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Membrane Pores (membrane + pore)

Distribution by Scientific Domains
Chemistry75%

Terms modified by Membrane Pores

  • membrane pore size
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    Selected Abstracts

    Hydrogen separation of methyltriethoxysilane templating silica membrane

    AICHE JOURNAL, Issue 12 2007
    Jong-Ho Moon
    Abstract Hydrogen separation on microporous methyltriethoxysilane-templating silica composite/,-alumina membranes (below MTES membrane) was studied using three binary gas mixtures: H2/N2, H2/CO2, and H2/CH4. The characteristics of unsteady and steady-state permeation/separation on the MTES membrane were compared to each other. Although permeation flux in the H2/N2 mixture was comparatively low, H2 selectivity was high (H2/N2 SF , 30,60). On the contrary, the H2/CO2 mixture showed high permeation flux but low H2 selectivity (H2/CO2 SF , 1.5,6.5). The H2/CH4 mixture showed a large difference between permselectivity (28,48) and separation factor (10,22). Results from this study revealed that it was difficult to predict the separation factor using the one-component permeation ratio (permselectivity) over the experimental range tested. These separation characteristics could be primarily ascribed to the molecular size and structure of each gas, which likely contributed to steric hindrance or molecular sieving within the membrane pore. In addition, the adsorption affinity of each molecule on the membrane surface acted as a key factor in separation performance because it significantly influenced surface diffusion. The generalized Maxwell-Stefan model incorporating the dust gas model, and the Langmuir model could successfully predict the transient and steady-state permeation/separation. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source]

    The role of pneumolysin in pneumococcal pneumonia and meningitis

    CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 2 2004
    R. A. HIRST
    SUMMARY Diseases caused by Streptococcus pneumoniae include pneumonia, septicaemia and meningitis. All these are associated with high morbidity and mortality. The pneumococcus can colonize the nasopharynx, and this can be a prelude to bronchopneumonia and invasion of the vasculature space. Proliferation in the blood can result in a breach of the blood,brain barrier and entry into the cerebrospinal fluid (CSF) where the bacteria cause inflammation of the meningeal membranes resulting in meningitis. The infected host may develop septicaemia and/or meningitis secondary to bronchopneumonia. Also septicaemia is a common precursor of meningitis. The mechanisms surrounding the sequence of infection are unknown, but will be dependent on the properties of both the host and bacterium. Treatment of these diseases with antibiotics leads to clearance of the bacteria from the infected tissues, but the bacteriolytic nature of antibiotics leads to an acute release of bacterial toxins and thus after antibiotic therapy the patients can be left with organ-specific deficits. One of the main toxins released from pneumococci is the membrane pore forming toxin pneumolysin. Here we review the extensive studies on the role of pneumolysin in the pathogenesis of pneumococcal diseases. [source]

    Direct integration of cell-free-synthesized connexin-43 into liposomes and hemichannel formation

    FEBS JOURNAL, Issue 16 2010
    Yuki Moritani
    Proteoliposomes were directly prepared by synthesizing membrane proteins with the use of minimal protein synthesis factors isolated from Escherichia coli (the PURE system) in the presence of liposomes. Connexin-43 (Cx43), which is a water-insoluble integral membrane protein that forms a hexameric complex in membranes, was cotranslationally integrated with an essentially uniform orientation in liposomes. The addition of liposomes following protein expression (post-translational presence of liposomes) did not lead to the integration of Cx43 into the liposome membranes. The amount of integrated Cx43 increased as the liposome concentration increased. The presence of liposomes did not influence the total amount of synthesized Cx43. The Cx43 integrated into the liposome membranes formed open membrane pores. These results indicate that the liposomes act in a chaperone-like manner by preventing Cx43 from aggregating in solution, because of integration into the bilayer, and also by functionalization of the integrated Cx43 in the membrane. This is the first report that cell-free-synthesized water-insoluble membrane protein is directly integrated with a uniform orientation as a functional oligomer into liposome membranes. This simple proteoliposome preparation procedure should be a valuable approach for structural and functional studies of membrane proteins. Structured digital abstract ,,MINT-7900670: Cx-43 (uniprotkb:P08050) and Cx-43 (uniprotkb:P08050) bind (MI:0407) by cross-linking study (MI:0030) [source]

    The membrane emulsification process,a review

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2004
    C Charcosset
    Abstract Membrane emulsification has received increasing attention over the last 10 years, with potential applications in many fields. In the membrane emulsification process, a liquid phase is pressed through the membrane pores to form droplets at the permeate side of a membrane; the droplets are then carried away by a continuous phase flowing across the membrane surface. Under specific conditions, monodispersed emulsions can be produced using this technique. The purpose of the present paper is to provide a review on the membrane emulsification process including: principles of membrane emulsification, influence of process parameters and industrial applications. Small-scale applications such as drug delivery systems, food emulsions, and the production of monodispersed microspheres are also included. Compared with conventional techniques for emulsification, membrane processes offer advantages such as control of average droplet diameter by average membrane pore size and lower energy input. Copyright © 2004 Society of Chemical Industry [source]

    Analysis of clogging behaviors of diatomaceous ceramic membranes during membrane filtration based upon specific deposit

