, Karina; van der Laan, Martin

    2017-09-01

    Mitochondria are multifunctional metabolic factories and integrative signaling organelles of eukaryotic cells. The structural basis for their numerous functions is a complex and dynamic double-membrane architecture. The outer membrane connects mitochondria to the cytosol and other organelles. The inner membrane is composed of a boundary region and highly folded cristae membranes. The evolutionarily conserved mitochondrial contact site and cristae organizing system (MICOS) connects the two inner membrane domains via formation and stabilization of crista junction structures. Moreover, MICOS establishes contact sites between inner and outer mitochondrial membranes by interacting with outer membrane protein complexes. MICOS deficiency leads to a grossly altered inner membrane architecture resulting in far-reaching functional perturbations in mitochondria. Consequently, mutations affecting the function of MICOS are responsible for a diverse spectrum of human diseases. In this article, we summarize recent insights and concepts on the role of MICOS in the organization of mitochondrial membranes. This article is part of a Special Issue entitled: Membrane Contact Sites edited by Christian Ungermann and Benoit Kornmann. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Hybrid membranes of metal-organic molecule nanocages for aromatic/aliphatic hydrocarbon separation by pervaporation.

    PubMed

    Zhao, Cui; Wang, Naixin; Wang, Lin; Huang, Hongliang; Zhang, Rong; Yang, Fan; Xie, Yabo; Ji, Shulan; Li, Jian-Rong

    2014-11-21

    Hybrid membranes composed of porous metal-organic molecule nanocages as fillers embedded in a hyperbranched polymer (Boltorn W3000) were fabricated, which exhibit excellent pervaporation separation performances towards aromatic/aliphatic hydrocarbons. The unique nature of the molecule-based fillers and their good dispersion and compatibility in/with the polymer are responsible for the good membrane properties.

  12. 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. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. 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.

  14. Monitoring the organization and dynamics of bovine hippocampal membranes utilizing Laurdan generalized polarization.

    PubMed

    Mukherjee, Soumi; Chattopadhyay, Amitabha

    2005-08-01

    Organization and dynamics of cellular membranes in the nervous system are crucial for the function of neuronal membrane receptors. The lipid composition of neuronal cells is unique and has been correlated with the increased complexity in the organization of the nervous system during evolution. Previous work from our laboratory has established bovine hippocampal membranes as a convenient natural source for studying neuronal receptors such as the G-protein coupled serotonin1A receptor. In this paper, we have explored the organization and dynamics of bovine hippocampal membranes using the amphiphilic environment-sensitive fluorescent probe Laurdan. Our results show that the emission spectra of Laurdan display an additional red shifted peak as a function of increasing temperature in native as well as cholesterol-depleted membranes and liposomes made from lipid extracts of the native membrane. Interestingly, wavelength dependence of Laurdan generalized polarization (GP) in native membranes indicates the presence of an ordered gel-like phase at low temperatures, whereas characteristics of the liquid-ordered phase are observed at high temperatures. Similar experiments performed using cholesterol-depleted membranes show fluidization of the membrane with increasing cholesterol depletion. In addition, results from fluorescence polarization of DPH indicate that the hippocampal membrane is fairly ordered even at physiological temperature. The temperature dependence of Laurdan excitation GP provides a measure of the apparent thermal transition temperature and extent of cooperativity in these membranes. Analysis of time-resolved fluorescence measurements of Laurdan shows reduction in mean fluorescence lifetime with increasing temperature due to change in environmental polarity. These results constitute novel information on the dynamics of hippocampal membranes and its modulation by cholesterol depletion monitored using Laurdan fluorescence.

  15. Natural Organic Matter Removal and Fouling in a Low Pressure Hybrid Membrane Systems

    PubMed Central

    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

  16. Studying lipid organization in biological membranes using liposomes and EPR spin labeling

    PubMed Central

    Subczynski, Witold K.; Raguz, Marija; Widomska, Justyna

    2015-01-01

    Summary Electron paramagnetic resonance (EPR) spin-labeling methods provide a unique opportunity to determine the lateral organization of lipid bilayer membranes by discrimination of coexisting membrane domains or coexisting membrane phases. In some cases, the coexisting membrane domains can be characterized by profiles of alkyl chain order, fluidity, hydrophobicity, and oxygen diffusion-concentration product in situ, without the need for their physical separation. This chapter briefly explains how the EPR spin-labeling methods can be used to obtain the above mentioned profiles across the lipid bilayer membranes (liposomes) derived from the lipid extract of certain biological membranes. These procedures will be illustrated by EPR measurements performed for multilamellar liposomes made of the lipid extracts from cortical and nuclear fractions of the fiber cell plasma membranes of a cow eye lens. To elucidate better the major factors that determine membrane properties, the results for eye lens lipid membranes will be compared with those obtained for simple model membranes resembling basic lipid composition of biological membranes. PMID:20013402

  17. 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.

  18. 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

  19. 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.

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

    PubMed

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

    2016-07-26

    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.

  1. 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

  2. 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.

  3. How sterol tilt regulates properties and organization of lipid membranes and membrane insertions

    PubMed Central

    Khelashvili, George; Harries, Daniel

    2013-01-01

    Serving as a crucial component of mammalian cells, cholesterol critically regulates the functions of biomembranes. This review focuses on a specific property of cholesterol and other sterols: the tilt modulus χ that quantifies the energetic cost of tilting sterol molecules inside the lipid membrane. We show how χ is involved in determining properties of cholesterol-containing membranes, and detail a novel approach to quantify its value from atomistic molecular dynamics (MD) simulations. Specifically, we link χ with other structural, thermodynamic, and mechanical properties of cholesterol-containing lipid membranes, and delineate how this useful parameter can be obtained from the sterol tilt probability distributions derived from relatively small-scale unbiased MD simulations. We demonstrate how the tilt modulus quantitatively describes the aligning field that sterol molecules create inside the phospholipid bilayers, and we relate χ to the bending rigidity of the lipid bilayer through effective tilt and splay energy contributions to the elastic deformations. Moreover, we show how χ can conveniently characterize the “condensing effect” of cholesterol on phospholipids. Finally, we demonstrate the importance of this cholesterol aligning field to the proper folding and interactions of membrane peptides. Given the relative ease of obtaining the tilt modulus from atomistic simulations, we propose that χ can be routinely used to characterize the mechanical properties of sterol/lipid bilayers, and can also serve as a required fitting parameter in multi-scaled simulations of lipid membrane models to relate the different levels of coarse-grained details. PMID:23291283

  4. Micro- to nanostructure and geochemistry of extant crinoidal echinoderm skeletons.

    PubMed

    Gorzelak, P; Stolarski, J; Mazur, M; Meibom, A

    2013-01-01

    This paper reports the results of micro- to nanostructural and geochemical analyses of calcitic skeletons from extant deep-sea stalked crinoids. Fine-scale (SEM, FESEM, AFM) observations show that the crinoid skeleton is composed of carbonate nanograins, about 20-100 nm in diameter, which are partly separated by what appears to be a few nm thick organic layers. Sub-micrometre-scale geochemical mapping of crinoid ossicles using a NanoSIMS ion microprobe, combined with synchrotron high-spatial-resolution X-ray micro-fluorescence (μ-XRF) maps and X-ray absorption near-edge structure spectroscopy (XANES) show that high Mg concentration in the central region of the stereom bars correlates with the distribution of S-sulphate, which is often associated with sulphated polysaccharides in biocarbonates. These data are consistent with biomineralization models suggesting a close association between organic components (including sulphated polysaccharides) and Mg ions. Additionally, geochemical analyses (NanoSIMS, energy dispersive spectroscopy) reveal that significant variations in Mg occur at many levels: within a single stereom trabecula, within a single ossicle and within a skeleton of a single animal. Together, these data suggest that physiological factors play an important role in controlling Mg content in crinoid skeletons and that great care should be taken when using their skeletons to reconstruct, for example, palaeotemperatures and Mg/Ca palaeo-variations of the ocean. © 2012 Blackwell Publishing Ltd.

  5. 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

  6. High-Flux Graphene Oxide Membranes Intercalated by Metal-Organic Framework with Highly Selective Separation of Aqueous Organic Solution.

    PubMed

    Ying, Yunpan; Liu, Dahuan; Zhang, Weixin; Ma, Jing; Huang, Hongliang; Yang, Qingyuan; Zhong, Chongli

    2017-01-18

    Graphene oxide (GO) membranes assembled by single-atom thick GO nanosheets have displayed huge potential application both in gas and liquid separation processes due to its facile and large-scale preparation resulting from various functional groups, such as hydroxyl, carboxyl, and epoxide groups. Taking advantage of these characters, GO membranes intercalated by superhydrophilic metal-organic frameworks (MOFs) as strengthening separation fillers were prepared on modified polyacrylonitrile (PAN) support by a novel pressure-assisted self-assembly (PASA) filtration technique instead of traditional vacuum filtration method for the first time. The synthesized MOF@GO membranes were characterized with several spectroscopic techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), as well as scanning electron microscopy (SEM). Compared with GO membrane, these MOF@GO membranes combine the unique properties of MOF and GO and thus have significant enhancements of pervaporation (PV) permeation flux and separation factor simultaneously for ethyl acetate/water mixtures (98/2, w/w) through the PV process, which are also superior to the reported other kinds of membranes. Especially, for MOF@GO-0.3 membrane (corresponding MOF loading: 23.08 wt %), the increments are 159% and 244%, respectively, at 303 K, and the permeate water content can reach as high as 99.5 wt % (corresponding separation factor, 9751) with a high permeation flux of 2423 g m(-2) h(-1). Moreover, the procedures of both the synthesis of MOF and membranes preparation are environmentally friendly that only water was used as solvent. Such a nanosized MOF-intercalating approach may be also extended to other laminated membranes, providing valuable insights in designing and developing of advanced membranes for effective separation of aqueous organic solution through nanostructure manipulation of the nanomaterials.

  7. 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)

  8. 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)

  9. 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.

  10. 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.

  11. Impact of dissolved oxygen concentration on membrane filtering resistance and soluble organic matter characteristics in membrane bioreactors.

    PubMed

    Min, Kyung-Nan; Ergas, Sarina J; Mermelstein, Anna

    2008-01-01

    This study investigated the impact of dissolved oxygen (DO) concentration on membrane filtering resistance, soluble organic matter (SOM) and extracellular polymeric substance (EPS) characteristics in a membrane bioreactor (MBR). A laboratory-scale MBR was operated under DO limited (0.2 mg L(-1) DO) and fully aerobic (3.7 and 5.4 mg L(-1) DO) conditions. Membrane filtering resistance was determined for the mixed liquor suspended solids (MLSS) and for resuspended microbial biomass after removing SOM. Regardless of the DO concentration, the cake resistance (Rc) was approximately 95 percent of the total resistance (Rt). The membrane cake resistance was found to decrease significantly after removing the SOM. The total resistance caused by the resuspended biomass was 29 percent of that caused by the MLSS under DO limited conditions, while the total resistance caused by resuspended biomass was 41 to 48 percent of that caused by the MLSS under fully aerobic conditions. Under DO limited conditions, SOM in the MLSS contained a larger amount of high molecular weight compounds, leading to higher cake resistance than under fully aerobic conditions. There was significant variation in the molecular weight fractions of the EPS, with no clear relationship with DO concentration. There was also no distinct relationship between membrane filtering resistance and molecular weight fraction of the EPS.

  12. Organization of an actin filament-membrane complex. Filament polarity and membrane attachment in the microvilli of intestinal epithelial cells

    PubMed Central

    1975-01-01

    The association of actin filaments with membranes is now recognized as an important parameter in the motility of nonmuscle cells. We have investigated the organization of one of the most extensive and highly ordered actin filament-membrane complexes in nature, the brush border of intestinal epithelial cells. Through the analysis of isolated, demembranated brush borders decorated with the myosin subfragment, S1, we have determined that all the microvillar actin filaments have the same polarity. The S1 arrowhead complexes point away from the site of attachment of actin filaments at the apical tip of the microvillar membrane. In addition to the end-on attachment of actin filaments at the tip of the microvillus, these filaments are also connected to the plasma membrane all along their lengths by periodic (33 nm) cross bridges. These bridges were best observed in isolated brush borders incubated in high concentrations of Mg++. Their visibility is attributed to the induction of actin paracrystals in the filament bundles of the microvilli. Finally, we present evidence for the presence of myosinlike filaments in the terminal web region of the brush border. A model for the functional organization of actin and myosin in the brush border is presented. PMID:1202021

  13. Nepenthes insignis uses a C2-portion of the carbon skeleton of L-alanine acquired via its carnivorous organs, to build up the allelochemical plumbagin.

    PubMed

    Rischer, Heiko; Hamm, Andreas; Bringmann, Gerhard

    2002-03-01

    Tropical pitcher plants (Nepenthes) catch animals in their specialized cup-shaped leaves, digest the prey by secreting enzymes, and actively take up the resulting compounds. The benefit of this behaviour is the ability to grow and compete in nutrient-poor habitats. Our present in vitro study shows that not only the nitrogen of alanine fed to the carnivorous organs is used by the plant but that in addition intact C2-units derived from C-2 and C-3 of stable isotope labelled L-alanine serve as building blocks, here exemplarily for the synthesis of the secondary metabolite plumbagin, a potent allelochemical. This result adds a new facet to the benefit of carnivory for plants. The availability of plumbagin by a de novo synthesis probably enhances the plants' fitness in their defence against phytophagous and pathogenic organisms. A missing specific uptake or CoA activation mechanism might be the reason that acetate fed to the pitchers was not incorporated into the naphthoquinone plumbagin. The dihydronaphthoquinone glucosides rossoliside and plumbaside A, here isolated for the first time from Nepenthes, by contrast, showed no incorporation after feeding of any of the two precursors, suggesting these compounds to be storage forms with probably very low turnover rates.

  14. Effects of whole body vibration on the skeleton and other organ systems in man and animal models: what we know and what we need to know.

    PubMed

    Prisby, Rhonda D; Lafage-Proust, Marie-Hélène; Malaval, Luc; Belli, Alain; Vico, Laurence

    2008-12-01

    Previous investigations reported enhanced osseous parameters subsequent to administration of whole body vibration (WBV). While the efficacy of WBV continues to be explored, scientific inquiries should consider several key factors. Bone remodeling patterns differ according to age and hormonal status. Therefore, WBV protocols should be designed specifically for the subject population investigated. Further, administration of WBV to individuals at greatest risk for osteoporosis may elicit secondary physiological benefits (e.g., improved balance and mobility). Secondly, there is a paucity of data in the literature regarding the physiological modulation of WBV on other organ systems and tissues. Vibration-induced modulation of systemic hormones may provide a mechanism by which skeletal tissue is enhanced. Lastly, the most appropriate frequencies, durations, and amplitudes of vibration necessary for a beneficial response are unknown, and the type of vibratory signal (e.g., sinusoidal) is often not reported. This review summarizes the physiological responses of several organ systems in an attempt to link the global influence of WBV. Further, we report findings focused on subject populations that may benefit most from such a therapy (i.e., the elderly, postmenopausal women, etc.) in hopes of eliciting multidisciplinary scientific inquiries into this potentially therapeutic aid which presumably has global ramifications.

  15. Effects of cholesterol on lipid organization in human erythrocyte membrane

    PubMed Central

    1980-01-01

    The molar ratio of cholesterol to phospholipid (C/P) in human erythrocyte membrane is modified by incubating the cells with liposomes of various C/P ratios. The observed increase in cell surface area may be accounted for by the addition of cholesterol molecules. Fusion between liposomes and cells or attachment of liposomes to cells is not a significant factor in the alteration of C/P ratio. Onset temperatures for lipid phase separation in modified membranes are measured by electron diffraction. The onset temperature increases with decreasing C/P ration from 2 degrees C at C/P = 0.95 to 20 degrees C at C/P = 0.5. Redistribution of intramembrane particles is observed in membranes freeze-quenched from temperatures below the onset temperature. The heterogeneous distribution of intramembrane particles below the onset temperature suggests phase separation of lipid, with concomitant segregation of intramembrane protein into domains, even in the presence of an intact spectrin network. PMID:7372709

  16. The study on pervaporation behaviors of dilute organic solution through PDMS/PTFE composite membrane.

    PubMed

    Zhang, Wei-dong; Sun, Wei; Yang, Jing; Ren, Zhong-qi

    2010-01-01

    As an energy-efficient alternative to distillation, pervaporation has been widely combined with fermentation to remove organic compounds from their dilute solutions in a fermentation broth. In this work, the organic permselective composite membrane is prepared by coating polydimethylsiloxane (PDMS) cross-linked with n-heptane on the substrate of polytetrafluoroethylene(PTFE) membrane. The separation behavior is studied in different dilute organic solutions, which include acetone dilute solution, butanone dilute solution, cyclohexanone dilute solution, ethanol dilute solution, isopropanol dilute solution, n-butyl alcohol dilute solution, acetic acid dilute solution, and ethyl acetate dilute solution. Most of these solutions are main reaction products or by-products from fermentation process. The effects of solubility of organics in the membrane, molecular weight, and polarity of the organics on the pervaporation performance are investigated. The effects of operating temperature and organic concentration in the feed solutions on the performance of composite membrane are studied as well. The experimental results show that molecular volume has less influence than solubility and molecular polarity for these organic solvent. The selectivity of PDMS membrane to ethyl acetate is relative high due to good solubility and diffusion of ethyl acetate molecules in polymer.

  17. Correlation between membrane fouling and soluble/colloidal organic substances in membrane bioreactors for municipal wastewater treatment.

    PubMed

    Lesjean, B; Rosenberger, S; Laabs, C; Jekel, M; Gnirss, R; Amy, G

    2005-01-01

    Two similar membrane bioreactors of 2 m3 each were operated in parallel over two years under the same operational conditions, fed with the same municipal wastewater. The only process and operational difference between both pilot plants was the position of the denitrification zone (pre-denitrification in pilot 1 and post-denitrification in pilot 2). Despite parallel operation, the two MBRs exhibited different fouling rates and decreases in permeability. These differences could not be accounted for by MLSS concentrations, loading rates, or filtration flux. In a one-year investigation, soluble and colloidal organic material in the activated sludge of both MBR was regularly analysed by spectrophotometric and Size Exclusion Chromatography (SEC) methods. The larger organic molecules present in the sludge water phase (i.e. polysaccharides, proteins and organic colloids) originating from microbial activity (extracellular polymeric substances) were found to impact on the fouling and to explain the difference in membrane performance between the two MBR units. In both pilot plants, a linear relationship could be clearly demonstrated between the fouling rate of the membrane and the concentration of polysaccharides in the sludge water phase during a 5 month operational period at an SRT of 8 days.

  18. Organization and Dynamics of Fas Transmembrane Domain in Raft Membranes and Modulation by Ceramide

    PubMed Central

    Castro, Bruno M.; de Almeida, Rodrigo F.M.; Goormaghtigh, Erik; Fedorov, Aleksander; Prieto, Manuel

    2011-01-01

    To comprehend the molecular processes that lead to the Fas death receptor clustering in lipid rafts, a 21-mer peptide corresponding to its single transmembrane domain (TMD) was reconstituted into mammalian raft model membranes composed of an unsaturated glycerophospholipid, sphingomyelin, and cholesterol. The peptide membrane lateral organization and dynamics, and its influence on membrane properties, were studied by steady-state and time-resolved fluorescence techniques and by attenuated total reflection Fourier transformed infrared spectroscopy. Our results show that Fas TMD is preferentially localized in liquid-disordered membrane regions and undergoes a strong reorganization as the membrane composition is changed toward the liquid-ordered phase. This results from the strong hydrophobic mismatch between the length of the peptide hydrophobic stretch and the hydrophobic thickness of liquid-ordered membranes. The stability of nonclustered Fas TMD in liquid-disordered domains suggests that its sequence may have a protective function against nonligand-induced Fas clustering in lipid rafts. It has been reported that ceramide induces Fas oligomerization in lipid rafts. Here, it is shown that neither Fas TMD membrane organization nor its conformation is affected by ceramide. These results are discussed within the framework of Fas membrane signaling events. PMID:21961589

  19. 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.

  20. Emerging role of chemoprotective agents in the dynamic shaping of plasma membrane organization.

    PubMed

    Fuentes, Natividad R; Salinas, Michael L; Kim, Eunjoo; Chapkin, Robert S

    2017-09-01

    In the context of an organism, epithelial cells by nature are designed to be the defining barrier between self and the outside world. This is especially true for the epithelial cells that form the lining of the digestive tract, which absorb nutrients and serve as a barrier against harmful substances. These cells are constantly bathed by a complex mixture of endogenous (bile acids, mucus, microbial metabolites) and exogenous (food, nutrients, drugs) bioactive compounds. From a cell biology perspective, this type of exposure would directly impact the plasma membrane, which consists of a myriad of complex lipids and proteins. The plasma membrane not only functions as a barrier but also as the medium in which cellular signaling complexes form and function. This property is mediated by the organization of the plasma membrane, which is exquisitely temporally (nanoseconds to minutes) and spatially (nanometers to micrometers) regulated. Since numerous bioactive compounds found in the intestinal lumen can directly interact with lipid membranes, we hypothesize that the dynamic reshaping of plasma membrane organization underlies the chemoprotective effect of select membrane targeted dietary bioactives (MTDBs). This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Design and properties of functional hybrid organic-inorganic membranes for fuel cells.

    PubMed

    Laberty-Robert, C; Vallé, K; Pereira, F; Sanchez, C

    2011-02-01

    This critical review presents a discussion on the major advances in the field of organic-inorganic hybrid membranes for fuel cells application. The hybrid organic-inorganic approach, when the organic part is not conductive, reproduces to some extent the behavior of Nafion where discrete hydrophilic and hydrophilic domains are homogeneously distributed. A large variety of proton conducting or non conducting polymers can be combined with various functionalized, inorganic mesostructured particles or an inorganic network in order to achieve high proton conductivity, and good mechanical and chemical properties. The tuning of the interface between these two components and the control over chemical and processing conditions are the key parameters in fabricating these hybrid organic-inorganic membranes with a high degree of reproducibility. This dynamic coupling between chemistry and processing requires the extensive use and development of complementary ex situ measurements with in situ characterization techniques, following in real time the molecular precursor solutions to the formation of the final hybrid organic-inorganic membranes. These membranes combine the intrinsic physical and chemical properties of both the inorganic and organic components. The development of the sol-gel chemistry allows a fine tuning of the inorganic network, which exhibits acid-based functionalized pores (-SO(3)H, -PO(3)H(2), -COOH), tunable pore size and connectivity, high surface area and accessibility. As such, these hybrid membranes containing inorganic materials are a promising family for controlling conductivity, mechanical and chemical properties (349 references).

  2. Studying the spatial organization of membrane proteins by means of tritium stratigraphy: bacteriorhodopsin in purple membrane.

    PubMed

    Shishkov, A V; Ksenofontov, A L; Bogacheva, E N; Kordyukova, L V; Badun, G A; Alekseevsky, A V; Tsetlin, V I; Baratova, L A

    2002-05-15

    The topography of bacteriorhodopsin (bR) in situ was earlier studied by using the tritium bombardment approach [Eur. J. Biochem. 178 (1988) 123]. Now, having the X-ray crystallography data of bR at atom resolution [Proc. Natl. Acad. Sci. 95 (1998) 11673], we estimated the influence of membrane environment (lipid and protein) on tritium incorporation into amino acid residues forming transmembrane helices. We have determined the tritium flux attenuation coefficients for residues 10-29 of helix A. They turned out to be low (0.04+/-0.02 A(-1)) for residues adjacent to the lipid matrix, and almost fourfold higher (0.15+/-0.05 A(-1)) for those oriented to the neighboring transmembrane helices. We believe that tritium incorporation data could help modeling transmembrane segment arrangement in the membrane.

  3. Exploring Alkaline Stable Organic Cations for Polymer Hydroxide Exchange Membranes

    DTIC Science & Technology

    2015-04-29

    2012, 219, 272- 279. [82] C. Chen, A. R. Hess , A. R. Jones, X. Liu, G. D. Barber, T. E. Mallouk, H. R. Allcock, Macromolecules 2012, 45, 1182-1189... Herman , J. R. Varcoe, Energy & Environmental Science 2012, 5, 8584-8597. [176] M. A. Hossain, Y. Lim, S. Lee, H. Jang, S. Choi, Y. Jeon, S. Lee, H. Ju, W...Catalysis a-Chemical 2007, 270, 123-126. [241] H. Herman , R. C. T. Slade, J. R. Varcoe, Journal of Membrane Science 2003, 218, 147-163. [242] G. G

  4. Hydrophilic fraction of natural organic matter causing irreversible fouling of microfiltration and ultrafiltration membranes.

