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Sample records for monocot thylakoid membranes

  1. Visualizing structural dynamics of thylakoid membranes

    Science.gov (United States)

    Iwai, Masakazu; Yokono, Makio; Nakano, Akihiko

    2014-01-01

    To optimize photosynthesis, light-harvesting antenna proteins regulate light energy dissipation and redistribution in chloroplast thylakoid membranes, which involve dynamic protein reorganization of photosystems I and II. However, direct evidence for such protein reorganization has not been visualized in live cells. Here we demonstrate structural dynamics of thylakoid membranes by live cell imaging in combination with deconvolution. We observed chlorophyll fluorescence in the antibiotics-induced macrochloroplast in the moss Physcomitrella patens. The three-dimensional reconstruction uncovered the fine thylakoid membrane structure in live cells. The time-lapse imaging shows that the entire thylakoid membrane network is structurally stable, but the individual thylakoid membrane structure is flexible in vivo. Our observation indicates that grana serve as a framework to maintain structural integrity of the entire thylakoid membrane network. Both the structural stability and flexibility of thylakoid membranes would be essential for dynamic protein reorganization under fluctuating light environments. PMID:24442007

  2. Interfacial properties and emulsification performance of thylakoid membrane fragments

    NARCIS (Netherlands)

    Tamayo Tenorio, A.; Jong, de E.W.M.; Nikiforidis, K.; Boom, R.M.; Goot, van der A.J.

    2017-01-01

    Thylakoids membranes are sophisticated, dynamic structures found in plant leaves, composed of protein complexes in a dynamic lipid matrix. The interfacial absorption dynamics and viscoelasticity of thylakoid membranes fragments were measured to assess the properties of the interfacial layer and to e

  3. Revealing the Dynamics of Thylakoid Membranes in Living Cyanobacterial Cells

    Science.gov (United States)

    Stingaciu, Laura-Roxana; O'Neill, Hugh; Liberton, Michelle; Urban, Volker S.; Pakrasi, Himadri B.; Ohl, Michael

    2016-01-01

    Cyanobacteria are photosynthetic prokaryotes that make major contributions to the production of the oxygen in the Earth atmosphere. The photosynthetic machinery in cyanobacterial cells is housed in flattened membrane structures called thylakoids. The structural organization of cyanobacterial cells and the arrangement of the thylakoid membranes in response to environmental conditions have been widely investigated. However, there is limited knowledge about the internal dynamics of these membranes in terms of their flexibility and motion during the photosynthetic process. We present a direct observation of thylakoid membrane undulatory motion in vivo and show a connection between membrane mobility and photosynthetic activity. High-resolution inelastic neutron scattering experiments on the cyanobacterium Synechocystis sp. PCC 6803 assessed the flexibility of cyanobacterial thylakoid membrane sheets and the dependence of the membranes on illumination conditions. We observed softer thylakoid membranes in the dark that have three-to four fold excess mobility compared to membranes under high light conditions. Our analysis indicates that electron transfer between photosynthetic reaction centers and the associated electrochemical proton gradient across the thylakoid membrane result in a significant driving force for excess membrane dynamics. These observations provide a deeper understanding of the relationship between photosynthesis and cellular architecture.

  4. Genome-wide analysis of thylakoid-bound ribosomes in maize reveals principles of cotranslational targeting to the thylakoid membrane.

    Science.gov (United States)

    Zoschke, Reimo; Barkan, Alice

    2015-03-31

    Chloroplast genomes encode ∼ 37 proteins that integrate into the thylakoid membrane. The mechanisms that target these proteins to the membrane are largely unexplored. We used ribosome profiling to provide a comprehensive, high-resolution map of ribosome positions on chloroplast mRNAs in separated membrane and soluble fractions in maize seedlings. The results show that translation invariably initiates off the thylakoid membrane and that ribosomes synthesizing a subset of membrane proteins subsequently become attached to the membrane in a nuclease-resistant fashion. The transition from soluble to membrane-attached ribosomes occurs shortly after the first transmembrane segment in the nascent peptide has emerged from the ribosome. Membrane proteins whose translation terminates before emergence of a transmembrane segment are translated in the stroma and targeted to the membrane posttranslationally. These results indicate that the first transmembrane segment generally comprises the signal that links ribosomes to thylakoid membranes for cotranslational integration. The sole exception is cytochrome f, whose cleavable N-terminal cpSecA-dependent signal sequence engages the thylakoid membrane cotranslationally. The distinct behavior of ribosomes synthesizing the inner envelope protein CemA indicates that sorting signals for the thylakoid and envelope membranes are distinguished cotranslationally. In addition, the fractionation behavior of ribosomes in polycistronic transcription units encoding both membrane and soluble proteins adds to the evidence that the removal of upstream ORFs by RNA processing is not typically required for the translation of internal genes in polycistronic chloroplast mRNAs.

  5. The molecular architecture of the chloroplast thylakoid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Stefansson, H.

    1996-08-01

    Non-detergent procedure for isolation of sub-thylakoid vesicle populations derived from different structural domains of the chloroplast thylakoid membrane has been developed. Sub-thylakoid vesicles representing the grana, grana core, stroma lamellae, and the grana margins have been isolated and their protein composition has been investigated. Furthermore a novel non-detergent procedure for investigating the pigment composition of photosynthetic complexes located in the different structural domains has been developed. This procedure circumvents selective extractions, an perturbing effect often combined with detergent isolations of membrane bound protein complexes. The fractionation experiments show that the NADPH dehydrogenase, suggested to operate as NADPH or ferredoxin-plastoquinone oxidoreductase in cyclic electron transport around photosystem I, is stoichiometrically depleted on photosystem I basis in the grana domain. The fractionation studies are consistent with the model of the thylakoid membrane where the photosystems in the grana are operating in a linear electron transport whereas the site of cyclic electron transport is in the stroma lamellae. It is suggested that partial destacking of grana, as a result of light-induced protein phosphorylation, may promote the exposure of the granal photosystem I centers to the chloroplast stroma and thereby enhance their participation in cyclic electron transport activity. 146 refs, 18 figs

  6. Protons, the thylakoid membrane, and the chloroplast ATP synthase.

    Science.gov (United States)

    Junge, W

    1989-01-01

    According to the chemiosmotic theory, proton pumps and ATP synthases are coupled by lateral proton flow through aqueous phases. Three long-standing challenges to this concept, all of which have been loosely subsumed under 'localized coupling' in the literature, were examined in the light of experiments carried out with thylakoids: (1) Nearest neighbor interaction between pumps and ATP synthases. Considering the large distances between photosystem II and CFoCF1, in stacked thylakoids this is a priori absent. (2) Enhanced proton diffusion along the surface of the membrane. This could not be substantiated for the outer side of the thylakoid membrane. Even for the interface between pure lipid and water, two laboratories have reported the absence of enhanced diffusion. (3) Localized proton ducts in the membrane. Intramembrane domains that can transiently trap protons do exist in thylakoid membranes, but because of their limited storage capacity for protons, they probably do not matter for photophosphorylation under continuous light. Seemingly in favor of localized proton ducts is the failure of a supposedly permeant buffer to enhance the onset lag of photophosphorylation. However, it was found that failure of some buffers and the ability of others in this respect were correlated with their failure/ability to quench pH transients in the thylakoid lumen, as predicted by the chemiosmotic theory. It was shown that the chemiosmotic concept is a fair approximation, even for narrow aqueous phases, as in stacked thylakoids. These are approximately isopotential, and protons are taken in by the ATP synthase straight from the lumen. The molecular mechanism by which F0F1 ATPases couple proton flow to ATP synthesis is still unknown. The threefold structural symmetry of the headpiece that, probably, finds a corollary in the channel portion of these enzymes appeals to the common wisdom that structural symmetry causes functional symmetry. "Rotation catalysis" has been proposed. It is

  7. Unique Thylakoid Membrane Architecture of a Unicellular N2-Fixing Cyanobacterium Revealed by Electron Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liberton, Michelle L.; Austin, Jotham R.; Berg, R. H.; Pakrasi, Himadri B.

    2011-04-01

    Cyanobacteria, descendants of the endosymbiont that gave rise to modern-day chloroplasts, are vital contributors to global biological energy conversion processes. A thorough understanding of the physiology of cyanobacteria requires detailed knowledge of these organisms at the level of cellular architecture and organization. In these prokaryotes, the large membrane protein complexes of the photosynthetic and respiratory electron transport chains function in the intracellular thylakoid membranes. Like plants, the architecture of the thylakoid membranes in cyanobacteria has direct impact on cellular bioenergetics, protein transport, and molecular trafficking. However, whole-cell thylakoid organization in cyanobacteria is not well understood. Here we present, by using electron tomography, an in-depth analysis of the architecture of the thylakoid membranes in a unicellular cyanobacterium, Cyanothece sp. ATCC 51142. Based on the results of three-dimensional tomographic reconstructions of near-entire cells, we determined that the thylakoids in Cyanothece 51142 form a dense and complex network that extends throughout the entire cell. This thylakoid membrane network is formed from the branching and splitting of membranes and encloses a single lumenal space. The entire thylakoid network spirals as a peripheral ring of membranes around the cell, an organization that has not previously been described in a cyanobacterium. Within the thylakoid membrane network are areas of quasi-helical arrangement with similarities to the thylakoid membrane system in chloroplasts. This cyanobacterial thylakoid arrangement is an efficient means of packing a large volume of membranes in the cell while optimizing intracellular transport and trafficking.

  8. Unique thylakoid membrane architecture of a unicellular N2-fixing cyanobacterium revealed by electron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liberton, Michelle; Austin II, Jotham R; Berg, R. Howard; Pakrasi, Himadri B

    2011-04-01

    Cyanobacteria, descendants of the endosymbiont that gave rise to modern-day chloroplasts, are vital contributors to global biological energy conversion processes. A thorough understanding of the physiology of cyanobacteria requires detailed knowledge of these organisms at the level of cellular architecture and organization. In these prokaryotes, the large membrane protein complexes of the photosynthetic and respiratory electron transport chains function in the intracellular thylakoid membranes. Like plants, the architecture of the thylakoid membranes in cyanobacteria has direct impact on cellular bioenergetics, protein transport, and molecular trafficking. However, whole-cell thylakoid organization in cyanobacteria is not well understood. Here we present, by using electron tomography, an in-depth analysis of the architecture of the thylakoid membranes in a unicellular cyanobacterium, Cyanothece sp. ATCC 51142. Based on the results of three-dimensional tomographic reconstructions of near-entire cells, we determined that the thylakoids in Cyanothece 51142 form a dense and complex network that extends throughout the entire cell. This thylakoid membrane network is formed from the branching and splitting of membranes and encloses a single lumenal space. The entire thylakoid network spirals as a peripheral ring of membranes around the cell, an organization that has not previously been described in a cyanobacterium. Within the thylakoid membrane network are areas of quasi-helical arrangement with similarities to the thylakoid membrane system in chloroplasts. This cyanobacterial thylakoid arrangement is an efficient means of packing a large volume of membranes in the cell while optimizing intracellular transport and trafficking.

  9. Unique thylakoid membrane architecture of a unicellular N2-fixing cyanobacterium revealed by electron tomography.

    Science.gov (United States)

    Liberton, Michelle; Austin, Jotham R; Berg, R Howard; Pakrasi, Himadri B

    2011-04-01

    Cyanobacteria, descendants of the endosymbiont that gave rise to modern-day chloroplasts, are vital contributors to global biological energy conversion processes. A thorough understanding of the physiology of cyanobacteria requires detailed knowledge of these organisms at the level of cellular architecture and organization. In these prokaryotes, the large membrane protein complexes of the photosynthetic and respiratory electron transport chains function in the intracellular thylakoid membranes. Like plants, the architecture of the thylakoid membranes in cyanobacteria has direct impact on cellular bioenergetics, protein transport, and molecular trafficking. However, whole-cell thylakoid organization in cyanobacteria is not well understood. Here we present, by using electron tomography, an in-depth analysis of the architecture of the thylakoid membranes in a unicellular cyanobacterium, Cyanothece sp. ATCC 51142. Based on the results of three-dimensional tomographic reconstructions of near-entire cells, we determined that the thylakoids in Cyanothece 51142 form a dense and complex network that extends throughout the entire cell. This thylakoid membrane network is formed from the branching and splitting of membranes and encloses a single lumenal space. The entire thylakoid network spirals as a peripheral ring of membranes around the cell, an organization that has not previously been described in a cyanobacterium. Within the thylakoid membrane network are areas of quasi-helical arrangement with similarities to the thylakoid membrane system in chloroplasts. This cyanobacterial thylakoid arrangement is an efficient means of packing a large volume of membranes in the cell while optimizing intracellular transport and trafficking.

  10. Thylakoid membrane maturation and PSII activation are linked in greening Synechocystis sp. PCC 6803 cells.

    Science.gov (United States)

    Barthel, Sandra; Bernát, Gábor; Seidel, Tobias; Rupprecht, Eva; Kahmann, Uwe; Schneider, Dirk

    2013-10-01

    Thylakoid membranes are typical and essential features of both chloroplasts and cyanobacteria. While they are crucial for phototrophic growth of cyanobacterial cells, biogenesis of thylakoid membranes is not well understood yet. Dark-grown Synechocystis sp. PCC 6803 cells contain only rudimentary thylakoid membranes but still a relatively high amount of phycobilisomes, inactive photosystem II and active photosystem I centers. After shifting dark-grown Synechocystis sp. PCC 6803 cells into the light, "greening" of Synechocystis sp. PCC 6803 cells, i.e. thylakoid membrane formation and recovery of photosynthetic electron transport reactions, was monitored. Complete restoration of a typical thylakoid membrane system was observed within 24 hours after an initial lag phase of 6 to 8 hours. Furthermore, activation of photosystem II complexes and restoration of a functional photosynthetic electron transport chain appears to be linked to the biogenesis of organized thylakoid membrane pairs.

  11. 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.

  12. Global Proteomic Analysis Reveals an Exclusive Role of Thylakoid Membranes in Bioenergetics of a Model Cyanobacterium.

    Science.gov (United States)

    Liberton, Michelle; Saha, Rajib; Jacobs, Jon M; Nguyen, Amelia Y; Gritsenko, Marina A; Smith, Richard D; Koppenaal, David W; Pakrasi, Himadri B

    2016-06-01

    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 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

  13. 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

  14. 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.

  15. Role of membrane glycerolipids in photosynthesis, thylakoid biogenesis and chloroplast development.

    Science.gov (United States)

    Kobayashi, Koichi

    2016-07-01

    The lipid bilayer of the thylakoid membrane in plant chloroplasts and cyanobacterial cells is predominantly composed of four unique lipid classes; monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG) and phosphatidylglycerol (PG). MGDG and DGDG are uncharged galactolipids that constitute the bulk of thylakoid membrane lipids and provide a lipid bilayer matrix for photosynthetic complexes as the main constituents. The glycolipid SQDG and phospholipid PG are anionic lipids with a negative charge on their head groups. SQDG and PG substitute for each other to maintain the amount of total anionic lipids in the thylakoid membrane, with PG having indispensable functions in photosynthesis. In addition to biochemical studies, extensive analyses of mutants deficient in thylakoid lipids have revealed important roles of these lipids in photosynthesis and thylakoid membrane biogenesis. Moreover, recent studies of Arabidopsis thaliana suggest that thylakoid lipid biosynthesis triggers the expression of photosynthesis-associated genes in both the nucleus and plastids and activates the formation of photosynthetic machineries and chloroplast development. Meanwhile, galactolipid biosynthesis is regulated in response to chloroplast functionality and lipid metabolism at transcriptional and post-translational levels. This review summarizes the roles of thylakoid lipids with their biosynthetic pathways in plants and discusses the coordinated regulation of thylakoid lipid biosynthesis with the development of photosynthetic machinery during chloroplast biogenesis.

  16. Light Activation of Rubisco by Rubisco Activase and Thylakoid Membranes : PROTEINS, ENZYMES AND METABOLISM

    OpenAIRE

    William J., Campbell; William L., OGREN; Photosynthesis Research Unit, Agricultural Research Service, United States Department of Agriculture

    1992-01-01

    A reconstituted system comprising ribulose bisphosphate carboxylase/oxygenase (rubisco), rubisco activase, washed thylakoid membranes, and ATP was used to demonstrate a light-dependent stimulation of rubisco activation. ATP, ribulose bisphosphate, H^+ , and Mg^ concentrations are normally light-dependent variables in the chloroplast but were maintained at pre-determined levels. Results indicated that rubisco activase and washed thylakoid membranes are sufficient to catalyze light stimulation ...

  17. Functional flexibility and acclimation of the thylakoid membrane.

    Science.gov (United States)

    Kanervo, Eira; Suorsa, Marjaana; Aro, Eva-Mari

    2005-12-01

    Light is an elusive substrate for the function of photosynthetic light reactions of photosynthesis in the thylakoid membrane. Therefore structural and functional dynamics, which occur in the timescale from seconds to several days, are required both at low and high light conditions. The best characterized short-time regulation mechanism at low light is a rapid state transition, resulting in higher absorption cross section of PSI at the expense of PSII. If the low light conditions continue, activation of the lhcb-genes and synthesis of the light-harvesting proteins will occur to optimize the functions of PSII and PSI. At high light, the transition to state 2 is completely inhibited, but the feedback de-excitation of absorbed energy as heat, known as the energy-dependent quenching (q(E)), is rapidly set up. It requires, at least, the DeltapH-dependent activation of violaxanthin de-epoxidase and involvement of the PsbS protein. Another crucial mechanism for protection against the high light stress is the PSII repair cycle. Furthermore, the water-water cycle, cyclic electron transfer around PSI and chlororespiration are important means induced under high irradiation, functioning mainly to avoid an excess production of reactive oxygen species.

  18. Multiple sources of carbonic anhydrase activity in pea thylakoids: soluble and membrane-bound forms.

    Science.gov (United States)

    Rudenko, Natalia N; Ignatova, Lyudmila K; Ivanov, Boris N

    2007-01-01

    Carbonic anhydrase (CA) activity of pea thylakoids, thylakoid membranes enriched with photosystem I (PSI-membranes), or photosystem II (PSII-membranes) as well as both supernatant and pellet after precipitation of thylakoids treated with detergent Triton X-100 were studied. CA activity of thylakoids in the presence of varying concentrations of Triton X-100 had two maxima, at Triton/chlorophyll (triton/Chl) ratios of 0.3 and 1.0. CA activities of PSI-membranes and PSII-membranes had only one maximum each, at Triton/Chl ratio 0.3 or 1.0, respectively. Two CAs with characteristics of the membrane-bound proteins and one CA with characteristics of the soluble proteins were found in the medium after thylakoids were incubated with Triton. One of the first two CAs had mobility in PAAG after native electrophoresis the same as that of CA residing in PSI-membranes, and the other CA had mobility the same as the mobility of CA residing in PSII-membranes, but the latter was different from CA situated in PSII core-complex (Ignatova et al. 2006 Biochemistry (Moscow) 71:525-532). The properties of the "soluble" CA removed from thylakoids were different from the properties of the known soluble CAs of plant cell: apparent molecular mass was about 262 kD and it was three orders more sensitive to the specific CA inhibitor, ethoxyzolamide, than soluble stromal CA. The data are discussed as indicating the presence of, at least, four CAs in pea thylakoids.

  19. Quantitative local photosynthetic flux measurements at isolated chloroplasts and thylakoid membranes using scanning electrochemical microscopy (SECM).

    Science.gov (United States)

    McKelvey, Kim; Martin, Sophie; Robinson, Colin; Unwin, Patrick R

    2013-07-01

    Scanning electrochemical microscopy (SECM) offers a fast and quantitative method to measure local fluxes within photosynthesis. In particular, we have measured the flux of oxygen and ferrocyanide (Fe(CN)6(4-)), from the artificial electron acceptor ferricyanide (Fe(CN)6(3-)), using a stationary ultramicroelectrode at chloroplasts and thylakoid membranes (sourced from chloroplasts). Oxygen generation at films of chloroplasts and thylakoid membranes was detected directly during photosynthesis, but in the case of thylakoid membranes, this switched to sustained oxygen consumption at longer illumination times. An initial oxygen concentration spike was detected over both chloroplast and thylakoid membrane films, and the kinetics of the oxygen generation were extracted by fitting the experimental data to a finite element method (FEM) simulation. In contrast to previous work, the oxygen generation spike was attributed to the limited size of the plastoquinone pool, a key component in the linear electron transport pathway and a contributing factor in photoinhibition. Finally, the mobile nature of the SECM probe, and its high spatial resolution, also allowed us to detect ferrocyanide produced from a single thylakoid membrane. These results further demonstrate the power of SECM for localized flux measurements in biological processes, in this case photosynthesis, and that the high time resolution, combined with FEM simulations, allows the elucidation of quantitative kinetic information.

  20. Isolation and characterization of a thylakoid membrane module showing partial light and dark reactions.

    Science.gov (United States)

    Dani, Diksha Narhar; Sainis, Jayashree Krishna

    2005-05-15

    A functional thylakoid membrane module of photosynthesis was isolated from cell free extracts of Anacystis nidulans by stepwise sequential ultracentrifugation. The thylakoid membrane fractions sedimenting at 40,000 x g, followed by 90,000 x g and finally at 150,000 x g were collected. These fractions had all the components of electron transport chain, ATP synthase, phycobiliproteins, ferredoxin-NADP reductase but no ferredoxin. Five sequential enzymes of Calvin cycle viz phosphoriboisomerase, phosphoribulokinase, RuBP carboxylase, 3-PGA kinase and glyceraldehyde-3-phosphate dehydrogenase were found to be associated with thylakoid membranes. Among the three different thylakoid fractions, the 150,000 x g fraction showed highest activities of these enzymes and also higher rate of whole chain electron transport activity on chlorophyll basis. An important finding was that the 150,000 x g fraction showed appreciably higher rate of R-5-P+ADP+Pi dependent CO2 fixation in light compared to the other two fractions, indicating the efficiency of this fraction in utilizing ATP for Calvin cycle. This thylakoid membrane fraction represents a fully functional module exhibiting a synchronized system of light and dark reactions of photosynthesis. Most of the components of this module remained together even after sucrose density gradient centrifugation. This is the first report on the isolation of a photosynthetic module involving membrane and soluble proteins.

  1. Carbonic anhydrase activity in Arabidopsis thaliana thylakoid membrane and fragments enriched with PSI or PSII.

    Science.gov (United States)

    Ignatova, Lyudmila K; Rudenko, Natalia N; Mudrik, Vilen A; Fedorchuk, Tat'yana P; Ivanov, Boris N

    2011-12-01

    The procedure of isolating the thylakoids and the thylakoid membrane fragments enriched with either photosystem I or photosystem II (PSI- and PSII-membranes) from Arabidopsis thaliana leaves was developed. It differed from the one used with pea and spinach in durations of detergent treatment and centrifugation, and in concentrations of detergent and Mg(2+) in the media. Both the thylakoid and the fragments preserved carbonic anhydrase (CA) activities. Using nondenaturing electrophoresis followed by detection of CA activity in the gel stained with bromo thymol blue, one low molecular mass carrier of CA activity was found in the PSI-membranes, and two carriers, a low molecular mass one and a high molecular mass one, were found in the PSII-membranes. The proteins in the PSII-membranes differed in their sensitivity to acetazolamide (AA), a specific CA inhibitor. AA at 5 × 10(-7) M inhibited the CA activity of the high molecular mass protein but stimulated the activity of the low molecular mass carrier in the PSII-membranes. At the same concentration, AA moderately inhibited, by 30%, the CA activity of PSI-membranes. CA activity of the PSII-membranes was almost completely suppressed by the lipophilic CA inhibitor, ethoxyzolamide at 10(-9) M, whereas CA activity of the PSI-membranes was inhibited by this inhibitor even at 5 × 10(-7) M just the same as for AA. The observed distribution of CA activity in the thylakoid membranes from A. thaliana was close to the one found in the membranes of pea, evidencing the general pattern of CA activity in the thylakoid membranes of C3-plants.

  2. Distribution and dynamics of electron transport complexes in cyanobacterial thylakoid membranes.

    Science.gov (United States)

    Liu, Lu-Ning

    2016-03-01

    The cyanobacterial thylakoid membrane represents a system that can carry out both oxygenic photosynthesis and respiration simultaneously. The organization, interactions and mobility of components of these two electron transport pathways are indispensable to the biosynthesis of thylakoid membrane modules and the optimization of bioenergetic electron flow in response to environmental changes. These are of fundamental importance to the metabolic robustness and plasticity of cyanobacteria. This review summarizes our current knowledge about the distribution and dynamics of electron transport components in cyanobacterial thylakoid membranes. Global understanding of the principles that govern the dynamic regulation of electron transport pathways in nature will provide a framework for the design and synthetic engineering of new bioenergetic machinery to improve photosynthesis and biofuel production. This article is part of a Special Issue entitled: Organization and dynamics of bioenergetic systems in bacteria, edited by Conrad Mullineaux.

  3. 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 membr

  4. Hydroponics on a chip: analysis of the Fe deficient Arabidopsis thylakoid membrane proteome.

    Science.gov (United States)

    Laganowsky, Arthur; Gómez, Stephen M; Whitelegge, Julian P; Nishio, John N

    2009-04-13

    The model plant Arabidopsis thaliana was used to evaluate the thylakoid membrane proteome under Fe-deficient conditions. Plants were cultivated using a novel hydroponic system, called "hydroponics on a chip", which yields highly reproducible plant tissue samples for physiological analyses, and can be easily used for in vivo stable isotope labeling. The thylakoid membrane proteome, from intact chloroplasts isolated from Fe-sufficient and Fe-deficient plants grown with hydroponics on a chip, was analyzed using liquid chromatography coupled to mass spectrometry. Intact masses of thylakoid membrane proteins were measured, many for the first time, and several proteins were identified with post-translational modifications that were altered by Fe deficiency; for example, the doubly phosphorylated form of the photosystem II oxygen evolving complex, PSBH, increased under Fe-deficiency. Increased levels of photosystem II protein subunit PSBS were detected in the Fe-deficient samples. Antioxidant enzymes, including ascorbate peroxidase and peroxiredoxin Q, were only detected in the Fe-deficient samples. We present the first biochemical evidence that the two major LHC IIb proteins (LHCB1 and LHCB2) may have significantly different functions in the thylakoid membrane. The study illustrates the utility of intact mass proteomics as an indispensable tool for functional genomics. "Hydroponics on a chip" provides the ability to grow A. thaliana under defined conditions that will be useful for systems biology.

  5. Digalactosyl-diacylglycerol-deficiency lowers the thermal stability of thylakoid membranes

    NARCIS (Netherlands)

    Krumova, S.K.B.; Laptenok, S.; Kovács, L.; Toth, T.; Hoek, van A.; Garab, G.; Amerongen, van H.

    2010-01-01

    We investigated the effects of digalactosyl-diacylglycerol (DGDG) on the organization and thermal stability of thylakoid membranes, using wild-type Arabidopsis thaliana and the DGDG-deficient mutant, dgd1. Circular-dichroism measurements reveal that DGDG-deficiency hampers the formation of the

  6. Supramolecular Organization of Thylakoid Membranes in De-etioplasts Upon Exposure to Light

    Institute of Scientific and Technical Information of China (English)

    Yangyang Wang; Weitong Cui; Shihua Shen; Hui Chen

    2012-01-01

    Chloroplast is the most prominent form of plastid occurring in all green plant tissues and contains a thylakoid membrane system that carries the photosynthetic electron transport chain converting light energy into chemical energy in the forms of ATP and NADPH.Thylakoids are the dominating structure inside fully mature chloroplasts.The formation and alteration of the thylakoid membrane structure and composition are closely connected to the development of the chloroplasts from simple,undifferentiated proplastids.Despite the importance of thylakoid membranes for photosynthesis and the energy metabolism of plants,the molecular processes connected to the origin,synthesis,maintenance and adaptation of thylakoid membranes remain poorly understood.In this study,the proteome difference in developing thylakoid membranes,including integral and peripheral proteins,in the process of de-etiolated rice seedlings were analyzed by 2-DE,and the structural changes and effects of such difference on photosynthetic ability were also examined.The ultrastructure of etioplasts changed notably upon exposure to light for 1 h,5 h and 9 h.After 5 h of illumination,paracrystalline PLB transformation was completed with transverse short tubules dispersed in stroma.The first stacked thylakoid membranes were observed at time point 9 h of illumination.In the continuous illumination,the formation of intergranal thylakoid was directly from PLB material without an intervening vesicular stage.In order to investigate the function and organization of the photosynthetic membrane proteins,the low-temperature (77 K) fluorescence emission spectra of membrane factions isolated from etioplasts,de-etioplasts and mature chloroplasts were investigated.The fluorescence emission spectra from de-etioplasts and mature chloroplasts exhibited a clear red maximum centered at 681 nm and a shoulder in the far-red region near 735 nm.The 681 nm band was slightly red-shifted with the increase of illumination duration

  7. Production of superoxide in chloroplast thylakoid membranes ESR study with cyclic hydroxylamines of different lipophilicity.

    Science.gov (United States)

    Kozuleva, Marina; Klenina, Irina; Proskuryakov, Ivan; Kirilyuk, Igor; Ivanov, Boris

    2011-04-06

    Accumulation of nitroxide radicals, DCP· or TMT·, under illumination of a thylakoid suspension containing either hydrophilic, DCP-H, or lipophilic, TMT-H, cyclic hydroxylamines that have high rate constants of the reaction with superoxide radicals, was measured using ESR. A slower accumulation of TMT· in contrast with DCP· accumulation was explained by re-reduction of TMT· by the carriers of the photosynthetic electron transport chain within the membrane. Superoxide dismutase suppressed TMT· accumulation to a lesser extent than DCP· accumulation. The data are interpreted as evidencing the production of intramembrane superoxide in thylakoids.

  8. Identification of Thylakoid Membrane Protein Complexes by Using a BN-Chip/MS Approach

    Institute of Scientific and Technical Information of China (English)

    Longquan Fan; Yinghong Pan

    2012-01-01

    Thylakoid membrane protein complexes of wheat (Triticum aestivum Linn.)play crucial roles in growth and crop production.Knowledge of the composition and structure of protein complexes,as well as protein interactions,will result in a much deeper understanding of metabolic pathways and cellular processes than protein identities alone,especially if the complexes can be separated in the native forms.Whereas the analysis of membrane protein complexes is a significant challenge due to their hydrophobic properties and relatively low abundance.A rapid and efficient method of identifying membrane protein complexes will greatly facilitate the investigation of agriculture.The present work developed an BN-Chip/MS approach for exhaustive separation and identification of protein complexes,by combining using blue-native polyacrylamide gel electrophoresis (BN-PAGE) and chip-based high-performance liquid chromatography quadruple time-of-flight tandem mass spectrometry (HPLC-Chip/ESI-QT-OF-MS,Chip/MS).By using this approach,seventy-five nonredundant proteins of wheat thylakoid membrane complexes were identified from digested 13 bands of BN-gel.When the protocol of BN separation was not used,only 37 nonredundant proteins had been identified and among of them 9 proteins were uniquely identi? ed.This BN-Chip/MS approach is rapid and efficient for identifying protein complexes in wheat thylakoid membranes,and also providing reliable foundations for further functional research of wheat chloroplast and for identifying protein complexes of other species.

  9. Anisotropic Circular Dichroism Signatures of Oriented Thylakoid Membranes and Lamellar Aggregates of LHCII

    Energy Technology Data Exchange (ETDEWEB)

    Miloslavina, Y.; Hind, G.; Lambrev, P. H.; Javorfi, T.; Varkonyi, Z.; Karlicky, V.; Wall, J. S.; Garab, G.

    2011-06-12

    In photosynthesis research, circular dichroism (CD) spectroscopy is an indispensable tool to probe molecular architecture at virtually all levels of structural complexity. At the molecular level, the chirality of the molecule results in intrinsic CD; pigment-pigment interactions in protein complexes and small aggregates can give rise to excitonic CD bands, while 'psi-type' CD signals originate from large, densely packed chiral aggregates. It has been well established that anisotropic CD (ACD), measured on samples with defined non-random orientation relative to the propagation of the measuring beam, carries specific information on the architecture of molecules or molecular macroassemblies. However, ACD is usually combined with linear dichroism and can be distorted by instrumental imperfections, which given the strong anisotropic nature of photosynthetic membranes and complexes, might be the reason why ACD is rarely studied in photosynthesis research. In this study, we present ACD spectra, corrected for linear dichroism, of isolated intact thylakoid membranes of granal chloroplasts, washed unstacked thylakoid membranes, photosystem II (PSII) membranes (BBY particles), grana patches, and tightly stacked lamellar macroaggregates of the main light-harvesting complex of PSII (LHCII). We show that the ACD spectra of face- and edge-aligned stacked thylakoid membranes and LHCII lamellae exhibit profound differences in their psi-type CD bands. Marked differences are also seen in the excitonic CD of BBY and washed thylakoid membranes. Magnetic CD (MCD) spectra on random and aligned samples, and the largely invariable nature of the MCD spectra, despite dramatic variations in the measured isotropic and anisotropic CD, testify that ACD can be measured without substantial distortions and thus employed to extract detailed information on the (supra)molecular organization of photosynthetic complexes. An example is provided showing the ability of CD data to indicate such an

  10. Anisotropic Circular Dichroism Signatures of Oriented Thylakoid Membranes and Lamellar Aggregates of LHCII

    Energy Technology Data Exchange (ETDEWEB)

    Miloslavina Y.; Hind G.; Lambrev, P. H.; Javorfi, T.; Varkonyi, Z.; Karlicky, V.; Wall, J. S.; Garab, G.

    2012-03-01

    In photosynthesis research, circular dichroism (CD) spectroscopy is an indispensable tool to probe molecular architecture at virtually all levels of structural complexity. At the molecular level, the chirality of the molecule results in intrinsic CD; pigment-pigment interactions in protein complexes and small aggregates can give rise to excitonic CD bands, while 'psi-type' CD signals originate from large, densely packed chiral aggregates. It has been well established that anisotropic CD (ACD), measured on samples with defined non-random orientation relative to the propagation of the measuring beam, carries specific information on the architecture of molecules or molecular macroassemblies. However, ACD is usually combined with linear dichroism and can be distorted by instrumental imperfections, which given the strong anisotropic nature of photosynthetic membranes and complexes, might be the reason why ACD is rarely studied in photosynthesis research. In this study, we present ACD spectra, corrected for linear dichroism, of isolated intact thylakoid membranes of granal chloroplasts, washed unstacked thylakoid membranes, photosystem II (PSII) membranes (BBY particles), grana patches, and tightly stacked lamellar macroaggregates of the main light-harvesting complex of PSII (LHCII). We show that the ACD spectra of face- and edge-aligned stacked thylakoid membranes and LHCII lamellae exhibit profound differences in their psi-type CD bands. Marked differences are also seen in the excitonic CD of BBY and washed thylakoid membranes. Magnetic CD (MCD) spectra on random and aligned samples, and the largely invariable nature of the MCD spectra, despite dramatic variations in the measured isotropic and anisotropic CD, testify that ACD can be measured without substantial distortions and thus employed to extract detailed information on the (supra)molecular organization of photosynthetic complexes. An example is provided showing the ability of CD data to indicate such an

  11. Salt-induced redox-independent phosphorylation of light harvesting chlorophyll a/b proteins in Dunaliella salina thylakoid membranes.

    Science.gov (United States)

    Liu, Xian-De; Shen, Yun-Gang

    2005-02-17

    This study investigated the regulation of the major light harvesting chlorophyll a/b protein (LHCII) phosphorylation in Dunaliella salina thylakoid membranes. We found that both light and NaCl could induce LHCII phosphorylation in D. salina thylakoid membranes. Treatments with oxidants (ferredoxin and NADP) or photosynthetic electron flow inhibitors (DCMU, DBMIB, and stigmatellin) inhibited LHCII phosphorylation induced by light but not that induced by NaCl. Furthermore, neither addition of CuCl(2), an inhibitor of cytochrome b(6)f complex reduction, nor oxidizing treatment with ferricyanide inhibited light- or NaCl-induced LHCII phosphorylation, and both salts even induced LHCII phosphorylation in dark-adapted D. salina thylakoid membranes as other salts did. Together, these results indicate that the redox state of the cytochrome b(6)f complex is likely involved in light- but not salt-induced LHCII phosphorylation in D. salina thylakoid membranes.

  12. Quantification of superoxide radical production in thylakoid membrane using cyclic hydroxylamines.

    Science.gov (United States)

    Kozuleva, Marina; Klenina, Irina; Mysin, Ivan; Kirilyuk, Igor; Opanasenko, Vera; Proskuryakov, Ivan; Ivanov, Boris

    2015-12-01

    Applicability of two lipophilic cyclic hydroxylamines (CHAs), CM-H and TMT-H, and two hydrophilic CHAs, CAT1-H and DCP-H, for detection of superoxide anion radical (O2(∙-)) produced by the thylakoid photosynthetic electron transfer chain (PETC) of higher plants under illumination has been studied. ESR spectrometry was applied for detection of the nitroxide radical originating due to CHAs oxidation by O2(∙-). CHAs and corresponding nitroxide radicals were shown to be involved in side reactions with PETC which could cause miscalculation of O2(∙-) production rate. Lipophilic CM-H was oxidized by PETC components, reducing the oxidized donor of Photosystem I, P700(+), while at the same concentration another lipophilic CHA, TMT-H, did not reduce P700(+). The nitroxide radical was able to accept electrons from components of the photosynthetic chain. Electrostatic interaction of stable cation CAT1-H with the membrane surface was suggested. Water-soluble superoxide dismutase (SOD) was added in order to suppress the reaction of CHA with O2(∙-) outside the membrane. SOD almost completely inhibited light-induced accumulation of DCP(∙), nitroxide radical derivative of hydrophilic DCP-H, in contrast to TMT(∙) accumulation. Based on the results showing that change in the thylakoid lumen pH and volume had minor effect on TMT(∙) accumulation, the reaction of TMT-H with O2(∙-) in the lumen was excluded. Addition of TMT-H to thylakoid suspension in the presence of SOD resulted in the increase in light-induced O2 uptake rate, that argued in favor of TMT-H ability to detect O2(∙-) produced within the membrane core. Thus, hydrophilic DCP-H and lipophilic TMT-H were shown to be usable for detection of O2(∙-) produced outside and within thylakoid membranes.

  13. Biochemical Properties and Inhibition Kinetics of Phosphatase from Wheat Thylakoid Membranes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A phosphatase that hydrolyses phosphate monoesters has been isolated from wheat thylakoid membranes.Biochemical properties and inhibition kinetics of the phosphatase were investigated using several ions, organic solvents, and inhibitors. Wheat (Triticum aestivum L. cv. PH82-2-2) thylakoid membrane phosphatase activity was activated by Mg2+, Ca2+, and Fe2+ and was inhibited by Mn2+ and Cu2+. For example, enzyme activity was activated 34.81% by 2 mmol/L Mg2+, but was inhibited 22.3% and 8.5% by 2 and 1 mmol/L Cu2+, respectively.Methanol, ethanol and glycol were all able to activate enzyme activity. Enzyme activity was activated 58.5%, 48.2%,and 8.7% by 40% ethanol, methanol and glycol, respectively. From these results, it can be seen that the degree of activation of the phosphatase was greatest for ethanol and the type of activation was uncompetitive. Moreover,the activity of the thylakoid membrane phosphatase was inhibited by molybdate, vanadate, phosphate, and fluoride and the type of inhibition produced by these elements was uncompetitive, non-competitive, competitive and mixed, respectively.

  14. The supramolecular architecture, function, and regulation of thylakoid membranes in red algae: an overview.

    Science.gov (United States)

    Su, Hai-Nan; Xie, Bin-Bin; Zhang, Xi-Ying; Zhou, Bai-Cheng; Zhang, Yu-Zhong

    2010-11-01

    Red algae are a group of eukaryotic photosynthetic organisms. Phycobilisomes (PBSs), which are composed of various types of phycobiliproteins and linker polypeptides, are the main light-harvesting antennae in red algae, as in cyanobacteria. Two morphological types of PBSs, hemispherical- and hemidiscoidal-shaped, are found in different red algae species. PBSs harvest solar energy and efficiently transfer it to photosystem II (PS II) and finally to photosystem I (PS I). The PS I of red algae uses light-harvesting complex of PS I (LHC I) as a light-harvesting antennae, which is phylogenetically related to the LHC I found in higher plants. PBSs, PS II, and PS I are all distributed throughout the entire thylakoid membrane, a pattern that is different from the one found in higher plants. Photosynthesis processes, especially those of the light reactions, are carried out by the supramolecular complexes located in/on the thylakoid membranes. Here, the supramolecular architecture, function and regulation of thylakoid membranes in red algal are reviewed.

  15. The evolutionarily conserved protein PHOTOSYNTHESIS AFFECTED MUTANT71 is required for efficient manganese uptake at the thylakoid membrane in Arabidopsis

    DEFF Research Database (Denmark)

    Schneider, Anja; Steinberger, Iris; Herdean, Andrei

    2016-01-01

    In plants, algae, and cyanobacteria, photosystem II (PSII) catalyzes the light-driven oxidation of water. The oxygen-evolving complex of PSII is a Mn4CaO5 cluster embedded in a well-defined protein environment in the thylakoid membrane. However, transport of manganese and calcium into the thylakoid...... by oxygen evolution rates) and for manganese incorporation. Manganese binding to PSII was severely reduced in pam71 thylakoids, particularly in PSII supercomplexes. In cation partitioning assays with intact chloroplasts, Mn2+ and Ca2+ ions were differently sequestered in pam71, with Ca2+ enriched in pam71...

  16. Change of proton motive force across thylakoid membrane in soybean leaf during state transitions

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Change of proton gradient across thylakoid membrane in soybean leaves was studied with millisecond delayed light emission (ms-DLE) during the course of state transitions which were indicated by the chlorophyll fluorescence at room temperature and 77 K. When dark-adapted leaves were induced to stateⅠ with far-red light, Fm/Fo, F685/F735 and the intensity of fast phase of ms-DLE were affected slightly. However, during the induction to stateⅡ with red light, both Fm/Fo and F685/F735 decreased immediately and the former were quicker than the latter. In this interval, the intensity of fast phase of ms-DLE increased to a maximum and then decreased to a lower value during the transition to stateⅡ. Nigericin, an uncoupler which eliminates the proton gradient across thylakoid membrane, inhibited the increase in the intensity of fast phase of ms-DLE during the transition to stateⅡ. Another uncoupler, valinomycin, which eliminates the membrane potential, did not affect the changes of the intensity of fast phase. These results suggest that the prompt increase in the intensity of fast phase of ms-DLE at the beginning of transitions to stateⅡ is correlated mainly with the proton gradient released from water oxidation in photosystemⅡ.

  17. The role of putrescine in the regulation of proteins and fatty acids of thylakoid membranes under salt stress.

    Science.gov (United States)

    Shu, Sheng; Yuan, Yinghui; Chen, Jie; Sun, Jin; Zhang, Wenhua; Tang, Yuanyuan; Zhong, Min; Guo, Shirong

    2015-10-05

    Polyamines can alleviate the inhibitory effects of salinity on plant growth by regulating photosynthetic efficiency. However, little information is available to explain the specific mechanisms underlying the contribution of polyamines to salt tolerance of the photosynthetic apparatus. Here, we investigated the role of putrescine (Put) on the photosynthetic apparatus of cucumber seedlings under salt stress. We found that NaCl stress resulted in severe ion toxicity and oxidative stress in cucumber chloroplasts. In addition, salinity caused a significant increase in the saturated fatty acid contents of thylakoid membranes. Put altered unsaturated fatty acid content, thereby alleviating the disintegration of thylakoid grana lamellae and reducing the number of plastoglobuli in thylakoid membranes. BN-PAGE revealed Put up-regulated the expression of ATP synthase, CP47, D1, Qb, and psbA proteins and down-regulated CP24, D2, and LHCII type III in NaCl-stressed thylakoid membranes. qRT-PCR analysis of gene expression was used to compare transcript and protein accumulation among 10 candidate proteins. For five of these proteins, induced transcript accumulation was consistent with the pattern of induced protein accumulation. Our results suggest that Put regulates protein expression at transcriptional and translational levels by increasing endogenous polyamines levels in thylakoid membranes, which may stabilise photosynthetic apparatus under salt stress.

  18. Nonlinear Dielectric Spectroscopy as an Indirect Probe of Metabolic Activity in Thylakoid Membrane

    Directory of Open Access Journals (Sweden)

    John H. Miller

    2011-01-01

    Full Text Available Nonlinear dielectric spectroscopy (NDS is a non-invasive probe of cellular metabolic activity with potential application in the development of whole-cell biosensors. However, the mechanism of NDS interaction with metabolic membrane proteins is poorly understood, partly due to the inherent complexity of single cell organisms. Here we use the light-activated electron transport chain of spinach thylakoid membrane as a model system to study how NDS interacts with metabolic activity. We find protein modification, as opposed to membrane pump activity, to be the dominant source of NDS signal change in this system. Potential mechanisms for such protein modifications include reactive oxygen species generation and light-activated phosphorylation.

  19. A bestrophin-like protein modulates the proton motive force across the thylakoid membrane in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Zhikun Duan; Fanna Kong; Lin Zhang; Wenjing Li; Jiao Zhang; Lianwei Peng

    2016-01-01

    During photosynthesis, photosynthetic electron transport generates a proton motive force (pmf) across the thylakoid membrane, which is used for ATP biosynthesis via ATP synthase in the chloroplast. The pmf is composed of an electric potential (DC) and an osmotic component (DpH). Partitioning between these components in chloroplasts is strictly regulated in response to fluctuating environments. However, our knowledge of the molecular mechanisms that regulate pmf partitioning is limited. Here, we report a bestrophin-like protein (AtBest), which is critical for pmf partitioning. While the DpH component was slightly reduced in atbest, the DC component was much greater in this mutant than in the wild type, resulting in less efficient activation of nonphotochemical quenching (NPQ) upon both illumination and a shift from low light to high light. Although no visible phenotype was observed in the atbest mutant in the greenhouse, this mutant exhibited stronger photoinhibition than the wild type when grown in the field. AtBest belongs to the bestrophin family proteins, which are believed to function as chloride (Cl?) channels. Thus, our findings reveal an important Cl? channel required for ion transport and homeo-stasis across the thylakoid membrane in higher plants. These processes are essential for fine-tuning photosynthesis under fluctuating environmental conditions.

  20. Selective nitration of PsbO1 inhibits oxygen evolution from isolated Arabidopsis thylakoid membranes.

    Science.gov (United States)

    Takahashi, Misa; Shigeto, Jun; Sakamoto, Atsushi; Morikawa, Hiromichi

    2017-04-03

    Treatment of isolated Arabidopsis thaliana thylakoid membranes with nitrogen dioxide (NO2) induces selective nitration of the tyrosine residue at the ninth amino acid ((9)Tyr) of PsbO1. This selective nitration is triggered by light and is inhibited by photosynthetic electron transport inhibitors. Therefore, we postulated that, similar to (161)Tyr of D1 (YZ), (9)Tyr of PsbO1 is redox active and is selectively oxidized by photosynthetic electron transport in response to illumination to a tyrosyl radical that is highly susceptible to nitration. This tyrosyl radical may combine rapidly at diffusion-controlled rates with NO2 to form 3-nitrotyrosine. If this postulation is correct, the nitration of (9)Tyr of PsbO1 should decrease oxygen evolution activity. We investigated the effects of PsbO1 nitration on oxygen evolution from isolated thylakoid membranes, and found that nitration decreased oxygen evolution to ≥ 0% of the control. Oxygen evolution and nitration were significantly negatively correlated. This finding is consistent with redox active properties of the (9)Tyr gene of PsbO1, and suggests that PsbO1 (9)Tyr acts as an electron relay, such as YZ in the photosystem II oxygenic electron transport chain.

  1. Relationships between unsaturation of thylakoid membrane lipids and xanthophyll cycle in rice under chilling and high light

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    To explore the differences of chilling induced sensitivity to photoinhibition between indica and japonica, xanthophyll cycle component, activity of violaxanthin deepoxidase (VDE), and unsaturation of thylakoid membrane lipids were measured. Varieties used were japonica 9516 and indica Shanyou 63 (SY 63).

  2. Ribosomal protein S6 kinase1 coordinates with TOR-Raptor2 to regulate thylakoid membrane biosynthesis in rice.

    Science.gov (United States)

    Sun, Linxiao; Yu, Yonghua; Hu, Weiqin; Min, Qiming; Kang, Huiling; Li, Yilu; Hong, Yue; Wang, Xuemin; Hong, Yueyun

    2016-07-01

    Ribosomal protein S6 kinase (S6K) functions as a key component in the target of rapamycin (TOR) pathway involved in multiple processes in eukaryotes. The role and regulation of TOR-S6K in lipid metabolism remained unknown in plants. Here we provide genetic and pharmacological evidence that TOR-Raptor2-S6K1 is important for thylakoid galactolipid biosynthesis and thylakoid grana modeling in rice (Oryza sativa L.). Genetic suppression of S6K1 caused pale yellow-green leaves, defective thylakoid grana architecture. S6K1 directly interacts with Raptor2, a core component in TOR signaling, and S6K1 activity is regulated by Raptor2 and TOR. Plants with suppressed Raptor2 expression or reduced TOR activity by inhibitors mimicked the S6K1-deficient phenotype. A significant reduction in galactolipid content was found in the s6k1, raptor2 mutant or TOR-inhibited plants, which was accompanied by decreased transcript levels of the set of genes such as lipid phosphate phosphatase α5 (LPPα5), MGDG synthase 1 (MGD1), and DGDG synthase 1 (DGD1) involved in galactolipid synthesis, compared to the control plants. Moreover, loss of LPPα5 exhibited a similar phenotype with pale yellow-green leaves. These results suggest that TOR-Raptor2-S6K1 is important for modulating thylakoid membrane lipid biosynthesis, homeostasis, thus enhancing thylakoid grana architecture and normal photosynthesis ability in rice.

  3. Loss of the SPHF homologue Slr1768 leads to a catastrophic failure in the maintenance of thylakoid membranes in Synechocystis sp. PCC 6803.

    Directory of Open Access Journals (Sweden)

    Samantha J Bryan

    Full Text Available BACKGROUND: In cyanobacteria the photosystems are localised to, and maintained in, specialist membranes called the thylakoids. The mechanism driving the biogenesis of the thylakoid membranes is still an open question, with only two potential biogenesis factors, Vipp1 and Alb3 currently identified. METHODOLOGY/PRINCIPAL FINDINGS: We generated a slr1768 knockout using the pGEM T-easy vector and REDIRECT. By comparing growth and pigment content (chlorophyll a fluoresence of the Δslr1768 mutant with the wild-type, we found that Δslr1768 has a conditional phenotype; specifically under high light conditions (130 µmol m(-2 s(-1 thylakoid biogenesis is disrupted leading to cell death on a scale of days. The thylakoids show considerable disruption, with loss of both structure and density, while chlorophyll a density decreases with the loss of thylakoids, although photosynthetic efficiency is unaffected. Under low light (30 µmol m(-2 s(-1 the phenotype is significantly reduced, with a growth rate similar to the wild-type and only a low frequency of cells with evident thylakoid disruption. CONCLUSIONS/SIGNIFICANCE: This is the first example of a gene that affects the maintenance of the thylakoid membranes specifically under high light, and which displays a phenotype dependent on light intensity. Our results demonstrate that Slr1768 has a leading role in acclimatisation, linking light damage with maintenance of the thylakoids.

  4. Changes in Unsaturated Levels of Fatty Acids in Thylakoid PSⅡ Membrane Lipids During Chilling-induced Resistance in Rice

    Institute of Scientific and Technical Information of China (English)

    Su-Qin Zhu; Chun-Mei Yu; Xin-Yan Liu; Ben-Hua Ji; De-Mao Jiao

    2007-01-01

    Temperature is one of the abiotic factors limiting growth and productivity of plants. In the present work, the effect of low non-freezing temperature, as an inducer of "chilling resistance", was studied in three cultivars of rice (Oryza sativa L.), japonica cv. 9516 (j-9516), the two parental lines of superhigh-yield hybrid rice between subspecies,Peiai/E32 (ji-PE), and the traditional indica hybrid rice Shanyou 63 (i-SY63). Leaves of chill-treated rice showed chilling-induced resistance, as an increase of their low-temperature tolerance was measured using chlorophyll fluorescence measurements, revealing a change in photosystem Ⅱ (PSⅡ) efficiency. After 5 d of exposure to 11℃ under low light (100 μ mol·m-2·s-1), levels of unsaturated fatty acids in PSⅡ thylakoid membrane lipids decreased during the initial 1-2 d, then increased slowly and reached 99.2%, 95.3% and 90.1% of the initial value (0 d) in j-9516,ji-PE and i-SY63, respectively, on the fifth day. However, under medium light (600 μmol·m-2·s-1), all cultivars experienced similar substantial photoinhibition, which approached steady state levels after a decline in levels of unsaturated fatty acids in PSII thylakoid membrane lipids to about 57.1%, 53.8% and 44.5% of the initial values (0 d) in j-9516,ji-PE and i-SY63 on the fifth day. Under either chilling-induced resistance (the former) or low temperature photoinhibition (the latter) conditions, the changes of other physiological parameters such as D1 protein contents,electron transport activities of PSII (ETA), Fv/Fm, xanthophyl cycle activities expressed by DES (deepoxide state)were consistent with that of levels of unsaturated fatty acids in PSⅡ thylakoid membrane lipids. So there were negative correlations between saturated levels of fatty acids (16:1(3t), 16:0, 18:0), especially the 16:1(3t) fatty acid on thylakoid membrane and other physiological parameters, such as D1 protein contents, ETA and (A+Z)/(A+V+Z). A specific role of

  5. 植物叶绿体类囊体膜及膜蛋白研究进展%Progress in chloroplast thylakoid membrane and membrane proteins

    Institute of Scientific and Technical Information of China (English)

    胡锋; 黄俊丽; 秦峰; 岳彩黎; 王贵学

    2011-01-01

    In plants and eukaryotic algae, photosynthesis takes place in chloroplasts. Light reaction occurs in the thylakoid membranes. Thylakoid membranes contain integral and peripheral membrane protein complexes,including the pigments that absorb light energy, which form the photosystems. Much attention has been focused on the thylakoid membranes because of its significance in photosynthesis. Analysis of thylakoid membranes will benefit the study of photosynthetic mechanism. The present review summarizes the three-dimensional conformation,membrane protein composition and function of thylakoid membranes.%叶绿体是植物和真核藻类进行光合作用的场所.存在于叶绿体类囊体膜上的蛋白质复合物含有光反应所需的光合色素和电子传递链组分,在光合作用过程中,光化学反应发生在类囊体膜上.因此,类囊体膜是光能向化学能转化的主要场所,因而也一直是光合作用研究的热点.叶绿体类囊体膜的深入研究可以促进光合作用的分子机理研究.该文就叶绿体类囊体膜的三维构象及类囊体膜蛋白的组成和功能研究进行了综述.

  6. Dynamic flexibility in the structure and function of photosystem II in higher plant thylakoid membranes: the grana enigma.

    Science.gov (United States)

    Anderson, Jan M; Chow, Wah Soon; De Las Rivas, Javier

    2008-01-01

    Grana are not essential for photosynthesis, yet they are ubiquitous in higher plants and in the recently evolved Charaphyta algae; hence grana role and its need is still an intriguing enigma. This article discusses how the grana provide integrated and multifaceted functional advantages, by facilitating mechanisms that fine-tune the dynamics of the photosynthetic apparatus, with particular implications for photosystem II (PSII). This dynamic flexibility of photosynthetic membranes is advantageous in plants responding to ever-changing environmental conditions, from darkness or limiting light to saturating light and sustained or intermittent high light. The thylakoid dynamics are brought about by structural and organizational changes at the level of the overall height and number of granal stacks per chloroplast, molecular dynamics within the membrane itself, the partition gap between appressed membranes within stacks, the aqueous lumen encased by the continuous thylakoid membrane network, and even the stroma bathing the thylakoids. The structural and organizational changes of grana stacks in turn are driven by physicochemical forces, including entropy, at work in the chloroplast. In response to light, attractive van der Waals interactions and screening of electrostatic repulsion between appressed grana thylakoids across the partition gap and most probably direct protein interactions across the granal lumen (PSII extrinsic proteins OEEp-OEEp, particularly PsbQ-PsbQ) contribute to the integrity of grana stacks. We propose that both the light-induced contraction of the partition gap and the granal lumen elicit maximisation of entropy in the chloroplast stroma, thereby enhancing carbon fixation and chloroplast protein synthesizing capacity. This spatiotemporal dynamic flexibility in the structure and function of active and inactive PSIIs within grana stacks in higher plant chloroplasts is vital for the optimization of photosynthesis under a wide range of environmental and

  7. Arabidopsis CHL27, located in both envelope and thylakoid membranes, is required for the synthesis of protochlorophyllide.

    Science.gov (United States)

    Tottey, Stephen; Block, Maryse A; Allen, Michael; Westergren, Tomas; Albrieux, Catherine; Scheller, Henrik V; Merchant, Sabeeha; Jensen, Poul Erik

    2003-12-23

    CHL27, the Arabidopsis homologue to Chlamydomonas Crd1, a plastid-localized putative diiron protein, is required for the synthesis of protochlorophyllide and therefore is a candidate subunit of the aerobic cyclase in chlorophyll biosynthesis. delta-Aminolevulinic acid-fed antisense Arabidopsis plants with reduced amounts of Crd1/CHL27 accumulate Mg-protoporphyrin IX monomethyl ester, the substrate of the cyclase reaction. Mutant plants have chlorotic leaves with reduced abundance of all chlorophyll proteins. Fractionation of Arabidopsis chloroplast membranes shows that Crd1/CHL27 is equally distributed on a membrane-weight basis in the thylakoid and inner-envelope membranes.

  8. N-terminal structure of maize ferredoxin:NADP+ reductase determines recruitment into different thylakoid membrane complexes.

    Science.gov (United States)

    Twachtmann, Manuel; Altmann, Bianca; Muraki, Norifumi; Voss, Ingo; Okutani, Satoshi; Kurisu, Genji; Hase, Toshiharu; Hanke, Guy T

    2012-07-01

    To adapt to different light intensities, photosynthetic organisms manipulate the flow of electrons through several alternative pathways at the thylakoid membrane. The enzyme ferredoxin:NADP(+) reductase (FNR) has the potential to regulate this electron partitioning because it is integral to most of these electron cascades and can associate with several different membrane complexes. However, the factors controlling relative localization of FNR to different membrane complexes have not yet been established. Maize (Zea mays) contains three chloroplast FNR proteins with totally different membrane association, and we found that these proteins have variable distribution between cells conducting predominantly cyclic electron transport (bundle sheath) and linear electron transport (mesophyll). Here, the crystal structures of all three enzymes were solved, revealing major structural differences at the N-terminal domain and dimer interface. Expression in Arabidopsis thaliana of maize FNRs as chimeras and truncated proteins showed the N-terminal determines recruitment of FNR to different membrane complexes. In addition, the different maize FNR proteins localized to different thylakoid membrane complexes on expression in Arabidopsis, and analysis of chlorophyll fluorescence and photosystem I absorbance demonstrates the impact of FNR location on photosynthetic electron flow.

  9. Herbicides affect fluorescence and electron transfer activity of spinach chloroplasts, thylakoid membranes and isolated Photosystem II.

    Science.gov (United States)

    Ventrella, Andrea; Catucci, Lucia; Agostiano, Angela

    2010-08-01

    In this work, studies on the effects produced by atrazine, terbutryn or diuron onto spinach photosynthetic materials were performed by observing changes in fluorescence emission and in electron transfer activities of the bio-samples in the presence of such herbicides; chloroplasts, thylakoids, Photosystem II-enriched thylakoids (BBYs) and isolated Photosystem II (PSII) were employed. This approach evidenced differences in the herbicide-photosynthetic material interactions going up-down from chloroplasts to proteins. Rapid emission increments were detected for chloroplasts and thylakoids, in particular in the presence of terbutryn; no remarkable emission increment was recorded when BBYs or PSII were used for this assay. The dependences of the chloroplast and thylakoid emission intensities upon herbicide concentration were investigated with responses even at concentrations below 10(-7)M. The influence of lowering the temperature was also tested, and the stabilizing effects on the resistances of the bio-samples against herbicides were recorded. Furthermore, Hill Reaction-based colorimetric assays were performed to monitor the electron transfer activities of the bio-samples in the presence of herbicides, after brief incubations. As a result, chloroplasts and thylakoids resulted to be sensitive tools in responding to concentrations even lower than 10(-7)M of most herbicides; nevertheless, an interesting sensitivity to herbicides was also observed for PSII. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  10. Monogalactosyldiacylglycerol deficiency in Arabidopsis affects pigment composition in the prolamellar body and impairs thylakoid membrane energization and photoprotection in leaves.

    Science.gov (United States)

    Aronsson, Henrik; Schöttler, Mark A; Kelly, Amélie A; Sundqvist, Christer; Dörmann, Peter; Karim, Sazzad; Jarvis, Paul

    2008-09-01

    Monogalactosyldiacylglycerol (MGDG) is the major lipid constituent of chloroplast membranes and has been proposed to act directly in several important plastidic processes, particularly during photosynthesis. In this study, the effect of MGDG deficiency, as observed in the monogalactosyldiacylglycerol synthase1-1 (mgd1-1) mutant, on chloroplast protein targeting, phototransformation of pigments, and photosynthetic light reactions was analyzed. The targeting of plastid proteins into or across the envelope, or into the thylakoid membrane, was not different from wild-type in the mgd1 mutant, suggesting that the residual amount of MGDG in mgd1 was sufficient to maintain functional targeting mechanisms. In dark-grown plants, the ratio of bound protochlorophyllide (Pchlide, F656) to free Pchlide (F631) was increased in mgd1 compared to the wild type. Increased levels of the photoconvertible pigment-protein complex (F656), which is photoprotective and suppresses photooxidative damage caused by an excess of free Pchlide, may be an adaptive response to the mgd1 mutation. Leaves of mgd1 suffered from a massively impaired capacity for thermal dissipation of excess light due to an inefficient operation of the xanthophyll cycle; the mutant contained less zeaxanthin and more violaxanthin than wild type after 60 min of high-light exposure and suffered from increased photosystem II photoinhibition. This is attributable to an increased conductivity of the thylakoid membrane at high light intensities, so that the proton motive force is reduced and the thylakoid lumen is less acidic than in wild type. Thus, the pH-dependent activation of the violaxanthin de-epoxidase and of the PsbS protein is impaired.

