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Sample records for caulobacter crescentus s-layer

  1. Two Outer Membrane Proteins Are Required for Maximal Type I Secretion of the Caulobacter crescentus S-Layer Protein

    OpenAIRE

    Toporowski, Michael C.; Nomellini, John F.; Awram, Peter; Smit, John

    2004-01-01

    Transport of RsaA, the crystalline S-layer subunit protein of Caulobacter crescentus, is mediated by a type I secretion mechanism. Two proteins have been identified that play the role of the outer membrane protein (OMP) component in the RsaA secretion machinery. The genes rsaFa and rsaFb were identified by similarity to the Escherichia coli hemolysin secretion OMP TolC by using the C. crescentus genome sequence. The rsaFa gene is located several kilobases downstream of the other transporter g...

  2. S-Layer-Mediated Display of the Immunoglobulin G-Binding Domain of Streptococcal Protein G on the Surface of Caulobacter crescentus: Development of an Immunoactive Reagent▿

    OpenAIRE

    Nomellini, John F.; Duncan, Gillian; Dorocicz, Irene R.; Smit, John

    2007-01-01

    The immunoglobulin G (IgG)-binding streptococcal protein G is often used for immunoprecipitation or immunoadsorption-based assays, as it exhibits binding to a broader spectrum of host species IgG and IgG subclasses than the alternative, Staphylococcus aureus protein A. Caulobacter crescentus produces a hexagonally arranged paracrystalline protein surface layer (S-layer) composed of a single secreted protein, RsaA, that is notably tolerant of heterologous peptide insertions while maintaining t...

  3. The Caulobacter crescentus Paracrystalline S-Layer Protein Is Secreted by an ABC Transporter (Type I) Secretion Apparatus

    OpenAIRE

    Awram, Peter; Smit, John

    1998-01-01

    Caulobacter crescentus is a gram-negative bacterium that produces a two-dimensional crystalline array on its surface composed of a single 98-kDa protein, RsaA. Secretion of RsaA to the cell surface relies on an uncleaved C-terminal secretion signal. In this report, we identify two genes encoding components of the RsaA secretion apparatus. These components are part of a type I secretion system involving an ABC transporter protein. These genes, lying immediately 3′ of rsaA, were found by screen...

  4. Immobilization of bacterial S-layer proteins from Caulobacter crescentus on iron oxide-based nanocomposite: Synthesis and spectroscopic characterization of zincite-coated Fe2O3 nanoparticles

    Science.gov (United States)

    Habibi, Neda

    Zinc oxide was coated on Fe2O3 nanoparticles using sol-gel spin-coating. Caulobacter crescentus have a crystalline surface layer (S-layer), which consist of one protein or glycoprotein species. The immobilization of bacterial S-layers obtained from C. crescentus on zincite-coated nanoparticles of iron oxide was investigated. The SDS PAGE results of S-layers isolated from C. crescentus showed the weight of 50 KDa. Nanoparticles of the Fe2O3 and zinc oxide were synthesized by a sol-gel technique. Fe2O3 nanoparticles with an average size of 50 nm were successfully prepared by the proper deposition of zinc oxide onto iron oxide nanoparticles surface annealed at 450 °C. The samples were characterized by field-emission scanning electron microscope (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR).

  5. Core-oscillator model of Caulobacter crescentus

    Science.gov (United States)

    Vandecan, Yves; Biondi, Emanuele; Blossey, Ralf

    2016-06-01

    The gram-negative bacterium Caulobacter crescentus is a powerful model organism for studies of bacterial cell cycle regulation. Although the major regulators and their connections in Caulobacter have been identified, it still is a challenge to properly understand the dynamics of its circuitry which accounts for both cell cycle progression and arrest. We show that the key decision module in Caulobacter is built from a limit cycle oscillator which controls the DNA replication program. The effect of an induced cell cycle arrest is demonstrated to be a key feature to classify the underlying dynamics.

  6. Caulobacter crescentus as a Whole-Cell Uranium Biosensor▿ †

    OpenAIRE

    Hillson, Nathan J; Hu, Ping; Andersen, Gary L.; Shapiro, Lucy

    2007-01-01

    We engineered a strain of the bacterium Caulobacter crescentus to fluoresce in the presence of micromolar levels of uranium at ambient temperatures when it is exposed to a hand-held UV lamp. Previous microarray experiments revealed that several Caulobacter genes are significantly upregulated in response to uranium but not in response to other heavy metals. We designated one of these genes urcA (for uranium response in caulobacter). We constructed a reporter that utilizes the urcA promoter to ...

  7. Periodic synthesis of phospholipids during the Caulobacter crescentus cell cycle.

    OpenAIRE

    O'Neill, E A; Bender, R A

    1987-01-01

    Net phospholipid synthesis is discontinuous during the Caulobacter crescentus cell cycle with synthesis restricted to two discrete periods. The first period of net phospholipid synthesis begins in the swarmer cell shortly after cell division and ends at about the time when DNA replication initiates. The second period of phospholipid synthesis begins at a time when DNA replication is about two-thirds complete and ends at about the same time that DNA replication terminates. Thus, considerable D...

  8. The core and O-polysaccharide structure of the Caulobacter crescentus lipopolysaccharide.

    Science.gov (United States)

    Jones, Michael D; Vinogradov, Evgeny; Nomellini, John F; Smit, John

    2015-01-30

    Here we describe the analysis of the structure of the lipopolysaccharide (LPS) from Caulobacter crescentus strain JS1025, a derivative of C. crescentus CB15 NA1000 with an engineered amber mutation in rsaA, leading to the loss of the protein S-layer and gene CCNA_00471 encoding a putative GDP-L-fucose synthase. LPS was isolated using an aqueous membrane disruption method. Polysaccharide and core oligosaccharide were produced by mild acid hydrolysis and analyzed by nuclear magnetic resonance spectroscopy and chemical methods. Spectra revealed the presence of two polysaccharides, one of them, a rhamnan, could be removed using periodate oxidation. Another polymer, built from 4-amino-4-deoxy-D-rhamnose (perosamine), mannose, and 3-O-methyl-glucose, should be the O-chain of the LPS according to genetic data. The attribution of the rhamnan as a part of LPS or a separate polymer was not possible. PMID:25498010

  9. The coding and noncoding architecture of the Caulobacter crescentus genome.

    Directory of Open Access Journals (Sweden)

    Jared M Schrader

    2014-07-01

    Full Text Available Caulobacter crescentus undergoes an asymmetric cell division controlled by a genetic circuit that cycles in space and time. We provide a universal strategy for defining the coding potential of bacterial genomes by applying ribosome profiling, RNA-seq, global 5'-RACE, and liquid chromatography coupled with tandem mass spectrometry (LC-MS data to the 4-megabase C. crescentus genome. We mapped transcript units at single base-pair resolution using RNA-seq together with global 5'-RACE. Additionally, using ribosome profiling and LC-MS, we mapped translation start sites and coding regions with near complete coverage. We found most start codons lacked corresponding Shine-Dalgarno sites although ribosomes were observed to pause at internal Shine-Dalgarno sites within the coding DNA sequence (CDS. These data suggest a more prevalent use of the Shine-Dalgarno sequence for ribosome pausing rather than translation initiation in C. crescentus. Overall 19% of the transcribed and translated genomic elements were newly identified or significantly improved by this approach, providing a valuable genomic resource to elucidate the complete C. crescentus genetic circuitry that controls asymmetric cell division.

  10. Diverse Functions for Six Glycosyltransferases in Caulobacter crescentus Cell Wall Assembly

    OpenAIRE

    Yakhnina, Anastasiya A.; Gitai, Zemer

    2013-01-01

    The essential process of peptidoglycan synthesis requires two enzymatic activities, transpeptidation and transglycosylation. While the PBP2 and PBP3 transpeptidases perform highly specialized functions that are widely conserved, the specific roles of different glycosyltransferases are poorly understood. For example, Caulobacter crescentus encodes six glycosyltransferase paralogs of largely unknown function. Using genetic analyses, we found that Caulobacter glycosyltransferases are primarily r...

  11. Whole-genome transcriptional analysis of heavy metal stresses inCaulobacter crescentus

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Ping; Brodie, Eoin L.; Suzuki, Yohey; McAdams, Harley H.; Andersen, Gary L.

    2005-09-21

    The bacterium Caulobacter crescentus and related stalkbacterial species are known for their distinctive ability to live in lownutrient environments, a characteristic of most heavy metal contaminatedsites. Caulobacter crescentus is a model organism for studying cell cycleregulation with well developed genetics. We have identified the pathwaysresponding to heavy metal toxicity in C. crescentus to provide insightsfor possible application of Caulobacter to environmental restoration. Weexposed C. crescentus cells to four heavy metals (chromium, cadmium,selenium and uranium) and analyzed genome wide transcriptional activitiespost exposure using a Affymetrix GeneChip microarray. C. crescentusshowed surprisingly high tolerance to uranium, a possible mechanism forwhich may be formation of extracellular calcium-uranium-phosphateprecipitates. The principal response to these metals was protectionagainst oxidative stress (up-regulation of manganese-dependent superoxidedismutase, sodA). Glutathione S-transferase, thioredoxin, glutaredoxinsand DNA repair enzymes responded most strongly to cadmium and chromate.The cadmium and chromium stress response also focused on reducing theintracellular metal concentration, with multiple efflux pumps employed toremove cadmium while a sulfate transporter was down-regulated to reducenon-specific uptake of chromium. Membrane proteins were also up-regulatedin response to most of the metals tested. A two-component signaltransduction system involved in the uranium response was identified.Several differentially regulated transcripts from regions previously notknown to encode proteins were identified, demonstrating the advantage ofevaluating the transcriptome using whole genome microarrays.

  12. Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

    OpenAIRE

    Yung, Mimi C.; Jiao, Yongqin

    2014-01-01

    Caulobacter crescentus is known to tolerate high levels of uranium [U(VI)], but its detoxification mechanism is poorly understood. Here we show that C. crescentus is able to facilitate U(VI) biomineralization through the formation of U-Pi precipitates via its native alkaline phosphatase activity. The U-Pi precipitates, deposited on the cell surface in the form of meta-autunite structures, have a lower U/Pi ratio than do chemically produced precipitates. The enzyme that is responsible for the ...

  13. Surface-layer protein from Caulobacter crescentus: expression, purification and X-ray crystallographic analysis.

    Science.gov (United States)

    Jones, Michael D; Chan, Anson C K; Nomellini, John F; Murphy, Michael E P; Smit, John

    2016-09-01

    Protein surface layers are self-assembling, paracrystalline lattices on the surface of many prokaryotes. Surface-layer proteins have not benefited from widespread structural analysis owing to their resistance to crystallization. Here, the successful expression of a truncated version of RsaA, the surface-layer protein from Caulobacter crescentus, from a Caulobacter protein-expression system is reported. The purification, crystallization and initial X-ray diffraction analysis of the truncated RsaA, the largest surface-layer protein studied to date and the first from a Gram-negative bacterium, are also reported. PMID:27599857

  14. Advantages and mechanisms of polarity and cell shape determination in Caulobacter crescentus

    OpenAIRE

    Lawler, Melanie L.; Brun, Yves V.

    2007-01-01

    The tremendous diversity of bacterial cell shapes and the targeting of proteins and macromolecular complexes to specific subcellular sites strongly suggest that cellular organization provides important advantages for bacteria in their environment. Key advances have been made in the understanding of the mechanism and function of polarity and cell shape by studying the aquatic bacterium Caulobacter crescentus, whose cell cycle progression involves the ordered synthesis of different polar struct...

  15. Proteome of Caulobacter crescentus cell cycle publicty accessible on SWICZ server

    Czech Academy of Sciences Publication Activity Database

    Vohradský, Jiří; Janda, Ivan; Grunenfelder, B.; Berndt, P.; Roder, D.; Langen, H.; Weiser, Jaroslav; Jenal, U.

    2003-01-01

    Roč. 3, - (2003), s. 1874-7882. ISSN 1615-9853 R&D Projects: GA ČR GA310/03/0293; GA AV ČR IAA5020211 Grant ostatní: GA Swiss National Science Foundation fellowship(XX) 31-59050.99 Institutional research plan: CEZ:AV0Z5020903 Keywords : bioinformatics * caulobacter * crescentus Subject RIV: EE - Microbiology, Virology Impact factor: 5.766, year: 2003

  16. Reduction of Cr(VI) and survival in Cr-contaminated sites by Caulobacter crescentus

    Science.gov (United States)

    Hu, P.; Chakraborty, R.; Brodie, E. L.; Andersen, G. L.; Hazen, T. C.

    2008-12-01

    The Caulobacter spp. is known to be able to live in low-nutrient environments, a characteristic of most heavy metal-contaminated sites. Recent studies have shown that Caulobacter crescentus can grow in chemically defined medium containing up to 1 mM uranium. Whole-genome transcriptional analysis and electron microscopic imaging of heavy metal stresses in Caulobacter crescentus also provided insight and evidence that the bacterium used an array of defensive mechanisms to deal with heavy metal stresses. In addition to up-regulated enzymes protecting against oxidative stress, DNA repair and down-regulated potential chromium transport, one of the major gene groups respond to chromium stress is "electron transport process and cytochrome oxidases", including cytochrome c oxidases, raising the possibility that the cells can employ the cytochromes to reduce chromium. Analysis of the microbial community at the chromium contaminated DOE site at Hanford, WA revealed the presence of Caulobacter spp. As an oligotroph, Caulobacter can play a significant role in chromium reduction in the environment where the nutrients are limited. This result was confirmed by both 16S rDNA based microarray (Phylochip) as well as by MDA-based clone library data. Based on these results we further investigated the capability of this organism to reduce Cr(VI) using the well known model strain Caulobacter crescentus CB15N. Preliminary cell suspension experiments were set up with glucose as the electron donor and Cr(VI) as the electron acceptor in phosphate based M2 salts buffer. After 22 hours almost 27% of Cr(VI) was reduced in the incubations containing active cells relative to the controls containing heat killed cells. Also, in another set of controls with no electron acceptor added, cells showed no increase in cell density during that time demonstrating that the reduction of Cr(VI) by cells of Caulobacter was due to biological activity. Future experiments will investigate the components

  17. Tn-seq of Caulobacter crescentus under uranium stress reveals genes essential for detoxification and stress tolerance

    International Nuclear Information System (INIS)

    Ubiquitous aquatic bacterium Caulobacter crescentus is highly resistant to uranium (U) and facilitates U biomineralization and thus holds promise as an agent of U bioremediation. In order to gain an understanding of how C. crescentus tolerates U, we employed transposon (Tn) mutagenesis paired with deep sequencing (Tn-seq) in a global screen for genomic elements required for U resistance. Of the 3,879 annotated genes in the C. crescentus genome, 37 were found to be specifically associated with fitness under U stress, 15 of which were subsequently tested through mutational analysis. Systematic deletion analysis revealed that mutants lacking outer membrane transporters (rsaFa and rsaFb), a stress-responsive transcription factor (cztR), or a ppGpp synthetase/hydrolase (spoT) exhibited a significantly lower survival rate under U stress. RsaFa and RsaFb, which are homologues of TolC in Escherichia coli, have previously been shown to mediate S-layer export. Transcriptional analysis revealed upregulation of rsaFa and rsaFb by 4- and 10-fold, respectively, in the presence of U. We additionally show that rsaFa mutants accumulated higher levels of U than the wild type, with no significant increase in oxidative stress levels. These results suggest a function for RsaFa and RsaFb in U efflux and/or maintenance of membrane integrity during U stress. In addition, we present data implicating CztR and SpoT in resistance to U stress. Together, our findings reveal novel gene targets that are key to understanding the molecular mechanisms of U resistance in C. crescentus

  18. A moving DNA replication factory in Caulobacter crescentus

    OpenAIRE

    Jensen, Rasmus B.; Wang, Sherry C.; Shapiro, Lucy

    2001-01-01

    The in vivo intracellular location of components of the Caulobacter replication apparatus was visualized during the cell cycle. Replisome assembly occurs at the chromosomal origin located at the stalked cell pole, coincident with the initiation of DNA replication. The replisome gradually moves to midcell as DNA replication proceeds and disassembles upon completion of DNA replication. Although the newly replicated origin regions of the chromosome are rapidly moved to opposite cell poles by an ...

  19. A stochastic spatiotemporal model of a response-regulator network in the Caulobacter crescentus cell cycle

    Science.gov (United States)

    Li, Fei; Subramanian, Kartik; Chen, Minghan; Tyson, John J.; Cao, Yang

    2016-06-01

    The asymmetric cell division cycle in Caulobacter crescentus is controlled by an elaborate molecular mechanism governing the production, activation and spatial localization of a host of interacting proteins. In previous work, we proposed a deterministic mathematical model for the spatiotemporal dynamics of six major regulatory proteins. In this paper, we study a stochastic version of the model, which takes into account molecular fluctuations of these regulatory proteins in space and time during early stages of the cell cycle of wild-type Caulobacter cells. We test the stochastic model with regard to experimental observations of increased variability of cycle time in cells depleted of the divJ gene product. The deterministic model predicts that overexpression of the divK gene blocks cell cycle progression in the stalked stage; however, stochastic simulations suggest that a small fraction of the mutants cells do complete the cell cycle normally.

  20. Biomineralization of uranium by PhoY phosphatase activity aids cell survival in Caulobacter crescentus.

    Science.gov (United States)

    Yung, Mimi C; Jiao, Yongqin

    2014-08-01

    Caulobacter crescentus is known to tolerate high levels of uranium [U(VI)], but its detoxification mechanism is poorly understood. Here we show that C. crescentus is able to facilitate U(VI) biomineralization through the formation of U-Pi precipitates via its native alkaline phosphatase activity. The U-Pi precipitates, deposited on the cell surface in the form of meta-autunite structures, have a lower U/Pi ratio than do chemically produced precipitates. The enzyme that is responsible for the phosphatase activity and thus the biomineralization process is identified as PhoY, a periplasmic alkaline phosphatase with broad substrate specificity. Furthermore, PhoY is shown to confer a survival advantage on C. crescentus toward U(VI) under both growth and nongrowth conditions. Results obtained in this study thus highlight U(VI) biomineralization as a resistance mechanism in microbes, which not only improves our understanding of bacterium-mineral interactions but also aids in defining potential ecological niches for metal-resistant bacteria. PMID:24878600

  1. Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

    Energy Technology Data Exchange (ETDEWEB)

    Yung, M C [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jiao, Y [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-07-22

    Caulobacter crescentus is known to tolerate high levels of uranium [U(VI)], but its detoxification mechanism is poorly understood. Here we show that C. crescentus is able to facilitate U(VI) biomineralization through the formation of U-Pi precipitates via its native alkaline phosphatase activity. The U-Pi precipitates, deposited on the cell surface in the form of meta-autunite structures, have a lower U/Pi ratio than do chemically produced precipitates. The enzyme that is responsible for the phosphatase activity and thus the biomineralization process is identified as PhoY, a periplasmic alkaline phosphatase with broad substrate specificity. Furthermore, PhoY is shown to confer a survival advantage on C. crescentus toward U(VI) under both growth and nongrowth conditions. Results obtained in this study thus highlight U(VI) biomineralization as a resistance mechanism in microbes, which not only improves our understanding of bacterium-mineral interactions but also aids in defining potential ecological niches for metal-resistant bacteria.

  2. The flagellar motor of Caulobacter crescentus generates more torque when a cell swims backwards

    Science.gov (United States)

    Lele, Pushkar P.; Roland, Thibault; Shrivastava, Abhishek; Chen, Yihao; Berg, Howard C.

    2016-02-01

    The bacterium Caulobacter crescentus swims by rotating a single right-handed helical filament. These cells have two swimming modes: a pusher mode, in which clockwise (CW) rotation of the filament thrusts the cell body forwards, and a puller mode, in which counterclockwise (CCW) rotation pulls it backwards. The situation is reversed in Escherichia coli, a bacterium that rotates several left-handed filaments CCW to drive the cell body forwards. The flagellar motor in E. coli generates more torque in the CCW direction than the CW direction in swimming cells. However, C. crescentus and other bacteria with single filaments swim forwards and backwards at similar speeds, prompting the assumption that motor torques in the two modes are the same. Here, we present evidence that motors in C. crescentus develop higher torques in the puller mode than in the pusher mode, and suggest that the anisotropy in torque generation is similar in the two species, despite the differences in filament handedness and motor bias.

  3. Phosphate starvation triggers production and secretion of an extracellular lipoprotein in Caulobacter crescentus.

    Directory of Open Access Journals (Sweden)

    Sophie Le Blastier

    Full Text Available Life in oligotrophic environments necessitates quick adaptive responses to a sudden lack of nutrients. Secretion of specific degradative enzymes into the extracellular medium is a means to mobilize the required nutrient from nearby sources. The aquatic bacterium Caulobacter crescentus must often face changes in its environment such as phosphate limitation. Evidence reported in this paper indicates that under phosphate starvation, C. crescentus produces a membrane surface-anchored lipoprotein named ElpS subsequently released into the extracellular medium. A complete set of 12 genes encoding a type II secretion system (T2SS is located adjacent to the elpS locus in the C. crescentus genome. Deletion of this T2SS impairs release of ElpS in the environment, which surprisingly remains present at the cell surface, indicating that the T2SS is not involved in the translocation of ElpS to the outer membrane but rather in its release. Accordingly, treatment with protease inhibitors prevents release of ElpS in the extracellular medium suggesting that ElpS secretion relies on a T2SS-secreted protease. Finally, secretion of ElpS is associated with an increase in alkaline phosphatase activity in culture supernatants, suggesting a role of the secreted protein in inorganic phosphate mobilization. In conclusion, we have shown that upon phosphate starvation, C. crescentus produces an outer membrane bound lipoprotein, ElpS, which is further cleaved and released in the extracellular medium in a T2SS-dependent manner. Our data suggest that ElpS is associated with an alkaline phosphatase activity, thereby allowing the bacterium to gather inorganic phosphates from a poor environment.

  4. Genome analysis of DNA repair genes in the alpha proteobacterium Caulobacter crescentus

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    Menck Carlos FM

    2007-03-01

    Full Text Available Abstract Background The integrity of DNA molecules is fundamental for maintaining life. The DNA repair proteins protect organisms against genetic damage, by removal of DNA lesions or helping to tolerate them. DNA repair genes are best known from the gamma-proteobacterium Escherichia coli, which is the most understood bacterial model. However, genome sequencing raises questions regarding uniformity and ubiquity of these DNA repair genes and pathways, reinforcing the need for identifying genes and proteins, which may respond to DNA damage in other bacteria. Results In this study, we employed a bioinformatic approach, to analyse and describe the open reading frames potentially related to DNA repair from the genome of the alpha-proteobacterium Caulobacter crescentus. This was performed by comparison with known DNA repair related genes found in public databases. As expected, although C. crescentus and E. coli bacteria belong to separate phylogenetic groups, many of their DNA repair genes are very similar. However, some important DNA repair genes are absent in the C. crescentus genome and other interesting functionally related gene duplications are present, which do not occur in E. coli. These include DNA ligases, exonuclease III (xthA, endonuclease III (nth, O6-methylguanine-DNA methyltransferase (ada gene, photolyase-like genes, and uracil-DNA-glycosylases. On the other hand, the genes imuA and imuB, which are involved in DNA damage induced mutagenesis, have recently been described in C. crescentus, but are absent in E. coli. Particularly interesting are the potential atypical phylogeny of one of the photolyase genes in alpha-proteobacteria, indicating an origin by horizontal transfer, and the duplication of the Ada orthologs, which have diverse structural configurations, including one that is still unique for C. crescentus. Conclusion The absence and the presence of certain genes are discussed and predictions are made considering the particular

  5. Regulation of the activity of the dual-function DnaA protein in Caulobacter crescentus.

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    Carmen Fernandez-Fernandez

    Full Text Available DnaA is a conserved essential bacterial protein that acts as the initiator of chromosomal replication as well as a master transcriptional regulator in Caulobacter crescentus. Thus, the intracellular levels of active DnaA need to be tightly regulated during the cell cycle. Our previous work suggested that DnaA may be regulated at the level of its activity by the replisome-associated protein HdaA. Here, we describe the construction of a mutant DnaA protein [DnaA(R357A]. The R357 residue in the AAA+ domain of the C. crescentus DnaA protein is equivalent to the R334 residue of the E. coli DnaA protein, which is required for the Regulatory Inactivation of DnaA (RIDA. We found that the expression of the DnaA(R357A mutant protein in C. crescentus, but not the expression of the wild-type DnaA protein at similar levels, causes a severe phenotype of over-initiation of chromosomal replication and that it blocks cell division. Thus, the mutant DnaA(R357A protein is hyper-active to promote the initiation of DNA replication, compared to the wild-type DnaA protein. DnaA(R357A could not replace DnaA in vivo, indicating that the switch in DnaA activity once chromosomal replication has started may be an essential process in C. crescentus. We propose that the inactivation of DnaA is the main mechanism ensuring that chromosomal replication starts only once per cell cycle. We further observed that the R357A substitution in DnaA does not promote the activity of DnaA as a direct transcriptional activator of four important genes, encoding HdaA, the GcrA master cell cycle regulator, the FtsZ cell division protein and the MipZ spatial regulator of cell division. Thus, the AAA+ domain of DnaA may play a role in temporally regulating the bifunctionality of DnaA by reallocating DnaA molecules from initiating DNA replication to transcribing genes within the unique DnaA regulon of C. crescentus.

  6. The curved shape of the bacterium Caulobacter crescentus enhances colonization of surfaces in flow

    Science.gov (United States)

    Persat, Alexandre; Gitai, Zemer; Stone, Howard

    2014-11-01

    Bacteria thrive in all types of fluid environments; flow is thus a ubiquitous aspect of their lives. Bacteria have evolved a variety of cellular components contributing to their growth in specific environments. However, cellular features that help them survive and develop in flow have been rarely characterized. Here, we show that Caulobacter crescentus may have evolved its curved shape to enhance the colonization of surfaces in flow. C. crescentus curvature is preserved in the wild but straight mutants have no known growth disadvantage in standard laboratory conditions. Leveraging microfluidics and single-cell imaging, we demonstrate that curvature enhances surface colonization in flow, promoting the formation of larger microcolonies. Cells attach to a surface from a single pole, so that flow affects their orientation. In flow, viscous forces generate a torque on the curved cell body, which reorients the cell in the direction of the flow. The curved cell appears to arc above the surface, optimally orienting its unattached pole towards the surface. This reduces the distance between the surface and the pole, thereby enhancing attachment of its progeny. Additionally, we show that curved shape enhances colony spreading across the direction of the flow, generating more robust biofilm compared to straight mutants.

  7. Two RND proteins involved in heavy metal efflux in Caulobacter crescentus belong to separate clusters within proteobacteria

    OpenAIRE

    Valencia, Estela Y; Vânia S. Braz; Guzzo, Cristiane; Marques, Marilis V.

    2013-01-01

    Background Heavy metal Resistance-Nodulation-Division (HME-RND) efflux systems help Gram-negative bacteria to keep the intracellular homeostasis under high metal concentrations. These proteins constitute the cytoplasmic membrane channel of the tripartite RND transport systems. Caulobacter crescentus NA1000 possess two HME-RND proteins, and the aim of this work was to determine their involvement in the response to cadmium, zinc, cobalt and nickel, and to analyze the phylogenetic distribution a...

  8. Development of an HIV-1 Microbicide Based on Caulobacter crescentus: Blocking Infection by High-Density Display of Virus Entry Inhibitors.

    Science.gov (United States)

    Farr, Christina; Nomellini, John F; Ailon, Evan; Shanina, Iryna; Sangsari, Sassan; Cavacini, Lisa A; Smit, John; Horwitz, Marc S

    2013-01-01

    The HIV/AIDS pandemic remains an enormous global health concern. Despite effective prevention options, 2.6 million new infections occur annually, with women in developing countries accounting for more than half of these infections. New prevention strategies that can be used by women are urgently needed. Topical microbicides specific for HIV-1 represent a promising prevention strategy. Conceptually, using harmless bacteria to display peptides or proteins capable of blocking entry provides an inexpensive approach to microbicide development. To avoid the potential pitfalls of engineering commensal bacteria, our strategy is to genetically display infection inhibitors on a non-native bacterium and rely on topical application of stabilized bacteria before potential virus exposure. Due to the high density cell-surface display capabilities and the inherent low toxicity of the bacterium, the S-layer mediated protein display capabilities of the non-pathogenic bacterium Caulobacter crescentus has been exploited for this approach. We have demonstrated that C. crescentus displaying MIP1α or CD4 interfered with the virus entry pathway and provided significant protection from HIV-1 pseudovirus representing clade B in a standard single cycle infection assay. Here we have expanded our C. crescentus based microbicide approach with additional and diverse classes of natural and synthetic inhibitors of the HIV-1 entry pathway. All display constructs provided variable but significant protection from HIV-1 infection; some with protection as high as 70%. Further, we describe protection from infection with additional viral clades. These findings indicate the significant potential for engineering C. crescentus to be an effective and readily adaptable HIV-1 microbicide platform. PMID:23840383

  9. Development of an HIV-1 Microbicide Based on Caulobacter crescentus: Blocking Infection by High-Density Display of Virus Entry Inhibitors.

    Directory of Open Access Journals (Sweden)

    Christina Farr

    Full Text Available The HIV/AIDS pandemic remains an enormous global health concern. Despite effective prevention options, 2.6 million new infections occur annually, with women in developing countries accounting for more than half of these infections. New prevention strategies that can be used by women are urgently needed. Topical microbicides specific for HIV-1 represent a promising prevention strategy. Conceptually, using harmless bacteria to display peptides or proteins capable of blocking entry provides an inexpensive approach to microbicide development. To avoid the potential pitfalls of engineering commensal bacteria, our strategy is to genetically display infection inhibitors on a non-native bacterium and rely on topical application of stabilized bacteria before potential virus exposure. Due to the high density cell-surface display capabilities and the inherent low toxicity of the bacterium, the S-layer mediated protein display capabilities of the non-pathogenic bacterium Caulobacter crescentus has been exploited for this approach. We have demonstrated that C. crescentus displaying MIP1α or CD4 interfered with the virus entry pathway and provided significant protection from HIV-1 pseudovirus representing clade B in a standard single cycle infection assay. Here we have expanded our C. crescentus based microbicide approach with additional and diverse classes of natural and synthetic inhibitors of the HIV-1 entry pathway. All display constructs provided variable but significant protection from HIV-1 infection; some with protection as high as 70%. Further, we describe protection from infection with additional viral clades. These findings indicate the significant potential for engineering C. crescentus to be an effective and readily adaptable HIV-1 microbicide platform.

  10. A DNA damage-induced, SOS-independent checkpoint regulates cell division in Caulobacter crescentus.

    Directory of Open Access Journals (Sweden)

    Joshua W Modell

    2014-10-01

    Full Text Available Cells must coordinate DNA replication with cell division, especially during episodes of DNA damage. The paradigm for cell division control following DNA damage in bacteria involves the SOS response where cleavage of the transcriptional repressor LexA induces a division inhibitor. However, in Caulobacter crescentus, cells lacking the primary SOS-regulated inhibitor, sidA, can often still delay division post-damage. Here we identify didA, a second cell division inhibitor that is induced by DNA damage, but in an SOS-independent manner. Together, DidA and SidA inhibit division, such that cells lacking both inhibitors divide prematurely following DNA damage, with lethal consequences. We show that DidA does not disrupt assembly of the division machinery and instead binds the essential division protein FtsN to block cytokinesis. Intriguingly, mutations in FtsW and FtsI, which drive the synthesis of septal cell wall material, can suppress the activity of both SidA and DidA, likely by causing the FtsW/I/N complex to hyperactively initiate cell division. Finally, we identify a transcription factor, DriD, that drives the SOS-independent transcription of didA following DNA damage.

  11. A DNA damage-induced, SOS-independent checkpoint regulates cell division in Caulobacter crescentus.

    Science.gov (United States)

    Modell, Joshua W; Kambara, Tracy K; Perchuk, Barrett S; Laub, Michael T

    2014-10-01

    Cells must coordinate DNA replication with cell division, especially during episodes of DNA damage. The paradigm for cell division control following DNA damage in bacteria involves the SOS response where cleavage of the transcriptional repressor LexA induces a division inhibitor. However, in Caulobacter crescentus, cells lacking the primary SOS-regulated inhibitor, sidA, can often still delay division post-damage. Here we identify didA, a second cell division inhibitor that is induced by DNA damage, but in an SOS-independent manner. Together, DidA and SidA inhibit division, such that cells lacking both inhibitors divide prematurely following DNA damage, with lethal consequences. We show that DidA does not disrupt assembly of the division machinery and instead binds the essential division protein FtsN to block cytokinesis. Intriguingly, mutations in FtsW and FtsI, which drive the synthesis of septal cell wall material, can suppress the activity of both SidA and DidA, likely by causing the FtsW/I/N complex to hyperactively initiate cell division. Finally, we identify a transcription factor, DriD, that drives the SOS-independent transcription of didA following DNA damage. PMID:25350732

  12. Growth control switch by a DNA-damage-inducible toxin-antitoxin system in Caulobacter crescentus.

    Science.gov (United States)

    Kirkpatrick, Clare L; Martins, Daniel; Redder, Peter; Frandi, Antonio; Mignolet, Johann; Chapalay, Julien Bortoli; Chambon, Marc; Turcatti, Gerardo; Viollier, Patrick H

    2016-01-01

    Bacterial toxin-antitoxin systems (TASs) are thought to respond to various stresses, often inducing growth-arrested (persistent) sub-populations of cells whose housekeeping functions are inhibited. Many such TASs induce this effect through the translation-dependent RNA cleavage (RNase) activity of their toxins, which are held in check by their cognate antitoxins in the absence of stress. However, it is not always clear whether specific mRNA targets of orthologous RNase toxins are responsible for their phenotypic effect, which has made it difficult to accurately place the multitude of TASs within cellular and adaptive regulatory networks. Here, we show that the TAS HigBA of Caulobacter crescentus can promote and inhibit bacterial growth dependent on the dosage of HigB, a toxin regulated by the DNA damage (SOS) repressor LexA in addition to its antitoxin HigA, and the target selectivity of HigB's mRNA cleavage activity. HigB reduced the expression of an efflux pump that is toxic to a polarity control mutant, cripples the growth of cells lacking LexA, and targets the cell cycle circuitry. Thus, TASs can have outcome switching activity in bacterial adaptive (stress) and systemic (cell cycle) networks. PMID:27572440

  13. Structural insights into ChpT, an essential dimeric histidine phosphotransferase regulating the cell cycle in Caulobacter crescentus

    OpenAIRE

    Fioravanti, Antonella; Clantin, Bernard; Dewitte, Frédérique; Lens, Zoé; Verger, Alexis; Biondi, Emanuele G; Villeret, Vincent

    2012-01-01

    Two-component and phosphorelay signal-transduction proteins are crucial for bacterial cell-cycle regulation in Caulobacter crescentus. ChpT is an essential histidine phosphotransferase that controls the activity of the master cell-cycle regulator CtrA by phosphorylation. Here, the 2.2 Å resolution crystal structure of ChpT is reported. ChpT is a homodimer and adopts the domain architecture of the intracellular part of class I histidine kinases. Each subunit consists of two distinct domains: a...

  14. Functional Characterization of UDP-Glucose:Undecaprenyl-Phosphate Glucose-1-Phosphate Transferases of Escherichia coli and Caulobacter crescentus

    OpenAIRE

    Patel, Kinnari B.; Toh, Evelyn; Fernandez, Ximena B.; Hanuszkiewicz, Anna; Hardy, Gail G.; Brun, Yves V.; Bernards, Mark A.; Valvano, Miguel A.

    2012-01-01

    Escherichia coli K-12 WcaJ and the Caulobacter crescentus HfsE, PssY, and PssZ enzymes are predicted to initiate the synthesis of colanic acid (CA) capsule and holdfast polysaccharide, respectively. These proteins belong to a prokaryotic family of membrane enzymes that catalyze the formation of a phosphoanhydride bond joining a hexose-1-phosphate with undecaprenyl phosphate (Und-P). In this study, in vivo complementation assays of an E. coli K-12 wcaJ mutant demonstrated that WcaJ and PssY ca...

  15. The cloning, expression, purification, characterization and modeled structure of Caulobacter crescentus β-Xylosidase I.

    Science.gov (United States)

    Graciano, Luciana; Corrêa, Juliana Moço; Gandra, Rinaldo Ferreira; Seixas, Flavio Augusto Vicente; Kadowaki, Marina Kimiko; Sampaio, Silvio César; Silva, José Luis da Conceição; Osaku, Clarice Aoki; Simão, Rita de Cássia Garcia

    2012-09-01

    The xynB1 gene (CCNA 01040) of Caulobacter crescentus that encodes a bifunctional enzyme containing the conserved β-Xylosidase and α-L-Arabinofuranosidase (β-Xyl I-α-L-Ara) domains was amplified by PCR and cloned into the vector pJet1.2Blunt. The xynB1 gene was subcloned into the vector pPROEX-hta that produces a histidine-fused translation product. The overexpression of recombinant β-Xyl I-α-L-Ara was induced with IPTG in BL21 (DE3) and the resulting intracellular protein was purified with pre-packaged nickel-Sepharose columns. The recombinant β-Xyl I-α-L-Ara exhibited a specific β-Xylosidase I activity of 1.25 U mg(-1) to oNPX and a specific α-L-Arabinofuranosidase activity of 0.47 U mg(-1) to pNPA. The predominant activity of the recombinant enzyme was its β-Xylosidase I activity, and the enzymatic characterization was focused on it. The β-Xylosidase I activity was high over the pH range 3-10, with maximal activity at pH 6. The enzyme activity was optimal at 45 °C, and a high degree of stability was verified over 240 min at this temperature. Moreover, β-Xylosidase activity was inhibited in the presence of the metals Zn(2+) and Cu(2+), and the enzyme exhibited K(M) and V(Max) values of 2.89 ± 0.13 mM and 1.4 ± 0.04 μM min(-1) to oNPX, respectively. The modeled structure of β-xylosidase I showed that its active site is highly conserved compared with other structures of the GH43 family. The increase in the number of contact residues responsible for maintaining the dimeric structure indicates that this dimer is more stable than the tetramer form. PMID:22806729

  16. Identification, crystallization and preliminary X-ray diffraction analysis of esterase A from Caulobacter crescentus CB15, a family VIII lipolytic enzyme

    International Nuclear Information System (INIS)

    Esterase A from C. crescentus CB15 was crystallized in space group C2221 and diffraction data were collected to a resolution of 1.62 Å. The structures and functions of family VIII lipolytic enzymes, which have moderate sequence identity to class C β-lactamases and penicillin-binding proteins, are largely unknown. Here, the X-ray crystallographic study of a family VIII esterase from Caulobacter crescentus CB15 (CcEstA) is described. Sequence analysis revealed that CcEstA has a conserved serine residue within the S-X-X-K motif which acts as a catalytic nucleophile. Recombinant protein containing an N-terminal His tag was expressed in Escherichia coli and purified to homogeneity. Functional studies showed that CcEstA acts on α- and β-naphthyl acetate as substrates. In addition, it can catalyze the hydrolysis of ketoprofen ethyl ester, a highly useful product in industrial applications. CcEstA was crystallized using a solution consisting of 1.0 M potassium/sodium tartrate, 0.1 M imidazole pH 8.0, 0.2 M NaCl, and X-ray diffraction data were collected to a resolution of 1.62 Å with an Rmerge of 9.4%. The crystals of CcEstA belonged to space group C2221, with unit-cell parameters a = 172.23, b = 176.68, c = 47.93 Å. Structure determination is in progress

  17. Activation and polar sequestration of PopA, a c-di-GMP effector protein involved in Caulobacter crescentus cell cycle control

    DEFF Research Database (Denmark)

    Ozaki, Shogo; Schalch-Moser, Annina; Zumthor, Ludwig; Manfredi, Pablo; Ebbensgaard, Anna Elisabeth; Schirmer, Tilman; Jenal, Urs

    2014-01-01

    When Caulobacter crescentus enters S-phase the replication initiation inhibitor CtrA dynamically positions to the old cell pole to be degraded by the polar ClpXP protease. Polar delivery of CtrA requires PopA and the diguanylate cyclase PleD that positions to the same pole. Here we present evidence...... that PopA originated through gene duplication from its paralogue response regulator PleD and subsequent co-option as c-di-GMP effector protein. While the C-terminal catalytic domain (GGDEF) of PleD is activated by phosphorylation of the N-terminal receiver domain, functional adaptation has reversed...... PopA to the cell pole in response to c-di-GMP binding. In agreement with the divergent activation and targeting mechanisms, distinct markers sequester PleD and PopA to the old cell pole upon S-phase entry. Together these data indicate that PopA adopted a novel role as topology specificity factor to...

  18. Cloning and expression of the xynA1 gene encoding a xylanase of the GH10 group in Caulobacter crescentus.

    Science.gov (United States)

    Graciano, Luciana; Corrêa, Juliana Moço; Vieira, Fabíola Giovanna Nesello; Bosetto, Adilson; Loth, Eduardo Alexandre; Kadowaki, Marina Kimiko; Gandra, Rinaldo Ferreira; Simão, Rita de Cássia Garcia

    2015-04-01

    Caulobacter crescentus (NA1000 strain) are aquatic bacteria that can live in environments of low nutritional quality and present numerous genes that encode enzymes involved in plant cell wall deconstruction, including five genes for β-xylosidases (xynB1-xynB5) and three genes for xylanases (xynA1-xynA3). The overall activity of xylanases in the presence of different agro-industrial residues was evaluated, and it was found that the residues from the processing of corn were the most efficient in inducing bacterial xylanases. The xynA1 gene (CCNA_02894) encoding a predicted xylanase of group 10 of glyco-hydrolases (GH10) that was efficiently overexpressed in Escherichia coli LMG194 using 0.02 % arabinose, after cloning into the vector pJet1.2blunt and subcloning into the expression vector pBAD/gIII, provided a fusion protein that contained carboxy-terminal His-tags, named XynA1. The characterization of pure XynA1 showed an enzymatic activity of 18.26 U mL(-1) and a specific activity of 2.22 U mg-(1) in the presence of xylan from beechwood as a substrate. XynA1 activity was inhibited by EDTA and metal ions such as Cu(2+) and Mg(2+). By contrast, β-mercaptoethanol, dithiothreitol (DTT), and Ca(2+) induced recombinant enzyme activity. Kinetic data for XynA1 revealed K M and V max values of 3.77 mg mL-(1) and 10.20 μM min-(1), respectively. Finally, the enzyme presented an optimum pH of 6 and an optimum temperature of 50 °C. In addition, 80 % of the activity of XynA1 was maintained at 50 °C for 4 h of incubation, suggesting a thermal stability for the biotechnological processes. This work is the first study concerning the cloning, overexpression, and enzymatic characterization of C. crescentus xylanase. PMID:25791579

  19. Analysis of the xynB5 gene encoding a multifunctional GH3-BglX β-glucosidase-β-xylosidase-α-arabinosidase member in Caulobacter crescentus.

    Science.gov (United States)

    Justo, Priscila Innocenti; Corrêa, Juliana Moço; Maller, Alexandre; Kadowaki, Marina Kimiko; da Conceição-Silva, José Luis; Gandra, Rinaldo Ferreira; Simão, Rita de Cássia Garcia

    2015-10-01

    The Caulobacter crescentus (NA1000) xynB5 gene (CCNA_03149) encodes a predicted β-glucosidase-β-xylosidase enzyme that was amplified by polymerase chain reaction; the product was cloned into the blunt ends of the pJet1.2 plasmid. Analysis of the protein sequence indicated the presence of conserved glycosyl hydrolase 3 (GH3), β-glucosidase-related glycosidase (BglX) and fibronectin type III-like domains. After verifying its identity by DNA sequencing, the xynB5 gene was linked to an amino-terminal His-tag using the pTrcHisA vector. A recombinant protein (95 kDa) was successfully overexpressed from the xynB5 gene in E. coli Top 10 and purified using pre-packed nickel-Sepharose columns. The purified protein (BglX-V-Ara) demonstrated multifunctional activities in the presence of different substrates for β-glucosidase (pNPG: p-nitrophenyl-β-D-glucoside) β-xylosidase (pNPX: p-nitrophenyl-β-D-xyloside) and α-arabinosidase (pNPA: p-nitrophenyl-α-L-arabinosidase). BglX-V-Ara presented an optimal pH of 6 for all substrates and optimal temperature of 50 °C for β-glucosidase and α-L-arabinosidase and 60 °C for β-xylosidase. BglX-V-Ara predominantly presented β-glucosidase activity, with the highest affinity for its substrate and catalytic efficiency (Km 0.24 ± 0.0005 mM, Vmax 0.041 ± 0.002 µmol min(-1) mg(-1) and Kcat/Km 0.27 mM(-1) s(-1)), followed by β-xylosidase (Km 0.64 ± 0.032 mM, Vmax 0.055 ± 0.002 µmol min(-1) mg(-1) and Kcat/Km 0.14 mM(-1)s(-1)) and finally α-L-arabinosidase (Km 1.45 ± 0.05 mM, Vmax 0.091 ± 0.0004 µmol min(-1) mg(-1) and Kcat/Km 0.1 mM(-1) s(-1)). To date, this is the first report to demonstrate the characterization of a GH3-BglX family member in C. crescentus that may have applications in biotechnological processes (i.e., the simultaneous saccharification process) because the multifunctional enzyme could play an important role in bacterial hemicellulose degradation. PMID:26264062

  20. Methylation involved in chemotaxis is regulated during Caulobacter differentiation.

    OpenAIRE

    Shaw, P; Gomes, S L; Sweeney, K; Ely, B; L. Shapiro

    1983-01-01

    Caulobacter crescentus carries a flagellum and is motile only during a limited time in its cell cycle. We have asked if the biochemical machinery that mediates chemotaxis exists coincident with the cell's structural ability to respond to a chemotactic signal. We first demonstrated that one function of the chemotaxis machinery, the ability to methylate the carboxyl side chains of a specific set of membrane proteins (methyl-accepting chemotaxis proteins, MCPs), is present in C. crescentus. This...

  1. A self-associating protein critical for chromosome attachment, division, and polar organization in caulobacter

    DEFF Research Database (Denmark)

    Ebersbach, Gitte; Briegel, Ariane; Jensen, Grant J; Jacobs-Wagner, Christine; Charbon, Gitte Ebersbach

    2008-01-01

    Cell polarization is an integral part of many unrelated bacterial processes. How intrinsic cell polarization is achieved is poorly understood. Here, we provide evidence that Caulobacter crescentus uses a multimeric pole-organizing factor (PopZ) that serves as a hub to concurrently achieve several...... suggests that localization of PopZ largely relies on PopZ multimerization in chromosome-free regions, consistent with a self-organizing mechanism.......Cell polarization is an integral part of many unrelated bacterial processes. How intrinsic cell polarization is achieved is poorly understood. Here, we provide evidence that Caulobacter crescentus uses a multimeric pole-organizing factor (PopZ) that serves as a hub to concurrently achieve several...

  2. Isolation and characterization of Caulobacter mutants impaired in adaptation to stationary phase

    OpenAIRE

    Italiani Valéria C. S.; Marques Marilis V

    2003-01-01

    The entry into stationary phase causes a change in the pattern of gene expression of bacteria, when the cells must express a whole set of genes involved mainly with resistance to starvation and to environmental stresses. As an attempt to identify genes important for the survival of Caulobacter crescentus in stationary phase, we have screened a library of 5,000 clones generated by random transposon mutagenesis for mutants that showed reduced viability after prolonged growth. Four clones were s...

  3. Isolation and characterization of Caulobacter mutants impaired in adaptation to stationary phase Isolamento e caracterização de mutantes de Caulobacter deficientes na adaptação à fase estacionária

    OpenAIRE

    Italiani, Valéria C. S.; Marques, Marilis V.

    2003-01-01

    The entry into stationary phase causes a change in the pattern of gene expression of bacteria, when the cells must express a whole set of genes involved mainly with resistance to starvation and to environmental stresses. As an attempt to identify genes important for the survival of Caulobacter crescentus in stationary phase, we have screened a library of 5,000 clones generated by random transposon mutagenesis for mutants that showed reduced viability after prolonged growth. Four clones were s...

  4. Depletion of the xynB2 gene upregulates β-xylosidase expression in C. crescentus.

    Science.gov (United States)

    Corrêa, Juliana Moço; Mingori, Moara Rodrigues; Gandra, Rinaldo Ferreira; Loth, Eduardo Alexandre; Seixas, Flávio Augusto Vicente; Simão, Rita de Cássia Garcia

    2014-01-01

    Caulobacter crescentus is able to express several enzymes involved in the utilization of lignocellulosic biomasses. Five genes, xynB1-5, that encode β-xylosidases are present in the genome of this bacterium. In this study, the xynB2 gene, which encodes β-xylosidase II (CCNA_02442), was cloned under the control of the PxylX promoter to generate the O-xynB2 strain, which overexpresses the enzyme in the presence of xylose. In addition, a null mutant strain, Δ-xynB2, was created by two homologous recombination events where the chromosomal xynB2 gene was replaced by a copy that was disrupted by the spectinomycin-resistant cassette. We demonstrated that C. crescentus cells lacking β-xylosidase II upregulates the xynB genes inducing β-xylosidase activity. Transcriptional analysis revealed that xynB1 (RT-PCR analysis) and xynB2 (lacZ transcription fusion) gene expression was induced in the Δ-xynB2 cells, and high β-xylosidase activity was observed in the presence of different agro-industrial residues in the null mutant strain, a characteristic that can be explored and applied in biotechnological processes. In contrast, overexpression of the xynB2 gene caused downregulation of the expression and activity of the β-xylosidase. For example, the β-xylosidase activity that was obtained in the presence of sugarcane bagasse was 7-fold and 16-fold higher than the activity measured in the C. crescentus parental and O-xynB2 cells, respectively. Our results suggest that β-xylosidase II may have a role in controlling the expression of the xynB1 and xynB2 genes in C. crescentus. PMID:24142353

  5. Report of the First Human Case of Caulobacter sp. Infection▿

    OpenAIRE

    Justesen, Ulrik S; Holt, Hanne M.; Thiesson, Helle C; Blom, Jens; Nielsen, Xiaohui C.; Dargis, Rimtas; Kemp, Michael; Christensen, Jens J.

    2007-01-01

    A Caulobacter sp. isolate was recovered from the dialysis fluid of a patient undergoing peritoneal dialysis. Bacterial identification included electron microscopy and 16S rDNA sequencing. To our knowledge, this is the first report of human Caulobacter infection. Special growth requirements suggest that Caulobacter spp. may be overlooked in the clinical microbiology laboratory.

  6. Caulobacter chromosome in vivo configuration matches model predictions for a supercoiled polymer in a cell-like confinement

    DEFF Research Database (Denmark)

    Hong, Sun-Hae; Toro, Esteban; Mortensen, Kim; de la Rosa, Mario A. Díaz; Doniach, Sebastian; Shapiro, Lucy; Spakowitz, Andrew J.; McAdams, Harley H.

    2013-01-01

    the contour length, and cell-to-cell distribution of the interloci distance r is a universal function of r/n0.22 with broad cell-to-cell variability. For DNA segments greater than about 300 kb, the mean interloci distances scale as n, in agreement with previous observations. The 0.22 value of the......We measured the distance between fluorescent-labeled DNA loci of various interloci contour lengths in Caulobacter crescentus swarmer cells to determine the in vivo configuration of the chromosome. For DNA segments less than about 300 kb, the mean interloci distances, 〈r〉, scale as n0.22, where n is...... scaling exponent for short DNA segments is consistent with theoretical predictions for a branched DNA polymer structure. Predictions from Brownian dynamics simulations of the packing of supercoiled DNA polymers in an elongated cell-like confinement are also consistent with a branched DNA structure, and...

  7. Distinct constrictive processes, separated in time and space,divide Caulobacter inner and outer membranes

    Energy Technology Data Exchange (ETDEWEB)

    Judd, Ellen M.; Comolli, Luis R.; Chen, Joseph C.; Downing,Kenneth H.; Moerner, W.E.; McAdams, Harley H.

    2005-05-01

    Cryo-electron microscope tomography (cryoEM) and a fluorescence loss in photobleaching (FLIP) assay were used to characterize progression of the terminal stages of Caulobacter crescentus cell division. Tomographic cryoEM images of the cell division site show separate constrictive processes closing first the inner, and then the outer, membrane in a manner distinctly different from septum-forming bacteria. The smallest observed pre-fission constrictions were 60 nm for both the inner and outer membrane. FLIP experiments had previously shown cytoplasmic compartmentalization, when cytoplasmic proteins can no longer diffuse between the two nascent progeny cell compartments, occurring 18 min before daughter cell separation in a 135 min cell cycle. Here, we used FLIP experiments with membrane-bound and periplasmic fluorescent proteins to show that (1) periplasmic compartmentalization occurs after cytoplasmic compartmentalization, consistent with the cryoEM observations, and (2) inner membrane and periplasmic proteins can diffuse past the FtsZ constriction site, indicating that the cell division machinery does not block membrane diffusion.

  8. Isolation and characterization of Caulobacter mutants impaired in adaptation to stationary phase

    Directory of Open Access Journals (Sweden)

    Italiani Valéria C. S.

    2003-01-01

    Full Text Available The entry into stationary phase causes a change in the pattern of gene expression of bacteria, when the cells must express a whole set of genes involved mainly with resistance to starvation and to environmental stresses. As an attempt to identify genes important for the survival of Caulobacter crescentus in stationary phase, we have screened a library of 5,000 clones generated by random transposon mutagenesis for mutants that showed reduced viability after prolonged growth. Four clones were selected, which displayed either lower viability or a longer time of recovery from stationary phase. The genes disrupted were identified, and the gene products were found to be mainly involved with amino acid metabolism (glutamate N-acetyltransferase, 4-hydroxyphenylpyruvate dioxygenase and L-aspartate oxidase or with recombination (exonuclease RecJ. Each mutant was tested for resistance to stresses, such as oxidative, saline, acidic, heat and UV exposure, showing different responses. Although the mutations obtained were not in genes involved specifically in stationary phase, our results suggest that amino acids metabolism may play an important role in keeping viability during this growth phase.

  9. Report of the first human case of Caulobacter sp. infection

    DEFF Research Database (Denmark)

    Justesen, Ulrik S; Holt, Hanne M; Thiesson, Helle;

    2007-01-01

    A Caulobacter sp. isolate was recovered from the dialysis fluid of a patient undergoing peritoneal dialysis. Bacterial identification included electron microscopy and 16S rDNA sequencing. To our knowledge, this is the first report of human Caulobacter infection. Special growth requirements suggest...

  10. S-layer nanoglycobiology of bacteria

    OpenAIRE

    Messner, Paul; Steiner, Kerstin; Zarschler, Kristof; Schäffer, Christina

    2008-01-01

    Cell surface layers (S-layers) are common structures of the bacterial cell envelope with a lattice-like appearance that are formed by a self-assembly process. Frequently, the constituting S-layer proteins are modified with covalently linked glycan chains facing the extracellular environment. S-layer glycoproteins from organisms of the Bacillaceae family possess long, O-glycosidically linked glycans that are composed of a great variety of sugar constituents. The observed variations already exc...

  11. S-layer nanoglycobiology of bacteria.

    Science.gov (United States)

    Messner, Paul; Steiner, Kerstin; Zarschler, Kristof; Schäffer, Christina

    2008-08-11

    Cell surface layers (S-layers) are common structures of the bacterial cell envelope with a lattice-like appearance that are formed by a self-assembly process. Frequently, the constituting S-layer proteins are modified with covalently linked glycan chains facing the extracellular environment. S-layer glycoproteins from organisms of the Bacillaceae family possess long, O-glycosidically linked glycans that are composed of a great variety of sugar constituents. The observed variations already exceed the display found in eukaryotic glycoproteins. Recent investigations of the S-layer protein glycosylation process at the molecular level, which has lagged behind the structural studies due to the lack of suitable molecular tools, indicated that the S-layer glycoprotein glycan biosynthesis pathway utilizes different modules of the well-known biosynthesis routes of lipopolysaccharide O-antigens. The genetic information for S-layer glycan biosynthesis is usually present in S-layer glycosylation (slg) gene clusters acting in concert with housekeeping genes. To account for the nanometer-scale cell surface display feature of bacterial S-layer glycosylation, we have coined the neologism 'nanoglycobiology'. It includes structural and biochemical aspects of S-layer glycans as well as molecular data on the machinery underlying the glycosylation event. A key aspect for the full potency of S-layer nanoglycobiology is the unique self-assembly feature of the S-layer protein matrix. Being aware that in many cases the glycan structures associated with a protein are the key to protein function, S-layer protein glycosylation will add a new and valuable component to an 'S-layer based molecular construction kit'. In our long-term research strategy, S-layer nanoglycobiology shall converge with other functional glycosylation systems to produce 'functional' S-layer neoglycoproteins for diverse applications in the fields of nanobiotechnology and vaccine technology. Recent advances in the field of

  12. Composite S-layer lipid structures.

    Science.gov (United States)

    Schuster, Bernhard; Sleytr, Uwe B

    2009-10-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state of the art survey how S-layer proteins, lipids, and polysaccharides may be used as basic building blocks for the assembly of S-layer supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas for application of composite S-layer membrane systems concern sensor systems involving specific membrane functions. PMID:19303933

  13. Composite S-layer lipid structures

    OpenAIRE

    Schuster, Bernhard; Sleytr, Uwe B.

    2009-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state of the art survey how S-layer proteins, lipids, and polysaccharides may be u...

  14. Reassembly of S-layer proteins

    Science.gov (United States)

    Pum, Dietmar; Sleytr, Uwe B.

    2014-08-01

    Crystalline bacterial cell surface layers (S-layers) represent the outermost cell envelope component in a broad range of bacteria and archaea. They are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. They are highly porous protein mesh works with unit cell sizes in the range of 3 to 30 nm, and pore sizes of 2 to 8 nm. S-layers are usually 5 to 20 nm thick (in archaea, up to 70 nm). S-layer proteins are one of the most abundant biopolymers on earth. One of their key features, and the focus of this review, is the intrinsic capability of isolated native and recombinant S-layer proteins to form self-assembled mono- or double layers in suspension, at solid supports, the air-water interface, planar lipid films, liposomes, nanocapsules, and nanoparticles. The reassembly is entropy-driven and a fascinating example of matrix assembly following a multistage, non-classical pathway in which the process of S-layer protein folding is directly linked with assembly into extended clusters. Moreover, basic research on the structure, synthesis, genetics, assembly, and function of S-layer proteins laid the foundation for their application in novel approaches in biotechnology, biomimetics, synthetic biology, and nanotechnology.

  15. Conserved S-Layer-Associated Proteins Revealed by Exoproteomic Survey of S-Layer-Forming Lactobacilli.

    Science.gov (United States)

    Johnson, Brant R; Hymes, Jeffrey; Sanozky-Dawes, Rosemary; Henriksen, Emily DeCrescenzo; Barrangou, Rodolphe; Klaenhammer, Todd R

    2016-01-01

    The Lactobacillus acidophilus homology group comprises Gram-positive species that include L. acidophilus, L. helveticus, L. crispatus, L. amylovorus, L. gallinarum, L. delbrueckii subsp. bulgaricus, L. gasseri, and L. johnsonii. While these bacteria are closely related, they have varied ecological lifestyles as dairy and food fermenters, allochthonous probiotics, or autochthonous commensals of the host gastrointestinal tract. Bacterial cell surface components play a critical role in the molecular dialogue between bacteria and interaction signaling with the intestinal mucosa. Notably, the L. acidophilus complex is distinguished in two clades by the presence or absence of S-layers, which are semiporous crystalline arrays of self-assembling proteinaceous subunits found as the outermost layer of the bacterial cell wall. In this study, S-layer-associated proteins (SLAPs) in the exoproteomes of various S-layer-forming Lactobacillus species were proteomically identified, genomically compared, and transcriptionally analyzed. Four gene regions encoding six putative SLAPs were conserved in the S-layer-forming Lactobacillus species but not identified in the extracts of the closely related progenitor, L. delbrueckii subsp. bulgaricus, which does not produce an S-layer. Therefore, the presence or absence of an S-layer has a clear impact on the exoproteomic composition of Lactobacillus species. This proteomic complexity and differences in the cell surface properties between S-layer- and non-S-layer-forming lactobacilli reveal the potential for SLAPs to mediate intimate probiotic interactions and signaling with the host intestinal mucosa. PMID:26475115

  16. Fluorescent S-layer fusion proteins

    International Nuclear Information System (INIS)

    This work describes the construction and characterisation of fluorescent S-layer fusion proteins used as building blocks for the fabrication of nanostructured monomolecular biocoatings on silica particles with defined fluorescence properties. The S-layer protein SgsE of Geobacillus stearothermophilus NRS 2004/3a was fused with the pH-dependant cyan, green and yellow variant of the green fluorescent protein (GFP) and the red fluorescent protein mRFP1. These fluorescent S-layer fusion proteins, acting as scaffold and optical sensing element simultaneously, were able to reassemble in solution and on silica particles forming 2D nanostructures with p2 lattice symmetry (a=11 ±0.5 nm, b=14 ±0.4 nm, g=80 ±1o). The pH-dependant fluorescence behaviour was studied with fluorimetry, confocal microscopy and flow cytometry. These fluorescent S-layer fusion proteins can be used as pH-sensor. 50% of the fluorescence intensity decreases at their calculated pKa values (pH6 - pH5). The fluorescence intensity of the GFP variants vanished completely between pH4 and pH3 whereas the chromophore of the red protein mRFP1 was only slightly affected in acidic conditions. At the isoelectric point of the S-layer coated silica particles (pH4.6 ±0.2) an increase in particle aggregation was detected by flow cytometry. The cyan and yellow fluorescent proteins were chosen to create a bi-fluorescent S-layer tandem fusion protein with the possibility for resonance energy transfer (FRET). A transfer efficiency of 20% and a molecular distance between the donor (ECFP) and acceptor (YFP) chromophores of around 6.2 nm could be shown. This bi-fluorescent ECFP-SgsE-YFP tandem fusion protein was able to reassemble on solid surfaces. The remarkable combination of fluorescence and self-assembly and the design of bi-functional S-layer tandem fusion protein matrices makes them to a promising tool in nanobiotechnology. (author)

  17. S-layer architectures : extending the morphogenetic potential of S-layer protein self-assembly

    International Nuclear Information System (INIS)

    Self-assembly of molecular building blocks is a common principle for bottom up based building principles in nature. One example are crystalline bacterial surface layers, termed S-layers, which are the most commonly observed cell surface structures in prokaryotic organisms. They recrystallize into highly ordered, porous protein meshworks with unit cell sizes of 3 to 30 nm and pore sizes of 2 to 8 nm. In this work, S-layers were self-assembled on various three dimensional scaffolds in order to fabricate novel S-layer architectures. Exploiting the stabilizing effect of silica deposited on the S-layer protein meshwork led to the construction of hollow S-layer nano-containers derived from coated liposomes. Transmission electron microscopy (TEM) techniques and release experiments with fluorescent dyes confirmed the dissolution of the supporting lipids. Silica deposition on different spherical particles in solution, as well as on planar S-layer coated surfaces, could be monitored by measuring the ζ-potential, the decline of monosilicic acid in solution, by using scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis or by quartz crystal microbalance with dissipation monitoring (QCM-D). Both, ζ-potential and release experiments showed differences between silicified plain liposomes and silicified S-layer coated liposomes. In addition, nanocapsules with calcium carbonate cores served as another template for the construction of silica supported S-layer architectures. These were investigated by SEM and fluorescence microscopy after fluorescence labeling. Additional coating with polyelectrolytes increased the stability of the nanocapsules. Their mechanical properties were characterized by atomic force microscopy (AFM). The influence of silica deposition was investigated by AFM and SEM. Further on, emulsomes and gas filled lipid supported microbubbles may serve as other templates for the design of spherical protein constructs although extraction of the

  18. Función de la proteína CdnL en las bacterias Myxococcus xanthus y Caulobacter crescentus

    OpenAIRE

    Gallego García, Aranzazu

    2015-01-01

    La proteína CarD es un regulador transcripcional de acción global en la bacteria Myxococcus xanthus, que se requiere para la actividad de varios factores σ-ECF (extracytoplasmatic function). CarD presenta una arquitectura de dominios única, con un dominio C-terminal de unión al DNA similar a las proteínas eucarióticas HMGA (high-mobility group A), y un dominio N-terminal, típicamente bacteriano, que define a la familia de proteínas PF02559. Dicha familia incluye el dominio de interacción con ...

  19. Genome Sequence of Selenium-Solubilizing Bacterium Caulobacter vibrioides T5M6

    DEFF Research Database (Denmark)

    Wang, Yihua; Qin, Yanan; Kot, Witold;

    2016-01-01

    Caulobacter vibrioides T5M6 is a Gram-negative strain that strongly solubilizes selenium (Se) mineral into Se(IV) and was isolated from a selenium mining area in Enshi, southwest China. This strain produces the phytohormone IAA and promotes plant growth. Here we present the genome of this strain ...

  20. Bacterial S-layer protein coupling to lipids

    DEFF Research Database (Denmark)

    Weygand, M.; Wetzer, B.; Pum, D.;

    1999-01-01

    -filled cavities near its center. The protein volume fraction reaches maxima of >60% in two horizontal sections of the S-layer, close to the lipid monolayer and close to the free subphase. In between it drops to similar to 20%. Four S-layer protein monomers are located within the unit cell of a square lattice with...

  1. S-layer templated bioinspired synthesis of silica

    OpenAIRE

    Göbel, Caren; Schuster, Bernhard; Baurecht, Dieter; Sleytr, Uwe B.; Pum, Dietmar

    2009-01-01

    The current understanding of the molecular mechanisms involved in the bioinspired formation of silica structures laid foundation for investigating the potential of the S-layer protein SbpA from Lysinibacillus sphaericus CCM 2177 as catalyst, template and scaffold for the generation of novel silica architectures. SbpA reassembles into monomolecular lattices with square (p4) lattice symmetry and a lattice constant of 13.1 nm. Silica layers on the S-layer lattice were formed using tetramethoxysi...

  2. Bacterial S-layer protein coupling to lipids

    DEFF Research Database (Denmark)

    Weygand, M.; Wetzer, B.; Pum, D.; Sleytr, U.B.; Cuvillier, N.; Kjær, K.; Howes, P.B.; Lösche, M.

    1999-01-01

    The coupling of bacterial surface (S)-layer proteins to lipid membranes is studied in molecular detail for proteins from Bacillus sphaericus CCM2177 and B. coagulans E38-66 recrystallized at dipalmitoylphosphatidylethanolamine (DPPE) monolayers on aqueous buffer. A comparison of the monolayer str...

  3. S-layers at second glance? Altiarchaeal grappling hooks (hami resemble archaeal S-layer proteins in structure and sequence

    Directory of Open Access Journals (Sweden)

    Alexandra Kristin Perras

    2015-06-01

    Full Text Available The uncultivated Ca. Altiarchaeum hamiconexum (formerly known as SM1 Euryarchaeon carries highly specialized nano-grappling hooks (hami on its cell surface. Until now little is known about the major protein forming these structured fibrous cell surface appendages, the genes involved or membrane anchoring of these filaments. These aspects were analyzed in depth in this study using environmental transcriptomics combined with imaging methods. Since a laboratory culture of this archaeon is not yet available, natural biofilm samples with high Ca. A. hamiconexum abundance were used for the entire analyses. The filamentous surface appendages spanned both membranes of the cell, which are composed of glycosyl-archaeol. The hami consisted of multiple copies of the same protein, the corresponding gene of which was identified via metagenome-mapped transcriptome analysis. The hamus subunit proteins, which are likely to self-assemble due to their predicted beta sheet topology, revealed no similiarity to known microbial flagella-, archaella-, fimbriae- or pili-proteins, but a high similarity to known S-layer proteins of the archaeal phylum at their N-terminal region (47-44% identity. Our results provide new insights into the structure of the unique hami and their major protein and indicate their divergent evolution with S-layer proteins.

  4. The S-Layer Glycome—Adding to the Sugar Coat of Bacteria

    Directory of Open Access Journals (Sweden)

    Robin Ristl

    2011-01-01

    Full Text Available The amazing repertoire of glycoconjugates present on bacterial cell surfaces includes lipopolysaccharides, capsular polysaccharides, lipooligosaccharides, exopolysaccharides, and glycoproteins. While the former are constituents of Gram-negative cells, we review here the cell surface S-layer glycoproteins of Gram-positive bacteria. S-layer glycoproteins have the unique feature of self-assembling into 2D lattices providing a display matrix for glycans with periodicity at the nanometer scale. Typically, bacterial S-layer glycans are O-glycosidically linked to serine, threonine, or tyrosine residues, and they rely on a much wider variety of constituents, glycosidic linkage types, and structures than their eukaryotic counterparts. As the S-layer glycome of several bacteria is unravelling, a picture of how S-layer glycoproteins are biosynthesized is evolving. X-ray crystallography experiments allowed first insights into the catalysis mechanism of selected enzymes. In the future, it will be exciting to fully exploit the S-layer glycome for glycoengineering purposes and to link it to the bacterial interactome.

  5. Functional Analysis of an S-Layer-Associated Fibronectin-Binding Protein in Lactobacillus acidophilus NCFM.

    Science.gov (United States)

    Hymes, Jeffrey P; Johnson, Brant R; Barrangou, Rodolphe; Klaenhammer, Todd R

    2016-05-01

    Bacterial surface layers (S-layers) are crystalline arrays of self-assembling proteinaceous subunits called S-layer proteins (Slps) that comprise the outermost layer of the cell envelope. Many additional proteins that are associated with or embedded within the S-layer have been identified inLactobacillus acidophilusNCFM, an S-layer-forming bacterium that is widely used in fermented dairy products and probiotic supplements. One putative S-layer-associated protein (SLAP), LBA0191, was predicted to mediate adhesion to fibronectin based on thein silicodetection of a fibronectin-binding domain. Fibronectin is a major component of the extracellular matrix (ECM) of intestinal epithelial cells. Adhesion to intestinal epithelial cells is considered an important trait for probiotic microorganisms during transit and potential association with the intestinal mucosa. To investigate the functional role of LBA0191 (designated FbpB) inL. acidophilusNCFM, anfbpB-deficient strain was constructed. TheL. acidophilusmutant with a deletion offbpBlost the ability to adhere to mucin and fibronectinin vitro Homologues offbpBwere identified in five additional putative S-layer-forming species, but no homologues were detected in species outside theL. acidophilushomology group. PMID:26921419

  6. S-layer production by Lactobacillus acidophilus IBB 801 under environmental stress conditions.

    Science.gov (United States)

    Grosu-Tudor, Silvia-Simona; Brown, Lucia; Hebert, Elvira M; Brezeanu, Aurelia; Brinzan, Alexandru; Fadda, Silvina; Mozzi, Fernanda; Zamfir, Medana

    2016-05-01

    The ability of microorganisms to synthesize S-layer, the outermost structure of the microbial cell envelope composed of non-covalently bound proteins, has been ascribed to help microorganisms to exert their probiotic properties in the host. In this work, formation of S-layer by the potentially probiotic strain Lactobacillus acidophilus IBB 801 under different stress culture conditions (high incubation temperatures, presence of bile salts or NaCl, and acidic pH) was assayed. A marked S-layer synthesis by L. acidophilus IBB 801 was detected when the strain was grown at 42 °C and in the presence of 0.05 % bile salts or 2.0 % NaCl. The presence of S-layer proteins was further confirmed by transmission electron microscopy and protein identification by MS/MS. The differential expression of the proteome of this strain at 42 °C, when a marked formation of S-layer was detected, revealed the overexpression of six proteins mainly related to general stress and protein biosynthesis and translation, while four proteins detected in lower amounts were involved in DNA repair and energy metabolism. As L. acidophilus IBB 801 produces both a bacteriocin and S-layer proteins, the strain could be of interest to be used in the formulation of functional food products with specific properties. PMID:26910041

  7. FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions

    Science.gov (United States)

    Gerbino, E.; Mobili, P.; Tymczyszyn, E.; Fausto, R.; Gómez-Zavaglia, A.

    2011-02-01

    FTIR spectroscopy was used to structurally characterize the interaction of S-layer proteins extracted from two strains of Lactobacillus kefir (the aggregating CIDCA 8348 and the non-aggregating JCM 5818) with metal ions (Cd +2, Zn +2, Pb +2 and Ni +2). The infrared spectra indicate that the metal/protein interaction occurs mainly through the carboxylate groups of the side chains of Asp and Glut residues, with some contribution of the NH groups belonging to the peptide backbone. The frequency separation between the νCOO - anti-symmetric and symmetric stretching vibrations in the spectra of the S-layers in presence of the metal ions was found to be ca. 190 cm -1 for S-layer CIDCA 8348 and ca. 170 cm -1 for JCM 5818, denoting an unidentate coordination in both cases. Changes in the secondary structures of the S-layers induced by the interaction with the metal ions were also noticed: a general trend to increase the amount of β-sheet structures and to reduce the amount of α-helices was observed. These changes allow the proteins to adjust their structure to the presence of the metal ions at minimum energy expense, and accordingly, these adjustments were found to be more important for the bigger ions.

  8. Colorimetric As (V) detection based on S-layer functionalized gold nanoparticles.

    Science.gov (United States)

    Lakatos, Mathias; Matys, Sabine; Raff, Johannes; Pompe, Wolfgang

    2015-11-01

    Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50 nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50 nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24 ppb was detectable. PMID:26452816

  9. A Collagen-Binding S-Layer Protein in Lactobacillus crispatus

    OpenAIRE

    Toba, T.; Virkola, R.; Westerlund, B; Bjorkman, Y.; Sillanpaa, J.; Vartio, T.; Kalkkinen, N.; Korhonen, T K

    1995-01-01

    Two S-layer-expressing strains, Lactobacillus crispatus JCM 5810 and Lactobacillus acidophilus JCM 1132, were assessed for adherence to proteins of the mammalian extracellular matrix. L. crispatus JCM 5810 adhered efficiently to immobilized type IV and I collagens, laminin, and, with a lower affinity, to type V collagen and fibronectin. Strain JCM 1132 did not exhibit detectable adhesiveness. Within the fibronectin molecule, JCM 5810 recognized the 120-kDa cell-binding fragment of the protein...

  10. Anatomy of a bacterial cell cycle

    OpenAIRE

    Amick, Jean D; Brun, Yves V.

    2001-01-01

    Two recent reports describe mRNA and protein expression patterns in the bacterium Caulobacter crescentus. The combined use of DNA microarray and proteomic analyses provides a powerful new perspective for unraveling the global regulatory networks of this complex bacterium.

  11. Partial analysis of the central domain of the Bacillus sphaericus JG-A12 S-layer protein

    International Nuclear Information System (INIS)

    310 amino acids from the central domain of the B. sphaericus JG-A12 S-layer were analyzed. In contrast to the N-terminal domain of this protein, which possesses a unique structure, the part studied in this work shares a significant identity with the corresponding parts of several other B. sphaericus S-layers. (orig.)