    PubMed

    Yamamura, Hiroshi; Okimoto, Kenji; Kimura, Katsuki; Watanabe, Yoshimasa

    2014-05-01

    Although membrane filtration is a promising technology in the field of drinking water treatment, persistent membrane fouling remains a major disadvantage. For more efficient operation, causative agents of membrane fouling need to be identified. Membrane fouling can be classified into physically reversible and irreversible fouling on basis of the removability of the foulants by physical cleaning. Four types of natural organic matter (NOM) in river water used as a source of drinking water were fractionated into hydrophobic and hydrophilic fractions, and their potential to develop irreversible membrane fouling was evaluated by a bench-scale filtration experiment together with spectroscopic and chromatographic analyses. In this study, only dissolved NOM was investigated without consideration of interactions of NOM fractions with particulate matter. Results demonstrated that despite identical total organic carbon (TOC), fouling development trends were significantly different between hydrophilic and hydrophobic fractions. The hydrophobic fractions did not increase membrane resistance, while the hydrophilic fractions caused severe loss of membrane permeability. These results were identical with the case when the calcium was added to hydrophobic and hydrophilic fractions. The largest difference in NOM characteristics between hydrophobic and hydrophilic fractions was the presence or absence of macromolecules; the primary constituent causing irreversible fouling was inferred to be "biopolymers", including carbohydrates and proteins. In addition, the results demonstrated that the extent of irreversible fouling was considerably different depending on the combination of membrane materials and NOM characteristics. Despite identical nominal pore size (0.1 μm), a polyvinylidene fluoride (PVDF) membrane was found to be more rapidly fouled than a PE membrane. This is probably explained by the generation of strong hydrogen bonding between hydroxyl groups of biopolymers and fluorine

  5. Bones in the heart skeleton of the otter (Lutra lutra)

    PubMed Central

    EGERBACHER, MONIKA; WEBER, HEIKE; HAUER, SILKE

    2000-01-01

    In most mammalian species the cardiac skeleton is composed of coarse collagen fibres, fibrocartilage, and pieces of hyaline cartilage. Bone, the os cordis, is a regular constituent of the ruminant heart. The cardiac skeleton of the otter (Lutra lutra) has not previously been described. The skeleton in 30 otter hearts was studied by x-ray analysis and light microscopy. Serial sections were cut parallel to the atrioventricular plane and histochemical staining methods were performed to identify connective tissue fibres, glycosaminoglycans, mineral deposits, and bone. Age and sex of the animals under investigation were considered. The otter heart skeleton was composed of coarse collagen fibres with intercalated pieces of fibrous and/or hyaline cartilage, calcified cartilage, and lamellar bone with red or white marrow. Pieces of hyaline cartilage were not clearly defined: a perichondrial layer was missing and coarse connective tissue continuously transformed into fibrous and hyaline cartilage. In both sexes the amount of cartilage and bone were found to increase with age. Our results establish the presence of bony material in the heart skeleton of the otter, a small mammalian species. This finding indicates that differentiation of bone is not exclusively related to the size of the organ. Increasing amounts of calcified cartilage and bone correlated with increasing age. PMID:10853970

  6. The spatial organization of Descemet's membrane-associated type IV collagen in the avian cornea

    PubMed Central

    1990-01-01

    The organization of type IV collagen in the unconventional basement membrane of the corneal endothelium (Descemet's membrane) was investigated in developing chicken embryos using anti-collagen mAbs. Both immunofluorescence histochemistry and immunoelectron microscopy were performed. In mature embryos (greater than 15 d of development), the type IV collagen of Descemet's membrane was present as an array of discrete aggregates of amorphous material at the interface between Descemet's membrane and the posterior corneal stroma. Immunoreactivity for type IV collagen was also observed in the posterior corneal stroma as irregular plaques of material with a morphology similar to that of the Descemet's membrane-associated aggregates. This arrangement of Descemet's membrane-associated type IV collagen developed from a subendothelial mat of type IV collagen-containing material. This mat, in which type IV collagen-specific immunoreactivity was always discontinuous, first appeared at the time a confluent endothelium was established, well before the onset of Descemet's membrane formation. Immunoelectron microscopy of mature corneas revealed that the characteristic nodal matrix of Descemet's membrane itself was unreactive for type IV collagen, but was penetrated at intervals by projections of type IV collagen-containing material. These projections frequently appeared to contact cell processes from the underlying corneal endothelium. This spatial arrangement of type IV collagen suggests that it serves to suture the corneal endothelium/Descemet's membrane to the dense interfacial matrix of the posterior stroma. PMID:2182654

  7. 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.

  8. An inorganic-organic proton exchange membrane for fuel cells with a controlled nanoscale pore structure.

    PubMed

    Moghaddam, Saeed; Pengwang, Eakkachai; Jiang, Ying-Bing; Garcia, Armando R; Burnett, Daniel J; Brinker, C Jeffrey; Masel, Richard I; Shannon, Mark A

    2010-03-01

    Proton exchange membrane fuel cells have the potential for applications in energy conversion and energy storage, but their development has been impeded by problems with the membrane electrode assembly. Here, we demonstrate that a silicon-based inorganic-organic membrane offers a number of advantages over Nafion--the membrane widely used as a proton exchange membrane in hydrogen fuel cells--including higher proton conductivity, a lack of volumetric size change, and membrane electrode assembly construction capabilities. Key to achieving these advantages is fabricating a silicon membrane with pores with diameters of approximately 5-7 nm, adding a self-assembled molecular monolayer on the pore surface, and then capping the pores with a layer of porous silica. The silica layer reduces the diameter of the pores and ensures their hydration, resulting in a proton conductivity that is two to three orders of magnitude higher than that of Nafion at low humidity. A membrane electrode assembly constructed with this proton exchange membrane delivered an order of magnitude higher power density than that achieved previously with a dry hydrogen feed and an air-breathing cathode.

  9. Amiodarone effects on membrane organization evaluated by fluorescence polarization.

    PubMed

    Antunes-Madeira, M C; Videira, R A; Klüppel, M L; Madeira, V V

    1995-03-03

    The effects of amiodarone (0-100 microM) on the physical state of synthetic and native membranes were investigated by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH), probing the bilayer core, and of its anionic propionic acid derivative (DPH-PA), probing the outer regions of the bilayer. In the gel phase of dimyristoylphosphatidylcholine (DMPC) bilayers, amiodarone broadens the transition profile and shifts the phase transition midpoint to lower temperature values, as evaluated by both probes. On the other hand, the drug orders the fluid phase of the lipid either in hydrophobic core or in the outer regions of the bilayer, as detected by DPH and DPH-PA, respectively. The effects of amiodarone on the thermotropic behaviour of DPPC confirm and extend data in DMPC. Cholesterol concentration modulates to a great extent the effects of amiodarone in the fluid phase of DMPC. Thus, both probes, DPH and DPH-PA, detect either ordering effects of amiodarone for low cholesterol concentrations (< or = 20 mol%) or disordering amiodarone effects at higher cholesterol levels (> 20 mol%). In agreement with the results in models of synthetic lipids, the ordering effects of amiodarone in fluid native membranes of mitochondria and brain microsomes are depressed with the increase in intrinsic cholesterol. The ordering effects in mitochondria may induce bioenergetic dysfunctions and consequently disturbances in the electromechanic functioning of myocardium.

  10. 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

  11. 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.

  12. Impact of colloidal and soluble organic material on membrane performance in membrane bioreactors for municipal wastewater treatment.

    PubMed

    Rosenberger, S; Laabs, C; Lesjean, B; Gnirss, R; Amy, G; Jekel, M; Schrotter, J-C

    2006-02-01

    Two parallel membrane bioreactors (2 m3 each) were operated over a period of 2 years. Both pilots were optimised for nitrification, denitrification, and enhanced biological phosphorous elimination, treating identical municipal wastewater under comparable operating conditions. The only constructional difference between the pilots was the position of the denitrification zone (pre-denitrification in pilot 1 and post-denitrification in pilot 2). Despite identical modules and conditions, the two MBRs showed different permeabilities and fouling rates. The differences were not related to the denitrification scheme. In order to find an explanation for the different membrane performances, a one-year investigation was initiated and the membrane performance as well as the operating regime and characteristics of the activated sludge were closely studied. MLSS concentrations, solid retention time, loading rates, and filtration flux were found not to be responsible for the different performance of the submerged modules. These parameters were kept identical in the two pilot plants. Instead, the non-settable fraction of the sludges (soluble and colloidal material, i.e. polysaccharides, proteins and organic colloids) was found to impact fouling and to cause the difference in membrane performance between the two MBR. This fraction was analysed by spectrophotometric and size exclusion chromatography (SEC) methods. In a second step, the origin of these substances was investigated. The results point to microbiologically produced substances such as extracellular polymeric substances (EPS) or soluble microbial products (SMP).

  13. Anodized Aluminum Oxide Templated Synthesis of Metal-Organic Frameworks Used as Membrane Reactors.

    PubMed

    Yu, Yifu; Wu, Xue-Jun; Zhao, Meiting; Ma, Qinglang; Chen, Junze; Chen, Bo; Sindoro, Melinda; Yang, Jian; Han, Shikui; Lu, Qipeng; Zhang, Hua

    2017-01-09

    The incorporation of metal-organic frameworks (MOFs) into membrane-shaped architectures is of great importance for practical applications. The currently synthesized MOF-based membranes show many disadvantages, such as poor compatibility, low dispersity, and instability, which severely limit their utility. Herein, we present a general, facile, and robust approach for the synthesis of MOF-based composite membranes through the in situ growth of MOF plates in the channels of anodized aluminum oxide (AAO) membranes. After being used as catalysis reactors, they exhibit high catalytic performance and stability in the Knoevenagel condensation reaction. The high catalytic performance might be attributed to the intrinsic structure of MOF-based composite membranes, which can remove the products from the reaction zone quickly, and prevent the aggregation and loss of catalysts during reaction and recycling process.

  14. Separations of hazardous organics from gas and liquid feedstreams using phosphazene polymer membranes

    SciTech Connect

    Peterson, E.S.; Stone, M.L.; Cummings, D.G.; McCaffrey, R.R.

    1993-01-01

    The liquid-liquid and gas separation properties for the separation of hazardous organic feed streams using pervaporation and gas separation methods with poly[bis(phenoxy)phosphazene] based membranes are reported. Liquid transport behavior was determined using pervaporation techniques. The preliminary gas separations were studied using a mixed gas separation method which the authors have described previously. Using the membrane pervaporation technique, separation factors of 10,000 have been routinely achieved for the separation of methylene chloride from water. Other tests have shown similar results for the removal of hydrocarbon vapors from air. Membranes were prepared using solution casting techniques. Solvent evaporation rates during the casting and subsequent curing processes were controlled to provide a consistent membrane microstructure. These results suggest that polyphosphazene membrane technology could effectively be used in cleaning up air and ground water that has been contaminated with chlorinated hydrocarbons.

  15. Membrane air stripping: A process for removal of organics from aqueous solutions

    SciTech Connect

    Mahmud, H.; Kumar, A.; Narbaitz, R.M.; Matsuura, T.

    1998-10-01

    The membrane air-stripping (MAS) process using microporous polypropylene hollow fiber membranes has shown potential for the removal of volatile organics from aqueous streams over conventional treatment processes, particularly in reducing the size of the equipment. This paper reviews the theoretical aspects and experimental investigations on the performance of these membranes in terms of overall mass transfer capabilities in the removal of organics from aqueous solutions. The reported findings of the effect of pH, ozone, chlorine, influence of packing density and possible fouling on the performance of these hollow fibers membranes are presented. The fate of the stripped air is discussed. Other possible applications as well as the future research needs are highlighted, along with critical assessment of the reported work.

  16. Organic fouling and chemical cleaning of nanofiltration membranes: measurements and mechanisms.

    PubMed

    Li, Qilin; Elimelech, Menachem

    2004-09-01

    Fouling and subsequent chemical cleaning of nanofiltration (NF) membranes used in water quality control applications are often inevitable. To unravel the mechanisms of organic fouling and chemical cleaning, it is critical to understand the foulant-membrane, foulant-foulant, and foulant-cleaning agent interactions at the molecular level. In this study, the adhesion forces between the foulant and the membrane surface and between the bulk foulant and the fouling layer were determined by atomic force microscopy (AFM). A carboxylate modified AFM colloid probe was used as a surrogate for humic acid, the major organic foulant in natural waters. The interfacial force data were combined with the NF membrane water flux measurements to elucidate the mechanisms of organic fouling and chemical cleaning. A remarkable correlation was obtained between the measured adhesion forces and the fouling and cleaning behavior of the membrane under various solution chemistries. The AFM measurements further confirmed that divalent calcium ions greatly enhance natural organic matter fouling by complexation and subsequent formation of intermolecular bridges among organic foulant molecules. Efficient chemical cleaning was achieved only when the calcium ion bridging was eliminated as a result of the interaction between the chemical cleaning agent and the fouling layer. The cleaning efficiency was highly dependent on solution pH and the concentration of the chemical cleaning agent.

  17. Cost factors and chemical pretreatment effects in the membrane filtration of waters containing natural organic matter.

    PubMed

    Schäfer, A I; Fane, A G; Waite, T D

    2001-04-01

    This paper compares the membrane processes available for water treatment. Membranes have the advantage of currently decreasing capital cost, a relatively small footprint compared to conventional treatment, generally a reduction in chemicals usage and comparably low maintenance requirements. Three membrane processes applicable to water treatment, micro- (MF), ultra- (UF), and nanofiltration (NF), are compared in terms of intrinsic rejection, variation of rejection due to membrane fouling and increase in rejection by ferric chloride pretreatment. Twelve different membranes are compared on the basis of their membrane pore size which was calculated from their molecular weight cut-off. A pore size of < 6 nm is required to achieve substantial (> 50%) organics removal. For a fouled membrane this pore size is about 11 nm. UV rejection is higher than DOC rejection. Coagulation pretreatment allows a higher rejection of organics by MF and UF and the cut-off criterion due to initial membrane pore size is no longer valid. A water quality parameter (WQP) is introduced which describes the product water quality achieved as a function of colloid, DOC and cation rejection. The relationship between log (pore size) and WQP is linear. Estimation of membrane costs as a function of WQP suggests that open UF is superior to MF (similar cost at higher WQP) and NF is superior to tight UF. Chemical pretreatment could compensate for the difference between MF and UF. However, when considering chemicals and energy costs, it appears that a process operated at a higher energy is cheaper at a guaranteed product quality (less dependent on organic type). This argument is further supported by environmental issues of chemicals usage, as energy may be provided from renewable sources.

  18. Acetylcholine Receptor Organization in Membrane Domains in Muscle Cells

    PubMed Central

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

    2011-01-01

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

  19. Selective Molecular Sieving in Self-Standing Porous Covalent-Organic-Framework Membranes.

    PubMed

    Kandambeth, Sharath; Biswal, Bishnu P; Chaudhari, Harshal D; Rout, Kanhu Charan; Kunjattu H, Shebeeb; Mitra, Shouvik; Karak, Suvendu; Das, Anuja; Mukherjee, Rabibrata; Kharul, Ulhas K; Banerjee, Rahul

    2017-01-01

    Self-standing, flexible, continuous, and crack-free covalent-organic-framework membranes (COMs) are fabricated via a simple, scalable, and highly cost-effective methodology. The COMs show long-term durability, recyclability, and retain their structural integrity in water, organic solvents, and mineral acids. COMs are successfully used in challenging separation applications and recovery of valuable active pharmaceutical ingredients from organic solvents.

  20. The Effect of Freezing on Thylakoid Membranes in the Presence of Organic Acids

    PubMed Central

    Santarius, Kurt A.

    1971-01-01

    The effect of salts of organic acids on washed and non-washed chloroplast membranes during freezing was investigated. Thylakoids were isolated from spinach leaves (Spinacia oleracea L.) and, prior to freezing, salts of various organic acids or inorganic salts or both were added. Freezing occurred for 3 to 4 hours at −25 C. After thawing membrane integrity was investigated by measuring the activity of cyclic photophosphorylation. At very low NaCl levels (1 to 3 mm, washed thylakoids) salts of organic acids either could not prevent membrane inactivation in the course of freezing (succinate) or were effective only at relatively high concentrations (0.1 m or more of acetate, pyruvate, malate, tartrate, citrate). If NaCl was present at higher concentrations (e.g., 0.1 m) some organic acids, e.g. succinate, malate, tartrate, and citrate, were able to protect frost-sensitive thylakoids at surprisingly low concentrations (10 to 20 mm). Other inorganic salts such as KCl, MgCl2, NaNO3 could also induce protection by organic acids which otherwise were ineffective or poorly effective. For effective protection, a more or less constant ratio between inorganic salt and organic acid or between two or more organic acids had to be maintained. Departure to either side from the optimal ratio led to progressive inactivation. The unspecificity of the protective effect of organic acids suggests that these compounds protect colligatively. There are also indications that, in addition, more specific interaction with the membranes contributes to protection. At temperatures above the freezing point, the presence of salts of organic acids decreased the rate of membrane inactivation by high electrolyte concentrations. PMID:16657754

  1. 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

  2. Chemical cleaning/disinfection and ageing of organic UF membranes: a review.

    PubMed

    Regula, C; Carretier, E; Wyart, Y; Gésan-Guiziou, G; Vincent, A; Boudot, D; Moulin, P

    2014-06-01

    Membrane separation processes have become a basic unit operation for process design and product development. These processes are used in a variety of separation and concentration steps, but in all cases, the membranes must be cleaned regularly to remove both organic and inorganic material deposited on the surface and/or into the membrane bulk. Cleaning/disinfection is a vital step in maintaining the permeability and selectivity of the membrane in order to get the plant to its original capacity, to minimize risks of bacteriological contamination, and to make acceptable products. For this purpose, a large number of chemical cleaning/disinfection agents are commercially available. In general, these cleaning/disinfection agents have to improve the membrane flux to a certain extent. However, they can also cause irreversible damages in membrane properties and performances over the long term. Until now, there is considerably less literature dedicated to membrane ageing than to cleaning/disinfection. The knowledge in cleaning/disinfection efficiency has recently been improved. But in order to develop optimized cleaning/disinfection protocols there still remains a challenge to better understand membrane ageing. In order to compensate for the lack of correlated cleaning/disinfection and ageing data from the literature, this paper investigates cleaning/disinfection efficiencies and ageing damages of organic ultrafiltration membranes. The final aim is to provide less detrimental cleaning/disinfection procedures and to propose some guidelines which should have been taken into consideration in term of membrane ageing studies. To carry out this study, this article will detail the background of cleaning/disinfection and aging membrane topics in a first introductive part. In a second part, key factors and endpoints of cleaning/disinfection and aging membranes will be discussed deeply: the membrane role and the cleaning parameters roles, such as water quality, storing conditions

  3. Comparison between a moving bed membrane bioreactor and a conventional membrane bioreactor on organic carbon and nitrogen removal.

    PubMed

    Yang, Shuai; Yang, Fenglin; Fu, Zhimin; Lei, Ruibo

    2009-04-01

    A membrane bioreactor filled with carriers instead of activated sludge named a moving bed membrane bioreactor (MBMBR) was investigated for simultaneously removing organic carbon and nitrogen in wastewater. Its performance was compared with a conventional membrane bioreactor (CMBR) at various influent COD/TN ratios of 8.9-22.1. The operational parameters were optimized to increase the treatment efficiency. COD removal efficiency averaged at 95.6% and 96.2%, respectively, for MBMBR and CMBR during the 4 months experimental period. The MBMBR system demonstrated good performance on nitrogen removal at different COD/TN ratios. When COD/TN was 8.9 and the total nitrogen (TN) load was 7.58 mg/l h, the TN and ammonium nitrogen removal efficiencies of the MBMBR were maintained over 70.0% and 80.0%, respectively, and the removed total nitrogen (TN) load reached to 5.31 mg/l h. Multifunctional microbial reactions in the carrier, such as simultaneous nitrification and denitrification (SND), play important roles in nitrogen removal. In comparison, the CMBR did not perform so well. Its TN removal was not stable, and the removed total nitrogen (TN) load was only 1.02 mg/l h at COD/TN ratio 8.9. The specific oxygen utilization rate (SOUR) showed that the biofilm has a better microbial activity than an activated sludge. Nevertheless, the membrane fouling behavior was more severe in the MBMBR than in the CMBR due to a thick and dense cake layer formed on the membrane surface, which was speculated to be caused by the filamentous bacteria in the MBMBR.

  4. Impact on lipid membrane organization by free branched-chain fatty acids.

    PubMed

    Lindström, Fredrick; Thurnhofer, Saskia; Vetter, Walter; Gröbner, Gerhard

    2006-11-07

    Here, we exploit the non-invasive techniques of solid-state NMR (nuclear magnetic resonance) and differential scanning calorimetry (DSC) to study the effect of free iso and ante-iso branched chain fatty acids (BCFAs) on the physicochemical properties of lipid membranes. Free fatty acids are present in biological membranes at low abundance, but can influence the cellular function by modulating the membrane organization. Solid state NMR spectra of dimyristoylphosphatidylcholine (DMPC) lipid membranes containing either free 12-methyltetradecanoic acid (a15:0) or free 13-methyltetradecanoic acid (i15:0), show significant differences in their impact on the lipid bilayer. Chain order profiles obtained by deuterium NMR on fully deuterated DMPC-d(67) bilayers revealed an ordering effect induced by both fatty acids on the hydrophobic membrane core. This behavior was also visible in the corresponding DSC thermograms where the main phase transition of DMPC bilayers-indicative of the hydrophobic membrane region-was shifted to higher temperatures, with the iso isomer triggering more pronounced changes as compared to the ante-iso isomer. This is probably due to a higher packing density in the core of the lipid bilayer, which causes reduced diffusion across membranes. By utilizing the naturally occurring spin reporters nitrogen-14 and phosphorus-31 present in the hydrophilic DMPC headgroup region, even fatty acid induced changes at the membrane interface could be detected, an observation reflecting changes in the lipid headgroup dynamics.

  5. Unique characteristics of algal dissolved organic matter and their association with membrane fouling behavior: a review.

    PubMed

    Ly, Quang Viet; Maqbool, Tahir; Hur, Jin

    2017-04-01

    Over the last several decades, the frequent occurrence of algal bloom in drinking water supplies, driven by increasing anthropogenic input and climate change, has posed serious problems for membrane filtration processes, resulting in reduced membrane permeability and increased energy consumption. It is essential to comprehensively understand the characteristics of algal dissolved organic matter (DOM) and the subsequent effects on the filtration processes for better insight into membrane fouling mitigation. Many studies have revealed that algal DOM has displayed unique characteristics distinguished from other sources of DOM with respect to the chemical composition, the structures, and the molecular weight distributions. Algal DOM is considered to be a major obstacle in understanding membrane fouling due to its complicated interactions among dissimilar algal DOM constituents as well as between algal DOM and membrane material matrices. The present review article summarizes (1) recent characterizing methods for algal DOM, (2) environmental factors affecting the characteristics of algal DOM, (3) the discrepancies between algal DOM and other sources of aquatic DOM, particularly terrestrial sources, and (4) potential fouling effects of algal DOM on membrane filtration processes and their associations with algal DOM characteristics. A broad understanding of algal DOM-driven membrane fouling can lead to breakthroughs in efficient membrane filtration processes to treat algal bloom water sources.

  6. Gel-impregnated pore membranes with mesh-size asymmetry for biohybrid artificial organs.

    PubMed

    Dai, W S; Barbari, T A

    2000-07-01

    Membranes based on mechanically supported poly(vinyl alcohol) (PVA) hydrogels with mesh-size asymmetry were developed for potential application in biohybrid artificial organs. The pores of cellulose ester microfiltration membranes were impregnated with a PVA solution, which was lightly crosslinked with glutaraldehyde and then modified under a glutaraldehyde gradient to produce mesh-size asymmetry. Permeation experiments were performed with the resulting homogeneous and asymmetric gel-impregnated pore membranes (GIPMs). 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. The transport properties of the GIPMs were compared to those of conventional ultrafiltration (UF) and dialysis membranes. Experimental results indicate that GIPMs with mesh-size asymmetry have thickness-normalized creatinine permeabilities that are slightly higher than those in cellulosic UF membranes but as much as 100% greater than those in polysulfone UF or cellulosic dialysis membranes. IgG permeabilities in the GIPMs are from 5 to 50 times lower than those in the UF membranes. Fab permeabilities are 6 to 40 times higher in the UF membranes than those in the GIPMs, but the required permeability for a therapeutic protein is application specific. GIPMs may also be suitable as an alternative for hemodialysis.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    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.

  8. 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. Copyright © 2016, American Association for the Advancement of Science.

  9. Melorheostosis involving the craniofacial skeleton.

    PubMed

    Ethunandan, Madanagopalan; Khosla, Nalin; Tilley, Elizabeth; Webb, Andrew

    2004-11-01

    Melorheostosis is a rare bone disorder, usually affecting the long bones and adjacent soft tissue. It was originally described by Leri and Joanny in 1922, after its classic x-ray features of flowing hyperostosis resembling dripping candle wax. There have been fewer than 10 reported cases of craniofacial involvement, and in most instances these have also involved the appendicular skeleton. The authors report a case of melorheostosis with isolated craniofacial involvement, describe the clinical course and radiologic and histologic features, and review the pertinent literature.