  11. Small-angle neutron scattering study of the ultrastructure of chloroplast thylakoid membranes - Periodicity and structural flexibility of the stroma lamellae

    DEFF Research Database (Denmark)

    Posselt, Dorthe; Nagy, Gergely; Kirkensgaard, Jacob J. K.

    2012-01-01

    The multilamellar organization of freshly isolated spinach and pea chloroplast thylakoid membranes was studied using small-angle neutron scattering. A broad peak at similar to 0.02 angstrom(-1) is ascribed to diffraction from domains of ordered, unappressed stroma lamellae, revealing a repeat dis...

  12. Changes in antenna sizes of photosystems during state transitions in granal and stroma-exposed thylakoid membrane of intact chloroplasts in Arabidopsis mesophyll protoplasts.

    Science.gov (United States)

    Kim, Eunchul; Ahn, Tae Kyu; Kumazaki, Shigeichi

    2015-04-01

    In chloroplasts of plants and algae, state transition is an important regulatory mechanism to maintain the excitation balance between PSI and PSII in the thylakoid membrane. Light-harvesting complex II (LHCII) plays a key role as the regulated energy distributor between PSI and PSII. It is widely accepted that LHCII, which is bound to PSII localized mainly in the granal thylakoid, migrates to bind with PSI localized mainly in the stroma-exposed thylakoid under preferential excitation of PSII. The phenomena have been extensively characterized by many methods. However, the exchange of LHCII between PSII and PSI has not been directly observed in vivo at physiological temperatures. Herein we applied fluorescence spectromicroscopy to Arabidopsis mesophyll protoplasts in order to observe in vivo changes in fluorescence spectra of granal and stromal thylakoid regions during the state transition. The microscopic fluorescence spectra obtained from a few sections with different depths were decomposed into PSI and PSII spectra and self-absorption effects were removed. We were able to determine amplitude changes of PSI and PSII in fluorescence spectra solely due to state transition. Subdomain analysis of granal and stromal thylakoid regions clarified variant behaviors in the different regions.

  13. Fingerprinting the macro-organisation of pigment-protein complexes in plant thylakoid membranes in vivo by circular-dichroism spectroscopy.

    Science.gov (United States)

    Tóth, Tünde N; Rai, Neha; Solymosi, Katalin; Zsiros, Ottó; Schröder, Wolfgang P; Garab, Győző; van Amerongen, Herbert; Horton, Peter; Kovács, László

    2016-09-01

    Macro-organisation of the protein complexes in plant thylakoid membranes plays important roles in the regulation and fine-tuning of photosynthetic activity. These delicate structures might, however, undergo substantial changes during isolating the thylakoid membranes or during sample preparations, e.g., for electron microscopy. Circular-dichroism (CD) spectroscopy is a non-invasive technique which can thus be used on intact samples. Via excitonic and psi-type CD bands, respectively, it carries information on short-range excitonic pigment-pigment interactions and the macro-organisation (chiral macrodomains) of pigment-protein complexes (psi, polymer or salt-induced). In order to obtain more specific information on the origin of the major psi-type CD bands, at around (+)506, (-)674 and (+)690nm, we fingerprinted detached leaves and isolated thylakoid membranes of wild-type and mutant plants and also tested the effects of different environmental conditions in vivo. We show that (i) the chiral macrodomains disassemble upon mild detergent treatments, but not after crosslinking the protein complexes; (ii) in different wild-type leaves of dicotyledonous and monocotyledonous angiosperms the CD features are quite robust, displaying very similar excitonic and psi-type bands, suggesting similar protein composition and (macro-) organisation of photosystem II (PSII) supercomplexes in the grana; (iii) the main positive psi-type bands depend on light-harvesting protein II contents of the membranes; (iv) the (+)506nm band appears only in the presence of PSII-LHCII supercomplexes and does not depend on the xanthophyll composition of the membranes. Hence, CD spectroscopy can be used to detect different macro-domains in the thylakoid membranes with different outer antenna compositions in vivo.

  14. Light-triggered selective nitration of PsbO1 in isolated Arabidopsis thylakoid membranes is inhibited by photosynthetic electron transport inhibitors.

    Science.gov (United States)

    Takahashi, Misa; Shigeto, Jun; Sakamoto, Atsushi; Morikawa, Hiromichi

    2016-12-01

    PsbO1 is exclusively nitrated when isolated thylakoid membranes are incubated in a buffer bubbled with nitrogen dioxide (NO2) containing NO2 and nitrite. NO2 is the primary intermediate for this selective nitration. Isolated thylakoid membranes were incubated in NO2-bubbled buffer at 25°C in the light or dark. Protein analysis confirmed the selective nitration of PsbO1. Illumination was found to be essential in PsbO1 nitration. A nitration mechanism whereby nitratable tyrosine residues of PsbO1 are, prior to nitration, selectively photo-oxidized by photosynthetic electron transport to tyrosyl radicals to combine with NO2 to form 3-nitrotyrosine was hypothesized. We tested the electron transport inhibitors 3-(3,4-dichlorophenyl)-1,1- dimethylurea, sodium azide, and 1,5-diphenylcarbazide and found distinct inhibition of nitration of PsbO1. We also propose a possible nitration mechanism.

  15. A fluorescence detected magnetic resonance investigation of the carotenoid triplet states associated with Photosystem II of isolated spinach thylakoid membranes

    CERN Document Server

    Santabarbara, S; Carbonera, D; Heathcote, P

    2005-01-01

    The carotenoid triplet populations associated with the fluorescence emission chlorophyll forms of Photosystem II have been investigated in isolated spinach thylakoid membranes by means of fluorescence detected magnetic resonance in zero field (FDMR). The spectra collected in the 680-690 nm emission range, have been fitted by a global analysis procedure. At least five different carotenoid triplet states coupled to the terminal emitting chlorophyll forms of PS II, peaking at 682 nm, 687 nm and 692 nm, have been characterised. The triplets associated with the outer antenna emission forms, at 682 nm, have zero field splitting parameters D = 0.0385 cm/sup -1/, E = 0.00367 cm/sup -1/; D = 0.0404 cm/sup -1/, E = 0.00379 cm/sup -1/ and D = 0.0386 cm/sup -1/, E = 0.00406 cm/sup -1/ which are very similar to those previously reported for the xanthophylls of the isolated LHC II complex. Therefore the FDMR spectra recorded in this work provide insights into the organisation of the LHC II complex in the unperturbed enviro...

  16. Research on the ultrafast fluorescence property of thylakoid membranes of the wild-type and mutant rice

    Institute of Scientific and Technical Information of China (English)

    任兆玉; 许晓明; 王水才; 辛越勇; 贺俊芳; 侯洵

    2003-01-01

    A high yielding rice variety mutant (Oryza sativa L., Zhenhui 249) with low chlorophyll b (Chl b) has been discovered in natural fields. It has a quality character controlled by a pair of recessive genes (nuclear gene). The partial loss of Chl b in content affects the efficiency of light harvest in a light harvest complex (LHC), thus producing the difference of the exciting energy transfer and the efficiency of photochemistry conversion between the mutant and wild-type rice in photosynthetic unit. The efficiency of utilizing light energy is higher in the mutant than that in the wildtype rice relatively. For further discussion of the above-mentioned difference and learning about the mechanism of the increase in the photochemical efficiency of the mutant, the pico-second resolution fluorescence spectrum measurement with delay-frame-scanning single photon counting technique is adopted. Thylakoid membranes of the mutant and the wild-type rice are excited by an Ar+ laser with a pulse width of 120ps, repetition rate of 4MHz and wavelength of 514nm. Compared with the time and spectrum property of exciting fluorescence, conclusions of those ultrafast dynamic experiments are: 1) The speeds of the exciting energy transferred in photo-system I are faster than that in photo-system II in both samples. 2) The speeds of the exciting energy transfer of mutant sample are faster than those of the wildtype. This might be one of the major reasons why the efficiency of photosynthesis is higher in mutant than that in the wild-type rice.

  17. The effect of microgravity on proton permeability of thylakoid membranes and contribution of II and I photosystems in photosynthetic electron transport in pea chloroplasts.

    Science.gov (United States)

    Zolotareva, E K; Onoiko, E B; Sytnik, S K; Podorvanov, V V

    1999-07-01

    According to a number investigations microgravity conditions affect membrane apparatus of photosynthesis in cells of higher plants and alga [for review, see Kordyum et al., 1994; Kordyum, 1997]. (see for review). Chloroplasts of space-grown pea plants showed disintegration of grana, shrinkage of the membrane constituting the grana stacks and other structural perturbance of the photosynthetic membranes. However there have been no studies on the effect of microgravity on proton permeability of thylakoid membranes and closely connected with this parameter their photochemical characteristics. The aim of the study is investigation of microgravity effects on protonic permeability of photosynthetic membrane and contribution of photosystem II (PSII) and photosystem I (PSI) in electron transfer from water to potassium ferrycianide (FeCy) in isolated pea chloroplasts. Pea.

  18. Adaptational changes in the lipids and fatty acid profile of the cell and thylakoid membrane of rice plants exposed to sunlight.

    Science.gov (United States)

    Vaz, Janet F; Sharma, Prabhat Kumar

    2010-07-01

    Adaptational changes occurring in the lipids and fatty acids of the cell and the thylakoid membrane in response to high light treatment, was studied in 30 days old rice (Oryza sativa L. cv. Jyothi) plants grown under low (150-200 μmol m(-2) s(-1)) or moderate (600-800 μmol m(-2) s(-1)) light conditions. Results were compared with rice plants grown in high (1200-2200 μmol m(-2) s(-1)) light conditions. Exposure of rice plants and isolated chloroplast to high light, resulted in an increase in the amount of malonaldehyde, indicating oxidation of membrane lipids. Qualitative and quantitative changes in the phosphoglycolipids and quantitative changes in neutral lipids were observed in rice plants grown under the different growth conditions. A few of the phosphoglycolipids and neutral lipids were present exclusively in plants grown at low or moderate or high light, indicating requirement of different type of lipid composition of rice plants in response to their different growth irradiances. However, no significant quantitative changes were observed in the different saturated and unsaturated fatty acid groups of total lipids in low, moderate and high light grown rice plants, as a result of exposure to high light. No qualitative changes in the fatty acid composition due to difference in growth irradiance or high light treatment were seen. The changes observed in the phosphoglycolipids and neutral lipid composition of cell and thylakoid membrane of low, moderate and high light grown rice plants in response to high light, are probably the result of physiological changes in the rice plants, to sustain optimum structure and function of the cell and thylakoid membrane to maintain active physiological functions to endure high light conditions.

  19. The synthesis of NPQ-effective zeaxanthin depends on the presence of a transmembrane proton gradient and a slightly basic stromal side of the thylakoid membrane.

    Science.gov (United States)

    Goss, Reimund; Opitz, Christian; Lepetit, Bernard; Wilhelm, Christian

    2008-11-01

    In the present study we address the question which factors during the synthesis of zeaxanthin determine its capacity to act as a non-photochemical quencher of chlorophyll fluorescence. Our results show that zeaxanthin has to be synthesized in the presence of a transmembrane proton gradient. However, it is not essential that the proton gradient is generated by the light-driven electron transport. NPQ-effective zeaxanthin can also be formed by an artificial proton gradient in the dark due to ATP hydrolysis. Zeaxanthin that is synthesized in the dark in the absence of a proton gradient by the low pH-dependent activation of violaxanthin de-epoxidase is not able to induce NPQ. The second important factor during the synthesis of zeaxanthin is the pH-value of the stromal side of the thylakoid membrane. Here we show that the stromal side has to be neutral or slightly basic in order to generate zeaxanthin which is able to induce NPQ. Thylakoid membranes in reaction medium pH 5.2, which experience low pH-values on both sides of the membrane, are unable to generate NPQ-effective zeaxanthin, even in the presence of an additional light-driven proton gradient. Analysing the pigment contents of purified photosystem II light-harvesting complexes we are further able to show that the NPQ ineffectiveness of zeaxanthin formed in the absence of a proton gradient is not caused by changes in its rebinding to the light-harvesting proteins. Purified monomeric and trimeric light-harvesting complexes contain comparable amounts of zeaxanthin when they are isolated from thylakoid membranes enriched in either NPQ-effective or ineffective zeaxanthin.

  20. Reciprocal regulation of protein synthesis and carbon metabolism for thylakoid membrane biogenesis.

    Directory of Open Access Journals (Sweden)

    Alexandra-Viola Bohne

    Full Text Available Metabolic control of gene expression coordinates the levels of specific gene products to meet cellular demand for their activities. This control can be exerted by metabolites acting as regulatory signals and/or a class of metabolic enzymes with dual functions as regulators of gene expression. However, little is known about how metabolic signals affect the balance between enzymatic and regulatory roles of these dual functional proteins. We previously described the RNA binding activity of a 63 kDa chloroplast protein from Chlamydomonas reinhardtii, which has been implicated in expression of the psbA mRNA, encoding the D1 protein of photosystem II. Here, we identify this factor as dihydrolipoamide acetyltransferase (DLA2, a subunit of the chloroplast pyruvate dehydrogenase complex (cpPDC, which is known to provide acetyl-CoA for fatty acid synthesis. Analyses of RNAi lines revealed that DLA2 is involved in the synthesis of both D1 and acetyl-CoA. Gel filtration analyses demonstrated an RNP complex containing DLA2 and the chloroplast psbA mRNA specifically in cells metabolizing acetate. An intrinsic RNA binding activity of DLA2 was confirmed by in vitro RNA binding assays. Results of fluorescence microscopy and subcellular fractionation experiments support a role of DLA2 in acetate-dependent localization of the psbA mRNA to a translation zone within the chloroplast. Reciprocally, the activity of the cpPDC was specifically affected by binding of psbA mRNA. Beyond that, in silico analysis and in vitro RNA binding studies using recombinant proteins support the possibility that RNA binding is an ancient feature of dihydrolipoamide acetyltransferases. Our results suggest a regulatory function of DLA2 in response to growth on reduced carbon energy sources. This raises the intriguing possibility that this regulation functions to coordinate the synthesis of lipids and proteins for the biogenesis of photosynthetic membranes.

  1. The transporter SynPAM71 is located in the plasma membrane and thylakoids, and mediates manganese tolerance in Synechocystis PCC6803

    DEFF Research Database (Denmark)

    Gandini, Chiara; Schmidt, Sidsel Birkelund; Husted, Søren

    2017-01-01

    symptoms were observed in WT cells exposed to excess Mn. Moreover, CyanoP, which is involved in the early steps of PSII assembly, is massively upregulated in ΔSynPAM71. SynPAM71 was detected in both the plasma membrane and, to a lesser extent, the thylakoid membranes. Our results suggest that SynPAM71...... to chloroplast Mn homeostasis in Arabidopsis thaliana. Here, we characterize the function of its homolog in Synechocystis (SynPAM71). We used a loss-of-function line (ΔSynPAM71), wild-type (WT) cells exposed to Mn stress and strains expressing a tagged variant of SynPAM71 to characterize the role of SynPAM71...... in cyanobacterial Mn homeostasis. The ΔSynPAM71 strain displays an Mn-sensitive phenotype with reduced levels of chlorophyll and PSI accumulation, defects in PSII photochemistry and intracellular Mn enrichment, particularly in the thylakoid membranes. These effects are attributable to Mn toxicity, as very similar...

  2. Quality control of Photosystem II: the mechanisms for avoidance and tolerance of light and heat stresses are closely linked to membrane fluidity of the thylakoids

    Directory of Open Access Journals (Sweden)

    Yasusi Yamamoto

    2016-08-01

    Full Text Available When oxygenic photosynthetic organisms are exposed to excessive light and/or heat, Photosystem II is damaged and electron transport is blocked. In these events, reactive oxygen species, endogenous radicals and lipid peroxidation products generated by photochemical reaction and/or heat cause the damage. Regarding light stress, plants first dissipate excessive light energy captured by light-harvesting chlorophyll protein complexes as heat to avoid the hazards, but once light stress is unavoidable, they tolerate the stress by concentrating damage in a particular protein in photosystem II, i.e. the reaction-center binding D1 protein of Photosystem II. The damaged D1 is removed by specific proteases and replaced with a new copy produced through de novo synthesis (reversible photoinhibition. When light intensity becomes extremely high, irreversible aggregation of D1 occurs and thereby D1 turnover is prevented. Once the aggregated products accumulate in Photosystem II complexes, removal of them by proteases is difficult, and irreversible inhibition of Photosystem II takes place (irreversible photoinhibition. Important is that various aspects of both the reversible and irreversible photoinhibition are highly dependent on the membrane fluidity of the thylakoids. Heat stress-induced inactivation of photosystem II is an irreversible process, which may be also affected by the fluidity of the thylakoid membranes. Here I describe why the membrane fluidity is a key to regulate the avoidance and tolerance of Photosystem II on environmental stresses.

  3. Spectroelectrochemistry of P700 in native photosystem I particles and diethyl ether-treated thylakoid membranes from spinach and Thermosynechococcus elongatus.

    Science.gov (United States)

    Zhang, Yanrong; Nakamura, Akimasa; Kuroiwa, Yoshinori; Kato, Yuki; Watanabe, Tadashi

    2008-04-02

    The redox potentials (E(composite function')) of P700 in intact and diethyl ether-treated thylakoid membranes as well as native photosystem (PS) I particles from spinach and Thermosynechococcus elongatus have been measured by a spectroelectrochemistry with an error range of +/-2-3 mV. Stepwise removal of antenna pigments by ether treatment caused distinct shifts of the E( composite function') value with increasing degree of water saturation in ether; negatively from +471 to +428 mV for spinach, but positively from +423 to +436 mV for T. elongatus. Such a contrasting behavior is discussed by invoking the mode of action of ether on the microenvironments around P700.

  4. Interdependence between oscillations and transients of delayed fluorescence induction processes in the thylakoid membrane of the intact maize leaf: Responses to effects of increased temperatures and drought

    Directory of Open Access Journals (Sweden)

    Radenović Čedomir N.

    2010-01-01

    Full Text Available Standard induction processes of delayed fluorescence (DF of chlorophyll (induction signals occur when an intact leaf segment of maize inbreds and hybrids is kept in the phosphoroscope darkroom for more than 15 minutes (t > 15 min, and at the same time the leaf is illuminated with the intermittent white light. Resolved induction processes of DF chlorophyll into transients: A, B, C, D and E occur when the intact leaf segment of maize inbreds and hybrids is kept in the phosphoroscope darkroom for a significantly shorter period (500 s > t > 30 s, with the time rate t of 30 s, prior to its illumination with the intermittent white light. Induction transients: A, B, C, D and E are characterized with the time of their generation: tA = 31±6 ms (A, tB = 5 ± 0,5 s (B, tC = 15±5 s (C, tD = 360±20 s (D and tE = 670±35 s (E, dynamics of changes in transients intensities (IA, IB, IC, ID and IE and mechanisms of their generation. The induction processes of chlorophyll DF of the intact leaf of maize inbreds and hybrids resolved into transients: A, B, C, D and E are accompanied by the occurrence and different levels of activation energy (Ea, kJ mol-1 that correspond to critical temperatures ranging from 28 to 33°C. The generation mechanisms of induction transients A, B, C, D and E classify them into two groups. Transients A and B are of a physical character, while the transients: C, D, and E are of a chemical character. It is shown that the generation of the induction transients: B, C, D and E simultaneously follows establishing of the oscillations of induction processes of the DF chlorophyll. Oscillating of induction processes of DF chlorophyll is explained by the ion (K+, Na+, H+, Cl- transport mechanism across the thylakoid membrane of the intact leaf of maize inbreds and hybrids grown under conditions of air drought, increased temperatures and water deficiency in the medium.

  5. Superoxide production in aprotic interior of chloroplast thylakoids.

    Science.gov (United States)

    Takahashi, M; Asada, K

    1988-12-01

    The site of superoxide production in spinach thylakoids was found to be the aprotic interior of the thylakoid membranes near the P700 chlorophyll a protein at the reaction center of photosystem I complexes. This conclusion was drawn from the following findings. (i) Cytochrome c reduction by illuminated thylakoids, which was confirmed to be superoxide dependent by the failure of this reaction to occur in anaerobiosis, was completely inhibited by a dibutyl catechol, but partially inhibited by a hydrophilic disulfonated derivative. (ii) P700 chlorophyll a proteins were preferentially iodinated by lactoperoxidase by the use of hydrogen peroxide that was derived from the disproportionation of superoxides in illuminated thylakoids. (iii) Hydrogen peroxide production and oxygen uptake were induced by ammonium chloride, a proton conductor that can permeate through thylakoid membranes, but whole superoxide in the bulk solution was oxidized back to molecular oxygen by cytochrome c. The effective concentration of ammonium chloride decreased to one-sixtieth of the original, when an ammonium ion ionophore, nonactin, was added. Thus, the weak acid allowed superoxide to yield hydrogen peroxide disproportionately in the thylakoid membrane interior.

  6. High Yield Non-detergent Isolation of Photosystem I-Light-harvesting Chlorophyll II Membranes from Spinach Thylakoids: IMPLICATIONS FOR THE ORGANIZATION OF THE PS I ANTENNAE IN HIGHER PLANTS.

    Science.gov (United States)

    Bell, Adam J; Frankel, Laurie K; Bricker, Terry M

    2015-07-24

    Styrene-maleic acid copolymer was used to effect a non-detergent partial solubilization of thylakoids from spinach. A high density membrane fraction, which was not solubilized by the copolymer, was isolated and was highly enriched in the Photosystem (PS) I-light-harvesting chlorophyll (LHC) II supercomplex and depleted of PS II, the cytochrome b6/f complex, and ATP synthase. The LHC II associated with the supercomplex appeared to be energetically coupled to PS I based on 77 K fluorescence, P700 photooxidation, and PS I electron transport light saturation experiments. The chlorophyll (Chl) a/b ratio of the PS I-LHC II membranes was 3.2 ± 0.9, indicating that on average, three LHC II trimers may associate with each PS I. The implication of these findings within the context of higher plant PS I antenna organization is discussed.

  7. Rethinking the existence of a steady-state Δψ component of the proton motive force across plant thylakoid membranes.

    Science.gov (United States)

    Johnson, Matthew P; Ruban, Alexander V

    2014-02-01

    Light-driven photosynthetic electron transport is coupled to the movement of protons from the chloroplast stroma to the thylakoid lumen. The resulting proton motive force that is generated is used to drive the conformational rotation of the transmembrane thylakoid ATPase enzyme which converts ADP (adenosine diphosphate) and Pi (inorganic phosphate) into ATP (adenosine triphosphate), the energy currency of the plant cell required for carbon fixation and other metabolic processes. According to Mitchell's chemiosmotic hypothesis, the proton motive force can be parsed into the transmembrane proton gradient (ΔpH) and the electric field gradient (Δψ), which are thermodynamically equivalent. In chloroplasts, the proton motive force has been suggested to be split almost equally between Δψ and ΔpH (Kramer et al., Photosynth Res 60:151-163, 1999). One of the central pieces of evidence for this theory is the existence of a steady-state electrochromic shift (ECS) absorption signal detected ~515 nm in plant leaves during illumination. The interpretation of this signal is complicated, however, by a heavily overlapping absorption change ~535 nm associated with the formation of photoprotective energy dissipation (qE) during illumination. In this study, we present new evidence that dissects the overlapping contributions of the ECS and qE-related absorption changes in wild-type Arabidopsis leaves using specific inhibitors of the ΔpH (nigericin) and Δψ (valinomycin) and separately using leaves of the Arabidopsis lut2npq1 mutant that lacks qE. In both cases, our data show that no steady-state ECS signal persists in the light longer than ~60 s. The consequences of our observations for the suggesting parsing of steady-state thylakoid proton motive force between (ΔpH) and the electric field gradient (Δψ) are discussed.

  8. The photoelectrical properties of thylakoid membrane from two plants fabricated on Nano-ZnO%两种植物类囊体膜在纳米ZnO上的组装和光电性质

    Institute of Scientific and Technical Information of China (English)

    刘双; 张攀辉; 邱宇; 张建; 于道永

    2012-01-01

    ZnO nanowires were synthesized on the FTO glass by hydrothermal method and characterized by atomic force microscopy(AFM) and scanning electron microscopy(SEM).Thylakoid membranes isolated from higher plant spinach and marine green alga Ulva lactuca were fabricated on the ZnO nanowires by using Langmuir Blodgett(LB) technique.The photoelectrical properties of these two resulting systems were assessed and compared by solar cell test system.Photocurrents were both observed the solar cells containing the LB films of the thylakoid membranes of these two plants.The photoelectric conversion efficiencies of solar cells were increased significantly with the numbers of LB film layer.In addition,the photoelectric conversion efficiency of cell containing Ulva thylakoid membrane was much higher than that of spinach.%用水热合成法在掺氟氧化锡(SnO2:F,FTO)导电玻璃上合成了ZnO纳米线并用原子力显微镜(AFM)和扫描电镜(SEM)对其进行了表征。利用LB膜技术将高等植物菠菜(Spinacia oleracea)和海洋绿藻石莼(Ulva lactuca)的类囊体膜分别固定在纳米ZnO上组装成光电池,用太阳能测试系统检测比较了其光电性质。研究表明,由两种植物的类囊体膜LB膜组成的光电池都能产生光生电流;蛋白LB膜的层数显著影响了光电池的光电转化效率,随着层数的增加,光电转化效率大大增加。此外,石莼类囊体膜组装的光电池光电转化效率明显高于菠菜类囊体膜。

  9. 盐胁迫对水稻幼苗类囊体膜脂肪酸组分的影响%Effects of Salt Stress on Fatty Acid Composition of Thylakoid Membrane of Two Rice Cultivars Differing in Salt Tolerance

    Institute of Scientific and Technical Information of China (English)

    王仁雷; 华春; 周峰; 周泉澄; 周斌伟

    2008-01-01

    [Objective] The aim of the study is to understand the changes of fatty acid composition of rice thylakoid membrane under salt stress. [Method] Under salt stress of different concentrations of NaCl, rice seedlings of Pokkali and Peta with six leaves and one central leaf were used as experimental materials to extract the fatty acid from their thylakoid membranes, and gas chromatograph(1890) was used to analyze fatty acid composition. [Result] Fatty acid component 14∶ 0, 18∶ 0, 16∶ 1(3t), 18∶ 1 in both the two experimental materials showed little variations in the first four days of salt stress, whereafter they increased slightly; while the fatty acid component 16∶ 0 and level of saturation of fatty acid (LSFA) showed the similar variation trend in the first four days of treatment compared to those of the fatty acid components mentioned above, whereafter they rose in Pokkali and presented an opposite variation trend in Peta; fatty acid component 18∶ 3 and level of unsaturation of fatty acid (LUFA) reduced all the time under stress condition, and the reducing amplitude in 100 mmol/L NaCl treatment group was smaller than that of 100 mmol/L NaCl treatment group, and in Pokkali was smaller than that in Peta under specific conditions. Meanwhile, level of saturation of fatty acid in both experimental materials increased, and the rising amplitude in Peta was smaller than that of Pokkali. [Conclusion] With regard to LUFA, Pokkali is endowed with more salt tolerance than Peta.

  10. Genome Size Dynamics and Evolution in Monocots

    Directory of Open Access Journals (Sweden)

    Ilia J. Leitch

    2010-01-01

    Full Text Available Monocot genomic diversity includes striking variation at many levels. This paper compares various genomic characters (e.g., range of chromosome numbers and ploidy levels, occurrence of endopolyploidy, GC content, chromosome packaging and organization, genome size between monocots and the remaining angiosperms to discern just how distinctive monocot genomes are. One of the most notable features of monocots is their wide range and diversity of genome sizes, including the species with the largest genome so far reported in plants. This genomic character is analysed in greater detail, within a phylogenetic context. By surveying available genome size and chromosome data it is apparent that different monocot orders follow distinctive modes of genome size and chromosome evolution. Further insights into genome size-evolution and dynamics were obtained using statistical modelling approaches to reconstruct the ancestral genome size at key nodes across the monocot phylogenetic tree. Such approaches reveal that while the ancestral genome size of all monocots was small (1C=1.9 pg, there have been several major increases and decreases during monocot evolution. In addition, notable increases in the rates of genome size-evolution were found in Asparagales and Poales compared with other monocot lineages.

  11. Structure and dynamics of thylakoids in land plants

    DEFF Research Database (Denmark)

    Pribil, Mathias; Labs, Mathias; Leister, Dario

    2014-01-01

    of the granum. Stacking of grana is thought to be due to adhesion between Lhcb proteins (LHCII or CP26) located in opposed thylakoid membranes. The grana margins contain oligomers of CURT1 proteins, which appear to control the size and number of grana discs in a dosage- and phosphorylation-dependent manner...

  12. 菊花黄绿叶突变体的光合与类囊体膜光谱%Characteristics of Photosynthesis and Spectra Properties of Thylakoid Membranes in the Yellow-Green Leaf Mutant of Chrysanthemum

    Institute of Scientific and Technical Information of China (English)

    常青山; 张利霞; 陈煜; 陈素梅; 刘兆磊; 房伟民; 陈发棣

    2013-01-01

    In order to study photosynthetic mechanism of the yellow-green leaf mutant- 'Jinglingguozi ' of chrysanthemum, the characteristics of photosynthesis and the spectra properties of thylakoid membrane in the green and yellow leaf tissue of the mutant were studied. We measured the photosynthesis, stomatal characteristics, room temperature absorption spectra, chlorophyll emission fluorescence spectra of thylakoid membrane. The results that compared to the green leaf tissue of the mutant, the yellow leaf tissue had lower net photosynthetic rate ( Pn ) , light saturation point (LSP) , dark respiration rate (Rd) , apparent quantum yield (AQY) , but higher light compensation point (LCP). The yellow leaf tissue had lower stomata limit value ( Ls ) , but higher non-stomata limit value. There was no significant difference in the characteristics of stomatal microstructure between the green leaf and yellow leaf tissue. The absorption spectra and fluorescence spectra significantly decreased in the yellow leaf tissue. The yellow leaf tissue had significantly lower capacity of the capture and excitation of light energy and lower the photosynthetic capacity than the green leaf tissue did, which was caused by non-stomata factors, such as a decrease of the function of thylakoid membrane.%以菊花‘金陵国紫’黄绿叶突变体为试验材料,研究该突变体黄绿叶的绿叶与黄叶组织光合与类囊体膜光谱特性.对突变体黄绿叶中绿叶与黄叶组织的光合速率、光响应曲线、气孔特征与类囊体膜光谱特性进行测定与分析.结果表明:与绿叶组织相比,突变体黄叶组织的净光合速率、光饱和点、暗呼吸速率、表观量子效率均显著低于绿叶组织,而光补偿点则显著高于绿叶组织;黄叶组织的气孔限制值低于绿叶组织,非气孔限制值则显著高于绿叶组织,而黄叶与绿叶组织的气孔特征并无显著性差异.突变体黄叶组织类囊体膜叶绿素捕光能力与受激

  13. Arabidopsis ANGULATA10 is required for thylakoid biogenesis and mesophyll development.

    Science.gov (United States)

    Casanova-Sáez, Rubén; Mateo-Bonmatí, Eduardo; Kangasjärvi, Saijaliisa; Candela, Héctor; Micol, José Luis

    2014-06-01

    The chloroplasts of land plants contain internal membrane systems, the thylakoids, which are arranged in stacks called grana. Because grana have not been found in Cyanobacteria, the evolutionary origin of genes controlling the structural and functional diversification of thylakoidal membranes in land plants remains unclear. The angulata10-1 (anu10-1) mutant, which exhibits pale-green rosettes, reduced growth, and deficient leaf lateral expansion, resulting in the presence of prominent marginal teeth, was isolated. Palisade cells in anu10-1 are larger and less packed than in the wild type, giving rise to large intercellular spaces. The ANU10 gene encodes a protein of unknown function that localizes to both chloroplasts and amyloplasts. In chloroplasts, ANU10 associates with thylakoidal membranes. Mutant anu10-1 chloroplasts accumulate H2O2, and have reduced levels of chlorophyll and carotenoids. Moreover, these chloroplasts are small and abnormally shaped, thylakoidal membranes are less abundant, and their grana are absent due to impaired thylakoid stacking in the anu10-1 mutant. Because the trimeric light-harvesting complex II (LHCII) has been reported to be required for thylakoid stacking, its levels were determined in anu10-1 thylakoids and they were found to be reduced. Together, the data point to a requirement for ANU10 for chloroplast and mesophyll development.

  14. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    Science.gov (United States)

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification.

  15. Transcript profiling of a novel plant meristem, the monocot cambium

    Science.gov (United States)

    Matthew Zinkgraf; Suzanne Gerttula; Andrew Groover

    2017-01-01

    While monocots lack the ability to produce a vascular cambium or woody growth, some monocot lineages evolved a novel lateral meristem, the monocot cambium, which supports secondary radial growth of stems. In contrast to the vascular cambium found in woody angiosperm and gymnosperm species, the monocot cambium produces secondary vascular bundles, which have an...

  16. The role of auxin transporters in monocots development

    Directory of Open Access Journals (Sweden)

    Sara eBalzan

    2014-08-01

    Full Text Available Auxin is a key regulator of plant growth and development, orchestrating cell division, elongation and differentiation, embryonic development, root and stem tropisms, apical dominance and transition to flowering. Auxin levels are higher in undifferentiated cell populations and decrease following organ initiation and tissue differentiation. This differential auxin distribution is achieved by polar auxin transport (PAT mediated by auxin transport proteins. There are 4 major families of auxin transporters in plants: PINs, ABCBs, AUX/LAXs and PILS. These families include proteins located at the plasma membrane (PM or at the Endoplasmic Reticulum (ER, which participate in auxin influx, efflux or both, from the apoplast into the cell or from the cytosol into the ER compartment. Auxin transporters have been largely studied in the dicotyledon model species Arabidopsis, but there is increasing evidence of their role in auxin regulated development in monocotyledon species. In monocots, families of auxin transporters are enlarged and often include duplicated genes and proteins with high sequence similarity. Some of these proteins underwent sub- and neo-functionalization with substantial modification to their structure and expression in organs such as adventitious roots, panicles, tassels and ears. Most of the present information on monocot auxin transporters function derives from studies conducted in rice, maize, sorghum and Brachypodium using pharmacological applications (PAT inhibitors or down-/up-regulation (over-expression and RNAi of candidate genes. Gene expression studies and comparison of predicted protein structures have also increased our knowledge of the role of PAT in monocots. However, knockout mutants and functional characterization of single genes are still scarce and the future availability of such resources will prove crucial to elucidate the role of auxin transporters in monocot development.

  17. TIR-NBS-LRR genes are rare in monocots: evidence from diverse monocot orders

    Directory of Open Access Journals (Sweden)

    Tarr D Ellen K

    2009-09-01

    Full Text Available Abstract Background Plant resistance (R gene products recognize pathogen effector molecules. Many R genes code for proteins containing nucleotide binding site (NBS and C-terminal leucine-rich repeat (LRR domains. NBS-LRR proteins can be divided into two groups, TIR-NBS-LRR and non-TIR-NBS-LRR, based on the structure of the N-terminal domain. Although both classes are clearly present in gymnosperms and eudicots, only non-TIR sequences have been found consistently in monocots. Since most studies in monocots have been limited to agriculturally important grasses, it is difficult to draw conclusions. The purpose of our study was to look for evidence of these sequences in additional monocot orders. Findings Using degenerate PCR, we amplified NBS sequences from four monocot species (C. blanda, D. marginata, S. trifasciata, and Spathiphyllum sp., a gymnosperm (C. revoluta and a eudicot (C. canephora. We successfully amplified TIR-NBS-LRR sequences from dicot and gymnosperm DNA, but not from monocot DNA. Using databases, we obtained NBS sequences from additional monocots, magnoliids and basal angiosperms. TIR-type sequences were not present in monocot or magnoliid sequences, but were present in the basal angiosperms. Phylogenetic analysis supported a single TIR clade and multiple non-TIR clades. Conclusion We were unable to find monocot TIR-NBS-LRR sequences by PCR amplification or database searches. In contrast to previous studies, our results represent five monocot orders (Poales, Zingiberales, Arecales, Asparagales, and Alismatales. Our results establish the presence of TIR-NBS-LRR sequences in basal angiosperms and suggest that although these sequences were present in early land plants, they have been reduced significantly in monocots and magnoliids.

  18. Acute Effects of a Spinach Extract Rich in Thylakoids on Satiety: A Randomized Controlled Crossover Trial

    OpenAIRE

    Rebello, Candida J.; Chu, Jessica; Beyl, Robbie; Edwall, Dan; Erlanson-Albertsson, Charlotte; Frank L. Greenway

    2015-01-01

    Objective: By retarding fat digestion, thylakoids, the internal photosynthetic membrane system of green plants, promote the release of satiety hormones. This study examined the effect of consuming a single dose of concentrated extract of thylakoids from spinach on satiety, food intake, lipids, and glucose compared to a placebo. Design: Sixty overweight and obese individuals enrolled in a double-blind randomized crossover study consumed the spinach extract or placebo in random order at least a...

  19. Molecular analysis of a thylakoid K+ channel

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-05-01

    The work undertaken during the prior granting period sought to use a novel probe to identify and clone plant ion (K) channels. It was also proposed that in vitro biochemical studies of cation transport across purified preparations of thylakoid membrane be employed to characterize a putative K channel in this membrane system. Over the last several years (including those of the previous grant period), an enormous data base of partially-sequenced mRNAs and numerous genomes (including those of plants) has evolved and provides a powerful alternative to this brute-force approach to identify and clone cDNAs ending physiologically important membrane proteins such as channels. The utility of searching genetic databases for relevant sequences, in addition to the difficulty of working with membrane proteins, led to changes in research focus during the prior granting period, and has resulted in the identification of a new class of plant ion channels, which will be the focus of research during the proposed new granting period.

  20. Increase in electron transfer activity in photosystem Ⅱ of spinach thylakoids caused by conversion of phosphatidyl-glycerol to phosphatidic acid molecules

    Institute of Scientific and Technical Information of China (English)

    WU Feng; YANG Zhenle; LI Liangbi; KUANG Tingyun

    2003-01-01

    The techniques of oxygen electrode polarography, sodium dodecyl sulfate-polyacryamide gel electrophoresis (SDS-PAGE) and thin layer chromatography (TLC) were employed to investigate the effect of phospholipase D treatment on physiological function of spinach thylakoids. It was shown that the phospholipase D treatment on thylakoid resulted in the degradation of phosphatidylglycerol (PG) and occurrence of phosphatidic acid (PA). The changes of PG to PA molecules caused an increase in oxygen evolution in photosystem Ⅱ (PSⅡ), which was accompanied by an uncoupling effect on thylakoid membrane. It was revealed that the head-groups of PG molecules play an important role in the maintenance of the appropriate physiological activity of thylakoid membrane.

  1. A difference gel electrophoresis study on thylakoids isolated from poplar leaves reveals a negative impact of ozone exposure on membrane proteins.

    Science.gov (United States)

    Bohler, Sacha; Sergeant, Kjell; Hoffmann, Lucien; Dizengremel, Pierre; Hausman, Jean-Francois; Renaut, Jenny; Jolivet, Yves

    2011-07-01

    Populus tremula L. x P. alba L. (Populus x canescens (Aiton) Smith), clone INRA 717-1-B4, saplings were subjected to 120 ppb ozone exposure for 28 days. Chloroplasts were isolated, and the membrane proteins, solubilized using the detergent 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC), were analyzed in a difference gel electrophoresis (DiGE) experiment comparing control versus ozone-exposed plants. Extrinsic photosystem (PS) proteins and adenosine triphosphatase (ATPase) subunits were detected to vary in abundance. The general trend was a decrease in abundance, except for ferredoxin-NADP(+) oxidoreductase (FNR), which increased after the first 7 days of exposure. The up-regulation of FNR would increase NAPDH production for reducing power and detoxification inside and outside of the chloroplast. Later on, FNR and a number of PS and ATPase subunits decrease in abundance. This could be the result of oxidative processes on chloroplast proteins but could also be a way to down-regulate photochemical reactions in response to an inhibition in Calvin cycle activity.

  2. Blue-light mediated accumulation of nuclear-encoded transcripts coding for proteins of the thylakoid membrane is absent in the phytochrome-deficient aurea mutant of tomato.

    Science.gov (United States)

    Oelmüller, R; Kendrick, R E; Briggs, W R

    1989-08-01

    Polyclonal antibodies against pea phytochrome detect 2 protein bands (about 116 and 120 kDa) on blots of crude protein extracts and protein of microsomal preparations of dark-grown tomato seedlings. Both protein bands are undetectable in Western blots of the aurea mutant extracts. Neither protein band is detectable after isogenic wild-type seedlings are illuminated with 3 h of red light, either in the crude extract or in the membrane fraction of the irradiated seedlings; this result is consistent with the hypothesis that both bands are phytochrome. When dark-grown wild-type seedlings are illuminated with 3 h of red light or blue light against a red light background, the transcript levels for chlorophyll a/b-binding proteins of photosystem I and II, plastocyanin, and the subunit II of photosystem I increase. In all cases, the same fluence rate of blue light is much more effective than red light alone, a result that indicates the involvement of a blue/UV-A light photoreceptor in addition to the involvement of the far-red-absorbing form of phytochrome, Pfr. The aurea mutant responds neither to red light nor to blue light. Thus, no Pfr-independent induction of the four transcripts by a blue/UV-A light photoreceptor can be measured in the aurea mutant.

  3. Two roles of thylakoid lipids in modifying the activity of herbicides which inhibit photosystem II

    Energy Technology Data Exchange (ETDEWEB)

    Kupatt, C.C. Jr.

    1985-01-01

    Thylakoid lipids may modify the activity of herbicides which inhibit electron transport at the Q/sub B/ protein of photosystem II in two ways: (1) lipids can act as a hydrophobic barrier to a binding site localized close to the loculus of the membrane, and (2) changes in lipid composition can reduce the ability of inhibitors to block electron transport, possibly due to a change in the conformation of the Q/sub B/ protein. The herbicide binding site was localized close to the locular side of the thylakoid membrane by determining the activity of a number of substituted phenylurea and s-triazine herbicides in inverted and non-inverted thylakoids. Quantitative structure-activity relationship analysis showed that inversion of thylakoids reduced the requirement of molecular lipophilicity deemed necessary for phenylurea activity in non-inverted membranes, whereas s-triazines exhibited no differences in the lipophilicity requirement in thylakoid membranes of either orientation. The binding affinity of /sup 14/C-diuron was reduced in bicarbonate-depleted thylakoids relative to reconstituted or control membranes, as is the case with atrazine binding. These observations support a model of the herbicide binding site containing both common and herbicide family specific binding domains. Thylakoids isolated either from detached lambs quarters (Chenopodium album L.) leaves, treated with SAN 6706, or from soybean (Glycine max L.), with norflurazon or pyrazon applied preemergence, exhibited decreased susceptibility to atrazine. The ability of lipid-modifying treatments to decrease the atrazine susceptibility of field-grown soybeans was also investigated.

  4. Proteins affecting thylakoid morphology - the key to understanding vesicle transport in chloroplasts?

    Science.gov (United States)

    Lindquist, Emelie; Aronsson, Henrik

    2014-01-01

    We recently showed that a Rab protein, CPRabA5e (CP = chloroplast localized), is located in chloroplasts of Arabidopsis thaliana where it is involved in various processes, such as thylakoid biogenesis and vesicle transport. Using a yeast two-hybrid method, CPRabA5e was shown to interact with a number of chloroplast proteins, including the CURVATURE THYLAKOID 1A (CURT1A) protein and the light-harvesting chlorophyll a/b binding protein (LHCB1.5). CURT1A has recently been shown to modify thylakoid architecture by inducing membrane curvature in grana, whereas LHCB1.5 is a protein of PSII (Photosystem II) facilitating light capture. LHCB1.5 is imported to chloroplasts and transported to thylakoid membranes using the post-translational Signal Recognition Particle (SRP) pathway. With this information as starting point, we here discuss their subsequent protein-protein interactions, given by the literature and Interactome 3D. CURT1A itself and several of the proteins interacting with CURT1A and LHCB1.5 have relations to vesicle transport and thylakoid morphology, which are also characteristics of cprabA5e mutants. This highlights the previous hypothesis of an alternative thylakoid targeting pathway for LHC proteins using vesicles, in addition to the SRP pathway.

  5. Transcript profiling of a novel plant meristem, the monocot cambium.

    Science.gov (United States)

    Zinkgraf, Matthew; Gerttula, Suzanne; Groover, Andrew

    2017-06-01

    While monocots lack the ability to produce a vascular cambium or woody growth, some monocot lineages evolved a novel lateral meristem, the monocot cambium, which supports secondary radial growth of stems. In contrast to the vascular cambium found in woody angiosperm and gymnosperm species, the monocot cambium produces secondary vascular bundles, which have an amphivasal organization of tracheids encircling a central strand of phloem. Currently there is no information concerning the molecular genetic basis of the development or evolution of the monocot cambium. Here we report high-quality transcriptomes for monocot cambium and early derivative tissues in two monocot genera, Yucca and Cordyline. Monocot cambium transcript profiles were compared to those of vascular cambia and secondary xylem tissues of two forest tree species, Populus trichocarpa and Eucalyptus grandis. Monocot cambium transcript levels showed that there are extensive overlaps between the regulation of monocot cambia and vascular cambia. Candidate regulatory genes that vary between the monocot and vascular cambia were also identified, and included members of the KANADI and CLE families involved in polarity and cell-cell signaling, respectively. We suggest that the monocot cambium may have evolved in part through reactivation of genetic mechanisms involved in vascular cambium regulation. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

  6. A Mr 95,000 polypeptide in Porphyridium cruentum phycobilisomes and thylakoids: Possible function in linkage of phycobilisomes to thylakoids and in energy transfer

    Science.gov (United States)

    Redlinger, Thomas; Gantt, Elisabeth

    1982-01-01

    Two pigmented polypeptides with the same molecular weight (Mr 95,000) were isolated from the photosynthetic apparatus of Porphyridium cruentum by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. A blue polypeptide from phycobilisomes had absorption and fluorescence emission spectra similar to those of allophycocyanin. A green-pigmented polypeptide from photosynthetic membranes (free of phycobilisomes) contained chlorophyll a. Several properties were common to the Mr 95,000 polypeptides from both sources: (i) identical molecular weights, (ii) identical gel electrophoresis patterns after limited protease digestion, and (iii) immunological crossreactivity with an IgG fraction directed against the Mr 95,000 polypeptide from phycobilisomes. On the basis of this evidence, a common polypeptide exists in phycobilisomes and thylakoids, and it probably anchors the phycobilisome to the thylakoid membrane. The fluorescence emission overlap of the blue and green polypeptides suggests that they are involved in the transfer of energy from phycobilisomes to thylakoids. Images PMID:16593227

  7. Consumption of thylakoid-rich spinach extract reduces hunger, increases satiety and reduces cravings for palatable food in overweight women.

    Science.gov (United States)

    Stenblom, Eva-Lena; Egecioglu, Emil; Landin-Olsson, Mona; Erlanson-Albertsson, Charlotte

    2015-08-01

    Green-plant membranes, thylakoids, have previously been found to increase postprandial release of the satiety hormone GLP-1, implicated in reward signaling. The purpose of this study was to investigate how treatment with a single dose of thylakoids before breakfast affects homeostatic as well as hedonic hunger, measured as wanting and liking for palatable food (VAS). We also examined whether treatment effects were correlated to scores for eating behavior. Compared to placebo, intake of thylakoids significantly reduced hunger (21% reduction, p satiety (14% increase, p hunger, associated with overeating and obesity. Individuals scoring higher for emotional eating behavior may have enhanced treatment effect on cravings for palatable food.

  8. A new concept for ferredoxin-NADP(H) oxidoreductase binding to plant thylakoids.

    Science.gov (United States)

    Benz, J Philipp; Lintala, Minna; Soll, Jürgen; Mulo, Paula; Bölter, Bettina

    2010-11-01

    During the evolution of photosynthesis, regulatory circuits were established that allow the precise coupling of light-driven electron transfer chains with downstream processes such as carbon fixation. The ferredoxin (Fd):ferredoxin-NADP(+) oxidoreductase (FNR) couple is an important mediator for these processes because it provides the transition from exclusively membrane-bound light reactions to the mostly stromal metabolic pathways. Recent progress has allowed us to revisit how FNR is bound to thylakoids and to revaluate the current view that only membrane-bound FNR is active in photosynthetic reactions. We argue that the vast majority of thylakoid-bound FNR of higher plants is not necessary for photosynthesis. We furthermore propose that the correct distribution of FNR between stroma and thylakoids is used to efficiently regulate Fd-dependent electron partitioning in the chloroplast. Copyright © 2010 Elsevier Ltd. All rights reserved.

  9. Extensins in graminaceous monocots and dicots compared

    Energy Technology Data Exchange (ETDEWEB)

    Kieliszewski, M.; Lamport, D.T.A.

    1987-04-01

    Is the cellulose-extensin warp-weft model of primary cell wall organization generally applicable, or restricted to dicots. Although wall-bound hydroxyproline is usually a quantitative measure of extensin content, it is not definitive at low hyp levels typical of graminaceous monocots. Therefore the authors searched for putative soluble extensins ionically-bound to the cell wall of maize cell suspension cultures. Fractionation of AlCl/sub 3/ eluates on cellex-P, Cellex-E, and Superose-6 gave two HRGPs CEV and CE1 which compositionally resembled extensins rather than the arabinogalactan HRGPs. CEV and CE1 did not react with Yariv's antigen, but did cross-react with antibodies raised against tomato extensin. A tryptic peptide map of CEV gave some major peptides enriched in hydroxyproline and proline residues, indicating peptide periodicity. TEM of the low-angle shadowed protein gave flexuous rodlike molecules of 80 nm contour length. This is the best evidence to date for extensin in monocots.

  10. Immunoelectron microscopy for locating calvin cycle enzymes in the thylakoids of synechocystis 6803.

    Science.gov (United States)

    Agarwal, Rachna; Ortleb, Stefan; Sainis, Jayashree Krishna; Melzer, Michael

    2009-01-01

    Unicellular cyanobacteria Synechocystis 6803 were fixed using high-pressure freezing (HPF) and freeze substitution without any chemical cross-linkers. Immunoelectron microscopy of these cells showed that five sequential enzymes of the Calvin cycle (phosphoriboisomerase, phosphoribulokinase, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), 3-phosphoglyceratekinase and glyceraldehyde-3-phosphate dehydrogenase) and the catalytic portion of the chloroplast H+-ATP synthase (CF1) are located adjacent to the thylakoid membranes. Cell-free extracts of Synechocystis were processed by ultracentrifugation to isolate thylakoid fractions sedimenting at 40,000, 90,000, and 150,000 g. Among these, the 150,000-g fraction showed the highest linked activity of the above five sequential Calvin cycle enzymes and also the highest coordinated activity of light and dark reactions as assessed by ribose-5-phosphate (R-5-P) +ADP dependent CO2 fixation. Immunogold labeling of this membrane fraction confirmed the presence of the above five enzymes as well as the catalytic portion of the CF1 ATP synthase. Notably, the protein A-gold labeling of the thylakoids was observed without use of chemical cross-linkers and in spite of the normal washing steps used during standard immunolabeling. The results showed that soluble Calvin cycle enzymes might be organized along the thylakoid membranes.

  11. Immunoelectron Microscopy for Locating Calvin Cycle Enzymes in the Thylakoids of Synechocystis 6803

    Institute of Scientific and Technical Information of China (English)

    Rachna Agarwal; Stefan Ortleb; Jayashree Krishna Saini; Michael Melzer

    2009-01-01

    Unicellular cyanobacteria Synechocystis 6803 were fixed using high-pressure freezing (HPF) and freeze substitution without any chemical cross-linkers. Immunoelectron microscopy of these cells showed that five sequential enzymes of the Calvin cycle (phosphoriboisomerase, phosphoribulokinase, ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBisCO), 3-phosphoglyceratekinase and glyceraldehyde-3-phosphate dehydrogenase) and the catalytic portion of the chloroplast H+-ATP synthase (CF1) are located adjacent to the thylakoid membranes. Cell-free extracts of Synechocystis were processed by ultracentrifugation to isolate thylakoid fractions sedimenting at 40 000, 90 000, and 150 000 g.Among these, the 150 000-g fraction showed the highest linked activity of the above five sequential Calvin cycle enzymes and also the highest coordinated activity of light and dark reactions as assessed by ribose-5-phosphate (R-5-P) +ADP dependent CO2 fixation. Immunogold labeling of this membrane fraction confirmed the presence of the above five enzymes as well as the catalytic portion of the CF1 ATP synthase. Notably, the protein A-gold labeling of the thylakoids was observed without use of chemical cross-linkers and in spite of the normal washing steps used during standard immunolabeling. The results showed that soluble Calvin cycle enzymes might be organized along the thylakoid membranes.

  12. Supplementation by thylakoids to a high carbohydrate meal decreases feelings of hunger, elevates CCK levels and prevents postprandial hypoglycaemia in overweight women.

    Science.gov (United States)

    Stenblom, Eva-Lena; Montelius, Caroline; Östbring, Karolina; Håkansson, Maria; Nilsson, Sofia; Rehfeld, Jens F; Erlanson-Albertsson, Charlotte

    2013-09-01

    Thylakoids are chlorophyll-containing membranes in chloroplasts that have been isolated from green leaves. It has been previously shown that thylakoids supplemented with a high-fat meal can affect cholecystokinin (CCK), ghrelin, insulin and blood lipids in humans, and can act to suppress food intake and prevent body weight gain in rodents. This study investigates the addition of thylakoids to a high carbohydrate meal and its effects upon hunger motivation and fullness, and the levels of glucose, insulin, CCK, ghrelin and tumour necrosis factor (TNF)-alpha in overweight women. Twenty moderately overweight female subjects received test meals on three different occasions; two thylakoid enriched and one control, separated by 1 week. The test meals consisted of a high carbohydrate Swedish breakfast, with or without addition of thylakoids. Blood samples and VAS-questionnaires were evaluated over a 4-h period. Addition of thylakoids suppressed hunger motivation and increased secretion of CCK from 180 min, and prevented postprandial hypoglycaemia from 90 min following food intake. These effects indicate that thylakoids may intensify signals of satiety. This study therefore suggests that the dietary addition of thylakoids could aid efforts to reduce food intake and prevent compensational eating later in the day, which may help to reduce body weight over time.

  13. Do global diversity patterns of vertebrates reflect those of monocots?

    Directory of Open Access Journals (Sweden)

    Lynsey McInnes

    Full Text Available Few studies of global diversity gradients in plants exist, largely because the data are not available for all species involved. Instead, most global studies have focussed on vertebrates, as these taxa have historically been associated with the most complete data. Here, we address this shortfall by first investigating global diversity gradients in monocots, a morphologically and functionally diverse clade representing a quarter of flowering plant diversity, and then assessing congruence between monocot and vertebrate diversity patterns. To do this, we create a new dataset that merges biome-level associations for all monocot genera with country-level associations for almost all ∼70,000 species. We then assess the evidence for direct versus indirect effects of this plant diversity on vertebrate diversity using a combination of linear regression and structural equation modelling (SEM. Finally, we also calculate overlap of diversity hotspots for monocots and each vertebrate taxon. Monocots follow a latitudinal gradient although with pockets of extra-tropical diversity, mirroring patterns in vertebrates. Monocot diversity is positively associated with vertebrate diversity, but the strength of correlation varies depending on the clades being compared. Monocot diversity explains marginal amounts of variance (<10% after environmental factors have been accounted for. However, correlations remain among model residuals, and SEMs apparently reveal some direct effects of monocot richness. Our results suggest that collinear responses to environmental gradients are behind much of the congruence observed, but that there is some evidence for direct effects of producer diversity on consumer diversity. Much remains to be done before broad-scale diversity gradients among taxa are fully explained. Our dataset of monocot distributions will aid in this endeavour.

  14. Cercosporoid fungi (Mycosphaerellaceae) 3. Species on monocots (Poaceae, true grasses)

    NARCIS (Netherlands)

    Braun, Uwe; Crous, Pedro W; Nakashima, Chiharu

    The third part of a series of monographic treatments of cercosporoid fungi (formerly Cercospora s. lat., Mycosphaerellaceae, Ascomycota) continues with a treatment of taxa on monocots (Liliopsida; Equisetopsida, Magnoliidae, Lilianae), covering asexual and holomorph species with mycosphaerella-like

  15. Molecular basis of development in petaloid monocot flowers

    DEFF Research Database (Denmark)

    Johansen, Bo; Frederiksen, Signe; Skipper, Martin

    2006-01-01

    -class genes and at least two copies of A-class genes: one is expressed in floral meristems, the other in inflorescence meristems. In monocots and non-core eudicots the validity of the ABC model is under discussion. Generally, more than one functional copy is found of at least one of the B-class genes. The A......-class genes apparently are expressed in meristems of both flower and inflorescence. Morphologically petaloid stamens and styles are well known within the petaloid monocots, whereas the phenomenon is rare in core eudicots. A simple model based on the extra copies of B-class genes can explain the molecular...

  16. Trichloroacetate affects the EPR SignalⅡslow and SignalⅠin the thylakoid of Chlamydomonas reinhardtii

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    One electron paramagnetic resonance (EPR) signal, named SignalⅡslow, originates from the oxidized Tyrosine 160 (YDo) of D2 polypeptide of photosystemⅡ reaction center. After adding high concentration trichloroacetate (TCA) to the Chlamydomonas reinhardtii thylakoid suspension, this signal was abolished in a minute. Treatment of TCA also removes a few of polypeptides, including three extrinsic polypeptides of oxygen-evolving complex, from the thylakoid membrane. Based upon the analysis of the microenvironment around YD with a three-dimensional model, it is indicated that relatively high hydrophobicity of this microenvironment may be the essential prerequisite for TCA to affect YD. It has been observed that TCA treatment also retards the decay of the SignalⅠ, produced by the oxidized reaction center chlorophyll dimer (P700+) of photosys- temⅠ.

  17. PERIANTH DEVELOPMENT IN THE BASAL MONOCOT TRIGLOCHIN MARITIMA (JUNCAGINACEAE)

    DEFF Research Database (Denmark)

    Buzgo, Matyas; Soltis, Douglas E.; Soltis, Pamela S.;

    2006-01-01

    Basal monocots exhibit considerable variation in inflorescence and floral structure. In some cases, such as Triglochin maritima, it is not clear whether the lateral and terminal structures of the inflores- cence are flowers or pseudanthia, or where the limits between flowers and inflorescence lie...

  18. Inhibition by penem of processing peptidases from cyanobacteria and chloroplast thylakoids.

    Science.gov (United States)

    Barbrook, A C; Packer, J C; Howe, C J

    1996-12-02

    Proteins targeted to the thylakoid lumen of plants and cyanobacteria and the periplasmic space of cyanobacteria are synthesised with N-terminal presequences which are removed following translocation across the membrane. These presequences are thought to direct translocation of the preprotein by a sec-type pathway. Detergent extracts of cyanobacterial and chloroplast membranes contain enzymes which are capable of processing precursors to the mature size. We show that the processing of a range of precursors by both cyanobacterial and chloroplast enzymes is inhibited by the penem SB216357. This is the first report of an inhibitor of these enzymes and indicates that they are type 1 signal peptidases.

  19. Fe deficiency induced changes in rice (Oryza sativa L.) thylakoids.

    Science.gov (United States)

    Wang, Yuwen; Xu, Chao; Li, Kang; Cai, Xiaojie; Wu, Min; Chen, Guoxiang

    2017-01-01

    Iron deficiency is an important abiotic stress that limits productivity of crops all over the world. We selected a hybrid rice (Oryza sativa L.), LYPJ, which is super high-yield and widely cultured in China, to investigate changes in the components and structure of thylakoid membranes and photosynthetic performance in response to iron deficiency. Our results demonstrated that photosystem I (PSI) is the primary target for iron deficiency, while the changes in photosystem II (PSII) are important for rebuilding a balance in disrupted energy utilization and dissipation caused by differential degradation of photosynthetic components. The result of immunoblot analysis suggested that the core subunit PsaA declined drastically, while PsbA remained relatively stable. Furthermore, several organizational changes of the photosynthetic apparatus were found by BN-PAGE, including a marked decrease in the PSI core complexes, the Cytb 6 /f complex, and the trimeric form of the LHCII antenna, consistent with the observed unstacking grana. The fluorescence induction analysis indicated a descending PSII activity with energy dissipation enhanced markedly. In addition, we proposed that the crippled CO2 assimilation could be compensated by the enhanced of phosphoenolpyruvate carboxylase (PEPC), which is suggested by the decreased ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and photosynthetic efficiency.

  20. RECOVERY ACT - Thylakoid Assembly and Folded Protein Transport by the Tat Pathway

    Energy Technology Data Exchange (ETDEWEB)

    Dabney-Smith, Carole [Miami Univ., Oxford, OH (United States)

    2016-07-18

    Assembly of functional photosystems complete with necessary intrinsic (membrane-bound) and extrinsic proteins requires the function of at least 3 protein transport pathways in thylakoid membranes. Our research focuses on one of those pathways, a unique and essential protein transport pathway found in the chloroplasts of plants, bacteria, and some archaebacteria, the Twin arginine translocation (Tat) system. The chloroplast Tat (cpTat) system is thought to be responsible for the proper location of ~50% of thylakoid lumen proteins, several of which are necessary for proper photosystem assembly, maintenance, and function. Specifically, cpTat systems are unique because they transport fully folded and assembled proteins across ion tight membranes using only three membrane components, Tha4, Hcf106, and cpTatC, and the protonmotive force generated by photosynthesis. Despite the importance of the cpTat system in plants, the mechanism of transport of a folded precursor is not well known. Our long-term goal is to investigate the role protein transport systems have on organelle biogenesis, particularly the assembly of membrane protein complexes in thylakoids of chloroplasts. The objective of this proposal is to correlate structural changes in the membrane-bound cpTat component, Tha4, to the mechanism of translocation of folded-precursor substrates across the membrane bilayer by using a cysteine accessibility and crosslinking approach. Our central hypothesis is that the precursor passes through a proteinaceous pore of assembled Tha4 protomers that have undergone a conformational or topological change in response to transport. This research is predicated upon the observations that Tha4 exists in molar excess in the membrane relative to the other cpTat components; its regulated assembly to the precursor-bound receptor; and our data showing oligomerization of Tha4 into very large complexes in response to transport. Our rationale for these studies is that understanding cp

  1. Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes

    NARCIS (Netherlands)

    Tietz, Stefanie; Puthiyaveetil, Sujith; Enlow, Heather M; Yarbrough, Robert; Wood, Magnus; Semchonok, Dmitry A; Lowry, Troy; Li, Zhirong; Jahns, Peter; Boekema, Egbert J; Lenhert, Steven; Niyogi, Krishna K; Kirchhoff, Helmut

    2015-01-01

    The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystall

  2. Light-dependent degradation of the QB-protein in isolated pea thylakoids

    Science.gov (United States)

    Ohad, I.; Kyle, D. J.; Hirschberg, J.

