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Sample records for protein stoichiometry collectively

  1. Differential Stoichiometry among Core Ribosomal Proteins

    Directory of Open Access Journals (Sweden)

    Nikolai Slavov

    2015-11-01

    Full Text Available Understanding the regulation and structure of ribosomes is essential to understanding protein synthesis and its dysregulation in disease. While ribosomes are believed to have a fixed stoichiometry among their core ribosomal proteins (RPs, some experiments suggest a more variable composition. Testing such variability requires direct and precise quantification of RPs. We used mass spectrometry to directly quantify RPs across monosomes and polysomes of mouse embryonic stem cells (ESC and budding yeast. Our data show that the stoichiometry among core RPs in wild-type yeast cells and ESC depends both on the growth conditions and on the number of ribosomes bound per mRNA. Furthermore, we find that the fitness of cells with a deleted RP-gene is inversely proportional to the enrichment of the corresponding RP in polysomes. Together, our findings support the existence of ribosomes with distinct protein composition and physiological function.

  2. Quantification of Lysine Acetylation and Succinylation Stoichiometry in Proteins Using Mass Spectrometric Data-Independent Acquisitions (SWATH)

    Science.gov (United States)

    Meyer, Jesse G.; D'Souza, Alexandria K.; Sorensen, Dylan J.; Rardin, Matthew J.; Wolfe, Alan J.; Gibson, Bradford W.; Schilling, Birgit

    2016-11-01

    Post-translational modification of lysine residues by NƐ-acylation is an important regulator of protein function. Many large-scale protein acylation studies have assessed relative changes of lysine acylation sites after antibody enrichment using mass spectrometry-based proteomics. Although relative acylation fold-changes are important, this does not reveal site occupancy, or stoichiometry, of individual modification sites, which is critical to understand functional consequences. Recently, methods for determining lysine acetylation stoichiometry have been proposed based on ratiometric analysis of endogenous levels to those introduced after quantitative per-acetylation of proteins using stable isotope-labeled acetic anhydride. However, in our hands, we find that these methods can overestimate acetylation stoichiometries because of signal interferences when endogenous levels of acylation are very low, which is especially problematic when using MS1 scans for quantification. In this study, we sought to improve the accuracy of determining acylation stoichiometry using data-independent acquisition (DIA). Specifically, we use SWATH acquisition to comprehensively collect both precursor and fragment ion intensity data. The use of fragment ions for stoichiometry quantification not only reduces interferences but also allows for determination of site-level stoichiometry from peptides with multiple lysine residues. We also demonstrate the novel extension of this method to measurements of succinylation stoichiometry using deuterium-labeled succinic anhydride. Proof of principle SWATH acquisition studies were first performed using bovine serum albumin for both acetylation and succinylation occupancy measurements, followed by the analysis of more complex samples of E. coli cell lysates. Although overall site occupancy was low (<1%), some proteins contained lysines with relatively high acetylation occupancy.

  3. A cell-free assay to determine the stoichiometry of plasma membrane proteins.

    Science.gov (United States)

    Trigo, Cesar; Vivar, Juan P; Gonzalez, Carlos B; Brauchi, Sebastian

    2013-04-01

    Plasma membrane receptors, transporters, and ion channel molecules are often found as oligomeric structures that participate in signaling cascades essential for cell survival. Different states of protein oligomerization may play a role in functional control and allosteric regulation. Stochastic GFP-photobleaching (SGP) has emerged as an affordable and simple method to determine the stoichiometry of proteins at the plasma membrane. This non-invasive optical approach can be useful for total internal reflection of fluorescence microscopy (TIRFM), where signal-to-noise ratio is very high at the plasma membrane. Here, we report an alternative methodology implemented on a standard laser scanning confocal microscope (LSCM). The simplicity of our method will allow for its implementation in any epifluorescence microscope of choice.

  4. Multi-signal sedimentation velocity analysis with mass conservation for determining the stoichiometry of protein complexes.

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    Chad A Brautigam

    Full Text Available Multi-signal sedimentation velocity analytical ultracentrifugation (MSSV is a powerful tool for the determination of the number, stoichiometry, and hydrodynamic shape of reversible protein complexes in two- and three-component systems. In this method, the evolution of sedimentation profiles of macromolecular mixtures is recorded simultaneously using multiple absorbance and refractive index signals and globally transformed into both spectrally and diffusion-deconvoluted component sedimentation coefficient distributions. For reactions with complex lifetimes comparable to the time-scale of sedimentation, MSSV reveals the number and stoichiometry of co-existing complexes. For systems with short complex lifetimes, MSSV reveals the composition of the reaction boundary of the coupled reaction/migration process, which we show here may be used to directly determine an association constant. A prerequisite for MSSV is that the interacting components are spectrally distinguishable, which may be a result, for example, of extrinsic chromophores or of different abundances of aromatic amino acids contributing to the UV absorbance. For interacting components that are spectrally poorly resolved, here we introduce a method for additional regularization of the spectral deconvolution by exploiting approximate knowledge of the total loading concentrations. While this novel mass conservation principle does not discriminate contributions to different species, it can be effectively combined with constraints in the sedimentation coefficient range of uncomplexed species. We show in theory, computer simulations, and experiment, how mass conservation MSSV as implemented in SEDPHAT can enhance or even substitute for the spectral discrimination of components. This should broaden the applicability of MSSV to the analysis of the composition of reversible macromolecular complexes.

  5. Characterization, stoichiometry, and stability of salivary protein-tannin complexes by ESI-MS and ESI-MS/MS.

    Science.gov (United States)

    Canon, Francis; Paté, Franck; Meudec, Emmanuelle; Marlin, Thérèse; Cheynier, Véronique; Giuliani, Alexandre; Sarni-Manchado, Pascale

    2009-12-01

    Numerous protein-polyphenol interactions occur in biological and food domains particularly involving proline-rich proteins, which are representative of the intrinsically unstructured protein group (IUP). Noncovalent protein-ligand complexes are readily detected by electrospray ionization mass spectrometry (ESI-MS), which also gives access to ligand binding stoichiometry. Surprisingly, the study of interactions between polyphenolic molecules and proteins is still an area where ESI-MS has poorly benefited, whereas it has been extensively applied to the detection of noncovalent complexes. Electrospray ionization mass spectrometry has been applied to the detection and the characterization of the complexes formed between tannins and a human salivary proline-rich protein (PRP), namely IB5. The study of the complex stability was achieved by low-energy collision-induced dissociation (CID) measurements, which are commonly implemented using triple quadrupole, hybrid quadrupole time-of-flight, or ion trap instruments. Complexes composed of IB5 bound to a model polyphenol EgCG have been detected by ESI-MS and further analyzed by MS/MS. Mild ESI interface conditions allowed us to observe intact noncovalent PRP-tannin complexes with stoichiometries ranging from 1:1 to 1:5. Thus, ESI-MS shows its efficiency for (1) the study of PRP-tannin interactions, (2) the determination of stoichiometry, and (3) the study of complex stability. We were able to establish unambiguously both their stoichiometries and their overall subunit architecture via tandem mass spectrometry and solution disruption experiments. Our results prove that IB5.EgCG complexes are maintained intact in the gas phase.

  6. A model for variable phytoplankton stoichiometry based on cell protein regulation

    Directory of Open Access Journals (Sweden)

    J. A. Bonachela

    2013-06-01

    Full Text Available The elemental ratios of marine phytoplankton emerge from complex interactions between the biotic and abiotic components of the ocean, and reflect the plastic response of individuals to changes in their environment. The stoichiometry of phytoplankton is, thus, dynamic and dependent on the physiological state of the cell. We present a theoretical model for the dynamics of the carbon, nitrogen and phosphorus contents of a phytoplankton population. By representing the regulatory processes controlling nutrient uptake, and focusing on the relation between nutrient content and protein synthesis, our model qualitatively replicates existing experimental observations for nutrient content and ratios. The population described by our model takes up nutrients in proportions that match the input ratios for a broad range of growth conditions. In addition, there are two zones of single-nutrient limitation separated by a wide zone of co-limitation. Within the co-limitation zone, a single point can be identified where nutrients are supplied in an optimal ratio. When different species compete, the existence of a wide co-limitation zone implies a more complex pattern of coexistence and exclusion compared to previous model predictions. However, additional comprehensive laboratory experiments are needed to test our predictions. Our model contributes to the understanding of the global cycles of oceanic nitrogen and phosphorus, as well as the elemental ratios of these nutrients in phytoplankton populations.

  7. Combining biophysical methods for the analysis of protein complex stoichiometry and affinity in SEDPHAT

    International Nuclear Information System (INIS)

    Zhao, Huaying; Schuck, Peter

    2015-01-01

    Global multi-method analysis for protein interactions (GMMA) can increase the precision and complexity of binding studies for the determination of the stoichiometry, affinity and cooperativity of multi-site interactions. The principles and recent developments of biophysical solution methods implemented for GMMA in the software SEDPHAT are reviewed, their complementarity in GMMA is described and a new GMMA simulation tool set in SEDPHAT is presented. Reversible macromolecular interactions are ubiquitous in signal transduction pathways, often forming dynamic multi-protein complexes with three or more components. Multivalent binding and cooperativity in these complexes are often key motifs of their biological mechanisms. Traditional solution biophysical techniques for characterizing the binding and cooperativity are very limited in the number of states that can be resolved. A global multi-method analysis (GMMA) approach has recently been introduced that can leverage the strengths and the different observables of different techniques to improve the accuracy of the resulting binding parameters and to facilitate the study of multi-component systems and multi-site interactions. Here, GMMA is described in the software SEDPHAT for the analysis of data from isothermal titration calorimetry, surface plasmon resonance or other biosensing, analytical ultracentrifugation, fluorescence anisotropy and various other spectroscopic and thermodynamic techniques. The basic principles of these techniques are reviewed and recent advances in view of their particular strengths in the context of GMMA are described. Furthermore, a new feature in SEDPHAT is introduced for the simulation of multi-method data. In combination with specific statistical tools for GMMA in SEDPHAT, simulations can be a valuable step in the experimental design

  8. Cellular Stoichiometry of Methyl-Accepting Chemotaxis Proteins in Sinorhizobium meliloti.

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    Zatakia, Hardik M; Arapov, Timofey D; Meier, Veronika M; Scharf, Birgit E

    2018-03-15

    The chemosensory system in Sinorhizobium meliloti has several important deviations from the widely studied enterobacterial paradigm. To better understand the differences between the two systems and how they are optimally tuned, we determined the cellular stoichiometry of the methyl-accepting chemotaxis proteins (MCPs) and the histidine kinase CheA in S. meliloti Quantitative immunoblotting was used to determine the total amount of MCPs and CheA per cell in S. meliloti The MCPs are present in the cell in high abundance (McpV), low abundance (IcpA, McpU, McpX, and McpW), and very low abundance (McpY and McpZ), whereas McpT was below the detection limit. The approximate cellular ratio of these three receptor groups is 300:30:1. The chemoreceptor-to-CheA ratio is 23.5:1, highly similar to that seen in Bacillus subtilis (23:1) and about 10 times higher than that in Escherichia coli (3.4:1). Different from E. coli , the high-abundance receptors in S. meliloti are lacking the carboxy-terminal NWETF pentapeptide that binds the CheR methyltransferase and CheB methylesterase. Using transcriptional lacZ fusions, we showed that chemoreceptors are positively controlled by the master regulators of motility, VisNR and Rem. In addition, FlbT, a class IIA transcriptional regulator of flagellins, also positively regulates the expression of most chemoreceptors except for McpT and McpY, identifying chemoreceptors as class III genes. Taken together, these results demonstrate that the chemosensory complex and the adaptation system in S. meliloti deviates significantly from the established enterobacterial paradigm but shares some similarities with B. subtilis IMPORTANCE The symbiotic soil bacterium Sinorhizobium meliloti is of great agricultural importance because of its nitrogen-fixing properties, which enhances growth of its plant symbiont, alfalfa. Chemotaxis provides a competitive advantage for bacteria to sense their environment and interact with their eukaryotic hosts. For a better

  9. The Search Engine for Multi-Proteoform Complexes: An Online Tool for the Identification and Stoichiometry Determination of Protein Complexes.

    Science.gov (United States)

    Skinner, Owen S; Schachner, Luis F; Kelleher, Neil L

    2016-12-08

    Recent advances in top-down mass spectrometry using native electrospray now enable the analysis of intact protein complexes with relatively small sample amounts in an untargeted mode. Here, we describe how to characterize both homo- and heteropolymeric complexes with high molecular specificity using input data produced by tandem mass spectrometry of whole protein assemblies. The tool described is a "search engine for multi-proteoform complexes," (SEMPC) and is available for free online. The output is a list of candidate multi-proteoform complexes and scoring metrics, which are used to define a distinct set of one or more unique protein subunits, their overall stoichiometry in the intact complex, and their pre- and post-translational modifications. Thus, we present an approach for the identification and characterization of intact protein complexes from native mass spectrometry data. © 2016 by John Wiley & Sons, Inc. Copyright © 2016 John Wiley & Sons, Inc.

  10. Isoform composition and stoichiometry of the ∼ 90-kDa heat shock protein associated with glucocorticoid receptors

    International Nuclear Information System (INIS)

    Mendel, D.B.; Orti, E.

    1988-01-01

    The authors observed that the ∼ 90-kDa non-steroid-binding component of nonactivated glucocorticoid receptors purified from WEHI-7 mouse thymoma cells (which has been identified as the ∼ 90-kDa heat shock protein) consistently migrates as a doublet during polyacrylamide gel electrophoresis under denaturing and reducing conditions. It has recently been reported that murine Meth A cells contain a tumor-specific transplantation antigen (TSTA) which is related or identical to the ∼ 90-kDa heat shock protein. The observation that TSTA and the ∼ 90-kDa heat shock protein isolated from these cells exists as two isoforms of similar molecular mass and charge has suggested that the doublet observed is also due to the existence of two isoforms. They have therefore conducted this study to determine whether TSTA and the ∼ 90-kDa component of glucocorticoid receptors are indeed related, to establish whether the receptor preferentially binds one isoform of the ∼ 90-kDa heat shock protein, and to investigate the stoichiometry of the nonactivated receptor complex. They used the BuGr1 and AC88 monoclonal antibodies to purify, respectively, receptor-associated and free ∼ 90-kDa heat shock protein from WEHI-7 cells grown for 48 h with [ 35 S]methionine to metabolically label proteins to steady state. The long-term metabolic labeling approach has also enabled them to directly determine that the purified non-activated glucocorticoid receptor contains a single steroid-binding protein and two ∼ 90-kDa non-steroid-binding subunits. The consistency with which a ∼ 1:2 stoichiometric ratio of steroid binding to ∼ 90-kDa protein is observed supports the view that the ∼ 90-kDa heat shock protein is a true component of nonactivated glucocorticoid-receptor complexes

  11. Protein adsorption/desorption and antibody binding stoichiometry on silicon interferometric biosensors examined with TOF-SIMS

    KAUST Repository

    Gajos, Katarzyna

    2018-03-05

    Time-of-flight secondary ion mass spectrometry has been employed to examine, with biomolecular discrimination, sensing arm areas (20 μm x 600 μm) of integrated onto silicon chips Mach-Zehnder interferometers aiming to optimize their biofunctionalization with regard to indirect immunochemical (competitive) detection of ochratoxin A. Sensing areas are examined after: modification with (3-aminopropyl)triethoxysilane, spotting of OTA-ovalbumin conjugate (probe) from solutions with different concentration, blocking with bovine serum albumin, reaction with OTA-specific mouse monoclonal antibody followed by goat anti-mouse IgG secondary antibody. Component mass loadings of all proteins involved in immunodetection are determined from TOF-SIMS micro-analysis combined with ellipsometry of planar surfaces. These data show that partial desorption of surface-bound probe and blocking protein takes place upon primary immunoreaction to a degree that depends on probe concentration in spotting solution. Taking into account this desorption, apparent binding stoichiometry of both antibodies in immune complexes formed onto chip surface is determined more accurately than the respective evaluation based on real-time sensor response. In addition, mass loadings for probe and secondary antibody is observed to saturate for optimum probe concentrations. Also, principal component analysis of TOF-SIMS data could resolve both immunoreactions and biofunctionalization and discriminate surfaces prepared with optimum probe concentrations from those prepared using suboptimum ones.

  12. Protein adsorption/desorption and antibody binding stoichiometry on silicon interferometric biosensors examined with TOF-SIMS

    KAUST Repository

    Gajos, Katarzyna; Budkowski, Andrzej; Petrou, Panagiota; Pagkali, Varvara; Awsiuk, Kamil; Rysz, Jakub; Bernasik, Andrzej; Misiakos, Konstantinos; Raptis, Ioannis; Kakabakos, Sotirios

    2018-01-01

    Time-of-flight secondary ion mass spectrometry has been employed to examine, with biomolecular discrimination, sensing arm areas (20 μm x 600 μm) of integrated onto silicon chips Mach-Zehnder interferometers aiming to optimize their biofunctionalization with regard to indirect immunochemical (competitive) detection of ochratoxin A. Sensing areas are examined after: modification with (3-aminopropyl)triethoxysilane, spotting of OTA-ovalbumin conjugate (probe) from solutions with different concentration, blocking with bovine serum albumin, reaction with OTA-specific mouse monoclonal antibody followed by goat anti-mouse IgG secondary antibody. Component mass loadings of all proteins involved in immunodetection are determined from TOF-SIMS micro-analysis combined with ellipsometry of planar surfaces. These data show that partial desorption of surface-bound probe and blocking protein takes place upon primary immunoreaction to a degree that depends on probe concentration in spotting solution. Taking into account this desorption, apparent binding stoichiometry of both antibodies in immune complexes formed onto chip surface is determined more accurately than the respective evaluation based on real-time sensor response. In addition, mass loadings for probe and secondary antibody is observed to saturate for optimum probe concentrations. Also, principal component analysis of TOF-SIMS data could resolve both immunoreactions and biofunctionalization and discriminate surfaces prepared with optimum probe concentrations from those prepared using suboptimum ones.

  13. Protein adsorption/desorption and antibody binding stoichiometry on silicon interferometric biosensors examined with TOF-SIMS

    Science.gov (United States)

    Gajos, Katarzyna; Budkowski, Andrzej; Petrou, Panagiota; Pagkali, Varvara; Awsiuk, Kamil; Rysz, Jakub; Bernasik, Andrzej; Misiakos, Konstantinos; Raptis, Ioannis; Kakabakos, Sotirios

    2018-06-01

    Time-of-flight secondary ion mass spectrometry has been employed to examine, with biomolecular discrimination, sensing arm areas (20 μm × 600 μm) of integrated onto silicon chips Mach-Zehnder interferometers aiming to optimize their biofunctionalization with regard to indirect immunochemical (competitive) detection of ochratoxin A. Sensing areas are examined after: modification with (3-aminopropyl)triethoxysilane, spotting of OTA-ovalbumin conjugate (probe) from solutions with different concentration, blocking with bovine serum albumin, reaction with OTA-specific mouse monoclonal antibody followed by goat anti-mouse IgG secondary antibody. Component mass loadings of all proteins involved in immunodetection are determined from TOF-SIMS micro-analysis combined with ellipsometry of planar surfaces. These data show that partial desorption of surface-bound probe and blocking protein takes place upon primary immunoreaction to a degree that depends on probe concentration in spotting solution. Taking into account this desorption, apparent binding stoichiometry of both antibodies in immune complexes formed onto chip surface is determined more accurately than the respective evaluation based on real-time sensor response. In addition, mass loadings for probe and secondary antibody is observed to saturate for optimum probe concentrations. Also, principal component analysis of TOF-SIMS data could resolve both immunoreactions and biofunctionalization and discriminate surfaces prepared with optimum probe concentrations from those prepared using suboptimum ones.

  14. The stoichiometry of peatlands

    Science.gov (United States)

    Moore, Tim

    2017-04-01

    Stoichiometric principles have been developed and successfully applied to freshwater and marine ecosystems, which are characterized by short-lived, structurally simple organisms, simple food webs and an environment which allows rapid movement of water and elements. The application has been less successful in peatlands, and other terrestrial ecosystems: not surprising given their long-lived, structurally complex organisms, slow rates of organic matter decomposition, complex food webs and low hydraulic conductivities slowing water and element movement. I examine some aspects of what we know about stoichiometry in peatlands, especially involving nutrients such as C, N, P, K, Ca and Mg. I follow the cascade of stoichiometry from peatland plants through litter and into decomposing peat, drawing upon data from the Mer Bleue peatland and peatlands in Ontario. There are consistent patterns in stoichiometries, such as C:N, N:P and C:P across diverse peatlands, whereas patterns involving K, Ca and Mg show greater variability. Most of the changes in stoichiometry occur in the early stages of decomposition, from Von Post values 1 through 4. Peatlands are affected by disturbances, such as elevated atmospheric deposition of N and P, and I look at how these changes affect stoichiometric relationships. Finally, I present data on the changes in the stoichiometry of C, H and O, from plants through peat to coal beds. I conclude that while ecological stoichiometry in peatlands is not as 'simple' as in aquatic ecosystems, it offers contributions to our understanding of how peatlands function and respond to disturbance.

  15. Topography and stoichiometry of acidic proteins in large ribosomal subunits from Artemia salina as determined by crosslinking

    International Nuclear Information System (INIS)

    Uchiumi, T.; Wahba, A.J.; Traut, R.R.

    1987-01-01

    The 60S subunits isolated from Artemia salina ribosomes were treated with the crosslinking reagent 2-iminothiolane under mild conditions. Proteins were extracted and fractions containing crosslinked acidic proteins were obtained by stepwise elution from CM-cellulose. Each fraction was analyzed by diagonal (two-dimensional nonreducing-reducing) NaDodSO 4 /polyacrylamide gel electrophoresis. Crosslinked proteins below the diagonal were radioiodinated and identified by two-dimensional acidic urea-NaDodSO 4 gel electrophoresis. Each of the acidic proteins P1 and P2 was crosslinked individually to the same third protein, PO. The fractions containing acidic proteins were also analyzed by two-dimensional nonequilibrium isoelectric focusing-NaDodSO 4 /polyacrylamide gel electrophoresis. Two crosslinked complexes were observed that coincide in isoelectric positions with monomeric P1 and P2, respectively. Both P1 and P2 appear to form crosslinked homodimers. These results suggest the presence in the 60S subunit of (P1) 2 and (P2) 2 dimers, each of which is anchored to PO. Protein PO appears to play the same role as L10 in Escherichia coli ribosomes and may form a pentameric complex with the two dimers in the 60S subunits

  16. S. aureus MscL is a pentamer in vivo but of variable stoichiometries in vitro: implications for detergent-solubilized membrane proteins.

    Directory of Open Access Journals (Sweden)

    Michael R Dorwart

    Full Text Available While the bacterial mechanosensitive channel of large conductance (MscL is the best studied biological mechanosensor and serves as a paradigm for how a protein can sense and respond to membrane tension, the simple matter of its oligomeric state has led to debate, with models ranging from tetramers to hexamers. Indeed, two different oligomeric states of the bacterial mechanosensitive channel MscL have been resolved by X-ray crystallography: The M. tuberculosis channel (MtMscL is a pentamer, while the S. aureus protein (SaMscL forms a tetramer. Because several studies suggest that, like MtMscL, the E. coli MscL (EcoMscL is a pentamer, we re-investigated the oligomeric state of SaMscL. To determine the structural organization of MscL in the cell membrane we developed a disulfide-trapping approach. Surprisingly, we found that virtually all SaMscL channels in vivo are pentameric, indicating this as the physiologically relevant and functional oligomeric state. Complementing our in vivo results, we purified SaMscL and assessed its oligomeric state using three independent approaches (sedimentation equilibrium centrifugation, crosslinking, and light scattering and established that SaMscL is a pentamer when solubilized in Triton X-100 and C(8E(5 detergents. However, performing similar experiments on SaMscL solubilized in LDAO, the detergent used in the crystallographic study, confirmed the tetrameric oligomerization resolved by X-ray crystallography. We further demonstrate that this stoichiometric shift is reversible by conventional detergent exchange experiments. Our results firmly establish the pentameric organization of SaMscL in vivo. Furthermore they demonstrate that detergents can alter the subunit stoichiometry of membrane protein complexes in vitro; thus, in vivo assays are necessary to firmly establish a membrane protein's true functionally relevant oligomeric state.

  17. S. aureus MscL is a pentamer in vivo but of variable stoichiometries in vitro: implications for detergent-solubilized membrane proteins.

    Science.gov (United States)

    Dorwart, Michael R; Wray, Robin; Brautigam, Chad A; Jiang, Youxing; Blount, Paul

    2010-12-07

    While the bacterial mechanosensitive channel of large conductance (MscL) is the best studied biological mechanosensor and serves as a paradigm for how a protein can sense and respond to membrane tension, the simple matter of its oligomeric state has led to debate, with models ranging from tetramers to hexamers. Indeed, two different oligomeric states of the bacterial mechanosensitive channel MscL have been resolved by X-ray crystallography: The M. tuberculosis channel (MtMscL) is a pentamer, while the S. aureus protein (SaMscL) forms a tetramer. Because several studies suggest that, like MtMscL, the E. coli MscL (EcoMscL) is a pentamer, we re-investigated the oligomeric state of SaMscL. To determine the structural organization of MscL in the cell membrane we developed a disulfide-trapping approach. Surprisingly, we found that virtually all SaMscL channels in vivo are pentameric, indicating this as the physiologically relevant and functional oligomeric state. Complementing our in vivo results, we purified SaMscL and assessed its oligomeric state using three independent approaches (sedimentation equilibrium centrifugation, crosslinking, and light scattering) and established that SaMscL is a pentamer when solubilized in Triton X-100 and C(8)E(5) detergents. However, performing similar experiments on SaMscL solubilized in LDAO, the detergent used in the crystallographic study, confirmed the tetrameric oligomerization resolved by X-ray crystallography. We further demonstrate that this stoichiometric shift is reversible by conventional detergent exchange experiments. Our results firmly establish the pentameric organization of SaMscL in vivo. Furthermore they demonstrate that detergents can alter the subunit stoichiometry of membrane protein complexes in vitro; thus, in vivo assays are necessary to firmly establish a membrane protein's true functionally relevant oligomeric state.

  18. Conformational Entropy as Collective Variable for Proteins.

    Science.gov (United States)

    Palazzesi, Ferruccio; Valsson, Omar; Parrinello, Michele

    2017-10-05

    Many enhanced sampling methods rely on the identification of appropriate collective variables. For proteins, even small ones, finding appropriate descriptors has proven challenging. Here we suggest that the NMR S 2 order parameter can be used to this effect. We trace the validity of this statement to the suggested relation between S 2 and conformational entropy. Using the S 2 order parameter and a surrogate for the protein enthalpy in conjunction with metadynamics or variationally enhanced sampling, we are able to reversibly fold and unfold a small protein and draw its free energy at a fraction of the time that is needed in unbiased simulations. We also use S 2 in combination with the free energy flooding method to compute the unfolding rate of this peptide. We repeat this calculation at different temperatures to obtain the unfolding activation energy.

  19. Ecological Stoichiometry of Ocean Plankton

    Science.gov (United States)

    Moreno, Allison R.; Martiny, Adam C.

    2018-01-01

    Marine plankton elemental stoichiometric ratios can deviate from the Redfield ratio (106C:16N:1P); here, we examine physiological and biogeochemical mechanisms that lead to the observed variation across lineages, regions, and seasons. Many models of ecological stoichiometry blend together acclimative and adaptive responses to environmental conditions. These two pathways can have unique molecular mechanisms and stoichiometric outcomes, and we attempt to disentangle the two processes. We find that interactions between environmental conditions and cellular growth are key to understanding stoichiometric regulation, but the growth rates of most marine plankton populations are poorly constrained. We propose that specific physiological mechanisms have a strong impact on plankton and community stoichiometry in nutrient-rich environments, whereas biogeochemical interactions are important for the stoichiometry of the oligotrophic gyres. Finally, we outline key areas with missing information that is needed to advance understanding of the present and future ecological stoichiometry of ocean plankton.

  20. Quantifying chaos for ecological stoichiometry.

    Science.gov (United States)

    Duarte, Jorge; Januário, Cristina; Martins, Nuno; Sardanyés, Josep

    2010-09-01

    The theory of ecological stoichiometry considers ecological interactions among species with different chemical compositions. Both experimental and theoretical investigations have shown the importance of species composition in the outcome of the population dynamics. A recent study of a theoretical three-species food chain model considering stoichiometry [B. Deng and I. Loladze, Chaos 17, 033108 (2007)] shows that coexistence between two consumers predating on the same prey is possible via chaos. In this work we study the topological and dynamical measures of the chaotic attractors found in such a model under ecological relevant parameters. By using the theory of symbolic dynamics, we first compute the topological entropy associated with unimodal Poincaré return maps obtained by Deng and Loladze from a dimension reduction. With this measure we numerically prove chaotic competitive coexistence, which is characterized by positive topological entropy and positive Lyapunov exponents, achieved when the first predator reduces its maximum growth rate, as happens at increasing δ1. However, for higher values of δ1 the dynamics become again stable due to an asymmetric bubble-like bifurcation scenario. We also show that a decrease in the efficiency of the predator sensitive to prey's quality (increasing parameter ζ) stabilizes the dynamics. Finally, we estimate the fractal dimension of the chaotic attractors for the stoichiometric ecological model.

  1. Unpacking students' atomistic uderstanding of stoichiometry

    Science.gov (United States)

    Baluyut, John Ysrael

    Despite the use by instructors of particulate nature of matter (PNOM) diagrams in the general chemistry classroom, misconceptions on stoichiometry continue to prevail among students tasked with conceptual problems on concepts of limiting and excess reagents, and reaction yields. This dissertation set out to explore students' understanding of stoichiometry at the microscopic level as they solved problems that using PNOM diagrams. In particular, the study investigated how students coordinated symbolic and microscopic representations to demonstrate their knowledge of stoichiometric concepts, quantified the prevalence and explained the nature of stoichiometric misconceptions in terms of dual processing and dual coding theories, and used eye tracking to identify visual behaviors that accompanied cognitive processes students used to solve conceptual stoichiometry problems with PNOM diagrams. Interviews with students asked to draw diagrams for specific stoichiometric situations showed dual processing systems were in play. Many students were found to have used these processing systems in a heuristic-analytic sequence. Heuristics, such as the factor-label method and the least amount misconception, were often used by students to select information for further processing in an attempt to reduce the cognitive load of the subsequent analytic stage of the solution process. Diagrams drawn by students were used then to develop an instrument administered over a much larger sample of the general chemistry student population. The robustness of the dual processing theory was manifested by response patterns observed with large proportions of the student samples. These response patterns suggest that many students seemed to rely on heuristics to respond to a specific item for one of two diagrams given for the same chemical context, and then used a more analytic approach in dealing with the same item for the other diagram. It was also found that many students incorrectly treated items

  2. Analysis of acetylation stoichiometry suggests that SIRT3 repairs nonenzymatic acetylation lesions

    DEFF Research Database (Denmark)

    Weinert, Brian T; Moustafa, Tarek; Iesmantavicius, Vytautas

    2015-01-01

    or suppresses acetylation. Using quantitative mass spectrometry, we measured acetylation stoichiometry in mouse liver tissue and found that SIRT3 suppressed acetylation to a very low stoichiometry at its target sites. By examining acetylation changes in the liver, heart, brain, and brown adipose tissue...... of fasted mice, we found that SIRT3-targeted sites were mostly unaffected by fasting, a dietary manipulation that is thought to regulate metabolism through SIRT3-dependent deacetylation. Globally increased mitochondrial acetylation in fasted liver tissue, higher stoichiometry at mitochondrial acetylation...... functions as a protein repair factor that removes acetylation lesions from lysine residues....

  3. Collective dynamics of protein hydration water by brillouin neutron spectroscopy.

    Science.gov (United States)

    Orecchini, Andrea; Paciaroni, Alessandro; De Francesco, Alessio; Petrillo, Caterina; Sacchetti, Francesco

    2009-04-08

    By a detailed experimental study of THz dynamics in the ribonuclease protein, we could detect the propagation of coherent collective density fluctuations within the protein hydration shell. The emerging picture indicates the presence of both a dispersing mode, traveling with a speed greater than 3000 m/s, and a nondispersing one, characterized by an almost constant energy of 6-7 meV. In agreement with molecular dynamics simulations [Phys. Rev. Lett. 2002, 89, 275501], the features of the dispersion curves closely resemble those observed in pure liquid water [Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relat. Interdiscip. Top. 2004, 69, 061203]. On the contrary, the observed damping factors are much larger than in bulk water, with the dispersing mode becoming overdamped at Q = 0.6 A(-1) already. Such novel experimental findings are discussed as a dynamic signature of the disordering effect induced by the protein surface on the local structure of water.

  4. Autotrophic stoichiometry emerging from optimality and variable co-limitation

    Directory of Open Access Journals (Sweden)

    Kai W Wirtz

    2016-11-01

    Full Text Available Autotrophic organisms reveal an astounding flexibility in their elemental stoichiometry, with potentially major implications on biogeochemical cycles and ecological functioning. Notwithstanding, stoichiometric regulation and co-limitation by multiple resources in autotrophs revt were in the past often described by heuristic formulations.In this study, we present a mechanistic model of autotroph growth, which features two major improvements over the existing schemes. First, we introduce the concept of metabolic network independence that defines the degree of phase-locking between accessory machines. Network independence is in particular suggested to be proportional to protein synthesis capability as quantified by variable intracellular N:C. Consequently, the degree of co-limitation becomes variable, contrasting with the dichotomous debate on the use of Liebig's law or the product rule, standing for constantly low and high co-limitation, respectively. Second, we resolve dynamic protein partitioning to light harvesting, carboxylation processes, and to an arbitrary number of nutrient acquisition machineries, as well as instantaneous activity regulation of nutrient uptake. For all regulatory processes we assume growth rate optimality, here extended by an explicit consideration of indirect feed-back effects.The combination of network independence and optimal regulation displays unprecedented skill in reproducing rich stoichiometric patterns collected from a large number of published chemostat experiments. This high skill indicates (1 that the current paradigm of fixed co-limitation is a critical short-coming of conventional models, and (2 that stoichiometric flexibility in autotrophs possibly reflects an optimality strategy. Numerical experiments furthermore show that regulatory mechanisms homogenize the effect of multiple stressors. Extended optimality alleviates the effect of the most limiting resource(s while down-regulating machineries for the

  5. Acetylation dynamics and stoichiometry in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Weinert, Brian Tate; Iesmantavicius, Vytautas; Moustafa, Tarek

    2014-01-01

    Lysine acetylation is a frequently occurring posttranslational modification; however, little is known about the origin and regulation of most sites. Here we used quantitative mass spectrometry to analyze acetylation dynamics and stoichiometry in Saccharomyces cerevisiae. We found that acetylation...

  6. Droplet networks with incorporated protein diodes show collective properties

    Science.gov (United States)

    Maglia, Giovanni; Heron, Andrew J.; Hwang, William L.; Holden, Matthew A.; Mikhailova, Ellina; Li, Qiuhong; Cheley, Stephen; Bayley, Hagan

    2009-07-01

    Recently, we demonstrated that submicrolitre aqueous droplets submerged in an apolar liquid containing lipid can be tightly connected by means of lipid bilayers to form networks. Droplet interface bilayers have been used for rapid screening of membrane proteins and to form asymmetric bilayers with which to examine the fundamental properties of channels and pores. Networks, meanwhile, have been used to form microscale batteries and to detect light. Here, we develop an engineered protein pore with diode-like properties that can be incorporated into droplet interface bilayers in droplet networks to form devices with electrical properties including those of a current limiter, a half-wave rectifier and a full-wave rectifier. The droplet approach, which uses unsophisticated components (oil, lipid, salt water and a simple pore), can therefore be used to create multidroplet networks with collective properties that cannot be produced by droplet pairs.

  7. Carbon and nitrogen stoichiometry across stream ecosystems

    Science.gov (United States)

    Wymore, A.; Kaushal, S.; McDowell, W. H.; Kortelainen, P.; Bernhardt, E. S.; Johnes, P.; Dodds, W. K.; Johnson, S.; Brookshire, J.; Spencer, R.; Rodriguez-Cardona, B.; Helton, A. M.; Barnes, R.; Argerich, A.; Haq, S.; Sullivan, P. L.; López-Lloreda, C.; Coble, A. A.; Daley, M.

    2017-12-01

    Anthropogenic activities are altering carbon and nitrogen concentrations in surface waters globally. The stoichiometry of carbon and nitrogen regulates important watershed biogeochemical cycles; however, controls on carbon and nitrogen ratios in aquatic environments are poorly understood. Here we use a multi-biome and global dataset (tropics to Arctic) of stream water chemistry to assess relationships between dissolved organic carbon (DOC) and nitrate, ammonium and dissolved organic nitrogen (DON), providing a new conceptual framework to consider interactions between DOC and the multiple forms of dissolved nitrogen. We found that across streams the total dissolved nitrogen (TDN) pool is comprised of very little ammonium and as DOC concentrations increase the TDN pool shifts from nitrate to DON dominated. This suggests that in high DOC systems, DON serves as the primary source of nitrogen. At the global scale, DOC and DON are positively correlated (r2 = 0.67) and the average C: N ratio of dissolved organic matter (molar ratio of DOC: DON) across our data set is approximately 31. At the biome and smaller regional scale the relationship between DOC and DON is highly variable (r2 = 0.07 - 0.56) with the strongest relationships found in streams draining the mixed temperate forests of the northeastern United States. DOC: DON relationships also display spatial and temporal variability including latitudinal and seasonal trends, and interactions with land-use. DOC: DON ratios correlated positively with gradients of energy versus nutrient limitation pointing to the ecological role (energy source versus nutrient source) that DON plays with stream ecosystems. Contrary to previous findings we found consistently weak relationships between DON and nitrate which may reflect DON's duality as an energy or nutrient source. Collectively these analyses demonstrate how gradients of DOC drive compositional changes in the TDN pool and reveal a high degree of variability in the C: N ratio

  8. Ghanaian Teacher Trainees' Conceptual Understanding of Stoichiometry

    Science.gov (United States)

    Hanson, Ruby

    2016-01-01

    Chemical stoichiometry is a conceptual framework that encompasses other concepts such as the mole, writing of chemical equations in word and representative form, balancing of equations and the equilibrium concept. The underlying concepts enable students to understand relationships among entities of matter and required amounts for use when…

  9. The SBASE protein domain library, release 8.0: a collection of annotated protein sequence segments.

    Science.gov (United States)

    Murvai, J; Vlahovicek, K; Barta, E; Pongor, S

    2001-01-01

    SBASE 8.0 is the eighth release of the SBASE library of protein domain sequences that contains 294 898 annotated structural, functional, ligand-binding and topogenic segments of proteins, cross-referenced to most major sequence databases and sequence pattern collections. The entries are clustered into over 2005 statistically validated domain groups (SBASE-A) and 595 non-validated groups (SBASE-B), provided with several WWW-based search and browsing facilities for online use. A domain-search facility was developed, based on non-parametric pattern recognition methods, including artificial neural networks. SBASE 8.0 is freely available by anonymous 'ftp' file transfer from ftp.icgeb.trieste.it. Automated searching of SBASE can be carried out with the WWW servers http://www.icgeb.trieste.it/sbase/ and http://sbase.abc. hu/sbase/.

  10. Plant–insect interactions: the role of ecological stoichiometry

    Directory of Open Access Journals (Sweden)

    Michał Filipiak

    2017-03-01

    Full Text Available The energy budget of organisms is a primary factor used to generate hypotheses in ecosystem ecology and evolutionary theory. Therefore, previous studies have focused on the energy costs and benefits of adaptations, the efficiency of energy acquisition and investment, and energy budget limitations. The maintenance of stoichiometric balance is equally important because inconsistency between the chemical composition of the consumer’s tissues and that of its food sources strongly affects the major life-history traits of the consumer and may influence the consumer’s fitness and shape plant–herbivore interactions. In this short review, the framework of ecological stoichiometry is introduced, focusing on plant–insect interactions in terrestrial ecosystems. The use of the trophic stoichiometric ratio (TSR index is presented as a useful tool for indicating the chemical elements that are scarce in food and have the potential to limit the growth and development of herbivores, thereby influencing plant – herbivorous insect interactions. As an example, the elemental composition and stoichiometry of a pollen consumer (mason bee Osmia bicornis and its preferred pollen are compared. The growth and development of O. bicornis may be colimited by the scarcity of K, Na, and N in pollen, whereas the development of the cocoon might be colimited by the scarcity of P, Mg, K, Na, Zn, Ca, and N. A literature review of the elemental composition of pollen shows high taxonomical variability in the concentrations of bee-limiting elements. The optimized collection of pollen species based on the elemental composition may represent a strategy used by bees to overcome stoichiometric mismatches, influencing their interactions with plants. It is concluded that the dependence of life-history traits on food stoichiometry should be considered when discussing life history evolution and plant–herbivore interactions. The TSR index may serve as a convenient and powerful tool

  11. Subunit Stoichiometry of Human Muscle Chloride Channels

    OpenAIRE

    Fahlke, Christoph; Knittle, Timothy; Gurnett, Christina A.; Campbell, Kevin P.; George, Alfred L.

    1997-01-01

    Voltage-gated Cl? channels belonging to the ClC family appear to function as homomultimers, but the number of subunits needed to form a functional channel is controversial. To determine subunit stoichiometry, we constructed dimeric human skeletal muscle Cl? channels in which one subunit was tagged by a mutation (D136G) that causes profound changes in voltage-dependent gating. Sucrose-density gradient centrifugation experiments indicate that both monomeric and dimeric hClC-1 channels in their ...

  12. Stoichiometry patterns in the androdioecious Acer tegmentosum.

    Science.gov (United States)

    Zhang, Xinna; Yao, Jie; Fan, Chunyu; Tan, Lingzhao; Zhang, Chunyu; Wang, Juan; Zhao, Xiuhai; von Gadow, Klaus

    2016-10-11

    This study evaluates stoichiometry patterns in the androdioecious Acer tegmentosum, a species characterized by a rare reproductive system where males and hermaphrodites coexist. Altogether 31 hermaphrodites and 29 male plants were harvested and samples of leaves, current-year shoots, branches and coarse roots were analyzed to explore gender differences in biomass, C, N and P concentrations of these four components. The nitrogen to phosphorus relationship of each component was examined using SMA estimates. Males had significantly greater amounts of leaf and coarse root dry matter content than hermaphrodites. C, N and P stoichiometry differed significantly between genders, especially in the newly emerging vegetative components (leaves and shoots). Males had higher C/N and C/P ratios in current-year shoots and lower C/P ratios in leaves and branches. Hermaphrodites had higher N/P ratios in the leaves and branches. Males had higher rates of increase in leaf P content than hermaphrodites. This study suggests that stoichiometry patterns may be significantly affected by gender.

  13. Stoichiometry of ferns in Hawaii: implications for nutrient cycling.

    Science.gov (United States)

    Amatangelo, Kathryn L; Vitousek, Peter M

    2008-10-01

    We asked if element concentrations in ferns differ systematically from those in woody dicots in ways that could influence ecosystem properties and processes. Phylogenetically, ferns are deeply separated from angiosperms; for our analyses we additionally separated leptosporangiate ferns into polypod ferns, a monophyletic clade of ferns which radiated after the rise of angiosperms, and all other leptosporangiate (non-polypod) ferns. We sampled both non-polypod and polypod ferns on a natural fertility gradient and within fertilized and unfertilized plots in Hawaii, and compared our data with shrub and tree samples collected previously in the same plots. Non-polypod ferns in particular had low Ca concentrations under all conditions and less plasticity in their N and P stoichiometry than did polypod ferns or dicots. Polypod ferns were particularly rich in N and P, with low N:P ratios, and their stoichiometry varied substantially in response to differences in nutrient availability. Distinguishing between these two groups has the potential to be useful both in and out of Hawaii, as they have distinct properties which can affect ecosystem function. These differences could contribute to the widespread abundance of polypod ferns in an angiosperm-dominated world, and to patterns of nutrient cycling and limitation in sites where ferns are abundant.

  14. Polarographic determination of uranium dioxide stoichiometry

    International Nuclear Information System (INIS)

    Viguie, J.; Uny, G.

    1966-10-01

    The method described allows the determination of small deviations from stoichiometry for uranium dioxide. It was applied to the study of surface oxidation of bulk samples. The sample is dissolved in phosphoric acid under an argon atmosphere; U(VI) is determined by polarography in PO 4 H 3 4.5 N - H 2 SO 4 4 N. U(IV) is determined by potentiometry. The detection limit is UO 2,0002 . The accuracy for a single determination at the 95% confidence level is ±20 per cent for samples with composition included between UO 2,001 and UO 2,01 . (authors) [fr

  15. Collective Excitations in Protein as a Measure of Balance Between its Softness and Rigidity

    International Nuclear Information System (INIS)

    Shrestha, Utsab R.; Bhowmik, Debsindhu; Van Delinder, Kurt W.; Mamontov, Eugene; O’Neill, Hugh

    2017-01-01

    Here, we elucidate the protein activity from the perspective of protein softness and flexibility by studying the collective phonon-like excitations in a globular protein, human serum albumin (HSA), and taking advantage of the state-of-the-art inelastic X-ray scattering (IXS) technique. Such excitations demonstrate that the protein becomes softer upon thermal denaturation due to disruption of weak noncovalent bonds. On the other hand, no significant change in the local excitations is detected in ligand- (drugs) bound HSA compared to the ligand-free HSA. These results clearly suggest that the protein conformational flexibility and rigidity are balanced by the native protein structure for biological activity.

  16. Collective Excitations in Protein as a Measure of Balance Between its Softness and Rigidity

    Energy Technology Data Exchange (ETDEWEB)

    Shrestha, Utsab R. [Wayne State Univ., Detroit, MI (United States). Dept. of Physics and Astronomy; Bhowmik, Debsindhu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Computational Science and Engineering Division; Van Delinder, Kurt W. [Wayne State Univ., Detroit, MI (United States). Dept. of Physics and Astronomy; Mamontov, Eugene [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division; O’Neill, Hugh [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biology and Soft Matter Division; Zhang, Qiu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biology and Soft Matter Division; Alatas, Ahmet [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source; Chu, Xiang-Qiang [Wayne State Univ., Detroit, MI (United States). Dept. of Physics and Astronomy

    2017-01-12

    Here, we elucidate the protein activity from the perspective of protein softness and flexibility by studying the collective phonon-like excitations in a globular protein, human serum albumin (HSA), and taking advantage of the state-of-the-art inelastic X-ray scattering (IXS) technique. Such excitations demonstrate that the protein becomes softer upon thermal denaturation due to disruption of weak noncovalent bonds. On the other hand, no significant change in the local excitations is detected in ligand- (drugs) bound HSA compared to the ligand-free HSA. These results clearly suggest that the protein conformational flexibility and rigidity are balanced by the native protein structure for biological activity.

  17. Symbols and definitions of quantities and units in isotope stoichiometry

    International Nuclear Information System (INIS)

    Junghans, P.; Krumbiegel, P.; Faust, H.

    1982-01-01

    On the basis of the International System of Units and recent recommendations of the IUPAC on 'Symbols and Terminology for Physicochemical Quantities and Units' a system is proposed of uniform and unambiguous symbols and definitions of quantities and units used in the isotope dilution technique. The close relationship between isotope stoichiometry and common stoichiometry is demonstrated. (author)

  18. Excited-state lifetimes of far-infrared collective modes in proteins

    NARCIS (Netherlands)

    Xie, A.; van der Meer, L.; Austin, R. H.

    2002-01-01

    Vibrational excitations of low frequency collective modes are essential for functionally important conformational transitions in proteins. Here we report the first direct measurement on the lifetime of vibrational excitations of the collective modes at 87 pm (115 cm(-1)) in bacteriorhodopsin, a

  19. Stoichiometry of ATP hydrolysis and chlorophyllide formation of dark-operative protochlorophyllide oxidoreductase from Rhodobacter capsulatus

    Energy Technology Data Exchange (ETDEWEB)

    Nomata, Jiro [Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 (Japan); Terauchi, Kazuki [Department of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577 (Japan); Fujita, Yuichi, E-mail: fujita@agr.nagoya-u.ac.jp [Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 (Japan)

    2016-02-12

    Dark-operative protochlorophyllide (Pchlide) oxidoreductase (DPOR) is a nitrogenase-like enzyme catalyzing a reduction of the C17 = C18 double bond of Pchlide to form chlorophyllide a (Chlide) in bacteriochlorophyll biosynthesis. DPOR consists of an ATP-dependent reductase component, L-protein (a BchL dimer), and a catalytic component, NB-protein (a BchN–BchB heterotetramer). The L-protein transfers electrons to the NB-protein to reduce Pchlide, which is coupled with ATP hydrolysis. Here we determined the stoichiometry of ATP hydrolysis and the Chlide formation of DPOR. The minimal ratio of ATP to Chlide (ATP/2e{sup –}) was 4, which coincides with that of nitrogenase. The ratio increases with increasing molar ratio of L-protein to NB-protein. This profile differs from that of nitrogenase. These results suggest that DPOR has a specific intrinsic property, while retaining the common features shared with nitrogenase. - Highlights: • The stoichiometry of nitrogenase-like protochlorophyllide reductase was determined. • The minimal ATP/2e{sup –} ratio was 4, which coincides with that of nitrogenase. • The ATP/2e{sup –} ratio increases with increasing L-protein/NB-protein molar ratio. • DPOR has an intrinsic property, but retains features shared with nitrogenase.

  20. Structure, stoichiometry and spectroscopy of oxide superconductors

    Science.gov (United States)

    Rao, C. N. R.

    In the new oxide superconductors, structure and oxygen stoichiometry play the most crucial role. Thus, all the high-temperature oxide superconductors are orthorhombic perovskites with low-dimensional features. Oxygen stoichiometry in YBa2Cu3O7-δ has an important bearing on the structure as well as superconductivity. This is equally true in the La3-xBa3+xCu 6O14+δ system of which only the 123 oxide (x = 1) with the orthorhombic structure shows high Tc. Orthorhombicity though not essential, is generally found ; it is necessary for the formation of twins. The nature of oxygen and copper in the cuprates has been examined by electron spectroscopy. Copper in these cuprates is only in 1 + and 2 + states. It seems likely that oxygen holes are responsible for superconductivity of the cuprates as well as Ba(Bi, Pb)O3. High Tc superconductivity is also found in oxides of the Bi-(Ca, Sr)-Cu-O and related oxides possessing Cu-O sheets. Dans les nouveaux oxydes supraconducteurs, la structure et la stoechiométrie de l'oxygène jouent un rôle absolument crucial. Ainsi, tous les oxydes supraconducteurs à haute température critique sont des pérovskites orthorhombiques possédant des propriétés de basse dimensionnalité. La stoechiométrie de l'oxygène dans YBa2Cu3O7- δ a une influence importante tant sur la structure que sur la supraconductibilité. Ceci est également valable pour les composés du type La3 -xBa3 + xCu 6O14 + δ parmi lesquels seul l'oxyde 123 (x = 1) à structure orthorhombique présente un grand T. Bien que ce ne soit pas essentiel, cette orthorhombicité est fréquente ; elle est nécessaire à la formation de macles. La nature de l'oxygène et du cuivre a été observée par spectroscopie électronique... Dans ces cuprates, le cuivre est dans les seuls états de valence + 1 et + 2. Vraisemblablement, les trous logés sur l'oxygène sont responsables de la supraconductibilité des cuprates comme de Ba(Bi, Pb)O3. La supraconductibilité existe aussi

  1. Morphological Dependence of Element Stoichiometry in the H. americanus Exoskeleton

    Science.gov (United States)

    Mergelsberg, S. T.; Ulrich, R. N.; Dove, P. M.

    2016-02-01

    The crustacean exoskeleton is a complex biocomposite of inorganic mineral and organic macromolecules that expresses highly divergent morphologies across different taxa. While the structures and compositions of the organic framework show complex links to environmental and developmental pressures, little is known about the mineral chemistry. Previous studies of the cuticle have assumed that magnesium, phosphorous, and other trace metals are largely contained in the inorganic mineral fraction. Due to analytical limitations of structural analyses and in situ spectroscopic methods, the stoichiometry of the organic and inorganic portions could not be resolved. For example, previous Raman and XRD studies conclude the higher concentrations of trace elements, such as P and Mg measured in reinforced structures, e.g. the claw and abdomen, are primarily determined by the mineral fraction. Using the American Lobster (Homarus americanus) as a model organism to establish relationships between body part function and cuticle composition, this study quantified the distributions of Mg and P in the mineral and organic fractions. The experiments were designed to dissolve the exoskeleton of 10 body parts using three types of solutions that were specific to extracting 1) the mineral phase, 2) protein, and 3) polysaccharide. Analysis of the solutions by ICP-OES shows the mineral phase contains magnesium and phosphorous at concentrations sufficient to support the formation of calcium-magnesium and phosphate minerals. The protein fraction of the body parts contains significantly more Mg and P than previously hypothesized, while the levels of P contained in the organic portion are fairly constant. The findings demonstrate the lobster cuticle contains a significant amount of non-mineralized P and Mg that is readily water-soluble in the protein component. However, for those body parts used for defense and food acquisition, such as the claw, the mineral component determines the overall

  2. General Protein Data Bank-Based Collective Variables for Protein Folding.

    Science.gov (United States)

    Ardevol, Albert; Palazzesi, Ferruccio; Tribello, Gareth A; Parrinello, Michele

    2016-01-12

    New, automated forms of data analysis are required to understand the high-dimensional trajectories that are obtained from molecular dynamics simulations on proteins. Dimensionality reduction algorithms are particularly appealing in this regard as they allow one to construct unbiased, low-dimensional representations of the trajectory using only the information encoded in the trajectory. The downside of this approach is that a different set of coordinates are required for each different chemical system under study precisely because the coordinates are constructed using information from the trajectory. In this paper, we show how one can resolve this problem by using the sketch-map algorithm that we recently proposed to construct a low-dimensional representation of the structures contained in the protein data bank. We show that the resulting coordinates are as useful for analyzing trajectory data as coordinates constructed using landmark configurations taken from the trajectory and that these coordinates can thus be used for understanding protein folding across a range of systems.

  3. "Why not stoichiometry" versus "stoichiometry--why not?" Part I: General context.

    Science.gov (United States)

    Michałowska-Kaczmarczyk, Anna Maria; Asuero, Agustin G; Michałowski, Tadeusz

    2015-01-01

    The elementary concepts involved with stoichiometry are considered from different viewpoints. Some examples of approximate calculations made according to the stoichiometric scheme are indicated, and correct resolution of the problems involved is presented. The principles of balancing chemical equations, based on their apparent similarities with algebraic equations, are criticized. The review concerns some peculiarities inherent in chemical reaction notation and its use (and abuse) in stoichiometric calculations that provide inconsistent results for various reasons. This "conventional" approach to stoichiometry is put in context with the generalized approach to electrolytic systems (GATES) established by Michałowski. The article contains a number of proposals that could potentially be taken into account and included in the next edition of the Orange Book. Notation of ions used in this article is not, deliberately, in accordance with actual IUPAC requirements in this respect. This article is intended to be provocative with the hope that some critical debate around the important topics treated should be generated and creatively expanded in the scientific community.

  4. Crystallization, diffraction data collection and preliminary crystallographic analysis of DING protein from Pseudomonas fluorescens

    International Nuclear Information System (INIS)

    Moniot, Sebastien; Elias, Mikael; Kim, Donghyo; Scott, Ken; Chabriere, Eric

    2007-01-01

    Crystallization of DING protein from P. fluorescens is reported. A complete data set was collected to 1.43 Å resolution. PfluDING is a phosphate-binding protein expressed in Pseudomonas fluorescens. This protein is clearly distinct from the bacterial ABC transporter soluble phosphate-binding protein PstS and is more homologous to eukaryotic DING proteins. Interestingly, bacterial DING proteins have only been detected in certain Pseudomonas species. Although DING proteins seem to be ubiquitous in eukaryotes, they are systematically absent from eukaryotic genomic databases and thus are still quite mysterious and poorly characterized. PfluDING displays mitogenic activity towards human cells and binds various ligands such as inorganic phosphate, pyrophosphate, nucleotide triphosphates and cotinine. Here, the crystallization of PfluDING is reported in a monoclinic space group (P2 1 ), with typical unit-cell parameters a = 36.7, b = 123.7, c = 40.8 Å, α = 90, β = 116.7, γ = 90°. Preliminary crystallographic analysis reveals good diffraction quality for these crystals and a 1.43 Å resolution data set has been collected

  5. Difference gel electrophoresis (DiGE) identifies differentially expressed proteins in endoscopically-collected pancreatic fluid

    Science.gov (United States)

    Paulo, Joao A.; Lee, Linda S.; Banks, Peter A.; Steen, Hanno; Conwell, Darwin L.

    2012-01-01

    Alterations in the pancreatic fluid proteome of individuals with chronic pancreatitis may offer insights into the development and progression of the disease. The endoscopic pancreas function test (ePFT) can safely collect large volumes of pancreatic fluid that are potentially amenable to proteomic analyses using difference gel electrophoresis (DiGE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Pancreatic fluid was collected endoscopically using the ePFT method following secretin stimulation from three individuals with severe chronic pancreatitis and three chronic abdominal pain controls. The fluid was processed to minimize protein degradation and the protein profiles of each cohort, as determined by DiGE and LC-MS/MS, were compared. This DiGE-LC-MS/MS analysis reveals proteins that are differentially expressed in chronic pancreatitis compared to chronic abdominal pain controls. Proteins with higher abundance in pancreatic fluid from chronic pancreatitis individuals include: actin, desmoplankin, alpha-1-antitrypsin, SNC73, and serotransferrin. Those of relatively lower abundance include carboxypeptidase B, lipase, alpha-1-antichymotrypsin, alpha-2-macroglobulin, Arp2/3 subunit 4, glyceraldehyde-3-phosphate dehydrogenase, and protein disulfide isomerase. Endoscopic collection (ePFT) in tandem with DiGE-LC-MS/MS is a suitable approach for pancreatic fluid proteome analysis, however, further optimization of our protocol, as outlined herein, may improve proteome coverage in future analyses. PMID:21792986

  6. Advances in membrane protein crystallography: in situ and in meso data collection

    International Nuclear Information System (INIS)

    Weyand, Simone; Tate, Christopher G.

    2015-01-01

    Membrane protein structural biology has made tremendous advances over the last decade but there are still many challenges associated with crystallization, data collection and structure determination. Two independent groups, Axford et al. [(2015), Acta Cryst. D71, 1228–1237] and Huang et al. [(2015), Acta Cryst. D71, 1238–1256], have published methods that make a major contribution to addressing these challenges

  7. Advances in membrane protein crystallography: in situ and in meso data collection

    Energy Technology Data Exchange (ETDEWEB)

    Weyand, Simone, E-mail: sw644@cam.ac.uk [Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA (United Kingdom); Tate, Christopher G., E-mail: sw644@cam.ac.uk [MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH (United Kingdom)

    2015-05-23

    Membrane protein structural biology has made tremendous advances over the last decade but there are still many challenges associated with crystallization, data collection and structure determination. Two independent groups, Axford et al. [(2015), Acta Cryst. D71, 1228–1237] and Huang et al. [(2015), Acta Cryst. D71, 1238–1256], have published methods that make a major contribution to addressing these challenges.

  8. The protein crystallography beamline BW6 at DORIS - automatic operation and high-throughput data collection

    CERN Document Server

    Blume, H; Bourenkov, G P; Kosciesza, D; Bartunik, H D

    2001-01-01

    The wiggler beamline BW6 at DORIS has been optimized for de-novo solution of protein structures on the basis of MAD phasing. Facilities for automatic data collection, rapid data transfer and storage, and online processing have been developed which provide adequate conditions for high-throughput applications, e.g., in structural genomics.

  9. Fecal collection methods for the determination of protein digestibility in bullfrogs

    Directory of Open Access Journals (Sweden)

    Marta Verardino De Stéfani

    2015-08-01

    Full Text Available Adequate methods for the determination of protein digestibility in bullfrogs are important for the understanding of nutrient utilization. Therefore, this study evaluated two methods of feces collection: intestinal dissection and fecal decantation, using cylindric-conical tanks. Frogs were fed with a commercial diet (45% crude protein which was ground and supplemented with 0.5% chromium oxide III. The frogs were fasted 48h before force-feeding (5% of the animal's live weight. For the decantation method, the animals were sacrificed 36 h after force-feeding and feces were collected directly from the large intestine. For the sedimentation method, feces were collected when they appeared in the tubes attached to the front end of the cylindric tanks. No significant difference (P>0.05 in the apparent digestibility coefficients of crude protein for dietary was observed between the methods tested (74.0% and 76.4% for the dissection and decantation methods, respectively. In conclusion, both methods can be used for the determination of protein digestibility of bullfrog feeds

  10. Cell-Sediment Separation and Elemental Stoichiometries in Extreme Environments

    Science.gov (United States)

    Neveu, M.; Poret-peterson, A. T.; Lee, Z. M.; Anbar, A. D.; Elser, J. J.

    2012-12-01

    counting by epifluorescence microscopy indicated a cell recovery yield between 6 and 40% in field-collected samples (95% for cultured E. coli). Aluminum, assumed to be non-biological in origin, was used to estimate the extent of mineral contamination of isolated cell communities. These results show that our method is successful at separating microbial cells from sediment collected in extreme environments and preserving them for analysis of a broad suite of elements. Photosynthetic sites yielded much more cell material than hotter, chemosynthetic sites (Cox et al., 2011). We are currently measuring cellular elemental abundances and ratios in samples from relatively low-temperature (25 to 65°C), photosynthetic areas, spanning a wide range of pH (2 to 9.5) and composition. These measurements will be compared to existing datasets on the bulk sediment stoichiometry of these ecosystems, and to previous observations of cellular elemental composition. References: Redfield, A.C. (1934) In Daniel, R.J. [Ed.], James Johnstone Memorial Volume, pp. 176-192, Univ. Press Liverpool. Sterner, R.W., Elser, J.J. (2002) Ecological Stoichiometry Princeton Univ. Press, 441p. Havig, J.R., et al. (2011) JGR 116, G01005. Amalfitano, S., Fazi, S. (2008) J. of Microbiol. Methods 75, 237-243. Cox, A., et al. (2011) Chem. Geol. 280, 344-351.

  11. Influence of argon-hydrogen atmosphere on vitroceramics stoichiometry

    International Nuclear Information System (INIS)

    Beleuta, I.L.

    1977-01-01

    The stoichiometry of UO 2 in several vitroceramics obtained by melting in different Ar-H 2 mixtures at about 2300 deg C was determined. The measurements are in good agreement with the stoichiometry diagram UO 2 sub(+x)-SiO 2 calculated for the melts in pure hydrogen, by using Δ G 02 , as a function of melting conditions: pressure, composition of the melt, temperature. The SiO 2 losses by evaporation are lower, and the samples cast into fusible moulds have smoother surfaces. (Author)

  12. Calcite growth kinetics: Modeling the effect of solution stoichiometry

    NARCIS (Netherlands)

    Wolthers, M.; Nehrke, G.; Gustafsson, J.P.; Van Cappellen, P.

    2012-01-01

    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth

  13. stoichiometry of pyrogallol/ammonium-nitrogen complex using ...

    African Journals Online (AJOL)

    BARTH EKWUEME

    2010-04-22

    Apr 22, 2010 ... calculations and so that analytical procedures can be properly defined. Since the complex is coloured (pale- yellow), its stoichiometry can be established using visible spectrometry to measure the absorbance of solutions of known composition. One method widely applicable is Job's method of continuous ...

  14. Stoichiometry of pyrogallol/ammonium-nitrogen complex using ...

    African Journals Online (AJOL)

    This complex, which we now refer to as P/NH4 +-N complex, can be the basis for the spectrophotometric determination of NH4 +-N in aqueous solution. Aqueous NH4 +-N is a very important pollution index. Therefore it is imperative that the stoichiometry of this complex be thoroughly understood. In this work, Job's method of ...

  15. In vacuo X-ray data collection from graphene-wrapped protein crystals

    International Nuclear Information System (INIS)

    Warren, Anna J.; Crawshaw, Adam D.; Trincao, Jose; Aller, Pierre; Alcock, Simon; Nistea, Ioana; Salgado, Paula S.; Evans, Gwyndaf

    2015-01-01

    A method is reported for collecting room-temperature data from protein crystals under vacuum by protecting them with a thin graphene layer. The measurement of diffraction data from macromolecular crystal samples held in vacuo holds the promise of a very low X-ray background and zero absorption of incident and scattered beams, leading to better data and the potential for accessing very long X-ray wavelengths (>3 Å) for native sulfur phasing. Maintaining the hydration of protein crystals under vacuum is achieved by the use of liquid jets, as with serial data collection at free-electron lasers, or is side-stepped by cryocooling the samples, as implemented at new synchrotron beamlines. Graphene has been shown to protect crystals from dehydration by creating an extremely thin layer that is impermeable to any exchanges with the environment. Furthermore, owing to its hydrophobicity, most of the aqueous solution surrounding the crystal is excluded during sample preparation, thus eliminating most of the background caused by liquid. Here, it is shown that high-quality data can be recorded at room temperature from graphene-wrapped protein crystals in a rough vacuum. Furthermore, it was observed that graphene protects crystals exposed to different relative humidities and a chemically harsh environment

  16. In vacuo X-ray data collection from graphene-wrapped protein crystals

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Anna J. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Crawshaw, Adam D. [Newcastle University, Newcastle upon Tyne NE2 4HH (United Kingdom); Trincao, Jose; Aller, Pierre; Alcock, Simon; Nistea, Ioana [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Salgado, Paula S. [Newcastle University, Newcastle upon Tyne NE2 4HH (United Kingdom); Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom)

    2015-09-26

    A method is reported for collecting room-temperature data from protein crystals under vacuum by protecting them with a thin graphene layer. The measurement of diffraction data from macromolecular crystal samples held in vacuo holds the promise of a very low X-ray background and zero absorption of incident and scattered beams, leading to better data and the potential for accessing very long X-ray wavelengths (>3 Å) for native sulfur phasing. Maintaining the hydration of protein crystals under vacuum is achieved by the use of liquid jets, as with serial data collection at free-electron lasers, or is side-stepped by cryocooling the samples, as implemented at new synchrotron beamlines. Graphene has been shown to protect crystals from dehydration by creating an extremely thin layer that is impermeable to any exchanges with the environment. Furthermore, owing to its hydrophobicity, most of the aqueous solution surrounding the crystal is excluded during sample preparation, thus eliminating most of the background caused by liquid. Here, it is shown that high-quality data can be recorded at room temperature from graphene-wrapped protein crystals in a rough vacuum. Furthermore, it was observed that graphene protects crystals exposed to different relative humidities and a chemically harsh environment.

  17. Differential expression of candidate salivary effector proteins in field collections of Hessian fly, Mayetiola destructor

    Science.gov (United States)

    Johnson, A J; Shukle, R H; Chen, M-S; Srivastava, S; Subramanyam, S; Schemerhorn, B J; Weintraub, P G; Abdel Moniem, H E M; Flanders, K L; Buntin, G D; Williams, C E

    2015-01-01

    Evidence is emerging that some proteins secreted by gall-forming parasites of plants act as effectors responsible for systemic changes in the host plant, such as galling and nutrient tissue formation. A large number of secreted salivary gland proteins (SSGPs) that are the putative effectors responsible for the physiological changes elicited in susceptible seedling wheat by Hessian fly, Mayetiola destructor (Say), larvae have been documented. However, how the genes encoding these candidate effectors might respond under field conditions is unknown. The goal of this study was to use microarray analysis to investigate variation in SSGP transcript abundance amongst field collections from different geographical regions (southeastern USA, central USA, and the Middle East). Results revealed significant variation in SSGP transcript abundance amongst the field collections studied. The field collections separated into three distinct groups that corresponded to the wheat classes grown in the different geographical regions as well as to recently described Hessian fly populations. These data support previous reports correlating Hessian fly population structure with micropopulation differences owing to agro-ecosystem parameters such as cultivation of regionally adapted wheat varieties, deployment of resistance genes and variation in climatic conditions. PMID:25528896

  18. Solvent friction effects propagate over the entire protein molecule through low-frequency collective modes.

    Science.gov (United States)

    Moritsugu, Kei; Kidera, Akinori; Smith, Jeremy C

    2014-07-24

    Protein solvation dynamics has been investigated using atom-dependent Langevin friction coefficients derived directly from molecular dynamics (MD) simulations. To determine the effect of solvation on the atomic friction coefficients, solution and vacuum MD simulations were performed for lysozyme and staphylococcal nuclease and analyzed by Langevin mode analysis. The coefficients thus derived are roughly correlated with the atomic solvent-accessible surface area (ASA), as expected from the fact that friction occurs as the result of collisions with solvent molecules. However, a considerable number of atoms with higher friction coefficients are found inside the core region. Hence, the influence of solvent friction propagates into the protein core. The internal coefficients have large contributions from the low-frequency modes, yielding a simple picture of the surface-to-core long-range damping via solvation governed by collective low-frequency modes. To make use of these findings in implicit-solvent modeling, we compare the all-atom friction results with those obtained using Langevin dynamics (LD) with two empirical representations: the constant-friction and the ASA-dependent (Pastor-Karplus) friction models. The constant-friction model overestimates the core and underestimates the surface damping whereas the ASA-dependent friction model, which damps protein atoms only on the solvent-accessible surface, reproduces well the friction coefficients for both the surface and core regions observed in the explicit-solvent MD simulations. Therefore, in LD simulation, the solvent friction coefficients should be imposed only on the protein surface.

  19. Acid-sensing ion channel (ASIC) 1a/2a heteromers have a flexible 2:1/1:2 stoichiometry.

    Science.gov (United States)

    Bartoi, Tudor; Augustinowski, Katrin; Polleichtner, Georg; Gründer, Stefan; Ulbrich, Maximilian H

    2014-06-03

    Acid-sensing ion channels (ASICs) are widely expressed proton-gated Na(+) channels playing a role in tissue acidosis and pain. A trimeric composition of ASICs has been suggested by crystallization. Upon coexpression of ASIC1a and ASIC2a in Xenopus oocytes, we observed the formation of heteromers and their coexistence with homomers by electrophysiology, but could not determine whether heteromeric complexes have a fixed subunit stoichiometry or whether certain stoichiometries are preferred over others. We therefore imaged ASICs labeled with green and red fluorescent proteins on a single-molecule level, counted bleaching steps from GFP and colocalized them with red tandem tetrameric mCherry for many individual complexes. Combinatorial analysis suggests a model of random mixing of ASIC1a and ASIC2a subunits to yield both 2:1 and 1:2 ASIC1a:ASIC2a heteromers together with ASIC1a and ASIC2a homomers.

  20. Quantitative localization microscopy: effects of photophysics and labeling stoichiometry.

    Directory of Open Access Journals (Sweden)

    Robert P J Nieuwenhuizen

    Full Text Available Quantification in localization microscopy with reversibly switchable fluorophores is severely hampered by the unknown number of switching cycles a fluorophore undergoes and the unknown stoichiometry of fluorophores on a marker such as an antibody. We overcome this problem by measuring the average number of localizations per fluorophore, or generally per fluorescently labeled site from the build-up of spatial image correlation during acquisition. To this end we employ a model for the interplay between the statistics of activation, bleaching, and labeling stoichiometry. We validated our method using single fluorophore labeled DNA oligomers and multiple-labeled neutravidin tetramers where we find a counting error of less than 17% without any calibration of transition rates. Furthermore, we demonstrated our quantification method on nanobody- and antibody-labeled biological specimens.

  1. Flipped Classroom as an Alternative Strategy for Teaching Stoichiometry

    OpenAIRE

    Norrie E. Gayeta

    2017-01-01

    This study aimed to compare the effectiveness of flipped classroom and traditional classroom instruction in measuring conceptual change and to determine if flipped classroom instruction would be an alternative method of teaching to traditional lecture method. This study covered the level of conceptual understanding of students on stoichiometry and the type of conceptual change before and after exposure to flipped and traditional classroom environment. Qualitative and quantitative ...

  2. Learning stoichiometry: A comparison of text and multimedia instructional formats

    Science.gov (United States)

    Evans, Karen L.

    Even after multiple instructional opportunities, first year college chemistry students are often unable to apply stoichiometry knowledge in equilibrium and acid-base chemistry problem solving. Cognitive research findings suggest that for learning to be meaningful, learners need to actively construct their own knowledge by integrating new information into, and reorganizing, their prior understandings. Scaffolded inquiry in which facts, procedures, and principles are introduced as needed within the context of authentic problem solving may provide the practice and encoding opportunities necessary for construction of a memorable and usable knowledge base. The dynamic and interactive capabilities of online technology may facilitate stoichiometry instruction that promotes this meaningful learning. Entering college freshmen were randomly assigned to either a technology-rich or text-only set of cognitively informed stoichiometry review materials. Analysis of posttest scores revealed a significant but small difference in the performance of the two treatment groups, with the technology-rich group having the advantage. Both SAT and gender, however, explained more of the variability in the scores. Analysis of the posttest scores from the technology-rich treatment group revealed that the degree of interaction with the Virtual Lab simulation was significantly related to posttest performance and subsumed any effect of prior knowledge as measured by SAT scores. Future users of the online course should be encouraged to engage with the problem-solving opportunities provided by the Virtual Lab simulation through either explicit instruction and/or implementation of some level of program control within the course's navigational features.

  3. Flipped Classroom as an Alternative Strategy for Teaching Stoichiometry

    Directory of Open Access Journals (Sweden)

    Norrie E. Gayeta

    2017-11-01

    Full Text Available This study aimed to compare the effectiveness of flipped classroom and traditional classroom instruction in measuring conceptual change and to determine if flipped classroom instruction would be an alternative method of teaching to traditional lecture method. This study covered the level of conceptual understanding of students on stoichiometry and the type of conceptual change before and after exposure to flipped and traditional classroom environment. Qualitative and quantitative research methods were used in the study. Respondents were two sections of third year Bachelor of Secondary Education, Biological Science. Frequency, percentage, ranking, mean, standard deviation, Hake factor test, and t-test were the statistical tools applied to answer specific questions. Results showed profound increase towards conceptual change representing a shift from intuitive understanding to correct incomplete understanding level. Thus, change for the better, in theoretical type was determined from pretest to posttest of students exposed to flipped and traditional classroom. Results also indicated that there is no significant difference on students’ conceptual change on stoichiometry exposed to flipped and traditional classroom environment thus, flipped classroom instruction can be used as an alternative teaching method to traditional lecture method in teaching stoichiometry

  4. [Research advances in ecological stoichiometry of marine plankton].

