Showing papers on "Membrane published in 2001"
TL;DR: In this paper, the authors explain the transport properties and the swelling behaviour of NAFION and different sulfonated polyetherketones in terms of distinct differences on the microstructures and in the p K a of the acidic functional groups.
2,755 citations
TL;DR: It is shown that mouse Apg12-Apg5 conjugate localizes to the isolation membranes in mouse embryonic stem cells, and the covalent modification of Apg5 with Apg 12 is not required for its membrane targeting, but is essential for involvement of ApG5 in elongation of the isolation membrane.
Abstract: In macroautophagy, cytoplasmic components are delivered to lysosomes for degradation via autophagosomes that are formed by closure of cup-shaped isolation membranes. However, how the isolation membranes are formed is poorly understood. We recently found in yeast that a novel ubiquitin-like system, the Apg12-Apg5 conjugation system, is essential for autophagy. Here we show that mouse Apg12-Apg5 conjugate localizes to the isolation membranes in mouse embryonic stem cells. Using green fluorescent protein–tagged Apg5, we revealed that the cup-shaped isolation membrane is developed from a small crescent-shaped compartment. Apg5 localizes on the isolation membrane throughout its elongation process. To examine the role of Apg5, we generated Apg5-deficient embryonic stem cells, which showed defects in autophagosome formation. The covalent modification of Apg5 with Apg12 is not required for its membrane targeting, but is essential for involvement of Apg5 in elongation of the isolation membranes. We also show that Apg12-Apg5 is required for targeting of a mammalian Aut7/Apg8 homologue, LC3, to the isolation membranes. These results suggest that the Apg12-Apg5 conjugate plays essential roles in isolation membrane development.
1,372 citations
TL;DR: Recent advances in the understanding of the mechanism of anhydrobiosis include the downregulation of metabolism, dehydration-induced partitioning of amphiphilic compounds into membranes and immobilization of the cytoplasm in a stable multicomponent glassy matrix.
1,312 citations
TL;DR: In this article, the most influential membrane properties governing colloidal fouling rate of reverse osmosis (RO) and nanofiltration (NF) membranes were identified for physical surface morphology, surface chemical properties, surface zeta potential, and specific surface chemical structure.
1,110 citations
TL;DR: In this article, an overview of the membrane development for proton-conductive polymer (composite) membranes for the application membrane fuel cells, focusing on the membrane developments in this field performed at ICVT.
1,006 citations
TL;DR: This electrode shows high selectivity for the response to cysteine, as compared with many common inorganic anions, salicylate, and other kinds of amino acids, and has a fast response time, micromolar detection limit, and good long-term stability.
Abstract: A novel cysteine-selective electrode based on lead phthalocyanine (PbPc) as ionophore is described. The electrode was prepared by incorporating PbPc into a plasticized poly(vinyl chloride) (PVC) membrane, which was directly coated on the surface of a graphite electrode. This electrode shows high selectivity for the response to cysteine, as compared with many common inorganic anions, salicylate, and other kinds of amino acids. The influence of membrane composition, pH, and the effect of lipophilic cationic and anionic additives on the response characteristics of the electrode were investigated. The resulting sensor demonstrates nernstian response over a wide linear range of cysteine concentration (1 × 10-6 to 5 × 10-2 M). The electrode has a fast response time, micromolar detection limit (∼1 × 10-6 M), and good long-term stability (more than 1 month). The prepared electrode was used for determination of cysteine in a synthetic human serum sample, and very good recovery results were obtained over a wide con...
958 citations
TL;DR: The GROMOS96 45A3 parameter set should be suitable for application to lipid aggregates such as membranes and micelles, for mixed systems of aliphatics with or without water, for polymers, and other apolar systems that may interact with different biomolecules.
Abstract: Over the past 4 years the GROMOS96 force field has been successfully used in biomolecular simulations, for example in peptide folding studies and detailed protein investigations, but no applications to lipid systems have been published yet. Here we provide a detailed investigation of aliphatic liquid systems. For liquids of larger aliphatic chains, n-heptane and longer, the standard GROMOS96 parameter sets 43A1 and 43A2 yield a too low pressure at the experimental density. Therefore, a reparametrization of the GROMOS96 force field regarding aliphatic carbons was initiated. The new force field parameter set 45A3 shows considerable improvements for n-alkanes, cyclo-, iso-, and neoalkanes and other branched aliphatics. Liquid densities and heat of vaporization are reproduced for almost all of these molecules. Excellent agreement is found with experiment for the free energy of hydration for alkanes. The GROMOS96 45A3 parameter set should, therefore, be suitable for application to lipid aggregates such as membranes and micelles, for mixed systems of aliphatics with or without water, for polymers, and other apolar systems that may interact with different biomolecules. c
856 citations
TL;DR: In this paper, the various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed, as well as the application of elastomeric membranes for protective clothing applications.