  10. Cell cycle dependent changes in the plasma membrane organization of mammalian cells.

    PubMed

    Denz, Manuela; Chiantia, Salvatore; Herrmann, Andreas; Mueller, Peter; Korte, Thomas; Schwarzer, Roland

    2017-03-01

    Lipid membranes are major structural elements of all eukaryotic and prokaryotic organisms. Although many aspects of their biology have been studied extensively, their dynamics and lateral heterogeneity are still not fully understood. Recently, we observed a cell-to-cell variability in the plasma membrane organization of CHO-K1 cells (Schwarzer et al., 2014). We surmised that cell cycle dependent changes of the individual cells from our unsynchronized cell population account for this phenomenon. In the present study, this hypothesis was tested. To this aim, CHO-K1 cells were arrested in different cell cycle phases by chemical treatments, and the order of their plasma membranes was determined by various fluorescent lipid analogues using fluorescence lifetime imaging microscopy. Our experiments exhibit significant differences in the membrane order of cells arrested in the G2/M or S phase compared to control cells. Our single-cell analysis also enabled the specific selection of mitotic cells, which displayed a significant increase of the membrane order compared to the control. In addition, the lipid raft marker GPImYFP was used to study the lateral organization of cell cycle arrested cells as well as mitotic cells and freely cycling samples. Again, significant differences were found between control and arrested cells and even more pronounced between control and mitotic cells. Our data demonstrate a direct correlation between cell cycle progression and plasma membrane organization, underlining that cell-to-cell heterogeneities of membrane properties have to be taken into account in cellular studies especially at the single-cell level.

  11. THE EFFECT OF ORGANIC IONS ON THE MEMBRANE POTENTIAL OF NERVES

    PubMed Central

    Wilbrandt, W.

    1937-01-01

    1. The effect of osmotic pressure on the nerve resting potential of frog sciatic nerve is in accordance with the assumption of a membrane potential; increased osmotic pressure raises, decreased osmotic pressure lowers the potential. 2. The potential of crab nerves is affected by organic and inorganic cations in the approximate series: Rb > K = diamylamine > dibutylamine > guanidine > tetraethylamine > diethylamine = dimethylamine > dipropylamine > tetramethylamine = choline = Na = Li. 3. The response of the potential to the series of dialkylamines (first decrease, then increase of response ascending in the series) is best understood by the assumption that the nerve membrane is a porous structure. 4. With respect to these salts as well as to other organic cations the dried collodion membrane as a model of a porous membrane shows a striking parallelism to the nerve membrane. 5. Both inorganic and organic anions (NO3, SCN, acetate, propionate, butyrate, lactate, pyruvate) have a definite, if slight, effect in raising the potential of crab nerves. This effect of anions indicates that the nerve membrane is not completely anion impermeable. 6. The effect of organic ions is, with certain restrictions, reversible. Its possible relation to the resting potential and to the after potentials of the electrical disturbance is discussed. 7. The response of the myelinated sciatic nerve of the frog and of the non-myelinated nerve of the spider crab show considerable agreement. There are some definite differences which are, however, not necessarily due to differences of the cell membranes involved, but may be ascribed to the difference of ionic conditions in Ringer and sea water. PMID:19873008

  12. Chlorotrifluoroethylcysteine interaction with rabbit proximal tubule cell basolateral membrane organic anion transport and apical membrane amino acid transport.

    PubMed

    Groves, C E; Morales, M N

    1999-11-01

    The interaction of the cysteine conjugate S-(1-chloro-1,2,2, -trifluoroethyl)-L-cysteine (CTFC) with organic anion and amino acid transport in the basolateral and apical membranes was examined with rabbit renal proximal tubule suspensions and primary cultures of rabbit renal proximal tubule cells. The apparent K(i) for CTFC inhibition of the 1-min uptake of [(3)H]p-aminohippurate in tubule suspensions was 105+/-3 microM and suggests that CTFC interacts with basolateral organic anion transport. Also, the addition of 1 mM CTFC decreased the secretion and intracellular accumulation of fluorescein by approximately 70 to 75%. The addition of 1 mM CTFC to the apical compartment decreased the reabsorption and intracellular accumulation of the amino acid [(3)H]phenylalanine by approximately 60 to 70%. Similar to CTFC, saturating concentrations of the organic anion [(3)H]p-aminohippurate and the amino acid phenylalanine reduced by approximately 75% fluorescein secretion and [(3)H]phenylalanine reabsorption, respectively, by approximately 60 to 70%. Thus, the cysteine conjugate CTFC appears to be a potent inhibitor of basolateral organic anion and apical amino acid transepithelial transport. In contrast to its effects on apical phenylalanine uptake, CTFC had no effect on the basal uptake of [(3)H]phenylalanine by primary cultures. The presence of CTFC in the external bath did trans-stimulate the efflux of fluorescein and [(3)H]phenylalanine across the basal and apical membrane in tubule suspensions or primary cultures, respectively, grown on plastic. Collectively, these data demonstrate that CTFC interacts with, and is transported by, two anatomically and functionally distinct transporters, the basolateral organic anion and apical neutral amino acid pathways, in the rabbit renal proximal tubule cell.

  13. 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. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  14. 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.

  15. 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.

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

    DOE PAGES

    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

  17. 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.

  18. Membrane bioreactor process of organic wastewater from brassylic acid manufacturing plant.

    PubMed

    Wu, Z C; Zeng, P; Wang, S F; Gao, T Y

    2001-04-01

    The wastewater treatment from brassylic acid manufacturing plant using membrane bioreactor (MBR) was studied. The membrane bioreactor consisted of batch-operation biological aeration tank and ultrafiltration evaluation tank. The content of test included the affection of variation operation conditions on ultrafiltration separation, the general characteristics of MBR process, and the difference comparing with the conventional biological treatment. The results are as follows: (1) among the test membrane material, polyether sulphone (PES) membrane is more suitable for the wastewater treatment; (2) when the cutoff molecular weight is among 10,000-50,000, the higher the cutoff molecular weight, the bigger the water flux is in the test; (3) under the operation pressure, water flux increases accompanying with the increasing of operation pressure; (4) the paper filtered COD concentration has more affection on the water flux than the suspended solid concentration; (5) as the volume loading of MBR increases, the accumulation of high molecule organic substance and colloid increases, the membrane permeate COD concentration and paper filtered COD concentration increase too, meanwhile the water flux reduces; (6) when the sludge retention time of activated sludge of MBR increases, the accumulation of high molecule organic substance and colloid reduces, the membrane permeate COD concentration and paper filtered COD concentration reduce too, and the water flux increases; (7) comparing with the conventional biological process, the microbial activity is higher, but the microbial species is less.

  19. 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

    2012-04-03

    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.

  20. Dynamic organization of myristoylated Src in the live cell plasma membrane

    DOE PAGES

    Smith, Adam W.; Huang, Hector H.; Endres, Nicholas F.; ...

    2016-01-15

    The spatial organization of lipid-anchored proteins in the plasma membrane directly influences cell signaling, but measuring such organization in situ is experimentally challenging. The canonical oncogene, c-Src, is a lipid anchored protein that plays a key role in integrin-mediated signal transduction within focal adhesions and cell–cell junctions. Because of its activity in specific plasma membrane regions, structural motifs within the protein have been hypothesized to play an important role in its subcellular localization. This study used a combination of time-resolved fluorescence fluctuation spectroscopy and super-resolution microscopy to quantify the dynamic organization of c-Src in live cell membranes. Pulsed-interleaved excitation fluorescencemore » cross-correlation spectroscopy (PIE–FCCS) showed that a small fraction of c-Src transiently sorts into membrane clusters that are several times larger than the monomers. Photoactivated localization microscopy (PALM) confirmed that c-Src partitions into clusters with low probability and showed that the characteristic size of the clusters is 10–80 nm. Finally, time-resolved fluorescence anisotropy measurements were used to quantify the rotational mobility of c-Src to determine how it interacts with its local environment. Altogether, these results build a quantitative description of the mobility and clustering behavior of the c-Src nonreceptor tyrosine kinase in the live cell plasma membrane.« less

  1. Dynamic organization of myristoylated Src in the live cell plasma membrane

    SciTech Connect

    Smith, Adam W.; Huang, Hector H.; Endres, Nicholas F.; Rhodes, Christopher; Groves, Jay T.

    2016-01-15

    The spatial organization of lipid-anchored proteins in the plasma membrane directly influences cell signaling, but measuring such organization in situ is experimentally challenging. The canonical oncogene, c-Src, is a lipid anchored protein that plays a key role in integrin-mediated signal transduction within focal adhesions and cell–cell junctions. Because of its activity in specific plasma membrane regions, structural motifs within the protein have been hypothesized to play an important role in its subcellular localization. This study used a combination of time-resolved fluorescence fluctuation spectroscopy and super-resolution microscopy to quantify the dynamic organization of c-Src in live cell membranes. Pulsed-interleaved excitation fluorescence cross-correlation spectroscopy (PIE–FCCS) showed that a small fraction of c-Src transiently sorts into membrane clusters that are several times larger than the monomers. Photoactivated localization microscopy (PALM) confirmed that c-Src partitions into clusters with low probability and showed that the characteristic size of the clusters is 10–80 nm. Finally, time-resolved fluorescence anisotropy measurements were used to quantify the rotational mobility of c-Src to determine how it interacts with its local environment. Altogether, these results build a quantitative description of the mobility and clustering behavior of the c-Src nonreceptor tyrosine kinase in the live cell plasma membrane.

  2. Membrane lipid phase transitions and phase organization studied by Fourier transform infrared spectroscopy.

    PubMed

    Lewis, Ruthven N A H; McElhaney, Ronald N

    2013-10-01

    Fourier transform infrared (FTIR) spectroscopy is a powerful yet relatively inexpensive and convenient technique for studying the structure and organization of membrane lipids in their various polymorphic phases. This spectroscopic technique yields information about the conformation and dynamics of all regions of the lipid molecule simultaneously without the necessity of introducing extrinsic probes. In this review, we summarize some relatively recent FTIR spectroscopic studies of the structure and organization primarily of fully hydrated phospholipids in their biologically relevant lamellar crystalline, gel and liquid-crystalline phases, and show that interconversions between these bilayer phases can be accurately monitored by this technique. We also briefly discuss how the structure and organization of potentially biologically relevant nonlamellar micellar or reversed hexagonal lipid phases can be studied and how phase transitions between lamellar and nonlamellar phases, or between various nonlamellar phases, can be followed as well. In addition, we discuss the potential for FTIR spectroscopy to yield fairly high resolution structural information about phospholipid packing in lamellar crystalline or gel phases. Finally, we show that many, but not all of these FTIR approaches can also yield valuable information about lipid-protein interactions in membrane protein- or peptide-containing lipid membrane bilayer model or even in biological membranes. This article is part of a Special Issue entitled: FTIR in membrane proteins and peptide studies.

  3. 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.

  4. Microstructural Engineering and Architectural Design of Metal-Organic Framework Membranes.

    PubMed

    Liu, Yi; Ban, Yujie; Yang, Weishen

    2017-08-01

    In the past decade, a huge development in rational design, synthesis, and application of molecular sieve membranes, which typically included zeolites, metal-organic frameworks (MOFs), and graphene oxides, has been witnessed. Owing to high flexibility in both pore apertures and functionality, MOFs in the form of membranes have offered unprecedented opportunities for energy-efficient gas separations. Reports on the fabrication of well-intergrown MOF membranes first appeared in 2009. Since then there has been tremendous growth in this area along with an exponential increase of MOF-membrane-related publications. In order to compete with other separation and purification technologies, like cryogenic distillation, pressure swing adsorption, and chemical absorption, separation performance (including permeability, selectivity, and long-term stability) of molecular sieve membranes must be further improved in an attempt to reach an economically attractive region. Therefore, microstructural engineering and architectural design of MOF membranes at mesoscopic and microscopic levels become indispensable. This review summarizes some intriguing research that may potentially contribute to large-scale applications of MOF membranes in the future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Impact of polymeric membrane filtration of oil sands process water on organic compounds quantification.

    PubMed

    Moustafa, Ahmed M A; Kim, Eun-Sik; Alpatova, Alla; Sun, Nian; Smith, Scott; Kang, Seoktae; Gamal El-Din, Mohamed

    2014-01-01

    The interaction between organic fractions in oil sands process-affected water (OSPW) and three polymeric membranes with varying hydrophilicity (nylon, polyvinylidene fluoride and polytetrafluoroethylene) at different pHs was studied to evaluate the impact of filtration on the quantification of acid-extractable fraction (AEF) and naphthenic acids (NAs). Four functional groups predominated in OSPW (amine, phosphoryl, carboxyl and hydroxyl) as indicated by the linear programming method. The nylon membranes were the most hydrophilic and exhibited the lowest AEF removal at pH of 8.7. However, the adsorption of AEF on the membranes increased as the pH of OSPW decreased due to hydrophobic interactions between the membrane surfaces and the protonated molecules. The use of ultra pressure liquid chromatography-high resolution mass spectrometry (UPLC/HRMS) showed insignificant adsorption of NAs on the tested membranes at pH 8.7. However, 26±2.4% adsorption of NAs was observed at pH 5.3 following the protonation of NAs species. For the nylon membrane, excessive carboxylic acids in the commercial NAs caused the formation of negatively charged assisted hydrogen bonds, resulting in increased adsorption at pH 8.2 (25%) as compared to OSPW (0%). The use of membranes for filtration of soluble compounds from complex oily wastewaters before quantification analysis of AEF and NAs should be examined prior to application.

  6. A palmitoylation switch mechanism regulates Rac1 function and membrane organization

    PubMed Central

    Navarro-Lérida, Inmaculada; Sánchez-Perales, Sara; Calvo, María; Rentero, Carles; Zheng, Yi; Enrich, Carlos; Del Pozo, Miguel A

    2012-01-01

    The small GTPase Rac1 plays important roles in many processes, including cytoskeletal reorganization, cell migration, cell-cycle progression and gene expression. The initiation of Rac1 signalling requires at least two mechanisms: GTP loading via the guanosine triphosphate (GTP)/guanosine diphosphate (GDP) cycle, and targeting to cholesterol-rich liquid-ordered plasma membrane microdomains. Little is known about the molecular mechanisms governing this specific compartmentalization. We show that Rac1 can incorporate palmitate at cysteine 178 and that this post-translational modification targets Rac1 for stabilization at actin cytoskeleton-linked ordered membrane regions. Palmitoylation of Rac1 requires its prior prenylation and the intact C-terminal polybasic region and is regulated by the triproline-rich motif. Non-palmitoylated Rac1 shows decreased GTP loading and lower association with detergent-resistant (liquid-ordered) membranes (DRMs). Cells expressing no Rac1 or a palmitoylation-deficient mutant have an increased content of disordered membrane domains, and markers of ordered membranes isolated from Rac1-deficient cells do not correctly partition in DRMs. Importantly, cells lacking Rac1 palmitoylation show spreading and migration defects. These data identify palmitoylation as a mechanism for Rac1 function in actin cytoskeleton remodelling by controlling its membrane partitioning, which in turn regulates membrane organization. PMID:22157745

  7. 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.

  8. The Plasma Membrane Potential and the Organization of the Actin Cytoskeleton of Epithelial Cells

    PubMed Central

    Chifflet, Silvia; Hernández, Julio A.

    2012-01-01

    The establishment and maintenance of the polarized epithelial phenotype require a characteristic organization of the cytoskeletal components. There are many cellular effectors involved in the regulation of the cytoskeleton of epithelial cells. Recently, modifications in the plasma membrane potential (PMP) have been suggested to participate in the modulation of the cytoskeletal organization of epithelia. Here, we review evidence showing that changes in the PMP of diverse epithelial cells promote characteristic modifications in the cytoskeletal organization, with a focus on the actin cytoskeleton. The molecular paths mediating these effects may include voltage-sensitive integral membrane proteins and/or peripheral proteins sensitive to surface potentials. The voltage dependence of the cytoskeletal organization seems to have implications in several physiological processes, including epithelial wound healing and apoptosis. PMID:22315611

  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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. PSF decomposition of nanoscopy images via Bayesian analysis unravels distinct molecular organization of the cell membrane

    PubMed Central

    Manzo, Carlo; van Zanten, Thomas S.; Saha, Suvrajit; Torreno-Pina, Juan A.; Mayor, Satyajit; Garcia-Parajo, Maria F.

    2014-01-01

    The spatial organization of membrane receptors at the nanoscale has major implications in cellular function and signaling. The advent of super-resolution techniques has greatly contributed to our understanding of the cellular membrane. Yet, despite the increased resolution, unbiased quantification of highly dense features, such as molecular aggregates, remains challenging. Here we describe an algorithm based on Bayesian inference of the marker intensity distribution that improves the determination of molecular positions inside dense nanometer-scale molecular aggregates. We tested the performance of the method on synthetic images representing a broad range of experimental conditions, demonstrating its wide applicability. We further applied this approach to STED images of GPI-anchored and model transmembrane proteins expressed in mammalian cells. The analysis revealed subtle differences in the organization of these receptors, emphasizing the role of cortical actin in the compartmentalization of the cell membrane. PMID:24619088

  11. PSF decomposition of nanoscopy images via Bayesian analysis unravels distinct molecular organization of the cell membrane.

    PubMed

    Manzo, Carlo; van Zanten, Thomas S; Saha, Suvrajit; Torreno-Pina, Juan A; Mayor, Satyajit; Garcia-Parajo, Maria F

    2014-03-12

    The spatial organization of membrane receptors at the nanoscale has major implications in cellular function and signaling. The advent of super-resolution techniques has greatly contributed to our understanding of the cellular membrane. Yet, despite the increased resolution, unbiased quantification of highly dense features, such as molecular aggregates, remains challenging. Here we describe an algorithm based on Bayesian inference of the marker intensity distribution that improves the determination of molecular positions inside dense nanometer-scale molecular aggregates. We tested the performance of the method on synthetic images representing a broad range of experimental conditions, demonstrating its wide applicability. We further applied this approach to STED images of GPI-anchored and model transmembrane proteins expressed in mammalian cells. The analysis revealed subtle differences in the organization of these receptors, emphasizing the role of cortical actin in the compartmentalization of the cell membrane.

  12. PSF decomposition of nanoscopy images via Bayesian analysis unravels distinct molecular organization of the cell membrane

    NASA Astrophysics Data System (ADS)

    Manzo, Carlo; van Zanten, Thomas S.; Saha, Suvrajit; Torreno-Pina, Juan A.; Mayor, Satyajit; Garcia-Parajo, Maria F.

    2014-03-01

    The spatial organization of membrane receptors at the nanoscale has major implications in cellular function and signaling. The advent of super-resolution techniques has greatly contributed to our understanding of the cellular membrane. Yet, despite the increased resolution, unbiased quantification of highly dense features, such as molecular aggregates, remains challenging. Here we describe an algorithm based on Bayesian inference of the marker intensity distribution that improves the determination of molecular positions inside dense nanometer-scale molecular aggregates. We tested the performance of the method on synthetic images representing a broad range of experimental conditions, demonstrating its wide applicability. We further applied this approach to STED images of GPI-anchored and model transmembrane proteins expressed in mammalian cells. The analysis revealed subtle differences in the organization of these receptors, emphasizing the role of cortical actin in the compartmentalization of the cell membrane.

  13. Self-organizing actin patterns shape membrane architecture but not cell mechanics

    NASA Astrophysics Data System (ADS)

    Fritzsche, M.; Li, D.; Colin-York, H.; Chang, V. T.; Moeendarbary, E.; Felce, J. H.; Sezgin, E.; Charras, G.; Betzig, E.; Eggeling, C.

    2017-02-01

    Cell-free studies have demonstrated how collective action of actin-associated proteins can organize actin filaments into dynamic patterns, such as vortices, asters and stars. Using complementary microscopic techniques, we here show evidence of such self-organization of the actin cortex in living HeLa cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. This process is primarily driven by Arp2/3 complex nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro. Concomitant measurements of mechanics and plasma membrane fluidity demonstrate that changes in actin patterning alter membrane architecture but occur functionally independent of macroscopic cortex elasticity. Consequently, tuning the activity of the Arp2/3 complex to alter filament assembly may thus be a mechanism allowing cells to adjust their membrane architecture without affecting their macroscopic mechanical properties.

  14. Self-organizing actin patterns shape membrane architecture but not cell mechanics

    PubMed Central

    Fritzsche, M.; Li, D.; Colin-York, H.; Chang, V. T.; Moeendarbary, E.; Felce, J. H.; Sezgin, E.; Charras, G.; Betzig, E.; Eggeling, C.

    2017-01-01

    Cell-free studies have demonstrated how collective action of actin-associated proteins can organize actin filaments into dynamic patterns, such as vortices, asters and stars. Using complementary microscopic techniques, we here show evidence of such self-organization of the actin cortex in living HeLa cells. During cell adhesion, an active multistage process naturally leads to pattern transitions from actin vortices over stars into asters. This process is primarily driven by Arp2/3 complex nucleation, but not by myosin motors, which is in contrast to what has been theoretically predicted and observed in vitro. Concomitant measurements of mechanics and plasma membrane fluidity demonstrate that changes in actin patterning alter membrane architecture but occur functionally independent of macroscopic cortex elasticity. Consequently, tuning the activity of the Arp2/3 complex to alter filament assembly may thus be a mechanism allowing cells to adjust their membrane architecture without affecting their macroscopic mechanical properties. PMID:28194011

  15. 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).

  16. 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

    2015-06-12

    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.

  17. 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

  18. Removal of organics from offshore produced waters using nanofiltration membrane technology

    SciTech Connect

    Dyke, C.A.; Bartels, C.R. )

    1990-08-01

    The separation of oil and produced water mixtures from oil and gas producing wells has traditionally been accomplished by gravity settlers (e.g., multi-phase separators, skimmers, and flotation cells). However, current EPA regulations on the organic content of discharged produced water have reached the limits of these separation techniques. The industry is in need of new technologies to treat these waters. One such technology that the authors have found promising is organics/water separation by nanofiltration membranes.

  19. Skeleton-based cerebrovascular quantitative analysis.

    PubMed

    Wang, Xingce; Liu, Enhui; Wu, Zhongke; Zhai, Feifei; Zhu, Yi-Cheng; Shui, Wuyang; Zhou, Mingquan

    2016-12-20

    Cerebrovascular disease is the most common cause of death worldwide, with millions of deaths annually. Interest is increasing toward understanding the geometric factors that influence cerebrovascular diseases, such as stroke. Cerebrovascular shape analyses are essential for the diagnosis and pathological identification of these conditions. The current study aimed to provide a stable and consistent methodology for quantitative Circle of Willis (CoW) analysis and to identify geometric changes in this structure. An entire pipeline was designed with emphasis on automating each step. The stochastic segmentation was improved and volumetric data were obtained. The L1 medial axis method was applied to vessel volumetric data, which yielded a discrete skeleton dataset. A B-spline curve was used to fit the skeleton, and geometric values were proposed for a one-dimensional skeleton and radius. The calculations used to derive these values were illustrated in detail. In one example(No. 47 in the open dataset) all values for different branches of CoW were calculated. The anterior communicating artery(ACo) was the shortest vessel, with a length of 2.6mm. The range of the curvature of all vessels was (0.3, 0.9) ± (0.1, 1.4). The range of the torsion was (-12.4,0.8) ± (0, 48.7). The mean radius value range was (3.1, 1.5) ± (0.1, 0.7) mm, and the mean angle value range was (2.2, 2.9) ± (0, 0.2) mm. In addition to the torsion variance values in a few vessels, the variance values of all vessel characteristics remained near 1. The distribution of the radii of symmetrical posterior cerebral artery(PCA) and angle values of the symmetrical posterior communicating arteries(PCo) demonstrated a certain correlation between the corresponding values of symmetrical vessels on the CoW. The data verified the stability of our methodology. Our method was appropriate for the analysis of large medical image datasets derived from the automated pipeline for populations. This method was applicable to

  20. Organization and regulation of intracellular plasma membrane-connected HIV-1 assembly compartments in macrophages

    PubMed Central

    2013-01-01

    Background In HIV-1-infected human monocyte-derived macrophages (MDMs), virus particles assemble primarily on intracellularly sequestered plasma membrane domains termed intracellular plasma membrane-connected compartments (IPMCs). Despite their clear role in virus formation, little is known of the organization, composition, dynamics or function of these compartments. Results We have used amphipathic membrane dyes to reveal the complex three-dimensional structure of IPMCs in whole MDMs and to visualize connections between IPMCs and the cell surface. The observation of similar IPMC structures in both infected and uninfected cells indicates that these compartments are not induced by virus infection, but are present constitutively in MDMs. By expressing a phospholipase Cδ pleckstrin homology domain linked to green fluorescent protein, we demonstrate that IPMCs contain phosphatidylinositol 4,5-bisphosphate. Live cell imaging of cells expressing this probe shows that IPMCs are dynamic, but relatively stable, sub-domains of the plasma membrane. As recent electron microscopy studies indicated that portions of IPMCs are coated with β2 integrin-containing focal adhesion-like complexes linked to actin, we investigated whether the actin cytoskeleton is required for the organization of IPMCs. In MDMs treated with the actin polymerization inhibitor latrunculin, the normally compact IPMCs dispersed into smaller structures that remained connected to the plasma membrane. Moreover, latrunculin enhanced the release of preformed, mature HIV-1 particles from infected MDMs. Conclusions IPMCs are constitutive features of MDMs that are continuous with the plasma membrane and are used as unique sites for the assembly of new virions following infection by HIV-1. A functionally intact actin cytoskeleton is required to maintain the organization of the IPMCs and, in HIV-1-infected cells, perturbation of the actin cytoskeleton influences both the organization of the compartment and the

  1. 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 ...