    1985-01-01

    The 32 000-dalton QB-protein of photosystem II (PS II) is rapidly damaged and removed from isolated pea thylakoids during incubation in the light resulting in a loss of photosynthetic electron flow through PS II. This in vitro photoinhibition is similar to that previously reported with intact Chlamydomonas cells. The damage occurs at a faster rate in vitro, however, due to the inability of isolated thylakoids to synthesize replacement QB-protein. The removal of the damaged QB-protein does not require any soluble components of the chloroplast stroma and is unaffected by the protease inhibitors phenyl-methylsulfonylfluoride or antipain. Unlike the effect of trypsin, no low mol. wt. membrane-bound or soluble fragments of the labelled QB-protein could be identified either by autoradiography or immunologically using polyclonal antibodies specific for the QB-protein. The lightinduced damage to the QB-protein (indicated by a loss of QB functional activity), preceded the removal of the protein from the membrane. We conclude that photodamage of the QB-protein generates a conformational change which renders the protein susceptible to attack by a highly efficient, intrinsic membrane protease. ImagesFig. 1.Fig. 3.Fig. 4.Fig. 5. PMID:16453621

  3. Artificially acquired chlorophyll b is highly acceptable to the thylakoid-lacking cyanobacterium, Gloeobacter violaceus PCC 7421.

    Science.gov (United States)

    Araki, Mie; Akimoto, Seiji; Mimuro, Mamoru; Tsuchiya, Tohru

    2014-08-01

    Unicellular cyanobacterium Gloeobacter violaceus is an only known oxygenic photosynthetic organism that lacks thylakoid membrane. Molecular phylogenetic analyses indicate that G. violaceus is an early-branching cyanobacterium within cyanobacterial clade. Therefore, the photosynthetic system of G. violaceus is considered to be partly similar to that of the ancestral cyanobacteria that would lack thylakoid membrane. G. violaceus possesses chlorophyll (Chl) a as the only chlorophyll species like most cyanobacteria. It was proposed that the ancestral oxygenic photosynthetic organism had not only Chl a and phycobilins but also Chl b. However, no organism which contains both Chl a and Chl b and lacks thylakoid membrane has been found in nature. Therefore, we introduced the chlorophyllide a oxygenase gene responsible for Chl b biosynthesis into G. violaceus. In the resultant transformant, Chl b accumulated at approximately 11% of total Chl independent of growth phase. Photosystem I complexes isolated from the transformant contained Chl b at 9.9% of total Chl. The presence of Chl b in the photosystem I complexes did not inhibit trimer formation. Furthermore, time-resolved fluorescence spectrum demonstrated that Chl b transferred energy to Chl a in the photosystem I complexes and did not disturb the energy transfer among the Chl a molecules. These results show that G. violaceus is tolerant to artificially produced Chl b and suggest the flexibility of photosystem for Chl composition in the ancestral oxygenic photosynthetic organism.

  4. Morphogenic Regulators Baby boom and Wuschel Improve Monocot Transformation.

    Science.gov (United States)

    Lowe, Keith; Wu, Emily; Wang, Ning; Hoerster, George; Hastings, Craig; Cho, Myeong-Je; Scelonge, Chris; Lenderts, Brian; Chamberlin, Mark; Cushatt, Josh; Wang, Lijuan; Ryan, Larisa; Khan, Tanveer; Chow-Yiu, Julia; Hua, Wei; Yu, Maryanne; Banh, Jenny; Bao, Zhongmeng; Brink, Kent; Igo, Elizabeth; Rudrappa, Bhojaraja; Shamseer, P M; Bruce, Wes; Newman, Lisa; Shen, Bo; Zheng, Peizhong; Bidney, Dennis; Falco, S Carl; RegisterIII, James C; Zhao, Zuo-Yu; Xu, Deping; Jones, Todd J; Gordon-Kamm, William James

    2016-09-06

    While transformation of the major monocot crops is currently possible, the process typically remains confined to one or two genotypes per species, often with poor agronomics, and efficiencies that place these methods beyond the reach of most academic laboratories. Here, we report a transformation approach involving overexpression of the maize (Zea mays) Baby boom (Bbm) and maize Wuschel2 (Wus2) genes, which produced high transformation frequencies in numerous previously non-transformable maize inbred lines. For example, the Pioneer inbred PHH5G is recalcitrant to biolistic and Agrobacterium transformation. However, when Bbm and Wus2 were expressed, transgenic calli were recovered from over 40% of the starting explants, with most producing healthy, fertile plants. Another limitation for many monocots is the intensive labor and greenhouse space required to supply immature embryos for transformation. This problem could be alleviated by using alternative target tissues that could be supplied consistently with automated preparation. As a major step toward this objective, we transformed Bbm and Wus2 directly into either embryo slices from mature seed or leaf segments from seedlings in a variety of Pioneer inbred lines, routinely recovering healthy, fertile T0 plants. Finally, we demonstrated that the maize Bbm and Wus2 genes stimulate transformation in sorghum (Sorghum bicolor) immature embryos, sugarcane (Saccharum officinarum) callus, and indica rice (Oryza sativa var. indica) callus. {copyright, serif} 2016 American Society of Plant Biologists. All rights reserved.

  5. Motif content comparison between monocot and dicot species

    Directory of Open Access Journals (Sweden)

    Matyas Cserhati

    2015-03-01

    Full Text Available While a number of DNA sequence motifs have been functionally characterized, the full repertoire of motifs in an organism (the motifome is yet to be characterized. The present study wishes to widen the scope of motif content analysis in different monocot and dicot species that include both rice species, Brachypodium, corn, wheat as monocots and Arabidopsis, Lotus japonica, Medicago truncatula, and Populus tremula as dicots. All possible existing motifs were analyzed in different regions of genomes such as were found in different sets of sequences in these species: the whole genome, core proximal and distal promoters, 5′ and 3′ UTRs, and the 1st introns. Due to the increased number of species involved in this study compared to previous works, species relationships were analyzed based on the similarity of common motif content. Certain secondary structure elements were inferred in the genomes of these species as well as new unknown motifs. The distribution of 20 motifs common to the studied species were found to have a significantly larger occurrence within the promoters and 3′ UTRs of genes, both being regulatory regions. Motifs common to the promoter regions of japonica rice, Brachypodium, and corn were also found in a number of orthologous and paralogous genes. Some of our motifs were found to be complementary to miRNA elements in Brachypodium distachyon and japonica rice.

  6. Carotenoid-chlorophyll coupling and fluorescence quenching correlate with protein packing density in grana-thylakoids.

    Science.gov (United States)

    Holleboom, Christoph-Peter; Yoo, Sunny; Liao, Pen-Nan; Compton, Ian; Haase, Winfried; Kirchhoff, Helmut; Walla, Peter Jomo

    2013-09-26

    The regulation of light-harvesting in photosynthesis under conditions of varying solar light irradiation is essential for the survival and fitness of plants and algae. It has been proposed that rearrangements of protein distribution in the stacked grana region of thylakoid membranes connected to changes in the electronic pigment-interaction play a key role for this regulation. In particular, carotenoid-chlorophyll interactions seem to be crucial for the down-regulation of photosynthetic light-harvesting. So far, it has been difficult to determine the influence of the dense protein packing found in native photosynthetic membrane on these interactions. We investigated the changes of the electronic couplings between carotenoids and chlorophylls and the quenching in grana thylakoids of varying protein packing density by two-photon spectroscopy, conventional chlorophyll fluorometry, low-temperature fluorescence spectroscopy, and electron micrographs of freeze-fracture membranes. We observed an increasing carotenoid-chlorophyll coupling and fluorescence quenching with increasing packing density. Simultaneously, the antennas size and excitonic connectivity of Photosystem II increased with increasing quenching and carotenoid-chlorophyll coupling whereas isolated, decoupled LHCII trimers decreased. Two distinct quenching data regimes could be identified that show up at different protein packing densities. In the regime corresponding to higher protein packing densities, quenching is strongly correlated to carotenoid-chlorophyll interactions whereas in the second regime, a weak correlation is apparent with low protein packing densities. Native membranes are in the strong-coupling data regime. Consequently, PSII and LHCII in grana membranes of plants are already quenched by protein crowding. We concluded that this ensures efficient electronic connection of all pigment-protein complexes for intermolecular energy transfer to the reaction centers and allows simultaneously

  7. Role of plastid transglutaminase in LHCII polyamination and thylakoid electron and proton flow.

    Directory of Open Access Journals (Sweden)

    Nikolaos E Ioannidis

    Full Text Available Transglutaminases function as biological glues in animal cells, plant cells and microbes. In energy producing organelles such as chloroplasts the presence of transglutaminases was recently confirmed. Furthermore, a plastidial transglutaminase has been cloned from maize and the first plants overexpressing tgz are available (Nicotiana tabacum TGZ OE. Our hypothesis is that the overexpression of plastidal transglutaminase will alter photosynthesis via increased polyamination of the antenna of photosystem II. We have used standard analytical tools to separate the antenna from photosystem II in wild type and modified plants, 6 specific antibodies against LHCbs to confirm their presence and sensitive HPLC method to quantify the polyamination level of these proteins. We report that bound spermidine and spermine were significantly increased (∼80% in overexpressors. Moreover, we used recent advances in in vivo probing to study simultaneously the proton and electron circuit of thylakoids. Under physiological conditions overexpressors show a 3-fold higher sensitivity of the antenna down regulation loop (qE to the elicitor (luminal protons which is estimated as the ΔpH component of thylakoidal proton motive force. In addition, photosystem (hyper-PSIIα with an exceptionally high antenna (large absorption cross section, accumulate in transglutaminase over expressers doubling the rate constant of light energy utilization (Kα and promoting thylakoid membrane stacking. Polyamination of antenna proteins is a previously unrecognized mechanism for the modulation of the size (antenna absorption cross section and sensitivity of photosystem II to down regulation. Future research will reveal which peptides and which residues of the antenna are responsible for such effects.

  8. Function and evolution of channels and transporters in photosynthetic membranes.

    Science.gov (United States)

    Pfeil, Bernard E; Schoefs, Benoît; Spetea, Cornelia

    2014-03-01

    Chloroplasts from land plants and algae originated from an endosymbiotic event, most likely involving an ancestral photoautotrophic prokaryote related to cyanobacteria. Both chloroplasts and cyanobacteria have thylakoid membranes, harboring pigment-protein complexes that perform the light-dependent reactions of oxygenic photosynthesis. The composition, function and regulation of these complexes have thus far been the major topics in thylakoid membrane research. For many decades, we have also accumulated biochemical and electrophysiological evidence for the existence of solute transthylakoid transport activities that affect photosynthesis. However, research dedicated to molecular identification of the responsible proteins has only recently emerged with the explosion of genomic information. Here we review the current knowledge about channels and transporters from the thylakoid membrane of Arabidopsis thaliana and of the cyanobacterium Synechocystis sp. PCC 6803. No homologues of these proteins have been characterized in algae, although similar sequences could be recognized in many of the available sequenced genomes. Based on phylogenetic analyses, we hypothesize a host origin for most of the so far identified Arabidopsis thylakoid channels and transporters. Additionally, the shift from a non-thylakoid to a thylakoid location appears to have occurred at different times for different transport proteins. We propose that closer control of and provision for the thylakoid by products of the host genome has been an ongoing process, rather than a one-step event. Some of the proteins recruited to serve in the thylakoid may have been the result of the increased specialization of its pigment-protein composition and organization in green plants.

  9. Cercosporoid fungi (Mycosphaerellaceae) 3. Species on monocots (Poaceae, true grasses).

    Science.gov (United States)

    Braun, Uwe; Crous, Pedro W; Nakashima, Chiharu

    2015-06-01

    The third part of a series of monographic treatments of cercosporoid fungi (formerly Cercospora s. lat., Mycosphaerellaceae, Ascomycota) continues with a treatment of taxa on monocots (Liliopsida; Equisetopsida, Magnoliidae, Lilianae), covering asexual and holomorph species with mycosphaerella-like sexual morphs on true grasses (Poaceae), which were excluded from the second part. The species concerned are keyed out, alphabetically listed, described, illustrated and supplemented by references to previously published descriptions, illustrations, and exsiccatae. A key to the recognised genera and a discussion of taxonomically relevant characters was published in the first part of this series. Several species are lecto- or neotypified. The following taxonomic novelties are introduced: Cercospora barretoana comb. nov., C. cymbopogonicola nom. nov., Cladosporium elymi comb. nov., Passalora agrostidicola sp. nov., P. brachyelytri comb. nov., and P. dichanthii-annulati comb. nov.

  10. Phylogenetic analysis of the thylakoid ATP/ADP carrier reveals new insights into its function restricted to green plants

    Directory of Open Access Journals (Sweden)

    Cornelia eSpetea

    2012-01-01

    Full Text Available ATP is the common energy currency of cellular metabolism in all living organisms. Most of them synthesize ATP in the cytosol or on the mitochondrial inner membrane, whereas land plants, algae and cyanobacteria also produce it on the thylakoid membrane during the light-dependent reactions of photosynthesis. From the site of synthesis, ATP is transported to the site of utilization via intracellular membranes transporters. One major type of ATP transporter is represented by the mitochondrial ADP/ATP carrier family. Here we review a recently characterized member, namely the thylakoid ATP/ADP carrier from Arabidopsis thaliana (AtTAAC. Thus far, no orthologues of this carrier have been characterized in other organisms, although similar sequences can be recognized in many sequenced genomes. Protein Sequence database searches and phylogenetic analyses indicate the absence of TAAC in cyanobacteria and its appearance early in the evolution of photosynthetic eukaryotes. The TAAC clade is composed of carriers found in land plants and some green algae, but no proteins from other photosynthetic taxa, such as red algae, brown algae and diatoms. This implies that TAAC-like sequences arose only once before the divergence of green algae and land plants. Based on these findings, it is proposed that TAAC may have evolved in response to the need of a new activity in higher photosynthetic eukaryotes. This activity may provide the energy to drive reactions during biogenesis and turnover of photosynthetic complexes, which are heterogenously distributed in a thylakoid membrane system composed of appressed and non-appressed regions.

  11. Wetland dicots and monocots differ in colonization by arbuscular mycorrhizal fungi and dark septate endophytes.

    Science.gov (United States)

    Weishampel, Peter A; Bedford, Barbara L

    2006-10-01

    As an initial step towards evaluating whether mycorrhizas influence composition and diversity in calcareous fen plant communities, we surveyed root colonization by arbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi (DSE) in 67 plant species in three different fens in central New York State (USA). We found colonization by AMF and DSE in most plant species at all three sites, with the type and extent of colonization differing between monocots and dicots. On average, AMF colonization was higher in dicots (58+/-3%, mean+/-SE) than in monocots (13+/-4%) but DSE colonization followed the opposite trend (24+/-3% in monocots and 9+/-1% in dicots). In sedges and cattails, two monocot families that are often abundant in fens and other wetlands, AMF colonization was usually very low (<10%) in five species and completely absent in seven others. However, DSE colonization in these species was frequently observed. Responses of wetland plants to AMF and DSE are poorly understood, but in the fen communities surveyed, dicots appear to be in a better position to respond to AMF than many of these more abundant monocots (e.g., sedges and cattails). In contrast, these monocots may be more likely to respond to DSE. Future work directed towards understanding the response of these wetland plants to AMF and DSE should provide insight into the roles these fungal symbionts play in influencing diversity in fen plant communities.

  12. DNA barcoding of the Lemnaceae, a family of aquatic monocots

    Directory of Open Access Journals (Sweden)

    Wang Wenqin

    2010-09-01

    Full Text Available Abstract Background Members of the aquatic monocot family Lemnaceae (commonly called duckweeds represent the smallest and fastest growing flowering plants. Their highly reduced morphology and infrequent flowering result in a dearth of characters for distinguishing between the nearly 38 species that exhibit these tiny, closely-related and often morphologically similar features within the same family of plants. Results We developed a simple and rapid DNA-based molecular identification system for the Lemnaceae based on sequence polymorphisms. We compared the barcoding potential of the seven plastid-markers proposed by the CBOL (Consortium for the Barcode of Life plant-working group to discriminate species within the land plants in 97 accessions representing 31 species from the family of Lemnaceae. A Lemnaceae-specific set of PCR and sequencing primers were designed for four plastid coding genes (rpoB, rpoC1, rbcL and matK and three noncoding spacers (atpF-atpH, psbK-psbI and trnH-psbA based on the Lemna minor chloroplast genome sequence. We assessed the ease of amplification and sequencing for these markers, examined the extent of the barcoding gap between intra- and inter-specific variation by pairwise distances, evaluated successful identifications based on direct sequence comparison of the "best close match" and the construction of a phylogenetic tree. Conclusions Based on its reliable amplification, straightforward sequence alignment, and rates of DNA variation between species and within species, we propose that the atpF-atpH noncoding spacer could serve as a universal DNA barcoding marker for species-level identification of duckweeds.

  13. Biotic stress induced demolition of thylakoid structure and loss in photoelectron transport of chloroplasts in papaya leaves.

    Science.gov (United States)

    Nanda, Rashmi Madhumita; Biswal, Basanti

    2008-04-01

    Papaya mosaic virus (PMV) causes severe mosaic symptoms in the papaya (Carica papaya L.) leaves. The PMV-induced alterations in photosystem II (PS II) structure and photochemical functions were probed. An increase in chlorophyll a (Chl a) fluorescence polarization suggests pathogen-induced transformation of thylakoid membrane to a gel phase. This transformation in physical state of thylakoid membrane may result in alteration in topology of pigments on pigment-binding proteins as reflected in pathogen-induced loss in the efficiency of energy transfer from carotenoids to chlorophylls. The fast Chl a fluorescence induction kinetics of healthy and PMV-infected plants by F(O)-F(J)-F(I)-F(P) transients revealed pathogen-induced perturbation on PS II acceptor side electron transfer equilibrium between Q(A) and Q(B) and in the pool size of electron transport acceptors. Pathogen-induced loss in photosynthetic pigments, changes in thylakoid structure and decrease in the ratio of F(V)/F(M) (photochemical potential of PS II) further correlate with the loss in photoelectron transport of PS II as probed by 2,6-dichlorophenol indophenol (DCPIP)-Hill reaction. Restoration of the loss by 1,5-diphenyl carbazide (DPC), an exogenous electron donor, that donates electron directly to reaction centre II bypassing the oxygen evolving system (OES), leads towards the conclusion that OES is one of the major targets of biotic stress. Further, the data suggest that chlorophyll fluorescence could be used as a non-invasive handy tool to assess the loss in photosynthetic efficiency and symptom severity in infected green tissues vis-a-vis the healthy ones.

  14. Spinach thylakoid polyphenol oxidase isolation, activation, and properties of the native chloroplast enzyme

    Energy Technology Data Exchange (ETDEWEB)

    Golbeck, J.H.; Cammarata, K.V.

    1981-05-01

    Polyphenol oxidase activity (E.C. 1.14,18.1) has been found in two enzyme species isolated from thylakoid membranes of spinach chloroplasts. The proteins were released from the membrane by sonication and purified >900-fold by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography. The enzymes appear to be the tetramer and monomer of a subunit with a molecular weight of 42,500 as determined by lithium dodecyl sulfate gel electrophoresis. Sonication releases polyphenol oxidase from the membrane largely in the latent state. In the absence of added fatty acids, the isolated enzyme spontaneously, but slowly, activates with time. Purified polyphenol oxidase utilizes o-diphenols as substrates and shows no detectable levels of monophenol or p-diphenol oxidase activities. Suitable substrates include chlorogenic acid, catechol, caffeic acid, pyrogallol, and dopamine; however, the enzyme is substrate-inhibited by the last four at concentrations near their K/sub m/. A large seasonal variation in polyphenol oxidase activity may result from a decrease in enzyme content rather than inhibition of the enzyme present.

  15. Membraner

    DEFF Research Database (Denmark)

    Bach, Finn

    2009-01-01

    Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner......Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner...

  16. Photosynthetic Membranes of Synechocystis or Plants Convert Sunlight to Photocurrent through Different Pathways due to Different Architectures.

    Directory of Open Access Journals (Sweden)

    Roy I Pinhassi

    Full Text Available Thylakoid membranes contain the redox active complexes catalyzing the light-dependent reactions of photosynthesis in cyanobacteria, algae and plants. Crude thylakoid membranes or purified photosystems from different organisms have previously been utilized for generation of electrical power and/or fuels. Here we investigate the electron transferability from thylakoid preparations from plants or the cyanobacterium Synechocystis. We show that upon illumination, crude Synechocystis thylakoids can reduce cytochrome c. In addition, this crude preparation can transfer electrons to a graphite electrode, producing an unmediated photocurrent of 15 μA/cm2. Photocurrent could be obtained in the presence of the PSII inhibitor DCMU, indicating that the source of electrons is QA, the primary Photosystem II acceptor. In contrast, thylakoids purified from plants could not reduce cyt c, nor produced a photocurrent in the photocell in the presence of DCMU. The production of significant photocurrent (100 μA/cm2 from plant thylakoids required the addition of the soluble electron mediator DCBQ. Furthermore, we demonstrate that use of crude thylakoids from the D1-K238E mutant in Synechocystis resulted in improved electron transferability, increasing the direct photocurrent to 35 μA/cm2. Applying the analogous mutation to tobacco plants did not achieve an equivalent effect. While electron abstraction from crude thylakoids of cyanobacteria or plants is feasible, we conclude that the site of the abstraction of the electrons from the thylakoids, the architecture of the thylakoid preparations influence the site of the electron abstraction, as well as the transfer pathway to the electrode. This dictates the use of different strategies for production of sustainable electrical current from photosynthetic thylakoid membranes of cyanobacteria or higher plants.

  17. Photosynthetic Membranes of Synechocystis or Plants Convert Sunlight to Photocurrent through Different Pathways due to Different Architectures.

    Science.gov (United States)

    Pinhassi, Roy I; Kallmann, Dan; Saper, Gadiel; Larom, Shirley; Linkov, Artyom; Boulouis, Alix; Schöttler, Mark-Aurel; Bock, Ralph; Rothschild, Avner; Adir, Noam; Schuster, Gadi

    2015-01-01

    Thylakoid membranes contain the redox active complexes catalyzing the light-dependent reactions of photosynthesis in cyanobacteria, algae and plants. Crude thylakoid membranes or purified photosystems from different organisms have previously been utilized for generation of electrical power and/or fuels. Here we investigate the electron transferability from thylakoid preparations from plants or the cyanobacterium Synechocystis. We show that upon illumination, crude Synechocystis thylakoids can reduce cytochrome c. In addition, this crude preparation can transfer electrons to a graphite electrode, producing an unmediated photocurrent of 15 μA/cm2. Photocurrent could be obtained in the presence of the PSII inhibitor DCMU, indicating that the source of electrons is QA, the primary Photosystem II acceptor. In contrast, thylakoids purified from plants could not reduce cyt c, nor produced a photocurrent in the photocell in the presence of DCMU. The production of significant photocurrent (100 μA/cm2) from plant thylakoids required the addition of the soluble electron mediator DCBQ. Furthermore, we demonstrate that use of crude thylakoids from the D1-K238E mutant in Synechocystis resulted in improved electron transferability, increasing the direct photocurrent to 35 μA/cm2. Applying the analogous mutation to tobacco plants did not achieve an equivalent effect. While electron abstraction from crude thylakoids of cyanobacteria or plants is feasible, we conclude that the site of the abstraction of the electrons from the thylakoids, the architecture of the thylakoid preparations influence the site of the electron abstraction, as well as the transfer pathway to the electrode. This dictates the use of different strategies for production of sustainable electrical current from photosynthetic thylakoid membranes of cyanobacteria or higher plants.

  18. Dynamics and evolution of the inverted repeat-large single copy junctions in the chloroplast genomes of monocots

    Directory of Open Access Journals (Sweden)

    Wu Chun-Lin

    2008-01-01

    Full Text Available Abstract Background Various expansions or contractions of inverted repeats (IRs in chloroplast genomes led to fluxes in the IR-LSC (large single copy junctions. Previous studies revealed that some monocot IRs contain a trnH-rps19 gene cluster, and it has been speculated that this may be an evidence of a duplication event prior to the divergence of monocot lineages. Therefore, we compared the organizations of genes flanking two IR-LSC junctions in 123 angiosperm representatives to uncover the evolutionary dynamics of IR-LSC junctions in basal angiosperms and monocots. Results The organizations of genes flanking IR-LSC junctions in angiosperms can be classified into three types. Generally each IR of monocots contains a trnH-rps19 gene cluster near the IR-LSC junctions, which differs from those in non-monocot angiosperms. Moreover, IRs expanded more progressively in monocots than in non-monocot angiosperms. IR-LSC junctions commonly occurred at polyA tract or A-rich regions in angiosperms. Our RT-PCR assays indicate that in monocot IRA the trnH-rps19 gene cluster is regulated by two opposing promoters, S10A and psbA. Conclusion Two hypotheses are proposed to account for the evolution of IR expansions in monocots. Based on our observations, the inclusion of a trnH-rps19 cluster in majority of monocot IRs could be reasonably explained by the hypothesis that a DSB event first occurred at IRB and led to the expansion of IRs to trnH, followed by a successive DSB event within IRA and lead to the expansion of IRs to rps19 or to rpl22 so far. This implies that the duplication of trnH-rps19 gene cluster was prior to the diversification of extant monocot lineages. The duplicated trnH genes in the IRB of most monocots and non-monocot angiosperms have distinct fates, which are likely regulated by different expression levels of S10A and S10B promoters. Further study is needed to unravel the evolutionary significance of IR expansion in more recently diverged

  19. MET1 is a thylakoid-associated TPR protein involved in photosystem II supercomplex formation and repair in Arabidopsis.

    Science.gov (United States)

    Bhuiyan, Nazmul H; Friso, Giulia; Poliakov, Anton; Ponnala, Lalit; van Wijk, Klaas J

    2015-01-01

    Photosystem II (PSII) requires constant disassembly and reassembly to accommodate replacement of the D1 protein. Here, we characterize Arabidopsis thaliana MET1, a PSII assembly factor with PDZ and TPR domains. The maize (Zea mays) MET1 homolog is enriched in mesophyll chloroplasts compared with bundle sheath chloroplasts, and MET1 mRNA and protein levels increase during leaf development concomitant with the thylakoid machinery. MET1 is conserved in C3 and C4 plants and green algae but is not found in prokaryotes. Arabidopsis MET1 is a peripheral thylakoid protein enriched in stroma lamellae and is also present in grana. Split-ubiquitin assays and coimmunoprecipitations showed interaction of MET1 with stromal loops of PSII core components CP43 and CP47. From native gels, we inferred that MET1 associates with PSII subcomplexes formed during the PSII repair cycle. When grown under fluctuating light intensities, the Arabidopsis MET1 null mutant (met1) showed conditional reduced growth, near complete blockage in PSII supercomplex formation, and concomitant increase of unassembled CP43. Growth of met1 in high light resulted in loss of PSII supercomplexes and accelerated D1 degradation. We propose that MET1 functions as a CP43/CP47 chaperone on the stromal side of the membrane during PSII assembly and repair. This function is consistent with the observed differential MET1 accumulation across dimorphic maize chloroplasts.

  20. The Arabidopsis Thylakoid Protein PAM68 Is Required for Efficient D1 Biogenesis and Photosystem II Assembly[W

    Science.gov (United States)

    Armbruster, Ute; Zühlke, Jessica; Rengstl, Birgit; Kreller, Renate; Makarenko, Elina; Rühle, Thilo; Schünemann, Danja; Jahns, Peter; Weisshaar, Bernd; Nickelsen, Jörg; Leister, Dario

    2010-01-01

    Photosystem II (PSII) is a multiprotein complex that functions as a light-driven water:plastoquinone oxidoreductase in photosynthesis. Assembly of PSII proceeds through a number of distinct intermediate states and requires auxiliary proteins. The photosynthesis affected mutant 68 (pam68) of Arabidopsis thaliana displays drastically altered chlorophyll fluorescence and abnormally low levels of the PSII core subunits D1, D2, CP43, and CP47. We show that these phenotypes result from a specific decrease in the stability and maturation of D1. This is associated with a marked increase in the synthesis of RC (the PSII reaction center-like assembly complex) at the expense of PSII dimers and supercomplexes. PAM68 is a conserved integral membrane protein found in cyanobacterial and eukaryotic thylakoids and interacts in split-ubiquitin assays with several PSII core proteins and known PSII assembly factors. Biochemical analyses of thylakoids from Arabidopsis and Synechocystis sp PCC 6803 suggest that, during PSII assembly, PAM68 proteins associate with an early intermediate complex that might contain D1 and the assembly factor LPA1. Inactivation of cyanobacterial PAM68 destabilizes RC but does not affect larger PSII assembly complexes. Our data imply that PAM68 proteins promote early steps in PSII biogenesis in cyanobacteria and plants, but their inactivation is differently compensated for in the two classes of organisms. PMID:20923938

  1. The Arabidopsis thylakoid protein PAM68 is required for efficient D1 biogenesis and photosystem II assembly.

    Science.gov (United States)

    Armbruster, Ute; Zühlke, Jessica; Rengstl, Birgit; Kreller, Renate; Makarenko, Elina; Rühle, Thilo; Schünemann, Danja; Jahns, Peter; Weisshaar, Bernd; Nickelsen, Jörg; Leister, Dario

    2010-10-01

    Photosystem II (PSII) is a multiprotein complex that functions as a light-driven water:plastoquinone oxidoreductase in photosynthesis. Assembly of PSII proceeds through a number of distinct intermediate states and requires auxiliary proteins. The photosynthesis affected mutant 68 (pam68) of Arabidopsis thaliana displays drastically altered chlorophyll fluorescence and abnormally low levels of the PSII core subunits D1, D2, CP43, and CP47. We show that these phenotypes result from a specific decrease in the stability and maturation of D1. This is associated with a marked increase in the synthesis of RC (the PSII reaction center-like assembly complex) at the expense of PSII dimers and supercomplexes. PAM68 is a conserved integral membrane protein found in cyanobacterial and eukaryotic thylakoids and interacts in split-ubiquitin assays with several PSII core proteins and known PSII assembly factors. Biochemical analyses of thylakoids from Arabidopsis and Synechocystis sp PCC 6803 suggest that, during PSII assembly, PAM68 proteins associate with an early intermediate complex that might contain D1 and the assembly factor LPA1. Inactivation of cyanobacterial PAM68 destabilizes RC but does not affect larger PSII assembly complexes. Our data imply that PAM68 proteins promote early steps in PSII biogenesis in cyanobacteria and plants, but their inactivation is differently compensated for in the two classes of organisms.

  2. Evaluation of Monocot and Eudicot Divergence Using the Sugarcane Transcriptome1[w

    Science.gov (United States)

    Vincentz, Michel; Cara, Frank A.A.; Okura, Vagner K.; da Silva, Felipe R.; Pedrosa, Guilherme L.; Hemerly, Adriana S.; Capella, Adriana N.; Marins, Mozart; Ferreira, Paulo C.; França, Suzelei C.; Grivet, Laurent; Vettore, Andre L.; Kemper, Edson L.; Burnquist, Willian L.; Targon, Maria L.P.; Siqueira, Walter J.; Kuramae, Eiko E.; Marino, Celso L.; Camargo, Luis E.A.; Carrer, Helaine; Coutinho, Luis L.; Furlan, Luiz R.; Lemos, Manoel V.F.; Nunes, Luiz R.; Gomes, Suely L.; Santelli, Roberto V.; Goldman, Maria H.; Bacci, Maurício; Giglioti, Eder A.; Thiemann, Otávio H.; Silva, Flávio H.; Van Sluys, Marie-Anne; Nobrega, Francisco G.; Arruda, Paulo; Menck, Carlos F.M.

    2004-01-01

    Over 40,000 sugarcane (Saccharum officinarum) consensus sequences assembled from 237,954 expressed sequence tags were compared with the protein and DNA sequences from other angiosperms, including the genomes of Arabidopsis and rice (Oryza sativa). Approximately two-thirds of the sugarcane transcriptome have similar sequences in Arabidopsis. These sequences may represent a core set of proteins or protein domains that are conserved among monocots and eudicots and probably encode for essential angiosperm functions. The remaining sequences represent putative monocot-specific genetic material, one-half of which were found only in sugarcane. These monocot-specific cDNAs represent either novelties or, in many cases, fast-evolving sequences that diverged substantially from their eudicot homologs. The wide comparative genome analysis presented here provides information on the evolutionary changes that underlie the divergence of monocots and eudicots. Our comparative analysis also led to the identification of several not yet annotated putative genes and possible gene loss events in Arabidopsis. PMID:15020759

  3. Long branch attraction, taxon sampling, and the earliest angiosperms: Amborella or monocots?

    Directory of Open Access Journals (Sweden)

    Rice Danny W

    2004-09-01

    Full Text Available Abstract Background Numerous studies, using in aggregate some 28 genes, have achieved a consensus in recognizing three groups of plants, including Amborella, as comprising the basal-most grade of all other angiosperms. A major exception is the recent study by Goremykin et al. (2003; Mol. Biol. Evol. 20:1499–1505, whose analyses of 61 genes from 13 sequenced chloroplast genomes of land plants nearly always found 100% support for monocots as the deepest angiosperms relative to Amborella, Calycanthus, and eudicots. We hypothesized that this conflict reflects a misrooting of angiosperms resulting from inadequate taxon sampling, inappropriate phylogenetic methodology, and rapid evolution in the grass lineage used to represent monocots. Results We used two main approaches to test this hypothesis. First, we sequenced a large number of chloroplast genes from the monocot Acorus and added these plus previously sequenced Acorus genes to the Goremykin et al. (2003 dataset in order to explore the effects of altered monocot sampling under the same analytical conditions used in their study. With Acorus alone representing monocots, strongly supported Amborella-sister trees were obtained in all maximum likelihood and parsimony analyses, and in some distance-based analyses. Trees with both Acorus and grasses gave either a well-supported Amborella-sister topology or else a highly unlikely topology with 100% support for grasses-sister and paraphyly of monocots (i.e., Acorus sister to "dicots" rather than to grasses. Second, we reanalyzed the Goremykin et al. (2003 dataset focusing on methods designed to account for rate heterogeneity. These analyses supported an Amborella-sister hypothesis, with bootstrap support values often conflicting strongly with cognate analyses performed without allowing for rate heterogeneity. In addition, we carried out a limited set of analyses that included the chloroplast genome of Nymphaea, whose position as a basal angiosperm was

  4. Long branch attraction, taxon sampling, and the earliest angiosperms: Amborella or monocots?

    Science.gov (United States)

    Stefanović, Saša; Rice, Danny W; Palmer, Jeffrey D

    2004-01-01

    Background Numerous studies, using in aggregate some 28 genes, have achieved a consensus in recognizing three groups of plants, including Amborella, as comprising the basal-most grade of all other angiosperms. A major exception is the recent study by Goremykin et al. (2003; Mol. Biol. Evol. 20:1499–1505), whose analyses of 61 genes from 13 sequenced chloroplast genomes of land plants nearly always found 100% support for monocots as the deepest angiosperms relative to Amborella, Calycanthus, and eudicots. We hypothesized that this conflict reflects a misrooting of angiosperms resulting from inadequate taxon sampling, inappropriate phylogenetic methodology, and rapid evolution in the grass lineage used to represent monocots. Results We used two main approaches to test this hypothesis. First, we sequenced a large number of chloroplast genes from the monocot Acorus and added these plus previously sequenced Acorus genes to the Goremykin et al. (2003) dataset in order to explore the effects of altered monocot sampling under the same analytical conditions used in their study. With Acorus alone representing monocots, strongly supported Amborella-sister trees were obtained in all maximum likelihood and parsimony analyses, and in some distance-based analyses. Trees with both Acorus and grasses gave either a well-supported Amborella-sister topology or else a highly unlikely topology with 100% support for grasses-sister and paraphyly of monocots (i.e., Acorus sister to "dicots" rather than to grasses). Second, we reanalyzed the Goremykin et al. (2003) dataset focusing on methods designed to account for rate heterogeneity. These analyses supported an Amborella-sister hypothesis, with bootstrap support values often conflicting strongly with cognate analyses performed without allowing for rate heterogeneity. In addition, we carried out a limited set of analyses that included the chloroplast genome of Nymphaea, whose position as a basal angiosperm was also, and very recently

  5. Dietary green-plant thylakoids decrease gastric emptying and gut transit, promote changes in the gut microbial flora, but does not cause steatorrhea

    DEFF Research Database (Denmark)

    Stenblom, Eva-Lena; Weström, Björn R.; Linninge, Caroline

    2016-01-01

    , and specifically the Bacteriodes fragilis group, were increased by thylakoid treatment versus placebo, while thylakoids did not cause steatorrhea. Dietary supplementation with thylakoids thus affects satiety both via appetite hormones and GI fullness, and affects the microbial composition without causing GI...... adverse effects such as steatorrhea. This suggests thylakoids as a novel agent in prevention and treatment of obesity....

  6. Bayesian phylogeny of sucrose transporters: Ancient origins, differential expansion and convergent evolution in monocots and dicots

    Directory of Open Access Journals (Sweden)

    Duo ePeng

    2014-11-01

    Full Text Available Sucrose transporters (SUTs are essential for the export and efficient movement of sucrose from source leaves to sink organs in plants. The angiosperm SUT family was previously classified into three or four distinct groups, Types I, II (subgroup IIB and III, with dicot-specific Type I and monocot-specific Type IIB functioning in phloem loading. To shed light on the underlying drivers of SUT evolution, Bayesian phylogenetic inference was undertaken using 41 sequenced plant genomes, including seven basal lineages at key evolutionary junctures. Our analysis supports four phylogenetically and structurally distinct SUT subfamilies, originating from two ancient groups (AG1 and AG2 that diverged early during terrestrial colonization. In both AG1 and AG2, multiple intron acquisition events in the progenitor vascular plant established the gene structures of modern SUTs. Tonoplastic Type III and plasmalemmal Type II represent evolutionarily conserved descendants of AG1 and AG2, respectively. Type I and Type IIB were previously thought to evolve after the dicot-monocot split. We show, however, that divergence of Type I from Type III SUT predated basal angiosperms, likely associated with evolution of vascular cambium and phloem transport. Type I SUT was subsequently lost in monocots along with vascular cambium, and independent evolution of Type IIB coincided with modified monocot vasculature. Both Type I and Type IIB underwent lineage-specific expansion. In multiple unrelated taxa, the newly-derived SUTs exhibit biased expression in reproductive tissues, suggesting a functional link between phloem loading and reproductive fitness. Convergent evolution of Type I and Type IIB for SUT function in phloem loading and reproductive organs supports the idea that differential vascular development in dicots and monocots is a strong driver for SUT family evolution in angiosperms.

  7. Genome-wide computational prediction and analysis of core promoter elements across plant monocots and dicots.

    Directory of Open Access Journals (Sweden)

    Sunita Kumari

    Full Text Available Transcription initiation, essential to gene expression regulation, involves recruitment of basal transcription factors to the core promoter elements (CPEs. The distribution of currently known CPEs across plant genomes is largely unknown. This is the first large scale genome-wide report on the computational prediction of CPEs across eight plant genomes to help better understand the transcription initiation complex assembly. The distribution of thirteen known CPEs across four monocots (Brachypodium distachyon, Oryza sativa ssp. japonica, Sorghum bicolor, Zea mays and four dicots (Arabidopsis thaliana, Populus trichocarpa, Vitis vinifera, Glycine max reveals the structural organization of the core promoter in relation to the TATA-box as well as with respect to other CPEs. The distribution of known CPE motifs with respect to transcription start site (TSS exhibited positional conservation within monocots and dicots with slight differences across all eight genomes. Further, a more refined subset of annotated genes based on orthologs of the model monocot (O. sativa ssp. japonica and dicot (A. thaliana genomes supported the positional distribution of these thirteen known CPEs. DNA free energy profiles provided evidence that the structural properties of promoter regions are distinctly different from that of the non-regulatory genome sequence. It also showed that monocot core promoters have lower DNA free energy than dicot core promoters. The comparison of monocot and dicot promoter sequences highlights both the similarities and differences in the core promoter architecture irrespective of the species-specific nucleotide bias. This study will be useful for future work related to genome annotation projects and can inspire research efforts aimed to better understand regulatory mechanisms of transcription.

  8. Identification of the Ndh (NAD(P)H-Plastoquinone-oxidoreductase) Complex in Etioplast Membranes of Barley : Changes during Photomorphogenesis of Chloroplasts

    OpenAIRE

    Alfredo, Guera; Pedro G.de, Nova; Bartolome, Sabater; Departamento de Biologia Vegetal, Universidad de Alcala de Henares

    2000-01-01

    In the last few years the presence in thylakoid membranes of chloroplasts of a NAD(P)H-plastoquinone oxidoreductase complex (Ndh complex) homologous to mitochondrial complex I has been well established. Herein, we report the identification of the Ndh complex in barley etioplast membranes. Two plastid DNA-encoded polypeptides of the Ndh complex (NDH-A and NDH-F) were relatively more abundant in etioplast membranes than in thylakoids from greening chloroplasts. Conversion of etioplast into chlo...

  9. PSB27: A thylakoid protein enabling Arabidopsis to adapt to changing light intensity

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Xin [Univ. of California, Berkeley, CA (United States). Dept of Plant and Microbial Biology; Garcia, Veder J. [Univ. of California, Berkeley, CA (United States). Dept of Plant and Microbial Biology; Buchanan, Bob B. [Univ. of California, Berkeley, CA (United States). Dept of Plant and Microbial Biology; Luan, Sheng [Univ. of California, Berkeley, CA (United States). Dept of Plant and Microbial Biology

    2016-08-22

    dissect the mechanism of action for CYP38. Our studies suggest an “autoinhibitory” model for CYP38 action. We plan to test this model and determine the mechanistic details for CYP38 function by biochemical and genetic procedures. 2. To determine the mechanism of action of FKBP20-2/FKBP16-3. Studies on FBKP16-3 and FKBP20-2 suggest that they may work together as a redox-dependent duo in PSII assembly. We will test this hypothesis using biochemical and genetic tools. 3. To determine the function of lumenal FKBPs by multi-gene mutagenesis approach. Using new genetic knockout (KO) procedures especially CRISPR/CAS9 system, we plan to generate multi-gene KO models that will likely provide vital information on those FKBPs with functional redundancy. 4. Functional analysis of thylakoid lumen network. We will focus our effort on objectives 1-3. Objective 4 represents a long-term goal to establish a more comprehensive network of proteins in the thylakoid lumen and their function in the assembly and maintenance of photosynthetic complexes. I hypothesize that the 16 immunophilin-type chaperones and foldases in the thylakoid lumen constitute an “assembly line” for the various components in the photosynthetic electron transport chain. Understanding this assembly line will enable further engineering of more efficient photosynthetic machines to capture more light energy and enhance plant productivity. Furthermore, it is envisioned that such molecular “assembly line” may be rebuilt to produce artificial photosynthesis in vitro or in non-photosynthetic organisms. These are highly relevant to the mission of “Photosynthetic Systems” and “Physical Biosciences” programs to “enhance our understanding of energy capture, conversion, and/or storage.” During the funding period, we have performed a number of experiments under the proposed objectives and obtained several new results. We have found in Objective 1 that CYP38 is associated to the thylokoid membrane with a larger

  10. Research Progress and Perspectives of Nitrogen Fixing Bacterium, Gluconacetobacter diazotrophicus, in Monocot Plants

    Directory of Open Access Journals (Sweden)

    N. Eskin

    2014-01-01

    Full Text Available Gluconacetobacter diazotrophicus is a nitrogen fixing bacterium originally found in monocotyledon sugarcane plants in which the bacterium actively fixes atmosphere nitrogen and provides significant amounts of nitrogen to plants. This bacterium mainly colonizes intercellular spaces within the roots and stems of plants and does not require the formation of the complex root organ like nodule. The bacterium is less plant/crop specific and indeed G. diazotrophicus has been found in a number of unrelated plant species. Importantly, as the bacterium was of monocot plant origin, there exists a possibility that the nitrogen fixation feature of the bacterium may be used in many other monocot crops. This paper reviews and updates the research progress of G. diazotrophicus for the past 25 years but focuses on the recent research development.

  11. Comparative analysis of ABCB1 reveals novel structural and functional conservation between monocots and dicots

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    Amandeep Kaur Dhaliwal

    2014-11-01

    Full Text Available Phytohormone auxin plays a critical role in modulating plant architecture by creating a gradient regulated via its transporters such as ATP-binding cassette (ABC B1. Except for Arabidopsis and maize, where it was shown to interrupt auxin transport, ABCB1’s presence, structure and function in crop species is not known. Here we describe the structural and putative functional organization of ABCB1 among monocots relative to that of dicots. Identified from various plant species following specific and stringent criteria, ZmABCB1’s ‘true’ orthologs sequence identity ranged from 56-90% at the DNA and 75-91% at the predicted amino acid (aa level. Relative to ZmABCB1, the size of genomic copies ranged from -27 to +1.5% and aa from -7.7 to +0.6%. With the average gene size being similar (5.8 kb in monocots and 5.7 kb in dicots, dicots have about triple the number of introns with an average size of 194 bp (total 1743 bp compared to 556 bp (total 1667 bp in monocots. The intron-exon junctions across species were however conserved. N-termini of the predicted proteins were highly variable: in monocots due to mismatches and small deletions of 1-13 aa compared to large, species-specific deletions of up to 77 aa in dicots. The species- family-, and group- specific conserved motifs were identified in the N-terminus and linker regions of protein, possibly responsible for the specific functions. The near-identical conserved motifs of Nucleotide Binding Domains (NBDs in two halves of the protein showed subtle aa changes possibly favoring ATP binding to the N-terminus. Predicted 3-D protein structures showed remarkable similarity with each other and for the residues involved in auxin binding.

  12. Localization of Membrane Proteins in the Cyanobacterium Synechococcus sp. PCC7942 (Radial Asymmetry in the Photosynthetic Complexes).

    Science.gov (United States)

    Sherman, D. M.; Troyan, T. A.; Sherman, L. A.

    1994-09-01

    Localization of membrane proteins in the cyanobacterium Synechococcus sp. PCC7942 was determined by transmission electron microscopy utilizing immunocytochemistry with cells prepared by freeze-substitution. This preparation procedure maintained cellular morphology and permitted detection of cellular antigens with high sensitivity and low background. Synechococcus sp. PCC7942 is a unicellular cyanobacterium with thylakoids organized in concentric layers toward the periphery of the cell. Cytochrome oxidase was localized almost entirely in the cytoplasmic membrane, whereas a carotenoprotein (P35) was shown to be a cell wall component. The major photosystem II (PSII) proteins (D1, D2 CP43, and CP47) were localized throughout the thylakoids. Proteins of the Cyt b6/f complex were found to have a similar distribution. Thylakoid luminal proteins, such as the Mn-stabilizing protein, were located primarily in the thylakoid, but a small, reproducible fraction was found in the outer compartment. The photosystem I (PSI) reaction center proteins and the ATP synthase proteins were found associated mostly with the outermost thylakoid and with the cytoplasmic membrane. These results indicated that the photosynthetic apparatus is not evenly distributed throughout the thylakoids. Rather, there is a radial asymmetry such that much of the PSI and the ATPase synthase is located in the outermost thylakoid. The relationship of this structure to the photosynthetic mechanism is discussed. It is suggested that the photosystems are separated because of kinetic differences between PSII and PSI, as hypothesized by H.-W. Trissl and C. Wilhelm (Trends Biochem Sci [1993] 18:415-419).

  13. In tropical lowland rain forests monocots have tougher leaves than dicots, and include a new kind of tough leaf

    DEFF Research Database (Denmark)

    Dominy, N.J.; Grubb, P.J.; Jackson, R.V.

    2008-01-01

    -tolerant or gap-demanding species were considered. Conclusions: It is predicted that monocots will be found to experience lower rates of herbivory by invertebrates than dicots. The tough monocot leaves include both stiff leaves containing relatively little water at saturation (e.g. palms), and leaves which lack...... stiffness, are rich in water at saturation and roll readily during dry weather or even in bright sun around midday (e.g. gingers, heliconias and marants). Monocot leaves also show that it is possible for leaves to be notably tough throughout the expansion phase of development, something never recorded...... for dicots. The need to broaden the botanist's mental picture of a ‘tough leaf' is emphasized.   Key words: Dicots, fracture toughness, herbivory, leaves, monocots, punch strength, tropical rain forest  ...

  14. Translocation of a phycoerythrin alpha subunit across five biological membranes.

    Science.gov (United States)

    Gould, Sven B; Fan, Enguo; Hempel, Franziska; Maier, Uwe-G; Klösgen, Ralf Bernd

    2007-10-12

    Cryptophytes, unicellular algae, evolved by secondary endosymbiosis and contain plastids surrounded by four membranes. In contrast to cyanobacteria and red algae, their phycobiliproteins do not assemble into phycobilisomes and are located within the thylakoid lumen instead of the stroma. We identified two gene families encoding phycoerythrin alpha and light-harvesting complex proteins from an expressed sequence tag library of the cryptophyte Guillardia theta. The proteins bear a bipartite topogenic signal responsible for the transport of nuclear encoded proteins via the ER into the plastid. Analysis of the phycoerythrin alpha sequences revealed that more than half of them carry an additional, third topogenic signal comprising a twin arginine motif, which is indicative of Tat (twin arginine transport)-specific targeting signals. We performed import studies with several derivatives of one member using a diatom transformation system, as well as intact chloroplasts and thylakoid vesicles isolated from pea. We demonstrated the different targeting properties of each individual part of the tripartite leader and show that phycoerythrin alpha is transported across the thylakoid membrane into the thylakoid lumen and protease-protected. Furthermore, we showed that thylakoid transport of phycoerythrin alpha takes place by the Tat pathway even if the 36 amino acid long bipartite topogenic signal precedes the actual twin arginine signal. This is the first experimental evidence of a protein being targeted across five biological membranes.

  15. The Primitive Thylakoid-Less Cyanobacterium Gloeobacter Is a Common Rock-Dwelling Organism.

    Directory of Open Access Journals (Sweden)

    Jan Mareš

    Full Text Available Cyanobacteria are an ancient group of photosynthetic prokaryotes, which are significant in biogeochemical cycles. The most primitive among living cyanobacteria, Gloeobacter violaceus, shows a unique ancestral cell organization with a complete absence of inner membranes (thylakoids and an uncommon structure of the photosynthetic apparatus. Numerous phylogenetic papers proved its basal position among all of the organisms and organelles capable of plant-like photosynthesis (i.e., cyanobacteria, chloroplasts of algae and plants. Hence, G. violaceus has become one of the key species in evolutionary study of photosynthetic life. It also numbers among the most widely used organisms in experimental photosynthesis research. Except for a few related culture isolates, there has been little data on the actual biology of Gloeobacter, being relegated to an "evolutionary curiosity" with an enigmatic identity. Here we show that members of the genus Gloeobacter probably are common rock-dwelling cyanobacteria. On the basis of morphological, ultrastructural, pigment, and phylogenetic comparisons of available Gloeobacter strains, as well as on the basis of three new independent isolates and historical type specimen, we have produced strong evidence as to the close relationship of Gloeobacter to a long known rock-dwelling cyanobacterial morphospecies Aphanothece caldariorum. Our results bring new clues to solving the 40 year old puzzle of the true biological identity of Gloeobacter violaceus, a model organism with a high value in several biological disciplines. A probable broader distribution of Gloeobacter in common wet-rock habitats worldwide is suggested by our data, and its ecological meaning is discussed taking into consideration the background of cyanobacterial evolution. We provide observations of previously unknown genetic variability and phenotypic plasticity, which we expect to be utilized by experimental and evolutionary researchers worldwide.

  16. The Primitive Thylakoid-Less Cyanobacterium Gloeobacter Is a Common Rock-Dwelling Organism

    Science.gov (United States)

    Mareš, Jan; Hrouzek, Pavel; Kaňa, Radek; Ventura, Stefano; Strunecký, Otakar; Komárek, Jiří

    2013-01-01

    Cyanobacteria are an ancient group of photosynthetic prokaryotes, which are significant in biogeochemical cycles. The most primitive among living cyanobacteria, Gloeobacter violaceus, shows a unique ancestral cell organization with a complete absence of inner membranes (thylakoids) and an uncommon structure of the photosynthetic apparatus. Numerous phylogenetic papers proved its basal position among all of the organisms and organelles capable of plant-like photosynthesis (i.e., cyanobacteria, chloroplasts of algae and plants). Hence, G. violaceus has become one of the key species in evolutionary study of photosynthetic life. It also numbers among the most widely used organisms in experimental photosynthesis research. Except for a few related culture isolates, there has been little data on the actual biology of Gloeobacter, being relegated to an “evolutionary curiosity” with an enigmatic identity. Here we show that members of the genus Gloeobacter probably are common rock-dwelling cyanobacteria. On the basis of morphological, ultrastructural, pigment, and phylogenetic comparisons of available Gloeobacter strains, as well as on the basis of three new independent isolates and historical type specimen, we have produced strong evidence as to the close relationship of Gloeobacter to a long known rock-dwelling cyanobacterial morphospecies Aphanothece caldariorum. Our results bring new clues to solving the 40 year old puzzle of the true biological identity of Gloeobacter violaceus, a model organism with a high value in several biological disciplines. A probable broader distribution of Gloeobacter in common wet-rock habitats worldwide is suggested by our data, and its ecological meaning is discussed taking into consideration the background of cyanobacterial evolution. We provide observations of previously unknown genetic variability and phenotypic plasticity, which we expect to be utilized by experimental and evolutionary researchers worldwide. PMID:23823729

  17. Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Δψ and ΔpH.

    Science.gov (United States)

    Davis, Geoffry A; Rutherford, A William; Kramer, David M

    2017-09-26

    There is considerable interest in improving plant productivity by altering the dynamic responses of photosynthesis in tune with natural conditions. This is exemplified by the 'energy-dependent' form of non-photochemical quenching (qE), the formation and decay of which can be considerably slower than natural light fluctuations, limiting photochemical yield. In addition, we recently reported that rapidly fluctuating light can produce field recombination-induced photodamage (FRIP), where large spikes in electric field across the thylakoid membrane (Δψ) induce photosystem II recombination reactions that produce damaging singlet oxygen ((1)O2). Both qE and FRIP are directly linked to the thylakoid proton motive force (pmf), and in particular, the slow kinetics of partitioning pmf into its ΔpH and Δψ components. Using a series of computational simulations, we explored the possibility of 'hacking' pmf partitioning as a target for improving photosynthesis. Under a range of illumination conditions, increasing the rate of counter-ion fluxes across the thylakoid membrane should lead to more rapid dissipation of Δψ and formation of ΔpH. This would result in increased rates for the formation and decay of qE while resulting in a more rapid decline in the amplitudes of Δψ-spikes and decreasing (1)O2 production. These results suggest that ion fluxes may be a viable target for plant breeding or engineering. However, these changes also induce transient, but substantial mismatches in the ATP : NADPH output ratio as well as in the osmotic balance between the lumen and stroma, either of which may explain why evolution has not already accelerated thylakoid ion fluxes. Overall, though the model is simplified, it recapitulates many of the responses seen in vivo, while spotlighting critical aspects of the complex interactions between pmf components and photosynthetic processes. By making the programme available, we hope to enable the community of photosynthesis researchers to

  18. Ultrastructural changes in the membrane system of isolated chloroplasts of spinach under the influence of carbonic anhydrase inhibitors AA and EA

    Directory of Open Access Journals (Sweden)

    Marina V. Vodka

    2013-04-01

    Full Text Available The effects of carbonic anhydrase inhibitors (АА and EA on the membrane system of isolated chloroplasts of spinach were investigated. Under the influence of AA the considerable alterations in granal structure occurred, the thickness of the granal thylakoids increased by 36% and the interspace between thylakoids by 10% comparable with the control. As a result of EA treatment, the thickness of granal thylakoids enhanced by 31% and the interspace between thylakoids increased by 8% in comparison to the control. It was shown that structure of the granal system of the chloroplast was more sensitive to AA than EA. The data obtained can indicate a decrease in the activity of the thylakoid carbonic anhydrase, inhibition of electron transport and photosynthetic process as a whole in the presence of carbonic anhydrase inhibitors (AA and EA.

  19. Similar genetic switch systems might integrate the floral inductive pathways in dicots and monocots

    DEFF Research Database (Denmark)

    Andersen, C.H.; Jensen, C.S.; Petersen, K.

    2004-01-01

    A recent paper by Million Tadege et A shows that a SOC1-like gene from rice, OsSOC1, can complement the Arabidopsis soc1 mutant, and that ectopic expression of the Arabidopsis floral repressor FLC in rice delays flowering and up-regulation of OsSOC1 These findings, together with the identificatio...... of the wheat vernalization VRN1 locus as an AP1 homologue, suggest that related genetic switch systems control floral transition in dicots and monocots but that they are based on different MADS-box transcription factors....

  20. Thylakoids suppress appetite by increasing cholecystokinin resulting in lower food intake and body weight in high-fat fed mice

    DEFF Research Database (Denmark)

    Köhnke, Rickard; Lindqvist, Andreas; Göransson, Nathanael

    2009-01-01

    affect food intake and body weight during long-term feeding in mice. Female apolipoprotein E-deficient mice were fed a high-fat diet containing 41% of fat by energy with and without thylakoids for 100 days. Mice fed the thylakoid-enriched diet had suppressed food intake, body weight gain and body fat...... fat mass. There was no sign of desensitization in the animals treated with thylakoids. The results suggest that thylakoids are useful to suppress appetite and body weight gain when supplemented to a high-fat food during long-term feeding....... compared with the high-fat fed control mice. Reduced serum glucose, serum triglyceride and serum free fatty acid levels were found in the thylakoid-treated animals. The satiety hormone cholecystokinin was elevated, suggesting this hormone mediates satiety. Leptin levels were reduced, reflecting a decreased...

  1. Chromosome studies in the aquatic monocots of Myanmar: A brief review with additional records

    Directory of Open Access Journals (Sweden)

    Yu Ito

    2014-05-01

    Full Text Available Myanmar (Burma constitutes a significant component of the Indo-Myanmar biodiversity hotspot, with elements of the Indian, the Indochina, and the Sino-Japanese floristic regions, yet thus far only a few reliable sources of the country's flora have been available. As a part of a contribution for the floristic inventory of Myanmar, since it is important in a floristic survey to obtain as much information as possible, in addition to previous two reports, here we present three more chromosome counts in the aquatic monocots of Myanmar: Limnocharis flava with 2n = 20, Sagittaria trifolia with 2n = 22 (Alismataceae, and Potamogeton distinctus × P. nodosus with 2n = 52 (Potamogetonaceae; the third one is new to science. A brief review of cytological researches in the floristic regions' 45 non-hybrid aquatic monocots plus well investigated two inter-specific hybrids that are recorded in Myanmar is given, indicating that the further works with a focus on species in Myanmar that has infra-specific chromosome variation in the floristic regions will address the precise evolutionary history of the aquatic flora of Myanmar.

  2. Chromosome studies in the aquatic monocots of Myanmar: A brief review with additional records.

    Science.gov (United States)

    Ito, Yu; Tanaka, Nobuyuki

    2014-01-01

    Myanmar (Burma) constitutes a significant component of the Indo-Myanmar biodiversity hotspot, with elements of the Indian, the Indochina, and the Sino-Japanese floristic regions, yet thus far only a few reliable sources of the country's flora have been available. As a part of a contribution for the floristic inventory of Myanmar, since it is important in a floristic survey to obtain as much information as possible, in addition to previous two reports, here we present three more chromosome counts in the aquatic monocots of Myanmar: Limnocharisflava with 2n = 20, Sagittariatrifolia with 2n = 22 (Alismataceae), and Potamogetondistinctus × Potamogetonnodosus with 2n = 52 (Potamogetonaceae); the third one is new to science. A brief review of cytological researches in the floristic regions' 45 non-hybrid aquatic monocots plus well investigated two inter-specific hybrids that are recorded in Myanmar is given, indicating that the further works with a focus on species in Myanmar that has infra-specific chromosome variation in the floristic regions will address the precise evolutionary history of the aquatic flora of Myanmar.

  3. KNOX1 genes regulate lignin deposition and composition in monocots and dicots.

    Directory of Open Access Journals (Sweden)

    Brad T Townsley

    2013-05-01

    Full Text Available Plant secondary cell walls are deposited mostly in vascular tissues such as xylem vessels, tracheids, and fibers. These cell walls are composed of a complex matrix of compounds including cellulose, hemicellulose, and lignin. Lignin functions primarily to maintain the structural and mechanical integrity of both the transport vessel and the entire plant itself. Since lignin has been identified as a major source of biomass for biofuels, regulation of secondary cell wall biosynthesis has been a topic of much recent investigation. Biosynthesis and patterning of lignin involves many developmental and environmental cues including evolutionarily conserved transcriptional regulatory modules and hormonal signals. Here, we investigate the role of the class I KNOX genes and gibberellic acid in the lignin biosynthetic pathway in a representative monocot and a representative eudicot. Knotted1 overexpressing mutant plants showed a reduction in lignin content in both maize and tobacco. Expression of four key lignin biosynthesis genes was analyzed and revealed that KNOX1 genes regulate at least two steps in the lignin biosynthesis pathway. The negative regulation of lignin both in a monocot and a eudicot by the maize Kn1 gene suggests that lignin biosynthesis may be preserved across large phylogenetic distances. The evolutionary implications of regulation of lignification across divergent species are discussed.

  4. Diversification of the RAB Guanosine Triphosphatase Family in Dicots and Monocots

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    RAB guanosine triphosphatases (GTPases) are key regulators of vesicle trafficking and are essential to the growth and development of all eukaryotic cells. During evolution, the RAB family has expanded in different patterns to facilitate distinct cellular, developmental and physiological adaptations. Yeast has only 11 family members, whereas mammalian RABs have expanded to 18 RAB subfamilies. Plant RABs have diversified primarily by duplicating members within a single subfamily. Plant RABs are divided into eight subfamilies, corresponding to mammalian RAB1, RAB2, RAB5, RAB6,RAB7, RAB8, RAB11 and RAB18. Functional diversification of these is exemplified by the RAB11s, orthologs of which are partitioned into unique cell compartments in plants where they function to transport vesicles during localized tip growth.Similarly, the RAB2 family in grasses is likely involved in vesicle secretion associated with wall expansion, as determined by analysis of over-expression mutants. We propose that dicots and monocots have also diverged in their RAB profiles to accommodate unique cellular functions between the two groups. Here we present a bioinformatics analysis comparing the RAB sub-families of rice, maize and Arabidopsis. These results will guide future functional studies to test for the role of diversification of subfamilies unique to monocots compared to dicots.

