Microbial activity catalyzes oxygen transfer in membrane-aerated nitritating biofilm reactors

DEFF Research Database (Denmark)

Pellicer i Nàcher, Carles; Domingo Felez, Carlos; Lackner, Susanne

2013-01-01

The remarkable oxygen transfer efficiencies attainable in membrane-aerated biofilm reactors (MABRs) are expected to favor their prompt industrial implementation. However, tests in clean water, currently used for the estimation of their oxygen transfer potential, lead to wrong estimates once biofilm...... is present, significantly complicating reactor modelling and control. This study shows for the first time the factors affecting oxygen mass transfer across membranes during clean water tests and reactor operation via undisturbed microelectrode inspection and bulk measurements. The mass transfer resistance...... of the liquid boundary layer developed at the membrane-liquid interface during clean water tests accounted for two thirds of the total mass transfer resistance, suggesting a strong underestimation of the oxygen transfer rates when it is absent (e.g. after biofilm growth). Reactor operation to attain partial...

Ligand and membrane-binding behavior of the phosphatidylinositol transfer proteins PITPα and PITPβ.

Science.gov (United States)

Baptist, Matilda; Panagabko, Candace; Cockcroft, Shamshad; Atkinson, Jeffrey

2016-12-01

Phosphatidylinositol transfer proteins (PITPs) are believed to be lipid transfer proteins because of their ability to transfer either phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane compartments, in vitro. However, the detailed mechanism of this transfer process is not fully established. To further understand the transfer mechanism of PITPs we examined the interaction of PITPs with membranes using dual polarization interferometry (DPI), which measures protein binding affinity on a flat immobilized lipid surface. In addition, a fluorescence resonance energy transfer (FRET)-based assay was also employed to monitor how quickly PITPs transfer their ligands to lipid vesicles. DPI analysis revealed that PITPβ had a higher affinity to membranes compared with PITPα. Furthermore, the FRET-based transfer assay revealed that PITPβ has a higher ligand transfer rate compared with PITPα. However, both PITPα and PITPβ demonstrated a preference for highly curved membrane surfaces during ligand transfer. In other words, ligand transfer rate was higher when the accepting vesicles were highly curved.

Acyl transfer from membrane lipids to peptides is a generic process.

Science.gov (United States)

Dods, Robert H; Bechinger, Burkhard; Mosely, Jackie A; Sanderson, John M

2013-11-15

The generality of acyl transfer from phospholipids to membrane-active peptides has been probed using liquid chromatography-mass spectrometry analysis of peptide-lipid mixtures. The peptides examined include melittin, magainin II, PGLa, LAK1, LAK3 and penetratin. Peptides were added to liposomes with membrane lipid compositions ranging from pure phosphatidylcholine (PC) to mixtures of PC with phosphatidylethanolamine, phosphatidylserine or phosphatidylglycerol. Experiments were typically conducted at pH7.4 at modest salt concentrations (90 mM NaCl). In favorable cases, lipidated peptides were further characterized by tandem mass spectrometry methods to determine the sites of acylation. Melittin and magainin II were the most reactive peptides, with significant acyl transfer detected under all conditions and membrane compositions. Both peptides were lipidated at the N-terminus by transfer from PC, phosphatidylethanolamine, phosphatidylserine or phosphatidylglycerol, as well as at internal sites: lysine for melittin; serine and lysine for magainin II. Acyl transfer could be detected within 3h of melittin addition to negatively charged membranes. The other peptides were less reactive, but for each peptide, acylation was found to occur in at least one of the conditions examined. The data demonstrate that acyl transfer is a generic process for peptides bound to membranes composed of diacylglycerophospholipids. Phospholipid membranes cannot therefore be considered as chemically inert toward peptides and by extension proteins. © 2013. Published by Elsevier Ltd. All rights reserved.

No Evidence for Spontaneous Lipid Transfer at ER-PM Membrane Contact Sites.

Science.gov (United States)

Merklinger, Elisa; Schloetel, Jan-Gero; Spitta, Luis; Thiele, Christoph; Lang, Thorsten

2016-04-01

Non-vesicular lipid transport steps play a crucial role in lipid trafficking and potentially include spontaneous exchange. Since membrane contact facilitates this lipid transfer, it is most likely to occur at membrane contact sites (MCS). However, to date it is unknown whether closely attached biological membranes exchange lipids spontaneously. We have set up a system for studying the exchange of lipids at MCS formed between the endoplasmic reticulum (ER) and the plasma membrane. Contact sites were stably anchored and the lipids cholesterol and phosphatidylcholine (PC) were not capable of transferring spontaneously into the opposed bilayer. We conclude that physical contact between two associated biological membranes is not sufficient for transfer of the lipids PC and cholesterol.

Analysis of mass transfer characteristics in a tubular membrane using CFD modeling.

Science.gov (United States)

Yang, Jixiang; Vedantam, Sreepriya; Spanjers, Henri; Nopens, Ingmar; van Lier, Jules B

2012-10-01

In contrast to the large amount of research into aerobic membrane bioreactors, little work has been reported on anaerobic membrane bioreactors (AMBRs). As to the application of membrane bioreactors, membrane fouling is a key issue. Membrane fouling generally occurs more seriously in AMBRs than in aerobic membrane bioreactors. However, membrane fouling could be managed through the application of suitable shear stress that can be introduced by the application of a two-phase flow. When the two-phase flow is applied in AMBRs, little is known about the mass transfer characteristics, which is of particular importance, in tubular membranes of AMBRs. In our present work, we have employed fluid dynamic modeling to analyze the mass transfer characteristics in the tubular membrane of a side stream AMBR in which, gas-lift two-phase flow was applied. The modeling indicated that the mass transfer capacity at the membrane surface at the noses of gas bubbles was higher than the mass transfer capacity at the tails of the bubbles, which is in contrast to the results when water instead of sludge is applied. At the given mass transfer rate, the filterability of the sludge was found to have a strong influence on the transmembrane pressure at a steady flux. In addition, the model also showed that the shear stress in the internal space of the tubular membrane was mainly around 20 Pa but could be as high as about 40 Pa due to gas bubble movements. Nonetheless, at these shear stresses a stable particle size distribution was found for sludge particles. Copyright © 2012 Elsevier Ltd. All rights reserved.

One-dimensional statistical model of active transfer of substances in membranes

International Nuclear Information System (INIS)

Melkikh, A.V.; Seleznev, V.D.

1995-01-01

A matrix of kinetic coefficients that describe the processes of particle and heat transfer in a double membrane is obtained. The kinetic coefficients are considered as functions of the membrane parameters. Conditions are found under which the energy expended on transfer of one atom through the membrane is minimum. The obtained theoretical value of this energy is compared with the corresponding value for active transport of ions in biomembranes

[Better performance of Western blotting: quick vs slow protein transfer, blotting membranes and the visualization methods].

Science.gov (United States)

Kong, Ling-Quan; Pu, Ying-Hui; Ma, Shi-Kun

2008-01-01

To study how the choices of the quick vs slow protein transfer, the blotting membranes and the visualization methods influence the performance of Western blotting. The cellular proteins were abstracted from human breast cell line MDA-MB-231 for analysis with Western blotting using quick (2 h) and slow (overnight) protein transfer, different blotting membranes (nitrocellulose, PVDF and nylon membranes) and different visualization methods (ECL and DAB). In Western blotting with slow and quick protein transfer, the prestained marker presented more distinct bands on nitrocellulose membrane than on the nylon and PVDF membranes, and the latter also showed clear bands on the back of the membrane to very likely cause confusion, which did not occur with nitrocellulose membrane. PVDF membrane allowed slightly clearer visualization of the proteins with DAB method as compared with nitrocellulose and nylon membranes, and on the latter two membranes, quick protein transfer was likely to result in somehow irregular bands in comparison with slow protein transfer. With slow protein transfer and chemiluminescence for visualization, all the 3 membranes showed clear background, while with quick protein transfer, nylon membrane gave rise to obvious background noise but the other two membranes did not. Different membranes should be selected for immunoblotting according to the actual needs of the experiment. Slow transfer of the proteins onto the membranes often has better effect than quick transfer, and enhanced chemiluminescence is superior to DAB for protein visualization and allows highly specific and sensitive analysis of the protein expressions.

Mass and Heat Transfer in Ion-Exchange Membranes Applicable to Solid Polymer Fuel Cells

Energy Technology Data Exchange (ETDEWEB)

Otteroey, M

1996-04-01

In this doctoral thesis, an improved emf method for determination of transference numbers of two counter ions in ion-exchange membranes is presented. Transference numbers were obtained as a continuous function of the composition. The method avoids problems with diffusion by using a stack of membranes. Water transference coefficients in ion-exchange membranes is discussed and reversible and irreversible water transfer is studied by emf methods. Efforts were made to get data relevant to the solid polymer fuel cell. The results support the findings of other researchers that the reversible water transfer is lower than earlier predicted. A chapter on the conductivity of ion-exchange membranes establishes a method to separate the very thin liquid layers surrounding the membranes in a stack. Using the method it was found that the conductivity is obtained with high accuracy and that the liquid layer in a membrane stack can contribute significantly to the total measured resistance. A four point impedance method was tested to measure the conductivity of membranes under fuel cell conditions. Finally, there is a discussion of reversible heat effects and heat transfer in ion-exchange membranes. 155 refs., 45 figs., 13 tabs.

Radiation-induced Mass Transfer through Membranes

Czech Academy of Sciences Publication Activity Database

Levdansky, V.V.; Smolík, Jiří; Moravec, Pavel

2009-01-01

Roč. 36, č. 2 (2009), s. 125-128 ISSN 0735-1933 R&D Projects: GA AV ČR(CZ) IAA400720804 Institutional research plan: CEZ:AV0Z40720504 Keywords : mass transfer * adiation * membrane Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.189, year: 2009

Membranes and mammalian glycolipid transferring proteins.

Science.gov (United States)

Tuuf, Jessica; Mattjus, Peter

2014-02-01

Glycolipids are synthesized in and on various organelles throughout the cell. Their trafficking inside the cell is complex and involves both vesicular and protein-mediated machineries. Most important for the bulk lipid transport is the vesicular system, however, lipids moved by transfer proteins are also becoming more characterized. Here we review the latest advances in the glycolipid transfer protein (GLTP) and the phosphoinositol 4-phosphate adaptor protein-2 (FAPP2) field, from a membrane point of view. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Cholesterol transfer from normal and atherogenic low density lipoproteins to Mycoplasma membranes

International Nuclear Information System (INIS)

Mitschelen, J.J.; St Clair, R.W.; Hester, S.H.

1981-01-01

The purpose of this study was to determine whether the free cholesterol of hypercholesterolemic low density lipoprotein from cholesterol-fed nonhuman primates has a greater potential for surface transfer to cell membranes than does the free cholesterol of normal low density lipoprotein. The low density lipoproteins were isolated from normal and hypercholesterolemic rhesus and cynomolgus monkeys, incubated with membranes from Acholeplasma laidlawii, a mycoplasma species devoid of cholesterol in its membranes, and the mass transfer of free cholesterol determined by measuring membrane cholesterol content. Since these membranes neither synthesize nor esterify cholesterol, nor degrade the protein or cholesterol ester moieties of low density lipoprotein, they are an ideal model with which to study differences in the cholesterol transfer potential of low density lipoprotein independent of the uptake of the intact low density lipoprotein particle. These studies indicate that, even though there are marked differences in the cholesterol composition of normal and hypercholesterolemic low density lipoproteins, this does not result in a greater chemical potential for surface transfer of free cholesterol. Consequently, if a difference in the surface transfer of free cholesterol is responsible for the enhanced ability of hypercholesterolemic low density lipoprotein to promote cellular cholesterol accumulation and, perhaps, also atherosclerosis, it must be the result of differences in the interaction to the hypercholesterolemic low density lipoprotein with the more complicated mammalian cell membranes, rather than differences in the chemical potential for cholesterol transfer

Heat transfer in a membrane assisted fluidized bed with immersed horizontal tubes

NARCIS (Netherlands)

Deshmukh, S.A.R.K.; Volkers, Sander; van Sint Annaland, M.; Kuipers, J.A.M.

2005-01-01

The effect of gas permeation through horizontally immersed membrane tubes on the heat transfer characteristics in a membrane assisted fluidized bed operated in the bubbling fluidization regime was investigated experimentally. Local time-averaged heat transfer coefficients from copper tubes arranged

Monitoring glycolipid transfer protein activity and membrane interaction with the surface plasmon resonance technique.

Science.gov (United States)

Ohvo-Rekilä, Henna; Mattjus, Peter

2011-01-01

The glycolipid transfer protein (GLTP) is a protein capable of binding and transferring glycolipids. GLTP is cytosolic and it can interact through its FFAT-like (two phenylalanines in an acidic tract) motif with proteins localized on the surface of the endoplasmic reticulum. Previous in vitro work with GLTP has focused mainly on the complete transfer reaction of the protein, that is, binding and subsequent removal of the glycolipid from the donor membrane, transfer through the aqueous environment, and the final release of the glycolipid to an acceptor membrane. Using bilayer vesicles and surface plasmon resonance spectroscopy, we have now, for the first time, analyzed the binding and lipid removal capacity of GLTP with a completely label-free technique. This technique is focused on the initial steps in GLTP-mediated transfer and the parameters affecting these steps can be more precisely determined. We used the new approach for detailed structure-function studies of GLTP by examining the glycolipid transfer capacity of specific GLTP tryptophan mutants. Tryptophan 96 is crucial for the transfer activity of the protein and tryptophan 142 is an important part of the proteins membrane interacting domain. Further, we varied the composition of the used lipid vesicles and gained information on the effect of membrane properties on GLTP activity. GLTP prefers to interact with more tightly packed membranes, although GLTP-mediated transfer is faster from more fluid membranes. This technique is very useful for the study of membrane-protein interactions and lipid-transfer rates and it can easily be adapted to other membrane-interacting proteins. Copyright © 2010 Elsevier B.V. All rights reserved.

Preparation of catalyst coated membrane by modified decal transfer method for proton exchange membrane fuel cell

Science.gov (United States)

Indriyati; Irmawati, Y.; Prihandoko, B.

2017-07-01

A new catalyst coated membrane (CCM) was prepared by modified decal transfer method. A structure of ionomer/catalyst/carbon/substrate was used to facilitate the transfer of catalyst layer from decal substrate to the membrane at quite low hot-pressing temperature (120 °C) for 8 min. Several decal substrates were tested to select a proper substrate, namely PTFE cloth, PTFE film, aluminium foil, and OHP transparent sheet. The transfer degree of catalyst layer was estimated. Elemental analysis and SEM-mapping were performed to evaluate the residue, whereas contact angle measurement was conducted to characterize the hydrophobicity of decal substrates. The results showed that PTFE cloth and PFTE film transferred approximately 90% of catalyst layer onto the membrane, while the other two substrates were around 70%. Furthermore, the elemental analysis of the residue on the substrate revealed that it was mainly composed of carbon and fluorine for PTFE cloth and PTFE film. This result supports other findings that PTFE cloth and PTFE film are suitable as decal substrate at low temperature hot pressing for fabricating CCM.

Protein-membrane interaction and fatty acid transfer from intestinal fatty acid-binding protein to membranes. Support for a multistep process.

Science.gov (United States)

Falomir-Lockhart, Lisandro J; Laborde, Lisandro; Kahn, Peter C; Storch, Judith; Córsico, Betina

2006-05-19

Fatty acid transfer from intestinal fatty acid-binding protein (IFABP) to phospholipid membranes occurs during protein-membrane collisions. Electrostatic interactions involving the alpha-helical "portal" region of the protein have been shown to be of great importance. In the present study, the role of specific lysine residues in the alpha-helical region of IFABP was directly examined. A series of point mutants in rat IFABP was engineered in which the lysine positive charges in this domain were eliminated or reversed. Using a fluorescence resonance energy transfer assay, we analyzed the rates and mechanism of fatty acid transfer from wild type and mutant proteins to acceptor membranes. Most of the alpha-helical domain mutants showed slower absolute fatty acid transfer rates to zwitterionic membranes, with substitution of one of the lysines of the alpha2 helix, Lys27, resulting in a particularly dramatic decrease in the fatty acid transfer rate. Sensitivity to negatively charged phospholipid membranes was also reduced, with charge reversal mutants in the alpha2 helix the most affected. The results support the hypothesis that the portal region undergoes a conformational change during protein-membrane interaction, which leads to release of the bound fatty acid to the membrane and that the alpha2 segment is of particular importance in the establishment of charge-charge interactions between IFABP and membranes. Cross-linking experiments with a phospholipid-photoactivable reagent underscored the importance of charge-charge interactions, showing that the physical interaction between wild-type intestinal fatty acid-binding protein and phospholipid membranes is enhanced by electrostatic interactions. Protein-membrane interactions were also found to be enhanced by the presence of ligand, suggesting different collisional complex structures for holo- and apo-IFABP.

UCP2 muscle gene transfer modifies mitochondrial membrane potential.

Science.gov (United States)

Marti, A; Larrarte, E; Novo, F J; Garcia, M; Martinez, J A

2001-01-01

The aim of this work was to evaluate the effect of uncoupling protein 2 (UCP2) muscle gene transfer on mitochondrial activity. Five week-old male Wistar rats received an intramuscular injection of plasmid pXU1 containing UCP2 cDNA in the right tibialis anterior muscles. Left tibialis anterior muscles were injected with vehicle as control. Ten days after DNA injection, tibialis anterior muscles were dissected and muscle mitochondria isolated and analyzed. There were two mitochondrial populations in the muscle after UCP2 gene transfer, one of low fluorescence and complexity and the other, showing high fluorescence and complexity. UCP2 gene transfer resulted in a 3.6 fold increase in muscle UCP2 protein levels compared to control muscles assessed by Western blotting. Furthermore, a significant reduction in mitochondria membrane potential assessed by spectrofluorometry and flow cytometry was observed. The mitochondria membrane potential reduction might account for a decrease in fluorescence of the low fluorescence mitochondrial subpopulation. It has been demonstrated that UCP2 muscle gene transfer in vivo is associated with a lower mitochondria membrane potential. Our results suggest the potential involvement of UCP2 in uncoupling respiration. International Journal of Obesity (2001) 25, 68-74

The transfer of rare earth elements through liquid extraction membranes

International Nuclear Information System (INIS)

Kapranchik, V.P.; Proyaev, V.V.; Kopyrin, A.A.

1988-01-01

The transfer of rare earth elements through liquid extraction membranes, presenting Dacron nuclear filters, impregnated by extractants of different types (tributylphosphine oxide; di-2-ethylhexylphosphoric acid, HDEHP; trioctylamine, TOA) is investigated. It is ascertained that in systems with extractant-carriers TOA and HDEHP inversion of dependences of flow values and distribution coefficients on the element atomic number is observed. Mathematical model of transfer, permitting to establish relation between extractional and transport characteristics of the membrane, is suggested

Probing membrane protein structure using water polarization transfer solid-state NMR.

Science.gov (United States)

Williams, Jonathan K; Hong, Mei

2014-10-01

Water plays an essential role in the structure and function of proteins, lipid membranes and other biological macromolecules. Solid-state NMR heteronuclear-detected (1)H polarization transfer from water to biomolecules is a versatile approach for studying water-protein, water-membrane, and water-carbohydrate interactions in biology. We review radiofrequency pulse sequences for measuring water polarization transfer to biomolecules, the mechanisms of polarization transfer, and the application of this method to various biological systems. Three polarization transfer mechanisms, chemical exchange, spin diffusion and NOE, manifest themselves at different temperatures, magic-angle-spinning frequencies, and pulse irradiations. Chemical exchange is ubiquitous in all systems examined so far, and spin diffusion plays the key role in polarization transfer within the macromolecule. Tightly bound water molecules with long residence times are rare in proteins at ambient temperature. The water polarization-transfer technique has been used to study the hydration of microcrystalline proteins, lipid membranes, and plant cell wall polysaccharides, and to derive atomic-resolution details of the kinetics and mechanism of ion conduction in channels and pumps. Using this approach, we have measured the water polarization transfer to the transmembrane domain of the influenza M2 protein to obtain information on the structure of this tetrameric proton channel. At short mixing times, the polarization transfer rates are site-specific and depend on the pH, labile protons, sidechain conformation, as well as the radial position of the residues in this four-helix bundle. Despite the multiple dependences, the initial transfer rates reflect the periodic nature of the residue positions from the water-filled pore, thus this technique provides a way of gleaning secondary structure information, helix tilt angle, and the oligomeric structure of membrane proteins. Copyright © 2014 Elsevier Inc. All

Membranes: A Variety of Energy Landscapes for Many Transfer Opportunities.

Science.gov (United States)

Bacchin, Patrice

2018-02-22

A membrane can be represented by an energy landscape that solutes or colloids must cross. A model accounting for the momentum and the mass balances in the membrane energy landscape establishes a new way of writing for the Darcy law. The counter-pressure in the Darcy law is no longer written as the result of an osmotic pressure difference but rather as a function of colloid-membrane interactions. The ability of the model to describe the physics of the filtration is discussed in detail. This model is solved in a simplified energy landscape to derive analytical relationships that describe the selectivity and the counter-pressure from ab initio operating conditions. The model shows that the stiffness of the energy landscape has an impact on the process efficiency: a gradual increase in interactions (such as with hourglass pore shape) can reduce the separation energetic cost. It allows the introduction of a new paradigm to increase membrane efficiency: the accumulation that is inherent to the separation must be distributed across the membrane. Asymmetric interactions thus lead to direction-dependent transfer properties and the membrane exhibits diode behavior. These new transfer opportunities are discussed.

Ozone mass transfer behaviors on physical and chemical absorption for hollow fiber membrane contactors.

Science.gov (United States)

Zhang, Yong; Li, Kuiling; Wang, Jun; Hou, Deyin; Liu, Huijuan

2017-09-01

To understand the mass transfer behaviors in hollow fiber membrane contactors, ozone fluxes affected by various conditions and membranes were investigated. For physical absorption, mass transfer rate increased with liquid velocity and the ozone concentration in the gas. Gas flow rate was little affected when the velocity was larger than the critical value, which was 6.1 × 10 -3 m/s in this study. For chemical absorption, the flux was determined by the reaction rate between ozone and the absorbent. Therefore, concentration, species, and pH affected the mass transfer process markedly. For different absorbents, the order of mass transfer rate was the same as the reaction rate constant, which was phenol, sodium nitrite, hydrogen peroxide, and oxalate. Five hydrophobic membranes with various properties were employed and the mass transfer behavior can be described by the Graetz-Lévèque equation for the physical absorption process. The results showed the process was controlled by liquid film and the gas phase conditions, and membrane properties did not affect the ozone flux. For the chemical absorption, gas film, membrane and liquid film affected the mass transfer together, and none of them were negligible.

Performance evaluation and mass transfer study of CO2 absorption in flat sheet membrane contactor using novel porous polysulfone membrane

International Nuclear Information System (INIS)

Nabian, Nima; Ghoreyshi, Ali Asghar; Rahimpour, Ahmad; Shakeri, Mohsen

2015-01-01

The performance of gas-liquid membrane contactor for CO 2 capture was investigated using a novel polysulfone (PSF) flat membrane prepared via non-solvent phase inversion method. Polyvinyl pyrrolidone (PVP) was used as an additive in the dope solution of PSF membranes. Morphological studies by scanning electron microscopy (SEM) analysis revealed that PSF membrane with PVP has a finger-like structure, but the PSF membrane without PVP has a sponge-like structure. Also, characterization results through atomic force microscopy (AFM) and contact angle measurement demonstrated that the porosity, surface roughness and hydrophobicity of the PSF membrane increased with addition of PVP to the dope solution. Mass transfer resistance analysis, based on CO 2 absorption flux, displayed that addition of PVP to the dope solution of PSF membrane decreased membrane mass transfer resistance, and significantly improved CO 2 absorption flux up to 2.7 and 1.8 times of absorption fluxes of PSF membrane without PVP and commercial PVDF, respectively.

Heat-And-Mass Transfer Relationship to Determine Shear Stress in Tubular Membrane Systems

DEFF Research Database (Denmark)

Ratkovich, Nicolas Rios; Nopens, Ingmar

2012-01-01

The main drawback of Membrane Bioreactors (MBRs) is the fouling of the membrane. One way to reduce this fouling is through controlling the hydrodynamics of the two-phase slug flow near the membrane surface. It has been proven in literature that the slug flow pattern has a higher scouring effect...... to remove particulates due to the high shear rates and high mass transfer between the membrane surface and the bulk region. However, to calculate the mass transfer coefficient in an efficient and accurate way is not straightforward. Indeed, for accurate determination, numerous complex experimental...

Towards a Biohybrid Lung: Endothelial Cells Promote Oxygen Transfer through Gas Permeable Membranes.

Science.gov (United States)

Menzel, Sarah; Finocchiaro, Nicole; Donay, Christine; Thiebes, Anja Lena; Hesselmann, Felix; Arens, Jutta; Djeljadini, Suzana; Wessling, Matthias; Schmitz-Rode, Thomas; Jockenhoevel, Stefan; Cornelissen, Christian Gabriel

2017-01-01

In patients with respiratory failure, extracorporeal lung support can ensure the vital gas exchange via gas permeable membranes but its application is restricted by limited long-term stability and hemocompatibility of the gas permeable membranes, which are in contact with the blood. Endothelial cells lining these membranes promise physiological hemocompatibility and should enable prolonged application. However, the endothelial cells increase the diffusion barrier of the blood-gas interface and thus affect gas transfer. In this study, we evaluated how the endothelial cells affect the gas exchange to optimize performance while maintaining an integral cell layer. Human umbilical vein endothelial cells were seeded on gas permeable cell culture membranes and cultivated in a custom-made bioreactor. Oxygen transfer rates of blank and endothelialized membranes in endothelial culture medium were determined. Cell morphology was assessed by microscopy and immunohistochemistry. Both setups provided oxygenation of the test fluid featuring small standard deviations of the measurements. Throughout the measuring range, the endothelial cells seem to promote gas transfer to a certain extent exceeding the blank membranes gas transfer performance by up to 120%. Although the underlying principles hereof still need to be clarified, the results represent a significant step towards the development of a biohybrid lung.

Energy transfer and clustering of photosynthetic light-harvesting complexes in reconstituted lipid membranes

International Nuclear Information System (INIS)

Dewa, Takehisa; Sumino, Ayumi; Watanabe, Natsuko; Noji, Tomoyasu; Nango, Mamoru

2013-01-01

Highlights: ► Photosynthetic light-harvesting complexes were reconstituted into lipid membranes. ► Energy transfers between light-harvesting complexes were examined. ► Atomic force microscopy indicated cluster formation of light-harvesting complexes. ► Efficient energy transfer was observed for the clustered complexes in the membranes. - Abstract: In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency

Energy transfer and clustering of photosynthetic light-harvesting complexes in reconstituted lipid membranes

Energy Technology Data Exchange (ETDEWEB)

Dewa, Takehisa, E-mail: takedewa@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Japan Science and Technology, PRESTO, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan); Sumino, Ayumi; Watanabe, Natsuko; Noji, Tomoyasu [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nango, Mamoru, E-mail: nango@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2013-06-20

Highlights: ► Photosynthetic light-harvesting complexes were reconstituted into lipid membranes. ► Energy transfers between light-harvesting complexes were examined. ► Atomic force microscopy indicated cluster formation of light-harvesting complexes. ► Efficient energy transfer was observed for the clustered complexes in the membranes. - Abstract: In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and light harvesting/reaction centre core complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a supramolecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. We addressed this issue by evaluating the energy transfer in reconstituted photosynthetic protein complexes LH2 and LH1-RC and studying the structures and the membrane environment of the LH2/LH1-RC assemblies, which had been embedded into various lipid bilayers. Thus, LH2 and LH1-RC from Rhodopseudomonas palustris 2.1.6 were reconstituted in phosphatidylglycerol (PG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Efficient energy transfer from LH2 to LH1-RC was observed in the PC and PE/PG/CL membranes. Atomic force microscopy revealed that LH2 and LH1-RC were heterogeneously distributed to form clusters in the PC and PE/PG/CL membranes. The results indicated that the phospholipid species influenced the cluster formation of LH2 and LH1-RC as well as the energy transfer efficiency.

Extended synaptotagmins are Ca2+-dependent lipid transfer proteins at membrane contact sites.

Science.gov (United States)

Yu, Haijia; Liu, Yinghui; Gulbranson, Daniel R; Paine, Alex; Rathore, Shailendra S; Shen, Jingshi

2016-04-19

Organelles are in constant communication with each other through exchange of proteins (mediated by trafficking vesicles) and lipids [mediated by both trafficking vesicles and lipid transfer proteins (LTPs)]. It has long been known that vesicle trafficking can be tightly regulated by the second messenger Ca(2+), allowing membrane protein transport to be adjusted according to physiological demands. However, it remains unclear whether LTP-mediated lipid transport can also be regulated by Ca(2+) In this work, we show that extended synaptotagmins (E-Syts), poorly understood membrane proteins at endoplasmic reticulum-plasma membrane contact sites, are Ca(2+)-dependent LTPs. Using both recombinant and endogenous mammalian proteins, we discovered that E-Syts transfer glycerophospholipids between membrane bilayers in the presence of Ca(2+) E-Syts use their lipid-accommodating synaptotagmin-like mitochondrial lipid binding protein (SMP) domains to transfer lipids. However, the SMP domains themselves cannot transport lipids unless the two membranes are tightly tethered by Ca(2+)-bound C2 domains. Strikingly, the Ca(2+)-regulated lipid transfer activity of E-Syts was fully recapitulated when the SMP domain was fused to the cytosolic domain of synaptotagmin-1, the Ca(2+)sensor in synaptic vesicle fusion, indicating that a common mechanism of membrane tethering governs the Ca(2+)regulation of lipid transfer and vesicle fusion. Finally, we showed that microsomal vesicles isolated from mammalian cells contained robust Ca(2+)-dependent lipid transfer activities, which were mediated by E-Syts. These findings established E-Syts as a novel class of LTPs and showed that LTP-mediated lipid trafficking, like vesicular transport, can be subject to tight Ca(2+)regulation.

Fluorescence energy transfer on erythrocyte membranes

International Nuclear Information System (INIS)

Fuchs, H.M.; Hof, M.; Lawaczeck, R.

1995-08-01

Stationary and time-dependent fluorescence have been measured for a donor/acceptor (DA) pair bound to membrane proteins of bovine erythrocyte ghosts. The donor N-(p-(2-benzoxazolyl)phenyl)-maleimid (BMI) and the acceptor fluram bind to SH- and NH 2 -residues, respectively. The fluorescence spectra and the time-dependent emission are consistent with a radiationless fluorescence energy transfer (RET). The density of RET-effective acceptor binding sites c=0.072 nm -2 was calculated on the basis of the two-dimensional Foerster-kinetic. Band3 protein is the only membrane spanning protein with accessible SH-groups, and therefore only effective binding sites on the band3 protein are counted for the RET measurements performed. (author). 23 refs, 4 figs, 2 tabs

Energy transfer in light-adapted photosynthetic membranes: from active to saturated photosynthesis.

Science.gov (United States)

Fassioli, Francesca; Olaya-Castro, Alexandra; Scheuring, Simon; Sturgis, James N; Johnson, Neil F

2009-11-04

In bacterial photosynthesis light-harvesting complexes, LH2 and LH1 absorb sunlight energy and deliver it to reaction centers (RCs) with extraordinarily high efficiency. Submolecular resolution images have revealed that both the LH2:LH1 ratio, and the architecture of the photosynthetic membrane itself, adapt to light intensity. We investigate the functional implications of structural adaptations in the energy transfer performance in natural in vivo low- and high-light-adapted membrane architectures of Rhodospirillum photometricum. A model is presented to describe excitation migration across the full range of light intensities that cover states from active photosynthesis, where all RCs are available for charge separation, to saturated photosynthesis where all RCs are unavailable. Our study outlines three key findings. First, there is a critical light-energy density, below which the low-light adapted membrane is more efficient at absorbing photons and generating a charge separation at RCs, than the high-light-adapted membrane. Second, connectivity of core complexes is similar in both membranes, suggesting that, despite different growth conditions, a preferred transfer pathway is through core-core contacts. Third, there may be minimal subareas on the membrane which, containing the same LH2:LH1 ratio, behave as minimal functional units as far as excitation transfer efficiency is concerned.

Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes.

Science.gov (United States)

Lüer, Larry; Carey, Anne-Marie; Henry, Sarah; Maiuri, Margherita; Hacking, Kirsty; Polli, Dario; Cerullo, Giulio; Cogdell, Richard J

2015-11-03

Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes

Energy Technology Data Exchange (ETDEWEB)

Lüer, Larry; Carey, Anne-Marie; Henry, Sarah; Maiuri, Margherita; Hacking, Kirsty; Polli, Dario; Cerullo, Giulio; Cogdell, Richard J.

2015-11-01

Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum.

Ultrahigh Flux Thin Film Boiling Heat Transfer Through Nanoporous Membranes.

Science.gov (United States)

Wang, Qingyang; Chen, Renkun

2018-05-09

Phase change heat transfer is fundamentally important for thermal energy conversion and management, such as in electronics with power density over 1 kW/cm 2 . The critical heat flux (CHF) of phase change heat transfer, either evaporation or boiling, is limited by vapor flux from the liquid-vapor interface, known as the upper limit of heat flux. This limit could in theory be greater than 1 kW/cm 2 on a planar surface, but its experimental realization has remained elusive. Here, we utilized nanoporous membranes to realize a new "thin film boiling" regime that resulted in an unprecedentedly high CHF of over 1.2 kW/cm 2 on a planar surface, which is within a factor of 4 of the theoretical limit, and can be increased to a higher value if mechanical strength of the membranes can be improved (demonstrated with 1.85 kW/cm 2 CHF in this work). The liquid supply is achieved through a simple nanoporous membrane that supports the liquid film where its thickness automatically decreases as heat flux increases. The thin film configuration reduces the conductive thermal resistance, leads to high frequency bubble departure, and provides separate liquid-vapor pathways, therefore significantly enhances the heat transfer. Our work provides a new nanostructuring approach to achieve ultrahigh heat flux in phase change heat transfer and will benefit both theoretical understanding and application in thermal management of high power devices of boiling heat transfer.

Polymer-inorganic hybrid proton conductive membranes: Effect of the interfacial transfer pathways

International Nuclear Information System (INIS)

Chen, Pingping; Hao, Lie; Wu, Wenjia; Li, Yifan; Wang, Jingtao

2016-01-01

Highlights: • A series of hybrid membranes are prepared using fillers with different structures. • The fillers (0-D, 1-D, and 2-D) are sulfonated to ensure close surface component. • The effect of filler’s structure on microstructure of hydrid membrane is explored. • For single-kind filler series, 2-D filler has the strongest conduction promotion. • The synergy effect of different kinds of fillers is systematacially investigated. - Abstract: For hybrid membrane, the polymer-inorganic interface along filler surface can be facilely created to be distinctive and controllable pathway for mass transfer. Herein, three kinds of fillers are used as inorganic additives including zero-dimensional silica (0-D, SiO_2), one-dimensional halloysite nanotube (1-D, HNT), and two-dimensional graphene oxide (2-D, GO), which are functionalized by sulfonated polymer layer to ensure close surface component. Then the fillers are incorporated into two types of polymer matrixes (phase-separated sulfonated poly(ether ether ketone) and non-phase-separated chitosan) to prepare three series of hybrid membranes with single-kind filler, double-kinds fillers, or triple-kinds fillers, respectively. The microstructures, physicochemical properties, and proton conduction properties (under hydrated and anhydrous conditions) of the membranes are extensively investigated. It is found that (i) for the single-kind filler-filled membranes, 2-D filler has the strongest promotion ability for proton conductivity of membrane due to the constructed wide and long-range pathways for proton transfer; (ii) while for the hybrid membranes with double-kinds fillers, instead of synergistic promotion effect, the fillers cause more tortuous transfer pathways within membranes and then decrease proton conductivity; (iii) the hybrid membranes with triple-kinds fillers exhibit similar behavior but a little higher conductivity than the membranes with double-kinds fillers.

Diffusive transfer to membranes as an effective interface between gel electrophoresis and mass spectrometry

Science.gov (United States)

Ogorzalek Loo, Rachel R.; Mitchell, Charles; Stevenson, Tracy I.; Loo, Joseph A.; Andrews, Philip C.

1997-12-01

Diffusive transfer was examined as a blotting method to transfer proteins from polyacrylamide gels to membranes for ultraviolet matrix-assisted laser desorption ionization (MALDI) mass spectrometry. The method is well-suited for transfers from isoelectric focusing (IEF) gels. Spectra have been obtained for 11 pmol of 66 kDa albumin loaded onto an IEF gel and subsequently blotted to polyethylene. Similarly, masses of intact carbonic anhydrase and hemoglobin were obtained from 14 and 20 pmol loadings. This methodology is also compatible with blotting high molecular weight proteins, as seen for 6 pmol of the 150 kDa monoclonal antibody anti-[beta]-galactosidase transferred to Goretex. Polypropylene, Teflon, Nafion and polyvinylidene difluoride (PVDF) also produced good spectra following diffusive transfer. Only analysis from PVDF required that the membrane be kept wet prior to application of matrix. Considerations in mass accuracy for analysis from large-area membranes with continuous extraction and delayed extraction were explored, as were remedies for surface charging. Vapor phase CNBr cleavage was applied to membrane-bound samples for peptide mapping.

Simulation study of transfer characteristics for spacer-filled membrane distillation desalination modules

International Nuclear Information System (INIS)

Chang, Hsuan; Hsu, Jian-An; Chang, Cheng-Liang; Ho, Chii-Dong; Cheng, Tung-Wen

2017-01-01

Highlights: • A 3D CFD model takes in transmembrane heat and mass transfer developed. • DCMD modules using spacer-filled and empty channels for desalination simulated. • Fluid flow, heat transfer and mass transfer profiles revealed. • Correlations of friction factor and Nusselt number developed. - Abstract: Membrane distillation (MD) is an emerging and promising membrane separation process, which can directly utilize renewable thermal energy or low-grade waste heat, for applications in water or wastewater treatment and food industry. However, a major drawback of MD process is its low energy efficiency. Spacer is the most suggested and studied eddy promoter to enhance the heat and mass transfer, which further improves both the separation and the energy utilization performance, of MD processes. This paper presents the results of a 3D computational fluid dynamics (CFD) simulation of DCMD (direct contact membrane distillation) modules using channels with and without spacers for desalination application. The model employs permeable wall boundary condition to take into account the transmembrane heat and mass transfer and simulates the entire module length. The simulation reveals similar fluctuating distributions of temperature polarization coefficient, transmembrane heat and mass fluxes as well as the shear stress on the membrane surface along the entire module length. Correlations have been developed for friction factor and average Nusselt number. These correlations are useful for the analysis and design of DCMD modules. The extent of heat transfer enhancement by spacers depends on the geometry of spacers and the Reynolds number of fluid.

Mass transfer, fluid flow and membrane properties in flat and corrugated plate hyperfiltration modules

NARCIS (Netherlands)

Racz, I.G.; Groot Wassink, J.; Klaassen, R.

1986-01-01

Concentration polarisation, decreasing the efficiency in membrane separation processes, can be reduced by increasing mass transfer between membrane surface and bulk of the feed stream. Analogous to techniques used in plate heat exchangers efforts have been made to enhance mass transfer in a plate

Extraction or adsorption? Voltammetric assessment of protamine transfer at ionophore-based polymeric membranes.

Science.gov (United States)

Garada, Mohammed B; Kabagambe, Benjamin; Amemiya, Shigeru

2015-01-01

Cation-exchange extraction of polypeptide protamine from water into an ionophore-based polymeric membrane has been hypothesized as the origin of a potentiometric sensor response to this important heparin antidote. Here, we apply ion-transfer voltammetry not only to confirm protamine extraction into ionophore-doped polymeric membranes but also to reveal protamine adsorption at the membrane/water interface. Protamine adsorption is thermodynamically more favorable than protamine extraction as shown by cyclic voltammetry at plasticized poly(vinyl chloride) membranes containing dinonylnaphthalenesulfonate as a protamine-selective ionophore. Reversible adsorption of protamine at low concentrations down to 0.038 μg/mL is demonstrated by stripping voltammetry. Adsorptive preconcentration of protamine at the membrane/water interface is quantitatively modeled by using the Frumkin adsorption isotherm. We apply this model to ensure that stripping voltammograms are based on desorption of all protamine molecules that are transferred across the interface during a preconcentration step. In comparison to adsorption, voltammetric extraction of protamine requires ∼0.2 V more negative potentials, where a potentiometric super-Nernstian response to protamine is also observed. This agreement confirms that the potentiometric protamine response is based on protamine extraction. The voltammetrically reversible protamine extraction results in an apparently irreversible potentiometric response to protamine because back-extraction of protamine from the membrane extremely slows down at the mixed potential based on cation-exchange extraction of protamine. Significantly, this study demonstrates the advantages of ion-transfer voltammetry over potentiometry to quantitatively and mechanistically assess protamine transfer at ionophore-based polymeric membranes as foundation for reversible, selective, and sensitive detection of protamine.

On the mechanism of boron transfer through the cation-exchange membrane MK-40

International Nuclear Information System (INIS)

Pilipenko, A.T.; Varvaruk, L.A.; Grebenyuk, V.D.; Trachevskij, V.V.

1985-01-01

Proceses of boron electromigration in solutions with different pH values are investigated. It is shown, that boron transfer through ion-exchange membranes is determined by pH of solution. Phenomenon of boron transfer (existing in the solution in the form of boric acid) through cation-exchange membrane MK-40 has been detected and described for the first time. The process of boron (3) complexing with sulfate groups of the membrane by means of competing reversible substitution of hydroxoligands is the basis of the phenomenon

RESEARCH OF THE MASS TRANSFER AT MEMBRANE CLEANING OF BIOGAZ

Directory of Open Access Journals (Sweden)

Marat SATAYEV

2015-04-01

Full Text Available Everyone has long known the benefits and effectiveness of biogas. Particularly, getting biogas from the agricultural waste is very promising. But, the question is if we can use such a useful and effective biogas at 100%. Today, we use only a half of the benefit, because to get the biogas we spend more energy than we get. In this regard, the work on the study of the biogas development is extremely important. The study of the biogas formation requires numerous experiments. This article analyzes the biogas mass transfer with the membrane purification and identification of the of mass transfer mechanisms through the membrane pores.

Temperature dependence of positronium reactivities with charge transfer molecules in bilayer membranes

International Nuclear Information System (INIS)

Jean, Y.C.; Yu, C.; Wang, Y.Y.; Yeh, Y.Y.

1984-01-01

Rate constants for positronium atoms reacting chemically with charge-transfer molecules such as p-benzoquinone, nitrobenzene, and coenzyme Q-10 in a model bilayer membrane, dipalmitoylphosphatidylcholine (DPPC), have been measured at temperatures between 23 and 65 0 C. A strong variation of the positronium chemical reactivities, k/sub Ps/ was observed in these systems: k/sub Ps/ increases with increasing temperature until the pretransition temperature of the membrane reaches a maximum value near the main transition temperature and decreases at temperatures higher than the main transition temperature. This variation is interpreted in terms of fluidity and permeability changes associated with the phase transitions of membranes and in terms of charge-transfer-complex formation between the solubilized molecules and the polar head of the membrane. These results demonstrate that positronium and its annihilation characteristics can be employed to investigate charge transport phenomena and microstructural changes of real biological membranes

Adiabatic transfer of energy fluctuations between membranes inside an optical cavity

Science.gov (United States)

Garg, Devender; Chauhan, Anil K.; Biswas, Asoka

2017-08-01

A scheme is presented for the adiabatic transfer of average fluctuations in the phonon number between two membranes in an optical cavity. We show that by driving the cavity modes with external time-delayed pulses, one can obtain an effect analogous to stimulated Raman adiabatic passage in the atomic systems. The adiabatic transfer of fluctuations from one membrane to the other is attained through a "dark" mode, which is robust against decay of the mediating cavity mode. The results are supported with analytical and numerical calculations with experimentally feasible parameters.

Membrane introduction proton-transfer-reaction mass spectrometry

International Nuclear Information System (INIS)

Alexander, M.; Boscaini, E.; Maerk, T.; Lindinger, W.

2002-01-01

Proton-transfer-reaction mass spectrometry (PTR-MS) is a rapidly expanding field with multiple applications in ion physics, atmospheric chemistry, food chemistry, volatile organic compounds monitoring and biology. Initial studies that combine PTR-MS and membrane introduction mass spectrometry (MIMS) were researched and outlined. First using PTR-MS, certain fundamental physical properties of a poly-dimethylsiloxane (PDMS) membrane including solubilities and diffusion coefficients were measured. Second, it was shown how the chemical selectivity of the (PDMS) can be used to extend the capabilities of the PTR-MS instrument by eliminating certain isobaric interferences and excluding water from volatile organic compounds (VOCs). Experiments with mixtures of several VOCs (toluene, benzene, acetone, propanal, methanol) are presented. (nevyjel)

Fabrication of perforated isoporous membranes via a transfer-free strategy: enabling high-resolution separation of cells.

Science.gov (United States)

Ou, Yang; Lv, Chang-Jiang; Yu, Wei; Mao, Zheng-Wei; Wan, Ling-Shu; Xu, Zhi-Kang

2014-12-24

Thin perforated membranes with ordered pores are ideal barriers for high-resolution and high-efficiency selective transport and separation of biological species. However, for self-assembled thin membranes with a thickness less than several micrometers, an additional step of transferring the membranes onto porous supports is generally required. In this article, we present a facile transfer-free strategy for fabrication of robust perforated composite membranes via the breath figure process, and for the first time, demonstrate the application of the membranes in high-resolution cell separation of yeasts and lactobacilli without external pressure, achieving almost 100% rejection of yeasts and more than 70% recovery of lactobacilli with excellent viability. The avoidance of the transfer step simplifies the fabrication procedure of composite membranes and greatly improves the membrane homogeneity. Moreover, the introduction of an elastic triblock copolymer increases the interfacial strength between the membrane and the support, and allows the preservation of composite membranes in a dry state. Such perforated ordered membranes can also be applied in other size-based separation systems, enabling new opportunities in bioseparation and biosensors.

Control of distributed heat transfer mechanisms in membrane distillation plants

KAUST Repository

Laleg-Kirati, Taous-Meriem

2017-01-05

Various examples are provided that are related to boundary control in membrane distillation (MD) processes. In one example, a system includes a membrane distillation (MD) process comprising a feed side and a permeate side separated by a membrane boundary layer; and processing circuitry configured to control a water production rate of the MD process based at least in part upon a distributed heat transfer across the membrane boundary layer. In another example, a method includes determining a plurality of estimated temperature states of a membrane boundary layer separating a feed side and a permeate side of a membrane distillation (MD) process; and adjusting inlet flow rate or inlet temperature of at least one of the feed side or the permeate side to maintain a difference temperature along the membrane boundary layer about a defined reference temperature based at least in part upon the plurality of estimated temperature states.

Lipid-regulated sterol transfer between closely apposed membranes by oxysterol-binding protein homologues.

Science.gov (United States)

Schulz, Timothy A; Choi, Mal-Gi; Raychaudhuri, Sumana; Mears, Jason A; Ghirlando, Rodolfo; Hinshaw, Jenny E; Prinz, William A

2009-12-14

Sterols are transferred between cellular membranes by vesicular and poorly understood nonvesicular pathways. Oxysterol-binding protein-related proteins (ORPs) have been implicated in sterol sensing and nonvesicular transport. In this study, we show that yeast ORPs use a novel mechanism that allows regulated sterol transfer between closely apposed membranes, such as organelle contact sites. We find that the core lipid-binding domain found in all ORPs can simultaneously bind two membranes. Using Osh4p/Kes1p as a representative ORP, we show that ORPs have at least two membrane-binding surfaces; one near the mouth of the sterol-binding pocket and a distal site that can bind a second membrane. The distal site is required for the protein to function in cells and, remarkably, regulates the rate at which Osh4p extracts and delivers sterols in a phosphoinositide-dependent manner. Together, these findings suggest a new model of how ORPs could sense and regulate the lipid composition of adjacent membranes.

Research on mass transfer and actual performance of the membrane regeneration air-conditioning system

International Nuclear Information System (INIS)

Li, Xiu-Wei; Zhang, Xiao-Song; Chen, Qing

2015-01-01

Highlights: • Experimental research has been made on the membrane air-conditioning system. • We develop mass transfer models for the membrane regeneration process. • The paper exposes the actual performance of the system. • Increase of membrane pairs improves the performance. - Abstract: Absorption air-conditioning system has great advantages in energy conservation and environmental protection. To improve the performance of the traditional system, the membrane regeneration absorption system was proposed. Its COP could approach 6 by regenerating absorbent solution with the ion exchange membranes. However, the theoretical conclusion has not been supported by the experiment. This paper presents the experimental research of the membrane regeneration process. It has investigated the mass transfer process, energy efficiency and actual performance under different working conditions. Based on that, a mass transfer model has been developed and the influences of some key parameters have been exposed. It found the regeneration performance is mainly influenced by the current intensity. The calculation results with the model agree well the experimental data. The actual efficiency was lower than 50%, caused by energy loss in heat and electrochemical reactions. The actual COP is between 1 and 3, lower current intensity and more membrane pairs could improve it.

Multifunctional nanocomposite hollow fiber membranes by solvent transfer induced phase separation.

Science.gov (United States)

Haase, Martin F; Jeon, Harim; Hough, Noah; Kim, Jong Hak; Stebe, Kathleen J; Lee, Daeyeon

2017-11-01

The decoration of porous membranes with a dense layer of nanoparticles imparts useful functionality and can enhance membrane separation and anti-fouling properties. However, manufacturing of nanoparticle-coated membranes requires multiple steps and tedious processing. Here, we introduce a facile single-step method in which bicontinuous interfacially jammed emulsions are used to form nanoparticle-functionalized hollow fiber membranes. The resulting nanocomposite membranes prepared via solvent transfer-induced phase separation and photopolymerization have exceptionally high nanoparticle loadings (up to 50 wt% silica nanoparticles) and feature densely packed nanoparticles uniformly distributed over the entire membrane surfaces. These structurally well-defined, asymmetric membranes facilitate control over membrane flux and selectivity, enable the formation of stimuli responsive hydrogel nanocomposite membranes, and can be easily modified to introduce antifouling features. This approach forms a foundation for the formation of advanced nanocomposite membranes comprising diverse building blocks with potential applications in water treatment, industrial separations and as catalytic membrane reactors.

Influence of high range of mass transfer coefficient and convection heat transfer on direct contact membrane distillation performance

KAUST Repository

Lee, Jung Gil; Jeong, Sanghyun; Alsaadi, Ahmad Salem; Ghaffour, NorEddine

2017-01-01

(>2.1×10−6kg/m2sPa: membranes under development) were simulated using an experimentally validated model at different ranges of convection heat transfer by varying the inlet flow rates and spacer enhancement factor. The effect of mass transfer

Invariant-based inverse engineering for fluctuation transfer between membranes in an optomechanical cavity system

Science.gov (United States)

Chen, Ye-Hong; Shi, Zhi-Cheng; Song, Jie; Xia, Yan

2018-02-01

In this paper, by invariant-based inverse engineering, we design classical driving fields to transfer quantum fluctuations between two suspended membranes in an optomechanical cavity system. The transfer can be quickly attained through a nonadiabatic evolution path determined by a so-called dynamical invariant. Such an evolution path allows one to optimize the occupancies of the unstable "intermediate" states; thus, the influence of cavity decays can be suppressed. Numerical simulation demonstrates that a perfect fluctuation transfer between two membranes can be rapidly achieved in one step, and the transfer is robust to both the amplitude noises and cavity decays.

Gas Transfer in Cellularized Collagen-Membrane Gas Exchange Devices.

Science.gov (United States)

Lo, Justin H; Bassett, Erik K; Penson, Elliot J N; Hoganson, David M; Vacanti, Joseph P

2015-08-01

Chronic lower respiratory disease is highly prevalent in the United States, and there remains a need for alternatives to lung transplant for patients who progress to end-stage lung disease. Portable or implantable gas oxygenators based on microfluidic technologies can address this need, provided they operate both efficiently and biocompatibly. Incorporating biomimetic materials into such devices can help replicate native gas exchange function and additionally support cellular components. In this work, we have developed microfluidic devices that enable blood gas exchange across ultra-thin collagen membranes (as thin as 2 μm). Endothelial, stromal, and parenchymal cells readily adhere to these membranes, and long-term culture with cellular components results in remodeling, reflected by reduced membrane thickness. Functionally, acellular collagen-membrane lung devices can mediate effective gas exchange up to ∼288 mL/min/m(2) of oxygen and ∼685 mL/min/m(2) of carbon dioxide, approaching the gas exchange efficiency noted in the native lung. Testing several configurations of lung devices to explore various physical parameters of the device design, we concluded that thinner membranes and longer gas exchange distances result in improved hemoglobin saturation and increases in pO2. However, in the design space tested, these effects are relatively small compared to the improvement in overall oxygen and carbon dioxide transfer by increasing the blood flow rate. Finally, devices cultured with endothelial and parenchymal cells achieved similar gas exchange rates compared with acellular devices. Biomimetic blood oxygenator design opens the possibility of creating portable or implantable microfluidic devices that achieve efficient gas transfer while also maintaining physiologic conditions.

Pressure modulation of Ras-membrane interactions and intervesicle transfer.