  12. Identification of multiple putative S-layer genes partly expressed by Lysinibacillus sphaericus JG-B53.

    Science.gov (United States)

    Lederer, Franziska L; Weinert, Ulrike; Günther, Tobias J; Raff, Johannes; Weiß, Stephan; Pollmann, Katrin

    2013-06-01

    Lysinibacillus sphaericus JG-B53 was isolated from the uranium mining waste pile Haberland near Johanngeorgenstadt, Germany. Previous studies have shown that many bacteria that have been isolated from these heavy metal contaminated environments possess surface layer (S-layer) proteins that enable the bacteria to survive by binding metals with high affinity. Conversely, essential trace elements are able to cross the filter layer and reach the interior of the cell. This is especially true of the S-layer of L. sphaericus JG-B53, which possesses outstanding recrystallization and metal-binding properties. In this study, S-layer protein gene sequences encoded in the genome of L. sphaericus JG-B53 were identified using next-generation sequencing technology followed by bioinformatic analyses. The genome of L. sphaericus JG-B53 encodes at least eight putative S-layer protein genes with distinct differences. Using mRNA analysis the expression of the putative S-layer protein genes was studied. The functional S-layer protein B53 Slp1 was identified as the dominantly expressed S-layer protein in L. sphaericus JG-B53 by mRNA studies, SDS-PAGE and N-terminal sequencing. B53 Slp1 is characterized by square lattice symmetry and a molecular mass of 116 kDa. The S-layer protein B53 Slp1 shows a high similarity to the functional S-layer protein of L. sphaericus JG-A12, which was isolated from the same uranium mining waste pile Haberland and has been described by previous research. These similarities indicate horizontal gene transfer and DNA rearrangements between these bacteria. The presence of multiple S-layer gene copies may enable the bacterial strains to quickly adapt to changing environments. PMID:23579690

  13. S layer protein A of Lactobacillus acidophilus NCFM regulates immature dendritic cell and T cell functions.

    Science.gov (United States)

    Konstantinov, Sergey R; Smidt, Hauke; de Vos, Willem M; Bruijns, Sven C M; Singh, Satwinder Kaur; Valence, Florence; Molle, Daniel; Lortal, Sylvie; Altermann, Eric; Klaenhammer, Todd R; van Kooyk, Yvette

    2008-12-01

    Dendritic cells (DCs) are antigen-presenting cells that play an essential role in mucosal tolerance. They regularly encounter beneficial intestinal bacteria, but the nature of these cellular contacts and the immune responses elicited by the bacteria are not entirely elucidated. Here, we examined the interactions of Lactobacillus acidophilus NCFM and its cell surface compounds with DCs. L. acidophilus NCFM attached to DCs and induced a concentration-dependent production of IL-10, and low IL-12p70. We further demonstrated that the bacterium binds to DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN), a DC- specific receptor. To identify the DC-SIGN ligand present on the bacterium, we took advantage of a generated array of L. acidophilus NCFM mutants. A knockout mutant of L. acidophilus NCFM lacking the surface (S) layer A protein (SlpA) was significantly reduced in binding to DC-SIGN. This mutant incurred a chromosomal inversion leading to dominant expression of a second S layer protein, SlpB. In the SlpB-dominant strain, the nature of the interaction of this bacterium with DCs changed dramatically. Higher concentrations of proinflammatory cytokines such as IL-12p70, TNFalpha, and IL-1beta were produced by DCs interacting with the SlpB-dominant strain compared with the parent NCFM strain. Unlike the SlpA-knockout mutant, T cells primed with L. acidophilus NCFM stimulated DCs produced more IL-4. The SlpA-DC-SIGN interaction was further confirmed as purified SlpA protein ligated directly to the DC-SIGN. In conclusion, the major S layer protein, SlpA, of L. acidophilus NCFM is the first probiotic bacterial DC-SIGN ligand identified that is functionally involved in the modulation of DCs and T cells functions. PMID:19047644

  14. Preparation and Characterization of TiO2/CdS Layers as Potential Photoelectrocatalytic Materials

    Directory of Open Access Journals (Sweden)

    Teofil-Danut Silipas

    2011-01-01

    Full Text Available The TiO2/CdS semiconductor composites were prepared on
    indium tin oxide (ITO substrates in di®erent mass proportions via wet-chemical techniques using bi-distilled water, acetyl-acetone, poly-propylene-glycol and Triton X-100 as additives. The composite layers were annealed in normal conditions at the temperature of 450±C, 120 min. with a rate of temperature increasing of 5±C/min. The structural and optical properties of all the TiO2/CdS ayers were characterized by X-ray di®raction, UV-VIS spectroscopy, spectrofluorimetry and FT/IR microscopy. The microstructural properties of the deposited TiO2/CdS layers can be modi¯ed by varying the mass proportions of TiO2:CdS. The good crystallinity level and the high optical adsorption of
    the TiO2/CdS layers make them attractive for photoelectrochemical cell applications.

  15. Langmuir–Blodgett films of cholesterol oxidase and S-layer proteins onto screen-printed electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Guimarães, Juliana Aguilar, E-mail: helen@peq.coppe.ufrj.br; Ferraz, Helen Conceição; Alves, Tito Lívio Moitinho

    2014-04-01

    Graphical abstract: - Highlights: • Langmuir and LB monolayers of ChOx and S-layer proteins were obtained. • Mixed ChOx/S-layer proteins films presented an ideal-like behavior. • Modified sensor showed stable peaks with moderate intensity. • The type of LB deposition affects the sensor ability of detecting cholesterol. • Mixed ChOx/S-layer proteins LB films improve sensor properties. - Abstract: Stable Langmuir monolayers of cholesterol oxidase (ChOx) and S-layer proteins were produced at the water–air interface and subsequently transferred onto the surface of screen-printed carbon electrodes by the Langmuir–Blodgett (LB) technique. The modified electrode surface was characterized by atomic force microscopy (AFM) and cyclic voltammetry (CV). AFM indicated the presence of deposited layers, showing reduction of surface roughness (RMS and Rt parameters). Significant changes in the shape of CVs were observed in modified electrodes compared to bare electrodes. The anodic peaks could be observed in cyclic voltammograms (CV), at a scan rate equal to 25 mV s{sup −1}, using electrodes with Z-type LB deposition. The presence of S-layer proteins in the ChOx LB film increases the oxidation peak intensity and reduces the oxidation potential. Altogether, these results demonstrate the feasibility of producing a cholesterol biosensor based on the immobilization of ChOx and S-layer proteins by LB technique.

  16. Zn(O, S) layers for chalcoyprite solar cells sputtered from a single target

    Science.gov (United States)

    Grimm, A.; Kieven, D.; Lauermann, I.; Lux-Steiner, M. Ch.; Hergert, F.; Schwieger, R.; Klenk, R.

    2012-09-01

    A simplified Cu(In, Ga)(S, Se)2/Zn(O, S)/ZnO:Al stack for chalcopyrite thin-film solar cells is proposed. In this stack the Zn(O, S) layer combines the roles of the traditional CdS buffer and undoped ZnO layers. It will be shown that Zn(O, S) films can be sputtered in argon atmosphere from a single mixed target without substrate heating. The photovoltaic performance of the simplified stack matches that of the conventional approach. Replacing the ZnO target with a ZnO/ZnS target may therefore be sufficient to omit the CdS buffer layer and avoid the associated complexity, safety and recycling issues, and to lower production cost.

  17. Crystalline Bacterial Surface Layer (S-Layer) Opens Golden Opportunities for Nanobiotechnology in Textiles.

    Science.gov (United States)

    Asadi, Narges; Chand, Nima; Rassa, Mehdi

    2015-12-01

    This study focuses on the successful recrystallization of bacterial S-layer arrays of the Lactobacillus acidophilus ATCC 4356 at textile surfaces to create a novel method and material. Optimum bacterial growth was obtained at approximately 45 °C, pH 5.0, and 14 h pi. The cells were resuspended in guanidine hydrochloride and the 43 kDa S-protein was dialyzed and purified. The optimum reassembly on the polypropylene fabric surface in terms of scanning electron microscopy (SEM), reflectance, and uniformity (spectrophotometry) was obtained at 30 °C, pH 5.0 for 30 minutes in the presence of 2 gr/l (liquor ratio; 1:40) of the S-protein. Overall, our data showed that the functional aspects and specialty applications of the fabric would be very attractive for the textile and related sciences, and result in advanced technical textiles. PMID:26552090

  18. Zn(O, S layers for chalcoyprite solar cells sputtered from a single target

    Directory of Open Access Journals (Sweden)

    Schwieger R.

    2012-09-01

    Full Text Available A simplified Cu(In, Ga(S, Se2/Zn(O, S/ZnO:Al stack for chalcopyrite thin-film solar cells is proposed. In this stack the Zn(O, S layer combines the roles of the traditional CdS buffer and undoped ZnO layers. It will be shown that Zn(O, S films can be sputtered in argon atmosphere from a single mixed target without substrate heating. The photovoltaic performance of the simplified stack matches that of the conventional approach. Replacing the ZnO target with a ZnO/ZnS target may therefore be sufficient to omit the CdS buffer layer and avoid the associated complexity, safety and recycling issues, and to lower production cost.

  19. Probing Peptide and Protein Insertion in a Biomimetic S-Layer Supported Lipid Membrane Platform

    Directory of Open Access Journals (Sweden)

    Samar Damiati

    2015-01-01

    Full Text Available The most important aspect of synthetic lipid membrane architectures is their ability to study functional membrane-active peptides and membrane proteins in an environment close to nature. Here, we report on the generation and performance of a biomimetic platform, the S-layer supported lipid membrane (SsLM, to investigate the structural and electrical characteristics of the membrane-active peptide gramicidin and the transmembrane protein α-hemolysin in real-time using a quartz crystal microbalance with dissipation monitoring in combination with electrochemical impedance spectroscopy. A shift in membrane resistance is caused by the interaction of α-hemolysin and gramicidin with SsLMs, even if only an attachment onto, or functional channels through the lipid membrane, respectively, are formed. Moreover, the obtained results did not indicate the formation of functional α-hemolysin pores, but evidence for functional incorporation of gramicidin into this biomimetic architecture is provided.

  20. Proteome analysis of Paenibacillus larvae reveals the existence of a putative S-layer protein.

    Science.gov (United States)

    Fünfhaus, Anne; Genersch, Elke

    2012-04-01

    Honey bee pathology has attracted much interest recently due to the problems with honey bee declines in many regions of the world. American Foulbrood (AFB) caused by Paenibacillus larvae is the most devastating bacterial brood disease of the Western honey bee (Apis mellifera) causing considerable economic losses to beekeepers worldwide. AFB outbreaks are mainly caused by two differentially virulent genotypes of P. larvae, P. larvae ERIC I and ERIC II. To better understand AFB pathogenesis and to complement already existing data from the genetic level we aimed at obtaining expression data from the protein level. We successfully developed a protocol for two-dimensional proteome analysis of P. larvae with subsequent mass-spectrometry based protein sequencing. Based on the obtained master protein maps of P. larvae genotypes ERIC I and II we identified the dominantly expressed cytosolic proteins of both genotypes, some of them presumably linked to pathogenesis and virulence. Comparing the master maps of both genotypes revealed differentially expressed proteins, i.e. a putative S-layer protein which is expressed by P. larvae ERIC II but absent from the proteome of P. larvae ERIC I. The implications of our findings for pathogenesis of AFB and virulence of P. larvae will be discussed. PMID:23757273

  1. Formation of CuxS Layers on Polypropylene Sulfurized by Molten Sulfur

    Directory of Open Access Journals (Sweden)

    Rasa ALABURDAITĖ

    2011-11-01

    Full Text Available The processes of formation of electrically conductive layers of copper sulfides CuxS by the sorption-diffusion method on polypropylene (PP using molten sulfur as sulfurizing agent was investigated. The amount of sorbed sulfur increased with the increase of the duration of treatment. Copper sulfide layers were formed on the surface of polypropylene after the treatment of sulfurized polymer with Cu(II/I salt solution. The amount of copper sulfide in layer increased with the increase of treatment duration in copper salt solution. XRD spectra of PP films treated for 3 min with molten sulfur and then with Cu(II/I salt solution for the different time showed that the copper sulfide phases, mostly digenite, Cu2-xS and a-chalcocite, Cu2S were formed in the layers. Electromotive force measurement results confirmed the composition of formed CuxS layers on PP. The phase composition of layers also changed after the annealing. The value of electrical resistance of copper sulfide layers on PP varied from 20 W/cm2 to 80 W/cm2 and after annealing at 80 °C - in the interval of 10 W/cm2 - 60 W/cm2.http://dx.doi.org/10.5755/j01.ms.17.4.776

  2. Bacterial S-layer protein coupling to lipids: x-ray reflectivity and grazing incidence diffraction studies.

    Science.gov (United States)

    Weygand, M; Wetzer, B; Pum, D; Sleytr, U B; Cuvillier, N; Kjaer, K; Howes, P B; Lösche, M

    1999-01-01

    The coupling of bacterial surface (S)-layer proteins to lipid membranes is studied in molecular detail for proteins from Bacillus sphaericus CCM2177 and B. coagulans E38-66 recrystallized at dipalmitoylphosphatidylethanolamine (DPPE) monolayers on aqueous buffer. A comparison of the monolayer structure before and after protein recrystallization shows minimal reorganization of the lipid chains. By contrast, the lipid headgroups show major rearrangements. For the B. sphaericus CCM2177 protein underneath DPPE monolayers, x-ray reflectivity data suggest that amino acid side chains intercalate the lipid headgroups at least to the phosphate moieties, and probably further beyond. The number of electrons in the headgroup region increases by more than four per lipid. Analysis of the changes of the deduced electron density profiles in terms of a molecular interpretation shows that the phosphatidylethanolamine headgroups must reorient toward the surface normal to accommodate such changes. In terms of the protein structure (which is as yet unknown in three dimensions), the electron density profile reveals a thickness lz approximately 90 A of the recrystallized S-layer and shows water-filled cavities near its center. The protein volume fraction reaches maxima of >60% in two horizontal sections of the S-layer, close to the lipid monolayer and close to the free subphase. In between it drops to approximately 20%. Four S-layer protein monomers are located within the unit cell of a square lattice with a spacing of approximately 131 A. PMID:9876158

  3. Haloferax volcanii archaeosortase is required for motility, mating, and C-terminal processing of the S-layer glycoprotein

    Energy Technology Data Exchange (ETDEWEB)

    Halim, Mohd F.; Pfeiffer, Friedhelm; Zou, James; Frisch, Andrew; Haft, Daniel H.; Wu, Si; Tolic, Nikola; Brewer, Heather M.; Payne, Samuel H.; Pasa-Tolic, Ljiljana; Pohlschroder, Mechthild

    2013-06-01

    Cell surfaces are decorated by a variety of proteins that facilitate interactions with their environments and support cell stability.These secreted proteins are anchored to the cell by mechanisms that are diverse, and, in archaea, poorly understood. Recently published in silico data suggest that in some species a subset of secreted euryarchaeal proteins, which includes the S-­‐layer glycoprotein, is processed and covalently linked tot he cell membrane by enzymes referred to as archaeosortases. In silico work led to the proposal that an independent, sortase-like system for proteolysis-coupled carboxy-terminal lipid modification exists in bacteria (exosortase) and archaea (archaeosortase). Here, we provide the first in vivo characterization of an archaeosortase in the haloarchaeal model organism Haloferax volcanii. Deletion of the artA gene (HVO_0915) resulted in multiple biological phenotypes: (a) poor growth, especially under low-salt conditions, (b) alterations in cell shape and the S-layer, (c) impaired motility, suppressors of which still exhibit poor growth, and (d) impaired conjugation. We studied one of the ArtA substrates, the S-layer glycoprotein, using detailed proteomic analysis. While the carboxy-terminal region of S-layer glycoproteins, consisting of a threonine-rich O-glycosylated region followed by a hydrophobic transmembrane helix, has been notoriously resistant to any proteomic peptide identification, we were able to identify two overlapping peptides from the transmembrane domain present in the ΔartA strain but not in the wild-type strain. This clearly shows that ArtA is involved in carboxy-terminal posttranslational processing of the S-layer glycoprotein. As it is known from previous studies that a lipid is covalently attached to the carboxy-terminal region of the S-layer glycoprotein, our data strongly support the conclusion that archaeosortase functions analogously to sortase, mediating proteolysis-coupled, covalent cell surface attachment.

  4. Review of Information Authentication in Mobile Cloud over SaaS & PaaS Layers

    Directory of Open Access Journals (Sweden)

    Vineet Guha

    2013-03-01

    Full Text Available The Revolution has begun; time has come when we no more have to worry about the size, format & storage of data at a single place. Cloud computing is a revolution which has made world of internet more like a place of dynamic storage & facilitator of new methodology, which generates tools for consumers in a very effective style of computations. Cloud Computing has made lots of changes not only in infrastructure side, but has also deeply impacted the software industry. Many Companies, Institutions are moving towards using Cloud computing technology, but with every new technology emerging in this Information technology world, with major issues holds with security models to implement & problem like how we can keep data secured & safe. Cloud Computing; do pose various new security concerns, which have not been well identified & worked on. When we talk about the security of data in Cloud computing the vendor’s has to ensure assurance to get confidence of customer on the security issues. Institutions & organizations are planning to use cloud computing for certain level of confidential issues for their business applications though guaranteeing the security is difficult task for now. With most of companies & IT giants planning to incorporate usage of Mobile technology to enrich their existing services & with more & more advance smart phones available in market, we can think of certain ideas & solutions to use mobile devices as alert medium & help securing use of data & network in cloud environment to an extent? It can also help us to keep a watch on intruders & we can impose checks on illegal access to data & network. So we can think of using Mobile Technology with Cloud Networks. We in this paper, review certain security concerns in Cloud computing technology & also about certain ways to restrict & overcome such issues over SaaS & PaaS Layers using mobile technologies. In this paper we try to focus ourselves to find answers to all such questions

  5. BslA, the S-layer adhesin of B. anthracis, is a virulence factor for anthrax pathogenesis

    OpenAIRE

    Kern, Justin; Schneewind, Olaf

    2009-01-01

    Microbial pathogens use adhesive surface proteins to bind to and interact with host tissues, events that are universal for the pathogenesis of infectious diseases. A surface adhesin of Bacillus anthracis, the causative agent of anthrax, required to mediate these steps has not been discovered. Previous work identified BslA, an S-layer protein, to be necessary and sufficient for adhesion of the anthrax vaccine strain, Bacillus anthracis Sterne, to host cells. Here we asked whether encapsulated ...

  6. Expression and cytosolic assembly of the S-layer fusion protein mSbsC-EGFP in eukaryotic cells

    Directory of Open Access Journals (Sweden)

    Veenhuis Marten

    2005-10-01

    Full Text Available Abstract Background Native as well as recombinant bacterial cell surface layer (S-layer protein of Geobacillus (G. stearothermophilus ATCC 12980 assembles to supramolecular structures with an oblique symmetry. Upon expression in E. coli, S-layer self assembly products are formed in the cytosol. We tested the expression and assembly of a fusion protein, consisting of the mature part (aa 31–1099 of the S-layer protein and EGFP (enhanced green fluorescent protein, in eukaryotic host cells, the yeast Saccharomyces cerevisiae and human HeLa cells. Results Upon expression in E. coli the recombinant mSbsC-EGFP fusion protein was recovered from the insoluble fraction. After denaturation by Guanidine (Gua-HCl treatment and subsequent dialysis the fusion protein assembled in solution and yielded green fluorescent cylindric structures with regular symmetry comparable to that of the authentic SbsC. For expression in the eukaryotic host Saccharomyces (S. cerevisiae mSbsC-EGFP was cloned in a multi-copy expression vector bearing the strong constitutive GPD1 (glyceraldehyde-3-phosophate-dehydrogenase promoter. The respective yeast transfomants were only slightly impaired in growth and exhibited a needle-like green fluorescent pattern. Transmission electron microscopy (TEM studies revealed the presence of closely packed cylindrical structures in the cytosol with regular symmetry comparable to those obtained after in vitro recrystallization. Similar structures are observed in HeLa cells expressing mSbsC-EGFP from the Cytomegalovirus (CMV IE promoter. Conclusion The mSbsC-EGFP fusion protein is stably expressed both in the yeast, Saccharomyces cerevisiae, and in HeLa cells. Recombinant mSbsC-EGFP combines properties of both fusion partners: it assembles both in vitro and in vivo to cylindrical structures that show an intensive green fluorescence. Fusion of proteins to S-layer proteins may be a useful tool for high level expression in yeast and HeLa cells of

  7. Lactobacillus helveticus MIMLh5-specific antibodies for detection of S-layer protein in Grana Padano protected-designation-of-origin cheese.

    Science.gov (United States)

    Stuknyte, Milda; Brockmann, Eeva-Christine; Huovinen, Tuomas; Guglielmetti, Simone; Mora, Diego; Taverniti, Valentina; Arioli, Stefania; De Noni, Ivano; Lamminmäki, Urpo

    2014-01-01

    Single-chain variable-fragment antibodies (scFvs) have considerable potential in immunological detection and localization of bacterial surface structures. In this study, synthetic phage-displayed antibody libraries were used to select scFvs against immunologically active S-layer protein of Lactobacillus helveticus MIMLh5. After three rounds of panning, five relevant phage clones were obtained, of which four were specific for the S-layer protein of L. helveticus MIMLh5 and one was also capable of binding to the S-layer protein of L. helveticus ATCC 15009. All five anti-S-layer scFvs were expressed in Escherichia coli XL1-Blue, and their specificity profiles were characterized by Western blotting. The anti-S-layer scFv PolyH4, with the highest specificity for the S-layer protein of L. helveticus MIMLh5, was used to detect the S-layer protein in Grana Padano protected-designation-of-origin (PDO) cheese extracts by Western blotting. These results showed promising applications of this monoclonal antibody for the detection of immunomodulatory S-layer protein in dairy (and dairy-based) foods. PMID:24242242

  8. Electronic and magnetic structures of GdS layers investigated by first principle and series expansions calculations

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco)

    2014-04-01

    Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full Potential Linear Augmented Plane Wave (FLAPW) method within GGA+U approximation, are performed to investigate both electronic and magnetic properties of the GdS layers. Polarized spin and spin–orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent Gd layers. Magnetic moment considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for the High Temperature Series Expansions (HTSEs) calculations to compute other magnetic parameters. Using the Heisenberg model, the exchange interactions between the magnetic atoms Gd–Gd in the same layer and between the magnetic atoms in the adjacent bilayers are estimated. This estimate is obtained using the antiferromagnetic and ferromagnetic energies computed by abinitio calculations for GdS layers. The High Temperature Series Expansions (HTSEs) of the magnetic susceptibility of GdS with antiferromagnetic moment (m{sub Gd}) is given up to sixth order series versus of (J{sub 11}(Gd–Gd)/k{sub B}T). The Néel temperature T{sub N} is obtained by mean field theory and by HTSEs of the magnetic susceptibility series using the Padé approximant method. The critical exponent γ associated with the magnetic susceptibility is calculated for GdS layers. - Highlights: • Electronic and magnetic properties of GdS are investigated using the ab initio calculations. • Obtained data from abinitio calculations are used as input for HTSEs to compute other magnetic parameters. • Néel temperature and critical exponent are deduced using HTSE method.

  9. Construction of a Functional S-Layer Fusion Protein Comprising an Immunoglobulin G-Binding Domain for Development of Specific Adsorbents for Extracorporeal Blood Purification

    OpenAIRE

    Völlenkle, Christine; Weigert, Stefan; Ilk, Nicola; Egelseer, Eva; Weber, Viktoria; Loth, Fritz; Falkenhagen, Dieter; Sleytr, Uwe B.; Sára, Margit

    2004-01-01

    The chimeric gene encoding a C-terminally-truncated form of the S-layer protein SbpA from Bacillus sphaericus CCM 2177 and two copies of the Fc-binding Z-domain was constructed, cloned, and heterologously expressed in Escherichia coli HMS174(DE3). The Z-domain is a synthetic analogue of the B-domain of protein A, capable of binding the Fc part of immunoglobulin G (IgG). The S-layer fusion protein rSbpA31-1068/ZZ retained the specific properties of the S-layer protein moiety to self-assemble i...

  10. Surface (S)-layer proteins of Deinococcus radiodurans and their utility as vehicles for surface localization of functional proteins.

    Science.gov (United States)

    Misra, Chitra Seetharam; Basu, Bhakti; Apte, Shree Kumar

    2015-12-01

    The radiation resistant bacterium, Deinococcus radiodurans contains two major surface (S)-layer proteins, Hpi and SlpA. The Hpi protein was shown to (a) undergo specific in vivo cleavage, and (b) closely associate with the SlpA protein. Using a non-specific acid phosphatase from Salmonella enterica serovar Typhi, PhoN as a reporter, the Surface Layer Homology (SLH) domain of SlpA was shown to bind deinococcal peptidoglycan-containing cell wall sacculi. The association of SlpA with Hpi on one side and peptidoglycan on the other, localizes this protein in the 'interstitial' layer of the deinoccocal cell wall. Gene chimeras of hpi-phoN and slh-phoN were constructed to test efficacy of S-layer proteins, as vehicles for cell surface localization in D. radiodurans. The Hpi-PhoN protein localized exclusively in the membrane fraction, and displayed cell-based phosphatase activity in vivo. The SLH-PhoN, which localized to both cytosolic and membrane fractions, displayed in vitro activity but no cell-based in vivo activity. Hpi, therefore, emerged as an efficient surface localizing protein and can be exploited for suitable applications of this superbug. PMID:26450150

  11. Heterologous protein display on the cell surface of lactic acid bacteria mediated by the s-layer protein

    Directory of Open Access Journals (Sweden)

    Han Lanlan

    2011-10-01

    Full Text Available Abstract Background Previous studies have revealed that the C-terminal region of the S-layer protein from Lactobacillus is responsible for the cell wall anchoring, which provide an approach for targeting heterologous proteins to the cell wall of lactic acid bacteria (LAB. In this study, we developed a new surface display system in lactic acid bacteria with the C-terminal region of S-layer protein SlpB of Lactobacillus crispatus K2-4-3 isolated from chicken intestine. Results Multiple sequence alignment revealed that the C-terminal region (LcsB of Lb. crispatus K2-4-3 SlpB had a high similarity with the cell wall binding domains SA and CbsA of Lactobacillus acidophilus and Lb. crispatus. To evaluate the potential application as an anchoring protein, the green fluorescent protein (GFP or beta-galactosidase (Gal was fused to the N-terminus of the LcsB region, and the fused proteins were successfully produced in Escherichia coli, respectively. After mixing them with the non-genetically modified lactic acid bacteria cells, the fused GFP-LcsB and Gal-LcsB were functionally associated with the cell surface of various lactic acid bacteria tested. In addition, the binding capacity could be improved by SDS pretreatment. Moreover, both of the fused proteins could simultaneously bind to the surface of a single cell. Furthermore, when the fused DNA fragment of gfp:lcsB was inserted into the Lactococcus lactis expression vector pSec:Leiss:Nuc, the GFP could not be secreted into the medium under the control of the nisA promoter. Western blot, in-gel fluorescence assay, immunofluorescence microscopy and SDS sensitivity analysis confirmed that the GFP was successfully expressed onto the cell surface of L. lactis with the aid of the LcsB anchor. Conclusion The LcsB region can be used as a functional scaffold to target the heterologous proteins to the cell surfaces of lactic acid bacteria in vitro and in vivo, and has also the potential for biotechnological

  12. The S-layer Protein DR_2577 Binds Deinoxanthin and under Desiccation Conditions Protects against UV-Radiation in Deinococcus radiodurans.

    Science.gov (United States)

    Farci, Domenica; Slavov, Chavdar; Tramontano, Enzo; Piano, Dario

    2016-01-01

    Deinococcus radiodurans has the puzzling ability to withstand over a broad range of extreme conditions including high doses of ultraviolet radiation and deep desiccation. This bacterium is surrounded by a surface layer (S-layer) built of a regular repetition of several proteins, assembled to form a paracrystalline structure. Here we report that the deletion of a main constituent of this S-layer, the gene DR_2577, causes a decrease in the UVC resistance, especially in desiccated cells. Moreover, we show that the DR_2577 protein binds the carotenoid deinoxanthin, a strong protective antioxidant specific of this bacterium. A further spectroscopical characterization of the deinoxanthin-DR_2577 complex revealed features which could suggest a protective role of DR_2577. We propose that, especially under desiccation, the S-layer shields the bacterium from incident ultraviolet light and could behave as a first lane of defense against UV radiation. PMID:26909071

  13. The S-layer protein DR_2577 binds deinoxanthin and under desiccation conditions protect against UV-radiation in Deinococcus radiodurans

    Directory of Open Access Journals (Sweden)

    Domenica eFarci

    2016-02-01

    Full Text Available Deinococcus radiodurans has the puzzling ability to withstand over a broad range of extreme conditions including high doses of ultraviolet radiation and deep desiccation. This bacterium is surrounded by a surface layer (S-layer built of a regular repetition of several proteins, assembled to form a paracrystalline structure. Here we report that the deletion of a main constituent of this S-layer, the gene DR_2577, causes a decrease in the UVC resistance, especially in dessicated cells. Moreover, we show that the DR_2577 protein binds the carotenoid deinoxanthin, a strong protective antioxidant specific of this bacterium. A further spectroscopical characterization of the deinoxanthin-DR_2577 complex revealed features which could suggest a protective role of DR_2577. We propose that, especially under dessication, the S-layer shields the bacterium from incident ultraviolet light and could behave as a first lane of defence against UV radiation.

  14. Capacity of graphite's layered structure to suppress the sputtering yield: A molecular dynamics study

    International Nuclear Information System (INIS)

    Highlights: • We simulated 20–120 keV C60 impact on carbon materials using MD method. • We found that small yield on graphite is mainly induced by its layered structure. • It is the first time that structure effect on sputtering is detailedly discussed. • Our results are consistent with previous experiments and simulations. - Abstract: 20–120 keV C60 bombardment on graphite and 20 keV C60 impact on diamond are studied by classical molecular dynamics (MD) simulations. The number of atoms ejected from graphite after a 20 keV C60 impact is found to be much smaller than that from diamond. By analyzing the microscopic sputtering process, we find this difference is due to the combined effects of graphite's low number density and layered structure. These two features of graphite make the pressure waves during the spike stage much weaker and the crater rim much more stable, compared to the case of diamond. While the role of atomic density on sputtering has been discussed in previous studies, effect of layered structure has not gained much attention yet. To affirm this effect and exclude the influence of density, we have also simulated C60 impact on an amorphous carbon (a-C) target whose density is very close to that of graphite. The yield of a-C is higher than that of graphite, certifying the capacity of graphite's layered structure to suppress the sputtering yield

  15. Exploring the molecular forces within and between CbsA S-layer proteins using single molecule force spectroscopy

    International Nuclear Information System (INIS)

    We used single molecule atomic force microscopy (AFM) to gain insight into the molecular forces driving the folding and assembly of the S-layer protein CbsA. Force curves recorded between tips and supports modified with CbsA proteins showed sawtooth patterns with multiple force peaks of 58±26 pN that we attribute to the unfolding of α-helices, in agreement with earlier secondary structure predictions. The average unfolding force increased with the pulling speed but was independent on the interaction time. Force curves obtained for CbsA peptides truncated in their C-terminal region showed similar periodic features, except that fewer force peaks were seen. Furthermore, the average unfolding force was 83±45 pN, suggesting the domains were more stable. By contrast, cationic peptides truncated in their N-terminal region showed single force peaks of 366±149 pN, presumably reflecting intermolecular electrostatic bridges rather than unfolding events. Interestingly, these large intermolecular forces increased not only with pulling speed but also with interaction time. We expect that the intra- and intermolecular forces measured here may play a significant role in controlling the stability and assembly of the CbsA protein

  16. Calcium dependent formation of tubular assemblies by recombinant S-layer proteins in vivo and in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Korkmaz, Nuriye; Ostermann, Kai; Roedel, Gerhard, E-mail: nuriye_korkmaz@yahoo.com, E-mail: kai.ostermann@tu-dresden.de, E-mail: gerhard.roedel@tu-dresden.de [Institut fuer Genetik, Technische Universitaet Dresden, Zellescher Weg 20b, 01217 Dresden (Germany)

    2011-03-04

    Surface layer proteins have the appealing property to self-assemble in nanosized arrays in solution and on solid substrates. In this work, we characterize the formation of assembly structures of the recombinant surface layer protein SbsC of Geobacillus stearothermophilus ATTC 12980, which was tagged with enhanced green fluorescent protein and expressed in the yeast Saccharomyces cerevisiae. The tubular structures formed by the protein in vivo are retained upon bursting the cells by osmotic shock; however, their average length is decreased. During dialysis, monomers obtained by treatment with chaotropic chemicals recrystallize again to form tube-like structures. This process is strictly dependent on calcium (Ca{sup 2+}) ions, with an optimal concentration of 10 mM. Further increase of the Ca{sup 2+} concentration results in multiple non-productive nucleation points. We further show that the lengths of the S-layer assemblies increase with time and can be controlled by pH. After 48 h, the average length at pH 9.0 is 4.13 {mu}m compared to 2.69 {mu}m at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications.

  17. Capacity of graphite's layered structure to suppress the sputtering yield: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Jiting [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Zheng, Tao, E-mail: tzheng@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Yang, Jiangyan; Kong, Shuyan; Xue, Jianming; Wang, Yugang [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Nordlund, Kai [Department of Physics, University of Helsinki, P.O. Box 43, Helsinki 00014 (Finland)

    2015-05-15

    Highlights: • We simulated 20–120 keV C{sub 60} impact on carbon materials using MD method. • We found that small yield on graphite is mainly induced by its layered structure. • It is the first time that structure effect on sputtering is detailedly discussed. • Our results are consistent with previous experiments and simulations. - Abstract: 20–120 keV C{sub 60} bombardment on graphite and 20 keV C{sub 60} impact on diamond are studied by classical molecular dynamics (MD) simulations. The number of atoms ejected from graphite after a 20 keV C{sub 60} impact is found to be much smaller than that from diamond. By analyzing the microscopic sputtering process, we find this difference is due to the combined effects of graphite's low number density and layered structure. These two features of graphite make the pressure waves during the spike stage much weaker and the crater rim much more stable, compared to the case of diamond. While the role of atomic density on sputtering has been discussed in previous studies, effect of layered structure has not gained much attention yet. To affirm this effect and exclude the influence of density, we have also simulated C{sub 60} impact on an amorphous carbon (a-C) target whose density is very close to that of graphite. The yield of a-C is higher than that of graphite, certifying the capacity of graphite's layered structure to suppress the sputtering yield.

  18. Isolation of surface (S) layer protein carrying Lactobacillus species from porcine intestine and faeces and characterization of their adhesion properties to different host tissues.

    Science.gov (United States)

    Jakava-Viljanen, Miia; Palva, Airi

    2007-10-01

    Surface-layer proteins (Slps) of lactobacilli have been shown to confer tissue adherence. This study aimed to isolate and identify Slps carrying Lactobacillus species from the porcine intestine and faeces and to characterize these S-layer-expressing strains for their ability to adhere to the pig and human intestinal cells and to extracellular matrix (ECM) proteins. In total 99 strains, putatively belonging to the genus Lactobacillus, were isolated as pure cultures. SDS-PAGE and a gene probe specific for the Lactobacillus brevis ATCC 8287 S-layer protein gene (slpA) were used to screen the presence of strains possessing putative Slps. Eight of the 99 pure cultures exhibited Slps according to the SDS-PAGE analyses. In these strains the presence of genes encoding Slps was confirmed by PCR and partial sequencing. Only one isolate of the 99 strains gave a positive hybridisation signal with the L. brevis slpA probe but did not appear to produce S-layer protein. Their taxonomic identification, based on phenotyping and the 16S rRNA sequences, revealed that the eight S-layer protein-producing strains were closely related to Lactobacillus amylovorus, Lactobacillus sobrius and Lactobacillus crispatus. The strain with the slpA positive hybridisation result was identified as Lactobacillus mucosae. The SDS-extractable protein profile, the size of the putative S-layer protein and binding capability of the strains varied greatly, even among the isolates belonging to the same Lactobacillus cluster. Removal of the intact Slps from the bacterial surface by extraction with guanidine hydrochloride reduced the adhesion of some strains to fibronectin and laminin, whereas, the adhesiveness to laminin increased with some strains. PMID:17544232

  19. The S-layer from Bacillus stearothermophilus DSM 2358 functions as an adhesion site for a high-molecular-weight amylase.

    OpenAIRE

    Egelseer, E; Schocher, I; Sára, M; Sleytr, U B

    1995-01-01

    The S-layer lattice from Bacillus stearothermophilus DSM 2358 completely covers the cell surface and exhibits oblique symmetry. During growth of B. stearothermophilus DSM 2358 on starch medium, three amylases with molecular weights of 58,000, 98,000, and 184,000 were secreted into the culture fluid, but only the high-molecular-weight enzyme was found to be cell associated. Studies of interactions between cell wall components and amylases revealed no affinity of the high-molecular-weight amyla...

  20. Identification and functional analysis of the S-layer protein SplA of Paenibacillus larvae, the causative agent of American Foulbrood of honey bees.

    Science.gov (United States)

    Poppinga, Lena; Janesch, Bettina; Fünfhaus, Anne; Sekot, Gerhard; Garcia-Gonzalez, Eva; Hertlein, Gillian; Hedtke, Kati; Schäffer, Christina; Genersch, Elke

    2012-01-01

    The gram-positive, spore-forming bacterium Paenibacillus larvae is the etiological agent of American Foulbrood (AFB), a globally occurring, deathly epizootic of honey bee brood. AFB outbreaks are predominantly caused by two genotypes of P. larvae, ERIC I and ERIC II, with P. larvae ERIC II being the more virulent genotype on larval level. Recently, comparative proteome analyses have revealed that P. larvae ERIC II but not ERIC I might harbour a functional S-layer protein, named SplA. We here determine the genomic sequence of splA in both genotypes and demonstrate by in vitro self-assembly studies of recombinant and purified SplA protein in combination with electron-microscopy that SplA is a true S-layer protein self-assembling into a square 2D lattice. The existence of a functional S-layer protein is novel for this bacterial species. For elucidating the biological function of P. larvae SplA, a genetic system for disruption of gene expression in this important honey bee pathogen was developed. Subsequent analyses of in vivo biological functions of SplA were based on comparing a wild-type strain of P. larvae ERIC II with the newly constructed splA-knockout mutant of this strain. Differences in cell and colony morphology suggest that SplA is a shape-determining factor. Marked differences between P. larvae ERIC II wild-type and mutant cells with regard to (i) adhesion to primary pupal midgut cells and (ii) larval mortality as measured in exposure bioassays corroborate the assumption that the S-layer of P. larvae ERIC II is an important virulence factor. Since SplA is the first functionally proven virulence factor for this species, our data extend the knowledge of the molecular differences between these two genotypes of P. larvae and contribute to explaining the observed differences in virulence. These results present an immense advancement in our understanding of P. larvae pathogenesis. PMID:22615573

  1. Recrystallized S-layer protein of a probiotic Propionibacterium: structural and nanomechanical changes upon temperature or pH shifts probed by solid-state NMR and AFM.

    Science.gov (United States)

    de sa Peixoto, Paulo; Roiland, Claire; Thomas, Daniel; Briard-Bion, Valérie; Le Guellec, Rozenn; Parayre, Sandrine; Deutsch, Stéphanie-Marie; Jan, Gwénaël; Guyomarc'h, Fanny

    2015-01-01

    Surface protein layers (S layers) are common constituents of the bacterial cell wall and originate from the assembly of strain-dependent surface layer proteins (Slps). These proteins are thought to play important roles in the bacteria's biology and to have very promising technological applications as biomaterials or as part of cell-host cross-talk in probiotic mechanism. The SlpA from Propionibacterium freudenreichii PFCIRM 118 strain was isolated and recrystallized to investigate organization and assembly of the protein using atomic force microscopy and solid-state (1)H and (13)C-nuclear magnetic resonance. SlpA was found to form hexagonal p1 monolayer lattices where the protein exhibited high proportions of disordered regions and of bound water. The lattice structure was maintained, but softened, upon mild heating or acidification, probably in relation with the increasing mobilities of the disordered protein regions. These results gave structural insights on the mobile protein regions exposed by S layer films, upon physiologically relevant changes of their environmental conditions. PMID:25479375

  2. Expression of an endotoxin-free S-layer/allergen fusion protein in gram-positive Bacillus subtilis 1012 for the potential application as vaccines for immunotherapy of atopic allergy

    OpenAIRE

    Egelseer Eva; Bohle Barbara; Schumi Christian-Thomas; Ilk Nicola; Sleytr Uwe B

    2011-01-01

    Abstract Background Genetic fusion of the major birch pollen allergen (Bet v1) to bacterial surface-(S)-layer proteins resulted in recombinant proteins exhibiting reduced allergenicity as well as immunomodulatory capacity. Thus, S-layer/allergen fusion proteins were considered as suitable carriers for new immunotherapeutical vaccines for treatment of Type I hypersensitivity. Up to now, endotoxin contamination of the fusion protein which occurred after isolation from the gram-negative expressi...

  3. The S-layer homology domain-containing protein SlhA from Paenibacillus alvei CCM 2051(T is important for swarming and biofilm formation.

    Directory of Open Access Journals (Sweden)

    Bettina Janesch

    Full Text Available Swarming and biofilm formation have been studied for a variety of bacteria. While this is well investigated for Gram-negative bacteria, less is known about Gram-positive bacteria, including Paenibacillus alvei, a secondary invader of diseased honeybee colonies infected with Melissococcus pluton, the causative agent of European foulbrood (EFB.Paenibacillus alvei CCM 2051(T is a Gram-positive bacterium which was recently shown to employ S-layer homology (SLH domains as cell wall targeting modules to display proteins on its cell surface. This study deals with the newly identified 1335-amino acid protein SlhA from P. alvei which carries at the C‑terminus three consecutive SLH-motifs containing the predicted binding sequences SRGE, VRQD, and LRGD instead of the common TRAE motif. Based on the proof of cell surface location of SlhA by fluorescence microscopy using a SlhA-GFP chimera, the binding mechanism was investigated in an in vitro assay. To unravel a putative function of the SlhA protein, a knockout mutant was constructed. Experimental data indicated that one SLH domain is sufficient for anchoring of SlhA to the cell surface, and the SLH domains of SlhA recognize both the peptidoglycan and the secondary cell wall polymer in vitro. This is in agreement with previous data from the S-layer protein SpaA, pinpointing a wider utilization of that mechanism for cell surface display of proteins in P. alvei. Compared to the wild-type bacterium ΔslhA revealed changed colony morphology, loss of swarming motility and impaired biofilm formation. The phenotype was similar to that of the flagella knockout Δhag, possibly due to reduced EPS production influencing the functionality of the flagella of ΔslhA.This study demonstrates the involvement of the SLH domain-containing protein SlhA in swarming and biofilm formation of P. alvei CCM 2051(T.

  4. Chemically deposited In2S3–Ag2S layers to obtain AgInS2 thin films by thermal annealing

    International Nuclear Information System (INIS)

    Highlights: ► We obtained polycrystalline silver indium sulfide thin films through the annealing of chemically deposited In2S3–Ag2S films. ► According to XRD chalcopyrite structure of AgInS2 was obtained. ► AgInS2 thin film has a band gap of 1.86 eV and a conductivity value of 1.2 × 10−3 (Ω cm)−1. - Abstract: AgInS2 thin films were obtained by the annealing of chemical bath deposited In2S3–Ag2S layers at 400 °C in N2 for 1 h. According to the XRD and EDX results the chalcopyrite structure of AgInS2 has been obtained. These films have an optical band gap, Eg, of 1.86 eV and an electrical conductivity value of 1.2 × 10−3 (Ω cm)−1.

  5. Development and application of a upp-based counterselective gene replacement system for the study of the S-layer protein SlpX of Lactobacillus acidophilus NCFM.

    Science.gov (United States)

    Goh, Yong Jun; Azcárate-Peril, M Andrea; O'Flaherty, Sarah; Durmaz, Evelyn; Valence, Florence; Jardin, Julien; Lortal, Sylvie; Klaenhammer, Todd R

    2009-05-01

    In silico genome analysis of Lactobacillus acidophilus NCFM coupled with gene expression studies have identified putative genes and regulatory networks that are potentially important to this organism's survival, persistence, and activities in the gastrointestinal tract. Correlation of key genotypes to phenotypes requires an efficient gene replacement system. In this study, use of the upp-encoded uracil phosphoribosyltransferase (UPRTase) of L. acidophilus NCFM was explored as a counterselection marker to positively select for recombinants that have resolved from chromosomal integration of pORI-based plasmids. An isogenic mutant carrying a upp gene deletion was constructed and was resistant to 5-fluorouracil (5-FU), a toxic uracil analog that is also a substrate for UPRTase. A 3.0-kb pORI-based counterselectable integration vector bearing a upp expression cassette, pTRK935, was constructed and introduced into the Deltaupp host harboring the pTRK669 helper plasmid. Extrachromosomal replication of pTRK935 complemented the mutated chromosomal upp allele and restored sensitivity to 5-FU. This host background provides a platform for a two-step plasmid integration and excision strategy that can select for plasmid-free recombinants with either the wild-type or mutated allele of the targeted gene in the presence of 5-FU. The efficacy of the system was demonstrated by in-frame deletion of the slpX gene (LBA0512) encoding a novel 51-kDa secreted protein associated with the S-layer complex of L. acidophilus. The resulting DeltaslpX mutant exhibited lower growth rates, increased sensitivity to sodium dodecyl sulfate, and greater resistance to bile. Overall, this improved gene replacement system represents a valuable tool for investigating the mechanisms underlying the probiotic functionality of L. acidophilus. PMID:19304841

  6. Expression of an endotoxin-free S-layer/allergen fusion protein in gram-positive Bacillus subtilis 1012 for the potential application as vaccines for immunotherapy of atopic allergy

    Directory of Open Access Journals (Sweden)

    Egelseer Eva

    2011-02-01

    Full Text Available Abstract Background Genetic fusion of the major birch pollen allergen (Bet v1 to bacterial surface-(S-layer proteins resulted in recombinant proteins exhibiting reduced allergenicity as well as immunomodulatory capacity. Thus, S-layer/allergen fusion proteins were considered as suitable carriers for new immunotherapeutical vaccines for treatment of Type I hypersensitivity. Up to now, endotoxin contamination of the fusion protein which occurred after isolation from the gram-negative expression host E. coli had to be removed by an expensive and time consuming procedure. In the present study, in order to achieve expression of pyrogen-free, recombinant S-layer/allergen fusion protein and to study the secretion of a protein capable to self-assemble, the S-layer/allergen fusion protein rSbpA/Bet v1 was produced in the gram-positive organism Bacillus subtilis 1012. Results The chimaeric gene encoding the S-layer protein SbpA of Lysinibacillus sphaericus CCM 2177 as well as Bet v1 was cloned and expressed in B. subtilis 1012. For that purpose, the E. coli-B. subtilis shuttle vectors pHT01 for expression in the B. subtilis cytoplasm and pHT43 for secretion of the recombinant fusion protein into the culture medium were used. As shown by western blot analysis, immediately after induction of expression, B. subtilis 1012 was able to secret rSbpA/Bet v1 mediated by the signal peptide amyQ of Bacillus amyloliquefaciens. Electron microscopical investigation of the culture medium revealed that the secreted fusion protein was able to form self-assembly products in suspension but did not recrystallize on the surface of the B. subtilis cells. The specific binding mechanism between the N-terminus of the S-layer protein and a secondary cell wall polymer (SCWP, located in the peptidoglycan-containing sacculi of Ly. sphaericus CCM 2177, could be used for isolation and purification of the secreted fusion protein from the culture medium. Immune reactivity of rSbpA/Bet v1

  7. Dicty_cDB: Contig-U10422-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available 148_3252( CP000148 |pid:none) Geobacter metallireducens GS-15... 494 e-138 CP000447_2705( CP000447 |pid:none) Shewanell...000613_385( CP000613 |pid:none) Rhodospirillum centenum SW, comp... 469 e-131 (Q5RBD5) RecName: Full...ig-U10422-1Q.Seq.d (1267 letters) Database: CSM 6905 sequences; 5,674,871 total letters Score E Sequences producing significant al...ig An07c010... 432 e-119 AE005673_2155( AE005673 |pid:none) Caulobacter crescentus CB15, c...o... 431 e-119 CP001340_2252( CP001340 |pid:none) Caulobacter crescentus NA1000,

  8. Bacterial cell curvature through mechanical control of cell growth

    DEFF Research Database (Denmark)

    Cabeen, M.; Charbon, Godefroid; Vollmer, W.;

    2009-01-01

    The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure that coll...... cell wall insertion to produce curved growth. Our study suggests that bacteria may use the cytoskeleton for mechanical control of growth to alter morphology......The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure that...

  9. Electronic and protein structural dynamics of a photosensory LOV histidine kinase †

    OpenAIRE

    Alexandre, Maxime T.A.; Purcell, Erin B.; van Grondelle, Rienk; Robert, Bruno; Kennis, John T. M.; Crosson, Sean

    2010-01-01

    The bacterium Caulobacter crescentus encodes a two-component signalling protein, LovK, that contains an N-terminal photosensory LOV domain coupled to a C-terminal histidine kinase. LovK binds a flavin cofactor, undergoes a reversible photocycle, and displays regulated ATPase and autophosphorylation activity in response to visible light. Femtosecond to nanosecond visible absorption spectroscopy demonstrates congruence between full-length LovK and isolated LOV domains in the mechanism and kinet...

  10. Single-Molecule and Superresolution Imaging in Live Bacteria Cells

    OpenAIRE

    Biteen, Julie S; Moerner, W. E.

    2010-01-01

    Single-molecule imaging enables biophysical measurements devoid of ensemble averaging, gives enhanced spatial resolution beyond the diffraction limit, and permits superresolution reconstructions. Here, single-molecule and superresolution imaging are applied to the study of proteins in live Caulobacter crescentus cells to illustrate the power of these methods in bacterial imaging. Based on these techniques, the diffusion coefficient and dynamics of the histidine protein kinase PleC, the locali...

  11. Allosteric Regulation of Histidine Kinases by Their Cognate Response Regulator Determines Cell Fate

    OpenAIRE

    Paul, Ralf; Jaeger, Tina; Abel, Sören; Wiederkehr, Irene; Folcher, Marc; Biondi, Emanuele G.; Laub, Michael T.; Jenal, Urs

    2008-01-01

    The two-component phosphorylation network is of critical importance for bacterial growth and physiology. Here, we address plasticity and interconnection of distinct signal transduction pathways within this network. In Caulobacter crescentus antagonistic activities of the PleC phosphatase and DivJ kinase localized at opposite cell poles control the phosphorylation state and subcellular localization of the cell fate determinator protein DivK. We show that DivK functions as an allosteric regulat...

  12. Characterization of CBD-CdS layers with different S/Cd ratios in the chemical bath and their relation with the efficiency of CdS/CdTe solar cells

    International Nuclear Information System (INIS)

    In previous papers we have reported the improvement of the efficiency of CdS/CdTe solar cells by varying the thiourea/CdCl2 ratio (R tc) in the chemical bath solution used for the deposition of the CdS layers. In this work, a more complete study concerning the physical properties of Chemical Bath Deposited (CBD) CdS layers studied by photoluminescence, X-ray diffraction and optical spectroscopy are correlated to the I-V characteristics under AM 1.5 sunlight and the spectral response of CdS/CdTe solar cells. It is confirmed that the optimum R tc for the CBD CdS films is R tc = 5, since in this case the best solar cells were obtained and these films show the better optical and structural characteristics

  13. Tuning band alignment by CdS layers using a SILAR method to enhance TiO2/CdS/CdSe quantum-dot solar-cell performance.

    Science.gov (United States)

    Zhang, Bingkai; Zheng, Jiaxin; Li, Xiaoning; Fang, Yanyan; Wang, Lin-Wang; Lin, Yuan; Pan, Feng

    2016-04-14

    We report tuning band alignment by optimized CdS layers using a SILAR method to achieve the recorded best performance with about 6% PCE in TiO2/CdS/CdSe QDSSCs. Combining experimental and theoretical studies, we find that a better lattices match between CdS and TiO2 assists the growth of CdSe, and the combined effect of charge transfer and surface dipole moment at the TiO2/CdS/CdSe interface shifts the energy levels of TiO2 upward and increases Voc of the solar cells. More importantly, the band gap of CdS buffer layers is sensitive to the distortion induced by lattice mismatch and numbers of CdS layers. For example, the barrier for charge transfer disappears when there are more than 4 layers of CdS, facilitating the charge injection from CdSe to TiO2. PMID:27040601

  14. Transcription rate and transcript length drive formation of chromosomal interaction domain boundaries.

    Science.gov (United States)

    Le, Tung Bk; Laub, Michael T

    2016-07-15

    Chromosomes in all organisms are highly organized and divided into multiple chromosomal interaction domains, or topological domains. Regions of active, high transcription help establish and maintain domain boundaries, but precisely how this occurs remains unclear. Here, using fluorescence microscopy and chromosome conformation capture in conjunction with deep sequencing (Hi-C), we show that in Caulobacter crescentus, both transcription rate and transcript length, independent of concurrent translation, drive the formation of domain boundaries. We find that long, highly expressed genes do not form topological boundaries simply through the inhibition of supercoil diffusion. Instead, our results support a model in which long, active regions of transcription drive local decompaction of the chromosome, with these more open regions of the chromosome forming spatial gaps in vivo that diminish contacts between DNA in neighboring domains. These insights into the molecular forces responsible for domain formation in Caulobacter likely generalize to other bacteria and possibly eukaryotes. PMID:27288403

  15. Branched signal wiring of an essential bacterial cell-cycle phosphotransfer protein

    OpenAIRE

    Blair, Jimmy A.; Xu, Qingping; Childers, W. Seth; Mathews, Irimpan I.; Kern, Justin W.; Eckart, Michael; Deacon, Ashley M.; Shapiro, Lucy

    2013-01-01

    Vital to bacterial survival is the faithful propagation of cellular signals, and in Caulobacter crescentus ChpT is an essential mediator within the cell cycle circuit. ChpT functions as a histidine-containing phosphotransfer protein (HPt) that shuttles a phosphoryl group from the receiver domain of CckA, the upstream hybrid histidine kinase (HK), to one of two downstream response regulators (RRs)—CtrA or CpdR—that controls cell cycle progression. To understand how ChpT interacts with multiple...

  16. A role for the weak DnaA binding sites in bacterial replication origins

    DEFF Research Database (Denmark)

    Charbon, Godefroid; Løbner-Olesen, Anders

    2011-01-01

    DnaA initiates the chromosomal DNA replication in nearly all bacteria, and replication origins are characterized by binding sites for the DnaA protein (DnaA-boxes) along with an ‘AT-rich’ region. However, great variation in number, spatial organization and specificity of DnaA-boxes is observed...... between species. In the study by Taylor et al. (2011), new and unexpectedly weak DnaA-boxes were identified within the Caulobacter crescentus origin of replication (Cori). The position of weak and stronger DnaA-boxes follows a pattern seen in Escherichia coli oriC. This raises the possibility that...

  17. Dicty_cDB: Contig-U10309-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available pickettii 12J chromos... 68 4e-12 CU207211_2890( CU207211 |pid:none) Herminiimonas arsenicoxydans ch... 67 ...Y344466 |pid:none) Tigriopus californicus isolate Abg... 99 3e-33 CP001340_503( CP001340 |pid:none) Caulobacter crescentus...iquinol-cytochrome c reductase iron-sul... 103 1e-20 CP000449_185( CP000449 |pid:none) Maricaulis maris MCS1...vvsqnqpavvvkwrgkplfirhrsaeeisesqavqlstlpdpq adnrsfkstrmdyfswclhsfrlypnfrww*lqwlvlsmswfsl**rwsy*kgscpneln rst...ontig-U10309-1Q.Seq.d Length = 1136 Score = 1536 bits (775), Expect = 0.0 Identities = 775/775 (100%) Strand = Plus / Plus

  18. A novel aldose-aldose oxidoreductase for co-production of D-xylonate and xylitol from D-xylose with Saccharomyces cerevisiae

    OpenAIRE

    Marilyn G. Wiebe; Nygård, Yvonne; Oja, Merja; Andberg, Martina; Ruohonen, Laura; Koivula, Anu; Penttilä, Merja; Toivari, Mervi

    2015-01-01

    An open reading frame CC1225 from the Caulobacter crescentus CB15 genome sequence belongs to the Gfo/Idh/MocA protein family and has 47 % amino acid sequence identity with the glucose-fructose oxidoreductase from Zymomonas mobilis (Zm GFOR). We expressed the ORF CC1225 in the yeast Saccharomyces cerevisiae and used a yeast strain expressing the gene coding for Zm GFOR as a reference. Cell extracts of strains overexpressing CC1225 (renamed as Cc aaor) showed some Zm GFOR type of activity, prod...

  19. Conserved S-Layer-Associated Proteins Revealed by Exoproteomic Survey of S-Layer-Forming Lactobacilli

    OpenAIRE

    Johnson, Brant R.; Hymes, Jeffrey; Sanozky-Dawes, Rosemary; Henriksen, Emily DeCrescenzo; Barrangou, Rodolphe; Klaenhammer, Todd R.

    2015-01-01

    The Lactobacillus acidophilus homology group comprises Gram-positive species that include L. acidophilus, L. helveticus, L. crispatus, L. amylovorus, L. gallinarum, L. delbrueckii subsp. bulgaricus, L. gasseri, and L. johnsonii. While these bacteria are closely related, they have varied ecological lifestyles as dairy and food fermenters, allochthonous probiotics, or autochthonous commensals of the host gastrointestinal tract. Bacterial cell surface components play a critical role in the molec...

  20. Complete genome of Phenylobacterium zucineum – a novel facultative intracellular bacterium isolated from human erythroleukemia cell line K562

    Directory of Open Access Journals (Sweden)

    Sun Jie

    2008-08-01

    Full Text Available Abstract Background Phenylobacterium zucineum is a recently identified facultative intracellular species isolated from the human leukemia cell line K562. Unlike the known intracellular pathogens, P. zucineum maintains a stable association with its host cell without affecting the growth and morphology of the latter. Results Here, we report the whole genome sequence of the type strain HLK1T. The genome consists of a circular chromosome (3,996,255 bp and a circular plasmid (382,976 bp. It encodes 3,861 putative proteins, 42 tRNAs, and a 16S-23S-5S rRNA operon. Comparative genomic analysis revealed that it is phylogenetically closest to Caulobacter crescentus, a model species for cell cycle research. Notably, P. zucineum has a gene that is strikingly similar, both structurally and functionally, to the cell cycle master regulator CtrA of C. crescentus, and most of the genes directly regulated by CtrA in the latter have orthologs in the former. Conclusion This work presents the first complete bacterial genome in the genus Phenylobacterium. Comparative genomic analysis indicated that the CtrA regulon is well conserved between C. crescentus and P. zucineum.

  1. High-resolution mapping of the spatial organization of a bacterial chromosome.

    Science.gov (United States)

    Le, Tung B K; Imakaev, Maxim V; Mirny, Leonid A; Laub, Michael T

    2013-11-01

    Chromosomes must be highly compacted and organized within cells, but how this is achieved in vivo remains poorly understood. We report the use of chromosome conformation capture coupled with deep sequencing (Hi-C) to map the structure of bacterial chromosomes. Analysis of Hi-C data and polymer modeling indicates that the Caulobacter crescentus chromosome consists of multiple, largely independent spatial domains that are probably composed of supercoiled plectonemes arrayed into a bottle brush-like fiber. These domains are stable throughout the cell cycle and are reestablished concomitantly with DNA replication. We provide evidence that domain boundaries are established by highly expressed genes and the formation of plectoneme-free regions, whereas the histone-like protein HU and SMC (structural maintenance of chromosomes) promote short-range compaction and the colinearity of chromosomal arms, respectively. Collectively, our results reveal general principles for the organization and structure of chromosomes in vivo. PMID:24158908

  2. Proteotoxic stress induces a cell-cycle arrest by stimulating Lon to degrade the replication initiator DnaA.

    Science.gov (United States)

    Jonas, Kristina; Liu, Jing; Chien, Peter; Laub, Michael T

    2013-08-01

    The decision to initiate DNA replication is a critical step in the cell cycle of all organisms. Cells often delay replication in the face of stressful conditions, but the underlying mechanisms remain incompletely defined. Here, we demonstrate in Caulobacter crescentus that proteotoxic stress induces a cell-cycle arrest by triggering the degradation of DnaA, the conserved replication initiator. A depletion of available Hsp70 chaperone, DnaK, either through genetic manipulation or heat shock, induces synthesis of the Lon protease, which can directly degrade DnaA. Unexpectedly, we find that unfolded proteins, which accumulate following a loss of DnaK, also allosterically activate Lon to degrade DnaA, thereby ensuring a cell-cycle arrest. Our work reveals a mechanism for regulating DNA replication under adverse growth conditions. Additionally, our data indicate that unfolded proteins can actively and directly alter substrate recognition by cellular proteases. PMID:23911325

  3. AcEST: DK958696 [AcEST

    Lifescience Database Archive (English)

    Full Text Available ia with plantlets Developmental stage gametophytes with sporophytes...us ka... 64 5e-10 sp|Q9KA70|RASP_BACHD Zinc metalloprotease rasP OS=Bacillus halod... 6...FV +DPE+ Sbjct: 62 LLPLGGFVRMAGEDPET 78 >sp|Q9KA70|RASP_BACHD Zinc metalloprotease rasP OS=Bacillus halo... 62 GGYVRMAGEDPE 73 >sp|Q9A710|MMPA_CAUCR Metalloprotease mmpA OS=Caulobacter crescentus GN=mmpA PE=1 SV=1 Length...662 Definition Adiantum capillus-veneris mRNA. clone: TST39A01NGRL0002_K24. 5' end sequence. Accession DK958696 Tissue type prothall

  4. Dicty_cDB: Contig-U15635-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available 252 |pid:none) Lawsonia intracellularis PHE/MN1... 107 2e-21 AE016830_1135( AE016830 |pid:none) Enterococcus faecal...s; 8,075,542 total letters Score E Sequences producing significant alignments: (bits) Value Contig-U15635-1 (Cont...M270312_10( AM270312 |pid:none) Aspergillus niger contig An14c004... 283 3e-74 AE016830_2264( AE016830 |pid:none) Enterococcus faecal...5673 |pid:none) Caulobacter crescentus CB15, co... 203 4e-50 CP000009_871( CP0000...7_1293( CP000937 |pid:none) Francisella philomiragia subsp.... 192 1e-46 CP000323_1140( CP000323 |pid:none) Psychrobacter cryohal

  5. Cell cycle control in Alphaproteobacteria.

    Science.gov (United States)

    Collier, Justine

    2016-04-01

    Alphaproteobacteria include many medically and environmentally important organisms. Despite the diversity of their niches and lifestyles, from free-living to host-associated, they usually rely on very similar mechanisms to control their cell cycles. Studies on Caulobacter crescentus still lay the foundation for understanding the molecular details of pathways regulating DNA replication and cell division and coordinating these two processes with other events of the cell cycle. This review highlights recent discoveries on the regulation and the mode of action of conserved global regulators and small molecules like c-di-GMP and (p)ppGpp, which play key roles in cell cycle control. It also describes several newly identified mechanisms that modulate cell cycle progression in response to stresses or environmental conditions. PMID:26871482

  6. Scaling laws governing stochastic growth and division of single bacterial cells

    CERN Document Server

    Iyer-Biswas, Srividya; Henry, Jonathan T; Lo, Klevin; Burov, Stanislav; Lin, Yihan; Crooks, Gavin E; Crosson, Sean; Dinner, Aaron R; Scherer, Norbert F

    2014-01-01

    Uncovering the quantitative laws that govern the growth and division of single cells remains a major challenge. Using a unique combination of technologies that yields unprecedented statistical precision, we find that the sizes of individual Caulobacter crescentus cells increase exponentially in time. We also establish that they divide upon reaching a critical multiple ($\\approx$1.8) of their initial sizes, rather than an absolute size. We show that when the temperature is varied, the growth and division timescales scale proportionally with each other over the physiological temperature range. Strikingly, the cell-size and division-time distributions can both be rescaled by their mean values such that the condition-specific distributions collapse to universal curves. We account for these observations with a minimal stochastic model that is based on an autocatalytic cycle. It predicts the scalings, as well as specific functional forms for the universal curves. Our experimental and theoretical analysis reveals a ...

  7. Noise in Exponential Growth

    Science.gov (United States)

    Iyer-Biswas, Srividya; Wright, Charles; Henry, Jon; Burov, Stas; Lin, Yihan; Crosson, Sean; Dinner, Aaron; Scherer, Norbert

    2013-03-01

    The interplay between growth and division of cells is has been studied in the context of exponential growth of bacterial cells (in suitable conditions) for decades. However, bulk culture studies obscure phenomena that manifest in single cells over many generations. We introduce a unique technology combining microfluidics, single-cell imaging, and quantitative analysis. This enables us to track the growth of single Caulobacter crescentus stalked cells over hundreds of generations. The statistics that we extract indicate a size thresholding mechanism for cell division and a non-trivial scaling collapse of division time distributions at different temperatures. In this talk I shall discuss these observations and a stochastic model of growth and division that captures all our observations with no free parameters.

  8. Dicty_cDB: Contig-U15518-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available pid:none) Herminiimonas arsenicoxydans ch... 70 3e-10 CP001392_2585( CP001392 |pid:none) Diaphorobacter sp. ...52 AE005673_923( AE005673 |pid:none) Caulobacter crescentus CB15, com... 151 3e-49 CP000449_864( CP000449 |pid:none) Maricau...tig-U15518-1Q.Seq.d (2022 letters) Database: CSM 8402 sequences; 8,075,542 total letters Score E Sequences producing significa...re = 3515 bits (1773), Expect = 0.0 Identities = 1831/1845 (99%) Strand = Plus / Plus Query: 112 gagttagactca...arch space: 15905079540 effective search space used: 15905079540 T: 0 A: 40 X1: 6 (11.9 bits) X2: 15

  9. Dicty_cDB: Contig-U05994-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available ; ... 229 1e-58 CU207211_3071( CU207211 |pid:none) Herminiimonas arsenicoxydans ch... 229 1e-58 FN392321_754...1( BT076534 |pid:none) Caligus rogercresseyi clone crog-e... 338 2e-91 (A6RW56) RecName: Full=ATP-dependent rRNA helicase...54202_287( CR954202 |pid:none) Ostreococcus tauri strain OTTH05... 327 4e-88 (Q2H1Q8) RecName: Full=ATP-dependent rRNA helicase...4e-59 AE005673_832( AE005673 |pid:none) Caulobacter crescentus CB15, com... 231 4e-59 CP000937_1787( CP000937 |pid:none) Francise...l=ATP-dependent RNA helicase drs1; ... 226 1e-57 AP006627_3931( AP006627 |pid:none) Bacillus claus

  10. Dicty_cDB: Contig-U12311-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available ns Agy99, c... 45 0.007 AY177427_2( AY177427 |pid:none) Oligella urethralis insertion sequ... 45 0.007 EU118... crescentus CB15, co... 49 4e-04 AM270345_13( AM270345 |pid:none) Aspergillus niger contig...927_2142( CP000927 |pid:none) Caulobacter sp. K31, complete g... 55 5e-06 CP000903_3117( CP000903 |pid:none) Bacillus wei... 46 0.002 CP000034_345( CP000034 |pid:none) Shigella dysenteriae Sd197, comp... 4...( CP000267 |pid:none) Rhodoferax ferrireducens T118, ... 45 0.004 CP001117_5( CP001117 |pid:none) Deinococcus desert

  11. Dicty_cDB: Contig-U13958-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available hii ATCC ... 41 0.086 AB017194_1( AB017194 |pid:none) Plectonema boryanum ORF270, prolin... 41 0.086 BA00004...( AW759085 ) sl34e01.y1 Gm-c1027 Glycine max cDNA clone GENOME... 52 3e-11 4 ( FC674402 ) CAXW9990.rev CAXW Lottia gigantea from fem...pionase, bet... 362 2e-98 AY829756_1( AY829756 |pid:none) Lonomia obliqua hypothe...) Brevibacillus agri strain NCHU1002... 148 5e-34 BA000030_1957( BA000030 |pid:none) Streptomyces avermi...onas syringae pv. tomato... 72 6e-11 AE005673_211( AE005673 |pid:none) Caulobacter crescentus CB15, com

  12. Dicty_cDB: Contig-U14072-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available |pid:none) Sulfurovum sp. NBC37-1 genomic ... 50 4e-05 AJ006687_1( AJ006687 |pid:none) Caulobacter crescentus major che...05 CP001227_190( CP001227 |pid:none) Rickettsia peacockii str. Rustic... 50 4e-05 AE004091_414( AE004091 |pi...rd Canis familiaris ... 44 4.9 1 ( EF085015 ) Picea sitchensis clone WS0283_H23 unkno... 44 4.9 1 ( ES853576 ) WS02759.CR_C20 SS-IL-A-FL-14 Picea sitchensis cDN... 44 4....BR_H23 SS-IB-A-FL-13 Picea sitchensis cDNA... 44 4.9 1 ( DR472723 ) WS00956.B21_P18 IS-B-N-A-10 Picea

  13. A novel aldose-aldose oxidoreductase for co-production of D-xylonate and xylitol from D-xylose with Saccharomyces cerevisiae.

    Science.gov (United States)

    Wiebe, Marilyn G; Nygård, Yvonne; Oja, Merja; Andberg, Martina; Ruohonen, Laura; Koivula, Anu; Penttilä, Merja; Toivari, Mervi

    2015-11-01

    An open reading frame CC1225 from the Caulobacter crescentus CB15 genome sequence belongs to the Gfo/Idh/MocA protein family and has 47 % amino acid sequence identity with the glucose-fructose oxidoreductase from Zymomonas mobilis (Zm GFOR). We expressed the ORF CC1225 in the yeast Saccharomyces cerevisiae and used a yeast strain expressing the gene coding for Zm GFOR as a reference. Cell extracts of strains overexpressing CC1225 (renamed as Cc aaor) showed some Zm GFOR type of activity, producing D-gluconate and D-sorbitol when a mixture of D-glucose and D-fructose was used as substrate. However, the activity in Cc aaor expressing strain was >100-fold lower compared to strains expressing Zm gfor. Interestingly, C. crescentus AAOR was clearly more efficient than the Zm GFOR in converting in vitro a single sugar substrate D-xylose (10 mM) to xylitol without an added cofactor, whereas this type of activity was very low with Zm GFOR. Furthermore, when cultured in the presence of D-xylose, the S. cerevisiae strain expressing Cc aaor produced nearly equal concentrations of D-xylonate and xylitol (12.5 g D-xylonate l(-1) and 11.5 g D-xylitol l(-1) from 26 g D-xylose l(-1)), whereas the control strain and strain expressing Zm gfor produced only D-xylitol (5 g l(-1)). Deletion of the gene encoding the major aldose reductase, Gre3p, did not affect xylitol production in the strain expressing Cc aaor, but decreased xylitol production in the strain expressing Zm gfor. In addition, expression of Cc aaor together with the D-xylonolactone lactonase encoding the gene xylC from C. crescentus slightly increased the final concentration and initial volumetric production rate of both D-xylonate and D-xylitol. These results suggest that C. crescentus AAOR is a novel type of oxidoreductase able to convert the single aldose substrate D-xylose to both its oxidized and reduced product. PMID:26264136

  14. Characterization of porcine-specific surface (S-) layer protein carrying Lactobacillus species, S-layer proteins and the adhesin of Escherichia coli F18 fimbriae

    OpenAIRE

    Jakava-Viljanen, Miia

    2007-01-01

    Pigs coexist with diverse and dense commensal microbiota in their gastrointestinal tract (GIT). Lactobacilli, identified as common members of porcine intestinal microbiota, have been considered to be an important group of bacteria in maintaining the stability of GIT, in preventing intestinal infections and generally, in supporting intestinal health. Because several species of lactobacilli have GRAS (generally regarded as safe) status and some of them have an ability to interact with intestina...

  15. Mathematical modeling of bacterial track-altering motors: Track cleaving through burnt-bridge ratchets

    Science.gov (United States)

    Shtylla, Blerta; Keener, James P.

    2015-04-01

    The generation of directed movement of cellular components frequently requires the rectification of Brownian motion. Molecular motor enzymes that use ATP to walk on filamentous tracks are typically involved in cell transport, however, a track-altering motor can arise when an enzyme interacts with and alters its track. In Caulobacter crescentus and other bacteria, an active DNA partitioning (Par) apparatus is employed to segregate replicated chromosome regions to specific locations in dividing cells. The Par apparatus is composed of two proteins: ParA, an ATPase that can form polymeric structures on the nucleoid, and ParB, a protein that can bind and destabilize ParA structures. It has been proposed that the ParB-mediated alteration of ParA structures could be responsible for generating the directed movement of DNA during bacterial division. How precisely these actions are coordinated and translated into directed movement is not clear. In this paper we consider the C. crescentus segregation apparatus as an example of a track altering motor that operates using a so-called burnt-bridge mechanism. We develop and analyze mathematical models that examine how diffusion and ATP-hydrolysis-mediated monomer removal (or cleaving) can be combined to generate directed movement. Using a mean first passage approach, we analytically calculate the effective ParA track-cleaving velocities, effective diffusion coefficient, and other higher moments for the movement a ParB protein cluster that breaks monomers away at random locations on a single ParA track. Our model results indicate that cleaving velocities and effective diffusion constants are sensitive to ParB-induced ATP hydrolysis rates. Our analytical results are in excellent agreement with stochastic simulation results.

  16. Preparation and Characterization of TiO2/CdS Layers as Potential Photoelectrocatalytic Materials

    OpenAIRE

    Teofil-Danut Silipas; Ioan Bratu; Simina-Virginia Dreve; Ramona-Crina Suciu; Marcela-Corina Rosu; Emil Indrea

    2011-01-01

    The TiO2/CdS semiconductor composites were prepared on
    indium tin oxide (ITO) substrates in di®erent mass proportions via wet-chemical techniques using bi-distilled water, acetyl-acetone, poly-propylene-glycol and Triton X-100 as additives. The composite layers were annealed in normal conditions at the temperature of 450±C, 120 min. with a rate of temperature increasing of 5±C/min. The structural and optical properties of all the TiO2/CdS ayers were ch...

  17. Molecule Recognition Imaging and Highly Ordered Gold Nanoparticle Templating of Functional Bacterial S-Layer Nanoarrays

    Institute of Scientific and Technical Information of China (English)

    Jilin TANG; Andreas Ebner; Helga Badelt-Lichtblau; Christian Rankl; Michael Leitner; Hermann J.Gruber; Uwe B.Sleytr; Nicola Ilk; Peter Hinterdorfer

    2009-01-01

    @@ Molecular recognition between receptors and their cognate ligands plays an important role in life sciences.Such specific interactions include those between complementary strands of DNA,enzyme and substrate,antigen and antibody,lectin and carbohydrate,ligands and cell surface receptors as well as between cell adhesion proteins.

  18. Two-Dimensional SiS Layers with Promising Electronic and Optoelectronic Properties: Theoretical Prediction.

    Science.gov (United States)

    Yang, Ji-Hui; Zhang, Yueyu; Yin, Wan-Jian; Gong, X G; Yakobson, Boris I; Wei, Su-Huai

    2016-02-10

    Two-dimensional (2D) semiconductors can be very useful for novel electronic and optoelectronic applications because of their good material properties. However, all current 2D materials have shortcomings that limit their performance. As a result, new 2D materials are highly desirable. Using atomic transmutation and differential evolution global optimization methods, we identified two group IV-VI 2D materials, Pma2-SiS and silicene sulfide. Pma2-SiS is found to be both chemically, energetically, and thermally stable. Most importantly, Pma2-SiS has shown good electronic and optoelectronic properties, including direct bandgaps suitable for solar cells, good mobility for nanoelectronics, good flexibility of property tuning by layer control and applied strain, and good air stability as well. Therefore, Pma2-SiS is expected to be a promising 2D material in the field of 2D electronics and optoelectronics. The designing principles demonstrated in identifying these two tantalizing examples have great potential to accelerate the finding of new functional 2D materials. PMID:26741149

  19. Magnetic Au Nanoparticles on Archaeal S-Layer Ghosts as Templates

    Directory of Open Access Journals (Sweden)

    Sonja Selenska-Pobell

    2011-10-01

    Full Text Available Cell‐ghosts representing empty cells of the archaeon Sulfolobus acidocaldarius, consisting only of their highly ordered and unusually stable outermost proteinaceous surface layer (S‐layer, were used as templates for Au nanoparticles fabrication. The properties of these archaeal Au nanoparticles differ significantly from those produced earlier by us onto bacterial S‐layer sheets. The archaeal Au nanoparticles, with a size of about 2.5 nm, consist exclusively of metallic Au(0, while those produced on the bacterial S‐layer had a size of about 4 nm and represented a mixture of Au(0 and Au(III in the ratio of 40 to 60 %. The most impressive feature of the archaeal Au nanoparticles is that they are strongly paramagnetic, in contrast to the bacterial ones and also to bulk gold. SQUID magnetometry and XMCD measurements demonstrated that the archaeal Au nanoparticles possess a rather large magnetic moment of about 0.1 µB/atom. HR‐ TEM‐EDX analysis revealed that the archaeal Au nanoparticles are linked to the sulfur atoms of the thiol groups of the amino acid cysteine, characteristic only for archaeal S‐layers. This is the first study demonstrating the formation of such unusually strong magnetic Au nanoparticles on a non‐modified archaeal S‐layer.