  2. 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...

  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. 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...

  5. PSII-LHCII supercomplex organizations in photosynthetic membrane by coarse-grained simulation.

    PubMed

    Lee, Cheng-Kuang; Pao, Chun-Wei; Smit, Berend

    2015-03-12

    Green plant photosystem II (PSII) and light-harvesting complex II (LHCII) in the stacked grana regions of thylakoid membranes can self-organize into various PSII-LHCII supercomplexes with crystalline or fluid-like supramolecular structures to adjust themselves with external stimuli such as high/low light and temperatures, rendering tunable solar light absorption spectrum and photosynthesis efficiencies. However, the mechanisms controlling the PSII-LHCII supercomplex organizations remain elusive. In this work, we constructed a coarse-grained (CG) model of the thylakoid membrane including lipid molecules and a PSII-LHCII supercomplex considering association/dissociation of moderately bound-LHCIIs. The CG interaction between CG beads were constructed based on electron microscope (EM) experimental results, and we were able to simulate the PSII-LHCII supramolecular organization of a 500 × 500 nm(2) thylakoid membrane, which is compatible with experiments. Our CGMD simulations can successfully reproduce order structures of PSII-LHCII supercomplexes under various protein packing fractions, free-LHCII:PSII ratios, and temperatures, thereby providing insights into mechanisms leading to PSII-LHCII supercomplex organizations in photosynthetic membranes.

  6. 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...

  7. 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...

  8. 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 ...

  9. 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...

  10. Spatial and temporal evolution of organic foulant layers on reverse osmosis membranes in wastewater reuse applications.

    PubMed

    Farias, Elizabeth L; Howe, Kerry J; Thomson, Bruce M

    2014-07-01

    Advanced treatment to remove trace constituents and emerging contaminants is an important consideration for wastewater treatment for potable reuse, and reverse osmosis (RO) can be a suitable technology to provide the necessary level of treatment. However, membrane fouling by biological and organic matter is a concern. This research examined the development of the RO membrane fouling layer using a bench-scale membrane bioreactor operating at different solids retention times (SRTs), followed by a custom-designed RO test cell. The RO test cell contained stacked plates that sandwich five sheets of RO membrane material, which can be extracted for autopsy at separate times over the course of an experiment without disturbing the remaining membranes. The MBR-RO system was run continuously for 2 weeks at each SRT. The RO membranes were stained for live and dead cells, protein, and carbohydrate-like materials, and visualized using confocal laser scanning microscopy. Images of the stained foulant layers were obtained at different depths within the foulant layer at each time point for all SRT conditions. As the RO foulant layer developed, changes occurred in the distribution and morphology of the live cells and carbohydrates, but not the proteins. These trends were similar for all three SRT conditions tested. RO membrane fouling increased with increased MBR SRT, and the highest SRT had the highest ratios of live to dead cells and carbohydrate-like material to dead cells. The autopsied membranes were also analyzed for protein and carbohydrate content, and it was found that the carbohydrate concentration on the membranes after 14 days increased as the SRT increased.

  11. 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

  12. Peptide environment specifies conformation. Helicity of hydrophobic segments compared in aqueous, organic, and membrane environments.

    PubMed

    Li, S C; Deber, C M

    1993-11-05

    Transmembrane segments in integral membrane proteins exist characteristically as helices in lipid bilayers, yet are often rich in residues considered helix-destabilizing (Val, Ile, Gly) in soluble proteins. We propose that helicity of a transmembrane segment is likely to be affected by factors other than the "intrinsic" helical propensities of its component amino acids. This hypothesis is tested by comparing the conformation(s) in aqueous, organic, membrane-mimetic (micellar), and membrane (bilayer) environments of designed model peptides with systematically altered helical propensity and/or segmental hydrophobicity. Peptides of prototypic sequence NH2-(Ser-Lys)2-Ala5-Leu6-Ala7-Ala8-Leu9-Ala10-++ +Trp11-Ala12-Leu13-Ala14- (Lys-Ser)3-OH were synthesized, which incorporate a hydrophobic core "guest" segment (residues 5-14) into a water-soluble hydrophilic host matrix. Related peptides featured substitution of Leu6,9,13-->Gly, Leu6,9,13-->Ala, and Ala7,10,14-->Gly. Circular dichroism spectra revealed that algorithms for soluble proteins correctly predicted peptide helical proclivities in aqueous solutions, but peptide helicity in organic (trifluoroethanol) solvents, membrane-mimetic SDS micelles, and negatively charged lipid bilayer vesicles, was found to be governed almost exclusively by the segmental hydrophobicity of the peptide mid-hydrophobic core segment. In related Trp fluorescence studies, peptide-membrane association was similarly correlated with extent of hydrophobic interaction.

  13. Efficient methods for screening of metal organic framework membranes for gas separations using atomically detailed models.

    PubMed

    Keskin, Seda; Sholl, David S

    2009-10-06

    Metal organic frameworks (MOFs) define a diverse class of nanoporous materials having potential applications in adsorption-based and membrane-based gas separations. We have previously used atomically detailed models to predict the performance of MOFs for membrane-based separations of gases, but these calculations require considerable computational resources and time. Here, we introduce an efficient approximate method for screening MOFs based on atomistic models that will accelerate the modeling of membrane applications. The validity of this approximate method is examined by comparison with detailed calculations for CH4/H2, CO2/CH4, and CO2/H2 mixtures at room temperature permeating through IRMOF-1 and CuBTC membranes. These results allow us to hypothesize a connection between two computationally efficient correlations predicting mixture adsorption and mixture self-diffusion properties and the validity of our approximate screening method. We then apply our model to six additional MOFs, IRMOF-8, -9, -10, and -14, Zn(bdc)(ted)0.5, and COF-102, to examine the effect of chemical diversity and interpenetration on the performance of metal organic framework membranes for light gas separations.

  14. Bifunctionalized organic-inorganic charged nanocomposite membrane for pervaporation dehydration of ethanol.

    PubMed

    Tripathi, Bijay P; Kumar, Mahendra; Saxena, Arunima; Shahi, Vinod K

    2010-06-01

    Chitosan was modified into N-p-carboxy benzyl chitosan (NCBC) by introducing an aromatic ring grafted with acidic -COOH group and highly stable and cross-linked nanostructured NCBC-silica composite membranes were prepared for pervaporation dehydration of water-ethanol mixture. These membranes were tailored to comprise three regions namely: hydrophobic region, highly charged region and selective region, in which weak acidic group (-COOH) was grafted at organic segment while strong acidic group (-SO(3)H) was grafted at inorganic segment to achieve high stability and less swelling in water-ethanol mixture. Cross-linking density and NCBC-silica content in membrane matrix has been systematically optimized to control the nanostructure of the developed polymer matrix for studying the effects of molecular structure on the swelling, and PV performance. Among prepared membranes, nanocomposite membrane with 3h cross-linking time and 90% (w/w) of NCBC-silica content (PCS-3-3) exhibited 1.66×10(-4)cm(3)(STP) cm/cm(2) s cmHg water permeability (P(W)), while 1.35×10(-7) cm(3)(STP) cm/cm(2) s cmHg ethanol permeability (P(EtOH)) of developed membrane and 1231 PV selectivity factor at 30 °C for separating water from 90% (w/w) ethanol mixture.

  15. 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

  16. Study on the removal of organic micropollutants from aqueous and ethanol solutions by HAP membranes with tunable hydrophilicity and hydrophobicity.

    PubMed

    He, Junyong; Li, Yulian; Cai, Xingguo; Chen, Kai; Zheng, Hejing; Wang, Chengming; Zhang, Kaisheng; Lin, Dongyue; Kong, Lingtao; Liu, Jinhuai

    2017-05-01

    A biocompatible and uniquely defined hydroxyapatite (HAP) adsorption membrane with a sandwich structure was developed for the removal of organic micropollutants for the first time. Both the adsorption and membrane technique were used for the removal of organic micropollutants. The hydrophilicity and hydrophobicity of the HAP adsorbent and membrane were tunable by controlling the surface structure of HAP. The adsorption of organic micropollutants on the HAP adsorbent was studied in batch experiments. The adsorption process was fit with the Freundlich model, while the adsorption kinetics followed the pseudo-second-order model. The HAP membrane could remove organic micropollutants effectively by dynamic adsorption in both aqueous and ethanol solutions. The removal efficiencies of organic micropollutants depended on the solution composition, membrane thickness and hydrophilicity, flow rate, and the initial concentration of organic micropollutants. The adsorption capacities of the HAP membrane with a sandwich structure (membrane thickness was 0.3 mm) were 6700, 6510, 6310, 5960, 5490, 5230, 4980 and 4360 L m(-2) for 1-naphthyl amine, 2-naphthol, bisphenol S, propranolol hydrochloride, metolachlor, ethinyl oestradiol, 2,4-dichlorophenol and bisphenol A, respectively, when the initial concentration was 3.0 mg L(-1). The biocompatible HAP adsorption membrane can be easily regenerated by methanol and was thus demonstrated to be a novel concept for the removal of organic micropollutants from both aqueous and organic solutions.

  17. Organ of Corti potentials and the motion of the basilar membrane.

    PubMed

    Fridberger, Anders; de Monvel, Jacques Boutet; Zheng, Jiefu; Hu, Ning; Zou, Yuan; Ren, Tianying; Nuttall, Alfred

    2004-11-10

    During sound stimulation, receptor potentials are generated within the sensory hair cells of the cochlea. Prevailing theory states that outer hair cells use the potential-sensitive motor protein prestin to convert receptor potentials into fast alterations of cellular length or stiffness that boost hearing sensitivity almost 1000-fold. However, receptor potentials are attenuated by the filter formed by the capacitance and resistance of the membrane of the cell. This attenuation would limit cellular motility at high stimulus frequencies, rendering the above scheme ineffective. Therefore, Dallos and Evans (1995a) proposed that extracellular potential changes within the organ of Corti could drive cellular motor proteins. These extracellular potentials are not filtered by the membrane. To test this theory, both electric potentials inside the organ of Corti and basilar membrane vibration were measured in response to acoustic stimulation. Vibrations were measured at sites very close to those interrogated by the recording electrode using laser interferometry. Close comparison of the measured electrical and mechanical tuning curves and time waveforms and their phase relationships revealed that those extracellular potentials indeed could drive outer hair cell motors. However, to achieve the sharp frequency tuning that characterizes the basilar membrane, additional mechanical processing must occur inside the organ of Corti.

  18. Organization and Flexibility of Cyanobacterial Thylakoid Membranes Examined by Neutron Scattering

    PubMed Central

    Liberton, Michelle; Page, Lawrence E.; O'Dell, William B.; O'Neill, Hugh; Mamontov, Eugene; Urban, Volker S.; Pakrasi, Himadri B.

    2013-01-01

    Cyanobacteria are prokaryotes that can use photosynthesis to convert sunlight into cellular fuel. Knowledge of the organization of the membrane systems in cyanobacteria is critical to understanding the metabolic processes in these organisms. We examined the wild-type strain of Synechocystis sp. PCC 6803 and a series of mutants with altered light-harvesting phycobilisome antenna systems for changes in thylakoid membrane architecture under different conditions. Using small-angle neutron scattering, it was possible to resolve correlation distances of subcellular structures in live cells on the nanometer scale and capture dynamic light-induced changes to these distances. Measurements made from samples with varied scattering contrasts confirmed that these distances could be attributed to the thylakoid lamellar system. We found that the changes to the thylakoid system were reversible between light- and dark-adapted states, demonstrating a robust structural flexibility in the architecture of cyanobacterial cells. Chemical disruption of photosynthetic electron transfer diminished these changes, confirming the involvement of the photosynthetic apparatus. We have correlated these findings with electron microscopy data to understand the origin of the changes in the membranes and found that light induces an expansion in the center-to-center distances between the thylakoid membrane layers. These combined data lend a dynamic dimension to the intracellular organization in cyanobacterial cells. PMID:23255600

  19. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. 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.

  1. 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.

  2. Weighted straight skeletons in the plane.

    PubMed

    Biedl, Therese; Held, Martin; Huber, Stefan; Kaaser, Dominik; Palfrader, Peter

    2015-02-01

    We investigate weighted straight skeletons from a geometric, graph-theoretical, and combinatorial point of view. We start with a thorough definition and shed light on some ambiguity issues in the procedural definition. We investigate the geometry, combinatorics, and topology of faces and the roof model, and we discuss in which cases a weighted straight skeleton is connected. Finally, we show that the weighted straight skeleton of even a simple polygon may be non-planar and may contain cycles, and we discuss under which restrictions on the weights and/or the input polygon the weighted straight skeleton still behaves similar to its unweighted counterpart. In particular, we obtain a non-procedural description and a linear-time construction algorithm for the straight skeleton of strictly convex polygons with arbitrary weights.

  3. Bayesian estimation of the shape skeleton.

    PubMed

    Feldman, Jacob; Singh, Manish

    2006-11-21

    Skeletal representations of shape have attracted enormous interest ever since their introduction by Blum [Blum H (1973) J Theor Biol 38:205-287], because of their potential to provide a compact, but meaningful, shape representation, suitable for both neural modeling and computational applications. But effective computation of the shape skeleton remains a notorious unsolved problem; existing approaches are extremely sensitive to noise and give counterintuitive results with simple shapes. In conventional approaches, the skeleton is defined by a geometric construction and computed by a deterministic procedure. We introduce a Bayesian probabilistic approach, in which a shape is assumed to have "grown" from a skeleton by a stochastic generative process. Bayesian estimation is used to identify the skeleton most likely to have produced the shape, i.e., that best "explains" it, called the maximum a posteriori skeleton. Even with natural shapes with substantial contour noise, this approach provides a robust skeletal representation whose branches correspond to the natural parts of the shape.

  4. Weighted straight skeletons in the plane☆

    PubMed Central

    Biedl, Therese; Held, Martin; Huber, Stefan; Kaaser, Dominik; Palfrader, Peter

    2015-01-01

    We investigate weighted straight skeletons from a geometric, graph-theoretical, and combinatorial point of view. We start with a thorough definition and shed light on some ambiguity issues in the procedural definition. We investigate the geometry, combinatorics, and topology of faces and the roof model, and we discuss in which cases a weighted straight skeleton is connected. Finally, we show that the weighted straight skeleton of even a simple polygon may be non-planar and may contain cycles, and we discuss under which restrictions on the weights and/or the input polygon the weighted straight skeleton still behaves similar to its unweighted counterpart. In particular, we obtain a non-procedural description and a linear-time construction algorithm for the straight skeleton of strictly convex polygons with arbitrary weights. PMID:25648398

  5. Reversed thermo-switchable molecular sieving membranes composed of two-dimensional metal-organic nanosheets for gas separation

    PubMed Central

    Wang, Xuerui; Chi, Chenglong; Zhang, Kang; Qian, Yuhong; Gupta, Krishna M.; Kang, Zixi; Jiang, Jianwen; Zhao, Dan

    2017-01-01

    It is highly desirable to reduce the membrane thickness in order to maximize the throughput and break the trade-off limitation for membrane-based gas separation. Two-dimensional membranes composed of atomic-thick graphene or graphene oxide nanosheets have gas transport pathways that are at least three orders of magnitude higher than the membrane thickness, leading to reduced gas permeation flux and impaired separation throughput. Here we present nm-thick molecular sieving membranes composed of porous two-dimensional metal-organic nanosheets. These membranes possess pore openings parallel to gas concentration gradient allowing high gas permeation flux and high selectivity, which are proven by both experiment and molecular dynamics simulation. Furthermore, the gas transport pathways of these membranes exhibit a reversed thermo-switchable feature, which is attributed to the molecular flexibility of the building metal-organic nanosheets. PMID:28205528

  6. Reversed thermo-switchable molecular sieving membranes composed of two-dimensional metal-organic nanosheets for gas separation

    NASA Astrophysics Data System (ADS)

    Wang, Xuerui; Chi, Chenglong; Zhang, Kang; Qian, Yuhong; Gupta, Krishna M.; Kang, Zixi; Jiang, Jianwen; Zhao, Dan

    2017-02-01

    It is highly desirable to reduce the membrane thickness in order to maximize the throughput and break the trade-off limitation for membrane-based gas separation. Two-dimensional membranes composed of atomic-thick graphene or graphene oxide nanosheets have gas transport pathways that are at least three orders of magnitude higher than the membrane thickness, leading to reduced gas permeation flux and impaired separation throughput. Here we present nm-thick molecular sieving membranes composed of porous two-dimensional metal-organic nanosheets. These membranes possess pore openings parallel to gas concentration gradient allowing high gas permeation flux and high selectivity, which are proven by both experiment and molecular dynamics simulation. Furthermore, the gas transport pathways of these membranes exhibit a reversed thermo-switchable feature, which is attributed to the molecular flexibility of the building metal-organic nanosheets.

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

    PubMed

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

    2016-07-04

    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).

  8. Membrane organization of virus and target cell plays a role in HIV entry.

    PubMed

    Dumas, Fabrice; Preira, Pascal; Salomé, Laurence

    2014-12-01

    The initial steps of the Human Immunodeficiency Virus (HIV) replication cycle play a crucial role that arbitrates viral tropism and infection efficiency. Before the release of its genome into the host cell cytoplasm, viruses operate a complex sequence of events that take place at the plasma membrane of the target cell. The first step is the binding of the HIV protein envelope (Env) to the cellular receptor CD4. This triggers conformational changes of the gp120 viral protein that allow its interaction with a co-receptor that can be either CCR5 or CXCR4, defining the tropism of the virus entering the cell. This sequential interaction finally drives the fusion of the viral and host cell membrane or to the endocytosis of the viruses. Here, we discuss how the membrane composition and organization of both the virus and the target cell can affect these steps and thus influence the capability of the viruses to infect cells.

  9. Metal-organic framework based mixed matrix membranes: a solution for highly efficient CO2 capture?

    PubMed

    Seoane, Beatriz; Coronas, Joaquin; Gascon, Ignacio; Etxeberria Benavides, Miren; Karvan, Oğuz; Caro, Jürgen; Kapteijn, Freek; Gascon, Jorge

    2015-04-21

    The field of metal-organic framework based mixed matrix membranes (M(4)s) is critically reviewed, with special emphasis on their application in CO2 capture during energy generation. After introducing the most relevant parameters affecting membrane performance, we define targets in terms of selectivity and productivity based on existing literature on process design for pre- and post-combustion CO2 capture. Subsequently, the state of the art in M(4)s is reviewed against these targets. Because final application of these membranes will only be possible if thin separation layers can be produced, the latest advances in the manufacture of M(4) hollow fibers are discussed. Finally, the recent efforts in understanding the separation performance of these complex composite materials and future research directions are outlined.

  10. Prospects for Human Erythrocyte Skeleton-Bilayer Dissociation during Splenic Flow.

    PubMed

    Zhu, Qiang; Salehyar, Sara; Cabrales, Pedro; Asaro, Robert J

    2017-08-22

    Prospects of vesiculation occurring during splenic flow of erythrocytes are addressed via model simulations of RBC flow through the venous slits of the human spleen. Our model is multiscale and contains a thermally activated rate-dependent description of the entropic elasticity of the RBC spectrin cytoskeleton, including domain unfolding/refolding. Our model also includes detail of the skeleton attachment to the fluidlike lipid bilayer membrane, including a specific accounting for the expansion/contraction of the skeleton that may occur via anchor protein diffusive motion, that is, band 3 and glycophorin, through the membrane. This ability allows us to follow the change in anchor density and thereby the strength of the skeleton/membrane attachment. We define a negative pressure between the skeleton/membrane connection that promotes separation; critical levels for this are estimated using published data on the work of adhesion of this connection. By following the maximum range of negative pressure, along with the observed slight decrease in skeletal density, we conclude that there must be biochemical influences that probably include binding of degraded hemoglobin, among other things, that significantly reduce effective attachment density. These findings are consistent with reported trends in vesiculation that are believed to occur in cases of various hereditary anemias and during blood storage. Our findings also suggest pathways for further study of erythrocyte vesiculation that point to the criticality of understanding the biochemical phenomena involved with cytoskeleton/membrane attachment. Copyright © 2017. Published by Elsevier Inc.

  11. 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

  12. The Skeleton in the Closet: Harvesting a Skeletonized IMA.

    PubMed

    Tribble, Curtis G

    2017-08-28

    There is a considerable amount of data that using more than one arterial graft provides a survival advantage for patients undergoing coronary bypass operations. The Society of Thoracic Surgeons has a set of official guidelines for the use of arterial grafts which include the following recommendations:Internal mammary arteries (IMA's) should be used to bypass the left anterior descending (LAD) artery when bypass of the LAD is indicated.As an adjunct to left internal mammary artery (LIMA), a second arterial graft (right IMA or radial artery [RA]) should be considered in appropriate patients.Use of bilateral IMA's (BIMA's) should be considered in patients who do not have an excessive risk of sternal complications.To reduce the risk of sternal infection with bilateral IMA's, skeletonized grafts should be considered, smoking cessation is recommended, glycemic control should be considered, and enhanced sternal stabilization may be considered.Use of arterial grafts should be a part of the discussion of the heart team in determining the optimal approach for each patient.         [Ann Thorac Surg 2016; 101: 801-9].

  13. Characterization of organic matter and disinfection by-products in membrane backwash water from drinking water treatment.

    PubMed

    Zhang, Lingling; Gu, Ping; Zhong, Zijie; Yang, Dong; He, Wenjie; Han, Hongda

    2009-09-15

    Two pilot-scale membrane plants were set up to produce drinking water, and membrane backwash water was discharged during the production process. This work studied the characteristics of dissolved organic matter (DOM) in membrane backwash water from submerged microfiltration (MBWS) and pressurized ultrafiltration (MBWP) both of which are coupled with the pre-coagulation process. The results showed that the two waters had similar molecular weight (MW) distributions. Dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP) in MBWS and MBWP were both mainly distributed in MW>30 kDa and MW<1 kDa, and UV(254) was mainly in MW<1 kDa. For Luan River water (LRW, the raw water for the two pilot-scale membrane plants in this study), organic matter enriched in membrane backwash water was mainly in sizes of MW>30 kDa. In addition, organic matter with MW>10 kDa was higher in MBWP than in MBWS. The quality of membrane backwash water was influenced by the changes in LRW quality during different periods. The quality of membrane backwash water was worse in alga-laden period than in normal period and organic matter concentrations in MW<1 kDa increased significantly in this period. The small size DOM in membrane backwash water was more reactive to form trihalomethanes (THMs) in the disinfection process. The variability of specific UV absorbance and THMFP/DOC was consistent in membrane backwash water.

  14. 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

  15. Identifying polyvinylidene fluoride ultrafiltration membrane fouling behavior of different effluent organic matter fractions using colloidal probes.

    PubMed

    Miao, Rui; Wang, Lei; Lv, Yongtao; Wang, Xudong; Feng, Ling; Liu, Ziwen; Huang, Danxi; Yang, Yongzhe

    2014-05-15

    The interaction forces between effluent organic matter (EfOM) fractions and membrane were measured by atomic force microscopy in conjunction with self-made membrane material colloidal probes. The inter-EfOM-fraction and intra-EfOM-fraction interactions were investigated using corresponding EfOM-fraction-coated colloidal probe. We combined this analysis with corresponding fouling experiments to identify the EfOM fractions responsible for polyvinylidene fluoride (PVDF) ultrafiltration membrane fouling. Results show that hydrophilic and hydrophobic fractions were the dominant fractions responsible for membrane fouling and flux decline in the initial and later filtration stages, respectively, which was mainly attributed to the stronger PVDF-hydrophilic fraction and intra-hydrophobic-fraction interaction forces. This phenomenon, in conjunction with the fact that each interaction force of PVDF-EfOM fraction was stronger than corresponding intra-EfOM-fraction force, suggests that the elimination of the PVDF-hydrophilic fraction interaction force is the best strategy for controlling EfOM fouling. Moreover, the inter-EfOM-fraction interaction force was mainly controlled by the corresponding intra-EfOM-fraction interaction forces. And, while the membrane-EfOM fraction and intra-EfOM-fraction interactions for each type of EfOM fraction are equivalent, the EfOM fractions with the molecular weight smaller than the molecular weight cutoff of the membranes used were mainly responsible for membrane fouling rather than the relatively high-molecular-weight fractions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Basement membrane procollagen is not converted to collagen in organ cultures of parietal yolk sac endoderm.