Science.gov (United States)

Kapoor, Shobhna; Werkmüller, Alexander; Goody, Roger S; Waldmann, Herbert; Winter, Roland

2013-04-24

Proteins attached to the plasma membrane frequently encounter mechanical stresses, including high hydrostatic pressure (HHP) stress. Signaling pathways involving membrane-associated small GTPases (e.g., Ras) have been identified as critical loci for pressure perturbation. However, the impact of mechanical stimuli on biological outputs is still largely terra incognita. The present study explores the effect of HHP on the membrane association, dissociation, and intervesicle transfer process of N-Ras by using a FRET-based assay to obtain the kinetic parameters and volumetric properties along the reaction path of these processes. Notably, membrane association is fostered upon pressurization. Conversely, depending on the nature and lateral organization of the lipid membrane, acceleration or retardation is observed for the dissociation step. In addition, HHP can be inferred as a positive regulator of N-Ras clustering, in particular in heterogeneous membranes. The susceptibility of membrane interaction to pressure raises the idea of a role of lipidated signaling molecules as mechanosensors, transducing mechanical stimuli to chemical signals by regulating their membrane binding and dissociation. Finally, our results provide first insights into the influence of pressure on membrane-associated Ras-controlled signaling events in organisms living under extreme environmental conditions such as those that are encountered in the deep sea and sub-seafloor environments, where pressures reach the kilobar (100 MPa) range.

Synthesis and transfer of galactolipids in the chloroplast envelope membranes of Arabidopsis thaliana.

Science.gov (United States)

Kelly, Amélie A; Kalisch, Barbara; Hölzl, Georg; Schulze, Sandra; Thiele, Juliane; Melzer, Michael; Roston, Rebecca L; Benning, Christoph; Dörmann, Peter

2016-09-20

Galactolipids [monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)] are the hallmark lipids of photosynthetic membranes. The galactolipid synthases MGD1 and DGD1 catalyze consecutive galactosyltransfer reactions but localize to the inner and outer chloroplast envelopes, respectively, necessitating intermembrane lipid transfer. Here we show that the N-terminal sequence of DGD1 (NDGD1) is required for galactolipid transfer between the envelopes. Different diglycosyllipid synthases (DGD1, DGD2, and Chloroflexus glucosyltransferase) were introduced into the dgd1-1 mutant of Arabidopsis in fusion with N-terminal extensions (NDGD1 and NDGD2) targeting to the outer envelope. Reconstruction of DGDG synthesis in the outer envelope membrane was observed only with diglycosyllipid synthase fusion proteins carrying NDGD1, indicating that NDGD1 enables galactolipid translocation between envelopes. NDGD1 binds to phosphatidic acid (PA) in membranes and mediates PA-dependent membrane fusion in vitro. These findings provide a mechanism for the sorting and selective channeling of lipid precursors between the galactolipid pools of the two envelope membranes.

Proton Transfer in Perfluorosulfonic Acid Fuel Cell Membranes with Differing Pendant Chains and Equivalent Weights.

Science.gov (United States)

Thomaz, Joseph E; Lawler, Christian M; Fayer, Michael D

2017-05-04

Proton transfer in the nanoscopic water channels of polyelectrolyte fuel cell membranes was studied using a photoacid, 8-hydroxypyrene-1,3,6-trisulfonic acid sodium salt (HPTS), in the channels. The local environment of the probe was determined using 8-methoxypyrene-1,3,6-trisulfonic acid sodium salt (MPTS), which is not a photoacid. Three fully hydrated membranes, Nafion (DuPont) and two 3M membranes, were studied to determine the impact of different pendant chains and equivalent weights on proton transfer. Fluorescence anisotropy and excited state population decay data that characterize the local environment of the fluorescent probes and proton transfer dynamics were measured. The MPTS lifetime and anisotropy results show that most of the fluorescent probes have a bulk-like water environment with a relatively small fraction interacting with the channel wall. Measurements of the HPTS protonated and deprotonated fluorescent bands' population decays provided information on the proton transport dynamics. The decay of the protonated band from ∼0.5 ns to tens of nanoseconds is in part determined by dissociation and recombination with the HPTS, providing information on the ability of protons to move in the channels. The dissociation and recombination is manifested as a power law component in the protonated band fluorescence decay. The results show that equivalent weight differences between two 3M membranes resulted in a small difference in proton transfer. However, differences in pendant chain structure did significantly influence the proton transfer ability, with the 3M membranes displaying more facile transfer than Nafion.

The role of phosphatidylinositol-transfer proteins at membrane contact sites.

Science.gov (United States)

Selitrennik, Michael; Lev, Sima

2016-04-15

Phosphatidylinositol-transfer proteins (PITPs) have been initially identified as soluble factors that accelerate the monomeric exchange of either phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane bilayersin vitro They are highly conserved in eukaryotes and have been implicated in different cellular processes, including vesicular trafficking, signal transduction, and lipid metabolism. Recent studies suggest that PITPs function at membrane contact sites (MCSs) to facilitate the transport of PI from its synthesis site at the endoplasmic reticulum (ER) to various membrane compartments. In this review, we describe the underlying mechanism of PITPs targeting to MCSs, discuss their cellular roles and potential mode of action. © 2016 Authors; published by Portland Press Limited.

Effect of membrane microheterogeneity and domain size on fluorescence resonance energy transfer.

Science.gov (United States)

Towles, Kevin B; Brown, Angela C; Wrenn, Steven P; Dan, Nily

2007-07-15

Studies of multicomponent membranes suggest lateral inhomogeneity in the form of membrane domains, but the size of small (nanoscale) domains in situ cannot be determined with current techniques. In this article, we present a model that enables extraction of membrane domain size from time-resolved fluorescence resonance energy transfer (FRET) data. We expand upon a classic approach to the infinite phase separation limit and formulate a model that accounts for the presence of disklike domains of finite dimensions within a two-dimensional infinite planar bilayer. The model was tested against off-lattice Monte Carlo calculations of a model membrane in the liquid-disordered (l(d)) and liquid-ordered (l(o)) coexistence regime. Simulated domain size was varied from 5 to 50 nm, and two fluorophores, preferentially partitioning into opposite phases, were randomly mixed to obtain the simulated time-resolved FRET data. The Monte Carlo data show clear differences in the efficiency of energy transfer as a function of domain size. The model fit of the data yielded good agreement for the domain size, especially in cases where the domain diameter is membrane domains using time-resolved FRET.

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

Science.gov (United States)

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

2016-06-06

Mitochondria exert critical functions in cellular lipid metabolism and promote the synthesis of major constituents of cellular membranes, such as phosphatidylethanolamine (PE) and phosphatidylcholine. Here, we demonstrate that the phosphatidylserine decarboxylase Psd1, located in the inner mitochondrial membrane, promotes mitochondrial PE synthesis via two pathways. First, Ups2-Mdm35 complexes (SLMO2-TRIAP1 in humans) serve as phosphatidylserine (PS)-specific lipid transfer proteins in the mitochondrial intermembrane space, allowing formation of PE by Psd1 in the inner membrane. Second, Psd1 decarboxylates PS in the outer membrane in trans, independently of PS transfer by Ups2-Mdm35. This latter pathway requires close apposition between both mitochondrial membranes and the mitochondrial contact site and cristae organizing system (MICOS). In MICOS-deficient cells, limiting PS transfer by Ups2-Mdm35 and reducing mitochondrial PE accumulation preserves mitochondrial respiration and cristae formation. These results link mitochondrial PE metabolism to MICOS, combining functions in protein and lipid homeostasis to preserve mitochondrial structure and function. © 2016 Aaltonen et al.

Tuning of Hemes b Equilibrium Redox Potential Is Not Required for Cross-Membrane Electron Transfer.

Science.gov (United States)

Pintscher, Sebastian; Kuleta, Patryk; Cieluch, Ewelina; Borek, Arkadiusz; Sarewicz, Marcin; Osyczka, Artur

2016-03-25

In biological energy conversion, cross-membrane electron transfer often involves an assembly of two hemesb The hemes display a large difference in redox midpoint potentials (ΔEm_b), which in several proteins is assumed to facilitate cross-membrane electron transfer and overcome a barrier of membrane potential. Here we challenge this assumption reporting on hemebligand mutants of cytochromebc1in which, for the first time in transmembrane cytochrome, one natural histidine has been replaced by lysine without loss of the native low spin type of heme iron. With these mutants we show that ΔEm_b can be markedly increased, and the redox potential of one of the hemes can stay above the level of quinone pool, or ΔEm_b can be markedly decreased to the point that two hemes are almost isopotential, yet the enzyme retains catalytically competent electron transfer between quinone binding sites and remains functionalin vivo This reveals that cytochromebc1can accommodate large changes in ΔEm_b without hampering catalysis, as long as these changes do not impose overly endergonic steps on downhill electron transfer from substrate to product. We propose that hemesbin this cytochrome and in other membranous cytochromesbact as electronic connectors for the catalytic sites with no fine tuning in ΔEm_b required for efficient cross-membrane electron transfer. We link this concept with a natural flexibility in occurrence of several thermodynamic configurations of the direction of electron flow and the direction of the gradient of potential in relation to the vector of the electric membrane potential. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Refractive-index-based screening of membrane-protein-mediated transfer across biological membranes.

Science.gov (United States)

Brändén, Magnus; Tabaei, Seyed R; Fischer, Gerhard; Neutze, Richard; Höök, Fredrik

2010-07-07

Numerous membrane-transport proteins are major drug targets, and therefore a key ingredient in pharmaceutical development is the availability of reliable, efficient tools for membrane transport characterization and inhibition. Here, we present the use of evanescent-wave sensing for screening of membrane-protein-mediated transport across lipid bilayer membranes. This method is based on a direct recording of the temporal variations in the refractive index that occur upon a transfer-dependent change in the solute concentration inside liposomes associated to a surface plasmon resonance (SPR) active sensor surface. The applicability of the method is demonstrated by a functional study of the aquaglyceroporin PfAQP from the malaria parasite Plasmodium falciparum. Assays of the temperature dependence of facilitated diffusion of sugar alcohols on a single set of PfAQP-reconstituted liposomes reveal that the activation energies for facilitated diffusion of xylitol and sorbitol are the same as that previously measured for glycerol transport in the aquaglyceroporin of Escherichia coli (5 kcal/mole). These findings indicate that the aquaglyceroporin selectivity filter does not discriminate sugar alcohols based on their length, and that the extra energy cost of dehydration of larger sugar alcohols, upon entering the pore, is compensated for by additional hydrogen-bond interactions within the aquaglyceroporin pore. Copyright 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Aromatic Side Chain Water-to-Lipid Transfer Free Energies Show a Depth Dependence across the Membrane Normal.

Science.gov (United States)

McDonald, Sarah K; Fleming, Karen G

2016-06-29

Quantitating and understanding the physical forces responsible for the interactions of biomolecules are fundamental to the biological sciences. This is especially challenging for membrane proteins because they are embedded within cellular bilayers that provide a unique medium in which hydrophobic sequences must fold. Knowledge of the energetics of protein-lipid interactions is thus vital to understand cellular processes involving membrane proteins. Here we used a host-guest mutational strategy to calculate the Gibbs free energy changes of water-to-lipid transfer for the aromatic side chains Trp, Tyr, and Phe as a function of depth in the membrane. This work reveals an energetic gradient in the transfer free energies for Trp and Tyr, where transfer was most favorable to the membrane interfacial region and comparatively less favorable into the bilayer center. The transfer energetics follows the concentration gradient of polar atoms across the bilayer normal that naturally occurs in biological membranes. Additional measurements revealed nearest-neighbor coupling in the data set are influenced by a network of aromatic side chains in the host protein. Taken together, these results show that aromatic side chains contribute significantly to membrane protein stability through either aromatic-aromatic interactions or placement at the membrane interface.

Can membrane-bound carotenoid pigment zeaxanthin carry out a transmembrane proton transfer?

Science.gov (United States)

Kupisz, Kamila; Sujak, Agnieszka; Patyra, Magdalena; Trebacz, Kazimierz; Gruszecki, Wiesław I

2008-10-01

Polar carotenoid pigment zeaxanthin (beta,beta-carotene-3,3'-diol) incorporated into planar lipid membranes formed with diphytanoyl phosphatidylcholine increases the specific electric resistance of the membrane from ca. 4 to 13 x 10(7) Omega cm2 (at 5 mol% zeaxanthin with respect to lipid). Such an observation is consistent with the well known effect of polar carotenoids in decreasing fluidity and structural stabilization of lipid bilayers. Zeaxanthin incorporated into the lipid membrane at 1 mol% has very small effect on the overall membrane resistance but facilitates equilibration of the transmembrane proton gradient, as demonstrated with the application of the H+-sensitive antimony electrodes. Relatively low changes in the electrical potential suggest that the equilibration process may be associated with a symport/antiport activity or with a transmembrane transfer of the molecules of acid. UV-Vis linear dichroism analysis of multibilayer formed with the same lipid-carotenoid system shows that the transition dipole moment of the pigment molecules forms a mean angle of 21 degrees with respect to the axis normal to the plane of the membrane. This means that zeaxanthin spans the membrane and tends to have its two hydroxyl groups anchored in the opposite polar zones of the membrane. Detailed FTIR analysis of beta-carotene and zeaxanthin indicates that the polyene chain of carotenoids is able to form weak hydrogen bonds with water molecules. Possible molecular mechanisms responsible for proton transport by polyenes are discussed, including direct involvement of the polyene chain in proton transfer and indirect effect of the pigment on physical properties of the membrane.

Transferable coarse-grained model for perfluorosulfonic acid polymer membranes

Science.gov (United States)

Kuo, An-Tsung; Okazaki, Susumu; Shinoda, Wataru

2017-09-01

Perfluorosulfonic acid (PFSA) polymer membranes are widely used as proton exchange membranes. Because the structure of the aqueous domain within the PFSA membrane is expected to directly influence proton conductance, many coarse-grained (CG) simulation studies have been performed to investigate the membrane morphology; these studies mostly used phenomenological models, such as dissipative particle dynamics. However, a chemically accurate CG model is required to investigate the morphology in realistic membranes and to provide a concrete molecular design. Here, we attempt to construct a predictive CG model for the structure and morphology of PFSA membranes that is compatible with the Sinoda-DeVane-Klein (SDK) CG water model [Shinoda et al., Mol. Simul. 33, 27 (2007)]. First, we extended the parameter set for the SDK CG force field to examine a hydrated PFSA membrane based on thermodynamic and structural data from experiments and all-atom (AA) molecular dynamics (MD) simulations. However, a noticeable degradation of the morphology motivated us to improve the structural properties by using the iterative Boltzmann inversion (IBI) approach. Thus, we explored a possible combination of the SDK and IBI approaches to describe the nonbonded interaction. The hybrid SDK/IBI model improved the structural issues of SDK, showing a better agreement with AA-MD in the radial distribution functions. The hybrid SDK/IBI model was determined to reasonably reproduce both the thermodynamic and structural properties of the PFSA membrane for all examined water contents. In addition, the model demonstrated good transferability and has considerable potential for application to realistic long-chained PFSA membranes.

Preferential transfer of certain plasma membrane proteins onto T and B cells by trogocytosis.

Directory of Open Access Journals (Sweden)

Sandrine Daubeuf

2010-01-01

Full Text Available T and B cells capture antigens via membrane fragments of antigen presenting cells (APC in a process termed trogocytosis. Whether (and how a preferential transfer of some APC components occurs during trogocytosis is still largely unknown. We analyzed the transfer onto murine T and B cells of a large panel of fluorescent proteins with different intra-cellular localizations in the APC or various types of anchors in the plasma membrane (PM. Only the latter were transferred by trogocytosis, albeit with different efficiencies. Unexpectedly, proteins anchored to the PM's cytoplasmic face, or recruited to it via interaction with phosphinositides, were more efficiently transferred than those facing the outside of the cell. For proteins spanning the PM's whole width, transfer efficiency was found to vary quite substantially, with tetraspanins, CD4 and FcRgamma found among the most efficiently transferred proteins. We exploited our findings to set immunodiagnostic assays based on the capture of preferentially transferred components onto T or B cells. The preferential transfer documented here should prove useful in deciphering the cellular structures involved in trogocytosis.

Low-energy ion beam bombardment effect on the plant-cell-envelope mimetic membrane for DNA transfer

International Nuclear Information System (INIS)

Prakrajang, K.; Sangwijit, K.; Anuntalabhochai, S.; Wanichapichart, P.; Yu, L.D.

2012-01-01

This study is a systematic analysis of the mechanisms involved in ion-beam induced DNA transfer, an important application of ion beam biotechnology. Cellulose membranes were used to mimic the plant cell envelope. Ion beams of argon (Ar) or nitrogen (N) at an energy of 25 keV bombarded the cellulose membranes at fluences ranging from 10 15 to 10 16 ions/cm 2 . The damage to the ion-beam-bombarded membranes was characterized using infrared spectroscopy, a micro tensile test and scanning electron microscopy (SEM). Chain scission was the dominant radiation damage type in the membrane. DNA diffusion across the membrane was significantly increased after ion beam bombardment. The increase in DNA transfer is therefore attributed to chain scission, which increases the permeability by increasing the number of pores in the membrane.

Lipid transfer proteins do their thing anchored at membrane contact sites… but what is their thing?

Science.gov (United States)

Wong, Louise H; Levine, Tim P

2016-04-15

Membrane contact sites are structures where two organelles come close together to regulate flow of material and information between them. One type of inter-organelle communication is lipid exchange, which must occur for membrane maintenance and in response to environmental and cellular stimuli. Soluble lipid transfer proteins have been extensively studied, but additional families of transfer proteins have been identified that are anchored into membranes by transmembrane helices so that they cannot diffuse through the cytosol to deliver lipids. If such proteins target membrane contact sites they may be major players in lipid metabolism. The eukaryotic family of so-called Lipid transfer proteins Anchored at Membrane contact sites (LAMs) all contain both a sterol-specific lipid transfer domain in the StARkin superfamily (related to StART/Bet_v1), and one or more transmembrane helices anchoring them in the endoplasmic reticulum (ER), making them interesting subjects for study in relation to sterol metabolism. They target a variety of membrane contact sites, including newly described contacts between organelles that were already known to make contact by other means. Lam1-4p target punctate ER-plasma membrane contacts. Lam5p and Lam6p target multiple contacts including a new category: vacuolar non-NVJ cytoplasmic ER (VancE) contacts. These developments confirm previous observations on tubular lipid-binding proteins (TULIPs) that established the importance of membrane anchored proteins for lipid traffic. However, the question remaining to be solved is the most difficult of all: are LAMs transporters, or alternately are they regulators that affect traffic more indirectly? © 2016 Authors; published by Portland Press Limited.

Spontaneous transfer of stearic acids between human serum albumin and PEG:2000-grafted DPPC membranes.

Science.gov (United States)

Pantusa, Manuela; Stirpe, Andrea; Sportelli, Luigi; Bartucci, Rosa

2010-05-01

Electron spin resonance (ESR) spectroscopy is used to study the transfer of stearic acids between human serum albumin (HSA) and sterically stabilized liposomes (SSL) composed of dipalmitoylphosphatidylcholine (DPPC) and of submicellar content of poly(ethylene glycol:2000)-dipalmitoylphosphatidylethanolamine (PEG:2000-DPPE). Protein/lipid dispersions are considered in which spin-labelled stearic acids at the 16th carbon atom along the acyl chain (16-SASL) are inserted either in the protein or in the SSL. Two component ESR spectra with different rotational mobility are obtained over a broad range of temperature and membrane composition. Indeed, superimposed to an anisotropic protein-signal, appears a more isotropic lipid-signal. Since in the samples only one matrix (protein or membranes) is spin-labelled, the other component accounts for the transfer of 16-SASL between albumin and membranes. The two components have been resolved and quantified by spectral subtractions, and the fraction, f (p) (16-SASL), of spin labels bound non-covalently to the protein has been used to monitor the transfer. It is found that it depends on the type of donor and acceptor matrix, on the physical state of the membranes and on the grafting density of the polymer-lipids. Indeed, it is favoured from SSL to HSA and the fraction of stearic acids transferred increases with temperature in both directions of transfer. Moreover, in the presence of polymer-lipids, the transfer from HSA to SSL is slightly attenuated, especially in the brush regime of the polymer-chains. Instead, the transfer from SSL to HSA is favoured by the polymer-lipids much more in the mushroom than in the brush regime.

Low-energy ion beam bombardment effect on the plant-cell-envelope mimetic membrane for DNA transfer

Energy Technology Data Exchange (ETDEWEB)

Prakrajang, K., E-mail: k.prakrajang@gmail.com [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Sangwijit, K.; Anuntalabhochai, S. [Molecular Biology Laboratory, Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wanichapichart, P. [Membrane Science and Technology Research Center, Department of Physics, Faculty of Science, Prince of Songkla University, Hat Yai, Songkla 90112 (Thailand); Yu, L.D., E-mail: yuld@fnrf.science.cmu.ac.th [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand)

2012-09-01

This study is a systematic analysis of the mechanisms involved in ion-beam induced DNA transfer, an important application of ion beam biotechnology. Cellulose membranes were used to mimic the plant cell envelope. Ion beams of argon (Ar) or nitrogen (N) at an energy of 25 keV bombarded the cellulose membranes at fluences ranging from 10{sup 15} to 10{sup 16} ions/cm{sup 2}. The damage to the ion-beam-bombarded membranes was characterized using infrared spectroscopy, a micro tensile test and scanning electron microscopy (SEM). Chain scission was the dominant radiation damage type in the membrane. DNA diffusion across the membrane was significantly increased after ion beam bombardment. The increase in DNA transfer is therefore attributed to chain scission, which increases the permeability by increasing the number of pores in the membrane.

Effect of high linear energy transfer radiation on biological membranes

International Nuclear Information System (INIS)

Choudhary, D.; Srivastava, M.; Kale, R.K.; Sarma, A.

1998-01-01

Cellular membranes are vital elements, and their integrity is extremely essential for the viability of the cells. We studied the effects of high linear energy transfer (LET) radiation on the membranes. Rabbit erythrocytes (1 x 10 7 cells/ml) and microsomes (0.6 mg protein/ml) prepared from liver of rats were irradiated with 7 Li ions of energy 6.42 MeV/u and 16 O ions of energy 4.25 MeV/u having maximum LET values of 354 keV/μm and 1130 keV/μm, respectively. 7 Li- and 16 O-induced microsomal lipid peroxidation was found to increase with fluence. The 16 O ions were more effective than 7 Li ions, which could be due to the denser energy distribution in the track and the yield of free radicals. These findings suggested that the biological membranes could be peroxidized on exposure to high-LET radiation. Inhibition of the lipid peroxidation was observed in the presence of a membrane-active drug, chlorpromazine (CPZ), which could be due to scavenging of free radicals (mainly HO. and ROO.), electron donation, and hydrogen transfer reactions. The 7 Li and 16 O ions also induced hemolysis in erythrocytes. The extent of hemolysis was found to be a function of time and fluence, and showed a characteristic sigmoidal pattern. The 16 O ions were more effective in the lower fluence range than 7 Li ions. These results were compared with lipid peroxidation and hemolysis induced by gamma-radiation. (orig.)

Energy transfer dynamics in an RC-LH1-PufX tubular photosynthetic membrane

International Nuclear Information System (INIS)

Hsin, J; Sener, M; Schulten, K; Struempfer, J; Qian, P; Hunter, C N

2010-01-01

Light absorption and the subsequent transfer of excitation energy are the first two steps in the photosynthetic process, carried out by protein-bound pigments, mainly bacteriochlorophylls (BChls), in photosynthetic bacteria. BChls are anchored in light-harvesting (LH) complexes, such as light-harvesting complex I (LH1), which directly associates with the reaction center (RC), forming the RC-LH1 core complex. In Rhodobacter sphaeroides, RC-LH1 core complexes contain an additional protein, PufX, and assemble into dimeric RC-LH1-PufX core complexes. In the absence of LH complex II (LH2), the former complexes can aggregate into a helically ordered tubular photosynthetic membrane. We have examined the excitation transfer dynamics in a single RC-LH1-PufX core complex dimer using the hierarchical equations of motion for dissipative quantum dynamics that accurately, yet in a computationally costly manner, treat the coupling between BChls and their protein environment. A widely employed description, the generalized Foerster (GF) theory, was also used to calculate the transfer rates of the same excitonic system in order to verify the accuracy of this computationally cheap method. Additionally, in light of the structural uncertainties in the Rba. sphaeroides RC-LH1-PufX core complex, geometrical alterations were introduced into the BChl organization. It is shown that the energy transfer dynamics are not affected by the considered changes in the BChl organization and that the GF theory provides accurate transfer rates. An all-atom model for a tubular photosynthetic membrane is then constructed on the basis of electron microscopy data, and the overall energy transfer properties of this membrane are computed.

Energy transfer dynamics in an RC-LH1-PufX tubular photosynthetic membrane

Energy Technology Data Exchange (ETDEWEB)

Hsin, J; Sener, M; Schulten, K [Department of Physics and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana (United States); Struempfer, J [Center for Biophysics and Computational Biology and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana (United States); Qian, P; Hunter, C N, E-mail: kschulte@ks.uiuc.ed [Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN (United Kingdom)

2010-08-15

Light absorption and the subsequent transfer of excitation energy are the first two steps in the photosynthetic process, carried out by protein-bound pigments, mainly bacteriochlorophylls (BChls), in photosynthetic bacteria. BChls are anchored in light-harvesting (LH) complexes, such as light-harvesting complex I (LH1), which directly associates with the reaction center (RC), forming the RC-LH1 core complex. In Rhodobacter sphaeroides, RC-LH1 core complexes contain an additional protein, PufX, and assemble into dimeric RC-LH1-PufX core complexes. In the absence of LH complex II (LH2), the former complexes can aggregate into a helically ordered tubular photosynthetic membrane. We have examined the excitation transfer dynamics in a single RC-LH1-PufX core complex dimer using the hierarchical equations of motion for dissipative quantum dynamics that accurately, yet in a computationally costly manner, treat the coupling between BChls and their protein environment. A widely employed description, the generalized Foerster (GF) theory, was also used to calculate the transfer rates of the same excitonic system in order to verify the accuracy of this computationally cheap method. Additionally, in light of the structural uncertainties in the Rba. sphaeroides RC-LH1-PufX core complex, geometrical alterations were introduced into the BChl organization. It is shown that the energy transfer dynamics are not affected by the considered changes in the BChl organization and that the GF theory provides accurate transfer rates. An all-atom model for a tubular photosynthetic membrane is then constructed on the basis of electron microscopy data, and the overall energy transfer properties of this membrane are computed.

Structure-function insights into direct lipid transfer between membranes by Mmm1-Mdm12 of ERMES.

Science.gov (United States)

Kawano, Shin; Tamura, Yasushi; Kojima, Rieko; Bala, Siqin; Asai, Eri; Michel, Agnès H; Kornmann, Benoît; Riezman, Isabelle; Riezman, Howard; Sakae, Yoshitake; Okamoto, Yuko; Endo, Toshiya

2018-03-05

The endoplasmic reticulum (ER)-mitochondrial encounter structure (ERMES) physically links the membranes of the ER and mitochondria in yeast. Although the ER and mitochondria cooperate to synthesize glycerophospholipids, whether ERMES directly facilitates the lipid exchange between the two organelles remains controversial. Here, we compared the x-ray structures of an ERMES subunit Mdm12 from Kluyveromyces lactis with that of Mdm12 from Saccharomyces cerevisiae and found that both Mdm12 proteins possess a hydrophobic pocket for phospholipid binding. However in vitro lipid transfer assays showed that Mdm12 alone or an Mmm1 (another ERMES subunit) fusion protein exhibited only a weak lipid transfer activity between liposomes. In contrast, Mdm12 in a complex with Mmm1 mediated efficient lipid transfer between liposomes. Mutations in Mmm1 or Mdm12 impaired the lipid transfer activities of the Mdm12-Mmm1 complex and furthermore caused defective phosphatidylserine transport from the ER to mitochondrial membranes via ERMES in vitro. Therefore, the Mmm1-Mdm12 complex functions as a minimal unit that mediates lipid transfer between membranes. © 2018 Kawano et al.

Mitochondrial cardiolipin/phospholipid trafficking: the role of membrane contact site complexes and lipid transfer proteins.

Science.gov (United States)

Schlattner, Uwe; Tokarska-Schlattner, Malgorzata; Rousseau, Denis; Boissan, Mathieu; Mannella, Carmen; Epand, Richard; Lacombe, Marie-Lise

2014-04-01

Historically, cellular trafficking of lipids has received much less attention than protein trafficking, mostly because its biological importance was underestimated, involved sorting and translocation mechanisms were not known, and analytical tools were limiting. This has changed during the last decade, and we discuss here some progress made in respect to mitochondria and the trafficking of phospholipids, in particular cardiolipin. Different membrane contact site or junction complexes and putative lipid transfer proteins for intra- and intermembrane lipid translocation have been described, involving mitochondrial inner and outer membrane, and the adjacent membranes of the endoplasmic reticulum. An image emerges how cardiolipin precursors, remodeling intermediates, mature cardiolipin and its oxidation products could migrate between membranes, and how this trafficking is involved in cardiolipin biosynthesis and cell signaling events. Particular emphasis in this review is given to mitochondrial nucleoside diphosphate kinase D and mitochondrial creatine kinases, which emerge to have roles in both, membrane junction formation and lipid transfer. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Wafer scale nano-membrane supported on a silicon microsieve using thin-film transfer technology

NARCIS (Netherlands)

Unnikrishnan, S.; Jansen, Henricus V.; Berenschot, Johan W.; Elwenspoek, Michael Curt

A new micromachining method to fabricate wafer scale nano-membranes is described. The delicate thin-film nano-membrane is supported on a robust silicon microsieve fabricated by plasma etching. The silicon sieve is micromachined independently of the thin-film, which is later transferred onto it by

Direct effects of ionizing radiation on integral membrane proteins. Noncovalent energy transfer requires specific interpeptide interactions

International Nuclear Information System (INIS)

Jhun, E.; Jhun, B.H.; Jones, L.R.; Jung, C.Y.

1991-01-01

The 12 transmembrane alpha helices (TMHs) of human erythrocyte glucose transporter were individually cut by pepsin digestion as membrane-bound 2.5-3.5-kDa peptide fragments. Radiation-induced chemical degradation of these fragments showed an average target size of 34 kDa. This is 10-12 x larger than the average size of an individual TMH, demonstrating that a significant energy transfer occurs among these TMHs in the absence of covalent linkage. Heating this TMH preparation at 100 degree C for 15 min reduced the target size to 5 kDa or less, suggesting that the noncovalent energy transfer requires specific helix-helix interactions. Purified phospholamban, a small (6-kDa) integral membrane protein containing a single TMH, formed a pentameric assembly in sodium dodecyl sulfate. The chemical degradation target size of this phospholamban pentamer was 5-6 kDa, illustrating that not all integral membrane protein assemblies permit intersubunit energy transfer. These findings together with other published observations suggest strongly that significant noncovalent energy transfer can occur within the tertiary and quaternary structure of membrane proteins and that as yet undefined proper molecular interactions are required for such covalent energy transfer. Our results with pepsin-digested glucose transporter also illustrate the importance of the interhelical interaction as a predominating force in maintaining the tertiary structure of a transmembrane protein

Acid sphingomyelinase activity is regulated by membrane lipids and facilitates cholesterol transfer by NPC2.

Science.gov (United States)

Oninla, Vincent O; Breiden, Bernadette; Babalola, Jonathan O; Sandhoff, Konrad

2014-12-01

During endocytosis, membrane components move to intraluminal vesicles of the endolysosomal compartment for digestion. At the late endosomes, cholesterol is sorted out mainly by two sterol-binding proteins, Niemann-Pick protein type C (NPC)1 and NPC2. To study the NPC2-mediated intervesicular cholesterol transfer, we developed a liposomal assay system. (Abdul-Hammed, M., B. Breiden, M. A. Adebayo, J. O. Babalola, G. Schwarzmann, and K. Sandhoff. 2010. Role of endosomal membrane lipids and NPC2 in cholesterol transfer and membrane fusion. J. Lipid Res. 51: 1747-1760.) Anionic lipids stimulate cholesterol transfer between liposomes while SM inhibits it, even in the presence of anionic bis(monoacylglycero)phosphate (BMP). Preincubation of vesicles containing SM with acid sphingomyelinase (ASM) (SM phosphodiesterase, EC 3.1.4.12) results in hydrolysis of SM to ceramide (Cer), which enhances cholesterol transfer. Besides SM, ASM also cleaves liposomal phosphatidylcholine. Anionic phospholipids derived from the plasma membrane (phosphatidylglycerol and phosphatidic acid) stimulate SM and phosphatidylcholine hydrolysis by ASM more effectively than BMP, which is generated during endocytosis. ASM-mediated hydrolysis of liposomal SM was also stimulated by incorporation of diacylglycerol (DAG), Cer, and free fatty acids into the liposomal membranes. Conversely, phosphatidylcholine hydrolysis was inhibited by incorporation of cholesterol, Cer, DAG, monoacylglycerol, and fatty acids. Our data suggest that SM degradation by ASM is required for physiological secretion of cholesterol from the late endosomal compartment, and is a key regulator of endolysosomal lipid digestion. Copyright © 2014 by the American Society for Biochemistry and Molecular Biology, Inc.

Hydration induced material transfer in membranes of osmotic pump tablets measured by synchrotron radiation based FTIR.

Science.gov (United States)

Wu, Li; Yin, Xianzhen; Guo, Zhen; Tong, Yajun; Feng, Jing; York, Peter; Xiao, Tiqiao; Chen, Min; Gu, Jingkai; Zhang, Jiwen

2016-03-10

Osmotic pump tablets are reliable oral controlled drug delivery systems based on their semipermeable membrane coating. This research used synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy and imaging to investigate the hydration induced material transfer in the membranes of osmotic pump tablets. SR-FTIR was applied to record and map the chemical information of a micro-region of the membranes, composed of cellulose acetate (CA, as the water insoluble matrix) and polyethylene glycol (PEG, as the soluble pore forming agent and plasticizing agent). The microstructure and chemical change of membranes hydrated for 0, 5, 10 and 30min were measured using SR-FTIR, combined with scanning electronic microscopy and atom force microscopy. The SR-FTIR microspectroscopy results indicated that there was a major change at the absorption range of 2700-3100cm(-1) in the membranes after different periods of hydration time. The absorption bands at 2870-2880cm(-1) and 2950-2960cm(-1) were assigned to represent CA and PEG, respectively. The chemical group signal distribution illustrated by the ratio of PEG to CA demonstrated that the trigger of drug release in the preliminary stage was due to the rapid transfer of PEG into liquid medium with a sharp decrease of PEG in the membranes. The SR-FTIR mapping results have demonstrated the hydration induced material transfer in the membranes of osmotic pump tablets and enabled reassessment of the drug release mechanism of membrane controlled osmotic pump systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Drug Release from ß-Cyclodextrin Complexes and Drug Transfer into Model Membranes Studied by Affinity Capillary Electrophoresis.

Science.gov (United States)

Darwish, Kinda A; Mrestani, Yahya; Rüttinger, Hans-Hermann; Neubert, Reinhard H H

2016-05-01

Is to characterize the drug release from the ß-cyclodextrin (ß-CD) cavity and the drug transfer into model membranes by affinity capillary electrophoresis. Phospholipid liposomes with and without cholesterol were used to mimic the natural biological membrane. The interaction of cationic and anionic drugs with ß-CD and the interaction of the drugs with liposomes were detected separately by measuring the drug mobility in ß-CD containing buffer and liposome containing buffer; respectively. Moreover, the kinetics of drug release from ß-CD and its transfer into liposomes with or without cholesterol was studied by investigation of changes in the migration behaviours of the drugs in samples, contained drug, ß-CD and liposome, at 1:1:1 molar ratio at different time intervals; zero time, 30 min, 1, 2, 4, 6, 8, 10 and 24 h. Lipophilic drugs such as propranolol and ibuprofen were chosen for this study, because they form complexes with ß-CD. The mobility of the both drug liposome mixtures changed with time to a final state. For samples of liposomal membranes with cholesterol the final state was faster reached than without cholesterol. The study confirmed that the drug release from the CD cavity and its transfer into the model membrane was more enhanced by the competitive displacement of the drug from the ß-CD cavity by cholesterol, the membrane component. The ACE method here developed can be used to optimize the drug release from CD complexes and the drug transfer into model membranes.

Modeling the ion transfer and polarization of ion exchange membranes in bioelectrochemical systems.

Science.gov (United States)

Harnisch, Falk; Warmbier, Robert; Schneider, Ralf; Schröder, Uwe

2009-06-01

An explicit numerical model for the charge balancing ion transfer across monopolar ion exchange membranes under conditions of bioelectrochemical systems is presented. Diffusion and migration equations have been solved according to the Nernst-Planck Equation and the resulting ion concentrations, pH values and the resistance values of the membrane for different conditions were computed. The modeling results underline the principle limitations of the application of ion exchange membranes in biological fuel cells and electrolyzers, caused by the inherent occurrence of a pH-gradient between anode and cathode compartment, and an increased ohmic membrane resistance at decreasing electrolyte concentrations. Finally, the physical and numerical limitations of the model are discussed.

Modeling the improvement of ultrafiltration membrane mass transfer when using biofiltration pretreatment in surface water applications.

Science.gov (United States)

Netcher, Andrea C; Duranceau, Steven J

2016-03-01

In surface water treatment, ultrafiltration (UF) membranes are widely used because of their ability to supply safe drinking water. Although UF membranes produce high-quality water, their efficiency is limited by fouling. Improving UF filtrate productivity is economically desirable and has been attempted by incorporating sustainable biofiltration processes as pretreatment to UF with varying success. The availability of models that can be applied to describe the effectiveness of biofiltration on membrane mass transfer are lacking. In this work, UF water productivity was empirically modeled as a function of biofilter feed water quality using either a quadratic or Gaussian relationship. UF membrane mass transfer variability was found to be governed by the dimensionless mass ratio between the alkalinity (ALK) and dissolved organic carbon (DOC). UF membrane productivity was optimized when the biofilter feed water ALK to DOC ratio fell between 10 and 14. Copyright © 2015 Elsevier Ltd. All rights reserved.

Transfer of fibroblast sheets cultured on thermoresponsive dishes with membranes.

Science.gov (United States)

Kawecki, Marek; Kraut, Małgorzata; Klama-Baryła, Agnieszka; Łabuś, Wojciech; Kitala, Diana; Nowak, Mariusz; Glik, Justyna; Sieroń, Aleksander L; Utrata-Wesołek, Alicja; Trzebicka, Barbara; Dworak, Andrzej; Szweda, Dawid

2016-06-01

In cell or tissue engineering, it is essential to develop a support for cell-to-cell adhesion, which leads to the generation of cell sheets connected by extracellular matrix. Such supports must be hydrophobic and should result in a detachable cell sheet. A thermoresponsive support that enables the cultured cell sheet to detach using only a change in temperature could be an interesting alternative in regenerative medicine. The aim of this study was to evaluate plates covered with thermoresponsive polymers as supports for the formation of fibroblast sheets and to develop a damage-free procedure for cell sheet transfer with the use of membranes as transfer tools. Human skin fibroblasts were seeded on supports coated with a thermoresponsive polymer: commercial UpCell™ dishes (NUNC™) coated with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and dishes coated with thermoresponsive poly(tri(ethylene glycol) monoethyl ether methacrylate) (P(TEGMA-EE)). Confluent fibroblast sheets were effectively cultured and harvested from both commercial PNIPAM-coated dishes and laboratory P(TEGMA-EE)-coated dishes. To transfer a detached cell sheet, two membranes, Immobilon-P(®) and SUPRATHEL(®), were examined. The use of SUPRATHEL for relocating the cell sheets opens a new possibility for the clinical treatment of wounds. This study established the background for implementing thermoresponsive supports for transplanting in vitro cultured fibroblasts.

Clean Transfer of Large Graphene Single Crystals for High-Intactness Suspended Membranes and Liquid Cells.

Science.gov (United States)

Zhang, Jincan; Lin, Li; Sun, Luzhao; Huang, Yucheng; Koh, Ai Leen; Dang, Wenhui; Yin, Jianbo; Wang, Mingzhan; Tan, Congwei; Li, Tianran; Tan, Zhenjun; Liu, Zhongfan; Peng, Hailin

2017-07-01

The atomically thin 2D nature of suspended graphene membranes holds promising in numerous technological applications. In particular, the outstanding transparency to electron beam endows graphene membranes great potential as a candidate for specimen support of transmission electron microscopy (TEM). However, major hurdles remain to be addressed to acquire an ultraclean, high-intactness, and defect-free suspended graphene membrane. Here, a polymer-free clean transfer of sub-centimeter-sized graphene single crystals onto TEM grids to fabricate large-area and high-quality suspended graphene membranes has been achieved. Through the control of interfacial force during the transfer, the intactness of large-area graphene membranes can be as high as 95%, prominently larger than reported values in previous works. Graphene liquid cells are readily prepared by π-π stacking two clean single-crystal graphene TEM grids, in which atomic-scale resolution imaging and temporal evolution of colloid Au nanoparticles are recorded. This facile and scalable production of clean and high-quality suspended graphene membrane is promising toward their wide applications for electron and optical microscopy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theoretical studies on membrane-based gas separation using computational fluid dynamics (CFD) of mass transfer

International Nuclear Information System (INIS)

Sohrabi, M.R.; Marjani, A.; Davallo, M.; Moradi, S.; Shirazian, S.

2011-01-01

A 2D mass transfer model was developed to study carbon dioxide removal by absorption in membrane contactors. The model predicts the steady state absorbent and carbon dioxide concentrations in the membrane by solving the conservation equations. The continuity equations for three sub domains of the membrane contactor involving the tube; membrane and shell were obtained and solved by finite element method (FEM). The model was based on 'non-wetted mode' in which the gas phase filled the membrane pores. Laminar parabolic velocity profile was used for the liquid flow in the tube side; whereas, the gas flow in the shell side was characterized by Happel's free surface model. Axial and radial diffusion transport inside the shell, through the membrane, and within the tube side of the contactor was considered in the mass transfer model. The predictions of percent CO/sub 2/ removal obtained by modeling were compared with the experimental values obtained from literature. They were the experimental results for CO/sub 2/ removal from CO/sub 2//N/sub 2/ gas mixture with amines aqueous solutions as the liquid solvent using polypropylene membrane contactor. The modeling predictions were in good agreement with the experimental values for different values of gas and liquid flow rates. (author)

Interosseous membrane window size for tibialis posterior tendon transfer-Geometrical and MRI analysis.

Science.gov (United States)

Wagner, Pablo; Ortiz, Cristian; Vela, Omar; Arias, Paul; Zanolli, Diego; Wagner, Emilio

2016-09-01

Tibialis posterior (TP) tendon transfer through the interosseous membrane is commonly performed in Charcot-Marie-Tooth disease. In order to avoid entrapment of this tendon, no clear recommendation relative to the interosseous membrane (IOM) incision size has been made. Analyze the TP size at the transfer level and therefore determine the most adequate IOM window size to avoid muscle entrapment. Eleven lower extremity magnetic resonances were analyzed. TP muscle measurements were made in axial views, obtaining the medial-lateral and antero-posterior diameter at various distances from the medial malleolus tip. The distance from the posterior to anterior compartment was also measured. These measurements were applied to a mathematical model to predict the IOM window size necessary to allow an ample TP passage in an oblique direction. The average tendon diameter (confidence-interval) at 15cm proximal to the medial malleolus tip was 19.47mm (17.47-21.48). The deep posterior compartment to anterior compartment distance was 10.97mm (9.03-12.90). Using a mathematical model, the estimated IOM window size ranges from 4.2 to 4.9cm. The IOM window size is of utmost importance in trans-membrane TP transfers, given that if equal or smaller than the transposed tendon oblique diameter, a high entrapment risk exists. A membrane window of 5cm or 2.5 times the size of the tendon diameter should be performed in order to theoretically diminish this complication. Copyright © 2015 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

M-momentum transfer between gravitons, membranes, and fivebranes as perturbative gauge theory processes

International Nuclear Information System (INIS)

Keski-Vakkuri, E.; Kraus, P.

1998-01-01

Polchinski and Pouliot have shown that M-momentum transfer between membranes in supergravity can be understood as a non-perturbative instanton effect in gauge theory. Here we consider a dual process: electric flux transmission between D-branes. We show that this process can be described in perturbation theory as virtual string pair creation, and is closely related to Schwinger's treatment of the pair creation of charged particles in a uniform electric field. Through the application of dualities, our perturbative calculation gives results for various non-perturbative amplitudes, including M-momentum transfer between gravitons, membranes and longitudinal fivebranes. Thus perturbation theory plus dualities are sufficient to demonstrate agreement between supergravity and gauge theory for a number of M-momentum transferring processes. A variety of other processes where branes are transmitted between branes, e.g. (p,q)-string transmission in IIB theory, can also be studied. We discuss the implications of our results for proving the eleven-dimensional Lorentz invariance of matrix theory. (orig.)

Evidence for Transfer of Membranes from Mesenchymal Stem Cells to HL-1 Cardiac Cells.

Science.gov (United States)

Boomsma, Robert A; Geenen, David L

2014-01-01

This study examined the interaction of mouse bone marrow mesenchymal stem cells (MSC) with cardiac HL-1 cells during coculture by fluorescent dye labeling and then flow cytometry. MSC were layered onto confluent HL-1 cell cultures in a 1 : 4 ratio. MSC gained gap junction permeant calcein from HL-1 cells after 4 hours which was partially reduced by oleamide. After 20 hours, 99% MSC gained calcein, unaffected by oleamide. Double-labeling HL-1 cells with calcein and the membrane dye DiO resulted in transfer of both calcein and DiO to MSC. When HL-1 cells were labeled with calcein and MSC with DiO, MSC gained calcein while HL-1 cells gained DiO. Very little fusion was observed since more than 90% Sca-1 positive MSC gained DiO from HL-1 cells while less than 9% gained gap junction impermeant CMFDA after 20 hours with no Sca-1 transfer to HL-1 cells. Time dependent transfer of membrane DiD was observed from HL-1 cells to MSC (100%) and vice versa (50%) after 20 hours with more limited transfer of CMFDA. These results demonstrate that MSC and HL-1 cells exchange membrane components which may account for some of the beneficial effect of MSC in the heart after myocardial infarction.

Determinants of oxygen and carbon dioxide transfer during extracorporeal membrane oxygenation in an experimental model of multiple organ dysfunction syndrome.

Science.gov (United States)

Park, Marcelo; Costa, Eduardo Leite Vieira; Maciel, Alexandre Toledo; Silva, Débora Prudêncio E; Friedrich, Natalia; Barbosa, Edzangela Vasconcelos Santos; Hirota, Adriana Sayuri; Schettino, Guilherme; Azevedo, Luciano Cesar Pontes

2013-01-01

Extracorporeal membrane oxygenation (ECMO) has gained renewed interest in the treatment of respiratory failure since the advent of the modern polymethylpentene membranes. Limited information exists, however, on the performance of these membranes in terms of gas transfers during multiple organ failure (MOF). We investigated determinants of oxygen and carbon dioxide transfer as well as biochemical alterations after the circulation of blood through the circuit in a pig model under ECMO support before and after induction of MOF. A predefined sequence of blood and sweep flows was tested before and after the induction of MOF with fecal peritonitis and saline lavage lung injury. In the multivariate analysis, oxygen transfer had a positive association with blood flow (slope = 66, Pmembrane PaCO(2) (slope = -0.96, P = 0.001) and SatO(2) (slope = -1.7, Ptransfer had a positive association with blood flow (slope = 17, Pmembrane PaCO(2) (slope = 1.2, Ptransfers were significantly determined by blood flow. Oxygen transfer was modulated by the pre-membrane SatO(2) and CO(2), while carbon dioxide transfer was affected by the gas flow, pre-membrane CO(2) and hemoglobin.

Electrostatic models of electron-driven proton transfer across a lipid membrane

Energy Technology Data Exchange (ETDEWEB)

Smirnov, Anatoly Yu; Nori, Franco [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan); Mourokh, Lev G [Department of Physics, Queens College, The City University of New York, Flushing, NY 11367 (United States)

2011-06-15

We present two models for electron-driven uphill proton transport across lipid membranes, with the electron energy converted to the proton gradient via the electrostatic interaction. In the first model, associated with the cytochrome c oxidase complex in the inner mitochondria membranes, the electrostatic coupling to the site occupied by an electron lowers the energy level of the proton-binding site, making proton transfer possible. In the second model, roughly describing the redox loop in a nitrate respiration of E. coli bacteria, an electron displaces a proton from the negative side of the membrane to a shuttle, which subsequently diffuses across the membrane and unloads the proton to its positive side. We show that both models can be described by the same approach, which can be significantly simplified if the system is separated into several clusters, with strong Coulomb interaction inside each cluster and weak transfer couplings between them. We derive and solve the equations of motion for the electron and proton creation/annihilation operators, taking into account the appropriate Coulomb terms, tunnel couplings, and the interaction with the environment. For the second model, these equations of motion are solved jointly with a Langevin-type equation for the shuttle position. We obtain expressions for the electron and proton currents and determine their dependence on the electron and proton voltage build-ups, on-site charging energies, reorganization energies, temperature, and other system parameters. We show that the quantum yield in our models can be up to 100% and the power-conversion efficiency can reach 35%.

Electrostatic models of electron-driven proton transfer across a lipid membrane

International Nuclear Information System (INIS)

Smirnov, Anatoly Yu; Nori, Franco; Mourokh, Lev G

2011-01-01

We present two models for electron-driven uphill proton transport across lipid membranes, with the electron energy converted to the proton gradient via the electrostatic interaction. In the first model, associated with the cytochrome c oxidase complex in the inner mitochondria membranes, the electrostatic coupling to the site occupied by an electron lowers the energy level of the proton-binding site, making proton transfer possible. In the second model, roughly describing the redox loop in a nitrate respiration of E. coli bacteria, an electron displaces a proton from the negative side of the membrane to a shuttle, which subsequently diffuses across the membrane and unloads the proton to its positive side. We show that both models can be described by the same approach, which can be significantly simplified if the system is separated into several clusters, with strong Coulomb interaction inside each cluster and weak transfer couplings between them. We derive and solve the equations of motion for the electron and proton creation/annihilation operators, taking into account the appropriate Coulomb terms, tunnel couplings, and the interaction with the environment. For the second model, these equations of motion are solved jointly with a Langevin-type equation for the shuttle position. We obtain expressions for the electron and proton currents and determine their dependence on the electron and proton voltage build-ups, on-site charging energies, reorganization energies, temperature, and other system parameters. We show that the quantum yield in our models can be up to 100% and the power-conversion efficiency can reach 35%.

Oxygen Transfer Model for a Flow-Through Hollow-Fiber Membrane Biofilm Reactor

DEFF Research Database (Denmark)

Gilmore, K. R.; Little, J. C.; Smets, Barth F.

2009-01-01

overpredicted the oxygen transfer by a factor of 1.3 relative to the result calculated from the outlet gas oxygen concentration, which was considered the most accurate of the measured benchmarks. A mass transfer coefficient derived from the clean water testing with oxygen sensors at the membrane......-liquid interface was the most accurate of the predictive models (overpredicted by a factor of 1.1) while a coefficient determined by measuring bulk liquid dissolved oxygen underpredicted the oxygen transfer by a factor of 3. The mechanistic model was found to be an adequate tool for design because it used...

Constructing Functional Ionic Membrane Surface by Electrochemically Mediated Atom Transfer Radical Polymerization

Directory of Open Access Journals (Sweden)

Fen Ran

2016-01-01

Full Text Available The sodium polyacrylate (PAANa contained polyethersulfone membrane that was fabricated by preparation of PES-NH2 via nonsolvent phase separation method, the introduction of bromine groups as active sites by grafting α-Bromoisobutyryl bromide, and surface-initiated electrochemically atom transfer radical polymerization (SI-eATRP of sodium acrylate (AANa on the surface of PES membrane. The polymerization could be controlled by reaction condition, such as monomer concentration, electric potential, polymerization time, and modifier concentration. The membrane surface was uniform when the monomer concentration was 0.9 mol/L, the electric potential was −0.12 V, the polymerization time was 8 h, and the modifier concentration was 2 wt.%. The membrane showed excellent hydrophilicity and blood compatibility. The water contact angle decreased from 84° to 68° and activated partial thromboplastin increased from 51 s to 84 s after modification of the membranes.

Interface for Light-Driven Electron Transfer by Photosynthetic Complexes Across Block Copolymer Membranes.

Science.gov (United States)

Kuang, Liangju; Olson, Tien L; Lin, Su; Flores, Marco; Jiang, Yunjiang; Zheng, Wan; Williams, JoAnn C; Allen, James P; Liang, Hongjun

2014-03-06

Incorporation of membrane proteins into nanodevices to mediate recognition and transport in a collective and scalable fashion remains a challenging problem. We demonstrate how nanoscale photovoltaics could be designed using robust synthetic nanomembranes with incorporated photosynthetic reaction centers (RCs). Specifically, RCs from Rhodobacter sphaeroides are reconstituted spontaneously into rationally designed polybutadiene membranes to form hierarchically organized proteopolymer membrane arrays via a charge-interaction-directed reconstitution mechanism. Once incorporated, the RCs are fully active for prolonged periods based upon a variety of spectroscopic measurements, underscoring preservation of their 3D pigment configuration critical for light-driven charge transfer. This result provides a strategy to construct solar conversion devices using structurally versatile proteopolymer membranes with integrated RC functions to harvest broad regions of the solar spectrum.

Intramolecular energy transfer at donor-acceptor interactions in model and biological membranes

International Nuclear Information System (INIS)

Umarova, Fatima T.

2011-01-01

Intramolecular triplet-triplet energy transfer between molecules of sensibilisator and photochrome for registration of protein interactions in the membrane preparation of Na,K-ATPase was investigated. Erythrosinithiocyanate (ERITC) was used as the triplet label of sensibilisator, and 4-acetoamido-4 -isothiocyanatostilbene-2,2 disullfonic acid (SITS) was used as the photochrome label. Na,K-ATPase preparations were covalently bound with ERITC in active centre of enzyme, and SITS molecules were covalently bound by NH2-groups. In model system, in chymotrypsinogene molecule, SITS and ERITC labels were used also. The cis-trans-isomerization of SITS was initiated by triplet-triplet energy transfer from light excited ERITC molecule to photochrome. The kinetics of isomerization was recorded by the SITS fluorescence measurements. The constant of rate of triplet-triplet energy transfer from ERITC to cis-isomers of SITS in Na,K-ATPase was determined as (3-7)x10 3 M -1 s -1 , and in model system it equals 1x 10 7 M 1 s -1 . The value of energy transfer between loos molecules of erythrosine and SITS in buffer solution equaled to 7x10 7 M -1 s -1 . This drop of R m y in the membrane preparation of Na,K-ATPase at 10 4 reflected the decrease in the frequency of label collisions caused by the increase in the media viscosity and steric hindrances. (author)

Neutralized ion beam modification of cellulose membranes for study of ion charge effect on ion-beam-induced DNA transfer

Science.gov (United States)

Prakrajang, K.; Sangwijit, K.; Anuntalabhochai, S.; Wanichapichart, P.; Yu, L. D.