  5. Enhanced Agrobacterium-mediated transformation efficiencies in monocot cells is associated with attenuated defense responses.

    Science.gov (United States)

    Zhang, Wan-Jun; Dewey, Ralph E; Boss, Wendy; Phillippy, Brian Q; Qu, Rongda

    2013-02-01

    Plant defense responses can lead to altered metabolism and even cell death at the sites of Agrobacterium infection, and thus lower transformation frequencies. In this report, we demonstrate that the utilization of culture conditions associated with an attenuation of defense responses in monocot plant cells led to highly improved Agrobacterium-mediated transformation efficiencies in perennial ryegrass (Lolium perenne L.). The removal of myo-inositol from the callus culture media in combination with a cold shock pretreatment and the addition of L-Gln prior to and during Agrobacterium-infection resulted in about 84 % of the treated calluses being stably transformed. The omission of myo-inositol from the callus culture media was associated with the failure of certain pathogenesis related genes to be induced after Agrobacterium infection. The addition of a cold shock and supplemental Gln appeared to have synergistic effects on infection and transformation efficiencies. Nearly 60 % of the stably transformed calluses regenerated into green plantlets. Calluses cultured on media lacking myo-inositol also displayed profound physiological and biochemical changes compared to ones cultured on standard growth media, such as reduced lignin within the cell walls, increased starch and inositol hexaphosphate accumulation, enhanced Agrobacterium binding to the cell surface, and less H(2)O(2) production after Agrobacterium infection. Furthermore, the cold treatment greatly reduced callus browning after infection. The simple modifications described in this report may have broad application for improving genetic transformation of recalcitrant monocot species.

  6. Monocot leaves are eaten less than dicot leaves in tropical lowland rain forests: correlations with toughness and leaf presentation

    DEFF Research Database (Denmark)

    Grubb, P.J.; Jackson, R.V.; Barberis, I.M.

    2008-01-01

    : At six sites on four continents, estimates were made of lamina area loss from the four most recently mature leaves of focal monocots and of the nearest dicot shoot. Measurements of leaf mass per unit area, and the concentrations of water and nitrogen were made for many of the species. In Panama...... of leaf mass per unit area, or concentrations of water or nitrogen. At only one site was the increase in loss from first to fourth mature leaf significant (also large and the same in monocots and dicots), but the losses sustained during expansion were much smaller in the monocots. In the leaf-cutter ant...... insects in tropical lowland rain forest, and that the relative importance varies widely with species. The difficulties of establishing unequivocally the roles of leaf toughness and leaf folding or rolling in a given case are discussed. Key words: anti-herbivore defences, dicots, herbivory, leaf folding...

  7. A twin arginine signal peptide and the pH gradient trigger reversible assembly of the thylakoid [Delta]pH/Tat translocase.

    Science.gov (United States)

    Mori, Hiroki; Cline, Kenneth

    2002-04-15

    The thylakoid DeltapH-dependent/Tat pathway is a novel system with the remarkable ability to transport tightly folded precursor proteins using a transmembrane DeltapH as the sole energy source. Three known components of the transport machinery exist in two distinct subcomplexes. A cpTatC-Hcf106 complex serves as precursor receptor and a Tha4 complex is required after precursor recognition. Here we report that Tha4 assembles with cpTatC-Hcf106 during the translocation step. Interactions among components were examined by chemical cross-linking of intact thylakoids followed by immunoprecipitation and immunoblotting. cpTatC and Hcf106 were consistently associated under all conditions tested. In contrast, Tha4 was only associated with cpTatC and Hcf106 in the presence of a functional precursor and the DeltapH. Interestingly, a synthetic signal peptide could replace intact precursor in triggering assembly. The association of all three components was transient and dissipated upon the completion of protein translocation. Such an assembly-disassembly cycle could explain how the DeltapH/Tat system can assemble translocases to accommodate folded proteins of varied size. It also explains in part how the system can exist in the membrane without compromising its ion and proton permeability barrier.

  8. Photoactivation of electrogenic activity in chloroplasts and its relation to photoinduced swelling of thylakoids

    NARCIS (Netherlands)

    Bulychev, A.A.; Vredenberg, W.J.

    2000-01-01

    In patch-clamp experiments on isolated chloroplasts of Peperomia metallica Lind. et Rodig. (Piperaceae), the replacement of 50 mM KCl in a medium with 50 mM NH4Cl strongly influenced the parameters of photocurrent known to reflect the generation of electric potential in thylakoids. The addition of N

  9. Thylakoids promote release of the satiety hormone cholecystokinin while reducing insulin in healthy humans

    DEFF Research Database (Denmark)

    Köhnke, Rickard; Lindbo, Agnes; Larsson, Therese

    2009-01-01

    (CCK, leptin and ghrelin), insulin and blood metabolites (glucose and free fatty acids). RESULTS: The CCK level increased, in particular between the 120 min time-point and onwards, the ghrelin level was reduced at 120 min and leptin level increased at 360 min after intake of the thylakoid-enriched meal...

  10. Phycobilisome-thylakoid Topography on Photosynthetically Active Vesicles of Porphyridium cruentum1

    Science.gov (United States)

    Dilworth, Machi F.; Gantt, Elisabeth

    1981-01-01

    Conditions are described for isolating functional phycobilisome-thylakoid vesicles from the red alga Porphyridium cruentum. Phycobilisome-thylakoid vesicles were prepared by brief sonication and centrifugation in a medium containing 0.5 molar sucrose, 0.5 molar potassium phosphate, and 0.3 molar sodium citrate (pH 7.0). They required ferricyanide as an oxidant and had O2 evolution rates (about 450 micromoles O2 per hour per milligram chlorophyll) higher than whole cells (about 250 micromoles O2 per hour per milligram chlorophyll). Energy transfer to photosystem II chlorophyll was evident from a high F695 nanometer (−196 C) emission peak. Preparations could be stored for over 24 hours and were considerably more stable than those from the cyanobacterium Anabaena variabilis (Katoh T, E Gantt 1979 Biochim Biophys Acta 546: 383-393). In electron micrographs of negatively stained material, the active thylakoid vesicles were found covered by closely spaced phycobilisomes on their external surface. The phycobilisome number in negatively stained vesicles was 450 per square micrometer, which was in the same range as the 400 per square micrometer observed in surface sections. A cell containing 1.5 × 10−6 micrograms phycoerythrin and 1.3 × 10−6 micrograms chlorophyll was found to contain 5 to 7 × 105 phycobilisomes on a thylakoid area of 1.1 to 1.6 × 103 square micrometers. Images PMID:16661723

  11. Proteomics of the chloroplast: systematic identification and targeting analysis of lumenal and peripheral thylakoid proteins

    DEFF Research Database (Denmark)

    Peltier, J B; Friso, G; Kalume, D E

    2000-01-01

    The soluble and peripheral proteins in the thylakoids of pea were systematically analyzed by using two-dimensional electrophoresis, mass spectrometry, and N-terminal Edman sequencing, followed by database searching. After correcting to eliminate possible isoforms and post-translational modificati...... of proteomics for plant biology and homology-based searching with mass spectrometry data is discussed....

  12. Reversible membrane reorganizations during photosynthesis in vivo: revealed by small-angle neutron scattering

    DEFF Research Database (Denmark)

    Nagy, Gergely; Posselt, Dorthe; Kovacs, Laszlo

    2011-01-01

    In the present study, we determined characteristic repeat distances of the photosynthetic membranes in living cyanobacterial and eukaryotic algal cells, and in intact thylakoid membranes isolated from higher plants with time-resolved small-angle neutron scattering. This non-invasive technique rev...

  13. Kinetics of structural reorganizations in multilamellarphotosynthetic membranes monitored by small-angle neutronscattering

    DEFF Research Database (Denmark)

    Nagy, Gergely; Kovacs, Laszlo; Unnep, Renata;

    2013-01-01

    We demonstrate the power of time-resolved small-angle neutron scattering experiments for the investigation of the structure and structural reorganizations of multilamellar photosynthetic membranes. In addition to briefly summarizing our results on thylakoid membranes isolated from higher plants a...

  14. Structure and membrane organization of photosystem II in green plants

    NARCIS (Netherlands)

    Hankamer, B; Barber, J; Boekema, EJ

    1997-01-01

    Photosystem II (PSII) is the pigment protein complex embedded in the thylakoid membrane of higher plants, algae, and cyanobacteria that uses solar energy to drive the photosynthetic water-splitting reaction. This chapter reviews the primary, secondary, tertiary, and quaternary structures of PSII as

  15. The changes in the chloroplast membranes of pea leaves under the influence of carbonic anhydrase inhibitors (ions of copper and zinc

    Directory of Open Access Journals (Sweden)

    M.V. Vodka

    2014-04-01

    Full Text Available Тhe effects of carbonic anhydrase inhibitors, such as ions Cu2+ and Zn2+, on the membrane system of chloroplasts in pea leaves were investigated. After treatment of pea leaves with 250 mM Cu2+ or 400 mM Zn2+ we observed changes in the granal structure and compactness of the thylakoids in granae. It was shown that the thickness of granal thylakoids and the interspace between thylakoids increased comparing to control. Changes of the size and structure of thylakoids and granae in treated leaves may be associated with the enhanced accumulation of CO2 in the membrane. It is suggested that the carbonic anhydrase may also play a structural role in chloroplast granae.

  16. Conserved Subgroups and Developmental Regulation in the Monocot rop Gene Family1[w

    Science.gov (United States)

    Christensen, Todd M.; Vejlupkova, Zuzana; Sharma, Yogesh K.; Arthur, Kirstin M.; Spatafora, Joseph W.; Albright, Carol A.; Meeley, Robert B.; Duvick, Jon P.; Quatrano, Ralph S.; Fowler, John E.

    2003-01-01

    Rop small GTPases are plant-specific signaling proteins with roles in pollen and vegetative cell growth, abscisic acid signal transduction, stress responses, and pathogen resistance. We have characterized the rop family in the monocots maize (Zea mays) and rice (Oryza sativa). The maize genome contains at least nine expressed rops, and the fully sequenced rice genome has seven. Based on phylogenetic analyses of all available Rops, the family can be subdivided into four groups that predate the divergence of monocots and dicots; at least three have been maintained in both lineages. However, the Rop family has evolved differently in the two lineages, with each exhibiting apparent expansion in different groups. These analyses, together with genetic mapping and identification of conserved non-coding sequences, predict orthology for specific rice and maize rops. We also identified consensus protein sequence elements specific to each Rop group. A survey of ROP-mRNA expression in maize, based on multiplex reverse transcriptase-polymerase chain reaction and a massively parallel signature sequencing database, showed significant spatial and temporal overlap of the nine transcripts, with high levels of all nine in tissues in which cells are actively dividing and expanding. However, only a subset of rops was highly expressed in mature leaves and pollen. Intriguingly, the grouping of maize rops based on hierarchical clustering of expression profiles was remarkably similar to that obtained by phylogenetic analysis. We hypothesize that the Rop groups represent classes with distinct functions, which are specified by the unique protein sequence elements in each group and by their distinct expression patterns. PMID:14605221

  17. Dietary thylakoids suppress blood glucose and modulate appetite-regulating hormones in pigs exposed to oral glucose tolerance test

    DEFF Research Database (Denmark)

    Montelius, Caroline; Szwiec, Katarzyna; Kardas, Marek

    2014-01-01

    BACKGROUND & AIMS: Dietary chloroplast thylakoids have previously been found to reduce food intake and body weight in animal models, and to change metabolic profiles in humans in mixed-food meal studies. The aim of this study was to investigate the modulatory effects of thylakoids on glucose......, and decreased late postprandial secretion of ghrelin. CONCLUSION: Dietary thylakoids may be a novel agent in reducing the glycaemic responses to high carbohydrate and high glycaemic index foods. Thylakoids may in the future be promising for treatment and prevention of diabetes, overweight and obesity....... metabolism and appetite-regulating hormones during an oral glucose tolerance test in pigs fed a high fat diet. METHODS: Six pigs were fed a high fat diet (36 energy% fat) for one month before oral glucose tolerance test (1 g/kg d-glucose) was performed. The experiment was designed as a cross-over study...

  18. The effect of metal chelators on the production of hydroxyl radicals in thylakoids.

    Science.gov (United States)

    Snyrychová, Iva; Pospísil, Pavel; Naus, Jan

    2006-06-01

    The effect of metal chelators (EDTA, DTPA and Desferal) on the metal-catalyzed decomposition of hydrogen peroxide was studied using EPR spin-trapping spectroscopy. The formation of hydroxyl radicals (OH*) in both chemical (Fenton reaction) and biological (thylakoids) systems was stimulated by EDTA. DTPA promoted the generation of OH* in the presence of strong reducing agents, whereas in their absence it acted as an antioxidant. Desferal suppressed OH* production even in the presence of reductants. In our study, we have shown that metal chelators can both stimulate and suppress the formation of OH*, depending on the experimental conditions. In illuminated thylakoids we have observed prooxidant effect of EDTA and DTPA, possibly due to their reduction by some component of the electron transport chain. According to our results, metal chelators should not be used as antioxidants without prior testing of their effect in given samples.

  19. Specific interaction of IM30/Vipp1 with cyanobacterial and chloroplast membranes results in membrane remodeling and eventually in membrane fusion.

    Science.gov (United States)

    Heidrich, Jennifer; Thurotte, Adrien; Schneider, Dirk

    2017-04-01

    The photosynthetic light reaction takes place within the thylakoid membrane system in cyanobacteria and chloroplasts. Besides its global importance, the biogenesis, maintenance and dynamics of this membrane system are still a mystery. In the last two decades, strong evidence supported the idea that these processes involve IM30, the inner membrane-associated protein of 30kDa, a protein also known as the vesicle-inducing protein in plastids 1 (Vipp1). Even though we just only begin to understand the precise physiological function of this protein, it is clear that interaction of IM30 with membranes is crucial for biogenesis of thylakoid membranes. Here we summarize and discuss forces guiding IM30-membrane interactions, as the membrane properties as well as the oligomeric state of IM30 appear to affect proper interaction of IM30 with membrane surfaces. Interaction of IM30 with membranes results in an altered membrane structure and can finally trigger fusion of adjacent membranes, when Mg(2+) is present. Based on recent results, we finally present a model summarizing individual steps involved in IM30-mediated membrane fusion. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.

  20. Mechanisms underlying the long-term survival of the monocot Dracaena marginata under drought conditions.

    Science.gov (United States)

    Jupa, Radek; Plichta, Roman; Paschová, Zuzana; Nadezhdina, Nadezhda; Gebauer, Roman

    2017-09-01

    Efficient water management is essential for the survival of vascular plants under drought stress. While interrelations among drought stress, plant anatomy and physiological functions have been described in woody dicots, similar research is very limited for non-palm arborescent and shrubby monocots despite their generally high drought tolerance. In this study, potted transplants of Dracaena marginata Lam. in primary growth stage were exposed to several short- and long-term drought periods. Continuous measurements of sap flow and stem diameter, the evaluation of capacitance and leaf conductance, the quantification of non-structural carbohydrates (NSC), and organ-specific anatomical analyses were performed to reveal the mechanisms promoting plant resistance to limited soil moisture. The plants showed sensitive stomata regulation in the face of drying soil, but only intermediate resistance to water loss through cuticular transpiration. The water losses were compensated by water release from stem characterized by densely interconnected, parenchyma-rich ground tissue and considerable hydraulic capacitance. Our results suggest that the high concentration of osmotically active NSC in aboveground organs combined with the production of root pressures supported water uptake and the restoration of depleted reserves after watering. The described anatomical features and physiological mechanisms impart D. marginata with high resistance to irregular watering and long-term water scarcity. These findings should help to improve predictions with respect to the impacts of droughts on this plant group. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. Lower Miocene plant assemblage with coastal-marsh herbaceous monocots from the Vienna Basin (Slovakia)

    Science.gov (United States)

    Kvaček, Zlatko; Teodoridis, Vasilis; Kováčová, Marianna; Schlögl, Ján; Sitár, Viliam

    2014-06-01

    A new plant assemblage of Cerová-Lieskové from Lower Miocene (Karpatian) deposits in the Vienna Basin (western Slovakia) is preserved in a relatively deep, upper-slope marine environment. Depositional conditions with high sedimentation rates allowed exceptional preservation of plant remains. The plant assemblage consists of (1) conifers represented by foliage of Pinus hepios and Tetraclinis salicornioides, a seed cone of Pinus cf. ornata, and by pollen of the Cupressaceae, Pinaceae, Pinus sp. and Cathaya sp., and (2) angiosperms represented by Cinnamomum polymorphum, Platanus neptuni, Potamogeton sp. and lauroid foliage, by pollen of Liquidambar sp., Engelhardia sp. and Craigia sp., and in particular by infructescences (so far interpreted as belonging to cereal ears). We validate genus and species assignments of the infructescences: they belong to Palaeotriticum Sitár, including P. mockii Sitár and P. carpaticum Sitár, and probably represent herbaceous monocots that inhabited coastal marshes, similar to the living grass Spartina. Similar infructescences occur in the Lower and Middle Miocene deposits of the Carpathian Foredeep (Slup in Moravia), Tunjice Hills (Žale in Slovenia), and probably also in the Swiss Molasse (Lausanne). This plant assemblage demonstrates that the paleovegetation was represented by evergreen woodland with pines and grasses in undergrowth, similar to vegetation inhabiting coastal brackish marshes today. It also indicates subtropical climatic conditions in the Vienna Basin (central Paratethys), similar to those implied by other coeval plant assemblages from Central Europe

  2. CRISPR/Cas9-Based Multiplex Genome Editing in Monocot and Dicot Plants.

    Science.gov (United States)

    Ma, Xingliang; Liu, Yao-Guang

    2016-07-01

    The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated genome targeting system has been applied to a variety of organisms, including plants. Compared to other genome-targeting technologies such as zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs), the CRISPR/Cas9 system is easier to use and has much higher editing efficiency. In addition, multiple "single guide RNAs" (sgRNAs) with different target sequences can be designed to direct the Cas9 protein to multiple genomic sites for simultaneous multiplex editing. Here, we present a procedure for highly efficient multiplex genome targeting in monocot and dicot plants using a versatile and robust CRISPR/Cas9 vector system, emphasizing the construction of binary constructs with multiple sgRNA expression cassettes in one round of cloning using Golden Gate ligation. We also describe the genotyping of targeted mutations in transgenic plants by direct Sanger sequencing followed by decoding of superimposed sequencing chromatograms containing biallelic or heterozygous mutations using the Web-based tool DSDecode. © 2016 by John Wiley & Sons, Inc.

  3. Lower Miocene plant assemblage with coastal-marsh herbaceous monocots from the Vienna Basin (Slovakia

    Directory of Open Access Journals (Sweden)

    Kvaček Zlatko

    2014-06-01

    Full Text Available A new plant assemblage of Cerová-Lieskové from Lower Miocene (Karpatian deposits in the Vienna Basin (western Slovakia is preserved in a relatively deep, upper-slope marine environment. Depositional conditions with high sedimentation rates allowed exceptional preservation of plant remains. The plant assemblage consists of (1 conifers represented by foliage of Pinus hepios and Tetraclinis salicornioides, a seed cone of Pinus cf. ornata, and by pollen of the Cupressaceae, Pinaceae, Pinus sp. and Cathaya sp., and (2 angiosperms represented by Cinnamomum polymorphum, Platanus neptuni, Potamogeton sp. and lauroid foliage, by pollen of Liquidambar sp., Engelhardia sp. and Craigia sp., and in particular by infructescences (so far interpreted as belonging to cereal ears. We validate genus and species assignments of the infructescences: they belong to Palaeotriticum Sitár, including P. mockii Sitár and P. carpaticum Sitár, and probably represent herbaceous monocots that inhabited coastal marshes, similar to the living grass Spartina. Similar infructescences occur in the Lower and Middle Miocene deposits of the Carpathian Foredeep (Slup in Moravia, Tunjice Hills (Žale in Slovenia, and probably also in the Swiss Molasse (Lausanne. This plant assemblage demonstrates that the paleovegetation was represented by evergreen woodland with pines and grasses in undergrowth, similar to vegetation inhabiting coastal brackish marshes today. It also indicates subtropical climatic conditions in the Vienna Basin (central Paratethys, similar to those implied by other coeval plant assemblages from Central Europe

  4. Functional conservation of the meiotic genes SDS and RCK in male meiosis in the monocot rice

    Institute of Scientific and Technical Information of China (English)

    Ling Chang; Hong Ma; Hong-Wei Xue

    2009-01-01

    The Arabidopsis SDS (SOLO DANCERS) and RCK (ROCK-N-ROLLERS) genes are important for male meiosis, but it is still unknown whether they represent conserved functions in plants. We have performed phylogenetic analy-ses of SDS and RCK and their respective homologs, and identified their putative orthologs in poplar and rice. Quan-titative real-time RT-PCR analysis indicated that rice SDS and RCK are expressed preferentially in young flowers, and transgenic RNAi rice lines with reduced expression of these genes exhibited normal vegetative development, but showed significantly reduced fertility with partially sterile flowers and defective pollens. SDS deficiency also caused a decrease in pollen amounts. Further cytological examination of male meiocytes revealed that the SDS deficiency led to defects in homolog interaction and bivalent formation in meiotic prophase I, and RCK deficiency resulted in defec-tive meiotic crossover formation. These results indicate that rice SDS and RCK genes have similar functions to their Arabidopsis orthologs. Because rice and Arabidopsis, respectively, are members of monocots and eudicots, two largest groups of flowering plants, our results suggest that the functions of SDS and RCK are likely conserved in flowering plants.

  5. Rice Brittleness Mutants: A Way to Open the 'Black Box' of Monocot Cell Wall Biosynthesis

    Institute of Scientific and Technical Information of China (English)

    Baocai Zhang; Yihua Zhou

    2011-01-01

    Rice is a model organism for studying the mechanism of cell wall biosynthesis and remolding in Gramineae.Mechanical strength is an important agronomy trait of rice(Oryza sativa L.)plants that affects crop lodging and grain yield.As a prominent physical property of cell walls,mechanical strength reflects upon the structure of different wall polymers and how they interact.Studies on the mechanisms that regulate the mechanical strength therefore consequently results in uncovering the genes functioning in cell wall biosynthesis and remodeling.Our group focuses on the study of isolation of brittle culm(bc)mutants and characterization of their corresponding genes.To date,several bc mutants have been reported.The identified genes have covered several pathways of cell wall biosynthesis,revealing many secrets of monocot cell wall biosynthesis.Here,we review the progress achieved in this research field and also highlight the perspectives in expectancy.All of those lend new insights into mechanisms of cell wall formation and are helpful for harnessing the waste rice straws for biofuel production.

  6. Systematic Comparisons of Orthologous Selenocysteine Methyltransferase and Homocysteine Methyltransferase Genes from Seven Monocots Species

    Directory of Open Access Journals (Sweden)

    De-yong ZHAO

    2015-06-01

    Full Text Available Identifying and manipulating genes underlying selenium metabolism could be helpful for increasing selenium content in crop grain, which is an important way to overcome diseases resulted from selenium deficiency. A reciprocal smallest distance algorithm (RSD approach was applied using two experimentally confirmed Homocysteine S-Methyltransferases genes (HMT1 and HMT2 and a putative Selenocysteine Methyltransferase (SMT from dicots plant Arabidopsis thaliana, to explore their orthologs in seven sequenced diploid monocot species: Oryza sativa, Zea mays, Sorghum bicolor, Brachypodium distachyon, Hordeum vulgare, Aegilops tauschii (the D-genome donor of common wheat and Triticum urartu (the A-genome donor of common wheat. HMT1 was apparently diverged from HMT2 and most of SMT orthologs were the same with that of HMT2 in this study, leading to the hypothesis that SMT and HMT originate from one common ancestor gene. Identifying orthologs provide candidates for further experimental confirmation; also it could be helpful in designing primers to clone SMT or HMT orthologs in other crops.

  7. Contractile roots in succulent monocots: convergence, divergence and adaptation to limited rainfall.

    Science.gov (United States)

    North, Gretchen B; Brinton, Erin K; Garrett, Tadao Y

    2008-08-01

    Contractile roots (CRs) that pull shoots further down in the soil are a possible example of convergent evolution in two monocot families, the Agavaceae and the Asphodelaceae. The association between CRs, water uptake and habitat aridity was investigated for agaves, yuccas and aloes by assessing the occurrence of CRs and the amount of root contraction for glasshouse-grown plants with respect to mean annual rainfall of their native habitats. Structural features of CRs as well as root hydraulic conductance were compared with those of non-contractile roots (NCRs). CRs occurred in 55% of the 73 species examined, including 64% of the agaves and 85% of the yuccas, but in none of the aloes despite the occurrence of CRs in related genera. The phylogenetic distribution of CRs was consistent with multiple acquisitions or losses of the trait. The amount of root contraction showed a highly significant negative relationship with mean annual rainfall, although other environmental factors may also be important. Radial hydraulic conductance of the basal (contractile) zone exceeded that of the midroot zone for CRs; for NCRs, the opposite was true. Thus, CRs in the species examined may provide a mechanism for greater water uptake near the soil surface in regions with limited rainfall.

  8. Structural Comparison, Substrate Specificity, and Inhibitor Binding of AGPase Small Subunit from Monocot and Dicot: Present Insight and Future Potential

    Directory of Open Access Journals (Sweden)

    Kishore Sarma

    2014-01-01

    Full Text Available ADP-glucose pyrophosphorylase (AGPase is the first rate limiting enzyme of starch biosynthesis pathway and has been exploited as the target for greater starch yield in several plants. The structure-function analysis and substrate binding specificity of AGPase have provided enormous potential for understanding the role of specific amino acid or motifs responsible for allosteric regulation and catalytic mechanisms, which facilitate the engineering of AGPases. We report the three-dimensional structure, substrate, and inhibitor binding specificity of AGPase small subunit from different monocot and dicot crop plants. Both monocot and dicot subunits were found to exploit similar interactions with the substrate and inhibitor molecule as in the case of their closest homologue potato tuber AGPase small subunit. Comparative sequence and structural analysis followed by molecular docking and electrostatic surface potential analysis reveal that rearrangements of secondary structure elements, substrate, and inhibitor binding residues are strongly conserved and follow common folding pattern and orientation within monocot and dicot displaying a similar mode of allosteric regulation and catalytic mechanism. The results from this study along with site-directed mutagenesis complemented by molecular dynamics simulation will shed more light on increasing the starch content of crop plants to ensure the food security worldwide.

  9. Genomic analysis of NAC transcription factors in banana (Musa acuminata) and definition of NAC orthologous groups for monocots and dicots.

    Science.gov (United States)

    Cenci, Albero; Guignon, Valentin; Roux, Nicolas; Rouard, Mathieu

    2014-05-01

    Identifying the molecular mechanisms underlying tolerance to abiotic stresses is important in crop breeding. A comprehensive understanding of the gene families associated with drought tolerance is therefore highly relevant. NAC transcription factors form a large plant-specific gene family involved in the regulation of tissue development and responses to biotic and abiotic stresses. The main goal of this study was to set up a framework of orthologous groups determined by an expert sequence comparison of NAC genes from both monocots and dicots. In order to clarify the orthologous relationships among NAC genes of different species, we performed an in-depth comparative study of four divergent taxa, in dicots and monocots, whose genomes have already been completely sequenced: Arabidopsis thaliana, Vitis vinifera, Musa acuminata and Oryza sativa. Due to independent evolution, NAC copy number is highly variable in these plant genomes. Based on an expert NAC sequence comparison, we propose forty orthologous groups of NAC sequences that were probably derived from an ancestor gene present in the most recent common ancestor of dicots and monocots. These orthologous groups provide a curated resource for large-scale protein sequence annotation of NAC transcription factors. The established orthology relationships also provide a useful reference for NAC function studies in newly sequenced genomes such as M. acuminata and other plant species.

  10. sparse inflorescence1 encodes a monocot-specific YUCCA-like gene required for vegetative and reproductive development in maize.

    Science.gov (United States)

    Gallavotti, Andrea; Barazesh, Solmaz; Malcomber, Simon; Hall, Darren; Jackson, David; Schmidt, Robert J; McSteen, Paula

    2008-09-30

    The plant growth hormone auxin plays a critical role in the initiation of lateral organs and meristems. Here, we identify and characterize a mutant, sparse inflorescence1 (spi1), which has defects in the initiation of axillary meristems and lateral organs during vegetative and inflorescence development in maize. Positional cloning shows that spi1 encodes a flavin monooxygenase similar to the YUCCA (YUC) genes of Arabidopsis, which are involved in local auxin biosynthesis in various plant tissues. In Arabidopsis, loss of function of single members of the YUC family has no obvious effect, but in maize the mutation of a single yuc locus causes severe developmental defects. Phylogenetic analysis of the different members of the YUC family in moss, monocot, and eudicot species shows that there have been independent expansions of the family in monocots and eudicots. spi1 belongs to a monocot-specific clade, within which the role of individual YUC genes has diversified. These observations, together with expression and functional data, suggest that spi1 has evolved a dominant role in auxin biosynthesis that is essential for normal maize inflorescence development. Analysis of the interaction between spi1 and genes regulating auxin transport indicate that auxin transport and biosynthesis function synergistically to regulate the formation of axillary meristems and lateral organs in maize.

  11. Biogenesis of cytochrome b6 in photosynthetic membranes.

    Science.gov (United States)

    Saint-Marcoux, Denis; Wollman, Francis-André; de Vitry, Catherine

    2009-06-29

    In chloroplasts, binding of a c'-heme to cytochrome b(6) on the stromal side of the thylakoid membranes requires a specific mechanism distinct from the one at work for c-heme binding to cytochromes f and c(6) on the lumenal side of membranes. Here, we show that the major protein components of this pathway, the CCBs, are bona fide transmembrane proteins. We demonstrate their association in a series of hetero-oligomeric complexes, some of which interact transiently with cytochrome b(6) in the process of heme delivery to the apoprotein. In addition, we provide preliminary evidence for functional assembly of cytochrome b(6)f complexes even in the absence of c'-heme binding to cytochrome b(6). Finally, we present a sequential model for apo- to holo-cytochrome b(6) maturation integrated within the assembly pathway of b(6)f complexes in the thylakoid membranes.

  12. Supplementation by thylakoids to a high carbohydrate meal decreases feelings of hunger, elevates CCK levels and prevents postprandial hypoglycaemia in overweight women

    DEFF Research Database (Denmark)

    Stenblom, Eva-Lena; Montelius, Caroline; Östbring, Karolina

    2013-01-01

    over a 4-h period. Addition of thylakoids suppressed hunger motivation and increased secretion of CCK from 180 min, and prevented postprandial hypoglycaemia from 90 min following food intake. These effects indicate that thylakoids may intensify signals of satiety. This study therefore suggests...

  13. Microoxic Niches within the Thylakoid Stroma of Air-Grown Chlamydomonas reinhardtii Protect [FeFe]-Hydrogenase and Support Hydrogen Production under Fully Aerobic Environment1[OPEN

    Science.gov (United States)

    Liran, Oded; Milrad, Yuval; Eilenberg, Haviva; Weiner, Iddo

    2016-01-01

    Photosynthetic hydrogen production in the microalga Chlamydomonas reinhardtii is catalyzed by two [FeFe]-hydrogenase isoforms, HydA1 and HydA2, both irreversibly inactivated upon a few seconds exposure to atmospheric oxygen. Until recently, it was thought that hydrogenase is not active in air-grown microalgal cells. In contrast, we show that the entire pool of cellular [FeFe]-hydrogenase remains active in air-grown cells due to efficient scavenging of oxygen. Using membrane inlet mass spectrometry, 18O2 isotope, and various inhibitors, we were able to dissect the various oxygen uptake mechanisms. We found that both chlororespiration, catalyzed by plastid terminal oxidase, and Mehler reactions, catalyzed by photosystem I and Flavodiiron proteins, significantly contribute to oxygen uptake rate. This rate is considerably enhanced with increasing light, thus forming local anaerobic niches at the proximity of the stromal face of the thylakoid membrane. Furthermore, we found that in transition to high light, the hydrogen production rate is significantly enhanced for a short duration (100 s), thus indicating that [FeFe]-hydrogenase functions as an immediate sink for surplus electrons in aerobic as well as in anaerobic environments. In summary, we show that an anaerobic locality in the chloroplast preserves [FeFe]-hydrogenase activity and supports continuous hydrogen production in air-grown microalgal cells. PMID:27443604

  14. Identification and characterization of NF-Y transcription factor families in the monocot model plant Brachypodium distachyon.

    Directory of Open Access Journals (Sweden)

    Shuanghe Cao

    Full Text Available BACKGROUND: Nuclear Factor Y (NF-Y is a heterotrimeric transcription factor composed of NF-YA, NF-YB and NF-YC proteins. Using the dicot plant model system Arabidopsis thaliana (Arabidopsis, NF-Y were previously shown to control a variety of agronomically important traits, including drought tolerance, flowering time, and seed development. The aim of the current research was to identify and characterize NF-Y families in the emerging monocot model plant Brachypodium distachyon (Brachypodium with the long term goal of assisting in the translation of known dicot NF-Y functions to the grasses. METHODOLOGY/PRINCIPAL FINDINGS: We identified, annotated, and further characterized 7 NF-YA, 17 NF-YB, and 12 NF-YC proteins in Brachypodium (BdNF-Y. By examining phylogenetic relationships, orthology predictions, and tissue-specific expression patterns for all 36 BdNF-Y, we proposed numerous examples of likely functional conservation between dicots and monocots. To test one of these orthology predictions, we demonstrated that a BdNF-YB with predicted orthology to Arabidopsis floral-promoting NF-Y proteins can rescue a late flowering Arabidopsis mutant. CONCLUSIONS/SIGNIFICANCE: The Brachypodium genome encodes a similar complement of NF-Y to other sequenced angiosperms. Information regarding NF-Y phylogenetic relationships, predicted orthologies, and expression patterns can facilitate their study in the grasses. The current data serves as an entry point for translating many NF-Y functions from dicots to the genetically tractable monocot model system Brachypodium. In turn, studies of NF-Y function in Brachypodium promise to be more readily translatable to the agriculturally important grasses.

  15. Dietary thylakoids reduce visceral fat mass and increase expression of genes involved in intestinal fatty acid oxidation in high-fat fed rats.

    Science.gov (United States)

    Stenblom, Eva-Lena; Egecioglu, Emil; Montelius, Caroline; Ramachandran, Deepti; Bonn, Britta; Weström, Björn; Mansouri, Abdelhak; Langhans, Wolfgang; Erlanson-Albertsson, Charlotte

    2016-09-01

    Thylakoids reduce body weight gain and body fat accumulation in rodents. This study investigated whether an enhanced oxidation of dietary fat-derived fatty acids in the intestine contributes to the thylakoid effects. Male Sprague-Dawley rats were fed a high-fat diet with (n = 8) or without thylakoids (n = 8) for 2 wk. Body weight, food intake, and body fat were measured, and intestinal mucosa was collected and analyzed. Quantitative real-time PCR was used to measure gene expression levels of key enzymes involved in fatty acid transport, fatty acid oxidation, and ketogenesis. Another set of thylakoid-treated (n = 10) and control rats (n = 10) went through indirect calorimetry. In the first experiment, thylakoid-treated rats (n = 8) accumulated 25% less visceral fat than controls. Furthermore, fatty acid translocase (Fat/Cd36), carnitine palmitoyltransferase 1a (Cpt1a), and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (Hmgcs2) genes were upregulated in the jejunum of the thylakoid-treated group. In the second experiment, thylakoid-treated rats (n = 10) gained 17.5% less weight compared with controls and their respiratory quotient was lower, 0.86 compared with 0.91. Thylakoid-intake resulted in decreased food intake and did not cause steatorrhea. These results suggest that thylakoids stimulated intestinal fatty acid oxidation and ketogenesis, resulting in an increased ability of the intestine to handle dietary fat. The increased fatty acid oxidation and the resulting reduction in food intake may contribute to the reduced fat accumulation in thylakoid-treated animals.

  16. OsWRKY22, a monocot WRKY gene, plays a role in the resistance response to blast.

    Science.gov (United States)

    Abbruscato, Pamela; Nepusz, Tamás; Mizzi, Luca; Del Corvo, Marcello; Morandini, Piero; Fumasoni, Irene; Michel, Corinne; Paccanaro, Alberto; Guiderdoni, Emmanuel; Schaffrath, Ulrich; Morel, Jean-Benoît; Piffanelli, Pietro; Faivre-Rampant, Odile

    2012-10-01

    With the aim of identifying novel regulators of host and nonhost resistance to fungi in rice, we carried out a systematic mutant screen of mutagenized lines. Two mutant wrky22 knockout lines revealed clear-cut enhanced susceptibility to both virulent and avirulent Magnaporthe oryzae strains and altered cellular responses to nonhost Magnaporthe grisea and Blumeria graminis fungi. In addition, the analysis of the pathogen responses of 24 overexpressor OsWRKY22 lines revealed enhanced resistance phenotypes on infection with virulent M. oryzae strain, confirming that OsWRKY22 is involved in rice resistance to blast. Bioinformatic analyses determined that the OsWRKY22 gene belongs to a well-defined cluster of monocot-specific WRKYs. The co-regulatory analysis revealed no significant co-regulation of OsWRKY22 with a representative panel of OsWRKYs, supporting its unique role in a series of transcriptional responses. In contrast, inquiring a subset of biotic stress-related Affymetrix data, a large number of resistance and defence-related genes were found to be putatively co-expressed with OsWRKY22. Taken together, all gathered experimental evidence places the monocot-specific OsWRKY22 gene at the convergence point of signal transduction circuits in response to both host and nonhost fungi encountering rice plants.

  17. A high throughput barley stripe mosaic virus vector for virus induced gene silencing in monocots and dicots.

    Directory of Open Access Journals (Sweden)

    Cheng Yuan

    Full Text Available Barley stripe mosaic virus (BSMV is a single-stranded RNA virus with three genome components designated alpha, beta, and gamma. BSMV vectors have previously been shown to be efficient virus induced gene silencing (VIGS vehicles in barley and wheat and have provided important information about host genes functioning during pathogenesis as well as various aspects of genes functioning in development. To permit more effective use of BSMV VIGS for functional genomics experiments, we have developed an Agrobacterium delivery system for BSMV and have coupled this with a ligation independent cloning (LIC strategy to mediate efficient cloning of host genes. Infiltrated Nicotiana benthamiana leaves provided excellent sources of virus for secondary BSMV infections and VIGS in cereals. The Agro/LIC BSMV VIGS vectors were able to function in high efficiency down regulation of phytoene desaturase (PDS, magnesium chelatase subunit H (ChlH, and plastid transketolase (TK gene silencing in N. benthamiana and in the monocots, wheat, barley, and the model grass, Brachypodium distachyon. Suppression of an Arabidopsis orthologue cloned from wheat (TaPMR5 also interfered with wheat powdery mildew (Blumeria graminis f. sp. tritici infections in a manner similar to that of the A. thaliana PMR5 loss-of-function allele. These results imply that the PMR5 gene has maintained similar functions across monocot and dicot families. Our BSMV VIGS system provides substantial advantages in expense, cloning efficiency, ease of manipulation and ability to apply VIGS for high throughput genomics studies.

  18. The phylogenetically-related pattern recognition receptors EFR and XA21 recruit similar immune signaling components in monocots and dicots.

    Directory of Open Access Journals (Sweden)

    Nicholas Holton

    2015-01-01

    Full Text Available During plant immunity, surface-localized pattern recognition receptors (PRRs recognize pathogen-associated molecular patterns (PAMPs. The transfer of PRRs between plant species is a promising strategy for engineering broad-spectrum disease resistance. Thus, there is a great interest in understanding the mechanisms of PRR-mediated resistance across different plant species. Two well-characterized plant PRRs are the leucine-rich repeat receptor kinases (LRR-RKs EFR and XA21 from Arabidopsis thaliana (Arabidopsis and rice, respectively. Interestingly, despite being evolutionary distant, EFR and XA21 are phylogenetically closely related and are both members of the sub-family XII of LRR-RKs that contains numerous potential PRRs. Here, we compared the ability of these related PRRs to engage immune signaling across the monocots-dicots taxonomic divide. Using chimera between Arabidopsis EFR and rice XA21, we show that the kinase domain of the rice XA21 is functional in triggering elf18-induced signaling and quantitative immunity to the bacteria Pseudomonas syringae pv. tomato (Pto DC3000 and Agrobacterium tumefaciens in Arabidopsis. Furthermore, the EFR:XA21 chimera associates dynamically in a ligand-dependent manner with known components of the EFR complex. Conversely, EFR associates with Arabidopsis orthologues of rice XA21-interacting proteins, which appear to be involved in EFR-mediated signaling and immunity in Arabidopsis. Our work indicates the overall functional conservation of immune components acting downstream of distinct LRR-RK-type PRRs between monocots and dicots.

  19. Comparative genomics of multiple strains of Pseudomonas cannabina pv. alisalensis, a potential model pathogen of both monocots and dicots.

    Directory of Open Access Journals (Sweden)

    Panagiotis F Sarris

    Full Text Available Comparative genomics of closely related pathogens that differ in host range can provide insights into mechanisms of host-pathogen interactions and host adaptation. Furthermore, sequencing of multiple strains with the same host range reveals information concerning pathogen diversity and the molecular basis of virulence. Here we present a comparative analysis of draft genome sequences for four strains of Pseudomonas cannabina pathovar alisalensis (Pcal, which is pathogenic on a range of monocotyledonous and dicotyledonous plants. These draft genome sequences provide a foundation for understanding host range evolution across the monocot-dicot divide. Like other phytopathogenic pseudomonads, Pcal strains harboured a hrp/hrc gene cluster that codes for a type III secretion system. Phylogenetic analysis based on the hrp/hrc cluster genes/proteins, suggests localized recombination and functional divergence within the hrp/hrc cluster. Despite significant conservation of overall genetic content across Pcal genomes, comparison of type III effector repertoires reinforced previous molecular data suggesting the existence of two distinct lineages within this pathovar. Furthermore, all Pcal strains analyzed harbored two distinct genomic islands predicted to code for type VI secretion systems (T6SSs. While one of these systems was orthologous to known P. syringae T6SSs, the other more closely resembled a T6SS found within P. aeruginosa. In summary, our study provides a foundation to unravel Pcal adaptation to both monocot and dicot hosts and provides genetic insights into the mechanisms underlying pathogenicity.

  20. Characterization of barley (Hordeum vulgare L. NAC transcription factors suggests conserved functions compared to both monocots and dicots

    Directory of Open Access Journals (Sweden)

    Gregersen Per L

    2011-08-01

    Full Text Available Abstract Background The NAC transcription factor family is involved in the regulation of traits in both monocots and dicots of high agronomic importance. Understanding the precise functions of the NAC genes can be of utmost importance for the improvement of cereal crop plants through plant breeding. For the cereal crop plant barley (Hordeum vulgare L. only a few NAC genes have so far been investigated. Results Through searches in publicly available barley sequence databases we have obtained a list of 48 barley NAC genes (HvNACs with 43 of them representing full-length coding sequences. Phylogenetic comparisons to Brachypodium, rice, and Arabidopsis NAC proteins indicate that the barley NAC family includes members from all of the eight NAC subfamilies, although by comparison to these species a number of HvNACs still remains to be identified. Using qRT-PCR we investigated the expression profiles of 46 HvNACs across eight barley tissues (young flag leaf, senescing flag leaf, young ear, old ear, milk grain, late dough grain, roots, and developing stem and two hormone treatments (abscisic acid and methyl jasmonate. Conclusions Comparisons of expression profiles of selected barley NAC genes with the published functions of closely related NAC genes from other plant species, including both monocots and dicots, suggest conserved functions in the areas of secondary cell wall biosynthesis, leaf senescence, root development, seed development, and hormone regulated stress responses.

  1. Enhancement of innate immune system in monocot rice by transferring the dicotyledonous elongation factor Tu receptor EFR

    Institute of Scientific and Technical Information of China (English)

    Fen Lu; Huiqin Wang; Shanzhi Wang; Wendi Jiang; Changlin Shan; Bin Li; Jun Yang; Shiyong Zhang; Wenxian Sun

    2015-01-01

    The elongation factor Tu (EF-Tu) receptor (EFR) in cruciferous plants specifical y recognizes the N-terminal acetylated elf18 region of bacterial EF-Tu and thereby activates plant immunity. It has been demonstrated that Arabidopsis EFR confers broad-spectrum bacterial resistance in the EFR transgenic solanaceous plants. Here, the transgenic rice plants (Oryza sativa L. ssp. japonica cv. Zhonghua 17) and cel cultures with constitutive expression of AtEFR were developed to investigate whether AtEFR senses EF-Tu and thus enhances bacterial resistance in the monocot plants. We demonstrated that the Xanthomonas oryzae-derived elf18 peptide induced oxidative burst and mitogen-activated protein kinase activa-tion in the AtEFR transgenic rice cel s and plants, respectively. Pathogenesis-related genes, such as OsPBZ1, were upregulated dramatical y in transgenic rice plant and cel lines in response to elf18 stimulation. Importantly, pretreatment with elf18 trig-gered strong resistance to X. oryzae pv. oryzae in the transgenic plants, which was largely dependent on the AtEFR expression level. These plants also exhibited enhanced resistance to rice bacterial brown stripe, but not to rice fungal blast. Col ectively, the results indicate that the rice plants with heterologous expression of AtEFR recognize bacterial EF-Tu and exhibit enhanced broad-spectrum bacterial disease resistance and that pattern recognition receptor-mediated immunity may be manipulated across the two plant classes, dicots and monocots.

  2. Diversification of genes encoding granule-bound starch synthase in monocots and dicots is marked by multiple genome-wide duplication events.

    Directory of Open Access Journals (Sweden)

    Jun Cheng

    Full Text Available Starch is one of the major components of cereals, tubers, and fruits. Genes encoding granule-bound starch synthase (GBSS, which is responsible for amylose synthesis, have been extensively studied in cereals but little is known about them in fruits. Due to their low copy gene number, GBSS genes have been used to study plant phylogenetic and evolutionary relationships. In this study, GBSS genes have been isolated and characterized in three fruit trees, including apple, peach, and orange. Moreover, a comprehensive evolutionary study of GBSS genes has also been conducted between both monocots and eudicots. Results have revealed that genomic structures of GBSS genes in plants are conserved, suggesting they all have evolved from a common ancestor. In addition, the GBSS gene in an ancestral angiosperm must have undergone genome duplication ∼251 million years ago (MYA to generate two families, GBSSI and GBSSII. Both GBSSI and GBSSII are found in monocots; however, GBSSI is absent in eudicots. The ancestral GBSSII must have undergone further divergence when monocots and eudicots split ∼165 MYA. This is consistent with expression profiles of GBSS genes, wherein these profiles are more similar to those of GBSSII in eudicots than to those of GBSSI genes in monocots. In dicots, GBSSII must have undergone further divergence when rosids and asterids split from each other ∼126 MYA. Taken together, these findings suggest that it is GBSSII rather than GBSSI of monocots that have orthologous relationships with GBSS genes of eudicots. Moreover, diversification of GBSS genes is mainly associated with genome-wide duplication events throughout the evolutionary course of history of monocots and eudicots.

  3. Multiple types of association of photosystem II and its light-harvesting antenna in partially solubilized photosystem II membranes

    NARCIS (Netherlands)

    Boekema, EJ; van Roon, H; Calkoen, F; Bassi, R; Dekker, JP; Dekker, Jan P.

    1999-01-01

    Photosystem II is a multisubunit pigment-protein complex embedded in the thylakoid membranes of chloroplasts. It utilizes light for photochemical energy conversion, and is heavily involved in the regulation of the energy flow. We investigated the structural organization of photosystem II and its ass

  4. Novel protein phosphorylation site identification in spinach stroma membranes by titanium dioxide microcolumns and tandem mass spectrometry

    DEFF Research Database (Denmark)

    Rinalducci, Sara; Larsen, Martin Røssel; Mohammed, Shabaz

    2006-01-01

    In this work, spinach stroma membrane, instead of thylakoid, has been investigated for the presence of phosphorylated proteins. We identified seven previously unknown phosphorylation sites by taking advantage of TiO(2) phosphopeptides enrichment coupled to mass spectrometric analysis. Upon illumi...

  5. Overexpression of thylakoidal ascorbate peroxidase shows enhanced resistance to chilling stress in tomato.

    Science.gov (United States)

    Duan, Ming; Feng, Hai-Long; Wang, Li-Yan; Li, Dong; Meng, Qing-Wei

    2012-06-15

    Photosynthesis provides a strong reducing power and a high risk for generation of reactive oxygen species (ROS) particularly under chilling stress. Ascorbate peroxidases (APXs) reduce H(2)O(2) to water and play an important role in the antioxidant system of plants. Though thylakoid ascorbate peroxidase (tAPX) has been thought to be key regulator of intracellular levels of H(2)O(2), its physiological significance in the response to chilling stress is still under discussion. To study the contribution of tAPX to the ROS scavenging, a tomato thylakoidal ascorbate peroxidase gene (LetAPX) was isolated and transgenic tomatoes were obtained. The LetAPX-GFP fusion protein was targeted to chloroplast in Arabidopsis mesophyll protoplast. RNA blotting analysis revealed that the LetAPX transcript expression was up-regulated by chilling, high light, exogenous salicylic acid (SA) and methyl viologen (MV). Over expression of LetAPX in tomatoes conferred tolerance to chilling stress by maintaining higher reduced glutathione (GSH) content, chlorophyll and APX activities compared with wild type (WT) plants. Furthermore, transgenic plants showed lower levels of hydrogen peroxide (H(2)O(2)) and ion leakage, lower malendialdehyde (MDA) content, higher net photosynthetic rate (Pn) and higher maximal photochemical efficiency of PSII (Fv/Fm). The oxidizable P700 decreased more obviously in WT than that in transgenic plants under chilling stress in low irradiance. The results suggested that over expression of tAPX played a key role both in alleviating photo inhibition of PSI and PSII and enhancing their tolerance to chilling stress.

  6. A Phylogeny of the Monocots, as Inferred from rbcL and atpA Sequence Variation, and a Comparison of Methods for Calculating Jackknife and Bootstrap Values

    DEFF Research Database (Denmark)

    Davis, Jerrold I.; Stevenson, Dennis W.; Petersen, Gitte;

    2004-01-01

    A phylogenetic analysis of the monocots was conducted on the basis of nucleotide sequence variation in two genes (atpA, encoded in the mitochondrial genome, and rbcL, encoded in the plastid genome). The taxon sample of 218 angiosperm terminals included 177 monocots and 41 dicots. Among the major ...

  7. Anchoring a plant cytochrome P450 via PsaM to the thylakoids in Synechococcus sp. PCC 7002: evidence for light-driven biosynthesis.

    Directory of Open Access Journals (Sweden)

    Lærke Münter Lassen

    Full Text Available Plants produce an immense variety of specialized metabolites, many of which are of high value as their bioactive properties make them useful as for instance pharmaceuticals. The compounds are often produced at low levels in the plant, and due to their complex structures, chemical synthesis may not be feasible. Here, we take advantage of the reducing equivalents generated in photosynthesis in developing an approach for producing plant bioactive natural compounds in a photosynthetic microorganism by functionally coupling a biosynthetic enzyme to photosystem I. This enables driving of the enzymatic reactions with electrons extracted from the photosynthetic electron transport chain. As a proof of concept, we have genetically fused the soluble catalytic domain of the cytochrome P450 CYP79A1, originating from the endoplasmic reticulum membranes of Sorghum bicolor, to a photosystem I subunit in the cyanobacterium Synechococcus sp. PCC 7002, thereby targeting it to the thylakoids. The engineered enzyme showed light-driven activity both in vivo and in vitro, demonstrating the possibility to achieve light-driven biosynthesis of high-value plant specialized metabolites in cyanobacteria.

  8. Nuevas citas de monocotiledóneas adventicias para la Argentina New records of adventitious monocots for Argentina

    Directory of Open Access Journals (Sweden)

    Julio A. Hurrell

    2009-12-01

    Full Text Available Este trabajo incluye cinco nuevos registros de monocotiledóneas adventicias para la Argentina: Aloe ciliaris Haw. (Asphodelaceae, Aspidistra elatior Blume (Convallariaceae, Sansevieria trifasciata Prain (Dracaenaceae, Phormium tenax J. R. Forst. & G. Forst. (Hemerocallidaceae y Ornithogalum arabicum L. (Hyacinthaceae, pertenecientes al orden Asparagales. También incluye una evaluación del estado actual de estas especies, en relación al proceso de naturalización: escapadas de cultivo ocasionales, naturalizadas.This paper includes five new records of adventitious monocots for Argentina: Aloe ciliaris Haw. (Asphodelaceae, Aspidistra elatior Blume (Convallariaceae, Sansevieria trifasciata Prain (Dracaenaceae, Phormium tenax J. R. Forst. & G. Forst. (Hemerocallidaceae and Ornithogalum arabicum L. (Hyacinthaceae, belonging to order Asparagales. Also includes an evaluation of its status in the naturalization process: casual alien, naturalized.

  9. Gene duplication and an accelerated evolutionary rate in 11S globulin genes are associated with higher protein synthesis in dicots as compared to monocots

    Directory of Open Access Journals (Sweden)

    Li Chun

    2012-01-01

    Full Text Available Abstract Background Seed storage proteins are a major source of dietary protein, and the content of such proteins determines both the quantity and quality of crop yield. Significantly, examination of the protein content in the seeds of crop plants shows a distinct difference between monocots and dicots. Thus, it is expected that there are different evolutionary patterns in the genes underlying protein synthesis in the seeds of these two groups of plants. Results Gene duplication, evolutionary rate and positive selection of a major gene family of seed storage proteins (the 11S globulin genes, were compared in dicots and monocots. The results, obtained from five species in each group, show more gene duplications, a higher evolutionary rate and positive selections of this gene family in dicots, which are rich in 11S globulins, but not in the monocots. Conclusion Our findings provide evidence to support the suggestion that gene duplication and an accelerated evolutionary rate may be associated with higher protein synthesis in dicots as compared to monocots.

  10. Lumichrome and riboflavin are two novel symbiotic signals eliciting developmental changes in both monocot and dicot plant species

    Directory of Open Access Journals (Sweden)

    Felix Dapare Dakora

    2015-09-01

    Full Text Available Lumichrome and riboflavin are novel molecules from rhizobial exudates that stimulate plant growth. Developmental changes elicited by lumichrome at very low nanomolar concentrations (5 nM include early initiation of trifoliate leaves, expansion of unifoliate and trifoliate leaves, increased stem elongation and leaf area, and consequently greater biomass accumulation in monocots and dicots. However, higher lumichrome concentration (50 nM depressed root development and reduced growth of unifoliate and second trifoliate leaves. Applying either 10 nM lumichrome, 10 nM ABA, or 10 ml of infective rhizobial cells (0.2 OD600 to roots of monocots and dicots for 44 h produced identical effects, which included decreased stomatal conductance and leaf transpiration in Bambara groundnut, soybean and maize, increased stomatal conductance and transpiration in cowpea and lupin, and elevated root respiration in maize (19% by rhizobia and 20% by lumichrome. Extracellular exudation of lumichrome, riboflavin and IAA was greater in N2-fixing rhizobia than non-fixing bacteria, indicating their role as symbiotic signals. Xylem concentration of lumichrome in cowpea and soybean was greater in plants inoculated with infective rhizobia and treated with lumichrome (61.2 µmol lumichrome.ml-1 sap, followed by uninoculated plants receiving lumichrome (41.12 µmol lumichrome.ml-1 sap, and lowest in uninoculated, lumichrome-free plants (26.8 µmol lumichrome.ml-1 sap. Overall, soybean showed greater xylem concentration of lumichrome and a correspondingly increased accumulation in leaves relative to cowpea. As a result, soybean exhibited dramatic developmental changes than cowpea. Taken together, lumichrome and riboflavin secreted by soil rhizobia function as environmental cues for sensing stress. The fact that exogenous application of ABA to plant roots caused the same effect as lumichrome on stomatal functioning suggests molecular cross-talk in plant response to environmental

  11. Nuclear, Virescent Mutants of Zea mays L. with High Levels of Chlorophyll (a/b) Light-Harvesting Complex during Thylakoid Assembly.

    Science.gov (United States)

    Polacco, M L; Chang, M T; Neuffer, M G

    1985-04-01

    We have found nuclear, recessive mutants in Zea mays L. where assembly of the major chlorophyll (a/b) light-harvesting complex (LHC) was not delayed relative to most other thylakoid protein complexes during thylakoid biogenesis. This contrasts with the normal development of maize chloroplasts (NR Baker, R Leech 1977 Plant Physiol 60: 640-644). All four mutants examined were allelic and virescent, and displayed visibly higher yields of leaf Chl fluorescence during greening. Fully greened mutants had normal leaf Chl fluorescence yield and normal levels of LHC, and grew to maturity under field conditions. Therefore, delayed LHC assembly is not an obligate feature of thylakoid differentiation.Assigning the molecular basis for the mutation should provide information concerning reguation of LHC assembly. Several possibilities are discussed. The pleiotropic mutant phenotype is not attributable to defects in thylakoid glycerolipid synthesis. Thylakoids isolated from greening mutant leaf sections had elevated glycerolipid/Chl ratios. In addition, both the molar distribution and acyl composition of four major glycerolipids were normal for developing mutant thylakoids.

  12. Nuclear, Virescent Mutants of Zea mays L. with High Levels of Chlorophyll (a/b) Light-Harvesting Complex during Thylakoid Assembly 1

    Science.gov (United States)

    Polacco, Mary L.; Chang, M. T.; Neuffer, M. Gerald

    1985-01-01

    We have found nuclear, recessive mutants in Zea mays L. where assembly of the major chlorophyll (a/b) light-harvesting complex (LHC) was not delayed relative to most other thylakoid protein complexes during thylakoid biogenesis. This contrasts with the normal development of maize chloroplasts (NR Baker, R Leech 1977 Plant Physiol 60: 640-644). All four mutants examined were allelic and virescent, and displayed visibly higher yields of leaf Chl fluorescence during greening. Fully greened mutants had normal leaf Chl fluorescence yield and normal levels of LHC, and grew to maturity under field conditions. Therefore, delayed LHC assembly is not an obligate feature of thylakoid differentiation. Assigning the molecular basis for the mutation should provide information concerning reguation of LHC assembly. Several possibilities are discussed. The pleiotropic mutant phenotype is not attributable to defects in thylakoid glycerolipid synthesis. Thylakoids isolated from greening mutant leaf sections had elevated glycerolipid/Chl ratios. In addition, both the molar distribution and acyl composition of four major glycerolipids were normal for developing mutant thylakoids. Images Fig. 2 PMID:16664140

  13. Thylakoid redox signals are integrated into organellar-gene-expression-dependent retrograde signalling in the prors1-1 mutant

    Directory of Open Access Journals (Sweden)

    Luca eTadini

    2012-12-01

    Full Text Available Perturbations in organellar gene expression (OGE and the thylakoid redox state (TRS activate retrograde signalling pathways that adaptively modify nuclear gene expression (NGE, according to developmental and metabolic needs. The prors1-1 mutation in Arabidopsis down-regulates the expression of the nuclear gene Prolyl-tRNA Synthetase1 (PRORS1 which acts in both plastids and mitochondria, thereby impairing protein synthesis in both organelles and triggering OGE-dependent retrograde signalling. Because the mutation also affects thylakoid electron transport, TRS-dependent signals may likewise have an impact on the changes in NGE observed in this genotype. In this study, we have investigated whether signals related to TRS are actually integrated into the OGE-dependent retrograde signalling pathway. To this end, the chaos mutation (for chlorophyll a/b binding protein harvesting-organelle specific, which shows a partial loss of PSII antennae proteins and thus a reduction in PSII light absorption capability, was introduced into the prors1-1 mutant background. The resulting double mutant displayed a prors1-1-like reduction in plastid translation rate and a chaos-like decrease in PSII antenna size, whereas the hyper-reduction of the thylakoid electron transport chain, caused by the prors1-1 mutation, was alleviated, as determined by monitoring chlorophyll (Chl fluorescence and thylakoid phosphorylation. Interestingly, a substantial fraction of the nucleus-encoded photosynthesis genes down-regulated in the prors1-1 mutant are expressed at nearly wild-type rates in prors1-1 chaos leaves, and this recovery is reflected in the steady-state levels of their protein products in the chloroplast. We therefore conclude that signals related to photosynthetic electron transport and TRS, and indirectly to carbohydrate metabolism and energy balance, are indeed fed into the OGE-dependent retrograde pathway to modulate NGE and adjust the abundance of chloroplast proteins.

  14. Chloroplast ATP Synthase Modulation of the Thylakoid Proton Motive Force: Implications for Photosystem I and Photosystem II Photoprotection

    Directory of Open Access Journals (Sweden)

    Atsuko Kanazawa

    2017-05-01

    Full Text Available In wild type plants, decreasing CO2 lowers the activity of the chloroplast ATP synthase, slowing proton efflux from the thylakoid lumen resulting in buildup of thylakoid proton motive force (pmf. The resulting acidification of the lumen regulates both light harvesting, via the qE mechanism, and photosynthetic electron transfer through the cytochrome b6f complex. Here, we show that the cfq mutant of Arabidopsis, harboring single point mutation in its γ-subunit of the chloroplast ATP synthase, increases the specific activity of the ATP synthase and disables its down-regulation under low CO2. The increased thylakoid proton conductivity (gH+ in cfq results in decreased pmf and lumen acidification, preventing full activation of qE and more rapid electron transfer through the b6f complex, particularly under low CO2 and fluctuating light. These conditions favor the accumulation of electrons on the acceptor side of PSI, and result in severe loss of PSI activity. Comparing the current results with previous work on the pgr5 mutant suggests a general mechanism where increased PSI photodamage in both mutants is caused by loss of pmf, rather than inhibition of CEF per se. Overall, our results support a critical role for ATP synthase regulation in maintaining photosynthetic control of electron transfer to prevent photodamage.

  15. Identification of an Atypical Membrane Protein Involved in the Formation of Protein Disulfide Bonds in Oxygenic Photosynthetic Organisms*S⃞

    OpenAIRE

    Singh, Abhay K.; Bhattacharyya-Pakrasi, Maitrayee; Pakrasi, Himadri B.