    PubMed

    Minor, R R; Clark, C C; Strause, E L; Koszalka, T R; Brent, R L; Kefalides, N A

    1976-03-25

    Basement membrane procollagen biosynthesis was studied in organ cultures of embryonic rat parietal yolk sac endoderm by following [14C]proline incorporation into nondialyzable proteins. After reduction with 2-mercaptoethanol the 14C-proteins synthesized were characterized by agarose gel filtration and disc electrophoresis in the presence of sodium dodecyl sulfate. The labeled procollagen was identified by its content of hydroxy[14C]proline, its sensitivity to digestion with bacterial collagenase, and its resistance to digestion with pepsin. In cultures which were continuously labeled for periods from 6 hours to 4 days, the pro-alpha chains consistently eluted as a single peak with an apparent molecular weight of 160,000. After pepsin digestion the resultant alpha chains had an apparent molecular weight between 125,000 and 140,000. This suggests that basement membrane procollagen either contains non-triple helical pepsin-resistant regions or a triple helical region which is larger than the corresponding region of interstitial procollagen. Two experiments were performed to determine whether the chains of newly synthesized basement membrane procollagen were cleaved to a smaller molecular species. In the first, the hydroxylation and secretion of procollagen were blocked with alpha, alpha'-dipyridyl, and the resulting intracellular chains of basement membrane protocollagen were found to co-elute with fully hydroxylated and secreted pro-alpha chains. In the second, cultures were labeled for 1 day and chased for 3 days with unlabeled medium. Autoradiography had shown that most of the label was chased into new basement membrane. Agarose chromotography showed that after 3-day chase the pro-alpha chains still eluted with an apparent molecular weight of 160,000. Thus, the data indicated that basement membrane procollagen was deposited in new basement membrane without undergoing a time-dependent extracellular conversion.

  17. Solute transport model for trace organic neutral and charged compounds through nanofiltration and reverse osmosis membranes.

    PubMed

    Kim, Tae-Uk; Drewes, Jörg E; Scott Summers, R; Amy, Gary L

    2007-09-01

    Rejection of trace organic compounds, including disinfection by-products (DBPs) and pharmaceutical active compounds (PhACs), by high-pressure membranes has become a focus of public interest internationally in both drinking water treatment and wastewater reclamation/reuse. The ability to simulate, or even predict, the rejection of these compounds by high-pressure membranes, encompassing nanofiltration (NF) and reverse osmosis (RO), will improve process economics and expand membrane applications. The objective of this research is to develop a membrane transport model to account for diffusive and convective contributions to solute transport and rejection. After completion of cross-flow tests and diffusion cell tests with target compounds, modeling efforts were performed in accordance with a non-equilibrium thermodynamic transport equation. Comparing the percentages of convection and diffusion contributions to transport, convection is dominant for most compounds, but diffusion is important for more hydrophobic non-polar compounds. Convection is also more dominant for looser membranes (i.e., NF). In addition, higher initial compound concentrations and greater J(0)/k ratios contribute to solute fluxes more dominated by convection. Given the treatment objective of compound rejection, compound transport and rejection trends are inversely related.

  18. Fluorescent natural organic matter responsible for ultrafiltration membrane fouling: Fate, contributions and fouling mechanisms.

    PubMed

    Wang, Hui; Ding, An; Gan, Zhendong; Qu, Fangshu; Cheng, Xiaoxiang; Bai, Langming; Guo, Shaodong; Li, Guibai; Liang, Heng

    2017-09-01

    Membrane fouling has been a main obstacle to the success of ultrafiltration (UF) technology. Recently, fluorescent natural organic matter (FNOM), including humic-like substances (HS) and protein-like substances, has been recognized as substances responsible for membrane fouling. In this study, the matrix of FNOM in natural river water was substantially modified by combined coagulation and powdered activated carbon adsorption to enhance the diversity of the FNOM matrix. Fluorescence excitation emission matrix spectroscopy was employed to characterize FNOM components during the UF process. The correlations between FNOM components of the feedwater and membrane fouling were evaluated for the initial period and long-term operation. Reliable correlations of the maximum fluorescence intensity of HS with initial membrane fouling indicated that HS were major foulants in the initial period. Furthermore, the protein-like component exhibited significant correlation with the concentration effect fouling (R(2) = 0.6131) and with irreversible fouling (R(2) = 0.8711). We found that the fouling mechanism changed from pore obstruction to a protein concentration polarization layer followed by protein cake layer filtration. Total fouling of the UF membrane over long-term operation was alleviated with powdered activated carbon (PAC) adsorption; however, the mitigation of irreversible fouling was dependent on whether PAC adsorbed protein-like substances. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Enhanced proton conductivity of Nafion composite membrane by incorporating phosphoric acid-loaded covalent organic framework

    NASA Astrophysics Data System (ADS)

    Yin, Yongheng; Li, Zhen; Yang, Xin; Cao, Li; Wang, Chongbin; Zhang, Bei; Wu, Hong; Jiang, Zhongyi

    2016-11-01

    Design and fabrication of efficient proton transport channels within solid electrolytes is crucial and challenging to new energy-relevant devices such as proton exchange membrane fuel cells (PEMFCs). In this study, the phosphoric acid (H3PO4) molecules are impregnated into SNW-1-type covalent organic frameworks (COFs) via vacuum assisted method. High loading of H3PO4 in SNW-1 and low guest leaching rate are achieved due to the similar diameter between H3PO4 and micropores in SNW-1. Then the COF-based composite membranes are fabricated for the first time with impregnated COFs (H3PO4@SNW-1) and Nafion matrix. For the composite membranes, the acid-base pairs formed between H3PO4@SNW-1 networks and Nafion optimize the interfacial interactions and hydrophilic domains. The acidic -PO3H2 groups in pores of H3PO4@SNW-1 provide abundant proton transfer sites. As a result, the continuous proton transfer channels with low energy barrier are created. At the filler content of 15 wt%, the composite membrane exhibits a superior proton conductivity of 0.0604 S cm-1 at 51% relative humidity and 80 °C. At the same time, the maximum power density of single fuel cell is 60.3% higher than that of the recast Nafion membrane.

  20. Assembly and structural organization of pigment-protein complexes in membranes of Rhodopseudomonas sphaeroides.

    PubMed

    Hunter, C N; Pennoyer, J D; Niederman, R A

    1982-01-01

    The B875 and B800-850 light-harvesting pigment-protein complexes of Rhodopseudomonas sphaeroides are characterized further by lithium dodecyl sulfate/polyacrylamide gel electrophoresis at 4 degrees C. Bacteriochlorophyll a was shown in reconstruction studies to remain complexed with its respective binding proteins during this procedure. From distributions in these gels, a quantitative description for the arrangement of the complexes is proposed. Assembly of the complexes was examined in delta-aminolevulinate-requiring mutant H-5 after a shift from high- to low-light intensity. After 10 h of delta-[3H]aminolevulinate labeling, the specific radioactivity of bacteriochlorophyll in a fraction containing putative membrane invaginations reached the maximal level, while that of the mature photosynthetic membrane was at only one-third this level. This suggests that membrane invaginations are sites of preferential bacteriochlorophyll synthesis in which completed pigment-proteins exist transiently. Analysis of the 3H distribution after electrophoretic separation further suggests that photosynthetic membranes grow mainly by addition of B800-850 to preformed membrane consisting largely of B875 and photochemical reaction centers. These results corroborate the above model for the structural organization of the light-harvesting system and indicate that the structurally and functionally discrete B800-850 pool is not completely assembled until all B875 sites for B800-850 interactions are occupied.

  1. 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

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

    PubMed

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

    2013-04-15

    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.

  3. Microbial community developments and biomass characteristics in membrane bioreactors under different organic loadings.

    PubMed

    Wu, Bing; Yi, Shan; Fane, Anthony G

    2011-07-01

    Microbial community developments and biomass characteristics (concentration, particle size, extracellular polymeric substances (EPS), and membrane fouling propensity) were compared when three MBRs were fed with the synthetic wastewater at different organic loadings. Results showed that the bacterial communities dynamically shifted in different ways and the EPS displayed dissimilar profiles under various organic loadings, which were associated with the ratios of food to microorganism and dissolved oxygen levels in the MBRs. The membrane fouling tendency of biomass in the low-loading MBR (0.57 g COD/L day) was insignificantly different from that in the medium-loading MBR (1.14 g COD/L day), which was apparently lower than that in the high-loading MBR (2.28 g COD/L day). The membrane fouling propensity of biomass was strongly correlated with their bound EPS contents, indicating cake layer fouling (i.e., deposition of microbial flocs) was predominant in membrane fouling at a high flux of 30 L/m(2)h. Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. 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.

  5. 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.

  6. CAST AWAY, a membrane-associated receptor-like kinase, inhibits organ abscission in Arabidopsis.

    PubMed

    Burr, Christian A; Leslie, Michelle E; Orlowski, Sara K; Chen, Iris; Wright, Catherine E; Daniels, Mark J; Liljegren, Sarah J

    2011-08-01

    Receptor-like kinase-mediated cell signaling pathways play fundamental roles in many aspects of plant growth and development. A pair of Arabidopsis (Arabidopsis thaliana) leucine-rich repeat receptor-like kinases (LRR-RLKs), HAESA (HAE) and HAESA-LIKE2 (HSL2), have been shown to activate the cell separation process that leads to organ abscission. Another pair of LRR-RLKs, EVERSHED (EVR) and SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE1, act as inhibitors of abscission, potentially by modulating HAE/HSL2 activity. Cycling of these RLKs to and from the cell surface may be regulated by NEVERSHED (NEV), a membrane trafficking regulator that is essential for organ abscission. We report here the characterization of CAST AWAY (CST), a receptor-like cytoplasmic kinase that acts as a spatial inhibitor of cell separation. Disruption of CST suppresses the abscission defects of nev mutant flowers and restores the discrete identity of the trans-Golgi network in nev abscission zones. After organ shedding, enlarged abscission zones with obscured boundaries are found in nev cst flowers. We show that CST is a dual-specificity kinase in vitro and that myristoylation at its amino terminus promotes association with the plasma membrane. Using the bimolecular fluorescence complementation assay, we have detected interactions of CST with HAE and EVR at the plasma membrane of Arabidopsis protoplasts and hypothesize that CST negatively regulates cell separation signaling directly and indirectly. A model integrating the potential roles of receptor-like kinase signaling and membrane trafficking during organ separation is presented.

  7. 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.

  8. 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.

  9. Polymers of intrinsic microporosity (PIMs): organic materials for membrane separations, heterogeneous catalysis and hydrogen storage.

    PubMed

    McKeown, Neil B; Budd, Peter M

    2006-08-01

    This tutorial review describes recent research directed towards the synthesis of polymer-based organic microporous materials termed Polymers of Intrinsic Microporosity (PIMs). PIMs can be prepared either as insoluble networks or soluble polymers with both types giving solids that exhibit analogous behaviour to that of conventional microporous materials such as activated carbons. Soluble PIMs may be processed into thin films for use as highly selective gas separation membranes. Preliminary results also demonstrate the potential of PIMs for heterogeneous catalysis and hydrogen storage.

  10. 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

  11. Thermodynamic factors in partitioning and rejection of organic compounds by polyamide composite membranes.

    PubMed

    Ben-David, Adi; Oren, Yoram; Freger, Viatcheslav

    2006-11-15

    The paper analyzes the mechanism of partitioning and rejection of organic solutes by polyamide membranes for reverse osmosis and nanofiltration. The partitioning of homologous series of alcohols and polyols, in which polarity changes with size in opposite ways, was measured using attenuated total reflection IR spectroscopy. The results show that the partitioning of polyols monotonously decreases with size, whereas for alcohols it is not monotonous and slightly decreases for small C1-C3 alcohols followed by a sharp increase for larger alcohols. These results may be explained by assuming a heterogeneous structure of polyamide comprising a hydrophobic polyamide matrix and a polar internal aqueous phase. The partitioning data could consistently explain the results of rejection in standard filtration experiments. They clearly demonstrate that high/low partitioning may play a significant role in achieving a low/high rejection of organics. In particular, this points to the need to account for the partitioning effect while using molecular probes such as polyols or sugars for estimating the effective "pore" size or molecular weight cutoff of a membrane and for choosing/developing organic-rejecting membranes.

  12. 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.

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

    PubMed

    Wang, J

    2016-11-01

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

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. Separation of organic pollutants by reverse osmosis and nanofiltration membranes: Mathematical models and experimental verification

    SciTech Connect

    Williams, M.E.; Hestekin, J.A.; Smothers, C.N.; Bhattacharyya, D.

    1999-10-01

    Predictive reverse osmosis (RO) models have been well-developed for many systems. However, the applications to dilute organic-water systems require the modification of transport models and the understanding of solute-polymer interactions. Studies with various substituted, nonionized phenolic compounds showed that these could cause substantial membrane water flux drop, even in dilute solutions with negligible osmotic pressure. Further, the organics could significantly adsorb on the cross-linked aromatic polyamide active layer. In some cases, even concentrations as low as 0.2 mM, 2,4-dinitrophenol (solution in particle-free, double-distilled water) can cause as much as a 70% flux drop with an aromatic polyamide membrane. Two models are presented in this paper: a modified steady-state solution diffusion model and an unsteady-state diffusion adsorption model which are able to predict flux and permeate concentrations from a single RO experiment. Further, the development of these models allows for the understanding of the mechanisms of organic-membrane interactions. For instance, it has been proposed that increased adsorption inherently leads to an increase in flux drop. However, the authors have found, on one hand, that due to specific interactions with membrane water transport groups, chloro-, and nitro-substituted phenols cause significant flux drops. On the other hand, benzene had a high physical adsorption but caused negligible flux drop. The results were further extended to nanofiltration experiments with an aromatic pollutant containing two types of charge groups. The adsorption and separation results are explained according to an ionization model.

  1. Effect of organic fouling on micro-pollutant rejection in membrane bioreactor treating municipal solid waste landfill leachate.

    PubMed

    Sanguanpak, Samunya; Chiemchaisri, Chart; Chiemchaisri, Wilai; Yamamoto, Kazuo

    2015-01-01

    Effect of membrane fouling on the removal of micro-pollutants from municipal solid waste landfill leachate, i.e. 4-methyl-2,6-di-tert-butylphenol (BHT), bisphenol A (BPA), and bis(2-ethylhexyl)phthalate (DEHP), in membrane bioreactor (MBR) was investigated. Modifications of membrane surface properties were analyzed to determine their relationship with their removals. Membrane fouling was simulated with foulants of different particle sizes on cellulose acetate (CA) microfiltration membrane to investigate the effect of foulant characteristics on BHT, BPA, and DEHP retention in the filtration experiment. The rejection efficiencies of the organic micro-pollutants in the MBR were 82-97% by fouled membrane, and 70-90% by cleaned membrane. The fouled membrane provided higher rejection of micro-pollutants from about 5% for BPA and BHT to 19% for DEHP. These improvements were due to the modification of membrane surface characteristics in terms of surface morphology, and contact angle after membrane fouling. The degree of rejection was found to be dependent upon the characteristics of foulant deposited on CA membrane surface. Increasing foulant particle size and its density shifted the mechanism of micro-pollutant rejection from membrane pore narrowing to pore blocking and cake formation while increasing pollutant adsorption capacity onto the foulant layer.

  2. A new conceptual model of the formation of coral skeleton

    NASA Astrophysics Data System (ADS)

    Juillet-Leclerc, A.

    2006-12-01

    Scleractinian corals constitute one of the major groups of calcifying animals. During a long time their skeleton has been considered as purely mineral and all the features not consistent with this concept were called " vital effects ". However, biology plays a key role in the skeleton genesis. Recent technological advances provided enough evidences to propose a new conceptual model of coral skeleton growth. Ion microprobe carried out both trace element and isotope analyses, which stressed the high variability of these geochemical tracers. It indicates that all measurements obtained at millimeter-length scale, especially data used for paleoclimatic purpose, are bulk data. The analyses performed on individual microstructures previously identified by SEMS observation revealed that the two different microstructures highlighted in coral skeleton present a specific geochemical signature. We have thus to explain how two specific microstructures could derive from a unique calcifying fluid. On the other hand, several methods converged to show that a thin organic matrix surrounds growth units at micro/nanometer size scale. The presence of organic compounds could alter the equilibrium thermodynamics of the mineral growth surface by modifying energy landscape. Knowing that chemical environment of each microstructure could be different according the nature of the growth units we assume that it induces different mechanism of deposition. By combining results from different approaches we deduce that kinetics is not restricted to isotopic fractionation. We conclude that coral aragonite deposit is dominated by a kinetic chemical disequilibrium and governed by supersaturation law. We demonstrate that this conceptual model is consistent with the observations and measurements earlier performed and coral remains the most relevant archive of the tropical ocean than ever.

  3. 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

    2016-03-23

    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.

  4. Extracorporeal membrane oxygenation support in potential organ donors for brain death determination.

    PubMed

    Hsieh, C-E; Lin, H-C; Tsui, Y-C; Lin, P-Y; Lin, K-H; Chang, Y-Y; Chen, Y-L

    2011-09-01

    Extracorporeal membrane oxygenation (ECMO) must be applied in early stages to perfuse organs before donation in order to expand the donor pool. The aim of this study was to examine the benefits of ECMO for potential organ donors with multiple complications. This retrospective review describes patients with ECMO support who were on the verge of brain death and therefore potential subjects for organ donation. Six organ donors with severe neurological damage under ECMO support completed the procedures, namely, two women and four men of ages 19 to 58 years (mean, 32 years). Three donors completed the brain-death determination procedure, one failed the procedure, and two experienced cardiac asystole prior to the procedure and were unable to be declared dead even after resuscitation. Nine kidneys and three livers were successfully retrieved from 5/6 donors, leading to 11 successful transplantations: eight kidneys, two livers, and one simultaneous kidney-liver transplantations. The organs functioned well and the recipients made full recoveries. ECMO allows for the maintenance of abdominal organ tissue perfusion without warm ischemia before organ procurement, providing sufficient time for safe organ donation procedures and reducing the risk of unpredictable cardiac arrest that could result in the donor death and graft loss. Copyright © 2011 Elsevier Inc. All rights reserved.

  5. Inorganic Nanoparticles/Metal Organic Framework Hybrid Membrane Reactors for Efficient Photocatalytic Conversion of CO2.

    PubMed

    Maina, James W; Schütz, Jürg A; Grundy, Luke; Des Ligneris, Elise; Yi, Zhifeng; Kong, Lingxue; Pozo-Gonzalo, Cristina; Ionescu, Mihail; Dumée, Ludovic F

    2017-09-29

    Photocatalytic conversion of carbon dioxide (CO2) to useful products has potential to address the adverse environmental impact of global warming. However, most photocatalysts used to date exhibit limited catalytic performance, due to poor CO2 adsorption capacity, inability to efficiently generate photoexcited electrons, and/or poor transfer of the photogenerated electrons to CO2 molecules adsorbed on the catalyst surface. The integration of inorganic semiconductor nanoparticles across metal organic framework (MOF) materials has potential to yield new hybrid materials, combining the high CO2 adsorption capacity of MOF and the ability of the semiconductor nanoparticles to generate photoexcited electrons. Herein, controlled encapsulation of TiO2 and Cu-TiO2 nanoparticles within zeolitic imidazolate framework (ZIF-8) membranes was successfully accomplished, using rapid thermal deposition (RTD), and their photocatalytic efficiency toward CO2 conversion was investigated under UV irradiation. Methanol and carbon monoxide (CO) were found to be the only products of the CO2 reduction, with yields strongly dependent upon the content and composition of the dopant semiconductor particles. CuTiO2 nanoparticle doped membranes exhibited the best photocatalytic performance, with 7 μg of the semiconductor nanoparticle enhancing CO yield of the pristine ZIF-8 membrane by 233%, and methanol yield by 70%. This work opens new routes for the fabrication of hybrid membranes containing inorganic nanoparticles and MOFs, with potential application not only in catalysis but also in electrochemical, separation, and sensing applications.

  6. 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

  7. 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.

  8. 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

  9. Dynamic changes of dissolved organic matter in membrane bioreactors at different organic loading rates: Evidence from spectroscopic and chromatographic methods.

    PubMed

    Maqbool, Tahir; Cho, Jinwoo; Hur, Jin

    2017-06-01

    Excitation emission matrix-parallel factor analysis (EEM-PARAFAC) and size exclusion chromatography (SEC) were utilized to explore the dynamics in extracellular polymeric substances (EPS), soluble microbial products (SMP), and effluent for the membrane bioreactors at two different organic loading rates (OLRs). Combination of three different fluorescent components explained the compositional changes of dissolved organic matter. The lower OLR resulted in a higher production of tryptophan-like component (C1) in EPS, while the opposite trends were found for the other two components (humic-like C2 and tyrosine-like C3), signifying the role of C1 in the endogenous condition. Larger sized molecules were more greatly produced in EPS at the lower OLR. Meanwhile, all the size fractions of SMP were more abundant at the higher OLR particular for the early phase of the operation. Irrespective of the OLR, the higher degrees of the membrane retention were found for relatively large sized and protein-like molecules. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Structural basis for plant plasma membrane protein dynamics and organization into functional nanodomains

    PubMed Central

    Gronnier, Julien; Crowet, Jean-Marc; Habenstein, Birgit; Nasir, Mehmet Nail; Bayle, Vincent; Hosy, Eric; Platre, Matthieu Pierre; Gouguet, Paul; Raffaele, Sylvain; Martinez, Denis; Grelard, Axelle; Loquet, Antoine; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia; Der, Christophe; Bayer, Emmanuelle M; Jaillais, Yvon; Deleu, Magali; Germain, Véronique; Lins, Laurence; Mongrand, Sébastien

    2017-01-01

    Plasma Membrane is the primary structure for adjusting to ever changing conditions. PM sub-compartmentalization in domains is thought to orchestrate signaling. Yet, mechanisms governing membrane organization are mostly uncharacterized. The plant-specific REMORINs are proteins regulating hormonal crosstalk and host invasion. REMs are the best-characterized nanodomain markers via an uncharacterized moiety called REMORIN C-terminal Anchor. By coupling biophysical methods, super-resolution microscopy and physiology, we decipher an original mechanism regulating the dynamic and organization of nanodomains. We showed that targeting of REMORIN is independent of the COP-II-dependent secretory pathway and mediated by PI4P and sterol. REM-CA is an unconventional lipid-binding motif that confers nanodomain organization. Analyses of REM-CA mutants by single particle tracking demonstrate that mobility and supramolecular organization are critical for immunity. This study provides a unique mechanistic insight into how the tight control of spatial segregation is critical in the definition of PM domain necessary to support biological function. DOI: http://dx.doi.org/10.7554/eLife.26404.001 PMID:28758890

  11. Organization and dynamics of membrane probes and proteins utilizing the red edge excitation shift.

    PubMed

    Haldar, Sourav; Chaudhuri, Arunima; Chattopadhyay, Amitabha

    2011-05-19

    Dynamics of confined water has interesting implications in the organization and function of molecular assemblies such as membranes. A direct consequence of this type of organization is the restriction imposed on the mobility of the constituent structural units. Interestingly, this restriction (confinement) of mobility couples the motion of solvent (water) molecules with the slow moving molecules in the assembly. It is in this context that the red edge excitation shift (REES) represents a sensitive approach to monitor the environment and dynamics around a fluorophore in such organized assemblies. A shift in the wavelength of maximum fluorescence emission toward higher wavelengths, caused by a shift in the excitation wavelength toward the red edge of the absorption band, is termed REES. REES relies on slow solvent reorientation in the excited state of a fluorophore that can be used to monitor the environment and dynamics around a fluorophore in a host assembly. In this article, we focus on the application of REES to monitor organization and dynamics of membrane probes and proteins. © 2011 American Chemical Society

  12. 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.

  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.

  14. 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

    2015-11-16

    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.

  15. n-3 Polyunsaturated fatty acids exert immunomodulatory effects on lymphocytes by targeting plasma membrane molecular organization

    PubMed Central

    Shaikh, Saame Raza; Jolly, Christopher A.; Chapkin, Robert S.