    Science.gov (United States)

    Chen, Lei; Li, Chao-Lun

    2014-10-01

    Ecological stoichiometry can be simply defined as: The biology of elements from molecules to the biosphere, which spans all levels of the environment and of the life. It's a new idea to build a unified theory and becomes an inevitable trend to develop the ecological science. Marine ecosystems, which contribute to 50% of the biosphere biomass, are the important component of the global biogeochemical cycles. Marine zooplankton plays an important role in the material circulation and energy flow of marine ecosystems and serves as a connecting link between the preceding and the following in a more precise understanding of the key elemental cycles. However, research on ecological stoichiometry of marine plankton is fragmentary and rare. This article summarized the ecological phenomena and mechanisms of limiting elements affecting marine plankton, the response of biochemical substances to nutrition limitation, and the food chain transmission and feedback of nutrition limitation. Meanwhile, we also put forward some perspectives for future research of ecological stoichiometry of plankton in China' s seas.

  5. 3D Microstructural Characterization of Uranium Oxide as a Surrogate Nuclear Fuel: Effect of Oxygen Stoichiometry on Grain Boundary Distributions

    Energy Technology Data Exchange (ETDEWEB)

    Rudman, K. [Arizona State Univ., Tempe, AZ (United States); Dickerson, P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Byler, Darrin David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Peralta, P. [Arizona State Univ., Tempe, AZ (United States); Lim, H. [Arizona State Univ., Tempe, AZ (United States); McDonald, R. [Arizona State Univ., Tempe, AZ (United States); Dickerson, R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mcclellan, Kenneth James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-06

    The initial microstructure of an oxide fuel can play a key role in its performance. At low burn-ups, the diffusion of fission products can depend strongly on grain size and grain boundary (GB) characteristics, which in turn depend on processing conditions and oxygen stoichiometry. Serial sectioning techniques using Focused Ion Beam were developed to obtain Electron Backscatter Diffraction (EBSD) data for depleted UO2 pellets that were processed to obtain 3 different oxygen stoichiometries. The EBSD data were used to create 3D microstructure reconstructions and to gather statistical information on the grain and GB crystallography, with emphasis on identifying the character (twist, tilt, mixed) for GBs that meet the Coincident Site Lattice (CSL) criterion as well as GBs with the most common misorientation angles. Data on dihedral angles at triple points were also collected. The results were compared across different samples to understand effects of oxygen content on microstructure evolution.

  6. In Planta Single-Molecule Pull-Down Reveals Tetrameric Stoichiometry of HD-ZIPIII:LITTLE ZIPPER Complexes.

    Science.gov (United States)

    Husbands, Aman Y; Aggarwal, Vasudha; Ha, Taekjip; Timmermans, Marja C P

    2016-08-01

    Deciphering complex biological processes markedly benefits from approaches that directly assess the underlying biomolecular interactions. Most commonly used approaches to monitor protein-protein interactions typically provide nonquantitative readouts that lack statistical power and do not yield information on the heterogeneity or stoichiometry of protein complexes. Single-molecule pull-down (SiMPull) uses single-molecule fluorescence detection to mitigate these disadvantages and can quantitatively interrogate interactions between proteins and other compounds, such as nucleic acids, small molecule ligands, and lipids. Here, we establish SiMPull in plants using the HOMEODOMAIN LEUCINE ZIPPER III (HD-ZIPIII) and LITTLE ZIPPER (ZPR) interaction as proof-of-principle. Colocalization analysis of fluorophore-tagged HD-ZIPIII and ZPR proteins provides strong statistical evidence of complex formation. In addition, we use SiMPull to directly quantify YFP and mCherry maturation probabilities, showing these differ substantially from values obtained in mammalian systems. Leveraging these probabilities, in conjunction with fluorophore photobleaching assays on over 2000 individual complexes, we determined HD-ZIPIII:ZPR stoichiometry. Intriguingly, these complexes appear as heterotetramers, comprising two HD-ZIPIII and two ZPR molecules, rather than heterodimers as described in the current model. This surprising result raises new questions about the regulation of these key developmental factors and is illustrative of the unique contribution SiMPull is poised to make to in planta protein interaction studies. © 2016 American Society of Plant Biologists. All rights reserved.

  7. Improvement of an automated protein crystal exchange system PAM for high-throughput data collection

    International Nuclear Information System (INIS)

    Hiraki, Masahiko; Yamada, Yusuke; Chavas, Leonard M. G.; Wakatsuki, Soichi; Matsugaki, Naohiro

    2013-01-01

    A special liquid-nitrogen Dewar with double capacity for the sample-exchange robot has been created at AR-NE3A at the Photon Factory, allowing continuous fully automated data collection. In this work, this new system is described and the stability of its calibration is discussed. Photon Factory Automated Mounting system (PAM) protein crystal exchange systems are available at the following Photon Factory macromolecular beamlines: BL-1A, BL-5A, BL-17A, AR-NW12A and AR-NE3A. The beamline AR-NE3A has been constructed for high-throughput macromolecular crystallography and is dedicated to structure-based drug design. The PAM liquid-nitrogen Dewar can store a maximum of three SSRL cassettes. Therefore, users have to interrupt their experiments and replace the cassettes when using four or more of them during their beam time. As a result of investigation, four or more cassettes were used in AR-NE3A alone. For continuous automated data collection, the size of the liquid-nitrogen Dewar for the AR-NE3A PAM was increased, doubling the capacity. In order to check the calibration with the new Dewar and the cassette stand, calibration experiments were repeatedly performed. Compared with the current system, the parameters of the novel system are shown to be stable

  8. Improvement of an automated protein crystal exchange system PAM for high-throughput data collection

    Energy Technology Data Exchange (ETDEWEB)

    Hiraki, Masahiko, E-mail: masahiko.hiraki@kek.jp; Yamada, Yusuke; Chavas, Leonard M. G. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Wakatsuki, Soichi [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS 69, Menlo Park, CA 94025-7015 (United States); Stanford University, Beckman Center B105, Stanford, CA 94305-5126 (United States); Matsugaki, Naohiro [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2013-11-01

    A special liquid-nitrogen Dewar with double capacity for the sample-exchange robot has been created at AR-NE3A at the Photon Factory, allowing continuous fully automated data collection. In this work, this new system is described and the stability of its calibration is discussed. Photon Factory Automated Mounting system (PAM) protein crystal exchange systems are available at the following Photon Factory macromolecular beamlines: BL-1A, BL-5A, BL-17A, AR-NW12A and AR-NE3A. The beamline AR-NE3A has been constructed for high-throughput macromolecular crystallography and is dedicated to structure-based drug design. The PAM liquid-nitrogen Dewar can store a maximum of three SSRL cassettes. Therefore, users have to interrupt their experiments and replace the cassettes when using four or more of them during their beam time. As a result of investigation, four or more cassettes were used in AR-NE3A alone. For continuous automated data collection, the size of the liquid-nitrogen Dewar for the AR-NE3A PAM was increased, doubling the capacity. In order to check the calibration with the new Dewar and the cassette stand, calibration experiments were repeatedly performed. Compared with the current system, the parameters of the novel system are shown to be stable.

  9. Action of DCCD on the H+/O stoichiometry of mitoplast cytochrome c oxidase.

    Science.gov (United States)

    Lehninger, A L; Reynafarje, B; Costa, L

    1985-01-01

    The mechanistic H+/O ejection stoichiometry of the cytochrome c oxidase reaction in rat liver mitoplasts is close to 4 at level flow when the reduced oxidase is pulsed with O2. Dicyclohexylcarbodiimide (DCCD) up to 30 nmol/mg protein fails to influence the rate of electron flow through the mitoplast oxidase, but inhibits H+ ejection. The inhibition of H+ ejection appears to be biphasic; ejection of 2-3 H+ per O is completely inhibited by very low DCCD, whereas inhibition of the remaining H+ ejection requires very much higher concentrations of DCCD. This effect suggests the occurrence of two types of H+ pumps in the native cytochrome oxidase of mitoplasts.

  10. Determination of the physiological 2:2 TLR5:flagellin activation stoichiometry revealed by the activity of a fusion receptor

    International Nuclear Information System (INIS)

    Ivičak-Kocjan, Karolina; Panter, Gabriela; Benčina, Mojca; Jerala, Roman

    2013-01-01

    Highlights: •The chimeric protein fusing flagellin to the TLR5 ectodomain is constitutively active. •Mutation P736H within the BB-loop of TLR5 TIR domain renders the receptor inactive. •The R90D mutation in flagellin inactivated autoactivation of the chimeric protein. •The 2:2 stoichiometry of the TLR5:flagellin complex is physiologically relevant. -- Abstract: Toll-like receptor 5 (TLR5) recognizes flagellin of most flagellated bacteria, enabling activation of the MyD88-dependent signaling pathway. The recently published crystal structure of a truncated zebrafish TLR5 ectodomain in complex with an inactive flagellin fragment indicated binding of two flagellin molecules to a TLR5 homodimer, however this complex did not dimerize in solution. In the present study, we aimed to determine the physiological stoichiometry of TLR5:flagellin activation by the use of a chimeric protein composed of an active flagellin fragment linked to the N-terminus of human TLR5 (SF-TLR5). This construct was constitutively active. Inactivation by the R90D mutation within flagellin demonstrated that autoactivation of the chimeric protein depended solely on the specific interaction between TLR5 and flagellin. Addition of wild-type hTLR5 substantially lowered autoactivation of SF-TLR5 in a concentration dependent manner, an effect which was reversible by the addition of exogenous Salmonella typhimurium flagellin, indicating the biological activity of a TLR5:flagellin complex with a 2:2 stoichiometry. These results, in addition to the combinations of inactive P736H mutation within the BB-loop of the TIR domain of TLR5 and SF-TLR5, further confirm the mechanism of TLR5 activation

  11. Determination of the physiological 2:2 TLR5:flagellin activation stoichiometry revealed by the activity of a fusion receptor

    Energy Technology Data Exchange (ETDEWEB)

    Ivičak-Kocjan, Karolina; Panter, Gabriela; Benčina, Mojca [Laboratory of Biotechnology, National Institute of Chemistry, 1000 Ljubljana (Slovenia); The Centre of Excellence EN-FIST, 1000 Ljubljana (Slovenia); Jerala, Roman, E-mail: roman.jerala@ki.si [Laboratory of Biotechnology, National Institute of Chemistry, 1000 Ljubljana (Slovenia); The Centre of Excellence EN-FIST, 1000 Ljubljana (Slovenia); The Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana (Slovenia)

    2013-05-24

    Highlights: •The chimeric protein fusing flagellin to the TLR5 ectodomain is constitutively active. •Mutation P736H within the BB-loop of TLR5 TIR domain renders the receptor inactive. •The R90D mutation in flagellin inactivated autoactivation of the chimeric protein. •The 2:2 stoichiometry of the TLR5:flagellin complex is physiologically relevant. -- Abstract: Toll-like receptor 5 (TLR5) recognizes flagellin of most flagellated bacteria, enabling activation of the MyD88-dependent signaling pathway. The recently published crystal structure of a truncated zebrafish TLR5 ectodomain in complex with an inactive flagellin fragment indicated binding of two flagellin molecules to a TLR5 homodimer, however this complex did not dimerize in solution. In the present study, we aimed to determine the physiological stoichiometry of TLR5:flagellin activation by the use of a chimeric protein composed of an active flagellin fragment linked to the N-terminus of human TLR5 (SF-TLR5). This construct was constitutively active. Inactivation by the R90D mutation within flagellin demonstrated that autoactivation of the chimeric protein depended solely on the specific interaction between TLR5 and flagellin. Addition of wild-type hTLR5 substantially lowered autoactivation of SF-TLR5 in a concentration dependent manner, an effect which was reversible by the addition of exogenous Salmonella typhimurium flagellin, indicating the biological activity of a TLR5:flagellin complex with a 2:2 stoichiometry. These results, in addition to the combinations of inactive P736H mutation within the BB-loop of the TIR domain of TLR5 and SF-TLR5, further confirm the mechanism of TLR5 activation.

  12. A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals

    Energy Technology Data Exchange (ETDEWEB)

    Nederlof, Igor; Genderen, Eric van; Li, Yao-Wang; Abrahams, Jan Pieter, E-mail: abrahams@chem.leidenuniv.nl [Leiden University, Einsteinweg 55, 2333 CC Leiden (Netherlands)

    2013-07-01

    An ultrasensitive Medipix2 detector allowed the collection of rotation electron-diffraction data from single three-dimensional protein nanocrystals for the first time. The data could be analysed using the standard X-ray crystallography programs MOSFLM and SCALA. When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e{sup −} Å{sup −2}), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLM and SCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins.

  13. A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre three-dimensional protein crystals

    International Nuclear Information System (INIS)

    Nederlof, Igor; Genderen, Eric van; Li, Yao-Wang; Abrahams, Jan Pieter

    2013-01-01

    An ultrasensitive Medipix2 detector allowed the collection of rotation electron-diffraction data from single three-dimensional protein nanocrystals for the first time. The data could be analysed using the standard X-ray crystallography programs MOSFLM and SCALA. When protein crystals are submicrometre-sized, X-ray radiation damage precludes conventional diffraction data collection. For crystals that are of the order of 100 nm in size, at best only single-shot diffraction patterns can be collected and rotation data collection has not been possible, irrespective of the diffraction technique used. Here, it is shown that at a very low electron dose (at most 0.1 e − Å −2 ), a Medipix2 quantum area detector is sufficiently sensitive to allow the collection of a 30-frame rotation series of 200 keV electron-diffraction data from a single ∼100 nm thick protein crystal. A highly parallel 200 keV electron beam (λ = 0.025 Å) allowed observation of the curvature of the Ewald sphere at low resolution, indicating a combined mosaic spread/beam divergence of at most 0.4°. This result shows that volumes of crystal with low mosaicity can be pinpointed in electron diffraction. It is also shown that strategies and data-analysis software (MOSFLM and SCALA) from X-ray protein crystallography can be used in principle for analysing electron-diffraction data from three-dimensional nanocrystals of proteins

  14. Collecting Protein Biomarkers in Breath Using Electret Filters: A Preliminary Method on New Technical Model and Human Study.

    Directory of Open Access Journals (Sweden)

    Wang Li

    Full Text Available Biomarkers in exhaled breath are useful for respiratory disease diagnosis in human volunteers. Conventional methods that collect non-volatile biomarkers, however, necessitate an extensive dilution and sanitation processes that lowers collection efficiencies and convenience of use. Electret filter emerged in recent decade to collect virus biomarkers in exhaled breath given its simplicity and effectiveness. To investigate the capability of electret filters to collect protein biomarkers, a model that consists of an atomizer that produces protein aerosol and an electret filter that collects albumin and carcinoembryonic antigen-a typical biomarker in lung cancer development- from the atomizer is developed. A device using electret filter as the collecting medium is designed to collect human albumin from exhaled breath of 6 volunteers. Comparison of the collecting ability between the electret filter method and other 2 reported methods is finally performed based on the amounts of albumin collected from human exhaled breath. In conclusion, a decreasing collection efficiency ranging from 17.6% to 2.3% for atomized albumin aerosol and 42% to 12.5% for atomized carcinoembryonic antigen particles is found; moreover, an optimum volume of sampling human exhaled breath ranging from 100 L to 200 L is also observed; finally, the self-designed collecting device shows a significantly better performance in collecting albumin from human exhaled breath than the exhaled breath condensate method (p0.05. In summary, electret filters are potential in collecting non-volatile biomarkers in human exhaled breath not only because it was simpler, cheaper and easier to use than traditional methods but also for its better collecting performance.

  15. Energy storage and fecundity explain deviations from ecological stoichiometry predictions under global warming and size-selective predation.

    Science.gov (United States)

    Zhang, Chao; Jansen, Mieke; De Meester, Luc; Stoks, Robby

    2016-11-01

    A key challenge for ecologists is to predict how single and joint effects of global warming and predation risk translate from the individual level up to ecosystem functions. Recently, stoichiometric theory linked these levels through changes in body stoichiometry, predicting that both higher temperatures and predation risk induce shifts in energy storage (increases in C-rich carbohydrates and reductions in N-rich proteins) and body stoichiometry (increases in C : N and C : P). This promising theory, however, is rarely tested and assumes that prey will divert energy away from reproduction under predation risk, while under size-selective predation, prey instead increase fecundity. We exposed the water flea Daphnia magna to 4 °C warming and fish predation risk to test whether C-rich carbohydrates increase and N-rich proteins decrease, and as a result, C : N and C : P increase under warming and predation risk. Unexpectedly, warming decreased body C : N, which was driven by reductions in C-rich fat and sugar contents while the protein content did not change. This reflected a trade-off where the accelerated intrinsic growth rate under warming occurred at the cost of a reduced energy storage. Warming reduced C : N less and only increased C : P and N : P in the fish-period Daphnia. These evolved stoichiometric responses to warming were largely driven by stronger warming-induced reductions in P than in C and N and could be explained by the better ability to deal with warming in the fish-period Daphnia. In contrast to theory predictions, body C : N decreased under predation risk due to a strong increase in the N-rich protein content that offsets the increase in C-rich fat content. The higher investment in fecundity (more N-rich eggs) under predation risk contributed to this stronger increase in protein content. Similarly, the lower body C : N of pre-fish Daphnia also matched their higher fecundity. Warming and predation risk independently shaped body

  16. Calcium-dependent stoichiometries of the KCa2.2 (SK) intracellular domain/calmodulin complex in solution.

    Science.gov (United States)

    Halling, D Brent; Kenrick, Sophia A; Riggs, Austen F; Aldrich, Richard W

    2014-02-01

    Ca(2+) activates SK Ca(2+)-activated K(+) channels through the protein Ca(2+) sensor, calmodulin (CaM). To understand how SK channels operate, it is necessary to determine how Ca(2+) regulates CaM binding to its target on SK. Tagless, recombinant SK peptide (SKp), was purified for binding studies with CaM at low and high Ca(2+) concentrations. Composition gradient multi-angle light scattering accurately measures the molar mass, stoichiometry, and affinity of protein complexes. In 2 mM Ca(2+), SKp and CaM bind with three different stoichiometries that depend on the molar ratio of SKp:CaM in solution. These complexes include 28 kD 1SKp/1CaM, 39 kD 2SKp/1CaM, and 44 kD 1SKp/2CaM. A 2SKp/2CaM complex, observed in prior crystallographic studies, is absent. At sedimentation coefficient is smaller for a 1SKp:1CaM solution than it is for either 2SKp:1CaM or 1SKp:2CaM. At low Ca(2+) and at >100 µM protein concentrations, a molar excess of SKp over CaM causes aggregation. Aggregation is not observed in Ca(2+) or with CaM in molar excess. In low Ca(2+) both 1SKp:1CaM and 1SKp:2CaM solutions have similar sedimentation coefficients, which is consistent with the absence of a 1SKp/2CaM complex in low Ca(2+). These results suggest that complexes with stoichiometries other than 2SKp/2CaM are important in gating.

  17. Consequences of warming and resource quality on the stoichiometry and nutrient cycling of a stream shredder.

    Directory of Open Access Journals (Sweden)

    Esther Mas-Martí

    Full Text Available As a result of climate change, streams are warming and their runoff has been decreasing in most temperate areas. These changes can affect consumers directly by increasing their metabolic rates and modifying their physiology and indirectly by changing the quality of the resources on which organisms depend. In this study, a common stream detritivore (Echinogammarus berilloni Catta was reared at two temperatures (15 and 20°C and fed Populus nigra L. leaves that had been conditioned either in an intermittent or permanent reach to evaluate the effects of resource quality and increased temperatures on detritivore performance, stoichiometry and nutrient cycling. The lower quality (i.e., lower protein, soluble carbohydrates and higher C:P and N:P ratios of leaves conditioned in pools resulted in compensatory feeding and lower nutrient retention capacity by E. berilloni. This effect was especially marked for phosphorus, which was unexpected based on predictions of ecological stoichiometry. When individuals were fed pool-conditioned leaves at warmer temperatures, their growth rates were higher, but consumers exhibited less efficient assimilation and higher mortality. Furthermore, the shifts to lower C:P ratios and higher lipid concentrations in shredder body tissues suggest that structural molecules such as phospholipids are preserved over other energetic C-rich macromolecules such as carbohydrates. These effects on consumer physiology and metabolism were further translated into feces and excreta nutrient ratios. Overall, our results show that the effects of reduced leaf quality on detritivore nutrient retention were more severe at higher temperatures because the shredders were not able to offset their increased metabolism with increased consumption or more efficient digestion when fed pool-conditioned leaves. Consequently, the synergistic effects of impaired food quality and increased temperatures might not only affect the physiology and survival of

  18. A New Strain Collection for Improved Expression of Outer Membrane Proteins

    Directory of Open Access Journals (Sweden)

    Ina Meuskens

    2017-11-01

    Full Text Available Almost all integral membrane proteins found in the outer membranes of Gram-negative bacteria belong to the transmembrane β-barrel family. These proteins are not only important for nutrient uptake and homeostasis, but are also involved in such processes as adhesion, protein secretion, biofilm formation, and virulence. As surface exposed molecules, outer membrane β-barrel proteins are also potential drug and vaccine targets. High production levels of heterologously expressed proteins are desirable for biochemical and especially structural studies, but over-expression and subsequent purification of membrane proteins, including outer membrane proteins, can be challenging. Here, we present a set of deletion mutants derived from E. coli BL21(DE3 designed for the over-expression of recombinant outer membrane proteins. These strains harbor deletions of four genes encoding abundant β-barrel proteins in the outer membrane (OmpA, OmpC, OmpF, and LamB, both single and in all combinations of double, triple, and quadruple knock-outs. The sequences encoding these outer membrane proteins were deleted completely, leaving only a minimal scar sequence, thus preventing the possibility of genetic reversion. Expression tests in the quadruple mutant strain with four test proteins, including a small outer membrane β-barrel protein and variants thereof as well as two virulence-related autotransporters, showed significantly improved expression and better quality of the produced proteins over the parent strain. Differences in growth behavior and aggregation in the presence of high salt were observed, but these phenomena did not negatively influence the expression in the quadruple mutant strain when handled as we recommend. The strains produced in this study can be used for outer membrane protein production and purification, but are also uniquely useful for labeling experiments for biophysical measurements in the native membrane environment.

  19. A method to quantify FRET stoichiometry with phasor plot analysis and acceptor lifetime ingrowth.

    Science.gov (United States)

    Chen, WeiYue; Avezov, Edward; Schlachter, Simon C; Gielen, Fabrice; Laine, Romain F; Harding, Heather P; Hollfelder, Florian; Ron, David; Kaminski, Clemens F

    2015-03-10

    FRET is widely used for the study of protein-protein interactions in biological samples. However, it is difficult to quantify both the FRET efficiency (E) and the affinity (Kd) of the molecular interaction from intermolecular FRET signals in samples of unknown stoichiometry. Here, we present a method for the simultaneous quantification of the complete set of interaction parameters, including fractions of bound donors and acceptors, local protein concentrations, and dissociation constants, in each image pixel. The method makes use of fluorescence lifetime information from both donor and acceptor molecules and takes advantage of the linear properties of the phasor plot approach. We demonstrate the capability of our method in vitro in a microfluidic device and also in cells, via the determination of the binding affinity between tagged versions of glutathione and glutathione S-transferase, and via the determination of competitor concentration. The potential of the method is explored with simulations. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  20. The stoichiometry of the TMEM16A ion channel determined in intact plasma membranes of COS-7 cells using liquid-phase electron microscopy.

    Science.gov (United States)

    Peckys, Diana B; Stoerger, Christof; Latta, Lorenz; Wissenbach, Ulrich; Flockerzi, Veit; de Jonge, Niels

    2017-08-01

    TMEM16A is a membrane protein forming a calcium-activated chloride channel. A homodimeric stoichiometry of the TMEM16 family of proteins has been reported but an important question is whether the protein resides always in a dimeric configuration in the plasma membrane or whether monomers of the protein are also present in its native state within in the intact plasma membrane. We have determined the stoichiometry of the human (h)TMEM16A within whole COS-7 cells in liquid. For the purpose of detecting TMEM16A subunits, single proteins were tagged by the streptavidin-binding peptide within extracellular loops accessible by streptavidin coated quantum dot (QD) nanoparticles. The labeled proteins were then imaged using correlative light microscopy and environmental scanning electron microscopy (ESEM) using scanning transmission electron microscopy (STEM) detection. The locations of 19,583 individual proteins were determined of which a statistical analysis using the pair correlation function revealed the presence of a dimeric conformation of the protein. The amounts of detected label pairs and single labels were compared between experiments in which the TMEM16A SBP-tag position was varied, and experiments in which tagged and non-tagged TMEM16A proteins were present. It followed that hTMEM16A resides in the plasma membrane as dimer only and is not present as monomer. This strategy may help to elucidate the stoichiometry of other membrane protein species within the context of the intact plasma membrane in future. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Quantitative imaging through a spectrograph : 2. stoichiometry mapping by Raman scattering

    NARCIS (Netherlands)

    Tolboom, R.A.L.; Dam, N.J.; Meulen, ter J.J.

    2004-01-01

    The Bayesian deconvolution algorithm described in a preceding paper [Appl. Opt. 43, 5669–5681 (2004)] is applied to measurement of the two-dimensional stoichiometry field in a combustible methane-air mixture by Raman imaging through a spectrograph. Stoichiometry (fuel equivalence ratio) is derived

  2. Quantitative imaging through a spectrograph. 2. Stoichiometry mapping by Raman scattering.

    NARCIS (Netherlands)

    Tolboom, R.A.L.; Dam, N.J.; Meulen, J.J. ter

    2004-01-01

    The Bayesian deconvolution algorithm described in a preceding paper [Appl. Opt. 43, 5669-5681 (2004)] is applied to measurement of the two-dimensional stoichiometry field in a combustible methane-air mixture by Raman imaging through a spectrograph. Stoichiometry (fuel equivalence ratio) is derived

  3. A Novel Code System for Revealing Sources of Students' Difficulties with Stoichiometry

    Science.gov (United States)

    Gulacar, Ozcan; Overton, Tina L.; Bowman, Charles R.; Fynewever, Herb

    2013-01-01

    A coding scheme is presented and used to evaluate solutions of seventeen students working on twenty five stoichiometry problems in a think-aloud protocol. The stoichiometry problems are evaluated as a series of sub-problems (e.g., empirical formulas, mass percent, or balancing chemical equations), and the coding scheme was used to categorize each…

  4. Influence of stoichiometry on electrochromic cerium-titanium oxide compounds

    International Nuclear Information System (INIS)

    Kullman, L.; Richardson, T.; Rubin, M.; Slack, J.; Rottkay, K. von

    1997-01-01

    CeO 2 -TiO 2 finds use as passive counter-electrode in electrochromic devices. Thin films were produced by de-sputtering in a wide range of compositions. Influence of total pressure and oxygen partial pressure on the optical constants of TiO 2 was investigated. Slightly substoichiometric Ti0 2 films exhibit a red-shift of the bandgap. The Ti0 2 content in the compound essentially determines the degree of cathodical coloring upon Li + intercalation [1]. However, pure TiO 2 films with comparable visible transmittance in the clear state behave differently during electrochemical cycling depending on oxygen stoichiometry. Films that are deposited at higher total pressure are more oxygen rich and require initial formatting until current voltage cycles become stable. CeO 2 -Ti0 2 films of intermediate compositions have the relatively highest charge capacity. Comparison with atomic force microscopy indicates a correlation of small grain size with high charge capacity

  5. Subunit stoichiometry of the chloroplast photosystem I complex

    International Nuclear Information System (INIS)

    Bruce, B.D.; Malkin, R.

    1988-01-01

    A native photosystem I (PS I) complex and a PS I core complex depleted of antenna subunits has been isolated from the uniformly 14 C-labeled aquatic higher plant, Lemna. These complexes have been analyzed for their subunit stoichiometry by quantitative sodium dodecyl sulfate-polyacrylamide gel electrophoresis methods. The results for both preparations indicate that one copy of each high molecular mass subunit is present per PS I complex and that a single copy of most low molecular mass subunits is also present. These results suggest that iron-sulfur center X, an early PS I electron acceptor proposed to bind to the high molecular mass subunits, contains a single [4Fe-4S] cluster which is bound to a dimeric structure of high molecular mass subunits, each providing 2 cysteine residues to coordinate this cluster

  6. Static light scattering to characterize membrane proteins in detergent solution

    NARCIS (Netherlands)

    Slotboom, Dirk Jan; Duurkens, Ria H.; Olieman, Kees; Erkens, Guus B.

    2008-01-01

    Determination of the oligomeric state or the subunit stoichiometry of integral membrane proteins in detergent solution is notoriously difficult, because the amount of detergent (and lipid) associated with the proteins is usually not known. Only two classical methods (sedimentation equilibrium

  7. Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere

    Directory of Open Access Journals (Sweden)

    Antonietta Quigg

    2012-05-01

    Full Text Available The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon in the diversification of the marine biosphere. Nutrient availability and phytoplankton stoichiometry played a critical role in the initial diversification of the marine biosphere during the Neoproterozoic. Initial biosphere expansion during this time resulted in the massive sequestration of nutrients into biomass which, along with the geologically slow input of nutrients from land, set the stage for severe nutrient limitation and relatively constant marine biodiversity during the rest of the Paleozoic. Given the slow nutrient inputs from land and low recycling rates, the growth of early-to-middle Paleozoic metazoans remained limited by their having to expend energy to first “burn off” (respire excess carbon in food before the associated nutrients could be utilized for growth and reproduction; the relative equilibrium in marine biodiversity during the Paleozoic therefore appears to be real. Limited nutrient availability and the consequent nutrient imbalance may have delayed the appearance of more advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests, greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability. During the Meso-Cenozoic, rising oxygen levels, the continued nutrient input from land, and, especially, increasing rates of bioturbation, enhanced nutrient availability, increasing the nutrient content of phytoplankton that fueled the diversification of the Modern Fauna.

  8. Environmental and organismal predictors of intraspecific variation in the stoichiometry of a neotropical freshwater fish.

    Science.gov (United States)

    El-Sabaawi, Rana W; Kohler, Tyler J; Zandoná, Eugenia; Travis, Joseph; Marshall, Michael C; Thomas, Steven A; Reznick, David N; Walsh, Matthew; Gilliam, James F; Pringle, Catherine; Flecker, Alexander S

    2012-01-01

    The elemental composition of animals, or their organismal stoichiometry, is thought to constrain their contribution to nutrient recycling, their interactions with other animals, and their demographic rates. Factors that affect organismal stoichiometry are generally poorly understood, but likely reflect elemental investments in morphological features and life history traits, acting in concert with the environmental availability of elements. We assessed the relative contribution of organismal traits and environmental variability to the stoichiometry of an insectivorous Neotropical stream fish, Rivulus hartii. We characterized the influence of body size, life history phenotype, stage of maturity, and environmental variability on organismal stoichiometry in 6 streams that differ in a broad suite of environmental variables. The elemental composition of R. hartii was variable, and overlapped with the wide range of elemental composition documented across freshwater fish taxa. Average %P composition was ∼3.2%(±0.6), average %N∼10.7%(±0.9), and average %C∼41.7%(±3.1). Streams were the strongest predictor of organismal stoichiometry, and explained up to 18% of the overall variance. This effect appeared to be largely explained by variability in quality of basal resources such as epilithon N:P and benthic organic matter C:N, along with variability in invertebrate standing stocks, an important food source for R. hartii. Organismal traits were weak predictors of organismal stoichiometry in this species, explaining when combined up to 7% of the overall variance in stoichiometry. Body size was significantly and positively correlated with %P, and negatively with N:P, and C:P, and life history phenotype was significantly correlated with %C, %P, C:P and C:N. Our study suggests that spatial variability in elemental availability is more strongly correlated with organismal stoichiometry than organismal traits, and suggests that the stoichiometry of carnivores may not be

  9. Environmental and organismal predictors of intraspecific variation in the stoichiometry of a neotropical freshwater fish.

    Directory of Open Access Journals (Sweden)

    Rana W El-Sabaawi

    Full Text Available The elemental composition of animals, or their organismal stoichiometry, is thought to constrain their contribution to nutrient recycling, their interactions with other animals, and their demographic rates. Factors that affect organismal stoichiometry are generally poorly understood, but likely reflect elemental investments in morphological features and life history traits, acting in concert with the environmental availability of elements. We assessed the relative contribution of organismal traits and environmental variability to the stoichiometry of an insectivorous Neotropical stream fish, Rivulus hartii. We characterized the influence of body size, life history phenotype, stage of maturity, and environmental variability on organismal stoichiometry in 6 streams that differ in a broad suite of environmental variables. The elemental composition of R. hartii was variable, and overlapped with the wide range of elemental composition documented across freshwater fish taxa. Average %P composition was ∼3.2%(±0.6, average %N∼10.7%(±0.9, and average %C∼41.7%(±3.1. Streams were the strongest predictor of organismal stoichiometry, and explained up to 18% of the overall variance. This effect appeared to be largely explained by variability in quality of basal resources such as epilithon N:P and benthic organic matter C:N, along with variability in invertebrate standing stocks, an important food source for R. hartii. Organismal traits were weak predictors of organismal stoichiometry in this species, explaining when combined up to 7% of the overall variance in stoichiometry. Body size was significantly and positively correlated with %P, and negatively with N:P, and C:P, and life history phenotype was significantly correlated with %C, %P, C:P and C:N. Our study suggests that spatial variability in elemental availability is more strongly correlated with organismal stoichiometry than organismal traits, and suggests that the stoichiometry of carnivores

  10. Protein and carbohydrate in P-POM collected from the fishing ground in Minnan-Taiwan Bank

    Science.gov (United States)

    Su, Yongquan; Zhang, Huan

    1992-06-01

    The analysis of the protein and carbohydrate in P-POM (Plankton and Particulate Organic Matter) samples collected from the fishing ground in Minnan-Taiwan Bank in five voyages (April, June, July, August and November, 1988) shows that the protein and carbohydrate contents and amounts in samples from four stations (501, 401, 301, 201) along the coast and another four stations (404, 304, 403, 204) south and southeast of the shoal were higher than those in April and November, indicating that this phenomenon is related to the upwelling in the two regions in summer.

  11. The elemental stoichiometry (C, Si, N, P) of the Hebrides Shelf and its role in carbon export

    NARCIS (Netherlands)

    Painter, S.C.; Hartman, S.E.; Kivimäe, C.; Salt, L.A.; Clargo, N.M.; Daniels, C.J.; Bozec, Y.; Daniels, L.; Allen, S.; Hemsley, V.S.; Moschonase, G.; Davidson, K.

    2017-01-01

    A detailed analysis of the internal stoichiometry of a temperate latitude shelf sea system is presented whichreveals strong vertical and horizontal gradients in dissolved nutrient and particulate concentrations and in theelemental stoichiometry of those pools. Such gradients have implications for

  12. Fluorescence correlation spectroscopy to study antibody binding and stoichiometry of complexes

    Science.gov (United States)

    Swift, Kerry M.; Matayoshi, Edmund D.

    2008-02-01

    FCS (fluorescence correlation spectroscopy) was used to study the association at the single molecule level of tumor necrosis factor alpha (TNF-α) and two of its protein antagonists Humira (TM) (adalimumab), a fully humanized monoclonal antibody, and Enbrel (TM) (etanercept), a soluble form of the TNF receptor. Single molecule approaches potentially have the advantage not only of enhanced sensitivity, but also of observing at equilibrium the details that would otherwise be lost in classical ensemble experiments where heterogeneity is averaged. We prepared fluorescent conjugates of the protein drugs and their biological target, the trimeric soluble form of TNF-α. The bivalency of adalimumab and the trimeric nature of TNF-α potentially allow several forms of associative complexes that may differ in stoichiometry. Detailed knowledge of this reaction may be relevant to understanding adalimumab's pharmacological properties. Our FCS data showed that a single trimeric TNF-α can bind up to three adalimumab molecules. Under some conditions even larger complexes are formed, apparently the result of cross-linking of TNF-α trimers by adalimumab. In addition, distinct differences between Humira and Enbrel were observed in their association with TNF-α.

  13. Collective estimation of multiple bivariate density functions with application to angular-sampling-based protein loop modeling

    KAUST Repository

    Maadooliat, Mehdi

    2015-10-21

    This paper develops a method for simultaneous estimation of density functions for a collection of populations of protein backbone angle pairs using a data-driven, shared basis that is constructed by bivariate spline functions defined on a triangulation of the bivariate domain. The circular nature of angular data is taken into account by imposing appropriate smoothness constraints across boundaries of the triangles. Maximum penalized likelihood is used to fit the model and an alternating blockwise Newton-type algorithm is developed for computation. A simulation study shows that the collective estimation approach is statistically more efficient than estimating the densities individually. The proposed method was used to estimate neighbor-dependent distributions of protein backbone dihedral angles (i.e., Ramachandran distributions). The estimated distributions were applied to protein loop modeling, one of the most challenging open problems in protein structure prediction, by feeding them into an angular-sampling-based loop structure prediction framework. Our estimated distributions compared favorably to the Ramachandran distributions estimated by fitting a hierarchical Dirichlet process model; and in particular, our distributions showed significant improvements on the hard cases where existing methods do not work well.

  14. Collective estimation of multiple bivariate density functions with application to angular-sampling-based protein loop modeling

    KAUST Repository

    Maadooliat, Mehdi; Zhou, Lan; Najibi, Seyed Morteza; Gao, Xin; Huang, Jianhua Z.

    2015-01-01

    This paper develops a method for simultaneous estimation of density functions for a collection of populations of protein backbone angle pairs using a data-driven, shared basis that is constructed by bivariate spline functions defined on a triangulation of the bivariate domain. The circular nature of angular data is taken into account by imposing appropriate smoothness constraints across boundaries of the triangles. Maximum penalized likelihood is used to fit the model and an alternating blockwise Newton-type algorithm is developed for computation. A simulation study shows that the collective estimation approach is statistically more efficient than estimating the densities individually. The proposed method was used to estimate neighbor-dependent distributions of protein backbone dihedral angles (i.e., Ramachandran distributions). The estimated distributions were applied to protein loop modeling, one of the most challenging open problems in protein structure prediction, by feeding them into an angular-sampling-based loop structure prediction framework. Our estimated distributions compared favorably to the Ramachandran distributions estimated by fitting a hierarchical Dirichlet process model; and in particular, our distributions showed significant improvements on the hard cases where existing methods do not work well.

  15. Effect of stoichiometry on magnetic and transport properties in polycrystalline Y2Ir2O7

    Science.gov (United States)

    Dwivedi, Vinod Kumar; Mukhopadhyay, Soumik

    2018-05-01

    In this paper we discuss synthesis of polycrystalline Y2Ir2O7 by solid state reaction route. XRD analysis shows deviation from stoichiometry which is also confirmed by SEM-EDX analysis. SEM analysis indicates average particle size ranging from 100 nm to 800 µm. EDX analysis gives clear evidence for deviation of stoichiometry of the product. Magnetic analysis is indicating effect of stoichiometry and showing ferromagnetic interaction unlike antiferromagnetic feature. Electrical resistivity is showing similar behavior as reported earlier and reveals no effect of different size of grains or grain boundaries from room temperature to 125 K.

  16. Fundamental study of ash formation and deposition: Effect of reducing stoichiometry

    Energy Technology Data Exchange (ETDEWEB)

    Helble, J.J.; Bool, L.E.; Kang, S.G. [and others

    1995-11-01

    This project is designed to examine the effects of combustion stoichiometry on the fundamental aspects of ash formation and ash deposit initiation. Emphasis is being placed on reducing stoichiometries associated with low-NOx combustion, although a range of oxidant/fuel ratios are being considered. Previous work has demonstrated that ash formation depends strongly upon coal mineralogy, including mineral type, size, amount, and the presence of organically associated inorganic species. Combustion temperature and the oxidation state of iron also play a significant role. As these latter items will vary with changes in stoichiometry, research to determine the net effect on deposition is required.

  17. Multielement stoichiometry of submerged macrophytes across Yunnan plateau lakes (China).

    Science.gov (United States)

    Xing, Wei; Wu, Haoping; Shi, Qiao; Hao, Beibei; Liu, Han; Wang, Zhixiu; Liu, Guihua

    2015-05-13

    Stoichiometric homeostasis of element composition is one of the central concepts of ecological stoichiometry. We analyzed concentrations of macroelements (C, N, P, Ca, K, Mg, S), microelements (Cu, Fe, Mn, Mo, Ni, Zn) and beneficial elements (Na, Se, Si) in submerged macrophytes, water and sediments across 20 Yunnan plateau lakes. We predicted that tissue element composition in submerged macrophytes is affected by lake trophic level and taxonomy, and submerged macrophytes have weak stoichiometric homeostasis for all above 16 elements. Canonical discriminant analyses successfully discriminated among trophic level groups and taxa groups. Of all the elements, C, N, P and S most effectively discriminated among trophic level groups across 20 lakes, revealing lake trophic level mostly affect tissue macroelement composition in submerged macrophytes; while Ca, K and Se most effectively discriminated among submerged macrophytes taxa groups, suggesting taxonomy mostly affect compositions of macroelements and beneficial elements in submerged macrophytes. In addition, the stoichiometric homeostatic coefficient of 1/HCa:C for all five taxa of submerged macrophytes were less than zero, suggesting submerged macrophytes in Yunnan plateau lakes have strong Ca stoichiometric homeostasis. Our findings, not only broaden the knowledge of multielement stoichiometric homeostasis, but also help to choose most appropriate lake management strategy.

  18. In vivo collection of rare proteins using kinesin-based "nano-harvesters".

    Energy Technology Data Exchange (ETDEWEB)

    Bachand, Marlene; Bachand, George David; Greene, Adrienne Celeste; Carroll-Portillo, Amanda

    2008-11-01

    In this project, we have developed a novel platform for capturing, transport, and separating target analytes using the work harnessed from biomolecular transport systems. Nanoharvesters were constructed by co-organizing kinesin motor proteins and antibodies on a nanocrystal quantum dot (nQD) scaffold. Attachment of kinesin and antibodies to the nQD was achieved through biotin-streptavidin non-covalent bonds. Assembly of the nanoharvesters was characterized using a modified enzyme-linked immunosorbent assay (ELISA) that confirmed attachment of both proteins. Nanoharvesters selective against tumor necrosis factor-{alpha} (TNF-{alpha}) and nuclear transcription factor-{kappa}B (NF-{kappa}B) were capable of detecting target antigens at <100 ng/mL in ELISAs. A motility-based assay was subsequently developed using an antibody-sandwich approach in which the target antigen (TNF-{alpha}) formed a sandwich with the red-emitting nanoharvester and green-emitting detection nQD. In this format, successful sandwich formation resulted in a yellow emission associated with surface-bound microtubules. Step-wise analysis of sandwich formation suggested that the motility function of the kinesin motors was not adversely affected by either antigen capture or the subsequent binding of the detection nQDs. TNF-{alpha} was detected as low as {approx}1.5 ng/mL TNF-{alpha}, with 5.2% of the nanoharvesters successfully capturing the target analyte and detection nQDs. Overall, these results demonstrate the ability to capture target protein analytes in vitro using the kinesin-based nanoharvesters in nanofluidic environments. This system has direct relevance for lab-on-a-chip applications where pressure-driven or electrokinetic movement of fluids is impractical, and offers potential application for in vivo capture of rare proteins within the cytoplasmic domain of live cells.

  19. (3,2)D GFT-NMR experiments for fast data collection from proteins

    International Nuclear Information System (INIS)

    Xia Youlin; Zhu Guang; Veeraraghavan, Sudha; Gao Xiaolian

    2004-01-01

    High throughput structure determination of proteins will contribute to the success of proteomics investigations. The G-Matrix Fourier Transformation NMR (GFT-NMR) method significantly shortens experimental time by reducing the number of the dimensions of data acquisition for isotopically labeled proteins (Kim, S. and Szyperski, T. (2003) J. Am. Chem. Soc.125, 1385). We demonstrate herein a suite of ten 3D → 2D or (3,2)D GFT-NMR experiments using 13 C/ 15 N-labeled ubiquitin. These experiments were completed within 18 hours, representing a 4- to 18-fold reduction in data acquisition time compared to the corresponding conventional 3D experiments. A subset of the GFT-NMR experiments, (3,2)D HNCO, HNCACB, HN(CO)CACB, and 2D 1 H- 15 N HSQC, which are necessary for backbone assignments, were carried out within 6 hours. To facilitate the analysis of the GFT-NMR spectra, we developed automated procedures for viewing and analyzing the GFT-NMR spectra. Our overall strategy allows (3,2)D GFT-NMR experiments to be readily performed and analyzed. Nevertheless, the increase in spectral overlap and the reduction in signal sensitivity in these fast NMR experiments presently limit their application to relatively small proteins

  20. Stoichiometry of excreta and excretion rates of a stream-dwelling plethodontid salamander

    Data.gov (United States)

    U.S. Environmental Protection Agency — Stoichiometry of excreta and excretion rates of a stream-dwelling plethodontid salamander in Cincinnati, OH, USA. This dataset is associated with the following...

  1. Impact of stoichiometry representation on simulation of genotype-phenotype relationships in metabolic networks

    DEFF Research Database (Denmark)

    Brochado, Ana Rita; Andrejev, Sergej; Maranas, Costas D.

    2012-01-01

    the formulation of the desired objective functions, by casting objective functions using metabolite turnovers rather than fluxes. By simulating perturbed metabolic networks, we demonstrate that the use of stoichiometry representation independent algorithms is fundamental for unambiguously linking modeling results...

  2. Is the stoichiometry of the europium nitrate complexes with neutral organophosphorus extractants be anticipated?

    International Nuclear Information System (INIS)

    Beudaert, Ph.; Lamare, V.; Wipff, G.

    2001-01-01

    Molecular dynamics simulations have been performed in water on europium nitrate complexes with three neutral organophosphorus extractants (TBP, TPPO and CMPO) in order to determine on what criteria it is possible to obtain by simulations the experimental 1:3 stoichiometry in organic solution. This stoichiometry was investigated by progressive saturation of the cation coordination sphere. When the nitrate counter-ions are bidentate, the 1:3 stoichiometry corresponds to the degree of saturation where the interaction energy between europium and water becomes repulsive. Beyond this stoichiometry, complexes with TPPO and CMPO are unstable, although a 1:4 complex with TBP may exist but its formation appears to be energetically unfavored. (author)

  3. Lake nutrient stoichiometry is less predictable than nutrient concentrations at regional and sub-continental scales.

    Science.gov (United States)

    Collins, Sarah M; Oliver, Samantha K; Lapierre, Jean-Francois; Stanley, Emily H; Jones, John R; Wagner, Tyler; Soranno, Patricia A

    2017-07-01

    Production in many ecosystems is co-limited by multiple elements. While a known suite of drivers associated with nutrient sources, nutrient transport, and internal processing controls concentrations of phosphorus (P) and nitrogen (N) in lakes, much less is known about whether the drivers of single nutrient concentrations can also explain spatial or temporal variation in lake N:P stoichiometry. Predicting stoichiometry might be more complex than predicting concentrations of individual elements because some drivers have similar relationships with N and P, leading to a weak relationship with their ratio. Further, the dominant controls on elemental concentrations likely vary across regions, resulting in context dependent relationships between drivers, lake nutrients and their ratios. Here, we examine whether known drivers of N and P concentrations can explain variation in N:P stoichiometry, and whether explaining variation in stoichiometry differs across regions. We examined drivers of N:P in ~2,700 lakes at a sub-continental scale and two large regions nested within the sub-continental study area that have contrasting ecological context, including differences in the dominant type of land cover (agriculture vs. forest). At the sub-continental scale, lake nutrient concentrations were correlated with nutrient loading and lake internal processing, but stoichiometry was only weakly correlated to drivers of lake nutrients. At the regional scale, drivers that explained variation in nutrients and stoichiometry differed between regions. In the Midwestern U.S. region, dominated by agricultural land use, lake depth and the percentage of row crop agriculture were strong predictors of stoichiometry because only phosphorus was related to lake depth and only nitrogen was related to the percentage of row crop agriculture. In contrast, all drivers were related to N and P in similar ways in the Northeastern U.S. region, leading to weak relationships between drivers and stoichiometry

  4. CZTS stoichiometry effects on the band gap energy

    International Nuclear Information System (INIS)

    Malerba, Claudia; Biccari, Francesco; Azanza Ricardo, Cristy Leonor; Valentini, Matteo; Chierchia, Rosa; Müller, Melanie; Santoni, Antonino; Esposito, Emilia; Mangiapane, Pietro; Scardi, Paolo; Mittiga, Alberto

    2014-01-01

    Highlights: • CZTS films with different compositions were grown from stacked-layer precursors. • The band-gap energy varies from 1.48 to 1.63 eV as the [Sn]/[Cu] ratio increases. • The Zn content seems not to be a critical parameter for the optical properties. • PDS data show an increase of the sub-gap absorption as the Sn content is reduced. • Formation of defects at low Sn content was proposed to explain the Eg variation. -- Abstract: The considerable spread of Cu 2 ZnSnS 4 (CZTS) optical properties reported in the literature is discussed in terms of material stoichiometry. To this purpose, kesterite thin films were prepared by sulfurization of multilayered precursors of ZnS, Cu and Sn, changing the relative amounts to obtain CZTS layers with different compositions. X-Ray Diffraction (XRD), Energy Dispersive X-Ray (EDX) spectroscopy, X-Ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy were used for structural and compositional analysis. XRD quantitative phase analysis provides the amount of spurious phases and information on Sn-site occupancy. The optical properties were investigated by spectrophotometric and Photothermal Deflection Spectroscopy (PDS) measurements to assess the absorption coefficient of samples with different compositions. The PDS data show an increase of the sub-band absorption as the Sn content decreases. The results are interpreted assuming the formation of additional defects as the tin content is reduced. Those defects can also be responsible for the decrease of the band gap energy value as the Sn/Cu ratio is decreased

  5. Protein scissors: Photocleavage of proteins at specific locations

    Indian Academy of Sciences (India)

    Unknown

    Binding of ligands to globular proteins at hydrophobic cavities while making specific ... ched to a PTI model A1010 monochromator. UV cut-off filter ..... >1:1 stoichiometry (protein to ligand), the binding equilibrium favors the thermo- dynamically ...

  6. Annotating gene sets by mining large literature collections with protein networks.

    Science.gov (United States)

    Wang, Sheng; Ma, Jianzhu; Yu, Michael Ku; Zheng, Fan; Huang, Edward W; Han, Jiawei; Peng, Jian; Ideker, Trey

    2018-01-01

    Analysis of patient genomes and transcriptomes routinely recognizes new gene sets associated with human disease. Here we present an integrative natural language processing system which infers common functions for a gene set through automatic mining of the scientific literature with biological networks. This system links genes with associated literature phrases and combines these links with protein interactions in a single heterogeneous network. Multiscale functional annotations are inferred based on network distances between phrases and genes and then visualized as an ontology of biological concepts. To evaluate this system, we predict functions for gene sets representing known pathways and find that our approach achieves substantial improvement over the conventional text-mining baseline method. Moreover, our system discovers novel annotations for gene sets or pathways without previously known functions. Two case studies demonstrate how the system is used in discovery of new cancer-related pathways with ontological annotations.

  7. Plant allometry, leaf nitrogen and phosphorus stoichiometry, and interspecific trends in annual growth rates.

    Science.gov (United States)

    Niklas, Karl J

    2006-02-01

    Life forms as diverse as unicellular algae, zooplankton, vascular plants, and mammals appear to obey quarter-power scaling rules. Among the most famous of these rules is Kleiber's (i.e. basal metabolic rates scale as the three-quarters power of body mass), which has a botanical analogue (i.e. annual plant growth rates scale as the three-quarters power of total body mass). Numerous theories have tried to explain why these rules exist, but each has been heavily criticized either on conceptual or empirical grounds. N,P-STOICHIOMETRY: Recent models predicting growth rates on the basis of how total cell, tissue, or organism nitrogen and phosphorus are allocated, respectively, to protein and rRNA contents may provide the answer, particularly in light of the observation that annual plant growth rates scale linearly with respect to standing leaf mass and that total leaf mass scales isometrically with respect to nitrogen but as the three-quarters power of leaf phosphorus. For example, when these relationships are juxtaposed with other allometric trends, a simple N,P-stoichiometric model successfully predicts the relative growth rates of 131 diverse C3 and C4 species. The melding of allometric and N,P-stoichiometric theoretical insights provides a robust modelling approach that conceptually links the subcellular 'machinery' of protein/ribosomal metabolism to observed growth rates of uni- and multicellular organisms. Because the operation of this 'machinery' is basic to the biology of all life forms, its allometry may provide a mechanistic explanation for the apparent ubiquity of quarter-power scaling rules.

  8. The upper and lower limits of the mechanistic stoichiometry of mitochondrial oxidative phosphorylation. Stoichiometry of oxidative phosphorylation.

    Science.gov (United States)

    Beavis, A D; Lehninger, A L

    1986-07-15

    Determination of the intrinsic or mechanistic P/O ratio of oxidative phosphorylation is difficult because of the unknown magnitude of leak fluxes. Applying a new approach developed to overcome this problem (see our preceding paper in this journal), the relationships between the rate of O2 uptake [( Jo)3], the net rate of phosphorylation (Jp), the P/O ratio, and the respiratory control ratio (RCR) have been determined in rat liver mitochondria when the rate of phosphorylation was systematically varied by three specific means. (a) When phosphorylation is titrated with carboxyatractyloside, linear relationships are observed between Jp and (Jo)3. These data indicate that the upper limit of the mechanistic P/O ratio is 1.80 for succinate and 2.90 for 3-hydroxybutyrate oxidation. (b) Titration with malonate or antimycin yields linear relationships between Jp and (Jo)3. These data give the lower limit of the mechanistic P/O ratio of 1.63 for succinate and 2.66 for 3-hydroxybutyrate oxidation. (c) Titration with a protonophore yields linear relationships between Jp, (Jo)3, and (Jo)4 and between P/O and 1/RCR. Extrapolation of the P/O ratio to 1/RCR = 0 yields P/O ratios of 1.75 for succinate and 2.73 for 3-hydroxybutyrate oxidation which must be equal to or greater than the mechanistic stoichiometry. When published values for the H+/O and H+/ATP ejection ratios are taken into consideration, these measurements suggest that the mechanistic P/O ratio is 1.75 for succinate oxidation and 2.75 for NADH oxidation.

  9. Protein and quality analyses of accessions from the USDA soybean germplasm collection for tofu production.

    Science.gov (United States)

    Meng, Shi; Chang, Sam; Gillen, Anne M; Zhang, Yan

    2016-12-15

    Food-grade soybeans with large seed size, uniformity, clear hilum and a high 11S/7S ratio are favoured by the food industry for making tofu. In order to search for soybean lines with desirable characteristics for making foods, 22 soybean lines were selected from the USDA-Soybean Germplasm Collection, were grown in Stoneville, MS for biochemical analysis and tofu texture and sensory quality tests. Eight lines were identified, from 22 lines harvested in 2014, to be suitable for tofu making, as judged by chemical composition and sensory quality of pressed tofu. In the filled tofu making and texture analysis study, the correlation between A3 subunit content and filled tofu firmness was significant (N=22, r=0.77, Pquality information for the selection of soybean genotypes for improving food quality. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Probing the Composition, Assembly and Activity of Protein Molecular Machines using Native Mass Spectrometry

    NARCIS (Netherlands)

    van de Waterbeemd, M.J.

    2017-01-01

    Native mass spectrometry and mass spectrometry in general, are powerful analytical tools for studying proteins and protein complexes. Native mass spectrometry may provide accurate mass measurements of large macromolecular assemblies enabling the investigation of their composition and stoichiometry.

  11. Crystallization, data collection and phasing of the molybdate-binding protein of the phytopathogen Xanthomonas axonopodis pv. citri

    International Nuclear Information System (INIS)

    Santacruz, C. P.; Balan, A.; Ferreira, L. C. S.; Barbosa, J. A. R. G.

    2006-01-01

    The molybdate-binding protein (ModA) from X. axonopodis pv. citri was crystallized with sodium molybdate in the presence of PEG or sulfate. The crystal diffracted to a maximum resolution of 1.7 Å and belongs to the orthorhombic space group C222 1, with unit-cell parameters a = 68.15, b = 172.14, c = 112.04 Å. Xanthomonas axonopodis pv. citri ModA protein is the ABC periplasmic binding component responsible for the capture of molybdate. The protein was crystallized with sodium molybdate using the hanging-drop vapour-diffusion method in the presence of PEG or sulfate. X-ray diffraction data were collected to a maximum resolution of 1.7 Å using synchrotron radiation. The crystal belongs to the orthorhombic space group C222 1 , with unit-cell parameters a = 68.15, b = 172.14, c = 112.04 Å. The crystal structure was solved by molecular-replacement methods and structure refinement is in progress

  12. Crystallization, data collection and phasing of the molybdate-binding protein of the phytopathogen Xanthomonas axonopodis pv. citri

    Energy Technology Data Exchange (ETDEWEB)

    Santacruz, C. P.; Balan, A.; Ferreira, L. C. S. [Departamento de Microbiologia, Instituto de Ciências Biomédicas II, Universidade de São Paulo, São Paulo, SP (Brazil); Barbosa, J. A. R. G., E-mail: joao@lnls.br [Centro de Biologia Molecular e Estrutural (CeBiMe), Laboratório Nacional de Luz Síncrotron (LNLS), CP 6192, Campinas, SP 13084-971 (Brazil); Departamento de Microbiologia, Instituto de Ciências Biomédicas II, Universidade de São Paulo, São Paulo, SP (Brazil)

    2006-03-01

    The molybdate-binding protein (ModA) from X. axonopodis pv. citri was crystallized with sodium molybdate in the presence of PEG or sulfate. The crystal diffracted to a maximum resolution of 1.7 Å and belongs to the orthorhombic space group C222{sub 1,} with unit-cell parameters a = 68.15, b = 172.14, c = 112.04 Å. Xanthomonas axonopodis pv. citri ModA protein is the ABC periplasmic binding component responsible for the capture of molybdate. The protein was crystallized with sodium molybdate using the hanging-drop vapour-diffusion method in the presence of PEG or sulfate. X-ray diffraction data were collected to a maximum resolution of 1.7 Å using synchrotron radiation. The crystal belongs to the orthorhombic space group C222{sub 1}, with unit-cell parameters a = 68.15, b = 172.14, c = 112.04 Å. The crystal structure was solved by molecular-replacement methods and structure refinement is in progress.

  13. Consequences of Modification of Photosystem Stoichiometry and Amount in Cyanobacteria

    Energy Technology Data Exchange (ETDEWEB)

    Vermaas, Willem [Arizona State Univ., Tempe, AZ (United States)

    2016-12-13

    The proposed research seeks to address two interconnected, important questions that impact photosynthetic processes and that reflect key differences between the photosynthetic systems of cyanobacteria and plants or algae. The first question is what are the reasons and consequences of the high photosystem I / photosystem II (PS I/PS II) ratio in many cyanobacteria, vs. a ratio that is close to unity in many plants and algae. The corresponding hypothesis is that most of PS I functions in cyclic electron transport, and that reduction in PS I will result primarily in a shortage of ATP rather than reducing power. This hypothesis will be tested by reducing the amount of PS I by changing the promoter region of the psaAB operon in the cyanobacterium Synechocystis sp. PCC 6803 and generating a range of mutants with different PS I content and thereby different PS I/PS II ratios, with some of the mutants having a PS II/PS I ratio closer to that in plants. The resulting mutants will be probed in terms of their growth rates, electron transfer rates, and P700 redox kinetics. A second question relates to a Mehler-type reaction catalyzed by two flavoproteins, Flv1 and Flv3, that accept electrons from PS I and that potentially function as an electron safety valve leading to no useful purpose of the photosynthesis-generated electrons. The hypothesis to be tested is that Flv1 and Flv3 use the electrons for useful purposes such as cyclic electron flow around PS I. This hypothesis will be tested by analysis of a mutant strain lacking flv3, the gene for one of the flavoproteins. This research is important for a more detailed understanding of the consequences of photosystem stoichiometry and amounts in a living system. Such an understanding is critical for not only insights in the regulatory systems of the organism but also to guide the development of biological or bio-hybrid systems for solar energy conversion into fuels.

  14. The acceleration of dissolved cobalt's ecological stoichiometry due to biological uptake, remineralization, and scavenging in the Atlantic Ocean

    Science.gov (United States)

    Saito, Mak A.; Noble, Abigail E.; Hawco, Nicholas; Twining, Benjamin S.; Ohnemus, Daniel C.; John, Seth G.; Lam, Phoebe; Conway, Tim M.; Johnson, Rod; Moran, Dawn; McIlvin, Matthew

    2017-10-01

    alkaline phosphatase enzyme to be prevalent in the upper water column, as well as a sulfolipid biosynthesis protein indicative of P sparing. The negative dCo : P relationships in the ocean interior became increasingly vertical with depth, and were consistent with the sum of scavenging and remineralization processes (as shown by their dCo : P vector sums). Attenuation of the remineralization with depth resulted in the increasingly vertical dCo : P relationships. Analysis of particulate Co with particulate Mn and particulate phosphate also showed positive linear relationships below the euphotic zone, consistent with the presence and increased relative influence of Mn oxide particles involved in scavenging. Visualization of dCo : P slopes across an ocean section revealed hotspots of scavenging and remineralization, such as at the hydrothermal vents and below the oxygen minimum zone (OMZ) region, respectively, while that of an estimate of Co* illustrated stoichiometrically depleted values in the mesopelagic and deep ocean due to scavenging. This study provides insights into the coupling between the dissolved and particulate phase that ultimately creates Redfield stoichiometric ratios, demonstrating that the coupling is not an instantaneous process and is influenced by the element inventory and rate of exchange between phases. Cobalt's small water column inventory and the influence of external factors on its biotic stoichiometry can erode its limited inertia and result in an acceleration of the dissolved stoichiometry towards that of the particulate phase in the upper euphotic zone. As human use of cobalt grows exponentially with widespread adoption of lithium ion batteries, there is a potential to affect the limited biogeochemical inertia of cobalt and its resultant ecology in the oceanic euphotic zone.

  15. Plant fertilization interacts with life history: variation in stoichiometry and performance in nettle-feeding butterflies.

    Directory of Open Access Journals (Sweden)

    Hélène Audusseau

    Full Text Available Variation in food stoichiometry affects individual performance and population dynamics, but it is also likely that species with different life histories should differ in their sensitivity to food stoichiometry. To address this question, we investigated the ability of the three nettle-feeding butterflies (Aglais urticae, Polygonia c-album, and Aglais io to respond adaptively to induced variation in plant stoichiometry in terms of larval performance. We hypothesized that variation in larval performance between plant fertilization treatments should be functionally linked to species differences in host plant specificity. We found species-specific differences in larval performance between plant fertilization treatments that could not be explained by nutrient limitation. We showed a clear evidence of a positive correlation between food stoichiometry and development time to pupal stage and pupal mass in A. urticae. The other two species showed a more complex response. Our results partly supported our prediction that host plant specificity affects larval sensitivity to food stoichiometry. However, we suggest that most of the differences observed may instead be explained by differences in voltinism (number of generations per year. We believe that the potential of some species to respond adaptively to variation in plant nutrient content needs further attention in the face of increased eutrophication due to nutrient leakage from human activities.

  16. Teaching Reaction Stoichiometry: Exploring and Acknowledging Nigerian Chemistry Teachers Pedagogical Content Knowledge

    Directory of Open Access Journals (Sweden)

    Ayoade Ejiwale Okanlawon

    2010-06-01

    Full Text Available Although there is a growing interest in studies of students’ problem-solving strategies and difficulties, and misconceptionsregarding stoichiometry, little is known about the way teachers understand and teach reaction stoichiometry. This articlepresents a case study of pedagogical content knowledge put into actions by chemistry teachers when teaching the topic ofstoichiometry to second year senior secondary school students. Fourteen chemistry teachers with teaching experience rangingfrom 5 to 20 years were involved in this study. Research data were obtained from classroom observations and videotapedrecordings of classroom practice. Analyses of the teachers’ teaching activities revealed their skillfulness, resourcefulness, andweaknesses in terms of pedagogical content knowledge displayed when teaching stoichiometry. The results of this exploratorystudy offer insight into the knowledge systems that need to be expanded, enriched, and elaborated for teaching stoichiometry.To better understand the findings of this study, the results obtained were presented under two separate sections: (1 resultsconcerning introducing reaction stoichiometry to students and (2 results concerning leading students to identify limitingreagents. Implications for instruction and teachers’ professional development are offered.

  17. From Elements to Function: Toward Unifying Ecological Stoichiometry and Trait-Based Ecology

    Directory of Open Access Journals (Sweden)

    Cédric L. Meunier

    2017-05-01

    Full Text Available The theories developed in ecological stoichiometry (ES are fundamentally based on traits. Traits directly linked to cell/body stoichiometry, such as nutrient uptake and storage, as well as the associated trade-offs, have the potential to shape ecological interactions such as competition and predation within ecosystems. Further, traits that indirectly influence and are influenced by nutritional requirements, such as cell/body size and growth rate, are tightly linked to organismal stoichiometry. Despite their physiological and ecological relevance, traits are rarely explicitly integrated in the framework of ES and, currently, the major challenge is to more closely inter-connect ES with trait-based ecology (TBE. Here, we highlight four interconnected nutrient trait groups, i.e., acquisition, body stoichiometry, storage, and excretion, which alter interspecific competition in autotrophs and heterotrophs. We also identify key differences between producer-consumer interactions in aquatic and terrestrial ecosystems. For instance, our synthesis shows that, in contrast to aquatic ecosystems, traits directly influencing herbivore stoichiometry in forested ecosystems should play only a minor role in the cycling of nutrients. We furthermore describe how linking ES and TBE can help predict the ecosystem consequences of global change. The concepts we highlight here allow us to predict that increasing N:P ratios in ecosystems should shift trait dominances in communities toward species with higher optimal N:P ratios and higher P uptake affinity, while decreasing N retention and increasing P storage.

  18. The effect of resource quantity and resource stoichiometry on microbial carbon-use-efficiency

    Science.gov (United States)

    Kleiblinger, K.M.; Hall, E.K.; Wanek, W.; Szukics, U.; Hämmerle, I.; Ellersdorfer, G.; Böck, S.; Strauss, J.; Sterflinger, K.; Richter, A.; Zechmeister-Boltenstern, S.

    2010-01-01

    The carbon-use-efficiency (CUE) of microorganisms is an important parameter in determining ecosystem-level carbon (C) cycling; however, little is known about how variance in resources affects microbial CUE. To elucidate how resource quantity and resource stoichiometry affect microbial CUE, we cultured four microorganisms - two fungi (Aspergillus nidulans and Trichoderma harzianum) and two bacteria (Pectobacterium carotovorum and Verrucomicrobium spinosum) - under 12 unique C, nitrogen (N) and phosphorus (P) ratios. Whereas the CUE of A. nidulans was strongly affected by C, bacterial CUE was more strongly affected by mineral nutrients (N and P). Specifically, CUE in P. carotovorum was positively correlated with P, while CUE of V. spinosum primarily depended on N. This resulted in a positive relationship between fungal CUE and resource C : nutrient stoichiometry and a negative relationship between bacterial CUE and resource C : nutrient stoichiometry. The difference in the direction of the relationship between CUE and C : nutrient for fungi vs. bacteria was consistent with differences in biomass stoichiometry and suggested that fungi have a higher C demand than bacteria. These results suggest that the links between biomass stoichiometry, resource demand and CUE may provide a mechanism for commonly observed temporal and spatial patterns in microbial community structure and function in natural habitats.

  19. Linking microbial and ecosystem ecology using ecological stoichiometry: a synthesis of conceptual and empirical approaches

    Science.gov (United States)

    Hall, E.K.; Maixner, F.; Franklin, O.; Daims, H.; Richter, A.; Battin, T.

    2011-01-01

    Currently, one of the biggest challenges in microbial and ecosystem ecology is to develop conceptual models that organize the growing body of information on environmental microbiology into a clear mechanistic framework with a direct link to ecosystem processes. Doing so will enable development of testable hypotheses to better direct future research and increase understanding of key constraints on biogeochemical networks. Although the understanding of phenotypic and genotypic diversity of microorganisms in the environment is rapidly accumulating, how controls on microbial physiology ultimately affect biogeochemical fluxes remains poorly understood. We propose that insight into constraints on biogeochemical cycles can be achieved by a more rigorous evaluation of microbial community biomass composition within the context of ecological stoichiometry. Multiple recent studies have pointed to microbial biomass stoichiometry as an important determinant of when microorganisms retain or recycle mineral nutrients. We identify the relevant cellular components that most likely drive changes in microbial biomass stoichiometry by defining a conceptual model rooted in ecological stoichiometry. More importantly, we show how X-ray microanalysis (XRMA), nanoscale secondary ion mass spectroscopy (NanoSIMS), Raman microspectroscopy, and in situ hybridization techniques (for example, FISH) can be applied in concert to allow for direct empirical evaluation of the proposed conceptual framework. This approach links an important piece of the ecological literature, ecological stoichiometry, with the molecular front of the microbial revolution, in an attempt to provide new insight into how microbial physiology could constrain ecosystem processes.

  20. EM structure of a helicase-loader complex depicting a 6:2 binding sub-stoichiometry from Geobacillus kaustophilus HTA426

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yen-Chen [Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan (China); Naveen, Vankadari [Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan (China); Molecular Cell Biology, Taiwan International Graduate Program, Institute of Molecular Biology, Academia Sinica, and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan (China); Hsiao, Chwan-Deng, E-mail: hsiao@gate.sinica.edu.tw [Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan (China); Molecular Cell Biology, Taiwan International Graduate Program, Institute of Molecular Biology, Academia Sinica, and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan (China)

    2016-04-22

    During DNA replication, bacterial helicase is recruited as a complex in association with loader proteins to unwind the parental duplex. Previous structural studies have reported saturated 6:6 helicase-loader complexes with different conformations. However, structural information on the sub-stoichiometric conformations of these previously-documented helicase-loader complexes remains elusive. Here, with the aid of single particle electron-microscopy (EM) image reconstruction, we present the Geobacillus kaustophilus HTA426 helicase-loader (DnaC-DnaI) complex with a 6:2 binding stoichiometry in the presence of ATPγS. In the 19 Å resolution EM map, the undistorted and unopened helicase ring holds a robust loader density above the C-terminal RecA-like domain. Meanwhile, the path of the central DNA binding channel appears to be obstructed by the reconstructed loader density, implying its potential role as a checkpoint conformation to prevent the loading of immature complex onto DNA. Our data also reveals that the bound nucleotides and the consequently induced conformational changes in the helicase hexamer are essential for active association with loader proteins. These observations provide fundamental insights into the formation of the helicase-loader complex in bacteria that regulates the DNA replication process. - Highlights: • Helicase-loader complex structure with 6:2 sub-stoichiometry is resolved by EM. • Helicase hexamer in 6:2 sub-stoichiometry is constricted and un-opened. • 6:2 binding ratio of helicase-loader complex could act as a DNA loading checkpoint. • Nucleotides stabilize helicase-loader complex at low protein concentrations.

  1. EM structure of a helicase-loader complex depicting a 6:2 binding sub-stoichiometry from Geobacillus kaustophilus HTA426

    International Nuclear Information System (INIS)

    Lin, Yen-Chen; Naveen, Vankadari; Hsiao, Chwan-Deng

    2016-01-01

    During DNA replication, bacterial helicase is recruited as a complex in association with loader proteins to unwind the parental duplex. Previous structural studies have reported saturated 6:6 helicase-loader complexes with different conformations. However, structural information on the sub-stoichiometric conformations of these previously-documented helicase-loader complexes remains elusive. Here, with the aid of single particle electron-microscopy (EM) image reconstruction, we present the Geobacillus kaustophilus HTA426 helicase-loader (DnaC-DnaI) complex with a 6:2 binding stoichiometry in the presence of ATPγS. In the 19 Å resolution EM map, the undistorted and unopened helicase ring holds a robust loader density above the C-terminal RecA-like domain. Meanwhile, the path of the central DNA binding channel appears to be obstructed by the reconstructed loader density, implying its potential role as a checkpoint conformation to prevent the loading of immature complex onto DNA. Our data also reveals that the bound nucleotides and the consequently induced conformational changes in the helicase hexamer are essential for active association with loader proteins. These observations provide fundamental insights into the formation of the helicase-loader complex in bacteria that regulates the DNA replication process. - Highlights: • Helicase-loader complex structure with 6:2 sub-stoichiometry is resolved by EM. • Helicase hexamer in 6:2 sub-stoichiometry is constricted and un-opened. • 6:2 binding ratio of helicase-loader complex could act as a DNA loading checkpoint. • Nucleotides stabilize helicase-loader complex at low protein concentrations.

  2. Effects of growth rate, cell size, motion, and elemental stoichiometry on nutrient transport kinetics.

    Science.gov (United States)

    Flynn, Kevin J; Skibinski, David O F; Lindemann, Christian

    2018-04-01

    Nutrient acquisition is a critical determinant for the competitive advantage for auto- and osmohetero- trophs alike. Nutrient limited growth is commonly described on a whole cell basis through reference to a maximum growth rate (Gmax) and a half-saturation constant (KG). This empirical application of a Michaelis-Menten like description ignores the multiple underlying feedbacks between physiology contributing to growth, cell size, elemental stoichiometry and cell motion. Here we explore these relationships with reference to the kinetics of the nutrient transporter protein, the transporter rate density at the cell surface (TRD; potential transport rate per unit plasma-membrane area), and diffusion gradients. While the half saturation value for the limiting nutrient increases rapidly with cell size, significant mitigation is afforded by cell motion (swimming or sedimentation), and by decreasing the cellular carbon density. There is thus potential for high vacuolation and high sedimentation rates in diatoms to significantly decrease KG and increase species competitive advantage. Our results also suggest that Gmax for larger non-diatom protists may be constrained by rates of nutrient transport. For a given carbon density, cell size and TRD, the value of Gmax/KG remains constant. This implies that species or strains with a lower Gmax might coincidentally have a competitive advantage under nutrient limited conditions as they also express lower values of KG. The ability of cells to modulate the TRD according to their nutritional status, and hence change the instantaneous maximum transport rate, has a very marked effect upon transport and growth kinetics. Analyses and dynamic models that do not consider such modulation will inevitably fail to properly reflect competitive advantage in nutrient acquisition. This has important implications for the accurate representation and predictive capabilities of model applications, in particular in a changing environment.

  3. Robustness of solvent/detergent treatment of plasma derivatives: a data collection from Plasma Protein Therapeutics Association member companies.