    2008-01-01

    The evolution of oxygenic photosynthesis in cyanobacteria nearly three billion years ago provided abundant reducing power and facilitated the elaboration of numerous oxygen-dependent reactions in our biosphere. Cyanobacteria contain an internal thylakoid membrane system, the site of photosynthesis, and a typical Gram-negative envelope membrane system. Like other organisms, the extracytoplasmic space in cyanobacteria houses numerous cysteine-containing proteins. However, the ...

  16. Chloroplast membrane transport: interplay of prokaryotic and eukaryotic traits.

    Science.gov (United States)

    Vothknecht, Ute C; Soll, Jürgen

    2005-07-18

    Chloroplasts are specific plant organelles of prokaryotic origin. They are separated from the surrounding cell by a double membrane, which represents an effective barrier for the transport of metabolites and proteins. Specific transporters in the inner envelope membrane have been described, which facilitate the exchange of metabolites. In contrast, the outer envelope has been viewed for a long time as a molecular sieve that offers a mere size constriction to the passage of molecules. This view has been challenged lately, and a number of specific and regulated pore proteins of the outer envelope (OEPs) have been identified. These pores seem to have originated by adaptation of outer membrane proteins of the cyanobacterial ancestor of the chloroplast. In a similar fashion, the transport of proteins across the two envelope membranes is achieved by two hetero-oligomeric protein complexes called Toc (translocon in the outer envelope of chloroplasts) and Tic (translocon in the inner envelope of chloroplasts). The phylogenetic provenance of the translocon components is less clear, but at least the channel protein of the Toc translocon is of cyanobacterial origin. Characteristic of cyanobacteria and chloroplasts is furthermore a specialized internal membrane system, the thylakoids, on which the components of the photosynthetic machinery are located. Despite the importance of this membrane, very little is known about its phylogenetic origin or the manner of its synthesis. Vipp1 appears to be a ubiquitous component of thylakoid formation, while in chloroplasts of land plants, additionally a vesicle transport system of eukaryotic origin might be involved in this process.

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

    Science.gov (United States)

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

    2015-03-12

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

  18. Development of a Transient Absorption Spectrometer for the Study of the Proton-motive Force (PMF) in Plant Thylakoid Membranes

    Science.gov (United States)

    Gardner, Jens Christopher

    A transient-absorption spectrometer to study the electric field component of the proton-motive force (PMF) has been developed. Excitation by an actinic light source (655nm) causes absorption changes of pigments in the sample at 520nm on the order of 0.1%. Using a probe light source at 520nm, the change in transmission before and after actinic excitation can be detected and quantified. Because the change in transmission is small, a high signal to noise ratio (SNR) is required. To reduce the effect of optical shot noise and front end electrical noise a high intensity source at 520nm is utilized. However, continuous high intensity light at 520nm over time can cause actinic excitation in the sample, so the 520nm probe is pulsed at high optical intensity and low duty cycle to reduce the net incident flux. The developed system includes 1) a LED driver to drive 1A current pulses through three high power probe LEDs and four high power actinic LEDs, 2) an analog front end which uses a 10mm by 10mm photodiode and a trans-impedance amplifier to detect the pulses, as well as several signal processing stages, 3) a microcontroller to generate the probe timing waveforms, digitize the detected signal, and send the data to a PC, and 4) a LabView computer interface to set input parameters, display the collected data, and save the data to a text file. Experimental verification of system peformance was performed by testing the system with and without a plant sample. The results show that the system works as expected and is capable of measuring the data required to determine the electric field component of the PMF.

  19. Structural variations among monocot emergent and amphibious species from lakes of the semi-arid region of Bahia, Brazil

    Directory of Open Access Journals (Sweden)

    KRB Leite

    Full Text Available Temporary lakes are common in the semi-arid region of the State of Bahia and form water mirrors in the rainy season. In this period, various vegetal species appear having different life forms adapted to the seasonality conditions of the rainfall regime. This work surveyed the adaptive anatomical structures of some emergent and amphibious monocot species occurring in these lakes. We studied the anatomy of roots, rhizomes, leaves and scapes of Cyperus odoratus, Oxycaryum cubense, Pycreus macrostachyos (Cyperaceae - amphibious species; and of Echinodorus grandiflorus (Alismataceae, Eichhornia paniculata (Pontederiaceae and Habenaria repens (Orchidaceae - emergent species. The anatomical features of the dermal, fundamental and vascular systems confirming the tendency of the adaptive convergence of these plants to temporary lacustrine the environment include: single layered epidermal cells with a thin cuticle layer in the aerial organs; the presence of air canals in all the organs; few or no supporting tissues; and less numerous conducting elements and thinner cell walls in the xylem. The reduction of the supporting tissues, the number of stomata, which can even be absent, and the number of conducting elements and the degree of cell wall lignification in the xylem of the emergent species is more accentuated than that of the amphibious species. The pattern of distribution of aerenchyma in the roots of the studied species was considered important to distinguish between amphibious and emergent life forms.

  20. Transcriptome analysis during somatic embryogenesis of the tropical monocot Elaeis guineensis: evidence for conserved gene functions in early development.

    Science.gov (United States)

    Lin, Hsiang-Chun; Morcillo, Fabienne; Dussert, Stéphane; Tranchant-Dubreuil, Christine; Tregear, James W; Tranbarger, Timothy John

    2009-05-01

    With the aim of understanding the molecular mechanisms underlying somatic embryogenesis (SE) in oil palm, we examined transcriptome changes that occur when embryogenic suspension cells are initiated to develop somatic embryos. Two reciprocal suppression subtractive hybridization (SSH) libraries were constructed from oil palm embryogenic cell suspensions: one in which embryo development was blocked by the presence of the synthetic auxin analogue 2,4-dichlorophenoxyacetic acid (2,4-D: ) in the medium (proliferation library); and another in which cells were stimulated to form embryos by the removal of 2,4-D: from the medium (initiation library). A total of 1867 Expressed Sequence Tags (ESTs) consisting of 1567 potential unigenes were assembled from the two libraries. Functional annotation indicated that 928 of the ESTs correspond to proteins that have either no similarity to sequences in public databases or are of unknown function. Gene Ontology (GO) terms assigned to the two EST populations give clues to the underlying molecular functions, biological processes and cellular components involved in the initiation of embryo development. Macroarrays were used for transcript profiling the ESTs during SE. Hierarchical cluster analysis of differential transcript accumulation revealed 4 distinct profiles containing a total of 192 statistically significant developmentally regulated transcripts. Similarities and differences between the global results obtained with in vitro systems from dicots, monocots and gymnosperms will be discussed.

  1. Efficient, Antibiotic Marker-Free Transformation of a Dicot and a Monocot Crop with Glutamate 1-Semialdehyde Aminotransferase Selectable Marker Genes.

    Science.gov (United States)

    Ferradini, Nicoletta; Giancaspro, Angelica; Nicolia, Alessandro; Gadaleta, Agata; Veronesi, Fabio; Rosellini, Daniele

    2016-01-01

    Antibiotic-free, efficient in vitro selection in plant genetic engineering can improve risk perception and speed up pre-market scrutiny of genetically modified crops. We provide a protocol for genetic transformation of two important crops, durum wheat and alfalfa, using a bacterial and a plant-derived selectable marker gene encoding mutated, gabaculine-insensitive glutamate 1-semialdehyde aminotransferase (GSA) enzymes. These methods can potentially be applied, with minor adaptations, to many other monocot and dicot crop plants.

  2. Analysis of ABCB phosphoglycoproteins (PGPs) and their contribution to monocot biomass, structural stability, and productivity

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Angus Stuart [Purdue University

    2014-09-23

    Efforts to manipulate production of plant secondary cell walls to improve the quality of biofuel feedstocks are currently limited by an inability to regulate the transport of small molecule components out of the cell. Plant ABCB p-glycoproteins are a small family of plasma membrane organic molecule transporters that have become primary targets for this effort, as they can potentially be harnessed to control the export of aromatic compounds and organic acids. However, unlike promiscuous mammalian ABCBs that function in multidrug resistance, all plant ABCB proteins characterized to date exhibit relatively narrow substrate specificity. Although ABCBs exhibit a highly conserved architecture, efforts to modify ABCB activity have been hampered by a lack of structural information largely because an eukaryotic ABCB protein crystal structure has yet to be obtained. Structure/ function analyses have been further impeded by the lack of a common heterologous expression system that can be used to characterize recombinant ABCB proteins, as many cannot be functionally expressed in S. cereviseae or other systems where proteins with analogous function can be readily knocked out. Using experimentally-determined plant ABCB substrate affinities and the crystal structure of the bacterial Sav1866 “half” ABC transporter, we have developed sequence/structure models for ABCBs that provide a testable context for mutational analysis of plant ABCB transporters. We have also developed a flexible heterologous expression system in Schizosaccharomyces pombe in which all endogenous ABC transporters have been knocked out. The effectiveness of this system for transport studies has been demonstrated by the successful functional expression all of the known PIN, AUX/LAX and ABCB auxin transporters. Our central hypothesis is that the domains of the ABCB proteins that we have identified as substrate docking sites and regulators of transport directionality can be altered or swapped to alter the

  3. Lipid composition determines the effects of arbutin on the stability of membranes.

    OpenAIRE

    Hincha, D K; Oliver, A E; Crowe, J H

    1999-01-01

    Arbutin (hydroquinone-beta-D-glucopyranoside) is an abundant solute in the leaves of many freezing- or desiccation-tolerant plants. Its physiological role in plants, however, is not known. Here we show that arbutin protects isolated spinach (Spinacia oleracea L.) thylakoid membranes from freeze-thaw damage. During freezing of liposomes, the presence of only 20 mM arbutin led to complete leakage of a soluble marker from egg PC (EPC) liposomes. When the nonbilayer-forming chloroplast lipid mono...

  4. Unassisted membrane insertion as the initial step in DeltapH/Tat-dependent protein transport.

    Science.gov (United States)

    Hou, Bo; Frielingsdorf, Stefan; Klösgen, Ralf Bernd

    2006-02-01

    In the thylakoid membrane of chloroplasts as well as in the cytoplasmic membrane of bacteria, the DeltapH/Tat-dependent protein transport pathway is responsible for the translocation of folded proteins. Using the chimeric 16/23 protein as model substrate in thylakoid transport experiments, we dissected the transport process into several distinct steps that are characterized by specific integral translocation intermediates. Formation of the early translocation intermediate Ti-1, which still exposes the N and the C terminus to the stroma, is observed with thylakoids pretreated with (i) solutions of chaotropic salts or alkaline pH, (ii) protease, or (iii) antibodies raised against TatA, TatB, or TatC. Membrane insertion takes place even into liposomes, demonstrating that proteinaceous components are not required. This suggests that Tat-dependent transport may be initiated by the unassisted insertion of the substrate into the lipid bilayer, and that interaction with the Tat translocase takes place only in later stages of the process.

  5. Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes*

    Science.gov (United States)

    Tietz, Stefanie; Puthiyaveetil, Sujith; Enlow, Heather M.; Yarbrough, Robert; Wood, Magnus; Semchonok, Dmitry A.; Lowry, Troy; Li, Zhirong; Jahns, Peter; Boekema, Egbert J.; Lenhert, Steven; Niyogi, Krishna K.; Kirchhoff, Helmut

    2015-01-01

    The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion. PMID:25897076

  6. Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes.

    Science.gov (United States)

    Tietz, Stefanie; Puthiyaveetil, Sujith; Enlow, Heather M; Yarbrough, Robert; Wood, Magnus; Semchonok, Dmitry A; Lowry, Troy; Li, Zhirong; Jahns, Peter; Boekema, Egbert J; Lenhert, Steven; Niyogi, Krishna K; Kirchhoff, Helmut

    2015-05-29

    The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion.

  7. A Robust CRISPR/Cas9 System for Convenient, High-Efficiency Multiplex Genome Editing in Monocot and Dicot Plants.

    Science.gov (United States)

    Ma, Xingliang; Zhang, Qunyu; Zhu, Qinlong; Liu, Wei; Chen, Yan; Qiu, Rong; Wang, Bin; Yang, Zhongfang; Li, Heying; Lin, Yuru; Xie, Yongyao; Shen, Rongxin; Chen, Shuifu; Wang, Zhi; Chen, Yuanling; Guo, Jingxin; Chen, Letian; Zhao, Xiucai; Dong, Zhicheng; Liu, Yao-Guang

    2015-08-01

    CRISPR/Cas9 genome targeting systems have been applied to a variety of species. However, most CRISPR/Cas9 systems reported for plants can only modify one or a few target sites. Here, we report a robust CRISPR/Cas9 vector system, utilizing a plant codon optimized Cas9 gene, for convenient and high-efficiency multiplex genome editing in monocot and dicot plants. We designed PCR-based procedures to rapidly generate multiple sgRNA expression cassettes, which can be assembled into the binary CRISPR/Cas9 vectors in one round of cloning by Golden Gate ligation or Gibson Assembly. With this system, we edited 46 target sites in rice with an average 85.4% rate of mutation, mostly in biallelic and homozygous status. We reasoned that about 16% of the homozygous mutations in rice were generated through the non-homologous end-joining mechanism followed by homologous recombination-based repair. We also obtained uniform biallelic, heterozygous, homozygous, and chimeric mutations in Arabidopsis T1 plants. The targeted mutations in both rice and Arabidopsis were heritable. We provide examples of loss-of-function gene mutations in T0 rice and T1 Arabidopsis plants by simultaneous targeting of multiple (up to eight) members of a gene family, multiple genes in a biosynthetic pathway, or multiple sites in a single gene. This system has provided a versatile toolbox for studying functions of multiple genes and gene families in plants for basic research and genetic improvement. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

  8. Photosynthetic pigment concentrations, gas exchange and vegetative growth for selected monocots and dicots treated with two contrasting coal fly ashes

    Energy Technology Data Exchange (ETDEWEB)

    Yunusa, I.A.M.; Burchett, M.D.; Manoharan, V.; DeSilva, D.L.; Eamus, D.; Skilbeck, C.G. [University of Technology Sydney, Sydney, NSW (Australia). Dept. of Environmental Science

    2009-07-15

    There is uncertainty as to the rates of coal fly ash needed for optimum physiological processes and growth. In the current study we tested the hyothesis that photosynthetic pigments concentrations and CO{sub 2} assimilation (A) are more sensitive than dry weights in plants grown on media amended with coal fly ash. We applied the Terrestrial Plant Growth Test (Guideline 208) protocols of the Organization for Economic Cooperation and Development (OECD) to monocots (barley (Hordeum vulgare) and ryegrass (Secale cereale)) and dicots (canola (Brasica napus), radish (Raphanus sativus), field peas (Pisum sativum), and lucerne (Medicago sativa)) on media amended with fly ashes derived from semi-bituminous (gray ash) or lignite (red ash) coals at rates of 0, 2.5, 5.0, 10, or 20 Mg ha(-1). The red ash had higher elemental concentrations and salinity than the gray ash. Fly ash addition had no significant effect on germination by any of the six species. At moderate rates ({<=}10 Mg ha{sup -1}) both ashes increased (P < 0.05) growth rates and concentrations of chlorophylls a and b, but reduced carotenoid concentrations. Addition of either ash increased A in radish and transpiration in barley. Growth rates and final dry weights were reduced for all of the six test species when addition rates exceeded 10 Mg ha{sup -1} for gray ash and 5 Mg ha{sup -1} for red ash. We concluded that plant dry weights, rather than pigment concentrations and/or instantaneous rates of photosynthesis, are more consistent for assessing subsequent growth in plants supplied with fly ash.

  9. Transcriptome Analysis of Cell Wall and NAC Domain Transcription Factor Genes during Elaeis guineensis Fruit Ripening: Evidence for Widespread Conservation within Monocot and Eudicot Lineages.

    Science.gov (United States)

    Tranbarger, Timothy J; Fooyontphanich, Kim; Roongsattham, Peerapat; Pizot, Maxime; Collin, Myriam; Jantasuriyarat, Chatchawan; Suraninpong, Potjamarn; Tragoonrung, Somvong; Dussert, Stéphane; Verdeil, Jean-Luc; Morcillo, Fabienne

    2017-01-01

    The oil palm (Elaeis guineensis), a monocotyledonous species in the family Arecaceae, has an extraordinarily oil rich fleshy mesocarp, and presents an original model to examine the ripening processes and regulation in this particular monocot fruit. Histochemical analysis and cell parameter measurements revealed cell wall and middle lamella expansion and degradation during ripening and in response to ethylene. Cell wall related transcript profiles suggest a transition from synthesis to degradation is under transcriptional control during ripening, in particular a switch from cellulose, hemicellulose, and pectin synthesis to hydrolysis and degradation. The data provide evidence for the transcriptional activation of expansin, polygalacturonase, mannosidase, beta-galactosidase, and xyloglucan endotransglucosylase/hydrolase proteins in the ripening oil palm mesocarp, suggesting widespread conservation of these activities during ripening for monocotyledonous and eudicotyledonous fruit types. Profiling of the most abundant oil palm polygalacturonase (EgPG4) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) transcripts during development and in response to ethylene demonstrated both are sensitive markers of ethylene production and inducible gene expression during mesocarp ripening, and provide evidence for a conserved regulatory module between ethylene and cell wall pectin degradation. A comprehensive analysis of NAC transcription factors confirmed at least 10 transcripts from diverse NAC domain clades are expressed in the mesocarp during ripening, four of which are induced by ethylene treatment, with the two most inducible (EgNAC6 and EgNAC7) phylogenetically similar to the tomato NAC-NOR master-ripening regulator. Overall, the results provide evidence that despite the phylogenetic distance of the oil palm within the family Arecaceae from the most extensively studied monocot banana fruit, it appears ripening of divergent monocot and eudicot fruit lineages are

  10. Photosynthetic electron transport inhibition by 2-substituted 4-alkyl-6-benzylamino-1,3,5-triazines with thylakoids from wild- type and atrazine-resistant Chenopodium album

    NARCIS (Netherlands)

    Okano, R.; Ohki, A.; Ohki, S.; Kohno, H.; Rensen, van J.J.S.; Böger, P.; Wakabayashi, K.

    2002-01-01

    The effect of 2-benzylamino-1,3,5-triazines on photosynthetic electron transport (PET) was measured with thylakoids isolated from atrazine-resistant, wild-type Chenopodium album, and spinach to find novel 1,3,5-triazine herbicides bearing a strong PET inhibition. The PET inhibition assay with Chenop

  11. Age dependent alterations in photosystem II acceptor side in Cucumis sativus cotyledonary leaf thylakoids: analysis of binding characteristics of herbicide [14C]-atrazine.

    Science.gov (United States)

    Prakash, J S; Baig, M A; Mohanty, P

    1999-02-01

    Senescence induced temporal changes in photosystems can be conveniently studied in cotyledonary leaves. We monitored the protein, chlorophyll and electron transport activities in Cucumis sativus cv Poinsette cotyledonary leaves and observed that by 20th day, there was a 50%, 41% and 30-33% decline in the chlorophyll, protein and photosystem II activity respectively when compared to 6th day cotyledonary leaves taken as control. We investigated the changes in photosystem II activity (O2 evolution) as a function of light intensity. The photosystem II functional antenna decreased by 27% and the functional photosystem II units decreased by 30% in 20-day old cotyledonary leaf thylakoids. The herbicide [14C]-atrazine binding assay to monitor specific binding of the herbicide to the acceptor side of photosystem II reaction centre protein, D1, showed an increase in the affinity for atrazine towards D1 protein and decrease in the QB binding sites in 20th day leaf thylakoids when compared to 6th day leaf thylakoids. The western blot analysis also suggested a decrease in steady state levels of D1 protein in 20th day cotyledonary leaf thylakoids as compared to 6th day sample which is in agreement with [14C]-atrazine binding assay and light saturation kinetics.

  12. A novel chloroplast localized Rab GTPase protein CPRabA5e is involved in stress, development, thylakoid biogenesis and vesicle transport in Arabidopsis.

    Science.gov (United States)

    Karim, Sazzad; Alezzawi, Mohamed; Garcia-Petit, Christel; Solymosi, Katalin; Khan, Nadir Zaman; Lindquist, Emelie; Dahl, Peter; Hohmann, Stefan; Aronsson, Henrik

    2014-04-01

    A novel Rab GTPase protein in Arabidopsis thaliana, CPRabA5e (CP = chloroplast localized) is located in chloroplasts and has a role in transport. Transient expression of CPRabA5e:EGFP fusion protein in tobacco (Nicotiana tabacum) leaves, and immunoblotting using Arabidopsis showed localization of CPRabA5e in chloroplasts (stroma and thylakoids). Ypt31/32 in the yeast Saccharomyces cerevisiae are involved in regulating vesicle transport, and CPRabA5e a close homolog of Ypt31/32, restores the growth of the ypt31Δ ypt32(ts) mutant at 37 °C in yeast complementation. Knockout mutants of CPRabA5e displayed delayed seed germination and growth arrest during oxidative stress. Ultrastructural studies revealed that after preincubation at 4 °C mutant chloroplasts contained larger plastoglobules, lower grana, and more vesicles close to the envelopes compared to wild type, and vesicle formation being enhanced under oxidative stress. This indicated altered thylakoid development and organization of the mutants. A yeast-two-hybrid screen with CPRabA5e as bait revealed 13 interacting partner proteins, mainly located in thylakoids and plastoglobules. These proteins are known or predicted to be involved in development, stress responses, and photosynthesis related processes, consistent with the stress phenotypes observed. The results observed suggest a role of CPRabA5e in transport to and from thylakoids, similar to cytosolic Rab proteins involved in vesicle transport.

  13. Photosynthetic electron transport inhibition by 2-substituted 4-alkyl-6-benzylamino-1,3,5-triazines with thylakoids from wild- type and atrazine-resistant Chenopodium album

    NARCIS (Netherlands)

    Okano, R.; Ohki, A.; Ohki, S.; Kohno, H.; Rensen, van J.J.S.; Böger, P.; Wakabayashi, K.

    2002-01-01

    The effect of 2-benzylamino-1,3,5-triazines on photosynthetic electron transport (PET) was measured with thylakoids isolated from atrazine-resistant, wild-type Chenopodium album, and spinach to find novel 1,3,5-triazine herbicides bearing a strong PET inhibition. The PET inhibition assay with

  14. Temporal and spatial expression of polygalacturonase gene family members reveals divergent regulation during fleshy fruit ripening and abscission in the monocot species oil palm

    Directory of Open Access Journals (Sweden)

    Roongsattham Peerapat

    2012-08-01

    Full Text Available Abstract Background Cell separation that occurs during fleshy fruit abscission and dry fruit dehiscence facilitates seed dispersal, the final stage of plant reproductive development. While our understanding of the evolutionary context of cell separation is limited mainly to the eudicot model systems tomato and Arabidopsis, less is known about the mechanisms underlying fruit abscission in crop species, monocots in particular. The polygalacturonase (PG multigene family encodes enzymes involved in the depolymerisation of pectin homogalacturonan within the primary cell wall and middle lamella. PG activity is commonly found in the separation layers during organ abscission and dehiscence, however, little is known about how this gene family has diverged since the separation of monocot and eudicots and the consequence of this divergence on the abscission process. Results The objective of the current study was to identify PGs responsible for the high activity previously observed in the abscission zone (AZ during fruit shedding of the tropical monocot oil palm, and to analyze PG gene expression during oil palm fruit ripening and abscission. We identified 14 transcripts that encode PGs, all of which are expressed in the base of the oil palm fruit. The accumulation of five PG transcripts increase, four decrease and five do not change during ethylene treatments that induce cell separation. One PG transcript (EgPG4 is the most highly induced in the fruit base, with a 700–5000 fold increase during the ethylene treatment. In situ hybridization experiments indicate that the EgPG4 transcript increases preferentially in the AZ cell layers in the base of the fruit in response to ethylene prior to cell separation. Conclusions The expression pattern of EgPG4 is consistent with the temporal and spatial requirements for cell separation to occur during oil palm fruit shedding. The sequence diversity of PGs and the complexity of their expression in the oil palm fruit

  15. Broad host range plasmid-based gene transfer system in the cyanobacterium Gloeobacter violaceus which lacks thylakoids

    Institute of Scientific and Technical Information of China (English)

    GUO Haitao; XU Xudong

    2004-01-01

    Gloeobacter violaceus, a cyanobacterium lack of thylakoids, is refractory to genetic manipulations because its cells are enveloped by a thick gelatinous sheath and in colonial form.In this study, a large number of single cells were obtained by repeated pumping with a syringe with the gelatinous sheath removed.And an exogenous broad host range plasmid pKT210 was conjugatively transferred into G.violaceus.Analyses with dot-blot hybridization and restriction mapping showed that the exogenous plasmid pKT210 had been introduced into G.violaceus and stably maintained with no alteration in its structure.pKT210 extracted from G.violaceus exconjugants could be transformed into the mcr- mrr- E.coli strain DH10B but not the mcr+ mrr+ strain DH5α, which suggests that a methylase system may be present in G.violaceus.

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

    Science.gov (United States)

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

    2016-04-01

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

  17. Mutants, Overexpressors, and Interactors of Arabidopsis Plastocyanin Isoforms: Revised Roles of Plastocyanin in Photosynthetic Electron Flow and Thylakoid Redox State

    Institute of Scientific and Technical Information of China (English)

    Paolo Pesaresi; Michael Scharfenberg; Martin Weigel; Irene Granlund; Wolfgang P. Schr(o)der; Giovanni Finazzi; Fabrice Rappaport; Simona Masiero; Antonella Furini; Peter Jahns; Dario Leister

    2009-01-01

    Two homologous plastocyanin isoforms are encoded by the genes PETE1 and PETE2 in the nuclear genome of Arabidopsis thaliana. The PETE2 transcript is expressed at considerably higher levels and the PETE2 protein is the more abundant isoform. Null mutations in the PETE genes resulted in plants, designated pete1 and pete2, with decreased plas-tocyanin contents. However, despite reducing plastocyanin levels by over~90%, a pete2 null mutation on its own affects rates of photosynthesis and growth only slightly, whereas pete1 knockout plants, with about 60-80% of the wild-type plastocyanin level, did not show any alteration. Hence, plastocyanin concentration is not limiting for photosynthetic elec-tron flow under optimal growth conditions, perhaps implying other possible physiological roles for the protein. Indeed, plastocyanin has been proposed previously to cooperate with cytochrome C6A (Cyt C6A) in thylakoid redox reactions, but we find no evidence for a physical interaction between the two proteins, using interaction assays in yeast. We observed homodimerization of Cyt C6A in yeast interaction assays, but also Cyt C6A homodimers failed to interact with plastocyanin. Moreover, phenotypic analysis of atc6-1 pete1 and atc6-1 pete2 double mutants, each lacking Cyt C6A and one of the two plastocyanin-encoding genes, failed to reveal any genetic interaction. Overexpression of either PETE1 or PETE2 in the pete1 pete2 double knockout mutant background results in essentially wild-type photosynthetic performance, excluding the possibility that the two plastocyanin isoforms could have distinct functions in thylakoid electron flow.

  18. Characterization of a 65 kDa NIF in the nuclear matrix of the monocot Allium cepa that interacts with nuclear spectrin-like proteins.

    Science.gov (United States)

    Pérez-Munive, Clara; Blumenthal, Sonal S D; de la Espina, Susana Moreno Díaz

    2012-01-01

    Plant cells have a well organized nucleus and nuclear matrix, but lack orthologues of the main structural components of the metazoan nuclear matrix. Although data is limited, most plant nuclear structural proteins are coiled-coil proteins, such as the NIFs (nuclear intermediate filaments) in Pisum sativum that cross-react with anti-intermediate filament and anti-lamin antibodies, form filaments 6-12 nm in diameter in vitro, and may play the role of lamins. We have investigated the conservation and features of NIFs in a monocot species, Allium cepa, and compared them with onion lamin-like proteins. Polyclonal antisera against the pea 65 kDa NIF were used in 1D and 2D Western blots, ICM (imunofluorescence confocal microscopy) and IEM (immunoelectron microscopy). Their presence in the nuclear matrix was analysed by differential extraction of nuclei, and their association with structural spectrin-like proteins by co-immunoprecipitation and co-localization in ICM. NIF is a conserved structural component of the nucleus and its matrix in monocots with Mr and pI values similar to those of pea 65 kDa NIF, which localized to the nuclear envelope, perichromatin domains and foci, and to the nuclear matrix, interacting directly with structural nuclear spectrin-like proteins. Its similarities with some of the proteins described as onion lamin-like proteins suggest that they are highly related or perhaps the same proteins.

  19. Roothairless5, which functions in maize (Zea mays L.) root hair initiation and elongation encodes a monocot-specific NADPH oxidase.

    Science.gov (United States)

    Nestler, Josefine; Liu, Sanzhen; Wen, Tsui-Jung; Paschold, Anja; Marcon, Caroline; Tang, Ho Man; Li, Delin; Li, Li; Meeley, Robert B; Sakai, Hajime; Bruce, Wesley; Schnable, Patrick S; Hochholdinger, Frank

    2014-09-01

    Root hairs are instrumental for nutrient uptake in monocot cereals. The maize (Zea mays L.) roothairless5 (rth5) mutant displays defects in root hair initiation and elongation manifested by a reduced density and length of root hairs. Map-based cloning revealed that the rth5 gene encodes a monocot-specific NADPH oxidase. RNA-Seq, in situ hybridization and qRT-PCR experiments demonstrated that the rth5 gene displays preferential expression in root hairs but also accumulates to low levels in other tissues. Immunolocalization detected RTH5 proteins in the epidermis of the elongation and differentiation zone of primary roots. Because superoxide and hydrogen peroxide levels are reduced in the tips of growing rth5 mutant root hairs as compared with wild-type, and Reactive oxygen species (ROS) is known to be involved in tip growth, we hypothesize that the RTH5 protein is responsible for establishing the high levels of ROS in the tips of growing root hairs required for elongation. Consistent with this hypothesis, a comparative RNA-Seq analysis of 6-day-old rth5 versus wild-type primary roots revealed significant over-representation of only two gene ontology (GO) classes related to the biological functions (i.e. oxidation/reduction and carbohydrate metabolism) among 893 differentially expressed genes (FDR <5%). Within these two classes the subgroups 'response to oxidative stress' and 'cellulose biosynthesis' were most prominently represented.

  20. 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...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  1. A Zea mays 39-kDa thylakoid transglutaminase catalyses the modification by polyamines of light-harvesting complex II in a light-dependent way.

    Science.gov (United States)

    Della Mea, M; Di Sandro, A; Dondini, L; Del Duca, S; Vantini, F; Bergamini, C; Bassi, R; Serafini-Fracassini, D

    2004-09-01

    A transglutaminase (TGase; EC 2.3.2.13) activity, which shared many properties with the TGase activity of the Helianthus tuberosus chloroplast, was observed in the Zea mays L. chloroplast and in its fractions. This activity was found to be prevalent in thylakoids; bis-(glutamyl) spermidine and bis-(glutamyl) putrescine were the main polyamine conjugates formed. Light stimulated the endogenous thylakoid activity. Putrescine, spermidine and spermine were conjugated to the isolated light-harvesting complex of photosystem II (LHCII) with different degrees of efficiency, spermine being the polyamine most efficiently conjugated. A TGase with a light-sensitive activity was identified in the photosystem II-enriched fraction. Its partial purification on a sucrose gradient allowed the separation of a 39-kDa band, which was immunorecognised by two anti-TGase antibodies (Ab-3 and rat prostatic gland-TGase). Both a colorimetric and a radiometric assay for TGase activity, the former carried out in the presence of biotinylated cadaverine and the latter in the presence of polyamines labelled with radioactive isotopes and resulting in the isolation of glutamyl-polyamines, further confirmed that the thylakoid enzyme is indeed a calcium-dependent transglutaminase (Thyl-TGase). At variance with guinea pig liver and erythrocyte TGases, which are insensitive to light, the activity of the thylakoid transglutaminase is affected by light. Moreover, this enzyme, when tested with purified LHCII as substrate, catalysed the production of mono- and bis-glutamyl-polyamines in equal amounts, whereas the 'animal' enzymes produced mainly mono-derivatives. Herein, it is discussed whether this light sensitivity is due to the enzyme or the substrate.

  2. Virus-Induced Gene Silencing in the Culinary Ginger (Zingiber officinale): An Effective Mechanism for Down-Regulating Gene Expression in Tropical Monocots

    Institute of Scientific and Technical Information of China (English)

    Tanya Renner; Jennifer Bragga; Heather E. Driscoll; Juliana Cho; Andrew O. Jackson; Chelsea D. Specht

    2009-01-01

    Virus-induced gene silencing (VIGS) has been shown to be effective for transient knockdown of gene expres-sion in plants to analyze the effects of specific genes in development and stress-related responses. VlGS is well established for studies of model systems and crops within the Solanaceae, Brassicaceae, Leguminaceae, and Poaceae, but only recently has been applied to plants residing outside these families. Here, we have demonstrated that barley stripe mosaic virus (BSMV) can infect two species within the Zingiberaceae, and that BSMV-VlGS can be applied to specifically down-regulate phytoene desaturase in the culinary ginger Zingiber officinale. These results suggest that extension of BSMV-VIGS to monocots other than cereals has the potential for directed genetic analyses of many important temperate and tropical crop species.

  3. Discovery of Linear Cyclotides in Monocot Plant Panicum laxum of Poaceae Family Provides New Insights into Evolution and Distribution of Cyclotides in Plants*

    Science.gov (United States)

    Nguyen, Giang Kien Truc; Lian, Yilong; Pang, Edmund Weng Hou; Nguyen, Phuong Quoc Thuc; Tran, Tuan Dinh; Tam, James P.

    2013-01-01

    Cyclotides are disulfide-rich macrocyclic peptides that display a wide range of bioactivities and represent an important group of plant defense peptide biologics. A few linear variants of cyclotides have recently been identified. They share a high sequence homology with cyclotides but are biosynthetically unable to cyclize from their precursors. All hitherto reported cyclotides and their acyclic variants were isolated from dicot plants of the Rubiaceae, Violaceae, Cucurbitaceae, and recently the Fabaceae and Solanaceae families. Although several cyclotide-like genes in the Poaceae family were known from the data mining of the National Center for Biotechnology Information (NCBI) nucleotide database, their expression at the protein level has yet to be proven. Here, we report the discovery and characterization of nine novel linear cyclotides, designated as panitides L1–9, from the Panicum laxum of the Poaceae family and provide the first evidence of linear cyclotides at the protein level in a monocot plant. Disulfide mapping of panitide L3 showed that it possesses a cystine knot arrangement similar to cyclotides. Several panitides were shown to be active against Escherichia coli and cytotoxic to HeLa cells. They also displayed a high stability against heat and proteolytic degradation. Oxidative folding of the disulfide-reduced panitide L1 showed that it can fold efficiently into its native form. The presence of linear cyclotides in both dicots and monocots suggests their ancient origin and existence before the divergence of these two groups of flowering plants. Moreover, the Poaceae family contains many important food crops, and our discovery may open up new avenues of research using cyclotides and their acyclic variants in crop protection. PMID:23195955

  4. Lack of S-RNase-Based Gametophytic Self-Incompatibility in Orchids Suggests That This System Evolved after the Monocot-Eudicot Split

    Directory of Open Access Journals (Sweden)

    Shan-Ce Niu

    2017-06-01

    Full Text Available Self-incompatibility (SI is found in approximately 40% of flowering plant species and at least 100 families. Although orchids belong to the largest angiosperm family, only 10% of orchid species present SI and have gametophytic SI (GSI. Furthermore, a majority (72% of Dendrobium species, which constitute one of the largest Orchidaceae genera, show SI and have GSI. However, nothing is known about the molecular mechanism of GSI. The S-determinants of GSI have been well characterized at the molecular level in Solanaceae, Rosaceae, and Plantaginaceae, which use an S-ribonuclease (S-RNase-based system. Here, we investigate the hypothesis that Orchidaceae uses a similar S-RNase to those described in Rosaceae, Solanaceae, and Plantaginaceae SI species. In this study, two SI species (Dendrobium longicornu and D. chrysanthum were identified using fluorescence microscopy. Then, the S-RNase- and SLF-interacting SKP1-like1 (SSK1-like genes present in their transcriptomes and the genomes of Phalaenopsis equestris, D. catenatum, Vanilla shenzhenica, and Apostasia shenzhenica were investigated. Sequence, phylogenetic, and tissue-specific expression analyses revealed that none of the genes identified was an S-determinant, suggesting that Orchidaceae might have a novel SI mechanism. The results also suggested that RNase-based GSI might have evolved after the split of monocotyledons (monocots and dicotyledons (dicots but before the split of Asteridae and Rosidae. This is also the first study to investigate S-RNase-based GSI in monocots. However, studies on gene identification, differential expression, and segregation analyses in controlled crosses are needed to further evaluate the genes with high expression levels in GSI tissues.

  5. Phylogenetic and comparative gene expression analysis of barley (Hordeum vulgare WRKY transcription factor family reveals putatively retained functions between monocots and dicots

    Directory of Open Access Journals (Sweden)

    Jansson Christer

    2008-04-01

    Full Text Available Abstract Background WRKY proteins belong to the WRKY-GCM1 superfamily of zinc finger transcription factors that have been subject to a large plant-specific diversification. For the cereal crop barley (Hordeum vulgare, three different WRKY proteins have been characterized so far as regulators in sucrose signaling, pathogen defense, and in response to cold and drought. However, their phylogenetic relationship remained unresolved. Results In this study, we used available sequence information to identify a minimum number of 45 barley WRKY transcription factor (HvWRKY genes. According to their structural features, the HvWRKY factors were classified into the previously defined polyphyletic WRKY subgroups 1 to 3. Furthermore, we could assign putative orthologs of the HvWRKY proteins in Arabidopsis and rice. While in most cases clades of orthologous proteins were formed within each group or subgroup, other clades were composed of paralogous proteins for the grasses and Arabidopsis only, which is indicative of specific gene radiation events. To gain insight into their putative functions, we examined expression profiles of WRKY genes from publicly available microarray data resources and found group specific expression patterns. While putative orthologs of the HvWRKY transcription factors have been inferred from phylogenetic sequence analysis, we performed a comparative expression analysis of WRKY genes in Arabidopsis and barley. Indeed, highly correlative expression profiles were found between some of the putative orthologs. Conclusion HvWRKY genes have not only undergone radiation in monocot or dicot species, but exhibit evolutionary traits specific to grasses. HvWRKY proteins exhibited not only sequence similarities between orthologs with Arabidopsis, but also relatedness in their expression patterns. This correlative expression is indicative for a putative conserved function of related WRKY proteins in monocot and dicot species.

  6. Genetic Analysis of Arabidopsis Mutants Impaired in Plastid Lipid Import Reveals a Role of Membrane Lipids in Chloroplast Division

    Energy Technology Data Exchange (ETDEWEB)

    Fan, J.; Xu, C.

    2011-03-01

    The biogenesis of photosynthetic membranes in plants relies largely on lipid import from the endoplasmic reticulum (ER) and this lipid transport process is mediated by TGD proteins in Arabidopsis. Such a dependency of chloroplast biogenesis on ER-to-plastid lipid transport was recently exemplified by analyzing double mutants between tgd1-1 or tgd4-3 and fad6 mutants. The fad6 mutants are defective in the desaturation of membrane lipids in chloroplasts and therefore dependent on import of polyunsaturated lipid precursors from the ER for constructing a competent thylakoid membrane system. In support of a critical role of TGD proteins in ER-to-plastid lipid trafficking, we showed that the introduction of the tgd mutations into fad6 mutant backgrounds led to drastic reductions in relative amounts of thylakoid lipids. Moreover, the tgd1-1 fad6 and tgd4-3 fad6 double mutants were deficient in polyunsaturated fatty acids in chloroplast membrane lipids, and severely compromised in the biogenesis of photosynthetic membrane systems. Here we report that these double mutants are severely impaired in chloroplast division. The possible role of membrane lipids in chloroplast division is discussed.

  7. Antisense-mediated suppression of tomato thylakoidal ascorbate peroxidase influences anti-oxidant network during chilling stress.

    Science.gov (United States)

    Duan, Ming; Ma, Na-Na; Li, Dong; Deng, Yong-Sheng; Kong, Fan-Ying; Lv, Wei; Meng, Qing-Wei

    2012-09-01

    Photosynthesis is a well-established source of reactive oxygen species (ROS) in plants particularly under chilling stress. Ascorbate peroxidase (APXs) plays an important role in the anti-oxidant system by utilizing AsA as specific electron donor to reduce H(2)O(2) to water. In order to investigate the possible mechanisms of ascorbate peroxidsae (APX) in photoprotection under chilling stress, a tomato (Lycopersicon esculentum Mill.) thylakoidal ascorbate peroxidase gene (LetAPX) was isolated and antisense transgenic tomato plants were produced. Under chilling stress, transgenic plants accumulated more H(2)O(2), and showed higher levels of ion leakage and malondialdehyde (MDA), lower net photosynthetic rate (Pn), lower maximal photochemical efficiency of PSII (Fv/Fm) and less content of D1 protein compared with wild type (WT) plants. On the other hand, after chilling stress, transgenic plants showed higher reduced ascorbate (AsA) and activities of catalase (CAT) and superoxide dismutase (SOD) than those in WT plants, and the expression of several known stress-responsive and antioxidative genes was also higher at the end of chilling treatment. These results suggested that the suppression of LetAPX gene induced compensatory anti-oxidant mechanisms in tomato, and inactivation of tAPX may have a regulatory role in facilitating redox signaling pathways under chilling stress. Furthermore, transient increases in ROS levels also have a vital role in stress signaling and thereby in the survival of plants under chilling conditions.

  8. Membrane associated qualitative differences in cell ultrastructure of chemically and high pressure cryofixed plant cells.

    Science.gov (United States)

    Zechmann, Bernd; Müller, Maria; Zellnig, Günther

    2007-06-01

    Membrane contrast can sometimes be poor in biological samples after high pressure freezing (HPF) and freeze substitution (FS). The addition of water to the FS-medium has been shown to improve membrane contrast in animal tissue and yeast. In the present study we tested the effects of 1% and 5% water added to the FS-medium (2% osmium with 0.2% uranyl acetate in anhydrous acetone) on the quality and visibility of membranes in high pressure frozen leaf samples of Cucurbita pepo L. plants and compared them to chemically fixed cells (3% glutaraldehyde post-fixed with 1% osmium tetroxide). The addition of water to the FS-medium drastically decreased the amounts of well preserved cells and did not significantly improve the quality nor visibility of membranes. In samples that were freeze substituted in FS-media containing 1% and 5% water the width of thylakoid membranes was found to be significantly increased of about 20% and the perinuclear space was up to 76% wider in comparison to what was found in samples which were freeze substituted without water. No differences were found in the thickness of membranes between chemically and cryofixed cells that were freeze substituted in the FS-medium without water. Nevertheless, in chemically fixed cells the intrathylakoidal space was about 120% wider than in cryofixed cells that were freeze substituted with or without water. The present results demonstrate that the addition of water to the FS-medium does not improve membrane contrast but changes the width of thylakoid membranes and the perinuclear space in the present plant material. The addition of water to the FS-medium is therefore not as essential for improved membrane contrast in the investigated plant samples as it was observed in cells of animal tissues and yeast cells.

  9. Flip-flop of phospholipids in proteoliposomes reconstituted from detergent extract of chloroplast membranes: kinetics and phospholipid specificity.

    Directory of Open Access Journals (Sweden)

    Archita Rajasekharan

    Full Text Available Eukaryotic cells are compartmentalized into distinct sub-cellular organelles by lipid bilayers, which are known to be involved in numerous cellular processes. The wide repertoire of lipids, synthesized in the biogenic membranes like the endoplasmic reticulum and bacterial cytoplasmic membranes are initially localized in the cytosolic leaflet and some of these lipids have to be translocated to the exoplasmic leaflet for membrane biogenesis and uniform growth. It is known that phospholipid (PL translocation in biogenic membranes is mediated by specific membrane proteins which occur in a rapid, bi-directional fashion without metabolic energy requirement and with no specificity to PL head group. A recent study reported the existence of biogenic membrane flippases in plants and that the mechanism of plant membrane biogenesis was similar to that found in animals. In this study, we demonstrate for the first time ATP independent and ATP dependent flippase activity in chloroplast membranes of plants. For this, we generated proteoliposomes from Triton X-100 extract of intact chloroplast, envelope membrane and thylakoid isolated from spinach leaves and assayed for flippase activity using fluorescent labeled phospholipids. Half-life time of flipping was found to be 6 ± 1 min. We also show that: (a intact chloroplast and envelope membrane reconstituted proteoliposomes can flip fluorescent labeled analogs of phosphatidylcholine in ATP independent manner, (b envelope membrane and thylakoid reconstituted proteoliposomes can flip phosphatidylglycerol in ATP dependent manner, (c Biogenic membrane ATP independent PC flipping activity is protein mediated and (d the kinetics of PC translocation gets affected differently upon treatment with protease and protein modifying reagents.

  10. Membrane reactor. Membrane reactor

    Energy Technology Data Exchange (ETDEWEB)

    Shindo, Y.; Wakabayashi, K. (National Chemical Laboratory for Industry, Tsukuba (Japan))

    1990-08-05

    Many reaction examples were introduced of membrane reactor, to be on the point of forming a new region in the field of chemical technology. It is a reactor to exhibit excellent function, by its being installed with membrane therein, and is generally classified into catalyst function type and reaction promotion type. What firstly belongs to the former is stabilized zirconia, where oxygen, supplied to the cathodic side of membrane with voltage, impressed thereon, becomes O {sup 2 {minus}} to be diffused through the membrane and supplied, as variously activated oxygenous species, on the anodic side. Examples with many advantages can be given such as methane coupling, propylene oxidation, methanating reaction of carbon dioxide, etc. Apart, palladium film and naphion film also belong to the former. While examples of the latter comprise, among others, decomposition of hydrogen sulfide by porous glass film and dehydrogenation of cyclohexane or palladium alloy film, which are expected to be developed and materialized in the industry. 33 refs., 8 figs.

  11. 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 pu

  12. 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....

  13. Identification of the Ndh (NAD(P)H-plastoquinone-oxidoreductase) complex in etioplast membranes of barley: changes during photomorphogenesis of chloroplasts.

    Science.gov (United States)

    Guéra, A; de Nova, P G; Sabater, B

    2000-01-01

    In the last few years the presence in thylakoid membranes of chloroplasts of a NAD(P)H-plastoquinone oxidoreductase complex (Ndh complex) homologous to mitochondrial complex I has been well established. Herein, we report the identification of the Ndh complex in barley etioplast membranes. Two plastid DNA-encoded polypeptides of the Ndh complex (NDH-A and NDH-F) were relatively more abundant in etioplast membranes than in thylakoids from greening chloroplasts. Conversion of etioplast into chloroplast, after light exposure of barley seedlings grown in the dark, was accompanied by a decrease in the NADH dehydrogenase activity associated to plastid membranes. Using native-PAGE and immunolabelling techniques we have determined that a NADH specific dehydrogenase activity associated with plastid membranes, which was more active in etioplasts than in greening chloroplasts, contained the NDH-A and NDH-F polypeptides. These results complemented by those obtained through blue-native-PAGE indicated that NDH-A and NDH-F polypeptides are part of a 580 kDa NADH dependent dehydrogenase complex present in etioplast membranes. This finding proves that accumulation of the Ndh complex is independent of light. The decrease in the relative levels and specific activity of this complex during the transition from etioplast to chloroplasts was accompanied by a parallel decrease in the specific activity of peroxidase associated to plastid membranes. Based on the mentioned observations it is proposed that an electron transport chain from NADH to H2O2 could be active in barley etioplasts.

  14. Proteomic analysis of chloroplast-to-chromoplast transition in tomato reveals metabolic shifts coupled with disrupted thylakoid biogenesis machinery and elevated energy-production components.

    Science.gov (United States)

    Barsan, Cristina; Zouine, Mohamed; Maza, Elie; Bian, Wanping; Egea, Isabel; Rossignol, Michel; Bouyssie, David; Pichereaux, Carole; Purgatto, Eduardo; Bouzayen, Mondher; Latché, Alain; Pech, Jean-Claude

    2012-10-01

    A comparative proteomic approach was performed to identify differentially expressed proteins in plastids at three stages of tomato (Solanum lycopersicum) fruit ripening (mature-green, breaker, red). Stringent curation and processing of the data from three independent replicates identified 1,932 proteins among which 1,529 were quantified by spectral counting. The quantification procedures have been subsequently validated by immunoblot analysis of six proteins representative of distinct metabolic or regulatory pathways. Among the main features of the chloroplast-to-chromoplast transition revealed by the study, chromoplastogenesis appears to be associated with major metabolic shifts: (1) strong decrease in abundance of proteins of light reactions (photosynthesis, Calvin cycle, photorespiration) and carbohydrate metabolism (starch synthesis/degradation), mostly between breaker and red stages and (2) increase in terpenoid biosynthesis (including carotenoids) and stress-response proteins (ascorbate-glutathione cycle, abiotic stress, redox, heat shock). These metabolic shifts are preceded by the accumulation of plastid-encoded acetyl Coenzyme A carboxylase D proteins accounting for the generation of a storage matrix that will accumulate carotenoids. Of particular note is the high abundance of proteins involved in providing energy and in metabolites import. Structural differentiation of the chromoplast is characterized by a sharp and continuous decrease of thylakoid proteins whereas envelope and stroma proteins remain remarkably stable. This is coincident with the disruption of the machinery for thylakoids and photosystem biogenesis (vesicular trafficking, provision of material for thylakoid biosynthesis, photosystems assembly) and the loss of the plastid division machinery. Altogether, the data provide new insights on the chromoplast differentiation process while enriching our knowledge of the plant plastid proteome.

  15. Isolation and comparative analysis of the wheat TaPT2 promoter: identification in silico of new putative regulatory motifs conserved between monocots and dicots.

    Science.gov (United States)

    Tittarelli, A; Milla, L; Vargas, F; Morales, A; Neupert, C; Meisel, L A; Salvo-G, H; Peñaloza, E; Muñoz, G; Corcuera, L J; Silva, H

    2007-01-01

    Phosphorus deficiency is one of the major nutrient stresses affecting plant growth. Plants respond to phosphate (Pi) deficiency through multiple strategies, including the synthesis of high-affinity Pi transporters. In this study, the expression pattern of one putative wheat high-affinity phosphate transporter, TaPT2, was examined in roots and leaves under Pi-deficient conditions. TaPT2 transcript levels increased in roots of Pi-starved plants. A 579 bp fragment of the TaPT2 promoter is sufficient to drive the expression of the GUS reporter gene specifically in roots of Pi-deprived wheat. This TaPT2 promoter fragment was also able to drive expression of the GUS reporter gene in transgenic Arabidopsis thaliana, under similar growth conditions. Conserved regions and candidate regulatory motifs were detected by comparing this promoter with Pi transporter promoters from barley, rice, and Arabidopsis. Altogether, these results indicate that there are conserved cis-acting elements and trans-acting factors that enable the TaPT2 promoter to be regulated in a tissue-specific and Pi-dependent fashion in both monocots and dicots.

  16. Characterization of tobacco expressing functional oat phytochrome. Domains responsible for the rapid degradation of Pfr are conserved between monocots and dicots

    Energy Technology Data Exchange (ETDEWEB)

    Cherry, J.R.; Vierstra, R.D. (Univ. of Wisconsin, Madison (United States)); Hershey, H.P. (E.I.du Pont de Nemours and Co., Wilmington, DE (United States))

    1991-07-01

    Constitutive expression of a chimeric oat phytochrome gene in tobacco (Nicotiana tabacum) results in the accumulation of a functional 124-kilodalton photoreceptor that markedly alters the phenotype of light-grown tobacco. Here, we provide a detailed phenotypic and biochemical characterization of homozygous tobacco expressing high levels of oat phytochrome. Phenotypic changes include a substantial inhibition of stem elongation, decreased apical dominance, increased leaf chlorophyll content, and delayed leaf senescence. Oat phytochrome synthesized in tobacco is indistinguishable from that present in etiolated oats, having photoreversible difference spectrum maxima at 665 and 730 nanometers, exhibiting negligible dark reversion of phytochrome - far red-absorbing from (Pfr) to phytochrome - red-absorbing form (Pr), and existing as a dimer with an apparent size of approximately 300 kilodaltons. Heterodimers between the oat and tobacco chromoproteins were detected. Endogenous tobacco phytochrome and transgenically expressed oat phytochrome are rapidly degraded in vivo upon photoconversion of Pr to Pfr. Breakdown of both oat and tobacco Pfr is associated with the accumulation of ubiquitin-phytochrome conjugates, suggesting that degradation occurs via the ubiquitin-dependent proteolytic pathway. This result indicates that the factors responsible for selective recognition of Pfr by the ubiquitin pathway are conserved between monocot and dicot phytochromes. More broadly, it demonstrates that the domains(s) within a plant protein responsible for its selective breakdown can be recognized by the degradation machinery of heterologous species.

  17. Three-Dimensional Visualization of the Tubular-Lamellar Transformation of the Internal Plastid Membrane Network during Runner Bean Chloroplast Biogenesis

    Science.gov (United States)

    Suski, Szymon

    2016-01-01

    Chloroplast biogenesis is a complex process that is integrated with plant development, leading to fully differentiated and functionally mature plastids. In this work, we used electron tomography and confocal microscopy to reconstruct the process of structural membrane transformation during the etioplast-to-chloroplast transition in runner bean (Phaseolus coccineus). During chloroplast development, the regular tubular network of paracrystalline prolamellar bodies (PLBs) and the flattened porous membranes of prothylakoids develop into the chloroplast thylakoids. Three-dimensional reconstruction is required to provide us with a more complete understanding of this transformation. We provide spatial models of the bean chloroplast biogenesis that allow such reconstruction of the internal membranes of the developing chloroplast and visualize the transformation from the tubular arrangement to the linear system of parallel lamellae. We prove that the tubular structure of the PLB transforms directly to flat slats, without dispersion to vesicles. We demonstrate that the grana/stroma thylakoid connections have a helical character starting from the early stages of appressed membrane formation. Moreover, we point out the importance of particular chlorophyll-protein complex components in the membrane stacking during the biogenesis. The main stages of chloroplast internal membrane biogenesis are presented in a movie that shows the time development of the chloroplast biogenesis as a dynamic model of this process. PMID:27002023

  18. Membranous nephropathy

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/000472.htm Membranous nephropathy To use the sharing features on this page, please enable JavaScript. Membranous nephropathy is a kidney disorder that leads to changes ...

  19. Firing membranes

    NARCIS (Netherlands)

    Kappert, Emiel Jan

    2015-01-01

    Thermal processing is commonly employed to alter the chemistry and microstructure of membrane layers. It can shape, strengthen, and give functionality to a membrane. A good understanding of the processes taking place during the thermal processing of a membrane material allows for optimization and tu

  20. Organization into Higher Ordered Ring Structures Counteracts Membrane Binding of IM30, a Protein Associated with Inner Membranes in Chloroplasts and Cyanobacteria.

    Science.gov (United States)

    Heidrich, Jennifer; Wulf, Verena; Hennig, Raoul; Saur, Michael; Markl, Jürgen; Sönnichsen, Carsten; Schneider, Dirk

    2016-07-15

    The IM30 (inner membrane-associated protein of 30 kDa), also known as the Vipp1 (vesicle-inducing protein in plastids 1), has a crucial role in thylakoid membrane biogenesis and maintenance. Recent results suggest that the protein binds peripherally to membranes containing negatively charged lipids. However, although IM30 monomers interact and assemble into large oligomeric ring complexes with different numbers of monomers, it is still an open question whether ring formation is crucial for membrane interaction. Here we show that binding of IM30 rings to negatively charged phosphatidylglycerol membrane surfaces results in a higher ordered membrane state, both in the head group and in the inner core region of the lipid bilayer. Furthermore, by using gold nanorods covered with phosphatidylglycerol layers and single particle spectroscopy, we show that not only IM30 rings but also lower oligomeric IM30 structures interact with membranes, although with higher affinity. Thus, ring formation is not crucial for, and even counteracts, membrane interaction of IM30.

  1. The microalga Chlamydomonas reinhardtii CW-15 as a solar cell for hydrogen peroxide photoproduction. Comparison between free and immobilized cells and thylakoids for energy conversion efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, W.; Galvan, F.; Rosa, F.F. de la [Instituto de Bioquimica Vegetal y Fotosintesis, Universidad de Sevilla y CSIC, Sevilla (Spain)

    1995-11-28

    Immobilized cells and thylakoid vesicles of the microalga Chlamydomonas reinhardtii CW-15 have been developed as a solar cell because of their capabilities of producing hydrogen peroxide. This compound is an efficient and clean fuel used for rocket propulsion, motors and for heating. Hydrogen peroxide is produced by the photosystem in a catalyst cycle in which a redox mediator (methyl viologen) is reduced by electrons obtained from water by the photosynthetic apparatus of the microalga and it is re-oxidized by the oxygen dissolved in the solution. The photoproduction has been investigated using a discontinuous system with whole cells, or thylakoid vesicles, free or immobilized on alginate. The stimulation by azide as an inhibitor of catalase has also been analyzed. Under determined optimum conditions, the photoproduction by Ca-alginate entrapped cells, with a rate of 33 {mu}mol H{sub 2}O{sub 2}/mg Chl.h, was maintained for several hours with an energy conversion efficiency of 0.25%

  2. 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.

  3. Localization of phosphatidylcholine in outer envelope membrane of spinach chloroplasts

    Science.gov (United States)

    1985-01-01

    We have examined the effects of phospholipase C from Bacillus cereus on the extent of phospholipid hydrolysis in envelope membrane vesicles and in intact chloroplasts. When isolated envelope vesicles were incubated in presence of phospholipase C, phosphatidylcholine and phosphatidylglycerol, but not phosphatidylinositol, were totally converted into diacylglycerol if they were available to the enzyme (i.e., when the vesicles were sonicated in presence of phospholipase C). These experiments demonstrate that phospholipase C can be used to probe the availability of phosphatidylcholine and phosphatidylglycerol in the cytosolic leaflet of the outer envelope membrane from spinach chloroplasts. When isolated, purified, intact chloroplasts were incubated with low amounts of phospholipase C (0.3 U/mg chlorophyll) under very mild conditions (12 degrees C for 1 min), greater than 80% of phosphatidylcholine molecules and almost none of phosphatidylglycerol molecules were hydrolyzed. Since we have also demonstrated, by using several different methods (phase-contrast and electron microscopy, immunochemical and electrophoretic analyses) that isolated spinach chloroplasts, and especially their outer envelope membrane, remained intact after mild treatment with phospholipase C, we can conclude that there is a marked asymmetric distribution of phospholipids across the outer envelope membrane of spinach chloroplasts. Phosphatidylcholine, the major polar lipid of the outer envelope membrane, is almost entirely accessible from the cytosolic side of the membrane and therefore is probably localized in the outer leaflet of the outer envelope bilayer. On the contrary, phosphatidylglycerol, the major polar lipid in the inner envelope membrane and the thylakoids, is probably not accessible to phospholipase C from the cytosol and therefore is probably localized mostly in the inner leaflet of the outer envelope membrane and in the other chloroplast membranes. PMID:3988805

  4. Photosynthetic membrane development studied using picosecond fluorescence kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Karukstis, K.K.; Sauer, K.

    1983-01-01

    Using measurements of the kinetics of chlorophyll a fluorescence emission, the development of the photosynthetic membrane during etioplast-to-chloroplast differentiation was investigated. Tthe chlorophyll fluorescence decay kinetics of pea chloroplasts from plants grown under intermittent (2 min light-118 min dark) and continuous light regimes were monitored with a single-proton timing system with picosecond resolution. The changes in the fluorescence yields and decay kinetics were associated with known structural and organizational developmental phenomena in the chloroplast. This correlation provides a more detailed assignment of the origins of the fluorescence decay components than has been previously obtained by studying only mature chloroplasts. In particular, the analysis of the variable kinetics and multiexponential character of the fluorescence emission during thylakoid development focuses on the organization of photosynthetic units and the degree of communication between reaction centers in the same photosystem. These results further demonstrate that the age of etiolated tissue is critical to plastid development.

  5. BIOGENESIS OF THYLAKOID MEMBRANES WITH RECONSTRUCTION OF CHLOROPHYLL-PROTEIN COMPLEXES IN DELETION-MUTANT OF ORF469 IN BLUE-GREEN ALGA

    Institute of Scientific and Technical Information of China (English)

    WuQingyu; WangRuiyong; XuHong; WireVermaas

    1997-01-01

    The transformable blue green alga is used productively for mutation and deletion studies to provide functional information regarding photosynthetic reaction center complexes. We wish to take the application of transformable blue-green algal systems one step further ,and set out the

  6. Localization of cyanobacterial photosystem II donor-side subunits by electron microscopy and the supramolecular organization of photosystem II in the thylakoid membrane

    NARCIS (Netherlands)

    Kuhl, Helena; Rögner, Matthias; Breemen, Jan F.L. van; Boekema, Egbert J.