  20. Defect characterization of Ga$_4$Se$_3$S layered single crystals by thermoluminescence

    Indian Academy of Sciences (India)

    Isik M; Delice S; Gasanly N

    2016-04-01

    Trapping centres in undoped Ga$_4$Se$_3$S single crystals grown by Bridgman method were characterized for the first time by thermoluminescence (TL) measurements carried out in the low temperature range of 15−300 K. After illuminating the sample with blue light (∼470 nm) at 15 K, TL glow curve exhibited one peak around 74 K when measured with a heating rate of 0.4 K/s.The results of the various analysis methods were in good agreement about the presence of one trapping centre with an activation energy of 27 meV. Analysis of curve fitting method indicated that mixed order of kinetics dominates the trapping process. Heating rate dependence and distribution of the traps associated with the observed TL peak were also studied. The shift of peak maximum temperature from 74 to 113 K with increasing rate from 0.4 to 1.2 K/s was revealed. Distribution of traps was investigated using an experimental technique based on cleaning the centres giving emission at lower temperatures. Activation energies of the levels were observed to be increasing from 27 to 40 meV by rising the stopping temperature from 15 to 36 K.

  1. Crystal growth, electrical and photophysical properties of Tl2S layered single crystals

    Indian Academy of Sciences (India)

    A M Badr; H A Elshaikh; I M Ashraf

    2009-05-01

    The Tl2S compound was prepared in a single crystal form using a special local technique, and the obtained crystals were analysed by X-ray diffraction. For the resultant crystals, the electrical properties (electrical conductivity and Hall effect) and steady-state photoconductivity were elucidated in this work. The electrical measurements extend from 170 to 430 K, where it was found that ⊥ = 8.82 × 10−5 Sm-1 when current flow direction makes right angle to the cleavage plane of the crystals. In the same range of temperatures, it was found that ∥ = 4.73 × 10−5 Sm-1 when the current flow is parallel to the cleavage plane. In line with the investigated range of temperatures, the widths of the band gaps were calculated and discussed as also the results of the electrical conductivity and Hall effect measurements. In addition, the anisotropy of the electrical conductivity (⊥/∥) for the obtained crystals was also studied in this work. Finally the photosensitivity was calculated for different levels of illumination as a result of the photoconductivity measurements, which showed that the recombination process in Tl2S single crystals is a monomolecular process.

  2. S-layer protein mediates the stimulatory effect of Lactobacillus helveticus MIMLh5 on innate immunity.

    Science.gov (United States)

    Taverniti, Valentina; Stuknyte, Milda; Minuzzo, Mario; Arioli, Stefania; De Noni, Ivano; Scabiosi, Christian; Cordova, Zuzet Martinez; Junttila, Ilkka; Hämäläinen, Sanna; Turpeinen, Hannu; Mora, Diego; Karp, Matti; Pesu, Marko; Guglielmetti, Simone

    2013-02-01

    The ability to positively affect host health through the modulation of the immune response is a feature of increasing importance in measuring the probiotic potential of a bacterial strain. However, the identities of the bacterial cell components involved in cross talk with immune cells remain elusive. In this study, we characterized the dairy strain Lactobacillus helveticus MIMLh5 and its surface-layer protein (SlpA) using in vitro and ex vivo analyses. We found that MIMLh5 and SlpA exert anti-inflammatory effects by reducing the activation of NF-κB on the intestinal epithelial Caco-2 cell line. On the contrary, MIMLh5 and SlpA act as stimulators of the innate immune system by triggering the expression of proinflammatory factors tumor necrosis factor alpha and COX-2 in the human macrophage cell line U937 via recognition through Toll-like receptor 2. In the same experiments, SlpA protein did not affect the expression of the anti-inflammatory cytokine interleukin-10. A similar response was observed following stimulation of macrophages isolated from mouse bone marrow or the peritoneal cavity. These results suggest that SlpA plays a major role in mediating bacterial immune-stimulating activity, which could help to induce the host's defenses against and responses toward infections. This study supports the concept that the viability of bacterial cells is not always essential to exert immunomodulatory effects, thus permitting the development of safer therapies for the treatment of specific diseases according to a paraprobiotic intervention. PMID:23220964

  3. Review of Information Authentication in Mobile Cloud over SaaS & PaaS Layers

    OpenAIRE

    Vineet Guha; Manish Shrivastava

    2013-01-01

    The Revolution has begun; time has come when we no more have to worry about the size, format & storage of data at a single place. Cloud computing is a revolution which has made world of internet more like a place of dynamic storage & facilitator of new methodology, which generates tools for consumers in a very effective style of computations. Cloud Computing has made lots of changes not only in infrastructure side, but has also deeply impacted the software industry. Many Companies, Institutio...

  4. Rapid pairing and resegregation of distant homologous loci enables double-strand break repair in bacteria.

    Science.gov (United States)

    Badrinarayanan, Anjana; Le, Tung B K; Laub, Michael T

    2015-08-01

    Double-strand breaks (DSBs) can lead to the loss of genetic information and cell death. Although DSB repair via homologous recombination has been well characterized, the spatial organization of this process inside cells remains poorly understood, and the mechanisms used for chromosome resegregation after repair are unclear. In this paper, we introduced site-specific DSBs in Caulobacter crescentus and then used time-lapse microscopy to visualize the ensuing chromosome dynamics. Damaged loci rapidly mobilized after a DSB, pairing with their homologous partner to enable repair, before being resegregated to their original cellular locations, independent of DNA replication. Origin-proximal regions were resegregated by the ParABS system with the ParA structure needed for resegregation assembling dynamically in response to the DSB-induced movement of an origin-associated ParB away from one cell pole. Origin-distal regions were resegregated in a ParABS-independent manner and instead likely rely on a physical, spring-like force to segregate repaired loci. Collectively, our results provide a mechanistic basis for the resegregation of chromosomes after a DSB. PMID:26240183

  5. Nutritional Control of DNA Replication Initiation through the Proteolysis and Regulated Translation of DnaA.

    Science.gov (United States)

    Leslie, David J; Heinen, Christian; Schramm, Frederic D; Thüring, Marietta; Aakre, Christopher D; Murray, Sean M; Laub, Michael T; Jonas, Kristina

    2015-07-01

    Bacteria can arrest their own growth and proliferation upon nutrient depletion and under various stressful conditions to ensure their survival. However, the molecular mechanisms responsible for suppressing growth and arresting the cell cycle under such conditions remain incompletely understood. Here, we identify post-transcriptional mechanisms that help enforce a cell-cycle arrest in Caulobacter crescentus following nutrient limitation and during entry into stationary phase by limiting the accumulation of DnaA, the conserved replication initiator protein. DnaA is rapidly degraded by the Lon protease following nutrient limitation. However, the rate of DnaA degradation is not significantly altered by changes in nutrient availability. Instead, we demonstrate that decreased nutrient availability downregulates dnaA translation by a mechanism involving the 5' untranslated leader region of the dnaA transcript; Lon-dependent proteolysis of DnaA then outpaces synthesis, leading to the elimination of DnaA and the arrest of DNA replication. Our results demonstrate how regulated translation and constitutive degradation provide cells a means of precisely and rapidly modulating the concentration of key regulatory proteins in response to environmental inputs. PMID:26134530

  6. The bacterial cell cycle regulator GcrA is a σ70 cofactor that drives gene expression from a subset of methylated promoters.

    Science.gov (United States)

    Haakonsen, Diane L; Yuan, Andy H; Laub, Michael T

    2015-11-01

    Cell cycle progression in most organisms requires tightly regulated programs of gene expression. The transcription factors involved typically stimulate gene expression by binding specific DNA sequences in promoters and recruiting RNA polymerase. Here, we found that the essential cell cycle regulator GcrA in Caulobacter crescentus activates the transcription of target genes in a fundamentally different manner. GcrA forms a stable complex with RNA polymerase and localizes to almost all active σ(70)-dependent promoters in vivo but activates transcription primarily at promoters harboring certain DNA methylation sites. Whereas most transcription factors that contact σ(70) interact with domain 4, GcrA interfaces with domain 2, the region that binds the -10 element during strand separation. Using kinetic analyses and a reconstituted in vitro transcription assay, we demonstrated that GcrA can stabilize RNA polymerase binding and directly stimulate open complex formation to activate transcription. Guided by these studies, we identified a regulon of ∼ 200 genes, providing new insight into the essential functions of GcrA. Collectively, our work reveals a new mechanism for transcriptional regulation, and we discuss the potential benefits of activating transcription by promoting RNA polymerase isomerization rather than recruitment exclusively. PMID:26545812

  7. Nutritional Control of DNA Replication Initiation through the Proteolysis and Regulated Translation of DnaA.

    Directory of Open Access Journals (Sweden)

    David J Leslie

    2015-07-01

    Full Text Available Bacteria can arrest their own growth and proliferation upon nutrient depletion and under various stressful conditions to ensure their survival. However, the molecular mechanisms responsible for suppressing growth and arresting the cell cycle under such conditions remain incompletely understood. Here, we identify post-transcriptional mechanisms that help enforce a cell-cycle arrest in Caulobacter crescentus following nutrient limitation and during entry into stationary phase by limiting the accumulation of DnaA, the conserved replication initiator protein. DnaA is rapidly degraded by the Lon protease following nutrient limitation. However, the rate of DnaA degradation is not significantly altered by changes in nutrient availability. Instead, we demonstrate that decreased nutrient availability downregulates dnaA translation by a mechanism involving the 5' untranslated leader region of the dnaA transcript; Lon-dependent proteolysis of DnaA then outpaces synthesis, leading to the elimination of DnaA and the arrest of DNA replication. Our results demonstrate how regulated translation and constitutive degradation provide cells a means of precisely and rapidly modulating the concentration of key regulatory proteins in response to environmental inputs.

  8. A bacterial toxin inhibits DNA replication elongation through a direct interaction with the β sliding clamp.

    Science.gov (United States)

    Aakre, Christopher D; Phung, Tuyen N; Huang, David; Laub, Michael T

    2013-12-12

    Toxin-antitoxin (TA) systems are ubiquitous on bacterial chromosomes, yet the mechanisms regulating their activity and the molecular targets of toxins remain incompletely defined. Here, we identify SocAB, an atypical TA system in Caulobacter crescentus. Unlike canonical TA systems, the toxin SocB is unstable and constitutively degraded by the protease ClpXP; this degradation requires the antitoxin, SocA, as a proteolytic adaptor. We find that the toxin, SocB, blocks replication elongation through an interaction with the sliding clamp, driving replication fork collapse. Mutations that suppress SocB toxicity map to either the hydrophobic cleft on the clamp that binds DNA polymerase III or a clamp-binding motif in SocB. Our findings suggest that SocB disrupts replication by outcompeting other clamp-binding proteins. Collectively, our results expand the diversity of mechanisms employed by TA systems to regulate toxin activity and inhibit bacterial growth, and they suggest that inhibiting clamp function may be a generalizable antibacterial strategy. PMID:24239291

  9. A cell cycle kinase with tandem sensory PAS domains integrates cell fate cues

    Science.gov (United States)

    Mann, Thomas H.; Seth Childers, W.; Blair, Jimmy A.; Eckart, Michael R.; Shapiro, Lucy

    2016-01-01

    All cells must integrate sensory information to coordinate developmental events in space and time. The bacterium Caulobacter crescentus uses two-component phospho-signalling to regulate spatially distinct cell cycle events through the master regulator CtrA. Here, we report that CckA, the histidine kinase upstream of CtrA, employs a tandem-PAS domain sensor to integrate two distinct spatiotemporal signals. Using CckA reconstituted on liposomes, we show that one PAS domain modulates kinase activity in a CckA density-dependent manner, mimicking the stimulation of CckA kinase activity that occurs on its transition from diffuse to densely packed at the cell poles. The second PAS domain interacts with the asymmetrically partitioned second messenger cyclic-di-GMP, inhibiting kinase activity while stimulating phosphatase activity, consistent with the selective inactivation of CtrA in the incipient stalked cell compartment. The integration of these spatially and temporally regulated signalling events within a single signalling receptor enables robust orchestration of cell-type-specific gene regulation. PMID:27117914

  10. The bacterial tubulin FtsZ requires its intrinsically disordered linker to direct robust cell wall construction.

    Science.gov (United States)

    Sundararajan, Kousik; Miguel, Amanda; Desmarais, Samantha M; Meier, Elizabeth L; Casey Huang, Kerwyn; Goley, Erin D

    2015-01-01

    The bacterial GTPase FtsZ forms a cytokinetic ring at midcell, recruits the division machinery and orchestrates membrane and peptidoglycan cell wall invagination. However, the mechanism for FtsZ regulation of peptidoglycan metabolism is unknown. The FtsZ GTPase domain is separated from its membrane-anchoring C-terminal conserved (CTC) peptide by a disordered C-terminal linker (CTL). Here we investigate CTL function in Caulobacter crescentus. Strikingly, production of FtsZ lacking the CTL (ΔCTL) is lethal: cells become filamentous, form envelope bulges and lyse, resembling treatment with β-lactam antibiotics. This phenotype is produced by FtsZ polymers bearing the CTC and a CTL shorter than 14 residues. Peptidoglycan synthesis still occurs downstream of ΔCTL; however, cells expressing ΔCTL exhibit reduced peptidoglycan crosslinking and longer glycan strands than wild type. Importantly, midcell proteins are still recruited to sites of ΔCTL assembly. We propose that FtsZ regulates peptidoglycan metabolism through a CTL-dependent mechanism that extends beyond simple protein recruitment. PMID:26099469

  11. Motility modes of the parasite Trypanosoma brucei

    Science.gov (United States)

    Temel, Fatma Zeynep; Qu, Zijie; McAllaster, Michael; de Graffenried, Christopher; Breuer, Kenneth

    2015-11-01

    The parasitic single-celled protozoan Trypanosoma brucei causes African Sleeping Sickness, which is a fatal disease in humans and animals that threatens more than 60 million people in 36 African countries. Cell motility plays a critical role in the developmental phases and dissemination of the parasite. Unlike many other motile cells such as bacteria Escherichia coli or Caulobacter crescentus, the flagellum of T. brucei is attached along the length of its awl-like body, producing a unique mode of motility that is not fully understood or characterized. Here, we report on the motility of T. brucei, which swims using its single flagellum employing both rotating and undulating propulsion modes. We tracked cells in real-time in three dimensions using fluorescent microscopy. Data obtained from experiments using both short-term tracking within the field of view and long-term tracking using a tracking microscope were analyzed. Motility modes and swimming speed were analyzed as functions of cell size, rotation rate and undulation pattern. Research supported by NSF.

  12. A cell cycle and nutritional checkpoint controlling bacterial surface adhesion.

    Directory of Open Access Journals (Sweden)

    Aretha Fiebig

    2014-01-01

    Full Text Available In natural environments, bacteria often adhere to surfaces where they form complex multicellular communities. Surface adherence is determined by the biochemical composition of the cell envelope. We describe a novel regulatory mechanism by which the bacterium, Caulobacter crescentus, integrates cell cycle and nutritional signals to control development of an adhesive envelope structure known as the holdfast. Specifically, we have discovered a 68-residue protein inhibitor of holdfast development (HfiA that directly targets a conserved glycolipid glycosyltransferase required for holdfast production (HfsJ. Multiple cell cycle regulators associate with the hfiA and hfsJ promoters and control their expression, temporally constraining holdfast development to the late stages of G1. HfiA further functions as part of a 'nutritional override' system that decouples holdfast development from the cell cycle in response to nutritional cues. This control mechanism can limit surface adhesion in nutritionally sub-optimal environments without affecting cell cycle progression. We conclude that post-translational regulation of cell envelope enzymes by small proteins like HfiA may provide a general means to modulate the surface properties of bacterial cells.

  13. Structure of a putative trans-editing enzyme for prolyl-tRNA synthetase from Aeropyrum pernix K1 at 1.7 Å resolution

    International Nuclear Information System (INIS)

    The three-dimensional structure of the APE2540 protein from A. pernix K1 has been determined by the multiple anomalous dispersion method at 1.7 Å resolution. The structure includes two monomers in the asymmetric unit and shares structural similarity with the YbaK protein or cysteinyl-tRNAPro deacylase from H. influenzae. The crystal structure of APE2540, the putative trans-editing enzyme ProX from Aeropyrum pernix K1, was determined in a high-throughput manner. The crystal belongs to the monoclinic space group P21, with unit-cell parameters a = 47.4, b = 58.9, c = 53.6 Å, β = 106.8°. The structure was solved by the multiwavelength anomalous dispersion method at 1.7 Å and refined to an R factor of 16.8% (Rfree = 20.5%). The crystal structure includes two protein molecules in the asymmetric unit. Each monomer consists of eight β-strands and seven α-helices. A structure-homology search revealed similarity between the trans-editing enzyme YbaK (or cysteinyl-tRNAPro deacylase) from Haemophilus influenzae (HI1434; 22% sequence identity) and putative ProX proteins from Caulobacter crescentus (16%) and Agrobacterium tumefaciens (21%)

  14. Dissection of recognition determinants of Escherichia coli sigma32 suggests a composite -10 region with an 'extended -10' motif and a core -10 element.

    Science.gov (United States)

    Koo, Byoung-Mo; Rhodius, Virgil A; Campbell, Elizabeth A; Gross, Carol A

    2009-05-01

    Sigma32 controls expression of heat shock genes in Escherichia coli and is widely distributed in proteobacteria. The distinguishing feature of sigma32 promoters is a long -10 region (CCCCATNT) whose tetra-C motif is important for promoter activity. Using alanine-scanning mutagenesis of sigma32 and in vivo and in vitro assays, we identified promoter recognition determinants of this motif. The most downstream C (-13) is part of the -10 motif; our work confirms and extends recognition determinants of -13C. Most importantly, our work suggests that the two upstream Cs (-16, -15) constitute an 'extended -10' recognition motif that is recognized by K130, a residue universally conserved in beta- and gamma-proteobacteria. This residue is located in the alpha-helix of sigmaDomain 3 that mediates recognition of the extended -10 promoter motif in other sigmas. K130 is not conserved in alpha- and delta-/epsilon-proteobacteria and we found that sigma32 from the alpha-proteobacterium Caulobacter crescentus does not need the extended -10 motif for high promoter activity. This result supports the idea that K130 mediates extended -10 recognition. Sigma32 is the first Group 3 sigma shown to use the 'extended -10' recognition motif. PMID:19400791

  15. A novel roseobacter phage possesses features of podoviruses, siphoviruses, prophages and gene transfer agents

    Science.gov (United States)

    Zhan, Yuanchao; Huang, Sijun; Voget, Sonja; Simon, Meinhard; Chen, Feng

    2016-07-01

    Bacteria in the Roseobacter lineage have been studied extensively due to their significant biogeochemical roles in the marine ecosystem. However, our knowledge on bacteriophage which infects the Roseobacter clade is still very limited. Here, we report a new bacteriophage, phage DSS3Φ8, which infects marine roseobacter Ruegeria pomeroyi DSS-3. DSS3Φ8 is a lytic siphovirus. Genomic analysis showed that DSS3Φ8 is most closely related to a group of siphoviruses, CbK-like phages, which infect freshwater bacterium Caulobacter crescentus. DSS3Φ8 contains a smaller capsid and has a reduced genome size (146 kb) compared to the CbK-like phages (205–279 kb). DSS3Φ8 contains the DNA polymerase gene which is closely related to T7-like podoviruses. DSS3Φ8 also contains the integrase and repressor genes, indicating its potential to involve in lysogenic cycle. In addition, four GTA (gene transfer agent) genes were identified in the DSS3Φ8 genome. Genomic analysis suggests that DSS3Φ8 is a highly mosaic phage that inherits the genetic features from siphoviruses, podoviruses, prophages and GTAs. This is the first report of CbK-like phages infecting marine bacteria. We believe phage isolation is still a powerful tool that can lead to discovery of new phages and help interpret the overwhelming unknown sequences in the viral metagenomics.

  16. A cell cycle kinase with tandem sensory PAS domains integrates cell fate cues.

    Science.gov (United States)

    Mann, Thomas H; Seth Childers, W; Blair, Jimmy A; Eckart, Michael R; Shapiro, Lucy

    2016-01-01

    All cells must integrate sensory information to coordinate developmental events in space and time. The bacterium Caulobacter crescentus uses two-component phospho-signalling to regulate spatially distinct cell cycle events through the master regulator CtrA. Here, we report that CckA, the histidine kinase upstream of CtrA, employs a tandem-PAS domain sensor to integrate two distinct spatiotemporal signals. Using CckA reconstituted on liposomes, we show that one PAS domain modulates kinase activity in a CckA density-dependent manner, mimicking the stimulation of CckA kinase activity that occurs on its transition from diffuse to densely packed at the cell poles. The second PAS domain interacts with the asymmetrically partitioned second messenger cyclic-di-GMP, inhibiting kinase activity while stimulating phosphatase activity, consistent with the selective inactivation of CtrA in the incipient stalked cell compartment. The integration of these spatially and temporally regulated signalling events within a single signalling receptor enables robust orchestration of cell-type-specific gene regulation. PMID:27117914

  17. Filament depolymerization can pull a chromosome during bacterial mitosis

    Science.gov (United States)

    Banigan, Edward; Gelbart, Michael; Gitai, Zemer; Liu, Andrea; Wingreen, Ned

    2011-03-01

    Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole and binds to a ParB-decorated chromosome, and then retracts via disassembly, thus pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that is disassembling it. We perform Brownian dynamics simulations with a simple and physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is ``self-diffusiophoretic'': by disassembling ParA, ParB generates a ParA concentration gradient so that the concentration of ParA is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is controlled by the product of an effective relaxation time for the chromosome and the rate of ParA disassembly. Our results provide a physical explanation of the mechanism of depolymerization-driven translocation and suggest physical explanations for recent experimental observations.

  18. Structure of the Bacterial Cytoskeleton Protein Bactofilin by NMR Chemical Shifts and Sequence Variation.

    Science.gov (United States)

    Kassem, Maher M; Wang, Yong; Boomsma, Wouter; Lindorff-Larsen, Kresten

    2016-06-01

    Bactofilins constitute a recently discovered class of bacterial proteins that form cytoskeletal filaments. They share a highly conserved domain (DUF583) of which the structure remains unknown, in part due to the large size and noncrystalline nature of the filaments. Here, we describe the atomic structure of a bactofilin domain from Caulobacter crescentus. To determine the structure, we developed an approach that combines a biophysical model for proteins with recently obtained solid-state NMR spectroscopy data and amino acid contacts predicted from a detailed analysis of the evolutionary history of bactofilins. Our structure reveals a triangular β-helical (solenoid) conformation with conserved residues forming the tightly packed core and polar residues lining the surface. The repetitive structure explains the presence of internal repeats as well as strongly conserved positions, and is reminiscent of other fibrillar proteins. Our work provides a structural basis for future studies of bactofilin biology and for designing molecules that target them, as well as a starting point for determining the organization of the entire bactofilin filament. Finally, our approach presents new avenues for determining structures that are difficult to obtain by traditional means. PMID:27276252

  19. Scaling laws governing stochastic growth and division of single bacterial cells.

    Science.gov (United States)

    Iyer-Biswas, Srividya; Wright, Charles S; Henry, Jonathan T; Lo, Klevin; Burov, Stanislav; Lin, Yihan; Crooks, Gavin E; Crosson, Sean; Dinner, Aaron R; Scherer, Norbert F

    2014-11-11

    Uncovering the quantitative laws that govern the growth and division of single cells remains a major challenge. Using a unique combination of technologies that yields unprecedented statistical precision, we find that the sizes of individual Caulobacter crescentus cells increase exponentially in time. We also establish that they divide upon reaching a critical multiple (≈ 1.8) of their initial sizes, rather than an absolute size. We show that when the temperature is varied, the growth and division timescales scale proportionally with each other over the physiological temperature range. Strikingly, the cell-size and division-time distributions can both be rescaled by their mean values such that the condition-specific distributions collapse to universal curves. We account for these observations with a minimal stochastic model that is based on an autocatalytic cycle. It predicts the scalings, as well as specific functional forms for the universal curves. Our experimental and theoretical analysis reveals a simple physical principle governing these complex biological processes: a single temperature-dependent scale of cellular time governs the stochastic dynamics of growth and division in balanced growth conditions. PMID:25349411

  20. AcEST: DK953058 [AcEST

    Lifescience Database Archive (English)

    Full Text Available orin OS=Homo sapiens GN=DCN PE=1 SV=1 31 4.6 sp|Q97CK6|COMB_THEVO Probable 2-phosphosulfolactate phosphatase... 318 >sp|Q97CK6|COMB_THEVO Probable 2-phosphosulfolactate phosphatase OS=Thermoplasma volcanium GN=comB PE=3...rized protein OS=Strep... 39 0.20 tr|B4D4G1|B4D4G1_9BACT Beta-lactamase OS=Chthoniobacte...rase OS=Streptomyces pristinaespirali... 37 1.3 tr|A7CQJ3|A7CQJ3_9BACT Beta-lactamase OS=Opitutaceae bacte...in OS=Crypt... 35 2.9 tr|Q9ABH2|Q9ABH2_CAUCR Esterase A OS=Caulobacter crescentus GN=C... 35 3.7 tr|B2ULQ7|B2ULQ7_AKKM8 Beta-lact

  1. A novel roseobacter phage possesses features of podoviruses, siphoviruses, prophages and gene transfer agents.

    Science.gov (United States)

    Zhan, Yuanchao; Huang, Sijun; Voget, Sonja; Simon, Meinhard; Chen, Feng

    2016-01-01

    Bacteria in the Roseobacter lineage have been studied extensively due to their significant biogeochemical roles in the marine ecosystem. However, our knowledge on bacteriophage which infects the Roseobacter clade is still very limited. Here, we report a new bacteriophage, phage DSS3Φ8, which infects marine roseobacter Ruegeria pomeroyi DSS-3. DSS3Φ8 is a lytic siphovirus. Genomic analysis showed that DSS3Φ8 is most closely related to a group of siphoviruses, CbK-like phages, which infect freshwater bacterium Caulobacter crescentus. DSS3Φ8 contains a smaller capsid and has a reduced genome size (146 kb) compared to the CbK-like phages (205-279 kb). DSS3Φ8 contains the DNA polymerase gene which is closely related to T7-like podoviruses. DSS3Φ8 also contains the integrase and repressor genes, indicating its potential to involve in lysogenic cycle. In addition, four GTA (gene transfer agent) genes were identified in the DSS3Φ8 genome. Genomic analysis suggests that DSS3Φ8 is a highly mosaic phage that inherits the genetic features from siphoviruses, podoviruses, prophages and GTAs. This is the first report of CbK-like phages infecting marine bacteria. We believe phage isolation is still a powerful tool that can lead to discovery of new phages and help interpret the overwhelming unknown sequences in the viral metagenomics. PMID:27460944

  2. Characterization of porcine-specific surface (S-) layer protein carrying Lactobacillus species, S-layer proteins and the adhesin of Escherichia coli F18 fimbriae : Potential applications for veterinary medicine

    OpenAIRE

    Jakava-Viljanen, Miia

    2007-01-01

    Lactobacilli, common members of porcine intestinal microbiota, have been considered to be an important group of bacteria in maintaining the stability of gastrointestinal tract (GIT), preventing intestinal infections and supporting intestinal health. Because several species of lactobacilli have GRAS (generally regarded as safe) status and some of them have an ability to interact with intestinal epithelial cells, their possible applications as mucosal vaccine vector and/or probiotics have arous...

  3. Fast and easy protocol for the purification of recombinant S-layer protein for synthetic biology applications

    KAUST Repository

    Norville, Julie E.

    2011-06-17

    A goal of synthetic biology is to make biological systems easier to engineer. One of the aims is to design, with nanometer-scale precision, biomaterials with well-defined properties. The surface-layer protein SbpA forms 2D arrays naturally on the cell surface of Lysinibacillus sphaericus, but also as the purified protein in solution upon the addition of divalent cations. The high propensity of SbpA to form crystalline arrays, which can be simply controlled by divalent cations, and the possibility to genetically alter the protein, make SbpA an attractive molecule for synthetic biology. To be a useful tool, however, it is important that a simple protocol can be used to produce recombinant wild-type and modified SbpA in large quantities and in a biologically active form. The present study addresses this requirement by introducing a mild and non-denaturing purification protocol to produce milligram quantities of recombinant, active SbpA.

  4. Two-component signal transduction pathways regulating growth and cell cycle progression in a bacterium: a system-level analysis.

    Directory of Open Access Journals (Sweden)

    Jeffrey M Skerker

    2005-10-01

    Full Text Available Two-component signal transduction systems, comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals. These systems allow cells to adapt to prevailing conditions by modifying cellular physiology, including initiating programs of gene expression, catalyzing reactions, or modifying protein-protein interactions. These signaling pathways have also been demonstrated to play a role in coordinating bacterial cell cycle progression and development. Here we report a system-level investigation of two-component pathways in the model organism Caulobacter crescentus. First, by a comprehensive deletion analysis we show that at least 39 of the 106 two-component genes are required for cell cycle progression, growth, or morphogenesis. These include nine genes essential for growth or viability of the organism. We then use a systematic biochemical approach, called phosphotransfer profiling, to map the connectivity of histidine kinases and response regulators. Combining these genetic and biochemical approaches, we identify a new, highly conserved essential signaling pathway from the histidine kinase CenK to the response regulator CenR, which plays a critical role in controlling cell envelope biogenesis and structure. Depletion of either cenK or cenR leads to an unusual, severe blebbing of cell envelope material, whereas constitutive activation of the pathway compromises cell envelope integrity, resulting in cell lysis and death. We propose that the CenK-CenR pathway may be a suitable target for new antibiotic development, given previous successes in targeting the bacterial cell wall. Finally, the ability of our in vitro phosphotransfer profiling method to identify signaling pathways that operate in vivo takes advantage of an observation that histidine kinases are endowed with a global kinetic preference for their cognate response regulators. We propose that this

  5. Filament depolymerization can explain chromosome pulling during bacterial mitosis.

    Directory of Open Access Journals (Sweden)

    Edward J Banigan

    2011-09-01

    Full Text Available Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole, binds to a ParB-decorated chromosome, and then retracts via disassembly, pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that disassembles it. We perform Brownian dynamics simulations with a simple, physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is "self-diffusiophoretic": by disassembling ParA, ParB generates a ParA concentration gradient so that the ParA concentration is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is most robust when ParB binds side-on to ParA filaments. In this case, robust translocation occurs over a wide parameter range and is controlled by a single dimensionless quantity: the product of the rate of ParA disassembly and a characteristic relaxation time of the chromosome. This time scale measures the time it takes for the chromosome to recover its average shape after it is has been pulled. Our results suggest explanations for observed phenomena such as segregation failure, filament-length-dependent translocation velocity, and chromosomal compaction.

  6. Elucidation of a novel lipid A α-(1,1)-GalA transferase gene (rgtF) from Mesorhizobium loti: Heterologous expression of rgtF causes Rhizobium etli to synthesize lipid A with α-(1,1)-GalA.

    Science.gov (United States)

    Brown, Dusty B; Muszynski, Artur; Carlson, Russell W

    2013-05-01

    An unusual α-(1,1)-galacturonic acid (GalA) lipid A modification has been reported in the lipopolysaccharide of a number of interesting Gram-negative bacteria, including the nitrogen-fixing bacteria Azospirillum lipoferum, Mesorhizobium huakuii and M. loti, the stalk-forming bacterium Caulobacter crescentus and the hyperthermophilic bacterium Aquifex aeolicus. However, the α-(1,1)-GalA transferase (GalAT) gene, which we have named RgtF, was not identified. Species of the Rhizobium genera produce lipid A with α-(1,4')-GalA but not α-(1,1)-GalA. The Rhizobium GalAT, RgtD, is the lipid A α-(1-4')-GalAT which utilizes the lipid donor dodecaprenyl-phosphate GalA (Dod-P-GalA) for GalA transfer. An additional Rhizobium GalAT, RgtE, is required for the biosynthesis of Dod-P-GalA. We predicted candidate rgtF genes in bacterial species known to produce lipid A with α-(1,1)-GalA. In order to determine the predicted rgtF gene function, we cloned the M. loti rgtF gene into an expression plasmid and introduced that plasmid into Rhizobium etli strains that do not contain the rgtF gene nor produce lipid A α-(1,1)-GalA. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis combined with NMR studies revealed that the lipid As from these rgtF-complemented strains were modified with an additional α-(1,1)-GalA attached to the proximal glucosamine. PMID:23283001

  7. Enhancement of flagellated bacterial motility in polymer solutions

    Science.gov (United States)

    Zhang, Wenyu; Sha, Sha; Pelcovits, Robert; Tang, Jay

    2015-11-01

    Measurements of the swimming speed of many species of flagellated bacteria in polymer solutions have shown that with the addition of high molecular weight polymers, the speed initially increases as a function of the kinematic viscosity. It peaks at around 1.5-2 cP with typically 10-30% higher values than in cell media without added polymers (~ 1 cP). Past the peak, the average speed gradually decreases as the solution becomes more viscous. Swimming motility persists until solution viscosity reaches 5-10 cP. Models have been proposed to account for this behavior, and the magnitude of the peak becomes a crucial test of theoretical predictions. The status of the field is complicated in light of a recent report (Martinez et al., PNAS, 2014), stressing that low-molecular weight impurities account for the peaked speed-viscosity curves in some cases. We measured the swimming speed of a uni-flagellated bacterium, caulobacter crescentus, in solutions of a number of polymers of several different sizes. Our findings confirm the peaked speed-viscosity curve, only as the molecular weight of the flexible polymers used surpassed ~ 50,000 da. The threshold molecular weight required to augment swimming speed varies somewhat with the polymer species, but it generally corresponds to radius of gyration over tens of nanometers. This general feature is consistent with the model of Powers et al. (Physics of Fluid, 2009), predicting that nonlinear viscoelasticity of the fluid enhances swimming motility. Work Supported by the NSF Fluid Physics Program (Award number CBET 1438033).

  8. ParABS system in chromosome partitioning in the bacterium Myxococcus xanthus.

    Directory of Open Access Journals (Sweden)

    Antonio A Iniesta

    Full Text Available Chromosome segregation is an essential cellular function in eukaryotic and prokaryotic cells. The ParABS system is a fundamental player for a mitosis-like process in chromosome partitioning in many bacterial species. This work shows that the social bacterium Myxococcus xanthus also uses the ParABS system for chromosome segregation. Its large prokaryotic genome of 9.1 Mb contains 22 parS sequences near the origin of replication, and it is shown here that M. xanthus ParB binds preferentially to a consensus parS sequence in vitro. ParB and ParA are essential for cell viability in M. xanthus as in Caulobacter crescentus, but unlike in many other bacteria. Absence of ParB results in anucleate cells, chromosome segregation defects and loss of viability. Analysis of ParA subcellular localization shows that it clusters at the poles in all cells, and in some, in the DNA-free cell division plane between two chromosomal DNA masses. This ParA localization pattern depends on ParB but not on FtsZ. ParB inhibits the nonspecific interaction of ParA with DNA, and ParA colocalizes with chromosomal DNA only when ParB is depleted. The subcellular localization of ParB suggests a single ParB-parS complex localized at the edge of the nucleoid, next to a polar ParA cluster, with a second ParB-parS complex migrating after the replication of parS takes place to the opposite nucleoid edge, next to the other polar ParA cluster.

  9. Functional Identification of Incorrectly Annotated Prolidases from the Amidohydrolase Superfamily of Enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.; Patskovsky, Y; Xu, C; Meyer, A; Sauder, J; Burley, S; Almo, S; Raushel, F

    2009-01-01

    The substrate profiles for two proteins from Caulobacter crescentus CB15 (Cc2672 and Cc3125) and one protein (Sgx9359b) derived from a DNA sequence (gi|44368820) isolated from the Sargasso Sea were determined using combinatorial libraries of dipeptides and N-acyl derivatives of amino acids. These proteins are members of the amidohydrolase superfamily and are currently misannotated in NCBI as catalyzing the hydrolysis of l-Xaa-l-Pro dipeptides. Cc2672 was shown to catalyze the hydrolysis of l-Xaa-l-Arg/Lys dipeptides and the N-acetyl and N-formyl derivatives of lysine and arginine. This enzyme will also hydrolyze longer peptides that terminate in either lysine or arginine. The N-methyl phosphonate derivative of l-lysine was a potent competitive inhibitor of Cc2672 with a Ki value of 120 nM. Cc3125 was shown to catalyze the hydrolysis of l-Xaa-l-Arg/Lys dipeptides but will not hydrolyze tripeptides or the N-formyl and N-acetyl derivatives of lysine or arginine. The substrate profile for Sgx9359b is similar to that of Cc2672 except that compounds with a C-terminal lysine are not recognized as substrates. The X-ray structure of Sgx9359b was determined to a resolution of 2.3 Angstroms. The protein folds as a (e/a)8-barrel and self-associates to form a homooctamer. The active site is composed of a binuclear metal center similar to that found in phosphotriesterase and dihydroorotase. In one crystal form, arginine was bound adventitiously to the eight active sites within the octamer. The orientation of the arginine in the active site identified the structural determinants for recognition of the a-carboxylate and the positively charged side chains of arginine-containing substrates. This information was used to identify 18 other bacterial sequences that possess identical or similar substrate profiles.

  10. Accommodation of GDP-Linked Sugars in the Active Site of GDP-Perosamine Synthase

    Energy Technology Data Exchange (ETDEWEB)

    Cook, Paul D.; Carney, Amanda E.; Holden, Hazel M. (UW)

    2009-01-12

    Perosamine (4-amino-4,6-dideoxy-d-mannose), or its N-acetylated form, is one of several dideoxy sugars found in the O-antigens of such infamous Gram-negative bacteria as Vibrio cholerae O1 and Escherichia coli O157:H7. It is added to the bacterial O-antigen via a nucleotide-linked version, namely GDP-perosamine. Three enzymes are required for the biosynthesis of GDP-perosamine starting from mannose 1-phosphate. The focus of this investigation is GDP-perosamine synthase from Caulobacter crescentus, which catalyzes the final step in GDP-perosamine synthesis, the conversion of GDP-4-keto-6-deoxymannose to GDP-perosamine. The enzyme is PLP-dependent and belongs to the aspartate aminotransferase superfamily. It contains the typically conserved active site lysine residue, which forms a Schiff base with the PLP cofactor. Two crystal structures were determined for this investigation: a site-directed mutant protein (K186A) complexed with GDP-perosamine and the wild-type enzyme complexed with an unnatural ligand, GDP-3-deoxyperosamine. These structures, determined to 1.6 and 1.7 {angstrom} resolution, respectively, revealed the manner in which products, and presumably substrates, are accommodated within the active site pocket of GDP-perosamine synthase. Additional kinetic analyses using both the natural and unnatural substrates revealed that the K{sub m} for the unnatural substrate was unperturbed relative to that of the natural substrate, but the k{sub cat} was lowered by a factor of approximately 200. Taken together, these studies shed light on why GDP-perosamine synthase functions as an aminotransferase whereas another very similar PLP-dependent enzyme, GDP-4-keto-6-deoxy-d-mannose 3-dehydratase or ColD, catalyzes a dehydration reaction using the same substrate.

  11. Catalytic Mechanism of Perosamine N-Acetyltransferase Revealed by High-Resolution X-ray Crystallographic Studies and Kinetic Analyses

    Energy Technology Data Exchange (ETDEWEB)

    Thoden, James B.; Reinhardt, Laurie A.; Cook, Paul D.; Menden, Patrick; Cleland, W.W.; Holden, Hazel M. (UW); (Mount Union); (UW-MED)

    2012-09-17

    N-Acetylperosamine is an unusual dideoxysugar found in the O-antigens of some Gram-negative bacteria, including the pathogenic Escherichia coli strain O157:H7. The last step in its biosynthesis is catalyzed by PerB, an N-acetyltransferase belonging to the left-handed {beta}-helix superfamily of proteins. Here we describe a combined structural and functional investigation of PerB from Caulobacter crescentus. For this study, three structures were determined to 1.0 {angstrom} resolution or better: the enzyme in complex with CoA and GDP-perosamine, the protein with bound CoA and GDP-N-acetylperosamine, and the enzyme containing a tetrahedral transition state mimic bound in the active site. Each subunit of the trimeric enzyme folds into two distinct regions. The N-terminal domain is globular and dominated by a six-stranded mainly parallel {beta}-sheet. It provides most of the interactions between the protein and GDP-perosamine. The C-terminal domain consists of a left-handed {beta}-helix, which has nearly seven turns. This region provides the scaffold for CoA binding. On the basis of these high-resolution structures, site-directed mutant proteins were constructed to test the roles of His 141 and Asp 142 in the catalytic mechanism. Kinetic data and pH-rate profiles are indicative of His 141 serving as a general base. In addition, the backbone amide group of Gly 159 provides an oxyanion hole for stabilization of the tetrahedral transition state. The pH-rate profiles are also consistent with the GDP-linked amino sugar substrate entering the active site in its unprotonated form. Finally, for this investigation, we show that PerB can accept GDP-3-deoxyperosamine as an alternative substrate, thus representing the production of a novel trideoxysugar.

  12. An Analysis of the Solution Structure and Signaling Mechanism of LovK, a Sensor Histidine Kinase Integrating Light and Redox Signals

    International Nuclear Information System (INIS)

    Flavin-binding LOV domains are broadly conserved in plants, fungi, archaea, and bacteria. These ∼100-residue photosensory modules are generally encoded within larger, multidomain proteins that control a range of blue light-dependent physiologies. The bacterium Caulobacter crescentus encodes a soluble LOV-histidine kinase, LovK, that regulates the adhesive properties of the cell. Full-length LovK is dimeric as are a series of systematically truncated LovK constructs containing only the N-terminal LOV sensory domain. Nonconserved sequence flanking the LOV domain functions to tune the signaling lifetime of the protein. Size exclusion chromatography and small-angle X-ray scattering (SAXS) demonstrate that the LOV sensor domain does not undergo a large conformational change in response to photon absorption. However, limited proteolysis identifies a sequence flanking the C-terminus of the LOV domain as a site of light-induced change in protein conformation and dynamics. On the basis of SAXS envelope reconstruction and bioinformatic prediction, we propose this dynamic region of structure is an extended C-terminal coiled coil that links the LOV domain to the histidine kinase domain. To test the hypothesis that LOV domain signaling is affected by cellular redox state in addition to light, we measured the reduction potential of the LovK FMN cofactor. The measured potential of -258 mV is congruent with the redox potential of Gram-negative cytoplasm during logarithmic growth (-260 to -280 mV). Thus, a fraction of LovK in the cytosol may be in the reduced state under typical growth conditions. Chemical reduction of the FMN cofactor of LovK attenuates the light-dependent ATPase activity of the protein in vitro, demonstrating that LovK can function as a conditional photosensor that is regulated by the oxidative state of the cellular environment.

  13. Comparative 3-D Modeling of tmRNA

    Directory of Open Access Journals (Sweden)

    Wower Iwona

    2005-06-01

    Full Text Available Abstract Background Trans-translation releases stalled ribosomes from truncated mRNAs and tags defective proteins for proteolytic degradation using transfer-messenger RNA (tmRNA. This small stable RNA represents a hybrid of tRNA- and mRNA-like domains connected by a variable number of pseudoknots. Comparative sequence analysis of tmRNAs found in bacteria, plastids, and mitochondria provides considerable insights into their secondary structures. Progress toward understanding the molecular mechanism of template switching, which constitutes an essential step in trans-translation, is hampered by our limited knowledge about the three-dimensional folding of tmRNA. Results To facilitate experimental testing of the molecular intricacies of trans-translation, which often require appropriately modified tmRNA derivatives, we developed a procedure for building three-dimensional models of tmRNA. Using comparative sequence analysis, phylogenetically-supported 2-D structures were obtained to serve as input for the program ERNA-3D. Motifs containing loops and turns were extracted from the known structures of other RNAs and used to improve the tmRNA models. Biologically feasible 3-D models for the entire tmRNA molecule could be obtained. The models were characterized by a functionally significant close proximity between the tRNA-like domain and the resume codon. Potential conformational changes which might lead to a more open structure of tmRNA upon binding to the ribosome are discussed. The method, described in detail for the tmRNAs of Escherichia coli, Bacillus anthracis, and Caulobacter crescentus, is applicable to every tmRNA. Conclusion Improved molecular models of biological significance were obtained. These models will guide in the design of experiments and provide a better understanding of trans-translation. The comparative procedure described here for tmRNA is easily adopted for the modeling the members of other RNA families.

  14. Study of Class I and Class III Polyhydroxyalkanoate (PHA) Synthases with Substrates Containing a Modified Side Chain.

    Science.gov (United States)

    Jia, Kaimin; Cao, Ruikai; Hua, Duy H; Li, Ping

    2016-04-11

    Polyhydroxyalkanoates (PHAs) are carbon and energy storage polymers produced by a variety of microbial organisms under nutrient-limited conditions. They have been considered as an environmentally friendly alternative to oil-based plastics due to their renewability, versatility, and biodegradability. PHA synthase (PhaC) plays a central role in PHA biosynthesis, in which its activity and substrate specificity are major factors in determining the productivity and properties of the produced polymers. However, the effects of modifying the substrate side chain are not well understood because of the difficulty to accessing the desired analogues. In this report, a series of 3-(R)-hydroxyacyl coenzyme A (HACoA) analogues were synthesized and tested with class I synthases from Chromobacterium sp. USM2 (PhaCCs and A479S-PhaCCs) and Caulobacter crescentus (PhaCCc) as well as class III synthase from Allochromatium vinosum (PhaECAv). It was found that, while different PHA synthases displayed distinct preference with regard to the length of the alkyl side chains, they could withstand moderate side chain modifications such as terminal unsaturated bonds and the azide group. Specifically, the specific activity of PhaCCs toward propynyl analogue (HHxyCoA) was only 5-fold less than that toward the classical substrate HBCoA. The catalytic efficiency (kcat/Km) of PhaECAv toward azide analogue (HABCoA) was determined to be 2.86 × 10(5) M(-1) s(-1), which was 6.2% of the value of HBCoA (4.62 × 10(6) M(-1) s(-1)) measured in the presence of bovine serum albumin (BSA). These side chain modifications may be employed to introduce new material functions to PHAs as well as to study PHA biogenesis via click-chemistry, in which the latter remains unknown and is important for metabolic engineering to produce PHAs economically. PMID:26974339

  15. Disease: H01148 [KEGG MEDICUS

    Lifescience Database Archive (English)

    Full Text Available H01148 Caulobacter infection The genus Caulobacter includes gram-negative bacteria characterized ... minoglycosides, tetracycline, chloramphenicol, and sulfadiazine . PMID:17267638 Justesen US, Holt HM, Thiesson HC, ...

  16. Preschool Facilities, City of Hutchinson polygon school(s) layer, Published in 2003, 1:600 (1in=50ft) scale, City of Hutchinson.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Preschool Facilities dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from Orthoimagery information as of 2003. It is described as...

  17. Functional Annotation of Two New Carboxypeptidases from the Amidohydrolase Superfamily of Enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.; Xu, C; Kumaran, D; Brown, A; Sauder, M; Burley, S; Swaminathan, S; Raushel, F

    2009-01-01

    Two proteins from the amidohydrolase superfamily of enzymes were cloned, expressed, and purified to homogeneity. The first protein, Cc0300, was from Caulobacter crescentus CB-15 (Cc0300), while the second one (Sgx9355e) was derived from an environmental DNA sequence originally isolated from the Sargasso Sea (gi|44371129). The catalytic functions and the substrate profiles for the two enzymes were determined with the aid of combinatorial dipeptide libraries. Both enzymes were shown to catalyze the hydrolysis of l-Xaa-l-Xaa dipeptides in which the amino acid at the N-terminus was relatively unimportant. These enzymes were specific for hydrophobic amino acids at the C-terminus. With Cc0300, substrates terminating in isoleucine, leucine, phenylalanine, tyrosine, valine, methionine, and tryptophan were hydrolyzed. The same specificity was observed with Sgx9355e, but this protein was also able to hydrolyze peptides terminating in threonine. Both enzymes were able to hydrolyze N-acetyl and N-formyl derivatives of the hydrophobic amino acids and tripeptides. The best substrates identified for Cc0300 were l-Ala-l-Leu with kcat and kcat/Km values of 37 s-1 and 1.1 x 105 M-1 s-1, respectively, and N-formyl-l-Tyr with kcat and kcat/Km values of 33 s-1 and 3.9 x 105 M-1 s-1, respectively. The best substrate identified for Sgx9355e was l-Ala-l-Phe with kcat and kcat/Km values of 0.41 s-1 and 5.8 x 103 M-1 s-1. The three-dimensional structure of Sgx9355e was determined to a resolution of 2.33 Angstroms with l-methionine bound in the active site. The a-carboxylate of the methionine is ion-paired to His-237 and also hydrogen bonded to the backbone amide groups of Val-201 and Leu-202. The a-amino group of the bound methionine interacts with Asp-328. The structural determinants for substrate recognition were identified and compared with other enzymes in this superfamily that hydrolyze dipeptides with different specificities.

  18. [Transgenic bioinsecticides inimical to parasites, but imical to environment].

    Science.gov (United States)

    Kucińska, Jolanta; Lonc, Elzbieta; Rydzanicz, Katarzyna

    2003-01-01

    Culex and Anopheles, and Bti--mostly to Culex, Aedes and some Simmulidae. Gram-negative bacteria (Asticcacaulis excentricus, Caulobacter crescentus and Ancylobacter aquaticus) turned out also to be effective delta-endotoxin producers. They grow on simple media and do not contain proteases which could degrade Cry proteins. In some cases, 100% mosquito larvae mortality was observed as a result of an exposure to transgenic microorganisms containing Bti genes. However, transgenic techniques are still not very popular in the world, despite their efficacy in biological control of insects. The transgenic organism construction is expensive and time-consuming. Genetic engineering is still raising a lot of anxieties and doubts concerning inappropriate use of modified organisms. On the other hand, this technology could solve many problems associated with vectors of important diseases, which are still unapproachable to contemporary medicine. PMID:16889013

  19. The biology of habitat dominance; can microbes behave as weeds?

    Science.gov (United States)

    Cray, Jonathan A; Bell, Andrew N W; Bhaganna, Prashanth; Mswaka, Allen Y; Timson, David J; Hallsworth, John E

    2013-09-01

    , such as Escherichia coli, Mycobacterium smegmatis and Pseudoxylaria spp., exhibit characteristics of both weed and non-weed species. We propose that the concept of nonweeds represents a 'dustbin' group that includes species such as Synodropsis spp., Polypaecilum pisce, Metschnikowia orientalis, Salmonella spp., and Caulobacter crescentus. We show that microbial weeds are conceptually distinct from plant weeds, microbial copiotrophs, r-strategists, and other ecophysiological groups of microorganism. Microbial weed species are unlikely to emerge from stationary-phase or other types of closed communities; it is open habitats that select for weed phenotypes. Specific characteristics that are common to diverse types of open habitat are identified, and implications of weed biology and open-habitat ecology are discussed in the context of further studies needed in the fields of environmental and applied microbiology. PMID:23336673

  20. Phylogenomics and signature proteins for the alpha Proteobacteria and its main groups

    Directory of Open Access Journals (Sweden)

    Mok Amy

    2007-11-01

    Full Text Available Abstract Background Alpha proteobacteria are one of the largest and most extensively studied groups within bacteria. However, for these bacteria as a whole and for all of its major subgroups (viz. Rhizobiales, Rhodobacterales, Rhodospirillales, Rickettsiales, Sphingomonadales and Caulobacterales, very few or no distinctive molecular or biochemical characteristics are known. Results We have carried out comprehensive phylogenomic analyses by means of Blastp and PSI-Blast searches on the open reading frames in the genomes of several α-proteobacteria (viz. Bradyrhizobium japonicum, Brucella suis, Caulobacter crescentus, Gluconobacter oxydans, Mesorhizobium loti, Nitrobacter winogradskyi, Novosphingobium aromaticivorans, Rhodobacter sphaeroides 2.4.1, Silicibacter sp. TM1040, Rhodospirillum rubrum and Wolbachia (Drosophila endosymbiont. These studies have identified several proteins that are distinctive characteristics of all α-proteobacteria, as well as numerous proteins that are unique repertoires of all of its main orders (viz. Rhizobiales, Rhodobacterales, Rhodospirillales, Rickettsiales, Sphingomonadales and Caulobacterales and many families (viz. Rickettsiaceae, Anaplasmataceae, Rhodospirillaceae, Acetobacteraceae, Bradyrhiozobiaceae, Brucellaceae and Bartonellaceae. Many other proteins that are present at different phylogenetic depths in α-proteobacteria provide important information regarding their evolution. The evolutionary relationships among α-proteobacteria as deduced from these studies are in excellent agreement with their branching pattern in the phylogenetic trees and character compatibility cliques based on concatenated sequences for many conserved proteins. These studies provide evidence that the major groups within α-proteobacteria have diverged in the following order: (Rickettsiales(Rhodospirillales (Sphingomonadales (Rhodobacterales (Caulobacterales-Parvularculales (Rhizobiales. We also describe two conserved inserts in DNA

  1. Gene : CBRC-ACAR-01-0857 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-ACAR-01-0857 Novel UN C UNKNOWN GLGB_CHLCV 0.21 31% ref|ZP_01422754.1| Integrase, catalytic ... region ... [Caulobacter sp. K31] gb|EAU09851.1| Integrase, ca ... talytic region ... [Caulobacter sp. K31] 1.0 39% MSGWIDRVGALLVSFIPMLF ...

  2. Synthetic strategies for controlling inter- and intramolecular interactions: Applications in single-molecule fluorescence imaging, bioluminescence imaging, and palladium catalysis

    Science.gov (United States)

    Conley, Nicholas R.

    proximity of the Cy3 and Cy5 fluorophores, behaves as an optical photoswitch in the presence of a thiol reagent. This unique property was employed to achieve sub-diffraction-limited imaging of the stalks of Caulobacter crescentus cells with 30-nm resolution using STORM (stochastic optical reconstruction microscopy). Lastly, the synthesis of the first selenium analogue of firefly luciferin is described, and this analogue is shown to be a competent substrate for firefly luciferase (fLuc). Remarkably, it exhibits red-shifted bioluminescence emission relative to the native sulfur analogue. The in vivo performance of the selenium and sulfur analogues in imaging are compared by tail-vein injection into nude mice bearing subcutaneous tumor xenografts of a human breast cancer cell line that was stably transduced to express fLuc. Part II of this thesis begins by addressing design considerations in the development of palladium catalysts that effect oxidative transformations under mild conditions (i.e., 1 atm air, room temperature) using molecular oxygen as the terminal oxidant. A newly synthesized cationic palladium complex, [(2,9-dimethylphenanthroline)Pd(OAc)]2[OTf]2, is shown to catalyze aerobic alcohol oxidation under such conditions with an unprecedented initial turnover frequency, but the presence of partially reduced oxygen species results in competitive ligand oxidation with concomitant decrease in catalyst activity. To remedy this, oxidatively resistant ligands, which are essential for the development of next-generation, high-turnover-frequency palladium catalysts that utilize oxygen as a terminal oxidant, have been prepared and effectively employed. In addition, the first general palladium-catalyzed route to the carbonylation of diols is reported. In this system, carbon monoxide (1 atm) serves the carbonyl source, (2,9-dimethylphenanthroline)Pd(OAc) 2 acts as the catalyst, and N-chlorosuccinimide and iodosobenzene are the oxidants for 1,2- and 1,3-diols, respectively. This

  3. Twenty-One Genome Sequences from Pseudomonas Species and 19 Genome Sequences from Diverse Bacteria Isolated from the Rhizosphere and Endosphere of Populus deltoides

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Steven D [ORNL; Utturkar, Sagar M [ORNL; Klingeman, Dawn Marie [ORNL; Johnson, Courtney M [ORNL; Martin, Stanton [ORNL; Land, Miriam L [ORNL; Lu, Tse-Yuan [ORNL; Schadt, Christopher Warren [ORNL; Doktycz, Mitchel John [ORNL; Pelletier, Dale A [ORNL

    2012-01-01

    To aid in the investigation of the Populus deltoides microbiome we generated draft genome sequences for twenty one Pseudomonas and twenty one other diverse bacteria isolated from Populus deltoides roots. Genome sequences for isolates similar to Acidovorax, Bradyrhizobium, Brevibacillus, Burkholderia, Caulobacter, Chryseobacterium, Flavobacterium, Herbaspirillum, Novosphingobium, Pantoea, Phyllobacterium, Polaromonas, Rhizobium, Sphingobium and Variovorax were generated.

  4. AcEST: DK943627 [AcEST

    Lifescience Database Archive (English)

    Full Text Available tor SUI1 homolog OS=... 39 0.008 sp|Q9QZW9|MNX1_MOUSE Motor neuron and pancreas homeobox protein ... 31 1.7 ...n protein ftsZ OS=Caulobacter c... 30 2.9 sp|P50219|MNX1_HUMAN Motor neuron and p

  5. System-level design of bacterial cell cycle control

    OpenAIRE

    McAdams, Harley H.; Shapiro, Lucy

    2009-01-01

    Understanding of the cell cycle control logic in Caulobacter has progressed to the point where we now have an integrated view of the operation of an entire bacterial cell cycle system functioning as a state machine. Oscillating levels of a few temporally-controlled master regulator proteins in a cyclical circuit drive cell cycle progression. To a striking degree, the cell cycle regulation is a whole cell phenomenon. Phospho-signaling proteins and proteases dynamically deployed to specific loc...

  6. Dicty_cDB: Contig-U09445-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available fisffsfpskislqlgdr***nyfikiffk kkkikkkhgksi*k******y*niksifk*knk*ir*fcisiri...rvqynhdtiliihyis--- ---FFVFLFFCSFFFLFFXYKIKKKKKKKKKKKKKKKK Frame C: dfshphfifflkfyffyfnflfffsflfffsfhffhflrkylcn*eidnnkiil*kff... CAWZ13685.fwd CAWZ Helobdella robusta Primary Lat... 40 0.006 2 ( AM449950 ) Vitis vinifera contig VV78X030...d:none) Rhizobium leguminosarum bv. trifo... 65 2e-09 CP000927_3597( CP000927 |pid:none) Caulobacter sp. K31...09 CP000491_527( CP000491 |pid:none) Paracoccus denitrificans PD1222 ... 64 4e-09 CP000439_968( CP000439 |pi

  7. AcEST: BP917236 [AcEST

    Lifescience Database Archive (English)

    Full Text Available e: Altschul, Stephen F., Thomas L. Madden, Alejandro A. Schaffer, Jinghui Zhang, Zheng Zhang, Webb Miller..., and David J. Lipman (1997), Gapped BLAST and PSI-BLAST: a new generation of protein databas...Y2965_CAUCR UPF0339 protein CC_2965 OS=Caulobacter cre... 29 8.2 sp|Q04AM0|FTHS_LACDB Forma...te--tetrahydrofolate ligase OS=Lactoba... 29 8.2 sp|Q1GA94|FTHS_LACDA Formate--tetrahydrofolate ligas...29 TEGYASKASAKNAIESIKKNGPEAEIDDQTD 59 >sp|Q04AM0|FTHS_LACDB Formate--tetrahydrofolate ligase OS=Lactobacillu

  8. Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Michael Laub

    2008-12-29

    Our team of investigators from MIT (Michael Laub) and Stanford (Harley McAdams and Lucy Shapiro) conducted a multi-faceted, systematic experimental analysis of the 106 Caulobacter two-component signal transduction system proteins (62 histidine kinases and 44 response regulators) to understand how they coordinate cell cycle progression, metabolism, and response to environmental changes. These two-component signaling proteins were characterized at the genetic, biochemical, and genomic levels. The results generated by our laboratories have provided numerous insights into how Caulobacter cells sense and respond to a myriad of signals. As nearly all bacteria use two-component signaling for cell regulation, the results from this project help to deepen our general understanding of bacterial signal transduction. The tools and approaches developed can be applied to other bacteria. In particular, work from the Laub laboratory now enables the systematic, rational rewiring of two-component signaling proteins, a major advance that stands to impact synthetic biology and the development of biosensors and other designer molecular circuits. Results are summarized from our work. Each section lists publications and publicly-available resources which result from the work described.

  9. AcEST: DK959581 [AcEST

    Lifescience Database Archive (English)

    Full Text Available ia with plantlets Developmental stage gametophytes with sporophytes...7 tr|B4B111|B4B111_9CHRO Membrane-associated zinc metalloprotease ... 91 7e-17 tr|Q10ZE4|Q10ZE4_TRIEI YUP8H12.25 ((Arabidopsis thal...ase mmpA OS=Caulobacter crescen... 57 1e-07 sp|Q9KA70|RASP_BACHD Zinc metalloprotease rasP OS=Bacillus halo...bjct: 64 YCG 66 >sp|Q5L0J5|RASP_GEOKA Zinc metalloprotease rasP OS=Geobacillus kaustophilus GN=rasP PE=3 SV=1 Length...680 Definition Adiantum capillus-veneris mRNA. clone: TST39A01NGRL0005_B11. 5' end sequence. Accession DK959581 Tissue type prothall

  10. Dicty_cDB: Contig-U11264-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available 7 2e-06 CP001053_1582( CP001053 |pid:none) Burkholderia phytofirmans PsJN ... 57 2e-06 AE005673_1559( AE005673 |pid:none) Caulobacter...681_1571( AM398681 |pid:none) Flavobacterium psychrophilum JI... 94 2e-17 AY458631_5( AY458631 |pid:none) Uncultured marine bacteri...1_647( CP000781 |pid:none) Xanthobacter autotrophicus Py2, ... 75 1e-11 CP000360_4038( CP000360 |pid:none) Acidobacteria bacteri... CP000497 |pid:none) Pichia stipitis CBS 6054 chromosom... 67 4e-11 AP009386_1248( AP009386 |pid:none) Burkholderia mult...... 63 3e-08 DQ077738_2( DQ077738 |pid:none) Uncultured bacterium clone pLR1 pu... 63 3e-08 BX

  11. Dicty_cDB: Contig-U15680-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available s) Database: CSM 8402 sequences; 8,075,542 total letters Score E Sequences producing significant alignments: (bits) Value Cont...AM270075_67( AM270075 |pid:none) Aspergillus niger contig An04c014... 209 e-104 T29637( T29637 ) hypothetical protein F49E8.3 - Caen...3e-79 BC059334_1( BC059334 |pid:none) Xenopus laevis hypothetical protei... 174 7e-79 CP000927_3( CP000927 |pid:none) Caulobacter...Sulfolobus islandicus Y.G.57.14... 132 6e-62 CP000414_448( CP000414 |pid:none) Leuconostoc mesenteroides sub... BT010001 |pid:none) Drosophila melanogaster RE31064 fu... 80 4e-15 T29564( T29564 )hypothetical protein T12E12.6 - Caen

  12. Dicty_cDB: Contig-U13457-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available s; 5,674,871 total letters Score E Sequences producing significant alignment...nicola strain ... 150 4e-44 D83379_1( D83379 |pid:none) Hemicentrotus pulcherrimus mRNA for re... 159 4e-44 ( P07278 ) RecName: Full...57 2e-09 CP000613_484( CP000613 |pid:none) Rhodospirillum centenum SW, comp... 66...2( CP001193 |pid:none) Rhizobium leguminosarum bv. trif... 50 2e-04 AE005673_1405( AE005673 |pid:none) Caulobacter crescent...=cAMP-dependent protein kinase type II reg... 150 7e-38 AY387673_1( AY387673 |pid:none) Aplysia californica

  13. Biodiversity characterization of cellulolytic bacteria present on native Chaco soil by comparison of ribosomal RNA genes.

    Science.gov (United States)

    Talia, Paola; Sede, Silvana M; Campos, Eleonora; Rorig, Marcela; Principi, Dario; Tosto, Daniela; Hopp, H Esteban; Grasso, Daniel; Cataldi, Angel

    2012-04-01

    Sequence analysis of the 16S ribosomal RNA gene was used to study bacterial diversity of a pristine forest soil and of two cultures of the same soil enriched with cellulolytic bacteria. Our analysis revealed high bacterial diversity in the native soil sample, evidencing at least 10 phyla, in which Actinobacteria, Proteobacteria and Acidobacteria accounted for more than 76% of all sequences. In both enriched samples, members of Proteobacteria were the most frequently represented. The majority of bacterial genera in both enriched samples were identified as Brevundimonas and Caulobacter, but members of Devosia, Sphingomonas, Variovorax, Acidovorax, Pseudomonas, Xanthomonas, Stenotrophomonas, Achromobacter and Delftia were also found. In addition, it was possible to identify cellulolytic taxa such as Acidothermus, Micromonospora, Streptomyces, Paenibacillus and Pseudomonas, which indicates that this ecosystem could be an attractive source for study of novel enzymes for cellulose degradation. PMID:22202170

  14. Dicty_cDB: Contig-U15214-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available e) Actinobacillus pleuropneumoniae... 107 4e-22 CP000927_3202( CP000927 |pid:none) Cau...lobacter sp. K31, complete g... 107 4e-22 CP000569_1501( CP000569 |pid:none) Actinobacillus pleuropneumoniae...000687_1497( CP000687 |pid:none) Actinobacillus pleuropneumoniae... 107 6e-22 (Q9...P001098_708( CP001098 |pid:none) Halothermothrix orenii H 168, co... 104 4e-21 (Q8RQM6) RecName: Full=Diaminopim... 83 9e-15 AE017283_1241( AE017283 |pid:none) Propionibacterium acnes KPA1712... 83 9e-15 (Q9X5M1) RecName: Full=Diaminopim

  15. Dicty_cDB: Contig-U16394-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available e) Ralstonia pickettii 12D chromoso... 61 2e-07 CP001087_4453( CP001087 |pid:non... 2e-07 CP001069_1086( CP001069 |pid:none) Ralstonia pickettii 12J chromos... 61 2...28158_890( CU928158 |pid:none) Escherichia fergusonii ATCC 3546... 55 1e-05 AJ011832_1( AJ011832 |pid:none) Yersini...e) Caulobacter sp. K31, complete g... 55 1e-05 CP000720_2725( CP000720 |pid:none) Yersinia pseudotuberculosi...s IP ... 55 1e-05 AM260480_2064( AM260480 |pid:none) Ralstonia eutropha H16 chromoso... 55 1e-05 AE017

  16. AcEST: DK952721 [AcEST

    Lifescience Database Archive (English)

    Full Text Available 21|Adiantum capillus-veneris mRNA, clone: TST38A01NGRL0014_N22, 5' (441 letters) Database: uniprot_sprot.fas...Definition tr|B0SUQ9|B0SUQ9_CAUSK Acriflavin resistance protein OS=Caulobacter sp. (strain K31) Align length..._hit_id Q6NH62 Definition sp|Q6NH62|ACNR_CORDI HTH-type transcriptional repr...NR_CORDI HTH-type transcriptional repressor acnR OS=... 34 0.30 sp|Q71F56|MD13L_HUMAN Mediator of RNA polymerase II transcri... OS=Echinococcus granulosus GN=T... 29 9.8 sp|Q92835|SHIP1_HUMAN Phosphatidylinositol-3,4,5-trisphosphate 5... 29 10.0 >sp

  17. Phylosenetic identification and microbial diversity in snow of the summit (8201 m) of Cho Oyu Mountain,Tibet

    Institute of Scientific and Technical Information of China (English)

    TONG XiaoMei; WANG Jian; CHEN Fang; YU Jun; HUA Sang; ASAN Ciren; LUOSANG JiangBai; WANG Wei; YU Liang; ZHENG XiaoGuang

    2008-01-01

    The bacterial diversity and abundance in snow of the summit (8201 m) of Cho Oyu mountain, Tibet,were analyzed by 16S rRNA gene sequencing followed by scanning electronic microscopy analysis. Most of bacteria were found to be of spherical or oval shape (>95%). Bacterial 16S rDNA sequences were classified into 5 genera (Caulobacter, Ralstonia, Cupriavidus, Pelomonas and Pseudornonas).Gammaproteobacteria were the most abundant (91.25%) among the library that consists of 594 clones. The sequences found in this study are highly similar to those previously retrieved from other cold en-vironments, such as ice core, sea ice, permafrost and snow. The results showed that the cold and barren environments strongly influence the survival of bacteria. The high similarity among sequences retrieved from snow sample and other places, such as ocean, soil and water, suggested that the bacte-ria in snow, soil and water environments have the same origin.

  18. Surface protein composition of Aeromonas hydrophila strains virulent for fish: identification of a surface array protein

    International Nuclear Information System (INIS)

    The surface protein composition of members of a serogroup of Aeromonas hydrophila was examined. Immunoblotting with antiserum raised against formalinized whole cells of A. hydrophila TF7 showed a 52K S-layer protein to be the major surface protein antigen, and impermeant Sulfo-NHS-Biotin cell surface labeling showed that the 52K S-layer protein was the only protein accessible to the Sulfo-NHS-Biotin label and effectively masked underlying outer membrane (OM) proteins. In its native surface conformation the 52K S-layer protein was only weakly reactive with a lactoperoxidase 125I surface iodination procedure. A UV-induced rough lipopolysaccharide (LPS) mutant of TF7 was found to produce an intact S layer, but a deep rough LPS mutant was unable to maintain an array on the cell surface and excreted the S-layer protein into the growth medium, indicating that a minimum LPS oligosaccharide size required for A. hydrophila S-layer anchoring. The native S layer was permeable to 125I in the lactoperoxidase radiolabeling procedure, and two major OM proteins of molecular weights 30,000 and 48,000 were iodinated. The 48K species was a peptidoglycan-associated, transmembrane protein which exhibited heat-modifiable SDS solubilization behavior characteristic of a porin protein. A 50K major peptidoglycan-associated OM protein which was not radiolabeled exhibited similar SDS heat modification characteristics and possibly represents a second porin protein

  19. Identification of extracellular surface-layer associated proteins in Lactobacillus acidophilus NCFM.

    Science.gov (United States)

    Johnson, Brant; Selle, Kurt; O'Flaherty, Sarah; Goh, Yong Jun; Klaenhammer, Todd

    2013-11-01

    Bacterial surface (S-) layers are crystalline arrays of self-assembling, proteinaceous subunits called S-layer proteins (Slps), with molecular masses ranging from 40 to 200 kDa. The S-layer-forming bacterium Lactobacillus acidophilus NCFM expresses three major Slps: SlpA (46 kDa), SlpB (47 kDa) and SlpX (51 kDa). SlpA has a demonstrated role in adhesion to Caco-2 intestinal epithelial cells in vitro, and has been shown to modulate dendritic cell (DC) and T-cell functionalities with murine DCs. In this study, a modification of a standard lithium chloride S-layer extraction revealed 37 proteins were solubilized from the S-layer wash fraction. Of these, 30 have predicted cleavage sites for secretion, 24 are predicted to be extracellular, six are lipid-anchored, three have N-terminal hydrophobic membrane spanning regions and four are intracellular, potentially moonlighting proteins. Some of these proteins, designated S-layer associated proteins (SLAPs), may be loosely associated with or embedded within the bacterial S-layer complex. Lba-1029, a putative SLAP gene, was deleted from the chromosome of L. acidophilus. Phenotypic characterization of the deletion mutant demonstrated that the SLAP LBA1029 contributes to a pro-inflammatory TNF-α response from murine DCs. This study identified extracellular proteins and putative SLAPs of L. acidophilus NCFM using LC-MS/MS. SLAPs appear to impart important surface display features and immunological properties to microbes that are coated by S-layers. PMID:24002751

  20. Systematic studies of protein immobilization by surface plasmon field-enhanced fluorescence spectroscopy

    OpenAIRE

    Liu, Jing

    2005-01-01

    The research interest of this study is to investigate surface immobilization strategies for proteins and other biomolecules by the surface plasmon field-enhanced fluorescence spectroscopy (SPFS) technique. The recrystallization features of the S-layer proteins and the possibility of combining the S-layer lattice arrays with other functional molecules make this protein a prime candidate for supramolecular architectures. The recrystallization behavior on gold or on the secondary cell wall po...

  1. Studies on CdTe solar cell front contact properties using X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    The chemical changes between transparent conducting oxide (TCO) and cadmium sulphide (CdS) layers were analyzed using X-ray photoelectron spectroscopy (XPS). Commercially available indium tin oxide (ITO) and ITO/SnO2 were used as substrates. The CdS layers were deposited in vacuum (∼ 10−2 Pa) at two different (low and high) substrate temperatures by close spaced sublimation technique. During the growth of CdS layer, the substrate temperature was increased from 25 to 250 °C for low temperature layer and from 490 to 550 °C for high temperature CdS layer due to the high crucible temperature. Similar to CdTe solar cell device process steps, the samples (TCO/CdS) were annealed in vacuum (10−2 Pa) at 520 °C and in air at 375 °C with and without CdCl2. The XPS depth profile analysis shows that annealing ITO/CdS sample in vacuum induces diffusion of indium into the CdS layer from ITO. The most of the diffused indium atoms are found on top of the CdS layer. No indium diffusion into the CdS layer was observed for the TCO with SnO2 buffer layer between ITO and CdS. However, at SnO2/CdS interface Cd atoms diffuse into the SnO2 buffer layer after CdCl2 activation. The change in chemical and electronic properties of the ITO/CdS and ITO/SnO2/CdS interfaces is discussed in detail. - Highlights: • The chemical change between different layers of CdTe solar cell is analyzed. • The annealing treatment induces diffusion of chemical elements. • SnO2 buffer layer acts as barrier for indium diffusion. • The CdCl2 annealing induces cadmium diffusion into tin oxide layer

  2. Cwp84, a Clostridium difficile cysteine protease, exhibits conformational flexibility in the absence of its propeptide

    International Nuclear Information System (INIS)

    Two structures of Cwp84, a cysteine protease from the S-layer of C. difficile, are presented after propeptide cleavage. They reveal the movement of three loops, two in the active-site groove and one on the surface of the lectin-like domain, exposing a hydrophobic pocket. In recent decades, the global healthcare problems caused by Clostridium difficile have increased at an alarming rate. A greater understanding of this antibiotic-resistant bacterium, particularly with respect to how it interacts with the host, is required for the development of novel strategies for fighting C. difficile infections. The surface layer (S-layer) of C. difficile is likely to be of significant importance to host–pathogen interactions. The mature S-layer is formed by a proteinaceous array consisting of multiple copies of a high-molecular-weight and a low-molecular-weight S-layer protein. These components result from the cleavage of SlpA by Cwp84, a cysteine protease. The structure of a truncated Cwp84 active-site mutant has recently been reported and the key features have been identified, providing the first structural insights into the role of Cwp84 in the formation of the S-layer. Here, two structures of Cwp84 after propeptide cleavage are presented and the three conformational changes that are observed are discussed. These changes result in a reconfiguration of the active site and exposure of the hydrophobic pocket

  3. Cwp84, a Clostridium difficile cysteine protease, exhibits conformational flexibility in the absence of its propeptide

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, William J. [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Roberts, April K.; Shone, Clifford C. [Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Acharya, K. Ravi, E-mail: bsskra@bath.ac.uk [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)

    2015-02-19

    Two structures of Cwp84, a cysteine protease from the S-layer of C. difficile, are presented after propeptide cleavage. They reveal the movement of three loops, two in the active-site groove and one on the surface of the lectin-like domain, exposing a hydrophobic pocket. In recent decades, the global healthcare problems caused by Clostridium difficile have increased at an alarming rate. A greater understanding of this antibiotic-resistant bacterium, particularly with respect to how it interacts with the host, is required for the development of novel strategies for fighting C. difficile infections. The surface layer (S-layer) of C. difficile is likely to be of significant importance to host–pathogen interactions. The mature S-layer is formed by a proteinaceous array consisting of multiple copies of a high-molecular-weight and a low-molecular-weight S-layer protein. These components result from the cleavage of SlpA by Cwp84, a cysteine protease. The structure of a truncated Cwp84 active-site mutant has recently been reported and the key features have been identified, providing the first structural insights into the role of Cwp84 in the formation of the S-layer. Here, two structures of Cwp84 after propeptide cleavage are presented and the three conformational changes that are observed are discussed. These changes result in a reconfiguration of the active site and exposure of the hydrophobic pocket.