2012-02-01

Low-energy ion beam biotechnology (IBBT) has recently been rapidly developed worldwide. Ion-beam-induced DNA transfer is one of the important applications of IBBT. However, mechanisms involved in this application are not yet well understood. In this study plasma-neutralized ion beam was applied to investigate ion charge effect on induction of DNA transfer. Argon ion beam at 7.5 keV was neutralized by RF-driven plasma in the beam path and then bombarded cellulose membranes which were used as the mimetic plant cell envelope. Electrical properties such as impedance and capacitance of the membranes were measured after the bombardment. An in vitro experiment on plasmid DNA transfer through the cellulose membrane was followed up. The results showed that the ion charge input played an important role in the impedance and capacitance changes which would affect DNA transfer. Generally speaking, neutral particle beam bombardment of biologic cells was more effective in inducing DNA transfer than charged ion beam bombardment.

Water Activated Graphene Oxide Transfer Using Wax Printed Membranes for Fast Patterning of a Touch Sensitive Device.

Science.gov (United States)

Baptista-Pires, Luis; Mayorga-Martínez, Carmen C; Medina-Sánchez, Mariana; Montón, Helena; Merkoçi, Arben

2016-01-26

We demonstrate a graphene oxide printing technology using wax printed membranes for the fast patterning and water activation transfer using pressure based mechanisms. The wax printed membranes have 50 μm resolution, longtime stability and infinite shaping capability. The use of these membranes complemented with the vacuum filtration of graphene oxide provides the control over the thickness. Our demonstration provides a solvent free methodology for printing graphene oxide devices in all shapes and all substrates using the roll-to-roll automatized mechanism present in the wax printing machine. Graphene oxide was transferred over a wide variety of substrates as textile or PET in between others. Finally, we developed a touch switch sensing device integrated in a LED electronic circuit.

Trans-membrane electron transfer in red blood cells immobilized in a chitosan film on a glassy carbon electrode

International Nuclear Information System (INIS)

Yu, Chunmei; Wang, Li; Zhu, Zhenkun; Bao, Ning; Gu, Haiying

2014-01-01

We have studied the trans-membrane electron transfer in human red blood cells (RBCs) immobilized in a chitosan film on a glassy carbon electrode (GCE). Electron transfer results from the presence of hemoglobin (Hb) in the RBCs. The electron transfer rate (k s ) of Hb in RBCs is 0.42 s −1 , and <1.13 s −1 for Hb directly immobilized in the chitosan film. Only Hb molecules in RBCs that are closest to the plasma membrane and the surface of the electrode can undergo electron transfer to the electrode. The immobilized RBCs displayed sensitive electrocatalytic response to oxygen and hydrogen peroxide. It is believed that this cellular biosensor is of potential significance in studies on the physiological status of RBCs based on observing their electron transfer on the modified electrode. (author)

Excitation energy transfer between Light-harvesting complex II and Photosystem I in reconstituted membranes.

Science.gov (United States)

Akhtar, Parveen; Lingvay, Mónika; Kiss, Teréz; Deák, Róbert; Bóta, Attila; Ughy, Bettina; Garab, Győző; Lambrev, Petar H

2016-04-01

Light-harvesting complex II (LHCII), the major peripheral antenna of Photosystem II in plants, participates in several concerted mechanisms for regulation of the excitation energy and electron fluxes in thylakoid membranes. In part, these include interaction of LHCII with Photosystem I (PSI) enhancing the latter's absorption cross-section - for example in the well-known state 1 - state 2 transitions or as a long-term acclimation to high light. In this work we examined the capability of LHCII to deliver excitations to PSI in reconstituted membranes in vitro. Proteoliposomes with native plant thylakoid membrane lipids and different stoichiometric ratios of LHCII:PSI were reconstituted and studied by steady-state and time-resolved fluorescence spectroscopy. Fluorescence emission from LHCII was strongly decreased in PSI-LHCII membranes due to trapping of excitations by PSI. Kinetic modelling of the time-resolved fluorescence data revealed the existence of separate pools of LHCII distinguished by the time scale of energy transfer. A strongly coupled pool, equivalent to one LHCII trimer per PSI, transferred excitations to PSI with near-unity efficiency on a time scale of less than 10ps but extra LHCIIs also contributed significantly to the effective antenna size of PSI, which could be increased by up to 47% in membranes containing 3 LHCII trimers per PSI. The results demonstrate a remarkable competence of LHCII to increase the absorption cross-section of PSI, given the opportunity that the two types of complexes interact in the membrane. Copyright © 2016 Elsevier B.V. All rights reserved.

Model of mouth-to-mouth transfer of bacterial lipoproteins through inner membrane LolC, periplasmic LolA, and outer membrane LolB.

Science.gov (United States)

Okuda, Suguru; Tokuda, Hajime

2009-04-07

Outer membrane-specific lipoproteins in Escherichia coli are released from the inner membrane by an ATP-binding cassette transporter, the LolCDE complex, which causes the formation of a soluble complex with a periplasmic molecular chaperone, LolA. LolA then transports lipoproteins to the outer membrane where an outer membrane receptor, LolB, incorporates lipoproteins into the outer membrane. The molecular mechanisms underlying the Lol-dependent lipoprotein sorting have been clarified in detail. However, it remained unclear how Lol factors interact with each other to conduct very efficient lipoprotein transfer in the periplasm where ATP is not available. To address this issue, a photo-reactive phenylalanine analogue, p-benzoyl-phenylalanine, was introduced at various positions of LolA and LolB, of which the overall structures are very similar and comprise an incomplete beta-barrel with a hydrophobic cavity inside. Cells expressing LolA or LolB derivatives containing the above analogue were irradiated with UV for in vivo photo-cross-linking. These analyses revealed a hot area in the same region of LolA and LolB, through which LolA and LolB interact with each other. This area is located at the entrance of the hydrophobic cavity. Moreover, this area in LolA is involved in the interaction with a membrane subunit, LolC, whereas no cross-linking occurs between LolA and the other membrane subunit, LolE, or ATP-binding subunit LolD, despite the structural similarity between LolC and LolE. The hydrophobic cavities of LolA and LolB were both found to bind lipoproteins inside. These results indicate that the transfer of lipoproteins through Lol proteins occurs in a mouth-to-mouth manner.

Mass transfer ranking of polylysine, poly-ornithine and poly-methylene-co-guanidine microcapsule membranes using a single low molecular mass marker

Directory of Open Access Journals (Sweden)

Rosinski Stefan

2003-01-01

Full Text Available On the long way to clinical transplantable hybrid systems, comprising of cells, acting as immuno-protected bioreactors microencapsulated in a polymeric matrix and delivering desired factors (proteins, hormones, enzymes etc to the patient's body, an important step is the optimization of the microcapsule. This topic includes the selection of a proper coating membrane which could fulfil, first of all, the mass transfer as well as biocompatibility, stability and durability requirements. Three different membranes from polymerised aminoacids, formed around exactly identical alginate gel cores, were considered, concerning their mass transport properties, as potential candidates in this task. The results of the evaluation of the mass ingress and mass transfer coefficient h for the selected low molecular mass marker, vitamin B12, in poly-L-lysine (HPLL poly-L-ornithine (HPLO and poly-methylene-co-guanidine hydrochloride (HPMCG membrane alginate microcapsules demonstrate the advantage of using the mass transfer approach to a preliminary screening of various microcapsule formulations. Applying a single marker and evaluating mass transfer coefficients can help to quickly rank the investigated membranes and microcapsules according to their permeability. It has been demonstrated that HPLL, HPLO and HPMCG microcapsules differ from each other by a factor of two concerning the rate of low molecular mass marker transport. Interesting differences in mass transfer through the membrane in both directions in-out was also found, which could possibly be related to the membrane asymmetry.

Transfer Printed Nanomembranes for Heterogeneously Integrated Membrane Photonics

Directory of Open Access Journals (Sweden)

Hongjun Yang

2015-11-01

Full Text Available Heterogeneous crystalline semiconductor nanomembrane (NM integration is investigated for single-layer and double-layer Silicon (Si NM photonics, III-V/Si NM lasers, and graphene/Si NM total absorption devices. Both homogeneous and heterogeneous integration are realized by the versatile transfer printing technique. The performance of these integrated membrane devices shows, not only intact optical and electrical characteristics as their bulk counterparts, but also the unique light and matter interactions, such as Fano resonance, slow light, and critical coupling in photonic crystal cavities. Such a heterogeneous integration approach offers tremendous practical application potentials on unconventional, Si CMOS compatible, and high performance optoelectronic systems.

The influence of polymeric membrane gas spargers on hydrodynamics and mass transfer in bubble column bioreactors.

Science.gov (United States)

Tirunehe, Gossaye; Norddahl, B

2016-04-01

Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air-water and air-CMC (Carboxymethyl cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas-liquid mediums. CMC solutions were employed in the study to simulate rheological properties of bioreactor broth. Gas holdup, bubble size distribution, interfacial area and gas-liquid mass transfer were studied in the homogeneous bubbly flow hydrodynamic regime with superficial gas velocity (U(G)) range of 0.0004-0.0025 m/s. The study indicated that the tubular membrane sparger produced the highest gas holdup and densely populated fine bubbles with narrow size distribution. An increase in liquid viscosity promoted a shift in bubble size distribution to large stable bubbles and smaller specific interfacial area. The tubular membrane sparger achieved greater interfacial area and an enhanced overall mass transfer coefficient (K(L)a) by a factor of 1.2-1.9 compared to the flat sheet membrane.

2,2'-Bis(monoacylglycero) PO4 (BMP), but Not 3,1'-BMP, increases membrane curvature stress to enhance α-tocopherol transfer protein binding to membranes.

Science.gov (United States)

Baptist, Matilda; Panagabko, Candace; Nickels, Jonathan D; Katsaras, John; Atkinson, Jeffrey

2015-03-01

Previous work revealed that α-tocopherol transfer protein (α-TTP) co-localizes with bis(monoacylglycero)phosphate (BMP) in late endosomes. BMP is a lipid unique to late endosomes and is believed to induce membrane curvature and support the multivesicular nature of this organelle. We examined the effect of BMP on α-TTP binding to membranes using dual polarization interferometry and vesicle-binding assay. α-TTP binding to membranes is increased by the curvature-inducing lipid BMP. α-TTP binds to membranes with greater affinity when they contain the 2,2'-BMP versus 3,1'-BMP isomers.

Tracing of backward energy transfer from LH1 to LH2 in photosynthetic membranes grown under high and low irradiation.

Directory of Open Access Journals (Sweden)

Lanzani G.

2013-03-01

Full Text Available By introducing derivative transient absorption spectroscopy, we obtain rate constants for backward and forward energy transfer between LH1 and LH2 complexes in purple bacterial membranes. We find that backward energy transfer is strongly reduced in membranes grown under low irradiation conditions, compared to high light grown ones. We conclude that backward energy transfer is managed actively by the bacteria to avoid LH1 exciton deactivation under high irradiation conditions. The analytical method is generally applicable to excitonically coupled systems.

Nonlinear Lyapunov-based boundary control of distributed heat transfer mechanisms in membrane distillation plant

KAUST Repository

Eleiwi, Fadi; Laleg-Kirati, Taous-Meriem

2015-01-01

This paper presents a nonlinear Lyapunov-based boundary control for the temperature difference of a membrane distillation boundary layers. The heat transfer mechanisms inside the process are modeled with a 2D advection-diffusion equation. The model

In Situ Blotting : A Novel Method for Direct Transfer of Native Proteins from Sectioned Tissue to Blotting Membrane

NARCIS (Netherlands)

Okabe, Masashi; Nyakas, Csaba; Buwalda, Bauke; Luiten, Paul G.M.

1993-01-01

We describe a novel technique for direct transfer of native proteins from unfixed frozen tissue sections to an immobilizing matrix, e.g., nitrocellulose, polyvinyliden difluoride, or positively charged nylon membranes. Proteins are directly blotted onto the membrane, providing optimal accessibility

Charge Transfer Resistance and Differential Capacity of the Plasticized PVC Membrane/Water Interface

Czech Academy of Sciences Publication Activity Database

Langmaier, Jan; Stejskalová, Květoslava; Samec, Zdeněk

2002-01-01

Roč. 521, 1/2 (2002), s. 81-86 ISSN 0022-0728 R&D Projects: GA AV ČR IAA4040902 Institutional research plan: CEZ:AV0Z4040901 Keywords : impedance * PVC plasticized membrane * ion transfer kinetics Subject RIV: CG - Electrochemistry Impact factor: 2.027, year: 2002

Analysis of the 22-NBD-cholesterol transfer between liposome membranes and its relation to the intermembrane exchange of 25-hydroxycholesterol.

Science.gov (United States)

Ishii, Haruyuki; Shimanouchi, Toshinori; Umakoshi, Hiroshi; Walde, Peter; Kuboi, Ryoichi

2010-05-01

The transfer of 22-NBD-cholesterol (22-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3-ol) between two liposome membranes was quantitatively analyzed by using the fluorescence resonance energy transfer (FRET) method. Liposomes labeled with both 22-NBD-cholesterol and a rhodamine-labeled phosphatidylethanolamine (Rh-DHPE) were used as donor liposomes, and the 22-NBD-cholesterol transfer from these donor liposomes to acceptor liposomes prepared from same type of phosphatidylcholine was monitored. The transfer kinetics was found to be composed of a fast and a slow phase, and all kinetic measurements could be fitted with a bi-exponential model. The results obtained indicate that the 22-NBD-cholesterol transfer kinetics between liposome membranes depends on the fluidity of the liposome used and that the curvature may affect the kinetics. Furthermore, the behavior of 22-NBD-cholesterol in lipid membrane is similar to that of the oxysterol 25-hydroxycholesterol rather than cholesterol. It is proposed that 22-NBD-cholesterol can be a useful fluorescent probe to mimic the intermembrane transfer of oxidized cholesterols like 25-hydroxycholesterol, rather than that of cholesterol itself. 2010 Elsevier B.V. All rights reserved.

Two-dimensional Forster resonance energy transfer (2-D FRET) and the membrane raft hypothesis

OpenAIRE

Acasandrei, Maria; Dale, Robert; VAN DE VEN, Martin; AMELOOT, Marcel

2006-01-01

A model for analyzing Forster resonance energy transfer (FRET) data in relation to the cell plasma membrane raft hypothesis is developed to take into account: (a) the distribution of FRET donors and acceptors at the surface of probing antibody fragments specific for a putative raft component; (b) partitioning of the raft component between raft and non-raft areas of the membrane; and (c) the dependence of the raft partition on the expression level of the considered component. Analysis of relev...

Membrane Contact Sites: Complex Zones for Membrane Association and Lipid Exchange

Science.gov (United States)

Quon, Evan; Beh, Christopher T.

2015-01-01

Lipid transport between membranes within cells involves vesicle and protein carriers, but as agents of nonvesicular lipid transfer, the role of membrane contact sites has received increasing attention. As zones for lipid metabolism and exchange, various membrane contact sites mediate direct associations between different organelles. In particular, membrane contact sites linking the plasma membrane (PM) and the endoplasmic reticulum (ER) represent important regulators of lipid and ion transfer. In yeast, cortical ER is stapled to the PM through membrane-tethering proteins, which establish a direct connection between the membranes. In this review, we consider passive and facilitated models for lipid transfer at PM–ER contact sites. Besides the tethering proteins, we examine the roles of an additional repertoire of lipid and protein regulators that prime and propagate PM–ER membrane association. We conclude that instead of being simple mediators of membrane association, regulatory components of membrane contact sites have complex and multilayered functions. PMID:26949334

Membrane Contact Sites: Complex Zones for Membrane Association and Lipid Exchange

OpenAIRE

Evan Quon; Christopher T. Beh

2016-01-01

Lipid transport between membranes within cells involves vesicle and protein carriers, but as agents of nonvesicular lipid transfer, the role of membrane contact sites has received increasing attention. As zones for lipid metabolism and exchange, various membrane contact sites mediate direct associations between different organelles. In particular, membrane contact sites linking the plasma membrane (PM) and the endoplasmic reticulum (ER) represent important regulators of lipid and ion transfer...

Mass transfer rate through liquid membranes: interfacial chemical reactions and diffusion as simultaneous permeability controlling factors

International Nuclear Information System (INIS)

Danesi, P.R.; Horwitz, E.P.; Vandegrift, G.F.; Chiarizia, R.

1981-01-01

Equations describing the permeability of a liquid membrane to metal cations have been derived taking into account aqueous diffusion, membrane diffusion, and interfacial chemical reactions as simultaneous permeability controlling factors. Diffusion and chemical reactions have been coupled by a simple model analogous to the one previously described by us to represent liquid-liquid extraction kinetics. The derived equations, which make use of experimentally determined interfacial reaction mechanisms, qualitatively fit unexplained literature data regarding Cu 2+ transfer through liquid membranes. Their use to predict and optimize membrane permeability in practical separation processes by setting the appropriate concentration of the membrane carrier [LIX 64 (General Mills), a commercial β-hydroxy-oxime] and the pH of the aqueous copper feed solution is briefly discussed. 4 figures

Lignin-based membranes for electrolyte transference

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiao; Garcia-Valls, Ricard [Departament d' Enginyeria Quimica, Escola Tecnica Superior d' Enginyeria Quimica, Universitat Rovira i Virgili, Av. Paisos Catalans 26, 43007 Tarragona (Spain); Benavente, Juana [Department of Applied Fisics, Faculty of Science, University of Malaga, Malaga (Spain)

2005-08-18

Homogeneous PSf-LS membranes are formed by incorporating Lignosulfonate (LS) into the Polysulfone (PSf) network. LS obtained from sulfite pulping process contains sulfonic acid groups that will act as proton transport media. PSf-LS membranes were characterized by reflectance Infrared and scanning electron microscopy. LS showed significant influence on membrane morphology. Higher LS concentration caused a decrease in macrovoid formation and induced larger pores. Precipitation temperature was investigated as influencing parameter. Proton fluxes through PSf-LS membranes were measured by transport experiments. Impedance analysis confirmed that PSf-LS membranes possess ion conductivity. The selected PSf-LS membranes exhibited high selectivity for proton over methanol, which indicates their potential applicability in direct methanol fuel cell (DMFC). (author)

Structural basis of sterol recognition and nonvesicular transport by lipid transfer proteins anchored at membrane contact sites.

Science.gov (United States)

Tong, Junsen; Manik, Mohammad Kawsar; Im, Young Jun

2018-01-30

Membrane contact sites (MCSs) in eukaryotic cells are hotspots for lipid exchange, which is essential for many biological functions, including regulation of membrane properties and protein trafficking. Lipid transfer proteins anchored at membrane contact sites (LAMs) contain sterol-specific lipid transfer domains [StARkin domain (SD)] and multiple targeting modules to specific membrane organelles. Elucidating the structural mechanisms of targeting and ligand recognition by LAMs is important for understanding the interorganelle communication and exchange at MCSs. Here, we determined the crystal structures of the yeast Lam6 pleckstrin homology (PH)-like domain and the SDs of Lam2 and Lam4 in the apo form and in complex with ergosterol. The Lam6 PH-like domain displays a unique PH domain fold with a conserved N-terminal α-helix. The Lam6 PH-like domain lacks the basic surface for phosphoinositide binding, but contains hydrophobic patches on its surface, which are critical for targeting to endoplasmic reticulum (ER)-mitochondrial contacts. Structures of the LAM SDs display a helix-grip fold with a hydrophobic cavity and a flexible Ω1-loop as a lid. Ergosterol is bound to the pocket in a head-down orientation, with its hydrophobic acyl group located in the tunnel entrance. The Ω1-loop in an open conformation is essential for ergosterol binding by direct hydrophobic interaction. Structural comparison suggested that the sterol binding mode of the Lam2 SD2 is likely conserved among the sterol transfer proteins of the StARkin superfamily. Structural models of full-length Lam2 correlated with the sterol transport function at the membrane contact sites.

Mass transfer modeling on the separation of tantalum and niobium from dilute hydrofluoric media through a hollow fiber supported liquid membrane

International Nuclear Information System (INIS)

Buachuang, Duenphen; Ramakul, Prakorn; Leepipatpiboon, Natchanun; Pancharoen, Ura

2011-01-01

Highlights: → Simultaneous separation of tantalum and niobium from the mixture solution. → An extraction through a hollow fiber supported liquid membrane (HFSLM). → The effect on tantalum removal found from Aliquat 336. → The mathematical model focusing on the extraction side of the liquid membrane system was presented. → The mass transfer coefficients of the aqueous feed (k i ) and the organic membrane phase (k m ) for the system were estimated as 1.19 x 10 -5 and 1.39 x 10 -7 cm/s, respectively. → Experimental data and theoretical values were found to be in good agreement when the concentration of Aliquat336 in the membrane phase was below 4% (v/v). - Abstract: The separation of a mixture of tantalum and niobium in dilute hydrofluoric media via hollow fiber supported liquid membrane (HFSLM) was examined. Quaternary ammonium salt (Aliquat336) diluted in kerosene was used as a carrier. The various effects on the transport and separation of tantalum and niobium were studied: concentration of hydrofluoric acid in the feed solution, concentration of the carrier (Aliquat336) in the membrane phase, types of stripping solutions (NaClO 4 , thiourea and HCl) and their concentration. The extraction of tantalum in the membrane phase from 0.3 M hydrofluoric acid (HF) by 3% (v/v) Aliquat336 was achieved by leaving niobium in the feed solution. Quantitative recovery of tantalum was achieved by 0.2 M NaClO 4 . Furthermore, a mathematical model focusing on the extraction side of the liquid membrane system was presented in order to predict the concentration of tantalum at different times. The mass transfer coefficients of the aqueous feed (k i ) and the organic membrane phase (k m ) were estimated as 1.19 x 10 -5 and 1.39 x 10 -7 cm/s, respectively. Therefore, the mass transfer limiting step is the diffusion of tantalum-Aliquat336 through the liquid membrane. Moreover, mass transfer modeling was performed and the validity of the developed model evaluated. Experimental

Mass transfer modeling on the separation of tantalum and niobium from dilute hydrofluoric media through a hollow fiber supported liquid membrane

Energy Technology Data Exchange (ETDEWEB)

Buachuang, Duenphen [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand); Ramakul, Prakorn [Department of Chemical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom 73000 (Thailand); Leepipatpiboon, Natchanun [Chromatography and Separation Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330 (Thailand); Pancharoen, Ura, E-mail: ura.p.@chula.ac.th [Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330 (Thailand)

2011-09-29

Highlights: > Simultaneous separation of tantalum and niobium from the mixture solution. > An extraction through a hollow fiber supported liquid membrane (HFSLM). > The effect on tantalum removal found from Aliquat 336. > The mathematical model focusing on the extraction side of the liquid membrane system was presented. > The mass transfer coefficients of the aqueous feed (k{sub i}) and the organic membrane phase (k{sub m}) for the system were estimated as 1.19 x 10{sup -5} and 1.39 x 10{sup -7} cm/s, respectively. > Experimental data and theoretical values were found to be in good agreement when the concentration of Aliquat336 in the membrane phase was below 4% (v/v). - Abstract: The separation of a mixture of tantalum and niobium in dilute hydrofluoric media via hollow fiber supported liquid membrane (HFSLM) was examined. Quaternary ammonium salt (Aliquat336) diluted in kerosene was used as a carrier. The various effects on the transport and separation of tantalum and niobium were studied: concentration of hydrofluoric acid in the feed solution, concentration of the carrier (Aliquat336) in the membrane phase, types of stripping solutions (NaClO{sub 4}, thiourea and HCl) and their concentration. The extraction of tantalum in the membrane phase from 0.3 M hydrofluoric acid (HF) by 3% (v/v) Aliquat336 was achieved by leaving niobium in the feed solution. Quantitative recovery of tantalum was achieved by 0.2 M NaClO{sub 4}. Furthermore, a mathematical model focusing on the extraction side of the liquid membrane system was presented in order to predict the concentration of tantalum at different times. The mass transfer coefficients of the aqueous feed (k{sub i}) and the organic membrane phase (k{sub m}) were estimated as 1.19 x 10{sup -5} and 1.39 x 10{sup -7} cm/s, respectively. Therefore, the mass transfer limiting step is the diffusion of tantalum-Aliquat336 through the liquid membrane. Moreover, mass transfer modeling was performed and the validity of the

A conserved endoplasmic reticulum membrane protein complex (EMC facilitates phospholipid transfer from the ER to mitochondria.

Directory of Open Access Journals (Sweden)

Sujoy Lahiri

2014-10-01

Full Text Available Mitochondrial membrane biogenesis and lipid metabolism require phospholipid transfer from the endoplasmic reticulum (ER to mitochondria. Transfer is thought to occur at regions of close contact of these organelles and to be nonvesicular, but the mechanism is not known. Here we used a novel genetic screen in S. cerevisiae to identify mutants with defects in lipid exchange between the ER and mitochondria. We show that a strain missing multiple components of the conserved ER membrane protein complex (EMC has decreased phosphatidylserine (PS transfer from the ER to mitochondria. Mitochondria from this strain have significantly reduced levels of PS and its derivative phosphatidylethanolamine (PE. Cells lacking EMC proteins and the ER-mitochondria tethering complex called ERMES (the ER-mitochondria encounter structure are inviable, suggesting that the EMC also functions as a tether. These defects are corrected by expression of an engineered ER-mitochondrial tethering protein that artificially tethers the ER to mitochondria. EMC mutants have a significant reduction in the amount of ER tethered to mitochondria even though ERMES remained intact in these mutants, suggesting that the EMC performs an additional tethering function to ERMES. We find that all Emc proteins interact with the mitochondrial translocase of the outer membrane (TOM complex protein Tom5 and this interaction is important for PS transfer and cell growth, suggesting that the EMC forms a tether by associating with the TOM complex. Together, our findings support that the EMC tethers ER to mitochondria, which is required for phospholipid synthesis and cell growth.

Is There Excitation Energy Transfer between Different Layers of Stacked Photosystem-II-Containing Thylakoid Membranes?

Science.gov (United States)

Farooq, Shazia; Chmeliov, Jevgenij; Trinkunas, Gediminas; Valkunas, Leonas; van Amerongen, Herbert

2016-04-07

We have compared picosecond fluorescence decay kinetics for stacked and unstacked photosystem II membranes in order to evaluate the efficiency of excitation energy transfer between the neighboring layers. The measured kinetics were analyzed in terms of a recently developed fluctuating antenna model that provides information about the dimensionality of the studied system. Independently of the stacking state, all preparations exhibited virtually the same value of the apparent dimensionality, d = 1.6. Thus, we conclude that membrane stacking does not affect the efficiency of the delivery of excitation energy toward the reaction centers but ensures a more compact organization of the thylakoid membranes within the chloroplast and separation of photosystems I and II.

Transfer in SDS of biotinylated proteins from acrylamide gels to an avidin-coated membrane filter.

Science.gov (United States)

Karlin, Arthur; Wang, Chaojian; Li, Jing; Xu, Qiang

2004-06-01

Avidin was covalently linked to aldehyde-derivatized polyethersulfone membrane filters. These filters were used in Western blot analysis of proteins reacted with biotinylation reagents and electrophoresed in sodium dodecyl sulfate (SDS) on polyacrylamide gels. Electrophoretic transfer from the gels to these filters was in 0.1% SDS, in which the covalently bound avidin retained its biotin-binding capacity. We compared Western blots on avidin-coated membrane filters of biotinylated and nonbiotinylated forms of mouse immunoglobulin G (IgG), mouse IgG heavy chain, muscle-type acetylcholine receptor alpha subunit, and fused alpha and beta subunits of receptor. Biotinylated proteins were captured with high specificity compared to their nonbiotinylated counterparts and sensitively detected on the avidin-coated membranes.

The influence of polymeric membrane gas spargers on hydrodynamics and mass transfer in bubble column bioreactors

DEFF Research Database (Denmark)

Tirunehe, Gossay; Norddahl, B.

2016-01-01

Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air–water and air–CMC (Carboxymethyl cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas–liquid mediums. CMC....../s. The study indicated that the tubular membrane sparger produced the highest gas holdup and densely populated fine bubbles with narrow size distribution. An increase in liquid viscosity promoted a shift in bubble size distribution to large stable bubbles and smaller specific interfacial area. The tubular...... membrane sparger achieved greater interfacial area and an enhanced overall mass transfer coefficient (KLa) by a factor of 1.2–1.9 compared to the flat sheet membrane....

From membrane tension to channel gating: A principal energy transfer mechanism for mechanosensitive channels.

Science.gov (United States)

Zhang, Xuejun C; Liu, Zhenfeng; Li, Jie

2016-11-01

Mechanosensitive (MS) channels are evolutionarily conserved membrane proteins that play essential roles in multiple cellular processes, including sensing mechanical forces and regulating osmotic pressure. Bacterial MscL and MscS are two prototypes of MS channels. Numerous structural studies, in combination with biochemical and cellular data, provide valuable insights into the mechanism of energy transfer from membrane tension to gating of the channel. We discuss these data in a unified two-state model of thermodynamics. In addition, we propose a lipid diffusion-mediated mechanism to explain the adaptation phenomenon of MscS. © 2016 The Protein Society.

Microgravity and Charge Transfer in the Neuronal Membrane: Implications for Computational Neurobiology

Science.gov (United States)

Wallace, Ron

1995-01-01

Evidence from natural and artificial membranes indicates that the neural membrane is a liquid crystal. A liquid-to-gel phase transition caused by the application of superposed electromagnetic fields to the outer membrane surface releases spin-correlated electron pairs which propagate through a charge transfer complex. The propagation generates Rydberg atoms in the lipid bilayer lattice. In the present model, charge density configurations in promoted orbitals interact as cellular automata and perform computations in Hilbert space. Due to the small binding energies of promoted orbitals, their automata are highly sensitive to microgravitational perturbations. It is proposed that spacetime is classical on the Rydberg scale, but formed of contiguous moving segments, each of which displays topological equivalence. This stochasticity is reflected in randomized Riemannian tensor values. Spacetime segments interact with charge automata as components of a computational process. At the termination of the algorithm, an orbital of high probability density is embedded in a more stabilized microscopic spacetime. This state permits the opening of an ion channel and the conversion of a quantum algorithm into a macroscopic frequency code.

Synthesis of Graphene Based Membranes: Effect of Substrate Surface Properties on Monolayer Graphene Transfer.

Science.gov (United States)

Kafiah, Feras; Khan, Zafarullah; Ibrahim, Ahmed; Atieh, Muataz; Laoui, Tahar

2017-01-21

In this work, we report the transfer of graphene onto eight commercial microfiltration substrates having different pore sizes and surface characteristics. Monolayer graphene grown on copper by the chemical vapor deposition (CVD) process was transferred by the pressing method over the target substrates, followed by wet etching of copper to obtain monolayer graphene/polymer membranes. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) measurements were carried out to explore the graphene layer transferability. Three factors, namely, the substrate roughness, its pore size, and its surface wetting (degree of hydrophobicity) are found to affect the conformality and coverage of the transferred graphene monolayer on the substrate surface. A good quality graphene transfer is achieved on the substrate with the following characteristics; being hydrophobic (CA > 90°), having small pore size, and low surface roughness, with a CA to RMS (root mean square) ratio higher than 2.7°/nm.

Selective enantioseparation of levocetirizine via a hollow fiber supported liquid membrane and mass transfer prediction

International Nuclear Information System (INIS)

Sunsandee, Niti; Leepipatpiboon, Natchanun; Ramakul, Prakorn

2013-01-01

The enantioselective separation of levocetirizine via a hollow fiber supported liquid membrane was examined. O,O'-dibenzoyl-(2R,3R)-tartaric acid ((-)-DBTA) diluted in 1-decanol was used as a chiral selector extractant. The influence of concentrations of feed and stripping phases, and extractant concentration in the membrane phase, was also investigated. A mathematical model focusing on the extraction side of the liquid membrane system was presented to predict the concentration of levocetirizine at different times. The extraction and recovery of levocetirizine from feed phase were 75.00% and 72.00%, respectively. The mass transfer coefficients at aqueous feed boundary layer (k_f) and the organic liquid membrane phase (k_m) were calculated as 2.41x10"2 and 1.89x10"2 cm/s, respectively. The validity of the developed model was evaluated through a comparison with experimental data, and good agreement was obtained

Membrane Transfer from Mononuclear Cells to Polymorphonuclear Neutrophils Transduces Cell Survival and Activation Signals in the Recipient Cells via Anti-Extrinsic Apoptotic and MAP Kinase Signaling Pathways.

Science.gov (United States)

Li, Ko-Jen; Wu, Cheng-Han; Shen, Chieh-Yu; Kuo, Yu-Min; Yu, Chia-Li; Hsieh, Song-Chou

2016-01-01

The biological significance of membrane transfer (trogocytosis) between polymorphonuclear neutrophils (PMNs) and mononuclear cells (MNCs) remains unclear. We investigated the biological/immunological effects and molecular basis of trogocytosis among various immune cells in healthy individuals and patients with active systemic lupus erythematosus (SLE). By flow cytometry, we determined that molecules in the immunological synapse, including HLA class-I and-II, CD11b and LFA-1, along with CXCR1, are exchanged among autologous PMNs, CD4+ T cells, and U937 cells (monocytes) after cell-cell contact. Small interfering RNA knockdown of the integrin adhesion molecule CD11a in U937 unexpectedly enhanced the level of total membrane transfer from U937 to PMN cells. Functionally, phagocytosis and IL-8 production by PMNs were enhanced after co-culture with T cells. Total membrane transfer from CD4+ T to PMNs delayed PMN apoptosis by suppressing the extrinsic apoptotic molecules, BAX, MYC and caspase 8. This enhancement of activities of PMNs by T cells was found to be mediated via p38- and P44/42-Akt-MAP kinase pathways and inhibited by the actin-polymerization inhibitor, latrunculin B, the clathrin inhibitor, Pitstop-2, and human immunoglobulin G, but not by the caveolin inhibitor, methyl-β-cyclodextrin. In addition, membrane transfer from PMNs enhanced IL-2 production by recipient anti-CD3/anti-CD28 activated MNCs, and this was suppressed by inhibitors of mitogen-activated protein kinase (PD98059) and protein kinase C (Rottlerin). Of clinical significance, decreased total membrane transfer from PMNs to MNCs in patients with active SLE suppressed mononuclear IL-2 production. In conclusion, membrane transfer from MNCs to PMNs, mainly at the immunological synapse, transduces survival and activation signals to enhance PMN functions and is dependent on actin polymerization, clathrin activation, and Fcγ receptors, while membrane transfer from PMNs to MNCs depends on MAP kinase and

Membrane Transfer from Mononuclear Cells to Polymorphonuclear Neutrophils Transduces Cell Survival and Activation Signals in the Recipient Cells via Anti-Extrinsic Apoptotic and MAP Kinase Signaling Pathways.

Directory of Open Access Journals (Sweden)

Ko-Jen Li

Full Text Available The biological significance of membrane transfer (trogocytosis between polymorphonuclear neutrophils (PMNs and mononuclear cells (MNCs remains unclear. We investigated the biological/immunological effects and molecular basis of trogocytosis among various immune cells in healthy individuals and patients with active systemic lupus erythematosus (SLE. By flow cytometry, we determined that molecules in the immunological synapse, including HLA class-I and-II, CD11b and LFA-1, along with CXCR1, are exchanged among autologous PMNs, CD4+ T cells, and U937 cells (monocytes after cell-cell contact. Small interfering RNA knockdown of the integrin adhesion molecule CD11a in U937 unexpectedly enhanced the level of total membrane transfer from U937 to PMN cells. Functionally, phagocytosis and IL-8 production by PMNs were enhanced after co-culture with T cells. Total membrane transfer from CD4+ T to PMNs delayed PMN apoptosis by suppressing the extrinsic apoptotic molecules, BAX, MYC and caspase 8. This enhancement of activities of PMNs by T cells was found to be mediated via p38- and P44/42-Akt-MAP kinase pathways and inhibited by the actin-polymerization inhibitor, latrunculin B, the clathrin inhibitor, Pitstop-2, and human immunoglobulin G, but not by the caveolin inhibitor, methyl-β-cyclodextrin. In addition, membrane transfer from PMNs enhanced IL-2 production by recipient anti-CD3/anti-CD28 activated MNCs, and this was suppressed by inhibitors of mitogen-activated protein kinase (PD98059 and protein kinase C (Rottlerin. Of clinical significance, decreased total membrane transfer from PMNs to MNCs in patients with active SLE suppressed mononuclear IL-2 production. In conclusion, membrane transfer from MNCs to PMNs, mainly at the immunological synapse, transduces survival and activation signals to enhance PMN functions and is dependent on actin polymerization, clathrin activation, and Fcγ receptors, while membrane transfer from PMNs to MNCs depends on

Methods of making membrane electrode assemblies

Science.gov (United States)

Kim, Yu Seung; Lee, Kwan -Soo; Rockward, Tommy Q. T.

2015-07-28

Method of making a membrane electrode assembly comprising: providing a membrane comprising a perfluorinated sulfonic acid; providing a first transfer substrate; applying to a surface of the first transfer substrate a first ink, said first ink comprising an ionomer and a catalyst; applying to the first ink a suitable non-aqueous swelling agent; forming an assembly comprising: the membrane; and the first transfer substrate, wherein the surface of the first transfer substrate comprising the first ink and the non-aqueous swelling agent is disposed upon one surface of the membrane; and heating the assembly at a temperature of 150.degree. C. or less and at a pressure of from about 250 kPa to about 3000 kPa or less for a time suitable to allow substantially complete transfer of the first ink and the second ink to the membrane; and cooling the assembly to room temperature and removing the first transfer substrate and the second transfer substrate.

Voltammetry of ion transfer across a polarized room-temperature ionic liquid membrane facilitated by valinomycin: theoretical aspects and application.

Science.gov (United States)

Langmaier, Jan; Samec, Zdenek

2009-08-01

Cyclic voltammetry is used to investigate the transfer of alkali-metal cations, protons, and ammonium ions facilitated by the complex formation with valinomycin at the interface between an aqueous electrolyte solution and a room-temperature ionic liquid (RTIL) membrane. The membrane is made of a thin (approximately 112 microm) microporous filter impregnated with an RTIL that is composed of tridodecylmethylammonium cations and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anions. An extension of the existing theory of voltammetry of ion transfer across polarized liquid membranes makes it possible to evaluate the standard ion-transfer potentials for the hydrophilic cations studied, as well as the stability constants (K(i)) of their 1:1 complexes with valinomycin, as log K(i) = 9.0 (H(+)), 11.1 (Li(+)), 12.8 (Na(+)), 17.2 (K(+)), 15.7 (Rb(+)), 15.1 (Cs(+)), and 14.7 (NH(4)(+)). These data point to the remarkably enhanced stability of the valinomycin complexes within RTIL, and to the enhanced selectivity of valinomycin for K(+) over all other univalent ions studied, compared to the conventional K(+) ion-selective liquid-membrane electrodes. Selective complex formation allows one to resolve voltammetric responses of K(+) and Na(+) in the presence of an excess of Mg(2+) or Ca(2+), which is demonstrated by determination of K(+) and Na(+) in the table and tap water samples.

Evaluation of the Standard Ion Transfer Potentials for PVC Plasticized Membranes from Voltammetric Measurements

Czech Academy of Sciences Publication Activity Database

Langmaier, Jan; Stejskalová, Květoslava; Samec, Zdeněk

2001-01-01

Roč. 496, č. 1 (2001), s. 143-147 ISSN 0022-0728. [Symposium in Kyoto. Kyoto, 02.03.2000] R&D Projects: GA AV ČR IAA4040902 Institutional research plan: CEZ:AV0Z4040901 Keywords : ion voltammetry * PVC plasticized membrane * standard ion transfer potential Subject RIV: CG - Electrochemistry Impact factor: 1.960, year: 2001

DETERMINATION OF THE MASS TRANSFER CHARACTERIZATION OF A CERAMIC-POLYMER COMPOSITE MEMBRANE IN THE PERVAPORATION MODE

Science.gov (United States)

The effect of the coating layer thickness on VOC extraction performance of a ceramic polymer composite membrane has been investigated. It was found, under experimental condiitons representing typical field operation, the overall mass transfer rates of feed components were control...

INSITU BLOTTING - A NOVEL METHOD FOR DIRECT TRANSFER OF NATIVE PROTEINS FROM SECTIONED TISSUE TO BLOTTING MEMBRANE - PROCEDURE AND SOME APPLICATIONS

NARCIS (Netherlands)

OKABE, M; NYAKAS, C; BUWALDA, B; LUITEN, PGM

We describe a novel technique for direct transfer of native proteins from unfixed frozen tissue sections to an immobilizing matrix, e.g., nitrocellulose, polyvinyliden difluoride, or positively charged nylon membranes. Proteins are directly blotted onto the membrane, providing optimal accessibility

Selective enantioseparation of levocetirizine via a hollow fiber supported liquid membrane and mass transfer prediction

Energy Technology Data Exchange (ETDEWEB)

Sunsandee, Niti [Government Pharmaceutical Organization, Bangkok (Thailand); Leepipatpiboon, Natchanun [Chulalongkorn University, Bangkok (Thailand); Ramakul, Prakorn [Silpakorn University, Nakhon Pathom (Thailand)

2013-06-15

The enantioselective separation of levocetirizine via a hollow fiber supported liquid membrane was examined. O,O'-dibenzoyl-(2R,3R)-tartaric acid ((-)-DBTA) diluted in 1-decanol was used as a chiral selector extractant. The influence of concentrations of feed and stripping phases, and extractant concentration in the membrane phase, was also investigated. A mathematical model focusing on the extraction side of the liquid membrane system was presented to predict the concentration of levocetirizine at different times. The extraction and recovery of levocetirizine from feed phase were 75.00% and 72.00%, respectively. The mass transfer coefficients at aqueous feed boundary layer (k{sub f}) and the organic liquid membrane phase (k{sub m}) were calculated as 2.41x10{sup 2} and 1.89x10{sup 2} cm/s, respectively. The validity of the developed model was evaluated through a comparison with experimental data, and good agreement was obtained.

Folding Membrane Proteins by Deep Transfer Learning

KAUST Repository

Wang, Sheng

2017-08-29

Computational elucidation of membrane protein (MP) structures is challenging partially due to lack of sufficient solved structures for homology modeling. Here, we describe a high-throughput deep transfer learning method that first predicts MP contacts by learning from non-MPs and then predicts 3D structure models using the predicted contacts as distance restraints. Tested on 510 non-redundant MPs, our method has contact prediction accuracy at least 0.18 better than existing methods, predicts correct folds for 218 MPs, and generates 3D models with root-mean-square deviation (RMSD) less than 4 and 5 Å for 57 and 108 MPs, respectively. A rigorous blind test in the continuous automated model evaluation project shows that our method predicted high-resolution 3D models for two recent test MPs of 210 residues with RMSD ∼2 Å. We estimated that our method could predict correct folds for 1,345–1,871 reviewed human multi-pass MPs including a few hundred new folds, which shall facilitate the discovery of drugs targeting at MPs.

FAD oxidizes the ERO1-PDI electron transfer chain: The role of membrane integrity

International Nuclear Information System (INIS)

Papp, Eszter; Nardai, Gabor; Mandl, Jozsef; Banhegyi, Gabor; Csermely, Peter

2005-01-01

The molecular steps of the electron transfer in the endoplasmic reticulum from the secreted proteins during their oxidation are relatively unknown. We present here that flavine adenine dinucleotide (FAD) is a powerful oxidizer of the oxidoreductase system, Ero1 and PDI, besides the proteins of rat liver microsomes and HepG2 hepatoma cells. Inhibition of FAD transport hindered the action of FAD. Microsomal membrane integrity was mandatory for all FAD-related oxidation steps downstream of Ero1. The PDI inhibitor bacitracin could inhibit FAD-mediated oxidation of microsomal proteins and PDI, but did not hinder the FAD-driven oxidation of Ero1. Our data demonstrated that Ero1 can utilize FAD as an electron acceptor and that FAD-driven protein oxidation goes through the Ero1-PDI pathway and requires the integrity of the endoplasmic reticulum membrane. Our findings prompt further studies to elucidate the membrane-dependent steps of PDI oxidation and the role of FAD in redox folding

Syngas fermentation to biofuel: evaluation of carbon monoxide mass transfer and analytical modeling using a composite hollow fiber (CHF) membrane bioreactor.

Science.gov (United States)

Munasinghe, Pradeep Chaminda; Khanal, Samir Kumar

2012-10-01

In this study, the volumetric mass transfer coefficients (Ka) for CO were examined in a composite hollow fiber (CHF) membrane bioreactor. The mass transfer experiments were conducted at various inlet gas pressures (from 5 to 30 psig (34.5-206.8 kPa(g))) and recirculation flow rates (300, 600, 900, 1200 and 1500 mL/min) through CHF module. The highest Ka value of 946.6 1/h was observed at a recirculation rate of 1500 mL/min and at an inlet gas pressure of 30 psig(206.8 kPa(g)). The findings of this study confirm that the use of CHF membranes is effective and improves the efficiency CO mass transfer into the aqueous phase. Copyright © 2012 Elsevier Ltd. All rights reserved.

Experimental study on mass transfer of contaminants through an enthalpy recovery unit with polymer membrane foils

DEFF Research Database (Denmark)

Nie, Jinzhe; Fang, Lei

2014-01-01

Laboratory experimental studies were conducted to investigate the mass transfer of contaminants through a total heat recovery unit with polymer membranes foils. The studies were conducted in twin climate chambers which simulated outdoor and indoor thermal climates. One manufacturd total heat...... chemical gases were used to simulate air contaminants. The concentrations of dosed contaminants in the supply and exhaust air upstream and downstream of the total heat recovery unit were measured with Multi-Gas Monitor Innova 1316 in real time. Experiment results showed that 5% to 9% of dosed contaminants...... could transfer from exhaust air to supply air through the enthalpy recovery unit. The mass transfer efficiency of contaminants was independent of the hygro-thermal differences between indoor and outdoor climate conditions. The mass transfer ratio of the chemical contaminants in the total heat recovery...

Influence of the membrane environment on cholesterol transfer.

Science.gov (United States)

Breidigan, Jeffrey Michael; Krzyzanowski, Natalie; Liu, Yangmingyue; Porcar, Lionel; Perez-Salas, Ursula

2017-12-01

Cholesterol, an essential component in biological membranes, is highly unevenly distributed within the cell, with most localized in the plasma membrane while only a small fraction is found in the endoplasmic reticulum, where it is synthesized. Cellular membranes differ in lipid composition and protein content, and these differences can exist across their leaflets too. This thermodynamic landscape that cellular membranes impose on cholesterol is expected to modulate its transport. To uncover the role the membrane environment has on cholesterol inter- and intra-membrane movement, we used time-resolved small angle neutron scattering to study the passive movement of cholesterol between and within membranes with varying degrees of saturation content. We found that cholesterol moves systematically slower as the degree of saturation in the membranes increases, from a palmitoyl oleyl phosphotidylcholine membrane, which is unsaturated, to a dipalmitoylphosphatidylcholine (DPPC) membrane, which is fully saturated. Additionally, we found that the energetic barrier to move cholesterol in these phosphatidylcholine membranes is independent of their relative lipid composition and remains constant for both flip-flop and exchange at ∼100 kJ/mol. Further, by replacing DPPC with the saturated lipid palmitoylsphingomyelin, an abundant saturated lipid of the outer leaflet of the plasma membrane, we found the rates decreased by a factor of two. This finding is in stark contrast with recent molecular dynamic simulations that predict a dramatic slow-down of seven orders of magnitude for cholesterol flipping in membranes with a similar phosphocholine and SM lipid composition. Copyright © 2017 by the American Society for Biochemistry and Molecular Biology, Inc.

Nonlinear Lyapunov-based boundary control of distributed heat transfer mechanisms in membrane distillation plant

KAUST Repository

Eleiwi, Fadi

2015-07-01

This paper presents a nonlinear Lyapunov-based boundary control for the temperature difference of a membrane distillation boundary layers. The heat transfer mechanisms inside the process are modeled with a 2D advection-diffusion equation. The model is semi-descretized in space, and a nonlinear state-space representation is provided. The control is designed to force the temperature difference along the membrane sides to track a desired reference asymptotically, and hence a desired flux would be generated. Certain constraints are put on the control law inputs to be within an economic range of energy supplies. The effect of the controller gain is discussed. Simulations with real process parameters for the model, and the controller are provided. © 2015 American Automatic Control Council.

A Molecular Dynamic Simulation of Hydrated Proton Transfer in Perfluorosulfonate Ionomer Membranes (Nafion 117

Directory of Open Access Journals (Sweden)

Hong Sun

2015-01-01

Full Text Available A molecular dynamic model based on Lennard-Jones Potential, the interaction force between two particles, molecular diffusion, and radial distribution function (RDF is presented. The diffusion of the hydrated ion, triggered by both Grotthuss and vehicle mechanisms, is used to study the proton transfer in Nafion 117. The hydrated ion transfer mechanisms and the effects of the temperature, the water content in the membrane, and the electric field on the diffusion of the hydrated ion are analyzed. The molecular dynamic simulation results are in good agreement with those reported in the literature. The modeling results show that when the water content in Nafion 117 is low, H3O+ is the main transfer ion among the different hydrated ions. However, at higher water content, the hydrated ion in the form of H+(H2O2 is the main transfer ion. It is also found that the negatively charged sulfonic acid group as the fortified point facilitates the proton transfer in Nafion 117 better than the free water molecule. The diffusion of the hydrated ion can be improved by increasing the cell temperature, the water content in Nafion, and the electric field intensity.

Effect of internal pressure and gas/liquid interface area on the CO mass transfer coefficient using hollow fibre membranes as a high mass transfer gas diffusing system for microbial syngas fermentation.

Science.gov (United States)

Yasin, Muhammad; Park, Shinyoung; Jeong, Yeseul; Lee, Eun Yeol; Lee, Jinwon; Chang, In Seop

2014-10-01

This study proposed a submerged hollow fibre membrane bioreactor (HFMBR) system capable of achieving high carbon monoxide (CO) mass transfer for applications in microbial synthesis gas conversion systems. Hydrophobic polyvinylidene fluoride (PVDF) membrane fibres were used to fabricate a membrane module, which was used for pressurising CO in water phase. Pressure through the hollow fibre lumen (P) and membrane surface area per unit working volume of the liquid (A(S)/V(L)) were used as controllable parameters to determine gas-liquid volumetric mass transfer coefficient (k(L)a) values. We found a k(L)a of 135.72 h(-1) when P was 93.76 kPa and AS/VL was fixed at 27.5m(-1). A higher k(L)a of 155.16 h(-1) was achieved by increasing AS/VL to 62.5m(-1) at a lower P of 37.23 kPa. Practicality of HFMBR to support microbial growth and organic product formation was assessed by CO/CO2 fermentation using Eubacterium limosum KIST612. Copyright © 2014 Elsevier Ltd. All rights reserved.

Membrane Transfer Phenomena (MTP)

Science.gov (United States)

Mason, Larry

1996-01-01

Progress has been made in several areas of the definition, design, and development of the Membrane Transport Apparatus (MTA) instrument and associated sensors and systems. Progress is also reported in the development of software modules for instrument control, experimental image and data acquisition, and data analysis.

Mass-charge-heat coupled transfers in a single cell of a proton exchange membrane fuel cell; Transferts couples masse-charge-chaleur dans une cellule de pile a combustible a membrane polymere

Energy Technology Data Exchange (ETDEWEB)

Ramousse, J

2005-11-15

Understanding and modelling of coupled mass, charges and heat transfers phenomena are fundamental to analyze the electrical behaviour of the system. The aim of the present model is to describe electrical performances of a PEFMC according to the fluidic and thermal operating conditions. The water content of the membrane and the water distribution in the single cell are estimated according to the coupled simulations of mass transport in the thickness of the single cell and in the feeding channels of the bipolar plates. A microscopic model of a Gas Diffusion Electrode is built up to describe charges transfer phenomena occurring at the electrodes. Completed by a study of heat transfer in the Membrane Electrode Assembly, conditions and preferential sites of water vapor condensation can be highlighted. A set of measurements of the effective thermal conductivity of carbon felts used in fuel cells as porous backing layers have also been performed. Although the value of this parameter is essential for the study of heat transfer, it is still under investigation because of the strong thermal anisotropy of the medium. (author)

A Method for Estimating Mass-Transfer Coefficients in a Biofilter from Membrane Inlet Mass Spectrometer Data

DEFF Research Database (Denmark)

Nielsen, Anders Michael; Nielsen, Lars Peter; Feilberg, Anders

2009-01-01

A membrane inlet mass spectrometer (MIMS) was used in combination with a developed computer model to study and improve management of a biofilter (BF) treating malodorous ventilation air from a meat rendering facility. The MIMS was used to determine percentage removal efficiencies (REs) of selected...... sulfur gases and to provide toluene retention profiles for the model to determine the air velocity and overall mass-transfer coefficient of toluene. The mass-transfer coefficient of toluene was used as a reference for determining the mass transfer of sulfur gases. By presenting the model to scenarios...... of a filter bed with a consortium of effective sulfur oxidizers, the most likely mechanism for incomplete removal of sulfur compounds from the exhaust air was elucidated. This was found to be insufficient mass transfer and not inadequate bacterial activity as anticipated by the manager of the BF. Thus...

