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Sample records for membrane complexes mmcs

  1. Membrane tethering complexes in the endosomal system

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    Anne eSpang

    2016-05-01

    Full Text Available Vesicles that are generated by endocytic events at the plasma membrane are destined to early endosomes. A prerequisite for proper fusion is the tethering of two membrane entities. Tethering of vesicles to early endosomes is mediated by the CORVET complex, while fusion of late endosomes with lysosomes depends on the HOPS complex. Recycling through the TGN and to the plasma membrane is facilitated by the GARP and EARP complexes, respectively. However, there are other tethering functions in the endosomal system as there are multiple pathways through which proteins can be delivered from endosomes to either the TGN or the plasma membrane. Furthermore, complexes that may be part of novel tethering complexes have been recently identified. Thus it is likely that more tethering factors exist. In this review, I will provide an overview of different tethering complexes of the endosomal system and discuss how they may provide specificity in membrane traffic.

  2. High speed dry machining of MMCs with diamond tools

    International Nuclear Information System (INIS)

    Collins, J.L.

    2001-01-01

    The increasing use of metal matrix composites (MMCs) has raised new issues in their machining. Industrial demands for higher speed and dry machining of MMCs with improved component production to closer tolerances have driven the development of new tool materials. In particular, the wear characteristics of synthetic diamond tooling satisfy many of the requirements imposed in cutting these highly abrasive workpieces. The use of diamond tool materials, such as polycrystalline diamond (PCD), has resulted in tool life improvements which, allied with environmental considerations, show great potential for the development of dry cutting. This paper explores the wear characteristics of PCD, which is highly suited to the dry machining of particulate silicon carbide MMCs. Also, two further diamond tool materials are evaluated - chemical vapor deposition (CVD) thick layer diamond and synthetic single crystal diamond. Their suitability for the efficient machining of high volume fraction MMC materials is shown and their potential impact an the subsequent acceptance and integration of MMCs into engineering components is discussed. (author)

  3. Characterising antimicrobial protein-membrane complexes

    International Nuclear Information System (INIS)

    Xun, Gloria; Dingley, Andrew; Tremouilhac, Pierre

    2009-01-01

    Full text: Antimicrobial proteins (AMPs) are host defence molecules that protect organisms from microbial infection. A number of hypotheses for AMP activity have been proposed which involve protein membrane interactions. However, there is a paucity of information describing AMP-membrane complexes in detail. The aim of this project is to characterise the interactions of amoebapore-A (APA-1) with membrane models using primarily solution-state NMR spectroscopy. APA-1 is an AMP which is regulated by a pH-dependent dimerisation event. Based on the atomic resolution solution structure of monomeric APA-1, it is proposed that this dimerisation is a prerequisite for ring-like hexameric pore formation. Due to the cytotoxicity of APA-1, we have developed a cell-free system to produce this protein. To facilitate our studies, we have adapted the cell-free system to isotope label APA-1. 13 C /15 N -enriched APA-1 sample was achieved and we have begun characterising APA-1 dimerisation and membrane interactions using NMR spectroscopy and other biochemical/biophysical methods. Neutron reflectometry is a surface-sensitive technique and therefore represents an ideal technique to probe how APA-1 interacts with membranes at the molecular level under different physiological conditions. Using Platypus, the pH-induced APA-1-membrane interactions should be detectable as an increase of the amount of protein adsorbed at the membrane surface and changes in the membrane properties. Specifically, detailed information of the structure and dimensions of the protein-membrane complex, the position and amount of the protein in the membrane, and the perturbation of the membrane phospholipids on protein incorporation can be extracted from the neutron reflectometry measurement. Such information will enable critical assessment of current proposed mechanisms of AMP activity in bacterial membranes and complement our NMR studies

  4. Advance on Al2O3 Particulates Reinforced Aluminum Metal Matrix Composites (Al-MMCs Manufactured by the Power Metallurgy(PM Methods- Improved PM Techniques

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    Xu Lina

    2016-01-01

    Full Text Available Aluminum metal matrix composites (Al-MMCs with Al2O3 particulates as reinforcement fabricated by the power metallurgy (PM methods have gained much attention due to their unique characteristics of the wide range of Al2O3 particles addition, easy-operating process and effectiveness. The improved PM techniques, such as the high energy ball milling, powder extruder and high pressure torsion were applied to further strengthening the properties or/and diminishing the agglomeration of strength particles. The formation of liquid phase assisted densification of compacts to promote the sintering of composites. Complex design of Al2O3 particles with other particles was another efficient method to tailor the properties of Al-MMCs.

  5. Biogenesis of membrane bound respiratory complexes in Escherichia coli

    OpenAIRE

    Price, Claire E.; Driessen, Arnold J.M.

    2010-01-01

    Escherichia colt is one of the preferred bacteria for studies on the energetics and regulation of respiration Respiratory chains consist of primary dehydrogenases and terminal reductases or oxidases linked by quinones. In order to assemble this complex arrangement of protein complexes, synthesis of the subunits occurs in the cytoplasm followed by assembly in the cytoplasm and/or membrane, the incorporation of metal or organic cofactors and the anchoring of the complex to the membrane In the c...

  6. 3D pressure field in lipid membranes and membrane-protein complexes

    DEFF Research Database (Denmark)

    Ollila, O H Samuli; Risselada, H Jelger; Louhivuori, Martti

    2009-01-01

    We calculate full 3D pressure fields for inhomogeneous nanoscale systems using molecular dynamics simulation data. The fields represent systems with increasing level of complexity, ranging from semivesicles and vesicles to membranes characterized by coexistence of two phases, including also...... a protein-membrane complex. We show that the 3D pressure field is distinctly different for curved and planar bilayers, the pressure field depends strongly on the phase of the membrane, and that an integral protein modulates the tension and elastic properties of the membrane....

  7. The ER membrane protein complex is a transmembrane domain insertase

    Science.gov (United States)

    Guna, Alina; Volkmar, Norbert; Christianson, John C.; Hegde, Ramanujan S.

    2018-01-01

    Insertion of proteins into membranes is an essential cellular process. The extensive biophysical and topological diversity of membrane proteins necessitates multiple insertion pathways that remain incompletely defined. Here, we found that known membrane insertion pathways fail to effectively engage tail-anchored membrane proteins with moderately hydrophobic transmembrane domains. These proteins are instead shielded in the cytosol by calmodulin. Dynamic release from calmodulin allowed sampling of the endoplasmic reticulum (ER), where the conserved ER membrane protein complex (EMC) was shown to be essential for efficient insertion in vitro and in cells. Purified EMC in synthetic liposomes catalyzed insertion of its substrates in a reconstituted system. Thus, EMC is a transmembrane domain insertase, a function that may explain its widely pleiotropic membrane-associated phenotypes across organisms. PMID:29242231

  8. Assembly factors for the membrane arm of human complex I.

    Science.gov (United States)

    Andrews, Byron; Carroll, Joe; Ding, Shujing; Fearnley, Ian M; Walker, John E

    2013-11-19

    Mitochondrial respiratory complex I is a product of both the nuclear and mitochondrial genomes. The integration of seven subunits encoded in mitochondrial DNA into the inner membrane, their association with 14 nuclear-encoded membrane subunits, the construction of the extrinsic arm from 23 additional nuclear-encoded proteins, iron-sulfur clusters, and flavin mononucleotide cofactor require the participation of assembly factors. Some are intrinsic to the complex, whereas others participate transiently. The suppression of the expression of the NDUFA11 subunit of complex I disrupted the assembly of the complex, and subcomplexes with masses of 550 and 815 kDa accumulated. Eight of the known extrinsic assembly factors plus a hydrophobic protein, C3orf1, were associated with the subcomplexes. The characteristics of C3orf1, of another assembly factor, TMEM126B, and of NDUFA11 suggest that they all participate in constructing the membrane arm of complex I.

  9. Influence of TiB2 particles on machinability and machining parameter optimization of TiB2/Al MMCs

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    Ruisong JIANG

    2018-01-01

    Full Text Available In situ formed TiB2 particle reinforced aluminum matrix composites (TiB2/Al MMCs have some extraordinary properties which make them be a promising material for high performance aero-engine blade. Due to the influence of TiB2 particles, the machinability is still a problem which restricts the application of TiB2/Al MMCs. In order to meet the industrial requirements, the influence of TiB2 particles on the machinability of TiB2/Al MMCs was investigated experimentally. Moreover, the optimal machining conditions for this kind of MMCs were investigated in this study. The major conclusions are: (1 the machining force of TiB2/Al MMCs is bigger than that of non-reinforced alloy and mainly controlled by feed rate; (2 the residual stress of TiB2/Al MMCs is compressive while that of non-reinforced alloy is nearly neutral; (3 the surface roughness of TiB2/Al MMCs is smaller than that of non-reinforced alloy under the same cutting speed, but reverse result was observed when the feed rate increased; (4 a multi-objective optimization model for surface roughness and material removal rate (MRR was established, and a set of optimal parameter combinations of the machining was obtained. The results show a great difference from SiC particle reinforced MMCs and provide a useful guide for a better control of machining process of this material.

  10. Membrane targeting of the yeast exocyst complex

    Czech Academy of Sciences Publication Activity Database

    Pleskot, Roman; Cwiklik, Lukasz; Jungwirth, Pavel; Žárský, Viktor; Potocký, Martin

    2015-01-01

    Roč. 1848, č. 7 (2015), s. 1481-1489 ISSN 0005-2736 R&D Projects: GA ČR GA13-19073S; GA ČR GBP208/12/G016 Grant - others:GA MŠk(CZ) LO1417 Institutional support: RVO:61389030 ; RVO:61388955 ; RVO:61388963 Keywords : The exocyst complex * Exo70p * Sec3p Subject RIV: EB - Genetics ; Molecular Biology; CF - Physical ; Theoretical Chemistry (UFCH-W) Impact factor: 3.687, year: 2015

  11. Surface glycosylation of polysulfone membrane towards a novel complexing membrane for boron removal.

    Science.gov (United States)

    Meng, Jianqiang; Yuan, Jing; Kang, Yinlin; Zhang, Yufeng; Du, Qiyun

    2012-02-15

    In this study, a novel complexing membrane was synthesized for boron removal from aqueous solution. A glycopolymer, poly(2-gluconamidoethyl methacrylate) (PGAMA), was grafted onto the chloromethylated polysulfone (CMPSF) microporous membrane via surface-initiated ATRP (SIATRP). The glycosylated PSF (GlyPSF) membrane was characterized by attenuated total refection-Flourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM). It was demonstrated that PGAMA was successfully anchored onto the membrane surface and the grafting yield can be tuned in a wide range up to 5.9 mg/cm(2) by varying the polymerization time. The complexing membrane can adsorb boron rapidly with the equilibrium reached within 2h and has a remarkable high boron adsorption capacity higher than 2.0 mmol/g at optimized conditions. Freundlich, Langmuir, and Dubinin-Radushkevich adsorption isotherms were applied, and the data were best described by Langmuir model. Kinetic data were analyzed, and the data fitted very well to the pseudo-second-order rate expression. The optimal pH for boron uptake is in a wide range of 6-9, and the optimal initial boron concentration is over 300 mg/L. Studies of ionic strength effects indicated the formation of inner-sphere surface complexes. The complexed boron can be leached quantitatively under acid condition. Copyright © 2011 Elsevier Inc. All rights reserved.

  12. MMCS: Multi-Module Charging Strategy for Increasing the Lifetime of Wireless Rechargeable Sensor Networks

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    Hong-Yi Chang

    2016-08-01

    Full Text Available In recent years, wireless charging technology has provided an alternative to charging equipment. Wireless charging technology has already proved to be useful in our daily lives in phones, buses, restaurants, etc. Wireless charging technology can also be applied in energy-bounded wireless sensor networks (WSNs, and these are called wireless rechargeable sensor networks (WRSNs. The optimized charging path problem is the most widely discussed issue in employing WRSNs with wireless charging vehicles (WCVs. This problem involves determining the most efficient path for charging sensor nodes. Further, charging-scheduling problems also need to be considered in the optimized charging path problem. In this paper, we proposed a multi-module charging strategy (MMCS used to prolong the lifetime of the entire WRSN. MMCS can be divided into three stages: the charging topology, charging scheduling, and charging strategy stages, with multiple modules in each stage. The best module combination of MMCS is the distance-based module in the charging topology stage, delay-based module in the charging schedule stage, and the average lifetime module in the charging strategy stage. The best module combination enables prolonging the lifetime efficiently, as it considers not only the priority of urgent nodes but also the travel distance of WCV; the delay-based module of the charging schedule stage considers the delay effect on the follow-up nodes. The experimental results show that the proposed MMCS can improve the lifetime of the entire WRSN and that it substantially outperforms the nearest job next with preemption (NJNP method in terms of lifetime improvement of the entire WRSN.

  13. Isolation of Synaptosomes, Synaptic Plasma Membranes, and Synaptic Junctional Complexes.

    Science.gov (United States)

    Michaelis, Mary L; Jiang, Lei; Michaelis, Elias K

    2017-01-01

    Isolation of synaptic nerve terminals or synaptosomes provides an opportunity to study the process of neurotransmission at many levels and with a variety of approaches. For example, structural features of the synaptic terminals and the organelles within them, such as synaptic vesicles and mitochondria, have been elucidated with electron microscopy. The postsynaptic membranes are joined to the presynaptic "active zone" of transmitter release through cell adhesion molecules and remain attached throughout the isolation of synaptosomes. These "post synaptic densities" or "PSDs" contain the receptors for the transmitters released from the nerve terminals and can easily be seen with electron microscopy. Biochemical and cell biological studies with synaptosomes have revealed which proteins and lipids are most actively involved in synaptic release of neurotransmitters. The functional properties of the nerve terminals, such as responses to depolarization and the uptake or release of signaling molecules, have also been characterized through the use of fluorescent dyes, tagged transmitters, and transporter substrates. In addition, isolated synaptosomes can serve as the starting material for the isolation of relatively pure synaptic plasma membranes (SPMs) that are devoid of organelles from the internal environment of the nerve terminal, such as mitochondria and synaptic vesicles. The isolated SPMs can reseal and form vesicular structures in which transport of ions such as sodium and calcium, as well as solutes such as neurotransmitters can be studied. The PSDs also remain associated with the presynaptic membranes during isolation of SPM fractions, making it possible to isolate the synaptic junctional complexes (SJCs) devoid of the rest of the plasma membranes of the nerve terminals and postsynaptic membrane components. Isolated SJCs can be used to identify the proteins that constitute this highly specialized region of neurons. In this chapter, we describe the steps involved

  14. Evidence for condensed complexes of cholesterol in lipid membranes

    Science.gov (United States)

    Ratajczak, Maria K.

    Although cholesterol is a predominant lipid in the eukaryotic plasma membrane, its interactions with other lipids are still not well understood. Insights into the nature of lipid assembly can be gained from examining lipid-cholesterol interaction using model systems. A key observation was the discovery of liquid-liquid phase diagrams with two critical points in the binary mixtures of cholesterol and lipids. The shape of the phase diagrams can be explained by a thermodynamic model of "condensed complexes". In our quest to characterize cholesterol-lipid interactions, we determined phase diagrams of cholesterol and phospholipids that point to the existence of condensed complexes. This complex formation hypothesis was further supported by experiments involving cholesterol removal by cyclodextrin, grazing x-ray diffraction and x-ray reflectivity studies and isothermal calorimetry. Our study aimed at establishing a correlation (or the lack of) between domain formation and complex formation, as well as determining the mode of cholesterol association with different lipids based on their structural and physical properties. We established a displacement assay by which we were able to probe cholesterol-lipid interactions by perturbing them in the presence of an intercalator that competes with cholesterol for association with lipids. Our data support the condensed complex model between cholesterol and lipids, and cholesterol when complexed with lipids shows low activity whereas free, uncomplexed cholesterol exhibits high activity. We were successful in modulating cholesterol activity by varying the level of intercalator while keeping the cholesterol content fixed. In this thesis, not only have we shown that cholesterol can be displaced by intercalators in model systems, we have further established that such displacement can take place in membranes of live cell.

  15. Membrane transporters and drought resistance – a complex issue

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    Karolina Maria Jarzyniak

    2014-12-01

    Full Text Available Land plants have evolved complex adaptation strategies to survive changes in water status in the environment. Understanding the molecular nature of such adaptive changes allows the development of rapid innovations to improve crop performance. Plant membrane transport systems play a significant role when adjusting to water scarcity. Here we put proteins participating in transmembrane allocations of various molecules in the context of stomatal, cuticular and root responses, representing a part of the drought resistance strategy. Their role in the transport of signaling molecules, ions or osmolytes is summarized and the challenge of the forthcoming research, resulting from the recent discoveries, is highlighted.

  16. Surface and permeability properties of membranes from polyelectrolyte complexes and polyelectrolyte surfactant complexes

    Czech Academy of Sciences Publication Activity Database

    Schwarz, H. H.; Lukáš, Jaromír; Richau, K.

    2003-01-01

    Roč. 218, 1-2 (2003), s. 1-9 ISSN 0376-7388 R&D Projects: GA AV ČR KSK4050111 Keywords : polyelectrolyte complex membranes * pervaporation * dehydration of organics Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.081, year: 2003

  17. Application of grey-taguchi method for optimization of dry sliding wear properties of aluminum MMCs

    Science.gov (United States)

    Siriyala, Rajesh; Alluru, Gopala Krishna; Penmetsa, Rama Murthy Raju; Duraiselvam, Muthukannan

    2012-09-01

    Through a pin-on-disc type wear setup, the dry sliding wear behavior of SiC-reinforced aluminum composites produced using the molten metal mixing method was investigated in this paper. Dry sliding wear tests were carried on SiC-reinforced metal matrix composites (MMCs) and its matrix alloy sliding against a steel counter face. Different contact stresses, reinforcement percentages, sliding distances, and sliding velocities were selected as the control variables, and the responses were selected as the wear volume loss (WVL) and coefficient of friction (COF) to evaluate the dry sliding performance. An L25 orthogonal array was employed for the experimental design. Initially, the optimization of the dry sliding performance of the SiC-reinforced MMCs was performed using grey relational analysis (GRA). Based on the GRA, the optimum level parameters for overall grey relational grade in terms of WVL and COF were identified. Analysis of variance was performed to determine the effect of individual factors on the overall grey relational grade. The results indicated that the sliding velocity was the most effective factor among the control parameters on dry sliding wear, followed by the reinforcement percentage, sliding distance, and contact stress. Finally, the wear surface morphology and wear mechanism of the composites were investigated through scanning electron microscopy.

  18. Complex descemet′s membrane tears and detachment during phacoemulsification

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    Faik Orucoglu

    2015-01-01

    Full Text Available Purpose: To report a case of complex Descemet′s membrane detachment (DMD and tears during phacoemulsification cataract surgery. Case Report: A 64-year-old woman underwent phacoemulsification surgery in her right eye and developed tears and partial loss of Descemet′s membrane (DM while the aspiration port was inserted through the main incision. Massive corneal edema obscured the view and the anterior chamber was barely visible the following day. Scheimpflug imaging was used to complement slit lamp examination in the postoperative period. Frequent topical corticosteroid drops were initiated. After 5 days of treatment, multiple tears and detachment of DM were visible and the anterior chamber was filled with air. After 5 weeks, the cornea regained much of its clarity despite large DM tears and focal loss of DM. Conclusion: Despite partial loss of DM, the corneal edema mostly disappeared after 5 weeks of air bubble injection. Scheimpflug imaging was beneficial in the diagnosis and monitoring of DM tears and detachments.

  19. Synthesis, microstructural and mechanical properties of ex situ zircon particles (ZrSiO4 reinforced Metal Matrix Composites (MMCs: a review

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    Satish Kumar Thandalam

    2015-07-01

    This review article details the current development on the synthesis, microstructure and mechanical properties of zircon reinforced MMCs, with specific attention on the abrasive wear behavior of the composites. This review also summarizes the work done by various research groups on zircon reinforced MMCs in achieving higher hardness and wear resistance in these composites.

  20. Effect of UV-irradiation on DNA-membrane complex of Bacillus subtilis

    International Nuclear Information System (INIS)

    Chefranova, O.A.; Gaziev, A.I.

    1979-01-01

    The UV radiation effect on DNA membrane complex of Bacillus subtilis has been studied. Increase of DNA content in the DNA membrane complex in two strains of 168 and recA - and its decrease in the polA - strain are shown. The above effect in the first two stamms is suppressed with caffeine and correlates with the change in protein content in the DNA membrane complex, determined by a radioactive label, but not lipids in other words, fixation of DNA and membrane goes through proteins. Capability of DNA content increase in the DNA membrane complex after UV irradiation and subsequent bacteria incubation in a total medium correlates with the relative sensitivity of stamm UV sensitivity. It is suggested, that the reparation synthesis goes in cells on the membrane and that binding of DNA and the membrane is necessary for the normal DNA reparation process

  1. Intermolecular detergent-membrane protein noes for the characterization of the dynamics of membrane protein-detergent complexes.

    Science.gov (United States)

    Eichmann, Cédric; Orts, Julien; Tzitzilonis, Christos; Vögeli, Beat; Smrt, Sean; Lorieau, Justin; Riek, Roland

    2014-12-11

    The interaction between membrane proteins and lipids or lipid mimetics such as detergents is key for the three-dimensional structure and dynamics of membrane proteins. In NMR-based structural studies of membrane proteins, qualitative analysis of intermolecular nuclear Overhauser enhancements (NOEs) or paramagnetic resonance enhancement are used in general to identify the transmembrane segments of a membrane protein. Here, we employed a quantitative characterization of intermolecular NOEs between (1)H of the detergent and (1)H(N) of (2)H-perdeuterated, (15)N-labeled α-helical membrane protein-detergent complexes following the exact NOE (eNOE) approach. Structural considerations suggest that these intermolecular NOEs should show a helical-wheel-type behavior along a transmembrane helix or a membrane-attached helix within a membrane protein as experimentally demonstrated for the complete influenza hemagglutinin fusion domain HAfp23. The partial absence of such a NOE pattern along the amino acid sequence as shown for a truncated variant of HAfp23 and for the Escherichia coli inner membrane protein YidH indicates the presence of large tertiary structure fluctuations such as an opening between helices or the presence of large rotational dynamics of the helices. Detergent-protein NOEs thus appear to be a straightforward probe for a qualitative characterization of structural and dynamical properties of membrane proteins embedded in detergent micelles.

  2. Lateral release of proteins from the TOM complex into the outer membrane of mitochondria.

    Science.gov (United States)

    Harner, Max; Neupert, Walter; Deponte, Marcel

    2011-07-15

    The TOM complex of the outer membrane of mitochondria is the entry gate for the vast majority of precursor proteins that are imported into the mitochondria. It is made up by receptors and a protein conducting channel. Although precursor proteins of all subcompartments of mitochondria use the TOM complex, it is not known whether its channel can only mediate passage across the outer membrane or also lateral release into the outer membrane. To study this, we have generated fusion proteins of GFP and Tim23 which are inserted into the inner membrane and, at the same time, are spanning either the TOM complex or are integrated into the outer membrane. Our results demonstrate that the TOM complex, depending on sequence determinants in the precursors, can act both as a protein conducting pore and as an insertase mediating lateral release into the outer membrane.

  3. Purification of highly active alphavirus replication complexes demonstrates altered fractionation of multiple cellular membranes.

    Science.gov (United States)

    Pietilä, Maija K; van Hemert, Martijn J; Ahola, Tero

    2018-01-24

    Positive-strand RNA viruses replicate their genomes in membrane-associated structures; alphaviruses and many other groups induce membrane invaginations called spherules. Here, we established a protocol to purify these membranous replication complexes (RCs) from cells infected with Semliki Forest virus (SFV). We isolated SFV spherules located on the plasma membrane and further purified them using two consecutive density gradients. This revealed that SFV infection strongly modifies cellular membranes. We removed soluble proteins, the Golgi and most of the mitochondria, but plasma membrane, endoplasmic reticulum (ER) and late endosome markers enriched in the membrane fraction that contained viral RNA synthesizing activity, replicase proteins and minus- and plus-strand RNA. Electron microscopy revealed that the purified membranes displayed spherule-like structures with a narrow neck. This membrane enrichment was specific to viral replication as such a distribution of membrane markers was only observed after infection. Besides the plasma membrane, SFV infection remodeled the ER, and the co-fractionation of the RC-carrying plasma membrane and ER suggests that SFV may recruit ER proteins or membrane to the site of replication. The purified RCs were highly active in synthesizing both genomic and subgenomic RNA. Detergent solubilization destroyed the replication activity demonstrating that the membrane association of the complex is essential. Most of the newly made RNA was in double-stranded replicative molecules but the purified complexes also produced single-stranded RNA as well as released newly made RNA. This indicates that the purification established here maintained the functionality of RCs and thus enables further structural and functional studies of active RCs. IMPORTANCE Similar to all positive-strand RNA viruses, the arthropod-borne alphaviruses induce membranous genome factories but little is known about the arrangement of viral replicase proteins and the

  4. Membrane proteins PmpG and PmpH are major constituents of Chlamydia trachomatis L2 outer membrane complex

    DEFF Research Database (Denmark)

    Mygind, Per H; Christiansen, Gunna; Roepstorff, P

    2000-01-01

    The outer membrane complex of Chlamydia is involved in the initial adherence and ingestion of Chlamydia by the host cell. In order to identify novel proteins in the outer membrane of Chlamydia trachomatis L2, proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. By....... By silver staining of the protein profile, a major protein doublet of 100-110 kDa was detected. In-gel tryptic digestion and matrix-assisted laser desorption/ionization mass spectrometry identified these proteins as the putative outer membrane proteins PmpG and PmpH....

  5. Identification and characterization of stable membrane protein complexes

    NARCIS (Netherlands)

    Spelbrink, R.E.J.

    2007-01-01

    Many membrane proteins exist as oligomers. Such oligomers play an important role in a broad variety of cellular processes such as ion transport, energy transduction, osmosensing and cell wall synthesis. We developed an electrophoresis-based method of identifying oligomeric membrane proteins that are

  6. Dissociation and purification of the endogenous membrane-bound Vo complex from Pichia pastoris.

    Science.gov (United States)

    Li, Sumei; Hong, Tao; Wang, Kun; Lu, Yinghong; Zhou, Min

    2017-10-01

    Most proteins occur and function in complexes rather than as isolated entities in membranes. In most cases macromolecules with multiple subunits are purified from endogenous sources. In this study, an endogenous membrane-protein complex was obtained from Pichia pastoris, which can be grown at high densities to significantly improve the membrane protein yield. We successfully isolated the membrane-bound Vo complex of V-ATPase from P. pastoris using a fusion FLAG tag attached to the C-terminus of subunit a to generate the vph-tag strain, which was used for dissociation and purification. After FLAG affinity and size exclusion chromatography purification, the production quantity and purity of the membrane-bound Vo complex was 20 μg l -1 and >98%, respectively. The subunits of the endogenous membrane-bound Vo complex observed in P. pastoris were similar to those obtained from S. cerevisiae, as demonstrated by liquid chromatography-tandem mass spectrometry (LC-MS-MS). Therefore, successful dissociation and purification of the membrane-bound Vo complex at a high purity and sufficient quantity was achieved via a rapid and simple procedure that can be used to obtain the endogenous membrane-protein complexes from P. pastoris. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. α-Lactalbumin:Oleic Acid Complex Spontaneously Delivers Oleic Acid to Artificial and Erythrocyte Membranes.

    Science.gov (United States)

    Wen, Hanzhen; Strømland, Øyvind; Halskau, Øyvind

    2015-09-25

    Human α-lactalbumin made lethal to tumor cells (HAMLET) is a tumoricidal complex consisting of human α-lactalbumin and multiple oleic acids (OAs). OA has been shown to play a key role in the activity of HAMLET and its related complexes, generally known as protein-fatty acid (PFA) complexes. In contrast to what is known about the fate of the protein component of such complexes, information about what happens to OA during their action is still lacking. We monitored the membrane, OA and protein components of bovine α-lactalbumin complexed with OA (BLAOA; a HAMLET-like substance) and how they associate with each other. Using ultracentrifugation, we found that the OA and lipid components follow each other closely. We then firmly identify a transfer of OA from BLAOA to both artificial and erythrocyte membranes, indicating that natural cells respond similarly to BLAOA treatment as artificial membranes. Uncomplexed OA is unable to similarly affect membranes at the conditions tested, even at elevated concentrations. Thus, BLAOA can spontaneously transfer OA to a lipid membrane. After the interaction with the membrane, the protein is likely to have lost most or all of its OA. We suggest a mechanism for passive import of mainly uncomplexed protein into cells, using existing models for OA's effect on membranes. Our results are consistent with a membrane destabilization mediated predominantly by OA insertion being a significant contribution to PFA cytotoxicity. Copyright © 2015. Published by Elsevier Ltd.

  8. Identification of multimolecular complexes and supercomplexes in compartment-selective membrane microdomains.

    Science.gov (United States)

    Mitsopoulos, Panagiotis; Madrenas, Joaquín

    2013-01-01

    Cellular membranes contain specialized microdomains that play important roles in a wide range of cellular processes. These microdomains can be found in the plasma membrane and other membranes within the cell. Initially labeled lipid rafts and defined as being resistant to extraction by nonionic detergents and enriched in cholesterol and glycosphingolipids, we now understand that these membrane microdomains are very dynamic and heterogeneous membrane structures whose composition and function can vary widely depending on their cellular location. Indeed, though they are classically associated with the plasma membrane and have been shown to facilitate a wide variety of processes, including signal transduction and membrane trafficking, specialized membrane microdomains have also been identified in other membranes including those in the mitochondria. These mitochondrial membrane microdomains are enriched in cardiolipin, the signature phospholipid of the mitochondria, and may have important implications in metabolism by facilitating optimal assembly and function of the mitochondrial respiratory chain. Furthermore, isolation of multimolecular complexes while retaining their supramolecular interactions has been critical to the study of mitochondrial respiratory supercomplexes. Here, we discuss methods to isolate various membrane microdomains, including detergent-insoluble glycosphingolipid microdomains, mitochondrial cardiolipin-enriched microdomains, and blue-native gel electrophoresis of mitochondrial membranes. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Seeing spots: complex phase behavior in simple membranes.

    Science.gov (United States)

    Veatch, Sarah L; Keller, Sarah L

    2005-12-30

    Liquid domains in model lipid bilayers are frequently studied as models of raft domains in cell plasma membranes. Micron-scale liquid domains are easily produced in vesicles composed of ternary mixtures of a high melting temperature lipid, a low melting temperature lipid, and cholesterol. Here, we describe the rich phase behavior observed in binary and ternary systems. We then discuss experimental challenges inherent in mapping phase diagrams of even simple lipid systems. For example, miscibility behavior varies with lipid type, lipid ratio, lipid oxidation, and level of impurity. Liquid domains are often circular, but can become noncircular when membranes are near critical points. Finally, we reflect on applications of phase diagrams in model systems to rafts in cell membranes.

  10. α-Synuclein oligomers distinctively permeabilize complex model membranes

    NARCIS (Netherlands)

    Stefanovic, Anja N D; Stöckl, Martin T; Claessens, Mireille M A E; Subramaniam, Vinod

    α-Synuclein oligomers are increasingly considered to be responsible for the death of dopaminergic neurons in Parkinson's disease. The toxicity mechanism of α-synuclein oligomers likely involves membrane permeabilization. Even though it is well established that α-synuclein oligomers bind and

  11. Specific Distribution of Phosphatidylglycerol to Photosystem Complexes in the Thylakoid Membrane

    Directory of Open Access Journals (Sweden)

    Koichi Kobayashi

    2017-11-01

    Full Text Available The thylakoid membrane is the site of photochemical and electron transport reactions of oxygenic photosynthesis. The lipid composition of the thylakoid membrane, with two galactolipids, one sulfolipid, and one phospholipid, is highly conserved among oxygenic photosynthetic organisms. Besides providing a lipid bilayer matrix, thylakoid lipids are integrated in photosynthetic complexes particularly in photosystems I and II and play important roles in electron transport processes. Thylakoid lipids are differentially allocated to photosynthetic complexes and the lipid bilayer fraction, but distribution of each lipid in the thylakoid membrane is unclear. In this study, based on published crystallographic and biochemical data, we estimated the proportions of photosynthetic complex-associated and bilayer-associated lipids in thylakoid membranes of cyanobacteria and plants. The data suggest that ∼30 mol% of phosphatidylglycerol (PG, the only major phospholipid in thylakoid membranes, is allocated to photosystem complexes, whereas glycolipids are mostly distributed to the lipid bilayer fraction and constitute the membrane lipid matrix. Because PG is essential for the structure and function of both photosystems, PG buried in these complexes might have been selectively conserved among oxygenic phototrophs. The specific and substantial allocation of PG to the deep sites of photosystems may need a unique mechanism to incorporate PG into the complexes possibly in coordination with the synthesis of photosynthetic proteins and pigments.

  12. Bromate determination in water after membrane complexation and total reflection X-ray fluorescence analysis.

    Science.gov (United States)

    Hatzistavros, Vasilios S; Koulouridakis, Pavlos E; Aretaki, Ioanna I; Kallithrakas-Kontos, Nikolaos G

    2007-04-01

    A new method for the determination of trace levels of bromates by selective membrane collection is presented. Various membranes containing a few micrograms of different complexing reagents in a poly(vinyl chloride) matrix were tested. These membranes were produced on the surface of quartz glass (reflectors), and they were immersed in solutions containing bromate and bromide ions. At the first stage the prepared membranes collected both bromate and bromide ions, so different bromide masking agents were put in the analyzed solutions to avoid bromide collection. By the end of the equilibration time, the reflectors were left to dry, and they were analyzed by total reflection X-ray fluorescence (TXRF). The poly(vinyl chloride) with aliquat-336 membrane and o-dianisidin complexing agent gave the best results. The minimum detection limit was equal to 0.9 ng/mL for ultrapure water and 1.0 ng/mL for drinking water.

  13. Integral and peripheral association of proteins and protein complexes with Yersinia pestis inner and outer membranes

    Directory of Open Access Journals (Sweden)

    Bunai Christine L

    2009-02-01

    Full Text Available Abstract Yersinia pestis proteins were sequentially extracted from crude membranes with a high salt buffer (2.5 M NaBr, an alkaline solution (180 mM Na2CO3, pH 11.3 and membrane denaturants (8 M urea, 2 M thiourea and 1% amidosulfobetaine-14. Separation of proteins by 2D gel electrophoresis was followed by identification of more than 600 gene products by MS. Data from differential 2D gel display experiments, comparing protein abundances in cytoplasmic, periplasmic and all three membrane fractions, were used to assign proteins found in the membrane fractions to three protein categories: (i integral membrane proteins and peripheral membrane proteins with low solubility in aqueous solutions (220 entries; (ii peripheral membrane proteins with moderate to high solubility in aqueous solutions (127 entries; (iii cytoplasmic or ribosomal membrane-contaminating proteins (80 entries. Thirty-one proteins were experimentally associated with the outer membrane (OM. Circa 50 proteins thought to be part of membrane-localized, multi-subunit complexes were identified in high Mr fractions of membrane extracts via size exclusion chromatography. This data supported biologically meaningful assignments of many proteins to the membrane periphery. Since only 32 inner membrane (IM proteins with two or more predicted transmembrane domains (TMDs were profiled in 2D gels, we resorted to a proteomic analysis by 2D-LC-MS/MS. Ninety-four additional IM proteins with two or more TMDs were identified. The total number of proteins associated with Y. pestis membranes increased to 456 and included representatives of all six β-barrel OM protein families and 25 distinct IM transporter families.

  14. The TIP30 protein complex, arachidonic acid and coenzyme A are required for vesicle membrane fusion.

    Directory of Open Access Journals (Sweden)

    Chengliang Zhang

    Full Text Available Efficient membrane fusion has been successfully mimicked in vitro using artificial membranes and a number of cellular proteins that are currently known to participate in membrane fusion. However, these proteins are not sufficient to promote efficient fusion between biological membranes, indicating that critical fusogenic factors remain unidentified. We have recently identified a TIP30 protein complex containing TIP30, acyl-CoA synthetase long-chain family member 4 (ACSL4 and Endophilin B1 (Endo B1 that promotes the fusion of endocytic vesicles with Rab5a vesicles, which transport endosomal acidification enzymes vacuolar (H⁺-ATPases (V-ATPases to the early endosomes in vivo. Here, we demonstrate that the TIP30 protein complex facilitates the fusion of endocytic vesicles with Rab5a vesicles in vitro. Fusion of the two vesicles also depends on arachidonic acid, coenzyme A and the synthesis of arachidonyl-CoA by ACSL4. Moreover, the TIP30 complex is able to transfer arachidonyl groups onto phosphatidic acid (PA, producing a new lipid species that is capable of inducing close contact between membranes. Together, our data suggest that the TIP30 complex facilitates biological membrane fusion through modification of PA on membranes.

  15. Complexing membrane for uranium detection by total reflection X-ray fluorescence.

    Science.gov (United States)

    Hatzistavros, Vasilios; Koulouridakis, Pavlos; Kallithrakas-Kontost, Nikolaos

    2005-07-01

    Selective membranes containing a few micrograms of various complexing reagents in a polyvinyl chloride (PVC) matrix were produced in order to determine low uranium concentrations in water. The membranes were produced on the surfaces of quartz glasses, and immersed in water solutions containing uranium salts (5 - 50 ng/mL). By the end of the equilibration time, the membranes were left to dry and analyzed based on the total reflection X-ray fluorescence. The effects of the complexing agents and their mass proportions added in the membranes were studied. The combination of the complexing reagents dithizone and thiourea gave the best result. The minimum detection limit was measured to be equal to 0.8 ng/mL.

  16. Selective mercury determination after membrane complexation and total reflection X-ray fluorescence analysis.

    Science.gov (United States)

    Koulouridakis, Pavlos E; Kallithrakas-Kontos, Nikolaos G

    2004-08-01

    A new method for low mercury concentration analysis in drinking waters is presented. Membranes containing a few micrograms of various complexing reagents were produced on the surface of quartz glasses (reflectors). The reflectors were immersed in water solutions containing various concentrations of inorganic mercury salts at low concentrations (1-40 ng/mL). The membranes were left to equilibrate in 5-500 mL of solution for many hours; when the equilibration stage was finished they were cleaned with ultrapure water and left to dry. Analyses were performed by total reflection X-ray fluorescence (TXRF). The effects of various experimental parameters (complexing agent, equilibrium time, sample volume, etc.) as well as the selectivity of the membranes were studied. The complexing reagent dithizone with a PVC-based membrane gave the best results. The limit of quantitation was 0.8 ng/mL.

  17. Membrane association of the PTEN tumor suppressor: neutron scattering and MD simulations reveal the structure of protein-membrane complexes.

    Science.gov (United States)

    Nanda, Hirsh; Heinrich, Frank; Lösche, Mathias

    2015-05-01

    Neutron reflection (NR) from planar interfaces is an emerging technology that provides unique and otherwise inaccessible structural information on disordered molecular systems such as membrane proteins associated with fluid bilayers, thus addressing one of the remaining challenges of structural biology. Although intrinsically a low-resolution technique, using structural information from crystallography or NMR allows the construction of NR models that describe the architecture of protein-membrane complexes at high resolution. In addition, a combination of these methods with molecular dynamics (MD) simulations has the potential to reveal the dynamics of protein interactions with the bilayer in atomistic detail. We review recent advances in this area by discussing the application of these techniques to the complex formed by the PTEN phosphatase with the plasma membrane. These studies provide insights in the cellular regulation of PTEN, its interaction with PI(4,5)P2 in the inner plasma membrane and the pathway by which its substrate, PI(3,4,5)P3, accesses the PTEN catalytic site. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Biogenesis of membrane bound respiratory complexes in Escherichia coli

    NARCIS (Netherlands)

    Price, Claire E.; Driessen, Arnold J. M.

    Escherichia colt is one of the preferred bacteria for studies on the energetics and regulation of respiration Respiratory chains consist of primary dehydrogenases and terminal reductases or oxidases linked by quinones. In order to assemble this complex arrangement of protein complexes, synthesis of

  19. Complexation-tailored morphology of asymmetric block copolymer membranes

    KAUST Repository

    Madhavan, Poornima

    2013-08-14

    Hydrogen-bond formation between polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) and -OH/-COOH functionalized organic molecules was used to tune morphology of asymmetric nanoporous membranes prepared by simultaneous self-assembly and nonsolvent induced phase separation. The morphologies were characterized by field emmision scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Hydrogen bonds were confirmed by infrared (IR), and the results were correlated to rheology characterization. The OH-functionalized organic molecules direct the morphology into hexagonal order. COOH-functionalized molecules led to both lamellar and hexagonal structures. Micelle formation in solutions and their sizes were determined using dynamic light scattering (DLS) measurements and water fluxes of 600-3200 L/m 2·h·bar were obtained. The pore size of the plain BCP membrane was smaller than with additives. The following series of additives led to pores with hexagonal order with increasing pore size: terephthalic acid (COOH-bifunctionalized) < rutin (OH-multifunctionalized) < 9-anthracenemethanol (OH-monofunctionalized) < 3,5-dihydroxybenzyl alcohol (OH-trifunctionalized). © 2013 American Chemical Society.

  20. Identification of chromatophore membrane protein complexes formed under different nitrogen availability conditions in Rhodospirillum rubrum

    DEFF Research Database (Denmark)

    Selao, Tiago Toscano; Branca, Rui; Chae, Pil Seok

    2011-01-01

    of two-dimensional Blue Native/SDS-PAGE and NSI-LC-LTQ-Orbitrap mass spectrometry. We have identified several membrane protein complexes, including components of the ATP synthase, reaction center, light harvesting, and NADH dehydrogenase complexes. Additionally, we have identified differentially...

  1. MICOS coordinates with respiratory complexes and lipids to establish mitochondrial inner membrane architecture.

    Science.gov (United States)

    Friedman, Jonathan R; Mourier, Arnaud; Yamada, Justin; McCaffery, J Michael; Nunnari, Jodi

    2015-04-28

    The conserved MICOS complex functions as a primary determinant of mitochondrial inner membrane structure. We address the organization and functional roles of MICOS and identify two independent MICOS subcomplexes: Mic27/Mic10/Mic12, whose assembly is dependent on respiratory complexes and the mitochondrial lipid cardiolipin, and Mic60/Mic19, which assembles independent of these factors. Our data suggest that MICOS subcomplexes independently localize to cristae junctions and are connected via Mic19, which functions to regulate subcomplex distribution, and thus, potentially also cristae junction copy number. MICOS subunits have non-redundant functions as the absence of both MICOS subcomplexes results in more severe morphological and respiratory growth defects than deletion of single MICOS subunits or subcomplexes. Mitochondrial defects resulting from MICOS loss are caused by misdistribution of respiratory complexes in the inner membrane. Together, our data are consistent with a model where MICOS, mitochondrial lipids and respiratory complexes coordinately build a functional and correctly shaped mitochondrial inner membrane.

  2. Contribution of cubilin and amnionless to processing and membrane targeting of cubilin-amnionless complex

    DEFF Research Database (Denmark)

    Coudroy, Gwénaëlle; Gburek, Jakub; Kozyraki, Renata

    2005-01-01

    retained in the endoplasmic reticulum or partially secreted into the medium. Coexpression with AMN led to efficient transport to the apical cell surface of the cubilin constructs, which included the EGF domains, and prevented release into the medium. AMN co-precipitated with cubilin and co-localized......Cubilin is a peripheral apical membrane receptor for multiple ligands that are taken up in several absorptive epithelia. Recently, amnionless (AMN) was identified to form a functional receptor complex with cubilin. By expression in transfected polarized MDCK cells of AMN and several cubilin...... fragments, including a functional "mini" version of cubilin, the processing, sorting, and membrane anchoring of the complex to the apical membrane were investigated. The results show that truncation mutants, including the N-terminal domain of cubilin, did not appear at the plasma membrane but instead were...

  3. Transport of organic anions through the erythrocyte membrane as K+-valinomycin complexes.

    Science.gov (United States)

    Marinetti, G V; Skarin, A; Whitman, P

    1978-04-26

    K+, Rb+, or Cs+ complexes of valinomycin form ion pair complexes with picric acid and trinitrobenzenesulfonate (TNBS). The formation of a picrate-K+-valinomycin complex is supported by spectral evidence. These complexes have zero net charge and readily permeate the intact erythrocyte membrane. The K+-valinomycin complex has been used to convert the nonpenetrating TNBS into a penetrating covalent probe, making it as useful vectorial probe to measure accessible amino groups of proteins and phospholipids on both sites of the erythrocyte membrane. The enhanced transport of TNBS into the cell by valinomycin is dependent on external K+ in the medium. The entry of TNBS into the cell is manifested by an increased labeling of hemoglobin and membrane phosphatidylethanolamine (PE). Stilbeneisothiocyanatedisulfonate (SITS) and anilinonaphthalenesulfonate (ANS) inhibit both the basal and K+-valinomycin stimulated labeling of PE and hemoglobin by TNBS. The data suggest two independent effects of ANS and SITS, one mediated by an inhibition of the anion transport protein and another by the incorporation of these hydrobic anions into the cell membrane with an increase in negative charge on the membrane which leads to an inhibition of TNBS permeation into the cell by electrostatic repulsion.

  4. Binding of canonical Wnt ligands to their receptor complexes occurs in ordered plasma membrane environments.

    Science.gov (United States)

    Sezgin, Erdinc; Azbazdar, Yagmur; Ng, Xue W; Teh, Cathleen; Simons, Kai; Weidinger, Gilbert; Wohland, Thorsten; Eggeling, Christian; Ozhan, Gunes

    2017-08-01

    While the cytosolic events of Wnt/β-catenin signaling (canonical Wnt signaling) pathway have been widely studied, only little is known about the molecular mechanisms involved in Wnt binding to its receptors at the plasma membrane. Here, we reveal the influence of the immediate plasma membrane environment on the canonical Wnt-receptor interaction. While the receptors are distributed both in ordered and disordered environments, Wnt binding to its receptors selectively occurs in more ordered membrane environments which appear to cointernalize with the Wnt-receptor complex. Moreover, Wnt/β-catenin signaling is significantly reduced when the membrane order is disturbed by specific inhibitors of certain lipids that prefer to localize at the ordered environments. Similarly, a reduction in Wnt signaling activity is observed in Niemann-Pick Type C disease cells where trafficking of ordered membrane lipid components to the plasma membrane is genetically impaired. We thus conclude that ordered plasma membrane environments are essential for binding of canonical Wnts to their receptor complexes and downstream signaling activity. © 2017 The Authors. The FEBS Journal published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

  5. Proteomic analysis reveals the diversity and complexity of membrane proteins in chickpea (Cicer arietinum L.

    Directory of Open Access Journals (Sweden)

    Jaiswal Dinesh Kumar

    2012-10-01

    Full Text Available Abstract Background Compartmentalization is a unique feature of eukaryotes that helps in maintaining cellular homeostasis not only in intra- and inter-organellar context, but also between the cells and the external environment. Plant cells are highly compartmentalized with a complex metabolic network governing various cellular events. The membranes are the most important constituents in such compartmentalization, and membrane-associated proteins play diverse roles in many cellular processes besides being part of integral component of many signaling cascades. Results To obtain valuable insight into the dynamic repertoire of membrane proteins, we have developed a proteome reference map of a grain legume, chickpea, using two-dimensional gel electrophoresis. MALDI-TOF/TOF and LC-ESI-MS/MS analysis led to the identification of 91 proteins involved in a variety of cellular functions viz., bioenergy, stress-responsive and signal transduction, metabolism, protein synthesis and degradation, among others. Significantly, 70% of the identified proteins are putative integral membrane proteins, possessing transmembrane domains. Conclusions The proteomic analysis revealed many resident integral membrane proteins as well as membrane-associated proteins including those not reported earlier. To our knowledge, this is the first report of membrane proteome from aerial tissues of a crop plant. The findings may provide a better understanding of the biochemical machinery of the plant membranes at the molecular level that might help in functional genomics studies of different developmental pathways and stress-responses.

  6. Formation of complexes between functionalized chitosan membranes and copper: A study by angle resolved XPS

    Energy Technology Data Exchange (ETDEWEB)

    Jurado-López, Belén [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga (Spain); Vieira, Rodrigo Silveira [Chemical Engineering Department, Universidade Federal do Ceará, UFC, 60455-760 Fortaleza, CE (Brazil); Rabelo, Rodrigo Balloni; Beppu, Marisa Masumi [School of Chemical Engineering, University of Campinas, UNICAMP, P.O. Box 6066, 13081-970 Campinas, SP (Brazil); Casado, Juan [Departamento de Química-Física, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga (Spain); Rodríguez-Castellón, Enrique, E-mail: castellon@uma.es [Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga (Spain)

    2017-01-01

    Chitosan is a biopolymer with potential applications in various fields. Recently, it has been used for heavy metals removal like copper, due to the presence of amino and hydroxyl groups in its structure. Chitosan membranes were crosslinked with epichlorohydrin and bisoxirano and functionalized with chelating agents, such as iminodiacetic acid, aspartic acid and tris-(2-amino-ethyl) polyamine. These membranes were used for copper adsorption and the formed complexes were characterized. Thermal and crystalline properties of chitosan membranes were studied by TG-DCS and X-ray diffraction. Raman, XPS and FT-IR data confirmed that copper is linked to the modified chitosan membranes by the amino groups. The oxidation state of copper-chitosan membranes were also studied by angle resolved XPS, and by UV–Vis diffuse reflectance spectroscopy. - Highlights: • Chitosan membranes were crosslinked with epichlorohydrin and bisoxirano and functionalized with chelating agents. • The chelating agent were iminodiacetic acid, aspartic acid and tris-(2-amino-ethyl) polyamine. • The functionalized membranes were used for copper adsorption and studied by ARXPS, Raman, TG-DCS, FT-IR and XRD. • Spectroscopic data confirmed that copper is linked to the modified chitosan membranes by the amino groups.

  7. Corrosion Behavior of Nickel Alloy (ASTM A 494 M) Reinforced with Fused SiO2 Chilled Metal Matrix Composites (MMCs) for Marine Applications

    Science.gov (United States)

    Hemanth, Joel, Dr.

    2017-08-01

    This paper presents the results obtained and the discussions made from a series of corrosion experiments involving Nickel alloy (ASTM A 494 M) reinforced with fused SiO2, size of the particles dispersed varies from 80-120 µm and amount of addition varies from 3 to 12 wt.% in steps of 3 wt.%. The resulting chilled MMCs are solidified under the influence of copper chill of 25 mm thickness to study the effect of corrosion behavior. Corrosion resistance was found to increase significantly with increase in SiO2 content in chilled MMCs. Nevertheless, even with high SiO2 content corrosion attack ie., pitting was found to be most severe during the initial stages of each test but it invariably decreased to a very low value in the later stages, due to the formation of an adherent protective layer on the MMCs developed.

  8. A tethering complex drives the terminal stage of SNARE-dependent membrane fusion

    Science.gov (United States)

    D'Agostino, Massimo; Risselada, Herre Jelger; Lürick, Anna; Ungermann, Christian; Mayer, Andreas

    2017-11-01

    Membrane fusion in eukaryotic cells mediates the biogenesis of organelles, vesicular traffic between them, and exo- and endocytosis of important signalling molecules, such as hormones and neurotransmitters. Distinct tasks in intracellular membrane fusion have been assigned to conserved protein systems. Tethering proteins mediate the initial recognition and attachment of membranes, whereas SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein complexes are considered as the core fusion engine. SNARE complexes provide mechanical energy to distort membranes and drive them through a hemifusion intermediate towards the formation of a fusion pore. This last step is highly energy-demanding. Here we combine the in vivo and in vitro fusion of yeast vacuoles with molecular simulations to show that tethering proteins are critical for overcoming the final energy barrier to fusion pore formation. SNAREs alone drive vacuoles only into the hemifused state. Tethering proteins greatly increase the volume of SNARE complexes and deform the site of hemifusion, which lowers the energy barrier for pore opening and provides the driving force. Thereby, tethering proteins assume a crucial mechanical role in the terminal stage of membrane fusion that is likely to be conserved at multiple steps of vesicular traffic. We therefore propose that SNAREs and tethering proteins should be considered as a single, non-dissociable device that drives fusion. The core fusion machinery may then be larger and more complex than previously thought.

  9. Roles of metal ion complexation and membrane permeability in the metal flux through lipophilic membranes. Labile complexes at permeation liquid membranes

    NARCIS (Netherlands)

    Zhang, Z.; Buffle, J.; Leeuwen, van H.P.; Wojciechowski, K.

    2006-01-01

    The various physicochemical factors that influence the flux of carrier-transported metal ions through permeation liquid membranes (PLM) are studied systematically. Understanding PLM behavior is important (i) to optimize the application of PLM as metal speciation sensors in environmental media and

  10. Stochastic approach to model fouling in membrane filters with complex pore morphology

    Science.gov (United States)

    Sanaei, Pejman; Gu, Binan; Kondic, Lou; Cummings, Linda J.

    2017-11-01

    Membrane filters are widely used in industrial applications to remove contaminants and undesired impurities (particles) from a solvent. During the filtration process the membrane internal void area becomes fouled with impurities and as a consequence the filter performance deteriorates, a process that depends on filter internal structure, particle concentration and flow dynamics. The complexity of membrane internal morphology and the random nature of the particle dynamics in the flow make the filtration and fouling challenging to predict; nonetheless, mathematical modeling can play a key role in investigating filter fouling, and in suggesting design modifications for more efficient filtration. To date, many models have been proposed to describe the effects of complexity of membrane structure, and the stochasticity of particle dynamics individually but very few studies focus on both together. In this work, we present an idealized mathematical model, in which a membrane consists of a series of bifurcating pores. Pores decrease in size as the membrane is traversed and particles are removed from the feed by adsorption within pores (which shrinks them) and stochastic sieving (pore blocking by large particles). NSF DMS 1615719.

  11. The membrane attack complex of the complement system is essential for rapid wallerian degeneration

    NARCIS (Netherlands)

    Ramaglia, Valeria; King, Rosalind Helen Mary; Nourallah, Michelle; Wolterman, Ruud; de Jonge, Rosalein; Ramkema, Marja; Vigar, Miriam Ann; van der Wetering, Sandra; Morgan, Brian Paul; Troost, Dirk; Baas, Frank

    2007-01-01

    The complement (C) system plays an important role in myelin breakdown during Wallerian degeneration (WD). The pathway and mechanism involved are, however, not clear. In a crush injury model of the sciatic nerve, we show that C6, necessary for the assembly of the membrane attack complex (MAC), is

  12. Single particle electron microscopy in combination with mass spectrometry to investigate novel complexes of membrane proteins

    NARCIS (Netherlands)

    Arteni, Ana A.; Nowaczyk, Marc; Lax, Julia; Rögner, Matthias; Boekema, Egbert J.; Kouril, R.; Rogner, M.

    2005-01-01

    Large data sets of molecular projections of the membrane proteins Photosystem I and Photosystem II from cyanobacteria were analyzed by single particle electron microscopy (EM). Analysis resulted in the averaging of 2D projections from the purified complexes but also in the simultaneous detection and

  13. Promotion of mitochondrial membrane complex assembly by a proteolytically inactive yeast Lon

    NARCIS (Netherlands)

    Rep, M; van Dijl, J M; Suda, K; Schatz, G; Grivell, L A; Suzuki, C K

    1996-01-01

    Afg3p and Rca1p are adenosine triphosphate (ATP)-dependent metalloproteases in yeast mitochondria. Cells lacking both proteins exhibit defects in respiration-dependent growth, degradation of mitochondrially synthesized proteins, and assembly of inner-membrane complexes. Defects in growth and protein

  14. Pengaruh Milling Time Terhadap Pembentukan Intermetalik ɣ-TiAl Sebagai Reinforced Dalam Metal Matrix Composite (MMCs Hasil Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    Mohammad Badrus Soleh

    2013-03-01

    Full Text Available Paduan TiAl mempunyai berbagai keunggulan dalam sifat mekanik serta sifat termal. Senyawa intermetalik γ-TiAl mempunyai sifat mekanik dan sifat termal yang sangat baik sehingga sesuai apabila diaplikasikan sebagai penguat pada metal matrix composite (MMCs. Penelitian ini bertujuan untuk mensintesis paduan TiAl sehingga terbentuk  fasa intermetalik γ-TiAl yang homogen. Sintesa dilakukan dengan metode mechanical alloying menggunakan modification horizontal ball mill dengan komposisi paduan Ti-36%wt Al dan variasi milling time 0,10,20 jam dengan kecepatan tetap 350rpm. Hasil milling dikompaksi dan di-annealing pada temperatur 9000C selama 30menit.  Fasa intermetalik γ-TiAl terbentuk setelah proses mechanical alloying 20 jam. Hasil pengujian difraksi sinar X menunjukkan ukuran kristal sebesar 198.92Å pada fasa γ-TiAl, memiliki kekerasan 678,1HV.

  15. Neural mechanisms underlying migrating motor complex formation in mouse isolated colon

    Science.gov (United States)

    Brierley, Stuart M; Nichols, Kim; Grasby, Dallas J; Waterman, Sally A

    2001-01-01

    Little is known about the intrinsic enteric reflex pathways associated with migrating motor complex (MMC) formation. Acetylcholine (ACh) mediates the rapid component of the MMC, however a non-cholinergic component also exists. The present study investigated the possible role of endogenous tachykinins (TKs) in the formation of colonic MMCs and the relative roles of excitatory and inhibitory pathways.MMCs were recorded from the circular muscle at four sites (proximal, proximal-mid, mid-distal and distal) along the mouse colon using force transducers.The tachykinin (NK1 and NK2) receptor antagonists SR-140 333 (250 nM) and SR-48 968 (250 nM) reduced the amplitude of MMCs at all recording sites, preferentially abolishing the long duration contraction. Residual MMCs were abolished by the subsequent addition of atropine (1 μM).The neuronal nitric oxide synthase inhibitor, Nωnitro-L-arginine (L-NOARG, 100 μM), increased MMC amplitude in the distal region, whilst reducing the amplitude in the proximal region. In preparations where MMCs did not migrate to the distal colon, addition of L-NOARG resulted in the formation of MMCs. Subsequent addition of apamin (250 nM) or suramin (100 μM) further increased MMC amplitude in the distal region, whilst suramin increased MMC amplitude in the mid-distal region. Apamin but not suramin reduced MMC amplitude in the proximal region. Subsequent addition of SR-140 333 and SR-48 968 reduced MMC amplitude at all sites. Residual MMCs were abolished by atropine (1 μM).In conclusion, TKs, ACh, nitric oxide (NO) and ATP are involved in the neural mechanisms underlying the formation of MMCs in the mouse colon. Tachykinins mediate the long duration component of the MMC via NK1 and NK2 receptors. Inhibitory pathways may be involved in determining whether MMCs are formed. PMID:11159701

  16. Electrode-analytical properties of polyvinylchloride membranes based on triple metal-polymeric complexes

    Directory of Open Access Journals (Sweden)

    Katerina V. Matorina

    2015-10-01

    Full Text Available The influence of the nature of the electrode-active substances (EAS, the composition of the external and internal solutions on the formation of the analytical signal of polyvinylchloride (PVC membranes based on associates and triple metal-polymeric complexes (TMPC was established. Dehumidification of synthesized membranes increases with the content of polyvinylpyrrolidone (PVP. The value of the swelling degree is more than two times greater for membranes, which contain as EAS TMPC, relative to membranes based on associates. The value of water absorption of membranes is determined by the nature of EAS. They formed a series of increasing of the swelling degree such as associate < background membrane < TMPC. Swelling of the background membrane is explained by the physical sorption of water molecules on the surface of plasticized membrane. Hydration of PVP macromolecules varies with the introduction of metal ions, macromolecules unit undergoes a conformational transition. PVP macromolecules form tunnels or cavities where complex particles distributed and additional water accumulated through the second coordination layer. Constructed sensors based on TMPC have slope of electrode function equal to 25 mV/pC. Linear dependence of potential on the polymer concentration is observed in the range of 5–7 pC units. Sensors based on associates have slope of the electrode function of 20–25 mV/pC that can be varied depending on the nature of the EAS. Working range is 4–8 pC. Response time of sensor is less than 1 min. The optimal time for conditioning of the synthesized PVC membrane is 24 hours. Potentiometric sensors have been developed for the determination of residual amounts of low molecular PVP which is a food additive E 1201 commonly used for thickening, stabilizing and clarifying of food products. The content of PVP was determined in real objects (apple juice, beer, red wine and cognac with using the polyvinylpyrrolidone sensors (Sr < 0.08. The

  17. Segregation of receptor-ligand complexes in cell adhesion zones: Phase diagrams and role of thermal membrane roughness

    OpenAIRE

    Rozycki, Bartosz; Lipowsky, Reinhard; Weikl, Thomas R.

    2010-01-01

    The adhesion zone of immune cells, the 'immunological synapse', exhibits characteristic domains of receptor-ligand complexes. The domain formation is likely caused by a length difference of the receptor-ligand complexes, and has been investigated in experiments in which T cells adhere to supported membranes with anchored ligands. For supported membranes with two types of anchored ligands, MHCp and ICAM1, that bind to the receptors TCR and LFA1 in the cell membrane, the coexistence of domains ...

  18. Cholesterol depletion of enterocytes. Effect on the Golgi complex and apical membrane trafficking

    DEFF Research Database (Denmark)

    Hansen, Gert Helge; Niels-Christiansen, L L; Thorsen, Evy

    2000-01-01

    Intestinal brush border enzymes, including aminopeptidase N and sucrase-isomaltase, are associated with "rafts" (membrane microdomains rich in cholesterol and sphingoglycolipids). To assess the functional role of rafts in the present work, we studied the effect of cholesterol depletion on apical......, the rates of the Golgi-associated complex glycosylation and association with rafts of newly synthesized aminopeptidase N were reduced, and less of the enzyme had reached the brush border membrane after 2 h of labeling. In contrast, the basolateral Na(+)/K(+)-ATPase was neither missorted nor raft...

  19. Trans-complex formation by proteolipid channels in the terminal phase of membrane fusion

    DEFF Research Database (Denmark)

    Peters, C; Bayer, M J; Bühler, S

    2001-01-01

    -complex formation occurs downstream from trans-SNARE pairing, and depends on both the Rab-GTPase Ypt7 and calmodulin. The maintenance of existing complexes and completion of fusion are independent of trans-SNARE pairs. Reconstituted proteolipids form sealed channels, which can expand to form aqueous pores in a Ca2......+/calmodulin-dependent fashion. V0 trans-complexes may therefore form a continuous, proteolipid-lined channel at the fusion site. We propose that radial expansion of such a protein pore may be a mechanism for intracellular membrane fusion....

  20. Spontaneous formation of complex structures made from elastic membranes in an aluminum-hydroxide-carbonate system

    Science.gov (United States)

    Kiehl, Micah; Kaminker, Vitaliy; Pantaleone, James; Nowak, Piotr; Dyonizy, Agnieszka; Maselko, Jerzy

    2015-06-01

    A popular playground for studying chemo-hydrodynamic patterns and instabilities is chemical gardens, also known as silicate gardens. In these systems, complex structures spontaneously form, driven by buoyant forces and either osmotic or mechanical pumps. Here, we report on systems that differ somewhat from classical chemical gardens in that the membranes are much more deformable and soluble. These properties lead to structures that self-construct and evolve in new ways. For example, they exhibit the formation of chemical balloons, a new growth mechanism for tubes, and also the homologous shrinking of these tubes. The stretching mechanism for the membranes is probably different than for other systems by involving membrane "self-healing." Other unusual properties are osmosis that sometimes occurs out of the structure and also small plumes that flow away from the structure, sometimes upwards, and sometimes downwards. Mathematical models are given that explain some of the observed phenomena.

  1. Binding of Signal Recognition Particle Gives Ribosome/Nascent Chain Complexes a Competitive Advantage in Endoplasmic Reticulum Membrane Interaction

    Science.gov (United States)

    Neuhof, Andrea; Rolls, Melissa M.; Jungnickel, Berit; Kalies, Kai-Uwe; Rapoport, Tom A.

    1998-01-01

    Most secretory and membrane proteins are sorted by signal sequences to the endoplasmic reticulum (ER) membrane early during their synthesis. Targeting of the ribosome-nascent chain complex (RNC) involves the binding of the signal sequence to the signal recognition particle (SRP), followed by an interaction of ribosome-bound SRP with the SRP receptor. However, ribosomes can also independently bind to the ER translocation channel formed by the Sec61p complex. To explain the specificity of membrane targeting, it has therefore been proposed that nascent polypeptide-associated complex functions as a cytosolic inhibitor of signal sequence- and SRP-independent ribosome binding to the ER membrane. We report here that SRP-independent binding of RNCs to the ER membrane can occur in the presence of all cytosolic factors, including nascent polypeptide-associated complex. Nontranslating ribosomes competitively inhibit SRP-independent membrane binding of RNCs but have no effect when SRP is bound to the RNCs. The protective effect of SRP against ribosome competition depends on a functional signal sequence in the nascent chain and is also observed with reconstituted proteoliposomes containing only the Sec61p complex and the SRP receptor. We conclude that cytosolic factors do not prevent the membrane binding of ribosomes. Instead, specific ribosome targeting to the Sec61p complex is provided by the binding of SRP to RNCs, followed by an interaction with the SRP receptor, which gives RNC–SRP complexes a selective advantage in membrane targeting over nontranslating ribosomes. PMID:9436994

  2. Reconstitution of membrane protein complexes involved in pneumococcal septal cell wall assembly.

    Directory of Open Access Journals (Sweden)

    Marjolaine Noirclerc-Savoye

    Full Text Available The synthesis of peptidoglycan, the major component of the bacterial cell wall, is essential to cell survival, yet its mechanism remains poorly understood. In the present work, we have isolated several membrane protein complexes consisting of the late division proteins of Streptococcus pneumoniae: DivIB, DivIC, FtsL, PBP2x and FtsW, or subsets thereof. We have co-expressed membrane proteins from S. pneumoniae in Escherichia coli. By combining two successive affinity chromatography steps, we obtained membrane protein complexes with a very good purity. These complexes are functional, as indicated by the retained activity of PBP2x to bind a fluorescent derivative of penicillin and to hydrolyze the substrate analogue S2d. Moreover, we have evidenced the stabilizing role of protein-protein interactions within each complex. This work paves the way for a complete reconstitution of peptidoglycan synthesis in vitro, which will be critical to the elucidation of its intricate regulation mechanisms.

  3. A Conserved Endoplasmic Reticulum Membrane Protein Complex (EMC) Facilitates Phospholipid Transfer from the ER to Mitochondria

    Science.gov (United States)

    Tavassoli, Shabnam; Wong, Andrew K. O.; Choudhary, Vineet; Young, Barry P.; Loewen, Christopher J. R.; Prinz, William A.

    2014-01-01

    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. PMID:25313861

  4. Cardiolipin synthesizing enzymes form a complex that interacts with cardiolipin-dependent membrane organizing proteins.

    Science.gov (United States)

    Serricchio, Mauro; Vissa, Adriano; Kim, Peter K; Yip, Christopher M; McQuibban, G Angus

    2018-04-01

    The mitochondrial glycerophospholipid cardiolipin plays important roles in mitochondrial biology. Most notably, cardiolipin directly binds to mitochondrial proteins and helps assemble and stabilize mitochondrial multi-protein complexes. Despite their importance for mitochondrial health, how the proteins involved in cardiolipin biosynthesis are organized and embedded in mitochondrial membranes has not been investigated in detail. Here we show that human PGS1 and CLS1 are constituents of large protein complexes. We show that PGS1 forms oligomers and associates with CLS1 and PTPMT1. Using super-resolution microscopy, we observed well-organized nanoscale structures formed by PGS1. Together with the observation that cardiolipin and CLS1 are not required for PGS1 to assemble in the complex we predict the presence of a PGS1-centered cardiolipin-synthesizing scaffold within the mitochondrial inner membrane. Using an unbiased proteomic approach we found that PGS1 and CLS1 interact with multiple cardiolipin-binding mitochondrial membrane proteins, including prohibitins, stomatin-like protein 2 and the MICOS components MIC60 and MIC19. We further mapped the protein-protein interaction sites between PGS1 and itself, CLS1, MIC60 and PHB. Overall, this study provides evidence for the presence of a cardiolipin synthesis structure that transiently interacts with cardiolipin-dependent protein complexes. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. The higher level of complexity of K-Ras4B activation at the membrane

    Science.gov (United States)

    Jang, Hyunbum; Banerjee, Avik; Chavan, Tanmay S.; Lu, Shaoyong; Zhang, Jian; Gaponenko, Vadim; Nussinov, Ruth

    2016-01-01

    Is nucleotide exchange sufficient to activate K-Ras4B? To signal, oncogenic rat sarcoma (Ras) anchors in the membrane and recruits effectors by exposing its effector lobe. With the use of NMR and molecular dynamics (MD) simulations, we observed that in solution, farnesylated guanosine 5′-diphosphate (GDP)-bound K-Ras4B is predominantly autoinhibited by its hypervariable region (HVR), whereas the GTP-bound state favors an activated, HVR-released state. On the anionic membrane, the catalytic domain adopts multiple orientations, including parallel (∼180°) and perpendicular (∼90°) alignments of the allosteric helices, with respect to the membrane surface direction. In the autoinhibited state, the HVR is sandwiched between the effector lobe and the membrane; in the active state, with membrane-anchored farnesyl and unrestrained HVR, the catalytic domain fluctuates reinlessly, exposing its effector-binding site. Dimerization and clustering can reduce the fluctuations. This achieves preorganized, productive conformations. Notably, we also observe HVR-autoinhibited K-Ras4B-GTP states, with GDP-bound-like orientations of the helices. Thus, we propose that the GDP/GTP exchange may not be sufficient for activation; instead, our results suggest that the GDP/GTP exchange, HVR sequestration, farnesyl insertion, and orientation/localization of the catalytic domain at the membrane conjointly determine the active or inactive state of K-Ras4B. Importantly, K-Ras4B-GTP can exist in active and inactive states; on its own, GTP binding may not compel K-Ras4B activation.—Jang, H., Banerjee, A., Chavan, T. S, Lu, S., Zhang, J., Gaponenko, V., Nussinov, R. The higher level of complexity of K-Ras4B activation at the membrane. PMID:26718888

  6. The higher level of complexity of K-Ras4B activation at the membrane.

    Science.gov (United States)

    Jang, Hyunbum; Banerjee, Avik; Chavan, Tanmay S; Lu, Shaoyong; Zhang, Jian; Gaponenko, Vadim; Nussinov, Ruth

    2016-04-01

    Is nucleotide exchange sufficient to activate K-Ras4B? To signal, oncogenic rat sarcoma (Ras) anchors in the membrane and recruits effectors by exposing its effector lobe. With the use of NMR and molecular dynamics (MD) simulations, we observed that in solution, farnesylated guanosine 5'-diphosphate (GDP)-bound K-Ras4B is predominantly autoinhibited by its hypervariable region (HVR), whereas the GTP-bound state favors an activated, HVR-released state. On the anionic membrane, the catalytic domain adopts multiple orientations, including parallel (∼180°) and perpendicular (∼90°) alignments of the allosteric helices, with respect to the membrane surface direction. In the autoinhibited state, the HVR is sandwiched between the effector lobe and the membrane; in the active state, with membrane-anchored farnesyl and unrestrained HVR, the catalytic domain fluctuates reinlessly, exposing its effector-binding site. Dimerization and clustering can reduce the fluctuations. This achieves preorganized, productive conformations. Notably, we also observe HVR-autoinhibited K-Ras4B-GTP states, with GDP-bound-like orientations of the helices. Thus, we propose that the GDP/GTP exchange may not be sufficient for activation; instead, our results suggest that the GDP/GTP exchange, HVR sequestration, farnesyl insertion, and orientation/localization of the catalytic domain at the membrane conjointly determine the active or inactive state of K-Ras4B. Importantly, K-Ras4B-GTP can exist in active and inactive states; on its own, GTP binding may not compel K-Ras4B activation.-Jang, H., Banerjee, A., Chavan, T. S, Lu, S., Zhang, J., Gaponenko, V., Nussinov, R. The higher level of complexity of K-Ras4B activation at the membrane. © FASEB.