  4. Microbial nitrogen cycling in Arctic snowpacks

    International Nuclear Information System (INIS)

    Arctic snowpacks are often considered as chemical reactors for a variety of chemicals deposited through wet and dry events, but are overlooked as potential sites for microbial metabolism of reactive nitrogen species. The fate of deposited species is critical since warming leads to the transfer of contaminants to snowmelt-fed ecosystems. Here, we examined the role of microorganisms and the potential pathways involved in nitrogen cycling in the snow. Next generation sequencing data were used to follow functional gene abundances and a 16S rRNA (ribosomal ribonucleic acid) gene microarray was used to follow shifts in microbial community structure during a two-month spring-time field study at a high Arctic site, Svalbard, Norway (79° N). We showed that despite the low temperatures and limited water supply, microbial communities inhabiting the snow cover demonstrated dynamic shifts in their functional potential to follow several different pathways of the nitrogen cycle. In addition, microbial specific phylogenetic probes tracked different nitrogen species over time. For example, probes for Roseomonas tracked nitrate concentrations closely and probes for Caulobacter tracked ammonium concentrations after a delay of one week. Nitrogen cycling was also shown to be a dominant process at the base of the snowpack. (letter)

  5. [Qualitative and quantitative determination of bacterial populations in an aquatic environment. 7. Development of bacterial growth on raw materials exposed to potable water].

    Science.gov (United States)

    Dott, W; Schoenen, D

    1985-05-01

    Refined steel plates coated with different materials that contained available organic compounds led to a microbial growth on the surface. Even plastics and bitumen which were used in the sphere of drinking water showed after an exposure time of three months up to 192 ml slime per square meter. The number of viable bacteria within the Aufwuchs was in the range of 10(7) cfu/ml. The production of slime increased with time. The relation of carbohydrate and protein content significantly changed from 2 at the beginning to 30 after 12 months of incubation the bitumen coating test plates. This indicates an increase synthesis of carbohydrate containing extracellular polymeric substances during the late phase of growth. The bacteria isolated from the Aufwuchs mainly belonged to the genera Pseudomonas, Flavobacterium, Acinetobacter, Caulobacter, sheated bacteria and other gramnegative physiologically nonreactiv roads. During exposure of the plates the relation changed within the bacterial communities of the main groups. Comparing the bacteria communities of inlet and outflow water it became evident that the later one was influenced by bacteria of the Aufwuchs. PMID:4024773

  6. Crude oil treatment leads to shift of bacterial communities in soils from the deep active layer and upper permafrost along the China-Russia Crude Oil Pipeline route.

    Directory of Open Access Journals (Sweden)

    Sizhong Yang

    Full Text Available The buried China-Russia Crude Oil Pipeline (CRCOP across the permafrost-associated cold ecosystem in northeastern China carries a risk of contamination to the deep active layers and upper permafrost in case of accidental rupture of the embedded pipeline or migration of oil spills. As many soil microbes are capable of degrading petroleum, knowledge about the intrinsic degraders and the microbial dynamics in the deep subsurface could extend our understanding of the application of in-situ bioremediation. In this study, an experiment was conducted to investigate the bacterial communities in response to simulated contamination to deep soil samples by using 454 pyrosequencing amplicons. The result showed that bacterial diversity was reduced after 8-weeks contamination. A shift in bacterial community composition was apparent in crude oil-amended soils with Proteobacteria (esp. α-subdivision being the dominant phylum, together with Actinobacteria and Firmicutes. The contamination led to enrichment of indigenous bacterial taxa like Novosphingobium, Sphingobium, Caulobacter, Phenylobacterium, Alicylobacillus and Arthrobacter, which are generally capable of degrading polycyclic aromatic hydrocarbons (PAHs. The community shift highlighted the resilience of PAH degraders and their potential for in-situ degradation of crude oil under favorable conditions in the deep soils.

  7. Comparison of reversible-jump Markov-chain-Monte-Carlo learning approach with other methods for missing enzyme identification.

    Science.gov (United States)

    Geng, Bo; Zhou, Xiaobo; Zhu, Jinmin; Hung, Y S; Wong, Stephen T C

    2008-04-01

    Computational identification of missing enzymes plays a significant role in accurate and complete reconstruction of metabolic network for both newly sequenced and well-studied organisms. For a metabolic reaction, given a set of candidate enzymes identified according to certain biological evidences, a powerful mathematical model is required to predict the actual enzyme(s) catalyzing the reactions. In this study, several plausible predictive methods are considered for the classification problem in missing enzyme identification, and comparisons are performed with an aim to identify a method with better performance than the Bayesian model used in previous work. In particular, a regression model consisting of a linear term and a nonlinear term is proposed to apply to the problem, in which the reversible jump Markov-chain-Monte-Carlo (MCMC) learning technique (developed in [Andrieu C, Freitas Nando de, Doucet A. Robust full Bayesian learning for radial basis networks 2001;13:2359-407.]) is adopted to estimate the model order and the parameters. We evaluated the models using known reactions in Escherichia coli, Mycobacterium tuberculosis, Vibrio cholerae and Caulobacter cresentus bacteria, as well as one eukaryotic organism, Saccharomyces Cerevisiae. Although support vector regression also exhibits comparable performance in this application, it was demonstrated that the proposed model achieves favorable prediction performance, particularly sensitivity, compared with the Bayesian method. PMID:17950040

  8. Isolation and characterization of culturable seed-associated bacterial endophytes from gnotobiotically grown Marama bean seedlings.

    Science.gov (United States)

    Chimwamurombe, Percy Maruwa; Grönemeyer, Jann Lasse; Reinhold-Hurek, Barbara

    2016-06-01

    Marama bean (Tylosema esculentum) is an indigenous non-nodulating legume to the arid agro-ecological parts of Southern Africa. It is a staple food for the Khoisan and Bantu people from these areas. It is intriguing how it is able to synthesize the high-protein content in the seeds since its natural habitat is nitrogen deficient. The aim of the study was to determine the presence of seed transmittable bacterial endophytes that may have growth promoting effects, which may be particularly important for the harsh conditions. Marama bean seeds were surface sterilized and gnotobiotically grown to 2 weeks old seedlings. From surface-sterilized shoots and roots, 123 distinct bacterial isolates were cultured using three media, and identified by BOX-PCR fingerprinting and sequence analyses of the 16S rRNA and nifH genes. Phylogenetic analyses of 73 putative endophytes assigned them to bacterial species from 14 genera including Proteobacteria (Rhizobium, Massilia, Kosakonia, Pseudorhodoferax, Caulobacter, Pantoea, Sphingomonas, Burkholderia, Methylobacterium), Firmicutes (Bacillus), Actinobacteria (Curtobacterium, Microbacterium) and Bacteroidetes (Mucilaginibacter, Chitinophaga). Screening for plant growth-promoting activities revealed that the isolates showed production of IAA, ACC deaminase, siderophores, endoglucanase, protease, AHLs and capacities to solubilize phosphate and fix nitrogen. This is the first report that marama bean seeds may harbor endophytes that can be cultivated from seedlings; in this community of bacteria, physiological characteristics that are potentially plant growth promoting are widespread. PMID:27118727

  9. iTRAQ-Based Quantitative Proteomic Analysis of the Antimicrobial Mechanism of Peptide F1 against Escherichia coli.

    Science.gov (United States)

    Miao, Jianyin; Chen, Feilong; Duan, Shan; Gao, Xiangyang; Liu, Guo; Chen, Yunjiao; Dixon, William; Xiao, Hang; Cao, Yong

    2015-08-19

    Antimicrobial peptides have received increasing attention in the agricultural and food industries due to their potential to control pathogens. However, to facilitate the development of novel peptide-based antimicrobial agents, details regarding the molecular mechanisms of these peptides need to be elucidated. The aim of this study was to investigate the antimicrobial mechanism of peptide F1, a bacteriocin found in Tibetan kefir, against Escherichia coli at protein levels using iTRAQ-based quantitative proteomic analysis. In response to treatment with peptide F1, 31 of the 280 identified proteins in E. coli showed alterations in their expression, including 10 down-regulated proteins and 21 up-regulated proteins. These 31 proteins all possess different molecular functions and are involved in different molecular pathways, as is evident in referencing the Kyoto Encyclopedia of Genes and Genomes pathways. Specifically, pathways that were significantly altered in E. coli in response to peptide F1 treatment include the tricarboxylic acid cycle, oxidative phosphorylation, glycerophospholipid metabolism, and the cell cycle-caulobacter pathways, which was also associated with inhibition of the cell growth, induction of morphological changes, and cell death. The results provide novel insights into the molecular mechanisms of antimicrobial peptides. PMID:26208148

  10. Characterization of bacterial communities associated with Brassica napus L. growing on a Zn-contaminated soil and their effects on root growth.

    Science.gov (United States)

    Montalbán, Blanca; Croes, Sarah; Weyens, Nele; Lobo, M Carmen; Pérez-Sanz, Araceli; Vangronsveld, Jaco

    2016-10-01

    The interaction between plant growth-promoting bacteria (PGPB) and plants can enhance biomass production and metal tolerance of the host plants. This work aimed at isolating and characterizing the cultivable bacterial community associated with Brassica napus growing on a Zn-contaminated site, for selecting cultivable PGPB that might enhance biomass production and metal tolerance of energy crops. The effects of some of these bacterial strains on root growth of B. napus exposed to increasing Zn and Cd concentrations were assessed. A total of 426 morphologically different bacterial strains were isolated from the soil, the rhizosphere, and the roots and stems of B. napus. The diversity of the isolated bacterial populations was similar in rhizosphere and roots, but lower in soil and stem compartments. Burkoholderia, Alcaligenes, Agrococcus, Polaromonas, Stenotrophomonas, Serratia, Microbacterium, and Caulobacter were found as root endophytes exclusively. The inoculation of seeds with Pseudomonas sp. strains 228 and 256, and Serratia sp. strain 246 facilitated the root development of B. napus at 1,000 µM Zn. Arthrobacter sp. strain 222, Serratia sp. strain 246, and Pseudomonas sp. 228 and 262 increased the root length at 300 µM Cd. PMID:27159736

  11. Indigenous bacteria may interfere with the biocontrol of plant diseases

    Science.gov (United States)

    Someya, Nobutaka; Akutsu, Katsumi

    2009-06-01

    Prodigiosin is a reddish antibiotic pigment that plays an important role in the biocontrol of plant diseases by the bacterium Serratia marcescens. However, its activity is unstable under agricultural conditions; further, it can be degraded by various environmental factors. To examine the effect of epiphytic microbes on the stability of prodigiosin used for biological control processes, we collected a total of 1,280 bacterial isolates from the phylloplane of cyclamen and tomato plants. Approximately 72% of the bacterial strains isolated from the cyclamen plants and 66% of those isolated from the tomato plants grew on minimal agar medium containing 100 μg ml-1 prodigiosin. Certain isolates obtained from both plant species exhibited prodigiosin-degrading activity. We compared the 16S rRNA gene sequences derived from the isolates with sequences in a database. The comparison revealed that the sequences determined for the prodigiosin-degrading isolates were homologous to those of the genera Pseudomonas, Caulobacter, Rhizobium, Sphingomonas, Janthinobacterium, Novosphingobium, and Rathayibacter. These results indicate that indigenous epiphytic microorganisms may interfere with the interaction between plant pathogens and biocontrol agents by degrading the antibiotics produced by the agents.

  12. The structure and assembly of surface layer proteins : a combined approach of in silico and experimental methods

    International Nuclear Information System (INIS)

    Self-assembly of matter is one of nature's most sophisticated strategies to organize molecules on a large scale and to create order from disorder. Surface (S-)layer proteins self-assemble in a highly reproducible and robust fashion in order to form crystalline layers that completely cover and protect prokaryotic cells. Long conserved during evolution, S-layers constitute a unique model system to study the molecular mechanisms of functional self-assembly, while additionally, they provide a basic matrix for the specific construction of ordered nanostructures. Due to their intrinsic capabilities to self-assemble into two-dimensional crystals, the elucidation of the three-dimensional structure of single S-layer proteins demands an approach beyond conventional structure determination methods. In this work, computer simulations were combined with experimental techniques in order to study the structure and intra- and intermolecular potentials guiding the proteins to self-assemble into lattices with different symmetries. Molecular dynamics, Monte Carlo methods, small-angle X-ray scattering involving a new theoretical description, and AFM-based single-molecule force spectroscopy yield new insights into the three-dimensional structure of S-layer proteins, the location, type and distribution of amino acids in S-layer lattices, the molecular mechanisms behind the self-assembly process, the mechanical stability and adaptive structural conformations that S-layer proteins are able to establish. In silico studies - embedded in an adequate experimental and theoretical scaffold - offer the possibility to calculate structural and thermodynamic features of proteins, while this work demonstrates the growing impact of such theoretical techniques in the fascinating field of biophysics at the nano-scale. (author)

  13. Zn-Al layered double hydroxide intercalated with porphyrin anions: molecular simulations and experiments

    Czech Academy of Sciences Publication Activity Database

    Kovář, P.; Pospíšil, M.; Futera, Z.; Lang, Kamil; Káfuňková, Eva; Taviot-Guého, Ch.; Bezdička, Petr

    Castellaneta Marina : AISA, 2009. s. 477. ISBN 978-88-7522-027-3. [International Clay Conference /14./. 14.06.2009-20.06.2009, Castellaneta Marina] R&D Projects: GA ČR(CZ) GA203/06/1244 Institutional research plan: CEZ:AV0Z40320502 Keywords : porphyrin s * layered double hydroxides * molecular modeling Subject RIV: CA - Inorganic Chemistry

  14. Fluorescent sensors based on bacterial fusion proteins

    International Nuclear Information System (INIS)

    Fluorescence proteins are widely used as markers for biomedical and technological purposes. Therefore, the aim of this project was to create a fluorescent sensor, based in the green and cyan fluorescent protein, using bacterial S-layers proteins as scaffold for the fluorescent tag. We report the cloning, expression and purification of three S-layer fluorescent proteins: SgsE-EGFP, SgsE-ECFP and SgsE-13aa-ECFP, this last containing a 13-amino acid rigid linker. The pH dependence of the fluorescence intensity of the S-layer fusion proteins, monitored by fluorescence spectroscopy, showed that the ECFP tag was more stable than EGFP. Furthermore, the fluorescent fusion proteins were reassembled on silica particles modified with cationic and anionic polyelectrolytes. Zeta potential measurements confirmed the particle coatings and indicated their colloidal stability. Flow cytometry and fluorescence microscopy showed that the fluorescence of the fusion proteins was pH dependent and sensitive to the underlying polyelectrolyte coating. This might suggest that the fluorescent tag is not completely exposed to the bulk media as an independent moiety. Finally, it was found out that viscosity enhanced the fluorescence intensity of the three fluorescent S-layer proteins. (paper)

  15. Analysis of ATPases of putative secretion operons in the thermoacidophilic archaeon Sulfolobus solfataricus

    NARCIS (Netherlands)

    Albers, SV; Driessen, AJM

    2005-01-01

    Gram-negative bacteria use a wide variety of complex mechanisms to secrete proteins across their membranes or to assemble secreted proteins into surface structures. As most archaea only possess a cytoplasmic membrane surrounded by a membrane-anchored S-layer, the organization of such complexes might

  16. The optics of gyrotropic crystals in the field of two counter-propagating ultrasound waves

    International Nuclear Information System (INIS)

    We consider oblique light propagation through a layer of a gyrotropic crystal in the field of two counter-propagating ultrasound waves. The problem is solved by Ambartsumyan's layer addition modified method. The results of the reflection spectra for different values of the problem parameters are presented. The possibilities of such system applications are discussed.

  17. The Bacterial Surface Layer Provides Protection against Antimicrobial Peptides

    OpenAIRE

    de la Fuente-Núñez, César; Mertens, Jan; Smit, John; Hancock, Robert E. W.

    2012-01-01

    This report describes a previously unrecognized role for bacterial surface layers as barriers that confer protection against antimicrobial peptides. As antimicrobial peptides exist in natural environments, S-layers may provide a bacterial survival mechanism that has been selected for through evolution.

  18. Formation and characterization of conductive thin layers of copper sulfide (Cu xS) on the surface of polyethylene and polyamide by the use of higher polythionic acids

    International Nuclear Information System (INIS)

    Layers of copper sulfide of varying composition and properties are formed on the surface of polyethylene and polyamide by a sorption-diffusion method using solutions of higher polythionic acids, H2S nO6. The concentration of sulfur adsorbed-diffused into PE and PA depends on the degree of the acid sulfurity, n, the temperature of the solution and the period of the polymer treatment. The amount of copper in a sulfide (Cu xS) layer formed after the sulfured polymer treatment with a solution of Cu(I-II) salt is strongly dependent on the concentration of sulfur in the PE and PA. By the chemical analysis of the obtained sulfide layers was determined that a value of x in the Cu xS layers varies in the interval 1 xS layers obtained seven phases: with x = 2 (chalcocite), 1.9375 (djurleite), 1.8 (digenite), 1.75 (anilite), 1.12 (yarrowite), 1.06 (talnakhite) and 1 (covellite). The measurements of the electrical conductance of Cu xS layers (0.1-4 S cm-2) showed that its value greatly depends on the conditions of PE and PA interaction with H2S nO6 and of further interaction with Cu(I-II) salt solution, on the chemical and phase composition of the layer

  19. Fluorescent sensors based on bacterial fusion proteins

    Science.gov (United States)

    Prats Mateu, Batirtze; Kainz, Birgit; Pum, Dietmar; Sleytr, Uwe B.; Toca-Herrera, José L.

    2014-06-01

    Fluorescence proteins are widely used as markers for biomedical and technological purposes. Therefore, the aim of this project was to create a fluorescent sensor, based in the green and cyan fluorescent protein, using bacterial S-layers proteins as scaffold for the fluorescent tag. We report the cloning, expression and purification of three S-layer fluorescent proteins: SgsE-EGFP, SgsE-ECFP and SgsE-13aa-ECFP, this last containing a 13-amino acid rigid linker. The pH dependence of the fluorescence intensity of the S-layer fusion proteins, monitored by fluorescence spectroscopy, showed that the ECFP tag was more stable than EGFP. Furthermore, the fluorescent fusion proteins were reassembled on silica particles modified with cationic and anionic polyelectrolytes. Zeta potential measurements confirmed the particle coatings and indicated their colloidal stability. Flow cytometry and fluorescence microscopy showed that the fluorescence of the fusion proteins was pH dependent and sensitive to the underlying polyelectrolyte coating. This might suggest that the fluorescent tag is not completely exposed to the bulk media as an independent moiety. Finally, it was found out that viscosity enhanced the fluorescence intensity of the three fluorescent S-layer proteins.

  20. Whole-Genome Sequence of Aeromonas hydrophila Strain AH-1 (Serotype O11).

    Science.gov (United States)

    Forn-Cuní, Gabriel; Tomás, Juan M; Merino, Susana

    2016-01-01

    Aeromonas hydrophila is an emerging pathogen of aquatic and terrestrial animals, including humans. Here, we report the whole-genome sequence of the septicemic A. hydrophila AH-1 strain, belonging to the serotype O11, and the first mesophilic Aeromonas with surface layer (S-layer) to be sequenced. PMID:27587829

  1. Genome Sequence of Lactobacillus amylovorus GRL1118, Isolated from Pig Ileum ▿

    OpenAIRE

    Kant, R.; Paulin, L.; Alatalo, E.; DE VOS W.M.; Palva, A.

    2011-01-01

    Lactobacillus amylovorus is a common member of the beneficial microbiota present in the pig gastrointestinal tract. Here, we report the genome sequence of the surface layer (S-layer) protein-carrying and potentially probiotic strain L. amylovorus GRL1118, which was isolated from porcine ileum and which shows strong adherence to pig intestinal epithelial cells.

  2. Genome sequence of Lactobacillus amylovorus GRL1118, isolated from pig ileum.

    Science.gov (United States)

    Kant, Ravi; Paulin, Lars; Alatalo, Edward; de Vos, Willem M; Palva, Airi

    2011-06-01

    Lactobacillus amylovorus is a common member of the beneficial microbiota present in the pig gastrointestinal tract. Here, we report the genome sequence of the surface layer (S-layer) protein-carrying and potentially probiotic strain L. amylovorus GRL1118, which was isolated from porcine ileum and which shows strong adherence to pig intestinal epithelial cells. PMID:21478337

  3. Genome sequence of Lactobacillus amylovorus GRL1118, isolated from pig ileum

    OpenAIRE

    Kant, R.; Vos, de, W.M.

    2011-01-01

    Lactobacillus amylovorus is a common member of the beneficial microbiota present in the pig gastrointestinal tract. Here, we report the genome sequence of the surface layer (S-layer) protein-carrying and potentially probiotic strain L. amylovorus GRL1118, which was isolated from porcine ileum and which shows strong adherence to pig intestinal epithelial cells

  4. Identification and characterization of metabolic properties of bacterial populations recovered from arsenic contaminated ground water of North East India (Assam).

    Science.gov (United States)

    Ghosh, Soma; Sar, Pinaki

    2013-12-01

    Diversity of culturable bacterial populations within the Arsenic (As) contaminated groundwater of North Eastern state (Assam) of India is studied. From nine As contaminated samples 89 bacterial strains are isolated. 16S rRNA gene sequence analysis reveals predominance of Brevundimonas (35%) and Acidovorax (23%) along with Acinetobacter (10%), Pseudomonas (9%) and relatively less abundant (<5%) Undibacterium, Herbaspirillum, Rhodococcus, Staphylococcus, Bosea, Bacillus, Ralstonia, Caulobacter and Rhizobiales members. High As(III) resistance (MTC 10-50 mM) is observed for the isolates obtained from As(III) enrichment, particularly for 3 isolates of genus Brevundimonas (MTC 50 mM). In contrast, high resistance to As(V) (MTC as high as 550 mM) is present as a ubiquitous property, irrespective of isolates' enrichment condition. Bacterial genera affiliated to other groups showed relatively lower degree of As resistance [MTCs of 15-20 mM As(III) and 250-350 mM As(V)]. As(V) reductase activity is detected in strains with high As(V) as well as As(III) resistance. A strong correlation could be established among isolates capable of reductase activity and siderophore production as well as As(III) tolerance. A large number of isolates (nearly 50%) is capable of anaerobic respiration using alternate inorganic electron acceptors [As(V), Se(VI), Fe(III), [NO(3)(2), SO(4)(2), S(2)O(3)(2). Ability to utilize different carbon sources ranging from C2-C6 compounds along with some complex sugars is also observed. Particularly, a number of strains is found to possess ability to grow chemolithotrophically using As(III) as the electron donor. The study reports for the first time the identity and metabolic abilities of bacteria in As contaminated ground water of North East India, useful to elucidate the microbial role in influencing mobilization of As in the region. PMID:24210546

  5. Efficacy of Various Chemical Disinfectants on Biofilms Formed in Spacecraft Potable Water System Component

    Science.gov (United States)

    Wong, Willy; Garcia, Veronica; Castro, Victoria; Ott, Mark; Duane

    2009-01-01

    As the provision of potable water is critical for successful habitation of the International Space Station (ISS), life support systems were installed in December 2008 to recycle both humidity from the atmosphere and urine to conserve available water in the vehicle. Pre-consumption testing from the dispensing needle at the Potable Water Dispenser (PWD) indicated that bacterial concentrations exceeded the current ISS specifications of 50 colony forming units (CFU) per ml. Subsequent investigations revealed that a corrugated stainless steel flex hose upstream of the dispensing needle in the PWD was filled with non-sterile water and left at room temperature for over one month before launch. To simulate biofilm formation that was suspected in the flight system, sterile flex hoses were seeded with a consortium of bacterial isolates previously recovered from other ISS water systems, which included Ralstonia pickettii, Burkholderia multivorans, Caulobacter vibrioides., and Cupriavidus pauculus. After 5 days of incubation, these hoses were challenged with various chemical disinfectants including hydrogen peroxide, colloidal silver, and buffered pH solutions to determine the ability of the disinfectants to decrease and maintain bacterial concentrations below ISS specifications. Disinfection efficacy over time was measured by collecting daily heterotrophic plate counts following exposure to the disinfectants. A single flush with either 6% hydrogen peroxide solution or a mixture of 3% hydrogen peroxide and 400 ppb colloidal silver effectively reduced the bacterial concentrations to less than 1 CFU/ml for a period of up to 2 months. Testing results indicated that hydrogen peroxide and mixtures of hydrogen peroxide and colloidal silver have tremendous potential as alternative disinfectants for ISS water systems.

  6. Bacterial Colonization of Cod (Gadus morhua L.) and Halibut (Hippoglossus hippoglossus) Eggs in Marine Aquaculture

    Science.gov (United States)

    Hansen, Geir Høvik; Olafsen, Jan A.

    1989-01-01

    Aquaculture has brought about increased interest in mass production of marine fish larvae. Problems such as poor egg quality and mass mortality of fish larvae have been prevalent. The intensive incubation techniques that often result in bacterial overgrowth on fish eggs could affect the commensal relationship between the indigenous microflora and opportunistic pathogens and subsequently hamper egg development, hatching, larval health, and ongrowth. Little information about the adherent microflora on fish eggs is available, and the present study was undertaken to describe the microbial ecology during egg development and hatching of two fish species of potential commercial importance in marine aquaculture. Attachment and development of the bacterial flora on cod (Gadus morhua L.) eggs from fertilization until hatching was studied by scanning electron microscopy. The adherent microflora on cod (G. morhua L.) and halibut (Hippoglossus hippoglossus) eggs during incubation was characterized and grouped by cluster analysis. Marked bacterial growth could be demonstrated 2 h after fertilization, and at hatching eggs were heavily overgrown. Members of the genera Pseudomonas, Alteromonas, Aeromonas, and Flavobacterium were found to dominate on the surface of both cod and halibut eggs. The filamentous bacterium Leucothrix mucor was found on eggs from both species. While growth of L. mucor on halibut eggs was sparse, cod eggs with a hairy appearance due to overgrowth by this bacterium close to hatching were frequently observed. Vibrio fischeri could be detected on cod eggs only, and pathogenic vibrios were not detected. Members of the genera Moraxella and Alcaligenes were found only on halibut eggs. Caulobacter and Seliberia spp. were observed attached to eggs dissected from cod ovaries under sterile conditions, indicating the presence of these bacteria in ovaries before spawning. Adherent strains did not demonstrate antibiotic resistance above a normal level. Attempts to

  7. Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study.

    Science.gov (United States)

    Callender, Katrina L; Roy, Sébastien; Khasa, Damase P; Whyte, Lyle G; Greer, Charles W

    2016-01-01

    Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM) fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal) alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI), and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS) region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas), metal sequestration (Brevundimonas and Caulobacter) and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas) increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN) assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude) and mineralization (five-fold). Genomic techniques proved useful in investigating

  8. Anterior foregut microbiota of the glassy-winged sharpshooter explored using deep 16S rRNA gene sequencing from individual insects.

    Directory of Open Access Journals (Sweden)

    Elizabeth E Rogers

    Full Text Available The glassy-winged sharpshooter (GWSS is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce's disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium of sharpshooters, where it may interact with other naturally-occurring bacterial species. To evaluate such interactions, a comprehensive list of bacterial species associated with the sharpshooter cibarium and precibarium is needed. Here, a survey of microbiota associated with the GWSS anterior foregut was conducted. Ninety-six individual GWSS, 24 from each of 4 locations (Bakersfield, CA; Ojai, CA; Quincy, FL; and a laboratory colony, were characterized for bacteria in dissected sharpshooter cibaria and precibaria by amplification and sequencing of a portion of the 16S rRNA gene using Illumina MiSeq technology. An average of approximately 150,000 sequence reads were obtained per insect. The most common genus detected was Wolbachia; sequencing of the Wolbachia ftsZ gene placed this strain in supergroup B, one of two Wolbachia supergroups most commonly associated with arthropods. X. fastidiosa was detected in all 96 individuals examined. By multilocus sequence typing, both X. fastidiosa subspecies fastidiosa and subspecies sandyi were present in GWSS from California and the colony; only subspecies fastidiosa was detected in GWSS from Florida. In addition to Wolbachia and X. fastidiosa, 23 other bacterial genera were detected at or above an average incidence of 0.1%; these included plant-associated microbes (Methylobacterium, Sphingomonas, Agrobacterium, and Ralstonia and soil- or water-associated microbes (Anoxybacillus, Novosphingobium, Caulobacter, and Luteimonas. Sequences belonging to species of the family Enterobacteriaceae also were detected but it was not possible to assign these to individual genera. Many of these species likely interact with X. fastidiosa in the

  9. Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study.

    Directory of Open Access Journals (Sweden)

    Katrina L Callender

    Full Text Available Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI, and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas, metal sequestration (Brevundimonas and Caulobacter and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude and mineralization (five-fold. Genomic techniques proved useful in

  10. Anterior foregut microbiota of the glassy-winged sharpshooter explored using deep 16S rRNA gene sequencing from individual insects.

    Science.gov (United States)

    Rogers, Elizabeth E; Backus, Elaine A

    2014-01-01

    The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce's disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where it may interact with other naturally-occurring bacterial species. To evaluate such interactions, a comprehensive list of bacterial species associated with the sharpshooter cibarium and precibarium is needed. Here, a survey of microbiota associated with the GWSS anterior foregut was conducted. Ninety-six individual GWSS, 24 from each of 4 locations (Bakersfield, CA; Ojai, CA; Quincy, FL; and a laboratory colony), were characterized for bacteria in dissected sharpshooter cibaria and precibaria by amplification and sequencing of a portion of the 16S rRNA gene using Illumina MiSeq technology. An average of approximately 150,000 sequence reads were obtained per insect. The most common genus detected was Wolbachia; sequencing of the Wolbachia ftsZ gene placed this strain in supergroup B, one of two Wolbachia supergroups most commonly associated with arthropods. X. fastidiosa was detected in all 96 individuals examined. By multilocus sequence typing, both X. fastidiosa subspecies fastidiosa and subspecies sandyi were present in GWSS from California and the colony; only subspecies fastidiosa was detected in GWSS from Florida. In addition to Wolbachia and X. fastidiosa, 23 other bacterial genera were detected at or above an average incidence of 0.1%; these included plant-associated microbes (Methylobacterium, Sphingomonas, Agrobacterium, and Ralstonia) and soil- or water-associated microbes (Anoxybacillus, Novosphingobium, Caulobacter, and Luteimonas). Sequences belonging to species of the family Enterobacteriaceae also were detected but it was not possible to assign these to individual genera. Many of these species likely interact with X. fastidiosa in the cibarium and

  11. Autochthonous bioaugmentation with environmental samples rich in hydrocarbonoclastic bacteria for bench-scale bioremediation of oily seawater and desert soil.

    Science.gov (United States)

    Ali, Nedaa; Dashti, Narjes; Salamah, Samar; Al-Awadhi, Husain; Sorkhoh, Naser; Radwan, Samir

    2016-05-01

    Oil-contaminated seawater and desert soil batches were bioaugmented with suspensions of pea (Pisum sativum) rhizosphere and soil with long history of oil pollution. Oil consumption was measured by gas-liquid chromatography. Hydrocarbonoclastic bacteria in the bioremediation batches were counted using a mineral medium with oil vapor as a sole carbon source and characterized by their 16S ribosomal RNA (rRNA)-gene sequences. Most of the oil was consumed during the first 2-4 months, and the oil-removal rate decreased or ceased thereafter due to nutrient and oxygen depletion. Supplying the batches with NaNO3 (nitrogen fertilization) at a late phase of bioremediation resulted in reenhanced oil consumption and bacterial growth. In the seawater batches bioaugmented with rhizospheric suspension, the autochthonous rhizospheric bacterial species Microbacterium oxidans and Rhodococcus spp. were established and contributed to oil-removal. The rhizosphere-bioaugmented soil batches selectively favored Arthrobacter nitroguajacolicus, Caulobacter segnis, and Ensifer adherens. In seawater batches bioaugmented with long-contaminated soil, the predominant oil-removing bacterium was the marine species Marinobacter hydrocarbonoclasticus. In soil batches on the other hand, the autochthonous inhabitants of the long-contaminated soil, Pseudomonas and Massilia species were established and contributed to oil removal. It was concluded that the use of rhizospheric bacteria for inoculating seawater and desert soil and of bacteria in long-contaminated soil for inoculating desert soil follows the concept of "autochthonous bioaugmentation." Inoculating seawater with bacteria in long-contaminated soil, on the other hand, merits the designation "allochthonous bioaugmentation." PMID:26801925

  12. Transcriptional analysis of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestial tract model

    DEFF Research Database (Denmark)

    Weiss, Gudrun Margarethe; Jespersen, Lene

    2010-01-01

    The aim of the present study was to investigate the transcription of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestinal tract model. As acidified milk exerted a protective effect on the bacteria leading to increased...... survival, the gene expression studies were carried out with pre-inoculation of L. acidophilus NCFM in acidified milk. The induction of the genes encoding the stress-related proteins GroEL, DnaK and ClpP, and adhesion-related genes encoding mucin-binding proteins, fibronectin-binding protein and S-layer was...... juice, but they were significantly upregulated during incubation in duodenal juice and bile (6- to 7-fold). A significant induction of the gene encoding the S-layer protein was not detected. Our results give a better understanding of the functionality of L. acidophilus NCFM and other probiotics during...

  13. Preparation of Cd(Zn)Te and CuInSe sub 2 films and devices by a two-stage process

    Energy Technology Data Exchange (ETDEWEB)

    Basol, B.M.; Kapur, V.K. (International Solar Electric Technology (ISET), Inglewood, CA (USA))

    1991-05-01

    The two-stage process was used to prepare thin films of Cd(Zn)Te and CuInSe{sub 2}. The technique involves first depositing the elemental components of the compound onto a substrate in the form of thin stacked layers and then reacting these elemental components to obtain a thin film of the desired compound. While CdTe films grown on thin CdS layers have uniform stoichiometries and sharp interfaces with the underlying CdS layers, CdZnTe films deposited onto similar substrates give rise to diffused CdZnTe-CdS interfaces because of the reactive nature of zinc. In CuInSe{sub 2} processing, the nature of the reacted compound film strongly depends on the nature of the Cu-In layers. CdS/CuInSe{sub 2} device efficiencies are also influenced by the method of deposition for the CdS window layers. (orig.).

  14. The effect of high-resistance SnO2 on CdS/CdTe device performance

    Science.gov (United States)

    Li, X.; Ribelin, R.; Mahathongdy, Y.; Albin, D.; Dhere, R.; Rose, D.; Asher, S.; Moutinho, H.; Sheldon, P.

    1999-03-01

    In this paper, we have studied the effect of high-resistance SnO2 buffer layers, deposited by low-pressure chemical-vapor deposition, on CdS/CdTe device performance. Our results indicate that when CdS/CdTe devices have a very thin layer of CdS or no CdS at all, the i-SnO2 buffer layer helps to increase device efficiency. When the CdS layer is thicker than 600 Å, the device performance is dominated by CdS thickness, not the i-SnO2 layer. If a very thin CdS layer is to be used to enhance device performance, we conclude that a better SnO2 buffer layer is needed.

  15. The enhancement of vortex pinning in ferromagnet/superconductor bilayers

    International Nuclear Information System (INIS)

    The magnetic-domain induced vortex pinning is studied in the ferromagnet/superconductor bilayers (FSB's), in which the F layers are Co/Pt multilayers with perpendicular magnetic anisotropy, and the S layers are either niobium or high temperature superconductor YBa2Cu3O7 (YBCO). The magnetization measurements reveal the enhancement of the flux pinning in both types of FSB's during the reversal of the magnetization of the F layer, but the details of the behavior depend on the type of the S layer. In the case of niobium FSB the maximum of pinning appears when the F layer is in the final stage of the magnetic reversal process, while the FSB with YBCO shows the maximum when the F layer is saturated. The possible origins of these differences are discussed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. The enhancement of vortex pinning in ferromagnet/superconductor bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cieplak, Marta Z.; Adamus, Z.; Abal' oshev, A.; Abal' osheva, I.; Berkowski, M. [Polish Academy of Sciences, Al. Lotnikw 32/46, 02668 Warsaw (Poland); Cheng, X.M.; Sang, Hai; Chien, C.L. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Md 21218 (United States)

    2005-03-01

    The magnetic-domain induced vortex pinning is studied in the ferromagnet/superconductor bilayers (FSB's), in which the F layers are Co/Pt multilayers with perpendicular magnetic anisotropy, and the S layers are either niobium or high temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO). The magnetization measurements reveal the enhancement of the flux pinning in both types of FSB's during the reversal of the magnetization of the F layer, but the details of the behavior depend on the type of the S layer. In the case of niobium FSB the maximum of pinning appears when the F layer is in the final stage of the magnetic reversal process, while the FSB with YBCO shows the maximum when the F layer is saturated. The possible origins of these differences are discussed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Characterization of CdS thin films electrodeposited by an alternating current electrolysis method

    International Nuclear Information System (INIS)

    Conventional electrochemical methods of making CdS films are anodic oxidation of cadmium in a solution containing sulfide ions, and cathodic reduction from solutions containing soluble metal and sulfur compounds. In this paper a method is presented in which a CdS layer is deposited by a.c. electrolysis. The substrate is a glass plate covered by a layer of tin oxide. The electrolyte is an aqueous solution containing cadmium sulphate, ammonium sulphate, sodium thiosulphate, sodium chloride and glycerol. The applied a.c. voltages correspond to symmetrical and asymmetrical rectangular waves. During the electrolysis two electrodes are alternately connected to positive and negative potentials. As a result, Cd/sup 2+/ and S/sup 2-/ particles deposit at each electrode by turns, which results in the formation of a CdS layer

  18. High efficiency Cu(In,Ga)Se{sub 2} thin film solar cells without intermediate buffer layers

    Energy Technology Data Exchange (ETDEWEB)

    Ramanathan, K.; Wiesner, H.; Asher, S.; Niles, D.; Bhattacharya, R.N.; Keane, J.; Contreras, M.A.; Noufi, R. [National Renewable Energy Lab., Golden, CO (United States). Electronic Materials and Devices Div.

    1998-09-01

    The nature of the interface between CuInGaSe{sub 2} (CIGS) and the chemical bath deposited CdS layer has been investigated. The authors show that heat-treating the absorbers in Cd- or Zn-containing solutions in the presence of ammonium hydroxide sets up an interfacial reaction with the possibility of an ion exchange occurring between Cd and Cu. The characteristics of devices made in this manner suggest that the reaction generates a thin, n-doped region in the absorber. The authors suggest that this aspect might be more important than the CdS layer in the formation of the junction. It is quite possible that the CdS/CuInSe{sub 2} device is a buried, shallow junction with a CdS window layer, rather than a heterojunction between CdS and CIGS. The authors use these ideas to develop methods for fabricating diodes without CdS or Cd.

  19. Proteomic analysis of secreted membrane vesicles of archaeal Sulfolobus species reveals the presence of endosome sorting complex components

    OpenAIRE

    Ellen, Albert F.; Albers, Sonja-Verena; Huibers, Wim; Pitcher, Angela; Hobel, Cedric F. V.; Schwarz, Heinz; Folea, Mihaela; Schouten, Stefan; Boekema, Egbert J.; Poolman, Bert; Driessen, Arnold J. M.

    2009-01-01

    The crenarchaea Sulfolobus acidocaldarius, S. solfataricus and S. tokodaii, release membrane vesicles into the medium. These membrane vesicles consist of tetraether lipids and are coated with an S-layer. A proteomic analysis reveals the presence of proteins homologous to subunits of the eukaryotic endosomal sorting complex required for transport (ESCRT). Immunodetection of one of these homologs suggest a cell surface localization in intact cells. These data suggest that the membrane vesicles ...

  20. An optimized efficient dual junction InGaN/CIGS solar cell: A numerical simulation

    Science.gov (United States)

    Farhadi, Bita; Naseri, Mosayeb

    2016-08-01

    The photovoltaic performance of an efficient double junction InGaN/CIGS solar cell including a CdS antireflector top cover layer is studied using Silvaco ATLAS software. In this study, to gain a desired structure, the different design parameters, including the CIGS various band gaps, the doping concentration and the thickness of CdS layer are optimized. The simulation indicates that under current matching condition, an optimum efficiency of 40.42% is achieved.

  1. Rearrangement of sapA homologs with conserved and variable regions in Campylobacter fetus.

    Science.gov (United States)

    Tummuru, M K; Blaser, M J

    1993-08-01

    The Campylobacter fetus surface-layer (S-layer) proteins mediate both complement resistance and antigenic variation in mammalian hosts. Wild-type strain 23D possesses the sapA gene, which encodes a 97-kDa S-layer protein, and several sapA homologs are present in both wild-type and mutant strains. Here we report that a cloned silent gene (sapA1) in C. fetus can express a functional full-length S-layer protein in Escherichia coli. Analysis of sapA and sapA1 and partial analysis of sapA2 indicate that a block of approximately 600 bp beginning upstream and continuing into the open reading frames is completely conserved, and then the sequences diverge completely, but immediately downstream of each gene is another conserved 50-bp sequence. Conservation of sapA1 among strains, the presence of a putative Chi (RecBCD recognition) site upstream of sapA, sapA1, and sapA2, and the sequence identities of the sapA genes suggest a system for homologous recombination. Comparison of the wild-type strain (23D) with a phenotypic variant (23D-11) indicates that variation is associated with removal of the divergent region of sapA from the expression locus and exchange with a corresponding region from a sapA homolog. We propose that site-specific reciprocal recombination between sapA homologs leads to expression of divergent S-layer proteins as one of the mechanisms that C. fetus uses for antigenic variation. PMID:8346244

  2. Nanocoating for biomolecule delivery using layer-by-layer self-assembly

    OpenAIRE

    KEENEY, M; Jiang, X. Y.; Yamane, M.; Lee, M.; Goodman, S.; Yang, F.

    2015-01-01

    Since its introduction in the early 1990s, layer-by-layer (LbL) self-assembly of films has been widely used in the fields of nanoelectronics, optics, sensors, surface coatings, and controlled drug delivery. The growth of this industry is propelled by the ease of film manufacture, low cost, mild assembly conditions, precise control of coating thickness, and versatility of coating materials. Despite the wealth of research on LbL for biomolecule delivery, clinical translation has been limited an...

  3. Crustal structure of the Columbia Plateau region, Washington

    International Nuclear Information System (INIS)

    Refraction data from blasts recorded in eastern Washington between 1980 and 1983 are used to determine the upper crustal structure of the Columbia Plateau. Fourteen blast sites with over 25 individual shots were recorded on the University of Washington regional seismic network made up of 36 short-period seismograph stations recorded digitally at 100 samples/s. Additional data were obtained from a 12-station dense digital network in the central plateau operated by the Rockwell Hanford Operations Basalt Waste Isolation Project. Major crustal refractors of 5.1 and 6.05 km/s are observed at distances of 15 to 50 km and 50 to 120 km, respectively. A time-term method is used to model layer thicknesses below the stations for each major refractor. A statistical source-receiver separation operation is used to handle the inherent nonindependence of the data. Constraints are used to fix the mean values of the time terms. Ray tracing through two-dimensional velocity structures is used to augment the interpretation of the time-term solutions for areas where the lateral velocity changes are large. Station delays for the 5.1-km/s layer show a good correlation with elevation and surficial geology. The areal extent of the 5.1-km/s layer roughly coincides with the Columbia River basalts. Time terms from the 6.05-km/s layer indicate a nearly uniform depth of 1 to 2 km in the northern plateau. Time terms in the central plateau indicate a depth to the 6.05-km/s layer of over 8 km, and a systematic thinning away from its center. Magnetotelluric studies indicate that the basalts are probably no thicker than 5 km in the central Columbia Plateau region

  4. Genome Sequence of Lactobacillus brevis Strain D6, Isolated from Smoked Fresh Cheese.

    Science.gov (United States)

    Kant, Ravi; Uroić, Ksenija; Hynönen, Ulla; Kos, Blaženka; Šušković, Jagoda; Palva, Airi

    2016-01-01

    The autochthonousLactobacillus brevisstrain D6, isolated from smoked fresh cheese, carries a 45-kDa S-layer protein. Strain D6 has shown adhesion to extracellular matrix proteins and to Caco-2 intestinal epithelial cells, as well as immunomodulatory potential and beneficial milk technological properties. Hence, it could be used as a potential probiotic starter culture for cheese production. PMID:27056237

  5. Phase Fluctuations and Non-Equilibrium Josephson Effect

    OpenAIRE

    Narozhny, B. N.; Aleiner, I. L.

    1999-01-01

    We consider a diffusive S-N-S junction with electrons in the normal layer driven out of equilibrium by external bias. We show that, the non-equilibrium fluctuations of the electron density in the normal layer cause the fluctuations of the phase of the order parameter in the S-layers. As a result, the magnitude of the Josephson current in the non-equilibrium junction is significantly supressed relative to its mean field value.

  6. Formation and characterization of conductive thin layers of copper sulfide (Cu {sub x}S) on the surface of polyethylene and polyamide by the use of higher polythionic acids

    Energy Technology Data Exchange (ETDEWEB)

    Ancutiene, Ingrida [Department of Inorganic Chemistry, Kaunas University of Technology, Radvilenu Str. 19, LT 50254, Kaunas 9 (Lithuania)]. E-mail: ingrida.ancutiene@ktu.lt; Janickis, Vitalijus [Department of Inorganic Chemistry, Kaunas University of Technology, Radvilenu Str. 19, LT 50254, Kaunas 9 (Lithuania); Ivanauskas, Remigijus [Department of Inorganic Chemistry, Kaunas University of Technology, Radvilenu Str. 19, LT 50254, Kaunas 9 (Lithuania)

    2006-04-15

    Layers of copper sulfide of varying composition and properties are formed on the surface of polyethylene and polyamide by a sorption-diffusion method using solutions of higher polythionic acids, H{sub 2}S {sub n}O{sub 6}. The concentration of sulfur adsorbed-diffused into PE and PA depends on the degree of the acid sulfurity, n, the temperature of the solution and the period of the polymer treatment. The amount of copper in a sulfide (Cu {sub x}S) layer formed after the sulfured polymer treatment with a solution of Cu(I-II) salt is strongly dependent on the concentration of sulfur in the PE and PA. By the chemical analysis of the obtained sulfide layers was determined that a value of x in the Cu {sub x}S layers varies in the interval 1 < x < 2. The microscopic investigation of transverse sections of PE and PA samples with copper sulfide layers showed that the major part of copper sulfide is in the surface matrix of the polymer. X-ray diffraction studies of the Cu {sub x}S layers obtained seven phases: with x = 2 (chalcocite), 1.9375 (djurleite), 1.8 (digenite), 1.75 (anilite), 1.12 (yarrowite), 1.06 (talnakhite) and 1 (covellite). The measurements of the electrical conductance of Cu {sub x}S layers (0.1-4 S cm{sup -2}) showed that its value greatly depends on the conditions of PE and PA interaction with H{sub 2}S {sub n}O{sub 6} and of further interaction with Cu(I-II) salt solution, on the chemical and phase composition of the layer.

  7. Activity of lysozyme on Lactobacillus hilgardii strains isolated from Port wine.

    Science.gov (United States)

    Dias, Rita; Vilas-Boas, Eduardo; Campos, Francisco M; Hogg, Tim; Couto, José António

    2015-08-01

    This work evaluated the effect of lysozyme on lactobacilli isolated from Port wine. Bacterial growth experiments were conducted in MRS/TJ medium and inactivation studies were performed in phosphate buffer (KH2PO4), distilled water and wine supplemented with different concentrations of lysozyme. The response of bacteria to lysozyme was found to be highly strain dependent. Some strains of Lactobacillus hilgardii together with Lactobacillus collinoides and Lactobacillus fructivorans were found to be resistant to concentrations of lysozyme as high as 2000 mg/L. It was observed that among the L. hilgardii taxon the resistant strains possess an S-layer coat. Apparently, the strains of L. collinoides and L. fructivorans studied are also S-layer producers as suggested by the total protein profile obtained by SDS-PAGE. Thus, the hypothetical protective role of the S-layer against the action of lysozyme was investigated. From the various treatments used to remove the protein from the surface of the cells, the one employing LiCl (5 M) was the most effective. LiCl pre-treated cells exposed to lysozyme (2000 mg/L) in KH2PO4 buffer maintained its resistance. However, when cells were suspended in distilled water an increased sensitivity to lysozyme was observed. Moreover, it was found that the addition of ethanol (20% v/v) to the suspension medium (distilled water) triggered a strong inactivation effect especially on cells previously treated with LiCl (reduction of >6 CFU log cycles). The results suggest that the S-layer exerts a protective effect against lysozyme and that the cell suspension medium influences the bacteriolysis efficiency. It was also noted that ethanol enhances the inactivation effect of lysozyme. PMID:25846910

  8. Formation and characterization of conductive thin layers of copper sulfide (Cu xS) on the surface of polyethylene and polyamide by the use of higher polythionic acids

    Science.gov (United States)

    Ancutiene, Ingrida; Janickis, Vitalijus; Ivanauskas, Remigijus

    2006-04-01

    Layers of copper sulfide of varying composition and properties are formed on the surface of polyethylene and polyamide by a sorption-diffusion method using solutions of higher polythionic acids, H 2S nO 6. The concentration of sulfur adsorbed-diffused into PE and PA depends on the degree of the acid sulfurity, n, the temperature of the solution and the period of the polymer treatment. The amount of copper in a sulfide (Cu xS) layer formed after the sulfured polymer treatment with a solution of Cu(I-II) salt is strongly dependent on the concentration of sulfur in the PE and PA. By the chemical analysis of the obtained sulfide layers was determined that a value of x in the Cu xS layers varies in the interval 1 < x < 2. The microscopic investigation of transverse sections of PE and PA samples with copper sulfide layers showed that the major part of copper sulfide is in the surface matrix of the polymer. X-ray diffraction studies of the Cu xS layers obtained seven phases: with x = 2 (chalcocite), 1.9375 (djurleite), 1.8 (digenite), 1.75 (anilite), 1.12 (yarrowite), 1.06 (talnakhite) and 1 (covellite). The measurements of the electrical conductance of Cu xS layers (0.1-4 S cm -2) showed that its value greatly depends on the conditions of PE and PA interaction with H 2S nO 6 and of further interaction with Cu(I-II) salt solution, on the chemical and phase composition of the layer.

  9. Direct observation of defect structure in protein crystals by atomic force and transmission electron microscopy.

    OpenAIRE

    Devaud, G; Furcinitti, P S; Fleming, J. C.; Lyon, M K; Douglas, K

    1992-01-01

    We have examined the structure of S-layers isolated from Sulfolobus acidocaldarius using atomic force microscopy (AFM) and transmission electron microscopy (TEM). From the AFM images, we were able to directly observe individual dimers of the crystal, defects in the crystal structure, and twin boundaries. We have identified two types of boundaries, one defined by a mirror plane and the other by a glide plane. This work shows that twin boundaries are highly structured regions that are directly ...

  10. Low resistivity Al-doped ZnS grown by MOVPE

    Science.gov (United States)

    Yasuda, T.; Hara, K.; Kukimoto, H.

    1986-09-01

    Low resistivity Al-doped ZnS layers have been grown by low pressure MOVPE using an adduct of diethylzinc-diethylsulfide (DEZn-DES) and H 2S as source materials and triethylaluminum (TEAl) as a dopant. The lowest resistivity achieved in this study is 3 × 10 -2 Ω cm for layers grown at a temperature of 350°C and at a TEAl transport rate ratio of {[TEAl]}/{[DEZn-DES]} = 4 × 10 -3.

  11. Influence of gamma irradiation on GeS nanostructured solar converter

    International Nuclear Information System (INIS)

    Full text : In recent years the scientists of North Cardin state of the United States have made a nanostrucutre similar to the flower of carnation from GeS layered crystals. From these nanostructures it is possible to make solar panels and batteries. The interest in layered semiconductor crystals is increasing rapidly. This is because the crystals are obtained by relatively easy technological method and its surface does not need extra gloss

  12. Metal-Controlled Assembly of Peptide and Protein-based Engineered Biomaterials

    OpenAIRE

    Smith, Sarah Jane

    2016-01-01

    Protein-protein interactions are ubiquitous throughout nature at many length and time scales—from transient interactions between individual proteins for signaling and electron transfer to the self-assembly over large distances of bacterial S-layer protein coats. Extensive research has been undertaken to attempt to mimic, interrogate, interrupt, or design protein-protein interactions, but natural protein-protein interactions often form as a result of many accumulated weak interactions over lar...

  13. Temperature dependent expression of flagella in Legionella

    OpenAIRE

    Ott, M.; Messner, P; Heesemann, J; Marre, R; Hacker, Jörg

    2011-01-01

    Legionel/a pneumophila, the causative agent of Legionnaires' disease, was analysed by electron microscopy for production of surface structures. Crystalline surface (S-) layers and fimbriae were not detected, but monotrichous flagellation was seen. Polyclonal antibodies specific for the 47 kDa ftagellin subunit of L. pneumophila Philadelphia I were used in Western blots to confirm the presence of flagella subunits in various L. pneumophila strains tested, but the antiserumalso reacted with fla...

  14. Cadmium sulfide/copper sulfide heterojunction cell research. Technical progress report No. 3, April 1--June 30, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Szedon, J. R.; Shirland, F. A.; Biter, W. J.; O& #x27; Keeffe, T. W.; Fonash, S. J.

    1978-08-23

    Extensive studies have been made of the structural details of Cu/sub 2/S films on evaporated polycrystalline CdS layers. Examinations of free standing films reveal Cu/sub 2/S penetration along grain boundaries of at least 5 ..mu..m on unetched CdS films and of 10 ..mu..m or more on etched films. Preliminary structural comparisons have been made on films yielding low (< 3%) and higher efficiency (approx. > 5%) cells. Minority carrier diffusion length values of about 0.3 ..mu..m have been obtained from photocurrent response to a laser spot scanned along a Cu/sub 2/S layer of graded thickness. Doubling the time of exposure to a 200/sup 0/C nitrogen ambient used in forming the Cu/sub 2/S layer does not significantly change the diffusion length. Anomalously high values of diffusion length (approx. > 1 ..mu..m) are indicated for a region associated with a crack in the CdS. Compositional profiling of Cu, S and Cd by ion scattering spectroscopy (ISS) and Auger electron spectroscopy (AES) have yielded generally similar results for Cu/sub 2/S films prepared on single crystal CdS substrates. Somewhat greater detail appears in certain of the profiles obtained with ISS which is attributed to less influence of depth averaging than in the AES case.

  15. The structure of the cysteine protease and lectin-like domains of Cwp84, a surface layer-associated protein from Clostridium difficile

    International Nuclear Information System (INIS)

    The crystal structure of Cwp84, an S-layer protein from Clostridium difficile is presented for the first time. The cathepsin L-like fold of cysteine protease domain, a newly observed ‘lectin-like’ domain and several other features are described. Clostridium difficile is a major problem as an aetiological agent for antibiotic-associated diarrhoea. The mechanism by which the bacterium colonizes the gut during infection is poorly understood, but undoubtedly involves a myriad of components present on the bacterial surface. The mechanism of C. difficile surface-layer (S-layer) biogenesis is also largely unknown but involves the post-translational cleavage of a single polypeptide (surface-layer protein A; SlpA) into low- and high-molecular-weight subunits by Cwp84, a surface-located cysteine protease. Here, the first crystal structure of the surface protein Cwp84 is described at 1.4 Å resolution and the key structural components are identified. The truncated Cwp84 active-site mutant (amino-acid residues 33–497; C116A) exhibits three regions: a cleavable propeptide and a cysteine protease domain which exhibits a cathepsin L-like fold followed by a newly identified putative carbohydrate-binding domain with a bound calcium ion, which is referred to here as a lectin-like domain. This study thus provides the first structural insights into Cwp84 and a strong base to elucidate its role in the C. difficile S-layer maturation mechanism

  16. The structure of the cysteine protease and lectin-like domains of Cwp84, a surface layer-associated protein from Clostridium difficile

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, William J. [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Kirby, Jonathan M. [Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Thiyagarajan, Nethaji [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Chambers, Christopher J.; Davies, Abigail H. [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Roberts, April K.; Shone, Clifford C. [Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Acharya, K. Ravi, E-mail: bsskra@bath.ac.uk [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)

    2014-07-01

    The crystal structure of Cwp84, an S-layer protein from Clostridium difficile is presented for the first time. The cathepsin L-like fold of cysteine protease domain, a newly observed ‘lectin-like’ domain and several other features are described. Clostridium difficile is a major problem as an aetiological agent for antibiotic-associated diarrhoea. The mechanism by which the bacterium colonizes the gut during infection is poorly understood, but undoubtedly involves a myriad of components present on the bacterial surface. The mechanism of C. difficile surface-layer (S-layer) biogenesis is also largely unknown but involves the post-translational cleavage of a single polypeptide (surface-layer protein A; SlpA) into low- and high-molecular-weight subunits by Cwp84, a surface-located cysteine protease. Here, the first crystal structure of the surface protein Cwp84 is described at 1.4 Å resolution and the key structural components are identified. The truncated Cwp84 active-site mutant (amino-acid residues 33–497; C116A) exhibits three regions: a cleavable propeptide and a cysteine protease domain which exhibits a cathepsin L-like fold followed by a newly identified putative carbohydrate-binding domain with a bound calcium ion, which is referred to here as a lectin-like domain. This study thus provides the first structural insights into Cwp84 and a strong base to elucidate its role in the C. difficile S-layer maturation mechanism.

  17. Chemical properties of litter in dark coniferous forest of Sejila Mountains in Tibet%西藏色季拉山暗针叶林凋落物层化学性质研究

    Institute of Scientific and Technical Information of China (English)

    钟国辉; 辛学兵

    2004-01-01

    The storage and chemical properties of the forest litter in dark coniferous forest of Sejila Mountain were studied. The results showed that the existing storage was 5.863t·hm-2 and the annual litter fall was 0.3205 t·hm-2. It implied that the forest litter decomposed slowly and accumulated quickly, and the turnover of nutrient circles was slow. The contents of N, Ca, Na, and Mn nutrient elements in litter layer were in the order of un-decomposed layer (U layer) > semi-decomposed layer (S layer) > decomposed layer (D layer), those of K, Fe, and Mg were in the order of D layer > S layer > U layer, and P element content was in the order of U layer > D layer > S layer. The pool of elements was 78.483 kg·hm-2 N, 3.843 kg·hm-2 P, 48.205 kg·hm-2 K, 23.115 kg·hm-2 Ca, 13.157 kg·hm-2 Na, 30.554 kg·hm-2 Fe, 2.113 kg·hm-2 Mn and 27.513 kg·hm-2 Mg. The turnover of forest litter was the total of nutrient release accumulation. K, Fe, and Mg were enriched, and N, Ca, Na, Mn, and P were released with the turnover rate in the order of N > Ca > Na > Mn >P.

  18. Functionalized biocompatible polyelectrolyte multilayers for drug delivery: In situ investigation of mechanical properties by dissipative quartz crystal microbalance

    International Nuclear Information System (INIS)

    Nanostructured polymeric capsules have been applied in different fields, and specifically are regarded as promising for smart drug delivery applications. The physical–chemical and mechanical properties, and thus the permeability of the polyelectrolyte multilayer shell, play an important role in efficient delivery. Quartz crystal microbalance working in liquid has been used for the characterization of the buildup process and of the viscoelastic properties of biocompatible multilayers and of their functionalization by S-layer proteins. Optical and scanning electron microscopy have been used for the morphological characterization of nanostructured capsules obtained at physiological conditions by the assembly of the characterized multilayers onto spherical cores and by their subsequent removal. The proposed functionalized biocompatible capsules can be regarded as promising candidates for smart drug delivery applications. - Graphical abstract: SEM image of nanostructured polymeric capsules made by 4 bilayers of collagen/alginate at pH 7.4. - Highlights: • Build-up of biocompatible multilayers and functionalization by S-layer proteins • Characterization of multilayer growth and mechanical properties by QCM • Fabrication of S-layer functionalized biocompatible capsules

  19. Functionalized biocompatible polyelectrolyte multilayers for drug delivery: In situ investigation of mechanical properties by dissipative quartz crystal microbalance

    Energy Technology Data Exchange (ETDEWEB)

    Habibi, Neda [Department of Informatics, Bioengineering, Robotics and Systems Engineering, University of Genova, Genova (Italy); Nanotechnology and Advanced Material Institute, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Pastorino, Laura, E-mail: laura.pastorino@unige.it [Department of Informatics, Bioengineering, Robotics and Systems Engineering, University of Genova, Genova (Italy); Ruggiero, Carmelina [Department of Informatics, Bioengineering, Robotics and Systems Engineering, University of Genova, Genova (Italy)

    2014-02-01

    Nanostructured polymeric capsules have been applied in different fields, and specifically are regarded as promising for smart drug delivery applications. The physical–chemical and mechanical properties, and thus the permeability of the polyelectrolyte multilayer shell, play an important role in efficient delivery. Quartz crystal microbalance working in liquid has been used for the characterization of the buildup process and of the viscoelastic properties of biocompatible multilayers and of their functionalization by S-layer proteins. Optical and scanning electron microscopy have been used for the morphological characterization of nanostructured capsules obtained at physiological conditions by the assembly of the characterized multilayers onto spherical cores and by their subsequent removal. The proposed functionalized biocompatible capsules can be regarded as promising candidates for smart drug delivery applications. - Graphical abstract: SEM image of nanostructured polymeric capsules made by 4 bilayers of collagen/alginate at pH 7.4. - Highlights: • Build-up of biocompatible multilayers and functionalization by S-layer proteins • Characterization of multilayer growth and mechanical properties by QCM • Fabrication of S-layer functionalized biocompatible capsules.

  20. Transcriptome changes and cAMP oscillations in an archaeal cell cycle

    Directory of Open Access Journals (Sweden)

    Soppa Jörg

    2007-06-01

    allowed to identify a strategy of transcript level regulation that is different from all previously characterized species. The transcript levels of only 3% of all genes are regulated, a fraction that is considerably lower than has been reported for four eukaryotic species (6% – 28% and for the bacterium C. crescentus (19%. It was shown that cAMP is present in significant concentrations in an archaeon, and the phylogenetic profile of the adenylate cyclase indicates that this signaling molecule is widely distributed in archaea. The occurrence of cell cycle-dependent oscillations of the cAMP concentration in an archaeon and in several eukaryotic species indicates that cAMP level changes might be a phylogenetically old signal for cell cycle progression.

  1. Functional Identification and Structure Determination of Two Novel Prolidases from cog1228 in the Amidohydrolase Superfamily

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Dao Feng; Patskovsky, Yury; Xu, Chengfu; Fedorov, Alexander A.; Fedorov, Elena V.; Sisco, Abby A.; Sauder, J. Michael; Burley, Stephen K.; Almo, Steven C.; Raushel, Frank M. (Einstein); (TAM); (Lilly)

    2010-12-07

    Two uncharacterized enzymes from the amidohydrolase superfamily belonging to cog1228 were cloned, expressed, and purified to homogeneity. The two proteins, Sgx9260c (gi|44242006) and Sgx9260b (gi|44479596), were derived from environmental DNA samples originating from the Sargasso Sea. The catalytic function and substrate profiles for Sgx9260c and Sgx9260b were determined using a comprehensive library of dipeptides and N-acyl derivative of L-amino acids. Sgx9260c catalyzes the hydrolysis of Gly-L-Pro, L-Ala-L-Pro, and N-acyl derivatives of L-Pro. The best substrate identified to date is N-acetyl-L-Pro with a value of k{sub cat}/K{sub m} of 3 x 10{sup 5} M{sup -1} s{sup -1}. Sgx9260b catalyzes the hydrolysis of L-hydrophobic L-Pro dipeptides and N-acyl derivatives of L-Pro. The best substrate identified to date is N-propionyl-L-Pro with a value of k{sub cat}/K{sub m} of 1 x 10{sup 5} M{sup -1} s{sup -1}. Three-dimensional structures of both proteins were determined by X-ray diffraction methods (PDB codes 3MKV and 3FEQ). These proteins fold as distorted ({beta}/{alpha})8-barrels with two divalent cations in the active site. The structure of Sgx9260c was also determined as a complex with the N-methylphosphonate derivative of L-Pro (PDB code 3N2C). In this structure the phosphonate moiety bridges the binuclear metal center, and one oxygen atom interacts with His-140. The {alpha}-carboxylate of the inhibitor interacts with Tyr-231. The proline side chain occupies a small substrate binding cavity formed by residues contributed from the loop that follows {beta}-strand 7 within the ({beta}/{alpha})8-barrel. A total of 38 other proteins from cog1228 are predicted to have the same substrate profile based on conservation of the substrate binding residues. The structure of an evolutionarily related protein, Cc2672 from Caulobacter crecentus, was determined as a complex with the N-methylphosphonate derivative of L-arginine (PDB code 3MTW).

  2. Photocatalytic hydrogen generation with simultaneous organic degradation by a visible light-driven CdS/ZnS film catalyst

    International Nuclear Information System (INIS)

    Highlights: • CdS/ZnS/Ru film catalyst is able to produce H2 under visible light. • The photocatalyst is capable of both H2 production and organic degradation. • ZnS layer improves the photoreactivity and stability of the CdS film. • CdS/ZnS/Ru in formic acid produces 123 mmol H2 and removes 1.9 g COD/m2-h. -- Abstract: A layered CdS/ZnS catalyst film was synthesized on glass using the stepped chemical bath deposition method. The film catalyst was shown as visible light-driven photocatalyst capable of producing H2 under visible light. The ZnS outer layer helped suppress the recombination of photo-generated electron–hole pairs on the CdS base layer, leading to faster H2 generation. The use of the ZnS layer also greatly improved the stability of the catalyst film and prevented the leaching of Cd2+ from the CdS layer. Deposition of Ru on the catalyst film further increased its photoreactivity for H2 production. The photocatalyst was effective in H2 production together with the degradation of model organic substances, such as formic acid, methanol, and ethanol. The greatest H2 production rates were achieved using the CdS/ZnS/Ru film in the formic acid solution at 123 μmol/m2-h under visible light and 135 mmol/m2-h under the simulated solar light. The corresponding theoretical reduction rates of chemical oxygen demand (COD) were 1.9 and 2.1 g/m2-h, respectively. As the multilayer CdS/ZnS/Ru film catalyst can be easily separated from water, it has a great potential for simultaneous photocatalytic hydrogen generation and organic wastewater treatment using solar energy

  3. Studies of CdS/CdTe interface: Comparison of CdS films deposited by close space sublimation and chemical bath deposition techniques

    International Nuclear Information System (INIS)

    The CdS layers were deposited by two different methods, close space sublimation (CSS) and chemical bath deposition (CBD) technique. The CdS/CdTe interface properties were investigated by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed a large CSS-CdS grain size in the range of 70-80 nm. The interface between CSS-CdS and CdTe were clear and sharp, indicating an abrupt hetero-junction. On the other hand, CBD-CdS layer had much smaller grain size in the 5-10 nm range. The interface between CBD-CdS and CdTe was not as clear as CSS-CdS. With the stepwise coverage of CdTe layer, the XPS core levels of Cd 3d and S 2p in CSS-CdS had a sudden shift to lower binding energies, while those core levels shifted gradually in CBD-CdS. In addition, XPS depth profile analyses indicated a strong diffusion in the interface between CBD-CdS and CdTe. The solar cells prepared using CSS-CdS yielded better device performance than the CBD-CdS layer. The relationships between the solar cell performances and properties of CdS/CdTe interfaces were discussed. - Highlights: • Studies of CdS deposited by close space sublimation and chemical bath deposition • An observation of CdS/CdTe interface by transmission electron microscope • A careful investigation of CdS/CdTe interface by X ray photoelectron spectra • An easier diffusion at the chemical bath deposition CdS and CdTe interface

  4. Studies of CdS/CdTe interface: Comparison of CdS films deposited by close space sublimation and chemical bath deposition techniques

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jun-feng, E-mail: pkuhjf@bit.edu.cn [Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, UMR CNRS 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France); Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Fu, Gan-hua; Krishnakumar, V.; Schimper, Hermann-Josef [Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); Liao, Cheng [Department of Physics, Peking University, Beijing 100871 (China); Jaegermann, Wolfram [Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); Besland, M.P. [Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, UMR CNRS 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France)

    2015-05-01

    The CdS layers were deposited by two different methods, close space sublimation (CSS) and chemical bath deposition (CBD) technique. The CdS/CdTe interface properties were investigated by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed a large CSS-CdS grain size in the range of 70-80 nm. The interface between CSS-CdS and CdTe were clear and sharp, indicating an abrupt hetero-junction. On the other hand, CBD-CdS layer had much smaller grain size in the 5-10 nm range. The interface between CBD-CdS and CdTe was not as clear as CSS-CdS. With the stepwise coverage of CdTe layer, the XPS core levels of Cd 3d and S 2p in CSS-CdS had a sudden shift to lower binding energies, while those core levels shifted gradually in CBD-CdS. In addition, XPS depth profile analyses indicated a strong diffusion in the interface between CBD-CdS and CdTe. The solar cells prepared using CSS-CdS yielded better device performance than the CBD-CdS layer. The relationships between the solar cell performances and properties of CdS/CdTe interfaces were discussed. - Highlights: • Studies of CdS deposited by close space sublimation and chemical bath deposition • An observation of CdS/CdTe interface by transmission electron microscope • A careful investigation of CdS/CdTe interface by X ray photoelectron spectra • An easier diffusion at the chemical bath deposition CdS and CdTe interface.

  5. Refractive indices of zinc sulfide and cryolite in multilayer stacks.

    Science.gov (United States)

    Netterfield, R P

    1976-08-01

    The refractive indices at 633 nm of ZnS and cryolite in multilayer stacks have been determined in the vacuum environment by measurements of the transmittance extrema during deposition. Estimates of the inhomogeneity of index as a function of layer thickness are given. The method gives average index measurements: (1) every lambda/4 for the first ZnS layer, (2) for an initial thickness as small as lambda/16, and thereafter every lambda/4 for the second layer, cryolite. The results are used to monitor the layer thicknesses of ZnS-cryolite multilayer stacks by theoretically predicting the transmittances of the system at the termination of each layer. PMID:20165308

  6. Expression of cbsA Encoding the Collagen-Binding S-Protein of Lactobacillus crispatus JCM5810 in Lactobacillus casei ATCC 393T

    OpenAIRE

    Martínez, Beatriz; Sillanpää, Jouko; Smit, Egbert,; Korhonen, Timo K.; Pouwels, Peter H.

    2000-01-01

    The cbsA gene encoding the collagen-binding S-layer protein of Lactobacillus crispatus JCM5810 was expressed in L. casei ATCC 393T. The S-protein was not retained on the surface of the recombinant bacteria but was secreted into the medium. By translational fusion of CbsA to the cell wall sorting signal of the proteinase, PrtP, of L. casei, CbsA was presented at the surface, rendering the transformants able to bind to immobilized collagens.

  7. The oscillation of the critical temperature of S-F multilayers

    International Nuclear Information System (INIS)

    The method of the analytical solution of Usadel equations for S-F systems with large exchange ferromagnetic field is proposed. It is shown that the critical temperature of S-F superlattices and critical current of S-F-S Josephson junctions oscillate as the exchange field and thickness of F-layers change. These oscillations are connected with the transition into the state where the phase of superconductivity order parameter is different on the adjacent S-layers. The possibilities of experimental observation of proposed effects are briefly discussed. (orig.)

  8. Simulation of the Efficiency of CdS/CdTe Tandem Multi-Junction Solar Cells

    OpenAIRE

    Mirkamali, Ashrafalsadat S.; Muminov, Khikmat Kh.

    2016-01-01

    In this paper we study CdS/CdTe solar cells by means of AMPS-1D software. First we study the effect of thickness of semiconductor layers on the output parameters of the CdS/CdTe solar cell, such as density of short-circuit current, open circuit voltage, fill factor and efficiency. Numerical simulation shows that the highest efficiency of single-junction CdS/CdTe solar cell equal to 18.3% is achieved when the CdTe layer thickness is 1000 nm and a CdS layer is 60 nm. Then, in order to obtain th...

  9. Prospects of Back Surface Field Effect in Ultra-Thin High-Efficiency CdS/CdTe Solar Cells from Numerical Modeling

    OpenAIRE

    Nowshad Amin; M. A. Matin; Aliyu, M. M.; Alghoul, M. A.; M. R. Karim; K. Sopian

    2010-01-01

    Polycrystalline CdTe shows greater promises for the development of cost-effective, efficient, and reliable thin film solar cells. Results of numerical analysis using AMPS-1D simulator in exploring the possibility of ultrathin, high efficiency, and stable CdS/CdTe cells are presented. The conventional baseline case structure of CdS/CdTe cell has been explored with reduced CdTe absorber and CdS window layer thickness, where 1 μm thin CdTe and 50 nm CdS layers showed reasonable efficiencies over...

  10. Analysis of the diode characteristics of thin film solar cells based on CdTe

    International Nuclear Information System (INIS)

    A physical approach to the optimization of photoelectric processes in thin film multilayer systems has been developed. By means of a simulation of the influence of light-diode characteristics on the efficiency factor, it is concluded that the optimization of the photoelectric processes in ITO/CdS/CdTe/Cu/Au film solar cells is mainly determined by two competing physical mechanisms: an increase in the efficiency of the process of distribution of nonequilibrium charge carriers and a reduction in the efficiency of their generation, as the CdS layer thickness grows

  11. Secretion Genes as Determinants of Bacillus anthracis Chain Length

    OpenAIRE

    Nguyen-Mau, Sao-Mai; Oh, So-Young; Kern, Valerie J.; Missiakas, Dominique M.; Schneewind, Olaf

    2012-01-01

    Bacillus anthracis grows in chains of rod-shaped cells, a trait that contributes to its escape from phagocytic clearance in host tissues. Using a genetic approach to search for determinants of B. anthracis chain length, we identified mutants with insertional lesions in secA2. All isolated secA2 mutants exhibited an exaggerated chain length, whereas the dimensions of individual cells were not changed. Complementation studies revealed that slaP (S-layer assembly protein), a gene immediately dow...

  12. CdS thin films obtained by thermal treatment of cadmium(II) complex precursor deposited by MAPLE technique

    International Nuclear Information System (INIS)

    Thin films of [Cd{SSi(O-But)3}(S2CNEt2)]2, precursor for semiconducting CdS layers, were deposited on silicon substrates by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. Structural analysis of the obtained films by Fourier transform infrared spectroscopy (FTIR) confirmed the viability of the procedure. After the deposition of the coordination complex, the layers are manufactured by appropriate thermal treatment of the system (thin film and substrate), according to the thermal analysis of the compound. Surface morphology of the thin films was investigated by atomic force microscopy (AFM) and spectroscopic-ellipsometry (SE) measurements.

  13. Inverse Proximity Effect in Superconductor-ferromagnet Bilayer Structures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Jing

    2010-04-05

    Measurements of the polar Kerr effect using a zero-area-loop Sagnac magnetometer on Pb/Ni and Al/(Co-Pd) proximity-effect bilayers show unambiguous evidence for the 'inverse proximity effect,' in which the ferromagnet (F) induces a finite magnetization in the superconducting (S) layer. To avoid probing the magnetic effects in the ferromagnet, the superconducting layer was prepared much thicker than the light's optical penetration depth. The sign and size of the effect, as well as its temperature dependence agree with recent predictions by Bergeret et al.[1].

  14. PbS colloidal quantum dot photodiodes for SWIR detection

    OpenAIRE

    Heves, Emre; Gürbüz, Yaşar; Gurbuz, Yasar

    2012-01-01

    In this work, PbS colloidal quantum dot based photodiodes are realized compatible for the integration on ROIC's. Schottky photodiode architecture is selected for its fast response and moderate sensitivity. The device is formed from Indium tin oxide (ITO) anode, the photosensitive PbS layer and a schottky contact formed of titanium and gold. Pinhole-free uniform PbS quantum dots film achieved by optimized layer by layer spin coating process. Solid-state ligand change procedure applied during f...