    Science.gov (United States)

    Dichtelmüller, Herbert O; Biesert, Lothar; Fabbrizzi, Fabrizio; Gajardo, Rodrigo; Gröner, Albrecht; von Hoegen, Ilka; Jorquera, Juan I; Kempf, Christoph; Kreil, Thomas R; Pifat, Dominique; Osheroff, Wendy; Poelsler, Gerhard

    2009-09-01

    Solvent/detergent (S/D) treatment is an established virus inactivation technology that has been applied in the manufacture of medicinal products derived from human plasma for more than 20 years. Data on the inactivation of enveloped viruses by S/D treatment collected from seven Plasma Protein Therapeutics Association member companies demonstrate the robustness, reliability, and efficacy of this virus inactivation method. The results from 308 studies reflecting production conditions as well as technical variables significantly beyond the product release specification were evaluated for virus inactivation, comprising different combinations of solvent and detergent (tri(n-butyl) phosphate [TNBP]/Tween 80, TNBP/Triton X-100, TNBP/Na-cholate) and different products (Factor [F]VIII, F IX, and intravenous and intramuscular immunoglobulins). Neither product class, process temperature, protein concentration, nor pH value has a significant impact on virus inactivation. A variable that did appear to be critical was the concentration of solvent and detergent. The data presented here demonstrate the robustness of virus inactivation by S/D treatment for a broad spectrum of enveloped test viruses and process variables. Our data substantiate the fact that no transmission of viruses such as human immunodeficiency virus, hepatitis B virus, hepatitis C virus, or of other enveloped viruses was reported for licensed plasma derivatives since the introduction of S/D treatment.

  4. Threshold stoichiometry for beam induced nitrogen depletion of SiN

    International Nuclear Information System (INIS)

    Timmers, H.; Weijers, T.D.M.; Elliman, R.G.; Uribasterra, J.; Whitlow, H.J.; Sarwe, E.-L.

    2002-01-01

    Measurements of the stoichiometry of silicon nitride films as a function of the number of incident ions using heavy ion elastic recoil detection (ERD) show that beam-induced nitrogen depletion depends on the projectile species, the beam energy, and the initial stoichiometry. A threshold stoichiometry exists in the range 1.3>N/Si≥1, below which the films are stable against nitrogen depletion. Above this threshold, depletion is essentially linear with incident fluence. The depletion rate correlates non-linearly with the electronic energy loss of the projectile ion in the film. Sufficiently long exposure of nitrogen-rich films renders the mechanism, which prevents depletion of nitrogen-poor films, ineffective. Compromising depth-resolution, nitrogen depletion from SiN films during ERD analysis can be reduced significantly by using projectile beams with low atomic numbers

  5. Shrub type dominates the vertical distribution of leaf C : N : P stoichiometry across an extensive altitudinal gradient

    Science.gov (United States)

    Zhao, Wenqiang; Reich, Peter B.; Yu, Qiannan; Zhao, Ning; Yin, Chunying; Zhao, Chunzhang; Li, Dandan; Hu, Jun; Li, Ting; Yin, Huajun; Liu, Qing

    2018-04-01

    Understanding leaf stoichiometric patterns is crucial for improving predictions of plant responses to environmental changes. Leaf stoichiometry of terrestrial ecosystems has been widely investigated along latitudinal and longitudinal gradients. However, very little is known about the vertical distribution of leaf C : N : P and the relative effects of environmental parameters, especially for shrubs. Here, we analyzed the shrub leaf C, N and P patterns in 125 mountainous sites over an extensive altitudinal gradient (523-4685 m) on the Tibetan Plateau. Results showed that the shrub leaf C and C : N were 7.3-47.5 % higher than those of other regional and global flora, whereas the leaf N and N : P were 10.2-75.8 % lower. Leaf C increased with rising altitude and decreasing temperature, supporting the physiological acclimation mechanism that high leaf C (e.g., alpine or evergreen shrub) could balance the cell osmotic pressure and resist freezing. The largest leaf N and high leaf P occurred in valley region (altitude 1500 m), likely due to the large nutrient leaching from higher elevations, faster litter decomposition and nutrient resorption ability of deciduous broadleaf shrub. Leaf N : P ratio further indicated increasing N limitation at higher altitudes. Interestingly, drought severity was the only climatic factor positively correlated with leaf N and P, which was more appropriate for evaluating the impact of water status than precipitation. Among the shrub ecosystem and functional types (alpine, subalpine, montane, valley, evergreen, deciduous, broadleaf, and conifer), their leaf element contents and responses to environments were remarkably different. Shrub type was the largest contributor to the total variations in leaf stoichiometry, while climate indirectly affected the leaf C : N : P via its interactive effects on shrub type or soil. Collectively, the large heterogeneity in shrub type was the most important factor explaining the overall leaf C : N : P variations

  6. Low stoichiometry operation of a polymer electrolyte membrane fuel cell employing the interdigitated flow field design

    DEFF Research Database (Denmark)

    Berning, Torsten; Odgaard, Madeleine; Kær, Søren Knudsen

    2011-01-01

    Fuel cell operation on dry reactant gases under low stoichiometry conditions employing the interdigitated flow field is investigated using a multi-fluid model. It is assumed that the MEA contains a water uptake layer which facilitates water absorption to the membrane and hence prevents the anode...

  7. Investigating the Effect of Complexity Factors in Stoichiometry Problems Using Logistic Regression and Eye Tracking

    Science.gov (United States)

    Tang, Hui; Kirk, John; Pienta, Norbert J.

    2014-01-01

    This paper includes two experiments, one investigating complexity factors in stoichiometry word problems, and the other identifying students' problem-solving protocols by using eye-tracking technology. The word problems used in this study had five different complexity factors, which were randomly assigned by a Web-based tool that we developed. The…

  8. Near Surface Stoichiometry in UO2: A Density Functional Theory Study

    Directory of Open Access Journals (Sweden)

    Jianguo Yu

    2015-01-01

    Full Text Available The mechanisms of oxygen stoichiometry variation in UO2 at different temperature and oxygen partial pressure are important for understanding the dynamics of microstructure in these crystals. However, very limited experimental studies have been performed to understand the atomic structure of UO2 near surface and defect effects of near surface on stoichiometry in which the system can exchange atoms with the external reservoir. In this study, the near (110 surface relaxation and stoichiometry in UO2 have been studied with density functional theory (DFT calculations. On the basis of the point-defect model (PDM, a general expression for the near surface stoichiometric variation is derived by using DFT total-energy calculations and atomistic thermodynamics, in an attempt to pin down the mechanisms of oxygen exchange between the gas environment and defected UO2. By using the derived expression, it is observed that, under poor oxygen conditions, the stoichiometry of near surface is switched from hyperstoichiometric at 300 K with a depth around 3 nm to near-stoichiometric at 1000 K and hypostoichiometric at 2000 K. Furthermore, at very poor oxygen concentrations and high temperatures, our results also suggest that the bulk of the UO2 prefers to be hypostoichiometric, although the surface is near-stoichiometric.

  9. Global biodiversity, stoichiometry and ecosystem function responses to human-induced C-N-P imbalances.

    Science.gov (United States)

    Carnicer, Jofre; Sardans, Jordi; Stefanescu, Constantí; Ubach, Andreu; Bartrons, Mireia; Asensio, Dolores; Peñuelas, Josep

    2015-01-01

    Global change analyses usually consider biodiversity as a global asset that needs to be preserved. Biodiversity is frequently analysed mainly as a response variable affected by diverse environmental drivers. However, recent studies highlight that gradients of biodiversity are associated with gradual changes in the distribution of key dominant functional groups characterized by distinctive traits and stoichiometry, which in turn often define the rates of ecosystem processes and nutrient cycling. Moreover, pervasive links have been reported between biodiversity, food web structure, ecosystem function and species stoichiometry. Here we review current global stoichiometric gradients and how future distributional shifts in key functional groups may in turn influence basic ecosystem functions (production, nutrient cycling, decomposition) and therefore could exert a feedback effect on stoichiometric gradients. The C-N-P stoichiometry of most primary producers (phytoplankton, algae, plants) has been linked to functional trait continua (i.e. to major axes of phenotypic variation observed in inter-specific analyses of multiple traits). In contrast, the C-N-P stoichiometry of higher-level consumers remains less precisely quantified in many taxonomic groups. We show that significant links are observed between trait continua across trophic levels. In spite of recent advances, the future reciprocal feedbacks between key functional groups, biodiversity and ecosystem functions remain largely uncertain. The reported evidence, however, highlights the key role of stoichiometric traits and suggests the need of a progressive shift towards an ecosystemic and stoichiometric perspective in global biodiversity analyses. Copyright © 2014 Elsevier GmbH. All rights reserved.

  10. Climate-driven changes in the ecological stoichiometry of aquatic ecosystems

    NARCIS (Netherlands)

    van de Waal, D.B.; Verschoor, A.M.; Verspagen, J.M.H.; van Donk, E.; Huisman, J.

    2010-01-01

    Advances in ecological stoichiometry, a rapidly expanding research field investigating the elemental composition of organisms and their environment, have shed new light on the impacts of climate change on freshwater and marine ecosystems. Current changes in the Earth's climate alter the availability

  11. Stoichiometry control in quantum dots: a viable analog to impurity doping of bulk materials.

    Science.gov (United States)

    Luther, Joseph M; Pietryga, Jeffrey M

    2013-03-26

    A growing body of research indicates that the stoichiometry of compound semiconductor quantum dots (QDs) may offer control over the materials' optoelectronic properties in ways that could be invaluable in electronic devices. Quantum dots have been characterized as having a stoichiometric bulk-like core with a highly reconstructed surface of a more flexible composition, consisting essentially of ligated, weakly bound ions. As such, many efforts toward stoichiometry-based control over material properties have focused on ligand manipulation. In this issue of ACS Nano, Murray and Kagan's groups instead demonstrate control of the conductive properties of QD arrays by altering the stoichiometry via atomic infusion using a thermal evaporation technique. In this work, PbSe and PbS QD films are made to show controlled n- or p-type behavior, which is key to developing optimized QD-based electronics. In this Perspective, we discuss recent developments and the future outlook in using stoichiometry as a tool to further manipulate QD material properties in this context.

  12. Students' Understanding of Conservation of Matter, Stoichiometry and Balancing Equations in Indonesia

    Science.gov (United States)

    Agung, Salamah; Schwartz, Marc S.

    2007-01-01

    This study examines Indonesian students' understanding of conservation of matter, balancing of equations and stoichiometry. Eight hundred and sixty-seven Grade 12 students from 22 schools across four different cities in two developed provinces in Indonesia participated in the study. Nineteen teachers also participated in order to validate the…

  13. E-cadherin Is Critical for Collective Sheet Migration and Is Regulated by the Chemokine CXCL12 Protein During Restitution*

    Science.gov (United States)

    Hwang, Soonyean; Zimmerman, Noah P.; Agle, Kimberle A.; Turner, Jerrold R.; Kumar, Suresh N.; Dwinell, Michael B.

    2012-01-01

    Chemokines and other immune mediators enhance epithelial barrier repair. The intestinal barrier is established by highly regulated cell-cell contacts between epithelial cells. The goal of these studies was to define the role for the chemokine CXCL12 in regulating E-cadherin during collective sheet migration during epithelial restitution. Mechanisms regulating E-cadherin were investigated using Caco2BBE and IEC-6 model epithelia. Genetic knockdown confirmed a critical role for E-cadherin in in vitro restitution and in vivo wound repair. During restitution, both CXCL12 and TGF-β1 tightened the monolayer by decreasing the paracellular space between migrating epithelial cells. However, CXCL12 differed from TGF-β1 by stimulating the significant increase in E-cadherin membrane localization during restitution. Chemokine-stimulated relocalization of E-cadherin was paralleled by an increase in barrier integrity of polarized epithelium during restitution. CXCL12 activation of its cognate receptor CXCR4 stimulated E-cadherin localization and monolayer tightening through Rho-associated protein kinase activation and F-actin reorganization. These data demonstrate a key role for E-cadherin in intestinal epithelial restitution. PMID:22549778

  14. Accurate quantification of site-specific acetylation stoichiometry reveals the impact of sirtuin deacetylase CobB on the E. coli acetylome

    DEFF Research Database (Denmark)

    Weinert, Brian Tate; Satpathy, Shankha; Hansen, Bogi Karbech

    2017-01-01

    B suppressed acetylation to lower than median stoichiometry in WT, ptaΔ, and ackAΔ cells. Together, our results provide a detailed view of acetylation stoichiometry in E. coli and suggest an evolutionarily conserved function of Sirtuin deacetylases in suppressing low stoichiometry acetylation....

  15. Looking inside the box: using Raman microspectroscopy to deconstruct microbial biomass stoichiometry one cell at a time

    Science.gov (United States)

    Hall, Edward K.; Singer, Gabriel A.; Pölzl, Marvin; Hämmerle, Ieda; Schwarz, Christian; Daims, Holger; Maixner, Frank; Battin, Tom J.

    2011-01-01

    Stoichiometry of microbial biomass is a key determinant of nutrient recycling in a wide variety of ecosystems. However, little is known about the underlying causes of variance in microbial biomass stoichiometry. This is primarily because of technological constraints limiting the analysis of macromolecular composition to large quantities of microbial biomass. Here, we use Raman microspectroscopy (MS), to analyze the macromolecular composition of single cells of two species of bacteria grown on minimal media over a wide range of resource stoichiometry. We show that macromolecular composition, determined from a subset of identified peaks within the Raman spectra, was consistent with macromolecular composition determined using traditional analytical methods. In addition, macromolecular composition determined by Raman MS correlated with total biomass stoichiometry, indicating that analysis with Raman MS included a large proportion of a cell's total macromolecular composition. Growth phase (logarithmic or stationary), resource stoichiometry and species identity each influenced each organism's macromolecular composition and thus biomass stoichiometry. Interestingly, the least variable peaks in the Raman spectra were those responsible for differentiation between species, suggesting a phylogenetically specific cellular architecture. As Raman MS has been previously shown to be applicable to cells sampled directly from complex environments, our results suggest Raman MS is an extremely useful application for evaluating the biomass stoichiometry of environmental microorganisms. This includes the ability to partition microbial biomass into its constituent macromolecules and increase our understanding of how microorganisms in the environment respond to resource heterogeneity.

  16. Stoichiometry of the U3O8 phase formed during calcination of some uranium compounds

    International Nuclear Information System (INIS)

    El-Fekey, S.A.; Farah, M.Y.; Rofail, N.H.

    1981-01-01

    Although recent work has shown U 3 O 8 phase to be the decomposition product obtained after calcining uranyl nitrate, sulphate or ammonium uranate, neither the necessary conditions for obtaining stoichiometric U 3 O 8 nor the details of the reaction have been established. Presence of sulphate or nitrate ions during preparation greatly affects the O/U of the obtained oxides and the physico-chemical properties of uranium tetrafluoride prepared afterwards from it (1-3). The aim of the present investigation was to study the effect of calcination regimes on the stoichiometry of the U 3 O 8 phase produced by the thermal decomposition of uranyl nitrate, sulphate, and ammonium uranate, which was prepared by precipitation from nuclear-pure uranyl sulphate. Stoichiometry of the U 3 O 8 phase formed during calcination of ammonium uranate precipitated from nuclear pure uranyl nitrate solution was reported before (1)

  17. Stoichiometry of Silicon Dioxide Films Obtained by Ion-Beam Sputtering

    Science.gov (United States)

    Telesh, E. V.; Dostanko, A. P.; Gurevich, O. V.

    2018-03-01

    The composition of SiOx films produced by ion-beam sputtering (IBS) of silicon and quartz targets were studied by infrared spectrometry. Films with thicknesses of 150-390 nm were formed on silicon substrates. It was found that increase in the partial pressure of oxygen in the working gas, increase in the temperature of the substrate, and the presence of a positive potential on the target during reactive IBS of silicon shifted the main absorption band νas into the high-frequency region and increased the composition index from 1.41 to 1.85. During IBS of a quartz target the stoichiometry of the films deteriorates with increase of the energy of the sputtering argon ions. This may be due to increase of the deposition rate. Increase in the current of the thermionic compensator, increase of the substrate temperature, and addition of oxygen led to the formation of SiOx films with improved stoichiometry.

  18. Effects of three global change drivers on terrestrial C:N:P stoichiometry

    DEFF Research Database (Denmark)

    Yue, Kai; Fornara, Dario A; Yang, Wanqin

    2017-01-01

    more common than synergistic or antagonistic interactions, (4) C:N:P stoichiometry of soil and soil microbial biomass shows high homeostasis under global change manipulations, and (5) C:N:P responses to global change are strongly affected by ecosystem type, local climate and experimental conditions......Over the last few decades there has been an increasing number of controlled-manipulative experiments to investigate how plants and soils might respond to global change. These experiments typically examined the effects of each of three global change drivers (i.e. nitrogen (N) deposition, warming...... of plants, soils and soil microbial biomass might respond to individual vs. combined effects of the three global change drivers. Our results show that (1) individual effects of N addition and elevated CO2 on C:N:P stoichiometry are stronger than warming, (2) combined effects of pairs of global change...

  19. Stoichiometry-Controlled Inversion of Supramolecular Chirality in Nanostructures Co-assembled with Bipyridines.

    Science.gov (United States)

    Wang, Fang; Feng, Chuan-Liang

    2018-02-01

    To control supramolecular chirality of the co-assembled nanostructures, one of the remaining issues is how stoichiometry of the different molecules involved in co-assembly influence chiral transformation. Through co-assembly of achiral 1,4-bis(pyrid-4-yl)benzene and chiral phenylalanine-glycine derivative hydrogelators, stoichiometry is found to be an effective tool for controlling supramolecular chirality inversion processes. This inversion is mainly mediated by a delicate balance between intermolecular hydrogen bonding interactions and π-π stacking of the two components, which may subtly change the stacking of the molecules, in turn, the self-assembled nanostructures. This study exemplifies a simplistic way to invert the handedness of chiral nanostructures and provide fundamental understanding of the inherent principles of supramolecular chirality. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. A simple way to constrain the stoichiometry of secondary smectites upon aqueous glass alteration

    International Nuclear Information System (INIS)

    Thien, Bruno M.J.

    2014-01-01

    Highlights: • Si/Al of different glasses were compared to Si/Al of associated secondary smectites. • Si/Al of secondary smectite is nearly equal to Si/Al of parent glass. • This is a simple way which can help to constrain smectite composition. • Accurate smectite composition cannot be measured in many cases. - Abstract: The comparison of the stoichiometry of several nuclear waste glasses and basaltic glasses with their associated secondary smectites evidenced that Si/Al ratios of secondary smectites are nearly equal to the Si/Al ratios of parent glasses. This information may be very useful in constraining secondary smectites structure and stoichiometry in cases where other identification methods are difficult to apply

  1. Surface stoichiometry of zinc sulfide and its effect on the adsorption behaviors of xanthate

    Directory of Open Access Journals (Sweden)

    Wang Meng

    2011-11-01

    Full Text Available Abstract In this paper, the surface stoichiometry, acid-base properties as well as the adsorption of xanthate at ZnS surfaces were studied by means of potentiometric titration, adsorption and solution speciation modeling. The surface proton binding site was determined by using Gran plot to evaluate the potentiometric titration data. Testing results implied that for stoichiometric surfaces of zinc sulfide, the proton and hydroxide determine the surface charge. For the nonstoichiometric surfaces, the surface charge is controlled by proton, hydroxide, zinc and sulfide ions depending on specific conditions. The xanthate adsorption decreases with increasing solution pH, which indicates an ion exchange reaction at the surfaces. Based on experimental results, the surface protonation, deprotonation, stoichiometry and xanthate adsorption mechanism were discussed.

  2. Determination of kinetics and stoichiometry of chemical sulfide oxidation in wastewater of sewer networks

    DEFF Research Database (Denmark)

    Nielsen, Asbjørn Haaning; Vollertsen, Jes; Hvitved-Jacobsen, Thorkild

    2003-01-01

    A method for determination of kinetics and stoichiometry of chemical sulfide oxidation by dissolved oxygen (DO) in wastewater is presented. The method was particularly developed to investigate chemical sulfide oxidation in wastewater of sewer networks at low DO concentrations. The method is based...... be considered constant during the course of the experiments although intermediates accumulated. This was explained by an apparent slow oxidation rate of the intermediates. The method was capable of determining kinetics and stoichiometry of chemical sulfide oxidation at DO concentrations lower than 1 g of O2 m...... on continuous measurement of the reactants allowing the kinetics to be determined at varying reactant concentrations during the course of the experiment. The kinetics determined was simulated by a rate equation. The precision of the method was assessed in terms of the standard deviation of the kinetic...

  3. The Stoichiometry of Nutrient Release by Terrestrial Herbivores and Its Ecosystem Consequences

    Directory of Open Access Journals (Sweden)

    Judith Sitters

    2017-04-01

    Full Text Available It is widely recognized that the release of nutrients by herbivores via their waste products strongly impacts nutrient availability for autotrophs. The ratios of nitrogen (N and phosphorus (P recycled through herbivore release (i.e., waste N:P are mainly determined by the stoichiometric composition of the herbivore's food (food N:P and its body nutrient content (body N:P. Waste N:P can in turn impact autotroph nutrient limitation and productivity. Herbivore-driven nutrient recycling based on stoichiometric principles is dominated by theoretical and experimental research in freshwater systems, in particular interactions between algae and invertebrate herbivores. In terrestrial ecosystems, the impact of herbivores on nutrient cycling and availability is often limited to studying carbon (C:N and C:P ratios, while the role of terrestrial herbivores in mediating N:P ratios is also likely to influence herbivore-driven nutrient recycling. In this review, we use rules and predictions on the stoichiometry of nutrient release originating from algal-based aquatic systems to identify the factors that determine the stoichiometry of nutrient release by herbivores. We then explore how these rules can be used to understand the stoichiometry of nutrient release by terrestrial herbivores, ranging from invertebrates to mammals, and its impact on plant nutrient limitation and productivity. Future studies should focus on measuring both N and P when investigating herbivore-driven nutrient recycling in terrestrial ecosystems, while also taking the form of waste product (urine or feces and other pathways by which herbivores change nutrients into account, to be able to quantify the impact of waste stoichiometry on plant communities.

  4. Warming differentially influences the effects of drought on stoichiometry and metabolomics in shoots and roots

    Czech Academy of Sciences Publication Activity Database

    Gargallo-Garriga, A.; Sardans, J.; Pérez-Trujillo, M.; Oravec, Michal; Urban, Otmar; Jentsch, A.; Kreyling, J.; Beierkuhnlein, C.; Parella, T.; Penuelas, J.

    2015-01-01

    Roč. 207, č. 3 (2015), s. 591-603 ISSN 1469-8137 R&D Projects: GA MŠk(CZ) LO1415; GA AV ČR(CZ) M200871201 Institutional support: RVO:67179843 Keywords : climate change * drought * HPLC-MS * nitrogen * phosphorus (N : P) * nuclear magnetic resonance (NMR) * stoichiometry * warming * abiotic stresses Subject RIV: EH - Ecology, Behaviour Impact factor: 6.545, year: 2013

  5. Non stoichiometry in U3O(8±x), its temperature and oxygen pressure dependence

    International Nuclear Information System (INIS)

    Rodriguez De Sastre, M.S.; Philippot, J.; Moreau, C.

    1967-01-01

    The deviation from stoichiometry in uranium oxide U 3 O 8 obtained by oxidation of UO 2 , has been studied with respect to its dependence on temperature and oxygen pressure. It is shown that the ratio r = O/U increases with oxygen pressure up to 200 mm Hg at any temperature. At higher pressures, this ratio tends toward a limit which decreases with increasing temperatures. The curve r = f(P) suggest a chemisorption phenomenon as the reaction limiting mechanism. (authors) [fr

  6. Stoichiometry in Context: Inquiry-Guided Problems of Chemistry for Encouraging Critical Thinking in Engineering Students

    OpenAIRE

    Gabriel Pinto; María Luisa Prolongo

    2013-01-01

    This paper focuses on examples of educational tools concerning the learning of chemistry for engineering students through different daily life cases. These tools were developed during the past few years for enhancing the active role of students. They refer to cases about mineral water, medicaments, dentifrices and informative panels about solar power, where an adequate quantitative treatment through stoichiometry calculations allows the interpretation of data and values announced by manufactu...

  7. Coexistence and community structure in a consumer resource model with implicit stoichiometry.

    Science.gov (United States)

    Orlando, Paul A; Brown, Joel S; Wise, David H

    2012-09-01

    We combine stoichiometry theory and optimal foraging theory into the MacArthur consumer-resource model. This generates predictions for diet choice, coexistence, and community structure of heterotroph communities. Tradeoffs in consumer resource-garnering traits influence community outcomes. With scarce resources, consumers forage opportunistically for complementary resources and may coexist via tradeoffs in resource encounter rates. In contrast to single currency models, stoichiometry permits multiple equilibria. These alternative stable states occur when tradeoffs in resource encounter rates are stronger than tradeoffs in elemental conversion efficiencies. With abundant resources consumers exhibit partially selective diets for essential resources and may coexist via tradeoffs in elemental conversion efficiencies. These results differ from single currency models, where adaptive diet selection is either opportunistic or selective. Interestingly, communities composed of efficient consumers share many of the same properties as communities based on substitutable resources. However, communities composed of relatively inefficient consumers behave similarly to plant communities as characterized by Tilman's consumer resource theory. The results of our model indicate that the effects of stoichiometry theory on community ecology are dependent upon both consumer foraging behavior and the nature of resource garnering tradeoffs. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. A Versatile System for High-Throughput In Situ X-ray Screening and Data Collection of Soluble and Membrane-Protein Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Broecker, Jana; Klingel, Viviane; Ou, Wei-Lin; Balo, Aidin R.; Kissick, David J.; Ogata, Craig M.; Kuo, Anling; Ernst, Oliver P.

    2016-10-12

    In recent years, in situ data collection has been a major focus of progress in protein crystallography. Here, we introduce the Mylar in situ method using Mylar-based sandwich plates that are inexpensive, easy to make and handle, and show significantly less background scattering than other setups. A variety of cognate holders for patches of Mylar in situ sandwich films corresponding to one or more wells makes the method robust and versatile, allows for storage and shipping of entire wells, and enables automated crystal imaging, screening, and goniometerbased X-ray diffraction data-collection at room temperature and under cryogenic conditions for soluble and membrane-protein crystals grown in or transferred to these plates. We validated the Mylar in situ method using crystals of the water-soluble proteins hen egg-white lysozyme and sperm whale myoglobin as well as the 7-transmembrane protein bacteriorhodopsin from Haloquadratum walsbyi. In conjunction with current developments at synchrotrons, this approach promises high-resolution structural studies of membrane proteins to become faster and more routine.

  9. Effects of Differences in Dietary Protein and Varying the Interval from Collection of Bovine Embryos to Freezing on Embryo Quality and Viability

    OpenAIRE

    Jousan, Frank Dean

    2002-01-01

    High levels of dietary protein may be detrimental to reproductive performance in cattle. The objective of Exp. 1 was to determine the effects of differences in dietary protein on the production and quality of bovine embryos collected from superovulated donors. Angus cows were randomly assigned to receive one of three experimental diets: a daily ration of 5.7 kg poultry litter, 2.0 kg hay, 3.1 kg corn, and 0.5 kg peanut hulls (LITTER; n = 15); a daily ration of 6.2 kg peanut hulls, 2.2 k...

  10. Progress in proton-detected solid-state NMR (SSNMR): Super-fast 2D SSNMR collection for nano-mole-scale proteins

    Science.gov (United States)

    Ishii, Yoshitaka; Wickramasinghe, Ayesha; Matsuda, Isamu; Endo, Yuki; Ishii, Yuji; Nishiyama, Yusuke; Nemoto, Takahiro; Kamihara, Takayuki

    2018-01-01

    Proton-detected solid-state NMR (SSNMR) spectroscopy has attracted much attention due to its excellent sensitivity and effectiveness in the analysis of trace amounts of amyloid proteins and other important biological systems. In this perspective article, we present the recent sensitivity limit of 1H-detected SSNMR using "ultra-fast" magic-angle spinning (MAS) at a spinning rate (νR) of 80-100 kHz. It was demonstrated that the high sensitivity of 1H-detected SSNMR at νR of 100 kHz and fast recycling using the paramagnetic-assisted condensed data collection (PACC) approach permitted "super-fast" collection of 1H-detected 2D protein SSNMR. A 1H-detected 2D 1H-15N correlation SSNMR spectrum for ∼27 nmol of a uniformly 13C- and 15N-labeled GB1 protein sample in microcrystalline form was acquired in only 9 s with 50% non-uniform sampling and short recycle delays of 100 ms. Additional data suggests that it is now feasible to detect as little as 1 nmol of the protein in 5.9 h by 1H-detected 2D 1H-15N SSNMR at a nominal signal-to-noise ratio of five. The demonstrated sensitivity is comparable to that of modern solution protein NMR. Moreover, this article summarizes the influence of ultra-fast MAS and 1H-detection on the spectral resolution and sensitivity of protein SSNMR. Recent progress in signal assignment and structural elucidation by 1H-detected protein SSNMR is outlined with both theoretical and experimental aspects.

  11. Resource stoichiometry and availability modulate species richness and biomass of tropical litter macro-invertebrates.

    Science.gov (United States)

    Jochum, Malte; Barnes, Andrew D; Weigelt, Patrick; Ott, David; Rembold, Katja; Farajallah, Achmad; Brose, Ulrich

    2017-09-01

    High biodiversity and biomass of soil communities are crucial for litter decomposition in terrestrial ecosystems such as tropical forests. However, the leaf litter that these communities consume is of particularly poor quality as indicated by elemental stoichiometry. The impact of resource quantity, quality and other habitat parameters on species richness and biomass of consumer communities is often studied in isolation, although much can be learned from simultaneously studying both community characteristics. Using a dataset of 780 macro-invertebrate consumer species across 32 sites in tropical lowland rain forest and agricultural systems on Sumatra, Indonesia, we investigated the effects of basal resource stoichiometry (C:X ratios of N, P, K, Ca, Mg, Na, S in local leaf litter), litter mass (basal resource quantity and habitat space), plant species richness (surrogate for litter habitat heterogeneity), and soil pH (acidity) on consumer species richness and biomass across different consumer groups (i.e. 3 feeding guilds and 10 selected taxonomic groups). In order to distinguish the most important predictors of consumer species richness and biomass, we applied a standardised model averaging approach investigating the effects of basal resource stoichiometry, litter mass, plant species richness and soil pH on both consumer community characteristics. This standardised approach enabled us to identify differences and similarities in the magnitude and importance of such effects on consumer species richness and biomass. Across consumer groups, we found litter mass to be the most important predictor of both species richness and biomass. Resource stoichiometry had a more pronounced impact on consumer species richness than on their biomass. As expected, taxonomic groups differed in which resource and habitat parameters (basal resource stoichiometry, litter mass, plant species richness and pH) were most important for modulating their community characteristics. The importance

  12. Marine phytoplankton stoichiometry mediates nonlinear interactions between nutrient supply, temperature, and atmospheric CO2

    Science.gov (United States)

    Moreno, Allison R.; Hagstrom, George I.; Primeau, Francois W.; Levin, Simon A.; Martiny, Adam C.

    2018-05-01

    Marine phytoplankton stoichiometry links nutrient supply to marine carbon export. Deviations of phytoplankton stoichiometry from Redfield proportions (106C : 1P) could therefore have a significant impact on carbon cycling, and understanding which environmental factors drive these deviations may reveal new mechanisms regulating the carbon cycle. To explore the links between environmental conditions, stoichiometry, and carbon cycling, we compared four different models of phytoplankton C : P: a fixed Redfield model, a model with C : P given as a function of surface phosphorus concentration (P), a model with C P given as a function of temperature, and a new multi-environmental model that predicts C : P as a function of light, temperature, and P. These stoichiometric models were embedded into a five-box ocean circulation model, which resolves the three major ocean biomes (high-latitude, subtropical gyres, and tropical upwelling regions). Contrary to the expectation of a monotonic relationship between surface nutrient drawdown and carbon export, we found that lateral nutrient transport from lower C : P tropical waters to high C : P subtropical waters could cause carbon export to decrease with increased tropical nutrient utilization. It has been hypothesized that a positive feedback between temperature and pCO2, atm will play an important role in anthropogenic climate change, with changes in the biological pump playing at most a secondary role. Here we show that environmentally driven shifts in stoichiometry make the biological pump more influential, and may reverse the expected positive relationship between temperature and pCO2, atm. In the temperature-only model, changes in tropical temperature have more impact on the Δ pCO2, atm (˜ 41 ppm) compared to subtropical temperature changes (˜ 4.5 ppm). Our multi-environmental model predicted a decline in pCO2, atm of ˜ 46 ppm when temperature spanned a change of 10 °C. Thus, we find that variation in marine phytoplankton

  13. Shrub type dominates the vertical distribution of leaf C : N : P stoichiometry across an extensive altitudinal gradient

    Directory of Open Access Journals (Sweden)

    W. Zhao

    2018-04-01

    Full Text Available Understanding leaf stoichiometric patterns is crucial for improving predictions of plant responses to environmental changes. Leaf stoichiometry of terrestrial ecosystems has been widely investigated along latitudinal and longitudinal gradients. However, very little is known about the vertical distribution of leaf C : N : P and the relative effects of environmental parameters, especially for shrubs. Here, we analyzed the shrub leaf C, N and P patterns in 125 mountainous sites over an extensive altitudinal gradient (523–4685 m on the Tibetan Plateau. Results showed that the shrub leaf C and C : N were 7.3–47.5 % higher than those of other regional and global flora, whereas the leaf N and N : P were 10.2–75.8 % lower. Leaf C increased with rising altitude and decreasing temperature, supporting the physiological acclimation mechanism that high leaf C (e.g., alpine or evergreen shrub could balance the cell osmotic pressure and resist freezing. The largest leaf N and high leaf P occurred in valley region (altitude 1500 m, likely due to the large nutrient leaching from higher elevations, faster litter decomposition and nutrient resorption ability of deciduous broadleaf shrub. Leaf N : P ratio further indicated increasing N limitation at higher altitudes. Interestingly, drought severity was the only climatic factor positively correlated with leaf N and P, which was more appropriate for evaluating the impact of water status than precipitation. Among the shrub ecosystem and functional types (alpine, subalpine, montane, valley, evergreen, deciduous, broadleaf, and conifer, their leaf element contents and responses to environments were remarkably different. Shrub type was the largest contributor to the total variations in leaf stoichiometry, while climate indirectly affected the leaf C : N : P via its interactive effects on shrub type or soil. Collectively, the large heterogeneity in shrub type was the most

  14. X-ray-excited optical luminescence of protein crystals: a new tool for studying radiation damage during diffraction data collection.

    Science.gov (United States)

    Owen, Robin L; Yorke, Briony A; Pearson, Arwen R

    2012-05-01

    During X-ray irradiation protein crystals radiate energy in the form of small amounts of visible light. This is known as X-ray-excited optical luminescence (XEOL). The XEOL of several proteins and their constituent amino acids has been characterized using the microspectrophotometers at the Swiss Light Source and Diamond Light Source. XEOL arises primarily from aromatic amino acids, but the effects of local environment and quenching within a crystal mean that the XEOL spectrum of a crystal is not the simple sum of the spectra of its constituent parts. Upon repeated exposure to X-rays XEOL spectra decay non-uniformly, suggesting that XEOL is sensitive to site-specific radiation damage. However, rates of XEOL decay were found not to correlate to decays in diffracting power, making XEOL of limited use as a metric for radiation damage to protein crystals. © 2012 International Union of Crystallography

  15. Fresh water influence on nutrient stoichiometry in a tropical estuary, Southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Martin, G.D.; Vijay, J.G.; Laluraj, C.M.; Madhu, N.V.; Joseph, T.; Nair, M.; Gupta, G.V.M.; Balachandran, K.K.

    et al.: Fresh water influence on nutrient stoichiometry in a tropical estuary, Southwest coast of India - 57 - APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 6(1): 57-64. http://www.ecology.uni-corvinus.hu ● ISSN 1589 1623  2008, Penkala Bt... estuary, Southwest coast of India - 58 - APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 6(1): 57-64. http://www.ecology.uni-corvinus.hu ● ISSN 1589 1623  2008, Penkala Bt., Budapest, Hungary natural and anthropogenic factors influencing the geochemistry...

  16. The influence of additives in the stoichiometry of hybrid lead halide perovskites

    Directory of Open Access Journals (Sweden)

    Ignasi Burgués-Ceballos

    2017-11-01

    Full Text Available We investigate the employment of carefully selected solvent additives in the processing of a commercial perovskite precursor ink and analyze their impact on the performance of organometal trihalide perovskite (CH3NH3PbI3−xClx photovoltaic devices. We provide evidence that the use of benzaldehyde can be used as an effective method to preserve the stoichiometry of the perovskite precursors in solution. Benzaldehyde based additive engineering shows to improve perovskite solid state film morphology and device performance of CH3NH3PbI3−xClx based solar cells.

  17. Report on a NASA astrobiology institute-funded workshop without walls: stellar stoichiometry.

    Science.gov (United States)

    Desch, Steven J; Young, Patrick A; Anbar, Ariel D; Hinkel, Natalie; Pagano, Michael; Truitt, Amanda; Turnbull, Margaret

    2014-04-01

    We report on the NASA Astrobiology Institute-funded Workshop Without Walls entitled "Stellar Stoichiometry," hosted by the "Follow the Elements" team at Arizona State University in April 2013. We describe several innovative practices we adopted that made effective use of the Workshop Without Walls videoconferencing format, including use of information technologies, assignment of scientific tasks before the workshop, and placement of graduate students in positions of authority. A companion article will describe the scientific results arising from the workshop. Our intention here is to suggest best practices for future Workshops Without Walls.

  18. Determination of Stoichiometry of Solutes in Molten Salt Solvents by Correlations of Relative Raman Band Intensities

    DEFF Research Database (Denmark)

    Boghosian, Soghomon; Berg, Rolf W.

    1999-01-01

    ); (2) Nb2O5 + nS(2)O(7)(2-) (1) --> Y2n- (1); (3) MoO3 + nS(2)O(7)(2-) (1) --> Z(2n)- (1). It is shown that the solute complex species formed in the studied reactions have, respectively, the following stoichiometries: (1) n = 2, (VO)(2)O(SO4)(4)(4-); (2) n = 3, NbO(SO4)(3)(3-); (3) n = 1, MoO(SO4)(2)(2-)....

  19. Impact of local order and stoichiometry on the ultrafast magnetization dynamics of Heusler compounds

    International Nuclear Information System (INIS)

    Steil, Daniel; Schmitt, Oliver; Fetzer, Roman; Aeschlimann, Martin; Cinchetti, Mirko; Kubota, Takahide; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Rodan, Steven; Blum, Christian G F; Wurmehl, Sabine; Balke, Benjamin

    2015-01-01

    Nowadays, a wealth of information on ultrafast magnetization dynamics of thin ferromagnetic films exists in the literature. Information is, however, scarce on bulk single crystals, which may be especially important for the case of multi-sublattice systems. In Heusler compounds, representing prominent examples for such multi-sublattice systems, off-stoichiometry and degree of order can significantly change the magnetic properties of thin films, while bulk single crystals may be generally produced with a much more well-defined stoichiometry and a higher degree of ordering. A careful characterization of the local structure of thin films versus bulk single crystals combined with ultrafast demagnetization studies can, thus, help to understand the impact of stoichiometry and order on ultrafast spin dynamics.Here, we present a comparative study of the structural ordering and magnetization dynamics for thin films and bulk single crystals of the family of Heusler alloys with composition Co 2 Fe 1 − x Mn x Si. The local ordering is studied by 59 Co nuclear magnetic resonance (NMR) spectroscopy, while the time-resolved magneto-optical Kerr effect gives access to the ultrafast magnetization dynamics. In the NMR studies we find significant differences between bulk single crystals and thin films, both regarding local ordering and stoichiometry. The ultrafast magnetization dynamics, on the other hand, turns out to be mostly unaffected by the observed structural differences, especially on the time scale of some hundreds of femtoseconds. These results confirm hole-mediated spin-flip processes as the main mechanism for ultrafast demagnetization and the robustness of this demagnetization channel against defect states in the minority band gap as well as against the energetic position of the band gap with respect to the Fermi energy. The very small differences observed in the magnetization dynamics on the picosecond time-scale, on the other hand, can be explained by considering the

  20. Stoichiometry and superconductive properties of YBaCuO films deposited by spray pyrolysis

    International Nuclear Information System (INIS)

    Conde-Gallardo, A.; Falcony, C.; Ortiz, A.

    1994-01-01

    The dependence of the stoichiometry and the superconducting characteristics of YBaCuO films deposited by spray pyrolysis on the spraying solution composition and the deposition conditions is reported. It has been found that a proper optimization of the starting materials concentration in the spraying solution results in superconducting films with zero resistance temperature of 91 K and a transition to superconducting state within a 3 K range. X-ray diffraction and resistance vs temperature measurements have been used to monitor the crystal composition and the conductive characteristics of the films as a function of the spraying solution composition and the deposition parameters

  1. The influence of additives in the stoichiometry of hybrid lead halide perovskites

    Science.gov (United States)

    Burgués-Ceballos, Ignasi; Savva, Achilleas; Georgiou, Efthymios; Kapnisis, Konstantinos; Papagiorgis, Paris; Mousikou, Androniki; Itskos, Grigorios; Othonos, Andreas; Choulis, Stelios A.

    2017-11-01

    We investigate the employment of carefully selected solvent additives in the processing of a commercial perovskite precursor ink and analyze their impact on the performance of organometal trihalide perovskite (CH3NH3PbI3-xClx) photovoltaic devices. We provide evidence that the use of benzaldehyde can be used as an effective method to preserve the stoichiometry of the perovskite precursors in solution. Benzaldehyde based additive engineering shows to improve perovskite solid state film morphology and device performance of CH3NH3PbI3-xClx based solar cells.

  2. The effects of air stoichiometry and air excess ratio on the transient response of a PEMFC under load change conditions

    International Nuclear Information System (INIS)

    Kim, Bosung; Cha, Dowon; Kim, Yongchan

    2015-01-01

    Highlights: • Effects of controlling parameters on the transient response of a PEMFC are studied. • The transient response is measured by varying air stoichiometry and air excess ratio. • Voltage drop, undershoot, and voltage fluctuation are analyzed under the load change. • Optimal air stoichiometry and air excess ratio are suggested for stable operation. - Abstract: The transient response of a proton exchange membrane fuel cell (PEMFC) is an important issue for transportation applications. The objective of this study is to investigate the effects of operating and controlling parameters on the transient response of a PEMFC for achieving more stable cell performance under load change conditions. The transient response of a PEMFC was measured and analyzed by varying air stoichiometry, air humidity, and air excess ratio (AER). The optimal air stoichiometry and AER were determined to minimize the voltage drop, undershoot, and voltage fluctuation under the load change, while maintaining high cell performance. Based on the present data, the optimal air stoichiometry was determined to be between 2.0 and 2.5, and the optimal AER was suggested to be between 1.65 and 2.0

  3. Application of a sensitive collection heuristic for very large protein families: Evolutionary relationship between adipose triglyceride lipase (ATGL and classic mammalian lipases

    Directory of Open Access Journals (Sweden)

    Berezovsky Igor

    2006-03-01

    Full Text Available Abstract Background Manually finding subtle yet statistically significant links to distantly related homologues becomes practically impossible for very populated protein families due to the sheer number of similarity searches to be invoked and analyzed. The unclear evolutionary relationship between classical mammalian lipases and the recently discovered human adipose triglyceride lipase (ATGL; a patatin family member is an exemplary case for such a problem. Results We describe an unsupervised, sensitive sequence segment collection heuristic suitable for assembling very large protein families. It is based on fan-like expanding, iterative database searches. To prevent inclusion of unrelated hits, additional criteria are introduced: minimal alignment length and overlap with starting sequence segments, finding starting sequences in reciprocal searches, automated filtering for compositional bias and repetitive patterns. This heuristic was implemented as FAMILYSEARCHER in the ANNIE sequence analysis environment and applied to search for protein links between the classical lipase family and the patatin-like group. Conclusion The FAMILYSEARCHER is an efficient tool for tracing distant evolutionary relationships involving large protein families. Although classical lipases and ATGL have no obvious sequence similarity and differ with regard to fold and catalytic mechanism, homology links detected with FAMILYSEARCHER show that they are evolutionarily related. The conserved sequence parts can be narrowed down to an ancestral core module consisting of three β-strands, one α-helix and a turn containing the typical nucleophilic serine. Moreover, this ancestral module also appears in numerous enzymes with various substrate specificities, but that critically rely on nucleophilic attack mechanisms.

  4. Protein kinase D stabilizes aldosterone-induced ERK1/2 MAP kinase activation in M1 renal cortical collecting duct cells to promote cell proliferation.

    LENUS (Irish Health Repository)

    McEneaney, Victoria

    2010-01-01

    Aldosterone elicits transcriptional responses in target tissues and also rapidly stimulates the activation of protein kinase signalling cascades independently of de novo protein synthesis. Here we investigated aldosterone-induced cell proliferation and extra-cellular regulated kinase 1 and 2 (ERK1\\/2) mitogen activated protein (MAP) kinase signalling in the M1 cortical collecting duct cell line (M1-CCD). Aldosterone promoted the proliferative growth of M1-CCD cells, an effect that was protein kinase D1 (PKD1), PKCdelta and ERK1\\/2-dependent. Aldosterone induced the rapid activation of ERK1\\/2 with peaks of activation at 2 and 10 to 30 min after hormone treatment followed by sustained activation lasting beyond 120 min. M1-CCD cells suppressed in PKD1 expression exhibited only the early, transient peaks in ERK1\\/2 activation without the sustained phase. Aldosterone stimulated the physical association of PKD1 with ERK1\\/2 within 2 min of treatment. The mineralocorticoid receptor (MR) antagonist RU28318 inhibited the early and late phases of aldosterone-induced ERK1\\/2 activation, and also aldosterone-induced proliferative cell growth. Aldosterone induced the sub-cellular redistribution of ERK1\\/2 to the nuclei at 2 min and to cytoplasmic sites, proximal to the nuclei after 30 min. This sub-cellular distribution of ERK1\\/2 was inhibited in cells suppressed in the expression of PKD1.

  5. X-CHIP: an integrated platform for high-throughput protein crystallization and on-the-chip X-ray diffraction data collection

    International Nuclear Information System (INIS)

    Kisselman, Gera; Qiu, Wei; Romanov, Vladimir; Thompson, Christine M.; Lam, Robert; Battaile, Kevin P.; Pai, Emil F.; Chirgadze, Nickolay Y.

    2011-01-01

    The X-CHIP (X-ray Crystallography High-throughput Integrated Platform) is a novel microchip that has been developed to combine multiple steps of the crystallographic pipeline from crystallization to diffraction data collection on a single device to streamline the entire process. The X-CHIP (X-ray Crystallization High-throughput Integrated Platform) is a novel microchip that has been developed to combine multiple steps of the crystallographic pipeline from crystallization to diffraction data collection on a single device to streamline the entire process. The system has been designed for crystallization condition screening, visual crystal inspection, initial X-ray screening and data collection in a high-throughput fashion. X-ray diffraction data acquisition can be performed directly on-the-chip at room temperature using an in situ approach. The capabilities of the chip eliminate the necessity for manual crystal handling and cryoprotection of crystal samples, while allowing data collection from multiple crystals in the same drop. This technology would be especially beneficial for projects with large volumes of data, such as protein-complex studies and fragment-based screening. The platform employs hydrophilic and hydrophobic concentric ring surfaces on a miniature plate transparent to visible light and X-rays to create a well defined and stable microbatch crystallization environment. The results of crystallization and data-collection experiments demonstrate that high-quality well diffracting crystals can be grown and high-resolution diffraction data sets can be collected using this technology. Furthermore, the quality of a single-wavelength anomalous dispersion data set collected with the X-CHIP at room temperature was sufficient to generate interpretable electron-density maps. This technology is highly resource-efficient owing to the use of nanolitre-scale drop volumes. It does not require any modification for most in-house and synchrotron beamline systems and offers

  6. X-CHIP: an integrated platform for high-throughput protein crystallization and on-the-chip X-ray diffraction data collection

    Energy Technology Data Exchange (ETDEWEB)

    Kisselman, Gera; Qiu, Wei; Romanov, Vladimir; Thompson, Christine M.; Lam, Robert [Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Toronto, Ontario M5G 2C4 (Canada); Battaile, Kevin P. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Pai, Emil F.; Chirgadze, Nickolay Y., E-mail: nchirgad@uhnresearch.ca [Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Toronto, Ontario M5G 2C4 (Canada); University of Toronto, Toronto, Ontario M5S 1A8 (Canada)

    2011-06-01

    The X-CHIP (X-ray Crystallography High-throughput Integrated Platform) is a novel microchip that has been developed to combine multiple steps of the crystallographic pipeline from crystallization to diffraction data collection on a single device to streamline the entire process. The X-CHIP (X-ray Crystallization High-throughput Integrated Platform) is a novel microchip that has been developed to combine multiple steps of the crystallographic pipeline from crystallization to diffraction data collection on a single device to streamline the entire process. The system has been designed for crystallization condition screening, visual crystal inspection, initial X-ray screening and data collection in a high-throughput fashion. X-ray diffraction data acquisition can be performed directly on-the-chip at room temperature using an in situ approach. The capabilities of the chip eliminate the necessity for manual crystal handling and cryoprotection of crystal samples, while allowing data collection from multiple crystals in the same drop. This technology would be especially beneficial for projects with large volumes of data, such as protein-complex studies and fragment-based screening. The platform employs hydrophilic and hydrophobic concentric ring surfaces on a miniature plate transparent to visible light and X-rays to create a well defined and stable microbatch crystallization environment. The results of crystallization and data-collection experiments demonstrate that high-quality well diffracting crystals can be grown and high-resolution diffraction data sets can be collected using this technology. Furthermore, the quality of a single-wavelength anomalous dispersion data set collected with the X-CHIP at room temperature was sufficient to generate interpretable electron-density maps. This technology is highly resource-efficient owing to the use of nanolitre-scale drop volumes. It does not require any modification for most in-house and synchrotron beamline systems and offers

  7. The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

    International Nuclear Information System (INIS)

    Belay, K.B.; Ridgway, M.C.; Llewellyn, D.J.

    1996-01-01

    The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs

  8. The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Belay, K.B.; Ridgway, M.C.; Llewellyn, D.J. [Australian National Univ., Canberra, ACT (Australia). Dept. of Physics

    1996-12-31

    The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs.

  9. The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Belay, K B; Ridgway, M C; Llewellyn, D J [Australian National Univ., Canberra, ACT (Australia). Dept. of Physics

    1997-12-31

    The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs.

  10. Quantifying Kinase-Specific Phosphorylation Stoichiometry Using Stable Isotope Labeling In a Reverse In-Gel Kinase Assay

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiang; Cox, Jonathan T.; Huang, Weiliang; Kane, Maureen; Tang, Keqi; Bieberich, Charles J.

    2016-12-06

    Reversible protein phosphorylation regulates essentially all cellular activities. Aberrant protein phosphorylation is an etiological factor in a wide array of diseases, including cancer1, diabetes2, and Alzheimer’s3. Given the broad impact of protein phosphorylation on cellular biology and organismal health, understanding how protein phosphorylation is regulated and the consequences of gain and loss of phosphoryl moieties from proteins is of primary importance. Advances in instrumentation, particularly in mass spectrometry, coupled with high throughput approaches have recently yielded large datasets cataloging tens of thousands of protein phosphorylation sites in multiple organisms4-6. While these studies are seminal in term of data collection, our understanding of protein phosphorylation regulation remains largely one-dimensional.

  11. FeII induced mineralogical transformations of ferric oxyhydroxides into magnetite of variable stoichiometry and morphology

    International Nuclear Information System (INIS)

    Usman, M.; Abdelmoula, M.; Hanna, K.

    2012-01-01

    The Mössbauer spectroscopy was used to monitor the mineralogical transformations of ferrihydrite (F), lepidocrocite (L) and goethite (G) into magnetite as a function of aging time. Ferric oxyhydroxides were reacted with soluble Fe II and OH – in stoichiometric amounts to form magnetite at an initial pH of ∼9.7. Observed transformation extent into magnetite followed the order: F>L>G with almost 30% of untransformed G after 1 month. The departure from stoichiometry, δ, of magnetite (Fe 3−δ O 4 ) generated from F (δ∼0.04) and L (δ∼0.05) was relatively low as compared to that in magnetite from G (δ∼0.08). The analysis by transmission electron microscopy and BET revealed that generated magnetite was also different in terms of morphology, particle size and surface area depending on the nature of initial ferric oxyhydroxide. This method of preparation is a possible way to form nano-sized magnetite. - Graphical abstract: Mössbauer spectrum of the early stage of magnetite formation formed from the interaction of adsorbed Fe II species with goethite. Highlights: ► Ferric oxides were reacted with hydroxylated Fe II to form magnetite. ► Magnetite formation was quantified as a function of aging time. ► Complete transformation of ferrihydrite and lepidocrocite was achieved. ► Almost 70% of initial goethite was transformed. ► Resulting magnetites have differences in stoichiometry and morphological properties.

  12. Synthesis, structure, morphology and stoichiometry characterization of cluster and nano magnetite

    Energy Technology Data Exchange (ETDEWEB)

    Singh, L. Herojit; Pati, S.S. [Institute of Physics, University of Brasilia, 70919-970, Brasilia, DF (Brazil); Guimarães, Edi M. [Institute of Geoscience, University of Brasilia, 70910-900, Brasilia, DF (Brazil); Rodrigues, P.A.M.; Oliveira, Aderbal C. [Institute of Physics, University of Brasilia, 70919-970, Brasilia, DF (Brazil); Garg, V.K., E-mail: vijgarg@gmail.com [Institute of Physics, University of Brasilia, 70919-970, Brasilia, DF (Brazil)

    2016-08-01

    We have studied the stoichiometry of magnetite nanoparticles using three spectroscopic techniques: Mössbauer, photoacoustic and ferromagnetic resonance (FMR). By varying the weight ratio of the Fe precursor to the reducing agent (sodium acetate) and a post-synthesis annealing, we were able to synthesize samples with different amounts of Fe vacancies, from stoichiometric Fe{sub 3}O{sub 4} to γ-Fe{sub 2}O{sub 3}. By synthesizing magnetite in the presence of zeolite we obtained nanoparticles within the 3–10 nm diameter range. The spectroscopic results show that there is a correlation between the amount of Fe vacancies and (i) the optical absorption and (ii) the g-values from the Electron paramagnetic resonance EPR spectra of the nanoparticles. - Highlights: • Magnetite nanoparticles and cluster synthesized. • Photoacoustic spectroscopy is effective in determining the stoichiometry. • Particles with 9 nm size has 0 < δ < 0.14. • Less than 9 nm gives 0.14 < δ < 0.3 and size <3 nm have δ = 0.33 (i.e. γ-Fe{sub 2}O{sub 3}).

  13. Evidence of different stoichiometries for the limiting carbonate complexes of lanthanides(3)

    International Nuclear Information System (INIS)

    Philippini, V.

    2007-12-01

    Two stoichiometries have been proposed by different laboratories to interpret measurements on the limiting carbonate complexes of An 3+ and Ln 3+ cations. The study of the solubility of double carbonates (AlkLn(CO 3 ) 2 ,xH 2 O) in concentrated carbonate solutions at room temperature and high ionic strengths has shown that on the one hand the lightest lanthanides (La and Nd) form Ln(CO 3 ) 4 5- whereas the heaviest (Eu and Dy) form Ln(CO 3 ) 3 3- in the studied chemical conditions, and on the other hand, that the kinetics of precipitation of double carbonates depends on the alkali metal and the lanthanide ions. The existence of two stoichiometries for the limiting carbonate complexes was confirmed by capillary electrophoresis hyphenated to an inductively coupled plasma mass spectrometer (CE-ICP-MS), used to extend the study to the whole series of lanthanides (except Ce, Pm and Yb). Two behaviours have been put forward comparing the electrophoretic mobilities: La to Tb form Ln(CO 3 ) 4 5- while Dy to Lu form Ln(CO 3 ) 3 3- . Measurements by time resolved laser fluorescence spectroscopy (TRLFS) on Eu(III) indicate small variations of the geometry of Eu(CO 3 ) 3 3- complex, specially with Cs + . Although analogies are currently used among the 4f-block trivalent elements, different aqueous speciations are evidenced in concentrated carbonate solutions across the lanthanide series. (author)

  14. Effect of microbial enzyme allocation strategies on stoichiometry of soil organic matter (SOM) decomposition

    Science.gov (United States)

    Wutzler, Thomas

    2014-05-01

    We explored different strategies of soil microbial community to invest resources into extracellular enzymes by conceptual modelling. Similar to the EEZY model by Moorhead et al. (2012), microbial community can invest into two separate pools of enzymes that depolymerize two different SOM pools. We show that with assuming that a fixed fraction of substrate uptake is allocated to enzymes, the microbial dynamics decouples from decomposition dynamics. We propose an alternative formulation where investment into enzymes is proportional to microbial biomass. Next, we show that the strategy of optimizing stoichiometry of decomposition flux according to microbial biomass stoichiometry yield less microbial growth than the strategy of optimizing revenue of the currently limiting element. However, both strategies result in better usage of the resources, i.e. less C overflow or N mineralization, than the strategy of equal allocation to both enzymes. Further, we discuss effects of those strategies on decomposition of SOM and priming at different time scales and discuss several abstractions from the detailed model dynamics for usage in larger scale models.

  15. Stoichiometry control of SrVO{sub 3} thin films grown by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Scheiderer, Philipp; Schmitt, Matthias; Sing, Michael; Claessen, Ralph [Universitaet Wuerzburg, Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), 97074 Wuerzburg (Germany)

    2016-07-01

    Oxide heterostructures exhibit fascinating properties, e.g., the coexistence of superconductivity and ferromagnetism at the interface of LaAlO{sub 3}/SrTiO{sub 3}, but the extraordinary electronic properties of transition metal oxides caused by electron correlation yet wait to be fully harnessed. One suitable candidate for future device applications is the correlated metal SrVO{sub 3}, which can be prepared by pulsed laser deposition (PLD) on commonly used substrates such as SrTiO{sub 3}. Sample fabrication by PLD offers a wide variety of possibilities to manipulate the structural and electronic properties of the grown films in a controlled way. Here we report on the manipulation of the cation and oxygen stoichiometry of SrVO{sub 3} thin films by tuning the laser flux density of the PLD-ablation process and the oxygen background pressure during growth, respectively. In situ photoemission, x-ray diffraction, and temperature dependent resistivity measurements enable us to monitor the structural and electronic changes: Cation off-stoichiometry causes a strong increase of the out-of-plane lattice constant as well as a lower residual resistivity ratio, while excess oxygen is found to induce a shift to higher vanadium valences. After exposure to air a similar shift is detected, indicating an overoxidation of the SrVO{sub 3} film.

  16. Non-stoichiometry defects and radiation hardness of lead tungstate crystals PbWO sub 4

    CERN Document Server

    Devitsin, E G; Potashov, S Yu; Terkulov, A R; Nefedov, V A; Polyansky, E V; Zadneprovski, B I; Kjellberg, P; Korbel, V

    2002-01-01

    It has been stated many times that the formation of radiation infringements in PbWO sub 4 is to a big extent stipulated by the non-stoichiometry defects of the crystals, arising in the process of their growth and annealing. To refine the idea of characteristics of the non-stoichiometry defects and their effect on the radiation hardness of PbWO sub 4 , the current study is aimed at the melt composition infringements during its evaporation and at optical transmission of crystals obtained in these conditions after their irradiation ( sup 1 sup 3 sup 7 Cs source). In the optical transmission measurements along with traditional techniques a method 'in situ' was used, which provided the measurements in fixed points of the spectrum (380, 470 and 535 nm) directly in the process of the irradiation. X-ray phase and fluorescence analysis of condensation products of vapours over PbWO sub 4 melt has found PbWO sub 4 phase in their content as well as compounds rich in lead PbO, Pb sub 2 WO sub 5 with overall ratio Pb/W (3....

  17. Non-stoichiometry Defects and Radiation Hardness of Lead Tungstate Crystals PbWO4

    CERN Document Server

    Devitsin, E G; Kozlov, V A; Nefedov, L; Polyansky, E V; Potashov, S Yu; Terkulov, A R; Zadneprovski, B I

    2001-01-01

    It has been stated many times that the formation of radiation infringements in PbWO4 is to big extent stipulated by non-stoichiometry defects of the crystals, arising in the process of their growth and annealing. To refine the idea of characteristics of non-stoichiometry defects and their effect on the radiation hardness of PbWO4 the current study is aimed at the melt composition infringements during its evaporation and at optical transmission of crystals obtained in these conditions after their irradiation (137Cs source). In the optical transmission measurements along with traditional techniques a method "in situ" was used, which provided the measurements in fixed points of the spectrum (380, 470 and 535 nm) directly in the process of the irradiation. X-ray phase and fluorescence analysis of condensation products of vapours over PbWO4 melt has found PbWO4 phase in their content as well as compounds rich in lead, PbO, Pb2WO5, with overall ratio Pb/W = 3.2. Correspondingly the lack of lead and variations in th...

  18. Investment in boney defensive traits alters organismal stoichiometry and excretion in fish.

    Science.gov (United States)

    El-Sabaawi, Rana W; Warbanski, Misha L; Rudman, Seth M; Hovel, Rachel; Matthews, Blake

    2016-08-01

    Understanding how trait diversification alters ecosystem processes is an important goal for ecological and evolutionary studies. Ecological stoichiometry provides a framework for predicting how traits affect ecosystem function. The growth rate hypothesis of ecological stoichiometry links growth and phosphorus (P) body composition in taxa where nucleic acids are a significant pool of body P. In vertebrates, however, most of the P is bound within bone, and organisms with boney structures can vary in terms of the relative contributions of bones to body composition. Threespine stickleback populations have substantial variation in boney armour plating. Shaped by natural selection, this variation provides a model system to study the links between evolution of bone content, elemental body composition, and P excretion. We measure carbon:nitrogen:P body composition from stickleback populations that vary in armour phenotype. We develop a mechanistic mass-balance model to explore factors affecting P excretion, and measure P excretion from two populations with contrasting armour phenotypes. Completely armoured morphs have higher body %P but excrete more P per unit body mass than other morphs. The model suggests that such differences are driven by phenotypic differences in P intake as well as body %P composition. Our results show that while investment in boney traits alters the elemental composition of vertebrate bodies, excretion rates depend on how acquisition and assimilation traits covary with boney trait investment. These results also provide a stoichiometric hypothesis to explain the repeated loss of boney armour in threespine sticklebacks upon colonizing freshwater ecosystems.

  19. Molecular simulation study to examine the possibility of detecting collective motion in protein by inelastic neutron scattering

    International Nuclear Information System (INIS)

    Yasumasa, Joti; Nobuhiro, Go; Akio, Kitao; Nobuhiro, Go

    2003-01-01

    Inelastic and quasielastic neutron scattering gives the information on the dynamics of biological macromolecules. The combination of computer simulation with neutron scattering experiments allows us to characterize a wide range of dynamical phenomena in condensed phase bio-molecular systems. In this work, the dynamic structure factors in (Q,ω)-space were calculated by using the results of bio-molecular simulations. From the simulated inelastic neutron scattering spectra, we discuss the (Q,ω)-range and the resolution of a detector needed to observe function-related protein dynamics. (authors)

  20. Variability within a pea core collection of LEAM and HSP22, two mitochondrial seed proteins involved in stress tolerance.

    Science.gov (United States)

    Avelange-Macherel, Marie-Hélène; Payet, Nicole; Lalanne, David; Neveu, Martine; Tolleter, Dimitri; Burstin, Judith; Macherel, David

    2015-07-01

    LEAM, a late embryogenesis abundant protein, and HSP22, a small heat shock protein, were shown to accumulate in the mitochondria during pea (Pisum sativum L.) seed development, where they are expected to contribute to desiccation tolerance. Here, their expression was examined in seeds of 89 pea genotypes by Western blot analysis. All genotypes expressed LEAM and HSP22 in similar amounts. In contrast with HSP22, LEAM displayed different isoforms according to apparent molecular mass. Each of the 89 genotypes harboured a single LEAM isoform. Genomic and RT-PCR analysis revealed four LEAM genes differing by a small variable indel in the coding region. These variations were consistent with the apparent molecular mass of each isoform. Indels, which occurred in repeated domains, did not alter the main properties of LEAM. Structural modelling indicated that the class A α-helix structure, which allows interactions with the mitochondrial inner membrane in the dry state, was preserved in all isoforms, suggesting functionality is maintained. The overall results point out the essential character of LEAM and HSP22 in pea seeds. LEAM variability is discussed in terms of pea breeding history as well as LEA gene evolution mechanisms. © 2014 John Wiley & Sons Ltd.

  1. The Impact of Variable Phytoplankton Stoichiometry on Projections of Primary Production, Food Quality, and Carbon Uptake in the Global Ocean

    Science.gov (United States)

    Kwiatkowski, Lester; Aumont, Olivier; Bopp, Laurent; Ciais, Philippe

    2018-04-01

    Ocean biogeochemical models are integral components of Earth system models used to project the evolution of the ocean carbon sink, as well as potential changes in the physical and chemical environment of marine ecosystems. In such models the stoichiometry of phytoplankton C:N:P is typically fixed at the Redfield ratio. The observed stoichiometry of phytoplankton, however, has been shown to considerably vary from Redfield values due to plasticity in the expression of phytoplankton cell structures with different elemental compositions. The intrinsic structure of fixed C:N:P models therefore has the potential to bias projections of the marine response to climate change. We assess the importance of variable stoichiometry on 21st century projections of net primary production, food quality, and ocean carbon uptake using the recently developed Pelagic Interactions Scheme for Carbon and Ecosystem Studies Quota (PISCES-QUOTA) ocean biogeochemistry model. The model simulates variable phytoplankton C:N:P stoichiometry and was run under historical and business-as-usual scenario forcing from 1850 to 2100. PISCES-QUOTA projects similar 21st century global net primary production decline (7.7%) to current generation fixed stoichiometry models. Global phytoplankton N and P content or food quality is projected to decline by 1.2% and 6.4% over the 21st century, respectively. The largest reductions in food quality are in the oligotrophic subtropical gyres and Arctic Ocean where declines by the end of the century can exceed 20%. Using the change in the carbon export efficiency in PISCES-QUOTA, we estimate that fixed stoichiometry models may be underestimating 21st century cumulative ocean carbon uptake by 0.5-3.5% (2.0-15.1 PgC).

  2. Soil carbon, nitrogen, and phosphorus stoichiometry of three dominant plant communities distributed along a small-scale elevation gradient in the East Dongting Lake

    Science.gov (United States)

    Hu, Cong; Li, Feng; Xie, Yong-hong; Deng, Zheng-miao; Chen, Xin-sheng

    2018-02-01

    Soil carbon (C), nitrogen (N), and phosphorus (P) stoichiometry greatly affects plant community succession and structure. However, few studies have examined the soil stoichiometric changes in different vegetation communities of freshwater wetland ecosystems along an elevation gradient distribution. In the present study, soil nutrient concentrations (C, N, and P), soil stoichiometry (C:N, C:P, and N:P ratios), and other soil physicochemical characteristics were measured and analyzed in 62 soil samples collected from three dominant plant communities (Carex brevicuspis, Artemisia selengensis, and Miscanthus sacchariflorus) in the East Dongting Lake wetlands. The concentration ranges of soil organic carbon (SOC), total soil nitrogen (TN), and total soil phosphorus (TP) were 9.42-45.97 g/kg, 1.09-5.50 g/kg, and 0.60-1.70 g/kg, respectively. SOC and TN concentrations were the highest in soil from the C. brevicuspis community (27.48 g/kg and 2.78 g/kg, respectively) and the lowest in soil from the A. selengensis community (17.97 g/kg and 1.71 g/kg, respectively). However, the highest and lowest TP concentrations were detected in soil from the A. selengensis (1.03 g/kg) and M. sacchariflorus (0.89 g/kg) communities, respectively, and the C:N ratios were the highest and lowest in soil from the M. sacchariflorus (12.72) and A. selengensis (12.01) communities, respectively. C:P and N:P ratios were the highest in soil from the C. brevicuspis community (72.77 and 6.46, respectively) and the lowest in soil from the A. selengensis community (45.52 and 3.76, respectively). Correlation analyses confirmed that SOC concentrations were positively correlated with TN and TP, and C:N and N:P ratios were positively correlated with C:P. These data indicated that soil C, N, and P stoichiometry differed significantly among different plant communities and that these differences might be accounted for by variations in the hydrological conditions of the three communities.

  3. Bridging Food Webs, Ecosystem Metabolism, and Biogeochemistry Using Ecological Stoichiometry Theory

    Directory of Open Access Journals (Sweden)

    Nina Welti

    2017-07-01

    Full Text Available Although aquatic ecologists and biogeochemists are well aware of the crucial importance of ecosystem functions, i.e., how biota drive biogeochemical processes and vice-versa, linking these fields in conceptual models is still uncommon. Attempts to explain the variability in elemental cycling consequently miss an important biological component and thereby impede a comprehensive understanding of the underlying processes governing energy and matter flow and transformation. The fate of multiple chemical elements in ecosystems is strongly linked by biotic demand and uptake; thus, considering elemental stoichiometry is important for both biogeochemical and ecological research. Nonetheless, assessments of ecological stoichiometry (ES often focus on the elemental content of biota rather than taking a more holistic view by examining both elemental pools and fluxes (e.g., organismal stoichiometry and ecosystem process rates. ES theory holds the promise to be a unifying concept to link across hierarchical scales of patterns and processes in ecology, but this has not been fully achieved. Therefore, we propose connecting the expertise of aquatic ecologists and biogeochemists with ES theory as a common currency to connect food webs, ecosystem metabolism, and biogeochemistry, as they are inherently concatenated by the transfer of carbon, nitrogen, and phosphorous through biotic and abiotic nutrient transformation and fluxes. Several new studies exist that demonstrate the connections between food web ecology, biogeochemistry, and ecosystem metabolism. In addition to a general introduction into the topic, this paper presents examples of how these fields can be combined with a focus on ES. In this review, a series of concepts have guided the discussion: (1 changing biogeochemistry affects trophic interactions and ecosystem processes by altering the elemental ratios of key species and assemblages; (2 changing trophic dynamics influences the transformation and

  4. Dry Etching of Copper Phthalocyanine Thin Films: Effects on Morphology and Surface Stoichiometry

    Directory of Open Access Journals (Sweden)

    Michael J. Brett

    2012-08-01

    Full Text Available We investigate the evolution of copper phthalocyanine thin films as they are etched with argon plasma. Significant morphological changes occur as a result of the ion bombardment; a planar surface quickly becomes an array of nanopillars which are less than 20 nm in diameter. The changes in morphology are independent of plasma power, which controls the etch rate only. Analysis by X-ray photoelectron spectroscopy shows that surface concentrations of copper and oxygen increase with etch time, while carbon and nitrogen are depleted. Despite these changes in surface stoichiometry, we observe no effect on the work function. The absorbance and X-ray diffraction spectra show no changes other than the peaks diminishing with etch time. These findings have important implications for organic photovoltaic devices which seek nanopillar thin films of metal phthalocyanine materials as an optimal structure.

  5. Prediction of seebeck coefficient for compounds without restriction to fixed stoichiometry: A machine learning approach.

    Science.gov (United States)

    Furmanchuk, Al'ona; Saal, James E; Doak, Jeff W; Olson, Gregory B; Choudhary, Alok; Agrawal, Ankit

    2018-02-05

    The regression model-based tool is developed for predicting the Seebeck coefficient of crystalline materials in the temperature range from 300 K to 1000 K. The tool accounts for the single crystal versus polycrystalline nature of the compound, the production method, and properties of the constituent elements in the chemical formula. We introduce new descriptive features of crystalline materials relevant for the prediction the Seebeck coefficient. To address off-stoichiometry in materials, the predictive tool is trained on a mix of stoichiometric and nonstoichiometric materials. The tool is implemented into a web application (http://info.eecs.northwestern.edu/SeebeckCoefficientPredictor) to assist field scientists in the discovery of novel thermoelectric materials. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  6. Stoichiometry in Context: Inquiry-Guided Problems of Chemistry for Encouraging Critical Thinking in Engineering Students

    Directory of Open Access Journals (Sweden)

    Gabriel Pinto

    2013-01-01

    Full Text Available This paper focuses on examples of educational tools concerning the learning of chemistry for engineering students through different daily life cases. These tools were developed during the past few years for enhancing the active role of students. They refer to cases about mineral water, medicaments, dentifrices and informative panels about solar power, where an adequate quantitative treatment through stoichiometry calculations allows the interpretation of data and values announced by manufacturers. These cases were developed in the context of an inquiry-guided instruction model. By bringing tangible chemistry examples into the classroom we provide an opportunity for engineering students to apply this science to familiar products in hopes that they will appreciate chemistry more, will be motivated to study concepts in greater detail, and will connect the relevance of chemistry to everyday life.

  7. A defect model for UO2+x based on electrical conductivity and deviation from stoichiometry measurements

    Science.gov (United States)

    Garcia, Philippe; Pizzi, Elisabetta; Dorado, Boris; Andersson, David; Crocombette, Jean-Paul; Martial, Chantal; Baldinozzi, Guido; Siméone, David; Maillard, Serge; Martin, Guillaume

    2017-10-01

    Electrical conductivity of UO2+x shows a strong dependence upon oxygen partial pressure and temperature which may be interpreted in terms of prevailing point defects. A simulation of this property along with deviation from stoichiometry is carried out based on a model that takes into account the presence of impurities, oxygen interstitials, oxygen vacancies, holes, electrons and clusters of oxygen atoms. The equilibrium constants for each defect reaction are determined to reproduce the experimental data. An estimate of defect concentrations and their dependence upon oxygen partial pressure can then be determined. The simulations carried out for 8 different temperatures (973-1673 K) over a wide range of oxygen partial pressures are discussed and resulting defect equilibrium constants are plotted in an Arrhenius diagram. This provides an estimate of defect formation energies which may further be compared to other experimental data or ab-initio and empirical potential calculations.

  8. Ion plasma deposition of oxide films with graded-stoichiometry composition: Experiment and simulation

    Science.gov (United States)

    Volpyas, V. A.; Tumarkin, A. V.; Mikhailov, A. K.; Kozyrev, A. B.; Platonov, R. A.

    2016-07-01

    A method of ion plasma deposition is proposed for obtaining thin multicomponent films with continuously graded composition in depth of the film. The desired composition-depth profile is obtained by varying the working gas pressure during deposition in the presence of an additional adsorbing screen in the drift space between a sputtered target and substrate. Efficiency of the proposed method is confirmed by Monte Carlo simulation of the deposition of thin films of Ba x Sr1- x TiO3 (BSTO) solid solution. It is demonstrated that, during sputtering of a Ba0.3Sr0.7TiO3 target, the parameter of composition stoichiometry in the growing BSTO film varies in the interval of x = 0.3-0.65 when the gas pressure is changed within 2-60 Pa.

  9. Study of Stoichiometry and Stability of some Fe(III)-Amino Acid Complexes

    International Nuclear Information System (INIS)

    Latif, S.; Shirin, K.; Nisar, S.; Zahida, T. M.