  7. A Covalent Linker Allows for Membrane Targeting of An Oxylipin Biosynthetic Complex

    Energy Technology Data Exchange (ETDEWEB)

    Gilbert, N.C.; Niebuhr, M.; Tsuruta, H.; Bordelon, T.; Ridderbusch, O.; Dassey, A.; Brash, A.R.; Bartlett, S.G.; Newcomer, M.E.

    2009-05-18

    A naturally occurring bifunctional protein from Plexaura homomalla links sequential catalytic activities in an oxylipin biosynthetic pathway. The C-terminal lipoxygenase (LOX) portion of the molecule catalyzes the transformation of arachidonic acid (AA) to the corresponding 8R-hydroperoxide, and the N-terminal allene oxide synthase (AOS) domain promotes the conversion of the hydroperoxide intermediate to the product allene oxide (AO). Small-angle X-ray scattering data indicate that in the absence of a covalent linkage the two catalytic domains that transform AA to AO associate to form a complex that recapitulates the structure of the bifunctional protein. The SAXS data also support a model for LOX and AOS domain orientation in the fusion protein inferred from a low-resolution crystal structure. However, results of membrane binding experiments indicate that covalent linkage of the domains is required for Ca2+-dependent membrane targeting of the sequential activities, despite the noncovalent domain association. Furthermore, membrane targeting is accompanied by a conformational change as monitored by specific proteolysis of the linker that joins the AOS and LOX domains. Our data are consistent with a model in which Ca2+-dependent membrane binding relieves the noncovalent interactions between the AOS and LOX domains and suggests that the C2-like domain of LOX mediates both protein-protein and protein-membrane interactions.

  8. Bioinspired tannic acid-copper complexes as selective coating for nanofiltration membranes

    KAUST Repository

    Chakrabarty, Tina

    2017-04-27

    Bio-polyphenols that are present in tea, date fruits, chockolate and many other plants have been recognized as scaffold material for the manufacture of composite filtration membranes. These phenolic biomolecules possess abundant gallol (1,2,3-trihydroxyphenyl) and catechol (1,2-dihydroxyphenyl) functional groups, which allow the spontaneous formation of a thin polymerized layer at the right pH conditions. Here, we report a facile and cost-effective method to coat porous membranes via the complexation of tannic acid (TA) and cupric acetate (mono hydrate) through co-deposition. The modified membranes were investigated by XPS, ATR/FTIR, water contact angle, SEM and water permeance for a structural and morphological analysis. The obtained results reveal that the modified membranes with TA and cupric acetate (CuII) developed a thin skin layer, which showed excellent hydrophilicity with good water permeance. These membranes were tested with different molecular weight polyethylene glycols (PEG) in aqueous solution; the MWCO was around 600 Daltons.

  9. Complexation-Induced Phase Separation: Preparation of Metal-Rich Polymeric Membranes

    KAUST Repository

    Villalobos Vazquez de la Parra, Luis Francisco

    2017-08-01

    The majority of state-of-the-art polymeric membranes for industrial or medical applications are fabricated by phase inversion. Complexation induced phase separation (CIPS)—a surprising variation of this well-known process—allows direct fabrication of hybrid membranes in existing facilities. In the CIPS process, a first step forms the thin metal-rich selective layer of the membrane, and a succeeding step the porous support. Precipitation of the selective layer takes place in the same solvent used to dissolve the polymer and is induced by a small concentration of metal ions. These ions form metal-coordination-based crosslinks leading to the formation of a solid skin floating on top of the liquid polymer film. A subsequent precipitation in a nonsolvent bath leads to the formation of the porous support structure. Forming the dense layer and porous support by different mechanisms while maintaining the simplicity of a phase inversion process, results in unprecedented control over the final structure of the membrane. The thickness and morphology of the dense layer as well as the porosity of the support can be controlled over a wide range by manipulating simple process parameters. CIPS facilitates control over (i) the thickness of the dense layer throughout several orders of magnitude—from less than 15 nm to more than 6 μm, (ii) the type and amount of metal ions loaded in the dense layer, (iii) the morphology of the membrane surface, and (iv) the porosity and structure of the support. The nature of the CIPS process facilitates a precise loading of a high concentration of metal ions that are located in only the top layer of the membrane. Moreover, these metal ions can be converted—during the membrane fabrication process—to nanoparticles or crystals. This simple method opens up fascinating possibilities for the fabrication of metal-rich polymeric membranes with a new set of properties. This dissertation describes the process in depth and explores promising

  10. Crystal Structure of the Herpesvirus Nuclear Egress Complex Provides Insights into Inner Nuclear Membrane Remodeling

    Directory of Open Access Journals (Sweden)

    Tzviya Zeev-Ben-Mordehai

    2015-12-01

    Full Text Available Although nucleo-cytoplasmic transport is typically mediated through nuclear pore complexes, herpesvirus capsids exit the nucleus via a unique vesicular pathway. Together, the conserved herpesvirus proteins pUL31 and pUL34 form the heterodimeric nuclear egress complex (NEC, which, in turn, mediates the formation of tight-fitting membrane vesicles around capsids at the inner nuclear membrane. Here, we present the crystal structure of the pseudorabies virus NEC. The structure revealed that a zinc finger motif in pUL31 and an extensive interaction network between the two proteins stabilize the complex. Comprehensive mutational analyses, characterized both in situ and in vitro, indicated that the interaction network is not redundant but rather complementary. Fitting of the NEC crystal structure into the recently determined cryoEM-derived hexagonal lattice, formed in situ by pUL31 and pUL34, provided details on the molecular basis of NEC coat formation and inner nuclear membrane remodeling.

  11. Gamma-irradiation and neutron effect on DNA-membrane complexes of mammalian cells

    International Nuclear Information System (INIS)

    Lapidus, I.L.; Nazarov, V.M.; Ehrtsgreber, G.

    1984-01-01

    The first results of radiobiological investigations in the biophysical channel of the JINR reactor IBR-2 are presented. Sedimentation behaviour of DNA-membrane complexes has been studied at irradiation of the Chinese hamster cells (VT9-4) in a wide dose range of 137 Cs γ-irradiation and neutrons. An earlier assumption of the authors on the role of DNA double-strand breaks in changing the relative sedimentation velocity of complexes at irradiation of cells with doses over 50 Gy has been confirmed

  12. Carbonic anhydrase activity of integral-functional complexes of thylakoid membranes of spinach chloroplasts

    Directory of Open Access Journals (Sweden)

    A. V. Semenihin

    2015-06-01

    Full Text Available Isolated thylakoid membranes were disrupted by treatment with nonionic detergents digitonin or dodecyl maltoside. Solubilized polypeptide complexes were separated by native gel charge shift electrophoresis. The position of ATP-synthase complex and its isolated catalytic part (CF1 within gel was determined using the color reaction for ATPase activity. Due to the presence of cytochromes, the red band in unstained gels corresponded to the cytochrome b6f complex. Localization of the cytochrome b6f complex, ATP synthase and coupling CF1 in the native gel was confirmed by their subunit composition determined after SDS-electrophoretic analysis. Carbonic anhydrase (CA activity in polypeptide zones of PS II, cytochrome b6f complex, and ATP-synthase CF1 was identified in native gels using indicator bromothymol blue. CA activity of isolated CF1 in solution was determined by infrared gas analysis as the rate of bicarbonate dehydration. The water-soluble acetazolamide, an inhibitor of CA, unlike lipophilic ethoxyzolamide inhibited CA activity of CF1. Thus, it was shown for the first time that ATP-synthase has a component which is capable of catalyzing the interconversion of forms of carbonic acid associated with proton exchange. The data obtained suggest the presence of multiple forms of carbonic anhydrase in the thylakoid membranes of spinach chloroplasts and confirm their involvement in the proton transfer to the ATP synthase.

  13. The Golgi puppet master: COG complex at center stage of membrane trafficking interactions.

    Science.gov (United States)

    Willett, Rose; Ungar, Daniel; Lupashin, Vladimir

    2013-09-01

    The central organelle within the secretory pathway is the Golgi apparatus, a collection of flattened membranes organized into stacks. The cisternal maturation model of intra-Golgi transport depicts Golgi cisternae that mature from cis to medial to trans by receiving resident proteins, such as glycosylation enzymes via retrograde vesicle-mediated recycling. The conserved oligomeric Golgi (COG) complex, a multi-subunit tethering complex of the complexes associated with tethering containing helical rods family, organizes vesicle targeting during intra-Golgi retrograde transport. The COG complex, both physically and functionally, interacts with all classes of molecules maintaining intra-Golgi trafficking, namely SNAREs, SNARE-interacting proteins, Rabs, coiled-coil tethers, vesicular coats, and molecular motors. In this report, we will review the current state of the COG interactome and analyze possible scenarios for the molecular mechanism of the COG orchestrated vesicle targeting, which plays a central role in maintaining glycosylation homeostasis in all eukaryotic cells.

  14. Antibacterial activity of ruthenium(II) polypyridyl complex manipulated by membrane permeability and cell morphology.

    Science.gov (United States)

    Sun, Dongdong; Zhang, Weiwei; Lv, Mengting; Yang, Endong; Zhao, Qian; Wang, Weiyun

    2015-01-01

    This study investigates the antibacterial effects of the ruthenium(II) complex RuBP and the mechanism of RuBP action on bacteria. Results show that RuBP can inhibit the growth of Gram-positive bacteria, such as Staphylococcus aureus and Micrococcus tetragenus. Cellular uptake and laser confocal microscopic studies reveal the efficient uptake of RuBP by M. tetragenus cells. Scanning electron microscopic observations of the morphologies of M. tetragenus and S. aureus treated with RuBP further confirm that direct contact of both bacteria with RuBP can damage the cell membrane and membrane integrity, which may eventually induce growth inhibition and bacterial death. After RuBP treatment, the electrical conductivity of the bacterial suspensions increases. Spectroscopic studies and agarose gel electrophoresis indicate that intact DNA and RNA decrease or disappear in RuBP-treated bacterial cells, thus demonstrating that RuBP performs its antibacterial function by increasing the permeability of cell membranes. This study provides new insights for understanding the antibacterial actions of RuBP and designing metal complex antibiotics for other biomedical applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Extracellular complex of chitinolytic enzymes of Clostridium paraputrificum strain J4 separated by membrane ultrafiltration.

    Science.gov (United States)

    Tishchenko, G; Koppová, I; Simůnek, J; Dohnálek, J

    2010-07-01

    Membrane diafiltration was used for separation of the extracellular complex of chitinolytic enzymes of C. paraputrificum J4 free from contaminants with molar mass higher than 100 kDa and lower than 30 kDa. The enzyme complex containing beta-N-acetylglucosaminidase (NAGase) and six endochitinases was concentrated on a membrane with cut-off 30 kDa. In this retentate, the NAGase/endochitinase specific activity was 13.5/6.5-times higher than in the initial culture filtrate. The proportion (in%) of endochitinases: 23 (90 kDa), 42 (86 kDa), 8 (72 kDa), 16 (68 kDa) and 8 (60 kDa) was calculated from their peak areas (determined by densitometry) in images of zymograms. NAGase (38 kDa) was less active and stable at pH lower than 4 and higher than 8 but it was more temperature-stable than endochitinases, especially at 40-60 degrees C. In contrast to endochitinases, the pH optimum of NAGase activity was shifted by ca. 0.7 pH units to the alkaline region. Extracellular NAGase together with six endochitinases secreted by C. paraputrificum J4 were separated by membrane diafiltration and characterized by molar mass, stability and activity in dependence on pH and temperature. The knowledge of composition of chitinolytic enzymes, their pH and temperature stability is useful for optimization of the separation process.

  16. Deformation behaviour of aluminium low-micron MMCs and MMNCs at warm working temperatures (0.3—0.5 Tm)

    CSIR Research Space (South Africa)

    Gxowa, Zizo

    2016-10-01

    Full Text Available , operating at high temperatures has the disadvantages of high energy costs, reduced equipment and tool life, poor surface finish and low dimensional accuracy (Rajput, 2007). These disadvantages mean that hot- worked MMC and MMNC components are expensive...-micron MMCs and MMNCs Warm working has been shown to have some advantages over both cold and hot working (Rao et al., 1999). Advantages of warm working over cold working include (Cavaliere, 2002): � Less strain hardening – fewer annealing operations...

  17. Molecular Architecture of the Major Membrane Ring Component of the Nuclear Pore Complex.

    Science.gov (United States)

    Upla, Paula; Kim, Seung Joong; Sampathkumar, Parthasarathy; Dutta, Kaushik; Cahill, Sean M; Chemmama, Ilan E; Williams, Rosemary; Bonanno, Jeffrey B; Rice, William J; Stokes, David L; Cowburn, David; Almo, Steven C; Sali, Andrej; Rout, Michael P; Fernandez-Martinez, Javier

    2017-03-07

    The membrane ring that equatorially circumscribes the nuclear pore complex (NPC) in the perinuclear lumen of the nuclear envelope is composed largely of Pom152 in yeast and its ortholog Nup210 (or Gp210) in vertebrates. Here, we have used a combination of negative-stain electron microscopy, nuclear magnetic resonance, and small-angle X-ray scattering methods to determine an integrative structure of the ∼120 kDa luminal domain of Pom152. Our structural analysis reveals that the luminal domain is formed by a flexible string-of-pearls arrangement of nine repetitive cadherin-like Ig-like domains, indicating an evolutionary connection between NPCs and the cell adhesion machinery. The 16 copies of Pom152 known to be present in the yeast NPC are long enough to form the observed membrane ring, suggesting how interactions between Pom152 molecules help establish and maintain the NPC architecture. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Turnip mosaic virus Moves Systemically through Both Phloem and Xylem as Membrane-Associated Complexes1

    Science.gov (United States)

    Zheng, Huanquan

    2015-01-01

    Plant viruses move systemically in plants through the phloem. They move as virions or as ribonucleic protein complexes, although it is not clear what these complexes are made of. The approximately 10-kb RNA genome of Turnip mosaic virus (TuMV) encodes a membrane protein, known as 6K2, that induces endomembrane rearrangements for the formation of viral replication factories. These factories take the form of vesicles that contain viral RNA (vRNA) and viral replication proteins. In this study, we report the presence of 6K2-tagged vesicles containing vRNA and the vRNA-dependent RNA polymerase in phloem sieve elements and in xylem vessels. Transmission electron microscopy observations showed the presence in the xylem vessels of vRNA-containing vesicles that were associated with viral particles. Stem-girdling experiments, which leave xylem vessels intact but destroy the surrounding tissues, confirmed that TuMV could establish a systemic infection of the plant by going through xylem vessels. Phloem sieve elements and xylem vessels from Potato virus X-infected plants also contained lipid-associated nonencapsidated vRNA, indicating that the presence of membrane-associated ribonucleic protein complexes in the phloem and xylem may not be limited to TuMV. Collectively, these studies indicate that viral replication factories could end up in the phloem and the xylem. PMID:25717035

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

    Directory of Open Access Journals (Sweden)

    L. Vanysacker

    2013-01-01

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

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

    Science.gov (United States)

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

    2013-01-01

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

  1. The membrane attack complex as an indicator of complement hyperactivation in type 2 diabetes mellitus

    OpenAIRE

    Elina Aleksandrovna Arakelova; Meri Robertovna Ovsepyan; Anna Surenovna Boyadzhyan; Arsen Artashesovich Arakelyan; Astkhik Artavazdovna Gevorkyan; Ashot Andreevich Mamikonyan

    2011-01-01

    Aim. Comparative analysis of the levels of the membrane attack complex (MAC) - an end product of complement activation, and of hemolytic activities of C1 and C3 complement components in sera of patients with diabetes mellitus 2 (DM2) and healthy subjects. Materials and methods. 37 DM2 patients (7 men, 26 women, mean age 58±9 years (M±б) and 37 healthy subjects without a family history of hereditary diabetes (17 men, 20 women, mean age 52±12 years). Serum MAC levels were measured by E...

  2. Native proteomic analysis of protein complexes in murine intestinal brush border membranes

    Czech Academy of Sciences Publication Activity Database

    Babušiak, M.; Man, Petr; Petrák, J.; Vyoral, D.

    2007-01-01

    Roč. 7, č. 1 (2007), s. 121-129 ISSN 1615-9853 R&D Projects: GA ČR(CZ) GD204/03/H066; GA AV ČR KJB500200612; GA MŠk LC545 Grant - others:GA ČR(CZ) GA303/04/0003; GA MZd(CZ) NR8930; GA MŠk(CZ) LC06044; CZ(CZ) 023736; GA MZd(CZ) NR8317 Program:NR Institutional research plan: CEZ:AV0Z50200510 Keywords : blue native electrophoresis * brush border membranes * protein complexes Subject RIV: EE - Microbiology, Virology Impact factor: 5.479, year: 2007

  3. Novel surfactant-selective membrane electrode based on polyelectrolyte-surfactant complex.

    Science.gov (United States)

    Zorin, Ivan; Scherbinina, Tatiana; Fetin, Petr; Makarov, Ivan; Bilibin, Alexander

    2014-12-01

    Novel class of active ionophores for surfactant selective electrodes is proposed. PVC membrane doped with polyelectrolyte-surfactant stoichiometric complex is used for ion-selective electrode construction responsive to cetyltrimethyl ammonium bromide and related surfactants. New ionophore is quite stable and completely insoluble in aqueous media in wide range of pH. The electrode displays nearly Nernstian slope in CTAB concentration range 10(-6)-10(-3)M. Polyelectrolyte platform allows to design wide range of different ionophores responsive to cationic organic substances. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Membrane Processes Based on Complexation Reactions of Pollutants as Sustainable Wastewater Treatments

    Directory of Open Access Journals (Sweden)

    Teresa Poerio

    2009-11-01

    Full Text Available Water is today considered to be a vital and limited resource due to industrial development and population growth. Developing appropriate water treatment techniques, to ensure a sustainable management, represents a key point in the worldwide strategies. By removing both organic and inorganic species using techniques based on coupling membrane processes and appropriate complexing agents to bind pollutants are very important alternatives to classical separation processes in water treatment. Supported Liquid Membrane (SLM and Complexation Ultrafiltration (CP-UF based processes meet the sustainability criteria because they require low amounts of energy compared to pressure driven membrane processes, low amounts of complexing agents and they allow recovery of water and some pollutants (e.g., metals. A more interesting process, on the application point of view, is the Stagnant Sandwich Liquid Membrane (SSwLM, introduced as SLM implementation. It has been studied in the separation of the drug gemfibrozil (GEM and of copper(II as organic and inorganic pollutants in water. Obtained results showed in both cases the higher efficiency of SSwLM with respect to the SLM system configuration. Indeed higher stability (335.5 vs. 23.5 hours for GEM; 182.7 vs. 49.2 for copper(II and higher fluxes (0.662 vs. 0.302 mmol·h-1·m-2 for GEM; 43.3 vs. 31.0 for copper(II were obtained by using the SSwLM. Concerning the CP-UF process, its feasibility was studied in the separation of metals from waters (e.g., from soil washing, giving particular attention to process sustainability such as water and polymer recycle, free metal and water recovery. The selectivity of the CP-UF process was also validated in the separate removal of copper(II and nickel(II both contained in synthetic and real aqueous effluents. Thus, complexation reactions involved in the SSwLM and the CP-UF processes play a key role to meet the sustainability criteria.

  5. From isolated light-harvesting complexes to the thylakoid membrane: a single-molecule perspective

    Science.gov (United States)

    Gruber, J. Michael; Malý, Pavel; Krüger, Tjaart P. J.; Grondelle, Rienk van

    2018-01-01

    The conversion of solar radiation to chemical energy in plants and green algae takes place in the thylakoid membrane. This amphiphilic environment hosts a complex arrangement of light-harvesting pigment-protein complexes that absorb light and transfer the excitation energy to photochemically active reaction centers. This efficient light-harvesting capacity is moreover tightly regulated by a photoprotective mechanism called non-photochemical quenching to avoid the stress-induced destruction of the catalytic reaction center. In this review we provide an overview of single-molecule fluorescence measurements on plant light-harvesting complexes (LHCs) of varying sizes with the aim of bridging the gap between the smallest isolated complexes, which have been well-characterized, and the native photosystem. The smallest complexes contain only a small number (10-20) of interacting chlorophylls, while the native photosystem contains dozens of protein subunits and many hundreds of connected pigments. We discuss the functional significance of conformational dynamics, the lipid environment, and the structural arrangement of this fascinating nano-machinery. The described experimental results can be utilized to build mathematical-physical models in a bottom-up approach, which can then be tested on larger in vivo systems. The results also clearly showcase the general property of biological systems to utilize the same system properties for different purposes. In this case it is the regulated conformational flexibility that allows LHCs to switch between efficient light-harvesting and a photoprotective function.

  6. Roles of dynamic metal speciation and membrane permeability in metal flux through lipophilic membranes: General theory and experimental validation with nonlabile complexes

    NARCIS (Netherlands)

    Zeshi, Zhang; Buffle, J.; Leeuwen, van H.P.

    2007-01-01

    The study of the role of dynamic metal speciation in lipophilic membrane permeability in aqueous solution requires accurate interpretation of experimental data. To meet this goal, a general theory is derived for describing 1:1 metal complex flux, under steady-state and ligand excess conditions,

  7. Crystal structure of the potassium-importing KdpFABC membrane complex

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ching-Shin; Pedersen, Bjørn Panyella; Stokes, David L.

    2017-06-21

    Cellular potassium import systems play a fundamental role in osmoregulation, pH homeostasis and membrane potential in all domains of life. In bacteria, the kdp operon encodes a four-subunit potassium pump that maintains intracellular homeostasis, cell shape and turgor under conditions in which potassium is limiting1. This membrane complex, called KdpFABC, has one channel-like subunit (KdpA) belonging to the superfamily of potassium transporters and another pump-like subunit (KdpB) belonging to the superfamily of P-type ATPases. Although there is considerable structural and functional information about members of both superfamilies, the mechanism by which uphill potassium transport through KdpA is coupled with ATP hydrolysis by KdpB remains poorly understood. Here we report the 2.9 Å X-ray structure of the complete Escherichia coli KdpFABC complex with a potassium ion within the selectivity filter of KdpA and a water molecule at a canonical cation site in the transmembrane domain of KdpB. The structure also reveals two structural elements that appear to mediate the coupling between these two subunits. Specifically, a protein-embedded tunnel runs between these potassium and water sites and a helix controlling the cytoplasmic gate of KdpA is linked to the phosphorylation domain of KdpB. On the basis of these observations, we propose a mechanism that repurposes protein channel architecture for active transport across biomembranes.

  8. Structural and thermodynamic characterization of doxycycline/β-cyclodextrin supramolecular complex and its bacterial membrane interactions.

    Science.gov (United States)

    Suárez, Diego F; Consuegra, Jessika; Trajano, Vivianne C; Gontijo, Sávio M L; Guimarães, Pedro P G; Cortés, Maria E; Denadai, Ângelo L; Sinisterra, Rubén D

    2014-06-01

    Doxycycline is a semi-synthetic antibiotic commonly used for the treatment of many aerobic and anaerobic bacteria. It inhibits the activity of matrix metalloproteinases (MMPs) and affects cell proliferation. In this study, the structural and thermodynamic parameters of free DOX and a DOX/βCD complex were investigated, as well as their interactions and effects on Staphylococcus aureus cells and cellular cytotoxicity. Complexation of DOX and βCD was confirmed to be an enthalpy- and entropy-driven process, and a low equilibrium constant was obtained. Treatment of S. aureus with higher concentrations of DOX or DOX/βCD resulted in an exponential decrease in S. aureus cell size, as well as a gradual neutralization of zeta potential. These thermodynamic profiles suggest that ion-pairing and hydrogen bonding interactions occur between DOX and the membrane of S. aureus. In addition, the adhesion of βCD to the cell membrane via hydrogen bonding is hypothesized to mediate a synergistic effect which accounts for the higher activity of DOX/βCD against S. aureus compared to pure DOX. Lower cytotoxicity and induction of osteoblast proliferation was also associated with DOX/βCD compared with free DOX. These promising findings demonstrate the potential for DOX/βCD to mediate antimicrobial activity at lower concentrations, and provides a strategy for the development of other antimicrobial formulations. Copyright © 2014. Published by Elsevier B.V.

  9. Fast axonal transport of the proteasome complex depends on membrane interaction and molecular motor function.

    Science.gov (United States)

    Otero, Maria G; Alloatti, Matías; Cromberg, Lucas E; Almenar-Queralt, Angels; Encalada, Sandra E; Pozo Devoto, Victorio M; Bruno, Luciana; Goldstein, Lawrence S B; Falzone, Tomás L

    2014-04-01

    Protein degradation by the ubiquitin-proteasome system in neurons depends on the correct delivery of the proteasome complex. In neurodegenerative diseases, aggregation and accumulation of proteins in axons link transport defects with degradation impairments; however, the transport properties of proteasomes remain unknown. Here, using in vivo experiments, we reveal the fast anterograde transport of assembled and functional 26S proteasome complexes. A high-resolution tracking system to follow fluorescent proteasomes revealed three types of motion: actively driven proteasome axonal transport, diffusive behavior in a viscoelastic axonema and proteasome-confined motion. We show that active proteasome transport depends on motor function because knockdown of the KIF5B motor subunit resulted in impairment of the anterograde proteasome flux and the density of segmental velocities. Finally, we reveal that neuronal proteasomes interact with intracellular membranes and identify the coordinated transport of fluorescent proteasomes with synaptic precursor vesicles, Golgi-derived vesicles, lysosomes and mitochondria. Taken together, our results reveal fast axonal transport as a new mechanism of proteasome delivery that depends on membrane cargo 'hitch-hiking' and the function of molecular motors. We further hypothesize that defects in proteasome transport could promote abnormal protein clearance in neurodegenerative diseases.

  10. Segregation of receptor-ligand complexes in cell adhesion zones: phase diagrams and the role of thermal membrane roughness

    Science.gov (United States)

    Różycki, B.; Lipowsky, R.; Weikl, T. R.

    2010-09-01

    The adhesion zone of immune cells, the 'immunological synapse', exhibits characteristic domains of receptor-ligand complexes. The domain formation is probably caused by a length difference of the receptor-ligand complexes, and has been investigated in experiments in which T cells adhere to supported membranes with anchored ligands. For supported membranes with two types of anchored ligands, MHCp and ICAM1, which bind to the T-cell receptor (TCR) and the receptor LFA1 in the cell membrane, the coexistence of domains of the TCR-MHCp and LFA1-ICAM1 complexes in the cell adhesion zone has been observed for a wide range of ligand concentrations and affinities. For supported membranes with long and short ligands that bind to the same cell receptor CD2, in contrast, domain coexistence has been observed for a quite narrow ratio of ligand concentrations. In this paper, we determine detailed phase diagrams for cells adhering to supported membranes with a statistical-physical model of cell adhesion. We find a characteristic difference between the adhesion scenarios in which two types of ligands in a supported membrane bind (i) to the same cell receptor or (ii) to two different cell receptors, which helps us to explain the experimental observations. Our phase diagrams fully include thermal shape fluctuations of the cell membranes on nanometer scales, which lead to a critical point for the domain formation and to a cooperative binding of the receptors and ligands.

  11. An experimental study of the elastic properties of the human Bruch's membrane-choroid complex: relevance to ageing.

    Science.gov (United States)

    Ugarte, M; Hussain, A A; Marshall, J

    2006-05-01

    To investigate the mechanical properties (stress-strain relation, elasticity, hysteresis, response to stress spikes and drops) of isolated human Bruch's membrane-choroid, as well as the effect of ageing and aged related macular degeneration (AMD). 13 Bruch's membrane-choroid complexes were obtained from human donors (21-97 years). Two samples (aged 85 and 95) showed signs of AMD including large, soft drusen, choroidal neovascularisation, and/or disciform scars. Various hydrostatic pressures (stress) were applied to the choroidal surface of mid-peripheral samples mounted in a modified open Ussing chamber. Linear scans of the tissue were recorded by optical coherence tomography (OCT) and the pressure induced deformation (strain), elasticity, hysteresis, and response to pressure spikes and drops measured. The elasticity of human Bruch's membrane-choroid complex decreased linearly with ageing (precoil capacity of Bruch's membrane-choroid was not affected by ageing. The response to pressure spikes/drops was similar in age matched normal and AMD eyes. The results suggest that although the aged induced decrease in Bruch's membrane elasticity may contribute to breaks in this membrane in AMD leading to neovascularisation this is not sufficient. The presence of other factors is required for its development. The elasticity of Bruch's membrane-choroid complex decreases with age while recoil capacity does not. The decrease was not exaggerated in AMD.

  12. Enhancement of the release of azelaic acid through the synthetic membranes by inclusion complex formation with hydroxypropyl-beta-cyclodextrin.

    Science.gov (United States)

    Manosroi, Jiradej; Apriyani, Maria Goretti; Foe, Kuncoro; Manosroi, Aranya

    2005-04-11

    The aim of this study was to investigate the release rates of azelaic acid and azelaic acid-hydroxypropyl-beta-cyclodextrin (HPbetaCD) inclusion complex through three types of synthetic membranes, namely cellophane, silicone and elastomer membranes. Solid inclusion complexes of azelaic acid-HPbetaCD at the molar ratio of 1:1 were prepared by coevaporation and freeze-drying methods, subsequently characterized by differential scanning calorimetry, X-ray diffractometry and dissolution studies. Solid inclusion complex obtained by coevaporation method which exhibited the inclusion of azelaic acid in the HPbetaCD cavity and gave the highest dissolution rate of azelaic acid was selected for the release study. Release studies of azelaic acid and this complex through the synthetic membranes were conducted using vertical Franz diffusion cells at 30 degrees C for 6 days. The release rates of azelaic acid through the synthetic membranes were enhanced by the formation of inclusion complex with HPbetaCD at the molar ratio of 1:1, with the increasing fluxes of about 41, 81 and 28 times of the uncomplexed system in cellophane, silicone and elastomer membranes, respectively. The result from this study can be applied for the development of azelaic acid for topical use.

  13. AMACO is a novel component of the basement membrane associated Fraser complex

    Science.gov (United States)

    Richardson, Rebecca J.; Gebauer, Jan M.; Zhang, Jin-Li; Kobbe, Birgit; Keene, Douglas R.; Karlsen, Kristina Røkenes; Richetti, Stefânia; Wohl, Alexander P.; Sengle, Gerhard; Neiss, Wolfram F.; Paulsson, Mats; Hammerschmidt, Matthias; Wagener, Raimund

    2015-01-01

    Fraser syndrome (FS) is a phenotypically variable, autosomal recessive disorder characterized by cryptophthalmus, cutaneous syndactyly and other malformations resulting from mutations in FRAS1, FREM2 and GRIP1. Transient embryonic epidermal blistering causes the characteristic defects of the disorder. Fras1, Frem1 and Frem2 form the extracellular Fraser complex, which is believed to stabilize the basement membrane (BM). However, several cases of FS could not be attributed to mutations in FRAS1, FREM2 or GRIP1, while Fraser syndrome displays high clinical variability, suggesting there is an additional genetic, possibly modifying contribution to this disorder. AMACO, encoded by the VWA2 gene, has a very similar tissue distribution to the Fraser complex proteins in both mouse and zebrafish. Here, we show that AMACO deposition is lost in Fras1 deficient zebrafish and mice and that Fras1 and AMACO interact directly via their CSPG and P2 domains. Knockdown of vwa2, which alone causes no phenotype, enhances the phenotype of hypomorphic Fras1 mutant zebrafish. Together, our data suggest that AMACO represents a novel member of the Fraser complex. PMID:24232570

  14. AMACO is a component of the basement membrane-associated Fraser complex.

    Science.gov (United States)

    Richardson, Rebecca J; Gebauer, Jan M; Zhang, Jin-Li; Kobbe, Birgit; Keene, Douglas R; Karlsen, Kristina Røkenes; Richetti, Stefânia; Wohl, Alexander P; Sengle, Gerhard; Neiss, Wolfram F; Paulsson, Mats; Hammerschmidt, Matthias; Wagener, Raimund

    2014-05-01

    Fraser syndrome (FS) is a phenotypically variable, autosomal recessive disorder characterized by cryptophthalmus, cutaneous syndactyly, and other malformations resulting from mutations in FRAS1, FREM2, and GRIP1. Transient embryonic epidermal blistering causes the characteristic defects of the disorder. Fras1, Frem1, and Frem2 form the extracellular Fraser complex, which is believed to stabilize the basement membrane. However, several cases of FS could not be attributed to mutations in FRAS1, FREM2, or GRIP1, and FS displays high clinical variability, suggesting that there is an additional genetic, possibly modifying contribution to this disorder. An extracellular matrix protein containing VWA-like domains related to those in matrilins and collagens (AMACO), encoded by the VWA2 gene, has a very similar tissue distribution to the Fraser complex proteins in both mouse and zebrafish. Here, we show that AMACO deposition is lost in Fras1-deficient zebrafish and mice and that Fras1 and AMACO interact directly via their chondroitin sulfate proteoglycan (CSPG) and P2 domains. Knockdown of vwa2, which alone causes no phenotype, enhances the phenotype of hypomorphic Fras1 mutant zebrafish. Together, our data suggest that AMACO represents a member of the Fraser complex.

  15. Experimental study of microstructure, mechanical and tribological properties of cBN particulates SS316 alloy based MMCs fabricated by DMLS technique

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, M.; Mandal, V.; Singh, P. K.; Kumar, P.; Kumar, V.; Das, A. K. [Indian Institute of Technology (ISM), Dhanbad (India)

    2017-06-15

    Direct metal laser sintering process (DMLS) was chosen to develop cBN particulates reinforced SS316 based Metal matrix composite (MMC) with 5 %, 7.5 % and 10 % cBN in the nitrogen gas atmosphere using continuous wave fibre laser of 400 W output capacity. Effects of process parameters such as laser power, beam scanning speed and the mixing ratio of powder on different physical properties of the developed MMC were investigated. It was found that the physical and mechanical properties such as friction and wear behavior, micro hardness and density come up with improved results. FESEM images indicate the microstructure of the composite and evidently confirms the presence of cubic boron nitride in the SS316 matrix where chromium nitride acted as a binder in the presence of nitrogen atmosphere. The Vickers hardness values of the developed MMCs with laser power 60 W and 65 W were found in the range of 276-478 HV{sub 0}.2 and 297-460 HV{sub 0}.2, respectively. It was found that Vickers hardness is directly proportional to the % of cBN in the powder mixture and the laser beam power. The wear resistance of the sintered MMCs increased with increasing cBN content in powder mixture and re- sults show that wear of MMCs are much lower than that of SS316. X-Ray diffraction (XRD) analysis of the fabricated MMC confirms the presence of different phases such as cBN, CrN, CrB{sub 2}, Cr{sub 2}N and Fe{sub 3}N as a consequence of a series of chemical reaction between cBN and different elements of SS316 in nitrogen atmosphere.

  16. Iodide-selective membrane electrode based on salophen complex of cobalt (III)

    OpenAIRE

    Zare,Hamid R.; Memarzadeh,Farkhondeh; Gorji,Alireza; Ardakani,Mohammad Mazloum

    2005-01-01

    A highly selective PVC membrane electrode based on a cobalt-salophen complex was prepared. The sensor displays an anti-Hofmeister selectivity sequence with a preference for iodide ion over many common anions. The electrode has a linear dynamic range between 5.0×10-7 to 1.0×10-1 mol L-1, with a Nernstian slope of -58.9 mV decade-1 and a detection limit of 3.0×10-7 mol L-1. The working pH range of the sensor is 3.1-9.8. It exhibits of a fast as 15 s and has a lifetime of about 2 months. The sel...

  17. Gibberellin DELLA signaling targets the retromer complex to redirect protein trafficking to the plasma membrane.

    Science.gov (United States)

    Salanenka, Yuliya; Verstraeten, Inge; Löfke, Christian; Tabata, Kaori; Naramoto, Satoshi; Glanc, Matouš; Friml, Jiří

    2018-02-20

    The plant hormone gibberellic acid (GA) is a crucial regulator of growth and development. The main paradigm of GA signaling puts forward transcriptional regulation via the degradation of DELLA transcriptional repressors. GA has also been shown to regulate tropic responses by modulation of the plasma membrane incidence of PIN auxin transporters by an unclear mechanism. Here we uncovered the cellular and molecular mechanisms by which GA redirects protein trafficking and thus regulates cell surface functionality. Photoconvertible reporters revealed that GA balances the protein traffic between the vacuole degradation route and recycling back to the cell surface. Low GA levels promote vacuolar delivery and degradation of multiple cargos, including PIN proteins, whereas high GA levels promote their recycling to the plasma membrane. This GA effect requires components of the retromer complex, such as Sorting Nexin 1 (SNX1) and its interacting, microtubule (MT)-associated protein, the Cytoplasmic Linker-Associated Protein (CLASP1). Accordingly, GA regulates the subcellular distribution of SNX1 and CLASP1, and the intact MT cytoskeleton is essential for the GA effect on trafficking. This GA cellular action occurs through DELLA proteins that regulate the MT and retromer presumably via their interaction partners Prefoldins (PFDs). Our study identified a branching of the GA signaling pathway at the level of DELLA proteins, which, in parallel to regulating transcription, also target by a nontranscriptional mechanism the retromer complex acting at the intersection of the degradation and recycling trafficking routes. By this mechanism, GA can redirect receptors and transporters to the cell surface, thus coregulating multiple processes, including PIN-dependent auxin fluxes during tropic responses. Copyright © 2018 the Author(s). Published by PNAS.

  18. Ruthenium complexes with phenylterpyridine derivatives target cell membrane and trigger death receptors-mediated apoptosis in cancer cells.

    Science.gov (United States)

    Deng, Zhiqin; Gao, Pan; Yu, Lianling; Ma, Bin; You, Yuanyuan; Chan, Leung; Mei, Chaoming; Chen, Tianfeng

    2017-06-01

    Elucidation of the communication between metal complexes and cell membrane may provide useful information for rational design of metal-based anticancer drugs. Herein we synthesized a novel class of ruthenium (Ru) complexes containing phtpy derivatives (phtpy = phenylterpyridine), analyzed their structure-activity relationship and revealed their action mechanisms. The result showed that, the increase in the planarity of hydrophobic Ru complexes significantly enhanced their lipophilicity and cellular uptake. Meanwhile, the introduction of nitro group effectively improved their anticancer efficacy. Further mechanism studies revealed that, complex (2c), firstly accumulated on cell membrane and interacted with death receptors to activate extrinsic apoptosis signaling pathway. The complex was then transported into cell cytoplasm through transferrin receptor-mediated endocytosis. Most of the intracellular 2c accumulated in cell plasma, decreasing the level of cellular ROS, inducing the activation of caspase-9 and thus intensifying the apoptosis. At the same time, the residual 2c can translocate into cell nucleus to interact with DNA, induce DNA damage, activate p53 pathway and enhance apoptosis. Comparing with cisplatin, 2c possesses prolonged circulation time in blood, comparable antitumor ability and importantly, much lower toxicity in vivo. Taken together, this study uncovers the role of membrane receptors in the anticancer actions of Ru complexes, and provides fundamental information for rational design of membrane receptor targeting anticancer drugs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Structure of the mycobacterial ESX-5 type VII secretion system membrane complex by single-particle analysis.

    Science.gov (United States)

    Beckham, Katherine S H; Ciccarelli, Luciano; Bunduc, Catalin M; Mertens, Haydyn D T; Ummels, Roy; Lugmayr, Wolfgang; Mayr, Julia; Rettel, Mandy; Savitski, Mikhail M; Svergun, Dmitri I; Bitter, Wilbert; Wilmanns, Matthias; Marlovits, Thomas C; Parret, Annabel H A; Houben, Edith N G

    2017-04-10

    Mycobacteria are characterized by their impermeable outer membrane, which is rich in mycolic acids 1 . To transport substrates across this complex cell envelope, mycobacteria rely on type VII (also known as ESX) secretion systems 2 . In Mycobacterium tuberculosis, these ESX systems are essential for growth and full virulence and therefore represent an attractive target for anti-tuberculosis drugs 3 . However, the molecular details underlying type VII secretion are largely unknown, due to a lack of structural information. Here, we report the molecular architecture of the ESX-5 membrane complex from Mycobacterium xenopi determined at 13 Å resolution by electron microscopy. The four core proteins of the ESX-5 complex (EccB 5 , EccC 5 , EccD 5 and EccE 5 ) assemble with equimolar stoichiometry into an oligomeric assembly that displays six-fold symmetry. This membrane-associated complex seems to be embedded exclusively in the inner membrane, which indicates that additional components are required to translocate substrates across the mycobacterial outer membrane. Furthermore, the extended cytosolic domains of the EccC ATPase, which interact with secretion effectors, are highly flexible, suggesting an as yet unseen mode of substrate interaction. Comparison of our results with known structures of other bacterial secretion systems demonstrates that the architecture of type VII secretion system is fundamentally different, suggesting an alternative secretion mechanism.

  20. Biologically Complex Planar Cell Plasma Membranes Supported on Polyelectrolyte Cushions Enhance Transmembrane Protein Mobility and Retain Native Orientation.

    Science.gov (United States)

    Liu, Han-Yuan; Chen, Wei-Liang; Ober, Christopher K; Daniel, Susan

    2018-01-23

    Reconstituted supported lipid bilayers (SLB) are widely used as in vitro cell-surface models because they are compatible with a variety of surface-based analytical techniques. However, one of the challenges of using SLBs as a model of the cell surface is the limited complexity in membrane composition, including the incorporation of transmembrane proteins and lipid diversity that may impact the activity of those proteins. Additionally, it is challenging to preserve the transmembrane protein native orientation, function, and mobility in SLBs. Here, we leverage the interaction between cell plasma membrane vesicles and polyelectrolyte brushes to create planar bilayers from cell plasma membrane vesicles that have budded from the cell surface. This approach promotes the direct incorporation of membrane proteins and other species into the planar bilayer without using detergent or reconstitution and preserves membrane constituents. Furthermore, the structure of the polyelectrolyte brush serves as a cushion between the planar bilayer and rigid supporting surface, limiting the interaction of the cytosolic domains of membrane proteins with this surface. Single particle tracking was used to analyze the motion of GPI-linked yellow fluorescent proteins (GPI-YFP) and neon-green fused transmembrane P2X2 receptors (P2X2-neon) and shows that this platform retains over 75% mobility of multipass transmembrane proteins in its native membrane environment. An enzyme accessibility assay confirmed that the protein orientation is preserved and results in the extracellular domain facing toward the bulk phase and the cytosolic side facing the support. Because the platform presented here retains the complexity of the cell plasma membrane and preserves protein orientation and mobility, it is a better representative mimic of native cell surfaces, which may find many applications in biological assays aimed at understanding cell membrane phenomena.

  1. Surfactant-free purification of membrane protein complexes from bacteria: application to the staphylococcal penicillin-binding protein complex PBP2/PBP2a

    International Nuclear Information System (INIS)

    Paulin, Sarah; Rosado, Helena; Taylor, Peter W; Jamshad, Mohammed; Dafforn, Timothy R; Garcia-Lara, Jorge; Foster, Simon J; Galley, Nicola F; Roper, David I

    2014-01-01

    Surfactant-mediated removal of proteins from biomembranes invariably results in partial or complete loss of function and disassembly of multi-protein complexes. We determined the capacity of styrene-co-maleic acid (SMA) co-polymer to remove components of the cell division machinery from the membrane of drug-resistant staphylococcal cells. SMA-lipid nanoparticles solubilized FtsZ-PBP2-PBP2a complexes from intact cells, demonstrating the close physical proximity of these proteins within the lipid bilayer. Exposure of bacteria to (-)-epicatechin gallate, a polyphenolic agent that abolishes β-lactam resistance in staphylococci, disrupted the association between PBP2 and PBP2a. Thus, SMA purification provides a means to remove native integral membrane protein assemblages with minimal physical disruption and shows promise as a tool for the interrogation of molecular aspects of bacterial membrane protein structure and function. (paper)

  2. Crystallization of Mitochondrial Respiratory Complex II fromChicken Heart: A Membrane-Protein Complex Diffracting to 2.0Angstrom

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Li-shar; Borders, Toni M.; Shen, John T.; Wang, Chung-Jen; Berry, Edward A.

    2004-12-17

    Procedure is presented for preparation of diffraction-quality crystals of a vertebrate mitochondrial respiratory Complex II. The crystals have the potential to diffract to at least 2.0 Angstrom with optimization of post-crystal-growth treatment and cryoprotection. This should allow determination of the structure of this important and medically relevant membrane protein complex at near-atomic resolution and provide great detail of the mode of binding of substrates and inhibitors at the two substrate-binding sites.

  3. Simultaneous membrane interaction of amphipathic peptide monomers, self-aggregates and cargo complexes detected by fluorescence correlation spectroscopy.

    Science.gov (United States)

    Vasconcelos, Luís; Lehto, Tõnis; Madani, Fatemeh; Radoi, Vlad; Hällbrink, Mattias; Vukojević, Vladana; Langel, Ülo

    2018-02-01

    Peptides able to translocate cell membranes while carrying macromolecular cargo, as cell-penetrating peptides (CPPs), can contribute to the field of drug delivery by enabling the transport of otherwise membrane impermeable molecules. Formation of non-covalent complexes between amphipathic peptides and oligonucleotides is driven by electrostatic and hydrophobic interactions. Here we investigate and quantify the coexistence of distinct molecular species in multiple equilibria, namely peptide monomer, peptide self-aggregates and peptide/oligonucleotide complexes. As a model for the complexes, we used a stearylated peptide from the PepFect family, PF14 and siRNA. PF14 has a cationic part and a lipid part, resembling some characteristics of cationic lipids. Fluorescence correlation spectroscopy (FCS) and fluorescence cross-correlation spectroscopy (FCCS) were used to detect distinct molecular entities in solution and at the plasma membrane of live cells. For that, we labeled the peptide with carboxyrhodamine 6G and the siRNA with Cyanine 5. We were able to detect fluorescent entities with diffusional properties characteristic of the peptide monomer as well as of peptide aggregates and peptide/oligonucleotide complexes. Strategies to avoid peptide adsorption to solid surfaces and self-aggregation were developed and allowed successful FCS measurements in solution and at the plasma membrane. The ratio between the detected molecular species was found to vary with pH, peptide concentration and the proximity to the plasma membrane. The present results suggest that the diverse cellular uptake mechanisms, often reported for amphipathic CPPs, might result from the synergistic effect of peptide monomers, self-aggregates and cargo complexes, distributed unevenly at the plasma membrane. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Detection of inhomogeneities in membrane ohmic resistance in geometrically complex systems

    DEFF Research Database (Denmark)

    Svirskis, G; Hounsgaard, J; Gutman, A

    2000-01-01

    DC field-evoked transients in arbitrarily shaped neurons and syncytia were analyzed theoretically. In systems with homogeneous passive membrane properties, the transients develop much faster than the membrane discharges. Conductance of the proximal membrane could be larger due to the injury impos...

  5. Metalophthalocyanine complexes as ion-carriers in membrane-selective electrodes for detection of thiosalicylic acid

    International Nuclear Information System (INIS)

    Shahrokhian, Saeed; Souri, Ali

    2004-01-01

    The potentiometric response properties of several PVC-based membrane electrodes using phthalocyanine complexes of aluminum (AlPc), nickel (NiPc) and copper (CuPc) as anion carriers, toward thiosalicylic acid (TSA) were investigated. The influences of lipophilic ionic additives (cationic and anionic) and the pH of the buffered solutions were used for the interpretation of the mechanism of the potentiometric response of sensors. The sensitivity, linear range, detection limit, and potentiometric selectivity of the membrane sensors show a considerable dependence on the nature of central metal of the ionophore. The membrane electrodes based on AlPc demonstrate sub-Nernstian responses toward TSA over the range of 0.01 to 1x10 -5 M. In the case of NiPc and CuPc as ionophores and in the presence of trioctylmethyl ammonium (TOMA + ) as a cationic additive, a Nernstian response could be established in a range of 4 orders of magnitudes of TSA concentration (0.01 to 1x10 -6 M). The results of potentiometric investigations revealed that from thermodynamic point of view, the axial coordination of thiosalicylate with the central metal of NiPc and CuPc is more efficient with respect to AlPc. This preference in response to TSA was discussed on the basis of the softness nature of NiPc and CuPc and more affinity for coordination with the thiolate group of thiosalicylate as a soft anion. These potentiometric sensors manifest prominent advantages of high selectivity for TSA over the various inorganic and organic anions, fast response times and micromolar detection limits and can be used over a wide pH range of 4.0-8.0. The prepared electrodes based on NiPc and CuPc were successfully applied in the potentiometric titration of sub-milimolar quantities of Hg 2+ in aqueous solutions and very good recovery results were obtained in these measurements. The results of complexometric studies between Hg 2+ and TSA using electrodes based on NiPc and CuPc as indicator electrodes were compared with

  6. Highly sensitive oxygen sensors based on Cu(I) complex-polystyrene composite nanofibrous membranes prepared by electrospinning.

    Science.gov (United States)

    Wang, Yinghui; Li, Bin; Liu, Yanhong; Zhang, Liming; Zuo, Qinghui; Shi, Linfang; Su, Zhongmin

    2009-10-21

    The first optical oxygen sensor based on Cu(I) complex-polystyrene composite nanofibrous membranes, showing high sensitivity (I(0)/I(100) = 15.56), good linear Stern-Volmer characteristics (R(2) = 0.9966) and short response/recovery time (t(decrease) (s) = 7 and t(increase) (s) = 14), has been prepared; these results represent the best values reported for oxygen sensors based on Cu(I) complexes.

  7. Mitochondrial membrane potential in human neutrophils is maintained by complex III activity in the absence of supercomplex organisation

    NARCIS (Netherlands)

    van Raam, Bram J.; Sluiter, Wim; de Wit, Elly; Roos, Dirk; Verhoeven, Arthur J.; Kuijpers, Taco W.

    2008-01-01

    BACKGROUND: Neutrophils depend mainly on glycolysis for their energy provision. Their mitochondria maintain a membrane potential (Deltapsi(m)), which is usually generated by the respiratory chain complexes. We investigated the source of Deltapsi(m) in neutrophils, as compared to peripheral blood

  8. Membrane fusion

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    At Stanford University, Boxer lab, I worked on membrane fusion of small unilamellar lipid vesicles to flat membranes tethered to glass surfaces. This geometry closely resembles biological systems in which liposomes fuse to plasma membranes. The fusion mechanism was studied using DNA zippering...... between complementary strands linked to the two apposing membranes closely mimicking the zippering mechanism of SNARE fusion complexes....

  9. Iron-complexed adsorptive membrane for As(V) species in water

    International Nuclear Information System (INIS)

    Shinde, Rakesh N.; Das, Sadananda; Acharya, R.; Rajurkar, N.S.; Pandey, Ashok K.

    2012-01-01

    Highlights: ► Functionalized membrane was prepared by graft polymerization in host membrane. ► Fe 3+ ions fixed in membrane made it selective for As(V) ions. ► As(V) preconcentrated selectively in membrane samples was quantified by INAA. ► As(V) in ground water sample was easily quantified in 2–3 ppb using membrane. ► Total inorganic arsenic could be quantified by oxidation of As(III) to As(V). - Abstract: Selective preconcentration of a target analyte in the solid phase is an effective route not only to enhance detection limit of the conventional analytical method but also for elimination of interfering matrix. An adsorptive membrane was developed for selective preconcentration and quantification of ultra-trace (ppb) amounts of As(V) present in a variety of aqueous samples. The precursor membrane was prepared by UV-initiator induced graft polymerization of sulphate and phosphate bearing monomers (1:1 mol proportion) in pores of the host microporous poly(propylene) membrane. Fe 3+ ions were loaded in the precursor membrane to make it selective for As(V) ions. The presence of phosphate functional groups prevent leaching of Fe 3+ ions from the membrane when it comes in contact with solution like seawater having high ionic strength. The optimized membrane was characterized in terms of its physical structure, chemical structure and experimental conditions affecting As(V) uptake in the membrane. The possibility of quantifying total preconcentration of As content was also explored by converting As(III) to As(V). To quantify As(V), the membrane samples were subjected to instrumental neutron activation analysis (INAA). The studies carried in the present work showed that quantification of inorganic arsenic species in natural water samples is easily possible in 2–3 ppb concentration range.

  10. NMR spectroscopic and analytical ultracentrifuge analysis of membrane protein detergent complexes

    Directory of Open Access Journals (Sweden)

    Choe Senyon

    2007-11-01

    Full Text Available Abstract Background Structural studies of integral membrane proteins (IMPs are hampered by inherent difficulties in their heterologous expression and in the purification of solubilized protein-detergent complexes (PDCs. The choice and concentrations of detergents used in an IMP preparation play a critical role in protein homogeneity and are thus important for successful crystallization. Results Seeking an effective and standardized means applicable to genomic approaches for the characterization of PDCs, we chose 1D-NMR spectroscopic analysis to monitor the detergent content throughout their purification: protein extraction, detergent exchange, and sample concentration. We demonstrate that a single NMR measurement combined with a SDS-PAGE of a detergent extracted sample provides a useful gauge of the detergent's extraction potential for a given protein. Furthermore, careful monitoring of the detergent content during the process of IMP production allows for a high level of reproducibility. We also show that in many cases a simple sedimentation velocity measurement provides sufficient data to estimate both the oligomeric state and the detergent-to-protein ratio in PDCs, as well as to evaluate the homogeneity of the samples prior to crystallization screening. Conclusion The techniques presented here facilitate the screening and selection of the extraction detergent, as well as help to maintain reproducibility in the detergent exchange and PDC concentration procedures. Such reproducibility is particularly important for the optimization of initial crystallization conditions, for which multiple purifications are routinely required.

  11. The morphogenetic MreBCD proteins of Escherichia coli form an essential membrane-bound complex

    DEFF Research Database (Denmark)

    Kruse, Torben; Bork-Jensen, J.; Gerdes, Kenn

    2005-01-01

    . subtilis and C. crescentus, the mreB gene is essential. However, in E. coli, mreB was inferred not to be essential. Using a tight, conditional gene depletion system, we systematically investigated whether the E. coli mreBCD-encoded components were essential. We found that cells depleted of mreBCD became......D. In contrast, MreB and MreD did not interact in this assay. Thus, we conclude that the E. coli MreBCD form an essential membrane-bound complex. Curiously, MreB did not form cables in cell depleted for MreC, MreD or RodA, indicating a mutual interdependency between MreB filament morphology and cell shape. Based......MreB proteins of Escherichia coli, Bacillus subtilis and Caulobacter crescentus form actin-like cables lying beneath the cell surface. The cables are required to guide longitudinal cell wall synthesis and their absence leads to merodiploid spherical and inflated cells prone to cell lysis. In B...

  12. Crystallinity and order of poly(ethylene oxide)/lithium triflate complex confined in nanoporous membranes

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, Christina [Department of Chemical Engineering, The University of Tulsa, 800 S. Tucker Drive, Tulsa, OK 74104 (United States); Teeters, Dale [Department of Chemistry and Biochemistry, University of Tulsa, 800 S. Tucker Drive, Tulsa, OK 74104 (United States)], E-mail: dale-teeters@utulsa.edu

    2009-06-30

    The confinement of poly(ethylene oxide), PEO, electrolyte in pores of 13, 35, 55 and 100 nm in diameter in nanoporous alumina membranes was seen to have effects on the ionic conduction properties. Specific conductivity values for the PEO/lithium triflate complex in the 13 and 35 nm pores, for temperatures below the melt temperatures, were increased by a factor of four compared to the non-confined polymer and the 55 and 100 nm pore systems. Thermal analysis data indicate the melting temperature for the PEO electrolyte in the pores is directly proportional to the pore size such that as the pore size of confinement is decreased, the T{sub m} decreases as well. The same behavior is seen for the amount of crystallinity, with less crystallinity being observed as the pores become smaller. Perhaps the observed conduction behavior could be attributed to less crystallinity. However, it is known that confinement of polyethers in pores results in stretching and ordering of the backbone and that such ordering can increase ion conduction. This ordering would seem to be the major factor involved in these results. The enhanced conduction only being seen in the 13 and 35 nm pores and not the 55 and 100 nm pores is attributed to the larger size for the latter which allows a more bulk-like behavior with less ordering.

  13. The Structure of Herpesvirus Fusion Glycoprotein B-Bilayer Complex Reveals the Protein-Membrane and Lateral Protein-Protein Interaction

    NARCIS (Netherlands)

    Maurer, Ulrike E.; Zeev-Ben-Mordehai, Tzviya; Pandurangan, Arun Prasad; Cairns, Tina M.; Hannah, Brian P.; Whitbeck, J. Charles; Eisenberg, Roselyn J.; Cohen, Gary H.; Topf, Maya; Huiskonen, Juha T.; Gruenewald, Kay

    2013-01-01

    Glycoprotein B (gB) is a key component of the complex herpesvirus fusion machinery. We studied membrane interaction of two gB ectodomain forms and present an electron cryotomography structure of the gB-bilayer complex. The two forms differed in presence or absence of the membrane proximal region

  14. BID is cleaved by caspase-8 within a native complex on the mitochondrial membrane

    NARCIS (Netherlands)

    Schug, Z. T.; Gonzalvez, F.; Houtkooper, R. H.; Vaz, F. M.; Gottlieb, E.

    2011-01-01

    Caspase-8 stably inserts into the mitochondrial outer membrane during extrinsic apoptosis. Inhibition of caspase-8 enrichment on the mitochondria impairs caspase-8 activation and prevents apoptosis. However, the function of active caspase-8 on the mitochondrial membrane remains unknown. In this

  15. An amperometric immunosensor with a DNA polyion complex membrane/gold nanoparticles-backbone for antibody immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Li Na [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Zhao Hongwen [Department of kidney, Southwest Hospital, The Third Military Medical University, Chongqing 400038 (China); Yuan Ruo [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)], E-mail: yuanruo@swu.edu.cn; Peng Kanfu [Department of kidney, Southwest Hospital, The Third Military Medical University, Chongqing 400038 (China)], E-mail: talkmanpeng@sohu.com; Chai Yaqin [Chongqing Key Laboratory of Analytical Chemistry, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2008-12-30

    A new and effective strategy for constructing a mediator-type amperometric immunosensor based on the unique characteristics of DNA-PDDA polyion complex membrane and gold nanoparticles was described. A poly(toluidine blue O) (PTOB) film deposited on a DNA-PDDA polyion complex membrane surface, exhibited excellent electrochemical redox property. Stable and well-defined redox peaks for the PTOB redox couple were obtained in pH 6.5 phosphate buffer solution (PBS). The introduction of DNA-PDDA polyion complex film not only enhanced the electrode surface area for construction of efficient biosensors, but also acted as a charge carrier to facilitate the electron transfer. Moreover, as a host matrix, the DNA-PDDA polyion complex could firmly immobilise the PTOB membrane on the surface of electrode by strong interaction. With carcinoembryonic antigen (CEA) as a model antigen, the presence of gold nanoparticles provided a congenial microenvironment for adsorbing biomolecules and decreased the electron transfer impedance. The fabrication process of the immunosensor was characterized by atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The immunosensor displayed a high-sensitivity for the detection of CEA and had good correlation for the detection of CEA in the range of 0.5-120.0 ng/ml with a detection limit of 0.3 ng/ml (estimated at a signal-to-noise ratio of 3). The proposed immunosensor showed a broader linear range, good reproducibility, and storage stability.

  16. Evaluation of hydroacid complex in the forward osmosis–membrane distillation (FO–MD) system for desalination

    KAUST Repository

    Wang, Peng

    2015-11-01

    The incorporation of membrane distillation (MD) into forward osmosis (FO) provides process sustainability to regenerate the draw solution and to produce clean water simultaneously. However, the reverse salt flux is the major hurdle in the FO-MD system because it not only reduces the effective osmotic driving force across the membrane but also increases the replenishment cost and scaling issue. For the first time, a hydroacid complex with abundant hydrophilic groups and ionic species is evaluated as the draw solutes in the hybrid FO-MD system consisting of multi-bore PVDF MD membranes for seawater/brackish desalination. In order to evaluate the practicality of the hydroacid complex in the FO-MD system, FO and MD experiments were conducted at elevated temperatures and concentrations. The hydroacid complex has displayed desired properties such as high solubility, low viscosity, excellent thermal stability and minimal reverse salt flux suitable for FO and MD operations. FO-MD desalination process was demonstrated with a highest seawater desalination flux of 6/32 LMH (FO/MD). This study may open up the prospective of employing the hydroacid complex as the draw solute in FO-MD hybrid systems for seawater /brackish desalination. © 2015 Elsevier B.V.

  17. Contribution of the complement Membrane Attack Complex to the bactericidal activity of human serum.

    Science.gov (United States)

    Berends, Evelien T M; Mohan, Sarbani; Miellet, Willem R; Ruyken, Maartje; Rooijakkers, Suzan H M

    2015-06-01

    Direct killing of Gram-negative bacteria by serum is usually attributed to the Membrane Attack Complex (MAC) that is assembled upon activation of the complement system. In serum bactericidal assays, the activity of the MAC is usually blocked by a relatively unspecific method in which certain heat-labile complement components are inactivated at 56°C. The goal of this study was to re-evaluate MAC-driven lysis towards various Gram-negative bacteria. Instead of using heat-treatment, we included the highly specific C5 cleavage inhibitor OmCI to specifically block the formation of the MAC. Using a C5 conversion analysis tool, we monitored the efficacy of the inhibitor during the incubations. Our findings indicate that 'serum-sensitive' bacteria are not necessarily killed by the MAC. Other heat-labile serum factors can contribute to serum bactericidal activity. These unidentified factors are most potent at serum concentrations of 10% and higher. Furthermore, we also find that some bacteria can be killed by the MAC at a slower rate. Our data demonstrate the requirement for the use of specific inhibitors in serum bactericidal assays and revealed that the classification of serum-sensitive and resistant strains needs re-evaluation. Moreover, it is important to determine bacterial viability at multiple time intervals to differentiate serum susceptibility between bacterial species. In conclusion, these data provide new insights into bacterial killing by the humoral immune system and may guide future vaccine development studies for the treatment of pathogenic serum-resistant bacteria. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Complex interplay between the P-glycoprotein multidrug efflux pump and the membrane: its role in modulating protein function

    Directory of Open Access Journals (Sweden)

    Frances Jane Sharom

    2014-03-01

    Full Text Available Multidrug resistance in cancer is linked to expression of the P-glycoprotein multidrug transporter (Pgp, ABCB1, which exports many structurally diverse compounds from cells. Substrates first partition into the bilayer and then interact with a large flexible binding pocket within the transporter’s transmembrane regions. Pgp has been described as a hydrophobic vacuum cleaner or an outwardly-directed drug/lipid flippase. Recent X-ray crystal structures have shed some light on the nature of the drug-binding pocket and suggested routes by which substrates can enter it from the membrane. Detergents have profound effects on Pgp function, and several appear to be substrates. Biochemical and biophysical studies in vitro, some using purified reconstituted protein, have explored the effects of the membrane environment. They have demonstrated that Pgp is involved in a complex relationship with its lipid environment, which modulates the behaviour of its substrates, as well as various functions of the protein, including ATP hydrolysis, drug binding and drug transport. Membrane lipid composition and fluidity, phospholipid headgroup and acyl chain length all influence Pgp function. Recent studies focusing on thermodynamics and kinetics have revealed some important principles governing Pgp-lipid and substrate-lipid interactions, and how these affect drug binding and transport. In some cells, Pgp is associated with cholesterol-rich microdomains which may modulate its functions. The relationship between Pgp and cholesterol remains an open question; however it clearly affects several aspects of its function in addition to substrate-membrane partitioning. The action of Pgp modulators appears to depend on their membrane permeability, and membrane fluidizers and surfactants reverse drug resistance, likely via an indirect mechanism. A detailed understanding of how the membrane affects Pgp substrates and Pgp’s catalytic cycle may lead to new strategies to combat

  19. Targeting and Assembly of Components of the TOC Protein Import Complex at the Chloroplast Outer Envelope Membrane

    Directory of Open Access Journals (Sweden)

    Lynn G.L. Richardson

    2014-06-01

    Full Text Available The translocon at the outer envelope membrane of chloroplasts (TOC initiates the import of thousands of nuclear encoded preproteins required for chloroplast biogenesis and function. The multimeric TOC complex contains two GTP-regulated receptors, Toc34 and Toc159, which recognize the transit peptides of preproteins and initiate protein import through a β–barrel membrane channel, Toc75. Different isoforms of Toc34 and Toc159 assemble with Toc75 to form structurally and functionally diverse translocons, and the composition and levels of TOC translocons is required for the import of specific subsets of coordinately expressed proteins during plant growth and development. Consequently, the proper assembly of the TOC complexes is key to ensuring organelle homeostasis. This review will focus on our current knowledge of the targeting and assembly of TOC components to form functional translocons at the outer membrane. Our analyses reveal that the targeting of TOC components involves elements common to the targeting of other outer membrane proteins, but also include unique features that appear to have evolved to specifically facilitate assembly of the import apparatus.

  20. Rab11A-controlled assembly of the inner membrane complex is required for completion of apicomplexan cytokinesis.

    Directory of Open Access Journals (Sweden)

    Carolina Agop-Nersesian

    2009-01-01

    Full Text Available The final step during cell division is the separation of daughter cells, a process that requires the coordinated delivery and assembly of new membrane to the cleavage furrow. While most eukaryotic cells replicate by binary fission, replication of apicomplexan parasites involves the assembly of daughters (merozoites/tachyzoites within the mother cell, using the so-called Inner Membrane Complex (IMC as a scaffold. After de novo synthesis of the IMC and biogenesis or segregation of new organelles, daughters bud out of the mother cell to invade new host cells. Here, we demonstrate that the final step in parasite cell division involves delivery of new plasma membrane to the daughter cells, in a process requiring functional Rab11A. Importantly, Rab11A can be found in association with Myosin-Tail-Interacting-Protein (MTIP, also known as Myosin Light Chain 1 (MLC1, a member of a 4-protein motor complex called the glideosome that is known to be crucial for parasite invasion of host cells. Ablation of Rab11A function results in daughter parasites having an incompletely formed IMC that leads to a block at a late stage of cell division. A similar defect is observed upon inducible expression of a myosin A tail-only mutant. We propose a model where Rab11A-mediated vesicular traffic driven by an MTIP-Myosin motor is necessary for IMC maturation and to deliver new plasma membrane to daughter cells in order to complete cell division.

  1. Targeting and assembly of components of the TOC protein import complex at the chloroplast outer envelope membrane.

    Science.gov (United States)

    Richardson, Lynn G L; Paila, Yamuna D; Siman, Steven R; Chen, Yi; Smith, Matthew D; Schnell, Danny J

    2014-01-01

    The translocon at the outer envelope membrane of chloroplasts (TOC) initiates the import of thousands of nuclear encoded preproteins required for chloroplast biogenesis and function. The multimeric TOC complex contains two GTP-regulated receptors, Toc34 and Toc159, which recognize the transit peptides of preproteins and initiate protein import through a β-barrel membrane channel, Toc75. Different isoforms of Toc34 and Toc159 assemble with Toc75 to form structurally and functionally diverse translocons, and the composition and levels of TOC translocons is required for the import of specific subsets of coordinately expressed proteins during plant growth and development. Consequently, the proper assembly of the TOC complexes is key to ensuring organelle homeostasis. This review will focus on our current knowledge of the targeting and assembly of TOC components to form functional translocons at the outer membrane. Our analyses reveal that the targeting of TOC components involves elements common to the targeting of other outer membrane proteins, but also include unique features that appear to have evolved to specifically facilitate assembly of the import apparatus.

  2. Multi-membrane-bound structures of Apicomplexa: II. the ovoid mitochondrial cytoplasmic (OMC) complex of Toxoplasma gondii tachyzoites.

    Science.gov (United States)

    Köhler, Sabine

    2006-03-01

    Apicomplexa including the causative agents of toxoplasmosis and malaria reportedly possess one or few tubular-shaped mitochondria that permeate, more or less branched, throughout these unicellular parasites. Electron micrographs generated herein from serial-sectioned Toxoplasma gondii tachyzoites demonstrated, however, a greater diversity regarding both the shape of the cultured parasite's single mitochondrion and its sub-structural organization. Moreover, a unique subcellular construction was detected that basically comprised a pouch-shaped subdivision of the tachyzoite mitochondrion plus a fraction of parasitic cytoplasm enclosed therein. This composite assembling, termed ovoid mitochondrial cytoplasmic (OMC) complex, characteristically displayed a highly reduced matrix lumen of its mitochondrial border construction, which furthermore often failed to possess any cristae or contained tightly pleated cristae, thus creating a pouch-shaped multi-laminar wall of four or more membranous layers, respectively. Given this architecture, cross-sectioned OMC complexes of T. gondii tachyzoites frequently mimicked in size and shape the parasites' plastid-like organelle (apicoplast). Moreover, like the apicoplast, the OMC complex was often found adjacent to the tachyzoite's single Golgi complex and constantly located in close proximity to the outer membrane of the parasite's nuclear envelope. The T. gondii OMC complex differed, however, from the apicoplast in its exact fine structural organization and a stage-restricted presence that was apparently linked to mitochondrial growth and/or division. Any special function(s) possibly performed by the T. gondii OMC complex remains, nevertheless, to be elucidated.

  3. Kinetic and spectroscopic studies of cytochrome b-563 in isolated cytochrome b/f complex and in thylakoid membranes

    Energy Technology Data Exchange (ETDEWEB)

    Hind, G.; Clark, R.D.; Houchins, J.P.

    1983-01-01

    Extensive studies, performed principally by Hauska, Hurt and collaborators, have shown that a cytochrome (cyt) b/f complex isolated from photosynthetic membranes of spinach or Anabaena catalyzes electron transport from plastoquinol (PQH/sub 2/) to plastocyanin or algal cyt c-552. The complex from spinach thylakoids generated a membrane potential when reconstituted into liposomes, and although the electrogenic mechanism remains unknown, a key role for cyt b-563 is widely accepted. Electrogenesis by a Q-cycle mechanism requires a plastoquinone (PQ) reductase to be associated with the stromal side of the thylakoid b/f complex though this activity has yet to be demonstrated. It seemed possible that more gentle isolation of the complex might yield a form containing additional polypeptides, perhaps including a PQ reductase or a component involved in returning electrons from reduced ferredoxin to the complex in cyclic electron flow. Optimization of the isolation of cyt b/f complex for Hybrid 424 spinach from a growth room was also required. The procedure we devised is compared to the protocol of Hurt and Hauska (1982). 13 references.