Nonlinear observer-based Lyapunov boundary control of distributed heat transfer mechanisms for membrane distillation plant

KAUST Repository

Eleiwi, Fadi

2016-09-19

This paper presents a nonlinear observer-based Lyapunov control for a membrane distillation (MD) process. The control considers the inlet temperatures of the feed and the permeate solutions as inputs, transforming it to boundary control process, and seeks to maintain the temperature difference along the membrane boundaries around a sufficient level to promote water production. MD process is modeled with advection diffusion equation model in two dimensions, where the diffusion and convection heat transfer mechanisms are best described. Model analysis, effective order reduction and parameters physical interpretation, are provided. Moreover, a nonlinear observer has been designed to provide the control with estimates of the temperature evolution at each time instant. In addition, physical constraints are imposed on the control to have an acceptable range of feasible inputs, and consequently, better energy consumption. Numerical simulations for the complete process with real membrane parameter values are provided, in addition to detailed explanations for the role of the controller and the observer. (C) 2016 Elsevier Ltd. All rights reserved.

Role of Tim50 in the transfer of precursor proteins from the outer to the inner membrane of mitochondria.

Science.gov (United States)

Mokranjac, Dejana; Sichting, Martin; Popov-Celeketić, Dusan; Mapa, Koyeli; Gevorkyan-Airapetov, Lada; Zohary, Keren; Hell, Kai; Azem, Abdussalam; Neupert, Walter

2009-03-01

Transport of essentially all matrix and a number of inner membrane proteins is governed, entirely or in part, by N-terminal presequences and requires a coordinated action of the translocases of outer and inner mitochondrial membranes (TOM and TIM23 complexes). Here, we have analyzed Tim50, a subunit of the TIM23 complex that is implicated in transfer of precursors from TOM to TIM23. Tim50 is recruited to the TIM23 complex via Tim23 in an interaction that is essentially independent of the rest of the translocase. We find Tim50 in close proximity to the intermembrane space side of the TOM complex where it recognizes both types of TIM23 substrates, those that are to be transported into the matrix and those destined to the inner membrane, suggesting that Tim50 recognizes presequences. This function of Tim50 depends on its association with TIM23. We conclude that the efficient transfer of precursors between TOM and TIM23 complexes requires the concerted action of Tim50 with Tim23.

Ion transfer through solvent polymeric membranes driven by an exponential current flux.

Science.gov (United States)

Molina, A; Torralba, E; González, J; Serna, C; Ortuño, J A

2011-03-21

General analytical equations which govern ion transfer through liquid membranes with one and two polarized interfaces driven by an exponential current flux are derived. Expressions for the transient and stationary E-t, dt/dE-E and dI/dE-E curves are obtained, and the evolution from transient to steady behaviour has been analyzed in depth. We have also shown mathematically that the voltammetric and stationary chronopotentiometric I(N)-E curves are identical (with E being the applied potential for voltammetric techniques and the measured potential for chronopotentiometric techniques), and hence, their derivatives provide identical information.

Radioiodinated, photoactivatable phosphatidylcholine and phosphatidylserine: transfer properties and differential photoreactive interaction with human erythrocyte membrane proteins

International Nuclear Information System (INIS)

Schroit, A.J.; Madsen, J.; Ruoho, A.E.

1987-01-01

An isotopically labeled cross-linking reagent, succinimido 3-(3-[ 125 I]iodo-4-azidophenyl)propionate, has been synthesized and coupled to 1-acyl-2-(aminocaproyl)phosphatidylcholine according to previously described procedures. 125 I- and N 3 -labeled phosphatidylserine ( 125 I-N 3 -PS) was produced from the phosphatidylcholine (PC) analog by phospholipase D catalyzed base exchange in the presence of L-serine. These phospholipid analogues are photoactivatable, are labeled with 125 I at high specific activity, completely incorporate into synthetic vesicles, and spontaneously transfer between membranes. When an excess of acceptor vesicles or red blood cells (RBC) was mixed with a population of donor vesicles containing the 125 I-N 3 -phospholipids, approximately 40% of the analogues transferred to the acceptor population. After transfer in the dark to RBC, all of the 125 I-N 3 -PC incorporated into the cells could be removed by washing with serum, whereas the 125 I-N 3 -PS could not. After photolabeling of intact RBC, ∼50% of the PC and 20% of the PS cross-linked to membrane proteins as determined by their insolubility in CHCl 3 /MeOH. Analysis of probe distribution by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that 125 I-N 3 -PS preferentially labeled a M/sub r/ 30,000 peptide which contained ∼30% of the protein-bound label

The effective recovery of praseodymium from mixed rare earths via a hollow fiber supported liquid membrane and its mass transfer related

International Nuclear Information System (INIS)

Wannachod, Pharannalak; Chaturabul, Srestha; Pancharoen, Ura; Lothongkum, Anchaleeporn W.; Patthaveekongka, Weerawat

2011-01-01

Graphical abstract: Display Omitted Research highlights: → Maximum percentage of praseodymium extraction at 91.7% from 10% (v/v) bis (2,4,4-trimethylpentyl) phosphinic acid as extractant carrier in multi cycle operation through single HFLSM module. → Mass transfer mechanism of this system was investigated. → The rate-controlling step of this system was the diffusion of praseodymium ions through the film layer between the feed solution and the liquid membrane. → Model prediction of the dimensionless concentrations and separation factors showed promising agreement with the experimental data. - Abstract: The recovery of praseodymium from mixed rare earths via a hollow fiber supported liquid membrane (HFSLM) was examined. Bis(2,4,4-trimethylpentyl) phosphinic acid - known as Cyanex 272 - was used as an extractant carrier. The stripping solution was hydrochloric acid solution. The experiments examined in functions of the concentrations of the carrier in liquid membrane, the (initial) pH's of initial feed solution within the acidic-pH range, the concentrations of hydrochloric acid, the flow rates of feed and stripping solution, and the operation mode of runs through the hollow fiber module. In addition, the influence of circulation of the stripping solution at various numbers of runs through the HFSLM on the outlet concentration of praseodymium ions in the stripping solution was observed. Mass transfer mechanism in the system was investigated. Extraction equilibrium constant (K ex ), distribution ratio (D), permeability (P) and mass transfer coefficients were determined. The aqueous-phase mass-transfer coefficient (k i ) and organic-phase mass-transfer coefficient (k m ) were reported to 0.0103 and 0.788 cm s -1 , respectively, in which k m is much higher than the k i . Thus it suggests the rate-controlling step is the diffusion of praseodymium ions through the film layer between the feed solution and the liquid membrane. Model prediction of the dimensionless

Membrane microparticles mediate transfer of P-glycoprotein to drug sensitive cancer cells.

Science.gov (United States)

Bebawy, M; Combes, V; Lee, E; Jaiswal, R; Gong, J; Bonhoure, A; Grau, G E R

2009-09-01

Multidrug resistance (MDR), a significant impediment to the successful treatment of cancer clinically, has been attributed to the overexpression of P-glycoprotein (P-gp), a plasma membrane multidrug efflux transporter. P-gp maintains sublethal intracellular drug concentrations by virtue of its drug efflux capacity. The cellular regulation of P-gp expression is currently known to occur at either pre- or post-transcriptional levels. In this study, we identify a 'non-genetic' mechanism whereby microparticles (MPs) serve as vectors in the acquisition and spread of MDR. MPs isolated from drug-resistant cancer cells (VLB(100)) were co-cultured with drug sensitive cells (CCRF-CEM) over a 4 h period to allow for MP binding and P-gp transfer. Presence of P-gp on MPs was established using flow cytometry (FCM) and western blotting. Whole-cell drug accumulation assays using rhodamine 123 and daunorubicin (DNR) were carried out to validate the transfer of functional P-gp after co-culture. We establish that MPs shed in vitro from drug-resistant cancer cells incorporate cell surface P-gp from their donor cells, effectively bind to drug-sensitive recipient cells and transfer functional P-gp to the latter. These findings serve to substantially advance our understanding of the molecular basis for the emergence of MDR in cancer clinically and lead to new treatment strategies which target and inhibit MP mediated transfer of P-gp during the course of treatment.

Transferred nuclear Overhauser effect analyses of membrane-bound enkephalin analogues by sup 1 H nuclear magnetic resonance: Correlation between activities and membrane-bound conformations

Energy Technology Data Exchange (ETDEWEB)

Milon, Alain; Miyazawa, Tatsuo; Higashijima, Tsutomu (Univ. of Tokyo (Japan))

1990-01-09

Leu-enkephalin, (D-Ala{sup 2})Leu-enkephalin, and (D-Ala{sup 2})Leu-enkephalinamide (agonists) and (L-Ala{sup 2})Leu-enkephalin (inactive analogue) bind to lipid bilayer consisting of phosphatidylcholine and phosphatidylserine. The conformations that these compounds assume, once bound to perdeuterated phospholipid bilayer, have been shown to be unique, as shown by the transferred nuclear Overhauser effect (TRNOE) of {sup 1}H NMR spectroscopy. In addition, their location in the bilayer was analyzed by TRNOE in the presence of spin-labeled phospholipids. These analyses showed a clear relationship between the activity and the peptide-membrane interaction. The three active peptides, when bound to membranes, adopt the same conformation, characterized by a type II{prime} {beta}-turn around Gly{sup 3}-Phe and a {gamma}-turn around Gly{sup 2} (or D-Ala{sup 2}). The inactive analogue, (L-Ala{sup 2})Leu-enkephalin, displayed a completely different TRNOE pattern corresponding to a different conformation in the membrane-bound state. The tyrosine residue of the active compounds is not inserted into the interior of membrane, but it is inserted into the bilayer for the L-Ala{sup 2} analogue. According to these results, (L-Ala{sup 2})Leu-enkephalin may be explained to be inactive because the mode of binding to the membranes is different from that of active compounds.

A comparison of mass transfer coefficients between trickle-bed, hollow fiber membrane and stirred tank reactors.

Science.gov (United States)

Orgill, James J; Atiyeh, Hasan K; Devarapalli, Mamatha; Phillips, John R; Lewis, Randy S; Huhnke, Raymond L

2013-04-01

Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H2 to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L)) of three reactor types; the TBR with 3 mm and 6 mm beads, five different modules of HFRs, and the STR. The analysis was performed using O2 as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest K(tot)A/V(L) (1062 h(-1)), followed by the TBR with 6mm beads (421 h(-1)), and then the STR (114 h(-1)). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Large aperture deformable mirror with a transferred single-crystal silicon membrane actuated using large-stroke PZT Unimorph Actuators

Science.gov (United States)

Hishinumat, Yoshikazu; Yang, Eui - Hyeok (EH)

2005-01-01

We have demonstrated a large aperture (50 mm x 50 mm) continuous membrane deformable mirror (DM) with a large-stroke piezoelectric unimorph actuator array. The DM consists of a continuous, large aperture, silicon membrane 'transferred' in its entirety onto a 20 x 20 piezoelectric unimorph actuator array. A PZT unimorph actuator, 2.5 mm in diameter with optimized PZT/Si thickness and design showed a deflection of 5.7 [m at 20V. An assembled DM showed an operating frequency bandwidth of 30 kHz and influence function of approximately 30%.

MEMBRANE BIOTREATMENT OF VOC-LADEN AIR

Science.gov (United States)

The paper discusses membrane biotreatment of air laden with volatile organic compounds (VOCs). Microporous flat-sheet and hollow-fiber membrane contactors were used to support air-liquid mass transfer interfaces. These modules were used in a two-step process to transfer VOCs fr...

A simple agar plate preparation for effective transfer of Ureaplasma colonies onto nitrocellulose membranes for colony immunoblotting.

Science.gov (United States)

Zimmerman, Carl-Ulrich R; Stiedl, Thomas; Spergser, Joachim; Rosengarten, Renate

2014-09-01

A simple method for preparing agar plates is presented, which allows an efficient transfer of Ureaplasma colonies to nitrocellulose membranes for subsequent immunological detection. This simple and reproducible procedure was used to demonstrate antigenic variation in the phase-variable mba-locus of Ureaplasma parvum serovar 3. Copyright © 2014 Elsevier B.V. All rights reserved.

CO2 clearance by membrane lungs.

Science.gov (United States)

Sun, Liqun; Kaesler, Andreas; Fernando, Piyumindri; Thompson, Alex J; Toomasian, John M; Bartlett, Robert H

2018-05-01

Commercial membrane lungs are designed to transfer a specific amount of oxygen per unit of venous blood flow. Membrane lungs are much more efficient at removing CO 2 than adding oxygen, but the range of CO 2 transfer is rarely reported. Commercial membrane lungs were studied with the goal of evaluating CO 2 removal capacity. CO 2 removal was measured in 4 commercial membrane lungs under standardized conditions. CO 2 clearance can be greater than 4 times that of oxygen at a given blood flow when the gas to blood flow ratio is elevated to 4:1 or 8:1. The CO 2 clearance was less dependent on surface area and configuration than oxygen transfer. Any ECMO system can be used for selective CO 2 removal.

Performance modeling of direct contact membrane distillation (DCMD) seawater desalination process using a commercial composite membrane

KAUST Repository

Lee, Junggil

2015-01-10

This paper presents the development of a rigorous theoretical model to predict the transmembrane flux of a flat sheet hydrophobic composite membrane, comprising both an active layer of polytetrafluoroethylene and a scrim-backing support layer of polypropylene, in the direct contact membrane distillation (DCMD) process. An integrated model includes the mass, momentum, species and energy balances for both retentate and permeate flows, coupled with the mass transfer of water vapor through the composite membrane and the heat transfer across the membrane and through the boundary layers adjacent to the membrane surfaces. Experimental results and model predictions for permeate flux and performance ratio are compared and shown to be in good agreement. The permeate flux through the composite layer can be ignored in the consideration of mass transfer pathways at the composite membrane. The effect of the surface porosity and the thickness of active and support layers on the process performance of composite membrane has also been studied. Among these parameters, surface porosity is identified to be the main factor significantly influencing the permeate flux and performance ratio, while the relative influence of the surface porosity on the performance ratio is less than that on flux.

Cyclic voltammetry of ion transfer across a room temperature ionic liquid membrane supported by a microporous filter

Czech Academy of Sciences Publication Activity Database

Langmaier, Jan; Samec, Zdeněk

2007-01-01

Roč. 9, č. 9 (2007), s. 2633-2638 ISSN 1388-2481 R&D Projects: GA AV ČR IAA400400704 Institutional research plan: CEZ:AV0Z40400503 Keywords : room-temperature ionic membrane * cyclic voltammetry * standard Gibbs energy of ion transfer * linear Gibbs energy relationship Subject RIV: CG - Electrochemistry Impact factor: 4.186, year: 2007

EFFECTS OF A BASKETBALL ACTIVITY ON LUNG CAPILLARY BLOOD VOLUME AND MEMBRANE DIFFUSING CAPACITY, MEASURED BY NO/CO TRANSFER IN CHILDREN

Directory of Open Access Journals (Sweden)

Rim Dridi

2006-09-01

Full Text Available In both children and adults, acute exercise increases lung capillary blood volume (Vc and membrane factor (DmCO. We sought to determine whether basketball training affected this adaptation to exercise in children. The purpose of this study was to determine the effects of two years sport activity on the components of pulmonary gas transfer in children. Over a 2-yr period, we retested 60 nine year old boys who were initially separated in two groups: 30 basketball players (P (9.0 ± 1.0 yrs; 35.0 ± 5.2 kg; 1.43 ± 0.05 m, and matched non players controls (C (8.9 ± 1.0 yrs; 35.0 ± 6.0 kg; 1.44 ± 0.06 m who did not perform any extracurricular activity, Vc and DmCO were measured by the NO/CO transfer method at rest and during sub-maximal exercise. Maximal aerobic power and peak power output was 12% higher in the trained group compared to matched controls (p < 0.05. Nitric oxide lung transfer (TLNO per unit lung volume and thus, DmCO per unit of lung volume (VA were higher at rest and during exercise in the group which had undergone regular basketball activity compared to matched controls (p < 0.05. Neither lung capillary blood volume nor total lung transfer for carbon monoxide (TLCO were significantly different between groups. These results suggest that active sport can alter the properties of the lung alveolo-capillary membrane by improving alveolar membrane conductance in children

A cost-effective device for the rapid transfer of gel-separated proteins onto membranes.

Science.gov (United States)

Tam, Hann W; Huang, Yu-Chen; Tam, Ming F

2009-03-01

We describe here the fabrication of a cost-effective semi-dry blotting apparatus for the transfer of proteins onto membranes. Graphite sheets were used as electrodes. Protein mixtures were separated on NuPAGE 4% to 12% polyacrylamide gradient gels. With a Tris-bicine buffer, we demonstrated that close to 80% of the proteins with apparent molecular mass of 80kDa or less were removed from the gels after 8min of blotting. The process is much faster than the techniques reported previously in the literature.

Cell-free transfer of sterols by plant fractions

International Nuclear Information System (INIS)

Morre, D.J.; Wilkinson, F.E.; Morre, D.M.; Moreau, P.; Sandelius, A.S.; Penel, C.; Greppin, H.

1990-01-01

Microsomes from etiolated hypocotyls of soybean or leaves of light-grown spinach radiolabeled in vivo with [ 3 H]acetate or in vitro with [ 3 H]squalene or [ 3 H]cholesterol as donor transferred radioactivity to unlabeled acceptor membranes immobilized on nitrocellulose. Most efficient transfer was with plasma membrane or tonoplast as the acceptor. The latter were highly purified by aqueous two-phase partition (plasma membrane) and preparative free-flow electrophoresis (tonoplast and plasma membrane). Plasma membrane- and tonoplast-free microsomes and purified mitochondria were less efficient acceptors. Sterol transfer was verified by thin-layer chromatography of extracted lipids. Transfer was time- and temperature-dependent, required ATP but was not promoted by cytosol. The nature of the donor (endoplasmic reticulum, Golgi apparatus or both) and of the transfer mechanism is under investigation

Moisture transfer through the membrane of a cross-flow energy recovery ventilator: Measurement and simple data-driven modeling

Science.gov (United States)

CR Boardman; Samuel V. Glass

2015-01-01

The moisture transfer effectiveness (or latent effectiveness) of a cross-flow, membrane based energy recovery ventilator is measured and modeled. Analysis of in situ measurements for a full year shows that energy recovery ventilator latent effectiveness increases with increasing average relative humidity and surprisingly increases with decreasing average temperature. A...

Dynamic Modeling and Control of Distributed Heat Transfer Mechanisms: Application to a Membrane Distillation Module

KAUST Repository

Eleiwi, Fadi

2015-12-01

Sustainable desalination technologies are the smart solution for producing fresh water and preserve the environment and energy by using sustainable renewable energy sources. Membrane distillation (MD) is an emerging technology which can be driven by renewable energy. It is an innovative method for desalinating seawater and brackish water with high quality production, and the gratitude is to its interesting potentials. MD includes a transfer of water vapor from a feed solution to a permeate solution through a micro-porous hydrophobic membrane, rejecting other non-volatile constituents present in the influent water. The process is driven by the temperature difference along the membrane boundaries. Different control applications and supervision techniques would improve the performance and the efficiency of the MD process, however controlling the MD process requires comprehensive mathematical model for the distributed heat transfer mechanisms inside the process. Our objective is to propose a dynamic mathematical model that accounts for the time evolution of the involved heat transfer mechanisms in the process, and to be capable of hosting intermittent energy supplies, besides managing the production rate of the process, and optimizing its energy consumption. Therefore, we propose the 2D Advection-Diffusion Equation model to account for the heat diffusion and the heat convection mechanisms inside the process. Furthermore, experimental validations have proved high agreement between model simulations and experiments with less than 5% relative error. Enhancing the MD production is an anticipated goal, therefore, two main control strategies are proposed. Consequently, we propose a nonlinear controller for a semi-discretized version of the dynamic model to achieve an asymptotic tracking for a desired temperature difference. Similarly, an observer-based feedback control is used to track sufficient temperature difference for better productivity. The second control strategy

Experimental evaluation of enthalpy efficiency and gas-phase contaminant transfer in an enthalpy recovery unit with polymer membrane foils

DEFF Research Database (Denmark)

Nie, Jinzhe; Yang, Jianrong; Fang, Lei

2015-01-01

Experimental studies were conducted in a laboratory setting to investigate the enthalpy efficiency and gas-phase contaminant transfer in a polymer membrane enthalpy recovery unit. One commercially available polymer membrane enthalpy recovery unit was used as a reference unit. Simulated indoor air...... and outdoor air by twin chambers was connected to the unit. Three chemical gases were dosed to the indoor exhaust air to mimic indoor air contaminants. Based on the measurements of temperature, humidity ratio, and contaminant concentrations of the indoor exhaust air and outdoor air supply upstream...

Antifouling coatings via plasma polymerization and atom transfer radical polymerization on thin film composite membranes for reverse osmosis

Science.gov (United States)

Hirsch, Ulrike; Ruehl, Marco; Teuscher, Nico; Heilmann, Andreas

2018-04-01

A major drawback to otherwise highly efficient membrane-based desalination techniques like reverse osmosis (RO) is the susceptibility of the membranes to biofouling. In this work, a combination of plasma activation, plasma bromination and surface-initiated atom transfer radical polymerization (si-ATRP) of hydrophilic and zwitterionic monomers, namely hydroxyethyl methacrylate (HEMA), 2-methacryloyloxyethyl phosphorylcholine (MPC) and [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was applied to generate non-specific, anti-adhesive coatings on thin film composite (TFC) membranes. The antifouling effect of the coatings was shown by short-time batch as well as long-time steady state cultivation experiments with the microorganism Pseudomonas fluorescens. It could be shown that plasma functionalization and polymerization is possible on delicate thin film composite membranes without restricting their filtration performance. All modified membranes showed an increased resistance towards the adhesion of Pseudomonas fluorescens. On average, the biofilm coverage was reduced by 51.4-12.6% (for HEMA, SBMA, and MPC), the highest reduction was monitored for MPC with a biofilm reduction by 85.4%. The hydrophilic coatings applied did not only suppress the adhesion of Pseudomonas fluorescens, but also significantly increase the permeate flux of the membranes relative to uncoated membranes. The stability of the coatings was however not ideal and will have to be improved for future commercial use.

Nanothin Coculture Membranes with Tunable Pore Architecture and Thermoresponsive Functionality for Transfer-Printable Stem Cell-Derived Cardiac Sheets.

Science.gov (United States)

Ryu, Seungmi; Yoo, Jin; Jang, Yeongseon; Han, Jin; Yu, Seung Jung; Park, Jooyeon; Jung, Seon Yeop; Ahn, Kyung Hyun; Im, Sung Gap; Char, Kookheon; Kim, Byung-Soo

2015-10-27

Coculturing stem cells with the desired cell type is an effective method to promote the differentiation of stem cells. The features of the membrane used for coculturing are crucial to achieving the best outcome. Not only should the membrane act as a physical barrier that prevents the mixing of the cocultured cell populations, but it should also allow effective interactions between the cells. Unfortunately, conventional membranes used for coculture do not sufficiently meet these requirements. In addition, cell harvesting using proteolytic enzymes following coculture impairs cell viability and the extracellular matrix (ECM) produced by the cultured cells. To overcome these limitations, we developed nanothin and highly porous (NTHP) membranes, which are ∼20-fold thinner and ∼25-fold more porous than the conventional coculture membranes. The tunable pore size of NTHP membranes at the nanoscale level was found crucial for the formation of direct gap junctions-mediated contacts between the cocultured cells. Differentiation of the cocultured stem cells was dramatically enhanced with the pore size-customized NTHP membrane system compared to conventional coculture methods. This was likely due to effective physical contacts between the cocultured cells and the fast diffusion of bioactive molecules across the membrane. Also, the thermoresponsive functionality of the NTHP membranes enabled the efficient generation of homogeneous, ECM-preserved, highly viable, and transfer-printable sheets of cardiomyogenically differentiated cells. The coculture platform developed in this study would be effective for producing various types of therapeutic multilayered cell sheets that can be differentiated from stem cells.

Characterization of membrane protein interactions in plasma membrane derived vesicles with quantitative imaging Förster resonance energy transfer.

Science.gov (United States)

Sarabipour, Sarvenaz; Del Piccolo, Nuala; Hristova, Kalina

2015-08-18

Here we describe an experimental tool, termed quantitative imaging Förster resonance energy transfer (QI-FRET), that enables the quantitative characterization of membrane protein interactions. The QI-FRET methodology allows us to acquire binding curves and calculate association constants for complex membrane proteins in the native plasma membrane environment. The method utilizes FRET detection, and thus requires that the proteins of interest are labeled with florescent proteins, either FRET donors or FRET acceptors. Since plasma membranes of cells have complex topologies precluding the acquisition of two-dimensional binding curves, the FRET measurements are performed in plasma membrane derived vesicles that bud off cells as a result of chemical or osmotic stress. The results overviewed here are acquired in vesicles produced with an osmotic vesiculation buffer developed in our laboratory, which does not utilize harsh chemicals. The concentrations of the donor-labeled and the acceptor-labeled proteins are determined, along with the FRET efficiencies, in each vesicle. The experiments utilize transient transfection, such that a wide variety of concentrations is sampled. Then, data from hundreds of vesicles are combined to yield dimerization curves. Here we discuss recent findings about the dimerization of receptor tyrosine kinases (RTKs), membrane proteins that control cell growth and differentiation via lateral dimerization in the plasma membrane. We focus on the dimerization of fibroblast growth factor receptor 3 (FGFR3), a RTK that plays a critically important role in skeletal development. We study the role of different FGFR3 domains in FGFR3 dimerization in the absence of ligand, and we show that FGFR3 extracellular domains inhibit unliganded dimerization, while contacts between the juxtamembrane domains, which connect the transmembrane domains to the kinase domains, stabilize the unliganded FGFR3 dimers. Since FGFR3 has been documented to harbor many pathogenic

Osmotic Power Generation by Inner Selective Hollow Fiber Membranes: An investigation of thermodynamics, mass transfer, and module scale modelling

KAUST Repository

Xiong, Jun Ying

2016-12-29

A comprehensive analysis of fluid motion, mass transport, thermodynamics and power generation during pressure retarded osmotic (PRO) processes was conducted. This work aims to (1) elucidate the fundamental relationship among various membrane properties and operation parameters and (2) analyse their individual and combined impacts on PRO module performance. A state-of-the-art inner-selective thin-film composite (TFC) hollow fiber membrane was employed in the modelling. The analyses of mass transfer and Gibbs free energy of mixing indicate that the asymmetric nature of hollow fibers results in more significant external concentration polarization (ECP) in the lumen side of the inner-selective hollow fiber membranes. In addition, a trade-off relationship exists between the power density (PD) and the specific energy (SE). The PD vs. SE trade-off upper bound may provide a useful guidance whether the flowrates of the feed and draw solutions should be further optimized in order to (1) minimize the boundary thickness and (2) maximize the osmotic power generation. Two new terms, mass transfer efficiency and power harvesting efficiency for osmotic power generation, have been proposed. This work may provide useful insights to design and operate PRO modules with enhanced performance so that the PRO process becomes more promising in real applications in the near future.

Specificity and kinetics of alpha-synuclein binding to model membranes determined with fluorescent excited state intramolecular proton transfer (ESIPT) probe.

Science.gov (United States)

Shvadchak, Volodymyr V; Falomir-Lockhart, Lisandro J; Yushchenko, Dmytro A; Jovin, Thomas M

2011-04-15

Parkinson disease is characterized cytopathologically by the deposition in the midbrain of aggregates composed primarily of the presynaptic neuronal protein α-synuclein (AS). Neurotoxicity is currently attributed to oligomeric microaggregates subjected to oxidative modification and promoting mitochondrial and proteasomal dysfunction. Unphysiological binding to membranes of these and other organelles is presumably involved. In this study, we performed a systematic determination of the influence of charge, phase, curvature, defects, and lipid unsaturation on AS binding to model membranes using a new sensitive solvatochromic fluorescent probe. The interaction of AS with vesicular membranes is fast and reversible. The protein dissociates from neutral membranes upon thermal transition to the liquid disordered phase and transfers to vesicles with higher affinity. The binding of AS to neutral and negatively charged membranes occurs by apparently different mechanisms. Interaction with neutral bilayers requires the presence of membrane defects; binding increases with membrane curvature and rigidity and decreases in the presence of cholesterol. The association with negatively charged membranes is much stronger and much less sensitive to membrane curvature, phase, and cholesterol content. The presence of unsaturated lipids increases binding in all cases. These findings provide insight into the relation between membrane physical properties and AS binding affinity and dynamics that presumably define protein localization in vivo and, thereby, the role of AS in the physiopathology of Parkinson disease.

Membrane fusion between baculovirus budded virus-enveloped particles and giant liposomes generated using a droplet-transfer method for the incorporation of recombinant membrane proteins.

Science.gov (United States)

Nishigami, Misako; Mori, Takaaki; Tomita, Masahiro; Takiguchi, Kingo; Tsumoto, Kanta

2017-07-01

Giant proteoliposomes are generally useful as artificial cell membranes in biochemical and biophysical studies, and various procedures for their preparation have been reported. We present here a novel preparation technique that involves the combination of i) cell-sized lipid vesicles (giant unilamellar vesicles, GUVs) that are generated using the droplet-transfer method, where lipid monolayer-coated water-in-oil microemulsion droplets interact with oil/water interfaces to form enclosed bilayer vesicles, and ii) budded viruses (BVs) of baculovirus (Autographa californica nucleopolyhedrovirus) that express recombinant transmembrane proteins on their envelopes. GP64, a fusogenic glycoprotein on viral envelopes, is activated by weak acids and is thought to cause membrane fusion with liposomes. Using confocal laser scanning microscopy (CLSM), we observed that the single giant liposomes fused with octadecyl rhodamine B chloride (R18)-labeled wild-type BV envelopes with moderate leakage of entrapped soluble compounds (calcein), and the fusion profile depended on the pH of the exterior solution: membrane fusion occurred at pH ∼4-5. We further demonstrated that recombinant transmembrane proteins, a red fluorescent protein (RFP)-tagged GPCR (corticotropin-releasing hormone receptor 1, CRHR1) and envelope protein GP64 could be partly incorporated into membranes of the individual giant liposomes with a reduction of the pH value, though there were also some immobile fluorescent spots observed on their circumferences. This combination may be useful for preparing giant proteoliposomes containing the desired membranes and inner phases. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparison of Theoretical and Experimental Mass Transfer Coefficients of Gases in Supported Ionic Liquid Membranes

Czech Academy of Sciences Publication Activity Database

Kárászová, Magda; Šimčík, Miroslav; Friess, K.; Randová, A.; Jansen, J. C.; Růžička, Marek; Sedláková, Zuzana; Izák, Pavel

2013-01-01

Roč. 118, 30 OCT (2013), s. 255-263 ISSN 1383-5866 R&D Projects: GA ČR GAP106/10/1194; GA MŠk(CZ) 7C11009 Grant - others:RFCS(XE) RFCR-CT-2010-00009; INP(IT) PON01_01840; HA MŠk(CZ) CZ.1.05/2.1.00/03.0071 Institutional support: RVO:67985858 Keywords : biogas purification * supported ionic liquid membranes * mass transfer coefficients Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.065, year: 2013

Performance modeling of direct contact membrane distillation (DCMD) seawater desalination process using a commercial composite membrane

KAUST Repository

Lee, Junggil; Kim, Youngdeuk; Kim, Wooseung; Francis, Lijo; Amy, Gary L.; Ghaffour, NorEddine

2015-01-01

membrane and the heat transfer across the membrane and through the boundary layers adjacent to the membrane surfaces. Experimental results and model predictions for permeate flux and performance ratio are compared and shown to be in good agreement

Electrochemical ion transfer mediated by a lipophilic Os(ii)/Os(iii) dinonyl bipyridyl probe incorporated in thin film membranes.

Science.gov (United States)

Jansod, Sutida; Wang, Lu; Cuartero, Maria; Bakker, Eric

2017-09-28

A new lipophilic dinonyl bipyridyl Os(ii)/Os(iii) complex successfully mediates ion transfer processes across voltammetric thin membranes. An added lipophilic cation-exchanger may impose voltammetric anion or cation transfer waves of Gaussian shape that are reversible and repeatable. The peak potential is found to shift with the ion concentration in agreement with the Nernst equation. The addition of tridodecylmethylammonium nitrate to the polymeric film dramatically reduces the peak separation from 240 mV to 65 mV, and the peak width to a near-theoretical value of 85 mV, which agrees with a surface confined process. It is suggested that the cationic additive serves as a phase transfer catalyst.

Time to delivery: Transfers for threatened preterm labour and prelabour rupture of membranes in Western Australia.

Science.gov (United States)

Hollingworth, Jade; Pietsch, Rachel; Epee-Bekima, Mathias; Nathan, Elizabeth

2018-02-01

To describe the outcomes of patients transferred to King Edward Memorial Hospital (KEMH) with signs of labour at preterm gestations. A retrospective observational study of the 69 cases transferred to KEMH during 2015. Patient transfers from all locations across Western Australia (WA) to the sole tertiary perinatal centre in Perth. Pregnant women within WA with threatened or actual preterm labour (PTL) or preterm prelabour rupture of membranes (PPROM) between 23 and 32 weeks gestation. The occurrence of delivery during the admission and time-to-delivery as well as length of admission and association between clinical factors and time-to-delivery. The percentage of the study population delivered during the admission following transfer was 72.5%. Eighty-six per cent of those who delivered did so within 72 hours of transfer. The median time from transfer to delivery was 1 day. Sixty-three per cent of those who did not deliver during the admission progressed to 36 weeks gestation. Patients transferred with PPROM were less likely to deliver during the admission compared to those with uterine activity (50% versus 19.6%, P = 0.007) and nulliparas were more likely to deliver (93.5% versus 55.3%, P < 0.001). The majority of women transferred with signs of PTL progress to delivery during the same admission with the highest risk of delivery being the first 72 hours following transfer. If the pregnancy is ongoing at 72 hours, there is a reasonable chance of progression to late preterm gestation supporting the return of woman to their place of origin for antenatal care following discharge. © 2017 National Rural Health Alliance Inc.

Mechanisms of proton conductance in polymer electrolyte membranes

DEFF Research Database (Denmark)

Eikerling, M.; Kornyshev, A. A.; Kuznetsov, A. M.

2001-01-01

We provide a phenomenological description of proton conductance in polymer electrolyte membranes, based on contemporary views of proton transfer processes in condensed media and a model for heterogeneous polymer electrolyte membrane structure. The description combines the proton transfer events...... in a single pore with the total pore-network performance and, thereby, relates structural and kinetic characteristics of the membrane. The theory addresses specific experimentally studied issues such as the effect of the density of proton localization sites (equivalent weight) of the membrane material...

A Solution of the Convective-Diffusion Equation for Solute Mass Transfer inside a Capillary Membrane Bioreactor

Directory of Open Access Journals (Sweden)

B. Godongwana

2010-01-01

Full Text Available This paper presents an analytical model of substrate mass transfer through the lumen of a membrane bioreactor. The model is a solution of the convective-diffusion equation in two dimensions using a regular perturbation technique. The analysis accounts for radial-convective flow as well as axial diffusion of the substrate specie. The model is applicable to the different modes of operation of membrane bioreactor (MBR systems (e.g., dead-end, open-shell, or closed-shell mode, as well as the vertical or horizontal orientation. The first-order limit of the Michaelis-Menten equation for substrate consumption was used to test the developed model against available analytical results. The results obtained from the application of this model, along with a biofilm growth kinetic model, will be useful in the derivation of an efficiency expression for enzyme production in an MBR.

Optimization of the southern electrophoretic transfer method

International Nuclear Information System (INIS)

Allison, M.A.; Fujimura, R.K.

1987-01-01

The technique of separating DNA fragments using agarose gel electrophoresis is essential in the analysis of nucleic acids. Further, after the method of transferring specific DNA fragments from those agarose gels to cellulose nitrate membranes was developed in 1975, a method was developed to transfer DNA, RNA, protein and ribonucleoprotein particles from various gels onto diazobenzyloxymethyl (DBM) paper using electrophoresis as well. This paper describes the optimum conditions for quantitative electrophoretic transfer of DNA onto nylon membranes. This method exemplifies the ability to hybridize the membrane more than once with specific RNA probes by providing sufficient retention of the DNA. Furthermore, the intrinsic properties of the nylon membrane allow for an increase in the efficiency and resolution of transfer while using somewhat harsh alkaline conditions. The use of alkaline conditions is of critical importance since we can now denature the DNA during transfer and thus only a short pre-treatment in acid is required for depurination. 9 refs., 7 figs

Membrane bioreactors for waste gas treatment.

NARCIS (Netherlands)

Reij, M.W.; Keurentjes, J.T.F.; Hartmans, S.

1998-01-01

This review describes the recent development of membrane reactors for biological treatment of waste gases. In this type of bioreactor gaseous pollutants are transferred through a membrane to the liquid phase, where micro-organisms degrade the pollutants. The membrane bioreactor combines the

Membrane bioreactors for waste gas treatment

NARCIS (Netherlands)

Reij, M.W.; Keurentjes, J.T.F.; Hartmans, S.

1998-01-01

This review describes the recent development of membrane reactors for biological treatment of waste gases. In this type of bioreactor gaseous pollutants are transferred through a membrane to the liquid phase, where micro-organisms degrade the pollutants. The membrane bioreactor combines the

Study of coupled heat and water transfer in proton exchange membrane fuel cells by the way of internal measurements

International Nuclear Information System (INIS)

Thomas, A; Maranzana, G; Didierjean, S; Dillet, J; Lottin, O

2012-01-01

Measurements of electrode temperatures within a proton exchange membrane fuel cell were performed using platinum wires. A temperature difference of 7°C between the electrodes and the bipolar plates was observed for a cell operating at a current density of 1.5 A.cm −2 . These measurements show a strong non-uniformity of the temperature profile through membrane electrode assembly (MEA) that future phenomenological models must take into account. In addition, the simultaneous measurements of heat and water flux through the MEA leads to the conclusion that produced water crosses the diffusion layer in vapor phase. A very simple heat transfer model is proposed.

GLTP mediated non-vesicular GM1 transport between native membranes.

Directory of Open Access Journals (Sweden)

Ines Lauria

Full Text Available Lipid transfer proteins (LTPs are emerging as key players in lipid homeostasis by mediating non-vesicular transport steps between two membrane surfaces. Little is known about the driving force that governs the direction of transport in cells. Using the soluble LTP glycolipid transfer protein (GLTP, we examined GM1 (monosialotetrahexosyl-ganglioside transfer to native membrane surfaces. With artificial GM1 donor liposomes, GLTP can be used to increase glycolipid levels over natural levels in either side of the membrane leaflet, i.e., external or cytosolic. In a system with native donor- and acceptor-membranes, we find that GLTP balances highly variable GM1 concentrations in a population of membranes from one cell type, and in addition, transfers lipids between membranes from different cell types. Glycolipid transport is highly efficient, independent of cofactors, solely driven by the chemical potential of GM1 and not discriminating between the extra- and intracellular membrane leaflet. We conclude that GLTP mediated non-vesicular lipid trafficking between native membranes is driven by simple thermodynamic principles and that for intracellular transport less than 1 µM GLTP would be required in the cytosol. Furthermore, the data demonstrates the suitability of GLTP as a tool for artificially increasing glycolipid levels in cellular membranes.

Effect of membranes on oxygen transfer rate and consumption within a newly developed three-compartment bioartificial liver device: Advanced experimental and theoretical studies.

Science.gov (United States)

Hilal-Alnaqbi, Ali; Mourad, Abdel-Hamid I; Yousef, Basem F

2014-01-01

A mathematical model is developed to predict oxygen transfer in the fiber-in-fiber (FIF) bioartificial liver device. The model parameters are taken from the constructed and tested FIF modules. We extended the Krogh cylinder model by including one more zone for oxygen transfer. Cellular oxygen uptake was based on Michaelis-Menten kinetics. The effect of varying a number of important model parameters is investigated, including (1) oxygen partial pressure at the inlet, (2) the hydraulic permeability of compartment B (cell region), (3) the hydraulic permeability of the inner membrane, and (4) the oxygen diffusivity of the outer membrane. The mathematical model is validated by comparing its output against the experimentally acquired values of an oxygen transfer rate and the hydrostatic pressure drop. Three governing simultaneous linear differential equations are derived to predict and validate the experimental measurements, e.g., the flow rate and the hydrostatic pressure drop. The model output simulated the experimental measurements to a high degree of accuracy. The model predictions show that the cells in the annulus can be oxygenated well even at high cell density or at a low level of gas phase PG if the value of the oxygen diffusion coefficient Dm is 16 × 10(-5) . The mathematical model also shows that the performance of the FIF improves by increasing the permeability of polypropylene membrane (inner fiber). Moreover, the model predicted that 60% of plasma has access to the cells in the annulus within the first 10% of the FIF bioreactor axial length for a specific polypropylene membrane permeability and can reach 95% within the first 30% of its axial length. © 2013 International Union of Biochemistry and Molecular Biology, Inc.

Flux Enhancement in Membrane Distillation Using Nanofiber Membranes

Directory of Open Access Journals (Sweden)

T. Jiříček

2016-01-01

Full Text Available Membrane distillation (MD is an emerging separation technology, whose largest application potential lies in the desalination of highly concentrated solutions, which are out of the scope of reverse osmosis. Despite many attractive features, this technology is still awaiting large industrial application. The main reason is the lack of commercially available membranes with fluxes comparable to reverse osmosis. MD is a thermal separation process driven by a partial vapour pressure difference. Flux, distillate purity, and thermal efficiency are always in conflict, all three being strictly connected with pore size, membrane hydrophobicity, and thickness. The world has not seen the ideal membrane yet, but nanofibers may offer a solution to these contradictory requirements. Membranes of electrospun PVDF were tested under various conditions on a direct contact (DCMD unit, in order to determine the optimum conditions for maximum flux. In addition, their performance was compared to commonly available PTFE, PE, and PES membranes. It was confirmed that thinner membranes have higher fluxes and a lower distillate purity and also higher energy losses via conduction across the membrane. As both mass and heat transfer are connected, it is best to develop new membranes with a target application in mind, for the specific membrane module and operational conditions.

One dimensional transient numerical study of the mass heat and charge transfer in a proton exchange membrane for PEMFC

Energy Technology Data Exchange (ETDEWEB)

Haddad, Djamel; Benmoussa, Hocine [Laboratory (LESEI), Faculty of Engineering, University of Batna (Algeria); Bourmada, Noureddine; Oulmi, Kafia [Laboratory LCCE, Faculty of Science, University of Batna (Algeria); Mahmah, Bouziane; Belhamel, Maiouf [CDER, BP, 62 Avenue-Observatoire, Bouzareah, Alger (Algeria)

2009-06-15

The objective of our study is to quantify the mass water transferred by various modes: diffusion, convection and migration. For the water transfer, the principal forces considered in the model are, the convection force, the osmotic force (i.e. diffusion) and the electric force (migration). The first of these forces results from a pressure gradient, the second of a concentration gradient and the third of a protons' migration from the anode to the cathode, which has an effect on the dipole of the water molecules (resistance force to the advancement). The numerical tool used to solve the equations' system is the finite element method. The results obtained numerically considering this method are concentration profiles and concentration variation with time and membrane thickness. These results illustrate the contribution of each mass transfer mode. (author)

Control of distributed heat transfer mechanisms in membrane distillation plants

KAUST Repository

Laleg-Kirati, Taous-Meriem; Eleiwi, Fadi; Karam, Ayman M.

2017-01-01

Various examples are provided that are related to boundary control in membrane distillation (MD) processes. In one example, a system includes a membrane distillation (MD) process comprising a feed side and a permeate side separated by a membrane

Direct transfer of graphene onto flexible substrates

Science.gov (United States)

Martins, Luiz G. P.; Song, Yi; Zeng, Tingying; Dresselhaus, Mildred S.; Kong, Jing; Araujo, Paulo T.

2013-01-01

In this paper we explore the direct transfer via lamination of chemical vapor deposition graphene onto different flexible substrates. The transfer method investigated here is fast, simple, and does not require an intermediate transfer membrane, such as polymethylmethacrylate, which needs to be removed afterward. Various substrates of general interest in research and industry were studied in this work, including polytetrafluoroethylene filter membranes, PVC, cellulose nitrate/cellulose acetate filter membranes, polycarbonate, paraffin, polyethylene terephthalate, paper, and cloth. By comparing the properties of these substrates, two critical factors to ensure a successful transfer on bare substrates were identified: the substrate’s hydrophobicity and good contact between the substrate and graphene. For substrates that do not satisfy those requirements, polymethylmethacrylate can be used as a surface modifier or glue to ensure successful transfer. Our results can be applied to facilitate current processes and open up directions for applications of chemical vapor deposition graphene on flexible substrates. A broad range of applications can be envisioned, including fabrication of graphene devices for opto/organic electronics, graphene membranes for gas/liquid separation, and ubiquitous electronics with graphene. PMID:24127582

Direct transfer of graphene onto flexible substrates.

Science.gov (United States)

Martins, Luiz G P; Song, Yi; Zeng, Tingying; Dresselhaus, Mildred S; Kong, Jing; Araujo, Paulo T

2013-10-29

In this paper we explore the direct transfer via lamination of chemical vapor deposition graphene onto different flexible substrates. The transfer method investigated here is fast, simple, and does not require an intermediate transfer membrane, such as polymethylmethacrylate, which needs to be removed afterward. Various substrates of general interest in research and industry were studied in this work, including polytetrafluoroethylene filter membranes, PVC, cellulose nitrate/cellulose acetate filter membranes, polycarbonate, paraffin, polyethylene terephthalate, paper, and cloth. By comparing the properties of these substrates, two critical factors to ensure a successful transfer on bare substrates were identified: the substrate's hydrophobicity and good contact between the substrate and graphene. For substrates that do not satisfy those requirements, polymethylmethacrylate can be used as a surface modifier or glue to ensure successful transfer. Our results can be applied to facilitate current processes and open up directions for applications of chemical vapor deposition graphene on flexible substrates. A broad range of applications can be envisioned, including fabrication of graphene devices for opto/organic electronics, graphene membranes for gas/liquid separation, and ubiquitous electronics with graphene.

Mass transfer in corrugated-plate membrane modules. I. Hyperfiltration experiments

NARCIS (Netherlands)

van der Waal, M.J.; Racz, I.G.

1989-01-01

The application of corrugations as turbulence promoters in membrane filtration was studied. This study showed that it is possible to deform an originally flat membrane to a corrugated shape without damaging it. In hyperfiltration experiments using corrugated cellulose acetate membranes it was found

Mass transfer in corrugated-plate membrane modules. II. Ultrafiltration experiments

NARCIS (Netherlands)

van der Waal, M.J.; Stevanovic, S.; Racz, I.G.

1989-01-01

The application of corrugations as turbulence promoters in membrane filtration was studied. In ultrafiltration experiments with polysulfone membranes using Dextran T70 as solute, it was found that the corrugations result in reduced energy consumption or pressure drop compared with flat membranes at

Preparation of high-capacity, weak anion-exchange membranes by surface-initiated atom transfer radical polymerization of poly(glycidyl methacrylate) and subsequent derivatization with diethylamine

International Nuclear Information System (INIS)

Qian, Xiaolei; Fan, Hua; Wang, Chaozhan; Wei, Yinmao

2013-01-01

Ion-exchange membrane is of importance for the development of membrane chromatography. In this work, a high-capacity anion-exchange membrane was prepared by grafting of glycidyl methacrylate (GMA) onto the surface of regenerated cellulose (RC) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequent derivatization with diethylamine. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize changes in the chemical functionality, surface topography and pore morphology of the modified membranes. The static capacity of the prepared anion-exchange membrane was evaluated with bovine serum albumin (BSA) as a model protein. The results indicated that the anion-exchange membrane which could reach a maximum capacity of 96 mg/mL for static adsorption possesses a higher adsorption capacity, and the adsorption capacity increases with the polymerization time. The effect of pH and salt concentration confirmed that the adsorption of BSA followed ion-exchange mechanism. The established method would have potential application in the preparation of anion-exchange membrane.

Modelling of a tubular membrane contactor for pre-combustion CO2 capture using ionic liquids: Influence of the membrane configuration, absorbent properties and operation parameters

Directory of Open Access Journals (Sweden)

Zhongde Dai

2016-10-01

Full Text Available A membrane contactor using ionic liquids (ILs as solvent for pre-combustion capture CO2 at elevated temperature (303–393 K and pressure (20 bar has been studied using mathematic model in the present work. A comprehensive two-dimensional (2D mass-transfer model was developed based on finite element method. The effects of liquid properties, membrane configurations, as well as operation parameters on the CO2 removal efficiency were systematically studied. The simulation results show that CO2 can be effectively removed in this process. In addition, it is found that the liquid phase mass transfer dominated the overall mass transfer. Membranes with high porosity and small thickness could apparently reduce the membrane resistance and thus increase the separation efficiency. On the other hand, the membrane diameter and membrane length have a relatively small influence on separation performance within the operation range. Keywords: CO2 capture, Pre-combustion, Membrane contactor, Ionic liquids, Modelling

Oxygen-transfer performance of a newly designed, very low-volume membrane oxygenator.

Science.gov (United States)

Burn, Felice; Ciocan, Sorin; Carmona, Natalia Mendez; Berner, Marion; Sourdon, Joevin; Carrel, Thierry P; Tevaearai Stahel, Hendrik T; Longnus, Sarah L

2015-09-01

Oxygenation of blood and other physiological solutions are routinely required in fundamental research for both in vitro and in vivo experimentation. However, very few oxygenators with suitable priming volumes (parallel-oriented microporous polypropylene hollow fibres, placed inside a hollow shell with a lateral-luer outlet, and sealed at both extremities. With this design, perfusate is delivered via the core-tube to the centre of the mini-oxygenator, and exits via the luer port. A series of mini-oxygenators were constructed and tested in an in vitro perfusion circuit by monitoring oxygen transfer using modified Krebs-Henseleit buffer or whole porcine blood. Effects of perfusion pressure and temperature over flows of 5-60 ml × min(-1) were assessed. Twelve mini-oxygenators with a mean priming volume of 1.5 ± 0.3 ml were evaluated. With buffer, oxygen transfer reached a maximum of 14.8 ± 1.0 ml O2 × l(-1) (pO2: 450 ± 32 mmHg) at perfusate flow rates of 5 ml × min(-1) and decreased with an increase in perfusate flow to 7.8 ± 0.7 ml ml O2 × l(-1) (pO2: 219 ± 24 mmHg) at 60 ml × min(-1). Similarly, with blood perfusate, oxygen transfer also decreased as perfusate flow increased, ranging from 33 ± 5 ml O2 × l(-1) at 5 ml × min(-1) to 11 ± 2 ml O2 × l(-1) at 60 ml × min(-1). Furthermore, oxygen transfer capacity remained stable with blood perfusion over a period of at least 2 h. We have developed a new miniaturized membrane oxygenator with an ultra-low priming volume (circuits, such as small animal extracorporeal circulation and ex vivo organ perfusion. © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Influence of estrogenic pesticides on membrane integrity and membrane transfer of monosaccharide into the human red cell

International Nuclear Information System (INIS)

Ingermann, R.L.

1989-01-01

Some natural and synthetic estrogens inhibit carrier-mediated transport of glucose into human red blood cells and membrane vesicles from the placenta. The inhibitory action of these estrogens on transport appears to be a direct effect at the membrane and does not involve receptor binding and protein synthesis. It is not clear, however, whether such inhibition is a common feature among estrogenic agents. Several chlorinated hydrocarbon pesticides have been shown to possess estrogenic activity. These pesticides could have inhibitory effects on the human sodium-independent glucose transporter. Owing to the apparent importance of this membrane transporter in human tissues, direct interaction of hormones and xenobiotics with the glucose transporter is of fundamental significance. Some pesticides have been shown to alter membrane structure directly and alter the passive permeability of membranes. Whether the estrogenic pesticides influence passive diffusion of sugars across membranes has not been established. Finally, preliminary observations have suggested that some estrogens and pesticides have lytic effects on intact cells. Consequently, this study focuses on the ability of several estrogens and estrogenic pesticides to disrupt the cell membrane, influence the monosaccharide transporter, and alter the rate of monosaccharide permeation through the membrane by simple diffusion

Molecular, dynamic, and structural origin of inhomogeneous magnetization transfer in lipid membranes.

Science.gov (United States)

Swanson, Scott D; Malyarenko, Dariya I; Fabiilli, Mario L; Welsh, Robert C; Nielsen, Jon-Fredrik; Srinivasan, Ashok

2017-03-01

To elucidate the dynamic, structural, and molecular properties that create inhomogeneous magnetization transfer (ihMT) contrast. Amphiphilic lipids, lamellar phospholipids with cholesterol, and bovine spinal cord (BSC) specimens were examined along with nonlipid systems. Magnetization transfer (MT), enhanced MT (eMT, obtained with double-sided radiofrequency saturation), ihMT (MT - eMT), and dipolar relaxation, T 1D , were measured at 2.0 and 11.7 T. The amplitude of ihMT ratio (ihMTR) is positively correlated with T 1D values. Both ihMTR and T 1D increase with increasing temperature in BSC white matter and in phospholipids and decrease with temperature in other lipids. Changes in ihMTR with temperature arise primarily from alterations in MT rather than eMT. Spectral width of MT, eMT, and ihMT increases with increasing carbon chain length. Concerted motions of phospholipids in white matter decrease proton spin diffusion leading to increased proton T 1D times and increased ihMT amplitudes, consistent with decoupling of Zeeman and dipolar spin reservoirs. Molecular specificity and dynamic sensitivity of ihMT contrast make it a suitable candidate for probing myelin membrane disorders. Magn Reson Med 77:1318-1328, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Surface modification of polysulfone membranes applied for a membrane reactor with immobilized alcohol dehydrogenase

DEFF Research Database (Denmark)

Hoffmann, Christian; Silau, Harald; Pinelo, Manuel

2018-01-01

activated by lithiation followed by functionalization with acid chlorides at 0 °C, permitting modification of commercial PSf membranes without compromising the mechanical integrity of the membrane. Post-functionalization polymer grafting was illustrated through both, a “grafting from” approach by surface...... initiated atom transfer radical polymerization (SI-ATRP) and by a “grafting to” approach exploiting Cu(I) catalyzed 1,3-cycloadditions of alkynes with azides (CuAAC) introducing hydrophilic polymers onto the membrane surface. Poly(1-vinyl imidazole) (pVim) grafted membranes were exploited as support...