    2005-01-01

    The complexation of ferric with three amino acids (Glycine, Glutamic acid and Aspartic acid) was studied spectrophotometrically and potentiometrically at pH 5.0 and in aqueous medium. The stoichiometry was calculated spectrophotometrically using mole ratio method and is found to be ML3 for Fe (III)-Glycine and ML2 for Fe (III)-Glutamate for Fe (III)-Glutamate and Aspartate complex. The stabilities of these complexes were calculated spectrophotometrically and potentiometrically. The experimental results of potentiometric titrations were treated by well known computer program B EST . The values were further refined till least sigma fit i.e. 0.03. The complexes were not formed under normal conditions. Each complex was studied at more than one wavelength and no kmax was obtained because Fe (III) solution and the complexes absorb in similar wavelength region. The formation constants of all these complexes are not very high shows weak complexation of Fe (III) with these amino acids. (author)

  10. Relationship between stoichiometry and ecosystem services in organic crop production systems

    DEFF Research Database (Denmark)

    Fan, Fan

    contribute to and mitigate global ES loss. Organic farming has been suggested as one possible solution to alleviate the loss of ES in agro-ecosystems due to its environmental benefits compared with conventional farming. However, only a few studies have accounted for the economic value of ES in different...... organic crop production systems and little is known about how anthropogenic activities affect the supply of ES in such organic crop production systems. Ecological stoichiometry, which is the study of the fluxes of chemical elements and the ratio between them, has been considered as a new approach....... The organic farming systems with a high soil C:N stoichiometric ratio had a potential to produce more food, sequester more carbon from the atmosphere, store more water in the soil, attract more aphid predators, and regulate more nitrogen compared with the organic farming systems with a low soil C...

  11. Experiments to investigate the effects of small changes in fuel stoichiometry on fission gas release

    Energy Technology Data Exchange (ETDEWEB)

    Copeland, P S; Smith, R C [Windscale Lab., AEA Technology, Seascale, Cumbria (United Kingdom)

    1997-08-01

    Fuel pin failure in-reactor leads to fission product and in the case of a PWR fuel debris release to the coolant. For economic reasons immediate shutdown and discharge of failed fuel needs to be avoided but this needs to be counter-balanced against the increasing dose to operators. PWR practice is to continue running wit failed rods, monitoring coolant activity, and only shutting down the reactor and discharging the fuel when circuit activity levels become unacceptable. The rate of fission product release under failed fuel conditions is of key importance and considerable effort has been directed towards establishing the dependency of release on temperature, heating rate, burn-up, and also the extent of fuel oxidation. As a precursor to a possible wider investigation of this area, a small programme was mounted during 1992/1993 to confirm whether small changes in the oxidation state of the fuel, for example those caused by minor cladding defects, would significantly effect fuel behaviour during postulated design basis faults. The objective of the programme was to determine the effects of small departures from stoichiometric fuel composition on fission gas release, and to compare the results with the current methodology for calculating releases under fault conditions. A total of eight experiments was performed. Two were intended as baseline tests to provide a reference with which to compare the effect of oxidation state influenced behaviour with that of thermal effects. It was found that small changes in stoichiometry of {sup {approx}}1 x 10{sup -6} had little or no effect on release but that changes of {sup {approx}} 1 x 10{sup -4} were observed to increase the diffusion coefficient, for {sup 85}Kr, by up to an order of magnitude and hence greatly increase the release rate. The stoichiometry of the sample used in these tests was, for convenience, adjusted using He/H{sub 2}/H{sub 2}O atmospheres. (Abstract Truncated)

  12. Simultaneous shifts in elemental stoichiometry and fatty acids of Emiliania huxleyi in response to environmental changes

    Science.gov (United States)

    Bi, Rong; Ismar, Stefanie M. H.; Sommer, Ulrich; Zhao, Meixun

    2018-02-01

    Climate-driven changes in environmental conditions have significant and complex effects on marine ecosystems. Variability in phytoplankton elements and biochemicals can be important for global ocean biogeochemistry and ecological functions, while there is currently limited understanding on how elements and biochemicals respond to the changing environments in key coccolithophore species such as Emiliania huxleyi. We investigated responses of elemental stoichiometry and fatty acids (FAs) in a strain of E. huxleyi under three temperatures (12, 18 and 24 °C), three N : P supply ratios (molar ratios 10:1, 24:1 and 63:1) and two pCO2 levels (560 and 2400 µatm). Overall, C : N : P stoichiometry showed the most pronounced response to N : P supply ratios, with high ratios of particulate organic carbon vs. particulate organic nitrogen (POC : PON) and low ratios of PON vs. particulate organic phosphorus (PON : POP) in low-N media, and high POC : POP and PON : POP in low-P media. The ratio of particulate inorganic carbon vs. POC (PIC : POC) and polyunsaturated fatty acid proportions strongly responded to temperature and pCO2, both being lower under high pCO2 and higher with warming. We observed synergistic interactions between warming and nutrient deficiency (and high pCO2) on elemental cellular contents and docosahexaenoic acid (DHA) proportion in most cases, indicating the enhanced effect of warming under nutrient deficiency (and high pCO2). Our results suggest differential sensitivity of elements and FAs to the changes in temperature, nutrient availability and pCO2 in E. huxleyi, which is to some extent unique compared to non-calcifying algal classes. Thus, simultaneous changes of elements and FAs should be considered when predicting future roles of E. huxleyi in the biotic-mediated connection between biogeochemical cycles, ecological functions and climate change.

  13. Transcriptional changes underlying elemental stoichiometry shifts in a marine heterotrophic bacterium

    Directory of Open Access Journals (Sweden)

    Leong-Keat eChan

    2012-05-01

    Full Text Available Marine bacteria drive the biogeochemical processing of oceanic dissolved organic carbon (DOC, a 750-Tg C reservoir that is a critical component of the global C cycle. Catabolism of DOC is thought to be regulated by the biomass composition of heterotrophic bacteria, as cells maintain a C:N:P ratio of ~50:10:1 during DOC processing. Yet a complicating factor in stoichiometry-based analyses is that bacteria can change the C:N:P ratio of their biomass in response to resource composition. We investigated the physiological mechanisms of resource-driven shifts in biomass stoichiometry in continuous cultures of the marine heterotrophic bacterium Ruegeria pomeroyi (a member of the Roseobacter clade under four element limitation regimes (C, N, P, and S. Microarray analysis indicated that the bacterium scavenged for alternate sources of the scarce element when cells were C-, N-, or P-limited; reworked the ratios of biomolecules when C- and P- limited; and exerted tighter control over import/export and cytoplasmic pools when N-limited. Under S-limitation, a scenario not existing naturally for surface ocean microbes, stress responses dominated transcriptional changes. Resource-driven changes in C:N ratios of up to 2.5-fold and in C:P ratios of up to 6-fold were measured in R. pomeroyi biomass. These changes were best explained if the C and P content of the cells was flexible in the face of shifting resources but N content was not, achieved through the net balance of different transcriptional strategies. The cellular-level metabolic trade-offs that govern biomass stoichiometery in R. pomeroyi may have implications for global carbon cycling. Strong homeostatic responses to N limitation by heterotrophic marine bacteria would intensify competition with autotrophs. Modification of cellular inventories in C- and P-limited heterotrophs would vary the elemental ratio of particulate organic matter sequestered in the deep ocean.

  14. Oxidation of manganese(II) with ferrate: Stoichiometry, kinetics, products and impact of organic carbon.

    Science.gov (United States)

    Goodwill, Joseph E; Mai, Xuyen; Jiang, Yanjun; Reckhow, David A; Tobiason, John E

    2016-09-01

    Manganese is a contaminant of concern for many drinking water utilities, and future regulation may be pending. An analysis of soluble manganese (Mn(II)) oxidation by ferrate (Fe(VI)) was executed at the bench-scale, in a laboratory matrix, both with and without the presence of natural organic matter (NOM) and at two different pH values, 6.2 and 7.5. In the matrix without NOM, the oxidation of Mn(II) by Fe(VI) followed a stoichiometry of 2 mol Fe(VI) to 3 mol Mn(II). The presence of NOM did not significantly affect the stoichiometry of the oxidation reaction, indicating relative selectivity of Fe(VI) for Mn(II). The size distribution of resulting particles included significant amounts of nanoparticles. Resulting manganese oxide particles were confirmed to be MnO2 via X-ray photoelectron spectroscopy. The rate of the Mn(II) oxidation reaction was fast relative to typical time scales in drinking water treatment, with an estimated second order rate constant of approximately 1 × 10(4) M(-1) s(-1) at pH 9.2 and > 9 × 10(4) M(-1) s(-1) at pH 6.2. In general, ferrate is a potential option for Mn(II) oxidation in water treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Use of stoichiometry to predict the abundance and functioning of root symbioses

    Science.gov (United States)

    Johnson, N. C.

    2012-04-01

    Plants form nutritional symbioses with fungi and bacteria and the importance of these partnerships varies with the mineral fertility of soil. There is strong evidence that plants acclimate and adapt to their local soil conditions through root symbioses; nitrogen limitation is ameliorated by symbiosis with diazotrophic prokaryotes and mycorrhizas ameliorate phosphorus limitation. Corollaries of ecological stoichiometry may be useful for predicting the abundance and functioning of mycorrhizas and N-fixation symbioses. A series of field experiments show that arbuscular mycorrhizal (AM) symbioses in grasslands in North America and in the African Serengeti are most beneficial to plant nutrition when plants are phosphorus limited and have sufficient nitrogen and carbon. A reciprocal inoculation experiment shows that locally adapted communities of AM fungi, associated soil organisms and plants arise such that mutualistic benefits are maximized; both AM fungi and plants grew best in their "home" soil-symbiont combination compared to "away" soil-symbiont combinations. Plants in their home combination acquired more limiting resource (either phosphorus or nitrogen) and consequently grew larger; similarly, AM fungi in their home combination formed more arbuscules and extraradical hyphae. Genetic analysis of the AM fungi inside plant roots indicate that these results correspond to variation in the community composition of AM fungi and also to variation in the symbiotic performance of local isolates of one particular species of AM fungus. The next step is to conduct landscape scale studies of root symbioses to test the hypothesis that plants cultivate microbial communities in and around their roots such that the species and ecotypes of microorganisms within these communities is customized for optimal nutrient acquisition under site-specific environmental conditions. If locally adapted communities of root and rhizosphere organisms are common, then plants may be optimizing their

  16. Proton translocation stoichiometry of cytochrome oxidase: use of a fast-responding oxygen electrode.

    Science.gov (United States)

    Reynafarje, B; Alexandre, A; Davies, P; Lehninger, A L

    1982-01-01

    The mechanistic stoichiometry of vectorial H+ ejection coupled to electron transport from added ferrocytochrome c to oxygen by the cytochrome oxidase (EC 1.9.3.1) of rat liver mitoplasts was determined from measurements of the initial rates of electron flow and H+ ejection in the presence of K+ (with valinomycin). Three different methods of measuring electron flow were used: (a) dual-wavelength spectrophotometry of ferrocytochrome c oxidation, (b) uptake of scalar H+ for the reduction of O2 in the presence of a protonophore, and (c) a fast-responding membraneless oxygen electrode. The reliability of the rate measurements was first established against the known stoichiometry of the scalar reaction of cytochrome oxidase (2ferrocytochrome c + 2H+ + 1/2O2 leads to 2ferricytochrome c + H2O) in the presence of excess protonophore. With all three methods the directly observed vectorial H+/O ejection ratios in the presence of K+ + valinomycin significantly exceeded 3.0. However, because the rate of backflow of the ejected H+ into the mitoplasts is very high and increases with the increasing delta pH generated across the membrane, there is a very rapid decline in the observed H+/O ratio from the beginning of the reaction. Kinetic analysis of ferrocytochrome c oxidation by the mitoplasts, carried out with a fast-responding membraneless oxygen electrode, showed the reaction to be first order in O2 and allowed accurate extrapolation of the rates of O2 uptake and H+ ejection to zero time. At this point, at which there is zero delta pH across the membrane, the H+/O ejection ratio of the cytochrome oxidase reaction, obtained from the rates at zero time, is close to 4.0. PMID:6296824

  17. Forest wildfire increases soil microbial biomass C:N:P stoichiometry in long-term effects

    Science.gov (United States)

    Zhou, Xuan

    2017-04-01

    Boreal forest fire strongly influences carbon (C) stock in permafrost soil by thawing permafrost table which accelerated microbe decomposition process. We studied soil microbial biomass stoichiometry in a gradient of four (3 yr, 25 yr, 46 yr and more than 100 yr) ages since fire in Canada boreal forest. Soil microbial biomass (MB) in long-term after fire is significantly higher than in short-term. MB C and nitrogen (N) were mainly dominated by corresponding soil element concentration and inorganic P, while MB phosphorus (P) changes were fully explained by soil N. Fire ages and soil temperature positively increased MB N and P, indicating the negative impact by fire. Microbial C:N:P gradually increased with fire ages from 15:2:1 to 76:6:1 and then drop down to 17:2:1 in the oldest fire ages. The degree of homeostasis of microbial C, N and P are close to 1 indicates non-homoeostasis within microbial elements, while it of C:N:P is close to 8 shows a strong homeostasis within element ratios and proved microbial stoichiometric ratio is not driven by soil element ratios. In conclusion, i) microbial biomass elements highly depends on soil nutrient supply rather than fire ages; ii) wildfire decreased microbial stoichiometry immediate after fire but increased with years after fire (YF) which at least 3 times higher than > 100 fire ages; iii) microbial biomass C, N and P deviated from strict homeostasis but C:N:P ratio reflects stronger homeostasis.

  18. Evolution of nutrient uptake reveals a trade-off in the ecological stoichiometry of plant-herbivore interactions

    NARCIS (Netherlands)

    Branco, P.; Stomp, M.; Egas, M.; Huisman, J.

    2010-01-01

    Nutrient limitation determines the primary production and species composition of many ecosystems. Here we apply an adaptive dynamics approach to investigate evolution of the ecological stoichiometry of primary producers and its implications for plant‐herbivore interactions. The model predicts a

  19. Stoichiometry of monoclonal antibody neutralization of T-cell line-adapted human immunodeficiency virus type 1

    DEFF Research Database (Denmark)

    Schønning, Kristian; Lund, O; Lund, O S

    1999-01-01

    In order to study the stoichiometry of monoclonal antibody (MAb) neutralization of T-cell line-adapted human immunodeficiency virus type 1 (HIV-1) in antibody excess and under equilibrium conditions, we exploited the ability of HIV-1 to generate mixed oligomers when different env genes...

  20. Thermometric titration of beta-aryl-alpha-mercaptopropenoic acids and determination of the stoichiometry of their metal complexes.

    Science.gov (United States)

    Izquierdo, A; Carrasco, J

    1981-05-01

    Automatic thermometric titration was applied to some beta-aryl-alpha-mercaptopropenoic acids and the stoichiometry of their complexes with several metal ions was investigated. The heats of neutralization of the mercapto-acids with sodium hydroxide and the heats of their reaction with metal ions were calculated.

  1. The use of NH4+ rather than NO3- affects cell stoichiometry, C allocation, photosynthesis and growth in the cyanobacterium Synechococcus sp. UTEX LB 2380, only when energy is limiting.

    Science.gov (United States)

    Ruan, Zuoxi; Giordano, Mario

    2017-02-01

    The assimilation of N-NO 3 - requires more energy than that of N-NH 4 + . This becomes relevant when energy is limiting and may impinge differently on cell energy budget depending on depth, time of the day and season. We hypothesize that N-limited and energy-limited cells of the oceanic cyanobacterium Synechococcus sp. differ in their response to the N source with respect to growth, elemental stoichiometry and carbon allocation. Under N limitation, cells retained almost absolute homeostasis of elemental and organic composition, and the use of NH 4 + did not stimulate growth. When energy was limiting, however, Synechococcus grew faster in NH 4 + than in NO 3 - and had higher C (20%), N (38%) and S (30%) cell quotas. Furthermore, more C was allocated to protein, whereas the carbohydrate and lipid pool size did not change appreciably. Energy limitation also led to a higher photosynthetic rate relative to N limitation. We interpret these results as an indication that, under energy limitation, the use of the least expensive N source allowed a spillover of the energy saved from N assimilation to the assimilation of other nutrients. The change in elemental stoichiometry influenced C allocation, inducing an increase in cell protein, which resulted in a stimulation of photosynthesis and growth. © 2016 John Wiley & Sons Ltd.

  2. β-trace protein as a diagnostic marker for perilymphatic fluid fistula: a prospective controlled pilot study to test a sample collection technique.

    Science.gov (United States)

    Bachmann-Harildstad, Gregor; Stenklev, Niels Christian; Myrvoll, Elin; Jablonski, Greg; Klingenberg, Olav

    2011-01-01

    The diagnosis of perilymphatic fluid (PLF) fistula is still challenging. Perilymphatic fluid fistula is one possible complication after stapedotomy or cochlear implant surgery. We have performed a prospective diagnostic pilot study to further investigate β-trace protein (β-TP) as a marker for PLF fistula. In this pilot study, we tested the sensitivity of the β-TP marker using a simple method for sample collection from the tympanic cavity. Prospective controlled diagnostic study. Two-center tertiary referral hospitals. A total of 35 adult patients undergoing ear surgery were included. Subjects were divided into 2 groups: 1) 19 patients undergoing stapedotomy were investigated for PLF fistula in samples obtained from the tympanic cavity and 2) 16 patients undergoing myringoplasty were investigated for PLF fistula in samples from the tympanic cavity. This group served as the control. Mean age +/- SD at surgery was 49.9 +/- 8.0 years in the study group and 39.69 +/- 15.47 years in the control group. β-Trace protein (prostaglandin D synthase) in tympanic cavity samples and serum samples was analyzed. The samples were collected by gradually filling the tympanic cavity with 100 to 200 μl sodium chloride and by immediately collecting a volume of 60 to 100 μl in a mucus specimen set container. The concentration of β-TP was quantified using laser nephelometry. The median β-TP in the study group was 0.8 mg/L (range, 0.05-4.5 mg/L). In the control group, the median β-TP value was 0.16 mg/L (range, 0.01-0.36 mg/L). Thirty-five percent of the values in the study group were below the highest value in the negative control group. The β-TP values of the tympanic cavity samples were significantly higher in the study group than in controls (p = 0.0001). The serum values were 0.55 +/- 0.18 and 0.53 +/- 0.11 mg/L, respectively. It may be feasible to test for PLF fistula using β-TP in samples from the tympanic cavity. Our results, however, suggest a relative low diagnostic

  3. Notes on electropherograms of eye-lens, muscle proteins and zymograms of muscle esterases of fish collected during the first Brazilian expedition to the Antarctica

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    Van Ngan Phan

    1985-01-01

    Full Text Available A preliminary study was carried out on electropherograms of eye-lens, muscle proteins and zymograms of muscle esterases of ten Notothenia larseni, six Notothenia nudifrons and one lanternfish, Electrona antarctica. The fish were collected by the R/V "Prof. W. Besnard" of the Institute of Oceanography, University of São Paulo, during the First Brazilian Expedition to Antarctica. Eye-lens proteins were analysed on cellulose acetate membrane, muscle proteins and esterases on gel of polyaorylamide. Eye-lens proteins showed three types of electropherograms for N. larseni, and two types for N. nudifrons. One of the electropherograms of N. larseni can be readily distinguished from those of N. nudifrons. Electropherograms of muscle proteins of N. larseni and N. nudifrons are very similar and, consist of sixteen to seventeen fractions. Electropherograms of muscle proteins of N. larseni are severely affected by the conservation of the extracts overnight under -20ºC. All N. nudifrons were of the same zymograms of esterases while those of N. larseni varied. Electropherograms of eye-lens and muscle proteins as well as zymograms of esterases of the lanternfish are different from those of nototheniids.Foi realizado um estudo preliminar sobre eletroferogramas de proteínas de cristalino e de músculo esquelético, e zimogramas de esterases de músculo esquelético de dez Notothenia larseni, seis Notothenia nudifrons e de um peixe-lanterna, Electrona antarctica. Os peixes foram coletados pelo N/Oc. "Prof. W. Besnard" do Instituto Oceanográfico da Universidade de São Paulo durante a I Expedição Brasileira à Antártica. As proteinas do cristalino foram analisadas em membranas de acetato de celulose, enquanto que as proteínas e esterases do músculo esquelético, em gel de poliacrilamida. As proteínas do cristalino apresentam três tipos distintos de eletroferogramas para N. larseni, e dois para N. nudifrons. Um dos eletroferogramas de N. larseni, pode ser

  4. Simultaneous shifts in elemental stoichiometry and fatty acids of Emiliania huxleyi in response to environmental changes

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    R. Bi

    2018-02-01

    Full Text Available Climate-driven changes in environmental conditions have significant and complex effects on marine ecosystems. Variability in phytoplankton elements and biochemicals can be important for global ocean biogeochemistry and ecological functions, while there is currently limited understanding on how elements and biochemicals respond to the changing environments in key coccolithophore species such as Emiliania huxleyi. We investigated responses of elemental stoichiometry and fatty acids (FAs in a strain of E. huxleyi under three temperatures (12, 18 and 24 °C, three N : P supply ratios (molar ratios 10:1, 24:1 and 63:1 and two pCO2 levels (560 and 2400 µatm. Overall, C : N : P stoichiometry showed the most pronounced response to N : P supply ratios, with high ratios of particulate organic carbon vs. particulate organic nitrogen (POC : PON and low ratios of PON vs. particulate organic phosphorus (PON : POP in low-N media, and high POC : POP and PON : POP in low-P media. The ratio of particulate inorganic carbon vs. POC (PIC : POC and polyunsaturated fatty acid proportions strongly responded to temperature and pCO2, both being lower under high pCO2 and higher with warming. We observed synergistic interactions between warming and nutrient deficiency (and high pCO2 on elemental cellular contents and docosahexaenoic acid (DHA proportion in most cases, indicating the enhanced effect of warming under nutrient deficiency (and high pCO2. Our results suggest differential sensitivity of elements and FAs to the changes in temperature, nutrient availability and pCO2 in E. huxleyi, which is to some extent unique compared to non-calcifying algal classes. Thus, simultaneous changes of elements and FAs should be considered when predicting future roles of E. huxleyi in the biotic-mediated connection between biogeochemical cycles, ecological functions and climate change.

  5. Patterns in foliar nutrient resorption stoichiometry at multiple scales: controlling factors and ecosystem consequences (Invited)

    Science.gov (United States)

    Reed, S.; Cleveland, C. C.; Davidson, E. A.; Townsend, A. R.

    2013-12-01

    During leaf senescence, nutrient rich compounds are transported to other parts of the plant and this 'resorption' recycles nutrients for future growth, reducing losses of potentially limiting nutrients. Variations in leaf chemistry resulting from nutrient resorption also directly affect litter quality, in turn, regulating decomposition rates and soil nutrient availability. Here we investigated stoichiometric patterns of nitrogen (N) and phosphorus (P) resorption efficiency at multiple spatial scales. First, we assembled a global database to explore nutrient resorption among and within biomes and to examine potential relationships between resorption stoichiometry and ecosystem nutrient status. Next, we used a forest regeneration chronosequence in Brazil to assess how resorption stoichiometry linked with a suite of other nutrient cycling measures and with ideas of how nutrient limitation may change over secondary forest regrowth. Finally, we measured N:P resorption ratios of six canopy tree species in a Costa Rican tropical forest. We calculated species-specific resorption ratios and compared them with patterns in leaf litter and topsoil nutrient concentrations. At the global scale, N:P resorption ratios increased with latitude and decreased with mean annual temperature (MAT) and precipitation (MAP; P1 in latitudes >23°. Focusing on tropical sites in our global dataset we found that, despite fewer data and a restricted latitudinal range, a significant relationship between latitude and N:P resorption ratios persisted (PAmazon Basin chronosequence of regenerating forests, where previous work reported a transition from apparent N limitation in younger forests to P limitation in mature forests, we found N resorption was highest in the youngest forest, whereas P resorption was greatest in the mature forest. Over the course of succession, N resorption efficiency leveled off but P resorption continued to increase with forest age. In Costa Rica, though we found species

  6. Pelagic community production and carbon-nutrient stoichiometry under variable ocean acidification in an Arctic fjord

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    A. Silyakova

    2013-07-01

    clear that the pelagic ecosystem response to increasing CO2 is more complex than that represented in previous work, e.g. Bellerby et al. (2008. Carbon and nutrient uptake representation in models should, where possible, be more focused on individual plankton functional types as applying a single stoichiometry to a biogeochemical model with regard to the effect of increasing pCO2 may not always be optimal. The phase variability in NCP and stoichiometry may be better understood if CO2 sensitivities of the plankton's functional type biogeochemical uptake kinetics and trophic interactions are better constrained.

  7. High-frequency fire alters C : N : P stoichiometry in forest litter.

    Science.gov (United States)

    Toberman, Hannah; Chen, Chengrong; Lewis, Tom; Elser, James J

    2014-07-01

    Fire is a major driver of ecosystem change and can disproportionately affect the cycling of different nutrients. Thus, a stoichiometric approach to investigate the relationships between nutrient availability and microbial resource use during decomposition is likely to provide insight into the effects of fire on ecosystem functioning. We conducted a field litter bag experiment to investigate the long-term impact of repeated fire on the stoichiometry of leaf litter C, N and P pools, and nutrient-acquiring enzyme activities during decomposition in a wet sclerophyll eucalypt forest in Queensland, Australia. Fire frequency treatments have been maintained since 1972, including burning every 2 years (2yrB), burning every 4 years (4 yrB) and no burning (NB). C : N ratios in freshly fallen litter were 29-42% higher and C : P ratios were 6-25% lower for 2 yrB than NB during decomposition, with correspondingly lower 2yrB N : P ratios (27-32) than for NB (34-49). Trends in litter soluble and microbial N : P ratios were similar to the overall litter N : P ratios across fire treatments. Consistent with these, the ratio of activities for N-acquiring to P-acquiring enzymes in litter was higher for 2 yrB than NB, whereas 4 yrB was generally intermediate between 2 yrB and NB. Decomposition rates of freshly fallen litter were significantly lower for 2 yrB (72 ± 2% mass remaining at the end of experiment) than for 4 yrB (59 ± 3%) and NB (62 ± 3%), a difference that may be related to effects of N limitation, lower moisture content, and/or litter C quality. Results for older mixed-age litter were similar to those for freshly fallen litter although treatment differences were less pronounced. Overall, these findings show that frequent fire (2 yrB) decoupled N and P cycling, as manifested in litter C : N : P stoichiometry and in microbial biomass N : P ratio and enzymatic activities. Furthermore, these data indicate that fire induced a transient shift to N-limited ecosystem conditions

  8. Nitrogen Addition Changes the Stoichiometry and Growth Rate of Different Organs in Pinus tabuliformis Seedlings

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    Hang Jing

    2017-11-01

    Full Text Available Background: Nitrogen (N deposition could influence plant stoichiometry and growth rate and thus alter the structure and function of the ecosystem. However, the mechanism by which N deposition changes the stoichiometry and relative growth rate (RGR of plant organs, especially roots with different diameters, is unclear.Methods: We created a gradient of N availability (0–22.4 g N m-2 year-1 for Pinus tabuliformis seedlings for 3 years and examined changes in the carbon (C:N:phosphorus (P ratios and RGRs of the leaves, stems, and roots with four diameter classes (finest roots, <0.5 mm; finer roots, 0.5–1 mm; middle roots, 1–2 mm; and coarse roots, >2 mm.Results: (1 N addition significantly increased the C and N contents of the leaves and whole roots, the C content of the stems, the N:P ratios of the leaves and stems, and the C:P ratio of the whole roots. (2 In the root system, the C:N ratio of the finest roots and the C:P ratios of the finest and finer roots significantly changed with N addition. The N:P ratios of the finest, finer, and middle roots significantly increased with increasing amount of N added. The stoichiometric responses of the roots were more sensitive to N addition than those of the other organs (3 The RGR of all the organs significantly increased at low N addition levels (2.8–11.2 g N m-2 year-1 but decreased at high N addition levels (22.4 g N m-2 year-1. (4 The RGRs of the whole seedlings and leaves were not significantly correlated with their N:P ratios at low and high N addition levels. By contrast, the RGRs of the stems and roots showed a significantly positive correlation with their own N:P ratio only at low N addition level.Conclusion: Addition of N affected plant growth by altering the contents of C and N; the ratios of C, N, and P; and the RGRs of the organs. RGR is correlated with the N:P ratios of the stems and roots at low N addition level but not at high N addition level. This finding is inconsistent with the

  9. Stoichiometry and kinetics of single and mixed substrate uptake in Aspergillus niger.

    Science.gov (United States)

    Lameiras, Francisca; Ras, Cor; Ten Pierick, Angela; Heijnen, Joseph J; van Gulik, Walter M

    2018-02-01

    In its natural environment, the filamentous fungus Aspergillus niger grows on decaying fruits and plant material, thereby enzymatically degrading the lignocellulosic constituents (lignin, cellulose, hemicellulose, and pectin) into a mixture of mono- and oligosaccharides. To investigate the kinetics and stoichiometry of growth of this fungus on lignocellulosic sugars, we carried out batch cultivations on six representative monosaccharides (glucose, xylose, mannose, rhamnose, arabinose, and galacturonic acid) and a mixture of these. Growth on these substrates was characterized in terms of biomass yields, oxygen/biomass ratios, and specific conversion rates. Interestingly, in combination, some of the carbon sources were consumed simultaneously and some sequentially. With a previously developed protocol, a sequential chemostat cultivation experiment was performed on a feed mixture of the six substrates. We found that the uptake of glucose, xylose, and mannose could be described with a Michaelis-Menten-type kinetics; however, these carbon sources seem to be competing for the same transport systems, while the uptake of arabinose, galacturonic acid, and rhamnose appeared to be repressed by the presence of other substrates.

  10. Ecological stoichiometry of C, N and P on different time enclosed in desertification steppe soil

    Science.gov (United States)

    Yang, W. Z.; Jiao, Y.; Jia, Y. Q.

    2017-08-01

    It is the research object for the ecological stoichiometry of C, N and P on the different time of desertification grasslands enclosed and grazing grassland in Taibusi country of the Inner Mongolia, China. Through the measurement and analysis on ecological stoichiometric ratio of C, N and P in soil, the time of desertification grassland enclosed is determined. There are 13 soil of desertification grassland with different en-closure time, and 1 soil of grazing grassland. They are analyzed for the soil organic carbon, total nitro-gen, total phosphorus content and their density. The C/N of soil were increased with the extension of the time of desertification grassland enclosed. To 22 years enclosed, the C/N of grassland desertification soil enclosed is greater than the soil of grazing grassland that is 17. After the desertification grassland is en-closed, the C/N of soil is 13, and it is accumulated to maximum for C and N, and The grazing period is the best.

  11. Physical determinants of phytoplankton production, algal stoichiometry, and vertical nutrient fluxes.

    Science.gov (United States)

    Jäger, Christoph G; Diehl, Sebastian; Emans, Maximilian

    2010-04-01

    Most phytoplankters face opposing vertical gradients in light versus nutrient supplies but have limited capacities for vertical habitat choice. We therefore explored a dynamical model of negatively buoyant algae inhabiting a one-dimensional water column to ask how water column depth and turbulence constrain total (areal) phytoplankton biomass. We show that the population persistence boundaries in water column depth-turbulence space are set by sinking losses and light limitation but that nutrients are most limiting to total biomass in water columns that are neither too shallow or too weakly mixed (where sinking losses prevail) nor too deep and turbulent (where light limitation prevails). In shallow waters, the most strongly limiting process is nutrient influx to the bottom of the water column (e.g., from sediments). In deep waters, the most strongly limiting process is turbulent upward transport of nutrients to the photic zone. Consequently, the highest total biomasses are attained in turbulent waters at intermediate water column depths and in deep waters at intermediate turbulences. These patterns are insensitive to the assumption of fixed versus flexible algal carbon-to-nutrient stoichiometry, and they arise irrespective of whether the water column is a surface layer above a deep water compartment or has direct contact with sediments.

  12. Effects of stoichiometry on the transport properties of crystalline phase-change materials.

    Science.gov (United States)

    Zhang, Wei; Wuttig, Matthias; Mazzarello, Riccardo

    2015-09-03

    It has recently been shown that a metal-insulator transition due to disorder occurs in the crystalline state of the GeSb2Te4 phase-change compound. The transition is triggered by the ordering of the vacancies upon thermal annealing. In this work, we investigate the localization properties of the electronic states in selected crystalline (GeTe)x-(Sb2Te3)y compounds with varying GeTe content by large-scale density functional theory simulations. In our models, we also include excess vacancies, which are needed to account for the large carrier concentrations determined experimentally. We show that the models containing a high concentration of stoichiometric vacancies possess states at the Fermi energy localized inside vacancy clusters, as occurs for GeSb2Te4. On the other hand, the GeTe-rich models display metallic behavior, which stems from two facts: a) the tail of localized states shrinks due to the low probability of having sizable vacancy clusters, b) the excess vacancies shift the Fermi energy to the region of extended states. Hence, a stoichiometry-controlled metal-insulator transition occurs. In addition, we show that the localization properties obtained by scalar-relativistic calculations with gradient-corrected functionals are unaffected by the inclusion of spin-orbit coupling or the use of hybrid functionals.

  13. Influence of PEG Stoichiometry on Structure-Tuned Formation of Self-Assembled Submicron Nickel Particles

    Directory of Open Access Journals (Sweden)

    Bingxue Pu

    2018-01-01

    Full Text Available Self-assembled submicron nickel particles were successfully synthesized via the one-step surfactant-assisted solvothermal method. The impact of surfactant and reducing agent stoichiometry is investigated in this manuscript. Different morphologies and structures of Ni particles, including flower-like nanoflakes, hydrangea-like structures, chain structures, sphere-like structures, and hollow structures were prepared through different processing conditions with two parameters such as temperature and time. Based on scanning electron microscopy (SEM, X-ray diffraction (XRD, thermal gravimetric analysis (TGA and vibrating sample magnetometry (VSM, the submicron nickel particles show good saturation magnetization and excellent thermal stabilities with a possible growth mechanism for the variety of the structure-tuned formation. Importantly, the microwave absorption properties of the submicron nickel particles were studied. The lowest reflection loss of Ni-P9/T200/H15 with a thin layer thickness of 1.7 mm can reach −42.6 dB at 17.3 GHz.

  14. The control of stoichiometry in Epitaxial semiconductor structures. Interfacial Chemistry: Property relations. A workshop review

    Science.gov (United States)

    Bachmann, Klaus J.

    1995-01-01

    A workshop on the control of stoichiometry in epitaxial semiconductor structures was held on August 21-26, 1995 in the hotel Stutenhaus at Vesser in Germany. The secluded location of the workshop in the forest of Thuringia and its informal style stimulated extensive private discussions among the participants and promoted new contacts between young scientists from Eastern and Western Europe and the USA. Topics addressed by the presentations were interactions of precursors to heteroepitaxy and doping with the substrate surface, the control of interfacial properties under the conditions of heteroepitaxy for selected materials systems, methods of characterization of interfaces and native point defects in semiconductor heterostructures and an in depth evaluation of the present status of the control and characterization of the point defect chemistry for one specific semiconductor (ZnGeP2), including studies of both heterostructures and bulk single crystals. The selected examples of presentations and comments given here represent individual choices - made by the author to highlight major points of the discussions.

  15. The influence of titanium adhesion layer oxygen stoichiometry on thermal boundary conductance at gold contacts

    Science.gov (United States)

    Olson, David H.; Freedy, Keren M.; McDonnell, Stephen J.; Hopkins, Patrick E.

    2018-04-01

    We experimentally demonstrate the role of oxygen stoichiometry on the thermal boundary conductance across Au/TiOx/substrate interfaces. By evaporating two different sets of Au/TiOx/substrate samples under both high vacuum and ultrahigh vacuum conditions, we vary the oxygen composition in the TiOx layer from 0 ≤ x ≤ 2.85. We measure the thermal boundary conductance across the Au/TiOx/substrate interfaces with time-domain thermoreflectance and characterize the interfacial chemistry with x-ray photoemission spectroscopy. Under high vacuum conditions, we speculate that the environment provides a sufficient flux of oxidizing species to the sample surface such that one essentially co-deposits Ti and these oxidizing species. We show that slower deposition rates correspond to a higher oxygen content in the TiOx layer, which results in a lower thermal boundary conductance across the Au/TiOx/substrate interfacial region. Under the ultrahigh vacuum evaporation conditions, pure metallic Ti is deposited on the substrate surface. In the case of quartz substrates, the metallic Ti reacts with the substrate and getters oxygen, leading to a TiOx layer. Our results suggest that Ti layers with relatively low oxygen compositions are best suited to maximize the thermal boundary conductance.

  16. Stoichiometry of mitochondrial H+ translocation coupled to succinate oxidation at level flow.

    Science.gov (United States)

    Costa, L E; Reynafarje, B; Lehninger, A L

    1984-04-25

    The mechanistic stoichiometry of vectorial H+ translocation coupled to succinate oxidation by rat liver mitochondria in the presence of a permeant cation has been determined under level flow conditions with a membraneless fast responding O2 electrode kinetically matched with a glass pH electrode. The reactions were initiated by rapid injection of O2 into the anaerobically preincubated test system under conditions in which interfering H+ backflow was minimized. The rates of O2 uptake and H+ ejection, obtained from computer-fitted regression lines, were monotonic and first order over 75% of the course of O2 consumption. Extrapolation of the observed rates to zero time, at which zero delta mu H+ and thus level flow prevails, yielded vectorial H+/O flow ratios above 7 and closely approaching 8. The mitochondria undergo no irreversible change and give identical H+/O ratios on repeated tests. In a further refinement, the lower and upper limits of the mechanistic H+/O ratio were determined to be 7.55 and 8.56, respectively, from plots of the rates of O2 uptake versus H+ ejection at increasing malonate and increasing valinomycin concentrations, respectively. It is therefore concluded that the mechanistic H+/O ratio for energy-conserving sites 2 + 3 is 8, in confirmation of earlier measurements. KCl concentration is critical for maximal observed H+/O ratios. Optimum conditions and possible errors in determination of mechanistic H+/O translocation ratios are discussed.

  17. Stoichiometry of H+ ejection during respiration-dependent accumulation of Ca2+ by rat liver mitochondria.

    Science.gov (United States)

    Brand, M D; Chen, C H; Lehninger, A L

    1976-02-25

    We have investigated the energy-dependent uptake of Ca2+ by rat liver mitochondria with succinate as respiratory substrate with rotenone added to block NAD-linked electron transport. In the presence of 3-hydroxybutyric or other permeant monocarboxylic acids Ca2+ was taken up to extents approaching those seen in the presence of phosphate. The quantitative relationship between cation and anion uptake was determined from the slope of a plot of 3-hydroxybutyrate uptake against Ca2+ uptake, a method which allowed determination of the stoichiometry without requiring ambiguous corrections for early nonenergized or nonstoichiometric binding events. This procedure showed that 2 molecules of 3-hydroxtbutyrate were accumulated with each Ca2+ ion. Under these conditions close to 2 Ca2+ ions and 4 molecules of 3-hydroxybutyrate were accumulated per pair of electrons per energy-conserving site of the respiratory chain. Since 3-hydroxybutyrate must be protonated to pass the membrane as the undissociated free acid, it is concluded that 4 protons were ejected (and subsequently reabsorbed) per pair of electrons per energy-conserving site, in contrast to the value 2.0 postulated by the chemiosmotic hypothesis.

  18. Heteroleptic metallosupramolecular racks, rectangles, and trigonal prisms: stoichiometry-controlled reversible interconversion.

    Science.gov (United States)

    Neogi, Subhadip; Lorenz, Yvonne; Engeser, Marianne; Samanta, Debabrata; Schmittel, Michael

    2013-06-17

    A simple approach toward preparation of heteroleptic two-dimensional (2D) rectangles and three-dimensional (3D) triangular prisms is described utilizing the HETPYP (HETeroleptic PYridyl and Phenanthroline metal complexes) concept. By mixing metal-loaded linear bisphenanthrolines of varying lengths with diverse (multi)pyridine (py) ligands in a proper ratio, six different self-assembled architectures arise cleanly and spontaneously in the absence of any template. They are characterized by (1)H and DOSY NMR, ESI-FT-ICR mass spectrometry as well as by Job plots and UV-vis titrations. Density functional theory (DFT) computations provide information about each structure. A stoichiometry-controlled supramolecule-to-supramolecule interconversion based on the relative amounts of metal bisphenanthroline and bipyridine forces the rectangular assembly to reorganize to a rack architecture and back to the rectangle, as clearly supported by variable temperature and DOSY NMR as well as dynamic light scattering data. The highly dynamic nature of the assemblies represents a promising starting point for constitutional dynamic materials.

  19. Quantity and quality limit detritivore growth: mechanisms revealed by ecological stoichiometry and co-limitation theory.

    Science.gov (United States)

    Halvorson, Halvor M; Sperfeld, Erik; Evans-White, Michelle A

    2017-12-01

    Resource quantity and quality are fundamental bottom-up constraints on consumers. Best understood in autotroph-based systems, co-occurrence of these constraints may be common but remains poorly studied in detrital-based systems. Here, we used a laboratory growth experiment to test limitation of the detritivorous caddisfly larvae Pycnopsyche lepida across a concurrent gradient of oak litter quantity (food supply) and quality (phosphorus : carbon [P:C ratios]). Growth increased simultaneously with quantity and quality, indicating co-limitation across the resource gradients. We merged approaches of ecological stoichiometry and co-limitation theory, showing how co-limitation reflected shifts in C and P acquisition throughout homeostatic regulation. Increased growth was best explained by elevated consumption rates and improved P assimilation, which both increased with elevated quantity and quality. Notably, C assimilation efficiencies remained unchanged and achieved maximum 18% at low quantity despite pronounced C limitation. Detrital C recalcitrance and substantive post-assimilatory C losses probably set a minimum quantity threshold to achieve positive C balance. Above this threshold, greater quality enhanced larval growth probably by improving P assimilation toward P-intensive growth. We suggest this interplay of C and P acquisition contributes to detritivore co-limitation, highlighting quantity and quality as potential simultaneous bottom-up controls in detrital-based ecosystems, including under anthropogenic change like nutrient enrichment. © 2017 by the Ecological Society of America.

  20. Stoichiometry of Na/Ca antiport obtained by magnesium inhibition in cultured vascular smooth muscle cells

    International Nuclear Information System (INIS)

    Smith, J.B.; Higgins, B.L.; Smith, L.

    1987-01-01

    Cultured smooth muscle cells from rat aorta were loaded with Na, and Na/Ca antiport was assayed by measuring the initial rates of 45 Ca influx and 22 Na efflux. The replacement of extracellular Na with other monovalent ions, usually N-methyl-D-glucamine (NMG), was essential for obtaining significant antiport activity. Mg competitively inhibited 45 Ca influx via the antiporter (Ki = 100 uM). External Ca stimulated 22 Na efflux as expected for antiport activity. Mg did not stimulate 22 Na efflux indicating that Mg is not transported by the antiporter. Mg inhibited Ca-stimulated 22 Na efflux as expected from the 45 Ca influx data. The stoichiometry of the antiporter was calculated from the changes in the rates of 45 Ca influx and 22 Na efflux at 3 Mg concentrations: 2.87 +/- 0.25 (mean +/- SE, n=5). The replacement of external NMG with potassium, but not other monovalent ions (choline, Li), decreased the potency of Mg as an inhibitor of Na/Ca antiport by about 6 fold. Other divalent cations (Co, Mn, Cd, Ba) inhibited Na/Ca antiport and high external potassium decreased the potency of each by about 6 fold. The order of effectiveness of the divalent cations as inhibitors of Na/Ca antiport (Cd>Mn>Co>Ba>Mg) correlated with the crystal ionic radius of the cation

  1. Stoichiometry control of complex oxides by sequential pulsed-laser deposition from binary-oxide targets

    Energy Technology Data Exchange (ETDEWEB)

    Herklotz, A. [ORNL, Materials Science and Technology Division, Bethel Valley Road, Oak Ridge, Tennessee 37831-6056 (United States); Martin Luther University Halle-Wittenberg, Institute for Physics, Von-Danckelmann-Platz 3, 06120 Halle (Germany); Dörr, K. [Martin Luther University Halle-Wittenberg, Institute for Physics, Von-Danckelmann-Platz 3, 06120 Halle (Germany); Ward, T. Z.; Eres, G. [ORNL, Materials Science and Technology Division, Bethel Valley Road, Oak Ridge, Tennessee 37831-6056 (United States); Christen, H. M.; Biegalski, M. D. [ORNL, Center for Nanophase Materials Sciences, Bethel Valley Road, Oak Ridge, Tennessee 37831-6496 (United States)

    2015-03-30

    To have precise atomic layer control over interfaces, we examine the growth of complex oxides through the sequential deposition from binary targets by pulsed laser deposition. In situ reflection high-energy electron diffraction (RHEED) is used to control the growth and achieve films with excellent structural quality. The growth from binary oxide targets is fundamentally different from single target growth modes and shows more similarities to shuttered growth by molecular beam epitaxy. The RHEED intensity oscillations of non-stoichiometric growth are consistent with a model of island growth and accumulation of excess material on the surface that can be utilized to determine the correct stoichiometry for growth. Correct monolayer doses can be determined through an envelope frequency in the RHEED intensity oscillations. In order to demonstrate the ability of this growth technique to create complex heterostructures, the artificial n = 2 and 3 Sr{sub n+1}Ti{sub n}O{sub 3n+1} Ruddlesden-Popper phases are grown with good long-range order. This method enables the precise unit-cell level control over the structure of perovskite-type oxides, and thus the growth of complex materials with improved structural quality and electronic functionality.

  2. Non-Redfield, nutrient synergy and flexible internal elemental stoichiometry in a marine bacterium.

    Science.gov (United States)

    Trautwein, Kathleen; Feenders, Christoph; Hulsch, Reiner; Ruppersberg, Hanna S; Strijkstra, Annemieke; Kant, Mirjam; Vagts, Jannes; Wünsch, Daniel; Michalke, Bernhard; Maczka, Michael; Schulz, Stefan; Hillebrand, Helmut; Blasius, Bernd; Rabus, Ralf

    2017-05-01

    The stoichiometric constraints of algal growth are well understood, whereas there is less knowledge for heterotrophic bacterioplankton. Growth of the marine bacterium Phaeobacter inhibens DSM 17395, belonging to the globally distributed Roseobacter group, was studied across a wide concentration range of NH4+ and PO43-. The unique dataset covers 415 different concentration pairs, corresponding to 207 different molar N:P ratios (from 10-2 to 105). Maximal growth (by growth rate and biomass yield) was observed within a restricted concentration range at N:P ratios (∼50-120) markedly above Redfield. Experimentally determined growth parameters deviated to a large part from model predictions based on Liebig's law of the minimum, thus implicating synergistic co-limitation due to biochemical dependence of resources. Internal elemental ratios of P. inhibens varied with external nutrient supply within physiological constraints, thus adding to the growing evidence that aquatic bacteria can be flexible in their internal elemental composition. Taken together, the findings reported here revealed that P. inhibens is well adapted to fluctuating availability of inorganic N and P, expected to occur in its natural habitat (e.g. colonized algae, coastal areas). Moreover, this study suggests that elemental variability in bacterioplankton needs to be considered in the ecological stoichiometry of the oceans. © FEMS 2017.

  3. Stoichiometry and Life-History Interact to Determine the Magnitude of Cross-Ecosystem Element and Biomass Fluxes

    Directory of Open Access Journals (Sweden)

    Thomas M. Luhring

    2017-05-01

    Full Text Available Ecosystems are linked through the transfer of materials and energy. Studies examining material fluxes across habitat boundaries frequently quantify unidirectional flows of nutrients and energy. However, material fluxes can be multidirectional, and we lack a conceptual framework to describe how their quantity and stoichiometry influence the net transfer of individual elements between ecosystems. Here we develop a zero net transfer isocline (ZNTI framework that integrates the relative mass and stoichiometry of fluxes into and out of an ecosystem. We then use case studies with amphibians and salmon to elucidate how life history, ontogenetic shifts in stoichiometry, and trophic interactions shape relative fluxes of nutrients between aquatic and terrestrial ecosystems. Because they increase in both size and Ca content from ova to metamorphs, amphibian life histories strongly bias them toward net Ca export into the terrestrial environment. Because amphibian biomass, C, P, and Ca ZNTIs do not overlap, there is no value of survivorship where the net flux of biomass, C, P, and Ca are simultaneously balanced between terrestrial and aquatic habitats. The degree of iteroparity and semelparity in salmon strongly affects both the magnitude of net biomass and P flux between riverine and marine environments. While the net direction of biomass flux generally remains strongly biased toward import into the riverine system, net P flux can reach net export into the marine environment because of increasing adult breeding survival leading to reduced mass and %P of what they deposit in rivers (e.g., ova vs. whole carcasses. These examples highlight how ontogenetic shifts in body size and stoichiometry result in asymmetric fluxes of elements and biomass that can lead to simultaneous net imports and exports of different elements within the same system. Furthermore, they demonstrate how changes in life-history characteristics and stage-specific survivorship can lead to

  4. Chemical Genomic Screening of a Saccharomyces cerevisiae Genomewide Mutant Collection Reveals Genes Required for Defense against Four Antimicrobial Peptides Derived from Proteins Found in Human Saliva

    Science.gov (United States)

    Bhatt, Sanjay; Schoenly, Nathan E.; Lee, Anna Y.; Nislow, Corey; Bobek, Libuse A.

    2013-01-01

    To compare the effects of four antimicrobial peptides (MUC7 12-mer, histatin 12-mer, cathelicidin KR20, and a peptide containing lactoferricin amino acids 1 to 11) on the yeast Saccharomyces cerevisiae, we employed a genomewide fitness screen of combined collections of mutants with homozygous deletions of nonessential genes and heterozygous deletions of essential genes. When an arbitrary fitness score cutoffs of 1 (indicating a fitness defect, or hypersensitivity) and −1 (indicating a fitness gain, or resistance) was used, 425 of the 5,902 mutants tested exhibited altered fitness when treated with at least one peptide. Functional analysis of the 425 strains revealed enrichment among the identified deletions in gene groups associated with the Gene Ontology (GO) terms “ribosomal subunit,” “ribosome biogenesis,” “protein glycosylation,” “vacuolar transport,” “Golgi vesicle transport,” “negative regulation of transcription,” and others. Fitness profiles of all four tested peptides were highly similar, particularly among mutant strains exhibiting the greatest fitness defects. The latter group included deletions in several genes involved in induction of the RIM101 signaling pathway, including several components of the ESCRT sorting machinery. The RIM101 signaling regulates response of yeasts to alkaline and neutral pH and high salts, and our data indicate that this pathway also plays a prominent role in regulating protective measures against all four tested peptides. In summary, the results of the chemical genomic screens of S. cerevisiae mutant collection suggest that the four antimicrobial peptides, despite their differences in structure and physical properties, share many interactions with S. cerevisiae cells and consequently a high degree of similarity between their modes of action. PMID:23208710

  5. Effects of oxygen stoichiometry on the scaling behaviors of YBa2Cu3Ox grain boundary weak-links

    International Nuclear Information System (INIS)

    Wu, K.H.; Fu, C.M.; Jeng, W.J.

    1994-01-01

    The effects of oxygen stoichiometry on the transport properties of the pulsed laser deposited YBa 2 Cu 3 O x bicrystalline grain boundary weak-link junctions were studied. It is found that not only the cross boundary resistive transition foot structure can be manipulated repeatedly with oxygen annealling processes but the junction behaviors are also altered in accordance. In the fully oxygenated state i.e. with x=7.0 in YBa 2 Cu 3 O x stoichiometry, the junction critical current exhibits a power of 2 scaling behavior with temperature. In contrast, when annealed in the conditions of oxygen-deficient state (e.g. with x=6.9 in YBa 2 Cu 3 O x stoichiometry) the junction critical current switches to a linear temperature dependence behavior. The results are tentatively attributed to the modification of the structure in the boundary area upon oxygen annealing, which, in turn, will affect the effective dimension of the geometrically constrained weak-link bridges. The detailed discussion on the responsible physical mechanisms as well as the implications of the present results on device applications will be given

  6. Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe

    Energy Technology Data Exchange (ETDEWEB)

    Jirousek, Martin, E-mail: machozrut@mail.muni.c [Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno (Czech Republic); Hajek, Michal [Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno (Czech Republic); Bragazza, Luca [WSL Swiss Federal Institute for Forest, Snow and Landscape Research, Site Lausanne, Station 2, Case Postale 96, CH-1015 Lausanne (Switzerland); Ecole Polytechnique Federale de Lausanne (EPFL), Laboratory of Ecological Systems - ECOS, Batiment GR, Station 2, CH-1015 Lausanne (Switzerland); Department of Biology and Evolution, University of Ferrara, Corso Ercole I d' Este 32, I-44100 Ferrara (Italy)

    2011-02-15

    We investigated the variation of N:P and N:K ratio in ombrotrophic Sphagnum plants along a gradient of atmospheric N deposition from 1 to 2.5 g m{sup -2} year{sup -1} in Central-East Europe. The N:P and N:K ratio in Sphagnum capitula increased significantly along the N deposition gradient. Sphagnum species from the Cuspidata section were characterised by significantly lower ratios at low N deposition. When we compared the observed N:P ratios in Sphagnum plants with the values reported in a previous European-wide study, we found a correspondence in nutrient stoichiometry only for a few bogs: higher P concentration in Sphagnum capitula caused a lower N:P ratio in most of the study bogs so that Sphagnum plants still seem N-limited despite their N saturation. Interaction between summer water table decrease and aerial liming of surrounding forests is proposed as an explanation for this discrepancy. Local forestry practice interacting with climate thus alter N:P stoichiometry of Sphagnum along the N deposition gradient. - Research highlights: Despite high atmopsheric nitrogen deposition, Sphagnum mosses still have rather low N:P ratio. Regional climate and landscape management can enhance P and K availability in bogs. Sphagnum species of the Cuspidata section were characterised by lower N:P ratio. - Regional climate and local forestry practices are expected to alter nutrient stoichiometry in Sphagnum mosses at high atmospheric N deposition in Central-East Europe.

  7. Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe

    International Nuclear Information System (INIS)

    Jirousek, Martin; Hajek, Michal; Bragazza, Luca

    2011-01-01

    We investigated the variation of N:P and N:K ratio in ombrotrophic Sphagnum plants along a gradient of atmospheric N deposition from 1 to 2.5 g m -2 year -1 in Central-East Europe. The N:P and N:K ratio in Sphagnum capitula increased significantly along the N deposition gradient. Sphagnum species from the Cuspidata section were characterised by significantly lower ratios at low N deposition. When we compared the observed N:P ratios in Sphagnum plants with the values reported in a previous European-wide study, we found a correspondence in nutrient stoichiometry only for a few bogs: higher P concentration in Sphagnum capitula caused a lower N:P ratio in most of the study bogs so that Sphagnum plants still seem N-limited despite their N saturation. Interaction between summer water table decrease and aerial liming of surrounding forests is proposed as an explanation for this discrepancy. Local forestry practice interacting with climate thus alter N:P stoichiometry of Sphagnum along the N deposition gradient. - Research highlights: → Despite high atmopsheric nitrogen deposition, Sphagnum mosses still have rather low N:P ratio.→ Regional climate and landscape management can enhance P and K availability in bogs. → Sphagnum species of the Cuspidata section were characterised by lower N:P ratio. - Regional climate and local forestry practices are expected to alter nutrient stoichiometry in Sphagnum mosses at high atmospheric N deposition in Central-East Europe.

  8. Modification of Light Emission in Si-Rich Silicon Nitride Films Versus Stoichiometry and Excitation Light Energy

    Science.gov (United States)

    Torchynska, T.; Khomenkova, L.; Slaoui, A.

    2018-04-01

    Si-rich SiN x films with different stoichiometry were grown on Si substrate by plasma-enhanced chemical vapor deposition. The Si content was varied by changing the NH3/SiH4 gas flow ratio from 0.45 up to 1.0. Conventional furnace annealing at 1100°C for 30 min was applied to produce the Si quantum dots (QDs) in the SiN x films. Spectroscopic ellipsometry was used to determine the refractive index of the SiN x films that allowed estimating the film's stoichiometry. Fourier transform infrared spectroscopy has been also used to confirm the stoichiometry and microstructure. Photoluminescence (PL) spectra of Si-rich SiN x films are complex. A non-monotonous variation of the different PL peaks versus Si excess contents testifies to the competition of different radiative channels. The analysis of PL spectra, measured at the different excitation light energies and variable temperatures, has revealed that the PL bands with the peaks within the range 2.1-3.0 eV are related to the carrier recombination via radiative native defects in the SiN x host. Simultaneously, the PL bands with the peaks at 1.5-2.0 eV are caused by the exciton recombination in the Si QDs of different sizes. The way to control the SiN x emission is discussed.

  9. Measuring Conceptual Change on Stoichiometry Using Mental Models and IllStructured Problems In a Flipped Classroom Environment

    Directory of Open Access Journals (Sweden)

    Norrie E. Gayeta

    2017-05-01

    Full Text Available This study aimed to measure conceptual change on stoichiometry using mental models and ill-structured problems in flipped classroom environment. This study examined the level of conceptual understanding of students on stoichiometry before and after exposure to flipped and traditional lecture method. It also covered the type of conceptual change, and students’ description in flipped classroom environment. Qualitative and quantitative research methods were used in the study. Respondents were two sections of third year Bachelor of Secondary Education, Biological Science. Frequency, percentage, ranking, mean, standard deviation, Hake factor test, and t-test were the statistical tools applied to answer specific questions. Results showed profound increase towards conceptual change representing a shift from intuitive understanding to correct incomplete understanding level. Thus, change for the better, in theoretical type was determined from pretest to posttest of students exposed to flipped and traditional instruction. Results also indicated that there is no significant difference on students’ conceptual change on stoichiometry exposed to flipped and traditional lecture method. Furthermore, students strongly agreed that flipped classroom instruction helped them develop positive attitude towards chemistry and appropriate for learning college chemistry.

  10. Full-length cellular β-secretase has a trimeric subunit stoichiometry, and its sulfur-rich transmembrane interaction site modulates cytosolic copper compartmentalization.

    Science.gov (United States)

    Liebsch, Filip; Aurousseau, Mark R P; Bethge, Tobias; McGuire, Hugo; Scolari, Silvia; Herrmann, Andreas; Blunck, Rikard; Bowie, Derek; Multhaup, Gerd

    2017-08-11

    The β-secretase (BACE1) initiates processing of the amyloid precursor protein (APP) into Aβ peptides, which have been implicated as central players in the pathology of Alzheimer disease. BACE1 has been described as a copper-binding protein and its oligomeric state as being monomeric, dimeric, and/or multimeric, but the native cellular stoichiometry has remained elusive. Here, by using single-molecule fluorescence and in vitro cross-linking experiments with photo-activatable unnatural amino acids, we show that full-length BACE1, independently of its subcellular localization, exists as trimers in human cells. We found that trimerization requires the BACE1 transmembrane sequences (TMSs) and cytoplasmic domains, with residues Ala 463 and Cys 466 buried within the trimer interface of the sulfur-rich core of the TMSs. Our 3D model predicts that the sulfur-rich core of the trimeric BACE1 TMS is accessible to metal ions, but copper ions did not trigger trimerization. The results of functional assays of endogenous BACE1 suggest that it has a role in intracellular copper compartmentalization by transferring cytosolic copper to intracellular compartments, while leaving the overall cellular copper concentration unaltered. Adding to existing physiological models, our results provide novel insight into the atypical interactions between copper and BACE1 and into its non-enzymatic activities. In conclusion, therapeutic Alzheimer disease prevention strategies aimed at decreasing BACE1 protein levels should be regarded with caution, because adverse effects in copper homeostasis may occur. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  11. Effect of A-site stoichiometry on phase stability and electrical conductivity of the perovskite Las(Ni0.59Fe0.41)O3-δ and its compatibility with (La0.8

    DEFF Research Database (Denmark)

    Knudsen, J.; Friehling, P.B.; Bonanos, N.

    2005-01-01

    , prepared by the glycine nitrate combustion method. The chemical compatibility of La-0.99(Ni0.59Fe0.41)O3-delta with the cathode material (La0.85Sr0.15)(0.91)MnO3-delta and the electrolyte Y2O3-doped ZrO2 (8 mol%) was likewise studied by X-ray diffraction and scanning electron microscopy. Small deviations......To investigate the influence of A-site stoichiometry on phase stability and electrical conductivity of the perovskite based series La-S(Ni0.59Fe0.41)O3-delta for cathode current collection in solid oxide fuel cells, X-ray diffraction and DC electrical conductivity studies were performed on samples...... (similar to 1 at.%) in the A-site stoichiometry of the perovskite did not result in significant change to the electrical conductivity. Extensive reaction between La-0.99(Ni0.59Fe0.41)O3-delta and 8 mol% Y2O3 doped ZrO2 after sintering was observed by X-ray diffraction. Reaction between La-0.99(Ni0.59Fe0...

  12. Impact of Temperature and Nutrients on Carbon: Nutrient Tissue Stoichiometry of Submerged Aquatic Plants: An Experiment and Meta-Analysis

    Directory of Open Access Journals (Sweden)

    Mandy Velthuis

    2017-05-01

    Full Text Available Human activity is currently changing our environment rapidly, with predicted temperature increases of 1–5°C over the coming century and increased nitrogen and phosphorus inputs in aquatic ecosystems. In the shallow parts of these ecosystems, submerged aquatic plants enhance water clarity by resource competition with phytoplankton, provide habitat, and serve as a food source for other organisms. The carbon:nutrient stoichiometry of submerged aquatic plants can be affected by changes in both temperature and nutrient availability. We hypothesized that elevated temperature leads to higher carbon:nutrient ratios through enhanced nutrient-use efficiency, while nutrient addition leads to lower carbon:nutrient ratios by the luxurious uptake of nutrients. We addressed these hypotheses with an experimental and a meta-analytical approach. We performed a full-factorial microcosm experiment with the freshwater plant Elodea nuttallii grown at 10, 15, 20, and 25°C on sediment consisting of pond soil/sand mixtures with 100, 50, 25, and 12.5% pond soil. To address the effect of climatic warming and nutrient addition on the carbon:nutrient stoichiometry of submerged freshwater and marine plants we performed a meta-analysis on experimental studies that elevated temperature and/or added nutrients (nitrogen and phosphorus. In the microcosm experiment, C:N ratios of Elodea nuttallii decreased with increasing temperature, and this effect was most pronounced at intermediate nutrient availability. Furthermore, higher nutrient availability led to decreased aboveground C:P ratios. In the meta-analysis, nutrient addition led to a 25, 22, and 16% reduction in aboveground C:N and C:P ratios and belowground C:N ratios, accompanied with increased N content. No consistent effect of elevated temperature on plant stoichiometry could be observed, as very few studies were found on this topic and contrasting results were reported. We conclude that while nutrient addition

  13. Ribosomal binding region for the antibiotic tiamulin: stoichiometry, subunit location, and affinity for various analogs.

    Science.gov (United States)

    Högenauer, G; Ruf, C

    1981-01-01

    Equilibrium dialysis experiments with a highly purified preparation of labeled tiamulin, a semisynthetic derivative of the antibiotic pleuromutilin, and Escherichia coli ribosomes allowed the determination of two binding sites for the drug. The binding reaction showed a cooperative effect. Of the two subunits, the 50S particle was able to bind the antibiotic in a 1:1 stoichiometry. Hence, the 50S subunit contributed predominantly to the binding energy which held the antibiotic to the ribosomes. The 30S subunit, showing no strong affinity for the drug, may be needed for the generation of the second binding site in the 70S particle. If depleted of ammonium ions, 70S ribosomes lost their binding capacity for the antibiotic. The attachment sites for tiamulin could be restored by heating the ribosomes to 40 degrees C in the presence of either ammonium ions or the antibiotic. Other pleuromutilin derivatives displaced labeled tiamulin from its ribosomal binding sites. By quantifying this competition, the relative affinity of various pleuromutilin derivatives for E. coli ribosomes was determined. The binding correlated with the minimal inhibitory concentrations of these compounds against E. coli. When compared with the minimal inhibitory concentrations of these compounds against E. coli. When compared with the minimal inhibitory concentrations against E. coli. When compared with the minimal inhibitory concentrations against Staphylococcus aureus, the correlation was less strict, but the same trend prevailed. These results suggest that the antibacterial activities of various pleuromutilin derivatives on a given test organism are mainly determined by the strength of binding to the ribosomes within the bacterial cell. PMID:6751216

  14. Nutrient Partitioning and Stoichiometry in Unburnt Sugarcane Ratoon at Varying Yield Levels

    Directory of Open Access Journals (Sweden)

    José Marcos Leite

    2016-04-01

    Full Text Available Unraveling nutrient imbalances in contemporary agriculture is a research priority to improve whenever possible yield and nutrient use efficiency in sugarcane (Saccharum spp. systems while minimizing the costs of cultivation (e.g., use of fertilizers and environmental concerns. The main goal of this study was therefore to investigate biomass and nutrient [nitrogen (N, phosphorus (P, and potassium (K] content, partitioning, stoichiometry and internal efficiencies in sugarcane ratoon at varying yield levels. Three sites were established on highly weathered tropical soils located in the Southeast region of Brazil. At all sites, seasonal biomass and nutrient uptake patterns were synthesized from four sampling times taken throughout the sugarcane ratoon season. At all sites, in-season nutrient partitioning (in diverse plant components, internal efficiencies (yield to nutrient content ratio and nutrient ratios (N:P and N:K were determined at harvesting. Sugarcane exhibited three distinct phases of plant growth, as follows: lag, exponential-linear, and stationary. Across sites, nutrient requirement per unit of yield was 1.4 kg N, 0.24 kg P, and 2.7 kg K per Mg of stalk produced, but nutrient removal varied with soil nutrient status (based on soil plus fertilizer nutrient supply and crop demand (potential yield. Dry leaves had lower nutrient content (N, P, and K and broader N:P and N:K ratios when compared with tops and stalks plant fractions. Greater sugarcane yield and narrowed N:P ratio (6:1 were verified for tops of sugarcane when increasing both N and P content. High-yielding sugarcane systems were related to higher nutrient content and more balanced N:P (6:1 and N:K (0.5:1 ratios.

  15. Preparation and characterization of polymer-derived amorphous silicon carbide with silicon-rich stoichiometry

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Takashi, E-mail: mtakashi@jaist.ac.jp [School of Material and Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Iwasaka, Akira [School of Material and Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Takagishi, Hideyuki [Faculty of Symbiotic System Science, Fukushima University, 1 Kanayagawa, Fukushima-shi, Fukushima 960-1296 (Japan); Shimoda, Tatsuya [School of Material and Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2016-08-01

    Polydihydrosilane with pendant hexyl groups was synthesized to obtain silicon-rich amorphous silicon carbide (a-SiC) films via the solution route. Unlike conventional polymeric precursors, this polymer requires neither catalysts nor oxidation for its synthesis and cross-linkage. Therefore, the polymer provides sufficient purity for the fabrication of semiconducting a-SiC. Here, we investigated the correlation of Si/C stoichiometry between the polymer and the resultant a-SiC film. The structural, optical, and electrical properties of the films with various carbon contents were also explored. Experimental results suggested that the excess carbon that did not participate in Si−C configurations was decomposed and was evaporated during polymer-to-SiC conversion. Consequently, the upper limit of the carbon in resultant a-SiC film was < 50 at.%; namely, the polymer provided silicon-rich a-SiC, whereas the conventionally used polycarbosilane inevitably provides carbon-rich one. These features of this unusual polymer open up a frontier of polymer-derived SiC and solution-processed SiC electronics. - Highlights: • Polymeric precursor solution for silicon carbide (SiC) is synthesized. • Semiconducting amorphous SiC is prepared via solution route. • The excess carbon is decomposed during cross-linking resulting in Si-rich SiC films. • The grown SiC films contain substantial amount of hydrogen atoms as SiH{sub n}/CH{sub n} entities. • Presence of CH{sub n} entities induces dangling bonds, causing poor electrical properties.

  16. Nutrient Stoichiometry Shapes Microbial Community Structure in an Evaporitic Shallow Pond

    Directory of Open Access Journals (Sweden)

    Zarraz M.-P. Lee

    2017-05-01

    Full Text Available Nutrient availability and ratios can play an important role in shaping microbial communities of freshwater ecosystems. The Cuatro Ciénegas Basin (CCB in Mexico is a desert oasis where, perhaps paradoxically, high microbial diversity coincides with extreme oligotrophy. To better understand the effects of nutrients on microbial communities in CCB, a mesocosm experiment was implemented in a stoichiometrically imbalanced pond, Lagunita, which has an average TN:TP ratio of 122 (atomic. The experiment had four treatments, each with five spatial replicates – unamended controls and three fertilization treatments with different nitrogen:phosphorus (N:P regimes (P only, N:P = 16 and N:P = 75 by atoms. In the water column, quantitative PCR of the 16S rRNA gene indicated that P enrichment alone favored proliferation of bacterial taxa with high rRNA gene copy number, consistent with a previously hypothesized but untested connection between rRNA gene copy number and P requirement. Bacterial and microbial eukaryotic community structure was investigated by pyrosequencing of 16S and 18S rRNA genes from the planktonic and surficial sediment samples. Nutrient enrichment shifted the composition of the planktonic community in a treatment-specific manner and promoted the growth of previously rare bacterial taxa at the expense of the more abundant, potentially endemic, taxa. The eukaryotic community was highly enriched with phototrophic populations in the fertilized treatment. The sediment microbial community exhibited high beta diversity among replicates within treatments, which obscured any changes due to fertilization. Overall, these results showed that nutrient stoichiometry can be an important factor in shaping microbial community structure.

  17. Reversal of sodium pump inhibitor induced vascular smooth muscle contraction with digibind. Stoichiometry and its implications.

    Science.gov (United States)

    Krep, H H; Graves, S W; Price, D A; Lazarus, M; Ensign, A; Soszynski, P A; Hollenberg, N K

    1996-01-01

    The possibility that a circulating sodium pump inhibitor contributes to the pathogenesis of volume-dependent hypertension via an action on vascular smooth muscle (VSM) is supported by multiple lines of investigation, but remains controversial. We had two goals in this study. The first was to compare the pattern of contractile response of rabbit aorta induced by two candidates, ouabain and a labile sodium pump inhibitor that we have identified in the peritoneal dialysate of volume-expanded hypertensive patients with chronic renal failure. Our second goal was to examine the ability of Digibind, a Fab fragment of antisera directed against digoxin, to reverse VSM contraction induced by both agents. Ouabain induced a concentration-dependent contraction, which was delayed in onset, was gradual, and reached a stable plateau after many hours. The labile sodium pump inhibitor induced a qualitatively similar series of responses. Digibind rapidly reversed the contractile responses to both sodium pump inhibitors, with a rate of relaxation that matched that induced by physical removal of the pump inhibitor from the bath. For ouabain, the Digibind:ouabain stoichiometry was highly predictable. When Digibind was present in a molar concentration equivalent to that of ouabain, or less, it had no effect. When the Digibind concentration was twice that of ouabain, complete relaxation occurred. Although the concentration:VSM response relationship for ouabain was steep, the concentration:effect interaction with Digibind was even more steep. The molar concentration of Digibind required to reverse the effects of the labile endogenous inhibitor from peritoneal dialysate was consistently lower than that for ouabain, which is compatible with either greater potency of the labile factor in VSM or greater affinity for Digibind. These findings are compatible with a role for one or more endogenous sodium pump inhibitors as the determinant of vascular smooth muscle tone in the volume

  18. H+ stoichiometry of sites 1 + 2 of the respiratory chain of normal and tumor mitochondria

    Energy Technology Data Exchange (ETDEWEB)

    Villalobo, A.; Alexandre, A.; Lehninger, A.L.

    1984-09-01

    The mechanistic stoichiometry for vectorial H+ ejection coupled to electron transport through energy-conserving segments 1 + 2 was determined on cyanide-inhibited mitochondria from rat liver, rat heart, and Ehrlich ascites tumor cells, and on rat liver mitoplasts with ferricyanide or ferricytochrome c as electron acceptors. K+ (+ valinomycin) and Ca2+ were employed as permeant cations. Three different methods were employed. In the first, known pulses of ferricyanide were added, and the total H+ ejected was determined with a glass electrode. Such measurements gave H+/2e-values exceeding 7.0 for both normal and tumor mitochondria with beta-hydroxybutyrate and other NAD-linked substrates; uptake of Ca2+ was also measured and gave the expected q+/2e-ratios. The second type of measurement was initiated by addition of ferricytochrome c to rat liver mitoplasts, with H+ ejection monitored with the glass electrode and ferricytochrome c reduction by dual-wavelength spectrophotometry; the H+/2e-ratios generally exceeded 7.0. In the third type of measurement, mixing and dilution artifacts were eliminated by oxidizing ferrocytochrome c in situ with a small amount of ferricyanide. H+/2e-ratios for rat liver mitoplasts oxidizing beta-hydroxybutyrate consistently approached or exceeded 7.5. Over 150 measurements made under a variety of conditions gave observed H+/2e-ejection ratios significantly exceeding 7.0, which correlated closely with H+/2e-measurements on sites 1 + 2 + 3, sites 2 + 3, and site 2. Factors leading to the deficit of the observed ratios from the integral value 8 for sites 1 + 2 were discussed.

  19. Upper and lower limits of the proton stoichiometry of cytochrome c oxidation in rat liver mitoplasts.

    Science.gov (United States)

    Reynafarje, B; Costa, L E; Lehninger, A L

    1986-06-25

    The stoichiometry of vectorial H+ translocation coupled to oxidation of added ferrocytochrome c by O2 via cytochrome-c oxidase of rat liver mitoplasts was determined employing a fast-responding O2 electrode. Electron flow was initiated by addition of either ferrocytochrome c or O2. When the rates were extrapolated to level flow, the H+/O ratios in both cases were less than but closely approached 4; the directly observed H+/O ratios significantly exceeded 3.0. The mechanistic H+/O ratio was then more closely fixed by a kinetic approach that eliminates the necessity for measuring energy leaks and is independent of any particular model of the mechanism of energy transduction. From two sets of kinetic measurements, an overestimate and an underestimate and thus the upper and lower limits of the mechanistic H+/O ratio could be obtained. In the first set, the utilization of respiratory energy was systematically varied through changes in the concentrations of valinomycin or K+. From the slope of a plot of the initial rates of H+ ejection (JH) and O2 uptake (JO) obtained in such experiments, the upper limit of the H+/O ratio was in the range 4.12-4.19. In the second set of measurements, the rate of respiratory energy production was varied by inhibiting electron transport. From the slope of a plot of JH versus JO, the lower limit of the H+/O ratio, equivalent to that at level flow, was in the range 3.83-3.96. These data fix the mechanistic H+/O ratio for the cytochrome oxidase reaction of mitoplasts at 4.0, thus confirming our earlier measurements (Reynafarje, B., Alexandre, A., Davies, P., and Lehninger, A. L. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 7218-7222). Possible reasons for discrepancies in published reports on the H+/O ratio of cytochrome oxidase in various mitochondrial and reconstituted systems are discussed.