  4. The Cell Wall Teichuronic Acid Synthetase (TUAS Is an Enzyme Complex Located in the Cytoplasmic Membrane of Micrococcus luteus

    Directory of Open Access Journals (Sweden)

    Lingyi Lynn Deng

    2010-01-01

    composed of disaccharide repeating units [-4-β-D-ManNAcAp-(1→6α-D-Glcp−1-]n, which is covalently anchored to the peptidoglycan on the inner cell wall and extended to the outer surface of the cell envelope. An enzyme complex responsible for the TUA chain biosynthesis was purified and characterized. The 440 kDa enzyme complex, named teichuronic acid synthetase (TUAS, is an octomer composed of two kinds of glycosyltransferases, Glucosyltransferase, and ManNAcA-transferase, which is capable of catalyzing the transfer of disaccharide glycosyl residues containing both glucose and the N-acetylmannosaminuronic acid residues. TUAS displays hydrophobic properties and is found primarily associated with the cytoplasmic membrane. The purified TUAS contains carotinoids and lipids. TUAS activity is diminished by phospholipase digestion. We propose that TUAS serves as a multitasking polysaccharide assembling station on the bacterial membrane.

  5. [Effect of damage integrity rat brain synaptic membranes on the functional activity GABA(A)-receptor/Cl(-)-ionophore complex in the CNC].

    Science.gov (United States)

    Rebrov, I G; Kalinina, M V

    2013-01-01

    Functional activity of the CGABA(A)-receptor/Cl(-) ionophore complex was investigated the muscimol-stimulated entry of the radioactive isotope 36Cl(-) in synaptoneurosomes in changing the structure and permeability of neuronal membranes. Integrity of the membranes was damaged by removal of Ca(+2) and Mg(+2) from the incubation medium and by the method of freezing-thawing synaptoneurosomes. In both cases, an increase in basal 36Cl(-) entry into synaptoneurosomes, indicating increased nonspecific permeability of neuronal membranes, and decreased activity the CABA(A)-receptor/Cl(-) ionophore complex. The conclusion about the relationship of processes damage neuronal membranes and reducing the inhibitory processes in the epileptic focus.

  6. Sedimentation properties of DNA-membrane complexes and yield of DNA breaks at irradiation of mammalian cells

    International Nuclear Information System (INIS)

    Erzgraber, G.; Kozubek, S.; Lapidus, I.L.

    1985-01-01

    The dependence of the relative sedimentation velocity of DNA-membrane complexes on the dose of irradiation and time of incubation of Chinese Hamster cells is analysed. It is concluded that the initial part of the curve provides the information on the occurrence of single strand breaks in DNA; the position of the local maximum allows us to calculate the yield of DNA double strand breaks. The reparation decay constant can be estimated as well

  7. The interaction of equine lysozyme:oleic acid complexes with lipid membranes suggests a cargo off-loading mechanism

    DEFF Research Database (Denmark)

    Nielsen, Søren Bang; Wilhelm, Kristina; Vad, Brian

    2010-01-01

    The normal function of equine lysozyme (EL) is the hydrolysis of peptidoglycan residues of bacterial cell walls. EL is closely related to alpha-lactalbumins with respect to sequence and structure and further possesses the calcium binding site of alpha-lactalbumins. Recently, EL multimeric complexes...... suggest that ELOA may act as an OA carrier and facilitate OA transfer to the membrane. ELOA's properties illustrate that protein folding variants may possess specific functional properties distinct from the native protein....

  8. Coordination kinetics of different metal ions with the amidoximated polyacrylonitrile nanofibrous membranes and catalytic behaviors of their complexes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Fu; Dong, Yong Chun; Kang, Wei Min; Cheng, Bowen; Qu, Xiang; Cui, Guixin [School of Textiles, Tianjin Polytechnic University, Tianjin (China)

    2016-12-15

    Two transition metal ions (Fe{sup 3+} and Cu{sup 2+}) and a rare earth metal ion (Ce{sup 3+}) were selected to coordinate with amidoximated polyacrylonitrile (PAN) nanofibrous membrane for preparing three metal modified PAN nanofibrous membrane complexes (M-AO-n-PANs, M = Fe, Cu, or Ce) as the heterogeneous Fenton catalysts for the dye degradation in water under visible irradiation. The coordination kinetics of three metal ions with modified PAN nanofibrous membranes was studied and the catalytic properties of the resulting complexes were also compared. The results indicated that increasing metal ion concentrations in solution or higher coordination temperature led to a significant increase in metal content, particularly in Fe and Cu contents of the complexes. Their coordination process could be described using Langmuir isotherm and pseudo-second-order kinetic equations. Moreover, Fe-AO-n-PAN had the best photocatalytic efficiency for the dye degradation in acidic medium, but a lower photocatalytic activity than Cu-AO-n-PAN in alkali medium.

  9. Defining a Viral Membrane-Remodeling Complex on an Atomic Level.

    Science.gov (United States)

    Roberts, Mary F

    2017-01-03

    The Aichi RNA virus remodels host membranes by conscripting two host proteins, PI4KIIIβ (to generate PI4P in the remodeled vesicle) and ACBD3 (that tightly binds PI4KIIIβ), and localizing them on target membranes via Aichi protein 3A. In this issue of Structure, McPhail et al. (2017) reveal structural glimpses of the interfaces involved in this protein threesome using HDX-MS. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Separation of metallic cations by means of coupled filtration on a ceramic membrane. Use of a complexing heteropolyanion

    International Nuclear Information System (INIS)

    Brun, Stephane

    1999-01-01

    In the field of the high level nuclear waste reprocessing, the Nuclear French Agency is currently carrying out studies on several processes (including the SESAME process) which aim at separating radioactive elements in order to dispose them specifically or to transmute them. One of these processes concerns the selective extraction of americium at an upper oxidation state than Ill. This work deals with the separation of Am(IV) from Ln(Ill) by means of complexation-coupled tangential filtration on alumina-titanium ceramic membranes. The chosen selective complexing agent is a lacunar heteropolyanion from the tungstophosphate family α 2 P 2 W 17 O 61 10- , which synthesis and various properties in solution have been studied. The polyanion stability in 0.5 M nitric solution strongly depends on the quality of the synthesised product. Two analytical techniques were developed to check the quality of the synthesised sets: 31 P NMR and arsenazo-lanthanum complexometric titration. The separation studies on the cerium (IV)-neodymium (Ill) system were carried out to simulate americium(IV)/lanthanides(Ill) system. For the two alumina-titanium membranes studied (ultrafiltration and nano-filtration), the solvent flow can be described through a capillary mechanism which is characteristic of porous membranes. The ion transfer through the membranes, mainly governed by electrostatic interactions, strongly depends on the ionic strength at the membrane-solution interface. The best separation results, using nano-filtration, still remain below the expected performances, with a Ce(IV)/Nd(Ill) separation factor of 35 on a single stage in 0,5 M nitric medium. (author) [fr

  11. SARS-coronavirus replication/transcription complexes are membrane-protected and need a host factor for activity in vitro.

    Directory of Open Access Journals (Sweden)

    Martijn J van Hemert

    2008-05-01

    Full Text Available SARS-coronavirus (SARS-CoV replication and transcription are mediated by a replication/transcription complex (RTC of which virus-encoded, non-structural proteins (nsps are the primary constituents. The 16 SARS-CoV nsps are produced by autoprocessing of two large precursor polyproteins. The RTC is believed to be associated with characteristic virus-induced double-membrane structures in the cytoplasm of SARS-CoV-infected cells. To investigate the link between these structures and viral RNA synthesis, and to dissect RTC organization and function, we isolated active RTCs from infected cells and used them to develop the first robust assay for their in vitro activity. The synthesis of genomic RNA and all eight subgenomic mRNAs was faithfully reproduced by the RTC in this in vitro system. Mainly positive-strand RNAs were synthesized and protein synthesis was not required for RTC activity in vitro. All RTC activity, enzymatic and putative membrane-spanning nsps, and viral RNA cosedimented with heavy membrane structures. Furthermore, the pelleted RTC required the addition of a cytoplasmic host factor for reconstitution of its in vitro activity. Newly synthesized subgenomic RNA appeared to be released, while genomic RNA remained predominantly associated with the RTC-containing fraction. RTC activity was destroyed by detergent treatment, suggesting an important role for membranes. The RTC appeared to be protected by membranes, as newly synthesized viral RNA and several replicase/transcriptase subunits were protease- and nuclease-resistant and became susceptible to degradation only upon addition of a non-ionic detergent. Our data establish a vital functional dependence of SARS-CoV RNA synthesis on virus-induced membrane structures.

  12. A major prolactin-binding complex on human milk fat globule membranes contains cyclophilins A and B: the complex is not the prolactin receptor.

    Science.gov (United States)

    Lorenson, Mary Y; Ueda, Eric K; Chen, KuanHui E; Walker, Ameae M

    2012-03-01

    Prolactin (PRL) in milk influences maturation of gastrointestinal epithelium and development of both the hypothalamo-pituitary and immune systems of offspring. Here, we demonstrate that most PRL in human milk is part of a novel, high-affinity, multicomponent binding complex found on the milk fat globule membrane and not in whey. To examine properties of the complex, a sensitive ELISA was developed such that human PRL (hPRL) binding to the complex was measured by loss of hPRL detectability; thus, as much as 50 ng of hPRL was undetectable in the presence of 10 μl of human milk. Using the same methodology, no comparable complex formation was observed with human serum or amniotic fluid. hPRL complexation in milk was rapid, time dependent, and cooperative. Antibodies to or competitors of the hPRL receptor (placental lactogen and growth hormone) showed the hPRL receptor was not involved in the complex. However, hPRL complexation was antagonized by cyclosporine A and anti-cyclophilins. The complex was very stable, resisting dissociation in SDS, urea, and dithiothreitol. Western analysis revealed an ∼75-kDa complex that included hPRL, cyclophilins A and B, and a 16-kDa cyclophilin A. Compared with noncomplexed hPRL, complexed hPRL in whole milk showed similar activation of STAT5 but markedly delayed activation of ERK. Alteration of signaling suggests that complex formation may alter hPRL biological activity. This is the first report of a unique, multicomponent, high-capacity milk fat reservoir of hPRL; all other analyses of milk PRL have utilized defatted milk.

  13. NMR-Based Amide Hydrogen-Deuterium Exchange Measurements for Complex Membrane Proteins: Development and Critical Evaluation

    Science.gov (United States)

    Czerski, Lech; Vinogradova, Olga; Sanders, Charles R.

    2000-01-01

    A method for measuring site-specific amide hydrogen-deuterium exchange rates for membrane proteins in bilayers is reported and evaluated. This method represents an adaptation and extension of the approach of Dempsey and co-workers (Biophys. J. 70, 1777-1788 (1996)) and is based on reconstituting 15N-labeled membrane proteins into phospholipid bilayers, followed by lyophilization and rehydration with D2O or H2O (control). Following incubation for a time t under hydrated conditions, samples are again lyophilized and then solubilized in an organic solvent system, where 1H-15N HSQC spectra are recorded. Comparison of spectra from D2O-exposed samples to spectra from control samples yields the extent of the H-D exchange which occurred in the bilayers during time t. Measurements are site specific if specific 15N labeling is used. The first part of this paper deals with the search for a suitable solvent system in which to solubilize complex membrane proteins in an amide "exchange-trapped" form for NMR quantitation of amide peak intensities. The second portion of the paper documents application of the overall procedure to measuring site-specific amide exchange rates in diacylglycerol kinase, a representative integral membrane protein. Both the potential usefulness and the significant limitations of the new method are documented.

  14. Complexation induced phase separation: preparation of composite membranes with a nanometer thin dense skin loaded with metal ions

    KAUST Repository

    Villalobos Vazquez de la Parra, Luis Francisco

    2015-04-21

    We present the development of a facile phase-inversion method for forming asymmetric membranes with a precise high metal ion loading capacity in only the dense layer. The approach combines the use of macromolecule-metal intermolecular complexes to form the dense layer of asymmetric membranes with nonsolvent-induced phase separation to form the porous support. This allows the independent optimization of both the dense layer and porous support while maintaining the simplicity of a phase-inversion process. Moreover, it facilitates control over (i) the thickness of the dense layer throughout several orders of magnitude—from less than 15 nm to more than 6 μm, (ii) the type and amount of metal ions loaded in the dense layer, (iii) the morphology of the membrane surface, and (iv) the porosity and structure of the support. This simple and scalable process provides a new platform for building multifunctional membranes with a high loading of well-dispersed metal ions in the dense layer.

  15. Role for ribosome-associated complex and stress-seventy subfamily B (RAC-Ssb) in integral membrane protein translation.

    Science.gov (United States)

    Acosta-Sampson, Ligia; Döring, Kristina; Lin, Yuping; Yu, Vivian Y; Bukau, Bernd; Kramer, Günter; Cate, Jamie H D

    2017-12-01

    Targeting of most integral membrane proteins to the endoplasmic reticulum is controlled by the signal recognition particle, which recognizes a hydrophobic signal sequence near the protein N terminus. Proper folding of these proteins is monitored by the unfolded protein response and involves protein degradation pathways to ensure quality control. Here, we identify a new pathway for quality control of major facilitator superfamily transporters that occurs before the first transmembrane helix, the signal sequence recognized by the signal recognition particle, is made by the ribosome. Increased rates of translation elongation of the N-terminal sequence of these integral membrane proteins can divert the nascent protein chains to the ribosome-associated complex and stress-seventy subfamily B chaperones. We also show that quality control of integral membrane proteins by ribosome-associated complex-stress-seventy subfamily B couples translation rate to the unfolded protein response, which has implications for understanding mechanisms underlying human disease and protein production in biotechnology. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. Cobalt(II)-selective membrane sensor based on a [Me2(13)dieneN4] macrocyclic cobalt complex.

    Science.gov (United States)

    Singh, Ashok Kumar; Saxena, Puja; Mehtab, Sameena; Panwar, Amit

    2006-08-01

    A new poly(vinyl chloride)-based membrane was fabricated with the cobalt(II) complex of 2,4-dimethyl-1,5,8,11-tetraazacyclotrideca-1,4-diene [Me2(13)dieneN4] as an ion carrier. The membrane composition was Co2+ complex/PVC/NaTPB/DBP 15:50:15:20 (w/w). The sensor exhibited a Nernstian response for Co2+ ions over a wide concentration range (7.94x10(-6)-1.0x10(-1) M) at pH 2.5-7.0, a response time of 10 s, and it could be used for 3 months without any significant divergence in potential. The proposed membrane sensor exhibited good selectivity for Co2+ over a wide variety of other metal ions and in mixtures containing up to 25% (v/v) non-aqueous content. The sensor was successfully used as an indicator electrode in the potentiometric titration of Co2+ with EDTA and the direct determination of Co2+ in real samples.

  17. CELLULOSE SYNTHASE INTERACTIVE1 Is Required for Fast Recycling of Cellulose Synthase Complexes to the Plasma Membrane in Arabidopsis

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Lei; Singh, Abhishek; Bashline, Logan; Li, Shundai; Yingling, Yaroslava G.; Gu, Ying

    2015-10-06

    Plants are constantly subjected to various biotic and abiotic stresses and have evolved complex strategies to cope with these stresses. For example, plant cells endocytose plasma membrane material under stress and subsequently recycle it back when the stress conditions are relieved. Cellulose biosynthesis is a tightly regulated process that is performed by plasma membrane-localized cellulose synthase (CESA) complexes (CSCs). However, the regulatory mechanism of cellulose biosynthesis under abiotic stress has not been well explored. In this study, we show that small CESA compartments (SmaCCs) or microtubule-associated cellulose synthase compartments (MASCs) are critical for fast recovery of CSCs to the plasma membrane after stress is relieved in Arabidopsis thaliana. This SmaCC/MASC-mediated fast recovery of CSCs is dependent on CELLULOSE SYNTHASE INTERACTIVE1 (CSI1), a protein previously known to represent the link between CSCs and cortical microtubules. Independently, AP2M, a core component in clathrin-mediated endocytosis, plays a role in the formation of SmaCCs/MASCs. Together, our study establishes a model in which CSI1-dependent SmaCCs/MASCs are formed through a process that involves endocytosis, which represents an important mechanism for plants to quickly regulate cellulose synthesis under abiotic stress.

  18. Psp Stress Response Proteins Form a Complex with Mislocalized Secretins in theYersinia enterocoliticaCytoplasmic Membrane.

    Science.gov (United States)

    Srivastava, Disha; Moumene, Amal; Flores-Kim, Josué; Darwin, Andrew J

    2017-09-12

    The bacterial phage shock protein system (Psp) is a conserved extracytoplasmic stress response that is essential for the virulence of some pathogens, including Yersinia enterocolitica It is induced by events that can compromise inner membrane (IM) integrity, including the mislocalization of outer membrane pore-forming proteins called secretins. In the absence of the Psp system, secretin mislocalization permeabilizes the IM and causes rapid cell death. The Psp proteins PspB and PspC form an integral IM complex with two independent roles. First, the PspBC complex is required to activate the Psp response in response to some inducing triggers, including a mislocalized secretin. Second, PspBC are sufficient to counteract mislocalized secretin toxicity. Remarkably, secretin mislocalization into the IM induces psp gene expression without significantly affecting the expression of any other genes. Furthermore, psp null strains are killed by mislocalized secretins, whereas no other null mutants have been found to share this specific secretin sensitivity. This suggests an exquisitely specific relationship between secretins and the Psp system, but there has been no mechanism described to explain this. In this study, we addressed this deficiency by using a coimmunoprecipitation approach to show that the Psp proteins form a specific complex with mislocalized secretins in the Y. enterocolitica IM. Importantly, analysis of different secretin mutant proteins also revealed that this interaction is absolutely dependent on a secretin adopting a multimeric state. Therefore, the Psp system has evolved with the ability to detect and detoxify dangerous secretin multimers while ignoring the presence of innocuous monomers. IMPORTANCE The phage shock protein (Psp) response has been linked to important phenotypes in diverse bacteria, including those related to antibiotic resistance, biofilm formation, and virulence. This has generated widespread interest in understanding various aspects of

  19. Two-dimensional Al hydroxide interaction with cancerous cell membrane building units: Complexed free energy and orientation analysis

    Science.gov (United States)

    Tsukanov, A. A.; Psakhie, S. G.

    2017-09-01

    The application of hierarchical nanoparticles based on metal hydroxides in biomedicine, including anticancer therapy and medical imaging, is a rapidly developing field. Low-dimensional aluminum oxyhydroxide nanomaterials (AlOOH-NM) are quite promising base to develop hybrid theranostic nano-agents with core-shell architecture, which is determined by AlOOH-NMs physicochemical properties such as: large specific surface area, pH-dependent charge, amphoteric behavior, high surface density of polar groups capable to form non-covalent bonds, low or null cytotoxicity and biocompatibility. Characterization of the system behavior within interface between NM and plasmatic membrane is crucial for the understanding of nano-agent—cell interaction. In the present work the complex in silico study including the free energy estimation and orientation analysis of phosphatidylcholine (POPC) and phosphatidylethanolamine (POPE) lipids interacting with AlOOH nanosheet was conducted to understand the effect of such nanomaterial on cancerous cell plasmatic membrane.

  20. Computational Approaches for Designing Protein/Inhibitor Complexes and Membrane Protein Variants

    Science.gov (United States)

    Vijayendran, Krishna Gajan

    Drug discovery of small-molecule protein inhibitors is a vast enterprise that involves several scientific disciplines (i.e. genomics, cell biology, x-ray crystallography, chemistry, computer science, statistics), with each discipline focusing on a particular aspect of the process. In this thesis, I use computational and experimental approaches to explore the most fundamental aspect of drug discovery: the molecular interactions of small-molecules inhibitors with proteins. In Part I (Chapters I and II), I describe how computational docking approaches can be used to identify structurally diverse molecules that can inhibit multiple protein targets in the brain. I illustrate this approach using the examples of microtubule-stabilizing agents and inhibitors of cyclooxygenase(COX)-I and 5-lipoxygenase (5-LOX). In Part II (Chapters III and IV), I focus on membrane proteins, which are notoriously difficult to work with due to their low natural abundances, low yields for heterologous over expression, and propensities toward aggregation. I describe a general approach for designing water-soluble variants of membrane proteins, for the purpose of developing cell-free, label-free, detergent-free, solution-phase studies of protein structure and small-molecule binding. I illustrate this approach through the design of a water-soluble variant of the membrane protein Smoothened, wsSMO. This wsSMO stands to serve as a first-step towards developing membrane protein analogs of this important signaling protein and drug target.

  1. Direct coupling of supported liquid membranes to capillary electrophoresis for analysis of complex samples: A tutorial

    Czech Academy of Sciences Publication Activity Database

    Kubáň, Pavel; Boček, Petr

    2013-01-01

    Roč. 787, JUL (2013), s. 10-23 ISSN 0003-2670 R&D Projects: GA ČR(CZ) GA13-05762S Institutional support: RVO:68081715 Keywords : capillary electrophoresis * supported liquid membranes * direct coupling Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.517, year: 2013

  2. Selective laser melting-enabled electrospinning: Introducing complexity within electrospun membranes.

    Science.gov (United States)

    Paterson, Thomas E; Beal, Selina N; Santocildes-Romero, Martin E; Sidambe, Alfred T; Hatton, Paul V; Asencio, Ilida Ortega

    2017-06-01

    Additive manufacturing technologies enable the creation of very precise and well-defined structures that can mimic hierarchical features of natural tissues. In this article, we describe the development of a manufacturing technology platform to produce innovative biodegradable membranes that are enhanced with controlled microenvironments produced via a combination of selective laser melting techniques and conventional electrospinning. This work underpins the manufacture of a new generation of biomaterial devices that have significant potential for use as both basic research tools and components of therapeutic implants. The membranes were successfully manufactured and a total of three microenvironment designs (niches) were chosen for thorough characterisation. Scanning electron microscopy analysis demonstrated differences in fibre diameters within different areas of the niche structures as well as differences in fibre density. We also showed the potential of using the microfabricated membranes for supporting mesenchymal stromal cell culture and proliferation. We demonstrated that mesenchymal stromal cells grow and populate the membranes penetrating within the niche-like structures. These findings demonstrate the creation of a very versatile tool that can be used in a variety of tissue regeneration applications including bone healing.

  3. Analysis of proteins in Chlamydia trachomatis L2 outer membrane complex, COMC

    DEFF Research Database (Denmark)

    Birkelund, Svend; Morgan-Fisher, Marie; Timmerman, Evy

    2009-01-01

    amino groups of in vivo generated proteolytic cleavage sites facilitated identification of such sites in known outer membrane proteins (MOMPs). Our results further support a proposed prediction of the topology of the MOMPs. Furthermore, a previously unknown MOMP, CTL0626 (Ct372), was assigned as an MOMP...

  4. Comparison of dot-ELISA and standard ELISA for detection of Neisseria meningitidis outer membrane complex-specific antibodies

    Directory of Open Access Journals (Sweden)

    Elza FT Belo

    Full Text Available Dot-ELISA using the outer membrane complex antigens of Neisseria meningitidis as a target was standardized for rapid detection of meningococcal-specific antibodies in human serum. We investigated the level of meningococcal-specific IgG, IgA, and IgM in serum using dot-ELISA with outer membrane antigens prepared from Neisseria meningitidis serotype B:4.19:P1.15,3,7,9 (a strain isolated from a Brazilian epidemic. The dot-ELISA is based on the same principles as the standard ELISA and is useful for detection of anti-N. meningitidis B antibodies in serum of patients with meningococcal infections. For the assay, outer membrane complexes (OMCs were absorbed by nitrocellulose membrane and blocked with a 5% skim milk solution. Serum samples were drawn upon hospital admission and during convalescence from patients with meningococcal septicemia, and single samples were drawn from uninfected controls. We retrospectively examined a total of 57 serum samples: 35 from patients infected with N. meningitidis B, 12 from patients infected with Haemophilus influenzae b, and 10 from health individuals. When performed at room temperature, dot-ELISA took approximately four hours to perform, and the optimum antigen concentration was 0.42 µg per dot. The specificity of IgG, IgM, and IgA demonstrates that dot-ELISA using OMCs from N. meningitidis B as a target is suitable for serologic verification of clinically suspected meningococcal disease in patients and for titer determination of antibodies produced during different phases of natural infection. Furthermore, the sensitivity of dot-ELISA was comparable to that of standard ELISA. Overall, dot-ELISA is simple to perform, rapid, and low cost. Further validation of the test as a screening tool is required.

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

    Energy Technology Data Exchange (ETDEWEB)

    Shen, B.W. [Argonne National Lab., IL (United States). Biological and Medical Research Div.

    1995-02-01

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

  6. Vipp1 is required for basic thylakoid membrane formation but not for the assembly of thylakoid protein complexes.

    Science.gov (United States)

    Aseeva, Elena; Ossenbühl, Friederich; Sippel, Claudia; Cho, Won K; Stein, Bernhard; Eichacker, Lutz A; Meurer, Jörg; Wanner, Gerhard; Westhoff, Peter; Soll, Jürgen; Vothknecht, Ute C

    2007-02-01

    Vipp1 (vesicle inducing protein in plastids 1) is found in cyanobacteria and chloroplasts where it is essential for thylakoid formation. Arabidopsis thaliana mutant plants with a reduction of Vipp1 to about 20% of wild type content become albinotic at an early stage. We propose that this drastic phenotype results from an inability of the remaining Vipp1 protein to assemble into a homo-oligomeric complex, indicating that oligomerization is a prerequisite for Vipp1 function. A Vipp1-ProteinA fusion protein, expressed in the Deltavipp1 mutant background, is able to reinstate oligomerization and restore photoautotrophic growth. Plants containing Vipp1-ProteinA in amounts comparable to Vipp1 in the wild type exhibit a wild type phenotype. However, plants with a reduced amount of Vipp1-ProteinA protein are growth-retarded and significantly paler than the wild type. This phenotype is caused by a decrease in thylakoid membrane content and a concomitant reduction in photosynthetic activity. To the extent that thylakoid membranes are made in these plants they are properly assembled with protein-pigment complexes and are photosynthetically active. This strongly supports a function of Vipp1 in basic thylakoid membrane formation and not in the functional assembly of thylakoid protein complexes. Intriguingly, electron microscopic analysis shows that chloroplasts in the mutant plants are not equally affected by the Vipp1 shortage. Indeed, a wide range of different stages of thylakoid development ranging from wild-type-like chloroplasts to plastids nearly devoid of thylakoids can be observed in organelles of one and the same cell.

  7. Mitochondrial membrane potential in human neutrophils is maintained by complex III activity in the absence of supercomplex organisation.

    Directory of Open Access Journals (Sweden)

    Bram J van Raam

    Full Text Available BACKGROUND: Neutrophils depend mainly on glycolysis for their energy provision. Their mitochondria maintain a membrane potential (Deltapsi(m, which is usually generated by the respiratory chain complexes. We investigated the source of Deltapsi(m in neutrophils, as compared to peripheral blood mononuclear leukocytes and HL-60 cells, and whether neutrophils can still utilise this Deltapsi(m for the generation of ATP. METHODS AND PRINCIPAL FINDINGS: Individual activity of the oxidative phosphorylation complexes was significantly reduced in neutrophils, except for complex II and V, but Deltapsi(m was still decreased by inhibition of complex III, confirming the role of the respiratory chain in maintaining Deltapsi(m. Complex V did not maintain Deltapsi(m by consumption of ATP, as has previously been suggested for eosinophils. We show that complex III in neutrophil mitochondria can receive electrons from glycolysis via the glycerol-3-phosphate shuttle. Furthermore, respiratory supercomplexes, which contribute to efficient coupling of the respiratory chain to ATP synthesis, were lacking in neutrophil mitochondria. When HL-60 cells were differentiated to neutrophil-like cells, they lost mitochondrial supercomplex organisation while gaining increased aerobic glycolysis, just like neutrophils. CONCLUSIONS: We show that neutrophils can maintain Deltapsi(m via the glycerol-3-phosphate shuttle, whereby their mitochondria play an important role in the regulation of aerobic glycolysis, rather than producing energy themselves. This peculiar mitochondrial phenotype is acquired during differentiation from myeloid precursors.

  8. Molecular Dynamics Simulations to Provide Insights into Epitopes Coupled to the Soluble and Membrane-Bound MHC-II Complexes

    Science.gov (United States)

    Bello, Martiniano; Correa-Basurto, Jose

    2013-01-01

    Epitope recognition by major histocompatibility complex II (MHC-II) is essential for the activation of immunological responses to infectious diseases. Several studies have demonstrated that this molecular event takes place in the MHC-II peptide-binding groove constituted by the α and β light chains of the heterodimer. This MHC-II peptide-binding groove has several pockets (P1-P11) involved in peptide recognition and complex stabilization that have been probed through crystallographic experiments and in silico calculations. However, most of these theoretical calculations have been performed without taking into consideration the heavy chains, which could generate misleading information about conformational mobility both in water and in the membrane environment. Therefore, in absence of structural information about the difference in the conformational changes between the peptide-free and peptide-bound states (pMHC-II) when the system is soluble in an aqueous environment or non-covalently bound to a cell membrane, as the physiological environment for MHC-II is. In this study, we explored the mechanistic basis of these MHC-II components using molecular dynamics (MD) simulations in which MHC-II was previously co-crystallized with a small epitope (P7) or coupled by docking procedures to a large (P22) epitope. These MD simulations were performed at 310 K over 100 ns for the water-soluble (MHC-IIw, MHC-II-P7w, and MHC-II-P22w) and 150 ns for the membrane-bound species (MHC-IIm, MHC-II-P7m, and MHC-II-P22m). Our results reveal that despite the different epitope sizes and MD simulation environments, both peptides are stabilized primarily by residues lining P1, P4, and P6-7, and similar noncovalent intermolecular energies were observed for the soluble and membrane-bound complexes. However, there were remarkably differences in the conformational mobility and intramolecular energies upon complex formation, causing some differences with respect to how the two peptides are

  9. Light-induced spin crossover observed for a Fe(II) complex embedded in a Nafion membrane

    International Nuclear Information System (INIS)

    Winkler, H.; Rusanov, V.; McGarvey, J. J.; Toftlund, H.; Trautwein, A. X.; Wolny, J. A.

    2006-01-01

    Light-induced spin crossover has been observed for the first time by means of Moessbauer spectroscopy for a Fe(II) complex embedded in a Nafion membrane. The results obtained confirm other independent observations we have made, which point to the possibility of generating a long-lived HS state by means of laser irradiation of the same system (C. Brady, PhD thesis Queens University, Belfast 2002; J.A. Wolny, H. Toftlund, J.J. McGarvey, C. Brady, manuscript in preparation).

  10. Targeting the Human Complement Membrane Attack Complex to Selectively Kill Prostate Cancer Cells

    Science.gov (United States)

    2013-10-01

    reproductive tract of the fe- male. In this regard, seminal plasma is devoid of complement ac- tivity and actually has a strong anti-complement activity (8...article: EA, Ab-sensitized sheep erythrocyte; ES, sheep erythrocyte; PSA, prostate-specific Ag; PVDF, polyvinylidene difluoride. Copyright 2013 by The...addition of sample loading buffer. Proteins were separated by SDS-PAGE and transferred to PVDF membrane as described above. C3b/iC3b deposition assay Sheep

  11. Extracellular complex of chitinolytic enzymes of Clostridium paraputrificum strain J4 separated by membrane ultrafiltration

    Czech Academy of Sciences Publication Activity Database

    Tishchenko, Galina; Koppová, Ingrid; Šimůnek, Jiří; Dohnálek, Jan

    2010-01-01

    Roč. 55, č. 4 (2010), s. 386-389 ISSN 0015-5632 R&D Projects: GA ČR(CZ) GA525/08/0803; GA ČR GA310/09/1407 Institutional research plan: CEZ:AV0Z40500505; CEZ:AV0Z50450515 Keywords : chitinolytic enzymes * Clostridium paraputrificum * membrane diafiltration Subject RIV: FB - Endocrinology, Diabetology, Metabolism, Nutrition Impact factor: 0.977, year: 2010

  12. Phospholipid synthesis participates in the regulation of diacylglycerol required for membrane trafficking at the Golgi complex.

    Science.gov (United States)

    Sarri, Elisabet; Sicart, Adrià; Lázaro-Diéguez, Francisco; Egea, Gustavo

    2011-08-12

    The lipid metabolite diacylglycerol (DAG) is required for transport carrier biogenesis at the Golgi, although how cells regulate its levels is not well understood. Phospholipid synthesis involves highly regulated pathways that consume DAG and can contribute to its regulation. Here we altered phosphatidylcholine (PC) and phosphatidylinositol synthesis for a short period of time in CHO cells to evaluate the changes in DAG and its effects in membrane trafficking at the Golgi. We found that cellular DAG rapidly increased when PC synthesis was inhibited at the non-permissive temperature for the rate-limiting step of PC synthesis in CHO-MT58 cells. DAG also increased when choline and inositol were not supplied. The major phospholipid classes and triacylglycerol remained unaltered for both experimental approaches. The analysis of Golgi ultrastructure and membrane trafficking showed that 1) the accumulation of the budding vesicular profiles induced by propanolol was prevented by inhibition of PC synthesis, 2) the density of KDEL receptor-containing punctated structures at the endoplasmic reticulum-Golgi interface correlated with the amount of DAG, and 3) the post-Golgi transport of the yellow fluorescent temperature-sensitive G protein of stomatitis virus and the secretion of a secretory form of HRP were both reduced when DAG was lowered. We confirmed that DAG-consuming reactions of lipid synthesis were present in Golgi-enriched fractions. We conclude that phospholipid synthesis pathways play a significant role to regulate the DAG required in Golgi-dependent membrane trafficking.

  13. Dietary Tocotrienol/γ-Cyclodextrin Complex Increases Mitochondrial Membrane Potential and ATP Concentrations in the Brains of Aged Mice

    Directory of Open Access Journals (Sweden)

    Anke Schloesser

    2015-01-01

    Full Text Available Brain aging is accompanied by a decrease in mitochondrial function. In vitro studies suggest that tocotrienols, including γ- and δ-tocotrienol (T3, may exhibit neuroprotective properties. However, little is known about the effect of dietary T3 on mitochondrial function in vivo. In this study, we monitored the effect of a dietary T3/γ-cyclodextrin complex (T3CD on mitochondrial membrane potential and ATP levels in the brain of 21-month-old mice. Mice were fed either a control diet or a diet enriched with T3CD providing 100 mg T3 per kg diet for 6 months. Dietary T3CD significantly increased mitochondrial membrane potential and ATP levels compared to those of controls. The increase in MMP and ATP due to dietary T3CD was accompanied by an increase in the protein levels of the mitochondrial transcription factor A (TFAM. Furthermore, dietary T3CD slightly increased the mRNA levels of superoxide dismutase, γ-glutamyl cysteinyl synthetase, and heme oxygenase 1 in the brain. Overall, the present data suggest that T3CD increases TFAM, mitochondrial membrane potential, and ATP synthesis in the brains of aged mice.

  14. Evolution and architecture of the inner membrane complex in asexual and sexual stages of the malaria parasite.

    Science.gov (United States)

    Kono, Maya; Herrmann, Susann; Loughran, Noeleen B; Cabrera, Ana; Engelberg, Klemens; Lehmann, Christine; Sinha, Dipto; Prinz, Boris; Ruch, Ulrike; Heussler, Volker; Spielmann, Tobias; Parkinson, John; Gilberger, Tim W

    2012-09-01

    The inner membrane complex (IMC) is a unifying morphological feature of all alveolate organisms. It consists of flattened vesicles underlying the plasma membrane and is interconnected with the cytoskeleton. Depending on the ecological niche of the organisms, the function of the IMC ranges from a fundamental role as reinforcement system to more specialized roles in motility and cytokinesis. In this article, we present a comprehensive evolutionary analysis of IMC components, which exemplifies the adaptive nature of the IMCs' protein composition. Focusing on eight structurally distinct proteins in the most prominent "genus" of the Alveolata-the malaria parasite Plasmodium-we demonstrate that the level of conservation is reflected in phenotypic characteristics, accentuated in differential spatial-temporal patterns of these proteins in the motile stages of the parasite's life cycle. Colocalization studies with the centromere and the spindle apparatus reveal their discriminative biogenesis. We also reveal that the IMC is an essential structural compartment for the development of the sexual stages of Plasmodium, as it seems to drive the morphological changes of the parasite during the long and multistaged process of sexual differentiation. We further found a Plasmodium-specific IMC membrane matrix protein that highlights transversal structures in gametocytes, which could represent a genus-specific structural innovation required by Plasmodium. We conclude that the IMC has an additional role during sexual development supporting morphogenesis of the cell, which in addition to its functions in the asexual stages highlights the multifunctional nature of the IMC in the Plasmodium life cycle.

  15. Application of grey fuzzy logic for the optimization of CNC milling parameters for Al–4.5%Cu–TiC MMCs with multi-performance characteristics

    Directory of Open Access Journals (Sweden)

    Biswajit Das

    2016-06-01

    Full Text Available With the major application of MMCs, it is thus necessary to develop an appropriate technology for their efficient machining. Milling is the most common and versatile technology among different machining processes, characterized by an extensive range of metal cutting capacity that places it in a central role in the manufacturing industries. In the present study an attempt has been made to find out the most optimal level of process parameters for CNC milling of Al–4.5%Cu–TiC metal matrix composites using grey-fuzzy algorithm. Taguchi's L25 orthogonal array design is used for performing CNC milling operation on the composite plates. The Grey fuzzy optimization of CNC milling parameters consist of three different output characteristics; such as, cutting force Fc, surface roughness Ra and surface roughness Rz. It was found that a cutting speed of 600 rpm, feed of 40 mm/min and a depth of cut of 0.30 mm is the optimal combination of CNC milling parameters that has produced a high value of grey fuzzy reasoning grade of 0.8191 which is close to the reference value. ANOVA analysis is carried out and it is found that among three different process parameters, the cutting speed played a major role on the determination of GFRG.

  16. Translocation of the papillomavirus L2/vDNA complex across the limiting membrane requires the onset of mitosis.

    Science.gov (United States)

    Calton, Christine M; Bronnimann, Matthew P; Manson, Ariana R; Li, Shuaizhi; Chapman, Janice A; Suarez-Berumen, Marcela; Williamson, Tatum R; Molugu, Sudheer K; Bernal, Ricardo A; Campos, Samuel K

    2017-05-01

    The human papillomavirus type 16 (HPV16) L2 protein acts as a chaperone to ensure that the viral genome (vDNA) traffics from endosomes to the trans-Golgi network (TGN) and eventually the nucleus, where HPV replication occurs. En route to the nucleus, the L2/vDNA complex must translocate across limiting intracellular membranes. The details of this critical process remain poorly characterized. We have developed a system based on subcellular compartmentalization of the enzyme BirA and its cognate substrate to detect membrane translocation of L2-BirA from incoming virions. We find that L2 translocation requires transport to the TGN and is strictly dependent on entry into mitosis, coinciding with mitotic entry in synchronized cells. Cell cycle arrest causes retention of L2/vDNA at the TGN; only release and progression past G2/M enables translocation across the limiting membrane and subsequent infection. Microscopy of EdU-labeled vDNA reveals a rapid and dramatic shift in vDNA localization during early mitosis. At late G2/early prophase vDNA egresses from the TGN to a pericentriolar location, accumulating there through prometaphase where it begins to associate with condensed chromosomes. By metaphase and throughout anaphase the vDNA is seen bound to the mitotic chromosomes, ensuring distribution into both daughter nuclei. Mutations in a newly defined chromatin binding region of L2 potently blocked translocation, suggesting that translocation is dependent on chromatin binding during prometaphase. This represents the first time a virus has been shown to functionally couple the penetration of limiting membranes to cellular mitosis, explaining in part the tropism of HPV for mitotic basal keratinocytes.

  17. Translocation of the papillomavirus L2/vDNA complex across the limiting membrane requires the onset of mitosis.

    Directory of Open Access Journals (Sweden)

    Christine M Calton

    2017-05-01

    Full Text Available The human papillomavirus type 16 (HPV16 L2 protein acts as a chaperone to ensure that the viral genome (vDNA traffics from endosomes to the trans-Golgi network (TGN and eventually the nucleus, where HPV replication occurs. En route to the nucleus, the L2/vDNA complex must translocate across limiting intracellular membranes. The details of this critical process remain poorly characterized. We have developed a system based on subcellular compartmentalization of the enzyme BirA and its cognate substrate to detect membrane translocation of L2-BirA from incoming virions. We find that L2 translocation requires transport to the TGN and is strictly dependent on entry into mitosis, coinciding with mitotic entry in synchronized cells. Cell cycle arrest causes retention of L2/vDNA at the TGN; only release and progression past G2/M enables translocation across the limiting membrane and subsequent infection. Microscopy of EdU-labeled vDNA reveals a rapid and dramatic shift in vDNA localization during early mitosis. At late G2/early prophase vDNA egresses from the TGN to a pericentriolar location, accumulating there through prometaphase where it begins to associate with condensed chromosomes. By metaphase and throughout anaphase the vDNA is seen bound to the mitotic chromosomes, ensuring distribution into both daughter nuclei. Mutations in a newly defined chromatin binding region of L2 potently blocked translocation, suggesting that translocation is dependent on chromatin binding during prometaphase. This represents the first time a virus has been shown to functionally couple the penetration of limiting membranes to cellular mitosis, explaining in part the tropism of HPV for mitotic basal keratinocytes.

  18. Tracking energy transfer between light harvesting complex 2 and 1 in photosynthetic membranes grown under high and low illumination.

    Science.gov (United States)

    Lüer, Larry; Moulisová, Vladimíra; Henry, Sarah; Polli, Dario; Brotosudarmo, Tatas H P; Hoseinkhani, Sajjad; Brida, Daniele; Lanzani, Guglielmo; Cerullo, Giulio; Cogdell, Richard J

    2012-01-31

    Energy transfer (ET) between B850 and B875 molecules in light harvesting complexes LH2 and LH1/RC (reaction center) complexes has been investigated in membranes of Rhodopseudomonas palustris grown under high- and low-light conditions. In these bacteria, illumination intensity during growth strongly affects the type of LH2 complexes synthesized, their optical spectra, and their amount of energetic disorder. We used a specially built femtosecond spectrometer, combining tunable narrowband pump with broadband white-light probe pulses, together with an analytical method based on derivative spectroscopy for disentangling the congested transient absorption spectra of LH1 and LH2 complexes. This procedure allows real-time tracking of the forward (LH2 → LH1) and backward (LH2←LH1) ET processes and unambiguous determination of the corresponding rate constants. In low-light grown samples, we measured lower ET rates in both directions with respect to high-light ones, which is explained by reduced spectral overlap between B850 and B875 due to partial redistribution of oscillator strength into a higher energetic exciton transition. We find that the low-light adaptation in R. palustris leads to a reduced elementary backward ET rate, in accordance with the low probability of two simultaneous excitations reaching the same LH1/RC complex under weak illumination. Our study suggests that backward ET is not just an inevitable consequence of vectorial ET with small energetic offsets, but is in fact actively managed by photosynthetic bacteria.

  19. Modeling two-phase flow in three-dimensional complex flow-fields of proton exchange membrane fuel cells

    Science.gov (United States)

    Kim, Jinyong; Luo, Gang; Wang, Chao-Yang

    2017-10-01

    3D fine-mesh flow-fields recently developed by Toyota Mirai improved water management and mass transport in proton exchange membrane (PEM) fuel cell stacks, suggesting their potential value for robust and high-power PEM fuel cell stack performance. In such complex flow-fields, Forchheimer's inertial effect is dominant at high current density. In this work, a two-phase flow model of 3D complex flow-fields of PEMFCs is developed by accounting for Forchheimer's inertial effect, for the first time, to elucidate the underlying mechanism of liquid water behavior and mass transport inside 3D complex flow-fields and their adjacent gas diffusion layers (GDL). It is found that Forchheimer's inertial effect enhances liquid water removal from flow-fields and adds additional flow resistance around baffles, which improves interfacial liquid water and mass transport. As a result, substantial improvements in high current density cell performance and operational stability are expected in PEMFCs with 3D complex flow-fields, compared to PEMFCs with conventional flow-fields. Higher current density operation required to further reduce PEMFC stack cost per kW in the future will necessitate optimizing complex flow-field designs using the present model, in order to efficiently remove a large amount of product water and hence minimize the mass transport voltage loss.

  20. Inhibition of the Membrane Attack Complex by Dengue Virus NS1 through Interaction with Vitronectin and Terminal Complement Proteins.

    Science.gov (United States)

    Conde, Jonas Nascimento; da Silva, Emiliana Mandarano; Allonso, Diego; Coelho, Diego Rodrigues; Andrade, Iamara da Silva; de Medeiros, Luciano Neves; Menezes, Joice Lima; Barbosa, Angela Silva; Mohana-Borges, Ronaldo

    2016-11-01

    Dengue virus (DENV) infects millions of people worldwide and is a major public health problem. DENV nonstructural protein 1 (NS1) is a conserved glycoprotein that associates with membranes and is also secreted into the plasma in DENV-infected patients. The present study describes a novel mechanism by which NS1 inhibits the terminal complement pathway. We first identified the terminal complement regulator vitronectin (VN) as a novel DENV2 NS1 binding partner by using a yeast two-hybrid system. This interaction was further assessed by enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance (SPR) assay. The NS1-VN complex was also detected in plasmas from DENV-infected patients, suggesting that this interaction occurs during DENV infection. We also demonstrated that the DENV2 NS1 protein, either by itself or by interacting with VN, hinders the formation of the membrane attack complex (MAC) and C9 polymerization. Finally, we showed that DENV2, West Nile virus (WNV), and Zika virus (ZIKV) NS1 proteins produced in mammalian cells inhibited C9 polymerization. Taken together, our results points to a role for NS1 as a terminal pathway inhibitor of the complement system. Dengue is the most important arthropod-borne viral disease nowadays and is caused by dengue virus (DENV). The flavivirus NS1 glycoprotein has been characterized functionally as a complement evasion protein that can attenuate the activation of the classical, lectin, and alternative pathways. The present study describes a novel mechanism by which DENV NS1 inhibits the terminal complement pathway. We identified the terminal complement regulator vitronectin (VN) as a novel DENV NS1 binding partner, and the NS1-VN complex was detected in plasmas from DENV-infected patients, suggesting that this interaction occurs during DENV infection. We also demonstrated that the NS1-VN complex inhibited membrane attack complex (MAC) formation, thus interfering with the complement terminal pathway. Interestingly

  1. A complex microdeletion 17q12 phenotype in a patient with recurrent de novo membranous nephropathy

    Directory of Open Access Journals (Sweden)

    Hinkes Bernward

    2012-05-01

    Full Text Available Abstract Background Microdeletions on chromosome 17q12 cause of diverse spectrum of disorders and have only recently been identified as a rare cause of Mayer-Rokitansky-Kuester-Hauser-Syndrome (MRKH, which is characterized by uterus aplasia ± partial/complete vaginal aplasia in females with a regular karyotype. For the first time we report about a patient with a 17q12 microdeletion who is affected by MRKH in combination with a vascular and soft tissue disorder. Repeatedly she suffered from kidney transplant failure caused by consuming membranous nephropathy. Case presentation A 38-year-old female patient had been diagnosed with right kidney aplasia, left kidney dysplasia and significantly impaired renal function during infancy. Aged 16 she had to start hemodialysis. Three years later she received her first kidney transplant. Only then she was diagnosed with MRKH. The kidney transplant was lost due to consuming nephrotic syndrome caused by de novo membranous nephropathy, as was a second kidney transplant years later. In addition, a hyperelasticity syndrome affects the patient with congenital joint laxity, kyphoscoliosis, bilateral hip dysplasia, persistent hypermobility of both elbows, knees and hips. Her clinical picture resembles a combination of traits of a hypermobile and a vascular form of Ehlers-Danlos-Syndrome, but no mutations in the COL3A1 gene was underlying. Instead, array-based comparative genomic hybridisation (CGH detected a heterozygous 1.43 Mb deletion on chromosome 17q12 encompassing the two renal developmental genes HNF1β and LHX1. Conclusions Deletions of HNF1β have recently drawn significant attention in pediatric nephrology as an important cause of prenatally hyperechogenic kidneys, renal aplasia and renal hypodysplasia. In contrast, membranous nephropathy represents an often-unaccounted cause of nephrotic syndrome in the adult population. A causative connection between theses two conditions has never been postulated, but

  2. Feature Article: mTOR complex 2-Akt signaling at mitochondria-associated endoplasmic reticulum membranes (MAM) regulates mitochondrial physiology.

    Science.gov (United States)

    Betz, Charles; Stracka, Daniele; Prescianotto-Baschong, Cristina; Frieden, Maud; Demaurex, Nicolas; Hall, Michael N

    2013-07-30

    The target of rapamycin (TOR) is a highly conserved protein kinase and a central controller of growth. Mammalian TOR complex 2 (mTORC2) regulates AGC kinase family members and is implicated in various disorders, including cancer and diabetes. Here we report that mTORC2 is localized to the endoplasmic reticulum (ER) subcompartment termed mitochondria-associated ER membrane (MAM). mTORC2 localization to MAM was growth factor-stimulated, and mTORC2 at MAM interacted with the IP3 receptor (IP3R)-Grp75-voltage-dependent anion-selective channel 1 ER-mitochondrial tethering complex. mTORC2 deficiency disrupted MAM, causing mitochondrial defects including increases in mitochondrial membrane potential, ATP production, and calcium uptake. mTORC2 controlled MAM integrity and mitochondrial function via Akt mediated phosphorylation of the MAM associated proteins IP3R, Hexokinase 2, and phosphofurin acidic cluster sorting protein 2. Thus, mTORC2 is at the core of a MAM signaling hub that controls growth and metabolism.

  3. mTOR complex 2-Akt signaling at mitochondria-associated endoplasmic reticulum membranes (MAM) regulates mitochondrial physiology

    Science.gov (United States)

    Betz, Charles; Stracka, Daniele; Prescianotto-Baschong, Cristina; Frieden, Maud; Demaurex, Nicolas; Hall, Michael N.

    2013-01-01

    The target of rapamycin (TOR) is a highly conserved protein kinase and a central controller of growth. Mammalian TOR complex 2 (mTORC2) regulates AGC kinase family members and is implicated in various disorders, including cancer and diabetes. Here we report that mTORC2 is localized to the endoplasmic reticulum (ER) subcompartment termed mitochondria-associated ER membrane (MAM). mTORC2 localization to MAM was growth factor-stimulated, and mTORC2 at MAM interacted with the IP3 receptor (IP3R)-Grp75–voltage-dependent anion-selective channel 1 ER-mitochondrial tethering complex. mTORC2 deficiency disrupted MAM, causing mitochondrial defects including increases in mitochondrial membrane potential, ATP production, and calcium uptake. mTORC2 controlled MAM integrity and mitochondrial function via Akt mediated phosphorylation of the MAM associated proteins IP3R, Hexokinase 2, and phosphofurin acidic cluster sorting protein 2. Thus, mTORC2 is at the core of a MAM signaling hub that controls growth and metabolism. PMID:23852728

  4. Liquid Membranes as a Tool for Chemical Speciation of Metals in Natural Waters: Organic and Inorganic Complexes of Nickel.

    Science.gov (United States)

    Vergel, Cristina; Mendiguchía, Carolina; Moreno, Carlos

    2018-04-15

    The different species of nickel present in natural waters exhibit different transport behaviour through bulk liquid membranes (BLMs). This fact has been used to design and optimise a separation/pre-concentration system applicable to separate labile and non-labile nickel fractions. A hydrazone derivative-1,2-cyclohexanedione bis-benzoyl-hydrazone (1,2-CHBBH) dissolved in toluene/dimethyl formamide (2% DMF)-was used as a chemical carrier of nickel species, from an aqueous source solution (sample) to a receiving acidic solution. Both chemical and hydrodynamic conditions controlling the transport system were studied and optimised. Under optimum conditions, variations in the transport of nickel ions as a function of organic (humic acids) and inorganic (chloride ions) ligands were studied. Relationships between the permeability coefficient ( P ) or recovery efficiency (%R) and the concentrations of ligands and nickel species were analysed using Winhumic V software. A negative correlation between P and the concentration of organic nickel complexes was found, suggesting that only labile nickel species are transported through the liquid membrane, with non-labile complexes remaining in the water sample; allowing for their separation and subsequent quantification in natural waters.

  5. Sensitive determination of trace mercury by UV-visible diffuse reflectance spectroscopy after complexation and membrane filtration-enrichment.

    Science.gov (United States)

    Yin, Changhai; Iqbal, Jibran; Hu, Huilian; Liu, Bingxiang; Zhang, Lei; Zhu, Bilin; Du, Yiping

    2012-09-30

    A simple, sensitive and selective solid phase reflectometry method is proposed for the determination of trace mercury in aqueous samples. The complexation reagent dithizone was firstly injected into the properly buffered solution with vigorous stirring, which started a simultaneous formation of nanoparticles suspension of dithizone and its complexation reaction with the mercury(II) ions to make Hg-dithizone nanoparticles. After a definite time, the mixture was filtered with membrane, and then quantified directly on the surface of the membrane by using integrating sphere accessory of the UV-visible spectrophotometer. The quantitative analysis was carried out at a wavelength of 485 nm since it yielded the largest difference in diffuse reflectance spectra before and after reaction with mercury(II).A good linear correlation in the range of 0.2-4.0 μg/L with a squared correlation coefficient (R(2)) of 0.9944 and a detection limit of 0.12 μg/L were obtained. The accuracy of the method was evaluated by the analysis of spiked mercury(II) concentrations determined using this method along with those determined by the atomic fluorescence mercury vapourmeter and the results obtained were in good agreement. The proposed method was applied to the determination of mercury in tap water and river water samples with the recovery in an acceptable range (95.7-105.3%). Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Structure of a membrane-attack complex/perforin (MACPF) family protein from the human gut symbiont Bacteroides thetaiotaomicron

    International Nuclear Information System (INIS)

    Xu, Qingping; Abdubek, Polat; Astakhova, Tamara; Axelrod, Herbert L.; Bakolitsa, Constantina; Cai, Xiaohui; Carlton, Dennis; Chen, Connie; Chiu, Hsiu-Ju; Clayton, Thomas; Das, Debanu; Deller, Marc C.; Duan, Lian; Ellrott, Kyle; Farr, Carol L.; Feuerhelm, Julie; Grant, Joanna C.; Grzechnik, Anna; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K.; Klock, Heath E.; Knuth, Mark W.; Kozbial, Piotr; Krishna, S. Sri; Kumar, Abhinav; Lam, Winnie W.; Marciano, David; Miller, Mitchell D.; Morse, Andrew T.; Nigoghossian, Edward; Nopakun, Amanda; Okach, Linda; Puckett, Christina; Reyes, Ron; Tien, Henry J.; Trame, Christine B.; Bedem, Henry van den; Weekes, Dana; Wooten, Tiffany; Yeh, Andrew; Zhou, Jiadong; Hodgson, Keith O.; Wooley, John; Elsliger, Marc-André; Deacon, Ashley M.; Godzik, Adam; Lesley, Scott A.; Wilson, Ian A.

    2010-01-01

    The crystal structure of a novel MACPF protein, which may play a role in the adaptation of commensal bacteria to host environments in the human gut, was determined and analyzed. Membrane-attack complex/perforin (MACPF) proteins are transmembrane pore-forming proteins that are important in both human immunity and the virulence of pathogens. Bacterial MACPFs are found in diverse bacterial species, including most human gut-associated Bacteroides species. The crystal structure of a bacterial MACPF-domain-containing protein BT-3439 (Bth-MACPF) from B. thetaiotaomicron, a predominant member of the mammalian intestinal microbiota, has been determined. Bth-MACPF contains a membrane-attack complex/perforin (MACPF) domain and two novel C-terminal domains that resemble ribonuclease H and interleukin 8, respectively. The entire protein adopts a flat crescent shape, characteristic of other MACPF proteins, that may be important for oligomerization. This Bth-MACPF structure provides new features and insights not observed in two previous MACPF structures. Genomic context analysis infers that Bth-MACPF may be involved in a novel protein-transport or nutrient-uptake system, suggesting an important role for these MACPF proteins, which were likely to have been inherited from eukaryotes via horizontal gene transfer, in the adaptation of commensal bacteria to the host environment

  7. A β(IV)-spectrin/CaMKII signaling complex is essential for membrane excitability in mice.

    Science.gov (United States)

    Hund, Thomas J; Koval, Olha M; Li, Jingdong; Wright, Patrick J; Qian, Lan; Snyder, Jedidiah S; Gudmundsson, Hjalti; Kline, Crystal F; Davidson, Nathan P; Cardona, Natalia; Rasband, Matthew N; Anderson, Mark E; Mohler, Peter J

    2010-10-01

    Ion channel function is fundamental to the existence of life. In metazoans, the coordinate activities of voltage-gated Na(+) channels underlie cellular excitability and control neuronal communication, cardiac excitation-contraction coupling, and skeletal muscle function. However, despite decades of research and linkage of Na(+) channel dysfunction with arrhythmia, epilepsy, and myotonia, little progress has been made toward understanding the fundamental processes that regulate this family of proteins. Here, we have identified β(IV)-spectrin as a multifunctional regulatory platform for Na(+) channels in mice. We found that β(IV)-spectrin targeted critical structural and regulatory proteins to excitable membranes in the heart and brain. Animal models harboring mutant β(IV)-spectrin alleles displayed aberrant cellular excitability and whole animal physiology. Moreover, we identified a regulatory mechanism for Na(+) channels, via direct phosphorylation by β(IV)-spectrin-targeted calcium/calmodulin-dependent kinase II (CaMKII). Collectively, our data define an unexpected but indispensable molecular platform that determines membrane excitability in the mouse heart and brain.

  8. A βIV-spectrin/CaMKII signaling complex is essential for membrane excitability in mice

    Science.gov (United States)

    Hund, Thomas J.; Koval, Olha M.; Li, Jingdong; Wright, Patrick J.; Qian, Lan; Snyder, Jedidiah S.; Gudmundsson, Hjalti; Kline, Crystal F.; Davidson, Nathan P.; Cardona, Natalia; Rasband, Matthew N.; Anderson, Mark E.; Mohler, Peter J.

    2010-01-01

    Ion channel function is fundamental to the existence of life. In metazoans, the coordinate activities of voltage-gated Na+ channels underlie cellular excitability and control neuronal communication, cardiac excitation-contraction coupling, and skeletal muscle function. However, despite decades of research and linkage of Na+ channel dysfunction with arrhythmia, epilepsy, and myotonia, little progress has been made toward understanding the fundamental processes that regulate this family of proteins. Here, we have identified βIV-spectrin as a multifunctional regulatory platform for Na+ channels in mice. We found that βIV-spectrin targeted critical structural and regulatory proteins to excitable membranes in the heart and brain. Animal models harboring mutant βIV-spectrin alleles displayed aberrant cellular excitability and whole animal physiology. Moreover, we identified a regulatory mechanism for Na+ channels, via direct phosphorylation by βIV-spectrin–targeted calcium/calmodulin-dependent kinase II (CaMKII). Collectively, our data define an unexpected but indispensable molecular platform that determines membrane excitability in the mouse heart and brain. PMID:20877009

  9. Analytical use of multi-protein Fluorescence Resonance Energy Transfer to demonstrate membrane-facilitated interactions within cytokine receptor complexes.

    Science.gov (United States)

    Krause, Christopher D; Izotova, Lara S; Pestka, Sidney

    2013-10-01

    Experiments measuring Fluorescence Resonance Energy Transfer (FRET) between cytokine receptor chains and their associated proteins led to hypotheses describing their organization in intact cells. These interactions occur within a larger protein complex or within a given nano-environment. To illustrate this complexity empirically, we developed a protocol to analyze FRET among more than two fluorescent proteins (multi-FRET). In multi-FRET, we model FRET among more than two fluorophores as the sum of all possible pairwise interactions within the complex. We validated our assumption by demonstrating that FRET among pairs within a fluorescent triplet resembled FRET between each pair measured in the absence of the third fluorophore. FRET between two receptor chains increases with increasing FRET between the ligand-binding chain (e.g., IFN-γR1, IL-10R1 and IFN-λR1) and an acylated fluorescent protein that preferentially resides within subsections of the plasma membrane. The interaction of IL-10R2 with IFN-λR1 or IL-10R1 results in decreased FRET between IL-10R2 and the acylated fluorescent protein. Finally, we analyzed FRET among four fluorescent proteins to demonstrate that as FRET between IFN-γR1 and IFN-γR2 or between IFN-αR1 and IFN-αR2c increases, FRET among other pairs of proteins changes within each complex. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. Understanding Free Radicals: Isolating Active Thylakoid Membranes and Purifying the Cytochrome b6f Complex for Superoxide Generation Studies

    Directory of Open Access Journals (Sweden)

    Jason Stofleth

    2012-01-01

    Full Text Available All life persists in an environment that is rich in molecular oxygen. The production of oxygen free radicals, or superoxide, is a necessary consequence of the biogenesis of energy in cells. Both mitochondrial and photosynthetic electron transport chains have been found to produce superoxide associated with cell differentiation, proliferation, and cell death, thereby contributing to the effects of aging. Aerobic respiration in mitochondria consumes oxygen, whereas photosynthesis in chloroplasts or cyanobacteria produces oxygen. The increased concentration of molecular oxygen may serve to allow greater availability for the production of superoxide by cytochrome bc complexes in photosynthetic membranes compared to those of mitochondrial membranes. The isolation of well-coupled chloroplasts, containing the cytochrome b6f complex of oxygenic photosynthesis, is a vital initial step in the process of comparing the rate of production of superoxide to those of the homologous cytochrome bc1 complex of aerobic respiration. It is necessary to determine if the isolated chloroplasts have retained their oxygengenerating capability after isolation by an oxygen evolution assay with a Clark-type electrode. A necessary second step, which is the isolation of cytochrome b6f from spinach, has yet to be successfully performed. Oxygen measurements taken from chloroplasts in the presence of the uncoupler, NH4Cl, exhibited a rate of oxygen evolution over three times greater at 344 +/- 18 μmol O2/mg Chlorophyll a/hr than the rate of oxygen evolution without uncoupler at 109 +/- 29 μmol O2/mg Chlorophyll a/hr. These data demonstrate that the technique used to isolate spinach chloroplasts preserves their light-driven electron-transport activity, making them reliable for future superoxide assays.

  11. High-resolution Structures of Protein-Membrane Complexes by Neutron Reflection and MD Simulation: Membrane Association of the PTEN Tumor Suppressor

    Science.gov (United States)

    Lösche, Matthias

    2012-02-01

    The lipid matrix of biomembranes is an in-plane fluid, thermally and compositionally disordered leaflet of 5 nm thickness and notoriously difficult to characterize in structural terms. Yet, biomembranes are ubiquitous in the cell, and membrane-bound proteins are implicated in a variety of signaling pathways and intra-cellular transport. We developed methodology to study proteins associated with model membranes using neutron reflection measurements and showed recently that this approach can resolve the penetration depth and orientation of membrane proteins with ångstrom resolution if their crystal or NMR structure is known. Here we apply this technology to determine the membrane bindung and unravel functional details of the PTEN phosphatase, a key player in the PI3K apoptosis pathway. PTEN is an important regulatory protein and tumor suppressor that performs its phosphatase activity as an interfacial enzyme at the plasma membrane-cytoplasm boundary. Acting as an antagonist to phosphoinositide-3-kinase (PI3K) in cell signaling, it is deleted in many human cancers. Despite its importance in regulating the levels of the phosphoinositoltriphosphate PI(3,4,5)P3, there is little understanding of how PTEN binds to membranes, is activated and then acts as a phosphatase. We investigated the structure and function of PTEN by studying its membrane affinity and localization on in-plane fluid, thermally disordered synthetic membrane models. The membrane association of the protein depends strongly on membrane composition, where phosphatidylserine (PS) and phosphatidylinositol diphosphate (PI(4,5)P2) act synergetically in attracting the enzyme to the membrane surface. Membrane affinities depend strongly on membrane fluidity, which suggests multiple binding sites on the protein for PI(4,5)P2. Neutron reflection measurements show that the PTEN phosphatase ``scoots'' along the membrane surface (penetration PTEN's regulatory C-terminal tail is displaced from the membrane and

  12. Membrane Guanylyl Cyclase Complexes Shape the Photoresponses of Retinal Rods and Cones

    Directory of Open Access Journals (Sweden)

    Xiao-Hong eWen

    2014-06-01

    Full Text Available In vertebrate rods and cones, photon capture by rhodopsin leads to the destruction of cyclic GMP (cGMP and the subsequent closure of cyclic nucleotide gated (CNG ion channels in the outer segment plasma membrane. Replenishment of cGMP and reopening of the channels limit the growth of the photon response and are requisite for its recovery. In different vertebrate retinas, there may be as many as four types of membrane guanylyl cyclases (GCs for cGMP synthesis. Ten neuronal Ca2+ sensor proteins could potentially modulate their activities. The mouse is proving to be an effective model for characterizing the roles of individual components because its relative simplicity can be reduced further by genetic engineering. There are two types of guanylyl cyclase activating proteins (GCAPs and two types of GCs in mouse rods, whereas cones express one type of GCAP and one type of GC. Mutant mouse rods and cones bereft of both GCAPs have large, long lasting photon responses. Thus, GCAPs normally mediate negative feedback tied to the light-induced decline in intracellular Ca2+ that accelerates GC activity to curtail the growth and duration of the photon response. Rods from other mutant mice that express a single GCAP type reveal how the two GCAPs normally work together as a team. Because of its lower Ca2+ affinity, GCAP1 is the first responder that senses the initial decrease in Ca2+ following photon absorption and acts to limit response amplitude. GCAP2, with a higher Ca2+ affinity, is recruited later during the course of the photon response as Ca2+ levels continue to decline further. The main role of GCAP2 is to provide for a timely response recovery and it is particularly important after exposure to very bright light. The multiplicity of GC isozymes and GCAP homologs in the retinas of other vertebrates confers greater flexibility in shaping the photon responses in order to tune visual sensitivity, dynamic range and frequency response.

  13. Imaging and structural studies of DNA–protein complexes and membrane ion channels

    KAUST Repository

    Marini, Monica

    2017-01-17

    In bio-imaging by electron microscopy, damage of the sample and limited contrast are the two main hurdles for reaching high image quality. We extend a new preparation method based on nanofabrication and super-hydrophobicity to the imaging and structural studies of nucleic acids, nucleic acid-protein complexes (DNA/Rad51 repair protein complex) and neuronal ion channels (gap-junction, K+ and GABA(A) channels) as paradigms of biological significance and increasing complexity. The preparation method is based on the liquid phase and is compatible with physiological conditions. Only in the very last stage, samples are dried for TEM analysis. Conventional TEM and high-resolution TEM (HRTEM) were used to achieve a resolution of 3.3 and 1.5 angstrom, respectively. The EM dataset quality allows the determination of relevant structural and metrological information on the DNA structure, DNA-protein interactions and ion channels, allowing the identification of specific macromolecules and their structure.

  14. Trp[superscript 2313]-His[superscript 2315] of Factor VIII C2 Domain Is Involved in Membrane Binding Structure of a Complex Between the C[subscript 2] Domain and an Inhibitor of Membrane Binding

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhuo; Lin, Lin; Yuan, Cai; Nicolaes, Gerry A.F.; Chen, Liqing; Meehan, Edward J.; Furie, Bruce; Furie, Barbara; Huang, Mingdong (Harvard-Med); (UAH); (Maastricht); (Chinese Aca. Sci.)

    2010-11-03

    Factor VIII (FVIII) plays a critical role in blood coagulation by forming the tenase complex with factor IXa and calcium ions on a membrane surface containing negatively charged phospholipids. The tenase complex activates factor X during blood coagulation. The carboxyl-terminal C2 domain of FVIII is the main membrane-binding and von Willebrand factor-binding region of the protein. Mutations of FVIII cause hemophilia A, whereas elevation of FVIII activity is a risk factor for thromboembolic diseases. The C2 domain-membrane interaction has been proposed as a target of intervention for regulation of blood coagulation. A number of molecules that interrupt FVIII or factor V (FV) binding to cell membranes have been identified through high throughput screening or structure-based design. We report crystal structures of the FVIII C2 domain under three new crystallization conditions, and a high resolution (1.15 {angstrom}) crystal structure of the FVIII C2 domain bound to a small molecular inhibitor. The latter structure shows that the inhibitor binds to the surface of an exposed {beta}-strand of the C2 domain, Trp{sup 2313}-His{sup 2315}. This result indicates that the Trp{sup 2313}-His{sup 2315} segment is an important constituent of the membrane-binding motif and provides a model to understand the molecular mechanism of the C2 domain membrane interaction.

  15. Proteomic screen for multiprotein complexes in synaptic plasma membrane from rat hippocampus by blue native gel electrophoresis and tandem mass spectrometry.

    Science.gov (United States)

    Li, Xuanwen; Xie, Chunliang; Jin, Qihui; Liu, Mingjun; He, Quanyuan; Cao, Rui; Lin, Yong; Li, Jianglin; Li, Yan; Chen, Ping; Liang, Songping

    2009-07-01

    Neuronal synapses are specialized sites for information exchange between neurons. Many diseases, such as addiction and mood disorders, likely result from altered expression of synaptic proteins, or altered formation of synaptic complexes involved in neurotransmission or neuroplasticity. A detailed description of native multiprotein complexes in synaptic plasma membranes (PM) is therefore essential for understanding biological mechanisms and disease processes. For the first time in this study, two-dimensional Blue Native/SDS-PAGE electrophoresis, combined with tandem mass spectrometry, was used to screen multiprotein complexes in synaptic plasma membranes from rat hippocampus. As a result, 514 unique proteins were identified, of which 36% were integral membrane proteins. In addition, 19 potentially novel and known heterooligomeric multiprotein complexes were found, such as the SNARE and ATPase complexes. A potentially novel protein complex, involving syntaxin, synapsin I and Na+/K+ ATPase alpha-1, was further confirmed by co-immunoprecipitation and immunofluorescence staining. As demonstrated here, Blue Native-PAGE is a powerful tool for the separation of hydrophobic membrane proteins. The combination of Blue Native-PAGE and mass spectrometry could systematically identify multiprotein complexes.

  16. Efficiency of membrane technology, activated charcoal, and a micelle-clay complex for removal of the acidic pharmaceutical mefenamic acid.