    2011-01-01

    Fish oil, enriched in bioactive n-3 polyunsaturated fatty acids (PUFA), has therapeutic value for the treatment of inflammation-associated disorders. The effects of n-3 PUFAs are pleiotropic and complex; hence, an understanding of their cellular targets and molecular mechanisms of action remains incomplete. Here we focus on recent data indicating n-3 PUFAs exert immunosuppressive effects on the function of effector and regulatory CD4+ T cells. In addition, we also present emerging evidence that n-3 PUFAs have immunomodulatory effects on B cells. We then focus on one multifaceted mechanism of n-3 PUFAs, which is the alteration of the biophysical and biochemical organization of the plasma membrane. This mechanism is central for downstream signaling, eicosanoid production, transcriptional regulation and cytokine secretion. We highlight recent work demonstrating n-3 PUFA acyl chains in the plasma membrane target the lateral organization of membrane signaling assemblies (i.e. lipid rafts or signaling networks) and de novo phospholipid biosynthesis. We conclude by proposing new functional and mechanistic questions in this area of research that will aid in the development of fish oil as adjuvant therapy for treating unresolved chronic inflammation. PMID:22020145

  16. 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.

  17. Electricity production in membrane-less microbial fuel cell fed with livestock organic solid waste.

    PubMed

    Lee, Yunhee; Nirmalakhandan, Nagamany

    2011-05-01

    Two different MFC configurations designed for handling solid wastes as a feedstock were evaluated in batch mode: a single compartment combined membrane-electrodes (SCME) design; and a twin-compartment brush-type anode electrodes (TBE) design (reversed T-shape MFC with two-air cathode) without a proton exchange membrane (PEM). Cattle manure was tested as a model livestock organic solid waste feedstock. Under steady conditions, voltage of 0.38 V was recorded with an external resistance of 470Ω. When digested anaerobic sludge was used as the seed in the SCME design, a maximum power density of 36.6 mW/m(2) was recorded. When hydrogen-generating bacteria (HGB) were used as the seed used in the TBE design, a higher power density of 67 mW/m(2) was recorded.

  18. Red blood cells in Rett syndrome: oxidative stress, morphological changes and altered membrane organization.

    PubMed

    Ciccoli, Lucia; De Felice, Claudio; Leoncini, Silvia; Signorini, Cinzia; Cortelazzo, Alessio; Zollo, Gloria; Pecorelli, Alessandra; Rossi, Marcello; Hayek, Joussef

    2015-11-01

    In this review, we summarize the current evidence on the erythrocyte as a previously unrecognized target cell in Rett syndrome, a rare (1:10 000 females) and devastating neurodevelopmental disorder caused by loss-of-function mutations in a single gene (i.e. MeCP2, CDKL5, or rarely FOXG1). In particular, we focus on morphological changes, membrane oxidative damage, altered membrane fatty acid profile, and aberrant skeletal organization in erythrocytes from patients with typical Rett syndrome and MeCP2 gene mutations. The beneficial effects of ω-3 polyunsaturated fatty acids (PUFAs) are also summarized for this condition to be considered as a 'model' condition for autism spectrum disorders.

  19. Molecular organization and fine structure of the human tectorial membrane: is it replenished?

    PubMed

    Hayashi, Hisamitsu; Schrott-Fischer, Annelies; Glueckert, Rudolf; Liu, Wei; Salvenmoser, Willi; Santi, Peter; Rask-Andersen, Helge

    2015-12-01

    Auditory sensitivity and frequency resolution depend on the physical properties of the basilar membrane in combination with outer hair cell-based amplification in the cochlea. The physiological role of the tectorial membrane (TM) in hair cell transduction has been controversial for decades. New insights into the TM structure and function have been gained from studies of targeted gene disruption. Several missense mutations in genes regulating the human TM structure have been described with phenotypic expressions. Here, we portray the remarkable gradient structure and molecular organization of the human TM. Ultrastructural analysis and confocal immunohistochemistry were performed in freshly fixed human cochleae obtained during surgery. Based on these findings and recent literature, we discuss the role of human TMs in hair cell activation. Moreover, the outcome proposes that the α-tectorin-positive amorphous layer of the human TM is replenished and partly undergoes regeneration during life.

  20. Characterization of natural organic matter treated by iron oxide nanoparticle incorporated ceramic membrane-ozonation process.

    PubMed

    Park, Hosik; Kim, Yohan; An, Byungryul; Choi, Heechul

    2012-11-15

    In this study, changes in the physical and structural properties of natural organic matter (NOM) were observed during hybrid ceramic membrane processes that combined ozonation with ultrafiltration ceramic membrane (CM) or with a reactive ceramic membrane (RM), namely, an iron oxide nanoparticles (IONs) incorporated-CM. NOM from feed water and NOM from permeate treated with hybrid ceramic membrane processes were analyzed by employing several NOM characterization techniques. Specific ultraviolet absorbance (SUVA), high-performance size exclusion chromatography (HPSEC) and fractionation analyses showed that the hybrid ceramic membrane process effectively removed and transformed relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions. Fourier transform infrared spectroscopy (FTIR) and 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy revealed that this process caused a significant decrease of the aromaticity of humic-like structures and an increase in electron withdrawing groups. The highest removal efficiency (46%) of hydroxyl radical probe compound (i.e., para-Chlorobenzoic acid (pCBA)) in RM-ozonation process compared with that in CM without ozonation process (8%) revealed the hydroxyl radical formation by the surface-catalyzed reaction between ozone and IONs on the surface of RM. In addition, experimental results on flux decline showed that fouling of RM-ozonation process (15%) was reduced compared with that of CM without ozonation process (30%). These results indicated that the RM-ozonation process enhanced the destruction of NOM and reduced the fouling by generating hydroxyl radicals from the catalytic ozonation in the RM-ozonation process. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Rejection of trace organic compounds by forward osmosis membranes: a literature review.

    PubMed

    Coday, Bryan D; Yaffe, Bethany G M; Xu, Pei; Cath, Tzahi Y

    2014-04-01

    To meet surging water demands, water reuse is being sought as an alternative to traditional water resources. However, contamination of water resources by trace organic compounds (TOrCs), including pharmaceuticals, personal care products, disinfection byproducts, and industrial chemicals is of increasing concern. These compounds are not readily removed by conventional water treatment processes and require new treatment technologies to enable potable water reuse. Forward osmosis (FO) has been recognized in recent years as a robust process suitable for the treatment of highly impaired streams and a good barrier to TOrCs. To date, at least 14 studies have been published that investigated the rejection of various TOrCs by FO membranes under a variety of experimental conditions. In this paper, TOrC rejection by FO has been critically reviewed, evaluating the effects of membrane characteristics and orientation, experimental scale and duration, membrane fouling, feed solution chemistry, draw solution composition and concentration, and transmembrane temperature on process performance. Although it is important to continue to investigate the removal of diverse TOrCs by FO, and especially with new FO membranes, it is critically important to adhere to standard testing conditions to enable comparison of results between studies. Likewise, feed concentration of TOrCs during FO testing must be environmentally relevant (most commonly 10-100 ng/L range for most wastewaters) and not excessively high, and in addition to testing TOrC rejection in clean feedwater, the effects of real water matrix and membrane fouling on TOrC rejection must be evaluated.

  2. Mechanism of organic anion transport across the apical membrane of choroid plexus.

    PubMed

    Pritchard, J B; Sweet, D H; Miller, D S; Walden, R

    1999-11-19

    The mechanism and membrane localization of choroid plexus (CP) organic anion transport were determined in apical (or brush border) membrane vesicles isolated from bovine choroid plexus and in intact CP tissue from cow and rat. Brush border membrane vesicles were enriched in Na(+),K(+)-ATPase (20-fold; an apical marker in CP) and demonstrated specific, sodium-coupled transport of proline, glucose, and glutarate. Vesicular uptake of the anionic herbicide 2, 4-dichlorophenoxyacetic acid (2,4-D) was markedly stimulated by an inward sodium gradient but only in the presence of glutarate, indicating the presence of apical dicarboxylate/organic anion exchange. Consistent with this interpretation, an imposed outward glutarate gradient stimulated 2,4-D uptake in the absence of sodium. Under both conditions, uptake was dramatically slowed and overshoot was abolished by probenecid. Likewise, apical accumulation of 2,4-D by intact bovine choroid plexus tissue in vitro was stimulated by external glutarate in the presence of sodium. Glutarate stimulation was abolished by 5 mM LiCl. Identical findings were obtained using rat CP tissue, which showed both sodium/glutarate-stimulated 2,4-D (tissue/medium (T/M) approximately 8) and p-aminohippurate (T/M = 2) transport. Finally, since the renal exchanger (rROAT1) has been cloned in rat kidney, a rROAT1-green fluorescent protein construct was used to analyze exchanger distribution directly in transiently transfected rat CP. As predicted by the functional studies, the fluorescently tagged transporter was seen in apical but not basolateral membranes of the CP.

  3. Fate of organic pollutants in a pilot-scale membrane bioreactor-nanofiltration membrane system at high water yield in antibiotic wastewater treatment.

    PubMed

    Wang, Jianxing; Wei, Yuansong; Li, Kun; Cheng, Yutao; Li, Mingyue; Xu, Jianguo

    2014-01-01

    A double membrane system combining a membrane bioreactor (MBR) with a nanofiltration (NF) membrane at the pilot scale was tested to treat real antibiotic wastewater at a pharmaceutical company in Wuxi (China). The water yield of the pilot system reached over 92 ± 5.6% through recycling the NF concentrate to the MBR tank. Results showed that the pilot scale system operated in good conditions throughout the entire experiment period and obtained excellent water quality in which the concentrations of chemical oxygen demand and total organic carbon were stable at 35 and 5.7 mg/L, respectively. The antibiotic removal rates of both spiramycin (SPM) and new spiramycin in wastewater were over 95%. Organics analysis results showed that the main organics in the biological effluent were proteins, soluble microbial by-product-like, fulvic acid-like and humic-like substances. These organics could be perfectly rejected by the NF membrane. Most of the organics could be removed through recycling NF concentrate to the MBR tank and only a small part was discharged with NF concentrate and permeate.

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

    PubMed

    Keating, Joseph N; Marquart, Chloe L; Donoghue, Philip C J

    2015-06-01

    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 interpret the

  5. 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

  6. 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.

  7. Coordination-driven in situ self-assembly strategy for the preparation of metal-organic framework hybrid membranes.

    PubMed

    Zhang, Rong; Ji, Shulan; Wang, Naixin; Wang, Lin; Zhang, Guojun; Li, Jian-Rong

    2014-09-08

    Metal-organic frameworks (MOFs) have emerged as porous solids of a superior type for the fabrication of membranes. However, it is still challenging to prepare a uniformly dispersed robust MOF hybrid membrane. Herein, we propose a simple and powerful strategy, namely, coordination-driven in situ self-assembly, for the fabrication of MOF hybrid membranes. On the basis of the coordination interactions between metal ions and ligands and/or the functional groups of the organic polymer, this method was confirmed to be feasible for the production of a stable membrane with greatly improved MOF-particle dispersion in and compatibility with the polymer, thus providing outstanding separation ability. As an experimental proof of concept, a high-quality ZIF-8/PSS membrane was fabricated that showed excellent performance in the nanofiltration and separation of dyes from water.

  8. 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

  9. 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

  10. Consequences of alkaline treatment for the ultrastructure of the acetylcholine-receptor-rich membranes from Torpedo marmorata electric organ

    PubMed Central

    1981-01-01

    After fixation with glutaraldehyde and impregnation with tannic acid, the membrane that underlies the nerve terminals in Torpedo marmorata electroplaque presents a typical asymmetric triple-layered structure with an unusual thickness; in addition, it is coated with electron- dense material on its inner, cytoplasmic face. Filamentous structures are frequently found attached to these "subsynaptic densities." The organization of the subsynaptic membrane is partly preserved after homogenization of the electric organ and purification of acetylcholine- receptor (AchR)-rich membrane fragments. In vitro treatment at pH 11 and 4 degrees C of these AchR-rich membranes releases an extrinsic protein of 43,000 mol wt and at the same time causes the complete disappearance of the cytoplasmic condensations. Freeze-etching of native membrane fragments discloses remnants of the ribbonlike organization of the AchR rosettes. This organization disappears ater alkaline treatment and is replaced by a network which is not observed after rapid freezing and, therefore, most likely results from the lateral redistribution of the AchR rosettes during condition of slow freezing. A dispersion of the AchR rosettes in the plane of the membrane also occurs after fusion of the pH 11-treated fragments with phospholipid vesicles. These results are interpreted in terms of a structural stabilization and immobilization of the AchR by the 43,000- Mr protein binding to the inner face of the subsynaptic membrane. PMID:7287814

  11. Dopamine crosslinked graphene oxide membrane for simultaneous removal of organic pollutants and trace heavy metals from aqueous solution.

    PubMed

    Wang, Jing; Huang, Tiefan; Zhang, Lin; Yu, Qiming Jimmy; Hou, Li'an

    2017-09-08

    A graphene oxide-polydopamine-(β-cyclodextrin) (GPC) ultrafiltration membrane was fabricated by using the method of drop-coating combined with vacuum filtration. The prepared GPC membrane was characterized with FTIR and XPS spectrophotometry and evaluated for its performances for the rejection of organic molecules (methylene blue) and adsorption of trace heavy metals (Pb(2+)) from aqueous solutions. The membrane exhibited an excellent rejection coefficient of 99.2% for methylene blue and the permeation flux was 12 L m(-2) h(-1) at 0.1 bar. The membrane also exhibited fast adsorption kinetics for Pb(2+) and the adsorption capacity was 101.6 mg g(-1) at a solution pH of 6. The performance of the membrane could almost be completely recovered after a simple clean and regeneration process. These results indicate that the GPC membrane has potential applications in treatment of complex industrial wastewater streams.

  12. 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). Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Distraction Osteogenesis of the Craniofacial Skeleton.

    PubMed

    Yu, Jack C.; Fearon, Jeffrey; Havlik, Robert J.; Buchman, Steve R.; Polley, John W.

    2004-07-01

    LEARNING OBJECTIVES:: After studying this article, the participant should be able to: 1. Review the biomechanical principles and pertinent cellular and molecular biology of distraction osteogenesis of the craniofacial skeleton. 2. Describe the clinical indications and applications of distraction osteogenesis of the craniofacial skeleton. 3. Describe maxillary, mandibular, midface, and calvarial procedures in distraction osteogenesis. 4. Discuss the clinical outcomes and complications of distraction osteogenesis of the craniofacial skeleton.The year 2002 marked the end of the first decade in clinical distraction osteogenesis of the craniofacial skeleton. In this short period, its application has increased exponentially. More than 3000 cases have been performed according to a recent survey, and more than 700 articles have been written on this subject in the MEDLINE database since 1996. It is a powerful surgical tool and enables surgeons to achieve results not previously attainable. Despite all this, distraction osteogenesis is practiced by only a small number of plastic surgeons. This article reviews the biomechanical principles; the pertinent cellular and molecular biology; and the clinical indications, applications, controversies, and complications of distraction osteogenesis of the craniofacial skeleton.

  14. Update on approaches to the craniomaxillofacial skeleton.

    PubMed

    Villwock, Jennifer A; Suryadevara, Amar C

    2014-08-01

    A myriad of surgical approaches to the craniomaxillofacial skeleton exist. Depending on the purpose of the procedure and the anatomic area to be addressed, classically used approaches include coronal approach, midfacial degloving, eyelid incisions, and other cutaneous incisions. Over the last decade, endoscopic approaches have become more popular. Whether external, transoral, or endoscopic, a detailed knowledge of the indications, anatomy, limitations, and potential complications is critical to the successful employment of these approaches. This article reviews the recent literature on classic as well as novel advancements to the craniofacial skeleton. Multiple studies in the last 5 years have investigated the approaches to the craniofacial skeleton. Most of these focus on trauma. Recent advances have concentrated on external versus endoscopic approaches to the mandibular condyle, an endoscopic approach to the midface and orbit, three-dimensional imaging of the facial skeleton, and improving upon the existing classic approaches and techniques. Approaches to the craniomaxillofacial skeleton continue to evolve with the refinement of classic approaches and advent of new technologies and approaches. This study reviews the recent literature and provides a comprehensive review of options for craniofacial exposure and the most up-to-date surgical options.

  15. Bayesian estimation of the shape skeleton

    PubMed Central

    Feldman, Jacob; Singh, Manish

    2006-01-01

    Skeletal representations of shape have attracted enormous interest ever since their introduction by Blum [Blum H (1973) J Theor Biol 38:205–287], because of their potential to provide a compact, but meaningful, shape representation, suitable for both neural modeling and computational applications. But effective computation of the shape skeleton remains a notorious unsolved problem; existing approaches are extremely sensitive to noise and give counterintuitive results with simple shapes. In conventional approaches, the skeleton is defined by a geometric construction and computed by a deterministic procedure. We introduce a Bayesian probabilistic approach, in which a shape is assumed to have “grown” from a skeleton by a stochastic generative process. Bayesian estimation is used to identify the skeleton most likely to have produced the shape, i.e., that best “explains” it, called the maximum a posteriori skeleton. Even with natural shapes with substantial contour noise, this approach provides a robust skeletal representation whose branches correspond to the natural parts of the shape. PMID:17101989

  16. The human erythrocyte plasma membrane: a Rosetta Stone for decoding membrane-cytoskeleton structure.

    PubMed

    Fowler, Velia M

    2013-01-01

    The mammalian erythrocyte, or red blood cell (RBC), is a unique experiment of nature: a cell with no intracellular organelles, nucleus or transcellular cytoskeleton, and a plasma membrane with uniform structure across its entire surface. By virtue of these specialized properties, the RBC membrane has provided a template for discovery of the fundamental actin filament network machine of the membrane skeleton, now known to confer mechanical resilience, anchor membrane proteins, and organize membrane domains in all cells. This chapter provides a historical perspective and critical analysis of the biochemistry, structure, and physiological functions of this actin filament network in RBCs. The core units of this network are nodes of ~35-37 nm-long actin filaments, interconnected by long strands of (α1β1)₂-spectrin tetramers, forming a 2D isotropic lattice with quasi-hexagonal symmetry. Actin filament length and stability is critical for network formation, relying upon filament capping at both ends: tropomodulin-1 at pointed ends and αβ-adducin at barbed ends. Tropomodulin-1 capping is essential for precise filament lengths, and is enhanced by tropomyosin, which binds along the short actin filaments. αβ-adducin capping recruits spectrins to sites near barbed ends, promoting network formation. Accessory proteins, 4.1R and dematin, also promote spectrin binding to actin and, with αβ-adducin, link to membrane proteins, targeting actin nodes to the membrane. Dissection of the molecular organization within the RBC membrane skeleton is one of the paramount achievements of cell biological research in the past century. Future studies will reveal the structure and dynamics of actin filament capping, mechanisms of precise length regulation, and spectrin-actin lattice symmetry. © 2013 Elsevier Inc. All rights reserved.

  17. 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.

  18. Entropic forces drive self-organization and membrane fusion by SNARE proteins.

    PubMed

    Mostafavi, Hakhamanesh; Thiyagarajan, Sathish; Stratton, Benjamin S; Karatekin, Erdem; Warner, Jason M; Rothman, James E; O'Shaughnessy, Ben

    2017-05-23

    SNARE proteins are the core of the cell's fusion machinery and mediate virtually all known intracellular membrane fusion reactions on which exocytosis and trafficking depend. Fusion is catalyzed when vesicle-associated v-SNAREs form trans-SNARE complexes ("SNAREpins") with target membrane-associated t-SNAREs, a zippering-like process releasing ∼65 kT per SNAREpin. Fusion requires several SNAREpins, but how they cooperate is unknown and reports of the number required vary widely. To capture the collective behavior on the long timescales of fusion, we developed a highly coarse-grained model that retains key biophysical SNARE properties such as the zippering energy landscape and the surface charge distribution. In simulations the ∼65-kT zippering energy was almost entirely dissipated, with fully assembled SNARE motifs but uncomplexed linker domains. The SNAREpins self-organized into a circular cluster at the fusion site, driven by entropic forces that originate in steric-electrostatic interactions among SNAREpins and membranes. Cooperative entropic forces expanded the cluster and pulled the membranes together at the center point with high force. We find that there is no critical number of SNAREs required for fusion, but instead the fusion rate increases rapidly with the number of SNAREpins due to increasing entropic forces. We hypothesize that this principle finds physiological use to boost fusion rates to meet the demanding timescales of neurotransmission, exploiting the large number of v-SNAREs available in synaptic vesicles. Once in an unfettered cluster, we estimate ≥15 SNAREpins are required for fusion within the ∼1-ms timescale of neurotransmitter release.

  19. 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.

  20. Identification of effluent organic matter fractions responsible for low-pressure membrane fouling.

    PubMed

    Filloux, Emmanuelle; Gallard, Hervé; Croue, Jean-Philippe

    2012-11-01

    Anion exchange resin (AER), powder activated carbon (PAC) adsorption and ozonation treatments were applied on biologically treated wastewater effluent with the objective to modify the effluent organic matter (EfOM) matrix. Both AER and PAC led to significant total organic carbon (TOC) removal, while the TOC remained nearly constant after ozonation. Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis showed that the AER treatment preferentially removed high and intermediate molecular weight (MW) humic-like structures while PAC removed low MW compounds. Only a small reduction of the high MW colloids (i.e. biopolymers) was observed for AER and PAC treatments. Ozonation induced a large reduction of the biopolymers and an important increase of the low MW humic substances (i.e. building blocks). Single-cycle microfiltration (MF) and ultrafiltration (UF) tests were conducted using commercially available hollow fibres at a constant flux. After reconcentration to their original organic carbon content, the EfOM matrix modified by AER and PAC treatments exhibited higher UF membrane fouling compared to untreated effluent; result that correlated with the higher concentration of biopolymers. On the contrary, ozonation which induced a significant degradation of the biopolymers led to a minor flux reduction for both UF and MF filtration tests. Based on a single filtration, results indicate that biopolymers play a major role in low pressure membrane fouling and that intermediate and low MW compounds have minor impact. Thus, this approach has shown to be a valid methodology to identify the foulant fractions of EfOM. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Observations of the tissue-skeleton interface in the scleractinian coral Stylophora pistillata

    NASA Astrophysics Data System (ADS)

    Tambutté, E.; Allemand, D.; Zoccola, D.; Meibom, A.; Lotto, S.; Caminiti, N.; Tambutté, S.

    2007-09-01

    Recent micro-analytical studies of coral skeletons have led to the discovery that the effects of biology on the skeletal chemical and isotopic composition are not uniform over the skeleton. The aim of the present work was to provide histological observations of the coral tissue at the interface with the skeleton, using Stylophora pistillata as a model, and to discuss these observations in the context of skeletal ultra-structural organization and composition. Several important observations are reported: (1) At all scales of observation, there was a precise morphological correspondence between the tissues and the skeleton. The morphological features of the calicoblastic ectoderm correspond exactly to the shape of individual crystal fiber bundles in the underlying skeleton, indicating that the calicoblastic cell layer is in direct physical contact with the skeletal surface. This is consistent with the previously observed chemical and isotopic composition of the ultra-structural components in the skeleton. (2) The distribution and density of desmocyte cells, which anchor the calicoblastic ectoderm to the skeletal surface, vary spatially and temporally during skeletal growth. (3) The tissue above the coenosteal spines lack endoderm and consists only of ectodermal cell-layers separated by mesoglea. These findings have important implications for models of vital effects in coral skeletal chemistry and isotope composition.

  2. Impact of natural organic matter on floc size and structure effects in membrane filtration.

    PubMed

    Lee, Sangyun A; Fane, Anthony G; Waite, T David

    2005-09-01

    Hematite (10 mg of Fe/L) floc-humic acid assemblages have been formed at pH 4 either by first aggregating hematite particles with salt (100 mM KCl) and then adding humic acid (salt-particle-organic or SPO assemblages) or by suspending the hematite particles in humic acid solutions and then adding salt to induce aggregation (organic-particle-salt or OPS assemblages). The behavior of these assemblages upon deposition on microfiltration (MF) membranes has then been investigated. In the OPS case, the fractal dimension (dF) of the assemblages formed varied dramatically depending upon the extent of charge neutralization by added fulvic acid with dF values typical of diffusion-limited cluster aggregates at low (0.1-0.2 mg/L) humic acid concentrations and dF values typical of reaction-limited cluster aggregates either in the absence of humic acid or concentrations greater than 0.4-0.6 mg/L. In the SPO case, dF values on the order of 2.1 were initially observed and were found to decrease to around 1.8-1.9 for humic acid concentrations greater than 0.6-0.8 mg/L. OPS assemblages with low fractal dimensions were found to be highly compressible once deposited on MF membranes with significantly higher specific cake resistances than was the case for SPO assemblages at transmembrane pressures of 50 kPa and above. These results highlight the importance of both the choice of coagulant (e.g., preformed vs formed in situ) and the transmembrane pressure to which a membrane filtration process might be allowed to rise prior to removal of the fouling layer.