  20. Molecular Dynamics study of the effects of non-stoichiometry and oxygen Frenkel pairs on the thermal conductivity of uranium dioxide

    International Nuclear Information System (INIS)

    Nichenko, Sergii; Staicu, Dragos

    2013-01-01

    In the present work, calculations of the thermal conductivity of UO 2 were carried out applying classical Molecular Dynamics for the isothermal-isobaric (NPT) statistical ensemble, using the Green–Kubo approach. The thermal conductivity calculated for perfect stoichiometric UO 2 is in good agreement with the literature data over the temperature range corresponding to heat transfer by phonons (up to 1700 K). The effect of non-stoichiometry on the thermal conductivity was calculated taking into account the presence of polarons. It was found that for the same value of the stoichiometry deviation, the effect of oxygen vacancies (hypo-stoichiometry) is more pronounced than the effect of oxygen interstitials (hyper-stoichiometry). Then the influence of the oxygen Frenkel pairs on the thermal conductivity was calculated. The simultaneous impact of non-stoichiometry and OFP on the thermal conductivity was investigated and it was shown that the two effects can be combined using the interpretation obtained with the classical phonons scattering theory. Finally, simplified correlations were deduced for the calculation of the thermal conductivity of UO 2 taking into account the effect of non-stoichiometry and of Frenkel pairs, these two effects being present during irradiation

  1. Taxonomic and Environmental Variability in the Elemental Composition and Stoichiometry of Individual Dinoflagellate and Diatom Cells from the NW Mediterranean Sea.

    Directory of Open Access Journals (Sweden)

    Mariona Segura-Noguera

    Full Text Available Here we present, for the first time, the elemental concentration, including C, N and O, of single phytoplankton cells collected from the sea. Plankton elemental concentration and stoichiometry are key variables in phytoplankton ecophysiology and ocean biogeochemistry, and are used to link cells and ecosystems. However, most field studies rely on bulk techniques that overestimate carbon and nitrogen because the samples include organic matter other than plankton organisms. Here we used X-ray microanalysis (XRMA, a technique that, unlike bulk analyses, gives simultaneous quotas of C, N, O, Mg, Si, P, and S, in single-cell organisms that can be collected directly from the sea. We analysed the elemental composition of dinoflagellates and diatoms (largely Chaetoceros spp. collected from different sites of the Catalan coast (NW Mediterranean Sea. As expected, a lower C content is found in our cells compared to historical values of cultured cells. Our results indicate that, except for Si and O in diatoms, the mass of all elements is not a constant fraction of cell volume but rather decreases with increasing cell volume. Also, diatoms are significantly less dense in all the measured elements, except Si, compared to dinoflagellates. The N:P ratio of both groups is higher than the Redfield ratio, as it is the N:P nutrient ratio in deep NW Mediterranean Sea waters (N:P = 20-23. The results suggest that the P requirement is highest for bacterioplankton, followed by dinoflagellates, and lowest for diatoms, giving them a clear ecological advantage in P-limited environments like the Mediterranean Sea. Finally, the P concentration of cells of the same genera but growing under different nutrient conditions was the same, suggesting that the P quota of these cells is at a critical level. Our results indicate that XRMA is an accurate technique to determine single cell elemental quotas and derived conversion factors used to understand and model ocean biogeochemical

  2. Integrated survey of elemental stoichiometry (C, N, P from the western to eastern Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    M. Pujo-Pay

    2011-04-01

    Full Text Available This paper provides an extensive vertical and longitudinal description of the biogeochemistry along an East-West transect of 3000 km across the Mediterranean Sea during summer 2008 (BOUM cruise. During this period of strong stratification, the distribution of nutrients, particulate and dissolved organic carbon (DOC, nitrogen (DON and phosphorus (DOP were examined to produce a detailed spatial and vertically extended description of the elemental stoichiometry of the Mediterranean Sea. Surface waters were depleted in nutrients and the thickness of this depleted layer increased towards the East from about 10 m in the Gulf of Lion to more than 100 m in the Levantine basin, with the phosphacline deepening to a greater extent than that for corresponding nitracline and thermocline depths. We used the minimum oxygen concentration through the water column in combination with 2 fixed concentrations of dissolved oxygen to distinguish an intermediate layer (Mineralization Layer; ML from surface (Biogenic Layer; BL, and deep layers (DL. Whilst each layer was represented by different water masses, this approach allowed us to propose a schematic box-plot representation of the biogeochemical functioning of the two Mediterranean basins. Despite the increasing oligotrophic nature and the degree of P-depletion along the West to East gradient strong similarities were encountered between eastern and western ecosystems. Within the BL, the C:N:P ratios in all pools largely exceeded the Redfield ratios, but surprisingly, the nitrate vs. phosphate ratios in the ML and DL tended towards the canonical Redfield values in both basins. A change in particulate matter composition has been identified by a C increase relative to N and P along the whole water column in the western basin and between BL and ML in the eastern one. Our data showed a noticeable stability of the DOC:DON ratio (12–13 throughout the Mediterranean Sea. This is in good agreement with a P-limitation of

  3. Effects of stoichiometry and neutron irradiation in superconducting A-15 compounds

    International Nuclear Information System (INIS)

    Moehlecke, S.

    1978-01-01

    The A-15 (A 3 B) compounds comprise an important class of superconducting compounds. In order to gain a clearer understanding of the parameters influencing the superconductivity in these materials, several A-15 compounds have been prepared and the effects of varying stoichiometry, heat treatment, and irradiation with high energy neutrons (E > 1 MeV) on the superconducting transition temperature T/sub c/, Bragg--William order parameter S, and the lattice parameter a 0 , have been studied. The systems investigated include Nb 3 Ge, Nb 3 Al, Nb 3 Pt, Nb 3 Ir, V 3 Ga, V 3 Si and Mo 3 Os. Some of the results may be summarized as follows: 1) for Nb 3 Al, Nb 3 Pt and V 3 Ga, T/sub c/ is a strong function of composition, reaching a maximum value at the ideal stoichiometric composition of 3A: 1B, if that composition exists in the equilibrium phase diagram, 2) irradiation with high energy neutrons at temperatures of approx.150 0 C results in drastic lowering of T/sub c/ for Nb 3 Al, Nb 3 Pt and Nb 3 Ge, but not for Mo 3 Os, 3) T/sub c/ can be recovered by annealing, the recovery temperature being in the range 300-800 0 C depends on the particular compound, 4) the order parameter S, decreases with increasing neutron fluence (decreasing T/sub c/), and is also recoverable upon annealing at the appropriate temperature, 5) the lattice parameter a 0 , increases with increasing neutron fluence, and isalso restored to its original value by annealing. A simple hard sphere model is developed to calculate the dependence of a 0 on composition within the A-15 phase. Excellent agreement is obtained for the measured values in the Nb--Al, Nb--Pt and V--Ga systems. The results of both compositionally and irradiation induced disorder can be understood on the basis of site-exchange taking placee between the A and B sites in the A-15 structure

  4. Variation of crystallinity and stoichiometry in films of gallium oxide, gallium nitride and barium zirconate prepared by means of PLD

    International Nuclear Information System (INIS)

    Brendt, Jochen

    2011-01-01

    Pulsed Laser Deposition (PLD) is an ablation technique for thin film preparation of many materials. The film properties can be well controlled by the process parameters. Therefore, in many cases a given material can be deposited with different properties by changing one or more process parameters. In this thesis thin films of gallium oxide, gallium nitride and barium zirconate were deposited with a large variation in structure and stoichiometry by means of Pulsed Laser Deposition. The characterization of the film crystallinity, phase purity and short range structural order was completed by means of X-ray diffraction and X-ray absorption spectroscopy. The stoichiometry was investigated using electron probe microanalysis. For analyzing the correlation between the structure and stoichiometry with the optical and electrical properties, optical absorption and electrical conductivity measurements were carried out. The investigation of all three material systems showed that very unique properties can be realized when combining an amorphous structure and a non-stoichiometric composition. For example, in amorphous and oxygen deficient gallium oxide an insulator-metal-transition can be induced by partial crystallization of the as prepared phase accomplished by annealing at about 400 C in argon atmosphere (as shown in literature). Furthermore, amorphous and highly non-stoichiometric barium zirconate has the ability to split water molecules to hydrogen and oxygen at room temperature. A detailed analysis of both phenomena has been performed by means of photoemission and transmission electron microscopy in the case of gallium oxide and via X-ray absorption spectroscopy and gas chromatography in the case of barium zirconate.

  5. Effect of Wind on the Relation of Leaf N, P Stoichiometry with Leaf Morphology in Quercus Species

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2018-02-01

    Full Text Available Leaf nitrogen (N and phosphorus (P stoichiometry correlates closely to leaf morphology, which is strongly impacted by wind at multiple scales. However, it is not clear how leaf N, P stoichiometry and its relationship to leaf morphology changes with wind load. We determined the leaf N and P concentrations and leaf morphology—including specific leaf area (SLA and leaf dissection index (LDI—for eight Quercus species under a simulated wind load for seven months. Leaf N and P concentrations increased significantly under these conditions for Quercus acutissima, Quercus rubra, Quercus texana, and Quercus palustris—which have elliptic leaves—due to their higher N, P requirements and a resultant leaf biomass decrease, which is a tolerance strategy for Quercus species under a wind load. Leaf N:P was relatively stable under wind for all species, which supports stoichiometric homeostasis. Leaf N concentrations showed a positive correlation to SLA, leaf N and P concentrations showed positive correlations to LDI under each wind treatment, and the slope of correlations was not affected by wind, which indicates synchronous variations between leaf stoichiometry and leaf morphology under wind. However, the intercept of correlations was affected by wind, and leaf N and P use efficiency decreased under the wind load, which suggests that the Quercus species changes from “fast investment-return” in the control to “slow investment-return” under windy conditions. These results will be valuable to understanding functional strategies for plants under varying wind loads, especially synchronous variations in leaf traits along a wind gradient.

  6. Effect of charge state and stoichiometry on the structure and reactivity of nickel oxide clusters with CO

    Science.gov (United States)

    Johnson, Grant E.; Reilly, Nelly M.; Castleman, A. W., Jr.

    2009-02-01

    The collision induced fragmentation and reactivity of cationic and anionic nickel oxide clusters with carbon monoxide were studied experimentally using guided-ion-beam mass spectrometry. Anionic clusters with a stoichiometry containing one more oxygen atom than nickel atom (NiO2-, Ni2O3-, Ni3O4- and Ni4O5-) were found to exhibit dominant products resulting from the transfer of a single oxygen atom to CO, suggesting the formation of CO2. Of these four species, Ni2O3- and Ni4O5- were observed to be the most reactive having oxygen transfer products accounting for approximately 5% and 10% of the total ion intensity at a maximum pressure of 15 mTorr of CO. Our findings, therefore, indicate that anionic nickel oxide clusters containing an even number of nickel atoms and an odd number of oxygen atoms are more reactive than those with an odd number of nickel atoms and an even number of oxygen atoms. The majority of cationic nickel oxides, in contrast to anionic species, reacted preferentially through the adsorption of CO onto the cluster accompanied by the loss of either molecular O2 or nickel oxide units. The adsorption of CO onto positively charged nickel oxides, therefore, is exothermic enough to break apart the gas-phase clusters. Collision induced dissociation experiments, employing inert xenon gas, were also conducted to gain insight into the structural properties of nickel oxide clusters. The fragmentation products were found to vary considerably with size and stoichiometry as well as ionic charge state. In general, cationic clusters favored the collisional loss of molecular O2 while anionic clusters fragmented through the loss of both atomic oxygen and nickel oxide units. Our results provide insight into the effect of ionic charge state on the structure of nickel oxide clusters. Furthermore, we establish how the size and stoichiometry of nickel oxide clusters influences their ability to oxidize CO, an important reaction for environmental pollution abatement.

  7. High Variability in Cellular Stoichiometry of Carbon, Nitrogen, and Phosphorus Within Classes of Marine Eukaryotic Phytoplankton Under Sufficient Nutrient Conditions.

    Science.gov (United States)

    Garcia, Nathan S; Sexton, Julie; Riggins, Tracey; Brown, Jeff; Lomas, Michael W; Martiny, Adam C

    2018-01-01

    Current hypotheses suggest that cellular elemental stoichiometry of marine eukaryotic phytoplankton such as the ratios of cellular carbon:nitrogen:phosphorus (C:N:P) vary between phylogenetic groups. To investigate how phylogenetic structure, cell volume, growth rate, and temperature interact to affect the cellular elemental stoichiometry of marine eukaryotic phytoplankton, we examined the C:N:P composition in 30 isolates across 7 classes of marine phytoplankton that were grown with a sufficient supply of nutrients and nitrate as the nitrogen source. The isolates covered a wide range in cell volume (5 orders of magnitude), growth rate (temperature (2-24°C). Our analysis indicates that C:N:P is highly variable, with statistical model residuals accounting for over half of the total variance and no relationship between phylogeny and elemental stoichiometry. Furthermore, our data indicated that variability in C:P, N:P, and C:N within Bacillariophyceae (diatoms) was as high as that among all of the isolates that we examined. In addition, a linear statistical model identified a positive relationship between diatom cell volume and C:P and N:P. Among all of the isolates that we examined, the statistical model identified temperature as a significant factor, consistent with the temperature-dependent translation efficiency model, but temperature only explained 5% of the total statistical model variance. While some of our results support data from previous field studies, the high variability of elemental ratios within Bacillariophyceae contradicts previous work that suggests that this cosmopolitan group of microalgae has consistently low C:P and N:P ratios in comparison with other groups.

  8. Role of an extracellular loop in determining the stoichiometry of Na+–HCO3− cotransporters

    Science.gov (United States)

    Chen, Li-Ming; Liu, Ying; Boron, Walter F

    2011-01-01

    The Na+–HCO3− cotransporters (NBCs) of the solute carrier 4 family (SLC4) are critical for regulating pH in cells as well as in fluids such as blood and cerebrospinal fluid. Moreover, mutations and gene disruptions in NBC are linked to a wide range of pathologies. NBCe1 (SLC4A4) is electrogenic because it has an apparent Na+:HCO3− stoichiometry of 1:2 or 1:3, whereas NBCn1 (SLC4A7) is electroneutral because it has an apparent stoichiometry of 1:1. Because stoichiometry influences the effect of transport on membrane potential and vice versa, a central question is what structural features underlie electrogenicity versus electroneutrality. A previous study on rat NBCe1/n1 chimeras demonstrated that the structural elements determining the electrogenicity of NBCe1-A are located within the transmembrane domain, excluding the large third extracellular loop. In the present study we generated a series of chimeras of human NBCe1-A and human NBCn1-A. We found that replacing merely the predicted fourth extracellular loop (EL4) – containing 32 amino acid residues that include 7 prolines – of human NBCe1-A with EL4 of NBCn1-A creates an electroneutral NBC. The opposite switch converts an electroneutral construct to one with electrogenic properties. The introduction of an N-glycosylation site into EL4 confirms that at least a part of it is exposed to the extracellular fluid. We hypothesize that putative EL4 either contributes to the substrate-binding vestibule or indirectly influences substrate binding by interacting with one or more transmembrane segments, thereby controlling the nature of transport. PMID:21224233

  9. Oxygen Stoichiometry in Cation Deficient (La,Sr)_{1-z}MnO_3 SOFC Cathode Materials

    DEFF Research Database (Denmark)

    Zachau-Christiansen, Birgit; Jacobsen, Torben; Skaarup, Steen

    1997-01-01

    by the imposed potential.It is found that the oxygen stoichiometry and hence the defect chemistry is different whether A-site charge deficiency is established by Sr-doping or by A-site vacancies. Furthermore,A-site deficient lanthanum strontium manganates expel a secondary phase of manganese oxide when exposed...... to low oxygen partial pressures. The presence of small amounts of secondary phase isobserved and identified by its reoxidation peak. The amount of this foreign phase is determined by the charge used for its oxidation....

  10. A simple wet chemical method for the determination of cation stoichiometry of YBa2Cu3O7-d

    International Nuclear Information System (INIS)

    Sahasranaman, S.; Premila, M.; Sreedharan, O.M.

    1996-01-01

    A comprehensive wet chemical procedure for the rapid analysis of yttrium, barium and copper ions in dilute HNO 3 medium has been developed to facilitate a precise and accurate determination of cation non-stoichiometry in high temperature ceramic superconducting materials Y 1±x Ba 2±y Cu 3±z O 7-d . The ease of analysis for copper by electrogravimetry and of yttrium and barium by a complexometric titration of the same aliquot against complexone III using arsenazo I as the indicator under appropriate pH has been demonstrated with the help of individual standard solutions and with synthetic mixtures. (author)

  11. Effect of the Reburning Zone Stoichiometry on the Nox Concentration at the Three-Stage Combustion of Pulverized Coal

    Directory of Open Access Journals (Sweden)

    Chernetskaya Nelya

    2016-01-01

    Full Text Available Numerical study of heat and mass transfer taking into account the combustion of coal particles in the furnace at the three-stage combustion of pulverized coal was performed. Analysis of the reburning zone stoichiometry on the concentration of nitrogen oxides at the furnace outlet was made. The values of excess air in the primary and reburning combustion zones, providing for the concentration of nitrogen oxides at the furnace outlet is not more than 350 mg/m3 and unburned carbon not more than 1 % when burning coal with a high content of nitrogen were established.

  12. Supporting traditional instructional methods with a constructivist approach to learning: Promoting conceputal change and understanding of stoichiometry using e-learning tools

    Science.gov (United States)

    Abayan, Kenneth Munoz

    Stoichiometry is a fundamental topic in chemistry that measures a quantifiable relationship between atoms, molecules, etc. Stoichiometry is usually taught using expository teaching methods. Students are passively given information, in the hopes they will retain the transmission of information to be able to solve stoichiometry problems masterfully. Cognitive science research has shown that this kind of instructional teaching method is not very effecting in meaningful learning practice. Instead, students must take ownership of their learning. The students need to actively construct their own knowledge by receiving, interpreting, integrating and reorganizing that information into their own mental schemas. In the absence of active learning practices, tools must be created in such a way to be able to scaffold difficult problems by encoding opportunities necessary to make the construction of knowledge memorable, thereby creating a usable knowledge base. Using an online e-learning tool and its potential to create a dynamic and interactive learning environment may facilitate the learning of stoichiometry. The study entailed requests from volunteer students, IRB consent form, a baseline questionnaire, random assignment of treatment, pre- and post-test assessment, and post assessment survey. These activities were given online. A stoichiometry-based assessment was given in a proctored examination at the University of Texas at Arlington (UTA) campus. The volunteer students who took part in these studies were at least 18 of age and were enrolled in General Chemistry 1441, at the University of Texas at Arlington. Each participant gave their informed consent to use their data in the following study. Students were randomly assigned to one of 4 treatments groups based on teaching methodology, (Dimensional Analysis, Operational Method, Ratios and Proportions) and a control group who just received instruction through lecture only. In this study, an e-learning tool was created to

  13. Superconductivity in CeCu/sub 2/Si/sub 2/: dependence of Tsub(c) on alloying and stoichiometry

    Energy Technology Data Exchange (ETDEWEB)

    Spille, H; Rauchschwalbe, U; Steglich, F [Technische Hochschule Darmstadt (Germany, F.R.). Inst. fuer Festkoerperphysik

    1938-01-01

    The authors have determined the transition temperatures of the alloy systems (Ce,M)Cu/sub 2/Si/sub 2/ with M = La, Y, Sc, Ce(Cu,T)/sub 2/Si/sub 2/ with T = Ag, Au, Mn, Ru, Rh, Pd and CeCu/sub 2/(Si,Ge)/sub 2/ as well as of CeCu/sub 2/Si/sub 2/ samples with varying stoichiometry. In each case, alloying is found to depress Tsub(c), the critical concentrations necessary to destroy superconductivity ranging between < 1 at.% and 10 at.%. Off-stoichiometry samples with a Cu- or Ce-deficiency of a few at.% are not superconducting, while samples prepared with a comparable excess of Cu or Ce show sharp transitions at Tsub(c) >approx. 600 mK. It is inferred that stoichiometric CeCu/sub 2/Si/sub 2/ contains substantial concentrations of Cu- and Ce-vacancies, which hinder superconductivity. First results on CeCu/sub 2/Si/sub 2/ single crystals, which exhibit bulk superconductivity, are also reported.

  14. The effect of nutrient enrichment on the growth, nucleic acid concentrations, and elemental stoichiometry of coral reef macroalgae.

    Science.gov (United States)

    Reef, Ruth; Pandolfi, John M; Lovelock, Catherine E

    2012-08-01

    The growth rate hypothesis (GRH) links growth rates with organism elemental stoichiometry. Support for the GRH was found for many animal species, but less so for plants. This is the first study to test the GRH in macroalgae. Tropical coral reef macroalgae from three lineages, Caulerpa serrulata (Chlorophyta), Laurencia intricata (Rhodophyta), and Sargassum polyphyllum (Phaeophyceae) were grown enriched with nitrogen or phosphorous and under control conditions at Heron Island on the Great Barrier Reef, Australia. Growth rate, photosynthesis, nucleic acid composition, and elemental stoichiometry were measured. Nutrient enrichment had positive effects on photosynthetic rates and on investment in RNA. However, growth rate was not correlated with either photosynthetic rates or RNA content; thus, we did not find support for the GRH in tropical macroalgae. Macroalgae, especially L. intricata, accumulated P to very high levels (>0.6% of dry weight). The growth rate response to tissue P concentrations was unimodal. Above 0.21%, P accumulation had negative effects on growth. Nitrogen was not stored, but evidence of futile cycling was observed. The capacity to store large amounts of P is probably an adaptation to the low and patchy nutrient environment of the tropical oceans.

  15. Rapid top-down regulation of plant C:N:P stoichiometry by grasshoppers in an Inner Mongolia grassland ecosystem.

    Science.gov (United States)

    Zhang, Guangming; Han, Xingguo; Elser, James J

    2011-05-01

    Understanding how food web interactions alter the processing of limiting nutrient elements is an important goal of ecosystem ecology. An experiment manipulating densities of the grasshopper Oedaleus asiaticus was performed to assess top-down effects of grasshoppers on C:N:P stoichiometry of plants and soil in a grassland ecosystem in Inner Mongolia (China). With increased grasshopper feeding, plant biomass declined fourfold, litter abundance increased 30%, and the plant community became dominated by non-host plant taxa. Plant stoichiometric response depended on whether or not the plant was a grasshopper host food species: C:N and C:P ratios increased with increasing grasshopper density (GD) for host plants but decreased in non-host plants. These data suggest either a direct transfer of grasshopper-recycled nutrients from host to non-host plants or a release of non-host plants from nutrient competition with heavily grazed host plants. Litterfall C:N and C:P decreased across moderate levels of grasshopper density but no effects on C:N:P stoichiometry in the surface soil were observed, possibly due to the short experimental period. Our observations of divergent C:N:P stoichiometric response among plant species highlight the important role of grasshopper herbivory in regulating plant community structure and nutrient cycling in grassland ecosystems.

  16. Interplay between structure, stoichiometry, and electron transfer dynamics in SILAR-based quantum dot-sensitized oxides.

    Science.gov (United States)

    Wang, Hai; Barceló, Irene; Lana-Villarreal, Teresa; Gómez, Roberto; Bonn, Mischa; Cánovas, Enrique

    2014-10-08

    We quantify the rate and efficiency of picosecond electron transfer (ET) from PbS nanocrystals, grown by successive ionic layer adsorption and reaction (SILAR), into a mesoporous SnO2 support. Successive SILAR deposition steps allow for stoichiometry- and size-variation of the QDs, characterized using transmission electron microscopy. Whereas for sulfur-rich (p-type) QD surfaces substantial electron trapping at the QD surface occurs, for lead-rich (n-type) QD surfaces, the QD trapping channel is suppressed and the ET efficiency is boosted. The ET efficiency increase achieved by lead-rich QD surfaces is found to be QD-size dependent, increasing linearly with QD surface area. On the other hand, ET rates are found to be independent of both QD size and surface stoichiometry, suggesting that the donor-acceptor energetics (constituting the driving force for ET) are fixed due to Fermi level pinning at the QD/oxide interface. Implications of our results for QD-sensitized solar cell design are discussed.

  17. Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe.

    Science.gov (United States)

    Jiroušek, Martin; Hájek, Michal; Bragazza, Luca

    2011-02-01

    We investigated the variation of N:P and N:K ratio in ombrotrophic Sphagnum plants along a gradient of atmospheric N deposition from 1 to 2.5 g m(-2) year(-1) in Central-East Europe. The N:P and N:K ratio in Sphagnum capitula increased significantly along the N deposition gradient. Sphagnum species from the Cuspidata section were characterised by significantly lower ratios at low N deposition. When we compared the observed N:P ratios in Sphagnum plants with the values reported in a previous European-wide study, we found a correspondence in nutrient stoichiometry only for a few bogs: higher P concentration in Sphagnum capitula caused a lower N:P ratio in most of the study bogs so that Sphagnum plants still seem N-limited despite their N saturation. Interaction between summer water table decrease and aerial liming of surrounding forests is proposed as an explanation for this discrepancy. Local forestry practice interacting with climate thus alter N:P stoichiometry of Sphagnum along the N deposition gradient. Copyright © 2010 Elsevier Ltd. All rights reserved.

  18. Influence of the reaction stoichiometry on the mechanical and thermal properties of SWCNT-modified epoxy composites

    International Nuclear Information System (INIS)

    Ashrafi, Behnam; Johnston, Andrew; Martinez-Rubi, Yadienka; Kingston, Christopher T; Simard, Benoit; Khoun, Lolei; Yourdkhani, Mostafa; Hubert, Pascal

    2013-01-01

    Previous studies suggest that carbon nanotubes (CNTs) have a considerable influence on the curing behavior and crosslink density of epoxy resins. This invariably has an important effect on different thermal and mechanical properties of the epoxy network. This work focuses on the important role of the epoxy/hardener mixing ratio on the mechanical and thermal properties of a high temperature aerospace-grade epoxy (MY0510 Araldite as an epoxy and 4,4′-diaminodiphenylsulfone as an aromatic hardener) modified with single-walled carbon nanotubes (SWCNTs). The effects of three different stoichiometries (stoichiometric and off-stoichiometric) on various mechanical and thermal properties (fracture toughness, tensile properties, glass transition temperature) of the epoxy resin and its SWCNT-modified composites were obtained. The results were also supported by Raman spectroscopy and scanning electron microscopy (SEM). For the neat resin, it was found that an epoxy/hardener molar ratio of 1:0.8 provides the best overall properties. In contrast, the pattern in property changes with the reaction stoichiometry was considerably different for composites reinforced with unfunctionalized SWCNTs and reduced SWCNTs. A comparison among composites suggests that a 1:1 molar ratio considerably outperforms the other two ratios examined in this work (1:0.8 and 1:1.1). This composition at 0.2 wt% SWCNT loading provides the highest overall mechanical properties by improving fracture toughness, ultimate tensile strength and ultimate tensile strain of the epoxy resin by 40%, 34%, 54%, respectively. (paper)

  19. Revealing Linear Aggregates of Light Harvesting Antenna Proteins in Photosynthetic Membranes

    OpenAIRE

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

    2010-01-01

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

  20. Three-dimensional structure and stoichiometry of Helmintosporium victoriae190S totivirus

    International Nuclear Information System (INIS)

    Caston, Jose R.; Luque, Daniel; Trus, Benes L.; Rivas, German; Alfonso, Carlos; Gonzalez, Jose M.; Carrascosa, Jose L.; Annamalai, Padmanaban; Ghabrial, Said A.

    2006-01-01

    Most double-stranded RNA viruses have a characteristic capsid consisting of 60 asymmetric coat protein dimers in a so-called T = 2 organization, a feature probably related to their unique life cycle. These capsids organize the replicative complex(es) that is actively involved in genome transcription and replication. Available structural data indicate that their RNA-dependent RNA polymerase (RDRP) is packaged as an integral capsid component, either as a replicative complex at the pentameric vertex (as in reovirus capsids) or as a fusion protein with the coat protein (as in some totivirus). In contrast with members of the family Reoviridae, there are two well-established capsid arrangements for dsRNA fungal viruses, exemplified by the totiviruses L-A and UmV and the chrysovirus PcV. Whereas L-A and UmV have a canonical T = 2 capsid, the PcV capsid is based on a T = 1 lattice composed of 60 capsid proteins. We used cryo-electron microscopy combined with three-dimensional reconstruction techniques and hydrodynamic analysis to determine the structure at 13.8 A resolution of Helminthosporium victoriae 190S virus (Hv190SV), a totivirus isolated from a filamentous fungus. The Hv190SV capsid has a smooth surface and is based on a T = 2 lattice with 60 equivalent dimers. Unlike the RDRP of some other totiviruses, which are expressed as a capsid protein-RDRP fusion protein, the Hv190SV RDRP is incorporated into the capsid as a separate, nonfused protein, free or non-covalently associated to the capsid interior

  1. Analysis of odorant receptor protein function in the yellow fever mosquito, aedes aegypti

    Science.gov (United States)

    Odorant receptors (ORs) in insects are ligand-gated ion channels comprised of two subunits: a variable receptor and an obligatory co-receptor (Orco). This protein receptor complex of unknown stoichiometry interacts with an odor molecule leading to changes in permeability of the sensory dendrite, th...

  2. Environmentally sensitive probes for monitoring protein-membrane interactions at nanomolar concentrations

    Czech Academy of Sciences Publication Activity Database

    Shvadchak, Volodymyr V.; Kucherak, Oleksandr; Afitska, Kseniia; Dziuba, D.; Yushchenko, Dmytro A.

    2017-01-01

    Roč. 1859, č. 5 (2017), s. 852-859 ISSN 0005-2736 Institutional support: RVO:61388963 Keywords : solvatochromic probes * fluorescence * protein-membrane interaction * affinity * binding stoichiometry * alpha-synuclein Subject RIV: CE - Biochemistry OBOR OECD: Biochemistry and molecular biology Impact factor: 3.498, year: 2016

  3. Manifested luminescence and magnetic responses of stoichiometry dependent Cd{sub 1− x}Mn{sub x}Se quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Sarma, Runjun; Deka, Geetamoni; Mohanta, Dambarudhar, E-mail: best@tezu.ernet.in

    2015-02-15

    Highlights: • Thio-glycolic acid (TGA) coated Cd{sub 1−x}Mn{sub x}Se quantum dots have been prepared with varying x • Formation of QD heterostructure can be expected at a nonzero, but higher value of x. • The deep defect related emission can be attributed to V{sub Cd}–V{sub Se} di-vacancies, which is dominant for smaller values of x. • An appreciable charge transfer between Mn{sup 2+} ions and capping agent TGA is anticipated. - Abstract: We report on stoichiometry dependent manifested physical properties of thioglycolic acid (TGA) coated Cd{sub 1− x}Mn{sub x}Se QDs. While possessing a wurtzite phase, with increasing x, the QDs exhibited a notable blue-shifting of the onset of absorption. Attributed to V{sub Cd}–V{sub Se} di-vacancies, the QDs describe an intense deep-defect related emission response at smaller values of x (=0 to 0.3). Due to the facilitation of magnetic Mn{sup 2+} ion migration from the core to the QD surfaces, {sup 4}T{sub 1}–{sup 6}A{sub 1} transition based Mn{sup 2+} orange emission get suppressed at a higher x (=0.6 to 1). While the FT-IR spectra of the alloyed QDs display characteristic Mn–OH stretching mode at ∼644 cm{sup −1}, the peak located at ∼703 cm{sup −1} is assigned to Cd-Se bending. Furthermore, the QDs with a low x (=0.3), exhibit paramagnetic characteristics owing to the presence of uncorrelated, isolated Mn{sup 2+} spins. The collective luminescence and magnetic features would find immense scope in bio-labeling and imaging applications, apart from solid state luminescent components.

  4. Engineering the microstructure and magnetism of La2CoMnO6−δ thin films by tailoring oxygen stoichiometry

    International Nuclear Information System (INIS)

    Galceran, R.; Frontera, C.; Balcells, Ll.; Cisneros-Fernández, J.; López-Mir, L.; Bozzo, B.; Pomar, A.; Sandiumenge, F.; Martínez, B.; Roqueta, J.; Santiso, J.; Bagués, N.

    2014-01-01

    We report on the magnetic and structural properties of ferromagnetic-insulating La 2 CoMnO 6−δ thin films grown on top of (001) SrTiO 3 substrates by means of RF sputtering technique. Careful structural analysis, by using synchrotron X-ray diffraction, allows identifying two different crystallographic orientations that are closely related to oxygen stoichiometry and to the features (coercive fields and remanence) of the hysteresis loops. Both Curie temperature and magnetic hysteresis turn out to be dependent on the oxygen stoichiometry. In situ annealing conditions allow tailoring the oxygen content of the films, therefore controlling their microstructure and magnetic properties

  5. Crystallization, data collection and data processing of maltose-binding protein (MalE) from the phytopathogen Xanthomonas axonopodis pv. citri

    International Nuclear Information System (INIS)

    Souza, C. S.; Ferreira, L. C. S.; Thomas, L.; Barbosa, J. A. R. G.; Balan, A.

    2009-01-01

    The Xanthomonas axonopodis pv. citri maltose-binding protein MalE has been crystallized at 293 K using the hanging-drop vapour-diffusion method. Maltose-binding protein is the periplasmic component of the ABC transporter responsible for the uptake of maltose/maltodextrins. The Xanthomonas axonopodis pv. citri maltose-binding protein MalE has been crystallized at 293 K using the hanging-drop vapour-diffusion method. The crystal belonged to the primitive hexagonal space group P6 1 22, with unit-cell parameters a = 123.59, b = 123.59, c = 304.20 Å, and contained two molecules in the asymetric unit. It diffracted to 2.24 Å resolution

  6. Identifying the heterotrimeric complex stoichiometry of AMPK in skeletal muscle by immunoprecipitation

    DEFF Research Database (Denmark)

    Birk, Jesper Bratz; Wojtaszewski, Jørgen

    2018-01-01

    The 5'-AMP-activated protein kinase is a complicated enzyme consisting of three different subunits, each of which is expressed as two or three isoforms. This gives the possibility of 12 different heterotrimeric complexes, which could have diverse functions within the cell. To map out which of the...

  7. Possibly similar genetic basis of resistance to Bacillus thuringiensis Cry1Ab protein in 3 resistant colonies of the sugarcane borer collected from Louisiana, USA.

    Science.gov (United States)

    Yang, Fei; Chen, Mao; Gowda, Anilkumar; Kerns, David L; Huang, Fangneng

    2018-04-01

    The sugarcane borer, Diatraea saccharalis (F.), is a major maize borer pest and a target of transgenic maize expressing Bacillus thuringiensis (Bt) proteins in South America and the mid-southern region of the United States. Evolution of resistance in target pest populations is a great threat to the long-term efficacy of Bt crops. In this study, we compared the genetic basis of resistance to Cry1Ab protein in 3 resistant colonies of sugarcane borer established from field populations in Louisiana, USA. Responses of larvae to the Cry1Ab protein for the parental and 10 other cross colonies were assayed in a diet-incorporated bioassay. All 3 resistant colonies were highly resistant to the Cry1Ab protein with a resistance ratio of >555.6 fold. No maternal effect or sex linkage was evident for the resistance in the 3 colonies; and the resistance was functionally nonrecessive at the Cry1Ab concentrations of ≤ 3.16 μg/g, but it became recessive at ≥10 μg/g. In an interstrain complementation test for allelism, the F 1 progeny from crosses between any 2 of the 3 resistant colonies exhibited the similar resistance levels as their parental colonies, indicating that the 3 colonies most likely shared a locus of Cry1Ab resistance. Results generated from this study should provide useful information in developing effective strategies for managing Bt resistance in the insect. © 2016 Institute of Zoology, Chinese Academy of Sciences.

  8. Nasal secretions from patients with polyps and healthy individuals, collected with a new aspiration system: evaluation of total protein and immunoglobulin concentrations

    NARCIS (Netherlands)

    Biewenga, J.; Stoop, A. E.; Baker, H. E.; Swart, S. J.; Nauta, J. J.; van Kamp, G. J.; van der Baan, S.

    1991-01-01

    This study was designed, first, to test a new system for aspiration of human nasal secretions and, secondly, to evaluate protein and immunoglobulin concentrations in these secretions at different levels of secretory activity. The direct aspiration system combines the advantages of minimal irritation

  9. Effect of deviation from stoichiometry on the nature of shallow acceptor states in CdTe crystals

    International Nuclear Information System (INIS)

    Agrinskaya, N.V.; Shashkova, V.V.

    1988-01-01

    Photoconductivity and photoluminescence spectra in the region of donor-acceptor recombination of pure CdTe crystals, grown under conditions of different deviations from stoichiometry are investigated. It is shown that the predominant type of minor acceptors in n-type crystals (with Cd excess) differs from acceptors in p-type crystals (with Te excess). Residual acceptors replacing Te(P, As) prevail in n-type crystals and acceptors replacing Cd(Li, Na) prevail in p-type crystals. As a result of p-type crystal annealing a change of the type of prevailing aceptors accurs in Cd pairs (bands linked with P, As prevail) which testifies to the residual impurity reconstruction in Cd and Te sublattices

  10. Oxygen stoichiometry, superconductivity and structure of the Bi-2212 ceramics after thermal treatment in the inert atmosphere

    International Nuclear Information System (INIS)

    Bratukhin, P.V.; Aksenova, T.D.; Shavkin, S.V.; Komarov, A.O.; Voronkov, S.A.; Mozhaev, A.P.

    1993-01-01

    A complex study of the stoichiometry and superconducting properties has been performed as well as an X-ray structure analysis of Bi 1.6 Pb 0.4 Sr 2 Ca 1 Cu 2 O x ceramic samples after thermal treatment in the helium atmosphere. Annealing has been found to result in the reduction of the oxygen coefficient followed by the critical temperature rise and the decrease of the unit cell parameters which sharply distinguishes Bi2212 from Y123. Anisotropic widening of diffraction lines due to monoclinic distortions has been detected. Correlations between the monoclinic angle and the critical temperature have been disclosed. Structural changes in Bi2122 are 30-100 times smaller than in the Y123 structure under similar changes in T c

  11. Ceramic research on transformational superplasticity and stoichiometry effects on fracture. Research progress report, June 1, 1975--May 31, 1976

    International Nuclear Information System (INIS)

    Bradt, R.C.; Hoke, J.H.

    1976-01-01

    The progress of the program is reviewed by treating each of the areas separately. In the superplasticity investigation, the results of the Bi 2 WO 6 and Bi 2 MoO 3 systems are discussed both in terms of the transformational deformation and also the thermal cycling growth phenomenon. The growth phenomenon on thermal cycling through the phase transition shows some interesting bulk and microstructural features in terms of specimen strain and highly anisotropic grain growth. The stoichiometry effects on the fracture (K/sub Ic/ and K-V behavior) of TiO/sub 2-x/ and Fe/sub 1-x/ are reviewed as that study has been completed. Progress on the MgO . X Al 2 O 3 system is discussed

  12. Variable nutrient stoichiometry (carbon:nitrogen:phosphorus) across trophic levels determines community and ecosystem properties in an oligotrophic mangrove system.

    Science.gov (United States)

    Scharler, U M; Ulanowicz, R E; Fogel, M L; Wooller, M J; Jacobson-Meyers, M E; Lovelock, C E; Feller, I C; Frischer, M; Lee, R; McKee, K; Romero, I C; Schmit, J P; Shearer, C

    2015-11-01

    Our study investigated the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of mangrove island of the Mesoamerican Barrier Reef (Twin Cays, Belize). The C:N:P of abiotic and biotic components of this oligotrophic ecosystem was measured and served to build networks of nutrient flows for three distinct mangrove forest zones (tall seaward fringing forest, inland dwarf forests and a transitional zone). Between forest zones, the stoichiometry of primary producers, heterotrophs and abiotic components did not change significantly, but there was a significant difference in C:N:P, and C, N, and P biomass, between the functional groups mangrove trees, other primary producers, heterotrophs, and abiotic components. C:N:P decreased with increasing trophic level. Nutrient recycling in the food webs was highest for P, and high transfer efficiencies between trophic levels of P and N also indicated an overall shortage of these nutrients when compared to C. Heterotrophs were sometimes, but not always, limited by the same nutrient as the primary producers. Mangrove trees and the primary tree consumers were P limited, whereas the invertebrates consuming leaf litter and detritus were N limited. Most compartments were limited by P or N (not by C), and the relative depletion rate of food sources was fastest for P. P transfers thus constituted a bottleneck of nutrient transfer on Twin Cays. This is the first comprehensive ecosystem study of nutrient transfers in a mangrove ecosystem, illustrating some mechanisms (e.g. recycling rates, transfer efficiencies) which oligotrophic systems use in order to build up biomass and food webs spanning various trophic levels.

  13. Marine ecosystem community carbon and nutrient uptake stoichiometry under varying ocean acidification during the PeECE III experiment

    Directory of Open Access Journals (Sweden)

    R. G. J. Bellerby

    2008-11-01

    Full Text Available Changes to seawater inorganic carbon and nutrient concentrations in response to the deliberate CO2 perturbation of natural plankton assemblages were studied during the 2005 Pelagic Ecosystem CO2 Enrichment (PeECE III experiment. Inverse analysis of the temporal inorganic carbon dioxide system and nutrient variations was used to determine the net community stoichiometric uptake characteristics of a natural pelagic ecosystem perturbed over a range of pCO2 scenarios (350, 700 and 1050 μatm. Nutrient uptake showed no sensitivity to CO2 treatment. There was enhanced carbon production relative to nutrient consumption in the higher CO2 treatments which was positively correlated with the initial CO2 concentration. There was no significant calcification response to changing CO2 in Emiliania huxleyi by the peak of the bloom and all treatments exhibited low particulate inorganic carbon production (~15 μmol kg−1. With insignificant air-sea CO2 exchange across the treatments, the enhanced carbon uptake was due to increase organic carbon production. The inferred cumulative C:N:P stoichiometry of organic production increased with CO2 treatment from 1:6.3:121 to 1:7.1:144 to 1:8.25:168 at the height of the bloom. This study discusses how ocean acidification may incur modification to the stoichiometry of pelagic production and have consequences for ocean biogeochemical cycling.

  14. δ15N and nutrient stoichiometry of water, aquatic organisms and environmental implications in Taihu lake, China.

    Science.gov (United States)

    Tao, Yu; Dan, Dai; Kun, Lei; Chengda, He; Haibing, Cong; Guo, Fu; Qiujin, Xu; Fuhong, Sun; Fengchang, Wu

    2018-06-01

    Nitrogen pollution has become a worldwide problem and the source identification is important for the development of pertinent control measures. In this study, isotope end members (rain, nitrogen fertilizer, untreated/treated sewage), and samples (river water discharging to Taihu lake, lake water, aquatic organisms of different trophic levels) were taken during 2010-2015 to examine their δ 15 N values and nutrient stoichiometry. Results indicated that phytoplankton (primary producers), which directly take up and incorporate N from the lake water, had a similar δ 15 N value (14.1‰ ± 3.2) to the end member of treated sewage (14.0‰ ± 7.5), and the most frequently observed δ 15 N value in the lake water was 8-12‰, both indicating the dominant impact of the sewage discharge. Relationship analysis between N isotope value of nitrate and nitrate concentration indicated that different N cycling existed between the algae-dominated northwest lake (NW) and the macrophyte-dominated southeast lake (SE), which is a result of both impacts of river inputs and denitrification. Our nutrient stoichiometry analysis showed that the lake water had a significantly higher N:P ratio than that of algae (p economic development in the watershed further confirmed that the rapid population increase and urbanization have resulted in a great change in the N loading and source proportion. We suggest that although P control is necessary in terms of eutrophication control, N pollution control is urgent for the water quality and ecological recovery for Taihu lake. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Elemental stoichiometry indicates predominant influence of potassium and phosphorus limitation on arbuscular mycorrhizal symbiosis in acidic soil at high altitude.

    Science.gov (United States)

    Khan, Mohammad Haneef; Meghvansi, Mukesh K; Gupta, Rajeev; Veer, Vijay

    2015-09-15

    The functioning of high-altitude agro-ecosystems is constrained by the harsh environmental conditions, such as low temperatures, acidic soil, and low nutrient supply. It is therefore imperative to investigate the site-specific ecological stoichiometry with respect to AM symbiosis in order to maximize the arbuscular mycorrhizal (AM) benefits for the plants in such ecosystems. Here, we assess the elemental stoichiometry of four Capsicum genotypes grown on acidic soil at high altitude in Arunachal Pradesh, India. Further, we try to identify the predominant resource limitations influencing the symbioses of different Capsicum genotypes with the AM fungi. Foliar and soil elemental stoichiometric relations of Capsicum genotypes were evaluated with arbuscular mycorrhizal (AM) colonization and occurrence under field conditions. AM fungal diversity in rhizosphere, was estimated through PCR-DGGE profiling. Results demonstrated that the symbiotic interaction of various Capsicum genotypes with the AM fungi in acidic soil was not prominent in the study site as evident from the low range of root colonization (21-43.67%). In addition, despite the rich availability of carbon in plant leaves as well as in soil, the carbon-for-phosphorus trade between AMF and plants appeared to be limited. Our results provide strong evidences of predominant influence of the potassium-limitation, in addition to phosphorus-limitation, on AM symbiosis with Capsicum in acidic soil at high altitude. We also conclude that the potassium should be considered in addition to carbon, nitrogen, and phosphorus in further studies investigating the stoichiometric relationships with the AMF symbioses in high altitude agro-ecosystems. Copyright © 2015 Elsevier GmbH. All rights reserved.

  16. Response diversity of free-floating plants to nutrient stoichiometry and temperature: growth and resting body formation

    Directory of Open Access Journals (Sweden)

    Michael J. McCann

    2016-03-01

    Full Text Available Free-floating plants, like most groups of aquatic primary producers, can become nuisance vegetation under certain conditions. On the other hand, there is substantial optimism for the applied uses of free-floating plants, such as wastewater treatment, biofuel production, and aquaculture. Therefore, understanding the species-specific responses of floating plants to abiotic conditions will inform both management decisions and the beneficial applications of these plants. I measured the responses of three floating plant species common in the northeast United States (Lemna minor, Spirodela polyrhiza, and Wolffia brasiliensis to nutrient stoichiometry (nitrogen and phosphorus and temperature in the laboratory. I also used survey data to determine the pattern of species richness of floating plants in the field and its relationship with the dominance of this group. Floating plant species exhibited unique responses to nutrient stoichiometry and temperature in the laboratory, especially under low temperatures (18 °C and low nutrient conditions (0.5 mg N L−1, 0.083 mg P L−1. The three species displayed an apparent tradeoff with different strategies of growth or dormancy. In the field, water bodies with three or more species of floating plants were not more frequently dominated by this group. The response diversity observed in the lab may not be associated with the dominance of this group in the field because it is masked by environmental variability, has a weak effect, or is only important during transient circumstances. Future research to develop applied uses of floating plants should examine response diversity across a greater range of species or clones and environmental conditions.

  17. Response diversity of free-floating plants to nutrient stoichiometry and temperature: growth and resting body formation

    Science.gov (United States)

    2016-01-01

    Free-floating plants, like most groups of aquatic primary producers, can become nuisance vegetation under certain conditions. On the other hand, there is substantial optimism for the applied uses of free-floating plants, such as wastewater treatment, biofuel production, and aquaculture. Therefore, understanding the species-specific responses of floating plants to abiotic conditions will inform both management decisions and the beneficial applications of these plants. I measured the responses of three floating plant species common in the northeast United States (Lemna minor, Spirodela polyrhiza, and Wolffia brasiliensis) to nutrient stoichiometry (nitrogen and phosphorus) and temperature in the laboratory. I also used survey data to determine the pattern of species richness of floating plants in the field and its relationship with the dominance of this group. Floating plant species exhibited unique responses to nutrient stoichiometry and temperature in the laboratory, especially under low temperatures (18 °C) and low nutrient conditions (0.5 mg N L−1, 0.083 mg P L−1). The three species displayed an apparent tradeoff with different strategies of growth or dormancy. In the field, water bodies with three or more species of floating plants were not more frequently dominated by this group. The response diversity observed in the lab may not be associated with the dominance of this group in the field because it is masked by environmental variability, has a weak effect, or is only important during transient circumstances. Future research to develop applied uses of floating plants should examine response diversity across a greater range of species or clones and environmental conditions. PMID:26989619

  18. Variable nutrient stoichiometry (carbon:nitrogen:phosphorus) across trophic levels determines community and ecosystem properties in an oligotrophic mangrove system

    Science.gov (United States)

    Scharler, U.M.; Ulanowicz, Robert E.; Fogel, M.L.; Wooller, M.J.; Jacobson-Meyers, M.E.; Lovelock, C.E.; Feller, I.C.; Frischer, M.; Lee, R.; Mckee, Karen L.; Romero, I.C.; Schmit, J.P.; Shearer, C.

    2015-01-01

    Our study investigated the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of mangrove island of the Mesoamerican Barrier Reef (Twin Cays, Belize). The C:N:P of abiotic and biotic components of this oligotrophic ecosystem was measured and served to build networks of nutrient flows for three distinct mangrove forest zones (tall seaward fringing forest, inland dwarf forests and a transitional zone). Between forest zones, the stoichiometry of primary producers, heterotrophs and abiotic components did not change significantly, but there was a significant difference in C:N:P, and C, N, and P biomass, between the functional groups mangrove trees, other primary producers, heterotrophs, and abiotic components. C:N:P decreased with increasing trophic level. Nutrient recycling in the food webs was highest for P, and high transfer efficiencies between trophic levels of P and N also indicated an overall shortage of these nutrients when compared to C. Heterotrophs were sometimes, but not always, limited by the same nutrient as the primary producers. Mangrove trees and the primary tree consumers were P limited, whereas the invertebrates consuming leaf litter and detritus were N limited. Most compartments were limited by P or N (not by C), and the relative depletion rate of food sources was fastest for P. P transfers thus constituted a bottleneck of nutrient transfer on Twin Cays. This is the first comprehensive ecosystem study of nutrient transfers in a mangrove ecosystem, illustrating some mechanisms (e.g. recycling rates, transfer efficiencies) which oligotrophic systems use in order to build up biomass and food webs spanning various trophic levels.

  19. Development of Analytical Thinking Ability and Attitudes towards Science Learning of Grade-11 Students through Science Technology Engineering and Mathematics (STEM Education) in the Study of Stoichiometry

    Science.gov (United States)

    Chonkaew, Patcharee; Sukhummek, Boonnak; Faikhamta, Chatree

    2016-01-01

    The purpose of this study was to investigate the analytical thinking abilities and attitudes towards science learning of grade-11 students through science, technology, engineering, and mathematics (STEM) education integrated with a problem-based learning in the study of stoichiometry. The research tools consisted of a pre- and post-analytical…

  20. Composition control of low-volatile solids through chemical vapor transport reactions. III. The example of gallium monoselenide: Control of the polytypic structure, non-stoichiometry and properties

    International Nuclear Information System (INIS)

    Zavrazhnov, A.; Naumov, A.; Sidey, V.; Pervov, V.

    2012-01-01

    Highlights: ► This work is devoted to the composition control of solids with selective CVT method. ► Phase identity and non-stoichiometry of solids (GaSe, etc.) depend on CVT-temperatures. ► The interrelation between the properties of GaSe and CVT conditions is also found. ► For iodide transporting system the diagram of phase stability of solids is adjusted. ► High temperatures and Se-rich non-stoichiometry are necessary for γ-GaSe stability. - Abstract: By means of particular examples, the present work demonstrates the possibility of directed delicate non-destructive control of structure, composition and properties of inorganic solids using the method of selective chemical vapor transport (SCVT). Gallium monoselenide GaSe is the main model object. Additional, though less detailed, explanation is given by the example of gallium monosulfide GaS. Experimental evidences on the possibility of the control of polytypic structure, non-stoichiometry and properties of gallium monoselenide were obtained in non-isothermal variant of selective chemical vapor transport which has non-destructive character. Diagnostics of the phase (polytypic) composition and non-stoichiometry of GaSe was performed with the use of X-ray diffractometry as well as with the use of cathode luminescence spectra. It was experimentally found that there exists a connection of non-stoichiometry and the properties of gallium selenides with the determining conditions of selective chemical vapor transport: temperature of controlled sample (T 2 ) and the difference of temperatures between the hot and cold zones (ΔT). It is shown that the phase diagram of Ga–Se system needs to be partially revised near the composition of Ga 1 Se 1 . The reason for such revision is the fact that two polytypes (ε-GaSe and γ-GaSe) exist on this phase diagram as independent phases.

  1. Procedures of amino acid sequencing of peptides in natural proteins collection of knowledge and intelligence for construction of reliable chemical inference system

    OpenAIRE

    Kudo, Yoshihiro; Kanaya, Shigehiko

    1994-01-01

    In order to establish a reliable chemical inference system on amino acid sequencing of natural peptides, as various kinds of relevant knowledge and intelligence as possible are collected. Topics are on didemnins, dolastatin 3, TL-119 and/or A-3302-B, mycosubtilin, patellamide A, duramycin (and cinnamycin), bottoromycin A 2, A19009, galantin I, vancomycin, stenothricin, calf speleen profilin, neocarzinostatin, pancreatic spasmolytic polypeptide, cerebratulus toxin B-IV, RNAase U 2, ferredoxin ...

  2. Towards a molecular interpretation of astringency: synthesis, 3D structure, colloidal state, and human saliva protein recognition of procyanidins.

    Science.gov (United States)

    Cala, Olivier; Fabre, Sandy; Pinaud, Noël; Dufourc, Erick J; Fouquet, Eric; Laguerre, Michel; Pianet, Isabelle

    2011-07-01

    Astringency is a sensation in the mouth used in judging the quality of red wine. The rough, dry, and puckering sensation called astringency is the result of an interaction between tannins and saliva proteins, mainly proline-rich proteins (PRP), which leads to the formation and precipitation of a complex. A dry and rough sensation is then perceived in the mouth. To get an insight into astringency at the molecular level we investigated: (i) An efficient and iterative method for 4-8 procyanidin synthesis, which gives rise to all possible 4-8 procyanidins up to the tetramer with total control of degree of oligomerization and stereochemistry. (ii) The 3D-structural preferences, which take into account their internal movements, using 2D NMR and molecular modeling. (iii) The self-association process in water or hydroalcoholic solutions using diffusion NMR spectroscopy that gives the active proportion of tannins able to fix proteins. (iv) A comprehensive description of the PRP-procyanidin complex formation to get information about stoichiometry, binding site localization, and affinity constants for different procyanidins. The data collected suggest that the interactions are controlled by both procyanidin conformational and colloidal state preferences. All these results provide new insights into the molecular interpretation of tannin astringency. © Georg Thieme Verlag KG Stuttgart · New York.

  3. Effect of ‘A’-site non stoichiometry in strontium doped lanthanum ferrite based solid oxide fuel cell cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Koyel; Mukhopadhyay, Jayanta, E-mail: jayanta_mu@cgcri.res.in; Barman, Madhurima; Basu, Rajendra N., E-mail: rnbasu@cgcri.res.in

    2015-12-15

    Highlights: • La{sub 1−x}Sr{sub x}Co{sub y}Fe{sub 1−y}O{sub 3−δ}, x = 0.4; y = 0.2 system varying La-site (0.6–0.54) are studied. • Combustion synthesis technique is used to prepare the powder samples. • Highest electrical conductivity observed with largest A-site deficit composition. • Lowest cathode polarization is found with the same composition (0.02 Ω cm{sup 2}). • Composition with largest A-site deficiency exhibits best performance (2.84 A cm{sup −2}). - Abstract: Effect of A-site non-stoichiometry in strontium doped lanthanum cobalt ferrite (La{sub 1−x}Sr{sub x}Co{sub y}Fe{sub 1−y}O{sub 3−δ}, x = 0.4; y = 0.2) is studied in a systematic manner with variation of ‘A’ site stoichiometry from 1 to 0.94. The perovskite based cathode compositions are synthesized by combustion synthesis. Powder characterizations reveal rhombohedral crystal structure with crystallite size ranging from 29 to 34 nm with minimum lattice spacing of 0.271 nm. Detailed sintering studies along with total DC electrical conductivities are evaluated in the bulk form with variation of sintering temperatures. The electrode polarizations are measured in the symmetric cell configuration by impedance spectroscopy which is found to be the lowest (0.02 Ω cm{sup 2} at 800 °C) for cathode having highest degree of ‘A’-site deficiency. The same cathode composition exhibits a current density of 2.84 A cm{sup −2} (at 0.7 V, 800 °C) in anode-supported single cell. An attempt has been made to correlate the trend of electrical behaviour with increasing ‘A’-site deficiency for such cathode compositions.

  4. Label-Free Quantitation of Ribosomal Proteins from Bacillus subtilis for Antibiotic Research.

    Science.gov (United States)

    Schäkermann, Sina; Prochnow, Pascal; Bandow, Julia E

    2017-01-01

    Current research is focusing on ribosome heterogeneity as a response to changing environmental conditions and stresses, such as antibiotic stress. Altered stoichiometry and composition of ribosomal proteins as well as association of additional protein factors are mechanisms for shaping the protein expression profile or hibernating ribosomes. Here, we present a method for the isolation of ribosomes to analyze antibiotic-induced changes in the composition of ribosomes in Bacillus subtilis or other bacteria. Ribosomes and associated proteins are isolated by ultracentrifugation and proteins are identified and quantified using label-free mass spectrometry.

  5. Effluent composition prediction of a two-stage anaerobic digestion process: machine learning and stoichiometry techniques.

    Science.gov (United States)

    Alejo, Luz; Atkinson, John; Guzmán-Fierro, Víctor; Roeckel, Marlene

    2018-05-16

    Computational self-adapting methods (Support Vector Machines, SVM) are compared with an analytical method in effluent composition prediction of a two-stage anaerobic digestion (AD) process. Experimental data for the AD of poultry manure were used. The analytical method considers the protein as the only source of ammonia production in AD after degradation. Total ammonia nitrogen (TAN), total solids (TS), chemical oxygen demand (COD), and total volatile solids (TVS) were measured in the influent and effluent of the process. The TAN concentration in the effluent was predicted, this being the most inhibiting and polluting compound in AD. Despite the limited data available, the SVM-based model outperformed the analytical method for the TAN prediction, achieving a relative average error of 15.2% against 43% for the analytical method. Moreover, SVM showed higher prediction accuracy in comparison with Artificial Neural Networks. This result reveals the future promise of SVM for prediction in non-linear and dynamic AD processes. Graphical abstract ᅟ.

  6. Collective Improvisation

    Directory of Open Access Journals (Sweden)

    Clare M. Cooper

    2016-08-01

    Full Text Available Collective improvisation as a creative practice is intensely social, trusting, unpopular, anti-hierarchical and, for these reasons, political. Cooper describes the risks and rich rewards of improvising with fellow artists and identifies the parallels between improvising ensembles of musicians in Australia with the collectively painted protest banners of the Taring Padi Collective in Indonesia after a brief visit to Jogjakarta.

  7. The influence of carbon non-stoichiometry on the electronic properties of thorium monocarbide ThC

    International Nuclear Information System (INIS)

    Shein, I.R.; Ivanovskii, A.L.

    2010-01-01

    The first-principle band structure calculations are employed to examine the influence of carbon non-stoichiometry on the structural and electronic properties of the cubic thorium monocarbide ThC. As a result, the equilibrium geometries, electronic bands, densities of states (DOS), Sommerfeld constants and Pauli paramagnetic susceptibility for ThC 1-x (where x = 0, 0.25 and 0.50) are obtained and analyzed in comparison with available experimental data. Additionally, the formation energies of carbon vacancies are theoretically estimated for ThC 1-x . The results obtained indicate that the introduction of carbon vacancies in ThC is accompanied by pronounced DOS changes due to the appearance of novel 'vacancy states' in the near-Fermi region formed by comparable contributions of Th 6d and 5f states. The carbon deficiency strongly affects the structure and stability of thorium carbide. For example, for the hypothetical 'over-deficient' composition ThC 0.50 the initial cubic structure undergoes significant tetragonal distortions. On the contrary, for ThC 0.75 the value of Evf is positive and the cubic structure of this phase is preserved. (authors)

  8. Variation in decomposition rates in the fynbos biome, South Africa: the role of plant species and plant stoichiometry.

    Science.gov (United States)

    Bengtsson, Jan; Janion, Charlene; Chown, Steven L; Leinaas, Hans Petter

    2011-01-01

    Previous studies in the fynbos biome of the Western Cape, South Africa, have suggested that biological decomposition rates in the fynbos vegetation type, on poor soils, may be so low that fire is the main factor contributing to litter breakdown and nutrient release. However, the fynbos biome also comprises vegetation types on more fertile soils, such as the renosterveld. The latter is defined by the shrub Elytropappus rhinocerotis, while the shrub Galenia africana may become dominant in overgrazed areas. We examined decomposition of litter of these two species and the geophyte Watsonia borbonica in patches of renosterveld in an agricultural landscape. In particular, we sought to understand how plant species identity affects litter decomposition rates, especially through variation in litter stoichiometry. Decomposition (organic matter mass loss) varied greatly among the species, and was related to litter N and P content. G. africana, with highest nutrient content, lost 65% of its original mass after 180 days, while E. rhinocerotis had lost ca. 30%, and the very nutrient poor W. borbonica biome. Thus, biological decomposition has likely been underestimated and, along with small-scale variation in ecosystem processes, would repay further study.

  9. The influence of carbon non-stoichiometry on the electronic properties of thorium monocarbide ThC

    Energy Technology Data Exchange (ETDEWEB)

    Shein, I.R.; Ivanovskii, A.L. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)

    2010-09-15

    The first-principle band structure calculations are employed to examine the influence of carbon non-stoichiometry on the structural and electronic properties of the cubic thorium monocarbide ThC. As a result, the equilibrium geometries, electronic bands, densities of states (DOS), Sommerfeld constants and Pauli paramagnetic susceptibility for ThC{sub 1-x} (where x = 0, 0.25 and 0.50) are obtained and analyzed in comparison with available experimental data. Additionally, the formation energies of carbon vacancies are theoretically estimated for ThC{sub 1-x}. The results obtained indicate that the introduction of carbon vacancies in ThC is accompanied by pronounced DOS changes due to the appearance of novel 'vacancy states' in the near-Fermi region formed by comparable contributions of Th 6d and 5f states. The carbon deficiency strongly affects the structure and stability of thorium carbide. For example, for the hypothetical 'over-deficient' composition ThC{sub 0.50} the initial cubic structure undergoes significant tetragonal distortions. On the contrary, for ThC{sub 0.75} the value of Evf is positive and the cubic structure of this phase is preserved. (authors)

  10. Improvement of stoichiometry in (ZnO)1-x(GaN)x thin films grown by laser ablation

    International Nuclear Information System (INIS)

    Gopalakrishnan, N.; Shin, B.C.; Bhuvana, K.P.; Elanchezhiyan, J.; Balasubramanian, T.

    2008-01-01

    The fabrication of pure and GaN (1 mol%) doped ZnO thin films by KrF excimer laser have been addressed. The fabricated films on Si(1 1 1) substrates have been investigated by X-ray diffraction (XRD), photoluminescence (PL) and atomic force microscopy (AFM) in order to investigate the structural, optical and morphological properties, respectively. The XRD analysis shows that the full width at half maximum (FWHM) of ZnO film is found to be decreased as doped with GaN due to the improvement of the stoichiometery between Zn and O. The PL spectra reveal that the deep level emissions due to native donor defects in pure ZnO are suppressed upon doping with GaN. The images of AFM show that the RMS surface roughness of pure ZnO, 27 nm is reduced to18 nm while doped with 1 mol% GaN. The incorporation of nitrogen in the film is confirmed by glow discharge mass spectroscopy (GDMS). The improved structural, optical and morphological properties of ZnO by GaN dopant due to enhancement of stoichiometry have been discussed in detail

  11. Controlling the stoichiometry and strand polarity of a tetramolecular G-quadruplex structure by using a DNA origami frame

    Science.gov (United States)

    Rajendran, Arivazhagan; Endo, Masayuki; Hidaka, Kumi; Lan Thao Tran, Phong; Mergny, Jean-Louis; Sugiyama, Hiroshi

    2013-01-01

    Guanine-rich oligonucleotides often show a strong tendency to form supramolecular architecture, the so-called G-quadruplex structure. Because of the biological significance, it is now considered to be one of the most important conformations of DNA. Here, we describe the direct visualization and single-molecule analysis of the formation of a tetramolecular G-quadruplex in KCl solution. The conformational changes were carried out by incorporating two duplex DNAs, with G–G mismatch repeats in the middle, inside a DNA origami frame and monitoring the topology change of the strands. In the absence of KCl, incorporated duplexes had no interaction and laid parallel to each other. Addition of KCl induced the formation of a G-quadruplex structure by stably binding the duplexes to each other in the middle. Such a quadruplex formation allowed the DNA synapsis without disturbing the duplex regions of the participating sequences, and resulted in an X-shaped structure that was monitored by atomic force microscopy. Further, the G-quadruplex formation in KCl solution and its disruption in KCl-free buffer were analyzed in real-time. The orientation of the G-quadruplex is often difficult to control and investigate using traditional biochemical methods. However, our method using DNA origami could successfully control the strand orientations, topology and stoichiometry of the G-quadruplex. PMID:23863846

  12. Stoichiometry behavior of TaN, TaCN and TaC thin films produced by magnetron sputtering

    International Nuclear Information System (INIS)

    Vargas, M.; Castillo, H.A.; Restrepo-Parra, E.; De La Cruz, W.

    2013-01-01

    Thin films were synthesized in a magnetron sputtering system using a target of Ta with 99.99% purity and silicon substrates (1 1 1). The gases used for the film growth were (Ar + N 2 ), (Ar + CH 4 + N 2 ) and (Ar + CH 4 ) mixtures for TaN, TaCN and TaC, respectively. The substrate temperature increased from room temperature to 500 °C. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Ta-N, Ta-C-N, Ta-C and C-C bonds. Moreover, the crystallographic structure was analyzed using X-ray diffraction (XRD), indicating the presence of (1 1 1) and (2 0 0) planes belonging to a face-centered cubic structure. The stoichiometry variation dependence on the CH 4 and N 2 flow was analyzed, and the influence of the substrate temperature on the coatings was investigated. Finally, scanning electron microscopy (SEM) was used to determine the evolution on the grain formation in the coatings as the substrate temperature increased.

  13. Stoichiometry behavior of TaN, TaCN and TaC thin films produced by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, M. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico); Castillo, H.A. [Centro de Enseñanza Técnica y Superior, CETYS Universidad, Campus Tijuana, Tijuana, B.C. (Mexico); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Universidad Nacional de Colombia Sede Medellín Colombia, Facultad de Minas, Manizales (Colombia); De La Cruz, W. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico)

    2013-08-15

    Thin films were synthesized in a magnetron sputtering system using a target of Ta with 99.99% purity and silicon substrates (1 1 1). The gases used for the film growth were (Ar + N{sub 2}), (Ar + CH{sub 4} + N{sub 2}) and (Ar + CH{sub 4}) mixtures for TaN, TaCN and TaC, respectively. The substrate temperature increased from room temperature to 500 °C. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Ta-N, Ta-C-N, Ta-C and C-C bonds. Moreover, the crystallographic structure was analyzed using X-ray diffraction (XRD), indicating the presence of (1 1 1) and (2 0 0) planes belonging to a face-centered cubic structure. The stoichiometry variation dependence on the CH{sub 4} and N{sub 2} flow was analyzed, and the influence of the substrate temperature on the coatings was investigated. Finally, scanning electron microscopy (SEM) was used to determine the evolution on the grain formation in the coatings as the substrate temperature increased.

  14. Response of cellular stoichiometry and phosphorus storage of the cyanobacteria Aphanizomenon flos-aquae to small-scale turbulence

    Science.gov (United States)

    Li, Zhe; Xiao, Yan; Yang, Jixiang; Li, Chao; Gao, Xia; Guo, Jinsong

    2017-11-01

    Turbulent mixing, in particular on a small scale, affects the growth of microalgae by changing diffusive sublayers and regulating nutrient fluxes of cells. We tested the nutrient flux hypothesis by evaluating the cellular stoichiometry and phosphorus storage of microalgae under different turbulent mixing conditions. Aphanizomenon flos-aquae were cultivated in different stirring batch reactors with turbulent dissipation rates ranging from 0.001 51 m2/s3 to 0.050 58 m2/s3, the latter being the highest range observed in natural aquatic systems. Samples were taken in the exponential growth phase and compared with samples taken when the reactor was completely stagnant. Results indicate that, within a certain range, turbulent mixing stimulates the growth of A. flos-aquae. An inhibitory effect on growth rate was observed at the higher range. Photosynthesis activity, in terms of maximum effective quantum yield of PSII (the ratio of F v/ F m) and cellular chlorophyll a, did not change significantly in response to turbulence. However, Chl a/C mass ratio and C/N molar ratio, showed a unimodal response under a gradient of turbulent mixing, similar to growth rate. Moreover, we found that increases in turbulent mixing might stimulate respiration rates, which might lead to the use of polyphosphate for the synthesis of cellular constituents. More research is required to test and verify the hypothesis that turbulent mixing changes the diffusive sublayer, regulating the nutrient flux of cells.

  15. Foliar spray with vermiwash modifies the Arbuscular mycorrhizal dependency and nutrient stoichiometry of Bhut Jolokia (Capsicum assamicum.

    Directory of Open Access Journals (Sweden)

    Mohammad Haneef Khan

    Full Text Available Vermiwash (VW, a liquid extract obtained from vermicomposting beds, is used as an organic fertilizer for crop plants. The current study investigated the effect of a vermiwash foliar spray on the response of bhut jolokia (Capsicum assamicum exposed to two different arbuscular mycorrhizal fungi (AMF: Rhizophagus irregularis, RI and G. mosseae, GM in acidic soil under naturally ventilated greenhouse conditions. The VW spray significantly influenced the growth of plants receiving the dual treatment of AMF+VW. Plant growth was more prominent in the GM+VW treatment group than that in the RI+VW treatment group. The plant-AMF interactions in relation to growth and nutrient requirements were also significantly influenced by the application of VW. Interestingly, the VW treatment appeared to contribute more N to plants when compared to that under the AMF treatment, which led to changes in the C:N:P stoichiometry in plant shoots. Furthermore, the increased potassium dependency, as observed in the case of the dual treatments, suggests the significance of such treatments for improving crop conditions under salt stress. Overall, our study shows that the VW foliar spray modifies the response of a crop to inoculations of different AMF with regard to growth and nutrient utilization, which has implications for the selection of an efficient combination of nutrient source for improving crop growth.

  16. Use of portable analytical methods to determine the stoichiometry of reaction for hexahydrotriazine-based hydrogen sulfide scavenger operations.

    Science.gov (United States)

    Taylor, Grahame N; Matherly, Ron

    2014-05-20

    During the reaction between 1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine and hydrogen sulphide, the principle by-product is the organic sulphide 5-(2-hydroxyethyl)dithiazine. It can be determined by a novel, portable, field-capable ion mobility spectrometry method described herein and enables the "degree spent" to be determined. Dependant upon the level of carbon dioxide in the produced gas, a mixture of ethanolaminium bicarbonate and ethanolamine bisulphide is also produced. Using a field capable spectrophotometric method the level of inorganic sulphide can be determined, thus allowing the ethanolaminium bisulphide concentration to be calculated. Provided the fluid is only partially spent, and there is some unreacted 1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine remaining; the only source of inorganic sulphide is the amine salt. From a knowledge of the original fluid concentration, the combination of these two methods allows the effective stoichiometry, or observed molar reaction proportions between 1,3,5-tris(2-hydroxyethyl)hexahydro-s-triazine and hydrogen sulphide, to be measured for a specific field location.

  17. Foliar Spray with Vermiwash Modifies the Arbuscular Mycorrhizal Dependency and Nutrient Stoichiometry of Bhut Jolokia (Capsicum assamicum)

    Science.gov (United States)

    Gupta, Rajeev; Veer, Vijay; Singh, Lokendra; Kalita, Mohan C.

    2014-01-01

    Vermiwash (VW), a liquid extract obtained from vermicomposting beds, is used as an organic fertilizer for crop plants. The current study investigated the effect of a vermiwash foliar spray on the response of bhut jolokia (Capsicum assamicum) exposed to two different arbuscular mycorrhizal fungi (AMF: Rhizophagus irregularis, RI and G. mosseae, GM) in acidic soil under naturally ventilated greenhouse conditions. The VW spray significantly influenced the growth of plants receiving the dual treatment of AMF+VW. Plant growth was more prominent in the GM+VW treatment group than that in the RI+VW treatment group. The plant-AMF interactions in relation to growth and nutrient requirements were also significantly influenced by the application of VW. Interestingly, the VW treatment appeared to contribute more N to plants when compared to that under the AMF treatment, which led to changes in the C:N:P stoichiometry in plant shoots. Furthermore, the increased potassium dependency, as observed in the case of the dual treatments, suggests the significance of such treatments for improving crop conditions under salt stress. Overall, our study shows that the VW foliar spray modifies the response of a crop to inoculations of different AMF with regard to growth and nutrient utilization, which has implications for the selection of an efficient combination of nutrient source for improving crop growth. PMID:24651577

  18. C and P in aquatic food chain: A review on C:P stoichiometry and PUFA regulation

    Directory of Open Access Journals (Sweden)

    Saikia S.K.

    2010-09-01

    Full Text Available Carbon (C and phosphorous (P regulation in aquatic food chains are transferred from lower to upper trophic levels primarily as polyunsaturated fatty acids (PUFAs and C:P stoichiometry. The majority of C is transferred through algal based pathway. Microbial loop, though optionally contributes to C transfer, highly constrained by P limitation and bacterial predator type. Lack of essential PUFAs in bacteria is also responsible for its low trophic transfer of C. The seston size and algal taxonomic variations directly affect herbivore through P-dependent food quality and de novo synthesis of PUFAs. Change in algal community over a gradient could therefore determine C transfer. Feeding nature (herbivorous or carnivorous and predator sizes also regulate transfer efficiency of C and P to upper trophic levels. As trophic levels move up, P-limitation becomes higher compared to autotrophs. For Daphnia, as mostly studied aquatic herbivore member, P limitation becomes critical at C:P > 300 indicating excess C is not always invited under P-deficient situations. However, as a part of homeostasis mechanism for trophic upgrading, conversion of algal-zooplankton interface from qualitative to quantitative could minimize such critical C:P regulation at higher trophic levels. Protists, in turn, with high clearance rate by zooplankton predator could also compensate qualitative effect.