    Science.gov (United States)

    Khalaf, Samer; Al-Rimawi, Fuad; Khamis, Mustafa; Nir, Shlomo; Bufo, Sabino A; Scrano, Laura; Mecca, Gennaro; Karaman, Rafik

    2013-01-01

    The efficiency of sequential advanced membrane technology wastewater treatment plant towards removal of a widely used non-steroid anti-inflammatory drug (NSAID) mefenamic acid was investigated. The sequential system included activated sludge, ultrafiltration by hollow fibre membranes with 100 kDa cutoff, and spiral wound membranes with 20 kDa cutoff, activated carbon and a reverse osmosis (RO) unit. The performance of the integrated plant showed complete removal of mefenamic acid from spiked wastewater samples. The activated carbon column was the most effective component in removing mefenamic acid with a removal efficiency of 97.2%. Stability study of mefenamic acid in pure water and Al-Quds activated sludge revealed that the anti-inflammatory drug was resistant to degradation in both environments. Batch adsorption of mefenamic acid by activated charcoal and a composite micelle (otadecyltrimethylammonium (ODTMA)-clay (montmorillonite) was determined at 25.0°C. Langmuir isotherm was found to fit the data with Qmax of 90.9 mg g(-1) and 100.0 mg g(-1) for activated carbon and micelle-clay complex, respectively. Filtration experiment by micelle-clay columns mixed with sand in the mg L(-1) range revealed complete removal of the drug with much larger capacity than activated carbon column. The combined results demonstrated that an integration of a micelle-clay column in the plant system has a good potential to improve the removal efficiency of the plant towards NSAID drugs such as mefenamic acid.

  17. A highly sensitive PVC membrane iodide electrode based on complexes of mercury(II) as neutral carrier.

    Science.gov (United States)

    Chai, Y-Q; Yuan, R; Xu, L; Xu, W-J; Dai, J-Y; Jiang, F

    2004-09-01

    A novel solvent polymeric membrane electrode based on bis(1,3,4-thiadiazole) complexes of Hg(II) is described which has excellent selectivity and sensitivity toward iodide ion. The electrode, containing 1,4-bis(5-methyl-1,3,4-thiadiazole-2-yl-thio)butanemercury(II) [Hg(II)BMTB(NO3)4], has a Nernstian potentiometric response from 2.0 x 10(-8) to 2.0 x 10(-2) mol L(-1) with a detection limit of 8.0 x 10(-9) mol L(-1) and a slope of -59.0+/-0.5 mV/decade in 0.01 mol L(-1) phosphate buffer solution (pH 3.0, 20 degrees C). The selectivity sequence observed is iodide>bromide>thiocyanate>nitrite>nitrate>chloride>perchlorate>acetate>sulfate. The selectivity behavior is discussed in terms of the UV-Vis spectrum, and the process of transfer of iodide across the membrane interface is investigated by use of the AC impedance technique. The electrode was successfully applied to the determination of iodide in Jialing River and Spring in Jinyun Mountains, with satisfactory results.

  18. Large-scale preparation of the homogeneous LolA–lipoprotein complex and efficient in vitro transfer of lipoproteins to the outer membrane in a LolB-dependent manner

    OpenAIRE

    Watanabe, Shoji; Oguchi, Yuki; Yokota, Naoko; Tokuda, Hajime

    2007-01-01

    An ATP-binding cassette transporter LolCDE complex of Escherichia coli releases lipoproteins destined to the outer membrane from the inner membrane as a complex with a periplasmic chaperone, LolA. Interaction of the LolA–lipoprotein complex with an outer membrane receptor, LolB, then causes localization of lipoproteins to the outer membrane. As far as examined, formation of the LolA–lipoprotein complex strictly depends on ATP hydrolysis by the LolCDE complex in the presence of LolA. It has be...

  19. N-acetylation and phosphorylation of Sec complex subunits in the ER membrane

    Directory of Open Access Journals (Sweden)

    Soromani Christina

    2012-12-01

    Full Text Available Abstract Background Covalent modifications of proteins provide a mechanism to control protein function. Here, we have investigated modifications of the heptameric Sec complex which is responsible for post-translational protein import into the endoplasmic reticulum (ER. It consists of the Sec61 complex (Sec61p, Sbh1p, Sss1p which on its own mediates cotranslational protein import into the ER and the Sec63 complex (Sec63p, Sec62p, Sec71p, Sec72p. Little is known about the biogenesis and regulation of individual Sec complex subunits. Results We show that Sbh1p when it is part of the Sec61 complex is phosphorylated on T5 which is flanked by proline residues. The phosphorylation site is conserved in mammalian Sec61ß, but only partially in birds, and not in other vertebrates or unicellular eukaryotes, suggesting convergent evolution. Mutation of T5 to A did not affect the ability of mutant Sbh1p to complement the growth defect in a Δsbh1Δsbh2 strain, and did not result in a hypophosphorylated protein which shows that alternate sites can be used by the T5 kinase. A survey of yeast phosphoproteome data shows that Sbh1p can be phosphorylated on multiple sites which are organized in two patches, one at the N-terminus of its cytosolic domain, the other proximal to the transmembrane domain. Surprisingly, although N-acetylation has been shown to interfere with ER targeting, we found that both Sbh1p and Sec62p are cotranslationally N-acetylated by NatA, and N-acetyl-proteome data indicate that Sec61p is modified by the same enzyme. Mutation of the N-acetylation site, however, did not affect Sec62p function in posttranslational protein import into the ER. Disabling NatA resulted in growth retardation, but not in co- or posttranslational translocation defects or instability of Sec62p or Sbh1p. Conclusions We conclude that N-acetylation of transmembrane and tail-anchored proteins does not interfere with their ER-targeting, and that Sbh1p phosphorylation on T5

  20. Application of membrane LaF3 electrode in the determination of stability constants of Uranyl Fluoride complex in solution

    International Nuclear Information System (INIS)

    Muzakky; Iswani GS; Mintolo

    1996-01-01

    A membrane electrode LaF 3 has been applied in the determination of uranyl fluoride complex stability constant in solution. The determination is based on the detection of free F ion in solution as a result of hydrolysis reaction (process) of uranyl ions into the uranyl hydroxide form at low pH. The experiment results showed that there was no effect of ammonium carbonate 2 M titran, flow rate on the electrode response. The F release is optimum at pH 1. The free F ion in solution is calculated from the standard curve at pH 1, after the fluoride concentration at the same pH has been corrected. Using the plot of average number of ligand binding (n) versus minus log of free ligand (-log F) the value of β1 = 4.4, β2 = 7.48, β3=9.73, and β4 = 11.67

  1. Interaction of new butyltin citrate complex with lipid model membrane and DNA

    Czech Academy of Sciences Publication Activity Database

    Pruchnik, H.; Kral, Teresa; Hof, Martin

    2014-01-01

    Roč. 118, č. 2 (2014), s. 967-975 ISSN 1388-6150 R&D Projects: GA ČR GBP208/12/G016 Grant - others:GA MŠk(CZ) CZ.1.07/2.3.00/20.0092 Institutional support: RVO:61388955 Keywords : Butyltin citrate complex * Phase transition * DSC Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.042, year: 2014

  2. Isolation of thylakoid membrane complexes from rice by a new double-strips BN/SDS-PAGE and bioinformatics prediction of stromal ridge subunits interaction.

    Directory of Open Access Journals (Sweden)

    Jinzhen Shao

    Full Text Available Thylakoid membrane complexes of rice (Oryza sativa L. play crucial roles in growth and crop production. Understanding of protein interactions within the complex would provide new insights into photosynthesis. Here, a new "Double-Strips BN/SDS-PAGE" method was employed to separate thylakoid membrane complexes in order to increase the protein abundance on 2D-gels and to facilitate the identification of hydrophobic transmembrane proteins. A total of 58 protein spots could be observed and subunit constitution of these complexes exhibited on 2D-gels. The generality of this new approach was confirmed using thylakoid membrane from spinach (Spinacia oleracea and pumpkin (Cucurita spp. Furthermore, the proteins separated from rice thylakoid membrane were identified by the mass spectrometry (MS. The stromal ridge proteins PsaD and PsaE were identified both in the holo- and core- PSI complexes of rice. Using molecular dynamics simulation to explore the recognition mechanism of these subunits, we showed that salt bridge interactions between residues R19 of PsaC and E168 of PasD as well as R75 of PsaC and E91 of PsaD played important roles in the stability of the complex. This stromal ridge subunits interaction was also supported by the subsequent analysis of the binding free energy, the intramolecular distances and the intramolecular energy.

  3. Photophysical Studies of Bioconjugated Ruthenium Metal-Ligand Complexes Incorporated in Phospholipid Membrane Bilayers

    Science.gov (United States)

    Sharmin, Ayesha; Salassa, Luca; Rosenberg, Edward; Ross, J. B. Alexander; Abbott, Geoffrey; Black, Labe; Terwilliger, Michelle; Brooks, Robert

    2013-01-01

    Luminescent, mono-diimine, ruthenium complexes, [(H)Ru(CO)(PPh3)2(dcbpy)][PF6] (1, dcbpy = 4,4′-dicarboxy bipyridyl) and [(H)Ru(CO)(dppene)(5-amino-1,10-phen)][PF6] (2, dppene = bis diphenylphosphino-ethylene, phen = 9,10-phenanthroline), have been conjugated with 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DPPE) and with cholesterol in the case of 2. Compound 1 gives the bis-lipid derivative [(H)Ru(CO)(PPh3)2(dcbpy-N-DPPE2)][PF6] (3), while 2 provides the mono-lipid conjugate [(H)Ru(CO)(dppene)(1,10-phen-5-NHC(S)-N-DPPE)][ PF6] (4), and the cholesterol derivative [(H)Ru(CO)(dppene)(1,10-phen-5-NHC(O)OChol)][PF6] (5, Chol = cholesteryl), using standard conjugation techniques. These compounds were characterized by spectroscopic methods, and their photophysical properties were measured in organic solvents. The luminescence of lipid conjugates 3 and is quenched in organic solvents while compound 4 a weak, short-lived, blue-shifted emission in solution. The cholesterol conjugate shows the long-lived, microsecond-timescale emission associated with triplet metal-to-ligand charge-transfer (3MLCT) excited states. Incorporation of conjugate 3 in lipid bilayer vesicles restores the luminescence, but with blue shifts (~80 nm) accompanied by nanosecond-timescale lifetimes. In the vesicles conjugate 4 shows a similar short-lived and blue-shifted emission to that observed in solution but with increased intensity. Conjugation of the complex [(H)Ru(CO)(PhP2C2H4C(O)O-N-succinimidyl)2(bpy)][PF6] (6”) with DPPE gives the phosphine-conjugated complex [(H)Ru(CO)(PhP2C2H4C(O)-N-DPPE)2(bpy)][PF6] (7). Complex 7 also exhibits a short-lived and blue-shifted emission in solution and in vesicles as observed for 3 and 4. We have also conjugated the complex [Ru(bpy)2(5-amino-1,10-phenanthroline)][PF6]2 (8) with both cholesterol (9) and DPPE (10). Neither 9 nor the previously reported 10 exhibited the blue shifts observed for 3 and 4 when incorporated into LUVs. The anisotropies of

  4. Effect of partial or complete elimination of light-harvesting complexes on the surface electric properties and the functions of cyanobacterial photosynthetic membranes.

    Science.gov (United States)

    Dobrikova, Anelia G; Domonkos, Ildikó; Sözer, Özge; Laczkó-Dobos, Hajnalka; Kis, Mihály; Párducz, Árpád; Gombos, Zoltán; Apostolova, Emilia L

    2013-02-01

    Influence of the modification of the cyanobacterial light-harvesting complex [i.e. phycobilisomes (PBS)] on the surface electric properties and the functions of photosynthetic membranes was investigated. We used four PBS mutant strains of Synechocystis sp. PCC6803 as follows: PAL (PBS-less), CK (phycocyanin-less), BE (PSII-PBS-less) and PSI-less/apcE(-) (PSI-less with detached PBS). Modifications of the PBS content lead to changes in the cell morphology and surface electric properties of the thylakoid membranes as well as in their functions, such as photosynthetic oxygen-evolving activity, P700 kinetics and energy transfer between the pigment-protein complexes. Data reveal that the complete elimination of PBS in the PAL mutant causes a slight decrease in the electric dipole moments of the thylakoid membranes, whereas significant perturbations of the surface charges were registered in the membranes without assembled PBS-PSII macrocomplex (BE mutant) or PSI complex (PSI-less mutant). These observations correlate with the detected alterations in the membrane structural organization. Using a polarographic oxygen rate electrode, we showed that the ratio of the fast to the slow oxygen-evolving PSII centers depends on the partial or complete elimination of light-harvesting complexes, as the slow operating PSII centers dominate in the PBS-less mutant and in the mutant with detached PBS. Copyright © Physiologia Plantarum 2012.

  5. Membrane Association of the PTEN Tumor Suppressor: Molecular Details of the Protein-Membrane Complex from SPR Binding Studies and Neutron Reflection

    Science.gov (United States)

    Shenoy, Siddharth; Shekhar, Prabhanshu; Heinrich, Frank; Daou, Marie-Claire; Gericke, Arne; Ross, Alonzo H.; Lösche, Mathias

    2012-01-01

    The structure and function of the PTEN phosphatase is investigated by studying its membrane affinity and localization on in-plane fluid, thermally disordered synthetic membrane models. The membrane association of the protein depends strongly on membrane composition, where phosphatidylserine (PS) and phosphatidylinositol diphosphate (PI(4,5)P2) act pronouncedly synergistic in pulling the enzyme to the membrane surface. The equilibrium dissociation constants for the binding of wild type (wt) PTEN to PS and PI(4,5)P2 were determined to be Kd∼12 µM and 0.4 µM, respectively, and Kd∼50 nM if both lipids are present. Membrane affinities depend critically on membrane fluidity, which suggests multiple binding sites on the protein for PI(4,5)P2. The PTEN mutations C124S and H93R show binding affinities that deviate strongly from those measured for the wt protein. Both mutants bind PS more strongly than wt PTEN. While C124S PTEN has at least the same affinity to PI(4,5)P2 and an increased apparent affinity to PI(3,4,5)P3, due to its lack of catalytic activity, H93R PTEN shows a decreased affinity to PI(4,5)P2 and no synergy in its binding with PS and PI(4,5)P2. Neutron reflection measurements show that the PTEN phosphatase “scoots" along the membrane surface (penetration protein, ∼60 Å away from the bilayer surface, in a rather compact structure. The combination of binding studies and neutron reflection allows us to distinguish between PTEN mutant proteins and ultimately may identify the structural features required for membrane binding and activation of PTEN. PMID:22505997

  6. Distribution of interleukin-1 receptor complex at the synaptic membrane driven by interleukin-1β and NMDA stimulation.

    Science.gov (United States)

    Gardoni, Fabrizio; Boraso, Mariaserena; Zianni, Elisa; Corsini, Emanuela; Galli, Corrado L; Cattabeni, Flaminio; Marinovich, Marina; Di Luca, Monica; Viviani, Barbara

    2011-02-11

    Interleukin-1β (IL-1β) is a pro-inflammatory cytokine that contributes to neuronal injury in various degenerative diseases, and is therefore a potential therapeutic target. It exerts its biological effect by activating the interleukin-1 receptor type I (IL-1RI) and recruiting a signalling core complex consisting of the myeloid differentiation primary response protein 88 (MyD88) and the IL-1R accessory protein (IL-1RAcP). This pathway has been clearly described in the peripheral immune system, but only scattered information is available concerning the molecular composition and distribution of its members in neuronal cells. The findings of this study show that IL-1RI and its accessory proteins MyD88 and IL-1RAcP are differently distributed in the hippocampus and in the subcellular compartments of primary hippocampal neurons. In particular, only IL-1RI is enriched at synaptic sites, where it co-localises with, and binds to the GluN2B subunit of NMDA receptors. Furthermore, treatment with NMDA increases IL-1RI interaction with NMDA receptors, as well as the surface expression and localization of IL-1RI at synaptic membranes. IL-1β also increases IL-1RI levels at synaptic sites, without affecting the total amount of the receptor in the plasma membrane. Our results reveal for the first time the existence of a dynamic and functional interaction between NMDA receptor and IL-1RI systems that could provide a molecular basis for IL-1β as a neuromodulator in physiological and pathological events relying on NMDA receptor activation.

  7. Histones have high affinity for the glomerular basement membrane. Relevance for immune complex formation in lupus nephritis

    International Nuclear Information System (INIS)

    Schmiedeke, T.M.; Stoeckl, F.W.W.; Weber, R.; Sugisaki, Y.; Batsford, S.R.; Vogt, A.

    1989-01-01

    An effort has been made to integrate insights on charge-based interactions in immune complex glomerulonephritis with nuclear antigen involvement in lupus nephritis. Attention was focussed on the histones, a group of highly cationic nuclear constituents, which could be expected to bind to fixed anionic sites present in the glomerular basement membrane (GBM). We demonstrated that all histone subfractions, prepared according to Johns, have a high affinity for GBM and the basement membrane of peritubular capillaries. Tissue uptake of 125 I-labeled histones was measured by injecting 200 micrograms of each fraction into the left kidney via the aorta and measuring organ uptake after 15 min. In glomeruli isolated from the left kidneys, the following quantities of histones were found: f1, 13 micrograms; f2a (f2al + f2a2), 17 micrograms; f2b, 17 micrograms; and f3, 32 micrograms. Kinetic studies of glomerular binding showed that f1 disappeared much more rapidly than f2a. The high affinity of histones (pI between 10.5 and 11.0; mol wt 10,000-22,000) for the GBM correlates well with their ability to form aggregates (mol wt greater than 100,000) for comparison lysozyme (pI 11, mol wt 14,000), which does not aggregate spontaneously bound poorly (0.4 micrograms in isolated glomeruli). The quantity of histones and lysozyme found in the isolated glomeruli paralleled their in vitro affinity for a Heparin-Sepharose column (gradient elution studies). This gel matrix contains the sulfated, highly anionic polysaccharide heparin, which is similar to the negatively charged heparan sulfate present in the GBM. Lysozyme eluted with 0.15 M NaCl, f1 with 1 M NaCl, and f2a, f2b, and f3 could not be fully desorbed even with 2 M NaCl; 6 M guanidine-HCl was necessary

  8. Histones have high affinity for the glomerular basement membrane. Relevance for immune complex formation in lupus nephritis

    Energy Technology Data Exchange (ETDEWEB)

    Schmiedeke, T.M.; Stoeckl, F.W.W.; Weber, R.; Sugisaki, Y.; Batsford, S.R.; Vogt, A.

    1989-06-01

    An effort has been made to integrate insights on charge-based interactions in immune complex glomerulonephritis with nuclear antigen involvement in lupus nephritis. Attention was focussed on the histones, a group of highly cationic nuclear constituents, which could be expected to bind to fixed anionic sites present in the glomerular basement membrane (GBM). We demonstrated that all histone subfractions, prepared according to Johns, have a high affinity for GBM and the basement membrane of peritubular capillaries. Tissue uptake of /sup 125/I-labeled histones was measured by injecting 200 micrograms of each fraction into the left kidney via the aorta and measuring organ uptake after 15 min. In glomeruli isolated from the left kidneys, the following quantities of histones were found: f1, 13 micrograms; f2a (f2al + f2a2), 17 micrograms; f2b, 17 micrograms; and f3, 32 micrograms. Kinetic studies of glomerular binding showed that f1 disappeared much more rapidly than f2a. The high affinity of histones (pI between 10.5 and 11.0; mol wt 10,000-22,000) for the GBM correlates well with their ability to form aggregates (mol wt greater than 100,000) for comparison lysozyme (pI 11, mol wt 14,000), which does not aggregate spontaneously bound poorly (0.4 micrograms in isolated glomeruli). The quantity of histones and lysozyme found in the isolated glomeruli paralleled their in vitro affinity for a Heparin-Sepharose column (gradient elution studies). This gel matrix contains the sulfated, highly anionic polysaccharide heparin, which is similar to the negatively charged heparan sulfate present in the GBM. Lysozyme eluted with 0.15 M NaCl, f1 with 1 M NaCl, and f2a, f2b, and f3 could not be fully desorbed even with 2 M NaCl; 6 M guanidine-HCl was necessary.

  9. Membrane signalling complexes: implications for development of functionally selective ligands modulating heptahelical receptor signalling.

    Science.gov (United States)

    Piñeyro, Graciela

    2009-02-01

    Technological development has considerably changed the way in which we evaluate drug efficacy and has led to a conceptual revolution in pharmacological theory. In particular, molecular resolution assays have revealed that heptahelical receptors may adopt multiple active conformations with unique signalling properties. It is therefore becoming widely accepted that ligand ability to stabilize receptor conformations with distinct signalling profiles may allow to direct the stimulus generated by an activated receptor towards a specific signalling pathway. This capacity to induce only a subset of the ensemble of responses regulated by a given receptor has been termed "functional selectivity" (or "stimulus trafficking"), and provides the bases for a highly specific regulation of receptor signalling. Concomitant with these observations, heptahelical receptors have been shown to associate with G proteins and effectors to form multimeric arrays. These complexes are constitutively formed during protein synthesis and are targeted to the cell surface as integral signalling units. Herein we summarize evidence supporting the existence of such constitutive signalling arrays and analyze the possibility that they may constitute viable targets for developing ligands with "functional selectivity".

  10. N-terminal arginines modulate plasma-membrane localization of Kv7.1/KCNE1 channel complexes.

    Directory of Open Access Journals (Sweden)

    Zenawit Girmatsion

    Full Text Available BACKGROUND AND OBJECTIVE: The slow delayed rectifier current (I(Ks is important for cardiac action potential termination. The underlying channel is composed of Kv7.1 α-subunits and KCNE1 β-subunits. While most evidence suggests a role of KCNE1 transmembrane domain and C-terminus for the interaction, the N-terminal KCNE1 polymorphism 38G is associated with reduced I(Ks and atrial fibrillation (a human arrhythmia. Structure-function relationship of the KCNE1 N-terminus for I(Ks modulation is poorly understood and was subject of this study. METHODS: We studied N-terminal KCNE1 constructs disrupting structurally important positively charged amino-acids (arginines at positions 32, 33, 36 as well as KCNE1 constructs that modify position 38 including an N-terminal truncation mutation. Experimental procedures included molecular cloning, patch-clamp recording, protein biochemistry, real-time-PCR and confocal microscopy. RESULTS: All KCNE1 constructs physically interacted with Kv7.1. I(Ks resulting from co-expression of Kv7.1 with non-atrial fibrillation '38S' was greater than with any other construct. Ionic currents resulting from co-transfection of a KCNE1 mutant with arginine substitutions ('38G-3xA' were comparable to currents evoked from cells transfected with an N-terminally truncated KCNE1-construct ('Δ1-38'. Western-blots from plasma-membrane preparations and confocal images consistently showed a greater amount of Kv7.1 protein at the plasma-membrane in cells co-transfected with the non-atrial fibrillation KCNE1-38S than with any other construct. CONCLUSIONS: The results of our study indicate that N-terminal arginines in positions 32, 33, 36 of KCNE1 are important for reconstitution of I(Ks. Furthermore, our results hint towards a role of these N-terminal amino-acids in membrane representation of the delayed rectifier channel complex.

  11. Heterotrimeric G protein beta1gamma2 subunits change orientation upon complex formation with G protein-coupled receptor kinase 2 (GRK2) on a model membrane.

    Science.gov (United States)

    Boughton, Andrew P; Yang, Pei; Tesmer, Valerie M; Ding, Bei; Tesmer, John J G; Chen, Zhan

    2011-09-13

    Few experimental techniques can assess the orientation of peripheral membrane proteins in their native environment. Sum Frequency Generation (SFG) vibrational spectroscopy was applied to study the formation of the complex between G protein-coupled receptor (GPCR) kinase 2 (GRK2) and heterotrimeric G protein β(1)γ(2) subunits (Gβγ) at a lipid bilayer, without any exogenous labels. The most likely membrane orientation of the GRK2-Gβγ complex differs from that predicted from the known protein crystal structure, and positions the predicted receptor docking site of GRK2 such that it would more optimally interact with GPCRs. Gβγ also appears to change its orientation after binding to GRK2. The developed methodology is widely applicable for the study of other membrane proteins in situ.

  12. Two conformational states of the membrane-associated Bacillus thuringiensis Cry4Ba δ-endotoxin complex revealed by electron crystallography: Implications for toxin-pore formation

    International Nuclear Information System (INIS)

    Ounjai, Puey; Unger, Vinzenz M.; Sigworth, Fred J.; Angsuthanasombat, Chanan

    2007-01-01

    The insecticidal nature of Cry δ-endotoxins produced by Bacillus thuringiensis is generally believed to be caused by their ability to form lytic pores in the midgut cell membrane of susceptible insect larvae. Here we have analyzed membrane-associated structures of the 65-kDa dipteran-active Cry4Ba toxin by electron crystallography. The membrane-associated toxin complex was crystallized in the presence of DMPC via detergent dialysis. Depending upon the charge of the adsorbed surface, 2D crystals of the oligomeric toxin complex have been captured in two distinct conformations. The projection maps of those crystals have been generated at 17 A resolution. Both complexes appeared to be trimeric; as in one crystal form, its projection structure revealed a symmetrical pinwheel-like shape with virtually no depression in the middle of the complex. The other form revealed a propeller-like conformation displaying an obvious hole in the center region, presumably representing the toxin-induced pore. These crystallographic data thus demonstrate for the first time that the 65-kDa activated Cry4Ba toxin in association with lipid membranes could exist in at least two different trimeric conformations, conceivably implying the closed and open states of the pore

  13. Membrane-surfactant interactions. The role of surfactant in mitochondrial complex III-phospholipid-Triton X-100 mixed micelles

    International Nuclear Information System (INIS)

    Valpuesta, J.M.; Arrondo, J.L.; Barbero, M.C.; Pons, M.; Goni, F.M.

    1986-01-01

    Complex III (ubiquinol-cytochrome c reductase) was purified from beef heart mitochondria in the form of protein-phospholipid-Triton X-100 mixed micelles (about 1:80:100 molar ratio). Detergent may be totally removed by sucrose density gradient centrifugation, and the resulting lipoprotein complexes retain full enzyme activity. In order to understand the role of surfactant in the mixed micelles, and the interaction of Triton X-100 with integral membrane proteins and phospholipid bilayers, both the protein-lipid-surfactant mixed micelles and the detergent-free lipoprotein system were examined from the point of view of particle size and ultrastructure, enzyme activity, tryptophan fluorescence quenching, 31P NMR, and Fourier transform infrared spectroscopy. The NMR and IR spectroscopic studies show that surfactant withdrawal induces a profound change in phospholipid architecture, from a micellar to a lamellar-like phase. However, electron microscopic observations fail to reveal the existence of lipid bilayers in the absence of detergent. We suggest that, under these conditions, the lipid:protein molar ratio (80:1) is too low to permit the formation of lipid bilayer planes, but the relative orientation and mobility of phospholipids with respect to proteins is similar to that of the lamellar phase. Protein conformational changes are also detected as a consequence of surfactant removal. Fourier transform infrared spectroscopy indicates an increase of peptide beta-structure in the absence of Triton X-100; changes in the amide II/amide I intensity ratio are also detected, although the precise meaning of these observations is unclear

  14. PF-1355, a mechanism-based myeloperoxidase inhibitor, prevents immune complex vasculitis and anti-glomerular basement membrane glomerulonephritis.

    Science.gov (United States)

    Zheng, Wei; Warner, Roscoe; Ruggeri, Roger; Su, Chunyan; Cortes, Christian; Skoura, Athanasia; Ward, Jessica; Ahn, Kay; Kalgutkar, Amit; Sun, Dexue; Maurer, Tristan S; Bonin, Paul D; Okerberg, Carlin; Bobrowski, Walter; Kawabe, Thomas; Zhang, Yanwei; Coskran, Timothy; Bell, Sammy; Kapoor, Bhupesh; Johnson, Kent; Buckbinder, Leonard

    2015-05-01

    Small vessel vasculitis is a life-threatening condition and patients typically present with renal and pulmonary injury. Disease pathogenesis is associated with neutrophil accumulation, activation, and oxidative damage, the latter being driven in large part by myeloperoxidase (MPO), which generates hypochlorous acid among other oxidants. MPO has been associated with vasculitis, disseminated vascular inflammation typically involving pulmonary and renal microvasculature and often resulting in critical consequences. MPO contributes to vascular injury by 1) catabolizing nitric oxide, impairing vasomotor function; 2) causing oxidative damage to lipoproteins and endothelial cells, leading to atherosclerosis; and 3) stimulating formation of neutrophil extracellular traps, resulting in vessel occlusion and thrombosis. Here we report a selective 2-thiouracil mechanism-based MPO inhibitor (PF-1355 [2-(6-(2,5-dimethoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide) and demonstrate that MPO is a critical mediator of vasculitis in mouse disease models. A pharmacokinetic/pharmacodynamic response model of PF-1355 exposure in relation with MPO activity was derived from mouse peritonitis. The contribution of MPO activity to vasculitis was then examined in an immune complex model of pulmonary disease. Oral administration of PF-1355 reduced plasma MPO activity, vascular edema, neutrophil recruitment, and elevated circulating cytokines. In a model of anti-glomerular basement membrane disease, formerly known as Goodpasture disease, albuminuria and chronic renal dysfunction were completely suppressed by PF-1355 treatment. This study shows that MPO activity is critical in driving immune complex vasculitis and provides confidence in testing the hypothesis that MPO inhibition will provide benefit in treating human vasculitic diseases. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

  15. Membrane Recruitment of Aut7p in the Autophagy and Cytoplasm to Vacuole Targeting Pathways Requires Aut1p, Aut2p, and the Autophagy Conjugation Complex

    Science.gov (United States)

    Kim, John; Huang, Wei-Pang; Klionsky, Daniel J.

    2001-01-01

    Autophagy is a degradative pathway by which cells sequester nonessential, bulk cytosol into double-membrane vesicles (autophagosomes) and deliver them to the vacuole for recycling. Using this strategy, eukaryotic cells survive periods of nutritional starvation. Under nutrient-rich conditions, autophagy machinery is required for the delivery of a resident vacuolar hydrolase, aminopeptidase I, by the cytoplasm to vacuole targeting (Cvt) pathway. In both pathways, the vesicle formation process requires the function of the starvation-induced Aut7 protein, which is recruited from the cytosol to the forming Cvt vesicles and autophagosomes. The membrane binding of Aut7p represents an early step in vesicle formation. In this study, we identify several requirements for Aut7p membrane association. After synthesis in the cytosol, Aut7p is proteolytically cleaved in an Aut2p-dependent manner. While this novel processing event is essential for Aut7p membrane binding, Aut7p must undergo additional physical interactions with Aut1p and the autophagy (Apg) conjugation complex before recruitment to the membrane. Lack of these interactions results in a cytosolic distribution of Aut7p rather than localization to forming Cvt vesicles and autophagosomes. This study assigns a functional role for the Apg conjugation system as a mediator of Aut7p membrane recruitment. Further, we demonstrate that Aut1p, which physically interacts with components of the Apg conjugation complex and Aut7p, constitutes an additional factor required for Aut7p membrane recruitment. These findings define a series of steps that results in the modification of Aut7p and its subsequent binding to the sequestering transport vesicles of the autophagy and cytoplasm to vacuole targeting pathways. PMID:11149920

  16. Coordinated rearrangements between cytoplasmic and periplasmic domains of the membrane protein complex ExbB-ExbD of Escherichia coli.

    Science.gov (United States)

    Sverzhinsky, Aleksandr; Fabre, Lucien; Cottreau, Andrew L; Biot-Pelletier, Damien M P; Khalil, Sofia; Bostina, Mihnea; Rouiller, Isabelle; Coulton, James W

    2014-05-06

    Gram-negative bacteria rely on the ExbB-ExbD-TonB system for the import of essential nutrients. Despite decades of research, the stoichiometry, subunit organization, and mechanism of action of the membrane proteins of the Ton system remain unclear. We copurified ExbB with ExbD as an ∼240 kDa protein-detergent complex, measured by light scattering and by native gels. Quantitative Coomassie staining revealed a stoichiometry of ExbB4-ExbD2. Negative stain electron microscopy and 2D analysis showed particles of ∼10 nm diameter in multiple structural states. Nanogold labeling identified the position of the ExbD periplasmic domain. Random conical tilt was used to reconstruct the particles in three structural states followed by sorting of the single particles and refinement of each state. The different states are interpreted by coordinated structural rearrangements between the cytoplasmic domain and the periplasmic domain, concordant with in vivo predictions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Fabrication of copper-selective PVC membrane electrode based on newly synthesized copper complex of Schiff base as carrier

    Directory of Open Access Journals (Sweden)

    Sulekh Chandra

    2016-09-01

    Full Text Available The newly synthesized copper(II complex of Schiff base p-hydroxyacetophenone semicarbazone was explored as neutral ionophore for the fabrication of poly(vinylchloride (PVC based membrane electrode selective to Cu(II ions. The electrode shows a Nernstian slope of 29.8 ± 0.3 mV/decade with improved linear range of 1.8 × 10−7 to 1.0 × 10−1 M, comparatively lower detection limit 5.7 × 10−8 M between pH range of 2.0–8.0, giving a relatively fast response within 5s and can be used for at least 16 weeks without any divergence in potential. The selectivity coefficient was calculated using the fixed interference method (FIM. The electrode can also be used in partially non-aqueous media having up to 25% (v/v methanol, ethanol or acetone content with no significant change in the value of slope or working concentration range. It was successfully applied for the direct determination of copper content in water and tea samples with satisfactory results. The electrode has been used in the potentiometric titration of Cu2+ with EDTA.

  18. Genetic and biochemical characterization of ISP6, a small mitochondrial outer membrane protein associated with the protein translocation complex.

    OpenAIRE

    Kassenbrock, C K; Cao, W; Douglas, M G

    1993-01-01

    To search genetically for additional components of the protein translocation apparatus of mitochondria, we have used low fidelity PCR mutagenesis to generate temperature-sensitive mutants in the outer membrane translocation pore component ISP42. A high copy number suppressor of temperature-sensitive isp42 has been isolated and sequenced. This novel gene, denoted ISP6, encodes a 61 amino acid integral membrane protein of the mitochondrial outer membrane, which is oriented with its amino-termin...

  19. Membrane paradigm

    International Nuclear Information System (INIS)

    Price, R.H.; Thorne, K.S.

    1986-01-01

    The membrane paradigm is a modified frozen star approach to modeling black holes, with particles and fields assuming a complex, static, boundary-layer type structure (membrane) near the event horizon. The membrane has no effects on the present or future evolution of particles and fields above itself. The mathematical representation is a combination of a formalism containing terms for the shear and bulk viscosity, surface pressure, momentum, temperature, entropy, etc., of the horizon and the 3+1 formalism. The latter model considers a family of three-dimensional spacelike hypersurfaces in one-dimensional time. The membrane model considers a magnetic field threading the hole and undergoing torque from the hole rotation. The field is cleaned by the horizon and distributed over the horizon so that ohmic dissipation is minimized. The membrane paradigm is invalid inside the horizon, but is useful for theoretically probing the properties of slowly evolving black holes

  20. Malaria Parasite CLAG3, a Protein Linked to Nutrient Channels, Participates in High Molecular Weight Membrane-Associated Complexes in the Infected Erythrocyte.

    Directory of Open Access Journals (Sweden)

    Kayvan Zainabadi

    Full Text Available Malaria infected erythrocytes show increased permeability to a number of solutes important for parasite growth as mediated by the Plasmodial Surface Anion Channel (PSAC. The P. falciparum clag3 genes have recently been identified as key determinants of PSAC, though exactly how they contribute to channel function and whether additional host/parasite proteins are required remain unknown. To begin to answer these questions, I have taken a biochemical approach. Here I have used an epitope-tagged CLAG3 parasite to perform co-immunoprecipitation experiments using membrane fractions of infected erythrocytes. Native PAGE and mass spectrometry studies reveal that CLAG3 participate in at least three different high molecular weight complexes: a ~720kDa complex consisting of CLAG3, RHOPH2 and RHOPH3; a ~620kDa complex consisting of CLAG3 and RHOPH2; and a ~480kDa complex composed solely of CLAG3. Importantly, these complexes can be found throughout the parasite lifecycle but are absent in untransfected controls. Extracellular biotin labeling and protease susceptibility studies localize the 480kDa complex to the erythrocyte membrane. This complex, likely composed of a homo-oligomer of 160kDa CLAG3, may represent a functional subunit, possibly the pore, of PSAC.

  1. Primordial membranes

    DEFF Research Database (Denmark)

    Hanczyc, Martin M; Monnard, Pierre-Alain

    2017-01-01

    Cellular membranes, which are self-assembled bilayer structures mainly composed of lipids, proteins and conjugated polysaccharides, are the defining feature of cell physiology. It is likely that the complexity of contemporary cells was preceded by simpler chemical systems or protocells during...... the various evolutionary stages that led from inanimate to living matter. It is also likely that primitive membranes played a similar role in protocell 'physiology'. The composition of such ancestral membranes has been proposed as mixtures of single hydrocarbon chain amphiphiles, which are simpler versions...

  2. Correlation between spatial (3D) structure of pea and bean thylakoid membranes and arrangement of chlorophyll-protein complexes

    NARCIS (Netherlands)

    Rumak, Izabela; Mazur, Radoslaw; Gieczewska, Katarzyna; Koziol-Lipinska, Joanna; Kierdaszuk, Borys; Michalski, Wojtek P.; Shiell, Brian J.; Venema, Jan Henk; Vredenberg, Wim J.; Mostowska, Agnieszka; Garstka, Maciej

    2012-01-01

    Background: The thylakoid system in plant chloroplasts is organized into two distinct domains: grana arranged in stacks of appressed membranes and non-appressed membranes consisting of stroma thylakoids and margins of granal stacks. It is argued that the reason for the development of appressed

  3. Encapsulation and controlled release of lysozyme from electrospun poly(epsilon-caprolactone)/poly(ethylene glycol) non-woven membranes by formation of lysozyme-oleate complexes.

    Science.gov (United States)

    Li, Yan; Jiang, Hongliang; Zhu, Kangjie

    2008-02-01

    In this study, the concept of hydrophobic ion pairing was adopted for incorporating lysozyme into electrospun poly(epsilon-caprolactone) (PCL)/poly(ethylene glycol) (PEG) non-woven membranes. The solubility of lysozyme in organic solvent was enhanced through the formation of lysozyme-oleate complexes, which could be directly loaded into PCL/PEG membranes using electrospinning technique. The resultant PCL/PEG nanofibers have a compact structure with an average diameter ranged from about 0.4 microm to 0.9 microm. The addition of PEG into the PCL nanofibers not only improved the hydrophilicity of the membrane, but also played an important role on in vitro lysozyme release rate. It was found that the release rate of lysozyme was enhanced with the increase of PEG content. In addition, the increase of salt concentration in the release medium accelerated lysozyme release. It has also been shown that the released lysozyme retained most of its enzymatic activity.

  4. Contribution of LHC II complex to the electric properties of thylakoid membranes: an electric light scattering study of Chl b-less barley mutant.

    Science.gov (United States)

    Dobrikova, A G; Ivanov, A G; Morgan, R; Petkanchin, I B; Taneva, S G

    2000-08-01

    Electric light scattering measurements demonstrate a strong decline in the permanent electric dipole moment and electric polarizability of both thylakoid membranes and photosystem II-enriched particles of the Chlorina f2 mutant which has severely reduced levels of light-harvesting chlorophyll a/b-binding proteins compared to the wild type barley chloroplasts. The shift in the electric polarizability relaxation to higher frequencies in thylakoids and photosystem II particles from Chlorina f2 reflects higher mobility of the interfacial charges of the mutant than that of the wild type membranes. The experimental data strongly suggest that the major light-harvesting complex of photosystem II directly contribute to the electric properties of thylakoid membranes.

  5. Influence of thylakoid membrane lipids on the structure of aggregated light-harvesting complexes of the diatom Thalassiosira pseudonana and the green alga Mantoniella squamata.

    Science.gov (United States)

    Schaller-Laudel, Susann; Latowski, Dariusz; Jemioła-Rzemińska, Małgorzata; Strzałka, Kazimierz; Daum, Sebastian; Bacia, Kirsten; Wilhelm, Christian; Goss, Reimund

    2017-07-01

    The study investigated the effect of the thylakoid membrane lipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulphoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG) on the structure of two algal light-harvesting complexes (LHCs). In contrast to higher plants whose thylakoid membranes are characterized by an enrichment of the neutral galactolipids MGDG and DGDG, both the green alga Mantoniella squamata and the centric diatom Thalassiosira pseudonana contain membranes with a high content of the negatively charged lipids SQDG and PG. The algal thylakoids do not show the typical grana-stroma differentiation of higher plants but a regular arrangement. To analyze the effect of the membrane lipids, the fucoxanthin chlorophyll protein (FCP) complex of T. pseudonana and the LHC of M. squamata (MLHC) were prepared by successive cation precipitation using Triton X-100 as detergent. With this method, it is possible to isolate LHCs with a reduced amount of associated lipids in an aggregated state. The results from 77 K fluorescence and photon correlation spectroscopy show that neither the neutral galactolipids nor the negatively charged lipids are able to significantly alter the aggregation state of the FCP or the MLHC. This is in contrast to higher plants where SQDG and PG lead to a strong disaggregation of the LHCII whereas MGDG and DGDG induce the formation of large macroaggregates. The results indicate that LHCs which are integrated into thylakoid membranes with a high amount of negatively charged lipids and a regular arrangement are less sensitive to lipid-induced structural alterations than their counterparts in membranes enriched in neutral lipids with a grana-stroma differentiation. © 2017 Scandinavian Plant Physiology Society.

  6. A novel method for visualizing hair lipids at the cell membrane complex: argon sputter etching/scanning electron microscopy.

    Science.gov (United States)

    Masukawa, Yoshinori; Shimogaki, Hiromi; Manago, Kenji; Imokawa, Genji

    2005-01-01

    Hair lipids localized at the cell membrane complex (CMC) play a part in chemical diffusion, cell cohesion, and mechanical strength. There is no method currently available to visualize hair lipids at the CMC. We found that scanning electron microscopy (SEM) of a transversely polished hair plane followed by argon sputter etching (ASE) provides a specific characteristic image consisting of circular patterns (CP) and stitch patterns (SP) at the cortex. Both the CP and the SP are formed as convex structures and are associated with melanin granules and the CMC, respectively. While the convex formation of the CP is not affected by any treatments tested, that of the SP disappeared following treatment of hair fibers with organic solvents and reappeared following incubation of the solvent-treated hair fibers with melting lipids, which suggests that the hair lipids are responsible for the convex SP. Other treatments, such as chemical fixation, thin sectioning, and pre-/post-incubation of the hair plane, reduce or abolish the convex formation of the SP. These findings suggest that the following pathway leads to the convex formation of SP during ASE: (a) joule heat is generated on the surface by violent collisions of argon ions, (b) melting CMC lipids ooze out from the inside to the surface, and (c) CMC lipids that have oozed out are chemically changed, leading to the final convex formation of the SP. With ASE-SEM, visualization of hair lipids as convex structures of SP should enable us to characterize the fine structure and localization of hair lipids and to clarify the roles and functions of the CMC of human hair.

  7. Outer membrane protein complex of Meningococcus enhances the antipolysaccharide antibody response to pneumococcal polysaccharide-CRM₁₉₇ conjugate vaccine.

    Science.gov (United States)

    Lai, Zengzu; Schreiber, John R

    2011-05-01

    Bacterial polysaccharides (PS) are T cell-independent antigens that do not induce immunologic memory and are poor immunogens in infants. Conjugate vaccines in which the PS is covalently linked to a carrier protein have enhanced immunogenicity that resembles that of T cell-dependent antigens. The Haemophilus influenzae type b (Hib) conjugate vaccine, which uses the outer membrane protein complex (OMPC) from meningococcus as a carrier protein, elicits protective levels of anti-capsular PS antibody (Ab) after a single dose, in contrast to other conjugate vaccines, which require multiple doses. We have previously shown that OMPC robustly engages Toll-like receptor 2 (TLR2) and enhances the early anti-Hib PS Ab titer associated with an increase in TLR2-mediated induction of cytokines. We now show that the addition of OMPC to the 7-valent pneumococcal PS-CRM₁₉₇ conjugate vaccine during immunization significantly increases the anti-PS IgG and IgM responses to most serotypes of pneumococcus contained in the vaccine. The addition of OMPC also increased the likelihood of anti-PS IgG3 production against serotypes 4, 6B, 9V, 18C, 19F, and 23F. Splenocytes from mice who had received OMPC with the pneumococcal conjugate vaccine produced significantly more interleukin-2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ) than splenocytes from mice who received phosphate-buffered saline (PBS) plus the conjugate vaccine. We conclude that OMPC enhances the anti-PS Ab response to pneumococcal PS-CRM₁₉₇ conjugate vaccine, an effect associated with a distinct change in cytokine profile. It may be possible to reduce the number of conjugate vaccine doses required to achieve protective Ab levels by priming with adjuvants that are TLR2 ligands.

  8. Construction of Uranyl Selective Electrode Based on Complex of Uranyl Ion with New Ligand Carboxybenzotriazole in PVC Matrix Membrane

    Science.gov (United States)

    Abu-Dalo, M. A.; Al-Rawashdeh, N. A. F.; Al-Mheidat, I. R.; Nassory, N. S.

    2015-10-01

    In the present study uranyl selective electrodes in polyvinyl chloride (PVC) matrix membrane were prepared based on a complex of uranyl ion (UO2) with carboxybenzotriazole (CBT) as ligand. The effect of the nature of plasticizer in PVC matrix were evaluated using three different plasticizers, these are dibutyl phthalate (DBP), dioctyl phthalate (DOP) and bis(2-ethylhexyl) sebacate (BHS). The results of this study indicated that the best plasticizer could be used is the DBP, which may be attributed to its lowest viscosity value compared to DOP and BHS. The electrodes with DBP as plasticizer exhibits a Nernstian response with a slope of 28.0 mV/ decade, over a wide range of concentration from 3.0×10-5-6.0×10-2 M and a detection limit of 4.0×10-6 M. It can be used in the pH range of 4.0-10.0 with a response time of less than 10 s for DBP and 25 s for both DOP and BHS. The effects of ions interferences on the electrode response were evaluated. The di- and tri-valent cations were found to interfere less than univalent cations, which was attributed to the high diffusion and the exchange rate between the univalent ions and the uranyl ion solution. The electrodes were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron microscopy (SEM). The results of the standard addition method were satisfactory with errors less than 7%. The developed electrode was found to be fast, sensitive and reliable indicated its potential use in measuring the uranly ion concentration in the field.

  9. The CDC50A extracellular domain is required for forming a functional complex with and chaperoning phospholipid flippases to the plasma membrane.

    Science.gov (United States)

    Segawa, Katsumori; Kurata, Sachiko; Nagata, Shigekazu

    2018-02-09

    Flippases are enzymes that translocate phosphatidylserine (PtdSer) and phosphatidylethanolamine (PtdEtn) from the outer to the inner leaflet in the lipid bilayer of the plasma membrane, leading to the asymmetric distribution of aminophospholipids in the membrane. One mammalian phospholipid flippase at the plasma membrane is ATP11C, a type IV P-type ATPase (P4-ATPase) that forms a heterocomplex with the transmembrane protein CDC50A. However, the structural features in CDC50A that support the function of ATP11C and other P4-ATPases have not been characterized. Here, using error-prone PCR-mediated mutagenesis of human CDC50A cDNA followed by functional screening and deep sequencing, we identified 14 amino acid residues that affect ATP11C's flippase activity. These residues were all located in CDC50A's extracellular domain and were evolutionarily well-conserved. Most of the mutations decreased CDC50A's ability to chaperone ATP11C and other P4-ATPases to their destinations. The CDC50A mutants failed to form a stable complex with ATP11C and could not induce ATP11C's PtdSer-dependent ATPase activity. Notably, one mutant variant could form a stable complex with ATP11C and transfer ATP11C to the plasma membrane, yet the ATP11C complexed with this CDC50A variant had very weak or little PtdSer- or PtdEtn-dependent ATPase activity. These results indicated that the extracellular domain of CDC50A has important roles both in CDC50A's ability to chaperone ATP11C to the plasma membrane and in inducing ATP11C's ATP hydrolysis-coupled flippase activity. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

  10. Porous rod-like MgO complex membrane with good anti-bacterial activity directed by conjugated linolenic acid polymer

    Science.gov (United States)

    Wang, Hua-Jie; Chen, Meng; Mi, Li-Wei; Shi, Li-Hua; Cao, Ying

    2016-02-01

    The problem of infection in the tissue engineering substitutes is driving us to seek new coating materials. We previously found that conjugated linolenic acid (CLnA) has well biocompatibility and excellent membrane-forming property. The objective of this study is to endow the anti-bacterial activity to CLnA membra ne by linking with MgO. The results showed that the CLnA polymer membrane can be loaded with porous rod-like MgO and such complex membrane showed anti-bacterial sensitivity against gram-positive bacteria ( Staphylococcus aureus) even at the low concentration (0.15 μg/mm2). In the present study, the best zone of inhibition got to 18.2 ± 0.8 mm when the amount of MgO reach 2.42 ± 0.58 μg/mm2. It was deduced that the porous rod-like structure of MgO was directed by CLnA in its polymerization process. Such CLnA/MgO complex membrane can be helpful in the tissue engineering, medicine, food engineering, food preservation, etc. on the basis of its good anti-bacterial activity.

  11. Porous rod-like MgO complex membrane with good anti-bacterial activity directed by conjugated linolenic acid polymer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hua-Jie, E-mail: wanghuajie972001@163.com; Chen, Meng [Henan Normal University, College of Chemistry and Chemical Engineering (China); Mi, Li-Wei, E-mail: mlwzzu@163.com [Zhongyuan University of Technology, Center for Advanced Materials Research (China); Shi, Li-Hua [Anyang 101 Education Center (China); Cao, Ying, E-mail: caoying1130@sina.com [Zhongyuan University of Technology, Center for Advanced Materials Research (China)

    2016-02-15

    The problem of infection in the tissue engineering substitutes is driving us to seek new coating materials. We previously found that conjugated linolenic acid (CLnA) has well biocompatibility and excellent membrane-forming property. The objective of this study is to endow the anti-bacterial activity to CLnA membra ne by linking with MgO. The results showed that the CLnA polymer membrane can be loaded with porous rod-like MgO and such complex membrane showed anti-bacterial sensitivity against gram-positive bacteria (Staphylococcus aureus) even at the low concentration (0.15 μg/mm{sup 2}). In the present study, the best zone of inhibition got to 18.2 ± 0.8 mm when the amount of MgO reach 2.42 ± 0.58 μg/mm{sup 2}. It was deduced that the porous rod-like structure of MgO was directed by CLnA in its polymerization process. Such CLnA/MgO complex membrane can be helpful in the tissue engineering, medicine, food engineering, food preservation, etc. on the basis of its good anti-bacterial activity.

  12. Membrane microdomains and the cytoskeleton constrain AtHIR1 dynamics and facilitate the formation of an AtHIR1-associated immune complex.

    Science.gov (United States)

    Lv, Xueqin; Jing, Yanping; Xiao, Jianwei; Zhang, Yongdeng; Zhu, Yingfang; Julian, Russell; Lin, Jinxing

    2017-04-01

    Arabidopsis hypersensitive-induced reaction (AtHIR) proteins function in plant innate immunity. However, the underlying mechanisms by which AtHIRs participate in plant immunity remain elusive. Here, using VA-TIRFM and FLIM-FRET, we revealed that AtHIR1 is present in membrane microdomains and co-localizes with the membrane microdomain marker REM1.3. Single-particle tracking analysis revealed that membrane microdomains and the cytoskeleton, especially microtubules, restrict the lateral mobility of AtHIR1 at the plasma membrane and facilitate its oligomerization. Furthermore, protein proximity index measurements, fluorescence cross-correlation spectroscopy, and biochemical experiments demonstrated that the formation of the AtHIR1 complex upon pathogen perception requires intact microdomains and cytoskeleton. Taken together, these findings suggest that microdomains and the cytoskeleton constrain AtHIR1 dynamics, promote AtHIR1 oligomerization, and increase the efficiency of the interactions of AtHIR1 with components of the AtHIR1 complex in response to pathogens, thus providing valuable insight into the mechanisms of defense-related responses in plants. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

  13. PathogenicLeptospiraSecreted Proteases Target the Membrane Attack Complex: A Potential Role for Thermolysin in Complement Inhibition.

    Science.gov (United States)

    Amamura, Thais A; Fraga, Tatiana R; Vasconcellos, Sílvio A; Barbosa, Angela S; Isaac, Lourdes

    2017-01-01

    Leptospirosis is a zoonosis caused by spirochetes from the genus Leptospira . This disease is common in tropical and subtropical areas, constituting a serious public health problem. Pathogenic Leptospira have the ability to escape the human Complement System, being able to survive when in contact with normal human serum. In a previous study, our group demonstrated that supernatants of pathogenic Leptospira (SPL) inhibit the three activation pathways of the Complement System. This inhibition can be directly correlated with the activity of secreted proteases, which cleave the Complement molecules C3, Factor B (Alternative Pathway), C4 and C2 (Classical and Lectin Pathways). In this work, we analyze the activity of the leptospiral proteases on the components of Terminal Pathway of Complement, called the membrane attack complex (MAC). We observed that proteases present in SPL from different Leptospira strains were able to cleave the purified proteins C5, C6, C7, C8, and C9, while culture supernatant from non-pathogenic Leptospira strains (SNPL) had no significant proteolytic activity on these substrates. The cleavages occurred in a time-dependent and specificity manner. No cleavage was observed when we used whole serum as a source of C5-C9 proteins, probably because of the abundant presence of plasma protease inhibitors such as α 2 -macroglobulin. Complement protein cleavage by SPL was inhibited by 1,10-phenanthroline, indicating the involvement of metalloproteases. Furthermore, 1,10-phenanthroline- treated normal human serum diminished pathogenic leptospira survival. We also analyzed the proteolytic activity of thermolysin (LIC13322) a metalloprotease expressed exclusively by pathogenic Leptospira strains. Recombinant thermolysin was capable of cleaving the component C6, either purified or as part of the SC5b-9 complex. Furthermore, we found that the MAC proteins C6-C9 interact with thermolysin, indicating that this metalloprotease may have an additional inhibitory

  14. Pathogenic Leptospira Secreted Proteases Target the Membrane Attack Complex: A Potential Role for Thermolysin in Complement Inhibition

    Directory of Open Access Journals (Sweden)

    Thais A. Amamura

    2017-05-01

    Full Text Available Leptospirosis is a zoonosis caused by spirochetes from the genus Leptospira. This disease is common in tropical and subtropical areas, constituting a serious public health problem. Pathogenic Leptospira have the ability to escape the human Complement System, being able to survive when in contact with normal human serum. In a previous study, our group demonstrated that supernatants of pathogenic Leptospira (SPL inhibit the three activation pathways of the Complement System. This inhibition can be directly correlated with the activity of secreted proteases, which cleave the Complement molecules C3, Factor B (Alternative Pathway, C4 and C2 (Classical and Lectin Pathways. In this work, we analyze the activity of the leptospiral proteases on the components of Terminal Pathway of Complement, called the membrane attack complex (MAC. We observed that proteases present in SPL from different Leptospira strains were able to cleave the purified proteins C5, C6, C7, C8, and C9, while culture supernatant from non-pathogenic Leptospira strains (SNPL had no significant proteolytic activity on these substrates. The cleavages occurred in a time-dependent and specificity manner. No cleavage was observed when we used whole serum as a source of C5–C9 proteins, probably because of the abundant presence of plasma protease inhibitors such as α2-macroglobulin. Complement protein cleavage by SPL was inhibited by 1,10-phenanthroline, indicating the involvement of metalloproteases. Furthermore, 1,10-phenanthroline- treated normal human serum diminished pathogenic leptospira survival. We also analyzed the proteolytic activity of thermolysin (LIC13322 a metalloprotease expressed exclusively by pathogenic Leptospira strains. Recombinant thermolysin was capable of cleaving the component C6, either purified or as part of the SC5b-9 complex. Furthermore, we found that the MAC proteins C6–C9 interact with thermolysin, indicating that this metalloprotease may have an

  15. Pathogenic Leptospira Secreted Proteases Target the Membrane Attack Complex: A Potential Role for Thermolysin in Complement Inhibition

    Science.gov (United States)

    Amamura, Thais A.; Fraga, Tatiana R.; Vasconcellos, Sílvio A.; Barbosa, Angela S.; Isaac, Lourdes

    2017-01-01

    Leptospirosis is a zoonosis caused by spirochetes from the genus Leptospira. This disease is common in tropical and subtropical areas, constituting a serious public health problem. Pathogenic Leptospira have the ability to escape the human Complement System, being able to survive when in contact with normal human serum. In a previous study, our group demonstrated that supernatants of pathogenic Leptospira (SPL) inhibit the three activation pathways of the Complement System. This inhibition can be directly correlated with the activity of secreted proteases, which cleave the Complement molecules C3, Factor B (Alternative Pathway), C4 and C2 (Classical and Lectin Pathways). In this work, we analyze the activity of the leptospiral proteases on the components of Terminal Pathway of Complement, called the membrane attack complex (MAC). We observed that proteases present in SPL from different Leptospira strains were able to cleave the purified proteins C5, C6, C7, C8, and C9, while culture supernatant from non-pathogenic Leptospira strains (SNPL) had no significant proteolytic activity on these substrates. The cleavages occurred in a time-dependent and specificity manner. No cleavage was observed when we used whole serum as a source of C5–C9 proteins, probably because of the abundant presence of plasma protease inhibitors such as α2-macroglobulin. Complement protein cleavage by SPL was inhibited by 1,10-phenanthroline, indicating the involvement of metalloproteases. Furthermore, 1,10-phenanthroline- treated normal human serum diminished pathogenic leptospira survival. We also analyzed the proteolytic activity of thermolysin (LIC13322) a metalloprotease expressed exclusively by pathogenic Leptospira strains. Recombinant thermolysin was capable of cleaving the component C6, either purified or as part of the SC5b-9 complex. Furthermore, we found that the MAC proteins C6–C9 interact with thermolysin, indicating that this metalloprotease may have an additional inhibitory

  16. APC/β-catenin-rich complexes at membrane protrusions regulate mammary tumor cell migration and mesenchymal morphology

    International Nuclear Information System (INIS)

    Odenwald, Matthew A; Prosperi, Jenifer R; Goss, Kathleen H

    2013-01-01

    The APC tumor suppressor is mutated or downregulated in many tumor types, and is prominently localized to punctate clusters at protrusion tips in migratory cells, such as in astrocytes where it has been implicated in directed cell motility. Although APC loss is considered an initiating event in colorectal cancer, for example, it is less clear what role APC plays in tumor cell motility and whether loss of APC might be an important promoter of tumor progression in addition to initiation. The localization of APC and β-catenin was analyzed in multiple cell lines, including non-transformed epithelial lines treated with a proteasome inhibitor or TGFβ to induce an epithelial-to-mesenchymal transition (EMT), as well as several breast cancer lines, by immunofluorescence. APC expression was knocked down in 4T07 mammary tumor cells using lentiviral-mediated delivery of APC-specific short-hairpin (sh) RNAs, and assessed using quantitative (q) reverse-transcriptase (RT)-PCR and western blotting. Tumor cell motility was analyzed by performing wound-filling assays, and morphology via immunofluorescence (IF) and phase-contrast microscopy. Additionally, proliferation was measured using BrdU incorporation, and TCF reporter assays were performed to determine β-catenin/TCF-mediated transcriptional activity. APC/β-catenin-rich complexes were observed at protrusion ends of migratory epithelial cells treated with a proteasome inhibitor or when EMT has been induced and in tumor cells with a mesenchymal, spindle-like morphology. 4T07 tumor cells with reduced APC levels were significantly less motile and had a more rounded morphology; yet, they did not differ significantly in proliferation or β-catenin/TCF transcriptional activity. Furthermore, we found that APC/β-catenin-rich complexes at protrusion ends were dependent upon an intact microtubule cytoskeleton. These findings indicate that membrane protrusions with APC/β-catenin-containing puncta control the migratory potential and

  17. Regulation of microtubule nucleation from membranes by complexes of membrane-bound gamma-tubulin with Fyn kinase and phosphoinositide 3-kinase

    Czech Academy of Sciences Publication Activity Database

    Macůrek, Libor; Dráberová, Eduarda; Richterová, Věra; Sulimenko, Vadym; Sulimenko, Tetyana; Dráberová, Lubica; Marková, Vladimíra; Dráber, Pavel

    2008-01-01

    Roč. 416, č. 3 (2008), s. 421-430 ISSN 0264-6021 R&D Projects: GA MŠk LC545; GA ČR GA204/05/2375; GA ČR GA304/04/1273; GA MŠk(CZ) 1M0520 Institutional research plan: CEZ:AV0Z50520514 Keywords : detergent -resistant membrane * Fyn * PI3K gamma-tubulin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.371, year: 2008

  18. Differential Mobility of Pigment-Protein Complexes in Granal and Agranal Thylakoid Membranes of C-3 and C-4 Plants

    Czech Academy of Sciences Publication Activity Database

    Kirchhoff, H.; Sharpe, R.M.; Herbstová, Miroslava; Yarbrough, R.; Edwards, G.E.

    2013-01-01

    Roč. 161, č. 1 (2013), s. 497-507 ISSN 0032-0889 Institutional support: RVO:60077344 Keywords : Photosystem-II * Photosynthetic membranes * Electron tomography Subject RIV: ED - Physiology Impact factor: 7.394, year: 2013

  19. Role of PINK1 binding to the TOM complex and alternate intracellular membranes in recruitment and activation of the E3 ligase Parkin.

    Science.gov (United States)

    Lazarou, Michael; Jin, Seok Min; Kane, Lesley A; Youle, Richard J

    2012-02-14

    Mutations in the mitochondrial kinase PINK1 and the cytosolic E3 ligase Parkin can cause Parkinson's disease. Damaged mitochondria accumulate PINK1 on the outer membrane where, dependent on kinase activity, it recruits and activates Parkin to induce mitophagy, potentially maintaining organelle fidelity. How PINK1 recruits Parkin is unknown. We show that endogenous PINK1 forms a 700 kDa complex with the translocase of the outer membrane (TOM) selectively on depolarized mitochondria whereas PINK1 ectopically targeted to the outer membrane retains association with TOM on polarized mitochondria. Inducibly targeting PINK1 to peroxisomes or lysosomes, which lack a TOM complex, recruits Parkin and activates ubiquitin ligase activity on the respective organelles. Once there, Parkin induces organelle selective autophagy of peroxisomes but not lysosomes. We propose that the association of PINK1 with the TOM complex allows rapid reimport of PINK1 to rescue repolarized mitochondria from mitophagy, and discount mitochondrial-specific factors for Parkin translocation and activation. Copyright © 2012 Elsevier Inc. All rights reserved.

  20. Evidence that the assembly of the yeast cytochrome bc1 complex involves the formation of a large core structure in the inner mitochondrial membrane.

    Science.gov (United States)

    Zara, Vincenzo; Conte, Laura; Trumpower, Bernard L

    2009-04-01

    The assembly status of the cytochrome bc(1) complex has been analyzed in distinct yeast deletion strains in which genes for one or more of the bc(1) subunits were deleted. In all the yeast strains tested, a bc(1) sub-complex of approximately 500 kDa was found when the mitochondrial membranes were analyzed by blue native electrophoresis. The subsequent molecular characterization of this sub-complex, carried out in the second dimension by SDS/PAGE and immunodecoration, revealed the presence of the two catalytic subunits, cytochrome b and cytochrome c(1), associated with the noncatalytic subunits core protein 1, core protein 2, Qcr7p and Qcr8p. Together, these bc(1) subunits build up the core structure of the cytochrome bc(1) complex, which is then able to sequentially bind the remaining subunits, such as Qcr6p, Qcr9p, the Rieske iron-sulfur protein and Qcr10p. This bc(1) core structure may represent a true assembly intermediate during the maturation of the bc(1) complex; first, because of its wide distribution in distinct yeast deletion strains and, second, for its characteristics of stability, which resemble those of the intact homodimeric bc(1) complex. By contrast, the bc(1) core structure is unable to interact with the cytochrome c oxidase complex to form respiratory supercomplexes. The characterization of this novel core structure of the bc(1) complex provides a number of new elements clarifying the molecular events leading to the maturation of the yeast cytochrome bc(1) complex in the inner mitochondrial membrane.

  1. Evidence that assembly of the yeast cytochrome bc1 complex involves formation of a large core structure in the inner mitochondrial membrane

    Science.gov (United States)

    Zara, Vincenzo; Conte, Laura; Trumpower, Bernard L.

    2009-01-01

    The assembly status of the cytochrome bc1 complex has been analyzed in distinct yeast deletion strains in which genes for one or more of the bc1 subunits had been deleted. In all the yeast strains tested a bc1 sub-complex of about 500 kDa was found when the mitochondrial membranes were analyzed by blue native electrophoresis. The subsequent molecular characterization of this sub-complex, carried out in the second dimension by SDS-PAGE and immunodecoration, revealed the presence of the two catalytic subunits cytochrome b and cytochrome c1, associated with the non catalytic subunits core protein 1, core protein 2, Qcr7p and Qcr8p. Altogether these bc1 subunits build up the core structure of the cytochrome bc1 complex which is then able to sequentially bind the remaining subunits, such as Qcr6p, Qcr9p, the Rieske iron-sulfur protein and Qcr10p. This bc1 core structure may represent a true assembly intermediate during the maturation of the bc1 complex, first because of its wide distribution in distinct yeast deletion strains and second for its characteristics of stability which resemble those of the intact homodimeric bc1 complex. Differently from this latter, however, the bc1 core structure is not able to interact with the cytochrome c oxidase complex to form respiratory supercomplexes. The characterization of this novel core structure of the bc1 complex provides a number of new elements for clarification of the molecular events leading to the maturation of the yeast cytochrome bc1 complex in the inner mitochondrial membrane. PMID:19236481

  2. Molecular Interactions at Membranes

    DEFF Research Database (Denmark)

    Jagalski, Vivien

    Biological membranes are essential and complex structures in every living cell consisting of a fluid lipid bilayer sheet and membrane proteins. Its significance makes biological membranes not only interesting for medical research, but also has made it a target for toxins in the course of evolution....... Today, we know more than ever before about the properties of biological membranes. Advanced biophysical techniques and sophisticated membrane models allow us to answer specific questions about the structure of the components within membranes and their interactions. However, many detailed structural...... mechanisms of membrane compounds, including compounds associated with membranes, are still unknown due to the challenges that arise when probing the hydrophobic nature of the membrane's interior. For integral membrane proteins that span through the entire membrane, the amphiphilic environment is essential...

  3. A Rab11A/myosin Vb/Rab11-FIP2 complex frames two late recycling steps of langerin from the ERC to the plasma membrane.

    Science.gov (United States)

    Gidon, Alexandre; Bardin, Sabine; Cinquin, Bertrand; Boulanger, Jerome; Waharte, François; Heliot, Laurent; de la Salle, Henri; Hanau, Daniel; Kervrann, Charles; Goud, Bruno; Salamero, Jean

    2012-06-01

    A large body of knowledge relating to the constitution of Rab GTPase/Rab effector complexes and their impact on both membrane domain organization and overall membrane trafficking has been built up in recent years. However in the context of the live cell there are still many questions that remain to be answered, such as where and when these complexes assemble and where they perform their primary function(s). We describe here the dynamic processes that take place in the final steps of the Rab11A dependent recycling pathway, in the context of the membrane platform constituted by Myosin Vb, Rab11A, and Rab11-FIP2. We first confirm that a series of previously reported observations obtained during the study of a number of trafficking cargoes also apply to langerin. Langerin is a cargo molecule that traffics through Rab11A-positive membrane domains of the endosomal recycling pathway. In order to explore the relative dynamics of this set of partners, we make extensive use of a combinatory approach of Live-FRET, fast FRAP video, fast confocal and TIRF microscopy modalities. Our data show that the Myosin Vb/Rab11A/Rab11-FIP2 platform is spatially involved in the regulation of langerin trafficking at two distinct sites within live cells, first at the sorting site in the endosomal recycling compartment (ERC) where transport vesicles are formed, and subsequently, in a strict time-defined order, at the very late stage of docking/tethering and fusion of these langerin recycling vesicles to the plasma membrane. © 2012 John Wiley & Sons A/S.

  4. Basal membrane complex architecture is disrupted during posterior subcapsular cataract formation in Royal College of Surgeons rats

    Science.gov (United States)

    Joy, Anita

    2014-01-01

    Purpose Previous studies detailing the development of posterior subcapsular cataracts (PSC) in Royal College of Surgeons (RCS) rats have shown that aberrant fiber-end migration underlies the structural compromise. This investigation was conducted to examine the distribution of select basal membrane complex (BMC) components and to assess the intravitreal levels of specific cytokines during PSC formation. Methods Lenses from 52 RCS dystrophic rats (RCS/Lav) and 28 genetically matched control animals (RCS-rdy+/Lav) from 2 to 8 weeks old were used. After enucleation, vitreous was collected for eventual cytokine level analyses; lenses were then removed and processed for immunocytochemical localization of actin, cadherin, β integrin, vinculin, and cell nuclei. Results At 2–3 weeks postnatal, dystrophic lenses showed normal BMC distribution of actin, cadherin, and vinculin; however β integrin distribution was altered as compared to controls. By 4–6 weeks of age, F-actin was visible as bright foci arranged in a “rosette” pattern around fiber-end profiles. Concurrently, vinculin was rearranged into a diffuse pattern within the BMC. Cadherin delineated the fiber ends in dystrophic lenses until 5 weeks postnatal, after which it displayed diffuse cytoplasmic staining with more definitive labeling at the BMC periphery. β integrin was initially distributed as punctuate spots at 2–3 weeks postnatal; however, by 4–6 weeks it was co-localized with F-actin around the periphery of fiber ends. The distribution of F-actin, cadherin, and β integrin components did not undergo further changes after 6 weeks of age; however, vinculin was present predominantly at the periphery of the BMC in 7–8-week-old dystrophic lenses. Intravitreal cytokine levels were assessed for interleukin (IL)-1α, IL-4, IL-6, IL-8, tumor necrosis factor (TNF), and interferon (IFN)-γ. Levels of IL-1α, IL-4, TNF, and IFN-γ demonstrated a similar pattern, with concentrations increasing from 2 to 6

  5. Export of a Toxoplasma gondii rhoptry neck protein complex at the host cell membrane to form the moving junction during invasion.

    Directory of Open Access Journals (Sweden)

    Sébastien Besteiro

    2009-02-01

    Full Text Available One of the most conserved features of the invasion process in Apicomplexa parasites is the formation of a moving junction (MJ between the apex of the parasite and the host cell membrane that moves along the parasite and serves as support to propel it inside the host cell. The MJ was, up to a recent period, completely unknown at the molecular level. Recently, proteins originated from two distinct post-Golgi specialised secretory organelles, the micronemes (for AMA1 and the neck of the rhoptries (for RON2/RON4/RON5 proteins, have been shown to form a complex. AMA1 and RON4 in particular, have been localised to the MJ during invasion. Using biochemical approaches, we have identified RON8 as an additional member of the complex. We also demonstrated that all RON proteins are present at the MJ during invasion. Using metabolic labelling and immunoprecipitation, we showed that RON2 and AMA1 were able to interact in the absence of the other members. We also discovered that all MJ proteins are subjected to proteolytic maturation during trafficking to their respective organelles and that they could associate as non-mature forms in vitro. Finally, whereas AMA1 has previously been shown to be inserted into the parasite membrane upon secretion, we demonstrated, using differential permeabilization and loading of RON-specific antibodies into the host cell, that the RON complex is targeted to the host cell membrane, where RON4/5/8 remain associated with the cytoplasmic face. Globally, these results point toward a model of MJ organization where the parasite would be secreting and inserting interacting components on either side of the MJ, both at the host and at its own plasma membranes.