Transferable, conductive TiO{sub 2} nanotube membranes for optoelectronics

Energy Technology Data Exchange (ETDEWEB)

Liu, Guohua [School of Energy and Environment, Anhui University of Technology, Maanshan 243002 (China); Department of Micro and Nano Systems Technology, Vestfold University College, Horten 3184 (Norway); Chen, Ting [School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Sun, Yunlan; Chen, Guang [School of Energy and Environment, Anhui University of Technology, Maanshan 243002 (China); Wang, Kaiying, E-mail: Kaiying.Wang@hbv.no [Department of Micro and Nano Systems Technology, Vestfold University College, Horten 3184 (Norway)

2014-08-30

Graphical abstract: An optoelectronic device with vertical architecture offers straight conducting filaments for electron transportation. - Highlights: • Highly porous TiO{sub 2} nanotube membranes are prepared by two-step anodization. • An optoelectronic device is integrated with photocurrent transportation along the nanotube axial. • Straight conducting nano-filaments are beneficial for electron transportation. • Photoconductive performances are demonstrated under front/back-illumination. - Abstract: We report a facile approach for preparing free-standing and crystalline TiO{sub 2} nanotube membranes (TNMs) by taking advantage of differential mechanical stress between two anodic layers. The membrane exhibits visible light transmittance (∼40%) and UV absorption (∼99%) with good flexibility, which is favorable to integrate with substrates in optoelectronics. A sandwich-type device is assembled through stacking the membrane and substrates. The dependence of current-perpendicular-to-membrane vs applied voltage shows a remarkable photoconductive performance for both front and back illumination. The photocurrent value increases ∼2 or 3 orders magnitude under UV light radiation as compared to that in darkness. The photoresponse is arisen from high internal gain caused by hole trapping along the nanotube walls. This work is crucial for understanding intrinsic optical properties of nanostructured membranes.

Systematic implicit solvent coarse-graining of bilayer membranes: lipid and phase transferability of the force field

Energy Technology Data Exchange (ETDEWEB)

Wang Zunjing; Deserno, Markus, E-mail: zwang@cmu.ed, E-mail: deserno@andrew.cmu.ed [Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States)

2010-09-15

We study the lipid and phase transferability of our recently developed systematically coarse-grained solvent-free membrane model. The force field was explicitly parameterized to describe a fluid 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) bilayer at 310 K with correct structure and area per lipid, while gaining at least three orders of magnitude in computational efficiency (see Wang and Deserno 2010 J. Phys. Chem. B 114 11207-20). Here, we show that exchanging CG tails, without any subsequent re-parameterization, creates reliable models of 1,2-dioleoylphosphatidylcholine (DOPC) and 1,2-dipalmitoylphosphatidylcholine (DPPC) lipids in terms of structure and area per lipid. Furthermore, all CG lipids undergo a liquid-gel transition upon cooling, with characteristics like those observed in experiments and all-atom simulations during phase transformation. These studies suggest a promising transferability of our force field parameters to different lipid species and thermodynamic state points, properties that are a prerequisite for even more complex systems, such as mixtures.

Systematic implicit solvent coarse-graining of bilayer membranes: lipid and phase transferability of the force field

International Nuclear Information System (INIS)

Wang Zunjing; Deserno, Markus

2010-01-01

We study the lipid and phase transferability of our recently developed systematically coarse-grained solvent-free membrane model. The force field was explicitly parameterized to describe a fluid 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) bilayer at 310 K with correct structure and area per lipid, while gaining at least three orders of magnitude in computational efficiency (see Wang and Deserno 2010 J. Phys. Chem. B 114 11207-20). Here, we show that exchanging CG tails, without any subsequent re-parameterization, creates reliable models of 1,2-dioleoylphosphatidylcholine (DOPC) and 1,2-dipalmitoylphosphatidylcholine (DPPC) lipids in terms of structure and area per lipid. Furthermore, all CG lipids undergo a liquid-gel transition upon cooling, with characteristics like those observed in experiments and all-atom simulations during phase transformation. These studies suggest a promising transferability of our force field parameters to different lipid species and thermodynamic state points, properties that are a prerequisite for even more complex systems, such as mixtures.

Nonsymmetric gas transfer phenomena in nanoporous media

International Nuclear Information System (INIS)

Kurchatov, I.M.

2011-01-01

The regularities of nonsymmetric gas (nitrogen, helium, hydrogen, carbon dioxide) transfer in nanoporous materials are investigated. The effects of anisotropy and hysteresis of permeability in nanoporous media with pore gradient and porosity in objects of various nature are found out. The following objects are studied: polyethylene terephthalate track membranes with asymmetric pore form, commercial polyvinyl trimethylsilane gas-separation membranes with continuous distribution of pores over the membrane thickness and porous composite membranes (born nitride, silicon carbide, aluminium oxide) prepared by self-propagating high-temperature synthesis with abrupt change of pore dimensions over the thickness. The possible mechanisms of nonsymmetric gas transfer effects are under consideration [ru

Simple estimation of Förster Resonance Energy Transfer (FRET) orientation factor distribution in membranes.

Science.gov (United States)

Loura, Luís M S

2012-11-19

Because of its acute sensitivity to distance in the nanometer scale, Förster resonance energy transfer (FRET) has found a large variety of applications in many fields of chemistry, physics, and biology. One important issue regarding the correct usage of FRET is its dependence on the donor-acceptor relative orientation, expressed as the orientation factor k(2). Different donor/acceptor conformations can lead to k(2) values in the 0 ≤ k(2) ≤ 4 range. Because the characteristic distance for FRET, R(0), is proportional to (k(2))1/6, uncertainties in the orientation factor are reflected in the quality of information that can be retrieved from a FRET experiment. In most cases, the average value of k(2) corresponding to the dynamic isotropic limit ( = 2/3) is used for computation of R(0) and hence donor-acceptor distances and acceptor concentrations. However, this can lead to significant error in unfavorable cases. This issue is more critical in membrane systems, because of their intrinsically anisotropic nature and their reduced fluidity in comparison to most common solvents. Here, a simple numerical simulation method for estimation of the probability density function of k(2) for membrane-embedded donor and acceptor fluorophores in the dynamic regime is presented. In the simplest form, the proposed procedure uses as input the most probable orientations of the donor and acceptor transition dipoles, obtained by experimental (including linear dichroism) or theoretical (such as molecular dynamics simulation) techniques. Optionally, information about the widths of the donor and/or acceptor angular distributions may be incorporated. The methodology is illustrated for special limiting cases and common membrane FRET pairs.

Characterization of inclusion complexes of organic ions with hydrophilic hosts by ion transfer voltammetry with solvent polymeric membranes.

Science.gov (United States)

Olmos, José Manuel; Laborda, Eduardo; Ortuño, Joaquín Ángel; Molina, Ángela

2017-03-01

The quantitative characterization of inclusion complexes formed in aqueous phase between organic ions and hydrophilic hosts by ion-transfer voltammetry with solvent polymeric membrane ion sensors is studied, both in a theoretical and experimental way. Simple analytical solutions are presented for the determination of the binding constant of the complex from the variation with the host concentration of the electrochemical signal. These solutions are valid for any voltammetric technique and for solvent polymeric membrane ion sensors comprising one polarisable interface (1PI) and also, for the first time, two polarisable interfaces (2PIs). Suitable experimental conditions and data analysis procedures are discussed and applied to the study of the interactions of a common ionic liquid cation (1-octyl-3-metyl-imidazolium) and an ionisable drug (clomipramine) with two hydrophilic cyclodextrins: α-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin. The experimental study is performed via square wave voltammetry with 2PIs and 1PI solvent polymeric membranes and in both cases the electrochemical experiments enable the detection of inclusion complexes and the determination of the corresponding binding constant. Copyright © 2016 Elsevier B.V. All rights reserved.

Transfer of endogenous pyrogens across artificial membranes?

Science.gov (United States)

Lonnemann, G; Linnenweber, S; Burg, M; Koch, K M

1998-05-01

Synthetic high-flux dialyzer membranes used in continuous veno-venous hemofiltration are permeable to middle molecular size endogenous pyrogens, the pro-inflammatory cytokines IL-1 beta and TNF-alpha. The quantities removed by sieving are, however, negligible in vitro as well as in vivo. Adsorption of cytokines to the membrane polymer is the major mechanism of pyrogen removal. Adsorption seems to be semispecific for pro-inflammatory cytokines because levels of anti-inflammatory mediators were not changed or even increased during CVVH. Thus, CVVH may change cytokine profiles in septic patients supporting the predominance of anti-inflammatory over pro-inflammatory activity in plasma. It remains to be demonstrated whether modifications of extracorporeal blood purification systems (high-volume CVVH, plasma separation + adsorption) are able to amplify the change in cytokine profiles and whether this change influences outcome of septic patients.

A novel solution for reducing the transfer of particles and gases among adjacent apartments

DEFF Research Database (Denmark)

Iqbal, Ahsan; Afshari, Alireza

2016-01-01

of the sealing membrane reduced the transfer of UFP up to 86% and reduced the transfer of N2O up to 87.5% in comparison with the transfers without the membrane. A similar procedure of measuring the transfer of UFP and gases was adapted in situ measurements. In situ the sealing membrane was able to reduce...... the transfer of UFP up to 53%. A survey regarding occupant’s perception of the performance of the sealing membrane was also conducted after 4 months post occupancy. Before the renovation, the occupants were continuously irritated by the cigarette smells from their neighbours. However, after renovation......A unique type of fabric membrane has been developed by a Swedish company. That membrane is design to trap the emission from surfaces. To test the performance of the said membrane for trapping particles and gases, a study was conducted by the Danish Building Research Institute (SBi). The study...

Improving Hemocompatibility of Membranes for Extracorporeal Membrane Oxygenators by Grafting Nonthrombogenic Polymer Brushes.

Science.gov (United States)

Obstals, Fabian; Vorobii, Mariia; Riedel, Tomáš; de Los Santos Pereira, Andres; Bruns, Michael; Singh, Smriti; Rodriguez-Emmenegger, Cesar

2018-03-01

Nonthrombogenic modifications of membranes for extracorporeal membrane oxygenators (ECMOs) are of key interest. The absence of hemocompatibility of these membranes and the need of anticoagulation of patients result in severe and potentially life-threatening complications during ECMO treatment. To address the lack of hemocompatibility of the membrane, surface modifications are developed, which act as barriers to protein adsorption on the membrane and, in this way, prevent activation of the coagulation cascade. The modifications are based on nonionic and zwitterionic polymer brushes grafted directly from poly(4-methyl-1-pentene) (TPX) membranes via single electron transfer-living radical polymerization. Notably, this work introduces the first example of well-controlled surface-initiated radical polymerization of zwitterionic brushes. The antifouling layers markedly increase the recalcification time (a proxy of initiation of coagulation) compared to bare TPX membranes. Furthermore, platelet and leukocyte adhesion is drastically decreased, rendering the ECMO membranes hemocompatible. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Energy Technology Data Exchange (ETDEWEB)

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

2012-06-15

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

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

International Nuclear Information System (INIS)

Li Jianhua; Li Mizi; Miao Jing; Wang Jiabin; Shao Xisheng; Zhang Qiqing

2012-01-01

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

Gas separation with membranes

International Nuclear Information System (INIS)

Schulz, G.; Michele, H.; Werner, U.

1982-01-01

Gas separation with membranes has already been tested in numerous fields of application, e.g. uranium enrichment of H 2 separation. In many of these processes the mass transfer units, so-called permeators, have to be connected in tandem in order to achieve high concentrations. A most economical operating method provides for each case an optimization of the cascades with regard to the membrane materials, construction and design of module. By utilization of the concentration gradient along the membrane a new process development has been accomplished - the continuously operating membrane rectification unit. Investment and operating costs can be reduced considerably for a number of separating processes by combining a membrane rectification unit with a conventional recycling cascade. However, the new procedure requires that the specifications for the module construction, flow design, and membrane properties be reconsidered. (orig.) [de

Membrane assisted liquid-liquid extraction of cerium

International Nuclear Information System (INIS)

Soldenhoff, K.M.

2000-02-01

Membrane assisted liquid-liquid extraction of cerium was investigated, with emphasis placed on the study of the reaction chemistry and the kinetics of non-dispersive solvent extraction and stripping with microporous membranes. A bulk liquid membrane process was developed for the purification of cerium(IV) from sulfate solutions containing other rare earth elements. The cerium process was studied in both a flat sheet contained liquid membrane configuration and with hollow fibre contactors. Di-2-ethylhexyl phosphoric acid (DEHPA) was identified as a suitable extractant for cerium(IV) from sulfuric acid solution, with due consideration of factors such as extraction ability, resistance to degradation, solvent selectivity and potential for sulfate transfer into a strip solution. A detailed study of the extraction of cerium(IV) with DEHPA defined the extraction reaction chemistry. The Ce/DEHPA/sulfate system was also investigated with a flat sheet bulk liquid membrane configuration, using both sulfuric and hydrochloric acid as receiver solutions. These tests identified that hydrophobic membranes provide better mass transfer for extraction and hydrophilic membranes are better for stripping. The presence of an impurity, mono 2-ethylhexyl phosphoric acid (MEHPA), was found to have a dramatic accelerating effect on the rate of the chemical extraction reaction. This was attributed to its higher interfacial activity and population compared to DEHPA, and the fact that MEHPA was also found to be an active carrier for cerium(IV). The mass transfer rate of membrane assisted extraction and stripping of cerium, using hydrophobic and hydrophilic microporous membranes, respectively, was investigated using a modified Lewis-type cell. It was quantitatively demonstrated that the extraction process was mainly controlled by membrane diffusion and the stripping process was controlled by the chemical reaction rate, with membrane diffusion becoming important at low distribution coefficients

Coefficients of tracer transfer through membranes. Pt. 7

Energy Technology Data Exchange (ETDEWEB)

Dorabialska, A; Hawlicka, E; Plonka, A [Politechnika Lodzka (Poland)

1974-01-01

The doubled value of the tracer transfer coefficient in the self-diffusion process is equal to the sum of tracer transfer coefficients in the diffusion and interfusion processes. The fundamental phenomenological relation can be deduced for the coefficients of tracer transfer between two phases of electrolyte solutions spearated by a virtual boundary. Indeed, the doubled value of the tracer mobility in the self-diffusion experiment (no concentration gradient of the traced substance) is equal to the sum of the tracer mobilities in the diffusion (tracer movement along with the concentration gradient of the traced substance) and interfusion experiments (tracer movement against the concentration gradient of the traced substance). Thus the doubled value of the tracer transfer coefficient in the self-diffusion process should be equal to the sum of tracer transfer coefficients in the diffusion and interfusion processes. The experimental verification of that fundamental relation is presented.

Evaluation of in vitro absorption, decontamination and desorption of organophosphorous compounds from skin and synthetic membranes.

Science.gov (United States)

Mircioiu, Constantin; Voicu, Victor A; Ionescu, Mihaela; Miron, Dalia S; Radulescu, Flavian S; Nicolescu, Adrian C

2013-05-23

Chemical warfare agents, such as soman, and pesticides, such as chlorpyrifos, dichlorvos or malathion, are toxic organophosphorous compounds (OPCs) that are readily absorbed by the skin. Decontamination using solvents or surfactants may modify the cornified layer - the skin's main barrier against xenobiotic penetration. Thus, effective skin decontamination with fewer side effects is desired. We determined the membrane absorption, decontamination and desorption of toxic OPCs using human skin and synthetic membrane (cuprophane, cellulose acetate, methyl ethyl cellulose, acetophane and nylon) models, and estimated the efficacy of adsorptive powders (bentonite and magnesium trisilicate) at inhibiting this transfer. Using validated flow-through and static diffusion cell and HPLC methods, we found that the transfer of OPCs depends on their membrane affinity. The chlorpyrifos transfer decreased with a decrease in the membrane hydrophilicity, and that of malathion across hydrophilic membranes was less than half of that across hydrophobic membranes. We reliably modeled the toxicant transfer through the skin and synthetic membranes as first-order kinetic and/or square root law transfer processes, suggesting a potential application of synthetic membranes for predicting percutaneous absorption of OPCs. All tested adsorptive powders, applied either alone or as mixtures, significantly reduced the toxicant amount transferred across all membrane models, suggesting a potential therapeutic application with fewer later undesired effects on intact skin. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Cell-printing and transfer technology applications for bone defects in mice.

Science.gov (United States)

Tsugawa, Junichi; Komaki, Motohiro; Yoshida, Tomoko; Nakahama, Ken-ichi; Amagasa, Teruo; Morita, Ikuo

2011-10-01

Bone regeneration therapy based on the delivery of osteogenic factors and/or cells has received a lot of attention in recent years since the discovery of pluripotent stem cells. We reported previously that the implantation of capillary networks engineered ex vivo by the use of cell-printing technology could improve blood perfusion. Here, we developed a new substrate prepared by coating glass with polyethylene glycol (PEG) to create a non-adhesive surface and subsequent photo-lithography to finely tune the adhesive property for efficient cell transfer. We examined the cell-transfer efficiency onto amniotic membrane and bone regenerative efficiency in murine calvarial bone defect. Cell transfer of KUSA-A1 cells (murine osteoblasts) to amniotic membrane was performed for 1 h using the substrates. Cell transfer using the substrate facilitated cell engraftment onto the amniotic membrane compared to that by direct cell inoculation. KUSA-A1 cells transferred onto the amniotic membrane were applied to critical-sized calvarial bone defects in mice. Micro-computed tomography (micro-CT) analysis showed rapid and effective bone formation by the cell-equipped amniotic membrane. These results indicate that the cell-printing and transfer technology used to create the cell-equipped amniotic membrane was beneficial for the cell delivery system. Our findings support the development of a biologically stable and effective bone regeneration therapy. Copyright © 2011 John Wiley & Sons, Ltd.

Membrane distillation against a pressure difference

OpenAIRE

Keulen, L.; van der Ham, L.V.; Kuipers, N.J.M.; Hanemaaijer, J.H.; Vlugt, T.J.H.; Kjelstrup, S.

2017-01-01

Membrane distillation is an attractive technology for production of fresh water from seawater. The MemPower®MemPower® concept, studied in this work, uses available heat (86 °C) to produce pressurized water (2.2 bar and 46 °C) by membrane distillation, which again can be used to power a turbine for co-production of electricity. We develop a non-equilibrium thermodynamic model to accurately describe the transfer at the liquid-membrane interfaces, as well as through the hydrophobic membrane. The...

Diffuse Charge Effects in Fuel Cell Membranes

NARCIS (Netherlands)

Biesheuvel, P.M.; Franco, A.A.; Bazant, M.Z.

2009-01-01

It is commonly assumed that electrolyte membranes in fuel cells are electrically neutral, except in unsteady situations, when the double-layer capacitance is heuristically included in equivalent circuit calculations. Indeed, the standard model for electron transfer kinetics at the membrane/electrode

Revealing Linear Aggregates of Light Harvesting Antenna Proteins in Photosynthetic Membranes

OpenAIRE

He, Yufan; Zeng, Xiaohua; Mukherjee, Saptarshi; Rajapaksha, Suneth; Kaplan, Samuel; Lu, H. Peter

2010-01-01

How light energy is harvested in a natural photosynthetic membrane through energy transfer is closely related to the stoichiometry and arrangement of light harvesting antenna proteins in the membrane. The specific photosynthetic architecture facilitates a rapid and efficient energy transfer among the light harvesting proteins (LH2 and LH1) and to the reaction center. Here we report the identification of linear aggregates of light harvesting proteins, LH2, in the photosynthetic membranes under...

Gene transfer and expression in human neutrophils. The phox homology domain of p47phox translocates to the plasma membrane but not to the membrane of mature phagosomes

Directory of Open Access Journals (Sweden)

Brzezinska Agnieszka A

2006-12-01

Full Text Available Abstract Background Neutrophils are non-dividing cells with poor survival after isolation. Consequently, exogenous gene expression in neutrophils is challenging. We report here the transfection of genes and expression of active proteins in human primary peripheral neutrophils using nucleofection. Results Exogenous gene expression in human neutrophils was achieved 2 h post-transfection. We show that neutrophils transfected by nucleofection are functional cells, able to respond to soluble and particulate stimuli. They conserved the ability to undergo physiological processes including phagocytosis. Using this technique, we were able to show that the phox homology (PX domain of p47phox localizes to the plasma membrane in human neutrophils. We also show that RhoB, but not the PX domain of p47phox, is translocated to the membrane of mature phagosomes. Conclusion We demonstrated that cDNA transfer and expression of exogenous protein in human neutrophils is compatible with cell viability and is no longer a limitation for the study of protein function in human neutrophils.

Effect of membrane on carbonation and carbon dioxide uptake of Chlorella sp.

Directory of Open Access Journals (Sweden)

Suali Emma

2017-01-01

Full Text Available Recent studies showed that as low as 5% CO2 increased microalgae growth. However, common bioreactor operation resulted in low carbonation due to poor CO2 mass transfer and this inhibited CO2 uptake of microalgae. Although bubbling increases mass transfer of CO2-O2 exchange, preserving high dissolved CO2 remains the most challenging of microalgae cultivation in bioreactor. In order to increase high dissolved CO2 and CO2-O2 exchange, this study employed two types of membrane; hollow-fibre membrane for carbonation and hydrophobic membrane for deoxygenation. It was found that membrane increased carbonation from 20 % to 75 % when operated at control CO2 concentration. The hollow-fibre membrane capable of creating as small as 2 mm bubble which effective for high carbonation. At the same time, itincreased CO2 uptake up to 85% in bioreactor. The hydrophobic membrane removed 43% O2 from the bioreactor. Both membranes increased mass transfer of CO2-O2 exchange in bioreactor which stimulated microalgae growth.

A Mathematical Model of Membrane Gas Separation with Energy Transfer by Molecules of Gas Flowing in a Channel to Molecules Penetrating this Channel from the Adjacent Channel

Directory of Open Access Journals (Sweden)

Szwast Maciej

2015-06-01

Full Text Available The paper presents the mathematical modelling of selected isothermal separation processes of gaseous mixtures, taking place in plants using membranes, in particular nonporous polymer membranes. The modelling concerns membrane modules consisting of two channels - the feeding and the permeate channels. Different shapes of the channels cross-section were taken into account. Consideration was given to co-current and counter-current flows, for feeding and permeate streams, respectively, flowing together with the inert gas receiving permeate. In the proposed mathematical model it was considered that pressure of gas changes along the length of flow channels was the result of both - the drop of pressure connected with flow resistance, and energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel. The literature on membrane technology takes into account only the drop of pressure connected with flow resistance. Consideration given to energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel constitute the essential novelty in the current study. The paper also presents results of calculations obtained by means of a computer program which used equations of the derived model. Physicochemical data concerning separation of the CO2/CH4 mixture with He as the sweep gas and data concerning properties of the membrane made of PDMS were assumed for calculations.

Supported extractant membranes for americium and plutonium recovery

International Nuclear Information System (INIS)

Muscatello, A.C.; Navratil, J.D.; Killion, M.E.; Price, M.Y.

1987-01-01

Solid supported liquid membranes(SLM) are useful in transferring and concentrating americium and plutonium from nitrate solutions. Specifically, DHDECMP(dihexyl-N,N-diethylcarbamoylmethylphosphonate) supported on Accurel or Celgard polypropylene hollow fibers assembled in modular form transfers >95% of the americium and >70% of the plutonium from high nitrate (6.9 M), low acid (0.1 M) feeds into 0.25 M oxalic acid stripping solution. Membranes supporting TBP (tri-n-butylphosphate) also transfer these metal ions. Maximum permeabilities were observed to be 1 x 10 -3 cm sec -1 , similar to the values for other systems. The feed:strip volume ratio shows an inverse relationship to the fraction of metal ion transferred. Cation exchangers may be used to concentrate americium from the strip solution

A numerical study on the effects of temperature and mass transfer in high temperature PEM fuel cells with ab-PBI membrane

International Nuclear Information System (INIS)

Sun, Hong; Xie, Chen; Chen, Hao; Almheiri, Saif

2015-01-01

Highlights: • A two-dimensional model is developed to study the HT-PEMFC with ab-PBI membrane. • The temperature distribution in the ab-PBI membrane is uneven. • With the increase of temperature, the resistance in ab-PBI membrane decreases. • Porosity has the most significant effect on the performance of HT-PEMFC. - Abstract: A two-dimensional, single-phase model is developed to study high temperature proton exchange membrane (HT-PEM) fuel cell with poly(2,5-benzimidazole) (ab-PBI) membrane. In this model, simulation region not only includes the cathode and anode, but also includes ab-PBI membrane; the continuity boundary condition at the interface between the catalyst layer (CL) and the gas diffusion layer (GDL) at each side of the cell is omitted by including the catalyst layers in the respective unified domains for the cathode and the anode. The flows, species, energy, current density are all coupled in the model. Experiments have been conducted to validate the proposed numerical simulations, and it is found that there is a good agreement between the modeling results and those obtained experimentally. By this simulation, not only the oxygen and water fraction distribution in the cathode, but also the temperature distribution and resistance distribution in the ab-PBI membrane are obtained, and the effects of the cell temperature, the porosity in the diffusion layer and its thickness on the current density are analyzed. The innovative researching results are that the temperature distribution is uneven in the ab-PBI membrane and its resistance is greatly affected by the operating temperature. Other results show that the increase of the cell temperature and the porosity in the diffusion layer, and the decrease of the diffusion layer thickness all improve the performance of HT-PEM fuel cells by promoting its internal mass transfer.

Spontaneous charged lipid transfer between lipid vesicles.

Science.gov (United States)

Richens, Joanna L; Tyler, Arwen I I; Barriga, Hanna M G; Bramble, Jonathan P; Law, Robert V; Brooks, Nicholas J; Seddon, John M; Ces, Oscar; O'Shea, Paul

2017-10-03

An assay to study the spontaneous charged lipid transfer between lipid vesicles is described. A donor/acceptor vesicle system is employed, where neutrally charged acceptor vesicles are fluorescently labelled with the electrostatic membrane probe Fluoresceinphosphatidylethanolamine (FPE). Upon addition of charged donor vesicles, transfer of negatively charged lipid occurs, resulting in a fluorescently detectable change in the membrane potential of the acceptor vesicles. Using this approach we have studied the transfer properties of a range of lipids, varying both the headgroup and the chain length. At the low vesicle concentrations chosen, the transfer follows a first-order process where lipid monomers are transferred presumably through the aqueous solution phase from donor to acceptor vesicle. The rate of transfer decreases with increasing chain length which is consistent with energy models previously reported for lipid monomer vesicle interactions. Our assay improves on existing methods allowing the study of a range of unmodified lipids, continuous monitoring of transfer and simplified experimental procedures.

Flow-Injection Amperometric Determination of Tacrine based on Ion Transfer across a Water–Plasticized Polymeric Membrane Interface

Directory of Open Access Journals (Sweden)

C. Rueda

2007-07-01

Full Text Available A flow-injection pulse amperometric method for determining tacrine, based onion transfer across a plasticized poly(vinyl chloride (PVC membrane, was developed. Afour-electrode potentiostat with ohmic drop compensation was used, while a flow-throughcell incorporated the four electrodes and the membrane, which containedtetrabutylammonium tetraphenylborate. The influence of the applied potential and of theflow-injection variables on the determination of tacrine was studied. In the selectedconditions, a linear relationship between peak height and tacrine concentration was foundup to 4x10-5M tacrine. The detection limit was 1x10-7M. Good repeatability was obtained.Some common ions and pharmaceutical excipients did not interfere.

Polymalic Acid Tritryptophan Copolymer Interacts with Lipid Membrane Resulting in Membrane Solubilization

Directory of Open Access Journals (Sweden)

Hui Ding

2017-01-01

Full Text Available Anionic polymers with membrane permeation functionalities are highly desirable for secure cytoplasmic drug delivery. We have developed tritryptophan containing copolymer (P/WWW of polymalic acid (PMLA that permeates membranes by a mechanism different from previously described PMLA copolymers of trileucine (P/LLL and leucine ethyl ester (P/LOEt that use the “barrel stave” and “carpet” mechanism, respectively. The novel mechanism leads to solubilization of membranes by forming copolymer “belts” around planar membrane “packages.” The formation of such packages is supported by results obtained from studies including size-exclusion chromatography, confocal microscopy, and fluorescence energy transfer. According to this “belt” mechanism, it is hypothesized that P/WWW first attaches to the membrane surface. Subsequently the hydrophobic tryptophan side chains translocate into the periphery and insert into the lipid bilayer thereby cutting the membrane into packages. The reaction is driven by the high affinity between the tryptophan residues and lipid side chains resulting in a stable configuration. The formation of the membrane packages requires physical agitation suggesting that the success of the translocation depends on the fluidity of the membrane. It is emphasized that the “belt” mechanism could specifically function in the recognition of abnormal cells with high membrane fluidity and in response to hyperthermia.

Smart coating process of proton-exchange membrane for polymer electrolyte fuel cell

International Nuclear Information System (INIS)

Leu, Hoang-Jyh; Chiu, Kuo-Feng; Lin, Chiu-Yue

2013-01-01

Highlights: ► Using oxygen plasma and smart coating technique for membrane modification. ► Oxygen plasma treatment can increase the reaction area of the membrane. ► AFM, SEM, FT-IR, XPS, EIS spectra can prove the surface treatment process. ► Nafion membrane modification can reduce Rct and enhance current density. - Abstract: The interfaces of electrolyte|catalyst|electrode play an important role in the performance of proton-exchange membrane fuel cells (PEMFCs). Increasing the interface effective area and lowering the charge transfer resistance of the interface are significant issues to promote the cell performance. In this study, oxygen plasma treatment was used to increase the surface roughness of Nafion®117 membrane, and then a smart coating process was applied to fabricate the initial Pt/C catalyst layer, which served to reduce the charge transfer resistance of the interface. The morphology and surface characteristics of membranes have been qualified by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. These results show that the plasma treatments and smart coating processes were effective in reducing the interface charge transfer resistance. At optimal condition, the interface charge transfer resistance was 0.45 Ω/cm 2 which was 1–2 order less than the untreated ones

Design of UV-absorbing PVDF membrane via surface-initiated AGET ATRP

Science.gov (United States)

Dong, Li; Liu, Xiangdong; Xiong, Zhengrong; Sheng, Dekun; Zhou, Yan; Lin, Changhong; Yang, Yuming

2018-03-01

Herein, PVDF membranes with excellent UV-absorbing property were first synthesized through grafting the polymerizable low-molecular-weight organic UV-absorber 2-hydroxy-4-(3-methacryloxy-2-hydroxylpropoxy) benzophenone (BPMA) onto α-bromoester-functionalized PVDF membranes via the surface-initiated activator generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP). The surface initiators were immobilized by the reaction between 2-bromoisobutyryl bromide (BIBB) and the hydroxylated PVDF membranes. PVDF-g-PBPMA membranes with different grafting densities were obtained by tuning the polymerization time and the modified membranes were characterized by 1H-NMR, FT-IR, XPS, SEM, UV-vis Spectrophotometer, TGA and DSC. The experimental results indicated that PBPMA chains were successfully introduced onto PVDF membranes. Most importantly, the PVDF-g-PBPMA membranes exhibited outstanding UV-shielding property. UV-vis transmittance spectra showed that most UV light below 360 nm could be absorbed by PVDF-g-PBPMA membranes and the whole UV light region (200-400 nm) can be blocked with the reaction time increased.

Nitrogen transfer in the interface between the symbionts in pea root nodules

DEFF Research Database (Denmark)

Rosendahl, L.; Mouritzen, P.; Rudbeck, A.

2001-01-01

Transport mechanisms for transfer of nitrogen from the bacteroid side across the symbiosome membrane of pea (Pisum sativum L.) root nodules were identified by the use of energised bacteroid side-out symbiosome membrane vesicles. Such membrane vesicles were used to study a mechanism with high...... was not observed. The ammonium transporter has been identified as a voltage-driven channel whereas the symbiosome membrane aspartate transporter appears to be a H+/aspartate symport. The results suggest that nitrogen transfer between the symbionts in pea root nodules involves transfer of amino acids as well...... capacity for transport of ammonium and another mechanism capable of transporting aspartate. Both transport mechanisms are voltage driven and the rate of transport relates positively to the magnitude of the imposed membrane potentials. Competition for transport between ammonium and aspartate...

Problems with multiple use of transfer buffer in protein electrophoretic transfer.

Science.gov (United States)

Dorri, Yaser; Kurien, Biji T; Scofield, R Hal

2010-04-01

Two-dimensional gel electrophoresis (2DE) and SDS-PAGE are the two most useful methods in protein separation. Proteins separated by 2DE or SDS-PAGE are usually transferred to membranes using a variety of methods, such as electrophoretic transfer, heat-mediated transfer, or nonelectrophoretic transfer, for specific protein detection and/or analysis. In a recent study, Pettegrew et al. claim to reuse transfer buffer containing methanol for at least five times for transferring proteins from SDS-PAGE to polyvinylidene difluoride. They add 150-200 ml fresh transfer solution each time for extended use as a result of loss of transfer buffer. Finally, they test efficiency of each protein transfer by chemiluminescence detection. Here, we comment on this report, as we believe this method is not accurate and useful for protein analysis, and it can cause background binding as well as inaccurate protein analysis.

Kinetics of americium(VI) mass transfer through solid supported liquid membrane with HDEHP

International Nuclear Information System (INIS)

Mikheeva, M.N.; Novicoov, P.; Myasoedov, B.F.; Tikhomirov, S.V.

1994-01-01

The main regularities of membrane extraction of americium under conditions of different redox potentials in aqueous phases have been studied. The physico-chemical model of the process including steps of americium oxidation in feed solution, extraction by membrane, partial reduction on membrane surface, trans-membrane diffusion and reextraction to strip solution has been developed. The calculation of reduction rate constant on membrane surface has been carried out. (author) 9 refs.; 4 figs.; 3 tabs

Pore channel surface modification for enhancing anti-fouling membrane distillation

Science.gov (United States)

Qiu, Haoran; Peng, Yuelian; Ge, Lei; Villacorta Hernandez, Byron; Zhu, Zhonghua

2018-06-01

Membrane surface modification by forming a functional layer is an effective way to improve the anti-fouling properties of membranes; however, the additional layer and the potential blockage of bulk pores may increase the mass transfer resistance and reduce the permeability. In this study, we applied a novel method of preparing anti-fouling membranes for membrane distillation by dispersing graphene oxide (GO) on the channel surface of polyvinylidene fluoride membranes. The surface morphology and properties were characterized by scanning electron microscopy, atomic force microscope, and Fourier transform infrared spectrometry. Compared to the membrane surface modification by nanoparticles (e.g. SiO2), GO was mainly located on the pore surface of the membrane bulk, rather than being formed as an individual layer onto the membrane surface. The performance was evaluated via a direct-contact membrane distillation process with anionic and cationic surfactants as the foulants, separately. Compared to the pristine PVDF membrane, the anti-fouling behavior and distillate flux of the GO-modified membranes were improved, especially when using the anionic surfactant as the foulant. The enhanced anti-fouling performance can be attributed to the oxygen containing functional groups in GO and the healing of the membrane pore defects. This method may provide an effective route to manipulate membrane pore surface properties for anti-fouling separation without increasing mass transfer resistance.

Uranium preconcentration from seawater using adsorptive membranes

International Nuclear Information System (INIS)

Das, Sadananda; Pandey, A.K.; Manchanda, V.K.; Athawale, A.A.

2009-01-01

Uranium recovery from bio-aggressive but lean feed like seawater is a challenging problem as it requires in situ preconcentration of uranium in presence of huge excess of competing ions with fast sorption kinetics. In our laboratory, widely used amidoxime membrane (AO-membrane) was evaluated for uranium sorption under seawater conditions. This study indicated that AO-membrane was inherently slow because of the complexation chemistry involved in transfer of U(VI) from (UO 2 (CO 3 ) 3 ) 4 - to AO sites in membrane. In order to search better options, several chemical compositions of membrane were scanned for their efficacy for uranium preconcentration from seawater, and concluded that EGMP-membrane offers several advantages over AO-membrane. In this paper, the comparison of EGMP-membrane with AO-membrane for uranium sorption under seawater conditions has been reviewed. (author)

Advances in Membrane Distillation for Water Desalination and Purification Applications

Directory of Open Access Journals (Sweden)

Juan Gomez

2013-01-01

Full Text Available Membrane distillation is a process that utilizes differences in vapor pressure to permeate water through a macro-porous membrane and reject other non-volatile constituents present in the influent water. This review considers the fundamental heat and mass transfer processes in membrane distillation, recent advances in membrane technology, module configurations, and the applications and economics of membrane distillation, and identifies areas that may lead to technological improvements in membrane distillation as well as the application characteristics required for commercial deployment.

Interaction of the alpha-toxin of Staphylococcus aureus with the liposome membrane.

Science.gov (United States)

Ikigai, H; Nakae, T

1987-02-15

When the liposome membrane is exposed to the alpha-toxin of Staphylococcus aureus, fluorescence of the tryptophan residue(s) of the toxin molecule increases concomitantly with the degree of toxin-hexamer formation (Ikigai, H., and Nakae, T. (1985) Biochem. Biophys. Res. Commun. 130, 175-181). In the present study, the toxin-membrane interaction was distinguished from the hexamer formation by the fluorescence energy transfer from the tryptophan residue(s) of the toxin molecule to the dansylated phosphatidylethanolamine in phosphatidylcholine liposome. Measurement of these two parameters yielded the following results. The effect of the toxin concentration and phospholipid concentration on these two parameters showed first order kinetics. The effect of liposome size on the energy transfer and the fluorescence increment of the tryptophan residue(s) was only detectable in small liposomes. Under moderately acidic or basic conditions, the fluorescence energy transfer always preceded the fluorescence increment of the tryptophan residue(s). The fluorescence increment at 336 nm at temperatures below 20 degrees C showed a latent period, whereas the fluorescence energy transfer did not. These results were thought to indicate that when alpha-toxin damages the target membrane, the molecule interacts with the membrane first, and then undergoes oligomerization within the membrane.

Progress in surface and membrane science

CERN Document Server

Cadenhead, D A

1981-01-01

Progress in Surface and Membrane Science, Volume 14 covers the advances in the study of surface and membrane science. The book discusses statistical thermodynamics of monolayer adsorption from gas and liquid mixtures on homogeneous and heterogeneous solid surfaces; and the structure of the boundary layers of liquids and its influence on the mass transfer in fine pores. The text then describes the coupling of ionic and non-electrolyte fluxes in ion selective membranes; the electrocatalytic properties of matalloporphins at the interface; and the adsorption from binary gas and liquid phases. Phas

Cell membranes in radiation injury

International Nuclear Information System (INIS)

Koeteles, G.J.

1986-01-01

Cell membrane-related phenomena caused by low linear energy transfer radiation with doses lower than those producing cell killing are outlined. Micromorphological alterations as well as functional activities appearing with the receptors and in binding sites render it possible to reveal early and temporary changes. The cell injuries are suggested to transfer damaging conditions to surviving cells and to contribute to further development of non-stochastic effects in tissues

Cholesterol-dependent energy transfer between fluorescent proteins-insights into protein proximity of APP and BACE1 in different membranes in Niemann-Pick type C disease cells.

Science.gov (United States)

von Einem, Bjoern; Weber, Petra; Wagner, Michael; Malnar, Martina; Kosicek, Marko; Hecimovic, Silva; Arnim, Christine A F von; Schneckenburger, Herbert

2012-11-26

Förster resonance energy transfer (FRET) -based techniques have recently been applied to study the interactions between β-site APP-cleaving enzyme-GFP (BACE1-GFP) and amyloid precursor protein-mRFP (APP-mRFP) in U373 glioblastoma cells. In this context, the role of APP-BACE1 proximity in Alzheimer's disease (AD) pathogenesis has been discussed. FRET was found to depend on intracellular cholesterol levels and associated alterations in membrane stiffness. Here, NPC1 null cells (CHO-NPC1-/-), exhibiting increased cholesterol levels and disturbed cholesterol transport similar to that observed in Niemann-Pick type C disease (NPC), were used to analyze the influence of altered cholesterol levels on APP-BACE1 proximity. Fluorescence lifetime measurements of whole CHO-wild type (WT) and CHO-NPC1-/- cells (EPI-illumination microscopy), as well as their plasma membranes (total internal reflection fluorescence microscopy, TIRFM), were performed. Additionally, generalized polarization (GP) measurements of CHO-WT and CHO-NPC1-/- cells incubated with the fluorescence marker laurdan were performed to determine membrane stiffness of plasma- and intracellular-membranes. CHO-NPC1-/- cells showed higher membrane stiffness at intracellular- but not plasma-membranes, equivalent to cholesterol accumulation in late endosomes/lysosomes. Along with higher membrane stiffness, the FRET efficiency between BACE1-GFP and APP-mRFP was reduced at intracellular membranes, but not within the plasma membrane of CHO-NPC1-/-. Our data show that FRET combined with TIRF is a powerful technique to determine protein proximity and membrane fluidity in cellular models of neurodegenerative diseases.

Effect of rotation on convective mass transfer in rotating channels

International Nuclear Information System (INIS)

Pharoah, J.G.; Djilali, N.

2002-01-01

Laminar flow and mass transfer in rotating channels is investigated in the context of centrifugal membrane separation. The effect of orientation with respect to the rotational axis is examined for rectangular channels of aspect ratio 3 and the Rossby number is varied from 0.3 to 20.9. Both Ro and the channel orientation are found to have a significant effect on the flow. Mass transfer calculations corresponding to reverse osmosis desalination are carried out at various operating pressures and all rotating cases exhibit significant process enhancements at relatively low rotation rates. Finally, while it is common in the membrane literature to correlate mass transfer performance with membrane shear rates this is shown not to be valid in the cases presented herein. (author)

E.s.r. radiation studies of erythrocyte membrane-haemoglobin interaction

International Nuclear Information System (INIS)

Koter, M.; Kowalska, M.A.; Leyko, W.; Waterman, M.

1977-01-01

The dependence of the yield of free radicals in gamma-irradiated, freeze-dried erythrocyte membranes on their haemoglobin content was studied. A non-monotonous relationship was found, different from that observed in mixtures of freeze-dried membranes and haemoglobin, which suggests the existence of radiation-energy transfer between the membranes and bound haemoglobin. (author)

Water transport mechanisms across inorganic membranes in rad waste treatment by electro dialysis

International Nuclear Information System (INIS)

Andalaft, E.; Labayru, R.

1992-01-01

The work described in this paper deals with effects and mechanisms of water transport across an inorganic membrane, as related to some studied on the concentration of caesium, strontium, plutonium and other cations of interest to radioactive waste treatment. Several different water transport mechanisms are analysed and assessed as to their individual contribution towards the total transference of water during electro-dialysis using inorganic membranes. Water transfer assisted by proton jump mechanism, water of hydration transferred along with the ions, water related to thermo-osmotic effect, water transferred by concentration gradient and water transferred electrolytically under zeta potential surface charge drive are some of the different mechanism discussed. (author)

Model of mouth-to-mouth transfer of bacterial lipoproteins through inner membrane LolC, periplasmic LolA, and outer membrane LolB

OpenAIRE

Okuda, Suguru; Tokuda, Hajime

2009-01-01

Outer membrane-specific lipoproteins in Escherichia coli are released from the inner membrane by an ATP-binding cassette transporter, the LolCDE complex, which causes the formation of a soluble complex with a periplasmic molecular chaperone, LolA. LolA then transports lipoproteins to the outer membrane where an outer membrane receptor, LolB, incorporates lipoproteins into the outer membrane. The molecular mechanisms underlying the Lol-dependent lipoprotein sorting have been clarified in detai...

Ion beam heating of thin silicon membranes

International Nuclear Information System (INIS)

Tissot, P.E.; Hart, R.R.

1993-01-01

For silicon membranes irradiated by an ion beam in a vacuum environment, such as the masks used for ion beam lithography and the membranes used for thin film self-annealing, the heat transfer modes are radiation and limited conduction through the thin membrane. The radiation component depends on the total hemispherical emissivity which varies with the thickness and temperature of the membrane. A semiempirical correlation for the absorption coefficient of high resistivity silicon was derived and the variation of the total emissivity with temperature was computed for membranes with thicknesses between 0.1 and 10 μm. Based on this result, the temperatures reached during exposure to ion beams of varying intensities were computed. A proper modeling of the emissivity is shown to be important for beam heating of thin silicon membranes. (orig.)

Membranes for nanometer-scale mass fast transport

Science.gov (United States)

Bakajin, Olgica [San Leandro, CA; Holt, Jason [Berkeley, CA; Noy, Aleksandr [Belmont, CA; Park, Hyung Gyu [Oakland, CA

2011-10-18

Nanoporous membranes comprising single walled, double walled, and multiwalled carbon nanotubes embedded in a matrix material were fabricated for fluid mechanics and mass transfer studies on the nanometer scale and commercial applications. Average pore size can be 2 nm to 20 nm, or seven nm or less, or two nanometers or less. The membrane can be free of large voids spanning the membrane such that transport of material such as gas or liquid occurs exclusively through the tubes. Fast fluid, vapor, and liquid transport are observed. Versatile micromachining methods can be used for membrane fabrication. A single chip can comprise multiple membranes. These membranes are a robust platform for the study of confined molecular transport, with applications in liquid and gas separations and chemical sensing including desalination, dialysis, and fabric formation.

In-vivo identification of direct electron transfer from Shewanella oneidensis MR-1 to electrodes via outer-membrane OmcA-MtrCAB protein complexes

Energy Technology Data Exchange (ETDEWEB)

Okamoto, Akihiro [Department of Applied Chemistry, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nakamura, Ryuhei, E-mail: nakamura@light.t.u-tokyo.ac.jp [Department of Applied Chemistry, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Hashimoto, Kazuhito, E-mail: hashimoto@light.t.u-tokyo.ac.jp [Department of Applied Chemistry, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); ERATO/JST, HASHIMOTO Light Energy Conversion Project (Japan)

2011-06-30

Graphical abstract: . Display Omitted Highlights: > Monolayer biofilm of Shewanella cells was prepared on an ITO electrode. > Extracellular electron transfer (EET) process was examined with series of mutants. > Direct ET was confirmed with outer-membrane-bound OmcA-MtrCAB complex. > The EET process was not prominently influenced by capsular polysaccharide. - Abstract: The direct electron-transfer (DET) property of Shewanella bacteria has not been resolved in detail due to the complexity of in vivo electrochemistry in whole-cell systems. Here, we report the in vivo assignment of the redox signal indicative of the DET property in biofilms of Shewanella oneidensis MR-1 by cyclic voltammetry (CV) with a series of mutants and a chemical marking technique. The CV measurements of monolayer biofilms formed by deletion mutants of c-type cytochromes ({Delta}mtrA, {Delta}mtrB, {Delta}mtrC/{Delta}omcA, and {Delta}cymA), and pilin ({Delta}pilD), capsular polysaccharide ({Delta}SO3177) and menaquinone ({Delta}menD) biosynthetic proteins demonstrated that the electrochemical redox signal with a midpoint potential at 50 mV (vs. SHE) was due to an outer-membrane-bound OmcA-MtrCAB protein complex of decaheme cytochromes, and did not involve either inner-membrane-bound CymA protein or secreted menaquinone. Using the specific binding affinity of nitric monoxide for the heme groups of c-type cytochromes, we further confirmed this conclusion. The heterogeneous standard rate constant for the DET process was estimated to be 300 {+-} 10 s{sup -1}, which was two orders of magnitude higher than that previously reported for the electron shuttling process via riboflavin. Experiments using a mutant unable to produce capsular polysaccharide ({Delta}SO3177) revealed that the DET property of the OmcA-MtrCAB complex was not influenced by insulating and hydrophilic extracellular polysaccharide. Accordingly, under physiological conditions, S. oneidensis MR-1 utilizes a high density of outer-membrane

Checking transfer efficiency and equal loading via qualitative optical way in western blotting.

Science.gov (United States)

Gong, Jun-Hua; Gong, Jian-Ping; Zheng, Kai-Wen

2017-11-01

The ability to determine that successful transfer and equal loading occur prior to using primary antibodies is important. And total protein staining is commonly used to check transfer efficiency and normalization, which play a crucial role in western blotting. Ponceau S and coomassie blue are commonly used, but there are disadvantages reported in recent years. Therefore, we are interested in finding another method, which is cheap, easy and fast. As we know, protein binding region of PVDF membrane is still hydrophilic when carbinol volatilizes, however, the non-protein binding region of PVDF membrane became hydrophobic again. And this different wettability between non-protein binding region and protein binding region of Polyvinylidene difluoride membrane may be used to check transfer efficiency and equal loading in western blotting. Based on the principle above, we describe an optical approach where an experimenter can observe that the proteins have been transferred to the membrane without any staining within minutes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Voltammetry for the charge transfer at two immiscible electrolyte solutions interface

International Nuclear Information System (INIS)

Kihara, S.; Suzuki, M.; Maeda, K.; Ogura, K.; Matsui, M.; Yoshida, Z.

1989-01-01

The voltammetry for the charge transfer (VCT) at the interface of immicible solutions is a very powerful method for understanding the dynamic features of the charge transfer because of its unmatched advantage that the transfer energy and the number of charges transferred can be measured simultaneously and in situ. In the present paper, several novel systems for electron transfer are outlined, and the following topics are discussed based on results obtained by the current scan polarography at the solution dropping electrode developed as a technique for VCT: the relation between the half-wave potential in VCT for ion transfer and the characteristics of the ion transferred; the relation between the half-wave potential in VCT for electron transfer and the electrochemical nature of a redox couple added in water and that added in organic solution; and the ion transfer through a liquid membrane promoted by electron transfer. Observations are presented and discussion is made on the characteristics of ion transfer polarograms, those of electron transfer polarograms, and ion transfer promoted by electron transfer at a liquid/membrane interface. (N.K.)

Ceramic oxygen transport membrane array reactor and reforming method

Science.gov (United States)

Kelly, Sean M.; Christie, Gervase Maxwell; Robinson, Charles; Wilson, Jamie R; Gonzalez, Javier E.; Doraswami, Uttam R.

2017-10-03

The invention relates to a commercially viable modular ceramic oxygen transport membrane system for utilizing heat generated in reactively-driven oxygen transport membrane tubes to generate steam, heat process fluid and/or provide energy to carry out endothermic chemical reactions. The system provides for improved thermal coupling of oxygen transport membrane tubes to steam generation tubes or process heater tubes or reactor tubes for efficient and effective radiant heat transfer.

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

KAUST Repository

Lee, Jung Gil; Lee, Eui-Jong; Jeong, Sanghyun; Guo, Jiaxin; An, Alicia Kyoungjin; Guo, Hong; Kim, Joonha; Leiknes, TorOve; Ghaffour, NorEddine

2016-01-01

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

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

KAUST Repository

Lee, Jung Gil

2016-12-27

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

Nanostructured Polysulfone-Based Block Copolymer Membranes

KAUST Repository

Xie, Yihui

2016-01-01

polycondensation and reversible addition-fragmentation chain-transfer polymerization. The obtained membrane has a highly porous interconnected skin layer composed of elongated micelles with a flower-like arrangement, on top of the graded finger-like macrovoids

Rapid Preparation of a Plasma Membrane Fraction: Western Blot Detection of Translocated Glucose Transporter 4 from Plasma Membrane of Muscle and Adipose Cells and Tissues.

Science.gov (United States)

Yamamoto, Norio; Yamashita, Yoko; Yoshioka, Yasukiyo; Nishiumi, Shin; Ashida, Hitoshi

2016-08-01

Membrane proteins account for 70% to 80% of all pharmaceutical targets, indicating their clinical relevance and underscoring the importance of identifying differentially expressed membrane proteins that reflect distinct disease properties. The translocation of proteins from the bulk of the cytosol to the plasma membrane is a critical step in the transfer of information from membrane-embedded receptors or transporters to the cell interior. To understand how membrane proteins work, it is important to separate the membrane fraction of cells. This unit provides a protocol for rapidly obtaining plasma membrane fractions for western blot analysis. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

Sulfonated hydrocarbon graft architectures for cation exchange membranes

DEFF Research Database (Denmark)

Nielsen, Mads Møller; Jankova Atanasova, Katja; Hvilsted, Søren

2013-01-01

A synthetic strategy to hydrocarbon graft architectures prepared from a commercial polysulfone and aimed as ion exchange membrane material is proposed. Polystyrene is grafted from a polysulfone macroinitiator by atom transfer radical polymerization, and subsequently sulfonated with acetyl sulfate...... to various degrees. Series of grafting densities and graft lengths are prepared, and membranes are solvent cast from DMSO. The membrane properties in aqueous environments are evaluated from their water swelling behavior, and their thermal properties and stability are investigated by thermogravimetric...

Infrared emission of a freestanding plasmonic membrane

Science.gov (United States)

Monshat, Hosein; Liu, Longju; McClelland, John; Biswas, Rana; Lu, Meng

2018-01-01

This paper reports a free-standing plasmonic membrane as a thermal emitter in the near- and mid-infrared regions. The plasmonic membrane consists of an ultrathin gold film perforated with a two-dimensional array of holes. The device was fabricated using an imprint and transfer process and fixed on a low-emissivity metal grid. The thermal radiation characteristics of the plasmonic membrane can be engineered by controlling the array period and the thickness of the gold membrane. Plasmonic membranes with two different periods were designed using electromagnetic simulation and then characterized for their transmission and infrared radiation properties. The free-standing membranes exhibit extraordinary optical transmissions with the resonant transmission coefficient as high as 76.8%. After integration with a customized heater, the membranes demonstrate narrowband thermal emission in the wavelength range of 2.5 μm to 5.5 μm. The emission signatures, including peak emission wavelength and bandwidth, are associated with the membrane geometry. The ultrathin membrane infrared emitter can be adopted in applications, such as chemical analysis and thermal imaging.