  19. How to make a beetle out of wood: multi-elemental stoichiometry of wood decay, xylophagy and fungivory.

    Science.gov (United States)

    Filipiak, Michał; Weiner, January

    2014-01-01

    The majority of terrestrial biomass is wood, but the elemental composition of its potential consumers, xylophages, differs hugely from that of wood. This causes a severe nutritional imbalance. We studied the stoichiometric relationships of 11 elements (C, N, P, K, Ca, Mg, Fe, Zn, Mn, Cu, Na) in three species of pine-xylem-feeding insects, Stictoleptura rubra, Arhopalus rusticus (Coleoptera, Cerambycidae) and Chalcophora mariana (Coleoptera, Buprestidae), to elucidate their mechanisms of tissue growth and to match their life histories to their dietary constraints. These beetles do not differ from other Coleoptera in their absolute elemental compositions, which are approximately 1000 (N), 100 (P, Cu) and 50 (K, Na) times higher than in dead but undecayed pine wood. This discrepancy diminishes along the wood decay gradient, but the elemental concentrations remain higher by an order of magnitude in beetles than in highly decayed wood. Numerical simulation of the life history of S. rubra shows that feeding on nutrient-poor undecayed wood would extend its development time to implausible values, whereas feeding on highly decomposed wood (heavily infected with fungi) would barely balance its nutritional budget during the long development period of this species. The changes in stoichiometry indicate that the relative change in the nutrient levels in decaying wood cannot be attributed solely to carbon loss resulting from decomposer respiration: the action of fungi substantially enriches the decaying wood with nutritional elements imported from the outside of the system, making it a suitable food for wood-eating invertebrates.

  20. Engineering the microstructure and magnetism of La{sub 2}CoMnO{sub 6−δ} thin films by tailoring oxygen stoichiometry

    Energy Technology Data Exchange (ETDEWEB)

    Galceran, R.; Frontera, C.; Balcells, Ll.; Cisneros-Fernández, J.; López-Mir, L.; Bozzo, B.; Pomar, A.; Sandiumenge, F.; Martínez, B. [Institut de Ciència de Materials de Barcelona-CSIC, Campus UAB, E-08193 Bellaterra (Spain); Roqueta, J.; Santiso, J. [Institut Català de Nanociència i Nanotecnologia, ICN2-CSIC, Campus UAB, E-08193 Bellaterra (Spain); Bagués, N. [Institut de Ciència de Materials de Barcelona-CSIC, Campus UAB, E-08193 Bellaterra (Spain); Institut Català de Nanociència i Nanotecnologia, ICN2-CSIC, Campus UAB, E-08193 Bellaterra (Spain)

    2014-12-15

    We report on the magnetic and structural properties of ferromagnetic-insulating La{sub 2}CoMnO{sub 6−δ} thin films grown on top of (001) SrTiO{sub 3} substrates by means of RF sputtering technique. Careful structural analysis, by using synchrotron X-ray diffraction, allows identifying two different crystallographic orientations that are closely related to oxygen stoichiometry and to the features (coercive fields and remanence) of the hysteresis loops. Both Curie temperature and magnetic hysteresis turn out to be dependent on the oxygen stoichiometry. In situ annealing conditions allow tailoring the oxygen content of the films, therefore controlling their microstructure and magnetic properties.

  1. Assembly and stoichiometry of the core structure of the bacterial flagellar type III export gate complex.

    Science.gov (United States)

    Fukumura, Takuma; Makino, Fumiaki; Dietsche, Tobias; Kinoshita, Miki; Kato, Takayuki; Wagner, Samuel; Namba, Keiichi; Imada, Katsumi; Minamino, Tohru

    2017-08-01

    The bacterial flagellar type III export apparatus, which is required for flagellar assembly beyond the cell membranes, consists of a transmembrane export gate complex and a cytoplasmic ATPase complex. FlhA, FlhB, FliP, FliQ, and FliR form the gate complex inside the basal body MS ring, although FliO is required for efficient export gate formation in Salmonella enterica. However, it remains unknown how they form the gate complex. Here we report that FliP forms a homohexameric ring with a diameter of 10 nm. Alanine substitutions of conserved Phe-137, Phe-150, and Glu-178 residues in the periplasmic domain of FliP (FliPP) inhibited FliP6 ring formation, suppressing flagellar protein export. FliO formed a 5-nm ring structure with 3 clamp-like structures that bind to the FliP6 ring. The crystal structure of FliPP derived from Thermotoga maritia, and structure-based photo-crosslinking experiments revealed that Phe-150 and Ser-156 of FliPP are involved in the FliP-FliP interactions and that Phe-150, Arg-152, Ser-156, and Pro-158 are responsible for the FliP-FliO interactions. Overexpression of FliP restored motility of a ∆fliO mutant to the wild-type level, suggesting that the FliP6 ring is a functional unit in the export gate complex and that FliO is not part of the final gate structure. Copurification assays revealed that FlhA, FlhB, FliQ, and FliR are associated with the FliO/FliP complex. We propose that the assembly of the export gate complex begins with FliP6 ring formation with the help of the FliO scaffold, followed by FliQ, FliR, and FlhB and finally FlhA during MS ring formation.

  2. Material balance in coal. 2. Oxygen determination and stoichiometry of 33 coals

    International Nuclear Information System (INIS)

    Volborth, A.; Miller, G.E.; Garner, C.K.; Jerabek, P.A.

    1977-01-01

    The chemical analysis of coal can be supplemented by the determination of oxygen in high and low temperature ash, in coal as received and in coal dried at 105 0 C. The rapid method utilizes fast-neutron activation. The reaction 16 O(n,p) 16 N and counting of the 6.1 and 7.1 MeV gammas of 7.3 second half-life are used. A specially designed dual transfer and simultaneous counting system gives very accurate results. Oxygen in 33 coals ranging from lignite to low volatile bituminous coal is determined and compared with ''oxygen by difference.'' Considerable discrepancies are observed. Better stoichiometric results are obtained if oxygen in coal ash, in wet coal and in the dried coal is determined. This permits the estimation of the true material balances using data of the ultimate and the proximate coal analysis. The oxygen determination provides the coal chemist with an accurate basis and can be used to rank coal. The summation of the percent of carbon, nitrogen, hydrogen, sulfur, and oxygen becomes more meaningful and some errors can be detected and the state of completeness of coal analysis thus evaluated. Total sulfur can be estimated and oxidation effects during drying can be detected. These affect the moisture determination. It appears that after more data are collected, the interpretation of solid fuel analyses may be facilitated and will be stoichiometrically more meaningful. It is shown that it may be possible to simplify the present time-consuming methods of coal analysis

  3. Phase stability and oxygen non-stoichiometry of SrCo0.8Fe0.2O3-d measured by in-situ neutron diffraction

    NARCIS (Netherlands)

    McIntosh, Steven; McIntosh, S.; Vente, Jaap F.; Haije, Wim G.; Blank, David H.A.; Bouwmeester, Henricus J.M.

    2006-01-01

    The phase stability, oxygen stoichiometry and expansion properties of SrCo0.8Fe0.2O3−δ (SCF) were determined by in situ neutron diffraction between 873 and 1173 K and oxygen partial pressures of 5×10−4 to 1 atm. At a pO2 of 1 atm, SCF adopts a cubic perovskite structure, space group Pm3¯m, across

  4. Selectivity and stoichiometry boosting of beta-cyclodextrin in cationic/anionic surfactant systems: when host-guest equilibrium meets biased aggregation equilibrium.

    Science.gov (United States)

    Jiang, Lingxiang; Yu, Caifang; Deng, Manli; Jin, Changwen; Wang, Yilin; Yan, Yun; Huang, Jianbin

    2010-02-18

    Cationic surfactant/anionic surfactant/beta-CD ternary aqueous systems provide a platform for the coexistence of the host-guest (beta-CD/surfactant) equilibrium and the biased aggregation (monomeric/aggregated surfactants) equilibrium. We report here that the interplay between the two equilibria dominates the systems as follows. (1) The biased aggregation equilibrium imposes an apparent selectivity on the host-guest equilibrium, namely, beta-CD has to always selectively bind the major surfactant (molar fraction > 0.5) even if binding constants of beta-CD to the pair of surfactants are quite similar. (2) In return, the host-guest equilibrium amplifies the bias of the aggregation equilibrium, that is, the selective binding partly removes the major surfactant from the aggregates and leaves the aggregate composition approaching the electroneutral mixing stoichiometry. (3) This composition variation enhances electrostatic attractions between oppositely charged surfactant head groups, thus resulting in less-curved aggregates. In particular, the present apparent host-guest selectivity is of remarkably high values, and the selectivity stems from the bias of the aggregation equilibrium rather than the difference in binding constants. Moreover, beta-CD is defined as a "stoichiometry booster" for the whole class of cationic/anionic surfactant systems, which provides an additional degree of freedom to directly adjust aggregate compositions of the systems. The stoichiometry boosting of the compositions can in turn affect or even determine microstructures and macroproperties of the systems.

  5. Effects of oxygen stoichiometry on the scaling behaviors of YBa{sub 2}Cu{sub 3}O{sub x} grain boundary weak-links

    Energy Technology Data Exchange (ETDEWEB)

    Wu, K.H.; Fu, C.M.; Jeng, W.J. [National Chiao-Tung Univ., Taiwan (China)] [and others

    1994-12-31

    The effects of oxygen stoichiometry on the transport properties of the pulsed laser deposited YBa{sub 2}Cu{sub 3}O{sub x} bicrystalline grain boundary weak-link junctions were studied. It is found that not only the cross boundary resistive transition foot structure can be manipulated repeatedly with oxygen annealling processes but the junction behaviors are also altered in accordance. In the fully oxygenated state i.e. with x=7.0 in YBa{sub 2}Cu{sub 3}O{sub x} stoichiometry, the junction critical current exhibits a power of 2 scaling behavior with temperature. In contrast, when annealed in the conditions of oxygen-deficient state (e.g. with x=6.9 in YBa{sub 2}Cu{sub 3}O{sub x} stoichiometry) the junction critical current switches to a linear temperature dependence behavior. The results are tentatively attributed to the modification of the structure in the boundary area upon oxygen annealing, which, in turn, will affect the effective dimension of the geometrically constrained weak-link bridges. The detailed discussion on the responsible physical mechanisms as well as the implications of the present results on device applications will be given.

  6. The use of NH4+ rather than NO3- affects cell stoichiometry, C allocation, photosynthesis and growth in the cyanobacterium Synechococcus sp UTEX LB 2380, only when energy is limiting

    Czech Academy of Sciences Publication Activity Database

    Ruan, Z.; Giordano, Mario

    2017-01-01

    Roč. 40, č. 2 (2017), s. 227-236 ISSN 0140-7791 Institutional support: RVO:61388971 Keywords : carbon allocation * cyanobacteria * elemental stoichiometry Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 6.173, year: 2016

  7. Effect of the stoichiometry of Si-rich silicon nitride thin films on their photoluminescence and structural properties

    Energy Technology Data Exchange (ETDEWEB)

    Torchynska, T.V., E-mail: ttorch@esfm.ipn.mx [ESFM—Instituto Politecnico Nacional, Mexico DF 07738 (Mexico); Casas Espinola, J.L. [ESFM—Instituto Politecnico Nacional, Mexico DF 07738 (Mexico); Vergara Hernandez, E. [UPIITA—Instituto Politecnico Nacional, Mexico DF 07320 (Mexico); Khomenkova, L., E-mail: khomen@ukr.net [V. Lashkaryov Institute of Semiconductor Physics, 45 Pr. Nauky, 03028 Kyiv (Ukraine); Delachat, F.; Slaoui, A. [ICube, 23 rue du Loess, BP 20 CR, 67037 Strasbourg Cedex 2 (France)

    2015-04-30

    Si-rich Silicon nitride films were grown on silicon substrates by plasma enhanced chemical vapor deposition. The film stoichiometry was controlled via the variation of NH{sub 3}/SiH{sub 4} ratio from 0.45 up to 1.0. Thermal annealing at 1100 °C for 30 min in the nitrogen flow was applied to form the Si nanocrystals in the films that have been investigated by means of photoluminescence and Raman scattering methods, as well as transmission electron microscopy. Several emission bands have been detected with the peak positions at: 2.8–3.0 eV, 2.5–2.7 eV, 2.10–2.25 eV, and 1.75–1.98 eV. The temperature dependences of photoluminescence spectra were studied with the aim to confirm the types of optical transitions and the nature of light emitting defects in silicon nitride. The former three bands were assigned to the defects in silicon nitride, whereas the last one (1.75–1.98 eV) was attributed to the exciton recombination inside of Si nanocrystals. The photoluminescence mechanism is discussed. - Highlights: • Substoichiometric silicon nitride films were grown by PECVD technique. • The variation of the NH{sub 3}/SiH{sub 4} ratio controls excess Si content in the films. • Both Si nanocrystals and amorphous Si phase were observed in annealed films. • Temperature evolution of carrier recombination via Si nanocrystals and host defects.

  8. Stoichiometry of photosystem I, photosystem II, and phycobilisomes in the red alga Porphyridium cruentum as a function of growth irradiance

    Energy Technology Data Exchange (ETDEWEB)

    Cunningham, F.X. Jr.; Mustardy, L.; Gantt, E. (Univ. of Maryland, College Park (USA)); Dennenberg, R.J.; Jursinic, P.A. (Department of Agriculture, Peoria, IL (USA))

    1989-11-01

    Cells of the red alga Porphyridium cruentum (ATCC 50161) exposed to increasing growth irradiance exhibited up to a three-fold reduction in photosystems I and II (PSI and PSII) and phycobilisomes but little change in the relative numbers of these components. Batch cultures of P. cruentum were grown under four photon flux densities of continuous white light; 6 (low light LL), 35 (medium light, ML), 180 (high light, HL), and 280 (very high light, VHL) microeinsteins per square meter per second and sampled in the exponential phase of growth. Ratios of PSII to PSI ranged between 0.43 and 0.54. About three PSII centers per phycobilisome were found, regardless of growth irradiance. The phycoerythrin content of phycobilisomes decreased by about 25% for HL and VHL compared to LL and ML cultures. The unit sizes of PSI (chlorophyll/P{sub 700}) and PSII (chlorophyll/Q{sub A}) decreased by about 20% with increase in photon flux density from 6 to 280 microeinsteins per square meter per second. A threefold reduction in cell content of chlorophyll at the higher photon flux densities was accompanied by a twofold reduction in {beta}-carotene, and a drastic reduction in thylakoid membrane area. Cell content of zeaxanthin, the major carotenoid in P. cruentum, did not vary with growth irradiance, suggesting a role other than light-harvesting. HL cultures had a growth rate twice that of ML, eight times that of LL, and slightly greater than that of VHL cultures. Cell volume increased threefold from LL to VHL, but volume of the single chloroplast did not change. From this study it is evident that a relatively fixed stoichiometry of PSI, PSII, and phycobilisomes is maintained in the photosynthetic apparatus of this red alga over a wide range of growth irradiance.

  9. Cocrystals of the antimalarial drug 11-azaartemisinin with three alkenoic acids of 1:1 or 2:1 stoichiometry.

    Science.gov (United States)

    Nisar, Madiha; Wong, Lawrence W Y; Sung, Herman H Y; Haynes, Richard K; Williams, Ian D

    2018-06-01

    The stoichiometry, X-ray structures and stability of four pharmaceutical cocrystals previously identified from liquid-assisted grinding (LAG) of 11-azaartemisinin (11-Aza; systematic name: 1,5,9-trimethyl-14,15,16-trioxa-11-azatetracyclo[10.3.1.0 4,13 .0 8,13 ]hexadecan-10-one) with trans-cinnamic (Cin), maleic (Mal) and fumaric (Fum) acids are herein reported. trans-Cinnamic acid, a mono acid, forms 1:1 cocrystal 11-Aza:Cin (1, C 15 H 23 NO 4 ·C 9 H 8 O 2 ). Maleic acid forms both 1:1 cocrystal 11-Aza:Mal (2, C 15 H 23 NO 4 ·C 4 H 4 O 4 ), in which one COOH group is involved in self-catenation, and 2:1 cocrystal 11-Aza 2 :Mal (3, 2C 15 H 23 NO 4 ·C 4 H 4 O 4 ). Its isomer, fumaric acid, only affords 2:1 cocrystal 11-Aza 2 :Fum (4). All cocrystal formation appears driven by acid-lactam R 2 2 (8) heterosynthons with short O-H...O=C hydrogen bonds [O...O = 2.56 (2) Å], augmented by weaker C=O...H-N contacts. Despite a better packing efficiency, cocrystal 3 is metastable with respect to 2, probably due to a higher conformational energy for the maleic acid molecule in its structure. In each case, the microcrystalline powders from LAG were useful in providing seeding for the single-crystal growth.

  10. Linkages of plant stoichiometry to ecosystem production and carbon fluxes with increasing nitrogen inputs in an alpine steppe.

    Science.gov (United States)

    Peng, Yunfeng; Li, Fei; Zhou, Guoying; Fang, Kai; Zhang, Dianye; Li, Changbin; Yang, Guibiao; Wang, Guanqin; Wang, Jun; Yang, Yuanhe

    2017-12-01

    Unprecedented levels of nitrogen (N) have entered terrestrial ecosystems over the past century, which substantially influences the carbon (C) exchange between the atmosphere and biosphere. Temperature and moisture are generally regarded as the major controllers over the N effects on ecosystem C uptake and release. N-phosphorous (P) stoichiometry regulates the growth and metabolisms of plants and soil organisms, thereby affecting many ecosystem C processes. However, it remains unclear how the N-induced shift in the plant N:P ratio affects ecosystem production and C fluxes and its relative importance. We conducted a field manipulative experiment with eight N addition levels in a Tibetan alpine steppe and assessed the influences of N on aboveground net primary production (ANPP), gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE); we used linear mixed-effects models to further determine the relative contributions of various factors to the N-induced changes in these parameters. Our results showed that the ANPP, GEP, ER, and NEE all exhibited nonlinear responses to increasing N additions. Further analysis demonstrated that the plant N:P ratio played a dominate role in shaping these C exchange processes. There was a positive relationship between the N-induced changes in ANPP (ΔANPP) and the plant N:P ratio (ΔN:P), whereas the ΔGEP, ΔER, and ΔNEE exhibited quadratic correlations with the ΔN:P. In contrast, soil temperature and moisture were only secondary predictors for the changes in ecosystem production and C fluxes along the N addition gradient. These findings highlight the importance of plant N:P ratio in regulating ecosystem C exchange, which is crucial for improving our understanding of C cycles under the scenarios of global N enrichment. © 2017 John Wiley & Sons Ltd.

  11. RRh2Al10 (R = Ce, Yb): New intermetallic compounds in the 1 : 2 : 10 stoichiometry series

    Science.gov (United States)

    Strydom, A. M.; Djoumessi, R. F.; Blinova, M.; Tursina, A.; Nesterenko, S.; Avzuragova, V.

    2018-05-01

    The orthorhombic, space group Cmcm YbFe2Al10 structure type series of compounds are known to form with practically the entire series of rare-earth elements R, but only with the three d - electron elements Fe, Ru, and Os. The Ce-derivatives in particular have been of much interest since the first reports of their highly unusual physical properties. Classified as Kondo insulators, CeRu2Al10 and CeOs2Al10 controversially order magnetically and with uncharacteristically high Néel temperatures of ≃ 28 K. CeFe2Al10 on the other hand shows pronounced semiconducting and Kondo features but remains paramagnetic. As part of our ongoing studies into the rich physics of this class of materials we have succeeded in synthesizing new members of the 1:2:10 stoichiometry involving the chemical element Rh for the first time. CeRh2Al10 is found to crystallize in the tetragonal system with space group I41 / amd . Yb Rh2Al10 on the other hand forms in the serial Cmcm orthorhombic structure type. We discuss important similarities between the two types. At 5.310 Å the shortest Ce-Ce distance is, likewise to the situation in CeRu2Al10 and CeOs2Al10 , also well above the Hill limit of 3.40 Å. Despite the cage-like structure and large rare-earth separation distances, this study reveals the onset of long-range magnetic ordering in CeRh2Al10 at 3.9 K. The magnetic ordering develops out of an incoherent Kondo state that dominates the electrical resistivity below about 40 K.

  12. Sustained effects of volcanic ash on biofilm stoichiometry, enzyme activity and community composition in North- Patagonia streams.

    Science.gov (United States)

    Carrillo, Uara; Díaz-Villanueva, Verónica; Modenutti, Beatriz

    2018-04-15

    Volcanic eruptions are extreme perturbations that affect ecosystems. These events can also produce persistent effects in the environment for several years after the eruption, with increased concentrations of suspended particles and the introduction of elements in the water column. On 4th June 2011, the Puyehue-Cordón Caulle Volcanic Complex (40.59°S-72.11°W, 2200m.a.s.l.) erupted explosively in southern Chile. The area affected by the volcano was devastated; a thick layer of volcanic ash (up to 30cm) was deposited in areas 50 km east of the volcano towards Argentina. The aim of the present study was to evaluate the effect of volcanic ash deposits on stream ecosystems four years after the eruption, comparing biofilm stoichiometry, alkaline phosphatase activity, and primary producer's assemblage in streams which were severely affected by the volcano with unaffected streams. We confirmed in the laboratory that ash deposited in the catchment of affected streams still leach phosphorus (P) into the water four years after eruption. Results indicate that affected streams still receive volcanic particles and that these particles release P, thus stream water exhibits high P concentration. Biofilm P content was higher and the C:P ratio lower in affected streams compared to unaffected streams. As a consequence of less P in unaffected streams, the alkaline phosphatase activity was higher compared to affected streams. Cyanobacteria increased their abundances (99.9% of total algal biovolume) in the affected streams suggesting that the increase in P may positively affect this group. On the contrary, unaffected streams contained a diatom dominant biofilm. In this way, local heterogeneity was created between sub-catchments located within 30 km of each other. These types of events should be seen as opportunities to gather valuable ecological information about how severe disturbances, like volcanic eruptions, shape landscapes and lotic systems for several years after the event

  13. Polarographic determination of uranium dioxide stoichiometry; La determination polarographique de la stoechiometrie du dioxyde d'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Viguie, J.; Uny, G. [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Grenoble, 38 (France)

    1966-10-01

    The method described allows the determination of small deviations from stoichiometry for uranium dioxide. It was applied to the study of surface oxidation of bulk samples. The sample is dissolved in phosphoric acid under an argon atmosphere; U(VI) is determined by polarography in PO{sub 4}H{sub 3} 4.5 N - H{sub 2}SO{sub 4} 4 N. U(IV) is determined by potentiometry. The detection limit is UO{sub 2,0002}. The accuracy for a single determination at the 95% confidence level is {+-}20 per cent for samples with composition included between UO{sub 2,001} and UO{sub 2,01}. (authors) [French] La methode decrite permet de determiner les faibles ecarts a la stoechiometrie du dioxyde d'uranium. Elle a ete appliquee a l'etude de l'oxydation superficielle des echantillons. La mise en solution s'effectue dans l'acide phosphorique concentre sous atmosphere d'argon; U(VI) est dose par polarographie dans le milieu PO{sub 4}H{sub 3} 4,5 N et H{sub 2}SO{sub 4} 4 N; U(IV) est dose par potentiometrie. La limite de detection est UO{sub 2,0002}. La precision obtenue pour une determination au taux de certitude 0,95 est de l'ordre de 20 pour cent pour des echantillons dont la teneur est comprise entre UO{sub 2,001} et UO{sub 2,01}. (auteurs)

  14. Influence of chronic alcoholism and oestrogen deficiency on the variation of stoichiometry of hydroxyapatite within alveolar bone crest of rats.

    Science.gov (United States)

    Marchini, Adriana M P S; Deco, Camila P; Lodi, Karina B; Marchini, Leonardo; Santo, Ana M E; Rocha, Rosilene F

    2012-10-01

    Previous findings suggest that chronic alcoholism and oestrogenic deficiency may affect bones in general (including alveolar bone) and increase individuals' susceptibility to the development of periodontal disease. The aim of this study was to assess possible alterations in the chemical composition of alveolar bone in rats subjected to chronic alcoholism, oestrogen deficiency or both. Fifty-four rats were initially divided into two groups: ovariectomized (Ovx), and Sham operated (Sham). A month after surgery, the groups were sub-divided and received the following dietary intervention for eight weeks: 20% alcohol, isocaloric diet and ad libitum diet. Samples of the mandible, in the alveolar bone crest region, were analyzed to verify possible changes in the stoichiometric composition of bone hydroxyapatite, by measuring the relationship between the concentration of calcium and phosphorus (Ca/P ratios), using micro X-ray fluorescence spectrometry. The ad libitum groups presented the highest average values of Ca/P ratios, while the groups with dietary restrictions presented the smallest average values. The Ovx ad libitum group presented the highest values of Ca/P ratios (2.03 ± 0.04). However, these values were not considered statistically different (p>0.05) from the Sham ad libitum group (2.01 ± 0.01). The Ovx alcohol group presented lower values for Ca/P ratios (1.92 ± 0.06), being the only group statistically different (palcohol consumption at 20% significantly changed the stoichiometry composition of hydroxyapatite in the alveolar bone crest, leading to a reduction in Ca/P ratios. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Folding DNA into a Lipid-Conjugated Nanobarrel for Controlled Reconstitution of Membrane Proteins.

    Science.gov (United States)

    Dong, Yuanchen; Chen, Shuobing; Zhang, Shijian; Sodroski, Joseph; Yang, Zhongqiang; Liu, Dongsheng; Mao, Youdong

    2018-02-19

    Building upon DNA origami technology, we introduce a method to reconstitute a single membrane protein into a self-assembled DNA nanobarrel that scaffolds a nanodisc-like lipid environment. Compared with the membrane-scaffolding-protein nanodisc technique, our approach gives rise to defined stoichiometry, controlled sizes, as well as enhanced stability and homogeneity in membrane protein reconstitution. We further demonstrate potential applications of the DNA nanobarrels in the structural analysis of membrane proteins. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. A new look on protein-polyphenol complexation during honey storage: is this a random or organized event with the help of dirigent-like proteins?

    Directory of Open Access Journals (Sweden)

    Katrina Brudzynski

    Full Text Available Honey storage initiates melanoidin formation that involves a cascade of seemingly unguided redox reactions between amino acids/proteins, reducing sugars and polyphenols. In the process, high molecular weight protein-polyphenol complexes are formed, but the mechanism involved remains unknown. The objective of this study was twofold: to determine quantitative and qualitative changes in proteins in honeys stored for prolonged times and in different temperatures and to relate these changes to the formation of protein-polyphenol complexes. Six -month storage decreased the protein content by 46.7% in all tested honeys (t-test, p<0.002 with the rapid reduction occurring during the first three month. The changes in protein levels coincided with alterations in molecular size and net charge of proteins on SDS -PAGE. Electro-blotted proteins reacted with a quinone-specific nitro blue tetrazolium (NBT on nitrocellulose membranes indicating that quinones derived from oxidized polyphenols formed covalent bonds with proteins. Protein-polyphenol complexes isolated by size-exclusion chromatography differed in size and stoichiometry and fall into two categories: (a high molecular weight complexes (230-180 kDa enriched in proteins but possessing a limited reducing activity toward the NBT and (b lower molecular size complexes (110-85 kDa enriched in polyphenols but strongly reducing the dye. The variable stoichiometry suggest that the large, "protein-type" complexes were formed by protein cross-linking, while in the smaller, "polyphenol-type" complexes polyphenols were first polymerized prior to protein binding. Quinones preferentially bound a 31 kDa protein which, by the electrospray quadrupole time of flight mass spectrometry (ESI-Qtof-MS analysis, showed homology to dirigent-like proteins known for assisting in radical coupling and polymerization of phenolic compounds. These findings provide a new look on protein-polyphenol interaction in honey where the

  17. Culture collections.

    Science.gov (United States)

    Smith, David

    2012-01-01

    Culture collections no matter their size, form, or institutional objectives play a role in underpinning microbiology, supplying the resources for study, innovation, and discovery. Their basic roles include providing a mechanism for ex situ conservation of organisms; they are repositories for strains subject to publication, taking in safe, confidential, and patent deposits from researchers. They supply strains for use; therefore, the microorganisms provided must be authentic and preserved well, and any associated information must be valid and sufficient to facilitate the confirmation of their identity and to facilitate their use. The organisms must be collected in compliance with international conventions, international and national legislation and distributed to users indicating clearly the terms and conditions under which they are received and can be used. Collections are harmonizing approaches and characterizing strains to meet user needs. No one single collection can carry out this task alone, and therefore, it is important that output and strategy are coordinated to ensure culture collections deliver the basic resources and services microbiological innovation requires. This chapter describes the types of collection and how they can implement quality management systems and operate to deliver their basic functions. The links to information sources given not only provide support for the practitioners within collections but also provide guidance to users on accessing the huge resource available and how they can help ensure microbiology has the resources and a solid platform for future development. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Collective Efficacy

    DEFF Research Database (Denmark)

    Chen, Ying; Zhou, Xiaohu; Klyver, Kim

    2018-01-01

    at manufacturing companies show that benevolent leadership and moral leadership, both components of paternalistic leadership, are positively related to organizational commitment and further that collective efficacy mediates the moral leadership–organizational commitment relationship. We did not find a relationship...... between authoritarian leadership and organizational commitment. Besides, it was found that team cohesion negatively moderates the relationship between moral leadership and collective efficacy and positively moderates the relationship between collective efficacy and organizational commitment. Explanations......Based on social cognitive theory, we theorize that collective efficacy plays a mediating role in the relationship between paternalistic leadership and organizational commitment and that this mediating role depends on team cohesion. The empirical results from a study of 238 employees from 52 teams...

  19. Pressure cryocooling protein crystals

    Science.gov (United States)

    Kim, Chae Un [Ithaca, NY; Gruner, Sol M [Ithaca, NY

    2011-10-04

    Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.

  20. Structure and stoichiometry

    International Nuclear Information System (INIS)

    Gai, P.L.

    1992-01-01

    Structural and stoichiometric variations and their role in superconducting properties of bulk cuprate ceramics are elucidated. Atomic structure and chemistry of defect microstructures, including vacancy and interstitial defects, weak-link problems, structural modulations and coherent intergrowths leading to new structures are studies and quantitatively interpreted. They are shown to play a critical role in controlling hole concentration, critical currents and flux pinning. These phenomena underpin the solid state chemistry which determines the physical properties of the nonstoichiometric oxide superconductors. In this paper technological implications, synthesis of related novel materials and recent developments are discussed

  1. Impact of protein and ligand impurities on ITC-derived protein-ligand thermodynamics.

    Science.gov (United States)

    Grüner, Stefan; Neeb, Manuel; Barandun, Luzi Jakob; Sielaff, Frank; Hohn, Christoph; Kojima, Shun; Steinmetzer, Torsten; Diederich, François; Klebe, Gerhard

    2014-09-01

    The thermodynamic characterization of protein-ligand interactions by isothermal titration calorimetry (ITC) is a powerful tool in drug design, giving valuable insight into the interaction driving forces. ITC is thought to require protein and ligand solutions of high quality, meaning both the absence of contaminants as well as accurately determined concentrations. Ligands synthesized to deviating purity and protein of different pureness were titrated by ITC. Data curation was attempted also considering information from analytical techniques to correct stoichiometry. We used trypsin and tRNA-guanine transglycosylase (TGT), together with high affinity ligands to investigate the effect of errors in protein concentration as well as the impact of ligand impurities on the apparent thermodynamics. We found that errors in protein concentration did not change the thermodynamic properties obtained significantly. However, most ligand impurities led to pronounced changes in binding enthalpy. If protein binding of the respective impurity is not expected, the actual ligand concentration was corrected for and the thus revised data compared to thermodynamic properties obtained with the respective pure ligand. Even in these cases, we observed differences in binding enthalpy of about 4kJ⋅mol(-1), which is considered significant. Our results indicate that ligand purity is the critical parameter to monitor if accurate thermodynamic data of a protein-ligand complex are to be recorded. Furthermore, artificially changing fitting parameters to obtain a sound interaction stoichiometry in the presence of uncharacterized ligand impurities may lead to thermodynamic parameters significantly deviating from the accurate thermodynamic signature. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Collective Security

    DEFF Research Database (Denmark)

    Galster, Kjeld

    in worldwide market conditions left perceptible ripples in Danish economy, budget discussions grew in importance over this period. The pacifist stance entailed disinclination to accept that the collective security concept and international treaties and accords signed by Denmark should necessitate credible...... and other international treaties provided arguments for adjusting the foreign and security policy ambitions, and since the general flux in worldwide market conditions left perceptible ripples in Danish economy, budget discussions grew in importance over this period. The pacifist stance entailed......Collective Security: National Egotism (Abstract) In Danish pre-World War I defence debate the notion of collective security is missing. During the early years of the 19th century, the political work is influenced by a pervasive feeling of rising tension and danger on the continent of Europe...

  3. Locals Collection

    Directory of Open Access Journals (Sweden)

    Stephen Hastings-King

    2010-03-01

    Full Text Available A locals collection is a set of parameters that are used to delimit data-mining operations. This piece uses a collection of locals from around Essex Massachusetts to shape and delimit an interrogation of post-reality in contemporary America. It explores the notion of crisis, the possibility of a crisis of empire that may or may not emerge in a media-space that does not allow crisis of empire to be mentioned and relations this maybe-crisis to the various levels of economic dysfunction that have become evident since late 2008. But mostly this piece explores ways in which particular stories about particular people do and do not link/link to these larger-scale narratives. This is the first of a potential series of locals collections that will mine the American post-real.

  4. [Leaf nitrogen and phosphorus stoichiometry of shrubland plants in the rocky desertification area of Southwestern Hunan, China.

    Science.gov (United States)

    Jing, Yi Ran; Deng, Xiang Wen; Wei, Hui; Li, Yan Qiong; Deng, Dong Hua; Liu, Hao Jian; Xiang, Wen Hua

    2017-02-01

    In this paper, we took the leaves of shrubland plants in rocky desertification area in Southwestern Hunan as the research object to analyze the nitrogen (N) and phosphorus (P) stoichiometry characteristics for different functional groups and different grades of rocky desertification, i.e., light rocky desertification (LRD), moderate rocky desertification (MRD) and intense rocky desertification (IRD). The results showed that the average contents of N and P were 12.89 and 1.19 g·kg -1 , respectively, and N/P was 11.24 in common shrubland plants in the study area, which indicated that the growth of most plants were mainly limited by N. The content of N was declined in order of deciduous shrubs > evergreen shrubs > annual herbs > perennial herbs. The content of P and N/P were higher in deciduous shrubs than in perennial herbs. Significant differences were found among the main families of plants in terms of the contents of N, P and N/P in the study sites. The plants of Gramineae had the lowest contents of N and P, andtheir growth was mostly restricted by N, while Leguminosae had the highest content of N and N/P, and their productivity was majorly controlled by P. The contents of N and P in the leaves were significantly higher in dicotyledon plants and C3 plants than in monocotyledon plants and C4 plants, but the N/P was not significantly diffe-rent between these two plant categories. The nitrogen-fixing plants had higher content of N and N/P than the non-nitrogen-fixing plants, but the P content was not significantly different between these two plant groups. There were significant correlations between contents of N and P, N/P and N in all study plots. No significant correlation was found between N/P and P content in the examined rocky desertification sites, except for that in MRD. There were no significant differences of the contents of N, P and N/P under different grades of rocky desertification.

  5. GLT-1 Transport Stoichiometry Is Constant at Low and High Glutamate Concentrations when Chloride Is Substituted by Gluconate.

    Directory of Open Access Journals (Sweden)

    Anatoli Y Kabakov

    Full Text Available Glutamate is the major excitatory neurotransmitter, but prolonged exposure even at micromolar concentrations causes neuronal death. Extracellular glutamate is maintained at nanomolar level by glutamate transporters, which, however, may reverse transport and release glutamate. If and when the reverse occurs depends on glutamate transport stoichiometry (GTS. Previously we found that in the presence of chloride, the coupled GLT-1 glutamate transporter current and its relationship to radiolabeled glutamate flux significantly decreased when extracellular glutamate concentration increased above 0.2 mM, which implies a change in GTS. Such high concentrations are feasible near GLT-1 expressed close to synaptic release site during excitatory neurotransmission. The aim of this study was to determine GLT-1 GTS at both low (19-75 μM and high (300-1200 μM glutamate concentration ranges. GTS experiments were conducted in the absence of chloride to avoid contributions by the GLT-1 uncoupled chloride conductance. Mathematical analysis of the transporter thermodynamic equilibrium allowed us to derive equations revealing the number of a particular type of ion transported per elementary charge based on the measurements of the transporter reversal potential. We found that GLT-1a expressed in COS-7 cells co-transports 1.5 Na+, 0.5 Glu-, 0.5 H+ and counter-transports 0.6 K+ per elementary charge in both glutamate concentration ranges, and at both 37°C and 26°C temperatures. The thermodynamic parameter Q10 = 2.4 for GLT-1 turnover rate of 19 s-1 (37°C, -50 mV remained constant in the 10 μM-10 mM glutamate concentration range. Importantly, the previously reported decrease in the current/flux ratio at high glutamate concentration was not seen in the absence of chloride in both COS-7 cells and cultured rat neurons. Therefore, only in the absence of chloride, GLT-1 GTS remains constant at all glutamate concentrations. Possible explanations for why apparent GTS might

  6. Carbon, nitrogen, and phosphorus stoichiometry of plankton and the nutrient regime in Cabo Frio Bay, SE Brazil.

    Science.gov (United States)

    Kütter, Vinicius T; Wallner-Kersanach, Monica; Sella, Silvia M; Albuquerque, Ana Luiza S; Knoppers, Bastiaan A; Silva-Filho, Emmanoel V

    2014-01-01

    This long-term study, performed during the years 2003-2005 and 2008-2009, investigated the carbon (C), nitrogen (N), and phosphorus (P) contents of the phyto- and zooplankton communities and the nutrient regime of Cabo Frio Bay, SE Brazil. The information intends to serve as baseline of the plankton C, N, and P stoichiometry for the calibration of biogeochemical and ecological models in support to future findings related to the local and regional phenomena of climatic change. Cabo Frio Bay is a small semienclosed system set adjacent to a region subject to sporadic coastal upwelling. Zooplankton exhibited average annual C, N, and P contents of 11.6 ± 6.9 %, 2.8 ± 1.8 %, and 0.18 ± 0.08 %, and phytoplankton (>20 μm) 6.8 ± 6.0 %, 1.6 ± 1.5 %, and 0.09 ± 0.08 %, respectively. The C/N/P ratios correspond to the lowest already found to date for a marine environment. The low C contents must have been brought about by a predominance of gelatinous zooplankton, like Doliolids/ Salps and also Pteropods. Average annual nutrient concentrations in the water were 0.21 ± 0.1 μM for phosphate, 0.08 ± 0.1 μM for nitrite, 0.74 ± 1.6 μM for nitrate, and 1.27 ± 1.1 μM for ammonium. N/P ratios were around 8:1 during the first study period and 12:1 during the second. The plankton C/N/P and N/P nutrient ratios and elemental concentrations suggest that the system was oligotrophic and nitrogen limited. The sporadic intrusions of upwelling waters during the first study period had no marked effect upon the systems metabolism, likely due to dilution effects and the short residence times of water of the bay.

  7. Microbial C:P stoichiometry is shaped by redox conditions along an elevation gradient in humid tropical rainforests

    Science.gov (United States)

    Lin, Y.; Gross, A.; Silver, W. L.

    2017-12-01

    Elemental stoichiometry of microorganisms is intimately related to ecosystem carbon and nutrient fluxes and is ultimately controlled by the chemical (plant tissue, soil, redox) and physical (temperature, moisture, aeration) environment. Previous meta-analyses have shown that the C:P ratio of soil microbial biomass exhibits significant variations among and within biomes. Little is known about the underlying causes of this variability. We examined soil microbial C:P ratios along an elevation gradient in the Luquillo Experimental Forest in Puerto Rico. We analyzed soils from mixed forest paired with monodominant palm forest every 100 m from 300 m to 1000 m a.s.l.. Mean annual precipitation increased with increasing elevation, resulting in stronger reducing conditions and accumulation of soil Fe(II) at higher elevations. The mean value and variability of soil microbial C:P ratios generally increased with increasing elevation except at 1000 m. At high elevations (600-900 m), the average value of microbial C:P ratio (108±10:1) was significantly higher than the global average ( 55:1). We also found that soil organic P increased with increasing elevation, suggesting that an inhibition of organic P mineralization, not decreased soil P availability, may cause the high microbial C:P ratio. The soil microbial C:P ratio was positively correlated with soil HCl-extractable Fe(II), suggesting that reducing conditions may be responsible for the elevational changes observed. In a follow-up experiment, soils from mixed forests at four elevation levels (300, 500, 700, and 1000 m) were incubated under aerobic and anaerobic conditions for two weeks. We found that anaerobic incubation consistently increased the soil microbial C:P ratio relative to the aerobic incubation. Overall, our results indicate that redox conditions can shift the elemental composition of microbial biomass. The high microbial C:P ratios induced under anoxic conditions may reflect inhibition of microbial P

  8. Impact of the natural Fe-fertilization on the magnitude, stoichiometry and efficiency of particulate biogenic silica, nitrogen and iron export fluxes

    Science.gov (United States)

    Lemaitre, N.; Planquette, H.; Dehairs, F.; van der Merwe, P.; Bowie, A. R.; Trull, T. W.; Laurenceau-Cornec, E. C.; Davies, D.; Bollinger, C.; Le Goff, M.; Grossteffan, E.; Planchon, F.

    2016-11-01

    The Kerguelen Plateau is characterized by a naturally Fe-fertilized phytoplankton bloom that extends more than 1000 km downstream in the Antarctic Circumpolar Current. During the KEOPS2 study, in austral spring, we measured particulate nitrogen (PN), biogenic silica (BSi) and particulate iron (PFe) export fluxes in order to investigate how the natural fertilization impacts the stoichiometry and the magnitude of export fluxes and therefore the efficiency of the biological carbon pump. At 9 stations, we estimated elemental export fluxes based on element concentration to 234Th activity ratios for particulate material collected with in-situ pumps and 234Th export fluxes (Planchon et al., 2015). This study revealed that the natural Fe-fertilization increased export fluxes but to variable degrees. Export fluxes for the bloom impacted area were compared with those of a high-nutrient, low-chlorophyll (HNLC), low-productive reference site located to the south-west of Kerguelen and which had the lowest BSi and PFe export fluxes (2.55 mmol BSi m-2 d-1 and 1.92 μmol PFem-2 d-1) and amongst the lowest PN export flux (0.73 mmol PN m-2 d-1). The impact of the Fe fertilization was the greatest within a meander of the polar front (PF), to the east of Kerguelen, with fluxes reaching 1.26 mmol PN m-2 d-1; 20.4 mmol BSi m-2 d-1 and 22.4 μmol PFe m-2 d-1. A highly productive site above the Kerguelen Plateau, on the contrary, was less impacted by the fertilization with export fluxes reaching 0.72 mmol PN m-2 d-1; 4.50 mmol BSi m-2 d-1 and 21.4 μmol PFe m-2 d-1. Our results suggest that ecosystem features (i.e. type of diatom community) could play an important role in setting the magnitude of export fluxes of these elements. Indeed, for the PF meander, the moderate productivity was sustained by the presence of large and strongly silicified diatom species while at the higher productivity sites, smaller and slightly silicified diatoms dominated. Interestingly, our results suggest that

  9. Continuous Ecosystem Stoichiometry (C:N:P) in a Large Spring-fed River Reveals Decoupled N and P Assimilatory Dynamics

    Science.gov (United States)

    Cohen, M. J.; Douglass, R. L.; Martin, J. B.; Thomas, R. G.; Heffernan, J. B.; Foster, C. R.

    2010-12-01

    Diel variation in solutes offers insight into lotic ecosystem processes. Diel variation in dissolved oxygen (DO) is the standard method to estimate aquatic primary production (C fixation). Recently, diel variation in nitrate concentration was used to infer rates and pathways of N processing. From coupled C and N measurements, stoichiometric ratios of nutrient assimilation can be obtained, and variation therein linked back to environmental drivers and ecological changes. Here we present data obtained using an in situ phosphate sensor (Cycle-P, WetLabs, Philomath OR) that permits coupled high frequency C, N and P measurements. We collected hourly samples over 3 two-week deployments in the Ichetucknee River, a large (Q ~ 10 m3 s-1), productive (GPP ~ 6 g C m-2 d-1), entirely spring-fed river in north Florida. We observed average soluble reactive P (SRP) concentrations of 44, 41 and 45 µg/L for Dec-09, Feb-10 and Apr-10, respectively, and marked diel variation that averaged 6.7±0.9 µg/L. Observed river concentrations were consistently at or below the flow-weighted average input concentration of the 6 main springs that feed the river (49 µg/L) suggesting net SRP removal over the 5 km reach. Removal from co-precipitation with calcite or Fe-oxides is unlikely since variation in Fe and Ca is smaller than, and out of phase with, P variation. Since internal stores are presumed to be at steady-state given conditions of constant discharge, the balance of P export likely occurs as organic matter. Based on discharge during each deployment, diel variation of P concentrations indicate system-wide assimilation of 1505 ± 423 g P d-1, or 8.0 ± 2.3 mg P m-2 d-1 over the 17 ha of benthic surface area. Contemporaneous measurements of DO and nitrate implied average ecosystem stoichiometry (C:N:P) of 267:14:1, consistent with production dominated by submerged aquatic macrophytes rather than algae and other microflora. Of particular interest is the observation that diel variation in

  10. Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.

    2007-01-01

    High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.

  11. Determination of stoichiometry and concentration of trace elements in thin BaxSr1-xTiO3 perovskite layers.

    Science.gov (United States)

    Becker, J S; Boulyga, S F

    2001-07-01

    This paper describes an analytical procedure for determining the stoichiometry of BaxSr1-xTiO3 perovskite layers using inductively coupled plasma mass spectrometry (ICP-MS). The analytical results of mass spectrometry measurements are compared to those of X-ray fluorescence analysis (XRF). The performance and the limits of solid-state mass spectrometry analytical methods for the surface analysis of thin BaxSr1-xTiO3 perovskite layers sputtered neutral mass spectrometry (SNMS)--are investigated and discussed.

  12. Production, partitioning and stoichiometry of organic matter under variable nutrient supply during mesocosm experiments in the tropical Pacific and Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    J. M. S. Franz

    2012-11-01

    Full Text Available Oxygen-deficient waters in the ocean, generally referred to as oxygen minimum zones (OMZ, are expected to expand as a consequence of global climate change. Poor oxygenation is promoting microbial loss of inorganic nitrogen (N and increasing release of sediment-bound phosphate (P into the water column. These intermediate water masses, nutrient-loaded but with an N deficit relative to the canonical N:P Redfield ratio of 16:1, are transported via coastal upwelling into the euphotic zone. To test the impact of nutrient supply and nutrient stoichiometry on production, partitioning and elemental composition of dissolved (DOC, DON, DOP and particulate (POC, PON, POP organic matter, three nutrient enrichment experiments were conducted with natural microbial communities in shipboard mesocosms, during research cruises in the tropical waters of the southeast Pacific and the northeast Atlantic. Maximum accumulation of POC and PON was observed under high N supply conditions, indicating that primary production was controlled by N availability. The stoichiometry of microbial biomass was unaffected by nutrient N:P supply during exponential growth under nutrient saturation, while it was highly variable under conditions of nutrient limitation and closely correlated to the N:P supply ratio, although PON:POP of accumulated biomass generally exceeded the supply ratio. Microbial N:P composition was constrained by a general lower limit of 5:1. Channelling of assimilated P into DOP appears to be the mechanism responsible for the consistent offset of cellular stoichiometry relative to inorganic nutrient supply and nutrient drawdown, as DOP build-up was observed to intensify under decreasing N:P supply. Low nutrient N:P conditions in coastal upwelling areas overlying O2-deficient waters seem to represent a net source for DOP, which may stimulate growth of diazotrophic phytoplankton. These results demonstrate that microbial nutrient assimilation and

  13. Defect chemistry modelling of oxygen-stoichiometry, vacancy concentrations, and conductivity of (La1-xSrx)(y)MnO3 +/-delta

    DEFF Research Database (Denmark)

    Poulsen, F.W.

    2000-01-01

    model, based on delocalised electrons, electron holes and all B-ions being trivalent is given in Appendix A. The sequential mathematical method allows us to calculate the high temperature oxygen partial pressure dependent properties of (La1-xSrx)(y)MnO3+/-delta in a unified manner irrespective...... are calculated by the small polaron model containing only ionic species - the B-ion may be Mn-B' (Mn2+), Mn-B(x) (Mn3+), and Mn-B(Mn4+). The A/B-ratio = y greatly influences the oxygen stoichiometry, oxygen ion vacancy- and cation vacancy concentrations and the total conductivity. Calculations are given...

  14. Comparing the Ecological Stoichiometry in Green and Brown Food Webs – A Review and Meta-analysis of Freshwater Food Webs

    Directory of Open Access Journals (Sweden)

    Michelle A. Evans-White

    2017-06-01

    Full Text Available The framework of ecological stoichiometry was developed primarily within the context of “green” autotroph-based food webs. While stoichiometric principles also apply in “brown” detritus-based systems, these systems have been historically understudied and differ from green ones in several important aspects including carbon (C quality and the nutrient [nitrogen (N and phosphorus (P] contents of food resources for consumers. In this paper, we review work over the last decade that has advanced the application of ecological stoichiometry from green to brown food webs, focusing on freshwater ecosystems. We first review three focal areas where green and brown food webs differ: (1 bottom–up controls by light and nutrient availability, (2 stoichiometric constraints on consumer growth and nutritional regulation, and (3 patterns in consumer-driven nutrient dynamics. Our review highlights the need for further study of how light and nutrient availability affect autotroph–heterotroph interactions on detritus and the subsequent effects on consumer feeding and growth. To complement this conceptual review, we formally quantified differences in stoichiometric principles between green and brown food webs using a meta-analysis across feeding studies of freshwater benthic invertebrates. From 257 datasets collated across 46 publications and several unpublished studies, we compared effect sizes (Pearson’s r of resource N:C and P:C on growth, consumption, excretion, and egestion between herbivorous and detritivorous consumers. The meta-analysis revealed that both herbivore and detritivore growth are limited by resource N:C and P:C contents, but effect sizes only among detritivores were significantly above zero. Consumption effect sizes were negative among herbivores but positive for detritivores in the case of both N:C and P:C, indicating distinct compensatory feeding responses across resource stoichiometry gradients. Herbivore P excretion rates responded

  15. The stoichiometry of synthetic alunite as a function of hydrothermal aging investigated by solid-state NMR spectroscopy, powder X-ray diffraction and infrared spectroscopy

    DEFF Research Database (Denmark)

    Grube, Elisabeth; Nielsen, Ulla Gro

    2015-01-01

    The stoichiometry of a series of synthetic alunite (nominally KAl3(SO4)2(OH)6) samples prepared by hydrothermal methods as a function of reaction time (1 – 31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic...... of potassium defects present, from 17.261(1) to 17.324(5) Å. Solid-state 27Al MAS NMR revealed a decrease in the defect concentration as a function of time and showed the presence of 7-10 % impurities in the samples....

  16. Concurrent Collections

    OpenAIRE

    Budimlić, Zoran; Burke, Michael; Cavé, Vincent; Knobe, Kathleen; Lowney, Geoff; Newton, Ryan; Palsberg, Jens; Peixotto, David; Sarkar, Vivek; Schlimbach, Frank; Taşırlar, Sağnak

    2010-01-01

    We introduce the Concurrent Collections (CnC) programming model. CnC supports flexible combinations of task and data parallelism while retaining determinism. CnC is implicitly parallel, with the user providing high-level operations along with semantic ordering constraints that together form a CnC graph. We formally describe the execution semantics of CnC and prove that the model guarantees deterministic computation. We evaluate the performance of CnC implementations on several applications an...

  17. Synthesis, growth, and studies (crystal chemistry, magnetic chemistry) of actinide-based intermetallic compounds and alloys with a 1.1.1 stoichiometry

    International Nuclear Information System (INIS)

    Kergadallan, Yann

    1993-01-01

    The first part of this research thesis reports the study of the synthesis and reactivity of intermetallic compounds with a 1.1.1 stoichiometry. It presents the thermal properties of 1.1.1 compounds: general presentation of physical transitions, and of solid solutions and formation heat, application to actinides (reactivity analysis from phase diagrams, techniques of crystal synthesis and crystal growth. It describes experimental techniques: synthesis, determination of fusion temperature by dilatometry, methods used for crystal growth, characterisation techniques (metallography, X ray diffraction on powders, dilatometry). It discusses the obtained results in terms of characterisation of synthesised samples, of crystal growth, and of measurements of fusion temperature. The second part addresses crystal chemistry studies: structure of compounds with a 1.1.1 stoichiometry (Laves structures, Zr, Ti and Pu compounds), techniques of analysis by X-ray diffraction (on powders and on single crystals), result interpretation (UNiX compounds, AnTAl compounds with T being a metal from group VIII, AnTGa compounds, AnNiGe compounds, distance comparison, structure modifications under pressure). The third part concerns physical issues. The author addresses the following topics: physical properties of intermetallic 1.1.1 compounds (magnetism of yttrium phases, behaviour of uranium-based Laves phases, analysis of pseudo-binary diagrams, physical characteristics of uranium-based 1.1.1 compounds, predictions of physical measurements), analysis techniques (Moessbauer spectroscopy, SQUID for Superconducting Quantum Interference Device), and result interpretation

  18. Changes in nutrient stoichiometry, elemental homeostasis and growth rate of aquatic litter-associated fungi in response to inorganic nutrient supply.

    Science.gov (United States)

    Gulis, Vladislav; Kuehn, Kevin A; Schoettle, Louie N; Leach, Desiree; Benstead, Jonathan P; Rosemond, Amy D

    2017-12-01

    Aquatic fungi mediate important energy and nutrient transfers in freshwater ecosystems, a role potentially altered by widespread eutrophication. We studied the effects of dissolved nitrogen (N) and phosphorus (P) concentrations and ratios on fungal stoichiometry, elemental homeostasis, nutrient uptake and growth rate in two experiments that used (1) liquid media and a relatively recalcitrant carbon (C) source and (2) fungi grown on leaf litter in microcosms. Two monospecific fungal cultures and a multi-species assemblage were assessed in each experiment. Combining a radioactive tracer to estimate fungal production (C accrual) with N and P uptake measurements provided an ecologically relevant estimate of mean fungal C:N:P of 107:9:1 in litter-associated fungi, similar to the 92:9:1 obtained from liquid cultures. Aquatic fungi were found to be relatively homeostatic with respect to their C:N ratio (~11:1), but non-homeostatic with respect to C:P and N:P. Dissolved N greatly affected fungal growth rate and production, with little effect on C:nutrient stoichiometry. Conversely, dissolved P did not affect fungal growth and production but controlled biomass C:P and N:P, probably via luxury P uptake and storage. The ability of fungi to immobilize and store excess P may alter nutrient flow through aquatic food webs and affect ecosystem functioning.

  19. Stoichiometry and local bond configuration of In{sub 2}S{sub 3}:Cl thin films by Rutherford backscattering spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Juma, Albert O., E-mail: jumaa@biust.ac.bw

    2016-10-15

    In{sub 2}S{sub 3} thin films deposited using chemical methods always contain residual elements from the precursors, which modify their properties. As buffer layers in solar cells, the residual elements in the In{sub 2}S{sub 3} layer affect the performance of these devices. The stoichiometry of In{sub 2}S{sub 3} thin films deposited by spray ion layer gas reaction (ILGAR) was studied as a function of the residual Cl from InCl{sub 3} precursor by varying the deposition parameters. The chemical formula was deduced from the elemental composition determined using Rutherford backscattering (RBS). Incomplete sulfurization of the precursor implies that residual Cl{sup −} remains bonded to the In{sup 3+} ions while some occupy interstitial and/or antisite positions in the In{sub 2}S{sub 3} matrix. This results in thin films with different stoichiometry, described by the formula In{sub 4}S{sub 6−x}Cl{sub 2x+2y}. This changes the local bond configuration and geometry and underpins the influence of residual Cl on the physical properties of In{sub 2}S{sub 3} thin films.

  20. [Characteristics of 'salt island' and 'fertile island' for Tamarix chinensis and soil carbon, nitrogen and phosphorus ecological stoichiometry in saline-alkali land].

    Science.gov (United States)

    Zhang, Li-hua; Chen, Xiao-bing

    2015-03-01

    To clarify the nutrient characteristics of 'salt island' and 'fertile island' effects in saline-alkali soil, the native Tamarix chinensis of the Yellow River Delta (YRD) was selected to measure its soil pH, electrical conductivity (EC), organic carbon (SOC), total nitrogen (N), total phosphorus (P) and their stoichiometry characteristics at different soil depths. The results showed that soil pH and EC increased with the increasing soil depth. Soil EC and P in the 0-20 cm layer decreased and increased from canopied area to interspace, respectively. SOC, N, N/P and C/P in the 20-40 cm soil layer decreased, and C/N increased from the shrub center to interspace. SOC and N contents between island and interspace both decreased but P content decreased firstly and then increased with the increasing soil depth. Soil pH correlated positively with EC. In addition, pH and EC correlated negatively with C, N, P contents and their ecological stoichiometry.

  1. Stoichiometry and phase purity control of radio frequency magnetron sputter deposited Ba0.45Sr0.55TiO3 thin films for tunable devices

    Science.gov (United States)

    Alema, Fikadu; Reinholz, Aaron; Pokhodnya, Konstantin

    2013-11-01

    The systematic study of the oxygen partial pressure (OPP) and total chamber gas pressure (TGP) effects on the stoichiometry and crystal structure of rf sputtered Ba0.45Sr0.55TiO3 (BST) films and their phase purity allowed identifying close to optimal sputtering parameters for BST single phase polycrystalline film. The film with a Ba/Sr ratio equal to that of the source target and (Ba + Sr)/Ti ratio close to unity demonstrated the enhanced permittivity value of 553 and tunability of 69%. It was confirmed that the increase of TGP enables better match of the film and target stoichiometry. However, using O2/Ar ratio as a parameter should be utilized cautiously since exceeding a threshold OPP (2 mTorr in our case) may facilitate secondary phase formation. Relatively large dielectric losses were observed in both films sputtered at high (30 mTorr) and low (5 mTor) TGPs. The presence of oxygen vacancies was identified as a probable cause of losses, which is indirectly confirmed by the deviation of the film lattice constant from that of the bulk target.

  2. Improvements of uniformity and stoichiometry for zone-leveling Czochralski growth of MgO-doped LiNbO3 crystals

    International Nuclear Information System (INIS)

    Tsai, C.B.; Hsu, W.T.; Shih, M.D.; Tai, C.Y.; Hsieh, C.K.; Hsu, W.C.; Hsu, R.T.; Lan, C.W.

    2006-01-01

    The zone-leveling Czochralski (ZLCz) technique is a continuous feeding process and can be used for the growth of near-stoichiometric lithium niobate (SLN) single crystals. However, the finite crucible length can cause the variation of the zone length and thus the composition and stoichiometry, especially in the growth of a large diameter crystal. To solve the problems, several approaches were proposed for the growth of 4 cm-diameter 1 mol% MgO-doped SLN. The modification of the hot zone to minimize the zone variation was found useful for the uniformity, but the stoichiometry was inadequate even with the zone composition up to 60 mol% Li 2 O. A Li-excess feed was further used and a good Li/Nb ratio was obtained. Adding K 2 O (16 mol%) into the solution zone was useful as well, but it was inferior to using the Li-excess feed. In addition, a much lower growth rate was needed for getting an inclusion-free crystal

  3. Effects of taxonomy, sediment, and water column on C:N:P stoichiometry of submerged macrophytes in Yangtze floodplain shallow lakes, China.

    Science.gov (United States)

    Su, Haojie; Wu, Yao; Xie, Ping; Chen, Jun; Cao, Te; Xia, Wulai

    2016-11-01

    Carbon (C), nitrogen (N) and phosphorus (P) are the three most important essential elements limiting growth of primary producers. Submerged macrophytes generally absorb nutrients from sediments by root uptake. However, the C:N:P stoichiometric signatures of plant tissue are affected by many additional factors such as taxonomy, nutrient availability, and light availability. We first revealed the relative importance of taxonomy, sediment, and water column on plant C:N:P stoichiometry using variance partitioning based on partial redundancy analyses. Results showed that taxonomy was the most important factor in determining C:N:P stoichiometry, then the water column and finally the sediment. In this study, a significant positive relationship was found between community C concentration and macrophyte community biomass, indicating that the local low C availability in macrophytes probably was the main reason why submerged macrophytes declined in Yangtze floodplain shallow lakes. Based on our study, it is suggested that submerged macrophytes in Yangtze floodplain shallow lakes are primarily limited by low light levels rather than nutrient availability.

  4. Effects of elevated carbon dioxide and nitrogen addition on foliar stoichiometry of nitrogen and phosphorus of five tree species in subtropical model forest ecosystems

    International Nuclear Information System (INIS)

    Huang Wenjuan; Zhou Guoyi; Liu Juxiu; Zhang Deqiang; Xu Zhihong; Liu Shizhong

    2012-01-01

    The effects of elevated carbon dioxide (CO 2 ) and nitrogen (N) addition on foliar N and phosphorus (P) stoichiometry were investigated in five native tree species (four non-N 2 fixers and one N 2 fixer) in open-top chambers in southern China from 2005 to 2009. The high foliar N:P ratios induced by high foliar N and low foliar P indicate that plants may be more limited by P than by N. The changes in foliar N:P ratios were largely determined by P dynamics rather than N under both elevated CO 2 and N addition. Foliar N:P ratios in the non-N 2 fixers showed some negative responses to elevated CO 2 , while N addition reduced foliar N:P ratios in the N 2 fixer. The results suggest that N addition would facilitate the N 2 fixer rather than the non-N 2 fixers to regulate the stoichiometric balance under elevated CO 2 . - Highlights: ► Five native tree species in southern China were more limited by P than by N. ► Shifts in foliar N:P ratios were driven by P dynamic under the global change. ► N addition lowered foliar N:P ratios in the N 2 fixer under elevated CO 2 . - N addition could facilitate the N 2 fixer rather than the non-N 2 fixers to regulate foliar N and P stoichiometry under elevated CO 2 in subtropical forests.

  5. Collective Success or Collective Failure?

    DEFF Research Database (Denmark)

    Fayyaz, Anjum

    study of soccer village project to learn how various attempts at facilitating joint CSR action in the Pakistani football manufacturing have consistently failed in addressing international CSR compliance demands. I conclude that this form of collective failure – along with technological changes, lack...... of innovation, and government failure - can partly explain why Sialkot has been marginalized in terms of its overall share of world football manufacturing in the last decade....

  6. Spatial and seasonal distribution of carbon, nitrogen, phosphorus, and sulfur and their ecological stoichiometry in wetland soils along a water and salt gradient in the Yellow River Delta, China

    Science.gov (United States)

    Lu, Qiongqiong; Bai, Junhong; Zhang, Guangliang; Zhao, Qingqing; Wu, Jianjun

    2018-04-01

    Top soils (0-10 cm) were collected in three sampling belts during four seasons in 2014, including bare land (HN1), Calamagrostis epigeios (HN2), Typha orientalis (HN3), Phragmites australis (HN4), Tamarix chinensis (HN5) and Suaeda salsa (HN6) along a water and salinity gradient in the Yellow River Delta, China. Soil organic carbon (SOC), total nitrogen (TN), total phosphorous (TP), total sulfur (TS) and their ecological stoichiometry were measured to investigate their seasonal and horizontal distribution patterns, as well as their important influencing factors such as electric conductivity (EC) and water content (WC). Our results showed that the contents of SOC and TN exhibited similar changing tendency along the water and salinity gradient. The TP contents followed the order HN5 ≈ HN2 > HN3 ≈ HN6 > HN4 > HN1. TS levels generally increased with increasing salinity from HN1 to HN6. The higher levels of SOC and TP were mostly observed in October and August, respectively, while the seasonal variations in TN were heterogeneous under different plant covers. TS contents were lower in August compared with other sampling periods except for HN4. The mean values of the C/N, C/P and C/S ratios along a water-salinity gradient ranged from 26 to 72, 20 to 74, and 61 to 292, respectively. Generally, higher C/P ratios were observed in sampling sites with plant covers in October expect for HN1, whereas they were lower in January or August. SOC, TN and TP were significantly positively correlated with soil organic matter (SOM), silt, WC and cation exchange capacity (CEC) (p 0.05). Bulk density (BD) had a great influence on C/N ratio, C/P ratio were mainly effected by SOM, EC and silt, while C/S ratio showed a significant negative correlation with BD, EC, K+, Na+, and Mg2+ (p < 0.05).

  7. Oxygen Non-Stoichiometry and Electrical Conductivity of LA0.2Sr0.8Fe0.8B0.2O3-d, B = Fe, Ti, Ta

    NARCIS (Netherlands)

    Lohne, O.F.; Phung, T.N.; Grande, T.; Bouwmeester, Henricus J.M.; Hendriksen, P.V.; Sogaard, M.; Wiik, K.

    2014-01-01

    The oxygen non-stoichiometry was determined by coulometric titration for the perovskite oxides La0.2Sr0.8FeO3−δ and La0.2Sr0.8Fe0.8B0.2O3−δ (B = Ti4+ and Ta5+) in the temperature range 600 ◦C ≤ T ≤ 900 ◦C and the oxygen partial pressure range: 1 · 10−15 ≤ pO2 ≤ 0.209 atm. The non-stoichiometry (δ)

  8. The influence of Hurricanes Katrina and Rita on the inflammatory cytokine response and protein expression in A549 cells exposed to PM2.5 collected in the Baton Rouge-Port Allen industrial corridor of Southeastern Louisiana in 2005.

    Science.gov (United States)

    Bourgeois, Brian; Owens, John Wesley

    2014-03-01

    Hurricanes Katrina and Rita hit the coast of Louisiana in 2005 and killed more than 2000 people. The two storms resulted in a significant spike in particulate matter (PM2.5) levels across the state of Louisiana. This report focuses on PM2.5 samples collected in 2005 from two monitoring sites in the neighboring cities of Baton Rouge and Port Allen, Louisiana. Inductively coupled plasma (ICP) revealed the presence of PM2.5-adsorbed representative and Fenton-active transition metals. Gas chromatography/mass spectrometry (GC-MS) analyses revealed the presence of 23 PAH compounds. Endotoxins were also detected. Metals and endotoxins were extracted with water. PAH were extracted with dichloromethane. In order to assess cytotoxicity, aqueous PM2.5 extracts were introduced to A549 Human Epithelial Lung Carcinoma Cells. Results indicated decreased cell viability in a dose-dependent manner, with an LC50 of 235 µg/ml and 250 µg/ml, respectively, for the two sites featured here. Endotoxins alone were not cytotoxic. The concentration of reactive oxygen species (ROS) and released LDH activity increased following exposure of A549 cells to aqueous PM2.5 extracts. Fluorescence microscopy revealed apoptotic and necrotic cell death mechanisms. ELISA revealed increased secretion of primary pro-inflammatory cytokines, IL-6, IL-8, and TNF-α. Global PCR gene expression revealed up-regulation of proteins associated with the cytokine storm; e.g. interleukins, chemokines, and TNF-α. Global antibody microarray was consistent with an inflammatory response, with up-regulation of cytokines involved in the down-field activation of the caspase cascade and kinase pathways. The up-regulation of metal-redox sensitive transcription factors, NF-κβ and AP-1, is consistent with a cell death mechanism initiated by Fenton-active transition metal redox catalysis.

  9. Exploring the Spatiotemporal Organization of Membrane Proteins in Living Plant Cells.

    Science.gov (United States)

    Wang, Li; Xue, Yiqun; Xing, Jingjing; Song, Kai; Lin, Jinxing

    2018-04-29

    Plasma membrane proteins have important roles in transport and signal transduction. Deciphering the spatiotemporal organization of these proteins provides crucial information for elucidating the links between the behaviors of different molecules. However, monitoring membrane proteins without disrupting their membrane environment remains difficult. Over the past decade, many studies have developed single-molecule techniques, opening avenues for probing the stoichiometry and interactions of membrane proteins in their native environment by providing nanometer-scale spatial information and nanosecond-scale temporal information. In this review, we assess recent progress in the development of labeling and imaging technology for membrane protein analysis. We focus in particular on several single-molecule techniques for quantifying the dynamics and assembly of membrane proteins. Finally, we provide examples of how these new techniques are advancing our understanding of the complex biological functions of membrane proteins.

  10. Chromosome-wise Protein Interaction Patterns and Their Impact on Functional Implications of Large-Scale Genomic Aberrations

    DEFF Research Database (Denmark)

    Kirk, Isa Kristina; Weinhold, Nils; Belling, Kirstine González-Izarzugaza

    2017-01-01

    Gene copy-number changes influence phenotypes through gene-dosage alteration and subsequent changes of protein complex stoichiometry. Human trisomies where gene copy numbers are increased uniformly over entire chromosomes provide generic cases for studying these relationships. In most trisomies......, gene and protein level alterations have fatal consequences. We used genome-wide protein-protein interaction data to identify chromosome-specific patterns of protein interactions. We found that some chromosomes encode proteins that interact infrequently with each other, chromosome 21 in particular. We...... combined the protein interaction data with transcriptome data from human brain tissue to investigate how this pattern of global interactions may affect cellular function. We identified highly connected proteins that also had coordinated gene expression. These proteins were associated with important...

  11. Stoichiometry and Change of the mRNA Closed-Loop Factors as Translating Ribosomes Transit from Initiation to Elongation

    Czech Academy of Sciences Publication Activity Database

    Wang, X.; Xi, W.; Toomey, S.; Chiang, Y.-CH.; Hašek, Jiří; Laue, T.M.; Denis, C.L.

    2016-01-01

    Roč. 11, č. 3 (2016), e0150616 E-ISSN 1932-6203 Institutional support: RVO:61388971 Keywords : DEADENYLATION IN-VIVO * SACCHAROMYCES-CEREVISIAE * POLY(A)-BINDING PROTEIN Subject RIV: EE - Microbiology, Virology Impact factor: 2.806, year: 2016

  12. MAD data collection - current trends

    International Nuclear Information System (INIS)

    Dementieva, I.; Evans, G.; Joachimiak, A.; Sanishvili, R.; Walsh, M. A.

    1999-01-01

    The multi-wavelength anomalous diffraction, or MAD, method of determining protein structure is becoming routine in protein crystallography. An increase in the number of tuneable synchrotrons beamlines coupled with the widespread availability position-sensitive X-ray detectors based on charged-coupled devices and having fast readout raised MAD structure determination to a new and exciting level. Ultra-fast MAD data collection is now possible. Recognition of the value of selenium for phasing protein structures and improvement of methods for incorporating selenium into proteins in the form of selenomethionine have attracted greater interest in the MAD method. Recent developments in crystallographic software are complimenting the above advances, paving the way for rapid protein structure determination. An overview of a typical MAD experiment is described here, with emphasis on the rates and quality of data acquisition now achievable at beamlines developed at third-generation synchrotrons sources

  13. Oxygen stoichiometry shift of irradiated LWR-fuels at high burn-ups: Review of data and alternative interpretation of recently published results

    International Nuclear Information System (INIS)

    Spino, J.; Peerani, P.

    2008-01-01

    The available oxygen potential data of LWR-fuels by the EFM-method have been reviewed and compared with thermodynamic data of equivalent simulated fuels and mixed oxide systems, combined with the analysis of lattice parameter data. Up to burn-ups of 70-80 GWd/tM the comparison confirmed traditional predictions anticipating the fuels to remain quasi stoichiometric along irradiation. However, recent predictions of a fuel with average burn-up around 100 GWd/tM becoming definitely hypostoichiometric were not confirmed. At average burn-ups around 80 GWd/tM and above, it is shown that the fuels tend to acquire progressively slightly hyperstoichiometric O/M ratios. The maximum derived O/M ratio for an average burn-up of 100 GWd/tM lies around 2.001 and 2.002. Though slight, the stoichiometry shift may have a measurable accelerating impact on fission gas diffusion and release

  14. Impact of cation stoichiometry on the early stage of growth of SrTiO{sub 3} deposited by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Chencheng, E-mail: c.xu@fz-juelich.de; Moors, Marco; Dittmann, Regina

    2015-12-30

    Highlights: • Stoichiometry dependence of SrTiO{sub 3} sub-monolayer growth monitored by RHEED/AFM. • Reduced surface diffusion of non-stoichiometric SrTiO{sub 3} was detected. • A modified step density model correlates surface diffusion and RHEED minimum. - Abstract: By performing in situ growth studies during pulsed laser deposition, we observed a strong reduction of the surface diffusion coefficients for slightly non-stoichiometric SrTiO{sub 3}. Both, stoichiometric and non-stoichiometric thin films exhibit 2D layer by layer growth. However, in the non-stoichiometric case the 2D island coalescence is significantly delayed, which goes along with a shift of the reflection high electron energy diffraction (RHEED) minimum. We could explain this shift of the RHEED minimum by developing a model for the step density evolution taking into account finite surface diffusion.

  15. Correlation of the superconducting transition to oxygen stoichiometry in single-crystal Ba1-xKxBiO3-y

    Science.gov (United States)

    Mosley, W. D.; Dykes, J. W.; Klavins, P.; Shelton, R. N.; Sterne, P. A.; Howell, R. H.

    1993-07-01

    Temperature-dependent positron-lifetime experiments have been performed from room temperature to 15 K on single crystals of the oxide superconductor Ba1-xKxBiO3-y. Results indicate that the filling of oxygen vacancies has a marked impact on the superconducting properties of this system. Cation defect concentrations were below the detectable limit of positron-annihilation-analysis techniques in this material, which is in sharp contrast to identical studies on polycrystalline samples. We find that the positron lifetime in these electrochemically deposited single crystals is determined by the oxygen stoichiometry of the lattice, but there is no experimental signature of strong positron localization. By performing a subsequent oxygen anneal on the crystals, the superconducting transition is sharpened and the onset is raised. The observed change in positron lifetime associated with this annealing procedure is in quantitative agreement with theory.