  15. Potential of CuS cap to prevent decomposition of Cu2ZnSnS4 during annealing

    OpenAIRE

    Larsen, Jes K.; Scragg, Jonathan JS; Frisk, Christopher; Ren, Yi; Platzer-Björkman, Charlotte

    2015-01-01

    One of the challenges associated with processing of Cu2ZnSnS4 (CZTS) is the thermal decomposition reaction that causes loss of S and SnS from the absorber surface. To reduce the decomposition a sufficiently high SnS and S partial pressure must be supplied during annealing. The absorber surface can alternatively be protected with a thin cap. Aiming to obtain a more flexible process, CZTS precursors were capped with a thin CuS layer before annealing. The cap was subsequently removed with a KCN ...

  16. Analysis Of SnS2 Buffer Layer And SnS Back Surface Layer Based CZTS Solar Cells Using SCAPS

    OpenAIRE

    Kumar, Atul; Thakur, Ajay D.

    2015-01-01

    A Copper-Zinc-Tin-Sulphide (CZTS)based solar cell with a modified ce3ll configuration of Mo/SnS/CZTS/SnS2/ZnO is simulated using SCAPS. An SnS2 buffer layer is used in simulation instead of the standard CdS layer. An additional back surface passivation layer of SnS is added in the modified cell configuration. An improvement in the solar cell efficiency compared to the standard CdS buffer based solar cell configuration Mo/CZTS/CdS/ZnO is found. The observations suggest the possibility of using...

  17. Electric and electroluminescence properties of mis-structures on the base of CdS crystals

    International Nuclear Information System (INIS)

    Optoelectronic properties of MIS-structures, which were obtained by thermal evaporation of insulating ZnSe layers on low-resistance CdS layers are researched. The voltage-current characteristics of diodes can be described with the help of current's theory, which are limited by space charges. The main parameters of insulating ZnSe layers are determined. The efficiency of injection electroluminescence from the structures under study in the green-blue region reaches 10-3 quantum/electron at 80 K

  18. The Type II Pullulanase of Thermococcus hydrothermalis: Molecular Characterization of the Gene and Expression of the Catalytic Domain

    OpenAIRE

    Erra-Pujada, Marta; Debeire, Philippe; Duchiron, Francis; O’Donohue, Michael J.

    1999-01-01

    The gene encoding a hyperthermostable type II pullulanase produced by Thermococcus hydrothermalis (Th-Apu) has been isolated. Analysis of a total of 5.2 kb of genomic DNA has revealed the presence of three open reading frames, one of which (apuA) encodes the pullulanase. This enzyme is composed of 1,339 amino acid residues and exhibits a multidomain structure. In addition to a typical N-terminal signal peptide, Th-Apu possesses a catalytic domain, a domain bearing S-layer homology-like motifs...

  19. Conjugation by Mosquito Pathogenic Strains of Bacillus sphaericus

    OpenAIRE

    Correa Margarita; Yousten Allan A

    1997-01-01

    A mosquito pathogenic strain of Bacillus sphaericus carried out the conjugal transfer of plasmid pAMß1 to other strains of its own and two other serotypes. However, it was unable to conjugate with mosquito pathogens from three other serotypes, with B. sphaericus of other DNA homology groups or with three other species of Bacillus. Conjugation frequency was highest with a strain having an altered surface layer (S layer). Conjugal transfer of pAMß1 was not detected in mosquito larval cadavers. ...

  20. Acoustic Streaming, The “Small Invention” of Cianobacteria?

    OpenAIRE

    Koiller, Jair; Ehlers, Kurt M.; Chalub, Fabio

    2010-01-01

    Micro-engineering pumping devices without mechanical parts appeared “way back” in the early 1990’s. The working principle is acoustic streaming. Has Nature “rediscovered” this invention 2.7 Gyr ago? Strands of marine cyanobacteria Synechococcus swim 25 diameters per second without any visible means of propulsion. We show that nanoscale amplitude vibrations on the S-layer (a crystalline shell outside the outer membrane present in motile strands) and frequencies of the order of 0.5-1.5 MHz (ach...

  1. A crime novel (title redacted) : from theory to publication

    OpenAIRE

    Johnston, Paul

    2013-01-01

    Title redacted at the request of the author. 31/1/14 The first part of the thesis comprises Chapters 1 to 40 of the novel, written under a pseudonym, followed by a synopsis of the remaining chapters, 41 to 155. The potential jacket copy will refer to the protagonists, a male and a female detective. The second part of the thesis is a critical study of the novel. Literary theory and critical methods are used to investigate the writing process and to explicate the text’s layer...

  2. Do large structures control their own growth in a mixing layer? - An assessment

    Science.gov (United States)

    Kaul, Upender K.

    1988-01-01

    Two different two-dimensional free shear layers, the T-layer developing in time from an initial tangential velocity discontinuity separating the two half-spaces, and the S-layer which develops downstream of the origin where two uniform streams of unequal velocity are brought into tangential contact, are compared. Calculations are performed in order to determine to what extent the perturbations induced upstream by large concentrations of vorticity found downstream hasten or retard the subharmonic instability that leads to the formations of these large structures. The results show that the elliptic influence, or the feedback, in a mixing layer is relatively small for small velocity ratios.

  3. Smart SOA platforms in cloud computing architectures

    CERN Document Server

    Exposito , Ernesto

    2014-01-01

    This book is intended to introduce the principles of the Event-Driven and Service-Oriented Architecture (SOA 2.0) and its role in the new interconnected world based on the cloud computing architecture paradigm. In this new context, the concept of "service" is widely applied to the hardware and software resources available in the new generation of the Internet. The authors focus on how current and future SOA technologies provide the basis for the smart management of the service model provided by the Platform as a Service (PaaS) layer.

  4. In situ variations of carrier decay and proton induced luminescence characteristics in polycrystalline CdS

    Energy Technology Data Exchange (ETDEWEB)

    Gaubas, E., E-mail: eugenijus.gaubas@ff.vu.lt; Ceponis, T.; Jasiunas, A.; Kalesinskas, V.; Meskauskaite, D.; Pavlov, J.; Tamulaitis, G.; Tekorius, A. [Institute of Applied Research, Vilnius University, Vilnius LT-10222 (Lithuania); Brytavskyi, I. [Odessa I.I.Mechnikov National University, Odessa 65082 (Ukraine); Kovalevskij, V.; Remeikis, V. [Centre for Physical Sciences and Technology, Vilnius LT-02300 (Lithuania)

    2014-06-28

    Evolution of the microwave-probed photoconductivity transients and of the proton induced luminescence has simultaneously been examined in polycrystalline CdS layers evaporated in vacuum during exposure to a 1.6 MeV proton beam. The decrease of the intensity of luminescence peaked at 510 and 709 nm wavelengths and of values of the effective carrier lifetime has been correlated in dependence of proton irradiation fluence. The defect introduction rate has been evaluated by the comparative analysis of the laser and proton beam induced luminescence. The difference of a carrier pair generation mechanism inherent for light and for a proton beam has been revealed.

  5. Development of nitride-layer of AISI 304 austenitic stainless steel during high-temperature ammonia gas-nitriding

    International Nuclear Information System (INIS)

    Ammonia-gas nitriding of AISI 304 austenitic stainless steel was studied at temperatures higher than 800 deg. C using SEM and X-ray diffraction. The result showed that S-phase, an expanded austenite, was formed even at such high temperatures due to a high nitriding potential of ammonia gas. The equilibrium phase, CrN was formed through a decomposition of S-layer in two different modes; the one was through continuous precipitation of particles at the surface-side of S-layer due to a higher nitriding potential; the other through a discontinuous(-like) precipitation at the austenite interface-side, producing a fine lamellar structure of austenite and CrN. The γ-phase in the surface-side resulting from the precipitation of CrN particles subsequently transformed into Fe4N because of a fast enrichment of N atoms and a limited mobility of Cr atoms at the surface-side. A coarse lamellar structure made of austenite and Cr2N was developed in front of fine lamellae composed of austenite and CrN by the decomposition of supersaturated austenite through a discontinuous precipitation via grain boundary movement.

  6. A NEW CONCEPT TOWARD INDUSTRIALIZATION OF Cu-Ⅲ-Ⅵ2 THIN FILM SOLAR CELLS AND SOME PRELIMINARY EXPERIMENT RESULTS

    Institute of Scientific and Technical Information of China (English)

    L.X. Shao; H.L. Hwang

    2005-01-01

    A new concept of full vacuum manufacturing for Cu-Ⅲ-Ⅳ2 thin-film solar cells has been discussed. Cu-Ⅲ-Ⅳ2 thin-film solar cells manufactured using full in-line reactive sputtering will result in lower cost than that of the conventional method with CdS layer fabricated with chemical bath deposition (CBS) method. Using reactive sputtering process with organometallic gases, the compositions and electronic properties of Cu-Ⅲ-Ⅳ2 thin-film can be fine-tuned and precisely controlled. n-type Cu-Ⅲ-Ⅳ2 film and ZnS suffer layer can also be deposited using the in-line sputtering instead of using the CdS layer. The environmental pollution problems arising from using CdS can be eliminated and the ultimate goal of full in-line process development can then be realized. Some preliminary experimental results on a modal solar cell fabricated by the new technique in the new concept have been presented.

  7. Transcriptional analysis of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestinal tract model.

    Science.gov (United States)

    Weiss, G; Jespersen, L

    2010-01-01

    The aim of the present study was to investigate the transcription of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestinal tract model. As acidified milk exerted a protective effect on the bacteria leading to increased survival, the gene expression studies were carried out with pre-inoculation of L. acidophilus NCFM in acidified milk. The induction of the genes encoding the stress-related proteins GroEL, DnaK and ClpP, and adhesion-related genes encoding mucin-binding proteins, fibronectin-binding protein and S-layer was analyzed by real-time PCR. The genes encoding GroEL, DnaK and ClpP were significantly up-regulated (9- to 16-fold) during gastric digestion and declined upon subsequent duodenal digestion. The genes encoding mucin-binding proteins and fibronectin-binding protein were not influenced by saliva and gastric juice, but they were significantly upregulated during incubation in duodenal juice and bile (6- to 7-fold). A significant induction of the gene encoding the S-layer protein was not detected. Our results give a better understanding of the functionality of L. acidophilus NCFM and other probiotics during passage through the gastrointestinal tract; hence, they provide an implementable basis for the selection of prospective probiotic candidates. PMID:20559014

  8. CdTe thin film solar cells with reduced CdS film thickness

    International Nuclear Information System (INIS)

    A study was performed to reduce the CdS film thickness in CdTe thin film solar cells to minimize losses in quantum efficiency. Using close space sublimation deposition for CdS and CdTe a maximum efficiency of ∼ 9.5% was obtained with the standard CdS film thickness of ∼ 160 nm. Reduction of the film CdS thickness to less than 100 nm leads to poor cell performance with ∼ 5% efficiency, mainly due to a lower open circuit voltage. An alternative approach has been tested to reduce the CdS film thickness (∼ 80 nm) by depositing a CdS double layer. The first CdS layer was deposited at high substrate temperature in the range of 520-540 deg. C and the second CdS layer was deposited at low substrate temperature of ∼ 250 deg. C. The cell prepared using a CdS double layer show better performance with cell efficiency over 10%. Quantum efficiency measurement confirmed that the improvement in the device performance is due to the reduction in CdS film thickness. The effect of double layer structure on cell performance is also observed with chemical bath deposited CdS using fluorine doped SnO2 as substrate.

  9. Equatorial sporadic E-layer abnormal density enhancement during the recovery phase of the December 2006 magnetic storm: A case study

    Science.gov (United States)

    Resende, L. C. A.; Denardini, C. M.

    2012-04-01

    Sporadic layers appear in the equatorial region ( E sq) between 90 and 130 km mainly due to irregularities in the electrojet equatorial (EEJ) current. In the present work, we have analyzed the behavior of the frequency parameters associated with these sporadic layers, covering the days before, during, and subsequent to, the intense magnetic storm that occurred on December 14, 2006. The parameters used in our analyses are the top frequency ( f t E s) and blanketing frequency ( f b E s) of the E s layer as measured over São Luís, Brazil (2.33°S, 44.2°W, dip: -4.5°) by digital ionosonde. A tentative association between these parameters and X-ray data measured by sensors on board the GOES satellite was carried out. Also, we investigated the effects on the dynamics of the equatorial electrojet using magnetometer data related to the presence of these E s layers. Our analyses show that there are notable changes in the f b E s, which are characterized by the occurrence of peaks that exceed the ambient background values.

  10. Microfabricated instruments and methods to treat recurrent corneal erosions

    Energy Technology Data Exchange (ETDEWEB)

    Britton, Jr., Charles L.; D' urso, Brian R.; Chaum, Edward; Simpson, John T.; Baba, Justin S.; Ericson, M. Nance; Warmack, Robert J.

    2015-06-02

    In one embodiment, the present invention provides a device and method for treating recurrent corneal erosion. In one embodiment, the method includes the steps of contacting an epithelium layer of a cornea with an array of glass micro-rods including a plurality of sharp features having a length that penetrates a Bowman's layer of the eye, wherein the plurality of sharp features of the array of glass micro-rods produces a plurality of punctures in the Bowman's layer of the eye that are of micro-scale or less. In another embodiment, the present invention provides a method and device for drug delivery. In one embodiment, the device includes an array of glass micro-rods, wherein at least one glass micro-rod of the array of glass micro-rods includes a sharp feature opposite a base of the array of glass micro-rods, wherein the sharp feature includes a treated surface for delivering a chemical compound to the eye.

  11. Investigation of the potassium fluoride post deposition treatment on the CIGSe/CdS interface using hard X-ray photoemission spectroscopy - a comparative study.

    Science.gov (United States)

    Ümsür, Bünyamin; Calvet, Wolfram; Steigert, Alexander; Lauermann, Iver; Gorgoi, Mihaela; Prietzel, Karsten; Greiner, Dieter; Kaufmann, Christian A; Unold, Thomas; Lux-Steiner, Martha Ch

    2016-05-18

    The impact of the potassium fluoride post deposition treatment on CIGSe chalcopyrite absorbers is investigated by means of depth resolved hard X-ray photoemission spectroscopy of the near surface region. Two similar, slightly Cu-poor CIGSe absorbers were used with one being treated by potassium fluoride prior to the chemical bath deposition of an ultrathin CdS layer. The thickness of the CdS layer was chosen to be in the range of about 10 nm in order to allow the investigation of the CIGSe/CdS interface by the application of hard X-rays, increasing the information depth up to 30 nm. Besides strong intermixing on both samples, an increased Cu depletion of the KF treated absorber was observed in combination with an increased accumulation of Cd and S. In addition, a general shift of about 0.15 eV to higher binding energies of the CIGSe valence band at the absorber surface as well as the CIGSe and CdS related core levels was measured on the KF treated sample. This phenomenon is attributed to the impact of additional cadmium which acts as donor and releases further electrons into the conduction band of the absorber. Finally, the electrons accumulate at the CdS surface after having passed the interface region. This additional surface charge leads to a pronounced shift in the photoemission spectra as observed on the KF treated CIGSe absorber compared to the non-treated absorber. PMID:27160389

  12. Archaeal membrane-associated proteases: insights on Haloferax volcanii and other haloarchaea

    Directory of Open Access Journals (Sweden)

    Maria Ines Giménez

    2015-02-01

    Full Text Available The function of membrane proteases range from general house-keeping to regulation of cellular processes. Although the biological role of these enzymes in archaea is poorly understood, some of them are implicated in the biogenesis of the archaeal cell envelope and surface structures. The membrane-bound ATP-dependent Lon protease is essential for cell viability and affects membrane carotenoid content in Haloferax volcanii. At least two different proteases are needed in this archaeon to accomplish the posttranslational modifications of the S-layer glycoprotein. The rhomboid protease RhoII is involved in the N-glycosylation of the S-layer protein with a sulfoquinovose-containing oligosaccharide while archaeosortase ArtA mediates the proteolytic processing coupled-lipid modification of this glycoprotein facilitating its attachment to the archaeal cell surface. Interestingly, two different signal peptidase I homologs exist in H. volcanii, Sec11a and Sec11b, which likely play distinct physiological roles. Type IV prepilin peptidase PibD processes flagellin/pilin precursors, being essential for the biogenesis and function of the archaellum and other cell surface structures in H. volcanii.

  13. Electroluminescence of Tb(o-BBA)3(phen) based on an organic-inorganic heterostructure

    International Nuclear Information System (INIS)

    An organic-inorganic heterostructure device was designed to improve the electroluminescence intensity of terbium ion. In this heterostructure, a mixed solution of (Tb(o-BBA)3(phen)) and poly(N-vinylcarbazole) (PVK) was prepared with a weight ratio of 3:1 which was acted as a hole transporting and emitting layer. A wide band semiconductor zinc sulfide (ZnS) layer was used as an electron transporting and hole blocking layer. Characteristic emissions of terbium ion from the organic-inorganic heterostructure device were observed and the electroluminescence intensity of terbium ion increased abruptly when the driving voltage went beyond 20.5 V. This may be due to a directly impact excitation of terbium ion by hot electrons, accelerated in ZnS layer, and then a recombination with the injected holes. The electroluminescence mechanism of Tb(o-BBA)3(phen)-doped PVK was the charge-carrier trapping process by the dopant molecule according to the emission spectra of PVK and the excitation spectra of Tb(o-BBA)3(phen)

  14. The synthesis of CdSe quantum dots with carboxyl group and study on their optical characteristics

    International Nuclear Information System (INIS)

    Quantum dots are nanocrystal semiconductors which attract lots of research interests due to their peculiar optical properties. CdSe/ZnS quantum dots have been synthesized via pyrolysis of organometallic reagents. The color of the quantum dot changes from yellow-green to red as their size increases with reaction time. Photoluminescence quantum efficiency of CdSe quantum dots have been enhanced by passivating the surface of CdSe quantum dots with ZnS layers. Quantum dots are nanocrystal semiconductors which attract lots of research interests due to their peculiar optical properties. CdSe/ZnS quantum dots have been synthesized via pyrolysis of organometallic reagents. The color of the quantum dot changes from yellow-green to red as their size increases with reaction time. Photoluminescence quantum efficiency of CdSe quantum dots have been enhanced by passivating the surface of CdSe quantum dots with ZnS layers. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. The specificationof nano-structure superficial layers in some of the pathogen bacteria

    Directory of Open Access Journals (Sweden)

    Shilla Jalalpoor

    2010-11-01

    Full Text Available Background: The superficial layer is a part of the cellular envelop that is seen in bacteria and archaea. This superficial layer is a single layer structure composed of subordinate proteins or glycoproteins. The superficial layer is the outer most cellular structure that is in the exchange and reaction around environment with bacteria. This structure has very diversity in bacteria different types.Materials and Method: The related articles to superficial layer were extracted of these articles: Pubmed, Elsevier Science, and Yahoo, from 1995 to 2010 years. For this purpose keywords were searched including superficial layer, pathogenesis, pathogen bacteria,Results: There is consensus in the case of the superficial layer and about the existence of this superficial structure lead to increased pathogenesis in bacteria, in all of the research articles.Conclusion: S-layers in pathogen bacteria with bacteria protection against bacteriophages and phagocytosis, resistance against low pH, adhesion, stabilisation of the membrane and providing adhesion sites for exoproteins caused pathogenesis, infection resistant and antibiotic resistant in host.The result of this study shows the prevalence of considerable S-layer in pathogen bacteria and this matter identified the bacteria generator importance of this structure in the laboratory

  16. Annealing effect for SnS thin films prepared by high-vacuum evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Revathi, Naidu, E-mail: revathi.naidu@ttu.ee; Bereznev, Sergei; Loorits, Mihkel; Raudoja, Jaan; Lehner, Julia; Gurevits, Jelena; Traksmaa, Rainer; Mikli, Valdek; Mellikov, Enn; Volobujeva, Olga [Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, Tallinn 19086 (Estonia)

    2014-11-01

    Thin films of SnS are deposited onto molybdenum-coated soda lime glass substrates using the high-vacuum evaporation technique at a substrate temperature of 300 °C. The as-deposited SnS layers are then annealed in three different media: (1) H{sub 2}S, (2) argon, and (3) vacuum, for different periods and temperatures to study the changes in the microstructural properties of the layers and to prepare single-phase SnS photoabsorber films. It is found that annealing the layers in H{sub 2}S at 400 °C changes the stoichiometry of the as-deposited SnS films and leads to the formation of a dominant SnS{sub 2} phase. Annealing in an argon atmosphere for 1 h, however, causes no deviations in the composition of the SnS films, though the surface morphology of the annealed SnS layers changes significantly as a result of a 2 h annealing process. The crystalline structure, surface morphology, and photosensitivity of the as-deposited SnS films improves significantly as the result of annealing in vacuum, and the vacuum-annealed films are found to exhibit promising properties for fabricating complete solar cells based on these single-phase SnS photoabsorber layers.

  17. Complex formation of U(VI) with Bacillus-isolates from a uranium mining waste pile

    International Nuclear Information System (INIS)

    Accumulation studies with vegetative cells and spores of three Bacillus isolates (JG-A 30, JG-A 12, JG-A 22, classified as Bacillus cereus, Bacillus sphaericus, Bacillus megaterium) from a uranium mining waste pile (Johanngeorgenstadt, Saxony) and their corresponding reference strains have shown that Bacilli accumulate high amounts of U(VI) in the concentration range examined (11-214 mg/L). Information on the binding strength and the reversibility were obtained from extraction studies with different extractants. With 0.01 M EDTA solution the uranium bound to the biomass was released almost quantitatively. The characterization of the bacterial-UO22+-complexes by time-resolved laser fluorescence spectroscopy (TRLFS) showed the formation of inner-sphere complexes with phosphate groups of the biomass. The results lead to the conclusion that the cell wall components with phosphate residues e.g., polysaccharides, teichoic and teichuroic acids or phospholipide layers of the membranes are responsible for the uranium binding. The spectroscopic studies of the U(VI)-complexes with isolated bacterial cell walls and isolated surface-layer proteins of the strain Bacillus sphaericus NCTC 9602 after cell fractionation have shown that the complexation of U(VI) with intact cells (vegetative cells or spores) is different from the coordination with isolated cell wall components, especially with the S-layer proteins. For all Bacillus strains studied in this work, a significant contribution of the S-layer proteins to the binding of uranyl to living cells can be excluded. (orig.)

  18. Systematic Studies of Shock Revival and the Subsequent Evolutions in Core-collapse Supernovae with Parametric Progenitor Models

    Science.gov (United States)

    Yamamoto, Yu; Yamada, Shoichi

    2016-02-01

    We conducted one-dimensional and two-dimensional hydrodynamic simulations of post-shock revival evolutions in core-collapse supernovae, employing the simple neutrino light bulb approximation to produce explosions rather easily. In order to estimate the explosion energy, we took into proper account nuclear recombinations and fusions consistently with the equation of state for matter not in statistical equilibrium in general. The methodology is similar to our previous work, but is somehow improved. In this paper, we studied the influence of the progenitor structure on the dynamics systematically. In order to expedite our understanding of the systematics, we constructed six parametric progenitor models, which are different in masses of Fe iron core and Si+S layer, instead of employing realistic models provided by stellar evolution calculations, which are sometimes of stochastic nature as a function of stellar mass on the main sequence. We found that the explosion energy is tightly correlated with the mass accretion rate at shock revival irrespective of dimension and the progenitors with light iron cores but with rather high entropies, which have yet to be produced by realistic stellar evolution calculations, may reproduce the canonical values of explosion energy and nickel mass. The mass of the Si+S layer is also important in the mass accretion history after bounce, on the other hand; the higher mass accretion rates and resultant heavier cores tend to hamper strong explosions.

  19. Continental subsurface waters support unique but diverse C-acquisition strategies

    Science.gov (United States)

    Lau, C. M.; Magnabosco, C.; Brown, C. T.; Grim, S. L.; Lacrampe Couloume, G.; Wilkie, K. M.; Sherwood Lollar, B.; Simkus, D.; Slater, G. F.; Hendrickson, S.; Pullin, M. J.; Kieft, T. L.; Li, L.; Snyder, L.; Kuloyo, O.; Linage, B.; Borgonie, G.; Vermeulen, J.; Maleke, M.; Tlalajoe, N.; Moloantoa, K.; van Heerden, E.; Vermeulen, F.; Pienaar, M.; Munro, A.; Joubert, L.; Ackerman, J.; van Jaarsveld, C.; Onstott, T. C.

    2013-12-01

    Terrestrial subsurface environments generally support two orders of magnitude fewer microorganisms than submarine environments where energy and C sources are more abundant. However, our research on the geochemistry and stable isotopes has suggested that the microbial communities residing in the continental subsurface waters, aged more than thousands of years, do not live by a monotypic metabolic network across sites. We evaluated the taxonomic and functional diversity of microbial communities from three localities in South Africa and their relationship to the environmental parameters associated with each fracture water. The borehole at Tau Tona Au mine (TT107; 3,100 mbls), Masimong Au mine (MM5; 1,900 mbls) and Zondereinde Pt mine (NO14; 2,100 mbls) contain saline fracture water of paleometeroic origin but the anaerobic ecosystems were driven by distinctive C-assimilation strategies. Archaea and Bacteria are present in all samples with the latter being dominant (>75%). The similarity between the Δ14C and δ13C-PLFA with those of the DIC indicates that the majority of cellular C in the TT107 sample was derived from the DIC (0.6 mM), even though dissolved CH4 (8.8 mM) is more available. The DIC may have supported a wide variety of chemoautotrophs including the predominant firmicutes, e.g. Thermincola sp. and Ca. Desulforudis audaxviator. Interestingly, a considerable percentage of sequences related to oligotrophic α-proteobacteria Caulobacter sp. was detected, which warrants further investigation as the aerobic heterotrophic microorganism has a unique dimorphic life cycle. For the MM5 sample, the δ13C and δ2H of the CH4 indicate it was produced via CO2 reduction from DIC, which is consistent with the relatively high abundance of hydrogenotrophic methanogen Methanothermobacter sp. that scavenged the abiogenic H2 and utilized the DIC (0.43 mM) leading to its enriched δ13C signature. In contrast to the TT107 sample, the much-depleted δ13C-CH4 indicates that the

  20. Electrical and optical characteristics of Au/PbS/n-6H-SiC structures prepared by electrodeposition of PbS thin film on n-type 6H-SiC substrate

    Energy Technology Data Exchange (ETDEWEB)

    Guelen, Y. [Department of Physics, Faculty of Sciences, Ataturk University, 25240 Erzurum (Turkey); Alanyalioglu, M. [Department of Chemistry, Faculty of Sciences, Ataturk University, 25240 Erzurum (Turkey); Ejderha, K. [Department of Physics, Faculty of Sciences and Arts, Bingoel University, Bingoel (Turkey); Nuhoglu, C. [Department of Physics, Faculty of Sciences, Ataturk University, 25240 Erzurum (Turkey); Turut, A., E-mail: aturut@atauni.edu.tr [Department of Physics, Faculty of Sciences, Ataturk University, 25240 Erzurum (Turkey)

    2011-02-10

    Research highlights: > The diffraction profile of the PbS thin film from XRD experiments has been extracted. > An optical energy band gap value of the PbS film was obtained from the optical absorption spectra. > The Au/PbS/n-6H-SiC Schottky diodes have been formed. > The Schottky barrier height increase has been succeeded by the PbS interlayer. - Abstract: To realize Schottky barrier height (SBH) modification in the Au/n-6H-SiC Schottky diodes, lead sulfide (PbS) thin films were grown on n-6H-SiC by electrodeposition method. At first, XRD experiments were performed to investigate the crystal structure of the PbS film electrodeposited on n-6H-SiC. It has been deduced from the diffraction profile that the PbS thin film has a crystal structure more strongly oriented along the [2 0 0] direction. An optical energy band gap value of 1.42 eV for the PbS film was obtained from its optical absorption spectra. Then, we have prepared Au/PbS/n-6H-SiC Schottky barrier diodes (SBDs) with interface layer and reference Au/n-6H-SiC/Ni SBDs. The SBH enhancement has been succeeded by the PbS interlayer, influencing the space charge region of the SiC. The SBH values of 1.03 and 0.97 eV for the samples with and without the interfacial PbS layer were obtained from the forward bias current-voltage (I-V) characteristics. The SBH increase in the Au/PbS/n-6H-SiC SBD with the interfacial PbS layer has been attributed to the fact that the interface states contain a net negative interface charge in metal/n-type semiconductor contact due to the presence of the interfacial PbS layer.

  1. Electrical and optical characteristics of Au/PbS/n-6H-SiC structures prepared by electrodeposition of PbS thin film on n-type 6H-SiC substrate

    International Nuclear Information System (INIS)

    Research highlights: → The diffraction profile of the PbS thin film from XRD experiments has been extracted. → An optical energy band gap value of the PbS film was obtained from the optical absorption spectra. → The Au/PbS/n-6H-SiC Schottky diodes have been formed. → The Schottky barrier height increase has been succeeded by the PbS interlayer. - Abstract: To realize Schottky barrier height (SBH) modification in the Au/n-6H-SiC Schottky diodes, lead sulfide (PbS) thin films were grown on n-6H-SiC by electrodeposition method. At first, XRD experiments were performed to investigate the crystal structure of the PbS film electrodeposited on n-6H-SiC. It has been deduced from the diffraction profile that the PbS thin film has a crystal structure more strongly oriented along the [2 0 0] direction. An optical energy band gap value of 1.42 eV for the PbS film was obtained from its optical absorption spectra. Then, we have prepared Au/PbS/n-6H-SiC Schottky barrier diodes (SBDs) with interface layer and reference Au/n-6H-SiC/Ni SBDs. The SBH enhancement has been succeeded by the PbS interlayer, influencing the space charge region of the SiC. The SBH values of 1.03 and 0.97 eV for the samples with and without the interfacial PbS layer were obtained from the forward bias current-voltage (I-V) characteristics. The SBH increase in the Au/PbS/n-6H-SiC SBD with the interfacial PbS layer has been attributed to the fact that the interface states contain a net negative interface charge in metal/n-type semiconductor contact due to the presence of the interfacial PbS layer.

  2. BaCdSnS4 and Ba3CdSn2S8: syntheses, structures, and non-linear optical and photoluminescence properties.

    Science.gov (United States)

    Zhen, Ni; Wu, Kui; Wang, Ying; Li, Qiang; Gao, Wenhui; Hou, Dianwei; Yang, Zhihua; Jiang, Huaidong; Dong, Yongjun; Pan, Shilie

    2016-06-28

    Two non-centrosymmetric metal chalcogenides, BaCdSnS4 and Ba3CdSn2S8, were synthesized using a high temperature solid-state reaction in an evacuated silica tube. Although the two compounds have the same building units in their structures, namely CdS4, SnS4 and BaS8 units, both of them have different structures. BaCdSnS4 crystallizes in the orthorhombic space group Fdd2 and its structure can be characterized by the two-dimensional ∞[Cd-Sn-S] layers composed of corner- and edge-sharing CdS4 and SnS4 tetrahedra with Ba atoms located between the two adjacent ∞[Cd-Sn-S] layers. Ba3CdSn2S8 crystallizes in the space group I4[combining macron]3d of the orthorhombic system and the CdS4 and SnS4 groups are connected with each other via corner-sharing to form a three-dimensional framework, which is different from the 2D ∞[Cd-Sn-S] layer structure in BaCdSnS4. The UV-vis-NIR diffuse-reflectance spectra show that the experimental band gaps are about 2.30 eV for BaCdSnS4 and 2.75 eV for Ba3CdSn2S8, respectively. IR and Raman measurement results indicate that their transparent ranges are up to 25 μm. Second-order NLO measurements show that BaCdSnS4 exhibits strong powder second-harmonic generation (SHG) intensities at 2.09 μm laser pumping that are ∼5 and 0.7 times that of AgGaS2 in the particle size 38-55 and 150-200 μm, respectively, whereas Ba3CdSn2S8 only exhibits SHG intensities of about 0.8 and 0.1 times that of AgGaS2 at the same particle sizes. The origin of the NLO response in BaCdSnS4 may originate from the macroscopic arrangement of the SnS4 and CdS4 tetrahedra. Furthermore, the photoluminescence properties of the two compounds have also been investigated and show obvious blue and green light emission. PMID:27272926

  3. 乳酸菌S-层蛋白及其黏附性相关研究技术%Lactobacillus Surface Layer Proteins and Research Techniques for Their Adhesion:A Review

    Institute of Scientific and Technical Information of China (English)

    范郁冰; 肖荣; 李宗军

    2012-01-01

    乳酸菌为人体的重要生理性细菌,在维持人体肠道生态环境、提高机体免疫力等方面起到重要的作用。然而,乳酸菌发挥这些生理功能的重要前提是黏附到肠细胞的表面。随着研究的深入,越来越多的研究表明乳酸菌S-层蛋白对宿主细胞具有黏附性,如罗伊氏乳酸菌S-层蛋白可与黏蛋白及人结肠癌细胞HT-29进行黏附。在研究乳酸菌S-层蛋白对宿主细胞的黏附时,人们采用了不同的方法。一些常用的基本方法有SDS-PAGE、层析纯化技术、显微镜观察技术等。随着新技术的应用,表面等离子共振技术、免疫学技术等也用于研究S-层蛋白的黏附性。本文将着重介绍S-层蛋白及S-层蛋白黏附性研究的相关技术。%Lactobacillus,an important kind of physiological bacteria in the human body,plays an important role in maintaining human intestinal ecosystem environment and intestinal health.However,the most important premise for lactobacillus to execute its physiological functions is the adhesion on the surface of intestinal cells.More and more studies have showed that S-layer protein has the ability to adhere to intestinal cells.For example,Lactobacillus reuteri can adhere to mucoprotein and HT-9 cells.Various methods such as SDS-PAGE,chromatographic purification,and microscopic observation have been successfully applied to study the adhesion of Lactobacillus to intestinal cells.The applications of surface plasma resonance and immunological techniques to study S-layer protein adhesion have gained extensive attention as a result of the development of new techniques.In this paper,recent research advances in Lactobacillus S-layer proteins and their adhesion are reviewed.

  4. The main Aeromonas pathogenic factors.

    Science.gov (United States)

    Tomás, J M

    2012-01-01

    The members of the Aeromonas genus are ubiquitous, water-borne bacteria. They have been isolated from marine waters, rivers, lakes, swamps, sediments, chlorine water, water distribution systems, drinking water and residual waters; different types of food, such as meat, fish, seafood, vegetables, and processed foods. Aeromonas strains are predominantly pathogenic to poikilothermic animals, and the mesophilic strains are emerging as important pathogens in humans, causing a variety of extraintestinal and systemic infections as well as gastrointestinal infections. The most commonly described disease caused by Aeromonas is the gastroenteritis; however, no adequate animal model is available to reproduce this illness caused by Aeromonas. The main pathogenic factors associated with Aeromonas are: surface polysaccharides (capsule, lipopolysaccharide, and glucan), S-layers, iron-binding systems, exotoxins and extracellular enzymes, secretion systems, fimbriae and other nonfilamentous adhesins, motility and flagella. PMID:23724321

  5. The Prevalence of STIV c92-Like Proteins in Acidic Thermal Environments

    Directory of Open Access Journals (Sweden)

    Jamie C. Snyder

    2011-01-01

    Full Text Available A new type of viral-induced lysis system has recently been discovered for two unrelated archaeal viruses, STIV and SIRV2. Prior to the lysis of the infected host cell, unique pyramid-like lysis structures are formed on the cell surface by the protrusion of the underlying cell membrane through the overlying external S-layer. It is through these pyramid structures that assembled virions are released during lysis. The STIV viral protein c92 is responsible for the formation of these lysis structures. We searched for c92-like proteins in viral sequences present in multiple viral and cellular metagenomic libraries from Yellowstone National Park acidic hot spring environments. Phylogenetic analysis of these proteins demonstrates that, although c92-like proteins are detected in these environments, some are quite divergent and may represent new viral families. We hypothesize that this new viral lysis system is common within diverse archaeal viral populations found within acidic hot springs.

  6. Cadmium sulfide nanowires for the window semiconductor layer in thin film CdS-CdTe solar cells

    International Nuclear Information System (INIS)

    Thin film CdS/CdTe heterojunction device is a leading technology for the solar cells of the next generation. We report on two novel device configurations for these cells where the traditional CdS window layer is replaced by nanowires (NW) of CdS, embedded in an aluminum oxide matrix or free-standing. An estimated 26.8% improvement in power conversion efficiency over the traditional device structure is expected, primarily because of the enhanced spectral transmission of sunlight through the NW-CdS layer and a reduction in the junction area/optical area ratio. In initial experiments, nanostructured devices of the two designs were fabricated and a power conversion efficiency value of 6.5% was achieved.

  7. Buffer layer selection for CuIn1 − xGa xSe2 based thin film solar cells

    International Nuclear Information System (INIS)

    In this work, device modeling and simulation studies have been carried out with a variety of buffer layers over CIGS absorption layer. The band diagram, electric field variation and I/V curves are analyzed and device performance parameters i.e. efficiency, open circuit voltage, short circuit current, quantum efficiency are calculated. The efficiency of CIGS solar cell with ZnSe buffer layer is found comparable with that of CdS layer. The highest short circuit current is found for solar cell with ZnSe buffer layer, whereas the ZnS/CIGS heterojunction provides the highest quantum efficiency in the structures considered. The device physics is discussed and the effect of thickness of buffer layers and absorption layer is studied in order to find a more efficient and stable solar cell. (papers)

  8. CuInS2 thin films obtained through the annealing of chemically deposited In2S3-CuS thin films

    International Nuclear Information System (INIS)

    In this work, we report the formation of CuInS2 thin films on glass substrates by heating chemically deposited multilayers of copper sulfide (CuS) and indium sulfide (In2S3) at 300 and 350 deg. C in nitrogen atmosphere at 10 Torr. CIS thin films were prepared by varying the CuS layer thickness in the multilayers with indium sulfide. The XRD analysis showed that the crystallographic structure of the CuInS2 (JCPDS 27-0159) is present on the deposited films. From the optical analysis it was estimated the band gap value for the CIS film (1.49 eV). The electrical conductivity varies from 3 x 10-8 to 3 Ω-1 cm-1 depending on the thickness of the CuS film. CIS films showed p-type conductivity.

  9. Optical modeling and optimizations of Cu2ZnSnSe4 solar cells using the modified transfer matrix method.

    Science.gov (United States)

    Cozza, Dario; Ruiz, Carmen M; Duché, David; Giraldo, Sergio; Saucedo, Edgardo; Simon, Jean Jacques; Escoubas, Ludovic

    2016-09-01

    The fast and computationally inexpensive Modified Transfer Matrix Method (MTM) is employed to simulate the optical response of kesterite Cu2ZnSnSe4 solar cells. This method can partially take into account the scattering effects due to roughness at the interfaces between the layers of the stack. We analyzed the optical behavior of the whole cell structure by varying the thickness of the TCO layer (iZnO + ITO) between 50 and 1200 nm and the buffer CdS layer between 0 and 100 nm. We propose optimal combinations of the TCO/CdS thicknesses that can locally maximize the device photocurrent. We provide experimental data that qualitatively confirm our theoretical predictions. PMID:27607723

  10. Synthesis and spectroscopic investigations of Cu- and Pb-doped colloidal ZnS nanocrystals.

    Science.gov (United States)

    Ehlert, Oliver; Osvet, Andres; Batentschuk, Miroslaw; Winnacker, Albrecht; Nann, Thomas

    2006-11-23

    A novel organometallic synthesis method for the preparation of colloidal ZnS nanoparticles is presented. This method enables the synthesis of undoped ZnS nanocrystals as well as doping with Cu, Pb, or both. The particles can be covered with an undoped layer of ZnS, forming core/shell-type particles with the ZnS:Pb, ZnS:Cu, or ZnS:Cu,Pb cores. The particles were characterized via TEM, XRD, dynamic light scattering, and optical spectroscopy. We investigated the extrinsic surface defects and their coverage with an additional ZnS layer in detail by temperature-dependent luminescence and luminescence lifetime spectroscopy. PMID:17107162

  11. Effects of annealing conditions of electrodes on the photovoltaic properties of sintered cadmium sulfide/cadmium telluride solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.S.; Im, H.B. (Korea Advanced Inst. of Science, Seoul (Republic of Korea). Dept. of Materials Science)

    1990-01-01

    Polycrystalline n-CdS/p-CdTe solar cells with a commercial carbon paint on the p-CdTe layer and an In- Ag paint on the n-CdS layer were fabricated by a coating and sintering method. Electrical properties of the conducting paints and solar cell parameters of the heterojunction solar cells were investigated as a function of electrode annealing conditions. The sintered CdS/CdTe solar cells whose electrode contacts were annealed at 350{degrees}C for 10 min in nitrogen showed maximum values of short-circuit current density, fill factor, and solar efficiency. Commercial carbon and silver paints can be used as electrodes to fabricate sintered CdS/CdTe solar cells with efficiency over 10%.

  12. Flexible CdTe solar cells on polymer films

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, A.N.; Romeo, A.; Baetzner, D.; Zogg, H. [ETH Swiss Federal Inst. of Technology, Thin Film Physics Group, Zurich (Switzerland)

    2001-07-01

    Lightweight and flexible CdTe/CdS solar cells on polyimide films have been developed in a 'superstrate configuration' where the light is absorbed in CdTe after passing through the polyimide substrate. The average optical transmission of the approximately 10-{mu}m-thin spin-coated polyimide substrate layer is more than {approx}75% for wavelengths above 550 nm. RF magnetron sputtering was used to grow transparent conducting ZnO:Al layers on polyimide films. CdTe/CdS layers were grown by evaporation of compounds, and a CdCl{sub 2} annealing treatment was applied for the recrystallisation and junction activation. Solar cells of 8.6% efficiency with V{sub oc} = 763 mV, I{sub sc} = 20.3 mA/cm{sup 2} and FF = 55.7% were obtained. (Author)

  13. CdS thin films obtained by thermal treatment of cadmium(II) complex precursor deposited by MAPLE technique

    Energy Technology Data Exchange (ETDEWEB)

    Rotaru, Andrei [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Mietlarek-Kropidlowska, Anna [Gdansk University of Technology, Chemistry Faculty, 11/12 G. Narutowicza Str., PL-90-233 Gdansk (Poland); Constantinescu, Catalin, E-mail: catalin.constantinescu@inflpr.ro [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Scarisoreanu, Nicu; Dumitru, Marius [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Strankowski, Michal [Gdansk University of Technology, Chemistry Faculty, 11/12 G. Narutowicza Str., PL-90-233 Gdansk (Poland); Rotaru, Petre [University of Craiova, Faculty of Physics, 13 A.I. Cuza St., Craiova RO-200585, Dolj (Romania); Ion, Valentin [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Vasiliu, Cristina [INOE 2000 - National Institute for Optoelectronics, 1 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Becker, Barbara [Gdansk University of Technology, Chemistry Faculty, 11/12 G. Narutowicza Str., PL-90-233 Gdansk (Poland); Dinescu, Maria [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania)

    2009-05-15

    Thin films of [Cd{l_brace}SSi(O-Bu{sup t}){sub 3}{r_brace}(S{sub 2}CNEt{sub 2})]{sub 2}, precursor for semiconducting CdS layers, were deposited on silicon substrates by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. Structural analysis of the obtained films by Fourier transform infrared spectroscopy (FTIR) confirmed the viability of the procedure. After the deposition of the coordination complex, the layers are manufactured by appropriate thermal treatment of the system (thin film and substrate), according to the thermal analysis of the compound. Surface morphology of the thin films was investigated by atomic force microscopy (AFM) and spectroscopic-ellipsometry (SE) measurements.

  14. Atom-probe tomographic study of interfaces of Cu{sub 2}ZnSnS{sub 4} photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Tajima, S., E-mail: e0954@mosk.tytlabs.co.jp; Asahi, R.; Itoh, T.; Hasegawa, M.; Ohishi, K. [Toyota Central R and D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Isheim, D.; Seidman, D. N. [Northwestern University, Evanston, Illinois 60208-3108 (United States)

    2014-09-01

    The heterophase interfaces between the CdS buffer layer and the Cu{sub 2}ZnSnS{sub 4} (CZTS) absorption layers are one of the main factors affecting photovoltaic performance of CZTS cells. We have studied the compositional distributions at heterophase interfaces in CZTS cells using three-dimensional atom-probe tomography. The results demonstrate: (a) diffusion of Cd into the CZTS layer; (b) segregation of Zn at the CdS/CZTS interface; and (c) a change of oxygen and hydrogen concentrations in the CdS layer depending on the heat treatment. Annealing at 573 K after deposition of CdS improves the photovoltaic properties of CZTS cells probably because of the formation of a heterophase epitaxial junction at the CdS/CZTS interface. Conversely, segregation of Zn at the CdS/CZTS interface after annealing at a higher temperature deteriorates the photovoltaic properties.

  15. A theoretical investigation of the (0001) covellite surfaces

    International Nuclear Information System (INIS)

    We report on the properties of the (0001) covellites surfaces, which we investigate by periodic slab density functional theory calculations. The absolute surface energies have been computed for all bulk terminations, showing that surfaces terminated by the flat CuS layer are associated with the lowest surface energy. Cleavage is predicted to occur across the [0001] interlayer Cu–S bond. The surfaces obtained by lowest energy cleavage are analyzed in terms of the atomic vertical relaxation, workfunction, and surface band structure. Our study predicts the presence of a shallow pz-derived surface state located 0.26 eV below the Fermi level, which is set to play an important role in the surface reactivity of covellite

  16. A theoretical investigation of the (0001) covellite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gaspari, Roberto, E-mail: roberto.gaspari@iit.it [D3-Computation, Istituto Italiano di Tecnologia, via Morego 30, Genova 16163 (Italy); Manna, Liberato [Department of Nanochemistry, Istituto Italiano di Tecnologia, via Morego 30, Genova 16163 (Italy); Cavalli, Andrea [D3-Computation, Istituto Italiano di Tecnologia, via Morego 30, Genova 16163 (Italy); Department of Pharmacy and Biotechnology, University of Bologna, via Belmeloro 6, I-40126 Bologna (Italy)

    2014-07-28

    We report on the properties of the (0001) covellites surfaces, which we investigate by periodic slab density functional theory calculations. The absolute surface energies have been computed for all bulk terminations, showing that surfaces terminated by the flat CuS layer are associated with the lowest surface energy. Cleavage is predicted to occur across the [0001] interlayer Cu–S bond. The surfaces obtained by lowest energy cleavage are analyzed in terms of the atomic vertical relaxation, workfunction, and surface band structure. Our study predicts the presence of a shallow p{sub z}-derived surface state located 0.26 eV below the Fermi level, which is set to play an important role in the surface reactivity of covellite.

  17. Magnetic and structural properties of EuS-PbS multilayers grown on n-PbS (100) substrates

    International Nuclear Information System (INIS)

    Magnetic properties of semiconductor EuS(t)-PbS(d)-EuS(t) ferromagnetic trilayers (t = 30-300 A and d = 7.5-70 A) grown on n-type monocrystalline PbS (100) substrate were studied by SQUID magnetometry and ferromagnetic resonance technique yielding, in particular, the dependence of the ferromagnetic Curie temperature on the thickness of the EuS layer. Structural parameters of layers were examined by X-ray rocking curve width indicating the values of the order 100 arcsec and by atomic force microscopy revealing the presence on the cleft PbS surface regions practically flat in the atomic scale over the area of 1 x 0.1 μm2. (author)

  18. Magnetic anisotropy in EuS-PbS multilayers

    International Nuclear Information System (INIS)

    We present the results of ferromagnetic resonance studies of the thickness dependence of magnetic anisotropy in 2 series of EuS-PbS multilayers grown on (111) BaF2 and (100) KCl substrates with the EuS thickness varying in the range d = 6-70 A. The anisotropy constant K was found to follow the dependence K(d) = KV + 2KS/d, with the surface term KS larger for layers grown on BaF2 as compared to KCl.This difference is discussed in terms of different thermal stress-induced distortions of cubic crystal lattice of EuS. We found that the thickness of EuS layer required for the perpendicular (to the layer) magnetization is d ≤ 2-3 A, i,e., it is below 1 monolayer. (author)

  19. Magnetic properties of wide gap layered semiconductor (La1-xMxo)Cu1-yTyS (M=Ca, Ce; T=Mn, Co, Zn)

    International Nuclear Information System (INIS)

    We have investigated on carrier and magnetic moment injections into a wide gap layered semiconductor (LaO)CuS with alternating LaO and CuS layers. By the substitution of 3d transition metal or Zn ions for Cu sites and of rare earth metal or Ca ions for La sites, electrical and magnetic properties of the compound can be changed. For the Ca or Ce substitution, the decrease of the electrical resistivity is shown accompanied by the small localized magnetic moments for the latter. The localized magnetic moments and the electrical resistivity enhancement due to compensation of the existing acceptor levels are observed for the simultaneous substitution of Ca and Co and that of Ca and Mn

  20. {\\pi}-Control: A Personal Cloud Control Centre

    CERN Document Server

    Spillner, Josef

    2012-01-01

    Consumption of online services and cloud computing offerings is on the rise, largely due to compelling advantages over traditional local applications. From a user perspective, these include zero-maintenance of software, the always-on nature of such services, mashups of different applications and the networking effect with other users. Associated disadvantages are known, but effective means and tools to limit their effect are not yet well-established and not yet generally available to service users. We propose (1) a user-centric model of cloud elements beyond the conventional aaS layers, including activities across trust zones, and (2) a personal control console for all individual and collaborative user activities in the cloud.

  1. Unanticipated Proximity Behavior in Ferromagnet-Superconductor Heterostructures with Controlled Magnetic Noncollinearity

    Science.gov (United States)

    Zhu, L. Y.; Liu, Yaohua; Bergeret, F. S.; Pearson, J. E.; te Velthuis, S. G. E.; Bader, S. D.; Jiang, J. S.

    2013-04-01

    Magnetization noncollinearity in ferromagnet-superconductor (F/S) heterostructures is expected to enhance the superconducting transition temperature (Tc) according to the domain-wall superconductivity theory, or to suppress Tc when spin-triplet Cooper pairs are explicitly considered. We study the proximity effect in F/S structures where the F layer is a Sm-Co/Py exchange-spring bilayer and the S layer is Nb. The exchange-spring contains a single, controllable and quantifiable domain wall in the Py layer. We observe an enhancement of superconductivity that is nonmonotonic as the Py domain wall is increasingly twisted via rotating a magnetic field, different from theoretical predictions. We have excluded magnetic fields and vortex motion as the source of the nonmonotonic behavior. This unanticipated proximity behavior suggests that new physics is yet to be captured in the theoretical treatments of F/S systems containing noncollinear magnetization.

  2. Conjugation by Mosquito Pathogenic Strains of Bacillus sphaericus

    Directory of Open Access Journals (Sweden)

    Correa Margarita

    1997-01-01

    Full Text Available A mosquito pathogenic strain of Bacillus sphaericus carried out the conjugal transfer of plasmid pAMß1 to other strains of its own and two other serotypes. However, it was unable to conjugate with mosquito pathogens from three other serotypes, with B. sphaericus of other DNA homology groups or with three other species of Bacillus. Conjugation frequency was highest with a strain having an altered surface layer (S layer. Conjugal transfer of pAMß1 was not detected in mosquito larval cadavers. B. sphaericus 2362 was unable to mobilize pUB110 for transfer to strains that had served as recipients of pAMß1. These observations suggest that it is unlikely that genetically engineered B. sphaericus carrying a recombinant plasmid could pass that plasmid to other bacteria

  3. Bifacial solar cell with SnS absorber by vapor transport deposition

    International Nuclear Information System (INIS)

    The SnS absorber layer in solar cell devices was produced by vapor transport deposition (VTD), which is a low-cost manufacturing method for solar modules. The performance of solar cells consisting of Si/Mo/SnS/ZnO/indium tin oxide (ITO) was limited by the SnS layer's surface texture and field-dependent carrier collection. For improved performance, a fluorine doped tin oxide (FTO) substrate was used in place of the Mo to smooth the topography of the VTD SnS and to make bifacial solar cells, which are potentially useful for multijunction applications. A bifacial SnS solar cell consisting of glass/FTO/SnS/CdS/ZnO/ITO demonstrated front- and back-side power conversion efficiencies of 1.2% and 0.2%, respectively.

  4. Bifacial solar cell with SnS absorber by vapor transport deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wangperawong, Artit [Stanford University, Stanford, California 94305 (United States); Department of Electrical Engineering, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Bangkok 10140 (Thailand); Hsu, Po-Chun; Yee, Yesheng; Herron, Steven M.; Clemens, Bruce M.; Cui, Yi; Bent, Stacey F., E-mail: sbent@stanford.edu [Stanford University, Stanford, California 94305 (United States)

    2014-10-27

    The SnS absorber layer in solar cell devices was produced by vapor transport deposition (VTD), which is a low-cost manufacturing method for solar modules. The performance of solar cells consisting of Si/Mo/SnS/ZnO/indium tin oxide (ITO) was limited by the SnS layer's surface texture and field-dependent carrier collection. For improved performance, a fluorine doped tin oxide (FTO) substrate was used in place of the Mo to smooth the topography of the VTD SnS and to make bifacial solar cells, which are potentially useful for multijunction applications. A bifacial SnS solar cell consisting of glass/FTO/SnS/CdS/ZnO/ITO demonstrated front- and back-side power conversion efficiencies of 1.2% and 0.2%, respectively.

  5. Bifacial solar cell with SnS absorber by vapor transport deposition

    Science.gov (United States)

    Wangperawong, Artit; Hsu, Po-Chun; Yee, Yesheng; Herron, Steven M.; Clemens, Bruce M.; Cui, Yi; Bent, Stacey F.

    2014-10-01

    The SnS absorber layer in solar cell devices was produced by vapor transport deposition (VTD), which is a low-cost manufacturing method for solar modules. The performance of solar cells consisting of Si/Mo/SnS/ZnO/indium tin oxide (ITO) was limited by the SnS layer's surface texture and field-dependent carrier collection. For improved performance, a fluorine doped tin oxide (FTO) substrate was used in place of the Mo to smooth the topography of the VTD SnS and to make bifacial solar cells, which are potentially useful for multijunction applications. A bifacial SnS solar cell consisting of glass/FTO/SnS/CdS/ZnO/ITO demonstrated front- and back-side power conversion efficiencies of 1.2% and 0.2%, respectively.

  6. Atomic layer deposition of absorbing thin films on nanostructured electrodes for short-wavelength infrared photosensing

    International Nuclear Information System (INIS)

    Atomic layer deposition (ALD), prized for its high-quality thin-film formation in the absence of high temperature or high vacuum, has become an industry standard for the large-area deposition of a wide array of oxide materials. Recently, it has shown promise in the formation of nanocrystalline sulfide films. Here, we demonstrate the viability of ALD lead sulfide for photodetection. Leveraging the conformal capabilities of ALD, we enhance the absorption without compromising the extraction efficiency in the absorbing layer by utilizing a ZnO nanowire electrode. The nanowires are first coated with a thin shunt-preventing TiO2 layer, followed by an infrared-active ALD PbS layer for photosensing. The ALD PbS photodetector exhibits a peak responsivity of 10−2 A W−1 and a shot-derived specific detectivity of 3 × 109 Jones at 1530 nm wavelength

  7. Mechanism of charge transport in ligand-capped crystalline CdTe nanoparticles according to surface photovoltaic and photoacoustic results

    International Nuclear Information System (INIS)

    By combining surface photovoltaic and photoacoustic techniques, we probed the photogenerated charge transport channels of 3-mercaptopropionic acid (MPA)- and 2-mercaptoethylamine (MA)-capped crystalline CdTe nanoparticles on illumination with UV-near IR light. The results experimentally confirmed the presence of a CdS shell outside the CdTe core that formed through the self-assembly and decomposition of mercapto ligands during CdTe preparation. The data revealed that the CdS layer was partly responsible for the deexcitation behavior of the photogenerated carriers, which is related to the quantum tunnel effect. Experiments demonstrated that two quantum wells were located at wavelengths of 440 and 500 nm in buried interfacial space-charge regions, whereas the formation of a ligand layer obstructed charge transfer transitions of the core CdTe nanoparticles to a certain extent.

  8. Bicolor Mn-doped CuInS2/ZnS core/shell nanocrystals for white light-emitting diode with high color rendering index

    International Nuclear Information System (INIS)

    We synthesized bicolor Mn-doped CuInS2 (CIS)/ZnS core/shell nanocrystals (NCs), in which Mn2+ ions and the CIS core were separated with a ZnS layer, and both Mn2+ ions and CIS cores could emit simultaneously. Transmission electron microscopy and powder X-ray diffraction measurements indicated the epitaxial growth of ZnS shell on the CuInS2 core, and electron paramagnetic resonance spectrum indicated that Mn2+ ions were on the lattice points of ZnS shell. By integrating these bicolor NCs with commercial InGaN-based blue-emitting diodes, tricolor white light-emitting diodes with color rendering index of 83 were obtained

  9. Physical properties of thin film Cu/sub 2/S/Znsub(x)Cdsub(1-x)S heterojunction solar cells fabricated by aqueous treatment and solid state reaction

    Energy Technology Data Exchange (ETDEWEB)

    Razykov, T.M.; Vialiy, V.I.; Khodjaeva, M.A.

    1984-11-09

    A comparative analysis is given of the electrical and photoelectrical properties of thin film Cu/sub 2/S/Znsub(x)Cdsub(1-x)S heterojunctions prepared by chemical treatment of Znsub(x)Cdsub(1-x)S films with a hot aqueous CuCl solution and with CuCl in a solid state reaction. The characteristics of the physicochemical processes taking place in the formation of a Cu/sub 2/S barrier layer by these two methods are discussed. It is shown that in the solid state reaction the Cu/sub 2/S layer is formed mainly on the outer surface of the Znsub(x)Cdsub(1-x)S film, whereas in the aqueous method the barrier layer is formed both on the outer surface and along grain boundaries of the Znsub(x)Cdsub(1-x)S.

  10. Ab Initio Study of the Dielectric and Electronic Properties of Multilayer GaS Films.

    Science.gov (United States)

    Li, Yan; Chen, Hui; Huang, Le; Li, Jingbo

    2015-03-19

    The dielectric properties of multilayer GaS films have been investigated using a Berry phase method and a density functional perturbation theory approach. A linear relationship has been observed between the number of GaS layers and slab polarizability, which can be easily converged at a small supercell size and has a weak correlation with different stacking orders. Moreover, the intercoupling effect of the stacking pattern and applied vertical field on the electronic properties of GaS bilayers has been discussed. The band gaps of different stacking orders show various downward trends with the increasing field, which is interpreted as giant Stark effect. Our study demonstrates that the slab polarizability as the substitution of conventional dielectric constant can act as an independent and reliable parameter to elucidate the dielectric properties of low-dimensional systems and that the applied electric field is an effective method to modulate the electric properties of nanostructures. PMID:26262870

  11. Electrical and optical characterization of the influence of chemical bath deposition time and temperature on CdS/Cu(In,Ga)Se2 junction properties in Cu(In,Ga)Se2 solar cells

    International Nuclear Information System (INIS)

    The effects of varying the conditions for the chemical bath deposition (CBD) of cadmium sulfide (CdS) layers on CdS/Cu(In,Ga)Se2 (CIGS) hetero-junctions were investigated using photoluminescence (PL), electroluminescence (EL), deep level transient spectroscopy (DLTS), and red-light-illuminated current-voltage (I–V) measurements. We demonstrated that varying CBD-CdS conditions such as the temperature and time influenced the recombination pathways around the CdS/CIGS junction via the formation of different electronic defects, which eventually changed the photovoltaic conversion efficiency. As the CBD-CdS time and temperature were increased, the cell efficiency decreased. PL measurements revealed that this degradation of the cell efficiency was accompanied by increases in the defect-related recombination, which were attributed to the existence of donor defects around CdS/CIGS having an energy level of 0.65 eV below conduction band, as revealed by DLTS. Increasing distortions in the red-light-illuminated I–V characteristics suggested that the related defects might also have played a critical role in metastable changes around the CdS/CIGS junction. Because the CBD-CdS time and temperature were considered to influence the diffusion of impurities into the CIGS surface, the evolution of the efficiency, PL spectra, defect populations, and red-light-illuminated I–V characteristics observed in this work could be attributed to the diffusion of impurities during the CBD-CdS process. - Highlights: • CdS layers were grown by chemical bath deposition (CBD). • The CBD-CdS influenced the efficiency of Cu(In,Ga)Se2 (CIGS) solar cell. • It could be related to slight alteration in carrier recombination around CdS/CIGS. • Photo- and electroluminescence spectra detected those alterations in recombination. • The variation of results could be related to the changes in deep-level defects

  12. Heterologous Expression of Mannanase and Developing a New Reporter Gene System in Lactobacillus casei and Escherichia coli.

    Science.gov (United States)

    Lin, Jinzhong; Zou, Yexia; Ma, Chengjie; She, Qunxin; Liang, Yunxiang; Chen, Zhengjun; Ge, Xiangyang

    2015-01-01

    Reporter gene systems are useful for studying bacterial molecular biology, including the regulation of gene expression and the histochemical analysis of protein products. Here, two genes, β-1,4-mannanase (manB) from Bacillus pumilus and β-glucuronidase (gusA) from Escherichia coli K12, were cloned into the expression vector pELX1. The expression patterns of these reporter genes in Lactobacillus casei were investigated by measuring their enzymatic activities and estimating their recombinant protein yields using western blot analysis. Whereas mannanase activity was positively correlated with the accumulation of ManB during growth, GusA activity was not; western blot analysis indicated that while the amount of GusA protein increased during later growth stages, GusA activity gradually decreased, indicating that the enzyme was inactive during cell growth. A similar trend was observed in E. coli JM109. We chose to use the more stable mannanase gene as the reporter to test secretion expression in L. casei. Two pELX1-based secretion vectors were constructed: one carried the signal peptide of the unknown secretion protein Usp45 from Lactococcus lactis (pELSH), and the other contained the full-length SlpA protein from the S-layer of L. acidophilus (pELWH). The secretion of ManB was detected in the supernatant of the pELSH-ManB transformants and in the S-layer of the cell surface of the pELWH-ManB transformants. This is the first report demonstrating that the B. pumilus manB gene is a useful reporter gene in L. casei and E.coli. PMID:26562012

  13. A comparative study of (ZnO, In2O3: SnO2, SnO2)/CdS/CdTe/(Cu/)Ni heterojunctions

    International Nuclear Information System (INIS)

    The influence of the manufacturing technology on the structural properties of CdTe and CdS layers, components of the CdS/CdTe solar cells, has been investigated. CdTe based solar cells have been prepared using glass substrates coated with different transparent conductive oxides (TCOs: SnO2, In2O3: SnO2 (ITO), ZnO:Al, ZnO:Al/i-ZnO). The analysis of the technology combined with various investigation methods allowed to determine optimum deposition parameters for CdS and CdTe for each type of TCO used. X-ray diffraction (XRD) and grazing incidence XRD analysis have been carried out for TCO, CdS, and CdTe layers at different deposition stages before and after annealing in the presence of CdCl2 in air. The reflection spectra in the 100–600 cm−1 spectral region have been thoroughly studied by using Fourier transform infrared spectroscopy. It was found that (i) the best quality possess CdS and CdTe thin films sequentially deposited on ZnO:Al substrates and that (ii) the pre-treatment defects can be effectively cured and most of the secondary phases can be removed by annealing, while the basic structure of the investigated thin films does not essentially change. - Highlights: ► Deposition technology of CdS and CdTe thin films. ► Slightly improved CdS film quality obtained for deposition on ZnO:Al substrates. ► Improved quality of CdTe deposited on CdS layers grown at high substrate temperature. ► Defects and secondary phases removal as a result of thermal annealing

  14. Fabrication and electrical characteristics of TFTs based on chemically deposited CdS films, using glycine as a complexing agent

    International Nuclear Information System (INIS)

    In this work, we report on the fabrication and electrical characteristics of thin film transistors (TFTs) using chemically deposited cadmium sulfide (CdS) thin films as the semiconductor active layer in back-gated devices. The CdS thin films were deposited by the chemical bath deposition (CBD) technique using glycine as the complexing agent. The CdS layers were deposited on SiO2/Si-n substrates and lift-off was used to define the source and drain contacts (Au) on top of these layers. The Si-n wafer with a chromium-gold back contact served as the common gate for the transistors. Several devices with different channel lengths ranging from 10 to 80 µm were fabricated by this process. We studied the properties of the CdS layers deposited by this glycine-based CBD process and the electrical behavior of the transistors as a function of the channel length. The experimental results show that as-deposited CdS are n-type in character and devices exhibit typical pinch-off in drain current versus source–drain voltage (IDS–VDS) curves for several gate voltages. The values of the threshold voltage of the devices were in the range from 8.5 to 8.9 V, depending on the channel length. Channel mobility was between 4.3 and 5.2 cm2 V−1 s−1. This research implies that CdS TFTs produced by a simple and low-cost technique could be applicable to electronic devices

  15. Structural characterization of the N-linked pentasaccharide decorating glycoproteins of the halophilic archaeon Haloferax volcanii.

    Science.gov (United States)

    Kandiba, Lina; Lin, Chia-Wei; Aebi, Markus; Eichler, Jerry; Guerardel, Yann

    2016-07-01

    N-Glycosylation is a post-translational modification performed in all three domains of life. In the halophilic archaea Haloferax volcanii, glycoproteins such as the S-layer glycoprotein are modified by an N-linked pentasaccharide assembled by a series of Agl (archaeal glycosylation) proteins. In the present study, mass spectrometry (MS) and nuclear magnetic resonance spectroscopy were used to define the structure of this glycan attached to at least four of the seven putative S-layer glycoprotein N-glycosylation sites, namely Asn-13, Asn-83, Asn-274 and Asn-279. Such approaches detected a trisaccharide corresponding to glucuronic acid (GlcA)-β1,4-GlcA-β1,4-glucose-β1-Asn, a tetrasaccharide corresponding to methyl-O-4-GlcA-β-1,4-galacturonic acid-α1,4-GlcA-β1,4-glucose-β1-Asn, and a pentasaccharide corresponding to hexose-1,2-[methyl-O-4-]GlcA-β-1,4-galacturonic acid-α1,4-GlcA-β1,4-glucose-β1-Asn, with previous MS and radiolabeling experiments showing the hexose at the non-reducing end of the pentasaccharide to be mannose. The present analysis thus corrects the earlier assignment of the penultimate sugar as a methyl ester of a hexuronic acid, instead revealing this sugar to be a methylated GlcA. The assignments made here are in good agreement with what was already known of the Hfx. volcanii N-glycosylation pathway from previous genetic and biochemical efforts while providing new insight into the process. PMID:26863921

  16. Development of copper sulfide/cadmium sulfide thin-film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Szedon, J. R.; Biter, W. J.; Dickey, H. C.

    1982-03-08

    The most important accomplishments during this period were to demonstrate and to elucidate further the complex effects that occur during the aging of Cu/sub 2/S/CdS thin-film solar cells in flowing wet oxygen. There are two distinct effects. At constant illumination, the short-circuit current of cells aged at room temperature consistently decreases with time. The second effect, related to diode opposing current, is more involved and may result from several competing mechanisms. Over the short term (approx. 4 to 5 hours), the magnitude of diode opposing current decreases. After approx. 20 hours of aging, opposing current generally returns to the level achieved after hydrogen annealing which immediately preceded the aging sequence. Optical measurements of the spectral transmission of the Cu/sub 2/S layers in a cell content have been made using a silicon detector epoxied to the back of a CdS cell after the copper foil substrate was removed. There is no significant change in Cu/sub 2/S transmission behavior for wavelengths ranging from 525 to 1000 nm during wet-oxygen aging for periods of 2 to 36 hours. This suggests that the decrease in J/sub SC/ at constant illumination, for the aging experiments in a flowing wet-oxygen ambient, arises because of changes in minority-carrier transport properties of the Cu/sub 2/S. Before developing a method for using an epoxied silicon detector to measure optical behavior of the Cu/sub 2/S layer, we explored the possibility of using a junction-containing wafer of silicon as a substrate for deposited CdS films. Some monolithic structures were successfully fabricated. Comparisons were made of CdS grain structure details in the junction detector area and in an adjacent metallized area.

  17. Josephson junctions with ferromagnetic alloy interlayer

    International Nuclear Information System (INIS)

    Josephson junctions are used as active devices in superconducting electronics and quantum information technology. Outstanding properties are their distinct non-linear electrical characteristics and a usually sinusoidal relation between the current and the superconducting phase difference across the junction. In general the insertion of ferromagnetic material in the barrier of a Josephson junction is associated with a suppression of superconducting correlations. But also new phenomena can arise which may allow new circuit layouts and enhance the performance of applications. This thesis presents a systematic investigation for two concepts to fabricate Josephson junctions with a rather uncommon negative critical current. Such devices exhibit an intrinsic phase slip of π between the electrodes, so they are also known as π junctions. Both studies go well beyond existing experiments and in one system a π junction is shown for the first time. All the thin film junctions are based on superconducting Nb electrodes. In a first approach, barriers made from Si and Fe were investigated with respect to the realisation of π junctions by spin-flip processes. The distribution of Fe in the Si matrix was varied from pure layers to disperse compounds. The systematic fabrication of alloy barriers was facilitated by the development of a novel timing-based combinatorial sputtering technique for planetary deposition systems. An orthogonal gradient approach allowed to create binary layer libraries with independent variations of thickness and composition. Second, Nb vertical stroke AlOx vertical stroke Nb vertical stroke Ni60Cu40 vertical stroke Nb (SIsFS) double barrier junctions were experimentally studied for the occurrence of proximity effect induced order parameter oscillations. Detailed dependencies of the critical current density on the thickness of s-layer and F-layer were acquired and show a remarkable agreement to existing theoretical predictions. Especially a variation of jc

  18. Results of Experimental and Theoretical Studies of the Atmospheric Turbulence, Internal Gravity Waves and Sporadic-E Layers by Resonant Scattering of Radio Waves on Artificial Periodic Irregularities

    Science.gov (United States)

    Bakhmetieva, Nataliya V.; Grigoriev; Tolmacheva, Ariadna V.

    predominant metallic ions at the E _{s}-layer height is one of the API applications (Bakhmetieva N.V. and Belikovich V.V. Radiophys. Quantum Electron., 2008, Vol. 51, No 11, pp. 956-969). It is based on the observed fact of the local maximum of the API relaxation time at the sporadic E-layer location. The long-lived metallic ions cause the growth of the API relaxation time tauτ at the E _{s}-layer height. It is shown by API technique the sporadic E-layers contain Mg (+) , Ca (+) and Fe (+) ions predominantly at heights of 95-110 km. The new applications are based on the so-called two-frequency method of the API creation and their diagnostics. The method allows one to define the neutral atmosphere and the ionosphere parameters with high accuracy. The main results of the lower ionosphere studies carried out in 2006-2012 by the API technique using the SURA heating facility (56,1 N; 46,15 E) are presented and discussed. We aslo discuss the studies of the HF pumping effects on the formation and parameters of the sporadic E-layers and the modification of the semitransparent E _{s}-layer by the powerful radio wave and diagnostics by the API technique. The work was supported by Russian Foundation for Basic Research under project No 13-02-97067, 13-02-12074 and 13-05-00511.

  19. Josephson junctions with ferromagnetic alloy interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Himmel, Nico

    2015-07-23

    Josephson junctions are used as active devices in superconducting electronics and quantum information technology. Outstanding properties are their distinct non-linear electrical characteristics and a usually sinusoidal relation between the current and the superconducting phase difference across the junction. In general the insertion of ferromagnetic material in the barrier of a Josephson junction is associated with a suppression of superconducting correlations. But also new phenomena can arise which may allow new circuit layouts and enhance the performance of applications. This thesis presents a systematic investigation for two concepts to fabricate Josephson junctions with a rather uncommon negative critical current. Such devices exhibit an intrinsic phase slip of π between the electrodes, so they are also known as π junctions. Both studies go well beyond existing experiments and in one system a π junction is shown for the first time. All the thin film junctions are based on superconducting Nb electrodes. In a first approach, barriers made from Si and Fe were investigated with respect to the realisation of π junctions by spin-flip processes. The distribution of Fe in the Si matrix was varied from pure layers to disperse compounds. The systematic fabrication of alloy barriers was facilitated by the development of a novel timing-based combinatorial sputtering technique for planetary deposition systems. An orthogonal gradient approach allowed to create binary layer libraries with independent variations of thickness and composition. Second, Nb vertical stroke AlO{sub x} vertical stroke Nb vertical stroke Ni{sub 60}Cu{sub 40} vertical stroke Nb (SIsFS) double barrier junctions were experimentally studied for the occurrence of proximity effect induced order parameter oscillations. Detailed dependencies of the critical current density on the thickness of s-layer and F-layer were acquired and show a remarkable agreement to existing theoretical predictions. Especially

  20. Grain size distribution, clay mineralogy and chemistry of bottom sediments from the outer Thermaikos Gulf, Aegean Sea, Greece

    Directory of Open Access Journals (Sweden)

    K.G. PEHLIVANOGLOU

    2012-12-01

    Full Text Available The Thermaikos Gulf constitutes the NW part of the North Aegean Sea and is limited eastward from the Chalkidiki Peninsula and westward from the Pieria Prefecture. Its plateau covers an area of 3,500 km2. The mechanisms responsible for the grain size distribution into the Gulf, the clay mineralogy and the chemistry of some bottom sediments from the outer Thermaikos Gulf, are examined. Source mixing during transportation, flocculation, differential settling processes and organic matter appear to be the main mechanisms for the distribution of clay minerals in shallow waters. All grain size fractions studied present a wide range of values confirming the extreme variations of the discharged load and the variability in marine processes. Plagioclases predominate over K-feldspars, while quartz is the most abundant mineral present. In addition, micas, chlorites, amphiboles and pyroxenes exist as primary and/or accessory minerals in all samples. Among clay minerals, illite predominates over smectite and smectite over chlorite (+ kaolinite. The ordered interstratified phase of I/S, with 30-35% S layers, is present in the 2-0.25µm fraction. The randomly interstratified phase of I/S, with 50% S layers, is present in the <0.25& micro; m fraction. On average the clay mineral content of the studied samples is: 48% I, 23% S, 17% Ch (+K and 12% others for the 2-0.25µm fraction and 50% I, 30% S and 20% Ch (+K for the <0.25 µm fraction. All these minerals are the weathering products of the rocks from the drainage basins of the rivers flowing into the Gulf, as well as of the Neogene and Quaternary unconsolidated sediments of the surrounding coasts. The terrigenous input, the water mass circulation and, to a lesser extent, the quality of the discharged material and the differential settling of grains, control the grain size distribution within the outer Thermaikos Gulf. The chemical composition of the analysed samples is generally in agreement with their mineral

  1. Genotype-phenotype correlations of TGFBI p.Leu509Pro, p.Leu509Arg, p.Val613Gly, and the allelic association of p.Met502Val-p.Arg555Gln mutations

    Science.gov (United States)

    Niel-Butschi, Florence; Kantelip, Bernadette; Iwaszkiewicz, Justyna; Zoete, Vincent; Boimard, Mathieu; Delpech, Marc; Bourges, Jean-Louis; Renard, Gilles; D’Hermies, François; Pisella, Pierre-Jean; Hamel, Christian; Delbosc, Bernard

    2011-01-01

    Purpose Investigate the genotype-phenotype correlations for five TGFBI (transforming growth factor, beta-induced) mutations including one novel pathogenic variant and one complex allele affecting the fourth FAS1 domain of keratoepithelin, and their potential effects on the protein’s structure. Methods Three unrelated families were clinically diagnosed with lattice corneal dystrophy (CD) and one with an unclassified CD of Bowman’s layer. Mutations in the TGFBI gene were detected by direct sequencing, and the functional impact of each variant was predicted using in silico algorithms. Corneal phenotypes, including histological examinations, were compared with the literature data. Furthermore, molecular modeling studies of these mutations were performed. Results Two distinct missense mutations affecting the same residue at position 509 of keratoepithelin: p.Leu509Pro (c.1526T>C) and p.Leu509Arg (c.1526T>G) were found to be associated with a lattice-type CD. The novel p.Val613Gly (c.1828T>G) TGFBI mutation was found in a sporadic case of an Algerian individual affected by lattice CD. Finally, the Bowman’s layer CD was linked to the association in cis of the p.Met502Val and p.Arg555Gln variants, leading to the reclassification of this CD as atypical Thiel-Behnke CD. Structural modeling of these TGFBI mutations argues in favor of these mutations being responsible for instability and/or incorrect folding of keratoepithelin, predictions that are compatible with the clinical diagnoses. Conclusions Description of a novel TGFBI mutation and a complex TGFBI allele further extends the mutational spectrum of TGFBI. Moreover, we show convincing evidence that TGFBI mutations affecting Leu509 are linked to the lattice phenotype in two unrelated French families, contrasting with findings previously reported. The p.Leu509Pro was reported to be associated with both amyloid and non-amyloid aggregates, whereas p.Leu509Arg has been described as being responsible for Epithelial

  2. 一种 KLEIN 密码的差分故障分析%A DIFFERENTIAL FAULT ANALYSIS METHOD FOR KLEIN CIPHER

    Institute of Scientific and Technical Information of China (English)

    范存洋; 魏悦川; 潘晓中

    2015-01-01

    In this article,we present an available method of differential fault analysis on KLEIN cryptographic algorithm,and study the security of KLEIN cipher on differential fault analysis.After many times of analysis and try,we choose to inject 1 bit random fault into each of the 16 nibbles separately,this corresponds to inducing 16 random faults each time.By inducing 1 bit random fault into each nibble before the 12th-round permutation operation of S-layer of KLEIN cipher,and by constructing the differential distinguisher of S-layer to search the possible differential value,we eventually recover the 64-bit master key.Experimental results show that to recover the master key,we just need to induce 2.73 times in average such type of fault,and the search space is reduced greatly as well.%针对 KLEIN 密码算法提出一种可行的差分故障分析方法,研究 KLEIN 密码对差分故障分析的安全性。经多次分析尝试,选择分别向16个字节处各导入1比特随机故障,相当于每次引入16个随机故障。通过在 KLEIN 密码第12轮 S 盒置换操作之前对各字节引入1比特随机故障,并构造了 S 盒差分区分器来搜索差分值,最终恢复64比特密钥。实验结果表明,平均2.73次诱导此类故障即可恢复主密钥,同时大大降低了搜索空间。

  3. First-Principles Study on Cd Doping in Cu2ZnSnS4 and Cu2ZnSnSe4

    Science.gov (United States)

    Maeda, Tsuyoshi; Nakamura, Satoshi; Wada, Takahiro

    2012-10-01

    To quantitatively evaluate the substitution energies of Cd atom for Cu, Zn, or Sn atom in indium-free photovoltaic semiconductors Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe), first-principles pseudopotential calculations using plane-wave basis functions were performed. The substitution energies of Cd atom in kesterite-type CZTS and CZTSe were calculated in consideration of the atomic chemical potentials of the constituent elements of Cu, Zn, Sn, and the doping atom of Cd. During the chemical bath deposition (CBD) of the CdS layer on the CZTS or CZTSe layer, Cu, Zn, and Cd atoms dissolved in the ammonia aqueous solution and formed [Cu(NH3)2]+, [Zn(NH3)4]2+, and [Cd(NH3)4]2+ complex ions. Therefore, the chemical potentials of Cu, Zn, and Cd atoms in [Cu(NH3)2]+, [Zn(NH3)4]2+, and [Cd(NH3)4]2+ complex ions were calculated. We found that the substitution energies of n-type CdCu and charge-neutral CdZn in CZTS and CZTSe are smaller than that of p-type CdSn. The substitution energies of CdCu in CZTS and CZTSe are smaller than that in chalcopyrite-type CuInSe2 (CIS). However, the substitution energies of CdCu, CdZn, and CdSn are positive values. The formation energy of charge-neutral Cd doping with the Cu vacancy (CdCu + VCu) pair is a negative value and greatly smaller than those of donor-type CdCu and neutral CdZn in CZTS and CZTSe. These results indicate that the charge-neutral (CdCu + VCu) vacancy pair is easily formed during the CBD of the CdS layer on the CZTS or CZTSe layer. A small amount of n-type CdCu and neutral CdZn would also be formed.