Membrane Lipid Replacement for chronic illnesses, aging and cancer using oral glycerolphospholipid formulations with fructooligosaccharides to restore phospholipid function in cellular membranes, organelles, cells and tissues.

Science.gov (United States)

Nicolson, Garth L; Ash, Michael E

2017-09-01

Membrane Lipid Replacement is the use of functional, oral supplements containing mixtures of cell membrane glycerolphospholipids, plus fructooligosaccharides (for protection against oxidative, bile acid and enzymatic damage) and antioxidants, in order to safely replace damaged, oxidized, membrane phospholipids and restore membrane, organelle, cellular and organ function. Defects in cellular and intracellular membranes are characteristic of all chronic medical conditions, including cancer, and normal processes, such as aging. Once the replacement glycerolphospholipids have been ingested, dispersed, complexed and transported, while being protected by fructooligosaccharides and several natural mechanisms, they can be inserted into cell membranes, lipoproteins, lipid globules, lipid droplets, liposomes and other carriers. They are conveyed by the lymphatics and blood circulation to cellular sites where they are endocytosed or incorporated into or transported by cell membranes. Inside cells the glycerolphospholipids can be transferred to various intracellular membranes by lipid globules, liposomes, membrane-membrane contact or by lipid carrier transfer. Eventually they arrive at their membrane destinations due to 'bulk flow' principles, and there they can stimulate the natural removal and replacement of damaged membrane lipids while undergoing further enzymatic alterations. Clinical trials have shown the benefits of Membrane Lipid Replacement in restoring mitochondrial function and reducing fatigue in aged subjects and chronically ill patients. Recently Membrane Lipid Replacement has been used to reduce pain and other symptoms as well as removing hydrophobic chemical contaminants, suggesting that there are additional new uses for this safe, natural medicine supplement. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights

Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

Science.gov (United States)

Kelly, Sean M; Kromer, Brian R; Litwin, Michael M; Rosen, Lee J; Christie, Gervase Maxwell; Wilson, Jamie R; Kosowski, Lawrence W; Robinson, Charles

2014-01-07

A method and apparatus for producing heat used in a synthesis gas production is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the stream reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5.

Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

Science.gov (United States)

Kelly, Sean M.; Kromer, Brian R.; Litwin, Michael M.; Rosen, Lee J.; Christie, Gervase Maxwell; Wilson, Jamie R.; Kosowski, Lawrence W.; Robinson, Charles

2016-01-19

A method and apparatus for producing heat used in a synthesis gas production process is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the steam reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5

Vitreous membranes used in the biogas purification

International Nuclear Information System (INIS)

Ortega Viera, L.; Rodriguez Munoz, S.; Fernandez Santana, E.; Martines Ramirez, Y.; Crespo Artigas, A.; Viera Gallardo, Y.

2016-01-01

In the present work 10 vitreous membranes with different masses of zinc oxide (ZnO(s)) and particle diameters charcoal (DPC) are used in the purification of biogas. The porosity and tortuosity of the membranes is obtained, showing the variation with respect to the composition thereof. From these structural features specific flow of H 2 S(g) is obtained which is transferred using the Fick's diffusion equation in the membranes and its value increases with increasing mass of ZnO(s). By X-ray diffraction membrane made with 3.16 g of ZnO(s) forming zinc sulfide it is shown, so we can say that the removal of H 2 S(g) occurs by a process of absorption with chemical reaction in the membranes. (Author)

Membrane technology for treating of waste nanofluids coolant: A review

Science.gov (United States)

Mohruni, Amrifan Saladin; Yuliwati, Erna; Sharif, Safian; Ismail, Ahmad Fauzi

2017-09-01

The treatment of cutting fluids wastes concerns a big number of industries, especially from the machining operations to foster environmental sustainability. Discharging cutting fluids, waste through separation technique could protect the environment and also human health in general. Several methods for the separation emulsified oils or oily wastewater have been proposed as three common methods, namely chemical, physicochemical and mechanical and membrane technology application. Membranes are used into separate and concentrate the pollutants in oily wastewater through its perm-selectivity. Meanwhile, the desire to compensate for the shortcomings of the cutting fluid media in a metal cutting operation led to introduce the using of nanofluids (NFs) in the minimum quantity lubricant (MQL) technique. NFs are prepared based on nanofluids technology by dispersing nanoparticles (NPs) in liquids. These fluids have potentially played to enhance the performance of traditional heat transfer fluids. Few researchers have studied investigation of the physical-chemical, thermo-physical and heat transfer characteristics of NFs for heat transfer applications. The use of minimum quantity lubrication (MQL) technique by NFs application is developed in many metal cutting operations. MQL did not only serve as a better alternative to flood cooling during machining operation and also increases better-finished surface, reduces impact loads on the environment and fosters environmental sustainability. Waste coolant filtration from cutting tools using membrane was treated by the pretreated process, coagulation technique and membrane filtration. Nanomaterials are also applied to modify the membrane structure and morphology. Polyvinylidene fluoride (PVDF) is the better choice in coolant wastewater treatment due to its hydrophobicity. Using of polyamide nanofiltration membranes BM-20D and UF-PS-100-100, 000, it resulted in the increase of permeability of waste coolant filtration. Titanium dioxide

Transfer buffer containing methanol can be reused multiple times in protein electrotransfer.

Science.gov (United States)

Pettegrew, Colin J; Jayini, Renuka; Islam, M Rafiq

2009-04-01

We investigated the feasibility of repeated use of transfer buffer containing methanol in electrotransfer of proteins from sodium dodecyl sulfate-polyacrylamide gels to polyvinylidene difluoride (PVDF) membrane using a prestained protein marker of broad molecular sizes. Transfer of the antitumor protein p53 in HEK293T cell extracts, using fresh and used transfer buffer, followed by detection with anti-p53 antibody was also performed to test detectability in immunoblot. Results from these experiments indicate that the transfer buffer can be reused at least five times and maintain a similar extent of protein transfer to PVDF membrane. Repeated use of the transfer buffer containing methanol will significantly reduce the volume of hazardous waste generated and its disposal cost as well as its adverse effect on environment.

MStern Blotting–High Throughput Polyvinylidene Fluoride (PVDF) Membrane-Based Proteomic Sample Preparation for 96-Well Plates*

OpenAIRE

Berger, Sebastian T.; Ahmed, Saima; Muntel, Jan; Cuevas Polo, Nerea; Bachur, Richard; Kentsis, Alex; Steen, Judith; Steen, Hanno

2015-01-01

We describe a 96-well plate compatible membrane-based proteomic sample processing method, which enables the complete processing of 96 samples (or multiples thereof) within a single workday. This method uses a large-pore hydrophobic PVDF membrane that efficiently adsorbs proteins, resulting in fast liquid transfer through the membrane and significantly reduced sample processing times. Low liquid transfer speeds have prevented the useful 96-well plate implementation of FASP as a widely used mem...

Membrane complexes of Syntrophomonas wolfei involved in syntrophic butyrate degradation and hydrogen formation

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Bryan Regis Crable

2016-11-01

Full Text Available Syntrophic butyrate metabolism involves the thermodynamically unfavorable production of hydrogen and/or formate from the high potential electron donor, butyryl-CoA. Such redox reactions can occur only with energy input by a process called reverse electron transfer. Previous studies have demonstrated that hydrogen production from butyrate requires the presence of a proton gradient, but the biochemical machinery involved has not been clearly elucidated. In this study, the gene and enzyme systems involved in reverse electron transfer by Syntrophomonas wolfei were investigated using proteomic and gene expression approaches. S. wolfei was grown in coculture with Methanospirillum hungatei or Dehalococcoides mccartyi under conditions requiring reverse electron transfer and compared to both axenic S. wolfei cultures and cocultures grown in conditions that do not require reverse electron transfer. Blue native gel analysis of membranes solubilized from syntrophically grown cells revealed the presence of a membrane-bound hydrogenase, Hyd2, which exhibited hydrogenase activity during in gel assays. Bands containing a putative iron-sulfur (FeS oxidoreductase were detected in membranes of crotonate-grown and butyrate grown S. wolfei cells. The genes for the corresponding hydrogenase subunits, hyd2ABC, were differentially expressed at higher levels during syntrophic butyrate growth when compared to growth on crotonate. The expression of the FeS oxidoreductase gene increased when S. wolfei was grown with M. hungatei. Additional membrane-associated proteins detected included FoF1 ATP synthase subunits and several membrane transporters that may aid syntrophic growth. Furthermore, syntrophic butyrate metabolism can proceed exclusively by interspecies hydrogen transfer, as demonstrated by growth with D. mccartyi, which is unable to use formate. These results argue for the importance of Hyd2 and FeS oxidoreductase in reverse electron transfer during syntrophic

Transient response simulation of gas separation membrane module for an atmosphere detritiation system

International Nuclear Information System (INIS)

Sugiyama, Takahiko; Tanaka, Masahiro; Munakata, Kenzo; Yamamoto, Ichiro

2012-01-01

Transient response of a gas separation membrane module for the atmosphere detritiation system was numerically simulated with a mass transfer model. The module contains thousands of hollow fiber type polyimide membranes. The simulation model took into account permeation of water vapor through the dense layer of the membrane, diffusive transfer through the porous support layer and adsorption/desorption of water vapor into the matrix of the porous layer. The slow responses of the water vapor concentration in the retentate and the permeation rate were well reproduced by the present simulation, and transient changes in a follow fiber membrane were investigated in detail. The inventory and the mean residence time of water vapor at 303 K were estimated for the commercial membrane module (UMS-B2, Ube industries, Ltd.) as 5.7 × 10 −3 mol and 380 s, respectively.

Semiconductor particle mediated photoelectron transfers in bilayer lipid membranes

International Nuclear Information System (INIS)

Fendler, J.H.; Baral, S.

1989-01-01

This paper discusses semiconductor particles in situ generated on the cis surface of glyceryl monooleate (GMO) bilayer lipid membranes (BLMs), that have been used to mediate photoelectric effects. The presence of semiconductors on the BLM surface is addressed. The observed photoelectric effects are rationalized and presented

Transport dynamics in membranes of photosynthetic purple bacteria

Science.gov (United States)

Caycedo, Felipe; Rodriguez, Ferney; Quiroga, Luis; Fassioli, Francesca; Johnson, Neil

2007-03-01

Photo-Syntethic Unit (PSU) of purple bacteria is conformed by three basic constituents: Light Harvesting Complex 2 (LH2) antenna complexes, where chromophores are distributed in a ring in close contact with caroteniods with a function of collecting light; LH1s, ring shaped structures of chromophores which harvest and funnel excitations to the Reaction Centre (RC), where phtosynthesis takes place. Studies concerning a single PSU have been capable of reproducing experimental transfer times, but incapable of explaining the fact that architecture LH2-LH1-RC of phototosynthetic membranes changes as light intensity conditions vary. The organization of antenna complexes in the membranes that support PSU seems to have its own functionality. A hopping model where excitations are transferred within a membrane is used, and populations of RC, LH1 and LH2 are investigated. Different statistics concerning arrival times of excitations that excite a single PSU are considered and compared with the global model where coordinates of a great portion of a membrane are included. The model permits in a classical basis to understand which parameters make photosynthesis in purple bateria efficient and reliable.

Multi-layered nanoparticles for penetrating the endosome and nuclear membrane via a step-wise membrane fusion process.

Science.gov (United States)

Akita, Hidetaka; Kudo, Asako; Minoura, Arisa; Yamaguti, Masaya; Khalil, Ikramy A; Moriguchi, Rumiko; Masuda, Tomoya; Danev, Radostin; Nagayama, Kuniaki; Kogure, Kentaro; Harashima, Hideyoshi

2009-05-01

Efficient targeting of DNA to the nucleus is a prerequisite for effective gene therapy. The gene-delivery vehicle must penetrate through the plasma membrane, and the DNA-impermeable double-membraned nuclear envelope, and deposit its DNA cargo in a form ready for transcription. Here we introduce a concept for overcoming intracellular membrane barriers that involves step-wise membrane fusion. To achieve this, a nanotechnology was developed that creates a multi-layered nanoparticle, which we refer to as a Tetra-lamellar Multi-functional Envelope-type Nano Device (T-MEND). The critical structural elements of the T-MEND are a DNA-polycation condensed core coated with two nuclear membrane-fusogenic inner envelopes and two endosome-fusogenic outer envelopes, which are shed in stepwise fashion. A double-lamellar membrane structure is required for nuclear delivery via the stepwise fusion of double layered nuclear membrane structure. Intracellular membrane fusions to endosomes and nuclear membranes were verified by spectral imaging of fluorescence resonance energy transfer (FRET) between donor and acceptor fluorophores that had been dually labeled on the liposome surface. Coating the core with the minimum number of nucleus-fusogenic lipid envelopes (i.e., 2) is essential to facilitate transcription. As a result, the T-MEND achieves dramatic levels of transgene expression in non-dividing cells.

Indium-bump-free antimonide superlattice membrane detectors on silicon substrates

Energy Technology Data Exchange (ETDEWEB)

Zamiri, M., E-mail: mzamiri@chtm.unm.edu, E-mail: skrishna@chtm.unm.edu; Klein, B.; Schuler-Sandy, T.; Dahiya, V.; Cavallo, F. [Center for High Technology Materials, Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87106 (United States); Myers, S. [SKINfrared, LLC, Lobo Venture Lab, 801 University Blvd., Suite 10, Albuquerque, New Mexico 87106 (United States); Krishna, S., E-mail: mzamiri@chtm.unm.edu, E-mail: skrishna@chtm.unm.edu [Center for High Technology Materials, Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87106 (United States); SKINfrared, LLC, Lobo Venture Lab, 801 University Blvd., Suite 10, Albuquerque, New Mexico 87106 (United States)

2016-02-29

We present an approach to realize antimonide superlattices on silicon substrates without using conventional Indium-bump hybridization. In this approach, PIN superlattices are grown on top of a 60 nm Al{sub 0.6}Ga{sub 0.4}Sb sacrificial layer on a GaSb host substrate. Following the growth, the individual pixels are transferred using our epitaxial-lift off technique, which consists of a wet-etch to undercut the pixels followed by a dry-stamp process to transfer the pixels to a silicon substrate prepared with a gold layer. Structural and optical characterization of the transferred pixels was done using an optical microscope, scanning electron microscopy, and photoluminescence. The interface between the transferred pixels and the new substrate was abrupt, and no significant degradation in the optical quality was observed. An Indium-bump-free membrane detector was then fabricated using this approach. Spectral response measurements provided a 100% cut-off wavelength of 4.3 μm at 77 K. The performance of the membrane detector was compared to a control detector on the as-grown substrate. The membrane detector was limited by surface leakage current. The proposed approach could pave the way for wafer-level integration of photonic detectors on silicon substrates, which could dramatically reduce the cost of these detectors.

Investigation of separation factors of neptunium and plutonium in the process of mass transfer through liquid impregnated membranes with di-2-ethylhexylphosphoric acid

International Nuclear Information System (INIS)

Novikov, A.P.; Mikheeva, M.N.; Myasoedov, B.F.

1990-01-01

Kinetics of joint transfer of neptunium(6) and plutonium(4) through liquid membranes with di-2-ethylhexylphosphoric acid, depending on the concentration of the carrier, nature of reextracting agent and ratio of metal concentrations, was investigated. The optimal conditions for selective isolation of microimpurity of one of the elements from solutions of the other were determined. Solution of ammonium carbonate with carrier concentration of 0.1-0.2 mol/l can be expediently utilized as reextracting phase for neptunium impurity removal

A Piezoelectric Unimorph Deformable Mirror Concept by Wafer Transfer for Ultra Large Space Telescopes

Science.gov (United States)

Yang, Eui-Hyeok; Shcheglov, Kirill

2002-01-01

Future concepts of ultra large space telescopes include segmented silicon mirrors and inflatable polymer mirrors. Primary mirrors for these systems cannot meet optical surface figure requirements and are likely to generate over several microns of wavefront errors. In order to correct for these large wavefront errors, high stroke optical quality deformable mirrors are required. JPL has recently developed a new technology for transferring an entire wafer-level mirror membrane from one substrate to another. A thin membrane, 100 mm in diameter, has been successfully transferred without using adhesives or polymers. The measured peak-to-valley surface error of a transferred and patterned membrane (1 mm x 1 mm x 0.016 mm) is only 9 nm. The mirror element actuation principle is based on a piezoelectric unimorph. A voltage applied to the piezoelectric layer induces stress in the longitudinal direction causing the film to deform and pull on the mirror connected to it. The advantage of this approach is that the small longitudinal strains obtainable from a piezoelectric material at modest voltages are thus translated into large vertical displacements. Modeling is performed for a unimorph membrane consisting of clamped rectangular membrane with a PZT layer with variable dimensions. The membrane transfer technology is combined with the piezoelectric bimorph actuator concept to constitute a compact deformable mirror device with a large stroke actuation of a continuous mirror membrane, resulting in a compact A0 systems for use in ultra large space telescopes.

Far Western: probing membranes.

Science.gov (United States)

Einarson, Margret B; Pugacheva, Elena N; Orlinick, Jason R

2007-08-01

INTRODUCTIONThe far-Western technique described in this protocol is fundamentally similar to Western blotting. In Western blots, an antibody is used to detect a query protein on a membrane. In contrast, in a far-Western blot (also known as an overlay assay) the antibody is replaced by a recombinant GST fusion protein (produced and purified from bacteria), and the assay detects the interaction of this protein with target proteins on a membrane. The membranes are washed and blocked, incubated with probe protein, washed again, and subjected to autoradiography. The GST fusion (probe) proteins are often labeled with (32)P; alternatively, the membrane can be probed with unlabeled GST fusion protein, followed by detection using commercially available GST antibodies. The nonradioactive approach is substantially more expensive (due to the purchase of antibody and detection reagents) than using radioactively labeled proteins. In addition, care must be taken to control for nonspecific interactions with GST alone and a signal resulting from antibody cross-reactivity. In some instances, proteins on the membrane are not able to interact after transfer. This may be due to improper folding, particularly in the case of proteins expressed from a phage expression library. This protocol describes a way to overcome this by washing the membrane in denaturation buffer, which is then serially diluted to permit slow renaturation of the proteins.

Northern blots: capillary transfer of RNA from agarose gels and filter hybridization using standard stringency conditions.

Science.gov (United States)

Rio, Donald C

2015-03-02

In this protocol, an RNA sample, fractionated by gel electrophoresis, is transferred from the gel onto a membrane by capillary transfer. Short-wave UV light is used to fix the transferred RNA to the membrane. The membrane is then pretreated to block nonspecific probe-binding sites, and hybridization of the immobilized RNA to a (32)P-labeled DNA or RNA probe specific for the mRNA of interest is performed. Finally, the membrane is washed and subjected to autoradiography or phosphorimaging. Because exposure to UV cross-links the RNA to the membrane, the membrane can be stripped and hybridized with other probes. The procedure is suitable for detecting poly(A)(+)-selected mRNA or mRNA in total cellular RNA if the target transcript is relatively abundant. Using DNA or RNA probes labeled to 1 × 10(8)-10 × 10(8) cpm/µg, it should be possible to detect ∼5 pg of a specific RNA. © 2015 Cold Spring Harbor Laboratory Press.

Sweeping Gas Membrane Desalination Using Commercial Hydrophobic Hollow Fiber Membranes; TOPICAL

International Nuclear Information System (INIS)

EVANS, LINDSEY; MILLER, JAMES E.

2002-01-01

Water shortages affect 88 developing countries that are home to half of the world's population. In these places, 80-90% of all diseases and 30% of all deaths result from poor water quality. Furthermore, over the next 25 years, the number of people affected by severe water shortages is expected to increase fourfold. Low cost methods of purifying freshwater, and desalting seawater are required to contend with this destabilizing trend. Membrane distillation (MD) is an emerging technology for separations that are traditionally accomplished via conventional distillation or reverse osmosis. As applied to desalination, MD involves the transport of water vapor from a saline solution through the pores of a hydrophobic membrane. In sweeping gas MD, a flowing gas stream is used to flush the water vapor from the permeate side of the membrane, thereby maintaining the vapor pressure gradient necessary for mass transfer. Since liquid does not penetrate the hydrophobic membrane, dissolved ions are completely rejected by the membrane. MD has a number of potential advantages over conventional desalination including low temperature and pressure operation, reduced membrane strength requirements, compact size, and 100% rejection of non-volatiles. The present work evaluated the suitability of commercially available technology for sweeping gas membrane desalination. Evaluations were conducted with Celgard Liqui-Cel(reg s ign) Extra-Flow 2.5X8 membrane contactors with X-30 and X-40 hydrophobic hollow fiber membranes. Our results show that sweeping gas membrane desalination systems are capable of producing low total dissolved solids (TDS) water, typically 10 ppm or less, from seawater, using low grade heat. However, there are several barriers that currently prevent sweeping gas MD from being a viable desalination technology. The primary problem is that large air flows are required to achieve significant water yields, and the costs associated with transporting this air are prohibitive. To

Performance Investigation of O-Ring Vacuum Membrane Distillation Module for Water Desalination

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Adnan Alhathal Alanezi

2016-01-01

Full Text Available A new O-ring flat sheet membrane module design was used to investigate the performance of Vacuum Membrane Distillation (VMD for water desalination using two commercial polytetrafluoroethylene (PTFE and polyvinylidene fluoride (PVDF flat sheet hydrophobic membranes. The design of the membrane module proved its applicability for achieving a high heat transfer coefficient of the order of 103 (W/m2 K and a high Reynolds number (Re. VMD experiments were conducted to measure the heat and mass transfer coefficients within the membrane module. The effects of the process parameters, such as the feed temperature, feed flow rate, vacuum degree, and feed concentration, on the permeate flux have been investigated. The feed temperature, feed flow rate, and vacuum degree play an important role in enhancing the performance of the VMD process; therefore, optimizing all of these parameters is the best way to achieve a high permeate flux. The PTFE membrane showed better performance than the PVDF membrane in VMD desalination. The obtained water flux is relatively high compared to that reported in the literature, reaching 43.8 and 52.6 (kg/m2 h for PVDF and PTFE, respectively. The salt rejection of NaCl was higher than 99% for both membranes.

Performance of Hollow Fiber Membrane Gas-Liquid Contactors to Absorb CO2 Using Diethanolamine (Dea as a Solvent

Directory of Open Access Journals (Sweden)

Sutrasno Kartohardjono

2010-10-01

Full Text Available This study uses DEA solution to absorb CO2 from the gas flow through the hollow fiber membrane contactors. This study aims to evaluate the performance of hollow fiber membrane contactors to absorb CO2 gas using DEA solution as solvent through mass transfer and hydrodynamics studies. The use of DEA solution is to reduce the mass transfer resistance in the liquid phase, and on the other side, the large contact area of the membrane surface can cover the disadvantage of membrane contactors; additional mass transfer resistance in the membrane phase. During experiments, CO2 feed flows through the fiber lumens, while the 0.01 M DEA solution flows in the shell side of membrane contactors. Experimental results show that the mass transfer coefficients and fluxes of CO2 increase with an increase in both water and DEA solution flow rates. Increasing the amount of fibers in the contactors will decrease the mass transfer and fluxes at the same DEA solution flow rate. Mass transfer coefficients and CO2 fluxes using DEA solution can achieve 28,000 and 7.6 million times greater than using water as solvent, respectively. Hydrodynamics studies show that the liquid pressure drops in the contactors increase with increasing liquid flow rate and number of fibers in the contactors. The friction between water and the fibers in the contactor was more pronounced at lower velocities, and therefore, the value of the friction factor is also higher at lower velocities.

Influence of the boundary conditions on heat and mass transfer in spacer-filled channels

Science.gov (United States)

Ciofalo, M.; La Cerva, M. F.; Di Liberto, M.; Tamburini, A.

2017-11-01

The purpose of this study is to discuss some problems which arise in heat or mass transfer in complex channels, with special reference to the spacer-filled channels adopted in membrane processes. Among the issues addressed are the consistent definition of local and mean heat or mass transfer coefficients; the influence of the wall boundary conditions; the influence of one-side versus two-side heat/mass transfer. Most of the results discussed were obtained by finite volume CFD simulations concerning heat transfer in Membrane Distillation or mass transfer in Electrodialysis and Reverse Electrodialysis, but many of the conclusions apply also to different processes involving geometrically complex channels

Uranium extraction process in a sulfuric medium by means of liquid emulsified membranes

International Nuclear Information System (INIS)

Monteillet, A.

1985-02-01

Uranium ore processing, after leaching by sulfuric acid, by liquid-liquid extraction is a rather heavy process, not suitable for small deposits. Extraction by emulsions was suggested. In this process the leachate is contacted with an oil in water type emulsion, a liquid organic membrane is formed by the continuous phase. Uranium complexes diffuse through the liquid membrane towards the dispersed aqueous phase of the emulsion (stripping solution). Uranium is recovered by breaking the emulsion. Are successively studied: development of stable emulsions, influence of emulsion composition on uranium transfer kinetics, transfer mechanisms through the membrane and modelling of kinetics data obtained in the experimental study [fr

Continuous esterification to produce biodiesel by SPES/PES/NWF composite catalytic membrane in flow-through membrane reactor: experimental and kinetic studies.

Science.gov (United States)

Shi, Wenying; He, Benqiao; Cao, Yuping; Li, Jianxin; Yan, Feng; Cui, Zhenyu; Zou, Zhiqun; Guo, Shiwei; Qian, Xiaomin

2013-02-01

A novel composite catalytic membrane (CCM) was prepared from sulfonated polyethersulfone (SPES) and polyethersulfone (PES) blend supported by non-woven fabrics, as a heterogeneous catalyst to produce biodiesel from continuous esterification of oleic acid with methanol in a flow-through mode. A kinetic model of esterification was established based on a plug-flow assumption. The effects of the CCM structure (thickness, area, porosity, etc.), reaction temperature and the external and internal mass transfer resistances on esterification were investigated. The results showed that the CCM structure had a significant effect on the acid conversion. The external mass transfer resistance could be neglected when the flow rate was over 1.2 ml min(-1). The internal mass transfer resistance impacted on the conversion when membrane thickness was over 1.779 mm. An oleic acid conversion kept over 98.0% for 500 h of continuous running. The conversions obtained from the model are in good agreement with the experimental data. Copyright © 2012 Elsevier Ltd. All rights reserved.

Porous polybenzimidazole membranes doped with phosphoric acid: Preparation and application in high-temperature proton-exchange-membrane fuel cells

International Nuclear Information System (INIS)

Li, Jin; Li, Xiaojin; Yu, Shuchun; Hao, Jinkai; Lu, Wangting; Shao, Zhigang; Yi, Baolian

2014-01-01

Highlights: • Porous polybenzimidazole membrane was prepared with glucose as porogen. • Phosphoric acid content was as high as 15.7 mol H 3 PO 4 per PBI repeat unit. • 200 h Constant current density test was carried out at 150 °C. • Degradation was due to the gap between membrane and catalyst layer. - Abstract: In this paper, the preparation and characterization of porous polybenzimidazole membranes doped with phosphoric acid were reported. For the preparation of porous polybenzimidazole membranes, glucose and saccharose were selected as porogen and added into PBI resin solution before solvent casting. The prepared porous PBI membranes had high proton conductivity and high content of acid doping at room temperature with 15.7 mol H 3 PO 4 per PBI repeat unit, much higher than pure PBI membrane at the same condition. Further, the performance and stability of the porous PBI membrane in high-temperature proton-exchange-membrane fuel cells was tested. It was found that the cell performance remained stable during 200 h stability test under a constant current discharge of 0.5 A cm −2 except for the last fifty hours. The decay in the last fifty hours was ascribed to the delamination between the catalyst layer and membrane increasing the charge-transfer resistance

Biogenesis and Membrane Targeting of Lipoproteins.

Science.gov (United States)

Narita, Shin-Ichiro; Tokuda, Hajime

2010-09-01

Bacterial lipoproteins represent a unique class of membrane proteins, which are anchored to membranes through triacyl chains attached to the amino-terminal cysteine. They are involved in various functions localized in cell envelope. Escherichia coli possesses more than 90 species of lipoproteins, most of which are localized in the outer membrane, with others being in the inner membrane. All lipoproteins are synthesized in the cytoplasm with an N-terminal signal peptide, translocated across the inner membrane by the Sec translocon to the periplasmic surface of the inner membrane, and converted to mature lipoproteins through sequential reactions catalyzed by three lipoprotein-processing enzymes: Lgt, LspA, and Lnt. The sorting of lipoproteins to the outer membrane requires a system comprising five Lol proteins. An ATP-binding cassette transporter, LolCDE, initiates the sorting by mediating the detachment of lipoproteins from the inner membrane. Formation of the LolA-lipoprotein complex is coupled to this LolCDE-dependent release reaction. LolA accommodates the amino-terminal acyl chain of lipoproteins in its hydrophobic cavity, thereby generating a hydrophilic complex that can traverse the periplasmic space by diffusion. Lipoproteins are then transferred to LolB on the outer membrane and anchored to the inner leaflet of the outer membrane by the action of LolB. In contrast, since LolCDE does not recognize lipoproteins possessing Asp at position +2, these lipoproteins remain anchored to the inner membrane. Genes for Lol proteins are widely conserved among gram-negative bacteria, and Lol-mediated outer membrane targeting of lipoproteins is considered to be the general lipoprotein localization mechanism.

Application research of computational mass-transfer differential equation in MBR concentration field simulation.

Science.gov (United States)

Li, Chunqing; Tie, Xiaobo; Liang, Kai; Ji, Chanjuan

2016-01-01

After conducting the intensive research on the distribution of fluid's velocity and biochemical reactions in the membrane bioreactor (MBR), this paper introduces the use of the mass-transfer differential equation to simulate the distribution of the chemical oxygen demand (COD) concentration in MBR membrane pool. The solutions are as follows: first, use computational fluid dynamics to establish a flow control equation model of the fluid in MBR membrane pool; second, calculate this model by adopting direct numerical simulation to get the velocity field of the fluid in membrane pool; third, combine the data of velocity field to establish mass-transfer differential equation model for the concentration field in MBR membrane pool, and use Seidel iteration method to solve the equation model; last but not least, substitute the real factory data into the velocity and concentration field model to calculate simulation results, and use visualization software Tecplot to display the results. Finally by analyzing the nephogram of COD concentration distribution, it can be found that the simulation result conforms the distribution rule of the COD's concentration in real membrane pool, and the mass-transfer phenomenon can be affected by the velocity field of the fluid in membrane pool. The simulation results of this paper have certain reference value for the design optimization of the real MBR system.

Interfacial Water-Transport Effects in Proton-Exchange Membranes

Energy Technology Data Exchange (ETDEWEB)

Kienitz, Brian; Yamada, Haruhiko; Nonoyama, Nobuaki; Weber, Adam

2009-11-19

It is well known that the proton-exchange membrane is perhaps the most critical component of a polymer-electrolyte fuel cell. Typical membranes, such as Nafion(R), require hydration to conduct efficiently and are instrumental in cell water management. Recently, evidence has been shown that these membranes might have different interfacial morphology and transport properties than in the bulk. In this paper, experimental data combined with theoretical simulations will be presented that explore the existence and impact of interfacial resistance on water transport for Nafion(R) 21x membranes. A mass-transfer coefficient for the interfacial resistance is calculated from experimental data using different permeation cells. This coefficient is shown to depend exponentially on relative humidity or water activity. The interfacial resistance does not seem to exist for liquid/membrane or membrane/membrane interfaces. The effect of the interfacial resistance is to flatten the water-content profiles within the membrane during operation. Under typical operating conditions, the resistance is on par with the water-transport resistance of the bulk membrane. Thus, the interfacial resistance can be dominant especially in thin, dry membranes and can affect overall fuel-cell performance.

Glycosaminoglycan blotting on nitrocellulose membranes treated with cetylpyridinium chloride after agarose-gel electrophoretic separation.

Science.gov (United States)

Maccari, Francesca; Volpi, Nicola

2002-09-01

We describe a method for blotting and immobilizing several nonsulfated and sulfated complex polysaccharides on membranes made hydrophilic and positively charged by a cationic detergent after their separation by conventional agarose gel electrophoresis. Nitrocellulose membranes were derivatized with the cationic detergent cetylpyridinium chloride (CPC) and mixtures of glycosaminoglycans (GAGs) were capillary-blotted after their separation in agarose gel electrophoresis in barium acetate/1,2-diaminopropane. Single purified species of variously sulfated polysaccharides were transferred onto the derivatized membranes after electrophoresis with an efficiency of 100% and stained with alcian blue (irreversible staining) and toluidine blue (reversible staining) permitting about 0.1 nug threshold of detection. Nonsulfated polyanions, hyaluronic acid, a fructose-containing polysaccharide with a chondroitin backbone purified from Escherichia coli U1-41, and its defructosylated product, were also electrophoretically separated and transferred onto membranes. The limit of detection for desulfated GAGs was about 0.1-0.5 nug after irreversible or reversible staining. GAG extracts from bovine, lung and aorta, and human aorta and urine were separated by agarose gel electrophoresis and blotted on CPC-treated nitrocellulose membranes. The polysaccharide composition of these extracts was determined. The membrane stained with toluidine blue (reversible staining) was destained and the same lanes used for immunological detection or other applications. Reversible staining was also applied to recover single species of polysaccharides after electrophoretic separation of mixtures of GAGs and their transfer onto membranes. Single bands were released from the membrane with an efficiency of 70-100% for further biochemical characterization.

Super liquid-repellent gas membranes for carbon dioxide capture and heart-lung machines.

Science.gov (United States)

Paven, Maxime; Papadopoulos, Periklis; Schöttler, Susanne; Deng, Xu; Mailänder, Volker; Vollmer, Doris; Butt, Hans-Jürgen

2013-01-01

In a gas membrane, gas is transferred between a liquid and a gas through a microporous membrane. The main challenge is to achieve a high gas transfer while preventing wetting and clogging. With respect to the oxygenation of blood, haemocompatibility is also required. Here we coat macroporous meshes with a superamphiphobic-or liquid repellent-layer to meet this challenge. The superamphiphobic layer consists of a fractal-like network of fluorinated silicon oxide nanospheres; gas trapped between the nanospheres keeps the liquid from contacting the wall of the membrane. We demonstrate the capabilities of the membrane by capturing carbon dioxide gas into a basic aqueous solution and in addition use it to oxygenate blood. Usually, blood tends to clog membranes because of the abundance of blood cells, platelets, proteins and lipids. We show that human blood stored in a superamphiphobic well for 24 h can be poured off without leaving cells or adsorbed protein behind.

Ceramic membrane defouling (cleaning) by air Nano Bubbles.

Science.gov (United States)

Ghadimkhani, Aliasghar; Zhang, Wen; Marhaba, Taha

2016-03-01

Ceramic membranes are among the most promising technologies for membrane applications, owing to their excellent resistance to mechanical, chemical, and thermal stresses. However, membrane fouling is still an issue that hampers the applications at large scales. Air Nano Bubbles (NBs), due to high mass transfer efficiency, could potentially prevent fouling of ceramic membrane filtration processes. In this study, bench and pilot scale ceramic membrane filtration was performed with air NBs to resist fouling. To simulate fouling, humic acid, as an organic foulant, was applied to the membrane flat sheet surface. Complete membrane clogging was achieved in less than 6 h. Membrane defouling (cleaning) was performed by directly feeding of air NBs to the membrane cells. The surface of the ceramic membrane was superbly cleaned by air NBs, as revealed by atomic force microscope (AFM) images before and after the treatment. The permeate flux recovered to its initial level (e.g., 26.7 × 10(-9) m(3)/m(2)/s at applied pressure of 275.8 kPa), which indicated that NBs successfully unclogged the pores of the membrane. The integrated ceramic membrane and air NBs system holds potential as an innovative sustainable technology. Copyright © 2015 Elsevier Ltd. All rights reserved.

Surface modification of polypropylene membrane by polyethylene glycol graft polymerization

Energy Technology Data Exchange (ETDEWEB)

Abednejad, Atiye Sadat, E-mail: atiyeabednejad@gmail.com [Department of Biomedical Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box 14395-1561, Tehran (Iran, Islamic Republic of); Amoabediny, Ghasem [Department of Life Science Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box 14395-1561, Tehran (Iran, Islamic Republic of); Research Center for New Technologies in Life Science Engineering, University of Tehran, P.O. Box 63894-14179, Tehran (Iran, Islamic Republic of); Ghaee, Azadeh [Department of Biomedical Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box 14395-1561, Tehran (Iran, Islamic Republic of)

2014-09-01

Polypropylene hollow fiber microporous membranes have been used in a wide range of applications, including blood oxygenator. The hydrophobic feature of the polypropylene surface causes membrane fouling. To minimize fouling, a modification consisting of three steps: surface activation in H{sub 2} and O{sub 2} plasma, membrane immersion in polyethylene glycol (PEG) and plasma graft polymerization was performed. The membranes were characterized by contact angle measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Oxygen transfer of modified membranes was also tested. The stability of grafted PEG was measured in water and in phosphate buffer saline (PBS) at 37 °C. Blood compatibility of modified surfaces was evaluated by the platelet adhesion method. Water contact angel reduction from 110° to 72° demonstrates the enhanced hydrophilicity, and XPS results verify the presence of oxygenated functional groups due to the peak existence in 286 eV as a result of PEG grafting. The results clearly indicate that plasma graft-polymerization of PEG is an effective way for antifouling improvement of polypropylene membranes. Also, the results show that oxygen transfer changes in PEG grafted membranes are not significant. - Highlights: • H{sub 2} and O{sub 2} plasma graft polymerization of PEG on polypropylene membrane was carried out. • Changes in surface properties were investigated by FTIR, XPS, SEM, and AFM. • Surface wettability enhanced as a result of poly ethylene glycol grafting. • PEG grafting degree increase causes reduction of fouling and adhesion.

Membrane-bound 2,3-diphosphoglycerate phosphatase of human erythrocytes.

Science.gov (United States)

Schröter, W; Neuvians, M

1970-12-01

Gradual osmotic hemolysis of human erythrocytes reduces the cell content of whole protein, hemoglobin, 2,3-diphosphoglycerate and triosephosphate isomerase extensively, but not that of membrane protein and 2,3-diphosphoglycerate phosphatase. After the refilling of the ghosts with 2,3-diphosphoglycerate and reconstitution of the membrane, the 2,3-diphosphoglycerate phosphatase activity equals that of intact red cells. The membrane-bound 2,3-diphosphoglycerate phosphatase can be activated by sodium hyposulfite. The enzyme system of ghosts seems to differ from that of intact red cells with regard to the optima of pH and temperature. It remains to be elucidated if the membrane binding of the 2,3-diphosphoglycerate phosphatase is related to the transfer of inorganic phosphate across the red cell membrane.

Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.

Science.gov (United States)

Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao

2014-12-10

In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ± 3.5 and 67 ± 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 μmol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 μmol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be

Metabolism of fatty acids in rat brain in microsomal membranes

International Nuclear Information System (INIS)

Aeberhard, E.E.; Gan-Elepano, M.; Mead, J.F.

1980-01-01

Using a technique in which substrate fatty acids are incorporated into microsomal membranes followd by comparison of their rates of desaturation or elongation with those of exogenous added fatty acids it has been found that the desaturation rate is more rapid for the membrane-bound substrate than for the added fatty acid. Moreover, the product of the membrane-bound substrate is incorporated into membrane phospholipid whereas the product of the exogenous substrate is found in di- and triacyl glycerols and in free fatty acids as well. These and other findings point to a normal sequence of reaction of membrane liqids with membrane-bound substrates involving transfer of fatty acid from phospholipid to the coupled enzyme systems without ready equilibration with the free fatty acid pool

Hybrid Membrane/Absorption Process for Post-combustion CO2 Capture

Energy Technology Data Exchange (ETDEWEB)

Li, Shiguang; Shou, S.; Pyrzynski, Travis; Makkuni, Ajay; Meyer, Howard

2013-12-31

This report summarizes scientific/technical progress made for bench-scale membrane contactor technology for post-combustion CO2 capture from DOE Contract No. DE-FE-0004787. Budget Period 1 (BP1) membrane absorber, Budget Period 2 (BP2) membrane desorber and Budget Period 3 (BP3) integrated system and field testing studies have been completed successfully and met or exceeded the technical targets (≥ 90% CO2 removal and CO2 purity of 97% in one membrane stage). Significant breakthroughs are summarized below: BP1 research: The feasibility of utilizing the poly (ether ether ketone), PEEK, based hollow fiber contractor (HFC) in combination with chemical solvents to separate and capture at least 90% of the CO2 from simulated flue gases has been successfully established. Excellent progress has been made as we have achieved the BP1 goal: ≥ 1,000 membrane intrinsic CO2 permeance, ≥ 90% CO2 removal in one stage, ≤ 2 psi gas side pressure drop, and ≥ 1 (sec)-1 mass transfer coefficient. Initial test results also show that the CO2 capture performance, using activated Methyl Diethanol Amine (aMDEA) solvent, was not affected by flue gas contaminants O2 (~3%), NO2 (66 ppmv), and SO2 (145 ppmv). BP2 research: The feasibility of utilizing the PEEK HFC for CO2-loaded solvent regeneration has been successfully established High CO2 stripping flux, one order of magnitude higher than CO2 absorption flux, have been achieved. Refined economic evaluation based on BP1 membrane absorber and BP2 membrane desorber laboratory test data indicate that the CO2 capture costs are 36% lower than DOE’s benchmark amine absorption technology. BP3 research: A bench-scale system utilizing a membrane absorber and desorber was integrated into a continuous CO2 capture process using contactors containing 10 to 20 ft2 of membrane area. The integrated process operation was stable through a 100-hour laboratory test, utilizing a simulated flue gas stream. Greater than 90% CO2 capture combined with 97

ATP-dependent calcium transport across basal plasma membranes of human placental trophoblast

International Nuclear Information System (INIS)

Fisher, G.J.; Kelley, L.K.; Smith, C.H.

1987-01-01

As a first step in understanding the cellular basis of maternal-fetal calcium transfer, the authors examined the characteristics of calcium uptake by a highly purified preparation of the syncytiotrophoblast basal (fetal facing) plasma membrane. In the presence of nanomolar concentrations of free calcium, basal membranes demonstrated substantial ATP-dependent calcium uptake. This uptake required magnesium, was not significantly affected by Na + or K + (50 mM), or sodium azide (10 mM). Intravesicular calcium was rapidly and completely released by the calcium ionophore rapidly and completely released by the calcium ionophore A23187. Calcium transport was significantly stimulated by the calcium-dependent regulatory protein calmodulin. Placental membrane fractions enriched in endoplasmic reticulum (ER) and mitochondria also demonstrated ATP-dependent calcium uptake. In contrast to basal membrane, mitochondrial calcium uptake was completely inhibited by azide. The rate of calcium uptake was completely inhibited by azide. The rate of calcium uptake by the ER was only 20% of that of basal membranes. They conclude that the placental basal plasma membrane possesses a high-affinity calcium transport system similar to that found in plasma membranes of a variety of cell types. This transporter is situated to permit it to function in vivo in maternal-fetal calcium transfer

Sensibilization of escherichia coli cells by cholesterol incorporated into their membrane

International Nuclear Information System (INIS)

Breslev, S.E.; Rozenberg, O.A.; Noskin, L.A.; Stepanova, I.M.; Beketova, A.G.; Loshakova, L.V.; Kovaleva, I.G.

1984-01-01

It has been established earlier that a level of cell radiosensitivity is defined by membrane viscosity changing in a wide temperature range. Therefore in epsilon coli cells of a natural type lethal doses of gamma rays are increased approximately a 3.5 times at 45 deg C, as compared to 4 deg C. Cholesterol changing a phase state of membrane lipids was used as a modifying factor. Liposomes were used with the goal of effective bacteria transfer to a membrane. It is established that liposomes without cholesterol do not affect their radioresistance and an increase of its content leads to resistance decrease. The effect is attained only at a sufficient long time of incubation of cells with liposomes (10-16 h). At 4 deg C lipids of E. coli membrane are in a solid-crystalline state independently on pholesterol presence, because of this, radiosensitivity does not change. Temperature increase up to 45 deg C transfer a part of lipids to a liquid-crystalline state, thus decreasing membrane viscosity. In this case cholesterol manifests itself. The authors explain viscosity increase with a violation in functioning of those enzyme systems, which activity is connected with membrane structural state, including enzymes of DNA repair. The authors assume that the radiosensibilization effect of cholesterol introduction into a bacterial membrane in high-temperature cell irradiation is explained by this phenomenon

Spontaneous insertion of GPI anchors into cholesterol-rich membrane domains

Directory of Open Access Journals (Sweden)

Jing Li

2018-05-01

Full Text Available GPI-Anchored proteins (GPI-APs can be exogenously transferred onto bilayer membranes both in vivo and in vitro, while the mechanism by which this transfer process occurs is unknown. In this work, we used atomistic molecular dynamics simulations and free energy calculations to characterize the essential influence of cholesterol on insertion of the GPI anchors into plasma membranes. We demonstrate, both dynamically and energetically, that in the presence of cholesterol, the tails of GPI anchors are able to penetrate inside the core of the lipid membrane spontaneously with a three-step mechanism, while in the absence of cholesterol no spontaneous insertion was observed. We ascribe the failure of insertion to the strong thermal fluctuation of lipid molecules in cholesterol-free bilayer, which generates a repulsive force in entropic origin. In the presence of cholesterol, however, the fluctuation of lipids is strongly reduced, thus decreasing the barrier for the anchor insertion. Based on this observation, we propose a hypothesis that addition of cholesterol creates vertical creases in membranes for the insertion of acyl chains. Moreover, we find that the GPI anchor could also spontaneously inserted into the boundary between cholesterol-rich and cholesterol-depleted domains. Our results shed light on the mechanism of cholesterol-mediated interaction between membrane proteins with acyl chain and plasma membranes in living cells.

Spontaneous insertion of GPI anchors into cholesterol-rich membrane domains

Science.gov (United States)

Li, Jing; Liu, Xiuhua; Tian, Falin; Yue, Tongtao; Zhang, Xianren; Cao, Dapeng

2018-05-01

GPI-Anchored proteins (GPI-APs) can be exogenously transferred onto bilayer membranes both in vivo and in vitro, while the mechanism by which this transfer process occurs is unknown. In this work, we used atomistic molecular dynamics simulations and free energy calculations to characterize the essential influence of cholesterol on insertion of the GPI anchors into plasma membranes. We demonstrate, both dynamically and energetically, that in the presence of cholesterol, the tails of GPI anchors are able to penetrate inside the core of the lipid membrane spontaneously with a three-step mechanism, while in the absence of cholesterol no spontaneous insertion was observed. We ascribe the failure of insertion to the strong thermal fluctuation of lipid molecules in cholesterol-free bilayer, which generates a repulsive force in entropic origin. In the presence of cholesterol, however, the fluctuation of lipids is strongly reduced, thus decreasing the barrier for the anchor insertion. Based on this observation, we propose a hypothesis that addition of cholesterol creates vertical creases in membranes for the insertion of acyl chains. Moreover, we find that the GPI anchor could also spontaneously inserted into the boundary between cholesterol-rich and cholesterol-depleted domains. Our results shed light on the mechanism of cholesterol-mediated interaction between membrane proteins with acyl chain and plasma membranes in living cells.

Mass and Heat Transfer Analysis of Membrane Humidifier with a Simple Lumped Mass Model

International Nuclear Information System (INIS)

Lee, Young Duk; Bae, Ho June; Ahn, Kook Young; Yu, Sang Seok; Hwang, Joon Young

2009-01-01

The performance of proton exchange membrane fuel cell (PEMFC) is seriously changed by the humidification condition which is intrinsic characteristics of the PEMFC. Typically, the humidification of fuel cell is carried out with internal or external humidifier. A membrane humidifier is applied to the external humidification of residential power generation fuel cell due to its convenience and high performance. In this study, a simple static model is constructed to understand the physical phenomena of the membrane humidifier in terms of geometric parameters and operating parameters. The model utilizes the concept of shell and tube heat exchanger but the model is also able to estimate the mass transport through the membrane. Model is constructed with FORTRAN under Matlab/Simulink □ environment to keep consistency with other components model which we already developed. Results shows that the humidity of wet gas and membrane thickness are critical parameters to improve the performance of the humidifier

Molecular cloning and characterization of the plasma membrane ...

African Journals Online (AJOL)

User

2011-05-09

May 9, 2011 ... Southern blot analysis indicated that OvPIP gene was present in O. ... Key words: Orychophragmus violaceus, plasma membrane, tonoplast aquaporins .... fractionated by 0.8% agarose gel electrophoresis and transferred to.

Conjugate heat and mass transfer in heat mass exchanger ducts

CERN Document Server

Zhang, Li-Zhi

2013-01-01

Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts bridges the gap between fundamentals and recent discoveries, making it a valuable tool for anyone looking to expand their knowledge of heat exchangers. The first book on the market to cover conjugate heat and mass transfer in heat exchangers, author Li-Zhi Zhang goes beyond the basics to cover recent advancements in equipment for energy use and environmental control (such as heat and moisture recovery ventilators, hollow fiber membrane modules for humidification/dehumidification, membrane modules for air purification, desi

Temperature-dependence of stress and elasticity in wet-transferred graphene membranes

Science.gov (United States)

De Alba, Roberto; Abhilash, T. S.; Hui, Aaron; Storch, Isaac R.; Craighead, Harold G.; Parpia, Jeevak M.

2018-03-01

We report measurements of the mechanical properties of two suspended graphene membranes in the temperature range of 80 K to 550 K. For this entire range, the resonant frequency and quality factor of each device were monitored continuously during cooling and heating. Below 300 K, we have additionally measured the resonant frequency's tunability via electrostatic force, and modeled this data to determine graphene's tension and elastic modulus; both of these parameters are found to be strongly temperature-dependent in this range. Above 300 K, we observe a resonant frequency (and therefore tension) minimum near room temperature. This suggests that the thermal expansion coefficient is positive for temperatures below roughly 315 K, and negative for higher temperatures. Lastly, we observe a large, reproducible hysteresis in the resonant frequency as our graphene devices are cycled between 300 K and 550 K. After returning to 300 K, the measured frequency evolves exponentially in time with a time constant of ˜24 h. Our results clash with expectations for pristine graphene membranes, but are consistent with expectations for composite membranes composed of graphene coated by a thin layer of polymer residue.

Polymeric membranes for guided bone regeneration.

Science.gov (United States)

Gentile, Piergiorgio; Chiono, Valeria; Tonda-Turo, Chiara; Ferreira, Ana M; Ciardelli, Gianluca

2011-10-01

In this review, different barrier membranes for guided bone regeneration (GBR) are described as a useful surgical technique to enhance bone regeneration in damaged alveolar sites before performing implants and fitting other dental appliances. The GBR procedure encourages bone regeneration through cellular exclusion and avoids the invasion of epithelial and connective tissues that grow at the defective site instead of bone tissue. The barrier membrane should satisfy various properties, such as biocompatibility, non-immunogenicity, non-toxicity, and a degradation rate that is long enough to permit mechanical support during bone formation. Other characteristics such as tissue integration, nutrient transfer, space maintenance and manageability are also of interest. In this review, various non-resorbable and resorbable commercially available membranes are described, based on expanded polytetrafluoroethylene, poly(lactic acid), poly(glycolic acid) and their copolymers. The polyester-based membranes are biodegradable, permit a single-stage procedure, and have higher manageability than non-resorbable membranes; however, they have shown poor biocompatibility. In contrast, membranes based on natural materials, such as collagen, are biocompatible but are characterized by poor mechanical properties and stability due to their early degradation. Moreover, new approaches are described, such as the use of multi-layered, graft-copolymer-based and composite membranes containing osteoconductive ceramic fillers as alternatives to conventional membranes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermodynamic analysis of Cr(VI) extraction using TOPO impregnated membranes

Energy Technology Data Exchange (ETDEWEB)

Praveen, Prashant; Loh, Kai-Chee, E-mail: chelohkc@nus.edu.sg

2016-08-15

Highlights: • Cr(VI) extraction by extractant impregnated membranes (EIM) was investigated. • EIM exhibited high extraction efficiency, mass transfer rate and stability. • Mass transfer mechanism was proposed based on kinetics and equilibrium data. • Uptake of Cr(VI) by EIMs was endothermic and spontaneous. • Cr(VI) extraction by EIMs was dominated by physical interactions. - Abstract: Solid/liquid extraction of Cr(VI) was accomplished using trioctylphosphine oxide impregnated polypropylene hollow fiber membranes. Extraction of 100–500 mg/L Cr(VI) by the extractant impregnated membranes (EIM) was characterized by high uptake rate and capacity, and equilibrium was attained within 45 min of contact. Extraction equilibrium was pH-dependent (at an optimal pH 2), whereas stripping using 0.2 M sodium hydroxide yielded the highest recovery of 98% within 60 min. The distribution coefficient was independent of initial Cr(VI) concentration, and the linear distribution equilibrium isotherm could be modeled using Freundlich isotherm. The mass transfer kinetics of Cr(VI) was examined using pseudo-second-order and intraparticle diffusion models and a mass transfer mechanism was deduced. The distribution coefficient increased with temperature, which indicated endothermic nature of the reaction. Enthalpy and entropy change during Cr(VI) extraction were positive and varied in the range of 37–49 kJ/mol and 114–155 J/mol, respectively. The free energy change was negative, confirming the feasibility and spontaneity of the mass transfer process. Results obtained suggest that EIMs are efficient and sustainable for extraction of Cr(VI) from wastewater.

Wastewater treatment with ion-exchange chitin membrane

International Nuclear Information System (INIS)

Paulenova, A.; Fjeld, R. A.; Visacky, V.