    1999-01-01

    A large set of electron microscopy projections of photosystem II (PSII) dimers isolated from the cyanobacterium Synechococcus elongatus was characterized by single particle image analysis. In addition to previously published maps at lower resolution [Boekema, E.J., Hankamer, B., Bald, D., Kruip, J.,

  7. Light-dependent reversal of dark-chilling induced changes in chloroplast structure and arrangement of chlorophyll-protein complexes in bean thylakoid membranes

    NARCIS (Netherlands)

    Garstka, M; Drozak, A; Rosiak, M; Venema, JH; Kierdaszuk, B; Simeonova, E; van Hasselt, PR; Dobrucki, J; Mostowska, A

    2005-01-01

    Changes in chloroplast structure and rearrangement of chlorophyll-protein (CP) complexes were investigated in detached leaves of bean (Phaseolus vulgaris L. cv. Eureka), a chilling-sensitive plant, during 5-day dark-chilling at 1 degrees C and subsequent 3-h photoactivation under white light (200 mu

  8. Large-Scale Gene Disruption in Magnaporthe oryzae Identifies MC69, a Secreted Protein Required for Infection by Monocot and Dicot Fungal Pathogens

    Science.gov (United States)

    Saitoh, Hiromasa; Fujisawa, Shizuko; Mitsuoka, Chikako; Ito, Akiko; Hirabuchi, Akiko; Ikeda, Kyoko; Irieda, Hiroki; Yoshino, Kae; Yoshida, Kentaro; Matsumura, Hideo; Tosa, Yukio; Win, Joe; Kamoun, Sophien; Takano, Yoshitaka; Terauchi, Ryohei

    2012-01-01

    To search for virulence effector genes of the rice blast fungus, Magnaporthe oryzae, we carried out a large-scale targeted disruption of genes for 78 putative secreted proteins that are expressed during the early stages of infection of M. oryzae. Disruption of the majority of genes did not affect growth, conidiation, or pathogenicity of M. oryzae. One exception was the gene MC69. The mc69 mutant showed a severe reduction in blast symptoms on rice and barley, indicating the importance of MC69 for pathogenicity of M. oryzae. The mc69 mutant did not exhibit changes in saprophytic growth and conidiation. Microscopic analysis of infection behavior in the mc69 mutant revealed that MC69 is dispensable for appressorium formation. However, mc69 mutant failed to develop invasive hyphae after appressorium formation in rice leaf sheath, indicating a critical role of MC69 in interaction with host plants. MC69 encodes a hypothetical 54 amino acids protein with a signal peptide. Live-cell imaging suggested that fluorescently labeled MC69 was not translocated into rice cytoplasm. Site-directed mutagenesis of two conserved cysteine residues (Cys36 and Cys46) in the mature MC69 impaired function of MC69 without affecting its secretion, suggesting the importance of the disulfide bond in MC69 pathogenicity function. Furthermore, deletion of the MC69 orthologous gene reduced pathogenicity of the cucumber anthracnose fungus Colletotrichum orbiculare on both cucumber and Nicotiana benthamiana leaves. We conclude that MC69 is a secreted pathogenicity protein commonly required for infection of two different plant pathogenic fungi, M. oryzae and C. orbiculare pathogenic on monocot and dicot plants, respectively. PMID:22589729

  9. Large-scale gene disruption in Magnaporthe oryzae identifies MC69, a secreted protein required for infection by monocot and dicot fungal pathogens.

    Directory of Open Access Journals (Sweden)

    Hiromasa Saitoh

    Full Text Available To search for virulence effector genes of the rice blast fungus, Magnaporthe oryzae, we carried out a large-scale targeted disruption of genes for 78 putative secreted proteins that are expressed during the early stages of infection of M. oryzae. Disruption of the majority of genes did not affect growth, conidiation, or pathogenicity of M. oryzae. One exception was the gene MC69. The mc69 mutant showed a severe reduction in blast symptoms on rice and barley, indicating the importance of MC69 for pathogenicity of M. oryzae. The mc69 mutant did not exhibit changes in saprophytic growth and conidiation. Microscopic analysis of infection behavior in the mc69 mutant revealed that MC69 is dispensable for appressorium formation. However, mc69 mutant failed to develop invasive hyphae after appressorium formation in rice leaf sheath, indicating a critical role of MC69 in interaction with host plants. MC69 encodes a hypothetical 54 amino acids protein with a signal peptide. Live-cell imaging suggested that fluorescently labeled MC69 was not translocated into rice cytoplasm. Site-directed mutagenesis of two conserved cysteine residues (Cys36 and Cys46 in the mature MC69 impaired function of MC69 without affecting its secretion, suggesting the importance of the disulfide bond in MC69 pathogenicity function. Furthermore, deletion of the MC69 orthologous gene reduced pathogenicity of the cucumber anthracnose fungus Colletotrichum orbiculare on both cucumber and Nicotiana benthamiana leaves. We conclude that MC69 is a secreted pathogenicity protein commonly required for infection of two different plant pathogenic fungi, M. oryzae and C. orbiculare pathogenic on monocot and dicot plants, respectively.

  10. Studies on the interactions of bisphenols with anionic phospholipids of decomposer membranes in model systems.

    Science.gov (United States)

    Broniatowski, Marcin; Sobolewska, Katarzyna; Flasiński, Michał; Wydro, Paweł

    2016-04-01

    Bisphenol A (BPA) and other bisphenols constitute a class of organic pollutants, which because of their estrogenic properties, low dose activity and bioaccumulation pose considerable risk for public health as well as for the environment. Accumulated in the sediment bisphenols can endanger the decomposers' populations being incorporated into their cellular membranes; however, the mechanism of their membrane activity is unknown. Therefore, to study these phenomena we applied anionic phospholipid Langmuir monolayers as simple but versatile models of decomposers biomembranes. Phosphatidylglycerols and cardiolipins are not only the main components of bacterial membranes but also of crucial importance in mitochondrial and thylakoid membranes in eukaryotic cells. In our investigations we applied five compounds of the bisphenol class most commonly detected in the environment. To characterize the bisphenols-model membrane interactions we applied multiple mutually independent methods of physical chemistry; namely: the Langmuir monolayer technique, surface potential measurements, Brewster angle microscopy for the visualization of the monolayers' texture and grazing incidence X-ray diffraction for the discussion of the phospholipids packing within the monolayers. Our studies indicated that all the investigated bisphenols interact with the model membrane, but the strength of the interactions is dependent on the bisphenol structure and hydrophobicity and the fluidity of the model membranes. We proved that bisphenol S often treated as the least toxic BPA analog can also be incorporated to the model membranes changing their structure and fluidity.

  11. Expression conservation within the circadian clock of a monocot: natural variation at barley Ppd-H1 affects circadian expression of flowering time genes, but not clock orthologs

    Directory of Open Access Journals (Sweden)

    Campoli Chiara

    2012-06-01

    Full Text Available Abstract Background The circadian clock is an endogenous mechanism that coordinates biological processes with daily changes in the environment. In plants, circadian rhythms contribute to both agricultural productivity and evolutionary fitness. In barley, the photoperiod response regulator and flowering-time gene Ppd-H1 is orthologous to the Arabidopsis core-clock gene PRR7. However, relatively little is known about the role of Ppd-H1 and other components of the circadian clock in temperate crop species. In this study, we identified barley clock orthologs and tested the effects of natural genetic variation at Ppd-H1 on diurnal and circadian expression of clock and output genes from the photoperiod-response pathway. Results Barley clock orthologs HvCCA1, HvGI, HvPRR1, HvPRR37 (Ppd-H1, HvPRR73, HvPRR59 and HvPRR95 showed a high level of sequence similarity and conservation of diurnal and circadian expression patterns, when compared to Arabidopsis. The natural mutation at Ppd-H1 did not affect diurnal or circadian cycling of barley clock genes. However, the Ppd-H1 mutant was found to be arrhythmic under free-running conditions for the photoperiod-response genes HvCO1, HvCO2, and the MADS-box transcription factor and vernalization responsive gene Vrn-H1. Conclusion We suggest that the described eudicot clock is largely conserved in the monocot barley. However, genetic differentiation within gene families and differences in the function of Ppd-H1 suggest evolutionary modification in the angiosperm clock. Our data indicates that natural variation at Ppd-H1 does not affect the expression level of clock genes, but controls photoperiodic output genes. Circadian control of Vrn-H1 in barley suggests that this vernalization responsive gene is also controlled by the photoperiod-response pathway. Structural and functional characterization of the barley circadian clock will set the basis for future studies of the adaptive significance of the circadian clock in

  12. Expression conservation within the circadian clock of a monocot: natural variation at barley Ppd-H1 affects circadian expression of flowering time genes, but not clock orthologs.

    Science.gov (United States)

    Campoli, Chiara; Shtaya, Munqez; Davis, Seth J; von Korff, Maria

    2012-06-21

    The circadian clock is an endogenous mechanism that coordinates biological processes with daily changes in the environment. In plants, circadian rhythms contribute to both agricultural productivity and evolutionary fitness. In barley, the photoperiod response regulator and flowering-time gene Ppd-H1 is orthologous to the Arabidopsis core-clock gene PRR7. However, relatively little is known about the role of Ppd-H1 and other components of the circadian clock in temperate crop species. In this study, we identified barley clock orthologs and tested the effects of natural genetic variation at Ppd-H1 on diurnal and circadian expression of clock and output genes from the photoperiod-response pathway. Barley clock orthologs HvCCA1, HvGI, HvPRR1, HvPRR37 (Ppd-H1), HvPRR73, HvPRR59 and HvPRR95 showed a high level of sequence similarity and conservation of diurnal and circadian expression patterns, when compared to Arabidopsis. The natural mutation at Ppd-H1 did not affect diurnal or circadian cycling of barley clock genes. However, the Ppd-H1 mutant was found to be arrhythmic under free-running conditions for the photoperiod-response genes HvCO1, HvCO2, and the MADS-box transcription factor and vernalization responsive gene Vrn-H1. We suggest that the described eudicot clock is largely conserved in the monocot barley. However, genetic differentiation within gene families and differences in the function of Ppd-H1 suggest evolutionary modification in the angiosperm clock. Our data indicates that natural variation at Ppd-H1 does not affect the expression level of clock genes, but controls photoperiodic output genes. Circadian control of Vrn-H1 in barley suggests that this vernalization responsive gene is also controlled by the photoperiod-response pathway. Structural and functional characterization of the barley circadian clock will set the basis for future studies of the adaptive significance of the circadian clock in Triticeae species.

  13. The 1.7 Å resolution structure of At2g44920, a pentapeptide-repeat protein in the thylakoid lumen of Arabidopsis thaliana

    Energy Technology Data Exchange (ETDEWEB)

    Ni, Shuisong; McGookey, Michael E.; Tinch, Stuart L.; Jones, Alisha N.; Jayaraman, Seetharaman; Tong, Liang; Kennedy, Michael A. (Miami U); (Columbia)

    2012-01-09

    At2g44920 belongs to a diverse family (Pfam PF00805) of pentapeptide-repeat proteins (PRPs) that are present in all known organisms except yeast. PRPs contain at least eight tandem-repeating sequences of five amino acids with an approximate consensus sequence (STAV)(D/N)(L/F)(S/T/R)(X). Recent crystal structures show that PRPs adopt a highly regular four-sided right-handed {beta}-helical structure consisting mainly of type II and type IV {beta}-turns, sometimes referred to as a repeated five-residue (or Rfr) fold. Among sequenced genomes, PRP genes are most abundant in cyanobacteria, leading to speculation that PRPs play an important role in the unique lifestyle of photosynthetic cyanobacteria. Despite the recent structural characterization of several cyanobacterial PRPs, most of their functions remain unknown. Plants, whose chloroplasts are of cyanobacterial origin, have only four PRP genes in their genomes. At2g44920 is one of three PRPs located in the thylakoid lumen. Here, the crystal structure of a double methionine mutant of residues 81-224 of At2g44920, the naturally processed fragment of one of its full-length isoforms, is reported at 1.7 {angstrom} resolution. The structure of At2g44920 consists of the characteristic Rfr fold with five uninterrupted coils made up of 25 pentapeptide repeats and {alpha}-helical elements capping both termini. A disulfide bridge links the two {alpha}-helices with a conserved loop between the helical elements at its C-terminus. This structure represents the first structure of a PRP protein whose subcellular location has been experimentally confirmed to be the thylakoid lumen in a plant species.

  14. Iron stabilizes thylakoid protein-pigment complexes in Indian mustard during Cd-phytoremediation as revealed by BN-SDS-PAGE and ESI-MS/MS.

    Science.gov (United States)

    Qureshi, M Irfan; D'Amici, Gian Maria; Fagioni, Marco; Rinalducci, Sara; Zolla, Lello

    2010-07-01

    Two-dimensional BN-SDS-PAGE, ESI-MS/MS and electron microscopy (EM) were used to study the role of iron (Fe) under cadmium (Cd) stress in retention of thylakoidal multiprotein complexes (MPCs) and chloroplast ultrastructure of Indian mustard, a moderate hyperaccumulator plant. Mustard was grown hydroponically with or without iron for 17 days and then exposed to CdCl2 for 3 days. Fe deficiency led to an increase in oxidative stress and damage to chloroplast/thylakoids accompanied by a decrease in chlorophyll content; exposure of plants to Cd further enhanced the oxidative stress and Cd accumulation (more in -Fe plants). However, the presence of iron aided plants in the suppression of oxidative stress and retention of chloroplasts and chlorophylls under Cd stress. Proteomic analyses by 2D BN-SDS-PAGE and mass spectrometry showed that Fe deficiency considerably decreased the amount of LHCII trimer, ATPase-F1 portion, cyt b6/f and RuBisCO. No or less reduction, was observed for PSI(RCI+LHCI), the PSII-core monomer, and the PSII subcomplex, while an increase in the LHCII monomer was noted. Under iron deficiency, Cd proved to be very deleterious to MPCs, except for the PSII subcomplex, the LHCII monomer and free proteins which were increased. Iron proved to be very protective in retaining almost all the complexes. MPCs showed greater susceptibility to Cd than Fe deficiency, mainly at the level of RuBisCO and cyt b6/f; an increase in the amount of the PSII subcomplex, LHCII monomer and free proteins indicates differences in the mechanisms affected by Fe deficiency and Cd stress when compared to Fe-fed plants. This study furthers our understanding of the sites actually damaged in MPCs under Fe deficiency and Cd stress. A role emerges for iron in the protection of MPCs and, hence, of the chloroplast. The present study also indicates the importance of iron for efficient phytoextraction/phytoremediation.

  15. Immunogold localization of acyl carrier protein in plants and Escherichia coli: Evidence for membrane association in plants.

    Science.gov (United States)

    Slabas, A R; Smith, C G

    1988-08-01

    Immunogold labelling was used to study the distribution of acyl carrier protein (ACP) in Escherichia coli and a variety of plant tissues. In E. coli, ACP is distributed throughout the cytoplasm, confirming the observation of S. Jackowski et al. (1985, J. Bacteriol., 162, 5-8_. In the mesocarp of Avocado (Persea americana) and maturing seeds of oil-seed rape (Brassica napus cv. Jet Neuf), over 95% of the ACP is localised to plastids. The protein is almost exclusively located in the chloroplasts of leaf material from oil-seed rape. Approximately 80% of the gold particles associated with the ACP were further localized to the thylakoid membrane of the chloroplast. Since acetyl-CoA carboxylase has been reported to be localized to the thylakoid membrane (C.G. Kannangara and C.J. Jensen, 1975, Eur. J. Biochem., 54, 25-30), these results are consistent with the view that the two sequential enzymes in fatty-acid synthesis are in close spacial proximity.

  16. 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...

  17. 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...

  18. Thylakoid-Inspired Multishell g-C3N4 Nanocapsules with Enhanced Visible-Light Harvesting and Electron Transfer Properties for High-Efficiency Photocatalysis.

    Science.gov (United States)

    Tong, Zhenwei; Yang, Dong; Li, Zhen; Nan, Yanhu; Ding, Fei; Shen, Yichun; Jiang, Zhongyi

    2017-01-24

    Inspired by the orderly stacked nanostructure and highly integrated function of thylakoids in a natural photosynthesis system, multishell g-C3N4 (MSCN) nanocapsule photocatalysts have been prepared by SiO2 hard template with different shell layers. The resultant triple-shell g-C3N4 (TSCN) nanocapsules display superior photocatalysis performance to single-shell and double-shell counterparts owing to excellent visible-light harvesting and electron transfer properties. Specially, with the increase of the shell layer number, light harvesting is greatly enhanced. There is an increase of the entire visible range absorption arising from the multiple scattering and reflection of the incident light within multishell nanoarchitectures as well as the light transmission within the porous thin shells, and an increase of absorption edge arising from the decreased quantum size effect. The electron transfer is greatly accelerated by the mesopores in the thin shells as nanoconduits and the high specific surface area of TSCN (310.7 m(2) g(-1)). With the tailored hierarchical nanostructure features, TSCN exhibits a superior visible-light H2-generation activity of 630 μmol h(-1) g(-1) (λ > 420 nm), which is among one of the most efficient metal-free g-C3N4 photocatalysts. This study demonstrates a bioinspired approach to the rational design of high-performance nanostructured visible-light photocatalysts.

  19. Flow-force relationships in lettuce thylakoids. 2. Effect of the uncoupler FCCP on local proton resistances at the ATPase level.

    Science.gov (United States)

    Sigalat, C; de Kouchkovsky, Y; Haraux, F

    1993-09-28

    The relationship between the steady-state proton gradient (delta pH) and the rate of phosphorylation was investigated in thylakoids under various conditions. Under partial uncoupling by carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), the rate of ATP synthesis was reduced by less than expected from the decrease of delta pH. This was observed in the case of the pyocyanine-mediated cyclic electron flow around photosystem 1, but not with the H2O-->photosystem 2-->cytochrome b6f-->photosystem 1-->methyl viologen system. In state 4, a unique relation was found between delta pH and the "phosphate potential", delta Gp, regardless of whether the energy level was controlled by light input or FCCP. The anomalous effect of FCCP on the rate of ATP synthesis disappeared when the ATPase was partially blocked by the reversible inhibitor venturicidin, but not in the presence of tentoxin, an irreversible inhibitor. These results are consistent with the existence of a small kinetic barrier for protons, limiting their access to the ATPase. This resistance would be collapsed by FCCP.

  20. Regulation and Levels of the Thylakoid K+/H+ Antiporter KEA3 Shape the Dynamic Response of Photosynthesis in Fluctuating Light.

    Science.gov (United States)

    Armbruster, Ute; Leonelli, Lauriebeth; Correa Galvis, Viviana; Strand, Deserah; Quinn, Erica H; Jonikas, Martin C; Niyogi, Krishna K

    2016-07-01

    Crop canopies create environments of highly fluctuating light intensities. In such environments, photoprotective mechanisms and their relaxation kinetics have been hypothesized to limit photosynthetic efficiency and therefore crop yield potential. Here, we show that overexpression of the Arabidopsis thylakoid K(+)/H(+) antiporter KEA3 accelerates the relaxation of photoprotective energy-dependent quenching after transitions from high to low light in Arabidopsis and tobacco. This, in turn, enhances PSII quantum efficiency in both organisms, supporting that in wild-type plants, residual light energy quenching following a high to low light transition represents a limitation to photosynthetic efficiency in fluctuating light. This finding underscores the potential of accelerating quenching relaxation as a building block for improving photosynthetic efficiency in the field. Additionally, by overexpressing natural KEA3 variants with modification to the C-terminus, we show that KEA3 activity is regulated by a mechanism involving its lumen-localized C-terminus, which lowers KEA3 activity in high light. This regulatory mechanism fine-tunes the balance between photoprotective energy dissipation in high light and maximum quantum yield in low light, likely to be critical for efficient photosynthesis in fluctuating light conditions.

  1. Age-dependent variation in membrane lipid synthesis in leaves of garden pea (Pisum sativum L.)

    DEFF Research Database (Denmark)

    Hellgren, Lars; Sandelius, A.S.

    2001-01-01

    leaf of older plants, acetate was predominantly allocated into phosphatidylglycerol (PG), which remained the major radiolabelled lipid during the 3 d studied. The proportion of radioactivity recovered in MGDG decreased with increasing plant age up to 20 d, suggesting that, in expanded leaves, MGDG...... is more stable and requires renewal to a lower extent than PG. When the second oldest leaf approached senescence, labelling of MGDG again increased, indicating an increased need for thylakoid repair. The proportion of acetate allocated into phosphatidylethanolamine and free sterols was largest in leaves...... of 18-26-d-old plants and in the youngest leaves, respectively. Thus, these results demonstrate that the distribution of newly synthesized fatty acids between acyl lipid synthesis in the chloroplast and extraplastidial membranes strongly varies with leaf age, as do the proportion utilized for sterol...

  2. Description of Gloeomargarita lithophora gen. nov., sp. nov., a thylakoid-bearing basal-branching cyanobacterium with intracellular carbonates, and proposal for Gloeomargaritales ord. nov.

    Science.gov (United States)

    Moreira, David; Tavera, Rosaluz; Benzerara, Karim; Skouri-Panet, Fériel; Couradeau, Estelle; Gérard, Emmanuelle; Loussert Fonta, Céline; Novelo, Eberto; Zivanovic, Yvan; López-García, Purificación

    2016-11-21

    A unicellular cyanobacterium, strain Alchichica-D10, was isolated from microbialites of the alkaline Lake Alchichica, Mexico. The cells were short rods (3.9 ± 0.6 μm in length and 1.1 ± 0.1 μm in width) forming biofilms of intense emerald green color. They exhibited red autofluorescence under UV light excitation. UV-visible absorption spectra revealed that they contain chlorophyll a and phycocyanin, and electron microscopy showed the presence of thylakoids. The strain grew within a temperature range of 15-30 °C. Genomic DNA G+C content was 52.2 mol%. The most remarkable feature of this species was its granular cytoplasm, due to the presence of numerous intracellular spherical granules (16-26 per cell) with an average diameter of 270 nm. These granules, easily visible under scanning electron microscopy, were composed of amorphous carbonate containing Ca, Mg, Ba, and Sr. A multi-gene phylogeny based on the analysis of 59 conserved protein markers supported robustly that this strain occupies a deep position in the cyanobacterial tree. Based on its phenotypic characters and phylogenetic position, strain Alchichica-D10 is considered to represent a new genus and novel species of cyanobacteria for which the name Gloeomargarita lithophora gen. nov., sp. nov. is proposed. The type strain is Alchichica-D10 (Culture Collection of Algae and Protozoa CCAP strain 1437/1; Collections de Cyanobactéries et Microalgues Vivantes of the Museum National d'Histoire Naturelle in Paris strain PMC 919.15). Furthermore, a new family, Gloeomargaritaceae, and a new order, Gloeoemargaritales, are proposed to accommodate this species under the International Code of Nomenclature for algae, fungi, and plants.

  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. Microporous Inorganic Membranes as Proton Exchange Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Vichi, F.M. Tejedor-Tejedor, M.I. Anderson, Marc A

    2002-08-28

    Porous oxide electrolyte membranes provide an alternative approach to fabricating proton exchange membrane fuel cells based on inorganic materials. This study focused on elucidating the properties of these inorganic membranes that make them good electrolyte materials in membrane electrode assemblies; in particular, we investigated several properties that affect the nature of proton conductivity in these membranes. This report discusses our findings on the effect of variables such as site density, amount of surface protonation and surface modification on the proton conductivity of membranes with a fixed pore structure under selected conditions. Proton conductivities of these inorganic membranes are similar to conductivities of nafion, the polymeric membrane most commonly used in low temperature fuel cells.

  5. Anaerobic membrane bioreactors: Are membranes really necessary?

    NARCIS (Netherlands)

    Davila, M.; Kassab, G.; Klapwijk, A.; Lier, van J.B.

    2008-01-01

    Membranes themselves represent a significant cost for the full scale application of anaerobic membrane bioreactors (AnMBR). The possibility of operating an AnMBR with a self-forming dynamic membrane generated by the substances present in the reactor liquor would translate into an important saving. A

  6. 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...... controlled by membrane structure, permeability and curvature as well as membrane proteins by using a wide range of biochemical, biophysical and microscopic techniques. This review gives an overview of some currently used model biomembrane systems. We will also discuss some key membrane protein properties...... that are relevant for protein-membrane interactions in terms of protein structure and how it is affected by membrane composition, phase behavior and curvature....

  7. Erythrocyte membrane proteins and membrane skeleton

    Institute of Scientific and Technical Information of China (English)

    LU Yiqin; LIU Junfan

    2007-01-01

    Considerable advances in the research field of erythrocyte membrane were achieved in the recent two decades.New findings in the structure-function correlation and interactions of erythrocyte membrane proteins have attracted extensive attention.Interesting progress was also made in the molecular pathogenesis of erythrocyte membrane disorders.Advances in the composition,function and interaction of erythrocyte membrane proteins,erythrocyte membrane skeleton,and relevant diseases are briefly described and summarized here on the basis of domestic and world literatures.

  8. Changes in membrane lipids and carotenoids during light acclimation in a marine cyanobacterium Synechococcus sp.

    Indian Academy of Sciences (India)

    Olimpio Montero; Alberto Sánchez-Guijo; Luis M Lubián; Gonzalo Martínez-Rodríguez

    2012-09-01

    Time course of carotenoid and membrane lipid variation during high light (HL) acclimation (about 85 mol m−2 s−1), after transfer from low light (LL) (5–10 μmol m−2 s−1), was determined in a marine Synechococcus strain. High-performance liquid chromatography (HPLC) coupled to diode array detector (DAD) or electrospray ionization mass spectrometry (ESI-MS) was used for compound separation and detection. Myxoxanthophyll rose within a time interval of 8 h to 24 h after the onset of exposure to HL. -carotene content started to decrease after 4 h of the onset of exposure to HL. Zeaxanthin content rose with exposure to HL, but it was only significant after 24 h of exposure. Carotenoid changes are in agreement with a coordinated activity of the enzymes of the myxoxanthophyll biosynthetic pathway, with no rate-limiting intermediate steps. Lipid analysis showed all species with a C18:3/C16:0 composition increased their content, the changes of PG(18:3/16:0) and MGDG(18:3/16:0) being primarily significant. Major lipid changes were also found to occur within 24 h. These changes might suggest reduction and reorganization of the thylakoid membrane structure. Hypotheses are also drawn on the role played by lipid molecule shape and their possible effect in membrane fluidity and protein accommodation.

  9. Single particle analysis of thylakoid proteins from Thermosynechococcus elongatus and Synechocystis 6803 : Localization of the CupA subunit of NDH-1

    NARCIS (Netherlands)

    Folea, I. Mihaela; Zhang, Pengpeng; Nowaczyk, Marc M.; Ogawa, Teruo; Aro, Eva-Marl; Boekema, Egbert J.; Aro, Eva-Mari

    2008-01-01

    The larger protein complexes of the cyanobacterial photosynthetic membrane of Thermosynechoccus elongatus and Synechocystis 6803 were studied by single particle electron microscopy after detergent solubilization, without any purification steps. Besides the "standard" L-shaped NDH-1L complex, related

  10. Single particle analysis of thylakoid proteins from Thermosynechococcus elongatus and Synechocystis 6803 : Localization of the CupA subunit of NDH-1

    NARCIS (Netherlands)

    Folea, I. Mihaela; Zhang, Pengpeng; Nowaczyk, Marc M.; Ogawa, Teruo; Aro, Eva-Marl; Boekema, Egbert J.; Aro, Eva-Mari

    2008-01-01

    The larger protein complexes of the cyanobacterial photosynthetic membrane of Thermosynechoccus elongatus and Synechocystis 6803 were studied by single particle electron microscopy after detergent solubilization, without any purification steps. Besides the "standard" L-shaped NDH-1L complex, related

  11. Endomembrane Cation Transporters and Membrane Trafficking

    Energy Technology Data Exchange (ETDEWEB)

    Sze, Heven [Univ. of Maryland, College Park, MD (United States). Dept. of Cell Biology & Molecular Genetics

    2017-04-01

    fertilization. Based on localization and mutant analyses, we conclude that CHXs modulate the ion balance, pH or both in micro-regions of endoplasmic reticulum, endosomes and prevacuolar compartment (PVC), and so influence membrane trafficking and signaling resulting in proper osmoregulation in guard cells and seed formation. We also demonstrated for the first time that AtKEA2 associates with chloroplasts, especially at the two poles of developing plastids. These results show that AtKEA1 and AtKEA2 transporters in specific microdomains of the inner envelope link local osmotic, ionic, and pH homeostasis to plastid division and thylakoid membrane formation. The first 3-D structure model of AtCHX was generated, and architecture-directed mutagenesis identified critical residues of the transport core giving insights to the transport mode of this family. Thus we have revealed for the first time crucial roles of an unknown K+/H+ transport family on plant growth (KEA), gas exchange, pollen cell wall, and different phases of reproduction (CHXs). The dynamic endomembrane of plant cells is integral to cytokinesis, cell expansion, defense, and cell wall formation, thus these studies are directly relevant to the mission of the Department of Energy and to a better understanding of determinants for enhancing plant biomass and plant tolerance to abiotic stress.

  12. 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.

  13. Compositional asynchronous membrane systems

    Institute of Scientific and Technical Information of China (English)

    Cosmin Bonchis; Cornel Izbasa; Gabriel Ciobanu

    2007-01-01

    This paper presents an algorithmic way of building complex membrane systems by coupling elementary membranes. Its application seems particularly valuable in the case of asynchronous membrane systems, since the resulting membrane system remains asynchronous. The composition method is based on a handshake mechanism implemented by using antiport rules and promoters.

  14. Composite sensor membrane

    Science.gov (United States)

    Majumdar, Arun; Satyanarayana, Srinath; Yue, Min

    2008-03-18

    A sensor may include a membrane to deflect in response to a change in surface stress, where a layer on the membrane is to couple one or more probe molecules with the membrane. The membrane may deflect when a target molecule reacts with one or more probe molecules.

  15. Light-harvesting Complexes (LHCs) Cluster Spontaneously in Membrane Environment Leading to Shortening of Their Excited State Lifetimes.

    Science.gov (United States)

    Natali, Alberto; Gruber, J Michael; Dietzel, Lars; Stuart, Marc C A; van Grondelle, Rienk; Croce, Roberta

    2016-08-05

    The light reactions of photosynthesis, which include light-harvesting and charge separation, take place in the amphiphilic environment of the thylakoid membrane. The light-harvesting complex II (LHCII) is the main responsible for light absorption in plants and green algae and is involved in photoprotective mechanisms that regulate the amount of excited states in the membrane. The dual function of LHCII has been extensively studied in detergent micelles, but recent results have indicated that the properties of this complex differ in a lipid environment. In this work we checked these suggestions by studying LHCII in liposomes. By combining bulk and single molecule measurements, we monitored the fluorescence characteristics of liposomes containing single complexes up to densely packed proteoliposomes. We show that the natural lipid environment per se does not alter the properties of LHCII, which for single complexes remain very similar to that in detergent. However, we show that LHCII has the strong tendency to cluster in the membrane and that protein interactions and the extent of crowding modulate the lifetimes of the excited state in the membrane. Finally, the presence of LHCII monomers at low concentrations of complexes per liposome is discussed.

  16. N-terminal processing of membrane-targeted MnSOD and formation of multiple active superoxide dismutase dimers in the nitrogen-fixing cyanobacterium Anabaena sp. strain PCC7120.

    Science.gov (United States)

    Raghavan, Prashanth S; Rajaram, Hema; Apte, Shree K

    2013-10-01

    Anabaena sp. strain PCC7120 expresses a 30 kDa manganese-dependent superoxide dismutase (MnSOD) comprising a hydrophobic region (signal peptide + linker peptide) attached to a catalytic unit. Bioinformatics predicted cleavage of the signal peptide at (25)CQPQ by signal peptidase and of the linker peptide by an Arg-C-like protease at the Arg52/Arg59 residue. The three predicted forms of MnSOD were immunodetected in Anabaena, with the 30 kDa MnSOD found exclusively in the membrane and the shorter 27 and 24 kDa forms found both in the membrane and soluble fractions. The corresponding sodA gene was truncated for (a) the first eight residues, or, (b) the signal peptide, or (c) the entire hydrophobic region, or (d) the Arg52/Arg59 residues were modified to serine. Overexpression of these MnSOD variants in recombinant Anabaena strains revealed that (a) the 30 kDa membrane-targeted MnSOD was cleaved by membrane-localized signal peptidase either during or after its transport through the membrane to release the 27 kDa form, either in the cytosol or in the periplasmic/thylakoid lumen, (b) the 27 kDa form was further cleaved to the 24 kDa form by Arg-C-like protease, both in the cytosol and in the periplasmic/thylakoid lumen, (c) deletion of signal peptide localized the MnSOD forms in the cytosol, and (d) alteration of the signal/linker peptide cleavage sites interfered with MnSOD localization and processing. Homo/heterodimerization of the 24 and 27 kDa forms of MnSOD and the cytosolic iron-dependent SOD results in multiple SOD activities, from a single MnSOD gene (sodA), in different cellular compartments of Anabaena.

  17. 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.

  18. Spatial variation in photosynthetic CO(2) carbon and oxygen isotope discrimination along leaves of the monocot triticale (Triticum × Secale) relates to mesophyll conductance and the Péclet effect.

    Science.gov (United States)

    Kodama, Naomi; Cousins, Asaph; Tu, Kevin P; Barbour, Margaret M

    2011-09-01

    Carbon and oxygen isotope discrimination of CO(2) during photosynthesis (Δ(13)C(obs) and Δ(18)O(obs)) were measured along a monocot leaf, triticale (Triticum × Secale). Both Δ(13)C(obs) and Δ(18)O(obs) increased towards the leaf tip. While this was expected for Δ(18)O(obs) , because of progressive enrichment of leaf water associated with the Péclet effect, the result was surprising for Δ(13) C(obs). To explore parameters determining this pattern, we measured activities of key photosynthetic enzymes [ribulose bis-phosphate carboxylase-oxygenase (Rubisco), phosphoenolpyruvate carboxylase (PEPC) and carbonic anhydrase) as well as maximum carboxylation and electron transport rates (V(cmax) and J(max)) along the leaf. Patterns in leaf internal anatomy along the leaf were also quantified. Mesophyll conductance (g(m)) is known to have a strong influence on Δ(13)C(obs) , so we used three commonly used estimation methods to quantify variation in g(m) along the leaf. Variation in Δ(13)C(obs) was correlated with g(m) and chloroplast surface area facing the intercellular air space, but unrelated to photosynthetic enzyme activity. The observed variation could cause errors at higher scales if the appropriate portion of a leaf is not chosen for leaf-level measurements and model parameterization. Our study shows that one-third of the way from the base of the leaf represents the most appropriate portion to enclose in the leaf chamber. © 2011 Blackwell Publishing Ltd.

  19. Membrane targeting of MnSOD is essential for oxidative stress tolerance of nitrogen-fixing cultures of Anabaena sp. strain PCC7120.

    Science.gov (United States)

    Raghavan, Prashanth S; Rajaram, Hema; Apte, Shree Kumar

    2015-07-01

    The nitrogen-fixing cyanobacterium, Anabaena PCC7120 encodes for a membrane-targeted 30 kDa Mn-superoxide dismutase (MnSOD) and a cytosolic FeSOD. The MnSOD is post-translationally processed to 27 and 24 kDa forms in the cytosol and periplasm/thylakoid lumen. The extent of cleavage of signal and linker peptides at the N-terminus is dependent on the availability of combined nitrogen during growth. While the 24 and 27 kDa forms are present in near equal proportions under nitrogen-fixing conditions, the 24 kDa form is predominant under nitrogen-supplemented conditions. Individual contribution of these forms of MnSOD to total oxidative stress tolerance was analysed using recombinant Anabaena strains overexpressing either different molecular forms of MnSOD or MnSOD defective in the cleavage of signal/linker peptide. Targeting of MnSOD to the membrane and subsequent cleavage to release both the 24 and 27 kDa forms was essential for oxidative stress tolerance under nitrogen-fixing conditions. On the other hand, the cleavage of linker peptide was absolutely essential and the release of cytosolic 24 kDa form of MnSOD was obligatory for developing oxidative stress tolerance under nitrogen-supplemented conditions. Thus, a single MnSOD caters to the reduction of superoxide radical in both cytosol and thylakoid lumen/periplasm irrespective of the N-status of growth by regulating its cleavage. This is the first report on the physiological advantage of membrane-targeting and processing of MnSOD in either bacteria or plants. The higher oxidative stress tolerance offered by the cytosolic form of MnSOD has possibly resulted in retention of only the cytosolic form in bacterial non-nitrogen-fixers during evolution.

  20. Membrane Automata with Priorities

    Institute of Scientific and Technical Information of China (English)

    Luděk Cienciala; Lucie Ciencialová

    2004-01-01

    In this paper the one-way P automata with priorities are introduced. Such automata are P systemshere the membranes are only allowed to consume objects from parent membranes, under the given conditions. The result of computation of these systems is the set of multiset sequences consumed by skin membrane intc the system. The rules associated in some order with each membrane cannot modify any objects, they can only move them through membrane. We show that P automata with priorities and two membranes can accept every recursively enumerated language.

  1. Composite zeolite membranes

    Science.gov (United States)

    Nenoff, Tina M.; Thoma, Steven G.; Ashley, Carol S.; Reed, Scott T.

    2002-01-01

    A new class of composite zeolite membranes and synthesis techniques therefor has been invented. These membranes are essentially defect-free, and exhibit large levels of transmembrane flux and of chemical and isotopic selectivity.

  2. 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....

  3. Hybrid adsorptive membrane reactor

    Science.gov (United States)

    Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

    2011-01-01

    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.

  4. Solvent resistant nanofiltration membranes

    OpenAIRE

    Dutczak, S.M.

    2011-01-01

    This thesis describes preparation and characterization of membranes for organic solvent filtration (OSF). The main aim was developing membranes for solvent resistant nanofiltration (SRNF) with molecular weight cut-off below 500 g mol-1.

  5. 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.

  6. Ionene membrane battery separator

    Science.gov (United States)

    Moacanin, J.; Tom, H. Y.

    1969-01-01

    Ionic transport characteristics of ionenes, insoluble membranes from soluble polyelectrolyte compositions, are studied for possible application in a battery separator. Effectiveness of the thin film of separator membrane essentially determines battery lifetime.

  7. Hybrid adsorptive membrane reactor

    Science.gov (United States)

    Tsotsis, Theodore T.; Sahimi, Muhammad; Fayyaz-Najafi, Babak; Harale, Aadesh; Park, Byoung-Gi; Liu, Paul K. T.

    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.

  8. 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 dev

  9. 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

  10. Tracking membrane protein association in model membranes.

    Directory of Open Access Journals (Sweden)

    Myriam Reffay

    Full Text Available Membrane proteins are essential in the exchange processes of cells. In spite of great breakthrough in soluble proteins studies, membrane proteins structures, functions and interactions are still a challenge because of the difficulties related to their hydrophobic properties. Most of the experiments are performed with detergent-solubilized membrane proteins. However widely used micellar systems are far from the biological two-dimensions membrane. The development of new biomimetic membrane systems is fundamental to tackle this issue.We present an original approach that combines the Fluorescence Recovery After fringe Pattern Photobleaching technique and the use of a versatile sponge phase that makes it possible to extract crucial informations about interactions between membrane proteins embedded in the bilayers of a sponge phase. The clear advantage lies in the ability to adjust at will the spacing between two adjacent bilayers. When the membranes are far apart, the only possible interactions occur laterally between proteins embedded within the same bilayer, whereas when membranes get closer to each other, interactions between proteins embedded in facing membranes may occur as well.After validating our approach on the streptavidin-biotinylated peptide complex, we study the interactions between two membrane proteins, MexA and OprM, from a Pseudomonas aeruginosa efflux pump. The mode of interaction, the size of the protein complex and its potential stoichiometry are determined. In particular, we demonstrate that: MexA is effectively embedded in the bilayer; MexA and OprM do not interact laterally but can form a complex if they are embedded in opposite bilayers; the population of bound proteins is at its maximum for bilayers separated by a distance of about 200 A, which is the periplasmic thickness of Pseudomonas aeruginosa. We also show that the MexA-OprM association is enhanced when the position and orientation of the protein is restricted by the

  11. Separation membrane development

    Energy Technology Data Exchange (ETDEWEB)

    Lee, M.W. [Savannah River Technology Center, Aiken, SC (United States)

    1998-08-01

    A ceramic membrane has been developed to separate hydrogen from other gases. The method used is a sol-gel process. A thin layer of dense ceramic material is coated on a coarse ceramic filter substrate. The pore size distribution in the thin layer is controlled by a densification of the coating materials by heat treatment. The membrane has been tested by permeation measurement of the hydrogen and other gases. Selectivity of the membrane has been achieved to separate hydrogen from carbon monoxide. The permeation rate of hydrogen through the ceramic membrane was about 20 times larger than Pd-Ag membrane.

  12. Structure and function of PspA and Vipp1 N-terminal peptides: Insights into the membrane stress sensing and mitigation.

    Science.gov (United States)

    McDonald, Christopher; Jovanovic, Goran; Wallace, B A; Ces, Oscar; Buck, Martin

    2017-01-01

    The phage shock protein (Psp) response maintains integrity of the inner membrane (IM) in response to extracytoplasmic stress conditions and is widely distributed amongst enterobacteria. Its central component PspA, a member of the IM30 peripheral membrane protein family, acts as a major effector of the system through its direct association with the IM. Under non-stress conditions PspA also negatively regulates its own expression via direct interaction with the AAA+ ATPase PspF. PspA has a counterpart in cyanobacteria called Vipp1, which is implicated in protection of the thylakoid membranes. PspA's and Vipp1's conserved N-terminal regions contain a putative amphipathic helix a (AHa) required for membrane binding. An adjacent amphipathic helix b (AHb) in PspA is required for imposing negative control upon PspF. Here, purified peptides derived from the putative AH regions of PspA and Vipp1 were used to directly probe their effector and regulatory functions. We observed direct membrane-binding of AHa derived peptides and an accompanying change in secondary structure from unstructured to alpha-helical establishing them as bona fide membrane-sensing AH's. The peptide-binding specificities and their effects on membrane stability depend on membrane anionic lipid content and stored curvature elastic stress, in agreement with full length PspA and Vipp1 protein functionalities. AHb of PspA inhibited the ATPase activity of PspF demonstrating its direct regulatory role. These findings provide new insight into the membrane binding and function of PspA and Vipp1 and establish that synthetic peptides can be used to probe the structure-function of the IM30 protein family. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  13. Water Membrane Evaporator

    Science.gov (United States)

    Ungar, Eugene K.; Almlie, Jay C.

    2010-01-01

    A water membrane evaporator (WME) has been conceived and tested as an alternative to the contamination-sensitive and corrosion-prone evaporators currently used for dissipating heat from space vehicles. The WME consists mainly of the following components: An outer stainless-steel screen that provides structural support for the components mentioned next; Inside and in contact with the stainless-steel screen, a hydrophobic membrane that is permeable to water vapor; Inside and in contact with the hydrophobic membrane, a hydrophilic membrane that transports the liquid feedwater to the inner surface of the hydrophobic membrane; Inside and in contact with the hydrophilic membrane, an annular array of tubes through which flows the spacecraft coolant carrying the heat to be dissipated; and An inner exclusion tube that limits the volume of feedwater in the WME. In operation, a pressurized feedwater reservoir is connected to the volume between the exclusion tube and the coolant tubes. Feedwater fills the volume, saturates the hydrophilic membrane, and is retained by the hydrophobic membrane. The outside of the WME is exposed to space vacuum. Heat from the spacecraft coolant is conducted through the tube walls and the water-saturated hydrophilic membrane to the liquid/vapor interface at the hydrophobic membrane, causing water to evaporate to space. Makeup water flows into the hydrophilic membrane through gaps between the coolant tubes.

  14. MapA, an iron-regulated, cytoplasmic membrane protein in the cyanobacterium Synechococcus sp. strain PCC7942.

    Science.gov (United States)

    Webb, R; Troyan, T; Sherman, D; Sherman, L A

    1994-08-01

    Growth of Synechococcus sp. strain PCC 7942 in iron-deficient media leads to the accumulation of an approximately 34-kDa protein. The gene encoding this protein, mapA (membrane-associated protein A), has been cloned and sequenced (GenBank accession number, L01621). The mapA transcript is not detectable in normally grown cultures but is stably accumulated by cells grown in iron-deficient media. However, the promoter sequence for this gene does not resemble other bacterial iron-regulated promoters described to date. The carboxyl-terminal region of the derived amino acid sequence of MapA resembles bacterial proteins involved in iron acquisition, whereas the amino-terminal end of MapA has a high degree of amino acid identity with the abundant, chloroplast envelope protein E37. An approach employing improved cellular fractionation techniques as well as electron microscopy and immunocytochemistry was essential in localizing MapA protein to the cytoplasmic membrane of Synechococcus sp. strain PCC 7942. When these cells were grown under iron-deficient conditions, a significant fraction of MapA could also be localized to the thylakoid membranes.

  15. 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.

  16. 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

  17. Salt shock-inducible Photosystem I cyclic electron transfer in Synechocystis PCC6803 relies on binding of ferredoxin : NADP(+) reductase to the thylakoid membranes via its CpcD phycobilisome-linker homologous N-terminal domain

    NARCIS (Netherlands)

    van Thor, JJ; Jeanjean, R; Havaux, M; Sjollema, KA; Joset, F; Hellingwerf, KJ; Matthijs, HCP

    2000-01-01

    Relative to ferredoxin:NADP(+) reductase (FNR) from chloroplasts, the comparable enzyme in cyanobacteria contains an additional 9 kDa domain at its amino-terninus, The domain is homologous to the phycocyanin associated linker polypeptide CpcD of the light harvesting phycobilisome antennae. The pheno

  18. 具异型胞蓝细菌Anabaena sp. PCC 71 20 质膜和%Isolation of Plasma and Thylakoid Membranes from the Heterocystous Cyanobacterium Anabaena sp. PCC 7120

    Institute of Scientific and Technical Information of China (English)

    李斌; 徐冬一; 赵进东

    2001-01-01

    利用水溶性多聚体双相法分离蓝细菌Anabaena sp. PCC 7120质膜和类囊体膜两种膜系统.吸收光谱分析表明,质膜相和类囊体膜相的主要色素分别为类胡萝卜素和叶绿素.SDS_ 凝胶电泳显示这两种膜系统蛋白组成有很大差别.这种分离方法容易操作,对研究蓝细菌的膜蛋白和膜脂非常有用.

  19. Salt shock-inducible Photosystem I cyclic electron transfer in Synechocystis PCC6803 relies on binding of ferredoxin : NADP(+) reductase to the thylakoid membranes via its CpcD phycobilisome-linker homologous N-terminal domain

    NARCIS (Netherlands)

    van Thor, JJ; Jeanjean, R; Havaux, M; Sjollema, KA; Joset, F; Hellingwerf, KJ; Matthijs, HCP

    2000-01-01

    Relative to ferredoxin:NADP(+) reductase (FNR) from chloroplasts, the comparable enzyme in cyanobacteria contains an additional 9 kDa domain at its amino-terninus, The domain is homologous to the phycocyanin associated linker polypeptide CpcD of the light harvesting phycobilisome antennae. The pheno

  20. 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.

  1. Proteins causing membrane fouling in membrane bioreactors.

    Science.gov (United States)

    Miyoshi, Taro; Nagai, Yuhei; Aizawa, Tomoyasu; Kimura, Katsuki; Watanabe, Yoshimasa

    2015-01-01

    In this study, the details of proteins causing membrane fouling in membrane bioreactors (MBRs) treating real municipal wastewater were investigated. Two separate pilot-scale MBRs were continuously operated under significantly different operating conditions; one MBR was a submerged type whereas the other was a side-stream type. The submerged and side-stream MBRs were operated for 20 and 10 days, respectively. At the end of continuous operation, the foulants were extracted from the fouled membranes. The proteins contained in the extracted foulants were enriched by using the combination of crude concentration with an ultrafiltration membrane and trichloroacetic acid precipitation, and then separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The N-terminal amino acid sequencing analysis of the proteins which formed intensive spots on the 2D-PAGE gels allowed us to partially identify one protein (OmpA family protein originated from genus Brevundimonas or Riemerella anatipestifer) from the foulant obtained from the submerged MBR, and two proteins (OprD and OprF originated from genus Pseudomonas) from that obtained from the side-stream MBR. Despite the significant difference in operating conditions of the two MBRs, all proteins identified in this study belong to β-barrel protein. These findings strongly suggest the importance of β-barrel proteins in developing membrane fouling in MBRs.

  2. 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.

  3. 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.

  4. Membrane binding domains

    OpenAIRE

    Hurley, James H.

    2006-01-01

    Eukaryotic signaling and trafficking proteins are rich in modular domains that bind cell membranes. These binding events are tightly regulated in space and time. The structural, biochemical, and biophysical mechanisms for targeting have been worked out for many families of membrane binding domains. This review takes a comparative view of seven major classes of membrane binding domains, the C1, C2, PH, FYVE, PX, ENTH, and BAR domains. These domains use a combination of specific headgroup inter...

  5. Applications of membrane computing

    CERN Document Server

    Ciobanu, Gabriel; Păun, Gheorghe

    2006-01-01

    Membrane computing is a branch of natural computing which investigates computing models abstracted from the structure and functioning of living cells and from their interactions in tissues or higher-order biological structures. The models considered, called membrane systems (P systems), are parallel, distributed computing models, processing multisets of symbols in cell-like compartmental architectures. In many applications membrane systems have considerable advantages - among these are their inherently discrete nature, parallelism, transparency, scalability and nondeterminism. In dedicated cha

  6. 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.

  7. Anion exchange membrane

    Science.gov (United States)

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  8. Photoresponsive nanostructured membranes

    KAUST Repository

    Madhavan, P.

    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.

  9. How a membrane agent buys goods in a membrane store

    Institute of Scientific and Technical Information of China (English)

    Rudolf Freund; Marion Oswald; Thomas Schirk

    2007-01-01

    In this paper we consider a specific model of membrane systems, i.e. membrane systems with attributes. In these systems, the information is placed at the membranes in form of attributes, no objects are considered inside the membranes except for other membranes. The membrane system with attributes evolves according to rules that compute new values for the attributes from the attributes assigned to the membranes involved in the rule. The model of membrane systems with attributes allows us to specify business transactions in a precise way and to simulate different models for such transactions with a suitable tool for membrane systems with attributes.

  10. Plasma membrane ATPases

    DEFF Research Database (Denmark)

    Palmgren, Michael Broberg; Bækgaard, Lone; Lopez Marques, Rosa Laura

    2011-01-01

    The plasma membrane separates the cellular contents from the surrounding environment. Nutrients must enter through the plasma membrane in order to reach the cell interior, and toxic metabolites and several ions leave the cell by traveling across the same barrier. Biological pumps in the plasma me...

  11. Thin supported silica membranes

    NARCIS (Netherlands)

    Zivkovic, Tijana

    2007-01-01

    This thesis discusses several transport-related aspects relevant for the application of thin supported silica membranes for gas separation and nanofiltration. The influence of support geometry on overall membrane performance is investigated. Planar (i.e., flat plate), tubular, and multichannel suppo

  12. Membrane capacitive deionization

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Wal, van der A.

    2010-01-01

    Membrane capacitive deionization (MCDI) is an ion-removal process based on applying an electrical potential difference across an aqueous solution which flows in between oppositely placed porous electrodes, in front of which ion-exchange membranes are positioned. Due to the applied potential, ions ar

  13. 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.

  14. Ion-conducting membranes

    Energy Technology Data Exchange (ETDEWEB)

    Masel, Richard L.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

    2016-06-21

    An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums and pyridiniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a 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.

  15. Ion-conducting membranes

    Energy Technology Data Exchange (ETDEWEB)

    Masel, Richard I.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

    2017-02-28

    An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums, pyridiniums, pyrazoliums, pyrrolidiniums, pyrroliums, pyrimidiums, piperidiniums, indoliums, and triaziniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a 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.

  16. Comparative Genomic Analysis Revealed a Gene for Monoglucosyldiacylglycerol Synthase, an Enzyme for Photosynthetic Membrane Lipid Synthesis in Cyanobacteria1

    Science.gov (United States)

    Awai, Koichiro; Kakimoto, Takatoshi; Awai, Chie; Kaneko, Takakazu; Nakamura, Yuki; Takamiya, Ken-ichiro; Wada, Hajime; Ohta, Hiroyuki

    2006-01-01

    Cyanobacteria have a thylakoid lipid composition very similar to that of plant chloroplasts, yet cyanobacteria are proposed to synthesize monogalactosyldiacylglycerol (MGDG), a major membrane polar lipid in photosynthetic membranes, by a different pathway. In addition, plant MGDG synthase has been cloned, but no ortholog has been reported in cyanobacterial genomes. We report here identification of the gene for monoglucosyldiacylglycerol (MGlcDG) synthase, which catalyzes the first step of galactolipid synthesis in cyanobacteria. Using comparative genomic analysis, candidates for the gene were selected based on the criteria that the enzyme activity is conserved between two species of cyanobacteria (unicellular [Synechocystis sp. PCC 6803] and filamentous [Anabaena sp. PCC 7120]), and we assumed three characteristics of the enzyme; namely, it harbors a glycosyltransferase motif, falls into a category of genes with unknown function, and shares significant similarity in amino acid sequence between these two cyanobacteria. By a motif search of all genes of Synechocystis, BLAST searches, and similarity searches between these two cyanobacteria, we identified four candidates for the enzyme that have all the characteristics we predicted. When expressed in Escherichia coli, one of the Synechocystis candidate proteins showed MGlcDG synthase activity in a UDP-glucose-dependent manner. The ortholog in Anabaena also showed the same activity. The enzyme was predicted to require a divalent cation for its activity, and this was confirmed by biochemical analysis. The MGlcDG synthase and the plant MGDG synthase shared low similarity, supporting the presumption that cyanobacteria and plants utilize different pathways to synthesize MGDG. PMID:16714404

  17. Extracorporeal membrane oxygenation circuitry.

    Science.gov (United States)

    Lequier, Laurance; Horton, Stephen B; McMullan, D Michael; Bartlett, Robert H

    2013-06-01

    The extracorporeal membrane oxygenation circuit is made of a number of components that have been customized to provide adequate tissue oxygen delivery in patients with severe cardiac and/or respiratory failure for a prolonged period of time (days to weeks). A standard extracorporeal membrane oxygenation circuit consists of a mechanical blood pump, gas-exchange device, and a heat exchanger all connected together with circuit tubing. Extracorporeal membrane oxygenation circuits can vary from simple to complex and may include a variety of blood flow and pressure monitors, continuous oxyhemoglobin saturation monitors, circuit access sites, and a bridge connecting the venous access and arterial infusion limbs of the circuit. Significant technical advancements have been made in the equipment available for short- and long-term extracorporeal membrane oxygenation applications. Contemporary extracorporeal membrane oxygenation circuits have greater biocompatibility and allow for more prolonged cardiopulmonary support time while minimizing the procedure-related complications of bleeding, thrombosis, and other physiologic derangements, which were so common with the early application of extracorporeal membrane oxygenation. Modern era extracorporeal membrane oxygenation circuitry and components are simpler, safer, more compact, and can be used across a wide variety of patient sizes from neonates to adults.

  18. Ordered ceramic membranes

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, M.A.; Hill, C.G. Jr.; Zeltner, W.A.

    1991-10-01

    Ceramic membranes have been formed from colloidal sols coated on porous clay supports. These supported membranes have been characterized in terms of their permeabilities and permselectivities to various aqueous test solutions. The thermal stabilities and pore structures of these membranes have been characterized by preparing unsupported membranes of the correpsonding material and performing N{sub 2} adsorption-desorption and X-ray diffraction studies on these membranes. To date, membranes have been prepared from a variety of oxides, including TiO{sub 2}, SiO{sub 2}, ZrO{sub 2}, and Al{sub 2}O{sub 3}, as well as Zr-, Fe-, and Nb-doped TiO{sub 2}. In many of these membranes pore diameters are less than 2 nm, while in others the pore diameters are between 3 and 5 nm. Procedures for fabricating porous clay supports with reproducible permeabilities for pure water are also discussed. 30 refs., 59 figs., 22 tabs.

  19. CENTRIFUGAL MEMBRANE FILTRATION

    Energy Technology Data Exchange (ETDEWEB)

    Daniel J. Stepan; Bradley G. Stevens; Melanie D. Hetland

    1999-10-01

    The overall project consists of several integrated research phases related to the applicability, continued development, demonstration, and commercialization of the SpinTek centrifugal membrane filtration process. Work performed during this reporting period consisted of Phase 2 evaluation of the SpinTek centrifugal membrane filtration technology and Phase 3, Technology Partnering. During Phase 1 testing conducted at the EERC using the SpinTek ST-IIL unit operating on a surrogate tank waste, a solids cake developed on the membrane surface. The solids cake was observed where linear membrane velocities were less than 17.5 ft/s and reduced the unobstructed membrane surface area up to 25%, reducing overall filtration performance. The primary goal of the Phase 2 research effort was to enhance filtration performance through the development and testing of alternative turbulence promoter designs. The turbulence promoters were designed to generate a shear force across the entire membrane surface sufficient to maintain a self-cleaning membrane capability and improve filtration efficiency and long-term performance. Specific Phase 2 research activities included the following: System modifications to accommodate an 11-in.-diameter, two-disk rotating membrane assembly; Development and fabrication of alternative turbulence promoter designs; Testing and evaluation of the existing and alternative turbulence promoters under selected operating conditions using a statistically designed test matrix; and Data reduction and analysis; The objective of Phase 3 research was to demonstrate the effectiveness of SpinTek's centrifugal membrane filtration as a pretreatment to remove suspended solids from a liquid waste upstream of 3M's WWL cartridge technology for the selective removal of technetium (Tc).

  20. Electrochemically switchable polypyrrole coated membranes

    Energy Technology Data Exchange (ETDEWEB)

    Weidlich, Claudia, E-mail: weidlich@dechema.d [DECHEMA e.V., Karl-Winnacker-Institut, Theodor-Heuss-Allee 25, D-60486 Frankfurt am Main (Germany); Mangold, Klaus-Michael [DECHEMA e.V., Karl-Winnacker-Institut, Theodor-Heuss-Allee 25, D-60486 Frankfurt am Main (Germany)

    2011-04-01

    A method for coating membranes with polypyrrole (PPy) has been developed. Different membranes, such as microfiltration as well as ion exchanger membranes have been coated with PPy to yield electrical conductivity of the membranes. The coated membranes have been investigated by cyclic voltammetry and scanning electron microscopy and their permeability and permselectivity have been tested. The results show that PPy can be tailored as cation or anion exchanger and its porosity can be controlled to avoid any impairment of the membrane by the polymer layer. These PPy coated membranes can be applied as electrochemically switchable, functionalised membranes with controllabel and variable separation properties.

  1. Nanoengineered membrane electrode assembly interface

    Science.gov (United States)

    Song, Yujiang; Shelnutt, John A

    2013-08-06

    A membrane electrode structure suitable for use in a membrane electrode assembly (MEA) that comprises membrane-affixed metal nanoparticles whose formation is controlled by a photochemical process that controls deposition of the metal nanoparticles using a photocatalyst integrated with a polymer electrolyte membrane, such as an ionomer membrane. Impregnation of the polymer membrane with the photocatalyst prior to metal deposition greatly reduces the required amount of metal precursor in the deposition reaction solution by restricting metal reduction substantially to the formation of metal nanoparticles affixed on or near the surface of the polymer membrane with minimal formation of metallic particles not directly associated with the membrane.

  2. Hydrogen transport membranes

    Science.gov (United States)

    Mundschau, Michael V.

    2005-05-31

    Composite hydrogen transport membranes, which are used for extraction of hydrogen from gas mixtures are provided. Methods are described for supporting metals and metal alloys which have high hydrogen permeability, but which are either too thin to be self supporting, too weak to resist differential pressures across the membrane, or which become embrittled by hydrogen. Support materials are chosen to be lattice matched to the metals and metal alloys. Preferred metals with high permeability for hydrogen include vanadium, niobium, tantalum, zirconium, palladium, and alloys thereof. Hydrogen-permeable membranes include those in which the pores of a porous support matrix are blocked by hydrogen-permeable metals and metal alloys, those in which the pores of a porous metal matrix are blocked with materials which make the membrane impervious to gases other than hydrogen, and cermets fabricated by sintering powders of metals with powders of lattice-matched ceramic.

  3. Synthesis of zeolite membranes

    Institute of Scientific and Technical Information of China (English)

    JIANG Haiyang; ZHANG Baoquan; Y. S. Lin; LI Yongdan

    2004-01-01

    Zeolite membranes offer great application potentials in membrane separation and/or reaction due to their excellent separation performance and catalytic ability. Up to present, various synthesis methods of zeolite membranes have been developed, including embedded method,in-situ hydrothermal synthesis method, and secondary growth method etc. Compared with the in-situ hydrothermal synthesis method, the secondary growth method possesses a variety of advantages such as easier operation, higher controllability in crystal orientation, microstructure and film thickness, leading to much better reproducibility. This review provides a concise summary and analysis of various synthesis methods reported in the literature. In particular, the secondary growth method was discussed in detail in terms of crystal orientation, defects and crystal grain layers. Some critical issues were also highlighted, which were conducive to the improvement in the synthesis technology of zeolite membranes.

  4. 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.

  5. Membranes and Fluorescence microscopy

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2009-01-01

    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...

  6. Gel layer formation on membranes in Membrane Bioreactors

    NARCIS (Netherlands)

    Van den Brink, P.F.H.

    2014-01-01

    The widespread application of membrane bioreactors (MBRs) for municipal wastewater treatment is hampered by membrane fouling. Fouling increases energy demand, reduces process performance and creates the need for more frequent (chemical) membrane cleaning or replacement. Membrane fouling in MBRs is k

  7. Impact on floating membranes

    OpenAIRE

    Vandenberghe, Nicolas; Duchemin, Laurent

    2016-01-01

    When impacted by a rigid object, a thin elastic membrane with negligible bending rigidity floating on a liquid pool deforms. Two axisymmetric waves radiating from the impact point propagate. In the first place, a longitudinal wave front -- associated with in-plane deformation of the membrane and traveling at constant speed -- separates an outward stress free domain with a stretched but flat domain. Then, in the stretched domain a dispersive transverse wave travels at a wave speed that depends...

  8. Criticality in Plasma Membranes

    Science.gov (United States)

    Machta, Benjamin; Papanikolaou, Stefanos; Sethna, James; Veatch, Sarah

    2011-03-01

    We are motivated by recent observations of micron-sized critical fluctuations in the 2d Ising Universality class in plasma membrane vesicles that are isolated from cortical cytoskeleton. We construct a minimal model of the plasma membrane's interaction with intact cytoskeleton which explains why large scale phase separation has not been observed in Vivo. In addition, we use analytical techniques from conformal field theory and numerical simulations to investigate the form of effective forces mediated by the membrane's proximity to criticality. We show that the range of this force is maximized near a critical point and we quantify its usefulness in mediating communication using techniques from information theory. Finally we use theoretical techniques from statistical physics in conjunction with Monte-Carlo simulations to understand how criticality can be used to increase the efficiency of membrane bound receptor mediated signaling. We expect that this sort of analysis will be broadly useful in understanding and quantifying the role of lipid ``rafts'' in a wide variety of membrane bound processes. Generally, we demonstrate that critical fluctuations provide a physical mechanism to organize and spatially segregate membrane components by providing channels for interaction over relatively large distances.

  9. 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.

  10. 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.

  11. Membrane development in purple photosynthetic bacteria in response to alterations in light intensity and oxygen tension.