  4. REGIM OF COMPACTATION OF TRENCHED SOIL IN CONDITIONS OF ORCHARDS AND GROUND IN CROP

    Directory of Open Access Journals (Sweden)

    Tatiana Nagacevschi

    2007-10-01

    Full Text Available We have investigated the influence of soil`s cultivation on the physical proprieties (apparent density,structure,pore proprieties modifications space and differentiated porosity resistance penetration ,hydrological proprieties,water`s permeability in the gardens. Soil`s cultivation in the gardens leads to the formation of compacted horizon on the soil depth of 10-20-30 cm in which density of constitution is essentially increasing as compared with soils used for field`s cultures ( tf> t0,05.The most compaction was determined by tracks of the machine`s wheels where the density of constitution reaches 1,59-1,70 g/cm³.Investigated soils possess a satisfactorily structure, structure coefficient 1. Maintenance of water resistance units >0,25mm,decreases in arable horizon and in compacted layer, especially in chernozem of the new terracy where these indexes decrease till 36%-18%. These soil’s layers have a satisfactorily structure in the line, unsatisfactorily and badly by tracks machine’s wheels. The comparative research of trenched soil used for orchards cultivation and of land in crop demonstrates the difference between physical proprieties of the superior stratum. Trenched soils used for orchards cultivation are characterized by the formation of a settled stratum,disturbed at 10-30 cm deep also illustrating a more obvious technogenesys of these soils,as well as the regularities of physical in orchards soils.

  5. Dead zones in colloidal quantum dot photovoltaics: evidence and implications

    KAUST Repository

    Barkhouse, D. Aaron R.

    2010-09-01

    In order to fabricate photovoltaic (PV) cells incorporating light-trapping electrodes, flexible foil substrates, or more than one junction, illumination through the top-contact (i.e.: non-substrate) side of a photovoltaic device is desirable. We investigate the relative collection efficiency for illumination through the top vs. bottom of PbS colloidal quantum dot (CQD) PV devices. The external quantum efficiency spectra of FTO/TiO2/PbS CQD/ITO PV devices with various PbS layer thicknesses were measured for illumination through either the top (ITO) or bottom (FTO) contacts. By comparing the relative shapes and intensities of these spectra with those calculated from an estimation of the carrier generation profile and the internal quantum efficiency as a function of distance from the TiO2 interface in the devices, a substantial dead zone, where carrier extraction is dramatically reduced, is identified near the ITO top contact. The implications for device design, and possible means of avoiding the formation of such a dead zone, are discussed.

  6. Synthesis of Copper-Antimony-Sulfide Nanocrystals for Solution-Processed Solar Cells.

    Science.gov (United States)

    Suehiro, Satoshi; Horita, Keisuke; Yuasa, Masayoshi; Tanaka, Tooru; Fujita, Katsuhiko; Ishiwata, Yoichi; Shimanoe, Kengo; Kida, Tetsuya

    2015-08-17

    The p-type nanocrystals (NCs) of copper-based chalcogenides, such as CuInSe2 and Cu2ZnSnS4, have attracted increasing attention in photovoltaic applications due to their potential to produce cheap solution-processed solar cells. Herein, we report the synthesis of copper-antimony-sulfide (CAS) NCs with different crystal phases including CuSbS2, Cu3SbS4, and Cu12Sb4S13. In addition, their morphology, crystal phase, and optical properties were characterized using transmission electron microscopy, X-ray diffractometry, UV-vis-near-IR spectroscopy, and photoemission yield spectroscopy. The morphology, crystal phase, and electronic structure were significantly dependent on the chemical composition in the CAS system. Devices were fabricated using particulate films consisting of CAS NCs prepared by spin coating without a high-temperature treatment. The CAS NC-based devices exhibited a diode-like current-voltage characteristic when coupled with an n-type CdS layer. In particular, the CuSbS2 NC devices exhibited photovoltaic responses under simulated sunlight, demonstrating its applicability for use in solution-processed solar cells. PMID:26237216

  7. Complex boron redistribution kinetics in strongly doped polycrystalline-silicon/nitrogen-doped-silicon thin bi-layers

    Energy Technology Data Exchange (ETDEWEB)

    Abadli, S. [Department of Electrical Engineering, University Aout 1955, Skikda, 21000 (Algeria); LEMEAMED, Department of Electronics, University Mentouri, Constantine, 25000 (Algeria); Mansour, F. [LEMEAMED, Department of Electronics, University Mentouri, Constantine, 25000 (Algeria); Pereira, E. Bedel [CNRS-LAAS, 7 avenue du colonel Roche, 31077 Toulouse (France)

    2012-10-15

    We have investigated the complex behaviour of boron (B) redistribution process via silicon thin bi-layers interface. It concerns the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method at 480 C, by using in-situ nitrogen-doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P{sup +}) layer. To avoid long-range B redistributions, thermal annealing was carried out at relatively low-temperatures (600 C and 700 C) for various times ranging between 30 min and 2 h. To investigate the experimental secondary ion mass spectroscopy (SIMS) doping profiles, a redistribution model well adapted to the particular structure of two thin layers and to the effects of strong-concentrations has been established. The good adjustment of the simulated profiles with the experimental SIMS profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders. The increasing kinetics of the B peak concentration near the bi-layers interface is well reproduced by the established model. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Complex Boron Redistribution in P+ Doped-polysilicon / Nitrogen Doped Silicon Bi-layers during Activation Annealing

    Science.gov (United States)

    Abadli, S.; Mansour, F.; Perrera, E. Bedel

    We have investigated and modeled the complex phenomenon of boron (B) redistribution process in strongly doped silicon bilayers structure. A one-dimensional two stream transfer model well adapted to the particular structure of bi- layers and to the effects of strong-concentrations has been developed. This model takes into account the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method, using in-situ nitrogen- doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P+) layer. To avoid long redistributions, thermal annealing was carried out at relatively lowtemperatures (600 °C and 700 °C) for various times ranging between 30 minutes and 2 hours. The good adjustment of the simulated profiles with the experimental secondary ion mass spectroscopy (SIMS) profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders kinetics.

  9. Emerging pathogens: Aeromonas spp.

    Science.gov (United States)

    Merino, S; Rubires, X; Knochel, S; Tomas, J M

    1995-12-01

    Aeromonas spp. are Gram-negative rods of the family Vibrionaceae. They are normal water inhabitants and are part of the regular flora of poiquilotherm and homeotherm animals. They can be isolated from many foodstuffs (green vegetables, raw milk, ice cream, meat and seafood). Mesophilic Aeromonas spp. have been classified following the AeroKey II system (Altwegg et al., 1990; Carnahan et al., 1991). The major human diseases caused by Aeromonas spp. can be classified in two major groups: septicemia (mainly by strains of A. veronii subsp. sobria and A. hydrophila), and gastroenteritis (any mesophilic Aeromonas spp. but principally A. hydrophila and A. veronii). Most epidemiological studies have shown Aeromonas spp. in stools to be more often associated with diarrhea than with the carrier state; an association with the consumption of untreated water was also conspicuous. Acute self-limited diarrhea is more frequent in young children, in older patients chronic enterocolitis may also be observed. Fever, vomiting, and fecal leukocytes or erythrocytes (colitis) may be present (Janda, 1991). The main putative virulence factors are: exotoxins, endotoxin (LPS), presence of S-layers, fimbriae or adhesins and the capacity to form capsules. PMID:8750664

  10. Dynamic analysis of the photoenhancement process of colloidal quantum dots with different surface modifications

    Energy Technology Data Exchange (ETDEWEB)

    Valledor Llopis, Marta; Campo Rodriguez, Juan Carlos; Ferrero Martin, Francisco J [Departamento de Ingenieria Electrica, Electronica, C y S Universidad de Oviedo, Campus de Gijon s/n, 33204 Gijon, Asturias, (Spain); Coto, Ana Maria; Fernandez-Argueelles, Maria T; Costa-Fernandez, J M; Sanz-Medel, A [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, Campus del Cristo, 33006 Oviedo, Asturias (Spain)

    2011-09-23

    Photoinduced fluorescence enhancement of colloidal quantum dots (QDs) is a hot topic addressed in many studies due to its great influence on the bioanalytical performance of such nanoparticles. However, understanding of this process is not a simple task, and it cannot be explained by a general mechanism as it greatly depends on the QDs' nature, solubilization strategies, surrounding environment, etc. In this vein, we have critically compared the behavior of CdSe QDs (widely used in bioanalytical applications) with different surface modifications (ligand exchange and polymer coating), in different controlled experimental conditions, in the presence-absence of the ZnS layer and in different media when exposed for long times to intense UV irradiation. Thus six different types of colloidal QDs were finally studied. This research was carried out from a novel perspective, based on the analysis of the dynamic behavior of the photoactivation process (of great interest for further applications of QDs as labels in biomedical applications). The results showed a different behavior of the studied colloidal QDs after UV irradiation in terms of their photoluminescence characteristics, potential toxicity due to metal release to the environment, nanoparticle stability and surface coating degradation.

  11. Cu{sub 2}S as ohmic back contact for CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Türck, Johannes; Siol, Sebastian; Mayer, Thomas; Klein, Andreas; Jaegermann, Wolfram, E-mail: jaegermann@surface.tu-darmstadt.de

    2015-05-01

    We prepared a back contact for CdTe solar cells with Cu{sub 2}S as primary contact. Cu{sub 2}S was evaporated on CdCl{sub 2} treated CdTe solar cells in superstrate configuration. The CdTe and CdS layers were deposited by Closed Space Sublimation. Direct interface studies with X-ray photoelectron spectroscopy have revealed a strongly reactive interface between CdTe and Cu{sub 2}S. A valence band offset of 0.4-0.6 eV has been determined. The performance of solar cells with Cu{sub 2}S back contacts was studied in comparison to cells with an Au contact that deposited onto a CdCl{sub 2}-treated CdTe surface that was chemically etched using a nitric-phosphoric etch. The solar cells were analyzed by current-voltage curves and external quantum efficiency measurements. After several post deposition annealing steps, 13% efficiency was reached with the Cu{sub 2}S back contact, which was significantly higher than the ones obtained for the NP-etched back contacts. - Highlights: • A new back contact for CdTe solar out of Cu{sub 2}S has been tested. • With a direct interface experiment the valence band offset was determined. • Post deposition heat treatment has been carried out for the solar cells. • 13% efficiency has been reached with the Cu{sub 2}S back contact.

  12. Proximity effect between a ferromagnetic insulator and a superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Michael J.; Beckmann, Detlef [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Nanotechnologie; Huebler, Florian [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Nanotechnologie; Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Festkoerperphysik; Suergers, Christoph [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Physikalisches Inst.; Loehneysen, Hilbert von [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Festkoerperphysik; Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Physikalisches Inst.

    2012-07-01

    Electron transfer through spin-active interfaces can be modeled by the transmission amplitudes and a relative phase shift between spin-up and spin-down wavefunctions, the spin-mixing angle. Recently, Andreev bound states have been observed in F/S tunnel contacts which imply a non-zero spin-mixing angle of the ultrathin F/S barrier. In order to separate the spin-active interface from the detector tunnel contact, we have fabricated normal metal/superconductor tunnel contacts on top of a ferromagnetic insulator. We prepared EuS thin films (d{approx}20 nm) on top of Si(111) substrates by means of e-beam evaporation and created Al/Al-Oxide/Cu tunnel contacts by means of shadow evaporation. In an applied magnetic field, the tunnel spectra show an enhanced Zeeman splitting which is due to the presence of the exchange field of the EuS layer. Furthermore, we observe small peaks in the subgap region of the tunnel spectra which may be attributed to Andreev bound states due to a non-zero spin-mixing angle at the EuS/Al interface. The results suggest the use of EuS thin films for generating equal-spin triplet superconductivity.

  13. Atomic-scale decoration for improving the pitting corrosion resistance of austenitic stainless steels

    Science.gov (United States)

    Zhou, Y. T.; Zhang, B.; Zheng, S. J.; Wang, J.; San, X. Y.; Ma, X. L.

    2014-01-01

    Stainless steels are susceptible to the localized pitting corrosion that leads to a huge loss to our society. Studies in the past decades confirmed that the pitting events generally originate from the local dissolution in MnS inclusions which are more or less ubiquitous in stainless steels. Although a recent study indicated that endogenous MnCr2O4 nano-octahedra within the MnS medium give rise to local nano-galvanic cells which are responsible for the preferential dissolution of MnS, effective solutions of restraining the cells from viewpoint of electrochemistry are being tantalizingly searched. Here we report such a galvanic corrosion can be greatly resisted via bathing the steels in Cu2+-containing solutions. This chemical bath generates Cu2-δS layers on the surfaces of MnS inclusions, invalidating the nano-galvanic cells. Our study provides a low-cost approach via an atomic scale decoration to improve the pitting corrosion resistance of stainless steels in a volume-treated manner.

  14. New Method for Determining the Elemental Composition and Distribution in Semiconductor Core-Shell Quantum Dots

    Science.gov (United States)

    Zorn, Gilad; Dave, Shivang R.; Gao, Xiaohu; Castner, David G.

    2011-01-01

    In the biological sciences the use of core-shell quantum dots (QDs) has gained wide usage, but analytical challenges still exist for characterizing the QD structure. The application of energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy (XPS) to bulk materials is relatively straightforward, however, for meaningful applications of surface science techniques to multilayer nanoparticles requires novel modifications and analysis methods. To experimentally characterize the elemental composition and distribution in CdSe/CdS/ZnS QDs, we first develop a XPS signal subtraction technique capable of separating the overlapped selenium 3s (core) and sulfur 2s (shell) peaks (both peaks have binding energies near 230eV) with higher precision than is typically reported in the nanoparticle literature. This method is valid for any nanoparticle containing selenium and sulfur. Then we apply a correction formula to the XPS data and determine that the 2 nm stoichiometric CdSe core is surrounded by 2 CdS layers and a stoichimetric ZnS monolayer. These findings and the multi-approach methodology represent a significant advancement in the detailed surface science study of multi-layer nanoparticles. In agreement with recent surprising findings, the time-of-flight secondary mass spectrometry measurements suggest that the surface sites of the QDs used in this study are primarily covered with a mixture of octadecylphosphonic acid and trioctylphophine oxide. PMID:21226467

  15. Stable core/shell CdTe/Mn-CdS quantum dots sensitized three-dimensional, macroporous ZnO nanosheet photoelectrode and their photoelectrochemical properties.

    Science.gov (United States)

    Li, Weili; Sheng, Pengtao; Feng, Hongyan; Yin, Xuehua; Zhu, Xuewei; Yang, Xu; Cai, Qingyun

    2014-08-13

    A novel photoelectrode based on ZnS/CdTe/Mn-CdS/ZnS-sensitized three-dimensional macroporous ZnO nanosheet (NS) has been prepared by electrodeposition and successive ion layer adsorption and reaction (SILAR) method. The photoelectrode performances were significantly improved through the coupling of the core/shell CdTe/Mn-CdS quantum dots (QDs) with ZnO NS, and the introduction of the ZnS layer as a potential barrier. The photocurrent density systematically increases from ZnO NS (0.45 mA/cm(2)), CdTe/Mn-CdS/ZnO NS (4.98 mA/cm(2)), to ZnS/CdTe/Mn-CdS/ZnS/ZnO (6.23 mA/cm(2)) under the irradiation of AM 1.5G simulated sunlight. More important, the ZnS/CdTe/Mn-CdS/ZnS-sensitized ZnO NS photoelectrode provides a remarkable photoelectrochemical cell efficiency of 4.20% at -0.39 V vs Ag/AgCl. PMID:25010851

  16. The ultrastructure of Ignicoccus: Evidence for a novel outer membrane and for intracellular vesicle budding in an archaeon

    Directory of Open Access Journals (Sweden)

    Reinhard Rachel

    2002-01-01

    Full Text Available A novel genus of hyperthermophilic, strictly chemolithotrophic archaea, Ignicoccus, has been described recently, with (so far three isolates in pure culture. Cells were prepared for ultrastructural investigation by cultivation in cellulose capillaries and processing by high-pressure freezing, freeze-substitution and embedding in Epon. Cells prepared in accordance with this protocol consistently showed a novel cell envelope structure previously unknown among the Archaea: a cytoplasmic membrane; a periplasmic space with a variable width of 20 to 400 nm, containing membrane-bound vesicles; and an outer sheath, approximately 10 nm wide, resembling the outer membrane of gram-negative bacteria. This sheath contained three types of particles: numerous tightly, irregularly packed single particles, about 8 nm in diameter; pores with a diameter of 24 nm, surrounded by tiny particles, arranged in a ring with a diameter of 130 nm; and clusters of up to eight particles, each particle 12 nm in diameter. Freeze-etched cells exhibited a smooth surface, without a regular pattern, with frequent fracture planes through the outer sheath, indicating the presence of an outer membrane and the absence of an S-layer. The study illustrates the novel complex architecture of the cell envelope of Ignicoccus as well as the importance of elaborate preparation procedures for ultrastructural investigations.

  17. Preparation and Characterization of Coevaporated Cd1−xZnxS Alloy Thin Films

    Directory of Open Access Journals (Sweden)

    Wei Li

    2011-01-01

    Full Text Available Cd1-xZnxS thin films have been prepared by the vacuum coevaporation method. The structural, compositional, and optical properties of Cd1-xZnxS thin films have been investigated using X-ray diffraction, X-ray fluorescence, and optical transmittance spectra. As-deposited Cd1-xZnxS thin films are polycrystalline and show the cubic structure for x=1 and hexagonal one for x<1 with the highly preferential orientation. The composition of Cd1-xZnxS thin films determined from Vegard's law and quartz thickness monitors agrees with that determined from the X-ray fluorescence spectra. Optical absorption edge of optical transmittance for Cd1-xZnxS thin films shows a blue shift with the increase of the zinc content. The band gap for Cd1-xZnxS thin films can be tuned nonlinearly with x from about 2.38 eV for CdS to 3.74 eV for ZnS. A novel structure for CuInS2-based solar cells with a Cd0.4Zn0.6S layer is proposed in this paper.

  18. Improving the performance of quantum dot sensitized solar cells through CdNiS quantum dots with reduced recombination and enhanced electron lifetime.

    Science.gov (United States)

    Gopi, Chandu V V M; Venkata-Haritha, Mallineni; Seo, Hyunwoong; Singh, Saurabh; Kim, Soo-Kyoung; Shiratani, Masaharu; Kim, Hee-Je

    2016-05-28

    To make quantum dot-sensitized solar cells (QDSSCs) competitive, we investigated the effect of Ni(2+) ion incorporation into a CdS layer to create long-lived charge carriers and reduce the electron-hole recombination. The Ni(2+)-doped CdS (simplified as CdNiS) QD layer was introduced to a TiO2 surface via the simple successive ionic layer adsorption and reaction (SILAR) method in order to introduce intermediate-energy levels in the QDs. The effects of different Ni(2+) concentrations (5, 10, 15, and 20 mM) on the physical, chemical, and photovoltaic properties of the QDSSCs were investigated. The Ni(2+) dopant improves the light absorption of the device, accelerates the electron injection kinetics, and reduces the charge recombination, which results in improved charge transfer and collection. The 15% CdNiS cell exhibits the best photovoltaic performance with a power conversion efficiency (η) of 3.11% (JSC = 8.91 mA cm(-2), VOC = 0.643 V, FF = 0.543) under one full sun illumination (AM 1.5 G). These results are among the best achieved for CdS-based QDSSCs. Electrochemical impedance spectroscopy (EIS) and open circuit voltage decay (OCVD) measurements confirm that the Ni(2+) dopant can suppress charge recombination, prolong the electron lifetime, and improve the power conversion efficiency of the cells. PMID:27111597

  19. Structure-dependent gas detection ability of clustered ZnS crystallites with heterostructure and tube-like architecture

    International Nuclear Information System (INIS)

    ZnS crystallites with a core–shell heterostructure (ZnO–ZnS core–shell rods) and tube-like architecture were synthesized through a facile chemical solution route. Many tiny ZnS particles were clustered and compacted to form the shell layer of the ZnO–ZnS core–shell rods and the wall of the ZnS tubes during sulfidation of vertically aligned ZnO rods. X-ray diffraction and transmittance electron microscopy images revealed that the ZnS shell layer of the ZnO–ZnS core–shell rods and the wall of the tubes were polycrystalline, and that many domains or grain boundaries were present in the ZnS layers. The sensitivities of ZnO–ZnS core–shell rods and ZnS tubes to reducing and oxidizing gases differed. The ZnO–ZnS core–shell rods were more sensitive to reducing gases, whereas the ZnS tubes were more sensitive to oxidizing gases. The different gas sensing properties of the ZnS-based heterostructures and tubes are further discussed in relation to their microstructures. The heterojunction at the ZnO/ZnS interfacial region resulted in the differing gas sensing properties of the ZnS-based heterostructures and tubes in this study

  20. Cu2ZnSnSe4 nanocrystals capped with S2− by ligand exchange: utilizing energy level alignment for efficiently reducing carrier rec ombination

    Science.gov (United States)

    2014-01-01

    In this work, we employed a convenient one-step synthesis method for synthesizing Cu2ZnSnSe4 (CZTSe) nanocrystals (NCs) in an excess selenium environment. This excess selenium situation enhanced the reaction of metal acetylacetonates with selenium, resulting in the burst nucleation of NCs at relatively low temperatures. The phase morphology and surface and optoelectronic properties of NCs before and after ligand exchange were discussed in depth. It was found that pure tetragonal-phase structure CZTSe NCs with approximately 1.7-eV bandgap could be synthesized. The removal of large organic molecules on CZTSe NCs after ligand exchange by S2− decreased the resistivity. The bandgap of the films after ligand exchange by 550°C selenization was also decreased due to better crystallinity. For potential application in CZTSe solar cells, we constructed an energy level diagram to explain the mutual effect between the absorption layer and CdS layer. Using cyclic voltammetry (CV) measurement, we found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of CZTSe films shifted down after ligand exchange. After energy level alignment at the CdS/CZTSe interface, a type I band alignment structure was more conveniently formed after ligand exchange. This structure acted as the barrier against injection electrons from ZnO to the CZTSe layer, and recombination would subsequently be depressed. PMID:24994951

  1. Evolution of Na-S(-O) Compounds on the Cu2ZnSnS4 Absorber Surface and Their Effects on CdS Thin Film Growth.

    Science.gov (United States)

    Ren, Yi; Scragg, Jonathan J S; Edoff, Marika; Larsen, Jes K; Platzer-Björkman, Charlotte

    2016-07-20

    Formation of Na-containing surface compounds is an important phenomenon in the Cu2ZnSnS4 (CZTS) quaternary material synthesis for solar cell applications. Still, identification of these compounds and the understanding of their potential influence on buffer layer growth and device performance are scarce. In this work, we discovered that the evolution of Na-S(-O) compounds on the CZTS surface substantially affect the solution/CZTS interface during the chemical bath deposition of CdS buffer film. We showed that Na2S negatively affects the growth of CdS, and that this compound is likely to form on the CZTS surface after annealing. It was also demonstrated that the Na2S compound can be oxidized to Na2SO4 by air exposure of the annealed CZTS surface or be removed using water dipping instead of the commonly used KCN etching process, resulting in significantly better quality of the CdS layer. Lastly, 6.5% CZTS solar cells were fabricated with air exposure treatment without incorporation of the KCN etching process. This work provides new insight into the growth of the CdS/CZTS interface for solar cell applications and opens new possibilities for improving likewise Cd-free buffer materials that are grown with a similar chemical bath deposition process. PMID:27356214

  2. Cu2ZnSnSe4 nanocrystals capped with S(2-) by ligand exchange: utilizing energy level alignment for efficiently reducing carrier rec ombination.

    Science.gov (United States)

    Wang, Xia; Kou, Dong-Xing; Zhou, Wen-Hui; Zhou, Zheng-Ji; Wu, Si-Xin; Cao, Xuan

    2014-01-01

    In this work, we employed a convenient one-step synthesis method for synthesizing Cu2ZnSnSe4 (CZTSe) nanocrystals (NCs) in an excess selenium environment. This excess selenium situation enhanced the reaction of metal acetylacetonates with selenium, resulting in the burst nucleation of NCs at relatively low temperatures. The phase morphology and surface and optoelectronic properties of NCs before and after ligand exchange were discussed in depth. It was found that pure tetragonal-phase structure CZTSe NCs with approximately 1.7-eV bandgap could be synthesized. The removal of large organic molecules on CZTSe NCs after ligand exchange by S(2-) decreased the resistivity. The bandgap of the films after ligand exchange by 550°C selenization was also decreased due to better crystallinity. For potential application in CZTSe solar cells, we constructed an energy level diagram to explain the mutual effect between the absorption layer and CdS layer. Using cyclic voltammetry (CV) measurement, we found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of CZTSe films shifted down after ligand exchange. After energy level alignment at the CdS/CZTSe interface, a type I band alignment structure was more conveniently formed after ligand exchange. This structure acted as the barrier against injection electrons from ZnO to the CZTSe layer, and recombination would subsequently be depressed. PMID:24994951

  3. Pt/In2S3/CdS/Cu2ZnSnS4 Thin Film as an Efficient and Stable Photocathode for Water Reduction under Sunlight Radiation.

    Science.gov (United States)

    Jiang, Feng; Gunawan; Harada, Takashi; Kuang, Yongbo; Minegishi, Tsutomu; Domen, Kazunari; Ikeda, Shigeru

    2015-10-28

    An electrodeposited Cu2ZnSnS4 (CZTS) compact thin film modified with an In2S3/CdS double layer and Pt deposits (Pt/In2S3/CdS/CZTS) was used as a photocathode for water splitting of hydrogen production under simulated sunlight (AM 1.5G) radiation. Compared to platinized electrodes based on a bare CZTS film (Pt/CZTS) and a CZTS film modified with a CdS single layer (Pt/CdS/CZTS), the Pt/In2S3/CdS/CZTS electrode exhibited a significantly high cathodic photocurrent. Moreover, the coverage of the In2S3 layer was found to be effective for stabilization against degradation induced by photocorrosion of the CdS layer. Bias-free water splitting with a power conversion efficiency of 0.28% was achieved by using a simple two-electrode cell consisting of the Pt/In2S3/CdS/CZTS photocathode and a BiVO4 photoanode. PMID:26479423

  4. Effect of microstructure of sintered CdS on the photovoltaic properties of polycrystalline CdS/CdTe solar cells

    Science.gov (United States)

    Lee, J. S.; Im, H. B.; Fahrenbruch, A. L.; Bube, R. H.

    1987-07-01

    Sintered CdS films with different microstructures and electronic properties have been prepared by changing sintering conditions and by heat-treatments after sintering. All-polycrystalline CdS/CdTe solar cells have been fabricated by coating a CdTe slurry on the sintered CdS films and sintering at 625 C for 1h in nitrogen, which increases the density of the CdTe films and leads to the formation of a n-p junction. As the average grain size of the sintered CdS layer becomes larger, increases are found in CdS film transmittance and, hence, the short-circuit current, whereas a decrease in the reverse saturation current results from the better microstructure of the junction. Both of these effects lead to improved solar-cell efficiency. The presence of residual CdCl2 in the sintered CdS films, on the other hand, causes the formation of a thick layer of CdS(1-x) Te(x) at the compositional interface and a deep n-p junction in the CdTe layer, both of which limit the solar efficiency.

  5. Colloidally prepared CdHgTe and HgTe quantum dots with strong near-infrared luminescence

    Energy Technology Data Exchange (ETDEWEB)

    Rogach, A.L.; Kornowski, A.; Eychmueller, A.; Weller, H. [Hamburg Univ. (Germany). Inst. fuer Physikalische Chemie; Harrison, M.T.; Kershaw, S.V.; Burt, M.G. [Corning Research Centre, Suffolk (United Kingdom)

    2001-03-01

    Several series of CdHgTe composite nanocrystals were prepared using thiol-capped CdTe nanocrystal precursors to which subsequent layers of HgTe and CdTe were added. The position of the 'excitonic' photoluminescence peak measured at room temperature was red-shifted to the near infrared to give emission wavelengths ranging from 800 to 1100 nm depending on the quantum dot composition, with quantum efficiency (QE) significantly increased over the pure CdTe material (QE up to around 40%). Thiol-capped HgTe nanocrystals synthesized in aqueous solution show a broad photoluminescence with a QE of {proportional_to}50%. It has been shown using D{sub 2}O as a solvent that by varying the synthesis conditions it is possible to tune the luminescence of HgTe quantum dots to the desired wavelength in the range of 900-2000 nm. HgTe nanocrystals passivated at the surface with a thick CdS layer have been shown to be much more robust towards heating and ''aging'' of the optical properties. (orig.)

  6. Interface transparency of superconductor/ferromagnetic multilayers

    International Nuclear Information System (INIS)

    We have investigated the behavior of the superconducting transition temperature Tc in superconducting/ferromagnetic (S/F) multilayers, as a function of the different layer thicknesses and for varying magnetic moment μF of the F-layer atoms. The system studied consists of superconducting V and ferromagnetic V1-xFex alloys with x such that μF on the Fe atom is varied between 2 and 0.25μB. We determined the superconducting coherence length in the F layer ξF, which is found to be inversely proportional to μF. We also determined the critical thickness of the S layer, above which superconductivity appears. This thickness is found to be strongly nonmonotonic as function of the Fe concentration in the alloys. By analyzing the data in terms of the proximity-effect theory, we show that with increasing μF, the increasing pair breaking in the F layer by the exchange field is counteracted by a decreasing transparency of the S/F interface for Cooper pairs. copyright 1997 The American Physical Society

  7. Proximity effect in dirty N/S multilayers

    International Nuclear Information System (INIS)

    The proximity effect in S/N multilayer is studied theoretically for the general case of arbitrary transparency of NS boundary and arbitrary parameters of N and S materials. Small mean free paths are assumed in both metals (dirty limit). The approach based on the microscopic Usadel equations is used. The main subject of the paper is the crossover from strongly coupled layers to the case of complete decoupling. For the simplest case of thin N and S layers the well-known approximations can be derived from the Usadel equations: the Cooper limit for the case of highly transparent NS boundaries and the McMillan tunneling model for the case of small transparency. The limits of applicability of both approximations are discussed, as well as that of the Werthamer (one-frequency) approximation. In general case the complete set of equations of the model is solved. Critical temperature of a multilayer and densities of states at different layers are calculated numerically as a function of NS boundary transparency

  8. Profile of Secreted Hydrolases, Associated Proteins, and SlpA in Thermoanaerobacterium saccharolyticum during the Degradation of Hemicellulose

    Energy Technology Data Exchange (ETDEWEB)

    Currie, Devin [Dartmouth College; Guss, Adam M [ORNL; Herring, Christopher [Mascoma Corporation; Giannone, Richard J [ORNL; Johnson, Courtney M [ORNL; Lankford, Patricia K [ORNL; Brown, Steven D [ORNL; Hettich, Robert {Bob} L [ORNL; Lynd, Lee R [Thayer School of Engineering at Dartmouth

    2014-01-01

    Thermoanaerobacterium saccharolyticum, a Gram-positive thermophilic anaerobic bacterium, grows robustly on insoluble hemicellulose, which requires a specialized suite of secreted and transmembrane proteins. We report here the characterization of proteins secreted by this organism. Cultures were grown on hemicellulose, glucose, xylose, starch, and xylan in pH-controlled bioreactors, and samples were analyzed via spotted microarrays and liquid chromatography-mass spectrometry. Key hydrolases and transporters employed by T. saccharolyticum for growth on hemicellulose were, for the most part, hitherto uncharacterized and existed in two clusters (Tsac_1445 through Tsac_1464 for xylan/xylose and Tsac_1344 through Tsac_1349 for starch). A phosphotransferase system subunit, Tsac_0032, also appeared to be exclusive to growth on glucose. Previously identified hydrolases that showed strong conditional expression changes included XynA (Tsac_1459), XynC (Tsac_0897), and a pullulanase, Apu (Tsac_1342). An omnipresent transcript and protein making up a large percentage of the overall secretome, Tsac_0361, was tentatively identified as the primary S-layer component in T. saccharolyticum, and deletion of the Tsac_0361 gene resulted in gross morphological changes to the cells. The view of hemicellulose degradation revealed here will be enabling for metabolic engineering efforts in biofuel-producing organisms that degrade cellulose well but lack the ability to catabolize C5 sugars

  9. Emergence of Metallic Properties at LiFePO4 Surfaces and LiFePO4/Li2S Interfaces: An Ab Initio Study.

    Science.gov (United States)

    Timoshevskii, Vladimir; Feng, Zimin; Bevan, Kirk H; Zaghib, Karim

    2015-08-26

    The atomic and electronic structures of the LiFePO4 (LFP) surface, both bare and reconstructed upon possible oxygenation, are theoretically studied by ab initio methods. On the basis of total energy calculations, the atomic structure of the oxygenated surface is proposed, and the effect of surface reconstruction on the electronic properties of the surface is clarified. While bare LFP(010) surface is insulating, adsorption of oxygen leads to the emergence of semimetallic behavior by inducing the conducting states in the band gap of the system. The physical origin of these conducting states is investigated. We further demonstrate that deposition of Li2S layers on top of oxygenated LFP(010) surface leads to the formation of additional conducting hole states in the first layer of Li2S surface because of the charge transfer from sulfur p-states to the gap states of LFP surface. This demonstrates that oxygenated LFP surface not only provides conducting layers itself, but also induces conducting channels in the top layer of Li2S. These results help to achieve further understanding of potential role of LFP particles in improving the performance of Li-S batteries through emergent interface conductivity. PMID:26237114

  10. High-contrast top-emitting organic light-emitting diodes with a Ni/ZnS/CuPc/Ni contrast-enhancing stack and a ZnS anti-reflection layer

    Science.gov (United States)

    Chen, Shufen; Xie, Jun; Yang, Yang; Chen, Chunyan; Huang, Wei

    2010-09-01

    High-contrast top-emitting organic light-emitting diodes are successfully fabricated using a Ni/ZnS/copper-phthalocyanine (CuPc)/Ni contrast-enhancing stack (CES) and a ZnS anti-reflection (AR) layer. The CES and AR layer that are outside the active region reduce the complexity of the device design although their utilization affects the device electrical performance due to morphological deterioration of the device films. After the thickness optimization of the CES and AR coating, high contrast ratios of 139.4 : 1 and 462.3 : 1 are obtained under on-state luminances of 300 and 1000 cd m-2 and an ambient luminance of 140 lux. The reduced reflectance of ambient illumination is mainly due to the anti-reflection ZnS layer and the strong absorption of ambient illumination by the Ni layers, where the CES structure is beneficial for the absorption of ambient illumination by the interfacial reflection of Ni/ZnS and CuPc/Ni.

  11. by ligand exchange: utilizing energy level alignment for efficiently reducing carrier rec ombination

    Science.gov (United States)

    Wang, Xia; Kou, Dong-Xing; Zhou, Wen-Hui; Zhou, Zheng-Ji; Wu, Si-Xin; Cao, Xuan

    2014-05-01

    In this work, we employed a convenient one-step synthesis method for synthesizing Cu2ZnSnSe4 (CZTSe) nanocrystals (NCs) in an excess selenium environment. This excess selenium situation enhanced the reaction of metal acetylacetonates with selenium, resulting in the burst nucleation of NCs at relatively low temperatures. The phase morphology and surface and optoelectronic properties of NCs before and after ligand exchange were discussed in depth. It was found that pure tetragonal-phase structure CZTSe NCs with approximately 1.7-eV bandgap could be synthesized. The removal of large organic molecules on CZTSe NCs after ligand exchange by S2- decreased the resistivity. The bandgap of the films after ligand exchange by 550°C selenization was also decreased due to better crystallinity. For potential application in CZTSe solar cells, we constructed an energy level diagram to explain the mutual effect between the absorption layer and CdS layer. Using cyclic voltammetry (CV) measurement, we found that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of CZTSe films shifted down after ligand exchange. After energy level alignment at the CdS/CZTSe interface, a type I band alignment structure was more conveniently formed after ligand exchange. This structure acted as the barrier against injection electrons from ZnO to the CZTSe layer, and recombination would subsequently be depressed.

  12. Dynamic analysis of the photoenhancement process of colloidal quantum dots with different surface modifications

    International Nuclear Information System (INIS)

    Photoinduced fluorescence enhancement of colloidal quantum dots (QDs) is a hot topic addressed in many studies due to its great influence on the bioanalytical performance of such nanoparticles. However, understanding of this process is not a simple task, and it cannot be explained by a general mechanism as it greatly depends on the QDs' nature, solubilization strategies, surrounding environment, etc. In this vein, we have critically compared the behavior of CdSe QDs (widely used in bioanalytical applications) with different surface modifications (ligand exchange and polymer coating), in different controlled experimental conditions, in the presence-absence of the ZnS layer and in different media when exposed for long times to intense UV irradiation. Thus six different types of colloidal QDs were finally studied. This research was carried out from a novel perspective, based on the analysis of the dynamic behavior of the photoactivation process (of great interest for further applications of QDs as labels in biomedical applications). The results showed a different behavior of the studied colloidal QDs after UV irradiation in terms of their photoluminescence characteristics, potential toxicity due to metal release to the environment, nanoparticle stability and surface coating degradation.

  13. Simulation of the Efficiency of CdS/CdTe Tandem Multi-Junction Solar Cells

    CERN Document Server

    Mirkamali, Ashrafalsadat S

    2016-01-01

    In this paper we study CdS/CdTe solar cells by means of AMPS-1D software. First we study the effect of thickness of semiconductor layers on the output parameters of the CdS/CdTe solar cell, such as density of short-circuit current, open circuit voltage, fill factor and efficiency. Numerical simulation shows that the highest efficiency of single-junction CdS/CdTe solar cell equal to 18.3% is achieved when the CdTe layer thickness is 1000 nm and a CdS layer is 60 nm. Then, in order to obtain the maximal value of the efficiency, new tandem multi-junction structure consisting of layers of two solar cells connected with each other back to back are designed and engineered taking into account the results obtained for the single-junction solar cells. Numerical simulations show that its highest efficiency in 31.8% can be obtained when the thickness of CdS p-layer is equal to 50 nm, and the thickness of the CdS n-layer is equal to 200 nm, while thicknesses of the CdTe n-layer and CdTe p-layer are kept fixed and equal t...

  14. On paleodrainage evolution in mid-late Epipleistocene based on radar remote sensing in northeastern Ejin Banner, Inner Mongolia%基于雷达遥感的内蒙古额济纳旗东北部中晚早更新世古水系演化

    Institute of Scientific and Technical Information of China (English)

    WANG Xinyuan(王心源); GUO Huadong(郭华东); CHANG Yueming(常月明); ZHA Liangsong

    2004-01-01

    Radar remote sensing can acquire information of sub-surface covered by sand in arid area,detect surface roughness and vegetation coronet′s layer and linear feature such as linear structure and channel sensitively. With sediment facies analysis, this paper studies the features of environmental evolution in mid-late Epipleistocene (60 ka BP-20 ka BP) in northeastern Ejin Banner. The conclusions are listed as follows: (1) The evolution of the three lakes, i.e. Gaxunnur, Sugunur and Tian′e lakes, are dominated by faults and regional climate. (2) By analyzing sedimentary section of old Juyanze Lake,the three lakes used to be a large outflow lake before 50 ka BP in northeastern Ejin Banner, and at 50ka BP, temperature declined rapidly in northwestern China. The event caused the lake′s shrinkage. (3)By fault activity uplift in the northern part of old Juyan Lake and depression in the southern part, the lake′s water followed from north to south at around 35 ka BP, old Juyanze fluvial fan was formed. At the same time, Juyan Lake separated from Sugunur Lake and Wentugunr old channel was abandoned.(4) In recent 2000 years, Ruoshui River is a wandering river, sometimes it flows into Juyan Lake and sometimes Sugunur and Gaxunnur lakes. Due to human activities and over exploitation, the oasis ecosystem is rapidly degenerated in 15 years (1986-2000).

  15. Enhanced luminescence of quantum dot/dielectric layer/metal colloid multilayer thin films

    International Nuclear Information System (INIS)

    In this study, we reported the effect of the dielectric constants of the medium between quantum dots (QDs) and metal nanoparticles on the plasmon-enhanced fluorescence. The evaluation was conducted on (CdSe/ZnS)–(TiO2/SiO2)–(Au colloid) three-layer hybrid films prepared by the layer-by-layer coating. The CdSe/ZnS layer and the Au-nanoparticle layer were separated by a dielectric layer fabricated from tetraethyl orthosilicate and tetrabutyl orthotitanate. The dielectric constant of the dielectric layer was adjusted by varying the ratio of tetraethyl orthosilicate to tetrabutyl orthotitanate. We found that the optimal excitation wavelength for CdSe/ZnS QDs came with the localized surface plasmon resonance wavelength of Au colloids and could be controllable by virtue of adjusting the dielectric constant of the dielectric layer. Experimental results showed that both the optimal distance and the PL enhancement reduced with the increase of the dielectric constant. The decrease of the enhancement factor may arise from the increase of the rate of the resonant energy transfer from photo-excited CdSe/ZnS QDs to Au colloids. .

  16. Thiophene hydrodesulfurization on MoS 2; Theoretical aspects

    Science.gov (United States)

    Zonnevylle, Marjanne C.; Hoffmann, Roald; Harris, Suzanne

    Hydrodesulfurization (HDS), the removal of sulfur in the form of H 2S from petroleum, is a crucial step in the industrial refinement process. Using the extended Hückel tight binding method, we have examined the nature of the active site and the mechanism of desulfurization in the case of thiophene on MoS 2. The η 5-bound sites, in which the thiophene ring lies parallel to the surface, are particularly advantageous to weakening the SC bond. η 1-bound sites are less active. The removal of sorrounding surface sulfurs increases the HDS potential of the η 5 geometry, but is ineffective at promoting the poorer adsorption modes. Surface reconstruction has also been examined; the possibility of MoMo pairing is suggested. The effect of poisons and promoters is considered. The role they play in HDS catalysis may be determined by the position they occupy in the MoS 2 lattice. Metals which replace a surface molybdenum tend to poison HDS, whereas those which "pseudo-intercalate" between the SS layers can serve to promote the reaction.

  17. Vortex–antivortex dynamics in superconductor-antiparallel magnetic dipoles bilayers

    International Nuclear Information System (INIS)

    Highlights: • Vortex–antivortex (v–av) pairs dynamics in superconductor/ferromagnet hybrid systems is investigated. • Different dynamical phases can be observed. • Each dynamical phase has a specific number of v–av pairs creation and annihilation depends on external current applied. - Abstract: Artificial superconductor (S)/ferromagnet (F) hybrid structures composed by a S film and textured F layer have attracted great interest in the last fifteen years. In the limit of high values of magnetic moments, the ferromagnetic layer filled with magnetic particles (dipoles, nanodiscs, microrings, bars, etc.) can induce spontaneous creation and stabilization of vortex–antivortex (v–av) pairs in the S layer. These v–av molecules interact strongly with external applied currents inducing their annihilation or movement. Despite numerous studies about this subject, only a few of them emphasize the microscopic nature of this phenomena. In this work, the intricate dynamics of v–av molecules birth–death events and how this process influences macroscopic quantities are investigated

  18. Vortex–antivortex dynamics in superconductor-antiparallel magnetic dipoles bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Cléssio L.S., E-mail: clsl@df.ufpe.br

    2014-08-15

    Highlights: • Vortex–antivortex (v–av) pairs dynamics in superconductor/ferromagnet hybrid systems is investigated. • Different dynamical phases can be observed. • Each dynamical phase has a specific number of v–av pairs creation and annihilation depends on external current applied. - Abstract: Artificial superconductor (S)/ferromagnet (F) hybrid structures composed by a S film and textured F layer have attracted great interest in the last fifteen years. In the limit of high values of magnetic moments, the ferromagnetic layer filled with magnetic particles (dipoles, nanodiscs, microrings, bars, etc.) can induce spontaneous creation and stabilization of vortex–antivortex (v–av) pairs in the S layer. These v–av molecules interact strongly with external applied currents inducing their annihilation or movement. Despite numerous studies about this subject, only a few of them emphasize the microscopic nature of this phenomena. In this work, the intricate dynamics of v–av molecules birth–death events and how this process influences macroscopic quantities are investigated.

  19. GH10 XynA is the main xylanase identified in the crude enzymatic extract of Paenibacillus sp. A59 when grown on xylan or lignocellulosic biomass.

    Science.gov (United States)

    Ghio, Silvina; Insani, Ester M; Piccinni, Florencia E; Talia, Paola M; Grasso, Daniel H; Campos, Eleonora

    2016-01-01

    A novel bacterial isolate with polysaccharides degrading activity was identified as Paenibacillus sp., and named Paenibacillus sp. A59. Even though it is a strict mesophile, optimal xylanase activity of the crude enzymatic extract was achieved between 50°C and 70°C and more than 60% of the activity was retained after incubation for 48h at 50°C, indicating thermotolerance of the enzymes involved. The extract was also active on pre-treated sugarcane residue (SCR) and wheat straw, releasing xylobiose and xylose as the main products, therefore confirming its predominantly xylanolytic activity. By zymograms and mass spectrometry of crude enzymatic extracts of xylan or SCR cultures, a 32kDa GH10 beta- 1,4- endoxylanase with xylanase and no CMCase activity was identified. We named this enzyme XynA and it was the only xylanase identified under both conditions assayed, suggesting that it is a good candidate for recombinant expression and evaluation in hemicelluloses deconstruction applications. Also, a protein with two S-layer homology domains (SLH) and a large uncharacterized C-terminal domain as well as an ABC substrate binding protein were identified in crude extracts of SCR cultures. We propose that Paenibacillus sp. A59 uses a system similar to anaerobic and other Gram positive bacteria, with SLH-domain proteins anchoring polysaccharide-degrading enzymes close to the membrane and the substrate binding protein assisting translocation of simple sugars to the cell interior. PMID:27242139

  20. Structure determination of KScS₂, RbScS₂ and KLnS₂ (Ln = Nd, Sm, Tb, Dy, Ho, Er, Tm and Yb) and crystal-chemical discussion.

    Science.gov (United States)

    Havlák, Lubomír; Fábry, Jan; Henriques, Margarida; Dušek, Michal

    2015-07-01

    The title structures of KScS2 (potassium scandium sulfide), RbScS2 (rubidium scandium sulfide) and KLnS2 [Ln = Nd (potassium neodymium sufide), Sm (potassium samarium sulfide), Tb (potassium terbium sulfide), Dy (potassium dysprosium sulfide), Ho (potassium holmium sulfide), Er (potassium erbium sulfide), Tm (potassium thulium sulfide) and Yb (potassium ytterbium sulfide)] are either newly determined (KScS2, RbScS2 and KTbS2) or redetermined. All of them belong to the α-NaFeO2 structure type in agreement with the ratio of the ionic radii r(3+)/r(+). KScS2, the member of this structural family with the smallest trivalent cation, is an extreme representative of these structures with rare earth trivalent cations. The title structures are compared with isostructural alkali rare earth sulfides in plots showing the dependence of several relevant parameters on the trivalent cation crystal radius; the parameters thus compared are c, a and c/a, the thicknesses of the S-S layers which contain the respective constituent cations, the sulfur fractional coordinates z(S(2-)) and the bond-valence sums. PMID:26146403

  1. The local environment of Co2+ ions intercalated in vanadium oxide/hexadecylamine nanotubes

    Science.gov (United States)

    Saleta, M. E.; Aurelio, G.; Bardelli, F.; Sánchez, R. D.; Malta, M.; Torresi, R. M.

    2012-10-01

    Vanadium oxide nanotubes constitute promising materials for applications in nanoelectronics as cathode materials, in sensor technology and in catalysis. In this work we present a study on hybrid vanadium oxide/hexadecylamine multiwall nanotubes doped with Co ions using state of the art x-ray diffraction and absorption techniques, to address the issue of the dopant location within the nanotubes’ structure. The x-ray absorption near-edge structure analysis shows that the Co ions in the nanotubes are in the 2 + oxidation state, while extended x-ray absorption fine structure spectroscopy reveals the local environment of the Co2+ ions. Results indicate that Co atoms are exchanged at the interface between the vanadium oxide’s layers and the hexadecylamines, reducing the amount of amine chains and therefore the interlayer distance, but preserving the tubular shape. The findings in this work are important for describing Co2+ interaction with vanadium oxide nanotubes at the molecular level and will help to improve the understanding of their physicochemical behavior, which is desired in view of their promising applications.

  2. Cd1−xZnxS thin films with low Zn content obtained by an ammonia-free chemical bath deposition process

    International Nuclear Information System (INIS)

    Cd1−xZnxS films with low Zn content were obtained on glass substrates by an ammonia-free chemical bath deposition process. Alkaline reaction solutions were prepared using cadmium chloride, zinc chloride, sodium citrate, thiourea and potassium hydroxide. As a result of varying the mixture ratio between Cd and Zn precursors, microstructural studies from X-ray diffraction reveal that the resulting films have hexagonal, wurzite type, crystalline structure with changes in the preferential growth orientation. Important changes on the surface morphology and thickness of the Cd1−xZnxS films were also observed as effects of adding Zn to the CdS lattice. Optical studies show that Cd1−xZnxS thin films with energy band gaps in the range from 2.48 to 2.65 eV were obtained. - Highlights: • Cd1−xZnxS layers were grown on glass by ammonia-free chemical bath deposition • Films with low Zn content were obtained using reaction solutions with pH11.5 • Zn addition produced changes on the orientation growth and morphology of the films • Cd1−xZnxS films have energy band gap values from 2.48 to 2.65 eV

  3. Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs

    International Nuclear Information System (INIS)

    Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir’s layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied about the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir’s character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia

  4. Development of a SaaS application probe to the physical properties of the Earth's interior: An attempt at moving HPC to the cloud

    Science.gov (United States)

    Huang, Qian

    2014-09-01

    Scientific computing often requires the availability of a massive number of computers for performing large-scale simulations, and computing in mineral physics is no exception. In order to investigate physical properties of minerals at extreme conditions in computational mineral physics, parallel computing technology is used to speed up the performance by utilizing multiple computer resources to process a computational task simultaneously thereby greatly reducing computation time. Traditionally, parallel computing has been addressed by using High Performance Computing (HPC) solutions and installed facilities such as clusters and super computers. Today, it has been seen that there is a tremendous growth in cloud computing. Infrastructure as a Service (IaaS), the on-demand and pay-as-you-go model, creates a flexible and cost-effective mean to access computing resources. In this paper, a feasibility report of HPC on a cloud infrastructure is presented. It is found that current cloud services in IaaS layer still need to improve performance to be useful to research projects. On the other hand, Software as a Service (SaaS), another type of cloud computing, is introduced into an HPC system for computing in mineral physics, and an application of which is developed. In this paper, an overall description of this SaaS application is presented. This contribution can promote cloud application development in computational mineral physics, and cross-disciplinary studies.

  5. Synbiotic properties of Lactobacillus acidophilus M92

    Directory of Open Access Journals (Sweden)

    Jagoda Šušković

    2003-04-01

    Full Text Available The scientific basis for the development of probiotics, prebiotics or their combination (synbiotics stems from the knowledge that the gastrointestinal microflora is involved in protecting the host (man or animals against colonization of the intestinal tract by non-indigenous microorganisms. The use of probiotics (live beneficial microorganisms and prebiotics (non-digestible oligosaccharides as food/feed supplements beneficially affect the host by improving its intestinal microbial balance. Bacterial strain Lactobacillus acidophilus M92, which was selected for probiotic activity according to complex scientific in vitro selection criteria, is presented in this work. Accurate taxonomic identification of L. acidophilus M92 has been done by PCR method. The presence of S-layer proteins, hydrophobycity, autoaggregation, coaggregation and adhesion of L. acidophilus M92 to porcine ileal epithelial cells were determined. Because the concept of synbiotic became a part of probiotic concept in last few years, it was also investigated the ability of L. acidophilus M92 to assimilate the various kinds of prebiotic substrates (sorbitol, mannitol, lactulose, raffinose, oligofructose and inulin. The combination of probiotics and non-digestible carbohydrates (prebiotics may be a way of stabilisation and/or improvement of the probiotic effect. Such synbiotics indicate a realistic way of using biological preparationsin the prevention of gastrointestinal diseases in humans and animals.

  6. Functional characterization of WalRK: A two-component signal transduction system from Bacillus anthracis

    Directory of Open Access Journals (Sweden)

    Alisha Dhiman

    2014-01-01

    Full Text Available Two-component signal transduction systems (TCS, consisting of a sensor histidine protein kinase and its cognate response regulator, are an important mode of environmental sensing in bacteria. Additionally, they have been found to regulate virulence determinants in several pathogens. Bacillus anthracis, the causative agent of anthrax and a bioterrorism agent, harbours 41 pairs of TCS. However, their role in its pathogenicity has remained largely unexplored. Here, we show that WalRK of B. anthracis forms a functional TCS which exhibits some species-specific functions. Biochemical studies showed that domain variants of WalK, the histidine kinase, exhibit classical properties of autophosphorylation and phosphotransfer to its cognate response regulator WalR. Interestingly, these domain variants also show phosphatase activity towards phosphorylated WalR, thereby making WalK a bifunctional histidine kinase/phosphatase. An in silico regulon determination approach, using a consensus binding sequence from Bacillus subtilis, provided a list of 30 genes that could form a putative WalR regulon in B. anthracis. Further, electrophoretic mobility shift assay was used to show direct binding of purified WalR to the upstream regions of three putative regulon candidates, an S-layer protein EA1, a cell division ABC transporter FtsE and a sporulation histidine kinase KinB3. Our work lends insight into the species-specific functions and mode of action of B. anthracis WalRK.

  7. Rugged single domain antibody detection elements for Bacillus anthracis spores and vegetative cells.

    Directory of Open Access Journals (Sweden)

    Scott A Walper

    Full Text Available Significant efforts to develop both laboratory and field-based detection assays for an array of potential biological threats started well before the anthrax attacks of 2001 and have continued with renewed urgency following. While numerous assays and methods have been explored that are suitable for laboratory utilization, detection in the field is often complicated by requirements for functionality in austere environments, where limited cold-chain facilities exist. In an effort to overcome these assay limitations for Bacillus anthracis, one of the most recognizable threats, a series of single domain antibodies (sdAbs were isolated from a phage display library prepared from immunized llamas. Characterization of target specificity, affinity, and thermal stability was conducted for six sdAb families isolated from rounds of selection against the bacterial spore. The protein target for all six sdAb families was determined to be the S-layer protein EA1, which is present in both vegetative cells and bacterial spores. All of the sdAbs examined exhibited a high degree of specificity for the target bacterium and its spore, with affinities in the nanomolar range, and the ability to refold into functional antigen-binding molecules following several rounds of thermal denaturation and refolding. This research demonstrates the capabilities of these sdAbs and their potential for integration into current and developing assays and biosensors.

  8. Spin-coating deposition of PbS and CdS thin films for solar cell application

    International Nuclear Information System (INIS)

    In this work, we describe a simple spin-coating deposition technique for lead sulphide (PbS) and cadmium sulphide (CdS) films from a methanolic metal-thiourea complex. The characterization of the films by X-ray diffraction and X-ray photoelectron spectroscopy techniques revealed that pure cubic phase PbS and CdS layers were formed via this method. As shown by atomic force microscopy and scanning electron microscopy results, both films were homogeneous and presented a smooth surface. Optical properties showed that the energy band gap of PbS and CdS films were around 1.65 and 2.5 eV, respectively. The PbS film is p-type in nature with an electrical conductivity of around 0.8 S/cm. The hole concentration and mobility were 2.35 x 1018 cm-3 and 2.16 x 10-3 cm2/V/s, respectively, as determined from Hall measurement. Both films were used to develop a thin film solar cell device of graphite/PbS/CdS/ITO/glass. Device characterization showed the power conversion efficiency of around 0.24 %. The corresponding open circuit voltage, short circuit current and fill factor were 0.570 V, 1.32 mA/cm2 and 0.32, respectively. (orig.)

  9. The influence of magnetic domain landscape on the flux pinning in ferromagnetic/superconducting bilayers

    Science.gov (United States)

    Cieplak, Marta Z.; Adamus, Z.; Konczykowski, M.; Zhu, L. Y.; Chien, C. L.

    2009-03-01

    A line of miniature Hall sensors has been used to study the influence of the disorder in the magnetic domain landscape on flux pinning in the ferromagnetic/superconducting (F/S) bilayers. The bilayers consist of Nb as the S layer and Co/Pt multilayer with perpendicular magnetic anisotropy as the F layer, separated by a Si buffer layer to avoid the proximity effect. By changing of the Pt layer thickness, the magnetic domain landscape with different degree of disorder, ranging from uniformly distributed narrow domains (quasi-ordered landscape) to highly disordered landscape with domains of different sizes, can be predefined in the F layer. The flux behavior is then measured in the superconducting state using the Hall sensors. It is found that the quasi-ordered landscape with domains width comparable to the magnetic penetration depth produces large enhancement of the vortex pinning and smooth flux penetration. The more disordered magnetic domain patterns cause less pinning and create large edge barrier for vortex entry followed by strongly inhomogeneous flux penetration. The possible origins of this behavior will be discussed.

  10. Study and review on crust-mantle velocity structure in Bohai Bay and its vicinity

    Institute of Scientific and Technical Information of China (English)

    张成科; 张先康; 赵金仁; 任青芳; 张建狮; 海燕

    2002-01-01

    Observational data from some of the 10-odd deep seismic sounding profiles in Bohai Bay and its adjacent areas were processed with the methods of two-dimensional ray tracing, travel-time fitting and synthetic seismogram. The crust and upper-mantle velocity structure model in this area was built. The results show that the crust and upper mantle structures present obvious lateral and vertical inhomogeneity. The upper mantle uplifts near Yongqing of northeast Jizhong depression, in Bohai Bay of Huanghua depression and near Kenli of Jiyang depression, where crustal depths are about 31 km, 28 km and 29 km, respectively. According to the dynamic and kinetic characteristics of seismic waves as well as the seismic interfaces and velocity contour undulation in the 2-D velocity structure model, three deep crustal fault zones are inferred in the area. Low velocity (5.90~6.10 km/s) layers (bodies) exist on one or two sides of these deep crustal fault zones.

  11. Spin-coating deposition of PbS and CdS thin films for solar cell application

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Jayesh; Mighri, Frej [Laval University, CREPEC, Department of Chemical Engineering, Quebec, QC (Canada); Ajji, Abdellah [Ecole Polytechnique, CREPEC, Chemical Engineering Department, Montreal, QC (Canada); Tiwari, Devendra; Chaudhuri, Tapas K. [Charotar University of Science and Technology (CHARUSAT), Dr. K.C. Patel Research and Development Centre, Anand District, Gujarat (India)

    2014-12-15

    In this work, we describe a simple spin-coating deposition technique for lead sulphide (PbS) and cadmium sulphide (CdS) films from a methanolic metal-thiourea complex. The characterization of the films by X-ray diffraction and X-ray photoelectron spectroscopy techniques revealed that pure cubic phase PbS and CdS layers were formed via this method. As shown by atomic force microscopy and scanning electron microscopy results, both films were homogeneous and presented a smooth surface. Optical properties showed that the energy band gap of PbS and CdS films were around 1.65 and 2.5 eV, respectively. The PbS film is p-type in nature with an electrical conductivity of around 0.8 S/cm. The hole concentration and mobility were 2.35 x 10{sup 18} cm{sup -3} and 2.16 x 10{sup -3} cm{sup 2}/V/s, respectively, as determined from Hall measurement. Both films were used to develop a thin film solar cell device of graphite/PbS/CdS/ITO/glass. Device characterization showed the power conversion efficiency of around 0.24 %. The corresponding open circuit voltage, short circuit current and fill factor were 0.570 V, 1.32 mA/cm{sup 2} and 0.32, respectively. (orig.)

  12. Cu2S as ohmic back contact for CdTe solar cells

    International Nuclear Information System (INIS)

    We prepared a back contact for CdTe solar cells with Cu2S as primary contact. Cu2S was evaporated on CdCl2 treated CdTe solar cells in superstrate configuration. The CdTe and CdS layers were deposited by Closed Space Sublimation. Direct interface studies with X-ray photoelectron spectroscopy have revealed a strongly reactive interface between CdTe and Cu2S. A valence band offset of 0.4-0.6 eV has been determined. The performance of solar cells with Cu2S back contacts was studied in comparison to cells with an Au contact that deposited onto a CdCl2-treated CdTe surface that was chemically etched using a nitric-phosphoric etch. The solar cells were analyzed by current-voltage curves and external quantum efficiency measurements. After several post deposition annealing steps, 13% efficiency was reached with the Cu2S back contact, which was significantly higher than the ones obtained for the NP-etched back contacts. - Highlights: • A new back contact for CdTe solar out of Cu2S has been tested. • With a direct interface experiment the valence band offset was determined. • Post deposition heat treatment has been carried out for the solar cells. • 13% efficiency has been reached with the Cu2S back contact

  13. Cu2ZnSn(S,Se)4 solar cells based on chemical bath deposited precursors

    International Nuclear Information System (INIS)

    A low-cost method has been developed to fabricate Cu2ZnSn(S,Se)4 solar cells. By this method, firstly SnS, CuS, and ZnS layers are successively deposited on a molybdenum/soda lime glass (Mo/SLG) substrate by chemical bath deposition. The Cu2ZnSn(S,Se)4 thin films are obtained by annealing the precursor in a selenium atmosphere utilizing a graphite box in the furnace. The obtained Cu2ZnSn(S,Se)4 thin films show large crystalline grains. By optimizing the preparation process, Cu2ZnSn(S,Se)4 solar cells with efficiencies up to 4.5% are obtained. The results imply that the Cu2ZnSn(S,Se)4/CdS interface and the back contact may be limiting factors for solar cell efficiency. - Highlights: • A chemical bath deposition method is developed to prepare Cu2ZnSn(S,Se)4 thin films. • The Cu2ZnSn(S,Se)4 thin films show good crystallization. • Solar cells with efficiencies up to 4.5% can be prepared based on the Cu2ZnSn(S,Se)4 layer. • The limiting factors for the solar cell efficiency are analyzed

  14. Correlation of Interfacial Transportation Properties of CdS/CdTe Heterojunction and Performance of CdTe Polycrystalline Thin-Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Guanggen Zeng

    2015-01-01

    Full Text Available The light and dark output performances of CdS/CdTe solar cells made by close-spaced sublimation (CSS were investigated to elucidate the transportation properties of carriers at CdS/CdTe heterojunction interface. It has been found that the interfacial transportation properties were relatively sensitive to variations of the characteristics of heterojunction due to the series resistance and shunting effects. For the high quality cell with 12.1% efficiency, narrow depletion region of ~1.1 microns and large electric field intensity of ~1.3 V/μm allow the sufficient energy-band bending close to CdS layer at CdS/CdTe heterojunction, which changes the carrier transportation mechanism from emission to diffusion and leads to the optimal rectifying characteristics with small dark saturation current density ~6.4 × 10−10 A/cm2. As a result, the schematic diagram of heterojunction band structure corresponding to various performances of solar cells has also been presented.

  15. CdTe solar cells with open-circuit voltage breaking the 1 V barrier

    Science.gov (United States)

    Burst, J. M.; Duenow, J. N.; Albin, D. S.; Colegrove, E.; Reese, M. O.; Aguiar, J. A.; Jiang, C.-S.; Patel, M. K.; Al-Jassim, M. M.; Kuciauskas, D.; Swain, S.; Ablekim, T.; Lynn, K. G.; Metzger, W. K.

    2016-03-01

    CdTe solar cells have the potential to undercut the costs of electricity generated by other technologies, if the open-circuit voltage can be increased beyond 1 V without significant decreases in current. However, in the past decades, the open-circuit voltage has stagnated at around 800-900 mV. This is lower than in GaAs solar cells, even though GaAs has a smaller bandgap; this is because it is more difficult to achieve simultaneously high hole density and lifetime in II-VI materials than in III-V materials. Here, by doping the CdTe with a Group V element, we report lifetimes in single-crystal CdTe that are nearly radiatively limited and comparable to those in GaAs over a hole density range relevant for solar applications. Furthermore, the deposition on CdTe of nanocrystalline CdS layers that form non-ideal heterointerfaces with 10% lattice mismatch impart no damage to the CdTe surface and show excellent junction transport properties. These results enable the fabrication of CdTe solar cells with open-circuit voltage greater than 1 V.

  16. Simulation Study of Effects, Operating Temperature and Layer Thickness on Thin Film CIGS Solar Cell Performance

    Directory of Open Access Journals (Sweden)

    A.D. Pogrebnjak

    2011-01-01

    Full Text Available SCAPS- program is designed basically for the simulation and studying the properties of photonic devices. We explored the important controllable design parameters affecting the performance of the hetero junction solar cells, as operating temperature that we noticed increasing in J-V characteristics by increasing T, the effect of thickness of each layer on the performance of the cell was studied, an increasing of J-V characteristics with increasing p-layer , In the numerical example, 3 μm absorber layer and CdS layer 0.05 μm, ZnO layer 0.1 μm, works the best for given doping density, if we change the optimum value , the efficiency can reach to 17.72 % with FF 83.88 %, Voc = 0.725 Volt, Jsc = 29.07 mA/cm2 at 300 K, in this case, we have come out the optimum parameters to achieve the best performance of this type of cell, and then to made comparison with practical CIGS cell.

  17. Comparative genome analysis of Bacillus cereus group genomes withBacillus subtilis

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Iain; Sorokin, Alexei; Kapatral, Vinayak; Reznik, Gary; Bhattacharya, Anamitra; Mikhailova, Natalia; Burd, Henry; Joukov, Victor; Kaznadzey, Denis; Walunas, Theresa; D' Souza, Mark; Larsen, Niels; Pusch,Gordon; Liolios, Konstantinos; Grechkin, Yuri; Lapidus, Alla; Goltsman,Eugene; Chu, Lien; Fonstein, Michael; Ehrlich, S. Dusko; Overbeek, Ross; Kyrpides, Nikos; Ivanova, Natalia

    2005-09-14

    Genome features of the Bacillus cereus group genomes (representative strains of Bacillus cereus, Bacillus anthracis and Bacillus thuringiensis sub spp israelensis) were analyzed and compared with the Bacillus subtilis genome. A core set of 1,381 protein families among the four Bacillus genomes, with an additional set of 933 families common to the B. cereus group, was identified. Differences in signal transduction pathways, membrane transporters, cell surface structures, cell wall, and S-layer proteins suggesting differences in their phenotype were identified. The B. cereus group has signal transduction systems including a tyrosine kinase related to two-component system histidine kinases from B. subtilis. A model for regulation of the stress responsive sigma factor sigmaB in the B. cereus group different from the well studied regulation in B. subtilis has been proposed. Despite a high degree of chromosomal synteny among these genomes, significant differences in cell wall and spore coat proteins that contribute to the survival and adaptation in specific hosts has been identified.

  18. Profile of secreted hydrolases, associated proteins, and SlpA in Thermoanaerobacterium saccharolyticum during the degradation of hemicellulose.

    Science.gov (United States)

    Currie, D H; Guss, A M; Herring, C D; Giannone, R J; Johnson, C M; Lankford, P K; Brown, S D; Hettich, R L; Lynd, L R

    2014-08-01

    Thermoanaerobacterium saccharolyticum, a Gram-positive thermophilic anaerobic bacterium, grows robustly on insoluble hemicellulose, which requires a specialized suite of secreted and transmembrane proteins. We report here the characterization of proteins secreted by this organism. Cultures were grown on hemicellulose, glucose, xylose, starch, and xylan in pH-controlled bioreactors, and samples were analyzed via spotted microarrays and liquid chromatography-mass spectrometry. Key hydrolases and transporters employed by T. saccharolyticum for growth on hemicellulose were, for the most part, hitherto uncharacterized and existed in two clusters (Tsac_1445 through Tsac_1464 for xylan/xylose and Tsac_1344 through Tsac_1349 for starch). A phosphotransferase system subunit, Tsac_0032, also appeared to be exclusive to growth on glucose. Previously identified hydrolases that showed strong conditional expression changes included XynA (Tsac_1459), XynC (Tsac_0897), and a pullulanase, Apu (Tsac_1342). An omnipresent transcript and protein making up a large percentage of the overall secretome, Tsac_0361, was tentatively identified as the primary S-layer component in T. saccharolyticum, and deletion of the Tsac_0361 gene resulted in gross morphological changes to the cells. The view of hemicellulose degradation revealed here will be enabling for metabolic engineering efforts in biofuel-producing organisms that degrade cellulose well but lack the ability to catabolize C5 sugars. PMID:24907337

  19. Solar Synthesis of PbS-SnS2 Superstructure Nanoparticles.

    Science.gov (United States)

    Brontvein, Olga; Albu-Yaron, Ana; Levy, Moshe; Feuerman, Daniel; Popovitz-Biro, Ronit; Tenne, Reshef; Enyashin, Andrey; Gordon, Jeffrey M

    2015-08-25

    We report the synthesis and supporting density-functional-theory computations for a closed-cage, misfit layered-compound superstructure from PbS-SnS2, generated by highly concentrated sunlight from a precursor mixture of Pb, SnS2, and graphite. The unique reactor conditions created in our solar furnace are found to be particularly conducive to the formation of these nanomaterials. Detailed structural and chemical characterization revealed a spontaneous inside-out formation mechanism, with a broad range of nonhollow fullerene-like structures starting at a diameter of ∼20 nm and a wall thickness of ∼5 layers. The computations also reveal a counterintuitive charge transfer pathway from the SnS2 layers to the PbS layers, which indicates that, in contrast to binary-layered compounds where it is principally van der Waals forces that hold the layers together, polar forces appear to be as important in stabilizing superstructures of misfit layered compounds. PMID:26154896

  20. Cd{sub 1−x}Zn{sub x}S thin films with low Zn content obtained by an ammonia-free chemical bath deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Carreón-Moncada, I. [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Saltillo, Av. Industria Metalúrgica 1062, CP. 25900, Ramos Arizpe, Coah., México (Mexico); González, L.A., E-mail: luis.gonzalez@cinvestav.edu.mx [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Saltillo, Av. Industria Metalúrgica 1062, CP. 25900, Ramos Arizpe, Coah., México (Mexico); Pech-Canul, M.I. [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Saltillo, Av. Industria Metalúrgica 1062, CP. 25900, Ramos Arizpe, Coah., México (Mexico); Ramírez-Bon, R. [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Querétaro, Apartado Postal 1-798, CP. 76001 Querétaro, Qro., México (Mexico)

    2013-12-02

    Cd{sub 1−x}Zn{sub x}S films with low Zn content were obtained on glass substrates by an ammonia-free chemical bath deposition process. Alkaline reaction solutions were prepared using cadmium chloride, zinc chloride, sodium citrate, thiourea and potassium hydroxide. As a result of varying the mixture ratio between Cd and Zn precursors, microstructural studies from X-ray diffraction reveal that the resulting films have hexagonal, wurzite type, crystalline structure with changes in the preferential growth orientation. Important changes on the surface morphology and thickness of the Cd{sub 1−x}Zn{sub x}S films were also observed as effects of adding Zn to the CdS lattice. Optical studies show that Cd{sub 1−x}Zn{sub x}S thin films with energy band gaps in the range from 2.48 to 2.65 eV were obtained. - Highlights: • Cd{sub 1−x}Zn{sub x}S layers were grown on glass by ammonia-free chemical bath deposition • Films with low Zn content were obtained using reaction solutions with pH11.5 • Zn addition produced changes on the orientation growth and morphology of the films • Cd{sub 1−x}Zn{sub x}S films have energy band gap values from 2.48 to 2.65 eV.

  1. ZnxCd1-xS as a heterojunction partner for CuIn1-xGaxS2 thin film solar cells

    International Nuclear Information System (INIS)

    Zinc cadmium sulfide (ZnxCd1-xS) heterojunction partner layer prepared with chemical bath deposition (CBD) has exhibited better blue photon response and higher current densities due to its higher bandgap than that of conventional cadmium sulfide (CdS) layer for CuIn1-xGaxS2 (CIGS2) solar cells. CIGS2/ZnxCd1-xS devices have also shown higher open circuit voltage, Voc indicating improved junction properties. A conduction band offset has been observed by J-V curves at various temperatures indicating that still higher Voc can be obtained by optimizing the conduction band offset. This contribution discusses the effect of variation of parameters such as concentration of compounds, pH of solution and deposition time during CBD on device properties and composition and crystallinity of film. Efficiencies comparable to CIGS2/CdS devices have been achieved for CIGS2/ZnxCd1-xS devices

  2. Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Nurhandoko, Bagus Endar B., E-mail: bagusnur@bdg.centrin.net.id, E-mail: bagusnur@rock-fluid.com [Wave Inversion and Subsurface Fluid Imaging Research Laboratory (WISFIR), Basic Science Center A 4" t" hfloor, Physics Dept., FMIPA, Institut Teknologi Bandung (Indonesia); Rock Fluid Imaging Lab., Bandung (Indonesia); Susilowati, E-mail: bagusnur@bdg.centrin.net.id, E-mail: bagusnur@rock-fluid.com [Rock Fluid Imaging Lab., Bandung (Indonesia)

    2015-04-16

    Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir’s layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied about the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir’s character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia.