2001-01-01

Chitin, poly(N-acetyl-D glucosamine) and chitosan, its deacetylated derivates have recently obtained attention as bio-sorbents, because they shown a great ability to accumulate heavy metals and other pollutants. It was found that recovery of metals is strongly affected by pH. At low acidic pH range 4-5 chitin membrane exhibits better selectivity for lead than for cadmium or zinc. Sorption preference for metals decreases in the order: Pb > Cd > Zn. For uranium, as well for strontium was observed significant increase of recovery at decrease of pH to slightly acidic, close to neutral value. It was shown that chemical behavior of chitin membrane is excellent; ion-exchange nature of chitin was not changed during chitin membrane manufacturing process. Using of chitin membrane instead of chitin flake column brings significant increasing of driving force of the separation process, limited in the case of column experimental design by diffusion coefficient, while in the case of membrane process only by mass transfer coefficient. (authors)

Impact of the lipid bilayer on energy transfer kinetics in the photosynthetic protein LH2.

Science.gov (United States)

Ogren, John I; Tong, Ashley L; Gordon, Samuel C; Chenu, Aurélia; Lu, Yue; Blankenship, Robert E; Cao, Jianshu; Schlau-Cohen, Gabriela S

2018-03-28

Photosynthetic purple bacteria convert solar energy to chemical energy with near unity quantum efficiency. The light-harvesting process begins with absorption of solar energy by an antenna protein called Light-Harvesting Complex 2 (LH2). Energy is subsequently transferred within LH2 and then through a network of additional light-harvesting proteins to a central location, termed the reaction center, where charge separation occurs. The energy transfer dynamics of LH2 are highly sensitive to intermolecular distances and relative organizations. As a result, minor structural perturbations can cause significant changes in these dynamics. Previous experiments have primarily been performed in two ways. One uses non-native samples where LH2 is solubilized in detergent, which can alter protein structure. The other uses complex membranes that contain multiple proteins within a large lipid area, which make it difficult to identify and distinguish perturbations caused by protein-protein interactions and lipid-protein interactions. Here, we introduce the use of the biochemical platform of model membrane discs to study the energy transfer dynamics of photosynthetic light-harvesting complexes in a near-native environment. We incorporate a single LH2 from Rhodobacter sphaeroides into membrane discs that provide a spectroscopically amenable sample in an environment more physiological than detergent but less complex than traditional membranes. This provides a simplified system to understand an individual protein and how the lipid-protein interaction affects energy transfer dynamics. We compare the energy transfer rates of detergent-solubilized LH2 with those of LH2 in membrane discs using transient absorption spectroscopy and transient absorption anisotropy. For one key energy transfer step in LH2, we observe a 30% enhancement of the rate for LH2 in membrane discs compared to that in detergent. Based on experimental results and theoretical modeling, we attribute this difference to

Intelligent Membranes: Dream or Reality?

Directory of Open Access Journals (Sweden)

Annarosa Gugliuzza

2013-07-01

Full Text Available Intelligent materials are claimed to overcome current drawbacks associated with the attainment of high standards of life, health, security and defense. Membrane-based sensors represent a category of smart systems capable of providing a large number of benefits to different markets of textiles, biomedicine, environment, chemistry, agriculture, architecture, transport and energy. Intelligent membranes can be characterized by superior sensitivity, broader dynamic range and highly sophisticated mechanisms of autorecovery. These prerogatives are regarded as the result of multi-compartment arrays, where complementary functions can be accommodated and well-integrated. Based on the mechanism of “sense to act”, stimuli-responsive membranes adapt themselves to surrounding environments, producing desired effects such as smart regulation of transport, wetting, transcription, hydrodynamics, separation, and chemical or energy conversion. Hopefully, the design of new smart devices easier to manufacture and assemble can be realized through the integration of sensing membranes with wireless networks, looking at the ambitious challenge to establish long-distance communications. Thus, the transfer of signals to collecting systems could allow continuous and real-time monitoring of data, events and/or processes.

Mathematical Modeling for the Extraction of Uranium and Molybdenum with Emulsion Liquid Membrane, Including Industrial Application and Cost Evaluation of the Uranium Recovery

International Nuclear Information System (INIS)

Kris Tri Basuki

2008-01-01

Emulsion liquid membrane systems are double emulsion drops. Two immiscible phases are separated by a third phase which is immiscible with the other two phases. The liquid membrane systems were classified into two types: (1) carrier mediated mass transfer, (2) mass transfer without any reaction involved. Uranium extraction, molybdenum extraction and solvent extraction were used as purposed elements for each type of the membrane systems in the derivation of their mathematical models. Mass transfer in emulsion liquid membrane (ELM) systems has been modeled by several differential and algebraic equations. The models take into account the following : mass transfer of the solute from the bulk external phase to the external phase-membrane interface; an equilibrium reaction between the solute and the carrier to form the solute-carrier complex at the interface; mass transfer by diffusion of the solute-carrier complex in the membrane phase to the membrane-internal phase interface; another equilibrium reaction of the solute-carrier complex to release the solute at the membrane-internal phase interface into the internal phase. Models with or without the consideration of film resistances were developed and compared. The models developed in this study can predict the extraction rate through emulsion liquid membranes theoretically. All parameters required in the models can be determined before an experimental extraction run. Experimental data from literature (uranium extraction) and (molybdenum extraction and solvent extraction) were used to test the models. The agreements between the theoretical predictions and the experimental data were very good. The advantages of emulsion liquid membrane systems over traditional methods were discussed. The models developed in this research can be used directly for the design of emulsion liquid membrane systems. The results of this study represent a very significant step toward the practical applications of the emulsion liquid membrane

Experimental elucidation on rate-determining process of water transport in polymer electrolyte fuel cell membrane by magnetic resonance imaging

International Nuclear Information System (INIS)

Takita, Shinpei; Tsushima, Shohji; Hirai, Shuichiro; Kubo, Norio; Aotani, Koichiro

2007-01-01

We examined rate-determining process of water transport in polymer electrolyte membrane (PEM) used in fuel cells by using magnetic resonance imaging (MRI). We measured transversal water content distributions of the membrane by MRI and through-plane mass flux of water by hygrometers. Through place water flux has taken place in the membrane when relative humidify of supplied gas is not equal in both side of the membrane. MRI results revealed that diffusion coefficient of water in the membrane increases with water content of membrane, λ, whilst it shows intensive peak at λ=3-4. Diffusion resistance and mass transfer resistance involving evaporation and condensation on the interface are almost in the same order and thus water transport process in the membrane is determined by either concentration diffusion or mass transfer, depending on water content of membrane. (author)

Vesicle fusion observed by content transfer across a tethered lipid bilayer.

Science.gov (United States)

Rawle, Robert J; van Lengerich, Bettina; Chung, Minsub; Bendix, Poul Martin; Boxer, Steven G

2011-10-19

Synaptic transmission is achieved by exocytosis of small, synaptic vesicles containing neurotransmitters across the plasma membrane. Here, we use a DNA-tethered freestanding bilayer as a target architecture that allows observation of content transfer of individual vesicles across the tethered planar bilayer. Tethering and fusion are mediated by hybridization of complementary DNA-lipid conjugates inserted into the two membranes, and content transfer is monitored by the dequenching of an aqueous content dye. By analyzing the diffusion profile of the aqueous dye after vesicle fusion, we are able to distinguish content transfer across the tethered bilayer patch from vesicle leakage above the patch. Copyright © 2011 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Incorporation of adenylate cyclase into membranes of giant liposomes using membrane fusion with recombinant baculovirus-budded virus particles.

Science.gov (United States)

Mori, Takaaki; Kamiya, Koki; Tomita, Masahiro; Yoshimura, Tetsuro; Tsumoto, Kanta

2014-06-01

Recombinant transmembrane adenylate cyclase (AC) was incorporated into membranes of giant liposomes using membrane fusion between liposomes and baculovirus-budded virus (BV). AC genes were constructed into transfer vectors in a form fused with fluorescent protein or polyhistidine at the C-terminus. The recombinant BVs were collected by ultracentrifugation and AC expression was verified using western blotting. The BVs and giant liposomes generated using gentle hydration were fused under acidic conditions; the incorporation of AC into giant liposomes was demonstrated by confocal laser scanning microscopy through the emission of fluorescence from their membranes. The AC-expressing BVs were also fused with liposomes containing the substrate (ATP) with/without a specific inhibitor (SQ 22536). An enzyme immunoassay on extracts of the sample demonstrated that cAMP was produced inside the liposomes. This procedure facilitates direct introduction of large transmembrane proteins into artificial membranes without solubilization.

Hydrodynamics and mass transfer in trickle leaching process

International Nuclear Information System (INIS)

Jin Suoqing; Xiang Qinfang; Guo Jianzheng

1995-01-01

The initial research results of the hydrodynamic behavior and mass transfer of the trickle leaching process are summarized. It was shown that the dropping mode, the height of uranium ore heap and the flow rate of the dropping fluid affect the mass transfer of the trickle leaching process. Based on the concept of the keeping form of liquid in ore particle bed and the diffusion in porous medium, a mass transfer pattern, i.e. 'double-membrane transfer process' controlled by porous diffusion, was presented and proved for trickle leaching process

Removal of VOCs from groundwater using membrane-assisted solvent extraction

International Nuclear Information System (INIS)

Hutter, J.C.; Vandegrift, G.F.; Nunez, L.; Redfield, D.H.

1992-01-01

A membrane-assisted solvent extraction (MASX) system coupled to a membrane-assisted distillation stripping (MADS) system for use in decontaminating groundwater is discussed. Volatile organic compounds (VOCs) are extracted in the MASX using a sunflower oil solvent. In the MADS, VOCs are stripped from the sunflower oil, and the oil is recycled to the MASX. Thermodynamic data for the sunflower oil-water-VOCs system were experimentally collected. Published membrane-mass transfer results along with these data were used to design the MASX and MADS modules

Analysis of fluid-solid interaction in MHD natural convection in a square cavity equally partitioned by a vertical flexible membrane

International Nuclear Information System (INIS)

Mehryan, S.A.M.; Ghalambaz, Mohammad; Ismael, Muneer A.; Chamkha, Ali J.

2017-01-01

This paper investigates numerically the problem of unsteady natural convection inside a square cavity partitioned by a flexible impermeable membrane. The finite element method with the arbitrary Lagrangian-Eulerian (ALE) technique has been used to model the interaction of the fluid and the membrane. The horizontal walls of the cavity are kept adiabatic while the vertical walls are kept isothermal at different temperatures. A uniform magnetic field is applied onto the cavity with different orientations. The cavity has been provided by two eyelets to compensate volume changes due the movement of the flexible membrane. A parametric study is carried out for the pertinent parameters, which are the Rayleigh number (10"5–10"8), Hartmann number (0–200) and the orientation of the magnetic field (0–180°). The change in the Hartmann number affects the shape of the membrane and the heat transfer in the cavity. The angle of the magnetic field orientation also significantly affects the shape of the membrane and the heat transfer in the cavity. - Highlights: • Magnetohydrodynamics heat transfer in a partitioned cavity is studied. • There is a flexible membrane in the cavity. • The membrane is modeled using fluid-solid structure interaction. • A moving grid formulation based on ALE is adopted. • The effect of the magnetic field on the natural convection heat transfer is examined.

Analysis of fluid-solid interaction in MHD natural convection in a square cavity equally partitioned by a vertical flexible membrane

Energy Technology Data Exchange (ETDEWEB)

Mehryan, S.A.M., E-mail: a.mansuri1366@gmail.com [Department of Mechanical Engineering, Dezful Branch, Islamic Azad University, Dezful (Iran, Islamic Republic of); Ghalambaz, Mohammad, E-mail: m.ghalambaz@iaud.ac.ir [Department of Mechanical Engineering, Dezful Branch, Islamic Azad University, Dezful (Iran, Islamic Republic of); Ismael, Muneer A., E-mail: muneerismael@yahoo.com [Mechanical Engineering Department, Engineering College, University of Basrah, Basrah (Iraq); Chamkha, Ali J., E-mail: achamkha@pmu.edu.sa [Mechanical Engineering Department, Prince Mohammad Bin Fahd University, Al-Khobar 31952 (Saudi Arabia); Prince Sultan Endowment for Energy and Environment, Prince Mohammad Bin Fahd University, Al-Khobar 31952 (Saudi Arabia)

2017-02-15

This paper investigates numerically the problem of unsteady natural convection inside a square cavity partitioned by a flexible impermeable membrane. The finite element method with the arbitrary Lagrangian-Eulerian (ALE) technique has been used to model the interaction of the fluid and the membrane. The horizontal walls of the cavity are kept adiabatic while the vertical walls are kept isothermal at different temperatures. A uniform magnetic field is applied onto the cavity with different orientations. The cavity has been provided by two eyelets to compensate volume changes due the movement of the flexible membrane. A parametric study is carried out for the pertinent parameters, which are the Rayleigh number (10{sup 5}–10{sup 8}), Hartmann number (0–200) and the orientation of the magnetic field (0–180°). The change in the Hartmann number affects the shape of the membrane and the heat transfer in the cavity. The angle of the magnetic field orientation also significantly affects the shape of the membrane and the heat transfer in the cavity. - Highlights: • Magnetohydrodynamics heat transfer in a partitioned cavity is studied. • There is a flexible membrane in the cavity. • The membrane is modeled using fluid-solid structure interaction. • A moving grid formulation based on ALE is adopted. • The effect of the magnetic field on the natural convection heat transfer is examined.

Modelling of cross-flow membrane contactors : Physical mass transfer processes

NARCIS (Netherlands)

Dindore, V. Y.; Brilman, D. W. F.; Versteeg, G. F.

2005-01-01

Traditionally, hollow fiber membrane contactors used for gas-liquid contacting were designed in a shell and tube configuration with shell-side fluid flowing parallel to the fiber-side fluid, either in co-current or counter-current pattern. The primary limitations of these so-called 'parallel flow'

Soft grippers using micro-fibrillar adhesives for transfer printing.

Science.gov (United States)

Song, Sukho; Sitti, Metin

2014-07-23

The adhesive characteristics of fibrillar adhesives on a soft deformable membrane are reported. A soft gripper with an inflatable membrane covered by elastomer mushroom-shaped microfibers have a superior conformation to non-planar 3D part geometries, enabling the transfer printing of various parts serially or in parallel. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rab11b mediates melanin transfer between donor melanocytes and acceptor keratinocytes via coupled exo/endocytosis.

Science.gov (United States)

Tarafder, Abul K; Bolasco, Giulia; Correia, Maria S; Pereira, Francisco J C; Iannone, Lucio; Hume, Alistair N; Kirkpatrick, Niall; Picardo, Mauro; Torrisi, Maria R; Rodrigues, Inês P; Ramalho, José S; Futter, Clare E; Barral, Duarte C; Seabra, Miguel C

2014-04-01

The transfer of melanin from melanocytes to keratinocytes is a crucial process underlying maintenance of skin pigmentation and photoprotection against UV damage. Here, we present evidence supporting coupled exocytosis of the melanin core, or melanocore, by melanocytes and subsequent endocytosis by keratinocytes as a predominant mechanism of melanin transfer. Electron microscopy analysis of human skin samples revealed three lines of evidence supporting this: (1) the presence of melanocores in the extracellular space; (2) within keratinocytes, melanin was surrounded by a single membrane; and (3) this membrane lacked the melanosomal membrane protein tyrosinase-related protein 1 (TYRP1). Moreover, co-culture of melanocytes and keratinocytes suggests that melanin exocytosis is specifically induced by keratinocytes. Furthermore, depletion of Rab11b, but not Rab27a, caused a marked decrease in both keratinocyte-stimulated melanin exocytosis and transfer to keratinocytes. Thus, we propose that the predominant mechanism of melanin transfer is keratinocyte-induced exocytosis, mediated by Rab11b through remodeling of the melanosome membrane, followed by subsequent endocytosis by keratinocytes.

Heat Transfer Analogies

Energy Technology Data Exchange (ETDEWEB)

Bhattacharyya, A

1965-11-15

This report contains descriptions of various analogues utilised to study different steady-state and unsteady-state heat transfer problems. The analogues covered are as follows: 1 . Hydraulic: a) water flow b) air flow 2. Membrane 3. Geometric Electrical: a) Electrolytic-tank b) Conducting sheet 4. Network; a) Resistance b) R-C A comparison of the different analogues is presented in the form of a table.

Heat Transfer Analogies

International Nuclear Information System (INIS)

Bhattacharyya, A.

1965-11-01

This report contains descriptions of various analogues utilised to study different steady-state and unsteady-state heat transfer problems. The analogues covered are as follows: 1 . Hydraulic: a) water flow b) air flow 2. Membrane 3. Geometric Electrical: a) Electrolytic-tank b) Conducting sheet 4. Network; a) Resistance b) R-C A comparison of the different analogues is presented in the form of a table

Phospholipid transfer activities in toad oocytes and developing embryos

International Nuclear Information System (INIS)

Rusinol, A.; Salomon, R.A.; Bloj, B.

1987-01-01

The role of lipid transfer proteins during plasma membrane biogenesis was explored. Developing amphibia embryos were used because during their growth an active plasma membrane biosynthesis occurs together with negligible mitochondrial and endoplasmic reticulum proliferation. Sonicated vesicles, containing 14 C-labeled phospholipids and 3 H-labeled triolein, as donor particles and cross-linked erythrocyte ghosts as acceptor particles were used to measure phospholipid transfer activities in unfertilized oocytes and in developing embryos of the toad Bufo arenarum. Phosphatidylcholine transfer activity in pH 5.1 supernatant of unfertilized oocytes was 8-fold higher than the activity found in female toad liver supernatant, but dropped steadily after fertilization. After 20 hr of development, at the stage of late blastula, the phosphatidylcholine transfer activity had dropped 4-fold. Unfertilized oocyte supernatant exhibited phosphatidylinositol and phosphatidylethanolamine transfer activity also, but at the late blastula stage the former had dropped 18-fold and the latter was no longer detectable under our assay conditions. Our results show that fertilization does not trigger a phospholipid transport process catalyzed by lipid transfer proteins. Moreover, they imply that 75% of the phosphatidylcholine transfer activity and more than 95% of the phosphatidylinositol and phosphatidylethanolamine transfer activities present in pH 5.1 supernatants of unfertilized oocytes may not be essential for toad embryo development. Our findings do not rule out, however, that a phosphatidylcholine-specific lipid transfer protein could be required for embryo early growth

Ultrafast excited state deactivation of doped porous anodic alumina membranes

International Nuclear Information System (INIS)

Makhal, Abhinandan; Sarkar, Soumik; Pal, Samir Kumar; Yan, Hongdan; Wulferding, Dirk; Cetin, Fatih; Lemmens, Peter

2012-01-01

Free-standing, bi-directionally permeable and ultra-thin anodic aluminum oxide (AAO) membranes establish attractive templates (host) for the synthesis of nano-dots and rods of various materials (guest). This is due to their chemical and structural integrity and high periodicity on length scales of 5–150 nm which are often used to host photoactive nano-materials for various device applications including dye-sensitized solar cells. In the present study, AAO membranes are synthesized by using electrochemical methods and a detailed structural characterization using FEG-SEM, XRD and TGA confirms the porosity and purity of the material. Defect-mediated photoluminescence quenching of the porous AAO membrane in the presence of an electron accepting guest organic molecule (benzoquinone) is studied by means of steady-state and picosecond/femtosecond-resolved luminescence measurements. Using time-resolved luminescence transients, we have also revealed light harvesting of complexes of porous alumina impregnated with inorganic quantum dots (Maple Red) or gold nanowires. Both the Förster resonance energy transfer and the nano-surface energy transfer techniques are employed to examine the observed quenching behavior as a function of the characteristic donor–acceptor distances. The experimental results will find their relevance in light harvesting devices based on AAOs combined with other materials involving a decisive energy/charge transfer dynamics. (paper)

Ultrafast excited state deactivation of doped porous anodic alumina membranes

Science.gov (United States)

Makhal, Abhinandan; Sarkar, Soumik; Pal, Samir Kumar; Yan, Hongdan; Wulferding, Dirk; Cetin, Fatih; Lemmens, Peter

2012-08-01

Free-standing, bi-directionally permeable and ultra-thin anodic aluminum oxide (AAO) membranes establish attractive templates (host) for the synthesis of nano-dots and rods of various materials (guest). This is due to their chemical and structural integrity and high periodicity on length scales of 5-150 nm which are often used to host photoactive nano-materials for various device applications including dye-sensitized solar cells. In the present study, AAO membranes are synthesized by using electrochemical methods and a detailed structural characterization using FEG-SEM, XRD and TGA confirms the porosity and purity of the material. Defect-mediated photoluminescence quenching of the porous AAO membrane in the presence of an electron accepting guest organic molecule (benzoquinone) is studied by means of steady-state and picosecond/femtosecond-resolved luminescence measurements. Using time-resolved luminescence transients, we have also revealed light harvesting of complexes of porous alumina impregnated with inorganic quantum dots (Maple Red) or gold nanowires. Both the Förster resonance energy transfer and the nano-surface energy transfer techniques are employed to examine the observed quenching behavior as a function of the characteristic donor-acceptor distances. The experimental results will find their relevance in light harvesting devices based on AAOs combined with other materials involving a decisive energy/charge transfer dynamics.

Ultrafast excited state deactivation of doped porous anodic alumina membranes

Energy Technology Data Exchange (ETDEWEB)

Makhal, Abhinandan; Sarkar, Soumik; Pal, Samir Kumar [Department of Chemical, Biological and Macromolecular Sciences, S N Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Yan, Hongdan; Wulferding, Dirk; Cetin, Fatih; Lemmens, Peter [Institute for Condensed Matter Physics, TU Braunschweig, Mendelssohnstrasse 3, 38106 Braunschweig (Germany)

2012-08-03

Free-standing, bi-directionally permeable and ultra-thin anodic aluminum oxide (AAO) membranes establish attractive templates (host) for the synthesis of nano-dots and rods of various materials (guest). This is due to their chemical and structural integrity and high periodicity on length scales of 5-150 nm which are often used to host photoactive nano-materials for various device applications including dye-sensitized solar cells. In the present study, AAO membranes are synthesized by using electrochemical methods and a detailed structural characterization using FEG-SEM, XRD and TGA confirms the porosity and purity of the material. Defect-mediated photoluminescence quenching of the porous AAO membrane in the presence of an electron accepting guest organic molecule (benzoquinone) is studied by means of steady-state and picosecond/femtosecond-resolved luminescence measurements. Using time-resolved luminescence transients, we have also revealed light harvesting of complexes of porous alumina impregnated with inorganic quantum dots (Maple Red) or gold nanowires. Both the Foerster resonance energy transfer and the nano-surface energy transfer techniques are employed to examine the observed quenching behavior as a function of the characteristic donor-acceptor distances. The experimental results will find their relevance in light harvesting devices based on AAOs combined with other materials involving a decisive energy/charge transfer dynamics. (paper)

A conceptual design of catalytic gasification fuel cell hybrid power plant with oxygen transfer membrane

Science.gov (United States)

Shi, Wangying; Han, Minfang

2017-09-01

A hybrid power generation system integrating catalytic gasification, solid oxide fuel cell (SOFC), oxygen transfer membrane (OTM) and gas turbine (GT) is established and system energy analysis is performed. In this work, the catalytic gasifier uses steam, recycled anode off-gas and pure oxygen from OTM system to gasify coal, and heated by hot cathode off-gas at the same time. A zero-dimension SOFC model is applied and verified by fitting experimental data. Thermodynamic analysis is performed to investigate the integrated system performance, and system sensitivities on anode off-gas back flow ratio, SOFC fuel utilization, temperature and pressure are discussed. Main conclusions are as follows: (1) System overall electricity efficiency reaches 60.7%(HHV) while the gasifier operates at 700 °C and SOFC at 850 °C with system pressure at 3.04 bar; (2) oxygen enriched combustion simplify the carbon-dioxide capture process, which derives CO2 of 99.2% purity, but results in a penalty of 6.7% on system electricity efficiency; (3) with SOFC fuel utilization or temperature increasing, the power output of SOFC increases while GT power output decreases, and increasing system pressure can improve both the performance of SOFC and GT.

Dansyl-Galactoside, a Fluorescent Probe of Active Transport in Bacterial Membrane Vesicles*

Science.gov (United States)

Reeves, John P.; Shechter, Emanuel; Weil, Rudolf; Kaback, H. R.

1973-01-01

A fluorescent galactoside, 2-(N-dansyl)-aminoethyl β-D-thiogalactoside (dansyl-galactoside), competitively inhibits lactose transport by membrane vesicles of Escherichia coli, but is not actively transported. An increase in dansyl-galactoside fluorescence is observed upon addition of D-lactate. The fluorescence increase is not observed in membrane vesicles lacking the β-galactoside transport system, and is blocked or rapidly reversed by addition of β-galactosides, sulfhydryl reagents, inhibitors of D-lactate oxidation, or uncoupling agents. The fluorescence increase exhibits an emission maximum at 500 nm and excitation maxima at 345 nm and at 292 nm. The latter excitation maximum is absent unless D-lactate is added, indicating that the bound dansyl-galactoside molecules are excited by energy transfer from the membrane proteins. Titration of vesicles with dansyl-galactoside in the presence of D-lactate demonstrates that the β-galactoside carrier protein represents about 3.3% of the total membrane protein. The data indicate that D-lactate oxidation leads to binding of the fluorescent galactoside to the β-galactoside carrier protein in such a manner that the dansyl group is transferred to a hydrophobic environment within the membrane. PMID:4583021

Enabling fast electron transfer through both bacterial outer-membrane redox centers and endogenous electron mediators by polyaniline hybridized large-mesoporous carbon anode for high-performance microbial fuel cells

International Nuclear Information System (INIS)

Zou, Long; Qiao, Yan; Zhong, Canyu; Li, Chang Ming

2017-01-01

Both physical structure and chemical property of an electrode play critical roles in extracellular electron transfer from microbes to electrodes in microbial fuel cells (MFCs). Herein a novel polyaniline hybridized large mesoporous carbon (PANI-LMC) anode is fabricated from natural biomass by nanostructured CaCO 3 template-assisted carbonization followed by in situ chemical polymerizing PANI to enable fast extracellular electron transfer, in which the LMC with rich disorder-interconnected large mesopores (∼20−50 nm) and large surface area facilitates a fast mediated electron transfer through electron mediators, while the decorated PANI on LMC surface enables the direct electron transfer via bacterial outer-membrane redox centers. Owing to the unique synergistic effect from both excellent electron transfer paths, the PANI-LMC hybrid anode harvests high power electricity with a maximum output power density of 1280 mW m −2 in Shewanella putrefaciens CN32 MFCs, 10-fold higher than that of conventional carbon cloth. The findings from this work suggest a new insight on design of high-efficient anode according to the multiple and flexible electrochemical process for practical MFC applications.

An albumin-fixed membrane for the removal of protein-bound toxins

International Nuclear Information System (INIS)

Ge Dongtao; Wu Dewang; Shi Wei; Ma Yuanyuan; Tian Xiangdong; Liang Pengfei; Zhang Qiqing

2006-01-01

Established methods for kidney dialysis do not work for liver failure because kidney dialysis removes only water-soluble toxins, while the liver normally removes albumin-bound toxins. In the present study, a polysulfone dialysis membrane with a -OH reactive group was prepared by hydrolyzing the chloromethylated polysulfone membrane, and the bovine serum albumin molecules were fixed into the membrane with 1,1'-carbonyldiimidazole activation. The content of albumin of the albumin-fixed membrane was 121.3 mg (g membrane) -1 . The albumin-fixed dialysis membranes were used to remove protein-bound toxins, bilirubin, from the bilirubin-albumin solution. The transfer rate of bilirubin of the albumin-fixed membrane was obviously higher compared to the normal dialysis membrane. The clearance of bilirubin with the albumin-fixed membrane was 49.8%. The albumin-fixed membrane can easily be regenerated by the bovine serum albumin and NaOH solution. Regeneration of the membrane suggested good mechanical and chemical stability, as well as good clearance of bilirubin. In addition, the effects of membrane thickness and bilirubin initial concentration on the removal of bilirubin were discussed

Thermo-osmosis in Membrane Systems: A Review

Science.gov (United States)

Barragán, V. María; Kjelstrup, Signe

2017-06-01

We give a first review of experimental results for a phenomenon little explored in the literature, namely thermal osmosis or thermo-osmosis. Such systems are now getting increased attention because of their ability to use waste heat for separation purposes. We show that this volume transport of a solution or a pure liquid caused by a temperature difference across a membrane can be understood as a property of the membrane system, i. e. the membrane with its adjacent solutions. We present experimental values found in the literature of thermo-osmotic coefficients of neutral and hydrophobic as well as charged and hydrophilic membranes, with water and other permeant fluids as well as electrolyte solutions. We propose that the coefficient can be qualitatively explained by a formula that contains the entropy of adsorption of permeant into the membrane, the hydraulic permeability, and a factor that depends on the interface resistance to heat transfer. A variation in the entropy of adsorption with hydrophobic/hydrophilic membranes and structure breaking/structure making cations could then explain the sign of the permeant flux. Systematic experiments in the field are lacking and we propose an experimental program to mend this situation.

Assembly of the alpha-toxin-hexamer of Staphylococcus aureus in the liposome membrane.

Science.gov (United States)

Ikigai, H; Nakae, T

1987-02-15

It has been shown that the access of the alpha-toxin of Staphylococcus aureus to the target membrane and assembly of the hexamer can be monitored independently by respectively measuring the fluorescence energy transfer from the tryptophan residue(s) of the toxin to the dansylated phosphatidylethanolamine in the liposome membrane and the fluorescence increment of the toxin at 336 nm (Ikigai, H., and Nakae, T., (1987) J. Biol. Chem. 262, 2150-2155). Measurement of these parameters under various conditions showed the following results: when phosphatidylcholine (PC) liposomes composed of saturated fatty acids were mixed with the toxin, the fluorescence energy transfer occurred below, at, and above the transition temperature of the lipid, but the change of fluorescence at 336 nm was never detectable; when PC-liposomes containing unsaturated fatty acids were used, both the fluorescence energy transfer and the fluorescence increment of 336 nm were observed. These results suggested that the toxin-membrane interaction occurs in PC-membranes containing saturated and/or unsaturated fatty acids and that the oligomerization occurs only in the presence of PC containing unsaturated fatty acid(s). This conclusion was supported by the results of quantitative determination of the toxin-hexamer assembly and leakage of carboxyfluorescein from PC-liposomes under conditions similar to the above.

Endoplasmic Reticulum-Plasma Membrane Contact Sites.

Science.gov (United States)

Saheki, Yasunori; De Camilli, Pietro

2017-06-20

The endoplasmic reticulum (ER) has a broad localization throughout the cell and forms direct physical contacts with all other classes of membranous organelles, including the plasma membrane (PM). A number of protein tethers that mediate these contacts have been identified, and study of these protein tethers has revealed a multiplicity of roles in cell physiology, including regulation of intracellular Ca 2+ dynamics and signaling as well as control of lipid traffic and homeostasis. In this review, we discuss the cross talk between the ER and the PM mediated by direct contacts. We review factors that tether the two membranes, their properties, and their dynamics in response to the functional state of the cell. We focus in particular on the role of ER-PM contacts in nonvesicular lipid transport between the two bilayers mediated by lipid transfer proteins.

Membrane assisted fluidized bed reactor: experimental demonstration for partial oxidation of methanol

NARCIS (Netherlands)

Deshmukh, S.A.R.K.

2004-01-01

In this thesis the reactor concept has been developed on the basis of an experimental study on the effect of fluidization conditions on the membrane permeation rate in a MAFBR, the extent of gas back mixing and the tube-to-bed heat transfer rates in the presence of membrane bundles with and without

Hydrogen exchange kinetics in a membrane protein determined by 15N NMR spectroscopy: Use of the INEPT [insensitive nucleus enhancement by polarization transfer] experiment to follow individual amides in detergent-solubilized M13 coat protein

International Nuclear Information System (INIS)

Henry, G.D.; Sykes, B.D.

1990-01-01

The coat protein of the filamentous coliphage M13 is a 50-residue polypeptide which spans the inner membrane of the Escherichia coli host upon infection. Amide hydrogen exchange kinetics have been used to probe the structure and dynamics of M13 coat protein which has been solubilized in sodium dodecyl sulfate (SDS) micelles. In a previous 1 H nuclear magnetic resonance (NMR) study, multiple exponential analysis of the unresolved amide proton envelope revealed the existence of two slow kinetic sets containing a total of about 30 protons. The slower set (15-20 amides) originates from the hydrophobic membrane-spanning region and exchanges at least 10 5 -fold slower than the unstructured, non-H-bonded model polypeptide poly(DL-alanine). Herein the authors use 15 N NMR spectroscopy of biosynthetically labeled coat protein to follow individual, assigned, slowly exchanging amides in or near the hydrophobic segment. The INEPT (insensitive nucleus enhancement by polarization transfer) experiments can be used to transfer magnetization to the 15 N nucleus from a coupled proton; when 15 N-labeled protonated protein is dissolved in 2 H 2 O, the INEPT signal disappears with time as the amide protons are replaced by solvent deuterons. Amide hydrogen exchange is catalyzed by both H + and OH - ions. The time-dependent exchange-out experiment is suitable for slow exchange rates (k ex ). The INEPT experiment was also adapted to measure some of the more rapidly exchanging amides in the coat protein using either saturation transfer from water or exchange effects on the polarization transfer step itself. The results of all of these experiments are consistent with previous models of the coat protein in which a stable segment extends from the hydrophobic membrane-spanning region through to the C-terminus, whereas the N-terminal region is undergoing more extensive dynamic fluctuations

Modelling of air gap membrane distillation and its application in heavy metals removal

CSIR Research Space (South Africa)

Attia, H

2017-12-01

Full Text Available membranes. These parameters include feed, cooling water temperature and feed flow rate. Analytical models were used, with the aid of MATLAB, to predict the permeate flux of AGMD based on heat and mass transfer. Heat transfer was used to predict...

Synthesis of modified polymer inclusion membranes for photo-electrodeposition of cadmium using polarized electrodes

Energy Technology Data Exchange (ETDEWEB)

Yahia Cherif, Asma [Laboratory of Hydrometallurgy and Inorganic Molecular Chemistry, Faculty of Chemistry, USTHB, BP 32 El Alia, 16111, Algiers (Algeria); Arous, Omar, E-mail: omararous@yahoo.fr [Laboratory of Hydrometallurgy and Inorganic Molecular Chemistry, Faculty of Chemistry, USTHB, BP 32 El Alia, 16111, Algiers (Algeria); Center of Research in Physical and Chemical Analysis CRAPC, BP 248 Algiers, RP 16004, Algiers (Algeria); Amara, Mourad [Laboratory of Hydrometallurgy and Inorganic Molecular Chemistry, Faculty of Chemistry, USTHB, BP 32 El Alia, 16111, Algiers (Algeria); Omeiri, Said [Center of Research in Physical and Chemical Analysis CRAPC, BP 248 Algiers, RP 16004, Algiers (Algeria); Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry, USTHB, BP 32 El Alia, 16111, Algiers (Algeria); Kerdjoudj, Hacene [Laboratory of Hydrometallurgy and Inorganic Molecular Chemistry, Faculty of Chemistry, USTHB, BP 32 El Alia, 16111, Algiers (Algeria); Trari, Mohamed [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry, USTHB, BP 32 El Alia, 16111, Algiers (Algeria)

2012-08-15

Highlights: Black-Right-Pointing-Pointer Homogeneous PIM membranes containing water soluble polymers have been obtained under new experimental conditions. Black-Right-Pointing-Pointer Photoelectrodeposition of 'Cd' has been carried out using WO{sub 3} and CuFeO{sub 2} as electrode. Black-Right-Pointing-Pointer Using both photo-polarized electrodes enhances transference of cadmium compared to one. Black-Right-Pointing-Pointer Membrane with poly-phosphoric acid (PPA) give a rise of transferred amount of Cd. - Abstract: In this work, we have developed a novel class of polymeric inclusion membranes (PIMs) for the cations separation. The membrane is made up of cellulose triacetate modified by poly-electrolytes (poly-phosphoric acid, polyvinyl pyrolidone, polyacrylic acid, polyvinyl alcohol and poly-anetholsulfonic acid) using 2-hydroxy-5-dodecylbenzaldehyde incorporated into the polymer as carrier and tris ethyl hexyl phosphate or glycerine as plasticizers. Different PIMs are synthesized and characterized by the Fourier transform infrared, X-ray diffraction, thermal analysis and scanning electron microscopy. The influence of the membrane nature is studied using supports with different physical characteristics (porosity, thickness, hydrophobia). As application, the transport of Cd{sup 2+} using PIMs coupled with photo-electrodes is investigated. The photo-catalytic results indicate that the combined system p-CuFeO{sub 2}/membrane/n-WO{sub 3} enhances considerably the electrons transfer toward the delafossite CuFeO{sub 2}. The position of the conduction band of CuFeO{sub 2} is looked to be the key issue for the photo electrochemical Cd{sup 2+} reduction.

Mechanism of the lysosomal membrane enzyme acetyl coenzyme A: alpha-glucosaminide N-acetyltransferase

International Nuclear Information System (INIS)

Bame, K.J.

1986-01-01

Acetyl-CoA:α-glucosaminide N-acetyltransferase is a lysosomal membrane enzyme, deficient in the genetic disease Sanfilippo C syndrome. The enzyme catalyzes the transfer of an acetyl group from cytoplasmic acetyl-CoA to terminal α-glucosamine residues of heparan sulfate within the organelle. The reaction mechanism was examined using high purified lysosomal membranes from rat liver and human fibroblasts. The N-acetyltransferase reaction is optimal above pH 5.5 and a 2-3 fold stimulation of activity is observed in the presence of 0.1% taurodeoxycholate. Double reciprocal analysis and product inhibition studies indicate that the enzyme works by a Di-Iso Ping Pong Bi Bi mechanism. The binding of acetyl-CoA to the enzyme is measured by exchange label from [ 3 H]CoA to acetyl-CoA, and is optimal at pH's above 7.0. The acetyl-enzyme intermediate is formed by incubating membranes with [ 3 H]acetyl-CoA. The acetyl group can be transferred to glucosamine, forming [ 3 H]N-acetylglucosamine; the transfer is optimal between pH 4 and 5. Lysosomal membranes from Sanfilippo C fibroblasts confirm that these half reactions carried out by the N-acetyltransferase. The enzyme is inactivated by N-bromosuccinimide and diethylpyrocarbonate, indicating that a histidine is involved in the reaction. These results suggest that the histidine residue is at the active site of the enzyme. The properties of the N-acetyltransferase in the membrane, the characterization of the enzyme kinetics, the chemistry of a histidine mediated acetylation and the pH difference across the lysosomal membrane all support a transmembrane acetylation mechanism

Dynamics and energetics of the mammalian phosphatidylinositol transfer protein phospholipid exchange cycle

DEFF Research Database (Denmark)

Grabon, Aby; Orłowski, Adam; Tripathi, Ashutosh

2017-01-01

. However, the details of the PITP-mediated lipid exchange cycle remain entirely obscure. Here, all-atom molecular dynamics simulations of the mammalian StART-like PtdIns/phosphatidylcholine (PtdCho) transfer protein PITPα, both on membrane bilayers and in solvated systems, informed downstream biochemical...... analyses that tested key aspects of the hypotheses generated by the molecular dynamics simulations. These studies provided five key insights into the PITPα lipid exchange cycle: (i) interaction of PITPα with the membrane is spontaneous and mediated by four specific protein substructures; (ii) the ability......Phosphatidylinositol-transfer proteins (PITPs) regulate phosphoinositide signaling in eukaryotic cells. The defining feature of PITPs is their ability to exchange phosphatidylinositol (PtdIns) molecules between membranes, and this property is central to PITP-mediated regulation of lipid signaling...

An innovative membrane bioreactor for methane biohydroxylation.

Science.gov (United States)

Pen, N; Soussan, L; Belleville, M-P; Sanchez, J; Charmette, C; Paolucci-Jeanjean, D

2014-12-01

In this study, a membrane bioreactor (MBR) was developed for efficient, safe microbial methane hydroxylation with Methylosinus trichosporium OB3b. This innovative MBR, which couples a bioreactor with two gas/liquid macroporous membrane contactors supplying the two gaseous substrates (methane and oxygen) was operated in fed-batch mode. The feasibility and the reproducibility of this new biohydroxylation process were first demonstrated. The mass transfer within this MBR was twice that observed in a batch reactor in similar conditions. The productivity reached with this MBR was 75±25mgmethanol(gdrycell)(-1)h(-1). Compared to the literature, this value is 35times higher than that obtained with the only other fed-batch membrane bioreactor reported, which was run with dense membranes, and is comparable to those obtained with bioreactors fed by bubble-spargers. However, in the latter case, an explosive gas mixture can be formed, a problem that is avoided with the MBR. Copyright © 2014 Elsevier Ltd. All rights reserved.

Quantitative kinetic analysis of blood vessels in the outer membranes of chronic subdural hematomas

International Nuclear Information System (INIS)

Mori, Kentaro; Adachi, Keiji; Cho, Kajin; Ishimaru, Sumio; Maeda, Minoru

1998-01-01

Dynamic biologic modeling was used to calculate the transfer rate constant for gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) and capillary permeability in the outer membrane of chronic subdural hematomas and effusions. Following intravenous Gd-DTPA injection, Gd concentrations in the subdural fluid and in timed arterial blood samples were measured by ion-coupled plasma emission spectrometry in 53 chronic subdural hematomas and 18 chronic subdural effusions. The capillary surface area in outer membrane was assessed morphometrically. Transfer rate constants for subdural hematomas and subdural effusions were 12.4±1.0 and 20.6±1.7 (x 10 -4 )min -1 , respectively. Capillary permeabilities for subdural hematomas and subdural effusions were 16±1.2 and 19±3.7 ml·min -1 (mm 2 /mm 3 ) -1 , respectively. The capillary surface areas for subdural hematomas and subdural effusions were 48±3 and 77±10 mm 2 /mm 3 , respectively. The high degree of infiltration of Gd into subdural effusions reflects the high capillary surface area in the outer membrane rather than greater permeability of individual capillaries. The value of transfer rate constant was correlated inversely with the duration of the chronic subdural fluid collection. Immature outer membrane has a high transfer rate constant which allows extravasation of plasma components into the subdural space, resulting in increasing volume of the subdural effusion. Delayed magnetic resonance imaging following Gd administration may be clinically useful for estimating the age of chronic subdural fluid accumulations. (author)

Self-assembly of tissue spheroids on polymeric membranes.

Science.gov (United States)

Messina, Antonietta; Morelli, Sabrina; Forgacs, Gabor; Barbieri, Giuseppe; Drioli, Enrico; De Bartolo, Loredana

2017-07-01

In this study, multicellular tissue spheroids were fabricated on polymeric membranes in order to accelerate the fusion process and tissue formation. To this purpose, tissue spheroids composed of three different cell types, myoblasts, fibroblasts and neural cells, were formed and cultured on agarose and membranes of polycaprolactone (PCL) and chitosan (CHT). Membranes prepared by a phase-inversion technique display different physicochemical, mechanical and transport properties, which can affect the fusion process. The membranes accelerated the fusion process of a pair of spheroids with respect to the inert substrate. In this process, a critical role is played by the membrane properties, especially by their mechanical characteristics and oxygen and carbon dioxide mass transfer. The rate of fusion was quantified and found to be similar for fibroblast, myoblast and neural tissue spheroids on membranes, which completed the fusion within 3 days. These spheroids underwent faster fusion and maturation on PCL membrane than on agarose, the rate of fusion being proportional to the value of oxygen and carbon dioxide permeances and elastic characteristics. Consequently, tissue spheroids on the membranes expressed high biological activity in terms of oxygen uptake, making them more suitable as building blocks in the fabrication of tissues and organs. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Performances of nanofiltration and low pressure reverse osmosis membranes for desalination: characterization and modelling

Science.gov (United States)

Boussouga, Y. A.; Lhassani, A.

2017-03-01

The nanofiltration and the reverse osmosis processes are the most common techniques for the desalination of water contaminated by an excess of salts. In this present study, we were interested in the characterization of commercial, composite and asymmetric membranes of nanofiltration (NF90, NF270) and low pressure reverse osmosis (BW30LE). The two types of characterization that we opted for our study: (i) characterization of electrical proprieties, in terms of the surface charge of various membranes studied by the measurement of the streaming potential, (ii) hydrodynamic characterization in terms of hydraulic permeability with pure water, mass transfer and phenomenological parameters for each system membrane/salt using hydrodynamic approaches. The irreversible thermodynamics allowed us to model the observed retention Robs of salts (NaCl and Na2SO4) for the different membranes studied, to understand and to predict a good filtration with a membrane. A study was conducted on the type of mass transfer for each system membrane/salt: convection and diffusion. The results showed that all tested membranes are negatively charged for the solutions at neutral pH, this is explained by their material composition. The results also showed competitiveness between the different types of membranes. In view of that the NF remains effective in terms of selective retention with less energy consumption than LPRO.

Light induced generation of a proton motive force and Ca++- transport in membrane vesicles of Streptococcus cremoris fused with bacteriorhodopsin proteoliposomes

International Nuclear Information System (INIS)

Driessen, A.J.M.; Hellingwerf, K.J.; Konings, W.N.

1985-01-01

This paper demonstrates that S. cremoris membrane vesicles efficiently fuse with Brh proteoliposomes at low pH which leads to a functional incorporation of Brh into S. cremoris membrane vesicle. The growth of the cells and preparation of the membrane vesicles are described. Fusion, binding, and calcium transport assays were examined. In order to test fusion between S. cremoris membrane vesicles and Brh proteoliposomes the authors applied the resonance energy transfer fusion assay which monitors changes in the spatial organization of two fluorescent lipid probes in the membrane. It is shown that mixing of equal quantities of S. cremoris membrane vesicles and Brh proteoliposomes at low pH resulted in a decrease of the fluorescence energy transfer efficiency, monitored as a nincrease in NBD fluorescence

Experimental study on the membrane electrode assembly of a proton exchange membrane fuel cell: effects of microporous layer, membrane thickness and gas diffusion layer hydrophobic treatment

International Nuclear Information System (INIS)

Ferreira, Rui B.; Falcão, D.S.; Oliveira, V.B.; Pinto, A.M.F.R.

2017-01-01

Highlights: • EIS is employed to investigate the MEA design of a PEM fuel cell. • Effects of MPL, membrane thickness and GDL hydrophobic treatment are studied. • MPL increases cell output at low to medium currents but reduces it at high currents. • Better results are obtained when employing a thinner Nafion membrane. • GDL hydrophobic treatment improves the cell performance. - Abstract: In this study, electrochemical impedance spectroscopy (EIS) is employed to analyze the influence of microporous layer (MPL), membrane thickness and gas diffusion layer (GDL) hydrophobic treatment in the performance of a proton exchange membrane (PEM) fuel cell. Results show that adding a MPL increases cell performance at low to medium current densities. Because lower ohmic losses are observed when applying a MPL, such improvement is attributed to a better hydration state of the membrane. The MPL creates a pressure barrier for water produced at the cathode, forcing it to travel to the anode side, therefore increasing the water content in the membrane. However, at high currents, this same phenomenon seems to have intensified liquid water flooding in the anode gas channels, increasing mass transfer losses and reducing the cell performance. Decreasing membrane thickness results into considerably higher performances, due to a decrease in ohmic resistance. Moreover, at low air humidity operation, a rapid recovery from dehydration is observed when a thinner membrane is employed. The GDL hydrophobic treatment significantly improves the cell performance. Untreated GDLs appear to act as water-traps that not only hamper reactants transport to the reactive sites but also impede the proper humidification of the cell. From the different designs tested, the highest maximum power density is obtained from that containing a MPL, a thinner membrane and treated GDLs.

The properties of the outer membrane localized Lipid A transporter LptD

International Nuclear Information System (INIS)

Haarmann, Raimund; Ibrahim, Mohamed; Stevanovic, Mara; Bredemeier, Rolf; Schleiff, Enrico

2010-01-01

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

Membrane materials based on polyheteroarylenes and their application for pervaporation

International Nuclear Information System (INIS)

Pulyalina, A Yu; Polotskaya, G A; Toikka, A M

2016-01-01

Studies on the transport properties of membrane materials are topical in connection with the need to solve the fundamental problems and to analyze the applied aspects of the theory of membrane separation processes including, in particular, the development of the energy- and resource-saving, environmentally safe technologies. The aim of the review is to generalize the experimental data on the separation of practically valuable mixtures using membranes based on polyheteroarylenes (thermally stable and mechanically strong polymers). First of all, our analysis covers publications that give a detailed description of the physicochemical properties of the membranes and an interpretation of the specific features of mass transfer during pervaporation of liquid mixtures using membrane materials based on polyheteroarylenes. The dependences of the transport parameters of pervaporation on the process conditions and on the methods for production of membrane materials are discussed. The data presented may be useful for the development of the theory of membrane processes taking into account the chemical nature and physicochemical features of polymeric membrane materials. The bibliography includes 151 references

Nano-Pervaporation Membrane with Heat Exchanger Generates Medical-Grade Water

Science.gov (United States)

Tsai, Chung-Yi; Alexander, Jerry

2009-01-01

A nanoporous membrane is used for the pervaporation process in which potable water is maintained, at atmospheric pressure, on the feed side of the membrane. The water enters the non-pervaporation (NPV) membrane device where it is separated into two streams -- retentate water and permeated water. The permeated pure water is removed by applying low vapor pressure on the permeate side to create water vapor before condensation. This permeated water vapor is subsequently condensed by coming in contact with the cool surface of a heat exchanger with heat being recovered through transfer to the feed water stream.

Pre-concentration and quantification of uranium from lean feed by stir adsorptive membranes

International Nuclear Information System (INIS)

Das, Sadananda; Pandey, A.K.; Manchanda, V.K.; Athawale, A.A.

2010-01-01

Uranium recovery from bio-aggressive but lean feed like seawater is a challenging problem as it requires in situ preconcentration of uranium in presence of huge excess of competing ions with fast sorption kinetics. In our laboratory, widely used amidoxime membrane (AO-membrane) was evaluated for uranium sorption under seawater conditions. This study indicated that AO-membrane was inherently slow because of the complexation chemistry involved in transfer of U(VI) from (UO 2 (CO 3 ) 3 ) 4- to AO sites in membrane. In order to search better options, several chemical compositions of membrane were scanned for their efficacy for uranium preconcentration from seawater, and concluded that EGMP-membrane offers several advantages over AO-membrane. In this paper, the comparison of EGMP-membrane with AO-membrane for uranium sorption under seawater conditions has been reviewed. (author)

Use of a parallel artificial membrane system to evaluate passive absorption and elimination in small fish.

Science.gov (United States)

Kwon, Jung-Hwan; Katz, Lynn E; Liljestrand, Howard M

2006-12-01

A parallel artificial lipid membrane system was developed to mimic passive mass transfer of hydrophobic organic chemicals in fish. In this physical model system, a membrane filter-supported lipid bilayer separates two aqueous phases that represent the external and internal aqueous environments of fish. To predict bioconcentration kinetics in small fish with this system, literature absorption and elimination rates were analyzed with an allometric diffusion model to quantify the mass transfer resistances in the aqueous and lipid phases of fish. The effect of the aqueous phase mass transfer resistance was controlled by adjusting stirring intensity to mimic bioconcentration rates in small fish. Twenty-three simple aromatic hydrocarbons were chosen as model compounds for purposes of evaluation. For most of the selected chemicals, literature absorption/elimination rates fall into the range predicted from measured membrane permeabilities and elimination rates of the selected chemicals determined by the diffusion model system.

Cooperative tumour cell membrane targeted phototherapy

Science.gov (United States)

Kim, Heegon; Lee, Junsung; Oh, Chanhee; Park, Ji-Ho

2017-06-01

The targeted delivery of therapeutics using antibodies or nanomaterials has improved the precision and safety of cancer therapy. However, the paucity and heterogeneity of identified molecular targets within tumours have resulted in poor and uneven distribution of targeted agents, thus compromising treatment outcomes. Here, we construct a cooperative targeting system in which synthetic and biological nanocomponents participate together in the tumour cell membrane-selective localization of synthetic receptor-lipid conjugates (SR-lipids) to amplify the subsequent targeting of therapeutics. The SR-lipids are first delivered selectively to tumour cell membranes in the perivascular region using fusogenic liposomes. By hitchhiking with extracellular vesicles secreted by the cells, the SR-lipids are transferred to neighbouring cells and further spread throughout the tumour tissues where the molecular targets are limited. We show that this tumour cell membrane-targeted delivery of SR-lipids leads to uniform distribution and enhanced phototherapeutic efficacy of the targeted photosensitizer.

Interaction Free Energies of Eight Sodium Salts and a Phosphatidylcholine Membrane

DEFF Research Database (Denmark)

Wang, C. H.; Ge, Y.; Mortensen, J.

2011-01-01

Many recent reports have discussed specific effects of anions on the properties of lipid membranes and possible roles of such effects within biochemistry. One key parameter in both theoretical and experimental treatments of membrane-salt interactions is the net affinity, that is, the free energy...... salts by dialysis equilibrium measurements. This method provides model free thermodynamic data and allows investigations in the dilute concentration range where solution nonideality and perturbation of membrane structure is limited. The transfer free energy of DMPC from water to salt solutions, Delta mu...

Preliminary studies of using preheated carrier gas for on-line membrane extraction of semivolatile organic compounds.

Science.gov (United States)

Liu, Xinyu; Pawliszyn, Janusz

2007-04-01

In this paper, we present results for the on-line determination of semivolatile organic compounds (SVOCs) in air using membrane extraction with a sorbent interface-ion mobility spectrometry (MESI-IMS) system with a preheated carrier (stripping) gas. The mechanism of the mass transfer of SVOCs across a membrane was initially studied. In comparison with the extraction of volatile analytes, the mass transfer resistance that originated from the slow desorption from the internal membrane surface during the SVOC extraction processes should be taken into account. A preheated carrier gas system was therefore built to facilitate desorption of analytes from the internal membrane surface. With the benefit of a temperature gradient existing between the internal and external membrane surfaces, an increase in the desorption rate of a specific analyte at the internal surface and the diffusion coefficient within the membrane could be achieved while avoiding a decrease of the distribution constant on the external membrane interface. This technique improved both the extraction rate and response times of the MESI-IMS system for the analysis of SVOCs. Finally, the MESI-IMS system was shown to be capable of on-site measurement by monitoring selected polynuclear aromatic hydrocarbons emitted from cigarette smoke.