  6. NSF- and SNARE-mediated membrane fusion is required for nuclear envelope formation and completion of nuclear pore complex assembly in Xenopus laevis egg extracts.

    Science.gov (United States)

    Baur, Tina; Ramadan, Kristijan; Schlundt, Andreas; Kartenbeck, Jürgen; Meyer, Hemmo H

    2007-08-15

    Despite the progress in understanding nuclear envelope (NE) reformation after mitosis, it has remained unclear what drives the required membrane fusion and how exactly this is coordinated with nuclear pore complex (NPC) assembly. Here, we show that, like other intracellular fusion reactions, NE fusion in Xenopus laevis egg extracts is mediated by SNARE proteins that require activation by NSF. Antibodies against Xenopus NSF, depletion of NSF or the dominant-negative NSF(E329Q) variant specifically inhibited NE formation. Staging experiments further revealed that NSF was required until sealing of the envelope was completed. Moreover, excess exogenous alpha-SNAP that blocks SNARE function prevented membrane fusion and caused accumulation of non-flattened vesicles on the chromatin surface. Under these conditions, the nucleoporins Nup107 and gp210 were fully recruited, whereas assembly of FxFG-repeat-containing nucleoporins was blocked. Together, we define NSF- and SNARE-mediated membrane fusion events as essential steps during NE formation downstream of Nup107 recruitment, and upstream of membrane flattening and completion of NPC assembly.

  7. Mechanical properties of milk sphingomyelin bilayer membranes in the gel phase: Effects of naturally complex heterogeneity, saturation and acyl chain length investigated on liposomes using AFM.

    Science.gov (United States)

    Et-Thakafy, Oumaima; Delorme, Nicolas; Guyomarc'h, Fanny; Lopez, Christelle

    2018-01-01

    Sphingomyelin (SM) molecules are major lipid components of plasma membranes that are involved in functional domains. Among natural SMs, that found in milk (milk-SM) exhibits important acyl chain heterogeneities in terms of length and saturation, which could affect the biophysical properties and biological functions of the milk fat globule membrane or of liposome carriers. In this study, the thermotropic and mechanical properties of milk-SM, synthetic C16:0-SM, C24:0-SM and the binary mixtures C16:0-SM/C24:0-SM (50:50% mol) and C24:0-SM/C24:1-SM (95:5% mol) bilayer membranes were investigated using differential scanning calorimetry and atomic force microscopy, respectively. Results showed that acyl chain length, heterogeneity and unsaturation affected i) the temperature of phase transition of SM bilayers, and ii) the mechanical properties of liposome (diametermembranes in the gel phase, e.g. the Young modulus E and the bending rigidity k C . This study increases our knowledge about the key role of naturally complex lipid compositions in tailoring the physical properties of biological membranes. It could be also used in liposomes development e.g. to select the suitable lipid composition according to usage. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. The mechanism of anthracene interaction with photosynthetic apparatus: A study using intact cells, thylakoid membranes and PS II complexes isolated from Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Aksmann, Anna; Shutova, Tatiana; Samuelsson, Goeran; Tukaj, Zbigniew

    2011-01-01

    Intact cells of Chlamydomonas reinhardtii as well as isolated thylakoid membranes and photosystem II complexes were used to examine a possible mechanism of anthracene (ANT) interaction with the photosynthetic apparatus. Since ANT concentrations above 1 mM were required to significantly inhibit the rate of oxygen evolution in PS II membrane fragments it may indicate that the toxicant did not directly interact with this photosystem. On the other hand, stimulation of oxygen uptake by ANT-treated thylakoids suggested that ANT could either act as an artificial electron acceptor in the photosynthetic electron transport chain or function as an uncoupler. Electron transfer from excited chlorophyll to ANT is impossible due to the very low reduction potential of ANT and therefore we propose that toxic concentrations of ANT increase the thylakoid membrane permeability and thereby function as an uncoupler, enhancing electron transport in vitro. Hence, its unspecific interference with photosynthetic membranes in vitro suggests that the inhibitory effect observed on intact cell photosynthesis is caused by uncoupling of phosphorylation.

  9. Investigation on the Synergistic Complexation of Ni(II with 1,10-Phenanthroline and Dithizone at Hexane-Water Interface Using Centrifugal Liquid Membrane-Spectrophotometry

    Directory of Open Access Journals (Sweden)

    Yoki Yulizar

    2012-12-01

    Full Text Available Complex formation of Ni(II and 1,10-phenanthroline (C12H8N2/Phen with the addition of dithizone (C13H12N4S/HDz at the hexane-water interface has been studied by direct measurement spectrophotometry using the centrifugal liquid membrane (CLM method. Ni(II ion with Phen formed a cationic complex of Ni(C12H8N222+ or NiPhen22+. That complex dissolved in the aqueous phase and had two UV absorption spectrum maxima wavelengths, max 270 and 292 nm. Observation of complex formation was performed variations of pH and ligand concentration. The pH caused protonation that affected the amount of the formed complex. With the variations of ligand concentrations, the greater was the concentration of ligands the greater was the formed complex. Based on the Batch method, the HDz ligand addition into the NiPhen22+ cationic complex produced ion association complex of Ni(C13H11N4S2(C12H8N2 or NiDz2Phen at max 403 nm, and is extracted in the organic phase. Measurement results using CLM method showed that NiDz2Phen complex was formed at hexane-water interface with max 523 nm. Comparison of Phen with HDz ligand concentrations affected the initial formation rate of NiDz2Phen complex. The greater concentration of Phen ligand increased the initial rate of formation for synergistic complex. The obtained data using CLM method indicated that the synergistic complex formation rate constant of NiDz2Phen at the interface, k was 0.30 s-1.

  10. Dynamin-like protein 1 at the Golgi complex: A novel component of the sorting/targeting machinery en route to the plasma membrane

    Energy Technology Data Exchange (ETDEWEB)

    Bonekamp, Nina A. [Centre for Cell Biology and Department of Biology, University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro (Portugal); Vormund, Kerstin; Jacob, Ralf [Department of Cell Biology and Cell Pathology, University of Marburg, Robert-Koch-Str. 6, 35037 Marburg (Germany); Schrader, Michael, E-mail: mschrader@ua.pt [Centre for Cell Biology and Department of Biology, University of Aveiro, Campus Universitario de Santiago, 3810-193 Aveiro (Portugal)

    2010-12-10

    The final step in the liberation of secretory vesicles from the trans-Golgi network (TGN) involves the mechanical action of the large GTPase dynamin as well as conserved dynamin-independent fission mechanisms, e.g. mediated by Brefeldin A-dependent ADP-ribosylated substrate (BARS). Another member of the dynamin family is the mammalian dynamin-like protein 1 (DLP1/Drp1) that is known to constrict and tubulate membranes, and to divide mitochondria and peroxisomes. Here, we examined a potential role for DLP1 at the Golgi complex. DLP1 localized to the Golgi complex in some but not all cell lines tested, thus explaining controversial reports on its cellular distribution. After silencing of DLP1, an accumulation of the apical reporter protein YFP-GL-GPI, but not the basolateral reporter VSVG-SP-GFP at the Golgi complex was observed. A reduction in the transport of YFP-GL-GPI to the plasma membrane was confirmed by surface immunoprecipitation and TGN-exit assays. In contrast, YFP-GL-GPI trafficking was not disturbed in cells silenced for BARS, which is involved in basolateral sorting and trafficking of VSVG-SP-GFP in COS-7 cells. Our data indicate a new role for DLP1 at the Golgi complex and thus a role for DLP1 as a novel component of the apical sorting machinery at the TGN is discussed.

  11. Dynamin-like protein 1 at the Golgi complex: A novel component of the sorting/targeting machinery en route to the plasma membrane

    International Nuclear Information System (INIS)

    Bonekamp, Nina A.; Vormund, Kerstin; Jacob, Ralf; Schrader, Michael

    2010-01-01

    The final step in the liberation of secretory vesicles from the trans-Golgi network (TGN) involves the mechanical action of the large GTPase dynamin as well as conserved dynamin-independent fission mechanisms, e.g. mediated by Brefeldin A-dependent ADP-ribosylated substrate (BARS). Another member of the dynamin family is the mammalian dynamin-like protein 1 (DLP1/Drp1) that is known to constrict and tubulate membranes, and to divide mitochondria and peroxisomes. Here, we examined a potential role for DLP1 at the Golgi complex. DLP1 localized to the Golgi complex in some but not all cell lines tested, thus explaining controversial reports on its cellular distribution. After silencing of DLP1, an accumulation of the apical reporter protein YFP-GL-GPI, but not the basolateral reporter VSVG-SP-GFP at the Golgi complex was observed. A reduction in the transport of YFP-GL-GPI to the plasma membrane was confirmed by surface immunoprecipitation and TGN-exit assays. In contrast, YFP-GL-GPI trafficking was not disturbed in cells silenced for BARS, which is involved in basolateral sorting and trafficking of VSVG-SP-GFP in COS-7 cells. Our data indicate a new role for DLP1 at the Golgi complex and thus a role for DLP1 as a novel component of the apical sorting machinery at the TGN is discussed.

  12. Expression, purification, crystallization and preliminary X-ray analysis of calmodulin in complex with the regulatory domain of the plasma-membrane Ca2+-ATPase ACA8

    International Nuclear Information System (INIS)

    Tidow, Henning; Hein, Kim L.; Baekgaard, Lone; Palmgren, Michael G.; Nissen, Poul

    2010-01-01

    Plant plasma-membrane Ca 2+ -ATPase is regulated via binding of calmodulin to its autoinhibitory N-terminal domain. In this study, the expression, purification, crystallization and preliminary X-ray diffraction analysis of this protein complex from A. thaliana are reported. Plasma-membrane Ca 2+ -ATPases (PMCAs) are calcium pumps that expel Ca 2+ from eukaryotic cells to maintain overall Ca 2+ homoeostasis and to provide local control of intracellular Ca 2+ signalling. They are of major physiological importance, with different isoforms being essential, for example, for presynaptic and postsynaptic Ca 2+ regulation in neurons, feedback signalling in the heart and sperm motility. In the resting state, PMCAs are autoinhibited by binding of their C-terminal (in mammals) or N-terminal (in plants) tail to two major intracellular loops. Activation requires the binding of calcium-bound calmodulin (Ca 2+ -CaM) to this tail and a conformational change that displaces the autoinhibitory tail from the catalytic domain. The complex between calmodulin and the regulatory domain of the plasma-membrane Ca 2+ -ATPase ACA8 from Arabidopsis thaliana has been crystallized. The crystals belonged to space group C2, with unit-cell parameters a = 176.8, b = 70.0, c = 69.8 Å, β = 113.2°. A complete data set was collected to 3.0 Å resolution and structure determination is in progress in order to elucidate the mechanism of PMCA activation by calmodulin

  13. Isolation, purification, and partial characterization of a membrane-bound Cl-/HCO3--activated ATPase complex from rat brain with sensitivity to GABAAergic ligands.

    Science.gov (United States)

    Menzikov, Sergey A

    2017-02-07

    This study describes the isolation and purification of a protein complex with [Formula: see text]-ATPase activity and sensitivity to GABA A ergic ligands from rat brain plasma membranes. The ATPase complex was enriched using size-exclusion, affinity, and ion-exchange chromatography. The fractions obtained at each purification step were subjected to SDS-polyacrylamide gel electrophoresis (SDS-PAGE), which revealed four subunits with molecular mass ∼48, 52, 56, and 59 kDa; these were retained at all stages of the purification process. Autoradiography revealed that the ∼52 and 56 kDa subunits could bind [ 3 H]muscimol. The [Formula: see text]-ATPase activity of this enriched protein complex was regulated by GABA A ergic ligands but was not sensitive to blockers of the NKCC or KCC cotransporters.

  14. Purification, crystallization and preliminary X-ray analysis of the outer membrane complex HasA–HasR from Serratia marcescens

    International Nuclear Information System (INIS)

    Huché, Frédéric; Delepelaire, Philippe; Wandersman, Cécile; Welte, Wolfram

    2005-01-01

    The expression, purification, and crystallization in space group P2 1 2 1 2 1 of the complex HasA-HasR from S. marcescens are reported. Diffraction data have been collected and processed to 6.8 Å. Serratia marcescens is able to acquire iron using its haem-acquisition system (‘has’), which contains an outer membrane receptor HasR and a soluble haemophore HasA. After secretion, HasA binds free haem in the extracellular medium or extracts it from haemoproteins and delivers it to the receptor. Here, the crystallization of a HasA–HasR complex is reported. HasA and HasR have been overexpressed in Escherichia coli and the complex formed and crystallized. Small platelets and bunches of needles of dimensions 0.01 × 0.1 × 1 mm were obtained. A native data set has been collected to 6.8 Å

  15. The TIC complex uncovered: The alternative view on the molecular mechanism of protein translocation across the inner envelope membrane of chloroplasts.

    Science.gov (United States)

    Nakai, Masato

    2015-09-01

    Chloroplasts must import thousands of nuclear-encoded preproteins synthesized in the cytosol through two successive protein translocons at the outer and inner envelope membranes, termed TOC and TIC, respectively, to fulfill their complex physiological roles. The molecular identity of the TIC translocon had long remained controversial; two proteins, namely Tic20 and Tic110, had been proposed to be central to protein translocation across the inner envelope membrane. Tic40 also had long been considered to be another central player in this process. However, recently, a novel 1-megadalton complex consisting of Tic20, Tic56, Tic100, and Tic214 was identified at the chloroplast inner membrane of Arabidopsis and was demonstrated to constitute a general TIC translocon which functions in concert with the well-characterized TOC translocon. On the other hand, direct interaction between this novel TIC transport system and Tic110 or Tic40 was hardly observed. Consequently, the molecular model for protein translocation across the inner envelope membrane of chloroplasts might need to be extensively revised. In this review article, I intend to propose such alternative view regarding the TIC transport system in contradistinction to the classical view. I also would emphasize importance of reevaluation of previous works in terms of with what methods these classical Tic proteins such as Tic110 or Tic40 were picked up as TIC constituents at the very beginning as well as what actual evidence there were to support their direct and specific involvement in chloroplast protein import. This article is part of a Special Issue entitled: Chloroplast Biogenesis. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Role of a membrane-bound aldehyde dehydrogenase complex AldFGH in acetic acid fermentation with Acetobacter pasteurianus SKU1108.

    Science.gov (United States)

    Yakushi, Toshiharu; Fukunari, Seiya; Kodama, Tomohiro; Matsutani, Minenosuke; Nina, Shun; Kataoka, Naoya; Theeragool, Gunjana; Matsushita, Kazunobu

    2018-04-03

    Acetic acid fermentation is widely considered a consequence of ethanol oxidation by two membrane-bound enzymes-alcohol dehydrogenase and aldehyde dehydrogenase (ALDH)-of acetic acid bacteria. Here, we used a markerless gene disruption method to construct a mutant of the Acetobacter pasteurianus strain SKU1108 with a deletion in the aldH gene, which encodes the large catalytic subunit of a heterotrimeric ALDH complex (AldFGH), to examine the role of AldFGH in acetic acid fermentation. The ΔaldH strain grew less on ethanol-containing medium, i.e., acetic acid fermentation conditions, than the wild-type strain and significantly accumulated acetaldehyde in the culture medium. Unexpectedly, acetaldehyde oxidase activity levels of the intact ΔaldH cells and the ΔaldH cell membranes were similar to those of the wild-type strain, which might be attributed to an additional ALDH isozyme (AldSLC). The apparent K M values of the wild-type and ΔaldH membranes for acetaldehyde were similar to each other, when the cells were cultured in nonfermentation conditions, where ΔaldH cells grow as well as the wild-type cells. However, the membranes of the wild-type cells grown under fermentation conditions showed a 10-fold lower apparent K M value than those of the cells grown under nonfermentation conditions. Under fermentation conditions, transcriptional levels of a gene for AldSLC were 10-fold lower than those under nonfermentation conditions, whereas aldH transcript levels were not dramatically changed under the two conditions. We suggest that A. pasteurianus SKU1108 has two ALDHs, and the AldFGH complex is indispensable for acetic acid fermentation and is the major enzyme under fermentation conditions.

  17. 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

  18. TGF-α/HA complex promotes tympanic membrane keratinocyte migration and proliferation via ErbB1 receptor

    Energy Technology Data Exchange (ETDEWEB)

    Mei Teh, Bing, E-mail: bing.teh@earscience.org.au [Ear Sciences Centre, School of Surgery, The University of Western Australia, Nedlands, WA (Australia); Ear Science Institute Australia, Subiaco, WA (Australia); Department of Otolaryngology, Head, Neck and Skull Base Surgery, Sir Charles Gairdner Hospital, Nedlands, WA (Australia); Redmond, Sharon L. [Ear Sciences Centre, School of Surgery, The University of Western Australia, Nedlands, WA (Australia); Ear Science Institute Australia, Subiaco, WA (Australia); Shen, Yi [Ear Sciences Centre, School of Surgery, The University of Western Australia, Nedlands, WA (Australia); Ear Science Institute Australia, Subiaco, WA (Australia); Department of Otolaryngology, Head and Neck, Ningbo Lihuili Hospital (Ningbo Medical Centre), Ningbo, Zhejiang (China); Atlas, Marcus D. [Ear Sciences Centre, School of Surgery, The University of Western Australia, Nedlands, WA (Australia); Ear Science Institute Australia, Subiaco, WA (Australia); Department of Otolaryngology, Head, Neck and Skull Base Surgery, Sir Charles Gairdner Hospital, Nedlands, WA (Australia); Marano, Robert J.; Dilley, Rodney J. [Ear Sciences Centre, School of Surgery, The University of Western Australia, Nedlands, WA (Australia); Ear Science Institute Australia, Subiaco, WA (Australia)

    2013-04-01

    Tympanic membrane perforations are common and represent a management challenge to clinicians. Current treatments for chronic perforations involve a graft surgery and require general anaesthesia, including associated costs and morbidities. Bioactive molecules (e.g. growth factors, cytokines) play an important role in promoting TM wound healing following perforation and the use of growth factors as a topical treatment for tympanic membrane perforations has been suggested as an alternative to surgery. However, the choice of bioactive molecules best suited to promote wound healing has yet to be identified. We investigated the effects of hyaluronic acid, vitronectin, TGF-α, IL-24 and their combinations on migration, proliferation and adhesion of cultured human tympanic membrane-derived keratinocytes (hTM), in addition to their possible mechanisms of action. We found that TGF-α, TGF-α/HA and TGF-α/IL-24 promoted wound healing by significantly increasing both migration and proliferation. TGF-α and/or HA treated cells showed comparable cell–cell adhesion whilst maintaining an epithelial cell phenotype. With the use of receptor binding inhibitors for ErbB1 (AG1478) and CD44 (BRIC235), we revealed that the activation of ErbB1 is required for TGF-α/HA-mediated migration and proliferation. These results suggest factors that may be incorporated into a tissue-engineered membrane or directly as topical treatment for tympanic membrane perforations and hence reduce the need for a surgery. - Highlights: ► TGF-α, TGF-α/HA and TGF-α/IL-24 improved hTM keratinocyte migration and proliferation. ► TGF-α and/or HA maintained epithelial cell phenotype. ► TGF-α/HA-mediated migration and proliferation requires activation of ErbB1 receptor.

  19. Model cell membranes

    DEFF Research Database (Denmark)

    Günther-Pomorski, Thomas; Nylander, Tommy; Cardenas Gomez, Marite

    2014-01-01

    The high complexity of biological membranes has motivated the development and application of a wide range of model membrane systems to study biochemical and biophysical aspects of membranes in situ under well defined conditions. The aim is to provide fundamental understanding of processes control...

  20. Soluble form of membrane attack complex independently predicts mortality and cardiovascular events in patients with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention

    DEFF Research Database (Denmark)

    Lindberg, Søren; Pedersen, Sune H; Mogelvang, Rasmus

    2012-01-01

    The complement system is an important mediator of inflammation, which plays a pivotal role in atherosclerosis and acute myocardial infarction (AMI). Animal studies suggest that activation of the complement cascade resulting in the formation of soluble membrane attack complex (sMAC), contributes...... to both atherosclerosis and plaque rupture and may be the direct cause of tissue damage related to ischemia/reperfusion injury. However clinical data of sMAC during an AMI is sparse. Accordingly the aim was to investigate the prognostic role of sMAC in patients with ST-segment elevation myocardial...

  1. Evolution of cytochrome bc complexes: from membrane-anchored dehydrogenases of ancient bacteria to triggers of apoptosis in vertebrates

    Science.gov (United States)

    Dibrova, Daria V.; Cherepanov, Dmitry A.; Galperin, Michael Y.; Skulachev, Vladimir P.; Mulkidjanian, Armen Y.

    2013-01-01

    This review traces the evolution of the cytochrome bc complexes from their early spread among prokaryotic lineages and up to the mitochondrial cytochrome bc1 complex (complex III) and its role in apoptosis. The results of phylogenomic analysis suggest that the bacterial cytochrome b6f-type complexes with short cytochromes b were the ancient form that preceded in evolution the cytochrome bc1-type complexes with long cytochromes b. The common ancestor of the b6f-type and the bc1-type complexes probably resembled the b6f-type complexes found in Heliobacteriaceae and in some Planctomycetes. Lateral transfers of cytochrome bc operons could account for the several instances of acquisition of different types of bacterial cytochrome bc complexes by archaea. The gradual oxygenation of the atmosphere could be the key evolutionary factor that has driven further divergence and spread of the cytochrome bc complexes. On one hand, oxygen could be used as a very efficient terminal electron acceptor. On the other hand, auto-oxidation of the components of the bc complex results in the generation of reactive oxygen species (ROS), which necessitated diverse adaptations of the b6f-type and bc1-type complexes, as well as other, functionally coupled proteins. A detailed scenario of the gradual involvement of the cardiolipin-containing mitochondrial cytochrome bc1 complex into the intrinsic apoptotic pathway is proposed, where the functioning of the complex as an apoptotic trigger is viewed as a way to accelerate the elimination of the cells with irreparably damaged, ROS-producing mitochondria. PMID:23871937

  2. Polymeric membrane sensors based on Cd(II) Schiff base complexes for selective iodide determination in environmental and medicinal samples.

    Science.gov (United States)

    Singh, Ashok Kumar; Mehtab, Sameena

    2008-01-15

    The two cadmium chelates of schiff bases, N,N'-bis(salicylidene)-1,4-diaminobutane, (Cd-S(1)) and N,N'-bis(salicylidene)-3,4-diaminotoluene (Cd-S(2)), have been synthesized and explored as ionophores for preparing PVC-based membrane sensors selective to iodide(I) ion. Potentiometric investigations indicate high affinity of these receptors for iodide ion. Polyvinyl chloride (PVC)-based membranes of Cd-S(1) and Cd-S(2) using as hexadecyltrimethylammonium bromide (HTAB) cation discriminator and o-nitrophenyloctyl ether (o-NPOE), dibutylphthalate (DBP), acetophenone (AP) and tributylphosphate (TBP) as plasticizing solvent mediators were prepared and investigated as iodide-selective sensors. The best performance was shown by the membrane of composition (w/w) of (Cd-S(1)) (7%):PVC (31%):DBP (60%):HTAB (2%). The sensor works well over a wide concentration range 5.3x10(-7) to 1.0x10(-2)M with Nernstian compliance (59.2mVdecade(-1) of activity) within pH range 2.5-9.0 with a response time of 11s and showed good selectivity for iodide ion over a number of anions. The sensor exhibits adequate life (3 months) with good reproducibility (S.D.+/-0.24mV) and could be used successfully for the determination of iodide content in environmental water samples and mouth wash samples.

  3. From biological membranes to biomimetic model membranes

    Directory of Open Access Journals (Sweden)

    Eeman, M.

    2010-01-01

    Full Text Available Biological membranes play an essential role in the cellular protection as well as in the control and the transport of nutrients. Many mechanisms such as molecular recognition, enzymatic catalysis, cellular adhesion and membrane fusion take place into the biological membranes. In 1972, Singer et al. provided a membrane model, called fluid mosaic model, in which each leaflet of the bilayer is formed by a homogeneous environment of lipids in a fluid state including globular assembling of proteins and glycoproteins. Since its conception in 1972, many developments were brought to this model in terms of composition and molecular organization. The main development of the fluid mosaic model was made by Simons et al. (1997 and Brown et al. (1997 who suggested that membrane lipids are organized into lateral microdomains (or lipid rafts with a specific composition and a molecular dynamic that are different to the composition and the dynamic of the surrounding liquid crystalline phase. The discovery of a phase separation in the plane of the membrane has induced an explosion in the research efforts related to the biology of cell membranes but also in the development of new technologies for the study of these biological systems. Due to the high complexity of biological membranes and in order to investigate the biological processes that occur on the membrane surface or within the membrane lipid bilayer, a large number of studies are performed using biomimicking model membranes. This paper aims at revisiting the fundamental properties of biological membranes in terms of membrane composition, membrane dynamic and molecular organization, as well as at describing the most common biomimicking models that are frequently used for investigating biological processes such as membrane fusion, membrane trafficking, pore formation as well as membrane interactions at a molecular level.

  4. Production of Decorative Cast Metal Matrix Composites with a Complex Relief and Nonmetal Reinforcement Phase

    Directory of Open Access Journals (Sweden)

    Daniela Spasova

    2016-02-01

    Full Text Available The present paper is relevant to the research of possibilities for the production of decorative complex relief metal matrix composites (MMCs of the “invitro” type, with unformed and unchanging reinforcement (strengthening phase in the process of creating a composite. The research on the methods of metal matrix composites development in this paper has been brought to the application of different space vacuum schemes for composite synthesisof vacuuming the space for composites synthesis by using the notion of the “capillary forming”. In this method the metal matrix (copper alloy melt was infiltrated in the space between the pellets of reinforcement phase (quartz particles – SiO2, whereas the classical method adopted for the obtaining MMCs “in vitro”, uses a mechanism of forced insertion of the reinforcement phase into the ready for use melt, followed by homogenization of the composite structure. In the particular case, because the obtained composite will have a complex relief three-dimensional surface, the conditions for compacting the building phases in the three directions x, y, z should be virtually equalized. In order to accomplish the task set, a laboratory system is developed. The experiments were conducted with laboratory equipment elaborated on the base of another equipment for "capillary forming" with extra vacuum. The structures of the obtained MMCs were tested by metallographic analysis.

  5. Endolysosomal membrane trafficking complexes drive nutrient-dependent TORC1 signaling to control cell growth in Saccharomyces cerevisiae.

    Science.gov (United States)

    Kingsbury, Joanne M; Sen, Neelam D; Maeda, Tatsuya; Heitman, Joseph; Cardenas, Maria E

    2014-04-01

    The rapamycin-sensitive and endomembrane-associated TORC1 pathway controls cell growth in response to nutrients in eukaryotes. Mutations in class C Vps (Vps-C) complexes are synthetically lethal with tor1 mutations and confer rapamycin hypersensitivity in Saccharomyces cerevisiae, suggesting a role for these complexes in TORC1 signaling. Vps-C complexes are required for vesicular trafficking and fusion and comprise four distinct complexes: HOPS and CORVET and their minor intermediaries (i)-CORVET and i-HOPS. We show that at least one Vps-C complex is required to promote TORC1 activity, with the HOPS complex having the greatest input. The vps-c mutants fail to recover from rapamycin-induced growth arrest and show low levels of TORC1 activity. TORC1 promotes cell growth via Sch9, a p70(S6) kinase ortholog. Constitutively active SCH9 or hyperactive TOR1 alleles restored rapamycin recovery and TORC1 activity of vps-c mutants, supporting a role for the Vps-C complexes upstream of TORC1. The EGO GTPase complex Exit from G0 Complex (EGOC) and its homologous Rag-GTPase complex convey amino acid signals to TORC1 in yeast and mammals, respectively. Expression of the activated EGOC GTPase subunits Gtr1(GTP) and Gtr2(GDP) partially suppressed vps-c mutant rapamycin recovery defects, and this suppression was enhanced by increased amino acid concentrations. Moreover, vps-c mutations disrupted EGOC-TORC1 interactions. TORC1 defects were more severe for vps-c mutants than those observed in EGOC mutants. Taken together, our results support a model in which distinct endolysosomal trafficking Vps-C complexes promote rapamycin-sensitive TORC1 activity via multiple inputs, one of which involves maintenance of amino acid homeostasis that is sensed and transmitted to TORC1 via interactions with EGOC.

  6. A miniature condensed-phase membrane introduction mass spectrometry (CP-MIMS) probe for direct and on-line measurements of pharmaceuticals and contaminants in small, complex samples.

    Science.gov (United States)

    Duncan, Kyle D; Willis, Megan D; Krogh, Erik T; Gill, Christopher G

    2013-06-15

    High-throughput, automated analytical measurements are desirable in many analytical scenarios, as are rapid sample pre-screening techniques to identify 'positive' samples for subsequent measurements using more time-consuming conventional methodologies (e.g., liquid chromatography/mass spectrometry (LC/MS)). A miniature condensed-phase membrane introduction mass spectrometry (CP-MIMS) probe for the direct and continuous, on-line measurement of pharmaceuticals and environmental contaminants in small, complex samples is presented. A miniature polydimethylsiloxane hollow fibre membrane (PDMS-HFM) probe is coupled with an electrospray ionization (ESI) triple quadrupole mass spectrometer. Analytes are transported from the probe to the ESI source by a methanol acceptor phase. The probe can be autosampler mounted and directly inserted in small samples (≥400 μL) allowing continuous and simultaneous pptr-ppb level detection of target analytes (chlorophenols, triclosan, gemfibrozil, nonylphenol) in complex samples (artificial urine, beer, natural water, waste water, plant tissue). The probe has been characterized and optimized for acceptor phase flow rate, sample mixing and probe washing. Signal response times, detection limits and calibration data are given for selected ion monitoring (SIM) and tandem mass spectrometry (MS/MS) measurements of target analytes at trace levels. Comparisons with flow cell type CP-MIMS systems are given. Analyte depletion effects are evaluated for small samples (≥400 μL). On-line measurements in small volumes of complex samples, temporally resolved reaction monitoring and in situ/in vivo demonstrations are presented. The miniature CP-MIMS probe developed was successfully used for the direct, on-line detection of target analytes in small volumes (40 mL to 400 μL) of complex samples at pptr to low ppb levels. The probe can be readily automated as well as deployed for in situ/in vivo monitoring, including reaction monitoring, small sample

  7. PolyC-binding protein 1 interacts with 5'-untranslated region of enterovirus 71 RNA in membrane-associated complex to facilitate viral replication.

    Directory of Open Access Journals (Sweden)

    Zhen Luo

    Full Text Available Enterovirus 71 (EV71 is one causative agent of hand, foot, and mouth disease (HFMD, which may lead to severe neurological disorders and mortality in children. EV71 genome is a positive single-stranded RNA containing a single open reading frame (ORF flanked by 5'-untranslated region (5'UTR and 3'UTR. The 5'UTR is fundamentally important for virus replication by interacting with cellular proteins. Here, we revealed that poly(C-binding protein 1 (PCBP1 specifically binds to the 5'UTR of EV71. Detailed studies indicated that the RNA-binding K-homologous 1 (KH1 domain of PCBP1 is responsible for its binding to the stem-loop I and IV of EV71 5'UTR. Interestingly, we revealed that PCBP1 is distributed in the nucleus and cytoplasm of uninfected cells, but mainly localized in the cytoplasm of EV71-infected cells due to interaction and co-localization with the viral RNA. Furthermore, sub-cellular distribution analysis showed that PCBP1 is located in ER-derived membrane, in where virus replication occurred in the cytoplasm of EV71-infected cells, suggesting PCBP1 is recruited in a membrane-associated replication complex. In addition, we found that the binding of PCBP1 to 5'UTR resulted in enhancing EV71 viral protein expression and virus production so as to facilitate viral replication. Thus, we revealed a novel mechanism in which PCBP1 as a positive regulator involved in regulation of EV71 replication in the host specialized membrane-associated replication complex, which provides an insight into cellular factors involved in EV71 replication.

  8. A complex of seven vaccinia virus proteins conserved in all chordopoxviruses is required for the association of membranes and viroplasm to form immature virions

    International Nuclear Information System (INIS)

    Szajner, Patricia; Jaffe, Howard; Weisberg, Andrea S.; Moss, Bernard

    2004-01-01

    Early events in vaccinia virus (VAC) morphogenesis, particularly the formation of viral membranes and their association with viroplasm, are poorly understood. Recently, we showed that repression of A30 or G7 expression results in the accumulation of normal viral membranes that form empty-looking immature virions (IV), which are separated from large masses of electron-dense viroplasm. In addition, A30 and G7 physically and functionally interact with each other and with the F10 protein kinase. To identify other proteins involved in early morphogenesis, proteins from cells that had been infected with vaccinia virus expressing an epitope-tagged copy of F10 were purified by immunoaffinity chromatography and analyzed by gel electrophoresis. In addition to F10, A30, and G7, viral proteins A15, D2, D3, and J1 were identified by mass spectrometry of tryptic peptides. Further evidence for the complex was obtained by immunopurification of proteins associated with epitope-tagged A15, D2, and D3. The previously unstudied A15, like other proteins in the complex, was expressed late in infection, associated with virus cores, and required for the stability and kinase activity of F10. Biochemical and electron microscopic analyses indicated that mutants in which A15 or D2 expression was regulated by the Escherichia coli lac operator system exhibited phenotypes characterized by the presence of large numbers of empty immature virions, similar to the results obtained with inducible A30 and G7 mutants. Empty immature virions were also seen by electron microscopy of cells infected with temperature-sensitive mutants of D2 or D3, though the numbers of membrane forms were reduced perhaps due to additional effects of high temperature

  9. CLIC5 stabilizes membrane-actin filament linkages at the base of hair cell stereocilia in a molecular complex with radixin, taperin, and myosin VI.

    Science.gov (United States)

    Salles, Felipe T; Andrade, Leonardo R; Tanda, Soichi; Grati, M'hamed; Plona, Kathleen L; Gagnon, Leona H; Johnson, Kenneth R; Kachar, Bechara; Berryman, Mark A

    2014-01-01

    Chloride intracellular channel 5 protein (CLIC5) was originally isolated from microvilli in complex with actin binding proteins including ezrin, a member of the Ezrin-Radixin-Moesin (ERM) family of membrane-cytoskeletal linkers. CLIC5 concentrates at the base of hair cell stereocilia and is required for normal hearing and balance in mice, but its functional significance is poorly understood. This study investigated the role of CLIC5 in postnatal development and maintenance of hair bundles. Confocal and scanning electron microscopy of CLIC5-deficient jitterbug (jbg) mice revealed progressive fusion of stereocilia as early as postnatal day 10. Radixin (RDX), protein tyrosine phosphatase receptor Q (PTPRQ), and taperin (TPRN), deafness-associated proteins that also concentrate at the base of stereocilia, were mislocalized in fused stereocilia of jbg mice. TPRQ and RDX were dispersed even prior to stereocilia fusion. Biochemical assays showed interaction of CLIC5 with ERM proteins, TPRN, and possibly myosin VI (MYO6). In addition, CLIC5 and RDX failed to localize normally in fused stereocilia of MYO6 mutant mice. Based on these findings, we propose a model in which these proteins work together as a complex to stabilize linkages between the plasma membrane and subjacent actin cytoskeleton at the base of stereocilia. © Published 2013 Wiley Periodicals, Inc. This article is a US government work and, as such, is in the public domain in the United States of America.

  10. A Cysteine-Rich Protein Kinase Associates with a Membrane Immune Complex and the Cysteine Residues Are Required for Cell Death.

    Science.gov (United States)

    Yadeta, Koste A; Elmore, James M; Creer, Athena Y; Feng, Baomin; Franco, Jessica Y; Rufian, Jose Sebastian; He, Ping; Phinney, Brett; Coaker, Gitta

    2017-01-01

    Membrane-localized proteins perceive and respond to biotic and abiotic stresses. We performed quantitative proteomics on plasma membrane-enriched samples from Arabidopsis (Arabidopsis thaliana) treated with bacterial flagellin. We identified multiple receptor-like protein kinases changing in abundance, including cysteine (Cys)-rich receptor-like kinases (CRKs) that are up-regulated upon the perception of flagellin. CRKs possess extracellular Cys-rich domains and constitute a gene family consisting of 46 members in Arabidopsis. The single transfer DNA insertion lines CRK28 and CRK29, two CRKs induced in response to flagellin perception, did not exhibit robust alterations in immune responses. In contrast, silencing of multiple bacterial flagellin-induced CRKs resulted in enhanced susceptibility to pathogenic Pseudomonas syringae, indicating functional redundancy in this large gene family. Enhanced expression of CRK28 in Arabidopsis increased disease resistance to P. syringae Expression of CRK28 in Nicotiana benthamiana induced cell death, which required intact extracellular Cys residues and a conserved kinase active site. CRK28-mediated cell death required the common receptor-like protein kinase coreceptor BAK1. CRK28 associated with BAK1 as well as the activated FLAGELLIN-SENSING2 (FLS2) immune receptor complex. CRK28 self-associated as well as associated with the closely related CRK29. These data support a model where Arabidopsis CRKs are synthesized upon pathogen perception, associate with the FLS2 complex, and coordinately act to enhance plant immune responses. © 2017 American Society of Plant Biologists. All Rights Reserved.

  11. Detection of phosphorylated subunits by combined LA-ICP-MS and MALDI-FTICR-MS analysis in yeast mitochondrial membrane complexes separated by blue native/SDS-PAGE

    Science.gov (United States)

    Krause-Buchholz, Udo; Becker, J. Susanne; Zoriy, Miroslav; Pickhardt, Carola; Przybylski, Michael; Rödel, Gerhard; Becker, J. Sabine

    2006-01-01

    We report on the identification of phosphorylated subunits of yeast mitochondrial ATPase using a novel screening technique in combination with BN/SDS-PAGE. Protein complexes present in yeast mitochondrial membranes were separated in their native state in the first dimension and their subunit composition was resolved by SDS-PAGE in the second dimension. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to rapidly screen for the presence of phosphorus in the subunits. The detection limits of elements investigated in selected protein spots are in the low [mu]g g-1 concentration range. Sulfur was used as the internal standard element for quantification. Phosphorus was detected in two of the proteins, that were identified by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) as subunits Atp1p and Atp2p of the ATPase. These results were confirmed by Western blot analysis using antibodies directed against phosphorylated amino acids. The combination of LA-ICP-MS and MALDI-FTICR-MS with BN/SDS-PAGE provides a fast and sensitive tool for structure analysis of phosphorus and metal-containing subunits of membrane protein complexes.

  12. Complexes of membrane-associated gamma-tubulin with Fyn kinase and phosphoinositide 3-kinase in differentiating cells

    Czech Academy of Sciences Publication Activity Database

    Sulimenko, Vadym; Macůrek, Libor; Dráberová, Eduarda; Richterová, Věra; Sulimenko, Tetyana; Dráberová, Lubica; Marková, Vladimíra; Dráber, Pavel

    2009-01-01

    Roč. 276, č. 1 (2009), s. 253-253 ISSN 1742-464X. [FEBS Congress /34/. 04.07.2009-09.07.2009, Praha] R&D Projects: GA MŠk 1M0506; GA MŠk LC545; GA ČR GA204/05/2375; GA ČR GA304/04/1273 Institutional research plan: CEZ:AV0Z50520514 Keywords : detergent -resistant membrane * Fyn * PI3K gamma-tubulin Subject RIV: EB - Genetics ; Molecular Biology

  13. A cyclopalladated complex interacts with mitochondrial membrane thiol-groups and induces the apoptotic intrinsic pathway in murine and cisplatin-resistant human tumor cells

    International Nuclear Information System (INIS)

    Serrano, Fabiana A; Machado, Joel Jr; Santos, Edson L; Pesquero, João B; Martins, Rafael M; Travassos, Luiz R; Caires, Antonio CF; Rodrigues, Elaine G; Matsuo, Alisson L; Monteforte, Priscila T; Bechara, Alexandre; Smaili, Soraya S; Santana, Débora P; Rodrigues, Tiago; Pereira, Felipe V; Silva, Luis S

    2011-01-01

    Systemic therapy for cancer metastatic lesions is difficult and generally renders a poor clinical response. Structural analogs of cisplatin, the most widely used synthetic metal complexes, show toxic side-effects and tumor cell resistance. Recently, palladium complexes with increased stability are being investigated to circumvent these limitations, and a biphosphinic cyclopalladated complex {Pd 2 [S (-) C 2 , N-dmpa] 2 (μ-dppe)Cl 2 } named C7a efficiently controls the subcutaneous development of B16F10-Nex2 murine melanoma in syngeneic mice. Presently, we investigated the melanoma cell killing mechanism induced by C7a, and extended preclinical studies. B16F10-Nex2 cells were treated in vitro with C7a in the presence/absence of DTT, and several parameters related to apoptosis induction were evaluated. Preclinical studies were performed, and mice were endovenously inoculated with B16F10-Nex2 cells, intraperitoneally treated with C7a, and lung metastatic nodules were counted. The cytotoxic effects and the respiratory metabolism were also determined in human tumor cell lines treated in vitro with C7a. Cyclopalladated complex interacts with thiol groups on the mitochondrial membrane proteins, causes dissipation of the mitochondrial membrane potential, and induces Bax translocation from the cytosol to mitochondria, colocalizing with a mitochondrial tracker. C7a also induced an increase in cytosolic calcium concentration, mainly from intracellular compartments, and a significant decrease in the ATP levels. Activation of effector caspases, chromatin condensation and DNA degradation, suggested that C7a activates the apoptotic intrinsic pathway in murine melanoma cells. In the preclinical studies, the C7a complex protected against murine metastatic melanoma and induced death in several human tumor cell lineages in vitro, including cisplatin-resistant ones. The mitochondria-dependent cell death was also induced by C7a in human tumor cells. The cyclopalladated C7a complex is

  14. Stimulation of Slack K+ Channels Alters Mass at the Plasma Membrane by Triggering Dissociation of a Phosphatase-Regulatory Complex

    Directory of Open Access Journals (Sweden)

    Matthew R. Fleming

    2016-08-01

    Full Text Available Human mutations in the cytoplasmic C-terminal domain of Slack sodium-activated potassium (KNa channels result in childhood epilepsy with severe intellectual disability. Slack currents can be increased by pharmacological activators or by phosphorylation of a Slack C-terminal residue by protein kinase C. Using an optical biosensor assay, we find that Slack channel stimulation in neurons or transfected cells produces loss of mass near the plasma membrane. Slack mutants associated with intellectual disability fail to trigger any change in mass. The loss of mass results from the dissociation of the protein phosphatase 1 (PP1 targeting protein, Phactr-1, from the channel. Phactr1 dissociation is specific to wild-type Slack channels and is not observed when related potassium channels are stimulated. Our findings suggest that Slack channels are coupled to cytoplasmic signaling pathways and that dysregulation of this coupling may trigger the aberrant intellectual development associated with specific childhood epilepsies.

  15. Mitochondrial membrane potential in human neutrophils is maintained by complex III activity in the absence of supercomplex organisation

    NARCIS (Netherlands)

    B.J. van Raam (Bram); W.J. Sluiter (Wim); F.R.C. de Wit (Frank); D. Roos (Dirk); A.J. Verhoeven (Arthur); T.W. Kuijpers (Taco W.)

    2008-01-01

    textabstractBackground: Neutrophils depend mainly on glycolysis for their enegry provision. Their mitochondria maintain a membrace potential (ΔΨm), which is usually generated by the repiratory chain complexes. We investigated the source of ΔΨm in neutrophils, as compared to peripheral blood

  16. Paracetamol biodegradation by activated sludge and photocatalysis and its removal by a micelle-clay complex, activated charcoal, and reverse osmosis membranes.

    Science.gov (United States)

    Karaman, Rafik; Khamis, Mustafa; Abbadi, Jehad; Amro, Ahmad; Qurie, Mohannad; Ayyad, Ibrahim; Ayyash, Fatima; Hamarsheh, Omar; Yaqmour, Reem; Nir, Shlomo; Bufo, Sabino A; Scrano, Laura; Lerman, Sofia; Gur-Reznik, Shirra; Dosoretz, Carlos G

    2016-10-01

    Kinetic studies on the stability of the pain killer paracetamol in Al-Quds activated sludge demonstrated that paracetamol underwent biodegradation within less than one month to furnish p-aminophenol in high yields. Characterizations of bacteria contained in Al-Quds sludge were accomplished. It was found that Pseudomonas aeruginosa is the bacterium most responsible for the biodegradation of paracetamol to p-aminophenol and hydroquinone. Batch adsorptions of paracetamol and its biodegradation product (p-aminophenol) by activated charcoal and a composite micelle (octadecyltrimethylammonium)-clay (montmorillonite) were determined at 25°C. Adsorption was adequately described by a Langmuir isotherm, and indicated better efficiency of removal by the micelle-clay complex. The ability of bench top reverse osmosis (RO) plant as well as advanced membrane pilot plant to remove paracetamol was also studied at different water matrixes to test the effect of organic matter composition. The results showed that at least 90% rejection was obtained by both plants. In addition, removal of paracetamol from RO brine was investigated by using photocatalytic processes; optimal conditions were found to be acidic or basic pH, in which paracetamol degraded in less than 5 min. Toxicity studies indicated that the effluent and brine were not toxic except for using extra low energy membrane which displayed a half maximal inhibitory concentration (IC-50) value of 80%.

  17. Purification, crystallization and preliminary X-ray analysis of the outer membrane complex HasA–HasR from Serratia marcescens

    Energy Technology Data Exchange (ETDEWEB)

    Huché, Frédéric, E-mail: huche@pasteur.fr [Fachbereich Biologie, Universität Konstanz, 78457 Konstanz (Germany); Unité des Membranes Bactériennes, CNRS URA 2172, Département de Microbiologie Fondamentale et Médicale, Institut Pasteur, 25-28 Rue du Dr Roux, 75724 Paris CEDEX 15 (France); Delepelaire, Philippe; Wandersman, Cécile [Unité des Membranes Bactériennes, CNRS URA 2172, Département de Microbiologie Fondamentale et Médicale, Institut Pasteur, 25-28 Rue du Dr Roux, 75724 Paris CEDEX 15 (France); Welte, Wolfram [Fachbereich Biologie, Universität Konstanz, 78457 Konstanz (Germany)

    2006-01-01

    The expression, purification, and crystallization in space group P2{sub 1}2{sub 1}2{sub 1} of the complex HasA-HasR from S. marcescens are reported. Diffraction data have been collected and processed to 6.8 Å. Serratia marcescens is able to acquire iron using its haem-acquisition system (‘has’), which contains an outer membrane receptor HasR and a soluble haemophore HasA. After secretion, HasA binds free haem in the extracellular medium or extracts it from haemoproteins and delivers it to the receptor. Here, the crystallization of a HasA–HasR complex is reported. HasA and HasR have been overexpressed in Escherichia coli and the complex formed and crystallized. Small platelets and bunches of needles of dimensions 0.01 × 0.1 × 1 mm were obtained. A native data set has been collected to 6.8 Å.

  18. Interaction of Newly Platinum(II) with Tris(2-carboxyethyl)phosphine Complex with DNA and Model Lipid Membrane

    Czech Academy of Sciences Publication Activity Database

    Pruchnik, H.; Kral, Teresa; Hof, Martin

    2017-01-01

    Roč. 250, č. 5 (2017), s. 461-470 ISSN 0022-2631 R&D Projects: GA ČR(CZ) GBP208/12/G016 Institutional support: RVO:61388955 Keywords : dna * DPPC bilayer * dsc * IR spectroscopy * Platinum(II) complex * tcspc-fcs Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 1.696, year: 2016

  19. The use of microbead-based spoligotyping for Mycobacterium tuberculosis complex to evaluate the quality of the conventional method: Providing guidelines for Quality Assurance when working on membranes

    Directory of Open Access Journals (Sweden)

    Garzelli Carlo

    2011-04-01

    Full Text Available Abstract Background The classical spoligotyping technique, relying on membrane reverse line-blot hybridization of the spacers of the Mycobacterium tuberculosis CRISPR locus, is used world-wide (598 references in Pubmed on April 8th, 2011. However, until now no inter-laboratory quality control study had been undertaken to validate this technique. We analyzed the quality of membrane-based spoligotyping by comparing it to the recently introduced and highly robust microbead-based spoligotyping. Nine hundred and twenty-seven isolates were analyzed totaling 39,861 data points. Samples were received from 11 international laboratories with a worldwide distribution. Methods The high-throughput microbead-based Spoligotyping was performed on CTAB and thermolyzate DNA extracted from isolated Mycobacterium tuberculosis complex (MTC strains coming from the genotyping participating centers. Information regarding how the classical Spoligotyping method was performed by center was available. Genotype discriminatory analyses were carried out by comparing the spoligotypes obtained by both methods. The non parametric U-Mann Whitney homogeneity test and the Spearman rank correlation test were performed to validate the observed results. Results Seven out of the 11 laboratories (63 %, perfectly typed more than 90% of isolates, 3 scored between 80-90% and a single center was under 80% reaching 51% concordance only. However, this was mainly due to discordance in a single spacer, likely having a non-functional probe on the membrane used. The centers using thermolyzate DNA performed as well as centers using the more extended CTAB extraction procedure. Few centers shared the same problematic spacers and these problematic spacers were scattered over the whole CRISPR locus (Mostly spacers 15, 14, 18, 37, 39, 40. Conclusions We confirm that classical spoligotyping is a robust method with generally a high reliability in most centers. The applied DNA extraction procedure (CTAB

  20. Equivalent complex conductivities representing the effects of T-tubules and folded surface membranes on the electrical admittance and impedance of skeletal muscles measured by external-electrode method

    Science.gov (United States)

    Sekine, Katsuhisa

    2017-12-01

    In order to represent the effects of T-tubules and folded surface membranes on the electrical admittance and impedance of skeletal muscles measured by the external-electrode method, analytical relations for the equivalent complex conductivities of hypothetical smooth surface membranes were derived. In the relations, the effects of each tubule were represented by the admittance of a straight cable. The effects of the folding of a surface membrane were represented by the increased area of surface membranes. The equivalent complex conductivities were represented as summation of these effects, and the effects of the T-tubules were different between the transversal and longitudinal directions. The validity of the equivalent complex conductivities was supported by the results of finite-difference method (FDM) calculations made using three-dimensional models in which T-tubules and folded surface membranes were represented explicitly. FDM calculations using the equivalent complex conductivities suggested that the electrically inhomogeneous structure due to the existence of muscle cells with T-tubules was sufficient for explaining the experimental results previously obtained using the external-electrode method. Results of FDM calculations in which the structural changes caused by muscle contractions were taken into account were consistent with the reported experimental results.

  1. A Characeae Cells Plasma Membrane as a Model for Selection of Bioactive Compounds and Drugs: Interaction of HAMLET-Like Complexes with Ion Channels of Chara corallina Cells Plasmalemma.

    Science.gov (United States)

    Kataev, Anatoly; Zherelova, Olga; Grishchenko, Valery

    2016-12-01

    Interaction of a HAMLET-like La-OA cytotoxic complex (human α-lactalbumin-oleic acid) and its constituents with the excitable plasmalemma of giant Chara corallina cells was investigated. The voltage-clamp technique was used to study Ca 2+ and Cl - transient currents in the plasmalemma of intact cells. The action of the complex and OA on the target cell membrane has a dose-dependent character. It was found that the La-OA complex has an inhibiting effect on Ca 2+ current across the plasmalemma, while α-lactalbumin alone does not affect the electrophysiological characteristics of the cellular membrane. However, oleic acid blocks Ca 2+ current across the plasmalemma. This is accompanied by the induction of a non-selective conductivity in the cellular membrane, a decrease in the resting potential and plasma membrane resistance of algal cells. We propose that the cytotoxicity of La-OA and other HAMLET-like complexes is determined by oleic acid acting as a blocker of potential-dependent Ca 2+ channels in the plasma membrane of target cells. The presented results show that the study model of green algae C. corallina cells plasmalemma is a convenient tool for the investigation of ion channels in many animal cells.

  2. Combining blue native polyacrylamide gel electrophoresis with liquid chromatography tandem mass spectrometry as an effective strategy for analyzing potential membrane protein complexes of Mycobacterium bovis bacillus Calmette-Guérin

    Directory of Open Access Journals (Sweden)

    Li Weijun

    2011-01-01

    Full Text Available Abstract Background Tuberculosis is an infectious bacterial disease in humans caused primarily by Mycobacterium tuberculosis, and infects one-third of the world's total population. Mycobacterium bovis bacillus Calmette-Guérin (BCG vaccine has been widely used to prevent tuberculosis worldwide since 1921. Membrane proteins play important roles in various cellular processes, and the protein-protein interactions involved in these processes may provide further information about molecular organization and cellular pathways. However, membrane proteins are notoriously under-represented by traditional two-dimensional polyacrylamide gel electrophoresis (2-D PAGE and little is known about mycobacterial membrane and membrane-associated protein complexes. Here we investigated M. bovis BCG by an alternative proteomic strategy coupling blue native PAGE to liquid chromatography tandem mass spectrometry (LC-MS/MS to characterize potential protein-protein interactions in membrane fractions. Results Using this approach, we analyzed native molecular composition of protein complexes in BCG membrane fractions. As a result, 40 proteins (including 12 integral membrane proteins, which were organized in 9 different gel bands, were unambiguous identified. The proteins identified have been experimentally confirmed using 2-D SDS PAGE. We identified MmpL8 and four neighboring proteins that were involved in lipid transport complexes, and all subunits of ATP synthase complex in their monomeric states. Two phenolpthiocerol synthases and three arabinosyltransferases belonging to individual operons were obtained in different gel bands. Furthermore, two giant multifunctional enzymes, Pks7 and Pks8, and four mycobacterial Hsp family members were determined. Additionally, seven ribosomal proteins involved in polyribosome complex and two subunits of the succinate dehydrogenase complex were also found. Notablely, some proteins with high hydrophobicity or multiple transmembrane

  3. Combining blue native polyacrylamide gel electrophoresis with liquid chromatography tandem mass spectrometry as an effective strategy for analyzing potential membrane protein complexes of Mycobacterium bovis bacillus Calmette-Guérin.

    Science.gov (United States)

    Zheng, Jianhua; Wei, Candong; Zhao, Lina; Liu, Liguo; Leng, Wenchuan; Li, Weijun; Jin, Qi

    2011-01-18

    Tuberculosis is an infectious bacterial disease in humans caused primarily by Mycobacterium tuberculosis, and infects one-third of the world's total population. Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccine has been widely used to prevent tuberculosis worldwide since 1921. Membrane proteins play important roles in various cellular processes, and the protein-protein interactions involved in these processes may provide further information about molecular organization and cellular pathways. However, membrane proteins are notoriously under-represented by traditional two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and little is known about mycobacterial membrane and membrane-associated protein complexes. Here we investigated M. bovis BCG by an alternative proteomic strategy coupling blue native PAGE to liquid chromatography tandem mass spectrometry (LC-MS/MS) to characterize potential protein-protein interactions in membrane fractions. Using this approach, we analyzed native molecular composition of protein complexes in BCG membrane fractions. As a result, 40 proteins (including 12 integral membrane proteins), which were organized in 9 different gel bands, were unambiguous identified. The proteins identified have been experimentally confirmed using 2-D SDS PAGE. We identified MmpL8 and four neighboring proteins that were involved in lipid transport complexes, and all subunits of ATP synthase complex in their monomeric states. Two phenolpthiocerol synthases and three arabinosyltransferases belonging to individual operons were obtained in different gel bands. Furthermore, two giant multifunctional enzymes, Pks7 and Pks8, and four mycobacterial Hsp family members were determined. Additionally, seven ribosomal proteins involved in polyribosome complex and two subunits of the succinate dehydrogenase complex were also found. Notablely, some proteins with high hydrophobicity or multiple transmembrane helixes were identified well in our work. In this

  4. Synergistic enhancement of chemokine generation and lung injury by C5a or the membrane attack complex of complement

    DEFF Research Database (Denmark)

    Czermak, B J; Lentsch, A B; Bless, N M

    1999-01-01

    demonstrated synergistic production of C-X-C (macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant) and C-C (macrophage inflammatory protein-1alpha and monocyte chemoattractant-1) chemokines. In the absence of the costimulus, C5a or MAC did not induce chemokine generation....... In in vivo studies, C5a and MAC alone caused limited or no intrapulmonary generation of chemokines, but in the presence of a costimulus (IgG immune complexes) C5a and MAC caused synergistic intrapulmonary generation of C-X-C and C-C chemokines but not of tumor necrosis factor alpha. Under these conditions...... increased neutrophil accumulation occurred, as did lung injury. These observations suggest that C5a and MAC function synergistically with a costimulus to enhance chemokine generation and the intensity of the lung inflammatory response....

  5. Tympanic-membrane and malleus–incus-complex co-adaptations for high-frequency hearing in mammals

    Science.gov (United States)

    Puria, Sunil; Steele, Charles

    2014-01-01

    The development of the unique capacity for high-frequency hearing in many mammals was due in part to changes in the middle ear, such as the evolution of three distinct middle-ear bones and distinct radial and circumferential collagen fiber layers in the eardrum. Ossicular moment(s) of inertia (MOI) and principal rotational axes, as well as eardrum surface areas, were calculated from micro-CT-based 3-D reconstructions of human, cat, chinchilla, and guinea pig temporal bones. For guinea pig and chinchilla, the fused malleus–incus complex rotates about an anterior–posterior axis, due to the relatively lightweight ossicles and bilateral symmetry of the eardrum. For human and cat, however, the MOI calculated for the unfused malleus are 5–6 times smaller for rotations about an inferior–superior axis than for rotations about the other two orthogonal axes. It is argued that these preferred motions, along with the presence of a mobile malleus–incus joint and asymmetric eardrum, enable efficient high-frequency sound transmission in spite of the relatively large ossicular masses of these species. This work argues that the upper-frequency hearing limit of a given mammalian species can in part be understood in terms of morphological co-adaptations of the eardrum and ossicular chain. PMID:19878714

  6. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...

  7. Autophagosomal membranes assemble at ER-plasma membrane contact sites.

    Science.gov (United States)

    Nascimbeni, Anna Chiara; Codogno, Patrice; Morel, Etienne

    2017-01-01

    The biogenesis of autophagosome, the double membrane bound organelle related to macro-autophagy, is a complex event requiring numerous key-proteins and membrane remodeling events. Our recent findings identify the extended synaptotagmins, crucial tethers of Endoplasmic Reticulum-plasma membrane contact sites, as key-regulators of this molecular sequence.

  8. In vivo test of the vertical phase separation hypothesis: the display of major histocompatibility complex (MHC) class I molecules on membranes of B cells from mice fed high-fat diets

    Science.gov (United States)

    Shaikh, Saame Raza; Boyle, Sarah; Hua, Jing; Li, Zhiping; Edidin, Michael

    2009-01-01

    The membrane vertical phase separation hypothesis predicts that a decrease in plasma membrane acyl chain order will increase major histocompatibility complex (MHC) class I surface expression. The hypothesis is based on modification of plasma membrane acyl chain order in cell culture and has not been tested in vivo. In the present study, we isolated splenic B cells from C57/BL6 mice fed either a normal diet or high-fat diets enriched in SFA or MUFA and assayed for changes in plasma membrane acyl chain order and MHC class I surface expression. Plasma membranes of B cells from MUFA-fed mice had significantly decreased acyl chain order and increased headgroup order. The decrease in acyl chain order correlated with a significant increase in the acyl chain unsaturation of B cells from the MUFA-fed mice. MHC class I surface levels on B cells were not affected by the MUFA-rich diet. This study suggests that the membrane vertical phase separation hypothesis may have limited application in a physiologically relevant setting. PMID:19283887

  9. Study of the nucleotide binding site of the yeast Schizosaccharomyces pombe plasma membrane H+-ATPase using formycin triphosphate-terbium complex

    International Nuclear Information System (INIS)

    Ronjat, M.; Lacapere, J.J.; Dufour, J.P.; Dupont, Y.

    1987-01-01

    The plasma membrane of yeasts contains an H+-ATPase similar to the other cation transport ATPases of eukaryotic organisms. This enzyme has been purified and shows H+ transport in reconstituted vesicles. In the presence of Mg2+, formycin triphosphate (FTP) is hydrolyzed by the H+-ATPase and supports H+ transport. When combined with terbium ion, FTP (Tb-FTP) and ATP (Tb-ATP) are no longer hydrolyzed. Competition between Mg-ATP and Tb-FTP for ATP hydrolysis indicates that terbium-associated nucleotides bind to the catalytic site of the H+-ATPase. The fluorescent properties of the Tb-FTP complex were used to study the active site of the H+-ATPase. Fluorescence of Tb-FTP is greatly enhanced upon binding into the nucleotide site of H+-ATPase with a dissociation constant of 1 microM. Tb-ATP, Tb-ADP, and Tb-ITP are competitive inhibitors of Tb-FTP binding with Ki = 4.5, 5.0, and 6.0 microM, respectively. Binding of Tb-FTP is observed only in the presence of an excess of Tb3+ with an activation constant Ka = 25 microM for Tb3+. Analysis of the data reveals that the sites for Tb-FTP and Tb3+ binding are independent entities. In standard conditions these sites would be occupied by Mg-ATP and Mg2+, respectively. These findings suggest an important regulatory role of divalent cations on the activity of H+-ATPase. Replacement of H 2 O by D 2 O in the medium suggests the existence of two types of nucleotide binding sites differing by the hydration state of the Tb3+ ion in the bound Tb-FTP complex

  10. Membrane-localized extra-large G proteins and Gbg of the heterotrimeric G proteins form functional complexes engaged in plant immunity in Arabidopsis.

    Science.gov (United States)

    Maruta, Natsumi; Trusov, Yuri; Brenya, Eric; Parekh, Urvi; Botella, José Ramón

    2015-03-01

    In animals, heterotrimeric G proteins, comprising Ga, Gb, and Gg subunits, are molecular switches whose function tightly depends on Ga and Gbg interaction. Intriguingly, in Arabidopsis (Arabidopsis thaliana), multiple defense responses involve Gbg, but not Ga. We report here that the Gbg dimer directly partners with extra-large G proteins (XLGs) to mediate plant immunity. Arabidopsis mutants deficient in XLGs, Gb, and Gg are similarly compromised in several pathogen defense responses, including disease development and production of reactive oxygen species. Genetic analysis of double, triple, and quadruple mutants confirmed that XLGs and Gbg functionally interact in the same defense signaling pathways. In addition, mutations in XLG2 suppressed the seedling lethal and cell death phenotypes of BRASSINOSTEROID INSENSITIVE1-associated receptor kinase1-interacting receptor-like kinase1 mutants in an identical way as reported for Arabidopsis Gb-deficient mutants. Yeast (Saccharomyces cerevisiae) three-hybrid and bimolecular fluorescent complementation assays revealed that XLG2 physically interacts with all three possible Gbg dimers at the plasma membrane. Phylogenetic analysis indicated a close relationship between XLGs and plant Ga subunits, placing the divergence point at the dawn of land plant evolution. Based on these findings, we conclude that XLGs form functional complexes with Gbg dimers, although the mechanism of action of these complexes, including activation/deactivation, must be radically different form the one used by the canonical Ga subunit and are not likely to share the same receptors. Accordingly, XLGs expand the repertoire of heterotrimeric G proteins in plants and reveal a higher level of diversity in heterotrimeric G protein signaling.

  11. N-Ethylmaleimide Dissociates α7 ACh Receptor from a Complex with NSF and Promotes Its Delivery to the Presynaptic Membrane.

    Science.gov (United States)

    Nishizaki, Tomoyuki

    2016-08-01

    N-Ethylmaleimide (NEM)-sensitive factor (NSF) associates with soluble NSF attachment protein (SNAP), that binds to SNAP receptors (SNAREs) including syntaxin, SNAP25, and synaptobrevin. The complex of NSF/SNAP/SNAREs plays a critical role in the regulation of vesicular traffic. The present study investigated NEM-regulated α7 ACh receptor translocation. NSF associated with β-SNAP and the SNAREs syntaxin 1 and synaptobrevin 2 in the rat hippocampus. NSF also associated with the α7 ACh receptor subunit, the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluA1 and GluA2, and the γ-aminobutyric acid A (GABAA) receptor γ2 subunit. NEM, an inhibitor of NSF, significantly dissociated the α7 ACh receptor subunit from a complex with NSF and increased cell surface localization of the receptor subunit, but such effect was not obtained with the GluA1, GluA2 or γ2 subunits. NEM, alternatively, dissociated synaptobrevin 2 from an assembly of NSF/β-SNAP/syntaxin 1/synaptobrevin 2. NEM significantly increased the rate of nicotine-triggered AMPA receptor-mediated miniature excitatory postsynaptic currents, without affecting the amplitude, in rat hippocampal slices. The results of the present study indicate that NEM releases the α7 ACh receptor subunit and synaptobrevin 2 from an assembly of α7 ACh receptor subunit/NSF/β-SNAP/syntaxin 1/synaptobrevin 2, thereby promoting delivery of the α7 ACh receptor subunit to presynaptic membrane.

  12. Assembly and Regulation of the Membrane Attack Complex Based on Structures of C5b6 and sC5b9

    Directory of Open Access Journals (Sweden)

    Michael A. Hadders

    2012-03-01

    Full Text Available Activation of the complement system results in formation of membrane attack complexes (MACs, pores that disrupt lipid bilayers and lyse bacteria and other pathogens. Here, we present the crystal structure of the first assembly intermediate, C5b6, together with a cryo-electron microscopy reconstruction of a soluble, regulated form of the pore, sC5b9. Cleavage of C5 to C5b results in marked conformational changes, distinct from those observed in the homologous C3-to-C3b transition. C6 captures this conformation, which is preserved in the larger sC5b9 assembly. Together with antibody labeling, these structures reveal that complement components associate through sideways alignment of the central MAC-perforin (MACPF domains, resulting in a C5b6-C7-C8β-C8α-C9 arc. Soluble regulatory proteins below the arc indicate a potential dual mechanism in protection from pore formation. These results provide a structural framework for understanding MAC pore formation and regulation, processes important for fighting infections and preventing complement-mediated tissue damage.

  13. A Schiff base complex of Zn(II) as a neutral carrier for highly selective PVC membrane sensors for the sulfate ion.

    Science.gov (United States)

    Shamsipur, M; Yousefi, M; Hosseini, M; Ganjali, M R; Sharghi, H; Naeimi, H

    2001-07-01

    Novel polymeric membrane (PME) and coated graphite (CGE) sulfate-selective electrodes based on a recently synthesized Schiff base complex of Zn(II) were prepared. The electrodes reveal a Nernstian behavior over wide SO4(2-) ion concentration ranges (5.0 x 10(-5)-1.0 x 10(-1) M for PME and 1.0 x 10(-7)-1.0 x 10(-1) M for CGE) and very low detection limits (2.8 x 10(-5) M for PME and 8.5 x 10(-8) M for CGE). The potentiometric response is independent of the pH of the solution in the pH range 3.0-7.0. The electrodes manifest advantages of low resistance, very fast response, and, most importantly, good selectivities relative to a wide variety of other anions. In fact, the selectivity behavior of the proposed SO4(2) ion-selective electrodes shows a great improvement compared to the previously reported electrodes for sulfate ion. The electrodes can be used for at least 3 months without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of sulfate and barium ions and in the determination of iron in ferrous sulfate tablets.

  14. Relation between sedimentation behaviour of DNA-membrane complexes and DNA single- and double-strand breaks after irradiation with gamma-rays, pulse neutrons and 12C ions

    International Nuclear Information System (INIS)

    Erzgraber, G.; Lapidus, I.L.

    1985-01-01

    The experimental data on sedimentation behaviour of DNA-membrane complexes at radiation of the Chinese hamster cells (V79-4) in a wide dose range of 127 Cs γ-rays, pulse neutrons (reactor IBR-2, Laboratory of Neutron Physics, JINR, Dubna) are accelerated 12 C ions (cyclotron U-200, Laboratory of Nuclear Reactions, JINR, Dubna) are presented An assumption on the role of DNA single- and double-strend breaks in changing the sedimentation properties of DNA-membrane complexes has been confirmed by the experiments with radiation of different quality. The possibility of estimating induction and repair of DNA breaks on the basis of dependence of the relative sedimentation velocity of complexes on the irradiation does is discussed

  15. Polyurethane Nanofiber Membranes for Waste Water Treatment by Membrane Distillation

    Directory of Open Access Journals (Sweden)

    T. Jiříček

    2017-01-01

    Full Text Available Self-sustained electrospun polyurethane nanofiber membranes were manufactured and tested on a direct-contact membrane distillation unit in an effort to find the optimum membrane thickness to maximize flux rate and minimize heat losses across the membrane. Also salt retention and flux at high salinities up to 100 g kg−1 were evaluated. Even though the complex structure of nanofiber layers has extreme specific surface and porosity, membrane performance was surprisingly predictable; the highest flux was achieved with the thinnest membranes and the best energy efficiency was achieved with the thickest membranes. All membranes had salt retention above 99%. Nanotechnology offers the potential to find modern solutions for desalination of waste waters, by introducing new materials with revolutionary properties, but new membranes must be developed according to the target application.

  16. Crystallization and preliminary X-ray crystallographic analysis of the Escherichia coli outer membrane cobalamin transporter BtuB in complex with the carboxy-terminal domain of TonB

    Energy Technology Data Exchange (ETDEWEB)

    Shultis, David D.; Purdy, Michael D. [Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 (United States); Banchs, Christian N. [Interdisciplinary Graduate Program in Biophysics, University of Virginia, Charlottesville, Virginia 22908 (United States); Wiener, Michael C., E-mail: mwiener@virginia.edu [Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908 (United States); Interdisciplinary Graduate Program in Biophysics, University of Virginia, Charlottesville, Virginia 22908 (United States)

    2006-07-01

    Crystals of a complex of the E. coli proteins BtuB (outer membrane cobalamin transporter) and TonB (carboxy-terminal domain) diffracting to 2.1 Å resolution have been obtained. The energy-dependent uptake of organometallic compounds and other micronutrients across the outer membranes of Gram-negative bacteria is carried out by outer membrane active-transport proteins that utilize the proton-motive force of the inner membrane via coupling to the TonB protein. The Escherichia coli outer membrane cobalamin transporter BtuB and a carboxy-terminal domain of the TonB protein, residues 147–239 of the wild-type protein, were expressed and purified individually. A complex of BtuB and TonB{sup 147–239} was formed in the presence of the substrate cyanocobalamin (CN-Cbl; vitamin B{sub 12}) and calcium and was crystallized. BtuB was purified in the detergent LDAO (n-dodecyl-N,N-dimethylamine-N-oxide) and the complex was formed in a detergent mixture of LDAO and C{sub 8}E{sub 4} (tetraethylene glycol monooctylether). Crystals were obtained by sitting-drop vapor diffusion, with the reservoir containing 30%(v/v) polyethylene glycol (PEG 300) and 100 mM sodium acetate pH 5.2. The crystals belong to space group P2{sub 1}2{sub 1}2{sub 1} (unit-cell parameters a = 74.3, b = 82.4, c = 122.6 Å). The asymmetric unit consists of a single BtuB–TonB complex. Data sets have been collected to 2.1 Å resolution at a synchrotron beamline (APS SER-CAT 22-ID)

  17. Biobased Membrane

    NARCIS (Netherlands)

    Koenders, E.A.B.; Zlopasa, J.; Picken, S.J.