  16. Unusual stoichiometry control in the atomic layer deposition of manganese borate films from manganese bis(tris(pyrazolyl)borate) and ozone

    International Nuclear Information System (INIS)

    Klesko, Joseph P.; Bellow, James A.; Saly, Mark J.; Winter, Charles H.; Julin, Jaakko; Sajavaara, Timo

    2016-01-01

    The atomic layer deposition (ALD) of films with the approximate compositions Mn 3 (BO 3 ) 2 and CoB 2 O 4 is described using MnTp 2 or CoTp 2 [Tp = tris(pyrazolyl)borate] with ozone. The solid state decomposition temperatures of MnTp 2 and CoTp 2 are ∼370 and ∼340 °C, respectively. Preparative-scale sublimations of MnTp 2 and CoTp 2 at 210 °C/0.05 Torr afforded >99% recoveries with <0.1% nonvolatile residues. Self-limited ALD growth was demonstrated at 325 °C for MnTp 2 or CoTp 2 with ozone as the coreactant. The growth rate for the manganese borate process was 0.19 Å/cycle within the ALD window of 300–350 °C. The growth rate for the cobalt borate process was 0.39–0.42 Å/cycle at 325 °C. X-ray diffraction of the as-deposited films indicated that they were amorphous. Atomic force microscopy of 35–36 nm thick manganese borate films grown within the 300–350 °C ALD window showed root mean square surface roughnesses of 0.4–0.6 nm. Film stoichiometries were assessed by x-ray photoelectron spectroscopy and time of flight-elastic recoil detection analysis. The differing film stoichiometries obtained from the very similar precursors MnTp 2 and CoTp 2 are proposed to arise from the oxidizing ability of the intermediate high valent manganese oxide layers and lack thereof for cobalt.

  17. Unusual stoichiometry control in the atomic layer deposition of manganese borate films from manganese bis(tris(pyrazolyl)borate) and ozone

    Energy Technology Data Exchange (ETDEWEB)

    Klesko, Joseph P.; Bellow, James A.; Saly, Mark J.; Winter, Charles H., E-mail: chw@chem.wayne.edu [Department of Chemistry, Wayne State University, Detroit, Michigan 48202 (United States); Julin, Jaakko; Sajavaara, Timo [Department of Physics, University of Jyväskylä, 40014 Jyväskylä (Finland)

    2016-09-15

    The atomic layer deposition (ALD) of films with the approximate compositions Mn{sub 3}(BO{sub 3}){sub 2} and CoB{sub 2}O{sub 4} is described using MnTp{sub 2} or CoTp{sub 2} [Tp = tris(pyrazolyl)borate] with ozone. The solid state decomposition temperatures of MnTp{sub 2} and CoTp{sub 2} are ∼370 and ∼340 °C, respectively. Preparative-scale sublimations of MnTp{sub 2} and CoTp{sub 2} at 210 °C/0.05 Torr afforded >99% recoveries with <0.1% nonvolatile residues. Self-limited ALD growth was demonstrated at 325 °C for MnTp{sub 2} or CoTp{sub 2} with ozone as the coreactant. The growth rate for the manganese borate process was 0.19 Å/cycle within the ALD window of 300–350 °C. The growth rate for the cobalt borate process was 0.39–0.42 Å/cycle at 325 °C. X-ray diffraction of the as-deposited films indicated that they were amorphous. Atomic force microscopy of 35–36 nm thick manganese borate films grown within the 300–350 °C ALD window showed root mean square surface roughnesses of 0.4–0.6 nm. Film stoichiometries were assessed by x-ray photoelectron spectroscopy and time of flight-elastic recoil detection analysis. The differing film stoichiometries obtained from the very similar precursors MnTp{sub 2} and CoTp{sub 2} are proposed to arise from the oxidizing ability of the intermediate high valent manganese oxide layers and lack thereof for cobalt.

  18. An analysis of diet quality, how it controls fatty acid profiles, isotope signatures and stoichiometry in the malaria mosquito Anopheles arabiensis.

    Directory of Open Access Journals (Sweden)

    Rebecca Hood-Nowotny

    Full Text Available Knowing the underlying mechanisms of mosquito ecology will ensure effective vector management and contribute to the overall goal of malaria control. Mosquito populations show a high degree of population plasticity in response to environmental variability. However, the principle factors controlling population size and fecundity are for the most part unknown. Larval habitat and diet play a crucial role in subsequent mosquito fitness. Developing the most competitive insects for sterile insect technique programmes requires a "production" orientated perspective, to deduce the most effective larval diet formulation; the information gained from this process offers us some insight into the mechanisms and processes taking place in natural native mosquito habitats.Fatty acid profiles and de-novo or direct assimilation pathways, of whole-individual mosquitoes reared on a range of larval diets were determined using pyrolysis gas chromatograph/mass spectrometry. We used elemental analysis and isotope ratio mass spectrometry to measure individual-whole-body carbon, nitrogen and phosphorous values and to assess the impact of dietary quality on subsequent population stoichiometry, size, quality and isotopic signature. Diet had the greatest impact on fatty acid (FA profiles of the mosquitoes, which exhibited a high degree of dietary routing, characteristic of generalist feeders. De-novo synthesis of a number of important FAs was observed. Mosquito C:N stoichiometry was fixed in the teneral stage. Dietary N content had significant influence on mosquito size, and P was shown to be a flexible pool which limited overall population size.Direct routing of FAs was evident but there was ubiquitous de-novo synthesis suggesting mosquito larvae are competent generalist feeders capable of survival on diet with varying characteristics. It was concluded that nitrogen availability in the larval diet controlled teneral mosquito size and that teneral CN ratio is a sex- and

  19. Influences of micro-geomorphology on the stoichiometry of C, N and P in Chenier Island soils and plants in the Yellow River Delta, China.

    Science.gov (United States)

    Qu, Fanzhu; Meng, Ling; Yu, Junbao; Liu, Jingtao; Sun, Jingkuan; Yang, Hongjun; Dong, Linshui

    2017-01-01

    Studies have indicated that consistent or well-constrained (relatively low variability) carbon:nitrogen:phosphorus (C:N:P) ratios exist in large-scale ecosystems, including both marine and terrestrial ecosystems. Little is known about the C, N and P stoichiometric ratios that exist in the soils and plants of Chenier Island in the Yellow River Delta (YRD). We examined the distribution patterns and relationships of C, N and P stoichiometry in the soils and plants of Chenier Island, as well as the potential influences of the island's micro-geomorphology. Based on a study of four soil profile categories and Phragmites australis and Suaeda heteroptera plant tissues, our results showed that micro-geomorphology could leave a distinct imprint on the soil and plant elemental stoichiometry of Chenier Island; significant variation in the atomic C:N:P ratios (RCNP) existed in soils and plants, indicating that the RCNP values in both the soil and plants are not well constrained at the Chenier Island scale. RCN and RCP in Chenier Island soils were high, whereas the RNP values were comparatively low, indicating that the ecosystems of Chenier Island are nutrient-limited by N and P. However, the RNP values in P. australis and S. heteroptera plant tissues were high, suggesting that the plants of Chenier Island are nutrient-limited by P. Finally, we suggest that soil and plant N:P ratios may be good indicators of the soil and plant nutrient status during soil development and plant growth, which could be a useful reference for restoring the degraded soils of Chenier Island.

  20. Mössbauer studies of stoichiometry of Fe{sub 3}O{sub 4}: characterization of nanoparticles for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, C. E., E-mail: cjohnson@utsi.edu; Johnson, J. A.; Hah, H. Y.; Cole, M.; Gray, S. [University of Tennessee Space Institute, Center for Laser Applications (United States); Kolesnichenko, V. [Xavier University, Department of Chemistry (United States); Kucheryavy, P. [Rutgers University, Department of Chemistry (United States); Goloverda, G. [Xavier University, Department of Chemistry (United States)

    2016-12-15

    The iron oxide Fe{sub 3}O{sub 4}, the mineral magnetite sometimes called ferrosoferric oxide, is notoriousy non-stoichiometric even in bulk form so its formula may be written Fe{sub 3−δ}O{sub 4}. In nanoparticle form, where it has applications in medicine and information technology, it is even more susceptible to oxidation. In this paper we report synthesis and studies of superparamagnetic Fe{sub 3}O{sub 4} nanoparticles with controlled diameters of 5.3, 10.6 and 11.9 nm. In room temperature spectra, departures from stoichiometry δ of up to 0.02 were estimated from the relative amounts of Fe {sup 3+}/ Fe {sup 2+} and from their isomer shifts. This cannot be used for very small particles of diameter 10.6 nm and less as they are superparamagnetic at room temperature and do not show hyperfine splitting owing to fast relaxation. Such particles have promise for use in enhancing MRI signals. The magnetic spectrum is restored by the application of a relatively small magnetic field (10 kG). As the temperature is lowered the relaxation slows down and 6-line magnetic hyperfine patterns appear below a blocking temperature T{sub B}. The values of T{sub B} obtained are lower than those of many other researchers reported in the literature, suggesting that our particles are less affected by magnetic interactions between them. At low temperatures all the spectra are similar and closely resemble that of bulk Fe{sub 3}O{sub 4} confirming that departures from stoichiometry are small.

  1. Cation non-stoichiometry in pulsed laser deposited Sr{sub 2+y}Fe{sub 1+x}Mo{sub 1-x}O₆ epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, T. L.; Woodward, P. M., E-mail: woodward.55@osu.edu [Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210-1117 (United States); Dixit, M.; Williams, R. E. A.; Susner, M. A.; Fraser, H. L.; McComb, D. W.; Sumption, M. D. [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210-1117 (United States); Lemberger, T. R. [Department of Physics, The Ohio State University, Columbus, Ohio 43210-1117 (United States)

    2014-07-07

    Sr₂FeMoO₆ (SFMO) films were grown on SrTiO₃ (100)- and (111)-oriented substrates via pulsed laser deposition (PLD). In order to study the fundamental characteristics of deposition, films were grown in two different PLD chambers. In chamber I, the best films were grown with a relatively long substrate-to-target distance (89 mm), high substrate temperature (850 °C), and low pressure (50 mTorr) in a 95% Ar/5% H₂ atmosphere. Although X-ray diffraction (XRD) measurements indicate these films are single phase, Rutherford Backscattering (RBS) measurements reveal considerable non-stoichiometry, corresponding to a Sr₂Fe{sub 1–x}Mo{sub 1+x}O₆ composition with x≅0.2–0.3. This level of non-stoichiometry results in inferior magnetic properties. In chamber II, the best films were grown with a much shorter substrate-to-target distance (38 mm), lower temperature (680 °C), and higher pressure (225 mTorr). XRD measurements show that the films are single phase, and RBS measurements indicate that they are nearly stoichiometric. The degree of ordering between Fe and Mo was dependent on both the temperature and pressure used during deposition, reaching a maximum order parameter of 85%. The saturation magnetization increases as the Fe/Mo ordering increases, reaching a maximum of 2.4 μB/f.u. Based on prior studies of bulk samples, one would expect a higher saturation magnetization for this degree of Fe/Mo order. The presence of extra strontium oxide layers in the form of Ruddlesden-Popper intergrowths appears to be responsible for the lower than expected saturation magnetization of these films.

  2. Defects, stoichiometry, and electronic transport in SrTiO{sub 3-δ} epilayers: A high pressure oxygen sputter deposition study

    Energy Technology Data Exchange (ETDEWEB)

    Ambwani, P.; Xu, P.; Jeong, J. S.; Deng, R.; Mkhoyan, K. A.; Jalan, B.; Leighton, C., E-mail: leighton@umn.edu [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Haugstad, G. [Characterization Facility, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2016-08-07

    SrTiO{sub 3} is not only of enduring interest due to its unique dielectric, structural, and lattice dynamical properties, but is also the archetypal perovskite oxide semiconductor and a foundational material in oxide heterostructures and electronics. This has naturally focused attention on growth, stoichiometry, and defects in SrTiO{sub 3}, one exciting recent development being such precisely stoichiometric defect-managed thin films that electron mobilities have finally exceeded bulk crystals. This has been achieved only by molecular beam epitaxy, however (and to a somewhat lesser extent pulsed laser deposition (PLD)), and numerous open questions remain. Here, we present a study of the stoichiometry, defects, and structure in SrTiO{sub 3} synthesized by a different method, high pressure oxygen sputtering, relating the results to electronic transport. We find that this form of sputter deposition is also capable of homoepitaxy of precisely stoichiometric SrTiO{sub 3}, but only provided that substrate and target preparation, temperature, pressure, and deposition rate are carefully controlled. Even under these conditions, oxygen-vacancy-doped heteroepitaxial SrTiO{sub 3} films are found to have carrier density, mobility, and conductivity significantly lower than bulk. While surface depletion plays a role, it is argued from particle-induced X-ray emission (PIXE) measurements of trace impurities in commercial sputtering targets that this is also due to deep acceptors such as Fe at 100's of parts-per-million levels. Comparisons of PIXE from SrTiO{sub 3} crystals and polycrystalline targets are shown to be of general interest, with clear implications for sputter and PLD deposition of this important material.

  3. The Effect of Barium Non-Stoichiometry on the Phase Structure, Sintering and Electrical Conductivity of BaZr0.7Pr0.1Y0.2O3

    KAUST Repository

    Mohamed Shibly, Kaamil

    2015-01-01

    This thesis attempts to test the effects of barium non stoichiometry and varying calcination temperatures on the microstructure and electrical conductivity of BaxZr0.7Pr0.1Y0.2O3- δ (x = 0.9, 1.0, 1.1). BZPY powders were fabricated using a

  4. The use of radiolabelled milk proteins to study thermally-induced interactions in milk systems

    International Nuclear Information System (INIS)

    Noh, B.

    1988-01-01

    Heat induced complexes between milk proteins are of considerable importance in determining the heat stability and rennin clottability of milk products. Thiol-disulfide interchange reactions have been suggested as the principal reaction mechanism for complex formation. Studies to data have not adequately established the mechanism and stoichiometry of complex formation in situ in total milk system. Tracer amounts of 14 C-β-lactoglobulin and α-lactalbumin were heated under various conditions. After clotting with rennet, radioactivity retained in the curd was counted to estimate extent of interaction of β-lactoglobulin with casein. 14 C- and 3 H-Methyl labelled proteins were used for the preparation of radiolabelled artificial casein micelles. These micelles with radiolabelled whey proteins were heated and heat-induced complexes were separated on Sephacryl S-300 eluting with 6 M guanidine hydrochloride to break all non-covalent bonds. Further separation of the protein complexes was obtained using CPG-10 or Sephacryl S-1000. The ratios of 3 H to 14 C labelled proteins in the protein complexes suggested that the stoichiometries of k-, α s2 -casein, β-lactoglobulin and α-lactalbumin in the heat-induced complexes varied as a function of the heat treatment

  5. Isotope coded protein labeling coupled immunoprecipitation (ICPL-IP): a novel approach for quantitative protein complex analysis from native tissue.

    Science.gov (United States)

    Vogt, Andreas; Fuerholzner, Bettina; Kinkl, Norbert; Boldt, Karsten; Ueffing, Marius

    2013-05-01

    High confidence definition of protein interactions is an important objective toward the understanding of biological systems. Isotope labeling in combination with affinity-based isolation of protein complexes has increased in accuracy and reproducibility, yet, larger organisms--including humans--are hardly accessible to metabolic labeling and thus, a major limitation has been its restriction to small animals, cell lines, and yeast. As composition as well as the stoichiometry of protein complexes can significantly differ in primary tissues, there is a great demand for methods capable to combine the selectivity of affinity-based isolation as well as the accuracy and reproducibility of isotope-based labeling with its application toward analysis of protein interactions from intact tissue. Toward this goal, we combined isotope coded protein labeling (ICPL)(1) with immunoprecipitation (IP) and quantitative mass spectrometry (MS). ICPL-IP allows sensitive and accurate analysis of protein interactions from primary tissue. We applied ICPL-IP to immuno-isolate protein complexes from bovine retinal tissue. Protein complexes of immunoprecipitated β-tubulin, a highly abundant protein with known interactors as well as the lowly expressed small GTPase RhoA were analyzed. The results of both analyses demonstrate sensitive and selective identification of known as well as new protein interactions by our method.

  6. Isotope Coded Protein Labeling Coupled Immunoprecipitation (ICPL-IP): A Novel Approach for Quantitative Protein Complex Analysis From Native Tissue*

    Science.gov (United States)

    Vogt, Andreas; Fuerholzner, Bettina; Kinkl, Norbert; Boldt, Karsten; Ueffing, Marius

    2013-01-01

    High confidence definition of protein interactions is an important objective toward the understanding of biological systems. Isotope labeling in combination with affinity-based isolation of protein complexes has increased in accuracy and reproducibility, yet, larger organisms—including humans—are hardly accessible to metabolic labeling and thus, a major limitation has been its restriction to small animals, cell lines, and yeast. As composition as well as the stoichiometry of protein complexes can significantly differ in primary tissues, there is a great demand for methods capable to combine the selectivity of affinity-based isolation as well as the accuracy and reproducibility of isotope-based labeling with its application toward analysis of protein interactions from intact tissue. Toward this goal, we combined isotope coded protein labeling (ICPL)1 with immunoprecipitation (IP) and quantitative mass spectrometry (MS). ICPL-IP allows sensitive and accurate analysis of protein interactions from primary tissue. We applied ICPL-IP to immuno-isolate protein complexes from bovine retinal tissue. Protein complexes of immunoprecipitated β-tubulin, a highly abundant protein with known interactors as well as the lowly expressed small GTPase RhoA were analyzed. The results of both analyses demonstrate sensitive and selective identification of known as well as new protein interactions by our method. PMID:23268931

  7. Modelling the interdependence between the stoichiometry of receptor oligomerization and ligand binding for a coexisting dimer/tetramer receptor system.

    Science.gov (United States)

    Rovira, X; Vivó, M; Serra, J; Roche, D; Strange, P G; Giraldo, J

    2009-01-01

    Many G protein-coupled receptors have been shown to exist as oligomers, but the oligomerization state and the effects of this on receptor function are unclear. For some G protein-coupled receptors, in ligand binding assays, different radioligands provide different maximal binding capacities. Here we have developed mathematical models for co-expressed dimeric and tetrameric species of receptors. We have considered models where the dimers and tetramers are in equilibrium and where they do not interconvert and we have also considered the potential influence of the ligands on the degree of oligomerization. By analogy with agonist efficacy, we have considered ligands that promote, inhibit or have no effect on oligomerization. Cell surface receptor expression and the intrinsic capacity of receptors to oligomerize are quantitative parameters of the equations. The models can account for differences in the maximal binding capacities of radioligands in different preparations of receptors and provide a conceptual framework for simulation and data fitting in complex oligomeric receptor situations.

  8. Stable intermediates determine proteins' primary unfolding sites in the presence of surfactants

    DEFF Research Database (Denmark)

    Petersen, Steen Vang; Andersen, Kell kleiner; Enghild, Jan J.

    2009-01-01

    Despite detailed knowledge of the overall structural changes and stoichiometries of surfactant binding, little is known about which protein regions constitute the preferred sites of attack for initial unfolding. Here we have exposed three proteins to limited proteolysis at anionic (SDS) and catio......Despite detailed knowledge of the overall structural changes and stoichiometries of surfactant binding, little is known about which protein regions constitute the preferred sites of attack for initial unfolding. Here we have exposed three proteins to limited proteolysis at anionic (SDS......) and cationic (DTAC) surfactant concentrations corresponding to specific conformational transitions, using the surfactant-robust broad-specificity proteases Savinase and Alcalase. Cleavage sites are identified by SDS-PAGE and N-terminal sequencing. We observe well-defined cleavage fragments, which suggest......, cleavage sites can be rationalized from the structure of the protein's folding transition state and the position of loops in the native state. Nevertheless, they are more sensitive to choice of surfactant and protease, probably reflecting a heterogeneous and fluctuating ensemble of partially unfolded...

  9. Unique self-assembly properties of a bridge-shaped protein dimer with quantum dots

    Science.gov (United States)

    Wang, Jianhao; Jiang, Pengju; Gao, Liqian; Yu, Yongsheng; Lu, Yao; Qiu, Lin; Wang, Cheli; Xia, Jiang

    2013-09-01

    How protein-protein interaction affects protein-nanoparticle self-assembly is the key to the understanding of biomolecular coating of nanoparticle in biological fluids. However, the relationship between protein shape and its interaction with nanoparticles is still under-exploited because of lack of a well-conceived binding system and a method to detect the subtle change in the protein-nanoparticle assemblies. Noticing this unresolved need, we cloned and expressed a His-tagged SpeA protein that adopts a bridge-shaped dimer structure, and utilized a high-resolution capillary electrophoresis method to monitor assembly formation between the protein and quantum dots (QDs, 5 nm in diameter). We observed that the bridge-shaped structure rendered a low SpeA:QD stoichiometry at saturation. Also, close monitoring of imidazole (Im) displacement of surface-bound protein revealed a unique two-step process. High-concentration Im could displace surface-bound SpeA protein and form a transient QD-protein intermediate, through a kinetically controlled displacement process. An affinity-driven equilibrium step then followed, resulting in re-assembling of the QD-protein complex in about 1 h. Through a temporarily formed intermediate, Im causes a rearrangement of His-tagged proteins on the surface. Thus, our work showcases that the synergistic interplay between QD-His-tag interaction and protein-protein interaction can result in unique properties of protein-nanoparticle assembly for the first time.

  10. A determination of the oxygen non-stoichiometry of the oxygen storage materials LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr)

    Energy Technology Data Exchange (ETDEWEB)

    Jeamjumnunja, Kannika; Gong, Wenquan; Makarenko, Tatyana; Jacobson, Allan J., E-mail: ajjacob@uh.edu

    2016-07-15

    The A-site ordered double-perovskite oxides, LnBaMn{sub 2}O{sub 5+δ} (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage properties of these materials. The present results are compared with our previous data for YBaMn{sub 2}O{sub 5+δ}. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn{sub 2}O{sub 5+δ}. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln{sup 3+} ions larger than Y{sup 3+}. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn{sub 2}O{sub 5} and fully-oxidized LnBaMn{sub 2}O{sub 6} during changes of the oxygen partial pressure between air and 1.99% H{sub 2}/Ar. In addition, the oxygen non-stoichiometries of GdBaMn{sub 2}O{sub 5+δ} and PrBaMn{sub 2}O{sub 5+δ} were determined as a function of pO{sub 2} at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching ~6. The stabilities of the LnBaMn{sub 2}O{sub 5+δ} phases extend over a wide range of oxygen partial pressures (∼10{sup −25}≤pO{sub 2} (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln{sup 3+} cation the lower pO{sub 2} for phase conversion. At some temperatures and pO{sub 2} conditions, the LnBaMn{sub 2}O{sub 5+δ} compounds are unstable with respect to decomposition to BaMnO{sub 3−δ} and LnMnO{sub 3}. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions. - Graphical abstract: Structure of Ln

  11. Workforce Competitiveness Collection. "LINCS" Resource Collection News

    Science.gov (United States)

    Literacy Information and Communication System, 2011

    2011-01-01

    This edition of "'LINCS' Resource Collection News" features the Workforce Competitiveness Collection, covering the topics of workforce education, English language acquisition, and technology. Each month Collections News features one of the three "LINCS" (Literacy Information and Communication System) Resource Collections--Basic…

  12. Structure and function of nanoparticle-protein conjugates

    International Nuclear Information System (INIS)

    Aubin-Tam, M-E; Hamad-Schifferli, K

    2008-01-01

    Conjugation of proteins to nanoparticles has numerous applications in sensing, imaging, delivery, catalysis, therapy and control of protein structure and activity. Therefore, characterizing the nanoparticle-protein interface is of great importance. A variety of covalent and non-covalent linking chemistries have been reported for nanoparticle attachment. Site-specific labeling is desirable in order to control the protein orientation on the nanoparticle, which is crucial in many applications such as fluorescence resonance energy transfer. We evaluate methods for successful site-specific attachment. Typically, a specific protein residue is linked directly to the nanoparticle core or to the ligand. As conjugation often affects the protein structure and function, techniques to probe structure and activity are assessed. We also examine how molecular dynamics simulations of conjugates would complete those experimental techniques in order to provide atomistic details on the effect of nanoparticle attachment. Characterization studies of nanoparticle-protein complexes show that the structure and function are influenced by the chemistry of the nanoparticle ligand, the nanoparticle size, the nanoparticle material, the stoichiometry of the conjugates, the labeling site on the protein and the nature of the linkage (covalent versus non-covalent)

  13. Identification of the protein kinase C phosphorylation site in neuromodulin

    International Nuclear Information System (INIS)

    Apel, E.D.; Byford, M.F.; Au, D.; Walsh, K.A.; Storm, D.R.

    1990-01-01

    Neuromodulin (P-57, GAP-43, B-50, F-1) is a neurospecific calmodulin binding protein that is phosphorylated by protein kinase C. Phosphorylation by protein kinase C has been shown to abolish the affinity of neuromodulin for calmodulin and the authors have proposed that the concentration of free CaM in neurons may be regulated by phosphorylation and dephosphorylation of neuromodulin. The purpose of this study was to identify the protein kinase C phosphorylation site(s) in neuromodulin using recombinant neuromodulin as a substrate. Toward this end, it was demonstrated that recombinant neuromodulin purified from Escherichia coli and bovine neuromodulin were phosphorylated with similar K m values and stoichiometries and that protein kinase C mediated phosphorylation of both proteins abolished binding to calmodulin-Sepharose. Recombinant neuromodulin was phosphorylated by using protein kinase C and [γ- 32 P]ATP and digested with trypsin, and the resulting peptides were separated by HPLC. Only one 32 P-labeled tryptic peptide was generated from phosphorylated neuromodulin. They conclude that serine-41 is the protein kinase C phosphorylation site of neuromodulin and that phosphorylation of this amino acid residue blocks binding of calmoculin to neuromodulin. The proximity of serine-41 to the calmodulin binding domain in neuromodulin very likely explains the effect of phosphorylation on the affinity of neuromodulin for calmodulin

  14. Expression and characterization of insulin growth factor-I-enhanced green fluorescent protein fused protein as a tracer for immunoassay

    Energy Technology Data Exchange (ETDEWEB)

    Shi Ruina [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Huang Yong [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Wang Dan [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Zhao Meiping [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Li Yuanzong [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)]. E-mail: yzli@pku.edu.cn

    2006-09-25

    The insulin-like growth factor-I (IGF-I) is an important polypeptide hormone under investigation for body metabolism study and for doping detection. Here, we describe for the first time the expression of a recombinant fusion protein of IGF-I and the enhanced green fluorescent protein (EGFP). The genetic fusion approach enables preparation of conjugates with 1:1 stoichiometry and homogeneous structure. The fused protein (EGFP-IGF-I) was expressed as a soluble protein in cytoplasm of Escherichia coli and its fluorescence and immunoreaction properties were thoroughly characterized. Finally, we demonstrated the utility of the EGFP-IGF-I fusion protein for the fluorescence immunoassay of IGF-1. The linear range of the assay is 1.6 x 10{sup -8} to 2.0 x 10{sup -6} M with a detection limit of 1.6 x 10{sup -8} M. To our knowledge, this is the first time that EGFP has been used as a quantitative label in a fusion protein to develop a quantitative assay for IGF-I. Furthermore, the use of genetically engineered fusion proteins, which combine peptide hormones with fluorescent protein, can lead to a new labeling approach to a number of bioanalytical applications.

  15. Expression and characterization of insulin growth factor-I-enhanced green fluorescent protein fused protein as a tracer for immunoassay

    International Nuclear Information System (INIS)

    Shi Ruina; Huang Yong; Wang Dan; Zhao Meiping; Li Yuanzong

    2006-01-01

    The insulin-like growth factor-I (IGF-I) is an important polypeptide hormone under investigation for body metabolism study and for doping detection. Here, we describe for the first time the expression of a recombinant fusion protein of IGF-I and the enhanced green fluorescent protein (EGFP). The genetic fusion approach enables preparation of conjugates with 1:1 stoichiometry and homogeneous structure. The fused protein (EGFP-IGF-I) was expressed as a soluble protein in cytoplasm of Escherichia coli and its fluorescence and immunoreaction properties were thoroughly characterized. Finally, we demonstrated the utility of the EGFP-IGF-I fusion protein for the fluorescence immunoassay of IGF-1. The linear range of the assay is 1.6 x 10 -8 to 2.0 x 10 -6 M with a detection limit of 1.6 x 10 -8 M. To our knowledge, this is the first time that EGFP has been used as a quantitative label in a fusion protein to develop a quantitative assay for IGF-I. Furthermore, the use of genetically engineered fusion proteins, which combine peptide hormones with fluorescent protein, can lead to a new labeling approach to a number of bioanalytical applications

  16. Careful stoichiometry monitoring and doping control during the tunneling interface growth of an n + InAs(Si)/p + GaSb(Si) Esaki diode

    Science.gov (United States)

    El Kazzi, S.; Alian, A.; Hsu, B.; Verhulst, A. S.; Walke, A.; Favia, P.; Douhard, B.; Lu, W.; del Alamo, J. A.; Collaert, N.; Merckling, C.

    2018-02-01

    In this work, we report on the growth of pseudomorphic and highly doped InAs(Si)/GaSb(Si) heterostructures on p-type (0 0 1)-oriented GaSb substrate and the fabrication and characterization of n+/p+ Esaki tunneling diodes. We particularly study the influence of the Molecular Beam Epitaxy shutter sequences on the structural and electrical characteristics of InAs(Si)/GaSb(Si) Esaki diodes structures. We use real time Reflection High Electron Diffraction analysis to monitor different interface stoichiometry at the tunneling interface. With Atomic Force Microscopy, X-ray diffraction and Transmission Electron Microscopy analyses, we demonstrate that an "InSb-like" interface leads to a sharp and defect-free interface exhibiting high quality InAs(Si) crystal growth contrary to the "GaAs-like" one. We then prove by means of Secondary Ion Mass Spectroscopy profiles that Si-diffusion at the interface allows the growth of highly Si-doped InAs/GaSb diodes without any III-V material deterioration. Finally, simulations are conducted to explain our electrical results where a high Band to Band Tunneling (BTBT) peak current density of Jp = 8 mA/μm2 is achieved.

  17. On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films.

    Science.gov (United States)

    Tileli, Vasiliki; Duchamp, Martial; Axelsson, Anna-Karin; Valant, Matjaz; Dunin-Borkowski, Rafal E; Alford, Neil McN

    2015-01-07

    The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces.

  18. Decolorization of malachite green, decolorization kinetics and stoichiometry of ozone-malachite green and removal of antibacterial activity with ozonation processes

    Energy Technology Data Exchange (ETDEWEB)

    Kusvuran, Erdal, E-mail: erdalkusvuran@yahoo.com [Chemistry Department, Arts and Sciences Faculty, Cukurova University, 01330 Balcali, Adana (Turkey); Gulnaz, Osman [Biology Department, Arts and Sciences Faculty, Cukurova University, 01330 Balcali, Adana (Turkey); Samil, Ali [Chemistry Department, Arts and Sciences Faculty, Sutcu Imam University, 46100 Kahramanmaras (Turkey); Yildirim, Ozlem [Chemistry Department, Arts and Sciences Faculty, Cukurova University, 01330 Balcali, Adana (Turkey)

    2011-02-15

    This study aimed to identify degradation intermediates and to investigate the stoichiometry of decolorization and degradation, decolorization kinetics, and removal of antibacterial activity of malachite green (MG) using ozonization processes. The decolorization of MG was optimal at an acidic pH value of 3 based on molecular ozone attack on MG molecules. The stoichiometric ratio of decolorization between ozone and MG was calculated to be 7.0 with a regression coefficient of 0.995, whereas the ratio for degradation was calculated as 13.1 with a regression coefficient of 0.998. With MG concentrations in the range of 0.30-1.82 mM, the concentration of decolorized MG increased with higher initial concentrations of MG, whereas the ozonolytic decolorization rates of MG, decreased with increasing initial concentration. The pseudo-first-order degradation rate constants (k') decreased with the initial concentration and ranged from 0.769 to 0.223 min{sup -1}. Twelve different intermediates were produced during the ozonation of MG with ozonation times between 5 min and 30 min and were identified by GC-MS. Although 86% of MG in the reaction mixture was removed by ozonation after 10 min, the decrease of antibacterial activity was very low (10%) for Bacillus subtilis and Staphylococcus epidermidis because the degradation intermediates, phenol and benzoic acid, also have antibacterial activity. The antibacterial activity of both MG and its intermediates were removed successfully with ozonation times above 26 min.

  19. Optimization of the Electrodeposition Parameters to Improve the Stoichiometry of In2S3 Films for Solar Applications Using the Taguchi Method

    Directory of Open Access Journals (Sweden)

    Maqsood Ali Mughal

    2014-01-01

    Full Text Available Properties of electrodeposited semiconductor thin films are dependent upon the electrolyte composition, plating time, and temperature as well as the current density and the nature of the substrate. In this study, the influence of the electrodeposition parameters such as deposition voltage, deposition time, composition of solution, and deposition temperature upon the properties of In2S3 films was analyzed by the Taguchi Method. According to Taguchi analysis, the interaction between deposition voltage and deposition time was significant. Deposition voltage had the largest impact upon the stoichiometry of In2S3 films and deposition temperature had the least impact. The stoichiometric ratios between sulfur and indium (S/In: 3/2 obtained from experiments performed with optimized electrodeposition parameters were in agreement with predicted values from the Taguchi Method. The experiments were carried out according to Taguchi orthogonal array L27 (3^4 design of experiments (DOE. Approximately 600 nm thick In2S3 films were electrodeposited from an organic bath (ethylene glycol-based containing indium chloride (InCl3, sodium chloride (NaCl, and sodium thiosulfate (Na2S2O3·5H2O, the latter used as an additional sulfur source along with elemental sulfur (S. An X-ray diffractometer (XRD, energy dispersive X-ray spectroscopy (EDS unit, and scanning electron microscope (SEM were, respectively, used to analyze the phases, elemental composition, and morphology of the electrodeposited In2S3 films.

  20. Decolorization of malachite green, decolorization kinetics and stoichiometry of ozone-malachite green and removal of antibacterial activity with ozonation processes

    International Nuclear Information System (INIS)

    Kusvuran, Erdal; Gulnaz, Osman; Samil, Ali; Yildirim, Ozlem

    2011-01-01

    This study aimed to identify degradation intermediates and to investigate the stoichiometry of decolorization and degradation, decolorization kinetics, and removal of antibacterial activity of malachite green (MG) using ozonization processes. The decolorization of MG was optimal at an acidic pH value of 3 based on molecular ozone attack on MG molecules. The stoichiometric ratio of decolorization between ozone and MG was calculated to be 7.0 with a regression coefficient of 0.995, whereas the ratio for degradation was calculated as 13.1 with a regression coefficient of 0.998. With MG concentrations in the range of 0.30-1.82 mM, the concentration of decolorized MG increased with higher initial concentrations of MG, whereas the ozonolytic decolorization rates of MG, decreased with increasing initial concentration. The pseudo-first-order degradation rate constants (k') decreased with the initial concentration and ranged from 0.769 to 0.223 min -1 . Twelve different intermediates were produced during the ozonation of MG with ozonation times between 5 min and 30 min and were identified by GC-MS. Although 86% of MG in the reaction mixture was removed by ozonation after 10 min, the decrease of antibacterial activity was very low (10%) for Bacillus subtilis and Staphylococcus epidermidis because the degradation intermediates, phenol and benzoic acid, also have antibacterial activity. The antibacterial activity of both MG and its intermediates were removed successfully with ozonation times above 26 min.

  1. Defect chemistry of ''BaCuO2''. Pt. 1. Oxygen non-stoichiometry, cation molecularity and X-ray diffraction determinations

    International Nuclear Information System (INIS)

    Spinolo, G.; Consiglio Nazionale delle Ricerche, Pavia; Anselmi-Tamburini, U.; Consiglio Nazionale delle Ricerche, Pavia; Arimondi, M.; Consiglio Nazionale delle Ricerche, Pavia; Ghigna, P.; Consiglio Nazionale delle Ricerche, Pavia; Flor, G.; Consiglio Nazionale delle Ricerche, Pavia

    1995-01-01

    ''BaCuO 2 '' is the key intermediate in the synthesis of the Ba 2 YCu 3 O 7-δ superconductor. Its very complex crystal structure is able to accommodate a large change in oxygen content. Oxygen non-stoichiometry of ''BaCuO 2 '' materials with 1:1 and 88:90 (Ba:Cu) molecularity has been investigated by polythermal X-ray powder diffraction coupled with isobaric-isothermal gravimetry determinations under different temperature and oxygen partial pressure conditions [300 ≤ T ≤ 820 C, 1 ≥ P(O 2 ) ≥3 . 10 -3 atm]. The 1:1 composition does not give well reproducible results, thus suggesting its polyphasic nature, at least in part of the investigated range. The results for the 88:90 ≅ 0.98 (Ba:Cu) composition are well reproducible and show that the material is single phase. Ba 0.98 CuO 1.98 + δ is oxygen over-stoichiometric in the whole investigated [T, P(O 2 )] range, with a maximum value δ ∼ 0.21. A Rietveld X-ray profile fitting is in agreement with previous single-crystal data. The trend of δ vs. P(O 2 ) is consistent with the presence of oxygen interstitial defects on (possibly different) crystallographic sites. (orig.)

  2. Surface stoichiometry modification and improved DC/RF characteristics by plasma treated and annealed AlGaN/GaN HEMTs

    Science.gov (United States)

    Upadhyay, Bhanu B.; Takhar, Kuldeep; Jha, Jaya; Ganguly, Swaroop; Saha, Dipankar

    2018-03-01

    We demonstrate that N2 and O2 plasma treatment followed by rapid thermal annealing leads to surface stoichiometry modification in a AlGaN/GaN high electron mobility transistor. Both the source/drain access and gate regions respond positively improving the transistor characteristics albeit to different extents. Characterizations indicate that the surface show the characteristics of that of a higher band-gap material like AlxOy and GaxOy along with N-vacancy in the sub-surface region. The N-vacancy leads to an increased two-dimensional electron gas density. The formation of oxides lead to a reduced gate leakage current and surface passivation. The DC characteristics show increased transconductance, saturation drain current, ON/OFF current ratio, sub-threshold swing and lower ON resistance by a factor of 2.9, 2.0, 103.3 , 2.3, and 2.1, respectively. The RF characteristics show an increase in unity current gain frequency by a factor of 1.7 for a 500 nm channel length device.

  3. CNP stoichiometry of a lipid-synthesising zooplankton, Calanus finmarchicus, from winter to spring bloom in a sub-Arctic sound

    Science.gov (United States)

    Aubert, A. B.; Svensen, C.; Hessen, D. O.; Tamelander, T.

    2013-02-01

    The aim of this study was to investigate the seasonal stoichiometry of the high-latitude lipid-synthesising copepod Calanus finmarchicus and assess how this would affect dietary demands with season, ontogeny and lipid storage. C:N:P ratios in different stages (adults, copepodite V and IV), in eggs and faecal pellets as well as in bulk food (seston) was analysed in a sub-Arctic Norwegian sound (69° 47'N, 19° 19'E) from late February to mid-May 2009. The period covered the phytoplankton bloom and was divided into four sequences of the bloom based on chl a and seston C:chl a ratio variations. The calculation of the somatic elemental C:N and C:P body ratios (without the lipid storage) indicates that nearly homeostatic control in C. finmarchicus is maintained in somatic tissues within stages, while not if the lipid storage pool is included. Nutrient limitation was assessed calculating threshold elemental ratios based on the somatic body ratios and for different sets of assimilation efficiencies, and indicated a predominant C limitation that may reflect demands for lipid storage. The results suggest that stoichiometric composition and demands in such high-latitude, lipid-storing species strongly depend on stage and season, and the large contribution of storage lipids highlights the need for a two-compartment approach for lipid-synthesising species, with different dietary requirements for somatic growth and for lipid storage.

  4. Structure of the protein which gives the mitochondrial ATPase its sensitivity to oligomycin (OSCP). Approach of OSCP structural parameters by neutron scattering and spectroscopic techniques

    International Nuclear Information System (INIS)

    Dupuis, Alain

    1983-01-01

    This research thesis reports the study of OSCP structure of beef heart mitochondria. The OSCP is a lysine-rich protein which contains five tyrosine residues exposed to a solvent and no tryptophan residue. The molecular mass is determined by gel electrophoresis. Small angle neutron scattering is used to show that OSCP is an elongated protein. The distribution of residues of amino acids in the protein, and the preferential localisation of lysine residues in equatorial regions of the molecules are noticed by using neutron scattering by OSCP in solution in D 2 O. A preliminary functional study determined the stoichiometry and the dissociation constants with which OSCP interacts with mitochondrial ATPase [fr

  5. Stoichiometric balance of protein copy numbers is measurable and functionally significant in a protein-protein interaction network for yeast endocytosis.

    Science.gov (United States)

    Holland, David O; Johnson, Margaret E

    2018-03-01

    Stoichiometric balance, or dosage balance, implies that proteins that are subunits of obligate complexes (e.g. the ribosome) should have copy numbers expressed to match their stoichiometry in that complex. Establishing balance (or imbalance) is an important tool for inferring subunit function and assembly bottlenecks. We show here that these correlations in protein copy numbers can extend beyond complex subunits to larger protein-protein interactions networks (PPIN) involving a range of reversible binding interactions. We develop a simple method for quantifying balance in any interface-resolved PPINs based on network structure and experimentally observed protein copy numbers. By analyzing such a network for the clathrin-mediated endocytosis (CME) system in yeast, we found that the real protein copy numbers were significantly more balanced in relation to their binding partners compared to randomly sampled sets of yeast copy numbers. The observed balance is not perfect, highlighting both under and overexpressed proteins. We evaluate the potential cost and benefits of imbalance using two criteria. First, a potential cost to imbalance is that 'leftover' proteins without remaining functional partners are free to misinteract. We systematically quantify how this misinteraction cost is most dangerous for strong-binding protein interactions and for network topologies observed in biological PPINs. Second, a more direct consequence of imbalance is that the formation of specific functional complexes depends on relative copy numbers. We therefore construct simple kinetic models of two sub-networks in the CME network to assess multi-protein assembly of the ARP2/3 complex and a minimal, nine-protein clathrin-coated vesicle forming module. We find that the observed, imperfectly balanced copy numbers are less effective than balanced copy numbers in producing fast and complete multi-protein assemblies. However, we speculate that strategic imbalance in the vesicle forming module

  6. Analysis of Ba{sub x}Sr{sub y}TiO{sub 3} perovskite layers. II. Development of analytical method for the determination of the stoichiometry and trace impurities by ICP-MS

    Energy Technology Data Exchange (ETDEWEB)

    Boulyga, S.F. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen]|[Radiation Physics and Chemistry Problems Inst., Minsk (Belarus); Becker, J.S. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen

    2000-11-01

    Determination of stoichiometry in semiconducting and non-conducting thin layers is of importance for the study of growth mechanisms and for the control of defects during their development and production. An analytical procedure for inductively coupled plasma mass spectrometry (ICP-MS) was developed using different ICP-MS instruments [one double-focusing sector field ICP-MS (DF-ICP-MS) and two quadrupole ICP-MS without and with hexapole collision cell (ICP-QMS and HEX-ICP-QMS, respectively)] for the determination of stoichiometry and trace impurities in thin Ba{sub x}Sr{sub y}TiO{sub 3} (BST) perovskite layers on silicon substrates after dissolution of layer. Maximum sensitivity, lowest detection limits and best precision was achieved in DF-ICP-MS. ICP-QMS with hexapole collision cell yielded better sensitivity and lower limits of detection in comparison to conventional quadrupole ICP-MS. (orig.)

  7. Impact of fluorescent protein fusions on the bacterial flagellar motor.

    Science.gov (United States)

    Heo, M; Nord, A L; Chamousset, D; van Rijn, E; Beaumont, H J E; Pedaci, F

    2017-10-03

    Fluorescent fusion proteins open a direct and unique window onto protein function. However, they also introduce the risk of perturbation of the function of the native protein. Successful applications of fluorescent fusions therefore rely on a careful assessment and minimization of the side effects, but such insight is still lacking for many applications. This is particularly relevant in the study of the internal dynamics of motor proteins, where both the chemical and mechanical reaction coordinates can be affected. Fluorescent proteins fused to the stator of the Bacterial Flagellar Motor (BFM) have previously been used to unveil the motor subunit dynamics. Here we report the effects on single motors of three fluorescent proteins fused to the stators, all of which altered BFM behavior. The torque generated by individual stators was reduced while their stoichiometry remained unaffected. MotB fusions decreased the switching frequency and induced a novel bias-dependent asymmetry in the speed in the two directions. These effects could be mitigated by inserting a linker at the fusion point. These findings provide a quantitative account of the effects of fluorescent fusions to the stator on BFM dynamics and their alleviation- new insights that advance the use of fluorescent fusions to probe the dynamics of protein complexes.

  8. Oxygen Non-Stoichiometry and Electrical Conductivity of La0.2Sr0.8Fe0.8B0.2O3 − δ, B = Fe, Ti, Ta

    DEFF Research Database (Denmark)

    Lohne, Ørjan Fossmark; Phung, Tan Nhut; Grande, Tor

    2014-01-01

    The oxygen non-stoichiometry was determined by coulometric titration for the perovskite oxides La0.2Sr0.8FeO3 − δ and La0.2Sr0.8Fe0.8B0.2O3 − δ (B = Ti4+ and Ta5+) in the temperature range 600 °C ⩽ T ⩽ 900 °C and the oxygen partial pressure range: 1⋅10-15≤po2≤0.209 atm. The non-stoichiometry (δ...... for the substituted materials. The electrical conductivity was measured at T = 900 °C in the oxygen partial pressure range: 1⋅10-17≤po2≤0.209 atm. The electrical conductivity and charge carrier mobility decrease upon 20% substitution of Fe roughly by a factor of 2, but do not show a significant dependence......) is observed to decrease with B-site substitution of Fe. The data can be well fitted with simple defect chemistry models. At low oxygen non-stoichiometry all compositions show a deviation from a localized electrons defect model. The standard and partial molar thermodynamic quantities were obtained...

  9. Collection Directions: The Evolution of Library Collections and Collecting

    Science.gov (United States)

    Dempsey, Lorcan; Malpas, Constance; Lavoie, Brian

    2014-01-01

    This article takes a broad view of the evolution of collecting behaviors in a network environment and suggests some future directions based on various simple models. The authors look at the changing dynamics of print collections, at the greater engagement with research and learning behaviors, and at trends in scholarly communication. The goal is…

  10. A centrifugation-based physicochemical characterization method for the interaction between proteins and nanoparticles

    Science.gov (United States)

    Bekdemir, Ahmet; Stellacci, Francesco

    2016-10-01

    Nanomedicine requires in-depth knowledge of nanoparticle-protein interactions. These interactions are studied with methods limited to large or fluorescently labelled nanoparticles as they rely on scattering or fluorescence-correlation signals. Here, we have developed a method based on analytical ultracentrifugation (AUC) as an absorbance-based, label-free tool to determine dissociation constants (KD), stoichiometry (Nmax), and Hill coefficient (n), for the association of bovine serum albumin (BSA) with gold nanoparticles. Absorption at 520 nm in AUC renders the measurements insensitive to unbound and aggregated proteins. Measurements remain accurate and do not become more challenging for small (sub-10 nm) nanoparticles. In AUC, frictional ratio analysis allows for the qualitative assessment of the shape of the analyte. Data suggests that small-nanoparticles/protein complexes significantly deviate from a spherical shape even at maximum coverage. We believe that this method could become one of the established approaches for the characterization of the interaction of (small) nanoparticles with proteins.

  11. Protein Kinase B/Akt Binds and Phosphorylates PED/PEA-15, Stabilizing Its Antiapoptotic Action

    OpenAIRE

    Trencia, Alessandra; Perfetti, Anna; Cassese, Angela; Vigliotta, Giovanni; Miele, Claudia; Oriente, Francesco; Santopietro, Stefania; Giacco, Ferdinando; Condorelli, Gerolama; Formisano, Pietro; Beguinot, Francesco

    2003-01-01

    The antiapoptotic protein PED/PEA-15 features an Akt phosphorylation motif upstream from Ser116. In vitro, recombinant PED/PEA-15 was phosphorylated by Akt with a stoichiometry close to 1. Based on Western blotting with specific phospho-Ser116 PED/PEA-15 antibodies, Akt phosphorylation of PED/PEA-15 occurred mainly at Ser116. In addition, a mutant of PED/PEA-15 featuring the substitution of Ser116→Gly (PEDS116→G) showed 10-fold-decreased phosphorylation by Akt. In intact 293 cells, Akt also i...

  12. On the Relationship of Magnetocrystalline Anisotropy and Stoichiometry in Epitaxial L1{sub 0} CoPt(001) and FePt(001) Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Barmak, K

    2004-08-10

    Two series of epitaxial CoPt and FePt films, with nominal thicknesses of 42 or 50 nm, were prepared by sputtering onto single crystal MgO(001) substrates in order to investigate the chemical ordering and the resultant magnetic properties as a function of alloy composition. In the first series, the film composition was kept constant, while the substrate temperature was increased from 144 to 704 C. In the second series the substrate temperature was kept constant at 704 C for CoPt and 620 C for FePt, while the alloy stoichiometry was varied in the nominalrange of 40-60 at% Co(Fe). Film compositions and thicknesses were measured via Rutherford backscattering spectrometry. The lattice and long-range order parameter for the L1{sub 0} phase were obtained for both sets of films using x-ray diffraction. The room-temperature magnetocrystalline anisotropy constants were determined for a subset of the films using torque magnetometry. The order parameter was found to increase with increasing temperature, with ordering occurring more readily in FePt when compared with CoPt. A perpendicular anisotropy developed in CoPt for substrate temperatures above 534 C and in FePt above 321 C. The structure and width of the magnetic domains in CoPt and FePt, as seen by magnetic force microscopy, also demonstrated an increase in magnetic anisotropy with increasing temperature. For the films deposited at the highest temperatures (704 C for CoPt and 620 C for FePt), the order parameter reached a maximum near the equiatomic composition, whereas the magnetocrystalline anisotropy increased as the concentration of Co or Fe was increased from below to slightly above the equiatomic composition. It is concluded that non-stoichiometric L1{sub 0} CoPt and FePt, with a slight excess of Co or Fe, are preferable for applications requiring the highest anisotropies.

  13. Dependency of the properties of Sr xBi yTa2O9 thin films on the Sr and Bi stoichiometry

    International Nuclear Information System (INIS)

    Viapiana, Matteo; Schwitters, Michael; Wouters, Dirk J.; Maes, Herman E.; Van der Biest, Omer

    2005-01-01

    In this study the properties of ferroelectric SBT thin films crystallized at 700 deg. C have been investigated as function of the Sr and Bi stoichiometry. A matrix of 130 nm Sr x Bi y Ta 2 O 9 films with 0.7 ≤ x ≤ 1.0 and 2.0 ≤ y ≤ 2.4 has been realized by metal-organic spin-on deposition technique on Pt/IrO 2 /Ir/TiAlN/SiO 2 /Si substrates. Within this composition range, we found that the ferroelectric properties peak into a narrow window of 0.8 ≤ x ≤ 0.9 and y ∼ 2.25 with Pr and Ec of 6.5 μC/cm 2 and 50 kV/cm, respectively (at 2.5 V). Outside this composition window, the Pr decreases while the hysteresis loop becomes slanted. For some Sr/Bi-ratios even no ferroelectricity was achieved. 2Ec-tendencies were seen as function of the x/y-ratios, too. Examination of the microstructure of the films by scanning electron microscopy showed that film grain size increased with decreasing Sr-deficiency and that nucleation increased with increasing Bi-excess. At high Sr-deficiency and low Bi-excess, no complete crystallization of the SBT film occurs. From the film morphology, also different phases can be discriminated. X-ray diffraction analysis showed a strong correlation of the film orientation with the film composition. While our results show a clear correlation of Pr, film grain size and orientation with composition, further investigations are required to clarify the relation of the hysteresis parameters with film orientation

  14. Short-Term Effects of Drying-Rewetting and Long-Term Effects of Nutrient Loading on Periphyton N:P Stoichiometry

    Directory of Open Access Journals (Sweden)

    Andres D. Sola

    2018-01-01

    Full Text Available Nitrogen (N and phosphorus (P concentrations and N:P ratios critically influence periphyton productivity and nutrient cycling in aquatic ecosystems. In coastal wetlands, variations in hydrology and water source (fresh or marine influence nutrient availability, but short-term effects of drying and rewetting and long-term effects of nutrient exposure on periphyton nutrient retention are uncertain. An outdoor microcosm experiment simulated short-term exposure to variation in drying-rewetting frequency on periphyton mat nutrient retention. A 13-year dataset from freshwater marshes of the Florida Everglades was examined for the effect of long-term proximity to different N and P sources on mat-forming periphyton nutrient standing stocks and stoichiometry. Field sites were selected from one drainage with shorter hydroperiod and higher connectivity to freshwater anthropogenic nutrient supplies (Taylor Slough/Panhandle, TS/Ph and another drainage with longer hydroperiod and higher connectivity to marine nutrient supplies (Shark River Slough, SRS. Total P, but not total N, increased in periphyton mats exposed to both low and high drying-rewetting frequency with respect to the control mats in our experimental microcosm. In SRS, N:P ratios slightly decreased downstream due to marine nutrient supplies, while TS/Ph increased. Mats exposed to short-term drying-rewetting had higher nutrient retention, similar to nutrient standing stocks from long-term field data. Periphyton mat microbial communities may undergo community shifts upon drying-rewetting and chronic exposure to nutrient loads. Additional work on microbial species composition may further explain how periphyton communities interact with drying-rewetting dynamics to influence nutrient cycling and retention in wetlands.

  15. The role of C:N:P stoichiometry in affecting denitrification in sediments from agricultural surface and tile-water wetlands.

    Science.gov (United States)

    Grebliunas, Brian D; Perry, William L

    2016-01-01

    Nutrient stoichiometry within a wetland is affected by the surrounding land use, and may play a significant role in the removal of nitrate (NO3-N). Tile-drained, agricultural watersheds experience high seasonal inputs of NO3-N, but low phosphorus (PO4-P) and dissolved organic carbon (DOC) loads relative to surface water dominated systems. This difference may present stoichiometric conditions that limit denitrification within receiving waterways. We investigated how C:N:P ratios affected denitrification rates of sediments from tile-drained mitigation wetlands incubated for: 0, 5, 10, and 20 days. We then tested whether denitrification rates of sediments from surface-water and tile-drained wetlands responded differently to C:N ratios of 2:1 versus 4:1. Ratios of C:N:P (P tile-drained wetland sediments. Carbon limitation of denitrification became evident at elevated NO3-N concentrations (20 mg L(-1)). Denitrification measured from tile water and surface water wetland sediments increased significantly (P < 0.05) at the 2:1 and 4:1 C:N treatments. The results from both experiments suggest wetland sediments provide a limiting pool of labile DOC to maintain prolonged NO3-N removal. Also, DOC limitation became more evident at elevated NO3-N concentrations (20 mg L(-1)). Irrespective of NO3-N concentrations, P did not limit denitrification rates. In addition to wetting period, residence time, and maintenance of anaerobic conditions, the availability of labile DOC is playing an important limiting role in sediment denitrification within mitigation wetlands.

  16. How Diverse Detrital Environments Influence Nutrient Stoichiometry between Males and Females of the Co-Occurring Container Mosquitoes Aedes albopictus, Ae. aegypti, and Culex quinquefasciatus.

    Science.gov (United States)

    Yee, Donald A; Kaufman, Michael G; Ezeakacha, Nnaemeka F

    2015-01-01

    Allocation patterns of carbon and nitrogen in animals are influenced by food quality and quantity, as well as by inherent metabolic and physiological constraints within organisms. Whole body stoichiometry also may vary between the sexes who differ in development rates and reproductive allocation patterns. In aquatic containers, such as tree holes and tires, detrital inputs, which vary in amounts of carbon and nitrogen, form the basis of the mosquito-dominated food web. Differences in development times and mass between male and female mosquitoes may be the result of different reproductive constraints, which could also influence patterns of nutrient allocation. We examined development time, survival, and adult mass for males and females of three co-occurring species, Aedes albopictus, Ae. aegypti, and Culex quinquefasciatus, across environments with different ratios of animal and leaf detritus. We quantified the contribution of detritus to biomass using stable isotope analysis and measured tissue carbon and nitrogen concentrations among species and between the sexes. Development times were shorter and adults were heavier for Aedes in animal versus leaf-only environments, whereas Culex development times were invariant across detritus types. Aedes displayed similar survival across detritus types whereas C. quinquefasciatus showed decreased survival with increasing leaf detritus. All species had lower values of 15N and 13C in leaf-only detritus compared to animal, however, Aedes generally had lower tissue nitrogen compared to C. quinquefasciatus. There were no differences in the C:N ratio between male and female Aedes, however, Aedes were different than C. quinquefasciatus adults, with male C. quinquefasciatus significantly higher than females. Culex quinquefasciatus was homeostatic across detrital environments. These results allow us to hypothesize an underlying stoichiometric explanation for the variation in performance of different container species under similar

  17. Spectrofluorimetric determination of stoichiometry and association constants of the complexes of harmane and harmine with beta-cyclodextrin and chemically modified beta-cyclodextrins.

    Science.gov (United States)

    Martín, L; León, A; Olives, A I; Del Castillo, B; Martín, M A

    2003-06-13

    The association characteristics of the inclusion complexes of the beta-carboline alkaloids harmane and harmine with beta-cyclodextrin (beta-CD) and chemically modified beta-cyclodextrins such as hydroxypropyl-beta-cyclodextrin (HPbeta-CD), 2,3-di-O-methyl-beta-cyclodextrin (DMbeta-CD) and 2,3,6-tri-O-methyl-beta-cyclodextrin (TMbeta-CD) are described. The association constants vary from 112 for harmine/DMbeta-CD to 418 for harmane/HPbeta-CD. The magnitude of the interactions between the host and the guest molecules depends on the chemical and geometrical characteristics of the guest molecules and therefore the association constants vary for the different cyclodextrin complexes. The steric hindrance is higher in the case of harmine due to the presence of methoxy group on the beta-carboline ring. The association obtained for the harmane complexes is stronger than the one observed for harmine complexes except in the case of harmine/TMbeta-CD. Important differences in the association constants were observed depending on the experimental variable used in the calculations (absolute value of fluorescence intensity or the ratio between the fluorescence intensities corresponding to the neutral and cationic forms). When fluorescence intensity values were considered, the association constants were higher than when the ratio of the emission intensity for the cationic and neutral species was used. These differences are a consequence of the co-existence of acid-base equilibria in the ground and in excited states together with the complexation equilibria. The existence of a proton transfer reaction in the excited states of harmane or harmine implies the need for the experimental dialysis procedure for separation of the complexes from free harmane or harmine. Such methodology allows quantitative results for stoichiometry determinations to be obtained, which show the existence of both 1:1 and 1:2 beta-carboline alkaloid:CD complexes with different solubility properties.

  18. Effect of precursors stoichiometry on morphology, crystallinity and electrical properties of ZnTe epilayers grown on (100)GaAs by MOVPE

    International Nuclear Information System (INIS)

    Paiano, P.; Lovergine, N.; Mancini, A.M.; Prete, P.

    2005-01-01

    The effect of precursors vapour stoichiometry on the morphological, structural and electrical properties of nominally undoped ZnTe grown on (100)GaAs by metalorganic vapour phase epitaxy is reported. The epilayers were grown at 350 C using dimethylzinc (Me 2 Zn) and di-isopropyltelluride, varying their molar flow rate ratios (MFRs) between 0.17 and 3.10. Growth in nearly stoichiometric (MFR=1.03) conditions results in best surface morphology, while samples grown in Te-rich conditions (MFR>1.7) showed micron-size hollow defects (with surface densities up to ∝10 6 cm -2 ) elongated in one of the left angle 011 right angle in-plane directions. The defects are associated to a local structural disorder of the material, ascribed to the formation of a Ga 2 Te 3 extrinsic phase at the ZnTe/GaAs interface. Ohmic contacts to p -ZnTe epilayers were prepared by tungsten evaporation and annealing at 350 C. The RT hole concentration in the epilayers varies almost linearly with Me 2 Zn molar flow between 2 x 10 15 cm -3 and 5 x 10 16 cm -3 . Temperature-dependent Hall measurements performed on samples grown at MFR≤1.03 demonstrate that the material p-type conductivity originates from a single acceptor centre with an ionisation energy between 94.7 meV and 118 meV, its concentration being in the 10 16 cm -3 range and slowly increasing with Me 2 Zn flow. We ascribe this acceptor to a complex formed by a substitutional carbon atom on a Te site and a donor on a nearest neighbor site (C Te -D Zn ), the donor impurity being further identified as Ga diffusing from the substrate. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Crystal structure of axolotl (Ambystoma mexicanum) liver bile acid-binding protein bound to cholic and oleic acid.

    Science.gov (United States)

    Capaldi, Stefano; Guariento, Mara; Perduca, Massimiliano; Di Pietro, Santiago M; Santomé, José A; Monaco, Hugo L

    2006-07-01

    The family of the liver bile acid-binding proteins (L-BABPs), formerly called liver basic fatty acid-binding proteins (Lb-FABPs) shares fold and sequence similarity with the paralogous liver fatty acid-binding proteins (L-FABPs) but has a different stoichiometry and specificity of ligand binding. This article describes the first X-ray structure of a member of the L-BABP family, axolotl (Ambystoma mexicanum) L-BABP, bound to two different ligands: cholic and oleic acid. The protein binds one molecule of oleic acid in a position that is significantly different from that of either of the two molecules that bind to rat liver FABP. The stoichiometry of binding of cholate is of two ligands per protein molecule, as observed in chicken L-BABP. The cholate molecule that binds buried most deeply into the internal cavity overlaps well with the analogous bound to chicken L-BABP, whereas the second molecule, which interacts with the first only through hydrophobic contacts, is more external and exposed to the solvent. (c) 2006 Wiley-Liss, Inc.

  20. Total protein

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/003483.htm Total protein To use the sharing features on this page, please enable JavaScript. The total protein test measures the total amount of two classes ...

  1. Proteins engineering

    International Nuclear Information System (INIS)

    2000-01-01

    At the - Departement d'Ingenierie et d'etudes de proteines (Deip) of the CEA more than seventy researchers are working hard to understand the function of proteins. For that they use the molecular labelling technique (F.M.)

  2. Whey Protein

    Science.gov (United States)

    ... reliable information about the safety of taking whey protein if you are pregnant or breast feeding. Stay on the safe side and avoid use. Milk allergy: If you are allergic to cow's milk, avoid using whey protein.

  3. Chemical synthesis and X-ray structure of a heterochiral {D-protein antagonist plus vascular endothelial growth factor} protein complex by racemic crystallography.

    Science.gov (United States)

    Mandal, Kalyaneswar; Uppalapati, Maruti; Ault-Riché, Dana; Kenney, John; Lowitz, Joshua; Sidhu, Sachdev S; Kent, Stephen B H

    2012-09-11

    Total chemical synthesis was used to prepare the mirror image (D-protein) form of the angiogenic protein vascular endothelial growth factor (VEGF-A). Phage display against D-VEGF-A was used to screen designed libraries based on a unique small protein scaffold in order to identify a high affinity ligand. Chemically synthesized D- and L- forms of the protein ligand showed reciprocal chiral specificity in surface plasmon resonance binding experiments: The L-protein ligand bound only to D-VEGF-A, whereas the D-protein ligand bound only to L-VEGF-A. The D-protein ligand, but not the L-protein ligand, inhibited the binding of natural VEGF(165) to the VEGFR1 receptor. Racemic protein crystallography was used to determine the high resolution X-ray structure of the heterochiral complex consisting of {D-protein antagonist + L-protein form of VEGF-A}. Crystallization of a racemic mixture of these synthetic proteins in appropriate stoichiometry gave a racemic protein complex of more than 73 kDa containing six synthetic protein molecules. The structure of the complex was determined to a resolution of 1.6 Å. Detailed analysis of the interaction between the D-protein antagonist and the VEGF-A protein molecule showed that the binding interface comprised a contact surface area of approximately 800 Å(2) in accord with our design objectives, and that the D-protein antagonist binds to the same region of VEGF-A that interacts with VEGFR1-domain 2.

  4. Structure of the cold-shock domain protein from Neisseria meningitidis reveals a strand-exchanged dimer

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Jingshan [The Oxford Protein Production Facility, Henry Wellcome Building for Genomic Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Division of Structural Biology, Henry Wellcome Building for Genomic Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Nettleship, Joanne E.; Sainsbury, Sarah [The Oxford Protein Production Facility, Henry Wellcome Building for Genomic Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Saunders, Nigel J. [Bacterial Pathogenesis and Functional Genomics Group, Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE (United Kingdom); Owens, Raymond J., E-mail: ray@strubi.ox.ac.uk [The Oxford Protein Production Facility, Henry Wellcome Building for Genomic Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN (United Kingdom)

    2008-04-01

    The X-ray crystal structure of the cold-shock domain protein from N. meningitidis reveals a strand-exchanged dimer. The structure of the cold-shock domain protein from Neisseria meningitidis has been solved to 2.6 Å resolution and shown to comprise a dimer formed by the exchange of two β-strands between protein monomers. The overall fold of the monomer closely resembles those of other bacterial cold-shock proteins. The neisserial protein behaved as a monomer in solution and was shown to bind to a hexathymidine oligonucleotide with a stoichiometry of 1:1 and a K{sub d} of 1.25 µM.

  5. Detection and quantification of proteins and cells by use of elemental mass spectrometry: progress and challenges.

    Science.gov (United States)

    Yan, Xiaowen; Yang, Limin; Wang, Qiuquan

    2013-07-01

    Much progress has been made in identification of the proteins in proteomes, and quantification of these proteins has attracted much interest. In addition to popular tandem mass spectrometric methods based on soft ionization, inductively coupled plasma mass spectrometry (ICPMS), a typical example of mass spectrometry based on hard ionization, usually used for analysis of elements, has unique advantages in absolute quantification of proteins by determination of an element with a definite stoichiometry in a protein or attached to the protein. In this Trends article, we briefly describe state-of-the-art ICPMS-based methods for quantification of proteins, emphasizing protein-labeling and element-tagging strategies developed on the basis of chemically selective reactions and/or biospecific interactions. Recent progress from protein to cell quantification by use of ICPMS is also discussed, and the possibilities and challenges of ICPMS-based protein quantification for universal, selective, or targeted quantification of proteins and cells in a biological sample are also discussed critically. We believe ICPMS-based protein quantification will become ever more important in targeted quantitative proteomics and bioanalysis in the near future.

  6. Stoichiometry and food chain dynamics.

    NARCIS (Netherlands)

    Kuijper, L.D.J.; Kooi, B.W.; Anderson, T.R.; Kooijman, S.A.L.M.

    2004-01-01

    Traditional models of chemostat systems looking at interactions between predator, prey and nutrients have used only a single currency, such as energy or nitrogen. In reality, growth of autotrophs and heterotrophs may be limited by various elements, e.g. carbon, nitrogen, phosphorous or iron. In this

  7. 77 FR 9663 - Agency Information Collection Activities; Proposed Collection; Comment Request; Request for...

    Science.gov (United States)

    2012-02-17

    ... submitted to the Agency. DATES: Submit either electronic or written comments on the collection of information by April 17, 2012. ADDRESSES: Submit electronic comments on the collection of information to http... biological products (e.g., Albumin, Plasma Protein Fraction, and therapeutic biological products) that are...

  8. A determination of the oxygen non-stoichiometry of the oxygen storage materials LnBaMn2O5+δ (Ln=Gd, Pr)

    Science.gov (United States)

    Jeamjumnunja, Kannika; Gong, Wenquan; Makarenko, Tatyana; Jacobson, Allan J.

    2016-07-01

    The A-site ordered double-perovskite oxides, LnBaMn2O5+δ (Ln=Gd, Pr), were synthesized and investigated to understand the effect of A site cation substitution on the oxygen storage properties of these materials. The present results are compared with our previous data for YBaMn2O5+δ. The results clearly reveal that changing the Ln cation strongly influences the oxidation/reduction behavior of LnBaMn2O5+δ. Based on thermogravimetric analysis data, oxygen uptake begins at lower temperatures in both air and oxygen in compounds with Ln3+ ions larger than Y3+. These oxides exhibit almost complete and reversible oxygen uptake/release between fully-reduced LnBaMn2O5 and fully-oxidized LnBaMn2O6 during changes of the oxygen partial pressure between air and 1.99% H2/Ar. In addition, the oxygen non-stoichiometries of GdBaMn2O5+δ and PrBaMn2O5+δ were determined as a function of pO2 at 600, 650, 700 and 750 °C by Coulometric titration at near-equilibrium conditions. The results confirm that these materials have two distinct phases on oxidation/reduction with δ≈0, 0.5 and a third phase with a range of composition with an oxygen content (5+δ) approaching 6. The stabilities of the LnBaMn2O5+δ phases extend over a wide range of oxygen partial pressures (∼10-25≤pO2 (atm)≤∼1) depending on temperature. Isothermal experiments show that the larger the Ln3+ cation the lower pO2 for phase conversion. At some temperatures and pO2 conditions, the LnBaMn2O5+δ compounds are unstable with respect to decomposition to BaMnO3-δ and LnMnO3. This instability is more apparent in Coulometric titration experiments than in thermogravimetric analysis. The Coulometric titration experiments are necessarily slow in order to achieve equilibrium oxygen compositions.

  9. Leaf non-structural carbohydrate allocation and C:N:P stoichiometry in response to light acclimation in seedlings of two subtropical shade-tolerant tree species.

    Science.gov (United States)

    Xie, Hongtao; Yu, Mukui; Cheng, Xiangrong

    2018-03-01

    Light availability greatly affects plant growth and development. In shaded environments, plants must respond to reduced light intensity to ensure a regular rate of photosynthesis to maintain the dynamic balance of nutrients, such as leaf non-structural carbohydrates (NSCs), carbon (C), nitrogen (N) and phosphorus (P). To improve our understanding of the nutrient utilization strategies of understory shade-tolerant plants, we compared the variations in leaf NSCs, C, N and P in response to heterogeneous controlled light conditions between two subtropical evergreen broadleaf shade-tolerant species, Elaeocarpus sylvestris (E. sylvestris) and Illicium henryi (I. henryi). Light intensity treatments were applied at five levels (100%, 52%, 33%, 15% and 6% full sunlight) for 30 weeks to identify the effects of reduced light intensity on leaf NSC allocation patterns and leaf C:N:P stoichiometry characteristics. We found that leaf soluble sugar, starch and NSC concentrations in E. sylvestris showed decreasing trends with reduced light intensity, whereas I. henryi presented slightly increasing trends from 100% to 15% full sunlight and then significant decreases at extremely low light intensity (6% full sunlight). The soluble sugar/starch ratio of E. sylvestris decreased with decreasing light intensity, whereas that of I. henryi remained stable. Moreover, both species exhibited increasing trends in leaf N and P concentrations but limited leaf N:P and C:P ratio fluctuations with decreasing light intensity, revealing their adaptive strategies for poor light environments and their growth strategies under ideal light environments. There were highly significant correlations between leaf NSC variables and C:N:P stoichiometric variables in both species, revealing a trade-off in photosynthesis production between leaf NSC and carbon allocation. Thus, shade-tolerant plants readjusted their allocation of leaf NSCs, C, N and P in response to light acclimation. Redundancy analysis showed

  10. Carbon, nitrogen and phosphorus accumulation and partitioning, and C:N:P stoichiometry in late-season rice under different water and nitrogen managements.

    Directory of Open Access Journals (Sweden)

    Yushi Ye

    Full Text Available Water and nitrogen availability plays an important role in the biogeochemical cycles of essential elements, such as carbon (C, nitrogen (N and phosphorus (P, in agricultural ecosystems. In this study, we investigated the seasonal changes of C, N and P concentrations, accumulation, partitioning, and C:N:P stoichiometric ratios in different plant tissues (root, stem-leaf, and panicle of late-season rice under two irrigation regimes (continuous flooding, CF; alternate wetting and drying, AWD and four N managements (control, N0; conventional urea at 240 kg N ha(-1, UREA; controlled-release bulk blending fertilizer at 240 kg N ha(-1, BBF; polymer-coated urea at 240 kg N ha(-1, PCU. We found that water and N treatments had remarkable effects on the measured parameters in different plant tissues after transplanting, but the water and N interactions had insignificant effects. Tissue C:N, N:P and C:P ratios ranged from 14.6 to 52.1, 3.1 to 7.8, and 76.9 to 254.3 over the rice growing seasons, respectively. The root and stem-leaf C:N:P and panicle C:N ratios showed overall uptrends with a peak at harvest whereas the panicle N:P and C:P ratios decreased from filling to harvest. The AWD treatment did not affect the concentrations and accumulation of tissue C and N, but greatly decreased those of P, resulting in enhanced N:P and C:P ratios. N fertilization significantly increased tissue N concentration, slightly enhanced tissue P concentration, but did not affect tissue C concentration, leading to a significant increase in tissue N:P ratio but a decrease in C:N and C:P ratios. Our results suggested that the growth of rice in the Taihu Lake region was co-limited by N and P. These findings broadened our understanding of the responses of plant C:N:P stoichiometry to simultaneous water and N managements in subtropical high-yielding rice systems.

  11. Stoichiometry of water-soluble ions in PM2.5: Application in source apportionment for a typical industrial city in semi-arid region, Northwest China

    Science.gov (United States)

    Zhou, Haijun; Lü, Changwei; He, Jiang; Gao, Manshu; Zhao, Boyi; Ren, Limin; Zhang, Lijun; Fan, Qingyun; Liu, Tao; He, Zhongxiang; Dudagula; Zhou, Bin; Liu, Hualin; Zhang, Yu

    2018-05-01

    Water-soluble ions (WSIs) are major components of PM2.5 and it is valuable for understanding physical and chemical characteristics, sources, behaviors and formation mechanism of WSIs. Baotou is a traditionally industrial city in semi-arid region and frequently subjected to dust storms from March to May. In recent years, air pollution has been listed as one of the most important environmental problems in Baotou. To investigate the seasonal variations and sources of WSIs in PM2.5, the WSIs including SO42-, NO3-, Cl-, F-, NH4+, K+, Na+, Ca2+ and Mg2+ were monitored at six urban sites in Baotou. The results showed that high concentrations of Ca2+ and Na+ were found responding to dust storm events, while high concentrations of SO42-, NO3-, NH4+, K+ and Cl- were observed during haze days. The correlations analysis indicated that excess sulfuric and nitric acid was likely neutralized by carbonate minerals such as calcite, aragonite and dolomite in normal days and cations were fully neutralized during all the sampling periods, while cations were excessive in dust storm days. The concentrations of [NH4+ + SO42- + NO3-], [Na+ + Ca2+ + Mg2+] and [Cl- + K+ + F-] indicated the northwest and southeast region of Baotou presented comparatively high contributions of secondary aerosol and crustal dust, respectively, which were mainly related to the industrial distribution and urbanization process. The cluster analysis, ternary diagram and principal component analysis have a good agreement in source apportionment, where crustal dust sources, secondary aerosol source and the mixture of coal combustion, biomass burning and industrial pollution sources were the main sources of WSIs in PM2.5. The seasonal pattern of sulfur oxidation ratio (SOR) was September > April > November > January, while the nitrogen oxidation ratio (NOR) April > January > November > September in Baotou. This work evaluated the seasonal variation, distribution and source of WSIs on the basis of its stoichiometry in

  12. Enhancing Thermoelectric Figure-of-Merit of Polycrystalline Na y CoO2 by a Combination of Non-stoichiometry and Co-substitution

    Science.gov (United States)

    Mallick, Md. Mofasser; Vitta, Satish

    2018-06-01

    Co-oxides with a layered structure are of interest for high-temperature thermoelectric applications as they can be tuned to enhance their electrical conductivity while retaining their low thermal conductivity. The figure-of-merit of Na y CoO2 has been enhanced using the combined effects of Na-non-stoichiometry and non-isoelectronic Co-substitution. A series of compounds Na0.7Co1- x Ni x O2 with x ≤ 0.1 have been synthesized using conventional techniques. Structural analysis using x-ray diffraction and Rietveld refinement shows the formation of a γ-NaCoO2-type phase in all the compounds. The presence of a small amount of NiO for x > 0.05 indicates that the solubility limit of Ni in Na0.7CoO2 is 5 at.%. All the compounds have been found to be p-type with the thermopower reaching a maximum of 220 μV K-1 at 1023 K for x = 0.1. The thermopower has been found to vary linearly with temperature for all the compounds; a degenerate metallic behavior. The electrical resistivity varies between 3 and 10 mΩ cm at all temperatures and has a metallic temperature dependence in agreement with the thermopower results. The power factor for the x = 0.1 compound reaches a maximum value of 0.55 mW m-1 K-2 at ˜ 900 K compared to 0.45 mW m-1 K-2 for the compound with no substitution. The thermal conductivity at 1023 K decreases from 1.2 to 0.9 W m-1 K-1 for x = 0.1. These factors lead to an increase of the figure-of-merit, zT, to 0.58 at 1023 K for x = 0.1, an increase of 57% compared to the unsubstituted compound. The magnetic studies show that Na0.7CoO2 is paramagnetic with an antiferromagnetic transition at ˜ 36 K. Substitution of Ni2+ for Co3+ has been found to induce a ferromagnetic-like transition at ˜ 240 K which is suppressed at high fields.