    Science.gov (United States)

    Niederman, Robert A

    2013-10-01

    Studies on membrane development in purple bacteria during adaptation to alterations in light intensity and oxygen tension are reviewed. Anoxygenic phototrophic such as the purple α-proteobacterium Rhodobacter sphaeroides have served as simple, dynamic, and experimentally accessible model organisms for studies of the photosynthetic apparatus. A major landmark in photosynthesis research, which dramatically illustrates this point, was provided by the determination of the X-ray structure of the reaction center (RC) in Blastochloris viridis (Deisenhofer and Michel, EMBO J 8:2149-2170, 1989), once it was realized that this represented the general structure for the photosystem II RC present in all oxygenic phototrophs. This seminal advance, together with a considerable body of subsequent research on the light-harvesting (LH) and electron transfer components of the photosynthetic apparatus has provided a firm basis for the current understanding of how phototrophs acclimate to alterations in light intensity and quality. Oxygenic phototrophs adapt to these changes by extensive thylakoid membrane remodeling, which results in a dramatic supramolecular reordering to assure that an appropriate flow of quinone redox species occurs within the membrane bilayer for efficient and rapid electron transfer. Despite the high level of photosynthetic unit organization in Rba. sphaeroides as observed by atomic force microscopy (AFM), fluorescence induction/relaxation measurements have demonstrated that the addition of the peripheral LH2 antenna complex in cells adapting to low-intensity illumination results in a slowing of the rate of electron transfer turnover by the RC of up to an order of magnitude. This is ascribed to constraints in quinone redox species diffusion between the RC and cytochrome bc1 complexes arising from the increased packing density as the intracytoplasmic membrane (ICM) bilayer becomes crowded with LH2 rings. In addition to downshifts in light intensity as a paradigm

  12. 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.

  13. 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.

  14. Biomimetic membranes and methods of making biomimetic membranes

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Fractal reconstruction of rough membrane surface related with membrane fouling in a membrane bioreactor.

    Science.gov (United States)

    Zhang, Meijia; Chen, Jianrong; Ma, Yuanjun; Shen, Liguo; He, Yiming; Lin, Hongjun

    2016-09-01

    In this paper, fractal reconstruction of rough membrane surface with a modified Weierstrass-Mandelbrot (WM) function was conducted. The topography of rough membrane surface was measured by an atomic force microscopy (AFM), and the results showed that the membrane surface was isotropous. Accordingly, the fractal dimension and roughness of membrane surface were calculated by the power spectrum method. The rough membrane surface was reconstructed on the MATLAB platform with the parameter values acquired from raw AFM data. The reconstructed membrane was much similar to the real membrane morphology measured by AFM. The parameters (including average roughness and root mean square (RMS) roughness) associated with membrane morphology for the model and real membrane were calculated, and a good match of roughness parameters between the reconstructed surface and real membrane was found, indicating the feasibility of the new developed method. The reconstructed membrane surface can be potentially used for interaction energy evaluation.

  16. Membrane biology: fission behind BARs.

    Science.gov (United States)

    Haucke, Volker

    2012-06-05

    Membrane bending is accomplished in part by amphipathic helix insertion into the bilayer and the assembly of BAR domain scaffolds preparing the membrane for fission. Two recent studies highlight the roles of amphipathic helices and BAR scaffolds in membrane fission and establish the structural basis of membrane bending by the N-BAR protein endophilin.

  17. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-11-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the current research, the electrical conductivity and Seebeck coefficient were measured as a function of temperature in air. Based on these measurements, the charge carrier concentration, net acceptor dopant concentration, activation energy of conduction and mobility were estimated. The studies on the fracture toughness of the LSFT and dual phase membranes at room temperature have been completed and reported previously. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affects the mechanical properties. To study the effect of temperature on the membranes when exposed to an inert environment, the membranes (LAFT and Dual phase) were heat treated at 1000 C in air and N{sub 2} atmosphere and hardness and fracture toughness of the membranes were studied after the treatment. The indentation method was used to find the fracture toughness and the effect of the heat treatment on the mechanical properties of the membranes. Further results on the investigation of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appears to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model will serve to study ''frozen'' profiles in patterned or composite membranes.

  18. Evolutionary origins of membrane proteins

    Science.gov (United States)

    Mulkidjanian, Armen Y.; Galperin, Michael Y.

    Although the genes that encode membrane proteins make about 30% of the sequenced genomes, the evolution of membrane proteins and their origins are still poorly understood. Here we address this topic by taking a closer look at those membrane proteins the ancestors of which were present in the Last Universal Common Ancestor, and in particular, the F/V-type rotating ATPases. Reconstruction of their evolutionary history provides hints for understanding not only the origin of membrane proteins, but also of membranes themselves. We argue that the evolution of biological membranes could occur as a process of coevolution of lipid bilayers and membrane proteins, where the increase in the ion-tightness of the membrane bilayer may have been accompanied by a transition from amphiphilic, pore-forming membrane proteins to highly hydrophobic integral membrane complexes.

  19. Electrical properties of polar membranes

    CERN Document Server

    Mosgaard, Lars D; Heimburg, Thomas

    2014-01-01

    Biological membranes are capacitors that can be charged by applying a field across the membrane. The charges on the capacitor exert a force on the membrane that leads to electrostriction, i.e. a thinning of the membrane. Since the force is quadratic in voltage, negative and positive voltage have an identical influence on the physics of symmetric membranes. However, this is not the case for a membrane with an asymmetry leading to a permanent electric polarization. Positive and negative voltages of identical magnitude lead to different properties. Such an asymmetry can originate from a lipid composition that is different on the two monolayers of the membrane, or from membrane curvature. The latter effect is called 'flexoelectricity'. As a consequence of permanent polarization, the membrane capacitor is discharged at a voltage different from zero. This leads to interesting electrical phenomena such as outward or inward rectification of membrane permeability. Here, we introduce a generalized theoretical framework...

  20. 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....

  1. Surface glycosylation of polymeric membranes

    Institute of Scientific and Technical Information of China (English)

    DAI ZhengWei; WAN LingShu; XU ZhiKang

    2008-01-01

    Surface glycosylation of polymeric membranes has been inspired by the structure of natural biomembranes. It refers to that glycosyl groups are introduced onto the membrane surface by various strategies, which combine the separation function of the membrane with the biological function of the saccharides in one system. In this review, progress in the surface glycosylation of polymeric membranes is highlighted in two aspects, i.e. the glycosylation methods and the potential applications of the surface-glycosylated membranes.

  2. 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 m

  3. 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.

  4. 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.

  5. Recent Advances in Pd-Based Membranes for Membrane Reactors.

    Science.gov (United States)

    Arratibel Plazaola, Alba; Pacheco Tanaka, David Alfredo; Van Sint Annaland, Martin; Gallucci, Fausto

    2017-01-01

    Palladium-based membranes for hydrogen separation have been studied by several research groups during the last 40 years. Much effort has been dedicated to improving the hydrogen flux of these membranes employing different alloys, supports, deposition/production techniques, etc. High flux and cheap membranes, yet stable at different operating conditions are required for their exploitation at industrial scale. The integration of membranes in multifunctional reactors (membrane reactors) poses additional demands on the membranes as interactions at different levels between the catalyst and the membrane surface can occur. Particularly, when employing the membranes in fluidized bed reactors, the selective layer should be resistant to or protected against erosion. In this review we will also describe a novel kind of membranes, the pore-filled type membranes prepared by Pacheco Tanaka and coworkers that represent a possible solution to integrate thin selective membranes into membrane reactors while protecting the selective layer. This work is focused on recent advances on metallic supports, materials used as an intermetallic diffusion layer when metallic supports are used and the most recent advances on Pd-based composite membranes. Particular attention is paid to improvements on sulfur resistance of Pd based membranes, resistance to hydrogen embrittlement and stability at high temperature.

  6. Recent Advances in Pd-Based Membranes for Membrane Reactors

    Directory of Open Access Journals (Sweden)

    Alba Arratibel Plazaola

    2017-01-01

    Full Text Available Palladium-based membranes for hydrogen separation have been studied by several research groups during the last 40 years. Much effort has been dedicated to improving the hydrogen flux of these membranes employing different alloys, supports, deposition/production techniques, etc. High flux and cheap membranes, yet stable at different operating conditions are required for their exploitation at industrial scale. The integration of membranes in multifunctional reactors (membrane reactors poses additional demands on the membranes as interactions at different levels between the catalyst and the membrane surface can occur. Particularly, when employing the membranes in fluidized bed reactors, the selective layer should be resistant to or protected against erosion. In this review we will also describe a novel kind of membranes, the pore-filled type membranes prepared by Pacheco Tanaka and coworkers that represent a possible solution to integrate thin selective membranes into membrane reactors while protecting the selective layer. This work is focused on recent advances on metallic supports, materials used as an intermetallic diffusion layer when metallic supports are used and the most recent advances on Pd-based composite membranes. Particular attention is paid to improvements on sulfur resistance of Pd based membranes, resistance to hydrogen embrittlement and stability at high temperature.

  7. [Amniotic membrane in conjunctivoplasty].

    Science.gov (United States)

    Samoila, O; Lacramioara, Totu; Mihu, D

    2012-01-01

    The basic principles of conjunctival reconstruction are similar in all pathologies that inflict conjunctival tissue loss. Large conjunctival defects are difficult to treat, with little conjunctival reserve that can be used to close the defect. The study had the objective to find alternatives to conjunctival autograft. Frozen amniotic membrane was investigated. From 27 cases, 22 cases were reconstructed using amniotic membrane alone, but in 5 cases conjunctival autograft was also needed. Bulbar conjunctiva was reconstructed in 23 cases, of which 19 with pterygium, 3 with conjunctival tumors, one operatory plague. Fornix reconstruction was carried out in 4 cases, one tumor and 3 symblepharons (2 after conjunctival burns and one pemfigus). The rate of pterygium recurrence was 7,14%. Amniotic membrane can heal large defects of the conjunctiva, either bulbar or forniceal.

  8. Impact on floating membranes

    CERN Document Server

    Vandenberghe, Nicolas

    2016-01-01

    When impacted by a rigid object, a thin elastic membrane with negligible bending rigidity floating on a liquid pool deforms. Two axisymmetric waves radiating from the impact point propagate. In the first place, a longitudinal wave front -- associated with in-plane deformation of the membrane and traveling at constant speed -- separates an outward stress free domain with a stretched but flat domain. Then, in the stretched domain a dispersive transverse wave travels at a wave speed that depends on the local stretching rate. We study the dynamics of this fluid-body system and we show that the wave dynamics is similar to the capillary waves that propagate at a liquid-gas interface but with a surface tension coefficient that depends on impact speed. We emphasize the role of the stretching in the membrane in the wave dynamics but also in the development of a buckling instability that give rise to radial wrinkles.

  9. Effect of membrane curvature on lateral distribution of membrane proteins

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Several membrane proteins exhibit interesting shapes that increases their preference for certain membrane curvatures. Both peripheral and transmembrane proteins are tested with respect to their affinity for a spectrum of high membrane curvatures. We generate high membrane curvatures by pulling...... membrane tubes out of Giant Unilamellar lipid Vesicles (GUVs). The tube diameter can be tuned by aspirating the GUV into a micropipette for controlling the membrane tension. By using fluorescently labled proteins we have shown that sorting of proteins like e.g. FBAR onto tubes is significantly increased...

  10. 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

  11. Membrane accessibility of glutathione

    DEFF Research Database (Denmark)

    Garcia, Alvaro; Eljack, Nasma D; Sani, Marc-Antoine

    2015-01-01

    Regulation of the ion pumping activity of the Na(+),K(+)-ATPase is crucial to the survival of animal cells. Recent evidence has suggested that the activity of the enzyme could be controlled by glutathionylation of cysteine residue 45 of the β-subunit. Crystal structures so far available indicate...... that this cysteine is in a transmembrane domain of the protein. Here we have analysed via fluorescence and NMR spectroscopy as well as molecular dynamics simulations whether glutathione is able to penetrate into the interior of a lipid membrane. No evidence for any penetration of glutathione into the membrane...

  12. Reference: 757 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available of prothylakoids and transition into mature thylakoid stacks. The AtTerC gene encodes an integral membrane ...nt chloroplasts lacked thylakoids, did not have grana stacks, and showed numerous globular structures of var

  13. 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.

  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. Graphene Trans-Electrode Membranes

    Science.gov (United States)

    Kuan, Aaron; Bo, Lu; Rollings, Ryan; Dressen, Don; Branton, Daniel; Golovchenko, Jene

    2014-03-01

    We report an electrical study of suspended single-layer graphene membranes separating reservoirs of electrolyte solution. Because the opposing reservoirs are separated only by an atomically thin membrane, the trans-conductance (ionic current response to a voltage across the membrane) is extremely sensitive to nanoscale defects in the membrane. This sensitivity allows the precise examination and characterization of intrinsic defects in graphene membranes, as well as engineered defects for devices. We will discuss methods for creating single nanopores or distributed defects in our graphene membranes, with the applications of nanopore DNA sequencing and water desalination in mind.

  16. Mutual Mobile Membranes with Timers

    Directory of Open Access Journals (Sweden)

    Gabriel Ciobanu

    2009-10-01

    Full Text Available A feature of current membrane systems is the fact that objects and membranes are persistent. However, this is not true in the real world. In fact, cells and intracellular proteins have a well-defined lifetime. Inspired from these biological facts, we define a model of systems of mobile membranes in which each membrane and each object has a timer representing their lifetime. We show that systems of mutual mobile membranes with and without timers have the same computational power. An encoding of timed safe mobile ambients into systems of mutual mobile membranes with timers offers a relationship between two formalisms used in describing biological systems.

  17. 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.

  18. 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...

  19. Composite oxygen transport membrane

    Energy Technology Data Exchange (ETDEWEB)

    Christie, Gervase Maxwell; Lane, Jonathan A.

    2016-11-15

    A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

  20. Fusion of biological membranes

    Indian Academy of Sciences (India)

    K Katsov; M Müller; M Schick

    2005-06-01

    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 field theory is applied to examine the free energy barriers in the different scenarios.

  1. Composite oxygen transport membrane

    Science.gov (United States)

    Christie, Gervase Maxwell; Lane, Jonathan A.

    2014-08-05

    A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

  2. Hydrogen-selective membrane

    Science.gov (United States)

    Collins, J.P.; Way, J.D.

    1995-09-19

    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.

  3. M, Membranes, and OM

    CERN Document Server

    García, J A; Vergara, J D; Guijosa, Alberto

    2003-01-01

    We examine the extent to which the action for the membrane of M-theory (the eleven-dimensional construct which underlies and unifies all of the known string theories) simplifies in the so-called Open Membrane (OM) limit, a limit which lies at the root of the various manifestations of noncommutativity in the string context. In order for the discussion to be relatively self-contained, we start out by reviewing why the strings of ten-dimensional string theory are in fact membranes (M2-branes) living in eleven dimensions. After that, we recall the definition of OM theory, as well as the arguments showing that it is part of a larger, eleven-dimensional structure known as Galilean or Wrapped M2-brane (WM2) theory. WM2 theory is a rich theoretical construct which is interesting for several reasons, in particular because it is essentially a toy model of M-theory. We then proceed to deduce a membrane action for OM/WM2 theory, and spell out its implications for the four different types of M2-branes one can consider in ...

  4. Dirac membrane and hadrons

    CERN Document Server

    Trzetrzelewski, Maciej

    2011-01-01

    In c=1 units the product (mass x radius) for the neutron and the proton is about 4.7\\hbar assuming their radii equal to 1fm. We show that the corresponding products for the Dirac neutral and charged membrane coincide and are equal 1.6\\hbar.

  5. Bioelectrochemistry II: Membrane Phenomena,

    Science.gov (United States)

    1984-12-11

    techniques for studying protein-lipid interactions and molecular movements in membranes. He discussed spin labels, fluorescent probes, NMR studies and recent...transduction in chloroplasts . Re reviewed the components and reactions at the two reaction centers In photosynthesis, and carefully correlated the structure...particularly useful for considering biological problems involving charge movement (e.g., ion transport, energy transduction, and electrical excitation

  6. Imaging of membranous dysmenorrhea

    Energy Technology Data Exchange (ETDEWEB)

    Rouanet, J.P.; Daclin, P.Y.; Turpin, F.; Karam, R.; Prayssac-Salanon, A. [Dept. of Radiology, C. M. C. Beausoleil, Montpellier (France); Courtieu, C.R. [Dept. of Gynecology, C. M. C. Beausoleil, Montpellier (France); Maubon, A.J. [Dept. of Radiology, C. M. C. Beausoleil, Montpellier (France); Dept. of Radiology, C. H. U. Dupuytren, Limoges (France)

    2001-06-01

    Membranous dysmenorrhea is an unusual clinical entity. It is characterized by the expulsion of huge fragments of endometrium during the menses, favored by hormonal abnormality or drug intake. This report describes a case with clinical, US, and MRI findings before the expulsion. Differential diagnoses are discussed. (orig.)

  7. Synthetic membranes and membrane processes with counterparts in biological systems

    Science.gov (United States)

    Matson, Stephen L.

    1996-02-01

    Conventional synthetic membranes, fashioned for the most part from rather unremarkable polymeric materials, are essentially passive structures that achieve various industrial and biomedical separations through simple and selective membrane permeation processes. Indeed, simplicity of membrane material, structure, and function has long been perceived as a virtue of membranes relative to other separation processes with which they compete. The passive membrane separation processes -- exemplified by micro- and ultrafiltration, dialysis, reverse osmosis, and gas permeation -- differ from one another primarily in terms of membrane morphology or structure (e.g., porous, gel-type, and nonporous) and the permeant transport mechanism and driving force (e.g., diffusion, convection, and 'solution/diffusion'). The passive membrane separation processes have in common the fact that interaction between permeant and membrane material is typically weak and physicochemical in nature; indeed, it is frequently an objective of membrane materials design to minimize interaction between permeant and membrane polymer, since such strategies can minimize membrane fouling. As a consequence, conventional membrane processes often provide only modest separation factors or permselectivities; that is, they are more useful in performing 'group separations' (i.e., the separation of different classes of material) than they are in fractionating species within a given class. It has long been recognized within the community of membrane technologists that biological membrane structures and their components are extraordinarily sophisticated and powerful as compared to their synthetic counterparts. Moreover, biomembranes and related biological systems have been 'designed' according to a very different paradigm -- one that frequently maximizes and capitalizes on extraordinarily strong and biochemically specific interactions between components of the membrane and species interacting with them. Thus, in recent

  8. Dynamics of multicomponent lipid membranes

    Science.gov (United States)

    Camley, Brian Andrew

    We present theoretical and computational descriptions of the dynamics of multicomponent lipid bilayer membranes. These systems are both model systems for "lipid rafts" in cell membranes and interesting physical examples of quasi-two-dimensional fluids. Our chief tool is a continuum simulation that uses a phase field to track the composition of the membrane, and solves the hydrodynamic equations exactly using the appropriate Green's function (Oseen tensor) for the membrane. We apply this simulation to describe the diffusion of domains in phase-separated membranes, the dynamics of domain flickering, and the process of phase separation in lipid membranes. We then derive an analytical theory to describe domain flickering that is consistent with our simulation results, and use this to analyze experimental measurements of membrane domains. Through this method, we measure the membrane viscosity solely from fluorescence microscopy measurements. We study phase separation in quasi-two-dimensional membranes in depth with both simulations and scaling theory, and classify the different scaling regimes and morphologies, which differ from pure two-dimensional fluids. Our results may explain previous inconsistent measurements of the dynamical scaling exponent for phase separation in membranes. We also extend our theory beyond the simplest model, including the possibility that the membrane will be viscoelastic, as well as considering the inertia of the membrane and the fluid surrounding the membrane.

  9. Purification of recombinant BtpA and Ycf3, proteins involved in membrane protein biogenesis in Synechocystis PCC 6803.

    Science.gov (United States)

    Schwabe, Tatjana M E; Gloddek, Kirsten; Schluesener, Daniela; Kruip, Jochen

    2003-03-25

    The gene products Ycf3 (hypothetical chloroplast open reading frame) and BtpA (biogenesis of thylakoid protein) are thought to be involved in the biogenesis of the membrane protein complex photosystem I (PSI) from Synechocystis PCC 6803. PSI consists of 12 different subunits and binds more than 100 cofactors, making it a model protein to study different aspects of membrane protein biogenesis. For a detailed biophysical characterization of Ycf3 and BtpA pure proteins must be available in sufficient quantities. Therefore we cloned the corresponding genes into expression vectors. To facilitate purification we created His-tagged versions of Ycf3 and BtpA in addition to the unmodified forms. Immobilized metal affinity chromatography (IMAC) yielded His-tagged proteins which were used for the production of antibodies. Purification strategies for non-tagged proteins could also be established: Ycf3 could be purified in soluble form using a two-step purification in which ammonium sulfate precipitation was combined with anion-exchange chromatography (IEC). BtpA had to be purified from inclusion bodies by two-consecutive IEC steps under denaturing conditions. An optimized refolding protocol was established that yielded pure BtpA. In all cases, MALDI-TOF peptide mass fingerprinting (PMF) was used to confirm protein identity. Initially, size exclusion chromatography and CD-spectroscopy were used for biophysical characterization of the proteins. Both Ycf3 and BtpA show homo-oligomerization in vitro. In summary, purification protocols for Ycf3 and BtpA have been designed that yield pure proteins which can be used to probe the molecular function of these proteins for membrane protein biogenesis.

  10. Selective permeability of PVA membranes. I - Radiation-crosslinked membranes

    Science.gov (United States)

    Katz, M. G.; Wydeven, T., Jr.

    1981-01-01

    The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution-diffusion model for transport across the membranes, in which pressure-dependent permeability coefficients are employed.

  11. Selective Permeability of PVA Membranes. I: Radiation-Crosslinked Membranes

    Science.gov (United States)

    Katz, Moshe G.; Wydeven, Theodore, Jr.

    1981-01-01

    The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution-diffusion model for transport across the membranes, in which pressure-dependent permeability coefficients are employed.

  12. Influence of membrane properties on fouling in submerged membrane bioreactors

    NARCIS (Netherlands)

    Marel, van der P.; Zwijnenburg, A.; Kemperman, A.; Wessling, M.; Temmink, B.G.; Meer, van der W.

    2010-01-01

    Polymeric flat-sheet membranes with different properties were used in filtration experiments with activated sludge from a pilot-scale MBR to investigate the influence of membrane pore size, surface porosity, pore morphology, and hydrophobicity on membrane fouling. An improved flux-step method was us

  13. Disorders of the erythrocyte membrane

    Directory of Open Access Journals (Sweden)

    Sophia Delicou

    2015-12-01

    Full Text Available Hemolytic anemia due to abnormalities of the erythrocyte membrane comprises an important group of inherited disorders. These include hereditary spherocytosis, hereditary elliptocytosis, hereditary pyropoikilocytosis, and the hereditary stomatocytosis syndromes. The erythrocyte membrane skeleton composed of spectrin, actin, and several other proteins is essential for the maintenance of the erythrocyte shape, reversible deformability, and membrane structural integrity in addition to controlling the lateral mobility of integral membrane proteins. These disorders are characterized by clinical and laboratory heterogeneity and, as evidenced by recent molecular studies, by genetic heterogeneity. Defects in various proteins involved in linking the lipid bilayer to membrane skeleton result in loss in membrane cohesion leading to surface area loss and hereditary spherocytosis while defects in proteins involved in lateral interactions of the spectrin-based skeleton lead to decreased mechanical stability, membrane fragmentation and hereditary elliptocytosis. The disease severity is primarily dependent on the extent of membrane surface area loss. Treatment with splenectomy is curative in most patients.

  14. Biological Fuel Cells and Membranes.

    Science.gov (United States)

    Ghassemi, Zahra; Slaughter, Gymama

    2017-01-17

    Biofuel cells have been widely used to generate bioelectricity. Early biofuel cells employ a semi-permeable membrane to separate the anodic and cathodic compartments. The impact of different membrane materials and compositions has also been explored. Some membrane materials are employed strictly as membrane separators, while some have gained significant attention in the immobilization of enzymes or microorganisms within or behind the membrane at the electrode surface. The membrane material affects the transfer rate of the chemical species (e.g., fuel, oxygen molecules, and products) involved in the chemical reaction, which in turn has an impact on the performance of the biofuel cell. For enzymatic biofuel cells, Nafion, modified Nafion, and chitosan membranes have been used widely and continue to hold great promise in the long-term stability of enzymes and microorganisms encapsulated within them. This article provides a review of the most widely used membrane materials in the development of enzymatic and microbial biofuel cells.

  15. Novicidin interactions with phospholipid membranes

    DEFF Research Database (Denmark)

    Balakrishnan, Vijay Shankar

    Antimicrobial peptides target bacterial cell membranes and are considered as potential antibiotics. Their interactions with cell membranes are studied using different approaches. This thesis comprises of the biophysical investigations on the antimicrobial peptide Novicidin, interacting with lipos...

  16. Extra-corporeal membrane oxygenation

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/007234.htm Extracorporeal membrane oxygenation To use the sharing features on this page, please enable JavaScript. Extracorporeal membrane oxygenation (ECMO) is a treatment that uses a ...

  17. 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)

  18. 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)

  19. Membrane distillation for milk concentration

    NARCIS (Netherlands)

    Moejes, S.N.; Romero Guzman, Maria; Hanemaaijer, J.H.; Barrera, K.H.; Feenstra, L.; Boxtel, van A.J.B.

    2015-01-01

    Membrane distillation is an emerging technology to concentrate liquid products while producing high quality water as permeate. Application for desalination has been studied extensively the past years, but membrane distillation has also potential to produce concentrated food products like concentrate

  20. Nonphotochemical quenching of excitation energy in photosystem II. A picosecond time-resolved study of the low yield of chlorophyll a fluorescence induced by single-turnover flash in isolated spinach thylakoids.

    Science.gov (United States)

    Vasil'ev, S; Bruce, D

    1998-08-04

    Chlorophyll a fluorescence emission is widely used as a noninvasive measure of a number of parameters related to photosynthetic efficiency in oxygenic photosynthetic organisms. The most important component for the estimation of photochemistry is the relative increase in fluorescence yield between dark-adapted samples which have a maximal capacity for photochemistry and a minimal fluorescence yield (F0) and light-saturated samples where photochemistry is saturated and fluorescence yield is maximal (Fm). However, when photosynthesis is saturated with a short (less than 50 micro(s)) flash of light, which induces only one photochemical turnover of photosystem II, the maximal fluorescence yield is significantly lower (Fsat) than when saturation is achieved with a millisecond duration multiturnover flash (Fm). To investigate the origins of the difference in fluorescence yield between these two conditions, our time-resolved fluorescence apparatus was modified to allow collection of picosecond time-resolved decay kinetics over a short time window immediately following a saturating single-turnover flash (Fsat) as well as after a multiturnover saturating pulse (Fm). Our data were analyzed with a global kinetic model based on an exciton radical pair equilibrium model for photosystem II. The difference between Fm and Fsat was modeled well by changing only the rate constant for quenching of excitation energy in the antenna of photosystem II. An antenna-based origin for the quenching was verified experimentally by the observation that addition of the antenna quencher 5-hydroxy-1,4-naphthoquinone to thylakoids under Fm conditions resulted in decay kinetics and modeled kinetic parameters very similar to those observed under Fsat conditions in the absence of added quinone. Our data strongly support the origin of low fluorescence yield at Fsat to be an antenna-based nonphotochemical quenching of excitation energy in photosystem II which has not usually been considered explicitly in

  1. 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.

  2. An Electrochromic Bipolar Membrane Diode.

    Science.gov (United States)

    Malti, Abdellah; Gabrielsson, Erik O; Crispin, Xavier; Berggren, Magnus

    2015-07-01

    Conducting polymers with bipolar membranes (a complementary stack of selective membranes) may be used to rectify current. Integrating a bipolar membrane into a polymer electrochromic display obviates the need for an addressing backplane while increasing the device's bistability. Such devices can be made from solution-processable materials.

  3. 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 str...

  4. Mesoporous and microporous titania membranes

    NARCIS (Netherlands)

    Sekulic-Kuzmanovic, Jelena

    2004-01-01

    The research described in this thesis deals with the synthesis and properties of ceramic oxide membrane materials. Since most of the currently available inorganic membranes with required separation properties have limited reliability and long-term stability, membranes made of new oxide materials tha

  5. Impact of sludge flocs on membrane fouling in membrane bioreactors

    DEFF Research Database (Denmark)

    Christensen, Morten Lykkegaard; Niessen, Wolfgang; Jørgensen, Mads Koustrup

    Membrane bioreactors (MBR) are widely used for wastewater treatment, but membrane fouling reduces membrane performance and thereby increases the cost for membranes and fouling control. Large variation in filtration properties measured as flux decline was observed for the different types of sludges...... and the physico-chemical properties, is an efficient method to reduce membrane fouling in the MBR. High concentration of suspended extracellular substances (EPS) and small particles (up to 10 µm) resulted in pronounced fouling propensity. The membrane fouling resistance was reduced at high concentration...... flocs reduced membrane fouling, and more compact and strong flocs were formed if the concentration of divalent ions were high. Sludge was fractionated by centrifugation providing supernatant with soluble EPS and colloidal particles but without flocs. Filtration test on untreated sludge and supernatant...

  6. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-02-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. Thermogravimetric analysis (TGA) was carried out on La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} to investigate oxygen deficiency ({delta}) of the sample. The TGA was performed in a controlled atmosphere using oxygen, argon, carbon monoxide and carbon dioxide with adjustable gas flow rates. In this experiment, the weight loss and gain of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} was directly measured by TGA. The weight change of the sample was evaluated at between 600 and 1250 C in air or 1000 C as a function of oxygen partial pressure. The oxygen deficiencies calculated from TGA data as a function of oxygen activity and temperature will be estimated and compared with that from neutron diffraction measurement in air. The LSFT and LSFT/CGO membranes were fabricated from the powder obtained from Praxair Specialty Ceramics. The sintered membranes were subjected to microstructure analysis and hardness analysis. The LSFT membrane is composed of fine grains with two kinds of grain morphology. The grain size distribution was characterized using image analysis. In LSFT/CGO membrane a lot of grain pullout was observed from the less dense, porous phase. The hardness of the LSFT and dual phase membranes were studied at various loads. The hardness values obtained from the cross section of the membranes were also compared to that of the values obtained from the surface. An electrochemical cell has been designed and built for measurements of the Seebeck coefficient as a function of temperature and pressure. Measurements on La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} as a function of temperature an oxygen partial pressure are reported. Further analysis of the dilatometry data obtained previously is presented. A series of isotope transients

  7. 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.

  8. 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...

  9. Membrane separation of hydrocarbons

    Science.gov (United States)

    Chang, Y. Alice; Kulkarni, Sudhir S.; Funk, Edward W.

    1986-01-01

    Mixtures of heavy oils and light hydrocarbons may be separated by passing the mixture through a polymeric membrane. The membrane which is utilized to effect the separation comprises a polymer which is capable of maintaining its integrity in the presence of hydrocarbon compounds and which has been modified by being subjected to the action of a sulfonating agent. Sulfonating agents which may be employed will include fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, etc., the surface or bulk modified polymer will contain a degree of sulfonation ranging from about 15 to about 50%. The separation process is effected at temperatures ranging from about ambient to about 100.degree. C. and pressures ranging from about 50 to about 1000 psig.

  10. 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...

  11. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-07-01

    This is the fourth quarterly report on a new study to develop a ceramic membrane/metal joint. The first experiments using the La-Sr-Fe-O ceramic are reported. Some of the analysis performed on the samples obtained are commented upon. A set of experiments to characterize the mechanical strength and thermal fatigue properties of the joints has been designed and begun. Finite element models of joints used to model residual stresses are described.

  12. Electrochemical polymer electrolyte membranes

    CERN Document Server

    Fang, Jianhua; Wilkinson, David P

    2015-01-01

    Electrochemical Polymer Electrolyte Membranes covers PEMs from fundamentals to applications, describing their structure, properties, characterization, synthesis, and use in electrochemical energy storage and solar energy conversion technologies. Featuring chapters authored by leading experts from academia and industry, this authoritative text: Discusses cutting-edge methodologies in PEM material selection and fabricationPoints out important challenges in developing PEMs and recommends mitigation strategies to improve PEM performanceAnalyzes the cur

  13. Membrane Transport Phenomena (MTP)

    Science.gov (United States)

    Mason, Larry W.

    1997-01-01

    The third semi-annual period of the MTP project has been involved with performing experiments using the Membrane Transport Apparatus (MTA), development of analysis techniques for the experiment results, analytical modeling of the osmotic transport phenomena, and completion of a DC-9 microgravity flight to test candidate fluid cell geometries. Preparations were also made for the MTP Science Concept Review (SCR), held on 13 June 1997 at Lockheed Martin Astronautics in Denver. These activities are detailed in the report.

  14. Viral membrane fusion

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, Stephen C., E-mail: harrison@crystal.harvard.edu

    2015-05-15

    Membrane fusion is an essential step when enveloped viruses enter cells. Lipid bilayer fusion requires catalysis to overcome a high kinetic barrier; viral fusion proteins are the agents that fulfill this catalytic function. Despite a variety of molecular architectures, these proteins facilitate fusion by essentially the same generic mechanism. Stimulated by a signal associated with arrival at the cell to be infected (e.g., receptor or co-receptor binding, proton binding in an endosome), they undergo a series of conformational changes. A hydrophobic segment (a “fusion loop” or “fusion peptide”) engages the target-cell membrane and collapse of the bridging intermediate thus formed draws the two membranes (virus and cell) together. We know of three structural classes for viral fusion proteins. Structures for both pre- and postfusion conformations of illustrate the beginning and end points of a process that can be probed by single-virion measurements of fusion kinetics. - Highlights: • Viral fusion proteins overcome the high energy barrier to lipid bilayer merger. • Different molecular structures but the same catalytic mechanism. • Review describes properties of three known fusion-protein structural classes. • Single-virion fusion experiments elucidate mechanism.

  15. Quantum charged rigid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Cordero, Ruben [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del I.P.N., Unidad Adolfo Lopez Mateos, Edificio 9, 07738 Mexico, D.F. (Mexico); Molgado, Alberto [Unidad Academica de Fisica, Universidad Autonoma de Zacatecas, Zacatecas Zac. (Mexico); Rojas, Efrain, E-mail: cordero@esfm.ipn.mx, E-mail: amolgado@fisica.uaz.edu.mx, E-mail: efrojas@uv.mx [Departamento de Fisica, Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico)

    2011-03-21

    The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski-Hamiltonian approach, we observed that the theory comprises the management of both first- and second-class constraints. We thus show that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits us to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.

  16. Novel Catalytic Membrane Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Stuart Nemser, PhD

    2010-10-01

    There are many industrial catalytic organic reversible reactions with amines or alcohols that have water as one of the products. Many of these reactions are homogeneously catalyzed. In all cases removal of water facilitates the reaction and produces more of the desired chemical product. By shifting the reaction to right we produce more chemical product with little or no additional capital investment. Many of these reactions can also relate to bioprocesses. Given the large number of water-organic compound separations achievable and the ability of the Compact Membrane Systems, Inc. (CMS) perfluoro membranes to withstand these harsh operating conditions, this is an ideal demonstration system for the water-of-reaction removal using a membrane reactor. Enhanced reaction synthesis is consistent with the DOE objective to lower the energy intensity of U.S. industry 25% by 2017 in accord with the Energy Policy Act of 2005 and to improve the United States manufacturing competitiveness. The objective of this program is to develop the platform technology for enhancing homogeneous catalytic chemical syntheses.

  17. Quantum charged rigid membrane

    CERN Document Server

    Cordero, Ruben; Rojas, Efrain

    2010-01-01

    The early Dirac proposal to model the electron as a charged membrane is reviewed. A rigidity term, instead of the natural membrane tension, involving linearly the extrinsic curvature of the worldvolume swept out by the membrane is considered in the action modeling the bubble in the presence of an electromagnetic field. We set up this model as a genuine second-order derivative theory by considering a non-trivial boundary term which plays a relevant part in our formulation. The Lagrangian in question is linear in the bubble acceleration and by means of the Ostrogradski-Hamiltonian approach we observed that the theory comprises the management of both first- and second-class constraints. We show thus that our second-order approach is robust allowing for a proper quantization. We found an effective quantum potential which permits to compute bounded states for the system. We comment on the possibility of describing brane world universes by invoking this kind of second-order correction terms.

  18. Virus separation using membranes.

    Science.gov (United States)

    Grein, Tanja A; Michalsky, Ronald; Czermak, Peter

    2014-01-01

    Industrial manufacturing of cell culture-derived viruses or virus-like particles for gene therapy or vaccine production are complex multistep processes. In addition to the bioreactor, such processes require a multitude of downstream unit operations for product separation, concentration, or purification. Similarly, before a biopharmaceutical product can enter the market, removal or inactivation of potential viral contamination has to be demonstrated. Given the complexity of biological solutions and the high standards on composition and purity of biopharmaceuticals, downstream processing is the bottleneck in many biotechnological production trains. Membrane-based filtration can be an economically attractive and efficient technology for virus separation. Viral clearance, for instance, of up to seven orders of magnitude has been reported for state of the art polymeric membranes under best conditions.This chapter summarizes the fundamentals of virus ultrafiltration, diafiltration, or purification with adsorptive membranes. In lieu of an impractical universally applicable protocol for virus filtration, application of these principles is demonstrated with two examples. The chapter provides detailed methods for production, concentration, purification, and removal of a rod-shaped baculovirus (Autographa californica M nucleopolyhedrovirus, about 40 × 300 nm in size, a potential vector for gene therapy, and an industrially important protein expression system) or a spherical parvovirus (minute virus of mice, 22-26 nm in size, a model virus for virus clearance validation studies).

  19. Recycling of used perfluorosulfonic acid membranes

    Science.gov (United States)

    Grot, Stephen; Grot, Walther

    2007-08-14

    A method for recovering and recycling catalyst coated fuel cell membranes includes dissolving the used membranes in water and solvent, heating the dissolved membranes under pressure and separating the components. Active membranes are produced from the recycled materials.

  20. Surface glycosylation of polymeric membranes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Surface glycosylation of polymeric membranes has been inspired by the structure of natural biomem-branes. It refers to that glycosyl groups are introduced onto the membrane surface by various strate-gies, which combine the separation function of the membrane with the biological function of the sac-charides in one system. In this review, progress in the surface glycosylation of polymeric membranes is highlighted in two aspects, i.e. the glycosylation methods and the potential applications of the sur-face-glycosylated membranes.

  1. [Effect of Membrane Wettability on Membrane Fouling and Chemical Durability of SPG Membranes].

    Science.gov (United States)

    Zhang, Jing; Xiao, Tai-min; Zhang, Jing; Cao, Li-ya; Du, Ya-wei; Liu, Chun; Zhang, Lei

    2015-05-01

    Shirasu porous glass (SPG) membranes have been applied for microbubble aeration in aerobic wastewater treatment. In the present study, both hydrophilic and hydrophobic SPG membranes were used in a microbubble-aerated biofilm reactor with online chemical cleaning, and their membrane fouling and chemical durability were determined to be strongly dependent on the membrane wettability. The fouling layer formed on the surface of both membranes was confirmed to be mainly organic fouling, and the hydrophobic membrane showed a relatively stronger resistance to the organic fouling. The severe chemical corrosion of the hydrophilic membrane was observed due to exposure to the alkaline sodium hypochlorite solution used for chemical cleaning, which resulted in significant increases in the median pore diameter and the porosity. On the other hand, the pore structure of the hydrophobic membrane changed slightly when exposed to the alkaline sodium hypochlorite solution, suggesting its strong alkali-resistance due to the non-wetting surface. However, the surface hydrophobic groups of hydrophobic membrane could be oxidized by sodium hypochlorite solution, resulting in more wettable membrane surface. The hydrophobic membrane also showed better performance in the respects of oxygen transfer, contaminant removal and energy-saving. Therefore, the hydrophobic membrane seemed more appropriate to be applied for microbubble aeration in aerobic wastewater treatment process.

  2. Bleb Nucleation through Membrane Peeling

    CERN Document Server

    Alert, Ricard

    2016-01-01

    We study the nucleation of blebs, i.e., protrusions arising from a local detachment of the membrane from the cortex of a cell. Based on a simple model of elastic linkers with force-dependent kinetics, we show that bleb nucleation is governed by membrane peeling. By this mechanism, the growth or shrinkage of a detached membrane patch is completely determined by the linker kinetics, regardless of the energetic cost of the detachment. We predict the critical nucleation radius for membrane peeling and the corresponding effective energy barrier. These may be typically smaller than those predicted by classical nucleation theory, implying a much faster nucleation. We also perform simulations of a continuum stochastic model of membrane-cortex adhesion to obtain the statistics of bleb nucleation times as a function of the stress on the membrane. The determinant role of membrane peeling changes our understanding of bleb nucleation and opens new directions in the study of blebs.

  3. Solid-state membrane module

    Science.gov (United States)

    Gordon, John Howard; Taylor, Dale M.

    2011-06-07

    Solid-state membrane modules comprising at least one membrane unit, where the membrane unit has a dense mixed conducting oxide layer, and at least one conduit or manifold wherein the conduit or manifold comprises a dense layer and at least one of a porous layer and a slotted layer contiguous with the dense layer. The solid-state membrane modules may be used to carry out a variety of processes including the separating of any ionizable component from a feedstream wherein such ionizable component is capable of being transported through a dense mixed conducting oxide layer of the membrane units making up the membrane modules. For ease of construction, the membrane units may be planar.

  4. CHARMM-GUI Membrane Builder toward realistic biological membrane simulations.

    Science.gov (United States)

    Wu, Emilia L; Cheng, Xi; Jo, Sunhwan; Rui, Huan; Song, Kevin C; Dávila-Contreras, Eder M; Qi, Yifei; Lee, Jumin; Monje-Galvan, Viviana; Venable, Richard M; Klauda, Jeffery B; Im, Wonpil

    2014-10-15

    CHARMM-GUI Membrane Builder, http://www.charmm-gui.org/input/membrane, is a web-based user interface designed to interactively build all-atom protein/membrane or membrane-only systems for molecular dynamics simulations through an automated optimized process. In this work, we describe the new features and major improvements in Membrane Builder that allow users to robustly build realistic biological membrane systems, including (1) addition of new lipid types, such as phosphoinositides, cardiolipin (CL), sphingolipids, bacterial lipids, and ergosterol, yielding more than 180 lipid types, (2) enhanced building procedure for lipid packing around protein, (3) reliable algorithm to detect lipid tail penetration to ring structures and protein surface, (4) distance-based algorithm for faster initial ion displacement, (5) CHARMM inputs for P21 image transformation, and (6) NAMD equilibration and production inputs. The robustness of these new features is illustrated by building and simulating a membrane model of the polar and septal regions of E. coli membrane, which contains five lipid types: CL lipids with two types of acyl chains and phosphatidylethanolamine lipids with three types of acyl chains. It is our hope that CHARMM-GUI Membrane Builder becomes a useful tool for simulation studies to better understand the structure and dynamics of proteins and lipids in realistic biological membrane environments.

  5. Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Choe, Yoong-Kee [National Institute of Advanced Industrial Science and Technology, Umezono 1-1-1, Tsukuba (Japan); Henson, Neil J.; Kim, Yu Seung [Los Alamos National Laboratory, Los Alamos, NM (United States)

    2015-12-31

    Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane should enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.

  6. Membrane fouling control by ultrasound in an anaerobic membrane bioreactor

    Institute of Scientific and Technical Information of China (English)

    SUI Pengzhe; WEN Xianghua; HUANG Xia

    2007-01-01

    In this study,ultrasound was used to control the membrane fouling online in an anaerobic membrane bioreactor (AMBR).Short-term running experiments were carried out under different operating conditions to explore feasible ultrasonic parameters.The experimental results indicated that when the crossflow velocity was more than 1.0 m/s,membrane fouling could be controlled effectively only by hydrodynamic methods without ultrasound.When ultrasound was applied,an ultrasonic power range of 60-150 W was suitable for the membrane fouling control in the experimental system.The experimental results showed that the membrane fouling was controlled so well that membrane filtration resistance(ΣR) could stay at 5×1011 m-1 for more than a week with the crossflow velocity of 0.75 m/s,which equaled the effect of crossflow velocity of more than 1.0 m/s without ultrasound.

  7. Polyazole hollow fiber membranes for direct contact membrane distillation

    KAUST Repository

    Maab, Husnul

    2013-08-07

    Porous hollow fiber membranes were fabricated from fluorinated polyoxadiazole and polytriazole by a dry-wet spinning method for application in desalination of Red Sea water by direct contact membrane distillation (DCMD). The data were compared with commercially available hollow fiber MD membranes prepared from poly(vinylidene fluoride). The membranes were characterized by electron microscopy, liquid entry pressure (LEP), and pore diameter measurements. Finally, the hollow fiber membranes were tested for DCMD. Salt selectivity as high as 99.95% and water fluxes as high as 35 and 41 L m -2 h-1 were demonstrated, respectively, for polyoxadiazole and polytriazole hollow fiber membranes, operating at 80 C feed temperature and 20 C permeate. © 2013 American Chemical Society.

  8. POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

    DEFF Research Database (Denmark)

    2001-01-01

    A method for preparing polybenzimidazole or polybenzimidazole blend membranes and fabricating gas diffusion electrodes and membrane-electrode assemblies is provided for a high temperature polymer electrolyte membrane fuel cell. Blend polymer electrolyte membranes based on PBI and various thermopl......A method for preparing polybenzimidazole or polybenzimidazole blend membranes and fabricating gas diffusion electrodes and membrane-electrode assemblies is provided for a high temperature polymer electrolyte membrane fuel cell. Blend polymer electrolyte membranes based on PBI and various...... thermoplastic polymers for high temperature polymer electrolyte fuel cells have also been developed. Miscible blends are used for solution casting of polymer membranes (solid electrolytes). High conductivity and enhanced mechanical strength were obtained for the blend polymer solid electrolytes...... electrolyte membrane by hot-press. The fuel cell can operate at temperatures up to at least 200 °C with hydrogen-rich fuel containing high ratios of carbon monoxide such as 3 vol% carbon monoxide or more, compared to the carbon monoxide tolerance of 10-20 ppm level for Nafion$m(3)-based polymer electrolyte...

  9. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-08-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the previous research, the reference point of oxygen occupancy was determined and verified. In the current research, the oxygen occupancy was investigated at 1200 C as a function of oxygen activity and compared with that at 1000 C. The cause of bumps at about 200 C was also investigated by using different heating and cooling rates during TGA. The fracture toughness of LSFT and dual phase membranes at room temperature is an important mechanical property. Vicker's indentation method was used to evaluate this toughness. Through this technique, a K{sub Ic} (Mode-I Fracture Toughness) value is attained by means of semi-empirical correlations between the indentation load and the length of the cracks emanating from the corresponding Vickers indentation impression. In the present investigation, crack propagation behavior was extensively analyzed in order to understand the strengthening mechanisms involved in the non-transforming La based ceramic composites. Cracks were generated using Vicker's indenter and used to identify and evaluate the toughening mechanisms involved. Preliminary results of an electron microscopy study of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Modeling of the isotopic transients on operating membranes (LSCrF-2828 at 900 C) and a ''frozen'' isotope profile have been analyzed in conjunction with a 1-D model to reveal the gradient in oxygen diffusivity through the membrane under conditions of high chemical gradients.

  10. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-02-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. The in situ electrical conductivity and Seebeck coefficient measurements were made on LSFT at 1000 and 1200 C over the oxygen activity range from air to 10{sup -15} atm. The electrical conductivity measurements exhibited a p to n type transition at an oxygen activity of 1 x 10{sup -10} at 1000 C and 1 x 10{sup -6} at 1200 C. Thermogravimetric studies were also carried out over the same oxygen activities and temperatures. Based on the results of these measurements, the chemical and mechanical stability range of LSFT were determined and defect structure was established. The studies on the fracture toughness of the LSFT and dual phase membranes exposed to air and N{sub 2} at 1000 C was done and the XRD and SEM analysis of the specimens were carried out to understand the structural and microstructural changes. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affect the mechanical properties. A complete transformation of fracture behavior was observed in the N{sub 2} treated LSFT samples. Further results to investigate the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Recent results on transient kinetic data are presented. The 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model is used to study ''frozen'' profiles in patterned or composite membranes.

  11. Molecularly Imprinted Membranes

    Directory of Open Access Journals (Sweden)

    Fabrizio Caldera

    2012-07-01

    Full Text Available Although the roots of molecularly imprinted polymers lie in the beginning of 1930s in the past century, they have had an exponential growth only 40–50 years later by the works of Wulff and especially by Mosbach. More recently, it was also proved that molecular imprinted membranes (i.e., polymer thin films that show recognition properties at molecular level of the template molecule are used in their formation. Different procedures and potential application in separation processes and catalysis are reported. The influences of different parameters on the discrimination abilities are also discussed.

  12. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana; X.-D Zhou; Q. Cai; J. Yang; W.B. Yelon; W.J. James; H.U. Anderson; Alan Jacobson; C.A. Mims

    2004-05-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In this report, in situ neutron diffraction was used to characterize the chemical and structural properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} (here after as L2SF55T) specimen, which was subject to measurements of neutron diffraction from room temperature to 900 C. It was found that space group of R3c yielded a better refinement than a cubic structure of Pm3m. Oxygen occupancy was nearly 3 in the region from room temperature to 700 C, above which the occupancy decreased due to oxygen loss. Dense OTM bars provided by Praxair were loaded to fracture at varying stress rates. Studies were done at room temperature in air and at 1000 C in a specified environment to evaluate slow crack growth behavior. The X-Ray data and fracture mechanisms points to non-equilibrium decomposition of the LSFCO OTM membrane. The non-equilibrium conditions could probably be due to the nature of the applied stress field (stressing rates) and leads to transition in crystal structures and increased kinetics of decomposition. The formations of a Brownmillerite or Sr2Fe2O5 type structures, which are orthorhombic are attributed to the ordering of oxygen vacancies. The cubic to orthorhombic transitions leads to 2.6% increase in strains and thus residual stresses generated could influence the fracture behavior of the OTM membrane. Continued investigations on the thermodynamic properties (stability and phase-separation behavior) and total conductivity of prototype membrane materials were carried out. The data are needed together with the kinetic information to develop a complete model for the membrane transport. Previously characterization, stoichiometry and conductivity measurements for samples of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} were reported. In this report

  13. Oxygen Transport Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay

    2008-08-30

    The focus of this research was to develop new membrane materials by synthesizing different compounds and determining their defect structures, crystallographic structures and electrical properties. In addition to measuring electrical conductivity, oxygen vacancy concentration was also evaluated using thermogravimetry, Neutron diffraction and Moessbauer Spectroscopy. The reducing conditions (CO{sub 2}/CO/H{sub 2} gas mixtures with steam) as encountered in a reactor environment can be expected to have significant influence on the mechanical properties of the oxides membranes. Various La based materials with and without Ti were selected as candidate membrane materials for OTM. The maximum electrical conductivity of LSF in air as a function of temperature was achieved at < 600 C and depends on the concentration of Sr (acceptor dopant). Oxygen occupancy in LSF was estimated using Neutron diffractometry and Moessbauer Spectroscopy by measuring magnetic moment changes depending on the Fe{sup 3+} and Fe{sup 4+} ratio. After extensive studies of candidate materials, lanthanum ferrites (LSF and LSFT) were selected as the favored materials for the oxygen transport membrane (OTM). LSF is a very good material for an OTM because of its high electronic and oxygen ionic conductivity if long term stability and mechanical strength are improved. LSFT not only exhibits p-type behavior in the high oxygen activity regime, but also has n-type conduction in reducing atmospheres. Higher concentrations of oxygen vacancies in the low oxygen activity regime may improve the performance of LSFT as an OTM. The hole concentration is related to the difference in the acceptor and donor concentration by the relation p = [Sr'{sub La}]-[Ti{sm_bullet}{sub Fe}]. The chemical formulation predicts that the hole concentration is, p = 0.8-0.45 or 0.35. Experimental measurements indicated that p is about {approx} 0.35. The activation energy of conduction is 0.2 eV which implies that LSCF conducts via the

  14. Electrically Conductive Porous Membrane

    Science.gov (United States)

    Burke, Kenneth Alan (Inventor)

    2014-01-01

    The present invention relates to an electrically conductive membrane that can be configured to be used in fuel cell systems to act as a hydrophilic water separator internal to the fuel cell, or as a water separator used with water vapor fed electrolysis cells, or as a water separator used with water vapor fed electrolysis cells, or as a capillary structure in a thin head pipe evaporator, or as a hydrophobic gas diffusion layer covering the fuel cell electrode surface in a fuel cell.

  15. Membrane filters and membrane-filtration processes for health care.

    Science.gov (United States)

    Eudailey, W A

    1983-11-01

    The development of membrane-filtration processes is reviewed, and current types and uses of membrane filtration in health care is discussed. Development of adequate support structures for filters and of disposable filtration devices has facilitated development of filtration processes for pharmaceutical industry, manufacturing in hospital pharmacies, and direct patient care. Hydrophobic filters have also been developed; aqueous solutions cannot wet the pore structures of these filters and therefore cannot pass. Sterility-testing systems have also been developed. There are two types of filters: depth (constructed of compacted fibers) and membrane (which have a homogeneous internal structure). Depth filters retain only a portion of particles in a particular size range and are generally not acceptable for use in health care. Membrane filters retain all particles of a given size. Types of membrane filters are selected for specific uses based on needed flow rates, particulate load, and retention capability. Membrane filters may be validated using bacterial-passage, bubble-point, and diffusion tests. Most membrane filters used in health care are microporous filters that retain particles in the 0.1-10-micron size range. Applications are currently being developed for ultrafilters, which retain both particles and substances with large molecular structures such as proteins, and reverse-osmosis filter membranes, which allow only water or water-miscible solvents of very low molecular weights to pass. Experience in engineering designs, quality assurance, and test procedures has led to the development of many safe, reliable, and effective membrane products for health care.

  16. Spherical membranes in Matrix theory

    CERN Document Server

    Kabat, D; Kabat, Daniel; Taylor, Washington

    1998-01-01

    We consider membranes of spherical topology in uncompactified Matrix theory. In general for large membranes Matrix theory reproduces the classical membrane dynamics up to 1/N corrections; for certain simple membrane configurations, the equations of motion agree exactly at finite N. We derive a general formula for the one-loop Matrix potential between two finite-sized objects at large separations. Applied to a graviton interacting with a round spherical membrane, we show that the Matrix potential agrees with the naive supergravity potential for large N, but differs at subleading orders in N. The result is quite general: we prove a pair of theorems showing that for large N, after removing the effects of gravitational radiation, the one-loop potential between classical Matrix configurations agrees with the long-distance potential expected from supergravity. As a spherical membrane shrinks, it eventually becomes a black hole. This provides a natural framework to study Schwarzschild black holes in Matrix theory.

  17. Composite oxygen transport membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zigui; Plonczak, Pawel J.; Lane, Jonathan A.

    2016-11-08

    A method is described of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. Preferred materials are (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.7Fe.sub.0.3O.sub.3-.delta. for the porous fuel oxidation layer, (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer, and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.3Fe.sub.0.7O.sub.3-.delta. for the porous surface exchange layer. Firing the said fuel activation and separation layers in nitrogen atmosphere unexpectedly allows the separation layer to sinter into a fully densified mass.

  18. 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.

  19. Impact on floating membranes

    Science.gov (United States)

    Vandenberghe, Nicolas; Duchemin, Laurent

    2016-05-01

    When impacted by a rigid body, a thin elastic membrane with negligible bending rigidity floating on a liquid pool deforms. Two axisymmetric waves radiating from the impact point propagate. First, a longitudinal wave front, associated with in-plane deformation of the membrane and traveling at constant speed, separates an outward stress-free domain from a stretched domain. Then, in the stretched domain a dispersive transverse wave travels at a speed that depends on the local stretching rate. The dynamics is found to be self-similar in time. Using this property, we show that the wave dynamics is similar to the capillary waves that propagate at a liquid-gas interface but with a surface tension coefficient that depends on impact speed. During wave propagation, we observe the development of a buckling instability that gives rise to radial wrinkles. We address the dynamics of this fluid-body system, including the rapid deceleration of an impactor of finite mass, an issue that may have applications in the domain of absorption of impact energy.

  20. 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.

  1. Thermal treatment for nanofibrous membrane

    Directory of Open Access Journals (Sweden)

    Liu Hong-Ying

    2014-01-01

    Full Text Available Poly(vinylidene fluoride nanofibrous membranes with high porosity, large electrolyte solution uptake, and adequate mechanical properties were prepared by electrospinning. The physical properties of the electrospun poly(vinylidene fluoride membranes can be improved by thermal treatment. Results showed after the thermal treatment, there had appeared ever-increasing tensile strength and elongation of the poly(vinylidene fluoride membranes. The crystal structures of poly(vinylidene fluoride fibers were greatly improved.

  2. 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...... affected by the lipid environment. Theoretical predictions are pointed out, and compared to experimental findings, if available. Among others, the following phenomena are discussed: interactions of interfacially adsorbed peptides, pore-forming amphipathic peptides, adsorption of charged proteins onto...... 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....

  3. Proton exchange membrane fuel cells

    CERN Document Server

    Qi, Zhigang

    2013-01-01

    Preface Proton Exchange Membrane Fuel CellsFuel CellsTypes of Fuel CellsAdvantages of Fuel CellsProton Exchange Membrane Fuel CellsMembraneCatalystCatalyst LayerGas Diffusion MediumMicroporous LayerMembrane Electrode AssemblyPlateSingle CellStackSystemCell Voltage Monitoring Module (CVM)Fuel Supply Module (FSM)Air Supply Module (ASM)Exhaust Management Module (EMM)Heat Management Module (HMM)Water Management Module (WMM)Internal Power Supply Module (IPM)Power Conditioning Module (PCM)Communications Module (COM)Controls Module (CM)SummaryThermodynamics and KineticsTheoretical EfficiencyVoltagePo

  4. Permeability testing of biomaterial membranes

    Energy Technology Data Exchange (ETDEWEB)

    Dreesmann, L; Hajosch, R; Nuernberger, J Vaz; Schlosshauer, B [NMI Natural and Medical Sciences Institute at University Tuebingen, Markwiesenstr. 55, D-72770 Reutlingen (Germany); Ahlers, M [GELITA AG, Gammelsbacher Str. 2, D-69412 Eberbach (Germany)], E-mail: schlosshauer@nmi.de

    2008-09-01

    The permeability characteristics of biomaterials are critical parameters for a variety of implants. To analyse the permeability of membranes made from crosslinked ultrathin gelatin membranes and the transmigration of cells across the membranes, we combined three technical approaches: (1) a two-chamber-based permeability assay, (2) cell culturing with cytochemical analysis and (3) biochemical enzyme electrophoresis (zymography). Based on the diffusion of a coloured marker molecule in conjunction with photometric quantification, permeability data for a gelatin membrane were determined in the presence or absence of gelatin degrading fibroblasts. Cytochemical evaluation after cryosectioning of the membranes was used to ascertain whether fibroblasts had infiltrated the membrane inside. Zymography was used to investigate the potential release of proteases from fibroblasts, which are known to degrade collagen derivatives such as gelatin. Our data show that the diffusion equilibrium of a low molecular weight dye across the selected gelatin membrane is approached after about 6-8 h. Fibroblasts increase the permeability due to cavity formation in the membrane inside without penetrating the membrane for an extended time period (>21 days in vitro). Zymography indicates that cavity formation is most likely due to the secretion of matrix metalloproteinases. In summary, the combination of the depicted methods promises to facilitate a more rational development of biomaterials, because it provides a rapid means of determining permeability characteristics and bridges the gap between descriptive methodology and the mechanistic understanding of permeability alterations due to biological degradation.

  5. Chromatic adaptation of photosynthetic membranes.

    Science.gov (United States)

    Scheuring, Simon; Sturgis, James N

    2005-07-15

    Many biological membranes adapt in response to environmental conditions. We investigated how the composition and architecture of photosynthetic membranes of a bacterium change in response to light, using atomic force microscopy. Despite large modifications in the membrane composition, the local environment of core complexes remained unaltered, whereas specialized paracrystalline light-harvesting antenna domains grew under low-light conditions. Thus, the protein mixture in the membrane shows eutectic behavior and can be mimicked by a simple model. Such structural adaptation ensures efficient photon capture under low-light conditions and prevents photodamage under high-light conditions.

  6. Composite membrane with integral rim

    Science.gov (United States)

    Routkevitch, Dmitri; Polyakov, Oleg G

    2015-01-27

    Composite membranes that are adapted for separation, purification, filtration, analysis, reaction and sensing. The composite membranes can include a porous support structure having elongate pore channels extending through the support structure. The composite membrane also includes an active layer comprising an active layer material, where the active layer material is completely disposed within the pore channels between the surfaces of the support structure. The active layer is intimately integrated within the support structure, thus enabling great robustness, reliability, resistance to mechanical stress and thermal cycling, and high selectivity. Methods for the fabrication of composite membranes are also provided.

  7. Characterization of Polymeric Nanofiltration Membranes

    Directory of Open Access Journals (Sweden)

    Simoncic, B.

    2007-11-01

    Full Text Available As membrane processes are increasingly used in industrial applications, there is a growing interest in methods of membrane characterization. Traditional membrane characteristics, such as cut-off value and pore size distribution, are being supplemented by membrane surface characteristics, such as charge density or zeta potential and hydrophobicity. This study, therefore, characterizes the three different polymeric membranes used (NFT-50, DL and DK. The molecular mass cut-off (MMCO value was determined using a set of reference solutes within the molecular range 150-600 Da, whereas streaming potential measurements enabled quantification of the surface charge characteristics. Hydrophobicity was studied using contact angle measurements. The results indicated that even though all three membranes had very similar layer compositions which consisted of poly(piperazneamide, as top layers they showed different values of measured quantitive. The NFT-50 membrane had the lowest MMCO value and the most hydrophilic membrane surface, followed by DK and DL. Membrane fouling as measured by flux reduction was determined by streaming potential measurements and accompanied by a positive change in zeta potential.