    2015-01-01

    The present invention is in the field of a composition for forming a bio-compatible membrane applicable to building material, such as concrete, cement, etc., to a meth od of applying said composition for forming a bio-compatible membrane, a biocompatible membrane, use of said membrane for various

  18. Crosslinked sulfonated poly(arylene ether ketone) membranes bearing quinoxaline and acid-base complex cross-linkages for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xinbing; Chen, Pei; An, Zhongwei [Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Materials Science, Shaanxi Normal University, Xi' an 710062 (China); Chen, Kangcheng; Okamoto, Kenichi [Graduate School of Science and Engineering, Yamaguchi University, Tokiwadai 2-16-1, Ube, Yamaguchi 755-8611 (Japan)

    2011-02-15

    A series of crosslinkable sulfonated poly(arylene ether ketone)s (SPAEKs) were synthesized by copolymerization of 4,4'-biphenol with 2,6-difluorobenzil and 5,5'-carbonyl-bis(2-fluorobenzene-sulfonate). A facile crosslinking method was successfully developed, based on the cyclocondensation reaction of benzil moieties in polymer chain with 3,3'-diaminobenzidine to form quinoxaline groups acting as covalent and acid-base ionic crosslinking. The uncrosslinked and crosslinked SPAEK membranes showed high mechanical properties and the isotropic membrane swelling, while the later became insoluble in tested polar aprotic solvents. The crosslinking significantly improved the membrane performance, i.e., the crosslinked membranes had the lower membrane dimensional change, lower methanol permeability and higher oxidative stability than the corresponding precursor membranes, with keeping the reasonably high proton conductivity. The crosslinked membrane (C-B4) with an ion exchange capacity of 2.02 mequiv. g{sup -1} showed a reasonably high proton conductivity of 111 mS cm{sup -1} with a low water uptake of 42 wt% at 80 C. C-B4 exhibited a low methanol permeability of 0.55 x 10{sup -6} cm{sup 2} s{sup -1} for 32 wt% methanol solution at 25 C. The crosslinked SPAEK membranes have potential for PEFC and DMFC applications. (author)

  19. Sporozoite neutralizing antibodies elicited in mice and rhesus macaques immunized with a Plasmodium falciparum repeat peptide conjugated to meningococcal outer membrane protein complex

    Directory of Open Access Journals (Sweden)

    Craig ePrzysiecki

    2012-11-01

    Full Text Available Antibodies that neutralize infectivity of malaria sporozoites target the central repeat region of the circumsporozoite (CS protein, which in Plasmodium falciparum is comprised primarily of 30-40 tandem NANP tetramer repeats. We evaluated immunogenicity of an alum-adsorbed (NANP6 peptide conjugated to an outer membrane protein complex (OMPC derived from Neisseria meningitidis, a carrier protein used in a licensed H. influenzae pediatric vaccine. Mice immunized with alum-adsorbed (NANP6-OMPC, with or without Iscomatrix© as co-adjuvant, developed high levels of anti-repeat peptide antibody that inhibited in vitro invasion of human hepatoma cells by transgenic P. berghei sporozoites that express P. falciparum CS repeats (PfPb. Inhibition of sporozoite invasion in vitro correlated with in vivo resistance to challenge by the bites of PfPb infected mosquitoes. Challenged mice had > 90% reduction of hepatic stage parasites as measured by real-time PCR, and either sterile immunity, i.e. no detectable blood stage parasites, or delayed prepatent periods which indicate neutralization of a majority, but not all, sporozoites. Rhesus macaques immunized with two doses of (NANP6-OMPC/MAA formulated with Iscomatrix© developed anti-repeat antibodies that persisted for ~2 years. A third dose of (NANP6-OMPC/MAA+ Iscomatrix© at that time elicited strong anamnestic antibody responses. Rhesus macaque immune sera obtained post second and third dose of vaccine displayed high levels of sporozoite neutralizing activity in vitro that correlated with presence of high anti-repeat antibody titers. These preclinical studies in mice of different MHC haplotypes and a non-human primate support use of CS peptide-OMPC conjugates as a highly immunogenic platform to evaluate CS protective epitopes. Potential pre-erythrocytic vaccines can be combined with sexual blood stage vaccines as a multi-antigen malaria vaccine to block invasion and transmission of Plasmodium parasites

  20. Effective As(III) Removal by A Multi-Charged Hydroacid Complex Draw Solute Facilitated Forward Osmosis-Membrane Distillation (FO-MD) Processes.

    Science.gov (United States)

    Ge, Qingchun; Han, Gang; Chung, Tai-Shung

    2016-03-01

    Effective removal of As(III) from water by an oxalic acid complex with the formula of Na3[Cr(C2O4)3] (Na-Cr-OA) is demonstrated via an forward osmosis-membrane distillation (FO-MD) hybrid system in this study. Na-Cr-OA first proved its superiority as a draw solute with high water fluxes and negligible reverse fluxes in FO, then a systematic investigation of the Na-Cr-OA promoted FO process was conducted to ascertain the factors in As(III) removal. Relatively high water fluxes of 28 LMH under the FO mode and 74 LMH under the pressure retarded osmosis (PRO) mode were achieved when using a 1000 ppm As(III) solution as the feed and 1.0 M Na-Cr-OA as the draw solution at 60 °C. As(III) removal with a water recovery up to 21.6% (FO mode) and 48.3% (PRO mode) were also achieved in 2 h. An outstanding As(III) rejection with 30-3000 μg/L As(III) in the permeate was accomplished when As(III) feed solutions varied from 5 × 10(4) to 1 × 10(6) μg/L, superior to the best FO performance reported for As(III) removal. Incorporating MD into FO not only makes As(III) removal sustainable by reconcentrating the Na-Cr-OA solution simultaneously, but also reduces the As(III) concentration below 10 μg/L in the product water, meeting the WHO standard.

  1. Effective As(III) Removal by A Multi-Charged Hydroacid Complex Draw Solute Facilitated Forward Osmosis-Membrane Distillation (FO-MD) Processes

    KAUST Repository

    Ge, Qingchun

    2016-01-29

    © 2016 American Chemical Society. Effective removal of As(III) from water by an oxalic acid complex with the formula of Na3[Cr(C2O4)3] (Na-Cr-OA) is demonstrated via an forward osmosis-membrane distillation (FO-MD) hybrid system in this study. Na-Cr-OA first proved its superiority as a draw solute with high water fluxes and negligible reverse fluxes in FO, then a systematic investigation of the Na-Cr-OA promoted FO process was conducted to ascertain the factors in As(III) removal. Relatively high water fluxes of 28 LMH under the FO mode and 74 LMH under the pressure retarded osmosis (PRO) mode were achieved when using a 1000 ppm As(III) solution as the feed and 1.0 M Na-Cr-OA as the draw solution at 60 °C. As(III) removal with a water recovery up to 21.6% (FO mode) and 48.3% (PRO mode) were also achieved in 2 h. An outstanding As(III) rejection with 30-3000 μg/L As(III) in the permeate was accomplished when As(III) feed solutions varied from 5 × 104 to 1 × 106 μg/L, superior to the best FO performance reported for As(III) removal. Incorporating MD into FO not only makes As(III) removal sustainable by reconcentrating the Na-Cr-OA solution simultaneously, but also reduces the As(III) concentration below 10 μg/L in the product water, meeting the WHO standard.

  2. Multi-scaled normal mode analysis method for dynamics simulation of protein-membrane complexes: A case study of potassium channel gating motion correlations

    Science.gov (United States)

    Wu, Xiaokun; Han, Min; Ming, Dengming

    2015-10-01

    Membrane proteins play critically important roles in many cellular activities such as ions and small molecule transportation, signal recognition, and transduction. In order to fulfill their functions, these proteins must be placed in different membrane environments and a variety of protein-lipid interactions may affect the behavior of these proteins. One of the key effects of protein-lipid interactions is their ability to change the dynamics status of membrane proteins, thus adjusting their functions. Here, we present a multi-scaled normal mode analysis (mNMA) method to study the dynamics perturbation to the membrane proteins imposed by lipid bi-layer membrane fluctuations. In mNMA, channel proteins are simulated at all-atom level while the membrane is described with a coarse-grained model. mNMA calculations clearly show that channel gating motion can tightly couple with a variety of membrane deformations, including bending and twisting. We then examined bi-channel systems where two channels were separated with different distances. From mNMA calculations, we observed both positive and negative gating correlations between two neighboring channels, and the correlation has a maximum as the channel center-to-center distance is close to 2.5 times of their diameter. This distance is larger than recently found maximum attraction distance between two proteins embedded in membrane which is 1.5 times of the protein size, indicating that membrane fluctuation might impose collective motions among proteins within a larger area. The hybrid resolution feature in mNMA provides atomic dynamics information for key components in the system without costing much computer resource. We expect it to be a conventional simulation tool for ordinary laboratories to study the dynamics of very complicated biological assemblies. The source code is available upon request to the authors.

  3. Elastic membranes in confinement.

    Science.gov (United States)

    Bostwick, J B; Miksis, M J; Davis, S H

    2016-07-01

    An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. © 2016 The Author(s).

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

    Science.gov (United States)

    Levental, Kandice R; Levental, Ilya

    2015-01-01

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

  5. Biopores/membrane proteins in synthetic polymer membranes.

    Science.gov (United States)

    Garni, Martina; Thamboo, Sagana; Schoenenberger, Cora-Ann; Palivan, Cornelia G

    2017-04-01

    Mimicking cell membranes by simple models based on the reconstitution of membrane proteins in lipid bilayers represents a straightforward approach to understand biological function of these proteins. This biomimetic strategy has been extended to synthetic membranes that have advantages in terms of chemical and mechanical stability, thus providing more robust hybrid membranes. We present here how membrane proteins and biopores have been inserted both in the membrane of nanosized and microsized compartments, and in planar membranes under various conditions. Such bio-hybrid membranes have new properties (as for example, permeability to ions/molecules), and functionality depending on the specificity of the inserted biomolecules. Interestingly, membrane proteins can be functionally inserted in synthetic membranes provided these have appropriate properties to overcome the high hydrophobic mismatch between the size of the biomolecule and the membrane thickness. Functional insertion of membrane proteins and biopores in synthetic membranes of compartments or in planar membranes is possible by an appropriate selection of the amphiphilic copolymers, and conditions of the self-assembly process. These hybrid membranes have new properties and functionality based on the specificity of the biomolecules and the nature of the synthetic membranes. Bio-hybrid membranes represent new solutions for the development of nanoreactors, artificial organelles or active surfaces/membranes that, by further gaining in complexity and functionality, will promote translational applications. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider. Copyright © 2016. Published by Elsevier B.V.

  6. Membrane-bound versus soluble major histocompatibility complex Class I-related chain A and major histocompatibility complex Class I-related chain B differential expression: Mechanisms of tumor eradication versus evasion and current drug development strategies

    Directory of Open Access Journals (Sweden)

    P K Suresh

    2016-01-01

    Full Text Available Major histocompatibility complex Class I-related chain A/chain B (MICA/MICB is stress-inducible, highly polymorphic ligands whose expression at the transcript level has been detected in all tissues except the central nervous system. However, their restricted protein expression is due to their regulation at the posttranslational level. Its levels are elevated in virally infected and neoplastically transformed cells. Membrane expression of this NKG2DL marks the aberrant cells for elimination by those immune effector cells that express the cognate NKG2D receptor. Among the evasion strategies developed by tumors, the metalloprotease-dependent shedding of MICA/MICB from tumors (either the free or the exosome form can contribute to the inhibition of cytolysis by the immune effector cells (all NK cells, most NKT cells; γδ CD8+ T cells and αβ CD8+ T cells, as well as some αβ CD4+ T cells. There are micro-RNA clusters that regulate surface expression and shedding. Polymorphic variants can be used as susceptibility/associative markers and can also possibly be used to correlate with tumor survival as well as staging/grading of tumors. Variations in the expression level require quantification of this marker for diagnostic/prognostic and therapeutic purposes. Mechanism-based studies would provide a better tumor-specific understanding of their relative roles in the processes of tumor cell elimination versus growth and progression. Last but not least, conventional, interlaboratory validated assays (for, e.g., antibody-based methods should be replaced by robust, reproducible, feasible biophysics-based methods using tumor biopsies. Further, correlative DNA polymorphism-based studies can be done using biological fluids (for, e.g., human saliva that can be sampled by minimally invasive means.

  7. Membrane-bound versus soluble major histocompatibility complex Class I-related chain A and major histocompatibility complex Class I-related chain B differential expression: Mechanisms of tumor eradication versus evasion and current drug development strategies.

    Science.gov (United States)

    Suresh, P K

    2016-01-01

    Major histocompatibility complex Class I-related chain A/chain B (MICA/MICB) is stress-inducible, highly polymorphic ligands whose expression at the transcript level has been detected in all tissues except the central nervous system. However, their restricted protein expression is due to their regulation at the posttranslational level. Its levels are elevated in virally infected and neoplastically transformed cells. Membrane expression of this NKG2DL marks the aberrant cells for elimination by those immune effector cells that express the cognate NKG2D receptor. Among the evasion strategies developed by tumors, the metalloprotease-dependent shedding of MICA/MICB from tumors (either the free or the exosome form) can contribute to the inhibition of cytolysis by the immune effector cells (all NK cells, most NKT cells; γδ CD8+ T cells and αβ CD8+ T cells, as well as some αβ CD4+ T cells). There are micro-RNA clusters that regulate surface expression and shedding. Polymorphic variants can be used as susceptibility/associative markers and can also possibly be used to correlate with tumor survival as well as staging/grading of tumors. Variations in the expression level require quantification of this marker for diagnostic/prognostic and therapeutic purposes. Mechanism-based studies would provide a better tumor-specific understanding of their relative roles in the processes of tumor cell elimination versus growth and progression. Last but not least, conventional, interlaboratory validated assays (for, e.g., antibody-based methods) should be replaced by robust, reproducible, feasible biophysics-based methods using tumor biopsies. Further, correlative DNA polymorphism-based studies can be done using biological fluids (for, e.g., human saliva) that can be sampled by minimally invasive means.

  8. Membranous nephropathy

    Science.gov (United States)

    ... check for hepatitis B, hepatitis C, and syphilis Complement levels Cryoglobulin test Treatment The goal of treatment ... not as helpful for people with membranous nephropathy. Medicines used treat membranous nephropathy include: Angiotensin-converting enzyme ( ...

  9. Silver(I) complexation of linked 2,2'-dipyridylamine derivatives. Synthetic, solvent extraction, membrane transport and X-ray structural studies.

    Science.gov (United States)

    Antonioli, Bianca; Bray, David J; Clegg, Jack K; Gloe, Kerstin; Gloe, Karsten; Kataeva, Olga; Lindoy, Leonard F; McMurtrie, John C; Steel, Peter J; Sumby, Christopher J; Wenzel, Marco

    2006-10-28

    Synthesis of the 2,2'-dipyridylamine derivatives di-2-pyridylaminomethylbenzene 1, 1,2-bis(di-2-pyridylaminomethyl)benzene 2, 1,3-bis(di-2-pyridylaminomethyl)benzene 3, 2,6-bis(di-2-pyridylaminomethyl)pyridine 4, 1,4-bis(di-2-pyridylaminomethyl)benzene 5, and 1,3,5-tris(di-2-pyridylaminomethyl)benzene 6 are reported together with the single-crystal X-ray structures of 2, 3, and 5. Reaction of individual salts of the type AgX (where X = NO(3)(-), PF(6)(-), ClO(4)(-), or BF(4)(-)) with the above ligands has led to the isolation of thirteen Ag(I) complexes, nine of which have also been characterised by X-ray diffraction. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a range of coordination arrangements. A series of liquid-liquid (H(2)O/CHCl(3)) extraction experiments of Ag(I) with varying concentrations of 1-6 in the organic phase have been undertaken, with the counter ion in the aqueous phase being respectively picrate, perchlorate and nitrate. In general, extraction efficiencies for a given ionophore followed the Hofmeister order of picrate > perchlorate > nitrate; in each case the tris-dpa derivative 6 acting as the most efficient extractant of the six systems investigated. Competitive seven-metal bulk membrane transport experiments (H(2)O/CHCl(3)/H(2)O) employing the above ligands as the ionophore in the organic phase and equimolar concentrations of Co(II), Ni(II), Zn(II), Cu(II), Cd(II), Pb(II) and Ag(I) in the aqueous source phase were also undertaken, with transport occurring against a pH gradient. Under the conditions employed 1 and 5 yielded negligible transport of any of the metals present in the source phase while sole transport selectivity for Ag(I) was observed for 2-4 and 6.

  10. Membrane Biophysics

    CERN Document Server

    Ashrafuzzaman, Mohammad

    2013-01-01

    Physics, mathematics and chemistry all play a vital role in understanding the true nature and functioning of biological membranes, key elements of living processes. Besides simple spectroscopic observations and electrical measurements of membranes we address in this book the phenomena of coexistence and independent existence of different membrane components using various theoretical approaches. This treatment will be helpful for readers who want to understand biological processes by applying both simple observations and fundamental scientific analysis. It provides a deep understanding of the causes and effects of processes inside membranes, and will thus eventually open new doors for high-level pharmaceutical approaches towards fighting membrane- and cell-related diseases.

  11. Nanodisc-solubilized membrane protein library reflects the membrane proteome.

    Science.gov (United States)

    Marty, Michael T; Wilcox, Kyle C; Klein, William L; Sligar, Stephen G

    2013-05-01

    The isolation and identification of unknown membrane proteins offers the prospect of discovering new pharmaceutical targets and identifying key biochemical receptors. However, interactions between membrane protein targets and soluble ligands are difficult to study in vitro due to the insolubility of membrane proteins in non-detergent systems. Nanodiscs, nanoscale discoidal lipid bilayers encircled by a membrane scaffold protein belt, have proven to be an effective platform to solubilize membrane proteins and have been used to study a wide variety of purified membrane proteins. This report details the incorporation of an unbiased population of membrane proteins from Escherichia coli membranes into Nanodiscs. This solubilized membrane protein library (SMPL) forms a soluble in vitro model of the membrane proteome. Since Nanodiscs contain isolated proteins or small complexes, the SMPL is an ideal platform for interactomics studies and pull-down assays of membrane proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the protein population before and after formation of the Nanodisc library indicates that a large percentage of the proteins are incorporated into the library. Proteomic identification of several prominent bands demonstrates the successful incorporation of outer and inner membrane proteins into the Nanodisc library.

  12. Fluorescent detection of apoptotic cells using a family of zinc coordination complexes with selective affinity for membrane surfaces that are enriched with phosphatidylserine.

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Bradley D. (University of Notre Dame, Notre Dame, Indiana); Lambert, Timothy N.; Lakshmi, C. (University of Notre Dame, Notre Dame, Indiana); Hanshaw, Roger, G. (University of Notre Dame, Notre Dame, Indiana)

    2005-03-01

    The appearance of phosphatidylserine on the membrane surface of apoptotic cells (Jurkat, CHO, HeLa) is monitored by using a family of bis(Zn{sup 2+}-2,2{prime}-dipicolylamine) coordination compounds with appended fluorescein or biotin groups as reporter elements. The phosphatidylserine affinity group is also conjugated directly to a CdSe/CdS quantum dot to produce a probe suitable for prolonged observation without photobleaching. Apoptosis can be detected under a wide variety of conditions, including variations in temperature, incubation time, and binding media. Binding of each probe appears to be restricted to the cell membrane exterior, because no staining of organelles or internal membranes is observed.

  13. The Type VI Secretion TssEFGK-VgrG Phage-Like Baseplate Is Recruited to the TssJLM Membrane Complex via Multiple Contacts and Serves As Assembly Platform for Tail Tube/Sheath Polymerization.

    Directory of Open Access Journals (Sweden)

    Yannick R Brunet

    2015-10-01

    Full Text Available The Type VI secretion system (T6SS is a widespread weapon dedicated to the delivery of toxin proteins into eukaryotic and prokaryotic cells. The 13 T6SS subunits assemble a cytoplasmic contractile structure anchored to the cell envelope by a membrane-spanning complex. This structure is evolutionarily, structurally and functionally related to the tail of contractile bacteriophages. In bacteriophages, the tail assembles onto a protein complex, referred to as the baseplate, that not only serves as a platform during assembly of the tube and sheath, but also triggers the contraction of the sheath. Although progress has been made in understanding T6SS assembly and function, the composition of the T6SS baseplate remains mostly unknown. Here, we report that six T6SS proteins-TssA, TssE, TssF, TssG, TssK and VgrG-are required for proper assembly of the T6SS tail tube, and a complex between VgrG, TssE,-F and-G could be isolated. In addition, we demonstrate that TssF and TssG share limited sequence homologies with known phage components, and we report the interaction network between these subunits and other baseplate and tail components. In agreement with the baseplate being the assembly platform for the tail, fluorescence microscopy analyses of functional GFP-TssF and TssK-GFP fusion proteins show that these proteins assemble stable and static clusters on which the sheath polymerizes. Finally, we show that recruitment of the baseplate to the apparatus requires initial positioning of the membrane complex and contacts between TssG and the inner membrane TssM protein.

  14. The cation diffusion facilitator proteins MamB and MamM of Magnetospirillum gryphiswaldense have distinct and complex functions, and are involved in magnetite biomineralization and magnetosome membrane assembly

    DEFF Research Database (Denmark)

    Uebe, René; Junge, Katja; Henn, Verena

    2011-01-01

    with the magnetosome membrane of Magnetospirillum gryphiswaldense are MamB and MamM, which were implicated in magnetosomal iron transport because of their similarity to the cation diffusion facilitator family. Here we demonstrate that MamB and MamM are multifunctional proteins involved in several steps of magnetosome...... formation. Whereas both proteins were essential for magnetite biomineralization, only deletion of mamB resulted in loss of magnetosome membrane vesicles. MamB stability depended on the presence of MamM by formation of a heterodimer complex. In addition, MamB was found to interact with several other proteins...... including the PDZ1 domain of MamE. Whereas any genetic modification of MamB resulted in loss of function, site‐specific mutagenesis within MamM lead to increased formation of polycrystalline magnetite particles. A single amino acid substitution within MamM resulted in crystals consisting of haematite, which...

  15. Membrane-bound MinDE complex acts as a toggle switch that drives Min oscillation coupled to cytoplasmic depletion of MinD

    Science.gov (United States)

    Vecchiarelli, Anthony G.; Li, Min; Mizuuchi, Michiyo; Hwang, Ling Chin; Seol, Yeonee; Neuman, Keir C.; Mizuuchi, Kiyoshi

    2016-01-01

    The Escherichia coli Min system self-organizes into a cell-pole to cell-pole oscillator on the membrane to prevent divisions at the cell poles. Reconstituting the Min system on a lipid bilayer has contributed to elucidating the oscillatory mechanism. However, previous in vitro patterns were attained with protein densities on the bilayer far in excess of those in vivo and failed to recapitulate the standing wave oscillations observed in vivo. Here we studied Min protein patterning at limiting MinD concentrations reflecting the in vivo conditions. We identified “burst” patterns—radially expanding and imploding binding zones of MinD, accompanied by a peripheral ring of MinE. Bursts share several features with the in vivo dynamics of the Min system including standing wave oscillations. Our data support a patterning mechanism whereby the MinD-to-MinE ratio on the membrane acts as a toggle switch: recruiting and stabilizing MinD on the membrane when the ratio is high and releasing MinD from the membrane when the ratio is low. Coupling this toggle switch behavior with MinD depletion from the cytoplasm drives a self-organized standing wave oscillator. PMID:26884160

  16. Capillary electrophoresis with capacitively coupled contactless conductivity detection: A universal tool for the determination of supported liquid membrane selectivity in electromembrane extraction of complex samples

    Czech Academy of Sciences Publication Activity Database

    Kubáň, Pavel; Boček, Petr

    2012-01-01

    Roč. 1267, SI (2012), s. 96-101 ISSN 0021-9673 R&D Projects: GA ČR GAP206/10/1219 Institutional research plan: CEZ:AV0Z40310501 Keywords : supported liquid membranes * selectivity measurements * capillary electrophoresis Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.612, year: 2012

  17. 19-DEJ-1, a hemidesmosome-anchoring filament complex-associated monoclonal antibody. Definition of a new skin basement membrane antigenic defect in junctional and dystrophic epidermolysis bullosa

    DEFF Research Database (Denmark)

    Fine, J D; Horiguchi, Y; Couchman, J R

    1989-01-01

    50% of patients with recessive dystrophic EB further suggests, for the first time, that an inherited defect in basement membrane is shared in patients with junctional and some recessive dystrophic EB. The difference in site of skin cleavage in the latter two disorders gives additional support...

  18. Association of polioviral proteins of the P2 genomic region with the viral replication complex and virus-induced membrane synthesis as visualized by electron microscopic immunocytochemistry and autoradiography.

    Science.gov (United States)

    Bienz, K; Egger, D; Pasamontes, L

    1987-09-01

    Using high resolution electron microscopic autoradiography and immunocytochemistry with monoclonal antibodies against poliovirus proteins of the P2 genomic region, the location of these proteins in respect to the virus-induced vesicle formation and the viral RNA synthesis was followed during the viral replication cycle. It was found that P2 proteins become rER associated soon after their synthesis. At the site of protein and rER interaction, electron-dense patches appear. Simultaneously, membrane protrusions grow and form vesicles which finally budd off, carrying the patches on their outer surface. As shown by autoradiography, these patches are the site of viral RNA replication and, therefore, they represent the poliovirus replication complex. The vesicles with the replication complex, including replicating and replicated viral RNA, move away from the rER to form a continuously growing vesiculated area in the center of the infected cell, where virus maturation takes place. A likely function of the 2C protein is to attach the replication complex, or some of its components, to the vesicular membranes.

  19. Reconstitutions of mitochondrial inner membrane remodeling.

    Science.gov (United States)

    Barbot, Mariam; Meinecke, Michael

    2016-10-01

    Biological membranes exhibit function-related shapes, leading to a plethora of complex and beautiful cell and cell organellar morphologies. Most if not all of these structures have evolved for a particular physiological reason. The shapes of these structures are formed by physical forces that operate on membranes. To create particular shaped cells and cell organelles, membranes must undergo deformations which are determined by the structure and elasticity of the membrane and this process is most probable driven by proteins, lipids and/or interplay of both Zimmerberg and Kozlov (2006). Therefore, an important question of current cell biology in conjunction with physics and mathematics is to elucidate the functional cause for these different membrane morphologies as well as how they are formed. One of the most peculiar membrane shapes is observed in mitochondria. These organelles are surrounded by two membranes and especially the convoluted inner membrane displays a complex ultra-structure. A molecular understanding of how this membrane is shaped is missing to a large extent. Unlike membrane remodeling in classical curvature-dependent processes like clathrin-mediated endocytosis, mitochondria are most likely shaped by integral membrane proteins. Following, we will review the current knowledge of inner mitochondrial membrane architecture and discuss recent findings and advances in understanding the factors that shape this membrane. We will address pending questions especially with regard to the experimentally challenging nature of investigating membrane bending by hydrophobic integral membrane proteins. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Membrane processes

    Science.gov (United States)

    Staszak, Katarzyna

    2017-11-01

    The membrane processes have played important role in the industrial separation process. These technologies can be found in all industrial areas such as food, beverages, metallurgy, pulp and paper, textile, pharmaceutical, automotive, biotechnology and chemical industry, as well as in water treatment for domestic and industrial application. Although these processes are known since twentieth century, there are still many studies that focus on the testing of new membranes' materials and determining of conditions for optimal selectivity, i. e. the optimum transmembrane pressure (TMP) or permeate flux to minimize fouling. Moreover the researchers proposed some calculation methods to predict the membrane processes properties. In this article, the laboratory scale experiments of membrane separation techniques, as well their validation by calculation methods are presented. Because membrane is the "heart" of the process, experimental and computational methods for its characterization are also described.

  1. Atomistic Monte Carlo simulation of lipid membranes

    DEFF Research Database (Denmark)

    Wüstner, Daniel; Sklenar, Heinz

    2014-01-01

    Biological membranes are complex assemblies of many different molecules of which analysis demands a variety of experimental and computational approaches. In this article, we explain challenges and advantages of atomistic Monte Carlo (MC) simulation of lipid membranes. We provide an introduction...... of local-move MC methods in combination with molecular dynamics simulations, for example, for studying multi-component lipid membranes containing cholesterol....

  2. Lipid organization of the plasma membrane

    NARCIS (Netherlands)

    Ingólfsson, Helgi I; Melo, Manuel N; van Eerden, Floris J; Arnarez, Clément; Lopez, Cesar A; Wassenaar, Tsjerk A; Periole, Xavier; de Vries, Alex H; Tieleman, D Peter; Marrink, Siewert J

    2014-01-01

    The detailed organization of cellular membranes remains rather elusive. Based on large-scale molecular dynamics simulations, we provide a high-resolution view of the lipid organization of a plasma membrane at an unprecedented level of complexity. Our plasma membrane model consists of 63 different

  3. Cell-free system for synthesizing membrane proteins cell free method for synthesizing membrane proteins

    Science.gov (United States)

    Laible, Philip D; Hanson, Deborah K

    2013-06-04

    The invention provides an in vitro method for producing proteins, membrane proteins, membrane-associated proteins, and soluble proteins that interact with membrane-associated proteins for assembly into an oligomeric complex or that require association with a membrane for proper folding. The method comprises, supplying intracytoplasmic membranes from organisms; modifying protein composition of intracytoplasmic membranes from organism by modifying DNA to delete genes encoding functions of the organism not associated with the formation of the intracytoplasmic membranes; generating appropriate DNA or RNA templates that encode the target protein; and mixing the intracytoplasmic membranes with the template and a transcription/translation-competent cellular extract to cause simultaneous production of the membrane proteins and encapsulation of the membrane proteins within the intracytoplasmic membranes.

  4. High molecular weight complex analysis of Epstein-Barr virus Latent Membrane Protein 1 (LMP-1): structural insights into LMP-1's homo-oligomerization and lipid raft association.

    Science.gov (United States)

    Wrobel, Christopher M; Geiger, Timothy R; Nix, Rebecca N; Robitaille, Aaron M; Weigand, Sandra; Cervantes, Alfredo; Gonzalez, Miguel; Martin, Jennifer M

    2013-12-26

    LMP-1 is a constitutively active Tumor Necrosis Factor Receptor analog encoded by Epstein-Barr virus. LMP-1 activation correlates with oligomerization and raft localization, but direct evidence of LMP-1 oligomers is limited. We report that LMP-1 forms multiple high molecular weight native LMP-1 complexes when analyzed by BN-PAGE, the largest of which are enriched in detergent resistant membranes. The largest of these high molecular weight complexes are not formed by purified LMP-1 or by loss of function LMP-1 mutants. Consistent with these results we find a dimeric form of LMP-1 that can be stabilized by disulfide crosslinking. We identify cysteine 238 in the C-terminus of LMP-1 as the crosslinked cysteine. Disulfide crosslinking occurs post-lysis but the dimer can be crosslinked in intact cells with membrane permeable crosslinkers. LMP-1/C238A retains wild type LMP-1 NF-κB activity. LMP-1's TRAF binding, raft association and oligomerization are associated with the dimeric form of LMP-1. Our results suggest the possibility that the observed dimeric species results from inter-oligomeric crosslinking of LMP-1 molecules in adjacent core LMP-1 oligomers. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Identification of a TcpC-TcpQ Outer Membrane Complex Involved in the Biogenesis of the Toxin-Coregulated Pilus of Vibrio cholerae

    OpenAIRE

    Bose, Niranjan; Taylor, Ronald K.

    2005-01-01

    The toxin-coregulated pilus (TCP) of Vibrio cholerae and the soluble TcpF protein that is secreted via the TCP biogenesis apparatus are essential for intestinal colonization. The TCP biogenesis apparatus is composed of at least nine proteins but is largely uncharacterized. TcpC is an outer membrane lipoprotein required for TCP biogenesis that is a member of the secretin protein superfamily. In the present study, analysis of TcpC in a series of strains deficient in each of the TCP biogenesis p...

  6. Bcs1p can rescue a large and productive cytochrome bc(1) complex assembly intermediate in the inner membrane of yeast mitochondria.

    Science.gov (United States)

    Conte, Laura; Trumpower, Bernard L; Zara, Vincenzo

    2011-01-01

    The yeast cytochrome bc(1) complex, a component of the mitochondrial respiratory chain, is composed of ten distinct protein subunits. In the assembly of the bc(1) complex, some ancillary proteins, such as the chaperone Bcs1p, are actively involved. The deletion of the nuclear gene encoding this chaperone caused the arrest of the bc(1) assembly and the formation of a functionally inactive bc(1) core structure of about 500-kDa. This immature bc(1) core structure could represent, on the one hand, a true assembly intermediate or, on the other hand, a degradation product and/or an incorrect product of assembly. The experiments here reported show that the gradual expression of Bcs1p in the yeast strain lacking this protein was progressively able to rescue the bc(1) core structure leading to the formation of the functional homodimeric bc(1) complex. Following Bcs1p expression, the mature bc(1) complex was also progressively converted into two supercomplexes with the cytochrome c oxidase complex. The capability of restoring the bc(1) complex and the supercomplexes was also possessed by the mutated yeast R81C Bcsp1. Notably, in the human ortholog BCS1L, the corresponding point mutation (R45C) was instead the cause of a severe bc(1) complex deficiency. Differently from the yeast R81C Bcs1p, two other mutated Bcs1p's (K192P and F401I) were unable to recover the bc(1) core structure in yeast. This study identifies for the first time a productive assembly intermediate of the yeast bc(1) complex and gives new insights into the molecular mechanisms involved in the last steps of bc(1) assembly. Copyright © 2010 Elsevier B.V. All rights reserved.

  7. Membrane interaction of retroviral Gag proteins

    Directory of Open Access Journals (Sweden)

    Robert Alfred Dick

    2014-04-01

    Full Text Available Assembly of an infectious retroviral particle relies on multimerization of the Gag polyprotein at the inner leaflet of the plasma membrane. The three domains of Gag common to all retroviruses-- MA, CA, and NC-- provide the signals for membrane binding, assembly, and viral RNA packaging, respectively. These signals do not function independently of one another. For example, Gag multimerization enhances membrane binding and is more efficient when NC is interacting with RNA. MA binding to the plasma membrane is governed by several principles, including electrostatics, recognition of specific lipid head groups, hydrophobic interactions, and membrane order. HIV-1 uses many of these principles while Rous sarcoma virus (RSV appears to use fewer. This review describes the principles that govern Gag interactions with membranes, focusing on RSV and HIV-1 Gag. The review also defines lipid and membrane behavior, and discusses the complexities in determining how lipid and membrane behavior impact Gag membrane binding.

  8. 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)

  9. A cytochrome c fusion protein domain for convenient detection, quantification, and enhanced production of membrane proteins in Escherichia coli--expression and characterization of cytochrome-tagged Complex I subunits.

    Science.gov (United States)

    Gustavsson, Tobias; Trane, Maria; Moparthi, Vamsi K; Miklovyte, Egle; Moparthi, Lavanya; Górecki, Kamil; Leiding, Thom; Arsköld, Sindra Peterson; Hägerhäll, Cecilia

    2010-08-01

    Overproduction of membrane proteins can be a cumbersome task, particularly if high yields are desirable. NADH:quinone oxidoreductase (Complex I) contains several very large membrane-spanning protein subunits that hitherto have been impossible to express individually in any appreciable amounts in Escherichia coli. The polypeptides contain no prosthetic groups and are poorly antigenic, making optimization of protein production a challenging task. In this work, the C-terminal ends of the Complex I subunits NuoH, NuoL, NuoM, and NuoN from E. coli Complex I and the bona fide antiporters MrpA and MrpD were genetically fused to the cytochrome c domain of Bacillus subtilis cytochrome c(550). Compared with other available fusion-protein tagging systems, the cytochrome c has several advantages. The heme is covalently bound, renders the proteins visible by optical spectroscopy, and can be used to monitor, quantify, and determine the orientation of the polypeptides in a plethora of experiments. For the antiporter-like subunits NuoL, NuoM, and NuoN and the real antiporters MrpA and MrpD, unprecedented amounts of holo-cytochrome fusion proteins could be obtained in E. coli. The NuoHcyt polypeptide was also efficiently produced, but heme insertion was less effective in this construct. The cytochrome c(550) domain in all the fusion proteins exhibited normal spectra and redox properties, with an E(m) of about +170 mV. The MrpA and MrpD antiporters remained functional after being fused to the cytochrome c-tag. Finally, a his-tag could be added to the cytochrome domain, without any perturbations to the cytochrome properties, allowing efficient purification of the overexpressed fusion proteins.

  10. Complex Membrane Channel Blockade: A Unifying Hypothesis for the Prodromal and Acute Neuropsychiatric Sequelae Resulting from Exposure to the Antimalarial Drug Mefloquine

    Directory of Open Access Journals (Sweden)

    Jane C. Quinn

    2015-01-01

    Full Text Available The alkaloid toxin quinine and its derivative compounds have been used for many centuries as effective medications for the prevention and treatment of malaria. More recently, synthetic derivatives, such as the quinoline derivative mefloquine (bis(trifluoromethyl-(2-piperidyl-4-quinolinemethanol, have been widely used to combat disease caused by chloroquine-resistant strains of the malaria parasite, Plasmodium falciparum. However, the parent compound quinine, as well as its more recent counterparts, suffers from an incidence of adverse neuropsychiatric side effects ranging from mild mood disturbances and anxiety to hallucinations, seizures, and psychosis. This review considers how the pharmacology, cellular neurobiology, and membrane channel kinetics of mefloquine could lead to the significant and sometimes life-threatening neurotoxicity associated with mefloquine exposure. A key role for mefloquine blockade of ATP-sensitive potassium channels and connexins in the substantia nigra is considered as a unifying hypothesis for the pathogenesis of severe neuropsychiatric events after mefloquine exposure in humans.

  11. Physics of biological membranes

    Science.gov (United States)

    Mouritsen, Ole G.

    The biological membrane is a complex system consisting of an aqueous biomolecular planar aggregate of predominantly lipid and protein molecules. At physiological temperatures, the membrane may be considered a thin (˜50Å) slab of anisotropic fluid characterized by a high lateral mobility of the various molecular components. A substantial fraction of biological activity takes place in association with membranes. As a very lively piece of condensed matter, the biological membrane is a challenging research topic for both the experimental and theoretical physicists who are facing a number of fundamental physical problems including molecular self-organization, macromolecular structure and dynamics, inter-macromolecular interactions, structure-function relationships, transport of energy and matter, and interfacial forces. This paper will present a brief review of recent theoretical and experimental progress on such problems, with special emphasis on lipid bilayer structure and dynamics, lipid phase transitions, lipid-protein and lipid-cholesterol interactions, intermembrane forces, and the physical constraints imposed on biomembrane function and evolution. The paper advocates the dual point of view that there are a number of interesting physics problems in membranology and, at the same time, that the physical properties of biomembranes are important regulators of membrane function.

  12. Membrane fouling and wetting in membrane distillation and their mitigation by novel membranes with special wettability.

    Science.gov (United States)

    Wang, Zhangxin; Lin, Shihong

    2017-04-01

    Membrane distillation (MD) has been identified as a promising technology to desalinate the hypersaline wastewaters from fracking and other industries. However, conventional hydrophobic MD membranes are highly susceptible to fouling and/or wetting by the hydrophobic and/or amphiphilic constituents in these wastewaters of complex compositions. This study systematically investigates the impact of the surface wetting properties on the membrane wetting and/or fouling behaviors in MD. Specifically, we compare the wetting and fouling resistance of three types of membranes of different wetting properties, including hydrophobic and omniphobic membranes as well as composite membranes with a hydrophobic substrate and a superhydrophilic top surface. We challenged the MD membranes with hypersaline feed solutions that contained a relatively high concentration of crude oil with and without added synthetic surfactants, Triton X-100. We found that the composite membranes with superhydrophilic top surface were robustly resistant to oil fouling in the absence of Triton X-100, but were subject to pore wetting in the presence of Triton X-100. On the other hand, the omniphobic membranes were easily fouled by oil-in-water emulsion without Triton X-100, but successfully sustained stable MD performance with Triton X-100 stabilized oil-in-water emulsion as the feed solution. In contrast, the conventional hydrophobic membranes failed readily regardless whether Triton X-100 was present, although via different mechanisms. These findings are corroborated by contact angle measures as well as oil-probe force spectroscopy. This study provides a holistic picture regarding how a hydrophobic membrane fails in MD and how we can leverage membranes with special wettability to prevent membrane failure in MD operations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Helicobacter pylori-elicited induction in gastric mucosal matrix metalloproteinase-9 (MMP-9) release involves ERK-dependent cPLA2 activation and its recruitment to the membrane-localized Rac1/p38 complex.

    Science.gov (United States)

    Slomiany, B L; Slomiany, A

    2016-06-01

    Matrix metalloproteinases (MMPs) are a family of endopeptidases implicated in a wide rage of degenerative and inflammatory diseases, including Helicobacter pylori-associated gastritis, and gastric and duodenal ulcer. As gastric mucosal inflammatory responses to H. pylori are characterized by the rise in MMP-9 production, as well as the induction in mitogen-activated protein kinase (MAPK) and Rac1 activation, we investigated the role of Rac1/MAPK in the processes associated with the release of MMP-9. We show that H. pylori LPS-elicited induction in gastric mucosal MMP-9 release is associated with MAPK, ERK and p38 activation, and occurs with the involvement of Rac1 and cytosolic phospholipase A2 (cPLA2). Further, we demonstrate that the LPS-induced MMP-9 release requires ERK-mediated phosphorylation of cPLA2 on Ser(505) that is essential for its membrane localization with Rac1, and that this process necessitates p38 participation. Moreover, we reveal that the activation and membrane translocation of p38 to the Rac1-GTP complex plays a pivotal role in cPLA2-dependent enhancement in MMP-9 release. Hence, our findings provide a strong evidence for the role of ERK/cPLA2 and Rac1/p38/cPLA2 cascade in H. pylori LPS-induced up-regulation in gastric mucosal MMP-9 release.

  14. Membrane bending by protein-protein crowding.

    Science.gov (United States)

    Stachowiak, Jeanne C; Schmid, Eva M; Ryan, Christopher J; Ann, Hyoung Sook; Sasaki, Darryl Y; Sherman, Michael B; Geissler, Phillip L; Fletcher, Daniel A; Hayden, Carl C

    2012-09-01

    Curved membranes are an essential feature of dynamic cellular structures, including endocytic pits, filopodia protrusions and most organelles. It has been proposed that specialized proteins induce curvature by binding to membranes through two primary mechanisms: membrane scaffolding by curved proteins or complexes; and insertion of wedge-like amphipathic helices into the membrane. Recent computational studies have raised questions about the efficiency of the helix-insertion mechanism, predicting that proteins must cover nearly 100% of the membrane surface to generate high curvature, an improbable physiological situation. Thus, at present, we lack a sufficient physical explanation of how protein attachment bends membranes efficiently. On the basis of studies of epsin1 and AP180, proteins involved in clathrin-mediated endocytosis, we propose a third general mechanism for bending fluid cellular membranes: protein-protein crowding. By correlating membrane tubulation with measurements of protein densities on membrane surfaces, we demonstrate that lateral pressure generated by collisions between bound proteins drives bending. Whether proteins attach by inserting a helix or by binding lipid heads with an engineered tag, protein coverage above ~20% is sufficient to bend membranes. Consistent with this crowding mechanism, we find that even proteins unrelated to membrane curvature, such as green fluorescent protein (GFP), can bend membranes when sufficiently concentrated. These findings demonstrate a highly efficient mechanism by which the crowded protein environment on the surface of cellular membranes can contribute to membrane shape change.

  15. Drug-model membrane interactions

    International Nuclear Information System (INIS)

    Deniz, Usha K.

    1994-01-01

    In the present day world, drugs play a very important role in medicine and it is necessary to understand their mode of action at the molecular level, in order to optimise their use. Studies of drug-biomembrane interactions are essential for gaining such as understanding. However, it would be prohibitively difficult to carry out such studies, since biomembranes are highly complex systems. Hence, model membranes (made up of these lipids which are important components of biomembranes) of varying degrees of complexity are used to investigate drug-membrane interactions. Bio- as well as model-membranes undergo a chain melting transition when heated, the chains being in a disordered state above the transition point, T CM . This transition is of physiological importance since biomembranes select their components such that T CM is less than the ambient temperature but not very much so, so that membrane flexibility is ensured and porosity, avoided. The influence of drugs on the transition gives valuable clues about various parameters such as the location of the drug in the membrane. Deep insights into drug-membrane interactions are obtained by observing the effect of drugs on membrane structure and the mobilities of the various groups in lipids, near T CM . Investigation of such changes have been carried out with several drugs, using techniques such as DSC, XRD and NMR. The results indicate that the drug-membrane interaction not only depends on the nature of drug and lipids but also on the form of the model membrane - stacked bilayer or vesicles. The light that these results shed on the nature of drug-membrane interactions is discussed. (author). 13 refs., 13 figs., 1 tab

  16. Robotic membranes

    DEFF Research Database (Denmark)

    Ramsgaard Thomsen, Mette

    2008-01-01

    , Vivisection and Strange Metabolisms, were developed at the Centre for Information Technology and Architecture (CITA) at the Royal Danish Academy of Fine Arts in Copenhagen as a means of engaging intangible digital data with tactile physical material. As robotic membranes, they are a dual examination...

  17. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2003-01-01

    In the present quarter, the possibility of using a more complex interfacial engineering approach to the development of reliable and stable oxygen transport perovskite ceramic membranes/metal seals is discussed. Experiments are presented and ceramic/metal interactions are characterized. Crack growth and fracture toughness of the membrane in the reducing conditions are also discussed. Future work regarding this approach is proposed are evaluated for strength and fracture in oxygen gradient conditions. Oxygen gradients are created in tubular membranes by insulating the inner surface from the reducing environment by platinum foils. Fracture in these test conditions is observed to have a gradient in trans and inter-granular fracture as opposed to pure trans-granular fracture observed in homogeneous conditions. Fracture gradients are reasoned to be due to oxygen gradient set up in the membrane, variation in stoichiometry across the thickness and due to varying decomposition of the parent perovskite. The studies are useful in predicting fracture criterion in actual reactor conditions and in understanding the initial evolution of fracture processes.

  18. SusG: A Unique Cell-Membrane-Associated [alpha]-Amylase from a Prominent Human Gut Symbiont Targets Complex Starch Molecules

    Energy Technology Data Exchange (ETDEWEB)

    Koropatkin, Nicole M.; Smith, Thomas J. (Danforth)

    2010-09-21

    SusG is an {alpha}-amylase and part of a large protein complex on the outer surface of the bacterial cell and plays a major role in carbohydrate acquisition by the animal gut microbiota. Presented here, the atomic structure of SusG has an unusual extended, bilobed structure composed of amylase at one end and an unprecedented internal carbohydrate-binding motif at the other. Structural studies further demonstrate that the carbohydrate-binding motif binds maltooligosaccharide distal to, and on the opposite side of, the amylase catalytic site. SusG has an additional starch-binding site on the amylase domain immediately adjacent to the active cleft. Mutagenesis analysis demonstrates that these two additional starch-binding sites appear to play a role in catabolism of insoluble starch. However, elimination of these sites has only a limited effect, suggesting that they may have a more important role in product exchange with other Sus components.

  19. The cristal membrane of mitochondria is the principal site of oxidative phosphorylation.

    Science.gov (United States)

    Gilkerson, Robert W; Selker, Jeanne M L; Capaldi, Roderick A

    2003-07-10

    The inner membrane system of mitochondria us known to consist of two contiguous but distinct membranes: the inner boundary membrane, which apposes the outer membrane, and the cristal membrane, which forms tubules or lamellae in the interior. Using immunolabeling and transmission electron microscopy of bovine heart tissue, we have calculated that around 94% of both Complex III of the respiratory chain and the ATP synthase are located in the cristal membrane, and only around 6% of either is in the inner boundary membrane. When accounting for the topographical ratio of cristal membrane versus inner boundary membrane, we find that both complexes exist at a 2.2-2.6-fold higher concentration in the cristal membrane. The residual protein in the inner boundary membrane may be newly assembled complexes destined for cristal membranes. Our results argue for restricted diffusion of complexes through the cristal junctions and indicate that the mitochondrial cristae comprise a regulated submitochondrial compartment specialized for ATP production.

  20. Curcumin Pretreatment Prevents Potassium Dichromate-Induced Hepatotoxicity, Oxidative Stress, Decreased Respiratory Complex I Activity, and Membrane Permeability Transition Pore Opening

    Directory of Open Access Journals (Sweden)

    Wylly Ramsés García-Niño

    2013-01-01

    Full Text Available Curcumin is a polyphenol derived from turmeric with recognized antioxidant properties. Hexavalent chromium is an environmental toxic and carcinogen compound that induces oxidative stress. The objective of this study was to evaluate the potential protective effect of curcumin on the hepatic damage generated by potassium dichromate (K2Cr2O7 in rats. Animals were pretreated daily by 9-10 days with curcumin (400 mg/kg b.w. before the injection of a single intraperitoneal of K2Cr2O7 (15 mg/kg b.w.. Groups of animals were sacrificed 24 and 48 h later. K2Cr2O7-induced damage to the liver was evident by histological alterations and increase in the liver weight and in the activity of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase in plasma. In addition, K2Cr2O7 induced oxidative damage in liver and isolated mitochondria, which was evident by the increase in the content of malondialdehyde and protein carbonyl and decrease in the glutathione content and in the activity of several antioxidant enzymes. Moreover, K2Cr2O7 induced decrease in mitochondrial oxygen consumption, in the activity of respiratory complex I, and permeability transition pore opening. All the above-mentioned alterations were prevented by curcumin pretreatment. The beneficial effects of curcumin against K2Cr2O7-induced liver oxidative damage were associated with prevention of mitochondrial dysfunction.

  1. Curcumin Pretreatment Prevents Potassium Dichromate-Induced Hepatotoxicity, Oxidative Stress, Decreased Respiratory Complex I Activity, and Membrane Permeability Transition Pore Opening

    Science.gov (United States)

    García-Niño, Wylly Ramsés; Tapia, Edilia; Zazueta, Cecilia; Zatarain-Barrón, Zyanya Lucía; Hernández-Pando, Rogelio; Vega-García, Claudia Cecilia; Pedraza-Chaverrí, José

    2013-01-01

    Curcumin is a polyphenol derived from turmeric with recognized antioxidant properties. Hexavalent chromium is an environmental toxic and carcinogen compound that induces oxidative stress. The objective of this study was to evaluate the potential protective effect of curcumin on the hepatic damage generated by potassium dichromate (K2Cr2O7) in rats. Animals were pretreated daily by 9-10 days with curcumin (400 mg/kg b.w.) before the injection of a single intraperitoneal of K2Cr2O7 (15 mg/kg b.w.). Groups of animals were sacrificed 24 and 48 h later. K2Cr2O7-induced damage to the liver was evident by histological alterations and increase in the liver weight and in the activity of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase in plasma. In addition, K2Cr2O7 induced oxidative damage in liver and isolated mitochondria, which was evident by the increase in the content of malondialdehyde and protein carbonyl and decrease in the glutathione content and in the activity of several antioxidant enzymes. Moreover, K2Cr2O7 induced decrease in mitochondrial oxygen consumption, in the activity of respiratory complex I, and permeability transition pore opening. All the above-mentioned alterations were prevented by curcumin pretreatment. The beneficial effects of curcumin against K2Cr2O7-induced liver oxidative damage were associated with prevention of mitochondrial dysfunction. PMID:23956771

  2. Structural requirements for recognition of major histocompatibility complex class II by membrane-associated RING-CH (MARCH) protein E3 ligases.

    Science.gov (United States)

    Jahnke, Martin; Trowsdale, John; Kelly, Adrian P

    2012-08-17

    MARCH E3 ligases play a key role in controlling MHC class II surface expression by regulated ubiquitination of a lysine residue in the β-chain. Little is known concerning how these enzymes target their specific substrates. Here we show that recognition of HLA-DR by MARCH proteins is complex. Several features associated with the transmembrane domain and bordering regions influence the overall efficiency of receptor internalization. A cluster of residues at the interface of the lipid bilayer and the cytosol plays the most important role in MARCH8 recognition of HLA-DRβ. Variation in this sequence also determines specificity of MARCH9 for HLA-DQ. Residues located in helical face four of HLA-DRβ together with a charged residue at the boundary with the stalk region also contribute significantly to recognition. Truncation analysis suggested that a dileucine-like motif in the DRβ cytoplasmic tail influences the efficiency of co-localization of HLA-DR with MARCH8. The DRβ-encoded acceptor lysine functioned optimally when placed in its natural location relative to the bilayer. In the DRα/DRβ dimer most other amino acids in the cytoplasmic tail could be substituted for alanine with minimal influence on function. Our data support a model whereby multiple features of HLA-DR are involved in substrate recognition by MARCH8. The single most important region is located at the interface between the transmembrane domain and the cytosol. Variation in sequence in this location between different class II isotypes controls efficiency of recognition by different MARCH E3 ligases.

  3. Membrane manufacture for peptide separations

    KAUST Repository

    Kim, Dooli

    2016-06-07

    Nanostructured polymeric membranes are key tools in biomedical applications such as hemodialysis, protein separations, in the food industry, and drinking water supply from seawater. Despite of the success in different separation processes, membrane manufacture itself is at risk, since the most used solvents are about to be banned in many countries due to environmental and health issues. We propose for the first time the preparation of polyethersulfone membranes based on dissolution in the ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DEP). We obtained a series of membranes tailored for separation of solutes with molecular weight of 30, 5, 1.3, and 1.25 kg mol-1 with respective water permeances of 140, 65, 30 and 20 Lm-2h-1bar-1. We demonstrate their superior efficiency in the separation of complex mixtures of peptides with molecular weights in the range of 800 to 3500 gmol-1. Furthermore, the thermodynamics and kinetics of phase separation leading to the pore formation in the membranes were investigated. The rheology of the solutions and the morphology of the prepared membranes were examed and compared to those of polyethersulfone in organic solvents currently used for membrane manufacture.

  4. How external osmolarity affects the activity of the contractile vacuole complex, the cytosolic osmolarity and the water permeability of the plasma membrane in Paramecium multimicronucleatum.

    Science.gov (United States)

    Stock, C; Allen, R D; Naitoh, Y

    2001-01-01

    The rate of fluid expulsion, R(CVC), from the contractile vacuole complex (CVC) of Paramecium multimicronucleatum was estimated from the volume of the contractile vacuoles (CVs) immediately before the start of fluid discharge and from the time elapsing between discharges. The R(CVC) increased when the cell was exposed to a strongly hypotonic solution and decreased in a weakly hypotonic solution. When the cell was exposed to an isotonic or a hypertonic solution, R(CVC) fell to zero. The time constant, tau, used to describe the change in R(CVC) in response to a change in external osmolarity shortened after a short-term exposure to a strongly hypotonic solution and lengthened after a short-term exposure to a less hypotonic solution. A remarkable lengthening of tau occurred after a short-term exposure to isotonic or hypertonic solution. Under natural conditions, mechanisms for controlling R(CVC) are effective in maintaining the cytosolic osmolarity hypertonic within a narrow concentration range despite changes in the external osmolarity, which is normally hypotonic to the cytosol. Cells exposed to an isotonic or hypertonic solution resumed CV activity when left in the solution for 12 h. The cytosolic osmolarity was found to increase and to remain hypertonic to the external solution. This will permit cells to continue to acquire water. The increase in the cytosolic osmolarity occurred in a stepwise fashion, rather than linearly, as the external osmolarity increased. That is, the cytosolic osmolarity first remained more-or-less constant at an increased level until the external osmolarity exceeded this level. Thereupon, the cytosolic osmolarity increased to a new higher level in 12 h, so that the cytosol again became hypertonic to the external solution and the cells resumed CV activity. These results imply that the cell needs to maintain water segregation activity even after it has been exposed to an isotonic or hypertonic environment. This supports the idea that the CVC

  5. 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...

  6. Assembly of intermediates for rapid membrane fusion.

    Science.gov (United States)

    Harner, Max; Wickner, William

    2018-01-26

    Membrane fusion is essential for intracellular protein sorting, cell growth, hormone secretion, and neurotransmission. Rapid membrane fusion requires tethering and Sec1-Munc18 (SM) function to catalyze R-, Qa-, Qb-, and Qc-SNARE complex assembly in trans , as well as SNARE engagement by the SNARE-binding chaperone Sec17/αSNAP. The hexameric vacuolar HOPS ( ho motypic fusion and vacuole p rotein s orting) complex in the yeast Saccharomyces cerevisiae tethers membranes through its affinities for the membrane Rab GTPase Ypt7. HOPS also has specific affinities for the vacuolar SNAREs and catalyzes SNARE complex assembly, but the order of their assembly into a 4-SNARE complex is unclear. We now report defined assembly intermediates on the path to membrane fusion. We found that a prefusion intermediate will assemble with HOPS and the R, Qa, and Qc SNAREs, and that this assembly undergoes rapid fusion upon addition of Qb and Sec17. HOPS-tethered membranes and all four vacuolar SNAREs formed a complex that underwent an even more dramatic burst of fusion upon Sec17p addition. These findings provide initial insights into an ordered fusion pathway consisting of the following intermediates and events: 1) Rab- and HOPS-tethered membranes, 2) a HOPS:R:Qa:Qc trans -complex, 3) a HOPS:4-SNARE trans -complex, 4) an engagement with Sec17, and 5) the rapid lipid rearrangements during fusion. In conclusion, our results indicate that the R:Qa:Qc complex forms in the context of membrane, Ypt7, HOPS, and trans -SNARE assembly and serves as a functional intermediate for rapid fusion after addition of the Qb-SNARE and Sec17 proteins. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

  7. Increasing Diversity of Biological Membrane Fission Mechanisms.

    Science.gov (United States)

    Renard, Henri-François; Johannes, Ludger; Morsomme, Pierre

    2018-01-04

    Membrane fission is essential to life. It is required for many fundamental cellular processes, as diverse as cyto- and karyokinesis, organelle division, membrane repair, and membrane trafficking and endocytosis. While membrane fission was originally seen as resulting from the action of mechanoenzymes such as dynamin, it is clear that the reality is more complex. In this review, we propose an updated overview of fission mechanisms, and try to extract essential requirements for each. We also present examples of cellular processes that involve these fission mechanisms. Finally, we list pending questions, whether they are specific to a peculiar fission mechanism or more general to the field. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Catalytic Membrane Sensors

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, T.J.; Brinker, C.J.; Gardner, T.J.; Hughes, R.C.; Sault, A.G.

    1998-12-01

    The proposed "catalytic membrane sensor" (CMS) was developed to generate a device which would selectively identify a specific reagent in a complex mixture of gases. This was to be accomplished by modifying an existing Hz sensor with a series of thin films. Through selectively sieving the desired component from a complex mixture and identifying it by decomposing it into Hz (and other by-products), a Hz sensor could then be used to detect the presence of the select component. The proposed "sandwich-type" modifications involved the deposition of a catalyst layered between two size selective sol-gel layers on a Pd/Ni resistive Hz sensor. The role of the catalyst was to convert organic materials to Hz and organic by-products. The role of the membraneo was to impart both chemical specificity by molecukir sieving of the analyte and converted product streams, as well as controlling access to the underlying Pd/Ni sensor. Ultimately, an array of these CMS elements encompassing different catalysts and membranes were to be developed which would enable improved selectivity and specificity from a compiex mixture of organic gases via pattern recognition methodologies. We have successfully generated a CMS device by a series of spin-coat deposited methods; however, it was determined that the high temperature required to activate the catalyst, destroys the sensor.

  9. Fatty acid profiles from the plasma membrane and detergent resistant membranes of two plant species.

    Science.gov (United States)

    Carmona-Salazar, Laura; El Hafidi, Mohammed; Gutiérrez-Nájera, Nora; Noyola-Martínez, Liliana; González-Solís, Ariadna; Gavilanes-Ruíz, Marina

    2015-01-01

    It is essential to establish the composition of the plant plasma membrane in order to understand its organization and behavior under continually changing environments. Knowledge of the lipid phase, in particular the fatty acid (FA) complex repertoire, is important since FAs determine many of the physical-chemical membrane properties. FAs are constituents of the membrane glycerolipid and sphingolipid backbones and can also be linked to some sterols. In addition, FAs are components of complex lipids that can constitute membrane micro-domains, and the use of detergent-resistant membranes is a common approach to study their composition. The diversity and cellular allocation of the membrane lipids containing FAs are very diverse and the approaches to analyze them provide only general information. In this work, a detailed FA analysis was performed using highly purified plasma membranes from bean leaves and germinating maize embryos and their respective detergent-resistant membrane preparations. The analyses showed the presence of a significant amount of very long chain FAs (containing 28C, 30C and 32C), in both plasma membrane preparations from bean and maize, that have not been previously reported. Herein is demonstrated that a significant enrichment of very long chain saturated FAs and saturated FAs can occur in detergent-resistant membrane preparations, as compared to the plasma membranes from both plant species. Considering that a thorough analysis of FAs is rarely performed in purified plasma membranes and detergent-resistant membranes, this work provides qualitative and quantitative evidence on the contributions of the length and saturation of FAs to the organization of the plant plasma membrane and detergent-resistant membranes. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Layer-by-layer cell membrane assembly

    Science.gov (United States)

    Matosevic, Sandro; Paegel, Brian M.

    2013-11-01

    Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

  11. Isomeric Detergent Comparison for Membrane Protein Stability

    DEFF Research Database (Denmark)

    Cho, Kyung Ho; Hariharan, Parameswaran; Mortensen, Jonas S.

    2016-01-01

    Membrane proteins encapsulated by detergent micelles are widely used for structural study. Because of their amphipathic property, detergents have the ability to maintain protein solubility and stability in an aqueous medium. However, conventional detergents have serious limitations in their scope...... and utility, particularly for eukaryotic membrane proteins and membrane protein complexes. Thus, a number of new agents have been devised; some have made significant contributions to membrane protein structural studies. However, few detergent design principles are available. In this study, we prepared meta....../stability of the membrane proteins. We propose that interplay between the hydrophile–lipophile balance (HLB) and alkyl chain length is of central importance for high detergent efficacy. In addition, differences in inter-alkyl-chain distance between the isomers influence the ability of the detergents to stabilise membrane...

  12. Modeling branching pore structures in membrane filters

    Science.gov (United States)

    Sanaei, Pejman; Cummings, Linda J.

    2016-11-01

    Membrane filters are in widespread industrial use, and mathematical models to predict their efficacy are potentially very useful, as such models can suggest design modifications to improve filter performance and lifetime. Many models have been proposed to describe particle capture by membrane filters and the associated fluid dynamics, but most such models are based on a very simple structure in which the pores of the membrane are assumed to be simple circularly-cylindrical tubes spanning the depth of the membrane. Real membranes used in applications usually have much more complex geometry, with interconnected pores which may branch and bifurcate. Pores are also typically larger on the upstream side of the membrane than on the downstream side. We present an idealized mathematical model, in which a membrane consists of a series of bifurcating pores, which decrease in size as the membrane is traversed. Feed solution is forced through the membrane by applied pressure, and particles are removed from the feed either by sieving, or by particle adsorption within pores (which shrinks them). Thus the membrane's permeability decreases as the filtration progresses, ultimately falling to zero. We discuss how filtration efficiency depends on the characteristics of the branching structure. Partial support from NSF DMS 1261596 is gratefully acknowledged.

  13. Examining hemodialyzer membrane performance using proteomic technologies.

    Science.gov (United States)

    Bonomini, Mario; Pieroni, Luisa; Di Liberato, Lorenzo; Sirolli, Vittorio; Urbani, Andrea

    2018-01-01

    The success and the quality of hemodialysis therapy are mainly related to both clearance and biocompatibility properties of the artificial membrane packed in the hemodialyzer. Performance of a membrane is strongly influenced by its interaction with the plasma protein repertoire during the extracorporeal procedure. Recognition that a number of medium-high molecular weight solutes, including proteins and protein-bound molecules, are potentially toxic has prompted the development of more permeable membranes. Such membrane engineering, however, may cause loss of vital proteins, with membrane removal being nonspecific. In addition, plasma proteins can be adsorbed onto the membrane surface upon blood contact during dialysis. Adsorption can contribute to the removal of toxic compounds and governs the biocompatibility of a membrane, since surface-adsorbed proteins may trigger a variety of biologic blood pathways with pathophysiologic consequences. Over the last years, use of proteomic approaches has allowed polypeptide spectrum involved in the process of hemodialysis, a key issue previously hampered by lack of suitable technology, to be assessed in an unbiased manner and in its full complexity. Proteomics has been successfully applied to identify and quantify proteins in complex mixtures such as dialysis outflow fluid and fluid desorbed from dialysis membrane containing adsorbed proteins. The identified proteins can also be characterized by their involvement in metabolic and signaling pathways, molecular networks, and biologic processes through application of bioinformatics tools. Proteomics may thus provide an actual functional definition as to the effect of a membrane material on plasma proteins during hemodialysis. Here, we review the results of proteomic studies on the performance of hemodialysis membranes, as evaluated in terms of solute removal efficiency and blood-membrane interactions. The evidence collected indicates that the information provided by proteomic

  14. 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.

  15. Poly/vinyl alcohol/ membranes for reverse osmosis

    Science.gov (United States)

    Katz, M. G.; Wydeven, T., Jr.

    1981-01-01

    A description is presented of the results of studies of the water and salt transport properties of PVA membranes, taking into account radiation crosslinked PVA membranes, diffusive salt permeability through PVA membranes, and heat treated PVA membranes. The experimental findings support an occurrence of independent water, and salt permeation processes. It is suggested that the salt permeation is governed by a solution-diffusion transport mechanism. The preparation of thin skinned, asymmetric PVA membranes is also discussed. The employed method has a certain similarity to the classical phase inversion method, which is widely applied in the casting of asymmetric reverse osmosis membranes. Instead of using a gelling bath composed of a nonsolvent for the membrane material and miscible with the solvent from which the membrane is cast, a 'complexing' bath is used, which is a solution of a complexing agent in water.

  16. Metal ion separations using reactive membranes

    International Nuclear Information System (INIS)

    Way, J.D.

    1993-01-01

    A membrane is a barrier between two phases. If one component of a mixture moves through the membrane faster than another mixture component, a separation can be accomplished. Membranes are used commercially for many applications including gas separations, water purification, particle filtration, and macromolecule separations (Abelson). There are two points to note concerning this definition. First, a membrane is defined based on its function, not the material used to make the membrane. Secondly, a membrane separation is a rate process. The separation is accomplished by a driving force, not by equilibrium between phases. Liquids that are immiscible with the feed and product streams can also be used as membrane materials. Different solutes will have different solubilities and diffusion coefficients in a liquid. The product of the diffusivity and the solubility is known as the permeability coefficient, which is proportional to the solute flux. Differences in permeability coefficient will produce a separation between solutes at constant driving force. Because the diffusion coefficients in liquids are typically orders of magnitude higher than in polymers, a larger flux can be obtained. Further enhancements can be accomplished by adding a nonvolatile complexation agent to the liquid membrane. One can then have either coupled or facilitated transport of metal ions through a liquid membrane. The author describes two implementations of this concept, one involving a liquid membrane supported on a microporous membrane, and the other an emulsion liquid membrane, where separation occurs to internal receiving phases. Applications and costing studies for this technology are reviewed, and a brief summary of some of the problems with liquid membranes is presented

  17. Magnetically controlled permeability membranes

    KAUST Repository

    Kosel, Jurgen

    2013-10-31

    A bioactive material delivery system can include a thermoresponsive polymer membrane and nanowires distributed within the thermoresponsive polymer membrane. Magnetic activation of a thermoresponsive polymer membrane can take place via altering the magnetization or dimensions of nanowires dispersed or ordered within the membrane matrix.

  18. Membrane Disordering is not Sufficient for Membrane Permeabilization by Islet Amyloidogenic Polypeptide: Studies of IAPP(20-29) Fragments

    Science.gov (United States)

    Brender, Jeffrey R.; Heyl, Deborah L.; Samisetti, Shyamprasad; Kotler, Samuel A.; Osborne, Joshua M.; Pesaru, Ranadheer R.; Ramamoorthy, Ayyalusamy

    2013-01-01

    A key factor in the development of type II diabetes is the loss of insulin-producing beta-cells. Human islet amyloid polypeptide protein (human-IAPP) is believed to play a crucial role in this process by forming small aggregates that exhibit toxicity by disrupting the cell membrane. The actual mechanism of membrane disruption is complex and appears to involve an early component before fiber formation and later component associated with fiber formation on the membrane. By comparing the peptide-lipid interactions derived from solid-state NMR experiments of two IAPP fragments that bind the membrane and cause membrane disordering to IAPP derived peptides known to cause significant early membrane permeabilization, we show here that membrane disordering is not likely to be sufficient by itself to cause the early membrane permeabilization observed by IAPP, and may play a lesser role in IAPP membrane disruption than expected. PMID:23493863

  19. Polymeric Membrane Reactors

    OpenAIRE

    José M. Sousa; Luís M. Madeira; João C. Santos; Adélio Mendes

    2008-01-01

    The aim of this chapter is the study of membrane reactors with polymeric membranes, particularly catalytic polymeric membranes. After an introduction where the main advantages and disadvantages of the use of polymeric membranes are summarised, a review of the main areas where they have been applied, integrated in chemical reactors, is presented. This excludes the field of bio-membranes processes, which is analysed in a specific chapter of this book. Particular attention is then given to model...

  20. The native architecture of a photosynthetic membrane

    NARCIS (Netherlands)

    Bahatyrova, S.; Frese, R.N.; Siebert, C.A.; Olsen, J.D.; van der Werf, K.O.; van Grondelle, R.; Niederman, R.A.; Bullough, P.A.; Otto, C.; Hunter, C.N.

    2004-01-01

    In photosynthesis, the harvesting of solar energy and its subsequent conversion into a stable charge separation are dependent upon an interconnected macromolecular network of membrane-associated chlorophyll-protein complexes. Although the detailed structure of each complex has been determined, the

  1. GLP-1 suppresses gastrointestinal motility and inhibits the migrating motor complex in healthy subjects and patients with irritable bowel syndrome

    DEFF Research Database (Denmark)

    Hellström, P M; Näslund, E; Edholm, T

    2008-01-01

    with irritable bowel syndrome (IBS). Antro-duodeno-jejunal manometry was carried out during a 4-h control period with saline, followed by a 4-h period with intravenous GLP-1 (healthy: 0.7 and 1.2 pmol kg(-1) min(-1) (n = 16); IBS, 1.2 and 2.5 pmol kg(-1) min(-1) (n = 14). Plasma was analysed for GLP-1 and gut...... hormones, and gut tissue expression of GLP-1 receptor was studied. In healthy subjects, GLP-1 0.7 pmol kg(-1) min(-1) reduced the migrating motor complexes (MMCs) from a median of 2 (range 2-3) to 0.5 (0-2), and motility index from 4.9 +/- 0.1 to 4.3 +/- 0.3 ln Sigma(mmHg*s min(-1)) in jejunum, while GLP-1...