852 citations
TL;DR: In this paper, the authors give a brief outline of the field that has emerged on the basis of theoretical models on porous as well as non-porous membranes, and discuss mainly the solution cast polymeric membranes.
667 citations
TL;DR: In this paper, a systematic investigation of the conductivity of Nafion 117 and sulfonated polyether ether ketone (S-PEEK) membranes was performed as a function of relative humidity (rh) in a wide range of temperature (80-160°C).
603 citations
TL;DR: Track membrane (TM) technology is an example of industrial application of track etching technique as discussed by the authors, and it has been used in many applications, such as process filtration, cell culture, and laboratory filtering.
TL;DR: In this article, the first large-scale NaA zeolite membrane plant was put into industrial operation and the successful fabrication of the plant and the high level of PV properties of the module were discussed.
TL;DR: A review of the development of carbon membranes in the last 30 years and a clear future direction in research for carbon membrane can be found in this article, where carbon membranes can be divided into four major configurations: flat sheet, membrane supported on tube, capillary, and hollow fiber.
TL;DR: In this paper, the authors report approaches to the development of high temperature membranes for proton exchange membrane fuel cells; composite perfluorinated sulfonic acid membranes were prepared to improve water retention, and non-aqueous proton conducting membrane was prepared to circumvent the loss of water.
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09 Jul 2001
TL;DR: In this article, the state-of-the-art of Pervaporation processes in the chemical industry is described. But, as discussed in Section 2.1, it is based on the separation of organic molecules from gas streams by means of Membranes.
Abstract: List of Contributors. MEMBRANE MATERIALS AND MEMBRANE PREPARATION. Introduction. Membrane Market. Membrane Preparation. Presently Available Membranes for Liquid Separation. Surface Modification of Membranes. Gas Separation with Membranes. CURRENT APPLICATIONS AND PERSPECTIVES. The Separation of Organic Vapors from Gas Streams by Means of Membranes (K. Ohlrogge & K. St?rken). Gas Separation Membrane Applications (D. Stookey). State-of-Art of Pervaporation Processes in the Chemical Industry (H. Br?schke). Nanofiltration of Charged Organic Molecules in Aqueous and Non-aqueous Solvents: Separation Results and Mechanisms (J. Hestekin, et al.). Industrial Membrane Reactors (M. Kemmere & J. Keurentjes). Electromembrane Processes (T. Davis, et al.). Membrane Technology in the Chemical Industry: Future Directions (R. Baker). Subject Index.
TL;DR: Two new adaptor-related protein complexes, AP-3 and AP-4, have recently been identified, and both have been implicated in protein sorting at the trans-Golgi network (TGN) and/or endosomes.
TL;DR: In this paper, progress made over the past years in the functionalisation of polybenzimidazole and polyetherketones with a view to increasing their proton conduction properties without detriment to their thermohydrolytic and chemical stability such that corresponding membranes may be employed in hydrogen oxygen (air) or direct methanol fuel cells.
TL;DR: In this paper, a one-dimensional non-isothermal model of a proton exchange membrane (PEM) fuel cell has been developed to investigate the effect of various design and operating conditions on the cell performance, thermal response and water management.
TL;DR: In this article, the authors examined how bridged polysilsesquioxanes are prepared, processed, characterized, and used, and described how attaching several "inorganic" cross-linking trialkoxysilanes on organic bridging groups permits facile formation of network polymers and gels with high levels of chemical functionality.
Abstract: The class of hybrid organic−inorganic materials called bridged polysilsesquioxanes are used for everything from surface modifiers and coatings to catalysts and membrane materials. This paper examines how bridged polysilsesquioxanes are prepared, processed, characterized, and used. In particular, it describes how attaching several “inorganic” cross-linking trialkoxysilanes on organic bridging groups permits facile formation of network polymers and gels with high levels of chemical functionality. There are a number of synthetic entries into bridged polysilsesquioxane monomers that have allowed a multitude of different bridging groups to be integrated into xerogels (dry gels) or aerogels (supercritically dried “air gels”). Much of the research to date has been successfully focused on engineering of the size of pores through the choice of the bridging groups. For example, materials with some of the highest known surface areas in porous materials have been prepared, and parameters allowing control of the pore ...