  8. Oxygen Transport Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay

    2008-08-30

    The focus of this research was to develop new membrane materials by synthesizing different compounds and determining their defect structures, crystallographic structures and electrical properties. In addition to measuring electrical conductivity, oxygen vacancy concentration was also evaluated using thermogravimetry, Neutron diffraction and Moessbauer Spectroscopy. The reducing conditions (CO{sub 2}/CO/H{sub 2} gas mixtures with steam) as encountered in a reactor environment can be expected to have significant influence on the mechanical properties of the oxides membranes. Various La based materials with and without Ti were selected as candidate membrane materials for OTM. The maximum electrical conductivity of LSF in air as a function of temperature was achieved at < 600 C and depends on the concentration of Sr (acceptor dopant). Oxygen occupancy in LSF was estimated using Neutron diffractometry and Moessbauer Spectroscopy by measuring magnetic moment changes depending on the Fe{sup 3+} and Fe{sup 4+} ratio. After extensive studies of candidate materials, lanthanum ferrites (LSF and LSFT) were selected as the favored materials for the oxygen transport membrane (OTM). LSF is a very good material for an OTM because of its high electronic and oxygen ionic conductivity if long term stability and mechanical strength are improved. LSFT not only exhibits p-type behavior in the high oxygen activity regime, but also has n-type conduction in reducing atmospheres. Higher concentrations of oxygen vacancies in the low oxygen activity regime may improve the performance of LSFT as an OTM. The hole concentration is related to the difference in the acceptor and donor concentration by the relation p = [Sr'{sub La}]-[Ti{sm_bullet}{sub Fe}]. The chemical formulation predicts that the hole concentration is, p = 0.8-0.45 or 0.35. Experimental measurements indicated that p is about {approx} 0.35. The activation energy of conduction is 0.2 eV which implies that LSCF conducts via the

  9. Membrane emulsification with vibrating membranes: A numerical study

    NARCIS (Netherlands)

    Kelder, J.D.H.; Janssen, J.J.M.; Boom, R.M.

    2007-01-01

    Membrane emulsification of oil in water may be enhanced by mechanically exciting the membrane, thereby enabling the formation of smaller droplets of a narrower size distribution, combined with higher specific production rate. To evaluate this potential, a force balance model was developed that

  10. Self-Segregation of Myelin Membrane Lipids in Model Membranes

    NARCIS (Netherlands)

    Yurlova, Larisa; Kahya, Nicoletta; Aggarwal, Shweta; Kaiser, Hermann-Josef; Chiantia, Salvatore; Bakhti, Mostafa; Pewzner-Jung, Yael; Ben-David, Oshrit; Futerman, Anthony H.; Bruegger, Britta; Simons, Mikael

    2011-01-01

    Rapid conduction of nerve impulses requires coating of axons by myelin sheaths, which are multilamellar, lipid-rich membranes produced by oligodendrocytes in the central nervous system. To act as an insulator, myelin has to form a stable and firm membrane structure. In this study, we have analyzed t

  11. Adaptive silicone-membrane lenses: planar vs. shaped membrane

    CSIR Research Space (South Africa)

    Schneider, F

    2009-08-01

    Full Text Available -section. The lens systems incorporate a piezo actuator which is operated in a regime of ±40 V. The shaped membrane lenses show lower wave front errors than the planar ones, down to 24 nm. However, the system with a planar membrane achieves a larger refractive power...

  12. How Membrane-Active Peptides Get into Lipid Membranes.

    Science.gov (United States)

    Sani, Marc-Antoine; Separovic, Frances

    2016-06-21

    The structure-function relationship for a family of antimicrobial peptides (AMPs) from the skin of Australian tree frogs is discussed and compared with that of peptide toxins from bee and Australian scorpion venoms. Although these membrane-active peptides induce a similar cellular fate by disrupting the lipid bilayer integrity, their lytic activity is achieved via different modes of action, which are investigated in relation to amino acid sequence, secondary structure, and membrane lipid composition. In order to better understand what structural features govern the interaction between peptides and lipid membranes, cell-penetrating peptides (CPPs), which translocate through the membrane without compromising its integrity, are also discussed. AMPs possess membrane lytic activities that are naturally designed to target the cellular membrane of pathogens or competitors. They are extremely diverse in amino acid composition and often show specificity against a particular strain of microbe. Since our antibiotic arsenal is declining precariously in the face of the rise in multiantibiotic resistance, AMPs increasingly are seen as a promising alternative. In an effort to understand their molecular mechanism, biophysical studies of a myriad of AMPs have been reported, yet no unifying mechanism has emerged, rendering difficult the rational design of drug leads. Similarly, a wide variety of cytotoxic peptides are found in venoms, the best known being melittin, yet again, predicting their activity based on a particular amino acid composition or secondary structure remains elusive. A common feature of these membrane-active peptides is their preference for the lipid environment. Indeed, they are mainly unstructured in solution and, in the presence of lipid membranes, quickly adsorb onto the surface, change their secondary structure, eventually insert into the hydrophobic core of the membrane bilayer, and finally disrupt the bilayer integrity. These steps define the molecular

  13. Mechanisms of Membrane Curvature Generation in Membrane Traffic

    Directory of Open Access Journals (Sweden)

    Hye-Won Shin

    2012-02-01

    Full Text Available During the vesicular trafficking process, cellular membranes undergo dynamic morphological changes, in particular at the vesicle generation and fusion steps. Changes in membrane shape are regulated by small GTPases, coat proteins and other accessory proteins, such as BAR domain-containing proteins. In addition, membrane deformation entails changes in the lipid composition as well as asymmetric distribution of lipids over the two leaflets of the membrane bilayer. Given that P4-ATPases, which catalyze unidirectional flipping of lipid molecules from the exoplasmic to the cytoplasmic leaflets of the bilayer, are crucial for the trafficking of proteins in the secretory and endocytic pathways, changes in the lipid composition are involved in the vesicular trafficking process. Membrane remodeling is under complex regulation that involves the composition and distribution of lipids as well as assembly of proteins.

  14. Pretreatment and Membrane Hydrophilic Modification to Reduce Membrane Fouling

    Directory of Open Access Journals (Sweden)

    Huaqiang Chu

    2013-09-01

    Full Text Available The application of low pressure membranes (microfiltration/ultrafiltration has undergone accelerated development for drinking water production. However, the major obstacle encountered in its popularization is membrane fouling caused by natural organic matter (NOM. This paper firstly summarizes the two factors causing the organic membrane fouling, including molecular weight (MW and hydrophilicity/hydrophobicity of NOM, and then presents a brief introduction of the methods which can prevent membrane fouling such as pretreatment of the feed water (e.g., coagulation, adsorption, and pre-oxidation and membrane hydrophilic modification (e.g., plasma modification, irradiation grafting modification, surface coating modification, blend modification, etc.. Perspectives of further research are also discussed.

  15. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; T. Nithyanantham

    2006-12-31

    Ti doping on La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} (LSF) tends to increase the oxygen equilibration kinetics of LSF in lower oxygen activity environment because of the high valence state of Ti. However, the addition of Ti decreases the total conductivity because the acceptor ([Sr{prime}{sub La}]) is compensated by the donor ([Ti{sub Fe}{sup {sm_bullet}}]) which decreases the carrier concentration. The properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 1-x}Ti{sub x}O{sub 3-{delta}} (LSFT, x = 0.45) have been experimentally and theoretically investigated to elucidate (1) the dependence of oxygen occupancy and electrochemical properties on temperature and oxygen activity by thermogravimetric analysis (TGA) and (2) the electrical conductivity and carrier concentration by Seebeck coefficient and electrical measurements. In the present study, dual phase (La{sub 0.2}Sr{sub 0.8}Fe{sub 0.6}Ti{sub 0.4}O{sub 3-{delta}}/Ce{sub 0.9}Gd{sub 0.1}O{sub 2-{delta}}) membranes have been evaluated for structural properties such as hardness, fracture toughness and flexural strength. The effect of high temperature and slightly reducing atmosphere on the structural properties of the membranes was studied. The flexural strength of the membrane decreases upon exposure to slightly reducing conditions at 1000 C. The as-received and post-fractured membranes were characterized using XRD, SEM and TG-DTA to understand the fracture mechanisms. Changes in structural properties of the composite were sought to be correlated with the physiochemical features of the two-phases. We have reviewed the electrical conductivity data and stoichiometry data for La{sub 0.2}Sr{sub 0.8}Cr{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} some of which was reported previously. Electrical conductivity data for La{sub 0.2}Sr{sub 0.8}Cr{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCrF) were obtained in the temperature range, 752 {approx} 1055 C and in the pO{sub 2} range, 10{sup -18} {approx} 0.5 atm. The slope of the plot of log {sigma} vs

  16. Matrix membranes and integrability

    Energy Technology Data Exchange (ETDEWEB)

    Zachos, C. [Argonne National Lab., IL (United States); Fairlie, D. [University of Durham (United Kingdom). Dept. of Mathematical Sciences; Curtright, T. [University of Miami, Coral Gables, FL (United States). Dept. of Physics

    1997-06-01

    This is a pedagogical digest of results reported in Curtright, Fairlie, {ampersand} Zachos 1997, and an explicit implementation of Euler`s construction for the solution of the Poisson Bracket dual Nahm equation. But it does not cover 9 and 10-dimensional systems, and subsequent progress on them Fairlie 1997. Cubic interactions are considered in 3 and 7 space dimensions, respectively, for bosonic membranes in Poisson Bracket form. Their symmetries and vacuum configurations are explored. Their associated first order equations are transformed to Nahm`s equations, and are hence seen to be integrable, for the 3-dimensional case, by virtue of the explicit Lax pair provided. Most constructions introduced also apply to matrix commutator or Moyal Bracket analogs.

  17. High Flux Metallic Membranes for Hydrogen Recovery and Membrane Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Buxbaum, Robert

    2010-06-30

    We made and tested over 250 new alloys for use as lower cost, higher flux hydrogen extraction membrane materials. Most of these were intermetallic, or contained significant intermetallic content, particularly based on B2 alloy compositions with at least one refractory component; B2 intermetallics resemble BCC alloys, in structure, but the atoms have relatively fixed positions, with one atom at the corners of the cube, the other at the centers. The target materals we were looking for would contain little or no expensive elements, no strongly toxic or radioactive elements, would have high flux to hydrogen, while being fabricable, brazable, and relatively immune to hydrogen embrittlement and corrosion in operation. The best combination of properties of the membrane materials we developed was, in my opinion, a Pd-coated membrane consisting of V -9 atomic % Pd. This material was relatively cheap, had 5 times the flux of Pd under the same pressure differential, was reasonably easy to fabricate and braze, and not bad in terms of embrittlement. Based on all these factors we project, about 1/3 the cost of Pd, on an area basis for a membrane designed to last 20 years, or 1/15 the cost on a flux basis. Alternatives to this membrane replaced significant fractions of the Pd with Ni and or Co. The cost for these membranes was lower, but so was the flux. We produced successful brazed products from the membrane materials, and made them into flat sheets. We tested, unsuccessfully, several means of fabricating thematerials into tubes, and eventually built a membrane reactor using a new, flat-plate design: a disc and doughnut arrangement, a design that seems well- suited to clean hydrogen production from coal. The membranes and reactor were tested successfully at Western Research. A larger equipment company (Chart Industries) produced similar results using a different flat-plate reactor design. Cost projections of the membrane are shown to be attractive.

  18. Bacteria/virus filter membrane

    Science.gov (United States)

    Lysaght, M. S.; Goodwin, F.; Roebelen, G.

    1977-01-01

    Hollow acrylate fiber membrane that filters bacterial and viral organisms can be used with closed-cycle life-support systems for underwater habitations or laboratories. Membrane also has applications in fields of medicine, gnotobiotics, pharmaceutical production, and industries and research facilities that require sterile water. Device eliminates need for strong chemicals or sterilizing agents, thereby reducing costs.

  19. 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 ...

  20. Lipid membranes on nanostructured silicon.

    Energy Technology Data Exchange (ETDEWEB)

    Slade, Andrea Lynn; Lopez, Gabriel P. (University of New Mexico, Albuquerque, NM); Ista, Linnea K. (University of New Mexico, Albuquerque, NM); O' Brien, Michael J. (University of New Mexico, Albuquerque, NM); Sasaki, Darryl Yoshio; Bisong, Paul (University of New Mexico, Albuquerque, NM); Zeineldin, Reema R. (University of New Mexico, Albuquerque, NM); Last, Julie A.; Brueck, Stephen R. J. (University of New Mexico, Albuquerque, NM)

    2004-12-01

    A unique composite nanoscale architecture that combines the self-organization and molecular dynamics of lipid membranes with a corrugated nanotextured silicon wafer was prepared and characterized with fluorescence microscopy and scanning probe microscopy. The goal of this project was to understand how such structures can be assembled for supported membrane research and how the interfacial interactions between the solid substrate and the soft, self-assembled material create unique physical and mechanical behavior through the confinement of phases in the membrane. The nanometer scale structure of the silicon wafer was produced through interference lithography followed by anisotropic wet etching. For the present study, a line pattern with 100 nm line widths, 200 nm depth and a pitch of 360 nm pitch was fabricated. Lipid membranes were successfully adsorbed on the structured silicon surface via membrane fusion techniques. The surface topology of the bilayer-Si structure was imaged using in situ tapping mode atomic force microscopy (AFM). The membrane was observed to drape over the silicon structure producing an undulated topology with amplitude of 40 nm that matched the 360 nm pitch of the silicon structure. Fluorescence recovery after photobleaching (FRAP) experiments found that on the microscale those same structures exhibit anisotropic lipid mobility that was coincident with the silicon substructure. The results showed that while the lipid membrane maintains much of its self-assembled structure in the composite architecture, the silicon substructure indeed influences the dynamics of the molecular motion within the membrane.

  1. Membranes and microfluidics: a review

    NARCIS (Netherlands)

    de Jong, J.; Lammertink, Rob G.H.; Wessling, Matthias

    2006-01-01

    The integration of mass transport control by means of membrane functionality into microfluidic devices has shown substantial growth over the last 10 years. Many different examples of mass transport control have been reported, demonstrating the versatile use of membranes. This review provides an

  2. Membranes from academia to industry

    Science.gov (United States)

    2017-02-01

    Andrew Livingston (Imperial College London) and Richard Baker (Membrane Technology and Research) talk to Nature Materials about the perks and pitfalls of membrane research and development, and how activities at the new Barrer Centre might lead to next-generation separation technologies.

  3. Asymmetry effects in membrane catalysis

    NARCIS (Netherlands)

    Teplyakov, V. V.; Pisarev, G. I.; Magsumov, M. I.; Tsodikov, M. V.; Zhu, W.; Kapteijn, F.

    2006-01-01

    Catalytic processes using porous ceramic where catalytic coatings on the microchannel walls are of current interest for the creation of high speed and compact membrane reactors, especially for the reactions of C-1-substrates. Nanoporous ceramic membranes with variation of pore size as a non-linear g

  4. Bacteria/virus filter membrane

    Science.gov (United States)

    Lysaght, M. S.; Goodwin, F.; Roebelen, G.

    1977-01-01

    Hollow acrylate fiber membrane that filters bacterial and viral organisms can be used with closed-cycle life-support systems for underwater habitations or laboratories. Membrane also has applications in fields of medicine, gnotobiotics, pharmaceutical production, and industries and research facilities that require sterile water. Device eliminates need for strong chemicals or sterilizing agents, thereby reducing costs.

  5. Lipids of the Golgi membrane

    NARCIS (Netherlands)

    van Meer, G.

    1998-01-01

    The thin membrane of the endoplasmic reticulum matures into the thick plasma membrane in the Golgi apparatus. Along the way, the concentrations of cholesterol and sphingolipids increase. Here, Gerrit van Meer discusses how this phenomenon may reflect an intricate lipid-protein sorting machinery. Syn

  6. A membrane - foulant interaction study.

    NARCIS (Netherlands)

    Fontyn, M.

    1991-01-01

    In this thesis the problem of membrane fouling has been considered from different points of view. The aim of the study is to gather information on the physical and chemical mechanisms of membrane fouling, so that selective solutions can be introduced to overcome or to diminish the problem.Anti-foami

  7. Ceramic Membranes for Ammonia Recovery

    Energy Technology Data Exchange (ETDEWEB)

    Camus, O.; Perera, S.; Crittenden, B. [Department of Chemical Engineering, University of Bath, Bath, BA2 7AY (United Kingdom); Van Delft, Y.C.; Meyer, D.F.; Pex, P.P.A.C. [ECN Solar Energy, Westerduinweg 3, P.O. Box 1, 1755 ZG Petten (Netherlands); Kumakiri, I.; Miachon, S.; Dalmon, J.A. [CNRS-Institut de Recherches sur la Catalyse 2, av. A. Einstein, 69626 Villeurbanne (France); Tennison, S. [MAST Carbon, Ltd., Henley Park, Guildford, Surrey, GU3 2AF (United Kingdom); Chanaud, P. [Pall-Exekia, BP1, Usine a Bazet (France); Groensmit, E. [Kemira GrowHow SA/NV, Avenue Einstein 11, B-1300 Wavre (Belgium); Nobel, W. [Continental Engineers BV, Rustenburg 114, 1506 AZ Zaandam (Netherlands)

    2008-12-15

    An extensive screening program has been performed to find a suitable membrane configuration and operating conditions for the effective recovery of ammonia from the syngas loop. All the experiments have been performed at steady state. MFI zeolite membranes in tubular and multi-channel fiber configurations have been tested along with tubular silica membranes. At 80C, a high ammonia permeance (2.1 x 10{sup -7} mol.m{sup -2}.s{sup -1}.Pa{sup -1}), and a selectivity of about 10 were found with the tubular zeolite membrane, whereas for the silica membrane an even higher ammonia permeance was measured (7.6 x 10{sup -7} mol.m{sup -2}.s{sup -1}.Pa{sup -1}) with a selectivity of about 7. For both silica and zeolite membranes, the selectivity was found to increase with increasing temperature up to 80C. This is a combined effect of weaker adsorption of ammonia and increased diffusion at higher temperature. The results have been modeled using both the well-mixed reactor and the log mean pressure difference approaches. To overcome their limitations in addressing changes in feed concentration along the membrane surface, a segmental model has been used to obtain suitable operating conditions and membrane areas required for an industrial application.

  8. Fabrication of green polymeric membranes

    KAUST Repository

    Kim, Dooli

    2017-06-16

    Provided herein are methods of fabricating membranes using polymers with functionalized groups such as sulfone (e.g., PSf and PES), ether (e.g., PES), acrylonitrile (e.g., PAN), fluoride(e.g., pvdf and other fluoropolymers), and imide (e.g., extem) and ionic liquids. Also provided are membranes made by the provided methods.

  9. Challenges in commercializing biomimetic membranes

    DEFF Research Database (Denmark)

    Perry, Mark; Madsen, Steen Ulrik; Jørgensen, Tine Elkjær

    2015-01-01

    of these barriers and challenges associated with introducing biomimetic aquaporin membranes. These include technical issues in membrane production and product testing. Then we discuss possible business models for introducing new technologies in general, followed by a presentation of beach-head market segments...

  10. Pore dynamics in lipid membranes

    Science.gov (United States)

    Gozen, I.; Dommersnes, P.

    2014-09-01

    Transient circular pores can open in plasma membrane of cells due to mechanical stress, and failure to repair such pores lead to cell death. Similar pores in the form of defects also exist among smectic membranes, such as in myelin sheaths or mitochondrial membranes. The formation and growth of membrane defects are associated with diseases, for example multiple sclerosis. A deeper understanding of membrane pore dynamics can provide a more refined picture of membrane integrity-related disease development, and possibly also treatment options and strategies. Pore dynamics is also of great importance regarding healthcare applications such as drug delivery, gene or as recently been implied, cancer therapy. The dynamics of pores significantly differ in stacks which are confined in 2D compared to those in cells or vesicles. In this short review, we will summarize the dynamics of different types of pores that can be observed in biological membranes, which include circular transient, fusion and hemi-fusion pores. We will dedicate a section to floral and fractal pores which were discovered a few years ago and have highly peculiar characteristics. Finally, we will discuss the repair mechanisms of large area pores in conjunction with the current cell membrane repair hypotheses.

  11. Electro-catalytic membrane reactors and the development of bipolar membrane technology

    NARCIS (Netherlands)

    Balster, J.; Stamatialis, D.F.; Wessling, M.

    2004-01-01

    Membrane reactors are currently under extensive research and development. Hardly any concept, however, is realized yet in practice. Frequently, forgotten as membrane reactors are electro-catalytic membrane reactors where electrodes perform chemical conversations and membranes separate the locations

  12. Hydrogen Selective Exfoliated Zeolite Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Tsapatsis, Michael [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Daoutidis, Prodromos [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Elyassi, Bahman [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Lima, Fernando [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Iyer, Aparna [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Agrawal, Kumar [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science; Sabnis, Sanket [Univ. of Minnesota, Minneapolis, MN (United States). Department of Chemical Engineering and Materials Science

    2015-04-06

    The objective of this project was to develop and evaluate an innovative membrane technology at process conditions that would be representative of Integrated Gasification Combined Cycle (IGCC) advanced power generation with pre-combustion capture of carbon dioxide (CO2). This research focused on hydrogen (H2)-selective zeolite membranes that could be utilized to separate conditioned syngas into H2-rich and CO2-rich components. Both experiments and process design and optimization calculations were performed to evaluate the concept of ultra-thin membranes made from zeolites nanosheets. In this work, efforts in the laboratory were made to tackle two fundamental challenges in application of zeolite membranes in harsh industrial environments, namely, membrane thickness and membrane stability. Conventional zeolite membranes have thicknesses in the micron range, limiting their performance. In this research, we developed a method for fabrication of ultimately thin zeolite membranes based on zeolite nanosheets. A range of layered zeolites (MWW, RWR, NSI structure types) suitable for hydrogen separation was successfully exfoliated to their constituent nanosheets. Further, membranes were made from one of these zeolites, MWW, to demonstrate the potential of this group of materials. Moreover, long-term steam stability of these zeolites (up to 6 months) was investigated in high concentrations of steam (35 mol% and 95 mole%), high pressure (10 barg), and high temperatures (350 °C and 600 °C) relevant to conditions of water-gas-shift and steam methane reforming reactions. It was found that certain nanosheets are stable, and that stability depends on the concentration of structural defects. Additionally, models that represent a water-gas-shift (WGS) membrane reactor equipped with the zeolite membrane were developed for systems studies. These studies had the aim of analyzing the effect of the membrane reactor integration into IGCC plants

  13. Current-Induced Membrane Discharge

    DEFF Research Database (Denmark)

    Andersen, Mathias Bækbo; van Soestbergen, M.; Mani, A.;

    2012-01-01

    Possible mechanisms for overlimiting current (OLC) through aqueous ion-exchange membranes (exceeding diffusion limitation) have been debated for half a century. Flows consistent with electro-osmotic instability have recently been observed in microfluidic experiments, but the existing theory...... neglects chemical effects and remains to be quantitatively tested. Here, we show that charge regulation and water self-ionization can lead to OLC by "current-induced membrane discharge'' (CIMD), even in the absence of fluid flow, in ion-exchange membranes much thicker than the local Debye screening length....... Salt depletion leads to a large electric field resulting in a local pH shift within the membrane with the effect that the membrane discharges and loses its ion selectivity. Since salt co-ions, H+ ions, and OH- ions contribute to OLC, CIMD interferes with electrodialysis (salt counterion removal...

  14. Staged membrane oxidation reactor system

    Science.gov (United States)

    Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

    2013-04-16

    Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

  15. Ceramic membrane development in NGK

    Science.gov (United States)

    Araki, Kiyoshi; Sakai, Hitoshi

    2011-05-01

    NGK Insulators, Ltd. was established in 1919 to manufacture the electric porcelain insulators for power transmission lines. Since then, our business has grown as one of the world-leading ceramics manufacturing companies and currently supply with the various environmentally-benign ceramic products to worldwide. In this paper, ceramic membrane development in NGK is described in detail. We have been selling ceramic microfiltration (MF) membranes and ultra-filtration (UF) membranes for many years to be used for solid/liquid separation in various fields such as pharmaceutical, chemical, food and semiconductor industries. In Corporate R&D, new ceramic membranes with sub-nanometer sized pores, which are fabricated on top of the membrane filters as support, are under development for gas and liquid/liquid separation processes.

  16. Ceramic membrane development in NGK

    Energy Technology Data Exchange (ETDEWEB)

    Araki, Kiyoshi; Sakai, Hitoshi, E-mail: kinsakai@ngk.co.jp [Corporate R and D, NGK Insulators, Ltd., Nagoya 467-8530 (Japan)

    2011-05-15

    NGK Insulators, Ltd. was established in 1919 to manufacture the electric porcelain insulators for power transmission lines. Since then, our business has grown as one of the world-leading ceramics manufacturing companies and currently supply with the various environmentally-benign ceramic products to worldwide. In this paper, ceramic membrane development in NGK is described in detail. We have been selling ceramic microfiltration (MF) membranes and ultra-filtration (UF) membranes for many years to be used for solid/liquid separation in various fields such as pharmaceutical, chemical, food and semiconductor industries. In Corporate R and D, new ceramic membranes with sub-nanometer sized pores, which are fabricated on top of the membrane filters as support, are under development for gas and liquid/liquid separation processes.

  17. Olefin separation membrane and process

    Science.gov (United States)

    Pinnau, Ingo; Toy, Lora G.; Casillas, Carlos

    1997-01-01

    A membrane and process for separating unsaturated hydrocarbons from fluid mixtures. The membrane and process differ from previously known membranes and processes, in that the feed and permeate streams can both be dry, the membrane need not be water or solvent swollen, and the membrane is characterized by a selectivity for an unsaturated hydrocarbon over a saturated hydrocarbon having the same number of carbon atoms of at least about 20, and a pressure-normalized flux of said unsaturated hydrocarbon of at least about 5.times.10.sup.-6 cm.sup.3 (STP)/cm.sup.2 .multidot.s.multidot.cmHg, said flux and selectivity being measured with a gas mixture containing said unsaturated and saturated hydrocarbons, and in a substantially dry environment.

  18. POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

    DEFF Research Database (Denmark)

    2001-01-01

    A method for preparing polybenzimidazole or polybenzimidazole blend membranes and fabricating gas diffusion electrodes and membrane-electrode assemblies is provided for a high temperature polymer electrolyte membrane fuel cell. Blend polymer electrolyte membranes based on PBI and various...... thermoplastic polymers for high temperature polymer electrolyte fuel cells have also been developed. Miscible blends are used for solution casting of polymer membranes (solid electrolytes). High conductivity and enhanced mechanical strength were obtained for the blend polymer solid electrolytes....... With the thermally resistant polymer, e.g., polybenzimidazole or a mixture of polybenzimidazole and other thermoplastics as binder, the carbon-supported noble metal catalyst is tape-cast onto a hydrophobic supporting substrate. When doped with an acid mixture, electrodes are assembled with an acid doped solid...

  19. Centrifugal membrane filtration -- Task 9

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    The Energy and Environmental Research Center (EERC) has teamed with SpinTek Membrane Systems, Inc., the developer of a centrifugal membrane filtration technology, to demonstrate applications for the SpinTek technology within the US Department of Energy (DOE) Environmental management (EM) Program. The technology uses supported microporous membranes rotating at high rpm, under pressure, to separate suspended and colloidal solids from liquid streams, yielding a solids-free permeate stream and a highly concentrated solids stream. This is a crosscutting technology that falls under the Efficient Separations and Processing Crosscutting Program, with potential application to tank wastes, contaminated groundwater, landfill leachate, and secondary liquid waste streams from other remediation processes, including decontamination and decommissioning systems. Membrane-screening tests were performed with the SpinTek STC-X4 static test cell filtration unit, using five ceramic membranes with different pore size and composition. Based on permeate flux, a 0.25-{micro}m TiO{sub 2}/Al{sub 2}O{sub 3} membrane was selected for detailed performance evaluation using the SpinTek ST-IIL centrifugal membrane filtration unit with a surrogate tank waste solution. An extended test run of 100 hr performed on a surrogate tank waste solution showed some deterioration in filtration performance, based on flux, apparently due to the buildup of solids near the inner portion of the membrane where relative membrane velocities were low. Continued testing of the system will focus on modifications to the shear pattern across the entire membrane surface to affect improved long-term performance.

  20. Membrane alterations in irreversibly sickled cells: hemoglobin--membrane interaction.

    Science.gov (United States)

    Lessin, L S; Kurantsin-Mills, J; Wallas, C; Weems, H

    1978-01-01

    Irreversibly sickled cells (ISCs) are sickle erythrocytes which retain bipolar elongated shapes despite reoxygenation and owe their biophysical abnormalities to acquired membrane alterations. Freeze-etched membranes both of ISCs produced in vitro and ISCs isolated in vivo reveal microbodies fixed to the internal (PS) surface which obscure spectrin filaments. Intramembranous particles (IMPs) on the intramembrane (PF) surface aggregate over regions of subsurface microbodies. Electron microscopy of diaminobenzidine-treated of ISC ghosts show the microbodies to contain hemoglobin and/or hemoglobin derivatives. Scanning electron microscopy and freeze-etching demonstrate that membrane--hemoglobin S interaction in ISCs enhances the membrane loss by microspherulation. Membrane-bound hemoglobin is five times greater in in vivo ISCs than non-ISCs, and increases during ISC production, parallelling depletion of adenosine triphosphate. Polyacrylamide gel electrophoresis of ISC membranes shows the presence of high-molecular-weight heteropolymers in the pre--band 1 region, a decrease in band 4.1 and an increase in bands 7, 8, and globin. The role of cross-linked membrane protein polymers in the generation of ISCs is discussed and is synthesized in terms of a unified concept for the determinants of the genesis of ISCs.

  1. Electrospun superhydrophobic membranes with unique structures for membrane distillation.

    Science.gov (United States)

    Liao, Yuan; Loh, Chun-Heng; Wang, Rong; Fane, Anthony G

    2014-09-24

    With modest temperature demand, low operating pressure, and high solute rejection, membrane distillation (MD) is an attractive option for desalination, waste treatment, and food and pharmaceutical processing. However, large-scale practical applications of MD are still hindered by the absence of effective membranes with high hydrophobicity, high porosity, and adequate mechanical strength, which are important properties for MD permeation fluxes, stable long-term performance, and effective packing in modules without damage. This study describes novel design strategies for highly robust superhydrophobic dual-layer membranes for MD via electrospinning. One of the newly developed membranes comprises a durable and ultrathin 3-dimensional (3D) superhydrophobic skin and porous nanofibrous support whereas another was fabricated by electrospinning 3D superhydrophobic layers on a nonwoven support. These membranes exhibit superhydrophobicity toward distilled water, salty water, oil-in-water emulsion, and beverages, which enables them to be used not only for desalination but also for other processes. The superhydrophobic dual-layer membrane #3S-N with nanofibrous support has a competitive permeation flux of 24.6 ± 1.2 kg m(-2) h(-1) in MD (feed and permeate temperate were set as 333 and 293 K, respectively) due to the higher porosity of the nanofibrous scaffold. Meanwhile, the membranes with the nonwoven support exhibit greater mechanical strength due to this support combined with better long-term performance because of the thicker 3D superhydrophobic layers. The morphology, pore size, porosity, mechanical properties, and liquid enter pressure of water of these superhydrophobic composite membranes with two different structures are reported and compared with commercial polyvinylidene fluoride membranes.

  2. The Membrane: Transertion as an organizing principle in membrane heterogeneity

    Directory of Open Access Journals (Sweden)

    Kouji eMatsumoto

    2015-06-01

    Full Text Available The bacterial membrane exhibits a significantly heterogeneous distribution of lipids and proteins. This heterogeneity results mainly from lipid-lipid, protein-protein and lipid-protein associations which are orchestrated by the coupled transcription, translation and insertion of nascent proteins into and through membrane (transertion. Transertion is central not only to the individual assembly and disassembly of large physically linked groups of macromolecules (alias hyperstructures but also to the interactions between these hyperstructures. We review here these interactions in the context of the processes in Bacillus subtilis and Escherichia coli of nutrient sensing, membrane synthesis, cytoskeletal dynamics, DNA replication, chromosome segregation and cell division.

  3. Oxygen Transport Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    S. Bandopadhyay; N. Nagabhushana; X.-D Zhou; Q. Cai; J. Yang; W.B. Yelon; W.J. James; H.U. Anderson; Alan Jacobson; C.A. Mims

    2004-10-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In this report, Moessbauer spectroscopy was used to study the local environmentals of LSFT with various level of oxygen deficiency. Ionic valence state, magnetic interaction and influence of Ti on superexchange are discussed Stable crack growth studies on Dense OTM bars provided by Praxair were done at elevated temperature, pressure and elevated conditions. Post-fracture X-ray data of the OTM fractured at 1000 C in environment were refined by FullProf code and results indicate a distortion of the parent cubic perovskite to orthorhombic structure with reduced symmetry. TGA-DTA studies on the post-fracture samples also indicated residual effect arising from the thermal and stress history of the samples. An electrochemical cell has been designed and built for measurements of the Seebeck coefficient as a function of temperature and pressure. The initial measurements on La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} are reported. Neutron diffraction measurements of the same composition are in agreement with both the stoichiometry and the kinetic behavior observed in coulometric titration measurements. A series of isotope transients under air separation mode (small gradient) were completed on the membrane of LSCrF-2828 at 900 C. Low pO{sub 2} atmospheres based on with CO-CO{sub 2} mixtures have also been admitted to the delivery side of the LSCrF-2828 membrane to produce the gradients which exist under syngas generation conditions. The COCO{sub 2} mixtures have normal isotopic {sup 18}O abundances. The evolution of {sup 18}O on the delivery side in these experiments after an {sup 18}O pulse on the air side reveals a wealth of information about the oxygen transport processes.

  4. 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.

  5. Gas Separations using Ceramic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Paul KT Liu

    2005-01-13

    This project has been oriented toward the development of a commercially viable ceramic membrane for high temperature gas separations. A technically and commercially viable high temperature gas separation membrane and process has been developed under this project. The lab and field tests have demonstrated the operational stability, both performance and material, of the gas separation thin film, deposited upon the ceramic membrane developed. This performance reliability is built upon the ceramic membrane developed under this project as a substrate for elevated temperature operation. A comprehensive product development approach has been taken to produce an economically viable ceramic substrate, gas selective thin film and the module required to house the innovative membranes for the elevated temperature operation. Field tests have been performed to demonstrate the technical and commercial viability for (i) energy and water recovery from boiler flue gases, and (ii) hydrogen recovery from refinery waste streams using the membrane/module product developed under this project. Active commercializations effort teaming with key industrial OEMs and end users is currently underway for these applications. In addition, the gas separation membrane developed under this project has demonstrated its economical viability for the CO2 removal from subquality natural gas and landfill gas, although performance stability at the elevated temperature remains to be confirmed in the field.

  6. Inflation and Failure of Polymeric Membranes

    DEFF Research Database (Denmark)

    Hassager, Ole; Neergaard, Jesper

    2000-01-01

    We consider the inflation of an axisymmetric polymeric membrane.Some membranes composed of viscoelastic materialsdescribed by a Mooney-Rivlin model show a monotone increasingpressure during inflation. These materialsdevelop a homogeneous membrane thickness in agreement with the Considere-Pearson ......We consider the inflation of an axisymmetric polymeric membrane.Some membranes composed of viscoelastic materialsdescribed by a Mooney-Rivlin model show a monotone increasingpressure during inflation. These materialsdevelop a homogeneous membrane thickness in agreement with the Considere...

  7. Tympanic membrane gangrene

    Directory of Open Access Journals (Sweden)

    D R Surya Prakash

    2015-01-01

    Full Text Available Necrosis of tympanic membrane (TM can be due to infections, drugs, radiation, and foreign body. Strain of group A Streptococcus is associated with acute otitis media or in immunocompromised individuals resulting in TM necrosis. Gangrene of lower limb has been described, but the selective loss of TM due to emboli is an uncommon finding. A 62-year-old female presented with sudden behavioral changes and irrelevant talk. After 2 days, she noticed a discharge from left ear. There was perforation of left TM in posterior superior and inferior quadrant with areas of the black patch around the perforation suggesting a loss of blood supply. Patient was recently detected retrovirus positive with multiple lung shadows. Patient is not on any anti-retroviral medications or other medications. The discharge started 2 days after an episode of left middle cerebral artery infarct due to emboli with no previous history of ear symptoms. Culture of discharge showed no growth. This suggests that TM might have gone for gangrene due to emboli affecting deep auricular artery branch or posterior tympanic branch, which is a branch of the stylomastoid artery.

  8. Hierarchy in inorganic membranes.

    Science.gov (United States)

    Caro, Juergen

    2016-06-13

    Thin films of a few μm thickness for particle filtration and gas separation cannot be applied as self-supporting layers since they are mechanically insufficiently strong. Therefore, these top layers for particle filtration and gas separation are usually deposited on porous mechanically strong supports with a hierarchical pore structure. To reduce the pressure drop of a gas stream over the membrane and to ensure high fluxes in filtration and gas separation, the cross section of the support is usually asymmetric or graded with a small thickness of the layer with the smallest pore size called the top layer. Since the pressure drop over a capillary with radius r is ∼r(4), the layer with the smallest pore size should be as thin as possible. The disk-like planar supports are usually prepared by sequential tape casting which is an expensive technology. Tubular supports with a hierarchical cross section can be prepared in one step by hollow fiber spinning, double mantle spinning or centrifugal casting.

  9. Ultrastructure of Reissner's membrane in the rabbit

    DEFF Research Database (Denmark)

    Qvortrup, K.; Rostgaard, Jørgen; Bretlau, P.

    1994-01-01

    Anatomy, Reissner's membrane, electron microscopy, tubulocisternal endoplasmic reticulum, subsurface cisterns, rabbit......Anatomy, Reissner's membrane, electron microscopy, tubulocisternal endoplasmic reticulum, subsurface cisterns, rabbit...

  10. Polyunsaturated Lipids Regulate Membrane Domain Stability by Tuning Membrane Order.

    Science.gov (United States)

    Levental, Kandice R; Lorent, Joseph H; Lin, Xubo; Skinkle, Allison D; Surma, Michal A; Stockenbojer, Emily A; Gorfe, Alemayehu A; Levental, Ilya

    2016-04-26

    The plasma membrane (PM) serves as the functional interface between a cell and its environment, hosting extracellular signal transduction and nutrient transport among a variety of other processes. To support this extensive functionality, PMs are organized into lateral domains, including ordered, lipid-driven assemblies termed lipid rafts. Although the general requirements for ordered domain formation are well established, how these domains are regulated by cell-endogenous mechanisms or exogenous perturbations has not been widely addressed. In this context, an intriguing possibility is that dietary fats can incorporate into membrane lipids to regulate the properties and physiology of raft domains. Here, we investigate the effects of polyunsaturated fats on the organization of membrane domains across a spectrum of membrane models, including computer simulations, synthetic lipid membranes, and intact PMs isolated from mammalian cells. We observe that the ω-3 polyunsaturated fatty acid docosahexaenoic acid is robustly incorporated into membrane lipids, and this incorporation leads to significant remodeling of the PM lipidome. Across model systems, docosahexaenoic acid-containing lipids enhance the stability of ordered raft domains by increasing the order difference between them and coexisting nonraft domains. The relationship between interdomain order disparity and the stability of phase separation holds for a spectrum of different perturbations, including manipulation of cholesterol levels and high concentrations of exogenous amphiphiles, suggesting it as a general feature of the organization of biological membranes. These results demonstrate that polyunsaturated fats affect the composition and organization of biological membranes, suggesting a potential mechanism for the extensive effects of dietary fat on health and disease.

  11. Effect of membrane polymeric materials on relationship between surface pore size and membrane fouling in membrane bioreactors

    Science.gov (United States)

    Miyoshi, Taro; Yuasa, Kotaku; Ishigami, Toru; Rajabzadeh, Saeid; Kamio, Eiji; Ohmukai, Yoshikage; Saeki, Daisuke; Ni, Jinren; Matsuyama, Hideto

    2015-03-01

    We investigated the effect of different membrane polymeric materials on the relationship between membrane pore size and development of membrane fouling in a membrane bioreactor (MBR). Membranes with different pore sizes were prepared using three different polymeric materials, cellulose acetate butyrate (CAB), polyvinyl butyral (PVB), and polyvinylidene fluoride (PVDF), and the development of membrane fouling in each membrane was evaluated by batch filtration tests using a mixed liquor suspension obtained from a laboratory-scale MBR. The results revealed that the optimal membrane pore size to mitigate membrane fouling differed depending on membrane polymeric material. For PVDF membranes, the degree of membrane fouling decreased as membrane pore size increased. In contrast, CAB membranes with smaller pores had less fouling propensity than those with larger ones. Such difference can be attributed to the difference in major membrane foulants in each membrane; in PVDF, they were small colloids or dissolved organics in which proteins are abundant, and in CAB, microbial flocs. The results obtained in this study strongly suggested that optimum operating conditions of MBRs differ depending on the characteristics of the used membrane.

  12. Changes in components of pigments and proteins in rice photosynthetic membrane during chilling stress%低温胁迫期间水稻光合膜色素 与蛋白水平的变化

    Institute of Scientific and Technical Information of China (English)

    曾乃燕; 何军贤; 赵文; 梁厚果

    2000-01-01

    A comparative study on changes in components of pigments and proteins in rice thylakoid membranes during 4℃ and 11℃ chilling stress was conducted.The results showed that low temperature at 4℃ not only decreased the contents of photosynthetic pigments (chlorophylls and carotenoids) but caused a profound variation in contents of the proteins in thylakoid membranes:most membrane proteins decreased progressively as the stress developed,and a new protein with a molecular mass of about 32.5 kD appeared on the third day of stress.Compared with 4℃,stress at 11℃ only caused decrease in contents of photosynthetic pigments,but had little effect on components and levels of thylakoid proteins.It was also found that treatments at both temperatures caused evident variation in the chla/b ratio.The chla/b ratio decreased at first during the early period of chilling stress (4℃,1 d and 11℃,2 d) but increased thereafter,suggesting that the reaction centres of the photosynthetic apparatus in plants are probably more sensitive to low temperature than the antenna components%对4℃和11℃两种低温胁迫过程中水稻类囊体膜色素与蛋白组成的变化进行了比较研究。结果表明:4℃低温不仅使类囊体膜中的光合色素(叶绿素、类胡萝卜素)含量降低,而且还引起膜蛋白组成的深刻变化,表现在大部分原有膜蛋白组分的含量在低温下明显降低,同时在低温处理的第3天诱导出一条32.5 kD的新蛋白带。与4℃处理相比,11℃低温处理只引起了光合色素含量的降低,而对类囊体膜蛋白组成的影响不大。另外发现,两种低温处理在引起光合色素含量降低的同时,还引起chla/b比值的明显变化。在低温处理的初期(4℃,1 d和11℃,2 d),chla/b比值有一明显下降,而此后又逐渐升高。这一结果暗示,植物光合器的反应中心可能比其天线组分对低温胁迫更敏感。

  13. Applicability of dynamic membrane technology in anaerobic membrane bioreactors.

    Science.gov (United States)

    Ersahin, Mustafa Evren; Ozgun, Hale; Tao, Yu; van Lier, Jules B

    2014-01-01

    This study investigated the applicability of dynamic membrane technology in anaerobic membrane bioreactors for the treatment of high strength wastewaters. A monofilament woven fabric was used as support material for dynamic membrane formation. An anaerobic dynamic membrane bioreactor (AnDMBR) was operated under a variety of operational conditions, including different sludge retention times (SRTs) of 20 and 40 days in order to determine the effect of SRT on both biological performance and dynamic membrane filtration characteristics. High COD removal efficiencies exceeding 99% were achieved during the operation at both SRTs. Higher filtration resistances were measured during the operation at SRT of 40 days in comparison to SRT of 20 days, applying a stable flux of 2.6 L/m(2) h. The higher filtration resistances coincided with lower extracellular polymeric substances concentration in the bulk sludge at SRT of 40 days, likely resulting in a decreased particle flocculation. Results showed that dynamic membrane technology achieved a stable and high quality permeate and AnDMBRs can be used as a reliable and satisfactory technology for treatment of high strength wastewaters.

  14. Lateral proton transfer between the membrane and a membrane protein.

    Science.gov (United States)

    Ojemyr, Linda; Sandén, Tor; Widengren, Jerker; Brzezinski, Peter

    2009-03-17

    Proton transport across biological membranes is a key step of the energy conservation machinery in living organisms, and it has been proposed that the membrane itself plays an important role in this process. In the present study we have investigated the effect of incorporation of a proton transporter, cytochrome c oxidase, into a membrane on the protonation kinetics of a fluorescent pH-sensitive probe attached at the surface of the protein. The results show that proton transfer to the probe was slightly accelerated upon attachment at the protein surface (approximately 7 x 1010 s(-1) M(-1), compared to the expected value of (1-2) x 10(10) s(-1) M(-1)), which is presumably due to the presence of acidic/His groups in the vicinity. Upon incorporation of the protein into small unilamellar phospholipid vesicles the rate increased by more than a factor of 400 to approximately 3 x 10(13) s(-1) M(-1), which indicates that the protein-attached probe is in rapid protonic contact with the membrane surface. The results indicate that the membrane acts to accelerate proton uptake by the membrane-bound proton transporter.

  15. Geometry of Membrane Sigma Models

    CERN Document Server

    Vysoky, Jan

    2015-01-01

    String theory still remains one of the promising candidates for a unification of the theory of gravity and quantum field theory. One of its essential parts is relativistic description of moving multi-dimensional objects called membranes (or p-branes) in a curved spacetime. On the classical field theory level, they are described by an action functional extremalising the volume of a manifold swept by a propagating membrane. This and related field theories are collectively called membrane sigma models. Differential geometry is an important mathematical tool in the study of string theory. It turns out that string and membrane backgrounds can be conveniently described using objects defined on a direct sum of tangent and cotangent bundles of the spacetime manifold. Mathematical field studying such object is called generalized geometry. Its integral part is the theory of Leibniz algebroids, vector bundles with a Leibniz algebra bracket on its module of smooth sections. Special cases of Leibniz algebroids are better ...

  16. Basement membrane proteoglycans and development

    DEFF Research Database (Denmark)

    Couchman, J R; Abrahamson, D R; McCarthy, K J

    1993-01-01

    Basement membranes contain distinct collagen, glycoprotein and proteoglycan species, and these exhibit considerable heterogeneity in isoform or type when different tissue types are compared. Additionally, many components are differentially expressed in organogenesis. We have considered the distri...

  17. Aniseikonia associated with epiretinal membranes

    OpenAIRE

    Ugarte, M.; Williamson, T H

    2005-01-01

    Aims: To determine whether the computerised version of the new aniseikonia test (NAT) is a valid, reliable method to measure aniseikonia and establish whether aniseikonia occurs in patients with epiretinal membranes (ERM) with preserved good visual acuity.

  18. Mathematical modelling of membrane separation

    DEFF Research Database (Denmark)

    Vinther, Frank

    This thesis concerns mathematical modelling of membrane separation. The thesis consists of introductory theory on membrane separation, equations of motion, and properties of dextran, which will be the solute species throughout the thesis. Furthermore, the thesis consist of three separate mathemat......This thesis concerns mathematical modelling of membrane separation. The thesis consists of introductory theory on membrane separation, equations of motion, and properties of dextran, which will be the solute species throughout the thesis. Furthermore, the thesis consist of three separate....... It is found that the probability of entering the pore is highest when the largest of the radii in the ellipse is equal to half the radius of the pore, in case of molecules with circular radius less than the pore radius. The results are directly related to the macroscopic distribution coefficient...

  19. Membrane solutions to Horava gravity

    CERN Document Server

    Argüelles, Carlos R

    2010-01-01

    We investigated purely gravitational membrane solutions to Ho\\v rava nonrelativistic theory of gravity with detailed balance in $3+1$ dimensions. We find that for arbitrary values of the running parameter $\\lambda>1/3$ two branches of membrane solutions exist, and that in the special case $\\lambda=1$ one of them is degenerate, the lapse function being undetermined. For negative values of the cosmological constant, the solution contains a single membrane sitting at the center of a space, which extends infinitely in the transverse direction approaching a Lifshitz metric. For positive values of the cosmological constant, the solution represents a space that is bounded in the transverse direction, with two parallel membranes hidden behind event horizons sitting at each of the boundaries.

  20. Disorders of red cell membrane

    National Research Council Canada - National Science Library

    An, Xiuli; Mohandas, Narla

    2008-01-01

    Summary Studies during the last three decades have enabled the development of detailed molecular insights into the structural basis of altered function in various inherited red cell membrane disorders...

  1. Composite solid polymer electrolyte membranes

    Energy Technology Data Exchange (ETDEWEB)

    Formato, Richard M. (Shrewsbury, MA); Kovar, Robert F. (Wrentham, MA); Osenar, Paul (Watertown, MA); Landrau, Nelson (Marlborough, MA); Rubin, Leslie S. (Newton, MA)

    2001-06-19

    The present invention relates to composite solid polymer electrolyte membranes (SPEMs) which include a porous polymer substrate interpenetrated with an ion-conducting material. SPEMs of the present invention are useful in electrochemical applications, including fuel cells and electrodialysis.

  2. Electronic polymers in lipid membranes.

    Science.gov (United States)

    Johansson, Patrik K; Jullesson, David; Elfwing, Anders; Liin, Sara I; Musumeci, Chiara; Zeglio, Erica; Elinder, Fredrik; Solin, Niclas; Inganäs, Olle

    2015-06-10

    Electrical interfaces between biological cells and man-made electrical devices exist in many forms, but it remains a challenge to bridge the different mechanical and chemical environments of electronic conductors (metals, semiconductors) and biosystems. Here we demonstrate soft electrical interfaces, by integrating the metallic polymer PEDOT-S into lipid membranes. By preparing complexes between alkyl-ammonium salts and PEDOT-S we were able to integrate PEDOT-S into both liposomes and in lipid bilayers on solid surfaces. This is a step towards efficient electronic conduction within lipid membranes. We also demonstrate that the PEDOT-S@alkyl-ammonium:lipid hybrid structures created in this work affect ion channels in the membrane of Xenopus oocytes, which shows the possibility to access and control cell membrane structures with conductive polyelectrolytes.

  3. WOOD CELLULOSE ACETATE MEMBRANE 179

    African Journals Online (AJOL)

    DR. AMINU

    2013-06-01

    Jun 1, 2013 ... process. The harnessed cellulose was acetylated by the process of step-wise acetylation to a degree of acetylation (DA) of ... several fields including oil recovery (Heinrich and ..... removed by filtration using the membrane was.

  4. Robust mixed conducting membrane structure

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention provides a membrane structure, comprising in said order a first electronically conducting layer, an ionically conducting layer, and a second electronically conducting layer, characterized in that the first and second electronically conducting layers are internally short circ...

  5. Alphavirus Entry and Membrane Fusion

    Directory of Open Access Journals (Sweden)

    Margaret Kielian

    2010-03-01

    Full Text Available The study of enveloped animal viruses has greatly advanced our understanding of the general properties of membrane fusion and of the specific pathways that viruses use to infect the host cell. The membrane fusion proteins of the alphaviruses and flaviviruses have many similarities in structure and function. As reviewed here, alphaviruses use receptor-mediated endocytic uptake and low pH-triggered membrane fusion to deliver their RNA genomes into the cytoplasm. Recent advances in understanding the biochemistry and structure of the alphavirus membrane fusion protein provide a clearer picture of this fusion reaction, including the protein’s conformational changes during fusion and the identification of key domains. These insights into the alphavirus fusion mechanism suggest new areas for experimental investigation and potential inhibitor strategies for anti-viral therapy.

  6. Current-Induced Membrane Discharge

    OpenAIRE

    Andersen, MB; Soestbergen, van, M Michiel; A Mani; Bruus, H.; Biesheuvel, PM; Bazant, MZ

    2012-01-01

    Possible mechanisms for overlimiting current (OLC) through aqueous ion-exchange membranes (exceeding diffusion limitation) have been debated for half a century. Flows consistent with electro-osmotic instability have recently been observed in microfluidic experiments, but the existing theory neglects chemical effects and remains to be quantitatively tested. Here, we show that charge regulation and water self-ionization can lead to OLC by “current-induced membrane discharge” (CIMD), even in the...

  7. Sulfonated Polyetherimide and Its Membranes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Polyetherimide (PEI) was sulfonated by chlorosulfonic acid for the first time. The sulfonated products were characterized by FT-IR, DSC, ion exchange capacity and water sorption measurement. The hydrophilicity of PEI was improved by the sulfonation. The PEI was blended with the sodium salt form of sulfonated PEI (SPEI) to prepare microporous membranes. The morphologies of the membranes were studied with Scanning Electron Microscope (SEM).

  8. Mobility in geometrically confined membranes.

    Science.gov (United States)

    Domanov, Yegor A; Aimon, Sophie; Toombes, Gilman E S; Renner, Marianne; Quemeneur, François; Triller, Antoine; Turner, Matthew S; Bassereau, Patricia

    2011-08-02

    Lipid and protein lateral mobility is essential for biological function. Our theoretical understanding of this mobility can be traced to the seminal work of Saffman and Delbrück, who predicted a logarithmic dependence of the protein diffusion coefficient (i) on the inverse of the size of the protein and (ii) on the "membrane size" for membranes of finite size [Saffman P, Delbrück M (1975) Proc Natl Acad Sci USA 72:3111-3113]. Although the experimental proof of the first prediction is a matter of debate, the second has not previously been thought to be experimentally accessible. Here, we construct just such a geometrically confined membrane by forming lipid bilayer nanotubes of controlled radii connected to giant liposomes. We followed the diffusion of individual molecules in the tubular membrane using single particle tracking of quantum dots coupled to lipids or voltage-gated potassium channels KvAP, while changing the membrane tube radius from approximately 250 to 10 nm. We found that both lipid and protein diffusion was slower in tubular membranes with smaller radii. The protein diffusion coefficient decreased as much as 5-fold compared to diffusion on the effectively flat membrane of the giant liposomes. Both lipid and protein diffusion data are consistent with the predictions of a hydrodynamic theory that extends the work of Saffman and Delbrück to cylindrical geometries. This study therefore provides strong experimental support for the ubiquitous Saffman-Delbrück theory and elucidates the role of membrane geometry and size in regulating lateral diffusion.

  9. Robust mixed conducting membrane structure

    DEFF Research Database (Denmark)

    2010-01-01

    The present invention provides a membrane structure, comprising in said order a first electronically conducting layer, an ionically conducting layer, and a second electronically conducting layer, characterized in that the first and second electronically conducting layers are internally short...... circuited. The present invention further provides a method of producing the above membrane structure, comprising the steps of : providing a ionically conducting layer; applying at least one layer of electronically conducting material on each side of said ionically conducting layer; sintering the multilayer...

  10. Membranes in Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Junbo Hou

    2012-07-01

    Full Text Available Lithium ion batteries have proven themselves the main choice of power sources for portable electronics. Besides consumer electronics, lithium ion batteries are also growing in popularity for military, electric vehicle, and aerospace applications. The present review attempts to summarize the knowledge about some selected membranes in lithium ion batteries. Based on the type of electrolyte used, literature concerning ceramic-glass and polymer solid ion conductors, microporous filter type separators and polymer gel based membranes is reviewed.

  11. Membranes in lithium ion batteries.

    Science.gov (United States)

    Yang, Min; Hou, Junbo

    2012-07-04

    Lithium ion batteries have proven themselves the main choice of power sources for portable electronics. Besides consumer electronics, lithium ion batteries are also growing in popularity for military, electric vehicle, and aerospace applications. The present review attempts to summarize the knowledge about some selected membranes in lithium ion batteries. Based on the type of electrolyte used, literature concerning ceramic-glass and polymer solid ion conductors, microporous filter type separators and polymer gel based membranes is reviewed.

  12. Membrane fusion during poxvirus entry.

    Science.gov (United States)

    Moss, Bernard

    2016-12-01

    Poxviruses comprise a large family of enveloped DNA viruses that infect vertebrates and invertebrates. Poxviruses, unlike most DNA viruses, replicate in the cytoplasm and encode enzymes and other proteins that enable entry, gene expression, genome replication, virion assembly and resistance to host defenses. Entry of vaccinia virus, the prototype member of the family, can occur at the plasma membrane or following endocytosis. Whereas many viruses encode one or two proteins for attachment and membrane fusion, vaccinia virus encodes four proteins for attachment and eleven more for membrane fusion and core entry. The entry-fusion proteins are conserved in all poxviruses and form a complex, known as the Entry Fusion Complex (EFC), which is embedded in the membrane of the mature virion. An additional membrane that encloses the mature virion and is discarded prior to entry is present on an extracellular form of the virus. The EFC is held together by multiple interactions that depend on nine of the eleven proteins. The entry process can be divided into attachment, hemifusion and core entry. All eleven EFC proteins are required for core entry and at least eight for hemifusion. To mediate fusion the virus particle is activated by low pH, which removes one or more fusion repressors that interact with EFC components. Additional EFC-interacting fusion repressors insert into cell membranes and prevent secondary infection. The absence of detailed structural information, except for two attachment proteins and one EFC protein, is delaying efforts to determine the fusion mechanism.

  13. Plant actin controls membrane permeability.

    Science.gov (United States)

    Hohenberger, Petra; Eing, Christian; Straessner, Ralf; Durst, Steffen; Frey, Wolfgang; Nick, Peter

    2011-09-01

    The biological effects of electric pulses with low rise time, high field strength, and durations in the nanosecond range (nsPEFs) have attracted considerable biotechnological and medical interest. However, the cellular mechanisms causing membrane permeabilization by nanosecond pulsed electric fields are still far from being understood. We investigated the role of actin filaments for membrane permeability in plant cells using cell lines where different degrees of actin bundling had been introduced by genetic engineering. We demonstrate that stabilization of actin increases the stability of the plasma membrane against electric permeabilization recorded by penetration of Trypan Blue into the cytoplasm. By use of a cell line expressing the actin bundling WLIM domain under control of an inducible promotor we can activate membrane stabilization by the glucocorticoid analog dexamethasone. By total internal reflection fluorescence microscopy we can visualize a subset of the cytoskeleton that is directly adjacent to the plasma membrane. We conclude that this submembrane cytoskeleton stabilizes the plasma membrane against permeabilization through electric pulses. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Tethered bimolecular lipid membranes - A novel model membrane platform

    Energy Technology Data Exchange (ETDEWEB)

    Knoll, Wolfgang; Koeper, Ingo; Naumann, Renate; Sinner, Eva-Kathrin [Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany)

    2008-10-01

    This contribution summarizes some of our efforts in designing, synthesizing, assembling, and characterizing functional tethered bimolecular lipid membranes (tBLMs) as a novel platform for biophysical studies of and with artificial membranes or for sensor development employing, e.g., membrane integral receptor proteins. Chemical coupling schemes based on thiol groups for Au substrates or silanes used in the case of oxide surfaces allow for the covalent and, hence, chemically and mechanically robust attachment of anchor lipids to the solid support, stabilizing the proximal layer of a tethered membrane on the transducer surface. Surface plasmon optics, the quartz crystal microbalance, fluorescence- and IR spectroscopies, and electrochemical techniques are used to characterize the build-up of these complex supramolecular interfacial architectures. We demonstrate, in particular, that bilayers with a specific electrical resistance of better than 10 M{omega} cm{sup 2} can be achieved routinely with this approach. The functionalization of the lipid membranes by the incorporation of peptides is demonstrated for the carrier valinomycin which shows in our tBLMs the expected discrimination by four orders of magnitude between the translocation of K{sup +}- and Na{sup +}-ions across the hydrophobic barrier. For the synthetic channel-forming peptide M2 the high electrical resistance of the bilayer with the correspondingly low background current allows for the recording of even single channel current fluctuations. From the many membrane proteins that we reconstituted so far we describe results obtained with the redox-protein cytochrome c oxidase. Here, we also use a genetically modified mutant with a His-tag at either the C- or the N-terminus for the oriented attachment of the protein via the NTA/Ni{sup 2+} approach. With this strategy, we not only can control the density of the immobilized functional units, we introduce a completely new and alternative concept for the

  15. The Molecules of the Cell Membrane.

    Science.gov (United States)

    Bretscher, Mark S.

    1985-01-01

    Cell membrane molecules form a simple, two-dimensional liquid controlling what enters and leaves the cell. Discusses cell membrane molecular architecture, plasma membranes, epithelial cells, cycles of endocytosis and exocytosis, and other topics. Indicates that some cells internalize, then recycle, membrane area equivalent to their entire surface…

  16. Nonadhesive acoustic membranes based on polyimide

    Directory of Open Access Journals (Sweden)

    Vorob'ev A.V.

    2014-02-01

    Full Text Available The paper presents a comparison of technical characteristics of acoustic membranes with an adhesive layer and nonadhesive membranes. The authors present the manufacturing technology for acoustic membranes based on aluminum-polyimide film dielectrics and analyze the advantages of such membranes in comparison to other sound emitters.

  17. Hydrogen purifier module with membrane support

    Science.gov (United States)

    A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

    2012-07-24

    A hydrogen purifier utilizing a hydrogen-permeable membrane to purify hydrogen from mixed gases containing hydrogen is disclosed. Improved mechanical support for the permeable membrane is described, enabling forward or reverse differential pressurization of the membrane, which further stabilizes the membrane from wrinkling upon hydrogen uptake.

  18. Characterisation of adaptive fluidic silicone membrane lenses

    CSIR Research Space (South Africa)

    Schneider, F

    2009-09-01

    Full Text Available membrane shapes for a lens volume of 1 µl at divorce homogeneous membrane thicknesses. The measurement of the system behaviour is realized by the laser-profilometer in the dynamic mode. For the lens with a homogeneous membrane the membrane surface...

  19. Ninth International Workshop on Plant Membrane Biology

    Energy Technology Data Exchange (ETDEWEB)

    1993-12-31

    This report is a compilation of abstracts from papers which were discussed at a workshop on plant membrane biology. Topics include: plasma membrane ATP-ases; plant-environment interactions, membrane receptors; signal transduction; ion channel physiology; biophysics and molecular biology; vaculor H+ pumps; sugar carriers; membrane transport; and cellular structure and function.

  20. Characterization of organic membrane foulants in a forward osmosis membrane bioreactor treating anaerobic membrane bioreactor effluent.

    Science.gov (United States)

    Ding, Yi; Tian, Yu; Li, Zhipeng; Liu, Feng; You, Hong

    2014-09-01

    In this study, two aerobic forward osmosis (FO) membrane bioreactors (MBR) were utilized to treat the effluent of mesophilic (35°C) and atmospheric (25°C) anaerobic MBRs, respectively. The results showed that the FO membrane process could significantly improve the removal efficiencies of N and P. Meanwhile, the flux decline of the FOMBR treating effluent of mesophilic AnMBR (M-FOMBR) was higher than that treating effluent of atmospheric AnMBR (P-FOMBR). The organic membrane foulants in the two FOMBRs were analyzed to understand the membrane fouling behavior in FO processes. It was found that the slightly increased accumulation of protein-like substances into external foulants did not cause faster flux decline in P-FOMBR than that in M-FOMBR. However, the quantity of organic matter tended to deposit or adsorb into FO membrane pores in P-FOMBR was less than that in M-FOMBR, which was accordance with the tendency of membrane fouling indicated by flux decline.