  2. Sheet Membrane Spacesuit Water Membrane Evaporator

    Science.gov (United States)

    Bue, Grant; Trevino, Luis; Zapata, Felipe; Dillion, Paul; Castillo, Juan; Vonau, Walter; Wilkes, Robert; Vogel, Matthew; Frodge, Curtis

    2013-01-01

    A document describes a sheet membrane spacesuit water membrane evaporator (SWME), which allows for the use of one common water tank that can supply cooling water to the astronaut and to the evaporator. Test data showed that heat rejection performance dropped only 6 percent after being subjected to highly contaminated water. It also exhibited robustness with respect to freezing and Martian atmospheric simulation testing. Water was allowed to freeze in the water channels during testing that simulated a water loop failure and vapor backpressure valve failure. Upon closing the backpressure valve and energizing the pump, the ice eventually thawed and water began to flow with no apparent damage to the sheet membrane. The membrane evaporator also serves to de-gas the water loop from entrained gases, thereby eliminating the need for special degassing equipment such as is needed by the current spacesuit system. As water flows through the three annular water channels, water evaporates with the vapor flowing across the hydrophobic, porous sheet membrane to the vacuum side of the membrane. The rate at which water evaporates, and therefore, the rate at which the flowing water is cooled, is a function of the difference between the water saturation pressure on the water side of the membrane, and the pressure on the vacuum side of the membrane. The primary theory is that the hydrophobic sheet membrane retains water, but permits vapor pass-through when the vapor side pressure is less than the water saturation pressure. This results in evaporative cooling of the remaining water.

  3. Oxygen Transport Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay

    2008-08-30

    small polaron conduction mechanism. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were used to develop strategies to detect and characterize vacancy creation, dopant segregations and defect association in the oxygen conducting membrane material. The pO{sub 2} and temperature dependence of the conductivity, non-stoichiometry and thermal-expansion behavior of compositions with increasing complexity of substitution on the perovskite A and B sites were studied. Studies with the perovskite structure show anomalous behavior at low oxygen partial pressures (<10{sup -5} atm). The anomalies are due to non-equilibrium effects and can be avoided by using very strict criteria for the attainment of equilibrium. The slowness of the oxygen equilibration kinetics arises from two different mechanisms. In the first, a two phase region occurs between an oxygen vacancy ordered phase such as brownmillerite SrFeO{sub 2.5} and perovskite SrFeO{sub 3-x}. The slow kinetics is associated with crossing the two phase region. The width of the miscibility gap decreases with increasing temperature and consequently the effect is less pronounced at higher temperature. The preferred kinetic pathway to reduction of perovskite ferrites when the vacancy concentration corresponds to the formation of significant concentrations of Fe{sup 2+} is via the formation of a Ruddlesden-Popper (RP) phases as clearly observed in the case of La{sub 0.5}Sr{sub 0.5}FeO{sub 3-x} where LaSrFeO{sub 4} is found together with Fe. In more complex compositions, such as LSFTO, iron or iron rich phases are observed locally with no evidence for the presence of discrete RP phase. Fracture strength of tubular perovskite membranes was determined in air and in reducing atmospheric conditions. The strength of the membrane decreased with temperature and severity of reducing conditions although the strength distribution (Weibull parameter, m) was relatively unaltered. Surface and volume

  4. Optimal operation of batch membrane processes

    CERN Document Server

    Paulen, Radoslav

    2016-01-01

    This study concentrates on a general optimization of a particular class of membrane separation processes: those involving batch diafiltration. Existing practices are explained and operational improvements based on optimal control theory are suggested. The first part of the book introduces the theory of membrane processes, optimal control and dynamic optimization. Separation problems are defined and mathematical models of batch membrane processes derived. The control theory focuses on problems of dynamic optimization from a chemical-engineering point of view. Analytical and numerical methods that can be exploited to treat problems of optimal control for membrane processes are described. The second part of the text builds on this theoretical basis to establish solutions for membrane models of increasing complexity. Each chapter starts with a derivation of optimal operation and continues with case studies exemplifying various aspects of the control problems under consideration. The authors work their way from th...

  5. Membrane processes in nuclear technologies

    International Nuclear Information System (INIS)

    Zakrzewska-Trznadel, G.

    2006-01-01

    to the pressure-driven processes, e.g. ultrafiltration and reverse osmosis, which were studied on a laboratory and pilot scale. Verification of the potential application of reverse osmosis on an industrial scale for treatment of liquid low- and intermediate-level radioactive wastes has been carried out with the installation particularly designed and constructed for the Department of Radioactive Waste Processing, Institute of Atomic Energy at Swierk. The thin-layer composite membranes made from a cross-linked aromatic polyamide of high retention of NaCl (99,4-99,7%) were applied in this process. It has been proved that a three-stage installation enables the radioactive waste of specific radioactivity below 10 5 Bq/dm 3 to be cleaned down to 10 Bq/dm 3 in permeate, with simultaneous 7-15-fold reduction of the activity in the concentrate. The results of own studies concerning the removal of selected radionuclides from model aqueous solutions and radioactive wastes with ultra-filtration enhanced by complexation and sorption were also presented in this work. In these cases, the mineral (ceramic) porous membranes made from a-alumina, titanium and zirconium oxides were applied. These membranes exhibited a high resistance against ionizing radiation, aggressive chemical environment and high temperatures. The high effectiveness of removal of the main components of liquid radioactive waste like 134 Cs, 137 Cs, 60 Co, 124 Sb, 85 Sr, 152 Eu and 154 Eu with a hybrid ultrafiltration/complexation process has been experimentally proved. The effects of this type of complexing agent, its concentration and pH of the processed solution on the complexation effectiveness have been studied. Efficacy of the method was tested with real radioactive wastes. The monograph performs results of the studies on membrane distillation which has been proposed by the author for processing of liquid radioactive wastes, and the analysis of its applicability for nuclear desalination and the production of

  6. Plasma membrane associated membranes (PAM) from Jurkat cells contain STIM1 protein is PAM involved in the capacitative calcium entry?

    Science.gov (United States)

    Kozieł, Katarzyna; Lebiedzinska, Magdalena; Szabadkai, Gyorgy; Onopiuk, Marta; Brutkowski, Wojciech; Wierzbicka, Katarzyna; Wilczyński, Grzegorz; Pinton, Paolo; Duszyński, Jerzy; Zabłocki, Krzysztof; Wieckowski, Mariusz R

    2009-12-01

    A proper cooperation between the plasma membrane, the endoplasmic reticulum and the mitochondria seems to be essential for numerous cellular processes involved in Ca(2+) signalling and maintenance of Ca(2+) homeostasis. A presence of microsomal and mitochondrial proteins together with those characteristic for the plasma membrane in the fraction of the plasma membrane associated membranes (PAM) indicates a formation of stabile interactions between these three structures. We isolated the plasma membrane associated membranes from Jurkat cells and found its significant enrichment in the plasma membrane markers including plasma membrane Ca(2+)-ATPase, Na(+), K(+)-ATPase and CD3 as well as sarco/endoplasmic reticulum Ca(2+) ATPase as a marker of the endoplasmic reticulum membranes. In addition, two proteins involved in the store-operated Ca(2+) entry, Orai1 located in the plasma membrane and an endoplasmic reticulum protein STIM1 were found in this fraction. Furthermore, we observed a rearrangement of STIM1-containing protein complexes isolated from Jurkat cells undergoing stimulation by thapsigargin. We suggest that the inter-membrane compartment composed of the plasma membrane and the endoplasmic reticulum, and isolated as a stabile plasma membrane associated membranes fraction, might be involved in the store-operated Ca(2+) entry, and their formation and rebuilding have an important regulatory role in cellular Ca(2+) homeostasis.

  7. Performance enhancement of membrane electrode assemblies with plasma etched polymer electrolyte membrane in PEM fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Yong-Hun; Yoon, Won-Sub [School of Advanced Materials Engineering, Kookmin University, 861-1 Jeongneung-dong, Seongbuk-gu, Seoul 136-702 (Korea); Bae, Jin Woo; Cho, Yoon-Hwan; Lim, Ju Wan; Ahn, Minjeh; Jho, Jae Young; Sung, Yung-Eun [World Class University (WCU) program of Chemical Convergence for Energy and Environment (C2E2), School of Chemical and Biological Engineering, College of Engineering, Seoul National University (SNU), 599 Gwanak-Ro, Gwanak-gu, Seoul 151-744 (Korea); Kwon, Nak-Hyun [Fuel Cell Vehicle Team 3, Advanced Technology Center, Corporate Research and Development Division, Hyundai-Kia Motors, 104 Mabuk-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-912 (Korea)

    2010-10-15

    In this work, a surface modified Nafion 212 membrane was fabricated by plasma etching in order to enhance the performance of a membrane electrode assembly (MEA) in a polymer electrolyte membrane fuel cell. Single-cell performance of MEA at 0.7 V was increased by about 19% with membrane that was etched for 10 min compared to that with untreated Nafion 212 membrane. The MEA with membrane etched for 20 min exhibited a current density of 1700 mA cm{sup -2} at 0.35 V, which was 8% higher than that of MEA with untreated membrane (1580 mA cm{sup -2}). The performances of MEAs containing etched membranes were affected by complex factors such as the thickness and surface morphology of the membrane related to etching time. The structural changes and electrochemical properties of the MEAs with etched membranes were characterized by field emission scanning electron microscopy, Fourier transform-infrared spectrometry, electrochemical impedance spectroscopy, and cyclic voltammetry. (author)

  8. Synthetic Biological Membrane (SBM)

    Data.gov (United States)

    National Aeronautics and Space Administration — The ultimate goal of the Synthetic Biological Membrane project is to develop a new type of membrane that will enable the wastewater treatment system required on...

  9. Oxygen transport membrane

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof.......The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof....

  10. Hybrid adsorptive membrane reactor

    Science.gov (United States)

    Tsotsis, Theodore T [Huntington Beach, CA; Sahimi, Muhammad [Altadena, CA; Fayyaz-Najafi, Babak [Richmond, CA; Harale, Aadesh [Los Angeles, CA; Park, Byoung-Gi [Yeosu, KR; Liu, Paul K. T. [Lafayette Hill, PA

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  11. Premature rupture of membranes

    Science.gov (United States)

    ... gov/ency/patientinstructions/000512.htm Premature rupture of membranes To use the sharing features on this page, ... water that surrounds your baby in the womb. Membranes or layers of tissue hold in this fluid. ...

  12. Transmembrane Signalling: Membrane messengers

    Science.gov (United States)

    Cockroft, Scott L.

    2017-05-01

    Life has evolved elaborate means of communicating essential chemical information across cell membranes. Inspired by biology, two new artificial mechanisms have now been developed that use synthetic messenger molecules to relay chemical signals into or across lipid membranes.

  13. Kinetics and Thermodynamics of Membrane Protein Folding

    Directory of Open Access Journals (Sweden)

    Ernesto A. Roman

    2014-03-01

    Full Text Available Understanding protein folding has been one of the great challenges in biochemistry and molecular biophysics. Over the past 50 years, many thermodynamic and kinetic studies have been performed addressing the stability of globular proteins. In comparison, advances in the membrane protein folding field lag far behind. Although membrane proteins constitute about a third of the proteins encoded in known genomes, stability studies on membrane proteins have been impaired due to experimental limitations. Furthermore, no systematic experimental strategies are available for folding these biomolecules in vitro. Common denaturing agents such as chaotropes usually do not work on helical membrane proteins, and ionic detergents have been successful denaturants only in few cases. Refolding a membrane protein seems to be a craftsman work, which is relatively straightforward for transmembrane β-barrel proteins but challenging for α-helical membrane proteins. Additional complexities emerge in multidomain membrane proteins, data interpretation being one of the most critical. In this review, we will describe some recent efforts in understanding the folding mechanism of membrane proteins that have been reversibly refolded allowing both thermodynamic and kinetic analysis. This information will be discussed in the context of current paradigms in the protein folding field.

  14. Real-life applications with membrane computing

    CERN Document Server

    Zhang, Gexiang; Gheorghe, Marian

    2017-01-01

    This book thoroughly investigates the underlying theoretical basis of membrane computing models, and reveals their latest applications. In addition, to date there have been no illustrative case studies or complex real-life applications that capitalize on the full potential of the sophisticated membrane systems computational apparatus; gaps that this book remedies. By studying various complex applications – including engineering optimization, power systems fault diagnosis, mobile robot controller design, and complex biological systems involving data modeling and process interactions – the book also extends the capabilities of membrane systems models with features such as formal verification techniques, evolutionary approaches, and fuzzy reasoning methods. As such, the book offers a comprehensive and up-to-date guide for all researchers, PhDs and undergraduate students in the fields of computer science, engineering and the bio-sciences who are interested in the applications of natural computing models.

  15. Idiopathic epiretinal membrane

    NARCIS (Netherlands)

    Bu, Shao-Chong; Kuijer, Roelof; Li, Xiao-Rong; Hooymans, Johanna M M; Los, Leonoor I

    2014-01-01

    Background: Idiopathic epiretinal membrane (iERM) is a fibrocellular membrane that proliferates on the inner surface of the retina at the macular area. Membrane contraction is an important sight-threatening event and is due to fibrotic remodeling. Methods: Analysis of the current literature

  16. Membrane contactor applications

    NARCIS (Netherlands)

    Klaassen, R.; Feron, P.H.M.; Jansen, A.

    2008-01-01

    In a membrane contactor the membrane separation is completely integrated with an extraction or absorption operation in order to exploit the benefits of both technologies fully. Membrane contactor applications that have been developed can be found in both water and gas treatment. Several recently

  17. On "spinning" membrane models

    NARCIS (Netherlands)

    Bergshoeff, E.; Sezgin, E.; Townsend, P.K.

    1988-01-01

    Several alternative actions for a bosonic membrane have recently been proposed. We show that a linearly realized locally world-volume-supersymmetric (spinning membrane) extension of any of these actions implies an analogous extension of the standard Dirac membrane action. We further show that a

  18. Meniscus Membranes For Separation

    Science.gov (United States)

    Dye, Robert C.; Jorgensen, Betty; Pesiri, David R.

    2005-09-20

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  19. Meniscus membranes for separations

    Science.gov (United States)

    Dye, Robert C [Irvine, CA; Jorgensen, Betty [Jemez Springs, NM; Pesiri, David R [Aliso Viejo, CA

    2004-01-27

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  20. Plasma membrane ATPases

    DEFF Research Database (Denmark)

    Palmgren, Michael Broberg; Bækgaard, Lone; Lopez Marques, Rosa Laura

    2011-01-01

    membrane include ABC transporters, vacuolar (V-type) H+ pumps, and P-type pumps. These pumps all utilize ATP as a fuel for energizing pumping. This review focuses on the physiological roles of plasma membrane P-type pumps, as they represent the major ATP hydrolytic activity in this membrane....

  1. Global Proteomic Analysis Reveals an Exclusive Role of Thylakoid Membranes in Bioenergetics of a Model Cyanobacterium

    Energy Technology Data Exchange (ETDEWEB)

    Liberton, Michelle; Saha, Rajib; Jacobs, Jon M.; Nguyen, Amelia Y.; Gritsenko, Marina A.; Smith, Richard D.; Koppenaal, David W.; Pakrasi, Himadri B.

    2016-04-07

    Cyanobacteria are photosynthetic microbes with highly differentiated membrane systems. These organisms contain an outer membrane, plasma membrane, and an internal system of thylakoid membranes where the photosynthetic and respiratory machinery are found. This existence of compartmentalization and differentiation of membrane systems poses a number of challenges for cyanobacterial cells in terms of organization and distribution of proteins to the correct membrane system. Proteomics studies have long sought to identify the components of the different membrane systems, and to date about 450 different proteins have been attributed to either the plasma membrane or thylakoid membrane. Given the complexity of these membranes, many more proteins remain to be identified in these membrane systems, and a comprehensive catalog of plasma membrane and thylakoid membrane proteins is needed. Here we describe the identification of 635 proteins in Synechocystis sp. PCC 6803 by quantitative iTRAQ isobaric labeling; of these, 459 proteins were localized to the plasma membrane and 176 were localized to the thylakoid membrane. Surprisingly, we found over 2.5 times the number of unique proteins identified in the plasma membrane compared to the thylakoid membrane. This suggests that the protein composition of the thylakoid membrane is more homogeneous than the plasma membrane, consistent with the role of the plasma membrane in diverse cellular processes including protein trafficking and nutrient import, compared to a more specialized role for the thylakoid membrane in cellular energetics. Overall, the protein composition of the Synechocystis 6803 plasma membrane and thylakoid membrane is quite similar to the E.coli plasma membrane and Arabidopsis thylakoid membrane, respectively. Synechocystis 6803 can therefore be described as a gram-negative bacterium that has an additional internal membrane system that fulfils the energetic requirements of the cell.

  2. Global Proteomic Analysis Reveals an Exclusive Role of Thylakoid Membranes in Bioenergetics of a Model Cyanobacterium

    Energy Technology Data Exchange (ETDEWEB)

    Liberton, Michelle; Saha, Rajib; Jacobs, Jon M.; Nguyen, Amelia Y.; Gritsenko, Marina A.; Smith, Richard D.; Koppenaal, David W.; Pakrasi, Himadri B.

    2016-04-07

    Cyanobacteria are photosynthetic microbes with highlydifferentiated membrane systems. These organisms contain an outer membrane, plasma membrane, and an internal system of thylakoid membranes where the photosynthetic and respiratory machinery are found. This existence of compartmentalization and differentiation of membrane systems poses a number of challenges for cyanobacterial cells in terms of organization and distribution of proteins to the correct membrane system. Proteomics studies have long sought to identify the components of the different membrane systems in cyanobacteria, and to date about 450 different proteins have been attributed to either the plasma membrane or thylakoid membrane. Given the complexity of these membranes, many more proteins remain to be identified, and a comprehensive catalogue of plasma membrane and thylakoid membrane proteins is needed. Here we describe the identification of 635 differentially localized proteins in Synechocystis sp. PCC 6803 by quantitative iTRAQ isobaric labeling; of these, 459 proteins were localized to the plasma membrane and 176 were localized to the thylakoid membrane. Surprisingly, we found over 2.5 times the number of unique proteins identified in the plasma membrane compared with the thylakoid membrane. This suggests that the protein composition of the thylakoid membrane is more homogeneous than the plasma membrane, consistent with the role of the plasma membrane in diverse cellular processes including protein trafficking and nutrient import, compared with a more specialized role for the thylakoid membrane in cellular energetics. Thus, our data clearly define the two membrane systems with distinct functions. Overall, the protein compositions of the Synechocystis 6803 plasma membrane and thylakoid membrane are quite similar to that of the plasma membrane of Escherichia coli and thylakoid membrane of Arabidopsis chloroplasts, respectively. Synechocystis 6803 can therefore be described as a Gram

  3. Cell membrane structures during exocytosis.

    Science.gov (United States)

    Savigny, Pascale; Evans, John; McGrath, Kathryn M

    2007-08-01

    Exocytosis is a key biological process that controls the neurotransmission and release of hormones from cells. In endocrine cells, hormones are packed into secretory vesicles and released into the extracellular environment via openings in the plasma membrane, a few hundred nanometers wide, which form as a result of fusion of the membranes of the granule and cell. The complex processes and dynamics that result in the formation of the fusion pore, as well as its structure, remain scantly understood. A number of different exocytosis mechanisms have been postulated. Furthermore, the possibility exists that several mechanisms occur simultaneously. We present here an investigation of the cell membrane dynamics during exocytosis in anterior pituitary cells, especially gonadotropes, which secrete LH, a hormone central to ovulation. Gonadotrope enrichment was achieved using immunolabeled magnetic nanobeads. Three complementary imaging techniques were used to realize a fine structure study of the dynamics of the exocytosis-like sites occurring during secretion. Living pituitary and gonadotrope-enriched cells were imaged with atomic force microscopy, as well as cells that had been fixed to obtain better resolution. Atomic force microscopy, along with scanning and transmission electron microscopy, studies of these cells revealed that there are at least two different site configurations: simple single fusion pores and a complex association of pores consisting of a simple primary site combined with secondary attachments.

  4. Late Cretaceous Localized Crustal Thickening as a Primary Control on the 3-D Architecture and Exhumation Histories of Cordilleran Metamorphic Core Complexes

    Science.gov (United States)

    Gans, P. B.; Wong, M.

    2014-12-01

    The juxtaposition of mylonitic mid-crustal rocks and faulted supracrustal rocks in metamorphic core complexes (MMCs) is usually portrayed in 2 dimensions and attributed to a single event of large-scale slip ± isostatic doming along a low-angle "detachment fault"/ shear zone. This paradigm does not explain dramatic along strike (3-D) variations in slip magnitude, footwall architecture, and burial / exhumation histories of most MMCs. A fundamental question posed by MMCs is how did their earlier thickening and exhumation histories influence the geometric evolution and 3-D slip distribution on the subsequent detachment faults? New geologic mapping and 40Ar/39Ar thermochronology from the Snake Range-Kern Mts-Deep Creek Mts (SKDC) complex in eastern Nevada offer important insights into this question. Crustal shortening and thickening by large-scale non-cylindrical recumbent folds and associated thrust faults during the late Cretaceous (90-80 Ma) resulted in deep burial (650°C, 20-25 km) of the central part of the footwall, but metamorphic grade decreases dramatically to the N and S in concert with decreasing amplitude on the shortening structures. Subsequent Paleogene extensional exhumation by normal faulting and ESE-directed mylonitic shearing is greatest in areas of maximum earlier thickening and brought highest grade rocks back to depths of~10-12 km. After ≥15 Ma of quiescence, rapid E-directed slip initiated along the brittle Miocene Snake Range detachment at 20 Ma and reactivated the Eocene shear zone. The ≥200°C gradient across the footwall at this time implies that the Miocene slip surface originated as a moderately E-dipping normal fault. This Miocene slip surface can be tracked for more than 100 km along strike, but the greatest amount of Miocene slip also coincides with parts of the footwall that were most deeply buried in the Cretaceous. These relations indicate that not only is the SKDC MMC a composite feature, but that the crustal welt created by

  5. Basement membrane proteoglycans in glomerular morphogenesis: chondroitin sulfate proteoglycan is temporally and spatially restricted during development

    DEFF Research Database (Denmark)

    McCarthy, K J; Bynum, K; St John, P L

    1993-01-01

    basement membrane (GBM) but present in other basement membranes of the nephron, including collecting ducts, tubules, Bowman's capsule, and the glomerular mesangium. In light of this unique pattern of distribution and of the complex histoarchitectural reorganization occurring during nephrogenesis...

  6. Microporous silica membranes

    DEFF Research Database (Denmark)

    Boffa, Vittorio; Yue, Yuanzheng

    2012-01-01

    Hydrothermal stability is a crucial factor for the application of microporous silica-based membranes in industrial processes. Indeed, it is well established that steam exposure may cause densification and defect formation in microporous silica membranes, which are detrimental to both membrane...... permeability and selectivity. Numerous previous studies show that microporous transition metal doped-silica membranes are hydrothermally more stable than pure silica membranes, but less permeable. Here we present a quantitative study on the impact of type and concentration of transition metal ions...... on the microporous structure, stability and permeability of amorphous silica-based membranes, providing information on how to design chemical compositions and synthetic paths for the fabrication of silica-based membranes with a well accessible and highly stabile microporous structure....

  7. Clustering on Membranes

    DEFF Research Database (Denmark)

    Johannes, Ludger; Pezeshkian, Weria; Ipsen, John H

    2018-01-01

    Clustering of extracellular ligands and proteins on the plasma membrane is required to perform specific cellular functions, such as signaling and endocytosis. Attractive forces that originate in perturbations of the membrane's physical properties contribute to this clustering, in addition to direct...... protein-protein interactions. However, these membrane-mediated forces have not all been equally considered, despite their importance. In this review, we describe how line tension, lipid depletion, and membrane curvature contribute to membrane-mediated clustering. Additional attractive forces that arise...... from protein-induced perturbation of a membrane's fluctuations are also described. This review aims to provide a survey of the current understanding of membrane-mediated clustering and how this supports precise biological functions....

  8. Application of dynamic membranes in anaerobic membranes in anaerobic membrane bioreactor systems

    NARCIS (Netherlands)

    Erşahin, M.E.

    2015-01-01

    Anaerobic membrane bioreactors (AnMBRs) physically ensure biomass retention by the application of a membrane filtration process. With growing application experiences from aerobic membrane bioreactors (MBRs), the combination of membrane and anaerobic processes has received much attention and become

  9. Versatile membrane deformation potential of activated pacsin.

    Directory of Open Access Journals (Sweden)

    Shih Lin Goh

    Full Text Available Endocytosis is a fundamental process in signaling and membrane trafficking. The formation of vesicles at the plasma membrane is mediated by the G protein dynamin that catalyzes the final fission step, the actin cytoskeleton, and proteins that sense or induce membrane curvature. One such protein, the F-BAR domain-containing protein pacsin, contributes to this process and has been shown to induce a spectrum of membrane morphologies, including tubules and tube constrictions in vitro. Full-length pacsin isoform 1 (pacsin-1 has reduced activity compared to its isolated F-BAR domain, implicating an inhibitory role for its C-terminal Src homology 3 (SH3 domain. Here we show that the autoinhibitory, intramolecular interactions in pacsin-1 can be released upon binding to the entire proline-rich domain (PRD of dynamin-1, resulting in potent membrane deformation activity that is distinct from the isolated F-BAR domain. Most strikingly, we observe the generation of small, homogenous vesicles with the activated protein complex under certain experimental conditions. In addition, liposomes prepared with different methods yield distinct membrane deformation morphologies of BAR domain proteins and apparent activation barriers to pacsin-1's activity. Theoretical free energy calculations suggest bimodality of the protein-membrane system as a possible source for the different outcomes, which could account for the coexistence of energetically equivalent membrane structures induced by BAR domain-containing proteins in vitro. Taken together, our results suggest a versatile role for pacsin-1 in sculpting cellular membranes that is likely dependent both on protein structure and membrane properties.

  10. Supported ionic liquid membrane in membrane reactor

    Science.gov (United States)

    Makertihartha, I. G. B. N.; Zunita, M.; Dharmawijaya, P. T.; Wenten, I. G.

    2017-01-01

    Membrane reactor is a device that integrates membrane based separation and (catalytic) chemical reaction vessel in a single device. Ionic liquids, considered to be a relatively recent magical chemical due to their unique properties, have a large variety of applications in all areas of chemical industries. Moreover, the ionic liquid can be used as membrane separation layer and/or catalytically active site. This paper will review utilization of ionic liquid in membrane reactor related applications especially Fischer-Tropsch, hydrogenation, and dehydrogenation reaction. This paper also reviews about the capability of ionic liquid in equilibrium reaction that produces CO2 product so that the reaction will move towards the product. Water gas shift reaction in ammonia production also direct Dimethyl Ether (DME) synthesis that produces CO2 product will be discussed. Based on a review of numerous articles on supported ionic liquid membrane (SILM) indicate that ionic liquids have the potential to support the process of chemical reaction and separation in a membrane reactor.

  11. Polymer and Membrane Design for Low Temperature Catalytic Reactions

    KAUST Repository

    Villalobos, Luis Francisco

    2016-02-29

    Catalytically active asymmetric membranes have been developed with high loadings of palladium nanoparticles located solely in the membrane\\'s ultrathin skin layer. The manufacturing of these membranes requires polymers with functional groups, which can form insoluble complexes with palladium ions. Three polymers have been synthesized for this purpose and a complexation/nonsolvent induced phase separation followed by a palladium reduction step is carried out to prepare such membranes. Parameters to optimize the skin layer thickness and porosity, the palladium loading in this layer, and the palladium nanoparticles size are determined. The catalytic activity of the membranes is verified with the reduction of a nitro-compound and with a liquid phase Suzuki-Miyaura coupling reaction. Very low reaction times are observed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Homeoviscous adaptation and the regulation of membrane lipids

    DEFF Research Database (Denmark)

    Ernst, Robert; Ejsing, Christer S; Antonny, Bruno

    2016-01-01

    Biological membranes are complex and dynamic assemblies of lipids and proteins. Poikilothermic organisms including bacteria, fungi, reptiles, and fish do not control their body temperature and must adapt their membrane lipid composition in order to maintain membrane fluidity in the cold. This ada......Biological membranes are complex and dynamic assemblies of lipids and proteins. Poikilothermic organisms including bacteria, fungi, reptiles, and fish do not control their body temperature and must adapt their membrane lipid composition in order to maintain membrane fluidity in the cold...... such as neurons maintain unique lipid compositions with specific physicochemical properties. To date little is known about the sensory mechanisms regulating the acyl chain profile in such specialized cells or during adaptive responses. Here we summarize our current understanding of lipid metabolic networks...

  13. Sorting of bacterial lipoproteins to the outer membrane by the Lol system.

    Science.gov (United States)

    Narita, Shin-ichiro; Tokuda, Hajime

    2010-01-01

    Bacterial lipoproteins comprise a subset of membrane proteins with a lipid-modified cysteine residue at their amino termini through which they are anchored to the membrane. In Gram-negative bacteria, lipoproteins are localized on either the inner or the outer membrane. The Lol system is responsible for the transport of lipoproteins to the outer membrane.The Lol system comprises an inner-membrane ABC transporter LolCDE complex, a periplasmic carrier protein, LolA, and an outer membrane receptor protein, LolB. Lipoproteins are synthesized as precursors in the cytosol and then translocated across the inner membrane by the Sec translocon to the outer leaflet of the inner membrane, where lipoprotein precursors are processed to mature lipoproteins. The LolCDE complex then mediates the release of outer membrane-specific lipoproteins from the inner membrane while the inner membrane-specific lipoproteins possessing Asp at position 2 are not released by LolCDE because it functions as a LolCDE avoidance signal, causing the retention of these lipoproteins in the inner membrane. A water-soluble lipoprotein-LolA complex is formed as a result of the release reaction mediated by LolCDE. This complex traverses the hydrophilic periplasm to reach the outer membrane, where LolB accepts a lipoprotein from LolA and then catalyzes its incorporation into the inner leaflet of the outer membrane.

  14. Determination of structure of the MinD-ATP complex reveals the orientation of MinD on the membrane and the relative location of the binding sites for MinE and MinC

    Science.gov (United States)

    Wu, Wei; Park, Kyung-Tae; Holyoak, Todd; Lutkenhaus, Joe

    2011-01-01

    Summary The three Min proteins spatially regulate Z ring positioning in E. coli and are dynamically associated with the membrane. MinD binds to vesicles in the presence of ATP and can recruit MinC or MinE. Biochemical and genetic evidence indicate the binding sites for these two proteins on MinD overlap. Here we solved the structure of a hydrolytic-deficient mutant of MinD truncated for the C-terminal amphipathic helix involved in binding to the membrane. The structure solved in the presence of ATP is a dimer and reveals the face of MinD abutting the membrane. Using a combination of random and extensive site-directed mutagenesis additional residues important for MinE and MinC binding were identified. The location of these residues on the MinD structure confirms that the binding sites overlap and reveals that the binding sites are at the dimer interface and exposed to the cytosol. The location of the binding sites at the dimer interface offers a simple explanation for the ATP-dependency of MinC and MinE binding to MinD. PMID:21231967

  15. Dissipative dynamics of fluid lipid membranes enriched in cholesterol.

    Science.gov (United States)

    Arriaga, Laura R; Rodríguez-García, Ruddi; Moleiro, Lara H; Prévost, Sylvain; López-Montero, Iván; Hellweg, Thomas; Monroy, Francisco

    2017-09-01

    Cholesterol is an intriguing component of fluid lipid membranes: It makes them stiffer but also more fluid. Despite the enormous biological significance of this complex dynamical behavior, which blends aspects of membrane elasticity with viscous friction, their mechanical bases remain however poorly understood. Here, we show that the incorporation of physiologically relevant contents of cholesterol in model fluid membranes produces a fourfold increase in the membrane bending modulus. However, the increase in the compression rigidity that we measure is only twofold; this indicates that cholesterol increases coupling between the two membrane leaflets. In addition, we show that although cholesterol makes each membrane leaflet more fluid, it increases the friction between the membrane leaflets. This dissipative dynamics causes opposite but advantageous effects over different membrane motions: It allows the membrane to rearrange quickly in the lateral dimension, and to simultaneously dissipate out-of-plane stresses through friction between the two membrane leaflets. Moreover, our results provide a clear correlation between coupling and friction of membrane leaflets. Furthermore, we show that these rigid membranes are optimal to resist slow deformations with minimum energy dissipation; their optimized stability might be exploited to design soft technological microsystems with an encoded mechanics, vesicles or capsules for instance, useful beyond classical applications as model biophysical systems. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Emulsification using microporous membranes

    Directory of Open Access Journals (Sweden)

    Goran T. Vladisavljević

    2011-10-01

    Full Text Available Membrane emulsification is a process of injecting a pure dispersed phase or pre-emulsion through a microporous membrane into the continuous phase. As a result of the immiscibility of the two phases, droplets of the dispersed phase are formed at the outlets of membrane pores. The droplets formed in the process are removed from the membrane surface by applying cross-flow or stirring of the continuous phase or using a dynamic (rotating or vibrating membrane. The most commonly used membrane for emulsification is the Shirasu Porous Glass (SPG membrane, fabricated through spinodal decomposition in a melt consisting of Japanese volcanic ash (Shirasu, boric acid and calcium carbonate. Microsieve membranes are increasingly popular as an alternative to highly tortuous glass and ceramic membranes. Microsieves are usually fabricated from nickel by photolithography and electroplating or they can be manufactured from silicon nitride via Reactive Ion Etching (RIE. An advantage of microsieves compared to the SPG membrane is in much higher transmembrane fluxes and higher tolerance to fouling by the emulsion ingredients due to the existence of short, straight through pores. Unlike conventional emulsification devices such as high-pressure valve homogenisers and rotor-stator devices, membrane emulsification devices permit a precise control over the mean pore size over a wide range and during the process insignificant amount of energy is dissipated as heat. The drop size is primarily determined by the pore size, but it depends also on other parameters, such as membrane wettability, emulsion formulation, shear stress on the membrane surface, transmembrane pressure, etc.

  17. Nanoscale Membrane Domain Formation Driven by Cholesterol

    DEFF Research Database (Denmark)

    Javanainen, Matti; Martinez-Seara, Hector; Vattulainen, Ilpo

    2017-01-01

    Biological membranes generate specific functions through compartmentalized regions such as cholesterol-enriched membrane nanodomains that host selected proteins. Despite the biological significance of nanodomains, details on their structure remain elusive. They cannot be observed via microscopic...... dipalmitoylphosphatidylcholine and cholesterol - the "minimal standard" for nanodomain formation. The simulations reveal how cholesterol drives the formation of fluid cholesterol-rich nanodomains hosting hexagonally packed cholesterol-poor lipid nanoclusters, both of which show registration between the membrane leaflets....... The complex nanodomain substructure forms when cholesterol positions itself in the domain boundary region. Here cholesterol can also readily flip-flop across the membrane. Most importantly, replacing cholesterol with a sterol characterized by a less asymmetric ring region impairs the emergence of nanodomains...

  18. Plasma membrane disruption: repair, prevention, adaptation

    Science.gov (United States)

    McNeil, Paul L.; Steinhardt, Richard A.

    2003-01-01

    Many metazoan cells inhabit mechanically stressful environments and, consequently, their plasma membranes are frequently disrupted. Survival requires that the cell rapidly repair or reseal the disruption. Rapid resealing is an active and complex structural modification that employs endomembrane as its primary building block, and cytoskeletal and membrane fusion proteins as its catalysts. Endomembrane is delivered to the damaged plasma membrane through exocytosis, a ubiquitous Ca2+-triggered response to disruption. Tissue and cell level architecture prevent disruptions from occurring, either by shielding cells from damaging levels of force, or, when this is not possible, by promoting safe force transmission through the plasma membrane via protein-based cables and linkages. Prevention of disruption also can be a dynamic cell or tissue level adaptation triggered when a damaging level of mechanical stress is imposed. Disease results from failure of either the preventive or resealing mechanisms.

  19. Hydro-osmotic Instabilities in Active Membrane Tubes

    Science.gov (United States)

    Al-Izzi, Sami C.; Rowlands, George; Sens, Pierre; Turner, Matthew S.

    2018-03-01

    We study a membrane tube with unidirectional ion pumps driving an osmotic pressure difference. A pressure-driven peristaltic instability is identified, qualitatively distinct from similar tension-driven Rayleigh-type instabilities on membrane tubes. We discuss how this instability could be related to the function and biogenesis of membrane bound organelles, in particular, the contractile vacuole complex. The unusually long natural wavelength of this instability is in agreement with that observed in cells.

  20. Role of plasma membrane surface charges in dictating the feasibility of membrane-nanoparticle interactions

    Science.gov (United States)

    Sinha, Shayandev; Jing, Haoyuan; Sachar, Harnoor Singh; Das, Siddhartha

    2017-12-01

    Receptor-ligand (R-L) binding mediated interactions between the plasma membrane (PM) and a nanoparticle (NP) require the ligand-functionalized NPs to come to a distance of separation (DOS) of at least dRL (length of the R-L complex) from the receptor-bearing membranes. In this letter, we establish that the membrane surface charges and the surrounding ionic environment dictate whether or not the attainment of such a critical DOS is possible. The negatively charged membrane invariably induces a negative electrostatic potential at the NP surface, repelling the NP from the membrane. This is countered by the attractive influences of the thermal fluctuations and van der Waals (vdw) interactions that drive the NP close to the membrane. For a NP approaching the membrane from a distance, the ratio of the repulsive (electrostatic) and attractive (thermal and vdW) effects balances at a critical NP-membrane DOS of dg,c. For a given set of parameters, there can be two possible values of dg,c, namely, dg,c,1 and dg,c,2 with dg,c,1 ≫ dg,c,2. We establish that any R-L mediated NP-membrane interaction is possible only if dRL > dg,c,1. Therefore, our study proposes a design criterion for engineering ligands for a NP that will ensure the appropriate length of the R-L complex in order to ensure the successful membrane-NP interaction in the presence of a given electrostatic environment. Finally, we discuss the manner in which our theory can help designing ligand-grafted NPs for targeted drug delivery, design biomimetics NPs, and also explain various experimental results.

  1. Ion-conducting membranes

    Energy Technology Data Exchange (ETDEWEB)

    Masel, Richard I.; Sajjad, Syed Dawar; Gao, Yan; Liu, Zengcai; Chen, Qingmei

    2017-12-26

    An anion-conducting polymeric membrane comprises a terpolymer of styrene, vinylbenzyl-R.sub.s and vinylbenzyl-R.sub.x. R.sub.s is a positively charged cyclic amine group. R.sub.x is at least one constituent selected from the group consisting Cl, OH and a reaction product between an OH or Cl and a species other than a simple amine or a cyclic amine. The total weight of the vinylbenzyl-R.sub.x groups is greater than 0.3% of the total weight of the membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

  2. 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

  3. Linking molecular motors to membrane cargo.

    Science.gov (United States)

    Akhmanova, Anna; Hammer, John A

    2010-08-01

    Three types of motors, myosins, kinesins, and cytoplasmic dynein, cooperate to transport intracellular membrane organelles. Transport of each cargo is determined by recruitment of specific sets of motors and their regulation. Targeting of motors to membranes often depends on the formation of large multiprotein assemblies and can be influenced by membrane lipid composition. Motor activity can be regulated by cargo-induced conformational changes such as unfolding or dimerization. The architecture and function of motor: cargo complexes can also be controlled by phosphorylation, calcium signaling, and proteolysis. The complexity of transport systems is further increased by mechanical and functional cross-talk between different types of motors on the same cargo and by participation of the same motor in the movement of different organelles. Copyright 2010 Elsevier Ltd. All rights reserved.

  4. Chelating polymeric membranes

    KAUST Repository

    Peinemann, Klaus-Viktor

    2015-01-22

    The present application offers a solution to the current problems associated with recovery and recycling of precious metals from scrap material, discard articles, and other items comprising one or more precious metals. The solution is premised on a microporous chelating polymeric membrane. Embodiments include, but are not limited to, microporous chelating polymeric membranes, device comprising the membranes, and methods of using and making the same.

  5. Polyarylether composition and membrane

    Science.gov (United States)

    Hung, Joyce; Brunelle, Daniel Joseph; Harmon, Marianne Elisabeth; Moore, David Roger; Stone, Joshua James; Zhou, Hongyi; Suriano, Joseph Anthony

    2010-11-09

    A composition including a polyarylether copolymer is provided. The copolymer includes a polyarylether backbone; and a sulfonated oligomeric group bonded to the polyarylether suitable for use as a cation conducting membrane. Method of bonding a sulfonated oligomeric group to the polyarylether backbone to form a polyarylether copolymer. The membrane may be formed from the polyarylether copolymer composition. The chain length of the sulfonated oligomeric group may be controlled to affect or control the ion conductivity of the membrane.

  6. The role of antioxidant-protein interactions in biological membrane

    International Nuclear Information System (INIS)

    McGillivray, Duncan J; Singh, Rachna; Melton, Laurence D.; Worcester, David L.; Gilbert, Elliot P.

    2009-01-01

    Full text: Oxidative damage of cellular membranes has been linked to a variety of disease pathologies, including cardiac disease, Alzheimer's and complications due to diabetes. The oxidation of unsaturated and polyunsaturated fatty acid chains found in cellular membranes leads to significant alteration in membrane physical properties, including lipid orientation and membrane permeability, which ultimately affect biological function. Polyphenols are naturally occurring phytochemicals present in a number of fruit and vegetables that are of interest for their anti-oxidative powers. These polyphenols inhibit lipid oxidation in cellular membrane surfaces, although the mechanism of this inhibition is not entirely clear. Moreover, the polyphenols have significant binding affinity for proteins, which can lead to the formation of soluble and insoluble protein-polyphenol complexes Significantly, in the presence of casein proteins the oxidation inhibition the polyphenols in the membrane is significantly enhanced (as assessed by Lipid Peroxidation Inhibition Capacity assays). Thus the antioxidant pathway appears to involve these protein/polyphenol complexes, as well as direct antioxidant action by the polyphenol. Here we discuss neutron and x-ray scattering results from phospholipid membranes, looking at the positioning of two examples of polyphenolic antioxidants in phospholipid membranes, quercetin and phloretin, the antioxidants' impact on the membrane organisation, and the interaction between antioxidant and extra-membranous protein. This information sheds light on the mechanism of antioxidant protection in these systems, which may be used to understand biological responses to oxidative stress.

  7. Fabrication of Ceramic Membrane Chromatography for Biologics Purification

    Directory of Open Access Journals (Sweden)

    Maizirwan Mel

    2011-12-01

    Full Text Available Chromatography is one of the most important separation processes of choice for the recovery/purification of proteins and complex bio-structures. Fabrication of chromatographic membranes and their efficiency in the chromatography process has been the subject of many recent researches. In this study, a coin-like, 13 mm diameter and 3 mm thick, ceramic membrane was fabricated to be used as a chromatographic medium. The membrane is used to replace the conventional resin-based chromatography columns. Hydroxyapatite (HA powder was used as a material for the membrane fabrication. In this project, a HA powder was produced using starch as pore creating agents. Characterization processes were done for the ceramic membrane using the suitable apparatuses. Three parameters of the fabrication process (starch wt %, compaction pressure and sintering temperature were manipulated to optimize the performance of the membrane. The fabricated membrane was placed in a (FPLC system to be tested for its performance as an adsorptive membrane. (IMAC process was run by immobilizing Ni2+ ions at the membrane particles surfaces. NP protein of the (NDV was used to test the membrane's ability to bind Histidine-tagged proteins. The optimum set of process parameters that yielded in the highest porosity and good chromatogram was determined to be 5 wt % starch, 3000 psi compaction pressure and 1100°C sintering temperature.ABSTRAK: Kromatografi merupakan satu daripada proses pengasingan yang penting yang dipilih untuk perolehan/penapisan protein dan biostruktur yang kompleks. Pemfabrikatan membran kromatografi dan kecekapannya dalam proses kromatografi merupakan fokus beberapa kajian terkini. Dalam kajian ini, membran seramik berbentuk duit syiling, berdiameter 13 mm dengan ketebalan 3 mm, direka untuk digunakan sebagai perantara kromatografi. Membran ini digunakan untuk menggantikan turus kromatografi berasaskan resin yang lazim. Serbuk hidroksiapatit (HA digunakan sebagai bahan

  8. Highly Branched Pentasaccharide-Bearing Amphiphiles for Membrane Protein Studies

    DEFF Research Database (Denmark)

    Ehsan, Muhammad; Du, Yang; Scull, Nicola J

    2016-01-01

    Detergents are essential tools for membrane protein manipulation. Micelles formed by detergent molecules have the ability to encapsulate the hydrophobic domains of membrane proteins. The resulting protein-detergent complexes (PDCs) are compatible with the polar environments of aqueous media, maki...

  9. Nidovirus replication structures : hijacking membranes to support viral RNA synthesis

    NARCIS (Netherlands)

    Knoops, Kèvin

    2011-01-01

    Positive-stranded RNA viruses replicate in the cytoplasm of host cells and their replication complexes are associated with modified cell membranes. We investigated the structure of the nidovirus-induced membrane modifications and found that nidoviruses transform the endoplasmic reticulum into a

  10. Photoresponsive nanostructured membranes

    KAUST Repository

    Madhavan, Poornima

    2016-07-26

    The perspective of adding stimuli-response to isoporous membranes stimulates the development of separation devices with pores, which would open or close under control of environment chemical composition, temperature or exposure to light. Changes in pH and temperature have been previously investigated. In this work, we demonstrate for the first time the preparation of photoresponsive isoporous membranes, applying self-assembly non-solvent induced phase separation to a new light responsive block copolymer. First, we optimized the membrane formation by using poly(styrene-b-anthracene methyl methacrylate-b-methylmethacrylate) (PS-b-PAnMMA-b-PMMA) copolymer, identifying the most suitable solvent, copolymer block length, and other parameters. The obtained final triblock copolymer membrane morphologies were characterized using atomic force and electron microscopy. The microscopic analysis reveals that the PS-b-PAnMMA-b-PMMA copolymer can form both lamellar and ordered hexagonal nanoporous structures on the membrane top layer in appropriate solvent compositions. The nanostructured membrane emits fluorescence due to the presence of the anthracene mid-block. On irradiation of light the PS-b-PAnMMA-b-PMMA copolymer membranes has an additional stimuli response. The anthracene group undergoes conformational changes by forming [4 + 4] cycloadducts and this alters the membrane\\'s water flux and solute retention. © 2016 The Royal Society of Chemistry.

  11. Gas separation membranes

    Science.gov (United States)

    Schell, William J.

    1979-01-01

    A dry, fabric supported, polymeric gas separation membrane, such as cellulose acetate, is prepared by casting a solution of the polymer onto a shrinkable fabric preferably formed of synthetic polymers such as polyester or polyamide filaments before washing, stretching or calendering (so called griege goods). The supported membrane is then subjected to gelling, annealing, and drying by solvent exchange. During the processing steps, both the fabric support and the membrane shrink a preselected, controlled amount which prevents curling, wrinkling or cracking of the membrane in flat form or when spirally wound into a gas separation element.

  12. Mesothelium of Reissner's membrane in guinea pigs

    DEFF Research Database (Denmark)

    Qvortrup, K; Rostgaard, Jørgen

    1990-01-01

    The mesothelial cells of Reissner's membrane in guinea pigs were found to be connected by junctional complexes. No cell discontinuities or gaps were observed by scanning or transmission electron microscopy. These results are not in accordance with previous studies. They were achieved by in vivo...

  13. Adamantane-based amphiphiles (ADAs) for membrane protein study: importance of a detergent hydrophobic group in membrane protein solubilisation.

    Science.gov (United States)

    Chae, Pil Seok; Bae, Hyoung Eun; Das, Manabendra

    2014-10-21

    We prepared adamantane-containing amphiphiles and evaluated them using a large membrane protein complex in terms of protein solubilisation and stabilization efficacy. These agents were superior to conventional detergents, especially in terms of the membrane protein solubilisation efficiency, implying a new detergent structure-property relationship.

  14. A cerium(III) selective polyvinyl chloride membrane sensor based on a Schiff base complex of N,N'-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine

    International Nuclear Information System (INIS)

    Gupta, Vinod Kumar; Singh, A.K.; Gupta, Barkha

    2006-01-01

    A polyvinyl chloride (PVC) based membrane sensor for cerium ions was prepared by employing N,N'-bis[2-(salicylideneamino)ethyl]ethane-1,2-diamine as an ionophore, oleic acid (OA) as anion excluder and o-nitrophenyloctyl ether (o-NPOE) as plasticizer. The plasticized membrane sensor exhibits a Nernstian response for Ce(III) ions over a wide concentration range (1.41 x 10 -7 to 1.0 x 10 -2 M) with a limit of detection as low as 8.91 x 10 -8 M. It has a fast response time (<10 s) and can be used for 4 months. The sensor revealed a very good selectivity with respect to common alkali, alkaline earth and heavy metal ions. The response of the proposed sensor is independent of pH between 3.0 and 8.0. It was used as an indicator electrode in potentiometric titration of fluoride, carbonate and oxalate anions and determination of cerium in simulated mixtures

  15. Isolation of Contact Sites Between Inner and Outer Mitochondrial Membranes.

    Science.gov (United States)

    Harner, Max

    2017-01-01

    Mitochondria are essential organelles of all eukaryotic cells. They perform a plethora of important metabolic functions and have a highly complex architecture that differs drastically between different cells and tissues. Mitochondria are delimited from the cytosol by the mitochondrial envelope that consists of the outer membrane and the inner membrane. The inner membrane is subdivided into the inner boundary membrane that runs parallel to the outer membrane and the crista membrane. Both sections of the inner membrane are linked by crista junctions. A further important architectural element of mitochondria are the contact sites between outer membrane and inner membrane. These sites were observed a long time ago by classical electron microscopy, but their molecular structure was identified only recently when it was recognized that proteins of crista junctions and proteins of the outer membrane are responsible for these strong contacts. Mitochondrial function is severely affected when contact sites are disturbed. This underlines the notion that mitochondrial architecture and function are intimately connected. In the following a method is described to generate and to isolate membrane vesicles from isolated yeast mitochondria that contain these contact sites.

  16. Enantioseparation with liquid membranes

    NARCIS (Netherlands)

    Gössi, Angelo; Riedl, Wolfgang; Schuur, Boelo

    Chiral resolution of racemic products is a challenging and important task in the pharmaceutical, agrochemical, flavor, polymer and fragrances industries. One of the options for these challenging separations is to use liquid membranes. Although liquid membranes have been known for almost four decades

  17. Porous ceramic membranes

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Biesheuvel, Pieter Maarten

    2000-01-01

    Synthetic membranes are increasingly used for energy-efficient separation of liquid and gaseous mixtures in household applications, environmental technology and the chemical and energy industry. Besides, membranes are used in component-specific sensors in gas and liquid streams, preferably combined

  18. Polymide gas separation membranes

    Science.gov (United States)

    Ding, Yong; Bikson, Benjamin; Nelson, Joyce Katz

    2004-09-14

    Soluble polyamic acid salt (PAAS) precursors comprised of tertiary and quaternary amines, ammonium cations, sulfonium cations, or phosphonium cations, are prepared and fabricated into membranes that are subsequently imidized and converted into rigid-rod polyimide articles, such as membranes with desirable gas separation properties. A method of enhancing solubility of PAAS polymers in alcohols is also disclosed.

  19. Membrane module assembly

    Science.gov (United States)

    Kaschemekat, Jurgen

    1994-01-01

    A membrane module assembly adapted to provide a flow path for the incoming feed stream that forces it into prolonged heat-exchanging contact with a heating or cooling mechanism. Membrane separation processes employing the module assembly are also disclosed. The assembly is particularly useful for gas separation or pervaporation.

  20. Membrane projection lithography

    Energy Technology Data Exchange (ETDEWEB)

    Burckel, David Bruce; Davids, Paul S; Resnick, Paul J; Draper, Bruce L

    2015-03-17

    The various technologies presented herein relate to a three dimensional manufacturing technique for application with semiconductor technologies. A membrane layer can be formed over a cavity. An opening can be formed in the membrane such that the membrane can act as a mask layer to the underlying wall surfaces and bottom surface of the cavity. A beam to facilitate an operation comprising any of implantation, etching or deposition can be directed through the opening onto the underlying surface, with the opening acting as a mask to control the area of the underlying surfaces on which any of implantation occurs, material is removed, and/or material is deposited. The membrane can be removed, a new membrane placed over the cavity and a new opening formed to facilitate another implantation, etching, or deposition operation. By changing the direction of the beam different wall/bottom surfaces can be utilized to form a plurality of structures.

  1. Membrane technology and applications

    International Nuclear Information System (INIS)

    Khalil, F.H.

    1997-01-01

    The main purpose of this dissertation is to prepare and characterize some synthetic membranes obtained by radiation-induced graft copolymerization of and A Am unitary and binary system onto nylon-6 films. The optimum conditions at which the grafting process proceeded homogeneously were determined. Some selected properties of the prepared membranes were studied. Differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), x-ray diffraction (XRD), mechanical properties and U.V./vis, instruments and techniques were used to characterize the prepared membranes. The use of such membranes for the decontamination of radioactive waste and some heavy metal ions as water pollutants were investigated. These grafted membranes showed good cation exchange properties and may be of practical interest in waste water treatment whether this water was radioactive or not. 4 tabs., 68 figs., 146 refs

  2. Miscibility Critical Points in Plasma Membranes

    Science.gov (United States)

    Machta, Benjamin; Veatch, Sarah; Papanikolaou, Stefanos; Sethna, James P.

    2009-03-01

    Lipid bilayers surround all cells and are home to a host of proteins and lipids that mediate interactions between the cell and its environment. Recent experimental work has shown that simple membranes composed of three lipid components show complex phase behavior at temperatures in the physiological range. For example, two liquid phases and a gel or solid phase are seen, and a second order phase transition with Ising critical behavior can be reached at a boundary of the liquid-liquid coexistence region [1]. Surprisingly, membrane vesicles isolated from living cells can be tuned with a single parameter (temperature) to criticality [1]. This suggests that cell membranes in vivo sit near miscibility critical points, and may help explain some of the paradoxes associated with putative lipid rafts proposed in other experiments. Here we report on work mapping phase diagrams for the simple membranes utilizing NMR and microscopy data. In addition, we use canonical models of phase transitions to understand the qualitative features of the membranes. Finally we explore ideas from information theory and self organized criticality to understand how and why real cells maintain a membrane near criticality. [1] Honerkamp-Smith, Veatch, and Keller, Biochim Biophys Acta. 2008 (in press)

  3. Proteins of the kidney microvillar membrane

    International Nuclear Information System (INIS)

    Booth, A.G.; Kenny, A.J.

    1980-01-01

    Two methods were used to label pig kidney microvillar membrane proteins from the luminal and cytoplasmic surfaces of closed membrane vesicles. The first method was lactoperoxidase-catalysed radioiodination. Lactoperoxidase and glucose oxidase were positioned inside or outside the vesicles, iodination being initiated by adding glucose and 125 I. After electrophoresis of the proteins, asymmetric labelling patterns on radioautographs were observed. However the major disadvantage of this method was the high degree of intramembrane labelling of the fatty acid chains of membrane lipids. The second method overcame this disadvantage. A new hydophilic photoreagent, 3,5-di( 125 I)iodo-4-azidobenzenesulphonate, was transported by a Na + -dependent system into microvillar vesicles, thus permitting labelling from either side of the membrane when the vesicles were photolysed. The activity of several microvillar peptidases survived the labelling reaction and they could be identified in the immunoprecipitates after resolution of the detergent-solubilized membrane proteins by crossed-immunoelectrophoresis. Treatment with papain converted the detergent-solubilized form of susceptible enzymes into the proteinase-solubilized form. Radioautography established that aminopeptidases M and A, dipeptidyl peptidase IV and neutral endopeptidase were transmembrane proteins. This novel approach may be applicable to the topological investigation of other complex membranes. (author)

  4. New penta-saccharide-bearing tripod amphiphiles for membrane protein structure studies

    DEFF Research Database (Denmark)

    Ehsan, Muhammad; Ghani, Lubna; Du, Yang

    2017-01-01

    Integral membrane proteins either alone or as complexes carry out a range of key cellular functions. Detergents are indispensable tools in the isolation of membrane proteins from biological membranes for downstream studies. Although a large number of techniques and tools, including a wide variety...

  5. Atomistic Monte Carlo simulation of lipid membranes

    DEFF Research Database (Denmark)

    Wüstner, Daniel; Sklenar, Heinz

    2014-01-01

    Biological membranes are complex assemblies of many different molecules of which analysis demands a variety of experimental and computational approaches. In this article, we explain challenges and advantages of atomistic Monte Carlo (MC) simulation of lipid membranes. We provide an introduction...... into the various move sets that are implemented in current MC methods for efficient conformational sampling of lipids and other molecules. In the second part, we demonstrate for a concrete example, how an atomistic local-move set can be implemented for MC simulations of phospholipid monomers and bilayer patches...

  6. Lipopolysaccharide Membranes and Membrane Proteins of Pseudomonas aeruginosa Studied by Computer Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Straatsma, TP

    2006-12-01

    Pseudomonas aeruginosa is a ubiquitous environmental Gram-negative bacterium with high metabolic versatility and an exceptional ability to adapt to a wide range of ecological environments, including soil, marches, coastal habitats, plant and animal tissues. Gram-negative microbes are characterized by the asymmetric lipopolysaccharide outer membrane, the study of which is important for a number of applications. The adhesion to mineral surfaces plays a central role in characterizing their contribution to the fate of contaminants in complex environmental systems by effecting microbial transport through soils, respiration redox chemistry, and ion mobility. Another important application stems from the fact that it is also a major opportunistic human pathogen that can result in life-threatening infections in many immunocompromised patients, such as lung infections in children with cystic fibrosis, bacteraemia in burn victims, urinary-tract infections in catheterized patients, hospital-acquired pneumonia in patients on respirators, infections in cancer patients receiving chemotherapy, and keratitis and corneal ulcers in users of extended-wear soft contact lenses. The inherent resistance against antibiotics which has been linked with the specific interactions in the outer membrane of P. aeruginosa makes these infections difficult to treat. Developments in simulation methodologies as well as computer hardware have enabled the molecular simulation of biological systems of increasing size and with increasing accuracy, providing detail that is difficult or impossible to obtain experimentally. Computer simulation studies contribute to our understanding of the behavior of proteins, protein-protein and protein-DNA complexes. In recent years, a number of research groups have made significant progress in applying these methods to the study of biological membranes. However, these applications have been focused exclusively on lipid bilayer membranes and on membrane proteins in lipid

  7. Imaging of blood plasma coagulation at supported lipid membranes.

    Science.gov (United States)

    Faxälv, Lars; Hume, Jasmin; Kasemo, Bengt; Svedhem, Sofia

    2011-12-15

    The blood coagulation system relies on lipid membrane constituents to act as regulators of the coagulation process upon vascular trauma, and in particular the 2D configuration of the lipid membranes is known to efficiently catalyze enzymatic activity of blood coagulation factors. This work demonstrates a new application of a recently developed methodology to study blood coagulation at lipid membrane interfaces with the use of imaging technology. Lipid membranes with varied net charges were formed on silica supports by systematically using different combinations of lipids where neutral phosphocholine (PC) lipids were mixed with phospholipids having either positively charged ethylphosphocholine (EPC), or negatively charged phosphatidylserine (PS) headgroups. Coagulation imaging demonstrated that negatively charged SiO(2) and membrane surfaces exposing PS (obtained from liposomes containing 30% of PS) had coagulation times which were significantly shorter than those for plain PC membranes and EPC exposing membrane surfaces (obtained from liposomes containing 30% of EPC). Coagulation times decreased non-linearly with increasing negative surface charge for lipid membranes. A threshold value for shorter coagulation times was observed below a PS content of ∼6%. We conclude that the lipid membranes on solid support studied with the imaging setup as presented in this study offers a flexible and non-expensive solution for coagulation studies at biological membranes. It will be interesting to extend the present study towards examining coagulation on more complex lipid-based model systems. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. The COMPLEXity in herpesvirus entry.

    Science.gov (United States)

    Sathiyamoorthy, Karthik; Chen, Jia; Longnecker, Richard; Jardetzky, Theodore S

    2017-06-01

    Enveloped viruses have evolved diverse transmembrane proteins and protein complexes to enable host cell entry by regulating and activating membrane fusion in a target cell-specific manner. In general terms, the entry process requires a receptor binding step, an activation step and a membrane fusion step, which can be encoded within a single viral protein or distributed among multiple viral proteins. HIV and influenza virus, for example, encode all of these functions in a single trimeric glycoprotein, HIV env or influenza virus hemagglutinin (HA). In contrast, herpesviruses have the host receptor binding, activation and fusogenic roles distributed among multiple envelope glycoproteins (ranging from three to six), which must coordinate their functions at the site of fusion. Despite the apparent complexity in the number of viral entry proteins, herpesvirus entry is fundamentally built around two core glycoprotein entities: the gHgL complex, which appears to act as an 'activator' of entry, and the gB protein, which is thought to act as the membrane 'fusogen'. Both are required for all herpesvirus fusion and entry. In many herpesviruses, gHgL either binds host receptors directly or assembles into larger complexes with additional viral proteins that bind host receptors, conferring specificity to the cells that are targeted for infection. These gHgL entry complexes (ECs) are centrally important to activating gB-mediated membrane fusion and establishing viral tropism, forming membrane bridging intermediates before gB triggering. Here we review recent structural and functional studies of Epstein-Barr virus (EBV) and Cytomegalovirus (CMV) gHgL complexes that provide a framework for understanding the role of gHgL in herpesvirus entry. Furthermore, a recently determined EM model of Herpes Simplex virus (HSV) gB embedded in exosomes highlights how gB conformational changes may promote viral and cellular membrane fusion. Copyright © 2017. Published by Elsevier B.V.

  9. PERSISTENT PUPILLARY MEMBRANE OR ACCESSORY IRIS MEMBRANE?.

    Science.gov (United States)

    Gavriş, Monica; Horge, Ioan; Avram, Elena; Belicioiu, Roxana; Olteanu, Ioana Alexandra; Kedves, Hanga

    2015-01-01

    Frequently, in literature and curent practice, accessory iris membrane (AIM) and persistant pupillary membrane (PPM) are confused. Both AIM and PPM are congenital iris anomalies in which fine or thick iris strands arrise form the collarette and obscure the pupil. AIM, which is also called iris duplication, closely resembles the normal iris tissue in color and thickness and presents a virtual second pseudopupil aperture in the centre while PPM even in its extreme forms presents as a translucent or opaque membranous structure that extends across the pupil and has no pseudopupil. Mydriatiscs, laser treatment or surgery is used to clear the visual axis and optimize visual development. Surgical intervention is reserved for large, dense AIMs and PPMs. Our patient, a 29 year old male, has come with bilateral dense AIM, bilateral compound hyperopic astigmatism, BCVA OD = 0.6, BCVA OS = 0.4, IOP OU = 17 mmHg. To improve the visual acuity of the patient we decided to do a bilateral membranectomy, restoring in this way transparency of the visual axis. After surgery, the visual acuity improved to BCVA OD= 0.8, BCVA OS=0.8.

  10. Fuel cell membrane humidification

    Science.gov (United States)

    Wilson, Mahlon S.

    1999-01-01

    A polymer electrolyte membrane fuel cell assembly has an anode side and a cathode side separated by the membrane and generating electrical current by electrochemical reactions between a fuel gas and an oxidant. The anode side comprises a hydrophobic gas diffusion backing contacting one side of the membrane and having hydrophilic areas therein for providing liquid water directly to the one side of the membrane through the hydrophilic areas of the gas diffusion backing. In a preferred embodiment, the hydrophilic areas of the gas diffusion backing are formed by sewing a hydrophilic thread through the backing. Liquid water is distributed over the gas diffusion backing in distribution channels that are separate from the fuel distribution channels.

  11. Extracorporeal membrane oxygenation

    Science.gov (United States)

    Extracorporeal membrane oxygenation (ECMO) is a treatment that uses a pump to circulate blood through an artificial lung back into the bloodstream of a very ill baby. This system provides heart-lung bypass support ...

  12. Novel Catalytic Membrane Reactors

    Energy Technology Data Exchange (ETDEWEB)

    None

    2009-02-01

    This factsheet describes a research project that will focus on the development and application of nonporous high gas flux perfluoro membranes with high temperature rating and excellent chemical resistance.

  13. Transmembrane protein sorting driven by membrane curvature

    Science.gov (United States)

    Strahl, H.; Ronneau, S.; González, B. Solana; Klutsch, D.; Schaffner-Barbero, C.; Hamoen, L. W.

    2015-11-01

    The intricate structure of prokaryotic and eukaryotic cells depends on the ability to target proteins to specific cellular locations. In most cases, we have a poor understanding of the underlying mechanisms. A typical example is the assembly of bacterial chemoreceptors at cell poles. Here we show that the classical chemoreceptor TlpA of Bacillus subtilis does not localize according to the consensus stochastic nucleation mechanism but accumulates at strongly curved membrane areas generated during cell division. This preference was confirmed by accumulation at non-septal curved membranes. Localization appears to be an intrinsic property of the protein complex and does not rely on chemoreceptor clustering, as was previously shown for Escherichia coli. By constructing specific amino-acid substitutions, we demonstrate that the preference for strongly curved membranes arises from the curved shape of chemoreceptor trimer of dimers. These findings demonstrate that the intrinsic shape of transmembrane proteins can determine their cellular localization.

  14. Adaptive transition rates in excitable membranes

    Directory of Open Access Journals (Sweden)

    Shimon Marom

    2009-02-01

    Full Text Available Adaptation of activity in excitable membranes occurs over a wide range of timescales. Standard computational approaches handle this wide temporal range in terms of multiple states and related reaction rates emanating from the complexity of ionic channels. The study described here takes a different (perhaps complementary approach, by interpreting ion channel kinetics in terms of population dynamics. I show that adaptation in excitable membranes is reducible to a simple Logistic-like equation in which the essential non-linearity is replaced by a feedback loop between the history of activation and an adaptive transition rate that is sensitive to a single dimension of the space of inactive states. This physiologically measurable dimension contributes to the stability of the system and serves as a powerful modulator of input-output relations that depends on the patterns of prior activity; an intrinsic scale free mechanism for cellular adaptation that emerges from the microscopic biophysical properties of ion channels of excitable membranes.

  15. Nanostructured Polysulfone-Based Block Copolymer Membranes

    KAUST Repository

    Xie, Yihui

    2016-05-01

    The aim of this work is to fabricate nanostructured membranes from polysulfone-based block copolymers through self-assembly and non-solvent induced phase separation. Block copolymers containing polysulfone are novel materials for this purpose providing better mechanical and thermal stability to membranes than polystyrene-based copolymers, which have been exclusively used now. Firstly, we synthesized a triblock copolymer, poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) through 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. Membrane surface hydrolysis was carried out in a combination with metal complexation to obtain metal-chelated membranes. The copper-containing membrane showed improved antibacterial capability. Secondly, a poly(acrylic acid)-b-polysulfone-b-poly(acrylic acid) triblock copolymer obtained by hydrolyzing poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) formed a thin film with cylindrical poly(acrylic acid) microdomains in polysulfone matrix through thermal annealing. A phase inversion membrane was prepared from the same polymer via self-assembly and chelation-assisted non-solvent induced phase separation. The spherical micelles pre-formed in a selective solvent mixture packed into an ordered lattice in aid of metal-poly(acrylic acid) complexation. The space between micelles was filled with poly(acrylic acid)-metal complexes acting as potential water channels. The silver0 nanoparticle-decorated membrane was obtained by surface reduction, having three distinct layers with different particle sizes. Other amphiphilic copolymers containing polysulfone and water-soluble segments such as poly(ethylene glycol) and poly(N-isopropylacrylamide) were also synthesized through coupling reaction and copper0-mediated

  16. Preparation and characterization of the PVDF-based composite membrane for direct methanol fuel cells

    OpenAIRE

    Qian Liu, Laizhou Song, Zhihui Zhang, Xiaowei Liu

    2010-01-01

    The polyvinylidene fluoride-sulfonated polystyrene composite membrane with proton exchange performance, denoted as PVDF-SPS, was prepared using a thermally induced polymerization technique. The thermal stability of the PVDF-SPS composite membrane was investigated using thermogravimetric (TG) analysis. The complex formation of the composite membrane was ascertained by Fourier transform infrared spectroscopy (FTIR). The surface compositions of the PVDF-SPS membrane were analyzed using X-ray pho...

  17. Inverse colloidal crystal membranes for hydrophobic interaction membrane chromatography.

    Science.gov (United States)

    Vu, Anh T; Wang, Xinying; Wickramasinghe, S Ranil; Yu, Bing; Yuan, Hua; Cong, Hailin; Luo, Yongli; Tang, Jianguo

    2015-08-01

    Hydrophobic interaction membrane chromatography has gained interest due to its excellent performance in the purification of humanized monoclonal antibodies. The membrane material used in hydrophobic interaction membrane chromatography has typically been commercially available polyvinylidene fluoride. In this contribution, newly developed inverse colloidal crystal membranes that have uniform pores, high porosity and, therefore, high surface area for protein binding are used as hydrophobic interaction membrane chromatography membranes for humanized monoclonal antibody immunoglobulin G purification. The capacity of the inverse colloidal crystal membranes developed here is up to ten times greater than commercially available polyvinylidene fluoride membranes with a similar pore size. This work highlights the importance of developing uniform pore size high porosity membranes in order to maximize the capacity of hydrophobic interaction membrane chromatography. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Fabrication of electrospun nanofibrous membranes for membrane distillation application

    KAUST Repository

    Francis, Lijo

    2013-02-01

    Nanofibrous membranes of Matrimid have been successfully fabricated using an electrospinning technique under optimized conditions. Nanofibrous membranes are found to be highly hydrophobic with a high water contact angle of 130°. Field emission scanning electron microscopy and pore size distribution analysis revealed the big pore size structure of electrospun membranes to be greater than 2 μm and the pore size distribution is found to be narrow. Flat sheet Matrimid membranes were fabricated via casting followed by phase inversion. The morphology, pore size distribution, and water contact angle were measured and compared with the electrospun membranes. Both membranes fabricated by electrospinning and phase inversion techniques were tested in a direct contact membrane distillation process. Electrospun membranes showed high water vapor flux of 56 kg/m2-h, which is very high compared to the casted membrane as well as most of the fabricated and commercially available highly hydrophobic membranes. ©2013 Desalination Publications.