  3. Novel CdS Hole-Blocking Layer for Photostable Perovskite Solar Cells.

    Science.gov (United States)

    Hwang, Insung; Yong, Kijung

    2016-02-17

    Currently, the stability issue of the perovskite solar cells (PSCs) is one of the most critical obstacles in the commercialization of PSCs. Although incredible advances in the photovoltaic efficiencies of PSCs have been achieved in the past few years, research on the stability of PSCs has been relatively less explored. In this study, a new kind of CdS hole-blocking layer replacing the traditional compact TiO2 layer is developed to improve the photostability of PSCs because the intrinsic oxygen vacancies of the TiO2 surface are suspected to be the main cause for the photoinduced degradation of PSCs. As a result, PSCs with the CdS layer exhibit considerably improved photostability, maintaining over 90% of the initial efficiency after continuous sunlight illumination for 12 h, while the TiO2 PSC retains only 18% of the initial efficiency under the same conditions. Charge-transfer characteristics related to photodegradation are investigated by various analyses including electrochemical impedance spectroscopy and open-circuit voltage decay and time-resolved photoluminescence decay measurements. the CdS PSC exhibits negligible degradation in the charge-carrier dynamics, while the TiO2 PSC suffers from severely damaged characteristics like increased charge recombination rate, charge-transfer resistance, and reduced charge extraction rate. PMID:26809352

  4. Growth of CdS thin films on indium coated glass substrates via chemical bath deposition and subsequent air annealing

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • CdS film grown on indium coated glass substrates via CBD and subsequent annealing. • Disappearance of the indium (1 1 2) peak confirms interdiffusion at 300 °C. • SIMS indicates the subsequent interdiffusion at progressively higher temperature. • Composite In–CdS layer showed lower photosensitivity compared to pure CdS. - Abstract: In the present work attempts were made to synthesize indium doped CdS films by fabricating In/CdS bilayers using CBD-CdS on vacuum evaporated In thin films and subsequent air annealing. 135 nm CdS films were grown onto 20 nm and 35 nm indium coated glass substrate employing chemical bath deposition technique. The In/CdS bilayers thus formed were subjected to heat treatment at the temperatures between 200 and 400 °C for 4 min in the muffle furnace to facilitate indium to diffuse into the CdS films. XRD pattern ascertained no noticeable shift in lattice constant implying grain boundary metal segregation, while secondary ion mass spectrometry indicated the diffusion profile of indium into CdS matrices. Mass spectrometry results showed that substantial diffusion of indium had been taken place within CdS at 400 °C. Dark and photocurrent with different illumination time were measured to ascertain the photosensitivity of pure and composite CdS films

  5. Growth of CdS thin films on indium coated glass substrates via chemical bath deposition and subsequent air annealing

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Biswajit; Kumar, Kamlesh; Singh, Balwant Kr; Banerjee, Pushan; Das, Subrata, E-mail: neillohit@yahoo.co.in

    2014-11-30

    Graphical abstract: - Highlights: • CdS film grown on indium coated glass substrates via CBD and subsequent annealing. • Disappearance of the indium (1 1 2) peak confirms interdiffusion at 300 °C. • SIMS indicates the subsequent interdiffusion at progressively higher temperature. • Composite In–CdS layer showed lower photosensitivity compared to pure CdS. - Abstract: In the present work attempts were made to synthesize indium doped CdS films by fabricating In/CdS bilayers using CBD-CdS on vacuum evaporated In thin films and subsequent air annealing. 135 nm CdS films were grown onto 20 nm and 35 nm indium coated glass substrate employing chemical bath deposition technique. The In/CdS bilayers thus formed were subjected to heat treatment at the temperatures between 200 and 400 °C for 4 min in the muffle furnace to facilitate indium to diffuse into the CdS films. XRD pattern ascertained no noticeable shift in lattice constant implying grain boundary metal segregation, while secondary ion mass spectrometry indicated the diffusion profile of indium into CdS matrices. Mass spectrometry results showed that substantial diffusion of indium had been taken place within CdS at 400 °C. Dark and photocurrent with different illumination time were measured to ascertain the photosensitivity of pure and composite CdS films.

  6. Long-term corrosion of copper in a dilute anaerobic sulfide solution

    International Nuclear Information System (INIS)

    The mechanism of corrosion of oxygen-free copper has been studied in stagnant aqueous sulfide solutions using corrosion potential and electrochemical impedance spectroscopy (EIS) measurements. Film structure and composition were examined on surfaces and on cross-sections prepared by focused ion beam (FIB) milling using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Experiments were conducted in anaerobic 5 x 10-5 mol dm-3 Na2S + 0.1 mol dm-3 NaCl solutions for exposure periods up to 4000 h (∼167 days) to mimic (at least partially) the conditions that could develop on a copper nuclear fuel waste container in a deep geologic repository. The corrosion film formed was a single cellular Cu2S layer with a non-uniform thickness. The film thickness increased approximately linearly with immersion time, which implied that the sulfide film formed on the Cu surface is non-protective under these conditions up to this exposure time. The film growth process was controlled by HS- diffusion partially in the aqueous solution in the pores in the cellular sulfide film and partially in the bulk of the aqueous solution.

  7. Improved Intrinsic Stability of CdTe Polycrystalline Thin Film Devices

    Energy Technology Data Exchange (ETDEWEB)

    Albin, D.; Berniard, T.; McMahon, T.; Noufi, R.; Demtsu, S.

    2005-01-01

    A systems-driven approach linking upstream solar cell device fabrication history with downstream performance and stability has been applied to CdS/CdTe small-area device research. The best resulting initial performance (using thinner CdS, thicker CdTe, no oxygen during VCC, and the use of NP etch) was shown to simultaneously correlate with poor stability. Increasing the CdS layer thickness significantly improved stability at only a slight decrease in overall performance. It was also determined that cell perimeter effects can accelerate degradation in these devices. A ''margined'' contact significantly reduces the contribution of edge shunting to degradation, and thus yields a more accurate determination of the intrinsic stability. Pspice discrete element models demonstrate how spatially localized defects can effectively dominate degradation. Mitigation of extrinsic shunting improved stabilized efficiency degradation levels (SEDL) to near 20% in 100 C tests. Further process optimization to reduce intrinsic effects improved SEDL to better than 10% at the same stress temperatures and times.

  8. Single molecule binding dynamics measured with atomic force microscopy

    International Nuclear Information System (INIS)

    We present a new method to analyse simultaneous Topography and RECognition Atomic Force Microscopy data such that it becomes possible to measure single molecule binding rates of surface bound proteins. We have validated this method on a model system comprising a S-layer surface modified with Strep-tagII for binding sites and strep-tactin bound to an Atomic Force Microscope tip through a flexible Poly-Ethylene-Glycol linker. At larger distances, the binding rate is limited by the linker, which limits the diffusion of the strep-tactin molecule, but at lateral distances below 3 nm, the binding rate is solely determined by the intrinsic molecular characteristics and the surface geometry and chemistry of the system. In this regime, Kon as determined from single molecule TREC data is in agreement with Kon determined using traditional biochemical methods. - Highlights: • We discuss the importance of studying single molecule binding rates for surface bound proteins. • We show measurements of single molecule binding rates on a model system using AFM. • We discuss the influence of various components on the measured binding rates

  9. n—ZnO:Al/i-ZnO/n-CdS/p—Cu2ZnSnS4太阳能电池光伏特性的分析%Investigation of the photovoltaic performance of n-ZnO:Al/i-ZnO/n-CdS/p-Cu2ZnSnS4 solar cell

    Institute of Scientific and Technical Information of China (English)

    许佳雄; 姚若河

    2012-01-01

    具有高光吸收系数的半导体Cu2ZnSnS4(CZTS)薄膜是一种新型太阳能电池材料.本文对n—ZnO:A1/i.ZnO/n—CdS/p.CZTS结构的CZTS薄膜太阳能电池进行分析,讨论CZTS薄膜的掺杂浓度、厚度、缺陷态和CdS薄膜的掺杂浓度、厚度对太阳能电池转换效率的影响以及太阳能电池的温度特性.分析表明,CZTS薄膜作为太阳能电池的主要光吸收层,CZTS薄膜的掺杂浓度和厚度的取值对太阳能电池的转换效率有显著影响,CZTS薄膜结构缺陷态的存在会导致太阳能电池性能的下降.CdS缓冲层的掺杂浓度、厚度对太阳能电池光伏特性的影响较小.经结构参数优化得到的n—ZnO:Al/i.ZnO/n,CdS/p—CZTS薄膜太阳能电池的最佳光伏特性为开路电压1.127V、短路电流密度27.39mA/cm2、填充因子87.5%、转换效率27.02%,转换效率温度系数为一0.14%/K.%The semiconducting Cu2ZnSnS4 (CZTS) thin film with high absorption coefficient has long been recognized as a novel solar cell material. In this work, the performances of n-ZnO:A1/i-ZnO/n-CdS/p-CZTS solar cells are analyzed by using semiconductor theory. The influences of doping concentration, thickness, and defect states of CZTS layer and the doping concentration and thickness of CdS layer on the performances of the solar cells and the temperature characteristics are investigated. The calculated results show that the CZTS layer is a main absorption layer in the solar ceil. The changes in doping concentration and thickness of CZTS layer have significant influence on the conversion efficiency of the solar cell. The density of defect states in CZTS can sharply degrade the photovoltaic performances. The influences of the doping concentration and thickness of CdS layer can be neglected. The calculated results show that the optimal n-ZnO:A1/i-ZnO/n-CdS/p-CZTS structure has open-circuit voltage of 1.127 V, short circuit

  10. 基于模块化理论的旅游云平台构建研究%The Co nstruction Cloud Plotform of T onrism with Modulariztion Theory

    Institute of Scientific and Technical Information of China (English)

    韩学伟

    2016-01-01

    Cloud Tourism is one of the new trends of tourism , Turism cloud is the technical basis of Cloud Tourism.Turism cloud platform can be structured by modularity theory.Each turism cloud forms a certain size of the market and exist in the whole system as a sub module .The lower cloud system organically integrates to the su-perior tourism cloud system by reconstruction and eucalyptus cloud installation.It ultimately realizes branch tourism cloud to tourism cloud.The technical system of tourism cloud platform consists of three levels:IaaS ( infra structure as a Service) , PaaS ( Platform as a Service) and SaaS ( Software as a Service) .The objectives and results of these cloud computing services is to build a tourism cloud platform although their open source software and services is dif-ferent.The establishment of tourism cloud platform is divided into four steps.Framework of turism cloud platform is made up of the user, teminal, SDU, portal, SaaS layer, IaaS layer.%云旅游是旅游新方向之一,旅游云是云旅游的技术基础。旅游云平台适用模块化理论进行构建,每个旅游云都能形成一定的市场规模,也都能作为一个子模块存在于整个系统中。下级旅游云系统通过重构有机整合到上级旅游云系统中,最终实现分旅游云到旅游云。下级旅游云系统到上级旅游云系统的有机整合通过Eucalyptus云安装实现。旅游云平台搭建的技术体系包括三个层级:基础设施即服务IaaS、平台即服务PaaS和软件即服务SaaS。不同层级的云计算服务使用的开源软件不同,提供的服务也不同,但目标和结果都是搭建旅游云平台,搭建旅游云平台的步骤都分为四步。旅游云平台总体架构由用户层、终端层、接入层、门户层、SaaS层、IaaS层等部分组成。

  11. A High Molecular-Mass Anoxybacillus sp. SK3-4 Amylopullulanase: Characterization and Its Relationship in Carbohydrate Utilization

    Directory of Open Access Journals (Sweden)

    Kian Mau Goh

    2013-05-01

    Full Text Available An amylopullulanase of the thermophilic Anoxybacillus sp. SK3-4 (ApuASK was purified to homogeneity and characterized. Though amylopullulanases larger than 200 kDa are rare, the molecular mass of purified ApuASK appears to be approximately 225 kDa, on both SDS-PAGE analyses and native-PAGE analyses. ApuASK was stable between pH 6.0 and pH 8.0 and exhibited optimal activity at pH 7.5. The optimal temperature for ApuASK enzyme activity was 60 °C, and it retained 54% of its total activity for 240 min at 65 °C. ApuASK reacts with pullulan, starch, glycogen, and dextrin, yielding glucose, maltose, and maltotriose. Interestingly, most of the previously described amylopullulanases are unable to produce glucose and maltose from these substrates. Thus, ApuASK is a novel, high molecular-mass amylopullulanase able to produce glucose, maltose, and maltotriose from pullulan and starch. Based on whole genome sequencing data, ApuASK appeared to be the largest protein present in Anoxybacillus sp. SK3-4. The α-amylase catalytic domain present in all of the amylase superfamily members is present in ApuASK, located between the cyclodextrin (CD-pullulan-degrading N-terminus and the α-amylase catalytic C-terminus (amyC domains. In addition, the existence of a S-layer homology (SLH domain indicates that ApuASK might function as a cell-anchoring enzyme and be important for carbohydrate utilization in a streaming hot spring.

  12. Campylobacter fetus Subspecies Contain Conserved Type IV Secretion Systems on Multiple Genomic Islands and Plasmids

    Science.gov (United States)

    van der Graaf–van Bloois, Linda; Miller, William G.; Yee, Emma; Gorkiewicz, Gregor; Forbes, Ken J.; Zomer, Aldert L.; Wagenaar, Jaap A.; Duim, Birgitta

    2016-01-01

    The features contributing to differences in pathogenicity of the Campylobacter fetus subspecies are unknown. Putative factors involved in pathogenesis are located in genomic islands that encode a type IV secretion system (T4SS) and fic domain (filamentation induced by cyclic AMP) proteins, which may disrupt host cell processes. In the genomes of 27 C. fetus strains, three phylogenetically-different T4SS-encoding regions (T4SSs) were identified: one was located in both the chromosome and in extra-chromosomal plasmids; one was located exclusively in the chromosome; and one exclusively in extra-chromosomal plasmids. We observed that C. fetus strains can contain multiple T4SSs and that homologous T4SSs can be present both in chromosomal genomic islands (GI) and on plasmids in the C. fetus strains. The GIs of the chromosomally located T4SS differed mainly by the presence of fic genes, insertion sequence elements and phage-related or hypothetical proteins. Comparative analysis showed that T4SS sequences, inserted in the same locations, were conserved in the studied C. fetus genomes. Using phylogenetic analysis of the T4SSs, it was shown that C. fetus may have acquired the T4SS regions from other Campylobacter species by horizontal gene transfer. The identified T4SSs and fic genes were found in Cff and Cfv strains, although the presence of T4SSs and fic genes were significantly associated with Cfv strains. The T4SSs and fic genes could not be associated with S-layer serotypes or geographical origin of the strains. PMID:27049518

  13. Structural studies in limestone sulfidation

    Energy Technology Data Exchange (ETDEWEB)

    Fenouil, L.A.; Lynn, S.

    1993-05-01

    This study investigates the sulfidation of limestone at high temperatures (700--900{degree}C) as the first step in the design of a High-Temperature Coal-Gas Clean-Up system using millimeter-size limestone particles. Several workers have found that the rate of this reaction significantly decreases after an initial 10 to 15% conversion of CaCO{sub 3} to CaS. The present work attempts to explain this feature. It is first established that millimeter-size limestone particles do not sinter at temperatures up to the CaCO{sub 3} calcination point (899{degree}C at 1.03 bar CO{sub 2} partial pressure). It is then shown that CaS sinters rapidly at 750 to 900{degree}C if CO{sub 2} is present in the gas phase. Scanning Electron Microscope (SEM) photographs and Electron Dispersive Spectroscopy (EDS) data reveal that the CaS product layer sinters and forms a quasi-impermeable coating around the CaCO{sub 3} grains that greatly hinders more H{sub 2}S from reaching the still unreacted parts of the stone. Moreover, most of the pores initially present within the limestone structure begin to disappear or, at least, are significantly reduced in size. From then on, subsequent conversion is limited by diffusion of H{sub 2}S through the CaS layer, possibly by S{sup 2{minus}} ionic diffusion. The kinetics is then adequately described by a shrinking-core model, in which a sharp front of completely converted limestone is assumed to progress toward the center of the pellet. Finally, experimental evidence and computer simulations using simple sintering models suggest that the CaS sintering, responsible for the sharp decrease in the sulfidation rate, is surface-diffusion controlled.

  14. Genetic transformation of novel isolates of chicken Lactobacillus bearing probiotic features for expression of heterologous proteins: a tool to develop live oral vaccines

    Directory of Open Access Journals (Sweden)

    Neumann Elisabeth

    2006-01-01

    Full Text Available Abstract Background The use of lactic acid bacteria as vehicles to delivery antigens to immunize animals is a promising issue. When genetically modified, these bacteria can induce a specific local and systemic immune response against selected pathogens. Gastric acid and bile salts tolerance, production of antagonistic substances against pathogenic microorganisms, and adhesive ability to gut epithelium are other important characteristics that make these bacteria useful for oral immunization. Results Bacteria isolated on de Man, Rogosa and Sharpe medium (MRS from different gastrointestinal portions of broiler chicks were evaluated for their resistance to artificial gastric acid and bile salts, production of hydrogen peroxide, and cell surface hydrophobicity. Thirty-eight isolates were first typed at species level by PCR amplification of 16S-23S rRNA intergenic spacers using universal primers that anneal within 16S and 23S genes, followed by restriction digestion analyses of PCR amplicons (PCR-ARDRA. An expression cassette was assembled onto the pCR2.1-Topo vector by cloning the promoter, leader peptide, cell wall anchor and terminator sequences derived from the laminin binding S-layer protein gene of L. crispatus strain F5.7 (lbs gene. A sequence encoding the green fluorescent protein (GFP was inserted as reporter gene, and an erythromycin resistance gene was added as selective marker. All constructs were able to express GFP in the cloning host E. coli XL1-Blue and different Lactobacillus strains as verified by FACS and laser scanning confocal microscopy. Conclusion Lactobacillus isolated from gastrointestinal tract of broiler chickens and selected for probiotic characteristics can be genetically modified by introducing an expression cassette into the lbs locus. The transformed bacteria expressed on its cell wall surface different fluorescent proteins used as reporters of promoter function. It is possible then that similar bacterial model

  15. Functional analysis of putative adhesion factors in Lactobacillus acidophilus NCFM.

    Science.gov (United States)

    Buck, B Logan; Altermann, Eric; Svingerud, Tina; Klaenhammer, Todd R

    2005-12-01

    Lactobacilli are major inhabitants of the normal microflora of the gastrointestinal tract, and some select species have been used extensively as probiotic cultures. One potentially important property of these organisms is their ability to interact with epithelial cells in the intestinal tract, which may promote retention and host-bacterial communication. However, the mechanisms by which they attach to intestinal epithelial cells are unknown. The objective of this study was to investigate cell surface proteins in Lactobacillus acidophilus that may promote attachment to intestinal tissues. Using genome sequence data, predicted open reading frames were searched against known protein and protein motif databases to identify four proteins potentially involved in adhesion to epithelial cells. Homologous recombination was used to construct isogenic mutations in genes encoding a mucin-binding protein, a fibronectin-binding protein, a surface layer protein, and two streptococcal R28 homologs. The abilities of the mutants to adhere to intestinal epithelial cells were then evaluated in vitro. Each strain was screened on Caco-2 cells, which differentiate and express markers characteristic of normal small-intestine cells. A significant decrease in adhesion was observed in the fibronectin-binding protein mutant (76%) and the mucin-binding protein mutant (65%). A surface layer protein mutant also showed reduction in adhesion ability (84%), but the effect of this mutation is likely due to the loss of multiple surface proteins that may be embedded in the S-layer. This study demonstrated that multiple cell surface proteins in L. acidophilus NCFM can individually contribute to the organism's ability to attach to intestinal cells in vitro. PMID:16332821

  16. Dry etched SiO2 Mask for HgCdTe Etching Process

    Science.gov (United States)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  17. Histological Evaluation of Retina after Photo Disruption for Vitreous Humor by Q-Switched Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) Laser

    Science.gov (United States)

    Kameel Ghaly, Sally; Foad Ghoneim, Dina; Abdelkawi Ahmed, Salwa; Medhat Abdel-Salam, Ahmed

    2013-01-01

    Introduction: Rabbits’ eyes were exposed to vitreous humor liquefaction with Q - switched (sometimes called “ giant pulses”) Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) laser using two different energy protocols (5 mJ X 100 pulse and 10 mJ X 50 pulse)with and without vitamin C administration. The histological changes in the retina were investigated to evaluate the protective role of vitamin C. Methods: The rabbits were divided into four main groups (n= 12 each). The first group was divided into three subgroups (n=4) and then treated with 5 mJ X 100 pulse (X means times) delivered to the anterior, middle and posterior vitreous humor respectively. The second group received a daily dose of 25 mg/Kg vitamin C for two weeks then was divided into three subgroups and treated with laser in the same manner as the first group.The third group was divided into three subgroups (n=4) and then treated with 10 mJ X 50 pulse delivered to the anterior, middle and posterior vitreous respectively. The fourth group received a daily dose of 25 mg/Kg vitamin C for two weeks then was divided into three subgroups and treated with laser in the same manner as the third group. After two weeks, rabbits were decapitated and histological examination for the retina was performed. Results: The results showed that, the anterior vitreous group exposed to 5mJX100 pulse and supplemented with vitamin C, showed no obvious change. Furthermore, all other treated groups showed alteration in retina’s tissues histology after laser. Conclusion: Application of Q-switched Nd: YAG laser in vitreous humor liquefaction induces changes in retina’s layers. Although there were some sorts of improvements in retinas supplemented with vitamin C, it cannot protect them against laser oxidative damage. PMID:25606329

  18. Upper crustal structure of the Yellowstone Caldera from seismic delay time analyses and gravity correlations

    International Nuclear Information System (INIS)

    The 1978 Yellowstone-Snake River Plain seismic experiment provided detailed refraction data that were recorded across a two-dimensional array of seismographs in Yellowstone National Park. A delay time analysis was applied to 173 crystalline basement P/sub g/ arrivals from these data to determine the three-dimensional distribution of velocities and the layer configuration of the upper crust beneath the Yellowstone caldera. The P wave velocity structure of the caldera is characterized by a surface layer of combined sediments and rhyolite flows, averaging 2.8 km/s, that range in thickness from 1.5 to 2.0 km. Adjacent to the caldera, the crystalline upper crustal layer has a velocity of 6.05 +- 0.01 km/s, but this layer decreases by 6% to 5.70 km/s beneath the caldera and extends northeast 15 km beyond the caldera. Smaller zones of very low P velocity, 4.0 km/s, a 30% velocity reduction compared to the 6.05 km/s layer, occur in the upper crust beneath the northeastern caldera rim and beneath the southwest caldera in the vicinity of the Upper and Midway Geyser basins. A three-dimensional gravity interpretation based upon densities derived from the seismic model suggests that the regional gravity low of -60 mGal over the caldera correlates directly with (1) the surface layer of combined sediments and rhyolite flows, (2) the low-velocity, 5.7-km/s, upper crustal layer, and (3) the 4.0-km/s low-velocity zone beneath the northeastern caldera rim. An interpretation of the seismic velocities and densities, based on experimental data and theoretical models is made

  19. Crustal structure of mainland China from deep seismic sounding data

    Science.gov (United States)

    Li, S.; Mooney, W.D.; Fan, J.

    2006-01-01

    Since 1958, about ninety seismic refraction/wide angle reflection profiles, with a cumulative length of more than sixty thousand kilometers, have been completed in mainland China. We summarize the results in the form of (1) a new contour map of crustal thickness, (2) fourteen representative crustal seismic velocity-depth columns for various tectonic units, and, (3) a Pn velocity map. We found a north-south-trending belt with a strong lateral gradient in crustal thickness in central China. This belt divides China into an eastern region, with a crustal thickness of 30-45??km, and a western region, with a thickness of 45-75??km. The crust in these two regions has experienced different evolutionary processes, and currently lies within distinct tectonic stress fields. Our compilation finds that there is a high-velocity (7.1-7.4??km/s) layer in the lower crust of the stable Tarim basin and Ordos plateau. However, in young orogenic belts, including parts of eastern China, the Tianshan and the Tibetan plateau, this layer is often absent. One exception is southern Tibet, where the presence of a high-velocity layer is related to the northward injection of the cold Indian plate. This high-velocity layer is absent in northern Tibet. In orogenic belts, there usually is a low-velocity layer (LVL) in the crust, but in stable regions this layer seldom exists. The Pn velocities in eastern China generally range from 7.9 to 8.1??km/s and tend to be isotropic. Pn velocities in western China are more variable, ranging from 7.7 to 8.2??km/s, and may display azimuthal anisotropy. ?? 2006.

  20. Photovoltaic properties of sintered CdS/CdTe solar cells doped with Cu

    International Nuclear Information System (INIS)

    In this paper, all polycrystalline CdS/CdTe solar cells doped with Cu are prepared by a screen printing and sintering method. Cell parameters of the sintered CdS/CdTe solar cells have been investigated in an attempt to find out the optimum doping conditions and concentrations of Cu by adding various amounts of CuCl2 either into CdTe layer or into back contact carbon layer. Cell parameters of the sintered CdS/CdTe solar cells which contained various amounts of CuCl2 in the CdTe layers before sintering stay at about the same values as the amount of CuCl2 increases up to 25 ppm, and then decreases sharply as the amount of CuCl2 further increases. The Cu added in the CdTe layer diffuses into the CdS layer during the sintering of the CdS-CdTe composite at 625 degrees C to densify the CdTe layer and causes the decrease in the optical transmission of CdS resulting in the degradation of the cell performance. In case the Cu dopant was dispersed in the back carbon paint and was followed by annealing, all cell parameters are improved significantly compared with those fabricated by adding CuCl2 in the CdTe layer before sintering. A sintered CdS/CdTe solar cell which contained 25 ppm CuCl2 in the carbon paste and was annealed at 350 degrees C for 10 min shows the highest efficiency. The efficiency of this cell is 12.4% under solar irradiation with an intensity of 80.4 mW/cm2

  1. Cadmium sulfide/copper sulfide heterojunction cell research. Final report, February 26, 1979-July 15, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Thornton, J. A.; Cornog, D. G.

    1980-06-30

    Extensive modifications were made to the multi-source deposition apparatus. These include the installation of a larger vacuum chamber on the existing system. The new chamber provides improved inter-source shielding, an improved substrate mounting and heating system, and a vacuum interlock for introducing substrates. CdS resistivity control by both In doping and off-stoichiometric deposition has been investigated. Indium doping has been achieved both by diffusion from a pre-deposited In layer and by using In doped sputtering targets. Resistivities in the range 0.1 to 5 ..cap omega..-cm have been obtained for target doping levels of from 0.1 to 1 at. percent of In. These resistivities were found to be critically dependent on the H/sub 2/S injection rate, apparently because of compensation by Cd vacancies. Off-stoichiometry CdS coatings with solar-illuminated resistivities of about 10/sup 2/ ..cap omega..-cm have been deposited, using a cyclic reactive sputtering process were the H/sub 2/S injection is periodically switched on and off. The Cu/sub x/S deposition process was found to be sensitive to the period of cathode operation prior to coating deposition, probably because of the conditioning of cathode and shield surfaces. All-sputter-deposited Cd(Zn)S/Cu/sub 2/S cells, with Cd(Zn)S layers deposited using a Cd-0.10 Zn target doped with 2 atomic percent In, have yielded efficiencies of approx. 0.4%. All-sputtered cells with efficiencies of approx. 0.6% have been fabricated, using undoped CdS deposited by the pulse injection process. Efficiencies of approx. 1.2% have been achieved for cells with undoped sputter-deposited CdS and CuCl dry processed Cu/sub 2/S.

  2. High-field domains in CdS adjacent to a junction of p-type solar cells

    Science.gov (United States)

    Böer, Karl W.

    2016-02-01

    A thin cover layer (150 Å preferred) of copper-doped CdS, when applied on top of any p-type solar cell, can connect this cell directly to an electron-blocking electrode without a pn-junction and increases the open circuit voltage close to its theoretical value; in the example of a CdS/CdTe cell, it increases Voc to its extrapolated value at T = 0 K of the band gap of 1.45 eV. This is caused by a high-field domain that is attached to the junction and limits the field to below tunneling to prevent junction leakage and connects to the CdS that has turned p-type. The large Debye length exceeding the thickness of the CdS forces a direct connection to the electron-blocking cathode with holes tunneling into the metal. The difference of junction-attached high-field domains to the electrode-attached domains, which were described earlier, are given and the consequences are delineated by increasing the conversion efficiency from 8% to 16% in CdTe, while also causing some series resistance limitation. The effect of the added CdS layer is discussed by drawing a to-scale model of the CdS/CdTe solar cell from all experimentally available data and the assumption of the continuity of the hole current. A small jump of the valence band downward is caused by interface recombination. The assistance of high-field domains in CdS is also exemplified by the results of an extremely simple production procedure of the CdS/Cu2S solar cells.

  3. Preparation and characterization of pulsed laser deposited a novel CdS/CdSe composite window layer for CdTe thin film solar cell

    Science.gov (United States)

    Yang, Xiaoyan; Liu, Bo; Li, Bing; Zhang, Jingquan; Li, Wei; Wu, Lili; Feng, Lianghuan

    2016-03-01

    A novel CdS/CdSe composite window structure was designed and then the corresponding films were prepared by pulsed laser deposition as an improved window layer for CdTe-based solar cells. Two types of this composite window structure with 5 cycles and 10 cycles CdS/CdSe respectively both combined with CdS layers were prepared at 200 °C compared with pure CdS window layer and finally were applied into CdTe thin film solar cells. The cross section and surface morphology of the two composite window layers were monitored by using scanning electron microscopy and the result shows that the pulsed laser deposited composite window layers with good crystallinity are stacking together as the design. The devices based on CdS/CdSe composite window layers have demonstrated the enhanced photocurrent collection from both short and long wavelength regions compared to CdS/CdTe solar cell. The efficiency of the best reference CdS/CdTe solar cell was 10.72%. And the device with 5 cycles CdS/CdSe composite window showed efficiency of 12.61% with VOC of 772.92 mV, JSC of 25.11 mA/cm2 and FF of 64.95%. In addition, there are some differences which exist within the optical transmittance spectra and QE curves between the two CdS/CdSe composite window samples, indicating that the volume proportion of CdSe may influence the performance of CdTe thin film solar cell.

  4. Electrical Properties Analysis of Copper doped CdTe/CdS Deposited Thin Films on ITO Coated Glass Substrates

    Science.gov (United States)

    Lesinski, Darren; Flaherty, James; Sahiner, M. Alper

    CdTe proves to be a viable source for renewable energy in the form of photovoltaic conversion. While CdTe/CdS naturally provide interesting results adding dopants to the cell can yield higher conversion efficiencies. Copper, famous for its electrical properties, can be used as a dopant in the CdTe layer. In conjunction with its dopant characteristics Copper also improves cell performance by acting as a low resistant and high current back contact. All thin films were synthesized using pulsed laser deposition onto ITO coated glass substrates. The CdS layer across all cells has an approximate thickness of 1500 Angstroms. The following CdTe layer has an approximate thickness of 5500 Angstroms. This created the base cell that was then doped. Cu, typically deposited using sublimation or vapor deposition, was done by PLD as well. Two of the three base cells were treated with Cu using the same deposition parameters. The third cell also received a CdCl treatment on top of the Cu layer to understand the effect when the oxygen layer is deferred. Ellipsometer measurements were used to confirm layer thickness. XRD analysis was used to confirm the presence of Cu and the crystal structure of the thin films. A Hall Effect Measurement system was used to measure active charge carrier concentration introduced by dopant. Also, a Keithley sourcemeter was utilized to determine photovoltaic properties. Notable results discussed will be the effects of Copper dopant on the electrical properties of CdS/CdTe based solar cells.

  5. Prospects of Back Surface Field Effect in Ultra-Thin High-Efficiency CdS/CdTe Solar Cells from Numerical Modeling

    Directory of Open Access Journals (Sweden)

    Nowshad Amin

    2010-01-01

    Full Text Available Polycrystalline CdTe shows greater promises for the development of cost-effective, efficient, and reliable thin film solar cells. Results of numerical analysis using AMPS-1D simulator in exploring the possibility of ultrathin, high efficiency, and stable CdS/CdTe cells are presented. The conventional baseline case structure of CdS/CdTe cell has been explored with reduced CdTe absorber and CdS window layer thickness, where 1 μm thin CdTe and 50 nm CdS layers showed reasonable efficiencies over 15%. The viability of 1 μm CdTe absorber layer together with possible back surface field (BSF layers to reduce minority carrier recombination loss at the back contact in ultra thin CdS/CdTe cells was investigated. Higher bandgap material like ZnTe and low bandgap materials like Sb2Te3 and As2Te3 as BSF were inserted to reduce the holes barrier height in the proposed ultra thin CdS/CdTe cells. The proposed structure of SnO2/Zn2SnO4/CdS/CdTe/As2Te3/Cu showed the highest conversion efficiency of 18.6% (Voc = 0.92 V, Jsc = 24.97 mA/cm2, and FF = 0.81. However, other proposed structures such as SnO2/Zn2SnO4/CdS/CdTe/Sb2Te3/Mo and SnO2/Zn2SnO4/CdS/CdTe/ZnTe/Al have also shown better stability at higher operating temperatures with acceptable efficiencies. Moreover, it was found that the cells normalized efficiency linearly decreased with the increased operating temperature with relatively lower gradient, which eventually indicates better stability of the proposed ultra thin CdS/CdTe cells.

  6. Clostridium chromiireducens sp. nov., isolated from Cr(VI)-contaminated soil.

    Science.gov (United States)

    Inglett, K S; Bae, H S; Aldrich, H C; Hatfield, K; Ogram, A V

    2011-11-01

    A Cr(VI)-resistant, Gram-positive, spore-forming, obligate anaerobe, designated GCAF-1(T), was isolated from chromium-contaminated soil by its ability to reduce Cr(VI) in low concentrations. Mixed acid fermentation during growth on glucose resulted in accumulation of acetate, butyrate, formate and lactate. Morphological studies indicated the presence of peritrichous flagella, pili and an S-layer. The major cellular fatty acids (>5 %) were C(16 : 0), C(14 : 0), summed feature 3 (comprising iso-C(15 : 0) 2-OH and/or C(16 : 1)ω7c), C(18 : 1)ω7c, C(16 : 1)ω9c, summed feature 4 (comprising iso-C(17 : 1) I and/or anteiso-C(17 : 1) B) and C(18 : 1)ω9c. The DNA G+C content of strain GCAF-1(T) was 30.7 mol%. Phylogenetic interference indicated that strain GCAF-1(T) clustered with group I of the genus Clostridium. Of strains within this cluster, strain GCAF-1(T) shared the highest 16S rRNA gene sequence similarities (98.1-98.9 %) with Clostridium beijerinckii DSM 791(T), C. saccharobutylicum NCP 262(T), C. saccharoperbutylacetonicum N1-4(T), C. puniceum DSM 2619(T) and C. roseum DSM 51(T). However, strain GCAF-1(T) could be clearly distinguished from its closest phylogenetic neighbours by low levels of DNA-DNA relatedness (Clostridium, for which the name Clostridium chromiireducens sp. nov. is proposed. PMID:21148674

  7. Imaging of lactic acid bacteria with AFM-elasticity and adhesion maps and their relationship to biological and structural data

    International Nuclear Information System (INIS)

    The adhesion of lactic acid bacteria to the intestinal epithelium is one of the most important factors determining probiotic ability of a bacterial strain. Studying bacterial adhesion requires knowledge of the structure and properties of the bacterial surface, which can be studied by atomic force microscopy under native conditions. The observation of the surface topography of bacteria from the species Lactobacillus crispatus, L. helveticus and L. johnsonii shows major differences between bacteria having a crystalline-like protein layer as part of the cell wall and those without such layers. Force volume images calculated into elasticity and adhesion force maps of different bacterial strains show that L. crispatus and L. helveticus have a surface with a homogeneous stiffness with no adhesion events. This is most likely caused by the S-layer, which completely covers the surface of the bacteria. We infer that the absence of adhesion peaks is caused by the semi-crystalline character of such protein layers, in agreement with the results obtained from electron microscopy. Analysis of a number of L. johnsonii strains shows that these bacteria have surface properties which strongly differ from the L. crispatus and L. helveticus strains. For L. johnsonii DMS20533 and L. johnsonii ATCC33200 high adhesion forces are observed, which can be related to a surface rich in polysaccharides. L. johnsonii ATCC332 has lower adhesion forces compared to the other two and, furthermore, the surface topography shows depressions. We suppose that this strain has a surface pattern consisting of crystalline-like proteins alternating with polysaccharide-rich domains. The wide variety in surface properties of lactobacilli could well have wide-ranging implications for food processing and for health benefits

  8. Low frequency ultrasonic nondestructive inspection of aluminum/adhesive fuselage lap splices

    Energy Technology Data Exchange (ETDEWEB)

    Patton, T.

    1994-01-04

    This thesis is a collection of research efforts in ultrasonics, conducted at the Center for Aviation Systems Reliability located at Iowa State University, as part of the Federal Aviation Administration`s ``Aging Aircraft Program.`` The research was directed toward the development of an ultrasonic prototype to inspect the aluminum/adhesive fuselage lap splices found on 1970`s vintage Boeing passenger aircraft. The ultrasonic prototype consists of a normal incidence, low frequency inspection technique, and a scanning adapter that allows focused immersion transducers to be operated in a direct contact manner in any inspection orientation, including upside-down. The inspection technique uses a computer-controlled data acquisition system to produce a C-scan image of a radio frequency (RF) waveform created by a low frequency, broadband, focused beam transducer, driven with a spike voltage pulser. C-scans produced by this technique are color representations of the received signal`s peak-to-peak amplitude (voltage) taken over an (x, y) grid. Low frequency, in this context, refers to a wavelength that is greater than the lap splice`s layer thicknesses. With the low frequency technique, interface echoes of the lap splice are not resolved and gating of the signal is unnecessary; this in itself makes the technique simple to implement and saves considerable time in data acquisition. Along with the advantages in data acquisition, the low frequency technique is relatively insensitive to minor surface curvature and to ultrasonic interference effects caused by adhesive bondline thickness variations in the lap splice.

  9. Room temperature atomic layerlike deposition of ZnS on organic thin films: Role of substrate functional groups and precursors

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zhiwei; Walker, Amy V., E-mail: amy.walker@utdallas.edu [Department of Materials Science and Engineering, University of Texas at Dallas, RL10, 800 W. Campbell Rd., Richardson, Texas 75080 (United States)

    2015-09-15

    The room temperature atomic layerlike deposition (ALLD) of ZnS on functionalized self-assembled monolayers (SAMs) was investigated, using diethyl zinc (DEZ) and in situ generated H{sub 2}S as reactants. Depositions on SAMs with three different terminal groups, –CH{sub 3,} –OH, and –COOH, were studied. It was found that the reaction of DEZ with the SAM terminal group is critical in determining the film growth rate. Little or no deposition is observed on –CH{sub 3} terminated SAMs because DEZ does not react with the methyl terminal group. ZnS does deposit on both –OH and –COOH terminated SAMs, but the grow rate on –COOH terminated SAMs is ∼10% lower per cycle than on –OH terminated SAMs. DEZ reacts with the hydroxyl group on –OH terminated SAMs, while on –COOH terminated SAMs it reacts with both the hydroxyl and carbonyl bonds of the terminal groups. The carbonyl reaction is found to lead to the formation of ketones rather than deposition of ZnS, lowering the growth rate on –COOH terminated SAMs. SIMS spectra show that both –OH and –COOH terminated SAMs are covered by the deposited ZnS layer after five ALLD cycles. In contrast to ZnO ALLD where the composition of the film differs for the first few layers on –COOH and –OH terminated SAMs, the deposited film composition is the same for both –COOH and –OH terminated SAMs. The deposited film is found to be Zn-rich, suggesting that the reaction of H{sub 2}S with the Zn-surface adduct may be incomplete.

  10. Effects of CdS film thickness on the photovoltaic properties of sintered CdS/CdTe solar cells

    Science.gov (United States)

    Lee, J. S.; Jun, Y. K.; Im, H. B.

    1987-01-01

    All polycrystalline CdS/CdTe heterojunction solar cells with various thicknesses of CdS film were prepared by the coating and sintering method in an attempt to optimize the thickness of the sintered CdSfilm whose role is to be the window as well as the front contact for the CdS/CdS/CdTe solar cell. The thickness of the CdS films was varied from 14 to 55 microns by changing the screen mesh size of a screen printer and the solid-liquid ratio of the slurry which consisted of CdS powder, 9 weight percent CdCl2 and propylene glycol. Average grain size of the sintered CdS films increases and porosity decreases with an increase in film thickness. Electrical resistivity of the sintered CdS films shows a minimum value in 35-micron thick film. Highest optical transmission is observed in 20-micron thick CdS film. The CdCl2 remaining in the CdS film after the sintering causes an increase in the thickness of the CdS(1-x)Te(x) solid solution layer, acting as a sintering aid, at the interface between the CdS and the CdTe films. The combination of the optical transmission, the solid solution layer, and the sheet resistance effects resulted in the highest solar efficiency in a CdS/CdTe heterojunction solar cell with 20-micron thick CdS layer.

  11. Facile method to prepare CdS nanostructure based on the CdTe films

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • CdS nanostructure is directly fabricated on CdTe film only by heating treatment under H2S/N2 mixed atmosphere at a relatively low temperature (450 °C) with gold layer as the intermediate. • Nanostructure of CdS layer, varying from nanowires to nanosheets, may be controlled by the thickness of gold film. • The change of morphology adjusts its luminescence properties. - Abstract: Nanostructured cadmium sulfide (CdS) plays critical roles in electronics and optoelectronics. In this paper, we report a method to fabricate CdS nanostructure directly on CdTe film, via a thermal annealing method in H2S/N2 mixed gas flow at a relatively low temperature (450 °C). The microstructure and optical properties of CdS nanostructure are investigated by X-ray diffraction, transmission electron microscopy, Raman, and photoluminescence. The morphology of CdS nanostructure, evolving from nanowires to nanosheets, can be controlled by the thickness of Au film deposited on the CdTe film. And CdS nanostructures are single crystalline with the hexagonal wurtzite structure. Raman spectroscopy under varying the excitation wavelengths confirm that synthesized CdS-CdTe films contain two layers, i.e., CdS nanostructure (top) and CdTe layer (bottom). The change of morphology modifies its luminescence properties. Obviously, through simply thermal annealing in H2S/N2 mixed gas, fabricating CdS nanostructure on CdTe film can open up the new possibility for obtaining high efficient CdTe solar cell

  12. Influence of CdCl2 activation treatment on ultra-thin Cd1−xZnxS/CdTe solar cells

    International Nuclear Information System (INIS)

    Ultra-thin CdTe photovoltaic solar cells with an absorber thickness of 0.5 μm were produced by metal organic chemical vapour deposition onto indium tin oxide coated boroaluminosilicate glass. A wide band gap Cd1−xZnxS alloy window layer was employed to improve spectral response in the blue region of the solar spectrum. X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy were used to monitor changes in the chemical composition and microstructure of the Cd1−xZnxS/CdTe solar cell after varying the post-deposition CdCl2 activation treatment time and annealing temperature. The CdCl2 treatment leached Zn from the Cd1−xZnxS layer causing a redshift in the spectral response onset of window absorption. S diffusion occurred across the Cd1−xZnxS/CdTe interface, which was more pronounced as the CdCl2 treatment was increased. A CdTe1−ySy alloy was formed at the interface, which thickened with CdCl2 treatment time. Small concentrations of S (up to 2 at.%) were observed throughout the CdTe layer as the degree of CdCl2 treatment was increased. Greater S diffusion across the Cd1−xZnxS/CdTe interface caused the device open-circuit voltage (Voc) to increase. The higher Voc is attributed to enhanced strain relaxation and associated reduction of defects in the interface region as well as the increase in CdTe grain size. - Highlights: • Increased CdCl2 activation treatment resulted in loss of Zn from Cd1−xZnxS. • Sulphur diffusion into CdTe was enhanced with greater CdCl2 activation treatment. • Improvement to Voc correlated with increased sulphur diffusion into CdTe

  13. Electrical characterization of annealed chemical-bath-deposited CdS films and their application in superstrate configuration CdTe/CdS solar cells

    International Nuclear Information System (INIS)

    Application of chemical-bath-deposited CdS in the superstrate configuration of CdTe/CdS solar cells involving CdCl2:O2 heat treatment of CdTe/CdS structures at about 400 °C is problematic. Namely, the vertical capillary surfaces (grain boundaries) between the columnar CdS grains perform as fast diffusion channels leading to the emergence of short circuits between the absorber and front contact. It was assumed that the grain boundaries contain residual hydroxy-oxide type compounds and form electrical barriers between columnar grains in the lateral direction of the CdS layer and that the electrical methods should be indicative of the behavior of grain boundaries in the annealing process. All samples were characterized by temperature dependence of DC conductivity in a temperature range of 50-300 K, X-ray diffraction, and scanning electron microscope. It has been found that the deeper layers of H2 and N2 annealed CdS preserve residual hydroxide, which released the gas phase in the recrystallization process of the chloride processing and created porosity on the CdTe/CdS interface. - Highlights: • We examine interface of CdS/CdTe structures after chloride heat treatment. • The mechanism of the formation of porosity in the CdS/CdTe interface is suggested. • Chloride heat treatment causes also recrystallization of CdS. • The gap between CdS and CdTe is minimal due to CdO on the grain boundaries of CdS

  14. Dry etched SiO2 Mask for HgCdTe Etching Process

    Science.gov (United States)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-04-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  15. Structure of the Middle America trench in Oaxaca, Mexico

    Science.gov (United States)

    Nava, F.; Núñez-Cornú, F.; Córdoba, D.; Mena, M.; Ansorge, J.; González, J.; Rodríguez, M.; Banda, E.; Mueller, S.; Udías, A.; García-García, M.; Calderón, G.; the Mexican Working GroupDeep Seismic Profiling

    1988-11-01

    Deep seismic profiling was carried out in south and central Oaxaca as a multinational (Mexico, Spain and Switzerland) project. Sixteen sea-bottom explosions, ranging from 20 to 1000 kg were recorded by thirty portable instruments along three profiles, two along the coast and one going inland in an approximate N-S direction. Gravity surveys were carried out over the seismic profile lines, and the resulting Bouguer anomalies are interpreted together with the seismic data. Preliminary results indicate changes in the crustal thickness along the coast, near the town of Pinotepa Nacional, from 23.5 km in the northwest to 19 km in the southeast, reaching a minimum of some 15 km near the middle of the profile, about 140 km northwest of Puerto Angel. The coastal structure section consists roughly of two layers, an upper one with P-wave velocities that range from 5.1-5.4 to 5.8-6.0 km/s and a lower one where the P velocity range is from 6.0-6.2 to 6.3-6.4 km/s, overlying material with P-wave velocities of 7.45 km/s. Along the coast from Puerto Angel to Salina Cruz, the dip of the Cocos plate appears to be much less than it is to the northwest. A low-velocity zone, which corresponds to the top of the subducted oceanic crust, with P-wave velocities of 6.5-6.9 km/s, is found beneath the 2-3 km thick 7.45 km/s layer. The possible presence of an intrusive body is suggested by anomalous seismic arrivals and by a large gravimetric anomaly near Puerto Angel, close to the southern tip of Mexico.

  16. The PorX Response Regulator of the Porphyromonas gingivalis PorXY Two-Component System Does Not Directly Regulate the Type IX Secretion Genes but Binds the PorL Subunit

    Science.gov (United States)

    Vincent, Maxence S.; Durand, Eric; Cascales, Eric

    2016-01-01

    The Type IX secretion system (T9SS) is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion or cell surface exposition of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY, and PorX encode typical two-component system (TCS) sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN, and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we demonstrate that PorX does not bind T9SS gene promoters and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS.

  17. The structure of Lactobacillus brevis surface layer reassembled on liposomes differs from native structure as revealed by SAXS.

    Science.gov (United States)

    Kontro, Inkeri; Wiedmer, Susanne K; Hynönen, Ulla; Penttilä, Paavo A; Palva, Airi; Serimaa, Ritva

    2014-08-01

    The reassembly of the S-layer protein SlpA of Lactobacillus brevis ATCC 8287 on positively charged liposomes was studied by small angle X-ray scattering (SAXS) and zeta potential measurements. SlpA was reassembled on unilamellar liposomes consisting of 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-3-trimethylammonium-propane, prepared by extrusion through membranes with pore sizes of 50nm and 100nm. Similarly extruded samples without SlpA were used as a reference. The SlpA-containing samples showed clear diffraction peaks in their SAXS intensities. The lattice constants were calculated from the diffraction pattern and compared to those determined for SlpA on native cell wall fragments. Lattice constants for SlpA reassembled on liposomes (a=9.29nm, b=8.03nm, and γ=84.9°) showed a marked change in the lattice constants b and γ when compared to those determined for SlpA on native cell wall fragments (a=9.41nm, b=6.48nm, and γ=77.0°). The latter are in good agreement with values previously determined by electron microscopy. This indicates that the structure formed by SlpA is stable on the bacterial cell wall, but SlpA reassembles into a different structure on cationic liposomes. From the (10) reflection, the lower limit of crystallite size of SlpA on liposomes was determined to be 92nm, corresponding to approximately ten aligned lattice planes. PMID:24796504

  18. The growth of sulfur adlayers on Au(100).

    Science.gov (United States)

    Jiang, Yue; Liang, Xihui; Ren, Shendong; Chen, Chi-Lu; Fan, Liang-Jen; Yang, Yaw-Wen; Tang, Jian-Ming; Luh, Dah-An

    2015-02-14

    We have studied the growth of S layers adsorbed on Au(100) with low-energy electron diffraction (LEED), X-ray photoemission spectra (XPS), and scanning tunneling microscope (STM). Three phases of S/Au(100)-(2 × 2), trimer, and c(2 × 4)-are identified; the latter two are not previously reported. A dose of S2 at 300 K transformed Au(100)-(5 × 20) initially into the (2 × 2) phase and formed the c(2 × 4) phase at a saturation coverage. The STM results show that monolayer Au islands formed during the initial S dose and remained throughout the growth, resulting in a rough c(2 × 4) surface. We show that a highly ordered c(2 × 4) phase can be obtained with a flat (2 × 2) phase as an intermediate step during growth. Based on the evolution of XPS and STM images with varied S2 dose, the components of S 2p are assigned and structural models for the various S/Au(100) phases are proposed. In the (2 × 2) phase, one S atom resides on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.25 ML; in the trimer phase, three S atoms form a trimer residing on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.75 ML; in the c(2 × 4) phase, there are five S atoms in each primitive unit cell of c(2 × 4); three of them form a trimer residing on a four-fold hollow site, and the other two form a dimer located on the top of the trimer, corresponding to a nominal S coverage of 1.25 ML. With the proposed structural models, the growth of S on Au(100) at 300 K is described in detail. PMID:25681936

  19. Traditionally produced sauerkraut as source of autochthonous functional starter cultures.

    Science.gov (United States)

    Beganović, Jasna; Kos, Blaženka; Leboš Pavunc, Andreja; Uroić, Ksenija; Jokić, Mladen; Šušković, Jagoda

    2014-01-01

    Spontaneous sauerkraut fermentation was performed at industrial scale in "Prehrana Inc.", Varaždin, in order to select autochthonous lactic acid bacteria (LAB) which were evaluated according probiotic criteria and tested for their capacity as probiotic starter cultures. At the end of the spontaneous sauerkraut fermentation, total LAB counts reached 9.0×10(5) CFU/ml. This underlines that the need for addition of the well characterised probiotic cultures, in appropriate viable cell counts, would be valuable in probiotic sauerkraut production. Phenotypic characterisation through API 50 CHL and SDS-PAGE of cell protein patterns revealed that Lactobacillus plantarum is predominant LAB strain in homofermentative phase of fermentation. Autochthonous LAB isolates SF1, SF2, SF4, SF9 and SF15 were selected based on the survival in in vitro gastrointestinal tract conditions. RAPD fingerprints indicated that the selected autochthonous LAB were distinct from one another. All of the strains efficiently inhibited the growth of indicator strains and satisfied technological properties such as acidification rate, tolerance to NaCl and viability during freeze-drying. Strains Lb. paraplantarum SF9 and Lb. brevis SF15, identified by AFLP DNA fingerprints, have shown the best properties to be applied as probiotic starter cultures, because of their highest adhesion to Caco-2 cells and expression of specific, protective S-layer proteins of 45 kDa in size. With addition of these strains, probiotic attribute of the sauerkraut will be achieved, including health promoting, nutritional, technological and economic advantages in large scale industrial sauerkraut production. PMID:24797236

  20. Probing photoluminescence dynamics of colloidal CdSe/ZnS core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Gurvir; Tripathi, S.K., E-mail: surya@pu.ac.in

    2014-11-15

    The paper presents the synthesis of thiol capped CdSe/ZnS core/shell nanoparticles with CdSe core and ZnS shell. The thickness of the ZnS shell has been controlled by the regulating the amount of Zn/S precursors for reaction. The steady and transient photoluminescence properties substantiate the growth of ZnS shell over the CdSe cores. High resolution transmission electron microscope and the X-ray diffraction patterns reveal nanocrystalline particles of an average size 3.4 nm packed in wurtzite lattice. Photoluminescence excitation spectra as well as the excitation–emission matrix of CdSe and CdSe/ZnS evidence the growth of ZnS for Type I hetero-junction without interfering the energy states of core. By this method, ZnS layer of 8.84 Å is optimum for fluorescence enhancement of the core/shell quantum dots. The multiexponential fluorescence decay of the quantum dots represents independent radiative recombinations with overlapped energies. It is revealed that the average fluorescence lifetimes of quantum dots decreased with increase in ZnS shell, which is due to the enhanced contribution from initially populated excitonic recombination and the reduction in the surface trap states with shell growth. - Highlights: • Synthesis of MAA capped CdSe/ZnS core/shell QDs with different shell thicknesses. • Shell thickness has been controlled by the amount of shell precursors added. • ZnS shell significantly enhanced the fluorescence quantum yield of QDs. • Superposition of quantum confinement energy model employed for shell thickness. • Probed the fluorescence dynamics of QDs by time resolved fluorescence spectroscopy.

  1. Synthesis and characterization of type-II semiconductor nano-heterostructures

    International Nuclear Information System (INIS)

    In the framework of this thesis shell-like constructed nano-heterostructures oc CdTe, CdS, and CdSe were fabricated and examined especially in view of their optical properties. A new variant of the CdTe nanocrystal synthesis in ODE as a highly-boiling, non-coordinating solvent was developed. These CdTe nanocrystals were coated both with CdS and with CdSe. Thereby for both kinds of the coatings different methods were tested, and each a synthesis method could be found, which yields core-shell nanocrystals with low polydispersity and good optical properties (narrow emission signals and high quantum yields). Furthermore core-shell-shell nanocrystals of CdTe/CdS/CdSe were synthesized. The optical properties (first electronic transition) of the fabricated core-shell and core-shell-shell particles were compared with theoretical calculations in the framework of the effective-mass approximation. This comparison resulted for the particles coated with CdSe a well, for the particles coated with CdS however only a moderate agreement. Also the transmission-electron-microscopical images suggest that especially the coating with CdS slopes non quantitatively concerning the applied precursor quantity. The emission lifetimes of the different systems show however, that the charge-carrier separation in the excited state of the CdTe/CdS/CdSe core-shell-shell nanocrystals theoretically to be expected really occurs. By introduction of the CdS layer an elongation of the emission lifetime of the nanocrystals could be reached. Especially it was shown that it is possible to fabricate different nanostructures, the emission lifetimes of which are different, although they emitt light at the same wavelength

  2. Transduction-like gene transfer in the methanogen Methanococcus voltae

    Science.gov (United States)

    Bertani, G.

    1999-01-01

    Strain PS of Methanococcus voltae (a methanogenic, anaerobic archaebacterium) was shown to generate spontaneously 4.4-kbp chromosomal DNA fragments that are fully protected from DNase and that, upon contact with a cell, transform it genetically. This activity, here called VTA (voltae transfer agent), affects all markers tested: three different auxotrophies (histidine, purine, and cobalamin) and resistance to BES (2-bromoethanesulfonate, an inhibitor of methanogenesis). VTA was most effectively prepared by culture filtration. This process disrupted a fraction of the M. voltae cells (which have only an S-layer covering their cytoplasmic membrane). VTA was rapidly inactivated upon storage. VTA particles were present in cultures at concentrations of approximately two per cell. Gene transfer activity varied from a minimum of 2 x 10(-5) (BES resistance) to a maximum of 10(-3) (histidine independence) per donor cell. Very little VTA was found free in culture supernatants. The phenomenon is functionally similar to generalized transduction, but there is no evidence, for the time being, of intrinsically viral (i.e., containing a complete viral genome) particles. Consideration of VTA DNA size makes the existence of such viral particles unlikely. If they exist, they must be relatively few in number;perhaps they differ from VTA particles in size and other properties and thus escaped detection. Digestion of VTA DNA with the AluI restriction enzyme suggests that it is a random sample of the bacterial DNA, except for a 0.9-kbp sequence which is amplified relative to the rest of the bacterial chromosome. A VTA-sized DNA fraction was demonstrated in a few other isolates of M. voltae.

  3. Detailed photoluminescence studies of thin film Cu2S for determination of quasi-Fermi level splitting and defect levels

    International Nuclear Information System (INIS)

    We have studied chalcocite (Cu2S) layers prepared by physical vapor deposition with varying deposition parameters by calibrated spectral photoluminescence (PL) and by confocal PL with lateral resolution of Δ x≈0.9 μm. Calibrated PL experiments as a function of temperature T and excitation fluxes were performed to obtain the absolute PL-yield and to calculate the splitting of the quasi-Fermi levels (QFLs) μ=Ef,n−Ef,p at an excitation flux equivalent to the AM 1.5 spectrum and the absorption coefficient α(ℏω), both in the temperature range of 20 K≤T≤400 K. The PL-spectra reveal two peaks at E#1=1.17 eV and E#2=1.3 eV. The samples show a QFL-splitting of μ>700 meV associated with a pseudo band gap of Eg=1.25 eV. The high-energy peak shows an unexpected temperature behavior, namely, an increase of PL-yield with rising temperature at variance with the behavior of QFL-splitting that decreases with rising T. Our observations indicate that, contrary to common believe, it is not the PL-yield, but rather the QFL-splitting that is the comprehensive indicator of the quality of the excited state in an illuminated semiconductor. A further examination of the lateral variation of opto-electronic properties by confocal PL and the surface contour shows no detectable correlation between Cu2S grains/grain boundaries and the PL-yield or QFL-splitting

  4. In Vivo Transcriptional Profiling of Listeria monocytogenes and Mutagenesis Identify New Virulence Factors Involved in Infection

    Science.gov (United States)

    Camejo, Ana; Buchrieser, Carmen; Couvé, Elisabeth; Carvalho, Filipe; Reis, Olga; Ferreira, Pierre; Sousa, Sandra; Cossart, Pascale; Cabanes, Didier

    2009-01-01

    Listeria monocytogenes is a human intracellular pathogen able to colonize host tissues after ingestion of contaminated food, causing severe invasive infections. In order to gain a better understanding of the nature of host–pathogen interactions, we studied the L. monocytogenes genome expression during mouse infection. In the spleen of infected mice, ≈20% of the Listeria genome is differentially expressed, essentially through gene activation, as compared to exponential growth in rich broth medium. Data presented here show that, during infection, Listeria is in an active multiplication phase, as revealed by the high expression of genes involved in replication, cell division and multiplication. In vivo bacterial growth requires increased expression of genes involved in adaptation of the bacterial metabolism and stress responses, in particular to oxidative stress. Listeria interaction with its host induces cell wall metabolism and surface expression of virulence factors. During infection, L. monocytogenes also activates subversion mechanisms of host defenses, including resistance to cationic peptides, peptidoglycan modifications and release of muramyl peptides. We show that the in vivo differential expression of the Listeria genome is coordinated by a complex regulatory network, with a central role for the PrfA-SigB interplay. In particular, L. monocytogenes up regulates in vivo the two major virulence regulators, PrfA and VirR, and their downstream effectors. Mutagenesis of in vivo induced genes allowed the identification of novel L. monocytogenes virulence factors, including an LPXTG surface protein, suggesting a role for S-layer glycoproteins and for cadmium efflux system in Listeria virulence. PMID:19478867

  5. Vortex pinning in ferromagnet-superconductor bilayer with tunable domain patterns

    Science.gov (United States)

    Cieplak, Marta Z.

    2011-03-01

    Ferromagnet superconductor hybrids provide a fascinating example of systems in which there is a rich interplay between two seemingly incompatible collective phenomena. Particularly interesting is the impact of the ferromagnet on the dynamics of vortices in the superconductor. The magnetic domains control the location of the vortices. Exquisite control of the dynamics can be achieved by careful tuning of the geometry of the magnetic domains. In this talk I will present the results of recent experiments on superconductor(S)-ferromagnet(F) bilayers with a focus on understanding the hitherto unexplained seemingly unpredictable dependence of the critical current density on the parameters of the experiment. In our experiments the S layer is made of niobium, the F layer is a Co/Pt multilayer with perpendicular magnetic anisotropy, and a thin insulating layer in-between eliminates proximity effect. We use various demagnetization procedures to define different domain patterns in the F layer. We show that some domain patterns produce highly inhomogeneous flux penetration and strong vortex confinement at the sample edge, while for others there is remerkable enhancement of the critical current density in excess of 15. This is the highest value reported to date. We have measured, for the first time in a single tunable structure, the dependence of the activation energy for vortex pinning on the domain width, temperature, and magnetic field. In collaboration with L.Y. Zhu, X. M. Cheng and C. L. Chien (Johns Hopkins), Z. Adamus (Polish Acad. Sci.) and M. Konczykowski (Ecole Polytechnique). Supported by NSF grant DMR05-20491, by the French-Polish Program PICS 4916, and by EU within the European Regional Development Fund, through the Innovative Economy grant POIG.01.01.02-00-108/09.

  6. Cost effective screening methods for pesticide residue analysis in fruits, vegetables and cereal grains

    International Nuclear Information System (INIS)

    This paper reports the results of studies performed to investigate the potential of applying thin layer chromatography (TLC) detection in combination with selected extraction and cleanup methods, for providing an alternative cost-effective analytical procedure for screening and confirmation of pesticide residues in plant commodities. The extraction was carried out with ethyl acetate and an on-line extraction method applying an acetone-dichloromethane mixture. The extracts were cleaned up with SX-3 gel, an adsorbent mixture of active carbon, magnesia, and diatomaceous earth, and on silica micro cartridges. The Rf values of 118 pesticides were tested in eleven elution systems with UV, and eight biotest methods or and chemical detection reagents. Cabbage, green peas, orange, and tomatoes were selected as representative sample matrices for fruits and vegetables, while maize, rice and wheat represented cereal grains. As an internal quality control measure, marker compounds were applied on each plate to verify the proper elution and detection conditions. The Rf values varied in the different elution systems. The best separation (widest Rf range) was achieved with silica gel (SG)-ethyl acetate (0.05-0.7), SG-benzene, (0.02-0.7) and reverse phase RP-18 F-254S layer with acetone:methanol:water (30:30:30 v/v) (0.1-0.8). The relative standard deviation of Rf values (CVRf) within-laboratory reproducibility was generally less than 20%, except below 0.2 Rf, where the CVRf rapidly increased with decreasing Rf values. The fungi spore inhibition, chloroplast inhibition and enzyme inhibition were found most suitable for detection of pesticides primarily for confirming their identity or screening for known substances. Their use for determination of pesticide residues in samples of unknown origin is not recommended. (author)

  7. Modeling heterogeneity in a low-permeability gas reservoir using geostatistical techniques, Hyde field, southern North Sea

    Energy Technology Data Exchange (ETDEWEB)

    Sweet, M.L.; Carter, A.M.; Mills, C.A. [BP Exploration, Aberdeen (United Kingdom)] [and others

    1996-11-01

    Hyde field is a small (133 Gcf reserves) gas field in the United Kingdom southern North Sea. The reservoir, the Permian Rotliegende group, contains eolian, fluvial, and sabkha facies. The eolian facies constitute the dominant flow units. Illite cementation results in low reservoir quality. In the eolian facies permeability averages 2.5 md and rarely exceeds 10 md. To maximize recovery from this field, with its thin gas column and low reservoir quality, Hyde has been developed with three long-reach horizontal wells. A reservoir model that could accurately predict future production had to include a full range of heterogeneities from the effects of thin muddy laminations at the core-plug scale to the spatial distribution of eolian, fluvial, and sabkha facies over the entire field at the largest scale. By carefully defining the model`s layering scheme, we incorporated strongly deterministic elements where facies trends were influenced by laterally extensive stratigraphic surfaces. The distribution of facies within stratigraphic units was modeled using geostatistical techniques. Average permeability for the eolian and sandy sabkha facies were determined by upscaling models of their internal permeability structure. The resulting distribution of permeabilities across the field, present in a 2.2-million-cell model, was upscaled into a coarser grid suitable for simulating the full field. This new model produced a significantly better match to dynamic data than did an earlier simple layer model that was used to take the field to sanction. The results of our work suggest that stochastic modeling allowed us to represent a level of heterogeneity that was not captured by the earlier simple layer model. By capturing this level of heterogeneity, we were able to achieve a significantly better match of model predictions to production data.

  8. Metal-Silicate-Sulfide Partitioning of U, Th, and K: Implications for the Budget of Volatile Elements in Mercury

    Science.gov (United States)

    Habermann, M.; Boujibar, A.; Righter, K.; Danielson, L.; Rapp, J.; Righter, M.; Pando, K.; Ross, D. K.; Andreasen, R.

    2016-01-01

    During formation of the solar system, the Sun produced strong solar winds, which stripped away a portion of the volatile elements from the forming planets. Hence, it was expected that planets closest to the sun, such as Mercury, are more depleted in volatile elements in comparison to other terrestrial planets. However, the MESSENGER mission detected higher than expected K/U and K/Th ratios on Mercury's surface, indicating a volatile content between that of Mars and Earth. Our experiments aim to resolve this discrepancy by experimentally determining the partition coefficients (D(sup met/sil)) of K, U, and Th between metal and silicate at varying pressure (1 to 5 GPa), temperature (1500 to 1900 C), oxygen fugacity (IW-2.5 to IW-6.5) and sulfur-content in the metal (0 to 33 wt%). Our data show that U, Th, and K become more siderophile with decreasing fO2 and increasing sulfur-content, with a stronger effect for U and Th in comparison to K. Using these results, the concentrations of U, Th, and K in the bulk planet were calculated for different scenarios, where the planet equilibrated at a fO2 between IW-4 and IW-7, assuming the existence of a FeS layer, between the core and mantle, with variable thickness. These models show that significant amounts of U and Th are partitioned into Mercury's core. The elevated superficial K/U and K/Th values are therefore only a consequence of the sequestration of U and Th into the core, not evidence of the overall volatile content of Mercury.

  9. Impact of CdS annealing atmosphere on the performance of CdS–CdTe solar cell

    International Nuclear Information System (INIS)

    Highlights: • Annealed CdS films are used for CdTe based solar cells. • CdS–CdTe solar cell with air annealed CdS shows better performance. • The air annealed CdS brings the O2 and chloride at the place of junction formation. • H2 removes the oxygen containing compounds from CdS grain boundaries. - Abstract: CdS thin films obtained by chemical bath deposition and annealed in hydrogen and air ambients were combined with CdTe absorbers obtained by close spaced sublimation. CdS–CdTe solar cells in superstrate configuration were characterized by current–voltage and quantum efficiency measurements while the analysis of annealed CdS films was made by scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy. It was found that in superstrate configuration, due to the big grains on CdS surface and gas emission from CdS film at high temperature deposition of the absorber, the delamination of layers take place. Annealing in H2 removes the oxygen compounds from CdS grain boundaries and opens them for formation of shortcutting through the CdS layer. The processing in air is most advantageous due to simultaneous presence of chloride and oxygen, contributing to the recrystallization and sintering of the highly textured columnar CdS. The direct influence of the CdS annealing on the solar cell parameters is shown for CdS–CdTe solar cell

  10. Facile method to prepare CdS nanostructure based on the CdTe films

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Ligang; Chen, Yuehui; Wei, Zelu; Cai, Hongling; Zhang, Fengming; Wu, Xiaoshan, E-mail: xswu@nju.edu.cn

    2015-09-15

    Graphical abstract: - Highlights: • CdS nanostructure is directly fabricated on CdTe film only by heating treatment under H{sub 2}S/N{sub 2} mixed atmosphere at a relatively low temperature (450 °C) with gold layer as the intermediate. • Nanostructure of CdS layer, varying from nanowires to nanosheets, may be controlled by the thickness of gold film. • The change of morphology adjusts its luminescence properties. - Abstract: Nanostructured cadmium sulfide (CdS) plays critical roles in electronics and optoelectronics. In this paper, we report a method to fabricate CdS nanostructure directly on CdTe film, via a thermal annealing method in H{sub 2}S/N{sub 2} mixed gas flow at a relatively low temperature (450 °C). The microstructure and optical properties of CdS nanostructure are investigated by X-ray diffraction, transmission electron microscopy, Raman, and photoluminescence. The morphology of CdS nanostructure, evolving from nanowires to nanosheets, can be controlled by the thickness of Au film deposited on the CdTe film. And CdS nanostructures are single crystalline with the hexagonal wurtzite structure. Raman spectroscopy under varying the excitation wavelengths confirm that synthesized CdS-CdTe films contain two layers, i.e., CdS nanostructure (top) and CdTe layer (bottom). The change of morphology modifies its luminescence properties. Obviously, through simply thermal annealing in H{sub 2}S/N{sub 2} mixed gas, fabricating CdS nanostructure on CdTe film can open up the new possibility for obtaining high efficient CdTe solar cell.

  11. Impact of CdS annealing atmosphere on the performance of CdS–CdTe solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Maticiuc, N., E-mail: nataliamaticiuc@yahoo.com; Spalatu, N.; Mikli, V.; Hiie, J.

    2015-09-30

    Highlights: • Annealed CdS films are used for CdTe based solar cells. • CdS–CdTe solar cell with air annealed CdS shows better performance. • The air annealed CdS brings the O{sub 2} and chloride at the place of junction formation. • H{sub 2} removes the oxygen containing compounds from CdS grain boundaries. - Abstract: CdS thin films obtained by chemical bath deposition and annealed in hydrogen and air ambients were combined with CdTe absorbers obtained by close spaced sublimation. CdS–CdTe solar cells in superstrate configuration were characterized by current–voltage and quantum efficiency measurements while the analysis of annealed CdS films was made by scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy. It was found that in superstrate configuration, due to the big grains on CdS surface and gas emission from CdS film at high temperature deposition of the absorber, the delamination of layers take place. Annealing in H{sub 2} removes the oxygen compounds from CdS grain boundaries and opens them for formation of shortcutting through the CdS layer. The processing in air is most advantageous due to simultaneous presence of chloride and oxygen, contributing to the recrystallization and sintering of the highly textured columnar CdS. The direct influence of the CdS annealing on the solar cell parameters is shown for CdS–CdTe solar cell.

  12. Determination of anisotropic velocity model by reflection tomography of compression and shear modes; Determination de modele de vitesse anisotrope par tomographie de reflexion des modes de compression et de cisaillement

    Energy Technology Data Exchange (ETDEWEB)

    Stopin, A.

    2001-12-01

    As the jump from 2D to 3D, seismic exploration lives a new revolution with the use of converted PS waves. Indeed PS converted waves are proving their potential as a tool for imaging through gas; lithology discrimination; structural confirmation; and more. Nevertheless, processing converted shear data and in particular determining accurate P and S velocity models for depth imaging of these data is still a challenging problem, especially when the subsurface is anisotropic. To solve this velocity model determination problem we propose to use reflection travel time tomography. In a first step, we derive a new approximation of the exact phase velocity equation of the SV wave in anisotropic (TI) media. This new approximation is valid for non-weak anisotropy and is mathematically simpler to handle than the exact equation. Then, starting from an isotropic reflection tomography tool developed at Lt-'P, we extend the isotropic bending ray tracing method to the anisotropic case and we implement the quantities necessary for the determination of the anisotropy parameters from the travel time data. Using synthetic data we then study the influence of the different anisotropy parameters on the travel times. From this analysis we propose a methodology to determine a complete anisotropic subsurface model (P and S layer velocities, interface geometries, anisotropy parameters). Finally, on a real data set from the Gulf of Mexico we demonstrate that this new anisotropic reflection tomography tool allows us to obtain a reliable subsurface model yielding kinematically correct and mutually coherent PP and PS images in depth; such a result could not be obtained with an isotropic velocity model. Similar results are obtained on a North Sea data set. (author)

  13. H2- and NH3-treated ZnO nanorods sensitized with CdS for photoanode enhanced in photoelectrochemical performance

    Science.gov (United States)

    Vuong, Nguyen Minh; Hien, Truong Thi; Quang, Nguyen Duc; Chinh, Nguyen Duc; Lee, Dong Suk; Kim, Dahye; Kim, Dojin

    2016-06-01

    A ZnO/CdS core-shell nanorod structure is studied for use as photoanode in photoelectrochemical cell for water splitting. The focus is to examine the effect of hydrogen and/or nitrogen doping of ZnO nanorods on its performance as photoanode. ZnO nanorods hydrothermally synthesized on ITO glass substrate are heat-treated in pure hydrogen ambient and then in atmospheric pressure of ammonia for H- and N-doping of ZnO. The H- and/or N-doped ZnO nanorod structure (N/H:ZnO) reveal an enhanced photocurrent and photo-to-current conversion efficiency in comparison to untreated ZnO nanorods by shifting the absorption edge towards visible region and increasing absorption of infrared region wavelengths. CdS sensitization of the nanorods is also studied. The morphology and properties of the samples are examined by SEM, XRD, UV-vis absorption and photoluminescence. Optimization of the ZnO nanorod growth and CdS coating processes are also undertaken. An optimized N/H:ZnO nanorods sensitized by CdS layer yields a photocurrent density of ∼12.61 mA cm-2 at 0 V (vs. SCE) and photon-to-current conversion efficiency of ∼4.5% (at -0.73 V vs. SCE) in 0.5 M Na2S solution under a simulated solar light. The H2 gas generation with the optimal structure is about 6 mL h-1 cm-2.

  14. Identification of peptide sequences as a measure of Anthrax vaccine stability during storage.

    Science.gov (United States)

    Whiting, Gail; Wheeler, Jun X; Rijpkema, Sjoerd

    2014-01-01

    The UK anthrax vaccine is an alum precipitate of a sterile filtrate of Bacillus anthracis Sterne culture (AVP). An increase in shelf life of AVP from 3 to 5 years prompted us to investigate the in vivo potency and the antigen content of 12 batches with a shelf life of 6.4 to 9.9 years and one bulk with a shelf life of 23.8 years. All batches, except for a 9.4-year-old batch, passed the potency test. Mass spectrometry (MS) and in-gel difference 2-dimensional gel electrophoresis (DIGE) were used to examine antigens of the pellet and supernatant of AVP. The pellet contained proteins with a MW in excess of 15 kDa. DIGE of desorbed proteins from the pellet revealed that with aging, 19 spots showed a significant change in size or intensity, a sign of protein degradation. MS identified 21 proteins including protective antigen (PA), enolase, lethal factor (LF), nucleoside diphosphate kinase, edema factor, and S-layer proteins. Fifteen proteins were detected for the first time including metabolic enzymes, iron binding proteins, and manganese dependent superoxide dismutase (MnSOD). The supernatant contained131 peptide sequences. Peptides representing septum formation inhibitor protein and repeat domain protein were most abundant. Five proteins were shared with the pellet: 2,3,4,5-tetrahydropyridine-6-dicarboxylate N-succinyltransferase, enolase, LF, MnSOD, and PA. The number of peptide sequences increased with age. Peptides from PA and LF appeared once batches exceeded their shelf life by 2 and 4 years, respectively. In conclusion, changes in antigen content resulting from decay or desorption only had a limited effect on in vivo potency of AVP. The presence of PA and LF peptides in the supernatant can inform on the age and stability of AVP. PMID:24637775

  15. Orphan Basin crustal structure from a dense wide-angle seismic profile - layered modeling

    Science.gov (United States)

    Lau, K. W. Helen; Watremez, Louise; Louden, Keith E.; Nedimović, Mladen R.; Karner, Garry D.