Diffusion and mass transfer

CERN Document Server

Vrentas, James S

2013-01-01

The book first covers the five elements necessary to formulate and solve mass transfer problems, that is, conservation laws and field equations, boundary conditions, constitutive equations, parameters in constitutive equations, and mathematical methods that can be used to solve the partial differential equations commonly encountered in mass transfer problems. Jump balances, Green’s function solution methods, and the free-volume theory for the prediction of self-diffusion coefficients for polymer–solvent systems are among the topics covered. The authors then use those elements to analyze a wide variety of mass transfer problems, including bubble dissolution, polymer sorption and desorption, dispersion, impurity migration in plastic containers, and utilization of polymers in drug delivery. The text offers detailed solutions, along with some theoretical aspects, for numerous processes including viscoelastic diffusion, moving boundary problems, diffusion and reaction, membrane transport, wave behavior, sedime...

Structural Changes of PVDF Membranes by Phase Separation Control

International Nuclear Information System (INIS)

Lee, Semin; Kim, Sung Soo

2016-01-01

Thermally induced phase separation (TIPS) and nonsolvent induced phase separation (NIPS) were simultaneously induced for the preparation of flat PVDF membranes. N-methyl-2-pyrrolidone (NMP) was used as a solvent and dibutyl-phthlate (DBP) was used as a diluent for PVDF. When PVDF was melt blended with NMP and DBP, crystallization temperature was lowered for TIPS and unstable region was expanded for NIPS. Ratio of solvent to diluent changed the phase separation mechanism to obtain the various membrane structures. Contact mode of dope solution with nonsolvent determined the dominant phase separation behavior. Since heat transfer rate was greater than mass transfer rate, surface structure was formed by NIPS and inner structure was by TIPS. Quenching temperature of dope solution also affected the phase separation mechanism and phase separation rate to result in the variation of structure

Ion transport restriction in mechanically strained separator membranes

Science.gov (United States)

Cannarella, John; Arnold, Craig B.

2013-03-01

We use AC impedance methods to investigate the effect of mechanical deformation on ion transport in commercial separator membranes and lithium-ion cells as a whole. A Bruggeman type power law relationship is found to provide an accurate correlation between porosity and tortuosity of deformed separators, which allows the impedance of a separator membrane to be predicted as a function of deformation. By using mechanical compression to vary the porosity of the separator membranes during impedance measurements it is possible to determine both the α and γ parameters from the modified Bruggeman relation for individual separator membranes. From impedance testing of compressed pouch cells it is found that separator deformation accounts for the majority of the transport restrictions arising from compressive stress in a lithium-ion cell. Finally, a charge state dependent increase in the impedance associated with charge transfer is observed with increasing cell compression.

Modelling of cross-flow membrane contactors : Mass transfer with chemical reactions

NARCIS (Netherlands)

Dindore, V. Y.; Brilman, D. W. F.; Versteeg, G. F.

2005-01-01

Conventionally, carbon dioxide and hydrogen sulphide are absorbed using aqueous alkanolamines or carbonate solution in column type of equipment. However, in view of the unparallel advantages offered, the use of microporous hollow fiber membrane modules is an attractive alternative. In the present

Supported liquid inorganic membranes for nuclear waste separation

Science.gov (United States)

Bhave, Ramesh R; DeBusk, Melanie M; DelCul, Guillermo D; Delmau, Laetitia H; Narula, Chaitanya K

2015-04-07

A system and method for the extraction of americium from radioactive waste solutions. The method includes the transfer of highly oxidized americium from an acidic aqueous feed solution through an immobilized liquid membrane to an organic receiving solvent, for example tributyl phosphate. The immobilized liquid membrane includes porous support and separating layers loaded with tributyl phosphate. The extracted solution is subsequently stripped of americium and recycled at the immobilized liquid membrane as neat tributyl phosphate for the continuous extraction of americium. The sequestered americium can be used as a nuclear fuel, a nuclear fuel component or a radiation source, and the remaining constituent elements in the aqueous feed solution can be stored in glassified waste forms substantially free of americium.

Lateral mobility of plasma membrane lipids in dividing Xenopus eggs.

Science.gov (United States)

Tetteroo, P A; Bluemink, J G; Dictus, W J; van Zoelen, E J; de Laat, S W

1984-07-01

The lateral mobility of plasma membrane lipids was analyzed during first cleavage of Xenopus laevis eggs by fluorescence photobleaching recovery (FPR) measurements, using the lipid analogs 5-(N-hexadecanoyl)aminofluorescein ("HEDAF") and 5-(N-tetradecanoyl)aminofluorescein ("TEDAF") as probes. The preexisting plasma membrane of the animal side showed an inhomogeneous, dotted fluorescence pattern after labeling and the lateral mobility of both probes used was below the detection limits of the FPR method (D much less than 10(-10) cm2/sec). In contrast, the preexisting plasma membrane of the vegetal side exhibited homogeneous fluorescence and the lateral diffusion coefficient of both probes used was relatively high (HEDAF, D = 2.8 X 10(-8) cm2/sec; TEDAF, D = 2.4 X 10(-8) cm2/sec). In the cleaving egg visible transfer of HEDAF or TEDAF from prelabeled plasma membrane to the new membrane in the furrow did not occur, even on the vegetal side. Upon labeling during cleavage, however, the new membrane was uniformly labeled and both probes were mobile, as in the vegetal preexisting plasma membrane. These data show that the membrane of the dividing Xenopus egg comprises three macrodomains: (i) the animal preexisting plasma membrane; (ii) the vegetal preexisting plasma membrane; (iii) the new furrow membrane.

Charge- and Size-Selective Molecular Separation using Ultrathin Cellulose Membranes

KAUST Repository

Puspasari, Tiara

2016-08-30

To date, it is still a challenge to prepare high-flux and highselectivity microporous membranes thinner than 20 nm without introducing defects. In this work, we report for the first time the application of cellulose membranes for selective separation of small molecules. A freestanding cellulose membrane as thin as 10 nm has been prepared through regeneration of trimethylsilyl cellulose (TMSC). The freestanding membrane can be transferred to any desired substrate and shows a normalized flux as high as 700 L m−2 h−1 bar−1 when supported by a porous alumina disc. According to filtration experiments, the membrane exhibits precise size-sieving performances with an estimated pore size between 1.5–3.5 nm depending on the regeneration period and initial TMSC concentration. A perfect discrimination of anionic molecules over neutral species is demonstrated. Moreover, the membrane demonstrates high reproducibility, high scale-up potential, and excellent stability over two months.

The theoretical advantage of affinity membrane-based immunoadsorption therapy of hypercholesterolemia

International Nuclear Information System (INIS)

Green, P.; Odell, R.; Schindhelm, K.

1996-01-01

Full text: Therapy of hypercholesterolemia using immunoadsorption of Low Density Lipoprotein (LDL) to a gel substrate is a current clinical technique (Bosch T., Biomat., Art. Cells and Immob. Biotech, 20: 1165- 1169, 1992). Recently, Affinity Membranes have been proposed as an alternate substrate for immunoadsorption (Brandt S and others, Bio Technology, 6:779-782, 1988). Potentially, the overall rate of adsorption to a membrane may be faster than to a gel because of the different geometry (ibid). This implies that for the same conditions, a membrane-based device will have a higher Number of Transfer Units, more efficient adsorption and a smaller device size than a gel. To test this hypothesis, we calculated two key theoretical design parameters: Separation Factor, R, and the Number of Transfer Units, N, for a functioning clinical-scale affinity membrane device: R=K d /K d +C 0 . Kd: Equilibrium Dissociation Constant (M) and Co: Feed Concentration (M) N=k a Q max V m /F. ka: Intrinsic reaction rate constant (M -1 min -1 ), Qmax: Substrate capacity (M), Vm: Membrane volume (m1) and F: Flow Rate (m1 min -1 ). We assumed 1 hr treatment time during which 1 plasma volume (3L) is treated, hence F=50 (m1 min -1 ). If we assume 2/3 of LDL is removed from an initial level of 3 g/L, we can calculate an average feed concentration Co = 2 g / L. There is some data available in the literature for typical values of Kd (10 -8 M) and ka ( 10 3 M -1 s -1 to 3 x 10 5 M -1 s -1 ) (Olsen WC and others, Molec. Immun: 26: 129-136, 1989). Since the intrinsic reaction kinetics may vary from very slow (10 3 M) to very fast (3 x 10 5 M), the Number of Transfer Units, N may vary from small (2) to large (650). Hence for a membrane device, we must select the antibody with the fastest reaction, ka, and highest capacity (Qmax) otherwise, there may be no advantage in a membrane-based device over a gel-based device

Surface modification of poly(vinylidene fluoride) hollow fibre membranes for biogas purification in a gas-liquid membrane contactor system.

Science.gov (United States)

Jin, Pengrui; Huang, Chuan; Li, Jiaxiang; Shen, Yadong; Wang, Liao

2017-11-01

The wetting of hollow fibre membranes decreases the performance of the liquid-gas membrane contactor for CO 2 capture in biogas upgrading. To solve this problem, in this work, a poly(vinylidene fluoride) (PVDF) hollow fibre membrane for a liquid-gas membrane contactor was coated with a superhydrophobic layer composed of a combination of hydrophobic SiO 2 nanoparticles and polydimethylsiloxane (PDMS) by the method of spray deposition. A rough layer of SiO 2 deposited on the PVDF membrane resulted in an enhanced surface hydrophobicity. The surface structure of the pristine PVDF significantly affected the homogeneity of the generated SiO 2 layer. A uniform surface coating on the PVDF upper layer resulted from the presence of micrometre and nanometre-sized roughness on the surface of the PVDF membrane, which was achieved with a SiO 2 concentration of 4.44 mg ml -1 (0.2 g/45 ml) in the coating solution. As a result, the water contact angle of the modified surface was recorded as 155 ± 3°, which is higher than that of the pristine surface. The high contact angle is advantageous for reducing the wetting of the membrane. Additional mass transfer resistance was introduced by the superhydrophobic layer. In addition, continuous CO 2 absorption tests were carried out in original and modified PVDF hollow fibre membrane contactors, using monoethanolamine (MEA) solution as the absorbent. A long-term stability test revealed that the modified PVDF hollow fibre membrane contactor was able to outperform the original membrane contactor and demonstrated outstanding long-term stability, suggesting that spray deposition is a promising approach to obtain superhydrophobic PVDF membranes for liquid-gas membrane absorption.

Study of the ion-channel behavior on glassy carbon electrode supported bilayer lipid membranes stimulated by perchlorate anion

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zhiquan; Shi, Jun; Huang, Weimin, E-mail: huangwm@jlu.edu.cn

2015-10-01

In this paper, a kind of didodecyldimethylammonium bromide (DDAB) layer membranes was supported on a glassy carbon electrode (GCE). We studied the ion channel behavior of the supported bilayer lipid membrane by scanning electrochemical microscopy (SCEM) in tris(2,2′-bipyridine) ruthenium(II) solution. Perchlorate anion was used as a presence of stimulus and ruthenium(II) complex cations as the probing ions for the measurement of SECM, the lipid membrane channel was opened and exhibited the behavior of distinct SECM positive feedback curve. The channel was in a closed state in the absence of perchlorate anions while reflected the behavior of SECM negative feedback curve. The rates of electron transfer reaction in the lipid membranes surface were detected and it was dependant on the potential of SECM. - Highlights: • The rates of electron transfer reaction in the lipid membranes surface were detected. • Dynamic investigations of ion-channel behavior of supported bilayer lipid membranes by scanning electrochemical microscopy • A novel way to explore the interaction between molecules and supported bilayer lipid membranes.

Development of hydrophobic clay–alumina based capillary membrane for desalination of brine by membrane distillation

Directory of Open Access Journals (Sweden)

Rakhi Das

2016-09-01

Full Text Available Clay–alumina compositions of 0, 20, 40 and 55 weight percent (wt% clay and rest alumina were maintained in porous support preparation by extrusion followed by sintering at 1300 °C for 2.5 h to obtain 3 mm/2 mm (outer diameter/inner diameter capillary. 1H,1H,2H,2H-perfluorodecyltriethoxysilane (97% (C8 was used to modify the capillary surface of all compositions without any intermediate membrane layer to impart hydrophobic characteristics and compared in terms of contact angle produced by the capillaries with water and liquid entry pressure (LEPw. FTIR analysis showed that the hydrophilic surface of the capillary membranes was efficiently modified by the proposed grafting method. Capillary with 55 wt% clay produced a pore size of 1.43 micron and was considered as an ideal candidate for grafting with C8 polymer to impart surface hydrophobicity. The contact angle and LEPw value obtained for this modified membrane (C-55-M were 145° and 1 bar, respectively. The modified capillary membrane was applied for desalination of brine by air gap membrane distillation (AGMD at a feed pressure of 0.85 bar. Maximum flux obtained for C-55-M membrane was 98.66 L/m2 day at a temperature difference of 60 °C with salt rejection of 99.96%. Mass transfer coefficient of C-55-M was 16 × 10−3 mm/s at feed temperature of 70 °C.

Fabrication and characterization of vertically aligned carbon-nanotube membranes

Science.gov (United States)

Castellano, Richard; Akin, Cevat; Purri, Matt; Shan, Jerry; Kim, Sangil; Fornasiero, Francesco

2015-11-01

Membranes having vertically-aligned carbon-nanotube (VACNT) pores offer promise as highly efficient and permeable membranes for use as breathable thin films, or in filtration and separation applications, among others. However, current membrane-fabrication techniques utilizing chemical-vapor-deposition-grown VACNT arrays are costly and difficult to scale up. We have developed a solution-based, electric-field-assisted approach as a cost-effective and scalable method to produce large-area VACNT membranes. Nanotubes are dispersed in a liquid polymer, and aligned and electrodeposited with the aid of an electric field prior to crosslinking the polymer to create VACNT membranes. We experimentally examine the electrodeposition process, focusing on parameters including the electric field, composition of the solution, and CNT functionalization that can affect the nanotube number density in the resulting membrane. We characterize the CNT pore size and number density and investigate the transport properties of the membrane. Size-exclusion tests are used to check for defects and infer the pore size of the VACNT membranes. Dry-gas membrane permeability is measured with a pressurized nitrogen-flow system, while moisture-vapor-transfer rate is measured with the ASTM-E96 upright-cup test. We discuss the measured transport properties of the solution-based, electric-field-fabricated VACNT membranes in reference to their application as breathable thin films. We would like to acknowledge DTRA for their funding and support of our research.

Ceramic membrane microfilter as an immobilized enzyme reactor.

Science.gov (United States)

Harrington, T J; Gainer, J L; Kirwan, D J

1992-10-01

This study investigated the use of a ceramic microfilter as an immobilized enzyme reactor. In this type of reactor, the substrate solution permeates the ceramic membrane and reacts with an enzyme that has been immobilized within its porous interior. The objective of this study was to examine the effect of permeation rate on the observed kinetic parameters for the immobilized enzyme in order to assess possible mass transfer influences or shear effects. Kinetic parameters were found to be independent of flow rate for immobilized penicillinase and lactate dehydrogenase. Therefore, neither mass transfer nor shear effects were observed for enzymes immobilized within the ceramic membrane. Both the residence time and the conversion in the microfilter reactor could be controlled simply by regulating the transmembrane pressure drop. This study suggests that a ceramic microfilter reactor can be a desirable alternative to a packed bed of porous particles, especially when an immobilized enzyme has high activity and a low Michaelis constant.

Membrane air stripping utilizing a plate and frame configuration

International Nuclear Information System (INIS)

Boswell, S.T.

1991-01-01

Membrane air stripping has recently been proposed as a possible method to remove volatile organic chemicals (VOCs) and radon from drinking water supplies. Current and anticipated regulatory requirements, driven by health consequences, make the removal of these contaminants mandatory. This work examines the use of plate and frame membrane air stripping for the removal of VOCs and radon from a water supply. The theoretical basis of membrane air stripping and a literature review are included. The advantages of membrane air stripping versus other methods of removal, as well as the advantages of a plate and frame configuration versus a hollow fiber configuration for membrane air stripping are discussed. Multiple regression/correlation techniques are used to model mass transfer coefficients and fluid resistances. An economic evaluation is performed using the developed models. The costs of comparable membrane and packed tower air stripping systems are 4.86 cents per thousand gallons versus 4.36 cents per thousand gallons, respectively. This work indicates that plate and frame membrane air stripping may, in fact, prove to be an economical alternative to packed tower aeration and carbon adsorption for the removal of VOCs and radon

Self-assembling peptides form nanodiscs that stabilize membrane proteins

DEFF Research Database (Denmark)

Midtgaard, Søren Roi; Pedersen, Martin Cramer; Kirkensgaard, Jacob Judas Kain

2014-01-01

-ray scattering (SAXS) and small-angle neutron scattering (SANS) supported by coarse-grained molecular dynamics simulations. The detailed structure of the discs was determined in unprecedented detail and it was found that they adopt a discoidal structure very similar to the ApoA1 based nanodiscs. We furthermore...... show that, like the ApoA1 and derived nanodiscs, these peptide discs can accommodate and stabilize a membrane protein. Finally, we exploit their dynamic properties and show that the 18A discs may be used for transferring membrane proteins and associated phospholipids directly and gently......New methods to handle membrane bound proteins, e.g. G-protein coupled receptors (GPCRs), are highly desirable. Recently, apoliprotein A1 (ApoA1) based lipoprotein particles have emerged as a new platform for studying membrane proteins, and it has been shown that they can self...

Bubble coalescence suppression driven carbon monoxide (CO)-water mass transfer increase by electrolyte addition in a hollow fiber membrane bioreactor (HFMBR) for microbial CO conversion to ethanol.

Science.gov (United States)

Jang, Nulee; Yasin, Muhammad; Kang, Hyunsoo; Lee, Yeubin; Park, Gwon Woo; Park, Shinyoung; Chang, In Seop

2018-05-04

This study investigated the effects of electrolytes (CaCl 2 , K 2 HPO 4 , MgSO 4 , NaCl, and NH 4 Cl) on CO mass transfer and ethanol production in a HFMBR. The hollow fiber membranes (HFM) were found to generate tiny gas bubbles; the bubble coalescence was significantly suppressed in electrolyte solution. The volumetric gas-liquid mass transfer coefficients (k L a) increased up to 414% compared to the control. Saturated CO (C ∗ ) decreased as electrolyte concentrations increased. Overall, the maximum mass transfer rate (R max ) in electrolyte solution ranged from 106% to 339% of the value obtained in water. The electrolyte toxicity on cell growth was tested using Clostridium autoethanogenum. Most electrolytes, except for MgSO 4 , inhibited cell growth. The HFMBR operation using a medium containing 1% MgSO 4 achieved 119% ethanol production compared to that without electrolytes. Finally, a kinetic simulation using the parameters got from the 1% MgSO 4 medium predicted a higher ethanol production compared to the control. Copyright © 2018 Elsevier Ltd. All rights reserved.

Studies on improved integrated membrane-based chromatographic process for bioseparation

Science.gov (United States)

Xu, Yanke

To improve protein separation and purification directly from a fermentation broth, a novel membrane filtration-cum-chromatography device configuration having a relatively impermeable coated zone near the hollow fiber module outlet has been developed. The integrated membrane filtration-cum-chromatography unit packed with chromatographic beads on the shell side of the hollow fiber unit enjoys the advantages of both membrane filtration and chromatography; it allows one to load the chromatographic media directly from the fermentation broth or lysate and separate the adsorbed proteins through the subsequent elution step in a cyclic process. Interfacial polymerization was carried out to coat the bottom section of the hollow fiber membrane while leaving the rest of the hollow fiber membrane unaffected. Myoglobin (Mb), bovine serum albumin (BSA) and a-lactalbumin (a-LA) were used as model proteins in binary mixtures. Separation behaviors of binary protein mixtures were studied in devices using either an ultrafiltration (UF) membrane or a microfiltration (MF) membrane. Experimental results show that the breakthrough time and the protein loading capacities were dramatically improved after coating in both UF and MF modules. For a synthetic yeast fermentation broth feed, the Mb and a-LA elution profiles for the four consecutive cyclic runs were almost superimposable. Due to the lower transmembrane flux in this device plus the periodical washing-elution during the chromatographic separation, fouling was not a problem as it is in conventional microfiltration. A mathematical model describing the hydrodynamic and protein loading behaviors of the integrated device using UF membrane with a coated zone was developed. The simulation results for the breakthrough agree well with the experimental breakthrough curves. The optimal length of the coated zone was obtained from the simulation. A theoretical analysis of the protein mass transfer was performed using a diffusion-convection model

Electrochemical Measurement of Electron Transfer Kinetics by Shewanella oneidensis MR-1*

Science.gov (United States)

Baron, Daniel; LaBelle, Edward; Coursolle, Dan; Gralnick, Jeffrey A.; Bond, Daniel R.

2009-01-01

Shewanella oneidensis strain MR-1 can respire using carbon electrodes and metal oxyhydroxides as electron acceptors, requiring mechanisms for transferring electrons from the cell interior to surfaces located beyond the cell. Although purified outer membrane cytochromes will reduce both electrodes and metals, S. oneidensis also secretes flavins, which accelerate electron transfer to metals and electrodes. We developed techniques for detecting direct electron transfer by intact cells, using turnover and single turnover voltammetry. Metabolically active cells attached to graphite electrodes produced thin (submonolayer) films that demonstrated both catalytic and reversible electron transfer in the presence and absence of flavins. In the absence of soluble flavins, electron transfer occurred in a broad potential window centered at ∼0 V (versus standard hydrogen electrode), and was altered in single (ΔomcA, ΔmtrC) and double deletion (ΔomcA/ΔmtrC) mutants of outer membrane cytochromes. The addition of soluble flavins at physiological concentrations significantly accelerated electron transfer and allowed catalytic electron transfer to occur at lower applied potentials (−0.2 V). Scan rate analysis indicated that rate constants for direct electron transfer were slower than those reported for pure cytochromes (∼1 s−1). These observations indicated that anodic current in the higher (>0 V) window is due to activation of a direct transfer mechanism, whereas electron transfer at lower potentials is enabled by flavins. The electrochemical dissection of these activities in living cells into two systems with characteristic midpoint potentials and kinetic behaviors explains prior observations and demonstrates the complementary nature of S. oneidensis electron transfer strategies. PMID:19661057

High-performance flexible thin-film transistors fabricated using print-transferrable polycrystalline silicon membranes on a plastic substrate

International Nuclear Information System (INIS)

Qin, Guoxuan; Yuan, Hao-Chih; Ma, Zhenqiang; Yang, Hongjun; Zhou, Weidong

2011-01-01

Inexpensive polycrystalline Si (poly-Si) with large grain size is highly desirable for flexible electronics applications. However, it is very challenging to directly deposit high-quality poly-Si on plastic substrates due to processing constrictions, such as temperature tolerance and residual stress. In this paper, we present our study on poly-Si membranes that are stress free and most importantly, are transferrable to any substrate including a low-temperature polyethylene terephthalate (PET) substrate. We formed poly-Si-on-insulator by first depositing small-grain size poly-Si on an oxidized Si wafer. We then performed high-temperature annealing for recrystallization to obtain larger grain size. After selective doping on the poly-Si-on-insulator, buried oxide was etched away. By properly patterning the poly-Si layer, residual stress in the released poly-Si membranes was completely relaxed. The flat membrane topology allows the membranes to be print transferred to any substrates. High-performance TFTs were demonstrated on the transferred poly-Si membranes on a PET substrate

The Golgi localization of phosphatidylinositol transfer protein beta requires the protein kinase C-dependent phosphorylation of serine 262 and is essential for maintaining plasma membrane sphingomyelin levels.

Science.gov (United States)

van Tiel, Claudia M; Westerman, Jan; Paasman, Marten A; Hoebens, Martha M; Wirtz, Karel W A; Snoek, Gerry T

2002-06-21

Recombinant mouse phosphatidylinositol transfer protein (PI-TP)beta is a substrate for protein kinase C (PKC)-dependent phosphorylation in vitro. Based on site-directed mutagenesis and two-dimensional tryptic peptide mapping, Ser(262) was identified as the major site of phosphorylation and Ser(165) as a minor phosphorylation site. The phospholipid transfer activities of wild-type PI-TP beta and PI-TP beta(S262A) were identical, whereas PI-TP beta(S165A) was completely inactive. PKC-dependent phosphorylation of Ser(262) also had no effect on the transfer activity of PI-TP beta. To investigate the role of Ser(262) in the functioning of PI-TP beta, wtPI-TP beta and PI-TP beta(S262A) were overexpressed in NIH3T3 fibroblast cells. Two-dimensional PAGE analysis of cell lysates was used to separate PI-TP beta from its phosphorylated form. After Western blotting, wtPI-TP beta was found to be 85% phosphorylated, whereas PI-TP beta(S262A) was not phosphorylated. In the presence of the PKC inhibitor GF 109203X, the phosphorylated form of wtPI-TP beta was strongly reduced. Immunolocalization showed that wtPI-TP beta was predominantly associated with the Golgi membranes. In the presence of the PKC inhibitor, wtPI-TP beta was distributed throughout the cell similar to what was observed for PI-TP beta(S262A). In contrast to wtPI-TP beta overexpressors, cells overexpressing PI-TP beta(S262A) were unable to rapidly replenish sphingomyelin in the plasma membrane upon degradation by sphingomyelinase. This implies that PKC-dependent association with the Golgi complex is a prerequisite for PI-TP beta to express its effect on sphingomyelin metabolism.

Membrane Protein Mobility and Orientation Preserved in Supported Bilayers Created Directly from Cell Plasma Membrane Blebs.

Science.gov (United States)

Richards, Mark J; Hsia, Chih-Yun; Singh, Rohit R; Haider, Huma; Kumpf, Julia; Kawate, Toshimitsu; Daniel, Susan

2016-03-29

Membrane protein interactions with lipids are crucial for their native biological behavior, yet traditional characterization methods are often carried out on purified protein in the absence of lipids. We present a simple method to transfer membrane proteins expressed in mammalian cells to an assay-friendly, cushioned, supported lipid bilayer platform using cell blebs as an intermediate. Cell blebs, expressing either GPI-linked yellow fluorescent proteins or neon-green fused transmembrane P2X2 receptors, were induced to rupture on glass surfaces using PEGylated lipid vesicles, which resulted in planar supported membranes with over 50% mobility for multipass transmembrane proteins and over 90% for GPI-linked proteins. Fluorescent proteins were tracked, and their diffusion in supported bilayers characterized, using single molecule tracking and moment scaling spectrum (MSS) analysis. Diffusion was characterized for individual proteins as either free or confined, revealing details of the local lipid membrane heterogeneity surrounding the protein. A particularly useful result of our bilayer formation process is the protein orientation in the supported planar bilayer. For both the GPI-linked and transmembrane proteins used here, an enzymatic assay revealed that protein orientation in the planar bilayer results in the extracellular domains facing toward the bulk, and that the dominant mode of bleb rupture is via the "parachute" mechanism. Mobility, orientation, and preservation of the native lipid environment of the proteins using cell blebs offers advantages over proteoliposome reconstitution or disrupted cell membrane preparations, which necessarily result in significant scrambling of protein orientation and typically immobilized membrane proteins in SLBs. The bleb-based bilayer platform presented here is an important step toward integrating membrane proteomic studies on chip, especially for future studies aimed at understanding fundamental effects of lipid interactions

A tunable sub-100 nm silicon nanopore array with an AAO membrane mask: reducing unwanted surface etching by introducing a PMMA interlayer

Science.gov (United States)

Lim, Namsoo; Pak, Yusin; Kim, Jin Tae; Hwang, Youngkyu; Lee, Ryeri; Kumaresan, Yogeenth; Myoung, Nosoung; Ko, Heung Cho; Jung, Gun Young

2015-08-01

Highly ordered silicon (Si) nanopores with a tunable sub-100 nm diameter were fabricated by a CF4 plasma etching process using an anodic aluminum oxide (AAO) membrane as an etching mask. To enhance the conformal contact of the AAO membrane mask to the underlying Si substrate, poly(methyl methacrylate) (PMMA) was spin-coated on top of the Si substrate prior to the transfer of the AAO membrane. The AAO membrane mask was fabricated by two-step anodization and subsequent removal of the aluminum support and the barrier layer, which was then transferred to the PMMA-coated Si substrate. Contact printing was performed on the sample with a pressure of 50 psi and a temperature of 120 °C to make a conformal contact of the AAO membrane mask to the Si substrate. The CF4 plasma etching was conducted to transfer nanopores onto the Si substrate through the PMMA interlayer. The introduced PMMA interlayer prevented unwanted surface etching of the Si substrate by eliminating the etching ions and radicals bouncing at the gap between the mask and the substrate, resulting in a smooth Si nanopore array.Highly ordered silicon (Si) nanopores with a tunable sub-100 nm diameter were fabricated by a CF4 plasma etching process using an anodic aluminum oxide (AAO) membrane as an etching mask. To enhance the conformal contact of the AAO membrane mask to the underlying Si substrate, poly(methyl methacrylate) (PMMA) was spin-coated on top of the Si substrate prior to the transfer of the AAO membrane. The AAO membrane mask was fabricated by two-step anodization and subsequent removal of the aluminum support and the barrier layer, which was then transferred to the PMMA-coated Si substrate. Contact printing was performed on the sample with a pressure of 50 psi and a temperature of 120 °C to make a conformal contact of the AAO membrane mask to the Si substrate. The CF4 plasma etching was conducted to transfer nanopores onto the Si substrate through the PMMA interlayer. The introduced PMMA interlayer

Modeling electrically active viscoelastic membranes.

Directory of Open Access Journals (Sweden)

Sitikantha Roy

Full Text Available The membrane protein prestin is native to the cochlear outer hair cell that is crucial to the ear's amplification and frequency selectivity throughout the whole acoustic frequency range. The outer hair cell exhibits interrelated dimensional changes, force generation, and electric charge transfer. Cells transfected with prestin acquire unique active properties similar to those in the native cell that have also been useful in understanding the process. Here we propose a model describing the major electromechanical features of such active membranes. The model derived from thermodynamic principles is in the form of integral relationships between the history of voltage and membrane resultants as independent variables and the charge density and strains as dependent variables. The proposed model is applied to the analysis of an active force produced by the outer hair cell in response to a harmonic electric field. Our analysis reveals the mechanism of the outer hair cell active (isometric force having an almost constant amplitude and phase up to 80 kHz. We found that the frequency-invariance of the force is a result of interplay between the electrical filtering associated with prestin and power law viscoelasticity of the surrounding membrane. Paradoxically, the membrane viscoelasticity boosts the force balancing the electrical filtering effect. We also consider various modes of electromechanical coupling in membrane with prestin associated with mechanical perturbations in the cell. We consider pressure or strains applied step-wise or at a constant rate and compute the time course of the resulting electric charge. The results obtained here are important for the analysis of electromechanical properties of membranes, cells, and biological materials as well as for a better understanding of the mechanism of hearing and the role of the protein prestin in this mechanism.

Development of robust fluorinated TiO2/PVDF composite hollow fiber membrane for CO2 capture in gas-liquid membrane contactor

Science.gov (United States)

Lin, Yuqing; Xu, Yilin; Loh, Chun Heng; Wang, Rong

2018-04-01

Gas-liquid membrane contactor (GLMC) is a promising method to attain high efficiency for CO2 capture from flue gas, biogas and natural gas. However, membranes used in GLMC are prone to pore wetting due to insufficient hydrophobicity and low chemical resistance, resulting in significant increase in mass transfer resistance. To mitigate this issue, inorganic-organic fluorinated titania/polyvinylidene fluoride (fTiO2/PVDF) composite hollow fiber (HF) membranes was prepared via facile in-situ vapor induced hydrolyzation method, followed by hydrophobic modification. The proposed composite membranes were expected to couple the superb chemical stability of inorganic and high permeability/low cost of organic materials. The continuous fTiO2 layer deposited on top of PVDF substrate was found to possess a tighter microstructure and better hydrophobicity, which effectively prevented the membrane from wetting and lead to a high CO2 absorption flux (12.7 × 10-3 mol m-2 s-1). In a stability test with 21-day operation of GLMC using 1M monoethanolamine (MEA) as the absorbent, the fTiO2/PVDF membrane remained to be intact with a CO2 absorption flux decline of ∼16%, while the pristine PVDF membrane suffered from a flux decline of ∼80% due to membrane damage. Overall, this work provides an insight into the preparation of high-quality inorganic/organic composite HF membranes for CO2 capture in GLMC application.

Transport of phosphoric acid through supported liquid membrane

International Nuclear Information System (INIS)

Zayzafoon, G.; Yassine, T.; Baidoun, R.

2003-01-01

The transport of phosphhoric acid through liquid membranes of amylalkohol, 1-octanol and 2-octanol was studied. It was found that phosphoric acid is transfered from feed side to strip side and the transport increased with the concentration of phosphoric acid up to 5M. The permeability in each membrane was determined for 5M phosphoic acid. It was found that the permeability values are 1.45 x 10 1 0 m 2 s 1 for amylakohol and ∼ 1x10 1 0 m 2 s 1 for each of 1-octanol and 2-octanol

Transfer of fatty acids from the 1-position of phosphatidyl-ethanolamine to the major outer membrane lipoprotein of E coli

International Nuclear Information System (INIS)

Jackowski, S.; Rock, C.O.

1986-01-01

The fatty acids esterified to Braun's lipoprotein are derived from the phospholipid pool in E. coli. Mutants lacking acyl-CoA synthetase activity (fadD) incorporated extracellular fatty acids specifically into the 1-position of phosphatidylethanolamine (PtdEtn). This pathway was blocked by chloramphenicol and was depressed by preventing the acylation of the amino terminus of the lipoprotein with globomycin. Transfer of fatty acids to lipoprotein was investigated in fadD mutants harboring hybrid plasmids containing either the lipoprotein gene or a lipoprotein-β-lactamase gene fusion under control of the lactose promoter. Labeling of the 1-position of the PtdEtn pool prior to induction of lipoprotein biosynthesis resulted in the transfer of fatty acids from PtdEtn to the lipoproteins. Induction of lipoprotein synthesis in the presence of exogenous [1- 14 C]palmitate increased the amount of radioactivity entering the PtdEtn pool and efficiently labeled lipoprotein acyl moieties. Lipoprotein fatty acids derived from the 1-position of PtdEtn were resistant to hydroxylamine hydrolysis, and globomycin reduced the incorporation of exogenous [1- 14 C]palmitic acid into lipoproteins by 80% suggesting that the fatty acid is attached to the amino terminus. These data illustrate the metabolic relationship between turnover of fatty acids in the 1-position of PtdEtn and the maturation of the major outer membrane lipoprotein

High Thermal Gradient in Thermo-electrochemical Cells by Insertion of a Poly(Vinylidene Fluoride) Membrane

Science.gov (United States)

Hasan, Syed Waqar; Said, Suhana Mohd; Sabri, Mohd Faizul Mohd; Bakar, Ahmad Shuhaimi Abu; Hashim, Nur Awanis; Hasnan, Megat Muhammad Ikhsan Megat; Pringle, Jennifer M.; Macfarlane, Douglas R.

2016-07-01

Thermo-Electrochemical cells (Thermocells/TECs) transform thermal energy into electricity by means of electrochemical potential disequilibrium between electrodes induced by a temperature gradient (ΔT). Heat conduction across the terminals of the cell is one of the primary reasons for device inefficiency. Herein, we embed Poly(Vinylidene Fluoride) (PVDF) membrane in thermocells to mitigate the heat transfer effects - we refer to these membrane-thermocells as MTECs. At a ΔT of 12 K, an improvement in the open circuit voltage (Voc) of the TEC from 1.3 mV to 2.8 mV is obtained by employment of the membrane. The PVDF membrane is employed at three different locations between the electrodes i.e. x = 2 mm, 5 mm, and 8 mm where ‘x’ defines the distance between the cathode and PVDF membrane. We found that the membrane position at x = 5 mm achieves the closest internal ΔT (i.e. 8.8 K) to the externally applied ΔT of 10 K and corresponding power density is 254 nWcm-2 78% higher than the conventional TEC. Finally, a thermal resistivity model based on infrared thermography explains mass and heat transfer within the thermocells.

Cell-secreted flavins bound to membrane cytochromes dictate electron transfer reactions to surfaces with diverse charge and pH.

Science.gov (United States)

Okamoto, Akihiro; Kalathil, Shafeer; Deng, Xiao; Hashimoto, Kazuhito; Nakamura, Ryuhei; Nealson, Kenneth H

2014-07-11

The variety of solid surfaces to and from which microbes can deliver electrons by extracellular electron transport (EET) processes via outer-membrane c-type cytochromes (OM c-Cyts) expands the importance of microbial respiration in natural environments and industrial applications. Here, we demonstrate that the bifurcated EET pathway of OM c-Cyts sustains the diversity of the EET surface in Shewanella oneidensis MR-1 via specific binding with cell-secreted flavin mononucleotide (FMN) and riboflavin (RF). Microbial current production and whole-cell differential pulse voltammetry revealed that RF and FMN enhance EET as bound cofactors in a similar manner. Conversely, FMN and RF were clearly differentiated in the EET enhancement by gene-deletion of OM c-Cyts and the dependency of the electrode potential and pH. These results indicate that RF and FMN have specific binding sites in OM c-Cyts and highlight the potential roles of these flavin-cytochrome complexes in controlling the rate of electron transfer to surfaces with diverse potential and pH.

Development and process optimization of an enzyme membrane reactor for lactose hydrolysis. Entwicklung und verfahrenstechnische Optimierung eines Enzym-Membranreaktors fuer die Hydrolyse von Laktose

Energy Technology Data Exchange (ETDEWEB)

Czermak, P

1990-01-01

The development and process optimization up to the production stage of a vapour sterilizable hollow-fiber membrane reactor for dialysis is illustrated by the example of enzymatic hydrolysis of lactose. The expected conversion efficiency of the membrane reactor is a function of the mass transfer resistance and by the deviations from the defined hydrodynamic status. The transport/reaction behaviour of membrane reactors is therefore described by a model for real reactors which takes account of the non-linear kinetics of the native enzyme, the real mixing conditions inside the reactor, and the mass transfer through the membrane. A coupled numerical solution is used for the calculations. The reaction kinetics, the mass transfer inside the membrane, the hydrodynamics and the conversion rate are determined experimentally. The model can calculate important design data from selected data of the reaction system. Measurements of conversion rates show that the results obtained with real substances, e.g. milk, are well compatible with the model calculations. (orig.) With 85 figs., 25 tabs.

Enhanced starch hydrolysis using α-amylase immobilized on cellulose ultrafiltration affinity membrane.

Science.gov (United States)

Konovalova, Viktoriia; Guzikevich, Kateryna; Burban, Anatoliy; Kujawski, Wojciech; Jarzynka, Karolina; Kujawa, Joanna

2016-11-05

In order to prepare ultrafiltration membranes possessing biocatalytic properties, α-amylase has been immobilized on cellulose membranes. Enzyme immobilization was based on a covalent bonding between chitosan and a surface of cellulose membrane, followed by an attachment of Cibacron Blue F3G-A dye as affinity ligand. Various factors affecting the immobilization process, such as enzyme concentration, pH of modifying solution, zeta-potential of membrane surface, and stability of immobilized enzyme were studied. The applicability of immobilized α-amylase has been investigated in ultrafiltration processes. The immobilization of α-amylase on membrane surface allows to increase the value of mass transfer coefficient and to decrease the concentration polarization effect during ultrafiltration of starch solutions. The enzyme layer on the membrane surface prevents a rapid increase of starch concentration due to the amylase hydrolysis of starch in the boundary layer. The presented affinity immobilization technique allows also for the regeneration of membranes from inactivated enzyme. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling and Simulation of Membrane-Based Dehumidification and Energy Recovery Process

Energy Technology Data Exchange (ETDEWEB)

Gao, Zhiming [ORNL; Abdelaziz, Omar [ORNL; Qu, Ming [ORNL

2017-01-01

This paper introduces a first-order physics-based model that accounts for the fundamental heat and mass transfer between a humid-air vapor stream on feed side to another flow stream on permeate side. The model comprises a few optional submodels for membrane mass transport; and it adopts a segment-by-segment method for discretizing heat and mass transfer governing equations for flow streams on feed and permeate sides. The model is able to simulate both dehumidifiers and energy recovery ventilators in parallel-flow, cross-flow, and counter-flow configurations. The predicted tresults are compared reasonably well with the measurements. The open-source codes are written in C++. The model and open-source codes are expected to become a fundament tool for the analysis of membrane-based dehumidification in the future.

Air dehumidification by membrane with cold water for manned spacecraft environmental control

Directory of Open Access Journals (Sweden)

Shang Yonghong

2017-01-01

Full Text Available The traditional condensation dehumidification method requires additional gas-liquid separation and water recovery process in the manned spacecraft humidity control system, which would increase weight and complexity of systems. A new membrane dehumidification with cold water is proposed, which uses water vapor partial pressure difference to promote water vapor transmembrane mass transfer for dehumidification. The permeability of the membrane was measured and the experimental results agree well with the theoretical calculations. Based on the simulation of dehumidification process of cold water-membrane, the influence of module structure and working condition on dehumidification performance was analyzed, which provided reference for the design of membrane module construct. It can be seen from the simulation and experiments that the cold water-membrane dehumidification can effectively reduce the thermal load of the manned spacecraft.

Profiling the outer membrane proteome during growth and development of the social bacterium Myxococcus xanthus by selective biotinylation and analyses of outer membrane vesicles.

Science.gov (United States)

Kahnt, Jörg; Aguiluz, Kryssia; Koch, Jürgen; Treuner-Lange, Anke; Konovalova, Anna; Huntley, Stuart; Hoppert, Michael; Søgaard-Andersen, Lotte; Hedderich, Reiner

2010-10-01

Social behavior in the bacterium Myxococcus xanthus relies on contact-dependent activities involving cell-cell and cell-substratum interactions. To identify outer membrane proteins that have a role in these activities, we profiled the outer membrane proteome of growing and starving cells using two strategies. First, outer membrane proteins were enriched by biotinylation of intact cells using the reagent NHS (N-hydroxysuccinimide)-PEO(12) (polyethylene oxide)-biotin with subsequent membrane solubilization and affinity chromatography. Second, the proteome of outer membrane vesicles (OMV) was determined. Comparisons of detected proteins show that these methods have different detection profiles and together provide a comprehensive view of the outer membrane proteome. From 362 proteins identified, 274 (76%) were cell envelope proteins including 64 integral outer membrane proteins and 85 lipoproteins. The majority of these proteins were of unknown function. Among integral outer membrane proteins with homologues of known function, TonB-dependent transporters comprise the largest group. Our data suggest novel functions for these transporters. Among lipoproteins with homologues of known function, proteins with hydrolytic functions comprise the largest group. The luminal load of OMV was enriched for proteins with hydrolytic functions. Our data suggest that OMV have functions in predation and possibly in transfer of intercellular signaling molecules between cells.

Electrochemical ion transfer across liquid/liquid interfaces confined within solid-state micropore arrays--simulations and experiments.

Science.gov (United States)

Strutwolf, Jörg; Scanlon, Micheál D; Arrigan, Damien W M

2009-01-01

Miniaturised liquid/liquid interfaces provide benefits for bioanalytical detection with electrochemical methods. In this work, microporous silicon membranes which can be used for interface miniaturisation were characterized by simulations and experiments. The microporous membranes possessed hexagonal arrays of pores with radii between 10 and 25 microm, a pore depth of 100 microm and pore centre-to-centre separations between 99 and 986 microm. Cyclic voltammetry was used to monitor ion transfer across arrays of micro-interfaces between two immiscible electrolyte solutions (microITIES) formed at these membranes, with the organic phase present as an organogel. The results were compared to computational simulations taking into account mass transport by diffusion and encompassing diffusion to recessed interfaces and overlapped diffusion zones. The simulation and experimental data were both consistent with the situation where the location of the liquid/liquid (l/l) interface was on the aqueous side of the silicon membrane and the pores were filled with the organic phase. While the current for the forward potential scan (transfer of the ion from the aqueous phase to the organic phase) was strongly dependent on the location of the l/l interface, the current peak during the reverse scan (transfer of the ion from the organic phase to the aqueous phase) was influenced by the ratio of the transferring ion's diffusion coefficients in both phases. The diffusion coefficient of the transferring ion in the gelified organic phase was ca. nine times smaller than in the aqueous phase. Asymmetric cyclic voltammogram shapes were caused by the combined effect of non-symmetrical diffusion (spherical and linear) and by the inequality of the diffusion coefficient in both phases. Overlapping diffusion zones were responsible for the observation of current peaks instead of steady-state currents during the forward scan. The characterisation of the diffusion behaviour is an important requirement

Supercapacitive bioelectrochemical solar cells using thylakoid membranes and carbon nanotubes

DEFF Research Database (Denmark)

Pankratov, Dmitrii; Pankratova, G.; Åkerlund, H.-E.

and storage in the form of electric charge within a singular contrivance, we have developed and investigated supercapacitive photo-bioanodes based on the carboxilized and amidized multiwalled carbon nanotubes (MWСNTs) in direct electron transfer (DET) communication with adsorbed thylakoid membranes...

Hybridization of plant virus ssRNAs Transferred to Hybond N membrane

International Nuclear Information System (INIS)

Kudela, O.; Kudelova, K.; Plaschke-Jakubik, K.

1998-01-01

In this paper we present a protocol for the non-denaturating agarose gel electrophoresis of plant virus ssRNAs, their blotting onto Hybond N membrane, and hybridization with [alpha 32 P]dNTP-labelled cDNA probe. The protocol is not pretentious on technical equipment, omits denaturation and neutralization steps and some chemical required in other modifications. (authors)

Removal of Radioactive Pollutants by Liquid Emulsion Membrane From Liquid Waste

International Nuclear Information System (INIS)

Yossef, Y.A.A.

2013-01-01

Radioactive liquid waste should be safely managed because it is potentially hazardous to human health and the environment. Several methods were used for treatment of liquid waste, such as liquid emulsion membrane (LEM). In this work, liquid emulsion membrane using Tri-butyl phosphate (TBP) plus Bis (2-ethylhexyl) phosphate (HDEHP) as mobile carriers, hydrochloric acid (HCl) as stripping agents and an emulsifying agent (span 80) was used for the extraction of uranium ions from radioactive liquid waste. Various parameters influencing the permeation of uranium ions through the membrane have been optimized to separate uranium ions from radioactive liquid waste such as: the effects of membrane material, carrier concentration, operating conditions, etc. were examined; moreover, the transport mechanism of this uranium was also studied. The internal mass transfer in the water/oil (W/O) emulsion drop, the external mass transfer around the drop, the rates of formation, and the decomposition of the complex at the external aqueous-organic interface were considered. The results show that, the liquid emulsion membrane which consists of (25% by volume HDEHP, 0.005 M + 75% by volume TBP, 0.01 M) as extractant (carrier), span 80, 4% (v/v) (sorbitan monooleate) as surfactant agent, hydrochloric acid (HCl), (1.0 M) as stripping agent. From the results, the maximum extraction percent of uranium ions (nearly about of 100%) occurred at the operating conditions: stirring speed =500 rpm, the ratio between LEM and feed phase (liquid waste) = 20 ml: 100 ml, the ratio between organic phase (membrane phase) to internal aqueous phase (stripping phase) = 1.0 and the ph value of the external aqueous phase equal to 5.0.

Study of radon 222 permeation through plastic membranes. Application to a measurement method of radon in water

International Nuclear Information System (INIS)

Labed, V.; Rannou, A.; Robe, M.C.

1990-01-01

Gaseous permeation is a complex phenomenon of gas transfer through some polymers. Original in respect of conventional studies where permeation occurs between two gaseous phases, the present study concerns radon 222 transfer between water and air through a membrane. Polypropylene membranes are tested with an experimental device following time evolution of the phenomenon by measurement of volume activity in water and in air. An application of this study to a method for determination of radon concentration in water by measurement of concentration in air is discussed [fr

A cell culture technique for human epiretinal membranes to describe cell behavior and membrane contraction in vitro.

Science.gov (United States)

Wertheimer, Christian; Eibl-Lindner, Kirsten H; Compera, Denise; Kueres, Alexander; Wolf, Armin; Docheva, Denitsa; Priglinger, Siegfried G; Priglinger, Claudia; Schumann, Ricarda G

2017-11-01

To introduce a human cell culture technique for investigating in-vitro behavior of primary epiretinal cells and membrane contraction of fibrocellular tissue surgically removed from eyes with idiopathic macular pucker. Human epiretinal membranes were harvested from ten eyes with idiopathic macular pucker during standard vitrectomy. Specimens were fixed on cell culture plastic using small entomological pins to apply horizontal stress to the tissue, and then transferred to standard cell culture conditions. Cell behavior of 400 epiretinal cells from 10 epiretinal membranes was observed in time-lapse microscopy and analyzed in terms of cell migration, cell velocity, and membrane contraction. Immunocytochemistry was performed for cell type-specific antigens. Cell specific differences in migration behavior were observed comprising two phenotypes: (PT1) epiretinal cells moving fast, less directly, with small round phenotype and (PT2) epiretinal cells moving slowly, directly, with elongated large phenotype. No mitosis, no outgrowth and no migration onto the plastic were seen. Horizontal contraction measurements showed variation between specimens. Masses of epiretinal cells with a myofibroblast-like phenotype expressed cytoplasmatic α-SMA stress fibers and correlated with cell behavior characteristics (PT2). Fast moving epiretinal cells (PT1) were identified as microglia by immunostaining. This in-vitro technique using traction application allows for culturing surgically removed epiretinal membranes from eyes with idiopathic macular pucker, demonstrating cell behavior and membrane contraction of primary human epiretinal cells. Our findings emphasize the abundance of myofibroblasts, the presence of microglia and specific differences of cell behavior in these membranes. This technique has the potential to improve the understanding of pathologies at the vitreomacular interface and might be helpful in establishing anti-fibrotic treatment strategies.

MStern Blotting-High Throughput Polyvinylidene Fluoride (PVDF) Membrane-Based Proteomic Sample Preparation for 96-Well Plates.

Science.gov (United States)

Berger, Sebastian T; Ahmed, Saima; Muntel, Jan; Cuevas Polo, Nerea; Bachur, Richard; Kentsis, Alex; Steen, Judith; Steen, Hanno

2015-10-01

We describe a 96-well plate compatible membrane-based proteomic sample processing method, which enables the complete processing of 96 samples (or multiples thereof) within a single workday. This method uses a large-pore hydrophobic PVDF membrane that efficiently adsorbs proteins, resulting in fast liquid transfer through the membrane and significantly reduced sample processing times. Low liquid transfer speeds have prevented the useful 96-well plate implementation of FASP as a widely used membrane-based proteomic sample processing method. We validated our approach on whole-cell lysate and urine and cerebrospinal fluid as clinically relevant body fluids. Without compromising peptide and protein identification, our method uses a vacuum manifold and circumvents the need for digest desalting, making our processing method compatible with standard liquid handling robots. In summary, our new method maintains the strengths of FASP and simultaneously overcomes one of the major limitations of FASP without compromising protein identification and quantification. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Characterization of membrane lipid fluidity in human embryo cells malignantly transfer med post 238Pu α irradiation

International Nuclear Information System (INIS)

Qi Zirong; Sun Ling; Liu Guolian; Shen Zhiyuan

1992-01-01

The membrane lipid fluidity of malignantly transformed human embryo cells following 238 Pu α particlce irradiation in vitro has been studied. The results indicate that the ontogenesis depends on irradiation dose (Gy) and the membrane lipid fluidity in malignantly transformed cells is higher than that in normal embryo cells. With the microviscosity (η) of cells plotted against the cell counts, the correlation coefficient (γ) is calculated to be between 0.9936 and 0.9999. Since the malignant transformation of irradiated embryo cells is manifested early on cell membrane lipid, the fluidity of membrane lipid can be used as an oncologic marker

Power Generation from Concentration Gradient by Reverse Electrodialysis in Dense Silica Membranes for Microfluidic and Nanofluidic Systems

Directory of Open Access Journals (Sweden)

Sang Woo Lee

2016-01-01

Full Text Available In this study, we investigate power generation by reverse electrodialysis in a dense silica membrane that is between two NaCl solutions with various combinations of concentrations. Each silica membrane is fabricated by depositing a silica layer on a porous alumina substrate via chemical vapor deposition. The measured potential-current (V-I characteristics of the silica membrane are used to obtain the transference number, diffusion potential, and electrical resistance. We develop empirical correlations for the transference number and the area-specific resistance, and present the results of power generation by reverse electrodialysis using the fabricated silica membranes. The highest measured power density is 0.98 mW/m2. In addition, we develop a contour map of the power density as a function of NaCl concentrations on the basis of the empirical correlations. The contour map shows that a power output density of 1.2 mW/m2 is achievable with the use of silica membranes and is sufficient to drive nanofluidic and microfluidic systems. The dense silica membrane has the potential for use in micro power generators in nanofluidic and microfluidic systems.

Influence of ionizing radiation on the spatial structure of erythrocyte membranes

International Nuclear Information System (INIS)

Dreval', V.Yi.; Syichevs'ka, L.V.; Doroshenko, A.O.; Roshal', O.D.

1998-01-01

Influence of gamma-radiation of doses of 10, 10 2 , 5 centre dot 10 2 , and 10 3 Gy on the structure of the protein-lipid complexes of erythrocyte membranes is investigated. The allotment of fluorescence of protein in the donor-acceptor pair of tryptophan-pyrene and the distance of protein from the surface of the lipid bilayer of a membrane are determined by the method of inductive-resonance transfer of energy. The pair is localized at the distance of above 3.2 nm from lipids. We find that the action of irradiation changes the space structure of proteins and lipids of the erythrocyte membrane