  19. Bacterial membrane proteomics.

    Science.gov (United States)

    Poetsch, Ansgar; Wolters, Dirk

    2008-10-01

    About one quarter to one third of all bacterial genes encode proteins of the inner or outer bacterial membrane. These proteins perform essential physiological functions, such as the import or export of metabolites, the homeostasis of metal ions, the extrusion of toxic substances or antibiotics, and the generation or conversion of energy. The last years have witnessed completion of a plethora of whole-genome sequences of bacteria important for biotechnology or medicine, which is the foundation for proteome and other functional genome analyses. In this review, we discuss the challenges in membrane proteome analysis, starting from sample preparation and leading to MS-data analysis and quantification. The current state of available proteomics technologies as well as their advantages and disadvantages will be described with a focus on shotgun proteomics. Then, we will briefly introduce the most abundant proteins and protein families present in bacterial membranes before bacterial membrane proteomics studies of the last years will be presented. It will be shown how these works enlarged our knowledge about the physiological adaptations that take place in bacteria during fine chemical production, bioremediation, protein overexpression, and during infections. Furthermore, several examples from literature demonstrate the suitability of membrane proteomics for the identification of antigens and different pathogenic strains, as well as the elucidation of membrane protein structure and function.

  20. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  1. Structural Characterization of Outer Membrane Components of the Type IV Pili System in Pathogenic Neisseria

    NARCIS (Netherlands)

    Jain, Samta; Moscicka, Katarzyna B.; Bos, Martine P.; Pachulec, Emilia; Stuart, Marc C. A.; Keegstra, Wilko; Boekema, Egbert J.; van der Does, Chris; B. Mościcka, K.; Ahmed, Niyaz

    2011-01-01

    Structures of the type IV pili secretin complexes from Neisseria gonorrhoeae and Neisseria meningitidis, embedded in outer membranes were investigated by transmission electron microscopy. Single particle averaging revealed additional domains not observed previously. Secretin complexes of N.

  2. Characterisation and comparison of bacterial communities on reverse osmosis membranes of a full-scale desalination plant by bacterial 16S rRNA gene metabarcoding

    OpenAIRE

    Nagaraj, Veena; Skillman, Lucy; Ho, Goen; Li, Dan; Gofton, Alexander

    2017-01-01

    Microbiomes of full-scale seawater reverse osmosis membranes are complex and subject to variation within and between membrane units. The pre-existing bacterial communities of unused membranes before operation have been largely ignored in biofouling studies. This study is novel as unused membranes were used as a critical benchmark for comparison. Fouled seawater reverse osmosis membrane biofilm communities from an array of autopsied membrane samples, following a 7-year operational life-span in...

  3. Biomimetic membranes and methods of making biomimetic membranes

    Science.gov (United States)

    Rempe, Susan; Brinker, Jeffrey C.; Rogers, David Michael; Jiang, Ying-Bing; Yang, Shaorong

    2016-11-08

    The present disclosure is directed to biomimetic membranes and methods of manufacturing such membranes that include structural features that mimic the structures of cellular membrane channels and produce membrane designs capable of high selectivity and high permeability or adsorptivity. The membrane structure, material and chemistry can be selected to perform liquid separations, gas separation and capture, ion transport and adsorption for a variety of applications.

  4. 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)

  5. NATO Advanced Study Institute on Synthetic Membranes : Science, Engineering and Applications

    CERN Document Server

    Lonsdale, H; Pinho, M

    1986-01-01

    The chapters in this book are based upon lectures given at the NATO Advanced Study Institute on Synthetic Membranes (June 26-July 8, 1983, Alcabideche, Portugal), which provided an integrated presentation of syn­ thetic membrane science and technology in three broad areas. Currently available membrane formation mechanisms are reviewed, as well as the manner in which synthesis conditions can be controlled to achieve desired membrane structures. Membrane performance in a specific separa­ tionprocess involves complex phenomena, the understanding of which re­ quires a multidisciplinary approach encompassing polymer chemistry, phys­ ical chemistry, and chemical engineering. Progress toward a global understanding of membrane phenomena is described in chapters on the principles of membrane transport. The chapters on membrane processes and applications highlight both established and emerging membrane processes, and elucidate their myriad applications. It is our hope that this book will be an enduring, comprehensi...

  6. Phase-field theories for mathematical modeling of biological membranes.

    Science.gov (United States)

    Lázaro, Guillermo R; Pagonabarraga, Ignacio; Hernández-Machado, Aurora

    2015-01-01

    Biological membranes are complex structures whose mechanics are usually described at a mesoscopic level, such as the Helfrich bending theory. In this article, we present the phase-field methods, a useful tool for studying complex membrane problems which can be applied to very different phenomena. We start with an overview of the general theory of elasticity, paying special attention to its derivation from a molecular scale. We then study the particular case of membrane elasticity, explicitly obtaining the Helfrich bending energy. Within the framework of this theory, we derive a phase-field model for biological membranes and explore its physical basis and interpretation in terms of membrane elasticity. We finally explain three examples of applications of these methods to membrane related problems. First, the case of vesicle pearling and tubulation, when lipidic vesicles are exposed to the presence of hydrophobic polymers that anchor to the membrane, inducing a shape instability. Finally, we study the behavior of red blood cells while flowing in narrow microchannels, focusing on the importance of membrane elasticity to the cell flow capabilities. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  7. Spatiotemporal Organization of Spin-Coated Supported Model Membranes

    Science.gov (United States)

    Simonsen, Adam Cohen

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

  8. Engineering Lipid Bilayer Membranes for Protein Studies

    Science.gov (United States)

    Khan, Muhammad Shuja; Dosoky, Noura Sayed; Williams, John Dalton

    2013-01-01

    Lipid membranes regulate the flow of nutrients and communication signaling between cells and protect the sub-cellular structures. Recent attempts to fabricate artificial systems using nanostructures that mimic the physiological properties of natural lipid bilayer membranes (LBM) fused with transmembrane proteins have helped demonstrate the importance of temperature, pH, ionic strength, adsorption behavior, conformational reorientation and surface density in cellular membranes which all affect the incorporation of proteins on solid surfaces. Much of this work is performed on artificial templates made of polymer sponges or porous materials based on alumina, mica, and porous silicon (PSi) surfaces. For example, porous silicon materials have high biocompatibility, biodegradability, and photoluminescence, which allow them to be used both as a support structure for lipid bilayers or a template to measure the electrochemical functionality of living cells grown over the surface as in vivo. The variety of these media, coupled with the complex physiological conditions present in living systems, warrant a summary and prospectus detailing which artificial systems provide the most promise for different biological conditions. This study summarizes the use of electrochemical impedance spectroscopy (EIS) data on artificial biological membranes that are closely matched with previously published biological systems using both black lipid membrane and patch clamp techniques. PMID:24185908

  9. The SEA complex – the beginning

    Directory of Open Access Journals (Sweden)

    Dokudovskaya S. S.

    2012-07-01

    Full Text Available The presence of distinctive internal membrane compartments, dynamically connected via selective transport pathways, is a hallmark of eukaryotic cells. Many of the proteins required for formation and maintenance of these compartments share an evolutionary history. We have recently identified a new conserved protein complex – the SEA complex – that possesses proteins with structural characteristics similar to the membrane coating complexes such as the nuclear pore complex (NPC, the COPII vesicle coating complex and HOPS/CORVET tethering complexes. The SEA complex in yeast is dynamically associated to the vacuole. The data on the function of the SEA complex remain extremely limited. Here we will discuss a possible role of the SEA complex based on the data from genetic assays and a number of functional studies in both yeast and other eukaryotes.

  10. Role of membrane contact sites in protein import into mitochondria.

    Science.gov (United States)

    Horvath, Susanne E; Rampelt, Heike; Oeljeklaus, Silke; Warscheid, Bettina; van der Laan, Martin; Pfanner, Nikolaus

    2015-03-01

    Mitochondria import more than 1,000 different proteins from the cytosol. The proteins are synthesized as precursors on cytosolic ribosomes and are translocated by protein transport machineries of the mitochondrial membranes. Five main pathways for protein import into mitochondria have been identified. Most pathways use the translocase of the outer mitochondrial membrane (TOM) as the entry gate into mitochondria. Depending on specific signals contained in the precursors, the proteins are subsequently transferred to different intramitochondrial translocases. In this article, we discuss the connection between protein import and mitochondrial membrane architecture. Mitochondria possess two membranes. It is a long-standing question how contact sites between outer and inner membranes are formed and which role the contact sites play in the translocation of precursor proteins. A major translocation contact site is formed between the TOM complex and the presequence translocase of the inner membrane (TIM23 complex), promoting transfer of presequence-carrying preproteins to the mitochondrial inner membrane and matrix. Recent findings led to the identification of contact sites that involve the mitochondrial contact site and cristae organizing system (MICOS) of the inner membrane. MICOS plays a dual role. It is crucial for maintaining the inner membrane cristae architecture and forms contacts sites to the outer membrane that promote translocation of precursor proteins into the intermembrane space and outer membrane of mitochondria. The view is emerging that the mitochondrial protein translocases do not function as independent units, but are embedded in a network of interactions with machineries that control mitochondrial activity and architecture. © 2014 The Protein Society.

  11. Parallel artificial liquid membrane extraction

    DEFF Research Database (Denmark)

    Gjelstad, Astrid; Rasmussen, Knut Einar; Parmer, Marthe Petrine

    2013-01-01

    This paper reports development of a new approach towards analytical liquid-liquid-liquid membrane extraction termed parallel artificial liquid membrane extraction. A donor plate and acceptor plate create a sandwich, in which each sample (human plasma) and acceptor solution is separated by an arti...... by an artificial liquid membrane. Parallel artificial liquid membrane extraction is a modification of hollow-fiber liquid-phase microextraction, where the hollow fibers are replaced by flat membranes in a 96-well plate format....

  12. An Integrated Framework Advancing Membrane Protein Modeling and Design.

    Directory of Open Access Journals (Sweden)

    Rebecca F Alford

    2015-09-01

    Full Text Available Membrane proteins are critical functional molecules in the human body, constituting more than 30% of open reading frames in the human genome. Unfortunately, a myriad of difficulties in overexpression and reconstitution into membrane mimetics severely limit our ability to determine their structures. Computational tools are therefore instrumental to membrane protein structure prediction, consequently increasing our understanding of membrane protein function and their role in disease. Here, we describe a general framework facilitating membrane protein modeling and design that combines the scientific principles for membrane protein modeling with the flexible software architecture of Rosetta3. This new framework, called RosettaMP, provides a general membrane representation that interfaces with scoring, conformational sampling, and mutation routines that can be easily combined to create new protocols. To demonstrate the capabilities of this implementation, we developed four proof-of-concept applications for (1 prediction of free energy changes upon mutation; (2 high-resolution structural refinement; (3 protein-protein docking; and (4 assembly of symmetric protein complexes, all in the membrane environment. Preliminary data show that these algorithms can produce meaningful scores and structures. The data also suggest needed improvements to both sampling routines and score functions. Importantly, the applications collectively demonstrate the potential of combining the flexible nature of RosettaMP with the power of Rosetta algorithms to facilitate membrane protein modeling and design.

  13. Stress-sensor device based on flexoelectric liquid crystalline membranes.

    Science.gov (United States)

    Rey, Alejandro D; Servio, Phillip; Herrera Valencia, Edtson Emilio

    2014-05-19

    Membrane flexoelectricity is an electromechanical coupling process that describes membrane bending and membrane electrical polarization caused by bending under electric fields. In this paper we propose, formulate, and characterize a stress-sensor device for mechanically loaded solids, consisting of a soft flexoelectric thin membrane attached to the loaded deformed solid. Because the curvature of the deformed solid is transferred to the attached flexoelectric membrane, the electromechanical transduction of the latter produces a charge that is proportional to the stress of the solid. The model of the stress-sensor device is based on the integration of the thermodynamics of polarizable membranes with isotropic solid elasticity, leading to a transfer function that identifies the elastic, electromechanical, and geometrical parameters involved in electrical-signal generation. The model is applied to representative normal bending and then to more complex off-axis bending of elastic bars. In all cases, a common transfer function shows the generic material and its geometric contributions. The sensor sensitivity increases linearly with flexoelectricity and the membrane-solid interface, and the sensitivity decreases with increasing membrane thickness and Young's modulus of the solid. The theoretical results contribute to ongoing experimental efforts towards the development of anisotropic soft-matter-based stress-sensor devices through solid-membrane interactions and electromechanical transduction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Smart membranes for monitoring membrane based desalination processes

    KAUST Repository

    Laleg-Kirati, Taous-Meriem

    2017-10-12

    Various examples are related to smart membranes for monitoring membrane based process such as, e.g., membrane distillation processes. In one example, a membrane, includes a porous surface and a plurality of sensors (e.g., temperature, flow and/or impedance sensors) mounted on the porous surface. In another example, a membrane distillation (MD) process includes the membrane. Processing circuitry can be configured to monitor outputs of the plurality of sensors. The monitored outputs can be used to determine membrane degradation, membrane fouling, or to provide an indication of membrane replacement or cleaning. The sensors can also provide temperatures or temperature differentials across the porous surface, which can be used to improve modeling or control the MD process.

  15. Recent advances on polymeric membranes for membrane reactors

    KAUST Repository

    Buonomenna, M. G.

    2012-06-24

    Membrane reactors are generally applied in high temperature reactions (>400 °C). In the field of fine chemical synthesis, however, much milder conditions are generally applicable and polymeric membranes were applied without their damage. The successful use of membranes in membrane reactors is primary the result of two developments concerning: (i) membrane materials and (ii) membrane structures. The selection of a suited material and preparation technique depends on the application the membrane is to be used in. In this chapter a review of up to date literature about polymers and configuration catalyst/ membranes used in some recent polymeric membrane reactors is given. The new emerging concept of polymeric microcapsules as catalytic microreactors has been proposed. © 2012 Bentham Science Publishers. All rights reserved.

  16. Specific interaction of postsynaptic densities with membrane rafts isolated from synaptic plasma membranes.

    Science.gov (United States)

    Liu, Qian; Yao, Wei-Dong; Suzuki, Tatsuo

    2013-06-01

    Postsynaptic membrane rafts are believed to play important roles in synaptic signaling, plasticity, and maintenance. We recently demonstrated the presence, at the electron microscopic level, of complexes consisting of membrane rafts and postsynaptic densities (PSDs) in detergent-resistant membranes (DRMs) prepared from synaptic plasma membranes (SPMs) ( Suzuki et al., 2011 , J Neurochem, 119, 64-77). To further explore these complexes, here we investigated the nature of the binding between purified SPM-DRMs and PSDs in vitro. In binding experiments, we used SPM-DRMs prepared after treating SPMs with n-octyl-β-d-glucoside, because at concentrations of 1.0% or higher it completely separates SPM-DRMs and PSDs, providing substantially PSD-free unique SPM-DRMs as well as DRM-free PSDs. PSD binding to PSD-free DRMs was identified by mass spectrometry, Western blotting, and electron microscopy. PSD proteins were not incorporated into SPMs, and significantly less PSD proteins were incorporated into DRMs prepared from liver membranes, providing in vitro evidence that binding of PSDs to DRMs is specific and suggestion of the presence of specific interacting molecules. These specific interactions may have important roles in synaptic development, function, and plasticity in vivo. In addition, the binding system we developed may be a good tool to search for binding molecules and binding mechanisms between PSDs and rafts.

  17. SNARE-fusion mediated insertion of membrane proteins into native and artificial membranes.

    Science.gov (United States)

    Nordlund, Gustav; Brzezinski, Peter; von Ballmoos, Christoph

    2014-07-02

    Membrane proteins carry out functions such as nutrient uptake, ATP synthesis or transmembrane signal transduction. An increasing number of reports indicate that cellular processes are underpinned by regulated interactions between these proteins. Consequently, functional studies of these networks at a molecular level require co-reconstitution of the interacting components. Here, we report a SNARE protein-based method for incorporation of multiple membrane proteins into artificial membrane vesicles of well-defined composition, and for delivery of large water-soluble substrates into these vesicles. The approach is used for in vitro reconstruction of a fully functional bacterial respiratory chain from purified components. Furthermore, the method is used for functional incorporation of the entire F1F0 ATP synthase complex into native bacterial membranes from which this component had been genetically removed. The novel methodology offers a tool to investigate complex interaction networks between membrane-bound proteins at a molecular level, which is expected to generate functional insights into key cellular functions.

  18. Membranes and Fluorescence microscopy

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2009-01-01

    Fluorescence spectroscopy-based techniques using conventional fluorimeters have been extensively applied since the late 1960s to study different aspects of membrane-related phenomena, i.e., mainly relating to lipid-lipid and lipid-protein (peptide) interactions. Even though fluorescence spectrosc......Fluorescence spectroscopy-based techniques using conventional fluorimeters have been extensively applied since the late 1960s to study different aspects of membrane-related phenomena, i.e., mainly relating to lipid-lipid and lipid-protein (peptide) interactions. Even though fluorescence...... spectroscopy approaches provide very valuable structurally and dynamically related information on membranes, they generally produce mean parameters from data collected on bulk solutions of many vesicles and lack direct information on the spatial organization at the level of single membranes, a quality that can...... be provided by microscopy-related techniques. In this chapter, I will attempt to summarize representative examples concerning how microscopy (which provides information on membrane lateral organization by direct visualization) and spectroscopy techniques (which provides information about molecular interaction...

  19. Liver plasma membranes: an effective method to analyze membrane proteome.

    Science.gov (United States)

    Cao, Rui; Liang, Songping

    2012-01-01

    Plasma membrane proteins are critical for the maintenance of biological systems and represent important targets for the treatment of disease. The hydrophobicity and low abundance of plasma membrane proteins make them difficult to analyze. The protocols given here are the efficient isolation/digestion procedures for liver plasma membrane proteomic analysis. Both protocol for the isolation of plasma membranes and protocol for the in-gel digestion of gel-embedded plasma membrane proteins are presented. The later method allows the use of a high detergent concentration to achieve efficient solubilization of hydrophobic plasma membrane proteins while avoiding interference with the subsequent LC-MS/MS analysis.

  20. The Tat System for Membrane Translocation of Folded Proteins Recruits the Membrane-stabilizing Psp Machinery in Escherichia coli*

    Science.gov (United States)

    Mehner, Denise; Osadnik, Hendrik; Lünsdorf, Heinrich; Brüser, Thomas

    2012-01-01

    Tat systems transport folded proteins across energized membranes of bacteria, archaea, and plant plastids. In Escherichia coli, TatBC complexes recognize the transported proteins, and TatA complexes are recruited to facilitate transport. We achieved an abstraction of TatA from membranes without use of detergents and observed a co-purification of PspA, a membrane-stress response protein. The N-terminal transmembrane domain of TatA was required for the interaction. Electron microscopy displayed TatA complexes in direct contact with PspA. PspB and PspC were important for the TatA-PspA contact. The activator protein PspF was not involved in the PspA-TatA interaction, demonstrating that basal levels of PspA already interact with TatA. Elevated TatA levels caused membrane stress that induced a strictly PspBC- and PspF-dependent up-regulation of PspA. TatA complexes were found to destabilize membranes under these conditions. At native TatA levels, PspA deficiency clearly affected anaerobic TMAO respiratory growth, suggesting that energetic costs for transport of large Tat substrates such as TMAO reductase can become growth limiting in the absence of PspA. The physiological role of PspA recruitment to TatA may therefore be the control of membrane stress at active translocons. PMID:22689583

  1. Membranes and pathophysiological mineralization.

    Science.gov (United States)

    Roszkowska, Monika; Strzelecka-Kiliszek, Agnieszka; Magne, David; Pikula, Slawomir; Bessueille, Laurence

    Vascular calcification accompanies the pathological process of atherosclerotic plaque formation. Artery calcification results from trans-differentiation of vascular smooth muscle cells (VSMCs) into cells resembling mineralization-competent cells such as osteoblasts and chondrocytes. The activity of tissue-nonspecific alkaline phosphatase (TNAP), a GPI-anchored enzyme necessary for physiological mineralization, is induced in VSMCs in response to inflammation. TNAP achieves its mineralizing function being anchored to plasma membrane of mineralizing cells and to the surface of their derived matrix vesicles (MVs), and numerous important reports indicate that membranes play a crucial role in initiating the crystal formation. In this review, we would like to highlight various functions of lipids and proteins associated to membranes at different stages of both physiological mineralization and vascular calcification, with an emphasis on the pathological process of atherosclerotic plaque formation.

  2. Characterization of graphene membranes

    Science.gov (United States)

    O'Hern, Sean; Lee, Jongho; Jain, Tarun; Karnik, Rohit; Idrobo, Juan; Laoui, Tahar; Atieh, Motaz

    2011-11-01

    Graphene, which exhibits very high breaking strength, atomistic thickness, and the ability to maintain stable nanometer-scale pores, has the potential to be a superior membrane material in both liquid- and gas-phase separation processes. We have recently demonstrated high-quality transfer of ~1 cm2 LPCVD graphene from copper foil to 200 nm polycarbonate track etch membranes with less than 0.3% of the area constituting holes or tears in the graphene, which is essential for characterizing transport through graphene. Through gallium ion bombardment we have introduced nanometer-scale pores in the transferred graphene and will report on the molecular and ionic transport through these membranes. Funded by the Center for Clean Energy and Water at MIT and KFUPM.

  3. Hybrid Filter Membrane

    Science.gov (United States)

    Laicer, Castro; Rasimick, Brian; Green, Zachary

    2012-01-01

    Cabin environmental control is an important issue for a successful Moon mission. Due to the unique environment of the Moon, lunar dust control is one of the main problems that significantly diminishes the air quality inside spacecraft cabins. Therefore, this innovation was motivated by NASA s need to minimize the negative health impact that air-suspended lunar dust particles have on astronauts in spacecraft cabins. It is based on fabrication of a hybrid filter comprising nanofiber nonwoven layers coated on porous polymer membranes with uniform cylindrical pores. This design results in a high-efficiency gas particulate filter with low pressure drop and the ability to be easily regenerated to restore filtration performance. A hybrid filter was developed consisting of a porous membrane with uniform, micron-sized, cylindrical pore channels coated with a thin nanofiber layer. Compared to conventional filter media such as a high-efficiency particulate air (HEPA) filter, this filter is designed to provide high particle efficiency, low pressure drop, and the ability to be regenerated. These membranes have well-defined micron-sized pores and can be used independently as air filters with discreet particle size cut-off, or coated with nanofiber layers for filtration of ultrafine nanoscale particles. The filter consists of a thin design intended to facilitate filter regeneration by localized air pulsing. The two main features of this invention are the concept of combining a micro-engineered straight-pore membrane with nanofibers. The micro-engineered straight pore membrane can be prepared with extremely high precision. Because the resulting membrane pores are straight and not tortuous like those found in conventional filters, the pressure drop across the filter is significantly reduced. The nanofiber layer is applied as a very thin coating to enhance filtration efficiency for fine nanoscale particles. Additionally, the thin nanofiber coating is designed to promote capture of

  4. Mechanism of coupling drug transport reactions located in two different membranes

    Directory of Open Access Journals (Sweden)

    Helen I. Zgurskaya

    2015-02-01

    Full Text Available Gram- negative bacteria utilize a diverse array of multidrug transporters to pump toxic compounds out of cells. Some transporters together with periplasmic membrane fusion proteins (MFPs and outer membrane channels assemble trans-envelope complexes that expel multiple antibiotics across outer membranes of Gram-negative bacteria and into the external medium. Others further potentiate this efflux by pumping drugs across the inner membrane into the periplasm. Together these transporters create a powerful network of efflux that protect bacteria against a broad range of antimicrobial agents. This review is focused on the mechanism of coupling transport reactions located in two different membranes of Gram-negative bacteria. Using a combination of biochemical, genetic and biophysical approaches we have reconstructed the sequence of events leading to the assembly of trans-envelope drug efflux complexes and characterized the roles of periplasmic and outer membrane proteins in this process. Our recent data suggest a critical step in the activation of intermembrane efflux pumps, which is controlled by MFPs. We propose that the reaction cycles of transporters are tightly coupled to the assembly of the trans-envelope complexes. Transporters and MFPs exist in the inner membrane as dormant complexes. The activation of complexes is triggered by MFP binding to the outer membrane channel, which leads to a conformational change in the membrane proximal domain of MFP needed for stimulation of transporters. The activated MFP-transporter complex engages the outer membrane channel to expel substrates across the outer membrane. The recruitment of the channel is likely triggered by binding of effectors (substrates to MFP or MFP-transporter complexes. This model together with recent structural and functional advances in the field of drug efflux provides a fairly detailed understanding of the mechanism of drug efflux across the two membranes.

  5. Membrane adsorber for endotoxin removal

    Directory of Open Access Journals (Sweden)

    Karina Moita de Almeida

    Full Text Available ABSTRACT The surface of flat-sheet nylon membranes was modified using bisoxirane as the spacer and polyvinyl alcohol as the coating polymer. The amino acid histidine was explored as a ligand for endotoxins, aiming at its application for endotoxin removal from aqueous solutions. Characterization of the membrane adsorber, analysis of the depyrogenation procedures and the evaluation of endotoxin removal efficiency in static mode are discussed. Ligand density of the membranes was around 7 mg/g dry membrane, allowing removal of up to 65% of the endotoxins. The performance of the membrane adsorber prepared using nylon coated with polyvinyl alcohol and containing histidine as the ligand proved superior to other membrane adsorbers reported in the literature. The lack of endotoxin adsorption on nylon membranes without histidine confirmed that endotoxin removal was due to the presence of the ligand at the membrane surface. Modified membranes were highly stable, exhibiting a lifespan of approximately thirty months.

  6. Doping phosphoric acid in polybenzimidazole membranes for high temperature proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    He, Ronghuan; Li, Qingfeng; Jensen, Jens Oluf

    2007-01-01

    Polybenzimidazole (PBI) membranes were doped in phosphoric acid solutions of different concentrations at room temperature. The doping chemistry was studied using the Scatchard method. The energy distribution of the acid complexation in polymer membranes is heterogeneous, that is, there are two...... different types of sites in PBI for the acid doping. The protonation constants of PBI by phosphoric acid are found to be 12.7 L mol(-1) (K-1) for acid complexing sites with higher affinity, and 0.19 L mol(-1) (K-2) for the sites with lower affinity. The dissociation constants for the complexing acid onto...... these two types of PBI sites are found to be 5.4 X 10(-4) and 3.6 X 10(-2), respectively, that is, about 10 times smaller than that of aqueous phosphoric acid in the first case but 5 times higher in the second. The proton conducting mechanism is also discussed....

  7. Fouling resistant membrane spacers

    KAUST Repository

    Ghaffour, Noreddine

    2017-10-12

    Disclosed herein are spacers having baffle designs and perforations for efficiently and effectively separating one or more membrane layers a membrane filtration system. The spacer (504) includes a body (524) formed at least in part by baffles (520) that are interconnected, and the baffles define boundaries of openings or apertures (525) through a thickness direction of the body of the spacer. Alternatively or additionally, passages or perforations (526A, 526B) may be present in the spacer layer or baffles for fluid flow there through, with the passages and baffles having a numerous different shapes and sizes.

  8. Mitigating leaks in membranes

    Energy Technology Data Exchange (ETDEWEB)

    Karnik, Rohit N.; Bose, Suman; Boutilier, Michael S.H.; Hadjiconstantinou, Nicolas G.; Jain, Tarun Kumar; O' Hern, Sean C.; Laoui, Tahar; Atieh, Muataz A.; Jang, Doojoon

    2018-02-27

    Two-dimensional material based filters, their method of manufacture, and their use are disclosed. In one embodiment, a membrane may include an active layer including a plurality of defects and a deposited material associated with the plurality of defects may reduce flow therethrough. Additionally, a majority of the active layer may be free from the material. In another embodiment, a membrane may include a porous substrate and an atomic layer deposited material disposed on a surface of the porous substrate. The atomic layer deposited material may be less hydrophilic than the porous substrate and an atomically thin active layer may be disposed on the atomic layer deposited material.

  9. Organic separations with membranes

    International Nuclear Information System (INIS)

    Funk, E.W.

    1993-01-01

    This paper presents an overview of present and emerging applications of membrane technology for the separation and purification of organic materials. This technology is highly relevant for programs aimed at minimizing waste in processing and in the treatment of gaseous and liquid effluents. Application of membranes for organic separation is growing rapidly in the petrochemical industry to simplify processing and in the treatment of effluents, and it is expected that this technology will be useful in numerous other industries including the processing of nuclear waste materials

  10. Unraveling the role of membrane microdomains during microbial infections.

    Science.gov (United States)

    Bagam, Prathyusha; Singh, Dhirendra P; Inda, Maria Eugenia; Batra, Sanjay

    2017-10-01

    Infectious diseases pose major socioeconomic and health-related threats to millions of people across the globe. Strategies to combat infectious diseases derive from our understanding of the complex interactions between the host and specific bacterial, viral, and fungal pathogens. Lipid rafts are membrane microdomains that play important role in life cycle of microbes. Interaction of microbial pathogens with host membrane rafts influences not only their initial colonization but also their spread and the induction of inflammation. Therefore, intervention strategies aimed at modulating the assembly of membrane rafts and/or regulating raft-directed signaling pathways are attractive approaches for the. management of infectious diseases. The current review discusses the latest advances in terms of techniques used to study the role of membrane microdomains in various pathological conditions and provides updated information regarding the role of membrane rafts during bacterial, viral and fungal infections.

  11. Silver-enhanced block copolymer membranes with biocidal activity

    KAUST Repository

    Madhavan, Poornima

    2014-11-12

    Silver nanoparticles were deposited on the surface and pore walls of block copolymer membranes with highly ordered pore structure. Pyridine blocks constitute the pore surfaces, complexing silver ions and promoting a homogeneous distribution. Nanoparticles were then formed by reduction with sodium borohydride. The morphology varied with the preparation conditions (pH and silver ion concentration), as confirmed by field emission scanning and transmission electron microscopy. Silver has a strong biocide activity, which for membranes can bring the advantage of minimizing the growth of bacteria and formation of biofilm. The membranes with nanoparticles prepared under different pH values and ion concentrations were incubated with Pseudomonas aeruginosa and compared with the control. The strongest biocidal activity was achieved with membranes containing membranes prepared under pH 9. Under these conditions, the best distribution with small particle size was observed by microscopy.

  12. Membrane order in the plasma membrane and endocytic recycling compartment.

    Science.gov (United States)

    Iaea, David B; Maxfield, Frederick R

    2017-01-01

    The cholesterol content of membranes plays an important role in organizing membranes for signal transduction and protein trafficking as well as in modulating the biophysical properties of membranes. While the properties of model or isolated membranes have been extensively studied, there has been little evaluation of internal membranes in living cells. Here, we use a Nile Red based probe, NR12S, and ratiometric live cell imaging, to analyze the membrane order of the plasma membrane and endocytic recycling compartment. We find that after a brief incubation to allow endocytosis, NR12S is distributed between the plasma membrane and the endocytic recycling compartment. The NR12S reports that the endocytic recycling compartment is more highly ordered than the plasma membrane. We also find that the plasma membrane and the endocytic recycling compartment are differentially affected by altering cellular cholesterol levels. The membrane order of the plasma membrane, but not the endocytic recycling compartment, is altered significantly when cellular cholesterol content is increased or decreased by 20%. These results demonstrate that changes in cellular cholesterol differentially alter membrane order within different organelles.

  13. Dimensional analysis of membrane distillation flux through fibrous membranes

    Science.gov (United States)

    Mauter, Meagan

    We developed a dimensional-analysis-based empirical modeling method for membrane distillation (MD) flux that is adaptable for novel membrane structures. The method makes fewer simplifying assumptions about membrane pore geometry than existing theoretical (i.e. mechanistic) models, and allows selection of simple, easily-measureable membrane characteristics as structural parameters. Furthermore, the model does not require estimation of membrane surface temperatures; it accounts for convective heat transfer to the membrane surface without iterative fitting of mass and heat transfer equations. The Buckingham-Pi dimensional analysis method is tested for direct contact membrane distillation (DCMD) using non-woven/fibrous structures as the model membrane material. Twelve easily-measured variables to describe DCMD operating conditions, fluid properties, membrane structures, and flux were identified and combined into eight dimensionless parameters. These parameters were regressed using experimentally-collected data for multiple electrospun membrane types and DCMD system conditions, achieving R2 values >95%. We found that vapor flux through isotropic fibrous membranes can be estimated using only membrane thickness, solid fraction, and fiber diameter as structural parameters. Buckingham-Pi model DCMD flux predictions compare favorably with previously-developed empirical and theoretical models, and suggest this simple yet theoretically-grounded empirical modeling method can be used practically for predicting MD vapor flux from membrane structural parameters.

  14. Fouling in Membrane Distillation, Osmotic Distillation and Osmotic Membrane Distillation

    Directory of Open Access Journals (Sweden)

    Mourad Laqbaqbi

    2017-03-01

    Full Text Available Various membrane separation processes are being used for seawater desalination and treatment of wastewaters in order to deal with the worldwide water shortage problem. Different types of membranes of distinct morphologies, structures and physico-chemical characteristics are employed. Among the considered membrane technologies, membrane distillation (MD, osmotic distillation (OD and osmotic membrane distillation (OMD use porous and hydrophobic membranes for production of distilled water and/or concentration of wastewaters for recovery and recycling of valuable compounds. However, the efficiency of these technologies is hampered by fouling phenomena. This refers to the accumulation of organic/inorganic deposits including biological matter on the membrane surface and/or in the membrane pores. Fouling in MD, OD and OMD differs from that observed in electric and pressure-driven membrane processes such electrodialysis (ED, membrane capacitive deionization (MCD, reverse osmosis (RO, nanofiltration (NF, ultrafiltration (UF, microfiltration (MF, etc. Other than pore blockage, fouling in MD, OD and OMD increases the risk of membrane pores wetting and reduces therefore the quantity and quality of the produced water or the concentration efficiency of the process. This review deals with the observed fouling phenomena in MD, OD and OMD. It highlights different detected fouling types (organic fouling, inorganic fouling and biofouling, fouling characterization techniques as well as various methods of fouling reduction including pretreatment, membrane modification, membrane cleaning and antiscalants application.

  15. Complexity explained

    CERN Document Server

    Erdi, Peter

    2008-01-01

    This book explains why complex systems research is important in understanding the structure, function and dynamics of complex natural and social phenomena. Readers will learn the basic concepts and methods of complex system research.

  16. [Formation of purple membranes during salt bacteria cultivation].

    Science.gov (United States)

    Chekulaeva, L N; Korolev, Iu N; Telegin, N L; Rikhireva, G T

    1975-01-01

    Experiments have been carried out on cultivation of halophile with probe selection in the interval of 1--2 hours to record the spectra of repeated disturbed completed inner reflection. Periodicity in the changes of spectral characteristics of the culture with the interval of 20--24 hours is revealed. A clearly expressed dichroism of the amid II band of the membrane complex is found, the absence of this dichroism in the protein isolated from the membrane complex is stated. It is suggested that dichroism revealed is a specific feature of the presence of purpuric membranes in the cells. Spontaneous plane orientation of protein macromolecules in purpuric membranes is established. The level of dichroism of amid II band is shown to depend on fermentation conditions of salt bacteria.

  17. Microencapsulation within crosslinked polyethyleneimine membranes.

    Science.gov (United States)

    Poncelet, D; Alexakis, T; Poncelet de Smet, B; Neufeld, R J

    1994-01-01

    A microencapsulation technique is proposed involving the formation of a polyethyleneimine (PEI) membrane crosslinked by an acid dichloride. The membranes were formed at pH 8 in a non-polar solvent, conditions which are better suited for the encapsulation of biocatalysts or fragile biochemicals than those using polyamide membranes. The mean diameter and size distribution of the PEI microcapsules were similar to that observed with nylon membranes. The resultant microcapsules were spherical, free-flowing with a strong membrane. The mass of membrane was seen to be independent of the reaction time (1-4 min), insensitive to the PEI concentration and proportional to the concentration of crosslinking agent.

  18. Complex chemistry

    International Nuclear Information System (INIS)

    Kim, Bong Gon; Kim, Jae Sang; Kim, Jin Eun; Lee, Boo Yeon

    2006-06-01

    This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

  19. Consequences of membrane protein overexpression in Escherichia coli.

    Science.gov (United States)

    Wagner, Samuel; Baars, Louise; Ytterberg, A Jimmy; Klussmeier, Anja; Wagner, Claudia S; Nord, Olof; Nygren, Per-Ake; van Wijk, Klaas J; de Gier, Jan-Willem

    2007-09-01

    Overexpression of membrane proteins is often essential for structural and functional studies, but yields are frequently too low. An understanding of the physiological response to overexpression is needed to improve such yields. Therefore, we analyzed the consequences of overexpression of three different membrane proteins (YidC, YedZ, and LepI) fused to green fluorescent protein (GFP) in the bacterium Escherichia coli and compared this with overexpression of a soluble protein, GST-GFP. Proteomes of total lysates, purified aggregates, and cytoplasmic membranes were analyzed by one- and two-dimensional gel electrophoresis and mass spectrometry complemented with flow cytometry, microscopy, Western blotting, and pulse labeling experiments. Composition and accumulation levels of protein complexes in the cytoplasmic membrane were analyzed with improved two-dimensional blue native PAGE. Overexpression of the three membrane proteins, but not soluble GST-GFP, resulted in accumulation of cytoplasmic aggregates containing the overexpressed proteins, chaperones (DnaK/J and GroEL/S), and soluble proteases (HslUV and ClpXP) as well as many precursors of periplasmic and outer membrane proteins. This was consistent with lowered accumulation levels of secreted proteins in the three membrane protein overexpressors and is likely to be a direct consequence of saturation of the cytoplasmic membrane protein translocation machinery. Importantly accumulation levels of respiratory chain complexes in the cytoplasmic membrane were strongly reduced. Induction of the acetate-phosphotransacetylase pathway for ATP production and a down-regulated tricarboxylic acid cycle indicated the activation of the Arc two-component system, which mediates adaptive responses to changing respiratory states. This study provides a basis for designing rational strategies to improve yields of membrane protein overexpression in E. coli.

  20. Detailed Analysis of the Human Mitochondrial Contact Site Complex Indicate a Hierarchy of Subunits

    OpenAIRE

    Ott, Christine; Dorsch, Eva; Fraunholz, Martin; Straub, Sebastian; Kozjak-Pavlovic, Vera

    2015-01-01

    Mitochondrial inner membrane folds into cristae, which significantly increase its surface and are important for mitochondrial function. The stability of cristae depends on the mitochondrial contact site (MICOS) complex. In human mitochondria, the inner membrane MICOS complex interacts with the outer membrane sorting and assembly machinery (SAM) complex, to form the mitochondrial intermembrane space bridging complex (MIB). We have created knockdown cell lines of most of the MICOS and MIB compo...

  1. The exocyst at the interface between cytoskeleton and membranes in eukaryotic cells

    Directory of Open Access Journals (Sweden)

    Lukas eSynek

    2014-01-01

    Full Text Available Delivery and final fusion of the secretory vesicles with the relevant target membrane are hierarchically organized and reciprocally interconnected multi-step processes involving not only specific protein-protein interactions, but also specific protein-phospholipid interactions. The exocyst was discovered as a tethering complex mediating initial encounter of arriving exocytic vesicles with the plasma membrane. The exocyst complex is regulated by Rab and Rho small GTPases, resulting in docking of exocytic vesicles to the plasma membrane and finally their fusion mediated by specific SNARE complexes. In model Opisthokont cells, the exocyst was shown to directly interact with both microtubule and microfilament cytoskeleton and related motor proteins as well as with the plasma membrane via phosphatidylinositol 4,5-bisphosphate specific binding, which directly affects cortical cytoskeleton and plasma membrane dynamics. Here we summarize the current knowledge on exocyst-cytoskeleton-plasma membrane interactions in order to open a perspective for future research in this area in plant cells.

  2. Adaptive silicone-membrane lenses: planar vs. shaped membrane

    CSIR Research Space (South Africa)

    Schneider, F

    2009-08-01

    Full Text Available In this paper the authors compare the performance and optical quality of two types of adaptive fluidic silicone-membrane lenses. The membranes feature either a homogeneous thickness, or it is shaped resulting in an inhomogeneous cross...

  3. Axon-glia interaction and membrane traffic in myelin formation

    OpenAIRE

    White, Robin; Krämer-Albers, Eva-Maria

    2014-01-01

    In vertebrate nervous systems myelination of neuronal axons has evolved to increase conduction velocity of electrical impulses with minimal space and energy requirements. Myelin is formed by specialized glial cells which ensheath axons with a lipid-rich insulating membrane. Myelination is a multi-step process initiated by axon-glia recognition triggering glial polarization followed by targeted myelin membrane expansion and compaction. Thereby, a myelin sheath of complex subdomain structure is...

  4. Hydrogen-selective membrane

    Science.gov (United States)

    Collins, J.P.; Way, J.D.

    1997-07-29

    A hydrogen-selective membrane comprises a tubular porous ceramic support having a palladium metal layer deposited on an inside surface of the ceramic support. The thickness of the palladium layer is greater than about 10 {micro}m but typically less than about 20 {micro}m. The hydrogen permeation rate of the membrane is greater than about 1.0 moles/m{sup 2} s at a temperature of greater than about 500 C and a transmembrane pressure difference of about 1,500 kPa. Moreover, the hydrogen-to-nitrogen selectivity is greater than about 600 at a temperature of greater than about 500 C and a transmembrane pressure of about 700 kPa. Hydrogen can be separated from a mixture of gases using the membrane. The method may include the step of heating the mixture of gases to a temperature of greater than about 400 C and less than about 1000 C before the step of flowing the mixture of gases past the membrane. The mixture of gases may include ammonia. The ammonia typically is decomposed to provide nitrogen and hydrogen using a catalyst such as nickel. The catalyst may be placed inside the tubular ceramic support. The mixture of gases may be supplied by an industrial process such as the mixture of exhaust gases from the IGCC process. 9 figs.

  5. Fusion of biological membranes

    Indian Academy of Sciences (India)

    small hemifusion diaphragm. To obtain a direct view of the fusion process, we have carried out extensive simulations of two bilayers, composed of block copolymers, which are immersed in a solvent which favors one of the blocks. As in the biological case, the membranes are placed under tension. This is essential as fusion ...

  6. Cell Membrane Coating Nanotechnology.

    Science.gov (United States)

    Fang, Ronnie H; Kroll, Ashley V; Gao, Weiwei; Zhang, Liangfang

    2018-03-27

    Nanoparticle-based therapeutic, prevention, and detection modalities have the potential to greatly impact how diseases are diagnosed and managed in the clinic. With the wide range of nanomaterials available, the rational design of nanocarriers on an application-specific basis has become increasingly commonplace. Here, a comprehensive overview is provided on an emerging platform: cell-membrane-coating nanotechnology. As a fundamental unit of biology, cells carry out a wide range of functions, including the remarkable ability to interface and interact with their surrounding environment. Instead of attempting to replicate such functions via synthetic techniques, researchers are now directly leveraging naturally derived cell membranes as a means of bestowing nanoparticles with enhanced biointerfacing capabilities. This top-down technique is facile, highly generalizable, and has the potential to greatly augment existing nanocarriers. Further, the introduction of a natural membrane substrate onto nanoparticles surfaces has enabled additional applications beyond those traditionally associated with nanomedicine. Despite its relative youth, there exists an impressive body of literature on cell membrane coating, which is covered here in detail. Overall, there is still significant room for development, as researchers continue to refine existing workflows while finding new and exciting applications that can take advantage of this developing technology. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Fusion of biological membranes

    Indian Academy of Sciences (India)

    Logo of the Indian Academy of Sciences. Indian Academy of ... Home; Journals; Pramana – Journal of Physics; Volume 64; Issue 6. Fusion of biological ... The process of membrane fusion has been examined by Monte Carlo simulation, and is found to be very different than the conventional picture. The differences in ...

  8. Bioelectrochemistry II membrane phenomena

    CERN Document Server

    Blank, M

    1987-01-01

    This book contains the lectures of the second course devoted to bioelectro­ chemistry, held within the framework of the International School of Biophysics. In this course another very large field of bioelectrochemistry, i. e. the field of Membrane Phenomena, was considered, which itself consists of several different, but yet related subfields. Here again, it can be easily stated that it is impossible to give a complete and detailed picture of all membrane phenomena of biological interest in a short course of about one and half week. Therefore the same philosophy, as the one of the first course, was followed, to select a series of lectures at postgraduate level, giving a synthesis of several membrane phenomena chosen among the most'important ones. These lectures should show the large variety of membrane-regulated events occurring in living bodies, and serve as sound interdisciplinary basis to start a special­ ized study of biological phenomena, for which the investigation using the dual approach, physico-che...

  9. Fusion of biological membranes

    Indian Academy of Sciences (India)

    Abstract. The process of membrane fusion has been examined by Monte Carlo simu- lation, and is found to be very different than the conventional picture. The differences in mechanism lead to several predictions, in particular that fusion is accompanied by tran- sient leakage. This prediction has recently been verified.

  10. Extracorporeal membrane oxygenation (ECMO)

    African Journals Online (AJOL)

    Extracorporeal membrane oxygenation (ECMO) is increasingly being employed in South African intensive care units for the management of patients with refractory hypoxaemia and for haemodynamic support, particularly following cardiothoracic procedures. ECMO is expensive, however, and there is a danger that this ...

  11. Fusion of biological membranes

    Indian Academy of Sciences (India)

    The process of membrane fusion has been examined by Monte Carlo simulation, and is found to be very different than the conventional picture. The differences in mechanism lead to several predictions, in particular that fusion is accompanied by transient leakage. This prediction has recently been verified. Self-consistent ...

  12. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-02-01

    This is the fifth quarterly report on a new study to develop a ceramic membrane/metal joint. Results of wetting experiments on commercially available Nickel based brazing alloys on perovskite surfaces are described. Additionally, experimental and numerical investigations on the strength of concentric ceramic/metal joints are presented.

  13. Nanodisc-solubilized membrane protein library reflects the membrane proteome

    OpenAIRE

    Marty, Michael T.; Wilcox, Kyle C.; Klein, William L.; Sligar, Stephen G.

    2013-01-01

    The isolation and identification of unknown membrane proteins offers the prospect of discovering new pharmaceutical targets and identifying key biochemical receptors. However, interactions between membrane protein targets and soluble ligands are difficult to study in vitro due to the insolubility of membrane proteins in non-detergent systems. Nanodiscs, nanoscale discoidal lipid bilayers encircled by a membrane scaffold protein belt, have proven to be an effective platform to solubilize membr...

  14. The plasma membrane proteome of germinating barley embryos

    DEFF Research Database (Denmark)

    Hynek, Radovan; Svensson, Birte; Jensen, O.N.

    2009-01-01

    Cereal seed germination involves a complex coordination between different seed tissues. Plasma membranes must play crucial roles in coordination and execution of germination; however, very little is known about seed plasma membrane proteomes due to limited tissue amounts combined with amphiphilic...... was used to reduce soluble protein contamination and enrich for hydrophobic proteins. Sixty-one proteins in 14 SDS-PAGE bands were identified by LC-MS/MS and database searches. The identifications provide new insight into the plasma membrane functions in seed germination....

  15. Structural Aspects of Bacterial Outer Membrane Protein Assembly.

    Science.gov (United States)

    Calmettes, Charles; Judd, Andrew; Moraes, Trevor F

    2015-01-01

    The outer membrane of Gram-negative bacteria is predominantly populated by β-Barrel proteins and lipid anchored proteins that serve a variety of biological functions. The proper folding and assembly of these proteins is essential for bacterial viability and often plays a critical role in virulence and pathogenesis. The β-barrel assembly machinery (Bam) complex is responsible for the proper assembly of β-barrels into the outer membrane of Gram-negative bacteria, whereas the localization of lipoproteins (Lol) system is required for proper targeting of lipoproteins to the outer membrane.

  16. Membrane interactions and antimicrobial effects of inorganic nanoparticles

    DEFF Research Database (Denmark)

    Malekkhaiat Häffner, Sara; Malmsten, Martin

    2017-01-01

    . Although the performance in these diverse applications is governed by a complex interplay between the nanomaterial, the properties of included drugs (if any), and the biological system, nanoparticle-membrane interactions constitute a key initial step and play a key role for the subsequent biological...... on nanoparticle properties, membrane composition, and external (e.g., light and magnetic) fields.......Interactions between nanoparticles and biological membranes are attracting increasing attention in current nanomedicine, and play a key role both for nanotoxicology and for utilizing nanomaterials in diagnostics, drug delivery, functional biomaterials, as well as combinations of these, e...

  17. Effect of γ-irradiated carbohydrates on isolated synaptic membranes

    International Nuclear Information System (INIS)

    Kaler, G.V.; Lyskova, T.I.; Shadyro, O.I.; Samoilenko, S.G.; Edimecheva, I.P.; Aksentsev, S.L.; Konev, S.V.

    1993-01-01

    The effect of γ-irradiated solutions of carbohydrates, mainly glucose, upon Na + , K + -ATPase and lipid peroxidation in rat brain synaptosomal membranes was studied. The membrane damage by irradiated glucose was enhanced in the presence of Fe 2+ and was diminished when a free-radical scavenger (BHT) or metal chelators (EDTA, EGTA) were present. It is suggested that a key element in the free-radical membrane damage by irradiated carbohydrates is an Fe 2+ -complex of some species of the radiolysis products. Participation of radiotoxins of carbohydrate origin in radiogbiological effects is discussed. (orig.)

  18. Membrane fission by protein crowding.

    Science.gov (United States)

    Snead, Wilton T; Hayden, Carl C; Gadok, Avinash K; Zhao, Chi; Lafer, Eileen M; Rangamani, Padmini; Stachowiak, Jeanne C

    2017-04-18

    Membrane fission, which facilitates compartmentalization of biological processes into discrete, membrane-bound volumes, is essential for cellular life. Proteins with specific structural features including constricting rings, helical scaffolds, and hydrophobic membrane insertions are thought to be the primary drivers of fission. In contrast, here we report a mechanism of fission that is independent of protein structure-steric pressure among membrane-bound proteins. In particular, random collisions among crowded proteins generate substantial pressure, which if unbalanced on the opposite membrane surface can dramatically increase membrane curvature, leading to fission. Using the endocytic protein epsin1 N-terminal homology domain (ENTH), previously thought to drive fission by hydrophobic insertion, our results show that membrane coverage correlates equally with fission regardless of the hydrophobicity of insertions. Specifically, combining FRET-based measurements of membrane coverage with multiple, independent measurements of membrane vesiculation revealed that fission became spontaneous as steric pressure increased. Further, fission efficiency remained equally potent when helices were replaced by synthetic membrane-binding motifs. These data challenge the view that hydrophobic insertions drive membrane fission, suggesting instead that the role of insertions is to anchor proteins strongly to membrane surfaces, amplifying steric pressure. In line with these conclusions, even green fluorescent protein (GFP) was able to drive fission efficiently when bound to the membrane at high coverage. Our conclusions are further strengthened by the finding that intrinsically disordered proteins, which have large hydrodynamic radii yet lack a defined structure, drove fission with substantially greater potency than smaller, structured proteins.

  19. Dialysis membranes for blood purification.

    Science.gov (United States)

    Sakai, K

    2000-01-01

    All of the artificial membranes in industrial use, such as a reverse-osmosis membrane, dialysis membrane, ultrafiltration membrane, microfiltration membrane and gas separation membrane, also have therapeutic applications. The most commonly used artificial organ is the artificial kidney, a machine that performs treatment known as hemodialysis. This process cleanses the body of a patient with renal failure by dialysis and filtration, simple physicochemical processes. Hemodialysis membranes are used to remove accumulated uremic toxins, excess ions and water from the patient via the dialysate, and to supply (deficit) insufficient ions from the dialysate. Dialysis membranes used clinically in the treatment of patients with renal failure account for by far the largest volume of membranes used worldwide; more than 70 million square meters are used a year. Almost all dialyzers now in use are of the hollow-fiber type. A hollow-fiber dialyzer contains a bundle of approximately 10000 hollow fibers, each with an inner diameter of about 200 microm when wet. The membrane thickness is about 20-45 microm, and the length is 160-250 mm. The walls of the hollow fibers function as the dialysis membrane. Various materials, including cellulose-based materials and synthetic polymers, are used for dialysis membranes. This paper reviews blood purification, hemodialysis and dialysis membranes.

  20. Alternative energy efficient membrane bioreactor using reciprocating submerged membrane.

    Science.gov (United States)

    Ho, J; Smith, S; Roh, H K

    2014-01-01

    A novel membrane bioreactor (MBR) pilot system, using membrane reciprocation instead of air scouring, was operated at constant high flux and daily fluctuating flux to demonstrate its application under peak and diurnal flow conditions. Low and stable transmembrane pressure was achieved at 40 l/m(2)/h (LMH) by use of repetitive membrane reciprocation. The results reveal that the inertial forces acting on the membrane fibers effectively propel foulants from the membrane surface. Reciprocation of the hollow fiber membrane is beneficial for the constant removal of solids that may build up on the membrane surface and inside the membrane bundle. The membrane reciprocation in the reciprocating MBR pilot consumed less energy than coarse air scouring used in conventional MBR systems. Specific energy consumption for the membrane reciprocation was 0.072 kWh/m(3) permeate produced at 40 LMH flux, which is 75% less than for a conventional air scouring system as reported in literature without consideration of energy consumption for biological aeration (0.29 kWh/m(3)). The daily fluctuating flux test confirmed that the membrane reciprocation is effective to handle fluctuating flux up to 50 LMH. The pilot-scale reciprocating MBR system successfully demonstrated that fouling can be controlled via 0.43 Hz membrane reciprocation with 44 mm or higher amplitude.

  1. Dissecting Escherichia coli outer membrane biogenesis using differential proteomics.

    Directory of Open Access Journals (Sweden)

    Alessandra M Martorana

    Full Text Available The cell envelope of Gram-negative bacteria is a complex multi-layered structure comprising an inner cytoplasmic membrane and an additional asymmetric lipid bilayer, the outer membrane, which functions as a selective permeability barrier and is essential for viability. Lipopolysaccharide, an essential glycolipid located in the outer leaflet of the outer membrane, greatly contributes to the peculiar properties exhibited by the outer membrane. This complex molecule is transported to the cell surface by a molecular machine composed of seven essential proteins LptABCDEFG that form a transenvelope complex and function as a single device. While advances in understanding the mechanisms that govern the biogenesis of the cell envelope have been recently made, only few studies are available on how bacterial cells respond to severe envelope biogenesis defects on a global scale. Here we report the use of differential proteomics based on Multidimensional Protein Identification Technology (MudPIT to investigate how Escherichia coli cells respond to a block of lipopolysaccharide transport to the outer membrane. We analysed the envelope proteome of a lptC conditional mutant grown under permissive and non permissive conditions and identified 123 proteins whose level is modulated upon LptC depletion. Most such proteins belong to pathways implicated in cell envelope biogenesis, peptidoglycan remodelling, cell division and protein folding. Overall these data contribute to our understanding on how E. coli cells respond to LPS transport defects to restore outer membrane functionality.

  2. Membrane Cells for Brine Electrolysis.

    Science.gov (United States)

    Tingle, M.

    1982-01-01

    Membrane cells were developed as alternatives to mercury and diaphragm cells for the electrolysis of brine. Compares the three types of cells, focusing on the advantages and disadvantages of membrane cells. (JN)

  3. Membrane Targeting of P-type ATPases in Plant Cells

    International Nuclear Information System (INIS)

    Harper, Jeffrey F.

    2004-01-01

    How membrane proteins are targeted to specific subcellular locations is a very complex and poorly understood area of research. Our long-term goal is to use P-type ATPases (ion pumps), in a model plant system Arabidopsis, as a paradigm to understand how members of a family of closely related membrane proteins can be targeted to different subcellular locations. The research is divided into two specific aims. The first aim is focused on determining the targeting destination of all 10 ACA-type calcium pumps (Arabidopsis Calcium ATPase) in Arabidopsis. ACAs represent a plant specific-subfamily of plasma membrane-type calcium pumps. In contrast to animals, the plant homologs have been found in multiple membrane systems, including the ER (ACA2), tonoplast (ACA4) and plasma membrane (ACA8). Their high degree of similarity provides a unique opportunity to use a comparative approach to delineate the membrane specific targeting information for each pump. One hypothesis to be tested is that an endomembrane located ACA can be re-directed to the plasma membrane by including targeting information from a plasma membrane isoform, ACA8. Our approach is to engineer domain swaps between pumps and monitor the targeting of chimeric proteins in plant cells using a Green Fluorescence Protein (GFP) as a tag. The second aim is to test the hypothesis that heterologous transporters can be engineered into plants and targeted to the plasma membrane by fusing them to a plasma membrane proton pump. As a test case we are evaluating the targeting properties of fusions made between a yeast sodium/proton exchanger (Sod2) and a proton pump (AHA2). This fusion may potentially lead to a new strategy for engineering salt resistant plants. Together these aims are designed to provide fundamental insights into the biogenesis and function of plant cell membrane systems

  4. Membrane Targeting of P-type ATPases in Plant Cells

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey F. Harper, Ph.D.

    2004-06-30

    How membrane proteins are targeted to specific subcellular locations is a very complex and poorly understood area of research. Our long-term goal is to use P-type ATPases (ion pumps), in a model plant system Arabidopsis, as a paradigm to understand how members of a family of closely related membrane proteins can be targeted to different subcellular locations. The research is divided into two specific aims. The first aim is focused on determining the targeting destination of all 10 ACA-type calcium pumps (Arabidopsis Calcium ATPase) in Arabidopsis. ACAs represent a plant specific-subfamily of plasma membrane-type calcium pumps. In contrast to animals, the plant homologs have been found in multiple membrane systems, including the ER (ACA2), tonoplast (ACA4) and plasma membrane (ACA8). Their high degree of similarity provides a unique opportunity to use a comparative approach to delineate the membrane specific targeting information for each pump. One hypothesis to be tested is that an endomembrane located ACA can be re-directed to the plasma membrane by including targeting information from a plasma membrane isoform, ACA8. Our approach is to engineer domain swaps between pumps and monitor the targeting of chimeric proteins in plant cells using a Green Fluorescence Protein (GFP) as a tag. The second aim is to test the hypothesis that heterologous transporters can be engineered into plants and targeted to the plasma membrane by fusing them to a plasma membrane proton pump. As a test case we are evaluating the targeting properties of fusions made between a yeast sodium/proton exchanger (Sod2) and a proton pump (AHA2). This fusion may potentially lead to a new strategy for engineering salt resistant plants. Together these aims are designed to provide fundamental insights into the biogenesis and function of plant cell membrane systems.

  5. Direct quantification of negatively charged functional groups on membrane surfaces

    KAUST Repository

    Tiraferri, Alberto

    2012-02-01

    Surface charge plays an important role in membrane-based separations of particulates, macromolecules, and dissolved ionic species. In this study, we present two experimental methods to determine the concentration of negatively charged functional groups at the surface of dense polymeric membranes. Both techniques consist of associating the membrane surface moieties with chemical probes, followed by quantification of the bound probes. Uranyl acetate and toluidine blue O dye, which interact with the membrane functional groups via complexation and electrostatic interaction, respectively, were used as probes. The amount of associated probes was quantified using liquid scintillation counting for uranium atoms and visible light spectroscopy for the toluidine blue dye. The techniques were validated using self-assembled monolayers of alkanethiols with known amounts of charged moieties. The surface density of negatively charged functional groups of hand-cast thin-film composite polyamide membranes, as well as commercial cellulose triacetate and polyamide membranes, was quantified under various conditions. Using both techniques, we measured a negatively charged functional group density of 20-30nm -2 for the hand-cast thin-film composite membranes. The ionization behavior of the membrane functional groups, determined from measurements with toluidine blue at varying pH, was consistent with published data for thin-film composite polyamide membranes. Similarly, the measured charge densities on commercial membranes were in general agreement with previous investigations. The relative simplicity of the two methods makes them a useful tool for quantifying the surface charge concentration of a variety of surfaces, including separation membranes. © 2011 Elsevier B.V.

  6. Pore-scale modeling and simulation of flow, transport, and adsorptive or osmotic effects in membranes: the influence of membrane microstructure

    KAUST Repository

    Calo, Victor M.

    2015-07-17

    The selection of an appropriate membrane for a particular application is a complex and expensive process. Computational modeling can significantly aid membrane researchers and manufacturers in this process. The membrane morphology is highly influential on its efficiency within several applications, but is often overlooked in simulation. Two such applications which are very important in the provision of clean water are forward osmosis and filtration using functionalized micro/ultra/nano-filtration membranes. Herein, we investigate the effect of the membrane morphology in these two applications. First we present results of the separation process using resolved finger- and sponge-like support layers. Second, we represent the functionalization of a typical microfiltration membrane using absorptive pore walls, and illustrate the effect of different microstructures on the reactive process. Such numerical modeling will aid manufacturers in optimizing operating conditions and designing efficient membranes.

  7. Correlation between membrane fluidity cellular development and stem cell differentiation

    KAUST Repository

    Noutsi, Pakiza

    2016-12-01

    Cell membranes are made up of a complex structure of lipids and proteins that diffuse laterally giving rise to what we call membrane fluidity. During cellular development, such as neuronal differentiation, cell membranes undergo dramatic structural changes induced by proteins such as ARC and Cofilin among others in the case of synaptic modification. In this study we used the generalized polarization (GP) property of fluorescent probe Laurdan using two-photon microscopy to determine membrane fluidity as a function of time and for various cell lines. A low GP value corresponds to a higher fluidity and a higher GP value is associated with a more rigid membrane. Four different cell lines were monitored such as hN2, NIH3T3, HEK293 and L6 cells. As expected, NIH3T3 cells have more rigid membrane at earlier stages of their development. On the other hand neurons tend to have the highest membrane fluidity early in their development emphasizing its correlation with plasticity and the need for this malleability during differentiation. This study sheds light on the involvement of membrane fluidity during neuronal differentiation and development of other cell lines.

  8. Design of block copolymer membranes using segregation strength trend lines

    KAUST Repository

    Sutisna, Burhannudin

    2016-05-18

    Block copolymer self-assembly and non-solvent induced phase separation are now being combined to fabricate membranes with narrow pore size distribution and high porosity. The method has the potential to be used with a broad range of tailor-made block copolymers to control functionality and selectivity for specific separations. However, the extension of this process to any new copolymer is challenging and time consuming, due to the complex interplay of influencing parameters, such as solvent composition, polymer molecular weights, casting solution concentration, and evaporation time. We propose here an effective method for designing new block copolymer membranes. The method consists of predetermining a trend line for the preparation of isoporous membranes, obtained by computing solvent properties, interactions and copolymer block sizes for a set of successful systems and using it as a guide to select the preparation conditions for new membranes. We applied the method to membranes based on poly(styrene-b-ethylene oxide) diblocks and extended it to newly synthesized poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) terpolymers. The trend line method can be generally applied to other new systems and is expected to dramatically shorten the path of isoporous membrane manufacture. The PS-b-P2VP-b-PEO membrane formation was investigated by in situ Grazing Incident Small Angle X-ray Scattering (GISAXS), which revealed a hexagonal micelle order with domain spacing clearly correlated to the membrane interpore distances.

  9. Modelling of proteins in membranes

    DEFF Research Database (Denmark)

    Sperotto, Maria Maddalena; May, S.; Baumgaertner, A.

    2006-01-01

    This review describes some recent theories and simulations of mesoscopic and microscopic models of lipid membranes with embedded or attached proteins. We summarize results supporting our understanding of phenomena for which the activities of proteins in membranes are expected to be significantly...... oppositely charged lipid membranes, lipid-induced tilting of proteins embedded in lipid bilayers, protein-induced bilayer deformations, protein insertion and assembly, and lipid-controlled functioning of membrane proteins....

  10. The lipid organisation of the cell membrane

    Directory of Open Access Journals (Sweden)

    Ladha, S.

    2000-04-01

    Full Text Available Lipids and proteins in biological membranes are arranged in a mosaic of domains in the membrane. These domains represent small-scale heterogeneities in composition, shape and fluidity within the plane of the membrane, over the range of hundreds of nanometers to a few micrometers. They arise from the complex interactions of the heterogeneous mixtures of phospholipids, sterols, and proteins that make up all biological membranes.Los lípidos y las proteínas en las membranas biológicas están dispuestos en un mosaico de campos en la membrana. Estos campos representan heterogeneidades a pequeña escala en la composición, forma y fluidez dentro del plano de la membrana, en un rango que va de los cientos de nanómetros a los pocos micrómetros. Estos campos se originan de las complejas interacciones de las mezclas heterogéneas de fosfolípidos, esteroles y proteínas de las que están hechas todas y cada una de las membranas biológicas.

  11. Fundamentals of membrane bioreactors materials, systems and membrane fouling

    CERN Document Server

    Ladewig, Bradley

    2017-01-01

    This book provides a critical, carefully researched, up-to-date summary of membranes for membrane bioreactors. It presents a comprehensive and self-contained outline of the fundamentals of membrane bioreactors, especially their relevance as an advanced water treatment technology. This outline helps to bring the technology to the readers’ attention, and positions the critical topic of membrane fouling as one of the key impediments to its more widescale adoption. The target readership includes researchers and industrial practitioners with an interest in membrane bioreactors.

  12. Cheap Thin Film Oxygen Membranes

    DEFF Research Database (Denmark)

    2009-01-01

    The present invention provides a membrane, comprising a porous support layer a gas tight electronically and ionically conducting membrane layer and a catalyst layer, characterized in that the electronically and ionically conducting membrane layer is formed from a material having a crystallite...

  13. Unit membrane parameters of electrically syncytial tissues.

    Science.gov (United States)

    Levin, D N

    1981-07-01

    A change in the holding voltage, exposure to channel-blocking agents, and similar interventions will induce changes in the membrane properties of electrically syncytial tissues. The altered membrane characteristics will produce changes in the input resistance (RIN) and the phase angle (phi) of the complex admittance of the whole preparation. Exact geometry-independent formulas are derived that give the intervention-induced changes in the membrane capacitance and conductance in terms of the measured changes in RIN and phi. The formulas automatically account for the effects of extracellular resistance in tissues such as skeletal muscle fibers, cardiac Purkinje fibers, and small cardiac "aggregates." The size, shape, and resistance of the extracellular space may be arbitrary and need not be measured. The surface (invaginated) membranes, which face the bath (extracellular space), are assumed to be characterized by an RC circuit with specific capacity Cme (Cmi) and specific conductivity gme (gmi). It is assumed that the intracellular voltage gradient between the electrodes and the membranes is negligible or reliably calculable. The intervention is assumed to leave the geometry and resistivity of the extracellular space unchanged. Under these circumstances the intervention-induced changes in Cme, Cmi, gme, and gmi are determined exactly in terms of the corresponding changes in RIN and certain frequency domain integrals over phi. The technique is illustrated by synthetic data for RIN and phi generated by the "disk" model of a skeletal muscle fiber in which Cme and Cmi depend upon holding voltage. The corresponding voltage dependence of RIN and phi is successfully "inverted" to expose the underlying voltage dependence of Cme and Cmi. These computations suggest that the formulas for Cme and Cmi will be useful in realistic situations, since they are not too sensitive to experimental error in the data for RIN and phi. This method makes it possible to detect voltage

  14. Membrane Assisted Enzyme Fractionation

    DEFF Research Database (Denmark)

    Yuan, Linfeng

    . In this thesis, separations using crossflow elecro-membrane filtration (EMF) of amino acids, bovine serum albumin (BSA) and industrial enzymes from Novozymes were performed. The main objective of this study was to investigate the technological feasibility of EMF in the application of industrial enzyme...... fractionation, such as removal of a side activity from the main enzyme activity. As a proof-of-concept, amino acids were used as model solution to test the feasibility of EMF in the application of amphoteric molecule separation. A single amino acid was used to illustrate the effect of an electric field...... on the separation performance were very small in the investigated range. The mass transport of each enzyme can be well explained by the Extended-Nernst-Planck equation. Better separation was observed at lower feed concentration, higher solution pH in the investigated range and with a polysulfone (PS) MF membrane...

  15. Building membrane nanopores

    Science.gov (United States)

    Howorka, Stefan

    2017-07-01

    Membrane nanopores--hollow nanoscale barrels that puncture biological or synthetic membranes--have become powerful tools in chemical- and biosensing, and have achieved notable success in portable DNA sequencing. The pores can be self-assembled from a variety of materials, including proteins, peptides, synthetic organic compounds and, more recently, DNA. But which building material is best for which application, and what is the relationship between pore structure and function? In this Review, I critically compare the characteristics of the different building materials, and explore the influence of the building material on pore structure, dynamics and function. I also discuss the future challenges of developing nanopore technology, and consider what the next-generation of nanopore structures could be and where further practical applications might emerge.

  16. Aquaporin-2 membrane targeting

    DEFF Research Database (Denmark)

    Olesen, Emma T B; Fenton, Robert A

    2017-01-01

    The targeting of the water channel aquaporin-2 (AQP2) to the apical plasma membrane of kidney collecting duct principal cells is regulated mainly by the antidiuretic peptide hormone arginine vasopressin (AVP). This process is of crucial importance for the maintenance of body water homeostasis....... In this brief review we assess the role of cyclic adenosine monophosphate (cAMP) and discuss the emerging concept that type 2 AVP receptor (V2R)-mediated AQP2 trafficking is cAMP-independent. the ability of the kidney to concentrate the urine and thereby maintain body water homeostasis depends on targeting....... For example, 1) stimulation with the nonspecific AC activator forskolin increases AQP2 membrane accumulation in a mouse cortical collecting duct cell line [e.g., Norregaard et al. (16)]; 2) cAMP increases CD water permeability (15); 3) the cAMP-activated protein kinase A (PKA) can phosphorylate AQP2 on its...

  17. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2003-01-01

    In the present quarter, experiments are presented on ceramic/metal interactions of Zirconia/Ni-B-Si system and with a thin Ti coating deposited on zirconia surface. Processing of perovskites of LSC, LSF and LSCF composition for evaluation of mechanical properties as a function of environment are begun. The studies are to be in parallel with LSFCO composition to characterize the segregation of cations and slow crack growth in environmental conditions. La{sub 1-x}Sr{sub x}FeO{sub 3-d} has also been characterized for paramagnetic ordering at room temperature and the evolution of magnetic moments as a function of temperature are investigated. Investigation on the thermodynamic properties of the membrane materials are continued to develop a complete model for the membrane transport.

  18. Application of dynamic membranes in anaerobic membranes in anaerobic membrane bioreactor systems

    OpenAIRE

    Erşahin, M.E.

    2015-01-01

    Anaerobic membrane bioreactors (AnMBRs) physically ensure biomass retention by the application of a membrane filtration process. With growing application experiences from aerobic membrane bioreactors (MBRs), the combination of membrane and anaerobic processes has received much attention and become more attractive and feasible, due to advantages provided by the combination with regard to developments for energy-efficient wastewater treatment. The major drawbacks of MBR technology are related w...

  19. Pulse radiolysis studies of model membranes

    International Nuclear Information System (INIS)

    Heijman, M.G.J.

    1984-01-01

    In this thesis the influence of the structure of membranes on the processes in cell membranes were examined. Different models of the membranes were evaluated. Pulse radiolysis was used as the technique to examine the membranes. (R.B.)