    2014-05-01

    The Orphan Basin is a large, deep water basin to the east of Newfoundland and northwest of Flemish Cap, Canada. It contains a considerably wide series of rift basins that provides an excellent opportunity to study continental crustal deformations under varying degrees of extension. We present a 500-km-long P-wave velocity model across the complete rift system of the Orphan Basin, from Flemish Cap to the Bonavista Platform, using high-resolution refraction and wide-angle reflection data from 89 ocean-bottom seismometers (OBS). This layered model builds on a first-arrival traveltime tomography model (Watremez et al., this session) and is formed using additional constraints from a coincident multichannel seismic reflection profile, gravity data and borehole data from three wells. The layered model helps detail deep sediment and crustal variations across this wide region of extended continental crust. The sedimentary section contains post-rift Tertiary (vp~1.7-3.5 km/s) and syn-rift Cretaceous and Jurassic (vp~4-5.4 km/s) layers within both the eastern and the western sub-basins, separated by three basement highs, suggesting that the two sub-basins may have opened during a single, extended rifting event. The crust is composed of three layers with vp of 5.4-6.1, 6.1-6.5 and 6.3-7.1 km/s of highly variable combined thicknesses, from 32 km beneath Flemish Cap and the Bonavista Platform to Orphan Basin, Porcupine Bank and the East Orphan Basin, and the Central Orphan High and Porcupine Bank. Unlike the Rockall and Porcupine Basins, no evidence for partial serpentinization of the upper mantle is observed beneath the E. Orphan trough. However, hyperextension (crustal thickness Orphan trough, which might have allowed the basement to have been covered by syn-rift sediment that inhibited the flow of water down the faults.

  16. Imaging of lactic acid bacteria with AFM-elasticity and adhesion maps and their relationship to biological and structural data

    Energy Technology Data Exchange (ETDEWEB)

    Schaer-Zammaretti, Prisca; Ubbink, Job

    2003-10-15

    The adhesion of lactic acid bacteria to the intestinal epithelium is one of the most important factors determining probiotic ability of a bacterial strain. Studying bacterial adhesion requires knowledge of the structure and properties of the bacterial surface, which can be studied by atomic force microscopy under native conditions. The observation of the surface topography of bacteria from the species Lactobacillus crispatus, L. helveticus and L. johnsonii shows major differences between bacteria having a crystalline-like protein layer as part of the cell wall and those without such layers. Force volume images calculated into elasticity and adhesion force maps of different bacterial strains show that L. crispatus and L. helveticus have a surface with a homogeneous stiffness with no adhesion events. This is most likely caused by the S-layer, which completely covers the surface of the bacteria. We infer that the absence of adhesion peaks is caused by the semi-crystalline character of such protein layers, in agreement with the results obtained from electron microscopy. Analysis of a number of L. johnsonii strains shows that these bacteria have surface properties which strongly differ from the L. crispatus and L. helveticus strains. For L. johnsonii DMS20533 and L. johnsonii ATCC33200 high adhesion forces are observed, which can be related to a surface rich in polysaccharides. L. johnsonii ATCC332 has lower adhesion forces compared to the other two and, furthermore, the surface topography shows depressions. We suppose that this strain has a surface pattern consisting of crystalline-like proteins alternating with polysaccharide-rich domains. The wide variety in surface properties of lactobacilli could well have wide-ranging implications for food processing and for health benefits.

  17. Proton and hydrogen transport through two-dimensional monolayers

    Science.gov (United States)

    Seel, Max; Pandey, Ravindra

    2016-06-01

    Diffusion of protons and hydrogen atoms in representative two-dimensional materials is investigated. Specifically, density functional calculations were performed on graphene, hexagonal boron nitride (h-BN), phosphorene, silicene, and molybdenum disulfide (MoS2) monolayers to study the surface interaction and penetration barriers for protons and hydrogen atoms employing finite cluster models. The calculated barrier heights correlate approximately with the size of the opening formed by the three-fold open sites in the monolayers considered. They range from 1.56 eV (proton) and 4.61 eV (H) for graphene to 0.12 eV (proton) and 0.20 eV (H) for silicene. The results indicate that only graphene and h-BN monolayers have the potential for membranes with high selective permeability. The MoS2 monolayer behaves differently: protons and H atoms become trapped between the outer S layers in the Mo plane in a well with a depth of 1.56 eV (proton) and 1.5 eV (H atom), possibly explaining why no proton transport was detected, suggesting MoS2 as a hydrogen storage material instead. For graphene and h-BN, off-center proton penetration reduces the barrier to 1.38 eV for graphene and 0.11 eV for h-BN. Furthermore, Pt acting as a substrate was found to have a negligible effect on the barrier height. In defective graphene, the smallest barrier for proton diffusion (1.05 eV) is found for an oxygen-terminated defect. Therefore, it seems more likely that thermal protons can penetrate a monolayer of h-BN but not graphene and defects are necessary to facilitate the proton transport in graphene.

  18. Formation Mechanism of CaS-Bearing Inclusions and the Rolling Deformation in Al-Killed, Low-Alloy Steel with Ca Treatment

    Science.gov (United States)

    Xu, Guang; Jiang, Zhouhua; Li, Yang

    2016-05-01

    The existing form of CaS inclusion in Ca-treated, Al-killed steel during secondary refining process was investigated with scanning electron microscopy and an energy-dispersive spectrometer (EDS). The results of 12 heats industrial tests showed that CaS has two kinds of precipitation forms. One form takes place by the direct reaction of Ca and S, and the other takes place by the reaction of CaO in calcium aluminates with dissolved Al and S in liquid steel. Thermodynamic research for different precipitation modes of CaS under different temperature was carried out. In particular, CaO-Al2O3-CaS isothermal section diagrams and component activities of calcium aluminates were calculated by the thermodynamic software FactSage. By thermodynamic calculation, a precipitation-area diagram of oxide-sulfide duplex inclusion was established by fixing the sulfur content. The quantity of CaS, which was precipitated in a reaction between [Al], [S] and (CaO), can be calculated and predicted based on the precipitation-area diagram of oxide-sulfide duplex inclusion. Electron probe microanalysis and EDS were used for observing rolling deformation of different types of CaS-bearing inclusions during the rolling process. Low modification of calcium aluminates wrapped by CaS has different degrees of harm to steel in the rolling process. A thick CaS layer can prevent some fragile calcium aluminates from being crushed during the rolling process. Some oxide-sulfide duplex inclusion contains little CaS performed better deformation during the rolling process, but when CaS in oxide-sulfide duplex inclusion becomes more, it will cause the whole inclusion to lose plastic yielding ability. The plastic deformation region of CaS-bearing inclusion in a CaO-Al2O3-CaS isothermal section diagram is confirmed.

  19. Synthesis and characterization of type-II semiconductor nano-heterostructures; Synthese und Charakterisierung von Typ-II Halbleiternanoheterostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Dorfs, D.

    2007-03-30

    In the framework of this thesis shell-like constructed nano-heterostructures oc CdTe, CdS, and CdSe were fabricated and examined especially in view of their optical properties. A new variant of the CdTe nanocrystal synthesis in ODE as a highly-boiling, non-coordinating solvent was developed. These CdTe nanocrystals were coated both with CdS and with CdSe. Thereby for both kinds of the coatings different methods were tested, and each a synthesis method could be found, which yields core-shell nanocrystals with low polydispersity and good optical properties (narrow emission signals and high quantum yields). Furthermore core-shell-shell nanocrystals of CdTe/CdS/CdSe were synthesized. The optical properties (first electronic transition) of the fabricated core-shell and core-shell-shell particles were compared with theoretical calculations in the framework of the effective-mass approximation. This comparison resulted for the particles coated with CdSe a well, for the particles coated with CdS however only a moderate agreement. Also the transmission-electron-microscopical images suggest that especially the coating with CdS slopes non quantitatively concerning the applied precursor quantity. The emission lifetimes of the different systems show however, that the charge-carrier separation in the excited state of the CdTe/CdS/CdSe core-shell-shell nanocrystals theoretically to be expected really occurs. By introduction of the CdS layer an elongation of the emission lifetime of the nanocrystals could be reached. Especially it was shown that it is possible to fabricate different nanostructures, the emission lifetimes of which are different, although they emitt light at the same wavelength.

  20. Characterization of intracellular palladium nanoparticles synthesized by Desulfovibrio desulfuricans and Bacillus benzeovorans

    Energy Technology Data Exchange (ETDEWEB)

    Omajali, Jacob B., E-mail: JBO037@bham.ac.uk, E-mail: jbomajali@gmail.com; Mikheenko, Iryna P. [University of Birmingham, Unit of Functional Bionanomaterials, School of Biosciences, Institute of Microbiology and Infection (United Kingdom); Merroun, Mohamed L. [University of Granada, Department of Microbiology, Faculty of Sciences (Spain); Wood, Joseph [University of Birmingham, School of Chemical Engineering (United Kingdom); Macaskie, Lynne E. [University of Birmingham, Unit of Functional Bionanomaterials, School of Biosciences, Institute of Microbiology and Infection (United Kingdom)

    2015-06-15

    Early studies have focused on the synthesis of palladium nanoparticles within the periplasmic layer or on the outer membrane of Desulfovibrio desulfuricans and on the S-layer protein of Bacillus sphaericus. However, it has remained unclear whether the synthesis of palladium nanoparticles also takes place in the bacterial cell cytoplasm. This study reports the use of high-resolution scanning transmission electron microscopy with a high-angle annular dark field detector and energy dispersive X-ray spectrometry attachment to investigate the intracellular synthesis of palladium nanoparticles (Pd NPs). We show the intracellular synthesis of Pd NPs within cells of two anaerobic strains of D. desulfuricans and an aerobic strain of B. benzeovorans using hydrogen and formate as electron donors. The Pd nanoparticles were small and largely monodispersed, between 0.2 and 8 nm, occasionally from 9 to 12 nm with occasional larger nanoparticles. With D. desulfuricans NCIMB 8307 (but not D. desulfuricans NCIMB 8326) and with B. benzeovorans NCIMB 12555, the NPs were larger when made at the expense of formate, co-localizing with phosphate in the latter, and were crystalline, but were amorphous when made with H{sub 2,} with no phosphorus association. The intracellular Pd nanoparticles were mainly icosahedrons with surfaces comprising {111} facets and about 5 % distortion when compared with that of bulk palladium. The particles were more concentrated in the cell cytoplasm than the cell wall, outer membrane, or periplasm. We provide new evidence for synthesis of palladium nanoparticles within the cytoplasm of bacteria, which were confirmed to maintain cellular integrity during this synthesis.

  1. Membrane Association and Catabolite Repression of the Sulfolobus solfataricus α-Amylase

    Directory of Open Access Journals (Sweden)

    Edith Soo

    2015-09-01

    Full Text Available Sulfolobus solfataricus is a thermoacidophilic member of the archaea whose envelope consists of an ether-linked lipid monolayer surrounded by a protein S-layer. Protein translocation across this envelope must accommodate a steep proton gradient that is subject to temperature extremes. To better understand this process in vivo, studies were conducted on the S. solfataricus glycosyl hydrolyase family 57 α-Amylase (AmyA. Cell lines harboring site specific modifications of the amyA promoter and AmyA structural domains were created by gene replacement using markerless exchange and characterized by Western blot, enzyme assay and culture-based analysis. Fusion of amyA to the malAp promoter overcame amyAp-mediated regulatory responses to media composition including glucose and amino acid repression implicating action act at the level of transcription. Deletion of the AmyA Class II N-terminal signal peptide blocked protein secretion and intracellular protein accumulation. Deletion analysis of a conserved bipartite C-terminal motif consisting of a hydrophobic region followed by several charged residues indicated the charged residues played an essential role in membrane-association but not protein secretion. Mutants lacking the C-terminal bipartite motif exhibited reduced growth rates on starch as the sole carbon and energy source; therefore, association of AmyA with the membrane improves carbohydrate utilization. Widespread occurrence of this motif in other secreted proteins of S. solfataricus and of related Crenarchaeota suggests protein association with membranes is a general trait used by these organisms to influence external processes.

  2. The characteristics exosporium antigens from different vaccine strains of bacillus antracis

    International Nuclear Information System (INIS)

    To develop of both test-systems for rapid detection and identification of B. anthracis spores and a new subunit vaccine the antigens on the spore surface should be characterized. Exosporium consists of two layers-basal and peripheral and has been form by protein, amino- and neutral polysaccharides, lipids and ash. Number of anthrax exosporium proteins was described and identified: glycoprotein BclA, BclB, alanine racemase, inosine hydrolase, glycosyl hydrolase, superoxid dismutase, ExsF, ExsY, ExsK,CotB,CotY and SoaA. So far no glycosylated proteins other then highly immunogenic glycoproteins BclA, BclB were detected in the B. anthracis spore extract although several exosporium-specific glycoprotein have been described in other members of the B.cereus family- B. thuringiensis and B. cereus. Although EA1 protein originally described as main component of S-layer from vegetative cells he can regular observed in different exosporium preparations and additionally some anti- EA1 monoclonal antibodies able to recognize spore surface. We have revealed that EA1 isolated from spore of Russians strain STI-1contain carbohydrate which determine immunogenicity of this antigen. Because some time ago we have found that exosporium protein's pattern variable among B. anthracis strains we investigated exosporium from spore of different strains of B. anthracis including STI-1, Ames, Stern and others. We have comparative characterized antigens by using Western Blotting, Two-Dimensional electrophoresis and Mass Spec analysis. The results of analysis will be presented and discussed.(author)

  3. Bacterial Sugar 3,4-Ketoisomerases: Structural Insight into Product Stereochemistry.

    Science.gov (United States)

    Thoden, James B; Vinogradov, Evgeny; Gilbert, Michel; Salinger, Ari J; Holden, Hazel M

    2015-07-28

    3-Acetamido-3,6-dideoxy-d-galactose (Fuc3NAc) and 3-acetamido-3,6-dideoxy-d-glucose (Qui3NAc) are unusual sugars found on the lipopolysaccharides of Gram-negative bacteria and on the S-layers of Gram-positive bacteria. The 3,4-ketoisomerases, referred to as FdtA and QdtA, catalyze the third steps in the respective biosynthetic pathways for these sugars. Whereas both enzymes utilize the same substrate, the stereochemistries of their products are different. Specifically, the hydroxyl groups at the hexose C-4' positions assume the "galactose" and "glucose" configurations in the FdtA and QdtA products, respectively. In 2007 we reported the structure of the apoform of FdtA from Aneurinibacillus thermoaerophilus, which was followed in 2014 by the X-ray analysis of QdtA from Thermoanaerobacterium thermosaccharolyticum as a binary complex. Both of these enzymes belong to the cupin superfamily. Here we report a combined structural and enzymological study to explore the manner in which these enzymes control the stereochemistry of their products. Various site-directed mutant proteins of each enzyme were constructed, and their dTDP-sugar products were analyzed by NMR spectroscopy. In addition, the kinetic parameters for these protein variants were measured, and the structure of one, namely, the QdtA Y17R/R97H double mutant form, was determined to 2.3-Å resolution. Finally, in an attempt to obtain a model of FdtA with a bound dTDP-linked sugar, the 3,4-ketoisomerase domain of a bifunctional enzyme from Shewanella denitrificans was cloned, purified, and crystallized in the presence of a dTDP-linked sugar analogue. Taken together, the results from this investigation demonstrate that it is possible to convert a "galacto" enzyme into a "gluco" enzyme and vice versa. PMID:26125548

  4. Synthetic smythite and monoclinic Fe3S4

    Science.gov (United States)

    Fleet, Michael E.

    1982-11-01

    Smythite and monoclinic Fe3S4 have been identified by X-ray diffraction procedures in quenched ironsulfide compositions. Both phases appear to be metastable under the conditions of the experiments and their development is structurally induced. Smythite occurs as a coherent twinned intergrowth with hexagonal 3C pyrrhotite. Individual single crystals contain about 50% smythite. Reciprocal lattice rows with h-k ≠ 3n show continuous diffraction streaks. The available data suggest that smythite forms via a “polytypic” displacive transformation, by the introduction of stacking faults in the hexagonal close-packed layers of S atoms in high-temperature 1C pyrrhotite. This is analogous to the transformation of 2H wurtzite to intermediate ordered and disordered ZnS layer sequences. The ideal formula of smythite appears to be Fe13S16. Monoclinic Fe3S4 ( a=5.93, b=3.42, c=10.64 Å, β=91.9°) is present in amounts up to 25% of total sulfides. It has a derivative NiAs-type structure, and is isomorphous with monoclinic Cr3S4 and Fe3Se4. It occurs as small lenticular lamellae within grains of 3C pyrrhotite, and apparently corresponds to the unidentified lamellar phase of Arnold (1962). The lamellae have a rhombohedral morphology, with a habit plane close to {1011}. In single crystal grains of pyrrhotite, monoclinic Fe3S4 in twinned in a manner consistent with transformation from high-temperature 1C pyrrhotite. Although Fe3S4 lamellae have the general appearance of plate martensite, they do not represent a diffusionless transformation.

  5. In silico and in vitro evaluation of PCR-based assays for the detection of Bacillus anthracis chromosomal signature sequences.

    Science.gov (United States)

    Ågren, Joakim; Hamidjaja, Raditijo A; Hansen, Trine; Ruuls, Robin; Thierry, Simon; Vigre, Håkan; Janse, Ingmar; Sundström, Anders; Segerman, Bo; Koene, Miriam; Löfström, Charlotta; Van Rotterdam, Bart; Derzelle, Sylviane

    2013-11-15

    Bacillus anthracis, the causative agent of anthrax, is a zoonotic pathogen that is relatively common throughout the world and may cause life threatening diseases in animals and humans. There are many PCR-based assays in use for the detection of B. anthracis. While most of the developed assays rely on unique markers present on virulence plasmids pXO1 and pXO2, relatively few assays incorporate chromosomal DNA markers due to the close relatedness of B. anthracis to the B. cereus group strains. For the detection of chromosomal DNA, different genes have been used, such as BA813, rpoB, gyrA, plcR, S-layer, and prophage-lambda. Following a review of the literature, an in silico analysis of all signature sequences reported for identification of B. anthracis was conducted. Published primer and probe sequences were compared for specificity against 134 available Bacillus spp. genomes. Although many of the chromosomal targets evaluated are claimed to be specific to B. anthracis, cross-reactions with closely related B. cereus and B. thuringiensis strains were often observed. Of the 35 investigated PCR assays, only 4 were 100% specific for the B. anthracis chromosome. An interlaboratory ring trial among five European laboratories was then performed to evaluate six assays, including the WHO recommended procedures, using a collection of 90 Bacillus strains. Three assays performed adequately, yielding no false positive or negative results. All three assays target chromosomal markers located within the lambdaBa03 prophage region (PL3, BA5345, and BA5357). Detection limit was further assessed for one of these highly specific assays. PMID:24005110

  6. Active source seismic experiment investigating the formation of the Ontong Java Plateau

    Science.gov (United States)

    Miura, S.; Noguchi, N.; Coffin, M. F.; Kawagle, S. A.; Verave, R. T.; Kodaira, S.; Fukao, Y.

    2010-12-01

    The Ontong Java Plateau (OJP) is one of the largest oceanic plateaus and possibly the most voluminous large igneous province (LIP) on Earth, and is thought to have formed by a non-plate tectonic mechanism such as 1) a plume head, 2) a bolide impact, or 3) atypical seafloor spreading. Due to massive magmatism over short durations of geological time, formations of the OJP and LIPs in general likely have had global scale environmental impacts (e.g., Oceanic Anoxic Events). Therefore, understanding how LIPs form is important not only for illuminating solid Earth processes, but also for advancing knowledge of associated environmental, including biospheric, changes. On the basis of the OJP’s shallow bathymetry, its crust has long been thought to be thicker than normal oceanic crust. However, previous seismic and gravimetric analyses of its crustal thickness produced inconsistent results. To understand how the OJP formed, we conducted a seismic survey using a multi-channel seismic (MCS) hydrophone streamer and 100 ocean bottom seismometers (OBS) in February-March 2010 (EOS, submitted). New MCS data confirm that sediment approximately 1 s (two-way travel time) thick covers the uppermost OJP. Sediment layers are generally flat-lying, except near seamounts, in a local depression, and around some faults. Because of the flat-lying seafloor and shallow water depths, several water-bottom multiples of large amplitude characterize the MCS data, making identification of sub-basement reflections challenging. On the northernmost part of the seismic line, a reflection event at about 12 s (two-way travel time) differs unambiguously from multiple reflections, and may represent the base of the OJP’s crust. OBS data show first refraction arrivals within 100-km offsets. First arrivals with an apparent velocity of 7 km/s can be identified at offsets greater than 100 km. This may indicate a thick high velocity (~7 km/s) layer in the OJP’s lower crust. This high velocity layer may be

  7. Understanding Urban Watersheds through Digital Interactive Maps, San Francisco Bay Area, California

    Science.gov (United States)

    Sowers, J. M.; Ticci, M. G.; Mulvey, P.

    2014-12-01

    Dense urbanization has resulted in the "disappearance" of many local creeks in urbanized areas surrounding the San Francisco Bay. Long reaches of creeks now flow in underground pipes. Municipalities and water agencies trying to reduce non-point-source pollution are faced with a public that cannot see and therefore does not understand the interconnected nature of the drainage system or its ultimate discharge to the bay. Since 1993, we have collaborated with the Oakland Museum, the San Francisco Estuary Institute, public agencies, and municipalities to create creek and watershed maps to address the need for public understanding of watershed concepts. Fifteen paper maps are now published (www.museumca.org/creeks), which have become a standard reference for educators and anyone working on local creek-related issues. We now present digital interactive creek and watershed maps in Google Earth. Four maps are completed covering urbanized areas of Santa Clara and Alameda Counties. The maps provide a 3D visualization of the watersheds, with cartography draped over the landscape in transparent colors. Each mapped area includes both Present and Past (circa 1800s) layers which can be clicked on or off by the user. The Present layers include the modern drainage network, watershed boundaries, and reservoirs. The Past layers include the 1800s-era creek systems, tidal marshes, lagoons, and other habitats. All data are developed in ArcGIS software and converted to Google Earth format. To ensure the maps are interesting and engaging, clickable icons pop-up provide information on places to visit, restoration projects, history, plants, and animals. Maps of Santa Clara Valley are available at http://www.valleywater.org/WOW.aspx. Maps of western Alameda County will soon be available at http://acfloodcontrol.org/. Digital interactive maps provide several advantages over paper maps. They are seamless within each map area, and the user can zoom in or out, and tilt, and fly over to explore

  8. Gravity, Topography, and Magnetic Field of Mercury from Messenger

    Science.gov (United States)

    Neumann, Gregory A.; Solomon, Sean C.; Zuber, Maria T.; Phillips, Roger J.; Barnouin, Olivier; Ernst, Carolyn; Goosens, Sander; Hauck, Steven A., II; Head, James W., III; Johnson, Catherine L.; Lemoine, Frank G.; Margot, Jean-Luc; McNutt, Ralph; Mazarico, Erwan M.; Oberst, Jurgen; Peale, Stanley J.; Perry, Mark; Purucker, Michael E.; Rowlands, David D.; Torrence, Mark H.

    2012-01-01

    On 18 March 2011, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was inserted into a 12-hour, near-polar orbit around Mercury, with an initial periapsis altitude of 200 km, initial periapse latitude of 60 deg N, and apoapsis at approximately 15,200 km altitude in the southern hemisphere. This orbit has permitted the mapping of regional gravitational structure in the northern hemisphere, and laser altimetry from the MESSENGER spacecraft has yielded a geodetically controlled elevation model for the same hemisphere. The shape of a planet combined with gravity provides fundamental information regarding its internal structure and geologic and thermal evolution. Elevations in the northern hemisphere exhibit a unimodal distribution with a dynamic range of 9.63 km, less than that of the Moon (19.9 km), but consistent with Mercury's higher surface gravitational acceleration. After one Earth-year in orbit, refined models of gravity and topography have revealed several large positive gravity anomalies that coincide with major impact basins. These candidate mascons have anomalies that exceed 100 mGal and indicate substantial crustal thinning and superisostatic uplift of underlying mantle. An additional uncompensated 1000-km-diameter gravity and topographic high at 68 deg N, 33 deg E lies within Mercury's northern volcanic plains. Mercury's northern hemisphere crust is generally thicker at low latitudes than in the polar region. The low-degree gravity field, combined with planetary spin parameters, yields the moment of inertia C/MR2 = 0.353 +/- 0.017, where M=3.30 x 10(exp 23) kg and R=2440 km are Mercury's mass and radius, and a ratio of the moment of inertia of Mercury's solid outer shell to that of the planet of Cm/C = 0.452 +/- 0.035. One proposed model for Mercury's radial density distribution consistent with these results includes silicate crust and mantle layers overlying a dense solid (possibly Fe-S) layer, a liquid Fe

  9. Forschungszentrum Rossendorf, Institute of Radiochemistry. Annual report 2004

    International Nuclear Information System (INIS)

    The Institute of Radiochemistry (IRC), one of the six Institutes of the Forschungszentrum Rossendorf (FZR) performs basic and applied research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Because of their high radiotoxicity and long half-life the actinides are of special interest. The research is focused on a better understanding of the chemical behavior of actinides in the environment on a molecular level. We will increase our efforts to study both the speciation of actinides on bio-molecular interfaces and their transport in bio-systems. Current topics of our research work are: aquatic chemistry of actinides, actinides in bio-systems, interaction of actinides with solid phases, Reactive transport of actinides. About 60 scientists, technicians and PhD students are employed at the Institute of Radiochemistry. We accomplished many new scientific results in the past year, which are presented in this annual report. Among them only few can be highlighted in this preface. Further progress was achieved in understanding the formation and characterization of uranium containing colloids. The newly installed method of laser-induced breakdown detection was very helpful for the identification of uranium colloids under anoxic conditions. We were very successful in the determination of formation pathways and structure of various actinide complexes. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces. The results achieved in the characterization of the properties, modification, and interaction of the S-layers of Bacillus sphaericus with uranium and some other heavy metals strengthen our hope to use this

  10. Sulfur solubility in reduced mafic silicate melts: Implications for the speciation and distribution of sulfur on Mercury

    Science.gov (United States)

    Namur, Olivier; Charlier, Bernard; Holtz, Francois; Cartier, Camille; McCammon, Catherine

    2016-08-01

    contains 7-11 wt.% S and that the metallic core of the planet has little sulfur (<1.5 wt.% S). The external part of the Mercurian core is likely to be made up of a thin (<90 km) FeS layer.

  11. Forschungszentrum Rossendorf, Institute of Radiochemistry. Annual report 2004

    Energy Technology Data Exchange (ETDEWEB)

    Bernhard, G. (ed.)

    2005-07-01

    The Institute of Radiochemistry (IRC), one of the six Institutes of the Forschungszentrum Rossendorf (FZR) performs basic and applied research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Because of their high radiotoxicity and long half-life the actinides are of special interest. The research is focused on a better understanding of the chemical behavior of actinides in the environment on a molecular level. We will increase our efforts to study both the speciation of actinides on bio-molecular interfaces and their transport in bio-systems. Current topics of our research work are: aquatic chemistry of actinides, actinides in bio-systems, interaction of actinides with solid phases, Reactive transport of actinides. About 60 scientists, technicians and PhD students are employed at the Institute of Radiochemistry. We accomplished many new scientific results in the past year, which are presented in this annual report. Among them only few can be highlighted in this preface. Further progress was achieved in understanding the formation and characterization of uranium containing colloids. The newly installed method of laser-induced breakdown detection was very helpful for the identification of uranium colloids under anoxic conditions. We were very successful in the determination of formation pathways and structure of various actinide complexes. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces. The results achieved in the characterization of the properties, modification, and interaction of the S-layers of Bacillus sphaericus with uranium and some other heavy metals strengthen our hope to use this

  12. TEM study of the (SbS){sub 1+δ}(NbS{sub 2}){sub n}, (n=1, 2, 3; δ~1.14, 1.20) misfit layer phases

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Herrero, A., E-mail: adriangh@pdi.ucm.es [ICTS Centro Nacional de Microscopía Electrónica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Landa-Cánovas, A.R. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); Otero-Díaz, L.C. [Dpto. Química Inorgánica, Fac. CC. Químicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2015-10-15

    In the Sb–Nb–S system four new misfit layer phases have been found and carefully investigated via Transmission Electron Microscopy (TEM). Their structures are of composite modulated structure type with stoichiometries that can be formulated as (SbS){sub 1+δ}(NbS{sub 2}){sub n}; for n=1, δ~1.14 and 1.19; for n=2, δ~1.18 and for n=3, δ~1.19. Selected Area Electron Diffraction (SAED) patterns show an almost commensurate fit between the pseudo-tetragonal (SbS) and the pseudo-orthohexagonal (NbS{sub 2}){sub n} subcells along the misfit direction a, with 3(SbS)≈5(NbS{sub 2}), being b the same for both sub-lattices and c the stacking direction. For n=1, a commensurate phase with 4a{sub SbS}=7a{sub NbS2} has also been observed. In addition to the characteristic misfit and associated modulation of the two sub-structures, a second modulation is also present which appears to be primarily associated with the (SbS) sub-structure of both the n=1 and n=2 phases. High Resolution Transmission Electron Microscopy (HRTEM) images show ordered stacking sequences between the (SbS) and (NbS{sub 2}){sub n} lamellae for each of the four phases, however, disordered intergrowths were also occasionally found. Most of the crystals showed different kinds of twinning defects on quite a fine scale. Many crystals showed curled up edges. In some cases the lamellar crystals were entirely folded giving rise to similar diffraction patterns as found for cylindrical crystals. - Graphical abstract: Idealized structure models of the first three members of the homologous series (SbS){sub 1+δ}(NbS{sub 2}){sub n}. - Highlights: • Transmission Electron Microscopy study of misfit layer sulfides (SbS){sub 1+δ}(NbS{sub 2}){sub n}. • The structures consist of a (SbS) layer interleaved between n (NbS{sub 2}) layers. • Two different members n=1, one n=2 and one n=3 have been studied. • Twinning, intergrowths and different modulations in the (SbS) substructure.

  13. Quantum dot-dye hybrid systems for energy transfer applications

    International Nuclear Information System (INIS)

    In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems. In the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stoeber silica particles with an outer silica shell of thickness 2-24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. New QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability, our QD

  14. Structure of the Ninetyeast Ridge North of the Equator, Eastern Indian Ocean.

    Science.gov (United States)

    Gopala Rao, D.; Sreekrishna, K.; Levchenko, O.; W. Sager, W.; Paul, C.

    2008-12-01

    The Ninetyeast Ridge in the eastern Indian Ocean is an aseismic volcanic ridge that marks the Keruguelen hotspot trace between 35°S and 17°N, depicting significant changes in morphology and crust/lithosphere structure. Age progression, younger ages in the south to older ages, 90 Ma (anomaly 34) in the north of the ridge has been reported from linear magnetic anomalies adjoining the ridge and rocks drilled from it during the DSDP/ODP cruises. The bathymetric expression of it is visible up to Lat. 10°N but seismic reflection data indicate its buried anticlinal shape beneath the Bengal Fan, extending up to about Lat.17°N. Gravity anomalies are strongly positive over the exposed segment of the ridge but are subdued over the buried portion. A prominent break in the continuity of the Sunda-trench gravity low reflects that the ridge impinges upon the island arc and seismic reflection data indicate that the ridge approaches close to the trench. The crest of the ridge consists of numerous peaks and sediment filled basins. The sediments are likely to be volcnoclastic and/or shallow water carbonates depending upon submarine to sub- aerial conditions of the parts of the ridge overlain by hemi-pelagic to turbidites of varied thickness. Seismic sequences of the sediments are 6 km over the ridge, along the eastern flank and on the western flank respectively. The velocity structure of the sedimentary sequences, from top to bottom, consists of 1.6 to 1.9, 2.4 to 2.7, 3.2 to 3.4, 4.5 to 4,6 and 5.2 to 5.7 km/s layers along the western flank, 1.7 to 2.0, 2.3 to 3.2 and 4.6 to 5.7 km/s of Quaternary, pre-Miocene and pre-Paleocene respectively over the crest of the ridge and 2.3, 2.9 and 4.8 km/s velocity along the eastern flank of the ridge underlain by 6.4 km/s velocity oceanic layer 2. Tight folds and closely spaced faults (normal and reverse), some of them extending to the basement and deforming the crust of the ridge, have been imaged seismically. The en- echelon block

  15. 直流磁控溅射法制备本征ZnO薄膜及光伏应用研究%Photovoltaic Applications and Characterization of Un-doped ZnO Films Prepared by Direct Current Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    杨志军; 王波; 张静全; 冯良桓; 武莉莉; 李卫; 黎兵

    2013-01-01

    Un-doped ZnO films were deposited by direct current (DC) magnetron sputtering and the film structure and properties were characterized by X-ray diffraction (XRD), UV/VIS spectrometer and atomic force microscope ( AFM), respectively. The effects of process parameters, such as oxygen partial pressure, on the properties of ZnO film were studied. It is shown that the average transmittance in the visible region can reach 88% and it increases with higher oxygen partial pressure, and the root mean square (RMS) roughness is about 0. 41 nm. For the solar cells with the structure of glass/ITO/ CdS/CdTe, un-doped ZnO films are deposited as the buffer layer between ITO layer and CdS layer, then the open voltage and filling factor of the cells are greatly improved. The conversion efficiency of the devices with ZnO films reaches up to 13.6%.%采用直流磁控溅射法制备了ZnO薄膜,研究了沉积过程中变换氧分压对薄膜光电性能的影响.采用XRD、紫外可见光分光光度计及AFM等方法对薄膜的结构和光电性质进行了表征.结果表明,ZnO薄膜在可见光范围内的透过率可达88%,并且随着氧分压的增大,薄膜的透过率也增大;制备出的ZnO薄膜表面粗糙度为0.41 nm.在glass/ITO/CdS/CdTe结构的太阳电池中,将本征ZnO薄膜作为高阻层加入到ITO与CdS之间,电池的开路电压和填充因子有明显的提高,加入高阻层之后,电池的转换效率最高可达13.6%.

  16. Synthesis and development of processes for the recovery of sulfur from acid gases. Part 1, Development of a high-temperature process for removal of H{sub 2}S from coal gas using limestone -- thermodynamic and kinetic considerations; Part 2, Development of a zero-emissions process for recovery of sulfur from acid gas streams

    Energy Technology Data Exchange (ETDEWEB)

    Towler, G.P.; Lynn, S.

    1993-05-01

    Limestone can be used more effectively as a sorbent for H{sub 2}S in high-temperature gas-cleaning applications if it is prevented from undergoing calcination. Sorption of H{sub 2}S by limestone is impeded by sintering of the product CaS layer. Sintering of CaS is catalyzed by CO{sub 2}, but is not affected by N{sub 2} or H{sub 2}. The kinetics of CaS sintering was determined for the temperature range 750--900{degrees}C. When hydrogen sulfide is heated above 600{degrees}C in the presence of carbon dioxide elemental sulfur is formed. The rate-limiting step of elemental sulfur formation is thermal decomposition of H{sub 2}S. Part of the hydrogen thereby produced reacts with CO{sub 2}, forming CO via the water-gas-shift reaction. The equilibrium of H{sub 2}S decomposition is therefore shifted to favor the formation of elemental sulfur. The main byproduct is COS, formed by a reaction between CO{sub 2} and H{sub 2}S that is analogous to the water-gas-shift reaction. Smaller amounts of SO{sub 2} and CS{sub 2} also form. Molybdenum disulfide is a strong catalyst for H{sub 2}S decomposition in the presence of CO{sub 2}. A process for recovery of sulfur from H{sub 2}S using this chemistry is as follows: Hydrogen sulfide is heated in a high-temperature reactor in the presence of CO{sub 2} and a suitable catalyst. The primary products of the overall reaction are S{sub 2}, CO, H{sub 2} and H{sub 2}O. Rapid quenching of the reaction mixture to roughly 600{degrees}C prevents loss Of S{sub 2} during cooling. Carbonyl sulfide is removed from the product gas by hydrolysis back to CO{sub 2} and H{sub 2}S. Unreacted CO{sub 2} and H{sub 2}S are removed from the product gas and recycled to the reactor, leaving a gas consisting chiefly of H{sub 2} and CO, which recovers the hydrogen value from the H{sub 2}S. This process is economically favorable compared to the existing sulfur-recovery technology and allows emissions of sulfur-containing gases to be controlled to very low levels.

  17. Strategies to prepare an efficient photoanode for ZnO nanowires-based CdS–CdSe co-sensitized solar cells

    International Nuclear Information System (INIS)

    Highlights: ► Methods to prepare well-aligned ZnO nanowire arrays with large aspect ratio. ► Deposition of quantum dots by a successive ionic-layer adsorption and reaction method. ► Optimization and analysis of the strategies to fabricate an efficient photoanode. ► Jsc as high as 18.63 mA/cm2 was obtained for the optimized device. -- Abstract: Strategies employed to fabricate an efficient photoanode with ZnO nanowires (NWs) arrays and CdS–CdSe co-sensitizers were investigated. A detailed procedure for growing long ZnO NWs which are suitable for the application in quantum dot sensitized solar cells was discussed, and several optimized parameters were obtained for fabrication of the ZnO NWs with large aspect ratio. CdS and CdSe layers were deposited on the surface of the ZnO NWs by a successive ionic-layer adsorption and reaction method and the deposition process was optimized according to the performance of the solar cells fabricated with the ZnO/CdS NWs and the ZnO/CdS/CdSe NWs arrays, respectively. The relationship between the thickness of the sensitizer layer and the performance of the devices was also discussed in detail. Transmission electron microscopy observation shows that ∼7 nm thick CdS layer and ∼5 nm thick CdSe layer can be easily achieved on the ZnO NWs at an optimal deposition condition. UV–vis absorption spectra demonstrate that the light absorption range of the ZnO/CdS/CdSe NWs can be almost extended to the whole visible range. Through an optimization of the photoanode fabrication, which mainly includes the synthesis of the ZnO NWs arrays and the deposition of the CdS and CdSe layers, a short circuit current density as high as 18.63 mA/cm2 with an overall efficiency of 3.06% can be obtained for the resulting device

  18. Study on thermal effects & sulfurized additives, in lubricating greases

    Science.gov (United States)

    Shah, Ami Atul

    understand the effects of the addition of sulphur from a sulfurized olefin to MoS2 through mechanical processing has been conducted. This mechanically processed additive mixed is tested through regular ASTM D2266 test. The hypothesis was to make more shear able MoS 2 layers available by using the sulphur from the olefin to form the basic FeS layer that reduces the continuous wear rate. The results have been studied using SEM and EDX imaging.

  19. Optical dynamics of MgO/Ga4Se3S interface

    International Nuclear Information System (INIS)

    Highlights: • A p–n interface made of MgO as an optical window to Ga4Se3S crystals is designed. • The device is studied by means of transmittance, reflectance and absorbance. • The reflection dependence on incident angle is investigated in the range of 30–80°. • The Brewster angles for the layers are determined. • The strong absorption domination conditions are reported. -- Abstract: A new p–n interface made of p-type MgO as an optical window to the n-type Ga4Se3S crystals is investigated by means of optical reflectance, transmittance and absorbance in the incident light wavelength (λ) range of 200–1100 nm. The reflectivity spectral analysis as a function of angle of incidence for MgO, Ga4Se3S and the Ga4Se3S/MgO layers revealed Brewster angles of 75°, 80° and 70° with the corresponding dielectric constants of 13.93, 32.16 and εMgO=7.55εGa4Se3S, respectively. To remove Brewster condition of reflection and obtain maximum absorption, the light must be incident from the MgO side. A novel light absorbability is observed. Namely, for all λ 4Se3S layer. For larger λ values, while the crystal absorbance decreases significantly, the bilayer absorbance increased by four times in the visible range and three times in the IR range of spectrum. In the MgO layer, two distinct sets of band tails of the localized states with the widths of 2.30 and 1.26 eV are determined from the absorption spectral analysis. These band tails shift up to 2.32 and 1.44 eV when the interface is constructed. In addition, an indirect energy band gaps (Eg) which are located at 3.10, 2.13 and 1.90 eV for the MgO, Ga4Se3S and the Ga4Se3S/MgO layers, respectively, are determined. The Eg value of the crystal shifts by a 0.23 eV upon bilayer construction. The reflection properties, the band tails, the energy gaps and related shifts make the Ga4Se3S/MgO interface attractive for fabrication of solar cells, narrow barrier resonant tunneling diodes or quantum dots, and as an optical

  20. The growth of sulfur adlayers on Au(100)

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yue; Ren, Shendong; Chen, Chi-Lu [Department of Physics, National Central University, Taoyuan 32001, Taiwan (China); Liang, Xihui [Department of Physics, National Central University, Taoyuan 32001, Taiwan (China); Guangzhou Research Institute of Optics-Mechanics-Electricity Technology, Guangzhou 510663 (China); Fan, Liang-Jen; Yang, Yaw-Wen [National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Tang, Jian-Ming [Department of Physics, University of New Hampshire, Durham, New Hampshire 03824 (United States); Luh, Dah-An, E-mail: luh.dah.an@gmail.com [Department of Physics, National Central University, Taoyuan 32001, Taiwan (China); National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China)

    2015-02-14

    We have studied the growth of S layers adsorbed on Au(100) with low-energy electron diffraction (LEED), X-ray photoemission spectra (XPS), and scanning tunneling microscope (STM). Three phases of S/Au(100)—(2 × 2), trimer, and c(2 × 4)—are identified; the latter two are not previously reported. A dose of S{sub 2} at 300 K transformed Au(100)-(5 × 20) initially into the (2 × 2) phase and formed the c(2 × 4) phase at a saturation coverage. The STM results show that monolayer Au islands formed during the initial S dose and remained throughout the growth, resulting in a rough c(2 × 4) surface. We show that a highly ordered c(2 × 4) phase can be obtained with a flat (2 × 2) phase as an intermediate step during growth. Based on the evolution of XPS and STM images with varied S{sub 2} dose, the components of S 2p are assigned and structural models for the various S/Au(100) phases are proposed. In the (2 × 2) phase, one S atom resides on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.25 ML; in the trimer phase, three S atoms form a trimer residing on a four-fold hollow site in each (2 × 2) unit cell, corresponding to a S coverage of 0.75 ML; in the c(2 × 4) phase, there are five S atoms in each primitive unit cell of c(2 × 4); three of them form a trimer residing on a four-fold hollow site, and the other two form a dimer located on the top of the trimer, corresponding to a nominal S coverage of 1.25 ML. With the proposed structural models, the growth of S on Au(100) at 300 K is described in detail.

  1. Development of CIGS2 thin film solar cells

    International Nuclear Information System (INIS)

    Research and development of CuIn1-xGa xSe2-yS y (CIGSS) thin-film solar cells on ultralightweight flexible metallic foil substrates is being carried out at FSEC PV Materials Lab for space applications. Earlier, the substrate size was limited to 3 cm x 2.5 cm. Large-area sputtering systems and scrubber for hydrogen selenide and sulfide have been designed and constructed for preparation of CIGSS thin-films on large (15 cm x 10 cm) substrates. A selenization/sulfurization furnace donated by Shell (formerly Siemens) Solar has also been refurbished and upgraded. The sputtering target assembly design was modified for proper clamping of targets and effective cooling. A new design of the magnetic assembly for large-area magnetron sputtering sources was implemented so as to achieve uniform deposition on large area. Lightweight stainless steel foil and ultralightweight titanium foil substrates were utilized to increase the specific power of solar cells. Sol-gel derived SiO2 layers were coated on titanium foil by dip coating method. Deposition parameters for the preparation of molybdenum back contact layers were optimized so as to minimize the residual stress as well as reaction with H2S. Presently large (15 cm x 10 cm) CuIn1-xGa xS2 (CIGS2) thin film solar cells are being prepared on Mo-coated titanium and stainless steel foil by sulfurization of CuGa/In metallic precursors in diluted Ar:H2S(4%). Heterojunction partner CdS layers are deposited by chemical bath deposition. The regeneration sequence of ZnO/ZnO:Al targets was optimized for obtaining consistently good-quality, transparent and conducting ZnO/ZnO:Al bilayer by RF magnetron-sputter deposition. Excellent facilities at FSEC PV Materials Lab are one of its kinds and could serve as a nucleus of a small pilot plant for CIGSS thin film solar cell fabrication

  2. Extremely halophilic archaea from ancient salt sediments and their possible survival in halite fluid inclusions

    Science.gov (United States)

    Stan-Lotter, H.; Fendrihan, S.; Gerbl, F. W.; Dornmayr-Pfaffenhuemer, M.; Frethem, C.

    2008-09-01

    Halophilic archaebacteria (haloarchaea) thrive in environments with salt concentrations approaching saturation, such as natural brines, marine solar salterns and alkaline salt lakes; they have also been isolated from ancient subsurface salt sediments of great geological age (195-280 million years) and some of those strains were described as novel species (1). The cells survived perhaps while being enclosed within small fluid inclusions in the halite. The characterization of subsurface microbial life is of astrobiological relevance since extraterrestrial halite has been detected and since microbial life on Mars, if existent, may have retreated into the subsurface. We attempted to simulate the embedding process of extremely halophilic archaea and to analyse any cellular changes which might occur. When enclosing haloarchaea in laboratory grown halite, cells accumulated preferentially in fluid inclusions, as could be demonstrated by pre-staining with fluorescent dyes. With increased time of embedding, rod-shaped cells of Halobacterium salinarum strains were found to assume roundish morphologies. Upon dissolution of the salt crystals, these spheres were stable and viable for months when kept in buffers containing 4 M NaCl. Scanning electron microscopy (SEM) following fixation with glutaraldehyde suggested a potentially gradual transformation from rods to spheres. This notion was supported by fluorescence microscopy of Halobacterium cells, following embedding in halite and staining with SYTO 9. One-dimensional protein patterns of rods and spheres, following SDS polyacrylamide gel electrophoresis, were similar except that the S-layer protein appeared reduced by about 15 - 20 % in spheres. The reddish-orange pigmentation of spheres was much lighter compared to that of rod-shaped cells, suggesting lowered concentrations of carotenoids; this was confirmed by extraction and spectrometry of pigments. The data suggested that Halobacterium cells are capable of forming specific

  3. Broad Band Antireflection Coatings for Silicon and Germanium Substrates.

    Science.gov (United States)

    Bezuidenhout, Dirk Francois

    Infrared antireflection coatings for silicon and germanium substrates and some of the associated problems are addressed in this thesis. One of the first problems identified and investigated was that of the adhesion of ZnS films to germanium substrates. The cleaning of the Ge discs was evaluated by means of Auger spectroscopy. The main contaminant species found were carbon, oxygen and in the case of germanium substrates sulphur. No sulphur was found on silicon substrates. A wash in a series of organic solutions followed by a bake inside the vacuum chamber lead to much improved though still not acceptable adhesion of ZnS films to germanium substrates. The influence of a contact layer between the substrate and ZnS was investigated. Firstly, metal contact layers (Ni, Cr, Cu) were tried to improve the adhesion of the ZnS films. These samples (germanium-metal-zinc sulphide) were annealed in air in order to transfer the germanium -metal film to a germanide region and thus high optical transmission at long wave-lengths. Slight absorption still results even after the annealing of these samples. A dielectric material, Y_2O_3 , was therefore tested replacing the metal films. The system Ge-Y_2O_3 -ZnS in conjunction with an organic wash and vacuum bake lead to excellent adhesion of the ZnS layers to the germanium substrates. The next problem area addressed was that of a low refractive index material replacement for ThF _4. Four materials were investigated, i.e. ZnS, PbF_2, Y_2O _3 and YF_3. The refractive indices found for these compounds in thin film form at a wavelength of 10 μm is 2,18 for ZnS, 1,7 for PbF_2, 1,42 for Y_2O_3 and 1,3 for YF_3. From these results YF_3 was chosen as low refractive index material in the coating designs. Multi-layer coatings incorporating ZnS, Ge and YF_3 films were designed and evaporated. Measured reflectance values below 0,2% were obtained from 9 μm to 11 mum. These systems were stable and robust. Finally, a silicon ball lens was

  4. Characterization of CuInS2 thin films prepared by chemical bath deposition and their implementation in a solar cell

    International Nuclear Information System (INIS)

    CuInS2 thin films were formed by the sequential deposition of In2S3–CuS layers on glass substrates, by chemical bath deposition technique, and heating these multilayer 1 h at 350 °C and 400 mPa. The morphology and thickness of the CuInS2 thin films were analysed by scanning electron microscopy, showing particles with elongated shape and length about 40 nm, and thickness of 267 and 348 nm for samples from 15 and 24 h of deposition time in the chemical bath of In2S3, respectively. The energy band gap values of the films were around 1.4 eV, whereas the electrical conductivity showed values from 64.91 to 4.11 × 10−3 Ω−1 cm−1 for the samples of 15 and 24 h of In2S3 deposition bath, respectively. The obtained CuInS2 films showed appropriate values for their application as an absorbing layer in photovoltaic structures of the type: glass/SnO2:F/CdS/Sb2S3/CuInS2/PbS/C/Ag. The whole structure was obtained through chemical bath deposition technique. The solar cell corresponding to 15 h of In2S3 deposition duration bath showed energy-conversion efficiency (η) of 0.53% with open circuit voltage (Voc) of 530 mV, short circuit current density (Jsc) of 2.43 mA cm−2, and fill factor (FF) of 0.41. In the case of the structure with 24 h of deposition of In2S3 bath, η = 0.43% was measured with the following parameters: Voc = 330 mV, Jsc = 4.78 mA cm−2 and FF = 0.27. - Highlights: • CuInS2 films were formed by chemical bath deposition followed by a heat treatment. • Prepared CuInS2 thin films can work as an effective absorbing layer in a solar cell. • A complete solar cell structure was made by a chemical bath deposition method

  5. Harvesting Solar Energy by Means of Charge-Separating Nanocrystals and Their Solids

    Science.gov (United States)

    Diederich, Geoffrey; O'Connor, Timothy; Moroz, Pavel; Kinder, Erich; Kohn, Elena; Perera, Dimuthu; Lorek, Ryan; Lambright, Scott; Imboden, Martene; Zamkov, Mikhail

    2012-01-01

    composite two-layer solid of PbS and TiO2 films. In this configuration, photoinduced electrons are injected into TiO2 and are subsequently picked up by an FTO electrode, while holes are channeled to a Au electrode via PbS layer6. To develop the latter we introduce a Semiconductor Matrix Encapsulated Nanocrystal Arrays (SMENA) strategy, which allows bonding PbS NCs into the surrounding matrix of CdS semiconductor. As a result, fabricated solids exhibit excellent thermal stability, attributed to the heteroepitaxial structure of nanocrystal-matrix interfaces, and show compelling light-harvesting performance in prototype solar cells7. PMID:22951526

  6. Characterization of CuInS{sub 2} thin films prepared by chemical bath deposition and their implementation in a solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Lugo, S.; López, I. [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria 66451, San Nicolás de los Garza, Nuevo León, México (Mexico); Peña, Y., E-mail: yolapm@gmail.com [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria 66451, San Nicolás de los Garza, Nuevo León, México (Mexico); Calixto, M. [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, C.P. 62580, Temixco, Morelos, México (Mexico); Hernández, T. [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria 66451, San Nicolás de los Garza, Nuevo León, México (Mexico); Messina, S. [Universidad Autónoma de Nayarit, Ciudad de la Cultura “Amado Nervo”, S/N C.P. 63155, Tepic, Nayarit, México (Mexico); and others

    2014-10-31

    CuInS{sub 2} thin films were formed by the sequential deposition of In{sub 2}S{sub 3}–CuS layers on glass substrates, by chemical bath deposition technique, and heating these multilayer 1 h at 350 °C and 400 mPa. The morphology and thickness of the CuInS{sub 2} thin films were analysed by scanning electron microscopy, showing particles with elongated shape and length about 40 nm, and thickness of 267 and 348 nm for samples from 15 and 24 h of deposition time in the chemical bath of In{sub 2}S{sub 3}, respectively. The energy band gap values of the films were around 1.4 eV, whereas the electrical conductivity showed values from 64.91 to 4.11 × 10{sup −3} Ω{sup −1} cm{sup −1} for the samples of 15 and 24 h of In{sub 2}S{sub 3} deposition bath, respectively. The obtained CuInS{sub 2} films showed appropriate values for their application as an absorbing layer in photovoltaic structures of the type: glass/SnO{sub 2}:F/CdS/Sb{sub 2}S{sub 3}/CuInS{sub 2}/PbS/C/Ag. The whole structure was obtained through chemical bath deposition technique. The solar cell corresponding to 15 h of In{sub 2}S{sub 3} deposition duration bath showed energy-conversion efficiency (η) of 0.53% with open circuit voltage (V{sub oc}) of 530 mV, short circuit current density (J{sub sc}) of 2.43 mA cm{sup −2}, and fill factor (FF) of 0.41. In the case of the structure with 24 h of deposition of In{sub 2}S{sub 3} bath, η = 0.43% was measured with the following parameters: V{sub oc} = 330 mV, J{sub sc} = 4.78 mA cm{sup −2} and FF = 0.27. - Highlights: • CuInS{sub 2} films were formed by chemical bath deposition followed by a heat treatment. • Prepared CuInS{sub 2} thin films can work as an effective absorbing layer in a solar cell. • A complete solar cell structure was made by a chemical bath deposition method.

  7. Study on Cracking Mechanism and Inhibiting Process of Near αTitanium Alloy Formed by SLM%激光选区熔化近α钛合金开裂机理及抑制研究

    Institute of Scientific and Technical Information of China (English)

    周旭; 周燕; 魏青松; 朱伟

    2015-01-01

    The cracking mechanism and inhibiting process were discussed through studying the crack morphology,propagation direction and crack source of a new near αphase titanium alloy speci-men fabricated by SLM using scanning electron microscopy and so on.The experimental results show that:uneven notches arose from the sidewall of the specimen during fabricationas well as Ti3 O,TiO, TiC which are hard and brittle.Under the actions of residual stress,the cracks originate in the sidewall notches and expand in the deposition along these hard and brittle compounds.When the laser power is 140 W,scanning speed is 450 mm/s,layer thickness is 0.03 mm,scanning space is 0.07 mm,preheating temperature is 350 ℃ during SLM and preserve 1 h,slow cooling to room temperature,the number of cracks reduce significantly.%研究了近α钛合金激光选区熔化(SLM)成形开裂机理及抑制工艺,利用扫描电子显微镜等研究了试件裂纹形貌及其扩展方向、裂纹源等问题。研究结果表明:SLM 成形过程中在试样侧壁形成凹凸不平的缺口及 Ti3 O、TiO、TiC 等硬脆化合物;在残余应力作用下,裂纹起源于侧壁缺口,在沉积层上沿硬脆化合物扩展。当工艺参数为激光功率140 W,扫描速度450 mm/s,铺粉层厚0.03 mm,扫描间距0.07 mm,SLM 成形温度350℃,保温1 h 缓冷至室温时,可有效抑制试件开裂。

  8. Influence of CdCl{sub 2} activation treatment on ultra-thin Cd{sub 1−x}Zn{sub x}S/CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, A.J., E-mail: a.clayton@glyndwr.ac.uk [Centre for Solar Energy Research, Glyndŵr University, OpTIC, St. Asaph LL17 0JD (United Kingdom); Baker, M.A.; Babar, S. [Faculty of Engineering & Physical Sciences, University of Surrey, Guildford GU2 7XH (United Kingdom); Gibson, P.N. [Institute for Health & Consumer Protection, Joint Research Centre, 21020 Ispra, VA (Italy); Irvine, S.J.C.; Kartopu, G.; Lamb, D.A.; Barrioz, V. [Centre for Solar Energy Research, Glyndŵr University, OpTIC, St. Asaph LL17 0JD (United Kingdom)

    2015-09-01

    Ultra-thin CdTe photovoltaic solar cells with an absorber thickness of 0.5 μm were produced by metal organic chemical vapour deposition onto indium tin oxide coated boroaluminosilicate glass. A wide band gap Cd{sub 1−x}Zn{sub x}S alloy window layer was employed to improve spectral response in the blue region of the solar spectrum. X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy were used to monitor changes in the chemical composition and microstructure of the Cd{sub 1−x}Zn{sub x}S/CdTe solar cell after varying the post-deposition CdCl{sub 2} activation treatment time and annealing temperature. The CdCl{sub 2} treatment leached Zn from the Cd{sub 1−x}Zn{sub x}S layer causing a redshift in the spectral response onset of window absorption. S diffusion occurred across the Cd{sub 1−x}Zn{sub x}S/CdTe interface, which was more pronounced as the CdCl{sub 2} treatment was increased. A CdTe{sub 1−y}S{sub y} alloy was formed at the interface, which thickened with CdCl{sub 2} treatment time. Small concentrations of S (up to 2 at.%) were observed throughout the CdTe layer as the degree of CdCl{sub 2} treatment was increased. Greater S diffusion across the Cd{sub 1−x}Zn{sub x}S/CdTe interface caused the device open-circuit voltage (V{sub oc}) to increase. The higher V{sub oc} is attributed to enhanced strain relaxation and associated reduction of defects in the interface region as well as the increase in CdTe grain size. - Highlights: • Increased CdCl{sub 2} activation treatment resulted in loss of Zn from Cd{sub 1−x}Zn{sub x}S. • Sulphur diffusion into CdTe was enhanced with greater CdCl{sub 2} activation treatment. • Improvement to V{sub oc} correlated with increased sulphur diffusion into CdTe.

  9. Interaction of Extreme Halophilic Archaea With the Evaporites of the Solar Salterns Guerrero Negro Baja California, Mexico

    Science.gov (United States)

    Tamez, P.; Lopez-Cortés, A.

    2008-12-01

    Hypersaline environments have been significant reservoirs for the long-term evolution of specifically adapted microorganisms. Characterized to have higher salt concentrations (up to 35 g/L), they are worldwide distributed and have a commercial significance. Exportadora de Sal, Guerrero Negro, Mexico has a multipond salterns system designed to harvest common salt (NaCl) from sea water. To achieve this purpose, sea water is pumped through a set of shallow ponds where water evaporates and salts concentrate. Sequential precipitation of CaCO3, CaSO4 2H2O and NaCl occurs in a mineral formations call it evaporites. In the interior of those gypsum-encrusted and halite-encrusted minerals, communities of extremely salt-loving archaea prosper. Previous studies have showed the influence of Haloarchaeal cells in the formation of larger fluid inclusions than crystals formed in sterile salt solutions. S-layer envelopes and cells of Haloarcula strain SP8807 contributed to the nucleation of new crystals of NaCl. Given the significance of the scope in phylogenetic archaeal diversity research, this study had a polyphasic approach. SEM micrographs from a 21- 31% (w/v) gradient salt multipond system evaporites, gave an insight profile of the extreme halophilic archaeal communities thriving in the surface of the gypsum and halite evaporites. Halite crystals were form after 21 days of incubation in solid medium with archaeal cells. Both culture and non-culture dependent methods, Nested-PCR-DGGE analysis and sequencing of 16S rDNA amplified fragment genes from environmental samples and isolated strains were used for this purpose. We isolate three strains from Pond 9 (21.07% total salt concentration) and one strain from Cristallizer 20 (25.15% total salt concentration). 16S rDNA signaling gave 99% of similarity with Halogeometricum borinquense, sequence AF002984, two other strains were 99% of similarity with Halobacterium salinarum, sequence AJ496185 these strains shown different colony

  10. Quantum dot-dye hybrid systems for energy transfer applications

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Ting

    2010-07-01

    In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems. In the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stoeber silica particles with an outer silica shell of thickness 2-24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. New QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability, our QD

  11. Study of optoelectronic properties of thin film solar cell materials Cu2ZnSn(S,Se)4 using multiple correlative spatially-resolved spectroscopy techniques

    Science.gov (United States)

    Chen, Qiong

    to understand the underlying microscopic material structures and predict the potential of improvement in device performance. First, by using an array of correlated aforementioned techniques, microscale inhomogeneity of the CdS layer thickness was found in CZTSe solar cells. Thicker CdS regions are found to cause more light-reflection loss thus yielding lower external quantum efficiencies (EQEs) than the general area. However, these regions show much less efficiency degradation at high illumination density, leading to an inversion of LBIC contrast between the CdS rich regions and general area. By improving the CdS layer uniformity, CZTSe device performance can be significantly boosted. And this finding also points out the possibility of operating thin-film photovoltaic device based on similar materials under substantially higher illumination density for concentrated photovoltaic and photo-detection. Second, Micro-Raman reveals multiple secondary phases such as ZnSe and SnSe within the CZTSe films, which are harmful for solar cell operation. In high-laser-power Raman study, CZTSe shows structural change and decomposition, which indicates poor thermal conductivity of the polycrystalline film. Different behaviors of CZTSe films prepared by different methods are observed in high-laser-power and high-temperature Raman studies, both of which offer effective approaches to examine microscopic structural variation of nominally similar CZTSe films. Because of the achieved high spatial resolution, applying micro-Raman and micro-LBIC, we are able to examine the depth variation of the thin absorber film (in the order of 1 microm) in terms of chemical composition, photo-response, and deposition method dependence. In the third part, micro-I-V curves offer direct measurements of electrical parameters reflecting the effects of the device structure, absorber thickness and elemental ratio on the CZTSe cell performance. NaF precursor, low copper and high zinc content are demonstrated

  12. 炭疽芽胞杆菌BslA(260-652)蛋白的表达纯化与黏附功能鉴定%Recombinant expression, purification and adhesion function identify of Bacillus anthracis BslA(260-652) protein

    Institute of Scientific and Technical Information of China (English)

    马坤; 王艳春; 陶好霞; 董杰; 曹诚; 张部昌; 刘纯杰

    2012-01-01

    :20000. Western blot showed the antiserum could specifically recognize endogenous BslA protein. The purified BslA(260_652) displayed a typical adhesion-like function. Either the anti-BslA serum or the BsIA(260-652), protein could inhibit A16R's Hela adherence. [ Conclusion]The recombinant BslA(M0_UJ) protein was successfully obtained, which would lay the foundation for further research of the anthrax vaccine and the role of this S-layer protein in the pathogenesis of anthrax.

  13. Synthesis of fluorophore encapsulated silica nanoparticles for the evaluation of the biological fate and toxicity of food relevant nanoparticles

    Science.gov (United States)

    Zane, Andrew Paul

    We show that commercially available TiO2, SiO2, and ZnO nanoparticles are all internalized by C2BBe1 intestinal epithelial cells, but do not appear to be toxic, even after long term repeat-exposures. When particles were exposed to a simulated digestion protocol mimicking the stomach and intestinal environment, TiO2 particles did show mild toxicity by MTT assay, indicating a decrease in metabolic activity. IR spectra of these particles indicate presence of material from the digestion media, and these absorbed species may be responsible for the effects noted. Though the three particles were not significantly toxic, we note internalization by the intestinal epithelial cells, opening a possibility for absorption into circulation where they may localize in organs throughout the body. This will be observed by functionalizing the particles with fluorophores, after which they can be measured via fluorescence. To optimize the quantum yield efficiency, and thus the brightness, of one such fluorophore, we seek to improve a microwave synthesis of CdSe/CdS/ZnS quantum dots our lab has previously reported. By coupling the microwave reactor to a fluorescence spectrometer via fiber optic cables, we were able to monitor the development of the particles throughout the microwave heating. Time-dependent fluorescence shows the development of an early fluorescence peak at 502 nm attributed to CdSe cores. We then note two isosbestic points which we attribute to the development of CdS layer around CdSe cores, and eventually the formation of outer ZnS shell. We utilize this in situ monitoring along with a study of various nucleation temperatures ranging from 0 to 100°C, and pre-and-post microwave heating UV exposure treatments to obtain optimized CdSe/CdS/ZnS particles with a QY of 40%. This is an improvement over our previous particles' 13% QY, and the highest yet reported for an aqueous synthesis of CdSe/ZnS type particles. Finally, we incorporate these QDs as well as two organic

  14. 甘蔗渣在高温液态水中的超微结构与组分变化%Change of ultrastructure and composition of sugarcane bagasse in liquid hot water

    Institute of Scientific and Technical Information of China (English)

    余强; 庄新姝; 袁振宏; 孔晓英; 亓伟; 王闻; 王琼; 谭雪松

    2014-01-01

    Native lignocellulosic biomass has limited accessibility to enzymes and microorganisms due to its complex cell wall structure of cellulose-hemicellulose-lignin. Therefore, pretreatment is a prerequisite to overcome recalcitrance of biomass and enhance bio-chemical conversion ratio of polysaccharides. Compared with other methods, high temperature liquid hot water pretreatment has the advantages of no chemical addition and less inhibitory products. In the present study, different structural changes at plant tissue, cellular, and cell wall levels were investigated to understand the decomposition mechanism of sugarcane bagasse cell wall in the liquid hot water pretreatment. Transmission electron microscopy (TEM) images showed that sugarcane bagasse cell walls were composed of middle lamella (ML) layers, primary wall (P) layers, and secondary wall layers (S). While after the pretreatment, the boundaries among the ML, P and S layers of treated samples could not be distinguished exactly. The data from scanning electron microscopy and energy dispersive X-ray analysis(SEM-EDXA)showed that migration of lignin happened among different cell wall layers. Moreover, pseudo-lignin, the degradation products of lignin and xylan, appeared on the surface of pretreated sugarcane bagasse. Furthermore, Raman spectra of treated sugarcane bagasse indicated that distribution of cellulose in the cell wall was homogenized, and the difference in chemical composition was reduced.%木质纤维素类物质中天然纤维素与半纤维素、木质素等组分交联形成了坚固的细胞壁,对纤维素酶水解和微生物消化表现出一定的抗性,原料预处理可以克服细胞壁抗性,提高木质纤维多糖生化转化效率。从细胞壁超微结构层次入手,对甘蔗渣细胞壁在高温液态水预处理过程中的解构机理进行了深入研究。未处理甘蔗渣细胞壁分层现象明显,由外至内分别为胞间层(ML)、初生壁(P)及次生壁(S),

  15. Magneto Optical Kerr Effect measurement of double exchange spring system

    Science.gov (United States)

    Yuan, Hanming

    Magnetic property of the symmetric Double Exchange Spring System, soft(S)/hard(H)/soft(S) ferromagnetic layers NiFe (Py)/SmFe/NiFe (Py), was investigated using Magneto Optical Kerr Effect (MOKE) measurement. Exchange spring magnet, H/S bilayer, shows a unique magnetic hysteresis curve due to the non-collinear magnetization developed by magnetic coupling of the two layers. In order to produce a symmetric non-collinearity in magnetization, the thicknesses of the two soft layers are controlled to be the same during the deposition. Due to the finite skin depth of MOKE measurement magnetic hysteresis loop for each soft layer could be measured separately by adjusting the right thickness of the layers. To measure the bottom soft layer transparent glass substrate was used for thin film deposition. We first observed an asymmetric hysteresis loop of the double exchange spring system by MOKE measurement. This is due to the existence of quadratic MOKE (QMOKE) signal caused by the in-plane magnetic anisotropy. Linear MOKE (LMOKE) and QMOKE signal were separated from the general MOKE signal using a symmetry operation. In general, the samples that have the induced easy axis have less significant QMOKE signal than those that do not have the easy axis. Second, from the LMOKE measurement, we found that the magnetic hysteresis loops for the bottom and the top S layers are not the same. The magnetic hysteresis loop from LMOKE measurements data was compared with the one measured by Alternating Gradient Magnetometer (AGM). AGM measures the total magnetization of the whole structure. Our data shows that the coercivity of the bottom S measured from LMOKE is closer to the coercivity of the first switching measured from AGM and is much smaller than that of the top S from MOKE. The coercivity of the top S from LMOKE is closer to that of the second switching from AGM. This indicates that the top S is, to some extent, strongly coupled with the hard layer causing them to switch together; while

  16. The role of Cd and Ga in the Cu(In,Ga)S{sub 2}/CdS heterojunction studied with X-ray spectroscopic methods

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Benjamin E.

    2010-08-15

    be CdS as this is readily dissolved by HCl. Also, because it is thought that Cd will replace the cations in the CIS lattice, most likely Cu, the resulting Cd-S bonds in CIS:Cd will be different from those in CdS. Further experiments could not exclude the possibility that Cd diffuses into the CIS. However, it was shown that Cu from the absorber diffuses into the buffer layer during junction formation, although the Cu does not reach the surface of a full {proportional_to}35 nm thick CdS layer. The valence band offset between Cu(In,Ga)S{sub 2} and CdS was independent of Ga concentration and had a value 1.35 eV{+-}0.20 eV. However, the position of the conduction band did show a dependence on Ga and moved to lower binding energies with increasing Ga concentration. {proportional_to}8% Ga on the absorber surface opened the Cu(In,Ga)S{sub 2} band gap by {proportional_to} 150 meV when compared to CuInS{sub 2}. Although the opening of the band gap exacerbates the conduction band offset in the CIS/CdS junction, the inclusion of Ga increases the open circuit voltage of the solar cell by {proportional_to}100 mV. (orig.)

  17. Designing Passivating, Carrier-Selective Contacts for Photovoltaic Devices

    Energy Technology Data Exchange (ETDEWEB)

    Boccard, Matthieu [Arizona State Univ., Tempe, AZ (United States); Koswatta, Priyaranga [Arizona State Univ., Tempe, AZ (United States); Holman, Zachary [Arizona State Univ., Tempe, AZ (United States)

    2015-04-06

    "The first step towards building a high-efficiency solar cell is to develop an absorber with few recombination-active defects. Many photovoltaic technologies have already achieved this (monocrystalline Si, III-V materials grown on lattice-matched substrates, perovskites, polycrystalline CdTe and CIGS); those that have not (a-Si:H, organics) have been limited to low open-circuit voltage. The second step is to develop contacts that both inhibit surface recombination and allow for low-resistance collection of either only electrons or only holes. For most photovoltaic technologies, this step is both more difficult and less explored than the first, and we are unaware of a prescribed methodology for selecting materials for contacts to solar cells. We elucidate a unified, conceptual understanding of contacts within which existing contacting schemes can be interpreted and future contacting schemes can be imagined. Whereas a split of the quasi-Fermi levels of holes and electrons is required in the absorber of any solar cell to generate a voltage, carriers are eventually collected through a metallic wire in which no such quasi-Fermi-level split exists. We define a contact to be all layers between the bulk of the absorber and the recombination-active interface through which carriers are extracted. The quasi-Fermi levels must necessarily collapse at this interface, and thus the transition between maximal quasi-Fermi-level splitting (in the absorber) and no splitting occurs entirely in the contact. Depending on the solar cell architecture, the contact will usually extend from the surface of the absorber to the surface of a metal or transparent conductive oxide layer, and may include deposited or diffused doped layers (e.g., as in crystalline and thin-film Si cells) and heterostructure buffer layers (e.g., the CdS layer in a CdTe device). We further define a passivating contact as one that enables high quasi-Fermi-level splitting in the absorber (large “internal” voltage

  18. Charge separation in contact systems with CdSe quantum dot layers

    International Nuclear Information System (INIS)

    ). The values of QD-ITO distance and trap density, determined with the simulation were consistent with transmission electron microscopy and photoluminescence measurements. The separation and diffusion of charge carriers was limited due to trapping of charge carriers. Smaller interparticle distances led to faster decays in CdSe QD monolayers. However the increase of traps, which resulted in a slower decay dominated and led to longer decay times of SPV transients of modified CdSe QD layers. By deposition of CdSe QDs on CdS a heterojunction was created. The CdS layer served as acceptor for electrons excited in CdSe QDs. Furthermore a CdSe QD/CdTe nanoparticle heterojunction was realized by successive electrophoretic deposition. CdSe QDs acted as electron acceptors, whereas CdTe nanoparticles acted as electron donors. Charge separation was dominated by the CdSe QD/CdTe nanoparticle interphase, as inverted layer stacking of CdSe QDs and CdTe nanoparticles gave an inverted SPV signal.

  19. PROCIS. Product identification, pilot plant design and market potential evaluation for copper indium disulphide (CuInS2) on copper tape substrates

    International Nuclear Information System (INIS)

    The new, innovative IST-technology for copper indium disulphide (CuInS2) solar cells on copper tapes (CISCuT) is a cost-effective series of consecutive roll-to-roll processes. One major feature of this technology is the multifunctionality of the copper tape (1 cm in width), serving as mechanical carrier, source for in-line CIS-formation and back contact of the solar cell, another is the potential to make flexible cells and modules. During the PROCIS project, the CISCuT technology has been further developed to a baseline for CuInS2 solar cell fabrication. In this sense, a major project effort has been the up scaling from the manually produced 2 mm2 dot cells at the beginning to large area tape (up to 10 cm in length). For the definition of the baseline equipment a comprehensive characterisation and modelling of CuInS2 material has been carried out. It was found that with standard processing conditions (a copper band speed of 3-4 cm/s and a temperature of 550C for the sulphurisation step) CuInS2 with an internal p-n junction is produced. This material consists of various Cu-In-S phases with the result that the photoelectrical properties of 'as-grown' CISCuT material differ from conventional CIS layers. Therefore, it requires different charge collecting layers with fortunately no need for the usually applied (toxic) CdS layer. The Cu/CuInS2/CuI/ZnO:Al configuration was selected as most promising in two aspects: the deposition equipment needed for the involved collecting layers could be integrated in the roll-to-roll technology and, with this cell concept the highest cell efficiency (η = 5.4% on 400 mm2) is achieved. In parallel, a simpler Cu/CuInS2/CuI/metal grid configuration was investigated. In this case, the metal grid replaces the ZnO:Al window layer. However, the up scaling of this cell concept is still in its infancy. Intensive research has been done to find suitable contacting and interconnection technologies. As a result, roof-tile integrated modules with

  20. Acoustic Streaming, The “Small Invention” of Cianobacteria?

    Directory of Open Access Journals (Sweden)

    Koiller, Jair

    2010-12-01

    Full Text Available Micro-engineering pumping devices without mechanical parts appeared “way back” in the early 1990’s. The working principle is acoustic streaming. Has Nature “rediscovered” this invention 2.7 Gyr ago? Strands of marine cyanobacteria Synechococcus swim 25 diameters per second without any visible means of propulsion. We show that nanoscale amplitude vibrations on the S-layer (a crystalline shell outside the outer membrane present in motile strands and frequencies of the order of 0.5-1.5 MHz (achievable by molecular motors, could produce steady streaming slip velocities outside a (Stokes boundary layer. Inside this boundary layer the flow pattern is rotational (hence biologically advantageous. In addition to this purported “swimming by singing”, we also indicate other possible instantiations of acoustic streaming. Sir James Lighthill has proposed that acoustic streaming occurs in the cochlear dynamics, and new findings on the outer hair cell membranes are suggestive. Other possibilities are membrane vibrations of yeast cells, enhancing its chemistry (beer and bread, keep it up, yeast!, squirming motion of red blood cells along capillaries, and fluid pumping by silicated diatoms.

    Los mecanismos de bombeo en microingeniería aparecieron al principio de la década de los 90. El principio detrás de esto es el de flujo acústico. ¿Ha descubierto la Naturaleza este invento de hace 2.700 millones de años? Algunas cianobacterias marinas de la especie Synechococcus nadan 25 diámetros por segundo sin ningún medio visible de propulsión. Especulamos en este artículo que vibraciones de amplitud de nanoescala del estrato S (una cáscara cristalina que cubre las membranas exteriores en las cepas móviles y con frecuencias del orden de 0,5-1,5 MHz (y esto es factible por los motores moleculares, podrían producir velocidades de deslizamiento del fluido, en el exterior de la frontera de la región Stokes. Dentro de esta capa límite (que