    AICHE JOURNAL, Issue 7 2010
    Eiji Iritani
    Abstract Fouling behaviors in membrane filtration of dilute suspension of polystyrene latex (PSL) were examined under constant-pressure conditions using diatomaceous ceramic membranes which are semi-permeable to the PSL. Flux decline behaviors were evaluated in consideration of the effect of the solid permeation through the membrane. The conventional characteristic filtration equation was modified by applying the Kozeny-Carman equation to the filtrate flow through the membrane pores. In the model, the porosity and specific surface area of the membrane were represented by unique functions of the solid deposit retained in the membrane pores. The variations of the filtration rate and filtrate volume with the filtration time were accurately described based upon the modified characteristic filtration equation. It was revealed that the extent of the membrane blocking per unit deposit load increased with the decrease in the pore size of the membrane and with decreasing pressure, but was little influenced by the suspension concentration. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

    Ultrafiltration characteristics of pegylated proteins

    BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2006
    Jessica R. Molek
    Abstract There is growing clinical interest in the use of pegylated recombinant proteins with enhanced stability, half-life, and bioavailability. The objective of this study was to develop a quantitative understanding of the ultrafiltration characteristics of a series of pegylated proteins with different degrees of pegylation. Sieving data were compared with available theoretical models and with corresponding results for the partition coefficient in size exclusion chromatography (SEC). The sieving coefficients of the pegylated proteins depended not only on the protein size and the total molecular weight of the polyethylene glycol (PEG) but also on the number of PEG chains. This is in sharp contrast to the partition coefficient in SEC, which was uniquely determined by the total molecular weight of the PEG and protein. This difference is due to the deformation and/or elongation of the PEG chains caused by the convective flow into the membrane pores, an effect that is not present in SEC. These results provide important insights into the transport and separation characteristics of pegylated proteins. © 2006 Wiley Periodicals, Inc. [source]

    Gating Characteristics of Thermo-Responsive Membranes with Grafted Linear and Crosslinked Poly(N -isopropylacrylamide) Gates

    CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2009
    Y.-C. Chen
    Abstract Thermo-responsive porous membranes with grafted linear and crosslinked poly(N -isopropylacrylamide) (PNIPAM) gates are successfully prepared at temperatures above and below the lower critical solution temperature (LCST) of PNIPAM by using a plasma-induced grafting polymerization method, and the effects of operation pressure and grafting temperature on the thermo-responsive gating characteristics of the prepared membranes are investigated systematically. The fluxes of water through the grafted membranes increase simply with increasing the operation pressure no matter whether the environmental temperature is 40,°C or 25,°C. Under high operation pressure (e.g., higher than 0.14,MPa), the grafted linear PNIPAM gates deform to a certain extent, whereas the grafted crosslinked PNIPAM gates do not deform. For both membranes with grafted linear and crosslinked PNIPAM gates, the membranes prepared at 25,°C (below the LCST of PNIPAM) show larger thermo-responsive gating coefficients than those prepared at 40,°C (above the LCST of PNIPAM), which results from different distributions of grafted PNIPAM gates in the membrane pores. When the PNIPAM gates are grafted at 25,°C, the grafted layer near the membrane surface is much thicker than that inside the membrane pores; on the other hand, when the PNIPAM gates are grafted at 40,°C, the grafted layer is homogeneously formed throughout the whole pore length. Both linear and crosslinked grafted PNIPAM gates in the membrane pores exhibit stable and repeatable thermo-responsive "open-close" switch performances under the operation pressure of 0.26,MPa. The results in this study provide valuable guidance for designing, fabricating, and operating thermo-responsive gating membranes with desirable performances. [source]

    Donor/Conductor/Acceptor Triads Spatially Organized on the Micrometer-Length Scale: An Alternative Approach to Photovoltaic Cells

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2007
    Francesc
    Abstract We have used porous anodised Al2O3 membranes as inert matrix for constructing and organizing spatially ternary donor/conductor/acceptor (DCA) systems exhibiting photovoltaic cell activity on the micrometric-length scale. These DCA triads were built stepwise by first growing a conducting polymer inside the membrane pores, thus forming nanorods that completely fill the internal pore space of the membrane. Then, an electron donor and an electron acceptor were adsorbed one on each side of the membrane, so that they were separated by a distance equal to the membrane thickness (ca. 60,,m), but electronically connected through the conductive polymer. When this device was placed between two electrodes and irradiated with visible light, electrons jumped from the donor molecule, crossed the membrane from side to side through the conductive polymer (a journey of about 60,,m!) until they finally reach the acceptor molecule. In so doing, an electric voltage was generated between the two electrodes, capable of maintaining an electric current flow from the membrane to an external circuit. Our DCA device constitutes the proof of a novel concept of photovoltaic cells, since it is based on the spatial organization at the micrometric scale of complementary, but not covalently linked, electron-donor and electron-acceptor organic species. Thus, our cell is based in translating photoinduced electron transfer between donors and acceptors, which is known to occur at the molecular nanometric scale, to the micrometric range in a spatially organised system. In addition our cell does not need the use of liquid electrolytes in order to operate, which is one of the main drawbacks in dye-sensitised solar cells. [source]