  3. Threshold concentration of easily assimilable organic carton in feedwater for biofouling of spiral-wound membranes.

    PubMed

    Hijnen, W A M; Biraud, D; Cornelissen, E R; van der Kooij, D

    2009-07-01

    One of the major impediments in the application of spiral-wound membranes in water treatment or desalination is clogging of the feed channel by biofouling which is induced by nutrients in the feedwater. Organic carbon is, under most conditions, limiting the microbial growth. The objective of this study is to assess the relationship between the concentration of an easily assimilable organic compound such as acetate in the feedwater and the pressure drop increase in the feed channel. For this purpose the membrane fouling simulator (MFS) was used as a model for the feed channel of a spiral-wound membrane. This MFS unit was supplied with drinking water enriched with acetate at concentrations ranging from 1 to 1000 microg C x L(-1). The pressure drop (PD) in the feed channel increased at all tested concentrations but not with the blank. The PD increase could be described by a first order process based on theoretical considerations concerning biofilm formation rate and porosity decline. The relationship between the first order fouling rate constant R(f) and the acetate concentration is described with a saturation function corresponding with the growth kinetics of bacteria. Under the applied conditions the maximum R(f) (0.555 d(-1)) was reached at 25 microg acetate-C x L(-1) and the half saturation constant k(f) was estimated at 15 microg acetate-C x L(-1). This value is higher than k(s) values for suspended bacteria grown on acetate, which is attributed to substrate limited growth conditions in the biofilm. The threshold concentration for biofouling of the feed channel is about 1 microg acetate-C x L(-1).

  4. MPK-1 ERK controls membrane organization in C. elegans oogenesis via a sex determination module

    PubMed Central

    Arur, Swathi; Ohmachi, Mitsue; Berkseth, Matt; Nayak, Sudhir; Hansen, David; Zarkower, David; Schedl, Tim

    2011-01-01

    Tissues that generate specialized cell-types in a production line must coordinate developmental mechanisms with physiological demand, although how this occurs is largely unknown. In the C. elegans hermaphrodite, the developmental sex-determination cascade specifies gamete sex in the distal germline, while physiological sperm signaling activates MPK-1/ERK in the proximal germline to control plasma membrane biogenesis/organization during oogenesis. We discovered repeated utilization of a self-contained negative regulatory module, consisting of NOS-3 translational repressor, FEM-CUL-2 (E3 ubiquitin ligase) and TRA-1 (Gli transcriptional repressor), which acts both in sex-determination and in physiological demand control of oogenesis, coordinating these processes. In the distal germline, where MPK-1 is not activated, TRA-1 represses the male fate as NOS-3 functions in translational repression leading to inactivation of the FEM-CUL-2 ubiquitin ligase. In the proximal germline, sperm-dependent physiological MPK-1 activation results in phosphorylation-based inactivation of NOS-3, FEM-CUL-2 mediated degradation of TRA-1 and the promotion of membrane organization during oogenesis. PMID:21571224

  5. MPK-1 ERK controls membrane organization in C. elegans oogenesis via a sex-determination module.

    PubMed

    Arur, Swathi; Ohmachi, Mitsue; Berkseth, Matt; Nayak, Sudhir; Hansen, David; Zarkower, David; Schedl, Tim

    2011-05-17

    Tissues that generate specialized cell types in a production line must coordinate developmental mechanisms with physiological demand, although how this occurs is largely unknown. In the Caenorhabditis elegans hermaphrodite, the developmental sex-determination cascade specifies gamete sex in the distal germline, while physiological sperm signaling activates MPK-1/ERK in the proximal germline to control plasma membrane biogenesis and organization during oogenesis. We discovered repeated utilization of a self-contained negative regulatory module, consisting of NOS-3 translational repressor, FEM-CUL-2 (E3 ubiquitin ligase), and TRA-1 (Gli transcriptional repressor), which acts both in sex determination and in physiological demand control of oogenesis, coordinating these processes. In the distal germline, where MPK-1 is not activated, TRA-1 represses the male fate as NOS-3 functions in translational repression leading to inactivation of the FEM-CUL-2 ubiquitin ligase. In the proximal germline, sperm-dependent physiological MPK-1 activation results in phosphorylation-based inactivation of NOS-3, FEM-CUL-2-mediated degradation of TRA-1 and the promotion of membrane organization during oogenesis. Copyright © 2011 Elsevier Inc. All rights reserved.

  6. A novel anaerobic electrochemical membrane bioreactor (AnEMBR) with conductive hollow-fiber membrane for treatment of low-organic strength solutions.

    PubMed

    Katuri, Krishna P; Werner, Craig M; Jimenez-Sandoval, Rodrigo J; Chen, Wei; Jeon, Sungil; Logan, Bruce E; Lai, Zhiping; Amy, Gary L; Saikaly, Pascal E

    2014-11-04

    A new anaerobic treatment system that combined a microbial electrolysis cell (MEC) with membrane filtration using electrically conductive, porous, nickel-based hollow-fiber membranes (Ni-HFMs) was developed to treat low organic strength solution and recover energy in the form of biogas. This new system is called an anaerobic electrochemical membrane bioreactor (AnEMBR). The Ni-HFM served the dual function as the cathode for hydrogen evolution reaction (HER) and the membrane for filtration of the effluent. The AnEMBR system was operated for 70 days with synthetic acetate solution having a chemical oxygen demand (COD) of 320 mg/L. Removal of COD was >95% at all applied voltages tested. Up to 71% of the substrate energy was recovered at an applied voltage of 0.7 V as methane rich biogas (83% CH4; <1% H2) due to biological conversion of the hydrogen evolved at the cathode to methane. A combination of factors (hydrogen bubble formation, low cathode potential and localized high pH at the cathode surface) contributed to reduced membrane fouling in the AnEMBR compared to the control reactor (open circuit voltage). The net energy required to operate the AnEMBR system at an applied voltage of 0.7 V was significantly less (0.27 kWh/m3) than that typically needed for wastewater treatment using aerobic membrane bioreactors (1-2 kWh/m3).

  7. Design of pervaporation membrane for organic-liquid separation based on solubility control by plasma-graft filling polymerization technique

    SciTech Connect

    Yamaguchi, Takeo; Nakao, Shinichi; Kimura, Shoji )

    1993-05-01

    Pervaporation performance through the membranes showed the same tendency as solubility results. The authors have prepared the filling-polymerized membrane for pervaporation of organic-liquid mixtures by the plasma-graft polymerization technique. The membrane is composed of two different polymers: a porous substrate which can suppress membrane swelling and a grafted polymer which forms in the pores of the substrate and exhibits selectivity due to its solubility. The objectives of the present study are to design a suitable membrane for an organic-mixture system by the control of the filling-polymer solubility. Specifically, a porous high-density polyethylene membrane and poly(methylacrylate/acrylamide) copolymer were employed as the porous substrate and grafted polymer, respectively, and grafted copolymer solubility was predicted by Hansen solubility parameters (HSP). The grafted polymer composition and its solubility behavior could be controlled by varying the monomer composition, and the solubility change was in accordance with the prediction by HSP. Pervaporation performance through the membranes showed the same tendency as solubility results. The authors concluded that an optimum pervaporation membrane can be designed on the basis of solubility control through use of these techniques for polymerization and prediction.

  8. Interactions of Organics within Hydrated Selective Layer of Reverse Osmosis Desalination Membrane: A Combined Experimental and Computational Study.

    PubMed

    Ghoufi, Aziz; Dražević, Emil; Szymczyk, Anthony

    2017-03-07

    In this work we have examined a computational approach in predicting the interactions between uncharged organic solutes and polyamide membranes. We used three model organic molecules with identical molecular weights (100.1 g/mol), 4-aminopiperidine, 3,3-dimethyl-2-butanone (pinacolone) and methylisobutyl ketone for which we obtained experimental data on partitioning, diffusion and separation on a typical seawater reverse osmosis (RO) membrane. The interaction energy between the solutes and the membrane phase (fully aromatic polyamide) was computed from molecular dynamics (MD) simulations and the resulting sequence was found to correlate well with the experimental rejections and sorption data. Sorption of the different organic solutes within the membrane skin layer determined from attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) nicely agreed with interaction energies computed from molecular simulations. Qualitative information about solute diffusivity inside the membrane was also extracted from MD simulations while ATR-FTIR experiments indicated strongly hindered diffusion with diffusion coefficients in the membrane about 10(-15) m(2)/s. The computational approach presented here could be a first step toward predicting rejections trends of, for example, hormones and pharmaceuticals by RO dense membranes.

  9. Impact of organic nutrient load on biomass accumulation, feed channel pressure drop increase and permeate flux decline in membrane systems.

    PubMed

    Bucs, Sz S; Valladares Linares, R; van Loosdrecht, M C M; Kruithof, J C; Vrouwenvelder, J S

    2014-12-15

    The influence of organic nutrient load on biomass accumulation (biofouling) and pressure drop development in membrane filtration systems was investigated. Nutrient load is the product of nutrient concentration and linear flow velocity. Biofouling - excessive growth of microbial biomass in membrane systems - hampers membrane performance. The influence of biodegradable organic nutrient load on biofouling was investigated at varying (i) crossflow velocity, (ii) nutrient concentration, (iii) shear, and (iv) feed spacer thickness. Experimental studies were performed with membrane fouling simulators (MFSs) containing a reverse osmosis (RO) membrane and a 31 mil thick feed spacer, commonly applied in practice in RO and nanofiltration (NF) spiral-wound membrane modules. Numerical modeling studies were done with identical feed spacer geometry differing in thickness (28, 31 and 34 mil). Additionally, experiments were done applying a forward osmosis (FO) membrane with varying spacer thickness (28, 31 and 34 mil), addressing the permeate flux decline and biofilm development. Assessed were the development of feed channel pressure drop (MFS studies), permeate flux (FO studies) and accumulated biomass amount measured by adenosine triphosphate (ATP) and total organic carbon (TOC). Our studies showed that the organic nutrient load determined the accumulated amount of biomass. The same amount of accumulated biomass was found at constant nutrient load irrespective of linear flow velocity, shear, and/or feed spacer thickness. The impact of the same amount of accumulated biomass on feed channel pressure drop and permeate flux was influenced by membrane process design and operational conditions. Reducing the nutrient load by pretreatment slowed-down the biofilm formation. The impact of accumulated biomass on membrane performance was reduced by applying a lower crossflow velocity and/or a thicker and/or a modified geometry feed spacer. The results indicate that cleanings can be delayed

  10. Hybrid biofilm-membrane bioreactor (Bf-MBR) for minimization of bulk liquid-phase organic substances and its positive effect on membrane permeability.

    PubMed

    Sun, F Y; Li, P; Li, J; Li, H J; Ou, Q M; Sun, T T; Dong, Z J

    2015-12-01

    Four biofilm membrane bioreactors (Bf-MBRs) with various fixed carrier volumes (C:M) were operated in parallel to investigate the effect of attached-growth mode biomass involvement to the change of liquid-phase organics characteristics and membrane permeability, by comparing with conventional MBR. The experiments displayed that C:M and co-existence of biofilm with suspended solids in Bf-MBRs resulted in slight difference in pollutants removal effectiveness, and in rather distinct biomass properties and bacterial activities. The membrane permeability and specific resistance of bulk suspension of Bf-MBRs related closely with the liquid-phase organic substance, including soluble microbial products (SMP) and biopolymer cluster (BPC). Compared with conventional MBR, Bf-MBR with proper C:M had a low total biomass content and food-chain, where biofilm formation and its dominance affected liquid-phase organics, especially through reducing their content and minimizing strongly and weakly hydrophobic components with small molecular weight, and thus to mitigate membrane fouling significantly. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Factors affecting the attachment of micro-organisms isolated from ultrafiltration and reverse osmosis membranes in dairy processing plants.

    PubMed

    Tang, X; Flint, S H; Brooks, J D; Bennett, R J

    2009-08-01

    To identify the types of micro-organisms involved in the formation of biofilms on dairy ultrafiltration and reverse osmosis membranes and investigate factors affecting the attachment of those isolates. Micro-organisms isolated from industrial membranes following standard cleaning were identified using the API culture identification system. Thirteen different isolates representing eight genera were isolated and their ability to attach to surfaces was compared using a microtitre plate assay. Three Klebsiella strains attached best, while mixed strains of Pseudomonas and Klebsiella attached better than individual strains. Whey enhanced the attachment of the isolates. The micro-organisms were characterized according to cell surface hydrophobicity using the microbial adhesion to hydrocarbon (MATH) test, and cell surface charge by measuring the zeta potential. These cell surface characteristics did not show a clear relationship with the attachment of our strains. A variety of different micro-organisms is associated with dairy ultrafiltration and reverse osmosis membranes after cleaning, suggesting several possible sources of contamination. The cleaning of these membranes may be inadequate. The attachment of the different isolates is highly variable and enhanced in the presence of whey. Knowledge of persistent microflora colonizing dairy membrane systems will help develop strategies to mitigate biofilm development in this environment, improving hygiene in membrane processing plants.

  12. Membrane Association via an Amino-terminal Amphipathic Helix Is Required for the Cellular Organization and Function of RNase II*

    PubMed Central

    Lu, Feng; Taghbalout, Aziz

    2013-01-01

    The subcellular localization of the exoribonuclease RNase II is not known despite the advanced biochemical characterization of the enzyme. Here we report that RNase II is organized into cellular structures that appear to coil around the Escherichia coli cell periphery and that RNase II is associated with the cytoplasmic membrane by its amino-terminal amphipathic helix. The helix also acts as an autonomous transplantable membrane binding domain capable of directing normally cytoplasmic proteins to the membrane. Assembly of the organized cellular structures of RNase II required the RNase II amphipathic membrane binding domain. Co-immunoprecipitation of the protein from cell extracts indicated that RNase II interacts with itself. The RNase II self-interaction and the ability of the protein to assemble into organized cellular structures required the membrane binding domain. The ability of RNase II to maintain cell viability in the absence of the exoribonuclease polynucleotide phosphorylase was markedly diminished when the RNase II cellular structures were lost due to changes in the amphipathicity of the amino-terminal helix, suggesting that membrane association and assembly of RNase II into organized cellular structures play an important role in the normal function of the protein within the bacterial cell. PMID:23344958

  13. Membrane association via an amino-terminal amphipathic helix is required for the cellular organization and function of RNase II.

    PubMed

    Lu, Feng; Taghbalout, Aziz

    2013-03-08

    The subcellular localization of the exoribonuclease RNase II is not known despite the advanced biochemical characterization of the enzyme. Here we report that RNase II is organized into cellular structures that appear to coil around the Escherichia coli cell periphery and that RNase II is associated with the cytoplasmic membrane by its amino-terminal amphipathic helix. The helix also acts as an autonomous transplantable membrane binding domain capable of directing normally cytoplasmic proteins to the membrane. Assembly of the organized cellular structures of RNase II required the RNase II amphipathic membrane binding domain. Co-immunoprecipitation of the protein from cell extracts indicated that RNase II interacts with itself. The RNase II self-interaction and the ability of the protein to assemble into organized cellular structures required the membrane binding domain. The ability of RNase II to maintain cell viability in the absence of the exoribonuclease polynucleotide phosphorylase was markedly diminished when the RNase II cellular structures were lost due to changes in the amphipathicity of the amino-terminal helix, suggesting that membrane association and assembly of RNase II into organized cellular structures play an important role in the normal function of the protein within the bacterial cell.

  14. Using patterned supported lipid membranes to investigate the role of receptor organization in intercellular signaling

    PubMed Central

    Nair, Pradeep M; Salaita, Khalid; Petit, Rebecca S; Groves, Jay T

    2014-01-01

    physical inputs, both internal and external to a cell, can directly alter the spatial organization of cell surface receptors and their associated functions. Here we describe a protocol that combines solid-state nanolithography and supported lipid membrane techniques to trigger and manipulate specific receptors on the surface of living cells and to develop an understanding of the interplay between spatial organization and receptor function. While existing protein-patterning techniques are capable of presenting cells with well-defined clusters of protein, this protocol uniquely allows for the control of the spatial organization of laterally fluid receptor-ligand complex at an intermembrane junction. a combination of immunofluorescence and single-cell microscopy methods and complementary biochemical analyses are used to characterize receptor signaling pathways and cell functions. the protocol requires 2–5 d to complete depending on the parameters to be studied. In principle, this protocol is widely applicable to eukaryotic cells and herein is specifically developed to study the role of physical organization and translocation of the EphA2 receptor tyrosine kinase across a library of model breast cancer cell lines. PMID:21455188

  15. Removal of sulfur-organic polar micropollutants in a membrane bioreactor treating industrial wastewater.

    PubMed

    Reemtsma, Thorsten; Zywicki, Britta; Stueber, Markus; Kloepfer, Achim; Jekel, Martin

    2002-03-01

    While membrane bioreactors (MBR) have proven their large potential to remove bulk organic matter from municipal as well as industrial wastewater, their suitability to remove poorly degradable polar wastewater contaminants is yet unknown. However, this is an important aspect for the achievable effluent quality and in terms of wastewater reuse. We have analyzed two classes of polar sulfur-organic compounds, naphthalene sulfonates and benzothiazoles, by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS) over a period of 3 weeks in the influent and effluent of a full-scale MBR with external ultrafiltration that treats tannery wastewater. While naphthalene monosulfonates were completely removed, total naphthalene disulfonate removal was limited to about 40%, and total benzothiazoles concentration decreased for 87%. Quantitative as well as qualitative data did not indicate an adaptation to or a more complete removal of these polar aromatic compounds by the MBR as compared to literature data on conventional activated sludge treatment. While quality improvements in receiving waters for bulk organic matter are documented and the same can be anticipated for apolar particle-associated contaminants, these data provide no indication that MBR will improve the removal of polar poorly biodegradable organic pollutants.

  16. Retention of pesticide Endosulfan by nanofiltration: influence of organic matter-pesticide complexation and solute-membrane interactions.

    PubMed

    De Munari, Annalisa; Semiao, Andrea Joana Correia; Antizar-Ladislao, Blanca

    2013-06-15

    Nanofiltration (NF) is a well-established process used in drinking water production to effectively remove Natural Organic Matter (NOM) and organic micropollutants. The presence of NOM has been shown to have contrasting results on micropollutant retention by NF membranes and removal mechanisms are to date poorly understood. The permeate water quality can therefore vary during operation and its decrease would be an undesired outcome for potable water treatment. It is hence important to establish the mechanisms involved in the removal of organic micropollutants by NF membranes in the presence of NOM. In this study, the retention mechanisms of pesticide Endosulfan (ES) in the presence of humic acids (HA) by two NF membranes, TFC-SR2 and TFC-SR3, a "loose" and a "tight" membrane, respectively, were elucidated. The results showed that two mechanisms were involved: (1) the formation of ES-HA complexes (solute-solute interactions), determined from solid-phase micro-extraction (SPME), increased ES retention, and (2) the interactions between HA and the membrane (solute-membrane interactions) increased membrane molecular weight cut-off (MWCO) and decreased ES retention. HA concentration, pH, and the ratio between micropollutant molecular weight (MW) and membrane MWCO were shown to influence ES retention mechanisms. In the absence of HA-membrane interactions at pH 4, an increase of HA concentration increased ES retention from 60% to 80% for the TFC-SR2 and from 80% to 95% for the TFC-SR3 due to ES-HA complex formation. At pH 8, interactions between HA and the loose TFC-SR2 increased the membrane MWCO from 460 to 496 g/mol and ES retention decreased from 55% to 30%, as HA-membrane interactions were the dominant mechanism for ES retention. In contrast, for the "tight" TFC-SR3 membrane the increase in the MWCO (from 165 to 179 g/mol), was not sufficient to decrease ES retention which was dominated by ES-HA interactions. Quantification of the contribution of both solute

  17. Free cholesterol and cholesterol esters in bovine oocytes: Implications in survival and membrane raft organization after cryopreservation.

    PubMed

    Buschiazzo, Jorgelina; Ríos, Glenda L; Canizo, Jesica R; Antollini, Silvia S; Alberio, Ricardo H

    2017-01-01

    Part of the damage caused by cryopreservation of mammalian oocytes occurs at the plasma membrane. The addition of cholesterol to cell membranes as a strategy to make it more tolerant to cryopreservation has been little addressed in oocytes. In order to increase the survival of bovine oocytes after cryopreservation, we proposed not only to increase cholesterol level of oocyte membranes before vitrification but also to remove the added cholesterol after warming, thus recovering its original level. Results from our study showed that modulation of membrane cholesterol by methyl-β-cyclodextrin (MβCD) did not affect the apoptotic status of oocytes and improved viability after vitrification yielding levels of apoptosis closer to those of fresh oocytes. Fluorometric measurements based on an enzyme-coupled reaction that detects both free cholesterol (membrane) and cholesteryl esters (stored in lipid droplets), revealed that oocytes and cumulus cells present different levels of cholesterol depending on the seasonal period. Variations at membrane cholesterol level of oocytes were enough to account for the differences found in total cholesterol. Differences found in total cholesterol of cumulus cells were explained by the differences found in both the content of membrane cholesterol and of cholesterol esters. Cholesterol was incorporated into the oocyte plasma membrane as evidenced by comparative labeling of a fluorescent cholesterol. Oocytes and cumulus cells increased membrane cholesterol after incubation with MβCD/cholesterol and recovered their original level after cholesterol removal, regardless of the season. Finally, we evaluated the effect of vitrification on the putative raft molecule GM1. Cholesterol modulation also preserved membrane organization by maintaining ganglioside level at the plasma membrane. Results suggest a distinctive cholesterol metabolic status of cumulus-oocyte complexes (COCs) among seasons and a dynamic organizational structure of cholesterol

  18. Mixed-matrix membranes incorporated with porous shape-persistent organic cages for gas separation.

    PubMed

    Mao, Hongchao; Zhang, Suobo

    2017-03-15

    There has been much recent interest in the use of porous materials derived from self-assembling, shape-persistent organic cages due to their solubility and easy post-synthetic modification. Herein we report the preparation of novel mixed-matrix membranes (MMMs) employing the porous organic cage Noria and its derivatives Noria-Boc and Noria-CO(t)Bu as the fillers, and a fluorine containing polyimide, 6FDA-DAM, as the polymeric matrix. The physical structures and properties of Noria and its derivatives were measured and investigated. Noria with substituents of Boc (cleaved by thermal treatment during the process of membrane fabrication) and CO(t)Bu groups tend to show much better compatibility with polyimide than Noria itself, resulting in homogeneous dispersion of nanoaggregates and fine adhesion between the two phases in the derived Noria/6FDA-DAM and Noria-CO(t)Bu/6FDA-DAM MMMs. Gas permeation tests revealed that Noria and Noria-CO(t)Bu nanoparticles have different effect on gas separation performance of MMMs. The introduction of Noria into 6FDA-DAM tends to enhance CO2/CH4 selectivity and thus improve its gas separation properties, though a decrease in the observed permeability could be observed. In contrast, the introduction of Noria-CO(t)Bu with higher surface area and larger pores tends to increase the free volume and gas permeability of MMMs. These results show that both the morphology and the gas separation properties of MMMs could be tuned by tailoring the structures of porous organic cages.

  19. Identification of a Novel Membrane Transporter Mediating Resistance to Organic Arsenic in Campylobacter jejuni

    PubMed Central

    Shen, Zhangqi; Luangtongkum, Taradon; Qiang, Zhiyi; Jeon, Byeonghwa; Wang, Liping

    2014-01-01

    Although bacterial mechanisms involved in the resistance to inorganic arsenic are well understood, the molecular basis for organic arsenic resistance has not been described. Campylobacter jejuni, a major food-borne pathogen causing gastroenteritis in humans, is highly prevalent in poultry and is reportedly resistant to the arsenic compound roxarsone (4-hydroxy-3-nitrobenzenearsonic acid), which has been used as a feed additive in the poultry industry for growth promotion. In this study, we report the identification of a novel membrane transporter (named ArsP) that contributes to organic arsenic resistance in Campylobacter. ArsP is predicted to be a membrane permease containing eight transmembrane helices, distinct from other known arsenic transporters. Analysis of multiple C. jejuni isolates from various animal species revealed that the presence of an intact arsP gene is associated with elevated resistance to roxarsone. In addition, inactivation of arsP in C. jejuni resulted in 4- and 8-fold reductions in the MICs of roxarsone and nitarsone, respectively, compared to that for the wild-type strain. Furthermore, cloning of arsP into a C. jejuni strain lacking a functional arsP gene led to 16- and 64-fold increases in the MICs of roxarsone and nitarsone, respectively. Neither mutation nor overexpression of arsP affected the MICs of inorganic arsenic, including arsenite and arsenate, in Campylobacter. Moreover, acquisition of arsP in NCTC 11168 led to accumulation of less roxarsone than the wild-type strain lacking arsP. Together, these results indicate that ArsP functions as an efflux transporter specific for extrusion of organic arsenic and contributes to the resistance to these compounds in C. jejuni. PMID:24419344

  20. Interfacial interactions between Skeletonema costatum extracellular organic matter and metal oxides: Implications for ceramic membrane filtration.