TL;DR: In this article, a series of sequenced sulfonated naphthalenic polyimides with improved solubility were prepared by polycondensation in m-cresol using aromatic diamines containing phenylether bonds and/or bulky groups.
TL;DR: In this article, the preparation, characterization, properties and applications of polypyrrole (PPY) are reviewed in detail according to the synthetic methods and their applications, and effects of various parameters such as doping anions, additives, and oxidant, on the PPY properties are also concerned.
Abstract: Polypyrrole (PPY) is one of the most promising materials for multifunctionalized applications. Preparation, characterization, properties and applications of PPYs are reviewed in this paper. In addition, the PPY composites are described in detail according to the synthetic methods and their applications. At the same time, effects of various parameters such as doping anions, additives, and oxidant, on the PPY properties are also concerned. The PPY films and membranes used for ion exchange, pervaporation, and gas separation are mentioned. In this review, ion exchange membranes are highlighted. Moreover, the further investigation of PPY composite membranes for oxygen enrichment is predicted. A total of 117 references are cited.
TL;DR: In this article, the authors discuss two different membrane reactor concepts which both rely on supported palladium, on the one hand as a permselective membrane material, and on the other hand as base component of a membrane-type hydrogenation catalyst.
Abstract: Membrane reactors applied to catalytic reactions are currently being studied in many places world-wide. Significant developments in membrane science and the vision of process intensification by multifunctional reactors have stimulated a lot of academic and industrial research, which is impressively demonstrated by more than 100 scientific papers on catalytic membrane reactors being published per year. Palladium as a noble metal with exceptional hydrogen permeation properties and, at the same time, broad applicability as a catalyst, first of all for hydrogenation, is part of many of these developments. This paper discusses two different membrane reactor concepts which both rely on supported palladium, on the one hand as a permselective membrane material, and on the other hand as base component of a membrane-type hydrogenation catalyst. Dense palladium composite membranes can be used for hydrogen separation from packed-bed catalysts in gas-phase hydrocarbon dehydrogenation reactions. Mesoporous membranes containing dispersed bimetallic Pd/X-clusters can be employed as so-called catalytic diffusers for liquid-phase hydrogenation, e.g. of nitrate and nitrite in water. The principles of both concepts are introduced, recently obtained experimental data are evaluated in connection with literature results, and the perspectives for further development are highlighted.
TL;DR: The N-terminal domain of the influenza hemagglutinin is deduced to be a kinked, predominantly helical amphipathic structure that could perturb lipid packing and facilitate lipid mixing between juxtaposed membranes.
Abstract: The N-terminal domain of the influenza hemagglutinin (HA) is the only portion of the molecule that inserts deeply into membranes of infected cells to mediate the viral and the host cell membrane fusion. This domain constitutes an autonomous folding unit in the membrane, causes hemolysis of red blood cells and catalyzes lipid exchange between juxtaposed membranes in a pH-dependent manner. Combining NMR structures determined at pHs 7.4 and 5 with EPR distance constraints, we have deduced the structures of the N-terminal domain of HA in the lipid bilayer. At both pHs, the domain is a kinked, predominantly helical amphipathic structure. At the fusogenic pH 5, however, the domain has a sharper bend, an additional 3(10)-helix and a twist, resulting in the repositioning of Glu 15 and Asp 19 relative to that at the nonfusogenic pH 7.4. Rotation of these charged residues out of the membrane plane creates a hydrophobic pocket that allows a deeper insertion of the fusion domain into the core of the lipid bilayer. Such an insertion mode could perturb lipid packing and facilitate lipid mixing between juxtaposed membranes.
TL;DR: The use of grafting material in combination with collagen membranes seems to improve clinical outcomes for furcation, but not intrabony, defects when compared to the use of membranes alone, and the properties that make collagen membranes attractive for use in regenerative therapy will be addressed.
Abstract: Collagen materials have been utilized in medicine and dentistry because of their proven biocompatability and capability of promoting wound healing. For guided tissue regeneration (GTR) procedures, collagen membranes have been shown to be comparable to non-absorbable membranes with regard to probing depth reduction, clinical attachment gain, and percent of bone fill. Although these membranes are absorbable, collagen membranes have been demonstrated to prevent epithelial down-growth along the root surfaces during the early phase of wound healing. The use of grafting material in combination with collagen membranes seems to improve clinical outcomes for furcation, but not intrabony, defects when compared to the use of membranes alone. Recently, collagen materials have also been applied in guided bone regeneration (GBR) and root coverage procedures with comparable success rates to non-absorbable expanded polytetrafluoroethylene (ePTFE) membranes and conventional subepithelial connective tissue grafts, respectively. Long-term clinical trials are still needed to further evaluate the benefits of collagen membranes in periodontal and peri-implant defects. This article will review the rationale for each indication and its related literature, both in vitro and in vivo studies. The properties that make collagen membranes attractive for use in regenerative therapy will be addressed. In addition, varieties of cross-linking techniques utilized to retard the degradation rate of collagen membranes will be discussed.