  13. Revisiting the concept of Redfield ratios applied to plankton stoichiometry - Addressing model uncertainties with respect to the choice of C:N:P ratios for phytoplankton

    Science.gov (United States)

    Kreus, Markus; Paetsch, Johannes; Grosse, Fabian; Lenhart, Hermann; Peck, Myron; Pohlmann, Thomas

    2017-04-01

    Ongoing Ocean Acidification (OA) and climate change related trends impact on physical (temperature), chemical (CO2 buffer capacity) and biological (stoichiometric) properties of the marine environment. These threats affect the global ocean but they appear particularly pronounced in marginal and shelf seas. Marine biogeochemical models are often used to investigate the impacts of climate change and changes in OA on the marine system as well as its exchange with the atmosphere. Different studies showed that both the structural composition of the models and the elemental ratios of particulate organic matter in the surface ocean affect the key processes controlling the ocean's efficiency storing atmospheric excess carbon. Recent studies focus on the variability of the elemental ratios of phytoplankton and found that the high plasticity of C:N:P ratios enables the storage of large amounts of carbon by incorporation into carbohydrates and lipids. Our analysis focuses on the North Sea, a temperate European shelf sea, for the period 2000-2014. We performed an ensemble of model runs differing only in phytoplankton stoichiometry, representing combinations of C:P = [132.5, 106, 79.5] and N:P=[20, 16, 12] (i.e., Redfield ratio +/- 25%). We examine systematically the variations in annual averages of net primary production (NPP), net ecosystem production in the upper 30 m (NEP30), export production below 30 m depth (EXP30), and the air-sea flux of CO2 (ASF). Ensemble average fluxes (and standard deviations) resulted in NPP = 15.4 (2.8) mol C m-2 a-1, NEP30 = 5.4 (1.1) mol C m-2 a-1, EXP30 = 8.1 (1.1) mol C m-2 a-1 and ASF = 1.1 (0.5) mol C m-2 a-1. All key parameters exhibit only minor variations along the axis of constant C:N, but correlate positively with increasing C:P and decreasing N:P ratios. Concerning regional differences, lowest variations in local fluxes due to different stoichiometric ratios can be found in the shallow southern and coastal North Sea. Highest

  14. Effect of precursors stoichiometry on morphology, crystallinity and electrical properties of ZnTe epilayers grown on (100)GaAs by MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Paiano, P.; Lovergine, N.; Mancini, A.M. [Dipartimento di Ingegneria dell' Innovazione, Universita di Lecce, Via Arnesano, I-73100 Lecce (Italy); Prete, P. [Istituto per la Microelettronica e Microsistemi del CNR, Sezione di Lecce, Via Arnesano, I-73100 Lecce (Italy)

    2005-11-01

    The effect of precursors vapour stoichiometry on the morphological, structural and electrical properties of nominally undoped ZnTe grown on (100)GaAs by metalorganic vapour phase epitaxy is reported. The epilayers were grown at 350 C using dimethylzinc (Me{sub 2}Zn) and di-isopropyltelluride, varying their molar flow rate ratios (MFRs) between 0.17 and 3.10. Growth in nearly stoichiometric (MFR=1.03) conditions results in best surface morphology, while samples grown in Te-rich conditions (MFR>1.7) showed micron-size hollow defects (with surface densities up to {proportional_to}10{sup 6} cm{sup -2}) elongated in one of the left angle 011 right angle in-plane directions. The defects are associated to a local structural disorder of the material, ascribed to the formation of a Ga{sub 2}Te{sub 3} extrinsic phase at the ZnTe/GaAs interface. Ohmic contacts to p -ZnTe epilayers were prepared by tungsten evaporation and annealing at 350 C. The RT hole concentration in the epilayers varies almost linearly with Me{sub 2}Zn molar flow between 2 x 10{sup 15} cm{sup -3} and 5 x 10{sup 16} cm{sup -3}. Temperature-dependent Hall measurements performed on samples grown at MFR{<=}1.03 demonstrate that the material p-type conductivity originates from a single acceptor centre with an ionisation energy between 94.7 meV and 118 meV, its concentration being in the 10{sup 16} cm{sup -3} range and slowly increasing with Me{sub 2}Zn flow. We ascribe this acceptor to a complex formed by a substitutional carbon atom on a Te site and a donor on a nearest neighbor site (C{sub Te}-D{sub Zn}), the donor impurity being further identified as Ga diffusing from the substrate. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Carbon, Nitrogen and Phosphorus Accumulation and Partitioning, and C:N:P Stoichiometry in Late-Season Rice under Different Water and Nitrogen Managements

    Science.gov (United States)

    Ye, Yushi; Liang, Xinqiang; Chen, Yingxu; Li, Liang; Ji, Yuanjing; Zhu, Chunyan

    2014-01-01

    Water and nitrogen availability plays an important role in the biogeochemical cycles of essential elements, such as carbon (C), nitrogen (N) and phosphorus (P), in agricultural ecosystems. In this study, we investigated the seasonal changes of C, N and P concentrations, accumulation, partitioning, and C:N:P stoichiometric ratios in different plant tissues (root, stem-leaf, and panicle) of late-season rice under two irrigation regimes (continuous flooding, CF; alternate wetting and drying, AWD) and four N managements (control, N0; conventional urea at 240 kg N ha−1, UREA; controlled-release bulk blending fertilizer at 240 kg N ha−1, BBF; polymer-coated urea at 240 kg N ha−1, PCU). We found that water and N treatments had remarkable effects on the measured parameters in different plant tissues after transplanting, but the water and N interactions had insignificant effects. Tissue C:N, N:P and C:P ratios ranged from 14.6 to 52.1, 3.1 to 7.8, and 76.9 to 254.3 over the rice growing seasons, respectively. The root and stem-leaf C:N:P and panicle C:N ratios showed overall uptrends with a peak at harvest whereas the panicle N:P and C:P ratios decreased from filling to harvest. The AWD treatment did not affect the concentrations and accumulation of tissue C and N, but greatly decreased those of P, resulting in enhanced N:P and C:P ratios. N fertilization significantly increased tissue N concentration, slightly enhanced tissue P concentration, but did not affect tissue C concentration, leading to a significant increase in tissue N:P ratio but a decrease in C:N and C:P ratios. Our results suggested that the growth of rice in the Taihu Lake region was co-limited by N and P. These findings broadened our understanding of the responses of plant C:N:P stoichiometry to simultaneous water and N managements in subtropical high-yielding rice systems. PMID:24992006

  16. Cartilage Acidic Protein 2 a hyperthermostable, high affinity calcium-binding protein.

    Science.gov (United States)

    Anjos, Liliana; Gomes, Ana S; Melo, Eduardo P; Canário, Adelino V; Power, Deborah M

    2013-03-01

    Cartilage Acidic Protein 2 (CRTAC2) is a novel protein present from prokaryotes to vertebrates with abundant expression in the teleost fish pituitary gland and an isoform of CRTAC1, a chondrocyte marker in humans. The two proteins are non-integrins containing N-terminal integrin-like Ca(2+)-binding motifs and their structure and function remain to be assigned. Structural studies of recombinant sea bream (sb)CRTAC2 revealed it is composed of 8.8% α-helix, 33.4% β-sheet and 57.8% unordered protein. sbCRTAC2 bound Ca(2+) with high affinity (K(d)=1.46nM) and favourable Gibbs free energy (∆G=-12.4kcal/mol). The stoichiometry for Ca(2+) bound to sbCRTAC2 at saturation indicated six Ca(2+) ligand-binding sites exist per protein molecule. No conformational change in sbCRTAC2 occurred in the presence of Ca(2+). Fluorescence emission revealed that the tertiary structure of the protein is hyperthermostable between 25°C and 95°C and the fully unfolded state is only induced by chemical denaturing (4M GndCl). sbCRTAC has a widespread tissue distribution and is present as high molecular weight aggregates, although strong reducing conditions promote formation of the monomer. sbCRTAC2 promotes epithelial cell outgrowth in vitro suggesting it may share functional homology with mammalian CRTAC1, recently implicated in cell-cell and cell-matrix interactions. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Unique self-assembly properties of a bridge-shaped protein dimer with quantum dots

    International Nuclear Information System (INIS)

    Wang, Jianhao; Jiang, Pengju; Gao, Liqian; Yu, Yongsheng; Lu, Yao; Qiu, Lin; Wang, Cheli; Xia, Jiang

    2013-01-01

    How protein–protein interaction affects protein–nanoparticle self-assembly is the key to the understanding of biomolecular coating of nanoparticle in biological fluids. However, the relationship between protein shape and its interaction with nanoparticles is still under-exploited because of lack of a well-conceived binding system and a method to detect the subtle change in the protein–nanoparticle assemblies. Noticing this unresolved need, we cloned and expressed a His-tagged SpeA protein that adopts a bridge-shaped dimer structure, and utilized a high-resolution capillary electrophoresis method to monitor assembly formation between the protein and quantum dots (QDs, 5 nm in diameter). We observed that the bridge-shaped structure rendered a low SpeA:QD stoichiometry at saturation. Also, close monitoring of imidazole (Im) displacement of surface-bound protein revealed a unique two-step process. High-concentration Im could displace surface-bound SpeA protein and form a transient QD–protein intermediate, through a kinetically controlled displacement process. An affinity-driven equilibrium step then followed, resulting in re-assembling of the QD–protein complex in about 1 h. Through a temporarily formed intermediate, Im causes a rearrangement of His-tagged proteins on the surface. Thus, our work showcases that the synergistic interplay between QD–His-tag interaction and protein–protein interaction can result in unique properties of protein–nanoparticle assembly for the first time

  18. Synergistic Control of Kinetochore Protein Levels by Psh1 and Ubr2.

    Directory of Open Access Journals (Sweden)

    Eva Herrero

    2016-02-01

    Full Text Available The accurate segregation of chromosomes during cell division is achieved by attachment of chromosomes to the mitotic spindle via the kinetochore, a large multi-protein complex that assembles on centromeres. The budding yeast kinetochore comprises more than 60 different proteins. Although the structure and function of many of these proteins has been investigated, we have little understanding of the steady state regulation of kinetochores. The primary model of kinetochore homeostasis suggests that kinetochores assemble hierarchically from the centromeric DNA via the inclusion of a centromere-specific histone into chromatin. We tested this model by trying to perturb kinetochore protein levels by overexpressing an outer kinetochore gene, MTW1. This increase in protein failed to change protein recruitment, consistent with the hierarchical assembly model. However, we find that deletion of Psh1, a key ubiquitin ligase that is known to restrict inner kinetochore protein loading, does not increase levels of outer kinetochore proteins, thus breaking the normal kinetochore stoichiometry. This perturbation leads to chromosome segregation defects, which can be partially suppressed by mutation of Ubr2, a second ubiquitin ligase that normally restricts protein levels at the outer kinetochore. Together these data show that Psh1 and Ubr2 synergistically control the amount of proteins at the kinetochore.

  19. Variation of crystallinity and stoichiometry in films of gallium oxide, gallium nitride and barium zirconate prepared by means of PLD; Variation von Kristallinitaet und Stoechiometrie in mittels PLD hergestellten Schichten aus Galliumoxid, Galliumnitrid und Bariumzirkonat

    Energy Technology Data Exchange (ETDEWEB)

    Brendt, Jochen

    2011-08-05

    Pulsed Laser Deposition (PLD) is an ablation technique for thin film preparation of many materials. The film properties can be well controlled by the process parameters. Therefore, in many cases a given material can be deposited with different properties by changing one or more process parameters. In this thesis thin films of gallium oxide, gallium nitride and barium zirconate were deposited with a large variation in structure and stoichiometry by means of Pulsed Laser Deposition. The characterization of the film crystallinity, phase purity and short range structural order was completed by means of X-ray diffraction and X-ray absorption spectroscopy. The stoichiometry was investigated using electron probe microanalysis. For analyzing the correlation between the structure and stoichiometry with the optical and electrical properties, optical absorption and electrical conductivity measurements were carried out. The investigation of all three material systems showed that very unique properties can be realized when combining an amorphous structure and a non-stoichiometric composition. For example, in amorphous and oxygen deficient gallium oxide an insulator-metal-transition can be induced by partial crystallization of the as prepared phase accomplished by annealing at about 400 C in argon atmosphere (as shown in literature). Furthermore, amorphous and highly non-stoichiometric barium zirconate has the ability to split water molecules to hydrogen and oxygen at room temperature. A detailed analysis of both phenomena has been performed by means of photoemission and transmission electron microscopy in the case of gallium oxide and via X-ray absorption spectroscopy and gas chromatography in the case of barium zirconate.

  20. Entropy as a collective variable

    Science.gov (United States)

    Parrinello, Michele

    Sampling complex free energy surfaces that exhibit long lived metastable states separated by kinetic bottlenecks is one of the most pressing issues in the atomistic simulations of matter. Not surprisingly many solutions to this problem have been suggested. Many of them are based on the identification of appropriate collective variables that span the manifold of the slow varying modes of the system. While much effort has been put in devising and even constructing on the fly appropriate collective variables there is still a cogent need of introducing simple, generic, physically transparent, and yet effective collective variables. Motivated by the physical observation that in many case transitions between one metastable state and another result from a trade off between enthalpy and entropy we introduce appropriate collective variables that are able to represent in a simple way these two physical properties. We use these variables in the context of the recently introduced variationally enhanced sampling and apply it them with success to the simulation of crystallization from the liquid and to conformational transitions in protein. Department of Chemistry and Applied Biosciences, ETH Zurich, and Facolta' di Informatica, Istituto di Scienze Computazionali, Universita' della Svizzera Italiana, Via G. Buffi 13, 6900 Lugano, Switzerland.

  1. Efeito do período de coleta de urina, dos níveis de concentrado e de fontes protéicas sobre a excreção de creatinina, de uréia e de derivados de purina e a produção microbiana em bovinos Nelore Effect of urinary collection days, concentrate levels and protein sources on creatinine, urea and purine derivatives excretions and microbial protein synthesis in Nellore cattle

    Directory of Open Access Journals (Sweden)

    Analívia Martins Barbosa

    2006-06-01

    categories of Nellore cattle: heifers, steers, bulls and lactating cows. Yield of Nmic estimated from spot urine samples was compared to that obtained by total urine collection. Sixteen feedlot Nellore animals were assigned to a completely randomized design in a split plot scheme with treatments (two levels of concentrate [25 or 50%] and four categories [heifers, steers, bulls and lactating cows] included in the plots (2 x 4 factorial arrangement and collection days (six days in the sub-plots. No significant interactions among concentrate levels, animal categories and collection days were observed. In addition, urinary volume was not affected by concentrate levels and collection days, although a significant effect was observed for cows. Neither treatments nor collection days significantly affected urinary excretion of creatinine that averaged 27.1 mg/kg0.75. Similar results were observed for absorbed purines and Nmic production. Production of Nmic estimated by spot urine sample did not differ from that obtained by total collection. The estimation of Nmic also was not affected by concentrate levels and animal category. It was concluded that 24-h urinary collection period is recommended for Nellore cattle and that was independent of animal category (heifers, steers, bulls and lactating cows. Therefore, spot urine samples can be used to estimate microbial protein synthesis.

  2. Towards modern petrological collections

    NARCIS (Netherlands)

    Kriegsman, L.M.

    2004-01-01

    Petrological collections result from sampling for academic research, for aesthetic or commercial reasons, and to document natural diversity. Selection criteria for reducing and enhancing collections include adequate documentation, potential for future use, information density, time and money

  3. Protein politics

    NARCIS (Netherlands)

    Vijver, Marike

    2005-01-01

    This study is part of the program of the interdisciplinary research group Profetas (protein foods, environment, technology and society). Profetas consists of technological, environmental and socio-economic research projects on protein food systems which result in the development of scenarios and

  4. Protein adhesives

    Science.gov (United States)

    Charles R. Frihart; Linda F. Lorenz

    2018-01-01

    Nature uses a wide variety of chemicals for providing adhesion internally (e.g., cell to cell) and externally (e.g., mussels to ships and piers). This adhesive bonding is chemically and mechanically complex, involving a variety of proteins, carbohydrates, and other compounds.Consequently,the effect of protein structures on adhesive properties is only partially...

  5. Métodos de coleta de fezes e determinação dos coeficientes de digestibilidade da fração protéica e da energia de alimentos para o pacu, Piaractus mesopotamicus (Holmberg, 1887 Fecal collection methods and determination of crude protein and of gross energy digestibility coefficients of feedstuffs for pacu, Piaractus mesopotamicus (Holmberg, 1887

    Directory of Open Access Journals (Sweden)

    Eduardo Gianini Abimorad

    2004-10-01

    concentrados protéicos pode ser utilizada como ótimas fontes de proteína, com exceção da farinha de sangue e a levedura, enquanto os alimentos energéticos confirmaram-se como excelentes fontes de energia em dietas para o pacu.To improve the pacu (Piaracatus mesopotamicus feeding in the growth phase, it's necessary to know the digestibility of the ingredients used in his diets. Initially, four fecal collection methods were analyzed (dissection, stripping, Guelph and modified Guelph, based on precision and versatility and also the most efficient time among fecal collection of the Guelph sedimentation systems, through crude protein digestibility coefficient of pacu basic diet. There was no difference among the fecal collection methods while the intervals of time among the collections were significantly different, which may interfere in the protein digestibility results. In a second stage, five proteins concentrated of animal origin, five of vegetable origin and four energetic were studied for estimating protein and energy digestibility coefficients using the stripping method. The rations contained 69.5% of a reference diet, 30.0% of the ingredient test and 0.5% of Cr2O3. In a general way, crude protein digestibility coefficients were high and did not differ from the wheat meal (93.89% and feather flour (75.73%, respectively. However, blood and yeast showed lower crude protein digestibility (57.72% and 68.86%, respectively. Gross energy digestibility coefficients varied considerably among the feedstuffs, showing high values (above 90% for the sorghum, rice meal and raw and toasted soy and lower values (smaller than 70% for poultry by-product and blood meal, soybean meal, cotton and yeast. However, with regard to the fecal collection methods, the results showed that anyone can be adopted with safety for digestibility determination, if used accurately. In a general way, most of protein concentrate can be used as a very good protein source, except for blood meal and the yeast

  6. Old tropical botanical collections

    DEFF Research Database (Denmark)

    Friis, Ib

    2017-01-01

    The early history of botanical collections is reviewed, with particular emphasis on old collections from the tropics. The information available about older and newer botanical collections from the tropics was much improved after World War Two, including better lists of validly published names, more...

  7. Tau protein

    DEFF Research Database (Denmark)

    Frederiksen, Jette Lautrup Battistini; Kristensen, Kim; Bahl, Jmc

    2011-01-01

    Background: Tau protein has been proposed as biomarker of axonal damage leading to irreversible neurological impairment in MS. CSF concentrations may be useful when determining risk of progression from ON to MS. Objective: To investigate the association between tau protein concentration and 14......-3-3 protein in the cerebrospinal fluid (CSF) of patients with monosymptomatic optic neuritis (ON) versus patients with monosymptomatic onset who progressed to multiple sclerosis (MS). To evaluate results against data found in a complete literature review. Methods: A total of 66 patients with MS and/or ON from...... the Department of Neurology of Glostrup Hospital, University of Copenhagen, Denmark, were included. CSF samples were analysed for tau protein and 14-3-3 protein, and clinical and paraclinical information was obtained from medical records. Results: The study shows a significantly increased concentration of tau...

  8. Satellite image collection optimization

    Science.gov (United States)

    Martin, William

    2002-09-01

    Imaging satellite systems represent a high capital cost. Optimizing the collection of images is critical for both satisfying customer orders and building a sustainable satellite operations business. We describe the functions of an operational, multivariable, time dynamic optimization system that maximizes the daily collection of satellite images. A graphical user interface allows the operator to quickly see the results of what if adjustments to an image collection plan. Used for both long range planning and daily collection scheduling of Space Imaging's IKONOS satellite, the satellite control and tasking (SCT) software allows collection commands to be altered up to 10 min before upload to the satellite.

  9. Collection time again.

    Science.gov (United States)

    Elder, D L

    1984-01-01

    Looking forward to your next round of collection calls? Few of us do, yet collections play a vital role in every group practice, large or small. This crop of practical collection tips is guaranteed to boost the morale of everyone involved in the collection process. Not only are the basics of a good collection call set down, but result-getting responses to frequent debtor excuses are provided. Telephoning the debtor patient need not be a dreaded task. Just have confidence, keep in mind that the patient does owe you for services rendered in good faith, and pick up the phone--it's a snap!

  10. Effect of Sr substituted La 2−x Sr x NiO 4+δ (x = 0, 0.2, 0.4, 0.6, and 0.8) on oxygen stoichiometry and oxygen transport properties

    KAUST Repository

    Inprasit, T.; Wongkasemjit, S.; Skinner, S. J.; Burriel, M.; Limthongkul, P.

    2015-01-01

    © The Royal Society of Chemistry 2015. Stoichiometry and oxygen diffusion properties of La2-xSrxNiO4±δ with x = 0.2, 0.4, 0.6, and 0.8 prepared via a sol-gel method were investigated in this study. Iodometric titration and thermogravimetric analysis were used to determine the oxygen non-stoichiometry. Over the entire compositional range, the samples exhibit oxygen hyperstoichiometry with the minimum value δ = 0.14 at x = 0.4. Mixed effects of reduction of oxygen excess and increasing valence of Ni were found to serve as charge compensation mechanisms; the former dominated at a low level of substitution, x < 0.4, while the latter dominated at higher levels of Sr (0.4 < x < 0.8). The highest oxygen diffusion coefficient was found for the minimum amount of Sr substitution, x = 0.2, continuously decreasing with x until x = 0.6. An unusual increase in D∗ was observed when the Sr content increased up to x = 0.8.

  11. In situ examination of oxygen non-stoichiometry in La0.80Sr0.20CoO3−δ thin films at intermediate and low temperatures by x-ray diffraction

    KAUST Repository

    Biegalski, M. D.

    2014-04-21

    Structural evolution of epitaxial La0.80Sr 0.20CoO3-δ thin films under chemical and voltage stimuli was examined in situ using X-ray diffraction. The changes in lattice parameter (chemical expansivity) were used to quantify oxygen reduction reaction processes and vacancy concentration changes in lanthanum strontium cobaltite. At 550 °C, the observed lattice parameter reduction at an applied bias of -0.6 V was equivalent to that from the reducing condition of a 2% carbon monoxide atmosphere with an oxygen non-stoichiometry δ of 0.24. At lower temperatures (200 °C), the application of bias reduced the sample much more effectively than a carbon monoxide atmosphere and induced an oxygen non-stoichiometry δ of 0.47. Despite these large changes in oxygen concentration, the epitaxial thin film was completely re-oxidized and no signs of crystallinity loss or film amorphization were observed. This work demonstrates that the effects of oxygen evolution and reduction can be examined with applied bias at low temperatures, extending the ability to probe these processes with in-situ analytical techniques. © 2014 AIP Publishing LLC.

  12. Collective Lyapunov modes

    International Nuclear Information System (INIS)

    Takeuchi, Kazumasa A; Chaté, Hugues

    2013-01-01

    We show, using covariant Lyapunov vectors in addition to standard Lyapunov analysis, that there exists a set of collective Lyapunov modes in large chaotic systems exhibiting collective dynamics. Associated with delocalized Lyapunov vectors, they act collectively on the trajectory and hence characterize the instability of its collective dynamics. We further develop, for globally coupled systems, a connection between these collective modes and the Lyapunov modes in the corresponding Perron–Frobenius equation. We thereby address the fundamental question of the effective dimension of collective dynamics and discuss the extensivity of chaos in the presence of collective dynamics. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’. (paper)

  13. Development of a Model Protein Interaction Pair as a Benchmarking Tool for the Quantitative Analysis of 2-Site Protein-Protein Interactions.

    Science.gov (United States)

    Yamniuk, Aaron P; Newitt, John A; Doyle, Michael L; Arisaka, Fumio; Giannetti, Anthony M; Hensley, Preston; Myszka, David G; Schwarz, Fred P; Thomson, James A; Eisenstein, Edward

    2015-12-01

    A significant challenge in the molecular interaction field is to accurately determine the stoichiometry and stepwise binding affinity constants for macromolecules having >1 binding site. The mission of the Molecular Interactions Research Group (MIRG) of the Association of Biomolecular Resource Facilities (ABRF) is to show how biophysical technologies are used to quantitatively characterize molecular interactions, and to educate the ABRF members and scientific community on the utility and limitations of core technologies [such as biosensor, microcalorimetry, or analytic ultracentrifugation (AUC)]. In the present work, the MIRG has developed a robust model protein interaction pair consisting of a bivalent variant of the Bacillus amyloliquefaciens extracellular RNase barnase and a variant of its natural monovalent intracellular inhibitor protein barstar. It is demonstrated that this system can serve as a benchmarking tool for the quantitative analysis of 2-site protein-protein interactions. The protein interaction pair enables determination of precise binding constants for the barstar protein binding to 2 distinct sites on the bivalent barnase binding partner (termed binase), where the 2 binding sites were engineered to possess affinities that differed by 2 orders of magnitude. Multiple MIRG laboratories characterized the interaction using isothermal titration calorimetry (ITC), AUC, and surface plasmon resonance (SPR) methods to evaluate the feasibility of the system as a benchmarking model. Although general agreement was seen for the binding constants measured using solution-based ITC and AUC approaches, weaker affinity was seen for surface-based method SPR, with protein immobilization likely affecting affinity. An analysis of the results from multiple MIRG laboratories suggests that the bivalent barnase-barstar system is a suitable model for benchmarking new approaches for the quantitative characterization of complex biomolecular interactions.

  14. Bacterial flagellar capping proteins adopt diverse oligomeric states

    Energy Technology Data Exchange (ETDEWEB)

    Postel, Sandra; Deredge, Daniel; Bonsor, Daniel A.; Yu, Xiong; Diederichs, Kay; Helmsing, Saskia; Vromen, Aviv; Friedler, Assaf; Hust, Michael; Egelman, Edward H.; Beckett, Dorothy; Wintrode, Patrick L.; Sundberg, Eric J. (UV); (Braunschweig); (Maryland-MED); (Konstanz); (Maryland); (Hebrew)

    2016-09-24

    Flagella are crucial for bacterial motility and pathogenesis. The flagellar capping protein (FliD) regulates filament assembly by chaperoning and sorting flagellin (FliC) proteins after they traverse the hollow filament and exit the growing flagellum tip. In the absence of FliD, flagella are not formed, resulting in impaired motility and infectivity. Here, we report the 2.2 Å resolution X-ray crystal structure of FliD fromPseudomonas aeruginosa, the first high-resolution structure of any FliD protein from any bacterium. Using this evidence in combination with a multitude of biophysical and functional analyses, we find thatPseudomonasFliD exhibits unexpected structural similarity to other flagellar proteins at the domain level, adopts a unique hexameric oligomeric state, and depends on flexible determinants for oligomerization. Considering that the flagellin filaments on which FliD oligomers are affixed vary in protofilament number between bacteria, our results suggest that FliD oligomer stoichiometries vary across bacteria to complement their filament assemblies.

  15. Protein Adsorption in Three Dimensions

    Science.gov (United States)

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  16. Reflections on collectivity

    International Nuclear Information System (INIS)

    Feshbach, H.

    1983-01-01

    Comments are made on papers presented to the International School of Nuclear Physics, Erice (1982) concerning collective bands and collectivity in nuclei. The importance of these collective modes of motion, the role of the Bohr-Mottelson model and the Interacting Boson Models (IBM-1 and IBM-2), and experimental evidence presented by a number of workers, are examined. The extensions of the models to take into account additional degrees of freedom both collective and non-collective, the discovery of new collective modes such as those corresponding to tri-axial shapes, and the possible existence of additional symmetries reported at the meeting, are discussed. Finally the importance is examined of relating the phenomenological models to a more fundamental underlying theory, which has been taken to be the nuclear shell model. (U.K.)

  17. Thermal proximity coaggregation for system-wide profiling of protein complex dynamics in cells.

    Science.gov (United States)

    Tan, Chris Soon Heng; Go, Ka Diam; Bisteau, Xavier; Dai, Lingyun; Yong, Chern Han; Prabhu, Nayana; Ozturk, Mert Burak; Lim, Yan Ting; Sreekumar, Lekshmy; Lengqvist, Johan; Tergaonkar, Vinay; Kaldis, Philipp; Sobota, Radoslaw M; Nordlund, Pär

    2018-03-09

    Proteins differentially interact with each other across cellular states and conditions, but an efficient proteome-wide strategy to monitor them is lacking. We report the application of thermal proximity coaggregation (TPCA) for high-throughput intracellular monitoring of protein complex dynamics. Significant TPCA signatures observed among well-validated protein-protein interactions correlate positively with interaction stoichiometry and are statistically observable in more than 350 annotated human protein complexes. Using TPCA, we identified many complexes without detectable differential protein expression, including chromatin-associated complexes, modulated in S phase of the cell cycle. Comparison of six cell lines by TPCA revealed cell-specific interactions even in fundamental cellular processes. TPCA constitutes an approach for system-wide studies of protein complexes in nonengineered cells and tissues and might be used to identify protein complexes that are modulated in diseases. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  18. Guanine nucleotide regulatory protein co-purifies with the D2-dopamine receptor

    International Nuclear Information System (INIS)

    Senogles, S.E.; Caron, M.G.

    1986-01-01

    The D 2 -dopamine receptor from bovine anterior pituitary was purified ∼1000 fold by affinity chromatography on CMOS-Sepharose. Reconstitution of the affinity-purified receptor into phospholipid vesicles revealed the presence of high and low affinity agonist sites as detected by N-n-propylnorapomorphine (NPA) competition experiments with 3 H-spiperone. High affinity agonist binding could be converted to the low affinity form by guanine nucleotides, indicating the presence of an endogenous guanine nucleotide binding protein (N protein) in the affinity-purified D 2 receptor preparations. Furthermore, this preparation contained an agonist-sensitive GTPase activity which was stimulated 2-3 fold over basal by 10 μM NPA. 35 S-GTPγS binding to these preparations revealed a stoichiometry of 0.4-0.7 mole N protein/mole receptor, suggesting the N protein may be specifically coupled with the purified D 2 -dopamine receptor and not present as a contaminant. Pertussis toxin treatment of the affinity purified receptor preparations prevented high affinity agonist binding, as well as agonist stimulation of the GTPase activity, presumably by inactivating the associated N protein. Pertussis toxin lead to the ADP-ribosylation of a protein of 39-40K on SDS-PAGE. These findings indicate that an endogenous N protein, N/sub i/ or N/sub o/, co-purifies with the D 2 -dopamine receptor which may reflect a precoupling of this receptor with an N protein within the membranes

  19. Collecting Taxes Database

    Data.gov (United States)

    US Agency for International Development — The Collecting Taxes Database contains performance and structural indicators about national tax systems. The database contains quantitative revenue performance...

  20. Estimate of dietary phosphorus intake using 24-h urine collection

    Science.gov (United States)

    Morimoto, Yuuka; Sakuma, Masae; Ohta, Hiroyuki; Suzuki, Akitsu; Matsushita, Asami; Umeda, Minako; Ishikawa, Makoto; Taketani, Yutaka; Takeda, Eiji; Arai, Hidekazu

    2014-01-01

    Increases in serum phosphorus levels and dietary phosphorus intake induces vascular calcification, arterial sclerosis and cardiovascular diseases. Limiting phosphorus intake is advisable, however, no assessment methods are capable of estimating dietary phosphorus intake. We hypothesized that urinary phosphorus excretion can be translated into estimation of dietary phosphorus intake, and we evaluated whether a 24-h urine collection method could estimate dietary phosphorus intake. Thirty two healthy subjects were recruited for this study. Subjects collected urine samples over 24 h and weighed dietary records. We calculated dietary protein intake and phosphorus intake from dietary records and urine collection, and investigated associations between the two methods in estimating protein and phosphorus intake. Significant positive correlations were observed between dietary records and UC for protein and phosphorus intake. The average intakes determined from dietary records were significantly higher than from urine collection for both protein and phosphorus. There was a significant positive correlation between both the phosphorus and protein difference in dietary records and urine collection. The phosphorus-protein ratio in urine collection was significantly higher than in dietary records. Our data indicated that the 24-h urine collection method can estimate the amount of dietary phosphorus intake, and the results were superior to estimation by weighed dietary record. PMID:25120281

  1. Visualization and characterization of individual type III protein secretion machines in live bacteria.

    Science.gov (United States)

    Zhang, Yongdeng; Lara-Tejero, María; Bewersdorf, Jörg; Galán, Jorge E

    2017-06-06

    Type III protein secretion machines have evolved to deliver bacterially encoded effector proteins into eukaryotic cells. Although electron microscopy has provided a detailed view of these machines in isolation or fixed samples, little is known about their organization in live bacteria. Here we report the visualization and characterization of the Salmonella type III secretion machine in live bacteria by 2D and 3D single-molecule switching superresolution microscopy. This approach provided access to transient components of this machine, which previously could not be analyzed. We determined the subcellular distribution of individual machines, the stoichiometry of the different components of this machine in situ, and the spatial distribution of the substrates of this machine before secretion. Furthermore, by visualizing this machine in Salmonella mutants we obtained major insights into the machine's assembly. This study bridges a major resolution gap in the visualization of this nanomachine and may serve as a paradigm for the examination of other bacterially encoded molecular machines.

  2. Solution structure of the human signaling protein RACK1

    Directory of Open Access Journals (Sweden)

    Papa Priscila F

    2010-06-01

    Full Text Available Abstract Background The adaptor protein RACK1 (receptor of activated kinase 1 was originally identified as an anchoring protein for protein kinase C. RACK1 is a 36 kDa protein, and is composed of seven WD repeats which mediate its protein-protein interactions. RACK1 is ubiquitously expressed and has been implicated in diverse cellular processes involving: protein translation regulation, neuropathological processes, cellular stress, and tissue development. Results In this study we performed a biophysical analysis of human RACK1 with the aim of obtaining low resolution structural information. Small angle X-ray scattering (SAXS experiments demonstrated that human RACK1 is globular and monomeric in solution and its low resolution structure is strikingly similar to that of an homology model previously calculated by us and to the crystallographic structure of RACK1 isoform A from Arabidopsis thaliana. Both sedimentation velocity and sedimentation equilibrium analytical ultracentrifugation techniques showed that RACK1 is predominantly a monomer of around 37 kDa in solution, but also presents small amounts of oligomeric species. Moreover, hydrodynamic data suggested that RACK1 has a slightly asymmetric shape. The interaction of RACK1 and Ki-1/57 was tested by sedimentation equilibrium. The results suggested that the association between RACK1 and Ki-1/57(122-413 follows a stoichiometry of 1:1. The binding constant (KB observed for RACK1-Ki-1/57(122-413 interaction was of around (1.5 ± 0.2 × 106 M-1 and resulted in a dissociation constant (KD of (0.7 ± 0.1 × 10-6 M. Moreover, the fluorescence data also suggests that the interaction may occur in a cooperative fashion. Conclusion Our SAXS and analytical ultracentrifugation experiments indicated that RACK1 is predominantly a monomer in solution. RACK1 and Ki-1/57(122-413 interact strongly under the tested conditions.

  3. Efficient Immutable Collections

    NARCIS (Netherlands)

    Steindorfer, M.J.

    2017-01-01

    This thesis proposes novel and efficient data structures, suitable for immutable collection libraries, that carefully balance memory footprint and runtime performance of operations, and are aware of constraints and platform co-design challenges on the Java Virtual Machine (JVM). Collection data

  4. Profiling a Periodicals Collection

    Science.gov (United States)

    Bolgiano, Christina E.; King, Mary Kathryn

    1978-01-01

    Libraries need solid information upon which to base collection development decisions. Specific evaluative methods for determining scope, access, and usefullness are described. Approaches used for data collection include analysis of interlibrary loan requests, comparison with major bibliographies, and analysis of accessibility through available…

  5. Preparing collections for digitization

    CERN Document Server

    Bulow, Anna E

    2010-01-01

    Most libraries, archives and museums are confronting the challenges of providing digital access to their collections. This guide offers guidance covering the end-to-end process of digitizing collections, from selecting records for digitization to choosing suppliers and equipment and dealing with documents that present individual problems.

  6. High Collection Nonimaging Optics

    Science.gov (United States)

    Winston, Roland

    1989-07-01

    Nonimaging optics departs from the methods of traditional optical design to develop instead techniques for maximizing the collecting power of concentrating elements and systems. Designs which exceed the concentration attainable with focusing techniques by factors of four or more and approach the theoretical limit are possible (ideal concentrators). The methodology for designing high collection nonirnaging systems is described.

  7. Collective Responsibility for Oppression

    NARCIS (Netherlands)

    Stahl, Titus

    2017-01-01

    Many contemporary forms of oppression are not primarily the result of formally organized collective action nor are they an unintended outcome of a combination of individual actions. This raises the question of collective responsibility. I argue that we can only determine who is responsible for

  8. Bloody Fast Blood Collection

    NARCIS (Netherlands)

    van Brummelen, Samuel Pieter Josephus

    2017-01-01

    This thesis consists of four parts: The first part contains an introduction, the second presents approaches for the evaluation of waiting times at blood collection sites, the third uses these to present approaches that improve waiting times at blood collection sites. The final part shows the

  9. UNO's Afghanistan Collection.

    Science.gov (United States)

    McKernan, M. D.

    This paper explores the background history and sources of the Afghanistan collection at the University Library, University of Nebraska at Omaha (UNO). Credit for the impetus behind the development of the collection is given to Chris Jung, a former UNO geography/geology faculty member; Ronald Roskens, then UNO chancellor; and the Afghanistan…

  10. Instructions for collecting Bamboos

    NARCIS (Netherlands)

    Corner, E.J.H.

    1962-01-01

    Although our knowledge of reproductive parts of bamboos is still very defective, an adequately collected vegetative specimen is valuable and sufficient for identification. Like in tree ferns (see p. 567) and in rattans, a well-collected specimen does not need to be excessively bulky, provided the

  11. Botanical Collections of Brass

    NARCIS (Netherlands)

    Brass, L.J.

    1966-01-01

    Earliest collections, made in southeastern parts of Queensland, were not numbered in sequence, and probably no duplicates were kept. Serious collecting began in 1919, when a start was made in sending specimens to C.T. White at the Queensland Herbarium.

  12. Quantitative Evaluation of Protein Heterogeneity within Herpes Simplex Virus 1 Particles.

    Science.gov (United States)

    El Bilali, Nabil; Duron, Johanne; Gingras, Diane; Lippé, Roger

    2017-05-15

    Several virulence genes have been identified thus far in the herpes simplex virus 1 genome. It is also generally accepted that protein heterogeneity among virions further impacts viral fitness. However, linking this variability directly with infectivity has been challenging at the individual viral particle level. To address this issue, we resorted to flow cytometry (flow virometry), a powerful approach we recently employed to analyze individual viral particles, to identify which tegument proteins vary and directly address if such variability is biologically relevant. We found that the stoichiometry of the U L 37, ICP0, and VP11/12 tegument proteins in virions is more stable than the VP16 and VP22 tegument proteins, which varied significantly among viral particles. Most interestingly, viruses sorted for their high VP16 or VP22 content yielded modest but reproducible increases in infectivity compared to their corresponding counterparts containing low VP16 or VP22 content. These findings were corroborated for VP16 in short interfering RNA experiments but proved intriguingly more complex for VP22. An analysis by quantitative Western blotting revealed substantial alterations of virion composition upon manipulation of individual tegument proteins and suggests that VP22 protein levels acted indirectly on viral fitness. These findings reaffirm the interdependence of the virion components and corroborate that viral fitness is influenced not only by the genome of viruses but also by the stoichiometry of proteins within each virion. IMPORTANCE The ability of viruses to spread in animals has been mapped to several viral genes, but other factors are clearly involved, including virion heterogeneity. To directly probe whether the latter influences viral fitness, we analyzed the protein content of individual herpes simplex virus 1 particles using an innovative flow cytometry approach. The data confirm that some viral proteins are incorporated in more controlled amounts, while

  13. Practices in prescribing protein substitutes for PKU in Europe

    DEFF Research Database (Denmark)

    Aguiar, A; Ahring, K; Almeida, M F

    2015-01-01

    BACKGROUND: There appears little consensus concerning protein requirements in phenylketonuria (PKU). METHODS: A questionnaire completed by 63 European and Turkish IMD centres from 18 countries collected data on prescribed total protein intake (natural/intact protein and phenylalanine-free protein...

  14. Thermodynamic investigations of protein's behaviour with ionic liquids in aqueous medium studied by isothermal titration calorimetry.

    Science.gov (United States)

    Bharmoria, Pankaj; Kumar, Arvind

    2016-05-01

    While a number of reports appear on ionic liquids-proteins interactions, their thermodynamic behaviour using suitable technique like isothermal titration calorimetry is not systematically presented. Isothermal titration calorimetry (ITC) is a key technique which can directly measure the thermodynamic contribution of IL binding to protein, particularly the enthalpy, heat capacities and binding stoichiometry. Ionic liquids (ILs), owing to their unique and tunable physicochemical properties have been the central area of scientific research besides graphene in the last decade, and growing unabated. Their encounter with proteins in the biological system is inevitable considering their environmental discharge though most of them are recyclable for a number of cycles. In this article we will cover the thermodynamics of proteins upon interaction with ILs as osmolyte and surfactant. The up to date literature survey of IL-protein interactions using isothermal titration calorimetry will be discussed and parallel comparison with the results obtained for such studies with other techniques will be highlighted to demonstrate the accuracy of ITC technique. Net stability of proteins can be obtained from the difference in the free energy (ΔG) of the native (folded) and denatured (unfolded) state using the Gibbs-Helmholtz equation (ΔG=ΔH-TΔS). Isothermal titration calorimetry can directly measure the heat changes upon IL-protein interactions. Calculation of other thermodynamic parameters such as entropy, binding constant and free energy depends upon the proper fitting of the binding isotherms using various fitting models. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Tracking individual membrane proteins and their biochemistry: The power of direct observation.

    Science.gov (United States)

    Barden, Adam O; Goler, Adam S; Humphreys, Sara C; Tabatabaei, Samaneh; Lochner, Martin; Ruepp, Marc-David; Jack, Thomas; Simonin, Jonathan; Thompson, Andrew J; Jones, Jeffrey P; Brozik, James A

    2015-11-01

    The advent of single molecule fluorescence microscopy has allowed experimental molecular biophysics and biochemistry to transcend traditional ensemble measurements, where the behavior of individual proteins could not be precisely sampled. The recent explosion in popularity of new super-resolution and super-localization techniques coupled with technical advances in optical designs and fast highly sensitive cameras with single photon sensitivity and millisecond time resolution have made it possible to track key motions, reactions, and interactions of individual proteins with high temporal resolution and spatial resolution well beyond the diffraction limit. Within the purview of membrane proteins and ligand gated ion channels (LGICs), these outstanding advances in single molecule microscopy allow for the direct observation of discrete biochemical states and their fluctuation dynamics. Such observations are fundamentally important for understanding molecular-level mechanisms governing these systems. Examples reviewed here include the effects of allostery on the stoichiometry of ligand binding in the presence of fluorescent ligands; the observation of subdomain partitioning of membrane proteins due to microenvironment effects; and the use of single particle tracking experiments to elucidate characteristics of membrane protein diffusion and the direct measurement of thermodynamic properties, which govern the free energy landscape of protein dimerization. The review of such characteristic topics represents a snapshot of efforts to push the boundaries of fluorescence microscopy of membrane proteins to the absolute limit. This article is part of the Special Issue entitled 'Fluorescent Tools in Neuropharmacology'. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Oxygen stoichiometry and the structure of Tl[sub 2]Ba[sub 2]Ca[sub 2]Cu[sub 3]O[sub 10-y]. A high-resolution powder neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Ogborne, D.M.; Weller, M.T.; Lanchester, P.C. (Dept. of Chemistry and Physics, Univ. of Southampton (United Kingdom))

    1992-09-15

    Samples of Tl[sub 2]Ba[sub 2]Ca[sub 2]Cu[sub 3]O[sub 10-y] have been prepared with three different oxygen stoichiometries by reaction under various oxygen gas partial pressures. Powder neutron diffraction studies on these materials show that for y > 0 oxygen vacancies exist in the thallium-oxygen layer; filling this site results in a contraction of the lattice with concomitant reduction in the apical Cu-O bond length but with an expansion of the copper-oxygen interlayer distance. These structural changes which occur as a function of oxygen content are discussed in terms of the superconducting properties of these materials. (orig.).

  17. Exploring PSI-MI XML Collections Using DescribeX

    Directory of Open Access Journals (Sweden)

    Samavi Reza

    2007-12-01

    Full Text Available PSI-MI has been endorsed by the protein informatics community as a standard XML data exchange format for protein-protein interaction datasets. While many public databases support the standard, there is a degree of heterogeneity in the way the proposed XML schema is interpreted and instantiated by different data providers. Analysis of schema instantiation in large collections of XML data is a challenging task that is unsupported by existing tools.

  18. Microalgal Culture Collection Transfers

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Milford Microalgal culture Collection holds over 200 live cultures representing 13 classes of of algae. The cultures are maintained in three different growing...

  19. Third Party Collection Program

    National Research Council Canada - National Science Library

    Young, Shelton

    1993-01-01

    United States Code, title 10, sec. 1095, allows DoD to collect from health insurance plans reasonable inpatient hospital costs incurred on behalf of insured military retirees and military dependants...

  20. Freedom and the Collective

    Directory of Open Access Journals (Sweden)

    Straume, Ingerid S.

    2008-12-01

    Full Text Available Since Isaiah Berlin’s epitomizing Cold War-essay, "Two Concepts of Liberty, " thinkers who emphasize collective concepts of social life have carried the burden of proof against charges of totalitarian tendencies. The background is a ground figure in contemporary political thought that sets notions of collectivity against individual freedom, in a zero sum game: Either one is in favour of the individual, or one is in favour of the collective, and hence, so the bias has it, willing to sacrifice the rights and liberties of individuals. Since it is impossible to favour the latter position and remain liberal, in the wide sense of the term, this dichotomy serves to rob contemporary political thought of both its classical and revolutionary connotations, leaving only individual initiatives like lobbying and voting. Cornelius Castoriadis offers a way around this – arguably false – dichotomy, by regarding individual and collective freedom as two sides of the same coin.

  1. Online Data Collection.

    Science.gov (United States)

    Topp, Neal W.; Pawloski, Bob

    2002-01-01

    Describes the eventful history of online data collection and presents a review of current literature following by a list of pros and cons to be considered when stepping into online surveying. (Contains 14 references.) (Author/YDS)

  2. Long-term collections

    CERN Multimedia

    Collectes à long terme

    2007-01-01

    The Committee of the Long Term Collections (CLT) asks for your attention for the following message from a young Peruvian scientist, following the earthquake which devastated part of her country a month ago.

  3. Turtle Photograph Collection

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Photos collected in marine turtle research programs are diverse, ranging from isolated observations of incidental encounters with turtles on the high-seas to...

  4. Glacier Photograph Collection

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Glacier Photograph Collection is a database of photographs of glaciers from around the world, some dating back to the mid-1850's, that provide an historical...

  5. NOS Hydrographic Surveys Collection

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The National Oceanic and Atmospheric Administration (NOAA) has the statutory mandate to collect hydrographic data in support of nautical chart compilation for safe...

  6. Shared collections collaborative stewardship

    CERN Document Server

    Hale, Dawn

    2016-01-01

    With practical advice on issues such as governance and business models, demand driven acquisition, rare works, and access, this monograph is a valuable resource for academic library directors, administrators, and collection development leaders.

  7. NLM Digital Collections

    Data.gov (United States)

    U.S. Department of Health & Human Services — The National Library of Medicine's (NLM) Digital Collections offers a search-based Web service that provides access to the Dublin Core metadata and full-text OCR of...

  8. 75 FR 66165 - Information Collection Activities: Proposed Collection; Comment Request

    Science.gov (United States)

    2010-10-27

    ... additional information should be collected to further the aims of government transparency. DATES: Comments... OFFICE OF MANAGEMENT AND BUDGET Information Collection Activities: Proposed Collection; Comment... are warranted. We are particularly interested in comments on whether the information collected in the...

  9. Evidence of different stoichiometries for the limiting carbonate complexes of lanthanides(3); Mise en evidence d'un changement de stoechiometrie du complexe carbonate limite au sein de la serie des lanthanides(3)

    Energy Technology Data Exchange (ETDEWEB)

    Philippini, V

    2007-12-15

    Two stoichiometries have been proposed by different laboratories to interpret measurements on the limiting carbonate complexes of An{sup 3+} and Ln{sup 3+} cations. The study of the solubility of double carbonates (AlkLn(CO{sub 3}){sub 2},xH{sub 2}O) in concentrated carbonate solutions at room temperature and high ionic strengths has shown that on the one hand the lightest lanthanides (La and Nd) form Ln(CO{sub 3}){sub 4}{sup 5-} whereas the heaviest (Eu and Dy) form Ln(CO{sub 3}){sub 3}{sup 3-} in the studied chemical conditions, and on the other hand, that the kinetics of precipitation of double carbonates depends on the alkali metal and the lanthanide ions. The existence of two stoichiometries for the limiting carbonate complexes was confirmed by capillary electrophoresis hyphenated to an inductively coupled plasma mass spectrometer (CE-ICP-MS), used to extend the study to the whole series of lanthanides (except Ce, Pm and Yb). Two behaviours have been put forward comparing the electrophoretic mobilities: La to Tb form Ln(CO{sub 3}){sub 4}{sup 5-} while Dy to Lu form Ln(CO{sub 3}){sub 3}{sup 3-}. Measurements by time resolved laser fluorescence spectroscopy (TRLFS) on Eu(III) indicate small variations of the geometry of Eu(CO{sub 3}){sub 3}{sup 3-} complex, specially with Cs{sup +}. Although analogies are currently used among the 4f-block trivalent elements, different aqueous speciations are evidenced in concentrated carbonate solutions across the lanthanide series. (author)

  10. Rehabilitating the Stroke Collection

    Directory of Open Access Journals (Sweden)

    Mary Grimmond

    2006-06-01

    Full Text Available Objective The aim of this project was to complete an analysis of monograph and audiovisual items held in the Central Coast Health Service (CCHS Libraries and containing information relevant to the treatment of acute stroke. Acute stroke is treated by multidisciplinary teams of clinicians based at two hospitals within the CCHS. The adequacy of the library collection was measured by subject coverage and age. Methods The methodology used consisted of three main steps: a literature review; design, administration, and analysis of a questionnaire to members of the CCHS Acute Stroke Team; and an analysis of the libraries’ collections. The research project utilised project management methodology and an evidence based librarianship framework. Results The questionnaire revealed that electronic resources were by far the most frequently used by participants, followed in order by print journals, books, interlibrary loan articles, and audiovisual items. Collection analysis demonstrated that the monograph and audiovisual collections were adequate in both scope and currency to support the information needs of Acute Stroke Team members, with the exception of resources to support patient education. Conclusion The researchers developed recommendations for future collection development in the area of acute stroke resources. Conducting this project within the evidence based librarianship framework helped to develop library staff members’ confidence in their ability to make future collection development decisions, informed by the target group’s information needs and preferences. The collection analysis methodology was designed to be replicated, and new specialist groups within the client base of the library will be targeted to repeat the collection analysis process.

  11. Collective excitations in nuclei

    International Nuclear Information System (INIS)

    Chomaz, Ph.

    1998-01-01

    The properties of the nucleus cannot be reduced to the properties of its constituents: it is a complex system. The fact that many properties of the nucleus are consequences of the existence of mean-field potential is a manifestation of this complexity. In particular, the nucleons can thus self-organize in collective motions such as giant resonances. Therefore the study of this collective motions is a very good tool to understand the properties of the nucleus itself. The purpose of this article is to stress some aspects of these collective vibrations. We have studied how an ensemble of fermions as the nucleus can self-organize in collective vibrations which are behaving like a gas of bosons in weak interaction. Understanding of these phenomena remains one of the important subjects of actuality in the context of quantal systems in strong interaction. In particular, the study of the states with one or two vibration quanta provides a direct information on the structure of nuclei close to their ground states. Moreover, some collective states appear to be very robust against the onset of chaos. This is the case of the hot giant dipole built on top of a hot nucleus which seems to survive up to rather high temperatures. Their sudden disappearance is still a subject of controversy. It may be that the mean-field and the associated collective states are playing a crucial role also in catastrophic processes such as the phase-transitions. Indeed, when the system is diluted the collective vibrations may become unstable and it seems that these unstable modes provide a natural explanation to the self organization of the system in drops. Finally, considering the diversity of the different structures of exotic nuclei one may expect new vibration types. All these studies are showing the diversity of the collective motions of strongly correlated quantum systems such as the nucleus but many open questions remain to be solved. (authors)

  12. Collective excitations in nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Chomaz, Ph. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France); Collaboration: La Direction des Sciences de la Matiere du CEA (FR); Le Fonds National de la Recherche Scientifique de Belgique (BE)

    1998-12-31

    The properties of the nucleus cannot be reduced to the properties of its constituents: it is a complex system. The fact that many properties of the nucleus are consequences of the existence of mean-field potential is a manifestation of this complexity. In particular, the nucleons can thus self-organize in collective motions such as giant resonances. Therefore the study of this collective motions is a very good tool to understand the properties of the nucleus itself. The purpose of this article is to stress some aspects of these collective vibrations. We have studied how an ensemble of fermions as the nucleus can self-organize in collective vibrations which are behaving like a gas of bosons in weak interaction. Understanding of these phenomena remains one of the important subjects of actuality in the context of quantal systems in strong interaction. In particular, the study of the states with one or two vibration quanta provides a direct information on the structure of nuclei close to their ground states. Moreover, some collective states appear to be very robust against the onset of chaos. This is the case of the hot giant dipole built on top of a hot nucleus which seems to survive up to rather high temperatures. Their sudden disappearance is still a subject of controversy. It may be that the mean-field and the associated collective states are playing a crucial role also in catastrophic processes such as the phase-transitions. Indeed, when the system is diluted the collective vibrations may become unstable and it seems that these unstable modes provide a natural explanation to the self organization of the system in drops. Finally, considering the diversity of the different structures of exotic nuclei one may expect new vibration types. All these studies are showing the diversity of the collective motions of strongly correlated quantum systems such as the nucleus but many open questions remain to be solved. (authors) 304 refs., 53 figs., 5 tabs.

  13. Collective field accelerator

    International Nuclear Information System (INIS)

    Luce, J.S.

    1978-01-01

    A collective field accelerator which operates with a vacuum diode and utilizes a grooved cathode and a dielectric anode that operates with a relativistic electron beam with a ν/γ of approx. 1, and a plurality of dielectric lenses having an axial magnetic field thereabout to focus the collectively accelerated electrons and ions which are ejected from the anode. The anode and lenses operate as unoptimized r-f cavities which modulate and focus the beam

  14. Sparse matrix test collections

    Energy Technology Data Exchange (ETDEWEB)

    Duff, I.

    1996-12-31

    This workshop will discuss plans for coordinating and developing sets of test matrices for the comparison and testing of sparse linear algebra software. We will talk of plans for the next release (Release 2) of the Harwell-Boeing Collection and recent work on improving the accessibility of this Collection and others through the World Wide Web. There will only be three talks of about 15 to 20 minutes followed by a discussion from the floor.

  15. Protein nanoparticles for therapeutic protein delivery.

    Science.gov (United States)

    Herrera Estrada, L P; Champion, J A

    2015-06-01

    Therapeutic proteins can face substantial challenges to their activity, requiring protein modification or use of a delivery vehicle. Nanoparticles can significantly enhance delivery of encapsulated cargo, but traditional small molecule carriers have some limitations in their use for protein delivery. Nanoparticles made from protein have been proposed as alternative carriers and have benefits specific to therapeutic protein delivery. This review describes protein nanoparticles made by self-assembly, including protein cages, protein polymers, and charged or amphipathic peptides, and by desolvation. It presents particle fabrication and delivery characterization for a variety of therapeutic and model proteins, as well as comparison of the features of different protein nanoparticles.

  16. A Survey of Collectives

    Science.gov (United States)

    Tumer, Kagan; Wolpert, David

    2004-01-01

    Due to the increasing sophistication and miniaturization of computational components, complex, distributed systems of interacting agents are becoming ubiquitous. Such systems, where each agent aims to optimize its own performance, but where there is a well-defined set of system-level performance criteria, are called collectives. The fundamental problem in analyzing/designing such systems is in determining how the combined actions of self-interested agents leads to 'coordinated' behavior on a iarge scale. Examples of artificial systems which exhibit such behavior include packet routing across a data network, control of an array of communication satellites, coordination of multiple deployables, and dynamic job scheduling across a distributed computer grid. Examples of natural systems include ecosystems, economies, and the organelles within a living cell. No current scientific discipline provides a thorough understanding of the relation between the structure of collectives and how well they meet their overall performance criteria. Although still very young, research on collectives has resulted in successes both in understanding and designing such systems. It is eqected that as it matures and draws upon other disciplines related to collectives, this field will greatly expand the range of computationally addressable tasks. Moreover, in addition to drawing on them, such a fully developed field of collective intelligence may provide insight into already established scientific fields, such as mechanism design, economics, game theory, and population biology. This chapter provides a survey to the emerging science of collectives.

  17. Theory of collective Hamiltonian

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Qingying

    1982-02-01

    Starting from the cranking model, we derive the nuclear collective Hamiltonian. We expand the total energy of the collective motion of the ground state of even--even nuclei in powers of the deformation parameter ..beta... In the first approximation, we only take the lowest-order non-vanished terms in the expansion. The collective Hamiltonian thus obtained rather differs from the A. Bohr's Hamiltonian obtained by the irrotational incompressible liquid drop model. If we neglect the coupling term between ..beta..-and ..gamma..-vibration, our Hamiltonian then has the same form as that of A. Bohr. But there is a difference between these collective parameters. Our collective parameters are determined by the state of motion of the nucleous in the nuclei. They are the microscopic expressions. On the contrary, A. Bohr's collective parameters are only the simple functions of the microscopic physical quantities (such as nuclear radius and surface tension, etc.), and independent of the state of motion of the nucleons in the nuclei. Furthermore, there exist the coupling term between ..beta..-and ..gamma..-vibration and the higher-order terms in our expansion. They can be treated as the perturbations. There are no such terms in A. Bohr's Hamiltonian. These perturbation terms will influence the rotational, vibrational spectra and the ..gamma..-transition process, etc.

  18. Protein-Protein Interaction Databases

    DEFF Research Database (Denmark)

    Szklarczyk, Damian; Jensen, Lars Juhl

    2015-01-01

    Years of meticulous curation of scientific literature and increasingly reliable computational predictions have resulted in creation of vast databases of protein interaction data. Over the years, these repositories have become a basic framework in which experiments are analyzed and new directions...

  19. The Development of Protein Microarrays and Their Applications in DNA-Protein and Protein-Protein Interaction Analyses of Arabidopsis Transcription Factors

    Science.gov (United States)

    Gong, Wei; He, Kun; Covington, Mike; Dinesh-Kumar, S. P.; Snyder, Michael; Harmer, Stacey L.; Zhu, Yu-Xian; Deng, Xing Wang

    2009-01-01

    We used our collection of Arabidopsis transcription factor (TF) ORFeome clones to construct protein microarrays containing as many as 802 TF proteins. These protein microarrays were used for both protein-DNA and protein-protein interaction analyses. For protein-DNA interaction studies, we examined AP2/ERF family TFs and their cognate cis-elements. By careful comparison of the DNA-binding specificity of 13 TFs on the protein microarray with previous non-microarray data, we showed that protein microarrays provide an efficient and high throughput tool for genome-wide analysis of TF-DNA interactions. This microarray protein-DNA interaction analysis allowed us to derive a comprehensive view of DNA-binding profiles of AP2/ERF family proteins in Arabidopsis. It also revealed four TFs that bound the EE (evening element) and had the expected phased gene expression under clock-regulation, thus providing a basis for further functional analysis of their roles in clock regulation of gene expression. We also developed procedures for detecting protein interactions using this TF protein microarray and discovered four novel partners that interact with HY5, which can be validated by yeast two-hybrid assays. Thus, plant TF protein microarrays offer an attractive high-throughput alternative to traditional techniques for TF functional characterization on a global scale. PMID:19802365

  20. The algebraic collective model

    International Nuclear Information System (INIS)

    Rowe, D.J.; Turner, P.S.

    2005-01-01

    A recently proposed computationally tractable version of the Bohr collective model is developed to the extent that we are now justified in describing it as an algebraic collective model. The model has an SU(1,1)xSO(5) algebraic structure and a continuous set of exactly solvable limits. Moreover, it provides bases for mixed symmetry collective model calculations. However, unlike the standard realization of SU(1,1), used for computing beta wave functions and their matrix elements in a spherical basis, the algebraic collective model makes use of an SU(1,1) algebra that generates wave functions appropriate for deformed nuclei with intrinsic quadrupole moments ranging from zero to any large value. A previous paper focused on the SO(5) wave functions, as SO(5) (hyper-)spherical harmonics, and computation of their matrix elements. This paper gives analytical expressions for the beta matrix elements needed in applications of the model and illustrative results to show the remarkable gain in efficiency that is achieved by using such a basis in collective model calculations for deformed nuclei

  1. Life Cycle Collection Management

    Directory of Open Access Journals (Sweden)

    Helen Shenton

    2003-09-01

    Full Text Available Life cycle collection management is a way of taking a long-term approach to the responsible stewardship of the British Library's collections and is one of the Library's strategic strands. It defines the different stages in a collection item's existence over time. These stages range from selection and acquisitions processing, cataloguing and press marking, through to preventive conservation, storage and retrieval. Life cycle collection management seeks to identify the costs of each stage in order to show the economic interdependencies between the phases over time. It thereby aims to demonstrate the long-term consequences of what the library takes into its collections, by making explicit the financial and other implications of decisions made at the beginning of the life cycle for the next 100 plus years. This paper describes the work over the past year at the British Library on this complex and complicated subject. It presents the emerging findings and suggests how it can be used for practical reasons (by individual curators and selectors and for economic, governance and political purposes. The paper describes the next steps in the project, for example, on a predictive data model. The British Library is seeking to benchmark itself against comparable organisations in this area. It intends to work with others on specific comparison for example, of life cycle costing of electronic and paper journals, as a prelude to eliding digital and 'traditional' formats.

  2. Carotenoid stoichiometry in the LH2 crystal: no spectral evidence for the presence of the second molecule in the alpha/beta-apoprotein dimer.

    Science.gov (United States)

    Gall, Andrew; Gardiner, Alastair T; Cogdell, Richard J; Robert, Bruno

    2006-07-10

    In this work we have investigated the carotenoid-protein interactions in LH2 complexes of Rhodopseudomonas acidophila both in "free in solution" mixed-micelles and in three-dimensional crystals by Raman spectroscopy in resonance with the carotenoid (Car) molecules. We show that the Car molecules when bound to their binding pockets show no significant differences when the complexes are "free in solution" or packed in crystalline arrays. Furthermore, there is no significant wavelength dependence in the Raman spectrum of the Car molecules of LH2. This indicates that there is only one Car configuration in LH2 and thus only one molecule per alpha/beta-heterodimer.

  3. Collection for Ecuador

    CERN Multimedia

    Staff Association

    2016-01-01

    After the violent earthquake that caused the death of hundreds of people, and left thousands wounded and homeless in Ecuador, we appeal to your generosity. We are starting a collection today to help the victims, and the funds will be donated to the INEPE Institute in Quito. This organization, known at CERN for many years as it has been supported by the Long Term Collections of the Staff Association, will be responsible for sending the proceeds of the collection directly to the victims in the field. On behalf of the CERN Management and the CERN Staff Association Fabiola Gianotti, Director General, and Alessandro Raimondo, President of the Staff Association =========================== Bank account details for donations: Bank account holder: Staff Association CERN - 1211 GENEVA 23 Account number: 279-HU106832.1 IBAN: CH85 0027 9279 HU10 6832 1 BIC: UBSWCHZH80A Please mention: Ecuador

  4. Curating Virtual Data Collections

    Science.gov (United States)

    Lynnes, Chris; Leon, Amanda; Ramapriyan, Hampapuram; Tsontos, Vardis; Shie, Chung-Lin; Liu, Zhong

    2015-01-01

    NASAs Earth Observing System Data and Information System (EOSDIS) contains a rich set of datasets and related services throughout its many elements. As a result, locating all the EOSDIS data and related resources relevant to particular science theme can be daunting. This is largely because EOSDIS data's organizing principle is affected more by the way they are produced than around the expected end use. Virtual collections oriented around science themes can overcome this by presenting collections of data and related resources that are organized around the user's interest, not around the way the data were produced. Virtual collections consist of annotated web addresses (URLs) that point to data and related resource addresses, thus avoiding the need to copy all of the relevant data to a single place. These URL addresses can be consumed by a variety of clients, ranging from basic URL downloaders (wget, curl) and web browsers to sophisticated data analysis programs such as the Integrated Data Viewer.

  5. Fostering collective intelligence education

    Directory of Open Access Journals (Sweden)

    Jaime Meza

    2016-06-01

    Full Text Available New educational models are necessary to update learning environments to the digitally shared communication and information. Collective intelligence is an emerging field that already has a significant impact in many areas and will have great implications in education, not only from the side of new methodologies but also as a challenge for education. This paper proposes an approach to a collective intelligence model of teaching using Internet to combine two strategies: idea management and real time assessment in the class. A digital tool named Fabricius has been created supporting these two elements to foster the collaboration and engagement of students in the learning process. As a result of the research we propose a list of KPI trying to measure individual and collective performance. We are conscious that this is just a first approach to define which aspects of a class following a course can be qualified and quantified.

  6. Collective Intelligence in Crises

    DEFF Research Database (Denmark)

    Büscher, Monika; Liegl, Michael; Thomas, Vanessa

    2014-01-01

    New practices of social media use in emergency response seem to enable broader `situation awareness' and new forms of crisis management. The scale and speed of innovation in this field engenders disruptive innovation or a reordering of social, political, economic practices of emergency response....... By examining these dynamics with the concept of social collective intelligence, important opportunities and challenges can be examined. In this chapter we focus on socio-technical aspects of social collective intelligence in crises to discuss positive and negative frictions and avenues for innovation...

  7. Collection for Nepal

    CERN Multimedia

    Staff Association

    2015-01-01

    Following the violent earthquake in Nepal and neighbouring countries, a collection of money to help the victims was organized at CERN. A sum of 34 800 CHF was collected, and transferred to the NGO Live to Love. On July 22, the NGO sent a letter to CERN thanking for the support (see below). You can also find more information concerning this NGO and how they use their funds on our website: http://staff-association.web.cern.ch/sites/staff-association.web.cern.ch/files/Docs/Live_to_Love.pdf

  8. Collective nuclear dynamics. Proceedings

    International Nuclear Information System (INIS)

    Ivanyuk, F.A.

    1994-01-01

    The Fourth International school on nuclear physics was help on 29 Aug - 7 Sep, 1994 in Ukraine. The specialists discussed following subjects:liquid drop and the shell correction method; nuclear deformation energy and fission; nuclear structure at high spins, superdeformed states, structure of excited and exotic nuclei; nuclear fluid dynamics and large scale collective motion; order and chaos as they relate to the collective motion; quantum and interference phenomena in nuclear collisions; quasi-fission and multinucleon fragmentation effects; shell effects in non-nuclear systems; new nuclear facilities

  9. Impedance and Collective Effects

    CERN Document Server

    Metral, E; Rumolo, R; Herr, W

    2013-01-01

    This document is part of Subvolume C 'Accelerators and Colliders' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Chapter '4 Impedance and Collective Effects' with the content: 4 Impedance and Collective Effects Introduction 4.1 Space Charge 4.2 Wake Fields and Impedances 4.3 Coherent Instabilities 4.4 Landau Damping 4.5 Two-Stream Effects (Electron Cloud and Ions) 4.6 Beam-Beam Effects 4.7 Numerical Modelling

  10. Collective nuclear dynamics. Abstracts

    International Nuclear Information System (INIS)

    Abrosimov, V.I.; Kolomietz, V.M.

    1994-01-01

    The fourth International school on nuclear physics was help on 29 Aug - 7 Sep, 1994 in Ukraine. The specialists discussed following subjects: liquid drop and the shell correction method; nuclear deformation energy and fission; nuclear structure at high spins, superdeformed states, structure of excited and exotic nuclei; nuclear fluid dynamics and large scale collective motion; order and chaos as they relate to the collective motion; quantum and interference phenomena in nuclear collisions; quasi-fission and multinucleon fragmentation effects; shell effects in non-nuclear systems; new nuclear facilities

  11. Husserl on Collective Intentionality

    DEFF Research Database (Denmark)

    Szanto, Thomas

    2016-01-01

    , respectively. On this background, I will concentrate on Husserl’s alternative construal and demonstrate how it entails a robust anti-individualism regarding both the form and the subject of we-intentions. I will suggest that, contrary to appearances, Husserl does not fall prey to committing a content/vehicle...... type of fallacy, by inferring from the jointness of the contents of collective intentionality that there is one joint vehicle or, worse, some collectively conscious bearer of such. Rather, the Husserlian alternative yields a robust formal-cum-subject anti-individualism and undercuts the need...

  12. Collective nuclear dynamics. Proceedings.

    Energy Technology Data Exchange (ETDEWEB)

    Ivanyuk, F A [eds.

    1994-12-31

    The Fourth International school on nuclear physics was help on 29 Aug - 7 Sep, 1994 in Ukraine. The specialists discussed following subjects:liquid drop and the shell correction method; nuclear deformation energy and fission; nuclear structure at high spins, superdeformed states, structure of excited and exotic nuclei; nuclear fluid dynamics and large scale collective motion; order and chaos as they relate to the collective motion; quantum and interference phenomena in nuclear collisions; quasi-fission and multinucleon fragmentation effects; shell effects in non-nuclear systems; new nuclear facilities.

  13. Collective academic supervision

    DEFF Research Database (Denmark)

    Nordentoft, Helle Merete; Thomsen, Rie; Wichmann-Hansen, Gitte

    2013-01-01

    Supervision of students is a core activity in higher education. Previous research on student supervision in higher education focus on individual and relational aspects in the supervisory relationship rather than collective, pedagogical and methodical aspects of the planning of the supervision...... process. This article fills these gaps by discussing potentials and challenges in “Collective Academic Supervision”, a model for supervision at the Master of Education in Guidance at Aarhus University in Denmark. The pedagogical rationale behind the model is that students’ participation and learning...

  14. Long-Term Collections

    CERN Multimedia

    Comité des collectes à long terme

    2011-01-01

    It is the time of the year when our fireman colleagues go around the laboratory for their traditional calendars sale. A part of the money of the sales will be donated in favour of the long-term collections. We hope that you will welcome them warmly.

  15. Collection for SOS animaux

    CERN Multimedia

    2005-01-01

    The Pays de Gex animal shelter is collecting funds. There will be things to buy. You will be able to make a donation and/or become a member of the association or simply get information. SOS Animaux stall (Hall, Build. 60, next to restaurant 1) On Wednesday 23 November 2005 (from 9h - 17h non-stop)

  16. Generating process model collections

    NARCIS (Netherlands)

    Yan, Z.; Dijkman, R.M.; Grefen, P.W.P.J.

    2017-01-01

    Business process management plays an important role in the management of organizations. More and more organizations describe their operations as business processes. It is common for organizations to have collections of thousands of business processes, but for reasons of confidentiality these

  17. Collection for Italy

    CERN Multimedia

    Fabiola Gianotti, Director-General, and Ghislain Roy, President of the Staff Association

    2016-01-01

    Following the earthquake of 24 August in central Italy, many of you have expressed your solidarity. The collection to support the victims raised a total of 10 000 CHF, which was transferred in its entirety to Italy’s civil protection through the Italian delegation to the CERN Council. The CERN Directorate and the CERN Staff Association sincerely thank you for your generosity.

  18. Pollen reference collection digitization

    NARCIS (Netherlands)

    Ercan, F.E.Z.; Donders, T.H.; Bijl, P.K.; Wagner, F.

    2016-01-01

    The extensive Utrecht University pollen reference collection holds thousands of pollen samples of many species and genera from all over the world and has been a basis for the widely-used North West European Pollen Flora. These samples are fixed on glass slides for microscopy use, but the aging

  19. Collective variables and dissipation

    International Nuclear Information System (INIS)

    Balian, R.

    1984-09-01

    This is an introduction to some basic concepts of non-equilibrium statistical mechanics. We emphasize in particular the relevant entropy relative to a given set of collective variables, the meaning of the projection method in the Liouville space, its use to establish the generalized transport equations for these variables, and the interpretation of dissipation in the framework of information theory

  20. Collective Action under Globalization

    DEFF Research Database (Denmark)

    Scheuer, Steen

    Collective action in the form of industrial conflict has declined dramatically since the high tide in the 1970s in Europe. This article argues that this decline is the result of significant changes in both economic and institutional factors, influencing the calculations of employees and of their ...