    PubMed

    Zaouri, Noor; Gutierrez, Leonardo; Dramas, Laure; Garces, Daniel; Croue, Jean-Philippe

    2017-06-01

    In the current study, the interfacial interactions between the high molecular weight (HMW) compounds of Skeletonema costatum (SKC) extracellular organic matter (EOM) and ZrO2 or Al2O3, were investigated by atomic force microscopy (AFM). HMW SKC-EOM was rigorously characterized and described as a hydrophilic organic compound mainly comprised of polysaccharide-like structures. Lipids and proteins were also observed, although in lower abundance. HMW SKC-EOM displayed attractive forces during approaching (i.e., leading to jump-to-contact events) and adhesion forces during retracting regime to both metal oxides at all solution conditions tested, where electrostatics and hydrogen bonding were suggested as dominant interacting mechanisms. However, the magnitude of these forces was significantly higher on ZrO2 surfaces, irrespective of cation type (Na(+) or Ca(2+)) or concentration. Interestingly, while HMW SKC-EOM interacting forces to Al2O3 were practically insensitive to solution chemistry, the interactions between ZrO2 and HMW SKC-EOM increased with increasing cation concentration in solution. The structure, and lower charge, hydrophilicity, and density of hydroxyl groups on ZrO2 surface would play a key role on favoring zirconia associations with HMW SKC-EOM. The current results contribute to advance our fundamental understanding of Algogenic Organic Matter (AOM) interfacial interactions with metal oxides (i.e., AOM membrane fouling), and would highly assist in the proper selection of membrane material during episodic algal blooms. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. DEMONSTRATION OF PILOT-SCALE PERVAPORATION SYSTEMS FOR VOLATILE ORGANIC COMPOUND REMOVAL FROM A SURFACTANT ENHANCED AQUIFER REMEDIATION FLUID. II. HOLLOW FIBER MEMBRANE MODULES

    EPA Science Inventory

    Pilot-scale demonstration of pervaporation-based removal of volatile organic compounds from a surfactant enhanced aquifer remediation (SEAR) fluid has been conducted at USEPA's Test & Evaluation Facility using hollow fiber membrane modules. The membranes consisted of microporous...

  2. DEMONSTRATION OF PILOT-SCALE PERVAPORATION SYSTEMS FOR VOLATILE ORGANIC COMPOUND REMOVAL FROM A SURFACTANT ENHANCED AQUIFER REMEDIATION FLUID. II. HOLLOW FIBER MEMBRANE MODULES

    EPA Science Inventory

    Pilot-scale demonstration of pervaporation-based removal of volatile organic compounds from a surfactant enhanced aquifer remediation (SEAR) fluid has been conducted at USEPA's Test & Evaluation Facility using hollow fiber membrane modules. The membranes consisted of microporous...

  3. Microbial adhesion and biofilm formation on microfiltration membranes: a detailed characterization using model organisms with increasing complexity.

    PubMed

    Vanysacker, L; Denis, C; Declerck, P; Piasecka, A; Vankelecom, I F J

    2013-01-01

    Since many years, membrane biofouling has been described as the Achilles heel of membrane fouling. In the present study, an ecological assay was performed using model systems with increasing complexity: a monospecies assay using Pseudomonas aeruginosa or Escherichia coli separately, a duospecies assay using both microorganisms, and a multispecies assay using activated sludge with or without spiked P. aeruginosa. The microbial adhesion and biofilm formation were evaluated in terms of bacterial cell densities, species richness, and bacterial community composition on polyvinyldifluoride, polyethylene, and polysulfone membranes. The data show that biofouling formation was strongly influenced by the kind of microorganism, the interactions between the organisms, and the changes in environmental conditions whereas the membrane effect was less important. The findings obtained in this study suggest that more knowledge in species composition and microbial interactions is needed in order to understand the complex biofouling process. This is the first report describing the microbial interactions with a membrane during the biofouling development.

  4. Microbial Adhesion and Biofilm Formation on Microfiltration Membranes: A Detailed Characterization Using Model Organisms with Increasing Complexity

    PubMed Central

    Vanysacker, L.; Denis, C.; Declerck, P.; Piasecka, A.; Vankelecom, I. F. J.

    2013-01-01

    Since many years, membrane biofouling has been described as the Achilles heel of membrane fouling. In the present study, an ecological assay was performed using model systems with increasing complexity: a monospecies assay using Pseudomonas aeruginosa or Escherichia coli separately, a duospecies assay using both microorganisms, and a multispecies assay using activated sludge with or without spiked P. aeruginosa. The microbial adhesion and biofilm formation were evaluated in terms of bacterial cell densities, species richness, and bacterial community composition on polyvinyldifluoride, polyethylene, and polysulfone membranes. The data show that biofouling formation was strongly influenced by the kind of microorganism, the interactions between the organisms, and the changes in environmental conditions whereas the membrane effect was less important. The findings obtained in this study suggest that more knowledge in species composition and microbial interactions is needed in order to understand the complex biofouling process. This is the first report describing the microbial interactions with a membrane during the biofouling development. PMID:23986906

  5. Controllable Preparation of Ultrathin Sandwich-Like Membrane with Porous Organic Framework and Graphene Oxide for Molecular Filtration

    PubMed Central

    Zhu, Yuanzhi; Xu, Danyun; Zhao, Qingshan; Li, Yang; Peng, Wenchao; Zhang, Guoliang; Zhang, Fengbao; Fan, Xiaobin

    2015-01-01

    Porous organic frameworks (POFs) based membranes have potential applications in molecular filtration, despite the lack of a corresponding study. This study reports an interesting strategy to get processable POFs dispersion and a novel ultrathin sandwich-like membrane design. It was accidentally found that the hydrophobic N-rich Schiff based POFs agglomerates could react with lithium-ethylamine and formed stable dispersion in water. By successively filtrating the obtained POFs dispersion and graphene oxide (GO), we successfully prepared ultrathin sandwich-like hybrid membranes with layered structure, which showed significantly improved separation efficiency in molecular filtration of organic dyes. This study may provide a universal way to the preparation of processable POFs and their hybrid membranes with GO. PMID:26455497

  6. Effect of a glucose-triazole-hydrogenated cardanol conjugate on lipid bilayer membrane organization and thermotropic phase transition

    NASA Astrophysics Data System (ADS)

    Swain, Jitendriya; Kamalraj, M.; Surya Prakash Rao, H.; Mishra, Ashok K.

    2015-02-01

    This work focuses on the membrane perturbation, solubilisation and thermotropic phase transition process of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) MLVs induced by a glucose-triazole-hydrogenated cardanol conjugate (GTHCC). GTHCC is a recently introduced non toxic sugar derivative. Differential scanning calorimetry (DSC) and fluorescence molecular probe based techniques have been used to understand the concentration dependent membrane perturbation, solubilisation and thermotropic phase transition process of DPPC MLVs. The phase transition temperature of DPPC MLVs decreases with increase in mol% of GTHCC. At higher concentration above 10 mol%, GTHCC was significantly perturbed the membrane organization. The intrinsic fluorescence of GTHCC is also found to be sensitive towards phase behaviour and changes in membrane organization of DPPC MLVs.

  7. Visualization of structural organization of ventral membranes of sheared-open resorbing osteoclasts attached to apatite pellets.

    PubMed

    Akisaka, Toshitaka; Yoshida, Atsushi

    2015-05-01

    Osteoclasts are highly polarized cells from both morphological and functional points of view. Using quick-freeze, rotary-replication methods combined with cell-shearing, we clarified the variability of cytoplasmic surface of the polarized membranes of osteoclasts seeded on apatite. As to the organization of actin filaments and clathrin sheets, we confirmed almost the same ventral membrane specializations of osteoclasts on apatite as seen on glass plates. The organized actin filaments and membrane-associated particles supported the ruffled border membranes. Inside the actin sealing zone, membrane specializations were not always occupied with the ruffled border but also with other types of membranes. Some osteoclasts formed an actin ring but lacked the ruffled border projections. We report a unique and distinctive membrane modification of apatite-attached osteoclasts, i.e., the presence of dense aggregates of membrane-associated particles and related structures not found in the osteoclasts seeded on glass plates. Actin filament polarity in the podosomes was determined by decoration with myosin S1. The actin filament polarity within podosome appears to be oriented predominantly with its barbed ends toward the core, whereas the interconnecting F-actin appears to be mixed oriented. Two different types of clathrin plaques displayed different distributions: clathrin-dependent endocytosis was observed in the ruffled border regions, whereas flat clathrin sheets were found in the leading edge of lamellipodia and near podosomes. The clathrin sheets adhered to the apatite surface tightly on the ventral membranes overlaying the resorption lacunae. All these membrane specializations as mentioned above may indicate the functional variability of osteoclasts seeded on apatite.

  8. LDRD final report on imaging self-organization of proteins in membranes by photocatalytic nano-tagging.

    SciTech Connect

    Zavadil, Kevin Robert; Shelnutt, John Allen; Sasaki, Darryl Yoshio; Song, Yujiang; Medforth, Craig J.

    2005-11-01

    We have developed a new nanotagging technology for detecting and imaging the self-organization of proteins and other components of membranes at nanometer resolution for the purpose of investigating cell signaling and other membrane-mediated biological processes. We used protein-, lipid-, or drug-bound porphyrin photocatalysts to grow in-situ nanometer-sized metal particles, which reveal the location of the porphyrin-labeled molecules by electron microscopy. We initially used photocatalytic nanotagging to image assembled multi-component proteins and to monitor the distribution of lipids and porphyrin labels in liposomes. For example, by exchanging the heme molecules in hemoproteins with a photocatalytic tin porphyrin, a nanoparticle was grown at each heme site of the protein. The result obtained from electron microscopy for a tagged multi-subunit protein such as hemoglobin is a symmetric constellation of a specific number of nanoparticle tags, four in the case of the hemoglobin tetramer. Methods for covalently linking photocatalytic porphyrin labels to lipids and proteins were also developed to detect and image the self-organization of lipids, protein-protein supercomplexes, and membrane-protein complexes. Procedures for making photocatalytic porphyrin-drug, porphyrin-lipid, and porphyrin-protein hybrids for non-porphyrin-binding proteins and membrane components were pursued and the first porphyrin-labeled lipids was investigated in liposomal membrane models. Our photocatalytic nanotagging technique may ultimately allow membrane self-organization and cell signaling processes to be imaged in living cells. Fluorescence and plasmonic spectra of the tagged proteins might also provide additional information about protein association and membrane organization. In addition, a porphyrin-aspirin or other NSAID hybrid may be used to grow metal nanotags for the pharmacologically important COX enzymes in membranes so that the distribution of the protein can be imaged at the

  9. Fabrication of Porous Matrix Membrane (PMM) Using Metal-Organic Framework as Green Template for Water Treatment

    PubMed Central

    Lee, Jian-Yuan; Tang, Chuyang Y.; Huo, Fengwei

    2014-01-01

    Pressure-driven membranes with high porosity can potentially be fabricated by removing template, such as low water stability metal-organic frameworks (MOFs) or other nanoparticles, in polymeric matrix. We report on the use of benign MOFs as green template to enhance porosity and interconnectivity of the water treatment membranes. Significantly enhanced separation performance was observed which might be attributed to the mass transfer coefficient of the substrate layer increased in ultrafiltration (UF) application. PMID:24435326

  10. Amorphous calcium carbonate particles form coral skeletons.

    PubMed

    Mass, Tali; Giuffre, Anthony J; Sun, Chang-Yu; Stifler, Cayla A; Frazier, Matthew J; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V; Marcus, Matthew A; Gilbert, Pupa U P A

    2017-08-28

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed "vital effects," that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene-Eocene Thermal Maximum that occurred 56 Mya.

  11. 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

  12. 3-D vascular skeleton extraction and decomposition.

    PubMed

    Chowriappa, Ashirwad; Seo, Yong; Salunke, Sarthak; Mokin, Maxim; Kan, Peter; Scott, Peter

    2014-01-01

    We introduce a novel vascular skeleton extraction and decomposition technique for computer-assisted diagnosis and analysis. We start by addressing the problem of vascular decomposition as a cluster optimization problem and present a methodology for weighted convex approximations. Decomposed vessel structures are then grouped using the vessel skeleton, extracted using a Laplace-based operator. The method is validated using presegmented sections of vasculature archived for 98 aneurysms in 112 patients. We test first for vascular decomposition and next for vessel skeleton extraction. The proposed method produced promising results with an estimated 80.5% of the vessel sections correctly decomposed and 92.9% of the vessel sections having the correct number of skeletal branches, identified by a clinical radiological expert. Next, the method was validated on longitudinal study data from n = 4 subjects, where vascular skeleton extraction and decomposition was performed. Volumetric and surface area comparisons were made between expert segmented sections and the proposed approach on sections containing aneurysms. Results suggest that the method is able to detect changes in aneurysm volumes and surface areas close to that segmented by an expert.

  13. Amorphous calcium carbonate particles form coral skeletons

    PubMed Central

    Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.

    2017-01-01

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya. PMID:28847944

  14. Isotropic microscale mechanical properties of coral skeletons

    PubMed Central

    Pasquini, Luca; Molinari, Alan; Fantazzini, Paola; Dauphen, Yannicke; Cuif, Jean-Pierre; Levy, Oren; Dubinsky, Zvy; Caroselli, Erik; Prada, Fiorella; Goffredo, Stefano; Di Giosia, Matteo; Reggi, Michela; Falini, Giuseppe

    2015-01-01

    Scleractinian corals are a major source of biogenic calcium carbonate, yet the relationship between their skeletal microstructure and mechanical properties has been scarcely studied. In this work, the skeletons of two coral species: solitary Balanophyllia europaea and colonial Stylophora pistillata, were investigated by nanoindentation. The hardness HIT and Young's modulus EIT were determined from the analysis of several load–depth data on two perpendicular sections of the skeletons: longitudinal (parallel to the main growth axis) and transverse. Within the experimental and statistical uncertainty, the average values of the mechanical parameters are independent on the section's orientation. The hydration state of the skeletons did not affect the mechanical properties. The measured values, EIT in the 76–77 GPa range, and HIT in the 4.9–5.1 GPa range, are close to the ones expected for polycrystalline pure aragonite. Notably, a small difference in HIT is observed between the species. Different from corals, single-crystal aragonite and the nacreous layer of the seashell Atrina rigida exhibit clearly orientation-dependent mechanical properties. The homogeneous and isotropic mechanical behaviour of the coral skeletons at the microscale is correlated with the microstructure, observed by electron microscopy and atomic force microscopy, and with the X-ray diffraction patterns of the longitudinal and transverse sections. PMID:25977958

  15. Novel skeleton sesquiterpenoids isolated from guava leaves.

    PubMed

    Ouyang, Wen; Zhu, Xiao-ai; Wang, Wei; Chen, Xue-Xiang; Chen, Yun-Jiao; Cao, Yong

    2016-01-01

    A chemical investigation of the plant Psidium guajava L., collected in Guangdong province, afforded two novel skeleton sesquiterpenoids 1 and 2. Compound 2 also known as isocaryolan-9-one was a new natural product. The structure of the novel compound 1 was determined as guavacid A by various spectroscopic methods. A possible biosynthetic pathway for 1 and 2 was proposed.

  16. Amorphous calcium carbonate particles form coral skeletons

    NASA Astrophysics Data System (ADS)

    Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.; Gilbert, Pupa U. P. A.

    2017-09-01

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya.

  17. Mast cell- and dendritic cell-derived exosomes display a specific lipid composition and an unusual membrane organization.

    PubMed Central

    Laulagnier, Karine; Motta, Claude; Hamdi, Safouane; Roy, Sébastien; Fauvelle, Florence; Pageaux, Jean-François; Kobayashi, Toshihide; Salles, Jean-Pierre; Perret, Bertrand; Bonnerot, Christian; Record, Michel

    2004-01-01

    Exosomes are small vesicles secreted from multivesicular bodies, which are able to stimulate the immune system leading to tumour cell eradication. We have analysed lipids of exosomes secreted either upon stimulation from rat mast cells (RBL-2H3 cells), or constitutively from human dendritic cells. As compared with parent cells, exosomes displayed an enrichment in sphingomyelin, but not in cholesterol. Phosphatidylcholine content was decreased, but an enrichment was noted in disaturated molecular species as in phosphatidylethanolamines. Lyso(bis)phosphatidic acid was not enriched in exosomes as compared with cells. Fluorescence anisotropy demonstrated an increase in exosome-membrane rigidity from pH 5 to 7, suggesting their membrane reorganization between the acidic multivesicular body compartment and the neutral outer cell medium. NMR analysis established a bilayer organization of exosome membrane, and ESR studies using 16-doxyl stearic acid demonstrated a higher flip-flop of lipids between the two leaflets as compared with plasma membrane. In addition, the exosome membrane exhibited no asymmetrical distribution of phosphatidylethanolamines. Therefore exosome membrane displays a similar content of the major phospholipids and cholesterol, and is organized as a lipid bilayer with a random distribution of phosphatidylethanolamines. In addition, we observed tight lipid packing at neutral pH and a rapid flip-flop between the two leaflets of exosome membranes. These parameters could be used as a hallmark of exosomes. PMID:14965343

  18. Membrane Organization and Ionization Behavior of the Minor but Crucial Lipid Ceramide-1-Phosphate

    SciTech Connect

    Kooijman, Edgar E.; Sot, Jesus; Montes, L.-Ruth; Alonso, Alicia; Gericke, Arne; de Kruijff, Ben; Kumar, Satyendra; Goni, Felix M.

    2008-08-06

    Ceramide-1-phosphate (Cer-1-P), one of the simplest of all sphingophospholipids, occurs in minor amounts in biological membranes. Yet recent evidence suggests important roles of this lipid as a novel second messenger with crucial tasks in cell survival and inflammatory responses. We present a detailed description of the physical chemistry of this hitherto little explored membrane lipid. At full hydration Cer-1-P forms a highly organized subgel (crystalline) bilayer phase (L{sub c}) at low temperature, which transforms into a regular gel phase (L{sub {beta}}) at {approx}45 C, with the gel to fluid phase transition (L{sub {beta}}-L{sub {alpha}}) occurring at {approx}65 C. When incorporated at 5mol % in a phosphatidylcholine bilayer, the pK{sub a2} of Cer-1-P, 7.39{+-}0.03, lies within the physiological pH range. Inclusion of phosphatidylethanolamine in the phosphatidylcholine bilayer, at equimolar ratio, dramatically reduces the pK{sub a2} to 6.64{+-}0.03. We explain these results in light of the novel electrostatic/hydrogen bond switch model described recently for phosphatidic acid. In mixtures with dielaidoylphosphatidylethanolamine, small concentrations of Cer-1-P cause a large reduction of the lamellar-to-inverted hexagonal phase transition temperature, suggesting that Cer-1-P induces, like phosphatidic acid, negative membrane curvature in these types of lipid mixtures. These properties place Cer-1-P in a class more akin to certain glycerophospholipids (phosphatidylethanolamine, phosphatidic acid) than to any other sphingolipid. In particular, the similarities and differences between ceramide and Cer-1-P may be relevant in explaining some of their physiological roles.

  19. Conditioning of sewage sludge by Fenton's reagent combined with skeleton builders.

    PubMed

    Liu, Huan; Yang, Jiakuan; Shi, Yafei; Li, Ye; He, Shu; Yang, Changzhu; Yao, Hong

    2012-06-01

    Physical conditioners, often known as skeleton builders, are commonly used to improve the dewaterability of sewage sludge. This study evaluated a novel joint usage of Fenton's reagent and skeleton builders, referred to as the F-S inorganic composite conditioner, focusing on their efficacies and the optimization of the major operational parameters. The results demonstrate that the F-S composite conditioner for conditioning sewage sludge is a viable alternative to conventional organic polymers, especially when ordinary Portland cement (OPC) and lime are used as the skeleton builders. Experimental investigations confirmed that Fenton reaction required sufficient time (80 min in this study) to degrade organics in the sludge. The optimal condition of this process was at pH=5, Fe(2+)=40 mg g(-1) (dry solids), H(2)O(2)=32 mg g(-1), OPC=300 mg g(-1) and lime=400 mg g(-1), in which the specific resistance to filtration reduction efficiency of 95% was achieved.

  20. Organization of lipids in the artificial outer membrane of bull spermatozoa reconstructed at the air-water interface.

    PubMed

    Le Guillou, J; Ropers, M-H; Gaillard, C; David-Briand, E; Desherces, S; Schmitt, E; Bencharif, D; Amirat-Briand, L; Tainturier, D; Anton, M

    2013-08-01

    Cryopreservation is widely used to preserve the quality of bull spermatozoa over time. Sequestration of seminal plasma proteins by low density lipoproteins and formation of a protective film around the spermatozoa membrane by low density lipoproteins were the main mechanisms proposed. However, the organization of lipids in the outer leaflet of the spermatozoa membrane has been never considered as a possible parameter. This study evaluated whether a change in the organization of the outer leaflet of the spermotozoa membrane could occur during cooling down. The organization of the main components of the spermatozoa membrane's outer layer at the liquid-gas interface was analysed. Cryopreservative media (at 8° and 34°C) were used to study the miscibility of the spermatozoa membrane lipids using epifluorescence imaging and by tensiometry on Langmuir films. The results show that the four lipids: sphingomyelin, cholesterol, 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PC) and plasmalogen 1-(1Z-octadecenyl)-2-docosahexaenoyl-sn-glycero-3-phosphocholine (P-PC) were not fully miscible and their organization was controlled by temperature. Cholesterol and sphingomyelin form condensed domains surrounded by a mixture of PC and P-PC at 34°C while these condensed domains are surrounded by separated domains of pure PC and pure P-PC at 8°C. The organization of the outer membrane lipids, in particular the separation of PC and P-PC lipids during cooling down, must be considered to fully understand preservation of membrane integrity during cryopreservation.

  1. Models of plasma membrane organization can be applied to mitochondrial membranes to target human health and disease with polyunsaturated fatty acids.

    PubMed

    Raza Shaikh, Saame; Brown, David A

    2013-01-01

    Bioactive n-3 polyunsaturated fatty acids (PUFA), abundant in fish oil, have potential for treating symptoms associated with inflammatory and metabolic disorders; therefore, it is essential to determine their fundamental molecular mechanisms. Recently, several labs have demonstrated the n-3 PUFA docosahexaenoic acid (DHA) exerts anti-inflammatory effects by targeting the molecular organization of plasma membrane microdomains. Here we briefly review the evidence that DHA reorganizes the spatial distribution of microdomains in several model systems. We then emphasize how models on DHA and plasma membrane microdomains can be applied to mitochondrial membranes. We discuss the role of DHA acyl chains in regulating mitochondrial lipid-protein clustering, and how these changes alter several aspects of mitochondrial function. In particular, we summarize effects of DHA on mitochondrial respiration, electron leak, permeability transition, and mitochondrial calcium handling. Finally, we conclude by postulating future experiments that will augment our understanding of DHA-dependent membrane organization in health and disease. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Effects of phloretin on lipid organization in the erythrocyte membrane as measured by EPR

    NASA Astrophysics Data System (ADS)

    Abumrad, Nada A.; Perkins, Ray C.; Dalton, Larry R.; Park, Charles R.; Park, Jane H.

    Phloretin is a lipophilic compound which has been widely studied as a broad spectrum effector of metabolite transport in red blood cells (RBC). Phloretin effects on the organization of lipids in the RBC membrane are investigated using the spin-labeled fatty acids, 5 and 16-nitroxyl stearate (5-NS and 16-NS, respectively). Phloretin at different concentrations produced biphasic effects on the lineshape of the EPR response from 16-NS-labeled RBC. The dependence of these changes on the flat cell orientation with respect to the magnetic field suggested that phloretin promoted lipid order at low concentrations (5 to 40 μ M) and disorder at high concentrations (40 to 250 μ M). The biphasic effects of phloretin occurred at concentrations which parallel its dual actions on metabolite transfer. Phloretin generally inhibits transport (protein-mediated) and stimulates diffusion (lipid-mediated) processes. The spectroscopic effects were best characterized through second-harmonic, in-phase detection. The possible contribution of other factors to the spectroscopic changes is discussed. When RBC were spin labeled with 5-NS, higher concentrations of the probe were required for adequate detection and only monophasic effects of phoretin were observed. The results suggest that membrane lipids are important in phloretin effects on transport and diffusion processes.

  3. DipM links peptidoglycan remodeling to outer membrane organization in Caulobacter

    PubMed Central

    Goley, Erin D.; Comolli, Luis R.; Fero, Katherine E.; Downing, Kenneth H.; Shapiro, Lucy

    2010-01-01

    Summary Cell division in Gram-negative organisms requires coordinated invagination of the multi-layered cell envelope such that each daughter receives an intact inner membrane (IM), peptidoglycan (PG) layer, and outer membrane (OM). Here, we identify DipM,