TL;DR: X-ray photoelectron spectroscopy demonstrated quantitatively that a considerable amount of the adsorbed particles were tightly self-assembled at the expense of the initial loss of those that were loosely bound, and became stabilized even after exposure to the various washing and harsh RO operating conditions.
Abstract: Hybrid organic/inorganic reverse osmosis (RO) membranes composed of aromatic polyamide thin films underneath titanium dioxide (TiO2) nanosized particles have been fabricated by a self-assembly process, aiming at breakthrough of biofouling problems. First, positively charged particles of the colloidal TiO2 were synthesized by a sol−gel process, and the diameter of the resulting particles in acidic aqueous solution was estimated to be ≈2 nm by analyzing the UV−visible absorption characteristics with a quantum mechanical model developed by Brus. Transmission electron microscopy (TEM) further confirmed the formation of the quantum-sized TiO2 particles (∼10 nm or less). The TiO2 particles appeared to exist in the crystallographic form of anatase as observed with the X-ray diffraction (XRD) pattern in comparison with those of commercial 100% rutile and commercial 70:30% anatase-to-rutile mixture. The hybrid thin-film-composite (TFC) aromatic polyamide membranes were prepared by self-assembly of the TiO2 nanopar...
TL;DR: It is proposed that these rates of mechanochemical processes, such as endocytosis, membrane extension and membrane resealing after cell wounding, are also controlled physically, through an apparently continuous adhesion between plasma membrane lipids and cytoskeletal proteins.
Abstract: The rates of mechanochemical processes, such as endocytosis, membrane extension and membrane resealing after cell wounding, are known to be controlled biochemically, through interaction with regulatory proteins. Here, I propose that these rates are also controlled physically, through an apparently continuous adhesion between plasma membrane lipids and cytoskeletal proteins.
TL;DR: The limited permeability of membranes to H(2)O(2), rationalizes the compartmentalization of scavenging systems and predicts that bacteria that excrete redox-cycling drugs do not experience the same H( 2)O (2) dose that they impose on their competitors.
Abstract: Escherichia coli generates about 14 microM hydrogen peroxide (H(2)O(2)) per s when it grows exponentially in glucose medium. The steady-state intracellular concentration of H(2)O(2) depends on the rates at which this H(2)O(2) is dissipated by scavenging enzymes and by efflux from the cell. The rates of H(2)O(2) degradation by the two major scavenging enzymes, alkyl hydroperoxide reductase and catalase, were quantified. In order to estimate the rate of efflux, the permeability coefficient of membranes for H(2)O(2) was determined. The coefficient is 1.6 x 10(-3) cm/s, indicating that permeability is substantial but not unlimited. These data allowed internal H(2)O(2) fluxes and concentrations to be calculated. Under these growth conditions, Ahp scavenges the majority of the endogenous H(2)O(2), with a small fraction degraded by catalase and virtually none persisting long enough to penetrate the membrane and exit the cell. The robust scavenging activity maintains the H(2)O(2) concentration inside glucose-grown cells at <10(-7) M, substantially below the level (10(-6) M) at which toxicity is evident. When extracellular H(2)O(2) is present, its flux into the cell can be rapid, but the internal concentration may still be an order of magnitude lower than that outside. The presence of such gradients was confirmed in experiments that revealed different degrees of oxidative stress in cocultured scavenger-deficient mutants. The limited permeability of membranes to H(2)O(2) rationalizes the compartmentalization of scavenging systems and predicts that bacteria that excrete redox-cycling drugs do not experience the same H(2)O(2) dose that they impose on their competitors.
TL;DR: A novel cell biological mechanism that disperses membrane fragments over large distances through the Drosophila imaginal disc epithelium is described, and the properties of argosomes are consistent with their being a vehicle for the spread of Wingless protein.
TL;DR: Filtration performance proved to depend on the concentration of mixed liquor suspended solids (MLSS), and better filtration performance with suspended growth was explained by the formation of dynamic membranes with suspended Solids.
TL;DR: The fouling mechanism controlling the flux decline involved the combined effects of adsorptive and colloidal fouling by the hydrophilic neutral fraction in the internal pore structure of the membrane.